A co-woven three-dimensional interpenetrating network reinforced aerogel composite material and a preparation method and application thereof

Abstract

The application provides a kind of co-woven three-dimensional interpenetrating network reinforced aerogel composite material and its preparation method and application.The composite material is composed of reinforced phase and matrix phase, the reinforced phase is three-dimensional interpenetrating network fiber felt prepared by integrated weaving or needling process, containing hollow fiber and solid quartz fiber, which are interpenetrated and entangled in three-dimensional space to form a continuous network skeleton;The matrix phase is silica-based aerogel filled and coated network pores.The preparation method includes the steps of forming, sol impregnation, gelation and aging, supercritical drying and other steps of co-woven preform, and can also include hydrophobic post-processing.The material has the characteristics of light weight, high strength, ultra-low thermal conductivity and excellent wave-transparent performance, and is suitable for hypersonic aircraft radome, antenna window, radar fairing and satellite communication wave-transparent components, which can meet the requirements of load bearing, heat insulation and wave-transparent integration.

Description

Technical Field

[0001] This invention relates to the field of advanced composite materials technology, and more specifically, to a co-woven three-dimensional interpenetrating network reinforced aerogel composite material, its preparation method, and its application. Background Technology

[0002] The rapid development of hypersonic vehicle technology has placed almost extreme demands on the integrated performance of its thermal protection and wave-transmitting components. Ideal component materials must simultaneously possess low density, high specific strength, ultra-low thermal conductivity, and a stable low dielectric constant and loss tangent across a wide temperature range. Silica aerogel, as one of the solid materials with the lowest known thermal conductivity, has attracted considerable attention for its super-insulating properties; however, its inherent brittleness and extremely low mechanical strength severely limit its direct application in load-bearing structural components.

[0003] To overcome the mechanical performance bottlenecks of aerogel materials, fiber reinforcement technology is considered an effective solution. Traditional fiber-reinforced aerogel composites typically employ a process where fiber preforms are directly impregnated into aerogel precursor sol. However, facing the high standards required for the synergistic optimization of "mechanical-thermal-electrical" performance in hypersonic vehicles, this simple physical composite or lamination method has gradually revealed its inherent limitations. The primary problem is that the interfacial bonding between the reinforcing fibers and the aerogel matrix is ​​usually weak, resulting in low load transfer efficiency and difficulty in fully utilizing the reinforcing and toughening effects of the fibers. Secondly, the distribution and orientation of fibers in three-dimensional space are difficult to precisely control, easily leading to significant anisotropy in the composite material's properties and the formation of structural weak points in local areas. More importantly, while the introduction of conventional solid quartz fibers improves toughness, it often inevitably and significantly increases the overall density and thermal conductivity of the composite material, which largely sacrifices the core thermal insulation advantage of aerogel as a matrix material. Therefore, there is an urgent need in this field to develop a novel reinforcement structure design and corresponding composite preparation process. This technology should be able to achieve a strong interfacial bond and efficient three-dimensional stress transfer between the reinforcing fiber and the matrix, based on the successful introduction of the reinforcing phase and significant improvement of the material's mechanical properties. Furthermore, through the fine design of the composition and spatial configuration of the reinforcing phase, the excellent thermal insulation and wave transmission properties of the aerogel matrix should be preserved to the maximum extent and even improved. Ultimately, the synergistic optimization of the material's comprehensive performance should be achieved to meet the urgent needs of high-end equipment applications. Summary of the Invention

[0004] The purpose of this invention is to provide a co-woven three-dimensional interpenetrating network reinforced aerogel composite material, its preparation method, and its application. This material has the characteristics of being lightweight and high-strength, having ultra-low thermal conductivity, and excellent wave transmission performance. It is suitable for hypersonic vehicle radomes, antenna windows, radar fairings, and satellite communication wave-transmitting components, and can synergistically meet the requirements of load-bearing, heat insulation, and wave transmission integration.

[0005] In a first aspect, the present invention provides a co-woven three-dimensional interpenetrating network reinforced aerogel composite material, which is composed of a reinforcing phase and a matrix phase;

[0006] The reinforcing phase is a three-dimensional interpenetrating network fiber structure, which is made by integrating hollow fibers and solid quartz fibers through a braiding or needle punching process, so that the hollow fibers and solid quartz fibers are intertwined and interwoven in three-dimensional space to form a continuous network skeleton.

[0007] The matrix phase is an aerogel material, which fills and encapsulates all the pores of the three-dimensional interpenetrating network structure.

