Method for preparing basalt flake reinforced silicon dioxide aerogel composite material through normal-pressure drying

Abstract

The invention discloses a method for preparing a basalt flake reinforced silicon dioxide aerogel composite material by normal pressure drying, which comprises the following steps: preparing composite wet gel by using a composite silicon source and a basalt flake reinforced material as raw materials, then carrying out aging treatment and primary solvent replacement on the composite wet gel, and then carrying out normal pressure drying to prepare BS / SA composite aerogel; the composite silicon source is a mixture of tetraethyl silicate and methyl trimethoxy silane / methyl triethoxy silane; after the wet gel is aged, surface modification does not need to be carried out, normal-pressure drying can be realized only through one-time solvent replacement, and the BS / SA composite aerogel with a complete structure is obtained. The aerogel prepared by the process has the characteristics of low cost, short process period, low thermal conductivity, excellent mechanical property, high thermal stability and the like.

Description

Technical Field

[0001] The invention relates to an aerogel material, in particular to a method for preparing a basalt flake reinforced silica aerogel composite material by drying at normal pressure. Background Art

[0002] Silica aerogel is a new type of lightweight thermal insulation material formed by cross-linking a silicon-oxygen skeleton network. It has a series of excellent properties such as extremely low thermal conductivity, large specific surface area and low density. It has great application value in the fields of thermal insulation, pollution adsorption, drug delivery and seawater desalination. However, pure silica aerogel itself has problems such as low strength, poor toughness and poor thermal stability, which greatly limits its engineering application. Therefore, in recent years, researchers have been committed to using reinforced materials with good mechanical properties to composite silica aerogel, trying to retain the advantages of silica aerogel such as high porosity, low density and high thermal insulation while overcoming the problems of poor mechanical properties and thermal stability. Currently, researchers mainly use basalt fiber to reinforce silica aerogel, and its preparation methods include supercritical drying, freeze drying and atmospheric pressure drying. The traditional supercritical drying method refers to drying the material in a supercritical state by continuously applying pressure. For example, "Dawei Kang, Shuaide Jia, Chonghang Zhao, et al. High-temperature resistance performance of silica aerogel composites through fiber reinforcement [J]. Ceramics International, 2024, 50: 26829-26838." used basalt fiber and glass fiber as reinforcement materials to prepare composite silica aerogel by supercritical drying. It has good thermal insulation and mechanical properties, but this method requires the composite wet gel to be treated for a long time at a temperature of 270°C and a critical pressure of 10 MPa to obtain a complete sample. The freeze-drying method dries the material by cooling and pumping out air in a vacuum state. For example, "Zheng Wangbo. Preparation and Performance Research of Basalt Fiber / SiO2 Aerogel Composite Insulation Materials[D]. Nanjing University of Aeronautics and Astronautics, 2021.DOI:10.27239 / d.cnki.gnhhu.2021.000900." uses basalt fiber as a skeleton and prepares basalt fiber / SiO2 aerogel with excellent comprehensive performance through freeze-drying. However, this process requires treatment at -60°C for 14 hours, which consumes a lot of energy and has a long process cycle. Although supercritical drying and freeze-drying can obtain silica composite aerogels with good performance, these two methods are highly dependent on equipment and have high energy consumption. At the same time, the high pressure of supercritical drying causes safety risks, and the freeze-drying method has low drying efficiency. The atmospheric pressure drying method is to perform surface modification and solvent replacement on the silica aerogel before the drying step, so that hydrophobic groups are distributed on its surface, and the water in the pores of the wet gel is replaced with solvents such as n-hexane or methanol with lower surface tension, and finally a heating drying treatment is performed under atmospheric pressure conditions.In comparison, atmospheric pressure drying offers significant cost advantages and avoids the dangers of high pressure and the efficiency issues associated with low-temperature drying, making it a drying method with greater potential for widespread application. However, the surface modification and solution replacement required in the atmospheric pressure drying process make the drying process lengthy and cumbersome. Simplifying the atmospheric pressure drying process and shortening the cycle time have become bottleneck issues of widespread concern. For example, "Huang Shilin; Man Xuefeng; Liu Yunyue; Chen Xiaofeng; Zeng Wenying; Wu Chuanyou. A basalt fiber-reinforced aerogel composite material atmospheric pressure drying process: 202310824760.3[P]. 2023-09-29." Basalt fiber-reinforced silica aerogel was prepared using an atmospheric pressure drying method. This method, to some extent, addresses the long atmospheric pressure drying cycle of silica aerogels in existing technologies. However, it still requires 6 to 8 hours of solvent replacement and 22 to 26 hours of surface modification before drying, resulting in suboptimal process cycles and reagent costs.

