Aerogel

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A block of silica aerogel in a hand. Aerogel hand.jpg
A block of silica aerogel in a hand.

Aerogels are a class of synthetic porous ultralight material derived from a gel, in which the liquid component for the gel has been replaced with a gas, without significant collapse of the gel structure. [1] The result is a solid with extremely low density [2] and extremely low thermal conductivity. Aerogels can be made from a variety of chemical compounds. [3] Silica aerogels feel like fragile styrofoam to the touch, while some polymer-based aerogels feel like rigid foams.

Contents

Aerogels are produced by extracting the liquid component of a gel through supercritical drying or freeze-drying. This allows the liquid to be slowly dried off without causing the solid matrix in the gel to collapse from capillary action, as would happen with conventional evaporation. The first aerogels were produced from silica gels. Kistler's later work involved aerogels based on alumina, chromia, and tin dioxide. Carbon aerogels were first developed in the late 1980s. [4]

History

The first documented example of an aerogel was created by Samuel Stephens Kistler in 1931, [5] as a result of a bet [6] with Charles Learned over who could replace the liquid in "jellies" with gas without causing shrinkage. [7] [8]

Properties

A flower resting on a piece of silica aerogel, which is suspended over a flame from a Bunsen burner. Aerogels have excellent insulating properties, and the flower is protected from the heat of the flame. Aerogelflower filtered.jpg
A flower resting on a piece of silica aerogel, which is suspended over a flame from a Bunsen burner. Aerogels have excellent insulating properties, and the flower is protected from the heat of the flame.

Despite the name, aerogels are solid, rigid, and dry materials that do not resemble a gel in their physical properties: the name comes from the fact that they are made from gels. Pressing softly on an aerogel typically does not leave even a minor mark; pressing more firmly will leave a permanent depression. Pressing extremely firmly will cause a catastrophic breakdown in the sparse structure, causing it to shatter like glass (a property known as friability ), although more modern variations do not suffer from this. Despite the fact that it is prone to shattering, it is very strong structurally. Its impressive load-bearing abilities are due to the dendritic microstructure, in which spherical particles of average size 2–5  nm are fused together into clusters. These clusters form a three-dimensional highly porous structure of almost fractal chains, with pores just under 100 nm. The average size and density of the pores can be controlled during the manufacturing process.

An aerogel material can range from 50% to 99.98% air by volume, but in practice most aerogels exhibit somewhere between 90 and 99.8% porosity. [9] Aerogels have a porous solid network that contains air pockets, with the air pockets taking up the majority of space within the material. [10]

Aerogels are good thermal insulators because they almost nullify two of the three methods of heat transfer – conduction (they are mostly composed of insulating gas) and convection (the microstructure prevents net gas movement). They are good conductive insulators because they are composed almost entirely of gases, which are very poor heat conductors. (Silica aerogel is an especially good insulator because silica is also a poor conductor of heat; a metallic or carbon aerogel, on the other hand, would be less effective.) They are good convective inhibitors because air cannot circulate through the lattice. Aerogels are poor radiative insulators because infrared radiation (which transfers heat) passes through them.

Owing to its hygroscopic nature, aerogel feels dry and acts as a strong desiccant. People handling aerogel for extended periods should wear gloves to prevent the appearance of dry brittle spots on their skin.

The slight colour it does have is due to Rayleigh scattering of the shorter wavelengths of visible light by the nano-sized dendritic structure. This causes it to appear smoky blue against dark backgrounds and yellowish against bright backgrounds.

Aerogels by themselves are hydrophilic, and if they absorb moisture they usually suffer a structural change, such as contraction, and deteriorate, but degradation can be prevented by making them hydrophobic, via a chemical treatment. Aerogels with hydrophobic interiors are less susceptible to degradation than aerogels with only an outer hydrophobic layer, especially if a crack penetrates the surface.

Structure

Aerogel structure results from a sol-gel polymerization, which is when monomers (simple molecules) react with other monomers to form a sol or a substance that consists of bonded, cross-linked macromolecules with deposits of liquid solution among them. When the material is critically heated, the liquid evaporates and the bonded, cross-linked macromolecule frame is left behind. The result of the polymerization and critical heating is the creation of a material that has a porous strong structure classified as aerogel. [11] Variations in synthesis can alter the surface area and pore size of the aerogel. The smaller the pore size the more susceptible the aerogel is to fracture. [12]

Porosity of aerogel

There are several ways to determine the porosity of aerogel: the three main methods are gas adsorption, mercury porosimetry, and scattering method. In gas adsorption, nitrogen at its boiling point is adsorbed into the aerogel sample. The gas being adsorbed is dependent on the size of the pores within the sample and on the partial pressure of the gas relative to its saturation pressure. The volume of the gas adsorbed is measured by using the Brunauer, Emmit and Teller formula (BET), which gives the specific surface area of the sample. At high partial pressure in the adsorption/desorption the Kelvin equation gives the pore size distribution of the sample. In mercury porosimetry, the mercury is forced into the aerogel porous system to determine the pores' size, but this method is highly inefficient since the solid frame of aerogel will collapse from the high compressive force. The scattering method involves the angle-dependent deflection of radiation within the aerogel sample. The sample can be solid particles or pores. The radiation goes into the material and determines the fractal geometry of the aerogel pore network. The best radiation wavelengths to use are X-rays and neutrons. Aerogel is also an open porous network: the difference between an open porous network and a closed porous network is that in the open network, gases can enter and leave the substance without any limitation, while a closed porous network traps the gases within the material forcing them to stay within the pores. [13] The high porosity and surface area of silica aerogels allow them to be used in a variety of environmental filtration applications.

