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Aerogel is an ultralight material with a very low density and little thermal conductivity. It is fairly translucent, yet has a rough texture when touched. Traditionally, aerogel is made through the process of supercritical drying, so you'll need to build your own supercritical dryer at home if you want to prepare the material on your own. There are versions that can be made without a supercritical dryer, but they tend to be more sensitive and more dense. Keep reading for information about making both types.
Steps
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Obtain a 20 lb (9 kg) cylinder of carbon dioxide. Make sure that you get a siphon container, with a tube that extends from the bottom to the outside of the cylinder. [1] X Research source
- This type of cylinder should allow you to get liquid carbon dioxide out of the container rather than merely gas.
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Take a look at the visual schematics. Instructions on how to assemble the supercritical dryer will be included here, but it is highly recommended that you take a look at the actual visual schematics provided by the aerogel website. [2] X Research source
- These schematics can be viewed here: http://www.aerogel.org/wp-content/uploads/2009/02/manuclave-design2.jpg
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Attach stainless steel 316 or 304 pipe fittings and valves to a non-welding stainless steel pipe tee body. This pipe tee body should be 3/4 inch (1.9 cm).
- To the two sides of the tee body, you should attach the pipe plugs or door.
- You could install a sight window on one side instead of a second pipe plug, if desired.
- At the bottom of the tee body, you should connect a ball valve using a 1/4 inch (6.35 mm) reduction bushing.
- To the top of the body, screw on, in order: 1/2 inch (1.2 cm) reduction bushing, 1/2 inch (1.2 cm) nipple fitting, and 1/2 inch (1.2 cm) cross.
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Finish assembling the top of the machine. The remainder of your valves and gauges will connect to this second cross pipe.
- Connect a Bimetal thermometer to the top of the cross pipe.
- To the left side, attach 1/4 inch by 1/2 inch (6.35 mm to 1.2 cm) nipple fitting. To date, attach a ball valve.
- To the right side, attach another 1/4 inch by 1/2 inch (6.35 mm to 1.2 cm) nipple fitting. To date, attach a 1/4 inch (6.35 mm) cross pipe with a pressure gauge fixed to the top and a pop-safety valve fixed to the bottom.
- On the open side arm of the smaller cross pipe, attach another 1/4 inch (6.35 mm) nipple fitting and a needle valve.
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Know what you can and cannot use. Stainless steel is preferable since it is clean and strong.
- You can have gauges with brass threads and valves with carbon steel bodies.
- Do not use pipe fittings made of brass or carbon steels, and do not use any part rated for lower than 2000 psi.
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Connect the carbon dioxide tank to the supercritical dryer. You will need to securely connect the tank to the dryer so that the liquid carbon dioxide can easily flow into the dryer.
- It is recommended that you look at the official schematics, found here: http://www.aerogel.org/wp-content/uploads/2009/02/gastank-1.jpg
- Connect to the carbon dioxide tank, in this order: CGA320 male thread, Teflon gasket, CGA inlet nipple, CGA inlet nut, 1/4 inch (6.35 mm) NPT female quick disconnect socket, 1/4 inch (6.35 mm) NPT male quick-disconnect plug, and a braided high-pressure hose, rigid 1/4 inch (6.35 mm) NPT, with female fittings.
- To the other side of the hose, attach in this order: 1/4 inch (6.35 mm) NPT male quick disconnect plug and 1/4 inch (6.35 mm) NPT male quick disconnect socket.
- Attach the final socket to the intake ball valve of the manuclave or dryer. With this, you should be ready to go. [3] X Research source
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Dilute concentrated ammonium hydroxide. Combine 4.86 g or 5.4 ml concentrated ammonium hydroxide with 1000 ml of water in a glass or plastic bottle. [4] X Research source
- This bottle should be labeled as "ammonium hydroxide stock solution." You can store it sealed and at room temperature to be reused at a later date.
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Mix the TMOS and methanol. Combine 10.2 g or 10 ml tetramethyl orthosilicate (TMOS) with 7.82 g or 10 ml methanol in a glass beaker. Stir until mixed.
- This should be labeled as "alkoxide solution" or "solution A."
- Note that TMOS can be very difficult to purchase since many chemical suppliers are hesitant to sell chemicals to individuals. [5] X Research source Even so, you must make sure that you obtain the TMOS from a reliable source so that there are no dangerous impurities in it.
