Aging and extraction of wet gels in a single vessel

Abstract

A method of aging a wet gel material is described herein. The method includes aging the wet gel material in an aging fluid by heating the wet gel material at an aging temperature above the normal boiling point of the aging fluid. This is achieved by maintaining the pressure of the aging fluid higher than the vapor pressure of the aging fluid during heating.

Description

[Technical Field]

[0001] The present invention relates generally to aerogel technology and more particularly, in various embodiments, to improved methods for producing aerogels and improved aerogel composites. [Background technology]

[0002] 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.

[0003] Large-scale production of aerogel materials or compositions can be complicated due to the difficulties associated with large-scale continuous formation of gel materials and the difficulties associated with liquid-phase extraction from large quantities of gel materials. It would be desirable to develop efficient techniques for large-scale production of aerogel materials. Summary of the Invention

[0004] It is an object of the present disclosure to obviate or mitigate at least one disadvantage of the conventional methods and materials described above. The methods and systems described herein are designed to improve the process of making aerogel materials.

[0005] In one aspect of the present disclosure, a method of aging a wet gel material includes placing the wet gel material in a container, introducing an aging fluid into the container, and aging the wet gel material by heating the wet gel material and the aging fluid at an aging temperature and an aging pressure, wherein during heating, the aging temperature is above the normal boiling point of the aging fluid and the pressure of the container is maintained above the vapor pressure of the aging fluid.

[0006] In one aspect of the present disclosure, the wet gel material is obtained by a method including providing a precursor solution including a silica gel precursor material and a solvent, and transitioning the silica gel precursor material in the precursor solution into a wet gel material, the wet gel material including a silica-based framework and the solvent.

[0007] In one embodiment of the present disclosure, the aging fluid comprises ethanol. In a further embodiment of the present disclosure, the aging pressure is a pressure above the vapor pressure of the aging fluid at the aging temperature, and the aging temperature is above the critical temperature of CO2. In one exemplary embodiment, during aging of the wet gel material, the wet gel material and aging fluid are heated to an aging temperature of about 80°C (176°F) to about 110°C (230°F) at an aging pressure of about 1000 psi to about 2500 psi. In another exemplary embodiment, during aging of the wet gel material, the wet gel material and aging fluid are heated to an aging temperature of about 95°C (203°F) to about 110°C (230°F) at an aging pressure of about 1000 psi to about 1500 psi. In one exemplary embodiment, the wet gel material is aged for a period of about 1 hour to about 24 hours. In another exemplary embodiment, the wet gel material is aged for a period of about 40 minutes to about 200 minutes. In one aspect of the present disclosure, the wet gel material is aged for a period of time determined from the aging temperature and the standard severity factor.

[0008] In one aspect of the present disclosure, an aging fluid is removed and substantially continuously introduced during aging of the wet gel material. In one aspect of the present disclosure, the wet gel material is washed with an aging fluid before heating the wet gel material. The aging fluid removes and replaces at least a portion of the liquid present in the wet gel material.

[0009] In one aspect of the present disclosure, the wet gel material includes a reinforcing material, which may be in the form of a continuous sheet.

[0010] In a further aspect of the present disclosure, a method of producing an aerogel composition includes placing a wet gel material in a container; introducing an aging fluid into the container; heating the wet gel material and the aging fluid at an aging temperature and an aging pressure, wherein during heating, the aging temperature is above the normal boiling point of the aging fluid and the pressure of the container is maintained above the vapor pressure of the aging fluid; and extracting the aging fluid from the aged gel material with an extraction fluid at an extraction temperature and an extraction pressure, wherein the extraction temperature and extraction pressure are above the critical temperature and critical pressure of the extraction fluid; wherein heating the wet gel material and extracting the aging fluid from the aged gel material are performed in the container without removing the aged gel material from the container between the heating and extracting steps and without reducing the temperature or pressure of the container between the heating and extracting steps.

[0011] In one aspect of the present disclosure, extracting the aging fluid from the aged gel material includes introducing an extraction fluid into a vessel, wherein the temperature and pressure of the extraction fluid entering the vessel are substantially the same as the aging temperature and aging pressure, and adjusting the temperature and pressure within the vessel to maintain the extraction fluid in a supercritical state. In one aspect of the present disclosure, during extraction of the aging fluid from the aged gel material, the extraction fluid is removed during extraction and the extraction fluid is introduced substantially continuously.

[0012] In one aspect of the present disclosure, the extraction process includes monitoring the density of the extraction fluid removed from the vessel. Extraction of the aging fluid may be continued until the density of the extraction fluid removed from the vessel is within 10% of the density of the extraction fluid entering the vessel. When the extraction fluid is supercritical carbon dioxide (CO2), the extraction process includes adjusting the pressure and / or temperature within the vessel to maintain the density of the supercritical fluid between about 0.30 g / cc and 0.60 g / cc.

[0013] In one aspect of the present disclosure, the extraction process further comprises removing fluid from the vessel as the extraction fluid is introduced into the vessel, the removed fluid comprising at least a portion of the aging fluid.

[0014] In one aspect of the present disclosure, the aging pressure is maintained at or above the critical pressure and above the critical temperature of the extraction fluid during heating of the wet gel material to form an aged gel material. In another aspect of the present disclosure, the aging temperature and pressure are increased to the extraction temperature and extraction pressure before introducing the extraction fluid into the vessel.

[0015] In one aspect of the present disclosure, a method for aging a wet gel material includes placing a wet gel material in a container, the wet gel comprising a silica-based framework; introducing ethanol into the container; and aging the wet gel material by heating the wet gel material and ethanol at an aging temperature and an aging pressure, wherein the aging temperature is greater than 80°C (186°F) and the pressure of the container is maintained at greater than 1000 psi during heating; and introducing carbon dioxide into the container, wherein the temperature and pressure of the carbon dioxide entering the container are substantially the same as the aging temperature and aging pressure. 1. A method for producing an aerogel composition, comprising: introducing carbon dioxide at a temperature and pressure substantially the same as an aging temperature and pressure; extracting an aging fluid from an aged gel material with supercritical carbon dioxide at an extraction temperature and pressure; and adjusting the extraction temperature and / or extraction pressure inside the container to maintain the carbon dioxide in a supercritical state, wherein heating the wet gel material and extracting the aging fluid from the aged gel material are carried out within the container without removing the aged gel material from the container between the heating and extraction steps, and without reducing the temperature or pressure of the container between the heating and extraction steps.

[0016] Advantages of the present invention will become apparent to those skilled in the art from the following detailed description of the embodiments and by reference to the accompanying drawings. [Brief explanation of the drawings]

[0017] [Figure 1] 1 shows a schematic diagram of a conventional method for processing a continuous roll of aerogel. [Figure 2] 1 depicts a schematic diagram of an improved process in which aging and extraction of wet gel material are accomplished in the same vessel. [Figure 3] A schematic of this process is shown, overlaid with the phase diagram of CO2. [Figure 4A]1 shows a comparison of the physical properties of gel materials produced using a combined aging / extraction process compared to a standard process in which aging and extraction are performed in different vessels. [Figure 4B] 1 shows a comparison of the physical properties of gel materials produced using a combined aging / extraction process compared to a standard process in which aging and extraction are performed in different vessels. [Figure 4C] 1 shows a comparison of the physical properties of gel materials produced using a combined aging / extraction process compared to a standard process in which aging and extraction are performed in different vessels.