[0008] The hollow fiber has a volume fraction of 10%-50% in the reinforcing phase to reduce the density of the composite material and improve its thermal insulation performance.

[0009] Preferably, the hollow fiber is selected from at least one of hollow ceramic fiber or hollow quartz fiber, the diameter of the solid quartz fiber is 5-20 μm, the inner diameter of the hollow fiber is 5-100 μm, and the wall thickness is 3-20 μm.

[0010] Preferably, the aerogel is a silica-based aerogel and has been treated with a hydrophobic modifier; more preferably, the hydrophobic modifier is a silane coupling agent containing organic functional groups, and the silane coupling agent is methyltrimethoxysilane or methyltriethoxysilane.

[0011] Secondly, the present invention provides a method for preparing the co-woven three-dimensional interpenetrating network reinforced aerogel composite material as described in any one of the above claims, comprising the following steps:

[0012] S1. Preparation of co-woven fiber preform: Hollow fibers and solid quartz fibers are integrated into a co-woven fiber preform with a predetermined geometric shape and pore structure by one or more of the following integrated forming processes: three-dimensional weaving, multi-layer needle punching and stitching, or blending into felt.

[0013] S2, Sol impregnation: The co-woven fiber preform is placed in a silica-based aerogel precursor sol and impregnated under vacuum or vacuum-pressure gradient assisted conditions to allow the sol to fully penetrate into the pores of the preform.

[0014] S3, Gelation and Aging: The impregnated sol undergoes a gelation reaction in a controlled temperature and humidity environment to form a wet gel complex, which is then aged in an alcohol solvent.

[0015] S4. Supercritical drying: Solvent replacement is performed on the aged wet gel composite, and then supercritical fluid drying technology is used to remove the liquid in the pores to obtain a co-woven three-dimensional interpenetrating network reinforced aerogel composite material.

[0016] Preferably, the specific method of vacuum-pressure gradient assisted impregnation in step S2 is as follows: first, the co-woven fiber preform is kept under a vacuum of -0.09MPa to -0.1MPa for 30-60 minutes, and then the sol is allowed to penetrate and pressure is maintained at 0.3-0.8MPa for 1-4 hours.

[0017] Preferably, in step S4, the supercritical fluid is liquid carbon dioxide, the drying conditions are 35-50℃, 8-12MPa, and the drying time is 6-36h.

[0018] Preferably, the preparation steps of the silica-based aerogel precursor sol in step S2, based on parts by weight, are as follows:

[0019] (1) Dissolve 10-20 parts of 3-methacryloxypropyltrimethoxysilane and 3-5 parts of vinyl-terminated polydimethylsiloxane in 60-70 parts of anhydrous toluene, add 0.1-0.3 parts of azobisisobutyronitrile, react in an oil bath at 63-67℃ for 10-12 hours under nitrogen protection, cool to room temperature, and obtain the prepolymer by vacuum distillation;

[0020] (2) Dissolve 20-30 parts of tetraethyl orthosilicate and 10-20 parts of silane coupling agent in 50-60 parts of anhydrous ethanol to obtain a silicon source solution; separately take 15-25 parts of deionized water, 1-3 parts of 0.5M HCl and 20-30 parts of anhydrous ethanol and mix them evenly to obtain an acidic aqueous solution. Slowly add the acidic aqueous solution to the silicon source solution at 1-2 ml / min at 400-450 rpm and stir the reaction at 48-52℃ for 6-8 h to obtain a co-hydrolyzed sol.

[0021] (3) Dissolve 5-10 parts of the prepolymer obtained in step (1) in 15-20 parts of anhydrous ethanol, and slowly add it to 30-40 parts of the cooled co-hydrolyzed sol at room temperature. Stir for 1-2 hours, then add 5-10 parts of deionized water and 0.5-1.5 parts of 0.1MHCl mixture, and continue stirring at 38-42℃ for 2-3 hours. Filter to obtain silica-based aerogel precursor sol.

[0022] Thirdly, the present invention also provides the application of the above-mentioned composite material in hypersonic vehicle radomes, antenna windows, radar fairings or satellite communication transparent components.