[0003] Therefore, it is necessary to solve the problems of harsh process conditions, complex process, and long process cycle of silica aerogel. Summary of the Invention

[0004] In light of this, the present invention aims to provide a method for preparing basalt flake-reinforced silica aerogel composites by atmospheric drying. This method eliminates the need for surface modification after wet gel aging and allows atmospheric drying with a single solvent exchange, yielding structurally intact BS / SA composite aerogels. The aerogels produced by this process exhibit low cost, short cycle times, low thermal conductivity, excellent mechanical properties, and high thermal stability.

[0005] A method for preparing a basalt flake reinforced silica aerogel composite material by drying at normal pressure of the present invention comprises the following steps:

[0006] A composite wet gel is prepared using a composite silicon source and a basalt flake reinforcement material as raw materials. The composite wet gel is then aged and subjected to a solvent replacement process before being dried at normal pressure to obtain a BS / SA composite aerogel. The composite silicon source is a mixture of tetraethyl silicate and methyltrimethoxysilane / methyltriethoxysilane.

[0007] Furthermore, the preparation method of the composite wet gel comprises the following steps:

[0008] S1, precursor preparation: add the composite silicon source to 2-4 times the volume of the water-alcohol mixture and stir thoroughly, then add the crosslinking agent and stir until it is clear and no layers are separated; prepare silica sol;

[0009] S2, preparing a composite wet gel by acid-base catalysis: first subjecting the silica sol to an acidic hydrolysis treatment, then to an alkaline catalytic treatment, and finally adding a basalt flake reinforcement material, stirring evenly and then allowing to stand to obtain a composite wet gel;

[0010] Furthermore, in step S1, the water-alcohol mixture is a mixture of anhydrous ethanol and deionized water, with anhydrous ethanol:deionized water = 5:1 to 1:2 by volume;

[0011] Furthermore, in step S2, the acidic hydrolysis treatment step includes: adding a low concentration of inorganic strong acid to the silica sol, adjusting the pH value to 2-3, and standing at 40-60° C. for 1-2 hours to fully hydrolyze the precursor;

[0012] Furthermore, in step S2, the alkaline catalytic treatment step includes: adding ammonia water to the silica sol after the acid hydrolysis treatment to adjust the pH value to 7-10;

[0013] Furthermore, the composite wet gel is aged by immersing in anhydrous ethanol, and the liquid is separated after the aging treatment. Then, a solvent is added to the composite wet gel and the gel is sealed and immersed for solvent replacement. The solvent is a mixture of n-hexane and ethanol, and the volume ratio of n-hexane to anhydrous ethanol is 2:1 to 1:2.

[0014] Furthermore, after solvent replacement, the mixture was first dried at a temperature of 50 to 70° C. under normal pressure, and then dried at a temperature of 100 to 120° C. under normal pressure to obtain a BS / SA composite aerogel.

[0015] Furthermore, in the composite silicon source, the mass ratio of tetraethyl silicate to methyltrimethoxysilane or methyltriethoxysilane is 1:2-1:5.