[0018] While the invention may be susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description are not intended to limit the invention to the disclosed form; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. DETAILED DESCRIPTION OF THE INVENTION

[0019] It is to be understood that the present invention is not limited to any particular device or method, which may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments 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 both 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., "may" or "can") and not its mandatory sense (i.e., "must"). The term "include" and its derivatives mean "including, but not limited to." The term "coupled" means directly or indirectly connected.

[0020] Aerogels are a class of open-cell porous materials that contain an interconnected structural framework with a corresponding network of pores integrated within the framework, and an interstitial phase within the pore network that is primarily composed of a gas, such as air. Aerogels are typically characterized by low density, high porosity, large surface area, and small pore size. Aerogels can be distinguished from other porous materials by their physical and structural properties.

[0021] Within the context of the present disclosure, in some examples, the term "framework" or "framework structure" refers to a network of nanoscale and / or microscale structural elements, such as fibrils, compacts, and / or colloidal particles, that form the solid structure of a gel or aerogel. The structural elements that make up the framework structure have at least one characteristic dimension (e.g., length, width, diameter) of about 100 angstroms or less. In the example of a pyrolytic or carbonized aerogel, the term "framework" or "framework structure" can refer to an interconnected network of linear fibrils, nanoparticles, a bicontinuous network (e.g., a network with both sides, transitioning between fibrillar and spherical morphologies), or a combination thereof. In some examples, the linear fibrils, nanoparticles, or other structural elements can be connected together (in some examples, at nodes) to form a framework that defines pores.

[0022] As used herein, the terms "aerogel" and "aerogel material" refer to a solid object, regardless of shape or size, that comprises a framework of interconnected solid structures, with a corresponding network of interconnected pores integrated within that framework, and that contains a gas, such as air, as the dispersed pore medium. Thus, an aerogel is an open, non-fluid colloidal or polymeric network that is expanded throughout its entire volume by a gas, formed by removing all swelling agents from a corresponding wet gel without substantial volume loss or network compression. Aerogels generally possess the following physical and structural properties (according to nitrogen porosimetry testing and helium density measurements) that are ascribed to aerogels: (a) an average pore size ranging from about 2 nm to about 100 nm, (b) a porosity of at least 60% or greater, and (c) a porosity of about 100 to about 1500 m by nitrogen adsorption analysis. 2 / g, etc., about 50m 2Aerogel materials are characterized by a specific surface area of ​​1 / g or greater. It can be appreciated that the inclusion of additives, such as reinforcing materials, can decrease the porosity and specific surface area of ​​the resulting aerogel composite. Densification can also decrease the porosity of the resulting aerogel composite. Aerogel materials of the present disclosure include any aerogel that meets the defining elements set forth in the previous paragraph.

[0023] The aerogels disclosed herein have a pore size distribution. As used herein, the term "pore size distribution" refers to the statistical distribution or relative amount of each pore size within a sample volume of a porous material. A narrower pore size distribution refers to a relatively large percentage of pores within a narrow range of pore sizes. In some embodiments, a narrow pore size distribution may be desirable, for example, to optimize the amount of pores available to accommodate electrochemically active species and maximize the use of available pore volume. Conversely, a wider pore size distribution refers to a relatively small percentage of pores within a narrow range of pore sizes. As such, pore size distribution is typically measured as a function of pore volume and reported as the unit size of the full width at half maximum of the main peak in a pore size distribution chart. The pore size distribution of a porous material can be determined by methods known in the art, including, but not limited to, surface area, skeletal density, and porosity measurements from which the pore size distribution can be calculated. Suitable methods for determining such characteristics include, but are not limited to, gas adsorption / desorption (e.g., nitrogen) measurements, helium density measurements, mercury porosimetry, etc. Pore size distribution measurements reported herein are obtained by nitrogen adsorption analysis unless otherwise specified.

[0024] The aerogel material or composition of the present disclosure can have a pore size at the largest peak from the distribution of about 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, 5 nm or less, 2 nm or less, or within a range between any two of these values.

[0025] The aerogels disclosed herein have a pore volume. As used herein, the term "pore volume" refers to the total volume of pores within a sample of porous material. Pore volume is specifically measured as the volume of open space within a porous material and is typically reported as cubic centimeters per gram (cm3 / g or cc / g). The pore volume of a porous material can be determined by methods known in the art, including, but not limited to, surface area and porosity analysis (e.g., nitrogen porosimetry, mercury porosimetry, helium density measurement, etc.). In certain embodiments, the polyimide or carbon aerogels of the present disclosure have a relatively large pore volume of about 1 cc / g or greater, 1.5 cc / g or greater, 2 cc / g or greater, 2.5 cc / g or greater, 3 cc / g or greater, 3.5 cc / g or greater, 4 cc / g or greater, or within a range between any two of these values. In other embodiments, the polyimide or carbon aerogels and xerogels of the present disclosure have a pore volume of about 0.03 cc / g or greater, 0.1 cc / g or greater, 0.3 cc / g or greater, 0.6 cc / g or greater, 0.9 cc / g or greater, 1.2 cc / g or greater, 1.5 cc / g or greater, 1.8 cc / g or greater, 2.1 cc / g or greater, 2.4 cc / g or greater, 2.7 cc / g or greater, 3.0 cc / g or greater, 3.3 cc / g or greater, 3.6 cc / g or greater, or within a range between any two of these values.

[0026] Aerogel frameworks can be made from a variety of precursor materials, including inorganic precursor materials (e.g., precursors used to make silica-based aerogels); organic precursor materials (e.g., precursors used to make carbon-based aerogels); hybrid inorganic / organic precursor materials; and combinations thereof. Within the context of this disclosure, the term "amalgam aerogel" refers to an aerogel made from a combination of two or more different gel precursors. Within the context of this disclosure, the term "framework" or "framework structure" refers to the network of interconnected oligomeric, polymeric, or colloidal particles that form the solid structure of the gel or aerogel. The polymers or particles that make up the framework structure typically have diameters of about 100 angstroms. However, the framework structure of this disclosure can also include a network of interconnected oligomeric, polymeric, or colloidal particles of any diameter size that form the solid structure in the gel or aerogel. Furthermore, the term "silica-based aerogel" or "silica-based framework" refers to an aerogel framework in which silica constitutes at least 50% (by weight) of the oligomeric, polymeric, or colloidal particles that form the solid framework structure within the gel or aerogel.

[0027] Inorganic aerogels are generally formed from metal oxide or metal alkoxide materials. The metal oxide or metal alkoxide materials can be based on the oxide or alkoxide of any metal capable of forming an oxide. Such metals include, but are not limited to, silicon, aluminum, titanium, zirconium, hafnium, yttrium, vanadium, and cerium. Inorganic silica aerogels are traditionally produced via the hydrolysis and condensation of silica-based alkoxides or via the gelation of silicic acid or water glass. Inorganic precursor materials for silica-based aerogel synthesis include, but are not limited to, metal silicates such as sodium silicate or potassium silicate; alkoxysilanes such as tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), and tetra-n-propoxysilane; partially hydrolyzed alkoxysilanes such as partially hydrolyzed TEOS and partially hydrolyzed TMOS; condensation polymers of alkoxysilanes such as condensation polymers of TEOS and TMOS; alkylalkoxysilanes; and combinations thereof.

