A composite silicon carbide fiber hard felt and preparation method thereof

Abstract

The present application relates to the field of composite fiber felt, and specifically discloses a composite silicon carbide fiber hard felt and a preparation method thereof. A preparation method for a composite silicon carbide fiber hard felt, comprising the following steps: placing a silicon carbide fiber cloth in a mass concentration of 5-8% potassium permanganate and immersing it for 30-40 minutes, taking it out for cleaning and drying; taking a carbon fiber cloth and a pretreated silicon carbide fiber cloth and alternately stacking and laying them, hot pressing and forming, to obtain a silicon carbide / carbon fiber composite preform; heating the prepared composite preform to 1500-2500°C under a carbon monoxide atmosphere for high-temperature treatment; composite densification: chemical deposition, impregnation, and high-temperature carbonization to obtain a composite silicon carbide fiber hard felt. The composition of the present application can be used in furnaces such as cemented carbide sintering furnaces, single crystal silicon furnaces, vacuum smelting furnaces, vacuum heat treatment furnaces, and vapor deposition furnaces, and has the advantages of good oxidation resistance and high temperature resistance.

Description

Technical Field

[0001] The present application relates to the technical field of composite fiber felt, and more specifically, to a composite silicon carbide fiber hard felt and a preparation method thereof. Background Art

[0002] Carbon fiber rigid felt, a high-performance composite material, is currently the most researched, successfully applied, and widely used vacuum high-temperature insulation material worldwide. It is widely used in furnaces such as cemented carbide sintering furnaces, single crystal silicon furnaces, vacuum smelting furnaces, vacuum heat treatment furnaces, and vapor deposition furnaces, playing a vital role in energy conservation, emission reduction, and product quality improvement. However, traditional rigid carbon felt, primarily composed of a single carbon fiber or graphite fiber, has a relatively simple structure and limited performance. Under high temperature and oxidizing conditions, these materials are prone to structural failure, resulting in a rapid decline in performance and failing to meet the growing material performance demands of modern industry.

[0003] To address the performance limitations of traditional hard carbon felt, researchers have begun exploring the development of novel composite materials. Silicon carbide ceramic fiber, due to its excellent resistance to high temperatures, oxidation, and wear, has become an ideal choice for enhancing the performance of hard carbon felt. By combining silicon carbide ceramic fiber with carbon fiber, a hard carbon felt with even higher performance and stability can be produced. However, it is susceptible to structural failure in high-temperature and oxidative environments, resulting in decreased performance.

[0004] Therefore, how to prepare a composite silicon carbide fiber hard felt with good thermal stability is a problem that needs to be solved urgently. Summary of the Invention

[0005] In order to improve the thermal stability of composite silicon carbide fiber hard felt, the present application provides a composite silicon carbide fiber hard felt and a preparation method thereof.

[0006] In a first aspect, the present application provides a method for preparing a composite silicon carbide fiber hard felt, which adopts the following technical solution:

[0007] A method for preparing a composite silicon carbide fiber hard felt comprises the following steps:

[0008] (1) Pretreatment of silicon carbide fiber: Immerse the silicon carbide fiber cloth in potassium permanganate with a mass concentration of 5-8% for 30-40 minutes, take it out, wash it, and dry it;

[0009] (2) Preform molding: carbon fiber cloth and pretreated silicon carbide fiber cloth are alternately stacked and laid, and hot pressed to obtain a silicon carbide / carbon fiber composite preform;

[0010] (3) High temperature treatment: The prepared composite preform is heated to 1500-2500°C in a carbon monoxide atmosphere;

[0011] (4) Composite densification: After the composite preform subjected to high temperature treatment is coated with a pyrolytic carbon layer, it is placed in an impregnating agent for immersion, and then taken out and carbonized at high temperature to obtain the composite silicon carbide fiber hard felt.

