Low compression set aerogels and aerogel composites, and methods for producing the same

Abstract

To provide an improved method for producing aerogels and improved aerogel composites having low compression set.SOLUTION: Provided is a method, comprising: (a) providing a first silica-based aerogel having a silica density of 0.055 g / cc to 0.095 g / cc and a compression set of greater than 15% as determined by ASTM D3574-Test D; (b) heating the first silica-based aerogel under an atmosphere comprising greater than 10% oxygen at a temperature between about 200°C and 400°C to obtain a second silica-based aerogel; wherein the first silica-based aerogel is heated for a time sufficient to alter the compression set of the first silica-based aerogel such that the obtained second silica-based aerogel has a compression set less than or equal to 15% as determined by ASTM D3574 - Test D.SELECTED DRAWING: None

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and benefit of U.S. Provisional Patent Application No. 63 / 290,977, filed December 17, 2021, entitled "Low Compression Set Aerogels and Aerogel Composites and Methods of Making," and U.S. Provisional Patent Application No. 63 / 386,892, filed December 9, 2022, entitled "Low Compression Set Aerogels and Aerogel Composites and Methods of Making," each of which is incorporated herein by reference in its entirety.

[0002] The present invention relates generally to aerogel technology. More specifically, the present invention relates, in various embodiments, to improved methods for producing aerogels and improved aerogel composites having low compression set. [Background technology]

[0003] Low-density aerogel materials are widely considered to be the best solid insulators available. Aerogels function as insulators primarily by minimizing conduction (low structural density provides a tortuous path for energy transfer through the solid framework), convection (large pore volume and very small pore size provide minimal convection), and radiation (IR-absorbing or scattering dopants are easily dispersed throughout the aerogel matrix). Aerogels can be used in a wide range of applications, including heating and cooling insulation, acoustic insulation, electronic dielectrics, aerospace, energy storage and production, and filtration. Furthermore, aerogel materials exhibit many other interesting acoustic, optical, mechanical, and chemical properties that make them extremely useful in a variety of insulating and non-insulating applications.

[0004] Aerogels are generally formed by extracting a liquid phase from a gel. The extraction of the liquid phase from the gel is done in a manner that reduces the shrinkage of the wet gel into a porous network and framework. However, the resulting aerogels tend to be brittle and friable. Aerogel composites are aerogels that contain reinforcing materials that improve characteristics such as flexibility and / or strength of the aerogel material. However, such composite aerogels can still suffer from high compression set. It is desirable to address deficiencies such as high compression set in aerogels and aerogel composites. Summary of the Invention

[0005] It is an object of the present disclosure to obviate or mitigate at least one of the disadvantages of the above-mentioned methods and materials. The methods and materials provided herein are designed to improve the compression set properties of aerogels and aerogel composites.

[0006] In one embodiment of the present disclosure, the compression set of the aerogel or aerogel composite can be improved by heating the aerogel at a temperature of about 200°C to 400°C in an atmosphere containing greater than 10% oxygen. The resulting heat-treated aerogel has improved compression set properties. In one embodiment of the present invention, the aerogel or aerogel composite has a compression set greater than 15% as determined by ASTM D3574-Test D. After heat treatment in an oxygen-containing atmosphere, the compression set of the aerogel is improved to 15% or less as determined by ASTM D3574-Test D. During heating of the aerogel or aerogel composite, the temperature is limited to temperatures below 400°C.

[0007] In one embodiment of the present disclosure, the atmosphere in which the heating is carried out contains about 15% to about 25% oxygen. In a preferred embodiment of the present disclosure, the atmosphere is air.

[0008] In one embodiment of the present disclosure, improved compression set of the aerogel or aerogel composite is achieved by heating the aerogel or aerogel composite to a temperature of about 200° C. to 400° C. for a time period of about 30 seconds or more. In one embodiment of the present disclosure, the aerogel or aerogel composite is heated for a time period of 30 seconds to 3 hours.

[0009] In one embodiment of the present disclosure, the aerogel or aerogel composite includes silica. The aerogel or aerogel composite may include a base. The base may be added to the gel-forming material to catalyze the gel formation of the aerogel precursor gel remaining in the aerogel. In one embodiment of the present disclosure, the base is an amine base. The aerogel may include at least about 0.5% of the base. In one embodiment of the present disclosure, the aerogel may include 0.5% to about 10% of the base. Heat-treating the aerogel or aerogel composite removes a portion of the base from the aerogel. In one embodiment of the present disclosure, the amount of base in the aerogel or aerogel composite before heat-treatment is greater than the amount of base in the aerogel or aerogel composite after heat-treatment.

[0010] In one aspect of the present disclosure, the aerogel is an aerogel composite comprised of an aerogel and a reinforcing material. In one aspect of the present disclosure, the reinforcing material is a fiber-reinforced material. The aerogel composite may also include an opacifying additive. Exemplary opacifying additives include, but are not limited to, boron carbide (BC), diatomaceous earth, manganese ferrite (MnFeO), manganese oxide (MnO), nickel oxide (NiO), tin oxide (SnO), silver oxide (AgO), bismuth oxide (BiO), titanium carbide (TiC), tungsten carbide (WC), silicon carbide (SiC), carbon black, titanium oxide (TiO), iron titanium oxide (FeTiO), zirconium silicate (ZrSiO), zirconium oxide (ZrO), iron (II) oxide (FeO), iron (III) oxide (FeO), manganese dioxide (MnO), iron titanium oxide (ilmenite, FeTiO), chromium oxide (CrO), or mixtures thereof. In a preferred embodiment of the present invention, the aerogel composite includes silicon carbide as an opacifying additive.

[0011] The methods described herein can be used to form aerogels and aerogel composites with improved compression set. These improved aerogels and aerogel composites can be used in a variety of applications. In one aspect of the present disclosure, the improved aerogels and aerogel composites can be used in insulating barriers in electrical storage systems.

[0012] In another aspect of the present disclosure, an insulating barrier comprising the improved aerogel or aerogel composite can be used in a battery module including a plurality of battery cells and one or more insulating barriers disposed between adjacent battery cells. The battery module can be used in a power system.

[0013] In one embodiment of the present disclosure, a device or vehicle includes a battery module or power system having an insulating barrier comprising an improved aerogel or aerogel composition. Exemplary devices include laptop computers, PDAs, mobile phones, tag scanners, audio devices, video devices, display panels, video cameras, digital cameras, desktop computers, military portable computers, military telephones, laser range finders, digital communication devices, intelligence gathering sensors, electronically integrated clothing, night vision devices, power tools, calculators, radios, remote-controlled appliances, GPS devices, handheld and portable televisions, car starters, flashlights, acoustic devices, portable heaters, portable vacuum cleaners, or portable medical instruments. The vehicle may be an electric vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0014] It is to be understood that the present invention is not limited to specific devices or methods, which may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular examples only, and is not intended to be limiting. As used in this specification and the appended claims, the singular forms "a," "an," and "the" include singular and plural referents unless the content clearly dictates otherwise. Furthermore, the word "may" is used throughout this application in its permissive sense (i.e., having the potential to, being able to) rather than its required sense (i.e., must). The term "comprises" and its derivatives mean "including, but not limited to." The term "coupled" means connected directly or indirectly.

[0015] As used herein, "about" means approximately or near within the context in which it is provided. In one embodiment, the term "about" may include conventional rounding to significant figures of a numerical value. Additionally, the phrase "about 'x' to 'y'" includes "about 'x' to about 'y'."

[0016] Aerogels are a class of porous materials that contain an interconnected structural framework with a corresponding network of pores integrated within the framework and an interstitial phase composed primarily of a gas, such as air. Aerogels are typically characterized by low density, high porosity, high surface area, and small pore size. Aerogels can be distinguished from other porous materials by their physical and structural properties. In the context of this disclosure, aerogels are defined as materials that have (a) an average pore size ranging from about 2 nm to about 100 nm, (b) a porosity of at least 80% or greater, and (c) a porosity of at least about 20 nm as determined using nitrogen porosimetry testing. 2 / g or greater. Thus, the aerogels of the present disclosure include any aerogel or other open-cell compound that meets these defining elements.

[0017] The aerogel material may also be further characterized by additional physical properties, such as (d) a pore volume of about 2.0 mL / g or greater, preferably about 3.0 mL / g or greater, (e) a density of about 0.50 g / cc or less, preferably about 0.25 g / cc or less, and (f) at least 50% of the total pore volume comprising pore diameters between 2 and 50 nm, although satisfying these additional properties is not essential to characterize the compound as an aerogel material.

[0018] Producing an aerogel generally involves i) forming a sol-gel solution, ii) forming a gel from the sol-gel solution, and iii) extracting the solvent from the gel material to obtain a dry aerogel material. This process is discussed in more detail below, specifically in the context of forming inorganic aerogels, such as silica aerogels. However, the specific examples and illustrations provided herein are not intended to limit the present disclosure to any particular type of aerogel and / or preparation method. The present disclosure may include any aerogel formed by any relevant preparation method known to one of ordinary skill in the art.

