Fiber-reinforced aerogel composite material and preparation method thereof

Abstract

The invention provides a fiber-reinforced silicon dioxide aerogel composite material, which is characterized in that a fiber felt formed by two kinds of glass fibers is used as a reinforcing material, one kind is hollow short fibers with the average diameter of 5.0-25 microns and the length of 0.5-2.0 mm, the other kind is superfine fibers with the average diameter of 0.6-5.0 microns and the length of 0.5-3.0 mm, and the difference between the average diameters of the two kinds of fibers is at least 3 microns. The fiber reinforced composite material provided by the invention has very strong mechanical properties and very low heat conductivity coefficient, and can exert excellent thermal insulation efficiency as a building thermal insulation material.

Description

Technical Field

[0001] The present invention relates to the field of inorganic materials, and in particular to a composite material of glass fiber and aerogel. Background Art

[0002] SiO2 aerogel is an amorphous solid-state thermal insulation material. Its unique three-dimensional mesh porous structure makes it exhibit many unique characteristics in thermal and other aspects. As one of the most popular aerogels, SiO2 aerogel is the lightest and most thermally insulating solid material known due to its unique advantages such as high porosity, low thermal conductivity and large specific surface area. It has broad application prospects in thermal insulation and other aspects. However, the three-dimensional network skeleton, high porosity and low density of aerogels lead to poor mechanical properties such as compressive strength and toughness. It also makes the network structure easily destroyed at high temperatures, affecting its thermal insulation performance. These shortcomings of silica aerogel make it impossible to use it alone as a bulk material in fields such as thermal insulation.

[0003] To address the above issues, there have been reports of combining SiO2 aerogel with fiber materials to improve its mechanical properties. One method is to introduce organic fibers into SiO2 aerogel. The resulting material can significantly increase its flexibility and strength, but the material's weather resistance is insufficient. Long-term exposure to the open air will cause the material to sag or age, reducing the material's service life. In some application areas, such as insulation materials for building exterior walls, inorganic fiber-filled aerogels, such as mullite fibers and glass fibers, are preferred. However, the introduction of inorganic fibers will significantly increase the thermal conductivity of the material, resulting in a decrease in thermal insulation performance. For example, SiO2 aerogel thermal insulation composite materials were prepared by supercritical drying with mullite fiber as the reinforcing phase. The introduction of short-cut mullite fiber increased the elastic modulus and mechanical strength of the composite material with the increase of fiber. The elastic modulus and mechanical strength of pure SiO2 aerogel were 2MPa and 0.02MPa, respectively. After adding 4wt% of mullite, they increased to 61MPa and 0.08MPa. At the same time, the thermal conductivity of the composite material also changed with the fiber content. When the fiber content was <3wt%, the thermal conductivity did not change much. When the fiber content was >3wt%, the thermal conductivity increased rapidly. This shows that the mechanical properties and thermal insulation properties of the composite material are inversely proportional to the increase in the amount of fiber added.

[0004] There is still a need in the art to find fiber-hydrogel composite materials with higher fiber content and maintaining low thermal conductivity. Summary of the Invention

[0005] In response to the above technical problems, the present invention proposes a fiber-reinforced silica aerogel composite material, characterized in that it contains a fiber mat formed by two types of glass fibers as a reinforcing material, one is a hollow short fiber with an average diameter of 5.0 to 25 microns and a length of 0.5 to 2.0 mm, and the other is an ultrafine fiber with an average diameter of 0.6 to 5.0 microns and a length of 0.5 to 3.0 mm. The average diameters of the two fibers differ by at least 3 microns.

[0006] In a specific aspect, the mass ratio of the hollow staple fibers to the ultrafine fibers is controlled in the range of 0.10 to 0.50:1, preferably 0.22 to 0.30:1.

[0007] In a specific aspect, the diameter of the short hollow fibers is in the range of 8.0 to 15 microns, and the diameter of the ultrafine fibers is in the range of 1.0 to 4.0 microns.

[0008] According to the silica aerogel composite material of the present invention, the fiber felt may account for 5.0 to 20% of the composite material by mass.

[0009] Preferably, the silicon source used is a composite silicon source of water glass and silica sol in a molar ratio of 1:0.8 to 1.5.

