Carbon fiber prepreg, preparation method and application thereof

Abstract

The application belongs to the technical field of carbon fiber composite materials, and particularly relates to a carbon fiber preform, a preparation method and application thereof. The preparation method of the carbon fiber preform comprises the following steps: carbon fibers are dipped in a phenolic resin slurry, taken out, wound, dried, and cut; in a vacuum environment, the pretreated carbon fibers are pyrolyzed at high temperature to obtain a carbon fiber preform with a pyrolysis carbon layer; in the vacuum environment, the carbon fiber preform with the pyrolysis carbon layer is subjected to silicon evaporation to obtain a carbon fiber preform containing a silicon carbide coating; the carbon fiber preform containing the silicon carbide coating is heated to 700-850 DEG C in a protective atmosphere, and an auxiliary agent mixture is injected to obtain a carbon fiber preform with carbon nanotubes growing thereon; the carbon fiber preform and the preparation method thereof form a silicon carbide coating on the carbon fibers to obtain a carbon fiber preform with a silicon carbide coating and carbon nanotubes on the surface, which is made into a multiphase ceramic composite material to improve high-temperature resistance and other performances.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber composite material technology, specifically relating to a carbon fiber preform, its preparation method, and its application. Background Technology

[0002] Carbon fibers, as a reinforcing phase, can effectively improve the performance of ultra-high temperature ceramics by achieving strengthening and toughening through mechanisms such as debonding and pull-out, bridging, and increasing crack propagation paths. However, the interface problem between carbon fibers and the ceramic matrix can weaken the composite material's performance; especially in high-temperature oxygen-containing environments, oxygen diffuses from the matrix surface to the internal fibers and initiates oxidation, leading to performance degradation. Therefore, a silicon carbide (SiC) coating needs to be prepared on the carbon fiber surface. At high temperatures, molten silica is generated in the matrix, changing the contact mode between oxygen and the matrix from direct oxidation to gas diffusion of oxygen within the silica layer. Because the diffusion rate of oxygen in molten silica is low, it can effectively isolate external oxygen and reduce the risk of further oxidation of the internal composite material.

[0003] Currently, common methods for preparing coatings on carbon fiber surfaces include chemical vapor deposition (CVD), sol-gel method, molten salt method, and embedding method. CVD is the most widely used, primarily utilizing the gaseous SiO generated from Si / SiO2 mixed powder at 1400–1600℃ to prepare a PyC / SiC composite coating on the surface of PyC coated carbon fibers through a chemical vapor phase reaction. However, the resulting coating surface is rough, containing a large number of nano-SiC particles, and both the gaseous SiO generation and carbothermic reduction processes require high temperatures, easily damaging the carbon fiber structure. The molten salt method is an emerging carbide coating preparation technology. It utilizes a mixture of salts such as NaCl, KCl, and NaF to melt at high temperatures, promoting the diffusion of elements such as Si, Ti, and Ta to the material surface and reacting with the carbon matrix to form a carbide coating. However, this method uses the carbon matrix as a reactant, constituting a sacrificial template process, which can damage the matrix material. The embedding method involves embedding carbon fibers in oxides or metal powders, and generating a carbide coating on the fiber surface through a carbothermic reduction reaction. This method requires a processing temperature as high as 1800℃, which can significantly reduce the mechanical properties of carbon fibers.

[0004] Chinese patent CN105350294A discloses a method for manufacturing short-cut carbon fibers coated with a SiC layer. The method involves mixing short-cut carbon fibers with nano-silicon powder, loading the mixture into a mold, performing spark plasma sintering, cooling it in the furnace, and then removing and grinding it to obtain the final product. However, this process involves spark plasma sintering and high-temperature treatment, which can easily cause the carbon fibers to oxidize and react with the silicon powder, resulting in microcracks on the surface and severely affecting the mechanical properties of the fibers.

[0005] Chinese patent CN110158309A discloses a method for preparing carbon fibers with a SiC coating. The method involves mixing SiC powder with methyl silicone rubber to obtain a slurry, then mixing the carbon fibers with the slurry, thoroughly impregnating the fibers, and treating the mixture in a muffle furnace at 400°C. After cooling, a coating is obtained. However, the SiC coating obtained by this method has an uneven surface and a large number of SiC grains are generated on the fiber surface, which also affects the mechanical properties of the carbon fibers. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of existing technologies, such as high temperature damage to fibers, matrix consumption, uneven coating quality, or complex processes. The present invention provides a carbon fiber preform and its preparation method, which forms a silicon carbide coating on carbon fibers to obtain a carbon fiber preform with a silicon carbide coating and carbon nanotubes on the surface, and then makes it into a multiphase ceramic composite material to improve its high temperature resistance and other properties.

