Method for preparing metal-based diamond heat-conducting composite material by using supercritical CO2 fluid

Abstract

The invention discloses a method for preparing a metal-based diamond heat-conducting composite material by using supercritical CO2 fluid. The method comprises the following steps: step 1, pretreating diamond particles; 2, a nanoscale metal or nonmetal-carbon composite interface layer is formed; and 3, preparing the composite material to obtain the metal-based diamond heat-conducting composite material. Diamond particles and a metal source or a non-metal source are put into a closed reaction container, CO2 is introduced to adjust the pressure and the temperature so that CO2 can reach the supercritical state, the supercritical environment is maintained so that CO2 and the diamond particles can fully act, and a nanoscale metal or non-metal-carbon composite interface layer is formed; and then the diamond is mixed with the metal matrix to prepare the metal-based diamond heat-conducting composite material, so that the interface bonding strength of the diamond and the metal matrix is effectively enhanced, the interface thermal resistance is reduced, the problems of poor interface bonding strength and high interface thermal resistance of the diamond and the metal matrix are solved, and the heat-conducting property and the comprehensive property of the composite material are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal-based composite materials, and in particular relates to a method for preparing a metal-based diamond thermal conductive composite material by utilizing supercritical CO2 fluid. Background Art

[0002] With the rapid development of electronic information technology, the power of electronic equipment continues to rise, and heat dissipation has become a key factor restricting the performance and reliability of equipment. Metal-based diamond thermal conductive composite materials have great application prospects in the field of electronic heat dissipation due to their advantages such as high thermal conductivity and adjustable thermal expansion coefficient. However, there are many problems with this type of composite material at present, among which the interface bonding strength between diamond and metal matrix is poor and the interface thermal resistance is high, which seriously affects the thermal conductivity and comprehensive performance of the composite material. Traditional methods to improve interface bonding, such as chemical plating and physical vapor deposition, have disadvantages such as complicated processes, high costs, and difficulty in accurately controlling the interface structure and performance.

[0003] Therefore, it is of great significance to develop a simple, efficient, and precise preparation method that can precisely control the interface structure and performance. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the above-mentioned prior art and provide a method for preparing a metal-based diamond thermally conductive composite material using supercritical CO2 fluid. This method utilizes the properties of supercritical CO2 fluid to successfully form a nanoscale metal or non-metal-carbon composite interface layer on the surface of diamond particles. This layer is then bonded to a metal matrix through powder metallurgy, hot pressing, or spray deposition to produce the metal-based diamond thermally conductive composite material. This method addresses the technical issues of poor interface bonding strength and high interfacial thermal resistance between diamond and the metal matrix in the prior art, thereby improving the thermal conductivity and overall performance of the composite material.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid, characterized in that the method comprises the following steps:

[0006] Step 1: Pre-treating diamond particles: screening diamond particles with a particle size of 5 μm to 900 μm, then washing them with an organic solvent and drying them for later use to obtain pre-treated diamond particles;

[0007] Step 2: Forming a nanoscale metal or non-metal-carbon composite interface layer: The pretreated diamond particles obtained in step 1 and a metal source or non-metal source are placed in a sealed reaction vessel, and then CO2 is charged to adjust the pressure to 20MPa to 40MPa and the temperature to 40°C to 80°C to make the CO2 reach a supercritical state, and the supercritical state is maintained for 3h to 8h to obtain diamond particles having a nanoscale metal or non-metal-carbon composite interface layer with a thickness of 10nm to 50nm;

[0008] Step 3: Preparation of composite materials: The diamond particles with nano-scale metal or non-metal-carbon composite interface layer obtained in step 3 are mixed with a metal matrix in a volume ratio of 1 to 3:2 to 5, and then subjected to powder metallurgy, hot pressing sintering or spray deposition to obtain a metal-based diamond thermal conductive composite material.

[0009] In the present invention, by screening the diamond particles to have a particle size of 5 μm to 30 μm, it is convenient to achieve interface bonding optimization. The appropriate particle size increases the contact area between the diamond particles and the metal matrix, while avoiding the interface stress concentration caused by overly large diamond particles or the agglomeration phenomenon caused by overly small diamond particles, thereby improving the interface bonding strength. In addition, the uniform particle size distribution helps to form a continuous heat conduction path, reduce thermal resistance, maximize the thermal conductivity of the composite material, and improve thermal conductivity.