[0010] The present invention also relates to a method for preparing the above-mentioned fiber-reinforced silica aerogel composite material, comprising the following steps:

[0011] 1) Fiber mat preparation: The hollow short fibers and ultrafine fibers are made into fiber mats using a web forming machine, and the fiber mats are cleaned and placed in a mold;

[0012] 2) Hydrolysis reaction: After adjusting the pH value of the silicon source, hydrolysis is carried out in a reactor;

[0013] 3) Gelation reaction: the hydrolyzed liquid is adjusted to a pH of 6-8 and then poured into the mold, and gelled at a temperature of 40-50° C. for 8-48 hours;

[0014] 4) Aging and aging: The wet gel is removed from the mold and placed in a container. The required amount of alcohol solvent is added and the container is sealed. The container is aged in a water bath at 45-60°C for 8-48 hours. The container is then aged several times, preferably 2-3 times, with n-hexane at 45-50°C, each time for 4-10 hours.

[0015] In a specific embodiment, in step 2), MTMS, ethanol and H2O are mixed in a volume ratio of 1:3:4 and then hydrolyzed at a pH value of 1 to 2; in step 3), the hydrolyzate in step 1) is mixed with silica sol in a molar ratio of 1 to 1:H2O, the pH value is adjusted to 6 to 7 with ammonia water, and then poured into a mold for gelation.

[0016] In another specific embodiment, in step 2), ethyl orthosilicate, ethanol, and H2O are added to a beaker in a volume ratio of 1:4:3 and stirred evenly. The pH is adjusted to 2 with hydrochloric acid and hydrolyzed in a 45°C water bath for 30 minutes. 40% sodium silicate and water are diluted in a volume ratio of 1:1 and stirred evenly before being added to the acidified solution. The treated cation exchange resin is then added to a solution having a pH between 1 and 2 to obtain a silica sol.

[0017] The fiber-reinforced composite material according to the present invention has strong mechanical properties and low thermal conductivity, and can exert excellent thermal insulation performance as a building thermal insulation material. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a photograph of the product obtained according to Example 1 of the present invention. DETAILED DESCRIPTION

[0019] The technical concept of the present invention is described in detail below in conjunction with specific embodiments. It is easy to understand that the embodiments described in this disclosure are only for illustrative purposes and are not all embodiments of the present invention. Those skilled in the art can obtain other ways of implementing the present invention without paying any creative work after obtaining the explanation of the basic concept of the present invention in this disclosure and combining it with the given embodiments. They can also make creative improvements on the basis of the basic concept of the present invention. All these variant embodiments or improvements fall within the scope defined by the claims of this application.

[0020] The method for preparing the aerogel composite material according to the present invention comprises the following main steps: preparing an aerogel precursor solution, forming a fiber-composite silica wet gel, aging, conditioning and modifying the wet gel, and drying the wet gel.

[0021] Preparation of aerogel precursor solution

[0022] In the present invention, the silicon source for preparing the silica aerogel can be water glass (Na2O-nSiO2), ammonium silicate, silica sol (SiO2 nanoparticles) and silicon alkoxide. Known examples of silicon alkoxide are tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS). A single silicon source or a composite silicon source can be used. Water glass is inexpensive, but has the disadvantage of long preparation period and the resulting aerogel contains sodium salt impurities. Silica sol is a dispersion of nanoscale silica particles in water or a solvent. Since the SiO2 in silica sol contains a large amount of water and hydroxyl groups, silica sol can also be expressed as SiO2-nH2O. Using silica sol as the silicon source, high-purity aerogel can be obtained, but the nanoscale size effect of the particles can cause agglomeration, resulting in larger pores and non-uniform structure of the resulting aerogel. Solving this problem requires a higher preparation method, and it is usually used in combination with other silicon sources. Silica sol can be prepared by treating a water glass solution with a cation exchange resin to exchange the sodium ions in the water glass.

[0023] Using silicon alkoxide as the silicon source, SiO2 aerogel with excellent performance can be prepared, but it is relatively expensive. The preferred embodiment of the present invention uses a composite silicon source. Typically, a composite of water glass and silicon alkoxide is used.