[0016] Furthermore, the mass ratio of the basalt flakes to the silica matrix is ​​0.8-1.4:1;

[0017] Furthermore, the cross-linking agent is cetyltrimethylammonium bromide (CTAB).

[0018] The beneficial effects of the present invention are as follows: the method for preparing basalt flake reinforced silica aerogel composite materials by normal pressure drying of the present invention uses a mixture of tetraethyl silicate and methyltrimethoxysilane / methyltriethoxysilane to surround the composite silicon source, and uses basalt flakes as the reinforcing material. After the wet gel is aged, it does not need to be surface modified. It can be dried at normal pressure through a simple one-time replacement treatment, which greatly saves the wet gel pretreatment time required before drying and effectively shortens the normal pressure drying process. At the same time, the hydrophobic skeleton formed by the composite silicon source effectively saves the amount of modifier and replacement fluid, further reducing the preparation cost of the material. On the other hand, the basalt flakes as a reinforcing material are compounded with the silica aerogel skeleton, which is conducive to the rapid formation of gel after the sol is hydrolyzed, retaining the high porosity and high thermal insulation properties of the silica aerogel, and improving the mechanical properties to a certain extent. In addition, BS / SA has excellent high-temperature thermal stability. The aerogel prepared by this process has the characteristics of low cost, short process cycle, low thermal conductivity, excellent mechanical properties and high thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0020] Figure 1 These are scanning electron microscope images of BS / SA and SA prepared in Example 1; (a-d) are scanning electron microscope images of SA; (e-f) are scanning electron microscope images of BS / SA;

[0021] Figure 2 is a comparison of the mechanical properties of BS / SA and SA prepared in Example 1;

[0022] Figure 3 This is a comparison chart of the thermal stability of BS / SA and SA prepared in Example 1;

[0023] Figure 4 This is a comparison chart of the fire resistance of BS / SA and SA prepared in Example 1 (comparison of the back surface temperature after 1300°C flame ablation and the morphology of the sample before and after). DETAILED DESCRIPTION

[0024] A method for preparing a basalt flake reinforced silica aerogel composite material by drying at normal pressure in this embodiment includes the following steps:

[0025] A composite wet gel was prepared using a composite silicon source and basalt flake reinforcement as raw materials. The composite wet gel was then aged and subjected to a solvent exchange process before being dried at atmospheric pressure to produce the BS / SA composite aerogel. The composite silicon source was a mixture of tetraethyl silicate (TEOS) and methyltrimethoxysilane (MTMS) / methyltriethoxysilane (MTOS). Basalt scales (BS) are high-performance, two-dimensional, flaky inorganic materials derived from volcanic basalt ore through a process of crushing the raw stone, melting it at high temperatures, homogenizing it, and then recycling and screening it. They inherit the excellent wear resistance, corrosion resistance, and high / low temperature resistance of basalt. Basalt fiber is commonly used to reinforce silica aerogels in the prior art. The addition of basalt fiber significantly improves the compressive strength of the composite while maintaining the aerogel's low thermal conductivity. Basalt fiber is a continuous fiber drawn from natural basalt. It is made by melting the basalt at 1450°C to 1500°C and then drawing it at high speed through a platinum-rhodium alloy drawing plate. Basalt continuous fiber not only has high strength but also possesses a variety of excellent properties, such as electrical insulation, corrosion resistance, and high-temperature resistance. The present invention uses tetraethyl silicate and methyltrimethoxysilane as a composite silicon source, or tetraethyl silicate and methyltriethoxysilane as a composite silicon source. The prepared wet gel is aged and subjected to a single solvent replacement before being dried at normal pressure. No modification of the wet gel is required; normal pressure drying can be performed through a simple single replacement treatment. This greatly reduces the pretreatment time required for the wet gel before drying and effectively shortens the normal pressure drying process. The shortest process cycle can be controlled within 12 hours. This avoids the safety risks caused by the high pressure caused by supercritical drying and the inefficiency caused by freeze-drying. At the same time, the normal pressure drying process is simplified and the normal pressure drying process cycle is shortened. The hydrophobic skeleton formed by the composite silicon source effectively saves the amount of modifier and replacement fluid, further reducing the material preparation cost. On the other hand, the basalt flakes used as a reinforcing material and the silica aerogel skeleton are combined, which is conducive to the rapid formation of gel after the sol hydrolysis. It not only retains the high porosity and high thermal insulation properties of the silica aerogel, but also improves the mechanical properties to a certain extent. In addition, the prepared basalt scale reinforced silica aerogel composite material (BS / SA) has excellent high-temperature thermal stability.

