Carbon@silicon carbide nanofiber aerogel, preparation method and application thereof

Abstract

The present application relates to carbon@silicon carbide nanofiber aerogel and its preparation method and application, belong to nanofiber aerogel technical field.Aim at the technical problem that the existing technology of silicon carbide nanofiber aerogel, heat insulation and mechanical property are not good, usually cannot be considered, the carbon@silicon carbide nanofiber aerogel provided in the present application adopts plasma cleaning graphite felt, and is coated with an additional carbon source outside graphite fiber, is immersed in the mixed solution of tetraethyl orthosilicate, ethanol and deionized water, is calcined at high temperature, and is prepared carbon@silicon carbide aerogel of amorphous carbon coated graphite carbon part sacrificial conversion.Silicon carbide shell is resistant to oxidation and ablation, and a large number of silicon carbide nanowires are still filled between carbon@silicon carbide fibers, the unique three-dimensional porous structure makes the material have heat insulation performance in the oxygen environment, and the core carbon fiber skeleton endows the material with super strong mechanical properties.The present application also provides a preparation method of silicon carbide nanofiber aerogel, which can realize large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of nanofiber aerogel technology, specifically, it relates to a method for preparing carbon@silicon carbide nanofiber aerogel. Background Technology

[0002] Aerogels, due to their superior properties such as high specific surface area, high porosity, low density, and low thermal conductivity, have been widely used in thermal insulation, adsorption, catalysis, and energy fields. However, as the application fields of aerogels become more extensive, traditional SiO2 aerogels, commonly used in thermal insulation applications at 650℃ and below, are prone to structural collapse at high temperatures, leading to material densification and loss of their excellent properties. The high-temperature thermal stability of other oxide-based aerogels also needs further improvement. These high-temperature limitations significantly restrict the application of oxide-based aerogels in high-temperature fields. Carbides are compounds with high hardness, high melting point, and stable chemical properties. They are generally prepared through in-situ generation methods. By controlling process parameters during preparation to form aerogel structures from carbides, the performance of aerogel materials can be improved. Compared with traditional silica aerogels, carbon aerogels have higher strength, greater porosity, smaller particle diameter, larger specific surface area, and lower high-temperature thermal conductivity, showing broad application prospects in catalyst supports, capacitors, and adsorption materials.

[0003] Carbon@silicon carbide composite aerogel is a core-shell structured aerogel with advantages such as light weight, non-ablative properties, oxidation resistance, and good high-temperature thermal stability. It is a highly efficient high-temperature insulation material with great application potential in high-temperature insulation applications such as aircraft end-face insulation and lithium battery module insulation. However, existing carbon@silicon carbide composite aerogels generally suffer from poor mechanical properties and high thermal conductivity, limiting their application in high-temperature insulation scenarios.

[0004] For example, Chinese patent application publication number CN114715896A, filed on April 14, 2022, entitled "Preparation Method of Silicon Carbide Nanotube Aerogel," discloses a method that involves mixing a silicon source and a solvent to obtain a silicon source solution; immersing a carbon felt in the silicon source solution to obtain an impregnation material; sintering the impregnation material in an inert atmosphere to obtain a SiC / C composite material; and calcining the SiC / C composite material to remove the carbon core, thereby obtaining a silicon carbide nanotube aerogel. While this method uses the carbon source of the carbon felt itself to improve the mechanical properties to some extent, its thermal insulation and mechanical properties still need improvement. For example, Chinese patent application publication number CN117003568A, filed on July 26, 2023, entitled "Preparation method and application of silicon carbide thermal insulation aerogel and its biomass in-situ conversion", discloses a preparation method that involves freeze-drying and carbonizing to prepare a carbon template. The carbon template is then immersed in a mixed solution of tetraethyl orthosilicate, ethanol, and deionized water. After the carbon template is removed, dried, and calcined at high temperature, silicon carbide thermal insulation aerogel with biomass in-situ conversion is obtained. Due to its unique three-dimensional porous structure, the silicon carbide thermal insulation aerogel has certain thermal insulation properties in an oxygen-containing environment. However, the mechanical properties of the aerogel prepared by this method need to be improved, and it cannot be used in application scenarios that require both thermal insulation and mechanical strength. Summary of the Invention

[0005] 1. The problem to be solved

[0006] Addressing the technical problem that existing carbon@silicon carbide nanofiber aerogels often suffer from poor thermal insulation and mechanical properties, making it difficult to achieve both simultaneously, this application provides a carbon@silicon carbide nanofiber aerogel that combines excellent mechanical properties with highly efficient thermal insulation performance. This application also provides a preparation method for the carbon@silicon carbide nanofiber aerogel and its applications. The process is simple and easy to operate, the reaction process is easily controlled, the production cycle is short, and the cost is low, enabling large-scale production. It can be used in high-temperature thermal insulation applications such as aircraft end faces or lithium battery modules.

