A ceramic composite coating for enhancing heat dissipation of an aluminum surface and a method of manufacturing the same

Abstract

The application discloses a preparation method of a ceramic composite coating for enhancing heat dissipation of an aluminum surface and belongs to the technical field of heat dissipation materials. The method comprises the following steps: S1, preparing paste-like coating material by using silicon carbide powder, aluminum alloy powder and brazing flux powder; S2, cutting a base plate sample on an aluminum alloy plate and cleaning the base plate sample; S3, applying the paste-like coating material in S1 to one side of the cleaned aluminum alloy base plate sample, and then performing atmosphere protection furnace brazing coating; and S4, after the brazing coating is completed, polishing the coating surface. The application discloses a ceramic composite coating for enhancing heat dissipation of an aluminum surface and a preparation method thereof. In the application, low-melting-point aluminum alloy filler is used to replace resin, so that the heat dissipation effect of the coating is improved. In addition, a brazing flux is used to promote metallurgical reaction of SiC and aluminum alloy filler liquid, a mechanical polishing method is used to expose silicon carbide on the coating surface, and the micro-roughness and heat dissipation area of the coating surface are increased. The process is simple, and the production efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation materials technology, and in particular to a ceramic composite coating for enhancing heat dissipation on aluminum surfaces and its preparation method. Background Technology

[0002] Electronic products generate heat during operation, leading to temperature increases. This heat needs to be dissipated promptly to prevent affecting the stability and safety of the products. Various types of heat sinks are commonly used to dissipate heat in electronic products. The heat dissipation effect of a heat sink is related to the thermal conductivity and surface thermal emissivity of the heat sink material. Aluminum is a primary material for heat sink manufacturing due to its high thermal conductivity, low price, and ease of processing. However, as a metallic material, aluminum has a relatively low surface thermal emissivity. Therefore, introducing a high thermal emissivity coating onto the aluminum surface is an important way to improve the performance of aluminum heat sinks.

[0003] The compositional characteristics of high thermal emissivity coatings on aluminum surfaces include fillers containing substances with high thermal emissivity. Metal oxides, nitrides, carbides, carbon black, and graphite are high emissivity substances and are the main fillers used in preparing high thermal emissivity coatings. Among them, silicon carbide, with its good thermal conductivity and thermal emissivity, is a valuable filler for high thermal emissivity coatings.

[0004] Harbison Refractory Materials (HWI) of the United States produces high-emissivity coatings with SiC as the main filler. These coatings have a normal emissivity of 0.82–0.92 at 1010–1400℃ and are primarily used in tunnel kilns for producing facing bricks to improve thermal efficiency and save 5%–15% of energy. Li Jinfeng mixed SiC powder with waterborne polyurethane resin to prepare a slurry, which was then applied to aluminum foil to create a coating. She found that a 20% SiC addition significantly improved the coating's heat dissipation. Nie Yujie et al. prepared a waterborne heat-dissipating and cooling coating with SiC as the filler. Their research showed that a SiC filler particle size of 60 nm, a filler mass fraction of 30%, and a coating thickness of 42 μm resulted in the best heat dissipation and cooling effect. These research findings all confirm that coatings containing SiC powder filler have excellent heat dissipation performance.

[0005] Furthermore, current heat dissipation coatings for aluminum alloy surfaces are generally prepared using resin-based coatings. Resin coatings mainly consist of resin, fillers, solvents, and additives, with resin being the primary component, imparting strength and structural integrity to the coating. Resin materials contain numerous interfaces and defects, resulting in generally low thermal conductivity, which significantly limits the heat dissipation effect of the coating. Using metal-based ceramic composites is key to improving the heat dissipation of SiC coatings. Unfortunately, due to the significant performance differences and poor metallurgical compatibility between SiC ceramics and aluminum, and the low melting point of aluminum which prevents high-temperature sintering, preparing non-resin-based SiC ceramic coatings on aluminum surfaces is technically very challenging.

[0006] Zhang prepared a SiC / hBN nanocomposite ceramic coating on an aluminum alloy surface using liquid-phase plasma-assisted electrophoretic sintering (LPES). The applied voltage was no less than 600V, and the electrolyte temperature was between 70 and 90°C. These unique parameters facilitated the synergistic electrophoresis of plasma-assisted SiC and hBN nanoparticles, which were then sintered together via a SiO2-based glass phase. The SiC / hBN nanocomposite coating enhanced the infrared emissivity in the 3–20 μm wavelength range, particularly reaching 0.86 in the 3–8 μm wavelength range. However, this method is not only complex and inefficient but also restricts practical applications due to limitations in the size and shape of the aluminum substrate. Summary of the Invention

[0007] The purpose of this invention is to provide a ceramic composite coating for enhancing heat dissipation on aluminum surfaces and its preparation method. A low-melting-point aluminum alloy solder is used instead of resin to improve the heat dissipation effect of the coating. Furthermore, flux is used to promote the metallurgical reaction between SiC and the liquid aluminum alloy solder. Mechanical polishing is employed to expose the silicon carbide on the coating surface, increasing the micro-roughness and heat dissipation area of ​​the coating surface. This process is simple and has high production efficiency.

