A method for preparing an anti-peel silicon carbide coating and a modified carbon fiber composite material

Abstract

This invention discloses a method for preparing an anti-peel silicon carbide coating and a modified carbon fiber composite material, belonging to the technical field of carbon fiber composite materials. The method includes: mixing and dispersing silicon powder, phenolic resin, and boric acid in a solvent to form a slurry; the mass ratio of boric acid to silicon powder is 1~2:100; activating the carbon fiber composite material through plasma to introduce active functional groups containing hydroxyl and carboxyl groups onto the surface, obtaining a CFRP pretreated substrate; coating the slurry onto the CFRP pretreated substrate to obtain a coated part, and then curing it; under a protective atmosphere, subjecting the cured coated part to high-temperature derivatization at 1200~1400℃ to achieve SiC phase formation and boron reactive doping, obtaining a boron-doped anti-peel silicon carbide coating. The aforementioned anti-peel silicon carbide coating exhibits strong compatibility with CFRP, good interfacial bonding, and anti-peel properties, providing high protective reliability and meeting long-term service requirements.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber composite material technology, and relates to a method for preparing an anti-peeling silicon carbide coating and a modified carbon fiber composite material. Background Technology

[0002] Carbon fiber reinforced polymer (CFRP) composites are mostly made by weaving together carbon fiber bundles with a resin matrix, typically 6-8 μm in diameter. Their specific strength is five times that of steel, and their coefficient of thermal expansion along the fiber direction is 1.5 × 10⁻⁶. -6 With its high specific strength, high specific modulus, low coefficient of thermal expansion, and excellent fatigue resistance, CFRP has become a core structural material for extreme environment equipment such as aerospace engine blades, chemical reactor linings, and high-speed aircraft shells. However, traditional CFRP has two inherent defects that limit its direct service. First, it has poor high-temperature stability. In oxygen-rich environments above 400℃, carbon fibers are easily oxidized to generate carbon dioxide (CO2), leading to matrix weight loss and a sharp drop in mechanical properties. For example, the weight loss rate can reach more than 20% after 500 hours at 800℃. Second, its surface is chemically inert, and the presence of fiber gaps and resin micropores makes it susceptible to corrosion by acid and alkali media, and it is difficult to form a stable bond with protective coatings.

[0003] To address one of the aforementioned defects, industry technicians typically employ a coating for protection. Among these, silicon carbide (SiC) ceramic coatings have a coefficient of thermal expansion of 4.5 × 10⁻⁶. -6 With a temperature range of / ℃, it can withstand temperatures above 1000℃ for extended periods, is resistant to strong acids and alkalis, and possesses advantages such as high-temperature oxidation resistance and strong corrosion resistance. Furthermore, its thermal expansion coefficient is relatively well-matched with CFRP, making it an ideal coating material for protecting CFRP. Currently, the mainstream preparation methods for CFRP-based SiC coatings include: Precursor Impregnation-Pyrolysis (PIP), Chemical Vapor Deposition (CVD), and Slurry Coating Derivative Method. The PIP method generates a SiC coating by impregnating, curing, and pyrolyzing a precursor solution at high temperature; its process is flexible but requires multiple cycles. The CVD method generates a SiC coating by depositing silicon-carbon source gas under high temperature and pressure; its coating density is high, but the equipment is complex. Relatively speaking, the slurry coating method has lower costs, can adapt to complex shapes, and is widely used in industrial applications; it mainly involves mixing silicon powder, resin carbon source, and solvent into a slurry, coating it onto a CFRP substrate, and then derivatizing it at high temperature to form a SiC protective coating.

[0004] However, the application of existing technologies on CFRP substrates still faces some significant core technological bottlenecks. Pure CFRP surfaces rarely contain active functional groups and often retain uncured resin. Current technologies only improve the surface condition through mechanical polishing or simple plasma treatment. The SiC coating and substrate mainly rely on physical adsorption for bonding; for example, the interfacial bonding strength generally does not exceed 3 MPa. This makes it prone to interface peeling under high-temperature cycling and external forces, resulting in poor bonding compatibility. Therefore, developing a silicon carbide coating technology that addresses the characteristics of the CFRP substrate while balancing interfacial bonding strength and protective properties is a key requirement for overcoming the bottleneck of CFRP's service life in extreme environments. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for preparing an anti-peel silicon carbide coating and a modified carbon fiber composite material. The anti-peel silicon carbide coating of the present invention has strong compatibility with CFRP, good interfacial bonding, anti-peel properties, and high protective reliability, which can meet the requirements of long-term service.

[0006] This invention provides a method for preparing an anti-peeling silicon carbide coating, comprising the following steps:

[0007] S1. Silicon powder, phenolic resin and boric acid are mixed and dispersed in a solvent to form a slurry; the mass ratio of boric acid to silicon powder is 1~2:100.

[0008] The carbon fiber composite material was activated by plasma to introduce active functional groups containing hydroxyl and carboxyl groups on the surface, resulting in a CFRP pretreated substrate.

[0009] S2. The slurry is coated onto a CFRP pretreated substrate to obtain a coated part, and then cured.

[0010] S3. Under a protective atmosphere, the cured coated part is subjected to high-temperature derivatization at 1200~1400℃ to achieve SiC phase generation and boron reactive doping, thereby obtaining a boron-doped anti-peeling silicon carbide coating.

[0011] Preferably, in step S1, the solvent is anhydrous ethanol; the boric acid has a particle size ≤1μm, the silicon powder has a particle size of 1~5μm, and the slurry has a viscosity of 230~270mPa·s at 25℃.

[0012] Preferably, in step S1, the plasma activation is achieved by argon plasma cleaning, with an argon flow rate of 0.1~1L / min and a processing power of 300-500W.

[0013] Preferably, in step S1, after plasma activation, the process further includes: pre-sealing the pores of the carbon fiber composite material with phenolic resin, and then grinding the surface of the pre-sealed material to obtain a CFRP pretreated substrate with a roughness of 1.2~1.8μm.

[0014] Preferably, in step S2, the slurry portion is coated with a first thin layer on the CFRP pretreated substrate, and air bubbles are removed by rolling; the remaining slurry is coated with a second thin layer to obtain a coated part with a wet coating; the coating directions of the first and second thin layers are different; the total coating weight of the coated part is 300~450g / m². 2 The thickness of the wet coating is 150~170μm.

[0015] Preferably, in step S2, the curing process is a low-temperature constant-temperature curing and shaping process at 80~110℃ for 1~3 hours.

