Lightweight carbon-ceramic heat prevention and insulation integrated material with SiC ceramic layer and preparation of lightweight carbon-ceramic heat prevention and insulation integrated material

Abstract

The invention discloses a light carbon-ceramic heat insulation integrated material and a preparation method thereof, and belongs to the technical field of ultrahigh-temperature heat protection materials. According to the preparation method, a nano-powder-induced SiC nanowire synergistic low-temperature gas-solid reaction ceramization technology is adopted, a nanowire growth induction layer containing nano ceramic powder is arranged on the surface of the light carbon-based composite material, the SiC nanowire is induced to be generated under a low-temperature silicon-carbon gas-solid reaction, and surface ceramization of the light carbon-based composite material is realized. The surface layer of the obtained material is a gradient SiC ceramic layer toughened by SiC nanowires with the size of 100-800 microns, the gradient SiC ceramic layer plays a role in resisting oxidation and ablation at the ultrahigh temperature, the bottom layer is an unreacted light carbon-based composite material substrate, the roles in heat insulation and bearing at the ultrahigh temperature are played, and then integration of non-ablative heat insulation and bearing at the ultrahigh temperature is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high temperature heat protection materials, and in particular to a heat protection, heat insulation and load-bearing integrated lightweight carbon-ceramic composite material and a preparation method thereof. Background Art

[0002] The new lightweight carbon-based composite material is a type of porous carbon material made of a three-dimensional carbon network as a matrix and carbon fibers as reinforcements. It has a very low density and a porosity of up to 80%-99%, and has great application prospects in thermal protection fields such as aerospace vehicles and their power systems. However, carbon matrices and carbon fibers are extremely easy to oxidize above 400°C, and their porous structure causes their oxidation rate to be faster than traditional graphite, carbon / carbon composites, etc., which greatly limits the application of such materials in high temperature and aerobic environments. Preparing an antioxidant coating on the surface of the material can significantly improve the antioxidant performance, which is expected to promote the application of new lightweight carbon-based composite materials in the field of thermal protection.

[0003] Ceramic coatings have the characteristics of dense structure and low oxygen permeability, and have been widely studied as anti-oxidation coatings for carbon-based composite materials. However, due to the inherent brittleness of ceramic coatings and the large mismatch between the structure and elastic modulus between ceramics and porous carbon substrates, the resulting ceramic coatings themselves are prone to cracking. It can be seen that the preparation of ceramic coatings with high fracture toughness is the key to ensuring anti-oxidation performance.

[0004] To this end, the present invention adopts nano-powder-induced SiC nanowires in synergistic low-temperature gas-solid reaction ceramicization technology. A nanowire growth induction layer containing nano-ceramic powder is set on the surface of a lightweight carbon-based composite material, and SiC nanowires are induced to form under a low-temperature silicon-carbon gas-solid reaction. The ceramicization transformation of the surface layer of the lightweight carbon-based composite material from carbon to ceramic is achieved, and finally a nanowire-toughened and anti-oxidation coating is prepared on the surface of the lightweight carbon-based composite material to provide reliable oxidation protection for the carbon substrate. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a novel nanowire toughened gradient SiC coating on the surface of a lightweight carbon-based composite material, so as to obtain a lightweight carbon-ceramic composite material with integrated heat protection, heat insulation and load bearing, thereby meeting the thermal protection requirements in ultra-high temperature aerobic environments.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The method for preparing a novel nanowire toughened gradient SiC coating on the surface of a lightweight carbon-based composite material comprises the following steps:

[0008] (1) Density 0.2~0.8g / cm 3 The lightweight carbon-based composite material is used as the substrate, processed into the required shape, ultrasonically cleaned with alcohol, and then placed in an oven at 80-120°C for 24-48 hours for use;

[0009] (2) Weigh a certain amount of nanopowder, dispersant (polyethyleneimine, PEI), and deionized water in a beaker, place it on a magnetic stirrer and stir for 5 to 10 hours until the ceramic powder is dispersed in the deionized water; transfer the above solid-liquid mixture into a ball mill and ball mill for 3 to 5 hours (ball milling to avoid agglomeration of nanopowder) to obtain nano-ceramic powder slurry.