[0007] 2. Technical Solution

[0008] To achieve the above objectives, the provided technical solution is as follows:

[0009] The method for preparing carbon@silicon carbide nanofiber aerogel of this application includes the following steps:

[0010] The graphite felt was cleaned with plasma water to obtain the cleaned graphite felt.

[0011] Prepare a solution containing a carbon source to obtain a carbon-containing solution;

[0012] The cleaned graphite felt was immersed in the carbon-containing solution and then dried to obtain carbon-coated graphite felt.

[0013] A solution containing tetraethyl orthosilicate, ethanol, and deionized water was prepared and adjusted to clarity with hydrochloric acid to obtain a mixed solution.

[0014] The carbon-coated graphite felt is immersed in the mixed solution and then dried to obtain impregnated graphite felt;

[0015] The impregnated graphite felt was kept at a high temperature to obtain the carbon@silicon carbide nanofiber aerogel.

[0016] Preferably, the cleaning process is as follows: the graphite felt is treated in a plasma cleaner for 5 to 20 minutes on both sides.

[0017] Furthermore, the carbon source is dopamine hydrochloride or phenolic resin.

[0018] Further, the carbon-containing solution is prepared by dissolving 10 mmol of tris(hydroxymethyl)aminomethane and 0.6–1.0 mmol of dopamine hydrochloride in 100 mL of deionized water, and then adding 1 mL of hydrochloric acid.

[0019] Preferably, the concentration of dopamine hydrochloride is 6–10 mM.

[0020] Further, the cleaned graphite felt is stirred in a carbon-containing solution at room temperature for 6 hours, then vacuum dried at 60°C for 12 hours; the temperature is then increased to 800-1000°C at a heating rate of 2-5°C / min and held for 1-3 hours.

[0021] Furthermore, the volume ratio of the mixed solution—tetraethyl orthosilicate, ethanol, and deionized water—is 2:2 to 3.66:1, and the pH is 2 to 4.

[0022] Preferably, the amount of hydrochloric acid added is 1 to 3% of the total volume of the mixed solution.

[0023] Further, the carbon-coated graphite felt is immersed in the mixed solution for 0.5 to 1 hour and then dried.

[0024] Preferably, the carbon-coated graphite felt is placed in a vacuum impregnation machine at room temperature and impregnated with silica sol at a vacuum degree of 0-20 mbar to fully remove the gas from the carbon-coated graphite felt and the solution. The drying parameters are: under a vacuum degree of -0.6 to -0.8 bar in a vacuum drying oven, heated to 60°C and dried for 12-48 hours.

[0025] Furthermore, the mixture is immersed in the mixed solution for a second time for 24–48 hours.

[0026] Preferably, the carbon-coated graphite felt is placed in a vacuum drying oven at room temperature and then impregnated with silica sol under vacuum conditions of -0.8 to -1 bar to ensure that the carbon-coated graphite felt is fully impregnated.

[0027] Furthermore, the parameters for heat preservation at high temperature are: heating at a rate of 1-5℃ / min to 1500-1700℃, and holding at that temperature for 4-6 hours.

[0028] Carbon@silicon carbide nanofiber aerogels were prepared using the method described above.

[0029] Application of carbon@silicon carbide nanofiber aerogel: Applying carbon@silicon carbide nanofiber aerogel to the preparation of high-temperature resistant thermal insulation materials.

