Questions and Answers

Got questions about aerogels?

We’d love to answer them for you, or have you answer them for us!

Post your questions in the comments form below and the Aerogel.org staff will try to answer them for you. And if you have a good answer to a question here, feel free to post it!

344 Responses to “Questions and Answers”

  1. Ahmed Eldabli says:

    hi
    if i have to ask about something about airloy
    if we have to make a curve by raising the temp over than 80 c , so the question is , are the material will lose it’s proberties at that case ?

  2. Ahmed Eldabli says:

    Hi
    I am doing a research on light and strength materials like Aerogel. I’d like to know the difference between Airloy and Aerogle in the Structure and why Airloy is more powerful than Aerogel as I have seen in some videos?

  3. israa says:

    why the shrinkage occur when we drying gel normal?

  4. r tomkins says:

    What, if any experiments have been conducted in using aerogel’s in the creation of room temperature super conductors?

  5. Tom says:

    Can Aerogels hold/suspend liquid? Can they be used as a carrier? If so what is the best kind?

    If someone could get back to me I would be super grateful.

    thanks,
    Tom

    • Emil says:

      Yes, but only liquids with low surface tension, e.g. liquid helium (3.5 mN/m), liquid hydrogen (2.0 mN/m).
      For liquids like water (72.8 mN/m) the porous structure cannot withstand the tension.
      I don’t know where the limit lies though but most probably depends also on the properties of the aerogel.
      You can check also “Imbibition of Liquid Helium in Aerogels” by Spathis et al.
      What kind of liquids do you consider, for which application area?

  6. Peter says:

    Hi

    Is it possible to make tents insulated with aerogel. If so how? Who can help me or sell me what I need?

  7. Carol Bouvier says:

    Hello, I am a high school teacher writing some curriculum for a nanotechnology class. I’m wondering if you have any experiments that could be done using your particles or blankets. I’m especially interested in the idea of daylighting. What could the particles be mixed with to make a clear coating to paint on glass to test the increased thermal properties? Could the larger particles be layered between two panes of glass? Any thoughts on what would be an interesting science fair project? Thanks,

  8. Tamanna says:

    Can ethanol be used as solvent in the solvent exchange steps in to make RF aerogel? In the recipe it is mentioned that acetone is the preferred solvent. How does it differ from other solvents like methanol or ethanol?

    Thanks
    Tamanna

  9. Tristan VanFossen says:

    Hello,

    I have a few questions:

    Is there a commercially available flexible aerogel in the tile format? I have been unable to find one other than the aerogel blankets sold by Aspen.

    Has the tensile strength and youngs modulus of the various Airloy aerogels been measured? The only specifications listed on their website is that for compressive strength and compressive modulus.

    With a flexible aerogel, such as an x aerogel, how durable is the material itself? Will the material hold up to repeated frictional wear?

    Thanks,

    Tristan VanFossen

  10. Lexie Chessin says:

    Hi,

    I’ve been trying to make Carbon-Resorcinol Aerogels but I have been having trouble with them shriveling up while in the oven at 80C before the three days of curing time is up. Do you have any suggestions as to what might be causing this?

    Thank you so much,

    Lexie

  11. Hossein says:

    Hi Sir,
    I am going to use this cylinder for weed control( by frosting of their tissues). is it good for this treatment?

  12. Lynne Morgan says:

    Would we be able to inject the silica based aerogel into the cavity between two pieces of glazing. Or better still spray a layer of aerogel onto a single glass sheet to increase the sheet’s R value ? I would like to insulate glass but still maintain light transparency for growing plants. can we use the areogel to store electricity for converting solar gain into LED output?

  13. Jindrich says:

    Hi,
    Is there any way of reusing TEOS/TMOS for another process? And what occures with that specific mixture? Thanks a lot.

  14. Nad says:

    Hi
    I would like to know whether there is any possible way to convert the hydrophobic aerogel sold by Cabot Corp (Enova Aerogel IC3100) to hydrophilic while being in an aqueous solution?

    Can anything be added in the solution to change the water-repellant behaviour of the aerogel?

    Thanks a lot.

    Regards,
    Nad

  15. Would it be possible to use airloys or SEAgel with nano carbon fiber to build snowboards , skateboards , surfboards , kayaks. I would like to startup a company in Hawaii building sporting goods using this method

  16. Patricia says:

    Hello, I am a student who is doing an oil project for school, and I need to come up with a solution of how to prevent oil spills. After researching I have found the product Aerogel, and I had a question. Can Aerogel be used in rivers, to soak up oil, after oil spills?

  17. jason says:

    Please refer me to the top groups who can custom manufacture carbon aerogels
    I have a serious large scale project in water treatment thta needs a top US based group to make material for our commercialization project.

  18. gade suraj says:

    Hello i am a mechanical engg. student my question is that is this material like other matetials like steel & alloys would will be used for producing different parts of AEROPLANE or not ?
    GIVE ME A QUICK REPLY PLEASE awaiting for your reply sinserely tHaNK yOu

    • Raman says:

      You need to define the application of the material.

      For example I could say in an aeroplane
      aerogels can be used for

      1. thermal insulation (-60C) in the aeroplane. Silica or PU aerogels can reduce the insulation material mass making the plane lighter
      2. amine modified aerogels ex: silica can be used for CO2/ethanol removal and air re-circulation
      3. carbon aerogels can be used for supercapacitance to store electrical energy

      They cannot replace steel as they are porous materials and have very low tensile and compressive strength compared to steel

  19. OnPointAlways says:

    Tbh i just want to know if Aerogel was ever supposed to go on a mission I need the answer as soon as possible. please and don’t use the email can u just post the answer for me of something if not i appreciate you trying and hope that i can find the answer on line. Thanks again

  20. Kab says:

    Can airloy be molded or 3D printed? I am planning to make miniature wheels, dimensions around diameter-26mm and depth-15mm and i want to make it hollow. Is there anyway can change the shape of airloy to fit my specifications? Its an aerogel btw 😛

  21. Greven says:

    Hi,

    We are experimenting with long term high temperature insulation, were working temperatures would be around 600c-1000c and have been looking into Aerogel when I found this awesome website and I’m very curious to pick your brain a bit, what type of aerogel would/could be best for our use? And what if we for example mix aerogel with for example perlite? To get a cheaper alternative.
    What more could you tell me about the use of Aerogel for this application?

    Thank you!
    Johan

  22. Peter says:

    Hi

    I am researching how to make the best cooler/freezer. Is aerogel duitable for making s rigid cooler or fridge?

    Does anyone make such a thing yet?

    Peter

    • Stephen Steiner says:

      Hi Peter,

      I would suggest using a bulk aerogel material like Spaceloft or Thermal Wrap which are insulating aerogel blankets. You would put them between other materials like plastic to make the cooler/freezer. The closest commercially available material for making a cooler/freezer out of one material would be Airloy X103-M or Airloy X103-L, which are lightweight superinsulating aerogel panels.

  23. Ahmed Eldabli says:

    can a car be made of Aerogel?

    • Stephen Steiner says:

      Hi Ahmed,

      A lot of parts in a car could be made with aerogel materials. Remember aerogels are a class of materials so different aerogels might be useful in different parts of a car. Silica aerogel insulation like Aspen Aerogels Spaceloft and Cabot Aerogel’s Thermal Wrap might be good for insulating an engine compartment from the passenger cabin. Carbon aerogels might be used in a supercapacitor in power management electronics such as the regenerative braking in a hybrid car. Strong aerogels like x-aerogels, organic aerogels, or Airloys might be used as structures in parts of the car to reduce mass and increase fuel efficiency. So yes a car can be made of aerogel, just not the whole thing.

  24. onar says:

    dear friends.

    i am doing a dissertaion about Airloy. i have managed to find out how Aerogel is made but the is no instruction at all about how an Airloy is made? would be greatfull if anyone can help me out

  25. Zack says:

    Hello everyone,

    I am currently seeking a method of producing aerogels via ambient drying without the need of using TMCS. However I found out it is quite difficult to completely remove water from the gels pores by just washing it using ethanol or acetone. One of the sign that the gels still contain water is that when I soak it in hexane, the gels will clotted and do not mix with hexane. How can I overcome this problem?

  26. Raman says:

    Hello Frank,

    So will a balloon filled with Helium.

    I would be very careful when considering the description of graphene aerogel being the lightest material in the world (lighter than air and all). You cannot subtract the mass of air in your material and call your material lighter than air. Thats just plain wrong interpretation of bulk density. Any open porous material bulk density can only come as close as the density of the medium which in this case is air.

    Regards,
    Raman

    • nitish kumar says:

      well said raman, I completly agree with you. It has to be true unless the pores are vacuum sealed, which is not possible.

  27. Isaac Malca Ruiz says:

    Awesome Scientists from the World!

    I was looking for any material which can be contracted or elonged when electricity was applied to it and after investigating through aerogels I read that they had this property. I have three questions
    1) If any aerogel has this property or only ones made of an specific material? If so from which materials? 2) Can they be found or made in the form of threads or wires?
    3) I was wondering if you know any other material wire/thread like which is contracted or elonged when electricity.

    Thanks!
    Isaac
    The E-Book for the Blinds building team from Perú

  28. Emre says:

    Hi everyone from Turkey… I need to lightest and strong material and found to “aerogel”… But I learned to its breakable with fingers..Then I saw to “airloy”… And I’m thinking to made a mechanism… How I get to “airloy” at the Turkey thanks…

  29. Max Podgorski says:

    Hello sir,
    I am interested in discussing your data regarding Aerogels, I am currently a high school sophomore enlisted in Science Research in search for a mentor. If you could take the time out of your day to contact me that would be much appreciated.
    Sincerely,
    Max Podgorski

  30. DJ Bourdow says:

    Hello,
    I have just purchased a piece of Spaceloft aerogel blanket and had a few questions regarding it. First, what is the best way to connect it to form a bag? Can I sew or fab the material and what would be the best way to connect it without losing any of its properties (ie. thermal, strength, water resistance). Also, can the material be coated with a spray liner, such as nylon or rubber material on one side without damaging or losing any of these properties. Any information would be great help.

    Thank you,

    DJ Bourdow

  31. Jimmy says:

    Would aerogel be able to withstand temps of up to 320C for really long sustained periods of time without breaking down? If so would it also be able to withstand repeated usage before breaking down, if at all? I’m looking to possibly use this in an experiment and need it for the insulating properties.

  32. Hi, I am working with nanocellulose aerogels which I extract from tropical seeds found in Ecuador. My aerogels are white, light, and exciting, but I don’t know if there is a market for this kind of material. May anyone provide some ideas in order to a future scaling up of my current lab production?
    Best,

    Javier Carvajal

  33. D.Z. says:

    Hello!

    I know this might sound stupid, but what is the cheapest kind of aerogel if you want to produce it in extra-super large scales, let’s say, 100 m^3 ? Also, is it theoretically possible to build an entire building out of aerogel?

    Thank you.

  34. anon says:

    can aerogels be produced in vacuum conditions

  35. Ashish says:

    I am a resarch scholar from India. I would like to know in detail the action of catalyst on the formation of aerogel ?

  36. Anjos Elson Gomez says:

    Dear friends,

    i am trying to create an aerogel based HME filter for ventilators for my college project. i need help from all you as well guidance in synthesis and pore size adjustment for the aerogel as my staffs seem a bit negative towards my idea. please do help i really want to do this project and prove my worth to my department.

    awaiting your positive help and guidance,
    Anjos

  37. MIDO says:

    hi ,
    i would like to ask you if i can form aerogel to be rubbery like in flexibility or even gelly like,
    if yes , how i can do that?,

  38. AHMED says:

    hi Sir,
    i need your help as i want to make gel and not a solid aerogel,
    i want it to be rubbery like,
    how i can do it

  39. Jake Smith says:

    I am trying to get some answers about custom uses of aerogels,
    I am an inline skater and the one problem is that skate boots are heavy, this weight is mostly cause by the large plastic components (frame to hold wheels and sould plate attached to the bottom of the boot) I was curious as to aerogels would be a suitable low friction alternative to these? they would have to be strong and able to withstand lots of scraping and sliding.
    Also does anyone know of anyone making footwear/boots out of aerogels? It would be interesting to see how much variance can be gained in the stiffness of aerogel fabrics and whether they could be both protective (in the toe and heel area) but also flexible in the cuff area. If anyone could point me in the right direction or offer a more informed opinion that would be great!

    Many Thanks
    Jake Smith

  40. Tamanna Rahman says:

    Hi, I cannot but appreciate your afford to build and maintain this website with such detailed information on aerogels. This is really helpful for all level of researchers working with aerogels.

    I am a graduate student in the department of Mechanical Engineering at Georgia institute of Technology. We are trying to synthesize transparent silica aerogels for the application of radiation detection. We followed the protocol described here for making gel. the gel looks good as expected. We did the ethanol exchange for 4-6 times. Then we did the drying in Tousimis dryer under supercritical conditions. We purged it with CO2 for 10 minutes and used 3 stasis cycles with 24 hrs interval. We got the transperant aerogel at the surface but it is opaque white inside. The samples are cracked as well. Could you please suggest what could be the reason and what are the parameters we can play with to fix it.

    Thanks
    Tamanna.

  41. Tamanna Rahman says:

    I can not but appreciate you for maintaining this website with such detailed information on aerogels. This is very helpful to all level of researchers working in this field.

    I am a graduate student in the department of Mechanical Engineering at Georgia Institute of Technology. We are trying to synthesize transparent silica by supercritical drying. We followed the gel synthesis protocol described in this website. The gel looks good as expected. then we did the ethanol exchange 4-6 times and put it in the Tousimis supercritical dryer. we purged it for 10 minutes with CO2 and with 24 hours of 3 stasis cycles. It is transperant aerogel at the surface but opaque white inside. the samples are cracked as well. Could you please suggest what could be the reason and what parameter should we play with to improve our samples?

    Thanks
    Tamanna.

    • Stephen Steiner says:

      Hi Tamanna,

      Thank you for your kind words!

      Your gel sounds like it didn’t supercritically dry well. That could be because of three things:

      • The gel was not adequately purified before supercritical drying (did you use absolute, i.e., water- and solvent-free, ethanol?)
      • The gel was not adequately solvent exchanged into liquid CO2 in the dryer (Are you sure the dryer was full of carbon dioxide? Consider cooling the vessel to encourage siphon action of liquid from the gas cylinder into the supercritical dryer, or alternatively is there a head-pressure bleed valve you can crack open to create a slight pressure differential? Also, are you sure your carbon dioxide tank is s SIPHON tank and not just a standard gas cylinder?)
      • The supercritical conditions were too low–remember you are not just exceeding the critical point of carbon dioxide, but the critical line of the carbon dioxide and ethanol, so you will want to take the supercritical fluid to over 45 deg C and about 1500 psi, not just 31.1 deg C and 1071 psi

      Hope this helps.

      • Tamanna Rahman says:

        Hi Stephen, Thanks for your reply. We finally could successfully make and dry our silica following your recipe. but it was not as transperant as desired. we are planning to play with the amount of stock solution that influences the gel time and clarity. could you please give us a range of the amount of stock solution that works? Is there any other factor we should consider to improve the clarity?

        Thanks
        Tamanna

      • Raman says:

        Hello Steven, Tamanna,

        Steven: Solvent exchange to liquid CO2 is a redundant step. Heated supercritical CO2 (refer a solvent/CO2 phase diagram) or heated autoclave will work just as well and will be much faster. Gel immersion in solvent is not necessary. Add small amount of solvent. In a closed system (vessel), VLE will be established (T dependent). So there will be no further evaporation. Take care about the mixture critical point (single phase region) when drying (CO2 replacement step). This is again dependent on T.

        Tamanna: The problem with your drying is the temperature. Increase the CO2 temperature (be careful with the pressure). It will work fine.
        You could simply make this check to see if water is the problem. heat the aerogel in an oven at 100C. Let me know what gives? ;).

        Cheers,
        Raman

  42. Nadia says:

    Hi Stephen,
    do you know a method for ambient pressure/temperature drying aerogel ?

    Thanks and Regards,
    Nadia

    • Stephen Steiner says:

      Hi Nadia,

      Sure. If you’re talking about silica aerogel, in general you need to make the gel hydrophobic using a hydrophobe such as trimethylchlorosilane or hexamethyldisilazane. Then, solvent exchange the gel into a solvent like pentane. Finally, allow the gel to evaporatively dry very slowly in a sealed container, for example, in a beaker sealed with Parafilm or a container with a pin-hole punched in it. This will allow you to make aerogel materials with >80% porosity or better. The important parts here are that you are taking steps to reduce the capillary stress between the liquid and gel backbone and that you are drying very slowly to allow for the gel to slowly adjust to microscopic shrinkage resulting from evaporation.

  43. Graham Keep says:

    Stephen,

    I am currently at a lab doing research related to aerogels. We have built or super critical dryer, with the design from your website, however my boss still has concerns about safety. Currently we have a 2000 psi brass pop safety valve and are thinking of purchasing a burst disk in a similar range. I was wondering if you would have any recommendations for further safety measures. Our initial inclination was to make or purchase a shield made of plexiglass to put in front of the device. Any help in this matter would be much appreciated.

    Graham

    • Stephen Steiner says:

      Hi Graham,

      A pop safety valve is an important thing to have and you could certainly add a burst disc if you would like. I would say building a sturdy frame is very important, and make sure to get valves with stiff handles for safe opening. You can chain or clamp the vessel to a rigid structure for added stability. Remember that the pressure vessel is rated to 3000 psi and you will only be operating as high as 1500 psi so you have a 100% safety factor. Keeping a clean workspace free of solvent spills and vapors is also good, and make sure to wear splash goggles or safety glasses when using. A welded design will help manage leaks better. Buying a plexiglass shield will protect against leaks or solvent spraying out, but in general the failure mode of the vessel is probably a leaky seal, an internal pressure gage rupture (which results in a non-explosive depressurization of the vessel), or operator error. Have a checklist and follow procedures carefully to help with the last one.

  44. FreznoBob says:

    When doing your supercritical drying of the gel containing liquid carbon dioxide is it possible to transition to a vacuum state and actually have partially evacuated pores instead of gas filled ones. I suppose it would take a specific gel to withstand the mechanical stress but it would seem this would lead to the lightest weight materials

    • Stephen Steiner says:

      Hi FreznoBob,

      Yes, actually you don’t need to do it during the supercritical drying phase. Aerogels are open-celled architectures so all you would need to do is to place the aerogel in a vacuum chamber and pull vacuum. In general any aerogel can be evacuated regardless of the stiffness of the aerogel, since the removal of gas from the pore network provided that it is not done too rapidly does not impart mechanical stress on the aerogel’s solid structure.

      • XerxesXerox says:

        Very interesting stuff! Good to see people spreading the good word of knowledge across the void! We all appreciate these tips and tutorials!

  45. Zabc says:

    Hello! I’m attempting to make subcritical silica aerogel at home using items available to the average consumer. So far, I’ve made samples but am not sure if I’m actually creating aerogel. My objective is to make something that will have great insulation properties but not cost a lot to make. Here’s what I’ve done so far:

    1. Pipette sodium silicate solution and water into a well (http://www.amazon.com/Sodium-Silicate-40%25-Solution-32oz/dp/B009GAQFJA/ref=sr_1_1?ie=UTF8&qid=1403226600&sr=8-1&keywords=sodium+silicate)
    2. Add cream of tartar (tartaric acid) from grocery store
    3. Stir mixture until a gel forms (looks slightly blue but clear in coloration)
    4. Add methanol over top of gel
    5. Repeat process of adding methanol and allowing to evaporate (solvent exchange).
    6. Allow to dry (the sample looks white but is very fragile; haven’t tested the insulative properties of the samples since I only get about a 1 inch sample each time)

    Any thoughts? Do you think what I’m making is actually aerogel/xerogel or what have you? I’ve tried substituting a 5% acetic acid solution (white vinegar) instead of cream of tartar and it works as well.

    • Stephen Steiner says:

      Hi Zabc,

      I applaud your creative and resourceful effort!

      A few things to note. First, you will want to remove excess ions (e.g., Na+) from your gel by ion exchange so that the resulting material can be adequately solvent exchanged and dried. Second, you will need to do something to make the material hydrophobic so that the material can be dried subcritically and not stick to itself internally. Perhaps there is some sort of glass treatment product you could use?

  46. jan maur says:

    Hey please could you help me .. i want To know which recipe should i use to get hydrophobic silica aerogel and how could i make it sprayable .. i want To make water repellent coating spray .. please help me

    • Stephen Steiner says:

      Hi Jan,

      Please check out the recipe at http://www.aerogel.org/?p=1443 as a start. To make it sprayable, you would either need to spray the gel precursor on a surface first and then do all of the subsequent hydrophobic treatments and drying on the part, or alternatively you could use a hydrophobic aerogel particle like Cabot Enova IC3100 which you could mix with a solvent or matrix and then apply to a surface. You can buy Enova IC3100 here.

  47. frank says:

    Could graphene aerogel be created as a closed cell construction? If so, could it be created within a wholly helium atmosphere? If both of these are possible, Then this new material, (helium encapsulated graphene aerogel “HEGA”) should become the world’s new lightest material. Not only would the framework be approximately 7X lighter than air, but it should float in atmospheric air as well.

    • Julian Constantine says:

      This interests me insofar as I have been interested for about 30 years now in the idea of creating lighter than air structures. not simply for dirigibles or insulation incremental savings but as an airbridge solution for cities. I have often considered the idea of creating the matrix in a helium environment, but my system which I called Heliflate involves lofting polycarbonate with helium inside an ultra thin skin, which is rather clunky compared to a closed cell nano foam. I would be interested to hear your thoughts on the subject.

  48. Connor Barker says:

    Not really a question, but I’m currently doing some coursework on materials. The others students researched into things like plastics or semiconductors, but I decided to go for something different and then, after several hours on the internet discovered and decided upon aerogels. Thanks so much for this blog, its been so much help for getting my head around aerogels, and making the coursework actually interesting and engaging!

  49. Zach says:

    Hey Aer-Heads (nickname usage rights reserved… Well not really, but compensation is always appreciated),
    Love the site, staff and discussions that make up this place. Fascinating in all regards. Here’s a Q for you. I just purchased one of the airloy samples, and while my initial use for it was simply as insulation, I wondered if the material could be used as a stopper for a small liquid nitrogen flask. Given it’s open cell structure and superior mechanical strength, I would think that it would make an excellent insulating stopper that could be threaded. Supposing this is possible, it would seem that you’d have better insulation, less spillage if the flask falls over, and the ability to vent as the ln2 evaporates, preventing a nasty little catastrophe. I do understand that ice building up in the cell structure could create blockage, but the period of time that the stopper would be needed in my application is less than an hour so there would be time in between runs to thaw. Would the moisture left behind in the cell structure after thawing affect it’s physical properties? Could the airloy be dried somehow to ensure safe use in subsequent runs? I’ll leave it at those questions, but any answers or other relevant information would be greatly appreciated. Thank you for providing this sexy resource, and for the love of god keep up the good work. :)

  50. Phil Jones says:

    Hi,

    I’d really like to know, if liquid CO2 could be replaced with liquid Helium or Hydrogen, to make an almost lighter than air material, with little or no weight.
    Furthermore would the hydrogen filled aerogel be flammable or explosive?
    Please could you try this with helium. (safer option).

    Also could this material be used as a new light weight, non bulky life jacket?1

  51. Dear Sirs,

    Is it possible to fill Aerogel powder into e.g an EVA based substance? We are working on making kind of a plastic tape which can be wound around an object thereby dramatically decreasing the lamba vaule of the flexible tape. We belive that Mixing a generous amount of aerogel powder into an existing recipe consisting of mainly EVA would do the trick. Your thaught on this matter would be most appreciated. If the latter is true, one could also argue that the EVA with a generous amont of Aerogel can be subjected to extrusion onto a surface with required adhesion. Anyways, your knowledgw in this matter would be most appreciated.

    Chris

  52. Oliver R says:

    Hello – I’m a Cornell student part of a senior research group on aerogels and we need to make basic bulk density measurements. We plan on doing this via Archimedes method and have seen literature examples which use Kerosene as the liquid. What are the advantages to this over water?

    Thank you,
    Oliver.

    • Stefan says:

      Oliver,

      submersed in any liquid, Aerogels will change their dimension. If you’re talking about silica aerogels, they might not last long in water as their backbone will break (AFAIR).
      In an open porous network like aerogels you should clarify, what you mean by “bulk” in bulk density. Using a “theoretical” liquid that does not affect the network of the backbone material (ie. zero surface tension) and with a visosity that allows to fill the entire network, you should end up with the density of the backbone material (e.g. Silica).

      Stefan

      • Oliver R says:

        Thanks Stefan! So it sounds like kerosene is an appropriate liquid, better than water, yes? Also I’m not sure what you mean by the backbone material – will the resulting density be of the silica or the aerogel as a whole?

        – O

        • Raman says:

          Aerogels are open porous materials. Imagine Eiffel tower shrunk down to nanometer scale. the steel structure is the backbone.

          I would avoid any use of liquids on aerogels.
          The easiest way to measure bulk density of an aerogel (if powder is to put it in a graduated cylinder and measure the mass). If a strong solid, measure the dimensions and the mass.
          Since these are very light materials the mass contributes more to the bulk density error than the volume. For example case 1: m=1 g V= 50 ml what is density? Case 2 m=1g V=53 ml what is the density? Case 3: m=2 g V=50 ml what is the density?

          The backbone density can be measured by Helium Pycnometry.

  53. Dennis Tomic says:

    Hello, I have a very specialised niche that needs to filled. After investigating aerogels I believe I have found the answer, but before I proceed with the purchase I need confirmation on which aerogel/technique needed.
    A hollow core around .017″ inches in diameter needs to be filled with a super-insulating substance. Insulation is the main trait sought, but extreme flexibility is needed, generally low production cost, and a good compressibility trait.
    Any, if not all, information provided by you on which aerogels/companies can successfully fill my needs will be greatly appreciated. The project i’m conducting is of the upmost importance. If you do not know the answer to my question, please forward this email.

    Regards,

    Dennis. Tomic

  54. Hamid Reza says:

    Hi
    We have a carbon dioxide supercritical fluid extractor, which could not be placed on freezer. So we have to work only at ambient temperatures as minimum reachable temperatures (20-25 ͦc). But elevating the temperatures is possible.
    I want to know: it could be employed for supercritical drying process in order to make a Metal oxide aerogel using epoxide assisted method?
    Details related to supercritical fluid extractor instrument are cited in following link:
    http://www.sitec-hp.ch/homepage/index.php?id=160 .

    Please guidance me. It is very valuable!!!

    Best Regards.

  55. Hamid Reza says:

    Dear Sir,
    I am going to making a cobalt ferrite (CoFe2O4) aerogel using citrate sol-gel procedure and following exchange solvent and supercritical drying processes. The question is: all type of gel (for example citrate gel), proceed by supercritical drying, could be resulted in aerogel? Please help me

  56. Peter says:

    Our amateur group of modellers are venturing into High Altitude Balloon flights with recoverable payloads. When the balloon bursts and the payload falls back to earth, we don’t want to have to chase the payload for hundreds of miles across the country-side. Using a radio beacon, we want to glide the payload back to the field where we are parked.

