Ceramic foam, method for producing same and use thereof

Abstract

A ceramic foam is provided. The ceramic foam can have a hierarchical pore gradient. The ceramic foam can be a silica aerogel. The ceramic foam can be produced by reacting one or more precursors in the presence of an inert gas generated by a pore-forming gas-forming additive. The ceramic foam can be used as an insulating material.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 62 / 791,778 (filed January 12, 2019) and U.S. Provisional Application No. 62 / 861,892 (filed June 14, 2019), the disclosures of which are incorporated herein by reference. [Background technology]

[0002] The search for lightweight and mechanically strong super-insulating materials (thermal and acoustic) is important for energy-efficient buildings and many other sectors, while low-cost manufacturing with scalability is essential for large-scale, practical and energy-saving applications.

[0003] HVAC (heating, ventilation, and air conditioning) in buildings accounts for 40% of the world's energy consumption. HVAC in existing buildings and future constructions can be improved by introducing improved insulation and reducing CO2 emissions. An economical approach to reduce heat loss in buildings is to install thicker layers of insulation. However, it will occupy more space and therefore the living space will be reduced. Silica aerogel can achieve the same insulation performance with half the thickness of traditionally installed insulation. Silica aerogel exhibits the lowest thermal conductivity of any known solid material, on the order of 0.015 W / mK at ambient temperature, pressure, and relative humidity. Such low thermal conductivity results from its low density in combination with the pores created during manufacture. In the building industry, space saving is one of the most important reasons for using high-performance insulation materials in building retrofits as well as thin facade insulation, side balcony, and roof balcony structures. The main drawback of the large-scale use of silica aerogel as a standard insulation material in buildings is their manufacturing cost.

[0004] Superinsulation materials require strict regulation of heat transfer. In this context, silica aerogel is one of the most efficient thermal insulation materials and can even reach ultralow thermal conductivity, less than still air. The superinsulation of ceramic aerogel arises from the geometric morphology of the porous material (including high pore volume, optimized void size, and porous solid walls with boundaries and defects), where limited heat conduction through gas voids and dissipative paths for heat transport through the low solid fraction under phonon scattering contribute to its good thermal insulation. Even with its superinsulation performance, large-scale silica aerogel application is prohibitively expensive due to its expensive and time-consuming fabrication by supercritical drying (avoiding capillary-induced structural degradation during the drying process). Moreover, the poor mechanical stability of aerogel prevents monolithic application. Additives such as carbon nanowires and polymer fibers are used blended with aerogel to enhance mechanical stability, but it is still very difficult to achieve mechanical strength without compromising the insulating performance.

[0005] Aerogel-like foam materials with pore size gradients inspired by human skin structure have recently attracted interest due to their asymmetric structure, which can not only impart excellent thermal insulation performance but also provide a basis for the development of new functionalities. Furthermore, such aerogel-like foam materials with pore gradient structures show more promise in optimizing mechanical properties than dense or porous materials with uniform pore sizes. Gradient-pore poly(lactic acid) foams with the same porosity were found to have ~20% improved sound absorption capacity than uniform foams. Silica foams with hollow nano / microstructures with tunable porosity, pore size, and controlled mass density have been implicated in the development of super-insulating materials.

[0006] For thermal insulation, lightweight aerogel materials may be desirable. However, poor mechanical integrity and high manufacturing costs have hindered their large-scale adoption for energy-efficient building insulation. Furthermore, achieving higher acoustic and thermal resistance properties would be important for temperature management.

[0007] The internal surface chemistry of silica aerogel is characterized by its very large surface-to-volume ratio (~2×10 9 m -1 ) and specific surface area (~900m 2 / g), plays a crucial role in its thermal and chemical behavior. Traditional supercritical drying is based on the idea that hydroxyl (-OH) groups (~5-OH / nm2) with strong hydrogen bonding ability (hydrophilicity) play a crucial role in the thermal and chemical behavior of the material. 2 ) to produce a surface covered only by SiO2. As a result, they absorb water from humid air, which increases their mass by up to 20%. Moreover, the condensation of water in the nanometer-scale pores exerts capillary forces strong enough to destroy the silica framework and collapse the aerogel monolith. In addition, at relatively high temperatures, the radiative component of heat conduction in silica aerogels has a large effect.

[0008] Silica aerogels are typically prepared via a sol-gel process combined with supercritical extraction to maintain structural integrity and high porosity. Traditional aerogel production by supercritical extraction suffers from many limitations, including high energy consumption, large environmental footprint, long processing times, and high material costs. However, the complex processing and high pressures involved in supercritical drying limit its scalability for large-scale production of silica aerogels for building insulation. The most common aerogel synthesis approach involves liquid extraction from the gel by critical point drying using low surface tension supercritical fluids (e.g., CO2 or CH4). However, supercritical extraction requires expensive high pressure equipment and can be a hazardous and time-consuming process. An alternative approach includes organic solvent stripping, which is difficult to scale up due to the energy-intensive requirements of high vacuum for solvent stripping and relatively low temperatures for freeze drying. Traditional atmospheric pressure drying processes replace the original solvent used in gel formation with low surface tension organic solvents (such as hexane, heptane, and octane) as a less energy-intensive alternative. Moreover, it usually results in the production of hydrochloric acid, which requires further organic solvents to be removed. Thus, the current APD method is still a time-consuming and costly process due to the use of large amounts of organic solvents. All these limit the large-scale production of aerogel for building insulation. According to a 2014 report by Allied Market Research, the rapid growth of the aerogel market has indicated interest in silica aerogel insulation ($18.5 / ft2-inch); in 2004, approximately $25 million of aerogel insulation was sold, which increased to $500 million by 2013 (projecting $1.927 billion by 2021). Furthermore, the main drawback of large-scale adoption of silica aerogels as a standard insulation material in buildings is their high manufacturing cost. As a result, current aerogel production is mostly used for industrial applications such as pipeline insulation.

[0009] New methods for insulating materials (e.g., insulating materials with gradient structures) having desirable mechanical integrity and low cost are desired, particularly for scalable manufacturing of insulating materials (e.g., insulating materials with gradient structures). Summary of the Invention

[0010] In the present disclosure, in various embodiments, scalable ceramic aerogels, such as pore-gradient ceramic aerogels, which may be referred to as ceramic foams, monoliths (e.g., PGAeros), have been designed and synthesized. Low-cost manufacturing of PGAeros is further facilitated by in-situ cell formation to support pore gradients. PGAeros can exhibit robust mechanical and thermal stability over a wide temperature range (e.g., compressive strengths of 0.040 W / mK and 100.56 MPa, respectively). For example, the monolithic ceramic monolith nature of PGAeros can exhibit robust acoustic and fire resistance. This demonstration of scalable manufacturing of ceramic aerogel materials can be used, for example, for thermal insulation applications with desirable thermal management, mechanical strength, low mass density, and acoustic and flame retardant performance.

[0011] In one aspect, the present disclosure provides a method of making a ceramic foam. The ceramic foam may also be referred to as a ceramic aerogel or a ceramic aerogel-like foam (e.g., a silica aerogel-like foam). The ceramic foam may be a silica aerogel. The silica aerogel may be a silica aerogel film. The method is based on the in situ generation of a pore-forming gas reaction. The reaction may be carried out in a closed environment (e.g., a reaction above ambient pressure). The ceramic foam may be formed under hydrothermal conditions. In one example, the method does not include the use of supercritical gas species. Non-limiting examples of the method are provided herein.

[0012] In various examples, a method for forming a ceramic foam includes contacting (e.g., in a sealed environment, such as a sealed container) one or more ceramic precursors (e.g., one or more silica precursors), one or more pore-forming gas-forming additives (one or more inert gas generants), one or more catalysts, and optionally one or more additives, where the contacting results in the formation of an inert gas (e.g., carbon dioxide) and a ceramic foam (e.g., silica aerogel). The ceramic foam (e.g., silica aerogel) can be formed under hydrothermal conditions. The reactants (one or more ceramic precursors, one or more pore-forming gas-forming additives, one or more catalysts, and optionally one or more additives) can be added / contacted in any order. The reactants can be contacted in a single container. The as-formed ceramic foam (e.g., silica aerogel) can be subjected to ambient pressure drying (APD). In various examples, the method further includes post-ceramic foam formation modification of at least a portion of the surface of the ceramic foam (e.g., silica aerogel). For example, advanced surface modifications including trimethylchlorosilane treatment and / or carbon coating can be used to engineer capillarity and superhydrophobicity. The process may be a continuous process (e.g., roll-to-roll process).

[0013] In one aspect, the present disclosure provides a ceramic foam. The ceramic foam may be a ceramic foam film. The ceramic foam may be referred to as a ceramic aerogel. The ceramic foam may be a silica aerogel. The silica aerogel may be a silica aerogel film. Non-limiting examples of ceramic foams are provided herein. A ceramic foam material (e.g., a ceramic foam composite) includes a ceramic foam. The ceramic foam includes a matrix of a ceramic material. The ceramic foam may be produced by the method of the present disclosure. The ceramic foam (e.g., silica aerogel) may have a variety of forms. For example, the ceramic foam (e.g., silica aerogel) is a monolith. In another example, the ceramic foam (e.g., silica aerogel) is a film. The ceramic foam (e.g., silica aerogel) film may be a free-standing film or may be disposed on a substrate. The ceramic foam (e.g., silica aerogel) film may be infiltrated into a substrate. The ceramic foam may be porous and may exhibit a hierarchical gradient pore structure. The ceramic matrix of the ceramic foam may be mesoporous. The ceramic foam material may be a composite material (e.g., a composite ceramic foam such as a composite silica aerogel). The composite material may include a polymer material in some or all of the pores of the ceramic foam (which may be referred to as a hybrid composite material or hybrid ceramic foam). The ceramic foam may have desirable sound transmission / insulation / insulation properties. In one example, the ceramic foam is used as an insulating material (e.g., a building material and / or a soundproofing material). In various examples, the ceramic foam is used as a composite material in applications such as catalysis, membranes, separations, and as a template or support substrate for coating with other functional materials. [Brief description of the drawings]

[0014] For a fuller understanding of the nature and objects of the present disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0015] FIG. 1 shows an example of the disclosed R2R process combined with in situ APD to produce low-cost silica aerogel.

[0016] FIG. 2 shows a scanning electron microscope (SEM) image of an example of a silica aerogel of the present disclosure.

[0017] FIG. 3 shows an SEM image of an example of a silica aerogel of the present disclosure.

[0018] FIG. 4 shows an EDX image of an example of a silica aerogel of the present disclosure.

[0019] FIG. 5 shows an EDX image of an example of a silica aerogel of the present disclosure.

[0020] FIG. 6 shows a thermal image (infrared image) of an example of a silica aerogel produced using the method described in Example 1.

[0021] FIG. 7 shows an image of an example of a silica aerogel produced using the method described in Example 2 being heated, demonstrating the flame retardant properties of the silica aerogel.

[0022] FIG. 8 shows an image of an example of a silica aerogel of the present disclosure and an image of a carbon material-coated silica aerogel of the present disclosure.