[0030] 3. Beneficial effects

[0031] Compared with existing known technologies, the technical solution provided by this invention has the following beneficial effects:

[0032] (1) The preparation method of carbon@silicon carbide nanofiber aerogel of the present invention uses graphite felt as the carbon source growth point and the original supporting skeleton. The graphite felt is treated with a plasma cleaner to remove impurities from the surface, making the carbon fiber surface hydrophilic and easy to be fully impregnated in the subsequent process. Moreover, the surface of the carbon fiber after treatment is rough, which reduces the reaction difficulty of graphite carbon and makes it easier to coat the carbon layer after carbonization of carbon source (such as polydopamine). After the graphite fiber felt with additional carbon layer is vacuum impregnated with silicon source for a second time, it is calcined at high temperature in an argon atmosphere, thereby transforming into carbon / silicon carbide nanofiber aerogel. The sacrificial carbon on the outer layer of carbon fiber reacts in situ to generate C-Si coated silicon carbide, which is more robust than ordinary coating. The carbon@silicon carbide nanofiber aerogel is obtained as a high-temperature heat insulation material, achieving fire resistance and heat insulation at a high temperature of 1300℃. The preparation method only requires common laboratory equipment, without special equipment or special reagents. The process is simple and easy to operate, the reaction process is easy to control, the production cycle is short, the cost is low, and it can be mass-produced.

[0033] (2) The carbon@silicon carbide nanofiber aerogel of the present invention, wherein the multi-scale structure of carbon / silicon carbide nanofibers and one-dimensional silicon carbide nanowires can effectively suppress air heat conduction, heat convection and solid skeleton phonon heat conduction, thereby significantly improving the thermal insulation effect of carbon / silicon carbide nanofiber aerogel. Moreover, the silicon carbide shell of the carbon fiber outer layer can better maintain good thermal and chemical stability in high-temperature oxygen environment, and has both lightweight and high-efficiency thermal insulation performance. At the same time, the ultra-strong carbon fiber skeleton endows the material with excellent mechanical properties.

[0034] (3) Application of the carbon@silicon carbide nanofiber aerogel of the present invention: Since the carbon@silicon carbide nanofiber aerogel prepared in this application has both excellent mechanical properties and efficient thermal insulation properties, it can be used in high-temperature thermal insulation scenarios such as aircraft end faces or lithium battery modules. Attached Figure Description

[0035] Figure 1These are optical photographs of the phased samples of the preparation process in Example 4, including the graphite felt after cutting, the carbon-coated graphite fiber felt after secondary impregnation with silicon source, and the carbon / silicon carbide nanofiber aerogel generated by high-temperature calcination.

[0036] Figure 2 The morphology of the carbon@silicon carbide nanofiber aerogels prepared in Examples 1-4 and Comparative Example 1 of this invention was detected by scanning electron microscopy at a magnification of 250, resulting in the obtained scanning electron microscope images.

[0037] Figure 3 The XRD patterns of the carbon@silicon carbide nanofiber aerogels prepared in Examples 1-4 and Comparative Example 1 of this invention were obtained by using an X-ray diffraction analyzer.

[0038] Figure 4 This is an optical photograph of the carbon@silicon carbide nanofiber aerogel prepared in Example 4 subjected to butane flame ablation using a butane torch.

[0039] Figure 5 The graph shows the thermal conductivity of the carbon@silicon carbide nanofiber aerogels prepared in Examples 1-4 and Comparative Example 1 from room temperature to 1100°C, as compared using a laser thermal conductivity meter.

[0040] Figure 6 The compressive stress-compression strain diagram of the carbon@silicon carbide nanofiber aerogel prepared in Example 4 was obtained by using an electronic universal testing machine. Detailed Implementation

[0041] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments.

[0042] Example 1

[0043] The preparation method of carbon@silicon carbide nanofiber aerogel in this embodiment includes the following steps:

[0044] Step S1: Treat both sides of the graphite felt in a plasma cleaner for 10 minutes each.

[0045] Step S2: Dissolve 10 mmol of tris(hydroxymethyl)aminomethane and 0.8 mmol of dopamine hydrochloride in 100 mL of deionized water, then add 1 mL of hydrochloric acid and stir well.

[0046] Step S3: Immerse the graphite felt obtained in step S1 in the carbon-containing solution obtained in step S2, stir at room temperature for 6 hours, and then vacuum dry at 60°C for 12 hours.

[0047] Step S4: The dried felt obtained in step S3 is heated to 800-1000℃ at a heating rate of 2-5℃ / min and kept at that temperature for 1-3 hours, and then cooled naturally to obtain carbon-coated graphite felt.