[0008] To achieve the above objectives, the present invention provides a method for preparing a ceramic composite coating for enhancing heat dissipation on aluminum surfaces, comprising the following steps:

[0009] S1. Mix silicon carbide powder, aluminum alloy powder and flux powder in a certain proportion and then ball mill them; adjust the ball-milled mixture with anhydrous ethanol to form a paste-like coating.

[0010] S2. Cut a substrate sample from the aluminum alloy plate and clean it.

[0011] S3. Apply the paste-like coating from S1 to one side of the cleaned aluminum alloy substrate sample, and then perform brazing in an atmosphere-protected furnace.

[0012] S4. After the brazing is completed, the coating surface is polished.

[0013] Preferably, in S1, the weight ratio of silicon carbide powder, aluminum alloy powder and flux powder is (0.5-5):1:1; the aluminum alloy powder is HL401 solder alloy powder with a chemical composition of Al-5Si-28Cu; the flux powder is QJ201 powder with a chemical composition of KCl-32LiCl-8ZnCl2-10NaF.

[0014] Preferably, in step S1, the ball milling process is carried out in a vacuum spherical ink tank, using an alternating forward and reverse milling mode, with a milling speed of 100-200 rpm and a milling time of 0.5-2 hours.

[0015] Preferably, in step S2, the aluminum alloy plate is grade 6061, and the aluminum alloy substrate sample has a size of 50mm × 50mm.

[0016] Preferably, in step S2, the cleaning process involves first cleaning the surface of the substrate sample with an alkaline cleaning solution, then immersing the cleaned substrate sample in a nitric acid aqueous solution for 3-4 seconds, and finally rinsing it with clean water.

[0017] The alkaline cleaning solution is Na2CO3-Na2CrO4-NaOH; the cleaning temperature is 80-100℃, and the cleaning time is 3-5 minutes.

[0018] Preferably, in step S3, the coating thickness is 0.5–2 mm; the brazing process in the atmosphere-protected furnace is as follows:

[0019] 1) Place the aluminum alloy substrate sample with the coating layer facing upward and horizontally in an electric furnace with ventilation protection. Close the furnace door in sequence, introduce argon gas, and heat it with electricity. The heating temperature is 550-600℃ and the time is 5-10 minutes. Then turn off the power and cool it down.

[0020] 2) When the furnace temperature drops below 300℃, open the furnace door, take out the aluminum alloy substrate sample, put it into warm water at 40-60℃ to cool for 1-5 minutes, and then take it out and dry it with cold air.

[0021] Preferably, in step S4, the grinding method is wire brush grinding, sandpaper grinding, or sandblasting grinding.

[0022] A ceramic composite coating that enhances heat dissipation on aluminum surfaces was prepared using the above method.

[0023] Preferably, the ceramic composite coating is composed of silicon carbide ceramic and aluminum alloy.

[0024] Therefore, the present invention provides a ceramic composite coating for enhancing heat dissipation on aluminum surfaces and its preparation method. It uses low-melting-point aluminum alloy brazing filler metal instead of resin to improve the heat dissipation effect of the coating. Furthermore, it uses flux to promote the metallurgical reaction between SiC and the aluminum alloy brazing filler metal liquid, and uses mechanical polishing to expose the silicon carbide on the coating surface, thereby increasing the micro-roughness and heat dissipation area of ​​the coating surface. The process is simple and has high production efficiency.

[0025] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0026] The technical solution of the present invention will be further described below through embodiments.

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0028] Example 1

[0029] S1. Preparation of paste-like coating:

[0030] (1) Weigh out SiC powder, HL401 brazing alloy powder and QJ201 flux powder in a weight ratio of 1:1:1, mix them together, put the mixed powder into a vacuum ball mill jar, use the alternating forward and reverse rotation mode, the ball milling speed is 120 rpm, and the ball milling is carried out for 1 hour.

[0031] (2) After ball milling, remove the mixed powder from the ball mill jar and mix it with anhydrous ethanol to form a paste coating.