[0007] The method for preparing the carbon fiber preform of the present invention includes the following steps: (1) Carbon fiber pretreatment: The carbon fiber is drawn and impregnated in phenolic resin slurry, then taken out, wound, dried and cut to obtain pretreated carbon fiber; (2) High-temperature pyrolysis: In a vacuum environment, the pretreated carbon fiber is pyrolyzed at a high temperature of 800~1200℃ to obtain a carbon fiber preform with a pyrolyzed carbon layer. (3) Silicon carbide coating: In a vacuum environment, the carbon fiber preform with the cracked carbon layer is subjected to silicon vapor deposition at 1200~1400℃ to obtain a carbon fiber preform containing a silicon carbide coating. (4) Carbon nanotube generation: The carbon fiber preform containing silicon carbide coating is heated to 700~850℃ in a protective atmosphere, and an auxiliary agent mixture is injected and blown onto the carbon fiber preform by airflow. During this process, the high temperature causes the carbon source to vaporize, and carbon fiber preform with carbon nanotubes is obtained. The additive mixture is a mixture of ethanol, xylene, ethylenediamine, and ferrocene.

[0008] The phenolic resin slurry in step (1) is prepared by mixing soluble phenolic resin and ethanol at a mass ratio of 1:20~40.

[0009] Step (1) The carbon fiber is impregnated in phenolic resin slurry. Specifically, the carbon fiber bundle is impregnated in the slurry tank by being pulled by a fiber winding machine, and then rotated and wound on a flat plate to form a neat planar unidirectional preform. Then it is dried for 3.0~5.0 hours.

[0010] The specific conditions for high-temperature pyrolysis in step (2) are: vacuum pressure of -0.09~-0.1MPa, heating to 800~1200℃ at a rate of 4~10℃ / min and holding for 1.0~4.0h.

[0011] Step (2) yields a carbon fiber preform with a carbon layer thickness of 200 nm to 1200 nm. The carbon layer is approximately circular in shape. The thickness here refers to the thickness of a single carbon fiber; the overall radius minus the radius of the carbon fiber itself is the thickness of the carbon layer.

[0012] The specific conditions for silicon vapor deposition in step (3) are: vacuum pressure of -0.098 to -0.09 MPa, heating to 1200 to 1400℃ at a rate of 4 to 10℃ / min and then holding at that temperature for 1.0 to 4.0 h.

[0013] Step (3) yields a carbon fiber preform with a silicon carbide coating thickness of 200 nm to 600 nm. During the silicon vapor deposition process, a silicon powder pad is placed under the preform without direct contact with the carbon fiber preform. A small portion of the silicon is vaporized to generate silicon vapor in a high-temperature vacuum environment. The silicon vapor then reacts with the preform to generate silicon carbide on the surface.

[0014] In step (4), the basic ratio of ethanol, xylene, ethylenediamine and ferrocene is 80~120mL:80~120mL:3~6mL:2~5g, or a multiple of the basic ratio.

[0015] The specific parameters for carbon nanotube generation in step (4) are as follows: Place the carbon fiber preform containing silicon carbide coating in a tube furnace, first introduce argon gas at a flow rate of 200~300 sccm for 20~30 min, heat it to 700~850℃ at a rate of 5~10℃ / min and hold it for 30~60 min, then inject the auxiliary agent mixture at 700~850℃ at an injection rate of 10~30 mL / h to obtain the carbon fiber preform with carbon nanotubes grown on it.

[0016] Application of the carbon fiber preform: The ceramic slurry is mixed with the carbon fiber preform and then hot-pressed and sintered to produce a multiphase ceramic composite material.

[0017] The ceramic slurry is made from conventional ceramic raw materials, such as silicon boron oxynitride powder, pure silicon powder, zirconium diboride powder, carbon black, and flake graphite raw materials. After mixing, the mixture is dry-mixed and ball-milled, and then alcohol is added to mix and obtain the ceramic slurry.

[0018] The ceramic slurry is mixed with the carbon fiber preform and loaded into a hot pressing sintering mold. After vacuuming, the mixture is heated and hot-pressed for sintering. After the hot pressing sintering is completed and the mixture is cooled in the furnace, it is removed from the furnace and demolded to obtain a carbon fiber reinforced ultra-high temperature multiphase ceramic composite material.

[0019] Specifically, the method for preparing the carbon fiber preform includes the following steps: (1) Carbon fiber pretreatment: The carbon fiber bundle is immersed in the phenolic resin slurry tank by the traction of the fiber winding machine. While the carbon fiber is wound on a plate, the phenolic solution is hung on the carbon fiber through the slurry tank. Then it is pulled to the plate and rotated and wound (after being separated from the slurry). The bundle is neatly arranged into a planar unidirectional preform. Then it is dried for 3.0~5.0h and cut into a suitable shape to obtain pretreated carbon fiber. The phenolic resin slurry is prepared by mixing soluble phenolic resin and ethanol at a mass ratio of 1:20~40.

[0020] (2) High temperature pyrolysis: The pretreated carbon fiber is placed in a vacuum furnace and heated to 800~1200℃ at a rate of 4~10℃ / min and held for 1.0~4.0h. The vacuum pressure is maintained at -0.09~-0.1MPa to obtain a carbon fiber preform with a pyrolyzed carbon layer. The carbon layer thickness is 200nm~1200nm.