[0028] In certain embodiments of the present disclosure, pre-hydrolyzed TEOS, such as Silbond H-5 (SBH5, Silbond Corp), which is hydrolyzed to a water / silica ratio of about 1.9 to 2, may be used as is or may be further hydrolyzed before being incorporated into the gelation process. Partially hydrolyzed TEOS or TMOS, such as polyethyl silicate (Silbond 40) or polymethyl silicate, may also be used as is or may be further hydrolyzed before being incorporated into the gelation process.

[0029] Inorganic aerogels may 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, such as gel stability and hydrophobicity. Within the context of the present disclosure, the term "hydrophobicity" refers to a measure of an aerogel material or composition's ability to repel water. The hydrophobicity of an aerogel material or composition can be expressed by measuring the equilibrium contact angle of a water droplet at the interface with the material surface. Aerogel materials or compositions of the present disclosure with a water contact angle greater than 90° are considered hydrophobic. Aerogel materials or compositions with a water contact angle less than 90° are considered hydrophilic.

[0030] Inorganic silica aerogels can specifically contain hydrophobic precursors such as alkylsilanes or arylsilanes. The hydrophobic gel precursor may 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 metal alkoxides in the formation of amalgam aerogels. Hydrophobic inorganic precursor materials for the synthesis of silica-based aerogels include, but are not limited to, trimethylmethoxysilane (TMS), dimethyldimethoxysilane (DMS), methyltrimethoxysilane (MTMS), trimethylethoxysilane, dimethyldiethoxysilane (DIVIDES), methyltriethoxysilane (MTES), ethyltriethoxysilane (ETES), diethyldiethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane (PhTES), hexamethyldisilazane, and hexaethyldisilazane.

[0031] In exemplary aspects of the present disclosure, the relative amount of hydrophobic gel precursor(s) to other inorganic precursor materials is selected to provide an aerogel material or composition with the hydrophobic properties disclosed herein while maintaining other properties, such as thermal conductivity, heat of combustion, onset of thermal decomposition, and / or processability. For example, using a lower amount of hydrophobic gel precursor(s) may reduce hydrophobic properties, providing a material with, for example, higher liquid water uptake or water vapor uptake. Using a higher amount of hydrophobic gel precursor(s) may adversely affect thermal conductivity, combustion, and / or self-heating properties. In exemplary embodiments, the hydrophobic aerogel materials and compositions of the present disclosure may have a hydrophobic content of about 20 wt%, about 30 wt%, about 40 wt%, about 50 wt%, or within a range between any two of these values. For example, an exemplary aerogel composition has a hydrophobic content of about 36 wt%. Further details regarding the synthesis and characterization of hydrophobic aerogels are provided in U.S. Patent Application Publication No. 2016 / 0096949 to Evans et al., which is incorporated herein by reference.

[0032] Producing aerogel generally involves the steps of: 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 described in more detail below, particularly in relation to the formation of inorganic aerogels, such as silica aerogels. However, the specific examples and descriptions 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.

[0033] The first step in forming inorganic aerogels is the formation of a precursor solution, typically via the hydrolysis and condensation of a metal alkoxide precursor in an alcohol-based solvent. Key variables in the formation of inorganic aerogels include the type of alkoxide precursor contained in the precursor solution, the nature of the solvent, the processing temperature and pH of the precursor solution (which can be altered by the addition of acid or base), and the precursor / solvent / water ratio within the precursor solution. Controlling these variables in the formation of the precursor solution can allow for 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.

[0034] The precursor solution is formed by mixing at least one gel precursor with a solvent. Suitable solvents for use in forming the precursor solution include lower alcohols with 1 to 6, preferably 2 to 4, carbon atoms, including any integers therebetween, although other solvents known to those skilled in the art may 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 to optimize the properties of the gel material. Therefore, the selection of the optimal solvent for the sol-gel and gel-formation process will vary depending 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.

[0035] Water may also be present in the precursor 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):

number

[0036] The resulting hydrolyzed metal hydroxide precursor remains suspended in the precursor 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:

number

[0037] Acids and bases can be incorporated into the precursor solution to control the pH of the precursor solution and to catalyze the hydrolysis and condensation reactions of the precursor materials. While any acid may be used to catalyze the precursor reaction and achieve a lower pH solution, preferred acids include HCl, H2SO4, H3PO4, oxalic acid, and acetic acid.

[0038] Similarly, any base may be used to catalyze the precursor reaction and obtain a higher pH solution. In one embodiment of the present disclosure, a base may be used to catalyze the precursor reaction or adjust the pH of the precursor solution. In one embodiment of the present disclosure, a metal hydroxide base may be used to catalyze the precursor reaction or adjust the pH of the precursor solution. Exemplary metal hydroxide bases include, but are not limited to, sodium hydroxide, lithium hydroxide, calcium hydroxide, potassium hydroxide, strontium hydroxide, and barium hydroxide. In another embodiment of the present disclosure, an amine base may be used to catalyze the precursor reaction and / or adjust the pH of the precursor solution. Exemplary amine bases include, but are not limited to, tetraalkylammonium hydroxide, choline hydroxide, trialkylamines, amidines, guanidines, and imidazoles. Specific examples of amine bases include tetramethylammonium hydroxide, tetrabutylammonium hydroxide, guanidine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), pyridine, imidazole, and 4,5-dihydroimidazole.

[0039] The precursor solution can include additional co-gelling precursors, as well as fillers and other additives. The filler materials and other additives can be dispensed into the precursor solution at any time before or during gel formation. The filler materials and other additives can also be incorporated into the gel material after gelation by various techniques known to those skilled in the art. Preferably, the precursor solution, including the gelling precursors, solvent, catalyst, water, filler materials, and other additives, is a homogeneous solution capable of effectively forming a gel under suitable conditions.

[0040] Once the precursor solution has been formed and optimized, the gel-forming components in the precursor solution can be transitioned into a gel material. The process of transitioning the gel-forming components into a gel material involves an initial gel formation step, in which the gel solidifies 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 and / or forms a substantially continuous polymeric framework throughout its volume. Various gel formation techniques are known in the art. Examples include, but are not limited to, maintaining the mixture quiescent for a sufficient period of time, adjusting the pH of the solution, adjusting the temperature of the solution, directing some form of energy (ultraviolet, visible, infrared, microwave, ultrasound, particle radiation, electromagnetic) to the mixture, or a combination thereof.

[0041] In certain embodiments, the gel materials of the present disclosure can be manufactured via a continuous injection molding and gelation process. In a continuous injection molding process, a continuous sheet of fibrous material can be used as a support during the continuous injection molding process. The fibrous support 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 material and forming a wet gel from the gel precursor composition. In one aspect of the present disclosure, the precursor solution is incorporated into the fiber-reinforced material, and the resulting composite is formed into a fiber-supported wet gel material.