[0019] The first step in forming inorganic aerogels is generally the formation of a sol-gel solution by hydrolysis and condensation of metal alkoxide precursors in an alcohol-based solvent. Key variables in the formation of inorganic aerogels include the type of alkoxide precursor included in the sol-gel solution, the nature of the solvent, the processing temperature and pH of the sol-gel solution (which can be altered by adding acid or base), and the precursor / solvent / water ratio within the sol-gel solution. Controlling these variables during the formation of the sol-gel solution can enable control of the growth and aggregation of the gel framework during the subsequent transition of the gel material from a "sol" state to a "gel" state. The properties of the resulting aerogel are affected by the pH and molar ratio of the reactants in the precursor solution; however, any pH and any molar ratio that allows for gel formation can be used in the present disclosure.

[0020] The sol-gel solution is formed by combining at least one gelation precursor with a solvent. Suitable solvents for use in forming the sol-gel solution include lower alcohols having 1 to 6, preferably 2 to 4, carbon atoms, although other solvents known to those skilled in the art can also be used. Examples of useful solvents include, but are not limited to, methanol, ethanol, isopropanol, ethyl acetate, ethyl acetoacetate, acetone, dichloromethane, and tetrahydrofuran. Multiple solvents can also be combined to achieve a desired level of dispersion or optimize the properties of the gel material. Therefore, the selection of the optimal solvent for the sol-gel and gel formation steps depends on the specific precursors, fillers, and additives incorporated into the sol-gel solution, the target processing conditions for gelation and liquid-phase extraction, and the desired properties of the final aerogel material.

[0021] Water may also be present in the precursor-solvent solution. The water acts to hydrolyze the metal alkoxide precursor to the metal hydroxide precursor. The hydrolysis reaction may be as follows (using TEOS in an ethanol solvent as an example): Si(OC2H5)4+4H2O→Si(OH)4+4(C2H5OH) (1)

[0022] The resulting hydrolyzed metal hydroxide precursor remains suspended in the solvent solution in a "sol" state, either as individual molecules or as small polymerized (or oligomerized) colloidal clusters of molecules. For example, polymerization / condensation of a Si(OH)4 precursor can occur as follows: 2Si(OH)4→(OH)3Si-O-Si(OH)3+H2O (2) This polymerization can continue until colloidal clusters of polymerized (or oligomerized) SiO2 (silica) molecules are formed.

[0023] Acids and bases can be incorporated into the sol-gel solution to control the pH of the solution and to catalyze the hydrolysis and condensation reactions of the precursor materials. While any acid can be used to catalyze the precursor reaction and achieve a lower pH solution, preferred acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), phosphoric acid (H3PO4), oxalic acid, and acetic acid.

[0024] Similarly, any base can be used to catalyze the precursor reaction and produce a higher pH solution, such as ammonium hydroxide (NH4OH). In one aspect of the present disclosure, an amine base can be used to catalyze the precursor reaction. In the context of the present disclosure, the term "amine base" refers to an organic compound containing an amine group. For example, amine bases according to embodiments herein include, but are not limited to, trialkylamines, amidines, guanidines, and imidazoles. Specific examples of amine bases include guanidines (e.g., guanidinium hydroxide), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), pyridine, imidazole, and 4,5-dihydroimidazole.

[0025] The sol-gel solution can include additional co-gelling precursors, as well as fillers and other additives. Fillers and other additives may be dispensed into the sol-gel solution at any time before or during the formation of the gel. Fillers and other additives may also be incorporated into the gelling material after gelation via various techniques known to those skilled in the art. Preferably, the sol-gel solution, including gelling precursors, solvent, catalyst, water, fillers, and other additives, is a homogeneous solution capable of effective gel formation under suitable conditions.

[0026] Once the sol-gel solution is formed and optimized, the gel-forming components in the sol-gel can be converted into a gel material. The process of converting the gel-forming components into a gel material includes an initial gel formation step in which the gel is solidified to the gel point of the gel material. The gel point of the gel material can be considered the point at which the gelling solution exhibits resistance to flow throughout its volume and / or forms a substantially continuous polymeric framework. A range of gel formation techniques are known to those skilled in the art. Examples include, but are not limited to, maintaining the mixture under quiescence for a sufficient period of time, adjusting the pH of the solution, adjusting the temperature of the solution, directing a form of energy (ultraviolet, visible, infrared, microwave, ultrasound, particle radiation, electromagnetic) at the mixture, or a combination thereof.

[0027] The process of transferring gel-forming components into a gel material can also include an aging step (also referred to as curing) prior to liquid-phase extraction. Aging a gel material after it has reached its gel point can further strengthen the gel framework by increasing the number of crosslinks within the network. The duration of gel aging can be adjusted to control various properties within the resulting aerogel material. This aging procedure can be useful to prevent volume loss and potential shrinkage during liquid-phase extraction. Aging can involve maintaining the gel at rest for an extended period of time (prior to extraction), maintaining the gel at an elevated temperature, adding a crosslinking-promoting compound, or any combination thereof. Preferred temperatures for aging are typically from about 10°C to about 100°C, although other suitable temperatures are contemplated herein. Aging of the gel material typically continues until liquid-phase extraction of the wet gel material.

[0028] The period of time for transitioning the gel-forming material into a gel material includes both the period of initial gel formation (from the onset of gelation to the gel point) and any subsequent period of hardening and aging of the gel material prior to liquid-phase extraction (from the gel point to the onset of liquid-phase extraction). The total period of time for transitioning the gel-forming material into a gel material typically ranges from about 1 minute to several days, preferably about 30 hours or less, about 24 hours or less, about 15 hours or less, about 10 hours or less, about 6 hours or less, about 4 hours or less, about 2 hours or less, about 1 hour or less, about 30 minutes or less, or about 15 minutes or less.

[0029] Aging of the wet gel material can be accomplished by heating the wet gel material for a time sufficient to complete the aging process. In a typical aging process, the wet gel material is placed in an aging vessel. The wet gel material is then heated to an aging temperature and maintained at the aging temperature until the aging process is complete. Optionally, the wet gel material may be washed with an aging fluid before and during heating. An aging fluid may be used to displace any primary reaction solvent present in the wet gel. Exemplary aging fluids are C1-C6 alcohols, cyclic alcohols, alicyclic alcohols, aromatic alcohols, polyhydric alcohols, ethers, ketones, or cyclic ethers. Preferred aging fluids include methanol and ethanol. During aging, the aging fluid may be substantially continuously passed over and / or through the wet gel material and the aging vessel. The aging fluid passing through the aging vessel and the wet gel may be fresh or recycled.

[0030] The amount of time required to complete the aging process is related to the aging temperature of the wet gel material. Generally, the higher the aging temperature, the faster the aging process is completed. However, the maximum temperature that can be used is limited by the liquid present in the wet gel material. At atmospheric pressure (1 atmosphere, 101,325 Pa), the aging temperature is limited to the boiling point of the liquid in the wet gel material. Furthermore, it is undesirable to heat the aging material at or near the boiling point of the liquid. Evaporation of the aging fluid when heating the aging fluid at or near its boiling point can damage the framework structure of the wet gel material. To reduce the possibility of damaging the wet gel material, the aging process is typically performed below the boiling point of the aging fluid in the wet gel material. For example, when ethanol is used as the aging fluid, the wet gel material is typically aged at a temperature of 160°F (71.1°C), which is below the boiling point of ethanol (bp 173°F (78.3°C) at 1 atmosphere (101,325 Pa)), for a period of 1 hour up to 24 hours.

[0031] In one aspect of the present disclosure, the aging time of a wet gel material can be reduced by increasing the aging temperature of the wet gel material. The aging temperature is generally limited to the normal boiling point of the aging fluid, but the temperature can be increased above the normal boiling point of the aging fluid by increasing the pressure in the aging vessel. Maintaining the pressure inside the aging vessel (the "aging pressure") above the vapor pressure of the aging fluid allows the temperature of the aging fluid to be increased above the normal boiling point of the aging fluid without boiling the aging fluid. As used herein, the "normal boiling point" of a liquid is the temperature at which the liquid boils at 1 atmosphere (101,325 Pa).

[0032] In one aspect of the present disclosure, the wet gel material is placed in a container that can be pressurized. The container also includes an inlet for an aging fluid and an outlet for the fluid to exit the container. The container is sealed, and the aging fluid is introduced into the container. The aging fluid can be the same fluid as or a different fluid from the fluid used to make the wet gel material. In a preferred aspect of the present disclosure, the aging fluid is an alcohol (e.g., methanol or ethanol). The aging fluid is heated while maintaining a pressure inside the container that exceeds the vapor pressure of the aging fluid. The aging fluid can be heated by a heating element located in or adjacent to the container.

[0033] In one aspect of the present disclosure, the aging fluid may be removed and substantially continuously introduced during aging of the wet gel material. For example, the aging fluid may be recirculated through the container. The aging fluid may be heated outside the container before being reintroduced into the container. During aging, the pressure inside the container (the "aging pressure") is maintained above the vapor pressure of the liquid, particularly the vapor pressure of the liquid at the aging temperature, because the vapor pressure of the aging fluid increases with increasing temperature.

[0034] Increasing the aging temperature by increasing the pressure can shorten the aging time. Under increased aging temperature, the aging time can be from 40 minutes to about 200 minutes.