[0021] (3) Silicon carbide coating: The carbon fiber preform with the cracked carbon layer is heated to 1200~1400℃ in a vacuum furnace at a rate of 4~10℃ / min and held for 1.0~4.0h. The vacuum pressure of silicon vapor is maintained at -0.098~-0.09MPa to obtain a carbon fiber preform with a silicon carbide coating. The thickness of the silicon carbide coating is 200nm~600nm.

[0022] (4) Carbon nanotube generation: The carbon fiber preform containing silicon carbide coating is placed in a tube furnace. Argon gas is first introduced and purged at a flow rate of 200-300 sccm for 20-30 min. The temperature is then increased to 700-850℃ at a rate of 5-10℃ / min and held for 30-60 min. Subsequently, an auxiliary agent mixture is injected at 700-850℃ at an injection rate of 10-30 mL / h to grow carbon nanotubes. The auxiliary agent mixture is prepared according to the ratio of 80-120 mL of ethanol, xylene, ethylenediamine and ferrocene: 80-120 mL: 3-6 mL: 2-5 g.

[0023] This invention first utilizes the low viscosity of phenolic resin / ethanol solution to uniformly coat the surface of each carbon fiber monofilament through traction impregnation. Under a vacuum high-temperature environment (800~1200℃), the methylene bridges and hydroxymethyl groups in the phenolic resin undergo bond breaking, dehydrogenation, and condensation reactions, gradually transforming into amorphous pyrolytic carbon with a disordered graphite structure. Simultaneously, volatile small molecules (H2, CH4, etc.) are promptly extracted, promoting carbon layer densification and ultimately forming a carbonaceous intermediate layer with controllable thickness (200~1200nm) and good bonding with the fiber matrix. This pyrolytic carbon layer is not the final functional layer but exists as a "sacrificial protective layer." Its core function is to isolate the original carbon fiber from active silicon vapor in subsequent reactions, providing a source of reactants for coating conversion while fundamentally preventing silanization damage to the fiber matrix.

[0024] At higher temperatures (1200~1400℃) and under high vacuum conditions, the solid silicon source sublimates to generate highly reactive Si vapor, which undergoes a typical gas-solid reaction with the pyrolytic carbon layer on the surface of the preform: Si(g) + C(s) → SiC(s). This reaction strictly follows a diffusion-controlled rate law, with Si vapor preferentially reacting with the outermost pyrolytic carbon layer to form β-SiC grains. The resulting dense SiC coating then acts as a diffusion barrier, firmly locking the interface for subsequent chemical reactions between the "already formed SiC coating / the remaining internal carbon layer," rather than the "SiC coating / the original carbon fiber" interface. This gradient conversion mechanism ensures that the thickness of the silicon carbide coating (200~600nm) is uniform and controllable, achieving complete ceramic coating coverage while completely isolating the fiber body from the erosion of silicon vapor, effectively preserving the original strength of the carbon fiber.

[0025] After heating to 700-850℃ in an inert atmosphere, the ferrocene in the additive thermally decomposes, releasing Fe atoms, which migrate and aggregate on the SiC coating surface to form nanoscale molten catalytic particles. Injected ethanol and xylene serve as a composite carbon source, adsorbing, dehydrogenating, and cracking on the Fe particle surface. The precipitated carbon atoms dissolve in the Fe droplets, and upon reaching supersaturation, precipitate from the bottom of the particles as graphene tubes, following a gas-liquid-solid (VLS) growth mechanism to drive the axial extension of carbon nanotubes. Simultaneously, the ·NH2 free radicals generated from the decomposition of ethylenediamine inhibit excessive deposition of amorphous carbon and introduce nitrogen doping to improve CNT structural defects; while the weak oxidizing properties of ethanol help remove carbon deposits on the catalyst surface, maintaining the long-term activity of the Fe particles. The synergistic effect of the ternary additives ensures high-density, uniform-diameter in-situ growth of carbon nanotubes on the SiC coating surface.

[0026] The resulting multi-level interface structure—"original carbon fiber → pyrolytic carbon transition layer → SiC ceramic coating → carbon nanotube dendrites"—imparts a triple-benefit effect to the composite material: First, the pyrolytic carbon layer acts as a flexible buffer layer, effectively alleviating the thermal mismatch stress caused by the difference in thermal expansion coefficients between the carbon fiber and the SiC coating, thus improving the interfacial bonding toughness. Second, the dense SiC coating acts as a chemical barrier, preventing corrosion of the fibers by harmful media such as oxygen and molten silicon in subsequent ceramic matrix sintering or high-temperature service environments. Third, the high aspect ratio carbon nanotube network on the surface acts as "micro-anchors" embedded in the matrix during subsequent composite with the ceramic matrix, consuming a large amount of fracture energy through pull-out and crack deflection effects. In summary, this invention, through a step-by-step reaction path, achieves the simultaneous construction of a high-bonding-strength coating and a nano-toughening phase without compromising the fiber's inherent strength, ultimately significantly improving the flexural strength and fracture toughness of the multiphase ceramic composite material.