[0032] S2. Coating preparation:

[0033] (1) Cut a substrate sample from an aluminum alloy plate with a thickness of 3mm. The grade of the aluminum alloy plate is 6061 and the substrate sample size is 50mm×50mm.

[0034] (2) The surface of the aluminum alloy substrate sample was cleaned with Na2CO3-Na2CrO4-NaOH. The cleaning solution temperature was 80℃ and the cleaning time was 3min.

[0035] (3) After cleaning with the above alkaline solution, the sample is placed in a 250 ml / l nitric acid aqueous solution for about 3 to 4 seconds, then rinsed with clean water and dried with cold air.

[0036] (4) Apply the paste-like coating prepared in S1 above to one side of the cleaned aluminum substrate with a coating thickness of 1 mm.

[0037] (5) Place the above aluminum substrate coating layer upward and horizontally in an electric furnace with ventilation protection, close the furnace door in sequence, introduce argon gas, turn on the power to heat, control the heating temperature to 550℃ and the holding time to 6min, and then turn off the power to cool.

[0038] (6) When the furnace temperature drops below 300°C, open the furnace door, take out the substrate sample, immerse it in 40°C warm water to cool for 2 minutes, and then take it out and dry it with cold air.

[0039] S3. Polishing the coating surface:

[0040] The surface of the coating after the above S2 treatment was polished with a wire brush to remove residual flux and some aluminum alloy brazing metal and exposed SiC.

[0041] Example 2

[0042] S1. Preparation of paste-like coating:

[0043] (1) Weigh out SiC powder, HL401 brazing alloy powder and QJ201 flux powder in a weight ratio of 3:1:1, mix them together, put the mixed powder into a vacuum ball mill jar, use the alternating forward and reverse rotation mode, the ball mill speed is 140 rpm, and the ball milling time is 1.5 hours.

[0044] (2) After ball milling, remove the mixed powder from the ball mill jar and mix it with anhydrous ethanol to form a paste coating.

[0045] S2. Coating preparation:

[0046] (1) Cut a substrate sample from an aluminum alloy plate with a thickness of 3mm. The grade of the aluminum alloy plate is 6061 and the substrate sample size is 50mm×50mm.

[0047] (2) The surface of the aluminum alloy substrate sample was cleaned with Na2CO3-Na2CrO4-NaOH. The cleaning solution temperature was 90℃ and the cleaning time was 4min.

[0048] (3) After cleaning with the above alkaline solution, the sample is placed in a 250 ml / l nitric acid aqueous solution for about 3 to 4 seconds, then rinsed with clean water and dried with cold air.

[0049] (4) Apply the paste-like coating prepared in S1 above to one side of the cleaned aluminum substrate with a coating thickness of 1.5 mm.

[0050] (5) Place the above aluminum substrate coating layer upward and horizontally in an electric furnace with ventilation protection, close the furnace door in sequence, introduce argon gas, turn on the power to heat, control the heating temperature to 590℃ and the holding time to 6min, and then turn off the power to cool.

[0051] (6) When the furnace temperature drops below 300°C, open the furnace door, take out the substrate sample, immerse it in 60°C warm water to cool for 3 minutes, and then take it out and dry it with cold air.

[0052] S3. Polishing of the coating surface:

[0053] The surface of the coating after the above S2 treatment was polished with a wire brush to remove residual flux and some aluminum alloy brazing metal and exposed SiC.

[0054] Example 3

[0055] S1. Preparation of paste-like coating:

[0056] (1) Weigh out SiC powder, HL401 brazing alloy powder and QJ201 flux powder in a weight ratio of 4:1:1, mix them together, put the mixed powder into a vacuum ball mill jar, use the alternating forward and reverse rotation mode, the ball milling speed is 200 rpm, and the ball milling is carried out for 2 hours.

[0057] (2) After ball milling, remove the mixed powder from the ball mill jar and mix it with anhydrous ethanol to form a paste coating.

[0058] S2. Coating preparation:

[0059] (1) Cut a substrate sample from an aluminum alloy plate with a thickness of 3mm. The grade of the aluminum alloy plate is 6061 and the substrate sample size is 50mm×50mm.

[0060] (2) The surface of the aluminum alloy substrate sample was cleaned with Na2CO3-Na2CrO4-NaOH. The cleaning solution temperature was 100℃ and the cleaning time was 5min.

[0061] (3) After cleaning with the above alkaline solution, the sample is placed in a 250 ml / l nitric acid aqueous solution for about 3 to 4 seconds, then rinsed with clean water and dried with cold air.

[0062] (4) Apply the paste-like coating prepared in S1 above to one side of the cleaned aluminum substrate with a coating thickness of 2 mm.