[0023] In summary, the present invention has the following beneficial effects:

[0024] 1. This invention constructs a reinforced skeleton with a three-dimensional interpenetrating network structure by integrating hollow fibers and solid quartz fibers through weaving or needle punching. This skeleton is then used as a carrier to composite silica-based aerogel, creating a composite material that integrates structure and function. The three-dimensional interpenetrating network skeleton design effectively overcomes the defects of weak interlayer bonding and easy delamination in traditional layered composite materials. The high tensile strength of the solid quartz fibers bears the main mechanical load, significantly improving the overall mechanical properties and structural integrity of the material. Simultaneously, the unique internal pore structure of the hollow fibers introduces a static air barrier, effectively extending the solid-phase heat conduction path while reducing the density of the reinforcing phase. This creates a synergistic thermal insulation effect with the aerogel matrix, achieving an organic unity of lightweight, high strength, ultra-low thermal conductivity, and excellent wave transmission performance. This meets the stringent requirements of load-bearing, thermal insulation, and wave transmission integration for components such as hypersonic vehicle radomes.

[0025] 2. The silica-based aerogel matrix precursor sol of the present invention is prepared by introducing compounds such as vinyl-terminated polydimethylsiloxane and 3-methacryloyloxypropyltrimethoxysilane with tetraethyl orthosilicate. This matrix, through the introduction of long-chain flexible segments and the construction of an organic-inorganic hybrid network structure, utilizes the energy dissipation mechanism of the flexible segments to effectively improve the inherent brittleness and low strength of traditional silica aerogels, significantly enhancing the fracture toughness of the matrix and its interfacial compatibility with the fiber-reinforced phase. Simultaneously, the hydrophobic groups introduced through molecular structure design endow the material with excellent hydrophobic and moisture-proof properties, avoiding the increase in dielectric constant and loss tangent caused by environmental moisture adsorption, ensuring the long-term stability of the dielectric properties of the material under complex climatic environments, and guaranteeing the electrical transmission efficiency of the wave-transparent components.

[0026] 3. The preparation method of this invention employs a combination of vacuum-pressure gradient-assisted sol impregnation and supercritical fluid drying. This process, through graded pressure control, forces the sol to overcome capillary resistance and deeply penetrate into the micropores and fiber bundles of the three-dimensional preform, achieving dense filling and all-round coating of the reinforcing skeleton by the aerogel matrix. This constructs a robust micro-interface bonding layer, effectively solving the interfacial defect problem caused by uneven penetration in traditional impregnation processes. Combined with supercritical fluid drying technology, the gas-liquid surface tension during the drying process is eliminated, maximizing the preservation of the integrity and high porosity of the aerogel nanoskeleton. Thus, while ensuring the material's mechanical strength, the excellent thermal insulation and wave transmission properties of the aerogel are fully preserved. Attached Figure Description

[0027] Figure 1 The image shows a SEM image of composite material sample 1 prepared in Example 1.

[0028] Figure 2 The image shows the SEM image of composite material sample 3 prepared in Example 3. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the experimental materials used, unless otherwise specified, were all purchased from conventional biochemical reagent stores. All quantitative experiments in the following examples were performed in triplicate, and the data are the average of the three replicates or the average ± standard deviation.

[0031] Hollow quartz fiber / solid quartz fiber, purchased from Anhui Yaoshi New Material Technology Co., Ltd.;

[0032] Ceramic fiber, purchased from Shandong Dongheng Guoxian New Material Co., Ltd.;

[0033] KBM-503, purchased from Guangzhou Soman Trading Co., Ltd., CAS No. 14814-09-6;

[0034] Vinyl-terminated polydimethylsiloxane, purchased from Hubei Guangao Biotechnology Co., Ltd., product number GA1248.

[0035] Unless otherwise specified, all parts mentioned in this invention are by mass; all concentrations and ratios mentioned are based on mass unless otherwise specified; all HCl concentrations mentioned are molar concentrations (mol / L).

[0036] Example 1

[0037] This embodiment provides a method for preparing a co-woven three-dimensional interpenetrating network reinforced aerogel composite material, using the following technical solution:

[0038] S1. Preparation of co-woven fiber preform

[0039] Short-cut hollow quartz fibers (20 μm inner diameter, 8 μm wall thickness, 15 mm length) and short solid quartz fibers (9 μm diameter, 15 mm length) were selected and uniformly mixed at a volume ratio of 3:7. KBM-503 (5% by weight of total fiber) and deionized water were added to prepare a slurry with a solid content of 15 wt%. The slurry was transferred to a high-speed disperser and stirred at 300 r / min for 20 min. Then, it was ultrasonically dispersed at 20 kHz and 80 W for 30 min. The dispersed slurry was evenly spread on the papermaking screen, dehydrated, pressed, and then the preform was placed in a box-type resistance furnace and heat-treated to 250℃ at 5℃ / min for 2 h. After natural cooling to room temperature, a felt-like co-woven fiber preform with a thickness of 8 mm and a porosity of 85% was obtained.