[0012] By adopting the above technical solution, potassium permanganate is used to pretreat silicon carbide fibers, which effectively removes impurities on the fiber surface, improves the purity of the fibers, and improves the physical and chemical properties of the fibers. To a certain extent, it can also improve the bonding strength between the fibers and materials such as the impregnating agent in subsequent operations, thereby improving the impregnation and deposition effects. The carbon fiber cloth and the silicon carbide fiber cloth are alternately stacked and arranged, and hot-pressed to prepare a preform with excellent layered structure and strength. High-temperature treatment is used to further improve the high-temperature structural stability of the preform, reduce the thermal stress at the fiber / matrix interface during the subsequent densification of the preform, and heal or eliminate possible defects such as pores and cracks at high temperatures. The temperature is controlled at a high temperature of 1500-2500°C, which helps to increase the contact area between the particles in the preform material, thereby accelerating the diffusion rate between atoms, which is beneficial to the bonding and sintering between the fiber cloth layers, enhancing the overall structural strength of the preform, and improving the thermal stability of the preform.

[0013] A silicon-based impregnating agent is selected, which can form a protective layer on the surface of the preform, effectively blocking the erosion of harmful substances such as oxygen and moisture in the external environment on the preform, thereby improving the heat resistance and oxidation resistance of the preform.

[0014] Optionally, the ratio of the number of carbon fiber cloth layers to the number of silicon carbide fiber cloth layers in the preform is 2:1.

[0015] By adopting the above technical solution, the combination of carbon fiber cloth and silicon carbide fiber cloth can complement each other's advantages and improve the comprehensive mechanical properties of the preform. Through a certain proportion of configuration, the advantages of high strength of carbon fiber cloth and high temperature resistance of silicon carbide fiber cloth are fully utilized, thereby producing a preform with high overall strength and structural stability at high temperatures.

[0016] Optionally, during the preform forming operation, the temperature is raised to 150-180° C. at 12-15 MPa for hot pressing.

[0017] Optionally, the coating of the pyrolytic carbon interface layer is carried out by chemical vapor infiltration, using boron trichloride and methane as raw gas with a gas flow rate of 15 L / min, using nitrogen as carrier gas with a carrier gas flow rate of 30 L / min, and depositing at 900-1100° C. for 2-3 hours.

[0018] By adopting this technical solution, a uniform coating of the pyrolytic carbon layer is achieved. Boron trichloride and methane are used as feed gases. By controlling their flow rates, the reaction rate and coating thickness are precisely adjusted, allowing the pyrolytic carbon interface layer to be evenly applied to the preform surface, thereby improving the preform's performance. The pyrolytic carbon layer exhibits excellent resistance to high temperatures, oxidation, and corrosion, effectively protecting the preform from harsh environments.

[0019] Optionally, the impregnation operation is to immerse the preform in an impregnating agent at a temperature of 140-170° C. and a pressure of 100-110 MPa for 20-30 minutes.

[0020] By adopting the above technical solution, under the action of temperature and pressure, the impregnant fully penetrates into the interior and surface of the preform, filling the tiny pores and defects in the preform, making the microstructure of the preform denser and more uniform.

[0021] Optionally, the silicon-based impregnating agent includes 8-10 parts of polysiloxane and 3-4 parts of carbon tetrachloride.

[0022] By adopting the above technical solution, polysiloxane contains silicon-oxygen bonds, which can undergo thermal decomposition and carbonization reactions at high temperatures to form silicon carbide. At the same time, it has good permeability. The added carbon tetrachloride further reduces the viscosity of the polysiloxane, helping the polysiloxane to penetrate into the voids of the preform. At the same time, the carbon tetrachloride is volatilized and removed during the curing and carbonization process, and the remaining polysiloxane is converted into silicon carbide to enhance the density and uniformity of the hard felt, reduce its internal pores and defects, and thus improve the thermal stability and mechanical properties of the hard felt.

[0023] Optionally, the high-temperature carbonization operation is a heat treatment at 2200-2750° C. for 2-4 hours.

[0024] By adopting the above technical solution, the impregnation layer is cured at 2200-2750℃, and the organic components in the preform are fully decomposed and carbonized. During the high-temperature carbonization process, the carbon atoms in the preform are rearranged to form a more stable crystal structure, eliminating internal residual stress and defects, optimizing the microstructure, and improving the ability of the hard felt to maintain stable performance in harsh working environments.

[0025] In the second aspect, the present application provides a composite silicon carbide fiber hard felt prepared by the method of the present application, comprising a silicon carbide / carbon fiber soft felt preform and a pyrolytic carbon interface layer and an impregnation layer sequentially coated on the surface of the preform; in the silicon carbide / carbon fiber soft felt preform, every two layers of carbon fiber felt layers have at least one silicon carbide fiber cloth layer, the carbon fiber felt layers and silicon carbide fiber cloth layers are alternately arranged, and both sides are carbon fiber felt layers.

