Preparation method of surface functionalized high-thermal-conductivity diamond micro-powder

Abstract

The application discloses a preparation method of surface functionalized high-thermal-conductivity diamond micro-powder, and the method comprises the following steps: firstly, the pretreated diamond micro-powder is sequentially subjected to ultrasonic sensitization and ultrasonic activation to obtain diamond micro-powder I; then, the diamond micro-powder I is dispersed in a chemical plating solution, the pH value is adjusted to 8-10, and the reaction is carried out at 80-95 DEG C for 1-4 h, so that a tungsten / phosphorus alloy layer or a molybdenum / phosphorus alloy layer is deposited on the surface of the diamond micro-powder I to obtain diamond micro-powder II; wherein, the chemical plating solution takes sodium tungstate or sodium molybdate as a main salt, sodium citrate or disodium EDTA as a complexing agent, nickel sulfate or nickel chloride as a promoter, and sodium hypophosphite as a reducing agent; finally, the diamond micro-powder II is subjected to heat treatment and then cooled to room temperature to obtain the surface functionalized high-thermal-conductivity diamond micro-powder product. The product has the advantages of low surface inertness, poor agglomeration, good interface compatibility and good high-temperature stability.

Description

Technical Field

[0001] This invention relates to the field of diamond micropowder preparation technology, and more specifically to a method for preparing surface-functionalized high thermal conductivity diamond micropowder. Background Technology

[0002] Diamond is the substance with the highest known thermal conductivity in nature, with single-crystal diamond exhibiting a thermal conductivity of up to 2000 W / (m·K). It also possesses a low coefficient of thermal expansion, excellent thermal stability, and superior mechanical properties. Therefore, high thermal conductivity diamond micropowder is an ideal filler material for preparing aluminum, copper, silver-based, and polymer-based thermally conductive composite materials, and can be widely used in various thermally conductive functional materials such as thermal pastes, thermal adhesives, and thermal pads.

[0003] However, diamond micropowder has extremely strong chemical inertness on its surface and very poor wettability with conventional metal matrices such as aluminum and copper, making it difficult to form a dense and compact composite interface. This results in problems such as weak interfacial bonding and high interfacial thermal resistance, which seriously hinder heat transfer and significantly limit the improvement of the overall thermal conductivity of the composite material, thus failing to fully utilize the intrinsic high thermal conductivity advantage of diamond.

[0004] Currently, the main methods for improving interfacial compatibility and reducing interfacial thermal resistance are surface modification of diamond and the deposition of metal layers such as titanium, chromium, tungsten, and molybdenum, or metal carbide transition layers. Among these methods, chemical plating has become the mainstream modification method for metallizing diamond surfaces due to its simple equipment, low cost, lack of need for a vacuum environment, suitability for ultrafine powders, and ability to be mass-produced.

[0005] However, traditional electroless plating processes still have some problems. The coating has poor uniformity and a loose structure, with only physical adhesion to the diamond substrate and no chemical bonding, resulting in low interfacial bonding strength. This leads to plating failures such as peeling, flaking, and delamination during subsequent lamination and use. Furthermore, simple metal plating exhibits insufficient interfacial reaction and instability when laminating with aluminum or copper substrates at high temperatures, failing to effectively eliminate the interfacial thermal resistance bottleneck. This results in limited improvement in the thermal conductivity of the composite material, making it difficult to meet the high-precision, high-stability thermal management requirements of high-end electronics and high-power devices. Therefore, this invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing surface-functionalized high thermal conductivity diamond micropowder in order to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention specifically adopts the following technical solution: A method for preparing surface-functionalized high thermal conductivity diamond micropowder includes steps S1 to S3.

[0008] S1. The pretreated diamond micro powder is subjected to ultrasonic sensitization and ultrasonic activation in sequence to obtain diamond micro powder I.

[0009] Furthermore, the diamond micro powder is selected from high thermal conductivity single crystal diamond micro powder, with a room temperature thermal conductivity ≥1500 W / (m・K).

