Method for improving conductivity of graphene-copper composite material by epitaxially depositing nano interface layer

Abstract

A method for improving the conductivity of a graphene-copper composite material by epitaxially depositing a nano interface layer comprises the following steps: depositing graphene on the surface of a copper foil by adopting a chemical vapor deposition (CVD) technology to form a graphene / copper composite foil; on the basis, a copper layer with the nano-scale thickness is deposited through magnetron sputtering, thermocompression bonding is carried out, and a nano-copper layer-graphene / copper composite element is prepared; and stacking a plurality of layers of nano-copper layer-graphene / copper composite elements layer by layer, and carrying out hot pressed sintering to obtain the graphene-copper-based composite material with remarkably optimized conductivity. According to the method, atomic-level stable combination is achieved, the contact performance of the composite interface is enhanced, the problems of electron scattering and the like caused by poor quality of the copper-carbon composite interface are effectively solved, further breakthrough of the conductivity is achieved, and production and preparation are easy.

Description

Technical Field

[0001] This invention relates to a technology in the field of metal matrix composites, specifically a method for preparing a highly conductive graphene-copper matrix composite with an electrical conductivity of 114% IACS. Background Technology

[0002] The rapidly developing fields of high-frequency transmission and electronic information have placed demands on copper-based materials for ultra-high conductivity. Traditional methods for preparing copper-based materials (such as single-crystal copper and oxygen-free copper) are approaching their physical limits, making further breakthroughs in the electrical properties of copper-based materials difficult. Graphene, with its high electron mobility and conductivity, can serve as an ideal reinforcement for achieving ultra-high conductivity in copper-based composites. However, due to lattice mismatch and non-wetting properties between the two, the weak copper-carbon bonding at the interface during densification reduces the interface quality of the composite mass. Poor interface flatness leads to electron scattering, thus limiting further improvements in the conductivity of graphene-copper composites. Summary of the Invention

[0003] This invention addresses the problems of weak copper-carbon bonding in existing graphene-copper composites, which reduces interfacial quality and leads to limited improvement in conductivity due to electron scattering, as well as the weak copper-carbon atomic bonding in existing composites. It proposes a method to improve the conductivity of graphene-copper composites by epitaxially depositing a nano-interfacial layer. A uniform graphene layer is grown on a copper foil surface using chemical vapor deposition, and a copper layer of nanoscale thickness is deposited on its surface by magnetron sputtering. The resulting nano-copper layer-graphene / copper composite units are then hot-pressed and sintered to prepare a layered, highly conductive graphene-copper composite material. This material introduces copper atoms enriched at the composite interface, forming a high-quality nano-interfacial transition layer. The thinner nano-copper layer, after hot-pressing bonding, can form a specific orientation, resulting in a higher lattice compatibility with graphene, which is beneficial for improving interfacial strength, achieving atomic-level stable bonding, enhancing the contact of the composite interface, effectively improving the electron scattering problems caused by poor copper-carbon composite interface quality, achieving a further breakthrough in conductivity, and is easy to manufacture.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a method for improving the electrical conductivity of graphene-copper composite materials by epitaxially depositing a nano-interface layer. The method involves depositing graphene on a copper foil surface using chemical vapor deposition (CVD) to form a graphene / copper composite foil; then depositing a copper layer of nanoscale thickness by magnetron sputtering and hot-pressing it to prepare a nano-copper layer-graphene / copper composite unit; finally, stacking several layers of the nano-copper layer-graphene / copper composite unit layer by layer and hot-pressing them to obtain a graphene-copper based composite material with significantly optimized electrical conductivity.

[0006] The chemical vapor deposition technology refers to the process of uniformly depositing graphene on the surface of copper foil in a hydrogen atmosphere at 800-1000℃ by introducing methane as a gaseous carbon source in a quartz tube furnace.

[0007] In the graphene / copper composite foil, the copper substrate is preferably a foil with a thickness of 10-100 μm, a purity of ≥99%, and high crystallinity; the graphene layers are preferably single or few, with a coverage of ≥95%.

[0008] The magnetron sputtering step refers to: in a magnetron sputtering coating system, using a copper target with a purity ≥99.99% to perform sputtering deposition of a nano-copper layer; the sputtering power is 100-300W, and the preferred thickness of the nano-copper layer is 5-50nm.