[0035] The aging temperature is controlled in part by increasing the vapor pressure in the aging vessel. For example, if an aging temperature of 230°F (110°C) is desired for ethanol as the aging fluid, the vapor pressure inside the vessel needs to be 315 kPa or greater to ensure that the liquid does not begin to damage the framework structure due to evaporation or boiling. In practice, the pressure in the vessel is maintained at at least 2, at least 3, at least 5, at least 10, or at least 20 times the vapor pressure of the aging liquid. For example, with ethanol as the aging fluid, the pressure inside the vessel can be maintained at at least 630 kPa, at least 945 kPa, at least 1575 kPa, at least 3150 kPa, or at least 6300 kPa.

[0036] Further details regarding high temperature and high pressure aging of wet gel materials are disclosed in US Provisional Patent Application No. 63 / 416,017, which is incorporated herein by reference.

[0037] The resulting gel material may be washed in a suitable secondary solvent to displace the primary reaction solvent present in the wet gel. Such secondary solvent may be a straight-chain monohydric alcohol having one or more aliphatic carbon atoms, a dihydric alcohol having two or more carbon atoms, a branched alcohol, a cyclic alcohol, an alicyclic alcohol, an aromatic alcohol, a polyhydric alcohol, an ether, a ketone, a cyclic ether, or a derivative thereof.

[0038] Once the gel material has been formed and processed, an extraction method can then be used to at least partially extract the liquid phase of the gel from the wet gel to form an aerogel material. Liquid phase extraction plays an important role in manipulating aerogel characteristics such as porosity and density, as well as related properties such as thermal conductivity, among other factors. Generally, aerogels are obtained when the liquid phase is extracted from the gel in a manner that reduces shrinkage of the wet gel into a porous network and framework.

[0039] Aerogels are generally formed by removing a liquid mobile phase from a gel material at temperatures and pressures near or above the critical point of the liquid mobile phase. When the critical point is reached (near-critical) or exceeded (supercritical) (i.e., the system pressure and temperature are at or above the critical pressure and critical temperature, respectively), a new supercritical phase, distinct from the liquid or vapor phase, emerges in the fluid. This allows solvent removal without introducing any of the associated mass transfer limitations typically associated with liquid-vapor interfaces, capillary pressures, or liquid-vapor boundaries. Additionally, supercritical phases are generally more miscible with organic solvents, thus providing better extraction performance. Cosolvents and solvent exchange are also commonly used to optimize supercritical fluid drying processes.

[0040] One embodiment for extracting the liquid phase from the wet gel uses supercritical carbon dioxide conditions, which involves, for example, first substantially exchanging the primary solvent present in the gel's pore network with liquid carbon dioxide, then heating the wet gel above the critical temperature of carbon dioxide (approximately 31.06°C) (typically in an autoclave) and increasing the system pressure to a pressure greater than the critical pressure of carbon dioxide (approximately 1070 psig). The pressure around the gel material can be slightly varied to facilitate the removal of the supercritical carbon dioxide fluid from the gel. The carbon dioxide can be recirculated through the extraction system to facilitate the continuous removal of the primary solvent from the wet gel. Finally, the temperature and pressure are slowly returned to ambient conditions to produce a dry aerogel material. The carbon dioxide can also be pretreated to a supercritical state before being injected into the extraction chamber.

[0041] Further details describing the synthesis of aerogels can be found in U.S. Patent Application Publication No. 2016 / 0096949 to Evans et al. and U.S. Patent Application Publication No. 2021 / 03095227 to Evans et al., both of which are incorporated herein by reference.

[0042] The aerogel composites of the present disclosure can have a thickness of 15 mm or less, 10 mm or less, 5 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less.

[0043] Aerogels made by the processes described herein can be brittle and friable unless additives or fillers are added to the gel precursor or gel. In particular, the use of fibers as a filler material during aerogel production can improve the flexibility and / or strength of the aerogel material. In one aspect of the present disclosure, an aerogel composite is formed by adding a gel precursor composition to a fiber-reinforced phase and forming a gel from the gel precursor composition. The gel is subjected to liquid extraction (e.g., using supercritical CO2) and dried to form an aerogel composite comprising aerogel mixed with fibers. Further details describing the synthesis of aerogel fiber composites can be found in U.S. Patent Application Publication No. 2016 / 0096949 to Evans et al. and U.S. Patent Application Publication No. 2021 / 03095227 to Evans et al., both of which are incorporated herein by reference.

[0044] The use of a reinforcing phase, e.g., a reinforcing material, to support the aerogel can make the resulting aerogel composite easier to handle and manipulate. The reinforcement can be in the form of a fiber or a foam. The reinforcement can be in the form of an elongated sheet of material. By selecting the appropriate ratio of aerogel to reinforcement, a flexible, mechanically robust aerogel composite can be obtained.

[0045] The reinforcing phase can be any material that provides increased flexibility, resilience, conformability, or structural stability to the aerogel material. Examples of well-known reinforcing materials include, but are not limited to, open-cell foam reinforcing materials, closed-cell foam reinforcing materials, open-cell membranes, honeycomb reinforcing materials, polymeric reinforcing materials, and fibrous reinforcing materials, such as discrete fibers, woven materials, nonwoven materials, battings, webs, mats, and felts. In addition, fibrous reinforcing materials may be combined with one or more other reinforcing materials and may be oriented continuously throughout the composition or in a limited, preferred portion of the composition.

[0046] Examples of foam reinforcing materials include, but are not limited to, materials made from organic polymeric materials. Examples include materials made from polyolefins, polyurethanes, phenolics, melamine, cellulose acetate, and polystyrene. Materials made from melamine or melamine derivatives are also preferred in certain embodiments.

[0047] Examples of fibrous reinforcement materials include, but are not limited to, discrete fibers, woven materials, nonwoven materials, batting, webs, mats, felts, or combinations thereof. Fiber reinforcement materials can comprise a wide variety of materials, including, but not limited to, polyester, polyolefin terephthalate, poly(ethylene) naphthalate, polycarbonate (e.g., rayon, nylon), cotton (e.g., Lycra manufactured by DuPont), carbon (e.g., graphite), polyacrylonitrile (PAN), oxidized PAN, non-carbonized heat-treated PAN (such as that manufactured by SGL carbon), glass fiber-based materials (such as S-glass, 901 glass, 902 glass, 475 glass, E-glass), silica-based fibers such as quartz (e.g., Quartz manufactured by Saint-Gobain), Q-felt (Johns Fibers such as Manville, Saffil (manufactured by Saffil), Durablanket (manufactured by Unifrax), and other silica fibers, combinations of silica-based fibers and glass-based fibers, Duraback (manufactured by Carborundum), Kevlar, Nomex, Sontera (all manufactured by DuPont), Conex (manufactured by Taijin), polyolefins such as Tyvek (manufactured by DuPont), Dyneema (manufactured by DSM), Spectra (manufactured by Honeywell), other polypropylene fibers such as Typar, Xavan (both manufactured by DuPont), fluoropolymers such as Teflon (manufactured by DuPont), PTFE under trade names such as Goretex (manufactured by WLGORE), silicon carbide fibers such as Nicalon (manufactured by COI), and the like. Ceramics), ceramic fibers such as Nextel (3M), acrylic polymers, wool, silk, linen, leather, suede fibers, PBO-Zylon fibers (Tyobo), liquid crystal materials such as Vectan (Hoechst), Cambrelle fibers (DuPont), polyurethane, polyamide, wood fibers, boron, aluminum, iron, stainless steel fibers, as well as other thermoplastics such as PEEK, PES, PEI, PEK, PPS.

[0048] One property of aerogel materials and aerogel composites that can vary significantly is compression set. As used herein, "compression set" is a measure of the permanent deformation of a material that remains after a force applied to the material is removed. In this disclosure, compression set is determined using ASTM D3574-Test D. Compression set is determined as the percentage change in thickness of a material before and after applying a given force. In one example of ASTM D3574-Test D, compression set can be determined from the following formula: C t =[(T o -T f ) / T o ] x 100 In the formula, C t is the compression set, and T o is the original thickness of the material, and T f is the final thickness of the material after the applied force is removed.

[0049] Aerogels that do not contain any additives to improve the flexibility of the material tend to have high compression set (i.e., the material returns to less than 50% of its original thickness after the application of force ceases). Even fiber-reinforced aerogels tend to have high compression set values. Therefore, there is a need to find ways to improve the compression set of aerogels and aerogel composites.

[0050] It has been found that heating an aerogel or aerogel composite in an oxygen-containing atmosphere can improve the compression set of the heated material. Without being bound by any theory, it is believed that problems associated with the resilience of aerogels or aerogel composites are related to the incomplete formation of the porous network. As the porous network forms, weak spots are formed where the gel material is incompletely reacted. These weak spots can cause the porous framework of the aerogel or aerogel composite to collapse. Once the aerogel collapses, it is unable to recover to its previous state (e.g., its previous thickness). It is believed that heating the aerogel in an oxygen atmosphere removes any residual catalyst (e.g., base) and eliminates the weak spots in the aerogel by promoting reaction at the incompletely reacted sites within the porous network.

[0051] In one embodiment of the present disclosure, a first aerogel is converted into a second aerogel having a better (i.e., lower) compression set than the first aerogel. This is accomplished by providing a first aerogel having a compression set greater than 15% as determined by ASTM D3574-Test D. The first aerogel is heated at a temperature between about 200°C and 400°C in an atmosphere containing greater than 10% oxygen to obtain a second aerogel. The first aerogel is heated for a time sufficient to modify the compression set of the second aerogel so that the compression set of the second aerogel is 15% or less as determined by ASTM D3574-Test D.

