阅读说明：本技术 一种以水玻璃为硅源制备二氧化硅/酚醛树脂复合气凝胶材料的方法 (Method for preparing silicon dioxide/phenolic resin composite aerogel material by taking water glass as silicon source ) 是由 杨延钊 吴文杰 杨斐 于 2020-12-31 设计创作，主要内容包括：本发明提供一种以水玻璃为硅源制备二氧化硅/酚醛树脂复合气凝胶材料的方法；包括步骤：将水玻璃、间甲酚、去离子水以及碱性物质混合均匀,得混合液；然后加入醛类化合物,混合均匀,形成溶胶；所得溶胶经水热反应得到二氧化硅/酚醛树脂复合凝胶；然后于三甲基氯硅烷、异丙醇和正己烷的混合溶液中进行表面改性；最后在常压条件下干燥得到二氧化硅/酚醛树脂复合气凝胶材料。本发明制备工艺简单,制备成本低；所制备的二氧化硅/酚醛树脂复合气凝胶具有低密度,高比表面积,高疏水性的特点,同时具有优异的机械强度与保温隔热性能。(The invention provides a method for preparing a silicon dioxide/phenolic resin composite aerogel material by taking water glass as a silicon source; the method comprises the following steps: uniformly mixing water glass, m-cresol, deionized water and an alkaline substance to obtain a mixed solution; then adding an aldehyde compound, and uniformly mixing to form sol; carrying out hydrothermal reaction on the obtained sol to obtain silicon dioxide/phenolic resin composite gel; then carrying out surface modification in a mixed solution of trimethylchlorosilane, isopropanol and normal hexane; and finally drying under normal pressure to obtain the silica/phenolic resin composite aerogel material. The preparation process is simple and the preparation cost is low; the prepared silicon dioxide/phenolic resin composite aerogel has the characteristics of low density, high specific surface area and high hydrophobicity, and has excellent mechanical strength and heat insulation performance.)

1. A method for preparing a silica/phenolic resin composite aerogel material by taking water glass as a silicon source comprises the following steps:

(1) uniformly mixing water glass, m-cresol, deionized water and an alkaline substance to obtain a mixed solution; then adding an aldehyde compound, and uniformly mixing to form sol;

(2) carrying out hydrothermal reaction on the sol obtained in the step (1) to obtain silicon dioxide/phenolic resin composite gel;

(3) immersing the silicon dioxide/phenolic resin composite gel obtained in the step (2) in an alcohol solution, and then carrying out surface modification in a mixed solution of trimethylchlorosilane, isopropanol and n-hexane; and finally drying under normal pressure to obtain the silica/phenolic resin composite aerogel material.

2. The method for preparing the silica/phenolic resin composite aerogel material by using water glass as a silicon source according to claim 1, wherein in the step (1), the mass ratio of the water glass to the m-cresol is 1-4: 1; the mol ratio of the m-cresol to the alkaline substance is 0.5-1: 1.

3. the method for preparing silica/phenolic resin composite by using water glass as silicon source according to claim 1The method for preparing the aerogel material is characterized in that the modulus of the water glass in the step (1) is 2.5-3.5, and SiO in the water glass₂The content of SiO in the mixed solution is 25 to 30 weight percent₂The content of (B) is 1-5 wt%.

4. The method for preparing the silica/phenolic resin composite aerogel material by using water glass as a silicon source according to claim 1, wherein the alkaline substance in the step (1) is one or a combination of sodium hydroxide and potassium hydroxide.

5. The method for preparing the silica/phenolic resin composite aerogel material by using water glass as a silicon source according to claim 1, wherein the aldehyde compound in the step (1) is formaldehyde; the molar ratio of the aldehyde compound to m-cresol is 1-3:1, preferably 2: 1.

6. The method for preparing the silica/phenolic resin composite aerogel material by using water glass as a silicon source as claimed in claim 1, wherein the hydrothermal reaction temperature in the step (2) is 140 ℃ and 180 ℃, and the hydrothermal reaction time is 8-12 h; preferably, the hydrothermal reaction temperature is 160 ℃, and the hydrothermal reaction time is 10 h.

7. The method for preparing the silica/phenolic resin composite aerogel material by using water glass as a silicon source according to claim 1, wherein the alcohol solution in the step (3) is selected from one or a combination of two of ethanol and isopropanol.

