An aerogel composite fiber material and a preparation method and application thereof

Abstract

The present application relates to aerogel composite material technical field, disclose a kind of aerogel composite fiber material and its preparation method and application, the composite material includes 15-50% polysilazane fiber and 50-85% silicon dioxide aerogel matrix according to percentage by weight, it is connected between the two by Si-O-Si chemical bonding, and there is an inert passivation layer at the interface of two. Its preparation method includes: the polysilazane fiber is immersed in silicon source precursor sol to carry out in-situ catalytic gelation;The alcohol gel composite material obtained is carried out gas phase treatment, and the byproduct generated is used to form inert passivation layer on the surface of fiber;The composite material after gas phase treatment is carried out normal pressure drying.The present application is significantly enhanced by in-situ catalysis and interface self-passivation design, and the mechanical properties of material, and gas phase treatment realizes the normal pressure drying of material, simplifies process, reduces production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogel composite materials, in particular to an aerogel composite fiber material and a preparation method and application thereof. BACKGROUND

[0002] Silica aerogel has a wide application prospect in the fields of aerospace, industrial thermal insulation and building energy saving due to its three-dimensional nano-porous network structure, which exhibits extremely low thermal conductivity and bulk density. However, the pure silica aerogel material is brittle and has low mechanical strength, which limits its application in load-bearing or complex working conditions. In order to improve its mechanical properties, the method of fiber reinforcement is usually used to prepare aerogel composites.

[0003] In the prior art, the reinforcing fibers are mostly quartz fibers or glass fibers with stable chemical properties. Such fibers can only form physical contact with the silica aerogel matrix, and the interfacial bonding force is weak. When the composite material is subjected to external force, the stress is difficult to be effectively transmitted from the matrix to the reinforcing fibers, resulting in easy debonding at the interface and limited improvement of the overall mechanical properties of the material.

[0004] In addition, the preparation process of traditional aerogels usually requires supercritical drying technology to remove the solvent inside the gel to maintain its porous structure from collapsing. The supercritical drying process has high equipment requirements and harsh operating conditions, accompanied by high energy consumption and production cost. Although the atmospheric drying process can significantly reduce the cost, the huge capillary force generated during the solvent evaporation process will directly lead to serious shrinkage and cracking of the gel skeleton, resulting in a dense material with high density and low porosity, which loses the performance advantages of aerogels. Therefore, it is a technical problem to be solved in the field to develop an aerogel composite material that can realize strong interfacial bonding and be prepared by low-cost atmospheric drying process. SUMMARY

[0005] The existing preparation technology of aerogel composites has the following disadvantages:

[0006] 1. The reinforcing fibers and the aerogel matrix are usually physically mixed, the interfacial bonding depends on physical adsorption, the mechanical property transmission efficiency is limited, and the interfacial delamination is easy to occur under stress;

[0007] 2. In order to obtain aerogels with low shrinkage, supercritical drying technology is usually required in the preparation process, which has high equipment cost, high energy consumption and high requirements for operating environment;

[0008] 3. The interface between the fiber and the matrix may have chemical instability in the subsequent processing or application environment.

[0009] The present application aims to provide an aerogel composite fiber material and a preparation method and application thereof to solve the above technical problems.

[0010] To solve the above technical problems, the present application provides the following technical solutions.

[0011] The present application provides a kind of aerogel composite fiber material, the aerogel composite fiber material includes polysilazane fiber and the silicon dioxide aerogel matrix of the polysilazane fiber is wrapped.

[0012] The content of the polysilazane fiber is 15-50% by weight, and the content of the silicon dioxide aerogel matrix is 50-85%.

[0013] The polysilazane fiber and the silicon dioxide aerogel matrix are connected by chemical bonding.The inert passivation layer is arranged at the interface between the polysilazane fiber and the silicon dioxide aerogel matrix.

[0014] In a preferred embodiment, the inert passivation layer is the product generated by the reaction of the acidic substance and the surface of the polysilazane fiber.

[0015] The present application provides a kind of aerogel composite fiber material, the aerogel composite fiber material includes polysilazane fiber and the silicon dioxide aerogel matrix of the polysilazane fiber is wrapped.

[0016] S1, in-situ catalytic gelation: the polysilazane fiber is immersed in the silicon source precursor sol. Without additional catalyst, the surface of the polysilazane fiber reacts with water in the silicon source precursor sol to release ammonia. The ammonia acts as a catalyst to initiate the hydrolysis and condensation reaction of the silicon source precursor sol to form an alcohol gel composite material.