[0010] Furthermore, the method for pretreating diamond micron powder in S1 includes: Diamond micro powder is immersed in sodium hydroxide or sodium carbonate aqueous solution and stirred for 1 to 3 hours at pH 12 to 14 and 60 to 80°C to remove oil, organic impurities and dust adhering to the surface of the micro powder. After rinsing the degreased diamond micro powder, it is immersed in a compound acidic solution of sulfuric acid and nitric acid. The solution is stirred and acid-washed for 2-5 hours at pH < 1 and 80-120℃. This process removes amorphous carbon, defective carbon, graphite impurities, and residual metal impurities from the surface of the micro powder. At the same time, hydroxyl and carboxyl oxygen-containing polar functional groups are stably generated on the surface of the diamond micro powder, thereby achieving surface hydrophilic activation. After acid washing, the diamond powder is washed and dried to obtain pretreated diamond powder.

[0011] Furthermore, the mass concentration of both the sodium hydroxide aqueous solution and the sodium carbonate aqueous solution is 5-15%.

[0012] Furthermore, the volume ratio of the sulfuric acid solution to the nitric acid solution is 3 to 5:1, the mass fraction of the sulfuric acid solution is ≥98%, and the mass fraction of the nitric acid solution is ≥65%.

[0013] Furthermore, the specific method for ultrasound sensitization in S1 includes: The pretreated diamond micropowder was dispersed in an acidic stannous chloride sensitizing solution and ultrasonically impregnated at room temperature and 30–60 kHz for 8–15 min to allow the surface of the micropowder to uniformly adsorb divalent tin ion reducing agent, thus completing the surface sensitization modification.

[0014] Furthermore, the pH of the stannous chloride acidic sensitizing solution is 1-2, and the stannous chloride acidic sensitizing solution is prepared by stannous chloride, hydrochloric acid solution and deionized water, with a stannous chloride concentration of 10-20 g / L and an hydrochloric acid solution addition amount of 30-50 mL / L.

[0015] Furthermore, the specific method for ultrasonic activation in S1 includes: After being sensitized by ultrasound, the diamond micropowder was washed and dispersed in an acidic palladium chloride activation solution. It was then ultrasonically impregnated for 5–10 min at room temperature and 30–60 kHz. The divalent tin ions adsorbed on the surface reduced the palladium ions, resulting in the uniform formation of nano-sized palladium catalytic active particles on the surface of the diamond micropowder.

[0016] Furthermore, the pH of the palladium chloride acidic activation solution is 2-3, and the palladium chloride acidic activation solution is prepared by palladium chloride, hydrochloric acid solution and deionized water, with a palladium chloride concentration of 0.05-0.15 g / L and a hydrochloric acid solution addition amount of 10-20 mL / L.

[0017] Furthermore, after ultrasonic activation, the activated diamond micro powder is thoroughly washed with deionized water to remove residual activation liquid and unadsorbed impurities from the surface, ultimately obtaining diamond micro powder I.

[0018] S2. Disperse diamond micro powder I in a chemical plating solution, adjust the pH to 8-10, and react at 80-95℃ for 1-4 hours to deposit a tungsten / phosphorus alloy layer or a molybdenum / phosphorus alloy layer on the surface of diamond micro powder I to obtain diamond micro powder II. The electroless plating solution uses sodium tungstate or sodium molybdate as the main salt, sodium citrate or disodium EDTA as the complexing agent, nickel sulfate or nickel chloride as the accelerator, and sodium hypophosphite as the reducing agent. S3. After heat treatment of diamond micro powder II, it is cooled to room temperature to obtain surface functionalized high thermal conductivity diamond micro powder product. Through high-temperature diffusion reaction, the tungsten / phosphorus alloy layer or molybdenum / phosphorus alloy layer on the surface reacts in situ with the carbon atoms on the surface of diamond micro powder II to generate a dense and continuous tungsten carbide interface layer or molybdenum carbide interface layer on the surface of diamond micro powder II. The tungsten carbide interface layer has a single-phase or multi-phase structure of WC or W2C, and the molybdenum carbide interface layer has a Mo2C structure. The interface layer is chemically bonded to the diamond matrix and has metallic properties on its surface, exhibiting good wettability with molten aluminum and copper.

[0019] Furthermore, the heat treatment in S3 is carried out at a temperature of 600–900°C for a time of 0.5–2 hours.

[0020] Furthermore, during the heat treatment, the diamond micro powder II is placed in an inert atmosphere or a reducing atmosphere.

[0021] The inert atmosphere is either nitrogen or argon, and the reducing atmosphere is a mixture of hydrogen and an inert gas.