[0010] In the present invention, the pressure and temperature of the CO2 are controlled to make the CO2 reach a supercritical state, and the supercritical environment is maintained for a certain time, so that the supercritical CO2 can fully react with the metal source or non-metal source and the diamond particles. The metal source or non-metal source and the carbon atoms on the diamond surface form metal or non-metal-carbon bonds through physical adsorption and chemical reactions (such as carbon thermal reduction and diffusion), thereby constructing a nano-scale metal or non-metal-carbon composite interface layer. In the supercritical CO2 fluid, the thickness of the nano-scale metal or non-metal-carbon composite interface layer changes by 0.3nm to 0.7nm for every 1h increase or decrease in the supercritical state. Therefore, the thickness of the nano-scale metal or non-metal-carbon composite interface layer obtained by controlling the time of maintaining the supercritical state is 10nm to 50nm, wherein the nano-scale metal or non-metal-carbon composite layer is 0.3nm to 0.7nm. The interface layer enhances the interface bonding strength between diamond and metal matrix. The interface layer significantly improves the bonding strength between diamond and metal matrix through chemical bonding (metal or non-metal-carbon bond) and mechanical interlocking, reduces the risk of interface debonding, and the continuous and uniform nanoscale interface layer can effectively reduce phonon scattering and promote efficient heat transfer at the interface, thereby improving the thermal conductivity of the composite material and reducing the interface thermal resistance. The thickness of the nanoscale metal or non-metal-carbon composite interface layer is controlled to be 10nm to 50nm, which has the best performance balance, ensures that the interface layer is complete and dense, and prevents the composition gradient from getting out of control. At the same time, it avoids the problems of too small thickness, incomplete interface layer, limited bonding strength and thermal conductivity improvement effect, and too large thickness, forming an excessive diffusion layer, introducing additional thermal resistance or brittle phase, and resulting in performance degradation.

[0011] It should be noted that the closed reaction vessel in the present invention has a pressure resistance of 60 MPa or above.

[0012] It should be noted that the mixing process of the diamond particles having a nano-scale metal or non-metal-carbon composite interface layer and the metal matrix of the present invention adopts a three-dimensional mixer to ensure mixing uniformity and improve the performance of the composite material.

[0013] The aforementioned method for preparing a metal-based diamond thermally conductive composite material using supercritical CO2 fluid is characterized in that the organic solvent in step 1 is an acetone solution, an ethanol solution, or a mixed solution of acetone and ethanol. By controlling the type of organic solvent, the present invention fully removes impurities from the surface of the diamond particles.

[0014] The above-mentioned method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid is characterized in that the process of drying after washing with an organic solvent in step 1 is as follows: placing the diamond particles in an organic solvent, washing them with an ultrasonic power of 80W to 180W for 10min to 20min, then transferring them to deionized water, washing them with an ultrasonic power of 80W to 180W for 8min to 12min, and then drying them in a vacuum of 1×10 -4 Pa~1×10-2 The present invention is carried out by ultrasonic cleaning in an organic solvent to fully remove oil stains, ultrasonic cleaning in deionized water to fully remove residual solvents and water-soluble impurities, and drying to ensure that the surface is free of water.

[0015] The above-mentioned method for preparing a metal-based diamond thermally conductive composite material using supercritical CO2 fluid is characterized in that the metal source in step 2 is titanium powder, zirconium powder, chromium powder, tungsten powder, or molybdenum powder, and the non-metallic source is boron powder or silicon powder. The mass purity of the metal source or non-metallic source is not less than 99.9%, and the particle size of the metal source or non-metallic source is 5nm to 500nm. The present invention forms different metal or non-metal-carbon bonds by controlling the composition of the metal source and non-metallic source to meet various application requirements. By controlling the particle size of the metal source or non-metallic source, the smooth formation of the metal or non-metal-carbon bond is ensured.