[0027] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention utilizes the characteristic of phenolic resin to decompose and generate carbon at high temperature as a carbon source. First, a thermally decomposed carbon layer is generated on the carbon fiber preform. Then, the thermally decomposed carbon layer is converted into a silicon carbide coating through silicon vapor reaction. This achieves a new technology for obtaining a carbon fiber preform containing a silicon carbide coating without damaging the carbon fiber and with a short cycle. Compared with directly generating a silicon carbide coating on the carbon fiber, this technology can reduce the reaction between silicon vapor and carbon fiber when generating the silicon carbide coating, thereby reducing the damage to the carbon fiber. Compared with chemical vapor deposition, this invention has the advantages of simple process, low production cost, and high bonding strength with the matrix.

[0028] (2) The process flow of the present invention is short, the production efficiency is high, the materials are simple, and the equipment requirements in the whole process flow are low, making it suitable for large-scale production in industry. Attached Figure Description

[0029] Figure 1 The cross-section of the carbon fiber preform prepared in step (1) of Example 1 is shown by SEM images at 20 μm and 10 μm. Figure 2 The cross-sections of the carbon fiber preform with a pyrolytic carbon layer prepared in step (2) of Example 1 are shown at 20 μm and 5 μm. Figure 3 SEM images of the cross sections of the carbon fiber preform with silicon carbide coating prepared in step (3) of Example 1 at 10 μm and 5 μm. Figure 4 The cross-section of the carbon fiber preform with silicon carbide coating prepared in step (3) of Example 1 is shown in the SEM image and EDS point marker diagram at 10 μm. Figure 5The energy spectrum curve of the EDSSpot1 measurement point; Figure 6 The energy spectrum curve of the EDSSpot2 measurement point; Figure 7 The energy spectrum curve of the EDSSpot3 measurement point; Figure 8 The energy spectrum curves for the EDSSpot4 measurement point are shown below. Figure 9 The energy spectrum curve of EDSSpot5 measurement point; Figure 10 The image shows the XRD pattern of the carbon fiber preform containing a silicon carbide coating prepared in step (3) of Example 1. Figure 11 SEM images of the surface of the carbon fiber preform containing silicon carbide coating and carbon nanotubes prepared in Example 1 at 20 μm and 10 μm. Figure 12 SEM images of the surface of the carbon fiber preform prepared for Comparative Example 1 at 20 μm and 2 μm. Figure 13 SEM images of the cross-section of the composite material prepared in Example 4 after a three-point bending test at 100 μm and 50 μm. Figure 14 The image shows the SEM morphology of the polished surface of the composite material prepared in Example 4 after oxidation experiment at 50 μm. Figure 15 The image shows the SEM morphology of the composite material prepared in Example 4 after oxidation experiments at 200 μm. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] The ethanol described in this invention is anhydrous ethanol.

[0032] The carbon fiber used below is purchased T300.

[0033] The soluble phenolic resin was purchased as W617C alcohol-soluble phenolic resin.

[0034] Example 1 The method for preparing the carbon fiber preform of the present invention includes the following steps: (1) Carbon fiber pretreatment: 10g of carbon fiber bundles are impregnated in a tank of 300g of phenolic resin slurry by a fiber winding machine, and then wound on a flat plate by rotation. The speed of the fiber winding machine is an average of 1.2g per minute. The bundles are neatly arranged into a planar unidirectional preform, and then dried for 4.0h. They are then cut into sheets, such as... Figure 1As shown, a large number of carbon fiber cross sections are clearly visible, with regular fiber cross-sectional shapes, and the fibers are interconnected by phenolic resin.

[0035] The phenolic resin slurry is prepared by mixing soluble phenolic resin and ethanol at a mass ratio of 1:30.

[0036] (2) High-temperature pyrolysis: The pretreated carbon fibers were placed in a vacuum furnace and heated to 1200℃ at a rate of 6℃ / min, and then held at that temperature for 2.0h. The vacuum pressure gauge was kept at -0.1MPa to obtain a carbon fiber preform with a pyrolyzed carbon layer. The thickness of the carbon layer is shown in Table 1. Figure 2 As shown, the carbon coating generated on the carbon fiber surface is uniformly covered without obvious damage, indicating that the generated carbon coating is relatively uniform.

[0037] (3) Silicon carbide coating: The carbon fiber preform with the cracked carbon layer is heated to 1400℃ in a vacuum furnace at a rate of 7℃ / min and held for 1.0h, maintaining the vacuum pressure of silicon vapor at -0.098MPa to obtain a carbon fiber preform with a silicon carbide coating. The thickness of the silicon carbide coating is shown in Table 1. Figure 3 As shown, it can be clearly seen that the generated silicon carbide coating is uniformly wrapped around the outer layer of the carbon fiber, and the surface of the generated silicon carbide coating is uniform and without obvious damage.