[0026] The specific operation steps are as follows: the preparation method of the composite wet gel comprises the following steps:

[0027] S1, Precursor Preparation: Add a composite silicon source to 2-4 times the volume of a water-alcohol mixture and stir thoroughly, then add a crosslinking agent and stir until clear and without stratification; prepare a silica sol; the composite silicon source comprises, by mass, tetraethyl silicate: methyltrimethoxysilane / methyltriethoxysilane = 1:2-1:5; methyltrimethoxysilane: methyltriethoxysilane = 1:2-1:5; the water-alcohol mixture is a mixture of anhydrous ethanol and deionized water, by volume, anhydrous ethanol: deionized water = 5:1-1:2;

[0028] S2, preparation of composite wet gel by acid-base catalysis: The silica sol is first subjected to acidic hydrolysis treatment, then to alkaline catalytic treatment, and finally basalt flake reinforcement material is added, stirred evenly and allowed to stand to obtain a composite wet gel; tetraethyl silicate (TEOS) undergoes hydrolysis reaction first, and the reaction is carried out in stages, and the reaction activity decreases step by step. As the reaction proceeds, the hydrolysis products undergo mutual condensation to form colloidal particles or sols; the size and degree of cross-linking of the sol particles are related to the intensity of the reaction. Both hydrolysis and polycondensation reactions are carried out under acid or base catalysis. Acidic hydrolysis treatment generally uses an inorganic strong acid to adjust the pH value to acidic, such as hydrochloric acid or nitric acid; then an alkaline substance is used to adjust the pH value to alkaline, and finally a composite wet gel is obtained. The formation of the gel network mainly includes two processes: hydrolysis and polycondensation.

[0029] Preferably, the acidic hydrolysis treatment step comprises: adding a low concentration of inorganic strong acid to the silica sol, adjusting the pH value to 2-3, and standing at 40-60° C. for 1-2 hours to fully hydrolyze the precursor;

[0030] The alkaline catalytic treatment step includes: adding ammonia water to the silica sol after the acid hydrolysis treatment to adjust the pH value to 7-10;

[0031] In this embodiment, the composite wet gel is aged by immersion in anhydrous ethanol. After aging, the liquid is separated, and then a solvent is added to the composite wet gel and sealed and immersed for solvent replacement. The solvent is a mixture of n-hexane and ethanol, with a volume ratio of n-hexane to anhydrous ethanol of 2:1 to 1:2. After solvent replacement, the gel is first dried at room temperature at 50 to 70°C and then dried at room temperature at 100 to 120°C to obtain a BS / SA composite aerogel. The wet gel film is immersed in a mother liquor or a low surface tension solvent (a mixture of n-hexane and ethanol) to enhance the skeleton cross-linking strength. Then, through solvent replacement, the water or high surface tension solvent in the pores of the wet gel is gradually replaced, so that the interactions within and between the polymer molecules are first suppressed and then restored, thereby causing the polymer to dissolve and cross-link. The key good solvent in this method (the mixture of n-hexane and ethanol) helps to stretch the polymer conformation and make the network uniform, forming a hydrogel with excellent rigidity, toughness, anti-swelling and underwater adhesion properties.

