A method for preparing a carbon fiber composite material with a gradient coating on the surface

Abstract

This invention discloses a method for preparing a carbon fiber composite material with a gradient coating on its surface, comprising: selecting a resin-based carbon fiber composite material as a substrate, and sequentially performing degreasing, roughening, and activation treatments on the substrate; subsequently performing a degassing treatment on the substrate; immersing the degassed substrate in a plating solution to form a Cu-Ni alloy gradient layer with a radially varying nickel content on the substrate surface; selecting copper as the plating material and preparing a copper film on the surface of the Cu-Ni alloy gradient layer; and performing an anti-oxidation treatment on the substrate with the Cu-Ni alloy gradient layer and the copper film to obtain a carbon fiber composite material with a gradient coating on its surface. This invention, by depositing a composite functional layer containing a Cu-Ni gradient layer and a pure copper layer on the surface of the carbon fiber composite material, alleviates interfacial thermal stress caused by the mismatch of thermal expansion coefficients, thereby significantly improving the bonding strength and long-term stability of the coating under extreme working conditions, and effectively suppressing gas release and dust generation behavior under stray light irradiation.

Description

Technical Field

[0001] This invention belongs to the field of optical system cleanliness control and material surface modification technology. More specifically, this invention relates to a method for preparing a carbon fiber composite material with a gradient coating on the surface, which is particularly suitable for applications in high-power laser devices and space optical payloads that have stringent requirements for optical cleanliness. Background Technology

[0002] In high-power laser systems and other next-generation high-precision optical systems, the release of contaminants caused by stray light irradiation of carbon fiber composite materials is one of the core bottlenecks leading to performance degradation of optical components and decreased system reliability. Carbon fiber composite materials, due to their high strength and lightweight properties, have become one of the core structural materials for high-power laser systems. However, the material itself has limited thermal conductivity, making it prone to localized overheating under stray light irradiation. Overheating inevitably generates particulate contaminants, which contaminate optical components, reduce their optical performance, and in severe cases, cause high-power laser system malfunctions.

[0003] To address the stray light temperature rise problem in carbon fiber composite materials in high-power laser systems, conventional surface treatment techniques either fail to achieve rapid heat dissipation due to insufficient thermal conductivity, or only adjust surface roughness to alter light absorption characteristics, offering limited suppression of temperature rise and potentially inducing surface structural defects. While some coating techniques attempt to use metal films, they fail to balance film uniformity and environmental oxidation resistance, leading to easy film detachment and rapid degradation of heat dissipation performance. Alternatively, a metal film can be directly applied to the carbon fiber surface, but due to the large film area and the common use of riveting, structural instability and uneven film thickness can occur, making it unsuitable for the complex operating environment of high-power laser systems, such as high dynamic mechanical loads and alternating low pressure and high vacuum.

[0004] To address the aforementioned issues, a functional film layer with both high thermal conductivity and stray light energy diffusion capability needs to be constructed on the surface of carbon fiber composites. Copper-based materials, due to their excellent thermal and electrical conductivity, are a potential choice. Compared to brass, cupronickel, and bronze, copper has the best electrical and thermal conductivity, excellent ductility, and is easy to prepare into a uniform film layer through chemical processes. Furthermore, it can rapidly conduct heat to the entire material surface under stray light irradiation, transforming a point heat source into a surface heat source, avoiding localized overheating, and thus preventing gas release and dust generation. Therefore, it is one of the optimal choices for surface modification of carbon fiber composites. Thus, there is an urgent need to propose a clean pretreatment method for carbon fiber composites that can ensure the laser damage resistance of optical components, which is of significant practical importance for extending the service life of optical systems. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0006] To achieve these and other advantages according to the present invention, the present invention provides a method for preparing a carbon fiber composite material with a gradient coating on its surface, comprising the following steps: Step 1: Select resin-based carbon fiber composite material as the substrate, and perform degreasing, roughening, and activation treatments on the substrate in sequence to form catalytic active sites on the substrate surface; then perform degassing treatment on the substrate. Step 2: Immerse the degassed substrate in the plating solution and form a Cu-Ni alloy gradient layer with a radially varying nickel content on the substrate surface using a chemical deposition method. Step 3: Select copper as the coating material and prepare a copper film on the surface of the Cu-Ni alloy gradient layer. Achieve uniform coverage of the copper film on the surface of the Cu-Ni alloy gradient layer through chemical reaction, and control the film thickness to be a thin coverage. Step 4: The substrate with Cu-Ni alloy gradient layer and copper film is subjected to copper film quality inspection. After passing the inspection, it is subjected to anti-oxidation treatment to obtain carbon fiber composite material with gradient coating on the surface.