[0040] S2, Sol impregnation

[0041] (1) Dissolve 10 parts of 3-methacryloxypropyltrimethoxysilane and 3 parts of vinyl-terminated polydimethylsiloxane in 60 parts of anhydrous toluene, add 0.1 parts of azobisisobutyronitrile, react in an oil bath at 63°C for 12 hours under nitrogen protection, cool to room temperature, and obtain the prepolymer by vacuum distillation.

[0042] (2) Dissolve 20 parts of tetraethyl orthosilicate and 10 parts of methyltriethoxysilane in 50 parts of anhydrous ethanol to obtain a silicon source solution; separately take 15 parts of deionized water, 1 part of 0.5M HCl and 20 parts of anhydrous ethanol and mix them evenly to obtain an acidic aqueous solution. Add the acidic aqueous solution slowly dropwise to the silicon source solution at 1 ml / min at 400 rpm and stir at 48℃ for 8 h to obtain a co-hydrolyzed sol.

[0043] (3) Dissolve 5 parts of the prepolymer obtained in step (1) in 15 parts of anhydrous ethanol, and slowly add it to 30 parts of the cooled co-hydrolyzed sol at room temperature. Stir for 2 hours, then add 5 parts of deionized water and 0.5 parts of 0.1MHCl mixture, and continue stirring at 38°C for 3 hours. Filter to obtain silica-based aerogel precursor sol.

[0044] (4) Sol impregnation: The felt-like co-woven fiber preform prepared in step S1 is placed in a vacuum impregnation tank, and the vacuum is drawn to -0.1MPa. The vacuum is maintained for 40 minutes. During this period, the impregnation tank is slightly vibrated every 10 minutes to remove the residual air in the pores of the preform. Then, the silica-based aerogel precursor sol prepared above is injected into the impregnation tank through a pressure pump. After the injection is completed, the pressure is slowly increased to 0.3MPa and maintained for 4 hours.

[0045] S3, gelation and aging

[0046] The fully impregnated preform obtained in step S2, along with the sol, is removed and placed in an environment of 45°C and 80% relative humidity for 6 hours to complete the gelation reaction and form a wet gel composite. The wet gel composite is then transferred to anhydrous ethanol at 50°C, with the amount of ethanol being 3 times the volume of the wet gel composite. The mixture is then slowly stirred at 100 rpm and aged for 72 hours, with the anhydrous ethanol being replaced every 24 hours to ensure that the small molecule byproducts inside the gel are fully diffused and dissolved.

[0047] S4, Supercritical Drying

[0048] The aged wet gel composite was removed, excess ethanol on the surface was absorbed with filter paper, and it was transferred to a supercritical drying vessel. Liquid carbon dioxide was added as the drying medium, with the amount of liquid carbon dioxide being 80% of the effective volume of the vessel. The mixture was stirred at 80 rpm and dried at 40℃ and 10 MPa for 8 hours to obtain sample 1 of the co-woven three-dimensional interpenetrating network reinforced aerogel composite material.

[0049] Performance testing

[0050] The performance of sample 1 was tested, and the results are as follows: density is 0.48 g / cm³. 3 The sample exhibits excellent lightweight, thermal insulation, wave transmission, and mechanical properties, with a room temperature thermal conductivity of 0.018 W / (m•K), a three-point bending strength of 9.8 MPa, a dielectric constant of 1.38 at 10 GHz at room temperature, and a loss tangent of 0.003. Figure 1 The image shows the SEM image of the composite material sample 1 prepared in Example 1. As can be seen from the image, sample 1 forms a continuous three-dimensional interpenetrating network structure. Silica aerogel is uniformly filled in the pores of the fiber skeleton. The fibers and the aerogel matrix are tightly bonded with no obvious interface defects. The aerogel nanoporous structure is intact and there is no obvious collapse.

[0051] Example 2

[0052] This embodiment provides a method for preparing a co-woven three-dimensional interpenetrating network reinforced aerogel composite material, using the following technical solution:

[0053] S1. Preparation of co-woven fiber preform

[0054] Short-cut hollow quartz fibers (inner diameter 40μm, wall thickness 12μm, length 15mm) and short solid quartz fibers (diameter 9μm, length 15mm) are selected and uniformly mixed at a volume ratio of 3:7. The mixture is fed into a blending equipment, and after opening and carding, it is blended and twisted at 200 twists / meter to produce yarn. This blended yarn is used as the warp and weft yarns, and a three-dimensional weaving process is used to weave a three-dimensional woven co-woven fiber preform with a thickness of 12mm.

