Spherical diamond / copper composite powder with core-shell structure and preparation method thereof

Abstract

The present application provides a spherical diamond / copper composite powder with a core-shell structure and a preparation method thereof, which belongs to the field of new material technology. It uses diamond powder with a modified surface by vapor deposition of metals such as tungsten, titanium, and chromium as raw material, and coats a complete and uniform copper deposition layer by chemical plating, and then further achieves copper plating of different thicknesses by roller plating to form a spherical diamond / copper composite powder with a core-shell structure. The spherical diamond / copper core-shell structure composite powder has high sphericity and good powder fluidity, is suitable for a variety of additive manufacturing processes, can reduce printing defects, enhance printing stability, improve printing density, and can adjust its diamond volume fraction over a wide range, regulate thermal conductivity and thermal expansion coefficient, and can be applied to the field of additive manufacturing of thermal management materials and structures for high-power devices.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a spherical diamond / copper composite powder with a core-shell structure and a preparation method thereof. Background Art

[0002] With the increasing integration of high-power devices such as electronic equipment, satellites, radars, and lasers, the resulting ultra-high heat loads can severely limit their performance, reliability, and lifespan. To effectively control the temperature of these devices and ensure stable operation, traditional heat dissipation materials alone are no longer sufficient. By leveraging a high-thermal-conductivity material-structure integrated design, the combined advantages of both the heat dissipation material and the heat dissipation structure can be effectively improved. Diamond / copper composites possess excellent thermal conductivity, and their thermal conductivity and thermal expansion coefficient can be manipulated by varying the diamond volume fraction, making them ideal heat dissipation materials and components for high-power devices. However, while traditional manufacturing methods such as casting, powder metallurgy, and infiltration can fabricate diamond / copper composites and some heat dissipation structures, achieving high performance in thermal management devices with complex heat dissipation channels, grids, and topology-optimized structures poses challenges. Additive manufacturing techniques can enable the fabrication of complex thermal management structures, but currently, there is a lack of diamond / copper powder materials suitable for additive manufacturing.

[0003] Common additive manufacturing processes include laser additive manufacturing, electron beam additive manufacturing, powder extrusion additive manufacturing, and photo-curing additive manufacturing. When diamond-copper mixed powders are prepared using mechanical powder mixing technology, due to the extremely poor wettability between diamond and copper and the significant density difference, various process defects are easily caused. The literature "Shape, microstructure and properties of diamond / copper composites prepared by binder jet additive manufacturing" (International Journal of Refractory Metals and Hard Materials, 2025, 130: 107148) uses binder additive printing to print diamond / copper composites, but the samples have various process defects such as powder delamination and macro cracking, and the sample density is less than 95%, and the sample thermal conductivity is poor; the literature "Additive manufacturing of high-quality NiCu / diamond composites through powder bed fusion" (Additive Manufacturing, 2024, 89: 104288-104288) used electron beam printing to produce diamond / copper-based composite materials, in which the diamond was modified with a metal surface to alleviate printing splashes. However, the prepared diamond / copper composite powders were mostly polyhedral in shape, with poor fluidity, which did not meet the basic requirements of additive manufacturing powders. In addition, the metal modification layer was thin, and the protective effect on the diamond during the printing process was limited. Defects such as diamond graphitization and interface cracking still existed in the samples presented by the authors, and further protective measures were still needed.

[0004] In response to various problems in the additive printing process, the present invention provides a spherical diamond / copper composite powder with a core-shell structure, which can be applied to a variety of additive manufacturing processes to achieve additive manufacturing of high thermal conductivity diamond / copper composite materials. Summary of the Invention

[0005] This invention provides a spherical diamond / copper composite powder with a core-shell structure and a method for preparing it. The powder can be used in various additive manufacturing processes, including selective laser melting, electron beam additive manufacturing, powder extrusion printing, and stereolithography, to produce diamond / copper composite materials. The spherical diamond / copper core-shell composite powder produced by this invention exhibits high sphericity and a flowability of better than 30 s / 50 g.

[0006] The invention provides a spherical diamond / copper composite powder with a core-shell structure and a preparation method thereof.