[0024] In one embodiment, a composite silicon source is used, in which water glass and silica sol are mixed in a molar ratio of 1:0.8-1.5. This approach can make up for the respective shortcomings of a single silicon source.

[0025] In one embodiment, a composite silicon source is used, in which the above-mentioned silicon alkoxide and water glass are mixed in a molar ratio of 1:0.5-2.0, preferably 1:0.8-1.2. This approach results in aerogel with stronger hydrophobicity, and the introduction of a composite silicon source can also shorten the preparation period of the aerogel, reduce production costs, and improve the thermal stability of the aerogel.

[0026] In another embodiment, silicon alkoxide and silica sol are used in a composite ratio of 1:0.5-2.0, preferably 1:0.8-1.2.

[0027] A certain amount of water needs to be included in the aerogel precursor solution, which will undergo hydrolysis with the silicon source. The amount of water has an effect on the speed of hydrolysis and gelation. The amount of water should not be less than the theoretical amount required for the hydrolysis of the silicon source, for example, four times the molar amount for TEOS. The more water used, the faster the hydrolysis, but too much water will prolong the gelation time and the subsequent aging and aging time. In the present invention, the amount of water can be 1-6 times, preferably 3-5 times, the volume of the silicate.

[0028] An appropriate amount of solvent is required in the aerogel precursor solution. In the prior art, alcohol solvents are mainly used, with ethanol being the most commonly used. Others include methanol, propanol, tert-butanol, etc. The choice of solvent is preferably based on the alkoxy group in the silicon alkoxide. For example, when using ethyl orthosilicate, ethanol is preferably used, and when using methyl orthosilicate, methanol is preferably selected. The amount of solvent used affects the porosity, pore size distribution, and gelation time of the gel. The more solvent is used, the longer the gelation time and the lower the aerogel density. If the amount is too little, the silicon source and water cannot be fully dissolved, which is not conducive to the synthesis of aerogels with uniform structure. When the solvent content is too high, the SiO2 aerogel obtained has low density, low strength, and poor mechanical properties. In the present invention, the amount of solvent used can be between 3-6 times the volume of the silicon source material. At this time, the silicon source can be fully dissolved in the solvent with water and react completely, and the resulting aerogel has a uniform structure and good performance.

[0029] During the hydrolysis and polycondensation reactions, it is preferred to use an acidic catalyst and a basic catalyst, respectively. The most commonly used acidic catalyst is hydrochloric acid, and other catalysts can be nitric acid, oxalic acid, hydrofluoric acid, sulfuric acid, etc. During the hydrolysis step, the pH value is adjusted to between 1 and 4. The hydrolysis reaction can be completed within 1 to 20 hours. The lower the pH, the faster the hydrolysis rate. Preferably, the pH is adjusted to between 1 and 2, and the reaction can be completed within 4 hours. When the hydrolysis is completed and the polycondensation is carried out, the pH value is raised with an alkaline catalyst, preferably controlled between 6 and 8. The polycondensation reaction can be completed within 48 hours.

[0030] fiber-reinforced materials

[0031] In the present invention, two types of glass fibers with different diameters are used as aerogel reinforcement materials. One is a hollow staple fiber with an average diameter of 5.0 to 25 microns and a length of 0.5 to 2.0 mm, and the other is an ultrafine fiber with an average diameter of 0.6 to 5.0 microns and a length of 0.5 to 3.0 mm. In the present invention, the average diameters of the two fibers differ by at least 3 microns, for example, they may differ by 4, 5 or 6 microns, or even higher. In a typical embodiment, the mass ratio of the hollow staple fiber to the ultrafine fiber is controlled in the range of 0.10 to 0.50:1, preferably 0.22 to 0.30:1. In one specific embodiment, the diameter of the hollow staple fiber is in the range of 9.0 to 15 microns, and the diameter of the ultrafine fiber is in the range of 1.0 to 5.0 microns. In another specific embodiment, the diameter of the hollow staple fiber is in the range of 15 to 25 microns, and the diameter of the ultrafine fiber is in the range of 1.0 to 5.0 microns. In the present invention, a combination of thick hollow short fibers and ultrafine glass fibers is used. The hollow short fibers act as a skeleton to improve mechanical properties, and the ultrafine glass fibers can effectively control the void size. Based on this void size, the composite aerogel is not easy to shed powder and has better thermal insulation performance.

