Mar. 03, 2026
Chemicals
Aerogel, a material created on a bet between two scientists in the late s, may be the most unique substance on Earth. It's the lightest solid in existence -- Guinness World Records even said so -- but it can support 500 to 4,000 times its own weight [source: NASA JPL, Guiness; Steiner, Zero-Gravity]. A cubic inch of aerogel could be spread out to cover an entire football field. It's breathable and fireproof, and it absorbs both oil and water.
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Aerogel is also amazingly strong, considering its weight. Aerogel insulation can be a great electrical conductor, yet when made from different materials, it can also be an effective thermal insulator [source: Steiner, Zero-Gravity].
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In this article, we'll explore what makes aerogels unique, from their discovery in California in the late s, to their trip to collect space dust in . We'll also see what the future holds for aerogels and whether they can be made more cost-effective for the general public. Finally, we'll show you how to make your own aerogel -- surprisingly, it can be done!
Having just read so many rare attributes, you must be wondering: Why doesn't aerogel insulation have the A-list name recognition it deserves? Unfortunately, producing such a unique product takes an extraordinary amount of time and money, in part because only a very small amount of aerogel is made in each batch.
Even though producing more aerogel at a time would bring its price down, the process and materials alone come with a high price tag of about $1.00 per cubic centimeter. At about $23,000 per pound, aerogel is currently more expensive than gold [source: NASA JPL, FAQs]!
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Such a valuable product would seem to belong next to diamonds and pearls in an heiress's jewelry box. But aerogel is more likely to be found insulating a rocket or thickening paint than adorning wealthy socialites. While aerogels may not be as glamorous as gold, they perform their tasks without peer.
Read on to learn more about how the world's lowest density solid first made an appearance and how this adaptable substance is made.
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The legend of the aerogel is shrouded in mystery. What we do know is that in the late s, American chemistry professor Samuel Kistler had a bet with colleague Charles Learned. Kistler believed what made an object a gel was not its liquid properties but its structure: specifically, its network of tiny, microscopic pores known as nanopores. Trying to prove this by simply evaporating the liquid led to the gel deflating like a soufflé. So, the object of the game was to be the first to replace the liquid in "jellies" with gas, but without causing damage to the structure [source: Steiner, Zero Gravity].
After much trial and error, Kistler was the first to successfully replace the gel's liquid with a gas, creating a substance that was structurally a gel, but without liquid. By he published his findings in an article called "Coherent Expanded Aerogels and Jellies" in the scientific journal Nature [source: Ayers, Pioneer].
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Aerogel begins as a gel, called alcogel. Alcogel is an amorphous silica gel with alcohol inside its pores. Simply evaporating the alcohol out of the silica gel structure would cause the structure to contract, much like a wet sponge will deform when left on a counter to dry. Instead of relying just on evaporation, the gel has to be supercritically dried. Here's what it takes:
Supercritical drying is how the liquid "alco" part of the alcogel turns into a gas within the silica's nanopores without the structure collapsing. The alcogel with its alcohol removed is now called aerogel, as the alcohol has been replaced by air. With only 50 to 99 percent of the original material's volume, aerogel is a porous structure that is light, flexible, and useful [source: Steiner, Zero Gravity].
Continue to the next page to learn about the most common types of aerogels in use today.
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The three most common types of aerogels are silica, carbon and metal oxides, but it's silica that is most often used experimentally and in practical applications. When people talk about aerogels, chances are they're talking about the silica type [source: Aerogel.org, Silica]. Silica is not to be confused with silicon, which is a semiconductor used in microchips. Silica is a glassy material often used for insulation.
Unlike the smoky-blue silica aerogels, carbon-based ones are black and feel like charcoal to the touch. What they lack in looks, they make up for in high surface area and electrically conductive capabilities. These properties make carbon aerogels useful for supercapacitors, fuel cells, and desalination systems [source: Aerogel.org, Organic].
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Metal oxide aerogels are made from metal oxides and are used as catalysts for chemical transformations. They are also used in the production of explosives and carbon nanotubes, and these aerogels can even be magnetic. What sets metal oxide aerogels such as iron oxide and chromia apart from their more common silica cousins is their range of startlingly bright colors. When made into an aerogel, iron oxide lends an aerogel in its trademark rust color. Chromia aerogels appear deep green or blue. Each type of metal oxide results in an aerogel of a slightly different color. [source: Aerogel.org, Metal].
