Frequently Asked Questions
Properties of Aerogels
What is aerogel?
Aerogels are a diverse class of ultralow density solids that combine multiple disparate and extreme materials properties into a single material envelope. Aerogel materials generally exhibit a high degree of porosity, high specific surface area, and superlative energy damping (thermal, acoustic, and impact) properties. The term aerogel refers to the sparse, porous solid backbone of a gel isolated from the liquid component of the gel and similar porous solid materials with mesoporosity, that is, primarily containing pores ranging from about 2-50 nm. The name aerogel may be misleading at first, as aerogels are dry, rigid or elastic foam-like materials and are not wet or wobbly. The name originates from the fact that aerogels are typically made by replacing the liquid component of a gelâ€”think something physically similar in consistency to edible gelatinâ€”with a gas or a vacuum in a way that preserves the structural integrity of gel’s sparse solid, porous backbone.
What is aerogel made of?
Historically, the most commonly researched and commercially available type of aerogel has been the holographic-looking “blue” silica type. Today, aerogels of numerous different substances can be prepared, including:
- Silica, both hydrophilic (water-absorbing) and hydrophobic (water-repelling)
- Transition metal oxides, lanthanide oxides, actinide oxides, main group oxides, and mixed matrix oxides
- Synthetic polymers such as phenolics, polyureas, polyurethanes, polyimides, and polyamides
- Biopolymers such as cellulose, alginate, and lignin
- Carbon allotropes such as amorphous carbon, graphitic carbon, carbon nanotubes, graphene, and diamond
- Metal chalcogenides and quantum dots
- Metals, carbides, and nitrides
Each of these different types of aerogels provides unique properties, which can include electrical conductivity (carbon and metal aerogels), extreme (up to 80%) elastic return (nanotube and graphene aerogels), catalytic functions (various oxide and metal aerogels), photoluminescence (quantum dot and metal chalcogenide aerogels), water repulsion and oil sorption (hydrophobic silica and polymer aerogels), and more.
How good of an insulator is aerogel?
The insulating ability (or thermal conductivity) of an aerogel material depends on its composition, form factor, and density, as well as the temperature of its environment. Silica aerogel-based materials are typically used for insulating applications, although AirloyÂ® and other polymer aerogels such as BASF’s SlentiteÂ® are beginning to be used as well. For a typical silica aerogel monolith with a density of ~100 mg/cc, the thermal conductivity is usually between 10-20 mW/m-K, or about 2-3 times more insulating per unit thickness than polyurethane foam (PUF) or StyrofoamÂ® (expanded polystyrene), which have thermal conductivities of 29-35 mW/m-K typically. Composite aerogel blankets such as Aspen Aerogels’ SpaceloftÂ® typically have a thermal conductivity of ~14-21 mW/m-K. Cabot Aerogel’s LumiraÂ® aerogel particles used for daylighting applications similarly have a thermal conductivity of ~9-12 mW/m-K. Cabot Aerogel’s Thermal Wrapâ„¢ blankets, used in construction, daylighting, and low-dust insulating applications, has a thermal conductivity of ~23 mW/m-K. In general, the thermal conductivity of an aerogel decreases (that is, its insulating ability increases) as its density decreases. While aerogels are available in a wide range of densities, from as low as 0.001 g/cc up to ~0.55 g/cc, in general only materials with densities in the range of 0.06-0.55 are practical for industrial applications. Thermal conductivity of non-silica aerogels depends on composition and density, with some materials being equal to or better than silica aerogels at the same density, and others exhibiting higher thermal conductivity at the same density.
Why are aerogels such good insulators?
Aerogels are extremely good thermal insulators for several reasons. First, it is important to understand how heat is transported through materials. Heat is transported through a material three different ways: through conductive transport, that is, through the solid part of the material; through convective transport, that is, by being carried by gas diffusing through a material; and through radiative transport, that is, by electromagnetic energy like infrared energy penetrating through the material.