[0052] In one embodiment of the present disclosure, the first aerogel is heated in an atmosphere of greater than 10% oxygen, greater than 11% oxygen, greater than 12% oxygen, greater than 13% oxygen, greater than 14% oxygen, greater than 15% oxygen, greater than 16% oxygen, greater than 17% oxygen, greater than 18% oxygen, greater than 19% oxygen, greater than 20% oxygen, greater than 21% oxygen, greater than 22% oxygen, greater than 23% oxygen, greater than 24% oxygen, or greater than 25% oxygen. In one embodiment of the present disclosure, the oxygen content of the atmosphere during heating of the first aerogel ranges from 10% oxygen to 30% oxygen, 15% oxygen to 25% oxygen, or 18% oxygen to 25% oxygen. In a preferred embodiment of the present disclosure, the first aerogel is heated in air.

[0053] In one embodiment of the present disclosure, the first aerogel is heated in an oxygen-containing atmosphere at a temperature of 200°C to 400°C, 225°C to 400°C, 250°C to 400°C, 250°C to 350°C, or 300°C to 400°C. During heating of the first aerogel, the temperature is limited to less than 400°C.

[0054] The first aerogel is heated for a time sufficient to modify the compression set of the first aerogel so that the resulting second aerogel has a compression set of 15% or less, as determined by ASTM D3574-Test D. Exemplary times required to achieve this transformation can be 10 seconds, 30 seconds, 1 minute, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hour, 2 hours, or 3 hours, or within a range of any two of these values. In one embodiment of the present disclosure, the heating time is 30 seconds to 3 hours, 30 seconds to 2 hours, 30 seconds to 1 hour, 30 seconds to 45 minutes, 30 seconds to 30 minutes, 30 seconds to 15 minutes, 30 seconds to 5 minutes, or 30 seconds to 1 minute.

[0055] Heating the aerogel or aerogel composite in an oxygen-containing atmosphere can improve the compression set of the aerogel material. In one aspect of the invention, the aerogel material after heat treatment in an oxygen-containing atmosphere has a compression set of 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less.

[0056] The process of heating aerogel in an oxygen-containing atmosphere can be applied to a variety of aerogels and aerogel composites. In one aspect of the present disclosure, a silica aerogel composite is heated in an oxygen-containing atmosphere to improve the compression set of the aerogel composite. In one aspect of the present disclosure, the silica aerogel is formed by hydrolysis and condensation of silica-based gel-forming materials. Exemplary silica-based gel-forming materials include, but are not limited to, silica-based alkoxides, metal silicates, alkoxysilanes, polyethylene silicates, and alkylalkoxysilanes.

[0057] In one embodiment of the present disclosure, the gel-forming material contains at least one hydrophobic group that can impart or improve certain properties of the gel, such as stability and hydrophobicity. Exemplary gel-forming materials containing hydrophobic groups include, but are not limited to, alkyl metal alkoxides, cycloalkyl metal alkoxides, and aryl metal alkoxides. In a specific embodiment of the present disclosure, the gel-forming material is a silica-based hydrophobic gel-forming material. Examples of silica-based gel-forming materials include, but are not limited to, trimethylmethoxysilane (TMS), dimethyldimethoxysilane (DMS), methyltrimethoxysilane (MTMS), trimethylethoxysilane, dimethyldiethoxysilane (DMDES), methyltriethoxysilane (MTES), ethyltriethoxysilane (ETES), diethyldiethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane (PhTES), hexamethyldisilane, and hexaethyldisilazane.

[0058] Gel-forming materials can be converted into gels using various techniques known in the art. In one embodiment of the present disclosure, gel-forming materials can be converted into gels using a base. Any base can be used to catalyze the gel-forming reaction. In one embodiment of the present disclosure, an amine base can be used to catalyze the gelation reaction. Exemplary bases that may be used include, but are not limited to, trialkylamines, amidines, guanidines, and imidazoles. Specific examples of amine bases include guanidine (e.g., guanidinium hydroxide), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), pyridine, imidazole, and 4,5-dihydroimidazole. The amount of amine base used can range from about 0.5% to about 10% of the gel-forming material. After gelation and solvent removal, the resulting aerogel has about 0.5% to about 10% amine base remaining in the aerogel.

[0059] It is believed that heating the aerogel at temperatures between 200°C and 400°C will remove some of the volatile base (e.g., amine base) from the aerogel. Therefore, the amount of volatile base (e.g., amine base) present in the initial aerogel composite is greater than the amount of volatile base remaining in the aerogel composite after heating.

[0060] Aerogel composites may be fiber reinforced with various fiber reinforcing materials to achieve a more flexible, resilient, and conformable composite product. The fiber reinforcing material may be added to the gel at any point during the gelation process to produce a wet fibrous gel composition. The wet gel composition may then be dried to produce the fiber-reinforced aerogel composite. The fiber reinforcing material may be in the form of discrete fibers, woven materials, nonwoven materials, battings, webs, mats, and felts. The fiber reinforcement may be made from organic fibrous materials, inorganic fibrous materials, or combinations thereof.Fiber reinforcement materials can include a wide variety of materials, including, but not limited to, polyester, polyolefin terephthalate, poly(ethylene) naphthalate, polycarbonate (e.g., rayon, nylon), cotton (e.g., Lycra manufactured by DuPont), carbon (e.g., graphite), polyacrylonitrile (PAN), oxidized PAN, non-carbonized heat-treated PAN (such as that manufactured by SGL carbon), glass fiber-based materials (such as S-glass, 901 glass, 902 glass, 475 glass, E-glass), silica-based fibers such as quartz (e.g., Quartz manufactured by Saint-Gobain), Q-felt (Johns Other examples of suitable fibers include: Manville, Saffil (manufactured by Saffil), Durablanket (manufactured by Unifrax), and other silica fibers; Duraback (manufactured by Carborundum), Kevlar, Nomex, Sontera (all manufactured by DuPont), Conex (manufactured by Taijin); polyolefins such as Tyvek (manufactured by DuPont), Dyneema (manufactured by DSM), Spectra (manufactured by Honeywell); other polypropylene fibers such as Typar and Xavan (both manufactured by DuPont); fluoropolymers such as Teflon (manufactured by DuPont), PTFE under trade names such as Goretex (manufactured by WLGORE); silicon carbide fibers such as Nicalon (COI); Ceramics), ceramic fibers such as Nextel (3M), acrylic polymers, wool, silk, linen, leather, suede fibers, PBO-Zylon fibers (Tyobo), liquid crystal materials such as Vectan (Hoechst), Cambrelle fibers (DuPont), polyurethane, polyamide, wood fibers, boron, aluminum, iron, stainless steel fibers, as well as other thermoplastics such as PEEK, PES, PEI, PEK, PPS.

[0061] In one aspect of the present disclosure, nonwoven fiber reinforcement materials are incorporated into aerogel composites as a continuous sheet of interconnected or interwoven fiber reinforcement material. This process involves first casting or impregnating a gel precursor solution onto or impregnating a continuous sheet of interconnected or interwoven fiber reinforcement material to produce a continuous sheet of fiber reinforced gel. The liquid phase may then be at least partially extracted from the fiber reinforced gel sheet to produce a sheet of fiber reinforced aerogel composite.

[0062] In one aspect of the present disclosure, the aerogel composite may include an opacifying additive to reduce the radiative component of heat transfer. The opacifying compound or its precursor may be dispersed in the mixture containing the gel-forming materials at any time prior to gel formation. Exemplary opacifying additives include, but are not limited to, boron carbide (BC), diatomaceous earth, manganese ferrite (MnFeO), manganese oxide (MnO), nickel oxide (NiO), tin oxide (SnO), silver oxide (AgO), bismuth oxide (BiO), titanium carbide (TiC), tungsten carbide (WC), silicon carbide (SiC), carbon black, titanium oxide (TiO), iron titanium oxide (FeTiO), zirconium silicate (ZrSiO), zirconium oxide (ZrO), iron (II) oxide (FeO), iron (III) oxide (FeO), manganese dioxide (MnO), iron titanium oxide (ilmenite, FeTiO), chromium oxide (CrO), or mixtures thereof. In a preferred embodiment of the present invention, the aerogel composite includes silicon carbide as an opacifying additive.

[0063] Inorganic aerogels can also include gel precursors containing at least one hydrophobic group, such as alkyl metal alkoxides, cycloalkyl metal alkoxides, and aryl metal alkoxides, which can impart or improve certain properties to the gel, such as stability and hydrophobicity. Inorganic silica aerogels can specifically include hydrophobic precursors, such as alkyl silanes or aryl silanes. Hydrophobic gel precursors can be used as the primary precursor material to form the framework of the gel material. However, hydrophobic gel precursors are more commonly used as co-precursors in combination with simple metal alkoxides to form amalgam aerogels. Hydrophobic inorganic precursor materials for silica-based aerogel synthesis include, but are not limited to, trimethylmethoxysilane [TMS], dimethyldimethoxysilane [DMS], methyltrimethoxysilane [MTMS], trimethylethoxysilane, dimethyldiethoxysilane [DMDS], methyltriethoxysilane [MTES], ethyltriethoxysilane [ETES], diethyldiethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane [PhTES], hexamethyldisilane, and hexaethyldisilazane.

