High-temperature resistant aerogel composite materials and their preparation methods

Abstract

This invention relates to the field of thermal insulation materials, and more particularly to a high-temperature resistant aerogel composite material and its preparation method. The high-temperature resistant aerogel composite material comprises the following components in parts by weight: 15-35 parts of reinforcing fiber matrix, 43-65 parts of a silicon-aluminum-zirconium ternary aerogel network, 3-12 parts of functional nanofillers, 2-8 parts of zinc borate flame-retardant component, and 0.5-2 parts of a surface hydrophobic modification layer. The reinforcing fiber matrix is ​​composed of aluminum silicate fibers, silicon carbide fibers, and alumina nanofibers; the molar ratio of silicon, aluminum, and zirconium in the silicon-aluminum-zirconium ternary aerogel network is 5:2:1; the functional nanofillers include alumina nanoparticles, titanium oxide nanoparticles, carbon nanotubes, and boron nitride nanosheets; the zinc borate flame-retardant component is zinc borate; and the surface hydrophobic modification layer includes an inner methyltrimethoxysilane modified layer and an outer hexamethyldisilazane modified layer. This invention significantly improves the high-temperature resistance and thermal shock stability of the material, employs a low-energy-consumption preparation process, and exhibits excellent comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials technology, and in particular to high-temperature resistant aerogel composite materials and their preparation methods. These materials can be used stably for a long time in high-temperature environments and have excellent thermal insulation properties, mechanical properties and environmental adaptability. They are especially suitable for high-temperature applications such as aerospace, industrial kilns, and petrochemicals. Background Technology

[0002] With the development of modern industry, the demand for high-performance thermal insulation materials is increasing. In high-temperature environments, traditional thermal insulation materials face problems such as insufficient temperature resistance, low mechanical strength, and poor environmental adaptability. Aerogel, as a novel nanoporous material, has broad application prospects in the field of high-temperature thermal insulation due to its ultra-low thermal conductivity and excellent thermal insulation performance.

[0003] Currently, existing technologies, such as CN109225079A, disclose high-temperature resistant aerogel composite materials and their preparation methods. This method includes four steps: fiber pretreatment, preparation of silica-alumina sol, composite molding, and aging drying. It can prepare materials with long-term temperature resistance of 1000-1300℃, a thermal conductivity of less than 0.06 W / (m·K) at 500℃, and a density of 160-240 kg / m³. 3 This technology utilizes a composite material. By pre-treating the high-temperature resistant fibers with heat, the wetting agent on the fiber surface is effectively removed, and a silicon-aluminum composite aerogel with good temperature resistance is obtained by controlling the silicon-aluminum ratio.

[0004] However, this technology still has the following shortcomings: 1. The preparation process relies on supercritical fluid drying, which consumes a lot of energy and requires high-end equipment, making it unsuitable for large-scale production; 2. It has poor stability in humid environments and lacks effective hydrophobic treatment, resulting in a limited service life in practical applications; 3. Under rapid temperature change conditions, it has insufficient thermal shock stability and is prone to structural damage; 4. The interfacial bonding between the fiber and the aerogel matrix is ​​not strong enough, and the mechanical properties need to be improved; 5. It has a single function and lacks additional functions such as flame retardancy and self-cleaning.

[0005] Therefore, there is an urgent need to develop a high-temperature resistant aerogel composite material with a simple preparation process and excellent comprehensive performance to meet the application requirements under harsh working conditions. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a multi-component synergistically reinforced ultra-high temperature resistant aerogel composite material and its low-energy-consumption preparation method. This material not only possesses excellent high-temperature resistance and thermal insulation properties, but also exhibits good mechanical strength, hydrophobicity, flame retardancy, and thermal shock stability, while simultaneously reducing preparation energy consumption and improving production efficiency.

[0007] To achieve the above objectives, the first aspect of the present invention provides a high-temperature resistant aerogel composite material, comprising the following components in parts by weight: 15-35 parts of reinforcing fiber matrix, 43-65 parts of silicon-aluminum-zirconium ternary aerogel network, 3-12 parts of functional nanofiller, 2-8 parts of zinc borate flame retardant component, and 0.5-2 parts of surface hydrophobic modification layer; wherein the reinforcing fiber matrix is ​​composed of aluminum silicate fiber, silicon carbide fiber, and alumina nanofiber; the molar ratio of silicon, aluminum, and zirconium in the silicon-aluminum-zirconium ternary aerogel network is 5:2:1; the functional nanofiller includes alumina nanoparticles, titanium oxide nanoparticles, carbon nanotubes, and boron nitride nanosheets; the zinc borate flame retardant component is zinc borate; and the surface hydrophobic modification layer includes an inner methyltrimethoxysilane modified layer and an outer hexamethyldisilazane modified layer.

[0008] Preferably, in the reinforcing fiber matrix, aluminosilicate fibers account for 70-90 wt%, with a diameter of 5-15 μm and a length of 1-5 cm; silicon carbide fibers account for 5-15 wt%, with a diameter of 8-12 μm; and alumina nanofibers account for 2-10 wt%, with a diameter of 50-200 nm.

[0009] Preferably, in the silicon-aluminum-zirconium ternary aerogel network, the silicon source is composed of tetraethyl orthosilicate and methyltrimethoxysilane mixed in a molar ratio of 9:1, the aluminum source is aluminum nitrate nonahydrate, and the zirconium source is zirconium oxychloride or zirconium acetate.

[0010] Preferably, in the functional nanofiller, alumina nanoparticles account for 0.5-3 wt% with a particle size of 20-50 nm; titanium dioxide nanoparticles account for 0.5-2 wt% with a particle size of 15-40 nm; carbon nanotubes account for 0.1-1 wt% with a length of 1-10 μm; and boron nitride nanosheets account for 1-3 wt% with a thickness of 10-50 nm.

[0011] The high-temperature resistant aerogel composite material has the following properties: long-term temperature resistance of 1200-1400℃, thermal shock stability of not less than 15 cycles, thermal conductivity of 0.015-0.020 W / (m·K) at 25℃, thermal conductivity of 0.035-0.045 W / (m·K) at 500℃, and density of 140-200 kg / m³. 3 The compressive strength at 10% strain is 0.8-1.5 MPa, the flexural strength is 0.5-0.8 MPa, the water contact angle is greater than 150°, and the oxygen index is not less than 35%.

[0012] A second aspect of the present invention provides a method for preparing the high-temperature resistant aerogel composite material, comprising the following steps:

[0013] S1: Multi-stage fiber pretreatment: The mixed reinforcing fibers are heat-treated at 650±20℃ for 30 min, cooled and then immersed in 1wt% KH-560 silane coupling agent ethanol solution, ultrasonically treated for 15 min, and dried at 70℃ for 4 h to obtain surface-modified fibers.

[0014] S2: Preparation of multi-component sols, including the preparation of silica sols, aluminum-zirconium composite sols, and functional component dispersions;

[0015] S3: Multi-level gradient impregnation composite molding;

[0016] S4: Low-energy drying;

[0017] S5: Thermal stability optimization treatment.

[0018] Preferably, the preparation of the multi-component sol in step S2 includes:

[0019] Preparation of silica sol: Tetraethyl orthosilicate: methyltrimethoxysilane: ethanol: water: nitric acid = 9:1:15:5:0.001 was mixed and stirred at room temperature for 2 hours to form a transparent sol;

[0020] Preparation of aluminum-zirconium composite sol: Aluminum nitrate nonahydrate was dissolved in water at a mass ratio of 1:10 and stirred until clear. The pH value was adjusted according to the aluminum:nitrate molar ratio of 1:1.2. Zirconium oxychloride solution was added, and the composition was controlled according to the silicon:aluminum:zirconium molar ratio of 5:2:1. The mixture was stirred at 60°C for 1 h to obtain a homogeneous sol.