8. The method for preparing the silica/phenolic resin composite aerogel material by using water glass as a silicon source according to claim 1, wherein the silica/phenolic resin composite aerogel in the step (3) is immersed in an alcohol solution and treated at 40-60 ℃ for 20-30 h.

9. The method for preparing the silica/phenolic resin composite aerogel material by using water glass as a silicon source according to claim 1, wherein in the step (3), the volume ratio of trimethylchlorosilane to isopropanol to n-hexane is 1:0.6: 20; the volume ratio of the mixed solution to the silicon dioxide/phenolic resin composite gel is 15-18: 1.

10. The method for preparing the silica/phenolic resin composite aerogel material by using water glass as a silicon source according to claim 1, wherein in the step (3), the temperature of surface modification is 40-50 ℃, and the time of surface modification is 40-55 h;

preferably, in the step (3), the drying under normal pressure is performed by: drying at 60 ℃ for 3-6 h, drying at 80 ℃ for 3-6 h, and drying at 120 ℃ for 2-4 h.

Technical Field

The invention relates to a method for preparing a silicon dioxide/phenolic resin composite aerogel material by taking water glass as a silicon source, belonging to the technical field of aerogel preparation.

Background

With the continuous development of society, the current traditional heat insulation material is difficult to meet the civil high-efficiency energy-saving requirement. The aerogel serving as a novel material has fine skeleton particles and nano-scale pore diameters, can effectively inhibit solid-state heat conduction and gaseous-state heat conduction, and has wide application prospect as a light heat-insulating material. However, because the traditional silica aerogel has high brittleness, the large-scale application in the aspect of engineering heat insulation is limited, and the silica aerogel heat insulation composite material needs to be prepared by strengthening and toughening.

As a novel material, the organic aerogel, such as phenolic aerogel, polyurethane aerogel, cellulose aerogel, polyvinyl alcohol aerogel, polyaniline aerogel and the like, overcomes the defects of low strength and easy fragmentation of inorganic aerogel, and retains the characteristics of low density, high porosity, high specific surface area and low thermal conductivity. However, since the pure organic aerogel does not resist high temperature and has limited oxidation resistance, the organic-inorganic composite aerogel material has become an important development direction.

Patent document CN105295298A discloses a bulk hydrophobic phenolic resin/silica composite aerogel and a preparation method thereof, which takes phenols, aldehydes, aminosilane and siloxane with one or two hydrocarbyl groups as raw materials, distilled water and alcohols as solvents, and adopts a one-pot method to prepare wet gel through a sol-gel method, and then the phenolic resin/silica composite aerogel is obtained.

Patent document CN106189066A discloses a phenolic resin silica composite aerogel material and a preparation method thereof, wherein the phenolic resin/silica composite aerogel material has a nano-network structure in which a silica phase and a resin phase are entangled with each other; the organic silicon/chitosan composite material is prepared from materials including an organic silicon precursor, a phenolic compound, an aldehyde compound and chitosan by a sol-gel method and supercritical carbon dioxide drying.

The above patent documents all adopt phenolic resin to compound silica aerogel, which improves the mechanical properties of aerogel, but all adopt organic silanol as raw material, which is expensive in preparation cost and not beneficial to commercial production. Therefore, the invention provides a brand new and rapid method, which directly takes the water glass as a silicon source and utilizes the sol-gel method and the normal pressure drying technology to prepare the silicon dioxide/phenolic resin composite aerogel material, thereby meeting more application fields.

Disclosure of Invention

The invention aims to provide a method for preparing a silicon dioxide/phenolic resin composite aerogel material by taking water glass as a silicon source; the method takes cheap industrial water glass as a silicon source, mixes the silicon source with deionized water, phenolic compounds and aldehyde compounds, and obtains the silicon dioxide/phenolic resin composite aerogel material by utilizing a sol-gel method and a normal pressure drying technology. The preparation process is simple and the preparation cost is low; the prepared silicon dioxide/phenolic resin composite aerogel has the characteristics of low density, high specific surface area and high hydrophobicity, and has excellent mechanical strength and heat insulation performance.

