Preparation method of low-cost high-temperature-resistant silicon oxide aerogel composite material

Abstract

The invention discloses a preparation method of a low-cost high-temperature-resistant silicon oxide aerogel composite material, which selects high-quality and low-cost inorganic silica sol as a silicon source, is doped with a functional additive and is compounded with a fiber reinforced material, so that the problems of high silicon source cost, poor high-temperature resistance, low strength, poor flame retardance and the like of the silicon oxide aerogel material are solved. Meanwhile, the material has certain flexibility and is convenient to construct.

Description

Technical Field

[0001] The invention belongs to the field of preparation of new materials and relates to a method for preparing a low-cost high-temperature resistant silicon oxide aerogel composite material. Background Art

[0002] Silica aerogel is a lightweight porous nanomaterial with excellent thermal insulation properties. Silica aerogel generally has problems such as low strength, poor high temperature resistance, and poor flame retardancy, which greatly limit the large-scale production and application of aerogel. Therefore, it is necessary to improve the strength, high temperature resistance, and flame retardancy of aerogel materials while reducing production costs.

[0003] Alkaline silica sol can be obtained by polymerization reaction to obtain gel, which has a low price and is a good silicon source. Low-cost high-temperature resistant silica aerogel composite materials can be obtained by doping functional additives and compounding with fiber reinforcement materials. Summary of the invention

[0004] In order to improve the existing silica aerogel materials such as high cost, low strength, poor high temperature resistance, poor flame retardancy, etc., the present invention selects high-quality and low-cost inorganic silica sol as the silicon source, dopes functional additives, and composites it with fiber reinforcement materials, thereby solving the problems of high silicon source cost, poor high temperature resistance, low strength, poor flame retardancy, etc. of silica aerogel materials. At the same time, the material has certain flexibility and is convenient for construction.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a low-cost high-temperature resistant silicon oxide aerogel composite material comprises the following steps:

[0007] (1) mixing an inorganic silica sol and water for 10 to 60 minutes, adding a functional dopant, mixing and stirring for 30 to 90 minutes, and adding acid to adjust the pH of the mixed solution to 6 to 8 to obtain an aerogel solution;

[0008] (2) placing the fiber reinforcement material in the aerogel solution and completely soaking it, and obtaining a silicon oxide wet gel after gelation, and placing it in a constant temperature room at 30° C. to 50° C. for aging for 12 to 24 hours;

[0009] (3) subjecting the wet gel obtained in step (2) to solvent replacement in an organic solvent for 8 to 24 hours at a temperature of 20 to 50° C.;

[0010] (4) adding a certain ratio of surface modifier to the wet gel obtained in step (3) for surface modification for 1 to 24 hours at a temperature of 20 to 50° C.;

[0011] (5) adding a certain amount of organic solvent mixture to the modified wet gel obtained in step (4) for solvent replacement, the replacement time is 6 to 12 hours, and the temperature is 20 to 50° C.;

[0012] (6) The wet gel in step (5) is subjected to supercritical drying or atmospheric pressure drying to obtain a low-cost, high-temperature resistant silica aerogel composite material.

[0013] Preferably, the inorganic silica sol described in step (1) is alkaline silica sol, the particle size of the alkaline silica sol is 5-20nm, and the SiO2 content of the silica sol is 15-40%; the functional additive is one of silicon carbide, carbon black, aluminum oxide, zirconium oxide, titanium oxide, and yttrium oxide; the acid adjustment mixed solution is one or a mixture of tartaric acid, oxalic acid, acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, sodium hydroxide or ammonia water, and the amount used is 0.01%-0.5% of the mass of the alkaline silica sol.

[0014] Preferably, the fiber-reinforced material described in step (2) is one of glass fiber material, basalt fiber material, aluminum silicate fiber material, and carbon fiber material.

[0015] Preferably, the organic solvent in step (3) is one or more of methanol, ethanol, acetone or n-hexane.

[0016] Preferably, the surface modifier described in step (4) is trimethylchlorosilane, polymethyltriethoxysilane, dimethyldiethoxysilane or hexamethyldisilazane.

[0017] Preferably, the organic solvent mixture in step (5) is an ethanol / n-hexane mixture or a methanol / n-hexane mixture.

[0018] Preferably, the supercritical drying solvent in step (6) is one of carbon dioxide and ethanol; the atmospheric pressure drying temperature is 50-90° C., and the drying time is 9-12 hours.

[0019] The present invention has the following beneficial effects:

[0020] 1. The present invention uses high-quality and low-cost alkaline silica sol as raw material, and adds functional additives to increase the high temperature resistance and flame retardant properties of silica aerogel. After the silica sol, functional additives and water are mixed, they are non-toxic and tasteless, and have no effect on the human body and the environment. No organic solvent is used in the sol-gel process, and there is no problem of organic solvent volatilization, which is conducive to reducing production costs.