The most common type, silica aerogels are blue for the same reason the sky is blue. The blue color occurs when white light encounters the aerogel's silica molecules, which are larger than the wavelengths of light. The aerogel scatters, or reflects, the shorter wavelengths of light more easily than the longer ones. Because blue and violet light have the shortest wavelengths, they scatter more than other colors of the visible spectrum. We see scattered wavelengths as color, and since our eyes are more sensitive to blue wavelengths, we never see the violet ones [source: Steiner, Zero-Gravity].
Read on to learn more about aerogels' applications in space.
Water vs. AlcoholAlcogels have their pores filled with alcohol, but what if you used water instead? In his first experiments, Kistler used hydrogels, which contained water. When drying, these gels behave much as Jell-O does. They break down into a gooey, messy blob because the liquid in the hydrogel evaporates too quickly for the substance to retain its shape. With each molecule that seeps out, others try to fill the gaps. This causes what's known as capillary stress within the pores of the gel, causing the entire structure to collapse [source: Hunt and Ayers, History].
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Aerogel's versatility has made it very important both on Earth and in space. It has fulfilled a variety of roles on several NASA missions, from insulating the Mars rovers' electrical equipment (as aerogel blankets) to capturing space dust from a speeding comet.
On the latter mission, in , NASA launched a spacecraft that traveled 4.8 billion kilometers (the equivalent of 6,000 trips to the moon) to reach comet Wild 2. Once there, the tennis-racket-shaped dust collector opened up and used its 260 aerogel cubes to capture the speedy particles of interstellar dust and preserve them in their natural state [source: NASA JPL, Aerogel].
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What's more, as particles bombarded the dust collector, they left trails within the collector's aerogel cubes while slowing to a stop. These trails enabled scientists to more easily find the tiny particles from space. Aerogel's durability allowed the dust collector to return from space intact with not a single aerogel tile missing. Scientists have been able to study the dust and crystals contained in the aerogel and await the insights they may bring [source: Bridges].
Next, we'll learn about some of aerogel's commercial applications.
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In their earliest days, aerogels were marketed as thickening agents and used in everything from makeup and paint to napalm. They were also used as cigarette filters and insulation for freezers. Monsanto was the first company to market aerogel's commercial applications. However, Kistler's supercritical drying method, though effective, was also dangerous, time-consuming and expensive. After 30 years of production, all these factors led Monsanto to discontinue its focus on aerogels in the s.
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Featured content:However, it wasn't the end of this thermal insulation. Not long after it was abandoned by Monsanto, scientists developed a process that made the production of aerogels less toxic by using a safer alkoxide compound. They also made it less dangerous by replacing supercritical alcohol with supercritical carbon dioxide in the drying process. These developments reduced the time spent drying the aerogels and reduced the hazardous and flammable nature of their production. Such advances made aerogel a bit more commercially viable again, and scientists grew intrigued by the product's possibilities. [source: Hunt and Ayers, History]
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As production was made less complicated and dangerous, its unique properties (including thermal conductivity) have made aerogel popular within a range of industries. Silicon manufacturers, homebuilding materials manufacturers and space agencies have all put aerogel to use. Its popularity has only been hindered by cost, though there is an increasingly successful push to create aerogels that are cost-efficient. In the meantime, aerogels can be found in a range of products:
[source: Aerogel.org, Modern History]
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Thanks to aerogel's unique structure, its use as an insulator is a no-brainer. The super-insulating air pockets with the aerogel's structure almost entirely counteract the three methods of heat transfer: convection, conduction and radiation [source: Cabot Corporation]. Even though aerogel is still quite expensive, the good news is that studies have shown that aerogel insulation used in wall framing and hard-to-insulate areas such as window flashing can save a homeowner up to $750 per year.
In addition to helping homeowners save money, aerogel insulation can significantly reduce your carbon footprint. [source: Aspen Aerogels, New Spaceloft]. Companies are racing to find a way to bring costs down, but for now, aerogels are more affordable for NASA than the general public. Still, aerogels are put to use by construction companies, power plants and refineries. Perhaps when it's more affordable, aerogel will achieve its overdue A-list status.
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From Earth to space, aerogels undoubtedly have a place in our future. Read on to learn about recent aerogel advancements and how you, too, can experiment with aerogel.
Although aerogel is expensive, researchers are still experimenting with ways to make it stronger, cheaper and less hazardous. For example, Professor Nicholas Leventis from the Missouri University of Science and Technology amazed the science world in with the announcement that he had developed a method for making non-brittle aerogels.