[0048] Step S5: Weigh 30 ml of tetraethyl orthosilicate and disperse it in 55 ml of ethanol and 15 ml of deionized water. Stir for 7 hours, then add hydrochloric acid dropwise to make the pH of the mixed solution 3. Stir again for 8 hours to obtain a clear solution.

[0049] Step S6: Immerse the felt in the clear solution obtained in step S5 for 40 minutes in a vacuum impregnation machine with a vacuum degree of 10 mbar, remove the gas from the felt and the solution, and perform the initial impregnation of the felt.

[0050] Step S7: At room temperature, the felt body after the initial impregnation is further impregnated in the clear solution obtained in step S5 for a second impregnation for 36 hours in a vacuum drying oven at a vacuum degree of -0.9 bar.

[0051] Step S8: After the second impregnation, the sample is heated to 60°C and dried in a vacuum drying oven for 24 hours at a vacuum degree of -0.7 bar.

[0052] Step S9: The dried felt impregnated with silica sol is placed into an alumina crucible and placed in a high-temperature tube furnace. The temperature is increased to 1500-1700℃ at a rate of 1-5℃ / min and held at this temperature for 4-6 hours. Finally, the temperature is allowed to drop naturally to obtain carbon@silicon carbide nanofiber aerogel.

[0053] Example 2

[0054] The preparation method of carbon@silicon carbide nanofiber aerogel in this embodiment includes the following steps:

[0055] Step S1: Treat both sides of the graphite felt in a plasma cleaner for 10 minutes each.

[0056] Step S2: Dissolve 10 mmol of tris(hydroxymethyl)aminomethane and 0.8 mmol of dopamine hydrochloride in 100 mL of deionized water, then add 1 mL of hydrochloric acid and stir well.

[0057] Step S3: Immerse the graphite felt obtained in step S1 in the mixed solution obtained in step S2, stir at room temperature for 6 hours, and then vacuum dry at 60°C for 12 hours.

[0058] Step S4: The dried felt obtained in step S3 is heated to 800-1000℃ at a heating rate of 2-5℃ / min and kept at that temperature for 1-3 hours, and then cooled naturally to obtain carbon-coated graphite felt.

[0059] Step S5: Weigh 32 ml of tetraethyl orthosilicate and disperse it in 42 ml of ethanol and 16 ml of deionized water. Stir for 7 h and then add hydrochloric acid dropwise to make the pH of the mixed solution 3. Stir again for 8 h to obtain a clear solution.

[0060] Step S6: Immerse the felt in the clear solution obtained in step S5 for 40 minutes in a vacuum impregnation machine with a vacuum degree of 10 mbar, remove the gas from the felt and the solution, and perform the initial impregnation of the felt.

[0061] Step S7: At room temperature, the felt body after the initial impregnation is further impregnated in the clear solution obtained in step S5 for a second impregnation for 36 hours in a vacuum drying oven at a vacuum degree of -0.9 bar.

[0062] Step S8: After the second impregnation, the sample is heated to 60°C and dried in a vacuum drying oven for 24 hours at a vacuum degree of -0.7 bar.

[0063] Step S9: The dried felt impregnated with silica sol is placed into an alumina crucible and placed in a high-temperature tube furnace. The temperature is increased to 1500-1700℃ at a rate of 1-5℃ / min and held at this temperature for 4-6 hours. Finally, the temperature is allowed to drop naturally to obtain carbon@silicon carbide nanofiber aerogel.

[0064] Example 3

[0065] The preparation method of carbon@silicon carbide nanofiber aerogel in this embodiment includes the following steps:

[0066] Step S1: Treat both sides of the graphite felt in a plasma cleaner for 10 minutes each.

[0067] Step S2: Dissolve 10 mmol of tris(hydroxymethyl)aminomethane and 0.8 mmol of dopamine hydrochloride in 100 mL of deionized water, then add 1 mL of hydrochloric acid and stir well.

[0068] Step S3: Immerse the graphite felt obtained in step S1 in the mixed solution obtained in step S2, stir at room temperature for 6 hours, and then vacuum dry at 60°C for 12 hours.