[0009] The hot-press bonding refers to hot-press bonding performed in a vacuum bonding machine, preferably at a pressure of 5-10 bar and a temperature of 80-200°C, for a bonding time of 30-90 minutes. Its function is to promote the effective bonding of the sputtered nano-copper layer with the graphene / copper composite foil and to induce an orientation change in the copper layer and the substrate.

[0010] In the aforementioned nano-copper layer-graphene / copper composite unit, the surface-sputtered nano-copper layer and copper substrate grains are single-crystal and are both (111) oriented.

[0011] The hot pressing sintering refers to hot pressing sintering in a rapid sintering furnace under argon protection using a graphite mold with a diameter of 30-40mm, at a sintering temperature of 700-1000℃, a pressure of 10-200MPa, and a holding time of 10-30min.

[0012] The present invention relates to a highly conductive graphene-copper-based composite material prepared by the above method, which is composed of several layers of nano-copper layer-graphene / copper composite units stacked one by one. Each nano-copper layer-graphene / copper composite unit is composed of copper foil with graphene deposited on the surface and nano-copper layer bonded together.

[0013] This invention relates to the application of the above-mentioned highly conductive graphene-copper-based composite material, which is used to prepare a conductor with an electrical conductivity of 114% IACS. Technical effect

[0014] This invention achieves a highly conductive graphene-copper composite material by sputtering and depositing a copper layer of nanoscale thickness on the surface of CVD-grown graphene / composite copper foil, followed by bonding and hot-pressing sintering of the resulting composite unit. Compared with existing technologies, this invention improves the surface flatness of the composite unit through the nanoscale copper layer, forming a flat nanoscale transition layer at the graphene-copper composite interface. The hot-pressed sputtered copper layer is tightly bonded to the graphene / copper foil, inducing a specific orientation between the copper layer and the substrate, resulting in a higher lattice fit between graphene and copper. By sputtering a thinner nanoscale copper layer and combining it with the bonding process, the weak copper-carbon bonding problem at the original interface can be solved, achieving stable atomic-level bonding on both sides of the interface, enhancing the contact of the composite interface, and effectively improving the interface quality in the graphene-copper composite material. The high lattice matching between the graphene layer and copper, along with the high flatness and stable bonding interface, provides a high-quality electron transport channel, achieving a further breakthrough in high conductivity. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the preparation process of highly conductive graphene-copper-based composite materials.

[0016] Figure 2 Scanning electron microscope images of the graphene / copper foil prepared in Example 2 before and after sputtering;

[0017] Figure 3 Atomic force microscopy images of the graphene / copper foil prepared in Example 2 before and after sputtering, and the corresponding surface roughness. Detailed Implementation Example 1

[0018] This embodiment includes the following steps:

[0019] Step 1) Place a 25μm thick copper foil substrate into a quartz tube furnace and grow graphene by chemical vapor deposition at 1000℃ in a hydrogen and methane atmosphere to obtain a graphene / copper composite foil.

[0020] Step 2) Place the graphene / copper composite foil in a magnetron sputtering coating system and perform sputtering deposition of a nano-copper layer at a power of 300W. The copper layer thickness is 5nm, resulting in a nano-copper layer-graphene / copper foil.

[0021] Step 3) Place the nano-copper layer-graphene / copper foil into a vacuum bonding machine and perform hot-press bonding at 120°C and 5 bar.

[0022] Step 4) Ten bonded nano-copper layers-graphene / copper foils are stacked one by one in a rapid sintering furnace and hot-pressed at 900℃, 50MPa and argon atmosphere to obtain graphene-copper based composite blocks.

[0023] Step 5) The composite bulk material prepared had a thickness of approximately 250 μm. Conductivity testing at room temperature was performed using a van der Bauer conductivity measurement device. This device consisted of a nanovoltmeter, a constant current source, and four probes. During the first measurement, probes 1 and 2 were energized, while probes 3 and 4 were used to measure voltage. During the second measurement, probes 2 and 3 were energized, while probes 1 and 4 were used to measure voltage. The final calculated conductivity of the graphene-copper composite bulk material was 64.39 × 10⁻⁶. 6 The S / m ratio is 111% IACS, exceeding the international standard for annealed copper. This indicates that the graphene-copper matrix composite material bulk prepared in this embodiment meets the application requirements. Example 2

[0024] This embodiment includes the following steps:

[0025] Step 1) Place a 25μm thick copper foil substrate into a quartz tube furnace and grow graphene by chemical vapor deposition at 1000℃ in a hydrogen and methane atmosphere to obtain a graphene / copper composite foil.

