Preparation process of dense carbonized silicon coating on surface of carbon fiber thermal insulation material

Abstract

The application provides a preparation process of a dense silicon carbide coating on the surface of a carbon fiber thermal insulation material, which comprises the following steps: surface treatment of a hard carbon fiber felt matrix, uniform coating of graphite milk on the surface of the treated matrix, formation of a graphite sealing blocking layer on the surface of the matrix after carbonization treatment and graphitization treatment, and generation of a double-layer silicon carbide coating on the surface of the graphite sealing blocking layer, which comprises a crack resistance layer and a dense layer. The product prepared by the application has improved strength of the coating on the surface of the matrix, the silicon carbide coating prepared on the basis has effectively improved the bonding strength between the coating and the matrix, and has the advantages of simple process and low production cost.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials, and in particular to a process for preparing a dense silicon carbide coating on the surface of carbon fiber thermal insulation materials. Background Technology

[0002] Rigid carbon fiber felt possesses characteristics such as low density, high stability, ablation resistance, corrosion resistance, and excellent high-temperature mechanical properties. Furthermore, the presence of numerous micropores within it gives it outstanding high-temperature insulation performance, making it a suitable material for high-temperature environments. Silicon carbide, as an excellent high-temperature structural ceramic, is considered a high-temperature wear-resistant structural material with broad application prospects. Due to its low coefficient of thermal expansion, good physicochemical compatibility with carbon materials, and similar coefficients of thermal expansion, silicon carbide is considered one of the best coating materials for high-temperature wear resistance and corrosion resistance. Moreover, the oxidation resistance, erosion resistance, and corrosion resistance of silicon carbide coatings are superior to other carbon-based coatings and claddings. This invention provides a process for preparing a dense silicon carbide coating on the surface of carbon fiber insulation materials. The silicon carbide coating prepared by this invention exhibits high bonding strength between the coating and the substrate, and also has the advantages of simple processing and low production cost. Summary of the Invention

[0003] This invention provides a process for preparing a dense silicon carbide coating on the surface of carbon fiber insulation materials. The process involves surface treatment of a rigid carbon fiber felt substrate, uniform coating of graphite emulsion on the treated substrate surface, followed by carbonization and graphitization treatments to form a graphite sealing and blocking layer on the substrate surface. A double-layer silicon carbide coating, including an anti-cracking layer and a dense layer, is then generated on the surface of the graphite sealing and blocking layer. The product prepared by this invention improves the strength of the coating covering the substrate surface. The silicon carbide coating prepared on this basis effectively improves the bonding strength between the coating and the substrate, while also possessing advantages such as simple process and low production cost.

[0004] A process for preparing a dense silicon carbide coating on the surface of a carbon fiber thermal insulation material, characterized in that the process includes:

[0005] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, dry, coat the substrate surface with zirconium nitrate solution, and dry.

[0006] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of carbon source gas and inert gas, carbonize at high temperature, and cool to room temperature;

[0007] 3) Disperse graphite emulsion, polycarbosilane, and nano-silicon powder in tetrachloroethylene, then add vinyltriethoxysilane, coat the resulting slurry onto the surface of the product from step 2, dry it, place it in a high-temperature furnace, heat and carbonize it under a sealed or inert atmosphere, and then heat it to graphitize it to obtain a graphite layer.

[0008] 4) Mix silicon carbide nanowires and silane coupling agent, add to toluene, heat to activate, and then dry; disperse the dried silicon carbide nanowires in an aqueous solution containing carbon source precursor, stir evenly, filter, dry, and then place in a high-temperature furnace for high-temperature carbonization under inert gas protection to obtain modified silicon carbide nanowires.

[0009] 5) Disperse modified silicon carbide nanowires, polycarbosilane, and silicon powder in tetrachloroethylene, then add vinyltriethoxysilane, coat the resulting slurry onto the surface of the product from step 3, place it in a high-temperature furnace, and heat it under a sealed or inert atmosphere to generate a silicon carbide layer.

[0010] 6) Mix phenolic resin, fumed silica powder and ethylene glycol evenly to obtain a slurry; coat the slurry onto the surface of the product from step 5, place it in a high-temperature furnace, introduce a mixture of silane and hydrogen gas, and heat it to obtain carbon fiber insulation material.

