Large-size high-strength wide-temperature-range low-thermal-conductivity mullite aerogel composite material and preparation method thereof

Abstract

The invention discloses a mullite aerogel composite material with large size, high strength, wide temperature range and low thermal conductivity and a preparation method thereof. According to the composite material, a high-temperature-resistant fiber preform of which the surface is modified with a nano layer is used as a macroscopic framework, and the macroscopic framework and a silicon-aluminum molecular sieve / mullite nano matrix are chemically bonded to form a'macroscopic-mesoscopic-nano 'multistage synergistic enhancement structure. The preparation method comprises the following steps: growing an interface layer on the fiber surface in situ through a hydrothermal method; preparing silicon-aluminum composite sol; impregnating a fiber preform and gelling; and performing aging, supercritical drying and heat treatment to obtain a final product. Through an infrared shielding effect and a phonon scattering effect of a multi-heterogeneous interface, high-temperature radiation heat transfer and solid heat conduction are remarkably inhibited, so that the material has high strength, low heat conduction and 1500 DEG C high-temperature stability while keeping low density and high specific surface area, and preparation of a large-size complete block is successfully realized; the method has great application prospects in the fields of high-temperature heat insulation, industrial high-temperature catalysis or adsorption and the like.

Description

Technical Field

[0001] This invention relates to the field of aerogel material preparation technology, and in particular to a large-size, high-strength, wide-temperature-range, low-thermal-conductivity mullite aerogel material and its preparation method. Background Technology

[0002] Aerogels, as the lightest solid materials in the world, possess extremely low thermal conductivity and extremely high porosity due to their unique nanoporous network structure, making them considered the ultimate solution in the field of thermal insulation and energy saving. However, three major bottlenecks—intrinsic brittleness, high-temperature structural instability, and difficulty in large-size fabrication—severely restrict their application and promotion in practical engineering. In high-temperature applications, common oxide aerogels such as silica and alumina have significant shortcomings. Silica aerogels undergo sintering and densification above 650℃; while alumina aerogels can withstand temperatures up to approximately 1000℃, they undergo an irreversible transformation from the γ phase to the α phase above 1200℃, accompanied by severe volume shrinkage and structural pulverization. Therefore, mullite (…), with its higher thermal stability… Aerogels have become a research hotspot. However, the preparation of high-performance mullite aerogels still faces huge challenges: on the one hand, complete mullitization usually requires heat treatment above 1200℃, which leads to the collapse of nanopores and a sharp decrease in specific surface area; on the other hand, the inherent brittleness of pure mullite aerogels makes it difficult to process into large and complex components.

[0003] Existing technologies attempt to address and improve these issues through various approaches. One focus is on improving the process for preparing silicon-aluminum composite aerogels. Patent CN109678519B uses a supercritical modification method to prepare silicon-aluminum composite aerogels, achieving a shrinkage rate controllable below 10% after heat treatment at 1200℃. However, this patent document does not mention mechanical strength data for the material, and the supercritical process is complex and costly. Patent CN104291781B employs high-temperature supercritical fluid technology, which also faces the problems of complex processes and difficulty in large-scale production. Another approach is to improve mechanical properties by introducing reinforcing phases. Patent CN116023165A uses whisker-reinforced silicon-aluminum composite aerogels, achieving a room-temperature compressive strength of 1.5 MPa. However, the introduced high-density whiskers significantly increase solid-phase thermal conductivity, causing the material's thermal conductivity to rise above 0.065 W / (m·K), severely sacrificing thermal insulation performance. Patent CN109081673B uses micro / nanofibers as a reinforcing phase, but it also suffers from the problem of a high overall thermal conductivity due to the high density of the reinforcing phase. By constructing a special nanostructure, Xiaodong Wu et al. (CX Su, TD Koudama, XD Wu, et al. Rational design of a novel mullite aerogel with extremely high mechanical strength and anti-oxidation behavior for advanced thermal protection in extreme environments, J. Eur. Ceram. Soc. 44 (2024)1761-1771.) achieved this by... Carbon-mullite aerogels were prepared by introducing a phenolic resin network into the aerogel and then sintering at high temperature. This material exhibits a high compressive strength of 15.5 MPa and a specific surface area of ​​481... However, due to the large amount of carbon in its system, it oxidizes in an aerobic environment above 800℃, leading to structural failure and limiting its high-temperature application in air. Patent CN114132940B provides a novel approach, using an aluminum-containing two-dimensional covalent organic framework and silicate ester as sources, to prepare ultralight mullite aerogels (with densities as low as 26) through freeze-drying and calcination at 1200℃. However, the aluminum source used in this method is extremely expensive, and the pore size formed by freeze drying is large and highly interconnected, resulting in a relatively high room temperature thermal conductivity and poor thermal insulation performance, making it difficult to apply on a large scale.

