Hollow fiber reinforced aerogel composites and methods of making the same

Abstract

The application provides a hollow fiber reinforced aerogel composite material and a preparation method thereof, and relates to the field of aerogel materials.The preparation method of the hollow fiber reinforced aerogel composite material comprises the following steps: preparing an aluminum-silicon sol, modifying and compounding, vacuum impregnation, gel aging and supercritical drying.The hollow fiber reinforced aerogel composite material and the preparation method thereof can effectively improve the sound insulation performance of the aerogel material, and simultaneously improve the strength, toughness and heat insulation performance of the aerogel material under the premise of overcoming the existing defects of the aerogel material (the defects of the porous structure of the aerogel itself, the weak binding force between the aerogel particles and the thermal stress caused by the mismatch of the thermal expansion coefficients of the aluminum-silicon components).

Description

Technical Field

[0001] This invention relates to the field of aerogel materials, and in particular to a hollow fiber reinforced aerogel composite material and its preparation method. Background Technology

[0002] With the continuous advancement and development of science and technology, the flight speed of aircraft is constantly improving. Achieving takeoff, acceleration, cruise, and maneuvering requires overcoming the aircraft's own gravity and drag generated by various factors. Aircraft engines convert energy into controllable thrust and power, and their performance significantly impacts the aircraft's flight speed, payload, and endurance. However, during engine operation, the core engine temperature can exceed 1000℃, causing varying degrees of thermal damage to the surrounding fuselage and precision equipment areas. Simultaneously, aerodynamic noise, combustion noise, and mechanical noise generated by unstable airflow can induce structural resonance, further threatening equipment safety. Therefore, the thermal insulation performance of the engine heat shield is particularly important during aircraft flight. Furthermore, in aircraft engine nacelles and special vibration-sensitive operating scenarios, utilizing heat shields for auxiliary noise reduction further leverages the multifunctionality of the materials.

[0003] Aerogel materials are nanoporous materials that combine lightweight, temperature resistance, and thermal insulation properties. Their lightweight nature allows them to reduce weight by more than 50% compared to traditional insulation materials, saving significant space. Furthermore, their porous structure not only reduces heat conduction between the solid and gas phases but also absorbs mid-to-high frequency sound waves, demonstrating excellent sound absorption and noise reduction effects. In the field of oxide aerogel materials, aluminosilicate aerogels can withstand temperatures up to 1200℃, exhibiting good temperature resistance and thermal insulation performance. However, due to the porous structure of aluminosilicate aerogels, the weak bonding between aerogel particles, and the thermal stress caused by the mismatch in the thermal expansion coefficients of the aluminum and silicon components, the strength of aerogel materials is relatively weak, limiting their application in the aerospace materials field.

[0004] Meanwhile, existing aerogel materials have poor sound insulation performance. When used as thermal insulation materials in the aerospace field, their effect on blocking aircraft noise is limited, and they cannot effectively prevent noise from entering the aircraft cabin or equipment areas. Existing sound insulation treatment methods for aerogel materials affect their strength, toughness, and thermal insulation performance, failing to simultaneously improve these properties while effectively enhancing their sound insulation performance.

[0005] Therefore, a hollow fiber reinforced aerogel composite material and its preparation method are provided. Under the premise of overcoming the existing defects of aerogel materials (the porous structure defects of aerogel itself, the weak bonding force between aerogel particles, and the thermal stress caused by the mismatch of the thermal expansion coefficients of aluminum and silicon components), the sound insulation performance of aerogel materials can be effectively improved, and the strength, toughness and thermal insulation performance of aerogel materials can be improved simultaneously. It has important technical significance and research value. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a hollow fiber reinforced aerogel composite material and its preparation method. Under the premise of overcoming the existing defects of aerogel materials (the porous structure defects of aerogel itself, the weak bonding force between aerogel particles, and the thermal stress caused by the mismatch of the thermal expansion coefficients of aluminum and silicon components), it can effectively improve the sound insulation performance of aerogel materials, and simultaneously improve the strength, toughness and thermal insulation performance of aerogel materials.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a hollow fiber reinforced aerogel composite material includes the following steps: preparing aluminosilicate sol, modifying and compositing, vacuum impregnation, gel aging, and supercritical drying;

[0009] The method for preparing aluminum silica sol is as follows: aluminum chloride hexahydrate is mixed with anhydrous ethanol and deionized water to obtain an aluminum source solution; tetraethyl orthosilicate is mixed with anhydrous ethanol and deionized water to obtain a silicon source solution; and the aluminum source solution and silicon source solution are mixed to obtain aluminum silica sol.