[0007] Specifically, a spherical diamond / copper composite powder with a core-shell structure and a preparation method thereof include the following steps:

[0008] Step 1: Prepare surface-metal-modified polyhedral diamond powder with a particle size of 1-600 μm. The metal surface modification element is not limited to tungsten, titanium, or chromium. The coating preparation method is not limited to chemical vapor deposition or magnetron sputtering. The thickness of the first metal layer is 50-200 nm. The metal-modified diamond powder is placed in an electroless plating solution to prepare a second copper coating. The electroless plating solution composition includes: 15-24 g / L copper sulfate, 15-20 g / L potassium sodium tartrate, 15-20 g / L disodium EDTA, and 5-15 ml / L formaldehyde. The plating temperature is 30-60°C, the pH is maintained at 11-13, the plating time is 10-200 min, and the solution is stirred at 10-80 rpm.

[0009] Preferably, the copper plating layer obtained in step 1 has a thickness between 0.2 and 2 μm.

[0010] Step 2: Wash and dry the powder in step 1, first wash it with deionized water 1 to 3 times, then wash it with alcohol 2 to 5 times, and dry it in a vacuum drying oven for 2 to 5 hours. The vacuum drying temperature is 45 to 60 ° C, and the vacuum degree is better than 10 Pa.

[0011] Step 3: The electroless-plated diamond powder is barrel-plated to thicken the copper coating and increase the weight of the powder, achieving the desired copper coating thickness and obtaining a spherical diamond / copper core-shell composite powder. The barrel plating solution used includes: 10-100 g / L copper pyrophosphate, 10-400 g / L potassium pyrophosphate, 10-100 g / L ammonium citrate, and 1-50 ml / L ammonia. The solution pH is maintained at 7.5-8.8 during the plating process. The barrel plating current is 1-10 A, the barrel plating temperature is 25-100°C, the barrel plating time is 1-100 h, and the barrel plating speed is 5-50 r / min.

[0012] Preferably, zirconium oxide ceramic balls are added in step three as a physical dispersant to prevent diamond powder from agglomerating during the plating process. The mass ratio of ceramic balls to diamonds is 1:10 to 2:3, and the diameter of the ceramic balls is 1 to 5 mm.

[0013] Preferably, the increase in thickness of the copper plating layer in step 3 is 1-150 μm, and the weight gain ratio of the powder after barrel plating is 120%-600%.

[0014] Preferably, the spherical diamond / copper core-shell structure composite powder prepared in step three is spherical.

[0015] Step 4: The diamond / copper composite powder prepared in Step 3 is cleaned and vacuum-dried, then screened to obtain a spherical diamond / copper core-shell composite powder. The barrel-plated diamond powder is first washed with deionized water 2-4 times until neutral, then rinsed 2-4 times with alcohol, and dried in a vacuum oven for 2-8 hours at a temperature of 40-100°C and a vacuum degree better than 10 Pa. After drying, it is screened with an 18-mesh screen to separate the spherical diamond / copper core-shell composite powder from the ceramic balls.

[0016] Step 5: The spherical diamond / copper core-shell structure composite powder in step 4 is mixed with pure copper powder in a desired proportion to obtain a mixed powder for additive manufacturing.

[0017] Preferably, the volume fraction of the spherical diamond / copper core-shell structure composite powder in the mixed powder in step five is 10% to 100%, and the copper powder particle size is 0.2 to 350 μm.

[0018] Preferably, the additive manufacturing technology mentioned in step five includes but is not limited to laser selective melting, electron beam additive manufacturing, powder extrusion printing and stereolithography.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] (1) The spherical diamond / copper composite powder involved in the present invention has a core-shell structure and has the advantages of continuously adjustable copper / diamond ratio, high sphericity, good fluidity, and controllable particle size. It can be adapted to various additive manufacturing technology requirements such as laser selective melting, electron beam additive manufacturing, powder extrusion printing, and photo-stereolithography.

[0021] (2) The spherical diamond / copper composite powder of the present invention is beneficial for improving process defects in various additive manufacturing printing processes. The metal coating can improve the wettability of the diamond and copper interface, achieving strong interface bonding. The copper coating can reduce high-temperature splashing during direct additive printing processes such as electron beam printing, and avoid graphitization caused by high-temperature impact. At the same time, the spherical diamond / copper core-shell structure composite powder has high sphericity and fluidity, allowing the diamond to be evenly distributed in the matrix, which is particularly effective for indirect additive processes such as photocuring and powder extrusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a secondary electron scanning image of the surface morphology of the copper-coated metal tungsten modified diamond prepared after chemical plating in Example 1.