[0055] S2, Sol impregnation

[0056] (1) Dissolve 15 parts of 3-methacryloxypropyltrimethoxysilane and 4 parts of vinyl-terminated polydimethylsiloxane in 65 parts of anhydrous toluene, add 0.2 parts of azobisisobutyronitrile, react in an oil bath at 65°C for 11 h under nitrogen protection, cool to room temperature, and obtain the prepolymer by vacuum distillation.

[0057] (2) Dissolve 25 parts of tetraethyl orthosilicate and 15 parts of methyltrimethoxysilane in 55 parts of anhydrous ethanol to obtain a silicon source solution; separately take 20 parts of deionized water, 2 parts of 0.5MHCl and 25 parts of anhydrous ethanol and mix them evenly to obtain an acidic aqueous solution. Add the acidic aqueous solution slowly dropwise to the silicon source solution at 1.5 ml / min at 420 rpm and stir at 50 °C for 7 h to obtain a co-hydrolyzed sol.

[0058] (3) Dissolve 8 parts of the prepolymer obtained in step (1) in 18 parts of anhydrous ethanol, and slowly add it to 35 parts of the cooled co-hydrolyzed sol at room temperature. Stir for 1.5 h, then add 8 parts of deionized water and 1 part of 0.1M HCl mixture, and continue stirring at 40°C for 2.5 h. Filter to obtain silica-based aerogel precursor sol.

[0059] (4) Sol impregnation: The three-dimensional woven co-woven fiber preform prepared in step S1 is placed in a vacuum impregnation tank, and the vacuum is drawn to -0.1MPa. The vacuum is maintained for 38 minutes. During this period, the impregnation tank is slightly vibrated every 10 minutes to remove the residual air in the pores of the preform. Then, the silica-based aerogel precursor sol prepared above is injected into the impregnation tank through a pressure pump. After the injection is completed, the pressure is slowly increased to 0.4MPa and maintained for 3.8 hours.

[0060] S3, gelation and aging

[0061] The fully impregnated preform obtained in step S2, along with the sol, is removed and placed in an environment of 50°C and 70% relative humidity for 5 hours to complete the gelation reaction and form a wet gel composite. The wet gel composite is then transferred to a mixture of ethanol and n-hexane at a volume ratio of 7:3 at 45°C, with the volume of the mixture being 4 times the volume of the wet gel composite. The mixture is then slowly stirred at 120 rpm and aged for 48 hours, with anhydrous ethanol replaced every 16 hours to ensure that small molecule byproducts inside the gel are fully diffused and dissolved.

[0062] S4, Supercritical Drying

[0063] The aged wet gel composite was removed, excess ethanol on the surface was absorbed with filter paper, and it was transferred to a supercritical drying vessel. Liquid carbon dioxide was added as the drying medium, with the amount of liquid carbon dioxide being 85% of the effective volume of the vessel. The mixture was stirred at 100 rpm and dried at 40°C and 10 MPa for 8 hours to obtain sample 2 of the co-woven three-dimensional interpenetrating network reinforced aerogel composite material.

[0064] Performance testing

[0065] The performance of sample 2 was tested, and the results are as follows: density is 0.55 g / cm³. 3 The sample has a thermal conductivity of 0.017 W / (m•K) at room temperature, a three-point bending strength of 11.2 MPa, and a dielectric constant of 1.42 at 10 GHz at room temperature, indicating that the sample is lightweight and has excellent hydrophobic, thermal insulation, wave transmission and higher mechanical strength.

[0066] Example 3

[0067] This embodiment provides a method for preparing a co-woven three-dimensional interpenetrating network reinforced aerogel composite material, using the following technical solution:

[0068] S1. Preparation of co-woven fiber preform

[0069] Short-cut hollow quartz fibers (inner diameter 40μm, wall thickness 12μm, length 15mm) and short solid quartz fibers (diameter 9μm, length 15mm) were selected and uniformly mixed at a volume ratio of 3:7. The mixture was then fed into a nonwoven fabric forming device to prepare two layers of blended nonwoven fabric with a thickness of 3mm. At the same time, a plain weave quartz fiber cloth with a thickness of 2mm was selected as the middle layer. The two layers of blended nonwoven fabric were used as the upper and lower surface layers, respectively, and the plain weave quartz fiber cloth was used as the middle layer. They were stacked to form a "sandwich" structure preform, which was then fed into a needle punching device for needle punching reinforcement to obtain a needle-punched co-woven fiber preform with a thickness of 10mm.