[0007] Preferably, in step one, degreasing refers to immersing the substrate in an alkaline degreasing solution at 58-62°C for 10-20 minutes to remove oil and organic impurities, then rinsing with running deionized water until neutral and pre-drying at 30-50°C for 5-15 minutes; the alkaline degreasing solution comprises: 40-60 g / L sodium hydroxide, 20-40 g / L sodium carbonate, and 10-30 g / L trisodium phosphate; Roughening refers to immersing the degreased substrate in a room-temperature acidic roughening solution for 5-10 minutes for etching, followed by neutralizing manganese ions with 25-30 g / L oxalic acid, with periodic turning to ensure uniformity. Subsequently, it is rinsed with plenty of deionized water for more than 5 minutes until neutral. If there are any residues, it can be briefly immersed in 1-10 wt% hydrochloric acid for neutralization. The acidic roughening solution includes 50-80 g / L potassium permanganate and 60-80 g / L sodium hydroxide. Activation refers to immersing the roughened substrate in a room temperature palladium salt activation solution for 1-5 minutes to deposit palladium nuclei. After removal, the substrate is quickly rinsed with deionized water 1-3 times to keep the surface of the substrate moist before proceeding to subsequent processing. The palladium salt activation solution includes 1-3 g / L palladium chloride and 40-60 mL / L hydrochloric acid. Degassing treatment includes: placing the carbon fiber composite material in 10 -3 Placed in a vacuum chamber at an ambient temperature of 60-80°C for 1-3 days.

[0008] Preferably, in step two, the plating solution contains 5-15 g / L copper sulfate, 10-30 g / L nickel sulfate, 20-40 g / L sodium hypophosphite, and 50-80 g / L sodium citrate, and the pH of the plating solution is adjusted to 8.5-10.5. By programmatically controlling the composition of the plating solution or the deposition parameters, the nickel content in the deposited layer gradually decreases from the carbon fiber surface to the outside. Specifically, the change in nickel content means that the percentage of Ni atoms near the substrate is 30%-60%, the percentage of Ni atoms away from the carbon fiber surface drops to below 5%, and the Ni content in the middle region shows a continuous decrease.

[0009] Preferably, in step two, the Cu-Ni alloy gradient layer is deposited on the substrate surface using a step-by-step solution exchange method, that is, different Ni / Cu ratios of plating solutions are used in sequence for step-by-step deposition to form a multi-layer structure, and the nickel content of each layer decreases sequentially, that is, the molar ratio of Ni to Cu in the plating solution decreases from 3:1 to 1:1, and finally to 1:3.

[0010] Preferably, in step two, the total thickness of the Cu-Ni alloy gradient layer is 0.5~3μm.

[0011] Preferably, in step three, the copper salt raw material used to prepare the electroless copper plating solution has a copper purity >99.95%, and during the plating process, Cu... 2+ The ions exist in the solution and are eventually reduced and deposited on the surface of the Cu-Ni alloy gradient layer as a high-purity solid copper film.

[0012] Preferably, in step three, the thickness of the copper film is 1~2μm, and the surface roughness of the copper film is between 2.58±0.04μm and 3.96±0.24μm.

[0013] Preferably, in step three, the specific method for depositing a copper film on the surface of the Cu-Ni alloy gradient layer includes: preparing a weakly alkaline, low-concentration plating solution with a pH of 10.5~11.0, and depositing the film at room temperature for 8~15 minutes using formaldehyde as a reducing agent and a palladium activation layer as a catalyst through an electrochemical reaction, while simultaneously introducing air and stirring to form a copper film with a thickness of 1~2 μm; wherein the weakly alkaline, low-concentration plating solution includes 15~20 g / L copper sulfate and 40~50 g / L sodium citrate.