[0017] S2, gas phase treatment: the alcohol gel composite material is placed in a sealed reactor, and at a temperature of 65-85 DEG C, first, the carrier gas containing dimethyldichlorosilane is introduced to carry out gas phase pinning enhancement treatment. The dimethyldichlorosilane reacts with the hydroxyl group in the alcohol gel composite material to generate hydrogen chloride byproduct. After the treatment is completed, the carrier gas containing dimethyldichlorosilane is stopped and kept sealed for 45-90 minutes. During this closed reaction stage, the hydrogen chloride byproduct reacts with the surface of the polysilazane fiber to form the inert passivation layer.

[0018] S3, atmospheric pressure drying: the composite material treated in step S2 is heated and dried at atmospheric pressure.

[0019] In a preferred embodiment, in step S1, the silicon source precursor sol is prepared by tetraethyl orthosilicate, anhydrous ethanol and deionized water in a molar ratio of 1: (15-35) : (5-8).

[0020] In a preferred embodiment, after forming the alcohol gel composite in step S1, a step of aging for 18-30 hours in a constant temperature environment of 25-45℃ is further included.

[0021] In a preferred embodiment, in the carrier gas containing dimethyldichlorosilane in step S2, the volume concentration of dimethyldichlorosilane is 8-18 vol%.

[0022] In a preferred embodiment, in step S2, the duration of the gas phase pinning enhancement treatment is 1.5-3.5 hours.

[0023] In a preferred embodiment, in step S2, the carrier gas is nitrogen.

[0024] In a preferred embodiment, the polysilazane fiber is prepared by the following method:

[0025] The dimethylchlorosilane is reacted with ammonia to obtain a liquid polysilazane precursor, the liquid polysilazane precursor is melt-spun, and cross-linking and curing are performed under the conditions of a temperature of 150-220℃ and a relative humidity of 70%-90% to obtain the polysilazane fiber.

[0026] In a preferred embodiment, in step S3, the specific procedure of the normal pressure drying is as follows:

[0027] Raising the temperature to 70℃ at a rate of 1℃ / min and maintaining the temperature for 2-4 hours, and then raising the temperature to 110-150℃ at a rate of 1℃ / min and maintaining the temperature for 4-6 hours.

[0028] The third aspect of the present application provides an application of the aerogel composite fiber material according to the first aspect, and the application is in the fields of aerospace, building insulation, industrial pipeline heat insulation, and new energy.

[0029] The present application provides an aerogel composite fiber material, a preparation method thereof, and an application thereof.

[0030] 1. The present application forms Si-O-Si chemical bonding between the polysilazane fiber and the silica aerogel matrix through in-situ catalytic gelation, which improves the transmission efficiency of the interfacial bonding strength and mechanical properties compared to the physical mixing method.

[0031] 2. The present application enhances the skeleton strength of the alcohol gel and makes it hydrophobic through gas phase treatment, so that subsequent normal pressure drying can be used, replacing the high-cost and high-energy consumption supercritical drying process, simplifying the preparation process, and reducing the production cost.

[0032] 3、The present application uses the hydrogen chloride by-product generated by the gas-phase pinning enhancement treatment in the subsequent closed reaction stage for the interfacial passivation of polysilazane fibers, which converts the reaction by-product into a functional reagent, and simultaneously completes the backbone enhancement, hydrophobic modification and interfacial stabilization in an integrated step, thereby improving the atomic economy of the process and the interfacial stability of the final product. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with examples, comparative examples and test examples of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0034] The sources and specifications of the main raw materials and reagents used in the following examples and comparative examples are as follows, and the reagents not specifically described are commercially available analytical pure or higher grade products.

[0035] Dichloromethylsilane, CAS No. 75-54-7;

[0036] Ammonia, CAS No. 7664-41-7;

[0037] Anhydrous toluene, CAS No. 108-88-3;

[0038] Tetraethyl orthosilicate, CAS No. 78-10-4;

[0039] Anhydrous ethanol, CAS No. 64-17-5;

[0040] Dimethyldichlorosilane, CAS No. 75-78-5.