[0016] Preferably, step S3 includes: placing the cured coated part into a high-temperature derivation unit with an atmosphere protection device, introducing a protective atmosphere, gradually increasing the temperature from room temperature to 1400°C at a heating rate of 1~5°C / min, and conducting a constant-temperature reaction to achieve SiC phase generation and boron reactive doping. After buffering and cooling at 600~800°C, a boron-doped anti-peeling silicon carbide coating is obtained.

[0017] Preferably, the high-temperature derivatization in step S3 further includes:

[0018] A boron-doped, peel-resistant silicon carbide coating is obtained by cross-spraying and curing a composite sealing agent to form a sealed pore layer; the composite sealing agent includes phenolic resin and nano-silicon carbide.

[0019] Preferably, the droplet size of the composite sealing agent in cross-spraying is 5~10μm; the curing temperature for forming the sealed pore layer is 140~150℃.

[0020] This invention provides a modified carbon fiber composite material, including an anti-peeling silicon carbide coating obtained by the preparation method described above.

[0021] To address the unique characteristics of CFRP substrates, this invention provides an innovative synergistic protection solution, comprising: mixing and dispersing silicon powder, phenolic resin, and boric acid in a solvent in a specific ratio to form a slurry; plasma-activating the CFRP to obtain a pretreated substrate containing hydroxyl and carboxyl groups; coating the slurry onto the pretreated CFRP substrate and curing it; and subjecting the cured coating to high-temperature derivatization under a protective atmosphere to obtain a boron-doped, peel-resistant silicon carbide coating. This invention utilizes in-situ boron doping reactions to generate BC / Si-B chemical bonds and a B4C-SiC-C composite transition layer, combined with optimized plasma pretreatment, to strengthen the interfacial bonding between the SiC coating and the CFRP substrate. This invention achieves highly efficient adaptation between the CFRP substrate and the SiC coating, increasing the interfacial bonding strength to over 5.5 MPa, thereby solving the problem of peeling under high-temperature cycling of existing protective coatings. Attached Figure Description

[0022] Figure 1 This is a process flow diagram for preparing an anti-peeling silicon carbide coating according to some embodiments of the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] Carbon fiber reinforced polymer (CFRP) has a strong chemical inertness. Existing technologies only improve the surface condition of CFRP through mechanical grinding or simple plasma treatment, without specifically removing residual resin on the surface or introducing a chemical bonding mechanism. As a result, the coating and the CFRP matrix rely solely on physical adsorption for bonding, resulting in weak interfacial adhesion and easy peeling.

[0025] This invention provides a method for preparing an anti-peeling silicon carbide coating, comprising the following steps:

[0026] S1. Silicon powder, phenolic resin and boric acid are mixed and dispersed in a solvent to form a slurry; the mass ratio of boric acid to silicon powder is 1~2:100.

[0027] The carbon fiber composite material was activated by plasma to introduce active functional groups containing hydroxyl and carboxyl groups on the surface, resulting in a CFRP pretreated substrate.

[0028] S2. The slurry is coated onto a CFRP pretreated substrate to obtain a coated part, and then cured.

[0029] S3. Under a protective atmosphere, the cured coated part is subjected to high-temperature derivatization at 1200~1400℃ to achieve SiC phase generation and boron reactive doping, thereby obtaining a boron-doped anti-peeling silicon carbide coating.

[0030] The anti-peel silicon carbide coating prepared by this invention has strong compatibility with CFRP, good interfacial bonding, anti-peel properties, and high protective reliability, which can meet the requirements of long-term service.

[0031] See Figure 1 , Figure 1 This is a process flow diagram for preparing an anti-peeling silicon carbide coating according to some embodiments of the present invention. The embodiments of the present invention first perform raw material screening, using silicon powder as the silicon source, typically selecting Si powder with a purity ≥99.9%. Preferably, Si powder with a particle size of 1~5μm is screened using a grading sieve to remove fine powder with a particle size less than 0.5μm and coarse powder with a particle size greater than 5μm, avoiding clogging of CFRP micropores and coating defects. In the embodiments of the present invention, boric acid (H3BO3) is weighed in a certain proportion, which can be a commercially available product with a purity ≥99.5%; preferably, it is ground in a grinder to a particle size ≤1μm, which is beneficial for the uniformity of subsequent boron doping.

[0032] This invention uses phenolic resin as a carbon source, preferably a low-viscosity phenolic resin with a viscosity of 50-200 mPa·s at 25°C; it is a conventional commercially available product, and more preferably, the resin has a residual carbon rate of ≥40% and a total metal ion content of ≤1 ppm. Specifically, the phenolic resin can be dissolved in a solvent to form a coating solution; its solid content is generally 5-15%, for example, 15%, to make the resin solution suitable for coating preparation requirements, etc. Preferably, the solvent is anhydrous ethanol (alcohol). In addition, this invention also mixes phenolic resin with anhydrous ethanol to prepare a low-concentration phenolic resin pre-blocking solution; the solid content of this pre-blocking solution can be 3-5%. The mass solid-liquid ratio involved in this application is the solid mass: anhydrous ethanol liquid mass; for example, to prepare a 5% pre-blocking solution: take 10 g of phenolic resin and add 200 g of anhydrous ethanol, which is a mass ratio of 1:20.

[0033] Most existing slurry coating technologies use solvents such as acetone and xylene as dispersion media. On the one hand, these organic solvents are highly toxic and easily lead to excessive emissions of volatile organic compounds (VOCs), resulting in poor environmental performance and limiting industrial applications. On the other hand, their high surface tension makes it difficult to effectively wet the powder and substrate, leading to severe Si powder agglomeration with particle sizes exceeding 30 μm. This results in uneven coating composition distribution and weak local protective performance.

[0034] In the embodiments of the present invention, anhydrous ethanol is preferably used as an environmentally friendly dispersion medium, which helps to reduce VOC emissions, while inhibiting Si powder agglomeration and ensuring the uniformity of coating composition.

[0035] This invention uses CFRP as a substrate and performs specific pretreatment operations. The characteristics of CFRP include: the overall structure is woven from carbon fiber bundles (e.g., 6-8 μm in diameter) and a resin matrix, generally in the form of a plain weave fabric; the surface has inter-fiber gaps (typically 1-5 μm in diameter) and resin micropores; the coefficient of thermal expansion along the fiber direction and perpendicular to the fiber direction is anisotropic; the carbon fiber surface has no active functional groups and is chemically inert; it is sensitive to high temperatures (resin is easily degraded at >150℃), chemical solvents (strong acids and alkalis easily corrode the resin), and mechanical forces (excessive abrasion easily breaks the fibers).