[0032] In this embodiment, the mass ratio of the basalt flakes to the silica matrix is ​​preferably 0.8-1.4:1; the crosslinking agent uses a conventional crosslinking agent for preparing silica aerogel, such as hexadecyltrimethylammonium bromide (CTAB), and the amount of the crosslinking agent is calculated and added based on the amount of each substance in the crosslinking reaction.

[0033] Example 1

[0034] 1. Precursor configuration: TEOS and MTMS are mixed as composite silicon sources in a molar ratio of 1:2, and added to a 2-fold volume of a water-alcohol mixture and stirred thoroughly (the volume ratio of anhydrous ethanol to deionized water is 5:1), and cetyltrimethylammonium bromide (CTAB) is added, and finally stirred thoroughly to obtain a clear and non-stratified silica sol.

[0035] 2. Acid-base catalysis to prepare wet gel, the steps are as follows:

[0036] ① Acidic hydrolysis: Add 0.8 mol / L hydrochloric acid to the silica sol in step 1, adjust the pH value to 2, and let it stand at 60°C for 1 hour to fully hydrolyze the precursor. After completion, pour it into the mold.

[0037] ②Alkaline catalysis: Prepare 0.4 mol / L ammonia water, slowly drip it into the silica sol in step ①, and adjust the pH value to 7.

[0038] ③ Basalt flake compounding: Weigh basalt flakes at a mass ratio of 0.8:1 to the silica matrix. Then, add the basalt flakes to the silica sol from step ②, stir to evenly distribute the mixture, and let it stand at room temperature for 40 minutes to obtain a wet gel.

[0039] 3. Wet gel processing, the steps are as follows:

[0040] ① Aging treatment: The wet gel obtained in step 2 was removed from the mold and immersed in anhydrous ethanol for 1 h for aging treatment.

[0041] ②Solvent replacement: After aging, separate and pour off the liquid. Add a mixture of n-hexane and ethanol (n-hexane: anhydrous ethanol volume ratio = 2:1) for solvent replacement. Seal the wet gel and soak it for 5 hours. Then remove the sample and recycle the supernatant n-hexane for reuse.

[0042] 4. Drying at normal pressure: Dry the wet gel obtained in step 3 at 50°C for 2 h, and then at 100°C for 2 h to finally obtain BS / SA composite aerogel.

[0043] Example 2

[0044] 1. Precursor configuration: A mixed solution of TEOS and MTMS was used as a composite silicon source, mixed at a molar ratio of 1:5, and added to a 4-fold volume of a water-alcohol mixture (where the volume ratio of anhydrous ethanol to deionized water was 1:2) and stirred thoroughly. Cetyltrimethylammonium bromide (CTAB) was then added and stirred thoroughly until a clear and non-stratified silica sol was obtained.

[0045] 2. Acid-base catalysis to prepare wet gel, the steps are as follows:

[0046] ① Acidic hydrolysis: Add 1.2 mol / L or nitric acid to the silica sol in step 1, adjust the pH value to 3, and let it stand at 40°C for 2 hours to fully hydrolyze the precursor. After completion, pour it into the mold.

[0047] ②Alkaline catalysis: Prepare 0.6 mol / L ammonia water, slowly drip it into the silica sol in step ①, and adjust the pH value to 10.

[0048] ③ Basalt flake compounding: Weigh basalt flakes at a mass ratio of 1.4:1 to the silica matrix. Then, add the basalt flakes to the silica sol from step ②, stir to evenly distribute the mixture, and let it stand at room temperature for 60 minutes to obtain a wet gel.

[0049] 3. Wet gel processing, the steps are as follows:

[0050] ① Aging treatment: The wet gel obtained in step 2 was removed from the mold and immersed in anhydrous ethanol for 2 h for aging treatment.

[0051] ②Solvent replacement: After aging, separate and pour off the liquid. Add a mixture of n-hexane and ethanol (n-hexane: anhydrous ethanol volume ratio = 1:2) for solvent replacement. Seal the wet gel and soak it for 10 hours. Then remove the sample and recycle the supernatant n-hexane for reuse.