[0023] Figure 2 This is a secondary electron scanning image of the surface morphology of the spherical diamond / copper core-shell structure composite powder prepared after roller plating thickening in Example 1.

[0024] Figure 3 This is the macroscopic morphology of the diamond / copper composite material prepared by the electron beam additive manufacturing process in Example 1.

[0025] Figure 4 This is a secondary electron scanning image of the cross section of the diamond / copper composite material prepared by the electron beam additive manufacturing process in Example 1.

[0026] Figure 5 This is a backscattered electron scanning image of the interface between diamond and copper matrix in the diamond / copper composite material prepared by the electron beam additive manufacturing process in Example 1.

[0027] Figure 6 This is the macroscopic morphology of the diamond / copper composite material prepared by the electron beam additive manufacturing process in Comparative Example 1.

[0028] Figure 7 This is a secondary electron scanning image of the cross section of the diamond / copper composite material prepared by the electron beam additive manufacturing process in Comparative Example 1.

[0029] Figure 8 This is a secondary electron morphology scanning image at the interface between diamond and copper substrate in the diamond / copper composite material prepared by the electron beam additive manufacturing process in Comparative Example 1.

[0030] Figure 1 The microscopic morphology of the metal tungsten modified diamond powder after the chemical copper plating process in Example 1 can be seen that the metal tungsten modified diamond powder in Example 1 is evenly coated with the copper plating layer without obvious plating leakage. The powder as a whole presents a polyhedral morphology with low sphericity.

[0031] Figure 2 The microscopic morphology of the spherical diamond / copper core-shell structure composite powder after the barrel plating process in Example 1 can be seen that the thickness of the diamond powder coating after the barrel plating in Example 1 is Figure 1 The coating is obviously deepened, with no obvious leakage phenomenon, the powder presents a nearly spherical shape, and the sphericity is greatly increased.

[0032] Figure 3 、 4 Figures 5 and 6 respectively show the macromorphology, cross-sectional morphology, and interfacial morphology of the diamond / copper composite material produced via electron beam additive manufacturing in Example 1. As can be seen from the figures, the composite material in Example 1 was well formed, with diamonds evenly distributed throughout the matrix, no obvious interfacial defects, and no significant thermal damage.

[0033] Figure 6 、 78 are scanning images of the macroscopic, cross-sectional and microscopic morphologies of the diamond / copper composite material prepared by the electron beam additive manufacturing process in Comparative Example 1. It can be seen that the diamond in Comparative Example 1 is evenly distributed in the copper matrix, the forming effect is poor, a large number of defects exist inside the composite material, there is obvious ablation on the surface of the diamond, and there are obvious interface defects between the diamond and the matrix. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention and comparative examples. Obviously, the described embodiments and comparative examples are part of the cases of the present invention, rather than all the embodiments. The present invention will be further described below in conjunction with the embodiments and comparative examples. These embodiments and comparative examples are merely examples of preferred embodiments of the present invention, and the scope of protection of the present invention should not be construed as being limited to these embodiments and comparative examples.

[0035] Example 1

[0036] A spherical diamond / copper composite powder with a core-shell structure and a preparation method thereof, comprising the following steps:

[0037] Step 1: Preparation of spherical diamond / copper core-shell structure composite powder

[0038] (1) Prepare tungsten-modified diamond with a diamond particle size of 65-75 μm and a tungsten-modified layer thickness of 100 nm.

[0039] (2) The metal tungsten modified diamond was placed in a chemical plating solution for surface copper plating. The plating was carried out in a water bath at 60 ° C and pH = 12 for 1 h. Mechanical stirring was performed during the plating process at a speed of 30 r / min to obtain a coating with a thickness of 1 μm. The chemical plating solution formula is: copper sulfate 15 g / L, potassium sodium tartrate 15 g / L, EDTA disodium 15 g / L, formaldehyde 10 ml / L. It was then washed with deionized water twice until neutral, and then washed with alcohol 3 times. It was low-temperature dried at 45 ° C for 4 h, and the vacuum degree was better than 10 Pa to obtain the following. Figure 1 The metal tungsten modified diamond powder after chemical copper plating is shown.

