High-temperature-resistant Al2O3-SiO2 aerogel and preparation method thereof

Abstract

This invention belongs to the field of thermal insulation materials technology and discloses a high-temperature resistant Al2O3-SiO2 aerogel and its preparation method. The nanoporous network framework unit of this aerogel is mainly composed of large-particle-size α-Al2O3 stable phase particles, surrounded by a nano-SiO2 insulating layer. This solves the problem of the transformation of alumina aerogel from an unstable transition phase to the α-Al2O3 stable phase at high temperatures, and the insulating layer inhibits the high-temperature sintering and growth tendency of the aerogel particles. The preparation method includes the following steps: using an aqueous α-Al2O3 monodisperse as the aluminum source, mixing and stirring with a silicon source and catalyst, and preparing the aerogel through sol preparation, gel-displacement, and supercritical drying. The obtained Al2O3-SiO2 aerogel has the advantages of high temperature resistance, low thermal conductivity, simple preparation method, and low cost, and can be used in high-temperature thermal insulation and catalysis fields such as aerospace, petrochemical, and industrial kilns.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation materials technology, and particularly relates to a high-temperature resistant Al2O3-SiO2 aerogel and its preparation method. Background Technology

[0002] Compared to silica (SiO2) aerogel, alumina (Al2O3) aerogel has a temperature resistance of up to 1000℃, making it a promising material for thermal insulation and catalyst support in aerospace, petrochemical, and high-temperature catalysis. However, when used above 1000℃, pure Al2O3 aerogel undergoes a transformation from unstable transition phases such as γ, δ, and θ to the stable α-Al2O3 phase, leading to aerogel sintering and a decrease in specific surface area.

[0003] Studies have shown that the temperature resistance of alumina aerogels can be improved by controlling the morphology of the alumina aerogel network framework (rod-like, sheet-like, etc.). For example, Peng et al. prepared nanorod-shaped alumina aerogels based on hydrothermal boehmite sol, and then obtained nanorod-shaped alumina aerogels through sol-gel and supercritical drying. After heat treatment at 1300 °C for 2 h, the aerogels still maintained a high specific surface area (95 m²). 2 The α-Al₂O₃ phase transition temperature was significantly delayed, exhibiting excellent thermal stability. Pakharukova et al., using aluminum isopropoxide as a precursor, prepared a two-dimensional sheet-like Al₂O₃-SiO₂ aerogel, delaying the γ-Al₂O₃ to α-Al₂O₃ transition temperature (1100°C) to 1200°C, while still retaining a 64m... 2 The specific surface area is 82.5 μm / g. Furthermore, introducing heterogeneous elements can also improve temperature resistance. For example, Tokudome et al. prepared lanthanum-doped alumina aerogel using aluminum chloride and lanthanum chloride as precursors via a sol-gel method. After heat treatment at 1100°C for 24 h, it still retained 82.5 μm of specific surface area. 2 The specific surface area was 166 m² / g. Zu et al. prepared Al₂O₃-SiO₂ aerogel via acetic acid-aniline in-situ water formation, supercritical fluid modification, and hexamethyldisilazane gas-phase modification. After heat treatment at 1200°C for 2 h, the specific surface area remained at 166 m² / g. 2 / g.

[0004] It is evident that most existing methods for preparing high-temperature resistant alumina aerogels are based on organic aluminum (aluminum isopropoxide, aluminum sec-butoxide, etc.) or inorganic aluminum sources (aluminum chloride, aluminum nitrate, etc.) as raw materials. These materials are processed (e.g., hydrothermal treatment, introduction of heterogeneous elements, etc.) to obtain a sol, which is then dried under normal pressure or supercritical pressure to obtain alumina aerogels with boehmite phase as the main component. These methods significantly improve the temperature resistance of alumina aerogels and delay the transformation of aerogels from unstable transition phases such as γ, δ, and θ to the stable α-Al2O3 phase.