[0021] Preparation of functional component dispersion: Alumina nanoparticles, titanium dioxide nanoparticles, carbon nanotubes and boron nitride nanosheets were ultrasonically dispersed in ethanol for 30 min. 0.5 wt% hydroxypropyl methylcellulose was added to stabilize the dispersion system. Surface-treated zinc borate was added to the dispersion, and ultrasonication was continued for 15 min to form a stable dispersion.

[0022] Preferably, the multi-level gradient impregnation composite molding in step S3 includes:

[0023] First stage impregnation: Impregnate the pretreated fibers with a low concentration of 2-5 wt% silica-alumina-zirconium sol, and vacuum-assisted permeation for 10 minutes;

[0024] Second stage impregnation: Impregnate with a medium concentration of 5-10 wt% functional component dispersion sol, with ultrasonic assistance for 5 min;

[0025] The third stage of impregnation: impregnation with a high-concentration 10-15wt% composite sol of silicon-aluminum-zirconium sol and functional fillers;

[0026] The 0.5 mol / L ammonia-ethanol solution was mixed with the final composite sol at a volume ratio of 1:0.6 and then sprayed onto the fiber.

[0027] Gel at room temperature for 12-24 hours.

[0028] Preferably, the low-energy drying in step S4 is a two-step drying process, including:

[0029] Solvent replacement: The gel samples were successively immersed in 30%, 60%, and 95% ethanol solutions for 12 hours each time;

[0030] Surface hydrophobic modification: The sample was immersed in a 3wt% hexamethyldisilazane-n-hexane solution for 24 hours;

[0031] Micro-vibration assisted drying: Apply 5-10Hz micro-vibration in the drying device, start at 40℃, raise to 120℃ at a rate of 1℃ / h, and keep at this temperature for 6 hours to complete the drying process, and obtain a crack-free aerogel composite material.

[0032] Preferably, the thermal stability optimization treatment in step S5 includes: heating the dried sample to 800°C at 2°C / min under a nitrogen atmosphere, holding it at that temperature for 2 hours to achieve in-situ bonding between the nanofiller and the aerogel matrix, and then treating it in a 1wt% hexamethyldisilazane gas phase for 4 hours after cooling to form a superhydrophobic surface.

[0033] The beneficial effects of this invention include:

[0034] By introducing zirconium components to construct a ternary aerogel network, the high temperature resistance and thermal shock stability of the material are significantly improved, and the long-term service temperature can reach 1200-1400℃, which is 100-200℃ higher than the existing technology.

[0035] The use of a zinc borate synergistic flame retardant system significantly improves the flame retardant performance of the material, with an oxygen index of over 35%.

[0036] The innovative use of a multi-level gradient impregnation process and micro-vibration-assisted drying technology enhances the interfacial bonding between fibers and aerogel, improves the mechanical properties of the material, and avoids the high energy consumption of supercritical drying, reducing the energy consumption of preparation by about 60%.

[0037] Through a double-layer hydrophobic modification design, the superhydrophobic properties of the material surface are achieved, with a contact angle greater than 150°, which significantly improves the service life of the material in humid environments.

[0038] The synergistic effect of multiple components endows the material with multifunctional properties, such as self-cleaning and thermal shock resistance, which greatly expands its application scenarios. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments. However, it should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0040] In carrying out this invention, unless otherwise explicitly specified and limited, terms such as the content of each component and reaction conditions shall have the ordinary meaning as understood by those skilled in the art.

[0041] The main raw materials used in this invention and their sources are as follows:

[0042] Aluminosilicate fiber: Model KS-1260 (purchased from Shandong Dongheng Guoxian New Material Co., Ltd.);

[0043] Silicon carbide fiber: Model XD-SiC-T800 (purchased from Weihai Guangwei Composite Materials Co., Ltd.);

[0044] Alumina nanofibers: Model ZD-Al2O3-NF (purchased from Shandong Dongheng Guoxian New Material Co., Ltd.);

[0045] Tetraethyl orthosilicate (TEOS): Aladdin reagent, purity ≥99.0% (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.);

[0046] Methyltrimethoxysilane (MTMS): Aladdin reagent, purity ≥98.0% (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.);

[0047] Aluminum nitrate nonahydrate: Sinopharm Chemical Reagent Co., Ltd., analytical grade;

[0048] Zirconium oxychloride: purity ≥ 98.0% (purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.);

[0049] Zirconium acetate: purity ≥ 99.0% (purchased from Baoji Funuokang Industrial Co., Ltd.);

[0050] Alumina nanoparticles: Shanghai Maclean Biochemical Technology Co., Ltd., particle size 20-50nm;

[0051] Titanium oxide nanoparticles: Shanghai Aladdin Biochemical Technology Co., Ltd., particle size 15-40nm;

[0052] Carbon nanotubes: Model SD-CNT-MWNT-OH (purchased from Shandong Dazhan Nanomaterials Co., Ltd.);

[0053] Boron nitride nanosheets: Model A13857 (purchased from Zhejiang Yamei Nanotechnology Co., Ltd.);

[0054] Zinc borate: Model WJ-ZB-F15 (purchased from Guangzhou Yuanda New Materials Co., Ltd.);

[0055] Hexamethyldisilazane (HMDS): Aladdin reagent, purity ≥99.0%;

[0056] KH-560 silane coupling agent: Jiangsu Huibo Polymer Materials Co., Ltd.;

[0057] Hydroxypropyl methylcellulose (HPMC): Shanghai Maclean Biochemical Technology Co., Ltd., viscosity 4000-6000 mPa·s;

[0058] Ethanol, nitric acid, ammonia, n-hexane, and other reagents were all of analytical grade and manufactured by Sinopharm Chemical Reagent Co., Ltd.

[0059] Example 1

[0060] The preparation method of high-temperature resistant aerogel composite material, the specific steps are as follows:

[0061] S1: Multi-stage fiber pretreatment

[0062] Aluminosilicate fibers (85 wt%), silicon carbide fibers (10 wt%), and alumina nanofibers (5 wt%) were mixed and heat-treated in a muffle furnace at 650 °C for 30 min to remove organic wetting agents from the fiber surface. After cooling to room temperature, the treated mixed fibers were immersed in a 1 wt% KH-560 silane coupling agent ethanol solution and sonicated for 15 min to enhance the activity of the fiber surface and interfacial bonding ability. Subsequently, they were dried in an oven at 70 °C for 4 h to obtain a surface-modified reinforced fiber matrix. The key to this step is the complete removal of organic wetting agents from the fiber surface through high-temperature treatment, while simultaneously introducing silicon-containing groups into the fiber surface through the silane coupling agent, forming Si-O-Si bond points, providing a chemical bonding basis for subsequent bonding with the aerogel network.

[0063] S2: Preparation of multi-component sol

[0064] (1) Preparation of silica sol: TEOS:MTMS:ethanol:water:HNO3 = 9:1:15:5:0.001 were mixed and stirred at room temperature for 2 hours to form a transparent sol. In this step, TEOS and MTMS co-hydrolyze to form a Si-O-Si network structure, where the methyl groups introduced by MTMS can endow the aerogel with certain flexibility and preliminary hydrophobicity. The TEOS hydrolysis process can be represented as follows:

[0065]

[0066] Subsequently, a condensation reaction occurs between the Si-OH groups:

[0067]

[0068] The addition of MTMS introduces hydrophobic methyl groups, forming Si-CH3 bonds. These methyl groups do not participate in the condensation reaction but remain in the final aerogel network, reducing the network's hydrophilicity.