The technical scheme of the invention is as follows:

a method for preparing a silica/phenolic resin composite aerogel material by taking water glass as a silicon source comprises the following steps:

(1) uniformly mixing water glass, m-cresol, deionized water and an alkaline substance to obtain a mixed solution; then adding an aldehyde compound, and uniformly mixing to form sol;

(2) carrying out hydrothermal reaction on the sol obtained in the step (1) to obtain silicon dioxide/phenolic resin composite gel;

(3) immersing the silicon dioxide/phenolic resin composite gel obtained in the step (2) in an alcohol solution, and then carrying out surface modification in a mixed solution of trimethylchlorosilane, isopropanol and n-hexane; and finally drying under normal pressure to obtain the silica/phenolic resin composite aerogel material.

According to the present invention, it is preferable that in the step (1), the mass ratio of the water glass to the m-cresol is 1-4: 1; the mol ratio of the m-cresol to the alkaline substance is 0.5-1: 1.

according to the present invention, it is preferable that the modulus of the water glass in the step (1) is 2.5 to 3.5 and SiO in the water glass₂The content of SiO in the mixed solution is 25 to 30 weight percent₂The content of (B) is 1-5 wt%.

According to the present invention, preferably, the alkaline substance in step (1) is one or a combination of two of sodium hydroxide and potassium hydroxide.

According to the present invention, it is preferred that the aldehyde compound in step (1) is formaldehyde; the molar ratio of the aldehyde compound to m-cresol is 1-3:1, preferably 2: 1.

According to the invention, the hydrothermal reaction temperature in the step (2) is preferably 140-180 ℃, and the hydrothermal reaction time is 8-12 h; preferably, the hydrothermal reaction temperature is 160 ℃, and the hydrothermal reaction time is 10 h.

According to the present invention, preferably, the alcohol solution in step (3) is selected from one or a combination of two of ethanol or isopropanol.

According to the invention, preferably, in the step (3), the silicon dioxide/phenolic resin composite gel is immersed in an alcohol solution and treated at 40-60 ℃ for 20-30 h.

According to the present invention, it is preferable that in the step (3), the volume ratio of trimethylchlorosilane to isopropanol to n-hexane is 1:0.6: 20; the volume ratio of the mixed solution to the silicon dioxide/phenolic resin composite gel is 15-18: 1.

According to the invention, in the step (3), the temperature of the surface modification is preferably 40-50 ℃, and the time of the surface modification is preferably 40-55 h.

According to the present invention, in step (3), the drying under normal pressure is preferably performed by: drying at 60 ℃ for 3-6 h, drying at 80 ℃ for 3-6 h, and drying at 120 ℃ for 2-4 h.

The principle of the invention is as follows:

firstly, adding an alkaline substance into a mixed solution of water glass, m-cresol and deionized water, so that the m-cresol can be dissolved in a water phase, and a phenolic resin gel network can be better combined with a silicon dioxide gel network; the high-temperature hydrothermal reaction accelerates the gelation speed and enhances the gel strength. According to the invention, the silicon dioxide gel network and the phenolic resin gel network are mutually interpenetrated and combined, and the mechanical strength of the silicon dioxide aerogel is greatly enhanced by adding the phenolic resin gel network. However, in the conventional phenolic resin, due to the existence of hydroxyl on the surface, water in pores cannot be completely replaced by n-hexane with low surface tension in the solvent exchange and surface modification processes, so that the density of the composite aerogel obtained after normal pressure drying is increased, and the problems of polycondensation and surface cracking are caused. The invention selects m-cresol as the raw material of the phenolic resin, introduces methyl into the phenolic resin gel network, ensures that the whole material has excellent hydrophobicity, improves the efficiency of solvent exchange and surface modification, and reduces the times of solvent exchange, thereby achieving the purposes of reducing the cost and improving the performance of aerogel.

The invention has the beneficial effects that:

1. in the synthesis process, the cheap industrial water glass is used for replacing expensive organic silanol as a raw material, the use of an alcohol solution for dissolving the organic silanol is omitted, and only deionized water is used as a solvent, so that the method is lower in cost and environment-friendly.

2. In the synthesis process, m-cresol is selected as a raw material of the phenolic resin, so that a phenolic resin gel network has hydrophobicity, water in pores is more favorably exchanged into n-hexane with low surface tension, the times of solvent exchange are reduced, the modification efficiency is improved, the process flow is greatly simplified, and the method is suitable for large-scale industrial production.

3. In the synthesis process, the silicon dioxide gel network and the phenolic resin gel network are combined, so that the integral mechanical strength of the aerogel is greatly enhanced, and the aerogel is more widely applied in the market.