[0070] S2, Sol impregnation

[0071] (1) Dissolve 20 parts of 3-methacryloxypropyltrimethoxysilane and 5 parts of vinyl-terminated polydimethylsiloxane in 70 parts of anhydrous toluene, add 0.3 parts of azobisisobutyronitrile, react in an oil bath at 67°C for 10 h under nitrogen protection, cool to room temperature, and obtain the prepolymer by vacuum distillation.

[0072] (2) Dissolve 30 parts of tetraethyl orthosilicate and 20 parts of silane coupling agent in 60 parts of anhydrous ethanol to obtain a silicon source solution; separately take 25 parts of deionized water, 3 parts of 0.5M HCl and 30 parts of anhydrous ethanol and mix them evenly to obtain an acidic aqueous solution. Add the acidic aqueous solution slowly dropwise to the silicon source solution at 2 ml / min at 450 rpm and stir at 52℃ for 6 h to obtain a co-hydrolyzed sol.

[0073] (3) Dissolve 10 parts of the prepolymer obtained in step (1) in 20 parts of anhydrous ethanol, and slowly add it to 40 parts of the cooled co-hydrolyzed sol at room temperature. Stir for 1 hour, then add 10 parts of deionized water and 1.5 parts of 0.1MHCl mixture, and continue stirring at 42°C for 2 hours. Filter to obtain silica-based aerogel precursor sol.

[0074] The subsequent processes, namely sol impregnation, gelation, aging and supercritical drying, were performed according to the parameters of Example 1 to obtain sample 3 of co-woven three-dimensional interpenetrating network reinforced aerogel composite material.

[0075] Performance testing

[0076] The performance of sample 3 was tested, and the results are as follows: density is 0.55 g / cm³. 3 The room temperature thermal conductivity is 0.019 W / (m•K), the three-point bending strength is 10.2 MPa, and the dielectric constant at 10 GHz at room temperature is 1.32. High-temperature performance: After heat treatment in air at 1000℃ for 1 hour, its bending strength retention rate is 82%, and its thermal conductivity at 1000℃ is 0.052 W / (m·K), demonstrating good high-temperature stability. Figure 2 The image shows the SEM image of the composite material sample 3 prepared in Example 3. As can be seen from the image, the needle-punched co-woven fiber preform forms a denser three-dimensional interpenetrating network structure, the fiber entanglement is more complete, the aerogel matrix is ​​uniformly coated on the fiber surface and completely fills the pores, and the nanoporous structure is well maintained, ensuring the excellent mechanical properties and high-temperature stability of the material.

[0077] Comparative Example 1

[0078] The difference from Example 1 is that only the fiber raw material composition of the preform preparation step S1 is different. Short-cut hollow quartz fibers are not used. Instead, short solid quartz fibers of the same specification as those in step S1 of Example 1 and with the same total feed weight are used. Pure quartz fiber felt is prepared as the preform using the same method and heat treatment curing process as in step S1 of Example 1. Except for the above differences, the raw material formulation, process parameters and operating conditions of the remaining steps S2-S4 are exactly the same as those in Example 1.

[0079] Performance testing

[0080] The density of the prepared sample C1 was tested and found to be 0.58 g / cm³. 3The room temperature thermal conductivity is 0.033 W / (m•K), and the three-point bending strength is 14.2 MPa. Compared with Example 1, although the bending strength of Comparative Example 1 is slightly improved (because the strength of solid quartz fiber is higher than that of hollow fiber), its density is significantly increased, and its thermal conductivity is significantly increased. This indicates that although the introduction of hollow fiber sacrifices a little ultimate strength, it significantly reduces the overall thermal conductivity of the material and reduces its weight by utilizing the heat-insulating effect of the static air layer in its cavity, thus achieving a balance between lightweight and thermal insulation.

[0081] Comparative Example 2

[0082] The difference from Example 1 lies only in the structural form of the fiber preform. Instead of using the co-weaving process of uniformly mixing hollow quartz fibers and solid quartz fibers, pure hollow quartz fiber felt and pure solid quartz fiber felt are prepared separately, and then the two layers of felt are simply physically stacked to obtain the preform. The raw material specifications, total volume ratio, total feed mass of the two fibers, the slurry formula for single felt preparation, the heat treatment curing process parameters, and the total thickness and porosity of the final preform are all completely consistent with step S1 of Example 1. Except for the above differences, the raw material formula, process parameters and operating conditions of the remaining steps S2-S4 are completely the same as those of Example 1.

