Aerogel composite material and preparation method thereof

Abstract

The invention belongs to the field of aerogel, and particularly relates to an aerogel composite material and a preparation method thereof. The preparation method of the aerogel composite material comprises the following steps: (1) preparing a glue solution containing a low-steric-hindrance modifier; the glue solution mainly comprises a silicon source, the low-steric-hindrance modifier, a catalyst and a solvent; the modifier with low steric hindrance is C1-3 alkyl and alkoxy silane; (2) dipping a base material in the glue solution, standing until gel is formed, drying, and performing gas phase modification by using a high steric hindrance modifier; and the high steric hindrance modifier is hexaalkyl disilazane. The aerogel composite material is provided with the rigid framework main body and the flexible surface layer, breaks through the shackle of'brittleness with strong strength and weakness with softness', realizes combination of rigidity and softness, and can well consider the strength and rebound resilience of the aerogel composite material.

Description

Technical Field

[0001] This invention belongs to the field of aerogels, specifically relating to an aerogel composite material and its preparation method. Background Technology

[0002] Silica aerogels possess properties such as a three-dimensional nanoparticle framework (2-5 nm in size) and a high specific surface area (~1000 m²). 2 / g), nanoscale pores (~20nm), low density (0.003 ~ 0.15g / cm³), 3 Due to their unique microstructures, aerogels exhibit distinctive properties in thermal, optical, electrical, and acoustic fields. In particular, their nanoporous structure effectively suppresses heat conduction in both solid and gaseous environments, resulting in excellent thermal insulation properties. They are currently recognized as the solid material with the lowest thermal conductivity, reaching as low as 0.01 to 0.03 W / (m·K) at room temperature.

[0003] Meanwhile, silica aerogel also exhibits a high operating temperature, maintaining a good porous network structure even at temperatures as high as 900℃. Therefore, compared to traditional insulation materials, SiO2 aerogel composite insulation materials with nanopores can achieve equivalent insulation effects with a lighter weight and smaller volume. This characteristic offers significant advantages in military, aerospace, petrochemical, chemical, and metallurgical industries.

[0004] Currently, aerogel composites have achieved industrialization and engineering applications. In their preparation, aerogels and fibers are typically composited by impregnating a fiber substrate (such as glass fiber mat, pre-oxidized fiber mat, ceramic fiber mat, etc.) with a sol. Subsequent processes include gelation, aging, hydrophobic treatment, and drying to manufacture the aerogel composite product. However, because the porous network structure of traditional silica aerogels is mostly dense and fragile, aerogels are prone to structural collapse under low stress, exhibiting disadvantages such as low strength and poor toughness. This significantly limits the practical application performance of aerogel composites.

[0005] Chinese invention patent application CN 120136525 A, published on June 13, 2025, discloses a method for preparing hydrophobic SiO2 aerogel through in-situ polymerization. The method involves first mixing an alcohol solvent, a silicon source, water, an in-situ modifier, and a catalyst to obtain a homogeneous solution. The resulting sol solution is then adjusted to pH 2-5 with an acid, allowed to stand for 2-4 hours for hydrolysis, and then adjusted to pH 6-8 with an alkali solution. After stirring for 10-25 minutes, the solution is allowed to stand again to allow polymerization. The silica sol solution is then impregnated into an inorganic fiber material using an impregnation process to obtain a composite material of silica sol and inorganic fiber material. After standing for 1.5-3 hours, a gel composite material is obtained. This gel composite material is then aged in an aging solution mixture, and finally, supercritical drying is performed to obtain the SiO2 aerogel composite material.

[0006] The aforementioned existing technology involves adding in-situ modifiers such as dimethyldiethoxysilane and trimethylmethoxysilane to the sol-gel solution, followed by aging using a siloxane / alcohol solvent mixture. The siloxanes include dimethyldiethoxysilane, trimethylmethoxysilane, and methyltrimethoxysilane. This in-situ polymerization process forms an organic-inorganic gel network, improving the hydrophobicity of the aerogel material and, to some extent, the strength of the aerogel network structure. However, problems with poor toughness and resilience still exist. Aerogels with poor resilience undergo permanent collapse of their pore structure under pressure, resulting in decreased porosity, a sharp increase in thermal conductivity, and a significant reduction in insulation performance. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing aerogel composite materials, which solves the problem that existing aerogel composite materials cannot simultaneously achieve both strength and resilience.