Knudsen effect

Aerogels may have a thermal conductivity smaller than that of the gas they contain. [14] [15] This is caused by the Knudsen effect, a reduction of thermal conductivity in gases when the size of the cavity encompassing the gas becomes comparable to the mean free path. Effectively, the cavity restricts the movement of the gas particles, decreasing the thermal conductivity in addition to eliminating convection. For example, thermal conductivity of air is about 25 mW·m−1·K−1 at STP and in a large container, but decreases to about 5 mW·m−1·K−1 in a pore 30 nanometers in diameter. [16]

Waterproofing

Aerogel contains particles that are 2–5 nm in diameter. After the process of creating aerogel, it will contain a large amount of hydroxyl groups on the surface. The hydroxyl groups can cause a strong reaction when the aerogel is placed in water, causing it to catastrophically dissolve in the water. One way to waterproof the hydrophilic aerogel is by soaking the aerogel with some chemical base that will replace the surface hydroxyl groups (–OH) with non-polar groups (–OR), a process which is most effective when R is an aliphatic group. [17]

Production

Comparison of aerogel fabrication strategies showing typical transitions into an aerogel: (a) the supercritical drying process where precursor materials undergo gelation prior to supercritical drying. (b) A standard freeze-drying technique where an aqueous solution is frozen. Aerogel fabrication strategies Polymers 2019.png
Comparison of aerogel fabrication strategies showing typical transitions into an aerogel: (a) the supercritical drying process where precursor materials undergo gelation prior to supercritical drying. (b) A standard freeze-drying technique where an aqueous solution is frozen.
A typical phase diagram for pure compounds. Two methods are shown for the gel to aerogel transition: The solid-gas transition (during freeze-drying) and the transition from a liquid to gas during supercritical drying. Phase diagram gel to aerogel transition Polymers 2019.png
A typical phase diagram for pure compounds. Two methods are shown for the gel to aerogel transition: The solid-gas transition (during freeze-drying) and the transition from a liquid to gas during supercritical drying.

Overview

The preparation of silica aerogels typically involves three distinct steps: [18] the sol-gel transition (gelation), [19] the network perfection (aging), and [20] the gel-aerogel transition (drying).

Gelation

Silica aerogels are typically synthesized by using a sol-gel process. The first step of the sol-gel process is the creation of a colloidal suspension of solid particles known as a "sol". The precursors are a liquid alcohol such as ethanol which is mixed with a silicon alkoxide, such as tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and polyethoxydisiloxane (PEDS) (earlier work used sodium silicates). [21] The solution of silica is mixed with a catalyst and allowed to gel during a hydrolysis reaction which forms particles of silicon dioxide. [22] The oxide suspension begins to undergo condensation reactions which result in the creation of metal oxide bridges (either M–O–M, "oxo" bridges, or M–OH–M, "ol" bridges) linking the dispersed colloidal particles. [23] These reactions generally have moderately slow reaction rates, and as a result either acidic or basic catalysts are used to improve the processing speed. Basic catalysts tend to produce more transparent aerogels and minimize the shrinkage during the drying process and also strengthen it to prevent pore collapse during drying. [22]

For some materials, the transition from a colloidal dispersion into a gel happens without the addition of crosslinking materials. [24] For others, crosslinking materials are added to the dispersion to promote the strong interaction of the solid particles in order to form the gel. [25] [26] The gelation time depends heavily on a variety of factors such as the chemical composition of the precursor solution, the concentration of the precursor materials and additives, the processing temperature, and the pH. [27] [28] [29] [30] [31] Many materials may require additional curing after gelation (i.e., network perfection) in order to strengthen the aerogel network. [32] [33] [34] [35] [36] [37]

Drying

Once the gelation is completed, the liquid surrounding the silica network is carefully removed and replaced with air, while keeping the aerogel intact. It is crucial that the gel is dried in such a way as to minimize the surface tension within the pores of the solid network. This is typically accomplished through supercritical fluid extraction using supercritical carbon dioxide (scCO2) or freeze-drying.This section briefly describes and compares the processing strategies of supercritical drying and freeze-drying.

Gels where the liquid is allowed to evaporate at a natural rate are known as xerogels (i. e. are not aerogels). As the liquid evaporates in such manner, forces caused by surface tensions of the liquid-solid interfaces are enough to destroy the fragile gel network. As a result, xerogels cannot achieve the high porosities and instead peak at lower porosities and exhibit large amounts of shrinkage after drying. [38] To avoid the collapse of fibers during slow solvent evaporation and reduce surface tensions of the liquid-solid interfaces, aerogels can be formed by lyophilization (freeze-drying). Depending on the concentration of the fibers and the temperature to freeze the material, the properties such as porosity of the final aerogel will be affected. [39]

In 1931, to develop the first aerogels, Kistler used a process known as supercritical drying which avoids a direct phase change. [40] By increasing the temperature and pressure he forced the liquid into a supercritical fluid state where by dropping the pressure he could instantly gasify and remove the liquid inside the aerogel, avoiding damage to the delicate three-dimensional network. While this can be done with ethanol, the high temperatures and pressures lead to dangerous processing conditions. A safer, lower temperature and pressure method involves a solvent exchange. This is typically done by exchanging the initial aqueous pore liquid for a CO2-miscible liquid such as ethanol or acetone, then onto liquid carbon dioxide, and then bringing the carbon dioxide above its critical point. [41] A variant on this process involves the direct injection of supercritical carbon dioxide into the pressure vessel containing the aerogel. The result of either process exchanges the initial liquid from the gel with carbon dioxide, without allowing the gel structure to collapse or lose volume. [22]

Supercritical Drying

To dry the gel, while preserving the highly porous network of an aerogel, supercritical drying employs the use of the liquid-gas transition that occurs beyond the critical point of a substance. By using this liquid-gas transition that avoids crossing the liquid-gas phase boundary, the surface tension that would arise within the pores due to the evaporation of a liquid is eliminated, thereby preventing the collapse of the pores. [42] Through heating and pressurization, the liquid solvent reaches its critical point, at which point the liquid and gas phases become indistinguishable. Past this point, the supercritical fluid is converted into the gaseous phase upon an isothermal de-pressurization. This process results in a phase change without crossing the liquid-gas phase boundary. This method is proven to be excellent at preserving the highly porous nature of the solid network without significant shrinkage or cracking. While other fluids have been reported for the creation of supercritically dried aerogels, scCO2 is the most common substance with a relatively mild supercritical point at 31 °C and 7.4 MPa. CO2 is also relatively non-toxic, non-flammable, inert, and cost-effective when compared to other fluids, such as methanol or ethanol. [43] While being a highly effective method for producing aerogels, supercritical drying takes several days, requires specialized equipment, and presents significant safety hazards due to its high-pressure operation.