[0014] Preferably, in step four, the antioxidant treatment includes a cleaning process, a polishing process, and a passivation process; wherein, the cleaning process includes: mixing limonene and deionized water at a volume ratio of 1:10~30 to obtain a cleaning solution, pouring the cleaning solution into an ultrasonic cleaning tank, placing the substrate with the Cu-Ni alloy gradient layer and copper film in the cleaning solution, heating the cleaning solution to 40~60℃, ultrasonically cleaning for 10~30 minutes, and then rinsing it clean with deionized water. The polishing process includes: polishing the copper in a polishing solution for 1-3 minutes, rinsing it clean, then immersing it in a stripping solution for 3-5 seconds, removing it and rinsing it clean; wherein the polishing solution is obtained by mixing hydrogen peroxide and deionized water in a volume ratio of 1:1-3, and the stripping solution is a 100-150g / L citric acid aqueous solution. The passivation process includes: placing the substrate with the Cu-Ni alloy gradient layer and the copper film in a chromium-free passivating agent for 10-15 minutes or more to form a dense passivation film with good chemical stability on the surface of the copper film; then removing the substrate, rinsing it clean, and drying it.

[0015] Preferably, the process also includes performance verification of the anti-oxidation treated samples by measuring their surface temperature rise through a 1064nm continuous laser irradiation experiment. Samples treated with different chemical processes and unplated raw carbon fiber samples are compared pairwise under the following conditions: stray laser power density of 1.27 W / cm². 2 and 52.92W / cm 2 The surface temperature change of carbon fiber composite material was tested at a wavelength of 1064 nm.

[0016] The present invention includes at least the following beneficial effects: The purpose of the present invention is to provide a method for preparing carbon fiber composite material with a gradient coating on the surface. By coating a composite functional layer containing a Cu-Ni gradient layer and a pure copper layer on the surface of carbon fiber, the interfacial thermal stress caused by the mismatch of thermal expansion coefficients is relieved, thereby significantly improving the bonding strength and long-term stability of the coating under extreme working conditions, thereby effectively suppressing the gas release and dust generation behavior under stray light irradiation.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0018] Figure 1 This is a process flow diagram for preparing carbon fiber composite materials with gradient coatings on the surface; Figure 2 A surface morphology image of carbon fiber before copper plating; Figure 3The images show the surface morphology of carbon fiber after being plated with copper using different chemical processes. Figure 4 This is a comparison chart showing the temperature rise of copper blocks with different surface roughness under different laser intensities. Figure 5 A comparison of temperature rise on the surface of a reflector under different light intensities using different processes; Figure 6 The surface temperature distribution of carbon fibers under different light intensities and processes is shown. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0020] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof. Example 1 like Figure 1 As shown, a method for preparing a carbon fiber composite material with a gradient coating on its surface includes the following steps: Step 1: First, perform substrate pretreatment and degassing synergistic treatment. After selecting resin-based carbon fiber composite material, complete the chemical plating pretreatment in sequence, including degreasing, roughening, and activation. The process involves several steps: Degreasing, immersing the substrate in an alkaline degreasing solution (containing 50 g / L sodium hydroxide, 30 g / L sodium carbonate, and 20 g / L trisodium phosphate) at 60 ± 2°C for 15 minutes to remove oil and organic impurities, rinsing with running deionized water until neutral, and pre-drying at 40°C for 10 minutes; Roughening, immersing the degreased substrate in a room-temperature acidic roughening solution (containing 60 g / L potassium permanganate and 70 g / L sodium hydroxide alkaline roughening solution) for 8 minutes, neutralizing manganese ions with 28 g / L oxalic acid, turning it regularly to ensure uniformity, rinsing with plenty of deionized water for at least 5 minutes until neutral, and briefly immersing in 5% hydrochloric acid if any residue remains; and Activation, immersing the roughened substrate in a room-temperature palladium salt activation solution (2 g / L palladium chloride + 50 mL / L hydrochloric acid) for 3 minutes to deposit palladium nuclei, rinsing twice quickly with deionized water to keep the substrate surface moist, and then transferring it to subsequent processing. By roughening the microstructure to create a rough, uneven surface, the adhesion of the film is enhanced, providing uniform active sites for copper plating. Simultaneously, the pretreated substrate is fixed in a vacuum chamber and subjected to [a process] at 10 [units of temperature]. -3 Under vacuum of 100 Pa and continuous degassing at 70°C for 2 days, residual gaseous contaminants and moisture in the pores of the substrate are thoroughly removed. This combined treatment solves the problem of film defects caused by contaminants inside the substrate in traditional processes, laying the foundation for subsequent uniform copper plating.

