A multi-scale copper graphene composite material and a preparation method thereof

Abstract

The present application belongs to the field of composite materials, and particularly relates to a multiscale copper graphene composite material and a preparation method thereof. The preparation method provided by the present application comprises the following steps: a) laying copper wires on a graphene surface layer of copper foil graphene and spraying a copper salt solution, and the laying of the copper wires and the spraying of the copper salt solution are not limited in sequence; b) stacking a plurality of copper foil graphenes treated in step a), and hot-pressing to obtain a multiscale copper graphene composite material. The present application adopts a multiscale material to prepare a copper graphene composite material, and through the comprehensive use of the "macro-mesoscopic-micro" multiscale material and a hot-pressing process, the long continuous distribution of the high-conductivity network of the graphene in the layer is effectively maintained, the formation of the high-conductivity chemical bond between the "copper foil-graphene-graphene-copper foil" layers is promoted, and the conductivity of the copper graphene composite material is significantly improved. Meanwhile, the regularly distributed copper wires between the layers can effectively promote the metallurgical bonding of the copper foils between the layers, and the thickness uniformity of the whole product is improved.

Description

Technical Field

[0001] The present invention belongs to the field of composite materials, and in particular relates to a multi-scale copper-graphene composite material and a preparation method thereof. Background Art

[0002] Graphene is a known material with high carrier mobility. Copper possesses a high carrier concentration. The proper distribution of graphene within a copper or copper alloy matrix can effectively enhance the mechanical and electrical properties of both materials. In recent years, the fabrication of copper-based graphene composites has become a research hotspot in the field of high-strength, high-conductivity materials. In a report on such composite materials, Zhang Xiaohui and others at the Automotive Research Institute used chemical vapor deposition (CVD) on copper foil to produce copper-graphene foil. Furthermore, by hot-pressing multilayer copper foil graphene, they achieved highly conductive sheets and bulk materials of macroscopic thickness, with electrical conductivity exceeding 115% IACS, with a peak of 118% IACS.

[0003] Hot pressing of graphene-copper foil is currently the most effective and commonly used method for manufacturing highly conductive copper-graphene composites. The basic principle is that during compression, the graphene breaks down, exposing the upper and lower layers of copper foil to each other. The thermal influence increases the mobility of copper atoms, stimulating their interdiffusion and achieving metallurgical bonding. However, the current process still has shortcomings and cannot maximize the high conductivity of the material, as shown in the following:

[0004] (1) During the hot pressing process, the interaction between the plastic deformation of the copper in the hot state and the elastic deformation of the graphite indenter under high pressure will cause the copper-graphene composite material to have uneven dimensional deformation in the height direction, which is specifically manifested as a shape that is high in the middle and thin around. Subsequent correction, machining or grinding is required to obtain a material with consistent thickness uniformity.

[0005] (2) Graphene is a material with a single atomic layer (or less than 10 layers) and cannot withstand excessive shear force during hot pressing and breaks, which directly affects the continuity of the distribution of high carrier mobility graphene. The C atoms at the edges of the broken graphene fragments are in an unsaturated bonding state and are easily diffused into the copper grains under the interaction of heat and pressure. The C atoms remaining in the copper grains become lattice distortion, causing scattering of the directional transmission of electrons.

[0006] Given the above two process limitations, it is difficult to further improve the performance of copper-graphene composite materials using existing technologies. Summary of the Invention

[0007] In view of this, the object of the present invention is to provide a multi-scale copper-graphene composite material and a preparation method thereof. The multi-scale copper-graphene composite material prepared by the method of the present invention has good thickness uniformity and very excellent electrical conductivity.

[0008] The present invention provides a method for preparing a multi-scale copper-graphene composite material, comprising the following steps:

[0009] a) laying copper wire on the graphene surface layer of the copper foil graphene and spraying a copper salt solution, wherein the laying of the copper wire and the spraying of the copper salt solution are not limited in order;

[0010] b) stacking and hot-pressing the multiple copper foil graphenes processed in step a) to obtain a multi-scale copper graphene composite material.

[0011] Preferably, in step a), the diameter of the copper wire is 30 to 300 μm.

[0012] Preferably, in step a), the copper wires are laid at a spacing of 30 μm to 3 cm.

[0013] Preferably, in step a), the copper wires are laid out at equal intervals on the graphene surface layer, or the copper wires are laid out with increasing intervals from the center to the edge of the graphene surface layer.

[0014] Preferably, in step a), the copper salt in the copper salt solution is one or more of copper nitrate, copper chloride and copper acetate.

