A method for preparing an integrated micro-arc oxidation layer on the surface of a SiC / Al composite material that is thermally conductive, insulating, and wear-resistant.

Abstract

This invention discloses a method for preparing an integrated thermally conductive, insulating, and wear-resistant micro-arc oxidation layer on the surface of a SiC / Al composite material, comprising the following steps: Step 1, pretreating the SiC-reinforced aluminum-based composite material substrate and preparing a micro-arc oxidation electrolyte; Step 2, adding an AlN dispersion to the micro-arc oxidation electrolyte to obtain a composite electrolyte; Step 3, immersing the pretreated SiC-reinforced aluminum-based composite material substrate as the anode in the composite electrolyte, using a stainless steel tank as the cathode, and performing micro-arc oxidation treatment using a bipolar pulse power supply; Step 4, post-treating the treated SiC-reinforced aluminum-based composite material substrate to obtain the SiC / Al composite material. This invention features improved coating uniformity and stability.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and more specifically, to a method for preparing an integrated micro-arc oxidation layer that is thermally conductive, insulating, and wear-resistant on the surface of a SiC / Al composite material. Background Technology

[0002] The battery system is typically located in the lower part of the vehicle during assembly, leaving the battery pack exposed or directly integrated into the frame and chassis. Therefore, during vehicle operation, the chassis inevitably comes into contact with water vapor, acid rain, various wastewater residues, chloride-containing de-icing agents, de-icing agents, mud, etc., leading to corrosion. It may also come into direct contact with ground protrusions or even scrape against them. All of these factors necessitate that the battery pack casing material possess excellent corrosion resistance and wear resistance to ensure the safety of the internal batteries. Heat dissipation and insulation are also considerations. Aluminum-based composite materials, as lightweight materials, are widely used in electric vehicle battery pack housings due to their excellent mechanical and processing properties. When used as electronic heat sinks, aluminum-based composite materials require excellent electrical insulation and high thermal conductivity on their surface, thus posing a significant challenge to surface modification technology.

[0003] Surface coating technology is one of the effective means to improve the surface properties of aluminum matrix composites. Among them, micro-arc oxidation technology is widely used in the surface modification of aluminum and aluminum alloy materials due to its advantages such as simple process, strong coating-substrate bonding and adjustable coating performance. This technology is based on ordinary anodizing. By applying high voltage, a micro-arc discharge phenomenon occurs on the substrate surface. The high temperature and high pressure environment generated during the discharge process causes complex physicochemical changes in the metal and electrolyte components on the substrate surface, thereby growing a thick and firmly bonded ceramic oxide layer in situ. However, the traditional micro-arc oxidation technology faces a key contradiction when used in SiC reinforced aluminum matrix composites: the alumina-based coating generated to obtain good insulation and protection properties generally has a low thermal conductivity, which seriously "shields" the high thermal conductivity advantage of the composite matrix and restricts its application in high-efficiency heat dissipation scenarios. Although existing research has tried to add hard particles such as SiO2 and ZrO2 to the electrolyte to improve the coating hardness or density, these particles have little effect on improving the thermal conductivity of the coating, and may even reduce the thermal conductivity by introducing more phonon scattering interfaces.

[0004] Aluminum nitride ceramics possess both extremely high thermal conductivity (theoretically up to 320 W / (m·K)) and excellent electrical insulation, making them ideal functional reinforcing phases. Introducing AlN particles into micro-arc oxidation coatings is expected to improve the coating's electrical insulation performance while maintaining good thermal conductivity, and may further optimize the coating's wear resistance. However, how to stably and uniformly introduce AlN particles into the micro-arc oxidation coating of SiC-reinforced aluminum matrix composites, and solve problems such as easy particle agglomeration in the electrolyte, weak bonding with the coating, and poor matching of process parameters, has become an urgent technical challenge to be solved. Summary of the Invention

[0005] The purpose of this invention is to design and develop a method for preparing an integrated micro-arc oxidation layer on the surface of SiC / Al composite materials that integrates thermal conductivity, insulation, and wear resistance. By adjusting the concentration of AlN functional particles, the synergistic optimization of insulation and thermal conductivity is achieved.