[0069] Step S4: The dried felt obtained in step S3 is heated to 800-1000℃ at a heating rate of 2-5℃ / min and kept at that temperature for 1-3 hours, and then cooled naturally to obtain carbon-coated graphite felt.

[0070] Step S5: Weigh 36 ml of tetraethyl orthosilicate and disperse it in 46 ml of ethanol and 18 ml of deionized water. Stir for 7 h and then add hydrochloric acid dropwise to make the pH of the mixed solution 3. Stir again for 8 h to obtain a clear solution.

[0071] Step S6: Immerse the felt in the clear solution obtained in step S5 for 40 minutes in a vacuum impregnation machine with a vacuum degree of 10 mbar, remove the gas from the felt and the solution, and perform the initial impregnation of the felt.

[0072] Step S7: At room temperature, the felt body after the initial impregnation is further impregnated in the clear solution obtained in step S5 for a second impregnation for 36 hours in a vacuum drying oven at a vacuum degree of -0.9 bar.

[0073] Step S8: After the second impregnation, the sample is heated to 60°C and dried in a vacuum drying oven for 24 hours at a vacuum degree of -0.7 bar.

[0074] Step S9: The dried felt impregnated with silica sol is placed into an alumina crucible and placed in a high-temperature tube furnace. The temperature is increased to 1500-1700℃ at a rate of 1-5℃ / min and held at this temperature for 4-6 hours. Finally, the temperature is allowed to drop naturally to obtain carbon@silicon carbide nanofiber aerogel.

[0075] Example 4

[0076] The preparation method of carbon@silicon carbide nanofiber aerogel in this embodiment includes the following steps:

[0077] Step S1: Treat both sides of the graphite felt in a plasma cleaner for 10 minutes each.

[0078] Step S2: Dissolve 10 mmol of tris(hydroxymethyl)aminomethane and 0.8 mmol of dopamine hydrochloride in 100 mL of deionized water, then add 1 mL of hydrochloric acid and stir well.

[0079] Step S3: Immerse the graphite felt obtained in step S1 in the mixed solution obtained in step S2, stir at room temperature for 6 hours, and then vacuum dry at 60°C for 12 hours.

[0080] Step S4: The dried felt obtained in step S3 is heated to 800-1000℃ at a heating rate of 2-5℃ / min and kept at that temperature for 1-3 hours, and then cooled naturally to obtain carbon-coated graphite felt.

[0081] Step S5: Weigh 40 ml of tetraethyl orthosilicate and disperse it in 40 ml of ethanol and 20 ml of deionized water. Stir for 7 hours, then add hydrochloric acid dropwise to make the pH of the mixed solution 3. Stir again for 8 hours to obtain a clear solution.

[0082] Step S6: Immerse the felt in the clear solution obtained in step S5 for 40 minutes in a vacuum impregnation machine with a vacuum degree of 10 mbar, remove the gas from the felt and the solution, and perform the initial impregnation of the felt.

[0083] Step S7: At room temperature, the felt body after the initial impregnation is further impregnated in the clear solution obtained in step S5 for a second impregnation for 36 hours in a vacuum drying oven at a vacuum degree of -0.9 bar.

[0084] Step S8: After the second impregnation, the sample is heated to 60°C and dried in a vacuum drying oven for 24 hours at a vacuum degree of -0.7 bar.

[0085] Step S9: The dried felt impregnated with silica sol is placed into an alumina crucible and placed in a high-temperature tube furnace. The temperature is increased to 1500-1700℃ at a rate of 1-5℃ / min and held at this temperature for 4-6 hours. Finally, the temperature is allowed to drop naturally to obtain carbon@silicon carbide nanofiber aerogel.

[0086] Comparative Example 1

[0087] The preparation method of the silicon carbide nanofiber aerogel in this comparative example includes the following steps:

[0088] Step S1: Cut the graphite felt into the required size and shape for later use.

[0089] Step S2: Weigh 40 ml of tetraethyl orthosilicate and disperse it in 40 ml of ethanol and 20 ml of deionized water. Stir for 7 hours, then add hydrochloric acid dropwise to make the pH of the mixed solution 3. Stir again for 8 hours to obtain a clear solution.

[0090] Step S3: Immerse the graphite felt in the clear solution obtained in step S2 for 40 minutes in a vacuum impregnation machine with a vacuum degree of 10 mbar, remove the gas from the graphite felt and the solution, and perform the initial impregnation of the graphite felt.

