A method for preparing bitumen-based rigid felt

Abstract

This invention discloses a method for preparing asphalt-based rigid felt, relating to the field of thermal insulation materials. The method includes the following steps: oxidizing isotropic asphalt fibers; impregnating the isotropic pre-oxidized asphalt fibers in a xylene solution of polycarbosilane to grow silicon carbide nanowires in situ on the fiber surface, obtaining silicon carbide-coated carbon fibers; mixing the silicon carbide-coated carbon fibers, phenolic resin powder, polyvinylpyrrolidone dispersant, and deionized water, then adding ceramic powder, stirring to form a slurry, and obtaining a green body after vacuum filtration, molding, and drying; subjecting the green body to thermosetting treatment, and then subjecting the cured green body to chemical vapor infiltration treatment under vacuum by introducing a reaction gas containing silicon tetrachloride vapor and hydrogen, thus obtaining the final product. The asphalt-based rigid felt prepared by this invention has excellent resistance to thermal oxidation and is suitable for application in the preparation of high-end special ceramic materials such as alumina ceramics and silicon carbide ceramics.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials technology, belonging to patent classification number C04B35 / 83, specifically a method for preparing asphalt-based rigid felt. Background Technology

[0002] In the manufacturing process of special ceramic products (such as ceramic valves, ceramic bearings, and high-temperature structural ceramics), high-temperature sintering is the core step that determines product performance. This step needs to be carried out in a high-temperature furnace at 1200-1800℃, requiring a uniform temperature field and low heat loss within the furnace. Simultaneously, it is crucial to prevent the insulation material from releasing impurities that contaminate the ceramic blank at high temperatures. Therefore, stringent requirements are placed on the thermal insulation performance, high-temperature stability, and purity of the furnace insulation material. Asphalt-based rigid felt, due to its high carbon content (typically >90%) and low bulk density (0.2-0.5 g / cm³), is suitable for this purpose. 3 Its characteristics of low thermal conductivity (<0.15W / (m・K) at room temperature) and low volatile matter make it one of the preferred insulation materials for high-temperature sintering furnaces of special ceramics. It can be used as an insulation layer for the furnace side walls, furnace roof, and furnace door, effectively reducing heat loss within the furnace, lowering energy consumption while ensuring stable sintering temperature, thereby improving the density and mechanical properties of special ceramic products. Currently, it has been applied in the large-scale production of high-end special ceramics such as alumina ceramics and silicon carbide ceramics.

[0003] However, existing bituminous hard felts still have a key performance shortcoming in practical applications: insufficient resistance to thermal oxidation. During the sintering process of special ceramics, although the furnace is mainly protected by inert gases (such as nitrogen and argon), it is difficult to completely avoid trace amounts of residual oxygen. Furthermore, some ceramic varieties (such as zirconia ceramics) require a weakly oxidizing atmosphere during sintering, causing the carbon-based components in the bituminous hard felt to easily react with oxygen at high temperatures (generating CO and CO2), leading to surface pulverization, loose structure, and even cracking. This not only causes a significant decrease in the thermal insulation performance of the hard felt after 3-5 service cycles (with a 20%-30% increase in thermal conductivity), but also may cause carbon powder to detach and contaminate the surface of the ceramic blank, resulting in product appearance defects or performance fluctuations. At the same time, frequent replacement of the hard felt increases the production cycle and cost of special ceramics, restricting its further application in the manufacturing of high-end special ceramics. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing asphalt-based rigid felt, thereby solving the technical problem of insufficient thermal oxidation resistance of asphalt-based rigid felt mentioned in the background art. The asphalt-based rigid felt prepared by this invention has excellent thermal oxidation resistance and is suitable for application in the preparation of high-end special ceramic materials such as alumina ceramics and silicon carbide ceramics.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing bituminous rigid felt includes the following steps:

[0007] S1. Isotropic asphalt fibers are oxidized to obtain isotropic pre-oxidized asphalt fibers.

[0008] S2. Immerse isotropic pitch-pre-oxidized fibers in a xylene solution of polycarbosilane, remove and dry them, and then heat-treat them under an inert atmosphere to grow silicon carbide nanowires on the fiber surface in situ, thus obtaining silicon carbide-coated carbon fibers.

[0009] S3. Silicon carbide-coated carbon fiber, phenolic resin powder, polyvinylpyrrolidone dispersant, and deionized water are mixed, and then ceramic powder is added. The mixture is stirred to form a slurry, which is then vacuum filtered, shaped, and dried to obtain a green body.

