Graphene and copper composite powder with core-shell structure and preparation method and application of graphene and copper composite powder

Abstract

According to the graphene copper composite powder with the core-shell structure, spherical copper powder serves as a core body of the composite powder, the surface of the core body is coated with 1-5 graphene layers, and the core-shell structure is formed; and nano ceramic particles are adsorbed on the outer surface of the graphene layer and are used for enhancing the laser absorptivity of the composite powder. The scheme can be suitable for the SLM technology, the laser absorptivity is effectively improved, the graphene structure is protected, and the graphene copper composite powder with excellent interface bonding can be achieved.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a core-shell structured graphene-copper composite powder for laser selective melting and its preparation method. Background Technology

[0002] Copper is a fundamental material in the electrical and electronic industries, characterized by high thermal and electrical conductivity. However, in applications such as high-current electrical equipment and high-current-density electronic interconnects, there is still a need to further improve the electrical and thermal conductivity of copper materials. Graphene-copper composites have the advantage of high theoretical electrical and thermal conductivity, but current preparation techniques (powder metallurgy, hot pressing, etc.) cannot fabricate graphene-copper materials with complex structures.

[0003] Selective laser melting (SLM) is a core technology in metal 3D printing, enabling the free fabrication of complex copper components. However, pure copper has extremely high reflectivity (over 95%) to near-infrared lasers (SLM commonly uses a 1064nm wavelength), resulting in extremely low laser energy utilization, unstable forming process, and easy generation of defects such as incomplete fusion and spheroidization, making it difficult to obtain high-density parts.

[0004] Graphene, as a two-dimensional nanomaterial, possesses extremely high strength, thermal conductivity, and electrical conductivity. Introducing graphene into a copper matrix can significantly improve its strength, wear resistance, and high-temperature performance, while maintaining excellent electrical and thermal conductivity. However, traditional mechanical mixing methods for preparing graphene / copper composite powders present two major challenges: 1) graphene is unevenly dispersed in the copper matrix and easily agglomerates; 2) the interfacial bonding between graphene and copper is poor, becoming a weak point in performance.

[0005] Furthermore, under the extremely high temperature field and rapid solidification conditions of the SLM process, graphene is prone to decomposition, ablation, or reaction with copper to form copper carbide, severely impairing its reinforcing effect. While there have been attempts to coat copper powder with graphene in existing technologies, these have failed to effectively address the high reflectivity of copper to the laser during the SLM process, and lack matching dedicated printing process parameters, resulting in poor print quality.

[0006] Therefore, developing a specialized composite powder and matching molding process that can simultaneously address the issues of high copper reflectivity, easy graphene decomposition, and interfacial bonding is crucial for promoting the application of graphene / copper composite materials in SLM technology. Summary of the Invention

[0007] To address the aforementioned shortcomings, the present invention aims to propose a graphene-copper composite powder that is applicable to SLM technology, effectively improves laser absorption rate, protects graphene structure, and achieves excellent interfacial bonding, as well as its preparation method and a dedicated SLM process, to obtain graphene-copper composite materials with irregular dimensions.

[0008] To achieve this objective, the present invention adopts the following technical solution: A core-shell structured composite powder for laser selective melting, wherein the composite powder has spherical copper powder as the core, and the surface of the core is coated with 1-5 layers of graphene to form a core-shell structure; nano-ceramic particles are adsorbed on the outer surface of the graphene layers, and the nano-ceramic particles are used to enhance the absorption rate of the composite powder to laser.

[0009] Preferably, the nano-ceramic particles are one or more of silicon carbide, silicon nitride, boron nitride, or titanium carbide, and their particle size is 20-100 nanometers.

[0010] Preferably, the spherical copper powder has a particle size range of 15-53 μm and a purity of not less than 99.9%.

[0011] Preferably, the graphene layer is a continuous or discontinuous complete coating layer.

[0012] A method for producing a core-shell composite powder includes the following steps: a. Pretreatment: The spherical copper powder is acid-washed and oxidized to form a catalytically active oxide layer on its surface; b. CVD growth of graphene: Pretreated copper powder is placed in a fluidized bed chemical vapor deposition furnace, carbon source gas and hydrogen are introduced, and 1-5 layers of graphene are catalytically grown on the surface of copper powder at a temperature of 400-600°C to obtain a graphene-coated copper composite powder. c. Adsorption of nano-ceramic particles: The composite powder obtained in step b and the nano-ceramic particles are placed in a low-speed mixer and dry-mixed under inert gas protection to make the nano-ceramic particles uniformly adsorbed on the outer surface of graphene.