    We are searching for a material that can be milled into a simple, solid “foamy” glider (think space shuttle or lifting-body) using a CNC. The basic craft will be fitted and balanced with avionics, battery’s, GPS, servos, flight surfaces, GoPro cameras, etc…all of which probably will not work if exposed directly to temperatures -70F and the soft-vacuum of near-space for a couple of hours. Our thinking is that aerogel can offer a flight structure and thermal protection if it can be laminated to the right size and then milled.

    FYI: We read the part about “Can you machine aerogel?” Apparently not, so, what would be the closest material to a millable aerogel that would most likely to be suitable for this application?

  57. Daemon Process says:

    Remember the scene in the first GhostBusters movie, the one where Ray gets his first look at what was to become Ghostbuster’s headquarters?

    “Hey does this pole still work? Wow … this place is great! When can we move in?
    You gotta try this pole! I’m, gonna get my stuff. Hey, we should sleep here, try it out…”

    I brought that up so you would know the purely objective and scientific reasons for my interests in Aerogels.

    I’m reading, but there are these questions bubbling, such as:

    Are the regimes used to create one aerogel automatically destructive to other aerogels?
    I’m thinking of a scaffolding of using, say, an iron oxide “wire frame” with a polymer “drywall,” for instance. Super noob? Doable?

    So that was question one.

    Two is about, recycling. I’m wondering how much recycling one could get out of approx $1500.00 (puts it in the dryer budget?) for the chemicals normally used. Worth it? If so I’d probably build one and after I got one working “open source” it here, if it was ok?

    How many passes, if any do you think one could get for that budget? Links anyone?

    Beautiful site, I have been thinking of ways to move open source beyond software; this is a great example.

    Thank you.

  58. shiraz says:

    Hi,

    Great Work!! Please can you explain the difference in process required to make a granular/powdered aerogel and monolithic aerogel. how is this made?

    Thanks

  59. Liam McCarty says:

    I was hoping you might be able to tell me whether or not a supercritical dryer built from the plans on this website would be able to reproduce the conditions of an experiment I’m hoping to reproduce. Here is an excerpt from this experiment:

    “In a typical experiment, the produced gel were wrapped separately in a filter paper and placed into the 4 l cylindrical stainless steel vessel. Supercritical CO2 was delivered using a high pressure diaphragm pump and was introduced from the top of the vessel at constant flow rate (100–200 g/min). Temperature was maintained constant (40 °C) using an oil heating jacket. At the outlet of the vessel, supercritical CO2 loaded with solvent was directed to another 2 l cylindrical stainless steel vessel (separator), where the solvent was separated. The pressure and temperature of the separator were maintained constant at 40 °C and 60 bar respectively. Solvent-lean CO2 was then recycled for the process. After 8 h the extraction was completed and the aerogel microspheres was removed from the 4 l autoclave and the solvent from the bottom of the separator. Typically the recycled CO2 was exchanged with a fresh CO2 at least four times during the extraction process to ensure complete extraction of the aerogel.”

    Is the supercritical dryer you have plans for capable of these operations? Thank you!

  60. ricardo says:

    HI, i am doing a architectural project and was researching for materials. This is a very futuristic proposal for self sufficient buildings. I was wondering two things about this material, 1) can it be created in any shape for example a pipe, and then filled with water on the inside? and 2) can it be use as a self supporting structure?

    than you.

    • Raman says:

      Q1,2 YES: There is a lot of work on mechanically robust aerogels. Refer airloy for ex. The hydrophobicity plays the most crucial role.
      What you specifically want to use it for will determine the practicality? ALso the costs…….

  61. falgunigoradia says:

    Dear Sir,
    I went through your site and found it very interesting. i am a pharmacist and working in surgical manufacturing unit researching on the medical devices i have come across a gelatin foam which is used as a medical device during surgical operations. I want to know this basically a natural foam or aerogel. iwant to know how it can be made if it is aerogel. i have heard that gelatin is crosslinked and the gel is foamed and dried to make a dry gelatin foam.if u have any information i would appreciate on this.

  62. Muhammad Belal Malick says:

    HI,
    I am a student of Polymer Enigineering and recently me and my friends came across this amazing substance aerogel while we were doing some research on silicones.Looking at all the usefull info provided on this website we have decided to undergo a thorough research on it and to make it on laboratory scale.I have read a lot about it on your webisite.Depending upon ur experiences, can u tell us that which one is the most easiest aerogel type to make on laboratory scale.And can we make silica aerogel by simply supercrital drying normal silicon gel avalible in markets for insulation purposes?Do keep in mind that i also have to build a supercritical dryier……Please give me an early reply so that i should start focousing on only that particular type of aerogel

  63. Justin says:

    Hi Stephen,

    I’m a graduate student at the University of Michigan and am highly interested in your work for use as a potential material in my own. I am currently conducting an engineering design project that may benefit from the incorporation of aerogels (though at the moment we are using alternative methods). I was hoping it might be possible to further discuss the potential for such an application. I was unable to find your email address on the aerogel site, but if you are interested, let me know the best way to contact you so as to elaborate on the details of my project.

  64. Hı, I am a R&D specialist from TURKEY.we are a manufacturer of vinyl siding exterior cladding. It ıs made from PVC and the other processing aids. At the ınsulation of buildings civil engineers use XPS foam for ınsulatıng of buildings and take up the vinyl siding. I think ıf we use aerogel form on the mixing of pvc compounds and than we are extrusing on the machine and made a self-insulated vinyl siding. Is there a possibility or do you think it possible?
    Thank you

    • Stephen Steiner says:

      Hi Bulent,

      Yes, I think it is definitely possible to use aerogel materials to make self-insulated vinyl siding. You should contact Cabot Aerogel who makes an aerogel performance additive called Enova aerogel that can be added to various construction materials. There are already a number of self-insulating materials such as rock wool made with it.

  65. Lya says:

    Dear Sir,

    Hello and Hi…

    We are doing project to produce alginate aerogel. I just want to ask u, can u explain what are actually happen during supercritical drying process and what are the mechanism? For example, we are use supercritical carbon dioxide to dry the aerogel that containing ethanol. So that, in term of process description, how carbon dioxide can remove the ethanol during the supercritical drying process? what are properties of the carbon dioxide and ethanol that play the important role during the mechanism of the process? Is it has any connection with density or polarity?

    Thank you for helping.
    Regards,
    Lya

    • Stephen Steiner says:

      Hi Lya,

      When you place a gel into a supercritical dryer, two things are actually happening. First, the liquor in the pores of the gel must be displaced by liquid carbon dioxide through diffusion. For this process, the density and polarity of the gel liquor should be as close as possible to carbon dioxide. Ethanol is okay but when mixed with liquid carbon dioxide the mixture contracts severely and can cause your gel to shrink and crack (although organic gels tend to be more resilient in this regard so it may not be a problem for you). Acetone and acetonitrile work well. Second, after soaking in liquid carbon dioxide (and successively draining and recharging the liquid carbon dioxide) the ethanol will have diffused out (as you will read in our section on Gel Drying Procedures) and the liquid in the pores of the gel will be substantially all liquid carbon dioxide. At the point, you heat the liquid carbon dioxide and its vapor pressure will increase until it reaches and exceeds its critical point, at which point the carbon dioxide loses its surface tension and can diffuse out of the pores of the gel without imparting capillary stress that would otherwise cause the gel to collapse. Once a supercritical fluid, the carbon dioxide behaves mechanically like a gas and can be depressurized.

      Hope this helps!

  66. Mike Kitson says:

    Hi Aerogel gurus:) We manufacture paddle boards and surfboards. Currently, we wrap carbon fiber fabric around a core of 2 lb density EPS foam. I am wondering if aerogel could be utilized to replace the foam core? We are looking for the strongest and lightest components possible in our manufacturing process. The foam core is shaped using a CNC, is rigid and bonds well to the epoxy which is used to attach the carbon fiber. Also the foam can withstand most sudden shocks caused by impacts with rocks, etc. Would aerogel be a suitable alternative to the foam? Any comments would be appreciated. Thank you!

    • Stephen Steiner says:

      Hi Mike,

      There is a new line of strong aerogels called Airloys that are really the first aerogel materials with the mechanical properties to stand up to such an application. The come in densities as low as 0.010 g/cc, which is about three times less dense than 2-lb density EPS foam. They are just now becoming commercially available (R&D collaboration phase). You could take a look at those!

      • nitish kumar says:

        stephen,
        can you please help me with some technical resource on airloy?,please do notify me if u have @
        nitishkumar.vaja@wmich.edu

      • Ted says:

        Based on the airloy presentation insaw on YouTube recently, it seems it would be a great board building material. That said, what is the largest piece of Airloy that would feasible to manufacture? If you’re building a short board your looking at a hunk of foam roughly 3’x2’x6-7′ and larger for longer boards. Is creating a volume of Airloy that large possible? Obviously everything is possible, but what is financially practical.

        Thanks!

  67. Stephen Lupton says:

    Is there any way to use electrolysis to remove water in its gaseous state from aerogel without having to add methanol and then put it into a supercritical dryer?

    Seems like it could potentially skip the hard part.

    Couldn’t find where it had been done before.

    Thanks!

    • Stephen Steiner says:

      Hi Stephen,

      It would be great if you could avoid supercritical drying (and there are ways to do it and we even tell you how to do it in the Make section). Regarding electrolysis, you’re welcome to give a try! I’ve thought about this too, but there are a couple issues:

      • This approach would probably only work with gels that have electrically conductive skeletons, of which there are very few (most electrically conductive aerogels are made by derivatizing non-conductive aerogels through pyrolysis after supercritical drying)
      • Electrolysis evolves gas bubbles at the electrode-electrolyte interface and these liquid-gas interfaces will create capillary stresses throughout the pore network, which will probably cause the gel backbone to collapse
      • The evolved bubbles will likely blow apart or create defects throughout the gel network
      • You may run into mass-transport limitations due to ions in the pore network being used up faster than they can be replenished by diffusing into the gel network from the surrounding electrolyte bath

      This said, try it! Maybe it works and it’s awesome!

      Alternatively, gels can be freeze dried to yield aerogels, however cracking is frequently a problem. In this case, you would likely purify the gel into water, carefully freeze the gel, and then remove the ice by subliming under vacuum.

  68. prix says:

    I am very limited on my funds and I want to make the high pressure reactor which is rated upto 3000 psi and has a window on it with a stirring option. The sample that I am going to place inside the reactor is 3″ in size. I dont know from where to start as I am very new to this field. Can you please help me with some suggestions with the design of reactor…I will be passing carbon dioxide through syringe pump for very controlled flow rate….I know the system is big..so my ISCO syringe pump wont b enough 2 take the reactor to 1500 psi..but still working on it…

    I know this is a aerogel website…but still I would like to built something like jerguson cell but dont have money…

    Plz help if you have any suggestions regarding designing

    • Stephen Steiner says:

      Hi prix,

      Well it sounds like you have a very ambitious and cool reactor in the works!

      Certainly the syringe pump is a concern as I don’t think they make syringe pumps that go to 1500 psi–they’re probably called something else (you may want to look at hydraulic pistons or cryogenic gas pumps).

      Regarding reactor design suggestions, we’ve put together a lot of information about designing a supercritical dryer that you should take a look at first! If you have any specific questions, feel free to post them here.

  69. Amanda says:

    Hi,

    This website gives a great overview of aerogels and is really helpful in enhancing understanding. I am doing a research project for a grad level electrochemistry course and I am exploring the electrochemical applications of carbon materials. I have come across various types of carbon foam and aerogel articles however I have found conflicting information as to whether a carbon foam is or is not the same as a carbon aerogel…one source suggested that carbon foams are made up of small graphite-like crystals, however they are not good electrical conductors. I can’t seem to find how the composition of a foam differs from a carbon aerogel that is a good conductor…any help clarifying the differences in chemical composition and electrical properties would be great!

    • Stephen Steiner says:

      Hi Amanda,

      Gee I sure hope this isn’t too late but given that it’s the end of the semester your course is probably over…

      In any case, carbon foams can have a wide range of compositions, from glassy carbon (which has few reactive surface moieties and excellent electrical conductivity) to activated carbon foams made by pyrolysis of organic foams, which present lots of defective sp3-hybridized carbon surface moieties.

      Carbon aerogels typically are very amorphous, with crystallite sizes in the range of 2 nm or less. The are electrically conductive but have conductivity similar to activated charcoal, and that conductivity tends to decrease with increased surface area and reduced density.

      However, there are a number of carbon nanotube aerogels now that have very good electrical properties and high surface area.

      Hope this helps!

  70. Gary Tillet says:

    I am drying isopropanol (IPA) alcogels (rinsed 4 times after synthesis with reagent grade isopropanol – but not necessarily dry because the bottle is open to humid air when pouring, etc.). I am pressurizing to roughly 1500 psi and heating to roughly 300 deg C (beyond the critical point of IPA). However, I am getting cracked, somewhat-shriveled pieces, and not un-shrunkened monoliths after sc-drying. I heat the sample in about 1 hour, hold beyond the critical point with periodic venting to prevent excess pressure for about 1 hour, hold isobarically and isothermally at about 300 deg C and 1500 psi for about 1 hour, and finally depressurize over 1 hour. I also pull a vacuum on the autoclave once it is fully depressurized until it cools to below the normal boiling point of IPA. Could the problem be residual water in the IPA (up to 12% by mass, unlike EtOH which picks up only ~5% water)? Is water soluble in scIPA? Am I depressurizing too fast? Any suggestions? Should I just do scCO2? If so, do I have to re-exchange the IPA away with acetone?

    • Stephen Steiner says:

      Hi Gary,

      Cool–high-temperature supercritical drying!

      Okay, so a few questions:

      • Are you filling your vessel partway (or all the way) with IPA or just putting the gel in by itself?
      • Are you reaching the critical temperature first or the critical pressure?
      • Are you using anhydrous (100%) IPA or reagent-grade 70% IPA?
      • What are the dimensions of your monoliths?

      Some suggestions:

      • Slow down everything–you should heat much slower and depressurize more slowly as well–depending on the dimensions of your monoliths you may not be giving the pore fluid throughout the gel network enough time to equilibrate
      • Water is soluble in scIPA but an IPA/water mixture will have a different critical point than pure IPA, and it is concentration dependent–once you drop below the critical point of the mixture water may precipitate from the fluid in the pore network of your gel and cause cracking
      • You could try supercritically drying from acetone or methanol to see if it works better, but IPA should work
      • Don’t give up on this–when you get it to work it will be much better than supercritical carbon dioxide
  71. ADEEBA says:

    Hye,
    my last experiment is about silica aerogel

    and now i am doing master project about carbon aerogel. However, my precursor now is from waste paper like newspaper as a carbon source, and it is
    not like usual precursors of carbon aerogel which are resorcinol and formaldehyde.
    The question is how the gel is form?. I am now trying to dissolve waste paper in sodium hydroxide.. and add with sulfuric acid to get ph7 in order to get gel… Do I have to add something like catalyst or what?

    Thank You
    From Malaysia

    • Stephen Steiner says:

      Hi ADEEBA,

      Well it sounds like you have a cool project but honestly this is research and probably nobody knows the answer to what you are trying to do yet. I would suggest the following:

      • Do chemical analysis to understand what the chemical and material make up of your input materials are, and what the dissolved product solution contains
      • You will need to make sure you have some sort of molecule in your precursor solution that is molecular (not micron-sized fibers) that can be crosslinked
      • You will need to identify what that crosslinkable molecule is, e.g., cellulose
      • You will need to make sure there is a sufficient concentration of that molecule in your solution, e.g., 30 wt %
      • You may need to add a crosslinking agent

      That’s the best advice I can give you for now. Happy to help further if you have more specific input or questions!

  72. Seraj says:

    Hello
    I’m a physics student and my friend is chemistry student .We have decided to have project about Aerogel and we are going to produce it for heat and sound isolation.
    We need a piece of advice to get started to produce it for industrial purposes in our country!
    Like what you can see in this video :
    http://www.youtube.com/watch?v=NaG9cJAgej8

    Thank you !

    • Stephen Steiner says:

      Hi Seraj,

      The material in the video is either Aspen Aerogel’s Spaceloft or Pyrogel aerogel composite blanket product. These materials are available commercially on a global scale, and are very high quality materials. I would suggest for a research project you try to innovate something new instead of copying existing industrial materials. Aspen Aerogels runs an excellent operation and is a fast-growing company. Their products are also a product of a decade of proprietary research which is not available in the public domain.

      I’d recommend reading more about how flexible aerogel blankets are made on our page about Strong and Flexible Aerogels starting at the section titled “Fiber-Reinforced Aerogel Composite Blankets from Aspen Aerogels”.

  73. Byron C. says:

    Hi Aerogel.org,

    I was wondering why the Glass-water process produced more fragile aerogels than Alkoxide-process aerogels?

    Thanks

    • Byron C. says:

      Is it because the Sodium ions grow become difficult to remove when washing?

    • Stephen Steiner says:

      Hi Byron,

      When using waterglass, a lot of sodium ions are present and need to be extracted. It is difficult to remove all of these ions and, as such, it’s easy for a residual amount to remain after supercritical drying. These ions can serve as stress concentrators/defects which make the material more prone to fracture. They can also make the material more hydrophilic, which can also weaken the structure. Using alkoxides allows you to make a material with a cleaner chemistry and to control the rate of formation and morphology of the nanostructure better than with waterglass. As a result, waterglass-derived silica aerogels can in many circumstances be more fragile than equivalent density alkoxide-derived silica aerogels.

  74. fareez says:

    hello guys,

    actually i’m doing a engineering project regarding this aerogel..so my question is if we can produce aerogel is lighter than air, can it support load to be floating on air?

    • 9a3 says:

      Aerogel which could safely contain hydrogen for lift in hybrid airships, I think, is a more immediately realizable goal as vacuum lift vessels would require something like ultrastrong graphene membranes. I think the scientists here must feel the lighter than air craft matter is radioactive, perhaps akin to UFO/ET consideration by the astronomical community 30 years ago. I would like someone to flood a mylar [or similar] coated piece of fire resistive aerogel with hydrogen. This would exhibit lift. Set a torch to it and see if it reacts explosively. Seems like an easy and obvious experiment to conduct.

      • Stephen Steiner says:

        Hi 9a3,

        You would need a very, very low density aerogel to make a material that would float on its own by putting hydrogen in its pore network and it really would not be able to lift anything with it. I’ve actually done the math and it is not a viable prospect for traditional aerogels, especially when you have to consider a mylar skin. It is possible to get very low density silica aerogels (with densities <3 mg/cc) to float, but they are very, very fragile and strong aerogels (e.g., x-aerogels) have densities of 100-500 mg/cc and are much too heavy to float.

        Keep thinking about it though!

        • 9a3 says:

          Thank you very much for replying, Prof. Steiner. Since reading your comment, I have attempted to determine the lift of Hydrogen gas, density of mylar, etc. Forgive me if my numbers are off:
          Lift of Hydrogen gas 1.08927 milligrams/cc
          Density of mylar (Dupont brand name for polyester film) 1.39 grams/cc
          Flexible, carbon nanotube multi-walled aerogel [this site] 4mg/cc
          So while my sphere of solid aerogel would not float, it appears lighter than air balloons with skins and/or internal partitions made of aerogels could be manufactured with existing technological limits. Key, I think, is whether the substitution of aerogels could make safer the containment of hydrogen for use in lighter than air craft. Helium is rare and expensive, hydrogen abundant and relatively cheap. Safe, lighter than air transportation would be ecologically friendly and wonderful.

          • 9a3 says:

            Another approach and application for specialty aerogels:
            http://members.gcronline.com/cbrauda/0005.htm
            “The bottom line is that a suffient charge accumulation on a capacitor, or any object for that matter, of suffiently small mass, would be accelerated more by the earth’s electric field than by acceleration due to the earth’s gravity field. It would fly.”

          • Stephen Steiner says:

            Hi 9a3,

            Well this sounds cool–I wonder if you could use high-surface-area carbon aerogels or multiwall carbon nanotube aerogels to do this!

          • Stephen Steiner says:

            Hi 9a3,

            Certainly propagation of a combustion front through an aerogel material, assuming it is non-combustible, would be stifled due to the tortuosity of the nanoporous network. To your point regarding helium, it is true that it is in diminishing supply with some questionable economics regarding its pricing in place, however aerogels of the density and size required for your application are also currently rare. I would be concerned about having carbon-based aerogels be the matrix material for this application, as they can burn. But there are other low-density aerogels that are non-flammable and structurally sound that may be interesting candidates, for example, methyltrimethoxysilane-based silica aerogels. I’m still not convinced that the math regarding lift works out favorably, but perhaps instead of a solid aerogel sphere/form you could use a hollow form with a wall that’s a few centimeters thick–this would potentially stifle combustion from the outside of the vessel but not chock the vessel full with unnecessary weight in the form of unneeded aerogel.

          • 9a3 says:

            I agree, very cool. I have no experience with or access to aerogels. I’m hoping some researchers will pursue some Thomas Edison type materials experiments. According to http://www.airships.net/helium-hydrogen-airships the LZ-129 Hindenburg’s Friedrichshafen to Rio de Janerio flight no. 10 payload for passengers, freight, mail with hydrogen was 21,076 lbs while the same trip using helium would have not been possible due to a lift of negative (-) 34,923. Of course, modern hybrid airships would have design advantages afforded by super-computer modeling, 80 years of aerodynamics/scientific advances, and aerogels/airloys! Here’s my wish materials “to do” [more like wish] list: 1.) Ignition/explosive risk management of small aerogel balloons with hydrogen to determine containment feasibility. 2.) Liquid nitrogen cooling of aerogels testing for super-low [lower than air] dielectric constants and 3.) Attempt to manufacture a super-capacitor which would satisfy the demands of the site on electrogravitic/flying carpet type lift. Actual Hindenburg dining room and passenger lounge.
            hindenburg-dining017web-385×243.jpghindenburg-lounge005web-276×385.jpg

    • Stephen Steiner says:

      Hi fareez,

      See the response below but generally if you can get an aerogel to float it will do so just barely. They need to be very low in density and such aerogels are very fragile. If you do the math, a hydrogen-filled or evacuated 3 mg/cc or less silica aerogel will not have enough buoyancy to lift anything substantial.

  75. JimmyZ says:

    could aerogel be used in place of an inner tube inside a bicycle tire? there exist at this time inner tube replacements made of closed cell plastic foam, but they are heavy and lack the desirable handling characteristics of tires with inner tubes. I imagine that an aerogel with the required rebound strength could outperform even tubeless and tubular tires as well as the two sorts I previously mentioned. Professional and / or competitive cyclists would certainly adopt aerogel filled tires if they offered lighter weight and superior durability and handling. Other tire applications for different sorts of vehicles might also be enhanced through use of aerogel.

    • Stephen Steiner says:

      Hi JimmyZ,

      Sounds like a great application for an x-aerogel. You would definitely need a mechanically strong aerogel for such an application and something with some elastic compliance so it could be stretch and tolerate impacts. They would potentially be lighter than cellular foams but still about 0.1-0.5 g/cc.

    • Stephen Steiner says:

      Hi JimmyZ,

      Although most aerogels would not be suitable for such an application x-aerogels would, and in fact run-flat tires are one target application for strong x-aerogel materials. A new class of commercially available materials called Airloys are just becoming available that could potentially be used for such applications, but yes, the combination of ultralow density and mechanical strength would be cool for racing cyclists!

  76. Stefan says:

    During my PhD in Prof. Fricke’s group in Würzburg, we developed another flavor, actually a strange one: PZT-aerogels.
    These are made from lead/titanate/zirconate close to the stoichiometry where ferroelectric behavior occurs. Strange, because during heat treatment, porosity goes well below a suitable limit, however still high enough to achieve improved acoustic impedance matching, compared to conventional PZT ceramics.
    One of the research papers dealing with the physics of this stuff is
    S. Geis, et al., “Electrical properties of PZT aerogels”, Journal of the European Ceramic Society, Volume 22, Issue 7, July 2002, Pages 1155–1161
    You can find more on how it is made with my collaboration partner’s work like
    P. Löbmann, et al. “PZT Aerogels: Sol-Gel Derived Piezoelectric 3-3 Composites”, Journal of Sol-Gel Science and Technology, Volume 19, Numbers 1-3, 2000-12-01, pp. 145-148

    If you would like some more information, let me know. I’d be glad to help out if I do have data available (I left academia in 2001).

    Stefan

    • Stephen Steiner says:

      Hi Stefan,

      Cool! For those of you who don’t know, PZT is an important piezoelectric material–that is, something that changes dimensions upon application of an electric field and, conversely, produces an electric field when it is strained. We’ll take at a look at your work and write something up about it! Thanks for the suggestion.

  77. DebraB says:

    Is there something that must be done to get access to the parts/schematics? I keep getting redirected to the “Warning” page – “Please agree to the terms and conditions”

  78. 9a3 says:

    This is an excellent website. The gentleman who interviewed Prof. Leventis is as well spoken as any broadcast professional I’ve heard. I am interested in how aerogels can improve efficiencies, from buildings to transportation. Please address/investigate how aerogels might be used to safely contain hydrogen gas for use in hybrid airships [modernized Zeppelins]. I have seen a video of a lighter than air solid called Seagel. If a small fire resistive silica (?) aerogel sphere the size of a basketball were coated for hydrogen-tightness and filled (with hydrogen), it would exhibit lift. But unlike the Hindenburg, might silica aerogel somehow act as a moderator so as to eliminate explosive risk or at least control any accidental burn? How much would it cost to construct such an aerogel balloon in order to put a match to it to see how or if it would burn? This seems like an experiment which could be conducted immediately using existing materials. If there is interest, and there should be, then researchers could investigate designing aerogels with fire-extinguishing properties–should the hydrogen in an aerogel lift cell begin to burn, the aerogel matrix would react and put out the fire. On a more exotic note, I would like to see attempts to construct vacuum balloons–lift obtained through vacuum, not lighter than air gas–using x-aerogels. Could a basketball size sphere be coated with air-tight material and then evacuated to the point of lift? Not only would such a device help revolutionize transport, but it would make a fine toy for kids young and old. Happy New Year to All!

    images?q=tbn:ANd9GcQG_JpgZYSWlvdEC6xLiGsLsGL1U2sVbIPR1uP5dKEoIA9Q6Rmfzeppelin-hotel-1.jpg

  79. Ottoberge says:

    I am investigating the idea of making a supercritical dryer using the instructions posted on this website. If anyone has any experience making one of these supercritical dryer, I would like to ask you a couple of questions.