[0026] Step 2) Place the graphene / copper composite foil in a magnetron sputtering coating system and perform sputtering deposition of a nano-copper layer at a power of 300W. The copper layer thickness is 10nm, resulting in a nano-copper layer-graphene / copper foil.

[0027] Step 3) Place the nano-copper layer-graphene / copper foil into a vacuum bonding machine and perform hot-press bonding at 120°C and 5 bar.

[0028] Step 4) Ten bonded nano-copper layers-graphene / copper foils are stacked one by one in a rapid sintering furnace and hot-pressed at 900℃, 50MPa and argon atmosphere to obtain graphene-copper based composite blocks.

[0029] Step 5) The thickness of the prepared composite bulk material is approximately 250 μm. The conductivity was measured at room temperature using a van der Bauer conductivity measuring device, following the same testing method as in Step 5 of Example 1. The final calculated conductivity of the graphene-copper composite bulk material is 66.24 × 10⁻⁶. 6 The S / m ratio is 114% IACS, exceeding the international standard for annealed copper. This indicates that the graphene-copper matrix composite material bulk prepared in this embodiment meets the application requirements.

[0030] like Figure 2 , Figure 3As shown in the scanning electron microscope and atomic force microscope images, the sputtered nano-copper layer-graphene / copper foil exhibits fewer surface wrinkles, lower roughness, and a smoother, flatter surface compared to the unsputtered graphene / copper foil. This will facilitate the formation of a flat nano-interface transition layer during the subsequent hot-pressing sintering process to prepare layered composite bulk materials. The hot-pressing bonding process results in a tighter bond between the sputtered copper layer and the graphene / copper foil, while simultaneously inducing a specific orientation shift in both the copper layer and the substrate, leading to a higher lattice fit between graphene and copper. The introduction of sputtering and bonding processes for thinner copper layers can solve the problem of weak copper-carbon bonding at the original interface, achieving stable bonding between copper atoms on both sides of the interface. This effectively improves the interface quality in the graphene-copper-based composite material, contributing to further enhancement of electrical conductivity. Example 3

[0031] This embodiment includes the following steps:

[0032] Step 1) Place a 25μm thick copper foil substrate into a quartz tube furnace and grow graphene by chemical vapor deposition at 1000℃ in a hydrogen and methane atmosphere to obtain a graphene / copper composite foil.

[0033] Step 2) Place the graphene / copper composite foil in a magnetron sputtering coating system and perform sputtering deposition of a nano-copper layer at a power of 300W. The copper layer thickness is 80nm, resulting in a nano-copper layer-graphene / copper foil.

[0034] Step 3) Place the nano-copper layer-graphene / copper foil into a vacuum bonding machine and perform hot-press bonding at 120°C and 5 bar.

[0035] Step 4) Ten bonded nano-copper layers-graphene / copper foils are stacked one by one in a rapid sintering furnace and hot-pressed at 900℃, 50MPa and argon atmosphere to obtain graphene-copper based composite blocks.

[0036] Step 5) The thickness of the prepared composite bulk material is approximately 250 μm. The conductivity test at room temperature was performed using a van der Bauer conductivity measurement device, following the same testing method as in Step 5 of Example 1. The final calculated conductivity of the graphene-copper composite bulk material is 61.58 × 10⁻⁶. 6 The S / m ratio is 106% IACS, exceeding the international standard for annealed copper. This indicates that the graphene-copper matrix composite material bulk prepared in this embodiment meets the application requirements. Example 4

[0037] This embodiment includes the following steps:

[0038] Step 1) Place a 25μm thick copper foil substrate into a quartz tube furnace and grow graphene by chemical vapor deposition at 1000℃ in a hydrogen and methane atmosphere to obtain a graphene / copper composite foil.

