Light-screening agent doped aluminum-silicon aerogel composite material and preparation method thereof

Abstract

The invention provides an opacifier doped aluminum-silicon aerogel composite material and a preparation method thereof, and relates to the field of aerogel materials. The preparation method of the opacifying agent doped aluminum-silicon aerogel composite material comprises the following steps: preparing graphene oxide doped aluminum-silicon sol, preparing a composite fiber felt, dipping the sol, aging the gel, and carrying out supercritical drying. According to the opacifying agent doped aluminum-silicon aerogel composite material and the preparation method thereof, the technical defects existing in existing related means for inhibiting phase change of aluminum oxide can be effectively overcome, and the high-temperature stability, the heat insulation performance and the mechanical performance of the opacifying agent doped aluminum-silicon aerogel composite material are further improved on the premise that the high specific surface area is obtained.

Description

Technical Field

[0001] The present invention relates to the field of aerogel materials, and in particular to a sunscreen-doped aluminum silicate aerogel composite material and a preparation method thereof. Background Art

[0002] With the progress of society and the rapid development of science and technology, human beings have more and more demands for living environment, convenient transportation, industrial production, aerospace and other fields. Among them, thermal insulation performance has become a key technical indicator in the fields of high-rise building insulation, new energy vehicles, high-temperature kilns, hypersonic aircraft, etc., which is an important factor in ensuring the normal operation of various fields. High-temperature resistant thermal insulation materials can block high-temperature radiation through their special structure, forming a good thermal insulation barrier, which has outstanding effects in reducing heat transfer and reducing energy consumption. Traditional thermal insulation materials currently have many problems, such as poor thermal insulation effect, poor temperature resistance, heavy weight, and the generation of harmful gases at high temperatures. Therefore, lightweight and efficient thermal insulation materials have become the key development direction of current thermal insulation materials.

[0003] Silica aerogel is a thermally insulating nanoporous solid material made by extracting liquid from the pores of wet gel through supercritical drying technology using the sol-gel method. Due to its special internal structure, silica aerogel has a wide range of physical properties, such as low thermal conductivity (14-25mW / mK), large specific surface area (200-1200m 2 / g), high porosity (80-99.8%), low density (0.003-0.5g / cm 3 ) and other characteristics, making it an excellent candidate in various fields such as aerospace technology, thermal insulation and sound insulation, chemical reaction catalyst carrier, biomedicine, energy storage and automobile.

[0004] Aerogels with similar characteristics to silica aerogels include alumina aerogels, which are low bulk density, high porosity and high surface area (350-700m 2 / g) of amorphous nanoporous network materials. Silica aerogel undergoes irreversible degradation and destruction of its porous structure when sintered at temperatures above 600°C. Alumina aerogel, however, possesses superior thermal and chemical stability due to its crystals and internal nano-network structure. However, alumina aerogel's heat resistance still cannot fully meet the requirements of high-end applications. It is prone to cracking and shrinking during aging and drying, and its high thermal conductivity limits its heat resistance. Furthermore, after heat treatment above 1000°C, the specific surface area decreases dramatically due to phase transformation of the alumina. Therefore, maintaining the nanostructure at high temperatures and increasing the specific surface area are the main focuses of alumina aerogel research. Existing research has shown that the addition of other elements (such as Si, La, Ba, or Zr) can inhibit the phase transformation of alumina, but this still suffers from poor elemental uniformity and poor high-temperature stability.

[0005] At the same time, in response to the aforementioned issues, Al2O3-SiO2 composite aerogel is also one of the important research directions at present; its uniformly distributed Si element can significantly inhibit the lattice vibration and rearrangement of Al atoms. The aerogel composite material formed can form a uniformly distributed mullite phase at 1200°C, changing the transition path from metastable Al2O3 to α-Al2O3, which is conducive to maintaining a high specific surface area at high temperatures. However, in thermal environments above 1000°C, the high infrared transparency of Al2O3-SiO2 composite aerogel increases infrared radiation at high temperatures, significantly increasing its thermal conductivity, and its mechanical properties and thermal insulation properties need to be further improved. Summary of the Invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a sunscreen-doped aluminum silicate aerogel composite material and a preparation method thereof, which can effectively overcome the technical defects of the existing means of inhibiting the phase change of alumina, and further improve the high-temperature stability, thermal insulation performance and mechanical properties of the sunscreen-doped aluminum silicate aerogel composite material while obtaining a high specific surface area.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows: A method for preparing a sunscreen-doped aluminum silicate aerogel composite material comprises the following steps: preparing graphene oxide-doped aluminum silicate sol, preparing composite fiber felt, sol impregnation, gel aging, and supercritical drying; The method for preparing graphene oxide doped aluminum silicate sol comprises the following steps: mixing aluminum chloride hexahydrate with anhydrous ethanol and deionized water to obtain an aluminum source solution; mixing ethyl orthosilicate with anhydrous ethanol and deionized water to obtain a silicon source solution; mixing the aluminum source solution and the silicon source solution to obtain aluminum silicate sol; and uniformly mixing the aluminum silicate sol and graphene oxide to obtain the graphene oxide doped aluminum silicate sol. The method for preparing the composite fiber felt comprises: uniformly mixing polycarbosilane, tetraethyl orthosilicate, and xylene to obtain a precursor liquid; pressing mullite fibers into a density of 0.22-0.25 g / cm 3 After the fiber felt is prepared, the fiber felt is vacuum impregnated with a precursor liquid, and then solidified and calcined to obtain a composite fiber felt; The mass concentration of polycarbosilane in the precursor liquid is 18-22wt%, and the mass concentration of ethyl orthosilicate is 1.3-1.4wt%; The sol impregnation method comprises vacuum impregnating the composite fiber felt with graphene oxide doped aluminum silicate sol containing an initiator to obtain an impregnated body; The impregnated body is subjected to gel aging and supercritical drying to obtain a sunscreen-doped aluminum silicate aerogel composite material.