[0036] In this embodiment of the invention, commercially available CFRP samples can be ultrasonically cleaned to remove resin residue and oil stains from the CFRP surface; after drying, plasma activation is performed to introduce active functional groups including hydroxyl (-OH) and carboxyl (-COOH) groups onto the CFRP surface.

[0037] As a specific example, CFRP samples (such as plain weave, with no special size restrictions) are placed in an ultrasonic cleaning tank, and a cleaning solution of anhydrous ethanol and isopropanol is added. Ultrasonic cleaning at 300W for 10-20 minutes is preferred to remove residual resin and oil from the surface. After cleaning, the samples are placed in a low-temperature oven at 100-120℃ and dried for 1-3 hours. Then, they are cooled to room temperature to avoid damaging the resin due to high temperatures.

[0038] The plasma activation described in this embodiment of the invention can introduce active functional groups such as -OH and -COOH onto the substrate surface. The operation includes: placing the dried CFRP into a plasma cleaner and introducing argon gas (Ar gas), preferably at a power of 300-500W, to break the chemical inertness of the CFRP surface. The argon gas flow rate can be 0.1~1L / min, more preferably 0.5L / min, and the treatment time is 5-10 min, for example 6 min, 7 min, or 8 min, to fully activate the surface functional groups.

[0039] After plasma activation, this embodiment of the invention uses phenolic resin to pre-seal the micropores of the substrate. Specifically, an ultrasonic atomizing pre-sealing sprayer can be used to uniformly spray the prepared phenolic resin pre-sealing solution onto the CFRP surface. The spraying rate can be 50~100mL / min, and it is preferred to cure at 100℃ to fill the gaps between fibers and the resin micropores.

[0040] In this embodiment of the invention, a CFRP pretreated substrate with a roughness Ra of 1.2~1.8μm is obtained by polishing the surface of the pre-sealed material. This surface fine-tuning treatment can form a mechanical interlocking structure without damaging the fiber bundles. For example, 1500~2000 grit sandpaper is used for polishing, and the fine sandpaper gently polishes to avoid mechanical damage to the fibers.

[0041] By employing the aforementioned synergistic pretreatment process, the substrate in the preferred embodiment of the present invention forms a micro-roughened surface with an activated adaptive coating, which is beneficial for strengthening interfacial bonding and solving the problems of resin residue, micropore penetration, and insufficient interfacial activation on the CFRP surface.

[0042] In a specific embodiment of this invention, an environmentally friendly slurry is prepared by following the batching and dispersion operations, achieving uniform dispersion of Si powder and boric acid while balancing environmental protection and stability. Screened Si powder and the prepared phenolic resin coating solution are added to the stirred tank of the environmentally friendly slurry preparation unit, followed by precisely adding ground boric acid at 1%~2% (preferably 1.5%) of the Si powder mass. The resulting slurry has a viscosity of 230~270 mPa·s at 25°C, thus avoiding CFRP micropore penetration.

[0043] The preferred method involves initial dispersion under mechanical stirring, followed by dual-frequency ultrasonic treatment using both low and high frequencies. The low surface tension of the dispersing solvent, alcohol, combined with the synergistic effect of the dual-frequency ultrasound, achieves uniform dispersion of Si powder and boric acid, preventing CFRP micropore penetration and reducing VOC emissions. In this dispersion system, alcohol has a low surface tension (22.3 mN / m at 25°C), which can quickly and effectively wet the surfaces of Si powder and boric acid, reducing van der Waals forces between particles and inhibiting particle agglomeration. The dual-frequency ultrasonic dispersion process consists of 20 kHz low-frequency wetting ultrasound and 40 kHz high-frequency dispersing ultrasound; its cavitation effect breaks up agglomerated particles, forming a uniformly dispersed slurry system.

[0044] After pretreatment such as CFRP pre-sealing and activation, the slurry coating process in this embodiment of the invention preferably involves multiple precise thin coatings to remove air bubbles, achieving uniform coating coverage and preventing slurry penetration. Specific operations include:

[0045] Using a precision coating equipment, the slurry is applied as a first thin coat on the CFRP pretreated substrate, which can be sprayed along the CFRP fiber direction; then immediately, a ceramic roller is used to gently roll along the fiber direction, with the roller pressure not exceeding 0.5MPa, to remove air bubbles inside the coating.

[0046] The slurry to be sprayed is initially set. The spraying direction is adjusted to be perpendicular to the fiber direction. The remaining slurry is then applied in a second thin coat. A ceramic roller is then used to roll the slurry perpendicular to the fiber direction to remove air bubbles again, resulting in a coated part with a wet coating. This ensures that the coating is free of pinholes and depressions.

[0047] In this embodiment of the invention, multiple thin coats and cross-spraying are used to avoid excessive penetration of the slurry into the CFRP micropores. Rolling removes air bubbles, reducing coating defects and ensuring a uniform coating that adheres tightly to the CFRP surface. The spraying pressure is adjustable from 0.2 to 0.5 MPa, preferably not exceeding 0.3 MPa; the total coating weight can be 300 to 450 g / m². 2Generally, it is applied in two coats, sprayed crosswise along the fiber direction / perpendicular to the fiber direction, with each coat being ≤200g / m². 2 Preferred concentration: 170~180g / m 2 The wet coating thickness is 150~170μm. This combination of coating processes is suitable for CFRP and can effectively solve the problems of slurry penetration and numerous coating defects caused by the gaps between fibers on the CFRP surface.

[0048] After obtaining the coated part, this embodiment of the invention performs low-temperature curing to solidify the resin and prevent the coating from peeling off or deforming during high-temperature derivation. Specific operations include: placing the rolled coated part into a low-temperature curing oven and curing it at a constant temperature of 80~110℃ for 1~3 hours to allow the phenolic resin to crosslink, cure, and solidify, forming a stable pre-coating (non-sticky, no dripping). The curing temperature is lower than the glass transition temperature of CFRP resin (120~150℃) to avoid damage to the substrate and provide stable structural support for subsequent high-temperature derivation.

[0049] In this embodiment of the invention, the coated part after curing is subjected to high-temperature derivation under gradient temperature control. Specifically, it can be placed in a high-temperature derivation unit with an atmosphere protection device, and a protective atmosphere is introduced. The temperature is gradually increased from room temperature to 1400°C at a heating rate of 1~5°C / min. The reaction is carried out at a constant temperature to achieve SiC phase generation, boron reactive doping and interface transition layer formation. Preferably, after buffering and cooling at 700~900°C, a boron-doped anti-peeling silicon carbide coating is obtained.