Freeze-Drying

Freeze-drying, also known as freeze-casting or ice-templating, offers an alternative to the high temperature and high-pressure requirements of supercritical drying. Additionally, freeze-drying offers more control of the solid structure development by controlling the ice crystal growth during freezing. [44] [45] [46] [47] In this method, a colloidal dispersion of the aerogel precursors is frozen, with the liquid component freezing into different morphologies depending on a variety of factors such as the precursor concentration, type of liquid, temperature of freezing, and freezing container. [48] [49] [50] As this liquid freezes, the solid precursor molecules are forced into the spaces between the growing crystals. Once completely frozen, the frozen liquid is sublimed into a gas through lyophilization, which removes much of the capillary forces, as was observed in supercritical drying. [51] [52] Though typically classified as a “cryogel”, aerogels produced through freeze-drying often experience some shrinkage and cracking while also producing a non-homogenous aerogel framework. [53] This often leads to freeze-drying being used for the creation of aerogel powders or as a framework for composite aerogels. [54] [55] [56] [57] [58]

Preparation of non-silica aerogels

Resorcinolformaldehyde aerogel (RF aerogel) is made in a way similar to production of silica aerogel. A carbon aerogel can then be made from this resorcinol–formaldehyde aerogel by pyrolysis in an inert gas atmosphere, leaving a matrix of carbon. [59] The resulting carbon aerogel may be used to produce solid shapes, powders, or composite paper. [60] Additives have been successful in enhancing certain properties of the aerogel for the use of specific applications. Aerogel composites have been made using a variety of continuous and discontinuous reinforcements. The high aspect ratio of fibers such as fiberglass have been used to reinforce aerogel composites with significantly improved mechanical properties.

Materials

A 2.5 kg brick is supported by a piece of aerogel with a mass of 2 g. Aerogelbrick.jpg
A 2.5 kg brick is supported by a piece of aerogel with a mass of 2 g.

Silica aerogel

Silica aerogels are the most common type of aerogel, and the primary type in use or study. [40] [61] It is silica-based and can be derived from silica gel or by a modified Stober process. Nicknames include frozen smoke, [62] solid smoke, solid air, solid cloud, and blue smoke, owing to its translucent nature and the way light scatters in the material. The lowest-density silica nanofoam weighs 1,000 g/m3, [63] which is the evacuated version of the record-aerogel of 1,900 g/m3. [64] The density of air is 1,200 g/m3 (at 20 °C and 1 atm). [65]

The silica solidifies into three-dimensional, intertwined clusters that make up only 3% of the volume. Conduction through the solid is therefore very low. The remaining 97% of the volume is composed of air in extremely small nanopores. The air has little room to move, inhibiting both convection and gas-phase conduction. [66]

Silica aerogel also has a high optical transmission of ~99% and a low refractive index of ~1.05. [67] It is very robust with respect to high power input beam in continuous wave regime and does not show any boiling or melting phenomena. [68] This property permits to study high intensity nonlinear waves in the presence of disorder in regimes typically unaccessible by liquid materials, making it promising material for nonlinear optics.

This aerogel has remarkable thermal insulative properties, having an extremely low thermal conductivity: from 0.03  W·m−1·K −1 [69] in atmospheric pressure down to 0.004 W·m−1·K−1 [63] in modest vacuum, which correspond to R-values of 14 to 105 (US customary) or 3.0 to 22.2 (metric) for 3.5 in (89 mm) thickness. For comparison, typical wall insulation is 13 (US customary) or 2.7 (metric) for the same thickness. Its melting point is 1,473 K (1,200 °C; 2,192 °F). It is also worth noting that even lower conductivities have been reported for experimentally produced monolithic samples in the literature, reaching 0.009 W·m−1·K−1 at 1atm. [70]

Until 2011, silica aerogel held 15 entries in Guinness World Records for material properties, including best insulator and lowest-density solid, though it was ousted from the latter title by the even lighter materials aerographite in 2012 [71] and then aerographene in 2013. [72] [73]

Carbon

Carbon aerogels are composed of particles with sizes in the nanometer range, covalently bonded together. They have very high porosity (over 50%, with pore diameter under 100 nm) and surface areas ranging between 400 and 1,000 m2/g. They are often manufactured as composite paper: non-woven paper made of carbon fibers, impregnated with resorcinolformaldehyde aerogel, and pyrolyzed. Depending on the density, carbon aerogels may be electrically conductive, making composite aerogel paper useful for electrodes in capacitors or deionization electrodes. Due to their extremely high surface area, carbon aerogels are used to create supercapacitors, with values ranging up to thousands of farads based on a capacitance density of 104 F/g and 77 F/cm3. Carbon aerogels are also extremely "black" in the infrared spectrum, reflecting only 0.3% of radiation between 250 nm and 14.3 μm, making them efficient for solar energy collectors.

The term "aerogel" to describe airy masses of carbon nanotubes produced through certain chemical vapor deposition techniques is incorrect. Such materials can be spun into fibers with strength greater than Kevlar, and unique electrical properties. These materials are not aerogels, however, since they do not have a monolithic internal structure and do not have the regular pore structure characteristic of aerogels.

Metal oxide

Metal oxide aerogels are used as catalysts in various chemical reactions/transformations or as precursors for other materials.

Aerogels made with aluminium oxide are known as alumina aerogels. These aerogels are used as catalysts, especially when "doped" with a metal other than aluminium. Nickel–alumina aerogel is the most common combination. Alumina aerogels are also being considered by NASA for capturing hypervelocity particles; a formulation doped with gadolinium and terbium could fluoresce at the particle impact site, with the amount of fluorescence dependent on impact energy.

One of the most notable differences between silica aerogels and metal oxide aerogel is that metal oxide aerogels are often variedly colored. [74]

AerogelColor
Silica, alumina, titania, zirconia Clear with Rayleigh scattering blue or white
Iron oxide Rust red or yellow, opaque
Chromia Deep green or deep blue, opaque
Vanadia Olive green, opaque
Neodymium oxide Purple, transparent
Samaria Yellow, transparent
Holmia, erbia Pink, transparent

Other

Organic polymers can be used to create aerogels. SEAgel is made of agar. AeroZero film is made of polyimide. Cellulose from plants can be used to create a flexible aerogel. [75]

GraPhage13 is the first graphene-based aerogel assembled using graphene oxide and the M13 bacteriophage. [76]

Chalcogel is an aerogel made of chalcogens (the column of elements on the periodic table beginning with oxygen) such as sulfur, selenium, and other elements. [77] Metals less expensive than platinum have been used in its creation.