[0008] A second objective of this invention is to provide an aerogel composite material obtained by the above preparation method to solve the aforementioned problems.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing an aerogel composite material includes the following steps: (1) Prepare a glue solution containing a low steric hindrance modifier; the glue solution mainly consists of a silicon source, the low steric hindrance modifier, a catalyst, and a solvent; the low steric hindrance modifier is C 1-3 Alkyl and alkoxysilanes; (2) The substrate is impregnated with the adhesive solution, allowed to stand until gelation is complete and then dried, and then modified in the gas phase using a high steric hindrance modifier; the high steric hindrance modifier is hexaalkyldisilazane.

[0010] This invention is an improved version. During the gelation process, a low-steric hindrance modifier is introduced to participate in the construction of the gel skeleton, allowing it to penetrate deep into the gel pores and form a rigid network with high cross-linking density. After gelation, a high-steric hindrance modifier is introduced to construct a flexible layer with low cross-linking density on the aerogel surface, dissipating external stress through molecular chain entanglement. This aerogel composite material possesses a rigid skeleton and a flexible surface layer, breaking through the constraint of "strong is brittle, flexible is weak," achieving a balance between rigidity and flexibility, and effectively balancing the strength and resilience of aerogel composite materials.

[0011] Preferably, the hexaalkyldisilazane is selected from one or both of hexamethyldisilazane and hexaethyldisilazane.

[0012] More preferably, the temperature of the gas phase modification is 100~130℃, the pressure is 0.05~0.09MPa, and the time is 3~5h, where the pressure represents the gas pressure of the high steric hindrance modifier.

[0013] Preferably, the C 1-3 The alkyl and alkoxysilanes are selected from one or any combination of methyltriethoxysilane, propyltriethoxysilane, and dimethyldiethoxysilane.

[0014] More preferably, the low steric hindrance modifier has a mass fraction of 1-3% in the adhesive solution.

[0015] Preferably, after gelation in step (2) and before drying, the gel is wet-modified with a long-chain trialkoxysilane, wherein the carbon chain length of the long-chain trialkoxysilane is 16-18. Long-chain trialkoxysilanes, such as C... 16-18 Alkyltrimethoxysilane.

[0016] More preferably, the wet modification adopts an impregnation method, the impregnation temperature is 30~40℃, and the time is 24~48h; long carbon chain trialkoxysilane and ethanol are mixed at a volume ratio of 1:(20~40) as impregnation solvent.

[0017] Preferably, the adhesive is composed of the following components in mass fractions: 1-3% low steric hindrance modifier, 0.01-0.03% fluoride salt, 0.1-0.5% ethanolamine, 12-15% silicon source, and the remainder being ethanol and water; the fluoride salt is selected from one or both of ammonium bifluoride and ammonium fluoride.

[0018] Preferably, step (1) involves preparing a filtrate solution composed of a fluoride salt, ethanolamine, a silicon source, and a solvent; step (2) involves impregnating the substrate with the filtrate solution, allowing it to stand until gelation is complete, then performing wet modification of the gel using a long-chain trialkoxysilane, drying it, and then performing gas-phase modification using a high steric hindrance modifier; the high steric hindrance modifier is hexaalkyldisilazane. The filtrate solution preferably consists of the following components in the indicated mass fractions: 0.01-0.03% fluoride salt, 0.1-0.5% ethanolamine, 12-15% silicon source, with the remainder being ethanol and water.

[0019] In the above-mentioned adhesive solution, the mass ratio of ethanol to water is preferably 14~20:1, more preferably 14~15:1.

[0020] An aerogel composite material prepared using the above-described preparation method.

[0021] The aerogel composite material prepared by the above method forms a gradient modified structure with a rigid inner layer and a flexible outer layer. The inner layer provides structural reinforcement, while the outer layer provides elastic buffering to resist external stress. This aerogel composite material takes into account both aerogel strength and resilience. During transportation, installation, or use, it can withstand repeated vibrations and stresses and maintain the aerogel structure, thereby giving full play to the excellent thermal insulation performance of the aerogel composite material. Attached Figure Description

[0022] Figure 1 The compression-rebound curves of the aerogel composite material in Comparative Example 1 are shown. Figure 2 The compression-rebound curves of the aerogel composite material in Comparative Example 2 are shown. Figure 3 The compression-rebound curves of the aerogel composite material in Comparative Example 3 are shown. Figure 4 The compression rebound curve of the aerogel composite material in Example 1 is shown. Figure 5 The compression rebound curve of the aerogel composite material in Example 2; Figure 6 The compression rebound curves of the aerogel composite material in Comparative Example 4 are shown. Detailed Implementation

[0023] (I) Preferred embodiments of the aerogel composite material and its preparation method of the present invention The technical concept of this invention is to first use a low steric hindrance modifier to participate in the gelation reaction to improve the strength of the aerogel network structure, and then use a high steric hindrance modifier and gas phase modification (non-liquid phase) after drying to form a flexible surface layer, thereby improving the resilience of the aerogel composite material.