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Mix the ammonium hydroxide solution with methanol. Combine 5 g or 5 ml of the stock solution previously prepared with 7.92 g or 10 ml of methanol in another glass beaker. Stir until well mixed.
- Label this beaker as "catalyst solution" or "solution B."
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Pour the catalyst solution into the alkoxide solution. Carefully pour the catalyst (solution B) into the alkoxide (solution A) and stir with a glass stirring rod until completely combined.
- Note that the resulting solution is called the "soul."
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Transfer the sol into molds. Line your molds with silicone-based baking paper before pouring the liquid sol into them. Let the sol sit until gel forms.
- This can take anywhere from 15 minutes to 1 hour.
- You could also pour the sol into syringes with no needles or tops. That way, you can remove the finished gel by pushing it out with the plunger.
- TMOS is the source of the silica in this method. The water allows the TMOS to polymerize, and the methanol lets both the water and TMOS enter into the same phase so that they can react. The ammonium hydroxide lets the reaction go faster.
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Let the gel age. After the gel sets, place it under methanol and let it age for a full 24 hours, at minimum.
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Diffuse the water out. Change the methanol out for fresh methanol, 200-proof ethanol, or acetone at least four times over the course of a week.
- This process draws the water out, leaving you with a pure methanol gel.
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Dry the gel in your supercritical dryer. Place the gel in the supercritical dryer's compartment and heat the carbon dioxide through its critical point, 31.1 °C (88.0 °F) and 72.9 bars, to about 45 °C (113 °F) at a pressure of about 100 bars.
- Super critical drying causes the methanol to get drawn out of the gel.
- Depressurize the machine at a rate of about 7 bar h-1.
- When done, you should be left with a finished silica aerogel.
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Prepare the aerogel as usual. Prepare the silica aerogel as instructed previously, combining the same chemical ingredients to produce the "sol," the liquid state of the gel.
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Purify the gel through solvent exchange as usual. Cover it in ethanol or acetone, changing the solution out four times over the course of a week.
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Prepare a hexane and ethanol solution. Mix one part hexane with three parts ethanol until you get a volume that is at least five times as great as the volume of gel currently being processed. [6] X Research source
- Note that you could use acetone instead of ethanol, if desired.
- As an example, if you are processing 20 ml of aerogel, you should prepare a solution of 25 ml hexane and 75 ml acetone or ethanol.
- Label this as your 25-75 mixture.
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Prepare two additional solutions of hexane and ethanol. For the second, use equal amounts of both. For the third, use three parts hexane to on part ethanol.
- As before, acetone can be used instead of ethanol.
- Label the second solution as your 50-50 mixture and the third as your 75-25 mixture.
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Soak the gel in all three mixtures. Let the gel soak in your 25-75 mixture for 12 to 48 hours.
- Afterward, let it soak in your 50-50 mixture for the same amount of time, finishing up by letting it soak in the 75-25 mixture for another 12 to 48 hours.
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Let the gel soak in hexane. Change out the pure hexane three times over the course of 24 to 72 hours.
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Prepare a trimethylsilyl chloride solution. Add TMCS to hexane so that 6 percent of the solution's weight is due to TMCS.
- Make enough so that you have roughly 15 times as much solution as you have gel.
- Label this as your TMCS solution.
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Soak the aerogel in the TMCS solution. Place the gel in a sealed, chemical-resistant container with a wide mouth. Add enough TMCS solution so that you have 5 to 10 times the volume of the gel. Seal the container.
- Lubricate the lid with silicone vacuum grease if using glass. Otherwise, the lid might get stuck.
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Heat and cool the container. Heat the container for 12 to 24 hours at a steady 60 °C (140 °F), using a hot plate or oven. Let it cool to room temperature before exchanging the TMCS solution with fresh solution.
- Repeat this procedure twice more.
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Let the cooled gel soak in pure hexane. Swap out the TMCS solution for pure hexane and allow the aerogel to soak in it for another 12 to 24 hours.
- Over the course of 24 to 72 hours, change out the hexane in the container for fresh hexane at least twice.
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Subcritically dry the gel. Place the gel in a jar with a little hexane and secure the lid only halfway. Let the gel dry out for 1 to 2 days in this manner.