[0013] Further, in step b, the carbon source gas is methane, acetylene, or ethylene, and the growth time is 10-60 minutes.

[0014] A method for selective laser melting and forming of core-shell structured composite powder, employing the following proprietary process parameters: Laser power: 300-500 W; Scanning speed: 600-1200 mm / s; Scanning interval: 0.08-0.12 mm; Layer thickness: 0.02-0.04 mm; Scanning strategy: Use checkerboard scanning or stripe scanning strategy, and rotate the scanning direction between adjacent layers by 67°; The atmosphere of the forming cavity is high-purity argon gas with an oxygen content of less than 100 ppm.

[0015] Furthermore, in the proprietary process parameters, the volumetric energy density Ev ranges from 60 to 120 J / mm³, and its calculation formula is: Ev = P / (v * h * t), where P is the laser power, v is the scanning speed, h is the scanning spacing, and t is the layer thickness.

[0016] A graphene / copper composite component is manufactured, wherein the component has a density of not less than 99.2%, a thermal conductivity of not less than 380 W / (m·K), and a tensile strength of not less than 350 MPa.

[0017] One of the above technical solutions includes the following beneficial effects: This invention provides a core-shell structured composite powder for selective laser melting (SLM). The powder uses spherical copper powder as its core (core), with 1-5 layers of graphene coating on its surface, forming a perfect core-shell structure. The most crucial innovation lies in the adsorption of nano-ceramic particles (such as SiC) on the outer surface of the graphene layers to enhance laser absorption.

[0018] (1) Advantages of core-shell structure: The copper powder core ensures the material's electrical and thermal conductivity; the graphene layer, as a coating layer, can act as a "nano barrier" to inhibit the excessive growth of copper grains in the subsequent SLM process, and it is also a high-performance reinforcing phase. The core-shell structure ensures the uniform distribution of graphene in the copper matrix and ideal interfacial bonding.

[0019] (2) Role of nano-ceramic particles: Nano-ceramic particles (such as SiC) have a much higher absorption rate for 1064nm laser than copper and graphene. These particles act as "laser absorption points," efficiently capturing laser energy and rapidly converting it into heat energy, which is then transferred to the internal copper core and graphene layer. This significantly reduces the laser power threshold required for forming, improves energy utilization, and stabilizes the molten pool. At the same time, these particles are small in size and few in number, and will not have a significant negative impact on the electrical and thermal conductivity of the composite material. Attached Figure Description

[0020] Figure 1 This is an installation structure diagram of one embodiment of the present invention. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] A core-shell structured composite powder for laser selective melting, wherein the composite powder has spherical copper powder as the core, and the surface of the core is coated with 1-5 layers of graphene to form a core-shell structure; nano-ceramic particles are adsorbed on the outer surface of the graphene layers, and the nano-ceramic particles are used to enhance the absorption rate of the composite powder to laser.

[0023] A core-shell structured composite powder for selective laser melting (SLM). This powder uses spherical copper powder as its core (core), with 1-5 layers of graphene coating the surface, forming a perfect core-shell structure. The most crucial innovation lies in the adsorption of nano-ceramic particles (such as SiC) on the outer surface of the graphene layers to enhance laser absorption.

[0024] Advantages of the core-shell structure: The copper powder core ensures the material's inherent electrical and thermal conductivity; the graphene layer, as a coating layer, acts as a "nano-barrier" to inhibit excessive copper grain growth during subsequent SLM processes, and is itself a high-performance reinforcing phase. The core-shell structure ensures uniform distribution of graphene in the copper matrix and ideal interfacial bonding.

[0025] (2) Role of nano-ceramic particles: Nano-ceramic particles (such as SiC) have a much higher absorption rate for 1064nm laser than copper and graphene. These particles act as "laser absorption points," efficiently capturing laser energy and rapidly converting it into heat energy, which is then transferred to the internal copper core and graphene layer. This significantly reduces the laser power threshold required for forming, improves energy utilization, and stabilizes the molten pool. At the same time, these particles are small in size and few in number, and will not have a significant negative impact on the electrical and thermal conductivity of the composite material.

[0026] The nano-ceramic particles are one or more of silicon carbide, silicon nitride, boron nitride, or titanium carbide, and their particle size is 20-100 nanometers.

[0027] The spherical copper powder has a particle size range of 15-53 μm and a purity of not less than 99.9%.

[0028] The graphene layer can be a continuous or discontinuous complete coating layer.