[0008] Preferably, in the preparation of the graphene oxide-doped aluminum silicate sol, 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 ethyl orthosilicate, anhydrous ethanol and deionized water used in the silicon source solution is 1-1.2:5-6:5-6.

[0009] Preferably, in the preparation of the graphene oxide-doped aluminum silicate sol, the aluminum source solution and the silicon source solution are mixed, and the molar ratio of aluminum chloride hexahydrate to tetraethyl orthosilicate is controlled to be 3-3.1:1-1.2; The added weight of graphene oxide is 0.3-0.6% of the weight of the aluminum silicate sol.

[0010] Preferably, in the preparation of the composite fiber mat, the volume ratio of the precursor liquid to the fiber mat used in the vacuum impregnation is 1:3-3.5; The vacuum degree of vacuum impregnation is 0.08-0.09 MPa, and the vacuum impregnation time is 40-50 minutes.

[0011] Preferably, in the preparation of the composite fiber mat, the curing is performed by heat-insulating and curing at a temperature of 120-130° C. for 1.5-2 hours, and then heat-insulating and curing at a temperature of 175-185° C. for 1-1.5 hours; The calcination is carried out under the protection of argon atmosphere, at a heating rate of 2-3°C / min, to raise the temperature to 1100-1150°C, and calcining for 1-2 hours to obtain a composite fiber felt.

[0012] Preferably, in the sol immersion, the immersion temperature is room temperature and the immersion time is 30-40 minutes; The initiator is propylene oxide, and the molar ratio of the initiator to the aluminum chloride hexahydrate used in the graphene oxide-doped aluminum silicate sol is 1:3-5; The liquid level of the initiator-containing graphene oxide-doped aluminum silicate sol is 1.2-1.6 times the thickness of the composite fiber felt.

[0013] Furthermore, the gel aging method is to place the impregnated body in a 48-52°C temperature environment, keep the gel warm, and then completely immerse it in anhydrous ethanol, and age it at a temperature of 48-52°C to obtain a composite body.

[0014] Preferably, during the gel aging, the heat preservation gel time is 3-5h; The static aging time is 72-96h; During the static aging process, anhydrous ethanol was replaced every 10-12 hours.

[0015] Furthermore, the supercritical drying method is as follows: after the impregnation body is subjected to gel aging to obtain a composite body, the supercritical drying temperature is controlled to 270-280°C and the pressure is 8-9MPa, and the composite body is supercritically dried for 2-4h to obtain a sunscreen-doped aluminum silicate aerogel composite material.

[0016] A sunscreen-doped aluminum silicate aerogel composite material is prepared by adopting the above-mentioned preparation method.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for preparing the sunscreen-doped aluminum silicate aerogel composite material of the present invention comprises the following steps: graphene oxide is doped into the aluminum silicate aerogel, and the graphene oxide sheets are uniformly composited with the aluminum silicate aerogel; wherein the -OH groups in the aluminum silicate solution can form covalent bonds with the oxygen-containing functional groups in the graphene oxide, thereby enhancing the interfacial bonding strength between the aerogels. At the same time, in the preparation of the composite fiber felt, polycarbosilane and ethyl orthosilicate are used as a precursor liquid, and after vacuum impregnation, curing, and calcination, a silicon carbide layer is in situ composited on the outer surface of the mullite fiber, directly blocking high-temperature infrared radiation. The sunscreen-doped graphene oxide aluminum silicate sol is combined with the sunscreen to inhibit thermal radiation, effectively improving the thermal insulation performance of the aerogel composite material and reducing its thermal conductivity. In addition, the silicon carbide layer on the outer surface of the fiber can further improve the interfacial bonding between the fiber felt and the aerogel, and disperse thermal stress through the fiber felt skeleton, thereby improving the mechanical properties, temperature resistance, and high-temperature stability of the aerogel composite material. The aforementioned technical means cooperate with each other and work synergistically to effectively overcome the technical defects of existing means of inhibiting alumina phase change, and further improve the high-temperature stability, thermal insulation and mechanical properties of the sunscreen-doped aluminum silicate aerogel composite material while obtaining a high specific surface area.