[0022] Furthermore, the specific processing method includes: using weak acid to clean and remove loose oxides from the surface, then washing with deionized water and ethanol in sequence, and drying to obtain surface-functionalized high thermal conductivity diamond micro powder product.

[0023] Furthermore, the weak acid is either dilute hydrochloric acid or dilute nitric acid, and the drying process is vacuum drying or hot air drying.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention uses high-temperature heat treatment to cause the tungsten / phosphorus alloy layer or molybdenum / phosphorus alloy layer deposited on the diamond surface to undergo an in-situ diffusion reaction with the carbon atoms on the diamond surface, thereby generating a dense and continuous WC / W2C or Mo2C carbide interface layer on the diamond matrix surface. The carbide layer is covalently bonded to the diamond matrix, which improves the structural stability of the modified powder. 2. The tungsten carbide interface layer and molybdenum carbide interface layer generated in situ by the present invention can improve the interfacial wettability between diamond and molten aluminum and copper metal matrices, eliminate porosity and delamination defects in the composite process, effectively reduce the interfacial contact thermal resistance between diamond and metal matrix, and improve the overall thermal conductivity of metal matrix composite materials. 3. This invention thoroughly removes oil, amorphous carbon, defective carbon, and metallic impurities from the diamond surface through acid-base graded pretreatment. At the same time, it introduces oxygen-containing active functional groups, which greatly enhances surface activity and lays the foundation for subsequent plating and interface reactions. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The materials and instruments used in the following embodiments are all commercially available.

[0026] A method for preparing surface-functionalized high thermal conductivity diamond micropowder includes steps S1 to S3.

[0027] S1. The pretreated diamond micro powder is subjected to ultrasonic sensitization and ultrasonic activation in sequence to obtain diamond micro powder I.

[0028] Furthermore, the method for pretreating diamond micron powder in S1 includes: Diamond micro powder is immersed in sodium hydroxide or sodium carbonate aqueous solution and stirred for 1 to 3 hours at pH 12–14 and 60–80°C to remove oil. After rinsing the degreased diamond micro powder, it is immersed in a compound acidic solution of sulfuric acid and nitric acid, and stirred and acid-washed for 2-5 hours at pH < 1 and 80-120℃. After acid washing, the diamond powder is washed and dried to obtain pretreated diamond powder.

[0029] Furthermore, the mass concentration of both the sodium hydroxide aqueous solution and the sodium carbonate aqueous solution is 5-15%.

[0030] Furthermore, the volume ratio of sulfuric acid solution to nitric acid solution is 3 to 5:1, the mass fraction of sulfuric acid solution is ≥98%, and the mass fraction of nitric acid solution is ≥65%.

[0031] Furthermore, the specific methods for ultrasound sensitization in S1 include: The pretreated diamond micropowder was dispersed in an acidic stannous chloride sensitizing solution and ultrasonically impregnated for 8–15 min at room temperature and 30–60 kHz.

[0032] Furthermore, the pH of the stannous chloride acidic sensitizing solution is 1-2. The stannous chloride acidic sensitizing solution is prepared by stannous chloride, hydrochloric acid solution and deionized water. The concentration of stannous chloride is 10-20 g / L and the amount of hydrochloric acid solution added is 30-50 mL / L.

[0033] Furthermore, the specific methods for ultrasonic activation in S1 include: After rinsing, the ultrasonically sensitized diamond micropowder was dispersed in an acidic palladium chloride activation solution and ultrasonically impregnated for 5–10 min at room temperature and 30–60 kHz.

[0034] Furthermore, the pH of the palladium chloride acidic activation solution is 2-3. The palladium chloride acidic activation solution is prepared by palladium chloride, hydrochloric acid solution and deionized water. The concentration of palladium chloride is 0.05-0.15 g / L and the amount of hydrochloric acid solution added is 10-20 mL / L.

[0035] S2. Disperse diamond micro powder I in a chemical plating solution, adjust the pH to 8-10, and react at 80-95℃ for 1-4 hours to deposit a tungsten / phosphorus alloy layer or a molybdenum / phosphorus alloy layer on the surface of diamond micro powder I to obtain diamond micro powder II. The electroless plating solution uses sodium tungstate or sodium molybdate as the main salt, sodium citrate or disodium EDTA as the complexing agent, nickel sulfate or nickel chloride as the accelerator, and sodium hypophosphite as the reducing agent.