[0015] Preferably, in step a), the concentration of the copper salt solution is 0.1 to 1 mmol / L.

[0016] Preferably, in step a), the spray coverage of the copper salt solution on the graphene surface layer is 20 to 100%.

[0017] Preferably, in step b), the number of stacked layers is 20 to 100.

[0018] Preferably, in step b), the hot pressing pressure is 20-100 MPa; the hot pressing temperature is 350-1050° C.; and the hot pressing time is 30-300 min.

[0019] The present invention provides a multi-scale copper-graphene composite material, which is prepared according to the preparation method described in the above technical solution.

[0020] Compared to the prior art, the present invention provides a multi-scale copper-graphene composite material and its preparation method. The preparation method provided by the present invention comprises the following steps: a) laying copper wire on the graphene surface layer of copper foil graphene and spraying a copper salt solution, wherein the laying of the copper wire and the spraying of the copper salt solution are not limited in any order; b) stacking and hot pressing multiple copper foil graphenes treated in step a) to obtain a multi-scale copper-graphene composite material. The present invention uses multi-scale materials to prepare the copper-graphene composite material, wherein copper foil is a macroscale material, copper wire is a micron-scale mesoscale material, copper nanoparticles (formed by high-temperature pyrolysis of copper salt), and graphene are nanoscale materials. Through the comprehensive use of the "macro-meso-micro" multi-scale materials and hot pressing process, the long continuous distribution of the highly conductive graphene network within the layer is effectively maintained, the formation of highly conductive chemical bonds between the "copper foil-graphene-graphene-copper foil" layers is promoted, and the conductive properties of the copper-graphene composite material are significantly improved. At the same time, the regularly distributed copper wires between layers can effectively promote the metallurgical bonding of the copper foil between layers, and effectively release and compensate for the uneven material thickness caused by the plastic deformation of the copper foil during the hot pressing process, thereby improving the overall thickness uniformity of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0022] Figure 1 It is a schematic diagram of the preparation process provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0024] The present invention provides a method for preparing a multi-scale copper-graphene composite material, comprising the following steps:

[0025] a) laying copper wire on the graphene surface layer of the copper foil graphene and spraying a copper salt solution, wherein the laying of the copper wire and the spraying of the copper salt solution are not limited in order;

[0026] b) stacking and hot-pressing the multiple copper foil graphenes processed in step a) to obtain a multi-scale copper graphene composite material.

[0027] In the preparation method provided by the present invention, in step a), the copper foil graphene includes a copper foil substrate and a graphene surface layer deposited on the surface of the copper foil substrate; the graphene surface layer can be a single atomic layer or a multilayer graphene; the number of layers of the multilayer graphene is preferably ≤10 layers, specifically 2 layers, 3 layers, 4 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers or 10 layers.

[0028] In the preparation method provided by the present invention, in step a), the thickness of the copper foil graphene is 10 to 50 μm, specifically 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm or 50 μm.

[0029] In the preparation method provided by the present invention, in step a), the diameter of the copper wire is preferably 30-300 μm, specifically 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, 260 μm, 270 μm, 280 μm, 290 μm or 300 μm.

[0030] In the preparation method provided by the present invention, in step a), the laying spacing of the copper wire is preferably 30μm to 3cm, specifically 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 120μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, 1μm, 1.2μm, 1.5μm, 2μm, 2.5μm or 3μm.

[0031] In the preparation method provided by the present invention, in step a), the copper wires can be laid out at equal intervals on the graphene surface layer, or the copper wires can be laid out with increasing spacing from the center to the edge of the graphene surface layer. In one embodiment provided by the present invention, the laying spacing of the copper wires increases at equal intervals from the center to the edge of the graphene surface layer, and the difference between two adjacent laying spacings is preferably 10 to 100 μm, specifically 60 μm.

[0032] In the preparation method provided by the present invention, in step a), the copper wire is preferably subjected to a hydrogen reduction treatment before being laid to remove the oxide film on the surface.

[0033] In the preparation method provided by the present invention, in step a), the copper salt in the copper salt solution is preferably one or more of copper nitrate, copper chloride and copper acetate.

[0034] In the preparation method provided by the present invention, in step a), the concentration of the copper salt solution is preferably 0.1 to 1 mmol / L, specifically 0.1 mmol / L, 0.2 mmol / L, 0.3 mmol / L, 0.4 mmol / L, 0.5 mmol / L, 0.6 mmol / L, 0.7 mmol / L, 0.8 mmol / L, 0.9 mmol / L or 1 mmol / L.