[0039] Step 2) Place the graphene / copper composite foil in a magnetron sputtering coating system and perform sputtering deposition of a nano-copper layer at a power of 300W. The copper layer thickness is 200nm, resulting in a nano-copper layer-graphene / copper foil.

[0040] Step 3) Place the nano-copper layer-graphene / copper foil into a vacuum bonding machine and perform hot-press bonding at 120°C and 5 bar.

[0041] Step 4) Ten bonded nano-copper layers-graphene / copper foils are stacked one by one in a rapid sintering furnace and hot-pressed at 900℃, 50MPa and argon atmosphere to obtain graphene-copper based composite blocks.

[0042] Step 5) The thickness of the prepared composite bulk material is approximately 250 μm. The conductivity was measured at room temperature using a van der Bauer conductivity measuring device, following the same testing method as in Step 5 of Example 1. The final calculated conductivity of the graphene-copper composite bulk material is 59.85 × 10⁻⁶. 6 The S / m value is 103% IACS, exceeding the international standard for annealed copper. This indicates that the graphene-copper matrix composite material bulk prepared in this embodiment meets the application requirements. Example 5

[0043] This embodiment includes the following steps:

[0044] Step 1) Place a 25μm thick copper foil substrate into a quartz tube furnace and grow graphene by chemical vapor deposition at 1000℃ in a hydrogen and methane atmosphere to obtain a graphene / copper composite foil.

[0045] Step 2) Place the graphene / copper composite foil in a magnetron sputtering coating system and perform sputtering deposition of a nano-copper layer at a power of 300W. The copper layer thickness is 10nm, resulting in a nano-copper layer-graphene / copper foil.

[0046] Step 3) Place the nano-copper layer-graphene / copper foil into a vacuum bonding machine and perform hot-press bonding at 90°C and 5 bar.

[0047] Step 4) Ten bonded nano-copper layers-graphene / copper foils are stacked one by one in a rapid sintering furnace and hot-pressed at 900℃, 50MPa and argon atmosphere to obtain graphene-copper based composite blocks.

[0048] Step 5) The thickness of the prepared composite bulk material is approximately 250 μm. The conductivity was measured at room temperature using a van der Bauer conductivity measuring device, following the same testing method as in Step 5 of Example 1. The final calculated conductivity of the graphene-copper composite bulk material is 63.92 × 10⁻⁶. 6The S / m value is 110% IACS, exceeding the international standard for annealed copper. This indicates that the graphene-copper matrix composite material bulk prepared in this embodiment meets the application requirements. Comparative Example 1

[0049] This comparative example includes the following steps:

[0050] Step 1) Place a 25μm thick copper foil substrate into a quartz tube furnace and grow graphene by chemical vapor deposition at 1000℃ in a hydrogen and methane atmosphere to obtain a graphene / copper composite foil.

[0051] Step 2) Place the graphene / copper composite foil in a magnetron sputtering coating system and perform sputtering deposition of a nano-copper layer at a power of 300W. The copper layer thickness is 10nm, resulting in a nano-copper layer-graphene / copper foil.

[0052] Step 3) Ten nano-copper layers-graphene / copper foils are stacked one by one in a rapid sintering furnace and hot-pressed at 900℃, 50MPa and argon atmosphere to obtain graphene-copper based composite blocks.

[0053] Step 4) The thickness of the prepared composite bulk material was approximately 250 μm. Conductivity testing at room temperature was performed using a van der Bauer conductivity measurement device. This device consisted of a nanovoltmeter, a constant current source, and four probes. During the first measurement, probes 1 and 2 were energized, while probes 3 and 4 were used to measure voltage. During the second measurement, probes 2 and 3 were energized, while probes 1 and 4 were used to measure voltage. The final calculated conductivity of the graphene-copper composite bulk material was 60.88 × 10⁻⁶. 6 S / m, 105% IACS, exceeding the international standard for annealed copper. This indicates that the graphene-copper matrix composite bulk prepared in this comparative example meets the application requirements. Comparative Example 2

[0054] This comparative example includes the following steps:

[0055] Step 1) Place a 25μm thick copper foil substrate into a quartz tube furnace and grow graphene by chemical vapor deposition at 1000℃ in a hydrogen and methane atmosphere to obtain a graphene / copper composite foil.