[0032] The glass fibers are introduced by the above method, and the amount of the introduced glass fibers can be 5.0-20% of the mass of the aerogel composite. With such a high content of the added proportion, the obtained material has high mechanical strength and maintains a very low thermal conductivity.

[0033] The two kinds of glass fibers are made into a fiber mat by using the air-laid technology. The fiber mat is made by a combination of one air-laid machine, two fiber carding machines and two air blowers. The carding machines card the short fibers and the ultrafine fibers respectively, and the air blowers produce two air flows with a predetermined angle to mix the two kinds of fibers on the webbing curtain of the air-laid machine to form the fiber mat. In a preferred embodiment, the outlet of the hollow short fibers is above, and the angle between the outlet and the webbing curtain is 90°, so that a solid-gas two-phase flow is formed in the channel at a high speed; the outlet of the ultrafine fibers is below, and the angle between the outlet and the webbing curtain is 10°-45°, so that a solid-gas two-phase flow is formed in the channel at a low speed. The mixing ratio of the two kinds of fibers is controlled by adjusting the feeding speed of the two carding machines and the air flow speed of the air flow channel.

[0034] In another embodiment, a melt-blowing device is combined with a short fiber carding machine and an air blower. The highly crimped short fibers are carded into single fiber state by the carding machine, and then are transported to the melt-blowing ultrafine fiber flow by the air flow generated by the air blower to be dispersed and mixed. Under the adhesion of the melt-blowing ultrafine fibers and the high-speed drawing air flow, the short fibers adhere to the melt-blowing ultrafine fibers, and finally are gathered on the webbing curtain to form the intercalated melt-blowing non-woven material.

[0035] Preparation of fiber composite wet gel

[0036] After the fiber mat is cleaned, it is laid in a mold. The required amount of hydrolyzed precursor solution is taken, an alkaline catalyst is added, and stirred for 1-5 min. The pH value is adjusted to 6-8, and then the solution is poured into the mold. After sealing, the temperature is increased to perform the gelation reaction. The reaction temperature is preferably maintained at 40-50°C, and the reaction is usually completed within 48 hours to obtain a wet gel. In the case of using a silanolate composite hydrogel, the content of the silanolate is different, and the gelation speed is also different. The more the content of the silanolate, the slower the gelation speed, but the gelation reaction is basically completed within a few hours.

[0037] 3) Aging and aging

[0038] The wet gel is taken out of the mold and placed in a container. The required amount of alcohol solvent is added, and the container is sealed. The container is aged in a water bath at 45-60°C for 8-48 hours. In a preferred embodiment of the present application, the alcohol solvent used is tert-butyl alcohol. The freezing point of tert-butyl alcohol is high, and the liquid in the pores of the gel is more likely to solidify into a solid at low temperature.

[0039] Next, the wet gel needs to be aged. This is typically done by enclosing the wet gel in n-hexane solvent. This process exchanges the alcohol solvent from the wet gel. This can be done in a 45-50°C water bath, with one to four exchanges, preferably two to three. Each incubation lasts for four to ten hours, followed by two exchanges, each lasting four to six hours.

[0040] If desired, the wet gel can be further hydrophobically modified to improve the material's compressive strength. To this end, the wet gel can be treated with a 10-20% by volume trimethylsilyl chloride solution in n-hexane for a predetermined period of time. This can be completed within 10-48 hours at a temperature between 20°C and 60°C. The modified wet gel is then soaked in n-hexane for 8-12 minutes to remove the surface modifier.

[0041] Drying of wet gel

[0042] In the present invention, the wet gel is preferably dried by supercritical drying, which can avoid this problem. The medium is brought to a supercritical state in an autoclave, eliminating the gas-liquid interface, avoiding the generation of surface tension during the solvent evaporation process, and reducing the shrinkage and density of the SiO2 aerogel. This process is divided into two methods: high-temperature supercritical drying and low-temperature supercritical drying. When using the high-temperature supercritical drying method, the wet gel must first be soaked in an alcohol solvent for a period of time so that the water in the gel is replaced by the alcohol solvent. During the drying process, the temperature and gas pressure inside the reactor must be higher than the critical point of the solvent. When using low-temperature supercritical drying, the water in the wet gel is first replaced with a solvent whose critical point is close to the ambient temperature, and then drying is carried out under a low-temperature and medium-pressure environment. From the perspective of SiO2 aerogel performance, supercritical drying still has irreplaceable advantages and is widely used.