[0010] (3) The lightweight carbon-based composite material substrate is completely immersed in the nano-ceramic powder slurry, and the substrate is taken out after being dipped in the slurry for 3 to 5 seconds. After the surface is dried at 80-120°C, the substrate is immersed in the slurry again and dipped. The above operation is repeated until the substrate surface is sufficiently covered with nano-ceramic powder.

[0011] (4) Boron carbide (B4C), silicon carbide (SiC), silicon dioxide (SiO2), aluminum oxide (Al2O3) and boron trioxide (B2O3) micron powders (particle size 3-5 μm) are sieved and weighed according to 25 wt.% of boron carbide, 25 wt.% of silicon carbide, 15 wt.% of silicon dioxide, 15 wt.% of aluminum oxide and 20 wt.% of boron trioxide, and then ball-milled with alcohol (the above powders have large differences in density, and ordinary dry mixing is prone to uneven stratification. The use of alcohol wet ball milling can obtain a more uniformly mixed powder slurry) for 8-10 hours to obtain a micron powder slurry.

[0012] (5) The micron powder slurry obtained in step (4) is applied to the surface of the lightweight carbon-based composite material substrate with nano powder on the surface obtained in step (3) by a brushing process, and then dried naturally at 100-130° C. for 2-5 hours for use.

[0013] (6) Sprinkle a certain amount of high-purity silicon powder evenly around the bottom of the graphite crucible, place the base material dried in step (5) on top of the silicon powder, and place it in a high-temperature furnace for high-temperature treatment: heat from room temperature to 1300-1600°C, with a heating rate of 5-10°C / min, keep warm at the target temperature for 1-5 hours, then cool to room temperature and take out the sample, finally obtain a SiC nanowire toughened gradient SiC ceramic layer in situ on the surface of the lightweight carbon-based composite material, and realize the preparation of a lightweight carbon-ceramic thermal insulation integrated material.

[0014] In the above step (2), the type and content of the nano-ceramic powder include but are not limited to one of the following three types:

[0015] (1) Nano-ceramic powder 1: ZrO2 powder 10-20wt.%, C powder 30-50wt.%, SiO2 powder 30-50wt.%;

[0016] (2) Nano-ceramic powder 2: ZrO2 powder 10-30wt.%, C powder 40-60wt.%, Al2O3 powder 20-50wt.%;

[0017] (3) Nano-ceramic powder 3: Al2O3 powder 20-30wt.%, C powder 30-40wt.%, SiO2 powder 40-50wt.%.

[0018] The surface layer of the obtained lightweight carbon-ceramic thermal insulation integrated material prepared by the present invention is a gradient SiC ceramic layer toughened by SiC nanowires with a thickness of 100 to 800 μm, which plays the role of ultra-high temperature oxidation resistance and ablation resistance, and the bottom layer is an unreacted lightweight carbon-based composite material substrate, which plays the role of ultra-high temperature heat insulation and load-bearing, thereby realizing ultra-high temperature non-ablative thermal insulation and load-bearing integration.

[0019] The design mechanism of the present invention is as follows:

[0020] The present invention uses nano oxide powder to induce nanowire growth without iron and nickel catalysts, generates a large number of SiC nanowires on the surface of the material, and relies on the reaction of gaseous silicon and carbon matrix to synthesize a gradient SiC ceramic layer in situ, hinders the diffusion of oxygen to the carbon substrate, and then gives the carbon material antioxidant properties. The principle is that part of the C in the nanowire induction layer reacts with nano-scale SiO2 or ZrO2 or Al2O3 to generate CO intermediates, and the intermediate CO reacts with Si vapor to generate SiC crystal nuclei, and accumulates to form nanowires according to the principle of minimum energy; at the same time, part of the silicon vapor directly reacts with the carbon particles in the induction layer to generate SiC particles; and part of the silicon will diffuse into the carbon matrix, so that it is ceramicized to generate a SiC ceramic layer.

[0021] The present invention has the following beneficial effects:

[0022] 1. The method of the present invention does not require a separate nanowire growth process, and nanowires can be generated synchronously during the ceramicization process, which has the significant feature of simple process.