[0069] (2) Preparation of aluminum-zirconium composite sol: Aluminum nitrate nonahydrate was dissolved in deionized water at a mass ratio of 1:10 and stirred until clear. The pH was adjusted to 2.5-3.0 according to an Al:HNO3 molar ratio of 1:1.2. This pH range is most suitable for the hydrolysis and polymerization rate of aluminum ions, which is conducive to the formation of stable alumino groups. Then, an aqueous solution of zirconium acetate (preferably zirconium acetate rather than zirconium oxychloride, because the acetate ligand provides better pH buffering capacity and sol stability) was added, and the final Si:Al:Zr molar ratio was controlled to be 5:2:1. The mixture was stirred at 60℃ for 1 h to obtain a homogeneous sol. Zirconium ions first form zirconium oxide groups [Zr(OH)2] in the aqueous solution. 2+ Then, it crosslinks with aluminum oxide and silicon oxide groups to form a complex Si-O-Al-O-Zr network structure. The introduction of zirconium components helps to improve the thermal stability and thermal shock resistance of the aerogel framework because ZrO2 has a low coefficient of thermal expansion and high phase stability at high temperatures.

[0070] (3) Preparation of functional component dispersion: Alumina nanoparticles (1.5 wt%), titanium dioxide nanoparticles (1.0 wt%), carbon nanotubes (0.5 wt%), and boron nitride nanosheets (2.0 wt%) were ultrasonically dispersed in ethanol for 30 min. 0.3 wt% hydroxypropyl methylcellulose was added to stabilize the dispersion and prevent nanoparticle aggregation. The amount of HPMC added was controlled at a low level (below 0.3 wt%) to ensure sufficient dispersion stability while ensuring complete decomposition during subsequent heat treatment without affecting the thermal stability of the final material. Surface-modified zinc borate (5.0 wt%) was added to the dispersion, and ultrasonication was continued for 15 min to form a stable dispersion. Surface pretreatment of zinc borate is crucial; coating with a silane coupling agent allows for better dispersion in organic solvents and reduces melt migration during high-temperature treatment, ensuring its uniform distribution in the final aerogel network. These functional nanofillers form a synergistic reinforcing system in the composite material: alumina provides thermal stability, titanium oxide provides photocatalytic self-cleaning function, carbon nanotubes enhance mechanical strength, and boron nitride controls the heat conduction path.

[0071] S3: Multi-level gradient impregnation composite molding

[0072] (1) First stage impregnation: The pretreated fibers were impregnated with a low-concentration (3wt%) silica-alumina-zirconium sol. The impregnation was assisted under vacuum conditions for 10 minutes to ensure that the sol fully penetrated into the fiber network to form an initial bonding layer. The low-concentration sol has low viscosity and high fluidity, which can penetrate into the interior of the fiber bundle and the intersections to form connecting bridges.

[0073] (2) Second stage impregnation: Impregnation was carried out using a medium concentration (7wt%) functional component dispersion sol, with ultrasonic assistance for 5 minutes to promote uniform distribution of nanofillers on the fiber surface. In this stage, the functional nanofillers were mainly deposited on the fiber surface and at fiber intersections, forming a functional reinforcement layer.

[0074] (3) Third stage impregnation: Impregnation is carried out using a high-concentration (12wt%) silica-alumina-zirconium sol and functional filler composite sol to form an outer protective film of the composite system. The high-concentration sol has high viscosity and can form a dense layer on the fiber surface, providing overall protection and structural support.

[0075] (4) A 0.5 mol / L ammonia-ethanol solution was mixed with the final composite sol at a volume ratio of 1:0.6 and sprayed onto the fiber, then gelled at room temperature for 18 hours. Ammonia, as an alkaline catalyst, can accelerate the condensation reaction of the silica-alumina-zirconium sol and promote the rapid formation of the three-dimensional network. This gradient impregnation process can significantly improve the interfacial bonding strength between the fiber and the aerogel, forming a gradient structure with functional changes from the inside to the outside, ensuring strong bonding of the internal structure and achieving diversification of external functions.

[0076] S4: Low-energy drying

[0077] (1) Solvent replacement: The gel sample was soaked in 30%, 60%, and 95% ethanol solutions sequentially for 12 hours each time to gradually replace the water in the gel pores. This stepwise replacement process can reduce the interfacial tension gradient and reduce the damage to the structure caused by capillary forces.

[0078] (2) Surface hydrophobic modification: The sample was immersed in a 3wt% HMDS-hexane solution for 24 h, allowing the hydroxyl groups (Si-OH) on the aerogel network surface to react chemically with HMDS to generate hydrophobic trimethylsilyl groups (Si-O-Si(CH3)3). The reaction can be represented as:

[0079]

[0080] This surface modification process transforms the aerogel network from hydrophilic to hydrophobic, significantly reducing capillary forces during solvent evaporation.

[0081] (3) Micro-vibration-assisted drying: The modified sample was placed in a specially designed drying device, and micro-vibration at 7 Hz was applied. The initial temperature was 40 ℃, and the temperature was increased to 120 ℃ at a rate of 1 ℃ / h. The temperature was maintained for 6 h to complete the drying process, resulting in a crack-free aerogel composite material. Micro-vibration technology is an innovative drying-assisted method. Its working principle is based on molecular dynamics theory: low-frequency vibration (5-10 Hz) can provide additional kinetic energy to solvent molecules, enabling them to overcome the adsorption force with the pore walls and promoting the uniform migration of solvent in the porous network. At the same time, vibration can also prevent stress concentration in local areas, disperse and release the internal stress generated during the drying process, thereby significantly reducing the formation of cracks. This drying method avoids the high-pressure equipment and high energy consumption of traditional supercritical drying, reducing energy consumption by about 60% while ensuring product quality.

[0082] S5: Thermal stability optimization treatment

[0083] The dried sample was heated to 800℃ at a rate of 2℃ / min under a nitrogen atmosphere and held for 2 hours to achieve in-situ bonding between the nanofiller and the aerogel matrix, enhancing thermal stability. During this heat treatment, the nitrogen atmosphere prevented oxidation of the material, while the temperature of 800℃ was sufficient to completely decompose residual organic matter (such as HPMC) and promote interfacial reactions and structural reorganization between inorganic components. It is important to note that this temperature is lower than the complete melting temperature of zinc borate (900-950℃), but sufficient to promote its interfacial bonding with the silicon-aluminum-zirconium network, forming a composite phase structure and preventing the migration and loss of zinc borate at higher temperatures. After cooling, the sample was treated in a 1wt% HMDS vapor phase for 4 hours to form a superhydrophobic surface, further improving the material's environmental adaptability. The vapor-phase HMDS treatment can repair hydrophilic groups that may have been exposed during the heat treatment, ensuring complete hydrophobicity of the material surface.