    1. I am considering using Parker A-lok fittings (http://www.belloil.com/data/pdf/parker/A-Lok%20Tube%20Fittings.pdf) instead of NTP fitting to build the dyer, b/c I have a lot of unused SS a-lok fitting in my lab. From my experience with a-lok fitting, they should be able to withstand these pressures and temperatures without the need of welding or pipe tape as well. Can anyone speak to why I wouldn’t want to the use a-lok fittings in this application?

    2. I need a slightly larger supercritical dryer then the one described here. I was wondering if it would be OK to extend the 1.5 in cross fitting with an additional 1 to 2 in tube. This tube will be in between the sight glass and the cross.

    Does anyone feel that this will somehow effect the integrity of the dryer?

    Thanks

  80. Cameron Kirk says:

    Would Xaerogel be a good material to make a ultra-light shoe?

  81. Pedr says:

    Are X-aerogel water resistant? or is there any way of making them hydrophobic if they aren’t already?
    Thanks
    Pedr

  82. Weld tech says:

    I am working with a ultra slim narrow groove weld head, we are operating the weld at 300 amps, while in the groove the weld head has the danger of shorting out on the sides of the weld head which is currently Stainless Steel, the working temp is an average of 800f.
    Is there a way to use the aerogel to insulate the sides of the weld head to act as a non conductive sheild.

    Your help is greatly appreciated, I look forward to hearing from you.

    Walter Vasquez
    Arc Machines Inc.
    walter.vasquez@arcmachines.com

  83. b says:

    Hi

    My question is could we lay this stuff on magma ? If so how long would it stay on top?

  84. Laurel says:

    Hi- I’m interested in preparing films on slides through the water glass method. I haven’t been able to find a more detailed prep than is in your summary of this method. (Okay, so I found G.S.Kim and H.H. Park’s papers but they are in Korean.) Is there a paper you can recommend? Thank you! -L

  85. Liam McCarty says:

    Can you make any aerogels without using hazardous chemicals? Just curious…

  86. Cookie says:

    I want know formation enthalpy of silica aerogel.

  87. Liam McCarty says:

    I am considering building a supercritical dryer to research aerogel applications as biomedical scaffolds. Are there any aerogels that you know of to be safe even when inside the human body? They would need to be non-toxic and generally not dissolve in water (though I’m intrigued about the possibility of a slowly dissolving aerogel). And, as I’m no chemistry buff, what kinds of materials can aerogels be made out of? In other words, what are the limitations in terms of what can be used?

    Thank you! This really is an incredibly helpful website.

  88. Doug Johnson says:

    Application questions! I have an application where vibration is present most of the time, although the body itself would not be impacted. What is the vibrational resistance of a silica aerogel? Is there a chemistry that is the most robust? Is there a lifetime to the aerogel? What is the mode of decomposition? Also, it seems silly to ask, but is this closed cell or open?

    A wonderful website.

  89. larisa schulze says:

    In the example shown of the flexible silica aerogels using MTMS, why is aerogel pictured white? Methyltrimethoxsilane is colorless – is it the combination of the two?

  90. eliott says:

    Hi, I am now tying to make aerogels.

    – On the pictures of the gel drying procedure, it seems that you always keep the intake valve open during solvent exchange, is that right?

    – Concerning the pressure what should be its value during solvent exchange: 7000kPa or so?

  91. christian says:

    Hi, I’m trying to put together a proposal for an art project using aerogel. My question is this: How long can the aerogel sustain close contact heat from a blowtorch? I want to have a disc of aerogel protecting a flower on display, but don’t know how long I can expose the gel to heat. also, i want to have blowtorches aimed at an enclosure made of aerogel blanket material, is it ok to simply aim torches at this material, or will it damage the material? thanks

  92. Eliott says:

    Hi,
    I’ve made my SC dryer and now I have to make my aerogels.
    I built a small dryer (1″) with no window. When I start to put CO2 inside, how should I know that I have put enough CO2 even with a scale? I guess I have to know the volume of my manuclave.

    Thanks for your answer

  93. Megan says:

    Hi Stephen,

    I’m a grad student just getting into aerogel fabrication; this website is such a great complement to academic papers. Thank you so much for putting it together and maintaining it.

    I have a question about hydrophobizing silica gels. Do you happen to know a method (or resource) I can use to calculate the diffusive speed of TMCS or another silane through a gel? Specifically, I’d like to know if your procedure allows sufficient time for TMCS to diffuse to center of a 4 ml monolith, such that the interior is as hydrophobic as the exterior.

    Thanks so much for your time!

    Megan

  94. PRIMERO QUE TODO FELICITARLOS POR MUY EXELENTE PAGINA ….ME RECOMENDARON EL MATERIAL Y
    TENGO UNA APLICACION DE UN AISLAMIENTO TERMICO EN TUBERIA CON TEMPERATURA FUENTE DE 800°C Y REQUIERO SACAR A UNA TEMPERATURA DE 60°C QUE ESPESOR DEL AISLANTE AEROGEL ME RECOMIENDAN PARA ESTA APLICACION DE ANTEMANO ENVIO LAS GRACIAS POR LA AYUDA QUE ME PUEDAN PRESTAR

  95. Eliott says:

    Hi,
    First of all, you did a great website about aerogels and it’s so usefull.
    I’m building a CS dryer and I’m quite a beginner in assembling parts of a machine.

    1. Is it normal that I cannot fit and thread pipes until the end of the thread? I can only go as far as mid distance about.

    2. I did not quite understand explanations about taping.Do I need to tape parts after screwing or before?

    • Stephen Steiner says:

      Hi Eliott,

      Thanks for your kind words about Aerogel.org and we’re glad you like it! Great to hear you’re building a supercritical dryer!

      1. It is normal that you cannot get pipe fittings to thread in all the way, especially with big pieces (1.5″ NPT pipe fittings and up)–you may only get them in about halfway. Please keep in mind the fittings must be wrapped with Teflon tape in order to get them to go in as far as possible, and make sure the fitting is screwed in as tightly as possible with a wrench. If a fitting grinds or poses a lot of resistance when threading it in, you are stripping the threads and may have damaged something.

      2. Absolutely you must tape the parts before screwing in. The point of the tape is to make the thread-thread interface smoother so the parts don’t get stuck (seize).

      Hope this helps!

  96. janet says:

    is it expensive?
    i mean how can i buy it

    • Stephen Steiner says:

      Hi Janet,

      Remember there is no “it” here–aerogels are a class of materials with various compositions, densities, and form factors (e.g., solid blocks, granules, composite blankets, etc.). But in general the cost of aerogels, while more expensive than common materials, is now quite reasonable!

      A good place to start is BuyAerogel.com, where you can get sample-sized pieces of various aerogel materials. Sample materials start around $15!

      At industrial scales, aerogel materials are very affordable. Entire buildings are now made with Cabot’s Lumira aerogel granules for skylights and insulated light-scattering windows.

      Hope this helps!

  97. lisa says:

    Why is a monolithic aerogel advantageous over the powdered form? (i.e. why are so many people focused on developing monoliths?)

    • Stephen Steiner says:

      Hi lisa,

      Monolithic aerogels have the advantages of maximizing a number of materials properties special to aerogels, that is, certain properties of aerogels are optimized when the material is a coherent solid. Many people are interested in monolithic aerogels also because this form preserves transparency, whereas granular or blanket forms are usually only translucent (transmit light but not a view). For some applications including particle detectors and transparent insulation, this is important. X-aerogels, strong monolithic aerogels, are interesting as lightweight structural materials as well.

      All in all, while many scientists may focus on monolithic aerogel production, not that many industrial players do. Aerogel Technologies is a major producer of monoliths, as are a few other minor players that do not sell directly to the public. Powdered or granular forms are generally easier to make (monoliths are time-consuming and tend to crack) and can be integrated into other legacy materials. For these reasons, most industrial players focus on these.

  98. Roey says:

    Hi there,

    first of all this is a great site!

    second, i want to understand something.
    if you take a piece of aerogel material, that it’s very very thin and has a very big surface.
    and you put in the air, which the density of the air is about 1.2 kg/meter^3
    will it or will it not approximately fly?
    to be more specific i mean that it’s velolcity towards down will be very small, so we almost couldn’t notice it. (according to the equation of drag force of air)
    Of course, the drag force by the air will be equal to the gravity force in opposites directions.

    i will be very grateful if someone can answer me.
    thanks
    Roey

    • Stephen Steiner says:

      Hi Roey,

      It is possible to make aerogels very low in density and back fill them with helium to make them float in air, but it is very challenging to make these aerogels and to get the trick to work. It’s easier to fill an aquarium with xenon and drop a low density aerogel into that instead. I’ve made aerogels that were so light when you drop them they float like a piece of lint or a feather. In any case, though, aerogels are open porous and will not retain any gas put inside them for very long, and any sealant you would put on them to keep the gas in adds to the weight enough that it ruins the ability for the aerogel to float.

  99. Scott says:

    Your blog mentions a forum but I can’t find it: “You’ll find forums where you can interact with others interested in making aerogels and discover user-generated recipes for making aerogels of all sorts.”

    • Stephen Steiner says:

      Hi Scott,

      Heh, yes. For now, the “forums” are our comment pages–we had experimented with a real forum platform but it didn’t work well. We hope to have a more social network structure or social network integration in the future. What do you think?

  100. May says:

    Hi, I am really thankful to you guys for making such a wonderful and informative website. It really helped me in preparing my report about Aerogels. However, there are some things that I would like to ask:
    1. What substances are usually used in making Aerogels? What is/are present in these substances that made them essential for making aerogels?
    2. Silica Aerogels and Chalcogels, I’ve heard, were the most common Aerogels produced. Are there any similarities (components, characteristics, etc.) that lead the Silica and Chalcogen group into the basic ingredients for wet gels and perhaps, Aerogel?
    3. How can we make hydrophilic and hydrophobic aerogels? What are their charactirstics or components that made them water-loving and water-fearing, respectively?

    • Stephen Steiner says:

      Hi May,

      Well we’re glad the website has been useful for you!

      1. To make silica aerogels, compounds such as tetramethoxysilane, tetraethoxysilane, or sodium silicate are used since they can make silica gels when reacted with other substances such as water and acids.
      2. Silica aerogels are certainly the most common type made. Chalcogels are NOT a commonly made type of aerogel, only a few groups work with these. This is what we call Wikipedia bias. The thing these two classes of materials have in common is that they both start out as wet gels,but the chemistry to make those gels is pretty different. In general, to make a gel, you need reactive monomers or nanoparticles that can polymerize and/or agglomerate together to form a gel. Once you’ve got a gel, you can dry that gel to make an aerogel!
      3. Hydrophilic aerogels are what typically result from preparing silica aerogels by low-temperature CO2 drying. They are hydrophilic (water-loving) because they have hydroxyl groups on their skeletal surfaces that water loves to stick to (because they look like water). Hydrophobic aerogels result from replacing these hydroxyl groups with something that repels water, like a methyl group (-CH3) or a trimethylsilyl group (-Si(CH3)3). This can be done by treating the wet gel with special waterproofing chemicals before supercritical drying, by supercritically drying the aerogel at high temperatures in methanol, or by post-treating the supercritically dried aerogel with a reactive chemical.

      Hope this helps!

  101. micifuzz says:

    Hi!
    Your website has been really useful to understand few things about this product. Right now I’m writing my dissertation about Spaceloft and walls, and I’m finding real problems dealing with the life-cycle analysis, specially about the manufacturing process, it looks really low in use of energy to be a “supercritical drying”. Could you put some light on that.
    Thanks in advance
    P.D: I would like also, if you do not mind, to send you a Questionnaire. If it is ok for you please drop me a line with your email, I will really appreciate it.

  102. Ragavendran SN says:

    Hi,

    I am currently working on preparation of silica aerogel from rice husk ash using ambient pressure process for my college project. We confirmed the occurence of silica gel by FTIR. The next step involves conversion of Silica gel to Silica Aerogel. After further processing of aging and strengthening of silica gel, it was to be dried in an Oven @ 50* and 200* C.

    But all we got was the opaque xerogel. We have repeated the experiment 5 times and we havent got the transperant blue color aerogel.

    Anybody here working on the same lines? I have a few questions regarding the processing and heating time. Any help would he much appreciated.

    Thanks much in advance for your time.

  103. kidrichmond says:

    Question for an expert wanting to assist in designing a more effective fire protection gel. I work in the major motion picture industry as a stunt coordinator and performer. Currently I use a protective gel to coat the skin of a performer when working with fire stunts. I’m interested to learn if there’s a way to create a jelly like substance out of aerogel that can be used instead of the current formula. Please reply if you’re interested. I’ve attached a photo of what my current gels are capable of. Though they’re limited in protection time. Right now I can burn for 15-30 seconds depending on the type of fuel used. Actor in the background, my hand in the foreground. fire_stunts_info1.jpg

  104. Jacey3000 says:

    Hey aerogel.org team. Really loving the work you guys have put into this incredibly informative and interesting website. I first looked into aerogels for my a-level materials presentation and am now back many years later writing my dissertation on a field of aerogel application. This website has proved to be an incredible resource, so much so that I’m worrying about not having enough other sources to make an adequate list of references. There does appear to be a change in one of the links you have posted. It would appear Prof James Hardy of the University of Akron has discontinued his two semester online chemistry tutorials! All but the final metabolic patherways site, so this section may need updating. This is a bit tough personally as it is a section I was intending to study. If you do know of way to find the said missing information, I would be most (extra) appreciative. Keep up the great work guys, it’s a pleasure to read.
    Jacey

  105. alex says:

    Hi:

    I’m new to this but

    Wow, what a resource here… I have a question – How does one bond to separate aerogels together to form different shapes?

    Or does the shape you have in mind have to be cast/ pre molded before the gel is made?

    Thanks

    alex.

  106. Jason Tafoya says:

    I am making some aerogel samples and am having difficulty in the supercritical drying stage. I basically put my sample in the chamber (pre-filled with enough ethanol to cover the sample), close the chamber and add liquid CO2. After the chamber is filled, I can watch the sample and after about 15 minutes, cracks start forming in the sample.

    These samples are TEOS based sol gel glasses and after making the gels, I exchange them in fresh ethanol every 2 days for about a week @40 C. I have also drained the alcohol and put fresh CO2 into the chamber, but the samples still crack. Does anyone know why these might be cracking?

    Jason

  107. Greg says:

    Great website. Just got interested by aerogels for something practical and found a lot of information. Thanks.
    I have a question: Is it possible to make a non-elastic film out of aerogel? Ideally the source material would be liquid and sprayed onto a shape to make a film that could be pulled out of the shape and keep a kind of structure, for example could be inflated.
    Thanks

    • Alex says:

      Hi:

      I’m new to this but

      Wow, what a resource here… I have a question – How does one bond to separate aerogels together to form different shapes?

      Or does the shape you have in mind have to be cast/ pre molded before the gel is made?

      Thanks

      alex.

  108. Mark Hightower says:

    I am particularly interested in the explosive aerogels made of thermite that Dr. Alex Gash refers to. What is the composition of these aerogels and how explosive are they? How does the composition relate to their explosiveness? Can they be high explosives, and if so, how? Is there information in the open literature that answers these questions?

    Thank you.

    Mark

  109. OttoBerge says:

    Does any one know of a TEOS sol-gel procedure that is water free? Thanks.

  110. Dear aerogel makers,
    your website is terrific !!!
    I would need some help. I’m living in France and I wish to test some bioaerogel in medical testing.
    I have no a lot of time to search for european companies that could provide me pieces required to build some CO2 supercritical dryer.
    Would it be possible that some members of aerogel.org team could sell and send one to me in order I do not waste time to built it ? Or eventually put me in contact with european guy who find out where to find the equipment required …
    many thanks in advance.
    best regards
    seb

  111. John Eastmond says:

    Hi,

    Could aerogel be used to store a gas at high density that can’t be easily liquified like hydrogen or methane?

    One could put aerogel inside a cylinder. If one then filled the cylinder with gas perhaps the presence of the aerogel would reduce the gas pressure necessary to store a certain amount of gas molecules. I imagine the gas molecules bouncing off the aerogel rather than the walls of the cylinder thus reducing the pressure on the cylinder walls.

    John

  112. arjuna says:

    Just to clarify on my post/question, I understand that transparent aerogel materials are not yet available. My question about applications for greenhouses were for potential deployment on the walls in order to reduce heatloss. It would obviously be great to have similar transparent materials for the roof, but I understand that’s some ways off.

    • Stephen Steiner says:

      Hi Again Arjuna,

      Transparent aerogels are available commercially but as small monoliths and at greater cost than Spaceloft. You are correct that Spaceloft is not transparent. Also Cabot Aerogel granules (previously called Nanogel) is available as a translucent fill for skylights and windows.

  113. arjuna says:

    I have been aware of aerogel for several years, but only discovered your website today. Very interesting.

    I am a consultant to a large horticulture (plants) company, and energy-use (both heating and cooling) is always an issue, given the very large spaces involved that must be kept at a relatively constant ambient temperature as well as the need to maximize sunlight coming in from above. Minimizing heating costs in the winter is probably the most important relevant issue.

    I saw the information on the Spaceloft blanket, and could envision the deployment of these along the walls of the greenhouse, but there are several issues that would need to be answered:

    Greenhouses are designed for the production of high volume, low price commodities and as such are buildings with both very large volumes (and thus outside surface area). The (typically fiberglass) walls are also exposed to high humidity or water exposure. So:

    1. Deployment of aerogel-based insulation would have to be cost-effective in this type of industry, and
    2. Would have to be made of robust material that could be exposed to humidity/water without losing effectiveness
    and
    3. Deployment of such insulation may have to be seasonal (i.e. it’s deployed during cool months and stored in summer).

    So my questions are:
    A. do you know of any such applications in this industry?
    B. how quickly are costs falling for materials that can address this kind of application?
    C. can such products be used in such environments without losing effectiveness (or growing a coat of algae!)? Alternatively, are blankets with waterproof top/bottom layers feasible (ex. mylar)?
    D. can these materials be deployed and then removed/stored easily?

    Thank you very much in advance.

    • Stephen Steiner says:

      Hi Arjuna,

      A. do you know of any such applications in this industry?

      I don’t know of Spaceloft being used explicitly for greenhouses but it is used in buildings as insulation.

      B. how quickly are costs falling for materials that can address this kind of application?

      Spaceloft is a reasonably affordable material if purchased in bulk so I would say it’s an investment that would reduce energy costs and pay for itself over 5-7 years.

      C. can such products be used in such environments without losing effectiveness (or growing a coat of algae!)? Alternatively, are blankets with waterproof top/bottom layers feasible (ex. mylar)?

      Spaceloft and other Aspen Aerogels blankets are all hydrophobic so they would perform well in a humid environment. Additionally, the materials are nanoporous and so biological organisms can’t fit in the pores to grow on them. The hydrophobic surface would also make it an undesirable surface for biological organisms to grow on.

      D. can these materials be deployed and then removed/stored easily?

      Spaceloft is very dusty but could be encapsulated to facilitate regular installation and storage.

  114. Andres Bustamante says:

    Hi,

    My name is Andres Bustamante I am a Grad Student of Furniture design in SCAD university, I am in a materials class and I wondering if I can use your product for my assignment about a new material. Is there any chance that you can send me a sample.

    Thanks a Lot,

    Andres Bustamante

    • Stephen Steiner says:

      Hi Andres,

      When you say our “product”, I guess you’re referring to aerogel, which is actually a class of materials. Also, Aerogel.org is an open-source education project, not a company, so I’m afraid there isn’t any “product” to send.

      With respect to using aerogels for furniture, there a couple of different potential opportunities. You could use aerogel blankets or granules to make a superinsulating snuggy-type blanket or cushion, for example. You could also put Cabot Aerogel granules inside a transparent form to make an interesting aerogel blue visual effect. Lastly, you could use monolithic x-aerogel forms, however this would be quite an undertaking.

      In any case, if you’re looking for samples of aerogel materials my best advise is to visit BuyAerogel.com. They have several different types!

  115. Weston Higgins says:

    I have just purchased some aerogel and was under the impression it would arrive cubed. Instead I have recieved a jar of powdered granules. How (if at all) can I go about forming these granules into a basic structure like a ball or a brick?

    • Stephen Steiner says:

      Hi Weston,

      Unfortunately, aerogel granules cannot be reassembled into a larger form without some sort of binder, which probably isn’t what you want. You could certainly try playing around with polyester resin or epoxy to see if you could make a composite, otherwise you’ll want to order an aerogel monolith in the shape you require, whicih will probably be more expensive than the granules you bought.

      Hope this helps!

  116. Anna Marcellan says:

    hello everyone!
    i’m a third year student of the University of aerospace engineering of padua,Italy. with my team we are designing an experiment for ESA to be performed in microgravity or on board the Airbus A300 ‘Zero-G’ (able to perform parabolic flights) or on the ZARM drop tower of Bremen, Germany.
    We are interested in designing a possible experiment on the aerogels under these conditions, and we decided to ask for advice about the latest research or tests that were carried out, and also to possible collaborations.
    thanks!
    anna

    • Stephen Steiner says:

      Hi Anna!

      Well I’m certainly a fan of microgravity aerogel experiments myself. MIT had a team working on a zero-g aerogel project but they’re working on other topics now. I’m always happy to advise however I can–this is an area I research.

      Feel free to post more questions as they come up! In the mean time take a look at this article about aerogels and zero-gravity.

  117. ScienceProjectGrade7 says:

    Hello! We are two 7th graders doing a science fair project, and we were wondering if you could answer some of our questions.

    1) Is “aeroclay” something that is based off of aerogel?
    2) Easiest way to obtain samples of aerogel?
    3) What form of silica gel is used to make aerogel?The acid or the solid little marble things that come in those little bags to keep your things dry?

    Thank you!

    (P.S.we have more questions stocked up)

    • Stephen Steiner says:

      Hi Team ScienceProjectGrade7,

      Happy to answer any and all questions that I am able to!

      1. 1) Aeroclay is a tradename for a freeze-dried class of porous materials primarily based on clay. Aeroclay materials are the least aerogel-like, but in general clay gives microstructured materials as opposed to nanostructured materials, which is a defining characteristic of aerogels. Certainly yu can make aerogels by freeze drying as long as the resulting material is primarily mesoporous, that is, most of its pores are between 2 and 50 nm). Yes, aeroclay is certainly related to aerogels and some aeroclay materials may meet the definition for being aerogels themselves.
      2. 2) Probably the easiest way to obtain samples of aerogels is at BuyAerogel.com. They’re the only reliable source for sample-sized aerogels of various forms. You can get a 1″ sample-sized disc of silica aerogel from them for about $35.
      3. 3) The gels used to make silica aerogel are specially-prepared wet gels, physically similar to gelatin except made of silica instead of collagen and glycans. The “silica gel” that comes in little packets like you’re talking about is actually silica xerogel, a densified verison of the kind of gels you use to make silica aerogels. That material is a good dessicant, that is, it helps to absorb moisture from a package efficiently to keep things like electronics from corroding during shipping. Take a look under the Learn Section for the article “How is Aerogel Made?” for more information, and then after that you can read more about the process used to make silica gels, the sol-gel process, under The Science of Aerogel.

      Lastly, feel free to ask more questions any time if you’ve got more!

  118. I have just discovered this fascinating realm of aerogels and have come across several references (mostly on other sites) to the fact that aerogels made from agar are non-toxic. Now my curiosity is piqued, and I have to wonder if it is possible to introduce flavours? That is, has anyone yet explored the potential for aerogels as a new culinary experience? The first thing that comes to my mind is the possibility of creating a dessert that could be, literally, as light as air. Any thoughts?

    • Stephen Steiner says:

      Hi Lorne,

      Sure it’s possible! Actually, Aerogel.org co-founder Will Walker has successfully made (and eaten) edible aerogels with various flavors. More to come on that!

      • John Harris says:

        Interesting that it’s actually been done. When I created a “running gag” in my Star Trek: Citadel fanfics (which take place on a planet where just about everyone is what we’d consider overweight, at best… some militantly so, hence the development of the “Fauxbar”), I never thought it had already been produced, albeit only experimentally.

        I could see things like “chocolate aerogel” being a popular way to get the flavor without the calories…

        (Apologies for digging up an old exchange, but the same question only recently came to me.)

  119. Mohit Jain says:

    sir,
    I would like to know whether aerogel has properties to be used as a building material ?

    • Stephen Steiner says:

      Hi Mohit,

      What do you mean by building material? As a structural material instead of wood or aluminum? Or as insulation for buildings?

      Keep in mind “aerogel” is not a substance or any one particular material–aerogels are a class of materials. There are strong aerogels called x-aerogels, invented by Prof. Nicholas Leventis at the Missouri University of Science and Technology, which are capable of serving in structural applications, and there are also flexible aerogel insulation composites, such as Spaceloft, which is made by Aspen Aerogels.

      Check out the page on strong and flexible aerogels for more information!

      Hope this helps!

  120. Dear Sirs,
    I am trying to achieve thermal insulation on textile substrates using hydrophobic silica aerogel in powder form. For this purpose I have been trying to disperse the aerogel powder in PU and Acrylic binder solutions. Which I have not been able to get. Can you please suggest me a suitable way to achieve thermal insulation using hydrophobic silica aerogel powder? What are the solvent system that can be used to apply aerogel on textile substrates.

    Thanks

    Munendra Singh
    IIT Delhi

    • Stephen Steiner says:

      Hi Munendra,

      I would encourage you to step back and think about the objectives of your problem to formulate your questions more helpfully. Instead of asking what solvent system can be used to apply aerogel powder onto textile substrates, ask, how can aerogel be rendered into a textile form? Perhaps it would be more effective to cast a gel over textile fibers and then to supercritically dry the composite, or to get the particles to stick to the fibers some other way than by putting them in a solution and trying to adhere them onto the fibers? Maybe you could put the binder on the fibers, and then roll the fibers in the aerogel powder?

      Hydrophobic aerogel powders are extremely difficult to work with for the following reasons:

      • – They are very light and get kicked up by even mild air currents
      • – They are hydrophobic and have few reactive sites on their surfaces, making them hard to chemically bond to
      • – They are porous and will wick up hydrophobic materials instead of reacting with them

      What kind of fibers are you trying to adhere the hydrophobic aerogel powder to?

      • Munendra says:

        Thanks a lot sir for your response.
        Say I am dealing with fabric not the fibers and mainly polyester fabric. I also understand that aerogels are difficult to work with but a homogeneous application is required which is not possible to get by just rolling aerogel on binder coated fabric, rather a homogeneous dispersion is required. For this reason I asked if it is possible to disperse them.

        Thanks

        • Stephen Steiner says:

          Hi Munendra,

          Hope you’ve had success on your project. Regarding dispersal of the particles, you could try using a surfactant and dispersing in water, or rapidly mixing the particles into some sort of organic solvent which won’t be wicked into the hydrophobic pore network.

  121. Hello! Comments are enabled again. Fire away!

  122. Stephen Steiner says:

    Hey Aerogel.org users! We’ve got a new comment system that lets us easily reply to your messages so from here on things should be streamlined.