[0023] 2. The method of the present invention does not require the addition of catalysts such as ferric nitrate and nickel nitrate to induce the growth of nanowires, thereby effectively avoiding the adverse effects of additives on the antioxidant properties of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The cross-sectional microscopic morphology of the lightweight carbon-ceramic material with coating in Example 1: (a) coating thickness, (b) magnified view of the outer coating structure showing the morphology of nanowires, (c) porous carbon matrix microstructure;

[0025] Figure 2 The microstructure of the lightweight carbon-ceramic material with coating in Example 1 after 10 thermal shocks at room temperature -1700°C;

[0026] Figure 3The macroscopic morphology and cross-sectional microstructure of the lightweight carbon-ceramic material with coating in Example 1 after oxyacetylene ablation at 1700°C for 300s;

[0027] Figure 4 The temperature variation curves of the ablated surface and the ablated back surface of the 10 mm thick lightweight carbon-ceramic material in Example 1 during the 1700° C. oxyacetylene ablation process;

[0028] Figure 5 The cross-sectional microstructure of the coated lightweight carbon-ceramic in Example 2: (a) coating thickness, (b) magnified view of the outer coating structure showing the morphology of nanowires, (c) porous carbon matrix microstructure;

[0029] Figure 6 The microstructure of the coated lightweight carbon-ceramic material of Example 2 after 10 thermal shocks at room temperature -1700°C;

[0030] Figure 7 The surface microstructure of the coated lightweight carbon-ceramic material in Example 2 after oxyacetylene ablation at 1700°C for 300s;

[0031] Figure 8 The temperature variation curves of the ablated surface and the ablated back surface of the 10 mm thick lightweight carbon-ceramic material in Example 2 during the 1700° C. oxyacetylene ablation process;

[0032] Fig. 9 The cross-sectional microstructure of the coating obtained in Comparative Example 1 without a nanowire inducing layer: (a) the microstructure of the coating and substrate, (b) an enlarged view of the outer coating structure, in which no nanowire distribution is observed. DETAILED DESCRIPTION

[0033] In order to further understand the present invention, the nanopowder-induced SiC nanowire synergistic low-temperature gas-solid reaction ceramicization technology is described below with reference to examples. However, the examples are only for further elaboration of the features and advantages of the present invention, rather than limitation of the claims of the present invention.

[0034] Example 1

[0035] (1) With a density of 0.6 g / cm 3 The lightweight carbon-based composite material (C / CA, Institute of Metal Research, Chinese Academy of Sciences) was used as the substrate and processed into a cylinder with a diameter of 30 mm and a thickness of 10 mm. After ultrasonic cleaning with alcohol, it was placed in an oven at 100°C for 24 hours for use.

[0036] (2) Weigh nano-ceramic powders according to the mass ratio: 20 wt.% ZrO2 powder, 50 wt.% C powder, and 30 wt.% SiO2 powder, and mix the above nano-ceramic powders with a dispersant (polyethyleneimine, PEI) and deionized water in a mass ratio of 2:1:1, and stir on a magnetic stirrer for 8 h until the ceramic powders are evenly dispersed in the deionized water; transfer the above solid-liquid mixture into a ball mill and ball mill for 5 h to obtain a nano-ceramic powder slurry.

[0037] (3) The lightweight carbon-based composite material substrate is completely immersed in the nano-ceramic powder slurry, dipped in the slurry for 5 seconds and then taken out. After drying the surface at 100°C, the above immersion, dipping and drying operations are repeated twice until the substrate surface is covered with nano-ceramic powders about 30 to 50 μm thick. The drying time after the last round of dipping is 24 hours.

[0038] (4) Boron carbide (B4C), silicon carbide (SiC), silicon dioxide (SiO2), aluminum oxide (Al2O3) and boron trioxide (B2O3) powders (the particle size of the above five powders is 3-5 μm) are sieved, weighed according to 25 wt.% of boron carbide, 25 wt.% of silicon carbide, 15 wt.% of silicon dioxide, 15 wt.% of aluminum oxide and 20 wt.% of boron trioxide, and then ball-milled and blended with alcohol at a solid-liquid mass ratio of 1:1 for 10 hours to obtain a micron powder slurry.

[0039] (5) The micron powder slurry obtained in step (4) is applied twice with a thickness of about 50 to 100 μm on the surface of the lightweight carbon-based composite material substrate with nanopowder on the surface obtained in step (3) by a brushing process, and then dried naturally at 120° C. for 2 h for later use.