[0018] (2) The sunscreen-doped aluminum silicate aerogel composite material of the present invention has a specific surface area of ​​840-868m 2 / g, the room temperature flexural strength is 1.27-1.31MPa, the room temperature thermal conductivity is 0.029-0.032W / m·K, and the temperature resistance is 1100-1150℃.

[0019] (3) After 20 thermal shock cycles (room temperature - 1100°C), the sunscreen-doped aluminum silicate aerogel composite material of the present invention has a room temperature flexural strength of 1.07 MPa and a strength retention rate of 81.7%.

[0020] (4) The preparation method of the sunscreen-doped aluminum silicate aerogel composite material of the present invention has a simple process flow, is easy to control during the preparation process, has high production safety, and is conducive to large-scale production. DETAILED DESCRIPTION

[0021] In order to provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described. It should be noted that the following detailed description is illustrative and is intended to further illustrate the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0022] It should be noted that the terms used herein are intended only to describe specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," and the like are used to distinguish similar objects and are not used to describe a specific order or precedence. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] An embodiment of the present invention provides a method for preparing a sunscreen-doped aluminum silicate aerogel composite material, comprising the following steps: preparing graphene oxide-doped aluminum silicate sol, preparing composite fiber felt, sol impregnation, gel aging, and supercritical drying.

[0024] The method for preparing graphene oxide-doped aluminum silicate sol comprises: using an inorganic aluminum salt and a silicon alkoxide precursor as an aluminum source (aluminum chloride hexahydrate) and a silicon source (ethyl orthosilicate), respectively; mixing a certain amount of the aluminum source and the silicon source with a certain proportion of anhydrous ethanol and deionized water, respectively; and stirring each for 30-50 minutes to prepare an aluminum source solution and a silicon source solution; mixing the aluminum source solution and the silicon source solution, and continuing to stir for 30-50 minutes to form a uniformly mixed aluminum silicate sol; and then mixing the aluminum silicate sol with graphene oxide prepared by an improved Hummer method, controlling the added weight of the graphene oxide to be 0.3-0.6% of the weight of the aluminum silicate sol, and stirring uniformly to prepare the graphene oxide-doped aluminum silicate sol.

[0025] In the embodiment of the present invention, preferably, in the preparation of the aluminum source solution, the molar ratio of aluminum chloride hexahydrate, anhydrous ethanol, and deionized water is 3-3.1:15-17:55-60.

[0026] In the embodiment of the present invention, preferably, in the preparation of the silicon source solution, the molar ratio of ethyl orthosilicate, anhydrous ethanol, and deionized water is 1-1.2:5-6:5-6.

[0027] In the embodiment of the present invention, preferably, 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.

[0028] The method for preparing the composite fiber felt comprises: adding polycarbosilane and tetraethyl orthosilicate into xylene, heating to 45-55° C., maintaining the temperature and stirring evenly to obtain a precursor liquid for standby use; pressing mullite fibers with a diameter of 5-10 μm into a density of 0.22-0.25 g / cm 3 After the fiber felt is completely immersed in 3-3.5 times the volume of the precursor liquid, it is evacuated to a vacuum degree of 0.08-0.09MPa, and the vacuum impregnation is maintained for 40-50min. The impregnated fiber felt is taken out and placed in a constant temperature box, and is heat-cured at 120-130℃ for 1.5-2h, and then heat-cured at 175-185℃ for 1-1.5h to obtain a cured fiber felt; then the cured fiber felt is placed in a calcining furnace, and under the protection of argon atmosphere, the temperature is increased to 1100-1150℃ at a heating rate of 2-3℃ / min, and the temperature is kept warm and calcined for 1-2h, and cooled with the furnace to obtain a mullite fiber felt with a silicon carbide coating on the fiber surface, that is, a composite fiber felt.

[0029] In the embodiment of the present invention, preferably, the mass concentration of polycarbosilane in the precursor liquid is 18-22 wt %, the mass concentration of ethyl orthosilicate is 1.3-1.4 wt %, and xylene provides a solvent environment.

