Highly conductive graphene / copper composite material and method for preparing the same

Abstract

The application discloses a kind of high-conductivity graphene / copper composite material and preparation method thereof, it is related to metal-based composite material technical field.The method first uses in-situ growth process to prepare the copper sheet powder that surface is evenly coated graphene, subsequently it is with specific proportion pure copper sheet powder and is mechanically mixed, obtains the uniformly mixed pure copper-graphene / copper flaky composite powder;Through vacuum hot-pressing sintering process, flaky powder is arranged along radial direction, and macroscopically dense laminated structure blank is constructed;Finally, through normal temperature drawing and subsequent annealing treatment, graphene / copper composite wire is obtained.The conductivity of composite wire prepared by the application can reach more than 100 %IACS, and by introducing low-cost pure copper powder to replace part of graphene / copper composite powder, the material cost is significantly reduced, and the problem of conductivity loss caused by uneven dispersion or graphene addition amount of traditional graphene / copper composite material is solved.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composite material preparation technology, and in particular to a highly conductive graphene / copper composite material and its preparation method. Background Technology

[0002] With the rapid development of new-generation information technology, high-voltage power transmission, and aerospace, higher requirements are being placed on the comprehensive performance of conductive materials. Pure copper, as a traditional conductive material, has a room-temperature conductivity limit of 100% IACS (International Standard for Annealed Copper). Graphene, as a two-dimensional material with ultra-high carrier mobility, excellent mechanical strength, and atomically thin layers, is an ideal reinforcing agent for improving the strong conductivity of copper and achieving a synergistic effect of strength and toughness.

[0003] However, existing graphene / copper composites face three main challenges in achieving high conductivity: 1. Interface scattering effect: In homogeneous graphene / copper composites prepared by traditional methods, graphene is distributed in a homogeneous, randomly oriented manner within the copper matrix. This homogeneous structure causes strong anisotropic scattering of electrons by the interfacial network formed by graphene, severely shortening the mean free path of electrons and limiting further improvements in conductivity. 2. Structural runaway: During powder metallurgy, it is difficult to achieve macroscopically oriented arrangement of graphene, resulting in the inability to synergistically optimize the material's performance in the direction of stress and conduction. 3. Long-range conductive channels: In homogeneous composites, almost every part of the copper matrix is ​​surrounded by graphene, lacking sufficiently long, scatter-free electron transport pathways.

[0004] To address the aforementioned issues and prepare highly conductive graphene / copper composites, researchers have explored various methods, such as in-situ co-deposition (CN202411254040.9), plasma-assisted deposition (CN202210095741.7), electroless plating (CN202410808303.X), and in-situ interfacial chemical bonding (CN202511368790.3). These methods have made significant progress in improving graphene dispersion, strengthening interfacial bonding, and promoting microstructure orientation. However, existing technologies are mostly based on a homogeneous composite approach with a single component, resulting in graphene interfaces that are either fully encapsulated or excessively finely dispersed within the matrix. This lack of continuous high-purity copper electron transport channels makes it difficult to further overcome conductivity bottlenecks while maintaining strengthening properties. Furthermore, although patent CN115351277B also employs in-situ graphene growth combined with hot pressing sintering and drawing processes, it is still based on a "single-component" composite powder and does not introduce pure copper sheet powder as an independent conductive phase structural unit. In this scheme, the graphene interface is continuously distributed within the matrix, lacking macroscopically sized non-scattering conductive channels, which limits further improvement in conductivity. Moreover, and most importantly, the full use of graphene / copper composite powder results in high raw material costs, hindering industrial-scale promotion.