[0024] The preparation process of the above-mentioned aerogel composite material is as follows: (1) Prepare a glue solution containing a low steric hindrance modifier; the glue solution mainly consists of a silicon source, the low steric hindrance modifier, a catalyst, and a solvent; the low steric hindrance modifier is selected from C 1-3 Alkyl and alkoxysilanes.

[0025] This step involves adding a low steric hindrance modifier to the gel solution used to prepare SiO2 aerogel. The low steric hindrance modifier is C. 1-3 Alkyl and alkoxysilanes, such as methyltriethoxysilane, propyltriethoxysilane, dimethyldiethoxysilane, or any combination thereof.

[0026] In the subsequent gelation reaction, the low steric hindrance modifier can penetrate into the deep pores of the aerogel, participate in the construction of the gel skeleton, form rigid nodes within the gel network, and provide a stable substrate. Controlling the mass fraction of the low steric hindrance modifier in the gel solution to 1-3%, for example 1.2-2.6%, can achieve a good skeleton modification effect.

[0027] The gel solution for preparing SiO2 aerogel can be any existing conventional gel solution system. It generally contains components such as silicon source, catalyst, and solvent.

[0028] The silicon source (precursor) can be a conventional substance such as tetraethyl orthosilicate or methyl orthosilicate. The mass fraction of the silicon source in the adhesive solution can be 12-15%.

[0029] Catalysts regulate the rate and equilibrium of hydrolysis and condensation reactions and control gel structure formation. Commonly used catalysts include acidic and basic catalysts. Acidic catalysts, such as HCl and oxalic acid, can more effectively promote hydrolysis. Basic catalysts, such as ammonia and ethanolamine, can more effectively promote condensation. Taking ethanolamine as an example, an ethanolamine solution with a concentration of 0.5~1 mol / L can be prepared, and the amount of ethanolamine solution added to the gel solution can be controlled at 3~4% to achieve the effect of promoting the formation of a good gel structure.

[0030] The solvent serves to dissolve the silicon source and provide a homogeneous reaction environment for the hydrolysis and condensation reactions. A mixture of alcohol and water is preferred. For example, a mixture of ethanol and water in a mass ratio of 14 to 20:1.

[0031] Preferably, the aerogel solution also contains a fluoride salt, which is selected from one or both of ammonium bifluoride and ammonium fluoride. The aqueous solution of the fluoride salt (e.g., an aqueous solution of ammonium fluoride) is weakly acidic. The weakly acidic environment provided by the ammonium ions can regulate the hydrolysis rate of precursors such as silanes, avoiding aggregation caused by excessively rapid hydrolysis. Simultaneously, the fluoride ions provide coordination, jointly optimizing the pore structure and molding effect of the aerogel. Furthermore, fluoride ions readily promote the formation of a highly cross-linked but uniform nanonetwork, exhibiting high specific surface area, high porosity, and a robust framework, facilitating the formation of large-volume aerogels.

[0032] Fluoride salts can be added in the form of a fluoride salt solution. The concentration of the fluoride salt solution can be controlled at 0.05~0.1 mol / L. The amount of fluoride salt solution added can be controlled at approximately 10~15%.

[0033] Overall, the above-mentioned adhesive consists of the following components by mass fraction: 1-3% low steric hindrance modifier, 10-15% fluoride salt solution of 0.05-0.1 mol / L, 3-4% ethanolamine solution of 0.5-1 mol / L, 12-15% silicon source, and the remainder being ethanol and water.

[0034] When preparing the adhesive solution, add alcohol, water, silicon source, low steric hindrance modifier, and fluoride salt in sequence, mix well, and then add catalyst and stir until well mixed.

[0035] (2) The substrate is impregnated with the adhesive solution, allowed to stand until gelation is complete and then dried, and then modified in the gas phase using a high steric hindrance modifier.