[0023] FIG. 9 shows images of examples of silica aerogels prepared using the method described in Example 2 (A is a white silica aerogel prepared using TEOS as the silica precursor; B is a transparent silica aerogel prepared using MTMS as the silica precursor) and Images of white silica aerogel (B, transparent) heat-treated under different conditions (C, 400 °C, 3 h, and D, 600 °C, 6 h) are shown. The heat treatment was performed in a tube furnace.

[0024] FIG. 10 shows thermal conductivity data for an example of a silica aerogel made using the method described in Example 2 (and TEOS as the silica precursor). The equation used for thermal resistance is q=P / A* d / ΔT, where P / A is recorded by the FluxTap, d is the thickness of the sample, and ΔT is calculated by subtracting the measurements of the two temperature sensors.

[0025] Figure 11 shows an SEM image of an example of a white silica aerogel produced using the method described in Example 2 (and TEOS as the silica precursor). The image shows a porous structure on the surface of the white silica aerogel.

[0026] 12 shows an SEM image of an example of a white silica aerogel produced using the method described in Example 2 (and TEOS as the silica precursor). The image shows the porous structure on the side of the white silica aerogel.

[0027] Figure 13 shows an SEM image of an example of a white silica aerogel produced using the method described in Example 2 (and TEOS as the silica precursor). The image shows a porous structure on the surface of the white silica aerogel.

[0028] 14 shows an SEM image of an example of a white silica aerogel produced using the method described in Example 2 (and TEOS as the silica precursor). The image shows the porous structure on the surface of the white silica aerogel. The pore structure includes small and large pores.

[0029] FIG. 15 shows an SEM image of an example of a white silica aerogel produced using the method described in Example 2 (and TEOS as the silica precursor).

[0030] 16 shows an SEM image of an example of a transparent silica aerogel produced using the method described in Example 2 (and MTMS as the silica precursor). The image shows a porous structure on the white silica aerogel surface.

[0031] 17 shows an SEM image of an example of a white silica aerogel produced using the method described in Example 2 (and TEOS as the silica precursor) and heated at 400° C. for 3 hours. The image shows the porous structure on the white silica aerogel surface.

[0032] FIG. 18 shows images illustrating mechanical testing of a silica aerogel sample of the present disclosure.

[0033] 19 shows mechanical testing data for an example of a white silica aerogel produced using the method described in Example 2 (and TEOS as the silica precursor). This material has a Young's modulus of 7.6054 MPa.

[0034] Figure 20 shows porosity data obtained using a pycnometer for an example of a white silica aerogel produced using the method described in Example 2 (and TEOS as the silica precursor). This material has a porosity of 89.587%.

[0035] Figure 21 shows porosity data obtained using a pycnometer for an example of a transparent silica aerogel produced using the method described in Example 2 (and MTMS as the silica precursor). This material has a porosity of 83.925%.

[0036] FIG. 22 shows an example image of a white silica aerogel produced using the method described in Example 2 (and TEOS as the silica precursor) heated to 2000° C., demonstrating the flame retardant properties of the silica aerogel.

[0037] [Figure 23] a) Schematic diagram of the three-step synthesis process of silica-PGAeros. Step 1: Formation of micelles assisted by CTAB in aqueous urea solution. Step 2: Hydrolysis of TEOS at the interface of CTAB micelles. Step 3: Decomposition of urea with release of NH3 and CO2. b) Optical image of a typical silica foam with a diameter of 6 cm. c) 0.6 cm thick polished silica PGAero sample. d) Typical SEM image of silica PGAero showing a sharp pore gradient. The inset shows the average pore size increasing from bottom to top. e, f) High resolution SEM images showing larger (e) and smaller (f) pores corresponding to the top and bottom areas of Figure 23d, respectively. g, h) Low-resolution and h) high-resolution TEM images of particles in PGAeros silica network.

[0038] [Figure 24] SEM images of silica PGAeros at a) 48 h and b) 72 h reaction times, inset shows the corresponding size distribution of pores. c) Thermal conductivity of silica-PGAeros synthesized by different reaction times.

[0039] [Figure 25] a)–f) SEM images of silica PGAeros synthesized by varying the amount of precursor (referred to as PGAero-1, 5, 6, 7, 8, and 9, respectively). g) The thermal conductivity of a series of PGAeros depended on the average pore size and porosity.

[0040] [Figure 26] a) Mechanical properties of silica PGAero before and after annealing at 400°C. Insets show SEM images before (top) and after (bottom) annealing. b) Schematic showing reduced heat and sound due to gradient structure of silica PGAero. c) Compare the sound insulation performance of Silica PGAero with polyurethane, Kevlar, and two types of ceramic fiber blankets from Unifrax (Ceramic Fiber 1: PC-Max 2000i, Ceramic Fiber 2: Saffil Alumina) under sound frequencies from 500Hz to 1800Hz. d) Sound insulation performance of silica PGAero and standard polystyrene foam under a frequency of 2000 Hz. e) Sound insulation performance plot of sound intensity vs sound insulation factor at frequencies of 500Hz, 800Hz and 2000Hz.

[0041] FIG. 27 shows SEM images of the PGAero-2 sample, a) large scale and b) enlarged.

[0042] FIG. 28 shows the change in porosity with reaction time.

[0043] FIG. 29 shows the details of the preparation of samples PGAero-1 and PGAero-5 to 10.

[0044] [Figure 30] a) to g) show the average pore size distributions of samples PGAero-1, PGAero-5 to PGAero-10.

[0045] [Figure 31] a) and b) show photographs of mechanical testing.

[0046] [Figure 32] a) Stress-strain curve of the initial specimen PGAero-1 under 6 lbs. b) Stress-strain curve of the initial specimen compressed until fracture. c) Stress-strain curve of a sample annealed at 400°C under 20 lbf.

[0047] FIG. 33 shows a photograph of the sample annealed at 1000° C. for 24 hours.

[0048] FIG. 34 shows the difference in acoustic intensity between blank, polystyrene foam, and silica PGAero at frequencies from 20 Hz to 5000 Hz.

[0049] Figure 35 shows the difference in sound intensity between 500 Hz and 800 Hz.

[0050] FIG. 36 shows humidity aging cycle measurements of silica foam under 60% and 80% humidity.

[0051] FIG. 37 is a schematic diagram showing the change in opaque and transparent phases as the concentration of surfactant increases. a) For the surfactant CTAB, the hydrophilic particles dominate in the precursor, so with increasing concentration of CTAB there is more of an opaque phase. b) For the surfactant SDS, as the concentration of SDS increases, there is more of a clear phase since the hydrophobic particles dominate in the precursor. c) As the concentration of SDS increases, the micelle formation of SDS changes: the micelle formation becomes more organized and each micelle particle becomes smaller as the concentration of SDS increases.

[0052] [Figure 38] a) Optical image of the gel portion is shown. b, c) SEM and TEM show the microstructure of the gel part. d) The density and porosity of the gel portion changed depending on the concentration of SDS. e) BET results of the gel section are shown. f) Relationship between thermal conductivity and average pore size and density.

[0053] [Figure 39] a, b, c) SEM images show the structure of the white areas changing from open to closed pores. d) Optical image of the white area. e) Density and porosity change with the concentration of SDS. f) Relationship between thermal conductivity, density, and average pore size.

[0054] [Figure 40] a) The strain-stress curves show high mechanical strength, which decreased with increasing SDS concentration. b) Young's modulus decreased with increasing density due to increasing SDS concentration. c) Optical images of 3.33% SDS sample before and after mechanical compression test.

[0055] [Figure 41] a) Sound insulation performance of different concentrations of SDS under high sound frequencies from 3000Hz to 8500Hz. b) Sound insulation performance of different concentrations of SDS under sound frequency of 500 Hz. c) Sound insulation performance of different concentrations of SDS under 800Hz sound frequency. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] Although the claimed subject matter has been described with reference to certain embodiments and examples, other embodiments and examples, including embodiments and examples that do not provide all of the advantages and features described herein, are also within the scope of this disclosure. Various structural, logical, and process step changes can be made without departing from the scope of the disclosure.

[0057] A range of values ​​is disclosed herein. The ranges are set forth with lower and upper limits. Unless otherwise stated, the ranges include all values ​​up to the minimum value (either the lower or upper limit) in magnitude, and ranges that lie between the values ​​in the stated ranges.

[0058] As used herein, unless otherwise stated, the term "group" refers to a chemical entity having one or more ends that can be covalently attached to another chemical species. Examples of groups include, but are not limited to, the following: [ka] The term "group" includes radicals.

[0059] As used herein, unless otherwise specified, the term "alkyl" refers to a branched or unbranched saturated hydrocarbon group. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, butyl, isopropyl, tert-butyl, and the like. For example, alkyl groups include C1 to C5 (e.g., C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C22, C23, C24, C25, C26, C27, C28, C29, C30, C31, C32, C33, C34, C35, C36, C37, C38, C39, C41, C42, C43, C44, C45, C46, ​​C47, C48, C49, C50, C51, C52, C53, C54, C55, C56, C57, C58, C59, C61, C62, C63, C64, C65, C66, C67, C68, C69, C71, C72, C73, C74, C75, C75, C76, C77, C78, ​​C79, C81, C82, C83, C84, C85, C86, C87, C88, C89, C91, C92, C93, C94, C95, C96, C97, C98, C99, C91, C92, C93, C94, C95, C96, C97, C98, C99, C99, C100, C111, C122, C132, C143, C 2、 C 3、 C 4、or a C5 alkyl group). The alkyl group can be unsubstituted or substituted with one or more substituents. Examples of substituents include, but are not limited to, halogens (-F, -Cl, -Br, and -I), aliphatic groups (e.g., alkyl, alkenyl, and alkynyl groups), aryl groups, alkoxide groups, carboxylate groups, carboxylic acids, ether groups, and the like, and combinations thereof.

[0060] As used herein, unless otherwise indicated, the term "alkoxy" refers to an -OR group, where R is an alkyl group as defined herein. Examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, and the like. In one embodiment, the alkoxy group comprises a C1-C5 alkyl group.

[0061] The present disclosure provides a ceramic foam body. The present disclosure also provides a method of making the ceramic foam body and uses of the ceramic foam body.

[0062] In the present disclosure, in various embodiments, scalable ceramic aerogels, such as pore-gradient ceramic aerogels, which may be referred to as ceramic foams, monoliths (e.g., PGAeros), have been designed and synthesized. Low-cost manufacturing of PGAeros is further facilitated by in-situ cell formation, which may support pore gradients. PGAeros may exhibit robust mechanical and thermal stability over a wide temperature range (e.g., compressive strengths of 0.040 W / mK and 100.56 MPa, respectively). For example, the monolithic ceramic monolith nature of PGAeros may exhibit robust acoustic and fire resistance. This demonstration of scalable manufacturing of ceramic aerogel materials may be used, for example, for thermal insulation applications with one or more or all of desirable thermal management, mechanical strength, low mass density, acoustic performance, and flame retardant performance.