[0011] Furthermore, in step 1, the concentration of the zirconium nitrate solution is 1-5 wt%.

[0012] Furthermore, in step 2, a mixture of carbon source gas and inert gas with a volume ratio of 1:2-3 is introduced, and the temperature is raised to 900-1000℃ and maintained for 2-4 hours.

[0013] Further, in step 3, graphite emulsion, polycarbosilane with a molecular weight of 1000-2000, and silicon powder with a wavelength of 100-150 nm are dispersed in tetrachloroethylene to obtain a slurry, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:25-50:20-30:150-200, and then vinyltriethoxysilane is added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 2-5:100; the slurry is coated on the surface of the product from step 2, dried, and then placed in a high-temperature furnace, protected by a sealed or inert atmosphere, and heated to 1100-1300℃ for 0.5-2 hours, and then heated to 1800-2000℃ for graphitization for 0.5-1 hour.

[0014] Further, in step 4, silicon carbide nanowires and aminopropyltriethoxysilane are mixed at a mass ratio of 10:1-2, then added to toluene, heated for 4-6 hours for activation, and then dried. The dried silicon carbide nanowires are dispersed in an aqueous solution containing 15-20 wt% carbon source precursor, stirred evenly, filtered, dried, and then placed in a high-temperature furnace under inert gas protection and heated to 600-700℃ for high-temperature carbonization to obtain modified silicon carbide nanowires.

[0015] Further, in step 5, modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1000-2000, and silicon powder with a particle size of 100-150 nm are dispersed in tetrachloroethylene to obtain a slurry, wherein the mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 15-20:25-50:20-30:150-200, and then vinyltriethoxysilane is added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 2-5:100; the slurry is coated on the surface of the product from step 3, placed in a high-temperature furnace, and heated at 1600-1800℃ under sealed or inert atmosphere protection for 1-4 hours.

[0016] Further, in step 6, phenolic resin, fumed silica powder, and ethylene glycol are mixed evenly in a mass ratio of 50-60:50-60:140-160 to obtain a slurry; the slurry is coated on the surface of the product from step 5, placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:2-4 is introduced, the temperature is raised to 850-950℃, maintained for 10-16 hours, and then cooled to obtain carbon fiber thermal insulation material.

[0017] A carbon fiber thermal insulation material, wherein the material is obtained using the aforementioned preparation process.

[0018] The beneficial technical effects of this invention compared to the prior art

[0019] 1) Sealing carbon fiber felt matrix: Carbon deposition modification is performed on the surface of rigid carbon fiber felt matrix. At high temperature, zirconium nitrate is converted into zirconium oxide. Under the catalysis of zirconium oxide, a carbon layer with high roughness is formed on the matrix surface. Graphite emulsion is coated on the carbon layer surface. At high temperature, tetrachloroethylene volatilization can remove metal impurities in graphite, thus forming a graphite sealing and blocking layer with a dense structure that is tightly bonded to the matrix after high temperature treatment.

[0020] 2) Improve the bonding strength of silicon carbide coating: The graphite sealing barrier layer has a certain adhesion force, which can further improve the strength of the silicon carbide coating covering the substrate surface and prevent silicon from diffusing into the substrate during high-temperature sintering, thereby forming a dense silicon carbide coating on the surface of the barrier layer.

[0021] 3) Improve the crack resistance and density of silicon carbide: The silicon carbide coating consists of a two-layer structure. The bottom layer of silicon carbide coating incorporates silicon carbide nanowires, which enhance the fracture resistance of the coating and increase its toughness. Simultaneously, a high-temperature protective layer is formed on the surface of the silicon carbide nanowires, preventing them from breaking down during high-temperature sintering. Furthermore, the carbon coating enhances the bonding strength between the silicon carbide nanowires and the silicon carbide coating, ensuring the mechanical properties of the coating. The top layer of silicon carbide coating incorporates a vapor-phase silicon source for deposition during sintering. Silicon carbide is generated in situ on the coating surface and in the pores, thereby increasing the density of the coating surface.

[0022] 4) The preparation process of the present invention is low in cost, simple and efficient, and has wide application value. Detailed Implementation

[0023] The present invention will be described in more detail below through specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0024] Example 1

[0025] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, dry, coat the substrate surface with a 3wt% zirconium nitrate solution, and dry.