[0005] However, existing alumina aerogel network frameworks still experience some degree of particle sintering and pore structure collapse at temperatures exceeding 1200℃. This is because, during the preparation of existing alumina aerogels, the nanoporous network framework units are still mainly composed of boehmite phase. During heating (approximately 600℃-800℃), the boehmite phase gradually transforms into γ-Al₂O₃. With further increases in temperature, γ-Al₂O₃ continues to transform into unstable δ and θ phases until it finally transforms into the stable α-Al₂O₃ phase. Therefore, existing alumina aerogels inevitably undergo phase transformations from unstable transition phases (γ, δ, θ, etc.) to the stable α-Al₂O₃ phase when heated, limiting their applications in high-temperature insulation and catalysis. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a high-temperature resistant Al2O3-SiO2 aerogel and its preparation method that can avoid the transformation of alumina aerogel from an unstable transition phase (γ, δ, θ, etc.) to the α-Al2O3 stable phase at high temperatures.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0008] A high-temperature resistant Al2O3-SiO2 aerogel has a three-dimensional nanoporous network framework structure. The unit of the framework structure is composed of α-Al2O3 stable phase particles. The α-Al2O3 stable phase particles are surrounded by a nano-SiO2 isolation layer with a thickness of 2nm~10nm.

[0009] Furthermore, in the aforementioned high-temperature resistant Al2O3-SiO2 aerogel, the average particle size of the α-Al2O3 stable phase particles is 130nm~210nm.

[0010] Furthermore, the high-temperature resistant Al2O3-SiO2 aerogel has a room-temperature thermal conductivity of 0.040~0.050 W / (m·K) and a specific surface area of ​​10 m² after furnace heat treatment at 1500℃ for 7200 s. 2 / g~25m 2 / g.

[0011] Furthermore, after the high-temperature resistant Al2O3-SiO2 aerogel is heat-treated at 1500℃ for 7200s, its microstructure maintains a nanoporous network structure, exhibiting only the α-Al2O3 stable phase (α) and the mullite phase (m).

[0012] Based on a general inventive concept, the present invention also provides a method for preparing high-temperature resistant Al2O3-SiO2 aerogel, comprising the following steps:

[0013] (1) The aluminum source, silicon source and catalyst are mixed in a volume ratio of 1:(0.05~0.3):(0.005~0.015), and the mixture is stirred to obtain Al2O3-SiO2 sol;

[0014] (2) The Al2O3-SiO2 sol was allowed to stand at 45℃~65℃ to gel, and then the water in the wet gel was replaced with anhydrous ethanol to obtain Al2O3-SiO2 gel.

[0015] (3) The Al2O3-SiO2 gel is subjected to supercritical drying to obtain the high-temperature resistant Al2O3-SiO2 aerogel.

[0016] The above-mentioned method for preparing high-temperature resistant Al2O3-SiO2 aerogel further includes the following steps (1): the mixing and stirring process is as follows: first, add the silicon source to the aluminum source and stir for 30 min to 60 min to allow the silicon source to hydrolyze; then add the catalyst and stir for 20 min to 40 min; and control the temperature at 25℃ to 45℃ during the mixing and stirring process.

[0017] Further, in step (1), the aluminum source is an aqueous α-Al2O3 monodisperse solution, the solid content of the aqueous α-Al2O3 monodisperse solution is 3wt%~20wt%, the average particle size of the α-Al2O3 is 130nm~210nm, and water is the solvent; the silicon source is selected from one or more of tetraethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, and dimethyldiethoxysilane; the catalyst is ammonia water with a concentration of 0.01mol / L~0.05mol / L.

[0018] Furthermore, in step (2), the standing time is 12h~24h, and the volume ratio of anhydrous ethanol to wet gel is (2~4):1.

[0019] Furthermore, in step (2), the temperature of the replacement is 40℃~50℃, and the replacement is performed once every 12 hours, for a total of 3 to 6 replacements.