[0021] Step 2: Construction of the Cu-Ni alloy gradient layer. A multi-layer step method was used to construct the Cu-Ni gradient layer. Three different Ni / Cu ratio plating solutions were prepared, with the specific compositions and ratios as follows: The pretreated carbon fiber samples were sequentially immersed in plating solutions A, B, and C, and deposited at 65°C for 5 minutes in each solution. Before each change of plating solution, the sample surface was gently rinsed with deionized water to avoid cross-contamination. After deposition, a three-layer Cu-Ni alloy gradient layer was obtained. The first layer, closest to the carbon fiber surface, has a Ni content of approximately 45% and a thickness of approximately 0.8 μm. The second layer, built upon the first layer, has a Ni content of approximately 20% and a thickness of approximately 0.7 μm. The outermost third layer has a Ni content of approximately 8% and a thickness of approximately 0.7 μm.

[0022] Step 3: Prepare a copper film using chemical deposition. The surface morphology of the carbon fiber surface before copper deposition is shown in the attached figure. Figure 2 The surface morphology of copper after being plated using different chemical processes is shown in the attached figure. Figure 3 Using the NP-1 process, the degassed substrate is immersed in a customized plating solution containing 15±2 g / L copper sulfate, 45±5 g / L sodium citrate, 12±1 mL / L formaldehyde (HCHO), 8±1 g / L sodium hydroxide, and 0.2±0.1 g / L gelatin. The reaction temperature is controlled at 25±2℃, the pH of the plating solution is controlled at 11.0, the reaction time is controlled at 30±2 min, and the stirring rate is controlled at 100±20 r / min, so that copper ions are uniformly deposited under catalysis.

[0023] Combined with appendix Figure 4 It can be seen that when the film roughness is in the range of Ra=2.58±0.04μm to Ra=3.09±0.06μm, the laser power density applied to the copper surface reaches 52.92W / cm². 2 The maximum surface temperature rise was only 0.45℃, which is negligible compared to fluctuations in ambient temperature. This indicates that copper has high thermal conductivity, and different roughness values ​​have little effect on the surface temperature rise of copper. This roughness range ensures a tight bond between the film and the substrate without affecting the high thermal conductivity of copper.

[0024] Step 4: Conduct quality inspection of the copper film, and treat it with anti-oxidation after passing the inspection. A qualified copper film requires a film thickness controlled between 1 and 2 μm with a deviation ≤ ±0.5 μm, no defects such as pores or pinholes observed under a confocal microscope, and a strong bond between the film and the carbon fiber substrate. It should not detach after peeling and cyclic irradiation. First, ultrasonic cleaning removes minute impurities from the film surface, then polishing optimizes the film's smoothness. Finally, a chromium-free passivating agent is used to form a dense passivation film on the copper film surface. Compared to traditional single passivation treatment, this combined process not only improves the film's smoothness but also extends the anti-oxidation time by blocking the contact between copper elements and air and moisture through the passivation film.

[0025] The cleaning process includes: mixing limonene and deionized water at a volume ratio of 1:20 to obtain a cleaning solution; pouring the cleaning solution into an ultrasonic cleaning tank; placing the substrate with the Cu-Ni alloy gradient layer and copper film in the cleaning solution; heating the cleaning solution to 50°C; ultrasonically cleaning for 20 minutes; and rinsing it with deionized water after removal. The polishing process includes: polishing the copper in a polishing solution for 2 minutes, rinsing it clean, then immersing it in a stripping solution for 5 seconds, removing it and rinsing it clean; wherein the polishing solution is obtained by mixing hydrogen peroxide and deionized water in a volume ratio of 1:2, and the stripping solution is a 120g / L citric acid aqueous solution. The passivation process includes: placing the substrate with the Cu-Ni alloy gradient layer and the copper film into a chromium-free passivating agent (MS0407 chromium-free passivating agent for copper materials) for more than 15 minutes to form a dense passivation film with good chemical stability on the surface of the copper film; after removal, rinsing and drying.