[0006] The technical solution provided by this invention is as follows:

[0007] A method for preparing an integrated thermally conductive, insulating, and wear-resistant micro-arc oxidation layer on the surface of a SiC / Al composite material includes the following steps:

[0008] Step 1: Pre-treat the SiC-reinforced aluminum matrix composite substrate and prepare the micro-arc oxidation electrolyte;

[0009] Step 2: Add the AlN dispersion to the micro-arc oxidation electrolyte to obtain a composite electrolyte;

[0010] Step 3: Immerse the pretreated SiC reinforced aluminum matrix composite substrate as the anode into the composite electrolyte, use a stainless steel tank as the cathode, and perform micro-arc oxidation treatment using a bipolar pulse power supply.

[0011] Step 4: Perform post-treatment on the treated SiC reinforced aluminum matrix composite substrate to obtain SiC / Al composite material.

[0012] Preferably, the preprocessing specifically includes:

[0013] SiC-reinforced aluminum matrix composite material was selected as the substrate and wet-ground until the surface was smooth. Then, it was washed with ethanol, ultrasonicated, washed with water and dried in sequence.

[0014] Preferably, step two further includes:

[0015] AlN particles need to be coated before dispersion.

[0016] Preferably, the coating process specifically includes:

[0017] Step 1: After calcining yttrium nitrate to remove the water of crystallization, dissolve it in anhydrous ethanol to prepare Yt. 3+A precursor solution with a concentration of 0.05 mol / L;

[0018] Step 2: Add AlN powder and polyethylene glycol to the precursor solution and form a uniform suspension under stirring conditions;

[0019] The target mass ratio of Y2O3 to AlN is 5:95;

[0020] Step 3: After ultrasonic treatment, the suspension is continuously mechanically stirred for 120 min to maintain dispersion stability;

[0021] Step 4: Prepare a mixed solution of ethylenediamine and ethanol at a mass ratio of 1:2 as a non-aqueous precipitant, and add it dropwise to the suspension at a rate of 1 drop every 3-5 seconds while continuously stirring, until the pH is adjusted to 9.3-9.5;

[0022] Step 5: After the above suspension is precipitated, the powder is obtained, and then washed with ethanol, dried and calcined in sequence to obtain AlN composite powder with uniform surface coating.

[0023] Preferably, the preparation process of the AlN dispersion is as follows:

[0024] AlN particles were dissolved in deionized water at a concentration of 4-8 g / L. The mixture was first magnetically stirred for 30 minutes, and then ultrasonically dispersed for 1 hour to obtain an AlN dispersion.

[0025] Preferably, the micro-arc oxidation electrolyte is:

[0026] 15 g / L sodium aluminate, 4 g / L sodium silicate and 1 g / L sodium hydroxide are dissolved in deionized water.

[0027] Preferably, the preparation process of the composite electrolyte is as follows:

[0028] An AlN dispersion was added to the micro-arc oxidation electrolyte, maintaining a volume ratio of 1:2 between the AlN dispersion and the micro-arc oxidation electrolyte, and the mixture was stirred to obtain a composite electrolyte.

[0029] Preferably, the micro-arc oxidation treatment specifically includes:

[0030] It adopts constant voltage mode, with a final operating voltage of 400-470V, a pulse frequency of 100-800Hz, a duty cycle of 10%-50%, and a processing time of 5 minutes.

[0031] Preferably, the post-processing specifically includes:

[0032] After the micro-arc oxidation process is completed, the substrate is removed and then washed and dried in sequence.

[0033] Preferably, the temperature of the micro-arc oxidation electrolyte is maintained at 20-40°C.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) The present invention designs and develops a method for preparing an integrated micro-arc oxidation layer for thermally conductive, insulating and wear-resistant SiC / Al composite material. Compared with the problems of easy hydrolysis of AlN particles and poor dispersibility in liquid systems in the prior art, by introducing a Y2O3 coating layer, on the one hand, a stable isolation interface can be formed on the surface of AlN particles, which can effectively inhibit the hydrolysis reaction caused by AlN contact with water, avoid particle failure and adverse effects on the electrolyte system; on the other hand, the introduction of the Y2O3 oxide layer improves the wettability of AlN particle surface, significantly reduces its floating tendency in liquid system, which is conducive to the uniform dispersion and stable existence of particles in subsequent micro-arc oxidation and pretreatment processes, and further ensures the uniformity and stability of coating performance.