[0038] like Figures 4 to 9 As can be seen from the EDS analysis, the interior is almost entirely composed of carbon, and based on the molar ratio, the outer layer can be determined to be either silicon carbide or elemental silicon. Figure 10 It can be seen that the peaks of the SiC PDF card correspond to the peaks of the sample. According to the XRD data, the carbon fiber preform with silicon carbide coating prepared into powder does indeed contain silicon carbide coating.

[0039] (4) Carbon nanotube generation: The carbon fiber preform containing silicon carbide coating is placed in a tube furnace. Argon gas is first introduced and purged at a flow rate of 250 sccm for 25 min. The temperature is then raised to 850℃ at a rate of 10℃ / min and held for 30 min. Subsequently, an auxiliary agent mixture is injected at 850℃ at an injection rate of 20 mL / h to grow carbon nanotubes and obtain a carbon fiber preform containing silicon carbide coating and carbon nanotubes. The auxiliary agent mixture is prepared by mixing ethanol, xylene, ethylenediamine and ferrocene in a ratio of 100 mL: 100 mL: 4 mL: 3 g.

[0040] The surface morphology of the carbon fiber preform containing silicon carbide coating and carbon nanotubes is shown in the figure. Figure 11 As shown, a large number of carbon nanotubes are prepared on the upper surface of the carbon fiber preform.

[0041] Example 2 The method for preparing the carbon fiber preform of the present invention includes the following steps: (1) Carbon fiber pretreatment: 10g of carbon fiber bundle is impregnated in a tank of 300g of phenolic resin slurry by the traction of a fiber winding machine, and then pulled to a plate for rotating winding, and neatly arranged into a planar unidirectional preform. The speed of the fiber winding machine is an average of 1.2g per minute. Then it is dried for 4.0h and cut into a suitable shape to obtain pretreated carbon fiber. The phenolic resin slurry is prepared by mixing soluble phenolic resin and ethanol at a mass ratio of 1:40.

[0042] (2) High temperature pyrolysis: The pretreated carbon fiber is placed in a vacuum furnace and heated to 1000℃ at a rate of 4℃ / min and held for 1.0h. The vacuum pressure gauge is kept at -0.1MPa to obtain a carbon fiber preform with a pyrolyzed carbon layer. The thickness of the carbon layer is shown in Table 1.

[0043] (3) Silicon carbide coating: The carbon fiber preform with the cracked carbon layer is heated to 1300℃ in a vacuum furnace at a rate of 10℃ / min and held for 1.0h. The vacuum pressure gauge of silicon vapor is kept at -0.098MPa to obtain the carbon fiber preform with silicon carbide coating. The thickness of silicon carbide coating is shown in Table 1.

[0044] (4) Carbon nanotube generation: The carbon fiber preform containing silicon carbide coating is placed in a tube furnace. Argon gas is first introduced and purged at a flow rate of 300 sccm for 20 min. The temperature is then increased to 800℃ at a rate of 10℃ / min and held for 30 min. Subsequently, an auxiliary agent mixture is injected at 800℃ at an injection rate of 30 mL / h to grow carbon nanotubes and obtain a carbon fiber preform containing silicon carbide coating and carbon nanotubes. The auxiliary agent mixture is prepared by mixing ethanol, xylene, ethylenediamine and ferrocene in a ratio of 120 mL: 120 mL: 3 mL: 2 g.

[0045] Example 3 The method for preparing the carbon fiber preform of the present invention includes the following steps: (1) Carbon fiber pretreatment: 10g of carbon fiber bundle is impregnated in a tank of 300g of phenolic resin slurry by the traction of a fiber winding machine, and then pulled to a plate for rotating winding, and neatly arranged into a planar unidirectional preform. The speed of the fiber winding machine is an average of 1.2g per minute. Then it is dried for 3.0h and cut into a suitable shape to obtain pretreated carbon fiber. The phenolic resin slurry is prepared by mixing soluble phenolic resin and ethanol in a mass ratio of 1:20.

[0046] (2) High temperature pyrolysis: The pretreated carbon fiber is placed in a vacuum furnace and heated to 1200℃ at a rate of 6℃ / min and held for 1.5h. The vacuum pressure gauge is kept at -0.1MPa to obtain a carbon fiber preform with a pyrolyzed carbon layer. The thickness of the carbon layer is shown in Table 1.

[0047] (3) Silicon carbide coating: The carbon fiber preform with the cracked carbon layer is heated to 1200℃ in a vacuum furnace at a rate of 9℃ / min and held for 4.0h. The vacuum pressure gauge of silicon vapor is kept at -0.095MPa to obtain the carbon fiber preform with silicon carbide coating. The thickness of silicon carbide coating is shown in Table 1.