[0004] In summary, most existing technical solutions can only solve a single problem, and often at the expense of other key properties: either sacrificing thermal insulation to improve strength, or sacrificing mechanical properties and cost to ensure temperature resistance. Developing a mullite aerogel composite material that can simultaneously achieve high strength, large-size molding, excellent high-temperature stability, and maintain efficient thermal insulation from room temperature to extremely high temperatures has become an urgent technical challenge to be overcome in this field. Summary of the Invention

[0005] To address the shortcomings of existing mullite aerogel materials in terms of mechanical properties, high-temperature insulation, and macroscopic molding, this invention aims to provide a mullite aerogel composite material that achieves performance breakthroughs through multi-scale structural design. This material innovatively constructs a "fiber macroscopic skeleton— The composite structure of "interfacial functional layer - molecular sieve nanonetwork" not only achieves cross-scale enhancement of mechanical properties, but also endows the material with excellent high-temperature infrared shielding and interfacial thermal resistance characteristics, which has broad application prospects in high-temperature insulation, catalysis and adsorption.

[0006] Another objective of this invention is to provide a method for preparing mullite aerogel composite materials. This method features high process integration, effectively linking steps such as hydrothermal modification, sol-gel composite, supercritical drying, and programmed heat treatment to achieve the controllable construction of complex multi-level structures, making it suitable for large-scale production.

[0007] The objective of this invention is achieved through the following technical solution.

[0008] A large-size, high-strength, wide-temperature-range, low-thermal-conductivity mullite aerogel composite material is provided. The large-size, high-strength mullite aerogel material is composed of a macroscopic reinforcing network, an interfacial functional layer, and a nanocomposite matrix. The macroscopic reinforcing network is a continuous three-dimensional skeleton composed of high-temperature resistant fibers.

[0009] In the above technical solution, the high-temperature resistant fiber is at least one of alumina fiber, mullite fiber or magnesium aluminum spinel fiber, and the fiber diameter is 0.05-20μm.

[0010] In the above technical solution, the material of the interface functional layer is a titanium dioxide nanocrystal layer grown in situ on the surface of the high-temperature resistant fiber by hydrothermal method. The thickness of the titanium dioxide nanocrystal layer is 50-500nm, and it is bonded to the high-temperature resistant fiber and the subsequently formed nanocomposite matrix through Ti-O-Si and Ti-O-Al chemical bonds.

[0011] In the above scheme, the nanocomposite matrix is ​​a biphase nanoporous network formed by the interpenetration of silica-alumina molecular sieves and mullite aerogel particles, wherein the mullite has a grain size of 30-200 nm, and the molecular sieve is one or a mixture of SBA-15, MCM-41 or ZSM-5.

[0012] A method for preparing a large-size, high-strength, low-thermal-conductivity mullite aerogel composite material includes the following steps: preparation @Fiber preforms; A silica-alumina sol and a silica-alumina molecular sieve solution were prepared by mixing the silica-alumina sol and the silica-alumina molecular sieve solution evenly and adding a coagulant to obtain a silica-alumina composite sol. Will @The fiber preform is impregnated in a silica-alumina composite sol, and then subjected to gelation and aging treatments to obtain... / Silicone-aluminum composite wet gel; Will / Silicone-aluminum composite wet gel was subjected to alcohol replacement and supercritical drying treatment to obtain silicon-aluminum modified composite aerogel. Large-size mullite aerogel composite materials were obtained by heat treatment of silicon-aluminum modified composite aerogel.

[0013] The following details each step in the above method.

[0014] Step 1, @Preparation of fiber preforms; Titanium flakes, melamine powder, and nitric acid were added to a hydrogen peroxide solution, and the mixture was magnetically stirred for a certain period of time to allow the reaction to proceed fully, resulting in a clear and transparent solution containing... The reaction solution. The fiber preform is immersed in the solution. The reaction solution was transferred to a polytetrafluoroethylene (PTFE) liner and subjected to a hydrothermal reaction at a specific temperature for a certain time. After the hydrothermal reaction was complete, the fiber preform was removed and washed with an ethanol solution until neutral, wherein the volume ratio of deionized water to ethanol was 10:1. Finally, it was dried at a specific temperature for a certain time to obtain... @Fiber preform material. Where @ indicates in-situ growth on the fiber surface. Interface functionality layer.

[0015] In step 1, the fiber preform is at least one of alumina fiber, mullite fiber or magnesium aluminum spinel fiber, and the fiber diameter is 0.05-20 μm.

[0016] In step 1, the mass-to-volume ratio of melamine powder, nitric acid and hydrogen peroxide solution is (0.2~0.6) g : (2~6) mL : 200 mL, and the concentration of hydrogen peroxide solution is 25~35 wt%.

[0017] In step 1, the thickness of the titanium sheet is 0.05~0.1mm, and the magnetic stirring time is 12~36h.

[0018] In step 1, the temperature of the hydrothermal reaction is 60~90℃, and the reaction time is 30~120min.

[0019] In step 1, the drying temperature is 50~80℃ and the drying time is 12~36 h.

[0020] Step 2, Preparation of silica-alumina sol; Aluminum alkoxide and solvent are added to a reaction vessel and heated to a certain temperature using a heating device. The mixture is stirred at a constant temperature for a certain time until it is homogeneous and clear, thus obtaining an aluminum sol. The aluminum sol is then cooled to room temperature. A certain amount of silicon precursor is added to the sol, and then it is mixed with an acid catalyst. After stirring thoroughly for a certain time, a silica-alumina sol is obtained.

[0021] In step 2, the solvent is any one of ethanol, isopropanol, acetone or n-butanol, and the stirring temperature for the constant temperature stirring for a certain period of time is 30~70℃, and the stirring time is 6~12h.

