Copper-aluminum composite conductive graphene material and preparation method thereof

Abstract

The invention discloses a copper-aluminum composite conductive graphene material and a preparation method thereof. The copper-aluminum composite conductive graphene material comprises a conductor structure and a laminated structure, the conductor junction comprises graphene copper composite layers located on the upper surface and the lower surface of the laminated structure. The laminated structure comprises a multi-layer composite structure formed by alternately laminating copper foil layers and aluminum sheet layers, and the outermost layers, in direct contact with the upper graphene copper composite layer and the lower graphene copper composite layer, in the laminated structure are the aluminum sheet layers; a transition layer in which copper and aluminum elements are mutually diffused is arranged between the copper foil layer and the aluminum sheet layer; the copper element in the graphene copper composite layer and the aluminum element in the aluminum sheet layer are subjected to bidirectional diffusion, and a copper-aluminum alloy transition layer with continuous component gradient is formed in the interface area of the graphene copper composite layer and the aluminum sheet layer. A copper foil and aluminum sheet alternate laminated structure is compounded with surface graphene, so that the substitution contradiction that a traditional copper conductor is scarce and expensive, and the conductivity of pure aluminum is insufficient is solved, and meanwhile the problems that when graphene and aluminum are compounded, the interface compatibility is poor, and an intermediate phase is generated are solved.

Description

Technical Field

[0001] This invention relates to the field of composite conductive materials technology, specifically to a copper-aluminum composite conductive graphene material and its preparation method. Background Technology

[0002] As core basic materials for power transmission, signal transmission, material conversion and device manufacturing, cables and wires are facing increasing demands from the market for comprehensive performance such as conductivity, tensile strength, elastic modulus and thermal conductivity due to the rapid development of industrial modernization, the popularization of 5G communication and the upgrading of the semiconductor industry. At the same time, higher demands are being placed on material cost control.

[0003] Currently, copper is widely used as the core material for conductors in the industry. Its core advantage lies in its high conductivity of 57-59 MS / M, which can meet the power and signal transmission needs in most scenarios.

[0004] However, copper materials have two major limitations: First, copper is a scarce mineral resource with a high market price, which leads to significant cost pressure on conductor materials and end products; second, with the increasing complexity of application scenarios, it is difficult to meet the comprehensive requirements of high tensile strength, high elastic modulus and high thermal conductivity by relying solely on the inherent properties of copper. Finding alternative materials that meet the performance requirements and are more cost-effective has become an urgent need for the industry.

[0005] Pure aluminum, with its low density, low melting point, and high tensile strength, as well as its abundant reserves and low market price, has been widely used in aerospace, rail transportation, electronic devices and other fields, and has a natural advantage as a substitute for copper conductors.

[0006] However, in the field of wires and cables, the conductivity of pure aluminum is significantly lower than that of pure copper, and this core shortcoming limits its application range as a direct replacement for copper conductors.

[0007] Therefore, preparing aluminum-based alloy materials with both high strength and high conductivity through composite modification technology has become a key direction for realizing the replacement of pure copper conductors with pure aluminum.

[0008] Graphene, as a highly promising reinforcing phase material, possesses excellent properties such as ultra-high carrier mobility, high tensile strength, high elastic modulus, and high thermal conductivity. It is recognized as the most promising aluminum-based composite material reinforcement in the field of electrical conductivity, and its combination with aluminum is expected to overcome the bottleneck of insufficient conductivity of pure aluminum.

[0009] Currently, the most common method for preparing graphene-aluminum composite materials in the industry is powder metallurgy. Its core process involves mixing graphene and pure aluminum powder through mechanical ball milling, followed by die casting to obtain the composite material.

[0010] This method has several technical drawbacks, including: 1) Damage to the integrity of graphene structure: The mechanical ball milling process damages the integrity and uniformity of graphene particles, making it difficult to prepare high-quality graphene films with large size and thin thickness. It also significantly increases the probability of graphene defects, preventing the full utilization of its excellent electrical and mechanical properties; 2) Prominent graphene agglomeration problem: Due to the poor interfacial compatibility between graphene and aluminum, graphene is prone to agglomeration in the aluminum matrix during the composite process, making it impossible to achieve uniform dispersion and thus affecting the performance stability of the composite material; 3) Formation of low-conductivity intermediate phase: Pure aluminum has a high carbon solubility and easily reacts with carbon elements in graphene during the composite process to form an AlC3 intermediate phase. This intermediate phase has extremely poor conductivity, which significantly reduces the overall conductivity of the composite material, restricting the performance improvement and application of graphene-aluminum composite materials.

[0011] The existing technology lacks a technical solution that can prepare high-quality graphene at low cost and solve the problems of poor interfacial compatibility and intermediate phase formation when graphene is combined with aluminum. As a result, graphene-aluminum composite materials are difficult to balance high conductivity and low cost, and cannot effectively replace copper conductors to meet the needs of industrial development. Summary of the Invention

[0012] To overcome the shortcomings of existing technologies, the purpose of this application is to provide a copper-aluminum composite conductive graphene material. It adopts an alternating stacked structure of copper foil and aluminum sheet with surface graphene to solve the contradiction of the scarcity and high cost of traditional copper conductors and the insufficient conductivity of pure aluminum. At the same time, it utilizes the surface skin effect to concentrate the alternating current charge on the surface super copper to improve conductivity, and solves the problems of poor interfacial compatibility and intermediate phase formation when graphene is composited with aluminum.

[0013] To solve the above problems, the technical solution adopted in this application is as follows: This application provides a copper-aluminum composite conductive graphene material, including a conductor structure and a stacked structure. The conductor structure includes graphene-copper composite layers located on the upper and lower surfaces of the stacked structure. The stacked structure includes a multilayer composite structure with alternating copper foil layers and aluminum sheet layers. The outermost layer in the stacked structure that is in direct contact with the upper and lower graphene-copper composite layers is an aluminum sheet layer. There is a transition layer between the copper foil layer and the aluminum sheet layer where copper and aluminum elements diffuse into each other. The copper element in the graphene-copper composite layer diffuses bidirectionally with the aluminum element in the aluminum sheet layer, forming a copper-aluminum alloy transition layer with a continuous compositional gradient at the interface region between the two.