Aerogels made of cadmium selenide quantum dots in a porous 3-D network have been developed for use in the semiconductor industry. [78]

Aerogel performance may be augmented for a specific application by the addition of dopants, reinforcing structures, and hybridizing compounds. For example, Spaceloft is a composite of aerogel with some kind of fibrous batting. [79]

Applications

Aerogels are used for a variety of applications:

Safety

Silica-based aerogels are not known to be carcinogenic or toxic. However, they are a mechanical irritant to the eyes, skin, respiratory tract, and digestive system. They can also induce dryness of the skin, eyes, and mucous membranes. [121] Therefore, it is recommended that protective gear including respiratory protection, gloves and eye goggles be worn whenever handling or processing bare aerogels, particularly when a dust or fine fragments may occur. [122]

See also

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References

Creative Commons by small.svg  This article incorporates text by Elizabeth Barrios, David Fox, Yuen Yee Li Sip, Ruginn Catarata, Jean E. Calderon, Nilab Azim, Sajia Afrin, Zeyang Zhang and Lei Zhai available under the CC BY 4.0 license.

  1. Definitions of terms relating to the structure and processing of sols, gels, networks, and inorganic-organic hybrid materials (IUPAC Recommendations 2007). Vol. 79. Pure and Applied Chemistry. 2007. pp. 1801–1829. doi:10.1351/goldbook.A00173. ISBN   978-0-9678550-9-7. Archived from the original on 30 November 2012.
  2. "Guinness Records Names JPL's Aerogel World's Lightest Solid". NASA. Jet Propulsion Laboratory. 7 May 2002. Archived from the original on 25 May 2009. Retrieved 25 May 2009.
  3. Aegerter, M.A.; Leventis, N.; Koebel, M. M. (2011). Aerogels Handbook. Springer publishing. ISBN   978-1-4419-7477-8.
  4. Pekala, R. W. (1989). "Organic aerogels from the polycondensation of resorcinol with formaldehyde". Journal of Materials Science. 24 (9): 3221–3227. Bibcode:1989JMatS..24.3221P. doi:10.1007/BF01139044. ISSN   0022-2461. S2CID   91183262.
  5. 1 2 Pajonk, G. M. (16 May 1991). "Aerogel catalysts". Applied Catalysis. 72 (2): 217–266. doi:10.1016/0166-9834(91)85054-Y. ISSN   0166-9834.
  6. Barron, Randall F.; Nellis, Gregory F. (2016). Cryogenic Heat Transfer (2nd ed.). CRC Press. p. 41. ISBN   9781482227451. Archived from the original on 22 November 2017.
  7. Kistler, S. S. (1931). "Coherent expanded aerogels and jellies". Nature . 127 (3211): 741. Bibcode:1931Natur.127..741K. doi: 10.1038/127741a0 . S2CID   4077344.
  8. Kistler, S. S. (1932). "Coherent Expanded-Aerogels". Journal of Physical Chemistry . 36 (1): 52–64. doi:10.1021/j150331a003.
  9. "What is Aerogel?". Aerogel.org. Retrieved 22 January 2023.
  10. "What is Aerogel? Theory, Properties and Applications". azom.com. 12 December 2013. Archived from the original on 9 December 2014. Retrieved 5 December 2014.
  11. Aerogel Structure Archived 25 December 2014 at the Wayback Machine . Str.llnl.gov. Retrieved on 31 July 2016.
  12. "Silica Aerogel". Aerogel.org. Archived from the original on 4 April 2016.
  13. Pore Structure of Silica Aerogels Archived 1 December 2014 at the Wayback Machine . Energy.lbl.gov. Retrieved on 31 July 2016.
  14. Zhang, Hu; Zhang, Chao; Ji, Wentao; Wang, Xian; Li, Yueming; Tao, Wenquan (30 August 2018). "Experimental Characterization of the Thermal Conductivity and Microstructure of Opacifier-Fiber-Aerogel Composite". Molecules. 23 (9): 2198. doi: 10.3390/molecules23092198 . ISSN   1420-3049. PMC   6225116 . PMID   30200271.
  15. Caps, R.; Fricke, J. (2004), Aegerter, Michel A.; Mennig, Martin (eds.), "Aerogels for Thermal Insulation", Sol-Gel Technologies for Glass Producers and Users, Boston, MA: Springer US, pp. 349–353, doi:10.1007/978-0-387-88953-5_46, ISBN   978-0-387-88953-5 , retrieved 29 March 2021
  16. Berge, Axel and Johansson, Pär (2012) Literature Review of High Performance Thermal Insulation Archived 21 November 2014 at the Wayback Machine . Department of Civil and Environmental Engineering, Chalmers University of Technology, Sweden
  17. The Surface Chemistry of Silica Aerogels Archived 1 December 2014 at the Wayback Machine . Energy.lbl.gov. Retrieved on 31 July 2016.
  18. Araby, S.; Qiu, A.; Wang, R.; Zhao, Z.; Wang, C.H.; Ma, J. Aerogels based on carbon nanomaterials. J. Mater. Sci. 2016, 51, 9157–9189.
  19. Pierre, A.C. History of Aerogels. In Aerogels Handbook. Advances in Sol-Gel Derived Materials and Technologies; Aegerter, M., Leventis, N., Koebel, M., Eds.; Springer: New York, NY, USA, 2011; pp. 3–18.
  20. Zhang, M.; Fang, S.; Zakhidov, A.A.; Lee, S.B.; Alieve, A.E.; Williams, C.D.; Atkinson, K.R.; Baughman, R.H. Strong, transparent, multifunctinoal, carbon nanotube sheets. Science 2005, 209, 1215–1220.
  21. Dorcheh, Soleimani; Abbasi, M. (2008). "Silica Aerogel; Synthesis, Properties, and Characterization". Journal of Materials Processing Technology. 199 (1–3): 10–26. doi:10.1016/j.jmatprotec.2007.10.060.
  22. 1 2 3 "Making silica aerogels". Lawrence Berkeley National Laboratory. Archived from the original on 14 May 2009. Retrieved 28 May 2009.