[0043] Another preferred drying method is freeze-drying. The wet gel is placed in a vacuum freeze dryer and then freeze-dried to produce a fiber-reinforced silica aerogel composite. The freeze-drying process consists of three stages: pre-freezing, sublimation drying, and desorption drying. In the pre-freezing stage, the wet gel is placed in the freeze dryer and rapidly cooled to below the eutectic point, completely freezing the water into solid ice crystals. This stabilizes the gel's three-dimensional structure and prevents collapse during subsequent drying. The pre-freezing rate influences the size of the ice crystals, thereby regulating the post-freeze-drying pore structure. During sublimation drying, the vacuum system is activated to reduce the chamber pressure to 10-35 Pa, while maintaining the cold trap temperature at ≤60°C. This keeps the gel temperature below the eutectic point. During this stage, the ice crystals sublime directly into water vapor, which is captured and condensed in the cold trap. During desorption drying, the system temperature is gradually increased to ≤40°C to further remove bound water, requiring precise temperature control.

[0044] In a specific embodiment of the present invention, the material is first pre-frozen at -30°C to -55°C for 2h to 3h and then vacuum dried. The heating rate of the sublimation drying stage is controlled to be 1°C / h to 5°C / h, and the heating rate of the desorption drying stage is 5°C / h to 10°C / h. The sublimation drying stage is fully vacuumed, and the air pressure in the freeze-drying chamber during the desorption drying stage is not higher than 100Pa. After a total of 24h to 72h of freeze-drying, a bimodal-scale heat-resistant fiber-reinforced silica aerogel composite material is obtained.

[0045] Example 1

[0046] Tetraethyl orthosilicate (TEOS), ethanol, and H2O were added to a beaker in a volume ratio of 1:4:3 and stirred evenly. The pH was adjusted to 2 with hydrochloric acid and hydrolyzed in a 45°C water bath for 30 minutes. 40% sodium silicate and water were diluted in a volume ratio of 1:1 and stirred evenly before being added to the acidified cation exchange resin. The solution, with a pH between 1 and 2, was collected to obtain a silica sol.

[0047] Hollow short fibers with a diameter of 9 to 15 microns and a length of 0.5 to 2.0 mm and ultrafine fibers with a diameter of 1.0 to 5.0 microns and a length of 1.0 to 3.0 mm were prepared into a fiber felt with a thickness of 1 cm using an air-laid machine at a mass ratio of 0.22:1. The fiber felt of the corresponding area was taken, cleaned with an ethanol solution, and then placed in a mold with a length of 300 mm × 300 mm × 10 mm.

[0048] After TEOS is completely hydrolyzed, it is mixed with silica sol and the pH is adjusted to 6-7 with a 0.5 mol / L ammonia solution. The molar ratio of TEOS to silica sol is 1:0.8. Before gel formation, it is added to a mold lined with glass fiber. In a 45°C water bath, gelation occurs within 30 minutes. The wet gel is then aged in tert-butyl alcohol in a 45°C water bath for 10 hours.

[0049] Freeze drying was carried out, pre-freezing at -40°C for 2 hours, and vacuum drying was performed. The heating rate was controlled at 2-4°C / h in the sublimation drying stage, and the heating rate was 7-10°C / h in the analytical drying stage. The air pressure in the freeze drying chamber was not higher than 100 Pa. After 48 hours, a fiber-reinforced aerogel composite material with a glass fiber content of 19% was obtained. Figure 1 It is a real photo of the product.

[0050] Comparative Example 1

[0051] The procedure of Example 1 was repeated, except that a fiber mat was prepared using only short hollow fibers having a diameter of 9 to 15 μm and a length of 0.5 to 2.0 mm. The fiber mat was placed into a mold at the same mass ratio to prepare a fiber-reinforced aerogel composite material having a glass fiber content of 19%.