[0016] The above-mentioned method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid is characterized in that the concentration of the metal source or non-metallic source in the closed reaction vessel in step 2 is 0.05 mol / L~0.3 mol / L, the flow rate of the CO2 is 15 mL / min~35 mL / min, the mass purity of the CO2 is not less than 99.99%, and stirring is added in the closed reaction vessel, and the stirring speed is 50 rpm~200 rpm. The thickness of the nanoscale metal or non-metal-carbon composite interface layer in the present invention is related to the concentration of the metal source or non-metal source, the flow rate of CO2, the time of maintaining the supercritical state and the stirring speed. The higher the metal source concentration, the slower the CO2 flow rate, and the stirring is performed, the higher the contact efficiency provided, the longer the time of maintaining the supercritical state, the more metal atoms deposited per unit time, and the thickness of the interface layer increases. By controlling the concentration of the metal source or non-metal source in the closed reaction vessel, the thickness of the nanoscale metal or non-metal-carbon composite interface layer changes by 0.15nm to 0.25nm for every increase or decrease of 0.01mol / L. However, if the metal source concentration is too high, the interface layer composition may be segregated (such as metal particle agglomeration), and if the concentration is too low, an incomplete interface layer may be formed. By controlling the flow rate of CO2, the nanoscale metal or non-metal-carbon composite interface layer may be changed by 0.15nm to 0.25nm for every increase or decrease of 0.01mol / L. The thickness of the carbon composite interface layer changes from 0.08nm to 0.12nm. The CO2 flow rate affects the mass transfer efficiency. A flow rate that is too fast may lead to uneven distribution of the metal source, affecting the uniformity of the interface layer. A flow rate that is too slow may prolong the reaction time and increase energy consumption. By changing the stirring speed of the closed reaction vessel, the contact efficiency between supercritical CO2 and diamond particles is regulated, the reaction process is further optimized. The contact efficiency between supercritical CO2 and diamond particles is improved, the uniform deposition of the metal source is promoted, and the uniformity of the interface layer and the reaction rate are further optimized. The stirring speed can be used as an additional control parameter. Therefore, by controlling the metal source concentration, the flow rate of CO2, the time of maintaining the supercritical state and the coordinated stirring speed, the thickness, composition gradient and structural uniformity of the interface layer are jointly optimized, the preparation accuracy of the interface layer is improved, and a nanoscale metal or non-metal-carbon composite interface layer of appropriate thickness is obtained.

[0017] The above-mentioned method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid is characterized in that the metal matrix in step three is a metal element powder or a metal alloy powder, the metal element powder is aluminum powder, copper powder, silver powder or magnesium powder, the metal alloy powder is aluminum alloy powder, copper alloy powder, silver alloy powder or magnesium alloy powder, the mass purity of the metal matrix is not less than 99.5%, and the particle size of the metal matrix is 10μm to 200μm. The present invention is suitable for different usage requirements by controlling the composition of the metal matrix. When copper powder is used, copper has excellent thermal conductivity (thermal conductivity of 401W / m·K), which matches the thermal expansion coefficient of diamond and is suitable for heat dissipation of high-frequency electronic devices. The obtained metal-based diamond thermal conductive composite material has significantly improved thermal conductivity, balanced comprehensive mechanical properties, and wide application. When silver powder is used, silver has the highest thermal conductivity (thermal conductivity of 429W / m·K) and excellent electrical conductivity, which is suitable for high-end microelectronic heat dissipation scenarios. The thermal conductivity of the obtained metal-based diamond thermal conductive composite material can be improved to the upper limit, but the cost is relatively high, which is suitable for high value-added fields. When aluminum alloy powder is used, aluminum alloy powder has low density and low cost. It is suitable for lightweight heat dissipation needs, such as avionics equipment. The obtained metal-based diamond thermal conductive composite material has good interface bonding strength, thermal conductivity increased by about 20%, and high comprehensive cost performance. When magnesium alloy powder is used, the density of magnesium alloy powder is the lowest, and thermal conductivity and mechanical properties are balanced, which is suitable for extreme lightweight scenarios, such as mobile electronic devices. The obtained metal-based diamond thermal conductive composite material has moderate thermal conductivity improvement, moderate interface bonding strength, and significant weight advantage. By controlling the particle size of the metal matrix, the bonding effect of diamond particles with a nano-scale metal or non-metal-carbon composite interface layer and the metal matrix is guaranteed, which further improves the performance of the metal-based diamond thermal conductive composite material.

[0018] The above-mentioned method for preparing a metal-based diamond thermally conductive composite material using supercritical CO2 fluid is characterized in that the powder metallurgy process described in step 3 is: sintering at a pressure of 120MPa to 250MPa and a temperature of 750°C to 950°C; the hot pressing sintering process is: hot pressing molding in a mold at a pressure of 180MPa to 300MPa and a temperature of 850°C to 1100°C; and the spray deposition process is: depositing the material onto a substrate at a temperature of 450°C to 650°C through a spray gun at a spray speed of 80m / s to 200m / s. The present invention prepares the metal-based diamond thermally conductive composite material by different methods and is suitable for the preparation of different types of metal-based diamond thermally conductive composite materials.