[0005] Therefore, developing a simple, efficient, low-cost, and scalable new method for assembling "long-range conductive channels" using pure copper-graphene / copper mixed sheet powders and achieving highly oriented graphene distribution is of great scientific and engineering significance for promoting the industrial application of high-performance graphene / copper composite wires. Summary of the Invention

[0006] To address the above shortcomings, this invention provides a highly conductive graphene / copper composite material and its preparation method. By mixing "copper flake powder with in-situ grown graphene" with "pure copper flake powder," a graphene / copper composite material with a high conductivity of 10²~10⁵ IACS is obtained, while also reducing costs. The specific technical solution is as follows: A method for preparing a highly conductive graphene / copper composite material includes the following steps: (1) Preparation of in-situ graphene / copper sheet powder: Graphene is grown in-situ on the surface of copper sheet powder by chemical vapor deposition to obtain graphene / copper composite sheet powder (component A) with single or few layers of graphene coating. (2) Heterogeneous powder gradation and mixing: The graphene / copper composite sheet powder (component A) and the copper sheet powder (component B) after reduction treatment in a reducing atmosphere are mixed in a predetermined mass ratio under a protective atmosphere to obtain a mixed powder; (3) Hot pressing sintering: The mixed powder is loaded into a mold and vacuum hot pressing sintering is performed to obtain a blank; this step mainly utilizes the directional rotation of the powder flakes under the pressure field to make its main planes parallel to the direction perpendicular to the pressure, thus constructing a composite material blank with a layered structure. (4) Drawing deformation process: The billet is subjected to multiple drawing deformation processes to further extend and densify the layered structure along the axial direction, induce graphene to produce a highly consistent directional arrangement, and prepare a composite wire. (5) Annealing treatment: The composite wire is subjected to post-annealing treatment to eliminate residual stress and repair crystal defects, thereby obtaining the highly conductive graphene / copper composite material.

[0007] Furthermore, in steps (1) and (2), the aspect ratio of the copper sheet powder is not less than 50, and the average particle size is 10~100 μm.

[0008] Further, in step (2), the process parameters for the reduction treatment are: 5% H2 / Ar reduction atmosphere, temperature 300~450℃, and time 1~3 hours.

[0009] Further, in step (2), the mass ratio of the graphene / copper powder to the reduced copper powder is 1:(1~4).

[0010] Further, in step (2), the mixing is carried out in a mixer filled with Ar gas, with a mixing speed of 80~120 rpm and a mixing time of 6~12 hours.

[0011] Further, in step (3), the process parameters for vacuum hot pressing sintering are: sintering temperature 800~950℃, pressure 20~80MPa, holding time 10~30 minutes, and vacuum degree not less than 10. -2 Pa.

[0012] Furthermore, in step (4), the total deformation rate (section reduction rate) of the drawing deformation is not less than 80%.

[0013] Furthermore, in step (5), the process parameters for the post-annealing treatment are: atmosphere Ar, annealing temperature 150~400℃, and annealing time 1~3 hours.

[0014] The above-mentioned layered structure with alternating soft and hard layers is formed by the graded mixing of component A and component B, followed by hot pressing sintering and drawing deformation. In this structure, the pure copper layer serves as a preferred conductive channel, while the graphene / copper layer provides reinforcement and interface constraint.

[0015] Another objective of this invention is to provide a highly conductive graphene / copper composite material, prepared by the above-described preparation method; in the composite material, the graphene is oriented along the drawing direction and the grains have a high aspect ratio.

[0016] Furthermore, the electrical conductivity of the composite material is not less than 100% IACS.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes sheet-like powder with a high aspect ratio. During hot-pressing sintering, the pressure field induces the powder to rotate and align parallel to the pressure direction, constructing a preliminary layered structure. Subsequent large-deformation drawing not only extends the layered structure axially but also induces highly consistent directional alignment of graphene. Through this microstructure control, the graphene in the final composite material exhibits a highly directional alignment along the drawing direction, significantly improving conductivity to at least 100% IACS, meaning the conductivity of the resulting wire surpasses that of pure copper. This has immense application potential in fields requiring high conductivity, solving the problem that traditional methods often lead to a decrease in conductivity when graphene is added.

[0018] 2. This invention employs in-situ grown graphene / copper composite powder (component A) and reduced pure copper powder (component B) for uniform mixing. In-situ growth ensures good interfacial bonding between graphene and the copper matrix, reducing interfacial defects; while the reduction treatment of the pure copper powder effectively removes its surface oxide layer, promoting metallurgical bonding between powders during subsequent sintering and deformation processes. This improves conductivity while also ensuring the mechanical integrity and densification of the material.