[0040] (6) According to 4g / cm 2 High-purity silicon powder is evenly sprinkled around the bottom of the graphite crucible, and the base material dried in step (5) is placed on the silicon powder, and placed in a high-temperature furnace for high-temperature treatment: the temperature is increased from room temperature to the target temperature of 1500°C, and the heating rate is 10°C / min. After being kept at the target temperature for 2 hours, the sample is cooled to room temperature and taken out, and finally a SiC nanowire toughened gradient SiC ceramic layer is obtained in situ on the surface of the lightweight carbon-based composite material, thereby realizing the preparation of a lightweight carbon-ceramic thermal insulation integrated material.

[0041] The surface layer of the lightweight carbon-ceramic thermal insulation integrated material obtained in the above steps is a gradient SiC ceramic layer toughened by SiC nanowires, with a thickness of about 750 μm (such as Figure 1 A large number of nanowires with diameters of about 20 to 50 nm can be observed from the surface to a thickness of about 150 μm (as shown in FIG. Figure 1 b); the bottom layer is an unreacted lightweight carbon-based composite material substrate, which still has nanoscale (diameter of about 70 to 100 nm, Figure 1 c) Porous carbon three-dimensional network skeleton. The material did not crack or peel after 10 thermal shocks at room temperature -1700℃. The microstructure is as follows Figure 2 As shown in the figure, the 10mm thick material was ablated by oxyacetylene at 1700℃ for 300s, and the ablated surface was flat (such as Figure 3 As shown), the ablation backside temperature is only 700℃, showing excellent heat insulation performance (as shown Figure 4 shown).

[0042] Example 2

[0043] (1) With a density of 0.4 g / cm 3 The lightweight carbon-based composite material (C / CA, Institute of Metal Research, Chinese Academy of Sciences) was used as the substrate and processed into a cylinder with a required diameter of 30 mm and a thickness of 10 mm. After ultrasonic cleaning with alcohol, it was placed in an oven at 100°C for 24 hours for use.

[0044] (2) Weigh nano-ceramic powders according to the mass ratio: ZrO2 powder 25wt.%, C powder 50wt.%, Al2O3 powder 25wt.%; mix the above nano-ceramic powders with a dispersant (polyethyleneimine, PEI) and deionized water in a mass ratio of 2:1:1, place on a magnetic stirrer and stir for 8h until the ceramic powders are evenly dispersed in the deionized water; transfer the above solid-liquid mixture into a ball mill and ball mill for 5h to obtain a nano-ceramic powder slurry.

[0045] (3) The lightweight carbon-based composite material substrate is completely immersed in the nano-ceramic powder slurry, dipped in the slurry for 5 seconds and then taken out. After drying the surface at 100°C, the above immersion, dipping and drying operations are repeated twice until the substrate surface is covered with nano-ceramic powders about 30 to 50 μm thick. The drying time after the last round of dipping is 24 hours.

[0046] (4) Boron carbide (B4C), silicon carbide (SiC), silicon dioxide (SiO2), aluminum oxide (Al2O3) and boron trioxide (B2O3) powders (the particle size of the above five powders is 3-5 μm) are sieved, weighed according to 25 wt.% of boron carbide, 25 wt.% of silicon carbide, 15 wt.% of silicon dioxide, 15 wt.% of aluminum oxide and 20 wt.% of boron trioxide, and then ball-milled and blended with alcohol at a solid-liquid mass ratio of 1:1 for 10 hours to obtain a micron powder slurry.

[0047] (5) The micron powder slurry obtained in step (4) is applied twice with a thickness of about 50 to 100 μm on the surface of the lightweight carbon-based composite material substrate with nanopowder on the surface obtained in step (3) by a brushing process, and then dried naturally at 120° C. for 2 h for later use.

[0048] (6) According to 3g / cm 2High-purity silicon powder is evenly sprinkled around the bottom of the graphite crucible, and the base material dried in step (5) is placed on the silicon powder, and placed in a high-temperature furnace for high-temperature treatment: the temperature is increased from room temperature to a target temperature of 1400°C, with a heating rate of 8°C / min, and after being kept at the target temperature for 1 hour, the sample is cooled to room temperature and taken out, and finally a SiC nanowire toughened gradient SiC ceramic layer is obtained in situ on the surface of the lightweight carbon-based composite material, thereby realizing the preparation of a lightweight carbon-ceramic thermal insulation integrated material.