[0052] Drying at normal pressure: The wet gel obtained in step 3 was dried at 70°C for 2 h, and then dried at 120°C for 2 h to finally obtain the BS / SA composite aerogel.

[0053] Example 3

[0054] 1. Precursor configuration: A mixed solution of TEOS and methyltriethoxysilane (MTOS) was used as a composite silicon source, mixed in a molar ratio of 1:3, and added to a 3-fold volume of a water-alcohol mixture (where the volume ratio of anhydrous ethanol to deionized water was 1:1) and stirred thoroughly. Hexadecyltrimethylammonium bromide (CTAB) was then added and stirred thoroughly until a clear and non-stratified silica sol was obtained.

[0055] 2. Acid-base catalysis to prepare wet gel, the steps are as follows:

[0056] ① Acidic hydrolysis: Add 1 mol / L nitric acid to the silica sol in step 1, adjust the pH to 3, and let it stand at 50°C for 1.5 hours to fully hydrolyze the precursor. After completion, pour it into the mold.

[0057] ②Alkaline catalysis: Prepare 0.5 mol / L ammonia water, slowly drip it into the silica sol in step ①, and adjust the pH value to 8.

[0058] ③ Basalt flake compounding: Weigh basalt flakes at a mass ratio of 1:1 to the silica matrix. Then, add the basalt flakes to the silica sol from step ②, stir to evenly distribute the mixture, and let it stand at room temperature for 50 minutes to obtain a wet gel.

[0059] 3. Wet gel processing, the steps are as follows:

[0060] ① Aging treatment: The wet gel obtained in step 2 was removed from the mold and immersed in anhydrous ethanol for 1.5 h for aging treatment.

[0061] ②Solvent replacement: After aging, separate and pour off the liquid. Add a mixture of n-hexane and ethanol (n-hexane: anhydrous ethanol, volume ratio = 1:1) for solvent replacement. Seal the wet gel and soak it for 8 hours. Then remove the sample and recycle the supernatant n-hexane for reuse.

[0062] 4. Drying at normal pressure: Dry the wet gel obtained in step 3 at 60°C for 2 h, and then at 110°C for 2 h to finally obtain BS / SA composite aerogel.

[0063] Example 4

[0064] 1. Precursor configuration: A mixed solution of TEOS and methyltriethoxysilane (MTOS) was used as a composite silicon source, mixed at a molar ratio of 1:4, and added to a 2-fold volume of a water-alcohol mixture (where the volume ratio of anhydrous ethanol to deionized water was 4:1) and stirred thoroughly. Hexadecyltrimethylammonium bromide (CTAB) was then added and stirred thoroughly until a clear, non-stratified silica sol was obtained.

[0065] 2. Acid-base catalysis to prepare wet gel, the steps are as follows:

[0066] ① Acidic hydrolysis: Add 1 mol / L hydrochloric acid to the silica sol in step 1, adjust the pH to 2, and let it stand at 45°C for 2 hours to fully hydrolyze the precursor. After completion, pour it into the mold.

[0067] ②Alkaline catalysis: Prepare 0.5 mol / L ammonia water, slowly drip it into the silica sol in step ①, and adjust the pH value to 9.

[0068] ③ Basalt flake compounding: Weigh basalt flakes at a mass ratio of 1.2:1 to the silica matrix. Then, add the basalt flakes to the silica sol from step ②, stir to evenly distribute the mixture, and let it stand at room temperature for 50 minutes to obtain a wet gel.

[0069] 3. Wet gel processing, the steps are as follows:

[0070] ① Aging treatment: The wet gel obtained in step 2 was removed from the mold and immersed in anhydrous ethanol for 2 h for aging treatment.

[0071] ②Solvent replacement: After aging, separate and pour off the liquid. Add a mixture of n-hexane and ethanol (n-hexane: anhydrous ethanol, volume ratio = 2:3) for solvent replacement. Seal the wet gel and soak for 9 hours. Then remove the sample and recycle the supernatant n-hexane for reuse.