  123. steph says:

    Hi, I was reading about aerogel and I was wondering if a skateboard could be made of aerogel?, is resistant enough?
    Thanks

    • Stephen Steiner says:

      Hi Steph,

      Totally, but you’d have to use one of the new formulations of strong aerogels such as the x-aerogels developed by Prof. Nicholas Leventis at the Missouri University of Science and Technology. These materials are light, strong, and not brittle. You can even machine them! So skate away–although these materials aren’t yet commercially available.

  124. Patrick says:

    I was wondering if anyone has managed to create a aerogel of boron nitride nanotubes, or any thing else that would work well for a gas core fission reactor.

  125. Patrick says:

    I was wondering if you could start a project to develop a new firefighters uniform primarily based on aero-gels for the thermal insulation, since it is now possible to make it flexible and since it can protect them from far greater heat that current uniforms can. I’m pretty sure that firefighters could really use more protection. I think that the publicity for aero-gels and funding and bump in the number of people working would be very good.

    I think that it would be best if it was open source like your site but will university help.

    things that you might what to test with it are:
    the new nano fibers, and the nano fibers that are injected with metal particles.
    metal rubber made by nanosonic.
    tera hertz imaging system for vision.
    thermal imaging.
    phase change fabric

    • Stephen Steiner says:

      Hi Patrick,

      Cool idea (pun intended)! There are lots of components to proposal, but as far as the aerogel materials go, a flexible insulating blanket like Aspen Aerogels Pyrogel might be suitable, although it is very dusty and would need to be encapsulated in another fire-resistant fabric. It would get very hot in there, though!

      Maybe we could find a fire department who would be willing to sponsor a prize?

      • Tony Verdecia says:

        Hello, I stumbled upon this Q&A session because I was researching aerogel for a Firefighting application as well. I am a firefighter in Orange County, California and am interested in performing some tests with the materials. Please let me know if there is any specific information about this I may need to know, and please inform me if there are companies already trying this for fire suppression activities. As a firefighter I can see that the aerogel thermal wrap could be VERY useful. Please respond with any insight or help.

        -Tony

  126. Stephen Steiner says:

    Hi Farjan,

    Q: i want to make final research in order to graduated. my i know how is the way to make carbon aerogel, and what are aerogel made off. please help me.

    We’ve got a lot of information here on Aerogel.org about carbon aerogels, and you’ll find references to journal articles that can provide you with even more information. Look at some of these pages:

    Learn > Flavors of Aerogel > Organic and Carbon Aerogels
    http://www.aerogel.org/?p=71

    Make > Aerogel Recipes > Organic and Carbon Aerogels
    http://www.aerogel.org/?cat=53

    See > Aerogel Image Gallery > Aerogels of Different Compositions
    http://www.aerogel.org/?p=891&px=%2FAerogels+of+Different+Compositions%2F

  127. Stephen Steiner says:

    Hi DW,

    I have had the oppurtunity to view and touch aero-gel, and found it fun, much like silly putty.

    Really? What aerogel did you experience? I’ve never played with an aerogel that felt like silly putty–silly putty to me is very stretchy and compliant, whereas aerogels are rigid forms, and usually very brittle (unless they’re x-aerogels). Do you mean it was fun like silly putty, or that it was fun because it was like silly putty?

    My question is regarding it’s use in a fiction novel. Can aero-gel be used for a small parachute?
    I read a spy novel and there was a gadget with aero-gel as one of it’s components. It was a small camera that hung overhead in the sky, much like a signal flare would. The camera was suspended from an aero-gel parachute. From the description I imagined it to be like one of those old plastic army guys with the parachute.

    I don’t think aerogels are the right material for the job. A parachute needs to have large surface area above all to create enough drag to slow your acceleration down. Aerogels, although light, are not easy to render into large foldable forms–even flexible aerogel insulation is a composite with fibers and isn’t particularly foldable like a parachute has to be. Not sure why they were using aerogel parachutes in this spy novel!

    I would imagine that such a parachute made of aerogel would not be feasible due to it’s slightly brittle nature. The weight of such a parachute would also end up weighing probably the same as if the parachute were to be made from silk or nylon.

    It would be like making a parachute out of a fiberglass boat hull–just not the right functional properties for a spy parachute. Some aerogels are not brittle but these materials are usually very stiff or marshmallow-like–they are not like fabrics.

    You could imagine a parachute made of x-aerogel that wouldn’t be very foldable but perhaps could be deployed as a bunch of small rigid sections that assemble together or fan out. It would have a density about three times lighter than water but there would be lots of logistical problems and you could probably get the same results with a much thinner piece of a high tensile strength material such as silk or nylon as you suggest. The issue here is that aerogels are not particularly strong in tension–they are strong in compression relative to their weight. In the context of a futuristic spy novel, for this type of application you would want an exotic material with a high tensile strength, such as carbon nanotube fiber made by Nanocomp Technologies maybe?

    By the way, no need to hyphenate aerogel (unless you also hyphenate aero-plane, auto-gyro, and co-operate).

  128. Stephen Steiner says:

    Hi Jeremy,

    Q: First, what would happen to aerogel if you were to submerge it somewhere hot like in molten lead (which melts at 327C) and how high of a temperature can you have before the aerogel can be damaged?

    It depends on the type of aerogel. A typical, non-hydrophobic silica aerogel could be dunked in lead no problem–and would probably be okay up to about 600 deg C where it may begin sintering (densifying).

    Second, can you make aerogel out of any metal oxide? such as the oxides of silver or gallium, and what about radioactive metals like the oxides of uranium or thorium?

    You can make an aerogel out of many metal oxides–the question is whether or not you can make a metal oxide gel. Silver oxide may be tough to get monolithic. Gallium oxide has been made. Radioactive oxides including the two you mentioned have also been made!

    Q: Lastly, can aerogel be used to generate water from the air?
    It is hygroscopic and absorbs water but how can you make the water come back out of the aerogel?

    Sure but not very efficiently. It is a good dessicant but then once the water is absorbed by the aerogel, it can’t absorb any more and you have to put a lot of energy into the aerogel to get the water to come off (basically you have to heat it to about 200 deg C). Also, once a hydrophilic aerogel absorbs water, it usually densifies and collapses, meaning you can only use it once.

    Hope this helps!

  129. Stephen Steiner says:

    Hi Ragavendran,

    This site is extremely useful for college students like me. Thank you for all the information.

    Great to hear! Glad we can help.

    Q: I was trying to find the thermal properties of aerogel but i could not find anything about the properties of aerogel at low temperature.

    What you are looking for is the thermal conductivity of (I assume silica) aerogel as a function of temperature. Take a look at these publications:

    Bernasconi, A.; Sleator, T.; Posselt, D.; Kjems, J. K.; Ott, H. R. “Low-temperature specific heat and thermal conductivity of silica aerogels”, Journal of Non-Crystalline Solids (1992), 145(1-3), 202-6.

    Scheuerpflug, P.; Hauck, M.; Fricke, J. “Thermal properties of silica aerogels between 1.4 and 330 K”, Journal of Non-Crystalline Solids (1992), 145(1-3), 196-201.

    Scheuerpflug, Peter; Morper, Hans Jochen; Neubert, Gerhard; Fricke, Jochen “Low-temperature thermal transport in silica aerogels”, Journal of Physics D: Applied Physics (1991), 24(8), 1395-403.

    Scull, L. L.; Arvidson, J. M. “Low-temperature mechanical property measurements of silica aerogel foam”, Advances in Cryogenic Engineering (1988), 34, 413-18.

    Bon, J.; Bonjour, E.; Calemczuk, R.; Salce, B. “Low-temperature acoustic properties of silica aerogels” Journal de Physique, Colloque (1987), C8, C8-483/C8-488.

    Calemczuk, R.; De Goer, A. M.; Salce, B.; Maynard, R.; Zarembowitch, A. “Low-temperature properties of silica aerogels” Europhysics Letters (1987), 3(11), 1205-11.

    Try using a tool like SciFinder, ScienceDirect, or Web of Science to find articles that relate to your research topic.

    Q: I also found that aerogel is like glass. Does brittleness increase with decrease in temperature in aerogels? (by low temp i mean in the range of 100 K)

    Great question–certainly if you rapidly cool an aerogel the thermally-induced stresses throughout the material could exacerbate fracture. I don’t have a good answer for you but from what I know and have read about low-temperature experiments with aerogels I would say they do become less fracture tough at lower temperatures.

    Hope this helps!

  130. Stephen Steiner says:

    Hi Simon,

    I have just purchased some aerogel and am thinking of incorporating this material into a water based paint.

    Care to let me know some of the challenges that I will encounter? My objective is to create a paint that can minimize the amount of heat from the sun onto the wall. I live in the tropics and the sun and heat can be quite an issue with air conditioning. How much aerogel granules would I need to get an effective heat insulating paint?

    Well you may have problems with mixing, and you may have problems getting a paint that will perform the way you expect. Cabot Corp is very helpful in advising how to formulate composites with their product so I would recommend contacting them to see if they have any advice!

  131. Stephen Steiner says:

    Hi Lars,

    Q: I have wondered why you dont have a seagel recepie ?

    Just haven’t gotten around to it.

    Q: It’s quite straightfoward, just over 1 g of agar agar to a liter of water, let it gel, freeze it and then freezedry it.
    Freeze drying can be done with a glass machine or similar in a metallic can with a glass lid ! ( the glass lid is important, to let radiant heat in ! ). It takes a bit of cycling but this is a ‘near’ aerogel that you can do at home.
    ( you can also use CaCl and ice to reach even lower temperature .. below -50 C if you precool the ice with ice & NaCl

    Great, now we have a SEAgel recipe.

    Thanks for the contribution! We’ll try it out and if it works for us we can might put it up in the Make section.

    Also has freeze drying been tested on the ‘elastic’ ( crossbound ) aerogels ? Since it works on agar it might work on any flexible aerogel.

    You probably mean crosslinked aerogels such as x-aerogels, or elastic aerogels made through reduced bonding such as those developed by Rao. I’m not aware of any specific papers talking about freeze drying of these materials but you’re probably right, you could freeze dry them and get aerogels (cryogels sometimes they’re called) instead of supercriticaly drying.

    Worth giving a shot!

    Best regards.

  132. Stephen Steiner says:

    Hi Storm,

    I dont know if its a silly question what would happen if you took rubber cement like a neoprene glue that uses a solvent to dry with and used the process to make an aerogel on it? would love to know.

    Not a silly question and actually a good idea! The question is whether or not you can get a gel to setup without the solvent drying. Might happen on its own, might need a crosslinker. Give it a shot! If you can get a gel, you’ll probably be able to purify it and do supercritical drying.

    Neoprene aerogels! Cool.

  133. Stephen Steiner says:

    Hi Again Jim,

    I found a useful list of denatured alcohol MSDS’s at: http://jwbasecamp.com/Articles/SuperCat2/MSDS.htm.

    Thanks for the contribution!

    Since I read (on aerogel.org) that ’some’ hardware store denatured alcohols work, and others do not, I wonder whether the distinction is whether there are hydrophobic components (i.e. kerosene) in them. MIBK (methyl isobutyl ketone) is probably not as hydrophobic as kerosene, but it will it work for aerogel? I wish this site included a ‘will work/won’t work’ alcohol list: We could easily derive from that list, a list of compatible v. non-compatible denaturants.

    It’s not always about whether or not the denaturant is hydrophobic, but rather whether or not it will interfere with the chemistry going on during gelation, which has many aspects to it. Best way to find out is to try! If you’d like to experiment and write up your findings, we’d be happy to post them!

  134. Stephen Steiner says:

    Hello Jim,

    1. Does SLX Denatured Alcohol (Klean Strip; with 1-4% of methyl isobutyl ketone, and about 47%each of ethanol and methanol) work for making alcogels/aerogels? http://www.wmbarr.com/msds.aspx?catid=13

    Good question–probably not. MEK tends to screw things during gelation up but it’s worth a shot. Might be okay for solvent exchange.

    2. What’s a good, cheap source for tetraethyl orthosilicate and ammonium fluoride?

    I would say Sigma-Aldrich is the best way to go for both. Ammonium fluoride is not expensive. TEOS you might be able to get cheaper at Gelest. The problem you’ll face is getting it deliver to a non-commercial address, in which case you may need to find a school or business to help you.

    3. Steve Steiner: Suppose _tomorrow_ somebody demonstrated an easy, cheap, extremely effective method to generate clear, colorless, non-hazy extremely-insulative aerogels suitable for window insulation. How long would it take industry to bring them to market?

    Three things:
    1) You’d need to address numerous manufacturing and handling issues to mitigate cracking and fragility.

    2) The market for window insulation is pretty small compared to the market for non-transparent insulation, so the business opportunity would not be obviously appealing to many investors.

    3) The more capital you’ve got the faster you can get it to industry!

    Dr. Tom Tillotson at Lawrence Livermore National Laboratory demonstrated a method for making essentially transparent silica aerogels in the early 1990’s by a two-step process that, when combined with high-temperature supercritical drying, gives very transparent, non-blue monoliths. The problem is that they are extremely low in density and very difficult to handle.

  135. Stephen Steiner says:

    Hi Szymon,

    Q: I want to second the Kalyan’s question. I’m planning to supercritically dry 8 pieces of silica gel which are in size of about 9mm x 5mm x 5mm. What kind of container sohould I put them into before putting everything into the chamber of my manuclave?

    Make a little wire mesh cage. Don’t use polymers or plastic mesh as many polymers are incompatible with supercritical CO2. Gauze used for Bunsen burners, screen door mesh, and even crumb cups for drains work well!

  136. Stephen Steiner says:

    Hi Amir,

    Q: i have tried TEOS aerogels recipe described in this website i made good gels but i could not get good results

    Oh no! I hate to hear when recipes don’t give you good results. Let’s see what we can do to diagnose.

    here are my questions :
    1)i made wet gels perfectly and keep them under ethanol for a couple of days, should i take the sample out of mold and soak it in ethanol and then drain all ethanol and then put sample in reactor?
    (a-transfering sample without mold and ethanol would be very tricky
    b-once i tried supercritical drying with ethanol in reactor and at the end the liguid ethanol was still there)

    1) You should place the gels under ethanol for a day or so, dump the ethanol out, then replace it with fresh ethanol and repeat this 2-4 more times. The amount of ethanol should be about 5-10x the volume of the monolith.

    2) Depending on the size of your gel monoliths, you may need longer soak times and more soaks. For example, if your monolith is a low-aspect-ratio form such as a cube of dimensions larger than 3 cm you will need more and longer exchanges.

    3) You can take the sample out of its mold to speed things up, but you may experience cracking when the gel contacts liquid CO2. If you have a large part and you are trying to purify it in its mold, this will slow down diffusion a lot and you may need longer solvent exchanges.

    4) You should place the gel under ethanol in the reactor but you should remove all of it before trying to do supercritical drying! Remember, there are two processes going on in the reactor–first, a solvent exchange of ethanol with liquid CO2 and second supercritical extraction. You need to drain/vent the ethanol from the vessel, refill with liquid CO2, let the gel soak in CO2 for a day or so, repeat 2-3 more times, then if you aren’t smelling ethanol in the exhaust and seeing ethanol leftover after the dry ice sublimes, then you are go for supercritical drying.

    So it sounds like your problem wasn’t with the TEOS recipe, but rather with your gel purification and supercritical drying procedures.

    3)how long each washing step (with CO2,non-super critical) should take?
    a-should depressurzing of these washing steps be as slowly as depressurezing of the supercritical step?

    It’s not about depressurizing–it’s about replacing the CO2. You don’t really want to depressurize the reactor during solvent exchange. You should keep the intake valve to your liquid CO2 tank open while draining your reactor to displace the ethanol-containing CO2 with new CO2.

    4)is it necessary to use 200-proof ethanol in all steps? (or only after gel has set)

    You can use less than 200-proof ethanol in the synthesis of the gels but not in the solvent exchanges to prepare the gels for supercritical drying unless it is anhydrous ethanol and does not contain ketones or aromatics. You can use acetone for the gel purification steps instead if that’s easier.

    5)how long should i keep the reactor in supercritical condition?

    -i am using a 0.5 lit bench-top reactor (Parr instruments) that can be operated up to 5000 psi
    and a simple water bath for heating the reactor.

    Taking the vessel to around 95 deg F and 1400 psi, you can let it equilibrate for about 30 min, start to depressurize, heat again, get to 1400 psi, depressurize, and repeat until you get to a temperature of 125-135 deg F. You don’t need to remain at supercritical conditions very long, actually. If you have a substantial amount of ethanol left in the reactor, the critical point of the ethanol-CO2 mixture will be much higher than the conditions I suggested so make sure you get as much of the ethanol (or acetone) out first as you can.

  137. Stephen Steiner says:

    Hi Randy,

    Q: Can silica AeroGel be compressed and injected at a high pressure into the BP oil blowout well? Since the density of aerogel is so low the net effect should be a lowered force coming out of the pipe, allowing BP to be able to seal the cap. If the injection pipe is deep enough into the well the silica AeroGel could also be beneficial in sealing cracks in the well casing. Perhaps a cement adhesive could be mixed in to seal any casing weaknesses or flaws caused by the blowout.

    I think using aerogel in the blowout well is a pretty neat idea and I had been thinking about it too (as had Cabot Corp, who makes aerogel granules called Nanogel) but for a different reason. Hydrophobic aerogel can absorb about 20 times its weight in oil–and then you can even recover the oil from it. Aerogel granules might be a good candidate for collecting oil off of the water surface. I’m not sure about the lowered force you propose or sealing cracks–aerogels aren’t particularly useful as sealants. I think the real issue is whether or not the volume of material available would have been enough to be any help.

    By the way, despite the best intentions of Lawrence Berkeley’s web page, you shouldn’t capitalize the “a” or “g” in aerogel–the correct (and easier) way to write it is just “aerogel”.

    Thanks for the comment!

  138. Stephen Steiner says:

    Hi Kalyan Ram,

    Q: Im planning to make silica aerogels in my college lab, and while studying the literature for making the aerogels it was suggested that a web-cage (mesh) could be used to contain the sol-gel while placing it in the manuclave for supercritical drying. I would like to know what kind of mesh would be suitable for containing the sol-gel without any of it leaking out. In particular, what should be the density of the mesh?

    What you refer to as the sol-gel should be a wet gel monolith (I don’t like the term “sol-gel” used for monoliths, it’s confusing). The gel monolith will be cohesive and cannot flow. If it flows then the sol has not gelled and the material is not suitable for supercritical drying. The gel should be something you can pick up with a scoopula or a spoon. It should retain a geometric form on its own. Any type of metallic mesh, for example, the kind you would use to make a screen door, should work fine. Spacing of a few millimeters is generally what you would look for. Just be careful that no straggling wires are poking into the inside of your wire cage–the tips of wires can slice through gels easily. You will want to put some sort of long retrieval wire on the wire cage too to make it easier to pick up and pull out without risking squeezing or compressing the aerogel.

  139. Stephen Steiner says:

    Dear Majid,

    Q: If an aerogel sample (for example RF aerogel) be immersed in water or other solvents (eg. acetone, …), will it shrink due to capillary forces after evaporate drying?

    Yes, this is generally correct. If the sample is suitably hydrophobic, however, this will not happen nearly as much.

    or would aerogel structure be collapsed in moist air (during a long time) because of Moisture absorption?

    Yes, this can happen as well. This is why typical silica aerogels can become white over time. They are very effective dessicants.

  140. Stephen Steiner says:

    Hello riyaz,

    is aerogel a sustainable material??

    Remember, aerogels are a diverse class of materials. Also, sustainability depends largely on how a material is made, not just what it’s made of or what it is.

    Some aerogels, made the right way, are certainly sustainable! Silica aerogels are appealing because silica is naturally found in the environment, although hydrophobic (water-proof) silica aerogel may not be as degradable. Using the right precursors, renewable energy, and recycling solvents, and with a recollection plan or built-in biodegradability, certainly aerogels could be made sustainably. Some organic formulations and biological polymer aerogels may be better candidates for sustainable aerogels, though.

    and if so, then which type of aerogel i can use for the exterior finish of buildings??

    What application do you specifically mean? As a matting agent to create a dull appearance perhaps? Or as an insulating barrier? Or as translucent paneling? Or windows?

    Let me know what you mean and I can try to provide a better answer. Silica aerogels are possibly acceptable for all of those applications, however some more-sustainable organic aerogels may be better than silica for some of those applications.

  141. fajran says:

    Dir Sir

    hi my name fajran. i am one of student’s in university who want to know about aerogel. i want to make final research in order to graduated. my i know how is the way to make carbon aerogel, and what are aerogel made off. please help me. if you don’t mind, i’ll be waiting your answer in my email.

    thank’s for your kindness,
    Fajran Rachman

  142. Stephen Steiner says:

    Hello Again Dinh,

    Second, the PEG I used has the role of modification surface beacuse I want to avoid the aggregation of silica partices.

    Aggregation of which particles? Nanoparticles in the sol or macroparticles formed from breaking up the gel monolith?

    Next, the term clotting I mentioned is used to describe the phenomenon in which after drying the small pieces of gel did not become powder form but into very big particle. So I had to grind by pestle and mortar to make it into powder form, and I am not sure that this powder has nano scale.

    Could you perhaps restate what your objective is? I believe you would like to make aerogel granules like Cabot Corp’s material. In that case, their material is small millimeter-sized granules, not a powder. Do you want a powder? If you have to grind a sol-gel material up into a powder, it will still be nanostructured provided it was dried properly.

    Last, maybe I used wrongly the term bursting. I see nano silica powder of Cabot and ambitiously I want to achieve like that. And , unluckily we do not have supercritical system and it is very difficult for me to find TMCS for spring-back effect in Vietnam.

    Cabot doesn’t use supercritical drying, they use the spring-back effect. The best you could do would be to soak your gels in deionized water, then transfer into acetone, then transfer into pentane and evaporate the pentane in a nitrogen-containing glove box. That will help you to minimize loss of volume by minimizing capillary stresses, but you’ll have to experiment quite a bit. Adding drying control chemical additives (DCCA’s) to the gel to bind up the hydroxyl groups will help, for example, formaldehyde, or glycerol, or PEG as you tried, perhaps.

    May I have some questions?

    You may!

    With Cabot aerogel, they will have monolithic gel, after modification surface and supercritical drying, will it itself become powder form or it need grinding?

    They do not supercritically dry their material. The gel monolith is ground up, surface treated, then dried ambiently.

    Next, if I want to make nano powder, is it necessary for me to break and grind monolithic before washing by deionized water?

    Doing any diffusion-exchange steps with smaller macroparticles is always more efficient. So, if you want to make a powder, you should grind the gel up while it’s wet as fine as possible, then do solvent exchanges.

    Hope this helps!

  143. DW says:

    I have had the oppurtunity to view and touch aero-gel, and found it fun, much like silly putty.

    My question is regarding it’s use in a fiction novel. Can aero-gel be used for a small parachute?
    I read a spy novel and there was a gadget with aero-gel as one of it’s components. It was a small camera that hung overhead in the sky, much like a signal flare would. The camera was suspended from an aero-gel parachute. From the description I imagined it to be like one of those old plastic army guys with the parachute.

    I would imagine that such a parachute made of aerogel would not be feasible due to it’s slightly brittle nature. The weight of such a parachute would also end up weighing probably the same as if the parachute were to be made from silk or nylon.

    Am I correct?

    Thank you for you future reply.

  144. Jeremy says:

    Hi
    I am a student in secondary school and I have a couple of questions.

    First, what would happen to aerogel if you were to submerge it somewhere hot like in molten lead (which melts at 327C) and how high of a temperature can you have before the aerogel can be damaged?

    Second, can you make aerogel out of any metal oxide? such as the oxides of silver or gallium, and what about radioactive metals like the oxides of uranium or thorium?

    Lastly, can aerogel be used to generate water from the air?
    It is hygroscopic and absorbs water but how can you make the water come back out of the aerogel?

    Hope you can help

    Thanks

  145. Ragavendran.S.N says:

    Dear Sirs,
    This site is extremely useful for college students like me. Thank you for all the information.
    I have a question though… I was trying to find the thermal properties of aerogel but i could not find anything about the properties of aerogel at low temperature. I also found that aerogel is like glass. Does brittleness increase with decrease in temperature in aerogels?

    (by low temp i mean in the range of 100 K)

  146. Simon Loh says:

    Hi,

    I have just purchased some aerogel and am thinking of incorporating this material into a water based paint. Care to let me know some of the challenges that I will encounter? My objective is to create a paint that can minimize the amount of heat from the sun onto the wall. I live in the tropics and the sun and heat can be quite an issue with air conditioning. How much aerogel granules would I need to get an effective heat insulating paint?

  147. SeaGel question

    I have wondered why you dont have a seagel recepie ?

    It’s quite straightfoward, just over 1 g of agar agar to a liter of water, let it gel, freeze it and then freezedry it.
    Freeze drying can be done with a glass machine or similar in a metallic can with a glass lid ! ( the glass lid is important, to let radiant heat in ! ). It takes a bit of cycling but this is a ‘near’ aerogel that you can do at home.
    ( you can also use CaCl and ice to reach even lower temperature .. below -50 C if you precool the ice with ice & NaCl

    Also has freeze drying been tested on the ‘elastic’ ( crossbound ) aerogels ? Since it works on agar it might work on any flexible aerogel.

    Best regards.

  148. S Morris says:

    I dont know if its a silly question what would happen if you took rubber cement like a neoprene glue that uses a solvent to dry with and used the process to make an aerogel on it? would love to know. thanks Storm

  149. jim bell says:

    I found a useful list of denatured alcohol MSDS’s at: http://jwbasecamp.com/Articles/SuperCat2/MSDS.htm. Since I read (on aerogel.org) that ‘some’ hardware store denatured alcohols work, and others do not, I wonder whether the distinction is whether there are hydrophobic components (i.e. kerosene) in them. MIBK (methyl isobutyl ketone) is probably not as hydrophobic as kerosene, but it will it work for aerogel? I wish this site included a ‘will work/won’t work’ alcohol list: We could easily derive from that list, a list of compatible v. non-compatible denaturants.

  150. jim bell says:

    1. Does SLX Denatured Alcohol (Klean Strip; with 1-4% of methyl isobutyl ketone, and about 47%each of ethanol and methanol) work for making alcogels/aerogels? http://www.wmbarr.com/msds.aspx?catid=13
    2. What’s a good, cheap source for tetraethyl orthosilicate and ammonium fluoride?

    3. Steve Steiner: Suppose _tomorrow_ somebody demonstrated an easy, cheap, extremely effective method to generate clear, colorless, non-hazy extremely-insulative aerogels suitable for window insulation. How long would it take industry to bring them to market?

  151. Szymon Bartus says:

    I want to second the Kalyan’s question. I’m planning to supercritically dry 8 pieces of silica gel which are in size of about 9mm x 5mm x 5mm. What kind of container sohould I put them into before putting everything into the chamber of my manuclave?