[0026] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of acetylene and nitrogen gas with a volume ratio of 1:2, heat to 900℃, maintain for 4 hours; then cool to room temperature.

[0027] 3) A slurry is prepared by dispersing graphite emulsion, polycarbosilane with a molecular weight of 1500, and silicon powder with a particle size of 100 nm in tetrachloroethylene, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:25:20:150. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 2:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 0.5 kg / m³. 2 After drying, it is placed in a high-temperature furnace and heated to 1100℃ under nitrogen protection for 2 hours, then heated to 1800℃ and held for 1 hour.

[0028] 4) Silicon carbide nanowires with a diameter of 0.5 μm and a length of 1 mm were mixed with aminopropyltriethoxysilane at a mass ratio of 10:1 and dispersed in toluene. The mixture was activated by heating at 75 °C for 4 h and then dried. The dried silicon carbide nanowires were dispersed in an aqueous solution containing 15 wt% glucose at a mass ratio of 1:10. After stirring evenly, the mixture was filtered, dried, and then placed in a high-temperature furnace. The temperature was raised to 600 °C under nitrogen protection and maintained for 8 h to obtain modified silicon carbide nanowires.

[0029] 5) Modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1500, and 100nm silicon powder are dispersed in tetrachloroethylene to obtain a slurry. The mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 15:25:20:150. Vinyltriethoxysilane is then added, with a mass ratio of vinyltriethoxysilane to the slurry of 2:100. The slurry is then coated onto the surface of the product from step 3, with a coating slurry dosage of 1.0 kg / m³. 2 Place it in a high-temperature furnace, heat it to 1600℃ under a sealed or inert atmosphere, and keep it there for 4 hours.

[0030] 6) Mix phenolic resin, fumed silica powder, and ethylene glycol in a mass ratio of 50:50:140 to obtain a slurry; coat the slurry onto the surface of the product from step 5, using 0.3 kg / m² of slurry. 2 The mixture is placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:2 is introduced. The temperature is raised to 850°C, maintained for 16 hours, and then cooled to obtain carbon fiber insulation material.

[0031] Example 2

[0032] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, ultrasonically clean it in anhydrous ethanol, dry it, coat the substrate surface with a 5wt% zirconium nitrate solution, and dry it.

[0033] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of acetylene and nitrogen gas with a volume ratio of 1:3, heat to 1000℃, maintain for 2 hours; cool to room temperature;

[0034] 3) A slurry is prepared by dispersing graphite emulsion, polycarbosilane with a molecular weight of 1500, and silicon powder with a particle size of 100 nm in tetrachloroethylene, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:50:30:200. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 5:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 0.5 kg / m³. 2After drying, it is placed in a high-temperature furnace and heated to 1300℃ under nitrogen protection, held for 0.5h, and then heated to 2000℃ and held for 0.5h.

[0035] 4) Silicon carbide nanowires with a diameter of 0.5 μm and a length of 1 mm were mixed with aminopropyltriethoxysilane at a mass ratio of 10:2 and dispersed in toluene. The mixture was activated by heating at 75 °C for 6 h and then dried. The dried silicon carbide nanowires were dispersed in an aqueous solution containing 20 wt% glucose at a mass ratio of 1:10. After stirring evenly, the mixture was filtered, dried, and then placed in a high-temperature furnace. The temperature was raised to 700 °C under nitrogen protection and maintained for 4 h to obtain modified silicon carbide nanowires.

[0036] 5) Modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1500, and silicon powder of 150 nm are dispersed in tetrachloroethylene to obtain a slurry, wherein the mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 20:50:30:200. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 5:100. The slurry is coated onto the surface of the product from step 3, with a coating slurry dosage of 1.0 kg / m³. 2 Place it in a high-temperature furnace, heat it to 1800℃ under a sealed or inert atmosphere, and keep it there for 1 hour.

[0037] 6) Mix phenolic resin, fumed silica powder, and ethylene glycol in a mass ratio of 60:60:160 to obtain a slurry; coat the slurry onto the surface of the product from step 5, using 0.3 kg / m² of slurry. 2 The mixture is placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:4 is introduced. The temperature is raised to 950°C, maintained for 10 hours, and then cooled to obtain carbon fiber insulation material.