[0021] 2. In the preparation process, the present invention adjusts the pH of the solution by acidity to control the gel time, and quickly undergoes polycondensation reaction to obtain wet gel, thereby shortening the gel time. The reaction conditions are convenient and controllable, and the cycle is short. The present invention uses fiber materials as reinforcing materials to improve the strength of the silica aerogel, and at the same time has a certain degree of flexibility, which is convenient for construction.

[0022] 3. The low-cost high-temperature resistant silica aerogel composite material prepared by the present invention has a thermal conductivity of 0.018-0.021 (W / m*K) at room temperature, 0.026-0.031 (W / m*K) at 100°C, 0.044-0.049 (W / m*K) at 300°C, and 0.058-0.061 (W / m*K) at 500°C. The density is 0.19-0.25 g / cm3, and the hydrophobic angle is 130°-135°. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a SEM of the high temperature resistant silica aerogel composite material sample prepared in Example 1;

[0024] Figure 2 is the thermal conductivity of the high temperature resistant silica aerogel composite material prepared in Example 1 at different temperatures. DETAILED DESCRIPTION

[0025] In order to demonstrate the essential features and significant improvements of the present invention, the following examples are used to further illustrate the implementation methods and effects.

[0026] Embodiment one:

[0027] 15 parts of alumina, 150 parts of alkaline silica sol and 70 parts of water were mixed and stirred for 90 minutes, and 0.7 parts of oxalic acid were added. The pH value of the solution was 6. The wet-process glass fiber felt was immersed in the uniformly mixed aerogel solution. The gel time was 1 hour.

[0028] After the gel is aged at 50℃ for 6h, ethanol solution is added for solvent replacement. The replacement time is 12h and the replacement temperature is 50℃. 25% trimethylchlorosilane is added to the wet gel after solvent replacement for surface modification. The modification time is 12h and the modification temperature is 50℃. A certain proportion of modifier is added to the ethanol solution, the wet gel material is placed in the modification container, and the solution is immersed and flowed through the pump circulation to complete the modification. The reaction principle is a hydrolysis-condensation reaction, which is attached to the surface of the product.

[0029] The modified wet gel was then immersed in a 1:1 ethanol / n-hexane mixed solution for solvent replacement, the replacement time was 12 hours, and the temperature was 50° C. Finally, the wet gel was subjected to CO2 supercritical drying to obtain a low-cost, high-temperature resistant silica aerogel composite material.

[0030] Low-cost, high-temperature resistant silica aerogel material with a density of 0.19 g / cm 3, the hydrophobic angle is 135°, the thermal conductivity at room temperature is 0.020 (W / m*K), the thermal conductivity at 100℃ is 0.026 (W / m*K), the thermal conductivity at 300℃ is 0.044 (W / m*K), and the thermal conductivity at 500℃ is 0.058 (W / m*K).

[0031] Embodiment two:

[0032] 10 parts of silicon carbide, 100 parts of alkaline silica sol and 30 parts of water were mixed and stirred for 30 minutes, and 0.5 parts of oxalic acid were added. The pH value of the solution was 7. The basalt fiber material was immersed in the uniformly mixed aerogel solution. The gelation time was 1.5 hours.

[0033] After gelation, the gel was aged at 50°C for 6h, and then ethanol solution was added for solvent replacement, the replacement time was 16h, and the replacement temperature was 50°C. A 25% mass fraction of polymethyltriethoxysilane solution was added to the wet gel after solvent replacement for surface modification, the modification time was 16h, and the modification temperature was 40°C.

[0034] The modified wet gel was then immersed in a 1:1 ethanol / n-hexane mixed solution for solvent replacement, the replacement time was 12 hours, and the temperature was 50° C. Finally, the wet gel was subjected to CO2 supercritical drying to obtain a low-cost, high-temperature resistant silica aerogel composite material.

[0035] The low-cost, high-temperature resistant silica aerogel material has a density of 0.25g / cm3, a hydrophobic angle of 133°, a thermal conductivity of 0.021 (W / m*K) at room temperature, 0.028 (W / m*K) at 100°C, 0.048 (W / m*K) at 300°C, and 0.061 (W / m*K) at 500°C.

[0036] Embodiment three:

[0037] 20 parts of zirconium oxide, 150 parts of alkaline silica sol and 80 parts of water were mixed and stirred for 60 minutes, and 0.55 parts of oxalic acid were added. The pH of the solution was 7. The aluminum silicate fiber material was immersed in the uniformly mixed aerogel solution. The gel time was 1.5 hours.

[0038] After gelation, the gel was aged at 50°C for 8h, and then ethanol solution was added for solvent replacement, the replacement time was 12h, and the replacement temperature was 50°C. A 30% mass fraction of dimethyldiethoxysilane solution was added to the wet gel after solvent replacement for surface modification, the modification time was 12h, and the modification temperature was 50°C.