[0010] The modified composite method is as follows: nano-aluminum titanate is heat-treated to obtain pretreated aluminum titanate; the pretreated aluminum titanate and deionized water are added to anhydrous ethanol, mixed evenly, the pH is adjusted to 8.5-9.5, the temperature is raised to 48-52℃, and tetraethyl orthosilicate solution is added dropwise while maintaining the temperature. After the addition is complete, the mixture is kept warm and stirred. A solid is obtained by separation, and the solid is washed and dried to obtain coated aluminum titanate; the coated aluminum titanate and nano-zirconia are added to aluminosilicate sol and mixed evenly to obtain a modified composite sol.

[0011] The vacuum impregnation method involves pressing hollow alumina fibers into hollow fiber felts, and then using a modified composite sol containing an initiator to vacuum impregnate the hollow fiber felts to obtain an impregnated body.

[0012] The impregnated body is subjected to gel aging and supercritical drying to obtain a hollow fiber reinforced aerogel composite material.

[0013] Preferably, the molar ratio of aluminum chloride hexahydrate, anhydrous ethanol, and deionized water used in the aluminum source solution is 3-3.1:15-17:55-60.

[0014] The silicon source solution uses tetraethyl orthosilicate, anhydrous ethanol, and deionized water in a molar ratio of 1-1.2:5-6:5-6.

[0015] In the mixing of the aluminum source solution and the silicon source solution, the molar ratio of aluminum chloride hexahydrate to tetraethyl orthosilicate is controlled to be 3-3.1:1-1.2.

[0016] Preferably, in the modified composite, the weight ratio of pretreated aluminum titanate to anhydrous ethanol is 1:70-75;

[0017] The volume of deionized water added is 3.5-4% of the volume of anhydrous ethanol;

[0018] The weight ratio of tetraethyl orthosilicate to nano-aluminum titanate in the tetraethyl orthosilicate solution is 0.18-0.21:1;

[0019] The weight ratio of coated aluminum titanate, nano-zirconia, and aluminum silica sol is 4.8-5.5:3.4-4.2:100.

[0020] Preferably, in the modified composite, the tetraethyl orthosilicate solution is an ethanol solution of tetraethyl orthosilicate with a concentration of 2.5-2.8 wt%;

[0021] The dropping rate of the tetraethyl orthosilicate solution is 0.4-0.5 mL / min;

[0022] After the tetraethyl orthosilicate solution has been added dropwise, continue to keep warm and stir for 5-6 hours.

[0023] Furthermore, in the modified composite, the nano-aluminum titanate is heat-treated at 110-120℃ for 1-2 hours to obtain pretreated aluminum titanate;

[0024] The particle size of the nano-aluminum titanate is 50-60 nm;

[0025] The nano-zirconia has a particle size of 20-30 nm.

[0026] Furthermore, the vacuum impregnation method is as follows: after pressing hollow alumina fibers into hollow fiber felt, the hollow fiber felt together with the mold is placed in a vacuum impregnation tank. In a vacuum environment at room temperature, the hollow fiber felt is vacuum impregnated for 30-40 minutes using a modified composite sol containing an initiator to obtain an impregnated body.

[0027] The initiator is propylene oxide; the molar ratio of the initiator to the modified composite sol using aluminum chloride hexahydrate is 1:3-5.

[0028] Furthermore, the gel aging method is as follows: after the impregnated body is kept in a temperature environment of 48-52℃ for gelation, it is completely immersed in anhydrous ethanol and allowed to stand for aging at a temperature of 48-52℃ to obtain the composite.

[0029] Preferably, during the gel aging process, the gel holding time is 3-5 hours;

[0030] The aging time is 72-96 hours.

[0031] During the static aging process, replace the ethanol with anhydrous ethanol every 10-12 hours.

[0032] Furthermore, the supercritical drying method involves, after the impregnated body undergoes gel aging to obtain a composite, controlling the supercritical drying temperature at 270-280℃ and the pressure at 8-9MPa, and subjecting the composite to supercritical drying for 2-4 hours to obtain a hollow fiber reinforced aerogel composite material.

[0033] A hollow fiber reinforced aerogel composite material is prepared using the aforementioned preparation method.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) The method for preparing hollow fiber reinforced aerogel composite material of the present invention uses specific aluminum and silicon sources to prepare aluminosilicate sol; in the modification and composite step, a silica layer is coated on the surface of nano-aluminum titanate in an in-situ coating manner to obtain coated aluminum titanate; the filling effect of nanoparticles (coated aluminum titanate, nano-zirconia) blocks the crack propagation path, improves the porous structure defects of aerogel, and improves the mechanical properties of composite material; at the same time, the bonding effect between aerogel particles is further improved by the bonding effect between coated aluminum titanate and the active groups of aluminosilicate sol; and by combining coated aluminum titanate, nano-zirconia and aluminosilicate sol to prepare modified composite sol, the near-zero expansion of coated aluminum titanate offsets the base The shrinkage effect of nano-zirconia further compensates for thermal expansion, and the overall coordination buffers the interfacial stress, realizing thermal stress buffering, effectively improving the thermal expansion matching of aluminum-silicon components, and improving the temperature resistance of aerogel composites. Then, hollow alumina fibers are pressed into hollow fiber felts, and the hollow fiber felts are vacuum impregnated with a modified composite sol containing an initiator. After gel aging and supercritical drying, hollow fiber reinforced aerogel composites are obtained. By combining hollow fibers with composite aluminum-silicon aerogels, the mechanical properties of aerogel composites are further improved. At the same time, the acoustic resonance and scattering effect of hollow fibers can scatter and absorb sound waves, giving aerogel composites excellent sound insulation properties.