[0038] Example 3

[0039] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, dry, coat the substrate surface with a 3wt% zirconium nitrate solution, and dry.

[0040] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of acetylene and nitrogen gas with a volume ratio of 1:2.5, heat to 950°C, maintain for 3 hours; then cool to room temperature.

[0041] 3) A slurry is prepared by dispersing graphite emulsion, polycarbosilane with a molecular weight of 1500, and silicon powder with a particle size of 120 nm in tetrachloroethylene, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 0.5 kg / m³. 2 After drying, it is placed in a high-temperature furnace and heated to 1200℃ under nitrogen protection, held for 1 hour, and then heated to 1900℃ and held for 1 hour.

[0042] 4) Silicon carbide nanowires with a diameter of 0.5 μm and a length of 1 mm were mixed with aminopropyltriethoxysilane at a mass ratio of 10:2 and dispersed in toluene. The mixture was activated by heating at 75 °C for 5 h and then dried. The dried silicon carbide nanowires were dispersed in an aqueous solution containing 18 wt% glucose at a mass ratio of 1:10. After stirring evenly, the mixture was filtered, dried, and then placed in a high-temperature furnace. The temperature was raised to 650 °C under nitrogen protection and held for 6 h to obtain modified silicon carbide nanowires.

[0043] 5) Modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1500, and silicon powder with a wavelength of 120 nm are dispersed in tetrachloroethylene to obtain a slurry. The mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 18:35:25:180. Vinyltriethoxysilane is then added, with a mass ratio of vinyltriethoxysilane to the slurry of 4:100. The slurry is then coated onto the surface of the product from step 3, with a coating slurry dosage of 1.0 kg / m². 2 Place it in a high-temperature furnace, heat it to 1700℃ under a sealed or inert atmosphere, and keep it there for 2 hours.

[0044] 6) Mix phenolic resin, fumed silica powder, and ethylene glycol in a mass ratio of 55:55:150 to obtain a slurry; coat the slurry onto the surface of the product from step 5, using 0.3 kg / m² of slurry. 2 The mixture is placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:3 is introduced. The temperature is raised to 900°C, maintained for 12 hours, and then cooled to obtain carbon fiber insulation material.

[0045] Comparative Example 1 (No carbon deposition performed)

[0046] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, and dry it.

[0047] 2) A slurry is prepared by dispersing graphite emulsion, polycarbosilane with a molecular weight of 1500, and silicon powder with a particle size of 120 nm in tetrachloroethylene, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 1, with a coating slurry dosage of 0.5 kg / m³. 2 After drying, it is placed in a high-temperature furnace and heated to 1200℃ under nitrogen protection, held for 1 hour, and then heated to 1900℃ and held for 1 hour.

[0048] 3) Silicon carbide nanowires with a diameter of 0.5 μm and a length of 1 mm were mixed with aminopropyltriethoxysilane at a mass ratio of 10:2 and dispersed in toluene. The mixture was activated by heating at 75 °C for 5 h and then dried. The dried silicon carbide nanowires were dispersed in an aqueous solution containing 18 wt% glucose at a mass ratio of 1:10. After stirring evenly, the mixture was filtered, dried, and then placed in a high-temperature furnace. The temperature was raised to 650 °C under nitrogen protection and maintained for 6 h to obtain modified silicon carbide nanowires.

[0049] 4) Modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1500, and silicon powder of 120 nm are dispersed in tetrachloroethylene to obtain a slurry, wherein the mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 18:35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 1.0 kg / m². 2 Place it in a high-temperature furnace, heat it to 1700℃ under a sealed or inert atmosphere, and keep it there for 2 hours.

[0050] 5) Mix phenolic resin, fumed silica powder, and ethylene glycol in a mass ratio of 55:55:150 to obtain a slurry; coat the slurry onto the surface of the product from step 4, using 0.3 kg / m² of slurry. 2 The mixture is placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:3 is introduced. The temperature is raised to 900°C, maintained for 12 hours, and then cooled to obtain carbon fiber insulation material.

[0051] Comparative Example 2 (without graphite layer)

[0052] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, dry, coat the substrate surface with a 3wt% zirconium nitrate solution, and dry.

[0053] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of acetylene and nitrogen gas with a volume ratio of 1:2.5, heat to 950°C, maintain for 3 hours; then cool to room temperature.