[0084] The high-temperature resistant aerogel composite material prepared through the above steps has the following weight proportions: 25 parts reinforcing fiber matrix, 58 parts silicon-aluminum-zirconium ternary aerogel network, 5 parts functional nanofiller, 5 parts zinc borate flame retardant component, and 1 part surface hydrophobic modification layer. This material exhibits the following properties: long-term temperature resistance of 1320℃, thermal shock stability of 18 cycles (1000℃↔ room temperature), thermal conductivity of 0.018 W / (m·K) at 25℃, thermal conductivity of 0.042 W / (m·K) at 500℃, and density of 180 kg / m³. 3 The 10% strain compressive strength is 1.0 MPa, the flexural strength is 0.6 MPa, the water contact angle is 155°, and the oxygen index is 38%.

[0085] Example 2

[0086] The preparation method of high-temperature resistant aerogel composite material, the specific steps are as follows:

[0087] S1: Multi-stage fiber pretreatment

[0088] Aluminosilicate fibers (80 wt%), silicon carbide fibers (15 wt%), and alumina nanofibers (5 wt%) were mixed and heat-treated in a muffle furnace at 630 °C for 25 min. After cooling to room temperature, the mixture was immersed in a 1 wt% KH-560 silane coupling agent ethanol solution and sonicated for 12 min. Subsequently, it was dried in an oven at 70 °C for 4 h to obtain a surface-modified reinforced fiber matrix.

[0089] S2: Preparation of multi-component sol

[0090] (1) Preparation of silica sol: TEOS:MTMS:ethanol:water:HNO3 = 9:1:18:6:0.001 were mixed and stirred at room temperature for 2.5 h to form a transparent sol. In this embodiment, the ratio of ethanol and water was appropriately increased, which helps to achieve complete hydrolysis of TEOS and uniform network formation.

[0091] (2) Preparation of aluminum-zirconium composite sol: Aluminum nitrate nonahydrate was dissolved in deionized water at a mass ratio of 1:12, and the pH was adjusted to 2.8 according to an Al:HNO3 molar ratio of 1:1.3. Zirconium oxychloride solution was added, controlling the Si:Al:Zr molar ratio to be 6:2:1, and the mixture was stirred at 65°C for 1 h. In this embodiment, zirconium oxychloride was used as the zirconium source. Under acidic conditions (pH 2.8), zirconium oxychloride can form a stable cationic species [ZrO]. 2+ This is more conducive to uniform cross-linking with aluminum oxide groups.

[0092] (3) Preparation of functional component dispersion: Alumina nanoparticles (2.0 wt%), titanium dioxide nanoparticles (1.5 wt%), carbon nanotubes (0.3 wt%), and boron nitride nanosheets (1.2 wt%) were ultrasonically dispersed in ethanol for 35 min. Then, 0.25 wt% hydroxypropyl methylcellulose and surface-treated zinc borate (3.0 wt%) were added, and the mixture was ultrasonically dispersed for another 15 min. In this embodiment, the carbon nanotube content was reduced, while the alumina and titanium dioxide contents were increased, which is more beneficial to the high-temperature stability of the material.

[0093] S3: Multi-level gradient impregnation composite molding

[0094] Three-stage impregnation was performed using sols of low concentration (2wt%), medium concentration (6wt%), and high concentration (10wt%), following steps S3(1)-(4), with a gelation time of 16 hours. This embodiment reduced the concentration of the sol at each stage, which is beneficial for more uniform penetration and the formation of a finer gradient structure.

[0095] S4: Low-energy drying

[0096] The solvent replacement and surface hydrophobic modification steps are the same as in Example 1, but the vibration frequency in the micro-vibration assisted drying is adjusted to 8 Hz and the heating rate is reduced to 0.8 °C / h. This slower heating rate further reduces stress accumulation during the drying process, which is beneficial for obtaining a higher quality aerogel structure.

[0097] S5: Thermal stability optimization treatment

[0098] The temperature was increased to 750℃ at a rate of 1.8℃ / min under a nitrogen atmosphere and held for 2.5 hours. After cooling, the HMDS vapor phase treatment time was extended to 5 hours. In this embodiment, the heat treatment temperature was slightly reduced and the holding time was extended. This parameter adjustment is more conducive to the uniform bonding of zinc borate and the matrix, and avoids local melting caused by excessively high temperatures.

[0099] The high-temperature resistant aerogel composite material prepared through the above steps has the following weight proportions: 20 parts reinforcing fiber matrix, 65 parts silicon-aluminum-zirconium ternary aerogel network, 5 parts functional nanofiller, 3 parts zinc borate flame retardant component, and 1.2 parts surface hydrophobic modification layer. This material exhibits the following properties: long-term temperature resistance of 1280℃, thermal shock stability after 16 cycles, thermal conductivity of 0.017 W / (m·K) at 25℃, thermal conductivity of 0.040 W / (m·K) at 500℃, and density of 165 kg / m³. 3 The 10% strain compressive strength is 1.2 MPa, the flexural strength is 0.65 MPa, the water contact angle is 158°, and the oxygen index is 36%.

[0100] Example 3

[0101] The preparation method of the high-temperature resistant aerogel composite material is basically the same as that in Example 1, except that:

[0102] The mixed fiber composition in S1 consists of aluminosilicate fibers (75 wt%), silicon carbide fibers (15 wt%), and alumina nanofibers (10 wt%). The heat treatment temperature is 670°C, and the time is 35 min. This embodiment increases the content of alumina nanofibers and improves the heat treatment temperature and time, which is beneficial for enhancing the high-temperature resistance of the fiber matrix.

[0103] The molar ratio of silica sol in S2 is TEOS:MTMS:ethanol:water:HNO3 = 8:2:16:5:0.001; increasing the proportion of MTMS improves the flexibility and initial hydrophobicity of the network. In the aluminum-zirconium composite sol, the molar ratio of Si:Al:Zr is 4:2:1, increasing the proportion of Al and Zr relative to Si, further enhancing high-temperature stability. The functional component dispersion contains alumina nanoparticles (0.8 wt%), titanium oxide nanoparticles (0.8 wt%), carbon nanotubes (0.6 wt%), and boron nitride nanosheets (2.8 wt%), with a zinc borate content of 6.0 wt%. This embodiment increases the content of boron nitride nanosheets and zinc borate, which is beneficial for controlling thermal conductivity and improving flame retardant properties.

[0104] The concentrations of the three-stage impregnation in S3 were 4 wt%, 8 wt%, and 14 wt%, respectively, and the gelation time was 20 h. Increasing the sol concentration can increase the density and strength of the final aerogel, while extending the gelation time is beneficial for the full development and cross-linking of the network.

[0105] In S4, the micro-vibration frequency is 6 Hz, and the heating rate is 1.2℃ / h. Lowering the vibration frequency can reduce interference with the fragile gel structure, while appropriately increasing the heating rate balances drying efficiency and structural integrity.

[0106] The heat treatment temperature in S5 is 820℃, and the holding time is 1.8h. Slightly increasing the heat treatment temperature can promote a more complete interfacial reaction between inorganic components and enhance high-temperature stability.

[0107] The high-temperature resistant aerogel composite material prepared through the above steps has the following weight proportions: 30 parts reinforcing fiber matrix, 50 parts silicon-aluminum-zirconium ternary aerogel network, 5 parts functional nanofiller, 6 parts zinc borate flame retardant component, and 1.5 parts surface hydrophobic modification layer. This material exhibits the following properties: long-term temperature resistance of 1350℃, thermal shock stability after 20 cycles, thermal conductivity of 0.019 W / (m·K) at 25℃, thermal conductivity of 0.043 W / (m·K) at 500℃, and density of 190 kg / m³. 3 The 10% strain compressive strength is 1.4 MPa, the flexural strength is 0.7 MPa, the water contact angle is 160°, and the oxygen index is 40%.