[0063] The present disclosure provides, in various embodiments, ceramic aerogel chemistry coupled with reactions in a confined environment (e.g., reactions at reaction conditions above ambient pressure) and in situ ambient pressure drying. The methods can produce ceramic aerogels with hierarchical pore gradients.

[0064] The present disclosure also provides, in various embodiments, surface modifications of ceramic foams. Surface modifications as described herein can provide ceramic foam materials with reduced capillarity and radiative components of thermal conduction: for example, supercritical drying-induced hydroxyl (-OH) groups (~5OH / nm) that generate strong hydrogen bonding and capillary forces. 2 ) are replaced with, for example, methyl groups (-CH3) and / or carbon material coatings to reduce capillary pressure and radiative transport of energy. In various examples, the surface modification is a moisture and / or fire resistant surface modification. The surface modification can form a fractal-like superhydrophobic network. In one example, nanocrystalline deposits on a silica framework result in smaller pore sizes, stronger mechanical integrity, higher moisture and fire resistance, and lower thermal conductivity.

[0065] In one example, coupling ceramic foam (e.g., silica aerogel) chemistry, in situ ambient pressure drying, and roll-to-roll (R2R) manufacturing efforts are expected to provide continuous low-cost (~90% reduction), high R-value, and highly durable ceramic foam (e.g., silica aerogel-like) building insulation. Thus, for example, coupling silica aerogel chemistry, in situ ambient pressure drying, and roll-to-roll (R2R) manufacturing efforts are expected to be used to continuously produce low-cost (~90% reduction), high R-value, and highly durable silica aerogel building insulation. It is believed that current manufacturing processes can be improved to enable cost-effective continuous manufacturing (e.g., rapid prototyping) of ceramic foam (e.g., silica aerogel-like) sheets while maintaining the desirable insulating properties of silica aerogel. It is believed that current R2R manufacturing processes can be improved to enable cost-effective continuous manufacturing (e.g., rapid prototyping) of silica aerogel sheets while maintaining the desirable insulating properties of silica aerogel. For example, a method for manufacturing low-cost silica aerogel insulation is shown in Figure 1. This approach combines 1) R2R manufacturing, which can improve production efficiency, 2) in situ ambient pressure drying (APD), which can control aerogel cost, and 3) surface modification to improve R-value and durability.

[0066] In the present disclosure, in various embodiments, silica aerogel chemistry is combined with in situ ambient pressure drying. The method can replace the current supercritical extraction step, a complex process using low surface tension organic solvents and high pressure supercritical drying, by using ambient pressure, e.g., drying with in situ generated pore support gas bubbles (e.g., carbon dioxide, ammonia, etc.). The process described herein can significantly reduce one or more or all of the energy input, time, and cost to produce silica aerogels with controlled porosity and pore size, e.g., less than 60 nm.

[0067] For example, R2R rapid prototyping fabrication of low-cost water-based APD silica aerogels, followed by successive surface modification, is expected to achieve smaller pore sizes (<60 nm, minimizing the gas component of thermal conductivity), enhanced durability (mechanical strength, water resistance, and fire resistance), and increased infrared radiation absorption (minimizing the radiative component of thermal conductivity). The advantage of using R2R fabrication of water-based gels is that continuous operation at ambient conditions allows for the synthesis and installation of scalable, low-cost, durable, rapid prototyping insulating materials.

[0068] In various embodiments, the present disclosure provides: 1) low-cost, scalable aqueous aerogel synthesis using, for example, tetraethoxysilane, CTAB, and urea to generate pore-supported silica gel in situ, enabling APD for significant reduction in energy, time, and cost in silica aerogel production; 2) surface modification to control pore size, reduce capillarity, inhibit radiative heat transfer, and meet durability requirements (related to fire, structural, moisture, and acoustic degradation); and 3) low-cost, robust installation enabled by roll-to-roll continuous manufacturing for rapid prototyping to enable easier installation.

[0069] The present disclosure provides, in various embodiments, methods for producing aerogel materials that can avoid expensive chemical processing steps and, in cases where the material is brittle, can avoid supercritical extraction processes. The methods of the present invention are based on in situ APD of silica aerogels, enabled, for example, by the incorporation of sodium bicarbonate, which produces carbon dioxide supporting pores in situ to significantly reduce the energy, time and cost in silica aerogel production.

[0070] This method can utilize processing at near room temperature and ambient pressure to reduce silica aerogel synthesis costs. Rapid prototyping of aerogel products with shape and size customization through R2R manufacturing can further reduce installation costs. For example, the introduction of elemental carbon into silica aerogel is effective in suppressing radiative heat transfer. For example, the addition of additional C to aerogel reduced the thermal conductivity from 0.016 to 0.0135 W / mK at ambient pressure.

[0071] In one aspect, the present disclosure provides a method of making a ceramic foam. The ceramic foam can be referred to as a ceramic aerogel or a ceramic aerogel-like foam (e.g., a silica aerogel-like foam). The ceramic foam can be a silica aerogel. The silica aerogel can be a silica aerogel film. The method is based on the in situ generation of a pore-forming gas reaction. The reaction can be carried out in a closed environment (e.g., a reaction above ambient pressure). The ceramic foam can be formed under hydrothermal conditions. In one example, the method does not include the use of supercritical gas species. Non-limiting examples of the method are provided herein.

[0072] In various examples, a method for forming a ceramic foam includes the steps of: contacting (e.g., in a reaction mixture in a closed environment such as a closed vessel) one or more ceramic precursors; one or more pore-forming gas-forming additives (one or more inert gas generators); one or more catalysts; and optionally one or more additives, where the contacting results in the formation of an inert gas (e.g., carbon dioxide) and a ceramic foam. The ceramic foam can be formed under hydrothermal conditions. The reactants (ceramic precursor(s), pore-forming gas-forming additive(s), catalyst(s), and optional additive(s)) can be added / contacted in any order. The reactants can be contacted in a single vessel.

[0073] In various examples, a method for forming silica aerogel (e.g., in a reaction mixture) includes contacting one or more silica precursors, one or more pore-forming gas-forming additives (one or more inert gas generators), one or more catalysts, and optionally one or more additives, which contact results in the formation of an inert gas (e.g., carbon dioxide) and silica aerogel. The silica aerogel can be formed under hydrothermal conditions. The reactants (silica precursor(s), pore-forming gas-forming additive(s), catalyst(s), and optional additive(s)) can be added / contacted in any order. The reactants can be contacted in a single vessel.

[0074] The reaction can be carried out in a closed environment. The reaction can be carried out in a closed vessel or a closed mold. As an illustrative, non-limiting example, the reaction is carried out in an autoclave. The pressure in the vessel can be autogenous (e.g., resulting from the closed nature of the vessel and the state of the reactants) or the pressure can be increased externally, for example, by pressurizing a sealed vessel to a desired pressure (e.g., 1-100 psi, all values ​​and ranges of 0.1 psi therebetween). The vessel can be pressurized by the addition of an exogenous gas (e.g., an inert gas, such as argon, nitrogen, etc., and combinations thereof).

[0075] In one example, a method of forming a ceramic foam (e.g., a silica aerogel-like foam) includes contacting in a closed vessel (e.g., in a reaction mixture) TEOS, MTMS, water glass / sodium silicate, or a combination of silica precursors (e.g., 57 mL of TEOS or MTMS, or a 1:3 to 3:1 TEOS:MTMS mixture); urea (e.g., 33.33 g) as a pore-forming gas-forming additive (inert gas generator); acetic acid, which may be in the form of an aqueous solution (e.g., 100 mL of a 1 mmol / L solution) as a catalyst; CTAB or SDS (e.g., 3.33 g) as a surface-active additive, where the contacting forms an inert gas (e.g., carbon dioxide, ammonia, etc.) and the silica aerogel-like foam is formed. In various examples, one or more or all of the values ​​in this example are varied by up to 5%, or up to 10%. In various examples, one or more additional additives are contacted (e.g., included in the reaction mixture).

[0076] In one example, a method of forming a silica aerogel includes contacting (e.g., in a reaction mixture) TEOS, MTMS, or a combination of their silica precursors (e.g., 57 mL of TEOS or MTMS, or a 1:3 to 3:1 TEOS:MTMS mixture); urea (e.g., 33.33 g) as a pore-forming gas-forming additive (inert gas generant); acetic acid, which may be in the form of an aqueous solution (e.g., 100 mL of a 1 mmol / L solution) as a catalyst; and CTAB (e.g., 3.33 g) as an additive, where the contacting results in the formation of an inert gas (e.g., carbon dioxide, ammonia, etc.) and the silica aerogel is formed. In various examples, one or more or all of the values ​​in this example are varied by up to 5%, or up to 10%. In various examples, one or more additional additives are provided for contacting (e.g., included in the reaction mixture).

[0077] A variety of ceramic precursors can be used. The precursor may be a sol-gel precursor. Suitable sol-gel precursors are known in the art. Non-limiting examples of precursors include silica precursors, alumina precursors, transition metal oxide precursors, and combinations thereof. In various examples, the silica precursor(s) is selected from tetraalkoxysilanes (e.g., TMOS, TEOS, etc.) (e.g., C1-C5 alkoxytetraalkoxysilanes), alkyltrialkoxysilanes (e.g., methyltrimethoxysilane (MTMS) etc.) (e.g., C1-C5 alkyl, C1-C5 alkoxyalkyltrialkoxysilanes), sodium metasilicates (e.g., water glass), alkyl, and combinations thereof. In various examples, the alumina precursor(s) is selected from aluminum alkoxides (e.g., C1-C6 aluminum alkoxides), alumatoranes, or tris(alumatranyloxy-i-propyl)amines, and the like, and combinations thereof. In various examples, the transition metal oxide precursor(s) are selected from transition metal alkoxides and the like (e.g., transition metal alkoxides having the formula M(OR)x, where M is a transition metal (e.g., Al, Ti (e.g., titanium(IV)-isopropoxide, etc.), Zr, W, Cr, Mo, etc.), R is an alkyl group, and x is, for example, 1, 2, 3, 4, or 5). Transition metals can be present in a variety of oxidation states (e.g., + 1. + 2. + 3. + 4, or + 5).

[0078] In one example, water glass is used as a silica precursor (e.g., alone or in combination with one or more additional silica precursors). Water glass is also called sodium silicate or soluble glass. In one example, water glass is a material that includes sodium oxide (Na2O) and silica (e.g., silicon dioxide, SiO2, etc.) that forms a glassy solid.

[0079] Combinations of ceramic precursors may also be used. For example, binary, ternary, and higher mixed oxide ceramic foams can be produced using mixtures of precursors. As an illustrative example, mixed oxide ceramic foams, such as ceramic foams having a compositional formula corresponding to a desired ratio of Al2O3 to TiO2, can be made using a combination of one or more Al2O3 sol-gel precursors (e.g., alumatoran, tris(alumatranyloxy-i-propyl)amine, or combinations thereof, etc.) and TiO2 sol-gel precursors (e.g., titanium(IV)-iso-propoxide, etc.). One skilled in the art will understand that a ceramic foam having a desired compositional formula can be formed by selection of the appropriate ceramic precursor(s) and / or relative amounts of precursors.