[0029] A method for producing a core-shell composite powder includes the following steps: a. Pretreatment: The spherical copper powder is acid-washed and oxidized to form a catalytically active oxide layer on its surface; b. CVD growth of graphene: Pretreated copper powder is placed in a fluidized bed chemical vapor deposition furnace, carbon source gas and hydrogen are introduced, and 1-5 layers of graphene are catalytically grown on the surface of copper powder at a temperature of 400-600°C to obtain a graphene-coated copper composite powder. c. Adsorption of nano-ceramic particles: The composite powder obtained in step b and the nano-ceramic particles are placed in a low-speed mixer and dry-mixed under inert gas protection to make the nano-ceramic particles uniformly adsorbed on the outer surface of graphene.

[0030] Further, in step b, the carbon source gas is methane, acetylene, or ethylene, and the growth time is 10-60 minutes.

[0031] A method for selective laser melting and forming of core-shell structured composite powder, employing the following proprietary process parameters: Laser power: 300-500 W; Scanning speed: 600-1200 mm / s; Scanning interval: 0.08-0.12 mm; Layer thickness: 0.02-0.04 mm; Scanning strategy: Use checkerboard scanning or stripe scanning strategy, and rotate the scanning direction between adjacent layers by 67°; The atmosphere of the forming cavity is high-purity argon gas with an oxygen content of less than 100 ppm.

[0032] Furthermore, in the proprietary process parameters, the volumetric energy density Ev ranges from 60 to 120 J / mm³, and its calculation formula is: Ev = P / (v * h * t), where P is the laser power, v is the scanning speed, h is the scanning spacing, and t is the layer thickness.

[0033] A graphene / copper composite component is manufactured, wherein the component has a density of not less than 99.2%, a thermal conductivity of not less than 380 W / (m·K), and a tensile strength of not less than 350 MPa.

[0034] The preparation method of the above-mentioned composite powder mainly includes: (1) Pretreatment: acid washing removes oxides and impurities from the surface of copper powder, followed by light oxidation to form a thin, catalytically active copper oxide / cuprous oxide layer on the surface.

[0035] (2) CVD growth of graphene: In a fluidized bed CVD reactor, using the catalytic effect of copper, a carbon source gas (such as methane) is introduced, and high-quality graphene with a controllable number of layers (1-5 layers) is grown in situ on the surface of copper powder at a relatively low temperature (400-600°C). The fluidized bed ensures that the powder is heated and the reaction is uniform.

[0036] (3) Adsorption of nano-ceramic particles: Using gentle dry ball milling or low-speed mixing, nano-ceramic particles are physically adsorbed onto the outer surface of graphene under inert gas protection. This process requires precise control to avoid damaging the core-shell structure.

[0037] 3. This invention provides exclusive process parameters for SLM forming using the aforementioned composite powder. This parameter system is specifically optimized for the characteristics of this composite powder (high laser absorption rate and the presence of thermosensitive graphene): (1) Lower laser power (300-500W) and higher scanning speed (600-1200mm / s): Since the nano-ceramic particles improve the laser absorption rate, they can be melted without excessive power; the higher scanning speed can shorten the laser action time and prevent graphene from being overheated and decomposed.

[0038] (2) Specific volumetric energy density (60-120 J / mm³): Within this energy density range, it can ensure that the copper powder is completely melted and densified, and the heat input can be controlled within the range that protects the graphene structure.

[0039] (3) 67° rotation checkerboard / stripes scanning strategy: This strategy can disperse thermal stress, reduce warping deformation, and make the melting trajectory more uniform, which helps to release internal pores and further improve density.

[0040] Example 1: Preparation of graphene-copper composite powder (1) Raw materials: spherical gas-atomized pure copper powder with a particle size of 15-53μm (purity 99.95%), and nano SiC particles (average particle size 50nm).

[0041] (2) Pretreatment: The copper powder was ultrasonically cleaned in dilute hydrochloric acid for 5 minutes, washed with deionized water until neutral, and dried. Then it was heated in air at 200°C for 10 minutes to form a thin oxide layer on its surface.

[0042] (3) CVD growth of graphene: Pretreated copper powder was loaded into a fluidized bed CVD furnace. After evacuation, argon and hydrogen (H2:Ar=1:4) were introduced, and the temperature was raised to 500°C. After stabilization, methane (CH4:H2=1:10) was introduced as a carbon source, and the reaction was carried out for 30 minutes. After the reaction was completed, the mixture was cooled to room temperature under argon protection to obtain copper composite powder (Cu@Gr) with about 3 layers of graphene on the surface.