[0020] Furthermore, in step (3), the supercritical drying is carried out in a high-pressure reactor. The specific process is as follows: the temperature is increased to 245℃~255℃ at a rate of 3℃ / min~5℃ / min. After the drying pressure reaches 6MPa~10MPa, no additional pressure is required. The ethanol gas in the high-pressure reactor is released directly at a rate of 3MPa / h~6MPa / h until the pressure in the high-pressure reactor drops to atmospheric pressure. After cooling, the high-temperature resistant Al2O3-SiO2 aerogel is obtained.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The Al2O3-SiO2 aerogel prepared by this invention has high temperature resistance: The aerogel framework unit prepared by this invention is composed of large-diameter α-Al2O3 particles, and the particles are surrounded by a layer of nano-SiO2 isolation layer. Since the aerogel framework particles are already α-Al2O3 stable phase ( Figure 4 , Figure 6 This completely solves the problem of phase transformation from unstable transition phases (γ, δ, θ, etc.) to the stable α-Al₂O₃ phase in existing alumina aerogels; the α-Al₂O₃ particles in the aerogel have a larger average diameter (130~210nm), and their resistance to sintering at high temperatures is much higher than that of traditional alumina aerogel particles (average diameter approximately 20nm~70nm); the SiO₂ nanolayer on the surface of the α-Al₂O₃ particles in the aerogel ( Figure 4 On the one hand, it isolates the direct contact between α-Al2O3 particles, significantly reducing the ability of α-Al2O3 particles to sinter due to direct contact. On the other hand, when heated at high temperatures, the SiO2 nanolayer will also react with α-Al2O3, forming a mullite stable phase in situ between the α-Al2O3 particles. Figure 6 Because mullite is very stable, this further inhibits the high-temperature sintering and growth trend of α-Al₂O₃ particles in the aerogel, thus giving the Al₂O₃-SiO₂ aerogel prepared in this invention excellent high-temperature resistance. Even after heat treatment at 1500℃ for 7200s, its specific surface area still remains at 10 m². 2 / g~25m 2 / g.

[0023] (2) The Al2O3-SiO2 aerogel prepared by the present invention has low thermal conductivity: In the Al2O3-SiO2 aerogel prepared by the present invention, the SiO2 nanolayers are coated around the α-Al2O3 particles to form an isolation layer ( Figure 4 Since the thermal conductivity of SiO2 is significantly lower than that of Al2O3, the problem of high solid heat transfer caused by direct contact between α-Al2O3 particles is cleverly solved, resulting in a very low thermal conductivity of Al2O3-SiO2 aerogel obtained in this invention (0.040 W / (m·K~0.050 W / (m·K)).

[0024] (3) The preparation method of the present invention is simple and low in cost: the material of the present invention uses an aqueous α-Al2O3 monodisperse solution as the aluminum source, and the raw material cost is low; the preparation process only includes three steps: sol preparation, gel-displacement, and supercritical drying. The preparation method is very simple, the manufacturing cycle is short, and it is easy to scale up production.

[0025] Therefore, the Al2O3-SiO2 aerogel provided by this invention has the advantages of high temperature resistance, low thermal conductivity, simple preparation process, and low cost. It is also easy to scale up production and can be applied to high-temperature insulation and catalysis fields such as aerospace, petrochemical, and industrial kilns, with a wide range of applications. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the overall process for preparing the high-temperature resistant Al2O3-SiO2 aerogel of the present invention;

[0028] Figure 2 This describes the typical macroscopic morphology of the Al2O3-SiO2 aerogel prepared in Example 1 of this invention;

[0029] Figure 3 This is a typical scanning electron microscope (SEM) morphology of the Al2O3-SiO2 aerogel prepared in Example 1 of this invention.

[0030] Figure 4 This is a typical transmission electron microscopy (TEM) morphology of the Al2O3-SiO2 aerogel prepared in Example 1 of this invention.