[0014] As a further preferred embodiment, in the copper-aluminum composite conductive graphene material described in this application, the graphene-copper composite layer located on the upper and lower surfaces of the stacked structure has the same thickness; the thickness of the graphene-copper composite layer is 10-30 μm; the graphene in the graphene-copper composite layer is a single-layer structure, uniformly covering the surface of the copper layer.

[0015] As a further preferred embodiment, in the stacked structure described in this application, the thickness of a single aluminum sheet layer is 100-150 μm, the thickness of a single copper foil layer is 5-15 μm, and the total thickness of the stacked structure is 1-1.5 mm.

[0016] As a further preferred embodiment, the copper-aluminum composite conductive graphene material described in this application has an internal porosity of ≤1% and a pore size of ≤50μm, with no through pores.

[0017] As a further preferred embodiment, in the copper-aluminum composite conductive graphene material described in this application, the mass fraction of the low-conductivity mesophase AlC3 is ≤0.5%.

[0018] This application also provides a method for preparing a copper-aluminum composite conductive graphene material. The method utilizes an alternating layering structure of upper and lower surface graphene copper sheets and intermediate copper foil and thick aluminum sheets. This is combined with a copper-aluminum alloy formed during vacuum hot-pressing sintering to achieve interlayer metallurgical bonding. This solves the problems of easily damaged graphene structure, poor compatibility between graphene and aluminum interface, and easy agglomeration in existing preparation processes. It also addresses the contradiction between the insufficient conductivity of pure aluminum and the scarcity and high cost of copper conductors as alternatives. The preparation method includes the following steps: Copper foil pretreatment: Surface cleaning and activation treatment of copper foil; Graphene growth: The pretreated copper foil is placed in a quartz tube reaction device, and a single layer of graphene is grown on the surface of the copper foil using chemical vapor deposition with carbon source precursor as carbon donor and argon as protective gas at a set temperature to obtain a graphene copper composite layer. Construction of the laminated structure: The laminated blank is constructed with graphene copper composite layers on the top and bottom surfaces and copper foil and aluminum sheets arranged alternately in the middle layer. Vacuum hot pressing sintering: The above-mentioned laminated blanks are placed in a vacuum hot pressing furnace for sintering to obtain copper-aluminum composite conductive graphene material.

[0019] As a further preferred embodiment, the copper foil pretreatment step described in this application is as follows: ultrasonic cleaning with anhydrous ethanol for 10-15 minutes to remove oil stains, and then immersing the copper foil in a surface treatment solution for activation. The surface treatment solution is selected from any one of hydrogen peroxide, dilute sulfuric acid, and dilute hydrochloric acid, and the activation time is 1-3 minutes.

[0020] As a further preferred embodiment, in the graphene growth step described in this application, the process parameters of the chemical vapor deposition method are: temperature 980-1000℃, carbon source precursor flow rate 50-60 sccm, argon flow rate 800-1000 sccm, and deposition time 30-60 minutes.

[0021] As a further preferred embodiment, in the vacuum hot pressing sintering step described in this application, the sintering temperature is 500–550°C and the vacuum degree is 10. -1 ~10 -3 Pa, sintering time 1-2 hours, sintering pressure 30-50 MPa, heating rate 5-10℃ / min, and cooling to room temperature with the furnace after holding.

[0022] As a further preferred embodiment, the preparation method described in this application also includes a post-processing step: the sintered composite material is surface-polished to remove the oxide layer, then cleaned with anhydrous ethanol and dried at a temperature of 60-80°C for 30-60 minutes.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the copper-aluminum composite conductive graphene material described in this application, a transition layer in which copper and aluminum elements diffuse into each other is formed between the copper foil layer and the aluminum sheet layer, and the graphene copper composite layer and the aluminum sheet layer form a copper-aluminum alloy transition layer with a continuous composition gradient through bidirectional diffusion, thereby realizing metallurgical bonding between the layers. This completely solves the problems of poor compatibility between graphene and aluminum interface and loose interlayer bonding that are easy to peel off in traditional composite methods, and greatly improves the overall structural integrity and long-term reliability of the material.

[0024] 2. In the copper-aluminum composite conductive graphene material described in this application, the copper-aluminum alloy transition layer with a continuous compositional gradient can effectively suppress the formation of the low-conductivity intermediate phase AlC3, avoiding its damage to conductivity. At the same time, the graphene-copper composite layers on the upper and lower surfaces, through the surface skin effect, concentrate the charge in the highly conductive surface region during alternating current transmission. Combined with the ultra-high carrier mobility of graphene itself, the conductivity of the material reaches a level close to or even partially exceeds that of pure copper, making up for the deficiency of conductivity of pure aluminum.

[0025] 3. In the copper-aluminum composite conductive graphene material described in this application, the middle layer adopts an alternating stacked structure of copper foil and aluminum sheet. Under the premise of ensuring conductivity and mechanical properties, the overall weight and production cost of the material are greatly reduced by reasonably allocating abundant and low-density aluminum material, thus solving the contradiction of replacing the scarcity and high cost of traditional copper conductors and the insufficient conductivity of pure aluminum.

[0026] 4. The copper-aluminum composite conductive graphene material described in this application has the combined advantages of high conductivity, high mechanical strength, and lightweight. It can be widely adapted to the stringent requirements of conductive materials in multiple fields such as industrial power, 5G communication, semiconductors, and rail transportation. It can replace traditional copper conductors or existing composite conductive materials with insufficient performance, and has broad application prospects.