[0108] Example 4

[0109] The preparation method of high-temperature resistant aerogel composite material, the specific steps are as follows:

[0110] S1: Multi-stage fiber pretreatment

[0111] Aluminosilicate fibers (90 wt%), silicon carbide fibers (5 wt%), and alumina nanofibers (5 wt%) were mixed and heat-treated in a muffle furnace at 600 °C for 40 min. After cooling to room temperature, the mixture was immersed in a 1.2 wt% KH-560 silane coupling agent ethanol solution and sonicated for 18 min. Subsequently, it was dried in an oven at 70 °C for 4 h. This embodiment increased the proportion of aluminosilicate fibers while extending the heat treatment and sonication times, thus improving the uniformity and surface activity of the fiber matrix.

[0112] S2: Preparation of multi-component sol

[0113] The silica sol molar ratio was TEOS:MTMS:ethanol:water:HNO3 = 9.5:0.5:15:5:0.001; reducing the proportion of MTMS increased the network rigidity and thermal stability. The Si:Al:Zr molar ratio in the aluminum-zirconium composite sol was 5.5:2:1; the functional component dispersion contained alumina nanoparticles (2.5 wt%), titanium oxide nanoparticles (1.8 wt%), carbon nanotubes (0.2 wt%), and boron nitride nanosheets (1.5 wt%), with a zinc borate content of 7.0 wt%. This embodiment increased the content of inorganic components (alumina, titanium oxide, zinc borate) and reduced the proportion of carbon nanotubes, further enhancing the high-temperature stability and flame retardant properties of the material.

[0114] Steps S3-S5 are basically the same as in Example 1, except that the concentrations of the three-stage impregnation in S3 are 5wt%, 9wt%, and 15wt%, respectively; the micro-vibration frequency in S4 is 9Hz; and the heat treatment temperature in S5 is 780℃. Increasing the impregnation sol concentration and micro-vibration frequency is beneficial to improving the density and strength of the material, while decreasing the heat treatment temperature is more conducive to controlling the distribution of zinc borate.

[0115] The high-temperature resistant aerogel composite material prepared through the above steps has the following weight proportions: 15 parts reinforcing fiber matrix, 68 parts silicon-aluminum-zirconium ternary aerogel network, 6 parts functional nanofiller, 7 parts zinc borate flame retardant component, and 0.8 parts surface hydrophobic modification layer. This material exhibits the following properties: long-term temperature resistance of 1250℃, thermal shock stability after 15 cycles, thermal conductivity of 0.016 W / (m·K) at 25℃, thermal conductivity of 0.038 W / (m·K) at 500℃, and density of 150 kg / m³. 3 The 10% strain compressive strength is 0.9 MPa, the flexural strength is 0.55 MPa, the water contact angle is 152°, and the oxygen index is 37%.

[0116] Example 5

[0117] The preparation method of high-temperature resistant aerogel composite material, the specific steps are as follows:

[0118] S1: Multi-stage fiber pretreatment

[0119] Aluminosilicate fibers (70 wt%), silicon carbide fibers (10 wt%), and alumina nanofibers (20 wt%) were mixed and heat-treated in a muffle furnace at 680 °C for 30 min. After cooling to room temperature, the mixture was immersed in a 0.8 wt% KH-560 silane coupling agent ethanol solution and sonicated for 20 min. It was then dried in an oven at 70 °C for 4 h. This embodiment significantly increased the proportion of alumina nanofibers and employed a higher heat treatment temperature, greatly improving the high-temperature stability of the fiber matrix.

[0120] S2: Preparation of multi-component sol

[0121] The molar ratio of the silica sol is TEOS:MTMS:ethanol:water:HNO3 = 7:3:15:5:0.001; increasing the MTMS ratio can increase the flexibility and thermal shock resistance of the network. The molar ratio of Si:Al:Zr in the aluminum-zirconium composite sol is 5:3:1; increasing the Al ratio is beneficial for suppressing phase transitions at high temperatures. The functional component dispersion contains alumina nanoparticles (3.0 wt%), titanium oxide nanoparticles (2.0 wt%), carbon nanotubes (1.0 wt%), and boron nitride nanosheets (3.0 wt%), with a zinc borate content of 8.0 wt%. This embodiment increases the content of each functional component to a high level, forming multiple synergistic enhancement effects.

[0122] The remaining steps S3-S5 are similar to those in Example 1, except that the micro-vibration frequency in S4 is 10 Hz and the heat treatment temperature in S5 is 850 °C. High-frequency micro-vibration helps to release drying stress more efficiently, while the higher heat treatment temperature promotes densification and structural stability of the inorganic components. For zinc borate content as high as 8.0 wt%, heat treatment at 850 °C promotes a tighter bond between it and the silicon-aluminum-zirconium network, forming a multiphase ceramic structure. Although there may be a small amount of local melting, pre-treatment surface modification and coating ensure its uniform distribution without large-scale migration.

[0123] The high-temperature resistant aerogel composite material prepared through the above steps has the following weight proportions: 35 parts reinforcing fiber matrix, 43 parts silicon-aluminum-zirconium ternary aerogel network, 9 parts functional nanofiller, 8 parts zinc borate flame retardant component, and 2 parts surface hydrophobic modification layer. This material exhibits the following properties: long-term temperature resistance of 1400℃, thermal shock stability after 22 cycles, thermal conductivity of 0.020 W / (m·K) at 25℃, thermal conductivity of 0.045 W / (m·K) at 500℃, and density of 200 kg / m³. 3 The 10% strain compressive strength is 1.5 MPa, the flexural strength is 0.8 MPa, the water contact angle is 162°, and the oxygen index is 42%.

[0124] Example 6

[0125] The preparation method of high-temperature resistant aerogel composite material, the specific steps are as follows:

[0126] S1: Multi-stage fiber pretreatment

[0127] Aluminosilicate fibers (85 wt%), silicon carbide fibers (8 wt%), and alumina nanofibers (7 wt%) were mixed and heat-treated in a muffle furnace at 640 °C for 35 min. After cooling, the mixture was immersed in a 1.0 wt% KH-560 silane coupling agent ethanol solution and sonicated for 15 min, then dried at 70 °C for 4 h.

[0128] S2: Preparation of multi-component sol

[0129] (1) The molar ratio of silica sol is TEOS:MTMS:ethanol:water:HNO3 = 8.5:1.5:15:5:0.001;

[0130] (2) The molar ratio of Si:Al:Zr in the aluminum-zirconium composite sol is 5:2.5:1; increasing the Al ratio can enhance the thermal stability of the network.

[0131] (3) The functional component dispersion contains alumina nanoparticles (0.5 wt%), titanium dioxide nanoparticles (0.5 wt%), carbon nanotubes (0.5 wt%), and boron nitride nanosheets (1.5 wt%), with a zinc borate content of 4.0 wt%. In this embodiment, the content of each functional component is moderate, forming a balanced comprehensive performance.

[0132] Steps S3-S5 are basically the same as in Example 1, except that the gelation time in S3 is 22 h; the micro-vibration frequency in S4 is 5 Hz; and the heat treatment temperature in S5 is 800℃, with a holding time of 2.2 h. Extending the gelation time is beneficial for the full development of the network, reducing the micro-vibration frequency reduces interference with the structure, and appropriate heat treatment temperature and time ensure the full binding of inorganic components and the uniform distribution of zinc borate.