[0036] (2) The method for preparing the integrated thermally conductive, insulating and wear-resistant micro-arc oxidation layer on the surface of SiC / Al composite material designed and developed in this invention is different from the blind addition of high-concentration functional particles in the prior art. Through systematic concentration gradient experiments, it was found that in the range of 4-8 g / L, the thermal conductivity and insulation performance of the coating increases synchronously with the increase of AlN concentration. When the concentration exceeds a certain critical value (such as >8 g / L), not only does the conductivity of the electrolyte change drastically, leading to process instability and easy defects in the film layer, but also the excessive particles in the coating form thermal resistance and defects, resulting in a decrease in overall performance. Therefore, this invention does not pursue simple high-concentration addition, but through experimental research, it has determined the AlN concentration that achieves the optimal synergy between insulation and thermal conductivity, thereby obtaining a coating with excellent performance while ensuring process stability.

[0037] (3) The present invention designs and develops a method for preparing an integrated micro-arc oxidation layer for thermally conductive, insulating, and wear-resistant SiC / Al composite materials. In the micro-arc oxidation process, AlN functional particles are introduced. The AlN particles are uniformly embedded in the micro-arc oxidation coating. Utilizing the excellent electrical insulation properties and high thermal conductivity of AlN, the prepared coating simultaneously possesses good electrical insulation properties (breakdown voltage ≥ 890V) and thermal conductivity properties (thermal conductivity ≥ 129 W·m). -1 ·K -1 This technology solves the technical challenge of the mutual constraint between the electrical insulation and thermal conductivity of existing coatings, meeting the application requirements of high-end fields such as electronic packaging. The uniformly dispersed AlN particles act as "micro-electrodes" or "discharge seeds" during micro-arc discharge, refining the discharge channel and promoting the formation of a denser, more uniform coating structure. This effectively reduces the porosity of the coating, thereby improving its wear resistance (reduced wear rate). Attached Figure Description

[0038] Figure 1 This is a SEM image of the composite material of Comparative Example 1 of the present invention.

[0039] Figure 2 This is a SEM schematic diagram of the composite material in Embodiment 2 of the present invention.

[0040] Figure 3 This is a bar chart showing the average friction coefficient and wear rate of the composite micro-arc oxidation layer prepared in Comparative Examples 1 and 2 and Examples 1-3 of the present invention.

[0041] Figure 4 This is a bar chart showing the breakdown voltage of the micro-arc oxidation layer of the composite material prepared in Comparative Examples 1 and 2 and Examples 1-3 of the present invention.

[0042] Figure 5 This is a columnar schematic diagram showing the thermal conductivity of the micro-arc oxidation layer of the composite material prepared in Comparative Examples 1 and 2 and Examples 1-3 of the present invention. Detailed Implementation

[0043] 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.

[0044] This invention provides a method for preparing an integrated micro-arc oxidation layer that is thermally conductive, insulating, and wear-resistant on the surface of a SiC / Al composite material, comprising the following steps:

[0045] Step 1: Pretreatment of SiC-reinforced aluminum matrix composite substrate:

[0046] SiC reinforced aluminum matrix composite material was selected as the substrate. The sample was wet-polished with sandpaper of 80#, 180#, 280#, 400#, 600#, 800# and 1200# in sequence until the surface was smooth and the surface cutting marks were removed. The polished sample was then placed in a 75% alcohol solution and sonicated for 10 min to remove surface oil. The sample was then rinsed with deionized water and dried with a hair dryer for later use.

[0047] Step 2: Prepare the micro-arc oxidation electrolyte and add the dispersed AlN particles to the micro-arc oxidation electrolyte to obtain a composite electrolyte;

[0048] The AlN particles selected were AlN particles with a particle size of 200 nm and a purity of 99.9%. They were added to deionized water and the concentration was controlled at 6 or 8 g / L. The mixture was first magnetically stirred for 30 minutes and then ultrasonically dispersed for 1 hour to obtain an AlN dispersion.