[0036] (2) The hollow fiber reinforced aerogel composite material of the present invention has a compressive strength of 0.18-0.20 MPa, a flexural strength of 1.4-1.6 MPa, and a coefficient of thermal expansion of 1.09-1.13 × 10⁻⁶ MPa. -6The thermal conductivity at room temperature is 0.025-0.026 W / m·K, and at 800℃ it is 0.036-0.039 W / m·K. The sound transmission loss is 42-45 dB, and the number of thermal shock cycles is 52-57.

[0037] (3) The preparation method of the hollow fiber reinforced aerogel composite material of the present invention has a simple process flow, is easy to control, has high production safety, and is conducive to large-scale production.

[0038] (4) The hollow fiber reinforced aerogel composite material of the present invention has the properties of high temperature resistance, high strength, heat insulation and sound insulation, which can give full play to the multifunctionality of aerogel materials and further expand the application scenarios of aerogel composite materials. Detailed Implementation

[0039] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] 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 exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. 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, devices, components, and / or combinations thereof.

[0041] This invention provides a method for preparing hollow fiber reinforced aerogel composite material, comprising the following steps: preparing aluminosilicate sol, modifying and compositing, vacuum impregnation, gel aging, and supercritical drying.

[0042] The method for preparing aluminum-silica sol is as follows: using inorganic aluminum salt and silanol salt precursors as aluminum source (aluminum chloride hexahydrate) and silicon source (tetraethyl orthosilicate), respectively, a certain amount of aluminum source and silicon source are mixed with a certain proportion of anhydrous ethanol and deionized water, and stirred for 30-50 min to prepare aluminum source solution and silicon source solution; after mixing the aluminum source solution and silicon source solution, stirring is continued for 30-50 min to form a uniformly mixed aluminum-silica sol for later use.

[0043] In this embodiment of the invention, preferably, the molar ratio of aluminum chloride hexahydrate, anhydrous ethanol, and deionized water used in the preparation of the aluminum source solution is 3-3.1:15-17:55-60.

[0044] In this embodiment of the invention, preferably, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, and deionized water used in the preparation of the silicon source solution is 1-1.2:5-6:5-6.

[0045] In this embodiment of the invention, preferably, the molar ratio of aluminum chloride hexahydrate to tetraethyl orthosilicate is controlled to be 3-3.1:1-1.2 in the mixing of aluminum source solution and silicon source solution.

[0046] The modified composite method involves placing nano-aluminum titanate with a particle size of 50-60 nm in a constant temperature chamber and maintaining it at 110-120℃ for 1-2 hours, then cooling it to obtain pretreated aluminum titanate. The pretreated aluminum titanate is then added to 70-75 times its weight of anhydrous ethanol, ultrasonically dispersed for 5-15 minutes, and then deionized water is added and mixed thoroughly. The pH is then adjusted to 8.5-9.5 using 25-28 wt% ammonia solution, and the mixture is stirred and heated to 48-52℃ and maintained at that temperature. The temperature is maintained at 0.4-0. Add tetraethyl orthosilicate solution dropwise at a rate of 5 mL / min. After the addition is complete, keep the mixture at 48-52℃ and stir for 5-6 hours. Centrifuge to obtain solids, wash the solids 2-3 times with anhydrous ethanol, place them in a vacuum drying oven, and dry them at 50-55℃ to constant weight under a vacuum of 0.07-0.08 MPa to obtain coated aluminum titanate. Then, add coated aluminum titanate and nano-zirconia (particle size 20-30 nm) into the aluminosilicate sol and disperse them evenly by ultrasonication to obtain the modified composite sol.

[0047] In this embodiment of the invention, preferably, the volume of deionized water added is 3.5-4% of the volume of anhydrous ethanol.

[0048] In this embodiment of the invention, the tetraethyl orthosilicate solution is an ethanol solution of tetraethyl orthosilicate with a concentration of 2.5-2.8 wt%; preferably, the weight ratio of tetraethyl orthosilicate to nano-aluminum titanate in the tetraethyl orthosilicate solution is 0.18-0.21:1.

[0049] In this embodiment of the invention, the weight ratio of coated aluminum titanate, nano-zirconia, and aluminosilicate sol is 4.8-5.5:3.4-4.2:100.