[0035] In the preparation method provided by the present invention, in step a), the spray coverage of the copper salt solution on the graphene surface layer is preferably 20% to 100%, specifically 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%; the spray amount (wet amount) in the spraying area is preferably 0.1 to 0.5 mg / cm 2 , specifically 0.1 mg / cm 2 , 0.15mg / cm 2 , 0.2mg / cm 2 , 0.25mg / cm 2 , 0.3mg / cm 2 , 0.35mg / cm 2 , 0.4mg / cm 2 , 0.45mg / cm 2 or 0.5 mg / cm 2 .

[0036] In the preparation method provided by the present invention, in step b), the number of stacked layers is preferably 20 to 100 layers, specifically 20 layers, 25 layers, 30 layers, 35 layers, 40 layers, 45 layers, 50 layers, 55 layers, 60 layers, 65 layers, 70 layers, 75 layers, 80 layers, 85 layers, 90 layers, 95 layers or 100 layers.

[0037] In the preparation method provided by the present invention, in step b), the angle between the copper wires laid on two adjacent layers of copper foil graphene is 0° to 90°, specifically 0° (i.e., parallel to each other), 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85° or 90° (i.e., perpendicular to each other).

[0038] In the preparation method provided by the present invention, in step b), the hot pressing is carried out in a vacuum environment or under protective gas; the hot pressing method is preferably hot isostatic pressing; the hot pressing pressure is preferably 20-100 MPa, more preferably 30-80 MPa, specifically 30 MPa, 35 MPa, 40 MPa, 45 MPa, 50 MPa, 55 MPa, 60 MPa, 65 MPa, 70 MPa, 75 MPa or 80 MPa; the hot pressing temperature is preferably 350-1050°C, more preferably 550-950°C, specifically 5 The temperature of the hot pressing step is preferably 50°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C or 950°C; the hot pressing time is preferably 30 to 300 min, specifically 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 170 min, 200 min, 230 min, 250 min, 270 min or 300 min.

[0039] For the sake of clarity, the technical principle of the present invention is described below:

[0040] (1) Copper-graphene composite materials are prepared using multi-scale materials, in which copper foil is a macro-scale material, copper wire is a micron-scale meso-scale material, copper nanoparticles (formed by high-temperature pyrolysis of copper salts) and graphene are nano-scale materials; through the comprehensive application of "macro-meso-micro" multi-scale materials and hot pressing technology, the comprehensive performance of copper-graphene composite materials is improved.

[0041] (2) The role of copper wire: ① It provides a gap between the copper foil and graphene layers, and is gradually compressed and deformed during the hot pressing process. Its slow release process of pressure can significantly reduce and weaken the tendency of graphene to fracture under pressure, which helps to maintain its distribution continuity after hot pressing; ② Compared with the surface contact type between copper foil and copper foil, the contact area between copper wire and copper foil is significantly smaller. Under the action of hot pressing, only the graphene at the contact surface is broken, and it is easier to cause atomic interdiffusion with the upper and lower copper foils, promoting the formation of metallurgical bonding between the copper foils and coordinated grain growth; ③ After the copper foil and graphene are laid, hot pressing will cause inconsistent deformation in the thickness direction of the material after solidification due to the dispersed pressure transmission layer by layer and uneven plastic deformation of the pressure head and copper foil in the plane direction. If the copper wire is laid regularly between the layers, the uneven thickness after hot pressing can be significantly reduced.

[0042] (3) The role of copper nanoparticles: Compared with macroscopic metal materials, metal nanoclusters have a large specific surface area and strong electronic polarization ability. Under the action of an external electric field, the copper atoms in the nanoclusters can share electron clouds with the carbon atoms in the graphene, which acts like a chemical bond for electron transfer. This constructs a vertical conductive network between the graphene and the copper foil, improving the material's conductivity in the vertical direction.

[0043] The preparation method provided by the present invention can enable the copper-graphene composite material to have a highly conductive network in the plane and an effective channel for electron transmission at the interlayer interface, while the overall hot-pressing deformation is small. More specifically, it has at least the following advantages:

[0044] (1) Through the comprehensive application of "macro-meso-micro" multi-scale materials and process methods, the long continuous distribution of the highly conductive graphene network within the layer is effectively maintained, and the formation of highly conductive chemical bonds between the "copper foil-graphene-graphene-copper foil" layers is promoted.

[0045] (2) The presence of regularly distributed copper wires can effectively promote the metallurgical bonding of the interlayer copper foils, and effectively release and compensate for the uneven thickness of the target material caused by the plastic deformation of the copper foil during the hot pressing process.