[0030] The sol impregnation method comprises the following steps: placing the composite fiber felt in a vacuum impregnation tank, evacuating the vacuum impregnation tank with a vacuum pump; adding an initiator to the graphene oxide-doped aluminum silicate sol, mixing the mixture evenly, and then siphoning the mixture into the vacuum impregnation tank; controlling the graphene oxide-doped aluminum silicate sol to completely impregnate the composite fiber felt; maintaining the vacuum and room temperature impregnation for 30-40 minutes, completing the sol impregnation treatment, and obtaining an impregnated body.

[0031] In the embodiment of the present invention, preferably, the initiator is propylene oxide; and the molar ratio of the initiator to the aluminum chloride hexahydrate used in the graphene oxide-doped aluminum silicate sol is 1:3-5.

[0032] In the embodiment of the present invention, preferably, the liquid level of the initiator-containing graphene oxide-doped aluminum silicate sol is 1.2-1.6 times the thickness of the composite fiber felt.

[0033] The gel aging method comprises placing the impregnated body in an oven and heating it to 48-52° C., keeping the gel warm for 3-5 hours, taking it out and completely immersing it in anhydrous ethanol, and aging it at a temperature of 48-52° C. for 72-96 hours, replacing the anhydrous ethanol every 10-12 hours during the aging process. After the aging is completed, a composite body is obtained.

[0034] In the embodiment of the present invention, preferably, the liquid level of anhydrous ethanol is controlled to be 1.5-2 times the thickness of the impregnated body during the aging process.

[0035] The supercritical drying method comprises placing the composite into a supercritical drying reactor, controlling the supercritical drying temperature to 270-280° C. and the pressure to 8-9 MPa, and performing supercritical drying for 2-4 hours; cooling after the supercritical drying is completed to obtain a sunscreen-doped aluminum silicate aerogel composite material.

[0036] In an embodiment of the present invention, graphene oxide is incorporated into the aluminum silicate aerogel, and the graphene oxide sheets are uniformly composited with the aluminum silicate aerogel; wherein, the -OH groups in the aluminum silicate solution can form covalent bonds with the oxygen-containing functional groups in the graphene oxide, which can enhance the interfacial bonding strength between the aerogels. At the same time, in the preparation of the composite fiber felt, polycarbosilane and ethyl orthosilicate are used as the precursor liquid. After vacuum impregnation, curing, and calcination, a silicon carbide layer is in situ composited on the outer surface of the mullite fiber to directly block high-temperature infrared radiation. The graphene oxide-doped aluminum silicate sol, as a sunscreen, suppresses thermal radiation, effectively improving the thermal insulation performance of the aerogel composite material and reducing its thermal conductivity. In addition, the silicon carbide layer on the outer surface of the fiber can further improve the interfacial bonding between the fiber felt and the aerogel, and disperse thermal stress through the fiber felt skeleton, thereby improving the mechanical properties and high-temperature stability of the aerogel composite material. The aforementioned technical means cooperate with each other and work synergistically to effectively overcome the technical defects of existing means of inhibiting alumina phase change, and further improve the high-temperature stability, thermal insulation and mechanical properties of the sunscreen-doped aluminum silicate aerogel composite material while obtaining a high specific surface area.

[0037] An embodiment of the present invention further provides a sunscreen-doped aluminum silicate aerogel composite material, which is prepared using the above-mentioned preparation method.

[0038] Example 1 This embodiment provides a method for preparing a sunscreen-doped aluminum silicate aerogel composite material, comprising the following steps: 1. Preparation of graphene oxide doped aluminum silicate sol Inorganic aluminum salt and silicon alkoxide precursors are used as aluminum source (aluminum chloride hexahydrate) and silicon source (ethyl orthosilicate), respectively. A certain amount of aluminum source and silicon source are mixed with a certain proportion of anhydrous ethanol and deionized water, and then stirred for 30 minutes to prepare aluminum source solution and silicon source solution. After the aluminum source solution and the silicon source solution are mixed, stirring is continued for 30 minutes to form a uniformly mixed aluminum silica sol. The aluminum silica sol is then mixed with graphene oxide prepared by an improved Hummer method, and the added weight of graphene oxide is controlled to be 0.3% of the weight of the aluminum silica sol. The mixture is stirred evenly to prepare graphene oxide-doped aluminum silica sol.

[0039] In the preparation of the aluminum source solution, the molar ratio of aluminum chloride hexahydrate, anhydrous ethanol, and deionized water is 3:15:55.

[0040] In the preparation of the silicon source solution, the molar ratio of ethyl orthosilicate, anhydrous ethanol, and deionized water is 1:5:5.

[0041] 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 3:1.