[0042] During large-scale production of aerogel, the fiber-reinforced material is in the form of a continuous sheet of interconnected or interlaced fiber-reinforced material. The precursor solution is incorporated into the aerogel composite as a continuous sheet of interconnected or interlaced fiber-reinforced material. The initial wet gel material is produced as a continuous sheet of fiber-reinforced gel by casting or impregnating a continuous sheet of interconnected or interlaced fiber-reinforced material with the gel precursor solution. As described in more detail below, the liquid phase may then be at least partially extracted from the fiber-reinforced wet gel material to produce a sheet of fiber-reinforced aerogel composite.

[0043] Aerogel composites may be reinforced with various fiber reinforcing materials to achieve more flexible, resilient, and conformable composite products. The fiber reinforcing materials may be in the form of discrete fibers, woven materials, nonwoven materials, batting, webs, mats, and felts. The fiber reinforcing materials may be made from organic fibrous materials, inorganic fibrous materials, or combinations thereof. Fiber reinforcing materials include 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, uncarbonized heat-treated PAN (e.g., manufactured by SGL carbon), glass fiber-based materials (e.g., S-glass, 901-glass, 902-glass, 475-glass, E-glass), quartz (e.g., Saint-Gobain Quartz), Q-felt (Johns Silica-based fibers such as Manville, Saffil, Durablanket (Unifrax), and other silica fibers; polyaramid fibers such as Duraback (Carborundum), Kevlar, Nomex, Sontera (all DuPont), and Conex (Taijin); polyolefins such as Tyvek (DuPont), Dyneema (DSM), and Spectra (Honeywell); other polypropylene fibers such as Typar and Xavan (both DuPont); fluoropolymers such as PTFE under the trade names Teflon (DuPont), Goretex (WLGORE); Nicalon (COI) The materials may include a variety of materials, including, but not limited to, silicon carbide fibers such as those manufactured by Epson Ceramics, ceramic fibers such as Nextel (manufactured by 3M), acrylic polymers, wool fibers, silk, linen, leather, suede leather, PBO-Zylon fibers (manufactured by Tyobo), liquid crystal materials such as Vectan (manufactured by Hoechst), cambrelle fibers (manufactured by DuPont), metal fibers such as polyurethane, polyamide, boron, aluminum, iron, and stainless steel fibers, and thermoplastics such as PEEK, PES, PEI, PEK, PPS, etc.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.

[0044] 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.

[0045] 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, BC, diatomaceous earth, manganese ferrite, MnO, NiO, SnO, AgO, BiO, TiC, WC, carbon black, titanium dioxide, iron titanium oxide, zirconium silicate, zirconium oxide, iron(I) oxide, iron(III) oxide, manganese dioxide, iron titanium oxide (ilmenite), chromium oxide, silicon carbide, or mixtures thereof.

[0046] The process of transitioning 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 reaches 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 potential volume loss and shrinkage during liquid-phase extraction. Aging can involve keeping the gel at rest for an extended period of time (prior to extraction), maintaining the gel at elevated temperatures, adding crosslink-promoting compounds, or any combination thereof.

[0047] The time period for transitioning the gel-forming material into a gel material includes both the initial gel formation period (from the onset of gelation to the gel point) and any subsequent 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 time period for transitioning the gel-forming material into a wet 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. Ideally, the total time period is minimized to allow efficient production of aerogel. While ethanol is described below as the aging fluid, different process conditions (e.g., temperature and pressure) may be adapted based on the base temperature and pressure boiling point of the particular aging fluid used.

[0048] 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. The aging fluid may be used to displace the 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, an aging fluid may be passed substantially continuously over and / or through the wet gel material and through the aging vessel. The aging fluid passed through the aging vessel and the wet gel may be fresh or recycled.

[0049] 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 more rapidly 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 atm, 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 heated at or near its boiling point can cause damage to the framework structure of the wet gel material. To reduce the possibility of damage to 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 using ethanol as the aging fluid, the wet gel material is typically aged for 1 hour up to 24 hours 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 atm (101,325 Pa).

[0050] 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. While the aging temperature is generally limited to the normal boiling point of the aging fluid, the temperature can be increased above the normal boiling point of the aging fluid by increasing the pressure within the aging vessel above its equilibrium value (i.e., by applying externally supplied pressure). To prevent the aging fluid from unintentionally boiling as the vessel is heated, the vessel is pressurized above the vapor pressure of the liquid throughout the heating process (i.e., while the vessel's temperature is increasing to the final aging temperature and during aging of the wet gel material). Maintaining the pressure within 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 atm (101,325 Pa).

[0051] 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.

[0052] 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 externally before being reintroduced into the container. Because the vapor pressure of the aging fluid increases with increasing temperature, 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.

[0053] 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.

[0054] Table 1 provides a vapor pressure-temperature table for ethanol. Such a table can be used to determine the minimum pressure inside the container required to raise the temperature of the aging fluid to the desired aging temperature. For example, if an aging temperature of 230°F (110°C) is desired, the vapor pressure inside the container 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 container 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, if ethanol is the aging fluid, the pressure inside the container 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. [Table 1]

[0055] As long as the aging chemistry follows first-order kinetics, the aging time will be halved for every 10°C increase in temperature. The relative effectiveness of different aging protocols can be estimated by comparing the severity factors. The severity factor (R0) is determined using equation (1):

number

[0056] The severity factor for a given system can be used to predict the aging time of a wet gel material at any given aging temperature. For a given aging process, the standard severity factor R can be calculated from equation (1). The standard severity factor can then be used to calculate the aging time (t) for any given temperature from equation (2):

number

[0057] In an exemplary case, the aging process is conventionally carried out at a temperature of 160°F (71.1°C), a pressure of 1 atm, and for 840 minutes using ethanol as the aging fluid. The standard severity factor can be calculated from Equation 1, shown below: R0=(840)*e (71.1-25) / 14.75) =19,126 Based on the standard severity factors calculated above, the aging time at any given temperature for the ethanol aging process can be calculated according to Equation 2. Table 2 lists the predicted aging times calculated from the standard severity factors (19,126) for exemplary ethanol aging processes. [Table 2]

[0058] Using a severity factor to estimate the aging time of a gel material can make it possible to determine the aging time without requiring lengthy trial-and-error testing and wasted material. During the formation of an aerogel composition, the gel material is heated in an aging fluid for a time sufficient to complete the chemical reactions that form the gel material framework. Once aging is complete, the liquid is removed from the gel material to produce the aerogel composition. After drying, the aerogel composition is tested to ensure that the aerogel framework is intact and that the aerogel composition has the desired properties. Until an aerogel is formed, it is difficult to determine whether the aging time was sufficient to produce an aerogel composition with the desired properties. To ensure that the aging process is complete, an excess aging time is used to complete the process. Once the aging time at standard temperature for the aging fluid is determined, a new aging time can be determined using the severity factor, with confidence that the properties of the resulting aged gel are satisfactory in terms of the desired performance.