    Regards,
    Szymon

  152. Amir says:

    Dear all,
    i have tried TEOS aerogels recipe described in this website i made good gels but i could not get good results
    here are my questions :
    1)i made wet gels perfectly and keep them under ethanol for a couple of days, should i take the sample out of mold and soak it in ethanol and then drain all ethanol and then put sample in reactor?
    (a-transfering sample without mold and ethanol would be very tricky
    b-once i tried supercritical drying with ethanol in reactor and at the end the liguid ethanol was still there)
    3)how long each washing step (with CO2,non-super critical) should take?
    a-should depressurzing of these washing steps be as slowly as depressurezing of the supercritical step?
    4)is it necessary to use 200-proof ethanol in all steps? (or only after gel has set)
    5)how long should i keep the reactor in supercritical condition?

    -i am using a 0.5 lit bench-top reactor (Parr instruments) that can be operated up to 5000 psi
    and a simple water bath for heating the reactor.

    thank you for your time,
    REgards
    Amir

  153. Can silica AeroGel be compressed and injected at a high pressure into the BP oil blowout well? Since the density of aerogel is so low the net effect should be a lowered force coming out of the pipe, allowing BP to be able to seal the cap. If the injection pipe is deep enough into the well the silica AeroGel could also be beneficial in sealing cracks in the well casing. Perhaps a cement adhesive could be mixed in to seal any casing weaknesses or flaws caused by the blowout.

  154. Kalyan Ram says:

    Hi,
    Im planning to make silica aerogels in my college lab, and while studying the literature for making the aerogels it was suggested that a web-cage (mesh) could be used to contain the sol-gel while placing it in the manuclave for supercritical drying. I would like to know what kind of mesh would be suitable for containing the sol-gel without any of it leaking out. In particular, what should be the density of the mesh?

  155. majid says:

    Dear Stephen!

    Firstly, thank you for your responses to my questions;
    I have another question!
    If an aerogel sample (for example RF aerogel) be immersed in water or other solvents (eg. acetone, …), will it shrink due to capillary forces after evaporate drying?
    or would aerogel structure be collapsed in moist air (during a long time) because of Moisture absorption?

    regards
    Majid

  156. riyaz says:

    sir,
    i am an architecture student. i need to know that for the exterior finishes of the building can we use aerogel?? if yes then which type of aerogel is better for the same??
    is aerogel a sustainable material??

  157. riyaz says:

    hi all!
    i am an architecture student and presently doing a thesis on sustainable architecture. i am interested in using aerogel products for the buildings.
    is aerogel a sustainable material?? and if so, then which type of aerogel i can use for the exterior finish of buildings??

  158. dinh hoa luong says:

    Thank you very much for your response, Stephen!
    According to your questions, my responses are these; firstly after aging I had a monolithic wet gel, I broke it into small pieces by using glass rod, and after that I soaked and stirred it in deionized water for several times, however I did not quantify the water I used and there was no exchanges in this step.
    Second, the PEG I used has the role of modification surface beacuse I want to avoid the aggregation of silica partices.
    Next, the term clotting I mentioned is used to describe the phenomenon in which after drying the small pieces of gel did not become powder form but into very big particle. So I had to grind by pestle and mortar to make it into powder form, and I am not sure that this powder has nano scale.
    Last, maybe I used wrongly the term bursting. I see nano silica powder of Cabot and ambitiously I want to achieve like that. And , unluckily we do not have supercritical system and it is very difficult for me to find TMCS for spring-back effect in Vietnam.
    May I have some questions?
    With Cabot aerogel, they will have monolithic gel, after modification surface and supercritical drying, will it itself become powder form or it need grinding?
    Next, if I want to make nano powder, is it necessary for me to break and grind monolithic before washing by deionized water?
    Thank you very much,
    Dinh Hoa Luong

  159. Stephen Steiner says:

    Hi Reef,

    Firstly, thank you for being such a great resource. This open-source forum is inspirational.

    We’re glad you like the open-source philosophy! We’re working to make this site more social and dynamic, and to revamp this lousy comments system.

    I’ve been in the process of fabricating silica aerogels for the past few months now, and have been somewhat successful. I wish I found your site earlier; it would have saved me several weeks of trial and error!

    You know working things out on your own will help you to understand a problem much better than getting the answer right away, so don’t be too hard on yourself!

    Q: I would like to experiment with Sodium Silicate (water glass) as a source of silica and was wondering if there would be a recipe uploaded soon? I’m eager, thats all!

    We have been planning on getting up a good procedure for a while but we like to thoroughly test what we post before we post it to make sure it works in advance.

    I would guess we’ll have it up in a month or so (mid-June).

  160. Stephen Steiner says:

    Hi Dinh,

    Q: First, you can make monolithic aerogel by using supercritical drying to avoid capillary force, but I see the product of Cabot, the nano silica in powder form. So I wonder that this nano silica powder also use supercritical drying or ambient drying with spring back effect?

    A: Yes, Cabot uses a subcritical drying method with the spring-back effect to make Nanogel. That is part of what it makes it so cost-effective.

    Q: Second, after cation-exchange, we adjust pH by using NH4OH. Next, gel formation appear and we need a certain time to age it. So, after aging I have monolithic wet gel, I also wash it several times by deionized water and disperse it in deionized water. You know that I also use PEG for surface modification,and finally I dry it. however, my silica powder has cloting phenomenon and it has no bursting as the commercial powder products! I think that I did not disperse it into nano scale?

    A: A few questions for you:

    • How do you wash it with deionized water? By soaking? How much water is there relative to the amount of gel? How long do you let it soak in the water? How many exchanges do you do?
    • Are you using poly(ethylene glycol) as a drying control chemical additive (DCCA)?
    • What do you mean by clotting phenomenon? Can you describe in more detail?
    • What do you mean by bursting? What are you trying to achieve? Are you trying to make aerogel by subcritical drying?

    If you can answer these questions with a little more detail I’ll be happy to respond!

  161. Stephen Steiner says:

    Hi Dana,

    Q: I’ve noticed that both Cabot and Aspen aerogels have aerogel embedded blankets; these provide excellent insulating properties. It seems that the big drawback to going mass market for clothing is the dust that is emitted from the blankets. has anyone figured out how to combat the dust from these aerogel blankets without compromising the insulating and breathability factors that make the aerogel blanket so unique?

    A: The dust is a problem but for many applications, including clothing where the aerogel blanket is sewn into a liner, it’s a non-issue. Cabot’s blankets are less dusty since they incorporate pre-made granules. There are technologies for making aerogel blankets less dusty, such as special coatings, but they may not be cost effective or that functionally useful.

  162. Stephen Steiner says:

    Hi mak,

    Q: sir, i m making a robot that can float on water.i m thinking to use superhydrophobic aerogel for this purpose…….. will it be right to use it………..? n also tell about the cost for this aerogel

    A: Sounds like a cool project! You could try using Nanogel like the kind you can buy on BuyAerogel.com which is hydrophobic–you probably don’t need superhydrophobic materials to do what you want to do–these are a special class of hydrophobic materials with contact angles above 165 degrees (that is, if you look a droplet of water on them, the angle between the substrate under the middle of the droplet and the edge of the droplet where it curves up is 165 degrees, hydrophobic materials still have large contact angles, though!). Nanogel is pretty inexpensive and you try lots of different things with it, maybe even epoxying it onto a substrate.

    Hope this helps.

  163. Reef says:

    Dear Stephen,

    Firstly, thank you for being such a great resource. This open-source forum is inspirational.

    I’ve been in the process of fabricating silica aerogels for the past few months now, and have been somewhat successful. I wish I found your site earlier; it would have saved me several weeks of trial and error! I would like to experiment with Sodium Silicate (water glass) as a source of silica and was wondering if there would be a recipe uploaded soon? I’m eager, thats all!

    Thanks again!

    Reef

  164. dinh hoa luong says:

    Hi everybody!
    I am Dinh Hoa Luong. Now I am a student of Ho Chi Minh University in Vietnam. Actually I am very interested in silica aerogel, and I have some questions about it.
    First, you can make monolithic aerogel by using supercritical drying to avoid capillary force, but I see the product of Cabot, the nano silica in powder form. So I wonder that this nano silica powder also use supercritical drying or ambient drying with spring back effect?
    Second, after cation-exchange, we adjust pH by using NH4OH. Next, gel formation appear and we need a certain time to age it. So, after aging I have monolithic wet gel, I also wash it several times by deionized water and disperse it in deionized water. You know that I also use PEG for surface modification,and finally I dry it. however, my silica powder has cloting phenomenon and it has no bursting as the commercial powder products! I think that I did not disperse it into nano scale?
    May you explain my questions for me?
    thank you very much for considering my comment!
    thank you again!
    Dinh Hoa Luong!

  165. Dana says:

    I’m fascinated by the aerogel clothing that made its debut in 2006 by Hugo Boss. Apparently it didn’t work out too well as many people complained that the aerogel lined jackets were too hot! I’ve noticed that both Cabot and Aspen aerogels have aerogel embedded blankets; these provide excellent insulating properties. It seems that the big drawback to going mass market for clothing is the dust that is emitted from the blankets. has anyone figured out how to combat the dust from these aerogel blankets without compromising the insulating and breathability factors that make the aerogel blanket so unique?

  166. mak says:

    sir,
    i m making a robot that can float on water.i m thinking to use superhydrophobic aerogel for this purpose……..
    will it be right to use it………..? n also tell about the cost for this aerogel

  167. Phyllis Gugenheim says:

    That’s perfect help, Sir! I appreciate it; you may have just saved our project!

    Phyllis

  168. Stephen Steiner says:

    Hi Phyllis,

    Ah, you have discovered an unfortunate conflict of convention!

    “Silica gel” powder like the kind you found is actually silica xerogel. It is formed by evaporation of the liquid from a wet silica gel, which causes the gel network to collapse into a dry solid. It’s basically densified silica powder and not soluble in water or alcohol. As a result, it’s not gonna work for what you want to do, unfortunately!

    The right way to make a silica gel is to do sol-gel chemistry with a silicon alkoxide or sodium silicate solution and form a gel. Look at the page on hydrophobic and subcritically dried aerogel for a recipe on how to make hydrophobic silica gels. If you don’t want to make aerogel you can stop at the Gel Drying section. I would also suggest you look at other recipes in the Make section and listen to our podcast on how to make silica gels for use in making silica aerogels.

    Hope this helps!

  169. Phyllis Gugenheim says:

    Hi, there, Aerogel.org!

    I’m doing a project for a materials science class, and I was trying to figure out what kind of “silica gel” is needed for the hydrophobic silica gel. We are trying to order some, and then actually found some in the lab that is grade 62 and 150 angstroms — a white powder-like substance that mentioned a use for chromatography on the front. Would this work?

    Also, even if it doesn’t, any silica gel that we could find / make appears to, at the end of the day, leave us with more of a powder than a gel to put into the solutions. How does this work? Is this the wrong type of silica gel? It is our understanding that the liquid within the gel is replaced with a gas, but it would appear there is no liquid in this gel (though it looks more like a powder). Is what we have okay, and if so, why is it okay? (aka, how does that work?)

    Thanks so much for your time!
    Phyllis Gugenheim

  170. Szymon Bartus says:

    Hello,

    Classic dynamite is made of nitroglycerin soaked in diatomaceous earth, which acts as stabilizer. Would it make sense to try aerogel as such stabilizer? Making therefore a gel with nitroglycerine as solvent? (by soaking the aerogel with it)

    Regards,
    Szymon

  171. Stephen Steiner says:

    Hi Angela,

    Q: For a project in my material science class, my group has chosen to use aerogel to insulate a cooler. It is all theoretical, but the problem we are facing is comparing the insulation of this theoretical aerogel cooler with existing coolers. Most coolers rate their insulation based on how long it keeps ice frozen, whereas with aerogel all we have is the R value. Any ideas of how to compare these beyond simply the assumption that aerogel will work much better? Also any suggestions on which specific aerogel to use? we were thinking spaceloft blankets since it’s on the cheaper end (I think, also hard to find exact numbers to compare)
    Any ideas or suggestions would be great!

    What I would do is research what materials are used in a cooler to insulate (what type of plastic for the body, Styrofoam vs. polyurethane foam (PUF) vs. air gap insulation, how thick the insulation is), find the R-values per inch of those materials, then multiply the R-value per inch for each material times the thickness of each material and sum to calculate the R-value for the cooler wall. You then would know that that R-value keeps ice frozen for a certain amount of time based on what the cooler says. You could then repeat the calculation with the R-value of an aerogel insulating material in place of the Styrofoam or air gap. The cooler would then assumedly keep ice frozen for a proportional amount of time equal to the R-value of aerogel cooler divided by the R-value of the as-bought cooler.

    For pricing you could start at BuyAerogel.com, which sells Pyrogel blankets, and assume Spaceloft would be the same price. You could then assume the price of the material for bulk production would be lower by some percentage.

    A couple points to keep in mind in doing your project:

    • R-value is usually given per unit length, so if Styrofoam has an R-value of 5 per inch, two inches of Styrofoam has an R-value of 10
    • You can find the R-value of Aspen Aerogels’ Spaceloft on their website
    • You can probably find out what the cooler is made out of by searching online; otherwise, buy one and cut it apart–if it’s white insulation it’s probably Styrofoam, if it’s yellow insulation it’s probably polyurethane foam, and if there’s nothing it’s an air gap
    • A still air gap still has an R-value of 5 per inch!

    You could also try buying a piece of aerogel blanket at BuyAerogel.com, making your own little cooler, do the same with Styrofoam from an art supplies store, and then test how long ice takes to melt in your two coolers.

    Hope this helps!

  172. angela palmer says:

    For a project in my material science class, my group has chosen to use aerogel to insulate a cooler. It is all theoretical, but the problem we are facing is comparing the insulation of this theoretical aerogel cooler with existing coolers. Most coolers rate their insulation based on how long it keeps ice frozen, whereas with aerogel all we have is the R value. Any ideas of how to compare these beyond simply the assumption that aerogel will work much better? Also any suggestions on which specific aerogel to use? we were thinking spaceloft blankets since it’s on the cheaper end (I think, also hard to find exact numbers to compare)
    Any ideas or suggestions would be great!

    Thanks,
    Angela

  173. majid says:

    Hi Stephen,

    I have another question about the measuring of the effective thermal conductivity of an aerogel sample. You mentioned some references about fundamentals of heat transfer in porous materials but the problem is how to measure this low thermal conductivity?
    I found some methods and setups in articles to measure it, but I need more details to build such a setup, like what you done in the section “Build a supercritical dryer” in this site for building a proper dryer,
    Do you have any references and/or comments about this problem?

    Thank you

  174. Stephen Steiner says:

    Greetings Per,

    Thank you for a very well written and organized site on aerogel.

    It’s great to hear you think the site is both well written and well organized. It will continue to grow over the next year and we will be revamping this stupid comments system into a better, more stream-lined active medium soon.

    Q: I´m a bit curious of why you think that silica areogel will have to wait until 2015-2020: “As far as insulation is concerned, the future of silica aerogel may be very well lie in already-developed technologies. Both transparent and opaque silica aerogel-based insulation has tremendous potential to displace technologies such as mineral wool, fiberglass, foams like Styrofoam® and polyurethane in the future, even thermalpane windows, but only once their production has reached a level of efficiency and cost competitiveness with existing technologies. That time is not far away (possibly 2015-2020), and companies like Aspen Aerogels have already started paving the way towards it.”

    I apologize that this statement has miscommunicated our intended opinion. As you have correctly pointed out, silica aerogel is already commercially available for building materials from both Aspen Aerogels and Cabot Corp. The context of this opinion is in regards to aerogel materials displacing common cheap insulations such as mineral wool, fiberglass, Styrofoam, etc., that is, when normal buildings and industrial plants begin using aerogel insulations instead of the ubiquitous (and cheap) building materials that are used today. Right now aerogel materials are used primarily in sub-sea oil pipelines, in refineries (where they are already displacing mineral wool), and in a few daylighting applications (skylights) in buildings around the world. But certainly aerogel materials are already working their way into buildings, and the demand for aerogels for these markets is growing quickly.

    We will be featuring how aerogel is changing the way we think about heating and lighting in buildings in a series of upcoming articles under Learn > Applications of Aerogels.

    As of today (2010), we note that such applications of aerogel for buildings were not viable even 8 years ago and are still new. For most buildings, existing insulation is cheap and good enough given the cost difference. But the cost difference is not large any more and is steadily dropping.

    We are cooperating with Cabot, Scobalit and Okalux on using areogel on transparent buildings materials in the buildings industry of Norway. The prize on the marker as compared one on one with glass and others materials is stiff, but when you look at the benefits and new ways of applying prefabricated building elements made from polycarbonate, fiber reinforced polyester and glass, and take into account the new regulations for the buildings industry towards “zero emitting buildings”, we think aerogel is a winner already, and not in 2015-2020. But so far, first and foremost as insulation where daylighting is a goal.

    No doubt aerogel is a winner already and will continue to be a winner. But the days of aerogel replacing Styrofoam are still a ways off (but not far).

    Are we too optimistic? And would you please write some more about aerogel in practical use in the building industry? We will try to provide some building projects using aerogel in Norway for your site, in a couple of months, hopefully.

    You are NOT too optimistic! Again, integration of aerogel into buildings is already happening and expanding.

    As stated, we’re already preparing a number of articles about practical applications of aerogel for building insulation and daylighting, actually in conjunction with Cabot Corp. We’ll keep ya’ posted!

  175. Stephen Steiner says:

    Hi Jing,

    Q: Now I have another problem. I want to use the 3 omega method to measure thermal conductivity of my aerogel and the system need to be vacuumed. I can’t figure out how to fix my sample since it is so light and so brittle. Do you have some advices?

    These are hard problems. A dumb suggestion would be try using double-sided tape or carbon tape like you would for scanning electron microscopy. Carbon tape is usually acceptable for high-vacuum (it is used for X-ray photoelectron spectroscopy which is 10-8 torr). You will then need to accommodate the thermal conductivity of the tape in your calculations.

    There are lots of papers on measuring the thermal conductivity of aerogels in the literature. I would suggest looking on SciFinder if you have that resource or otherwise look at some of the references in our response to Jon’s question from December 20th below!

    Hope this helps… let us know if you have any other problems and we’ll do our best to help or find an expert to comment! Anyone out there with experience in this area is welcome to post a comment as well.

  176. Stephen Steiner says:

    Hi Beth,

    Q: What sort of bonding is involved with Silica erogel?

    Silica aerogel and metal oxide aerogels are held together by covalent bonds bridging the silicon/metal centers with other silicon/metal centers. At the surface are hydroxyl groups that enable hydrogen bonding, so water and other molecules tend to stick inside their pores (although these hydroxyl groups can be replaced chemically to make the aerogel resistant to water or other chemical adsorption).

    Q: Is this correct?: Aerogels are strong becasue they have a very low density so when they econcounter a force the brittle fracture takes a long time to propagate because the structure is very spread out.

    Well let me give it a shot and you can tell me if this is what you’re thinking.

    First, strength is a multidimensional property of a material. There are many different types of strength including tensile strength, compressive strength, strength in bending, shear strength, etc. Stiffness, the ability for a material to resist straining (deforming) when force is applied, is also different, and there are many different types of stiffness, such as compressive stiffness (measured by Young’s modulus of compression), flexural stiffness (flexural modulus), etc. Additionally, materials have an inherent property called fracture toughness that describes if a flaw or crack is present inside the material, how much force can be applied before the crack reaches a size large enough to cause the material to suddenly fracture.

    So let’s look at silica aerogel. Relative to a similar sized piece of glass (the 0% porous version of a silica aerogel), the aerogel has virtually no strength. But relative to a similar weight piece of glass (imagine a little spec or chunk of glass next to a big cube of aerogel), the aerogel has impressive strength because it can bear a substantial amount of load despite being upwards of 99% air (100% can bear no load), and can bear a much larger area load since it is much larger. In fact, it is it’s strength-to-weight ratio that makes aerogel impressive as a structural material. The small amount of solid that comprises the silica aerogel is very efficiently distributed in space so that it can still bear load. Think of a large truss (mostly empty space) versus a pyramid (solid stone). Also, many aerogels such as silica aerogel have a fractal-like nanostructure. If you were to calculate what the most efficient structure for a solid would be to carry the most force at the least weight, you would get a structure very similar to an aerogel’s nanostructure.

    So inspired by this, let’s say you go to BuyAerogel.com and buy a disc of silica aerogel to plop a big weight on top of in order to witness this amazing strength-to-weight ratio, only to find out you have crushed your aerogel into a million little chunklettes. The impulse from rapidly applying the weight has created a dynamic force much higher than the weight of the weight your were trying to apply and this force was high enough to propagate an unseen flaw in the material past the critical flaw size. You have just witnessed the low fracture toughness of silica aerogels, that is, they are very brittle. Native silica aerogels are filled with little stress concentrators that you cannot see with the eye or often even an optical microscope that make them very susceptible to brittle rupture. These cracks grow when a large enough force is applied and, once they reach a critical size, the material almost instantly snaps apart. Normal glass does this too.

    Instead, let’s say you carefully lower the weight onto the disc. You will (probably) find the aerogel is just fine, bearing 2000 times its weight! Keep in mind, though, for a plate or disc that is not substantially longer than the height of the disc, a complex three-dimensional stress state can form in the aerogel, despite the fact that you are only applying the force in the down direction. As a result, the aerogel can be stressed in a way you wouldn’t have expected, aggravate a flaw, and cause brittle fracture.

    So the best way to break a silica aerogel? Poke it (stress concentration) or bend it (they have low flexural strength).

    Prof. Nicholas Leventis at the Missouri University of Science and Technology found that in fact silica aerogels are much stronger than we thought they were before, it’s just that their low fracture toughness causes them to break before more than ~2000x their weight can be applied (assumedly, this is the maximium force before a flaw grows past the critical flaw size, even in compression). He discovered that applying a conformal coating of a polymer to the skeleton of an aerogel makes the aerogels many many times stronger and essentially not brittle. These materials, called x-aerogels, look, feel, and insulate like other aerogels but are incredibly strong and flexible. You can read all about them under Learn > Flavors of Aerogel > Strong and Flexible Aerogels.

    Hope this helps!

  177. Jing Xie says:

    Hello Stephen,

    I am so glad you are back! I think the difference is the TEOS/ethanol/water ratio. I tried from 1:4:2 to 1:4: 12 and used a small amount of acetate acid to hydrolyze the sol and after 1h I added a little ammonia, the sol can change to gel immediately. So I think the reason I couldn’t get the aerogel is that the water content is too low and I shouldn’t put these three solutions together. Hope it will help others.

    In the past, I thought the solvent in the gel can’t be exchanged well with the mold, so I tried hard to let the gel out of the mold. If I can leave the gel in the mold when I perform all the solvent exchange and supercritical drying, I will do so. It is so easy! I can just use the vial cap to be as mold, which shape is perfect for me.

    Now I have another problem. I want to use the 3 omega method to measure thermal conductivity of my aerogel and the system need to be vacuumed. I can’t figure out how to fix my sample since it is so light and so brittle. Do you have some advices?

    Thanks so much!

    Jing

  178. Per Jaeger says:

    Thank you for a very well written and organized site on aerogel. I´m a bit curious of why you think that silica areogel will have to wait until 2015-2020: “As far as insulation is concerned, the future of silica aerogel may be very well lie in already-developed technologies. Both transparent and opaque silica aerogel-based insulation has tremendous potential to displace technologies such as mineral wool, fiberglass, foams like Styrofoam® and polyurethane in the future, even thermalpane windows, but only once their production has reached a level of efficiency and cost competitiveness with existing technologies. That time is not far away (possibly 2015-2020), and companies like Aspen Aerogels have already started paving the way towards it.”
    We are cooperating with Cabot, Scobalit and Okalux on using areogel on transparent buildings materials in the buildings industry of Norway. The prize on the marker as compared one on one with glass and others materials is stiff, but when you look at the benefits and new ways of applying prefabricated building elements made from polycarbonate, fiber reinforced polyester and glass, and take into account the new regulations for the buildings industry towards “zero emitting buildings”, we think aerogel is a winner already, and not in 2015-2020. But so far, first and foremost as insulation where daylighting is a goal.

    Are we too optimistic? And would you please write some more about aerogel in practical use in the building industry? We will try to provide some building projects using aerogel in Norway for your site, in a couple of months, hopefully.

  179. Stephen Steiner says:

    Dear Eden,

    Q: I just want to ask what are the mechanical properties of this material. Thank you so much.

    Remember, aerogels are a diverse class of materials! As a result, the mechanical properties of each type of aerogel vary depending on composition (whether it’s silica, polymer, carbon, etc.), morphology (string-of-pearls, fibrous, worm-like, etc.), density, and to some extent, surface functionality. Several methods for making mechanically strong aerogels are also now possible. You can learn about some of methods for making mechanically strong aerogels under Learn > Flavors of Aerogel > Strong and Flexible Aerogels. Also, measured values of various mechanical properties for different types of aerogels are found in the interactive aerogel materials properties database under Learn > About Aerogel > Properties of Aerogels.

  180. Stephen Steiner says:

    Dear Jing,

    My apologies we weren’t able to answer your question before you fixed it yourself, but congratulations! I’m glad the procedure under the Make section worked well for you. We’ll have the TMOS version of it posted in a couple weeks.

    I suspected your gel formulation was the problem and I’m glad you figured it out. What was the difference between your formulation and the Aerogel.org formulation? It would be helpful for others to learn!

    As far as molds go, here are a couple suggestions. Glass test tubes work well, as do syringes. Syringes are nice because then you can just pull out the plunger and then connect another syringe to the tip with a segment of plastic tubing and blow the gel out into a dish of alcohol. Silicone works well. Also, if you go to Walgreens or CVS, look for those 7-day pill boxes meant for sorting daily medicine. They’re nice little polypropylene rectangular boxes with snap-top lids and you can cut out individual boxes with a kitchen knife. Generally anything made of glass, polypropylene, aluminum, Teflon, or stainless steel can work. Getting gels out of their molds is tricky but using a silicone spray or silicone vacuum grease will help. Otherwise, leave the gel in the mold and perform all solvent exchanges in the mold and then supercritically dry in the mold.

  181. Jing Xie says:

    Dear Stephen,

    I got the silica aerogel finally. Sorry for the last comment. I think I don’t need to go to other groups.

    The difference between these two tries is the gel recipe. At first, I use my own recipe to prepare the gel while I use the recipe from aerogel.org. Even though both gels are transparent and look like the same, the result is totally different. Maybe the water is not easy to come out for my recipe. Your website has so many useful things. So wonderful! I found your recipe is more stable and I can always get the gel and it can prepare the gel in a very short time. Thanks for providing such good recipe.

    Now I have a new problem. I can’t find the proper mold to get the aerogel with fine shape. I need the flat, a little thinner sample to make it easy to be deposited. Actually I can use the vial cap as mold, but it’s so hard to let gel out of the cap. So what mold do you usually use? Do you let the gel soak in the pure ethanol with the mold or without the mold?

    Thank you so much.