[0064] Aerogels may also be treated to impart or improve hydrophobicity. Hydrophobic treatments can be applied to sol-gel solutions, wet gels before liquid-phase extraction, or to aerogels after liquid-phase extraction. Hydrophobic treatments are particularly common in the production of metal oxide aerogels, such as silica aerogels. Hydrophobic treatments are achieved by reacting hydroxy moieties on the gel, such as silanol groups (Si-OH) present on the silica gel framework, with functional groups on a hydrophobizing agent. The resulting reaction converts the silanol groups and hydrophobizing agent into hydrophobic groups on the silica gel framework. The hydrophobizing agent compound may react with the hydroxyl groups on the gel according to the following reaction: R N MX 4-N (Hydrophobizing agent) + MOH (silanol) → MOMR N (hydrophobic group) + HX The hydrophobic treatment may occur both on the outer macroscopic surface of the silica gel and on the inner pore surfaces within the porous network of the gel.

[0065] The gel can be immersed in a mixture of a hydrophobizing agent and an optional hydrophobic treatment solvent in which the hydrophobizing agent is soluble and which is also miscible with the gel solvent in the wet gel. A wide range of hydrophobic treatment solvents can be used, including solvents such as methanol, ethanol, isopropanol, xylene, toluene, benzene, dimethylformamide, and hexane. Alternatively, the hydrophobizing agent in liquid or gas form can be directly contacted with the gel to impart hydrophobicity.

[0066] The hydrophobic treatment step may include mixing or agitation to aid in the penetration of the hydrophobizing agent into the wet gel. The hydrophobic treatment step may also include varying other conditions, such as temperature and pH, to further enhance and optimize the treatment reaction. After the reaction is complete, the wet gel is washed to remove unreacted compounds and reaction by-products.

[0067] The hydrophobizing agent for the hydrophobic treatment of aerogel is generally a compound of the formula: RNMX 4-Nwhere M is a metal, R is a hydrophobic group such as CH3, CH2CH3, CH6, or a similar hydrophobic alkyl, cycloalkyl, or aryl moiety, and X is a halogen, usually Cl. Specific examples of hydrophobizing agents include, but are not limited to, trimethylchlorosilane [TMCS], triethylchlorosilane [TECS], triphenylchlorosilane [TPCS], dimethylchlorosilane [DMCS], dimethyldichlorosilane [DMDCS], and the like. The hydrophobizing agent can also be of the formula: Y(R3M)2, where M is a metal, Y is a bridging group such as NH or O, and R is a hydrophobic group such as CH3, CH2CH3, CH6, or a similar hydrophobic alkyl, cycloalkyl, or aryl moiety. Specific examples of such hydrophobizing agents include, but are not limited to, hexamethyldisilazane [HMDZ] and hexamethyldisiloxane [HMDSO]. The hydrophobizing agent may further comprise a compound of the formula: RNMV 4-N where V is a reactive or leaving group other than a halogen. Specific examples of such hydrophobizing agents include, but are not limited to, vinyltriethoxysilane and vinyltrimethoxysilane.

[0068] In the context of this disclosure, the term "hydrophobically bonded silicon" refers to silicon atoms within a gel or aerogel framework that contain at least one hydrophobic group covalently bonded to the silicon atom. Examples of hydrophobically bonded silicon include, but are not limited to, silicon atoms in silica groups within a gel framework formed from a gel precursor containing at least one hydrophobic group (such as MTES or DMDS). Hydrophobically bonded silicon also includes, but is not limited to, silicon atoms within a gel framework or on the surface of a gel that have been treated with a hydrophobizing agent (such as HMDZ) to impart or improve hydrophobicity by incorporating additional hydrophobic groups into the composition. Hydrophobic groups in the present disclosure include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertbutyl, octyl, phenyl, or other substituted or unsubstituted hydrophobic organic groups known to those skilled in the art. In the context of this disclosure, the terms "hydrophobic group," "hydrophobic organic material," and "hydrophobic organic content" specifically exclude readily hydrolyzable organosilicon-bonded alkoxy groups on the framework of the gel material that are the product of a reaction between an organic solvent and a silanol group.

[0069] In the context of this disclosure, the terms "aliphatic hydrophobic group," "aliphatic hydrophobic organic material," and "aliphatic hydrophobic organic content" describe hydrophobic groups on hydrophobically bonded silicon that are limited to aliphatic hydrocarbons, including, but not limited to, hydrocarbon moieties containing 1 to 40 carbon atoms, which can be saturated or unsaturated (but not aromatic), and which may include linear, branched, cyclic moieties (fused, bridged, and spiro-fused polycyclic), or combinations thereof, such as alkyl, alkenyl, alkynyl, (cyclo)alkyl, (cycloalkenyl)alkyl, or (cycloalkyl)alkenyl moieties, and heteroaliphatic moieties (where one or more carbon atoms are independently replaced with one or more atoms selected from the group consisting of oxygen, sulfur, nitrogen, or phosphorus). In certain embodiments of the present disclosure, at least 50% of the hydrophobic organic material in the aerogel composition is comprised of aliphatic hydrophobic groups.

[0070] In the context of this disclosure, the term "hydrophobic organic content" refers to the amount of hydrophobic organic material bound to the framework in an aerogel material or composition. The hydrophobic organic content of an aerogel material or composition can be expressed as a weight percent of the amount of hydrophobic organic material on the aerogel framework relative to the total amount of material in the aerogel material or composition. One skilled in the art can calculate the hydrophobic organic content based on the nature and relative concentrations of the materials used to produce the aerogel material or composition. Hydrophobic organic content can also be measured using thermogravimetric analysis (TGA) in an inert atmosphere. Specifically, the percentage of hydrophobic organic material in an aerogel can be correlated to the rate of weight loss in a hydrophobic aerogel material or composition when subjected to combustion heat temperatures during TGA analysis, adjusting for water loss, residual solvent loss, and readily hydrolyzable alkoxy groups during TGA analysis.

[0071] The aerogel materials or compositions of the present disclosure can have a hydrophobic organic content of 50% by weight or less, 40% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or a range between any two of these values.

[0072] Aerogel materials and aerogel composites have low thermal conductivity, making them ideal for thermal insulation applications. In one exemplary use, aerogel composites may be used as a thermal barrier between individual battery cells or groups. Battery cells are susceptible to catastrophic failure under "abuse conditions." Abuse conditions include mechanical, electrical, and thermal abuse. One or all of these abuse conditions can be externally or internally initiated. For example, service-induced stress, aging, and negligence in design parameters such as cell spacing, cell interconnection style, cell form factor, manufacturing, operation, and maintenance are internal mechanical factors that can cause various types of abuse. External mechanical factors include damage or injury to LIBs, such as from dropping or cell penetration. Electrical abuse conditions primarily include short circuits, overcharging, and overdischarging, both internal and external to the battery cell. Thermal abuse is typically caused by overheating. For example, overheating within a battery cell can occur by operating the battery cell at high ambient temperatures. Internally, thermal abuse can be caused by electrical and mechanical defects in the battery cells.

[0073] Thermal runaway can occur within a battery cell due to electrical, mechanical, or thermal abuse conditions. The term "thermal runaway" refers to a situation in which the internal reaction rate of a battery cell increases to the point where more heat is generated than can be extracted, resulting in a further increase in both reaction rate and heat production. During thermal runaway, high temperatures trigger a chain of heat-dissipating reactions within the battery, rapidly increasing the battery's temperature. Often, when thermal runaway occurs in one battery cell, the generated heat rapidly heats cells near the cell experiencing thermal runaway. Each cell that participates in the thermal runaway reaction contains additional energy to continue the reaction, causing thermal runaway propagation within the battery pack and ultimately leading to catastrophic failure of the battery pack due to fire or explosion. Rapid heat dissipation and effective blocking of heat transfer paths can be effective measures to reduce the hazards caused by thermal runaway propagation.

[0074] In one embodiment of the present disclosure, an aerogel or aerogel composite is heated at a temperature of about 200°C to 400°C in an atmosphere containing greater than 10% oxygen to reduce the compression set of the aerogel material. A heated aerogel or a heated aerogel composite with a compression set of 15% or less, as determined by ASTM D3574-Test D, can be used as a barrier material or as part of a multilayer barrier material disposed between battery cells. The improved compression set allows the aerogel or aerogel composite to contract and expand in response to the expansion and contraction of adjacent battery cells, respectively, without or with minimal permanent deformation of the aerogel or aerogel composite.

[0075] The battery modules and battery packs can be used to supply electrical energy to devices or vehicles. Devices that use the battery modules or battery packs include, but are not limited to, laptop computers, PDAs, mobile phones, tag scanners, audio devices, video devices, display panels, video cameras, digital cameras, desktop computers, military portable computers, military telephones, laser range finders, digital communication devices, intelligence gathering sensors, electronically integrated clothing, night vision devices, power tools, calculators, radios, remote-controlled appliances, GPS devices, handheld and portable televisions, car starters, flashlights, sound devices, portable heaters, portable vacuum cleaners, or portable medical equipment. When used in vehicles, the battery packs can be used in fully electric or hybrid vehicles. [Example]

[0076] The following examples are included to support preferred embodiments of the invention. It should be understood by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventors to function well in the practice of the invention, and as such can be considered to constitute preferred modes of practice thereof. However, those of skill in the art should, in light of the present disclosure, understand that many changes can be made in the specific embodiments disclosed and still obtain like or similar results without departing from the spirit and scope of the invention.