[0091] Step S4: At room temperature, the graphite felt that has been initially impregnated is further impregnated in the clear solution obtained in step S2 for 36 hours in a vacuum drying oven at a vacuum degree of -0.9 bar.

[0092] Step S5: After the second impregnation, the sample is heated to 60°C and dried in a vacuum drying oven for 24 hours at a vacuum degree of -0.7 bar.

[0093] Step S6: The dried graphite felt impregnated with silica sol is placed into an alumina crucible and placed in a high-temperature tube furnace. The temperature is increased to 1500-1700℃ at a rate of 1-5℃ / min and held at this temperature for 4-6 hours. Finally, the temperature is allowed to drop naturally to obtain silicon carbide nanofiber aerogel.

[0094] Morphological observation and performance testing

[0095] The morphology and performance of the carbon@silicon carbide nanofiber aerogels prepared in Examples 1-4 and Comparative Example 1 of this invention were observed and tested, and the following results were obtained:

[0096] (1) The intermediate process sample of the carbon@silicon carbide nanofiber aerogel prepared in Example 4 was photographed using an optical camera to obtain the following results: Figure 1 The optical photograph shown. (By...) Figure 1 It can be seen that the volume of the aerogel prepared in Example 4 of this application remains almost unchanged.

[0097] (2) The morphology of the carbon@silicon carbide nanofiber aerogels prepared in Examples 1-4 and Comparative Example 1 of this invention was examined using scanning electron microscopy to obtain the following results: Figure 2 The scanning electron microscope image shown is shown. Among them, Figure 2 a is a FESEM image of the carbon@silicon carbide nanofiber aerogel prepared in Example 1 of this application at a magnification of 250; Figure 2 b is a FESEM image of the carbon@silicon carbide nanofiber aerogel prepared in Example 2 of this application at a magnification of 250; Figure 2 c is a FESEM image of the carbon@silicon carbide nanofiber aerogel prepared in Example 3 of this application at a magnification of 250. Figure 2 d is a FESEM image of the carbon@silicon carbide nanofiber aerogel prepared in Example 4 of this application at a magnification of 250. Figure 2 e is a FESEM image of the carbon@silicon carbide nanofiber aerogel prepared in Comparative Example 1 of this application at a magnification of 250. Examples 1-4 show the cases where the front and back sides of the carbon-coated graphite felt were immersed in a mixed solution of tetraethyl orthosilicate:ethanol at a volume ratio of 1:1 to 2 after 10 min each. The comparative example shows the case where the graphite felt was directly immersed in a mixed solution of tetraethyl orthosilicate:ethanol at a volume ratio of 1:1 without plasma cleaning and dopamine coating. Figure 2 It can be seen that the higher the degree of dilution of the impregnation solution, the thicker the silicon carbide shell covering the carbon fiber in the carbon@silicon carbide nanofiber aerogel, and the more silicon carbide nanowires are in the structure. Comparative Example 1 is completely a felt morphology woven from carbon fiber.

[0098] (3) X-ray diffraction analysis was used to analyze the carbon@silicon carbide nanofiber aerogels and graphite felts prepared in Examples 1-4 and Comparative Example 1 of this application, respectively, to obtain the following results: Figure 3 The X-ray diffraction pattern shown; by Figure 3 It can be seen that the carbon@silicon carbide nanofiber aerogels prepared in Examples 1 to 4 of this application all show a pure β-SiC phase in the XRD pattern; the carbon@silicon carbide nanofiber aerogel prepared in Comparative Example 1 shows a pure β-SiC phase in the XRD pattern, but also contains a large number of graphite carbon peaks. This is because the graphite felt in the comparative example, which has not undergone plasma cleaning and coating, is not easy to react with the silicon source, and the carbon fibers are difficult to be completely coated with silicon carbide, resulting in a large amount of exposed carbon.

[0099] (4) The carbon@silicon carbide nanofiber aerogel prepared in Example 4 was subjected to butane flame ablation test using a butane spray gun to obtain the following results: Figure 4 The optical photograph shown; by Figure 4 It can be seen that the carbon@silicon carbide nanofiber aerogel prepared in Example 4 of this application can resist butane flame ablation at 1300℃.