[0019] The above-mentioned method for preparing a metal-based diamond thermally conductive composite material using supercritical CO2 fluid is characterized in that the metal-based diamond thermally conductive composite material described in step 3 has a thermal conductivity increased by 15% to 35% and an interfacial bonding strength increased by 25 MPa to 45 MPa compared to the metal-based diamond composite material. The metal-based diamond thermally conductive composite material prepared by the present invention has improved thermal conductivity and interfacial bonding strength compared to metal-based diamond composite materials prepared by traditional methods.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The present invention precisely controls the interface structure and properties, and utilizes the characteristics of supercritical CO2 fluid to successfully form a nanoscale metal or non-metal-carbon composite interface layer on the surface of diamond particles. Through multi-parameter regulation, the thickness and composition gradient of the interface layer are precisely controlled, effectively enhancing the interfacial bonding strength between diamond and metal matrix and reducing the interfacial thermal resistance. This solves the technical problems of poor interfacial bonding strength and high interfacial thermal resistance between diamond and metal matrix in the prior art, and improves the thermal conductivity and overall performance of the composite material.

[0022] 2. The metal-based diamond thermal conductive composite material prepared by the present invention has a thermal conductivity increased by 15% to 35% and an interface bonding strength increased by 25 MPa to 45 MPa compared to materials not prepared by this method, and has better overall performance.

[0023] 3. The preparation process of the present invention is relatively simple, does not require complex equipment and expensive reagents, has low production cost, and has good industrial application prospects.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a comparison curve of the thermal conductivity of the metal-based diamond thermally conductive composite materials prepared in Examples 1 to 5 of the present invention and the metal-based diamond composite materials prepared in Comparative Examples 1 to 5. DETAILED DESCRIPTION

[0026] Example 1

[0027] This embodiment includes the following steps:

[0028] Step 1: Pretreatment of diamond particles: Diamond particles with a particle size of 5 μm to 900 μm were screened, and then placed in acetone solution and cleaned with an ultrasonic power of 120 W for 15 min. Then, they were transferred to deionized water and cleaned with an ultrasonic power of 120 W for 10 min. -3 The pre-treated diamond particles were dried at 400 Pa for 3 h.

[0029] Step 2: Formation of a nanoscale non-metal-carbon composite interface layer: The pretreated diamond particles obtained in step 1 and boron powder with a particle size of 5nm to 500nm and a mass purity of 99.95% are placed in a special alloy steel sealed reaction vessel with a pressure resistance of 70MPa, so that the concentration of the boron powder in the sealed reaction vessel is 0.1mol / L, and then CO2 with a mass purity of 99.995% is charged at a flow rate of 20mL / min to adjust the pressure to 32MPa and the temperature to 65°C to make the CO2 reach a supercritical state. The sealed reaction vessel is stirred at a speed of 100rpm and the supercritical state is maintained for 5h to obtain diamond particles with a nanoscale non-metal-carbon composite interface layer with a thickness of 30nm;

[0030] Step 3: Preparation of composite materials: The diamond particles with a nano-scale non-metal-carbon composite interface layer obtained in step 3 are mixed with copper powder with a particle size of 10 μm to 200 μm and a mass purity of 99.6% in a volume ratio of 3:4, and then powder metallurgy is performed. The mixture is sintered at a pressure of 180 MPa and a temperature of 850°C to obtain a metal-based diamond thermal conductive composite material.

[0031] In this embodiment, the non-metallic source may also be silicon powder, and the metal element powder may also be aluminum powder, silver powder or magnesium powder.

[0032] Comparative Example 1

[0033] This comparative example comprises the following steps:

[0034] Step 1: Pretreatment of diamond particles: Diamond particles with a particle size of 5 μm to 900 μm were screened, and then placed in acetone solution and cleaned with an ultrasonic power of 120 W for 15 min. Then, they were transferred to deionized water and cleaned with an ultrasonic power of 120 W for 10 min. -3 The pre-treated diamond particles were dried at 400 Pa for 3 h.