[0050] The basic principle of Si powder derivatization to form SiC coating includes: Si powder (silicon source) and amorphous carbon (carbon source) generated by the pyrolysis of organic resin undergo a solid-phase reaction at 1200~1600℃ (Si+C→SiC).

[0051] In this embodiment of the invention, a one-step high-temperature derivation process under a protective atmosphere is used to pyrolyze phenolic resin and react to generate SiC. At the same time, boron doping solid solution reaction forms BC / Si-B chemical bonds, and a B4C-SiC-C composite interface transition layer is constructed, thereby strengthening the interfacial bonding between the coating and the CFRP substrate.

[0052] The specific derivative processing operations and implementation process are as follows:

[0053] 1. Atmosphere replacement: Place the cured coated part into the atmosphere protection furnace of the gradient temperature control high temperature derivation unit, close the furnace door, and introduce nitrogen to replace the air in the furnace, isolate oxygen, and avoid CFRP oxidation; nitrogen purity ≥99.99%, flow rate 0.5~1L / min adjustable;

[0054] 2. Slow Heating: Activate the three-stage temperature control system, and slowly increase the temperature at a rate of 1-5℃ / min, preferably to 1300℃ (the optimal derivation temperature for CFRP). Specific stages are as follows:

[0055] 2.1 First stage (room temperature ~ 600℃): Phenolic resin pyrolysis stage, releasing volatiles such as H2O and CO2 (volatile release rate ≤ 15%), forming an amorphous carbon network;

[0056] 2.2 Second stage (600~1000℃): Si-C reaction initiation stage, amorphous carbon reacts with Si powder to initially generate SiC primary phase;

[0057] 2.3 Third stage (1000~1300℃): Boron doping and transition layer formation stage. Boric acid decomposes into B2O3, which is further reduced to B atoms. Some of these atoms dissolve into the SiC lattice to form a B-SiC solid solution, while others diffuse to the CFRP interface and react with surface-active functional groups to form BC covalent bonds. Simultaneously, a 1~2μm thick B4C-SiC-C composite transition layer can be formed at the interface; the thermal expansion coefficient of this transition layer is 2.8×10⁻⁶. -6 / ℃, between CFRP-1.5×10 -6 / ℃, SiC-4.5×10 -6 Between / ℃, it is beneficial to achieve a smooth transition of the coefficient of thermal expansion and alleviate thermal stress;

[0058] 3. Isothermal reaction: It is preferred to maintain the temperature at 1300℃ for 3 hours to ensure complete Si-C reaction and uniform boron doping, with Si conversion rate ≥95%;

[0059] 4. Medium-temperature buffering and cooling: After the isothermal period, cool down slowly at a rate of 1-5℃ / min, preferably to 800℃, and hold at that temperature for 1 hour. This releases the thermal stress accumulated during the high-temperature derivation process and reduces the cracking rate of the coating. Then, cool down to room temperature at a rate of 1-5℃ / min and remove the coating to obtain the boron-doped silicon carbide coating preform. The preferred heating and cooling rates are both 3℃ / min.

[0060] This invention preferably employs a precise gradient temperature-controlled derivation process to simultaneously achieve SiC phase generation, boron doping for anti-peeling modification, and transition of thermal expansion coefficients, thus avoiding high-temperature damage to CFRP. In some embodiments of this invention, the CFRP surface has a micro-roughened structure with Ra = 1.2~1.8 μm, which can form mechanical interlocking; combined with BC bonds, Si-B bonds, and other chemical bonds, as well as the buffering effect of the transition layer, this triple synergistic effect significantly improves the interfacial bonding force, preventing peeling during high-temperature cycling and solving the peeling problem caused by thermal expansion coefficient mismatch.

[0061] This invention implements a gradient boron doping design, with an interface boron content of 1.5%~2% and an interior boron content of 0~1%, creating a gradient structure from the interface to the surface of the coating: "BC-SiC-C→B-SiC→pure SiC". The coefficient of thermal expansion ranges from 2.8 × 10⁻⁶. -6 / ℃ gradually increased to 4.5×10-6 / ℃, to avoid sudden changes in the coefficient of thermal expansion.

[0062] Existing PIP (Plasma Injection) technology requires 1-4 impregnation-pyrolysis cycles to compensate for porosity defects, resulting in redundant process steps, low production efficiency, and high costs. Furthermore, the curing temperature is close to the glass transition temperature of CFRP resin, which easily leads to resin degradation. Additionally, the mechanical abrasion intensity is not adapted to the characteristics of CFRP fibers, easily causing fiber bundle breakage and reducing mechanical properties. CVD (Chemical Vacuum Dioxide) technology relies on high-pressure vacuum equipment, with equipment investment 5-10 times that of conventional processes, making large-scale application difficult.

[0063] The simultaneous derivatization process of this invention is simple, can achieve high-efficiency production, and has high economic efficiency. The curing temperature and derivatization temperature (preferably 1300℃, under nitrogen protection) are both lower than the degradation temperature of CFRP resin and the oxidation temperature of fiber, which helps to maintain the mechanical properties of CFRP matrix and can solve the problem of damage to the mechanical properties of CFRP in the preparation process of existing technology.

[0064] In this embodiment of the invention, phenolic resin and nano-silicon carbide (nano-SiC) are used as a composite sealing agent. Through cross-spraying and curing, a sealed pore layer is formed, thereby obtaining a boron-doped, peel-resistant silicon carbide coating.

[0065] The composite sealing agent can be in the form of a solvent dispersion system, preferably anhydrous ethanol with a viscosity of 90~110 mPa·s at 25°C. The nano-SiC can fill the pores of the sealing agent, improving high-temperature resistance and density, and is suitable for subsequent cross-spraying processes.

[0066] Furthermore, the cross-spraying and curing operations are adapted to the CFRP fiber texture, sealing the micropores and fiber gaps in the coating, improving coating density, and blocking erosion channels. Preferably, the droplet size of the composite sealing agent in the cross-spraying is 5~10μm, and the cross-spraying sealing method can be as described above, facilitating complete coverage of the sealing agent along the fiber texture, filling the micropores and fiber gaps in the coating, and reducing porosity. The curing temperature can be 140~150℃, with low-temperature curing for 2 hours to form a tightly sealed pore layer.