[0036] S3. After heat treatment of diamond micro powder II, it is cooled to room temperature to obtain surface-functionalized high thermal conductivity diamond micro powder product.

[0037] Furthermore, the heat treatment in S3 is carried out at a temperature of 600–900 °C for a time of 0.5–2 h.

[0038] Furthermore, during heat treatment, diamond micron powder II is placed in an inert or reducing atmosphere.

[0039] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0040] Example 1 This embodiment provides a method for preparing surface-functionalized high thermal conductivity diamond micropowder, including the following steps: 20g of high thermal conductivity single crystal diamond powder with an average particle size of 50μm was selected. The diamond powder was immersed in a 10% sodium hydroxide aqueous solution, the pH was adjusted to 13, the reaction temperature was controlled at 70℃, and the mixture was stirred and soaked at a constant temperature for 2h. After degreasing, the diamond micro powder is repeatedly rinsed with deionized water until the washing solution is clear. Then, the rinsed powder is immersed in a compound acidic solution, in which the volume ratio of sulfuric acid solution (mass fraction ≥98%) to nitric acid solution (mass fraction ≥65%) is 4:1, the pH of the system is controlled to be <1, the temperature is raised to 100℃, and the acid washing is carried out by stirring at a constant temperature for 3.5h. After acid washing, the diamond powder is washed multiple times with deionized water until the washing solution is neutral. The washed powder is then placed in an 80℃ vacuum oven and dried for 12 hours to completely remove moisture, thus obtaining pretreated diamond powder. Using deionized water as a solvent, an acidic sensitizing solution containing 15 g / L stannous chloride and 40 mL / L hydrochloric acid was prepared, and the pH of the acidic sensitizing solution was adjusted to 1.5. 100 mL of the above acidic sensitizing solution was taken and dried pretreated diamond micro powder was added. The solution was then ultrasonically impregnated for 12 min at room temperature and 45 kHz. After sensitization, the powder was filtered and rinsed with deionized water to remove residual sensitization solution from the surface. Then, using deionized water as a solvent, an acidic activation solution of palladium chloride containing 0.1 g / L palladium chloride and 15 mL / L hydrochloric acid was prepared, and the pH of the acidic activation solution was adjusted to 2.5. 100 mL of the acidic activation solution of palladium chloride was taken, and the sensitized diamond micropowder was added. The solution was ultrasonically impregnated for 7.5 min at room temperature and 45 kHz. After activation, the powder was filtered, and the surface of the powder was washed with deionized water to obtain diamond micro powder I.

[0041] Using deionized water as a solvent, sodium tungstate (40 g / L), sodium citrate (80 g / L), nickel sulfate (20 g / L), and sodium hypophosphite (20 g / L) were added sequentially and stirred until dissolved. The pH was adjusted to 9.0 with ammonia water to obtain a chemical tungsten plating solution. 500 mL of the chemical tungsten plating solution was taken and diamond micro powder I was added. The solution was heated to 88°C in a water bath and stirred at a constant temperature for 2.5 h to uniformly deposit a tungsten / phosphorus alloy layer on the surface of diamond micro powder I. After the reaction was completed, the solution was naturally cooled to room temperature, the powder was filtered, and washed with deionized water to remove residual chemical tungsten plating solution from the powder surface to obtain diamond micro powder II. Diamond micro powder II was spread evenly in a tube furnace, and high-purity argon gas was introduced to create an inert protective atmosphere. The heating rate was set to 5℃ / min, and the temperature was raised to 750℃ and then kept at a constant temperature for 1.25h. After heat treatment, the powder was naturally cooled to room temperature in the furnace. The cooled powder was then immersed in a 5wt% nitric acid solution for 15 minutes, followed by washing with deionized water and anhydrous ethanol three times each. Finally, the washed powder was placed in an 80℃ oven to dry thoroughly, and the surface-functionalized high thermal conductivity diamond micro powder product was obtained.