[0056] Step 2) Place the graphene / copper composite foil into a vacuum bonding machine and perform hot-press bonding at 120°C and 5 bar.

[0057] Step 3) Stack 10 bonded graphene / copper composite foils layer by layer into a rapid sintering furnace and perform hot pressing sintering at 900℃, 50MPa and argon atmosphere to obtain graphene-copper based composite blocks.

[0058] Step 4) The thickness of the prepared composite bulk material was approximately 250 μm. The conductivity was measured at room temperature using a van der Bauer conductivity measuring device, following the same testing method as in Comparative Example 1, Step 4. The final calculated conductivity of the graphene-copper composite bulk material was 59.62 × 10⁻⁶. 6 S / m, 103% IACS, exceeding the international standard for annealed copper. This indicates that the graphene-copper matrix composite bulk prepared in this comparative example meets the application requirements. Comparative Example 3

[0059] This comparative example includes the following steps:

[0060] Step 1) Place a 25μm thick copper foil substrate into a quartz tube furnace. No carbon source is introduced. The other environments are the same as those for graphene chemical vapor deposition to obtain annealed pure copper foil.

[0061] Step 2) Place the annealed pure copper foil into a vacuum bonding machine and perform hot-press bonding at 120°C and 5 bar.

[0062] Step 3) Stack 10 bonded annealed pure copper foils layer by layer into a rapid sintering furnace and perform hot pressing sintering at 900℃, 50MPa and argon atmosphere to obtain pure copper blocks.

[0063] Step 4) The thickness of the prepared bulk material was approximately 250 μm. The conductivity was measured at room temperature using a van der Burg method conductivity measurement device, following the same testing method as in Comparative Example 1, Step 4. The final calculated conductivity of the graphene-copper composite bulk material was 57.48 × 10⁻⁶. 6 S / m, 99% IACS, slightly below the international standard for annealed copper, does not meet the usage requirements. Comparative Example 4

[0064] This comparative example includes the following steps:

[0065] Step 1) Place a 25μm thick copper foil substrate into a quartz tube furnace. No carbon source is introduced. The other environments are the same as those for graphene chemical vapor deposition to obtain annealed pure copper foil.

[0066] Step 2) Place the pure copper foil in the magnetron sputtering coating system and perform sputtering deposition of a nano-copper layer at a power of 300W. The copper layer thickness is 10nm, resulting in a nano-copper layer-pure copper foil.

[0067] Step 3) Place the nano-copper layer-pure copper foil into a vacuum bonding machine and perform hot-press bonding at 120°C and 5 bar.

[0068] Step 4) Stack 10 bonded nano-copper layers-pure copper foils one by one into a rapid sintering furnace and perform hot pressing sintering at 900℃, 50MPa and argon atmosphere to obtain pure copper bulk.

[0069] Step 5) The thickness of the prepared bulk material was approximately 250 μm. The conductivity was measured at room temperature using a van der Bauer conductivity measuring device, following the same testing method as in Step 4 of Comparative Example 1. The final calculated conductivity of the graphene-copper composite bulk material was 58.75 × 10⁻⁶. 6 S / m, 101% IACS, exceeding the international standard for annealed copper. This indicates that the pure copper bulk prepared in this comparative example meets the application requirements.

[0070] Table 1 shows the process parameters and material properties for each of the following embodiments.

[0071] Through specific experiments, a 10 nm thick copper layer was sputtered onto the surface of CVD-grown graphene / copper foil. This was followed by hot-press bonding at 120 °C to obtain a nano-copper layer-graphene / copper foil composite unit. Then, through layer-by-layer stacking and hot-press sintering at 900 °C, a graphene-copper composite material was obtained. The conductivity was tested at room temperature using a van der Bauer conductivity measurement device. This device consists of a constant current source, a nanovoltmeter, and four probes. In the first measurement, probes 1 and 2 were energized, while probes 3 and 4 measured voltage. In the second measurement, probes 2 and 3 were energized, while probes 1 and 4 measured voltage. The final conductivity obtained reached 114% IACS.