[0031] Figure 5 The typical scanning electron microscope morphology of the Al2O3-SiO2 aerogel prepared in Example 1 of the present invention after heat treatment in a muffle furnace at 1500℃ for 7200s.

[0032] Figure 6 The XRD patterns of the Al2O3-SiO2 aerogel prepared in Example 1 of this invention after heat treatment in a muffle furnace at different temperatures for 7200 s are shown. Detailed Implementation

[0033] The present invention discloses a method for preparing high-temperature resistant Al2O3-SiO2 aerogel, comprising the following steps:

[0034] The first step is to prepare the sol, the method is as follows:

[0035] Commercially available aluminum source, silicon source, and catalyst are mixed in a volume ratio of 1:(0.05~0.3):(0.005~0.015) according to a certain order of addition. After stirring at a certain temperature for a period of time, Al2O3-SiO2 sol is obtained.

[0036] The aluminum source is an aqueous α-Al₂O₃ monodisperse solution with a solid content of 3wt%~20wt% and an average particle size of 130nm~210nm, using water as the solvent; the silicon source is one or a mixture of any two of tetraethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, and dimethyldiethoxysilane; the catalyst is ammonia water with a molar concentration of 0.01mol / L~0.05mol / L; the feeding sequence, mixing temperature, and stirring time are as follows: first, the silicon source is added to the aluminum source and stirred for 30min~60min to allow the silicon source to hydrolyze; then the catalyst is added and stirred for 20min~40min, with the temperature controlled at 25℃~45℃ during mixing and stirring.

[0037] The second step, gel-displacement, is as follows:

[0038] The Al2O3-SiO2 sol obtained in the first step is allowed to stand at a certain temperature (45℃~65℃) for 12h~24h to gel. Then, it is replaced with anhydrous ethanol to replace the water in the wet gel with ethanol. The volume ratio of ethanol to wet gel is 2~4:1, the replacement temperature is 40℃~50℃, and replacement is performed once every 12h for a total of 3~6 times to obtain Al2O3-SiO2 gel.

[0039] The third step is supercritical drying, the method of which is:

[0040] The Al2O3-SiO2 gel obtained in the second step was placed in a sealed autoclave. The heating rate of the autoclave was controlled at 3℃ / min to 5℃ / min, so that the temperature inside the autoclave rose to 245℃ to 255℃. After the drying pressure reached 6MPa to 10MPa, no additional pressure holding was required. The ethanol gas inside the autoclave was directly and rapidly depressurized and released. The depressurization rate was controlled at 3MPa / h to 6MPa / h until the pressure inside the autoclave dropped to atmospheric pressure and the temperature dropped to room temperature. The gel was then removed to obtain the Al2O3-SiO2 aerogel.

[0041] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0042] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0043] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0044] Example 1

[0045] A method for preparing high-temperature resistant Al2O3-SiO2 aerogel, the process flow is as follows: Figure 1 As shown, it includes the following steps:

[0046] (1) Sol preparation

[0047] Commercially available aluminum source, silicon source, and catalyst were mixed in a volume ratio of 1:0.1:0.0075 according to a specific order of addition. After stirring at a certain temperature for a period of time, Al2O3-SiO2 sol was obtained. The aluminum source was an aqueous α-Al2O3 monodisperse solution with a solid content of 10wt% and an average particle size of 145nm, using water as the solvent; the silicon source was methyltrimethoxysilane; and the catalyst was ammonia water with a molar concentration of 0.02mol / L. The order of addition, mixing temperature, and stirring time were as follows: first, the silicon source was added to the aluminum source and stirred for 55 minutes to allow the silicon source to hydrolyze; then the catalyst was added and stirred for 28 minutes. The temperature was controlled at 35℃ during the mixing and stirring process.

[0048] (2) Gel-displacement

[0049] After the Al2O3-SiO2 sol was allowed to stand at 50℃ for 20 hours to gel, it was then replaced with anhydrous ethanol to replace the water in the wet gel. The volume ratio of ethanol to wet gel was 2:1, the replacement temperature was 45℃, and replacement was performed once every 12 hours for a total of 4 times to obtain the Al2O3-SiO2 gel.