4. In the synthesis process, the invention adopts normal pressure drying to replace the supercritical drying used in the traditional method. The supercritical drying process has complex process, high cost and certain danger, and is not beneficial to large-scale industrial production. The present invention thus avoids these problems by using atmospheric drying.

5. The method has simple integral preparation process and low preparation cost; the preparation method and the used raw materials are taken as a whole, and the combined action ensures that the prepared silicon dioxide/phenolic resin composite aerogel has the characteristics of low density, high specific surface area and high hydrophobicity, and has excellent mechanical strength and heat-insulating property.

Drawings

Fig. 1 is an SEM image of the silica/phenolic resin composite aerogel prepared in example 3.

Fig. 2 is a water contact angle diagram of the silica/phenolic resin composite aerogel prepared in example 4.

FIG. 3 is N of silica/phenolic resin composite aerogel prepared in example 4₂Adsorption and desorption isotherm diagram.

Fig. 4 is a pore size distribution diagram of the silica/phenolic resin composite aerogel prepared in example 4.

Detailed Description

The invention is further illustrated by the following specific examples, without limiting the scope of the invention thereto.

The raw materials used in the examples are commercially available unless otherwise specified; the methods used are conventional methods unless otherwise specified.

Example 1

A method for preparing a silica/phenolic resin composite aerogel material by taking water glass as a silicon source comprises the following steps:

1.13g of water glass (SiO) with a modulus of 3₂Content 26.5%) in a beaker, add deionized water to 10g and stir well. In addition, 0.81g m-cresol, 5g deionized water, 0.4g NaOH were mixed and stirred in a beaker. And (3) after the m-cresol is dissolved in water, mixing the two solutions, adding a formaldehyde water solution containing 0.015mol of formaldehyde, and stirring for 10min to obtain the sol. Then pouring the sol into a high-temperature hydrothermal kettle to react for 10 hours at 160 ℃ to obtain gel. Immersing the obtained gel in ethanol, carrying out solvent exchange at 50 ℃ for 24h, then adding the gel into a 250ml beaker, sequentially adding 200ml of n-hexane, 6ml of isopropanol and 10ml of trimethylchlorosilane, uniformly mixing (immersing the gel in a mixed solution), and carrying out surface modification in a water bath at 50 ℃ for 48 h. And (3) drying the modified composite gel at 60 ℃ for 4h, at 80 ℃ for 4h, and at 120 ℃ for 3h to obtain the silicon dioxide/phenolic resin composite aerogel.

The density of the silica/phenolic resin composite aerogel prepared in the embodiment is 0.257cm³Per g, specific surface area 516.26m²(iv)/g, average pore diameter of 3.40nm, compressive strength at 10% compression set of 0.103MPa, thermal conductivity of 0.0331W/(m.K), and water contact angle of 93.4 deg.

Example 2

A method for preparing a silica/phenolic resin composite aerogel material by taking water glass as a silicon source comprises the following steps:

1.69g of water glass (SiO) with a modulus of 3₂Content 26.5%) in a beaker, add deionized water to 10g and stir well. In addition, 0.81g m-cresol, 5g deionized water, 0.4g NaOH were mixed and stirred in a beaker. And (3) after the m-cresol is dissolved in water, mixing the two solutions, adding a formaldehyde water solution containing 0.015mol of formaldehyde, and stirring for 10min to obtain the sol. Then pouring the sol into a high-temperature hydrothermal kettle to react for 10 hours at 160 ℃ to obtain gel. Immersing the obtained gel in ethanol, carrying out solvent exchange at 50 ℃ for 24h, then adding the gel into a 250ml beaker, sequentially adding 200ml of n-hexane, 6ml of isopropanol and 10ml of trimethylchlorosilane, uniformly mixing (immersing the gel in a mixed solution), and carrying out surface modification in a water bath at 50 ℃ for 48 h. And (3) drying the modified composite gel at 60 ℃ for 4h, at 80 ℃ for 4h, and at 120 ℃ for 3h to obtain the silicon dioxide/phenolic resin composite aerogel.

The density of the silica/phenolic resin composite aerogel obtained in the example is 0.262cm³Per g, specific surface area 524.72m²(g), the average pore diameter is 4.42nm, the compressive strength of 10% compression set is 0.135MPa, the thermal conductivity is 0.0306W/(m.K), and the water contact angle is 102.3 degrees.