[0019] 3. This invention significantly reduces the preparation cost of raw materials and improves the market competitiveness of the product by introducing low-cost pure copper sheet powder to replace part of the graphene / copper composite powder, while ensuring or even improving the conductivity. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a technical roadmap of the preparation process of the present invention.

[0022] Figure 2 The SEM microstructure of the graphene / copper composite powder in Example 1 is shown. Figure 3 The SEM microstructure of the copper sheet powder after reduction treatment in Example 1; Figure 4 This is an EBSD image of the graphene / copper composite material after pull-out deformation in Example 1. Detailed Implementation

[0023] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0024] Example 1 A method for preparing a highly conductive graphene / copper composite material, comprising the following steps: Step 1: Take copper powder with an average particle size of 20 μm and an aspect ratio of 120. Using chemical vapor deposition, grow a single layer or few layers of graphene in situ on the surface of the copper powder to obtain graphene / copper composite powder (component A); the SEM microstructure of the graphene / copper composite powder is shown below. Figure 2 As shown in the figure, the powder surface is uniformly coated with graphene. Step 2: Take copper sheet powder of the same specifications as above, and anneal it at 350℃ for 2 hours in a 5% H2 / Ar mixed atmosphere to obtain component B, i.e., the reduced copper sheet powder. Its SEM microstructure is as follows. Figure 3 As shown in the figure, the oxide particles on the powder surface are eliminated after reduction treatment. Component A and component B are mixed at a mass ratio of 1:1 and mixed at 100 rpm for 12 hours in an Ar-filled mixer to obtain a mixed powder. Step 3: The mixed powder is placed into a graphite mold with a diameter of 40 mm and subjected to vacuum hot pressing sintering to achieve densification of the graphene / copper composite material. The sintering process parameters are: sintering temperature 950℃, sintering pressure 60MPa, holding time 20 minutes, and vacuum degree not less than 10. -2 Pa, to obtain composite material blank; Step 4: The billet is processed into a bar with a diameter of 10 mm, and then continuously drawn in multiple passes to a diameter of 0.5 mm to obtain wire; the EBSD microstructure of the wire after drawing deformation is as follows. Figure 4 As shown in the figure, the pure copper and graphene copper regions exhibit heterogeneous grain distribution.

[0025] Step 5: Perform post-annealing treatment on the wire at 300℃ in an Ar atmosphere for 2 hours to obtain the final product.

[0026] Example 2 A method for preparing a highly conductive graphene / copper composite material, comprising the following steps: Step 1: Take copper powder with an average particle size of 20 μm and an aspect ratio of 100. Use chemical vapor deposition to grow a single layer or few layers of graphene in situ on the surface of the copper powder to obtain graphene / copper composite powder (component A); Step 2: Take copper sheet powder of the same specifications as above, anneal it at 350℃ for 2 hours in a 5% H2 / Ar mixed atmosphere to obtain component B. Mix component A and component B at a mass ratio of 1:3, and mix them in an Ar-filled mixer at 100 rpm for 8 hours to obtain a heterogeneous mixed powder. Step 3: The mixed powder is placed into a graphite mold with a diameter of 40 mm and subjected to vacuum hot pressing sintering to achieve densification of the graphene / copper composite material. The sintering process parameters are: sintering temperature 950℃, sintering pressure 60MPa, holding time 20 minutes, and vacuum degree not less than 10. -2 Pa, to obtain composite material blank; Step 4: Process the billet into bars with a diameter of 10 mm, and then continuously draw them in multiple passes until the diameter is 0.5 mm to obtain wire. Step 5: Perform post-annealing treatment on the wire at 300℃ in an Ar atmosphere for 2 hours to obtain the final product.