[0067] In a preferred embodiment of the present invention, the CFRP micropores and fiber gaps are filled by pre-sealing treatment to prevent slurry penetration; the nano SiC in the composite sealing agent fills the pores of the sealing layer, and cross-spraying adapts to the fiber texture to form a double dense structure of "coating + sealing layer" with low porosity, blocking the penetration channels of oxygen and corrosive media.

[0068] Furthermore, the preparation process in this embodiment of the invention is mild, using environmentally friendly alcohol solvents throughout, without any toxic chemical media, thus avoiding corrosion of CFRP resin.

[0069] The silicon carbide coating preparation technology of this invention corresponds to a precisely structured preparation system device, including: a raw material pretreatment unit, an environmentally friendly slurry preparation unit, a CFRP substrate pretreatment unit, a coating unit, a gradient temperature-controlled high-temperature derivation unit, a fiber texture adaptation sealing unit, and an online performance testing unit. The preparation system can consist of 7 core units and 3 auxiliary modules, with the units connected in a closed loop via material transfer channels and control circuits. All units are adapted to the mild preparation requirements of CFRP, eliminating the need for high-pressure vacuum equipment and enabling large-scale continuous production.

[0070] In some embodiments, the raw material pretreatment unit ensures that the raw materials are suitable for CFRP coating requirements, and specifically includes the following components: an electronic balance with an accuracy of 0.001g; a Si powder grading sieve with a mesh size of 0.5 / 1 / 5μm for Si powder particle size classification; a grinder for boric acid micronization, with a particle size ≤1μm after grinding; and a phenolic resin dissolving kettle with temperature control and stirring equipment, and a rotation speed of 0~800rpm, to dissolve the phenolic resin alcohol system at a low concentration.

[0071] In some embodiments, the environmentally friendly slurry preparation unit is used to construct a phenolic resin-alcohol environmentally friendly dispersion system, achieving uniform dispersion of Si powder and boric acid, controlling the thixotropy of the slurry, and preventing CFRP micropore penetration; for example, the slurry viscosity is 250±20 mPa·s (25℃), and the sedimentation rate is ≤1%. It preferably includes: an alcohol storage tank (anhydrous ethanol purity ≥99.7%); a dual-frequency ultrasonic disperser with 20 / 40kHz dual-frequency switching and a power of 0~500W; a mechanical stirrer with a rotation speed of 0~1000 rpm; a sedimentation stability testing graduated cylinder (with scale); and a Forte 4 cup viscometer.

[0072] In some embodiments, the CFRP substrate pretreatment unit includes: an ultrasonic cleaning tank containing solvents such as anhydrous ethanol and 5% isopropanol; a plasma cleaner with an argon atmosphere and a power of 0-500W; a pre-sealing sprayer, ultrasonic atomizing type, with a spraying rate of 0-100mL / min; and a fine sandpaper polishing table (1500 / 2000 grit). It can remove resin residue and oil from the CFRP surface, activate surface functional groups, seal fiber gaps and micropores, and form a pretreated surface suitable for coating.

[0073] In some embodiments, the coating unit includes a dual-mode coating device and a coating amount control device. The nozzle diameter of the dual-mode coating device is adjustable from 0.8 to 1.2 mm, and the spraying pressure is adjustable from 0.2 to 0.5 MPa. It is equipped with a coating tool and a ceramic roller with a hardness of HRC65, Ra≤0.1 μm, and an adjustable pressure of 0 to 0.5 MPa. The coating amount control device monitors the coating amount in real time using a weighing method, achieving uniform coating of the slurry through multiple thin coats, eliminating air bubbles in the coating, and preventing excessive penetration of the slurry into the CFRP micropores.

[0074] In some embodiments, the gradient temperature control high-temperature derivative unit includes: an atmosphere protection furnace, wherein the nitrogen gas introduced has a purity ≥99.99% and a flow rate adjustable from 0.5 to 1 L / min; a three-stage temperature control device, wherein the heating and cooling rates are adjustable from 1 to 5 °C / min, and the maximum temperature is 1600 °C; and a medium-temperature buffer module, which maintains a constant temperature of 600 to 800 °C.

[0075] In some embodiments, the fiber texture-adaptive sealing unit includes: a nano-SiC dispersion vessel equipped with ultrasonic dispersion, wherein the nano-SiC particle size can be 50 nm; a composite sealing agent storage tank; a cross-spraying device with an adjustable droplet size of 5-10 μm and switchable spraying direction; and a low-temperature curing oven (adjustable from 50 to 200 °C). The prepared composite sealing agent preferably contains 5 wt% nano-SiC to improve high-temperature resistance, etc.; the spraying direction is preferably 0° / 90° intersecting the fiber; the curing temperature of the oven is, for example, 150 °C, lower than the glass transition temperature of the CFRP resin.

[0076] This invention primarily tests the core performance and CFR mechanical properties of the coating to form a quality closed loop, which can be achieved through an online performance testing unit. The testing unit may include: a coating adhesion tester, a porosity tester, a surface roughness tester, a high-temperature oxidation furnace (800℃ constant temperature), a tensile strength tester, etc. The specific testing methods are as follows:

[0077] 1. Coating adhesion test: The pull-off method (GB / T 5210-2006) is adopted, the equipment range is 1~20MPa, and a special CFRP fixture is used to test the interfacial adhesion between the coating and CFRP. The requirement is ≥5.5MPa.

[0078] 2. Porosity test: The Archimedes drainage method is used to test the porosity of the coating, which must be ≤0.5%;

[0079] 3. High-temperature oxidation test: Place the sample in a high-temperature oxidation furnace and oxidize at 800℃ for 500 hours. Test the weight loss rate of the CFRP matrix, which should be ≤0.1%.

[0080] 4. Mechanical Retention Rate Test: The tensile strength of the coated CFRP is tested using a tensile strength tester (GB / T 3354-2014), and the retention rate is required to be ≥95%.

[0081] 5. Surface defect detection: Visual inspection and microscopic observation (50x magnification) are used. The coating is required to be free of cracks and the pinhole defect rate is ≤1%. In addition, the surface roughness Ra is detected by a roughness tester in this embodiment of the invention.

[0082] Comprehensive performance testing process: Testing → Compliance → Finished product packaging → Finished product; Qualified products are selected to ensure they meet CFRP service requirements. All finished products that pass testing are wrapped with flexible foam, placed in scratch-resistant packaging boxes, and sealed for storage; this protects the integrity of the coating and ensures product delivery quality.

[0083] In addition to the seven core units mentioned above, the preparation system of this embodiment of the invention also includes three auxiliary modules, which are respectively designed for VOC processing, scratch-resistant transmission, and CFRP-specific central control.