[0080] After formation of the ceramic foam, the ceramic foam can be sintered. For example, the ceramic foam can be sintered at a temperature of 200-800° C. (e.g., 350-450° C. or about 400° C.; including all 0.1° C. values ​​and ranges therebetween). The ceramic foam can be sintered at air and / or ambient pressure (e.g., 1 atm). Without intending to be bound by any particular theory, it is believed that sintering can improve the properties of the ceramic foam. This improvement can result from carbonization of residual organic residues (if present).

[0081] In various embodiments, the method further includes a post-formation modification of at least a portion of the surface of the ceramic foam (e.g., silica aerogel). An example of a post-formation modification of the ceramic foam is forming a layer of a carbon-containing material on at least a portion of the surface (e.g., all of the surface, or all of the surface of the ceramic foam (e.g., silica aerogel)). The carbon-containing material can provide a superhydrophobic exterior surface. For example, a carbon soot coating can be formed by burning a candle under the ceramic foam sample to allow soot coating or by post-thermal annealing.

[0082] Capillarity and superhydrophobicity can be engineered using advanced surface modifications including trimethylchlorosilane treatment and carbon coating, which replaces surface hydroxyl groups with methyl groups on the silica gel surface by the formation of (CH3)3-Si-Si-O≡, followed by successive carbon material coatings. These modification steps control the pore size and surface chemistry to achieve the desired thermal insulation performance and durability.

[0083] For example, trimethylchlorosilane: (CH3)3SiCl can be combined with a continuous carbon material coating to meet the goals of surface modification with methyl group formation and nanocrystalline carbon coating to reduce both capillary and radiative transport modes of heat transfer at higher temperatures. The surface-modified silica will result in smaller pore size, stronger mechanical integrity, higher water and fire resistance, and lower thermal conductivity.

[0084] Another example of post-formation modification of the ceramic foam includes decorating or coating at least a portion of the surface, or all of the surface, of the ceramic foam with nanoparticles.

[0085] The process may be a continuous process. For example, the process is a roll-to-roll continuous manufacturing process. R2R allows for near-net-shape manufacturing and dimensional customization of ceramic foam formations, for example, on a low-cost, highly insulating inorganic paper substrate carrier.

[0086] Using roll-to-roll continuous manufacturing, aerogel-based insulation materials with improved R-values ​​can be formed at low cost using a silica gel precursor (e.g., tetraethoxysilane or water glass) and an inorganic ceramic fiber paper substrate carrier (e.g., Fiberfrax from Unifrax). (登録商標) ) using a roll-to-roll manufacturing process that allows for customization of shapes and dimensions, which is expected to lead to favorable material costs for silica aerogels.

[0087] The methods of the present disclosure can include a thermal annealing step. The thermal annealing step can be performed after the ceramic foam (e.g., silica aerogel) is formed, washed, and dried. For example, the thermal annealing is the last step in manufacturing the ceramic foam (e.g., silica aerogel). In various examples, the thermal annealing can be performed at 300° C. to 600° C. (including all integer values ​​and ranges of degrees C. therebetween) and for various times (e.g., 1 hour to 6 hours (including all integer values ​​and ranges of minutes therebetween)).

[0088] The ceramic network (e.g., silica network, alumina network, aluminosilicate network, transition metal oxide network, or combinations thereof), which may also be referred to as a ceramic matrix, may include ceramic nanoparticles (e.g., silica nanoparticles) of a ceramic aerogel that may be formed in the presence of a pore-forming gas, which may have a size (which may be a maximum dimension or a minimum dimension) of, for example, 20-200 nm (e.g., 150-200 or about 200 nm) (including all integer nm values ​​and ranges therebetween) or may have an average size (which may be an average maximum dimension or an average minimum dimension) of, for example, 20-200 nm (e.g., 150-200 or about 200 nm) (including all integer nm values ​​and ranges therebetween). The ceramic nanoparticles may have a narrow size distribution, with 90% or more, 95% or more, 99% or more, or all of the ceramic nanoparticles having a size and / or average size of 20-200 nm (e.g., 150-200 or about 200 nm) (including all integer nm values ​​and ranges therebetween). The pore-forming gas may be generated in the presence of the ceramic precursor (e.g., the pore-forming gas is generated during the formation of the silica network). In one example, substantially all of the ceramic matrix (e.g., silica matrix) formation is completed in the presence of the pore-forming gas. Substantially all of the ceramic matrix formation means that no additional processing is required to form the ceramic matrix (e.g., silica matrix) of the ceramic foam (e.g., silica aerogel). In various embodiments, 50% or more, 60% or more, 70% or more, 80% or more of the silica precursor reacts in the presence of the pore-forming gas.

[0089] In one aspect, the present disclosure provides a ceramic foam. The ceramic foam may be a ceramic foam film. The ceramic foam may also be referred to as a ceramic aerogel. The ceramic foam may be a silica aerogel. The silica aerogel may be a silica aerogel film. Non-limiting examples of ceramic foams are provided herein. A ceramic foam material (e.g., a ceramic foam composite) includes a ceramic foam. The ceramic foam includes a matrix of a ceramic material. The ceramic foam may be produced by the method of the present disclosure.

[0090] The ceramic foam may be an oxide. Non-limiting examples of oxides include silicon oxides (e.g., silica), aluminum oxides (e.g., alumina), transition metal oxides, and the like, and combinations thereof. The ceramic foam may be stoichiometric or non-stoichiometric.

[0091] The ceramic foam may be a mixture of oxides. The ceramic foam may be binary oxide based, ternary oxide based, or higher oxide based. Non-limiting illustrative examples of ceramic foams include aluminosilicate foams, aluminotitanate foams, and the like.

[0092] In one example, the ceramic foam and / or ceramic foam material does not have any fluorine atoms (e.g., fluorine atoms detectable by conventional methods known in the art), which may be fluorine atoms bonded to silicon atoms (e.g., -Si-F).

[0093] The ceramic foam (e.g., silica aerogel) can have a variety of forms. For example, the ceramic foam (e.g., silica aerogel) is a monolith. In another example, the ceramic foam (e.g., silica aerogel) is a film. The ceramic foam (e.g., silica aerogel) film may be a free-standing film or may be disposed on a substrate. The ceramic foam (e.g., silica aerogel) film may be infiltrated into a substrate.

[0094] Ceramic foams are porous and can exhibit a hierarchical gradient pore structure. Ceramic foams can be described as including a hierarchical hollow structure with micropores (also called macropores) (e.g., voids in a ceramic matrix) as interiors and mesopores within a shell (e.g., matrix). At least some or all of the pores may be interconnected. The pores may be mesopores and / or macropores. The pores may be mesopores as defined by IUPAC.

[0095] The pores of the ceramic foam may be referred to as micropores or macropores, but are not mesopores of the ceramic matrix, and may have a variety of sizes. For example, the size (e.g., average size, and / or 90%, 95%, 99%, 99.9%, or 100%) of the pores may be from 500 microns to 1 micron (including all 0.1 micron values ​​and ranges therebetween). The size may be at least one dimension (e.g., diameter) as measured in a plane parallel to the axis of the pore. For example, the pores may have a size (e.g., at least one dimension (e.g., diameter) as measured in a plane parallel to the axis of the pore and / or at least one dimension (e.g., height) as measured in a plane perpendicular to the axis of the pore) of from 500 microns to 1 micron (e.g., from 200 microns to 10 microns, from 200 microns to 1 micron, or from 100 microns to 1 micron). The size of the pores generally decreases or increases along a direction moving from a first surface of the ceramic foam to a second surface opposite the first surface. The gradient may be a linear gradient or a non-linear gradient.

[0096] The ceramic matrix of the ceramic foam may be mesoporous (e.g., including mesopores, which may be mesopores as defined by IUPAC). For example, the ceramic matrix includes a plurality of pores having a diameter of 2 nm to 100 nm (e.g., 2 nm to 60 nm, 10 nm to 60 nm, or 10 nm to 100 nm) (including 0.1 nm values ​​therebetween and ranges therebetween). For example, the ceramic matrix includes a plurality of pores having an average diameter of 2.5 nm to 30 nm (e.g., 2.5 nm to 10 nm or 15 nm to 30 nm) (including 0.1 nm values ​​therebetween and ranges therebetween). The pore size distribution may be multimodal, such as, for example, bimodal. For example, the ceramic matrix has a plurality of pores with an average diameter of 2 nm to 100 nm (eg, 2 nm to 60 nm, 10 nm to 60 nm, or 10 nm to 100 nm) and a plurality of pores with an average diameter of 2.5 nm to 30 nm (eg, 2.5 nm to 10 nm, or 15 nm to 30 nm).

[0097] The pore size and / or pore size distribution of the ceramic foam and / or ceramic matrix can be determined using methods known in the art, for example, the pore size and / or pore size distribution is determined using BET analysis.

[0098] Silica aerogel is porous. For example, silica aerogel has a plurality of pores with a diameter of 2 nm to 100 nm (e.g., 2 nm to 60 nm, 10 nm to 60 nm, or 10 nm to 100 nm) (including 0.1 nm values ​​and ranges therebetween). For example, silica aerogel has a plurality of pores with an average diameter of 2.5 nm to 30 nm (e.g., 2.5 nm to 10 nm or 15 nm to 30 nm) (including 0.1 nm values ​​and ranges therebetween). The pore size distribution may be bimodal. For example, silica aerogel has a plurality of pores with an average diameter of 2 nm to 100 nm (e.g., 2 nm to 60 nm, 10 nm to 60 nm, or 10 nm to 100 nm) (may be bimodal) and a plurality of pores with an average diameter of 2.5 nm to 30 nm (e.g., 2.5 nm to 10 nm, or 15 nm to 30 nm). The pore size and / or pore size distribution can be determined using methods known in the art, for example, the pore size and / or pore size distribution is determined using BET analysis.

[0099] The ceramic foam material may be a composite material (e.g., a composite ceramic foam such as a composite silica aerogel). The composite material may include a polymer material in some or all of the pores of the ceramic foam (which may be referred to as a hybrid composite material or hybrid ceramic foam). The polymer may be formed by in situ polymerization in the ceramic foam. Additionally or alternatively, the composite material may include a carbon coating on the ceramic foam (also referred to as a ceramic-carbon aerogel). For example, a ceramic foam (e.g., a ceramic foam monolith or a ceramic foam film) is at least partially (or completely) coated with a carbon material.

[0100] The silica aerogel material may be a composite material (which may be referred to as a silica-carbon aerogel) that includes a silica aerogel at least partially (or completely) coated with a carbon material (e.g., a silica aerogel monolith or a silica aerogel film).

[0101] Building insulation can include the ceramic foams (e.g., silica aerogels) of the present disclosure (e.g., ceramic foams such as silica aerogels) produced by the methods of the present disclosure.