[0072] Compared with existing technologies, this invention achieves a breakthrough in ultra-high conductivity by sputtering and depositing a copper layer of nanoscale thickness on the surface of a graphene / copper composite foil, followed by bonding to obtain a nano-copper layer-graphene / copper composite unit, which is then hot-pressed and sintered to prepare a composite bulk. The resulting graphene-copper-based composite material retains a relatively regular layered structure. The introduction of the thinner nano-copper layer improves the surface smoothness of the composite unit, and copper atoms are enriched at the interface to form a high-quality nano-transition layer. The bonding process promotes the bonding between the nano-copper layer and the graphene / copper foil and induces the copper matrix to shift towards an orientation favorable to matching the graphene lattice, solving the original weak copper-carbon bonding problem, achieving stable atomic-level bonding on both sides of the interface, enhancing interfacial contact, effectively improving the interfacial quality in the graphene-copper-based composite material, providing a more efficient path for electron transport, and further improving the conductivity of the graphene-copper-based composite material.

[0073] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for improving the electrical conductivity of graphene-copper composite materials by epitaxial deposition of a nano-interface layer, characterized in that, Graphene was deposited on the surface of copper foil using chemical vapor deposition (CVD) to form a graphene / copper composite foil. On this basis, a copper layer with a thickness of nanometer scale was deposited by magnetron sputtering and hot-pressed to prepare a nano-copper layer-graphene / copper composite unit. Then, several layers of nano-copper layer-graphene / copper composite units were stacked layer by layer and hot-pressed to obtain a graphene-copper based composite material with significantly optimized conductivity.

2. The method for improving the electrical conductivity of graphene-copper composite materials by epitaxial deposition of a nano-interface layer according to claim 1, characterized in that, The chemical vapor deposition technology refers to the process of uniformly depositing graphene on the surface of copper foil in a hydrogen atmosphere at 800-1000℃ by introducing methane as a gaseous carbon source in a quartz tube furnace.

3. The method for improving the electrical conductivity of graphene-copper composite materials by epitaxial deposition of a nano-interface layer according to claim 1, characterized in that, In the graphene / copper composite foil, the copper substrate is a foil material with a thickness of 10-100 μm, a purity of ≥99%, and is highly crystalline; The graphene coverage is ≥95%.

4. The method for improving the electrical conductivity of graphene-copper composite materials by epitaxial deposition of a nano-interface layer according to claim 1, characterized in that, The magnetron sputtering step refers to: in a magnetron sputtering coating system, using a copper target with a purity ≥99.99% to perform sputtering deposition of a nano-copper layer; the sputtering power is 100-300W, and the thickness of the nano-copper layer is 5-50nm.

5. The method for improving the electrical conductivity of graphene-copper composite materials by epitaxial deposition of a nano-interface layer according to claim 1, characterized in that, The hot-press bonding refers to hot-press bonding performed in a vacuum bonding machine at a pressure of 5-10 bar and a temperature of 80-200°C for a bonding time of 30-90 minutes. Its function is to promote the effective bonding of sputtered nano-copper layers with graphene / copper composite foils and to induce orientation changes in the copper layer and the substrate.

6. The method for improving the electrical conductivity of graphene-copper composite materials by epitaxial deposition of a nano-interface layer according to claim 1, characterized in that, In the aforementioned nano-copper layer-graphene / copper composite unit, the surface-sputtered nano-copper layer and copper substrate grains are single-crystal and are both (111) oriented.

7. The method for improving the electrical conductivity of graphene-copper composite materials by epitaxial deposition of a nano-interface layer according to claim 1, characterized in that, The hot pressing sintering refers to hot pressing sintering in a rapid sintering furnace under argon protection using a graphite mold with a diameter of 30-40mm, at a sintering temperature of 700-1000℃, a pressure of 10-200MPa, and a holding time of 10-30min.

8. A highly conductive graphene-copper-based composite material prepared by any one of the methods described in claims 1-7, characterized in that, It is composed of several layers of nano-copper layer-graphene / copper composite units stacked one by one. Each nano-copper layer-graphene / copper composite unit is composed of copper foil with graphene deposited on the surface and nano-copper layer bonded together.

9. An application of the highly conductive graphene-copper-based composite material according to claim 8, characterized in that, Used to prepare conductors with an electrical conductivity of 114% IACS.

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