[0050] (3) Supercritical drying

[0051] The Al2O3-SiO2 gel was placed in a sealed autoclave, and the heating rate of the autoclave was controlled at 4℃ / min, so that the temperature inside the autoclave rose to 250℃. After the drying pressure reached 8MPa, the pressure was released to release the ethanol gas inside the autoclave. The pressure release rate was controlled at 4MPa / h until the pressure inside the autoclave dropped to atmospheric pressure and the temperature dropped to room temperature. The gel was then removed to obtain the Al2O3-SiO2 aerogel.

[0052] The Al2O3-SiO2 aerogel prepared in Example 1 showed good bulking properties. Figure 2 ), exhibiting a typical nanoporous three-dimensional network framework structure ( Figure 3 Transmission electron microscopy images show that the aerogel consists of α-Al₂O₃ and a 3nm nano-SiO₂ insulating layer. Figure 4 Its thermal conductivity at room temperature is 0.045 W / (m·K), and its specific surface area is 54.2 m². 2 / g, after being heat-treated in a muffle furnace at 1500℃ for 7200s, still exhibits a nanoporous network structure in its microstructure. Figure 5 The aerogel still has a specific surface area of ​​17.8 m² after testing. 2 / g. XRD pattern ( Figure 6 The results show that, in addition to the diffraction peaks of the α-Al2O3 stable phase (α), a mullite phase (m) appeared after heat treatment at 1400℃, but no diffraction peaks of the unstable transition phases (γ, δ, θ, etc.) were ever observed. This indicates that the present invention avoids and solves the problem of the transformation of alumina aerogel from the unstable transition phase to the α-Al2O3 stable phase at high temperatures.

[0053] Example 2

[0054] A method for preparing high-temperature resistant Al2O3-SiO2 aerogel, the process flow is as follows: Figure 1 As shown, it includes the following steps:

[0055] (1) Sol preparation

[0056] Commercially available aluminum source, silicon source, and catalyst are mixed in a volume ratio of 1:0.05:0.005 according to a certain order of addition. After stirring at a certain temperature for a period of time, Al2O3-SiO2 sol is obtained.

[0057] The aluminum source is an aqueous α-Al₂O₃ monodisperse solution with a solid content of 5 wt% and an average particle size of 130 nm, using water as the solvent; the silicon source is a mixture of methyltrimethoxysilane and dimethyldiethoxysilane in a volume ratio of 1:1; the catalyst is ammonia water with a molar concentration of 0.01 mol / L; the order of addition, mixing temperature, and stirring time are as follows: first, the silicon source is added to the aluminum source and stirred for 30 min to allow the silicon source to hydrolyze; then the catalyst is added and stirred for 20 min. The temperature is controlled at 25℃ during the mixing, stirring, and standing process.

[0058] (2) Gel-displacement

[0059] After the Al2O3-SiO2 sol was allowed to gel at a certain temperature (45℃) for 12 hours, it was then replaced with anhydrous ethanol to replace the water in the wet gel. The volume ratio of ethanol to wet gel was 4:1, the replacement temperature was 40℃, and replacement was performed once every 12 hours for a total of 3 times to obtain the Al2O3-SiO2 gel.

[0060] (3) Supercritical drying

[0061] The Al2O3-SiO2 gel was placed in a sealed autoclave, and the heating rate of the autoclave was controlled at 3℃ / min, so that the temperature inside the autoclave rose to 245℃. After the drying pressure reached 6MPa, the pressure was released to release the ethanol gas inside the autoclave. The pressure release rate was controlled at 3MPa / h until the pressure inside the autoclave dropped to atmospheric pressure and the temperature dropped to room temperature. The gel was then removed to obtain the Al2O3-SiO2 aerogel.