    Jing

  182. Szymon Bartus says:

    Hello Matt,
    > Hi, if silica aerogel is 98% air, then can it float in gasses heavier than air? If so, what would
    > be such a gass?

    Yes, it can float. AFAIK, one guy did exactly this with xenon. Depends on the density of silica aerogel which you have made and the gas. I guess that sulfur fluoride and xenon should be fine for lighter aerogel samples.

    Regards,
    Szymon

  183. Matt says:

    Hi, if silica aerogel is 98% air, then can it float in gasses heavier than air? If so, what would be such a gass?

  184. Jing Xie says:

    Dear Stephen,

    Recently I found critical point dryer in my university. It is automatic and fantastic. I don’t need to increase the pressure and temperature manually by myself. But my final sample is still cloudy, after 3 exchanges with liquid CO2 for soaking 24 hours per time. I can’t make the aerogel even with such a good instrument. I feel very bad.

    So now I really want to go to other group who can synthesize aerogel to learn how to make it. Because preparing aerogel is not my ultimate goal. After I get aerogel, I need to synthesize aerogel with nanotubes and finally make the device. So I don’t want to waste so much time to explore how to synthesize aerogel. I am in New York, Binghamton University. Do you know some groups specialized in silica aerogel which are close to me. I think it will be much better to learn from others.

    Thanks so much for your help.

    Jing

  185. Eden May Dela Pena says:

    Good Day!
    I am currently taking my masteral degree in the University of the Philippines and got to know about aerogel. I just want to ask what are the mechanical properties of this material. Thank you so much.

  186. Stephen Steiner says:

    Happy New Year Jing!

    I use alkoxide method to prepare the gel. About the three CO2 exchange before the supercritical drying you mentioned, I need to soak my gel in the mixture of ethanol and liquid CO2 for 24 hours and after extracting all the solvent out, I let liquid CO2 go in the chamber and I repeat it for three times. Is it ture?

    You don’t need to let the gel soak in ethanol/liquid CO2 mixture very long–covering the gel with ethanol is just to protect the gel from drying out and/or cracking during rapid pressurization of the autoclave. As soon as the vessel is pressurized, you can drain off the ethanol and cover it with liquid CO2. Then I would let it soak under CO2 for 24 hours, drain the CO2, refill, soak for 24 hours, and then repeat two additional times.

    You may eventually find you need more or less soaking time and/or exchanges but this should be a good conservative start.

    In the past, I just extract a portion of solvent and let gel still soaked in the solvent, and then refill the chamber with liquid CO2. So it doesn’t matter for the gel standing in the chamber without any solvent soaking, right?

    If the gel has been soaking with liquid CO2 and then you drain off the solvent, keep in mind that the gel is immersed in an atmosphere rich with its pore fluid and so the rate of evaporation of liquid from the pores of the gel is exactly matched by the rate of recondensation of vapor into the pores (the pore fluid and surrounding atmosphere are in equilibrium). So in generally it’s okay if the gel is “naked” for a little while but generally I drain the CO2 until it’s just above the top of the gel, let it partially refill, drain a little bit more, then totlally refill. That said I have a vertical pressure vessel and you may have a horizontally-oriented one like a Polaron so you would want to partially drain and refill several times per exchange.

    I will try to increase the number of CO2 exchange and use your supercritical drying with several steps. Hope it will work! By the way, I use 200-proof absolute ethanol to extract water from the gel.

    Okay, it sounds like your gel preparation is just fine and that your problem is inadequate CO2 exchange.

    Please let us know if that solves your problem! Also check out the new articles on supercritical drying under Make > Gel Drying Procedures.

    Hope this helps.

  187. Stephen Steiner says:

    Happy New Year Majid!

    Q: In case the addition of carbon nanotube to an organic aerogel, what are the differences between adding single-walled and multi-walled CNTs? In other words, to what extent can each of them enhance the aerogel’s properties (like compression strength and modulus, thermal conductivity, electrical conductivity, flexibility and …) ?

    Generally I would use multiwalled CNTs (MWNTs) or double-walled CNTs (DWNTs). For improvements in electrical conductivity specifically, you want metallic tubes and statistically only 66% of SWNTs are metallic, whereas MWNTs are almost always metallic (since the probability of having at least one metallic shell is high). For modulus, my guess is that modulus is going to be higher with MWNTs since they are stiffer structures, so for more compliant aerogels like the ones made at Lawrence Livermore made by Dr. Marcus Worsley and Dr. Ted Baumann that exhibit 80% elastic return you’d probably want DWNTs as opposed to MWNTs. Similarly for flexibility you would want to use DWNTs. For compressive strength I feel like MWNTs would be better, but you will probably lose compliance (the material will be stiffer and/or more brittle).

    Remember, too, the aspect ratio (length vs. diameter) of the CNTs will impact all of these properties too, as will the loading concentration.

    Hope this helps.

  188. Jing Xie says:

    Hello Stephen,

    Thanks so much for your reply. It helps me a lot and I appreciate it. I use alkoxide method to prepare the gel. I will try the dye method to identify the water in the gel. It sounds great! About the three CO2 exchange before the supercritical drying you mentioned, I need to soak my gel in the mixture of ethanol and liquid CO2 for 24 hours and after extracting all the solvent out, I let liquid CO2 go in the chamber and I repeat it for three times. Is it ture? In the past, I just extract a portion of solvent and let gel still soaked in the solvent, and then refill the chamber with liquid CO2. So it doesn’t matter for the gel standing in the chamber without any solvent soaking, right?

    I will try to increase the number of CO2 exchange and use your supercritical drying with several steps. Hope it will work! By the way, I use 200-proof absolute ethanol to extract water from the gel.

    Happy new year and thanks a lot.

    Jing

  189. majid says:

    Hi Stephen

    Thanks a lot for the references you recommend me. My other question is about SWCNTs and MWCNTs. In case the addition of carbon nanotube to an organic aerogel, what are the differences between adding single-walled and multi-walled CNTs? In other words, to what extent can each of them enhance the aerogel’s properties (like compression strength and modulus, thermal conductivity, electrical conductivity, flexibility and …) ?

    regards

  190. Stephen Steiner says:

    Hi Efstratios,

    Q: Is there a type of aerogel that could serve as a ‘thermal diode’ allowing solar radiation to go through it to a metal plate while preventing heat from the plate from flowing in the opposite direction through conduction, convection, and radiation?

    Generally any transparent metal oxide aerogel such as silica or alumina would do so. In fact, Cabot Corp’s Nanogel granules are designed exactly for this application–it lets sunlight in but does not let heat back out through conduction or convection.

    I’ve read that aerogels in general (excepting some metal-bearing types) are excellent conductive and convective insulators. My concern is with radiation: I’ve read that carbon aerogels can be good transmitters of visible-light radiation and good absorbers of infrared radiation.

    No! Carbon aerogels are terrible transmitters of visible light. They are opaque and black! In fact, carbon black is added to transparent aerogels to lower radiative transport through them.

    Where did you read this?

    Q: Is there a carbon (or other type) of aerogel that could let solar infrared radiation (or the heat therefrom, if the radiation is absorbed by the aerogel) through to the metal plate while preventing much infrared radiation from the metal plate (at 130-150 F) being lost to the environment?

    Again most transparent aerogel materials would do this. By the time the radiation gets through the aerogel and finds something to heat up, I don’t think loss due to re-radiation at longer wavelengths, at least for most applications, is really that big of a concern.

    Do you have a particular application that needs to do this?

  191. Stephen Steiner says:

    Hi Andre,

    It’s important to understand a few things about the behavior of nanostructured oxides and metals at elevated temperatures to predict what would happen to these materials in a building fire, noting that very few materials currently used in buildings contain engineered nanomaterials. Understanding these behaviors is also helpful for understanding how to prepare various types of aerogels, especially the recently discovered metal aerogels and metal nanofoams.

    Q: I dont know if it is common that paints contains micron particles of iron oxide. but lets say the paint contains micron particles of iron oxide, will those particles also turn into nanoparticles of iron oxide? or would they turn into liquid iron in the fire?

    Iron oxide is used as a pigment for specific “classic” red and rust-brown colors but not commonly in architecture. By far the most common oxide found in paints is titanium dioxide, used as a white pigment, which, like alumina, would not be carbothermically reduced in a fire.

    Generally speaking, things don’t get nano on their own–they get macro. Nanoparticles have high surface energies due to their high surface-to-volume ratio, and any opportunity they can access to become larger, for example, through diffusion and particle coarsening, they will. So in general if you have nanoparticles of a substance and you heat them up, they will coarsen and agglomerate into bigger particles.

    Iron oxide would be reduced to iron metal in the presence of hydrogen or a fuel metal like aluminum but requires very high temperatures to get it to go (lighting thermite off is hard to do even when you want to). Iron carbide can form in the presence of carbon or an organic at elevated temepratures.

    Q: If these aluminum oxide and iron oxide nanoparticles that are held in close stable proximity by a durable matrix which is laminated to a hard homogeneous material was created in this process in a fire, wouldnt the fire make them react even though the aluminum oxide particles will not show the reactivity (reductive behavior) typical for the Al nanoparticles, and wouldnt this reaction turn them into micron sized particles of liquid iron and aluminum oxide?

    I don’t know of any architectural paint that includes both aluminum and iron oxide nanoparticles together. There is no particular aesthetic, cost, or functional benefit to doing so and it’s obviously a recipe for thermite.

    Q: You wouldnt for example expect to find them as very reactive small chips after the fire, that when ignited at only lets say 400C produces molten iron (elemental iron spheres) and flashes, correct?

    I would not expect this to occur.

    Hope this helps.

  192. I learned about aerogels just two days ago, and … uuuhhh … it made for what could be a Merry Christmas week, indeed. My question: is there a type of aerogel that could serve as a ‚Äòthermal diode‚Äô allowing solar radiation to go through it to a metal plate while preventing heat from the plate from flowing in the opposite direction through conduction, convection, and radiation?

    In other words: is there a type of aerogel that allows a high percentage of solar radiation (mainly visible light and near-infrared, with some ultraviolet) to flow through to the plate while prevent heat from the plate (whose temperature will rise to say 130-150 F) flowing back?

    I’ve read that aerogels in general (excepting some metal-bearing types) are excellent conductive and convective insulators. My concern is with radiation: I’ve read that carbon aerogels can be good transmitters of visible-light radiation and good absorbers of infrared radiation. Is there a carbon (or other type) of aerogel that could let solar infrared radiation (or the heat therefrom, if the radiation is absorbed by the aerogel) through to the metal plate while preventing much infrared radiation from the metal plate (at 130-150 F) being lost to the environment?

  193. Andre Lindgren says:

    Thanks for the help Stephen. I have a couple of more questions i greatly would appreciate if you could answer:

    I dont know if it is common that paints contains micron particles of iron oxide. but lets say the paint contains micron particles of iron oxide, will those particles also turn into nanoparticles of iron oxide? or would they turn into liquid iron in the fire?. If these aluminum oxide and iron oxide nanoparticles that are held in close stable proximity by a durable matrix which is laminated to a hard homogeneous material was created in this process in a fire, wouldnt the fire make them react even though the aluminum oxide particles will not show the reactivity (reductive behavior) typical for the Al nanoparticles, and wouldnt this reaction turn them into micron sized particles of liquid iron and aluminum oxide?.

    You wouldnt for example expect to find them as very reactive small chips after the fire, that when ignited at only lets say 400C produces molten iron (elemental iron spheres) and flashes, correct?.

    Thanks again for the help!
    Andre

  194. Stephen Steiner says:

    Hi Majid,

    Q: You know that aerogels (specially organic ones) have weak mechanical properties. One way in order to increase their mechanical properties, is the addition of some special fillers. One of the additives can be carbon nano tubes. CNTs can also enhance the thermal and electrical properties of an aerogel. What do you think about that? Have you seen any research work in this field? Is it feasible to have a good distribution of CNTs in an organic aerogel network?

    Yes, in fact, it is possible to get a good distribution of CNTs in an organic aerogel network. This is the focus of work done at Lawrence Livermore National Laboratory by Dr. Marcus Worsley and colleagues. We have a whole page about the intersection of carbon nanotubes and aerogels under the Flavors of Aerogel section here on Aerogel.org. On that page, look for the section titled “Carbon-Carbon Nanotube Aerogels”. See the reference Marcus A. Worsley, Joe H. Satcher Jr., and Theodore F. Baumann, “Synthesis and Characterization of Monolithic Carbon Aerogel Nanocomposites Containing Double-Walled Carbon Nanotubes”, Langmuir, 24, 17, 9763-9766 (2008) and other work done by them for more information.

    Let us know if you have any additional questions.

  195. Stephen Steiner says:

    Hi Andre,

    Q: Lets say there is a fire in a building where Micron Aluminum particles are used in paints and coatings, and pipes in the building are leaking. When the micron Aluminum mixes with the water which comes from the water leakage, and as the amount of water is small when it is compared with the amount of micron Aluminum, is it then possible for these Micron Aluminum particles in the fire/water to turn into nanoparticles of elemental aluminum (40nm) that are mixed in a sol-gel matrix of silicon, oxygen, and carbon?

    Well in this type of scenario it is difficult to predict what would happen. But let’s boil it down to its simplest elements in a put it in a lab setting:

    • micron-diameter aluminum particles
    • trace water
    • in a latex matrix (like paint)
    • heated up to combustion temperatures

    What you would most likely end up with is carbonized powder with micron-diameter aluminum nanoparticles embedded throughout. I don’t think you would etch the nanoparitcles because, as you correctly pointed out, aluminum reacts readily with oxygen or water to form a protective oxide barrier that inhibits further oxidation making the particles very stable. Additionally, aluminum oxide is hard to reduce to aluminum metal carbothermically, and so even under these conditions I’m confident the aluminum would not etch substantially.

    Your thinking is along the lines of combustion synthesis, which is the technique used to form metal nanofoams developed by Dr. Bryce Tappan at Los Alamos National Laboratory. Combustion synthesis techniques are tricky but when you find one that works you can do all sorts of cool stuff!

  196. Stephen Steiner says:

    Hi Kael,

    Q: I see a tremendous potential for the marketing of aerogels & aerogel-based products, but after browsing through articles from this site and other resources on the internet, the downside of this is that the manufacture of aerogels does not look too cost-effective. Ageing, soaking & supercritical drying would take long periods of time and consume lots of solvent like ethanol and also liquid CO2. This dilemma is comparable to that faced by those engaged in the biochem industry (e.g: Manufacture of penicillin, Synthesis of drugs, etc.). The big question I would like to ask now is… Will the cost of selling aerogel & aerogel-based products outweigh the cost of manufacturing it?

    In fact, aerogel materials are already manufactured in a cost-effective manner. As far as silica aerogels go, Cabot Corp and Aspen Aerogels manufacture industrial volumes of aerogel materials for thermal insulation, and Dow-Corning sells a hydrophobic silica aerogel powder as a thickening agent for cosmetics. Regarding carbon aerogels, Cooper-Bussmann makes a line of supercapacitors with carbon aerogel as the electrodes.

    Your concerns regarding solvents are merited. In a research setting, it doesn’t make sense to worry about recycling solvents unless you are making a lot of materials, and so the processes are kept simple. In an industrial setting, however, you must recycle solvents in order to make the process make sense for profit and the environment. In fact, this is what is done industrially.

    And don’t worry about the supercritical drying step–it’s just high pressure vessels. Industry has been using those for a long time. In fact, Monsanto manufactured aerogel in the 1940’s using supercritical drying and did so profitably for about 30 years.

    Hope this helps.

  197. majid says:

    Hi Stephen

    You know that aerogels (specially organic ones) have weak mechanical properties. One way in order to increase their mechanical properties, is the addition of some special fillers. One of the additives can be carbon nano tubes. CNTs can also enhance the thermal and electrical properties of an aerogel. What do you think about that? Have you seen any research work in this field? Is it feasible to have a good distribution of CNTs in an organic aerogel network?

  198. Andre Lindgren says:

    Hello. I have a question about the sol-gel process and nanoparticles.

    Lets say there is a fire in a building where Micron Aluminum particles are used in paints and coatings, and pipes in the building are leaking. When the micron Aluminum mixes with the water which comes from the water leakage, and as the amount of water is small when it is compared with the amount of micron Aluminum, is it then possible for these Micron Aluminum particles in the fire/water to turn into nanoparticles of elemental aluminum (40nm) that are mixed in a sol-gel matrix of silicon, oxygen, and carbon?.

    As i understand it, Aluminum NP’s cannot be created in uncontrolled conditions, an oxygen free environment is essential. The synthesis of aluminum nanoparticles can only occur in vacuum or an oxygen free environment.

  199. Kael says:

    Hello all. I would like to inquire on the business prospects of aerogel for the future.

    I see a tremendous potential for the marketing of aerogels & aerogel-based products, but after browsing through articles from this site and other resources on the internet, the downside of this is that the manufacture of aerogels does not look too cost-effective. Ageing, soaking & supercritical drying would take long periods of time and consume lots of solvent like ethanol and also liquid CO2. This dilemma is comparable to that faced by those engaged in the biochem industry (e.g: Manufacture of penicillin, Synthesis of drugs, etc.). The big question I would like to ask now is… Will the cost of selling aerogel & aerogel-based products outweigh the cost of manufacturing it?

  200. Jon says:

    Earlier I posed a question regarding the thermal conductivity of aerogels – Steven Steiner has answered, thanks Stephen.

    I would add that after quite a few Google searches including the term aerogel I finally found an article using a search phrase that did not include the word Aerogel ( I was searching on thermal conductivity ).

    The following article talks of the mean free path of air molecules with the inference that pore sizes smaller than mean free path up the probability of air molecules hitting aerogel rather than each other resulting in the heat being returned to the tortuous solid matter paths provided by the aerogel. This is the aspect that interests me most as conventional insulators do no better than the values of non-convective heat transfer in air 0.025 W/mK whereas aerogels do substantially better 0.003 W/mK (quoted values vary this is the best given at
    http://en.wikipedia.org/wiki/List_of_thermal_conductivities )

    Here is the link for the explanation I came across..

    http://eetd.lbl.gov/ECS/Aerogels/sa-thermal.html

    Thanks to Stephen for the titles of relevent articles, some intriguing titles there, it would be interesting to see a good vigorous mathematical treatment even if the physical structure has to be idealised.

    Jon

  201. Stephen Steiner says:

    Hi Jon,

    Q: One thing I search for now and then but never seem to find on the web is a detailed description/theory of the insulating properties of aerogels, I am happy to read scientific papers
    as I have a technical background.

    Solid conduction seems fairly obvious – long fractally twisted strands are going to be very poor conductors.

    What about air molecule thermal transport? Mean free path? is that a factor wrt to inter strand distance?

    As the last person asked – what about radiation between strands?

    Well it sounds like you have a good model of the structure of a typical silica aerogel in your mind. You are right about the solid conduction–the tortuous nanosized fractal-like path comprised of a good thermal insulator (silica) makes solid conduction extremely slow.

    As far as convection goes, the tortuous maze of nanopores serves to slow diffusion of gases through aerogels down dramatically. In fact diffusion of gas through an aerogel is the slowest for any porous material.

    Radiative transport does occur through transparent aerogels, although is partly scattered by the aerogel structure. As a result, opacifying agents such as carbon are often added to silica aerogels intended for high-temperature service where radiative transport is significant.

    As far as radiative transfer between the strands, I suppose you mean that the solid component of the aerogel is heating up like a blackbody and emitting its own radiation? Well generally the aerogel is serving as an insulating barrier between a region of low temperature and high temperature and so the entire aerogel would not equilibrate to a temperature where it is emitting substantial blackbody radiation, plus all of the other features described above including the fact that there really isn’t that much solid there would inhibit this type of thermal contribution from being a big deal.

    For further reading take a look at these articles. They are accessible at most college and university libraries, through interlibrary loan at a public library, or online in HTML and PDF formation from the publisher (for a fee of $25-$40 per article):

    • Thermal transport in porous superinsulations
      Fricke, J.
      Springer Proceedings in Physics (1986), 6(Aerogels), 94-103.
    • Thermal transport in fractal systems
      Kjems, Jorgen K.
      Physica A: Statistical Mechanics and Its Applications (Amsterdam, Netherlands) (1992), 191(1-4), 328-34.
    • Pore size distribution and apparent gas thermal conductivity of silica aerogel
      Zeng, S. Q.; Hunt, A. J.; Cao, W.; Greif, R.
      Journal of Heat Transfer (1994), 116(3), 756-8.
    • Mean free path and apparent thermal conductivity of a gas in a porous medium
      Zeng, S. Q.; Hunt, A.; Greif, R.
      Journal of Heat Transfer (1995), 117(3), 758-61.
    • The thermal conductivity of silica aerogel in the phonon, the fracton, and the particle-mode regime
      Posselt, D.; Kjems, J. K.; Bernasconi, A.; Sleator, T.; Ott, H. R.
      Europhysics Letters (1991), 16(1), 59-65.
    • Thermal transport in monolithic silica aerogel
      Caps, R.; Doell, G.; Fricke, J.; Heinemann, U.; Hetfleisch, J.
      Journal de Physique, Colloque (1989), (C4, Proc. Int. Symp. Aerogels–ISA 2, 2nd, 1988), C4-113/C4-118.
    • Low-temperature thermal transport in silica aerogels
      Scheuerpflug, Peter; Morper, Hans Jochen; Neubert, Gerhard; Fricke, Jochen
      Journal of Physics D: Applied Physics (1991), 24(8), 1395-403.

    Hope this helps.

  202. Stephen Steiner says:

    Hi Jing,

    Q: After so many failures, I finally got the sample (about 1cm*1cm*1cm) which is very like aerogel. The edge (about 1mm) of my sample is transparent, like blue smoke while the main body of the sample is like cloud. At first I think this should be due to the exchange time between pure ethanol and liquid CO2 is not enough.

    It’s not only the diffusion time that matters but also the number of exchanges you do, especially with supercritical extraction. If the concentration of ethanol in the liquid CO2 is above 1%, the critical point of the mixture will be much higher than for pure CO2, and more than likely, after dropping below the critical point, liquid-phase ethanol will recondense in the pores of the aerogel and make it white. The white color is a sign of unremoved solvent of any type, not just water.

    Regarding solvent exchanges:

    • Time serves to equilibrate the concentration of whatever is in the gel with its surroundings
    • Number of exchanges serves to decrease the concentration of whatever is pulled out by the equilibrated gel/surrounding fluid

    In your case, each exchange reduces the concentration of ethanol in the CO2.

    Then perform three CO2 exchanges, soaking for about 24 hours per exchange prior to supercritical drying. When doing the supercritical drying, make sure to do the following:

    1. Heat the vessel past 31.1 deg C to about 40 deg C, releasing pressure as it builds up so that the pressure is between 1100-1500 psi as you reach 31 deg C.
    2. Bring the pressure to around 1400-1500 psi with heating, then depressurize slowly (over about 10 min) to about 1150 psi.
    3. Heat again to 1400 psi or so and repeat this cycle 3-4 times or until the the pressure only rises very slowly with additional heating or a temperature of 50-60 deg C is reached.
    4. Slowly depressurize the vessel back to ambient.

    This process ensures you remove enough CO2 from the vessel and that the CO2 is hot enough so that when the pressure drops below the critical pressure there isn’t enough CO2 in the vessel to recondense into a liquid.

    Are you using the alkoxide method or the waterglass method to prepare your silica gels? If you are using the alkoxide method, it sounds like you are performing the ethanol exchanges more than adequately. Really all that is necessary is three full exchanges using 10 times the volume of the gel each for 24 hours. If you are using the waterglass method, don’t forget you must perform ion exchange and multiple washings with deionized water prior to solvent exchange with ethanol to remove excess sodium ions from the gel. If you are in fact using the waterglass method, excess ions bound to the silica framework could be causing the whiteness.

    Are you using absolute (200-proof) ethanol? You are not using denatured ethanol, correct?

    Q: Why my sample is cloud like in the body while blue smoke like in the very tiny edge? If my diffusion has some problems, what can I do to improve it?

    Your sample has what we call the “skin effect” possibly because of one of two things:

    • Only the outer edges have been adequately depleted of ethanol by the supercritical drying step and increasing the number of liquid CO2 exchanges should help, or
    • You are using the waterglass method and only the outer edges have been depleted by sodium ions and ethanol, which does not remove sodium ions well, is not diffusing into the gel past this outer skin due to an ionic barrier of sodium ions. In this case, performing an ion exchange with the gel followed by multiple exchanges with deionized water prior to solvent exchange with ethanol should fix the problem!

    Q: During the exchange water in the gel with ethanol, how can I determine the gel has only ethanol as solvent?

    Well that’s always a tricky question to answer but one way you can do it is to find a dye that is soluble in ethanol but not in water (some organic) and then soak a test gel in the ethanol/dye solution. Perform all exchanges with the ethanol/dye solution as you would with pure ethanol. After the exchanges are done, cut the gel open and see if the dye has penetrated into the interior of the gel.

    Hope this helps.

  203. Jon says:

    Hi,

    One thing I search for now and then but never seem to find on the web is a detailed description/theory of the insulating properties of aerogels, I am happy to read scientific papers
    as I have a technical background.

    Solid conduction seems fairly obvious – long fractally twisted strands are going to be very poor conductors.

    What about air molecule thermal transport? Mean free path? is that a factor wrt to inter strand distance?

    As the last person asked – what about radiation between strands?

    Regards

    Jon

  204. Jing Xie says:

    Hello,

    I have been preparing silica aerogel for several months. After so many failures, I finally got the sample (about 1cm*1cm*1cm) which is very like aerogel. The edge (about 1mm) of my sample is transparent, like blue smoke while the main body of the sample is like cloud. At first I think this should be due to the exchange time between pure ethanol and liquid CO2 is not enough. So I increase the exchange time to a whole week. But the sample was still cloud like in body and blue smoke like at the edge. These two samples are both brittle. I am so confused. I don’t know what’s wrong with my sample and which step for my experiment is wrong. Is it because water is still in the gel? Since I soaked my gel in pure ethanol for more than a week and exchanged the solution for decades of times. I thought water in the gel should be extracted. How can I determine the water in the gel come out completely?

    So concluding my questions as followed,

    First, why my sample is cloud like in the body while blue smoke like in the very tiny edge? If my diffusion has some problems, what can I do to improve it?

    Second, during the exchange water in the gel with ethanol, how can I determine the gel has only ethanol as solvent?

    I will appreciate your reply.

    Jing

  205. Stephen Steiner says:

    Hi Again Roy,

    my planned procedure
    1.Mix the sodium silicate with ammonia to activate the hydroxyl to form sol gel
    2.wash sodium silicate gel with acetone 5 or 6 times
    3.add polystyrene solution into the sodium silicate gel acetone solution
    4.give the polystyrene time to bond to the hydroxyl groups on the sodium silicate at 120F 24h
    5.exchange the acetone with Hexane and let the Aerogel dry
    sound ok?