[0022] In step 2, the aluminum alkoxide is either aluminum sec-butoxide or aluminum isopropoxide, and the mass ratio of the aluminum alkoxide to the solvent is (1~4):10.

[0023] In step 2, the silicon precursor is at least one of tetraethyl orthosilicate, tetramethyl orthosilicate, tetraethyl orthosilicate, tetraisopropyl orthosilicate, tetrabutyl orthosilicate, and tetraphenyl orthosilicate.

[0024] In step 2, the molar ratio of the aluminum alkoxide to the silicon precursor is (1~3):1; In step 2, the acid catalyst is a nitric acid solution with a molar concentration of 0.5–2 mol / L, the molar ratio of aluminum alkoxide to acid catalyst is 2:(1–1.5), and the stirring time for a certain period of time is 8–24 h.

[0025] Step 3, Preparation of the silica-alumina molecular sieve solution: A silica-alumina molecular sieve, modified additives, and solvent are ultrasonically treated and mixed evenly to obtain a silica-alumina molecular sieve solution.

[0026] In step 3, the silica-alumina molecular sieve includes one or a mixture of SBA-15, MCM-41 and ZSM-5.

[0027] In step 3, the modified additive includes , One of or a mixture of CoO.

[0028] In step 3, the mass ratio of the molecular sieve, the modified additive, and the solvent is (10~20):(1~5):100.

[0029] Step 4, Preparation of fiber / silica-alumina wet gel: This step involves mixing the silica-alumina sol prepared in step 2 with the silica-alumina molecular sieve solution from step 3, and adding a coagulant to obtain a silica-alumina composite sol. Then, the silica-alumina composite sol prepared in step 1 is... The fiber preform is impregnated in the composite sol, and then the system is sealed and allowed to stand to obtain... @Fiber / Silica-alumina wet gel.

[0030] In step 4, the volume ratio of the silica-alumina sol to the silica-alumina molecular sieve solution is (5~12):1.

[0031] In step 4, the coagulant is one or a mixture of two of propylene oxide or epichlorohydrin.

[0032] In step 4, the molar ratio of the aluminum alkoxide to the coagulant is 1:(5~12).

[0033] In step 4, the temperature for sealing and settling is 40~60℃, and the time is 3~10h.

[0034] Step 5, Preparation of fiber / silica alumina aerogel: The wet gel block obtained in step 4 is added to the aging solution and subjected to 5-7 displacement cycles in an oven at 30-75°C, with each aging period lasting 12-24 hours, to obtain... @Fiber composite gel; The prepared gel block is removed from the aging solution and subjected to alcohol replacement, then placed in an autoclave and subjected to supercritical drying under heat and pressure to produce a high-strength block. @Fiber / Silica-Alumina Molecular Sieves- Composite aerogel.

[0035] In step 5, the aging solution is one or a mixture of ethanol, methanol, acetone, or isopropanol.

[0036] In step 5, the supercritical drying method is a carbon dioxide supercritical drying method: carbon dioxide is used as the drying medium, the reaction temperature is 45~65℃, the pressure inside the high-pressure reactor is 8~12MPa, the gas release rate is 4~16L / min, and the drying time is 5~14h.

[0037] Step 6, Preparation of fiber / mullite aerogel composites: The composite aerogel obtained in step 5 is calcined in air to prepare a block-shaped aerogel. @Fiber / mullite aerogel composite material.

[0038] In step 6, the calcination treatment in air atmosphere is carried out at a temperature of 1000~1200℃, the heating rate is 1~5℃ / min, and the holding time is 1~4 hours.

[0039] The mullite aerogel composite material obtained by the above preparation method.

[0040] The above-mentioned large-size, high-strength, low-thermal-conductivity mullite aerogel composite materials are used in high-temperature insulation, industrial high-temperature catalysis, or adsorption materials.

[0041] Compared with the prior art, the present invention has the following advantages: (1) Multi-scale synergistic enhancement and high-temperature infrared shielding effect. This patent innovatively constructs a "macro-fiber skeleton— The interface functional layer and molecular sieve nanonetwork form a three-phase synergistic reinforcement structure. The macroscopic fiber skeleton effectively inhibits macroscopic cracking of the material during drying and heat treatment, enabling the preparation of large-sized, intact blocks at the centimeter scale. The interfacial functional layer achieves a robust bond between the fiber and the matrix by forming strong Ti-O-Si and Ti-O-Al chemical bonds, effectively transferring macroscopic loads to the nano-matrix and significantly improving the material's compressive strength. More importantly, the uniformly distributed fibers on the fiber surface... Nanocrystals, as a highly efficient infrared shielding agent, can effectively absorb and scatter thermal radiation at high temperatures, similar to "fiber- The strong phonon scattering effect generated by the multiple heterogeneous interfaces of "molecular sieve-mullite" works synergistically to form a dual barrier that suppresses radiative heat transfer and solid heat conduction, enabling the material to maintain excellent thermal insulation performance in a wide temperature range from room temperature to 1400℃ (room temperature thermal conductivity as low as 0.029 W / (m·K)).