[0052] Comparative Example 2

[0053] The operation of Example 1 was repeated, except that only ultrafine fibers with a diameter distribution of 1.0 to 5.0 μm and a length distribution of 1.0 to 3.0 mm were used to prepare a fiber mat, which was placed into a mold at the same mass ratio to prepare a fiber-reinforced aerogel composite material with a glass fiber content of 19%.

[0054] Example 2

[0055] Methyltrimethoxysilane (MTMS), ethanol, and H2O were added to a beaker in a volume ratio of 1:3:4 and stirred evenly. The pH was adjusted to 2 with hydrochloric acid and hydrolyzed in a 45°C water bath for 30 minutes. 40% sodium silicate and water were diluted and stirred evenly in a volume ratio of 1:1. The mixture was then added to the acidified cation exchange resin and the solution with a pH between 1 and 2 was collected to obtain a silica sol.

[0056] Hollow short fibers with a diameter of 9 to 15 microns and a length of 0.5 to 2.0 mm and ultrafine fibers with a diameter of 1.0 to 5.0 microns and a length of 1.0 to 3.0 mm are prepared into a fiber felt with a thickness of 1 cm using an air-laid machine at a mass ratio of 0.22:1. After being cleaned with an ethanol solution, the fiber felt is placed in a mold with a length of 300 mm × 300 mm × 10 mm.

[0057] After MTMS is completely hydrolyzed, it is mixed with silica sol and the pH is adjusted to 6-7 with a 0.5 mol / L ammonia solution. The molar ratio of MTMS to silica sol is 1:0.8. Before gel formation, it is added to a mold lined with glass fiber. In a 45°C water bath, gelation occurs within 30 minutes. The wet gel is then aged in tert-butyl alcohol in a 45°C water bath for 10 hours.

[0058] Freeze drying was performed, pre-freezing at -40°C for 2 hours, followed by vacuum drying. The heating rate during the sublimation drying phase was controlled at 2-4°C / h, and the heating rate during the desorption drying phase was controlled at 7-10°C / h. The pressure in the freeze drying chamber was not higher than 100 Pa. After 48 hours, a fiber-reinforced aerogel composite material with a glass fiber content of 8% was obtained. The appearance of the product was basically the same as that of the product in the example.

[0059] Comparative Example 3

[0060] The procedure of Example 1 was repeated, except that a fiber mat was prepared using only short hollow fibers having a diameter of 15 to 25 μm and a length of 0.5 to 2.0 mm. The fiber mat was placed into a mold at the same mass ratio to prepare a fiber-reinforced aerogel composite material having a glass fiber content of 8%.

[0061] Comparative Example 4

[0062] The procedure of Example 1 was repeated, except that a fiber mat was prepared using only ultrafine fibers having a diameter distribution of 1.0 to 5.0 μm and a length distribution of 1.0 to 3.0 mm. The fiber mat was placed into a mold at the same mass ratio to prepare a fiber-reinforced aerogel composite material having a glass fiber content of 8%.

[0063] The tensile strength and thermal conductivity of the samples obtained in each embodiment and comparative example were tested. The tensile strength test method was based on the standard JGJ / T 416, and the thermal conductivity test standard was based on the national standard GB / T10294-2008. The test results are shown in Table 1.

[0064] Table 1. Test results of samples obtained in various examples

[0065] Detection items Example 1 Comparison 1 Comparison 2 Example 2 Comparison 3 Comparison 4 Compressive strength / MPa 4.29 4.30 4.29 4.24 3.75 3.74 Bending strength / MPa 1.34 1.11 1.20 1.25 1.18 1.15 Thermal conductivity / W / mK 0.017 0.028 0.030 0.016 0.028 0.030

[0066] As shown in Table 1, Examples 1 and 2 are aerogel composite materials prepared according to the present invention, using a composite fiber mat of coarse hollow fibers and ultrafine fibers as the reinforcement. The fiber content in Example 1 is 19%, while that in Example 2 is 8%. While the mechanical properties of the two products vary somewhat, the thermal conductivity does not change significantly with the glass fiber content, remaining at a low level. The comparative examples, each using a single glass fiber as the reinforcement, also exhibit excellent mechanical properties, but their thermal conductivity is less than ideal.