[0054] 3) Silicon carbide nanowires with a diameter of 0.5 μm and a length of 1 mm were mixed with aminopropyltriethoxysilane at a mass ratio of 10:2 and dispersed in toluene. The mixture was activated by heating at 75 °C for 5 h and then dried. The dried silicon carbide nanowires were dispersed in an aqueous solution containing 18 wt% glucose at a mass ratio of 1:10. After stirring evenly, the mixture was filtered, dried, and then placed in a high-temperature furnace. The temperature was raised to 650 °C under nitrogen protection and maintained for 6 h to obtain modified silicon carbide nanowires.

[0055] 4) Modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1500, and silicon powder of 120 nm are dispersed in tetrachloroethylene to obtain a slurry, wherein the mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 18:35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 1.0 kg / m². 2 Place it in a high-temperature furnace, heat it to 1700℃ under a sealed or inert atmosphere, and keep it there for 2 hours.

[0056] 5) Mix phenolic resin, fumed silica powder, and ethylene glycol in a mass ratio of 55:55:150 to obtain a slurry; coat the slurry onto the surface of the product from step 4, using 0.3 kg / m² of slurry. 2 The mixture is placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:3 is introduced. The temperature is raised to 900°C, maintained for 12 hours, and then cooled to obtain carbon fiber insulation material.

[0057] Comparative Example 3 (without silicon carbide nanowires)

[0058] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, dry, coat the substrate surface with a 3wt% zirconium nitrate solution, and dry.

[0059] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of acetylene and nitrogen gas with a volume ratio of 1:2.5, heat to 950°C, maintain for 3 hours; then cool to room temperature.

[0060] 3) A slurry is prepared by dispersing graphite emulsion, polycarbosilane with a molecular weight of 1500, and silicon powder with a particle size of 120 nm in tetrachloroethylene, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 0.5 kg / m³. 2 After drying, it is placed in a high-temperature furnace and heated to 1200℃ under nitrogen protection, held for 1 hour, and then heated to 1900℃ and held for 1 hour.

[0061] 4) A slurry is prepared by dispersing polycarbosilane with a molecular weight of 1500 and silicon powder with a wavelength of 120 nm in tetrachloroethylene, wherein the mass ratio of polycarbosilane, silicon powder and tetrachloroethylene is 35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 3, with a coating slurry dosage of 1.0 kg / m³. 2 Place it in a high-temperature furnace, heat it to 1700℃ under a sealed or inert atmosphere, and keep it there for 2 hours.

[0062] 5) Mix phenolic resin, fumed silica powder, and ethylene glycol in a mass ratio of 55:55:150 to obtain a slurry; coat the slurry onto the surface of the product from step 4, using 0.3 kg / m² of slurry. 2 The mixture is placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:3 is introduced. The temperature is raised to 900°C, maintained for 12 hours, and then cooled to obtain carbon fiber insulation material.

[0063] Comparative Example 4 (without surface dense layer applied)

[0064] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, dry, coat the substrate surface with a 3wt% zirconium nitrate solution, and dry.

[0065] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of acetylene and nitrogen gas with a volume ratio of 1:2.5, heat to 950°C, maintain for 3 hours; then cool to room temperature.

[0066] 3) A slurry is prepared by dispersing graphite emulsion, polycarbosilane with a molecular weight of 1500, and silicon powder with a particle size of 120 nm in tetrachloroethylene, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 0.5 kg / m³. 2After drying, it is placed in a high-temperature furnace and heated to 1200℃ under nitrogen protection, held for 1 hour, and then heated to 1900℃ and held for 1 hour.

[0067] 4) Silicon carbide nanowires with a diameter of 0.5 μm and a length of 1 mm were mixed with aminopropyltriethoxysilane at a mass ratio of 10:2 and dispersed in toluene. The mixture was activated by heating at 75 °C for 5 h and then dried. The dried silicon carbide nanowires were dispersed in an aqueous solution containing 18 wt% glucose at a mass ratio of 1:10. After stirring evenly, the mixture was filtered, dried, and then placed in a high-temperature furnace. The temperature was raised to 650 °C under nitrogen protection and held for 6 h to obtain modified silicon carbide nanowires.