[0027] 5. The preparation method described in this application employs chemical vapor deposition, combined with copper foil pretreatment and precisely controlled temperature and gas parameters, which can stably grow large-size, defect-free monolayer graphene. This avoids the damage to the graphene structure caused by traditional powder metallurgy mechanical ball milling, ensuring that the excellent properties of graphene, such as ultra-high carrier mobility, are fully utilized. Furthermore, the preparation process parameters are easy to control and highly repeatable, making it suitable for large-scale production.

[0028] The gradient composition transition layer formed during sintering can alleviate the interfacial stress caused by the difference in thermal expansion coefficients of copper and aluminum through process control. Combined with the high tensile strength of graphene and the complementary properties of copper and aluminum materials, the material can simultaneously achieve high tensile strength and good structural toughness during the preparation process, avoiding the mechanical shortcomings of a single material, eliminating the need for additional strengthening processes, and simplifying the production process.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the structure of the copper-aluminum composite conductive graphene material described in the embodiments of this application.

[0032] Figure 2 The image shows the graphene-copper composite layer described in the application embodiment.

[0033] Figure 3 This is a SEM image of the graphene-copper composite layer described in the embodiments of this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0035] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0036] The term "comprising" and other equivalent descriptive terms used in the specification and claims of this application are intended to cover a non-exclusive inclusion, which includes both the contents explicitly described in the specification and claims and steps or units that are not described in the specification and claims but are inherent in the product, method or structure.

[0037] like Figures 1-3 As shown in the embodiments of this application, a copper-aluminum composite conductive graphene material is provided, including a conductor structure and a stacked structure. The conductor junction includes a graphene-copper composite layer located on the upper and lower surfaces of the stacked structure. Graphene itself has an ultra-high carrier mobility. After being combined with a highly conductive copper substrate, it can form a highly conductive surface layer. By utilizing the surface skin effect during alternating current transmission, the charge is concentrated on the surface layer for transmission, which greatly improves the overall conductivity of the material and makes up for the lack of conductivity of pure aluminum. Furthermore, the high tensile strength of graphene combined with the mechanical stability of copper can provide excellent surface protection and structural support for the material, improve the overall tensile strength, wear resistance, corrosion resistance, and extend the service life of the material.

[0038] The stacked structure comprises a multi-layered composite structure with alternating layers of copper foil and aluminum sheets. The outermost layer in the stacked structure that is in direct contact with the upper and lower graphene-copper composite layers is an aluminum sheet. By alternating the arrangement of copper and aluminum materials, complementary performance and a balance between cost and weight are achieved. The copper foil layer can help construct a continuous conductive path, alleviating the problem of insufficient conductivity of the aluminum sheet layer. Due to its low density, abundant reserves, and low cost, the aluminum sheet layer can significantly reduce the overall weight and production cost of the material, solving the pain point of the scarcity and high cost of traditional copper conductors. The multi-layered alternating structure can also disperse stress, improve the overall toughness of the material, and avoid the performance limitations of a single material.

[0039] There is a transition layer between the copper foil layer and the aluminum sheet, where copper and aluminum elements diffuse into each other. This transition layer transforms the physical bonding between the copper foil layer and the aluminum sheet layer into a metallurgical bond, significantly improving the interlayer bonding strength and completely solving the defects of loose interlayers and easy peeling in traditional composite materials.

[0040] The copper element in the graphene-copper composite layer diffuses bidirectionally with the aluminum element in the aluminum sheet layer, forming a copper-aluminum alloy transition layer with a continuous compositional gradient at the interface. This continuous compositional gradient design avoids abrupt changes in interface composition, further alleviating stress concentration and improving the strength and durability of the interlayer bonding. The aluminum alloy transition layer effectively blocks the direct contact reaction between carbon and aluminum elements in graphene, fundamentally inhibiting the formation of the low-conductivity intermediate phase AlC3 and ensuring that the material's conductivity is not compromised. The copper-aluminum alloy itself possesses certain conductivity and mechanical properties, and its gradient structure enables seamless connection of the conductive pathways between the surface graphene-copper composite layer and the intermediate stacked structure, ensuring smooth charge transfer and further enhancing the material's conductivity continuity and stability.

[0041] Furthermore, in some embodiments of this application, the copper-aluminum composite conductive graphene material has the same thickness of graphene copper composite layer on the upper and lower surfaces of the stacked structure. As the core area for AC transmission, the consistent thickness of the upper and lower surfaces allows for symmetrical distribution of charge in the concentrated areas of the upper and lower surfaces, avoiding uneven conductive paths and high local resistance caused by excessively thick or thin single-sided surfaces, thus ensuring stable and uniform overall conductivity of the material. The symmetrical thickness design can offset the asymmetrical stress caused by temperature changes and mechanical forces during the preparation and use of the material, reducing the risk of material bending, deformation, or interlayer delamination, and improving structural integrity and long-term reliability. The symmetrical structure also facilitates dimensional calibration and precision control during stacking, reducing the product defect rate caused by layer thickness deviations during production and improving the consistency of mass production.

[0042] Preferably, in this embodiment, the thickness of the graphene-copper composite layer is 10–30 μm. Within this thickness range, on the one hand, it ensures the formation of a complete and continuous highly conductive pathway on the surface, fully leveraging the synergistic conductivity of graphene and copper, meeting the spatial requirements for charge transport under the skin effect, and avoiding insufficient conductive area and increased resistance due to excessive thickness. On the other hand, it avoids excessive use of copper material, controlling the overall cost and weight of the material while ensuring conductivity, thus meeting the core requirements of lightweight and low cost. Therefore, this thickness range will not cause a significant increase in the overall density of the material due to an excessively thick surface layer, nor will it prevent the intermediate layers from being unable to provide stable structural support due to an excessively thin surface layer. At the same time, it can alleviate the interfacial stress caused by the difference in thermal expansion coefficients of copper and aluminum, and improve the overall mechanical balance of the material.