[0050] The vacuum impregnation method is as follows: hollow alumina fibers are pressed into hollow fiber felt using a mold, and then the hollow fiber felt together with the mold is placed into a vacuum impregnation tank. After the vacuum impregnation tank is evacuated using a vacuum pump, the initiator is added to the modified composite sol and mixed evenly, and then siphoned into the vacuum impregnation tank. The modified composite sol is controlled to completely impregnate the hollow fiber felt. The vacuum environment is maintained at room temperature for 30-40 minutes to complete the impregnation process and obtain the impregnated body.

[0051] In this embodiment of the invention, the initiator is propylene oxide; preferably, the molar ratio of the initiator to the modified composite sol using aluminum chloride hexahydrate is 1:3-5.

[0052] In this embodiment of the invention, the liquid level of the modified composite sol is 1.2-1.6 times the thickness of the hollow fiber felt.

[0053] The gel aging method is as follows: the impregnated body and the mold are placed in an oven and heated to 48-52°C. After the gel is kept warm for 3-5 hours, the mold with the impregnated body is removed from the gel and completely immersed in anhydrous ethanol. The gel is then allowed to stand for 72-96 hours at a temperature of 48-52°C, and the anhydrous ethanol is replaced every 10-12 hours during the aging process. After aging is completed, the composite is obtained.

[0054] In this embodiment of the invention, the liquid level of anhydrous ethanol is controlled to be 1.5-2 times the thickness of the impregnated body during the aging process.

[0055] The supercritical drying method involves placing the composite along with the mold into a supercritical drying reactor, controlling the supercritical drying temperature at 270-280℃ and the pressure at 8-9MPa, and performing supercritical drying for 2-4 hours; after supercritical drying is completed, the temperature is lowered, the mold is removed, and hollow fiber reinforced aerogel composite material is obtained.

[0056] In the preparation of hollow fiber reinforced aerogel composites, this invention utilizes specific aluminum and silicon sources to prepare aluminosilicate sol. In the modification and composite step, a silica layer is coated onto the surface of nano-aluminum titanate in an in-situ coating manner to obtain coated aluminum titanate. The filling effect of nanoparticles (coated aluminum titanate and nano-zirconia) blocks crack propagation paths, improves the porous structure defects of the aerogel, and enhances the mechanical properties of the composite material. Simultaneously, the bonding effect between the coated aluminum titanate and the active groups of the aluminosilicate sol further improves the interparticle bonding performance of the aerogel. Furthermore, by combining coated aluminum titanate, nano-zirconia, and the aluminosilicate sol to form a modified composite sol, the near-zero expansion of the coated aluminum titanate offsets the matrix. The shrinkage effect of nano-zirconia further compensates for thermal expansion, and the overall coordination buffers the interfacial stress, realizing thermal stress buffering, effectively improving the thermal expansion matching of aluminum-silicon components, and improving the temperature resistance of aerogel composites. Then, hollow alumina fibers are pressed into hollow fiber felts, and the hollow fiber felts are vacuum impregnated with a modified composite sol containing an initiator. After gel aging and supercritical drying, hollow fiber reinforced aerogel composites are obtained. By combining hollow fibers with composite aluminum-silicon aerogels, the mechanical properties of aerogel composites are further improved. At the same time, the acoustic resonance and scattering effect of hollow fibers can scatter and absorb sound waves, giving aerogel composites excellent sound insulation properties.

[0057] This invention also provides a hollow fiber reinforced aerogel composite material, which is prepared using the aforementioned preparation method.

[0058] The present invention will be further described below with reference to some specific embodiments.

[0059] Example 1

[0060] This embodiment provides a method for preparing hollow fiber reinforced aerogel composite materials, specifically as follows:

[0061] 1. Preparation of aluminum silica sol

[0062] Using inorganic aluminum salt and silanolate precursors as aluminum source (aluminum chloride hexahydrate) and silicon source (tetraethyl orthosilicate), respectively, a certain amount of aluminum source and silicon source were mixed with a certain proportion of anhydrous ethanol and deionized water, and stirred for 30 min each to prepare aluminum source solution and silicon source solution. The aluminum source solution and silicon source solution were mixed and stirred for another 30 min to form a uniformly mixed aluminum-silicon sol for later use.

[0063] In the preparation of the aluminum source solution, the molar ratio of aluminum chloride hexahydrate, anhydrous ethanol, and deionized water is 3:15:55.

[0064] In the preparation of the silicon source solution, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, and deionized water is 1:5:5.

[0065] In the mixing of aluminum source solution and silicon source solution, the molar ratio of aluminum chloride hexahydrate to tetraethyl orthosilicate is controlled at 3:1.