[0068] 5) Modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1500, and silicon powder with a wavelength of 120 nm are dispersed in tetrachloroethylene to obtain a slurry. The mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 18:35:25:180. Vinyltriethoxysilane is then added, with a mass ratio of vinyltriethoxysilane to the slurry of 4:100. The slurry is then coated onto the surface of the product from step 3, with a coating slurry dosage of 1.0 kg / m². 2 The material is placed in a high-temperature furnace and heated to 1700℃ under a sealed or inert atmosphere for 2 hours to obtain carbon fiber insulation material.

[0069] Comparative Example 5 (matrix not modified with zirconium nitrate)

[0070] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, and dry it.

[0071] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of acetylene and nitrogen gas with a volume ratio of 1:2.5, heat to 950°C, maintain for 3 hours; then cool to room temperature.

[0072] 3) A slurry is prepared by dispersing graphite emulsion, polycarbosilane with a molecular weight of 1500, and silicon powder with a particle size of 120 nm in tetrachloroethylene, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 0.5 kg / m³. 2 After drying, it is placed in a high-temperature furnace and heated to 1200℃ under nitrogen protection, held for 1 hour, and then heated to 1900℃ and held for 1 hour.

[0073] 4) Silicon carbide nanowires with a diameter of 0.5 μm and a length of 1 mm were mixed with aminopropyltriethoxysilane at a mass ratio of 10:2 and dispersed in toluene. The mixture was activated by heating at 75 °C for 5 h and then dried. The dried silicon carbide nanowires were dispersed in an aqueous solution containing 18 wt% glucose at a mass ratio of 1:10. After stirring evenly, the mixture was filtered, dried, and then placed in a high-temperature furnace. The temperature was raised to 650 °C under nitrogen protection and held for 6 h to obtain modified silicon carbide nanowires.

[0074] 5) Modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1500, and silicon powder with a wavelength of 120 nm are dispersed in tetrachloroethylene to obtain a slurry. The mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 18:35:25:180. Vinyltriethoxysilane is then added, with a mass ratio of vinyltriethoxysilane to the slurry of 4:100. The slurry is then coated onto the surface of the product from step 3, with a coating slurry dosage of 1.0 kg / m². 2 Place it in a high-temperature furnace, heat it to 1700℃ under a sealed or inert atmosphere, and keep it there for 2 hours.

[0075] 6) Mix phenolic resin, fumed silica powder, and ethylene glycol in a mass ratio of 55:55:150 to obtain a slurry; coat the slurry onto the surface of the product from step 5, using 0.3 kg / m² of slurry. 2 The mixture is placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:3 is introduced. The temperature is raised to 900°C, maintained for 12 hours, and then cooled to obtain carbon fiber insulation material.

[0076] Comparative Example 6 (Surface layer without silane gas deposition)

[0077] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, dry, coat the substrate surface with a 3wt% zirconium nitrate solution, and dry.

[0078] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of acetylene and nitrogen gas with a volume ratio of 1:2.5, heat to 950°C, maintain for 3 hours; then cool to room temperature.

[0079] 3) A slurry is prepared by dispersing graphite emulsion, polycarbosilane with a molecular weight of 1500, and silicon powder with a particle size of 120 nm in tetrachloroethylene, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 0.5 kg / m³. 2After drying, it is placed in a high-temperature furnace and heated to 1200℃ under nitrogen protection, held for 1 hour, and then heated to 1900℃ and held for 1 hour.

[0080] 4) Silicon carbide nanowires with a diameter of 0.5 μm and a length of 1 mm were mixed with aminopropyltriethoxysilane at a mass ratio of 10:2 and dispersed in toluene. The mixture was activated by heating at 75 °C for 5 h and then dried. The dried silicon carbide nanowires were dispersed in an aqueous solution containing 18 wt% glucose at a mass ratio of 1:10. After stirring evenly, the mixture was filtered, dried, and then placed in a high-temperature furnace. The temperature was raised to 650 °C under nitrogen protection and held for 6 h to obtain modified silicon carbide nanowires.

[0081] 5) Modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1500, and silicon powder with a wavelength of 120 nm are dispersed in tetrachloroethylene to obtain a slurry. The mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 18:35:25:180. Vinyltriethoxysilane is then added, with a mass ratio of vinyltriethoxysilane to the slurry of 4:100. The slurry is then coated onto the surface of the product from step 3, with a coating slurry dosage of 1.0 kg / m². 2 Place it in a high-temperature furnace, heat it to 1700℃ under a sealed or inert atmosphere, and keep it there for 2 hours.