Leventis's aerogels, known as x-aerogels, are not only stronger; they're also more flexible, waterproof and impact resistant. The downside is that x-aerogel production requires more hazardous chemicals and takes more time; these chemicals also decrease its insulation ability [source: Aerogel.org, Strong]. Despite some negatives, x-aerogels have the following possible applications:
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[source: Leventis]
Additionally, aerogels could help with the push for more "green" technology. Carbon aerogel holds great potential for supercapacitors and fuel cells for energy-efficient automobiles. In fact, the energy storage capacity of carbon aerogel could bring about a slew of new technologies, but only if aerogel's production price becomes more affordable for large scale operations.
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The good news is that you don't have to be a well-funded research scientist to experiment with making new aerogels. Want to make your own aerogel? Though it's possible to do this at home, it's best done in a laboratory that contains all the necessary materials, including an autoclave to supercritically dry your aerogel. (If you're feeling super productive, here are instructions on how to make your own supercritical dryer.) Ask around your local university or community college; chances are, if you tell them you have a recipe you want to work with, they may let you use their equipment [source: Hunt and Ayers, Making; Aerogel.org, Build].
Several web sites provide instruction on how to make aerogels, including aerogel.org. Regardless of where you make your aerogel, safety precautions are a must. Wear goggles, gloves (the best kind are dishwashing gloves), long pants, closed-toe shoes, and a painter's mask to protect yourself from hazardous fumes and flammable materials. [source: Steiner, How to Make; Hunt and Ayers, Making]
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Aerogels -- is there anything they can't do? Hopefully the public will be on a first-name basis with them in the near future. For more information on aerogels and related topics, check out the links on the next page.
Please copy/paste the following text to properly cite this HowStuffWorks.com article:
Picture preparing a bowl full of a sweet, gelatin dessert. The gelatin powder is mixed with hot water, and then the mixture is cooled in a refrigerator until it sets. It is now a gel. If that wiggly gel were placed in an oven and all of the moisture dried out of it, all that would be left would be a pile of powder.
But imagine if the dried gelatin maintained its shape, even after the liquid had been removed. The structure of the gel would remain, but it would be extremely light due to low density. This is precisely how aerogels are made.
Aerogels are among the lightest solid materials known to man. They are created by combining a polymer with a solvent to form a gel, and then removing the liquid from the gel and replacing it with air. Aerogels are extremely porous and very low in density. They are solid to the touch. This translucent material is considered one of the finest insulation materials available.
Although aerogels were first invented in the s, NASA’s Glenn Research Center in Cleveland has invented groundbreaking methods of creating new types of aerogels that could change the way we think about insulation.
Aerogels’ Porous Materials
Since their invention, aerogels have primarily been made of silica. The silica is combined with a solvent to create a gel. This gel is then subjected to supercritical fluid extraction. This supercritical fluid extraction involves introducing liquid carbon dioxide into the gel. The carbon dioxide surpasses its super critical point, where it can be either a gas or a liquid, and then is vented out. This exchange is performed multiple times to ensure that all liquids are removed from the gel. The resulting material is aerogel.
“That is the key step that makes an aerogel different from other porous materials,” says Mary Ann Meador, a research chemical engineer and team lead for aerogels at Glenn. “Maintaining the gel structure is the most important thing.”
Aerogels provide very effective insulation, because they are extremely porous and the pores are in the nanometer range. The nano pores aren’t visible to the human eye. The existence of these pores makes the aerogel so adept at insulating.
“The pores are so small, and gas phase heat conduction is very poor,” Meador says. “Molecules of air cannot travel through the aerogel, so there is poor heat transfer through the material.”
Traditional silica-based aerogels have been successfully used in many applications, such as providing insulation on a Mars Rover. They have also been used in many commercial products. When aerogels are used for commercial purposes, they are typically in pellet form or in a composite with other materials. Aerogels have been combined with batting to create insulating “blankets,” as well as filled in between panes of glass to create translucent panels for day-lighting applications.
Silica-based aerogels are very light, as they are about 95% porous. Silica aerogels are very useful, but they have limitations—they are very fragile.
Aerogel Innovations
NASA, along with industry partners, has investigated the use of different types of aerogels for multiple uses. With funding from NASA’s Fundamental Aeronautics Program (Hypersonics and Subsonic Fixed Wing Projects) and the Exploration Systems Mission Directorate, NASA’s Glenn Research Center has developed two cutting-edge methodologies that revolutionize aerogel technology.