[0042] Example 2 This embodiment provides a method for preparing surface-functionalized high thermal conductivity diamond micropowder, including the following steps: 20g of high thermal conductivity single crystal diamond powder with an average particle size of 50μm was selected. The diamond powder was immersed in a 5% sodium hydroxide aqueous solution, the pH was adjusted to 12, the reaction temperature was controlled at 60℃, and the mixture was stirred and soaked at a constant temperature for 1h. After degreasing, the acid washing operation of Example 1 was carried out. The powder was immersed in a compound acidic solution with a volume ratio of sulfuric acid solution to nitric acid solution of 3:1, the pH of the system was controlled to be less than 1, the temperature was raised to 80°C, and the acid washing was carried out by stirring at a constant temperature for 2 hours. After acid washing, the same washing and drying as in Example 1 were performed to obtain the pretreated diamond micro powder. Using the same sensitization solution preparation and ultrasonic operation as in Example 1, an acidic sensitization solution containing 10 g / L stannous chloride and 30 mL / L hydrochloric acid solution was prepared. The pH of the sensitization solution was adjusted to 1.0, and the pretreated diamond micropowder was ultrasonically impregnated at room temperature for 8 min. After sensitization and rinsing, the same activation solution was prepared and ultrasonically operated as in Example 1. The pH of the activation solution was adjusted to 2.0, and the mixture was ultrasonically immersed at room temperature for 5 minutes to obtain diamond micro powder I.

[0043] The same chemical tungsten plating solution preparation procedure as in Example 1 was adopted. The pH of the plating solution was adjusted to 8.0 with ammonia water. Diamond micro powder I was added to the plating solution, the water bath temperature was raised to 80°C, and the reaction was stirred at a constant temperature for 1 hour. After the reaction, the solution was cooled, filtered, and washed to obtain diamond micro powder II. Using the same heat treatment atmosphere and heating method as in Example 1, diamond micro powder II was heat-treated at a constant temperature of 600°C for 0.5 h. After cooling, the same pickling, washing, and drying post-treatment process as in Example 1 was used to finally obtain surface-functionalized high thermal conductivity diamond micro powder product.

[0044] Example 3 This embodiment provides a method for preparing surface-functionalized high thermal conductivity diamond micropowder, including the following steps: 20g of high thermal conductivity single crystal diamond powder with an average particle size of 50μm was selected. The diamond powder was immersed in a 15% sodium hydroxide aqueous solution, the pH was adjusted to 14, the reaction temperature was controlled at 80℃, and the mixture was stirred and soaked at a constant temperature for 3 minutes. After degreasing, the acid washing operation of Example 1 was carried out. The powder was immersed in a compound acidic solution with a volume ratio of sulfuric acid solution to nitric acid solution of 5:1, the pH of the system was controlled to be less than 1, the temperature was raised to 120°C, and the acid washing was carried out by stirring at a constant temperature for 5 hours. After acid washing, the same washing and drying as in Example 1 were performed to obtain the pretreated diamond micro powder. Using the same sensitization solution preparation and ultrasonic operation as in Example 1, an acidic sensitization solution containing 20 g / L stannous chloride and 50 mL / L hydrochloric acid solution was prepared. The pH of the sensitization solution was adjusted to 2.0, and the pretreated diamond micropowder was ultrasonically impregnated at room temperature for 15 min. After sensitization and rinsing, the same activation solution was prepared and ultrasonically operated as in Example 1. The pH of the activation solution was adjusted to 3.0, and the mixture was ultrasonically impregnated at room temperature for 10 minutes to obtain diamond micro powder I.

[0045] The same chemical tungsten plating solution preparation procedure as in Example 1 was adopted. The pH of the plating solution was adjusted to 10.0 with ammonia water. Diamond micro powder I was added to the plating solution, the water bath temperature was raised to 95°C, and the reaction was stirred at a constant temperature for 4 hours. After the reaction, the solution was cooled, filtered, and washed to obtain diamond micro powder II. Using the same heat treatment atmosphere and heating method as in Example 1, diamond micro powder II was heat-treated at 900°C for 2 hours. After cooling, the same pickling, washing, and drying post-treatment process as in Example 1 was used to finally obtain surface-functionalized high thermal conductivity diamond micro powder product.

[0046] The surface-functionalized high thermal conductivity diamond micro powder products prepared in Examples 1, 2 and 3 were tested, and the test results are shown in Table 1.