[0043] In the graphene-copper composite layer, the graphene is a single-layer structure, uniformly covering the surface of the copper layer. The single-layer graphene lacks the interlayer defects and resistance caused by multilayer stacking, fully releasing its ultra-high carrier mobility and avoiding the conductivity degradation caused by interlayer interactions in multilayer graphene, ensuring optimal surface conductivity. The uniform graphene coverage of the copper layer forms a conductive reinforcement layer without gaps or breaks, preventing direct exposure of the copper layer due to graphene deficiency in localized areas, which could lead to uneven resistance and localized heating, ensuring consistent surface conductivity. Furthermore, the uniformly covered single-layer graphene forms a tight and uniform interface with the copper layer, avoiding interface defects caused by graphene agglomeration or uneven coverage. It also provides a uniform interface foundation for the subsequent formation of a copper-aluminum alloy transition layer with the aluminum sheet, further ensuring the strength of the interlayer bonding and seamless connection of the conductive pathway.

[0044] Furthermore, in the laminated structure described in this application embodiment, the thickness of a single aluminum sheet layer is 100-150 μm. This thickness range fully leverages the low density of aluminum, significantly reducing the overall weight of the material through the proportion of the intermediate aluminum sheet, thus meeting the core requirements of lightweighting. It also ensures that the aluminum sheet layer has sufficient structural strength, preventing excessive deformation or damage during laminated construction, sintering, and subsequent use, providing a stable support foundation for the copper foil layer. The lower limit thickness of 100 μm ensures sufficient aluminum reserves, allowing for sufficient diffusion reaction with adjacent copper foil layers to form a continuous and complete copper-aluminum alloy transition layer, avoiding insufficient diffusion and transition layer breakage due to an excessively thin aluminum layer. The upper limit thickness of 150 μm prevents excessively thick aluminum layers from causing excessively long diffusion distances for copper and aluminum elements, ensuring uniform diffusion during sintering, while also preventing the overall weight of the material from becoming uncontrollable, thus balancing lightweighting and interlayer bonding quality.

[0045] In some embodiments of this application, the thickness of the single copper foil layer is 5 to 15 μm. This thickness range can provide sufficient copper elements to diffuse with the adjacent aluminum foil layer, meeting the composition requirements for forming a stable copper-aluminum alloy transition layer and avoiding insufficient copper elements and weak bonding force in the transition layer due to the copper foil being too thin. On the other hand, it can avoid the waste of copper materials caused by the copper foil being too thick (copper is more expensive than aluminum), and at the same time prevent the amplification of interface stress caused by the difference in thermal expansion coefficients of copper and aluminum due to the copper foil layer being too thick, thus taking into account both cost control and structural stability.

[0046] The thin copper foil layer can act as a conductive bridge, connecting the adjacent aluminum sheet layer and the surface graphene copper composite layer, making up for the insufficient conductivity of the aluminum sheet layer, so that the intermediate stack forms a segmented conductive structure of copper, aluminum, copper, and so on. Combined with the skin effect of the surface layer, it improves the overall conductivity continuity of the material. At the same time, the thin copper foil layer is easier to bond tightly with the aluminum sheet layer, reducing the interlayer gap and reducing the impact of porosity on conductivity.

[0047] In this application, the total thickness of the laminated structure is 1 to 1.5 mm. This thickness range will not result in insufficient mechanical strength due to excessive thickness, making it unable to withstand external forces such as tension and bending during installation and use; nor will it result in increased weight and decreased installation adaptability due to excessive thickness, while avoiding the increased difficulty of sintering process caused by excessive thickness.

[0048] A lower thickness of 1mm can accommodate 2 to 4 sets of alternating copper foil and aluminum sheet layers, so that the intermediate composite layer forms multiple sets of continuous copper-aluminum alloy transition layers. Through multi-layer synergy, the overall structure’s resistance to peeling and deformation is improved. An upper thickness of 1.5mm can avoid the difficulty of interlayer alignment caused by too many layers, reduce problems such as uneven conductivity and stress concentration caused by layer deviation, and ensure that the performance of each layer works synergistically.

[0049] Pores are insulating defects in conductive materials. In the embodiments of this application, the internal porosity of the copper-aluminum composite conductive graphene material is ≤1%. Controlling the porosity to within 1% can minimize the obstruction of charge transport by internal voids, avoid the breakage of conductive pathways and sudden increase in local resistance due to void aggregation, ensure the overall conductivity of the material is stable and uniform, and fully utilize the synergistic conductive effect of the graphene copper composite layer and the copper-aluminum alloy transition layer. Low porosity means a denser internal structure, reducing mechanical weaknesses caused by voids, significantly improving the tensile strength, fatigue resistance, and deformation resistance of the material, and preventing cracking or damage caused by stress concentration at voids during installation and use. Controlling the appropriate porosity can ensure that copper and aluminum elements diffuse fully during sintering, forming a continuous and complete copper-aluminum alloy transition layer, further strengthening the interlayer metallurgical bonding strength and preventing interlayer delamination. In addition, low porosity can reduce the channels for external moisture and corrosive media to penetrate into the material, reduce the risk of copper and aluminum oxidation and corrosion, and extend the service life of the material in complex environments.

[0050] Furthermore, in this embodiment, the pore size is controlled within the range of ≤50μm, which can prevent pores from becoming sources of local failure. Small-sized pores have a limited blocking effect on conductive paths, which will not cause a significant increase in local resistance, nor will they cause stress concentration in adjacent areas due to excessively large pores, thus ensuring the uniformity of material properties. At the same time, the stress concentration effect of small pores is extremely weak, which can effectively prevent the material from cracking along the pores under mechanical forces such as tension and bending, thus ensuring the structural toughness and reliability of the material. Moreover, it will not disrupt the diffusion path of copper and aluminum elements, nor will it cause the transition layer between adjacent layers to break, thus maintaining the structural integrity of the copper foil, aluminum sheet, and transition layer, and ensuring the synergistic effect of conductivity and mechanical properties.