Example 3

A method for preparing a silica/phenolic resin composite aerogel material by taking water glass as a silicon source comprises the following steps:

2.26g of water glass (SiO) with a modulus of 3₂Content 26.5%) in a beaker, add deionized water to 10g and stir well. In addition, 0.81g m-cresol, 5g deionized water, 0.4g NaOH were mixed and stirred in a beaker. And (3) after the m-cresol is dissolved in water, mixing the two solutions, adding a formaldehyde water solution containing 0.015mol of formaldehyde, and stirring for 10min to obtain the sol. Then dissolving in waterPouring the gel into a high-temperature hydrothermal kettle, and reacting for 10 hours at 160 ℃ to obtain gel. Immersing the obtained gel in ethanol, carrying out solvent exchange at 50 ℃ for 24h, then adding the gel into a 250ml beaker, sequentially adding 200ml of n-hexane, 6ml of isopropanol and 10ml of trimethylchlorosilane, uniformly mixing (immersing the gel in a mixed solution), and carrying out surface modification in a water bath at 50 ℃ for 48 h. And (3) drying the modified composite gel at 60 ℃ for 4h, at 80 ℃ for 4h, and at 120 ℃ for 3h to obtain the silicon dioxide/phenolic resin composite aerogel.

The density of the silica/phenolic resin composite aerogel obtained in the example is 0.281cm³Per g, specific surface area 437.16m²(g), the average pore diameter is 4.92nm, the compressive strength of 10 percent compression set is 0.172MPa, the thermal conductivity is 0.0301W/(m.K), and the water contact angle is 118.9 degrees.

Fig. 1 is an SEM image of the silica/phenolic resin composite aerogel prepared in this example, and it can be seen that the silica/phenolic resin composite aerogel belongs to a continuous porous solid material.

Example 4

A method for preparing a silica/phenolic resin composite aerogel material by taking water glass as a silicon source comprises the following steps:

2.82g of water glass (SiO) with a modulus of 3₂Content 26.5%) in a beaker, add deionized water to 10g and stir well. In addition, 0.81g m-cresol, 5g deionized water, 0.4g NaOH were mixed and stirred in a beaker. And (3) after the m-cresol is dissolved in water, mixing the two solutions, adding a formaldehyde water solution containing 0.015mol of formaldehyde, and stirring for 10min to obtain the sol. Then pouring the sol into a high-temperature hydrothermal kettle to react for 10 hours at 160 ℃ to obtain gel. Immersing the obtained gel in ethanol, carrying out solvent exchange at 50 ℃ for 24h, then adding the gel into a 250ml beaker, sequentially adding 200ml of n-hexane, 6ml of isopropanol and 10ml of trimethylchlorosilane, uniformly mixing (immersing the gel in a mixed solution), and carrying out surface modification in a water bath at 50 ℃ for 48 h. And (3) drying the modified composite gel at 60 ℃ for 4h, at 80 ℃ for 4h, and at 120 ℃ for 3h to obtain the silicon dioxide/phenolic resin composite aerogel.

The dioxide obtained in this exampleThe density of the silicon/phenolic resin composite aerogel is 0.31cm³Per g, specific surface area 460.01m²G, average pore diameter of 3.38nm, compressive strength of 10% compression set of 0.196MPa, thermal conductivity of 0.0317W/(m.K), and water contact angle of 126.6 deg.

Fig. 2 is a water contact angle diagram of the silica/phenolic resin composite aerogel prepared in this embodiment, and it can be seen that the silica/phenolic resin composite aerogel has excellent hydrophobicity.

FIGS. 3 and 4 show the N content of the silica/phenolic resin composite aerogel prepared in this example₂An adsorption and desorption isotherm diagram and a pore size distribution diagram, and the diagram shows that the silicon dioxide/phenolic resin composite aerogel belongs to a mesoporous material.