[0049] Weigh out 15 g / L sodium aluminate, 4 g / L sodium silicate, and 1 g / L sodium hydroxide, dissolve them in deionized water to obtain the micro-arc oxidation electrolyte, then add AlN dispersion to it, keeping the volume ratio of AlN dispersion to micro-arc oxidation electrolyte at 1:2, stir with a stirrer for 30 min to obtain the composite electrolyte;

[0050] In another embodiment, the amount of deionized water added can be increased or decreased proportionally according to the solubility of the raw materials.

[0051] Step 3: Immerse the pretreated SiC reinforced aluminum matrix composite substrate as the anode into the composite electrolyte, and use a stainless steel tank containing the composite electrolyte as the cathode to perform micro-arc oxidation treatment using a bipolar pulse power supply.

[0052] In this embodiment, the micro-arc oxidation treatment refers to the use of constant voltage mode, with a final working voltage of (400-470)V, a pulse frequency of (100-800)Hz, a duty cycle of 10%-50%, and a processing time of 5 minutes.

[0053] Step 4: Post-process the treated SiC reinforced aluminum matrix composite substrate:

[0054] After the micro-arc oxidation treatment is completed, the substrate is removed and then washed and dried in sequence to obtain a SiC / Al composite material with a high-performance micro-arc oxidation layer on the surface.

[0055] In step two, the AlN particles need to be coated before dispersion. Using AlN powder as a matrix, a Y2O3 coating layer is constructed on its surface using a non-aqueous precipitation-thermal decomposition method. The coating process is as follows:

[0056] Step 1: Calcine yttrium nitrate (Y(NO3)3·6H2O) at 260℃ for 30 min to remove water of crystallization, then dissolve it in anhydrous ethanol to prepare Y 3+ A precursor solution with a concentration of 0.05 mol / L;

[0057] Step 2: Measure 932 mL of precursor solution, add 100 g of AlN powder and 17.8 g of polyethylene glycol (PEG), and form a uniform suspension system under stirring conditions, in which PEG plays the role of dispersing and stabilizing particles;

[0058] Based on the stoichiometric relationship of complete conversion of yttrium nitrate to Y2O3, the target mass ratio of Y2O3 to AlN is controlled at 5:95.

[0059] Step 3: To improve the dispersibility of the suspension system and inhibit particle aggregation, the suspension is first ultrasonically treated for 60 min to break up the agglomerates, and then mechanically stirred continuously for 120 min to maintain dispersion stability.

[0060] Step 4: Prepare a mixed solution of ethylenediamine and ethanol at a mass ratio of 1:2 as a non-aqueous precipitant, and slowly add it dropwise to the suspension system at a rate of 1 drop every 3-5 seconds while continuously stirring. During the addition process, Y 3+ The precursor undergoes a coordination reaction with ethylenediamine to form a complex, and preferentially undergoes heterogeneous nucleation deposition on the surface of AlN particles to achieve uniform coating of the particles until the pH is adjusted to 9.3-9.5, and the powder is obtained by precipitation.

[0061] Step 5: Wash the obtained powder twice with ethanol to remove residual substances, and dry it at 60°C for 10 h. Then calcine it at 500°C for 2 h in air atmosphere to thermally decompose the yttrium-amine complex and transform it into a stable Y2O3 coating, finally obtaining a uniformly coated AlN composite powder.

[0062] In step two, the temperature of the micro-arc oxidation electrolyte is controlled at 20-40℃ by a cooling circulation device.

[0063] In step three, during the micro-arc oxidation process, the composite electrolyte is continuously stirred by a stirring device at a stirring speed of 100 r / min to ensure uniform composition of the composite electrolyte and promote heat dissipation, thereby preventing excessively high local temperatures from affecting the coating performance.

[0064] Comparative Example 1

[0065] ① Cut the SiC reinforced aluminum matrix composite material with a SiC volume fraction of 20% into 20mm×20mm×2mm samples. Wet-grind the samples with sandpaper of 80#, 180#, 280#, 400#, 600#, 800# and 1200# in sequence until the surface is smooth and the cutting marks are removed. Place the polished sample in an alcohol solution and sonicate for 10 minutes to remove surface oil. Then, rinse the sample with deionized water and dry it with a hair dryer for later use.

[0066] ② Weigh out 15 g / L sodium aluminate, 4 g / L sodium silicate, and 1 g / L sodium hydroxide, dissolve them in deionized water, and stir for 30 minutes to ensure the drugs are fully dissolved.