[0102] [Table 1]

[0103] The disclosed method is expected to provide low-cost building insulation. The disclosed method is expected to provide inexpensive large-scale production and installation of high R-value building insulation materials (e.g., ceramic foams such as silica aerogel) that can impact a wide range of building envelope applications, such as roofs and walls in existing buildings and future construction. For example, by replacing supercritically dried ceramic foams such as silica aerogel (e.g., Spaceloft®, July 2018) with the disclosed ceramic foams (e.g., silica aerogel) a cost reduction of 90% or more is expected over current technology. Also, the building energy efficiency of the disclosed ceramic foam insulation is expected to be at least 45%. The disclosed ceramic foam insulation can have an R-value and thermal conductivity comparable to commercially available ceramic foams at room temperature. However, the disclosed ceramic foam insulation (e.g., silica aerogel) can have an increased R-value at high temperatures (e.g., compared to commercially available ceramic foams) and can significantly reduce unit costs. The complex processing and volatile organic solvents involved in producing ceramic foams by conventional high pressure supercritical drying make their use cost prohibitive by building insulation manufacturers.

[0104] The building insulation material may be a thermal insulation sheet. The thermal insulation sheet may be used in commercial or residential applications. The thermal insulation sheet may also be formed using a R2R manufacturing method. The thermal insulation sheet may be used to retrofit existing buildings. In various examples, the thermal insulation sheet comprising the ceramic foam (e.g., silica aerogel) of the present disclosure is a R15 / inch thermal insulation sheet that may have a thermal conductivity of 0.01 W / mK or less.

[0105] In one example, the ceramic foam (e.g., silica aerogel) is formed using TEOS and is white in color. In another example, the ceramic foam (e.g., silica aerogel) is formed using MTMS and exhibits desirable transparency. For example, the ceramic foam (e.g., silica aerogel) formed using MTMS exhibits a visible light wavelength (e.g., light wavelengths of 400-800 nm, such as 530 nm) transmittance of 85% or more, 90% or more, 95% or more, or 98% or more (e.g., when measured at a sample thickness of 2-3 mm (e.g., 2.7 mm)). In yet another example, the ceramic foam (e.g., silica aerogel) is formed using TEOS and MTMS and has one or more white regions and one or more transparent regions (e.g., exhibits a visible light wavelength (e.g., light wavelengths of 400-800 nm) transmittance of 90% or more, 95% or more, or 98% or more).

[0106] In one example, the ceramic foam or ceramic foam material (e.g., silica aerogel or silica aerogel material) does not include any exogenous materials (e.g., any detectable exogenous materials that can be detected by conventional methods known in the art). Exogenous materials include, but are not limited to, materials used in forming building materials from silica materials (e.g., ceramic foam materials). Non-limiting examples of exogenous materials include binders (e.g., polymeric binders), polymers, and the like.

[0107] The ceramic foam (e.g., silica aerogel) can have desirable properties, such as a Young's modulus of 2 to 100 MPa (e.g., 2 to 8 MPa), including all integer MPa values ​​and ranges therebetween.

[0108] Ceramic foams can have desirable sound transmission / insulation / insulation properties. In various examples, the ceramic foams have at least 10%, at least 15%, at least 20%, or at least 25% improvement in sound insulation (e.g., increased sound insulation coefficient) over another material of a given thickness (e.g., organic polymer foam such as PS foam, PU foam, or ceramic fiber, etc.) at one or more, substantially all, or all of the frequencies from 500 to 2000 Hz. In another example, a silica aerogel-like foam (e.g., silica PGAeros) having a thickness of 0.014 m has better sound insulation performance compared to a reference PS foam at different frequencies of 500 Hz, 800 Hz, and 2,000 Hz, exhibiting noise reductions of 10.9%, 12.0%, and 28.4%, respectively.

[0109] In one example, the silica aerogel and / or silica aerogel material has no fluorine atoms (e.g., fluorine atoms detectable by conventional methods known in the art), which may be fluorine atoms bonded to silicon atoms (e.g., -Si-F).

[0110] In one aspect, the present disclosure provides a use of the ceramic foam of the present disclosure. The ceramic foam can be used in a variety of applications. The ceramic foam can be a super-insulating material or provide super-insulation. For example, the material has a thermal conductivity of 0.01 W / mK or less.

[0111] In one example, the ceramic foam is used as an insulating material (e.g., a building material or an acoustic insulation material) that can exhibit desirable thermal management and / or acoustic insulation properties.

[0112] In one example, ceramic foams are used as composite materials in applications such as catalysis, membranes, and separations, and as templates or support substrates for coating with other functional materials.

[0113] The method steps described in the various embodiments and examples disclosed herein are sufficient to carry out the disclosed method. Thus, in one example, the method consists essentially of a combination of the method steps disclosed herein. In another example, the method consists solely of such steps.