[0042] (2) Low-temperature mullitization and retention of high specific surface area structure. This invention introduces silica-alumina molecular sieves into the composite sol and modifies the fiber surface. By utilizing the synergistic catalytic effect of the acidic sites on the surfaces of both materials, the formation temperature of the mullite phase is significantly reduced, enabling the mullite formation reaction to be completed at ≤1150℃. Compared with existing technologies, the lower synthesis temperature effectively avoids the collapse of nanopores due to high-temperature sintering, allowing the final composite material to better retain its high specific surface area and abundant mesoporous structure, providing favorable conditions for its application in high-temperature insulation, catalysis, and adsorption.

[0043] (3) Strong process integration and excellent overall performance. This invention achieves this through... The infrared shielding effect and the phonon scattering effect of multiple heterogeneous interfaces significantly suppress high-temperature radiative heat transfer and solid-state thermal conduction, enabling the material to maintain a low density. ), high specific surface area ( While possessing high strength (compressive strength ≥7MPa), low thermal conductivity (room temperature ≤0.035W / (m·K)), and high-temperature stability at 1500℃, this invention successfully enables the preparation of large-size, intact bulk materials. This invention organically combines hydrothermal modification, sol-gel, and supercritical drying processes, resulting in a clear process flow, moderate equipment requirements, and avoidance of extremely expensive raw materials, thus possessing the potential for large-scale production. The prepared composite material successfully achieves a balance of multiple advantages, including high strength, low thermal conductivity, large-size molding, and high-temperature stability. Its excellent comprehensive performance provides an ideal material solution for thermal protection in extreme environments, which is of positive significance for promoting the practical application of mullite aerogel materials in high-temperature insulation, energy, and chemical industries. Attached Figure Description

[0044] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0045] Figure 1 This is a process flow diagram for preparing the large-size, high-strength, low-thermal-conductivity mullite aerogel composite material of the present invention.

[0046] Figure 2 A physical image of the large-size mullite aerogel material prepared for the implementation of Case 1.

[0047] Figure 3 This is a scanning electron microscope image of the mullite aerogel material finally prepared by the method of the present invention, wherein Mullite fiber is mullite fiber. Detailed Implementation

[0048] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0049] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0050] This invention provides a method for preparing large-size, high-strength, wide-temperature-range, low-thermal-conductivity mullite aerogel composite materials, the process of which is as follows: Figure 1 As shown, the main steps include: preparation @Fiber preform; Preparation of silica-alumina sol; Preparation of silica-alumina molecular sieve solution; Mixing silica-alumina sol and silica-alumina molecular sieve solution evenly to obtain silica-alumina composite sol; The fiber preform is impregnated in a silica-alumina composite sol, and a coagulant is added for gelation and aging treatment to obtain a composite wet gel. The composite wet gel is then subjected to alcohol displacement and supercritical drying to obtain a composite aerogel precursor. The composite aerogel precursor is then calcined to obtain the final product. @Fiber / mullite aerogel composite material.

[0051] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0052] The instruments used in the following embodiments are as follows: 5.0kV field emission scanning electron microscope (SEM, TDCLS-S4800, Japan), universal testing machine (CMT4303, Meister Industrial Systems, China), specific surface area and pore size analyzer (Nova 2200e, Quanta-chrome Instruments, USA), and thermal conductivity meter (TC3000, XIATECH Instrument, China). Example 1: The SBA-15 addition amount (SBA-15 mass) is prepared according to the following weight ratio: (SBA-15 mass + deionized water mass) = 1:10 and the molar ratio of aluminum isopropoxide to tetraethyl orthosilicate = 3:1.

[0053] 3g of aluminum isopropoxide and 30g of ethanol were added to a reaction vessel, heated to 40℃ in a water bath, and stirred at this temperature for 10 hours until homogeneous and clear, yielding an aluminum sol. After cooling to room temperature, 1.08g of tetraethyl orthosilicate was added, and stirring continued for 3 hours. Then, 3mL of nitric acid solution (2mol / L) was added, and the mixture was stirred thoroughly for 12 hours to obtain a silica-alumina sol. 10g of SBA-15 and 1.0g of CoO were added to 100g of water, and the mixture was subjected to ultrasonic treatment for 20 minutes and magnetic stirring for 60 minutes until homogeneous, yielding an SBA-15 solution. 1mL of the SBA-15 solution was added to 10mL of the silica-alumina sol, and the mixture was stirred magnetically for 2 hours until homogeneous. Then, propylene oxide was added at a molar ratio of aluminum to propylene oxide of 1:8, and the mixture was stirred for 10 minutes to obtain a silica-alumina composite sol. A pre-prepared... Alumina fiber preforms (10mm × 10mm × 1mm) were impregnated in a silica-alumina composite sol, and the system was then sealed and gelled in an oven at 45°C. After gelation, ethanol aging solution was added, and the mixture was subjected to five ethanol-based aging processes at 30°C, each lasting 12 hours. The wet gel was then subjected to ethanol aging and further processing. Supercritical drying was performed at a supercritical reaction temperature of 50℃. The reactor pressure was 10 MPa, the venting rate was 5 L / min, and the drying time was 12 h. @Fiber / SBA-15 composite aluminosilicate aerogel. This composite aerogel was heat-treated in air at 1050℃ with a heating rate of 2℃ / min and a holding time of 2h to obtain a block-shaped aerogel. @Fiber / mullite aerogel composite material.