[0067] ③ The SiC-reinforced aluminum matrix composite substrate pretreated in ① is fixed in the electrolyte reaction tank prepared in ②. The workpiece is used as the anode and the stainless steel tank is used as the cathode. Micro-arc oxidation is performed using a bipolar pulse power supply in constant voltage mode. The final working voltage is 470V, the pulse frequency is 500Hz, the duty cycle is 30%, the positive and negative pulse ratio is 1:1, and the processing time is 5 minutes. Circulating water cooling is turned on to keep the electrolyte temperature between 25℃ during the micro-arc oxidation process.

[0068] ④ After the micro-arc oxidation treatment is completed, the substrate is taken out and washed and dried in sequence to obtain a SiC composite material with a micro-arc oxidation layer on the surface.

[0069] The prepared micro-arc oxidation ceramic film was tested and found to be as follows: Figure 1 As shown, metallographic observation reveals that the film layer is tightly bonded to the substrate without defects, the film layer is uniform and continuous, and the film thickness is 37 μm. Figure 3 As shown, under dry friction test conditions, with the matrix (Al-20%SiC) as the benchmark, the average wear rate of the SiC composite material obtained in this comparative example is low, only 5.42 × 10⁻⁶. -5 mm 3 / N·m, but the average coefficient of friction is too high, reaching 0.728, such as Figure 4 As shown, the breakdown voltage of the film is 763.47V. X-ray diffraction analysis of the micro-arc oxidation film revealed that the film is composed of γ-Al₂O₃. 3、 Composed of αAl₂O₃ and mullite (Al₆Si₂O₃), it possesses excellent corrosion resistance, such as... Figure 5 As shown, the thermal conductivity is 111.901 (W·m). -1 ·K -1 As can be seen, the SiC composite material without AlN particles has poor wear resistance and thermal conductivity, and low breakdown voltage.

[0070] Comparative Example 2

[0071] ① Cut the SiC / Al composite material with a SiC volume fraction of 20% into 20mm×20mm×2mm samples. Wet-grind the samples with sandpaper of 80#, 180#, 280#, 400#, 600#, 800# and 1200# in sequence until the surface is smooth and the cutting marks are removed. Place the polished sample in an alcohol solution and sonicate for 10 minutes to remove surface oil. Then rinse the sample with deionized water and dry it with a hair dryer for later use.

[0072] ② Weigh out 15 g / L sodium aluminate, 4 g / L sodium silicate, and 1 g / L sodium hydroxide, dissolve them in deionized water, and stir for 30 minutes to ensure the drugs are fully dissolved.

[0073] ③ Select AlN particles with a particle size of 200 nm and a purity of 99.9%, add them to deionized water, control the concentration at 2 g / L, first perform magnetic stirring for 30 minutes, then perform ultrasonic dispersion for 1 hour to obtain a dispersion, add 2 g of the dispersion to 4 L of the electrolyte prepared in ②, and stir with a stirrer for 60 min.

[0074] ④ Fix the SiC-reinforced aluminum matrix composite sample pretreated in ① in the electrolyte reaction tank treated in ③. Use the workpiece as the anode and the stainless steel tank as the cathode. Use a bipolar pulse power supply for micro-arc oxidation treatment. Use constant voltage mode. The final working voltage is 470V, the pulse frequency is 500Hz, the duty cycle is 30%, the positive and negative pulse ratio is 1:1, and the treatment time is 5 minutes. Turn on the circulating water cooling to keep the electrolyte temperature between 25℃ during the micro-arc oxidation process.

[0075] ⑤ After the micro-arc oxidation treatment is completed, the substrate is taken out and then washed and dried in sequence to obtain a SiC / Al composite material with a micro-arc oxidation layer on the surface.

[0076] The prepared micro-arc oxidation ceramic film was tested and found to be as follows: Figure 3-5 As shown, the coating bonding state is similar to that of Comparative Example 1, the film breakdown voltage is 853.30V, and its thermal conductivity is 126.091 (W·m). -1 ·K -1 As can be seen, the thermal conductivity has been improved, but under dry friction test conditions, the average coefficient of friction is 0.523, and the average wear rate is significantly higher than that of the comparative example, reaching 3.80 × 10⁻⁶. -4 mm 3 / N•m, the wear resistance of the coating decreases, which is due to the low AlN content, which has a negative impact on tribological properties.