[0082] 6) Mix phenolic resin, fumed silica powder, and ethylene glycol in a mass ratio of 55:55:150 to obtain a slurry; coat the slurry onto the surface of the product from step 5, using 0.3 kg / m² of slurry. 2 The material is placed in a high-temperature furnace, heated to 900℃, held for 12 hours, and then cooled to obtain carbon fiber insulation material.

[0083] Comparative Example 7 (unmodified silicon carbide nanowires)

[0084] 1) Grind and polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, dry, coat the substrate surface with a 3wt% zirconium nitrate solution, and dry.

[0085] 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of acetylene and nitrogen gas with a volume ratio of 1:2.5, heat to 950°C, maintain for 3 hours; then cool to room temperature.

[0086] 3) A slurry is prepared by dispersing graphite emulsion, polycarbosilane with a molecular weight of 1500, and silicon powder with a particle size of 120 nm in tetrachloroethylene, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:35:25:180. Vinyltriethoxysilane is then added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. The slurry is then coated onto the surface of the product from step 2, with a coating slurry dosage of 0.5 kg / m³. 2 After drying, it is placed in a high-temperature furnace and heated to 1200℃ under nitrogen protection, held for 1 hour, and then heated to 1900℃ and held for 1 hour.

[0087] 4) Disperse silicon carbide nanowires with a diameter of 0.5 μm and a length of 1 mm, polycarbosilane with a molecular weight of 1500, and silicon powder with a wavelength of 120 nm in tetrachloroethylene to obtain a slurry. The mass ratio of silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 18:35:25:180. Then add vinyltriethoxysilane, wherein the mass ratio of vinyltriethoxysilane to the slurry is 4:100. Coat the surface of the product from step 3 with the slurry at a dosage of 1.0 kg / m³. 2 Place it in a high-temperature furnace, heat it to 1700℃ under a sealed or inert atmosphere, and keep it there for 2 hours.

[0088] 5) Mix phenolic resin, fumed silica powder, and ethylene glycol in a mass ratio of 55:55:150 to obtain a slurry; coat the slurry onto the surface of the product from step 4, using 0.3 kg / m² of slurry. 2 The mixture is placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:3 is introduced. The temperature is raised to 900°C, maintained for 12 hours, and then cooled to obtain carbon fiber insulation material.

[0089] Test data

[0090] The product performance in the embodiments and comparative examples of the present invention is tested by changing the parameters of the preparation process of the present invention to demonstrate the impact of the process parameters of the present invention on product performance.

[0091] The Young's modulus of the test sample was measured using a Vickers hardness tester; the Vickers hardness and crack length of the sample were also measured, and the fracture toughness K was calculated based on the applied load. IC The strain hardening index of the material, i.e. the indenter parameter, is set to 0.016.

[0092] After oxidation in air at 1200℃ for 72 hours, the sample was weighed and the weight loss rate was calculated.

[0093] The results are shown in Table 1.

[0094] Table 1

[0095] Example 1 5.68 0.212 Example 2 5.85 0.205 Example 3 5.76 0.210 Comparative Example 1 4.25 0.295 Comparative Example 2 3.82 0.340 Comparative Example 3 3.05 0.285 Comparative Example 4 4.05 0.372 Comparative Example 5 5.05 0.280 Comparative Example 6 5.65 0.274 Comparative Example 7 5.15 0.230

[0096] The comparison of the examples and comparative examples shows that the preparation process of the graphite sealing and isolation layer and the surface dense layer has a significant impact on the weight loss rate, while the addition of silicon carbide nanowires and surface treatment have a significant impact on the fracture toughness value. Furthermore, the comparison of the processes shows that the modification of zirconium salt and the choice of atmosphere in the preparation process of the dense layer also have a significant impact on the performance.

[0097] Graphite emulsion is coated on the surface of the carbon layer. At high temperature, the volatilization of tetrachloroethylene can remove metallic impurities from the graphite, thereby forming a dense graphite sealing and blocking layer that is tightly bonded to the substrate after high-temperature treatment. The graphite sealing and blocking layer has a certain adhesion, which can further improve the strength of the silicon carbide coating covering the substrate surface and prevent silicon from diffusing into the substrate during high-temperature sintering. This allows the silicon carbide coating to form a dense silicon carbide coating on the surface of the blocking layer.