[0051] The copper-aluminum composite conductive graphene material described in this application has no penetrating pores. On the one hand, this ensures seamless connection of conductive pathways between the surface and intermediate layers, guaranteeing the stability and reliability of the overall conductivity of the material. On the other hand, it avoids the problems of penetrating pores disrupting the interlayer continuity structure, allowing media to easily penetrate into the interlayer along the pores, and accelerating interface separation. In addition, the penetrating pores can form a dense protective barrier, preventing external moisture, dust, corrosive media, etc., from penetrating into the interior of the material, avoiding oxidation of the copper-aluminum substrate and failure of the transition layer, and significantly improving the corrosion resistance and long-term stability of the material.

[0052] Direct contact between carbon and aluminum produces the intermediate phase AlC3, which acts as a harmful impurity phase in copper-aluminum composite conductive graphene materials. AlC3 itself is a typical low-conductivity phase. Once it is generated and accumulates inside the material, it becomes an insulating barrier to charge transport, blocking the continuous conductive path formed by the copper matrix, graphene, and copper-aluminum alloy transition layer. This leads to a surge in the overall resistance and a significant decrease in conductivity, failing to meet the core performance requirements for replacing pure copper conductors. Furthermore, it tends to accumulate at the copper-aluminum interface and in the contact area between graphene and aluminum, forming conductive dead zones. This results in uneven and distorted conductive pathways inside the material, causing a sharp increase in local current density. AlC3 is also a typical brittle ceramic phase with no plastic deformation capability. Its crystal structure is hard and easily broken.

[0053] In addition, AlC3 weakens interlaminar bonding strength, causes interlaminar delamination, and reduces the tensile strength and fatigue resistance of the material.

[0054] Therefore, in the embodiments of this application, the mass fraction of the low-conductivity intermediate phase AlC3 in the copper-aluminum composite conductive graphene material is ≤0.5%, which can minimize the damage to the conductive pathways caused by the low-conductivity phase, ensuring that the ultra-high carrier mobility of graphene, the high conductivity of the copper matrix, and the conductivity continuity of the copper-aluminum alloy transition layer are fully utilized. The low content control can avoid AlC3 aggregation, ensure uniform distribution of conductive pathways, reduce local resistance differences, prevent abnormal heating, and ensure the stability and safety of the material during long-term energized use. At the same time, it can also maintain the gradient composition and dense structure of the copper-aluminum alloy transition layer, avoid the mechanical property degradation caused by the brittle phase, and ensure that the material has both high tensile strength and good toughness.

[0055] This application also provides a method for preparing a copper-aluminum composite conductive graphene material. The method utilizes an alternating layering structure of upper and lower surface graphene copper sheets and intermediate copper foil and thick aluminum sheets. This is combined with a copper-aluminum alloy formed during vacuum hot-pressing sintering to achieve interlayer metallurgical bonding. This solves the problems of easily damaged graphene structure, poor compatibility between graphene and aluminum interface, and easy agglomeration in existing preparation processes. It also addresses the contradiction between the insufficient conductivity of pure aluminum and the scarcity and high cost of copper conductors as alternatives. The preparation method includes the following steps: Copper foil pretreatment: Surface cleaning and activation treatment of copper foil; Graphene growth: The pretreated copper foil is placed in a quartz tube reaction device, and a single layer of graphene is grown on the surface of the copper foil using chemical vapor deposition with carbon source precursor as carbon donor and argon as protective gas at a set temperature to obtain a graphene copper composite layer. Construction of the laminated structure: The laminated blank is constructed with graphene copper composite layers on the top and bottom surfaces and copper foil and aluminum sheets arranged alternately in the middle layer. Vacuum hot pressing sintering: The laminated blanks obtained in the above steps are placed in a vacuum hot pressing furnace for sintering to obtain copper-aluminum composite conductive graphene material.

[0056] The copper foil pretreatment steps described in this application embodiment are as follows: using anhydrous ethanol for ultrasonic cleaning for 10-15 minutes to dissolve rolling oil, dust and other organic / inorganic contaminants on the surface of the copper foil, avoiding the introduction of additional impurities to contaminate the copper foil surface, ensuring the flatness and purity of the copper foil surface, and providing a clean substrate environment for subsequent graphene growth.

[0057] After cleaning with anhydrous ethanol, a very thin original oxide film may still remain on the surface of the copper foil. The ultrasonically cleaned copper foil is then immersed in a surface treatment solution for activation. The surface treatment solution is selected from hydrogen peroxide, dilute sulfuric acid, and dilute hydrochloric acid. The activation time is 1 to 3 minutes. Activation with the surface treatment solution exposes fresh copper atom surfaces and enhances the surface activity of the copper foil. After activation, a micro-rough structure can be formed on the surface of the copper foil, increasing the contact area between graphene and copper foil, strengthening the interfacial bonding force between the two, and preventing graphene from falling off during subsequent sintering or use. At the same time, the activated copper foil surface can reduce the energy barrier for graphene growth, promote the uniform nucleation and continuous growth of monolayer graphene, and avoid the multilayer stacking or incomplete coverage of graphene due to insufficient surface activity.

[0058] To achieve stable growth of high-quality monolayer graphene, this application precisely controls the core process parameters of chemical vapor deposition (CVD). Preferably, the temperature of CVD is controlled between 980 and 1000°C. This temperature range provides sufficient energy to the carbon source precursor (such as methane), enabling it to rapidly decompose into active carbon atoms. This avoids incomplete carbon source decomposition due to excessively low temperatures, which could result in amorphous carbon residues or insufficient graphene nucleation. At this temperature, the copper foil approaches its melting point, intensifying the thermal motion of surface atoms and forming an atomically flat step structure. This provides uniform nucleation sites for the epitaxial growth of graphene, ensuring a tight interfacial bond between the graphene and the copper foil substrate. Furthermore, copper has extremely low solubility for carbon. Within this temperature range, the decomposed active carbon atoms can only be adsorbed, migrated, and form monolayer graphene on the copper foil surface. This avoids excessive carbon atom aggregation leading to multilayer stacked structures due to excessively high temperatures, or discontinuous graphene growth due to excessively low temperatures.