[0041] Examples 1-3:

[0042] General preparation steps of polysilazane fibers in the examples:

[0043] Dichloromethylsilane is reacted with ammonia in anhydrous toluene to obtain a liquid polysilazane precursor, and then the liquid polysilazane precursor is melt-spun to obtain a fiber assembly. The fiber assembly is crosslinked and cured under specific temperature and relative humidity conditions to obtain polysilazane fibers. Example 1:

[0044] 1. Preparation of polysilazane fibers:

[0045] According to the general preparation procedure, dichloromethylsilane was reacted with ammonia gas in anhydrous toluene to obtain a liquid polysilazane precursor, followed by melt spinning of the liquid polysilazane precursor to obtain a fiber assembly. The fiber assembly was crosslinked and cured at a temperature of 150 °C and a relative humidity of 70% to obtain a polysilazane fiber.

[0046] 2. Preparation of aerogel composite fiber material:

[0047] S1, in-situ catalytic gelation: a silicon source precursor sol was prepared according to a molar ratio of tetraethyl orthosilicate: anhydrous ethanol: deionized water of 1: 15: 5, and the polysilazane fiber prepared in step 1 was immersed in the silicon source precursor sol to form an alcohol gel composite material in a constant temperature environment at 25 °C for 18 hours.

[0048] S2, gas phase treatment: the obtained alcohol gel composite material was placed in a sealed reactor, and nitrogen gas containing dimethyldichlorosilane with a volume concentration of 8 vol% was introduced at a temperature of 65 °C for gas phase pinning enhancement treatment for 1.5 hours; then the introduction of nitrogen gas containing dimethyldichlorosilane was stopped and the reactor was kept sealed for 45 minutes.

[0049] S3, atmospheric pressure drying: the composite material treated in step S2 was heated to 70 °C at a rate of 1 °C / min and kept at this temperature for 2 hours, and then heated to 110 °C at a rate of 1 °C / min and kept at this temperature for 4 hours.

[0050] Sample S1 was obtained. It was determined that in the obtained sample S1, the weight percentage of polysilazane fiber was 15%, and the weight percentage of silica aerogel matrix was 85%. Example 2:

[0051] 1. Preparation of polysilazane fiber:

[0052] According to the general preparation procedure, dichloromethylsilane was reacted with ammonia gas in anhydrous toluene to obtain a liquid polysilazane precursor, followed by melt spinning of the liquid polysilazane precursor to obtain a fiber assembly. The fiber assembly was crosslinked and cured at a temperature of 185 °C and a relative humidity of 80% to obtain a polysilazane fiber.

[0053] 2. Preparation of aerogel composite fiber material:

[0054] S1, in-situ catalytic gelation: a silicon source precursor sol was prepared according to a molar ratio of tetraethyl orthosilicate: anhydrous ethanol: deionized water of 1: 15: 5, and the polysilazane fiber prepared in step 1 was immersed in the silicon source precursor sol to form an alcohol gel composite material in a constant temperature environment at 25 °C for 18 hours.

[0055] S2, gas phase treatment: the obtained alcohol gel composite material was placed in a closed reactor, and dimethyldichlorosilane-containing nitrogen gas with a volume concentration of 13 vol% was introduced at a temperature of 75°C for gas phase pinning enhancement treatment for 2.5 hours; then the introduction of dimethyldichlorosilane-containing nitrogen gas was stopped and the closed reaction was maintained for 67.5 minutes.

[0056] S3, atmospheric pressure drying: the composite material treated in step S2 was heated to 70°C at a rate of 1°C / min and kept constant for 3 hours, and then heated to 130°C at a rate of 1°C / min and kept constant for 5 hours.

[0057] Sample S2 was obtained. It was determined that in the obtained sample S2, the weight percentage of polysilazane fibers was 30%, and the weight percentage of silica aerogel matrix was 70%. Example 3:

[0058] 1. Preparation of polysilazane fibers:

[0059] According to the general preparation procedure, dichloromethylsilane was reacted with ammonia gas in anhydrous toluene to obtain a liquid polysilazane precursor, and then the liquid polysilazane precursor was subjected to melt spinning to obtain a fiber assembly. The fiber assembly was crosslinked and cured at a temperature of 220°C and a relative humidity of 90% to obtain polysilazane fibers.

[0060] 2. Preparation of aerogel composite fiber material:

[0061] S1, in-situ catalytic gelation: a silica source precursor sol was prepared according to a molar ratio of tetraethyl orthosilicate: anhydrous ethanol: deionized water of 1:35:8, and the polysilazane fibers prepared in step 1 were immersed in the silica source precursor sol, and the alcohol gel composite material was formed by aging in a constant temperature environment at 45°C for 30 hours.