[0098] During the sintering process, a fumed silicon source is added to the surface silicon carbide coating for deposition. Silicon carbide is generated in situ on the coating surface and in the pores, thereby improving the density of the coating surface.

[0099] Improving the crack resistance and density of silicon carbide: The silicon carbide coating consists of a two-layer structure. The bottom layer of silicon carbide coating incorporates silicon carbide nanowires. The silicon carbide nanowires in the layer can improve the fracture resistance of the coating, thereby increasing the toughness of the coating. At the same time, by forming a high-temperature resistant protective layer on the surface of the silicon carbide nanowires, the silicon carbide nanowires are destroyed during high-temperature sintering. Furthermore, the silicon carbide nanowires are coated with a carbon coating, which can improve the bonding strength between the silicon carbide nanowires and the silicon carbide coating, ensuring the mechanical properties of the coating.

[0100] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as a limitation of the present invention.

Claims

1. A method for preparing a dense silicon carbide coating on the surface of a carbon fiber insulation material, characterized in that, The method includes: 1) Polish the surface of the rigid carbon fiber felt substrate, perform ultrasonic cleaning in anhydrous ethanol, dry, coat the substrate surface with zirconium nitrate solution, and dry. The concentration of the zirconium nitrate solution is 1-5 wt%. 2) Place the product from step 1 in a high-temperature furnace, introduce a mixture of carbon source gas and inert gas with a volume ratio of 1:2-3, heat to 900-1000℃, maintain high-temperature carbonization for 2-4 hours, and cool to room temperature. 3) Disperse graphite emulsion, polycarbosilane with a molecular weight of 1000-2000, and silicon powder with a wavelength of 100-150 nm in tetrachloroethylene to obtain a slurry, wherein the mass ratio of graphite emulsion, polycarbosilane, silicon powder, and tetrachloroethylene is 100:25-50:20-30:150-200, and then add vinyltriethoxysilane, wherein the mass ratio of vinyltriethoxysilane to the slurry is 2-5:100; coat the slurry onto the surface of the product from step 2, dry it, and then place it in a high-temperature furnace, and heat it to 1100-1300℃ under a sealed or inert atmosphere for 0.5-2 hours, and then heat it to 1800-2000℃ for graphitization for 0.5-1 hour to obtain a graphite layer; 4) Mix silicon carbide nanowires and aminopropyltriethoxysilane at a mass ratio of 10:1-2, then add to toluene, heat for 4-6 hours to activate, and then dry; disperse the dried silicon carbide nanowires in an aqueous solution containing 15-20 wt% carbon source precursor, stir evenly, filter, dry, and then place in a high-temperature furnace, heat to 600-700℃ under inert gas protection for high-temperature carbonization to obtain modified silicon carbide nanowires; 5) Modified silicon carbide nanowires, polycarbosilane with a molecular weight of 1000-2000, and silicon powder with a particle size of 100-150 nm are dispersed in tetrachloroethylene to obtain a slurry, wherein the mass ratio of modified silicon carbide nanowires, polycarbosilane, silicon powder, and tetrachloroethylene is 15-20:25-50:20-30:150-200, and then vinyltriethoxysilane is added, wherein the mass ratio of vinyltriethoxysilane to the slurry is 2-5:100; the slurry is coated on the surface of the product from step 3, placed in a high-temperature furnace, and heated at 1600-1800℃ under sealed or inert atmosphere protection for 1-4 hours to generate a silicon carbide layer; 6) Phenolic resin, fumed silica powder, and ethylene glycol are mixed evenly in a mass ratio of 50-60:50-60:140-160 to obtain a slurry; the slurry is coated on the surface of the product from step 5, placed in a high-temperature furnace, and a mixture of silane and hydrogen in a volume ratio of 1:2-4 is introduced, the temperature is raised to 850-950℃, maintained for 10-16 hours, and then cooled to obtain carbon fiber thermal insulation material.

2. A carbon fiber thermal insulation material, characterized in that: The material is obtained using the preparation method described in claim 1.