[0027] Example 3 A method for preparing a highly conductive graphene / copper composite material, comprising the following steps: Step 1: Take copper powder with an average particle size of 50 μm and an aspect ratio of 80. Use chemical vapor deposition to grow a single layer or few layers of graphene in situ on the surface of the copper powder to obtain graphene / copper composite powder (component A); Step 2: Take copper sheet powder of the same specifications as above, anneal it at 300℃ for 2 hours in a 5% H2 / Ar mixed atmosphere to obtain component B. Mix component A and component B at a mass ratio of 1:1.5, and mix them in an Ar-filled mixer at 100 rpm for 6 hours to obtain a heterogeneous mixed powder. Step 3: The mixed powder is placed into a graphite mold with a diameter of 40 mm and subjected to vacuum hot pressing sintering to achieve densification of the graphene / copper composite material. The sintering process parameters are: sintering temperature 900℃, sintering pressure 50MPa, holding time 30 minutes, and vacuum degree not less than 10. -2 Pa, to obtain composite material blank; Step 4: Process the billet into bars with a diameter of 10 mm, and then continuously draw them in multiple passes until the diameter is 0.5 mm to obtain wire. Step 5: Perform post-annealing treatment on the wire at 300℃ in an Ar atmosphere for 2 hours to obtain the final product.

[0028] Example 4 A method for preparing a highly conductive graphene / copper composite material, comprising the following steps: Step 1: Take copper powder with an average particle size of 20 μm and an aspect ratio of 60. Use chemical vapor deposition to grow a single layer or few layers of graphene in situ on the surface of the copper powder to obtain graphene / copper composite powder (component A); Step 2: Take copper sheet powder of the same specifications as above, anneal it at 300℃ for 2 hours in a 5% H2 / Ar mixed atmosphere to obtain component B. Mix component A and component B at a mass ratio of 1:2.5, and mix them in an Ar-filled mixer at 100 rpm for 6 hours to obtain a heterogeneous mixed powder. Step 3: The mixed powder is placed into a graphite mold with a diameter of 40 mm and subjected to vacuum hot pressing sintering to achieve densification of the graphene / copper composite material. The sintering process parameters are: sintering temperature 900℃, sintering pressure 50MPa, holding time 30 minutes, and vacuum degree not less than 10. -2Pa, to obtain composite material blank; Step 4: Process the billet into bars with a diameter of 10 mm, and then continuously draw them in multiple passes until the diameter is 0.5 mm to obtain wire. Step 5: Perform post-annealing treatment on the wire at 200℃ in an Ar atmosphere for 2 hours to obtain the final product.

[0029] Comparative Example 1 A method for preparing a highly conductive graphene / copper composite material differs from Example 1 in that pure copper powder (component B) is not added for graded mixing in step 2; all other process steps and parameters are completely consistent with Example 1. The specific steps are as follows: Step 1: Take copper powder with an average particle size of 20 μm and an aspect ratio of 120. Use chemical vapor deposition to grow a single layer or few layers of graphene in situ on the surface of the copper powder to obtain graphene / copper composite powder. Step 2: The powder is placed into a graphite mold with a diameter of 40 mm and subjected to vacuum hot pressing sintering to achieve densification of the graphene / copper composite material. The sintering process parameters are: sintering temperature 950℃, sintering pressure 60MPa, holding time 20 minutes, and vacuum degree not less than 10. -2 Pa, to obtain composite material blank; Step 3: Process the billet into bars with a diameter of 10 mm, and then continuously draw them in multiple passes until the diameter is 0.5 mm to obtain wire. Step 4: Perform post-annealing treatment on the wire at 300℃ in an Ar atmosphere for 2 hours to obtain the final product.

[0030] Comparative Example 2 A method for preparing a highly conductive graphene / copper composite material differs from Example 4 in that pure copper powder (component B) is not added for graded mixing in step 2; all other process steps and parameters are completely consistent with Example 4. The specific steps are as follows: Step 1: Take copper powder with an average particle size of 20 μm and an aspect ratio of 60. Use chemical vapor deposition to grow a single layer or few layers of graphene in situ on the surface of the copper powder to obtain graphene / copper composite powder. Step 2: The powder is placed into a graphite mold with a diameter of 40 mm and subjected to vacuum hot pressing sintering to achieve densification of the graphene / copper composite material. The sintering process parameters are: sintering temperature 900℃, sintering pressure 50MPa, holding time 30 minutes, and vacuum degree not less than 10. -2 Pa, to obtain composite material blank; Step 3: Process the billet into bars with a diameter of 10 mm, and then continuously draw them in multiple passes until the diameter is 0.5 mm to obtain wire. Step 4: Perform post-annealing treatment on the wire at 200℃ in an Ar atmosphere for 2 hours to obtain the final product.