[0010] S4. The preform is subjected to thermosetting treatment, and then the cured preform is subjected to chemical vapor infiltration treatment in a vacuum environment by introducing a reaction gas containing silicon tetrachloride vapor and hydrogen.

[0011] In this invention, isotropic pitch fibers are first oxidized to form a stable cross-linked structure, providing a foundation for subsequent high-temperature treatment and preventing melting. Then, silicon carbide nanowires are grown in situ to construct a three-dimensional network protective layer on the fiber surface. These nanowires not only significantly extend the path of oxygen diffusion to the fiber body through physical barriers, but also generate a dense silica glass film during high-temperature oxidation, preventing further oxygen intrusion. Next, ultra-high temperature ceramic powders (ZrB2 and B4C) are introduced into the system. These powders are uniformly dispersed in the matrix, acting as a kind of "self-healing" agent. When oxygen breaks through the surface defense at extreme temperatures, ZrB2 and B4C oxidize to generate zirconium oxide (ZrO2) and highly fluid boron oxide (B2O3) glass melt. B2O3 can rapidly flow and fill microcracks and pores caused by thermal stress inside the material, while ZrO2, as a high-melting-point skeleton, effectively inhibits the excessive volatilization of B2O3, thus repairing the surface material of the subsequent preform. Finally, a chemical vapor infiltration deposition (CVD) reaction occurs. CVD preferentially occurs in the region where the gas first reaches and has the highest concentration, namely the outer surface and shallow pores of the preform. As the pores gradually become blocked, the gas has difficulty reaching the deepest interior, naturally forming a structure that is dense on the outside and porous on the inside. This results in the deposition of a high-purity, high-density SiC ceramic layer on the outermost surface and adjacent areas, achieving densification of the preform surface, preventing external oxygen from contacting the internal material, and significantly improving the material's heat oxidation resistance. In summary, at medium and low temperatures, the densified SiC ceramic layer on the outermost layer of the fiber effectively blocks oxygen; at high temperatures, when oxygen breaches the surface defense, ZrB2 and B4C oxidize to form zirconium oxide (ZrO2) and highly fluid boron oxide (B2O3) glass melt, repairing surface cracks in the preform; finally, a small amount of oxygen entering the fiber interior is completely isolated by the dense silica glass film formed by the silicon carbide nanowires. Through the aforementioned synergistic effect, this invention enables bitumen-based rigid felt to possess excellent heat and oxidation resistance.

[0012] ZrB2 and B4C oxidize to form zirconium oxide (ZrO2) and highly fluid boron oxide (B2O3) glass melt, achieving...

[0013] Preferably, in step S1, the oxidation process is performed by heating and oxidizing in an air atmosphere.

[0014] Preferably, in step S2, the mass ratio of isotropic asphalt pre-oxidized fiber to polycarbosilane is 10:3 to 5.

[0015] Preferably, in step S2, the heat treatment temperature is 1100–1200°C and the heat treatment time is 0.5–2 hours.

[0016] Preferably, in step S3, the mass ratio of silicon carbide-coated carbon fiber to phenolic resin powder is 50:4-8.

[0017] Preferably, in step S3, the ceramic powder is composed of zirconium borate powder and boron carbide powder.

[0018] Preferably, the mass ratio of zirconium borate powder to boron carbide powder is 6:2 to 4.

[0019] Preferably, the ceramic powder undergoes surface modification treatment, including the following steps:

[0020] The ceramic powder was dispersed in a hydrochloric acid solution and stirred to react. After the reaction was completed, it was washed until neutral and dried. Then, the acid-treated ceramic powder was dispersed in an alcohol-water mixture, and γ-aminopropyltriethoxysilane was added to react. After the reaction was completed, it was washed and dried to obtain surface-modified ceramic powder.