[0035] Step 2: Interface layer formation: The pre-treated diamond particles obtained in step 1 are mixed evenly with boron powder with a particle size of 5nm to 500nm and a mass purity of 99.95% in a volume ratio of 1:2, and then -4 Pa vacuum conditions, heated to 1050 ° C and then kept warm for 2 h to obtain diamond particles with boron coating on the surface;

[0036] Step 3: Preparation of composite material: The boron-coated diamond particles obtained in step 3 are mixed with copper powder with a particle size of 10 μm to 200 μm and a mass purity of 99.6% in a volume ratio of 3:4, and then powder metallurgy is performed. The mixture is sintered at a pressure of 40 MPa and a temperature of 1050° C. to obtain a metal-based diamond composite material.

[0037] After testing, the thermal conductivity of the metal-based diamond composite material prepared in Comparative Example 1 is 442.56 W / (m·K), the thermal conductivity of the metal-based diamond thermally conductive composite material prepared in Example 1 is increased by 25% compared with Comparative Example 1, and the interface bonding strength is increased by 35 MPa.

[0038] By comparing Example 1 and Comparative Example 1, it can be seen that Example 1 utilizes the characteristics of supercritical CO2 fluid to successfully form a nanoscale metal or non-metal-carbon composite interface layer on the surface of diamond particles, effectively enhancing the interface bonding strength between diamond and metal matrix and reducing the interface thermal resistance, thereby solving the technical problems of poor interface bonding strength and high interface thermal resistance between diamond and metal matrix in the prior art and improving the thermal conductivity and comprehensive performance of the composite material.

[0039] Example 2

[0040] This embodiment includes the following steps:

[0041] Step 1: Pretreatment of diamond particles: Diamond particles with a particle size of 5 μm to 900 μm were screened, and then placed in an ethanol solution and cleaned with an ultrasonic power of 100 W for 12 min. Then, they were transferred to deionized water and cleaned with an ultrasonic power of 100 W for 8 min. -2 The pre-treated diamond particles were dried at 400 Pa for 2.5 h and then used for subsequent use.

[0042] Step 2: Formation of a nanoscale metal-carbon composite interface layer: The pretreated diamond particles obtained in step 1 and titanium powder with a particle size of 5nm to 500nm and a mass purity of 99.92% are placed in a special alloy steel sealed reaction vessel with a pressure resistance of 65MPa, so that the concentration of the titanium powder in the sealed reaction vessel is 0.15mol / L, and then CO2 with a mass purity of 99.995% is charged at a flow rate of 20mL / min to adjust the pressure to 25MPa and the temperature to 50°C to make the CO2 reach a supercritical state. The sealed reaction vessel is stirred at a speed of 200rpm and the supercritical state is maintained for 4h to obtain diamond particles with a nanoscale metal-carbon composite interface layer with a thickness of 20nm;

[0043] Step 3, preparation of composite materials: The diamond particles with a nano-scale metal-carbon composite interface layer obtained in step 3 are mixed with aluminum alloy powder with a particle size of 10μm to 200μm and a mass purity of 99.5% in a volume ratio of 2:3, and then hot-pressed and sintered. In a mold, hot pressing is performed at a pressure of 220MPa and a temperature of 950°C to obtain a metal-based diamond thermal conductive composite material.

[0044] In this embodiment, the metal source may also be zirconium powder, chromium powder, tungsten powder or molybdenum powder, and the metal alloy powder may also be copper alloy powder, silver alloy powder or magnesium alloy powder.

[0045] In this embodiment, the hot pressing sintering process may also be: hot pressing molding in a mold at a pressure of 180 MPa and a temperature of 1100° C., or hot pressing molding in a mold at a pressure of 300 MPa and a temperature of 850° C.

[0046] Comparative Example 2

[0047] The difference between this comparative example and comparative example 1 is that titanium powder is used in step 2.

[0048] After testing, the thermal conductivity of the metal-based diamond composite material prepared in Comparative Example 2 is 487.93 W / (m·K). The thermal conductivity of the metal-based diamond thermally conductive composite material prepared in Example 2 is increased by 20% compared with Comparative Example 2, and the interface bonding strength is increased by 30 MPa.

[0049] By comparing Example 2 and Comparative Example 2, it can be seen that Example 2 utilizes the characteristics of supercritical CO2 fluid to successfully form a nanoscale metal or non-metal-carbon composite interface layer on the surface of diamond particles, effectively enhancing the interface bonding strength between diamond and metal matrix, reducing the interface thermal resistance, solving the technical problems of poor interface bonding strength and high interface thermal resistance between diamond and metal matrix in the prior art, and improving the thermal conductivity and comprehensive performance of the composite material.