[0059] In chemical vapor deposition, controlling the carbon source injection rate balances the carbon source supply concentration and the graphene growth rate, avoiding performance defects caused by insufficient or excessive carbon source. Preferably, the carbon source precursor injection rate is 50-60 sccm. Within this range, it can ensure a sufficient supply of active carbon atoms to meet the needs of graphene nucleation and continuous growth, avoiding isolated defects or incomplete coverage of graphene due to insufficient carbon source. At the same time, it can avoid the aggregation of active carbon atoms that do not participate in growth due to excessive carbon source, forming amorphous carbon or multilayer graphene.

[0060] Argon, as an inert gas, can quickly replace the air inside the quartz tube, preventing the copper foil from oxidizing at high temperatures to form CuO and Cu2O oxide films, while also preventing the graphene from being oxidized and destroyed, providing an oxygen-free protective atmosphere for the growth process. By controlling the amount of argon introduced, a stable inert growth environment can be constructed, ensuring uniform diffusion of the carbon source and consistency in graphene growth. In the embodiments of this application, the argon introduction rate is 800-1000 sccm. Within this range, argon can form a stable airflow field, driving the carbon source precursor to diffuse uniformly inside the quartz tube, ensuring a consistent carbon source concentration in all areas of the copper foil surface, and avoiding differences in graphene thickness or uneven coverage due to uneven carbon source distribution. It can also moderately dilute the carbon source concentration, preventing excessive local carbon source concentration from forming impurities, while the airflow carries away reaction byproducts, maintaining the stability of the reaction system and improving the reproducibility of graphene growth.

[0061] Deposition time is a crucial factor in ensuring complete graphene coverage of the copper foil surface while avoiding structural defects caused by overgrowth. In the embodiments of this application, the deposition time is controlled to be 30-60 minutes. This not only ensures that graphene gradually expands from the nucleation sites and eventually uniformly covers the entire copper foil surface, preventing blank areas from appearing due to insufficient time, which would affect the conductivity continuity of subsequent composite layers, but also prevents graphene edge curling, interlayer stacking, or defects caused by continuous adsorption of active carbon atoms.

[0062] In the embodiments of this application, the settings of vapor deposition temperature, carbon source precursor injection rate, and deposition time work synergistically. A suitable temperature can reduce defects such as vacancies and dislocations during graphene growth, maintain the complete lattice structure of monolayer graphene, and fully utilize its ultra-high carrier mobility. The injection rate and temperature work together to control the graphene growth rate within a reasonable range, ensuring graphene quality while avoiding slow growth that leads to low production efficiency, thus meeting the needs of large-scale production. High carbon source decomposition efficiency at high temperatures and a moderate carbon source injection rate ensure sufficient nucleation while avoiding impurity generation.

[0063] In the vacuum hot pressing sintering step described in this application embodiment, the sintering temperature can balance the diffusion efficiency of copper and aluminum elements with structural stability, suppress the formation of harmful phases, and ensure the continuity and controllability of the transition layer. In this embodiment of the application, the sintering temperature is 500-550℃, which is close to the recrystallization temperature of aluminum and much lower than the melting point of aluminum. This allows copper and aluminum atoms to obtain sufficient thermal energy to achieve bidirectional diffusion across layers, forming a copper-aluminum alloy transition layer with a continuous compositional gradient. This avoids insufficient diffusion, transition layer breakage, or weak bonding due to excessively low temperatures. At the same time, it can prevent the aluminum sheet layer from melting and flowing, maintain the integrity of the alternating stacked structure of graphene copper composite layer, copper foil, and aluminum sheet, and avoid defects such as interlayer misalignment and uneven thickness caused by aluminum melting.

[0064] In addition, this sintering temperature allows the copper and aluminum matrix to undergo slight plastic deformation, and the pressure can effectively expel residual gas between layers, promote pore closure, and ensure that the internal porosity of the material is ≤1%.

[0065] In this application, the graphene growth substrate can be replaced with metals such as nickel, molybdenum, and cobalt.

[0066] Vacuum degree is a key factor in creating an oxygen-free and impurity-free sintering environment, ensuring the quality of interlayer bonding and material density; in this embodiment, the vacuum degree is 10. -1 ~10 -3 Pa can quickly replace the air inside the laminated billet and the furnace, and remove volatile substances generated during sintering, avoiding the formation of pores by residual gas, ensuring that the pore size is ≤50μm and there are no penetrating pores; at the same time, it can effectively isolate oxygen, avoid the formation of oxide film, and ensure the continuity of metallurgical bonding between layers.

[0067] In this application, a suitable sintering time can ensure sufficient diffusion of the multilayer stack to form a uniform and continuous transition layer, while avoiding performance degradation caused by over-sintering. In the embodiments of this application, the sintering time is 1 to 2 hours, which is sufficient time for copper and aluminum atoms to diffuse from the interface into the matrix to form a copper-aluminum alloy transition layer with uniform thickness and continuous composition. This avoids insufficient diffusion in some areas due to too short a time, resulting in weak interlayer bonding or broken conductive pathways. It can also avoid grain growth caused by too long a time, which would reduce the mechanical strength of the material.

[0068] Appropriate sintering pressure eliminates interlayer gaps, promotes tight interfacial contact, accelerates diffusion and pore closure, and strengthens interlayer bonding. In this embodiment, the sintering pressure is 30-50 MPa. Within this pressure range, the laminates can be effectively compacted, gaps eliminated, and the interfaces of the copper foil, aluminum sheet, and graphene copper composite layer can be tightly contacted, providing a physical basis for atomic diffusion and avoiding diffusion obstruction due to gaps. At the same time, by controlling the sintering pressure at 30-50 MPa and coordinating with temperature, the porosity can be controlled to ≤1%, with no penetrating pores, improving the material's structural density and mechanical strength, and avoiding structural damage.