[0040] (3) The metal tungsten modified diamond after chemical copper plating was rolled and plated, and zirconium oxide ceramic balls were added. The mass ratio of ceramic balls to powder was 1:5, and the plating time was 100 h. The formula of the rolling plating solution was: 70 g / L copper pyrophosphate, 300 g / L potassium pyrophosphate, 25 g / L ammonium citrate, 4 ml / L ammonia water, the current was 1 A, the plating temperature was 35 °C, and the plating bottle speed was 7 r / min. After the plating was completed, it was washed with deionized water 4 times until neutral, and then washed with alcohol 4 times. It was low-temperature dried at 45 °C for 8 h, and the vacuum degree was better than 10 Pa. After filtration and drying, the zirconium oxide ceramic balls and diamond powder were taken out and sieved with an 18-mesh sieve to obtain spherical diamond / copper core-shell structure composite powder such as Figure 2 shown.

[0041] Step 2: Mechanical mixing

[0042] Spherical diamond / copper core-shell structure composite powder and spherical pure copper powder were mechanically mixed with volume fractions of 30% and 70%, respectively. The mechanical mixing time was 4 h and the rotation speed was 150 r / min. The particle size of the spherical pure copper powder was between 45 and 115 μm.

[0043] Table 1 below shows a comparison of the fluidity of spherical diamond / copper composite powder and other powders. Compared to tungsten-modified diamond powder, its fluidity and particle size have been improved accordingly. Its own fluidity is close to that of spherical pure copper powder in the same particle size range. Even after mixing with spherical pure copper powder, its fluidity still reaches 15.6 s / 50 g, meeting the powder fluidity requirements for additive manufacturing.

[0044] Table 1 Performance comparison of spherical diamond / copper composite powder and other powders:

[0045] powder Tungsten modified diamond powder Tungsten modified diamond powder Spherical pure copper powder Spherical diamond / copper core-shell structure composite powder Copper powder mixed with 30% spherical diamond / copper core-shell structure composite powder Particle size 65~75 μm 105~115 μm 105~115 μm 105~115 μm 105~115 μm Sphericity Dodecahedron Dodecahedron >95 % ＞90 % >90 % Powder flowability 45.2 s / 50g 41.8 s / 50g 13.6 s / 50g 14.8 s / 50g 15.6 s / 50g

[0046] Step 3: Electron Beam Printing

[0047] The mixed spherical diamond / copper core-shell structure composite powder and copper powder were placed in the printing equipment. The electron beam printing parameters were as follows: a pure copper substrate was used, the base plate preheating temperature was 320 °C, and the vacuum degree was 1.0×10 -2 Pa, beam spot diameter 250 μm, powder layer thickness 150 μm, input current 10 mA, scanning speed 2.5 m / s. The electron beam scanning direction is parallel to the substrate edge and rotated 90° relative to the previous layer scanning direction. After printing is completed and cooled, the sample is removed from the substrate.

[0048] Step 4: Sample performance testing and analysis

[0049] The macroscopic morphology of the sample obtained in this embodiment is as follows Figure 3As shown, the formability is good, and the cross-sectional secondary electron morphology image observed by secondary electrons is as follows Figure 4 As shown, the diamond is evenly dispersed in the copper matrix, and the backscattered electron scanning image at the interface between the diamond and the copper matrix is ​​as follows Figure 5 As shown, the diamond-copper interface is well bonded, free of any interfacial defects, demonstrating excellent interfacial bonding. Further testing of the sample revealed that the composite material achieved a density of 99.8% and a thermal conductivity of 440 W / (m·K).

[0050] Comparative Example 1

[0051] This comparative example provides a method for additive manufacturing of a diamond / copper composite material, wherein the method does not perform any surface treatment on the metal tungsten-modified diamond, and comprises the following steps:

[0052] Step 1: Prepare tungsten-modified diamond with a diamond particle size of 65-75 μm and a tungsten layer thickness of 100 nm.

[0053] Step 2: Mechanical mixing

[0054] Different from Example 1, the mechanical mixing time was 6 h, and other conditions were the same.

[0055] Step 3: Electron Beam Printing

[0056] The print settings are the same as in Example 1.