[0049] The surface layer of the lightweight carbon-ceramic thermal insulation integrated material obtained in the above steps is a gradient SiC ceramic layer toughened by SiC nanowires, with a thickness of about 750 μm (such as Figure 5 A large number of nanowires with diameters of about 20 to 50 nm can be observed from the surface to about 150 μm thick (as shown in FIG. Figure 5 b); the bottom layer is an unreacted lightweight carbon-based composite material substrate, which still has nanoscale (diameter of about 70 to 100 nm, Figure 5 c) Porous carbon three-dimensional network skeleton. The material did not crack or peel after 10 thermal shocks at room temperature -1700℃. The microstructure is as follows Figure 6 As shown in the figure, after 5 cycles of oxyacetylene ablation at 1700℃ and 300s, the 10mm thick material has a flat surface and no exposed substrate (such as Figure 7 As shown). Since the density of the carbon substrate is lower than that in Example 1, the thermal insulation performance is better, and the ablation backside temperature is further reduced to 570°C, showing excellent thermal insulation performance (as shown). Figure 8 shown).

[0050] Comparative Example 1

[0051] (1) With a density of 0.6 g / cm 3 The lightweight carbon-based composite material (C / CA, Institute of Metal Research, Chinese Academy of Sciences) was used as the substrate and processed into a cylinder with a required diameter of 30 mm and a thickness of 10 mm. After ultrasonic cleaning with alcohol, it was placed in an oven at 100°C for 24 hours for use.

[0052] (2) Boron carbide (B4C), silicon carbide (SiC), silicon dioxide (SiO2), aluminum oxide (Al2O3) and boron trioxide (B2O3) powders (the particle size of the above five powders is 3-5 μm) are sieved, weighed according to 25 wt.% of boron carbide, 25 wt.% of silicon carbide, 15 wt.% of silicon dioxide, 15 wt.% of aluminum oxide and 20 wt.% of boron trioxide, and then ball-milled and blended with alcohol at a solid-liquid mass ratio of 1:1 for 10 hours to obtain a micron powder slurry.

[0053] (3) The micron powder slurry obtained in step (2) is applied twice with a thickness of about 50 to 100 μm on the surface of the lightweight carbon-based composite material substrate with nanopowder obtained in step (3) by a brushing process, and then dried naturally at 120° C. for 2 h for later use.

[0054] (6) According to 3g / cm 2 High-purity silicon powder is evenly sprinkled around the bottom of the graphite crucible, and the base material dried in step (3) is placed on top of the silicon powder. The crucible is placed in a high-temperature furnace for high-temperature treatment: the temperature is increased from room temperature to the target temperature of 1400°C at a heating rate of 8°C / min. After keeping the temperature at the target temperature for 1 hour, the sample is cooled to room temperature and then removed.

[0055] The coating thickness obtained in the above steps is about 350 μm (e.g. Fig. 9 a), no nanowires were observed from the surface to about 100 μm thick (as shown in Fig. 9 b). This is because the growth of nanowires requires the reaction intermediate CO, and the comparative example lacks nano-scale oxides such as SiO2 or ZrO2 or Al2O3 to react with C to generate CO, so it is difficult for the nanowires to nucleate and grow. It can be seen that in Example 1, the provision of a nanowire induction layer has a significant effect on promoting the generation of nanowires.