[0039] The modified wet gel was then immersed in a 1:1 ethanol / n-hexane mixed solution for solvent replacement, the replacement time was 12 hours, and the temperature was 50° C. Finally, the wet gel was subjected to CO2 supercritical drying to obtain a low-cost, high-temperature resistant silica aerogel composite material.

[0040] Low-cost, high-temperature resistant silica aerogel composite material with a density of 0.21 g / cm 3 , the hydrophobic angle is 130°, the thermal conductivity at room temperature is 0.023 (W / m*K), the thermal conductivity at 100℃ is 0.027 (W / m*K), the thermal conductivity at 300℃ is 0.045 (W / m*K), and the thermal conductivity at 500℃ is 0.059 (W / m*K).

[0041] Embodiment 4:

[0042] 5 parts of carbon black, 100 parts of alkaline silica sol and 30 parts of water were mixed and stirred for 40 minutes, 0.7 parts of oxalic acid were added, the pH of the solution was 6, and the carbon fiber material was immersed in the uniformly mixed aerogel solution, and the gel time was 2 hours.

[0043] After gelation, the gel was aged at 50°C for 8h, and then ethanol solution was added for solvent replacement, the replacement time was 12h, and the replacement temperature was 50°C. A 25% mass fraction of dimethyldiethoxysilane solution was added to the wet gel after solvent replacement for surface modification, the modification time was 12h, and the modification temperature was 60°C.

[0044] The modified wet gel was then immersed in a 1:1 ethanol / n-hexane mixed solution for solvent replacement, the replacement time was 12 hours, and the temperature was 50° C. Finally, the wet gel was subjected to CO2 supercritical drying to obtain a low-cost, high-temperature resistant silica aerogel composite material.

[0045] Low-cost, high-temperature resistant silica aerogel composite material with a density of 0.18 g / cm 3 , the hydrophobic angle is 132°, the thermal conductivity at room temperature is 0.025 (W / m*K), the thermal conductivity at 100℃ is 0.031 (W / m*K), the thermal conductivity at 300℃ is 0.048 (W / m*K), and the thermal conductivity at 500℃ is 0.061 (W / m*K).

[0046] Of course, the above embodiments of the present invention are only examples for illustrating the present invention, and are not intended to limit the specific implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above examples. It is impossible to give detailed examples of all implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a low-cost high-temperature resistant silica aerogel composite material, characterized in that: The steps include: (1) mixing an inorganic silica sol and water for 10 to 60 minutes, adding a functional dopant, mixing and stirring for 30 to 90 minutes, and adding acid to adjust the pH of the mixed solution to 6 to 8 to obtain an aerogel solution; wherein the volume ratio of the inorganic silica sol, water and the functional dopant is 100 to 200:30 to 100:5 to 20; (2) placing the fiber reinforcement material in the aerogel solution and completely soaking it, and obtaining a silicon oxide wet gel after gelation, and placing it in a constant temperature room at 30° C. to 50° C. for aging for 12 to 24 hours; (3) subjecting the wet gel obtained in step (2) to solvent replacement in an organic solvent for 8 to 24 hours at a temperature of 20 to 50° C.; (4) adding a certain ratio of surface modifier to the wet gel obtained in step (3) for surface modification for 1 to 24 hours at a temperature of 20 to 50° C.; (5) adding a certain amount of organic solvent mixture to the modified wet gel obtained in step (4) for solvent replacement, the replacement time is 6 to 12 hours, and the temperature is 20 to 50° C.; (6) The wet gel in step (5) is subjected to supercritical drying or atmospheric pressure drying to obtain a low-cost, high-temperature resistant silica aerogel composite material.

2. The preparation method according to claim 1, characterized in that: The inorganic silica sol described in step (1) is alkaline silica sol; the functional additive is one of silicon carbide, carbon black, aluminum oxide, zirconium oxide, titanium oxide, and yttrium oxide; the acid adjustment mixed solution is one or a mixture of tartaric acid, oxalic acid, acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, sodium hydroxide or ammonia water, and the amount used is 0.01%-0.5% of the mass of the alkaline silica sol.

3. The preparation method according to claim 1, characterized in that: The fiber-reinforced material described in step (2) is one of glass fiber material, basalt fiber material, aluminum silicate fiber material, and carbon fiber material.

4. The preparation method according to claim 1, characterized in that: The organic solvent described in step (3) is one or more of methanol, ethanol, acetone or n-hexane.

5. The preparation method according to claim 1, characterized in that: The surface modifier described in step (4) is one of trimethylchlorosilane, polymethyltriethoxysilane, dimethyldiethoxysilane or hexamethyldisilazane.

6. The preparation method according to claim 1, characterized in that: The organic solvent mixture described in step (5) is an ethanol / n-hexane mixture or a methanol / n-hexane mixture.

7. The preparation method according to claim 1, characterized in that: The supercritical drying solvent is one of carbon dioxide and ethanol; the normal pressure drying temperature is 50-90° C., and the drying time is 9-12 hours.

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