- At the conclusion of this step, your aerogel should be complete.
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Community Q&A
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QuestionIs it possible to make Aerogel in a day?Community AnswerNo. It takes at least a day to set up the experiments, plus several days for the material to settle.
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QuestionI've heard you can make areogel with graphene, and was wondering how much the strength of the silicon is affected after this process?Community AnswerThe strength of the silicon is increased by almost double. I own a facility that tests the strength of these substances. The gel can withstand a .50 caliber round at 500-foot distance.
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QuestionHow can I make the solution B and catalyst for materials other than TMOS to produce different aerogels?soniya kaleCommunity AnswerMix 5.0 g (5.0 mL) of ammonium hydroxide stock solution with 7.92 g (10.0 mL) of methanol in another beaker. This mixture is the catalyst solution or solution B.
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Warnings
- Ask someone to check in on you as you work in case something goes wrong.Thanks
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Thanks
- Protect your eyes by wearing safety goggles. Wear long sleeves and closed-toe shoes as you work.Thanks
- Do not substitute low-rated parts for properly-rated parts.Thanks
- Take your time. Do not rush the process, since doing so can cause you to make dangerous errors.Thanks
- Make sure that all seals are secure and avoid exposing tape seals to organic solvents. Doing so can help prevent a leakage of carbon dioxide.Thanks
- Also make sure that the pressure gauges are changed after every 30 to 50 runs, and tighten the valve handles well to prevent them from slipping open.Thanks
- TMOS is a hazardous material and can harm your lungs and eyes. Safety goggles and a chemical fume hood should prevent the vapors from harming you, though.Thanks
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Things You'll Need
- Plastic or rubber gloves
- Safety goggles
- Long sleeves
- Closed-toe shoes
- Apron
Supercritical Dryer
- 2 medium-pressure ball valve, 1/4 inch (6.35 mm) NPT, stainless steel 316
- 2 hex nipple, 1/2 inch (1.2 cm) reduced to 1/4 inch (6.35 mm) NPT, 1-11/16″ length, stainless steel 316
- Hex nipple, 1/2 inch (1.2 cm) NPT
- 2 hex nipples, 1/4 inch (6.35 mm) NPT
- Cross pipe, 1/2 inch (1.2 cm) NPT, stainless steel 316
- Cross pipe, 1/4 inch (6.35 mm) NPT, stainless steel 316
- Medium pressure, needle valve, female x female 1/4 inch (6.35 mm) NPT, stainless steel 316
- Brass ASME pop-safety valve, with pull-ring for testing, discharges to atmosphere, 1/4 inch (6.35 mm) NPT male
- Bimetal thermometer, 1/2 inch (1.2 cm) NPT male, stainless steel 304, dry dial
- Pressure gauge, 0-3000 psi/0-20000 kPa, 1/4 inch (6.35 mm) NPT bottom connection
- Heat gun or hair dryer
- Pipe thread sealant tape
- Crescent wrench
- 2 lb (9 kg) tank carbon dioxide, with a siphon tube and CGA320 connector
Silica Aerogel
- Tetramethoxysilane (tetramethyl orthosilicate)
- Methanol
- Deionized water
- Ammonium hydroxide, 28-30 wt % in water
- Ethanol (optional)
- Acetone (optional)
Alternate Subcritically Dried Silica Aerogel
- Pre-prepared silica gel
- 200-proof ethanol or acetone
- Hexane
- Trimethylsilyl chloride (TMCS)
- Chemical-resistant wide-mouth jar or bottle
- Oven or hotplate
- Chemical fume hood
- PentateuchPentateuch
- Hexamethyldisilazane (HMDS)
References
About This Article
Article Summary
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In order to make aerogel, mix TMOS and methanol, and combine with diluted ammonium hydroxide concentrate. Pour the solution into the alkoxide solution, then transfer the mixture into the molds. Dry the gel in a supercritical dryer, or alternatively, soak the gel in a mixture of hexane and ethanol, then in pure hexane. Add trimethylsilyl chloride, heat and cool the aerogel inside the container, then dry the aerogel in a jar with the lid secured only halfway. For step by step instructions on how to make aerogel, including how to construct your own supercritical dryer, keep reading.
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