[0114] The following provides examples of ceramic foams of the present disclosure, methods for making ceramic foams, and uses of the ceramic foams: Statement 1. A method of forming a ceramic foam (e.g., a hierarchical pore gradient ceramic foam) (e.g., a silica aerogel) comprises contacting (e.g., in a reaction mixture) a ceramic precursor (e.g., a silica precursor) (e.g., one or more ceramic precursors (e.g., silica precursors); a pore-forming gas forming additive (an inert gas generator (e.g., one or more pore-forming gas forming additives)); a catalyst (one or more catalysts); and optionally an additive (e.g., one or more additives) in a closed environment (e.g., a closed reaction vessel), where the contacting results in the formation of an inert gas (e.g., carbon dioxide, nitrogen, or a combination thereof) and a hierarchical pore gradient ceramic foam (e.g., a silica aerogel). For example, the hierarchical pore gradient ceramic foam is a film or a monolith. The method may include a sintering step, where the hierarchical pore gradient ceramic foam is sintered. Statement 2. 13. The method of claim 1, wherein the contacting is carried out at an initial pressure of 1 to 100 psi (including all 0.1 psi values ​​and ranges therebetween) (e.g., pressurizing the reaction vessel to 1 to 100 psi) before substantial reaction (e.g., 5%, 1%, or 0.1% reaction) of the one or more ceramic precursors and / or one or more pore forming gas forming additives and / or one or more additives, if present, has occurred. Statement 3. 3. The method of claim 1 or 2, wherein the one or more ceramic precursors are selected from silica precursors, alumina precursors, transition metal oxide precursors, and combinations thereof. Statement 4. The method of claim 3, wherein the silica precursor(s) is selected from tetraalkoxysilanes (e.g., TMOS, TEOS, etc.) (e.g., C1-C5 alkoxytetraalkoxysilanes), alkyltrialkoxysilanes (e.g., methyltrimethoxysilane (MTMS)), etc. (e.g., C1-C5 alkyl, C1-C5 alkoxy alkyltrialkoxysilanes), sodium metasilicate (e.g., water glass), alkyl, and combinations thereof. Statement 5. 5. The method of claim 3 or 4, wherein the alumina precursor(s) is selected from aluminum alkoxides (e.g., C1-C6 aluminum alkoxides), alumatoran, or tris(alumatranyloxy-i-propyl)amine, and the like, and combinations thereof. Statement 6. The transition metal oxide precursor(s) may be a transition metal alkoxide (e.g., a metal oxide precursor having the formula M(OR) x The method of claim 3 or 4, wherein M is a transition metal (e.g., Al, Ti (e.g., titanium(IV)-iso-propoxide, etc.), Zr, W, Cr, Mo, etc.), R is an alkyl group, and x is selected from 1, 2, 3, 4, or 5). The transition metal may be in various oxidation states (e.g., + 1. + 2. + 3. + 4. + 5). Statement 7. The method of any one of the preceding statements, wherein the one or more catalysts is a base catalyst (e.g., ammonia, ammonium fluoride, ammonium hydroxide, urea, cetyltrimethylammonium bromide, and the like, and combinations thereof). Statement 8. 7. The method of any one of claims 1 to 6, wherein the catalyst is an acid catalyst (e.g., a protonic acid (e.g., acetic acid, etc.), a hydrohalic acid, etc., and combinations thereof). Statement 9. The method of any one of the preceding statements, wherein the one or more pore-forming gas-forming additives (inert gas generators) are selected from sodium bicarbonate, urea, and combinations thereof (e.g., the pore-forming gas-forming additives (inert gas generators) provide a subcritical amount (e.g., pressure) of inert gas). The pore-forming gas (inert gas) may be carbon dioxide and / or nitrogen and / or ammonia. Statement 10. The method of any one of the preceding statements, wherein the one or more additives are selected from a surfactant (e.g., cetyltrimethylammonium bromide (CTAB)), urea, and combinations thereof. The surfactant can aid in pore formation. The surfactant can also provide surface functionalization. Statement 11. The method of any one of the preceding statements, wherein the one or more ceramic precursors (e.g., silica precursors), one or more pore-forming gas-forming additives (inert gas generators), and optionally one or more additives are contacted, and then the catalyst is contacted with the one or more ceramic precursors (e.g., silica precursors), one or more pore-forming gas-forming additives (inert gas generators), and optionally one or more additives. Statement 12. The method of any one of the preceding statements, wherein the contacting comprises mixing one or more ceramic precursors (e.g., silica precursors), which may be disposed (e.g., dissolved) in water, a solvent (e.g., an alcohol, such as ethanol), or a combination thereof; one or more pore-forming gas-forming additives (inert gas generators), which may be disposed (e.g., dissolved) in water; and one or more catalysts, which may be disposed (e.g., dissolved) in water. The ceramic precursor(s), inert gas generator(s), catalyst(s), and optionally additive(s) can be combined in any order. In one example, the catalyst(s) is the last component added. Statement 13. The method of any one of the preceding claims, wherein the one or more ceramic precursors (e.g., silica precursors) are present in an amount of 2 to 10 wt % (each if more than one) (based on the total weight of the one or more ceramic precursors (e.g., one or more silica precursors), one or more catalysts, one or more pore-forming gas-forming additives, and, if present, one or more additives). Statement 14. The method of any one of the preceding statements, wherein the one or more pore-forming gas-forming additives are present at 0.4 to 2 wt. % (based on the total weight of the one or more ceramic precursors (e.g., one or more silica precursors), one or more catalysts, one or more pore-forming gas-forming additives, and, if present, one or more additives). For example, the one or more ceramic precursors (e.g., one or more silica precursors) are at least 5 times the weight of the one or more pore-forming gas-forming additives (one or more inert gas generators). Statement 15. The method of any one of the preceding statements, wherein the one or more catalysts are present at 1 to 2 wt. % (based on the total weight of the one or more ceramic precursors (e.g., silica precursors), one or more catalysts, one or more pore-forming gas-forming additives, and, if present, one or more additives). Statement 16. The method of any one of the preceding statements, wherein the one or more additives are present in an amount between 200 and 1000 wt. % (based on the total weight of the one or more ceramic precursors (e.g., one or more silica precursors), one or more catalysts, one or more pore-forming gas forming additives). For example, the additive(s) are present in an amount between 2 and 10 times greater by weight than the ceramic precursor(s). For example, the one or more additives are present in an amount 10 times greater by weight than the one or more silica precursors, one or more catalysts, one or more pore-forming gas forming additives (based on the total weight of the one or more silica precursors, one or more catalysts, one or more pore-forming gas forming additives). Statement 17. The method of any one of the preceding statements, wherein the ratio of one or more ceramic precursors (e.g., one or more silica precursors):one or more pore forming gas forming additives:one or more catalysts:one or more additives is 5:1:1:50. In various embodiments, one or more of these values ​​are within 10% or 20% of each other. Statement 18. The method of any one of the preceding statements, wherein the contacting is carried out at a temperature between room temperature (e.g., 18-23° C.) and 70° C., and / or for a period between 1 minute and 96 hours (e.g., 1 to 24 hours (h)). Statement 19. The method of any one of the preceding statements, further comprising exchanging (e.g., removing) the solvent from the ceramic foam (e.g., silica aerogel). Statement 20. The method of any one of the preceding statements, further comprising washing the ceramic foam (e.g., silica aerogel). The washing step may be an exchange step in which undesirable materials (e.g., solvent, unreacted ceramic (e.g., silica) reaction components, etc.) are removed. In various embodiments, 90% or more, 95% or more, 99% or more, or all observable undesirable materials are removed from the film. Statement 21. 21. The method of claim 20, wherein the washing comprises contacting the ceramic foam (e.g., silica aerogel) with an aqueous solution (e.g., an alcohol-water solution). Statement 22. The method of any one of the preceding statements, wherein the method further comprises washing the ceramic foam (e.g., silica aerogel) with alcohol (e.g., ethanol) and / or drying the ceramic foam (e.g., silica aerogel). For example, the ceramic foam (e.g., silica aerogel) is heated (e.g., ceramic foam heated) to a temperature between room temperature (e.g., 18-23° C.) and 100° C. (e.g., 30-60° C.), where the treatment (or heating) may be under ambient conditions. For example, a hydrophobic coating is compatible with the ceramic foam structure (e.g., silica aerogel structure). Statement 23. The method of any one of the preceding statements, further comprising forming a layer (e.g., a film) of a hydrophobic carbon-containing material disposed on at least a portion or all of a surface of the ceramic foam (e.g., silica aerogel). In one example, the ceramic foam (e.g., silica aerogel) is contacted with a silane (e.g., a trialkylhalosilane such as trimethylchlorosilane (TMCS)), a carbon material (e.g., carbon soot), or a combination thereof. Statement 24. The method of any one of the preceding statements, comprising forming a film from the ceramic foam (e.g., silica aerogel). Statement 25. 25. The method of claim 24, wherein the film is formed on a substrate, such as where at least a portion of the ceramic foam (e.g., silica aerogel-like foam or silica aerogel) forming reaction occurs on the substrate. Non-limiting examples of substrates include paper, metal (e.g., aluminum, which may be aluminum foil, insulating paper substrates, fabric, etc.). Statement 26. 26. The method of claim 24 or 25, wherein the forming is performed in a continuous process (e.g., a continuous roll-to-roll process). Statement 27. 26. The method of claim 24 or 25, wherein forming is effected by doctor blading, drop casting, additive manufacturing (e.g., 3D printing), and / or the like. Statement 28. 26. The method of claim 24 or 25, wherein the film is formed by spray coating of the reaction mixture in a gelled (e.g., unsolidified) form, comprising one or more ceramic precursors, one or more pore-forming gas-forming additives, one or more catalysts, and optionally one or more additives. For example, the gelled form of the reaction mixture has a viscosity of 85 to 1,000 cP. Optionally, compressed air may be added to the gel to increase fluidity. Statement 29. 24. The method of any one of claims 1-23, comprising impregnating a substrate with the ceramic foam (e.g., silica aerogel-like foam or silica aerogel). The porous substrate can be immersed and incubated in the silica sol or gel solution for 1 hour to 24 hours. The composite material can then be ambient dried or low temperature thermally dried (300K to 355K) to form the impregnated substrate. Statement 30. The method of any one of the preceding statements, further comprising decorating or coating at least a portion of a surface (e.g., an exterior surface) of the ceramic foam body. Statement 31. 31. The method of claim 30, wherein the ceramic foam is decorated or coated with a substance (e.g., one or more nanoparticles, which may be metal oxide nanoparticles) (e.g., iron oxide nanoparticles, which may be magnetic nanoparticles). For example, the ceramic foam is decorated or coated using an in situ reaction by impregnating the foam with a substance (e.g., a nanoparticle precursor, which may be a metal oxide nanoparticle precursor), followed by solid state sintering at 200-1000°C (including all integer °C values ​​and ranges therebetween). Statement 32. 32. The method of claim 31, wherein the nanoparticles are formed by impregnating the ceramic foam with a nanoparticle precursor (e.g., CuCl2, FeCl3, etc., and combinations thereof), and the nanoparticles are formed by reaction of the nanoparticle precursor (e.g., heating the impregnated ceramic foam to form nanoparticles) to form a nanocomposite. Statement 33. A silica aerogel formed by the method according to any one of the preceding statements. Statement 34. A ceramic foam having (e.g., including) pores and a hierarchical pore gradient (e.g., a ceramic foam formed from a method according to any one of the preceding statements). At least some or all of the pores may be interconnected. The size of the pores (e.g., macropores) generally decreases or increases along a side moving from a first surface of the ceramic foam to a second surface opposite the first surface. The gradient may be a linear gradient. The ceramic foam may include mesopores and / or macropores. The mesopores may be mesopores as defined by IUPAC. Statement 35. 35. The ceramic foam of claim 34, wherein the ceramic foam comprises a ceramic matrix. The ceramic matrix can be formed from ceramic nanoparticles. The ceramic matrix can be mesoporous. Statement 36. 36. The ceramic foam of claim 35, wherein the ceramic foam comprises pores (e.g., macropores) having a size (e.g., at least one dimension (e.g., diameter) measured in a plane parallel to the pore axis and / or at least one dimension (e.g., height) measured in a plane perpendicular to the pore axis) of 500 microns to 1 micron (e.g., 200 microns to 1 micron, or 100 microns to 1 micron). Statement 37. 37. The ceramic foam of any one of claims 34 to 36, wherein the ceramic foam is silica aerogel-like or silica aerogel and transparent. Statement 38. 38. The ceramic foam (e.g., silica aerogel) of any one of claims 34-37, wherein the ceramic foam has one or more or all of the following characteristics: Ceramic foams (e.g., silica aerogels) are 90-99% air (e.g., at least 90%, at least 95%, or at least 98% air), have a desired porosity (<100 nm), and have a desired density (~0.003 g / cm 3 ) and has desirable thermal conductivity (typically .about.0.017 W / mK). Statement 39. The ceramic foam (e.g., silica aerogel) of any one of claims 34-38, wherein the ceramic foam (e.g., silica aerogel) comprises a layer of carbon-containing material disposed on at least a portion or all of a surface (e.g., an outer surface) of the ceramic foam, where, for example, the thickness (e.g., a dimension perpendicular to the surface of the ceramic foam) is 10 nm or less (e.g., 0.1-10 nm). Non-limiting examples of carbon-containing materials include carbon soot, alkylsilane groups, and additive (e.g., surfactant) residues (which may be produced by thermal annealing). The layer may be a continuous layer and / or a conformal layer, and / or may have a desired degree (low number) of defects (e.g., no observable defects (which may be visually observable defects)). The layer may be a molecular layer (e.g., a molecular layer of groups that may be hydrophobic groups). The layer may provide a hydrophobic outer surface. The carbon material (e.g., carbon soot) layer may be formed by combustion of a carbon source. Statement 40. 40. The ceramic foam body of any one of claims 34 to 39, further comprising nanoparticles disposed on at least a portion of a surface of the ceramic foam body. Statement 41. The ceramic foam of any one of statements 34-39, wherein the ceramic foam is a monolith, a free-standing film, or a film disposed on at least a portion or all of a substrate. In one example, the ceramic foam is a free-standing film (e.g., a sheet). In one example, the film does not include a binder (e.g., a polymeric binder). Examples of binders (e.g., polymeric binders) for ceramic foams (e.g., silica aerogel materials) are known in the art. Statement 42. 42. The ceramic film (e.g., silica aerogel) of claim 41, wherein the film has a thickness of 1 / 4 inch to 2 inches. Statement 43. 43. The ceramic foam (e.g., silica aerogel) of claim 41 or 42, wherein the film is disposed on at least a portion of a surface of a substrate (e.g., aluminum foil, insulating paper, fabric, etc.). Statement 44. 30. A ceramic foam-impregnated substrate formed by the method of any one of claims 25-29, wherein the impregnated substrate has a desired porosity (e.g., greater than 100 nm) and / or a desired conductivity (e.g., ∼0.017 W / mK, or ≤0.017 W / mK). Statement 45. 43. The ceramic foam of any one of claims 34 to 42, wherein the ceramic foam exhibits one or more or all of the following: Thermal stability (e.g., thermal stability up to at least 2000°C) Mechanical strength (e.g., mechanical strength of at least 100 MPa) · Soundproofing and acoustic insulation properties. Statement 46. A silica aerogel formed by the method of any one of statements 1-32, or a ceramic foam (e.g., silica aerogel) of any one of statements 34-45. In one example, the silica aerogel film is a free-standing film (e.g., a sheet). In one example, the film does not include a binder (e.g., a polymeric binder). Examples of binders (e.g., polymeric binders) for silica aerogel materials are known in the art. Statement 47. 29. A silica aerogel-impregnated substrate formed by the method of claim 28, wherein the impregnated substrate has a desired porosity (<100 nm) and a desired conductivity (~0.017 W / mK).

[0115] The following examples are presented to illustrate the present disclosure and are not intended to be limiting in any respect.

[0116] [Example 1] This example provides a description of the preparation and characterization of a silica aerogel material of the present disclosure.

[0117] 1 g of sodium bicarbonate was mixed with 7.08 ml of DI water and added to 4.59 ml of tetraethyl orthosilicate (TEOS) and 22.34 ml of pure ethanol. 1 ml of catalyst was also added to promote gel formation. The catalyst was a mixture of 1.457 ml of ammonium hydroxide (28%), 0.1 g of ammonium fluoride, and 4.35 ml of DI water. After 3 minutes, the gel was washed with DI water and then added to 500 ml of pure ethanol and immersed and stirred for 24 hours. After immersion, the ethanol was removed. Next, 10 ml of TMCS (98%) was dropped into the solution. Pure ethanol was also added. Continuous evolution of CO2 was observed for the next 24 hours. Finally, the gel was dried in ethanol for 24 hours in an ambient environment at 60°C to obtain the aerogel product.

[0118] [Example 2] This example provides a description of the preparation and characterization of a silica aerogel material of the present disclosure.

[0119] 3.3 g of cetyltrimethylammonium bromide (CTAB) and 33.3 g of urea were dissolved in an aqueous solution of acetic acid (1 mM, 100 mL) followed by stirring for 20 min. Then, 56.7 mL of tetraethyl orthosilicate (TEOS) was added. The solution was stirred vigorously for 30 min to form a uniform foam emulsion, which was sealed and then transferred to a preheated oven at 60 °C for reaction for 2 days. The as-prepared aerogel was washed with water and dried at room temperature. The resulting aerogel was low Density (about 0.15g / cm 3 ) and has good thermal insulation properties.