[0062] S2, gas phase treatment: the obtained alcohol gel composite material was placed in a closed reactor, and dimethyldichlorosilane-containing nitrogen gas with a volume concentration of 18 vol% was introduced at a temperature of 85°C for gas phase pinning enhancement treatment for 3.5 hours; then the introduction of dimethyldichlorosilane-containing nitrogen gas was stopped and the closed reaction was maintained for 90 minutes.

[0063] S3, atmospheric pressure drying: the composite material treated in step S2 was heated to 70°C at a rate of 1°C / min and kept constant for 4 hours, and then heated to 150°C at a rate of 1°C / min and kept constant for 6 hours.

[0064] Sample S3 was obtained. It was determined that in the obtained sample S3, the weight percentage of polysilazane fibers was 50%, and the weight percentage of silica aerogel matrix was 50%.

[0065] Comparative Examples 1-3:

[0066] Comparative Example 1:

[0067] Comparative Example 1 compared with Example 2, the difference is that the polysilazane fiber in step S1 is replaced by ordinary quartz fiber of the same mass, and the rest of the preparation steps and parameters are the same.

[0068] Comparative Example 2:

[0069] Comparative Example 2 compared with Example 2, the difference is that after the end of the gas phase pinning enhancement treatment in step S2, the step of maintaining the closed reaction is omitted, and the rest of the preparation steps and parameters are the same.

[0070] Comparative Example 3:

[0071] Comparative Example 3 compared with Example 2, the difference is that the gas phase treatment of step S2 is omitted, and the rest of the preparation steps and parameters are the same.

[0072] Test Examples 1-3:

[0073] Test Example 1: Performance Test

[0074] Test Method:

[0075] The samples S1-S3 and D1-D3 prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests under the same environment.

[0076] Bulk density test: The length, width and height of the sample to be tested were measured using an electronic caliper, and each dimension was measured three times to obtain an average value. The volume (V) of the sample was calculated. The mass (m) of the sample was measured using an electronic balance with an accuracy of 0.0001 g. The bulk density of the sample was calculated by the formula ρ=m / V. Three parallel samples were tested for each sample, and the results were averaged.

[0077] Thermal conductivity test: A transient plane heat source method thermal conductivity tester was used to test the thermal conductivity of the sample under the conditions of an ambient temperature of 25°C and a relative humidity of 50%. The probe was placed between two identical samples, and a slight pressure was applied to ensure contact. The test program was started and the stable thermal conductivity value was recorded. Three parallel samples were tested for each sample, and the results were averaged.

[0078] Compression performance test: A universal material testing machine was used, and a sample with a size of 20mm x 20mm x 10mm was placed between two parallel compression plates. The sample was subjected to uniaxial compression at a constant loading rate of 2mm / min. The stress-strain curve was recorded, and the compression stress value corresponding to a compression strain of 50% was extracted. Three parallel samples were tested for each sample, and the results were averaged.

[0079] Static water contact angle test: The contact angle measurement instrument was used to test under the condition of ambient temperature 25 °C and relative humidity 50%. The sample was placed on the sample stage, and a 5 μL droplet of deionized water was dropped on the sample surface using a microsyringe. After the water droplet was dropped for 30 seconds, the image of the water droplet on the sample surface was taken, and its static contact angle was measured. Each sample was measured five times at different positions, and the results were averaged.

[0080] Test results:

[0081] Table 1. Performance test results of each sample

[0082]

[0083] Result analysis:

[0084] From the test data in Table 1, the bulk density and thermal conductivity of samples S1-S3 are at a relatively low level, and the static water contact angle is greater than 140°. In contrast, the bulk density and thermal conductivity of sample D3 are significantly higher than those of S1-S3, and the static water contact angle is less than 10°. The reason for this phenomenon is that the preparation method of S1-S3 includes a gas phase treatment step, which makes the surface of the alcohol gel skeleton hydrophobic, effectively resisting the capillary force caused by solvent evaporation during atmospheric drying, thereby maintaining the porous network structure. The preparation method of D3 lacks this gas phase treatment step, resulting in a serious collapse of the alcohol gel structure during atmospheric drying, forming a dense material.