  23. Pierre, A. C.; Pajonk, G. M. (2002). "Chemistry of Aerogels and their Applications". Chemical Reviews . 102 (11): 4243–4265. doi:10.1021/cr0101306. PMID   12428989.
  24. Hüsing, N.; Schubert, U. Aerogels—Airy Materials: Chemistry, Structure, and Properties. Angew. Chem. Int. Ed. 1998, 37, 22–45.
  25. Capadona, L.A.; Meador, M.A.B.; Alunni, A.; Fabrizio, E.F.; Vassilaras, P.; Leventis, N. Flexible, low-density polymer crosslinked silica aerogels. Polymer 2006, 47, 5754–5761.
  26. Leventis, N.; Lu, H. Polymer-Crosslinked Aerogels. In Aerogels Handbook. Advances in Sol-Gel Derived Materials and Technologies; Aegerter, M., Leventis, N., Koebel, M., Eds.; Springer: New York, NY, USA, 2011; pp. 251–285.
  27. Capadona, L.A.; Meador, M.A.B.; Alunni, A.; Fabrizio, E.F.; Vassilaras, P.; Leventis, N. Flexible, low-density polymer crosslinked silica aerogels. Polymer 2006, 47, 5754–5761.
  28. Hench, L.L.; West, J.K. The sol-gel process. Chem. Rev. 1990, 90, 33–72.
  29. Mulik, S.; Sotiriou-leventis, C.; Leventis, N. Time-Efficient Acid-Catalyzed Synthesis of Resorcinol—Formaldehyde Aerogels. Chem. Mater. 2007, 19, 6138–6144.
  30. Zhang, J.; Cao, Y.; Feng, J.; Wu, P. Graphene-oxide-sheet-induced gelation of cellulose and promoted mechanical properties of composite aerogels. J. Phys. Chem. C 2012, 116, 8063–8068.
  31. Hdach, H.; Woignier, T.; Phalippou, J.; Scherer, G.W. Effect of aging and pH on the modulus of aerogels. J. Non-Cryst. Solids 1990, 121, 202–205.
  32. Capadona, L.A.; Meador, M.A.B.; Alunni, A.; Fabrizio, E.F.; Vassilaras, P.; Leventis, N. Flexible, low-density polymer crosslinked silica aerogels. Polymer 2006, 47, 5754–5761.
  33. Einarsrud, M.; Nilsen, E.; Rigacci, A.; Pajonk, G.M.; Buathier, S. Strengthening of silica gels and aerogels by washing and aging processes. J. Non-Cryst. Solids 2001, 285, 1–7.
  34. Soleimani Dorcheh, A.; Abbasi, M.H. Silica aerogel; synthesis, properties and characterization. J. Mater. Process. Technol. 2008, 199, 10–26.
  35. Hæreid, S.; Anderson, J.; Einarsrud, M.A.; Hua, D.W.; Smith, D.M. Thermal and temporal aging of TMOS-based aerogel precursors in water. J. Non-Cryst. Solids 1995, 185, 221–226.
  36. Omranpour, H.; Motahari, S. Effects of processing conditions on silica aerogel during aging: Role of solvent, time and temperature. J. Non-Cryst. Solids 2013, 379, 7–11.
  37. Cheng, C.-P.; Iacobucci, P.A. Inorganic Oxide Aerogels and Their Preparation. U.S. Patent 4,717,708, 5 January 1988.
  38. Fricke, Jochen; Emmerling, Andreas (1992). "Aerogels". Journal of the American Ceramic Society . 75 (8): 2027–2036. doi:10.1111/j.1151-2916.1992.tb04461.x.
  39. Zhang, Xuexia; Yu, Yan; Jiang, Zehui; Wang, Hankun (1 December 2015). "The effect of freezing speed and hydrogel concentration on the microstructure and compressive performance of bamboo-based cellulose aerogel". Journal of Wood Science. 61 (6): 595–601. doi: 10.1007/s10086-015-1514-7 . ISSN   1611-4663. S2CID   18169604.
  40. 1 2 Nguyen, Hong K. D.; Hoang, Phuong T.; Dinh, Ngo T.; Nguyen, Hong K. D.; Hoang, Phuong T.; Dinh, Ngo T. (August 2018). "Synthesis of Modified Silica Aerogel Nanoparticles for Remediation of Vietnamese Crude Oil Spilled on Water". Journal of the Brazilian Chemical Society . 29 (8): 1714–1720. doi: 10.21577/0103-5053.20180046 . ISSN   0103-5053.
  41. Tewari, Param H.; Hunt, Arlon J.; Lofftus, Kevin D. (1 July 1985). "Ambient-temperature supercritical drying of transparent silica aerogels". Materials Letters. 3 (9): 363–367. doi:10.1016/0167-577X(85)90077-1. ISSN   0167-577X.
  42. Gurav, J.L.; Jung, I.K.; Park, H.H.; Kang, E.S.; Nadargi, D.Y. Silica aerogel: Synthesis and applications. J. Nanomater. 2010, 2010, 23.
  43. Beckman, E.J. Supercritical or near-critical CO2 in green chemical synthesis and processing. J. Supercrit. Fluids 2004, 28, 121–191.
  44. Jin, H.; Nishiyama, Y.; Wada, M.; Kuga, S. Nanofibrillar cellulose aerogels. Colloids Surfaces A Physicochem. Eng. Asp. 2004, 240, 63–67.
  45. Jiménez-Saelices, C.; Seantier, B.; Cathala, B.; Grohens, Y. Effect of freeze-drying parameters on the microstructure and thermal insulating properties of nanofibrillated cellulose aerogels. J. Sol-Gel Sci. Technol. 2017, 84, 475–485.
  46. Wang, C.; Chen, X.; Wang, B.; Huang, M.; Wang, B.; Jiang, Y.; Ruoff, R.S. Freeze-Casting Produces a Graphene Oxide Aerogel with a Radial and Centrosymmetric Structure. ACS Nano 2018, 12, 5816–5825.
  47. Simon-Herrero, C.; Caminero-Huertas, S.; Romero, A.; Valverde, J.L.; Sanchez-Silva, L. Effects of freeze-drying conditions on aerogel properties. J. Mater. Sci. 2016, 51, 8977–8985.
  48. Jiménez-Saelices, C.; Seantier, B.; Cathala, B.; Grohens, Y. Effect of freeze-drying parameters on the microstructure and thermal insulating properties of nanofibrillated cellulose aerogels. J. Sol-Gel Sci. Technol. 2017, 84, 475–485.
  49. Wang, C.; Chen, X.; Wang, B.; Huang, M.; Wang, B.; Jiang, Y.; Ruoff, R.S. Freeze-Casting Produces a Graphene Oxide Aerogel with a Radial and Centrosymmetric Structure. ACS Nano 2018, 12, 5816–5825.