Aerogels are extremely low-density materials, typically 50-99.98% air by volume. This means aerogels have very little mass through which heat can conduct. Additionally, the solid part of an aerogel is highly disordered and thus makes conduction of heat through the little solid that is there inefficient.
Additionally, aerogels have extremely tiny pores, typically between 2-50 nm in diameter. These pores are actually so tiny that they are smaller than the mean free path of air at room temperature and pressure, that is, the average distance a molecule of air can travel before hitting another air molecule is greater than the width of the pores in a typical aerogel. As a result, air has an extremely difficult time diffusing through and thus carrying heat energy through an aerogel by convection. This phenomenon, called the Knudsen effect, differentiates aerogels from traditional foams, which typically have pore sizes of tens to thousands of microns in diameter and thus allow more heat through by convection.
Aerogels are not necessarily good at stifling radiative transport, however, and so at high temperatures, heat can pass through aerogels in the form of infrared energy. As a result, commercial aerogel insulation products include additional materials called IR opacifiers embedded in the aerogel to reflect and/or absorb infrared energy. This helps limit radiative transport, making aerogel insulators excellent insulators at high temperatures as well as room temperature.
How hot can an aerogel get? What is its maximum operating temperature?
The maximum operating temperature of an aerogel material depends on its composition. Monolithic silica aerogels remain generally in tact until about 650Â°C, at which point they begin to sinter (densify). At hotter temperatures, silica aerogels will eventually melt. Composite aerogel blankets such as Aspen Aerogels’ PyrogelÂ® XTE blanket can be used up to temperatures of about 650Â°C. Note that hydrophobic (water-repelling) aerogels, including hydrophobic composite aerogel blankets, will lose their hydrophobic surface features when heated above about 300Â°C. The maximum operating temperature of Airloy aerogels is product series dependent, however polyimide-based Airloy aerogels such as Airloy T116 offer operating temperatures up to 300Â°C. See our page about Airloy materials properties for specific information about different Airloy product temperature ratings.
I've heard aerogels are fragile, yet somehow also superstrong. How can that be?
First, not all aerogels are easy to break!Â Classic (or “legacy”) aerogels exhibit extremely high strength-to-weight ratios and are able (in principle) to hold thousands of times their weight in applied force, however also typically exhibit extremely low fracture toughness, that is, the ability to resist propagation of flaws in the material. As a result, it is possible for a classic aerogel block that is 96% air by volume to hold a brick thousands of times its own weight, but only if the weight is placed on the monolith gently and there are no major cracks in the aerogel.
New mechanically strong and machinable aerogels such as AirloyÂ® strong aerogels made by Aerogel Technologies fix this problem. Airloy aerogels are hundreds of times stronger and stiffer than classic aerogels and simultaneously durable and fracture tough. Unlike legacy aerogels, Airloy aerogels can be machined (drilled, tapped, turned, milled) and bent without breaking. The strength, stiffness, thermal conductivity, and other properties of Airloy aerogels depend on the product series. See our page about Airloy materials properties for specific information about the mechanical properties of different Airloy products.
Are aerogels open-celled or close-celled?
Aerogels are open-celled materials with typical average pore sizes of less than 50 nm in diameter (typically 5-20 nm)â€”about 3,000 to 30,000 times smaller than the diameter of a hair.
Are aerogels waterproof?
Some aerogel materials are waterproof and some are not. Industrial silica aerogel materials such as Cabot Aerogel’s LumiraÂ® and EnovaÂ® aerogel particles as well as Aspen Aerogels SpaceloftÂ®, CryogelÂ®, and PyrogelÂ® aerogel composite blankets are specially formulated to be hydrophobic (water-repelling). Classic silica aerogels and other oxide-based aerogels are not natively waterproof but can be modified to not only be waterproof, but superhydrophobic. Mechanically strong AirloyÂ® aerogels made by Aerogel Technologies are water-resistant with varying levels of hydrophobicity for different applications.