[0069] In the preparation method of this application, controlling the heating rate can alleviate thermal stress concentration and ensure the integrity of the laminated structure during the heating process. The heating rate is controlled at 5-10℃ / min, which allows the temperature of each layer to rise synchronously, release thermal stress gradually, and achieve the purpose of balancing the temperature gradient. Slow heating allows residual gas between the layers to be gradually discharged, avoiding pore bursting or the formation of through pores caused by rapid gas expansion. At the same time, it can prevent uneven softening and deformation of aluminum sheets in local areas due to instantaneous high temperature, and ensure the parallelism and dimensional accuracy of the laminated structure.

[0070] In the embodiments of this application, the sintered material is cooled to room temperature in the furnace after the heat preservation is completed, which can further release internal stress, maintain the stability of the transition layer and the stacked structure, and avoid defects during the cooling process.

[0071] As a further preferred embodiment, the preparation method described in this application also includes a post-processing step: the sintered composite material is surface-polished to remove the oxide layer. The polishing can make the surface roughness Ra≤0.8μm, so as to avoid the impact of uneven surface on subsequent installation and reduce the weakening of mechanical properties by surface defects; then it is cleaned with anhydrous ethanol and dried. The cleaning process quickly dissolves and removes residual impurities, avoiding the introduction of new contaminants; the drying temperature is 60~80℃ and the drying time is 30~60 minutes.

[0072] Example 1 like Figure 1 As shown, this embodiment provides a copper-aluminum composite conductive graphene material, including a conductor structure and a stacked structure; the conductor junction includes a graphene-copper composite layer located on the upper and lower surfaces of the stacked structure; the stacked structure includes a multi-layer composite structure in which copper foil layers and aluminum sheet layers are alternately stacked, and the outermost layer directly connected to the upper and lower graphene-copper composite layers in the stacked structure is an aluminum sheet layer.

[0073] The raw materials for preparing copper-aluminum composite conductive graphene materials include: electrolytic copper foil of different thicknesses with a purity of 99.95% (10 μm thick for preparing the graphene copper composite layer; 5 μm thick for the intermediate stacked copper foil layer); industrial pure aluminum sheets with a purity of 99.8% and a thickness of 100 μm; anhydrous ethanol (analytical grade); hydrogen peroxide with a mass concentration of 30%; methane with a purity of 99.99% as a carbon source precursor; and argon with a purity of 99.99% as a protective gas.

[0074] The preparation method of copper-aluminum composite conductive graphene material includes the following steps. Copper foil pretreatment: Take a copper foil with a thickness of 10μm, put it into anhydrous ethanol, and ultrasonically clean it for 10 minutes to remove the rolling oil and impurities on the surface. Take out the cleaned copper foil, let it air dry naturally, and then immerse it in 30% hydrogen peroxide solution for 1 minute to activate it. Then rinse it quickly with deionized water 3 times and blow it dry with nitrogen to obtain a clean and activated copper foil substrate. Graphene growth: The activated copper foil is placed into a quartz tube reaction apparatus, the quartz tube is closed, and a vacuum is drawn to 10. - 3P; Argon gas is introduced at a flow rate of 800 sccm, and the temperature inside the quartz tube is raised to 980℃ at a heating rate of 5℃ / min. The temperature is held for 30 minutes to remove residual oxygen from the tube. Methane gas is introduced at a flow rate of 50 sccm to form a mixed gas flow with the argon gas. Deposition is carried out for 30 minutes to grow a single layer of graphene on the copper foil surface. After deposition, the methane gas is turned off, while the argon gas flow rate is kept constant. The furnace is cooled to room temperature, and the graphene-copper composite layer is obtained. Layered construction: The laminated preform is constructed in the following order: upper graphene-copper composite layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, and lower graphene-copper composite layer. The middle layer consists of one copper foil layer (5 μm thick) and two aluminum sheet layers (100 μm thick / layer). The outermost layer that is in direct contact with the upper and lower graphene-copper composite layers is the aluminum sheet layer. After construction, the total thickness of the laminated preform is 1.0 mm. Vacuum hot pressing sintering: The laminated green bodies are placed in a vacuum hot pressing furnace, the furnace door is closed, and a vacuum is drawn to 10°C. -2 The temperature was increased to 500℃ at a rate of 5℃ / min. After reaching the set temperature, a sintering pressure of 30MPa was applied and the temperature was held for 1 hour. After the holding period, the temperature was kept under vacuum and cooled to room temperature in the furnace. The sintered composite material was then removed. Post-processing: The surface of the composite material was lightly polished with 2000-grit sandpaper to remove the extremely thin oxide layer and burrs. After polishing, the surface roughness Ra=0.6μm. The polished material was then immersed in anhydrous ethanol for 5 minutes and ultrasonically cleaned for 3 minutes to remove polishing residue. The material was then removed and placed in a drying oven at 60℃ for 30 minutes to obtain the final copper-aluminum composite conductive graphene material.

[0075] Example 2 A copper-aluminum composite conductive graphene material is provided, comprising a conductor structure and a stacked structure; the conductor structure includes a graphene-copper composite layer located on the upper and lower surfaces of the stacked structure; the stacked structure comprises a multilayer composite structure in which copper foil layers and aluminum sheet layers are alternately stacked, and the outermost layer directly connected to the upper and lower graphene-copper composite layers in the stacked structure is an aluminum sheet layer.

[0076] The raw materials for preparing copper-aluminum composite conductive graphene materials include: electrolytic copper foil of different thicknesses with a purity of 99.95% (30 μm thick for preparing the graphene copper composite layer; 15 μm thick for the intermediate stacked copper foil layer); industrial pure aluminum sheet with a purity of 99.8% and a thickness of 150 μm; anhydrous ethanol (analytical grade); 10% dilute sulfuric acid; 99.99% pure acetylene as a carbon source precursor; and 99.99% pure argon as a protective gas.