[0021] In the technical solution of this invention, as described above, the surface material of the preform is repaired by oxidizing ZrB2 and B4C to generate zirconium oxide and a highly fluid borosilicate glass melt. However, the research team found through experiments that ZrB2 and B4C are not uniformly dispersed on the surface of the preform, resulting in limited repair effects of the oxidized ZrO2 and B2O3 on the subsequent protective layer of the preform surface. That is, the protective layer of the preform surface cracks under extreme high temperature conditions, but there may not be enough zirconium oxide and borosilicate material to repair the cracked area. To further address the aforementioned technical problems, this invention modifies ceramic powder (ZrB2 and B4C) by grafting γ-aminopropyltriethoxysilane onto the acid-treated ceramic powder, thereby loading amino groups onto the surface of the ceramic powder. These amino groups react with phenolic resin at high temperatures, achieving uniform dispersion of the ceramic powder within the material. Subsequently, after the formation of the preform, ZrB2 and B4C are uniformly dispersed on the preform surface, enabling timely repair of the preform's protective layer, preventing further oxygen penetration, and further improving the thermal oxidation resistance of the asphalt-based rigid felt.

[0022] Preferably, in step S4, the thermosetting temperature is 210–220°C and the thermosetting time is 1–3 hours.

[0023] Preferably, in step S4, the volume flow ratio of silicon tetrachloride vapor to hydrogen is 1:3 to 4.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. During the low and medium temperature stages, the outermost dense SiC ceramic layer of the fiber effectively blocks oxygen. At high temperatures, when oxygen breaches the surface defense, ZrB2 and B4C oxidize to form zirconium oxide (ZrO2) and highly fluid boron oxide (B2O3) glass melt, repairing surface cracks in the preform. Finally, any small amount of oxygen entering the fiber is completely isolated by the dense silica glass film formed by the silicon carbide nanowires. Through this synergistic effect, the present invention enables the asphalt-based rigid felt to possess excellent heat oxidation resistance.

[0026] 2. By combining acid treatment with aminopropyltriethoxysilane grafting modification, amino groups are loaded onto the surface of ceramic powder. The amino groups can react with phenolic resin to ensure that the ceramic powder is evenly distributed in the green body. This avoids the failure of protection in the cracked areas on the surface of the green body due to insufficient repair material under extreme high temperatures, thus ensuring the repair effect and further enhancing the resistance to thermal oxidation. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing bituminous rigid felt includes the following steps:

[0030] Step 1: Take 100g of isotropic pitch-based fibers (approximately 15μm in diameter) and loosely spread them in an alumina crucible. Transfer the crucible to a programmable temperature-controlled furnace. Under a flowing air atmosphere (flow rate set to 200mL / min), the temperature is programmed to rise from room temperature to 280℃ at a rate of 2℃ / min, and held at this temperature for 5 hours to complete the oxidation treatment. After the treatment, allow the furnace to cool naturally to room temperature, and remove the isotropic pitch pre-oxidized fibers.

[0031] Step 2: Weigh 50g of isotropic pitch pre-oxidized fiber and 23g of polycarbosilane (PCS). Dissolve the PCS in 80g of xylene and stir magnetically until completely dissolved to prepare an impregnation solution. Completely impregnate the fiber in the PCS solution at room temperature for 2 hours with slow stirring. After removing the fiber, dry it in an 80℃ vacuum oven for 6 hours to completely remove the solvent. Loosely pack the dried fiber into a corundum boat and place it in a tube furnace. Under the protection of flowing argon gas (flow rate 100 mL / min), heat it to 1150℃ at a rate of 5℃ / min and hold it at that temperature for 1 hour. Then, allow it to cool naturally to room temperature to obtain silicon carbide-coated carbon fibers with uniformly grown β-SiC nanowires on the surface.

[0032] Step 3: Weigh 6.0 g of ZrB2 powder (particle size 1-2 μm) and 3.5 g of B4C powder (particle size 0.5-1 μm). Disperse them in 200 mL of 1 mol / L hydrochloric acid solution and react with mechanical stirring at 60 °C for 2 hours. After the reaction, wash with deionized water until neutral and dry under vacuum at 80 °C. Disperse the acid-treated powder in a mixed solution of 150 mL of ethanol and 50 mL of deionized water and sonicate for 30 minutes. Adjust the pH to 4-5 with acetic acid, add 0.13 g of γ-aminopropyltriethoxysilane (KH-550), and react at 70 °C for 3 hours. After the reaction, centrifuge and wash three times with ethanol, then dry under vacuum at 80 °C to obtain surface-amined modified ceramic powder.

[0033] Weigh out 50g of silicon carbide-coated carbon fiber and 17.5g of phenolic resin powder. Mix them with 0.5g of polyvinylpyrrolidone dispersant, 1800 mL of deionized water, and amination-modified ceramic powder. Mechanically stir (400 rpm) and intermittently sonicate for 2 hours to form a homogeneous slurry. Pour the slurry into a vacuum filtration mold and filter under a vacuum of -0.095 MPa to obtain a wet blank with a thickness of approximately 10mm. Place the wet blank in a 90℃ forced-air drying oven and dry for 12 hours to obtain a shaped green body.