[0133] The high-temperature resistant aerogel composite material prepared through the above steps has the following weight proportions: 28 parts reinforcing fiber matrix, 60 parts silicon-aluminum-zirconium ternary aerogel network, 3 parts functional nanofiller, 4 parts zinc borate flame retardant component, and 1 part surface hydrophobic modification layer. This material exhibits the following properties: long-term temperature resistance of 1300℃, thermal shock stability after 17 cycles, thermal conductivity of 0.017 W / (m·K) at 25℃, thermal conductivity of 0.041 W / (m·K) at 500℃, and density of 175 kg / m³. 3 The 10% strain compressive strength is 1.1 MPa, the flexural strength is 0.62 MPa, the water contact angle is 156°, and the oxygen index is 37%.

[0134] Comparative Example 1: Zirconium-free silica-alumina aerogel composite material

[0135] The preparation method is basically the same as in Example 1, but zirconium is not added in S2; only a silica-alumina binary aerogel is prepared with a Si:Al molar ratio of 5:2. The remaining steps are the same as in Example 1.

[0136] The composite material prepared has the following weight proportions: 25 parts of reinforcing fiber matrix, 58 parts of silica-alumina aerogel network, 5 parts of functional nanofiller, 5 parts of zinc borate flame retardant component, and 1 part of surface hydrophobic modification layer.

[0137] The material has a long-term temperature resistance of only 1100℃, a thermal shock stability of only 7 cycles, a thermal conductivity of 0.019 W / (m·K) at 25℃, and a thermal conductivity of 0.050 W / (m·K) at 500℃. Its density is 180 kg / m³. 3 The 10% strain compressive strength is 0.8 MPa, the flexural strength is 0.5 MPa, the water contact angle is 154°, and the oxygen index is 37%.

[0138] Compared to Example 1, the high-temperature resistance and thermal shock stability of this material are significantly reduced due to the absence of zirconium. This result fully demonstrates the crucial role of zirconium in improving the high-temperature stability of materials. Under high-temperature conditions, the silicon-aluminum network lacking zirconium is more prone to structural collapse and phase transformation, leading to a decrease in temperature resistance; simultaneously, the non-uniformity of the coefficient of thermal expansion also results in a significant reduction in thermal shock resistance. This result verifies the unique role of zirconium in ternary networks: the phase stability and low coefficient of thermal expansion of ZrO2 at high temperatures are key factors in the material's high-temperature resistance and thermal shock resistance.

[0139] Comparative Example 2: Composite material without zinc borate flame retardant components

[0140] The preparation method is basically the same as in Example 3, but zinc borate flame retardant components are not added in S2. The remaining steps are the same as in Example 3.

[0141] The composite material prepared has the following weight proportions: 30 parts of reinforcing fiber matrix, 50 parts of silicon-aluminum-zirconium ternary aerogel network, 5 parts of functional nanofiller, and 1.5 parts of surface hydrophobic modification layer.

[0142] The material has a long-term temperature resistance of 1340℃, a thermal shock stability of 19 cycles, a thermal conductivity of 0.018 W / (m·K) at 25℃, a thermal conductivity of 0.042 W / (m·K) at 500℃, and a density of 188 kg / m³. 3 It has a 10% strain compressive strength of 1.3 MPa, a flexural strength of 0.68 MPa, a water contact angle of 160°, but an oxygen index of only 28%.

[0143] Compared to Example 3, the flame retardant properties of this material were significantly reduced, with the oxygen index decreasing from 40% to 28%, indicating that the zinc borate flame retardant component played a decisive role in improving the material's flame retardant performance. This result verifies the multiple flame retardant mechanisms of zinc borate: during combustion, zinc borate first releases water of crystallization to absorb heat, then forms a glassy protective film to block oxygen diffusion, and finally forms a stable ceramic phase with the silicon-aluminum-zirconium network, resulting in a significant improvement in the material's flame retardant performance. Although the zinc borate-free material still maintains good high-temperature resistance and mechanical properties, it has significant shortcomings in fire safety and cannot meet the needs of certain critical application scenarios.

[0144] Comparative Example 3: Conventional drying methods replacing micro-vibration-assisted drying

[0145] The preparation method is basically the same as in Example 2, but in S4, a conventional atmospheric pressure drying method is used instead of micro-vibration-assisted technology. The solvent-displaced and hydrophobically modified sample is directly dried at 50°C for 24 hours, and then heated to 120°C for 6 hours.

[0146] The prepared composite material has the same component content as in Example 2, but obvious cracks appear on the surface of the material. The thermal conductivity at 25°C is 0.022 W / (m·K), the 10% strain compressive strength is only 0.7 MPa, the flexural strength is 0.45 MPa, and other performance indicators are also reduced accordingly.

[0147] This result fully demonstrates the crucial role of micro-vibration-assisted drying technology in preparing high-quality, crack-free aerogel composites. During conventional atmospheric pressure drying, the capillary forces caused by solvent evaporation generate significant stress within the material, leading to structural shrinkage and cracking. Micro-vibration-assisted drying, by providing additional energy, promotes uniform migration of solvent molecules while simultaneously dispersing and releasing internal stress, effectively preventing crack formation. This innovative technology not only improves product quality but also avoids the high energy consumption and demanding equipment requirements of traditional supercritical drying, offering significant process advantages and economic benefits.

[0148] Comparative Example 4: Composite material without surface hydrophobic modification

[0149] The preparation method is basically the same as in Example 4, but the surface hydrophobic modification step in S4 and the HMDS vapor phase treatment step in S5 are omitted.

[0150] The prepared composite material had the same component content as in Example 4, but without the surface hydrophobic modification layer. This material exhibited significant hydrophilicity with a water contact angle of only 65°. After being placed in an environment with 90% relative humidity for 7 days, its thermal conductivity increased to 0.035 W / (m·K), and its compressive strength decreased to 0.6 MPa.

[0151] This result demonstrates the significant role of surface hydrophobic modification in improving the environmental adaptability and long-term performance of materials. Aerogel materials without hydrophobic modification, due to the abundance of hydrophilic Si-OH groups on their surface, readily absorb moisture from the environment, leading to increased thermal conductivity and decreased mechanical properties. The bilayer hydrophobic modification design of this invention, through the synergistic effect of MTMS and HMDS, forms a dense hydrophobic layer on the aerogel network surface, effectively preventing moisture intrusion and ensuring that the material maintains excellent performance even in humid environments. This technology is of great importance for expanding the application scenarios of aerogel materials and extending their service life.

[0152] The performance testing method is as follows:

[0153] Long-term temperature resistance test: According to GB / T 17430 standard, the sample is placed at the specified temperature for 1000h and the weight loss rate is measured. A loss rate of less than 5% is considered to have passed the test.

[0154] Thermal shock stability test: Place the sample in a muffle furnace at 1000℃ for 30 minutes, then quickly remove it and cool it in a room temperature environment. Repeat this process until the sample shows obvious cracks or the strength decreases by more than 30%, and record the number of cycles.

[0155] Thermal conductivity test: The thermal conductivity of the samples was measured using the hot wire method (ASTM C518) at 25°C and 500°C.

[0156] Density test: Measure the volume and weight of the sample and calculate the density according to GB / T 6343 standard.

[0157] Compressive strength test: The compressive strength of the sample under 10% strain conditions is measured according to GB / T 8813 standard.

[0158] Bending strength test: The bending strength of the sample was measured by the three-point bending method according to GB / T 1040 standard.

[0159] Hydrophobicity test: The contact angle of a water droplet on the sample surface was measured using a contact angle meter according to ASTM D5725 standard.