[0062] The Al2O3-SiO2 aerogel prepared in Example 2 exhibits a typical nanoporous three-dimensional network framework structure. The aerogel consists of α-Al2O3 and a 2nm nano-SiO2 insulating layer; its thermal conductivity at room temperature is 0.040 W / (m·K), and its specific surface area is 67.2 m². 2 / g, after being heat-treated in a muffle furnace at 1500℃ for 7200s, still exhibits a nanoporous network structure in its microstructure, with a specific surface area of ​​20.3m². 2 / g.

[0063] Example 3

[0064] A method for preparing high-temperature resistant Al2O3-SiO2 aerogel, the process flow is as follows: Figure 1 As shown, it includes the following steps:

[0065] (1) Sol preparation

[0066] Commercially available aluminum source, silicon source, and catalyst are mixed in a volume ratio of 1:0.3:0.015 and added in a specific order. After stirring at a certain temperature for a period of time, Al2O3-SiO2 sol is obtained.

[0067] The aluminum source is an aqueous α-Al₂O₃ monodisperse solution with a solid content of 20 wt% and an average particle size of 210 nm. Water is used as the solvent. The silicon source is dimethyldiethoxysilane, and the catalyst is ammonia water with a molar concentration of 0.05 mol / L. The order of addition, mixing temperature, and stirring time are as follows: First, the silicon source is added to the aluminum source and stirred for 60 min to allow the silicon source to hydrolyze. Then, the catalyst is added and stirred for 40 min. The temperature is controlled at 40℃ during the mixing, stirring, and standing process.

[0068] (2) Gel-displacement

[0069] The Al2O3-SiO2 sol obtained in the first step was allowed to stand at a certain temperature (60℃) for 24 hours to gel. Then, it was replaced with anhydrous ethanol to replace the water in the wet gel. The volume ratio of ethanol to wet gel was 3:1, the replacement temperature was 50℃, and replacement was performed once every 12 hours for a total of 6 times to obtain Al2O3-SiO2 gel.

[0070] (3) Supercritical drying

[0071] The Al2O3-SiO2 gel obtained in the second step was placed in a sealed autoclave. The heating rate of the autoclave was controlled at 4.5℃ / min, so that the temperature inside the autoclave rose to 253℃. After the drying pressure reached 9MPa, the pressure was released to release the ethanol gas inside the autoclave. The pressure release rate was controlled at 5.6MPa / h until the pressure inside the autoclave dropped to atmospheric pressure and the temperature dropped to room temperature. The gel was then removed to obtain the Al2O3-SiO2 aerogel.

[0072] The Al2O3-SiO2 aerogel prepared in Example 3 exhibits a typical nanoporous three-dimensional network framework structure. The aerogel consists of α-Al2O3 and a 10nm nano-SiO2 insulating layer; its thermal conductivity at room temperature is 0.050 W / (m·K), and its specific surface area is 41.5 m². 2 / g, after being heat-treated in a muffle furnace at 1500℃ for 7200s, still exhibits a nanoporous network structure in its microstructure, with a specific surface area of ​​13.6m². 2 / g.