[0120] [Example 3] This example provides an illustration of the silica aerogel material of the present disclosure and its characterization.

[0121] Samples were prepared by performing the reaction on a substrate (Unifrax paper) in contact with the reaction mixture, which can be referred to as in-situ infiltration. SEM; energy dispersive X-ray spectroscopy (EDX); and thermal images were obtained (Figures 2-6).

[0122] [Example 4] This example provides a description of how to make and characterize the silica aerogel material of the present disclosure.

[0123] Trimethylchlorosilane (TMCS):(CH3)3SiCl was used for surface modification of silica gel, producing HCl as a by-product, which reacted spontaneously with sodium bicarbonate to generate pore-supported carbon dioxide in situ. The carbon dioxide formed was trapped in the wet silica gel, and the pressure in the resulting bubbles counteracted the capillary pressure, which prevented the pores from shrinking and collapsing during the ambient pressure drying step. The precursors of silica gel used were aqueous tetraethoxysilane (TEOS, Si(OC2H5)4) with sodium bicarbonate (NaHCO3), and trimethylchlorosilane (used for surface modification).

[0124] Low-cost production of aerogel insulation materials is expected with in situ APD and R2R fabrication. Well-formulated gels may be R2R deposited onto inorganic paper substrate carriers. Central to the production of aerogel materials using R2R fabrication is the formation of a gel precursor that is robust to printing. The rheological behavior of silica gel plays an important role for continuous deposition in the R2R process, which requires non-Newtonian liquids with shear-thinning behavior. The Weber number (We) and Ohnesorge (Oh) number (or reciprocal Z) were used to predict whether a stable deposition would be achieved:

number

[0125] The pore distribution of silica aerogels was investigated using nitrogen physisorption with fitting by the Brunauer-Emmett-Teller technique. The N2 adsorption-desorption isotherms of silica aerogels showed the presence of hierarchical pores and a relatively sharp pore distribution (major pore size <60 nm).

[0126] Mechanical properties are important for constructing silica aerogels. Honeycomb aerogel structures were fabricated to study the stress-strain curve. As can be seen from the following equation, the compressive strength σ * is the total density of the sample, ρ * is strongly influenced by.

number

[0127] Thermal insulation performance is an evaluation criterion for silica aerogel. The thermal insulation ability of 3D fabricated silica aerogel was investigated. Thermography analysis showed that silica aerogel could act as a thermal insulator. The thermal insulation property of silica aerogel depends on its thickness. The effective thermal conductivity can be calculated according to the effective medium percolation theory.

number

[0128] SEM and additional test data are shown in Figures 7-22.

[0129] [Example 5] This example provides a description of the preparation and characterization of a ceramic foam material of the present disclosure.

[0130] Pore-gradient silica aerogel-like foam monoliths (PGAeros) with controlled hierarchical hollow structure and gradient pore size were designed and synthesized by hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of acetic acid, urea, and cetrimonium bromide (CTAB). In situ foam formation from thermal decomposition of CTAB micellar network and urea induces the formation of hierarchical pores and pore gradient in PGAeros, respectively. The as-synthesized silica insulation material exhibits excellent thermal insulation, sound insulation, and fire resistance performance with thermal conductivity as low as 0.040 W / mK, and mechanical integrity with compressive strength of 100.56 MPa, which allows further shaping and customization for desired shapes and structures. The acoustic performance is also tested under different frequencies, showing better sound insulation properties (sound reduction of 28.3% or 22.3db at frequency 2000Hz / thickness 15mm) than the reference insulation foam.

[0131] Results and Discussion The scheme in Fig. 23a shows the formation of hierarchical hollow structured silica PGAeros achieved by a facile one-pot synthesis. Surfactant CTAB is used to form micelles in a mixed solution of TEOS and water. Hydrolysis of TEOS proceeds on the shell of the as-formed micelles, which acts as a template to guide the formation of silica shells. The addition of urea promotes the polymerization of silicon alkoxides by increasing the pH of the solution, while it can act as an in-situ foaming agent due to its thermohydrolysis to ammonia (NH3) and carbon dioxide (CO2). The as-formed silica PGAeros floats on the water surface due to its low mass density. The continuous decomposition of urea and the subsequent release of in-situ carbon dioxide and ammonia bubbles leads to high pressure at the top of the reaction chamber, which leads to a top-to-bottom foaming process resulting in a pore gradient in the PGAeros. Fig. 23b shows a typical photograph of the as-formed opaque silica PGAeros, which can be cut and polished into desired shapes for further study (as shown in Fig. 23c). The pore gradient can be easily observed from the scanning electron microscope (SEM) image (Figure 23d), which shows an increase in the average pore size from top to bottom, where the pore dimensions depend on the reaction conditions such as chemical concentration, reaction temperature, and time (which are discussed in the following sections). The average pore size of the PGAeros from the bottom to the top region was calculated, which showed an increase from 33.3 μm to 174.8 μm (inset of Figure 23d) with a ratio of TEOS:CTAB:urea=27.8:1:60.7. High-resolution SEM images of the PGAeros in the large and small pore regions are shown in Figures 23e and f, respectively. Moreover, the as-synthesized silica PGAeros showed a porosity of 94.1% and a porosity of 0.128 g / cm by pycnometer. 3The solid network of PGAero was constructed by nanoscale silica particles, which was further characterized by transmission electron microscopy (TEM). As shown in Figure 23g and h, numerous micropores were clearly observed in each particle, probably due to the templating effect of CTAB molecules. Therefore, due to the hierarchical hollow structure with gradient macroscale pores and mesopores inside the silica network, silica PGAero with high porosity and low density was obtained, and the as-synthesized silica PGAero with limited gas thermal conductivity and high phonon scattering can be expected to result in high insulation performance.

[0132] In order to understand and control the pore gradient formation in PGAeros, a series of experiments was designed to synthesize PGAeros with shorter reaction times of 24 h, 48 h, and 72 h (named PGAero-2, PGAero-3, and PGAero-4, respectively). Compared with the initial sample with pore gradient (called PGAero-1), synthesized by 96 h reaction time, the silica PGAeros with 24 h has a uniform pore size of 27.5 μm and a standard deviation of 9.4 μm (Figure 27a, b). With the increase of reaction time to 48 h, the gradient pores of PGAeros are gradually formed, resulting in a larger pore deviation, as shown in Figure 24a. With the increase of reaction time to 72 h, the pore size of PGAeros shows a wide range from 15 μm to 300 μm, with a much larger deviation of 85.3 μm (Figure 24b). The porosity of the silica PGAeros remained at about 80% and decreased slightly by increasing the reaction time due to the continuous growth of silica (Figure 28). The porosity gradient and the decrease in porosity with the increase in pore size show competing effects on the thermal insulation performance. The decrease in porosity of the synthesized silica PGAeros (from 24 to 48 h) mainly leads to an increase in thermal conductivity from 0.049 W / mK to 0.060 W / mK. On the other hand, the porosity gradient with the increased pore size dominates the insulation performance, leading to a lower thermal conductivity of 0.054 W / mK. Further increase in the reaction time leads to the formation of silica PGAeros with the lowest thermal conductivity of 0.040 W / mK (Figure 24c).

[0133] The average pore size and porosity were investigated by adjusting the reaction conditions and their correlation with the thermal conductivity of the PGAeros (Figure 29). Typical SEM cross-sectional images of silica PGAeros are shown in Figure 25a-f. The average pore size of each sample was calculated by counting more than 100 pores through the SEM images, as shown in Figure 30a-g. Increasing the concentration of TEOS from 1.4 mol / L (average pore size 138.3 μm, porosity 94.1%) for the PGAero-1 sample to 2.1 mol / L and 2.8 mol / L corresponding to PGAero-5 and PGAero-6 resulted in average pore sizes of 85.0 μm and 68.4 μm and porosities of 89% and 88% (Figure 25a-c). Increasing the TEOS concentration reduces the average pore size and porosity, resulting in densified silica PGAeros, which results in higher thermal conductivity from 0.040 W / mK to 0.049 W / mK (PGAero-5) and 0.055 W / mK (PGAero-6). The increase in thermal conductivity is mainly due to increased solid-state heat transport through the high component silica network. The concentration of CTAB primarily determines the pore size of the silica PGAeros, where less CTAB content results in smaller average pore size of the PGAeros (PGAero-7), by comparing Figures 25a and 25d. The urea addition acts as a mineralization chemical and in situ cell blowing agent, therefore increasing the urea addition can result in larger pore size and lower mass density. As shown in Figures 25f and 25g, the pore size of the as-formed silica PGAeros is significantly increased from 38.65 μm to 110.39 μm when changing urea from 1.5 mol / L (PGAero-8) to 4.5 mol / L (PGAero-9). The thermal insulation performance is highly correlated with the pore size and porosity of the silica PGAeros. Figure 25g shows the thermal conductivity of different silica PGAeros depending on the pore size and porosity. The larger the pore size and the higher the porosity, the lower the thermal conductivity of the PGAeros. The lowest thermal conductivity of 0.040 W / mK can be achieved by the silica PGAeros synthesized by TEOS:CTAB:urea=27.8:1:60.7.

[0134] The mechanical stability of silica aerogels is key to their large-scale commercial applications. Gradient pore structure has been reported to have great advantages in optimizing mechanical performance. The silica PGAeros with pore gradients synthesized as monolithic forms have high mechanical strength, which was characterized by uniaxial compression tests (Figure 31). The stress-strain curves of silica PGAero-1 show high mechanical strength with a high Young's modulus of 81.33 MPa, which can be further increased to 100.56 MPa by post-annealing treatment at 400 °C·2 h (Figures 26a and 32a-c). The inset in Figure 26a shows SEM images of silica PGAeros before (top) and after (bottom) annealing, and the robust pore structure endows silica PGAeros with good mechanical integrity. Silica PGAeros before and after annealing have thermal conductivities of 0.040 W / mK and 0.044 W / mK, respectively. The annealing treatment improves the mechanical properties without compromising the insulating performance. Importantly, the mechanically robust foam can maintain a low thermal conductivity of 0.060 W / mK after long-term annealing at 1000°C for 24 hours (Figure 33). The high degree of mechanical robustness and thermal stability makes the synthetic silica PGAero very promising for the increasing demands on insulating materials applied in extreme environments.