[0047] The detection method is as follows: 1) Method for detecting the ultrasonic peeling rate of coating: Take a quantitative amount of dried surface-functionalized high thermal conductivity diamond micro powder product, accurately weigh the initial mass, place it in deionized water, and use a 40kHz ultrasonic cleaner to oscillate at a constant temperature for 30 minutes. After oscillation, filter, wash, dry and weigh the powder again. Calculate the percentage of coating peeling mass by the difference between the initial and final mass values ​​to obtain the ultrasonic peeling rate of the coating. 2) Powder dispersion stability test method: Take equal amounts of the surface-functionalized high thermal conductivity diamond micro powder products obtained from the three sets of examples, disperse them in room temperature deionized water, stir evenly at a uniform speed, let stand, observe and record the time when the powder shows obvious stratification and sedimentation under a sealed and light-proof environment. 3) Surface water contact angle testing method: The surface functionalized high thermal conductivity diamond micro powder product is pressed into a flat and dense powder sheet. The static contact angle of deionized water on the powder surface is tested by the pendant drop method under normal temperature and pressure environment using a contact angle measuring instrument. 4) High-temperature thermogravimetric analysis method: Thermogravimetric analyzer is used to heat the powder to 800℃ at a heating rate of 10℃ / min under nitrogen protection and hold it at a constant temperature. The mass change of the powder throughout the process is tested and the mass loss rate of the powder under 800℃ conditions is statistically analyzed. Table 1. Test results of Examples 1-3 As shown in Table 1, the preparation method provided by this invention effectively solves the defects of the original diamond powder, such as strong surface inertness, easy agglomeration, poor interfacial compatibility, and insufficient high-temperature stability, through the synergistic effect of pretreatment of high thermal conductivity single-crystal diamond micropowder, ultrasonic sensitization activation, tungsten-phosphorus alloy chemical plating, and heat treatment. Among them, the coating peeling rate data proves that the surface activation modification of the obtained product is successful and the coating is firmly bonded; the dispersion sedimentation test confirms that the dispersion performance of the obtained product is optimized; the contact angle data shows that the interfacial wettability between the obtained product and the organic matrix is ​​greatly improved; and the thermogravimetric data verifies that the obtained product has enhanced high-temperature oxidation resistance and structural stability.

[0048] Comparative Example 1 The difference between this comparative example and Example 1 is that this comparative example does not perform the ultrasonic sensitization and ultrasonic activation processes, while the remaining steps and process parameters are the same as those in Example 1.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that this comparative example does not perform heat treatment after obtaining diamond micro powder II, and directly obtains the final product. The remaining steps and process parameters are the same as those in Example 1.

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is that this comparative example uses ordinary polycrystalline diamond powder, while the remaining steps and process parameters are the same as in Example 1.

[0051] The samples obtained from Comparative Examples 1-3 were tested below. The test results of Comparative Examples 1-3 and Example 1 are shown in Table 2.

[0052] Table 2 shows the test results for Comparative Examples 1-3 and Example 1. As can be seen from Table 2, Example 1, and Comparative Example 1: Comparative Example 1, which did not undergo ultrasonic sensitization and ultrasonic activation processes, showed a coating ultrasonic peeling rate as high as 11.8%, significantly higher than that of Example 1. Furthermore, it exhibited rapid powder settling, a large surface contact angle, and increased high-temperature thermal weight loss. Due to the extremely strong chemical inertness of the native diamond surface, conventional pretreatment methods cannot construct uniform and dense alloy nucleation sites on the powder surface. Without the synergistic activation effect of ultrasound, the tungsten / phosphorus alloy layer cannot be continuously and densely deposited, resulting in numerous defects such as missed plating and discontinuous coatings. This directly leads to extremely poor coating adhesion, failure of powder surface activation modification, and ultimately a comprehensive reduction in dispersion stability, interfacial compatibility, and high-temperature thermal stability. Comparative Example 2 did not undergo heat treatment after obtaining diamond micropowder II. This group of samples exhibited high coating peeling rates and thermal weight loss rates, and significantly reduced powder dispersion and interfacial wetting properties. Because the tungsten / phosphorus alloy directly deposited by electroless plating has a loose, amorphous precursor structure, it only physically adheres to the diamond surface. Without high-temperature crystallization and shaping, the coating structure is loose and has high porosity. This results in weak bonding strength with the substrate, making it prone to peeling and failure. Furthermore, it cannot form a dense protective layer, making it difficult to improve the inert defects on the powder surface and exhibiting extremely poor resistance to high-temperature oxidation. Comparative Example 3 used ordinary polycrystalline diamond micron powder. The coating quality, dispersion performance, interfacial properties and thermal stability of this group of samples were similar to those of Example 1. However, polycrystalline diamond has a large number of grain boundaries and lattice defects, resulting in large heat transfer and scattering losses. Under high heat flux density and long-term high temperature service conditions, the thermal conductivity attenuation is obvious, and it is only suitable for conventional thermally conductive composite materials.