[0077] Comparative Example 3

[0078] ① Cut the SiC reinforced aluminum matrix composite material with a SiC volume fraction of 20% into 20mm×20mm×2mm samples. Wet-grind the samples with sandpaper of 80#, 180#, 280#, 400#, 600#, 800# and 1200# in sequence until the surface is smooth and the cutting marks are removed. Place the polished sample in an alcohol solution and sonicate for 10 minutes to remove surface oil. Then rinse the sample with deionized water and dry it with a hair dryer for later use.

[0079] ② Weigh out 15 g / L sodium aluminate, 4 g / L sodium silicate, and 1 g / L sodium hydroxide, dissolve them in deionized water, and stir for 30 minutes to ensure the drugs are fully dissolved.

[0080] ③ Select AlN particles with a particle size of 200 nm and a purity of 99.9%, add them to deionized water, control the concentration at 4 g / L, first perform magnetic stirring for 30 minutes, then perform ultrasonic dispersion for 1 hour to obtain a dispersion, add 4 g of the dispersion to 8 L of the electrolyte prepared in ②, and stir with a stirrer for 60 min.

[0081] ④ The pretreated SiC-reinforced aluminum matrix composite sample from step ① is fixed in the electrolyte reaction tank prepared in step ③. The workpiece is used as the anode, and the stainless steel tank as the cathode. Micro-arc oxidation is performed using a bipolar pulse power supply in constant voltage mode. The final operating voltage is 470V, the pulse frequency is 500Hz, the duty cycle is 10%, the positive to negative pulse ratio is 1:1, and the processing time is 5 minutes. Circulating water cooling is activated to maintain the electrolyte temperature at around 25℃ during the micro-arc oxidation process.

[0082] ⑤ After the micro-arc oxidation treatment is completed, the substrate is taken out and then washed and dried in sequence to obtain a SiC / Al composite material with a high-performance micro-arc oxidation layer on the surface.

[0083] The prepared micro-arc oxidation ceramic film was tested and found to have a breakdown voltage of 898.73V and a thermal conductivity of 129.636 (W·m). -1 ·K -1 Under dry friction test conditions, its average friction coefficient was 0.526, and its average wear rate was significantly higher than that of comparative examples one and two, reaching 3.97 × 10⁻⁶. -4 mm 3 / N•m, its coating wear resistance further decreases.

[0084] Example 1

[0085] ① Cut the SiC reinforced aluminum matrix composite material with a SiC volume fraction of 20% into 20mm×20mm×2mm samples. Wet-grind the samples with sandpaper of 80#, 180#, 280#, 400#, 600#, 800# and 1200# in sequence until the surface is smooth and the cutting marks are removed. Place the polished sample in an alcohol solution and sonicate for 10 minutes to remove surface oil. Then rinse the sample with deionized water and dry it with a hair dryer for later use.

[0086] ② Weigh out 15 g / L sodium aluminate, 4 g / L sodium silicate, and 1 g / L sodium hydroxide, dissolve them in deionized water, and stir for 30 minutes to ensure the drugs are fully dissolved.

[0087] ③ Select AlN particles with a particle size of 200 nm and a purity of 99.9%, add them to deionized water, control the concentration at 6 g / L, first perform magnetic stirring for 30 minutes, then perform ultrasonic dispersion for 1 hour to obtain a dispersion, add 6 g of the dispersion to 12 L of the electrolyte prepared in ②, and stir with a stirrer for 60 min.

[0088] ④ Fix the SiC reinforced aluminum matrix composite sample pretreated in ① in the electrolyte reaction tank prepared in ③. Use the workpiece as the anode and the stainless steel tank as the cathode. Use a bipolar pulse power supply for micro-arc oxidation treatment. Use constant voltage mode. The final working voltage is 470V, the pulse frequency is 500Hz, the duty cycle is 30%, the positive and negative pulse ratio is 1:1, and the treatment time is 5 minutes. Turn on the circulating water cooling to keep the electrolyte temperature between 25℃ during the micro-arc oxidation process.

[0089] ⑤ After the micro-arc oxidation treatment is completed, the substrate is taken out and then washed and dried in sequence to obtain a SiC / Al composite material with a high-performance micro-arc oxidation layer on the surface.