Example 5

A method for preparing a silica/phenolic resin composite aerogel material by taking water glass as a silicon source comprises the following steps:

1.13g of water glass (SiO) with a modulus of 3₂Content 26.5%) in a beaker, add deionized water to 10g and stir well. Separately, 1.08g of m-cresol, 5g of deionized water and 0.4g of NaOH were mixed and stirred in a beaker. And (3) after the m-cresol is dissolved in water, mixing the two solutions, adding a formaldehyde water solution containing 0.015mol of formaldehyde, and stirring for 10min to obtain the sol. Then pouring the sol into a high-temperature hydrothermal kettle to react for 10 hours at 160 ℃ to obtain gel. Immersing the obtained gel in ethanol, carrying out solvent exchange at 50 ℃ for 24h, then adding the gel into a 250ml beaker, sequentially adding 200ml of n-hexane, 6ml of isopropanol and 10ml of trimethylchlorosilane, uniformly mixing (immersing the gel in a mixed solution), and carrying out surface modification in a water bath at 50 ℃ for 48 h. And (3) drying the modified composite gel at 60 ℃ for 4h, at 80 ℃ for 4h, and at 120 ℃ for 3h to obtain the silicon dioxide/phenolic resin composite aerogel.

The density of the silica/phenolic resin composite aerogel obtained in the example is 0.267cm³Per g, specific surface area 456.93m²(g), the average pore diameter is 3.65nm, the compressive strength of 10 percent compression set is 0.126MPa, the thermal conductivity is 0.0344W/(m.K), and the water contact angle is 125.1 degrees.

Comparative example 1

A method of preparing an aerogel material, comprising the steps of:

1.13g of water glass (SiO) with a modulus of 3₂Content 26.5%) in a beaker, add deionized water to 10g and stir well. Separately, 0.94g of phenol, 5g of deionized water, and 0.4g of NaOH were mixed and stirred in a beaker. And (3) after the m-cresol is dissolved in water, mixing the two solutions, adding a formaldehyde water solution containing 0.015mol of formaldehyde, and stirring for 10min to obtain the sol. Then pouring the sol into a high-temperature hydrothermal kettle to react for 10 hours at 160 ℃ to obtain gel. Immersing the obtained gel in ethanol, carrying out solvent exchange at 50 ℃ for 24h, then adding the gel into a 250ml beaker, sequentially adding 200ml of n-hexane, 6ml of isopropanol and 10ml of trimethylchlorosilane, uniformly mixing (immersing the gel in a mixed solution), and carrying out surface modification in a water bath at 50 ℃ for 48 h. And (3) drying the modified composite gel at 60 ℃ for 4h, at 80 ℃ for 4h, and at 120 ℃ for 3h to obtain the aerogel.

The aerogel obtained in this example shrinks severely, the block cracks, and it is not hydrophobic. The density is 0.754cm³Per g, specific surface area 160.74m²(iv)/g, average pore diameter 1.83 nm. Therefore, m-cresol can remarkably improve the performance of the silica/phenolic resin composite aerogel by being distinguished from phenol.

Comparative example 2

A method of preparing an aerogel material, comprising the steps of:

1.13g of water glass (SiO) with a modulus of 3₂Content 26.5%) in a beaker, add deionized water to 10g and stir well. In addition, 0.81g of o-methylphenol, 5g of deionized water and 0.4g of NaOH were mixed and stirred in a beaker. And (3) after the m-cresol is dissolved in water, mixing the two solutions, adding a formaldehyde water solution containing 0.015mol of formaldehyde, and stirring for 10min to obtain the sol. Then pouring the sol into a high-temperature hydrothermal kettle to react for 10 hours at 160 ℃ to obtain gel. Immersing the obtained gel in ethanol, carrying out solvent exchange at 50 ℃ for 24h, then adding the gel into a 250ml beaker, sequentially adding 200ml of n-hexane, 6ml of isopropanol and 10ml of trimethylchlorosilane, uniformly mixing (immersing the gel in a mixed solution), and carrying out surface modification in a water bath at 50 ℃ for 48 h. Will be provided withAnd drying the modified composite gel at 60 ℃ for 4h, drying at 80 ℃ for 4h, and drying at 120 ℃ for 3h to obtain the silicon dioxide/phenolic resin composite aerogel.

The strength of the gel obtained by the embodiment is too low, the gel is difficult to form, and massive aerogel cannot be obtained by normal pressure drying after surface modification. Therefore, m-cresol can not only improve the hydrophobicity of the composite aerogel, but also ensure the mechanical strength of the composite aerogel.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and the equivalent embodiments using a few modifications and equivalent changes made in the above technical content without departing from the technical scope of the present invention should be included in the protection scope of the present invention.