[0054] The density of the large-size high-strength mullite aerogel composite material was tested to be 0.115. The specific surface area is 281 The thermal conductivity at room temperature is 0.029. It has a compressive strength of 8.74 MPa and a temperature resistance of up to 1400℃.

[0055] from Figure 2 As can be seen, after heat treatment, the resulting mullite aerogel material has a controllable shape and does not exhibit sintering shrinkage. From... Figure 3 As can be seen, the aerogel structure exhibits a typical pearl chain structure, with a relatively uniform distribution of pores.

[0056] Example 2: The SBA-15 addition amount (SBA-15 mass) is prepared according to the following weight ratio: (SBA-15 mass + deionized water mass) = 1:20 and the molar ratio of aluminum isopropoxide to tetraethyl orthosilicate = 3:1.

[0057] 3g of aluminum isopropoxide and 30g of ethanol were added to a reaction vessel, heated to 40℃ in a water bath, and stirred at this temperature for 10 hours until homogeneous and clear, yielding an aluminum sol. After cooling to room temperature, 1.08g of tetraethyl orthosilicate was added, and stirring continued for 3 hours. Then, 3mL of nitric acid solution (2mol / L) was added, and the mixture was stirred thoroughly for 12 hours to obtain a silica-alumina sol. 10g of SBA-15 and 1.0g of CoO were added to 100g of water, and the mixture was subjected to ultrasonic treatment for 20 minutes and magnetic stirring for 60 minutes until homogeneous, yielding an SBA-15 solution. 1mL of the SBA-15 solution was added to 10mL of the silica-alumina sol, and the mixture was stirred magnetically for 2 hours until homogeneous. Then, propylene oxide was added at a molar ratio of aluminum to propylene oxide of 1:8, and the mixture was stirred for 10 minutes to obtain a silica-alumina composite sol. A pre-prepared... Alumina fiber preforms (10mm × 10mm × 1mm) were impregnated in a silica-alumina composite sol, and the system was then sealed and gelled in an oven at 45°C. After gelation, ethanol aging solution was added, and the mixture was subjected to five ethanol-based aging processes at 30°C, each lasting 12 hours. The wet gel was then subjected to ethanol aging and further processing. Supercritical drying was performed at a supercritical reaction temperature of 50℃. The reactor pressure was 10 MPa, the venting rate was 5 L / min, and the drying time was 12 h. @Fiber / SBA-15 composite aluminosilicate aerogel. This composite aerogel was heat-treated in air at 1050℃ with a heating rate of 2℃ / min and a holding time of 2h to obtain a block-shaped aerogel. / mullite aerogel composite material.

[0058] The density of the large-size high-strength mullite aerogel composite material was tested to be 0.121. Specific surface area is 245 The thermal conductivity at room temperature is 0.031. The compressive strength is 7.56 MPa.

[0059] Example 3: The SBA-15 addition amount (SBA-15 mass) is prepared according to the following weight ratio: (SBA-15 mass + deionized water mass) = 1:10 and the molar ratio of aluminum isopropoxide to tetraethyl orthosilicate = 3:1.

[0060] 3g of aluminum isopropoxide and 30g of ethanol were added to a reaction vessel, heated to 40℃ in a water bath, and stirred at this temperature for 10 hours until homogeneous and clear, yielding an aluminum sol. After cooling to room temperature, 1.08g of tetraethyl orthosilicate was added, and stirring continued for 3 hours. Then, 3mL of nitric acid solution (2mol / L) was added, and the mixture was stirred thoroughly for 12 hours to obtain a silica-alumina sol. 10g of SBA-15 was added to 100g of water, and the mixture was subjected to ultrasonic treatment for 20 minutes and magnetic stirring for 60 minutes until homogeneous, yielding an SBA-15 solution. 1mL of the SBA-15 solution was added to 10mL of the silica-alumina sol, and the mixture was stirred magnetically for 2 hours until homogeneous. Then, propylene oxide was added at a molar ratio of aluminum to propylene oxide of 1:8, and the mixture was stirred for 10 minutes to obtain a silica-alumina composite sol. A pre-prepared... Alumina fiber preforms (10mm × 10mm × 1mm) were impregnated in a silica-alumina composite sol, and the system was then sealed and gelled in an oven at 45°C. After gelation, ethanol aging solution was added, and the mixture was subjected to five ethanol-based aging processes at 30°C, each lasting 12 hours. The wet gel was then subjected to ethanol aging and further processing. Supercritical drying was performed at a supercritical reaction temperature of 50℃. The reactor pressure was 10 MPa, the venting rate was 5 L / min, and the drying time was 12 h. @Fiber / SBA-15 composite aluminosilicate aerogel. This composite aerogel was heat-treated in air at 1050℃ with a heating rate of 2℃ / min and a holding time of 2h to obtain a block-shaped aerogel. @Fiber / mullite aerogel composite material.

[0061] The density of the large-size high-strength mullite aerogel composite material was tested to be 0.118. Specific surface area is 265 The thermal conductivity at room temperature is 0.030. The compressive strength is 7.91 MPa.

[0062] Example 4: The SBA-15 addition amount (SBA-15 mass) is prepared according to the following weight ratio: (SBA-15 mass + deionized water mass) = 1:10 and the molar ratio of aluminum isopropoxide to tetraethyl orthosilicate = 3:1.