  50. Simon-Herrero, C.; Caminero-Huertas, S.; Romero, A.; Valverde, J.L.; Sanchez-Silva, L. Effects of freeze-drying conditions on aerogel properties. J. Mater. Sci. 2016, 51, 8977–8985.
  51. Deville, S. Ice-templating, freeze casting: Beyond materials processing. J. Mater. Res. 2013, 28, 2202–2219.
  52. Deville, S. The lure of ice-templating: Recent trends and opportunities for porous materials. Scr. Mater. 2018, 147, 119–124.
  53. Gurav, J.L.; Jung, I.K.; Park, H.H.; Kang, E.S.; Nadargi, D.Y. Silica aerogel: Synthesis and applications. J. Nanomater. 2010, 2010, 23.
  54. Shen, C.; Calderon, J.E.; Barrios, E.; Soliman, M.; Khater, A.; Jeyaranjan, A.; Tetard, L.; Gordon, A.; Seal, S.; Zhai, L. Anisotropic electrical conductivity in polymer derived ceramics induced by graphene aerogels. J. Mater. Chem. C 2017, 5, 11708–11716.
  55. Ali, I.; Chen, L.; Huang, Y.; Song, L.; Lu, X.; Liu, B.; Zhang, L.; Zhang, J.; Hou, L.; Chen, T. Humidity-Responsive Gold Aerogel for Real-Time Monitoring of Human Breath. Langmuir 2018, 34, 4908–4913.
  56. Cong, L.; Li, X.; Ma, L.; Peng, Z.; Yang, C.; Han, P.; Wang, G.; Li, H.; Song, W.; Song, G. High-performance graphene oxide/carbon nanotubes aerogel-polystyrene composites: Preparation and mechanical properties. Mater. Lett. 2018, 214, 190–193.
  57. Cao, N.; Lyu, Q.; Li, J.; Wang, Y.; Yang, B.; Szunerits, S.; Boukherroub, R. Facile synthesis of fluorinated polydopamine/chitosan/reduced graphene oxide composite aerogel for efficient oil/water separation. Chem. Eng. J. 2017, 326, 17–28.
  58. Jia, J.; Wang, C. A facile restructuring of 3D high water absorption aerogels from methoxy polyethylene glycol-polycaprolactone (mPEG-PCL) nanofibers. Mater. Sci. Eng. C 2019, 94, 965–975.
  59. Gan, Yong X.; Gan, Jeremy B. (June 2020). "Advances in Manufacturing Composite Carbon Nanofiber-Based Aerogels". Journal of Composites Science . 4 (2): 73. doi: 10.3390/jcs4020073 .
  60. "Carbon Aerogel - an overview | ScienceDirect Topics". ScienceDirect . Retrieved 29 March 2021.
  61. "Aerogels: Thinner, Lighter, Stronger". NASA . 15 April 2015. Retrieved 29 March 2021.
  62. Taher, Abul (19 August 2007). "Scientists hail 'frozen smoke' as material that will change world". Times Online. London. Archived from the original on 12 September 2007. Retrieved 22 August 2007.
  63. 1 2 Aerogels Terms. LLNL.gov
  64. "Lab's aerogel sets world record". LLNL Science & Technology Review. October 2003. Archived from the original on 9 October 2006.
  65. Groom, D.E. Abridged from Atomic Nuclear Properties Archived 27 February 2008 at the Wayback Machine . Particle Data Group: 2007.
  66. "About Aerogel". Aspen Aerogels. ASPEN AEROGELS, INC. Archived from the original on 26 May 2014. Retrieved 12 March 2014.
  67. 1 2 3 4 5 6 7 8 9 Gurav, Jyoti L.; Jung, In-Keun; Park, Hyung-Ho; Kang, Eul Son; Nadargi, Digambar Y. (11 August 2010). "Silica Aerogel: Synthesis and Applications". Journal of Nanomaterials . 2010: 1–11. doi: 10.1155/2010/409310 .
  68. Gentilini, S.; Ghajeri, F.; Ghofraniha, N.; Falco, A. Di; Conti, C. (27 January 2014). "Optical shock waves in silica aerogel". Optics Express. 22 (2): 1667–1672. Bibcode:2014OExpr..22.1667G. doi:10.1364/OE.22.001667. hdl: 10023/4490 . ISSN   1094-4087. PMID   24515173.
  69. "Thermal conductivity" in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN   0-8493-0486-5. Section 12, p. 227
  70. Cohen, E.; Glicksman, L. (1 August 2015). "Thermal Properties of Silica Aerogel Formula". Journal of Heat Transfer. 137 (8). ASME International: 081601. doi:10.1115/1.4028901. hdl: 1721.1/106629 . S2CID   55430528.
  71. Mecklenburg, Matthias (July 2012). "Aerographite: Ultra Lightweight, Flexible Nanowall, Carbon Microtube Material with Outstanding Mechanical Performance". Advanced Materials. 24 (26): 3486–90. Bibcode:2012AdM....24.3486M. doi:10.1002/adma.201200491. PMID   22688858. S2CID   2787227.
  72. Whitwam, Ryan (26 March 2013). Graphene aerogel is world's lightest material Archived 27 March 2013 at the Wayback Machine . gizmag.com
  73. Quick, Darren (24 March 2013). Graphene aerogel takes world's lightest material crown Archived 25 March 2013 at the Wayback Machine . gizmag.com
  74. "Metal Oxide Aerogels". Aerogel.org. Archived from the original on 12 August 2013. Retrieved 12 June 2013.
  75. Kobayashi, Yuri; Saito, Tsuguyuki; Isogai, Akira (2014). "Aerogels with 3D Ordered Nanofiber Skeletons of Liquid-Crystalline Nanocellulose Derivatives as Tough and Transparent Insulators". Angewandte Chemie International Edition. 53 (39): 10394–7. doi:10.1002/anie.201405123. PMID   24985785.
  76. Passaretti, P., et al. (2019). "Multifunctional graphene oxide-bacteriophage based porous three-dimensional micro-nanocomposites." Nanoscale 11(28): 13318-13329. https://doi.org/10.1039/C9NR03670A
  77. Biello, David Heavy Metal Filter Made Largely from Air. Archived 26 February 2015 at the Wayback Machine Scientific American, 26 July 2007. Retrieved on 2007-08-05.
  78. Yu, H; Bellair, R; Kannan, R. M.; Brock, S. L. (2008). "Engineering Strength, Porosity, and Emission Intensity of Nanostructured CdSe Networks By Altering The Building Block Shape". Journal of the American Chemical Society . 130 (15): 5054–5055. doi:10.1021/ja801212e. PMID   18335987.