[0059] As part of the aging process, the resulting wet gel material may be washed in a suitable secondary solvent to replace the primary reaction solvent present in the wet gel material. Such secondary solvents may be linear monohydric alcohols having one or more aliphatic carbon atoms, dihydric alcohols having two or more carbon atoms, branched alcohols, cyclic alcohols, alicyclic alcohols, aromatic alcohols, polyhydric alcohols, ethers, ketones, cyclic ethers, or derivatives thereof. In a preferred embodiment of the present disclosure, the initial wet gel material comprises water or a mixture of ethanol and water. Water from the initial wet gel material is washed with ethanol during the aging process.

[0060] Once the gel material has been formed and aged, the liquid phase of the gel can then be at least partially extracted from the wet gel using an extraction method to form an aerogel material. Liquid phase extraction, among other factors, plays an important role in manipulating aerogel properties such as porosity and density, as well as related properties such as thermal conductivity. Generally, aerogels are obtained when the liquid phase is extracted from the gel in a manner that reduces shrinkage of the porous network and framework of the wet gel.

[0061] Aerogels are typically 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. Furthermore, supercritical phases are generally more miscible with organic solvents, allowing for better extraction. Cosolvents and solvent exchange are also commonly used to optimize supercritical fluid drying processes.

[0062] One disclosed method for extracting the liquid phase from a 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, producing a dry aerogel material. The carbon dioxide can also be pretreated to a supercritical state before being injected into the extraction chamber.

[0063] In one aspect of the present disclosure, the aging process and the extraction of the liquid can be carried out in the same vessel. Using the same vessel for both the aging and extraction processes allows for the formation of an aerogel composition without removing the aged gel material from the vessel between the heating and extraction steps, and without reducing the temperature or pressure of the vessel between the heating and extraction steps.

[0064] In the combined aging and extraction process, the wet gel material is placed in a container. The container is selected so that it can be used at the pressure and temperature required to bring the extraction fluid to a supercritical condition. For example, if carbon dioxide is used as the supercritical fluid, the container should be rated for a temperature of at least 35°C and a pressure of at least about 1100 psig. In some embodiments, the container is rated for use at pressures and temperatures significantly exceeding those required to achieve the supercritical condition of the extraction fluid. For example, a container used for supercritical extraction of carbon dioxide should be rated for temperatures above 100°C and pressures above 2500 psig. In more general embodiments, the upper pressure limit is based on the pressure rating of the container.

[0065] After the wet gel material is placed in the container, an aging fluid is introduced into the container to begin the aging process. As mentioned above, the aging process is carried out at an aging temperature higher than the normal boiling point of the aging fluid by maintaining the pressure of the container higher than the vapor pressure of the aging fluid during heating. Because the container was selected to be able to handle the high temperature and pressure conditions for supercritical extraction, the container can also handle the high aging conditions (temperature and pressure) used during the aging process.

[0066] Once the aging process is complete, an extraction process is carried out in the container without removing the aged gel material from the container between the aging and extraction steps. After the aging process is complete, an extraction fluid is introduced into the container. In preferred aspects of the present disclosure, the temperature or pressure of the container is not reduced between the heating and extraction steps when transitioning from the aging process to the extraction process.

[0067] After introducing the extraction fluid into the aging vessel, the aged gel material is subjected to an extraction process by passing a supercritical fluid through the vessel. The extraction process is carried out at an extraction temperature and extraction pressure that are higher than the critical temperature and pressure of the extraction fluid. For example, if carbon dioxide is used as the extraction fluid, the extraction temperature is maintained above the supercritical temperature of carbon dioxide (31°C) and the extraction pressure is maintained above the supercritical temperature of carbon dioxide (1000 psi).

[0068] As described above, the aging process can be carried out at a temperature and pressure higher than the normal boiling point and normal vapor pressure of the aging fluid. To minimize stresses that may occur during the transition from the aging process to the extraction process, the vessel is maintained at or above the aging temperature and pressure. For example, in one embodiment, at the end of the aging process, the extraction fluid is introduced into the vessel without lowering the temperature or pressure inside the vessel. In another embodiment, at the end of the aging process, the temperature and pressure inside the vessel are raised to or near the supercritical conditions of the extraction fluid before the extraction fluid is introduced into the vessel.

[0069] In one embodiment of the present disclosure, the aging conditions are carried out at or near the supercritical point of the extraction fluid. For example, if the extraction fluid is supercritical carbon dioxide, the aging pressure is above the critical pressure of CO2 and the aging temperature is above the critical temperature of CO2. For example, if CO2 is used as the extraction fluid, the aging temperature is about 80°C (186°F) to about 110°C (230°F) and the aging pressure is about 1000 psi to about 2500 psi during aging of the wet gel material. Preferably, when supercritical CO2 is the extraction fluid, the wet gel material and aging fluid are heated to an aging temperature of about 95°C (203°F) to about 110°C (230°F) at an aging pressure of about 1000 psi to about 1500 psi during aging of the wet gel material. Aging the wet gel material at temperatures and pressures at, near, or above the supercritical temperature of the extraction fluid can minimize stress on the gel material during the transition from aging to extraction.

[0070] In one aspect of the present disclosure, an extraction fluid is introduced into the vessel after the aging process. The temperature and pressure of the extraction fluid entering the vessel are substantially the same as the aging temperature and pressure. After a sufficient amount of extraction fluid has been introduced into the vessel, the temperature and pressure inside the vessel are adjusted to maintain the extraction fluid in a supercritical state. In a preferred embodiment, the extraction fluid is carbon dioxide, and the temperature and pressure inside the vessel are maintained at or above the supercritical temperature and pressure of carbon dioxide.

[0071] During extraction, the aging fluid is introduced into and removed from the vessel substantially continuously during the extraction process. For example, the extraction fluid may be recirculated through the vessel. If the extraction fluid is recirculated, the recirculation loop may include a separator that removes at least a portion of the aging fluid from the extraction fluid before the extraction fluid is reintroduced into the vessel. The extraction fluid may be heated externally to the vessel before being reintroduced into the vessel. During extraction, the extraction pressure is maintained above the supercritical pressure of the extraction fluid. Similarly, the extraction temperature is maintained above the supercritical temperature of the extraction fluid. In a carbon dioxide extraction process, the vessel is maintained above the supercritical temperature of carbon dioxide (31°C) and the extraction pressure is maintained above the supercritical temperature of carbon dioxide (1000 psi).

[0072] Additionally, any aging fluid present in the pores of the aerogel material is also removed. This "pore fluid" is essentially a mixture of the aging fluid and unreacted precursors from the sol state. The composition of the pore fluid, in some embodiments, has a variable composition and a different composition than the bulk aging fluid. This is due to limited diffusion into and out of the pores. Because pore fluid detection is substantially difficult, this disclosure generally refers to fluids removed during the extraction process without specifically indicating the presence of pore fluid.

[0073] As with the aging process, it is difficult to determine when the extraction process is complete while the extraction is taking place. Because the extraction process is carried out at high temperatures and pressures, obtaining a sample for testing is difficult and time-consuming. To obtain a sample, the temperature and pressure must be lowered so that the sample can be obtained. Furthermore, if the extraction is not complete, the aged gel material must be returned to the extraction temperature and pressure. The process of increasing the temperature and pressure to supercritical conditions is time-consuming. Furthermore, significant changes in pressure and temperature within the vessel can stress the forming aerogel, potentially damaging the aerogel framework.