[0063] 3g of aluminum isopropoxide and 30g of ethanol were added to a reaction vessel, heated to 40℃ in a water bath, and stirred at this temperature for 10 hours until homogeneous and clear, yielding an aluminum sol. After cooling to room temperature, 1.08g of tetraethyl orthosilicate was added, and stirring continued for 3 hours. Then, 3mL of nitric acid solution (2mol / L) was added, and the mixture was stirred thoroughly for 12 hours to obtain a silica-alumina sol. 10g of SBA-15 and 1.0g of CoO were added to 100g of water, and the mixture was subjected to ultrasonic treatment for 20 minutes and magnetic stirring for 60 minutes until homogeneous, yielding an SBA-15 solution. 1mL of the SBA-15 solution was added to 10mL of the silica-alumina sol, and the mixture was stirred magnetically for 2 hours until homogeneous. Then, propylene oxide was added at a molar ratio of aluminum to propylene oxide of 1:8, and the mixture was stirred for 10 minutes to obtain a silica-alumina composite sol. A pre-prepared... Alumina fiber preforms (10mm × 10mm × 1mm) were impregnated in a silica-alumina composite sol, and the system was then sealed and gelled in an oven at 45°C. After gelation, ethanol aging solution was added, and the mixture was subjected to five ethanol-based aging processes at 30°C, each lasting 12 hours. The wet gel was then subjected to ethanol aging and further processing. Supercritical drying was performed at a supercritical reaction temperature of 50℃. The reactor pressure was 10 MPa, the venting rate was 5 L / min, and the drying time was 12 h. @Fiber / SBA-15 composite aluminosilicate aerogel. This composite aerogel was heat-treated in air at 1100℃ with a heating rate of 2℃ / min and a holding time of 2h to obtain a block-shaped aerogel. @Fiber / mullite aerogel composite material.

[0064] The density of the blocky high-temperature resistant mullite aerogel composite material was tested to be 0.120. Specific surface area is 255 The thermal conductivity at room temperature is 0.032. The compressive strength is 9.12 MPa.

[0065] Example 5: The SBA-15 addition amount (SBA-15 mass) is prepared according to the following weight ratio: (SBA-15 mass + deionized water mass) = 1:10 and the molar ratio of aluminum isopropoxide to tetraethyl orthosilicate = 2:1.

[0066] 2g of aluminum isopropoxide and 30g of ethanol were added to a reaction vessel, heated to 40℃ in a water bath, and stirred at this temperature for 10 hours until homogeneous and clear, yielding an aluminum sol. After cooling to room temperature, 1.08g of tetraethyl orthosilicate was added, and stirring continued for 3 hours. Then, 3mL of nitric acid solution (2mol / L) was added, and the mixture was stirred thoroughly for 12 hours to obtain a silica-alumina sol. 10g of SBA-15 and 1.0g of CoO were added to 100g of water, and the mixture was subjected to ultrasonic treatment for 20 minutes and magnetic stirring for 60 minutes until homogeneous, yielding an SBA-15 solution. 1mL of the SBA-15 solution was added to 10mL of the silica-alumina sol, and the mixture was stirred magnetically for 2 hours until homogeneous. Then, propylene oxide was added at a molar ratio of aluminum to propylene oxide of 1:8, and the mixture was stirred for 10 minutes to obtain a silica-alumina composite sol. A pre-prepared piece of... Alumina fiber preforms (10mm × 10mm × 1mm) were impregnated in a silica-alumina composite sol, and the system was then sealed and gelled in an oven at 45°C. After gelation, ethanol aging solution was added, and the mixture was subjected to five ethanol-based aging processes at 30°C, each lasting 12 hours. The wet gel was then subjected to ethanol aging and further processing. Supercritical drying was performed at a supercritical reaction temperature of 50℃. The reactor pressure was 10 MPa, the venting rate was 5 L / min, and the drying time was 12 h. @Fiber / SBA-15 composite aluminosilicate aerogel. This composite aerogel was heat-treated in air at 1050℃ with a heating rate of 2℃ / min and a holding time of 2h to obtain a block-shaped aerogel. @Fiber / mullite aerogel composite material.

[0067] The density of the blocky high-temperature resistant mullite aerogel composite material was tested to be 0.107. Specific surface area is 308 The thermal conductivity at room temperature is 0.027. The compressive strength is 7.53 MPa.

[0068] Example 6: The ingredients were prepared with aluminum isopropoxide and tetraethyl orthosilicate in a molar ratio of 3:1, without the addition of SBA-15 molecular sieve.