[0085] Comparing the data of samples S2 and D1, both have a low bulk density and a high static water contact angle, but the compression stress of S2 at 50% strain is much higher than that of D1. This is because the preparation method of S2 uses polysilazane fibers, which form Si-O-Si chemical bonds with the silicon source precursor during the in-situ catalytic gelation step. The quartz fibers used in D1 do not participate in the reaction and only form physical contact with the matrix. The chemical bonded interface can effectively transfer stress between the fiber and the matrix, so S2 exhibits higher compression stress.

[0086] Comparing the data of samples S2 and D2, both have similar low bulk density and high static water contact angle, but the compression stress of S2 at 50% strain is higher than that of D2. In the preparation method of S2, the gas phase treatment step includes a subsequent closed reaction stage. During this stage, the hydrogen chloride byproduct generated in the previous reaction reacts with the surface of the polysilazane fiber, forming an inert passivation layer. The preparation method of D2 omits this closed reaction stage and fails to form this passivation layer. The inert passivation layer enhances the interface region between the fiber and the matrix, allowing S2 to achieve higher compression stress.

[0087] Test Example 2: Thermal stability test

[0088] Test Method:

[0089] This test aims to evaluate the thermal decomposition behavior of the composite material. Thermogravimetric analysis is used to test the sample.

[0090] Sample Preparation: Samples are taken from the center of samples S2 and D1, with mass control at 5-10 mg.

[0091] Test Procedure: Place the sample in an alumina crucible and put it into the thermogravimetric analyzer. Heat from 30°C to 800°C at a rate of 10°C / min under a high-purity nitrogen atmosphere with a flow rate of 50 mL / min.

[0092] Data Recording: Record the curve of the sample's mass change with temperature, and determine the temperature corresponding to a 5% weight loss of the sample , which is taken as the starting temperature of thermal decomposition of the material. At the same time, record the residual mass percentage of the sample at 800°C.

[0093] Test Results:

[0094] Table 2. Test results of sample thermogravimetric analysis (TGA)

[0095]

[0096] Result Analysis:

[0097] From the test data in Table 2, the thermal decomposition starting temperature of sample S2 is higher than that of sample D1. This data shows that the composite material using polysilazane fibers has a higher temperature at which mass loss begins to occur under the action of heat. Although the residual mass of sample D1 at 800°C is slightly higher, this is related to the fact that quartz fibers themselves do not change in mass within the test temperature range, but the lower thermal decomposition starting temperature indicates the presence of areas with poor thermal stability in the composite structure.

[0098] The mechanism of this phenomenon lies in the differences in composition and interface structure of the material. Sample S2 uses polysilazane fibers, and during the in-situ catalytic gelation process, the reactive functional groups on its surface react with the silica matrix precursor to form Si-O-Si chemical bonds. This chemically bonded interface forms a thermodynamically stable connection, making the entire composite system less likely to decompose under the action of heat.

[0099] On the contrary, sample D1 uses quartz fibers, which are chemically inert, and only forms physical contact with the silica matrix, with weak interfacial bonding. The physical interface or residual organic groups near the interface may become structural weak points, causing the material to begin to lose mass at a relatively low temperature. Therefore, by using polysilazane fibers to form a chemically bonded structure with the matrix, the thermal stability of the composite material is effectively improved.

[0100] Test Example 3: Performance retention rate test after high temperature treatment

[0101] Test Method:

[0102] This test aims to evaluate the retention ability of the macroscopic structural integrity and mechanical properties of the composite material after experiencing high temperature environment.

[0103] High temperature treatment: Sample S2 and D1 (size 20 mm x 20 mm x 10 mm) were placed in a muffle furnace, heated to 600℃ at a rate of 5℃ / min in air atmosphere, and held at this temperature for 2 hours, and then naturally cooled to room temperature with the furnace. The treated samples are denoted as S2' and D1', respectively.

[0104] Performance characterization:

[0105] Visual observation: Observe and record the macroscopic morphology of samples S2' and D1', check for the presence of cracks, pulverization or obvious volume shrinkage.

[0106] Compression performance test: According to the compression performance test method disclosed in Test Example 1, samples S2' and D1' were tested to obtain the compression stress at 50% strain.

[0107] Performance retention rate calculation: Compression stress retention rate (%) = (compression stress after high temperature treatment / compression stress before treatment) x 100%.