[0026] In summary, this application has the following beneficial effects:

[0027] 1. Since the present application adopts silicon carbide fiber and carbon fiber to composite to prepare the composite hard felt which has the advantages of both carbon fiber and silicon carbide fiber, it has the advantages of high strength and good thermal stability.

[0028] 2. In this application, potassium permanganate is used to pretreat the silicon carbide fiber cloth to help remove impurities on the fiber surface, improve the fiber purity and uniformity, improve the overall performance of the fiber, reduce defects and stress concentration that may occur during high-temperature treatment, and promote the structural transformation of the crystals inside the fiber in conjunction with high-temperature treatment, thereby improving the strength and toughness of the fiber, and thereby improving the mechanical properties and high-temperature stability of the composite hard felt.

[0029] 3. A specific impregnating agent is used in this application. With the help of carbon tetrachloride, polysiloxane can better penetrate into the pores of the composite preform, fill and solidify, thereby reducing the pores and defects in the material and enhancing the strength of the entire structure. At the same time, the silicon element in the impregnating agent can effectively react with oxygen to form a dense oxide protective layer, organize oxygen to corrode the preform, and help improve the material's antioxidant properties. DETAILED DESCRIPTION

[0030] The present application is further described in detail below with reference to the embodiments.

[0031] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0032] Polysiloxane was purchased from Jiangsu Rayne Environmental Protection Technology Co., Ltd., CAS: 63148-62-9; carbon fiber cloth used was Toray 12K-T700SC, with a tensile strength of 3400 MPa and a linear density of 1.8 g / cm 3 Silicon carbide fiber cloth was purchased from Forsman Technology (Beijing) Co., Ltd., item number 1404011.

[0033] Preparation Example

[0034] Preparation Example 1

[0035] A silicon-based impregnating agent, the preparation of which comprises the following steps:

[0036] 8 kg of polysiloxane and 4 kg of carbon tetrachloride were put into a mixing container, and heated and stirred at 50° C. for 10 minutes to prepare the silicon-based impregnating agent.

[0037] Preparation Example 2

[0038] A silicon-based impregnating agent, the preparation of which comprises the following steps:

[0039] 10 kg of polysiloxane and 3 kg of carbon tetrachloride were put into a mixing container, and heated and stirred at 50° C. for 10 minutes to prepare the silicon-based impregnating agent. Example Example 1

[0040] A method for preparing a composite silicon carbide fiber hard felt, comprising the following steps:

[0041] (1) Pretreatment of silicon carbide fiber: Immerse the silicon carbide fiber cloth in a 5% potassium permanganate solution for 30 min, remove it, wash the unreacted solution with clean water, and dry it at 100 °C;

[0042] (2) Preform molding: Take carbon fiber cloth and pretreated silicon carbide fiber cloth and lay them alternately, first lay a layer of carbon fiber cloth, then lay a layer of silicon carbide fiber cloth on it, and then lay a layer of carbon fiber cloth, so that a layer of silicon carbide fiber cloth is sandwiched between the two layers of carbon fiber cloth, put it into a graphite mold, heat it to 150℃ at 15MPa and keep it at a constant temperature for 30min, and hot press it to obtain a silicon carbide / carbon fiber composite preform. The size of the prepared silicon carbide / carbon fiber composite preform is 1000mm×1000mm×60mm;

[0043] (3) High temperature treatment: Place the prepared composite preform into a heating furnace, introduce carbon monoxide, and heat it to 2000°C for 1 hour;

[0044] (4) Composite densification: The composite preform treated at high temperature is placed in a chemical deposition furnace, and boron trichloride and methane are introduced. The added gas flow rate is controlled to be 15 L / min, and nitrogen is introduced as a carrier gas with a carrier gas flow rate of 30 L / min. After heating to 1100°C and depositing for 2 hours, it is taken out and cooled to room temperature. It is placed in the impregnating agent prepared in Preparation Example 1 and immersed for 20 minutes. The temperature during the impregnation process is controlled to be 160°C and the pressure is 100 MPa. After the impregnation is completed, it is taken out and carbonized at 2200°C for 3 hours to obtain the composite silicon carbide fiber hard felt. Example 2

[0045] A method for preparing a composite silicon carbide fiber hard felt, comprising the following steps:

[0046] (1) Pretreatment of silicon carbide fiber: Immerse the silicon carbide fiber cloth in a potassium permanganate solution with a mass concentration of 8% for 30 minutes, remove it, wash the unreacted solution with clean water, and dry it at 100°C;

[0047] (2) Preform molding: Take carbon fiber cloth and pretreated silicon carbide fiber cloth and lay them alternately, first lay a layer of carbon fiber cloth, then lay a layer of silicon carbide fiber cloth on it, and then lay a layer of carbon fiber cloth, so that a layer of silicon carbide fiber cloth is sandwiched between the two layers of carbon fiber cloth, put it into a graphite mold, heat it to 180℃ at 12MPa and keep it at a constant temperature for 30min, and hot press it to obtain a silicon carbide / carbon fiber composite preform. The size of the prepared silicon carbide / carbon fiber composite preform is 1000mm×1000mm×60mm;

[0048] (3) High temperature treatment: Place the prepared composite preform into a heating furnace, introduce carbon monoxide, and heat it to 1500°C for 1 hour;

[0049] (4) Composite densification: The composite preform treated at high temperature is placed in a chemical deposition furnace, and boron trichloride and methane are introduced. The added gas flow rate is controlled to be 15 L / min, and nitrogen is introduced as a carrier gas with a carrier gas flow rate of 30 L / min. After heating to 900 ° C and depositing for 2 hours, it is taken out and cooled to room temperature. It is placed in the impregnating agent prepared in Preparation Example 1 and immersed for 30 minutes. The temperature during the impregnation process is controlled to be 140 ° C and the pressure is 110 MPa. After the impregnation is completed, it is taken out and carbonized at 2400 ° C for 3 hours to obtain the composite silicon carbide fiber hard felt. Example 3

[0050] A method for preparing a composite silicon carbide fiber hard felt, comprising the following steps:

[0051] (1) Pretreatment of silicon carbide fiber: Immerse the silicon carbide fiber cloth in a 7% potassium permanganate solution for 30 min, remove it, wash the unreacted solution with clean water, and dry it at 100 °C;

[0052] (2) Preform molding: Take carbon fiber cloth and pretreated silicon carbide fiber cloth and lay them alternately, first lay a layer of carbon fiber cloth, then lay a layer of silicon carbide fiber cloth on it, and then lay a layer of carbon fiber cloth, so that a layer of silicon carbide fiber cloth is sandwiched between the two layers of carbon fiber cloth, put it into a graphite mold, heat it to 165℃ at 13.5MPa and keep it at a constant temperature for 30min, and hot press it to obtain a silicon carbide / carbon fiber composite preform. The size of the prepared silicon carbide / carbon fiber composite preform is 1000mm×1000mm×60mm;

[0053] (3) High temperature treatment: Place the prepared composite preform into a heating furnace, introduce carbon monoxide, and heat it to 2000°C for 1 hour;

[0054] (4) Composite densification: The composite preform treated at high temperature is placed in a chemical deposition furnace, and boron trichloride and methane are introduced. The added gas flow rate is controlled to be 15 L / min, and nitrogen is introduced as a carrier gas with a carrier gas flow rate of 30 L / min. After heating to 1000°C and depositing for 3 hours, it is taken out and cooled to room temperature. It is placed in the impregnating agent prepared in Preparation Example 1 and immersed for 30 minutes. The temperature during the impregnation process is controlled to be 165°C and the pressure is 110 MPa. After the impregnation is completed, it is taken out and carbonized at 2750°C for 3 hours to obtain the composite silicon carbide fiber hard felt. Example 4

[0055] A method for preparing a composite silicon carbide fiber hard felt is different from Example 1 in that the impregnating agent prepared in Preparation Example 2 is used in this embodiment. Example 5

[0056] A method for preparing a composite silicon carbide fiber hard felt is different from Example 1 in that the impregnating agent used in this example is not diluted with carbon tetrachloride. Comparative Example

[0057] Comparative Example 1

[0058] A method for preparing a composite silicon carbide fiber hard felt is different from Example 1 in that no high-temperature treatment is performed in this comparative example. The preparation steps are as follows:

[0059] A method for preparing a composite silicon carbide fiber hard felt, comprising the following steps:

[0060] (1) Pretreatment of silicon carbide fiber: Immerse the silicon carbide fiber cloth in a 5% potassium permanganate solution for 30 min, remove it, wash the unreacted solution with clean water, and dry it at 100 °C;

[0061] (2) Preform molding: Take carbon fiber cloth and pretreated silicon carbide fiber cloth and lay them alternately, first lay a layer of carbon fiber cloth, then lay a layer of silicon carbide fiber cloth on it, and then lay a layer of carbon fiber cloth, so that a layer of silicon carbide fiber cloth is sandwiched between the two layers of carbon fiber cloth, put it into a graphite mold, heat it to 150℃ at 15MPa and keep it at a constant temperature for 30min, and hot press it to obtain a silicon carbide / carbon fiber composite preform. The size of the prepared silicon carbide / carbon fiber composite preform is 1000mm×1000mm×60mm;

[0062] (3) Composite densification: The above silicon carbide / carbon fiber composite preform was placed in a chemical deposition furnace, and boron trichloride and methane were introduced. The added gas flow rate was controlled to be 15 L / min, and nitrogen was introduced as a carrier gas with a carrier gas flow rate of 30 L / min. After heating to 1100°C and depositing for 2 hours, it was taken out and cooled to room temperature. It was placed in the impregnating agent prepared in Preparation Example 1 and immersed for 20 minutes. The temperature during the impregnation process was controlled to be 160°C and the pressure was 100 MPa. After the impregnation was completed, it was taken out and carbonized at 2200°C for 3 hours to obtain the composite silicon carbide fiber hard felt.

[0063] Comparative Example 2

[0064] A method for preparing a composite silicon carbide fiber hard felt, which is different from Example 1 in that the high-temperature treatment in this comparative example is performed after coating the pyrolytic carbon layer. The preparation steps are as follows:

[0065] A method for preparing a composite silicon carbide fiber hard felt, comprising the following steps:

[0066] (1) Pretreatment of silicon carbide fiber: Immerse the silicon carbide fiber cloth in a potassium permanganate solution with a mass concentration of 5-8% for 30 minutes, remove it, wash the unreacted solution with clean water, and dry it at 100°C;

[0067] (2) Preform molding: Take carbon fiber cloth and pretreated silicon carbide fiber cloth and lay them alternately, first lay a layer of carbon fiber cloth, then lay a layer of silicon carbide fiber cloth on it, and then lay a layer of carbon fiber cloth, so that a layer of silicon carbide fiber cloth is sandwiched between the two layers of carbon fiber cloth, put it into a graphite mold, heat it to 150℃ at 15MPa and keep it at a constant temperature for 30min, and hot press it to obtain a silicon carbide / carbon fiber composite preform. The size of the prepared silicon carbide / carbon fiber composite preform is 1000mm×1000mm×60mm;

[0068] (3) Composite densification: The composite preform that has been subjected to high temperature treatment is placed in a chemical deposition furnace and introduced with boron trichloride and methane. The added gas flow rate is controlled at 15 L / min, and nitrogen is introduced as a carrier gas at a carrier gas flow rate of 30 L / min. The composite preform is heated to 1100°C and deposited for 2 hours. After that, it is taken out and cooled to room temperature. The composite preform is placed in a heating furnace and introduced with carbon monoxide. The temperature is raised to 2000°C and treated at high temperature for 1 hour.

[0069] After cooling to room temperature, the mixture was placed in the impregnating agent prepared in Preparation Example 1 and immersed for 20 minutes. The temperature was controlled at 160°C and the pressure was 100 MPa during the immersion process. After the immersion was completed, the mixture was taken out and carbonized at 2200°C for 3 hours to obtain the composite silicon carbide fiber hard felt.

[0070] Comparative Example 3

[0071] A method for preparing a composite silicon carbide fiber hard felt is different from Example 1 in that potassium permanganate is not used to pretreat the silicon carbide fiber in this comparative example.

[0072] Performance testing

[0073] Detection method

[0074] Bending strength test: The hard felt prepared in the examples and comparative examples was tested with reference to GB / T 40398.2-2021 "Test methods for carbon-carbon composite materials - Part 2: Bending properties test";

[0075] Oxidation resistance test: After weighing the prepared sample, place it in a high-temperature furnace pre-heated to 1500℃, use air as the oxidant, keep the temperature constant for 30 minutes, then take out the sample and cool it down. Use a brush to remove the loose oxidized powder layer on the surface of the sample, weigh it and calculate the oxidation weight loss;

[0076] Thermal stability: After weighing the prepared sample, keep it at 1500℃ for 5 minutes, then heat it at room temperature for 5 minutes, and then cool it down and heat it up for 10 hours. Then weigh it and calculate the weight loss rate.