[0077] Comparative testing of aerogel composites using ASTM D3574-Test D Test 1 - Comparison of Nitrogen Annealing and Air Annealing A 2.25 mm thick silica-based aerogel composite was tested using ASTM D3574-Test D (aerogel sample S100142) before and after heat treatment. The aerogel composite had a silica density of 0.085 g / cc, a SiC content of 35%, and a hydrophobic content of 36%. The aerogel specimen was tested by compressing it to a maximum strain of 50% of its unstressed thickness, holding it in the compressed state for 20 minutes, releasing the compression on the specimen, and measuring the change in specimen thickness after 24 hours in the uncompressed state. The results of this test are summarized in Table 1. As shown in Table 1, the untreated aerogel composite has a compression set of 49.6%. Treatment of the aerogel composite by heating at 350 °C in a nitrogen atmosphere (oxygen content less than 10%) improves the compression set to 16%, 23%, or 31%, depending on the amount of time the aerogel composite was heated under nitrogen. Significant improvements in compression set were achieved by heating the aerogel composite in an air atmosphere. Treatment of the aerogel composite by heating at 350°C in an air atmosphere (oxygen content approximately 21%) improved the compression set to less than 15% (specifically, 5.6%, 10.2%, and 2.0%, depending on the amount of time the aerogel composite was heated in air). [Table 1]

[0078] Test 2 - Comparison of treatment temperatures A 2.25 mm thick silica-based aerogel composite was tested using ASTM D3574-Test D (aerogel sample S100142) before and after heat treatment. The aerogel composite had a silica density of 0.085 g / cc, a SiC content of 35%, and a hydrophobic content of 36%. The aerogel specimen was tested by compressing it to a maximum strain of 60% of its unstressed thickness, holding it in the compressed state for 20 minutes, releasing the compression on the specimen, and measuring the change in specimen thickness after 24 hours in the uncompressed state. The results of this test are summarized in Table 2. The effect of processing temperature was investigated in this test. As shown in Table 2, the best results were achieved at a processing temperature of 350 °C (2.86% compression set). Processing the sample in air above 400 °C can result in sample decomposition due to oxidation, which represents the upper limit for this processing. [Table 2]

[0079] Test 3 - Comparison of aerogel sample thickness for compression set A 4 mm thick silica-based aerogel composite was tested using ASTM D3574-Test D (aerogel sample S100144) before and after heat treatment. The aerogel composite had a silica density of 0.085 g / cc, a SiC content of 35%, and a hydrophobic content of 36%. The aerogel specimen was tested by compressing it to a maximum strain of 60% of its unstressed thickness, holding it in the compressed state for 10 minutes, releasing the compression on the specimen, and measuring the change in specimen thickness after 24 hours in the uncompressed state. The results of this test are summarized in Table 3. Similar to the results of Test 1, a reduction in compression set to less than 15% was achieved (11.17% compression set) at a processing temperature of 350 °C in air. [Table 3]

[0080] Test 4 - Effect of Annealing Temperature on Compression Set of Aerogel A 4 mm thick silica-based aerogel composite was tested using ASTM D3574-Test D (aerogel sample S100144) before and after heat treatment. The aerogel composite had a silica density of 0.085 g / cc, a SiC content of 35%, and a hydrophobic content of 36%. The aerogel specimen was tested by compressing it to a maximum strain of 50% of its unstressed thickness, holding it in the compressed state for 960 minutes, releasing the compression on the specimen, and measuring the change in specimen thickness after 24 hours in the uncompressed state. The results of this test are summarized in Table 4. Similar to the results of Test 3, a reduction in compression set to less than 15% was achieved (9.2% compression set) at a processing temperature of 350 °C in air. [Table 4]

[0081] Test 5 - Effect of Annealing Temperature on Compression Set A 4 mm thick silica-based aerogel composite was tested using ASTM D3574-Test D (aerogel sample S100144) before and after heat treatment. The aerogel composite had a silica density of 0.085 g / cc, a SiC content of 35%, and a hydrophobic content of 36%. The aerogel specimen was tested by compressing it to a maximum strain of 60% of its unstressed thickness, holding it in the compressed state for 20 minutes, releasing the compression on the specimen, and measuring the change in specimen thickness after 24 hours in the uncompressed state. The results of this test are summarized in Table 5. The effect of processing temperature was investigated in this test. As shown in Table 5, the best results were achieved at a processing temperature of 350 °C (12.71% compression set). Processing the sample in air above 400 °C can result in sample degradation due to oxidation, which represents the upper limit for this processing. [Table 5]

[0082] Test 6 - Comparison of bases used to form aerogels Silica-based aerogel composites were tested using ASTM D3574-Test D before and after heat treatment. A first silica-aerogel composite (guanidine) was formed using guanidine as the base to catalyze wet gel formation. The first silica-aerogel composite had a hydrophobic content of 36%. A second silica-aerogel composite (ammonia) was formed using ammonia as the base to catalyze wet gel formation. The second silica-aerogel composite had a hydrophobic content of 36%. The samples were tested by compressing the aerogel specimens to a maximum strain of 50% of their unstressed thickness, holding them in the compressed state for 20 minutes, releasing the compression on the specimens, and measuring the change in specimen thickness after 24 hours in the uncompressed state. The results of this test are summarized in Table 6. A more significant reduction in compression set is achieved for the samples formed using guanidine compared to the samples formed using ammonia. [Table 6]

[0083] Test 7 - Comparative Cyclic Test of Aerogel Composites A 2.25 mm thick silica-based aerogel composite was tested using cyclic compression (aerogel sample S100142). The aerogel composite had a silica density of 0.085 g / cc, a SiC content of 35%, and a hydrophobic content of 36%. This test was based on a custom method designed to evaluate the material's resilience in a cyclic test in which the material was subjected to a series of compression cycles. Specifically, the material was cycled at 2 mm / min to a peak strain target (60% strain), held at that strain target for 15 minutes, unloaded to a lower strain target (50% strain), held at this strain for 15 minutes, and then returned to the peak strain condition. This cycle was repeated 35 times for each material in the database, and the percent recovery of the material was reported after a 24-hour recovery period. The results of this test are summarized in Table 7. As shown in Table 7, the untreated aerogel composite had a compression set of 49.6%. Treatment of the aerogel composite by heating at 350°C in air atmosphere improves the compression set to 4.6% after cyclic testing. [Table 7]

[0084] Test 8 - Effect of Aging Temperature on Compression Set Silica-based aerogel composites were tested using ASTM D3574-Test D and cyclic testing (aerogel sample S100149) before and after heat treatment. The aerogel composites had a silica density of 0.055 g / cc, a SiC content of 35%, and a hydrophobic content of 36%. Silica-based aerogel composites were fabricated under standard aging conditions (standard) or high-temperature, high-pressure aging conditions (87°C, HTHP). All samples were annealed at 350°C in air. The samples were tested by compressing the aerogel specimens to a maximum strain of 60% of their unstressed thickness, holding them in the compressed state for 20 minutes, releasing the compression on the specimen, and measuring the change in specimen thickness after 24 hours in the uncompressed state. ASTM D3574 test results are shown in Table 8. For cyclic testing, the materials were cycled at 2 mm / min to a peak strain ranging from 50-60%, held at that strain target for 15 minutes, unloaded to a lower strain target (50% strain), held at this strain for 15 minutes, and then returned to the peak strain condition. This cycle was repeated 35 times for each material in the database, and the % recovery of the material was reported after the 24-hour recovery period. The results of the cyclic testing are summarized in Table 9. The results show that the unannealed HTHP sample is superior to the unannealed control sample. The full benefit of the annealed HTHP sample compared to the control sample is realized after cyclic testing. [Table 8] [Table 9]

[0085] Test 9 - Effect of Aging Temperature on Compression Set Silica-based aerogel composites were tested using single and cyclic compression tests. The aerogel composites had a silica density of 0.055 g / cc, a SiC content of 35%, and a hydrophobic content of 36%. Silica-based aerogel composites were fabricated under high-temperature, high-pressure aging conditions (HTHP) at temperatures of 80°C, 90°C, 100°C, and 110°C. All samples were annealed at 350°C in air. The aerogel specimens were tested by compressing them to a maximum strain of 50% of their unstressed thickness, holding them in the compressed state for 24 hours, and measuring the change in specimen thickness after 24 hours. The single compression test results are shown in Table 10. For cyclic testing, the materials were cycled at 2 mm / min to peak strains ranging from 50 to 60%, held at that strain target for 15 minutes, unloaded to a lower strain target (50% strain), held at this strain for 15 minutes, and then returned to the peak strain condition. This cycle was repeated 50 times for each material, and the percent recovery of the material was reported after a 24-hour recovery period. The results of the cyclic testing are summarized in Table 11. The results show that increasing the aging temperature improves compression set behavior. The cyclic testing results show that a higher aging temperature improves compression set, allowing the minimum stress value to remain above 40 kPa after 50 cycles. [Table 10] [Table 11]