[0048] (4) Carbon nanotube generation: The carbon fiber preform containing silicon carbide coating is placed in a tube furnace. Argon gas is first introduced and purged at a flow rate of 200 sccm for 30 min. The temperature is then raised to 850℃ at a rate of 10℃ / min and held for 60 min. Subsequently, an additive mixture is injected at 850℃ at an injection rate of 10 mL / h to grow carbon nanotubes and obtain a carbon fiber preform containing silicon carbide coating and carbon nanotubes. The additive mixture is prepared by mixing ethanol, xylene, ethylenediamine and ferrocene in a ratio of 100 mL: 100 mL: 4 mL: 3 g.

[0049] Example 4 The carbon fiber preform containing silicon carbide coating and carbon nanotubes prepared in Example 1 was applied in the following ways: Silicon boron oxynitride powder, pure silicon powder, zirconium diboride powder, carbon black, and flake graphite were dry-mixed in a mass ratio of 39:18:22:14:7 and ball-milled for 4 hours, with a material-to-ball ratio of 1:30 and a rotation speed of 160 rpm, to obtain the mixed powder. The mixed powder and alcohol (95%) were mixed in a mass ratio of 4:3 and stirred in a mixer for 1 hour to obtain a ceramic slurry. A composite material was obtained by impregnating a ceramic slurry with a silicon carbide-coated carbon fiber preform prepared in Example 1 (the ceramic slurry and preform were mixed at a mass ratio of 4:1). The composite material was loaded into a hot-pressing sintering mold, and after vacuuming, the temperature was raised to 1700°C at a rate of 10°C / min. It was then hot-pressed and sintered at 30 MPa uniaxial pressure for 2.0 h. After the hot-pressing sintering was completed and the material cooled in the furnace, it was removed from the furnace and demolded to obtain a carbon fiber reinforced ultra-high temperature multiphase ceramic composite material. Figures 13 to 15 Topographical diagram.

[0050] Example 5 The method for preparing the carbon fiber preform of the present invention includes the following steps: (1) Carbon fiber pretreatment: 10g of carbon fiber bundle is impregnated in a tank of 300g of phenolic resin slurry by the traction of a fiber winding machine, and then pulled to a plate for rotation and winding, and neatly arranged into a planar unidirectional preform. Then it is dried for 4.0h and cut into a suitable shape to obtain pretreated carbon fiber; the phenolic resin slurry is prepared by mixing soluble phenolic resin and ethanol at a mass ratio of 1:20.

[0051] (2) High temperature pyrolysis: The pretreated carbon fiber is placed in a vacuum furnace and heated to 800℃ at a rate of 4℃ / min and held for 1.0h. The vacuum pressure gauge is kept at -0.09MPa to obtain a carbon fiber preform with a pyrolyzed carbon layer. The thickness of the carbon layer is shown in Table 1.

[0052] (3) Silicon carbide coating: The carbon fiber preform with the cracked carbon layer is heated to 1300℃ in a vacuum furnace at a rate of 10℃ / min and held for 1.0h. The vacuum pressure gauge of silicon vapor is kept at -0.09MPa to obtain the carbon fiber preform with silicon carbide coating. The thickness of silicon carbide coating is shown in Table 1.

[0053] (4) Carbon nanotube generation: The carbon fiber preform containing silicon carbide coating is placed in a tube furnace. Argon gas is first introduced and purged at a flow rate of 300 sccm for 20 min. The temperature is then increased to 800℃ at a rate of 10℃ / min and held for 30 min. Subsequently, an additive mixture is injected at 700℃ at an injection rate of 30 mL / h to grow carbon nanotubes and obtain a carbon fiber preform containing silicon carbide coating and carbon nanotubes. The additive mixture is prepared by mixing ethanol, xylene, ethylenediamine and ferrocene in a ratio of 80 mL: 80 mL: 6 mL: 5 g.

[0054] Comparative Example 1 Carbon fibers were impregnated in a slurry made of phenolic resin and ethanol at a mass ratio of 1:30. After drying for 4.0 hours, the slurry was cut into sheet-like fiber preforms. The preforms were then heated to 1200℃ at a rate of 6℃ / min and held for 2.0 hours under a vacuum pressure of -0.10MPa to prepare a carbon layer. After the carbon layer was prepared, a silicon vapor deposition reaction was carried out in a vacuum hot press furnace, with the silicon vapor vacuum pressure maintained at -0.098MPa and the temperature increased to 1400℃ at a rate of 7℃ / min, followed by a holding time of 1.0 hour. Finally, a carbon fiber preform with a silicon carbide coating was obtained. A carbon fiber preform with a silicon carbide coating was placed in a tube furnace and heated to 850°C at a rate of 10°C / min, and held at that temperature for 30 min. Then, a mixed solution of ethanol, xylene, and ethylenediamine in a ratio of 100 mL:100 mL:3 mL was injected at 850°C, and carbon nanotubes were grown at an injection rate of 30 mL / h. Finally, a carbon fiber preform containing a silicon carbide coating and carbon nanotubes was obtained.