[0067] The technical solution of the present invention is described above in conjunction with the embodiments. It should be pointed out that for ordinary technicians in this technical field, without departing from the technical concept of the solution of the present invention, other similar implementation means based on the technical concept of the present invention are also within the protection scope of the embodiments of the present invention.

Claims

1. A fiber-reinforced silica aerogel composite material, characterized in that it comprises a fiber mat formed by two types of glass fibers as reinforcement materials, one of which is a hollow short fiber with an average diameter of 5.0 to 25 microns and a length of 0.5 to 2.0 mm, and the other is an ultrafine fiber with an average diameter of 0.6 to 5.0 microns and a length of 0.5 to 3.0 mm, and the average diameters of the two fibers differ by at least 3 microns.

2. The fiber-reinforced silica aerogel composite material according to claim 1, wherein: The mass ratio of the hollow short fibers to the ultrafine fibers is controlled in the range of 0.10 to 0.50:1, preferably in the range of 0.22 to 0.30:

1.

3. The fiber-reinforced silica aerogel composite material according to claim 1, wherein: The diameter of the hollow short fiber is in the range of 8.0 to 15 microns, and the diameter of the ultrafine fiber is in the range of 1.0 to 4.0 microns.

4. The fiber-reinforced silica aerogel composite material according to claim 1, wherein: The fiber felt accounts for 5.0-20% of the composite material by mass.

5. The fiber-reinforced silica aerogel composite material according to claim 1, wherein: The silicon source used is a composite silicon source of water glass and silica sol in a molar ratio of 1:0.8-1.

5.

6. The fiber-reinforced silica aerogel composite material according to claim 1, wherein: The silicon source used is a composite silicon source of silicon alkoxide and silica sol or water glass in a molar ratio of 1:0.5-2.0, preferably 1:0.8-1.

2. The silicate is selected from the group consisting of methyl orthosilicate, ethyl orthosilicate, methyltriethoxysilane and methyltrimethoxysilane.

7. A method for preparing the fiber-reinforced silica aerogel composite material according to any one of claims 1 to 6, comprising the following steps: 1) Fiber mat preparation: The hollow short fibers and ultrafine fibers are made into fiber mats using a web forming machine, and the fiber mats are cleaned and placed in a mold; 2) Hydrolysis reaction: After adjusting the pH value of the silicon source, hydrolysis is carried out in a reactor; 3) Gelation reaction: the hydrolyzed liquid is adjusted to a pH of 6-8 and then poured into the mold, and gelled at a temperature of 40-50° C. for 8-48 hours; 4) Aging and aging: The wet gel is removed from the mold and placed in a container. The required amount of alcohol solvent is added and the container is sealed. The container is aged in a water bath at 45-60°C for 8-48 hours. The container is then aged several times, preferably 2-3 times, with n-hexane at 45-50°C, each time for 4-10 hours.

8. The preparation method according to claim 7, wherein The alcohol solvent used in the aerogel precursor solution and aging process is tert-butyl alcohol.

9. The preparation method according to claim 8, wherein In step 2), ethyl orthosilicate, ethanol, and H2O are added to a beaker in a volume ratio of 1:4:3 and stirred evenly. The pH value is adjusted to 2 with hydrochloric acid, and the mixture is hydrolyzed in a 45°C water bath for 30 minutes to obtain a hydrolyzate. In step 3), 40% water glass and water are diluted and stirred evenly in a volume ratio of 1:1, and then added to the acidified cation exchange resin. A solution with a pH between 1 and 2 is collected to obtain a silica sol. The hydrolyzate and the silica sol are mixed in a molar ratio of 1:0.8, the pH value is adjusted to 6 to 7 with ammonia water, and then poured into a mold for gelation.

10. The preparation method according to claim 8, wherein In step 2), MTMS, ethanol, and H2O are mixed in a volume ratio of 1:3:4, and then hydrolyzed at a pH of 1 to 2. In step 3), 40% water glass and water are diluted and stirred in a volume ratio of 1:1, and then added to the acidified cation exchange resin. A solution with a pH between 1 and 2 is collected to obtain a silica sol. The hydrolyzate and the silica sol are mixed in a molar ratio of 1:0.8, and the pH is adjusted to 6 to 7 with ammonia water. The mixture is then poured into a mold for gelation.

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