[0042] 2. Preparation of composite fiber felt Put polycarbosilane and tetraethyl orthosilicate into xylene, heat to 45°C, keep warm and stir evenly to obtain a precursor liquid for standby use; press mullite fiber with a diameter of 8 μm into a density of 0.23 g / cm 3 After the fiber felt is formed, it is completely immersed in 3 times the volume of the precursor liquid, and the vacuum is evacuated to a vacuum degree of 0.08 MPa. After maintaining the vacuum impregnation for 40 minutes, the impregnated fiber felt is taken out and placed in a constant temperature box. After being heat-cured at 120°C for 1.5 hours, it is heat-cured at 175°C for 1 hour to obtain a cured fiber felt; then the cured fiber felt is placed in a calcining furnace, and under the protection of an argon atmosphere, the temperature is increased to 1100°C at a heating rate of 2°C / min, and the temperature is kept at calcined for 1 hour. The fiber felt is cooled with the furnace to obtain a mullite fiber felt with a silicon carbide coating on the fiber surface, that is, a composite fiber felt.

[0043] The mass concentration of polycarbosilane in the precursor liquid is 18 wt %, the mass concentration of ethyl orthosilicate is 1.3 wt %, and the balance is xylene.

[0044] 3. Sol impregnation The composite fiber felt is placed in a vacuum impregnation tank, and the vacuum impregnation tank is evacuated using a vacuum pump; the initiator is added to the graphene oxide-doped aluminum silicate sol, mixed evenly, and then siphoned into the vacuum impregnation tank, and the graphene oxide-doped aluminum silicate sol is controlled to completely impregnate the composite fiber felt. The vacuum impregnation is maintained at room temperature for 30 minutes to complete the sol impregnation treatment and obtain an impregnated body.

[0045] The initiator is propylene oxide; the molar ratio of the initiator to the aluminum chloride hexahydrate used in the graphene oxide-doped aluminum silicate sol is 1:3.

[0046] The liquid level of the initiator-containing graphene oxide-doped aluminum silicate sol is 1.2 times the thickness of the composite fiber felt.

[0047] 4. Gel aging The impregnated body was placed in an oven and heated to 48°C. After being kept warm for 3 hours to gel, it was taken out and completely immersed in anhydrous ethanol. It was aged at 48°C for 96 hours, and the anhydrous ethanol was replaced every 12 hours during the aging process. After the aging was completed, a composite was obtained.

[0048] During the aging process, the liquid level of anhydrous ethanol is controlled to be 1.5 times the thickness of the impregnated body.

[0049] 5. Supercritical drying The composite was placed in a supercritical drying reactor, the supercritical drying temperature was controlled to be 270°C and the pressure was 8 MPa, and supercritical drying was performed for 2 hours; after the supercritical drying was completed, the temperature was lowered to obtain a sunscreen-doped aluminum silicate aerogel composite material.

[0050] This embodiment also provides a sunscreen-doped aluminum silicate aerogel composite material prepared by the aforementioned method.

[0051] Example 2 This embodiment provides a method for preparing a sunscreen-doped aluminum silicate aerogel composite material, comprising the following steps: 1. Preparation of graphene oxide doped aluminum silicate sol Inorganic aluminum salt and silicon alkoxide precursors are used as aluminum source (aluminum chloride hexahydrate) and silicon source (ethyl orthosilicate), respectively. A certain amount of aluminum source and silicon source are mixed with a certain proportion of anhydrous ethanol and deionized water, and then stirred for 40 minutes to prepare aluminum source solution and silicon source solution. After the aluminum source solution and the silicon source solution are mixed, stirring is continued for 40 minutes to form a uniformly mixed aluminum silica sol. The aluminum silica sol is then mixed with graphene oxide prepared by an improved Hummer method, and the added weight of graphene oxide is controlled to be 0.5% of the weight of the aluminum silica sol. The mixture is stirred evenly to prepare graphene oxide-doped aluminum silica sol.

[0052] In the preparation of the aluminum source solution, the molar ratio of aluminum chloride hexahydrate, anhydrous ethanol, and deionized water is 3.05:16:57.

[0053] In the preparation of the silicon source solution, the molar ratio of ethyl orthosilicate, anhydrous ethanol, and deionized water is 1.1:5.5:5.5.

[0054] 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 3.05:1.1.

[0055] 2. Preparation of composite fiber felt Put polycarbosilane and tetraethyl orthosilicate into xylene, heat to 50°C, keep warm and stir evenly to obtain a precursor liquid for standby use; press mullite fiber with a diameter of 8 μm into a density of 0.23 g / cm 3 After the fiber felt is completely immersed in 3.2 times the volume of the precursor liquid, it is evacuated to a vacuum degree of 0.085 MPa. After maintaining the vacuum impregnation for 45 minutes, the impregnated fiber felt is taken out and placed in a constant temperature box. After being heat-cured at 125°C for 1.8 hours, it is heat-cured at 180°C for 1.2 hours to obtain a cured fiber felt; then the cured fiber felt is placed in a calcining furnace, and under the protection of an argon atmosphere, the temperature is increased to 1120°C at a heating rate of 2.5°C / min, and the temperature is kept calcined for 1.5 hours. It is cooled with the furnace to obtain a mullite fiber felt with a silicon carbide coating on the fiber surface, that is, a composite fiber felt.