[0083] Performance testing

[0084] The density of the prepared sample C2 was tested and found to be 0.50 g / cm³. 3 The thermal conductivity at room temperature is 0.026 W / (m•K), and the three-point bending strength is 6.5 MPa. The bending strength of Comparative Example 2 is significantly lower than that of Example 1. This is because the simple physical lamination cannot form an effective interpenetrating fiber network in the Z direction, resulting in weak interfacial bonding between the hollow fiber layer and the solid quartz fiber layer, as well as between the fiber and the aerogel matrix. The load cannot be efficiently transferred in three-dimensional space, and interlayer delamination is very likely to occur. This confirms the necessity of the "co-woven three-dimensional interpenetrating network" of the present invention for improving the overall structural integrity.

[0085] Comparative Example 3

[0086] The only difference from Example 1 is the drying process in step S4. Instead of supercritical carbon dioxide fluid drying, the aged wet gel composite is pretreated in the same way as in Example 1 and then placed in an 80°C forced-air drying oven for atmospheric pressure heat drying for 48 hours. Apart from the difference in the drying process, the raw material formulation, process parameters, operating conditions, and sample pretreatment methods in the remaining steps S1-S3 are exactly the same as in Example 1.

[0087] Performance testing

[0088] The prepared sample C3 was tested and found to have a density as high as 0.92 g / cm³. 3The thermal conductivity at room temperature deteriorated to 0.088 W / (m•K), the three-point bending strength was 9.1 MPa, and the dielectric constant at 10 GHz at room temperature increased to 2.0. During atmospheric pressure drying, the capillary tension at the gas-liquid interface caused the collapse of the fragile nanostructure of the aerogel, resulting in a sharp decrease in porosity and the loss of the aerogel's unique ultra-low density and thermal insulation properties. This demonstrates the irreplaceable role of supercritical drying in the preparation method of this invention.

[0089] Comparative Example 4

[0090] The only difference from Example 1 is the preparation process of the silica-based aerogel precursor sol. The synthesis step of the prepolymer containing a specific organic functional group in step (1) of step S2 in Example 1 is omitted. Instead of adding the prepolymer to the co-hydrolyzed sol, methyltrimethoxysilane (MTMS) with the same mass as the prepolymer in Example 1 is added in the silicon source solution preparation step to prepare the co-hydrolyzed sol. Apart from the core difference in sol preparation, the raw material formulation, process parameters, operating conditions of the other steps S1, S3, and S4, as well as the total amount of solvent, acid, reaction temperature, reaction time, and impregnation process in the sol preparation process are completely the same as in Example 1.

[0091] Performance testing

[0092] The density of the prepared sample C4 was tested to be 0.47 g / cm³. 3 Its room temperature thermal conductivity is 0.019 W / (m•K), but its three-point bending strength is only 7.1 MPa. Due to the lack of introduction of long-chain flexible segments and chemical coupling effects of active organic functional groups in specific silicon-containing precursors, although the nanoporous structure can be retained by supercritical drying process, thus maintaining low density and thermal conductivity, its mechanical properties, especially bending strength, are significantly degraded.

[0093] Experimental Results Analysis

[0094] The results of Examples 1-3 demonstrate that the "co-woven fiber mat reinforcement" method described in this invention successfully prepared a composite material with excellent comprehensive performance. Compared to Comparative Example 1 (C1, without hollow fibers), the material of this invention achieves a significant improvement in thermal insulation performance while sacrificing minor mechanical properties. Compared to Comparative Example 2 (C2, non-co-woven laminate), at similar density and thermal insulation levels, the material of this invention exhibits higher mechanical properties due to its superior reinforcement structure, proving the advantages of the "co-woven" structure in optimizing interfaces and load transfer. The comparison with Comparative Example 3 (C3, unconventional drying) highlights the irreplaceable role of supercritical drying technology in preserving the aerogel nanostructure to obtain superior thermal insulation and low dielectric properties. Compared to Comparative Example 4 (C4, without specific group precursors), this invention achieves significantly higher mechanical strength while maintaining ultra-low density and thermal conductivity. This clarifies that the present invention fundamentally improves the intrinsic brittleness of the matrix by synthesizing a hybrid precursor containing a long-chain flexible organosiloxane segment in the sol molecule design and chemically bonding it with an inorganic network, thereby achieving matrix toughening and interface strengthening.