[0160] Oxygen Index Test: The oxygen index value of the sample is measured according to GB / T 2406.2 standard.

[0161] Performance comparison of examples and comparative examples

[0162] The performance comparisons of the embodiments and comparative examples are shown in Table 1:

[0163] Table 1 Performance Comparison of Examples and Comparative Examples

[0164]

[0165] As can be seen from Table 1, the performance of Examples 1-6 is significantly better than that of Comparative Examples 1-4. Comparative Example 1 lacks zirconium component, resulting in a significant reduction in temperature resistance and thermal shock stability; Comparative Example 2 lacks zinc borate flame retardant component, resulting in a significant reduction in oxygen index; Comparative Example 3 does not use micro-vibration assisted drying technology, resulting in material cracks and reduced mechanical properties; Comparative Example 4 lacks surface hydrophobic modification, resulting in poor environmental adaptability of the material and rapid performance degradation in humid environments.

[0166] The mechanism of action is analyzed as follows:

[0167] 1. Synergistic Mechanism of Ternary Si / Al / ZrO2 Aerogel Network: Under high-temperature conditions, pure SiO2 aerogel is prone to crystallization and phase transition, leading to structural collapse. Adding Al2O3 can inhibit SiO2 crystallization, but significant structural changes still occur at ultra-high temperatures (>1200℃). This invention introduces ZrO2 to form a ternary Si / Al / ZrO2 network, achieving multiple synergistic effects. From a molecular structure perspective, ZrO2 tends to form tetragonal or monoclinic phase structures at high temperatures, which possess high thermodynamic stability and mechanical strength. 4+ Si in Ions and Networks 4+ And Al 3+ The formation of a -Si-O-Zr-O-Al-O-Si cross-linked structure improves the rigidity and stability of the overall network. Meanwhile, ZrO2 exhibits a low coefficient of thermal expansion (approximately 5-7 × 10⁻⁶). -6 / K), with SiO2 (0.5-1×10 -6 / K) and Al2O3 (7-9×10 -6 The complementary relationship between ZrO2 and K reduces the expansion mismatch of the overall material during thermal cycling, effectively preventing the initiation and propagation of microcracks and improving the thermal shock stability of the material. Furthermore, the high-temperature phase change endothermic properties of ZrO2 also provide an additional thermal protection mechanism for the material.

[0168] 2. Synergistic Flame Retardant Mechanism of Zinc Borate: Zinc borate (ZnB2O4) plays a multi-layered flame retardant role in aerogel composites. Chemically, zinc borate contains water of crystallization (3.5-4.5 mol water / mol ZnB2O4). In the temperature range of 400-600℃, this water of crystallization is released, absorbing a large amount of heat energy (approximately 300-400 J / g), reducing the surface temperature of the material and delaying the combustion process. At higher temperatures (600-800℃), zinc borate, after dehydration, forms a ZnO-B2O3 glassy protective film, covering the material surface. This dense film has a high melting point and a low oxygen diffusion coefficient, effectively blocking oxygen diffusion and heat transfer. From a reaction mechanism perspective, as the temperature further increases, the B2O3 component undergoes a solid-state reaction with SiO2 and Al2O3 in the silicon-aluminum-zirconium network, forming a boroaluminosilicate composite phase (such as Al4B2Si8O). 24 This further enhances the material's thermal stability and flame retardant properties. Simultaneously, the ZnO component acts as a catalyst, promoting the formation of the carbonized layer and strengthening the flame retardant effect. This multi-layered synergistic flame retardant mechanism significantly improves the material's oxygen index, achieving a high level of 35-42%. Notably, pre-treating the zinc borate surface ensures its uniform distribution during high-temperature processing without large-scale migration, maintaining a long-term stable flame retardant effect.

[0169] 3. Micro-vibration-assisted drying mechanism: In conventional drying processes, the capillary forces (up to 10-30 MPa) caused by solvent evaporation can lead to shrinkage and even cracking of the aerogel network structure. This invention employs micro-vibration-assisted drying technology, applying low-frequency vibrations of 5-10 Hz to achieve multiple physical effects. From a molecular dynamics perspective, low-frequency vibrations provide solvent molecules with additional kinetic energy (approximately 0.1-0.2 eV), making it easier for them to overcome van der Waals forces and hydrogen bonds with the pore walls (approximately 0.05-0.1 eV), accelerating their escape from micropores and mesopores. Simultaneously, vibrations also disrupt the liquid bridge structure within the pores, weakening the effect of capillary forces. From a mechanical perspective, vibrations effectively disperse stress concentration, redistributing energy from locally high-stress areas to the entire structure, preventing crack initiation and propagation. Furthermore, vibrations can promote microscopic restructuring and self-repair of the network structure, reducing defect formation. Meanwhile, the prior hydrophobic modification treatment replaced the hydrophilic -OH groups on the surface of the aerogel network with hydrophobic -Si(CH3)3 groups, reducing the surface energy from approximately 72 mJ / m 2 Reduced to approximately 20-25 mJ / m 2This significantly reduces capillary forces, further minimizing shrinkage and cracking during the drying process. This innovative process not only improves material quality but also avoids the high-pressure (7-12 MPa) equipment and high energy consumption (approximately 2.5-3.5 kWh / kg) required for traditional supercritical drying, reducing production costs and energy consumption (to approximately 1.0-1.4 kWh / kg).

[0170] 4. Multi-level Gradient Impregnation Mechanism: Traditional one-step impregnation processes struggle to achieve uniform bonding between fibers and aerogels, often resulting in weak interfacial adhesion and low interfacial shear strength (typically <0.2 MPa). This invention employs a three-level concentration gradient impregnation process (low-medium-high) to create a gradient structure with progressively changing functions from the inside out. From a hydrodynamic perspective, low-concentration (2-5 wt%) sols have low viscosity (approximately 1-3 mPa·s) and small molecular clusters (2-5 nm), enabling them to penetrate into the fiber bundle and at intersections, forming an initial bonding layer. Medium-concentration (5-10 wt%) sols have moderate viscosity (approximately 3-8 mPa·s), allowing them to carry functional nanofillers (10-100 nm) uniformly distributed on the fiber surface, forming a functional reinforcement layer. High-concentration (10-15 wt%) sols have high viscosity (approximately 8-15 mPa·s), forming a dense protective layer on the fiber surface, providing overall structural support. From an interfacial chemistry perspective, this gradient structure reduces the elastic modulus mismatch between fibers and aerogel (typically differing by 1-2 orders of magnitude), lowers interfacial stress concentration, and significantly improves the interfacial bonding strength (to 0.5-0.8 MPa) and overall mechanical properties of the composite material. Furthermore, the distribution of different functional components at different levels achieves optimized performance configuration: the inner layer focuses on bonding strength, the middle layer on functionality, and the outer layer on protection, forming a synergistic reinforcement effect.

[0171] 5. Synergistic Mechanism of Surface Hydrophobic Modification: This invention employs a dual-layer hydrophobic modification strategy, combining inner MTMS pre-modification with outer HMDS post-treatment, to achieve superhydrophobic properties in aerogel composites. From a chemical structure perspective, MTMS introduces Si-CH3 groups during the sol-gel process, forming an internal hydrophobic network; while HMDS post-treatment introduces more -Si(CH3)3 groups on the surface, forming a dense outer hydrophobic layer. This dual-layer design ensures that the material retains its hydrophobicity during long-term use; even if some of the outer hydrophobic groups are lost, the inner hydrophobic network still provides basic hydrophobic protection. From a surface science perspective, this treatment reduces the material's surface energy from approximately 72 mJ / m². 2 (Hydrophilicity) decreased to approximately 20-25 mJ / m 2The hydrophobic modification increases the water contact angle from <90° to >150°, achieving a superhydrophobic effect. From a molecular mechanics perspective, the hydrophobic modification also improves the flexibility of the aerogel network, enhancing the material's vibration and impact resistance. Notably, this hydrophobic property is crucial for the material's application in humid and hot environments, preventing structural damage and degradation of thermal insulation performance caused by moisture intrusion.