[0056] The mass concentration of polycarbosilane in the precursor liquid is 20 wt %, the mass concentration of ethyl orthosilicate is 1.35 wt %, and the balance is xylene.

[0057] 3. Sol impregnation The composite fiber felt is placed in a vacuum impregnation tank, and the vacuum impregnation tank is evacuated using a vacuum pump; the initiator is added to the graphene oxide-doped aluminum silicate sol, mixed evenly, and then siphoned into the vacuum impregnation tank, and the graphene oxide-doped aluminum silicate sol is controlled to completely impregnate the composite fiber felt. The vacuum is maintained at room temperature for 35 minutes to complete the sol impregnation treatment and obtain an impregnated body.

[0058] The initiator is propylene oxide; the molar ratio of the initiator to the aluminum chloride hexahydrate used in the graphene oxide-doped aluminum silicate sol is 1:3.5.

[0059] The liquid level of the initiator-containing graphene oxide-doped aluminum silicate sol is 1.5 times the thickness of the composite fiber felt.

[0060] 4. Gel aging The impregnated body was placed in an oven and heated to 50°C. After being kept warm for 4 hours to gel, it was taken out and completely immersed in anhydrous ethanol. It was aged at 50°C for 96 hours, and the anhydrous ethanol was replaced every 12 hours during the aging process. After the aging was completed, a composite was obtained.

[0061] During the aging process, the liquid level of anhydrous ethanol was controlled to be 1.8 times the thickness of the impregnated body.

[0062] 5. Supercritical drying The composite was placed in a supercritical drying reactor, the supercritical drying temperature was controlled to be 275°C and the pressure was 8.5 MPa, and supercritical drying was performed for 3 hours; after the supercritical drying was completed, the temperature was lowered to obtain a sunscreen-doped aluminum silicate aerogel composite material.

[0063] This embodiment also provides a sunscreen-doped aluminum silicate aerogel composite material prepared by the aforementioned method.

[0064] Example 3 This embodiment provides a method for preparing a sunscreen-doped aluminum silicate aerogel composite material, comprising the following steps: 1. Preparation of graphene oxide doped aluminum silicate sol Inorganic aluminum salt and silicon alkoxide precursors are used as aluminum source (aluminum chloride hexahydrate) and silicon source (ethyl orthosilicate), respectively. A certain amount of aluminum source and silicon source are mixed with a certain proportion of anhydrous ethanol and deionized water, and then stirred for 50 minutes to prepare aluminum source solution and silicon source solution. After the aluminum source solution and the silicon source solution are mixed, stirring is continued for 50 minutes to form a uniformly mixed aluminum silica sol. The aluminum silica sol is then mixed with graphene oxide prepared by an improved Hummer method, and the added weight of graphene oxide is controlled to be 0.6% of the weight of the aluminum silica sol. The mixture is stirred evenly to prepare graphene oxide-doped aluminum silica sol.

[0065] 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.

[0066] In the preparation of the silicon source solution, the molar ratio of ethyl orthosilicate, anhydrous ethanol, and deionized water is 1.2:6:6.

[0067] 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 3.1:1.2.

[0068] 2. Preparation of composite fiber felt Put polycarbosilane and tetraethyl orthosilicate into xylene, heat to 55°C, keep warm and stir evenly to obtain a precursor liquid for standby use; press mullite fiber with a diameter of 8 μm into a density of 0.23 g / cm 3 After the fiber felt is completely immersed in 3.5 times the volume of the precursor liquid, it is evacuated to a vacuum degree of 0.09 MPa. After maintaining the vacuum impregnation for 50 minutes, the impregnated fiber felt is taken out and placed in a constant temperature box. After being heat-cured at 130°C for 2 hours, it is heat-cured at 185°C for 1.5 hours to obtain a cured fiber felt; then the cured fiber felt is placed in a calcining furnace, and under the protection of an argon atmosphere, the temperature is increased to 1150°C at a heating rate of 3°C / min, and the temperature is kept warm and calcined for 2 hours. It is cooled with the furnace to obtain a mullite fiber felt with a silicon carbide coating on the fiber surface, that is, a composite fiber felt.

[0069] The mass concentration of polycarbosilane in the precursor liquid is 22 wt %, the mass concentration of ethyl orthosilicate is 1.4 wt %, and the balance is xylene.