Are aerogels flexible?
The flexibility of an aerogel material depends on its composition and density. Classic silica, metal oxide, and carbon aerogels are not flexible and are usually very fragile. Composite aerogel blankets such as Cabot Aerogel’s Thermal Wrapâ„¢ and Aspen Aerogels SpaceloftÂ® are extremely flexible and can be cut and flexed like other fabrics. AirloyÂ® strong aerogels from Aerogel Technologies are usually flexible but also very stiff (like bending a ballpoint pen), depending on the specific product. Specially-formulated polymer and silica aerogels and aerogel composites with extreme flexibility can also be made, with flexibility ranging from cloth-like to marshmallow-like.
How much does aerogel cost?
Aerogel materials vary in price depending on form factor and composition. Once very costly due to specialty manufacturing processes and lack of commercial availability, today aerogel materials of various types are produced commercially on massive scales at prices that are in many instances competitive with traditional materials technologies. Aerogel particles such as Cabot Aerogel’s LumiraÂ® aerogel, used in the daylighting panels in office buildings, gyms, and sports arenas around the world, while composite aerogel blankets such as Aspen Aerogels SpaceloftÂ® and Cabot Aerogel’s Thermal Wrapâ„¢ insulate subsea oil pipelines, refineries, and residential apartments. Strong aerogel panels such as AirloyÂ® strong aerogels from Aerogel Technologies are making planes, cars, and rockets lighter, more energy efficient, and cheaper to operate. Sub-bulk pricing for these and other aerogel products is available at BuyAerogel.com. Please contact us for bulk pricing requests.
Do you sell strong aerogels such as x-aerogels and polyimide aerogels?
See our line of revolutionary AirloyÂ® Ultramaterials for applications that demand materials that combine the lightness and superinsulating properties of aerogels with the strength, machinability, and durability of plastics.
How big can you make aerogel?
In principle there is no limit to how large an aerogel material can be. Classic monolithic aerogels typically require special high-pressure vessels to prepare and thus are often (but not always) limited to the inner dimensions of the pressure vessel available. AirloyÂ® strong aerogels from Aerogel Technologies are not restricted in this way, however, thanks to breakthrough Stelmakhâ„¢ technology that enables production of Airloy aerogels in unlimited lengths and widths with single-panel thicknesses up to 2 cm. Multi-panel laminated Airloy blanks of unlimited thickness are also available. Aerogel composite blankets from Aspen Aerogels typically come in 150-cm-wide (59″-wide) rolls. Low-dust aerogel composite blankets from Cabot Aerogel typically come in 56- to 76-cm-wide (22″-30″-wide) rolls.
What volume of aerogels can you produce?
Aerogel Technologies can accommodate production volumes large and small. Contact us to discuss your application needs.
Do you sell aerogel powders or particles?
Aerogel Technologies can produce specialty aerogel powders (e.g., hydrophilic silica, metal oxides, metals, carbon) for specific application needs. For silica aerogel performance additives, we recommend Cabot Aerogel’s EnovaÂ® aerogel line available at BuyAerogel.com. Please contact us for additional assistance.
I need a large quantity of aerogel materials. Do you offer volume pricing?
Different aerogel materials have different volume pricing schedules. Contact us to discuss your volume order needs.
Do you have distributors in Europe, Asia, Australia, the Middle East, or Africa?
Aerogel Technologies sells directly to universities, companies, government labs, and individuals all over the world. Contact us with any special ordering or shipping requirements you may have or buy aerogel materials online now at BuyAerogel.com.
I'm doing a science project/giving a presentation. Can I get a free sample of aerogel?
Check out BuyAerogel.com, our online store for aerogel materials. There you’ll find several very affordable samples of various aerogel materials.
Can you machine aerogels?
Classic monolithic aerogels are very difficult to machine. Never fearâ€”Aerogel Technologies is the world leader in shape control of monolithic aerogels and can assist in producing specially-shaped and featured aerogel parts. Contact us to discuss your custom aerogel shape or machining project.