[0077] Table 1 Test data

[0078]

[0079] Combining Examples 1-3 and Comparative Examples 1-2 with Table 1, it can be seen that high-temperature treatment of the fibers in appropriate operating steps is beneficial to reducing the thermal stress at the interface during the densification process of the preform, eliminating possible defects such as pores and cracks, enhancing the overall structural strength of the preform, and improving its thermal stability.

[0080] Combining Examples 1-3 with Comparative Example 3 and Table 1, it can be seen that the experimental data of Examples 1-3 are all better than those of Comparative Example 3, indicating that the silicon carbide fiber cloth pretreated with potassium permanganate can improve the bonding ability with the coating material in the later stage, preventing the coating from being oxidized and falling off, and the pretreated fiber has good stability and still has good antioxidant properties after cold and hot treatment.

[0081] From Examples 1-4 and Table 1, it can be seen that the impregnating agent prepared from polysiloxane and carbon tetrachloride can penetrate well into the small gaps in the preform, enhance the density and uniformity of the hard felt, and thus improve the thermal stability of the hard felt.

[0082] Combining Example 1 with Example 5 and Table 1, it can be seen that the various experimental data of Example 1 are better than those of Example 5, indicating that the use of carbon tetrachloride can help reduce the viscosity of polysiloxane, which is beneficial to improving the fluidity of polysiloxane, allowing polysiloxane to better penetrate into the voids of the preform, reducing internal voids, and helping to improve the thermal stability of the finally obtained hard felt.

[0083] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a composite silicon carbide fiber hard felt, characterized in that: The method comprises the following preparation steps: (1) Pretreatment of silicon carbide fiber: Immerse the silicon carbide fiber cloth in potassium permanganate with a mass concentration of 5-8% for 30-40 minutes, take it out, wash it, dry it and set it aside; (2) Preform molding: carbon fiber cloth and pretreated silicon carbide fiber cloth are alternately stacked and laid, and hot pressed to obtain a silicon carbide / carbon fiber composite preform; (3) High temperature treatment: The prepared composite preform is heated to 1500-2500°C in a carbon monoxide atmosphere; (4) Composite densification: After the pyrolytic carbon layer is deposited on the composite preform that has been subjected to high temperature treatment, it is placed in an impregnating agent for impregnation, and then taken out and carbonized at high temperature to obtain the composite silicon carbide fiber hard felt, wherein the impregnating agent is a silicon-based impregnating agent.

2. The method for preparing a composite silicon carbide fiber hard felt according to claim 1, characterized in that: The ratio of the number of carbon fiber cloth layers to the number of silicon carbide fiber cloth layers in the preform is 2:

1.

3. The method for preparing a composite silicon carbide fiber hard felt according to claim 1, characterized in that: During the preform forming operation, the temperature is raised to 150-180° C. under 12-15 MPa for hot pressing.

4. The method for preparing a composite silicon carbide fiber hard felt according to claim 1, wherein: The pyrolytic carbon layer is deposited by chemical vapor deposition, using boron trichloride and methane as raw gas with a gas flow rate of 15 L / min, using nitrogen as carrier gas with a carrier gas flow rate of 30 L / min, and depositing at 900-1100° C. for 2-3 hours.

5. The method for preparing a composite silicon carbide fiber hard felt according to claim 1, characterized in that: The impregnation operation is to immerse the preform in the impregnating agent at a temperature of 140-170° C. and a pressure of 100-110 MPa for 20-30 minutes.

6. The method for preparing a composite silicon carbide fiber hard felt according to claim 5, characterized in that: The silicon-based impregnating agent comprises 8-10 parts of polysiloxane and 3-4 parts of carbon tetrachloride.

7. The method for preparing a composite silicon carbide fiber hard felt according to claim 1, characterized in that: The high temperature carbonization operation is a heat treatment at 2200-2750° C. for 2-4 hours.

8. A composite silicon carbide fiber hard felt prepared by the preparation method according to any one of claims 1 to 7.

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