  79. "Strong and Flexible Aerogels". Aerogel.org. Archived from the original on 11 October 2014. Retrieved 17 July 2014.
  80. 1 2 3 Song, Yangxi; Li, Bin; Yang, Siwei; Ding, Guqiao; Zhang, Changrui; Xie, Xiaoming (15 May 2015). "Ultralight boron nitride aerogels via template-assisted chemical vapor deposition". Scientific Reports. 5 (1): 10337. Bibcode:2015NatSR...510337S. doi:10.1038/srep10337. ISSN   2045-2322. PMC   4432566 . PMID   25976019.
  81. Ganobjak, Michal; Brunner, Samuel; Wernery, Jannis (2020). "Aerogel materials for heritage buildings: Materials, properties and case studies". Journal of Cultural Heritage. 42 (March–April): 81–98. doi: 10.1016/j.culher.2019.09.007 . S2CID   209375441.
  82. Wernery, Jannis; Mancebo, Francisco; Malfait, Wim; O'Connor, Michael; Jelle, Bjørn Petter (2021). "The economics of thermal superinsulation in buildings". Energy & Buildings. 253 (December 2021): 111506. doi: 10.1016/j.enbuild.2021.111506 . hdl: 11250/2789460 . S2CID   239117650.
  83. Solar Decathon 2007. GATech.edu
  84. Gan, Guoqiang; Li, Xinyong; Fan, Shiying; Wang, Liang; Qin, Meichun; Yin, Zhifan; Chen, Guohua (2019). "Carbon Aerogels for Environmental Clean-Up". European Journal of Inorganic Chemistry . 2019 (27): 3126–3141. doi:10.1002/ejic.201801512. ISSN   1099-0682. S2CID   191132567.
  85. 1 2 Shi, Mingjia; Tang, Cunguo; Yang, Xudong; Zhou, Junling; Jia, Fei; Han, Yuxiang; Li, Zhenyu (2017). "Superhydrophobic silica aerogels reinforced with polyacrylonitrile fibers for adsorbing oil from water and oil mixtures". RSC Advances . 7 (7): 4039–4045. Bibcode:2017RSCAd...7.4039S. doi: 10.1039/C6RA26831E .
  86. Liu, Xianhu; Zhang, Mingtao; Hou, Yangzhe; Pan, Yamin; Liu, Chuntai; Shen, Changyu (September 2022). "Hierarchically Superhydrophobic Stereo-Complex Poly (Lactic Acid) Aerogel for Daytime Radiative Cooling". Advanced Functional Materials. 32 (46). doi:10.1002/adfm.202207414. S2CID   252076428 via Wiley.
  87. Li, Tao; Sun, Haoyang; Yang, Meng; Zhang, Chentao; Lv, Sha; Li, Bin; Chen, Longhao; Sun, Dazhi (2023). "All-Ceramic, Compressible and Scalable Nanofibrous Aerogels for Subambient Daytime Radiative Cooling". Chemical Engineering Journal. 452: 139518. doi:10.1016/j.cej.2022.139518. S2CID   252678873 via Elsevier Science Direct.
  88. Choi, Jinsoon; Suh, Dong Jin (1 September 2007). "Catalytic Applications of Aerogels". Catalysis Surveys from Asia. 11 (3): 123–133. doi:10.1007/s10563-007-9024-2. ISSN   1574-9266. S2CID   97092432.
  89. Spoon, Marianne English (25 February 2014). "'Greener' aerogel technology holds potential for oil and chemical clean-up". University of Wisconsin Madison News. Archived from the original on 28 April 2015. Retrieved 29 April 2015.
  90. "Taking control". Cosmetics Business. 1 April 2006. Archived from the original on 6 November 2020. Retrieved 29 March 2021.
  91. Chen, Hao; Xu, Yuanming; Tong, Yan; Hu, Junhao (15 March 2019). "The investigation of nanofluidic energy absorption system based on high porosity aerogel nano-materials". Microporous and Mesoporous Materials. 277: 217–228. doi:10.1016/j.micromeso.2018.09.032. ISSN   1387-1811. S2CID   105477931.
  92. Remington, Bruce A.; Park, Hye-Sook; Casey, Daniel T.; Cavallo, Robert M.; Clark, Daniel S.; Huntington, Channing M.; Kuranz, Carolyn C.; Miles, Aaron R.; Nagel, Sabrina R.; Raman, Kumar S.; Smalyuk, Vladimir A. (10 September 2019). "Rayleigh–Taylor instabilities in high-energy density settings on the National Ignition Facility". Proceedings of the National Academy of Sciences . 116 (37): 18233–18238. Bibcode:2019PNAS..11618233R. doi: 10.1073/pnas.1717236115 . ISSN   0027-8424. PMC   6744876 . PMID   29946021.
  93. Hrubesh, Lawrence W. (1 April 1998). "Aerogel applications". Journal of Non-Crystalline Solids. 225 (1): 335–342. Bibcode:1998JNCS..225..335H. doi:10.1016/S0022-3093(98)00135-5.
  94. Hüsing, Nicola; Schubert, Ulrich (1998). "Aerogels—Airy Materials: Chemistry, Structure, and Properties". Angewandte Chemie International Edition. 37 (1–2): 22–45. doi:10.1002/(SICI)1521-3773(19980202)37:1/2<22::AID-ANIE22>3.0.CO;2-I. ISSN   1521-3773. PMID   29710971.
  95. Tsou, Peter (2 June 1995). "Silica aerogel captures cosmic dust intact". Journal of Non-Crystalline Solids. Proceedings of the Fourth International Symposium on AEROGELS. 186: 415–427. Bibcode:1995JNCS..186..415T. doi:10.1016/0022-3093(95)00065-8. ISSN   0022-3093.
  96. "NASA - Catching Comet Dust With Aerogel". NASA . Retrieved 29 March 2021.
  97. Tsou, Peter. "Silica Aerogel Captures Cosmic Dust Intact" (PDF). NASA . Retrieved 29 March 2021.
  98. Preventing heat escape through insulation called "aerogel" Archived 13 October 2007 at the Wayback Machine , NASA CPL
  99. Down-to-Earth Uses for Space Materials Archived 30 September 2007 at the Wayback Machine , The Aerospace Corporation
  100. Nuckols, M. L.; Chao J. C.; Swiergosz M. J. (2005). "Manned Evaluation of a Prototype Composite Cold Water Diving Garment Using Liquids and Superinsulation Aerogel Materials". United States Navy Experimental Diving Unit Technical Report. NEDU-05-02. Archived from the original on 20 August 2008. Retrieved 21 April 2008.{{cite journal}}: CS1 maint: unfit URL (link)