[0057] Step 4: Sample performance testing and analysis

[0058] The macroscopic morphology of the sample obtained in this comparative example is as follows Figure 6 As shown, the forming effect is not good. The cross-sectional secondary electron morphology image observed by scanning electron microscope secondary electron imaging is as follows Figure 7 As shown in the figure, due to the splashing of printing, the number of diamond copper substrates is scarce, such as Figure 8 As shown in the figure, there are a large number of defects inside the composite material. Further testing of the sample showed that the density of the composite material was only 90.18%, and the thermal conductivity was 220 W / (m·K).

Claims

1. A spherical diamond / copper composite powder with a core-shell structure and a preparation method thereof, characterized in that The following steps are involved: Step 1: Copper is plated on the surface of the metal surface modified diamond by chemical plating; the diamond used is a polyhedral structure with a particle size of 1 to 600 μm, and a tungsten, titanium or chromium deposition layer with a thickness of 50 to 200 nm is deposited by a vapor deposition process; The chemical copper plating solution used includes: an aqueous solution of 15-24 g / L copper sulfate, 15-20 g / L potassium sodium tartrate, 15-20 g / L disodium EDTA, and 5-15 ml / L formaldehyde; the chemical plating process used is a plating temperature of 30-60°C, a plating time of 10 min-200 min, a solution pH value maintained at 11-13 during the plating process, and a stirring speed of 10-80 r / min; Step 2: The metal surface modified diamond prepared in step 1 and treated with chemical copper plating is cleaned and dried to obtain chemical copper-plated diamond powder; the process adopted is to first wash the chemically plated diamond powder with deionized water 1 to 3 times, then wash it with alcohol 3 to 5 times, and dry it in a vacuum drying oven for 2 to 5 hours at a vacuum drying temperature of 45 to 60°C and a vacuum degree better than 10Pa; Step 3: The chemical copper-plated diamond powder prepared in step 2 is subjected to barrel plating to thicken the copper plating layer and increase the weight of the powder to obtain a copper plating layer of desired thickness, and obtain a core-shell structured diamond / copper composite powder; the barrel plating solution used includes: 10-100 g / L copper pyrophosphate, 10-400 g / L potassium pyrophosphate, 10-100 g / L ammonium citrate, and 1-50 ml / L ammonia water; during the plating process, the solution pH is maintained at 7.5-8.8, the barrel plating current is 1-10 A, the barrel plating temperature is 25-100 ° C, the barrel plating time is 1-100 h, the barrel plating speed is 5-50 r / min, and ceramic balls are used as physical dispersants during barrel plating; Step 4: The diamond / copper composite powder prepared in step 3 is cleaned and vacuum-dried, and then sieved to finally obtain a spherical diamond / copper composite powder with a core-shell structure; the process adopted is to first wash the diamond powder after barrel plating with deionized water 2 to 4 times until it is neutral, then wash it with alcohol 2 to 4 times, and dry it in a vacuum drying oven for 2 to 8 hours. The vacuum drying temperature is 40 to 100 ° C, and the vacuum degree is better than 10 Pa; after drying, it is sieved with an 18-mesh screen to separate the spherical diamond / copper core-shell structure composite powder and the ceramic balls; Step 5: The spherical diamond / copper core-shell structure composite powder prepared in step 4 is mixed with pure copper powder in proportion to obtain a mixed powder for additive manufacturing.

2. The preparation method according to claim 1, wherein The thickness of the copper plating layer in step 1 is between 0.2 and 2 μm.

3. The preparation method according to claim 1, characterized in that In the step three, zirconium oxide ceramic balls are added as a physical dispersant during the barrel plating process, the mass ratio of ceramic balls to diamonds is 1:10-2:3, and the diameter of the ceramic balls is 1-5 mm.

4. The preparation method according to claim 1, characterized in that The copper plating layer thickness increase in step 3 is 1-150 μm, and the powder weight increase ratio after barrel plating is 120%-600%.

5. The preparation method according to claim 1, characterized in that The diamond / copper composite powder in step three is spherical.

6. The preparation method according to claim 1, characterized in that The volume fraction of the spherical diamond / copper core-shell structure composite powder in the mixed powder in step 5 is 10% to 100%, and the copper powder particle size is 0.2 to 350 μm.

7. The preparation method according to claim 1, characterized in that The additive manufacturing technology in step five includes laser selective melting, electron beam additive manufacturing, powder extrusion printing and photo-stereolithography.

8. Spherical diamond / copper composite powder with a core-shell structure for additive manufacturing is prepared by the preparation method according to any one of claims 1 to 7.

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