[0050] Example 3

[0051] This embodiment includes the following steps:

[0052] Step 1: Pretreatment of diamond particles: Diamond particles with a particle size of 5 μm to 900 μm were screened, and then placed in a mixed solution of acetone and ethanol, and cleaned with an ultrasonic power of 150 W for 18 minutes, then transferred to deionized water, and cleaned with an ultrasonic power of 150 W for 12 minutes, and then placed in a vacuum of 1×10 -4 The pre-treated diamond particles were dried at 400 Pa for 3.5 h and then used for subsequent use.

[0053] Step 2: Formation of a nanoscale metal-carbon composite interface layer: The pretreated diamond particles obtained in step 1 and chromium powder with a particle size of 5nm to 500nm and a mass purity of 99.9% are placed in a special alloy steel sealed reaction vessel with a pressure resistance of 80MPa, so that the concentration of the chromium powder in the sealed reaction vessel is 0.2mol / L, and then CO2 with a mass purity of 99.995% is charged at a flow rate of 25mL / min to adjust the pressure to 38MPa and the temperature to 75°C to make the CO2 reach a supercritical state. The sealed reaction vessel is stirred at a speed of 50rpm and the supercritical state is maintained for 6h to obtain diamond particles with a nanoscale metal-carbon composite interface layer with a thickness of 40nm;

[0054] Step 3, preparation of composite materials: The diamond particles with a nano-scale metal-carbon composite interface layer obtained in step 3 are mixed with magnesium alloy powder with a particle size of 10μm to 200μm and a mass purity of 99.5% in a volume ratio of 1:2, and then spray-deposited onto a substrate at a temperature of 550°C through a spray gun at a spray speed of 120m / s to obtain a metal-based diamond thermal conductive composite material.

[0055] In this embodiment, the metal source may also be titanium powder, zirconium powder, tungsten powder or molybdenum powder, and the metal alloy powder may also be aluminum alloy powder, copper alloy powder or silver alloy powder.

[0056] In this embodiment, the spray deposition process can also be: depositing onto a substrate at a temperature of 450°C through a spray gun at a spray speed of 80m / s, or depositing onto a substrate at a temperature of 650°C through a spray gun at a spray speed of 200m / s.

[0057] Comparative Example 3

[0058] The difference between this comparative example and comparative example 1 is that chromium powder is used in step 2.

[0059] After testing, the thermal conductivity of the metal-based diamond composite material prepared in Comparative Example 3 is 519.84 W / (m·K). The thermal conductivity of the metal-based diamond thermally conductive composite material prepared in Example 3 is increased by 18% compared with Comparative Example 3, and the interface bonding strength is increased by 28 MPa.

[0060] By comparing Example 3 and Comparative Example 3, it can be seen that Example 3 utilizes the characteristics of supercritical CO2 fluid to successfully form a nanoscale metal or non-metal-carbon composite interface layer on the surface of diamond particles, effectively enhancing the interface bonding strength between diamond and metal matrix and reducing the interface thermal resistance, thereby solving the technical problems of poor interface bonding strength and high interface thermal resistance between diamond and metal matrix in the prior art and improving the thermal conductivity and comprehensive performance of the composite material.

[0061] Example 4

[0062] This embodiment includes the following steps:

[0063] Step 1: Pretreatment of diamond particles: Diamond particles with a particle size of 5 μm to 900 μm were screened, and then placed in acetone solution and cleaned with an ultrasonic power of 80 W for 20 min. Then, they were transferred to deionized water and cleaned with an ultrasonic power of 80 W for 8 min. Then, the diamond particles were placed in a vacuum of 1×10 -4 The pre-treated diamond particles were dried at 400 Pa for 2 h.