[0026] Step 5: Verify the performance of the coated sample. The irradiation intensity is 1.27 W / cm². 2 and 52.92W / cm 2 The sample was continuously irradiated with laser light, and the following results were obtained: Figure 5 The temperature rise graph is shown. It can be seen from the graph that the copper treated with the NP-1 process performed best, reaching 52.92 W / cm². 2 The surface temperature rise under laser irradiation was only 6.57℃, which is better than that of KLY-1 and KM-0.5 under the same laser irradiation. In contrast, the temperature rise of the unplated copper sample exceeded 30℃ under 1.27W / cm² laser irradiation, indicating that this method can significantly alleviate the temperature rise problem. Figure 6 As shown, regardless of the chemical process used, the copper surface exhibits uniform color under both laser intensities, indicating that the point heat source can be successfully converted into a surface heat source.

[0027] This invention significantly reduces the temperature rise caused by stray light irradiation by forming a uniform copper coating on the surface of carbon fibers, thereby solving the problem of gas release and dust generation. At the same time, it increases the normal operating time of carbon fiber composite materials, providing reliable technical support for high-power laser systems.

[0028] Comparative Example 1 The difference between this comparative example and Example 1 is that in step two, only plating solution A is used to deposit a Cu-Ni alloy layer on the surface of the resin-based carbon fiber composite material. The process parameters for the remaining steps in this example are the same as those in Example 1.

[0029] The carbon fiber composite material prepared in this comparative example has a strength of 52.92 W / cm². 2 Under laser irradiation, the temperature rise of the copper surface was 18.69±1.25℃.

[0030] Comparative Example 2 The difference between this comparative example and Example 1 is that in step two, only plating solution B is used to deposit a Cu-Ni alloy layer on the surface of the resin-based carbon fiber composite material. The process parameters for the remaining steps in this example are the same as those in Example 1.

[0031] The carbon fiber composite material prepared in this comparative example has a strength of 52.92 W / cm². 2 Under laser irradiation, the temperature rise of the copper surface was 13.08±0.97℃.

[0032] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0033] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a carbon fiber composite material with a gradient coating on its surface, characterized in that, Includes the following steps: Step 1: Select resin-based carbon fiber composite material as the substrate, and perform degreasing, roughening, and activation treatments on the substrate in sequence to form catalytic active sites on the substrate surface; then perform degassing treatment on the substrate. Step 2: Immerse the degassed substrate in the plating solution and form a Cu-Ni alloy gradient layer with a radially varying nickel content on the substrate surface using a chemical deposition method. Step 3: Select copper as the coating material and prepare a copper film on the surface of the Cu-Ni alloy gradient layer. Achieve uniform coverage of the copper film on the surface of the Cu-Ni alloy gradient layer through chemical reaction, and control the film thickness to be a thin coverage. Step 4: The substrate with Cu-Ni alloy gradient layer and copper film is subjected to copper film quality inspection. After passing the inspection, it is subjected to anti-oxidation treatment to obtain carbon fiber composite material with gradient coating on the surface.

2. The method for preparing carbon fiber composite material with a gradient coating on the surface as described in claim 1, characterized in that, In step one, degreasing refers to immersing the substrate in an alkaline degreasing solution at 58-62°C for 10-20 minutes to remove oil and organic impurities, then rinsing it with running deionized water until neutral and pre-drying it at 30-50°C for 5-15 minutes. The alkaline degreasing solution comprises: 40~60g / L sodium hydroxide, 20~40g / L sodium carbonate, and 10~30g / L trisodium phosphate; Roughening refers to immersing the degreased substrate in a room-temperature acidic roughening solution for 5-10 minutes for etching, followed by neutralizing manganese ions with 25-30 g / L oxalic acid, with periodic turning to ensure uniformity. Subsequently, it is rinsed with plenty of deionized water for more than 5 minutes until neutral. If there are any residues, it can be briefly immersed in 1-10 wt% hydrochloric acid for neutralization. The acidic roughening solution includes 50-80 g / L potassium permanganate and 60-80 g / L sodium hydroxide. Activation refers to immersing the roughened substrate in a room temperature palladium salt activation solution for 1-5 minutes to deposit palladium nuclei. After removal, the substrate is quickly rinsed with deionized water 1-3 times to keep the surface of the substrate moist before proceeding to subsequent processing. The palladium salt activation solution includes 1-3 g / L palladium chloride and 40-60 mL / L hydrochloric acid. Degassing treatment includes: placing the carbon fiber composite material in 10 -3 Placed in a vacuum chamber at an ambient temperature of 60-80°C for 1-3 days.