  101. Trevino, Luis A.; Orndoff, Evelyne S.; Tang, Henry H.; Gould, George L.; Trifu, Roxana (15 July 2002). "Aerogel-Based Insulation for Advanced Space Suit". SAE Technical Paper Series. 1. Warrendale, PA: SAE International. doi:10.4271/2002-01-2316.
  102. Iwata, S.; Adachi, I.; Hara, K.; Iijima, T.; Ikeda, H.; Kakuno, H.; Kawai, H.; Kawasaki, T.; Korpar, S.; Križan, P.; Kumita, T. (1 March 2016). "Particle identification performance of the prototype aerogel RICH counter for the Belle II experiment". Progress of Theoretical and Experimental Physics . 2016 (33H01): 033H01. arXiv: 1603.02503 . doi: 10.1093/ptep/ptw005 . ISSN   2050-3911.
  103. Wang, Jieyu; Petit, Donald; Ren, Shenqiang (2020). "Transparent thermal insulation silica aerogels". Nanoscale Advances. 2 (12): 5504–5515. Bibcode:2020NanoA...2.5504W. doi: 10.1039/D0NA00655F . PMC   9417477 . PMID   36133881.
  104. Mulik, Sudhir; Sotiriou-Leventis, Chariklia (2011), Aegerter, Michel A.; Leventis, Nicholas; Koebel, Matthias M. (eds.), "Resorcinol–Formaldehyde Aerogels", Aerogels Handbook, Advances in Sol-Gel Derived Materials and Technologies, New York, NY: Springer, pp. 215–234, doi:10.1007/978-1-4419-7589-8_11, ISBN   978-1-4419-7589-8 , retrieved 29 March 2021
  105. Huang, Let; Wei, Min; Qi, Ruijuan; Dong, Chung-Li; Dang, Dai; Yang, Cheng-Chieh; Xia, Chenfeng; Chen, Chao; Zaman, Shahid; Li, Fu-Min; You, Bo; Xia, Bao Yu. "An integrated platinum-nanocarbon electrocatalyst for efficient oxygen reduction". Nat Commun. 13. Nature. doi: 10.1038/s41467-022-34444-w . PMC   9640595 .
  106. Smirnova I.; Suttiruengwong S.; Arlt W. (2004). "Feasibility study of hydrophilic and hydrophobic silica aerogels as drug delivery systems". Journal of Non-Crystalline Solids. 350: 54–60. Bibcode:2004JNCS..350...54S. doi:10.1016/j.jnoncrysol.2004.06.031.
  107. Juzkow, Marc (1 February 2002). "Aerogel Capacitors Support Pulse, Hold-Up, and Main Power Applications". Power Electronic Technology. Archived from the original on 15 May 2007.
  108. "Dunlop Expands Aerogel Line - Tennis Industry". Tennis Industry Magazine. July 2007. Retrieved 29 March 2021.
  109. Carmichael, Mary. First Prize for Weird: A bizarre substance, like 'frozen smoke,' may clean up rivers, run cell phones and power spaceships. Archived 17 August 2007 at the Wayback Machine Newsweek International, 13 August 2007. Retrieved on 2007-08-05.
  110. Mazrouei-Sebdani, Z.; Salimian, S.; Khoddami, A.; Shams-Ghahfarokhi, F. (1 August 2019). "Sodium silicate based aerogel for absorbing oil from water: the impact of surface energy on the oil/water separation". Materials Research Express. 6 (8): 085059. Bibcode:2019MRE.....6h5059M. doi:10.1088/2053-1591/ab1eed. ISSN   2053-1591. S2CID   155307402.
  111. Wang, Fei; Dai, Jianwu; Huang, Liqian; Si, Yang; Yu, Jianyong; Ding, Bin (28 July 2020). "Biomimetic and Superelastic Silica Nanofibrous Aerogels with Rechargeable Bactericidal Function for Antifouling Water Disinfection". ACS Nano . 14 (7): 8975–8984. doi:10.1021/acsnano.0c03793. ISSN   1936-0851. PMID   32644778. S2CID   220474580.
  112. Patel, Prachi (21 August 2020). "Loofah-inspired aerogel efficiently filters microbes from water". Chemical & Engineering News . Retrieved 29 March 2021.
  113. Halperin, W. P. and Sauls, J. A. Helium-Three in Aerogel. Arxiv.org (26 August 2004). Retrieved on 7 November 2011.
  114. "De-icing aeroplanes: Sooty skies". The Economist. 26 July 2013. Archived from the original on 30 December 2013. Retrieved 11 December 2013.
  115. Katakis, Manoli. (11 July 2013) NASA Aerogel Material Present In 2014 Corvette Stingray Archived 22 February 2014 at the Wayback Machine . GM Authority. Retrieved on 2016-07-31.
  116. Camelbak Podium Ice Insulated Bottle – Review Archived 3 October 2014 at the Wayback Machine . Pinkbike. Retrieved on 31 July 2016.
  117. Unparalleled Cold Weather Performance Archived 10 January 2016 at the Wayback Machine . 45NRTH. Retrieved on 31 July 2016.
  118. "Silica Aerogels - an overview". ScienceDirect . Retrieved 29 March 2021.
  119. Mazrouei-Sebdani, Zahra; Begum, Hasina; Schoenwald, Stefan; Horoshenkov, Kirill V.; Malfait, Wim J. (15 June 2021). "A review on silica aerogel-based materials for acoustic applications". Journal of Non-Crystalline Solids . 562: 120770. Bibcode:2021JNCS..56220770M. doi: 10.1016/j.jnoncrysol.2021.120770 . ISSN   0022-3093. S2CID   233562867.
  120. Last, Jonathan V. (18 May 2009). "The Fog of War: Forgetting what we once knew". The Weekly Standard . Vol. 14, no. 33. Archived from the original on 5 December 2018.
  121. Thapliyal, Prakash C.; Singh, Kirti (27 April 2014). "Aerogels as Promising Thermal Insulating Materials: An Overview". Journal of Materials . 2014: 1–10. doi: 10.1155/2014/127049 .
  122. Cryogel 5201, 10201 Safety Data Sheet Archived 23 December 2010 at the Wayback Machine . Aspen Aerogels. 13 November 2007
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