[0046] (3) The stacking process used is regular and can be easily mechanized.

[0047] (4) All raw materials are commercially available products, and the products are easy to industrialize and mass-produce.

[0048] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples and comparative examples.

[0049] Example 1

[0050] according to Figure 1 The multi-scale copper-graphene composite material is prepared by the process shown in the figure. The specific process is as follows:

[0051] 25μm thick copper foil graphene, 30μm diameter copper wire, and 0.5mmol / L copper acetate diluted solution were selected as the base materials. The graphene on the copper foil surface was a single layer. The copper wire was subjected to hydrogen reduction treatment to remove the surface oxide film and then laid on the graphene surface layer of the copper foil graphene at an equidistant spacing of 200μm. Subsequently, the copper acetate solution was evenly sprayed on the graphene surface layer of the copper foil graphene by spraying. The coverage rate of the droplets on the graphene surface layer was about 30%, and the spraying amount was about 0.1mg / cm 2 .

[0052] Repeat the above operation to obtain multiple processed copper foil graphene basic units; then, 40 layers of copper foil graphene basic units are stacked and laid according to the angle of 90° between the upper and lower copper wires; after fixing, a hot pressing process is carried out with a pressure of 50 MPa, a temperature of 800°C, and a holding time of 60 minutes to achieve metallurgical bonding and solidification of the material to obtain a multi-scale copper graphene composite material.

[0053] The heterogeneity of the multi-scale copper-graphene composite material prepared in this embodiment was measured and calculated using the formula: (center thickness-edge thickness) / edge thickness×100%, and the result was: 3%.

[0054] The conductive properties of the multi-scale copper-graphene composite material prepared in this embodiment were tested, and the results showed that the conductivity in the XY plane was 110% IACS measured by van der Pauw, and the conductivity in the Z-axis direction was 104% IACS measured by the four-probe method.

[0055] Example 2

[0056] according to Figure 1 The multi-scale copper-graphene composite material is prepared by the process shown in the figure. The specific process is as follows:

[0057] 25μm thick copper foil graphene, 30μm diameter copper wire, and 0.5mmol / L copper acetate diluted solution were selected as the base materials. The graphene on the copper foil surface was a single layer. The copper wire was subjected to hydrogen reduction treatment to remove the surface oxide film and then laid on the graphene surface layer of the copper foil graphene at an equal distance of 250μm. The copper acetate solution was then evenly sprayed on the graphene surface layer of the copper foil graphene by spraying. The coverage rate of the droplets on the graphene surface layer was about 60%, and the spraying amount was about 0.2mg / cm 2 .

[0058] Repeat the above operation to obtain multiple processed copper foil graphene basic units; then, 40 layers of copper foil graphene basic units are stacked and laid according to the angle of 45° between the upper and lower copper wires; after fixing, a hot pressing process is carried out with a pressure of 60 MPa, a temperature of 750°C, and a holding time of 80 minutes to achieve metallurgical bonding and solidification of the material to obtain a multi-scale copper graphene composite material.

[0059] The heterogeneity of the multi-scale copper-graphene composite material prepared in this embodiment was measured and the result was 3%.

[0060] The conductive properties of the multi-scale copper-graphene composite material prepared in this embodiment were tested, and the results showed that the conductivity in the XY plane was 108% IACS measured by van der Pauw, and the conductivity in the Z-axis direction was 105% IACS measured by the four-probe method.

[0061] Example 3

[0062] according to Figure 1 The multi-scale copper-graphene composite material is prepared by the process shown in the figure. The specific process is as follows:

[0063] 18μm thick copper foil graphene, 60μm diameter copper wire, and 1.5mmol / L copper acetate diluted solution were selected as the base materials. The graphene on the copper foil surface was a single layer. The copper wire was subjected to hydrogen reduction treatment to remove the surface oxide film and then laid on the graphene surface layer of the copper foil graphene at an equal distance of 350μm. The copper acetate solution was then evenly sprayed on the graphene surface layer of the copper foil graphene by spraying. The coverage of the droplets on the graphene surface layer was about 50%, and the spraying amount was about 0.35mg / cm 2 .

[0064] Repeat the above operation to obtain multiple processed copper foil graphene basic units; then, 40 layers of copper foil graphene basic units are stacked and laid according to the 90° angle between the upper and lower copper wires; after fixing, a hot pressing process is carried out with a pressure of 50 MPa, a temperature of 850°C, and a holding time of 120 minutes to achieve metallurgical bonding and solidification of the material to obtain a multi-scale copper graphene composite material.