[0072] 4. Drying at normal pressure: Dry the wet gel obtained in step 3 at 60°C for 2 h, and then at 100°C for 2 h to finally obtain BS / SA composite aerogel.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a basalt flake reinforced silica aerogel composite material by drying at atmospheric pressure, characterized in that: The following steps are involved: A composite wet gel is prepared using a composite silicon source and a basalt flake reinforcement material as raw materials. The composite wet gel is then aged and subjected to a solvent replacement process before being dried at normal pressure to obtain a BS / SA composite aerogel. The composite silicon source is a mixture of tetraethyl silicate and methyltrimethoxysilane / methyltriethoxysilane.

2. The method for preparing basalt flake reinforced silica aerogel composite material by drying at normal pressure according to claim 1, characterized in that: The preparation method of the composite wet gel comprises the following steps: S1, precursor preparation: add the composite silicon source to 2-4 times the volume of the water-alcohol mixture and stir thoroughly, then add the crosslinking agent and stir until it is clear and no layers are separated; prepare silica sol; S2, preparation of composite wet gel by acid-base catalysis: the silica sol is first subjected to acid hydrolysis treatment, then to alkaline catalysis treatment, and finally basalt flake reinforcement material is added, stirred evenly and allowed to stand to obtain a composite wet gel.

3. The method for preparing basalt flake reinforced silica aerogel composite material by drying at normal pressure according to claim 2, characterized in that: In step S1, the water-alcohol mixture is a mixture of anhydrous ethanol and deionized water, with anhydrous ethanol:deionized water ratio of 5:1 to 1:2 by volume.

4. The method for preparing basalt flake reinforced silica aerogel composite material by drying at normal pressure according to claim 2, characterized in that: In step S2, the acidic hydrolysis treatment step includes: adding an inorganic strong acid to the silica sol, adjusting the pH value to 2-3, and standing at 40-60°C for 1-2 hours to fully hydrolyze the precursor.

5. The method for preparing basalt flake reinforced silica aerogel composite material by drying at normal pressure according to claim 4, characterized in that: In step S2, the alkaline catalytic treatment step includes: adding ammonia water to the silica sol after the acid hydrolysis treatment, and adjusting the pH value to 7-10.

6. The method for preparing basalt flake reinforced silica aerogel composite material by drying at normal pressure according to claim 1, characterized in that: The composite wet gel is aged by immersing in anhydrous ethanol. After the aging treatment, the liquid is separated. Then, a solvent is added to the composite wet gel and the gel is sealed and immersed for solvent replacement. The solvent is a mixture of n-hexane and ethanol. The volume ratio of n-hexane to anhydrous ethanol is 2:1 to 1:

2.

7. The method for preparing basalt flake reinforced silica aerogel composite material by drying at normal pressure according to claim 1, characterized in that: After solvent replacement, the BS / SA composite aerogel is prepared by first drying the BS / SA composite aerogel at a temperature of 50-70° C. under normal pressure and then drying the BS / SA composite aerogel at a temperature of 100-120° C. under normal pressure.

8. The method for preparing basalt flake reinforced silica aerogel composite material by drying at normal pressure according to claim 1, characterized in that: In the composite silicon source, the mass ratio of tetraethyl silicate: methyltrimethoxysilane / methyltriethoxysilane is 1:2-1:5; and the mass ratio of methyltrimethoxysilane: methyltriethoxysilane is 1:2-1:

5.

9. The method for preparing basalt flake reinforced silica aerogel composite material by drying at normal pressure according to claim 1, characterized in that: The mass ratio of the basalt flakes to the silica matrix is ​​0.8-1.4:

1.

10. The method for preparing basalt flake reinforced silica aerogel composite material by drying at normal pressure according to claim 1, characterized in that: The cross-linking agent is hexadecyltrimethylammonium bromide.

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