[0055] Comparative Example 2 Carbon fibers were cut into sheet-like fiber preforms and subjected to silicon vapor deposition in a vacuum autoclave at a silicon vapor pressure gauge maintained at -0.098 MPa. The temperature was increased to 1400℃ at a rate of 7℃ / min and held for 1.0 h to obtain a carbon fiber preform with a silicon carbide coating. The carbon fiber preform with the silicon carbide coating was placed in a tube furnace and heated to 850℃ at a rate of 10℃ / min and held for 30 min. Subsequently, a mixed solution of ethanol, xylene, ethylenediamine, and ferrocene in a ratio of 100 mL:100 mL:4 mL:3 g was injected at 850℃ at a rate of 20 mL / h to grow carbon nanotubes. Finally, a carbon fiber preform with a silicon carbide coating and carbon nanotubes was obtained.

[0056] Comparative Example 3 Carbon fibers were impregnated in a slurry made of phenolic resin and ethanol at a mass ratio of 1:30. After drying for 4.0 hours, the slurry was cut into sheet-like fiber preforms. The preforms were then heated to 1200℃ at a rate of 6℃ / min and held for 2.0 hours under a vacuum pressure of -0.1MPa to prepare a pyrolysis carbon layer. After the pyrolysis, a silicon vapor deposition reaction was carried out in a vacuum hot press furnace, maintaining a silicon vapor vacuum pressure of -0.098MPa and heating to 1400℃ at a rate of 7℃ / min, followed by a holding time of 1.0 hour. Finally, a carbon fiber preform with a silicon carbide coating was obtained.

[0057] Silicon boron oxynitride powder, pure silicon powder, zirconium diboride powder, carbon black, and flake graphite were dry-mixed and ball-milled for 4 hours at a mass ratio of 39:18:22:14:7 to obtain a mixed powder, with a material-to-ball ratio of 1:30 and a rotation speed of 160 rpm. The mixed powder was then mixed with 95% alcohol at a mass ratio of 4:3 and stirred in a mixer for 1 hour to obtain a ceramic slurry. The ceramic slurry was then combined with a carbon fiber preform containing a silicon carbide coating using a slurry impregnation process to obtain a composite material (the ceramic slurry and preform were mixed at a mass ratio of 4:1). The composite material was loaded into a hot-pressing sintering mold, and after vacuuming, the temperature was raised to 1700℃ at a rate of 10℃ / min and held at 30MPa uniaxial pressure for 2.0 hours for hot-pressing sintering. After the hot-pressing sintering was completed and the material cooled in the furnace, it was removed from the furnace and demolded to obtain a carbon fiber reinforced ultra-high temperature multiphase ceramic composite material.

[0058] Comparative Example 4 Carbon fibers were arranged and cut into sheet-like fiber preforms. The carbon fiber preforms were placed in a tube furnace and heated to 850°C at a rate of 10°C / min, and held at that temperature for 30 min. Then, a mixed solution of ethanol, xylene, ethylenediamine, and ferrocene in a ratio of 100 mL:100 mL:4 mL:3 g was injected at 850°C, and carbon nanotubes were grown at an injection rate of 20 mL / h. Finally, a carbon fiber preform containing carbon nanotubes was obtained.

[0059] Silicon-boron-oxygen-nitrogen powder, pure silicon powder, zirconium diboride powder, carbon black, and flake graphite were dry-mixed and ball-milled for 4 hours at a mass ratio of 39:18:22:14:7 to obtain a mixed powder, with a material-to-ball ratio of 1:30 and a rotation speed of 160 rpm. The mixed powder was then mixed with 95% alcohol at a mass ratio of 4:3 and stirred in a mixer for 1 hour to obtain a ceramic slurry. The ceramic slurry was then combined with a carbon fiber preform containing carbon nanotubes using a slurry impregnation process to obtain a composite material (the ceramic slurry and preform were mixed at a mass ratio of 4:1). The composite material was loaded into a hot-pressing sintering mold, and after vacuuming, the temperature was raised to 1700℃ at a rate of 10℃ / min, and then held at 30MPa uniaxial pressure for 2.0 hours for hot-pressing sintering. After hot-pressing sintering and cooling in the furnace, the material was removed from the furnace and demolded to obtain a carbon fiber reinforced ultra-high temperature multiphase ceramic composite material.

[0060] The carbon fiber preforms prepared in Examples 1, 2, 3, 5 and Comparative Examples 1 and 2 were tested, and the results are shown in Table 1.

[0061] The ceramic composite materials prepared using carbon fiber preforms in Example 4 and Comparative Examples 3 and 4 were tested, and the results are shown in Table 2.

[0062] The densities in the table below were tested using Archimedes' displacement method; Bending strength: Refer to GB / T45763-2025; Fracture toughness: Refer to GB / T23806-2025; Residual flexural strength: Refer to GB / T45763-2025; Oxidative weight loss rate: Refer to JC-T 2530-2019.