[0070] 3. Sol impregnation The composite fiber felt is placed in a vacuum impregnation tank, and the vacuum impregnation tank is evacuated using a vacuum pump; the initiator is added to the graphene oxide-doped aluminum silicate sol, mixed evenly, and then siphoned into the vacuum impregnation tank, and the graphene oxide-doped aluminum silicate sol is controlled to completely impregnate the composite fiber felt. The vacuum impregnation is maintained at room temperature for 40 minutes to complete the sol impregnation treatment and obtain an impregnated body.

[0071] The initiator is propylene oxide; the molar ratio of the initiator to the aluminum chloride hexahydrate used in the graphene oxide-doped aluminum silicate sol is 1:3.8.

[0072] The liquid level of the initiator-containing graphene oxide-doped aluminum silicate sol is 1.6 times the thickness of the composite fiber felt.

[0073] 4. Gel aging The impregnated body was placed in an oven and heated to 52°C. After being kept warm for 5 hours, it was taken out and completely immersed in anhydrous ethanol. It was aged at 52°C for 96 hours, and the anhydrous ethanol was replaced every 12 hours during the aging process. After the aging was completed, a composite was obtained.

[0074] During the aging process, the liquid level of anhydrous ethanol is controlled to be twice the thickness of the impregnated body.

[0075] 5. Supercritical drying The composite was placed in a supercritical drying reactor, the supercritical drying temperature was controlled to be 280°C and the pressure was 9 MPa, and supercritical drying was performed for 4 hours; after the supercritical drying was completed, the temperature was lowered to obtain a sunscreen-doped aluminum silicate aerogel composite material.

[0076] This embodiment also provides a sunscreen-doped aluminum silicate aerogel composite material prepared by the aforementioned method.

[0077] Comparative Example 1 Comparative Example 1 adopts the technical solution of Example 2, except that the step of preparing the composite fiber mat is omitted, and the fiber mat pressed from mullite fibers is directly used in the subsequent sol impregnation step.

[0078] The specific surface area, room temperature flexural strength, room temperature thermal conductivity, and heat resistance temperature of the aerogel composite materials of Examples 1-3 and Comparative Example 1 were measured respectively. The heat resistance temperature was tested by placing each aerogel composite material in a muffle furnace and heat treating it at a predetermined temperature in an air atmosphere for 30 minutes. The highest temperature at which the linear shrinkage of the aerogel was ≤1% was the heat resistance temperature. The specific results are shown in the following table:

[0079] Furthermore, the thermal shock resistance of the aerogel composite materials of Example 2 and Comparative Example 1 was tested. Specifically, each aerogel composite material was placed in a calcination furnace, heated from room temperature to 1100°C at a heating rate of 10°C / min, kept at this temperature for 30 minutes, and then cooled to room temperature by water quenching. The above heating-cooling process was regarded as one thermal shock cycle. After repeating this process 20 times, the room temperature flexural strength of each aerogel composite material was tested and the strength retention rate was calculated. The specific results are shown in the following table:

[0080] It can be seen that the method for preparing the sunscreen-doped aluminum silicate aerogel composite material of the present invention incorporates graphene oxide into the aluminum silicate aerogel, resulting in a uniform composite of the graphene oxide sheets and the aluminum silicate aerogel. The -OH groups in the aluminum silicate solution can form covalent bonds with the oxygen-containing functional groups in the graphene oxide, thereby enhancing the interfacial bonding strength between the aerogels. Furthermore, in the preparation of the composite fiber felt, polycarbosilane and ethyl orthosilicate are used as a precursor liquid. After vacuum impregnation, curing, and calcination, a silicon carbide layer is in situ composited on the outer surface of the mullite fiber, directly blocking high-temperature infrared radiation. The sunscreen-doped graphene oxide-doped aluminum silicate sol suppresses thermal radiation, effectively improving the thermal insulation properties of the aerogel composite material and reducing its thermal conductivity. Furthermore, the silicon carbide layer on the outer surface of the fiber further improves the interfacial bonding between the fiber felt and the aerogel, dissipating thermal stress through the fiber felt skeleton, thereby improving the mechanical properties and high-temperature stability of the aerogel composite material. The aforementioned technical means cooperate with each other and work synergistically to effectively overcome the technical defects of existing means of inhibiting alumina phase change, and further improve the high-temperature stability, thermal insulation and mechanical properties of the sunscreen-doped aluminum silicate aerogel composite material while obtaining a high specific surface area.

[0081] Unless otherwise specified, all percentages used in the present invention are by mass.