The first innovation is a method of creating aerogels that are reinforced by polymers. The method changes the surface of the gel as it reacts with a polymer. The result is that the interior surface of the aerogel gets a thin layer of polymer, which greatly strengthens the aerogel.
“If you were to compare a polymer-enforced silica aerogel with the same density silica gel, the polymer reinforced aerogel is about two orders of magnitude stronger,” Meador says.
These polymer-enhanced aerogels offer the same insulation properties as typical aerogels and can be translucent. They share the same positive attributes of silica aerogels, and are much less fragile. The Glenn team has created many different aerogels featuring different polymers using their patented method. Glenn has also collaborated with Aspen Aerogel of Northborough, Mass. to create a polymer-enhanced aerogel that was combined with fibers to create a new product.
The second innovation is a method of creating aerogels made completely of polymers. These polymer-based aerogels are extremely strong and flexible. They can also be made into a bendable thin film.
Aerogels in Flight
The Glenn team is currently working on a NASA project called the Hypersonic Inflatable Aerodynamic Decelerator (HIAD). The HIAD is an inflatable reentry vehicle that is folded and stowed inside a launch vehicle. Prior to entering the atmosphere, the HIAD is inflated and becomes rigid. This helps the spacecraft slow down, safely descend and land on Earth, Mars, or any other planet that has an atmosphere.
The HIAD enables larger masses to be carried through the atmosphere more slowly and safely, and it reduces the heat to which the vehicle is subjected. The HIAD is covered by a Flexible Thermal Protection System, which uses aerogels as an insulator to protect the payload.
The thin film polymer-based aerogel is well suited to the needs of the HIAD. The HIAD (funded by the Hypersonics Project of the Fundamental Aeronautics Program) is scheduled to flight test in . An important component will be the Flexible Thermal Protection Systems (funded by the Hypersonics Project and the Space Technology Program under the NASA Chief Technologist). The Flexible Thermal Protection Systems use baseline aerogel insulation blankets, created by Aspen Aerogels. Subsequent test launches may include the new thin film polymer-based aerogel as an improvement over the baseline insulation.
“The project would like an aerogel that is more flexible, more foldable and doesn’t dust, doesn’t shed insulation particles, so it is not a hazard or messy to handle. In response to that, we started looking at different kinds of polymers and techniques that could make that sort of aerogel more flexible,” Meador says.
The team determined that the presence of silica in an aerogel precluded the ability of an aerogel to be flexible, so they started exploring ways to create an aerogel made completely with polymers. They developed a method of creating polymer based aerogels that are completely flexible, and can be made into an extremely thin film—a capability not previous available. These aerogels are also stable even when subjected to high temperatures.
The polymer-based aerogel is 85-95% porous, meaning it offers the same advantages of traditional aerogels. It is equally light in weight, and has the same properties of thermal conductivity as silica based aerogels. But these aerogels offer unprecedented flexibility, along with their durability and strength, and the ability to be made into a thin film.
“I was amazed and surprised when we determined it could be made into a flexible thin film,” Meador says. “It was a ‘whoa’ moment! It was better than we expected.”
Aerogel Applications
The thin films, which are fabricated through a collaboration with the University of Akron in Akron, Ohio, have also been sent to other government agencies and NASA centers, which has garnered interest in the technology.
“Usually when people see them, they say ‘Wow, this is an aerogel?’” Meador says.
Other NASA centers have expressed interest in further exploring these thin polymer aerogels, for applications like cryogenics or in the next space suit. Polymer aerogels are ideally suited for use in a vacuum, like in space, as well as in different gravity scenarios, such as the moon or other planets.
Governmental agencies are also interested in exploring the thin polymer aerogels for use in shelter applications, such as insulated tents. Industry has also taken notice, with possible applications in refrigeration, building and construction, updating historical structures, and many other insulation needs, especially when there isn’t a lot of room and smaller, more effective insulation is needed.
Aerogels and the Future
Polymer-enhanced aerogels and polymer-based aerogels have numerous potential applications, both in space, on distant planets and on our own Earth. They are light, durable and extremely effective at insulating and preventing heat transfer. NASA has taken aerogels to the next level, beyond what was previously imagined, and uncovered a world of possibilities for this versatile material.
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