[0036] The gelation time is typically 30-50 minutes. A wet gel is formed through the gelation reaction. During this process, the modifier penetrates deep into the pores of the aerogel, participating in the construction of the gel skeleton and forming rigid nodes within the gel network. This provides a stable substrate, preventing microcracks caused by stress concentration during subsequent drying, and increasing the strength and toughness of the aerogel skeleton. Ultrasonic waves can be used during the gelation process to remove air bubbles, thereby improving the uniformity of the gel skeleton and the strength of the final product.

[0037] Conventional supercritical CO2 drying methods can be used for drying.

[0038] After drying, a high steric hindrance modifier is used for gas-phase modification above the vaporization temperature. This gas-phase modification forms an external flexible modified layer. Taking hexamethyldisilazane as an example, a silanization reaction occurs during the gas-phase modification process. Its Si-N-Si bonds react with the Si-OH groups on the aerogel surface to form a trimethylsilyl ether-terminated product (–OSi(CH3)3), which is hydrophobic and has high steric hindrance. Hexamethyldisilazane, however, undergoes almost no crosslinking (hexamethyldisilazane has no multifunctional groups), forming a monolayer covering with extremely low crosslinking density.

[0039] The vapor-phase modification temperature is 100℃, and the time is 3 hours. Hexaalkyldisilazane can be selected as the high steric hindrance modifier. For example, hexaalkyldisilazane is selected from one or both of hexamethyldisilazane and hexaethyldisilazane.

[0040] Vapor-phase modification can further enhance the modification capability and structural stability of aerogels. A low-crosslink density flexible layer can be constructed on the surface of the aerogel, dissipating external stress through molecular chain entanglement. Since the aforementioned high steric hindrance modifiers may decompose under high temperature and high pressure drying conditions, it is necessary to ensure that supercritical drying completely removes ethanol and water from the aerogel. After supercritical drying, vapor-phase modification is applied to the aerogel surface to suppress capillary stress, increase structural stability, and improve resilience.

[0041] The preferred embodiments described above are illustrated below with specific examples. Unless otherwise specified, all raw materials involved are commercially available conventional raw materials, and all related processing techniques are conventional techniques in the art. Unless otherwise specified, "%" refers to mass percentages.

[0042] Example 1 The preparation method of the aerogel composite material in this embodiment adopts the following steps: (1) Prepare an adhesive solution containing a low steric hindrance modifier.

[0043] A gel solution was prepared using tetraethyl orthosilicate, methyltriethoxysilane, 0.05 mol / L ammonium fluoride solution, 0.5 mol / L ethanolamine solution, water, and ethanol. The gel solution consisted of the following components by mass fraction: tetraethyl orthosilicate 14.06%, methyltriethoxysilane 1.29%, 0.05 mol / L ammonium fluoride solution 10%, 0.5 mol / L ethanolamine solution 3.33%, water 5.4%, and ethanol 65.92%. On a pure substance basis, the mass percentage composition of each component was: tetraethyl orthosilicate 14.06%, methyltriethoxysilane 1.29%, ammonium fluoride 0.0185%, ethanolamine 0.1016%, water 5.4%, and ethanol 79.13%.

[0044] Ethanol, water, tetraethyl orthosilicate, and ammonium fluoride solution were mixed in proportion and stirred for 10 minutes. Then, ethanolamine solution was added and mixed thoroughly to obtain the gel.

[0045] (2) The substrate is impregnated with the adhesive solution, allowed to stand until gelation is complete and then dried, and then modified in the gas phase using a high steric hindrance modifier.

[0046] Impregnation and gelation: A 4mm thick pre-oxidized felt is impregnated with the resin solution and allowed to stand until gelation is complete (approximately 30 minutes) to obtain a wet gel with modified internal skeleton. After gelation, the gel is sealed with ethanol as a solvent, and then aged at room temperature for 24-48 hours to simultaneously complete aging and solvent replacement.

[0047] Drying + gas phase modification: Supercritical CO2 drying was performed, followed by gas phase modification using hexamethyldisilazane at 100℃ and 0.09MPa for 3 hours.

[0048] The aerogel composite material of this embodiment is prepared by the above-described method. It is a pre-oxidized fiber felt aerogel composite material with a density of 65-70 kg / m³. 3 Specific surface area is 900-1000 m² 2 / g, with a thermal conductivity of 0.019-0.021 W / (m•K).