[0069] 3g of aluminum isopropoxide and 30g of ethanol were added to a reaction vessel, heated to 40℃ in a water bath, and stirred at this temperature for 10 hours until homogeneous and clear, yielding an aluminum sol. After cooling to room temperature, 1.08g of tetraethyl orthosilicate was added, and stirring continued for 3 hours. Then, 3mL of nitric acid solution (2mol / L) was added, and the mixture was stirred thoroughly for 12 hours to obtain a silica-alumina sol. 1.0g of CoO was added to 100g of water, and the mixture was subjected to ultrasonic treatment for 20 minutes and magnetic stirring for 60 minutes until homogeneous, yielding a CoO solution. 1mL of the CoO solution was added to 10mL of the silica-alumina sol, and the mixture was stirred magnetically for 2 hours until homogeneous. Then, propylene oxide was added at a molar ratio of aluminum to propylene oxide of 1:8, and the mixture was stirred for 10 minutes to obtain a silica-alumina composite sol. A pre-prepared piece of... Alumina fiber preforms (10mm × 10mm × 1mm) were impregnated in a silica-alumina composite sol, and the system was then sealed and gelled in an oven at 45°C. After gelation, ethanol aging solution was added, and the mixture was subjected to five ethanol-based aging processes at 30°C, each lasting 12 hours. The wet gel was then subjected to ethanol aging and further processing. Supercritical drying was performed at a supercritical reaction temperature of 50℃. The reactor pressure was 10 MPa, the venting rate was 5 L / min, and the drying time was 12 h. @Fiber-composite aluminosilicate aerogel. This composite aerogel was heat-treated in air at 1050℃ with a heating rate of 2℃ / min and a holding time of 2h to obtain a block-shaped aerogel. @Fiber / mullite aerogel composite material.

[0070] The density of the blocky high-temperature resistant mullite aerogel composite material was tested to be 0.125. Specific surface area is 184 The thermal conductivity at room temperature is 0.037. Its compressive strength is 5.46 MPa.

[0071] Comparative Example 1: The batch was prepared using aluminum isopropoxide and tetraethyl orthosilicate in a molar ratio of 3:1, without adding SBA-15 molecular sieve or using [other materials]. @Fiber preforms.

[0072] 3g of aluminum isopropoxide and 30g of ethanol were added to a reaction vessel, heated to 40℃ in a water bath, and stirred at this temperature for 10 hours until homogeneous and clear, yielding an aluminum sol. After cooling to room temperature, 1.08g of tetraethyl orthosilicate was added, and stirring continued for 3 hours. Then, 3mL of nitric acid solution (2mol / L) was added, and the mixture was stirred thoroughly for 12 hours to obtain a silica-alumina sol. Propylene oxide was added to the silica-alumina sol at a molar ratio of aluminum to propylene oxide of 1:8, and stirred for 10 minutes to obtain a silica-alumina composite sol. The silica-alumina composite sol was poured into a mold and gelled in an oven at 45℃. After gelation, ethanol aging solution was added, and the mixture was subjected to five ethanol displacements at 30℃ for 12 hours each. The wet gel was then subjected to alcohol displacement and further processing. Aluminosilicate aerogel was obtained by supercritical drying at a supercritical reaction temperature of 50℃, with a reactor pressure of 10MPa, an venting rate of 5L / min, and a drying time of 12h. This aerogel was then heat-treated in air at 1050℃ with a heating rate of 2℃ / min and a holding time of 2h to obtain a bulk mullite aerogel material.

[0073] Testing revealed that the obtained pure mullite aerogel material cracked severely after molding, failing to form a complete block, and exhibited significant shrinkage; its density was measured to be 0.258. Specific surface area is 136 The thermal conductivity at room temperature is 0.052. The compressive strength is 3.46 MPa.

[0074] Summary: Comparing Examples 1 and 2, the addition ratio of SBA-15 as a nano-framework reinforcement material for aerogels significantly affects the specific surface area and strength of the material. Within a certain range, increasing the addition ratio leads to a corresponding increase in specific surface area and strength. The comparison between Examples 1 and 3 shows that the introduction of the modifier CoO helps optimize the mullite conversion process and improve the mechanical properties of the material. The comparison between Examples 1 and 4 shows that appropriately increasing the heat treatment temperature can make the mullite conversion more complete, thereby improving strength, but may lead to a slight decrease in specific surface area. The comparison between Examples 1 and 5 demonstrates the regulatory effect of the silicon-aluminum ratio on the material's structure and properties; increasing the silicon content helps form a more uniform nano-network, resulting in lower density and thermal conductivity. The comparison between Examples 1 and 6 proves the key role of the SBA-15 molecular sieve nanoframework in maintaining high specific surface area and excellent thermal insulation performance. The comprehensive comparison between Example 1 and Comparative Example 1 fully demonstrates the effectiveness of the method used in this invention. The synergistic reinforcement strategy of fiber preforms and molecular sieve frameworks is extremely important for achieving large-size molding, high strength and high specific surface area of ​​materials.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A large-size, high-strength, wide-temperature-range, low-thermal-conductivity mullite aerogel composite material, characterized in that, The mullite aerogel material is composed of a macroscopic reinforcing network, an interface functional layer, and a nanocomposite matrix. The macroscopic reinforcing network is a continuous three-dimensional skeleton composed of high-temperature resistant fibers.

2. The large-size, high-strength, wide-temperature-range, low-thermal-conductivity mullite aerogel composite material according to claim 1, characterized in that, The high-temperature resistant fiber is at least one of alumina fiber, mullite fiber or magnesium aluminum spinel fiber, and the fiber diameter is 0.05-20μm.

3. The large-size, high-strength, wide-temperature-range, low-thermal-conductivity mullite aerogel composite material according to claim 1, characterized in that, The interface functional layer is a titanium dioxide nanocrystal layer grown in situ on the surface of the high-temperature resistant fiber by hydrothermal method. The thickness of the titanium dioxide nanocrystal layer is 50-500 nm, and it is bonded to the high-temperature resistant fiber and nanocomposite matrix through Ti-O-Si and Ti-O-Al chemical bonds.