[0066] 2. Modified composite

[0067] Nano-sized aluminum titanate with a particle size of 50 nm was placed in a constant temperature chamber and kept at 110 °C for 2 h. After cooling, pretreated aluminum titanate was obtained. Then, the pretreated aluminum titanate was added to 70 times its weight of anhydrous ethanol and ultrasonically dispersed for 5 min. Deionized water was added and mixed evenly. The pH was then adjusted to 9 with 25 wt% ammonia water, and the mixture was stirred and heated to 48 °C and kept at that temperature. Tetraethyl orthosilicate solution was added dropwise at a rate of 0.4 mL / min. After the addition was complete, the mixture was kept at 48 °C and stirred for 5 h. The solid was obtained by centrifugation and washed three times with anhydrous ethanol. The solid was then placed in a vacuum drying oven and dried at 55 °C to constant weight under a vacuum of 0.07 MPa to obtain coated aluminum titanate. Then, coated aluminum titanate and nano-zirconia (particle size of 20 nm) were added to an aluminosilicate sol and ultrasonically dispersed evenly to obtain a modified composite sol.

[0068] The volume of deionized water added is 3.5% of the volume of anhydrous ethanol.

[0069] The tetraethyl orthosilicate solution is an ethanolic solution of tetraethyl orthosilicate with a concentration of 2.5 wt%; the weight ratio of tetraethyl orthosilicate to nano-aluminum titanate in the tetraethyl orthosilicate solution is 0.18:1.

[0070] The weight ratio of coated aluminum titanate, nano-zirconia, and aluminosilicate sol is 4.8:3.4:100.

[0071] 3. Vacuum impregnation

[0072] Hollow alumina fibers are pressed into hollow fiber felt using a mold. The hollow fiber felt, along with the mold, is then placed into a vacuum impregnation tank. The tank is evacuated using a vacuum pump. An initiator is added to the modified composite sol and mixed evenly before being siphoned into the vacuum impregnation tank. The modified composite sol is controlled to completely impregnate the hollow fiber felt. The impregnation process is maintained at room temperature for 30 minutes under vacuum to complete the impregnation process and obtain the impregnated body.

[0073] The initiator is propylene oxide; the molar ratio of the initiator to aluminum chloride hexahydrate used in the modified composite sol is 1:3.

[0074] The liquid level of the modified composite sol is 1.2 times the thickness of the hollow fiber felt.

[0075] 4. Gel aging

[0076] The impregnated body and the mold were placed in an oven and heated to 48°C. After the gel was kept warm for 3 hours, the mold with the impregnated body was removed from the gel and completely immersed in anhydrous ethanol. The mixture was then allowed to stand for 96 hours at 48°C, with the anhydrous ethanol being replaced every 12 hours during the aging process. After aging was completed, the composite was obtained.

[0077] During the aging process, the liquid level of anhydrous ethanol is controlled to be 1.5 times the thickness of the impregnated body.

[0078] 5. Supercritical drying

[0079] The composite material, along with the mold, was placed in a supercritical drying reactor. The supercritical drying temperature was controlled at 270℃ and the pressure at 8MPa for 2 hours. After the supercritical drying was completed, the temperature was lowered and the mold was removed to obtain the hollow fiber reinforced aerogel composite material.

[0080] This embodiment also provides a hollow fiber reinforced aerogel composite material prepared by the aforementioned method.

[0081] Example 2

[0082] This embodiment provides a method for preparing hollow fiber reinforced aerogel composite materials, specifically as follows:

[0083] 1. Preparation of aluminum silica sol

[0084] Using inorganic aluminum salt and silanol salt precursors as aluminum source (aluminum chloride hexahydrate) and silicon source (tetraethyl orthosilicate), respectively, a certain amount of aluminum source and silicon source were mixed with a certain proportion of anhydrous ethanol and deionized water, and stirred for 40 min to prepare aluminum source solution and silicon source solution, respectively. The aluminum source solution and silicon source solution were mixed and stirred for another 40 min to form a uniformly mixed aluminum-silicon sol for later use.

[0085] In the preparation of the aluminum source solution, the molar ratio of aluminum chloride hexahydrate, anhydrous ethanol, and deionized water is 3.05:16:58.

[0086] In the preparation of the silicon source solution, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, and deionized water is 1.1:5.5:5.5.

[0087] In the mixing of aluminum source solution and silicon source solution, the molar ratio of aluminum chloride hexahydrate to tetraethyl orthosilicate is controlled at 3.05:1.1.

[0088] 2. Modified composite

[0089] Nano-sized aluminum titanate with a particle size of 50 nm was placed in a constant temperature oven and kept at 115 °C for 1.5 h. After cooling, pretreated aluminum titanate was obtained. The pretreated aluminum titanate was then added to 72 times its weight of anhydrous ethanol and ultrasonically dispersed for 10 min. Deionized water was added and mixed evenly. The pH was then adjusted to 9 with 25 wt% ammonia solution, and the mixture was stirred and heated to 50 °C and kept at that temperature. Tetraethyl orthosilicate solution was added dropwise at a rate of 0.45 mL / min. After the addition was complete, the mixture was kept at 50 °C and stirred for 5.5 h. The solid was obtained by centrifugation and washed three times with anhydrous ethanol. The solid was then placed in a vacuum drying oven and dried at 52 °C to constant weight under a vacuum of 0.075 MPa to obtain coated aluminum titanate. The coated aluminum titanate and nano-zirconia (particle size of 20 nm) were then added to an aluminosilicate sol and ultrasonically dispersed evenly to obtain a modified composite sol.