[0034] Step 4: Place the dried blank in a hot press furnace, apply a pressure of 0.3 MPa, heat to 215℃ at a rate of 5℃ / min, and hold for 2 hours to complete the thermosetting process. Place the cured blank in a CVI furnace, and evacuate the system to a pressure ≤100 Pa. Heat to 1200℃ at a rate of 10℃ / min. Introduce a mixed reactive gas into the furnace for permeation treatment, wherein the silicon tetrachloride vapor flow rate is 50 mL / min, the hydrogen flow rate is 180 mL / min, and argon gas is introduced as a carrier gas at a flow rate of 200 mL / min. Maintain this condition for 30 hours. After the treatment, cool to room temperature under argon protection to obtain the final product.

[0035] Example 2

[0036] A method for preparing bituminous rigid felt includes the following steps:

[0037] Step 1: Take 100g of isotropic pitch-based fibers (approximately 15μm in diameter) and loosely spread them in an alumina crucible. Transfer the crucible to a programmable temperature-controlled furnace. Under a flowing air atmosphere (flow rate set to 200mL / min), the temperature is programmed to rise from room temperature to 280℃ at a rate of 2℃ / min, and held at this temperature for 5 hours to complete the oxidation treatment. After the treatment, allow the furnace to cool naturally to room temperature, and remove the isotropic pitch pre-oxidized fibers.

[0038] Step 2: Weigh 50g of isotropic pitch pre-oxidized fiber and 18g of polycarbosilane (PCS). Dissolve the PCS in 80g of xylene and stir magnetically until completely dissolved to prepare an impregnation solution. Completely impregnate the fiber in the PCS solution at room temperature for 2 hours with slow stirring. After removing the fiber, dry it in an 80℃ vacuum oven for 6 hours to completely remove the solvent. Loosely pack the dried fiber into a corundum boat and place it in a tube furnace. Under the protection of flowing argon gas (flow rate 100 mL / min), heat it to 1150℃ at a rate of 5℃ / min and hold it at that temperature for 1 hour. Then, allow it to cool naturally to room temperature to obtain silicon carbide-coated carbon fibers with uniformly grown β-SiC nanowires on the surface.

[0039] Step 3: Weigh 6.0 g of ZrB2 powder (particle size 1-2 μm) and 2.5 g of B4C powder (particle size 0.5-1 μm). Disperse them in 200 mL of 1 mol / L hydrochloric acid solution and react with mechanical stirring at 60 °C for 2 hours. After the reaction, wash with deionized water until neutral and dry under vacuum at 80 °C. Disperse the acid-treated powder in a mixed solution of 150 mL of ethanol and 50 mL of deionized water and sonicate for 30 minutes. Adjust the pH to 4-5 with acetic acid, add 0.13 g of γ-aminopropyltriethoxysilane (KH-550), and react at 70 °C for 3 hours. After the reaction, centrifuge and wash three times with ethanol, then dry under vacuum at 80 °C to obtain surface-amined modified ceramic powder.

[0040] Weigh out 50g of silicon carbide-coated carbon fiber and 17.5g of phenolic resin powder. Mix them with 0.5g of polyvinylpyrrolidone dispersant, 1800 mL of deionized water, and amination-modified ceramic powder. Mechanically stir (400 rpm) and intermittently sonicate for 2 hours to form a homogeneous slurry. Pour the slurry into a vacuum filtration mold and filter under a vacuum of -0.095 MPa to obtain a wet blank with a thickness of approximately 10mm. Place the wet blank in a 90℃ forced-air drying oven and dry for 12 hours to obtain a shaped green body.

[0041] Step 4: Place the dried blank in a hot press furnace, apply a pressure of 0.3 MPa, heat to 215℃ at a rate of 5℃ / min, and hold for 2 hours to complete the thermosetting process. Place the cured blank in a CVI furnace, and evacuate the system to a pressure ≤100 Pa. Heat to 1200℃ at a rate of 10℃ / min. Introduce a mixed reactive gas into the furnace for permeation treatment, wherein the silicon tetrachloride vapor flow rate is 50 mL / min, the hydrogen flow rate is 160 mL / min, and argon gas is introduced at a flow rate of 200 mL / min as a carrier gas. Maintain these conditions for 30 hours. After the treatment, cool to room temperature under argon protection to obtain the final product.