[0065] The heterogeneity of the multi-scale copper-graphene composite material prepared in this embodiment was measured and the result was 1%.

[0066] The conductive properties of the multi-scale copper-graphene composite material prepared in this embodiment were tested, and the results showed that the conductivity in the XY plane was 113% IACS measured by van der Pauw, and the conductivity in the Z-axis direction was 106% IACS measured by the four-probe method.

[0067] Example 4

[0068] according to Figure 1 The flowchart shows the preparation of the multi-scale copper graphene composite material, and the specific process is as follows:

[0069] The 18 μm thick copper foil graphene, 30 μm diameter copper wire, and 1.5 mmol / L concentration of copper acetate dilution solution are selected as the basic materials, wherein the graphene on the surface of the copper foil is single-layer; the copper wire is subjected to hydrogen reduction treatment to remove the surface oxide film; the copper wire is laid on the graphene surface layer from the center to the edge of the graphene surface layer of the copper foil graphene in an increasing interval of 60 μm, 120 μm, 180 μm, 240 μm, 300 μm, 360 μm, and the like; then the copper acetate solution is uniformly sprayed on the graphene surface layer of the copper foil graphene by spraying, and the coverage of the droplets on the graphene surface layer is about 70%, and the spraying amount is about 0.5 mg / cm 2 .

[0070] The above operation is repeated to obtain a plurality of treated copper foil graphene basic units; then, the 40 layers of copper foil graphene basic units are stacked and laid according to an angle of 45° between the upper and lower copper wires; after being fixed, a hot pressing process is performed, the pressure is 50 MPa, the temperature is 850℃, and the pressure holding time is 100 min, so as to realize metallurgical bonding and solidification of the material, and obtain the multi-scale copper graphene composite material.

[0071] The non-uniformity of the multi-scale copper graphene composite material prepared in this embodiment is calculated, and the result is 0.5%.

[0072] The conductivity of the multi-scale copper graphene composite material prepared in this embodiment is detected, and the result is that the conductivity measured by Van der Pauw in the X-Y plane is 115% IACS, and the conductivity measured by the four-probe method in the Z-axis direction is 106% IACS.

[0073] Comparative Example 1

[0074] After 40 layers of 25 μm thick copper foil graphene are stacked and laid and hot pressed, the graphene on the surface of the copper foil is single-layer, the pressure is set to 50 MPa, the temperature is 800℃, and the pressure holding time is 60 min, so as to realize metallurgical bonding between the copper foil graphene layers, and obtain the copper graphene composite material.

[0075] The non-uniformity of the copper graphene composite material prepared in this comparative example is calculated, and the result is 8%.

[0076] The conductivity of the copper graphene composite material prepared in this comparative example is detected, and the result is that the conductivity measured by Van der Pauw in the X-Y plane is 115% IACS, and the conductivity measured by the four-probe method in the Z-axis direction is 101% IACS.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a multi-scale copper-graphene composite material, characterized in that: The following steps are involved: a) laying copper wire on the graphene surface layer of the copper foil graphene and spraying a copper salt solution, wherein the laying of the copper wire and the spraying of the copper salt solution are not limited in order; In step a), the copper wires are laid out at equal intervals on the graphene surface layer, or the copper wires are laid out with increasing intervals from the center to the edge of the graphene surface layer; b) stacking and hot-pressing the multiple copper foil graphene sheets processed in step a) to obtain a multi-scale copper graphene composite material; In step b), the hot pressing temperature is 350-1050°C.

2. The preparation method according to claim 1, characterized in that In step a), the diameter of the copper wire is 30-300 μm.

3. The preparation method according to claim 1, characterized in that In step a), the copper wires are laid at a spacing of 30 μm to 3 cm.

4. The preparation method according to claim 1, characterized in that In step a), the copper salt in the copper salt solution is one or more of copper nitrate, copper chloride and copper acetate.

5. The preparation method according to claim 1, characterized in that In step a), the concentration of the copper salt solution is 0.1-1 mmol / L.

6. The preparation method according to claim 1, characterized in that In step a), the spray coverage of the copper salt solution on the graphene surface layer is 20-100%.

7. The preparation method according to claim 1, characterized in that In step b), the number of stacked layers is 20 to 100.

8. The preparation method according to claim 1, characterized in that In step b), the hot pressing pressure is 20-100 MPa; and the hot pressing time is 30-300 min.

9. A multi-scale copper-graphene composite material, characterized in that It is prepared according to the preparation method according to any one of claims 1 to 8.

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