[0063] Table 1. Test Results of Carbon Fiber Preforms

[0064] Table 2 Test Results of Ceramic Composite Materials

[0065] As can be seen from the data in Table 1, the different slurry concentrations used in each example resulted in variations in the thickness, uniformity, and density of the coating formed on the surface of the carbon fiber preform. Because the carbon fiber suffered some degree of thermal damage during coating preparation, its tensile strength decreased to some extent. In Comparative Example 1, the absence of ferrocene in the slurry for preparing carbon nanotubes resulted in a lack of catalyst for carbon nanotube growth, leading to a slower growth rate. Figure 11 and Figure 12 The results showed that the carbon nanotube growth effect in Comparative Example 1 was less than that of adding ferrocene in Example 1. In Comparative Example 2, because a pyrolytic carbon coating of phenolic resin was not prepared, the carbon fiber preform reacted directly with silicon vapor during the subsequent silicon vapor deposition process, damaging the carbon fiber itself and resulting in extremely low tensile strength of the prepared carbon fiber preform.

[0066] As can be seen from the data in Table 2, in Comparative Example 3, because the carbon fiber preform with carbon coating did not undergo carbon nanotube growth, the impregnation effect was poor when it was combined with ceramic slurry, resulting in lower physical properties of the final composite material. In Comparative Example 4, the lack of SiC coating mainly led to a decrease in oxidation resistance and high-temperature residual strength. This is because the lack of silicon carbide coating protection on the carbon fiber surface resulted in higher carbon fiber damage during oxidation, failing to provide toughening and instead increasing new internal defects.

Claims

1. A method for preparing a carbon fiber preform, characterized in that, Includes the following steps: (1) Carbon fiber pretreatment: The carbon fiber is drawn and impregnated in phenolic resin slurry, then taken out, wound, dried and cut to obtain pretreated carbon fiber; (2) High-temperature pyrolysis: In a vacuum environment, the pretreated carbon fiber is pyrolyzed at a high temperature of 800~1200℃ to obtain a carbon fiber preform with a pyrolyzed carbon layer. (3) Silicon carbide coating: In a vacuum environment, the carbon fiber preform with the cracked carbon layer is subjected to silicon vapor deposition at 1200~1400℃ to obtain a carbon fiber preform containing a silicon carbide coating. (4) Carbon nanotube generation: The carbon fiber preform containing silicon carbide coating is heated to 700~850℃ in a protective atmosphere, and an auxiliary agent mixture is injected and blown onto the carbon fiber preform by airflow to obtain a carbon fiber preform with carbon nanotubes grown. The additive mixture is a mixture of ethanol, xylene, ethylenediamine, and ferrocene.

2. The method for preparing the carbon fiber preform according to claim 1, characterized in that, The phenolic resin slurry in step (1) is prepared by mixing soluble phenolic resin and ethanol at a mass ratio of 1:20~40.

3. The method for preparing the carbon fiber preform according to claim 1, characterized in that, The specific conditions for high-temperature pyrolysis in step (2) are: vacuum pressure of -0.09~-0.1MPa, heating to 800~1200℃ at a rate of 4~10℃ / min and holding for 1.0~4.0h.

4. The method for preparing the carbon fiber preform according to claim 3, characterized in that, Step (2) yields a carbon layer thickness of 200 nm to 1200 nm on a single carbon fiber in a carbon fiber preform with a pyrolytic carbon layer.

5. The method for preparing carbon fiber preforms according to claim 1, characterized in that, The specific conditions for silicon vapor deposition in step (3) are: vacuum pressure of -0.098 to -0.09 MPa, heating to 1200 to 1400℃ at a rate of 4 to 10℃ / min and then holding at that temperature for 1.0 to 4.0 h.

6. The method for preparing the carbon fiber preform according to claim 1, characterized in that, Step (3) yields a silicon carbide coating thickness of 200 nm to 600 nm for a single carbon fiber in a carbon fiber preform containing a silicon carbide coating.

7. The method for preparing carbon fiber preforms according to claim 1, characterized in that, In step (4), the basic ratio of ethanol, xylene, ethylenediamine and ferrocene is 80~120mL:80~120mL:3~6mL:2~5g, or the ratio after scaling up the basic ratio.

8. The method for preparing the carbon fiber preform according to claim 7, characterized in that, The specific parameters for carbon nanotube generation in step (4) are as follows: Place the carbon fiber preform containing silicon carbide coating in a tube furnace, first introduce argon gas at a flow rate of 200~300 sccm for 20~30 min, heat it to 700~850℃ at a rate of 5~10℃ / min and hold it for 30~60 min, then inject the auxiliary agent mixture at 700~850℃ at an injection rate of 10~30 mL / h to obtain the carbon fiber preform with carbon nanotubes grown on it.

9. A carbon fiber preform prepared by the method for preparing a carbon fiber preform according to any one of claims 1 to 8.

10. An application of the carbon fiber preform as described in claim 9, characterized in that, A multiphase ceramic composite material is prepared by impregnating a carbon fiber preform in a ceramic slurry and hot-pressing and sintering it, with the carbon fiber preform accounting for 19-21% of the mass.

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