[0042] Example 3

[0043] A method for preparing bituminous rigid felt includes the following steps:

[0044] Step 1: Take 100g of isotropic pitch-based fibers (approximately 15μm in diameter) and loosely spread them in an alumina crucible. Transfer the crucible to a programmable temperature-controlled furnace. Under a flowing air atmosphere (flow rate set to 200mL / min), the temperature is programmed to rise from room temperature to 280℃ at a rate of 2℃ / min, and held at this temperature for 5 hours to complete the oxidation treatment. After the treatment, allow the furnace to cool naturally to room temperature, and remove the isotropic pitch pre-oxidized fibers.

[0045] Step 2: Weigh 50g of isotropic pitch pre-oxidized fiber and 20g of polycarbosilane (PCS). Dissolve the PCS in 80g of xylene and stir magnetically until completely dissolved to prepare an impregnation solution. Completely impregnate the fiber in the PCS solution at room temperature for 2 hours with slow stirring. After removing the fiber, dry it in an 80℃ vacuum oven for 6 hours to completely remove the solvent. Loosely pack the dried fiber into a corundum boat and place it in a tube furnace. Under the protection of flowing argon gas (flow rate 100 mL / min), heat it to 1150℃ at a rate of 5℃ / min and hold it at that temperature for 1 hour. Then, allow it to cool naturally to room temperature to obtain silicon carbide-coated carbon fibers with uniformly grown β-SiC nanowires on the surface.

[0046] Step 3: Weigh 6.0 g of ZrB2 powder (particle size 1-2 μm) and 3.0 g of B4C powder (particle size 0.5-1 μm). Disperse them in 200 mL of 1 mol / L hydrochloric acid solution and react with mechanical stirring at 60 °C for 2 hours. After the reaction, wash with deionized water until neutral and dry under vacuum at 80 °C. Disperse the acid-treated powder in a mixed solution of 150 mL of ethanol and 50 mL of deionized water and sonicate for 30 minutes. Adjust the pH to 4-5 with acetic acid, add 0.13 g of γ-aminopropyltriethoxysilane (KH-550), and react at 70 °C for 3 hours. After the reaction, centrifuge and wash three times with ethanol, then dry under vacuum at 80 °C to obtain surface-amined modified ceramic powder.

[0047] Weigh out 50g of silicon carbide-coated carbon fiber and 17.5g of phenolic resin powder. Mix them with 0.5g of polyvinylpyrrolidone dispersant, 1800 mL of deionized water, and amination-modified ceramic powder. Mechanically stir (400 rpm) and intermittently sonicate for 2 hours to form a homogeneous slurry. Pour the slurry into a vacuum filtration mold and filter under a vacuum of -0.095 MPa to obtain a wet blank with a thickness of approximately 10mm. Place the wet blank in a 90℃ forced-air drying oven and dry for 12 hours to obtain a shaped green body.

[0048] Step 4: Place the dried blank in a hot press furnace, apply a pressure of 0.3 MPa, heat to 215℃ at a rate of 5℃ / min, and hold for 2 hours to complete the thermosetting process. Place the cured blank in a CVI furnace, and evacuate the system to a pressure ≤100 Pa. Heat to 1200℃ at a rate of 10℃ / min. Introduce a mixed reactive gas into the furnace for permeation treatment, wherein the silicon tetrachloride vapor flow rate is 50 mL / min, the hydrogen flow rate is 160 mL / min, and argon gas is introduced at a flow rate of 200 mL / min as a carrier gas. Maintain these conditions for 30 hours. After the treatment, cool to room temperature under argon protection to obtain the final product.

[0049] Example 4

[0050] A method for preparing bituminous rigid felt includes the following steps:

[0051] Step 1: Take 100g of isotropic pitch-based fibers (approximately 15μm in diameter) and loosely spread them in an alumina crucible. Transfer the crucible to a programmable temperature-controlled furnace. Under a flowing air atmosphere (flow rate set to 200mL / min), the temperature is programmed to rise from room temperature to 280℃ at a rate of 2℃ / min, and held at this temperature for 5 hours to complete the oxidation treatment. After the treatment, allow the furnace to cool naturally to room temperature, and remove the isotropic pitch pre-oxidized fibers.