Claims

1. A method for preparing surface-functionalized high thermal conductivity diamond micropowder, characterized in that, Includes the following steps: S1. Diamond micro powder I is obtained by sequentially subjecting the pretreated diamond micro powder to ultrasonic sensitization and ultrasonic activation. S2. Disperse diamond micro powder I in a chemical plating solution, adjust the pH to 8-10, and react at 80-95℃ for 1-4 hours to deposit a tungsten / phosphorus alloy layer or a molybdenum / phosphorus alloy layer on the surface of diamond micro powder I to obtain diamond micro powder II. The electroless plating solution uses sodium tungstate or sodium molybdate as the main salt, sodium citrate or disodium EDTA as the complexing agent, nickel sulfate or nickel chloride as the accelerator, and sodium hypophosphite as the reducing agent. S3. After heat treatment of diamond micro powder II, it is cooled to room temperature to obtain surface-functionalized high thermal conductivity diamond micro powder product.

2. The method for preparing surface-functionalized high thermal conductivity diamond micropowder as described in claim 1, characterized in that, The method for pretreating diamond micro powder in S1 includes: Diamond micro powder is immersed in sodium hydroxide or sodium carbonate aqueous solution and stirred for 1 to 3 hours at pH 12–14 and 60–80°C to remove oil. After rinsing the degreased diamond micro powder, it is immersed in a compound acidic solution of sulfuric acid and nitric acid, and stirred and acid-washed for 2-5 hours at pH < 1 and 80-120℃. After acid washing, the diamond powder is washed and dried to obtain pretreated diamond powder.

3. The method for preparing surface-functionalized high thermal conductivity diamond micropowder as described in claim 2, characterized in that, The mass concentration of the sodium hydroxide aqueous solution and the sodium carbonate aqueous solution are both 5-15%.

4. The method for preparing surface-functionalized high thermal conductivity diamond micropowder as described in claim 2, characterized in that, The volume ratio of the sulfuric acid solution to the nitric acid solution is 3 to 5:1, the mass fraction of the sulfuric acid solution is ≥98%, and the mass fraction of the nitric acid solution is ≥65%.

5. The method for preparing surface-functionalized high thermal conductivity diamond micropowder as described in claim 1, characterized in that, The specific methods for ultrasound sensitization in S1 include: The pretreated diamond micropowder was dispersed in an acidic stannous chloride sensitizing solution and ultrasonically impregnated for 8–15 min at room temperature and 30–60 kHz.

6. The method for preparing surface-functionalized high thermal conductivity diamond micropowder as described in claim 5, characterized in that, The pH of the stannous chloride acidic sensitizing solution is 1-2. The stannous chloride acidic sensitizing solution is prepared by stannous chloride, hydrochloric acid solution and deionized water. The concentration of stannous chloride is 10-20 g / L and the amount of hydrochloric acid solution added is 30-50 mL / L.

7. The method for preparing surface-functionalized high thermal conductivity diamond micropowder as described in claim 1, characterized in that, The specific method for ultrasonic activation in S1 includes: After rinsing, the ultrasonically sensitized diamond micropowder was dispersed in an acidic palladium chloride activation solution and ultrasonically impregnated for 5–10 min at room temperature and 30–60 kHz.

8. The method for preparing surface-functionalized high thermal conductivity diamond micropowder as described in claim 7, characterized in that, The pH of the palladium chloride acidic activation solution is 2-3. The palladium chloride acidic activation solution is prepared by palladium chloride, hydrochloric acid solution and deionized water. The concentration of palladium chloride is 0.05-0.15 g / L and the amount of hydrochloric acid solution added is 10-20 mL / L.

9. The method for preparing surface-functionalized high thermal conductivity diamond micropowder as described in claim 1, characterized in that, The heat treatment in S3 is performed at a temperature of 600–900°C for a time of 0.5–2 hours.

10. The method for preparing surface-functionalized high thermal conductivity diamond micropowder as described in claim 9, characterized in that, During the heat treatment, the diamond micro powder II is placed in an inert atmosphere or a reducing atmosphere.

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