[0086] Effect of aging temperature / silica density on compression set for tests 10-60% strain Silica-based aerogel composites were tested using a single compression test. The aerogel composites had a SiC content of 35% and a hydrophobic content of 36%. The silica density of the aerogels was either 0.065 g / cc (Aero 65), 0.075 g / cc (Aero 75), 0.085 g / cc (Aero 85), or 0.095 g / cc (Aero 95). Silica-based aerogel composites were fabricated under high-temperature, high-pressure aging conditions (HTHP) at 110 °C. The width of the aerogel composites was either 2.5 mm or 5 mm. The aerogel specimens were tested by compressing them to a maximum strain of 60% of their unstressed thickness, holding them in the compressed state for 24 hours, releasing the compression on the specimen, and measuring the change in specimen thickness immediately (immediate) and after 24 hours in the uncompressed state (24 hours). The results of the single compression tests for 2.5 mm sample width are shown in Table 12, and the results for 5 mm sample width are shown in Table 13. Both immediate springback and ultimate compression set improve (decrease) with increasing silica density. [Table 12] [Table 13]

[0087] Test 11 - Effect of aging temperature / silica density on compression set at 80% strain Silica-based aerogel composites were tested using a single compression test. The aerogel composites had a SiC content of 35% and a hydrophobic content of 36%. The silica density of the aerogels was either 0.065 g / cc (Aero 65), 0.075 g / cc (Aero 75), 0.085 g / cc (Aero 85), or 0.095 g / cc (Aero 95). Silica-based aerogel composites were fabricated under high-temperature, high-pressure aging conditions (HTHP) at 110 °C. The width of the aerogel composites was 2.5 mm or 5 mm. The aerogel specimens were tested by compressing them to a maximum strain of 80% of their unstressed thickness, holding them in the compressed state for 24 hours, releasing the compression on the specimen, and measuring the change in specimen thickness immediately (immediate) and after 24 hours in the uncompressed state (24 hours). The results of the single compression test for 2.5 mm sample width are shown in Table 14. The results for 5 mm sample width are shown in Table 15. Both immediate springback and ultimate compression set improve (decrease) with increasing silica density. [Table 14] [Table 15]

[0088] Test 12 - Effect of Annealing Temperature on Compression Set of HTHP Samples Silica-based aerogel composites were tested using single compression and cyclic tests. The aerogel composites had a SiC content of 35% and a hydrophobic content of 36%. The silica-based aerogel composites were fabricated under high-temperature, high-pressure aging conditions (HTHP) at 110°C. The width of the aerogel composites was 5 mm. The samples were annealed in air at 250°C, 275°C, 300°C, 325°C, or 350°C. The samples were tested by compressing the aerogel specimens once to a maximum strain of 60% or 80% of their unstressed thickness, holding them in the compressed state for 20 minutes, releasing the compression on the specimens, and measuring the change in specimen thickness after 24 hours in the uncompressed state. For cyclic testing, the materials were cycled at 2 mm / min to peak strains ranging from 50 to 60%, held at that strain target for 15 minutes, unloaded to a lower strain target (50% strain), held at this strain for 15 minutes, and then returned to the peak strain condition. This cycle was repeated 50 times for each material, and the % recovery of the material was reported after a 24-hour recovery period. Results of single compression tests for 60% strain compression are shown in Table 16. Results of single compression tests for 80% strain compression are shown in Table 17. Results of cyclic compression tests are shown in Table 18. Higher heat treatment temperatures were found to be necessary to maintain resilience to increasingly severe mechanical compression (80%, cyclic tests). [Table 16] [Table 17] [Table 18]

[0089] Test 13 - Effect of MTES sol molecular weight on compression set Silica-based aerogel composites were tested using single-compression tests. The aerogel composites had a SiC content of 35% and a hydrophobic content of 36%. High-molecular-weight aerogel compositions (high MW) were prepared by increasing the molecular weight of the MTES sol as the solids content increased during hydrolysis. The molecular weight of the MTES sol was increased by a factor of two to three over the standard molecular weight formulation. The high-MW aerogel compositions were compared with the standard molecular weight formulation (standard). Silica-based aerogel composites were prepared under high-temperature, high-pressure aging conditions (HTHP) at 90°C. Aerogel composites were formed on Formosa batting (Formosa) or Canyue batting (Canyue) as reinforcement materials. The Formosa aerogel composites were 3.2 mm thick. The Canyue aerogel composites were 2.5 mm thick. Samples were annealed in air at 250°C, 300°C, or 350°C. The samples were tested by compressing the aerogel specimens to a maximum strain of 60% (Formosa) or 50% (Canyue) of the unstressed thickness, holding them in the compressed state for 24 hours, releasing the compression on the specimen, and measuring the change in specimen thickness in the uncompressed state. The results of the single compression tests on the Formosa specimens are shown in Table 19. The results of the single compression tests on the Canyue specimens are shown in Table 20. Increasing the MTES molecular weight improves compression set behavior over the standard MW formulation, especially after annealing. [Table 19] [Table 20]

[0090] Test 14 - Effect of Reinforced Aerogel Density on Compression Set Silica-based aerogel composites were tested using a single compression test. The aerogel composites had a hydrophobic content of 36%. The silica density of the aerogels was either 0.045 g / cc (Aero45R), 0.065 g / cc (Aero65R), or 0.085 g / cc (Aero85R). The aerogel composites were formed on melamine foam as a reinforcing material using guanidine as a base during wet gel formation. The melamine aerogel composites were 10 mm thick. The samples were annealed at 250°C in air. The samples were tested by compressing the aerogel specimen to a maximum strain of 80% of its unloaded thickness, holding it in the compressed state for 1 minute, releasing the compression on the sample, and measuring the change in thickness of the specimen in the uncompressed state. The results of the single compression test of the melamine aerogel composites are shown in Table 21. [Table 21]

[0091] Test 15 - Effect of Hydrophobic Content of Reinforced Aerogel on Compression Set Silica-based aerogel composites were tested using single-compression tests. The aerogel composites had a hydrophobic content of 36% MTES, 50% MTES, 65% MTES, 80% MTES, 100% MTES, or 100% MTMS. "100% MTES" is similar to the standard formulation, but uses 100% MTES instead of 36%. "100% MTMS" is MTES hydrolyzed with oxalic acid instead of the usual phosphoric acid, and the solvent is methanol instead of ethanol. The silica density of the aerogel material was 0.065 g / cc. During wet gel formation, guanidine was used as the base for MTES, and ammonia was used as the base for MTMS. The aerogel composites were formed on melamine foam as a reinforcement material. The melamine aerogel composites were 10 mm thick. The samples were annealed in air at 250 °C. The specimens were tested by compressing the aerogel specimens to a maximum strain of 80% of their unstressed thickness, holding them in the compressed state for 1 minute, releasing the compression on the specimen, and measuring the change in specimen thickness in the uncompressed state. The results of single compression tests on melamine aerogel composites are shown in Table 22. Without heat treatment, the resilience of 36–80% MTES was similar and did not improve until 100% MTES. After heat treatment, there was a trend toward improved resilience as the MTES percentage increased. MTES-derived aerogels may be more resilient than silica due to the resulting lower crosslink density. Although 100% MTES and 100% MTMS have similarly sized, large pores compared to the standard formulation, 100% MTMS was found to be more resilient, while 100% MTES was less resilient. Without being bound by any theory, this difference in resilience is likely due to the lower crosslink density of 100% MTMS. The resilience of 100% MTES can be improved by heat treatment, but it is still not as low as that of 100% MTMS. [Table 22]

[0092] Test 16 - Effect of Hydrophobic Content of Glass Fiber Reinforced Aerogel on Compression Set Silica-based aerogel composites were tested using single-compression tests. The aerogel composites had a hydrophobic content of 36% MTES, 50% MTES, 65% MTES, 80% MTES, 100% MTES, or 100% MTMS. "100% MTES" is similar to the standard formulation, but uses 100% MTES instead of 36%. "100% MTMS" is MTES hydrolyzed with oxalic acid instead of the usual phosphoric acid, and the solvent is methanol instead of ethanol. The silica density of the aerogel material was 0.065 g / cc. During wet gel formation, guanidine was used as the base for MTES, and ammonia was used as the base for MTMS. The aerogel composites were formed on glass fiber as a reinforcing material. The melamine aerogel composites were 3 mm thick. The samples were annealed at 350 °C in air. The specimens were tested by compressing aerogel specimens to a maximum strain of approximately 56% of their unstressed thickness, holding them in the compressed state for 24 hours, releasing the compression on the specimen, and measuring the change in specimen thickness in the uncompressed state. The results of single compression tests on melamine aerogel composites are shown in Table 23. Cyclic compression of aerogel composites was also performed. For cyclic testing, the materials were cycled at 2 mm / min to strains ranging from 50 to 60%, unloaded to the lower strain target (50% strain), and then returned to the peak strain condition. This cycle was repeated 35 times for each material, and the percent recovery of the material was reported. The results of cyclic compression tests on melamine aerogel composites are shown in Table 24. As seen in Test 15, without heat treatment, the recovery from 36 to 80% MTES was similar and did not improve significantly to 100% MTES. [Table 23] [Table 24]

[0093] Certain U.S. patents, U.S. patent applications, and other materials (e.g., articles) are incorporated by reference in this patent. However, the text of such U.S. patents, U.S. patent applications, and other materials is only incorporated by reference to the extent that there is no conflict between such text and the other descriptions and drawings set forth herein. In the event of such a conflict, the conflicting text in such U.S. patents, U.S. patent applications, and other materials incorporated by reference is specifically not incorporated by reference into this patent.