[0074] It is possible to monitor the progress of the extraction process without having to remove the aerogel composition from the container. The density of the supercritical fluid changes as the amount of aging fluid dissolved in the supercritical extraction fluid changes. In one aspect of the present disclosure, the density of the incoming supercritical fluid is compared to the density of the extraction fluid exiting the container. The density of the incoming extraction fluid is at or near the density of the pure extraction fluid. As the extraction fluid passes through the aged gel material, it may mix with the aging fluid to form an extraction / aging fluid mixture. The density of this mixture is generally significantly different from the density of the pure extraction fluid. Thus, if a significant amount of aging fluid is present in the container / aged gel material, the density of the extraction fluid exiting the container will be significantly different from the density of the fluid entering the container. As the extraction process approaches completion, the amount of aging fluid in the extraction fluid decreases, and its density begins to approach the density of the pure supercritical extraction fluid. If this point is reached during the extraction of the aged gel material, the extraction process may be considered complete. In one aspect of the present disclosure, extraction of the aging fluid is continued until the density of the extraction fluid removed from the vessel is within about 10%, within about 8%, within about 5%, within about 3%, within about 2%, or within about 1% of the density of the extraction fluid entering the vessel.

[0075] As noted above, the density of the mixture of extraction fluid and aging fluid is generally significantly different from the density of the pure extraction fluid. In one embodiment, the density of the extraction fluid exiting the vessel is monitored periodically or continuously. The density of the extraction fluid can be used to determine the approximate concentration of the extraction fluid in the vessel. As the mixture of extraction fluid and aging fluid is formed, the conditions for supercritical fluid formation change. It may be necessary to modify the extraction conditions (extraction temperature and / or extraction pressure) to maintain the fluid in the vessel at or near the supercritical temperature of the extraction fluid / aging fluid mixture. The density of the extraction fluid passing through the vessel is determined, in part, by monitoring the density of the exiting extraction fluid. If the density changes significantly, the temperature and / or pressure of the vessel may be increased to return the extraction fluid to supercritical conditions. For supercritical carbon dioxide-based extractions, the density of the liquid in the vessel should be maintained at a density of 0.30 g / cc to about 0.60 g / cc by adjusting the temperature and / or pressure of the vessel.

[0076] Further details describing the synthesis of aerogels can be found in U.S. Patent Application Publication Nos. 2016 / 0096949 to Evans et al. and 2021 / 03095227 to Evans et al., both of which are incorporated herein by reference.

[0077] 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.

[0078] 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 a mixture containing the gel-forming material at any point prior to gel formation. Exemplary opacifying additives include, but are not limited to, B4C, diatomaceous earth, manganese ferrite, MnO, NiO, SnO, Ag2O, Bi2O3, 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, silicon carbide, or mixtures thereof.

[0079] In some aspects of the present disclosure, the aerogel material or composition of the present disclosure is produced on a large scale and requires the use of large-scale extraction vessels. The large-scale extraction vessels of the present disclosure may include extraction vessels having a volume of about 0.1 m 3 or more, about 0.25 m 3 or more, about 0.5 m 3 or more, or about 0.75 m 3 or more.

[0080] FIG. 1 shows a schematic view of a conventional method for processing a continuous roll of aerogel. During the formation of the wet gel material, a continuous roll of fiber support material is used to supply the fiber support material through a loading system. The loading system includes a container for storing the aerogel precursor solution. When the fiber support material is transferred through the loading system, the aerogel precursor solution is applied to the fiber support material. After the aerogel precursor solution is distributed over the material, the fiber support material is collected within a take-up spool. The supported wet gel material is transferred to an aging station where it is placed in an aging container. The supported gel material is aged within the container as described herein. After the aging process is complete, the supported aged gel material is removed from the aging container and transferred to an extraction container. The indicated aged gel material is extracted as discussed herein. After the extraction process is complete, the resulting supported aerogel is removed from the extractor and transferred to a separate area for final processing.

[0081] Figure 2 shows a schematic diagram of an improved process in which aging and extraction of the wet gel material are accomplished in the same vessel. The initial step of forming the supported wet gel material is substantially the same as that used in conventional processes. Once the supported wet gel material is formed, it is transferred to an extraction vessel. Once loaded into the extraction vessel, the supported wet gel material is first aged. Aging can be performed at ambient pressure, or if the extraction vessel is rated for supercritical extraction conditions, the aging process can be performed at elevated temperature and pressure. As previously mentioned, aging the wet gel material at elevated temperature and pressure can significantly reduce the aging time. Once the aging process is complete, there is no need to transfer the wet gel material to a separate vessel. Instead, the extraction process is initiated by flushing the aging fluid from the vessel with extraction fluid. The extraction process is then initiated and completed without removing the initial wet gel material from the vessel. As in conventional processes, after the extraction process is complete, the resulting supported aerogel is removed from the extractor and transported to a separate area for final processing.

[0082] Aerogel materials and aerogel composites have low thermal conductivity, making them ideal for thermal insulation applications. In one exemplary application, aerogel composites can be used as a thermal barrier between individual battery cells or groups of battery cells. Battery cells are prone to catastrophic failure under "abuse conditions." Abuse conditions include mechanical, electrical, and thermal abuse. One or all of these abuse conditions can be initiated externally or internally. For example, service-induced stress, aging, design (e.g., cell spacing, cell interconnection style, cell form factor, and other configuration parameter errors), manufacturing, operation, and maintenance are internal mechanical factors that can cause various abuses. External mechanical factors include damage or injury to LIBs, such as from dropping or cell penetration. Electrical abuse conditions primarily include short circuits, overcharge, and overdischarge, both internal and external to the battery cells. Thermal abuse is typically induced by overheating. For example, overheating within a battery cell can be caused by operating the battery cell at high ambient temperatures. Internally, thermal abuse can be caused by electrical and mechanical defects in the battery cell.

[0083] 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 ranging devices, digital communication devices, intelligence gathering sensors, electronics-integrated clothing, night vision equipment, power tools, calculators, radios, remote-controlled appliances, GPS devices, handheld and portable televisions, automobile starters, flashlights, sound devices, portable heating devices, portable vacuum cleaners, or portable medical equipment. When used in vehicles, the battery packs can be used in fully electric or hybrid vehicles. [Example]

[0084] The following examples are included to demonstrate aspects of the present disclosure. Those of skill in the art should understand that the techniques disclosed in the examples below represent techniques discovered by the inventors to function well in the practice of the invention, and therefore 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 of the present disclosure and still obtain like or similar results without departing from the spirit and scope of the invention.

[0085] Aging and extraction method in a single vessel A silica-based wet gel composite consisting of wet gel embedded in a nonwoven fiber reinforcement is obtained as a continuous sheet. The continuous sheet is wrapped around a support and placed in an aging / extraction vessel. Ethanol is added to the vessel as an aging fluid. The temperature of the ethanol added to the vessel is 35°C (95°F). The heated ethanol is recirculated through the vessel during the aging process by continuously adding ethanol to the vessel while continuously removing ethanol from the vessel.