[0135] Acoustic insulation for soundproofing plays an important role in super insulation applications. As shown in Figure 26b, both sound waves and heat could be significantly reduced by silica PGAero with pore gradient structure. The detected acoustic intensity through no sample (blank control) and silica PGAeros as well as polystyrene standard are plotted as shown in Figure 34. In addition, some commonly used commercial soundproofing materials such as polyurethane, Kevlar and two kinds of ceramic fiber blankets are plotted. Silica PGAero shows low detected acoustic intensity over the entire frequency range (500Hz-1800Hz), which shows much better soundproofing performance compared to all commonly used commercial soundproofing materials shown in Figure 26c. Silica PGAeros with a thickness of 0.014m has better soundproofing performance at different frequencies of 500Hz, 800Hz and 2000Hz, showing 10.9%, 12.0% and 28.4% noise reduction respectively compared to standard PS foam (Figures 26e, 35a,b). Especially under a sound frequency of 2000 Hz (Fig. 26d). To calibrate the thickness-independent sound insulation performance, the sound insulation coefficient was defined by dividing the noise reduction by the sample thickness. The sound insulation coefficients of the silica PGAeros are 2.7, 2.0, and 18.2 times higher than that of the standard sample at 500 Hz, 800 Hz, and 2000 Hz, respectively. In addition to the mechanical and acoustic sound insulation properties, the moisture absorption performance of the silica PGAeros was investigated under humid environment. Two PGAeros with initial thermal conductivities of 0.045 W / mK and 0.052 W / mK were selected for the humidity experiments under 60% and 80% humidity, respectively. The high humidity condition leads to an increase in the thermal conductivity, which can be recovered after drying at 60 °C (Fig. 36). The cycle experiments showed that the thermal conductivity of the PGAeros can return to the initial point with a loss of less than 16%.

[0136] We have developed lightweight silica PGAeros with desirable porosity and desirable pore gradient for thermal and acoustic super insulation. The micelle-mediated growth of silica and gas foaming process by thermal hydrolysis of urea together result in pore generation and gradient formation. The well-designed monolithic shape with unique pore structure and ceramic properties provide such PGAeros with excellent thermal insulation and fire resistance performance over a wide temperature range (thermal conductivity as low as 0.040 W / mK and high mechanical integrity with compressive strength of 100.56 MPa). Such silica PGAeros also exhibit better sound insulation properties under various frequencies, with a sound reduction of 28.3% or 22.3 db at a thickness of 15 mm at a frequency of 2,000 Hz (higher than standard insulation foam). The stability under humid environment has also proven reliable for a long time. Materials with high thermal insulation and sound insulation performance while maintaining thermal conductivity are expected to be suitable for next-generation construction materials and other applications.

[0137] Materials and Experiments Experimental: Preparation: 3 mol / L urea (Sigma-Aldrich), 0.3 mol / L CTAB (VWR), 1 mmol acetic acid (EMD Millipore Corporation) were added and dissolved in distilled water, brought to 100 mL in a beaker, and stirred for 3 hours until all became clear liquid. Then, 1.4 mol / L TEOS (Sigma-Aldrich) was added to the solution. Stirring was continued for 10 minutes, and the solution turned into a homogeneous translucent. The solution was then transferred to a plastic bottle and the container was tightly sealed. The container was then placed in a preheated oven at 60°C for 4 days. After this gelation treatment, the sample was removed from the container and transferred to distilled water preheated at 60°C for 2 days. During this washing process, the water was replaced several times until the supernatant water became clear and all ammonia was removed. Immediately after the washing process was completed, the sample was placed in a preheated oven at 60°C for 2 days for drying purposes.

[0138] Characterization: The thermal conductivity measurement platform is customized according to the ASTM C518 standard thermal conductivity procedure. Heat flux sensors purchased from Fluxtaq and calibrated with standard polystyrene commercial insulation are used.

[0139] Acoustic testing, a customized sound box for home use (with sound insulation material) and an acoustic detector purchased from Kasuntest. Samples of different thicknesses are tested under different frequencies generated by the sound source.

[0140] Pycnometer testing uses helium gas to infiltrate a porous sample in a chamber to obtain the volume of the solid portion of the sample. If the solid portion of the sample is known, the porosity of a silica foam sample can be calculated.

[0141] Mechanical Testing: Both the pristine silica foam samples and the 400° C. thermally synthesized bulk samples were compression tested under different loads and multiple cycle times.

[0142] The humidity aging cycle test measures the thermal conductivity of the samples by exposing them to different humidity environments for 24 hours, drying them in a preheated oven for an additional 24 hours, and repeating the cycle.

[0143] [Example 6] This example provides a description of the preparation and characterization of a ceramic foam material of the present disclosure.

[0144] Testing Method: 3 mol / L urea (Sigma-Aldrich), 0.3 mol / L CTAB (cetyltrimethylammonium bromide) (VWR) / SDS (sodium dodecyl sulfate) (Sigma-Aldrich), 1 mmol acetic acid (EMD Millipore Corporation) were added and dissolved in distilled water, made up to 100 mL in a beaker, and stirred for 3 hours until the solution was completely clear. Then, 1.4 mol / L TEOS (Sigma-Aldrich) was added to the solution. Stirring was continued for 10 minutes, and the solution turned homogeneous and translucent. The solution was then transferred to an aluminum container and the container was tightly sealed. The container was then placed in an oven preheated to 60° C. for 4 days. After this gelation process, the sample (monolith and gel) was removed from the container and transferred to a container filled with distilled water preheated to 60° C. for 2 days. During this washing process, the water was changed several times until the supernatant water was clear and all ammonia was removed. The sample (gel) was then stored in a sealed container for further applications.

[0145] Figure 37 shows a schematic of the ceramic foam manufacturing process. Figures 38-41 show various features of the example ceramic foam produced in this example.

[0146] Although the present disclosure has been described with reference to one or more particular embodiments and / or examples, it will be understood that other embodiments and / or examples of the present disclosure may be made without departing from the scope of the present disclosure.

Claims

1. A method for producing a ceramic aerogel, comprising the steps of: Ceramic precursors; a pore-forming gas-forming additive selected from urea and a combination of sodium bicarbonate and urea; A catalyst; and Surfactants contacting the the contacting results in the formation of an inert gas and a ceramic aerogel; The method, wherein the ceramic aerogel has a pore gradient structure in which the pores decrease or increase in size along a direction moving from a first surface of the ceramic aerogel to a second surface opposite the first surface.

2. 10. The method of claim 1, wherein the ceramic precursor is selected from a silica precursor, an alumina precursor, a transition metal oxide precursor, and combinations thereof.

3. the silica precursor is selected from tetraalkoxysilanes, alkyltrialkoxysilanes, sodium metasilicate, and combinations thereof; the alumina precursor is selected from aluminum alkoxides, alumatoranes, tris(alumatranyloxy-i-propyl)amines, and combinations thereof; and / or The transition metal oxide precursor is selected from transition metal alkoxides; The method of claim 2.

4. 3. The method of claim 2, wherein the silica precursor is selected from tetramethyl orthosilicate, tetraethyl orthosilicate, methyltrimethoxysilane, sodium silicate, and combinations thereof.

5. 4. The method of claim 3, wherein the transition metal oxide precursor is selected from transition metal alkoxides having the formula M(OR)x, where M is a transition metal selected from Al, Ti, Zr, W, Cr, and Mo, R is alkyl, and x is selected from 1, 2, 3, 4, or 5.

6. 10. The method of claim 1, wherein the catalyst is a base catalyst selected from ammonia, ammonium fluoride, ammonium hydroxide, and combinations thereof.

7. 10. The method of claim 1, wherein the catalyst is an acid catalyst selected from a protonic acid, a hydrohalic acid, and combinations thereof.

8. The process of claim 1 , wherein the catalyst is acetic acid.

9. 2. The method of claim 1, wherein the surfactant is selected from cetyltrimethylammonium bromide and sodium dodecyl sulfate.

10. contacting the ceramic precursor, the pore forming gas forming additive, and the surfactant; and then contacting the catalyst with the ceramic precursor, the pore forming gas forming additive, and the surfactant; wherein the contact is the ceramic precursor, optionally disposed in a solvent; the pore-forming gas-forming additive, which may be disposed in water; and The catalyst may be disposed in water. or wherein the contacting is carried out at a temperature between room temperature and 70° C. and / or for a period between 1 minute and 96 hours; The method of claim 1.

11. the ceramic precursor is present at 2 to 10 weight percent, based on the total weight of the ceramic precursor, the catalyst, the pore forming gas forming additive, and the surfactant; the pore-forming gas forming additive is present at 0.4 to 2 weight percent, based on the total weight of the ceramic precursor, the catalyst, the pore-forming gas forming additive, and the surfactant; the catalyst is present at 1 to 2 wt. %, based on the total weight of the ceramic precursor, the catalyst, the pore forming gas forming additive, and the surfactant; the surfactant is present at 200 to 1000 wt. %, based on the total weight of the ceramic precursor, the catalyst, and the pore-forming gas-forming additive; or the ratio of said ceramic precursor: said pore forming gas forming additive: said catalyst: said surfactant is 5:1:1:50; The method of claim 1.

12. moreover, Removing the solvent from the ceramic aerogel; Washing the ceramic aerogel; and Drying the ceramic aerogel The method of claim 1 , comprising:

13. The method of claim 12 , wherein washing comprises contacting the ceramic aerogel with an aqueous solution.

14. moreover, forming a layer of a hydrophobic carbon-containing material disposed on at least a portion of a surface of the ceramic aerogel; forming a film from the ceramic aerogel, optionally wherein the film is formed on a substrate, wherein the forming is a continuous process, wherein the forming is performed by doctor blading, drop casting, or additive manufacturing, or wherein the film is formed by spray coating a gelled form of a reaction mixture comprising the ceramic precursor, the pore forming gas forming additive, the catalyst, and the surfactant; impregnating a substrate with the ceramic aerogel; or decorating or coating at least a portion of a surface of the ceramic aerogel, wherein the ceramic aerogel is decorated or coated with a substance, wherein the substance is a nanoparticle, wherein the nanoparticle is formed by impregnating the ceramic aerogel with a nanoparticle precursor to form a nanocomposite; The method of claim 1 , comprising:

15. A ceramic aerogel comprising a ceramic matrix and pores formed by the method of any one of claims 1 to 14, At least a portion of the pores are interconnected; A ceramic aerogel having a pore gradient structure in which the pores decrease or increase in size along a direction moving from a first surface of the ceramic aerogel to a second surface opposite the first surface.

16. Ceramic aerogel is a silica aerogel and is transparent.

16. The ceramic aerogel of claim 15.

17. 16. The ceramic aerogel of claim 15, wherein the pores have a size between 500 microns and 1 micron.

18. The ceramic aerogel is 90-99% air; The ceramic aerogel has an average pore size of less than 100 nm; Ceramic aerogel is about 0.003 g / cm 3 or The ceramic aerogel has a thermal conductivity of about 0.017 W / mK.

16. The ceramic aerogel of claim 15.

19. 16. The ceramic aerogel of claim 15, wherein the ceramic aerogel comprises a layer of a hydrophobic carbon-containing material disposed on at least a portion of a surface of the ceramic aerogel.

20. 16. The ceramic aerogel of claim 15, wherein the ceramic aerogel further comprises nanoparticles disposed on at least a portion of a surface of the ceramic aerogel.

21. The ceramic aerogel is a monolith, a free-standing film, or a film disposed on at least a portion of a substrate, wherein: the film has a thickness of ¼ inch (0.635 cm) to 2 inches (5.08 cm); or the film is disposed over at least a portion of a surface of a substrate; 16. The ceramic aerogel of claim 15.

22. Ceramic aerogel is A compressive strength of at least 100 MPa; or Soundproofing / acoustic insulation properties; 16. The ceramic aerogel of claim 15,

Images