[0084] Auxiliary module 1 is a VOC treatment module, which may include an activated carbon adsorption device and a condensation recovery tank. This embodiment of the invention does not use toxic solvents, only treating and recovering volatile alcohol components, achieving environmental compliance with VOC emissions ≤50mg / m3 after treatment. Auxiliary module 2 is a material transfer module, which may include: a high-temperature resistant conveyor belt with a temperature resistance of ≤200℃, the conveyor belt speed matching the process time of each unit; and a scratch-resistant material rack, such as a flexible rubber pad, to prevent scratches on the CFRP surface, thereby achieving damage-free transfer of workpieces between units. Auxiliary module 3 is a central control device, namely a PLC controller (connected to all unit temperature, pressure, and flow sensors), equipped with a touchscreen operating interface. It can preset plain / twill CFRP-specific parameter groups, supports one-click parameter recall, thereby achieving precise control of process parameters (error ≤±1%), and stores more than 10 sets of process parameters adapted to different CFRPs.

[0085] In a specific embodiment of the present invention, the output end of the raw material pretreatment unit is connected to the input end of the environmentally friendly slurry preparation unit via a material conveying pipe; the output end of the environmentally friendly slurry preparation unit is connected to the slurry inlet of the coating unit via a slurry conveying pump; the output end of the CFRP substrate-specific pretreatment unit is connected to the workpiece stage of the coating unit via an anti-scratch material rack; the output end of the coating unit is connected to the input end of the gradient temperature control high-temperature derivation unit via a high-temperature resistant conveyor belt; the output end of the gradient temperature control high-temperature derivation unit is connected to the input end of the fiber texture adaptation sealing unit; the output end of the fiber texture adaptation sealing unit is connected to the input end of the online performance testing unit; the qualified output end of the online performance testing unit is connected to the finished product storage area, and the unqualified output end is connected to the rework inlet of the fiber texture adaptation sealing unit via a return channel; the VOC treatment module is connected to the exhaust ports of the environmentally friendly slurry preparation unit, the coating unit, and the fiber texture adaptation sealing unit via pipelines; the central control device is connected to all units and auxiliary modules respectively via control lines to collect parameters such as temperature, pressure, flow rate, and coating amount in real time to achieve closed-loop control.

[0086] The process includes two quality control branches: sedimentation testing and performance testing. If the sedimentation stability test is passed, the next step is performed; otherwise, alcohol is added for redispersibility. All steps and systems are designed specifically for CFRP characteristics, eliminating the risk of matrix damage and requiring no high-pressure vacuum equipment. The central control unit has preset parameter sets for plain / twill CFRP, enabling efficient continuous production for ≤24 hours.

[0087] This invention provides a modified carbon fiber composite material, including an anti-peel silicon carbide coating obtained by the aforementioned preparation method. As a CFRP-based protective coating, the anti-peel silicon carbide coating not only possesses excellent properties, such as strong compatibility with CFRP, anti-peel properties, and dense durability, but also features mild preparation, simplified process, high environmental friendliness, and controllable cost.

[0088] The modified carbon fiber composite material has a protective coating porosity of ≤0.5% and a tensile strength retention rate of ≥95%, which can meet the requirements of coating anti-peeling, anti-oxidation, and mechanical protection in extreme environments.

[0089] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention. Unless otherwise specified, the materials used in the embodiments of this invention are commercially available products.

[0090] Example 1

[0091] Step 1, Raw material screening operation:

[0092] Select Si powder with a purity ≥99.9%; screen out Si powder with a particle size of 1~5μm through a grading sieve, remove fine powder <0.5μm and coarse powder >5μm, and set aside for later use.

[0093] Select boric acid (H3BO3, purity ≥99.5%), grind it in a grinder until the particle size is ≤1μm, and set aside for later use.

[0094] Low viscosity phenolic resin was selected (viscosity 120 mPa·s at 25℃, carbon residue 45%, total metal ion content ≤1 ppm).

[0095] Furthermore, anhydrous ethanol was added at a solid-liquid ratio of 1:20 by mass, and the mixture was stirred at 60°C and 500 rpm for 30 minutes in a phenolic resin dissolving vessel to obtain a phenolic resin-alcohol pre-sealing solution with a solid content of 5%; anhydrous ethanol was added at a solid-liquid ratio of 1:5 to obtain a phenolic resin-alcohol coating solution with a solid content of 15%, and these solutions were prepared separately.

[0096] Step 2, CFRP substrate-specific pretreatment procedures:

[0097] (1) Cleaning: Take a CFRP sample, plain weave, size 100mm×100mm×3mm, put it into an ultrasonic cleaning tank, add anhydrous ethanol + 5% isopropanol mixed solvent, ultrasonic cleaning at 300W for 15min to remove surface resin residue and oil stains; CFRP sample: density 1.78 g / cm³, tensile strength 1580 MPa, flexural strength 1320 MPa, elastic modulus 125 GPa.

[0098] (2) Drying: Take out the sample and put it into a low temperature oven, dry at 120°C for 2 hours, and then cool to room temperature;

[0099] (3) Plasma activation: The dried CFRP is placed in a plasma cleaner, argon gas is introduced (flow rate 0.5L / min), and the treatment is carried out at 300W power for 8min to introduce active functional groups such as -OH and -COOH on the surface;

[0100] (4) Pre-sealing: Using an ultrasonic atomizing pre-sealing sprayer, the 5% solid content phenolic resin-alcohol solution prepared in step 1 is uniformly sprayed onto the CFRP surface at a spraying rate of 50 mL / min and cured at 100℃ for 30 min to fill the fiber gaps and resin micropores.

[0101] (5) Surface fine adjustment: Lightly grind the pre-sealed CFRP surface with 2000-grit sandpaper and use a roughness tester to ensure Ra=1.2~1.8μm.

[0102] Step 3, Preparation of Environmentally Friendly Slurry:

[0103] (1) Ingredients: Add the Si powder screened in step 1 to the mixing tank of the environmental slurry preparation unit, add the coating solution at a mass ratio of Si powder to 15% phenolic resin-alcohol solution of 1:3, and add the ground boric acid at a mass ratio of 1.5% of the Si powder.

[0104] (2) Preliminary dispersion: Turn on the mechanical stirrer and stir at 800 rpm for 60 min to make boric acid evenly mixed in the resin-alcohol system;

[0105] (3) Dual-frequency ultrasound dispersion: First turn on the 20kHz low-frequency ultrasound and treat with 300W for 20 minutes, then switch to the 40kHz high-frequency ultrasound and treat with 300W for 20 minutes.