4. The large-size, high-strength, wide-temperature-range, low-thermal-conductivity mullite aerogel composite material according to claim 1, characterized in that, The nanocomposite matrix is ​​a biphase nanoporous network formed by the interpenetration of silica-alumina molecular sieves and mullite aerogel particles, wherein the mullite has a grain size of 30-200 nm and the molecular sieve is one or a mixture of SBA-15, MCM-41 or ZSM-5.

5. A method for preparing a large-size, high-strength, wide-temperature-range, low-thermal-conductivity mullite aerogel composite material, characterized in that, Includes the following steps: preparation @Fiber preforms; A silica-alumina sol and a silica-alumina molecular sieve solution were prepared by mixing the silica-alumina sol and the silica-alumina molecular sieve solution evenly and adding a coagulant to obtain a silica-alumina composite sol. Will @The fiber preform is impregnated in a silica-alumina composite sol, and then subjected to gelation and aging treatments to obtain... / Silicone-aluminum composite wet gel; Will / Silicone-aluminum composite wet gel was subjected to alcohol replacement and supercritical drying treatment to obtain silicon-aluminum modified composite aerogel. Large-size mullite aerogel composite materials were obtained by heat treatment of silicon-aluminum modified composite aerogel.

6. The method according to claim 5, characterized in that, The preparation @Fiber preforms, including: Titanium flakes, melamine powder, and nitric acid were added to a hydrogen peroxide solution, and the mixture was magnetically stirred for a certain period of time to allow the reaction to proceed fully, resulting in a clear and transparent solution containing... Reaction solution; Immerse the fiber preform in the The fiber preform was placed in a reaction solution and transferred to a polytetrafluoroethylene liner for hydrothermal reaction. After the hydrothermal reaction was completed, the fiber preform was removed, washed with ethanol solution until neutral, and dried to obtain the desired product. @Fiber preform materials; The fiber preform is at least one of alumina fiber, mullite fiber, or magnesium aluminum spinel fiber, with a fiber diameter of 0.05-20 μm; the mass-to-volume ratio of melamine powder, nitric acid, and hydrogen peroxide solution is (0.2-0.6) g: (2-6) mL: 200 mL; the concentration of the hydrogen peroxide solution is 25-35 wt%; the thickness of the titanium sheet is 0.05-0.1 mm; the magnetic stirring time is 12-36 h; the hydrothermal reaction temperature is 60-90℃, and the reaction time is 30-120 min; the drying temperature is 50-80℃, and the drying time is 12-36 h.

7. The method according to claim 5, characterized in that, The preparation steps of the silica-alumina sol include: Aluminum alkoxide and solvent are added to a reaction vessel, heated to a certain temperature using a heating device, and stirred at a constant temperature for a certain time until homogeneous and clear to obtain aluminum sol. The obtained aluminum sol is cooled to room temperature, a certain amount of silicon precursor is added to it, and then mixed with an acid catalyst. After stirring thoroughly for a certain time, a silica-alumina sol is obtained. The solvent is any one of ethanol, isopropanol, acetone or n-butanol, and the stirring temperature for the constant temperature stirring for a certain period of time is 30~70℃, and the stirring time is 6~12h. The aluminum alkoxide is either aluminum sec-butoxide or aluminum isopropoxide, and the mass ratio of the aluminum alkoxide to the solvent is (1~4):10; The silicon precursor is at least one of tetraethyl orthosilicate, tetramethyl orthosilicate, tetraethyl orthosilicate, tetraisopropyl orthosilicate, and tetraphenyl orthosilicate. The molar ratio of the aluminum alkoxide to the silicon precursor is (1~3):1; The acid catalyst is a nitric acid solution with a molar concentration of 0.5–2 mol / L. The molar ratio of aluminum alkoxide to acid catalyst is 2:(1–1.5). The stirring time for a certain period of time is 8–24 h.

8. The method according to claim 7, characterized in that, The preparation steps of the silica-alumina molecular sieve solution include: A silica-alumina molecular sieve, modified additives, and solvent are ultrasonically treated and mixed evenly to obtain a silica-alumina molecular sieve solution. The silica-aluminum molecular sieve includes one or a mixture of SBA-15, MCM-41 and ZSM-5; The modified additives include , and one or a mixture thereof of CoO; The mass ratio of the silica-alumina molecular sieve, the modified additive, and the solvent is (10~20):(1~5):

100.

9. The method according to claim 7, characterized in that, The volume ratio of the silica-alumina sol to the silica-alumina molecular sieve solution in the silica-alumina composite sol is (5~12):1; the coagulant is one or a mixture of two of propylene oxide or epichlorohydrin; the molar ratio of the aluminum alkoxide to the coagulant is 1:(5~12).

10. The method according to claim 5, characterized in that, The supercritical drying process employs supercritical carbon dioxide drying, using carbon dioxide as the drying medium. The reaction temperature is 45-65℃, the pressure inside the high-pressure reactor is 8-12MPa, the venting rate is 4-16L / min, and the drying time is 5-14h. The heat treatment temperature is 1000-1200℃, the heating rate is 1-5℃ / min, and the holding time is 1-4 hours.

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