[0043] (4) Adsorption of nanoparticles: The Cu@Gr powder and 1.0 wt% nano SiC powder were loaded into the mixing tank of a planetary ball mill and argon gas was introduced for protection. The mill was run at a low speed of 100 rpm for 60 minutes to allow the nano SiC particles to be uniformly adsorbed on the graphene surface, thus obtaining the final composite powder (Cu@Gr@SiC).

[0044] Comparative Example 1 Using a traditional mechanical mixing method, copper powder, graphene nanosheets, and micron-sized SiC powder in equal proportions were directly and rapidly ball-mixed for 2 hours.

[0045] Example 2: SLM forming and performance testing The Cu@Gr@SiC composite powder prepared in Example 1 was used for printing on an SLM device equipped with a 500W fiber laser.

[0046] Process parameters: laser power 400 W, scanning speed 800 mm / s, scanning spacing 0.10 mm, powder layer thickness 0.03 mm. A checkerboard scanning strategy is adopted, with a grid size of 5 mm x 5 mm, and the scanning direction of adjacent layers is rotated by 67°. The oxygen content in the forming cavity is maintained below 50 ppm.

[0047] Performance testing: The printed block sample was tested and found to have a density of 99.5%, a room temperature thermal conductivity of 395 W / (m·K), and a tensile strength of 375 MPa.

[0048] Comparative Example 2 Using conventional mixed powders from Comparative Example 1, SLM printing was performed under optimal process parameters (laser power 700 W, scanning speed 400 mm / s, other parameters the same). The resulting sample had a density of only 96.8%, and obvious unfused graphene agglomeration was observed internally. Its thermal conductivity was 320 W / (m·K), and its tensile strength was 280 MPa.

[0049] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A core-shell structured graphene-copper composite powder, characterized in that: The composite powder uses spherical copper powder as the core, and the surface of the core is coated with 1-5 layers of graphene to form a core-shell structure; the outer surface of the graphene layer is adsorbed with nano-ceramic particles, which are used to enhance the absorption rate of the composite powder to laser.

2. The core-shell structured composite powder according to claim 1, characterized in that: The nano-ceramic particles are one or more of silicon carbide, silicon nitride, boron nitride, or titanium carbide, and their particle size is 20-100 nanometers.

3. The core-shell structured composite powder according to claim 1 or 2, characterized in that: The spherical copper powder has a particle size range of 15-53 μm and a purity of not less than 99.9%.

4. The core-shell structured composite powder according to claim 1, characterized in that: The graphene layer can be a continuous or discontinuous complete coating layer.

5. A method for preparing the core-shell structured composite powder as described in any one of claims 1-4, characterized in that, Includes the following steps: a. Pretreatment: The spherical copper powder is acid-washed and oxidized to form a catalytically active oxide layer on its surface; b. CVD growth of graphene: Pretreated copper powder is placed in a fluidized bed chemical vapor deposition furnace, carbon source gas and hydrogen are introduced, and 1-5 layers of graphene are catalytically grown on the surface of copper powder at a temperature of 400-600°C to obtain a graphene-coated copper composite powder. c. Adsorption of nano-ceramic particles: The composite powder obtained in step b and the nano-ceramic particles are placed in a low-speed mixer and dry-mixed under inert gas protection to make the nano-ceramic particles uniformly adsorbed on the outer surface of graphene.

6. The method according to claim 5, characterized in that: In step b, the carbon source gas is methane, acetylene, or ethylene, and the growth time is 10-60 minutes.

7. A method for laser selective melting and forming using core-shell structured composite powder as described in any one of claims 1-4, characterized in that, The following proprietary process parameters are used: Laser power: 300-500 W; Scanning speed: 600-1200 mm / s; Scanning interval: 0.08-0.12 mm; Layer thickness: 0.02-0.04 mm; Scanning strategy: Use checkerboard scanning or stripe scanning strategy, and rotate the scanning direction between adjacent layers by 67°; The atmosphere of the forming cavity is high-purity argon gas with an oxygen content of less than 100 ppm.

8. The method according to claim 7, characterized in that: In the proprietary process parameters, the volumetric energy density Ev ranges from 60 to 120 J / mm³, and its calculation formula is: Ev = P / (v * h * t), where P is the laser power, v is the scanning speed, h is the scanning spacing, and t is the layer thickness.

9. A graphene / copper composite material component manufactured by the method of claim 7 or 8, characterized in that: The density of the component is not less than 99.2%, the thermal conductivity is not less than 380 W / (m·K), and the tensile strength is not less than 350 MPa.

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