[0031] The electrical conductivity of the composite materials prepared in each embodiment and each comparative example was tested, and the results are shown in Table 1: Table 1. Conductivity of each embodiment and comparative example As can be seen from Examples 1-4 in Table 1, after introducing pure copper sheet powder, the conductivity of the composite wires of this invention all reached over 102.5% IACS, significantly higher than that of Comparative Examples 1 and 2 without the introduction of pure copper sheet powder (conductivity of 97.2% IACS and 98.6% IACS, respectively). The mechanism is as follows: the pure copper sheet powder forms a continuous, low-defect conductive network during sintering and drawing, providing a continuous channel for high-speed electron transport; while the graphene / copper composite sheet powder plays a reinforcing and interface-regulating role. The two form a synergistic constraint effect at the heterogeneous interface, further optimizing the carrier transport path. This result verifies the effectiveness of the proposed "soft and hard bicomponent" structural design in improving conductivity. Finally, compared with the comparative examples, the examples, by introducing sheet-like pure copper powder, not only reduced costs but also significantly improved conductivity.

[0032] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a highly conductive graphene / copper composite material, characterized in that, Includes the following steps: (1) Preparation of in-situ graphene / copper sheet powder: Graphene was grown in-situ on the surface of copper sheet powder by chemical vapor deposition to obtain graphene-coated graphene / copper composite sheet powder. (2) Heterogeneous powder gradation and mixing: The graphene / copper composite sheet powder and the copper sheet powder after reduction treatment are mixed in a predetermined mass ratio under a protective atmosphere to obtain a mixed powder; (3) Hot pressing sintering: The mixed powder is subjected to vacuum hot pressing sintering to obtain a blank; (4) Drawing deformation process: The billet is subjected to multiple drawing deformation processes to obtain composite wire; (5) Annealing treatment: The composite wire is subjected to post-annealing treatment to obtain the highly conductive graphene / copper composite material.

2. The method for preparing a highly conductive graphene / copper composite material according to claim 1, characterized in that, In steps (1) and (2), the aspect ratio of the copper sheet powder is not less than 50, and the average particle size is 10~100 μm.

3. The method for preparing a highly conductive graphene / copper composite material according to claim 1, characterized in that, In step (2), the process parameters for the reduction treatment are: 5% H2 / Ar reduction atmosphere, temperature 300~450℃, and time 1~3 hours.

4. The method for preparing a highly conductive graphene / copper composite material according to claim 1, characterized in that, In step (2), the mass ratio of the graphene / copper powder to the reduced copper powder is 1:(1~4).

5. The method for preparing a highly conductive graphene / copper composite material according to claim 1, characterized in that, In step (2), the mixing is carried out in a mixer filled with Ar gas, with a mixing speed of 80~120 rpm and a mixing time of 6~12 hours.

6. The method for preparing a highly conductive graphene / copper composite material according to claim 1, characterized in that, In step (3), the process parameters for vacuum hot pressing sintering are: sintering temperature 800~950℃, pressure 20~80MPa, holding time 10~30 minutes, and vacuum degree not less than 10. -2 Pa.

7. The method for preparing a highly conductive graphene / copper composite material according to claim 1, characterized in that, In step (4), the total deformation rate of the drawing deformation is not less than 80%.

8. In the preparation method of a highly conductive graphene / copper composite material according to claim 1, the process parameters of the post-annealing treatment in step (5) are: atmosphere Ar, annealing temperature 150~400℃, annealing time 1~3 hours.

9. A highly conductive graphene / copper composite material, characterized in that, The composite material is prepared by the preparation method according to any one of claims 1 to 8; in the composite material, the graphene is oriented along the drawing direction and the grains have a high aspect ratio.

10. The highly conductive graphene / copper composite material according to claim 9, characterized in that, The conductivity of the composite material is not less than 100% IACS.

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