[0090] The volume of deionized water added is 3.8% of the volume of anhydrous ethanol.

[0091] The tetraethyl orthosilicate solution is an ethanolic solution of tetraethyl orthosilicate with a concentration of 2.7 wt%; the weight ratio of tetraethyl orthosilicate to nano-aluminum titanate in the tetraethyl orthosilicate solution is 0.2:1.

[0092] The weight ratio of coated aluminum titanate, nano-zirconia, and aluminosilicate sol is 5.1:3.9:100.

[0093] 3. Vacuum impregnation

[0094] Hollow alumina fibers are pressed into hollow fiber felt using a mold. The hollow fiber felt, along with the mold, is then placed into a vacuum impregnation tank. The tank is evacuated using a vacuum pump. An initiator is added to the modified composite sol and mixed evenly before being siphoned into the vacuum impregnation tank. The modified composite sol is controlled to completely impregnate the hollow fiber felt. The impregnation process is maintained at room temperature for 35 minutes under vacuum to complete the impregnation process and obtain the impregnated body.

[0095] The initiator is propylene oxide; the molar ratio of the initiator to aluminum chloride hexahydrate used in the modified composite sol is 1:3.5.

[0096] The liquid level of the modified composite sol is 1.5 times the thickness of the hollow fiber felt.

[0097] 4. Gel aging

[0098] The impregnated body and the mold were placed in an oven and heated to 50°C. After the gel was kept warm for 4 hours, the mold with the impregnated body was removed from the gel and completely immersed in anhydrous ethanol. The mixture was then allowed to stand for 96 hours at 50°C, with the anhydrous ethanol being replaced every 12 hours during the aging process. After aging was completed, the composite was obtained.

[0099] During the aging process, the liquid level of anhydrous ethanol is controlled to be 1.8 times the thickness of the impregnated body.

[0100] 5. Supercritical drying

[0101] The composite material, along with the mold, was placed in a supercritical drying reactor. The supercritical drying temperature was controlled at 275℃ and the pressure at 8.5MPa for 3 hours. After the supercritical drying was completed, the temperature was lowered and the mold was removed to obtain the hollow fiber reinforced aerogel composite material.

[0102] This embodiment also provides a hollow fiber reinforced aerogel composite material prepared by the aforementioned method.

[0103] Example 3

[0104] This embodiment provides a method for preparing hollow fiber reinforced aerogel composite materials, specifically as follows:

[0105] 1. Preparation of aluminum silica sol

[0106] Using inorganic aluminum salt and silanolate precursors as aluminum source (aluminum chloride hexahydrate) and silicon source (tetraethyl orthosilicate), respectively, a certain amount of aluminum source and silicon source were mixed with a certain proportion of anhydrous ethanol and deionized water, and stirred for 50 min each to prepare aluminum source solution and silicon source solution. The aluminum source solution and silicon source solution were then mixed and stirred for another 50 min to form a uniformly mixed aluminum-silicon sol for later use.

[0107] In the preparation of the aluminum source solution, the molar ratio of aluminum chloride hexahydrate, anhydrous ethanol, and deionized water is 3.1:17:60.

[0108] In the preparation of the silicon source solution, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, and deionized water is 1.2:6:6.

[0109] In the mixing of aluminum source solution and silicon source solution, the molar ratio of aluminum chloride hexahydrate to tetraethyl orthosilicate is controlled at 3.1:1.2.

[0110] 2. Modified composite

[0111] Nano-sized aluminum titanate with a particle size of 50 nm was placed in a constant temperature oven and kept at 120 °C for 2 h. After cooling, pretreated aluminum titanate was obtained. The pretreated aluminum titanate was then added to 75 times its weight of anhydrous ethanol and ultrasonically dispersed for 15 min. Deionized water was added and mixed evenly. The pH was then adjusted to 9 with 25 wt% ammonia solution, and the mixture was stirred and heated to 52 °C and kept at that temperature. Tetraethyl orthosilicate solution was added dropwise at a rate of 0.5 mL / min. After the addition was complete, the mixture was kept at 52 °C and stirred for 6 h. The solid was obtained by centrifugation and washed three times with anhydrous ethanol. The solid was then placed in a vacuum drying oven and dried at 50 °C to constant weight under a vacuum of 0.08 MPa to obtain coated aluminum titanate. The coated aluminum titanate and nano-zirconia (particle size of 20 nm) were then added to an aluminosilicate sol and ultrasonically dispersed evenly to obtain a modified composite sol.