[0100] (5) The thermal conductivity of the carbon@silicon carbide nanofiber aerogels prepared in Examples 1-4 and Comparative Example 1 of this application was measured using a laser thermal conductivity meter, thereby obtaining the following results: Figure 5 The thermal conductivity graph shown; by Figure 5 It can be seen that the carbon@silicon carbide nanofiber aerogels prepared in Examples 1 to 4 of this application have very low thermal conductivity at room temperature to 1100℃ and have good thermal insulation performance; while the carbon@silicon carbide nanofiber aerogel prepared in Comparative Example 1 has poor thermal insulation performance because it contains a large number of exposed carbon structures, which are more conducive to heat transfer and have a higher thermal conductivity.

[0101] (6) The carbon@silicon carbide nanofiber aerogel prepared in Example 4 of this application was subjected to a single pressure test at room temperature using an electronic universal testing machine, thereby obtaining the following results: Figure 6 The compressive stress-compressive strain diagram shown; by Figure 6 It can be seen that the carbon@silicon carbide nanofiber aerogel prepared in Example 4 of this application has a maximum compressive stress of 14.053 MPa at room temperature, which shows that it has super strong compressive strength.

[0102] In summary, the embodiments of this application not only have a simple preparation process, easy-to-control reaction process, short production cycle, and low cost, but also the prepared carbon@silicon carbide nanofiber aerogel has excellent high-temperature stability and good thermal insulation performance.

[0103] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications, improvements, and substitutions without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing carbon@silicon carbide nanofiber aerogels, characterized by: The method comprises the following steps: The graphite felt is cleaned with plasma water to obtain cleaned graphite felt; A solution containing a carbon source is prepared to obtain a carbon-containing solution; The cleaned graphite felt is immersed in the carbon-containing solution and then dried to obtain carbon-coated graphite felt; the carbon-containing solution is prepared by dissolving 10 mmol of tris-hydroxymethyl aminomethane and 0.6-1.0 mmol of dopamine hydrochloride in 100 mL of deionized water, and then adding 1 mL of hydrochloric acid; the cleaned graphite felt is stirred in the carbon-containing solution at room temperature for 6 h, and then vacuum dried at 60 ℃ for 12 h; the temperature is raised to 800-1000 ℃ at a temperature raising rate of 2-5 ℃ / min, and then kept for 1-3 h; A solution containing tetraethyl orthosilicate, ethanol and deionized water is prepared, and hydrochloric acid is added to adjust the solution to be clear to obtain a mixed solution; The carbon-coated graphite felt is immersed in the mixed solution and then dried to obtain impregnated graphite felt; The impregnated graphite felt is kept at high temperature to obtain the carbon@silicon carbide nanofiber aerogel.

2. The method for preparing carbon@silicon carbide nanofiber aerogel according to claim 1, characterized in that: The carbon source is dopamine hydrochloride or phenol formaldehyde.

3. The method for preparing carbon@silicon carbide nanofiber aerogel according to claim 1, characterized in that: The volume ratio of tetraethyl orthosilicate, ethanol and deionized water in the mixed solution is 2:2-3.66:1, and the pH is 2-4.

4. The method for preparing carbon@silicon carbide nanofiber aerogel according to claim 3, characterized in that: The carbon-coated graphite felt is immersed in the mixed solution for 0.5-1 h and then dried.

5. The method for preparing carbon@silicon carbide nanofiber aerogel according to claim 4, characterized in that: The carbon-coated graphite felt is immersed in the mixed solution for 0.5-1 h and then dried.

6. The method for preparing carbon@silicon carbide nanofiber aerogel according to claim 5, characterized in that: The carbon-coated graphite felt is immersed in the mixed solution for 0.5-1 h and then dried.

7. Carbon@silicon carbide nanofiber aerogels characterized in that: The parameters for keeping at high temperature are as follows: the temperature is raised to 1500-1700 ℃ at a temperature raising rate of 1-5 ℃ / min, and then kept for 4-6 h.

8. Use of carbon@silicon carbide nanofiber aerogels, characterized by: The carbon@silicon carbide nanofiber aerogel is prepared by the method of any one of claims 1-6. The carbon@silicon carbide nanofiber aerogel of claim 7 is applied to the preparation of high-temperature-resistant thermal insulation materials.

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