[0094] Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as merely illustrative and is intended to teach those skilled in the art the general manner of carrying out the invention. It is understood that the forms of the invention shown and described herein are to be considered exemplary embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and steps may be reversed, and certain features of the invention may be utilized independently, all of which will become apparent to those skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention, as set forth in the following claims. Some of the embodiments of the invention related to the present invention are shown below. [Embodiment 1] (a) providing a first aerogel having a compression set greater than 15% as determined by ASTM D3574-Test D; (b) heating the first aerogel at a temperature of about 200°C to 400°C in an atmosphere containing more than 10% oxygen to obtain a second aerogel; wherein the first aerogel is heated for a time sufficient to modify the compression set of the first aerogel such that the resulting second aerogel has a compression set of 15% or less as determined by ASTM D3574-Test D. [Embodiment 2] 2. The method of embodiment 1, wherein the atmosphere comprises between about 15% oxygen and about 25% oxygen. [Embodiment 3] 2. The method of embodiment 1, wherein the atmosphere is air. [Embodiment 4] 10. The method of any one of the preceding embodiments, wherein the first aerogel is heated for a period of about 30 seconds or more. [Embodiment 5] 10. The method of any one of the preceding embodiments, wherein the first aerogel is heated for a time period from about 30 seconds to about 3 hours. [Embodiment 6] 10. The method of any one of the preceding embodiments, wherein during heating of the first aerogel, the temperature is limited to a temperature below 400°C. [Embodiment 7] 10. The method of any one of the preceding embodiments, wherein the first aerogel comprises silica. [Embodiment 8] 10. The method of any one of the preceding embodiments, wherein the first aerogel comprises a base. [Embodiment 9] 9. The method of embodiment 8, wherein the base is an amine base. [Embodiment 10] 10. The method of claim 8 or 9, wherein the first aerogel comprises at least 0.5% of the base. [Embodiment 11] 10. The method of claim 8 or 9, wherein the first aerogel comprises 0.5% to about 10% of the base. [Embodiment 12] 10. The method of claim 8 or 9, wherein the amount of base in the first aerogel is greater than the amount of base in the second aerogel. [Embodiment 13] 10. The method of any one of the preceding embodiments, wherein the first aerogel is an aerogel composite including a reinforcing material. [Embodiment 14] 14. The method of embodiment 13, wherein the reinforcing material is a fiber reinforcing material. [Embodiment 15] 10. The method of any one of the preceding embodiments, wherein the first aerogel is an aerogel composite including an opacifying additive. [Embodiment 16] 16. The method of embodiment 15, wherein the opacifying additive is selected from the group consisting of BC, diatomaceous earth, manganese ferrite, MnO, NiO, SnO, AgO, BiO, TiC, WC, carbon black, titanium oxide, iron titanium oxide, zirconium silicate, zirconium oxide, iron(I) oxide, iron(III) oxide, manganese dioxide, iron titanium oxide (ilmenite), chromium oxide, or mixtures thereof. [Embodiment 17] 16. The method of embodiment 15, wherein the opacifying additive comprises silicon carbide. [Embodiment 18] forming a wet gel material; Aging the wet gel material by heating the wet gel material with an aging fluid at an aging temperature and an aging pressure, wherein the aging temperature is above the normal boiling point of the aging fluid and the pressure of a vessel is maintained above the vapor pressure of the aging fluid during heating; extracting the aging fluid from the heated wet gel material to form the first aerogel. [Embodiment 19] 10. An aerogel produced by the method of any one of the preceding embodiments. [Embodiment 20] 1. An aerogel comprising a porous framework, wherein the aerogel has a compression set of 15% or less as determined by ASTM D3574-Test D. [Embodiment 21] 20. The aerogel of embodiment 19, wherein the porous framework comprises silica. [Embodiment 22] 20. The aerogel of embodiment 19, wherein the aerogel is in the form of a sheet. [Embodiment 23] 20. The aerogel of embodiment 19, wherein the aerogel has a compression set of 10% or less as determined by ASTM D3574-Test D. [Embodiment 24] 20. The aerogel of embodiment 19, wherein the aerogel is an aerogel composite comprising a reinforcing material. [Embodiment 25] 24. The aerogel composition of embodiment 23, wherein the reinforcing material is a fiber reinforcing material. [Embodiment 26] 20. The aerogel composition of embodiment 19, wherein the aerogel is an aerogel composite comprising an opacifying additive. [Embodiment 27] 26. The aerogel composition of embodiment 25, wherein the opacifying additive is selected from the group consisting of BC, diatomaceous earth, manganese ferrite, MnO, NiO, SnO, AgO, BiO, TiC, WC, carbon black, titanium oxide, iron titanium oxide, zirconium silicate, zirconium oxide, iron(I) oxide, iron(III) oxide, manganese dioxide, iron titanium oxide (ilmenite), chromium oxide, or a mixture thereof. [Embodiment 28] 26. The aerogel composition of embodiment 25, wherein the opacifying additive comprises silicon carbide. [Embodiment 29] 28. An insulating barrier for use in an electrical storage system, comprising at least one insulating layer comprising the aerogel of any one of embodiments 19 to 27. [Embodiment 30] A battery module, A plurality of battery cells; and one or more insulating barriers according to embodiment 29, wherein at least one insulating barrier is disposed between adjacent battery cells. [Embodiment 31] A power system comprising one or more battery modules as described in embodiment 29. [Embodiment 32] A device or vehicle comprising a battery module according to embodiment 29. [Embodiment 33] The device of embodiment 31, wherein the device is a laptop computer, a PDA, a mobile phone, a tag scanner, an audio device, a video device, a display panel, a video camera, a digital camera, a desktop computer, a military portable computer, a military telephone, a laser range finder, a digital communication device, an information gathering sensor, an electronically integrated garment, a night vision device, a power tool, a calculator, a radio, a remote controlled appliance, a GPS device, a handheld and portable television, a car starter, a flashlight, an acoustic device, a portable heater, a portable vacuum cleaner, or a portable medical instrument. [Embodiment 34] 32. The vehicle of embodiment 31, wherein the vehicle is an electric vehicle.

Claims

1. (a) providing a first silica-based aerogel having a silica density of 0.055 g / cc to 0.095 g / cc and a compression set of greater than 15% as determined by ASTM D3574-Test D; (b) heating the first silica-based aerogel at a temperature of 200°C to 400°C in an atmosphere containing more than 10% oxygen to obtain a second silica-based aerogel; wherein the first silica-based aerogel is heated for a time sufficient to modify the compression set of the first silica-based aerogel such that the resulting compression set of the second silica-based aerogel is 15% or less as determined by ASTM D3574-Test D.

2. The method of claim 1, wherein the atmosphere comprises between 15% oxygen and 25% oxygen.

3. The method of claim 1 , wherein the atmosphere is air.

4. 3. The method of claim 1 or 2, wherein the first silica-based aerogel is heated for a period of 30 seconds or more.

5. 3. The method of claim 1, wherein the first silica-based aerogel is heated for a time period between 30 seconds and 3 hours.

6. 3. The method of claim 1 or 2, wherein during heating of the first silica-based aerogel, the temperature is limited to a temperature below 400°C.

7. The method of claim 1 , wherein the first silica-based aerogel comprises a base.

8. 8. The method of claim 7, wherein the base is an amine base.

9. 9. The method of claim 7 or 8, wherein the first silica-based aerogel comprises at least 0.5 wt.% of the base.

10. 9. The method of claim 7, wherein the first silica-based aerogel comprises 0.5% to 10% by weight of the base.

11. 9. The method of claim 7 or 8, wherein the amount of base in the first silica-based aerogel is greater than the amount of base in the second silica-based aerogel.

12. 3. The method of claim 1 or 2, wherein the first silica-based aerogel is an aerogel composite including a reinforcing material.

13. The method of claim 12 , wherein the reinforcing material is a fiber-reinforced material.

14. 3. The method of claim 1 or 2, wherein the first silica-based aerogel is an aerogel composite that includes an opacifying additive.

15. The opacifying additive is B ４ C, diatomaceous earth, manganese ferrite, MnO, NiO, SnO, Ag ２ O, Bi ２ O ３ 15. The method of claim 14, wherein the inorganic filler is selected from the group consisting of TiC, WC, carbon black, titanium oxide, iron titanium oxide, zirconium silicate, zirconium oxide, iron (I) oxide, iron (III) oxide, manganese dioxide, iron titanium oxide (ilmenite), chromium oxide, or mixtures thereof.

16. The method of claim 14 , wherein the opacifying additive comprises silicon carbide.

17. forming a wet gel material; Aging the wet gel material by heating the wet gel material with an aging fluid at an aging temperature and an aging pressure, wherein the aging temperature is above the normal boiling point of the aging fluid and the pressure of a vessel is maintained above the vapor pressure of the aging fluid during heating; 3. The method of claim 1 or 2, further comprising producing the first silica-based aerogel by steps comprising: extracting the aging fluid from the heated wet gel material to form the first silica-based aerogel.

18. 3. The method of claim 1 or 2, wherein the first silica-based aerogel has a SiC content of 35%.

19. 3. The method of claim 1 or 2, wherein the first silica-based aerogel has a hydrophobic content of 36%.

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