[0090] The prepared micro-arc oxidation ceramic film was tested and found to be as follows: Figure 2 As shown, scanning electron microscopy (SEM) observation revealed that the AlN particles were uniformly distributed on the coating surface. The film surface exhibited a uniform micron-level uneven morphology due to the adhesion of the AlN particles. Cross-sections showed good bonding between the particles and the substrate. The coating thickness was approximately 36 μm, and measurements at multiple points showed uniform thickness. Figure 3-5 As shown, the breakdown voltage is ≥1200V, and the thermal conductivity is 134.68 (W·m). -1 ·K -1 Under dry friction test conditions, its average wear rate was reduced by about 46% compared with the traditional micro-arc oxidation coating without AlN, and it was also significantly reduced compared with the substrate material. The average friction coefficient was also reduced compared with the control, indicating that the wear resistance was greatly improved.

[0091] Example 2

[0092] This embodiment specifically includes the following steps:

[0093] ① Cut the SiC reinforced aluminum matrix composite material with a SiC volume fraction of 20% into 20mm×20mm×2mm samples. Wet-grind the samples with sandpaper of 80#, 180#, 280#, 400#, 600#, 800# and 1200# in sequence until the surface is smooth and the cutting marks are removed. Place the polished sample in an alcohol solution and sonicate for 10 minutes to remove surface oil. Then rinse the sample with deionized water and dry it with a hair dryer for later use.

[0094] ② Weigh out 15 g / L sodium aluminate, 4 g / L sodium silicate, and 1 g / L sodium hydroxide, dissolve them in deionized water, and stir for 30 minutes to ensure the drugs are fully dissolved.

[0095] ③ Select AlN particles with a particle size of 200 nm and a purity of 99.9%, add them to deionized water, control the concentration at 8 g / L, first perform magnetic stirring for 30 minutes, then perform ultrasonic dispersion for 1 hour to obtain a dispersion, add 8 g of the dispersion to 16 L of the electrolyte prepared in ②, and stir with a stirrer for 60 min.

[0096] ④ Fix the SiC-reinforced aluminum matrix composite sample pretreated in ① in the electrolyte reaction tank prepared in ③. Use the workpiece as the anode and the stainless steel tank as the cathode. Use a bipolar pulse power supply for micro-arc oxidation treatment. Use constant voltage mode. The final working voltage is 470V, the pulse frequency is 500Hz, the duty cycle is 50%, the positive and negative pulse ratio is 1:1, and the treatment time is 5 minutes. Turn on the circulating water cooling to keep the electrolyte temperature between 20-40℃ during the micro-arc oxidation process.

[0097] ⑤ After the micro-arc oxidation treatment is completed, the substrate is taken out and then washed and dried in sequence to obtain a SiC / Al composite material with a high-performance micro-arc oxidation layer on the surface.

[0098] The prepared micro-arc oxidation ceramic film was tested and found to be as follows: Figure 3-5 As shown, the coating thickness is approximately 36 μm, the breakdown voltage is 1002.93 V, and the thermal conductivity is 138.091 (W·m). -1 ·K -1 Under dry friction test conditions, although the average wear rate was higher than that of the comparative example 1, reaching 5.16 × 10⁻⁶, it still achieved a higher average wear rate. -5 mm 3 The wear resistance is 0.668 N·m, which is lower than that of the matrix, and the average friction coefficient is 0.668, which is lower than that of Comparative Example 1. Its wear resistance is better than that of the composite material prepared by the matrix and Comparative Example 1.

[0099] This invention presents a method for preparing an integrated thermally conductive, insulating, and wear-resistant micro-arc oxidation layer on the surface of SiC / Al composite materials. This method can be implemented on conventional micro-arc oxidation equipment, requiring only the addition of an AlN particle suspension system. The process is simple, cost-controllable, and easy to scale up. The prepared micro-arc oxidation film has excellent comprehensive performance, providing an innovative surface solution for high-performance electronic packaging heat dissipation materials and precision wear-resistant components.

[0100] 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 embodiments shown and described herein.