[0049] Example 2 The preparation method of the aerogel composite material in this embodiment differs from that in Example 1 only in that the aerogel solution is composed of the following components by mass fraction: tetraethyl orthosilicate 13.33%, propyltriethoxysilane 1.98%, 0.05 mol / L ammonium fluoride solution 10%, 0.5 mol / L ethanolamine solution 3.33%, water 5.4%, and ethanol 65.95%. Based on pure substances, the mass percentages of each component are: tetraethyl orthosilicate 13.33%, propyltriethoxysilane 1.98%, ammonium fluoride 0.0185%, ethanolamine 0.1016%, water 5.4%, and ethanol 79.17%.

[0050] The aerogel composite material of this embodiment has basically the same parameters as that of Example 1, such as density, specific surface area, and thermal conductivity.

[0051] (ii) Comparative Example Comparative Example 1 The aerogel composite material in this comparative example is basically the same as that in Example 1, except that it is not modified by hexamethyldisilazane after supercritical CO2 drying.

[0052] Comparative Example 2 The aerogel composite material in this comparative example is basically the same as that in Example 2, except that it is not modified by hexamethyldisilazane after supercritical CO2 drying.

[0053] Comparative Example 3 The aerogel composite material of this comparative example was prepared using the following steps: (1) Prepare the adhesive solution.

[0054] The adhesive solution is composed of ethanol, water, tetraethyl orthosilicate, ammonium fluoride, and ethanolamine in a molar ratio of 321.4:71.5:23.3:1.0:12.8, and is prepared according to the method of Example 1. The mass percentage composition of each component, based on pure substances, is as follows: tetraethyl orthosilicate 15%, ammonium fluoride 0.0185%, ethanolamine 0.1016%, water 5.4%, and ethanol 79.48%.

[0055] (2) Preparation of aerogel composite materials The impregnation, gelation, and supercritical CO2 drying were performed in the same manner as in Example 1 to obtain an unmodified aerogel felt composite material.

[0056] Comparative Example 4 The aerogel composite material of this comparative example was prepared using the following steps: (1) Preparation of adhesive solution: The composition of the adhesive solution is the same as that of comparative example 3.

[0057] (2) Liquid phase modification + gas phase modification Impregnation and gelation: Impregnation and gelation were performed in the same manner as in Example 1 to obtain a wet gel mat.

[0058] Liquid-phase modification: The wet gel felt was impregnated in an ethanol solution of octadecyltrimethoxysilane and treated at 30°C for 24 hours to complete the liquid-phase modification. The ethanol solution of octadecyltrimethoxysilane was prepared by mixing octadecyltrimethoxysilane and ethanol at a volume ratio of 1:20.

[0059] In the liquid-phase modification process, octadecyltrimethoxysilane has a large molecular volume (containing C... 18 The long alkyl chain makes it difficult to penetrate deep into the pores, and it mainly modifies the outer surface and large pore areas. Its long chain steric hindrance inhibits further cross-linking, thus forming a low cross-linking or nearly monolayer grafted structure. The grafted long alkyl chain can also provide a certain degree of flexibility and hydrophobicity.

[0060] Drying + gas phase modification: After drying with supercritical CO2, gas phase modification was carried out in accordance with the method of Example 1.

[0061] (III) Experimental Examples This experiment tests the compression rebound rate of the aerogel composite materials in each embodiment and comparative example. The test method is as follows: each sample is compressed to 30% deformation thickness for 2 minutes, and the pressure is measured when it rebounds to 15% deformation thickness.

[0062] The rebound test curves of Comparative Examples 1, 2, and 3 are as follows: Figures 1-3 As shown.

[0063] The three sets of experiments (three samples tested in each set) show that: the aerogel composites of Comparative Examples 1 and 2 exhibit significantly larger forces during downward displacement in the universal testing machine (compared to Comparative Example 3), indicating that adding a low steric hindrance modifier during the gelation reaction can improve the overall strength of the aerogel composites; in addition, the forces in the three sets of experimental curves of Comparative Examples 1-3 approach 0N after 120s, indicating that the aerogels have no obvious resilience at this time, that is, the downward pressure destroys the aerogel structure.

[0064] The rebound test curves of Examples 1, 2, and 4 are as follows: Figures 4-6 As shown.

[0065] Analysis of the three sets of experiments in Example 1, Example 2, and Comparative Example 4 shows that the aerogel composite materials in Example 1, Example 2, and Comparative Example 4 did not exhibit significant force during the downward displacement process in the universal testing machine, but after 120s, the force curves in all three sets of data showed obvious rebound; indicating that after gas phase modification, the rigidity of the aerogel was reduced, and the resilience of the aerogel was improved.