Alternatively, our AirloyÂ® Ultramaterials are strong, durable aerogels that are easily machinable by the end user. Airloy aerogels can be drilled, tapped, turned, and milled just like other engineering materials. See our Airloy product overview for more information or buy Airloy materials today online at BuyAerogel.com.
How do you glue an aerogel to something?
Classic aerogel materials absorb liquids readily and are difficult to glue or adhere. For applications where adhesion of parts is required, we recommend AirloyÂ® strong aerogels, which are compatible with a wide variety of adhesive systems including cyanoacrylates, epoxies, polyurethanes, silicones, and more.
If you fill an aerogel with helium or seal a vacuum in an aerogel, will it float in air?
Unfortunately,, even the lightest aerogels, even if evacuated or backfilled with helium, would be too heavy to float in air, especially if laminated to seal the outer edges of the monolith. However, a helium-backfilled aerogel can be made to float if dropped into an aquarium filled with a dense gas such as xenon.
Environment, Health, and Safety
Are aerogel materials safe for the environment?
Silica aerogel materials are similar to minerals found in nature (silicates are the most abundant minerals on Earth) and do not contain or emit harmful chemicals. Carbon aerogels are also similar to minerals found in nature and are chemically no different than charcoal. Polymer aerogels such as RF aerogels and AirloyÂ® aerogels are also generally not harmful however like other polymers and plastics care must be considered regarding biodegradability and methods of proper disposal.
Are aerogels biodegradable?
Some aerogel materials are biodegradable and some are not. Biodegradability depends on the composition of the aerogel material.
One advantage of some industrial aerogel materials such as Cabot Aerogel’s LumiraÂ® aerogel particles is that they can be reused and are generally harmless to the environment even if released.
Where can I find safety data sheets (SDS's) for your products?
Safety data sheets for products manufactured by Aerogel Technologies and for products that we distribute which are manufactured by Cabot Aerogel, Aspen Aerogels, and our other manufacturing partners are available on the respective product page on BuyAerogel.com.
Is aerogel safe?
Monolithic aerogels and AirloyÂ® aerogels produced by Aerogel Technologies are made with synthetic amorphous silica gel and/or polymers that have been shown to be safe for human health. Precipitated silica like that which comprises silica aerogels and some Airloy aerogels is widely used in personal care products such as lotions, cosmetics, and toothpastes. Silica aerogel materials manufactured by Aerogel Technologies do not contain crystalline silica or quartz and are not known to be carcinogenic or mutagenic. As with other materials, though, we recommend wearing proper personal protective gear if you plan on grinding or otherwise mechanically processing monolithic classic aerogels or Airloy aerogels, handling aerogel particles, or handling insulating aerogel blankets, to avoid inhalation of nuisance particles.
Contacting Aerogel Technologies
I have a question that's not answered here. How can I get a hold of you?
We love answering questions about aerogels and figuring out how aerogels can be used to solve your technology application problems. Contact us to begin the conversation.
What's your phone number?
Aerogel Technologies can be reached toll-free in the United States at (844) AEROGEL ((844) 237-6435) or internationally at +1 (617) 800-0414.
Where are you located?
Aerogel Technologies, LLC
1 Westinghouse Plaza, Building D
Boston, MAÂ 02136
United States of America
Who can I contact about a custom quantity, size, shape, formulation, or application?
Aerogel Technologies is the world leader in custom aerogel materials solutions. Our team of scientists and engineers will work with you to find a solution for your technology application. Contact us to begin the conversation.
Who can I talk to regarding media inquiries?
For media inquiries, please contact us.
Who invented aerogel?
Aerogel was invented by Dr. Samuel Stephens Kistler at the College of the Pacific in Stockton, CA. Incredibly, aerogels were first reported by Kistler in 1931, and first commercialized by Monsanto in the 1940’s.
Read more about the history of aerogels on Aerogel.org.