    Well your procedure sounds fine in principle although I’m not sure the polystyrene will end up bonding to the hydroxyl groups as you expect. But give it a shot! You can also try the same with poly(methylmethacrylate) (aka plexiglass) but again not sure if you’ll get bonding between the hydroxyl groups and the polymer (my guess is you won’t). You might get a desirable material, though!

    Also, please exercise caution when heating solutions of acetone! Use a sealed container like a jar with a lid if you are going to place the solution in an oven or, better yet, use an heated water bath to heat the jar.

    Q: also how dense can you make aerogel being 2000 times stronger then steel is cool but would be really impressive if it could be made denser.
    The densest possible native silica aerogel, by definition, is 1.1 g cm-3, in which the material would be 50% porosity, 50% silica. Generally anything above 0.1-0.2 g cm-3 is not really much of an aerogel in its materials properties any more. With x-aerogels, generally a three-fold increase in density due to the incorporation of a conformal polymer coating over the aerogel skeletal framework results in 20-40 times increase in compressive strength and significant increase in fracture toughness (material is not fragile).

    Remember also that strength is a multidimensional property–there is compressive strength, tensile strength, shear strength, flexural strength, and many other metrics of strength depending on the material. So when we throw around terms like “2000 times stronger than steel” we really need to define in what way–I think the number you are talking about is specific compressive strength, namely, compressive strength divided by weight. Making strong materials with low density is highly desirable, so making aerogels denser doesn’t necessarily win you anything–it’s the strength to density ratio that really matters.

  206. Stephen Steiner says:

    Hi George,

    Q: do i actually need a subcritical dryer

    Well I think you mean supercritical dryer and, no, you do not need a supercritical dryer to make aerogels (see the response to Mark and MOHIT’s questions below about subcritical drying) but you will be limited to relatively small monoliths and generally silica and the metal oxides, although mechanically robust x-aerogels are also made subcritically.

  207. Stephen Steiner says:

    Hi Mark,

    Q: I’m a doctoral student from Brunel University in London, who is really interested in making some basic silica aerogels. In your ‘overview of how to make aerogels’, you mention that gel drying can either be done supercritically or evaporatively, depending on the recipe. Does this mean that in some cases it is not necessary to build an autoclave when making aerogel? If so, are there any recipes or step-by-step guides for the evaporative process?

    To add to Szymon’s response below, the classic way of preparing aerogels through subcritical drying is to treat the silica gel precursor with a hydrophobic agent such as trimethylchlorosilane (TMCS) or hexamethyldisilazane (HMDS) prior to evaporative drying. The trick here is to a) eliminate hydroxyl groups that will stick to each other when the gel shrinks a little bit and b) to balance the modulus of the gel matrix against the capillary stress induced by evaporation. The way this is done is by preparing a silica gel through any suitable method, exchanging the pore fluid into, say, acetone and then into hexane, then exchanging the gel into a solution of ~6 wt% TMCS in hexane one to three times, preferably at elevated temperature (say 60 deg C). After that you would purify the gel with additional hexane and then slowly evaporate the hexane. Gentle ambient heating sometimes is applied. This is basically the method described first by Smith, Desphande, and Brinker in Ceramic Transactions v31 1993. We will post the long-overdue procedure for subcritical drying of aerogels under the Make section later this week. Check out the response to MOHIT’s quiestion below as well.

    This Spring we will be posting a podcast with Prof. Jeff Brinker who developed this technique. He will talk in more detail about subcritical drying of aerogels, which is the same method Cabot Corp. uses to make Nanogel.

  208. Szymon Bartus says:

    Hello Mark,

    > Does this mean that in some cases it is not necessary to build an autoclave when making
    > aerogel? If so, are there any recipes or step-by-step guides for the evaporative process?

    Yes, you can obtain aerogels by evaporative drying. The key is to make a gel with very robust solid framework which can withstand the stress from capillary attraction.
    As far as I know two methods of producing such gel exist today:
    1. Soaking the gel in crosslinking agent before drying. X-aerogel is obtained.
    2. Making silica gel with reduced bonding, using methyltrimethoxysilane (MTMS).

    All of above is described with more details in “Strong and Flexible Aerogels” section in “Flavours of Aerogel”.
    Before making such gels I would just read the papers containing reports of invention of those gels (and further work on them). I think you will be able to find them after reading the section.

    Regards,
    Szymon B

  209. Mark Dowson says:

    Hello,

    I’m a doctoral student from Brunel University in London, who is really interested in making some basic silica aerogels. In your ‘overview of how to make aerogels’, you mention that gel drying can either be done supercritically or evaporatively, depending on the recipe. Does this mean that in some cases it is not necessary to build an autoclave when making aerogel? If so, are there any recipes or step-by-step guides for the evaporative process?

    Kind Regards
    Mark

  210. Rey dTutto says:

    Molecular Sieve in a 3A (3 Angstrom pore size) may be used to turn 190 Proof Grain Alcohol into 200 Proof Ethanol with a little parience.

    I noticed some of the recipies mention using Everclear, which will work, but I have found the 199+ proof ethanol (After drying with a Molecular Sieve) will not freeze in the valves during the CO2 Solvent exchange, whereas i have had some difficulties with 190 Proof and pin valves requiring heating the valve to maintain ethanol bleeding.

  211. Roy says:

    my planned procedure

    1.Mix the sodium silicate with ammonia to activate the hydroxyl to form sol gel

    2.wash sodium silicate gel with acetone 5 or 6 times

    3.add polystyrene solution into the sodium silicate gel acetone solution

    4.give the polystyrene time to bond to the hydroxyl groups on the sodium silicate at 120F 24h

    5.exchange the acetone with Hexane and let the Aerogel dry

    sound ok?

    also how dense can you make aerogel being 2000 times stronger then steel is cool but would be really impressive if it could be made denser.

  212. george says:

    do i actually need a subcritical dryer

  213. Stephen Steiner says:

    Hello Abidah,

    Q: I do a project about silica aerogels. I want to do the silica aerogel blanket where when the silica aerogels produced by using water glass as silica source and ambient pressure drying, then I want to embed that aerogels to the glass wool as blanket. How I want to embed the silica aerogels onto that glass wool?

    Sounds like a great project. I would try pouring the sol over the glass wool before it has set and allowing it to gel around the glass wool. Perform all solvent exchanges and drying on the gel/glass wool composite, then. If you are unsatisfied with the loading of gel on the glass wool, time the gel time of your solution so you know how long gelation will occur after mixing – that way you can try timing when to pour the solution over the glass wool so that the solution is viscous when you pour it on and clings better. You can use a heat lamp to try to speed gel time up but you would want to make sure the gelling solution is in a moist atmosphere so that it doesn’t dry out or concentrate while it’s being heated.

    Keep us posted on how your project goes!

  214. Stephen Steiner says:

    Hello Roy,

    Q: I am planing to make an X-Aerogel out of Sodium Silicate and Polystyrene (AKA Styrofoam). My Question is will this solution work for an X-Aerogel.

    Nothing wrong with using sodium silicate as a precursor. We need to get a recipe up using sodium silicate! I will see to it we do soon. The implementation of the polystyrene is a different issue. Leventis et al. have already shown it is possible to make x-aerogels using polystyrene as the conformal coating. They did so by introducing a solution containing monomeric styrene (which is a liquid) into the pores of the wet gel and incorporating a special radical initiator into the gel backbone. They they initiated polymerization, resulting in formation of a conformal polystyrene coating over the skeletal surface of the gel. The trick here is that there really is no attachment point for polystyrene on the gel surface unless you incorporate something into the gel backbone intentionally.

    I plan on using acetone as the solvent because Styrofoam will melt in it and because
    it has no hydroxyl groups. From there i plan to follow the directions on page http://www.aerogel.org/?p=1058

    To clarify, the styrofoam is dissolving, not melting. I would say give it a shot and see what happens! A few things to consider:

    • The polystyrene solution may end up viscous and may not penetrate well into the pores, so you may want to dilute accordingly
    • The polystyrene probably won’t bond covalently to the gel backbone, but maybe it will stick through another mechanism (for example adsorption or weak bonding)… try it and see
    • You might end up plugging up porosity as opposed to coating the skeletal surface of the gel–this will be indicated by a “skin effect” when cross-sectioning the gel (the outer edges of the gel will look one way but the inner core of the gel will look another)

    Also my Sodium Silicate solution is 40% so will i have to evaporate the H2O?

    No, actually, you will want to dilute it to a concentration between 4-10% with deionized water. It is already too concentrated as-is to use for making a gel suitable for producing aerogel.

    from there i plan to add hexane for the drying process. basically im asking for input before I throw all this stuff together. A rough estimate in the amount of materials i will have to use would be nice.

    Well give it a shot and keep us posted with the results! At this stage it’s cooking, not baking–go by feel for now, look for signs the gel has been penetrated by cross-sectioning after infiltrating with your polystyrene solution, after replacing the pore fluid with hexane, and after evaporative drying, and adjust your solutions accordingly to make the process go smoothly. Start with concentrations of polystyrene on the order of 5-10% and then around 50% and compare the results. Move accordingly from there.

  215. Stephen Steiner says:

    Hi Nick,

    Q: Is it possible to use aerogel for breast implants? I can see several realy strong points here;
    -The implants will be light-weight, thus reducing stress on the breasts and back of the girl.
    -The wide variety in density and structure will make it possible to get any shape and ‘touch’, some like the very natural shape and soft touch, others like the real round shape and very firm touch.

    Goes to show inspiration can strike anywhere!

    Well I’m sure you could potentially use aerogels for breast implants (or chest or calf implants, let’s not be sexist) but frankly I don’t think aerogels are the right material for the job. Remember, aerogels are dry rigid materials with densities 10 to 1000 times lower than water, while human body soft tissue is highly hydrated, compliant, and close to the density of water. It would be similar to the difference between a doll made with a stiff styrofoam form versus one filled with water to make it feel lifelike.

    Additionally, most aerogels are quite brittle and would not stand up to the mechanical stresses they would encounter as implants and so you would need to focus on a formulation of x-aerogel or some other mechanically robust aerogel, probably.

    There may be other opportunities for aerogels to be used as implants, though, for example, as scaffolds for bone or other tissue growth.

    Q: Also i was wondering how expensive the production of such implants would be?

    At mass production, the structures themselves would not necessarily be remarkably expensive, probably on the order of say $10 to $100 an implant; however FDA approval, insurance, and all the other stuff that moves stuff out of the lab and into the body would probably make them more expensive than that.

    Thanks for the question.

  216. Stephen Steiner says:

    Hi Majid,

    Q: You mention this formula to prepare an RF aerogel: Resorcinol (1 gram) + Formaldehyde 37% (1.47 gram) + Catalyst solution2gr/litr (2.41 grams) + Water (47.1 grams) then the solid content of solution is less than 4% wt. By taking into account that the skeletal density of polymeric aerogel and density of water are the same (~1 g/cc), the density of RF aerogel will be ~0.04 gr/cc but you give 0.2 gr/cc for density of product. What’s wrong with this?

    A: You are very observant and bring up a good question! This is an anomaly specific to some types of organic aerogels. Unlike silica aerogels, which exhibit a fractal-like nanostructure over relatively long ranges, resorcinol-formaldehyde aerogels generally do not, although they do still exhibit a string-of-pearls type morphology like silica aerogels. As a result, the nature of the particle interconnectivity is a bit different depending on density. In denser samples, the particle size is larger but the particle connectivity is less. In lower density samples, the particle size is smaller but the degree of interconnectivity apparently goes up. This means the increase in stiffness (modulus) of the gel network slows as gel density increases.

    As a result, the percent shrinkage for higher density organic aerogel samples upon supercritical drying is greater than for lower density organic aerogels, meaning that as you have correctly observed from the data posted on the recipe article, the density of the resulting aerogel will be higher than the theoretical density. In fact, lower density aerogels approach their theoretical density much more closely.

    This is a good point to note, actually–organic aerogels shrink quite a bit upon supercritical drying.

    This stuff was all figured out by Dr. Rick Pekala at Lawrence Livermore in the late 1980’s. You can read more at https://e-reports-ext.llnl.gov/pdf/208379.pdf and https://e-reports-ext.llnl.gov/pdf/220244.pdf.

    Hope this helps!

  217. adibah says:

    I do a project about silica aerogels.
    I want to do the silica aerogel blanket where when the silica aerogels produced by using water glass as silica source and ambient pressure drying, then I want to embed that aerogels to the glass wool as blanket.
    How I want to embed the silica aerogels onto that glass wool?

    thank you..
    Adibah
    student from Malaysia

  218. Roy Bellamy says:

    Dear Stephen Steiner

    I am planing to make an X-Aerogel out of Sodium Silicate and Polystyrene (AKA Styrofoam)

    My Question is will this solution work for an X-Aerogel.

    I plan on using acetone as the solvent because Styrofoam will melt in it and because
    it has no hydroxyl groups. From there i plan to follow the directions on page http://www.aerogel.org/?p=1058

    Also my Sodium Silicate solution is 40% so will i have to evaporate the H2O?

    from there i plan to add hexane for the drying process. basically im asking for input before I
    throw all this stuff together. A rough estimate in the amount of materials i will have to use would be nice.

    Sincerely Roy Bellamy

  219. Nick says:

    Hello,

    Is it possible to use aerogel for breast implants?

    I can see several realy strong points here;
    -The implants will be light-weight, thus reducing stress on the breasts and back of the girl.
    -The wide variety in density and structure will make it possible to get any shape and ‘touch’, some like the very natural shape and soft touch, others like the real round shape and very firm touch.

    Also i was wondering how expensive the production of such implants would be?

    Thanks for your help,

    Nick

  220. majid says:

    Hi,
    Thanks very much because of your fruitful information about aerogels;
    I have a question about your “Organic aerogel recipe” page.
    You mention this formula to prepare an RF aerogel:
    Resorcinol (1 gram) + Formaldehyde37% (1.47 gram) + Catalyst solution2gr/litr (2.41 grams) + Water (47.1 grams)
    then the solid content of solution is less than 4% wt.
    By taking into account that the skeletal density of polymeric aerogel and density of water are the same (~1 g/cc), the density of RF aerogel will be ~0.04 gr/cc but you give 0.2 gr/cc for density of product. What’s wrong with this?

  221. Jeff says:

    Thanks, Stephen!

    Q: Are you thinking that you would place a gel in a column and apply a pressure gradient across it to try to push the liquid through faster, for example?

    A: Yes! That is exactly it. I see that this is not a novel approach; it’s good to know that it’s been done before and can be successfully performed.

    I will try out a few water glass recipes and post which ones work the best.

    -Jeff

  222. Stephen Steiner says:

    Hi Jeff,

    Q: I was doing some reading on your website, and I came across the “waterglass gelation” section. I was wondering, what is the typical concentration of sodium silicate that is used for this step? I am only able to find 40% solutions on eBay. Will this suffice?

    A: More than enough. Most gelation procedures use a concentration of about 4%, not more than 10%. Remember, this concentration will be comparable to the % solid the aerogel will be, so if you want an aerogel that’s 95% air, a concentration of 5% would be around what you want.

    We will find a good waterglass procedure and post it in the Make section for you.

    Q: one more question — does anybody know if the purifying & waterproofing steps can be done via column chromatography? Or would that damage the gel’s infrastructure?

    A: How do you mean? Are you thinking that you would place a gel in a column and apply a pressure gradient across it to try to push the liquid through faster, for example? If that’s the case, you could certainly do this–applying a pressure gradient will help push fluid through the gel faster but in general this is tricky to implement as you need a sample with a shape that allows it to “plug up” your column or a column designed to accommodate odd shapes, not to mention the equipment to do it… there are some examples where people have done this to try to speed processing up or achieve a specific effect in the gel. The gel structure is remarkably resilient when loads are applied uniformly, especially hydrostatically as they are in supercritical drying, so that shouldn’t be an issue–it’s point stresses that cause/enable cracks to propagate through the brittle silica network that cause problems.

  223. Jeff says:

    one more question — does anybody know if the purifying & waterproofing steps can be done via column chromatography? Or would that damage the gel’s infrastructure?

    Thanks,
    -Jeff

  224. Jeff says:

    Hi Stephen,

    I was doing some reading on your website, and I came across the “waterglass gelation” section. I was wondering, what is the typical concentration of sodium silicate that is used for this step? I am only able to find 40% solutions on eBay. Will this suffice? Thanks,

    -Jeff

  225. Stephen Steiner says:

    Hi skelly,

    Q: Could you possibly shed some light on a couple of the physical properties of, say your basic silica aerogel?

    I encourage you to read about silica aerogels under Learn > Flavors of Aerogel > Silica Aerogels and you can peruse their properties on the interactive materials property database under Learn > About Aerogel > Properties of Aerogels.

    Q: 1) I’ve read that they are brittle – can they be machined into shapes, and/or attached to mechanically or chemically to connect in with components of a larger device (i.e. as a heat shield in a machine with moving parts)

    A: Remember, aerogels are a class of materials. NOT ALL AEROGELS ARE BRITTLE! Some aerogels can be machined. X-aerogels are incredibly strong and flexible materials–read all about them under Learn > Flavors of Aerogel > Strong and Flexible Aerogels. Certainly the typical silica aerogel is difficult to machine, although can be done with a high-speed vibrating needle. It is possible to chemically bond aerogels but doing so is pretty sciencey since, for example, if you simply tried gluing them to something, they would suck up the glue and shrink.

    Q: 2) Suddenly I’m baffled by the thermal insulation properties; specifically, considering the promotional image with the crayons atop the aerogel sample with the blow torch beneath, it strikes me that I don’t understand what happens with the heat. If it is not absorbed and retransmitted through the aerogel, is it deflected back toward the source? That energy has to go somewhere, right?

    A: The heat is in fact deflected back and the heated air will crawl around and diffuse up around the edges of the aerogel tile. So if you had a low-density silica aerogel box with a torch in it, for example, you wouldn’t really feel anything outside the box but inside would get hotter and hotter until the oxygen and/or fuel ran out.

    Let me know if you have any more questions.

  226. skelly says:

    Fascinating website – I was quite surprised to find this when doing some internet searches for sources of aerogel materials / samples for a research project I am working on. I’m not sure I want to get into making my own aerogels without first understanding that they will work for what I need them, but the information for consolidated here is really something nonetheless. Could you possibly shed some light on a couple of the physical properties of, say your basic silica aerogel?

    1) I’ve read that they are brittle – can they be machined into shapes, and/or attached to mechanically or chemically to connect in with components of a larger device (i.e. as a heat shield in a machine with moving parts)

    2) Suddenly I’m baffled by the thermal insulation properties; specifically, considering the promotional image with the crayons atop the aerogel sample with the blow torch beneath, it strikes me that I don’t understand what happens with the heat. If it is not absorbed and retransmitted through the aerogel, is it deflected back toward the source? That energy has to go somewhere, right?

    Thanks,
    -skelly

  227. Jeremy W says:

    Stephen,
    Thanks for pointing me in the direction of the Gash et al literature. I spent an afternoon going through the literature and ordered some chemicals. I have three methods I will try:

    (1) Ti-butoxide + Fe(NO3)3.9H2O in ethanol (analagous to the alumina method on this site)
    (2) TiCl3 solution + Fe(NO3)3.9H2O in ethanol or acetonitrile + epichlorohydrin (i.e. Cui, Zayat & Levy, 2005 amongst others)
    (3) Tetraethyl-orthotitanate + Fe(NO3)3.9H2O in ethanol + epichlorohydrin (seeing if I can achieve what others have done with epoxide assisted TEOS and Fe nitrate when making SiO2-Fe2O3 aerogels)

    I am using TiCl3 solution because we have some in the lab. Ditto for the TEOT.
    I am not aiming to make rigid monolithic gels, xerogels are fine since all I am after is a homogeneous, very fine material to calcine at various fO2s. I will let you know how it goes.

  228. Stephen Steiner says:

    Hi Szymon,

    Sorry for overdue answers to your questions. Here they are:

    Q: I’ve found in one scientific paper that there is a possibility to make “cryogels”. They are wet gels dryed by freeze drying: http://en.wikipedia.org/wiki/Freeze_drying There is also written that silica aerogels made that way were macroporous, non-transparent and non-monolithic. Can you say something more about cryogels? Can someone mention them in the section “science of aerogel”?

    A: Cryogels are aerogels that are made by cryogenically freezing a wet gel and then slowly allowing the frozen phase to sublime. This process is called “freeze drying” or “lyophilization” (since it makes a dry material that absorbs liquids readily or “loves solvent” (lyo=solvent/liquid, phile=lover)). This is the same freeze drying used to prepare dried strawberries for cereal, coffee, and astronaut ice cream. Depending on how you execute the freeze drying, the pore structure may be macroporous (average pore diameter > 50 nm) or mesoporous (average pore diameter between 2 and 50 nm). Dr. Bryce Tappan at Los Alamos National Laboratory, inventor of metal nanofoams, will talk about cryogels in an upcoming podcast this January. We’ll put an article up about cryogels under the Science of Aerogel as you suggest!

    Q: Why is this drying method so destructive to the gel stucture? If it damages gel then why is it used to prepare biological specimens (I think it’s called lyophilisation)?

    A: It is destructive because freezing stuff causes volume changes that can stress/damage the gel network, but again depending on how it’s done it can preserve materials quite well. In fact, particularly for biological materials, which can shrink/denature quite a bit due to solvent exchange with alcohol and especially CO2, freeze drying is often more effective at preserving pore structure than supercritical drying. You can see an example of a collagen-glycosaminoglycan cryogel used for artificial skin grafts that is better made by freeze drying than supercritical drying under Learn > Flavors of Aerogel > Organic and Carbon Aerogels.

    Q: What will happen if I exchange ethanol into liquid CO2 in my dryer and then slowly depressurize the chamber so that CO2 will slowly “boil away”? (without any heating) How would this work in comparison to supercritical drying?

    A: You will effectively be performing subcritical drying similar to but more effective than, say, slowly evaporating pentane or another solvent. I’ve done this on accident a couple times and you actually end up with materials which are pretty decent aerogels, although they will shrink 5-10% more than if you supercritically dry them.

    Q: What can you say about performing ethanol or methanol supercritical drying? All you need is to put the gel inside solvent-filled mould, heat it to about 300C (and the pressure will rise too) and slowly depressurize the chamber while being heated. Obtaining 300C at home or school is hardo, however.

    A: All you need, huh? Yes, in principle high-temperature organic supercritical drying is more elegant and actually yields intrinsically hydrophobic silica aerogels (the alcohol reacts with excess silanol groups on the gel skeleton at high temperatures and replaces them with less polar alkoxy groups) but the equipment needed to do it safely is a bit involved and expensive. The other drawback is that it only works for inorganic materials since most organic materials decompose or react at the temperatures needed in those solvents. Dr. John Poco and Dr. Larry Hrubesh at Lawrence Livermore National Laboratory have done a lot of great work with this technique.

    Aerogel.org is currently raising funds to develop a do-it-yourself high-temperature supercritical dryer and we will let you know when that’s ready!

    Q: In the papers I browsed, the heating/cooling rates and pressurisation/depressurisation rates in lab-grade manuclaves were very low. In my manuclave I can onyl pressurise my gel instantly (ball valve), heat it fastly (heat gun) and I’m not sure if my needle valve is precise enough to set the depressurization to, say, 7bar/h. How these affect properties of aerogels?
    I think the depressurisation rate is the most important since the gel structure might collapse.

    A: Most of these numbers are arbitrary anyways so it really just depends on your system. Don’t worry about the 7 bar h-1. Just do it slowish. You’ll get the feel for how fast you can go with practice. I generally depressurize slow between 600 and 1200 psi and a little faster below 600, and much faster below 200 psi. For your manuclave, you can pressurize slowly by just cracking the ball valve (that’s what I do). At this stage in the processing, as long as it’s slow enough, there should be no effect. The risk here is if the materials cool too fast and crack or rapidly depressurize and get blown apart. Remember after partially depressurizing the vessel at supercritical conditions, when you drop below the critical point the fluid in the pores of the gels has reverted to a gas phase, not a liquid phase, and can exert no capillary stress on the gels. It’s just high pressure gas at that point. Cracking and colllapse at this stage in the supercritical drying process is really due to unseen residual solvent in the aerogel.

    Remember this: supercritical drying rarely causes shrinkage or cracking. It is the CO2 solvent exchange prior that causes shrinkage and cracking.

  229. Stephen Steiner says:

    Hi James,

    Actually the waterglass method is sol-gel still, it just uses sodium silicate as the source of silica instead of TMOS or TEOS. Since it is a sol-gel process, nanoparticles of silica are still formed, which in turn connect to form a gel network if allowed to gel. Thus by performing the chemistry in a way that does not lead to gelation, for example, by making the solution too dilute or precipitating with base after a fixed amount of time, you could isolate nanoparticles. The term “Stöber particles” is sometimes used to refer to silica nanoparticles in a sol. Additionally, you could introduce a capping agent such as acetylacetonate to arrest nanoparticle growth and connecting.

  230. James says:

    Hi,

    can i make nanoparticles of silica from water-glass + ethanol then adding some acid to this solution????

    please help me. i dont wanna use sol-gel method i.e use TEOS

    thanks

  231. Stephen Steiner says:

    Hey Jeremy,

    You can totally make a mixed-matrix metal oxide aerogel using the epoxide-assisted gelation method. Why are you choosing to use TiCl3? You can use TiCl4 also, which might be easier. You do not need to use the nitrate for the iron salt–you can also use FeCl3. The technique is sensitive to the amount of water more than the pH, but as the reaction proceeds there is a slow, constant rise in the pH as the epoxide scavenges protons from the aquo complexes formed in solution. You’ll want to play around with solvents since TiCl3 and TiCl4 are both easily hydrolyzed and react with many protic polar organics such as ethanol and methanol and you will need to include water in the system from somewhere, for example, as water from a hydrated iron salt. Consult the papers of Gash et al. to see examples of what solvents might be best. You could try acetonitrile as a start.

  232. Jeremy W says:

    Hi Aerogel.org,
    I am trying to make a Ti-oxide doped Iron oxide gel. I have been playing with TiCl3 in acid solution and initiaing gellation with NH4OH, then adding an iron nitrate solution to hopfully form a Fe-Ti-hydroxide gel. It is sort of working, but I am having problems with getting the pH right to get quantitative precipitation/gellation of all the iron in solution.

    Could I use TiCl3 and iron nitrate with the propylene oxide method? To keep TiCl3 in solution, it has to be acid. Does pH affect the propylene oxide method?

  233. Stephen Steiner says:

    Hi Alexandre,

    There really aren’t a whole lot of aerogel producers in the world but what do you need aerogel for and what type of aerogel are you looking for?

    There are a few places in Europe we can steer you to if you can explain what your application is. Otherwise you’re welcome to try making aerogel on your own under the Make section!

  234. Stephen Steiner says:

    Dear MOHIT,

    Subcritical drying of aerogels is the topic of an upcoming article that will appear under Learn > The Science of Aerogel soon! But to get you started, here are the basics.