[0066] In Comparative Example 4, no modification was performed during the gelation stage, but two modifications were performed after gelation. However, its resilience performance was worse than that of Examples 1 and 2. It can be seen that the damage to the aerogel structure during the compression process was greater than that of Examples 1 and 2. That is, modification during the gelation stage helps to improve the strength of the aerogel structure.

[0067] The resilience of each group of experimental samples is summarized in Table 1.

[0068] Table 1 Resilience of each group of experimental samples

[0069] The experimental results above show that during liquid-phase modification, prolonged immersion in solvents (such as ethanol and n-hexane) can swell the gel skeleton, leading to localized structural shrinkage or collapse after drying, forming rigid "dead zones" that are difficult to recover after compression. Compared to liquid-phase modification, gas-phase modification uses gaseous modifiers that can uniformly cover all pore surfaces, forming a continuous and flexible modified layer (-Si-CH3), reducing stress concentration points and preserving the pore structure of the aerogel more completely.

[0070] The method of this invention can form a rigid inner layer and a flexible outer layer. The inner layer provides structural reinforcement, while the outer layer provides elastic cushioning to resist external stress. The aerogel composite material prepared using the above method maintains structural and functional integrity, breaking through the constraint of "strong is brittle, flexible is weak" and achieving a balance between rigidity and flexibility.

[0071] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is 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 of making an aerogel composite material, characterized by, The method comprises the following steps: (1) preparing a colloidal solution containing a low steric hindrance modifier; the colloidal solution mainly consists of a silicon source, the low steric hindrance modifier, a catalyst and a solvent; the low steric hindrance modifier is C 1-3 alkyl and alkoxy silane; (2) preparing a colloidal solution containing a low steric hindrance modifier; the colloidal solution mainly consists of a silicon source, the low steric hindrance modifier, a catalyst and a solvent; the low steric hindrance modifier is C 1-3 alkyl and alkoxy silane; (3) preparing a colloidal solution containing a low steric hindrance modifier; the colloidal solution mainly consists of (2) immersing the substrate in the glue solution, standing until the gelation is completed, drying, and then performing gas-phase modification using a high steric hindrance modifier; the high steric hindrance modifier is hexaalkyldisilazane.

2. The method of claim 1, wherein the aerogel composite is prepared by a process comprising: The hexaalkyldisilazane is selected from one or both of hexamethyldisilazane and hexaethyldisilazane.

3. The method of claim 2, wherein the aerogel composite is prepared by a process comprising: The temperature of the gas-phase modification is 100-130℃, the pressure is 0.05-0.09MPa, and the time is 3-5h.

4. The method of claim 1, wherein the aerogel composite is prepared by a process comprising: The C 1-3 The alkyl and alkoxysilane is selected from one or any combination of methyltriethoxysilane, propyltriethoxysilane, dimethyldiethoxysilane.

5. The method for preparing the aerogel composite material as described in claim 1, characterized in that, The mass fraction of the low steric hindrance modifier in the glue solution is 1-3%.

6. The method of claim 1, wherein the aerogel composite is prepared by a process comprising: After the gelation is completed, the drying is performed before the gel is modified using a long carbon chain trialkoxysilane in a wet method, and the long carbon chain trialkoxysilane has a carbon chain length of 16-18.

7. The method of claim 6, wherein the aerogel composite is prepared by a process comprising: The wet modification is performed using an immersion method, the temperature of the immersion is 30-40℃, and the time is 24-48h; the long carbon chain trialkoxysilane and ethanol are mixed in a volume ratio of 1:(20-40) to serve as the immersion solvent.

8. The method of claim 1, wherein the aerogel composite is prepared by a process comprising: The glue solution is composed of the following components in mass fractions: low steric hindrance modifier 1-3%, fluorinated salt 0.01-0.03%, ethanolamine 0.1-0.5%, silicon source 12-15%, and the rest is ethanol and water; the fluorinated salt is selected from one or both of ammonium bifluoride and ammonium fluoride.

9. The method of claim 1-7, wherein the aerogel composite is prepared by the steps of: Step (1) prepares a glue solution composed of a fluorinated salt, ethanolamine, a silicon source, and a solvent; step (2) immerses the substrate in the glue solution, stands until the gelation is completed, modifies the gel using a long carbon chain trialkoxysilane in a wet method, dries, and then performs gas-phase modification using a high steric hindrance modifier; the high steric hindrance modifier is hexaalkyldisilazane.

10. An aerogel composite prepared by the method of any one of claims 1-9.

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