[0172] Based on the above mechanistic analysis, it is evident that this invention, through multi-component synergistic design and innovative process optimization, successfully addresses the problems of existing aerogel composite materials in terms of high-temperature resistance, mechanical strength, environmental adaptability, and preparation energy consumption. It produces an ultra-high-temperature resistant aerogel composite material with excellent comprehensive performance and broad application prospects. In particular, the ternary silicon-aluminum-zirconium network provides ultra-high temperature stability, the zinc borate flame-retardant system provides excellent flame-retardant properties, the micro-vibration-assisted drying technology significantly reduces energy consumption and cost, the multi-level gradient impregnation process enhances the material's mechanical properties, and the double-layer hydrophobic modification design improves environmental adaptability. These innovative points synergistically produce a comprehensive effect exceeding the sum of individual technologies, demonstrating significant technological innovation value.

Claims

1. A high temperature resistant aerogel composite material, characterized in that, The components include the following weight parts: a reinforced fiber matrix 15-35 parts, a silicon-aluminum-zirconium ternary aerogel network 43-65 parts, a functional nano filler 3-12 parts, a zinc borate flame-retardant component 2-8 parts, and a surface hydrophobic modification layer 0.5-2 parts; The reinforced fiber matrix is composed of aluminum silicate fibers, silicon carbide fibers, and aluminum oxide nanofibers; The aluminum silicate fibers account for 70-90wt% of the reinforced fiber matrix, have a diameter of 5-15μm, and a length of 1-5cm, the silicon carbide fibers account for 5-15wt% of the reinforced fiber matrix, have a diameter of 8-12μm, and the aluminum oxide nanofibers account for 2-10wt% of the reinforced fiber matrix, have a diameter of 50-200nm; The molar ratio of silicon, aluminum, and zirconium in the silicon-aluminum-zirconium ternary aerogel network is 5:2:1; In the silicon-aluminum-zirconium ternary aerogel network, the silicon source is composed of tetraethyl orthosilicate and methyltrimethoxysilane mixed at a molar ratio of 9:1, the aluminum source is aluminum nitrate nonahydrate, and the zirconium source is zirconium oxychloride or zirconium acetate; The functional nano filler includes aluminum oxide nanoparticles, titanium oxide nanoparticles, carbon nanotubes, and boron nitride nanosheets, wherein the aluminum oxide nanoparticles account for 0.5-3wt% of the functional nano filler, have a particle size of 20-50nm, the titanium oxide nanoparticles account for 0.5-2wt% of the functional nano filler, have a particle size of 15-40nm, the carbon nanotubes account for 0.1-1wt% of the functional nano filler, have a length of 1-10μm, and the boron nitride nanosheets account for 1-3wt% of the functional nano filler, have a thickness of 10-50nm; The zinc borate flame-retardant component is a zinc borate; The surface hydrophobic modification layer includes an inner layer of methyltrimethoxysilane modification and an outer layer of hexamethyldisilazane modification.

2. The high temperature resistant aerogel composite of claim 1, wherein, The high-temperature-resistant aerogel composite material has the following properties: long-term temperature resistance of 1200-1400℃, thermal shock stability of not less than 15 cycles, thermal conductivity of 0.015-0.020 W / (m·K) at 25℃, thermal conductivity of 0.035-0.045 W / (m·K) at 500℃, density of 140-200 kg / m³, 10% strain compression strength of 0.8-1.5 MPa, bending strength of 0.5-0.8 MPa, water contact angle of more than 150°, and oxygen index of not less than 35%.

3. Process for the preparation of the high temperature resistant aerogel composite material according to claim 1 or 2, characterized in that, The method includes the following steps: S1: multi-stage pretreatment of fibers, the mixed reinforced fibers are heated at 650±20℃ for 30min, then immersed in a 1wt% KH-560 silane coupling agent ethanol solution after cooling, ultrasonic treatment for 15min, and dried at 70℃ for 4h to obtain surface modified fibers; S2: preparation of multi-component sol, including preparation of silica sol, aluminum-zirconium composite sol, and functional component dispersion; S3: multi-stage gradient impregnation composite molding; S4: low-energy consumption drying; S5: thermal stability optimization treatment.

4. The method of claim 3, wherein, The preparation of multi-component sol in step S2 includes: Preparation of silica sol: mix tetraethyl orthosilicate:methyltrimethoxysilane:ethanol:water:nitric acid at a molar ratio of 9:1:15:5:0.001, stir at room temperature for 2h to form a transparent sol; Preparation of aluminum-zirconium composite sol: aluminum nitrate nonahydrate and water were dissolved with a mass ratio of 1:10, stirred until clear, the pH value was adjusted according to the aluminum:nitric acid molar ratio of 1:1.2, zirconium oxychloride solution was added, the composition was controlled according to the silicon:aluminum:zirconium molar ratio of 5:2:1, and a uniform sol was obtained after stirring at 60°C for 1h; Preparation of functional component dispersion: alumina nanoparticles, titanium oxide nanoparticles, carbon nanotubes and boron nitride nanosheets were ultrasonically dispersed in ethanol for 30min, 0.5wt% hydroxypropyl methyl cellulose was added to stabilize the dispersion system, the surface treated zinc borate was added to the dispersion, and ultrasonic dispersion was continued for 15min to form a stable dispersion.

5. The method of claim 3, wherein, The multistage gradient impregnation composite forming in step S3 includes: First stage impregnation: the pretreated fiber is impregnated with a low concentration of 2-5wt% silicon aluminum zirconium sol, and vacuum assisted infiltration is performed for 10min; Second stage impregnation: impregnated with a medium concentration of 5-10wt% functional component dispersion sol, and ultrasonic assisted for 5min; Third stage impregnation: impregnated with a high concentration of 10-15wt% silicon aluminum zirconium sol and functional filler composite sol; 0.5 mol / L ammonia water ethanol solution was mixed with the final composite sol at a volume ratio of 1:0.6, and then sprayed on the fiber; Gelation at room temperature for 12-24h.

6. The method of claim 3, wherein, The low energy consumption drying in step S4 is a two-step drying method, including: Solvent replacement: the gel sample is sequentially immersed in 30%, 60%, and 95% ethanol solution for 12h each time; Surface hydrophobic modification: the sample is immersed in 3wt% hexamethyldisilazane n-hexane solution for 24h; Micro-vibration assisted drying: 5-10Hz micro-vibration is applied in the drying device, the initial temperature is 40°C, and the temperature is increased to 120°C at a rate of 1°C / h, and the drying is completed after 6h of heat preservation, obtaining a crack-free aerogel composite material.

7. The method of claim 3, wherein, The heat stability optimization treatment in step S5 includes: the dried sample is heated to 800°C at a rate of 2°C / min under nitrogen atmosphere, and heat preservation is performed for 2h to realize in-situ combination of nanofiller and aerogel matrix, and after cooling, the sample is treated in 1wt% hexamethyldisilazane gas phase for 4h to form a superhydrophobic surface.

Images