[0082] 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 aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a sunscreen-doped aluminum silicate aerogel composite material, characterized in that: The following steps are involved: Preparation of graphene oxide doped aluminum silicate sol, preparation of composite fiber felt, sol impregnation, gel aging, and supercritical drying; The method for preparing graphene oxide doped aluminum silicate sol comprises the following steps: mixing aluminum chloride hexahydrate with anhydrous ethanol and deionized water to obtain an aluminum source solution; mixing ethyl orthosilicate with anhydrous ethanol and deionized water to obtain a silicon source solution; mixing the aluminum source solution and the silicon source solution to obtain aluminum silicate sol; and uniformly mixing the aluminum silicate sol and graphene oxide to obtain the graphene oxide doped aluminum silicate sol. The method for preparing the composite fiber felt comprises: uniformly mixing polycarbosilane, tetraethyl orthosilicate, and xylene to obtain a precursor liquid; pressing mullite fibers into a density of 0.22-0.25 g / cm 3 After the fiber felt is prepared, the fiber felt is vacuum impregnated with a precursor liquid, and then solidified and calcined to obtain a composite fiber felt; The mass concentration of polycarbosilane in the precursor liquid is 18-22wt%, and the mass concentration of ethyl orthosilicate is 1.3-1.4wt%; The sol impregnation method comprises vacuum impregnating the composite fiber felt with graphene oxide doped aluminum silicate sol containing an initiator to obtain an impregnated body; The impregnated body is subjected to gel aging and supercritical drying to obtain a sunscreen-doped aluminum silicate aerogel composite material.

2. The method for preparing the sunscreen-doped aluminum silicate aerogel composite material according to claim 1, characterized in that: In the preparation of the graphene oxide-doped aluminum silicate sol, the aluminum source solution uses aluminum chloride hexahydrate, anhydrous ethanol, and deionized water in a molar ratio of 3-3.1:15-17:55-60; The molar ratio of ethyl orthosilicate, anhydrous ethanol and deionized water used in the silicon source solution is 1-1.2:5-6:5-6.

3. The method for preparing the sunscreen-doped aluminum silicate aerogel composite material according to claim 1, characterized in that: In the preparation of the graphene oxide-doped aluminum silicate sol, the aluminum source solution and the silicon source solution are mixed, and the molar ratio of aluminum chloride hexahydrate to tetraethyl orthosilicate is controlled to be 3-3.1:1-1.2; The added weight of graphene oxide is 0.3-0.6% of the weight of the aluminum silica sol.

4. The method for preparing the sunscreen-doped aluminum silicate aerogel composite material according to claim 1, characterized in that: In the preparation of the composite fiber mat, the volume ratio of the precursor liquid to the fiber mat used in the vacuum impregnation is 1:3-3.5; The vacuum degree of vacuum impregnation is 0.08-0.09 MPa, and the vacuum impregnation time is 40-50 minutes.

5. The method for preparing the sunscreen-doped aluminum silicate aerogel composite material according to claim 1, characterized in that: In the preparation of the composite fiber mat, curing is performed by heat-insulating and curing at a temperature of 120-130° C. for 1.5-2 hours, and then heat-insulating and curing at a temperature of 175-185° C. for 1-1.5 hours; The calcination is carried out under the protection of argon atmosphere, at a heating rate of 2-3°C / min, to raise the temperature to 1100-1150°C, and calcining for 1-2 hours to obtain a composite fiber felt.

6. The method for preparing the sunscreen-doped aluminum silicate aerogel composite material according to claim 1, characterized in that: During the sol impregnation, the impregnation temperature is room temperature and the impregnation time is 30-40 minutes; The initiator is propylene oxide, and the molar ratio of the initiator to the aluminum chloride hexahydrate used in the graphene oxide-doped aluminum silicate sol is 1:3-5; The liquid level of the initiator-containing graphene oxide-doped aluminum silicate sol is 1.2-1.6 times the thickness of the composite fiber felt.

7. The method for preparing the sunscreen-doped aluminum silicate aerogel composite material according to claim 1, characterized in that: The gel aging method comprises the following steps: placing the impregnated body in a 48-52° C. temperature environment, maintaining the gel, and then completely immersing the body in anhydrous ethanol, and allowing the body to stand for aging at a temperature of 48-52° C. to obtain a composite body.

8. The method for preparing the sunscreen-doped aluminum silicate aerogel composite material according to claim 7, characterized in that: During the gel aging process, the gelling time is 3-5 hours; The static aging time is 72-96h; During the static aging process, anhydrous ethanol was replaced every 10-12 hours.

9. The method for preparing the sunscreen-doped aluminum silicate aerogel composite material according to claim 1, characterized in that: The supercritical drying method is as follows: after the impregnation body is subjected to gel aging to obtain a composite body, the supercritical drying temperature is controlled to be 270-280° C. and the pressure is 8-9 MPa, and the composite body is supercritically dried for 2-4 hours to obtain a sunscreen-doped aluminum silicate aerogel composite material.

10. A sunscreen-doped aluminum silicate aerogel composite material, characterized in that: The method is prepared according to any one of claims 1 to 9.

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