Claims

1. A high-temperature resistant Al2O3-SiO2 aerogel, characterized in that, The high-temperature resistant Al2O3-SiO2 aerogel has a three-dimensional nanoporous network framework structure. The unit of the framework is composed of α-Al2O3 stable phase particles. The α-Al2O3 stable phase particles are surrounded by a nano-SiO2 isolation layer with a thickness of 2~10nm. The average particle size of the α-Al2O3 stable phase particles is 130~210nm. The preparation method of the high-temperature resistant Al2O3-SiO2 aerogel includes the following steps: (1) An aluminum source, a silicon source, and a catalyst are mixed in a volume ratio of 1:(0.05~0.3):(0.005~0.015), and stirred to obtain an Al2O3-SiO2 sol; the aluminum source is an aqueous α-Al2O3 monodisperse solution, the solid content of the aqueous α-Al2O3 monodisperse solution is 3~20wt%, the average particle size of the α-Al2O3 particles is 130~210nm, and water is used as the solvent; the silicon source is selected from one or more of tetraethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, and dimethyldiethoxysilane; the catalyst is ammonia water with a concentration of 0.01~0.05 mol / L; (2) After the Al2O3-SiO2 sol is allowed to stand at 45~65℃ to gel, a wet gel is obtained. Then, the water in the wet gel is replaced with anhydrous ethanol to obtain Al2O3-SiO2 gel. (3) The Al2O3-SiO2 gel is subjected to supercritical drying in an autoclave. The specific process is as follows: the temperature is increased to 245-255℃ at a rate of 3-5℃ / min. After the drying pressure reaches 6-10MPa, no additional pressure is required. The ethanol gas in the autoclave is released directly at a rate of 3-6MPa / h until the pressure in the autoclave drops to atmospheric pressure. After cooling, the high-temperature resistant Al2O3-SiO2 aerogel is obtained.

2. The high-temperature resistant Al2O3-SiO2 aerogel according to claim 1, characterized in that, The high-temperature resistant Al2O3-SiO2 aerogel has a room-temperature thermal conductivity of 0.040~0.050 W / (m·K), and its specific surface area after furnace heat treatment at 1500℃ for 7200s is 10~25 m². 2 / g.

3. The high-temperature resistant Al2O3-SiO2 aerogel according to any one of claims 1 to 2, characterized in that, After being subjected to furnace heat treatment at 1500℃ for 7200s, the high-temperature resistant Al2O3-SiO2 aerogel maintains its nanoporous network structure and exhibits only the α-Al2O3 stable phase and the mullite phase.

4. A method for preparing high-temperature resistant Al2O3-SiO2 aerogel as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) An aluminum source, a silicon source, and a catalyst are mixed in a volume ratio of 1:(0.05~0.3):(0.005~0.015), and stirred to obtain an Al2O3-SiO2 sol; the aluminum source is an aqueous α-Al2O3 monodisperse solution, the solid content of the aqueous α-Al2O3 monodisperse solution is 3~20wt%, the average particle size of the α-Al2O3 particles is 130~210nm, and water is used as the solvent; the silicon source is selected from one or more of tetraethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, and dimethyldiethoxysilane; the catalyst is ammonia water with a concentration of 0.01~0.05 mol / L; (2) After the Al2O3-SiO2 sol is allowed to stand at 45~65℃ to gel, a wet gel is obtained. Then, the water in the wet gel is replaced with anhydrous ethanol to obtain Al2O3-SiO2 gel. (3) The Al2O3-SiO2 gel is subjected to supercritical drying in an autoclave. The specific process is as follows: the temperature is increased to 245-255℃ at a rate of 3-5℃ / min. After the drying pressure reaches 6-10MPa, no additional pressure is required. The ethanol gas in the autoclave is released directly at a rate of 3-6MPa / h until the pressure in the autoclave drops to atmospheric pressure. After cooling, the high-temperature resistant Al2O3-SiO2 aerogel is obtained.

5. The method for preparing high-temperature resistant Al2O3-SiO2 aerogel according to claim 4, characterized in that, In step (1), the mixing and stirring process is as follows: first, add the silicon source to the aluminum source and stir for 30~60 minutes, then add the catalyst and stir for 20~40 minutes. During the mixing and stirring process, the temperature is controlled at 25~45℃.

6. The method for preparing high-temperature resistant Al2O3-SiO2 aerogel according to claim 4, characterized in that, In step (2), the standing time is 12-24 hours, and the volume ratio of anhydrous ethanol to wet gel is (2-4):

1.

7. The method for preparing high-temperature resistant Al2O3-SiO2 aerogel according to claim 4, characterized in that, In step (2), the temperature of the replacement is 40~50℃, and the replacement is performed once every 12 hours, for a total of 3~6 times.

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