[0112] The volume of deionized water added is 4% of the volume of anhydrous ethanol.

[0113] The tetraethyl orthosilicate solution is an ethanolic solution of tetraethyl orthosilicate with a concentration of 2.8 wt%; the weight ratio of tetraethyl orthosilicate to nano-aluminum titanate in the tetraethyl orthosilicate solution is 0.21:1.

[0114] The weight ratio of coated aluminum titanate, nano-zirconia, and aluminosilicate sol is 5.5:4.2:100.

[0115] 3. Vacuum impregnation

[0116] Hollow alumina fibers are pressed into hollow fiber felt using a mold. The hollow fiber felt, along with the mold, is then placed into a vacuum impregnation tank. The vacuum impregnation tank is evacuated using a vacuum pump. An initiator is added to the modified composite sol and mixed evenly before being siphoned into the vacuum impregnation tank. The modified composite sol is controlled to completely impregnate the hollow fiber felt. The impregnation process is maintained at room temperature for 40 minutes under vacuum to complete the impregnation process and obtain the impregnated body.

[0117] The initiator is propylene oxide; the molar ratio of the initiator to aluminum chloride hexahydrate used in the modified composite sol is 1:3.8.

[0118] The liquid level of the modified composite sol is 1.6 times the thickness of the hollow fiber felt.

[0119] 4. Gel aging

[0120] The impregnated body and the mold were placed in an oven and heated to 52°C. After the gel was kept warm for 5 hours, the mold with the impregnated body was removed from the gel and completely immersed in anhydrous ethanol. The mixture was then allowed to stand for 96 hours at 52°C, with the anhydrous ethanol being replaced every 12 hours during the aging process. After aging was completed, the composite was obtained.

[0121] During the aging process, the liquid level of anhydrous ethanol is controlled to be twice the thickness of the impregnated body.

[0122] 5. Supercritical drying

[0123] The composite material, along with the mold, was placed in a supercritical drying reactor. The supercritical drying temperature was controlled at 280℃ and the pressure at 9MPa for 4 hours. After the supercritical drying was completed, the temperature was lowered and the mold was removed to obtain the hollow fiber reinforced aerogel composite material.

[0124] This embodiment also provides a hollow fiber reinforced aerogel composite material prepared by the aforementioned method.

[0125] Comparative Example 1

[0126] Comparative Example 1 adopts the technical solution of Example 2, the difference being that the modification and composite step is omitted, and the aluminum silica sol is directly used in the vacuum impregnation step, and the hollow fiber felt is directly impregnated with aluminum silica sol.

[0127] The compressive strength, flexural strength, thermal conductivity at room temperature, thermal conductivity at 800℃, and sound transmission loss (sound frequency 3kHz) of the aerogel composite materials of Examples 1-3 and Comparative Example 1 were tested. Simultaneously, the aerogel composite materials of Examples 1-3 and Comparative Example 1 were placed in a calcining furnace and heated from room temperature to 800℃ at a heating rate of 10℃ / min, held at that temperature for 30 min, and then cooled to room temperature at a cooling rate of 10℃ / min. Each heating-cooling process was considered one thermal shock cycle. The number of thermal shock cycles at which destructive cracking occurred in each aerogel composite material was counted to verify its thermal shock cycle stability. Specific results are shown in the table below:

[0128]

[0129] The method for preparing hollow fiber reinforced aerogel composite material of the present invention involves preparing an aluminosilicate sol using specific aluminum and silicon sources. In the modification and composite step, a silica layer is coated onto the surface of nano-aluminum titanate in an in-situ coating manner to obtain coated aluminum titanate. The filling effect of nanoparticles (coated aluminum titanate and nano-zirconia) blocks the crack propagation path, improves the porous structure defects of the aerogel, and improves the mechanical properties of the composite material. Simultaneously, the bonding effect between the coated aluminum titanate and the active groups of the aluminosilicate sol further improves the bonding performance between aerogel particles. Furthermore, by combining coated aluminum titanate, nano-zirconia, and the aluminosilicate sol to form a modified composite sol, the near-zero expansion of the coated aluminum titanate offsets the shrinkage of the matrix. The nano-zirconia further compensates for thermal expansion through shrinkage, and the overall combination buffers the interfacial stress, achieving thermal stress buffering, effectively improving the thermal expansion matching of aluminum-silicon components, and improving the temperature resistance of aerogel composites. Then, hollow alumina fibers are pressed into hollow fiber felts, and the hollow fiber felts are vacuum impregnated with a modified composite sol containing an initiator. After gel aging and supercritical drying, hollow fiber reinforced aerogel composites are obtained. By combining hollow fibers with composite aluminum-silicon aerogels, the mechanical properties of aerogel composites are further improved. At the same time, the acoustic resonance and scattering effect of hollow fibers can scatter and absorb sound waves, giving aerogel composites excellent sound insulation properties.