Claims

1. A method for preparing an integrated micro-arc oxidation layer on the surface of a SiC / Al composite material that is thermally conductive, insulating, and wear-resistant, characterized in that, Includes the following steps: Step 1: Pre-treat the SiC-reinforced aluminum matrix composite substrate and prepare the micro-arc oxidation electrolyte; Step 2: Add the AlN dispersion to the micro-arc oxidation electrolyte to obtain a composite electrolyte; Step 3: Immerse the pretreated SiC reinforced aluminum matrix composite substrate as the anode into the composite electrolyte, use a stainless steel tank as the cathode, and perform micro-arc oxidation treatment using a bipolar pulse power supply. Step 4: Perform post-treatment on the treated SiC reinforced aluminum matrix composite substrate to obtain SiC / Al composite material.

2. The method for preparing an integrated thermally conductive, insulating, and wear-resistant micro-arc oxidation layer on the surface of SiC / Al composite material according to claim 1, characterized in that, The preprocessing specifically includes: SiC-reinforced aluminum matrix composite material was selected as the substrate and wet-ground until the surface was smooth. Then, it was washed with ethanol, ultrasonicated, washed with water and dried in sequence.

3. The method for preparing an integrated micro-arc oxidation layer on the surface of SiC / Al composite material according to claim 2, characterized in that, Step two also includes: AlN particles need to be coated before dispersion.

4. The method for preparing an integrated thermally conductive, insulating, and wear-resistant micro-arc oxidation layer on the surface of the SiC / Al composite material according to claim 3, characterized in that, The coating process specifically includes: Step 1: After calcining yttrium nitrate to remove the water of crystallization, dissolve it in anhydrous ethanol to prepare Yt. 3+ A precursor solution with a concentration of 0.05 mol / L; Step 2: Add AlN powder and polyethylene glycol to the precursor solution and form a uniform suspension under stirring conditions; The target mass ratio of Y2O3 to AlN is 5:95; Step 3: After ultrasonic treatment, the suspension is continuously mechanically stirred for 120 min to maintain dispersion stability; Step 4: Prepare a mixed solution of ethylenediamine and ethanol at a mass ratio of 1:2 as a non-aqueous precipitant, and add it dropwise to the suspension at a rate of 1 drop every 3-5 seconds while continuously stirring, until the pH is adjusted to 9.3-9.5, and the precipitate is obtained as powder; Step 5: The obtained powder is washed with ethanol, dried and calcined in sequence to obtain AlN composite powder with uniform surface coating.

5. The method for preparing an integrated micro-arc oxidation layer on the surface of SiC / Al composite material according to claim 4, characterized in that, The preparation process of the AlN dispersion is as follows: AlN particles were dissolved in deionized water at a concentration of 6 or 8 g / L. The mixture was first magnetically stirred for 30 minutes, and then ultrasonically dispersed for 1 hour to obtain an AlN dispersion.

6. The method for preparing an integrated micro-arc oxidation layer on the surface of SiC / Al composite material according to claim 5, characterized in that, The micro-arc oxidation electrolyte is: 15 g / L sodium aluminate, 4 g / L sodium silicate and 1 g / L sodium hydroxide are dissolved in deionized water.

7. The method for preparing an integrated micro-arc oxidation layer on the surface of SiC / Al composite material according to claim 6, characterized in that, The preparation process of the composite electrolyte is as follows: An AlN dispersion was added to the micro-arc oxidation electrolyte, maintaining a volume ratio of 1:2 between the AlN dispersion and the micro-arc oxidation electrolyte, and the mixture was stirred to obtain a composite electrolyte.

8. The method for preparing an integrated micro-arc oxidation layer on the surface of SiC / Al composite material according to claim 7, characterized in that, The micro-arc oxidation process specifically involves: It adopts constant voltage mode, with a final operating voltage of 400-470V, a pulse frequency of 100-800Hz, a duty cycle of 10%-50%, and a processing time of 5 minutes.

9. The method for preparing an integrated micro-arc oxidation layer on the surface of SiC / Al composite material according to claim 8, characterized in that, The post-processing specifically includes: After the micro-arc oxidation process is completed, the substrate is removed and then washed and dried in sequence.

10. The method for preparing an integrated thermally conductive, insulating, and wear-resistant micro-arc oxidation layer on the surface of SiC / Al composite material according to claim 9, characterized in that, The temperature of the micro-arc oxidation electrolyte is maintained at 20-40℃.

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