[0108] Test results:

[0109] Table 3. Performance comparison of samples before and after high temperature treatment

[0110] Sample No. Compressive Stress Before Treatment (kPa) Appearance After Treatment Compressive Stress After Treatment (kPa) Compressive Stress Retention Rate (%) S2 142 No crack 131 92.3 D1 35 Micro crack on surface 12 34.3

[0111] Result analysis:

[0112] From the test data in Table 3, after 600℃ high temperature treatment, the macroscopic structure of sample S2' remained intact, no cracks were observed, and the compression stress retention rate at 50% strain was 92.3%. In contrast, visible micro-cracks appeared on the surface of sample D1', and the compression stress value decreased significantly, with a retention rate of only 34.3%. This data shows that S2' maintains most of its mechanical properties after high temperature treatment, while the mechanical properties of D1' have been severely degraded.

[0113] The difference in performance is due to the difference in the internal interface structure of the two composites. For sample S2, the preparation method causes the formation of Si-O-Si chemical bonding between the polysilazane fibers and the silica aerogel matrix. This chemical bonding interface can effectively transfer the interfacial stress generated by the mismatch of the thermal expansion coefficients of the fibers and the matrix at high temperatures, inhibiting the initiation of interfacial debonding and microcracks, thereby maintaining the structural stability and mechanical properties of the material.

[0114] For sample D1, the quartz fibers only have physical contact with the silica matrix, and the interfacial bonding force is weak. In a high-temperature environment, thermal mismatch stress easily concentrates at the physical contact interface and leads to interface separation. This interface damage serves as an initial defect, which expands in subsequent compression tests, ultimately resulting in the destruction of the macroscopic structure of the material and a sharp decline in mechanical properties. Therefore, by constructing a chemical bonding interface, the structural and performance stability of the composite in a high-temperature environment is effectively improved.

Claims

1. An aerogel composite fiber material, characterized in that, The aerogel composite fiber material comprises, by weight percentage: 15-50% polysilazane fiber; The polysilazane fiber is prepared by the following method: Dichloromethylsilane was reacted with ammonia to obtain a liquid polysilazane precursor. The liquid polysilazane precursor was melt-spun and cross-linked and cured at a temperature of 150-220℃ and a relative humidity of 70%-90% to obtain polysilazane fibers. And a silica aerogel matrix of 50-85%; In this structure, a silica aerogel matrix encapsulates polysilazane fibers, and the polysilazane fibers are chemically bonded to the silica aerogel matrix. An inert passivation layer is provided at the interface between the polysilazane fiber and the silica aerogel matrix. The inert passivation layer is a product generated by the reaction of an acidic substance with the surface of the polysilazane fiber.

2. A method for preparing the aerogel composite fiber material according to claim 1, characterized in that, Includes the following steps: S1. In-situ catalytic gelation: Polysilazane fibers are immersed in silicon source precursor sol, and the polysilazane fibers themselves initiate the gelation reaction of the silicon source precursor sol to form an alcohol gel composite material. S2. Gas phase treatment: The alcohol gel composite material is placed in a closed reactor. At a temperature of 65-85℃, a carrier gas containing dimethyl dichlorosilane with a volume concentration of 8-18 vol% is first introduced to perform gas phase pinning reinforcement treatment. Then, the introduction of the carrier gas containing dimethyl dichlorosilane is stopped and the reaction is kept closed for 45-90 minutes to perform by-product-driven interface self-passivation. S3. Drying under normal pressure: The composite material after step S2 is dried by heating under normal pressure.

3. The method for preparing the aerogel composite fiber material according to claim 2, characterized in that, In step S1, after forming the alcohol gel composite material, the process further includes aging it in a constant temperature environment of 25-45°C for 18-30 hours.

4. The method for preparing the aerogel composite fiber material according to claim 2, characterized in that, In step S1, the silicon source precursor sol is prepared by tetraethyl orthosilicate, anhydrous ethanol and deionized water in a molar ratio of 1:(15-35):(5-8).

5. The method for preparing the aerogel composite fiber material according to claim 2, characterized in that, In step S2, the duration of the vapor phase pinning enhancement treatment is 1.5-3.5 hours.

6. The method for preparing the aerogel composite fiber material according to claim 2, characterized in that, In step S2, the carrier gas is nitrogen.

7. The method for preparing the aerogel composite fiber material according to claim 2, characterized in that, In step S3, the specific procedure for atmospheric pressure drying is as follows: heat to 70°C at a rate of 1°C / min and hold at that temperature for 2-4 hours, then heat to 110-150°C at a rate of 1°C / min and hold at that temperature for 4-6 hours.

8. The application of an aerogel composite fiber material as described in claim 1 in aerospace, building insulation, industrial pipeline insulation and new energy fields.

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