[0086] After the heated ethanol is introduced into the vessel, the extraction pressure inside the vessel is increased to an aging pressure of 1100 psig (7584 kPa) to begin the aging process. During the aging process, the temperature of the ethanol inside the vessel increases to 98.9°C (210°F). Further, during the aging process, the pressure may increase up to approximately 1500 psig (Pa). The aging process is carried out for approximately 130 minutes.

[0087] Once the aging process is complete, the extraction process begins. The pressure inside the vessel is increased to an extraction pressure of 2200 psig. The extraction temperature is initially 98.9°C (210°F), which is the final temperature of the vessel at the end of the aging process. The extraction process begins by introducing carbon dioxide into the vessel and continuously removing it while continuously introducing carbon dioxide into the vessel. The carbon dioxide removed from the vessel is depressurized, which separates the carbon dioxide from any ethanol and water carried out of the vessel by the carbon dioxide. The carbon dioxide can be recycled into the vessel after removing the ethanol and water from the carbon dioxide collected at the outlet. The carbon dioxide is introduced into the vessel at or near the current extraction temperature.

[0088] The extraction temperature is maintained at the aging temperature to minimize stress on the aerogel and save production time. The extraction pressure is approximately 2,200 psig and is adjusted to maintain the density of the supercritical carbon dioxide in the range of 0.36 to 0.60 g / cc.

[0089] In one aspect of the present disclosure, the extraction fluid can be used as an aging fluid for subsequent aging of the wet gel material. The extraction fluid removed from the vessel consists of a mixture of the extraction fluid and the aging fluid. The extraction fluid can be maintained at the extraction temperature and extraction pressure and introduced into another vessel for aging the wet gel material. In this aspect, the amount of aging fluid required to age multiple batches of wet gel material can be minimized. Furthermore, by reusing the extraction fluid as the aging fluid, the process times for filling (during the aging step) and draining (during the extraction step) can be minimized. In an exemplary process, supercritical carbon dioxide can be used as the extraction fluid to remove the ethanol used as the aging fluid. The supercritical carbon dioxide becomes saturated with ethanol during the extraction process and can be used as the aging fluid in the subsequent aging step.

[0090] Figure 3 shows a schematic of this process overlaid with the phase diagram of CO2.

[0091] By monitoring the density of the carbon dioxide removed from the vessel, three distinct extraction transitions are observed: 1) the evacuation of bulk aging ethanol from the vessel, 2) the evacuation of an ethanol and carbon dioxide mixture, and 3) the evacuation of carbon dioxide containing less than 10% ethanol / water. The timing and relative spacing of these transitions vary depending on the thickness of the aerogel sample. The junction between the transitions is defined by a characteristic density change. The extraction endpoint is observed by the convergence of the inlet and outlet densities of the supercritical carbon dioxide. The endpoint can also be predicted based on the volume of the vessel and the calculated total amount of ethanol removed. Once the extraction endpoint is reached and a certain safety margin is obtained, the evacuation procedure can be initiated to remove the carbon dioxide from the fully extracted aerogel material. As used herein, references to removing carbon dioxide refer to the process of reducing pressure so that the carbon dioxide returns to a gaseous state and diffuses out of the aerogel material (displaced by air). As used herein, references to removing carbon dioxide refer to the process of reducing pressure so that the carbon dioxide returns to a gaseous state and diffuses out of the aerogel material (displaced by air).

[0092] FIG. 4 shows a comparison of the physical properties of gel materials produced using a combined aging / extraction process compared to a standard process in which aging and extraction are performed in different vessels.

[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 incorporated by reference only to the extent that no conflict exists between such text and the other descriptions and drawings set forth herein. In the event of such a conflict, the conflicting text in the U.S. patents, U.S. patent applications, and other materials incorporated by reference shall not be expressly incorporated by reference into this patent.

[0094] Further modifications and alternative aspects of the present invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be construed as exemplary embodiments. Elements and materials may be substituted for those shown and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be 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 claims.

[0095] As used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps, or integers are included. The terms should not be interpreted as excluding the presence of other features, steps, or components. The present invention comprises, consists of, or consists essentially of the features disclosed and claimed.

[0096] The present invention may also broadly reside in any part, element, step, example, and / or feature referred to or shown herein individually, or in any combination of two or more of said parts, elements, steps, examples, and / or features collectively. In particular, one or more features in any of the embodiments, examples, and aspects described herein may be combined with one or more features from any other embodiment, example, and aspect described herein.

[0097] Protection may be sought for any feature disclosed in any one or more of the publications referenced herein in combination with the present disclosure.

[0098] Although specific exemplary embodiments of the present invention have been described, the appended claims are not intended to be limited to only these embodiments. The claims should be interpreted literally, flexibly, and / or to encompass equivalents.

Claims

1. 1. A method of aging a wet gel material, comprising: placing the wet gel material in a container; introducing an aging fluid into the container; aging the wet gel material at an aging temperature and an aging pressure, wherein during aging, the aging temperature is maintained above the standard (reference temperature / pressure) boiling point of the aging fluid and the aging pressure is maintained above the vapor pressure of the aging fluid.

2. The wet gel material is providing a precursor solution comprising a silica gel precursor material and a solvent; 10. The method of claim 1, wherein the method comprises: transitioning the silica gel precursor material in the precursor solution into a wet gel material, the wet gel material comprising a silica-based framework and the solvent.

3. The method of claim 1 or 2, wherein the aging fluid comprises ethanol.

4. The aging pressure is CO ２ and the aging temperature is a pressure above the critical pressure of CO ２ The method according to any one of claims 1 to 3, wherein the temperature exceeds the critical temperature of

5. 4. The method of claim 1, wherein during aging of the wet gel material, the wet gel material and aging fluid are heated to an aging temperature of about 80° C. (176° F.) to about 110° C. (230° F.) at an aging pressure of about 1000 psi to about 2500 psi.

6. 4. The method of claim 1, wherein during aging of the wet gel material, the wet gel material and aging fluid are heated to an aging temperature of about 95°C (203°F) to about 110°C (230°F) at an aging pressure of about 1100 psi to about 1500 psi.

7. The method of any one of claims 1 to 6, wherein the wet gel material is aged for a period of from about 1 hour to about 24 hours.

8. The method of any one of claims 1 to 6, wherein the wet gel material is aged for a period of about 40 minutes to about 200 minutes.

9. The method of any one of claims 1 to 8, wherein the wet gel material is aged for a period of time determined from the aging temperature and the standard severity factor.

10. 10. The method according to any one of claims 1 to 9, wherein during the ageing of the wet gel material, an aging fluid is removed and an aging fluid is introduced substantially continuously.

11. 11. The method of any one of claims 1 to 10, further comprising washing the wet gel material with the aging fluid before heating the wet gel material, wherein the aging fluid removes and replaces at least a portion of the liquid present in the wet gel material.