3. The method for preparing the carbon fiber composite material with a gradient coating on the surface as described in claim 1, characterized in that, In step two, the plating solution contains 5-15 g / L copper sulfate, 10-30 g / L nickel sulfate, 20-40 g / L sodium hypophosphite, and 50-80 g / L sodium citrate, and the pH of the plating solution is adjusted to 8.5-10.

5. By programmatically controlling the composition of the plating solution or the deposition parameters, the nickel content in the deposited layer gradually decreases from the carbon fiber surface to the outside. Specifically, the change in nickel content means that the percentage of Ni atoms near the substrate is 30%-60%, the percentage of Ni atoms on the side away from the carbon fiber surface drops to below 5%, and the Ni content in the middle region shows a continuous decrease.

4. The method for preparing the carbon fiber composite material with a gradient coating on the surface as described in claim 1, characterized in that, In step two, the Cu-Ni alloy gradient layer is deposited on the substrate surface using a step-by-step solution exchange method. That is, different Ni / Cu ratios of plating solutions are used in sequence for step-by-step deposition to form a multi-layer structure. The nickel content of each layer decreases sequentially, that is, the molar ratio of Ni to Cu in the plating solution decreases from 3:1 to 1:1, and finally to 1:

3.

5. The method for preparing the carbon fiber composite material with a gradient coating on the surface as described in claim 1, characterized in that, In step two, the total thickness of the Cu-Ni alloy gradient layer is 0.5~3μm.

6. The method for preparing the carbon fiber composite material with a gradient coating on the surface as described in claim 1, characterized in that, In step three, the copper salt raw material used to prepare the electroless copper plating solution has a copper purity >99.95%, and during the plating process, Cu... 2+ The ions exist in the solution and are eventually reduced and deposited on the surface of the Cu-Ni alloy gradient layer as a high-purity solid copper film.

7. The method for preparing the carbon fiber composite material with a gradient coating on the surface as described in claim 1, characterized in that, In step three, the thickness of the copper film is 1~2μm, and the surface roughness of the copper film is between 2.58±0.04μm and 3.96±0.24μm.

8. The method for preparing the carbon fiber composite material with a gradient coating on the surface as described in claim 1, characterized in that, In step three, the specific method for depositing a copper film on the surface of the Cu-Ni alloy gradient layer includes: preparing a weakly alkaline, low-concentration plating solution with a pH of 10.5~11.0; using formaldehyde as a reducing agent and a palladium activation layer as a catalyst, depositing the copper film at room temperature for 8~15 minutes with air introduced and stirring to form a copper film with a thickness of 1~2 μm; wherein the weakly alkaline, low-concentration plating solution includes 15~20 g / L copper sulfate and 40~50 g / L sodium citrate.

9. The method for preparing the carbon fiber composite material with a gradient coating on the surface as described in claim 1, characterized in that, In step four, the antioxidant treatment includes a cleaning process, a polishing process, and a passivation process. The cleaning process includes: mixing limonene and deionized water at a volume ratio of 1:10~30 to obtain a cleaning solution; pouring the cleaning solution into an ultrasonic cleaning tank; placing the substrate with the Cu-Ni alloy gradient layer and copper film in the cleaning solution; heating the cleaning solution to 40~60℃; ultrasonically cleaning for 10~30 minutes; and rinsing it with deionized water after removal. The polishing process includes: polishing the copper in a polishing solution for 1-3 minutes, rinsing it clean, then immersing it in a stripping solution for 3-5 seconds, removing it and rinsing it clean; wherein the polishing solution is obtained by mixing hydrogen peroxide and deionized water in a volume ratio of 1:1-3, and the stripping solution is a 100-150g / L citric acid aqueous solution. The passivation process includes: placing the substrate with the Cu-Ni alloy gradient layer and the copper film in a chromium-free passivating agent for 10-15 minutes or more to form a dense passivation film with good chemical stability on the surface of the copper film; then removing the substrate, rinsing it clean, and drying it.

10. The method for preparing a carbon fiber composite material with a gradient coating on its surface as described in claim 1, characterized in that, This also includes performance verification of the antioxidant-treated samples, measuring the surface temperature rise through a 1064nm continuous laser irradiation experiment, and comparing samples treated with different chemical processes with uncoated raw carbon fiber samples pairwise. The test conditions were: stray laser power density of 1.27W / cm². 2 and 52.92W / cm 2 The surface temperature change of carbon fiber composite material was tested at a wavelength of 1064 nm.

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