[0064] Step 2: Formation of a nanoscale metal-carbon composite interface layer: The pretreated diamond particles obtained in step 1 and molybdenum powder with a particle size of 5nm to 500nm and a mass purity of 99.9% are placed in a special alloy steel closed reaction vessel with a pressure resistance of 80MPa, so that the concentration of the molybdenum powder in the closed reaction vessel is 0.3mol / L, and then CO2 with a mass purity of 99.995% is charged at a flow rate of 15mL / min to adjust the pressure to 40MPa and the temperature to 40°C to make the CO2 reach a supercritical state, and the closed reaction vessel is stirred at a speed of 150rpm, and the supercritical state is maintained for 8h to obtain diamond particles with a nanoscale metal-carbon composite interface layer with a thickness of 50nm;

[0065] Step 3: Preparation of composite materials: The diamond particles with a nanoscale metal-carbon composite interface layer obtained in step 3 are mixed with silver powder with a particle size of 10 μm to 200 μm and a mass purity of 99.5% in a volume ratio of 3:5, and then powder metallurgy is performed. The mixture is sintered at a pressure of 120 MPa and a temperature of 950°C to obtain a metal-based diamond thermal conductive composite material.

[0066] In this embodiment, the metal source may also be titanium powder, zirconium powder, chromium powder or tungsten powder, and the metal element powder may also be aluminum powder, copper powder or magnesium powder.

[0067] Comparative Example 4

[0068] The difference between this comparative example and comparative example 1 is that molybdenum powder is used in step 2.

[0069] After testing, the thermal conductivity of the metal-based diamond composite material prepared in Comparative Example 4 is 401.25 W / (m·K), the thermal conductivity of the metal-based diamond thermally conductive composite material prepared in Example 4 is increased by 35% compared with Comparative Example 4, and the interface bonding strength is increased by 45 MPa.

[0070] By comparing Example 4 and Comparative Example 4, it can be seen that Example 4 utilizes the characteristics of supercritical CO2 fluid to successfully form a nanoscale metal or non-metal-carbon composite interface layer on the surface of the diamond particles, effectively enhancing the interface bonding strength between the diamond and the metal matrix and reducing the interface thermal resistance, thereby solving the technical problems of poor interface bonding strength and high interface thermal resistance between the diamond and the metal matrix in the prior art, and improving the thermal conductivity and comprehensive performance of the composite material.

[0071] Example 5

[0072] This embodiment includes the following steps:

[0073] Step 1: Pretreatment of diamond particles: Diamond particles with a particle size of 5 μm to 900 μm were screened, and then placed in acetone solution and cleaned with an ultrasonic power of 180 W for 10 min. Then, they were transferred to deionized water and cleaned with an ultrasonic power of 80 W for 10 min. -4 The pre-treated diamond particles were dried at 400 Pa for 4 h.

[0074] Step 2: Formation of a nanoscale non-metal-carbon composite interface layer: The pretreated diamond particles obtained in step 1 and silicon powder with a particle size of 5nm to 500nm and a mass purity of 99.9% are placed in a special alloy steel sealed reaction vessel with a pressure resistance of 80MPa, so that the concentration of silicon powder in the sealed reaction vessel is 0.05mol / L, and then CO2 with a mass purity of 99.995% is charged at a flow rate of 35mL / min to adjust the pressure to 20MPa and the temperature to 80°C to make the CO2 reach a supercritical state. The sealed reaction vessel is stirred at a speed of 100rpm and the supercritical state is maintained for 3h to obtain diamond particles with a nanoscale non-metal-carbon composite interface layer with a thickness of 10nm;

[0075] Step 3, preparation of composite materials: The diamond particles with a nano-scale non-metal-carbon composite interface layer obtained in step 3 are mixed with magnesium alloy powder with a particle size of 10 μm to 200 μm and a mass purity of 99.5% in a volume ratio of 2:5, and then powder metallurgy is performed. The mixture is sintered at a pressure of 250 MPa and a temperature of 750°C to obtain a metal-based diamond thermal conductive composite material.

[0076] In this embodiment, the non-metallic source may also be boron powder, and the metal alloy powder may also be aluminum alloy powder, copper alloy powder or silver alloy powder.

[0077] Comparative Example 5

[0078] The difference between this comparative example and comparative example 1 is that silicon powder is used in step 2.

[0079] After testing, the thermal conductivity of the metal-based diamond composite material prepared in Comparative Example 5 is 523.17 W / (m·K). The thermal conductivity of the metal-based diamond thermally conductive composite material prepared in Example 5 is increased by 15% compared with Comparative Example 5, and the interface bonding strength is increased by 25 MPa.