[0095] In summary, this invention, through its innovative "co-woven" reinforcement structure design and optimized composite process, effectively solves the problems of low strength of aerogel materials and the damage to their thermal insulation advantages caused by traditional reinforcement methods, providing a highly promising integrated thermal protection and wave transmission material solution for cutting-edge fields such as hypersonic vehicles.

[0096] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A co-woven three-dimensional interpenetrating network reinforced aerogel composite material, characterized in that, It is composed of a reinforcing phase and a matrix phase; The reinforcing phase is a three-dimensional interpenetrating network fiber structure, which is made by integrating hollow fibers and solid quartz fibers through a braiding or needle punching process, so that the hollow fibers and solid quartz fibers are intertwined and interwoven in three-dimensional space to form a continuous network skeleton. The matrix phase is an aerogel material, which is a silica-based aerogel that fills and encapsulates all the pores of the three-dimensional interpenetrating network fiber structure. The hollow fiber has a volume fraction of 10%-50% in the reinforcing phase to reduce the density of the composite material and improve its thermal insulation performance. The preparation steps of the silica-based aerogel precursor sol are as follows: (1) Dissolve 3-methacryloxypropyltrimethoxysilane and vinyl-terminated polydimethylsiloxane in anhydrous toluene, add azobisisobutyronitrile, react in an oil bath under nitrogen protection, cool to room temperature, and then distill under reduced pressure to obtain the prepolymer. (2) Dissolve tetraethyl orthosilicate and silane coupling agent in anhydrous ethanol to obtain a silicon source solution; separately, mix deionized water, dilute hydrochloric acid and anhydrous ethanol evenly to obtain an acidic aqueous solution, slowly add the acidic aqueous solution to the silicon source solution, and react with stirring to obtain a co-hydrolyzed sol; (3) Dissolve the prepolymer in anhydrous ethanol, slowly add it to the cooled co-hydrolyzed sol at room temperature and stir, then add a mixture of deionized water and dilute hydrochloric acid, continue stirring, and filter to obtain silica-based aerogel precursor sol.

2. The co-woven three-dimensional interpenetrating network reinforced aerogel composite material according to claim 1, characterized in that, The hollow fiber is selected from at least one of hollow ceramic fiber or hollow quartz fiber, and the diameter of the solid quartz fiber is 5-20 μm; the inner diameter of the hollow fiber is 5-100 μm and the wall thickness is 3-20 μm.

3. The co-woven three-dimensional interpenetrating network reinforced aerogel composite material according to claim 1, characterized in that, The aerogel is a silica-based aerogel and has been treated with a hydrophobic modifier; the hydrophobic modifier is a silane coupling agent containing organic functional groups, and the silane coupling agent is methyltrimethoxysilane or methyltriethoxysilane.

4. A method for preparing a co-woven three-dimensional interpenetrating network reinforced aerogel composite material as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Preparation of co-woven fiber preform: Hollow fibers and solid quartz fibers are combined through one or more integrated forming processes, such as three-dimensional weaving, multi-layer needle punching and sewing, or blending into felt, to make a co-woven fiber preform. S2, Sol impregnation: The co-woven fiber preform is placed in a silica-based aerogel precursor sol and impregnated under vacuum or vacuum-pressure gradient assisted conditions to allow the sol to penetrate into the pores of the preform at all levels. S3, Gelation and Aging: The impregnated sol undergoes a gelation reaction in a controlled temperature and humidity environment to form a wet gel complex, which is then aged in an alcohol solvent. S4. Supercritical drying: Solvent replacement is performed on the aged wet gel composite, and then supercritical fluid drying technology is used to remove the liquid in the pores to obtain a co-woven three-dimensional interpenetrating network reinforced aerogel composite material.

5. The method for preparing the co-woven three-dimensional interpenetrating network reinforced aerogel composite material according to claim 4, characterized in that, The specific method for vacuum-pressure gradient assisted impregnation in step S2 is as follows: first, the co-woven fiber preform is kept under a vacuum of -0.09MPa to -0.1MPa for 30-60 minutes, and then the sol is allowed to penetrate and pressure is maintained at 0.3-0.8MPa for 1-4 hours.

6. The method for preparing the co-woven three-dimensional interpenetrating network reinforced aerogel composite material according to claim 4, characterized in that, In step S4, the supercritical fluid is liquid carbon dioxide, and the drying conditions are 35-50℃, 8-12MPa, and drying time is 6-36h.

7. The application of the co-woven three-dimensional interpenetrating network reinforced aerogel composite material according to any one of claims 1-3 in hypersonic vehicle radomes, antenna windows, radar radomes, or satellite communication transparent components.

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