[0052] Step 2: Weigh 50g of isotropic pitch pre-oxidized fiber and 25g of polycarbosilane (PCS). Dissolve the PCS in 80g of xylene and stir magnetically until completely dissolved to prepare an impregnation solution. Completely impregnate the fiber in the PCS solution at room temperature for 2 hours with slow stirring. After removing the fiber, dry it in an 80℃ vacuum oven for 6 hours to completely remove the solvent. Loosely pack the dried fiber into a corundum boat and place it in a tube furnace. Under the protection of flowing argon gas (flow rate 100 mL / min), heat it to 1200℃ at a rate of 5℃ / min and hold it at that temperature for 2 hours. Then, allow it to cool naturally to room temperature to obtain silicon carbide-coated carbon fibers with uniformly grown β-SiC nanowires on the surface.

[0053] Step 3: Weigh 6.0 g of ZrB2 powder (particle size 1-2 μm) and 4.0 g of B4C powder (particle size 0.5-1 μm). Disperse them in 200 mL of 1 mol / L hydrochloric acid solution and react with mechanical stirring at 60 °C for 2 hours. After the reaction, wash with deionized water until neutral and dry under vacuum at 80 °C. Disperse the acid-treated powder in a mixed solution of 150 mL of ethanol and 50 mL of deionized water and sonicate for 30 minutes. Adjust the pH to 4-5 with acetic acid, add 0.13 g of γ-aminopropyltriethoxysilane (KH-550), and react at 70 °C for 3 hours. After the reaction, centrifuge and wash three times with ethanol, then dry under vacuum at 80 °C to obtain surface-amined modified ceramic powder.

[0054] Weigh out 50g of silicon carbide-coated carbon fiber and 17.5g of phenolic resin powder. Mix them with 0.5g of polyvinylpyrrolidone dispersant, 1800 mL of deionized water, and amination-modified ceramic powder. Mechanically stir (400 rpm) and intermittently sonicate for 2 hours to form a homogeneous slurry. Pour the slurry into a vacuum filtration mold and filter under a vacuum of -0.095 MPa to obtain a wet blank with a thickness of approximately 10mm. Place the wet blank in a 90℃ forced-air drying oven and dry for 12 hours to obtain a shaped green body.

[0055] Step 4: Place the dried blank in a hot press furnace, apply a pressure of 0.3 MPa, heat to 220℃ at a rate of 5℃ / min, and hold for 3 hours to complete the thermosetting process. Place the cured blank in a CVI furnace, and evacuate the system to a pressure ≤100 Pa. Heat to 1200℃ at a rate of 10℃ / min. Introduce a mixed reactive gas into the furnace for permeation treatment, wherein the silicon tetrachloride vapor flow rate is 50 mL / min, the hydrogen flow rate is 200 mL / min, and argon gas is introduced at a flow rate of 200 mL / min as a carrier gas. Maintain these conditions for 30 hours. After the treatment, cool to room temperature under argon protection to obtain the final product.

[0056] Example 5

[0057] A method for preparing bituminous rigid felt includes the following steps:

[0058] Step 1: Take 100g of isotropic pitch-based fibers (approximately 15μm in diameter) and loosely spread them in an alumina crucible. Transfer the crucible to a programmable temperature-controlled furnace. Under a flowing air atmosphere (flow rate set to 200mL / min), the temperature is programmed to rise from room temperature to 280℃ at a rate of 2℃ / min, and held at this temperature for 5 hours to complete the oxidation treatment. After the treatment, allow the furnace to cool naturally to room temperature, and remove the isotropic pitch pre-oxidized fibers.

[0059] Step 2: Weigh 50g of isotropic pitch pre-oxidized fiber and 15g of polycarbosilane (PCS). Dissolve the PCS in 80g of xylene and stir magnetically until completely dissolved to prepare an impregnation solution. Completely impregnate the fiber in the PCS solution at room temperature for 2 hours with slow stirring. After removing the fiber, dry it in an 80℃ vacuum oven for 6 hours to completely remove the solvent. Loosely pack the dried fiber into a corundum boat and place it in a tube furnace. Under the protection of flowing argon gas (flow rate 100 mL / min), heat it to 1100℃ at a rate of 5℃ / min and hold it at that temperature for 0.5 hours. Then, allow it to cool naturally to room temperature to obtain silicon carbide-coated carbon fibers with uniformly grown β-SiC nanowires on the surface.