[0080] By comparing Example 5 and Comparative Example 5, it can be seen that Example 5 utilizes the characteristics of supercritical CO2 fluid to successfully form a nanoscale metal or non-metal-carbon composite interface layer on the surface of the diamond particles, effectively enhancing the interface bonding strength between the diamond and the metal matrix and reducing the interface thermal resistance, thereby solving the technical problems of poor interface bonding strength and high interface thermal resistance between the diamond and the metal matrix in the prior art, and improving the thermal conductivity and comprehensive performance of the composite material.

[0081] Figure 1 The thermal conductivity comparison curve of the metal-based diamond composite material prepared in Examples 1 to 5 of the present invention and the metal-based diamond composite material prepared in Comparative Examples 1 to 5 is shown. Figure 1 It can be seen from the figures that the metal-based diamond thermal conductive composite materials prepared in Examples 1 to 5 of the present invention have higher thermal conductivity.

[0082] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid, characterized in that: The method comprises the following steps: Step 1: Pre-treating diamond particles: screening diamond particles with a particle size of 5 μm to 900 μm, then washing them with an organic solvent and drying them for later use to obtain pre-treated diamond particles; Step 2: Forming a nanoscale metal or non-metal-carbon composite interface layer: The pretreated diamond particles obtained in step 1 and a metal source or non-metal source are placed in a sealed reaction vessel, and then CO2 is charged to adjust the pressure to 20MPa to 40MPa and the temperature to 40°C to 80°C to make the CO2 reach a supercritical state, and the supercritical state is maintained for 3h to 8h to obtain diamond particles having a nanoscale metal or non-metal-carbon composite interface layer with a thickness of 10nm to 50nm; Step 3: Preparation of composite materials: The diamond particles with nano-scale metal or non-metal-carbon composite interface layer obtained in step 3 are mixed with a metal matrix in a volume ratio of 1 to 3:2 to 5, and then subjected to powder metallurgy, hot pressing sintering or spray deposition to obtain a metal-based diamond thermal conductive composite material.

2. The method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid according to claim 1, characterized in that: The organic solvent in step 1 is acetone solution, ethanol solution or a mixed solution of acetone and ethanol.

3. The method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid according to claim 1, characterized in that: The process of drying after organic solvent cleaning in step 1 is as follows: placing the diamond particles in an organic solvent, cleaning them with an ultrasonic power of 80W to 180W for 10min to 20min, then transferring them to deionized water, cleaning them with an ultrasonic power of 80W to 180W for 8min to 12min, and then drying them in a vacuum of 1×10 -4 Pa~1×10 -2 Dry under Pa for 2h~4h.

4. The method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid according to claim 1, characterized in that: The metal source in step 2 is titanium powder, zirconium powder, chromium powder, tungsten powder or molybdenum powder, and the non-metallic source is boron powder or silicon powder. The mass purity of the metal source or non-metallic source is not less than 99.9%, and the particle size of the metal source or non-metallic source is 5nm to 500nm.

5. The method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid according to claim 1, characterized in that: The concentration of the metal source or non-metallic source in the closed reaction vessel in step 2 is 0.05 mol / L to 0.3 mol / L, the flow rate of the CO2 is 15 mL / min to 35 mL / min, the mass purity of the CO2 is not less than 99.99%, and the closed reaction vessel is stirred at a speed of 50 rpm to 200 rpm.

6. The method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid according to claim 1, characterized in that: The metal matrix described in step three is a metal element powder or a metal alloy powder, the metal element powder is aluminum powder, copper powder, silver powder or magnesium powder, the metal alloy powder is aluminum alloy powder, copper alloy powder, silver alloy powder or magnesium alloy powder, the mass purity of the metal matrix is not less than 99.5%, and the particle size of the metal matrix is 10μm to 200μm.

7. The method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid according to claim 1, characterized in that: The powder metallurgy process described in step three is: sintering at a pressure of 120MPa~250MPa and a temperature of 750℃~950℃; the hot pressing sintering process is: hot pressing in a mold at a pressure of 180MPa~300MPa and a temperature of 850℃~1100℃; the spray deposition process is: depositing onto a substrate at a temperature of 450℃~650℃ through a spray gun at a spray speed of 80m / s~200m / s.

8. The method for preparing a metal-based diamond thermal conductive composite material using supercritical CO2 fluid according to claim 1, characterized in that: The thermal conductivity of the metal-based diamond thermal conductive composite material in step three is increased by 15% to 35% compared to the metal-based diamond composite material, and the interface bonding strength is increased by 25 MPa to 45 MPa.

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