[0063] (5) Place the above aluminum substrate coating layer upward and horizontally in an electric furnace with ventilation protection, close the furnace door in sequence, introduce argon gas, turn on the power to heat, control the heating temperature to 600℃ and the holding time to 9min, and then turn off the power to cool.

[0064] (6) When the furnace temperature drops below 300°C, open the furnace door, take out the substrate sample, immerse it in 50°C warm water to cool for 5 minutes, and then dry it with cold air.

[0065] S3. Polishing of the coating surface:

[0066] The surface of the coating after the above S2 treatment is treated by sandblasting to remove residual flux and surface brazing metal, expose SiC, and increase the roughness of the coating surface.

[0067] Therefore, the present invention provides a ceramic composite coating for enhancing heat dissipation on aluminum surfaces and its preparation method. It uses low-melting-point aluminum alloy brazing filler metal instead of resin to improve the heat dissipation effect of the coating. Furthermore, it uses flux to promote the metallurgical reaction between SiC and the aluminum alloy brazing filler metal liquid, and uses mechanical polishing to expose the silicon carbide on the coating surface, thereby increasing the micro-roughness and heat dissipation area of ​​the coating surface. The process is simple and has high production efficiency.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a ceramic composite coating for enhancing heat dissipation on aluminum surfaces, characterized in that, Includes the following steps: S1. Mix silicon carbide powder, aluminum alloy powder and flux powder in a certain proportion and then ball mill them; adjust the ball-milled mixture with anhydrous ethanol to form a paste-like coating. S2. Cut a substrate sample from the aluminum alloy plate and clean it. S3. Apply the paste-like coating from S1 to one side of the cleaned aluminum alloy substrate sample, and then perform brazing in an atmosphere-protected furnace. The process of brazing in an atmosphere-protected furnace is as follows: 1) Place the aluminum alloy substrate sample with the coating layer facing upward and horizontally in an electric furnace with ventilation protection. Close the furnace door in sequence, introduce argon gas, and heat it with electricity. The heating temperature is 590~600℃ and the time is 6~10min. Then turn off the power and cool it down. 2) When the furnace temperature drops below 300℃, open the furnace door, take out the aluminum alloy substrate sample, put it into warm water at 40~60℃ to cool for 1~5 minutes, and then dry it with cold air. S4. After the brazing is completed, the coating surface is polished. Mechanical polishing is used to expose the silicon carbide on the coating surface, thereby increasing the micro-roughness and heat dissipation area of ​​the coating surface.

2. The method for preparing a ceramic composite coating for enhancing heat dissipation on an aluminum surface according to claim 1, characterized in that: In S1, the weight ratio of silicon carbide powder, aluminum alloy powder and flux powder is (0.5~5):1:1; the aluminum alloy powder is HL401 solder alloy powder with a chemical composition of Al-5Si-28Cu; the flux powder is QJ201 powder with a chemical composition of KCl-32LiCl-8ZnCl2-10NaF.

3. The method for preparing a ceramic composite coating for enhancing heat dissipation on an aluminum surface according to claim 1, characterized in that: In step S1, the ball milling process is carried out in a vacuum ball milling jar, using an alternating forward and reverse mode, with a ball milling speed of 100~200 rpm and a ball milling time of 0.5~2 hours.

4. The method for preparing a ceramic composite coating for enhancing heat dissipation on an aluminum surface according to claim 1, characterized in that: In S2, the aluminum alloy plate is grade 6061, and the aluminum alloy substrate sample has a size of 50mm×50mm.

5. The method for preparing a ceramic composite coating for enhancing heat dissipation on an aluminum surface according to claim 1, characterized in that: In S2, the cleaning process is as follows: first, the surface of the substrate sample is cleaned with an alkaline cleaning solution; then, the cleaned substrate sample is placed in a nitric acid aqueous solution for 3-4 seconds; after that, it is taken out and rinsed with clean water. The temperature of the alkaline cleaning solution is 80~100℃, and the cleaning time is 3~5 minutes.

6. The method for preparing a ceramic composite coating for enhancing heat dissipation on an aluminum surface according to claim 1, characterized in that: In S4, the grinding method is wire brush grinding, sandpaper grinding, or sandblasting grinding.

7. A ceramic composite coating for enhancing heat dissipation on aluminum surfaces, characterized in that: It is prepared by the preparation method according to any one of claims 1-6.

8. A ceramic composite coating for enhancing heat dissipation on aluminum surfaces according to claim 7, characterized in that: The ceramic composite coating is composed of silicon carbide ceramic and aluminum alloy.