[0060] Step 3: Weigh 6.0 g of ZrB2 powder (particle size 1-2 μm) and 2.0 g of B4C powder (particle size 0.5-1 μm). Disperse them in 200 mL of 1 mol / L hydrochloric acid solution and react with mechanical stirring at 60 °C for 2 hours. After the reaction, wash with deionized water until neutral and dry under vacuum at 80 °C. Disperse the acid-treated powder in a mixed solution of 150 mL of ethanol and 50 mL of deionized water and sonicate for 30 minutes. Adjust the pH to 4-5 with acetic acid, add 0.13 g of γ-aminopropyltriethoxysilane (KH-550), and react at 70 °C for 3 hours. After the reaction, centrifuge and wash three times with ethanol, then dry under vacuum at 80 °C to obtain surface-amined modified ceramic powder.

[0061] Weigh out 50g of silicon carbide-coated carbon fiber and 17.5g of phenolic resin powder. Mix them with 0.5g of polyvinylpyrrolidone dispersant, 1800 mL of deionized water, and amination-modified ceramic powder. Mechanically stir (400 rpm) and intermittently sonicate for 2 hours to form a homogeneous slurry. Pour the slurry into a vacuum filtration mold and filter under a vacuum of -0.095 MPa to obtain a wet blank with a thickness of approximately 10mm. Place the wet blank in a 90℃ forced-air drying oven and dry for 12 hours to obtain a shaped green body.

[0062] Step 4: Place the dried blank in a hot press furnace, apply a pressure of 0.3 MPa, heat to 210℃ at a rate of 5℃ / min, and hold for 1 hour to complete the thermosetting process. Place the cured blank in a CVI furnace, and evacuate the system to a pressure ≤100 Pa. Heat to 1200℃ at a rate of 10℃ / min. Introduce a mixed reactive gas into the furnace for permeation treatment, wherein the silicon tetrachloride vapor flow rate is 50 mL / min, the hydrogen flow rate is 150 mL / min, and argon gas is introduced at a flow rate of 200 mL / min as a carrier gas. Maintain these conditions for 30 hours. After the treatment, cool to room temperature under argon protection to obtain the final product.

[0063] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that step 1 is omitted, that is, the isotropic pitch-based fibers are not pre-oxidized.

[0064] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that step 2 is omitted, that is, silicon carbide is not coated on the surface of the isotropic pitch pre-oxidized fiber.

[0065] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that no amination-modified ceramic powder is added in step 3.

[0066] Comparative Example 4: The difference between Comparative Example 3 and Example 1 is that in step 3, the amination-modified ceramic powder is replaced with unmodified ceramic powder.

[0067] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that in step 4, silicon tetrachloride / hydrogen treatment is not performed, that is, vapor phase infiltration deposition is not carried out.

[0068] Performance testing:

[0069] 1. Thermal oxidation resistance test: Samples measuring 10mm × 10mm × 5mm were cut from each example and comparative sample. The initial mass (m0) was weighed using an electronic balance with an accuracy of 0.1mg. The sample was placed in a muffle furnace and heated to 1000℃ at a rate of 5℃ / min in air atmosphere. After holding at this temperature for 50h, the sample was removed and cooled to room temperature in a desiccator. The mass (m1) after holding at this temperature was then weighed. The thermal oxidation resistance mass retention rate (%) was calculated using the formula "thermal oxidation resistance mass retention rate (%) = (m1 / m0) × 100". Three parallel samples were tested in each group, and the average value was taken. This indicator directly reflects the structural stability of the material under high-temperature oxidation conditions; the higher the retention rate, the stronger the thermal oxidation resistance. The test results are shown in Table 1.

[0070] 2. High-Temperature Antioxidant Weight Gain Test: Samples measuring 20mm × 20mm × 5mm were taken from each example and comparative sample, and their initial mass (m0) was measured. The samples were placed in a tube furnace, air was introduced (flow rate 150mL / min), and the temperature was increased to 1200℃ at a rate of 3℃ / min. After holding at this temperature for 20 hours, the samples were cooled to room temperature, and their final mass (m1) was measured. The weight gain rate (%) was calculated using the formula "weight gain rate (%) = (m1 - m0) / m0 × 100". Three parallel samples were tested in each group, and the average value was taken. Oxidation of materials at high temperatures is accompanied by the introduction of oxygen. The lower the weight gain rate, the weaker the oxidation reaction and the stronger the antioxidant capacity. The test results are shown in Table 1.