[0106] Stability test: Take 500mL of slurry and inject it into a graduated measuring cylinder. Let it stand at 25±5℃ for 30min. Calculate the sedimentation rate according to the formula "Sedimentation rate = Volume of upper clear liquid / Initial volume × 100%". If the sedimentation rate is ≤1%, it is qualified. If it is not qualified, add 5% anhydrous ethanol (0.5%~2% of the total mass of slurry) and repeat high-frequency sonication for 10min until it is qualified.

[0107] Viscosity control: The viscosity of the slurry was measured using a Forte 4 cup viscometer and adjusted to 250±20 mPa·s (25℃) to obtain the slurry; the agglomeration particle size was ≤5μm.

[0108] Step 4: "Thin Coating Multiple Times" and Air Bubble Removal Procedure:

[0109] (1) Fixing the workpiece: Fix the CFRP substrate sample after the pretreatment in step 2 on the coating worktable to ensure that the surface is level;

[0110] (2) First thin coat: The spraying mode of the coating equipment is adopted, the nozzle diameter of the spray gun is 1.0 mm, the spraying pressure is 0.3 MPa, and the coating amount is 175 g / m. 2 (Approximately 80μm thick), sprayed along the CFRP fiber direction;

[0111] (3) First rolling: Immediately use a ceramic roller (pressure 0.2MPa, speed 30rpm) to gently roll along the fiber direction to remove air bubbles inside the coating;

[0112] (4) Second thin coat: After a 10-minute interval, once the first coat of slurry has initially set, adjust the spraying direction to be perpendicular to the fiber direction, and apply a coating amount of 175 g / m². 2 Total coating amount: 350g / m 2 The total thickness is approximately 160 μm;

[0113] (5) Second rolling: Roll the coating with a ceramic roller perpendicular to the fiber direction to remove air bubbles again and ensure that the coating is free of pinholes and depressions.

[0114] Step 5, Low-temperature curing and setting operation:

[0115] After rolling, the coated part is placed in a low-temperature curing oven and cured at 100℃ for 2 hours to allow the phenolic resin to cross-link and cure, forming a stable pre-coating that is not sticky and does not drip.

[0116] Step 6, Gradient Temperature Control High-Temperature Derivative Operation Procedures:

[0117] (1) Atmosphere replacement: Place the cured coated part into the atmosphere protection furnace of the gradient temperature control high temperature derivative unit, close the furnace door, and introduce nitrogen (N2, purity ≥99.99%) at a flow rate of 0.75L / min to replace the air in the furnace for 15min;

[0118] (2) Slow heating: Start the three-stage temperature control system and heat up to 1300℃ at a heating rate of 3℃ / min;

[0119] (3) Isothermal reaction: keep at 1300℃ for 3 hours;

[0120] (4) Medium temperature buffering and cooling: After the constant temperature is completed, the temperature is lowered to 800℃ at 3℃ / min, and kept constant for 1 hour. Then the temperature is lowered to room temperature at 3℃ / min. The boron-doped silicon carbide coated blank is then obtained.

[0121] Step 7, Preparation of Composite Sealing Agent:

[0122] Take the 5% solid content phenolic resin-alcohol solution prepared in step 1, add 5% mass fraction of nano-SiC (particle size 50nm, purity ≥99.9%), put it into a nano-SiC dispersion vessel, and ultrasonically disperse it at 40kHz for 20min to ensure uniform dispersion of nano-SiC.

[0123] The viscosity of the sealing agent was tested and adjusted to 100±10 mPa·s (25℃) to obtain the phenolic resin-nano SiC composite sealing agent.

[0124] Step 8, Fiber Texture Adaptive Sealing Operation:

[0125] (1) Surface polishing: Use 2000-grit sandpaper to lightly polish the surface of the coated blank by hand to remove small protrusions and residual impurities, so that the surface Ra≤0.2μm;

[0126] (2) Cross-spraying sealing: Using a cross-spraying equipment with fiber texture adapted to sealing unit, the composite sealing agent prepared in step 7 is uniformly sprayed onto the coating surface. The first spray is along the fiber direction, with a spraying pressure of 0.2 MPa, a droplet size of 5~10 μm, and a spraying amount of 50 mL / min. After an interval of 15 min, the second spray is perpendicular to the fiber direction with the same parameters.

[0127] (3) Low temperature curing: Place the sealed workpiece in an oven and cure at 150°C for 2 hours to form a sealed pore layer.

[0128] The performance was tested according to the methods described above, and the finished product performance is as follows: interfacial bonding strength between coating and substrate (cross-cut tensile test): 5.6 MPa; CFRP substrate mechanical property retention rate: 95.2%; high-temperature oxidation weight loss rate (550℃ air, heat preservation for 8 h): 0.09%; coating porosity (SEM cross-sectional image method): 0.42%; coating surface crack and pinhole defect rate: 0.8%. Furthermore, the slurry settling rate after 30 min was 0.85%; the measured viscosity of the coating at 25℃ was 248 mPa·s; surface roughness (after sealing): Ra = 0.18 μm; after 100 cycles of high-temperature thermal shock, the coating showed no peeling or cracking.

[0129] Example 2

[0130] The process flow is basically the same as in Example 1, but there are the following differences:

[0131] The CFRP matrix is ​​made of twill woven carbon fiber composite material, and the sample size is still 100 mm × 100 mm × 3 mm.

[0132] In the preparation of the environmentally friendly slurry, the amount of boric acid added was adjusted to 1% of the mass of Si powder (1.5% in Example 1).

[0133] The solid content of the phenolic resin coating solution was adjusted to 10% (15% in Example 1).

[0134] In the gradient temperature control high-temperature derivation stage, the constant temperature reaction temperature was adjusted to 1200℃ and kept at a constant temperature for 3 hours. The other heating, cooling and medium-temperature buffer parameters were the same as in Example 1.

[0135] Performance test results: interfacial bonding strength 5.2 MPa; 550℃ air atmosphere insulation for 8 hours, high temperature oxidation weight loss rate 0.15%; coating porosity 0.50%; slurry settling rate ≤1% after standing at 25℃ for 30 min; coating surface is smooth, without obvious cracks or continuous pinholes, and still has excellent anti-peeling and high temperature protection performance, meeting the requirements of working conditions.