    When liquid is evaporated from a gel, capillary forces induced by the liquid evaporating from the nanopores of the gel exert stress on the struts of the gel’s solid framework and, as the liquid leaves, the framework collapses inwards a little bit. As the liquid continues to evaporate, the framework continues to collapse in on itself. The framework of the gel is lined with surface hydroxyl groups which terminate the silicon-oxygen-silicon network that makes up the framework. These hydroxyl groups love to stick to each other. In fact, hydroxyl groups are the reason why ScotchTM tape is sticky. These hydroxyl groups stick to each other by hydrogen bonding, which originates from the hydroxyl group being polar. Thus as the framework collapses inwards on itself, the struts of the framework stick to each other. Think of it like when you take the backside off of a band-aid and the sticky part of the band-aid accidentally folds over onto itself and never unsticks ever again, forcing you to throw the band-aid out and get a new band-aid. That but instead of a band-aid it’s hydroxyl-coated nanostruts of a silica gel. The result is a dense, solid material results which we call xerogel–basically glass with about 10% porosity.

    If instead you could replace these sticky hydroxyl groups that the line the solid skeletal framework of the gel with something non-polar, then the liquid in the gel’s framework wouldn’t interact with the framework as much and so as it evaporates from the pores it wouldn’t be able to exert as much force to draw the framework in on itself. Furthermore, even if the framework does collapse some, the struts won’t stick to each other, so you could, in principle, force the network to spring-back into an aerogel after it partially collapses.

    Alternatively, you can replace the fluid in the pores of the gel with something with low surface tension, which means it won’t stick to the framework of the gel as well as, for example, ethanol or water. Examples would be pentane, hexane, and liquid CO2.

    Even better, you can combine both approaches and address capillary collapse two ways–by eliminating surface hydroxyls (or enough of them, anyway) and by reducing the surface tension of the liquid in the pores.

    Replacing surface hydroxyls is usually done by forming a gel, performing solvent exchanges into a suitable aprotic solvent such as acetone or acetonitrile, then soaking the gel in a solution of a waterproofing agent such as trimethylchlorosilane, dimethyldichlorosilane, or hexamethyldisilazane. These compounds will then diffuse into the pores of the gel and spontaneously react with the hydroxyl groups on the surface, replacing them with big, bulky non-polar trimethylsilyl or dimethylsilyl groups, respectively. Excess reagents and byproducts are removed from the gel by subsequent solvent exchanges of the gel into pure aprotic solvent. Read the article on silica aerogels under Learn > Flavors of Aerogel > Silica Aerogel to see how this works with hexamethyldisilazane. It’s the same process used to waterproof aerogels as well!

    At this point, the gel can be exchanged into something like pentane, although you would want to start with half whatever solvent and half pentane to start and work your way up to pentane to minimize potential cracking. The pentane is then evaporated SLOWLY, for example, by leaving the gel in a jar with a bit of pentane and then putting the lid on but not screwing it on tightly. Shrinkage that results can be partially reversed by heating the resulting dry material under vacuum (this is called the “spring-back method”).

    Subcritical drying was pioneered by C. Jeffrey Brinker (who we hope to get for an upcoming podcast on Aerogel.org) and is used commercially by Cabot Corp. in the production of their NanogelTM granules.

    Disadvantages of subcritical drying include additional, reasonably toxic chemical substances, additional diffusion-controlled processes, and limitation on attainable monolith size. Subcritical drying tends to result in ~15% volume shrinkage (as opposed to <5% for supercritical drying). Materials made by subcritical drying, while still aerogels, are sometimes referred to as “ambigels”, short for “ambiently-dried gels”.

    Hopes this helps. We’ll dig out some good references and post links to them on the upcoming article too.

  235. Alexandre Martins says:

    Dear Sirs,
    I need urgently a list with names of Aerogel Producers in Europe for my Bachelor.
    I kann not find in Internet further informations. Could you help me?
    Thanks a lot.

  236. MOHIT says:

    Hi
    I want to prepare aerogels using subcritical drying.
    Can you please tell me the process and mechanism

  237. Kenneth Lerman says:

    Tom,

    Google: space shuttle tiles

    See: http://helios.augustana.edu/astronomy/space-shuttle-tiles.html
    Also: http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system

    The short answer is NO. They are not aerogels. The long answer is that they are made from similar stuff.

    Ken

  238. tom macfarlane says:

    hi all,

    i am 16 and starting 6 form and my physics teacher has set me work on ‘what are space shuttle tiles made of?’ I have looked about and i have got the idea that space shuttle tiles are made of aerogel. I am not 100% sure i am correct though this is why i want to ask if aerogel is used in making space shuttle tiles?

    thank you
    tom macfarlane

  239. Szymon Bartus says:

    Hello,

    1. I’ve found in one scientific paper that there is a possibility to make “cryogels”. They are wet gels dryed by freeze drying:
    http://en.wikipedia.org/wiki/Freeze_drying
    There is also written that silica aerogels made that way were macroporous, non-transparent and non-monolithic. Can you say something more about cryogels? Can someone mention them in the section “science of aerogel”?
    Why is this drying method so destructive to the gel stucture? If it damages gel then why is it used to prepare biological specimens (I think it’s called lyophilisation)?

    2. What will happen if I exchange ethanol into liquid CO2 in my dryer and then slowly depressurize the chamber so that CO2 will slowly “boil away”? (without any heating) How would this work in comparison to supercritical drying?

    3. What can you say about performing ethanol or methanol supercritical drying? All you need is to put the gel inside solvent-filled mould, heat it to about 300C (and the pressure will rise too) and slowly depressurize the chamber while being heated. Obtaining 300C at home or school is hardo, however.

    4. In the papers I browsed, the heating/cooling rates and pressurisation/depressurisation rates in lab-grade manuclaves were very low. In my manuclave I can onyl pressurise my gel instantly (ball valve), heat it fastly (heat gun) and I’m not sure if my needle valve is precise enough to set the depressurization to, say, 7bar/h. How these affect properties of aerogels?
    I think the depressurisation rate is the most important since the gel structure might collapse.

    Regards,
    Szymon B

  240. Stephen Steiner says:

    Hi Joe from Neutronics,

    So Sterno is this canned gel stuff you can burn for cooking food in the field. You can make Sterno by mixing aqueous calcium acetate with ethanol, which then just sets up into a gel. Unfortunately, subsequent solvent processing of this stuff tends to cause it to fall apart. That is about as close to making a calcium hydroxide gel I know of.

    Ken Johnson reports on
    http://www.madsci.org/posts/archives/may98/896138398.Ch.r.html:

    Sterno is gelled ethanol and is made from a saturated solution of calcium
    acetate in water (dissolve 200+ g Ca(OAc)2 in 600 mL H2O)

    Mix 40 mL 95% ethanol with 10 mL of above solution and stir. The mixture will
    solidify.

    The deal with the alkali metal oxides and alkaline earth metal oxides is that since these metals only make one and two bonds respectively, and the bonds tend to be ionic and not covalent, you can’t really get a network of bridging metal-oxygen-metal bonds to form the stable nanostructure for making a gel. In principle if you could, the surfaces of these gels would be terminated with hydroxyl groups and you would have your very high surface area hydroxide materials.

    The other thing about all of these hydroxides is that they are remarkably hygroscopic, which means they love to soak up water from the air. Nano-fy that and they will suck water out of the air real fast and probably become caustic mush.

    Your best chance to use an aerogel architecture to make the material you’re thinking of would be to try synthesizing a low-density silica gel, solvent exchanging the gel into a concentrated aqueous solution of the salts in the concentrations you want, then performing a solvent exchange into a polar organic in which the salts are definitely not soluble, and finally solvent exchanging into liquid CO2, which they most likely won’t be soluble in. You could then supercritically dry the gel and you would be left with a metal hydroxide-doped silica aerogel which would exhibit an efficient but “time-delayed” consumption of the hydroxide thanks to slow diffusion of gas through the nanoporosity of the aerogel.

    One thing you would need to look out for is that CO2 will react with alkali metal hydroxides to form a bicarbonate salt under certain conditions (the opposite of reacting baking soda with vinegar) so being surrounded by liquid or supercritical CO2 might interfere with the target chemistry of your nanocomposite. You could potentially do high-temperature supercritical drying from some carefully-picked organic solvent that would not dissolve out the hydroxides at supercritical conditions, but you’d probably need to do some trial and error to figure out how that would all work!

  241. Stephen Steiner says:

    Hi Ken,

    Regarding the manuclave design, you need to use gravity to help flush the liquids out of the vessel properly, including the liquid CO2. if you try to remove it by using a valve above the liquid line, you will cause the liquid to boil and could damage the gels.

    The objective isn’t so much to slowly displace alcohol from the vessel as it is to be able to flush liquid through, replace it with a volume of liquid CO2, and then let the gels soak in stationary liquid CO2 for several hours to allow the alcohol trapped in the tortuous nanoporous network of the gels to work its way out by diffusion. Repeat.

    You are right–I have not yet posted the article on how to operate the supercritical dryer yet. Gulp. Sorry, will get on that this week!

    Finally regarding burst discs you can totally use an 1800 psi burst disc instead of a pop-safety valve. No problem there. Just sucks that you can’t reuse it. But honestly I don’t think I’ve ever had a vessel go to 1800 psi (well, maybe once or twice…) but you shouldn’t need to get above 1400 psi in any of your processing.

  242. Kenneth Lerman says:

    Do you know if anyone is using a burst disk instead of a pressure relief valve in the manuclave design? I’ve found 1800 psi burst disks intended for CO2 service (used by the paint ball people) for under five dollars. (My initial searches for rupture disk and frangible disk lead me to the high priced versions.)

    Would you anticipate any problems using an 1800 psi disk?

    Ken

  243. Kenneth Lerman says:

    Joseph A Sosnowski:

    Are you thinking of using it as a CO2 absorber for, say, an anesthesia machine, a submarine, or a diver?

    It would be excellent if you could do that. I would think that a very porous “solid” would expose much more surface area than the course granules that are currently used. One problem might be that it could have too high a resistance to flow.

    Ken

  244. I am very intrigued with the entire Sol-Gel process and impressed at the progress that has been made since I first began following the Aerogel phenomena over 20 years ago. Our company, Neutronics Inc. is interested in the possibility of having Sol-Gels and then either aerogels, uniform spheres of higher density or very dense spheres being made from 95% Calcium Hydroxide, 2.5% Sodium Hydroxide and 2.5% Potassium Hydroxide mixtures. Is it possible to devise a recipe to accomplish any of these end products from this initial formulation?

    Thanks,

    Joe Sosnowski, CEO

  245. Kenneth Lerman says:

    In looking at the drawing of your manuclave and I see three “ports”. Two have ball valves, while the third has a needle valve. I would have thought that the CO2 supply would be connected to the bottom one and that the needle valve would be the outlet.

    The drawing showing how to connect the CO2 tank shows the tank connected to a horizontal port. That seems to be counter intuitive if one wanted to slowly flow the CO2 while displacing the alcohol or acetone solvent.

    I might have missed it, but I didn’t see clear directions on how to actually do the supercritical drying.

    Regards,

    Ken

  246. Kenneth Lerman says:

    Thanks for your comments. An interesting question is how long the o-ring seals on a hydraulic cylinder will last in the presence of our particular GXLs and SCFs. I guess I would just have to try it and see.

    Ken

  247. Stephen Steiner says:

    Hi Ken,

    Just a few notes about your comment:

    1 — Liquid carbon dioxide is normally stored in steel (not stainless) cylinders.
    Yes, you’re right. Carbon steel is compatible with liquid CO2,

    2 — Acetylene gas is normally distributed dissolved in acetone in steel (not stainless) cylinders.
    Yes, agreed.

    3 — Rail tank cars used to ship ethanol are made of carbon steel.
    Again agreed, ethanol is compatible with carbon steel.

    I conclude that none of these will adversely affect steel. Of course, that doesn’t mean that a combination of them is safe to have in a steel vessel under pressure.

    Honestly carbon steel will probably be fine for most of what you’ll be doing as long as you stay within the bounds of using only alcohols for solvent exchange, however officially stainless steel is the preferred material for supercritical CO2 service and that is what we stand behind here on Aerogel.org. Just keep in mind that gas-expanded liquids (GXLs) and supercritical fluids (SCFs) have the uncanny ability to dissolve and react with stuff that their components at normal conditions would not react with. For example, supercritical water eats through steel, and supercritical carbon dioxide can dissolve fluorinated hydrocarbons.

    Supercritical drying from CO2 can be done safely with readily available parts but if you’re going to spend the money to build a supercritical dryer my advice is to be conservative with your design and to use materials and components you are confident will be okay, can be welded if necessary, and are going to resist corrosion from the environment, especially after repeated heating and cooling cycles, which can accelerate corrosion damage.

  248. Stephen Steiner says:

    Hi Ken,

    Interesting idea–how would you access the inside (I guess you’ll be taking this hydraulic cylinder apart)? If you have a CNC milling machine, though, there’s nothing wrong with making your own vessel out of a block of stainless steel, although cylindrical shapes are generally strongest for pressure vessels of this type and so a lathe might be more appropriate.

    Also liquid CO2 doesn’t really “squirt” out of a leaky seal–it immediately boils upon escape and so you get more of a white gas plus dry ice spray.

  249. Kenneth Lerman says:

    Some more notes:

    1 — Liquid carbon dioxide is normally stored in steel (not stainless) cylinders.

    2 — Acetylene gas is normally distributed dissolved in acetone in steel (not stainless) cylinders.

    3 — Rail tank cars used to ship ethanol are made of carbon steel.

    I conclude that none of these will adversely affect steel. Of course, that doesn’t mean that a combination of them is safe to have in a steel vessel under pressure.

    Ken

  250. Kenneth Lerman says:

    Thank you for your quick response. In researching (I use the term loosely) alternatives, I took a look at hydraulic cylinders. Tie rod cylinders are made with interchangeable parts and have operational pressures of up to 3000 psi. Replacement parts are readily available, so one could use two butts with a cylinder. That would give a closed chamber with ports at each end.

    For $90 I can get one with a 4 inch diameter and 8 inch stroke.
    http://www.agrisupply.com/-asae-red-hydraulic-cylinder-/p/46896/cn/2500001/.

    Since the structural strength comes from the external tie rods, I suspect that this would be pretty safe. Of course, there is the possibility that the cylinder itself would be weakened by chemical reaction with the contents. It would be reasonable to measure this after each run. It appears that stainless cylinders are available if that became a problem.

    I wouldn’t expect failure of the o-ring seals to be catastrophic, but I would probably add an external shield to that if liquid CO2 came squirting out of a seal, it wouldn’t impinge on anything sensitive — like myself or another person.

    Ken

  251. Stephen Steiner says:

    Hey Szymon,

    I know you’re located in Poland but part number 3956K17 on Mcmaster-Carr is a suitable thermometer–most NPT bimetal thermometers are effectively a “pipe plug” from a pressure standpoint and thus can withstand the pressures you’ll encounter during supercritical drying. I’ve never had a problem with an NPT bimetal thermometer. As long as it’s made of stainless steel 304 or stainless steel 316 you should be fine.

  252. Stephen Steiner says:

    Hi Kenneth,

    In general using these alloys for a supercritical dryer is not a good idea.

    Carbon steel oxidizes over time, which can cause damage to threads and complicate sealing. Aluminum is difficult to weld and, because aluminum yields at lower stresses than steel, for elevated pressure service aluminum requires thicker walls than steels. Above all, gas-expanded liquids which form from mixing of organic solvents with near-critical carbon dioxide (for example, acetone/CO2) can be unexpectedly corrosive and, as such, stainless steel is recommended.

    If you are going to attempt machining your own vessel out of a solid block of whatever alloy PLEASE only do so if you know:

    • How to calculate the necessary wall thicknesses for the pressure range you need, keeping in mind this value is highly dependent on part geometry
    • The necessary flange thicknesses and diameters for any o-rings seals used
    • The compatability of all materials you plan on using with liquid CO2 and organic solvents, including o-rings
    • Safety factors of 2 or greater are built-in to all parts

    I’d be happy to review any designs you might be thinking about in advance–post them to the web some place and then post another comment here–you can embed the URL to your images by clicking the “You can add images to your comment by clicking here” link below the comment box.

    Be safe!

  253. Kenneth Lerman says:

    Since I have a CNC milling machine, I’m thinking of making my own manuclave out of a machined block using o-rings for seals. Could you explain why materials such as carbon steel or aluminum are not suitable for this? Which chemicals that are used affect those materials adversely.

    Thanks,

    Ken

  254. Szymon Bartus says:

    Hello,

    > Regarding pressure, most bimetal thermometers with NPT connections are suited for the
    > pressures you’ll need.

    My experience is so far completely different – I found thermometers that don’t have rating or that have too low rating, but I haven’t found any rated at 2000PSI or above.
    If anyone knows any place where I can buy a bimetal thermometer with 1/2″ NPT thread, bottom connection and for 2000PSI or above, then please tell!

    AND: congratulations to Stephen Steiner for successfuly making nanotubes with Zirconia catalysts and being mentioned on the frontpage of the MIT:
    http://web.mit.edu/newsoffice/2009/nanotubes-0810.html (“bling bling” article)

    Regards,
    Szymon B

  255. Stephen Steiner says:

    Cody-

    Your idea of making a thermoelectric device with carbon aerogel is a good one, but a significant challenge! The key is figuring out how to pair the right materials in the right way and to figure out how to impose a temperature gradient across the nanostructured interface in a way that makes sense.

    One promising material for thermoelectric devices are the carbon nanotube aerogels developed by Bryning and others (see Bryning, Mateusz B.; Milkie, Daniel E.; Islam, Mohammad F.; Hough, Lawrence A.; Kikkawa, James M.; Yodh, Arjun G. Advanced Materials (2007), 19(5), 661-664). You can read all about carbon nanotube aerogels under Learn > Flavors of Aerogel > Nanotube Aerogels.

    The metal chalcogenide aerogels (sometimes called “chalcogels”) developed by Prof. Stephanie Brock at Wayne State University are very promising for generation of electricity in solar panels. Some of the materials she is working with can potentially emit four electrons per photon impacted, enough to split water into hydrogen and oxygen.

    All cool ideas–keep thinking about them! Hope this answers your question.

  256. Stephen Steiner says:

    Szymon-

    In deciding on a thermometer for your manuclave, you want the end of the stem to be touching the volume where the bulk of the CO2 will reside. So a stem of several inches is not uncommon. In my experience if the stem is in a nipple and not protruding into the volume with the CO2 your temperature readings will be very inaccurate.

    Regarding pressure, most bimetal thermometers with NPT connections are suited for the pressures you’ll need. Take a look at the ones on McMaster-Carr listed on the Parts and Schematics page for an idea of what you should get.

  257. Cody R says:

    This is so interesting.

    Is there a way to make electricity with the carbon aerogel? Can it be used as a “thermal electric generator” somehow?

    Cody

  258. Szymon Bartus says:

    Hello,

    I’m deciding for the thermometer right now.
    1. How far can the stem be from the main chamber? Is it okay if the stem is several centimeters above the chamber? (but still in the nipple through which CO2 flows to chamber)
    2. I haven’t found thermomether with adeqate pressure rating and one vendor suggested using a thermowell. Will using a thermowell affect the temperature measurement?

    Regards,
    Szymon

  259. Stephen Steiner says:

    Hey Szymon,

    To answer your questions:
    1. For the big pipe plug you use for the door I would go for 4-6 and for smaller components that you don’t need to disassemble typically you might only need 2-3.
    2. It’s worth investing in a bigger adjustable crescent wrench (no teeth) if you can, otherwise a pipe wrench with teeth is okay–you might chew up your parts a little bit but it probably won’t matter too much if you’re careful.
    3. For NPT components that don’t need to be disassembled, I would tighten them as tight as you can get them with a long wrench (to maximize torque) and a vice such that they end up in the right orientation. So, for example, for valves, you will want them as tight as you can get them so that their handle faces an accessible angle. For the door you should tighten it as tight as you can get it with a wrench and your body weight. Obviously don’t get the parts stuck or force them on.

  260. Szymon Bartus says:

    Hello again,

    It’s awesome to hear this about Zero-G team.

    I’ve just bought some Teflon tape and tried mounting my manuclave parts.
    1. I have 0.075mm thick tape and 1/4″, 1/2″ and 1″ NPT threads. How many colis of tape should I put on them? Earlier, you suggested 4-6 – will this work in my case?
    2. My adjustible wrenches are too small for 1″ bushings and plug. Can I normally use my plumber wrench (which looks like skewed pliers)? I tried it today and it worked very well (without making scratches), but I just want to make sure.
    3. How far should I turn the fitting/pipe/valve? Should I stop at the moment when the needed torque increases significantly but it’s still possible to turn further?

    Regards,
    Szymon

  261. Stephen Steiner says:

    Hey Szymon,

    We’re excited to hear how your manuclave turns out! I’m sure when you get in to MIT the Zero-G Team will be happy to have a new member!

    Honestly the brass quickconnects you mention should be fine. The most important thing is that they meet and exceed the pressure ratings needed for the vessel within the temperature range you’ll be using. Since you are doing CO2 drying, I wouldn’t worry about the higher temperatures on the manuclave side derating your connectors since the max temperature the body will get is about 60 deg C, which is no big deal for this pressure rating, and near the connector it won’t even be 60 deg C. Actually my manuclaves have brass quickconnects too. Just be careful with brass not to overtighten or to force the connector onto a thread if it’s not going easily because you can strip the threads off and, although it will probably seal if you force it on that one time, if you ever have to take it off again you won’t be able to get it back on and seal again. So take your time, start over if you need to, and use Teflon tape.

  262. Szymon Bartus says:

    Hello everyone.

    I’m Szymon Bartus. I live in Poland.

    I have been fascinated by silica aerogel for a long time. I’m interested in building/flying RC aircraft, so when I heard from Stephen Steiner that he will upload some information about making aerogels as a DIY project, I was thrilled.
    I plan to build my own manuclave, to make various types of gels and experiment with them.
    Making aerogels would be not only fun workshop project for me, but also my aerogel experiments are going to be the topic of 4000-long essay required by my high school.
    After I learn to make gels and dry them I would love (maybe during my undergraduate studies?) to help some aerogel research team, if it’s possible. I plan to apply to the MIT, so I wonder if I can help MIT Zero-G team during my studies? Maybe as an UROP?

    I have entire manuclave exept quickconnects, hose (it is being shipped) and thermometer.

    I’m just before ordering my quickconnects. And here is my question… I will probably order 1/4 NPT quickconnects from Swagelok company.

    From their website:

    Stainless steel connectors:
    Pressure Rating Coupled at Max Temp: 100 PSIG @ 400 °F /6.8 BAR @ 204 °C
    Pressure Rating Coupled at Room Temp: 6000 PSIG @ 70 °F /413 BAR @ 21 °C

    Brass connectors:
    Pressure Rating Coupled at Max Temp: 100 PSIG @ 250 °F /6.8 BAR @ 121 °C
    Pressure Rating Coupled at Room Temp: 4000 PSIG @ 70 °F /275 BAR @ 21 °C

    Which should I buy? Two pairs of stainless steel would be expensive. On the other hand I don’t want to get shoot by a piece of brass during dryer operation! Maybe I should order one pair of steel and one pair of brass, to have steel on the side of hose that connects to manuclave? (because there is higher temperature on that side)

    Regards,
    Szymon

  263. Stephen Steiner says:

    Hi Evan,

    The Malaysian scientist you have heard about is Dr. Halimaton Hamdan who is a member of the faculty in the Department of Chemistry at the Universiti Teknologi in Johor, Malaysia. Her process involves the following:
    1) Rice husks are burned on a hot plate in air to give white silica ash.
    2) The silica ash is dissolved in sodium hydroxide to give a ratio of NaOH to SiO2 of 1:3.3.
    3) Concentrated sulfuric acid is added to the solution to form a gel (see Learn > Flavors of Aerogel > Silica Aerogel and read about the waterglass method).
    4) The gel is aged up to 40 days and solvent exchanged into methanol or ethanol.
    5) The gel is supercritically dried from carbon dioxide.

    The properties of these silica aerogels are comparable to waterglass-derived silica aerogels. They have densities ranging from 0.03 g/cm3 to 0.06 g/cm3, they are not terribly clear (pretty foggy), exhibit surface areas between 700 to 900 m2/g, and have a thermal conductivity of about 0.1 W m-1 K-1–about five times higher than a high-quality aerogel or Aspen Aerogels’ blankets. Their strength is weaker than alkoxide-derived silica aerogels but pretty close (they are fragile).

    Regarding costs, I disagree with the numbers reported. Frankly the cost of the alkoxide is not the major issue with scale production of aerogels, although certainly a cheap source of silica is always helpful. Since these materials still need to be supercritically dried and they are not as high quality as alkoxide-derived silica aerogels, the cost savings from the silica precursor may be irrelevant. That said, it is a reasonably sustainable technology and may one day be useful for preparing high-quality aerogels suitable for large-scale production.

    Cabot and Aspen are the big manufacturers today. Cabot sells to the public. If you see people selling big buckets of aerogel granules on the web they likely came from Cabot. These are ambiently-dried silica aerogel granules for daylighting applications with good insulating properties. United Nuclear, Marketech International, and newcomer Buyaerogel.com are sources for monolithic aerogels as well, but none of these sources sell on a scale that you could insulate a building with.

  264. Evan McCrann says:

    I read somewhere that Malaysian Scientists have created a form of aerogel out of rice that has reduced the costs of production by 80%. Do you have any information as to the properties such as strength, r-values, how much light is refracted in comparison to silica areogels?

    Also, besides Cabot, do you know are there any publicly traded companies that are researching aerogels applications and marketability?

    Finally, besides Aspen Aerogels who else sells Aerogels to the public?

  265. Stephen Steiner says:

    Dear Ken,

    Thanks for the props, we’re glad you found Aerogel.org useful!

    Silica aerogels, as you pointed out, are mostly transparent and, as a result, infrared radiation does pass through them, although it scatters somewhat like other visible wavelengths. For this reason, high-temperature aerogel insulation like Aspen Aerogel’s Pyrogel composite blankets are doped with an opacifying agent like carbon black. In the case of a blowtorch the majority of the heat is not being expressed radiatively. Although I suppose if you left it there long enough you might get the crayons to melt…

    Hope this helps.

  266. Ken Costello says:

    Dir Sirs,

    I enjoyed looking over your website and found the content very interesting and educational. I teach chemistry at a community college in Phoenix, Arizona and will undoubtedly direct students to this website. I do have a question about the thermal insulating qualities of aerogels. I can see why they can block conduction of heat, but I don’t see how they are blocking the infrared radiation. Take silica aerogel for example. The pictures show a blow torch hitting the bottom of an aerogel with crayons on top about 5 millimeters away. It seems that the infrared radiation would pass through the aerogel and melt the crayons. Air in the aerogel allows infrared light to pass through and I would guess the transparent silica-like make up of silica aerogel would also let infrared light to pass through. Do you have some insight as to why infrared radiation doesn’t go through aerogels?

    Thank you,
    Ken Costello

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