Claims

1. A method for preparing a lightweight carbon-ceramic thermal insulation integrated material having a SiC ceramic layer, characterized in that: The method adopts nano-powder induced SiC nanowires and low-temperature gas-solid reaction ceramicization technology to realize the preparation of a lightweight carbon-ceramic thermal insulation integrated material with a SiC nanowire toughened gradient SiC ceramic layer, which specifically includes the following steps: (1) Density 0.2~0.8g / cm 3 The lightweight carbon-based composite material is used as the substrate; (2) weighing nano-ceramic powder, dispersant (polyethyleneimine, PEI), and water in a container, stirring until the ceramic powder is dispersed in the water to obtain a solid-liquid mixture; transferring the solid-liquid mixture into a ball mill and ball milling for 3 to 5 hours to obtain a nano-ceramic powder slurry; (3) completely immersing the lightweight carbon-based composite material substrate in the nano-ceramic powder slurry, dipping the slurry for 3 to 5 seconds and then taking it out, drying the surface at 80-120° C., and repeating the above dipping and drying operations 0-4 times until the substrate surface is covered with 100 to 150 μm thick nano-ceramic powder; (4) Boron carbide (B4C), silicon carbide (SiC), silicon dioxide (SiO2), aluminum oxide (Al2O3) and boron trioxide (B2O3) powders (the particle size of the above five powders is 3-5 μm) are sieved, and then weighed according to 20-25 wt.% of boron carbide, 20-25 wt.% of silicon carbide, 15-20 wt.% of silicon dioxide, 10-15 wt.% of aluminum oxide and 20-25 wt.% of boron trioxide, and then mixed with alcohol ball mill for 8-10 hours to obtain a micron powder slurry; (5) using a brushing process to apply the micron powder obtained in step (4) to the surface of the lightweight carbon-based composite material substrate with nanopowder obtained in step (3) in two coats with a thickness of about 30 to 50 μm, and then drying it naturally at 100 to 130° C. for 2 to 5 hours for later use; (6) Sprinkle silicon powder evenly on the bottom of the graphite crucible, place the base material dried in step (5) on top of the silicon powder, and place it in a high-temperature furnace for high-temperature treatment: heat from room temperature to a target temperature of 1300-1600°C, with a heating rate of 5-10°C / min, keep the temperature at the target temperature for 1-5 hours, then cool to room temperature and take out the sample, finally obtain a SiC nanowire toughened gradient SiC ceramic layer in situ on the surface of the lightweight carbon-based composite material, and realize the preparation of a lightweight carbon-ceramic thermal insulation integrated material.

2. The preparation method according to claim 1, characterized in that: In step (2), the composition of the nano-ceramic powder includes but is not limited to any one of the following three: nano-ceramic powder 1: zirconium dioxide (ZrO2), carbon (C), SiO2; nano-ceramic powder 2: ZrO2, C, Al2O3; nano-ceramic powder 3: Al2O3, C, SiO2.

3. The preparation method according to claim 1 or 2, characterized in that: In step (2), the composition of the nano-ceramic powder includes but is not limited to any one of the following three types. In the nano-ceramic powder slurry, the mass fraction composition of the ceramic powder is: Nano-ceramic powder 1: ZrO2 powder 10-20wt.%, C powder 30-50wt.%, SiO2 powder 30-50wt.%; Nano-ceramic powder 2: ZrO2 powder 10-30wt.%, C powder 40-60wt.%, Al2O3 powder 20-50wt.%; Nano-ceramic powder 3: Al2O3 powder 20-30wt.%, C powder 30-40wt.%, SiO2 powder 40-50wt.%.

4. The preparation method according to claim 1, characterized in that: In step (2), the powder content in the nano-ceramic powder slurry is 40-50wt.%, the PEI content is 20-30wt.%, and the rest is water.

5. The preparation method according to claim 1, characterized in that: In step (2), nano-ceramic powder, dispersant (polyethyleneimine, PEI) and water are weighed in a container and stirred for 5 to 10 hours until the ceramic powder is dispersed in deionized water; the solid-liquid mixture is transferred into a ball mill and ball milled for 3 to 5 hours to obtain a nano-ceramic powder slurry.

6. The preparation method according to claim 1, characterized in that: In step (3), the lightweight carbon-based composite material substrate is dipped into the slurry 1-5 times; and the drying time after the last round of dipping is 24-48 hours.

7. The preparation method according to claim 1, characterized in that: In step (4), the powder and alcohol are mixed in a solid-liquid mass ratio of 1:1 to 1.

5.

8. The preparation method according to claim 1, characterized in that: In step (6), the amount of high-purity silicon powder sprinkled in the graphite crucible is 1-8 g / cm 2 The purity of silicon powder is 99% and the particle size is 1 to 3 μm.

9. The preparation method according to claim 1, characterized in that: In step (1), the density is 0.2 to 0.8 g / cm 3 The lightweight carbon-based composite material is used as the substrate, processed into the required shape, ultrasonically cleaned with alcohol, placed in an oven at 80-120°C for 24-48 hours and then used.

10. A lightweight carbon-ceramic thermal insulation integrated material prepared by the method according to any one of claims 1 to 9, characterized in that: The material consists of a 100-600μm thick SiC nanowire-toughened gradient SiC ceramic layer and an unreacted lightweight carbon-based composite material substrate. The material showed no cracking or peeling after 10 thermal shocks at room temperature -1700℃. The surface was flat after 5 cycles of oxyacetylene ablation at 1700℃ for 300s. The back temperature of the 10mm sample was 700℃, showing excellent thermal insulation properties.

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