[0136] Comparative Example 1

[0137] This comparative example uses a process of "simple plasma pretreatment + boric acid-free slurry + conventional derivatization", and the specific steps are as follows (unmentioned parts are the same as in Example 1):

[0138] CFRP matrix pretreatment (simplified version): Take the same plain-weave CFRP sample as in Example 1 (100mm×100mm×3mm, density 1.75g / cm³). 3 (Tensile strength 1500MPa) Only "anhydrous ethanol ultrasonic cleaning for 15min → drying at 120℃ for 2h → argon plasma activation (flow rate 0.5L / min, power 200W, time 5min)" was performed, omitting the phenolic resin pre-sealing step and surface polishing fine-tuning. The substrate surface roughness Ra=0.8~1.0μm. No pre-sealing, no polishing, and the roughness is too low.

[0139] Slurry preparation (boric acid-free system): No boric acid was added during the preparation. Only Si powder and 15% solid content phenolic resin coating solution (consistent with Example 1) were added. The dispersion process was the same as in Example 1. Boron-free doped slurry was prepared with a viscosity of 245 mPa·s at 25°C and a sedimentation rate of ≤1%.

[0140] Coating, curing, and sealing process: Same as in Example 1 (double cross-spraying, curing at 100℃ for 2 hours, and sealing with phenolic resin-nano SiC).

[0141] High-temperature derivatization process: Same as in Example 1 (1300℃ constant temperature for 3 hours, nitrogen protection, gradient temperature rise and fall).

[0142] Performance test results: interfacial bonding strength 3.8 MPa; 550℃ air atmosphere insulation for 8 hours, high temperature oxidation weight loss rate 0.35%; coating porosity 1.20%; after 50 high temperature thermal shocks, obvious micro-cracks appeared at the coating edge, and after 100 thermal shocks, local peeling and cracking occurred; the uniformity of slurry dispersion is acceptable, but there are tiny gaps at the interface between the coating and the substrate.

[0143] As can be seen from the above embodiments, in order to address the problems of weak interfacial bonding and slurry penetration caused by the inertness and numerous micropores of CFRP surfaces, the embodiments of the present invention achieve a strong bonding advantage of ≥5.5MPa interfacial bonding force by pre-treating CFRP and combining it with BC covalent bonds formed by boron doping and a composite transition layer. The CFRP substrate and SiC coating are efficiently adapted, effectively solving the problems of high-temperature cyclic peeling.

[0144] To address coating cracking caused by thermal expansion mismatch, the gradient boron doping and temperature-controlled derivation strategy in this embodiment of the invention allows for a smooth transition of the thermal expansion coefficient and full release of thermal stress, reducing the coating cracking rate to 0%. At the same time, it takes into account the high-temperature sensitivity of CFRP, ensuring that both the derivation temperature and curing temperature avoid the matrix damage range, thus guaranteeing a tensile strength retention rate of ≥95%.

[0145] Furthermore, the dual-frequency ultrasonic dispersion system using alcohol as an environmentally friendly solvent in this invention not only solves the environmental hazards of traditional toxic solvents but also achieves uniform dispersion of Si powder and boric acid. The synergistic effect of the "thin-coat multiple layers + cross-sealing" coating process and the composite sealing agent fills the gaps between CFRP fibers and the micropores of the coating, resulting in a porosity of ≤0.5% and a defect rate of ≤1%, significantly improving the reliability of protection. Simultaneously, the one-step high-temperature derivatization process in this invention replaces multiple cycles, shortening the production cycle to ≤24 hours, thus meeting the requirements of both efficient preparation and large-scale application.

[0146] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention. The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of various ranges, the endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for producing an anti-stripping silicon carbide coating, characterized by, Includes the following steps: S1. Silicon powder, phenolic resin and boric acid are mixed and dispersed in a solvent to form a slurry; the mass ratio of boric acid to silicon powder is 1~2:

100. Carbon fiber composites are activated by plasma to introduce active functional groups containing hydroxyl and carboxyl groups on the surface, resulting in a CFRP pretreated substrate. S2. The slurry is coated onto a CFRP pretreated substrate to obtain a coated part, and then cured. S3. Under a protective atmosphere, the cured coated part is subjected to high-temperature derivatization at 1200~1400℃ to achieve SiC phase generation and boron reactive doping, thereby obtaining a boron-doped anti-peeling silicon carbide coating.

2. The production method according to claim 1, characterized by, In step S1, the solvent is anhydrous ethanol; the boric acid has a particle size ≤1μm, the silicon powder has a particle size of 1~5μm, and the slurry has a viscosity of 230~270mPa·s at 25℃.

3. The preparation method according to claim 1, characterized in that, In step S1, the plasma activation is achieved by argon plasma cleaning, with an argon flow rate of 0.1~1L / min and a processing power of 300-500W.

4. The production method according to any one of claims 1 to 3, characterized by, In step S1, after plasma activation, the process further includes: pre-sealing the pores of the carbon fiber composite material with phenolic resin, and then grinding the surface of the pre-sealed material to obtain a CFRP pretreated substrate with a roughness of 1.2~1.8μm.

5. The preparation method according to any one of claims 1-3, characterized in that, In step S2, the slurry is first thinly coated on the CFRP pretreated substrate and air bubbles are removed by rolling. The remaining slurry is used for a second thin coat to obtain a coated part with a wet coating. The coating direction of the first thin coating and the second thin coating is different; the total coating amount of the coating member is 300-450 g / m 2 , and the wet coating thickness is 150-170 μm.

6. The preparation method according to claim 5, characterized in that, In step S2, the curing process is a low-temperature constant-temperature curing and shaping process at 80~110℃ for 1~3 hours.

7. The method of any one of claims 1-3, wherein, Step S3 includes: placing the cured coated part into a high-temperature derivation unit with an atmosphere protection device, introducing a protective atmosphere, and gradually heating it from room temperature to 1400°C at a heating rate of 1~5°C / min, reacting at a constant temperature to achieve SiC phase generation and boron reactive doping, and then buffering and cooling it at 600~800°C to obtain a boron-doped anti-peeling silicon carbide coating.

8. The method of any one of claims 1-3, wherein, The high-temperature derivatization in step S3 further includes: A boron-doped, peel-resistant silicon carbide coating is obtained by cross-spraying and curing a composite sealing agent to form a sealed pore layer; the composite sealing agent includes phenolic resin and nano-silicon carbide.

9. The preparation method according to claim 8, characterized in that, The droplet size of the cross-sprayed composite sealing agent is 5~10μm; the curing temperature for forming the sealed pore layer is 140~150℃.

10. A modified carbon fiber composite material, characterized by, Including the anti-peeling silicon carbide coating obtained by the preparation method according to any one of claims 1-9.

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