12. The method of any one of claims 1 to 11, wherein the wet gel material comprises a reinforcing material.

13. The method of claim 12 wherein the reinforcing material is in the form of a continuous sheet.

14. 1. A method of producing an aerogel composition, comprising: placing a wet gel material in a container; introducing an aging fluid into the container; heating the wet gel material and the aging fluid at an aging temperature and an aging pressure, wherein during heating, the aging temperature is maintained above the normal boiling point of the aging fluid and the aging pressure is maintained above the vapor pressure of the aging fluid; extracting the aging fluid from the aged gel material with an extraction fluid at an extraction temperature and extraction pressure, wherein the extraction temperature and extraction pressure are greater than a critical temperature and critical pressure of the extraction fluid; The method, wherein heating the wet gel material and extracting the aging fluid from the aged gel material are performed in the container without removing the aged gel material from the container between the heating and extracting steps, and without reducing the temperature or pressure of the container between the heating and extracting steps.

15. The wet gel material is providing a precursor solution comprising a silica gel precursor material and a solvent; 15. The method of claim 14, wherein the method comprises: transitioning the silica gel precursor material in the precursor solution into a wet gel material, the wet gel material comprising a silica-based framework and the solvent.

16. 16. The method of claim 14 or 15, wherein the aging fluid comprises ethanol.

17. Aging pressure is CO ２ and the aging temperature is a pressure above the critical pressure of CO ２ The method according to any one of claims 14 to 16, wherein the critical temperature of

18. 17. The method of any one of claims 14 to 16, wherein during aging of the wet gel material, the aging temperature is from about 80°C (86°F) to about 110°C (230°F) and the aging pressure is from about 1000 psi to about 2500 psi.

19. 18. The method of any one of claims 14 to 17, wherein during aging of the wet gel material, the aging temperature is from about 95°C (203°F) to about 110°C (230°F) and the aging pressure is from about 1000 psi to about 1500 psi.

20. 20. The method of any one of claims 14 to 19, wherein the wet gel material is aged for a period of from about 30 minutes to about 24 hours.

21. 20. The method of any one of claims 14 to 19, wherein the wet gel material is aged for a period of from about 40 minutes to about 200 minutes.

22. 22. The method of any one of claims 14 to 21, wherein the wet gel material is aged for a period of time determined from the aging temperature and the standard severity factor.

23. 23. The method according to any one of claims 14 to 22, wherein during the ageing of the wet gel material, an aging fluid is removed and an aging fluid is introduced substantially continuously.

24. 24. The method of any one of claims 14 to 23, further comprising washing the wet gel material with the aging fluid before heating the wet gel material, wherein the aging fluid removes and replaces at least a portion of the liquid present in the wet gel material.

25. The method of any one of claims 14 to 24, wherein the wet gel material comprises a reinforcing material.

26. 26. The method of claim 25, wherein the reinforcing material is in the form of a continuous sheet.

27. extracting the aging fluid from the aged gel material; introducing the extraction fluid into the vessel, wherein the temperature and pressure of the extraction fluid entering the vessel are substantially the same as the aging temperature and the aging pressure; and adjusting the temperature and pressure inside the vessel to maintain the extraction fluid in a supercritical state.

28. 28. The method of claim 27, wherein during extraction of the aging fluid from the aged gel material, extraction fluid is removed and extraction fluid is introduced substantially continuously during the extraction.

29. 30. The method of claim 28, further comprising monitoring the density of the extraction fluid removed from the vessel.

30. 30. The method of claim 29, wherein the extraction of the aging fluid is continued until the density of the extraction fluid removed from the vessel is within 10% of the density of the extraction fluid entering the vessel.

31. The method of any one of claims 14 to 30, wherein the supercritical fluid comprises carbon dioxide.

32. 32. The method of any one of claims 14 to 31, further comprising adjusting the pressure within the vessel to maintain a density of the supercritical fluid between about 0.30 g / cc and 0.60 g / cc.

33. 33. The method of any one of claims 14 to 32, further comprising removing fluid from the vessel as the extraction fluid is introduced into the vessel, the removed fluid comprising at least a portion of the aging fluid.

34. 34. The method of any one of claims 14 to 33, wherein the aging pressure is maintained at or above the critical pressure and above the critical temperature of the extraction fluid during heating of the wet gel material to form an aged gel material.

35. 35. The method of any one of claims 14 to 34, wherein the aging temperature and aging pressure are increased to the extraction temperature and extraction pressure before introducing the extraction fluid into the vessel.

36. 1. A method of producing an aerogel composition, comprising: placing a wet gel material into a container, the wet gel including a silica-based framework; introducing ethanol into the vessel; Aging the wet gel material by heating the wet gel material and the ethanol at an aging temperature and an aging pressure, wherein the aging temperature is greater than 80°C (186°F) and the pressure in the container is maintained greater than 1000 psi during heating; introducing carbon dioxide into the vessel, wherein the temperature and pressure of the carbon dioxide entering the vessel are substantially the same as the aging temperature and the aging pressure; extracting the aging fluid from the aged gel material using supercritical carbon dioxide at an extraction temperature and extraction pressure; and adjusting the extraction temperature and / or extraction pressure inside the vessel to maintain the carbon dioxide in a supercritical state; The method, wherein heating the wet gel material and extracting the aging fluid from the aged gel material are performed in the container without removing the aged gel material from the container between the heating and extracting steps, and without reducing the temperature or pressure of the container between the heating and extracting steps.

37. During aging of the wet gel material, the container ２ and the internal temperature of the vessel is increased to a pressure above the critical pressure of CO ２ 37. The method of claim 36, wherein the temperature exceeds a critical temperature of

38. 38. The method of claim 36 or 37, wherein during aging of the wet gel material, the wet gel material and aging fluid are heated to an aging temperature of about 95°C (203°F) to about 110°C (230°F) at an aging pressure of about 1000 psi to about 1500 psi.

39. 39. The method of any one of claims 36 to 38, wherein the wet gel material is aged for a period of from about 40 minutes to about 200 minutes.

40. 40. A method according to any one of claims 36 to 39, wherein an aging fluid is removed and an aging fluid is introduced substantially continuously during the ageing of the wet gel material.

41. 41. The method of any one of claims 36 to 40, wherein during extraction of the aging fluid from the aged gel material, carbon dioxide is removed during the extraction and extraction fluid is introduced substantially continuously.

42. 42. The method of any one of claims 36 to 41, further comprising monitoring the density of the carbon dioxide removed from the vessel, and wherein the extraction of the aging fluid is continued until the density of the extraction fluid removed from the vessel is within 10% of the density of the extraction fluid entering the vessel.

43. 43. The method of any one of claims 36 to 42, further comprising adjusting the extraction pressure within the vessel to maintain a density of the supercritical fluid between about 0.36 g / cc and 0.60 g / cc.

44. 43. The method of any one of claims 36 to 42, wherein during heating of the wet gel material to form the aged gel material, the aging pressure is maintained at or above the critical pressure of carbon dioxide, and the aging temperature is at or above the critical temperature of carbon dioxide.

45. 45. The method of any one of claims 36 to 44, wherein the aging temperature and aging pressure are increased to the extraction temperature and extraction pressure before introducing the extraction fluid into the vessel.

46. 46. ​​The method of any one of claims 36 to 45, wherein the wet gel material comprises a reinforcing material.

47. 47. The method of claim 46, wherein the reinforcing material is in the form of a continuous sheet.

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