[0130] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0131] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a hollow fiber-reinforced aerogel composite material, characterized by, The method comprises the following steps: Preparation of aluminum-silicon sol, modification and compounding, vacuum impregnation, gel aging, supercritical drying; The method for preparing the aluminum-silicon sol comprises the following steps: mixing aluminum chloride hexahydrate, anhydrous ethanol and deionized water to obtain an aluminum source solution; mixing tetraethyl orthosilicate, anhydrous ethanol and deionized water to obtain a silicon source solution; and mixing the aluminum source solution and the silicon source solution to obtain the aluminum-silicon sol; The method for modifying and compounding comprises the following steps: obtaining pretreated aluminum titanate by heat treating nano-aluminum titanate; adding the pretreated aluminum titanate and deionized water into anhydrous ethanol, uniformly mixing, adjusting the pH to 8.5-9.5, heating to 48-52℃, and then adding tetraethyl orthosilicate solution dropwise under constant temperature and stirring for 5-6 hours; separating to obtain a solid, washing and drying the solid to obtain coated aluminum titanate; and adding the coated aluminum titanate and nano-zirconium oxide into the aluminum-silicon sol, uniformly mixing to obtain a modified and compounded sol. In the modification and compounding, the tetraethyl orthosilicate solution is a 2.5-2.8wt% tetraethyl orthosilicate ethanol solution. The dropwise adding speed of the tetraethyl orthosilicate solution is 0.4-0.5mL / min. The weight ratio of tetraethyl orthosilicate in the tetraethyl orthosilicate solution to the nano-aluminum titanate is 0.18-0.21:

1. The weight ratio of the coated aluminum titanate, nano-zirconium oxide and aluminum-silicon sol is 4.8-5.5:3.4-4.2:

100. The particle size of the nano-aluminum titanate is 50-60nm, and the particle size of the nano-zirconium oxide is 20-30nm. The method for vacuum impregnation comprises the following steps: pressing hollow alumina fibers into a hollow fiber felt, and vacuum impregnating the hollow fiber felt with a modified and compounded sol containing an initiator to obtain an impregnated body. The impregnated body is subjected to gel aging and supercritical drying to obtain a hollow fiber reinforced aerogel composite material.

2. The method for preparing hollow fiber reinforced aerogel composite material according to claim 1, characterized in that, The molar ratio of aluminum chloride hexahydrate, anhydrous ethanol and deionized water used in the aluminum source solution is 3-3.1:15-17:55-60. The molar ratio of tetraethyl orthosilicate, anhydrous ethanol and deionized water used in the silicon source solution is 1-1.2:5-6:5-6. In the mixing of the aluminum source solution and the silicon source solution, the molar ratio of aluminum chloride hexahydrate to tetraethyl orthosilicate is controlled to be 3-3.1:1-1.

2.

3. The method for preparing hollow fiber reinforced aerogel composite material according to claim 1, characterized in that, In the modification and compounding, the weight ratio of the pretreated aluminum titanate to anhydrous ethanol is 1:70-75. The volume of deionized water added is 3.5-4% of the volume of anhydrous ethanol.

4. The method for preparing hollow fiber reinforced aerogel composite material according to claim 1, characterized in that, In the modification and compounding, the pretreated aluminum titanate is obtained by heat treating the nano-aluminum titanate at 110-120℃ for 1-2 hours.

5. The method for preparing hollow fiber reinforced aerogel composite material according to claim 1, characterized in that, The method for vacuum impregnation comprises the following steps: pressing hollow alumina fibers into a hollow fiber felt, and vacuum impregnating the hollow fiber felt with a modified and compounded sol containing an initiator to obtain an impregnated body. The initiator is propylene oxide; and the molar ratio of the initiator to aluminum chloride hexahydrate used in the modified and compounded sol is 1:3-5.

6. The method for preparing hollow fiber reinforced aerogel composite material according to claim 1, characterized in that, The method for aging the gel is that the impregnated body is completely immersed into anhydrous ethanol after the gel is preserved at a temperature of 48-52 ℃, and is aged at a temperature of 48-52 ℃ to obtain a composite.

7. The method for preparing hollow fiber reinforced aerogel composite material according to claim 6, characterized in that, In the gel aging, the gel preservation time is 3-5 h; The standing aging time is 72-96 h; The anhydrous ethanol is replaced every 10-12 h during the standing aging process.

8. The method for preparing hollow fiber reinforced aerogel composite material according to claim 1, characterized in that, The method for supercritical drying is that after the impregnated body is aged to obtain a composite, the temperature for supercritical drying is controlled to be 270-280 ℃, the pressure is controlled to be 8-9 MPa, the composite is supercritically dried for 2-4 h to obtain a hollow fiber reinforced aerogel composite material.

9. A hollow fiber reinforced aerogel composite, characterized in that, The hollow fiber reinforced aerogel composite material is prepared by using the preparation method in any one of claims 1-8.

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