[0071] 3. Bending strength test after high temperature treatment: The samples of the examples and comparative examples were processed into standard specimens of 80mm×10mm×5mm; firstly, high temperature treatment was carried out according to the test conditions for heat oxidation resistance (1000℃, air atmosphere, heat preservation for 50h); after cooling, a three-point bending test was carried out using a universal testing machine, with the span set at 60mm and the loading rate at 2mm / min, and the maximum load (F) at which the specimen broke was recorded; according to the formula "bending strength (MPa) = (3FL) / (2bh)", the bending strength was tested. 2 The calculation (where F is the maximum load, L is the span, b is the sample width, and h is the sample thickness) was performed, with 5 parallel samples tested in each group, and the average value was taken. This index reflects the retention of mechanical properties of the material after high-temperature oxidation; the higher the strength, the better the structural integrity of the material at high temperatures. The test results are shown in Table 1.

[0072] 4. Bulk Density Test: Referring to GB / T 2997-2015 "Test Methods for Bulk Density, Apparent Porosity and True Porosity of Dense Shaped Refractory Products", the water displacement method was used for testing: The mass of the sample in air (m1) and the suspended mass of the sample in distilled water (m2) were weighed using an electronic balance, the temperature of the distilled water (t) was recorded, and the density of the distilled water at that temperature (ρ) was found. 水 According to the formula "bulk density (g / cm³)", 3 =m1×ρ 水 The formula " / (m1-m2)" is used, with 3 parallel samples tested in each group, and the average value is taken. Bulk density is related to material compactness; a reasonable density range is (target 0.8-1.2 g / cm³). 3 It can balance thermal insulation and structural stability. The test results are shown in Table 1.

[0073] Table 1:

[0074]

[0075] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing bituminous hard felt, characterized in that, Includes the following steps: S1. Isotropic asphalt fibers are oxidized to obtain isotropic pre-oxidized asphalt fibers. S2. Immerse isotropic pitch-pre-oxidized fibers in a xylene solution of polycarbosilane, remove and dry them, and then heat-treat them under an inert atmosphere to grow silicon carbide nanowires on the fiber surface in situ, thus obtaining silicon carbide-coated carbon fibers. S3. Silicon carbide-coated carbon fiber, phenolic resin powder, polyvinylpyrrolidone dispersant, and deionized water are mixed, and then ceramic powder is added. The mixture is stirred to form a slurry, which is then vacuum filtered, shaped, and dried to obtain a green body. The ceramic powder is composed of zirconium borate powder and boron carbide powder; The ceramic powder undergoes surface modification treatment: Ceramic powder was dispersed in hydrochloric acid solution and stirred to react. After the reaction was completed, it was washed until neutral and dried. Then, the acid-treated ceramic powder was dispersed in an alcohol-water mixture, and γ-aminopropyltriethoxysilane was added to react. After the reaction was completed, it was washed and dried to obtain surface-modified ceramic powder. S4. The preform is subjected to thermosetting treatment, and then the cured preform is subjected to chemical vapor infiltration treatment in a vacuum environment by introducing a reaction gas containing silicon tetrachloride vapor and hydrogen.

2. The method for preparing a bitumen-based rigid felt according to claim 1, characterized in that, In step S1, the oxidation process involves heating and oxidizing the material in an air atmosphere.

3. The method for preparing a bitumen-based rigid felt according to claim 1, characterized in that, In step S2, the mass ratio of isotropic asphalt pre-oxidized fiber to polycarbosilane is 10:3 to 5.

4. The method for preparing a bitumen-based rigid felt according to claim 1, characterized in that, In step S2, the heat treatment temperature is 1100–1200℃ and the heat treatment time is 0.5–2h.

5. The method for preparing an asphalt-based rigid felt according to claim 1, characterized in that, In step S3, the mass ratio of silicon carbide-coated carbon fiber to phenolic resin powder is 50:15-20.

6. The method for preparing a bitumen-based rigid felt according to claim 1, characterized in that, The mass ratio of zirconium borate powder to boron carbide powder is 6:2 to 4.

7. The method for preparing a bitumen-based rigid felt according to claim 1, characterized in that, In step S4, the heat curing temperature is 210–220°C, and the heat curing time is 1–3 hours.

8. The method for preparing a bitumen-based rigid felt according to claim 1, characterized in that, In step S4, the volume flow ratio of silicon tetrachloride vapor to hydrogen is 1:3 to 4.

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