[0077] The preparation method of copper-aluminum composite conductive graphene material includes the following steps. Copper foil pretreatment: Take a copper foil with a thickness of 30μm, put it into anhydrous ethanol, and ultrasonically clean it for 15 minutes to remove the rolling oil and impurities on the surface. Take out the cleaned copper foil, let it air dry naturally, and then immerse it in a 10% dilute sulfuric acid solution for 3 minutes to activate it. Then rinse it quickly with deionized water 3 times and blow it dry with nitrogen to obtain a clean and activated copper foil substrate. Graphene growth: The activated copper foil is placed into a quartz tube reaction apparatus, the quartz tube is closed, and a vacuum is drawn to 10. - 3 P; Argon gas is introduced at a flow rate of 1000 sccm, and the temperature inside the quartz tube is raised to 1000℃ at a heating rate of 8℃ / min. The temperature is held for 30 minutes to remove residual oxygen from the tube. While maintaining the temperature, acetylene gas is introduced at a flow rate of 60 sccm to form a mixed gas flow with the argon gas. The mixture is deposited for 60 minutes to grow a single layer of graphene on the copper foil surface. After the deposition is completed, the acetylene gas is turned off, while the argon gas flow rate is kept constant. The furnace is cooled to room temperature, and the graphene-copper composite layer is obtained. Layered construction: The stacked preform is constructed in the following order: upper graphene-copper composite layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, and lower graphene-copper composite layer. The intermediate layers consist of two sets of copper foil layers (15μm thick) and three aluminum sheet layers (150μm thick / layer). The outermost layer that is in direct contact with the upper and lower graphene-copper composite layers is the aluminum sheet layer. After construction, the total thickness of the stacked preform is 1.5mm, with the thicknesses of the graphene-copper composite layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, and lower graphene-copper composite layer being 30μm, 150μm, 15μm, 150μm, 15μm, 150μm, and 30μm, respectively. Vacuum hot pressing sintering: The laminated green bodies are placed in a vacuum hot pressing furnace, the furnace door is closed, and a vacuum is drawn to 10°C. -3 The temperature was increased to 515℃ at a rate of 10℃ / min. After reaching the set temperature, a sintering pressure of 30MPa was applied and the temperature was held for 2 hours. After the holding period, the furnace was kept in a vacuum environment and cooled to room temperature. The sintered composite material was then removed. Post-processing: The surface of the composite material was lightly polished with 3000-grit sandpaper to remove the extremely thin oxide layer and burrs. After polishing, the surface roughness Ra=0.6μm. The polished material was then ultrasonically cleaned in anhydrous ethanol for 5 minutes to remove polishing residue. The material was then removed and placed in an 80℃ drying oven for 60 minutes to obtain the final copper-aluminum composite conductive graphene material.

[0078] Example 3 A copper-aluminum composite conductive graphene material is provided, comprising a conductor structure and a stacked structure; the conductor structure includes a graphene-copper composite layer located on the upper and lower surfaces of the stacked structure; the stacked structure comprises a multilayer composite structure in which copper foil layers and aluminum sheet layers are alternately stacked, and the outermost layer directly connected to the upper and lower graphene-copper composite layers in the stacked structure is an aluminum sheet layer.

[0079] The raw materials for preparing copper-aluminum composite conductive graphene materials include: electrolytic copper foil of different thicknesses with a purity of 99.95% (20 μm thick for preparing the graphene copper composite layer; 10 μm thick for the intermediate stacked copper foil layer); industrial pure aluminum sheet with a purity of 99.8% and a thickness of 120 μm; anhydrous ethanol (analytical grade); dilute hydrochloric acid with a mass concentration of 12%; ethylene with a purity of 99.99% as a carbon source precursor; and argon gas with a purity of 99.99% as a protective gas.

[0080] The preparation method of copper-aluminum composite conductive graphene material includes the following steps. Copper foil pretreatment: Take a copper foil with a thickness of 20μm, put it into anhydrous ethanol, and ultrasonically clean it for 12 minutes to remove the rolling oil and impurities on the surface. Take out the cleaned copper foil, let it air dry naturally, and then immerse it in a 12% dilute hydrochloric acid solution for 2 minutes to activate it. Then rinse it quickly with deionized water and blow it dry with nitrogen to obtain a clean and activated copper foil substrate. Graphene growth: The activated copper foil is placed into a quartz tube reaction apparatus, the quartz tube is closed, and a vacuum is drawn to 10. - 3 P; Argon gas is introduced at a flow rate of 900 sccm, and the temperature inside the quartz tube is raised to 990℃ at a heating rate of 7℃ / min. The temperature is held for 40 minutes to remove residual oxygen from the tube. While maintaining the temperature, ethylene gas is introduced at a flow rate of 55 sccm to form a mixed gas flow with the argon gas. The mixture is deposited for 45 minutes to grow a single layer of graphene on the copper foil surface. After the deposition is completed, the acetylene gas is turned off, and the argon gas flow rate is kept constant. The furnace is cooled to room temperature, and the graphene-copper composite layer is obtained. Layered construction: The laminated preform is constructed in the following order: upper graphene copper composite layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, and lower graphene copper composite layer. The intermediate layers include one set of copper foil layers (15μm thick) and two aluminum sheet layers (150μm thick / layer). After construction, the total thickness of the laminated preform is 1.2mm. The thicknesses of the middle graphene copper composite layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, and lower graphene copper composite layer are 20μm, 120μm, 10μm, 120μm, and 20μm, respectively. Vacuum hot pressing sintering: The laminated green bodies are placed in a vacuum hot pressing furnace, the furnace door is closed, and a vacuum is drawn to 10°C. -2The temperature was increased to 530℃ at a rate of 8℃ / min. After reaching the set temperature, a sintering pressure of 30MPa was applied and the temperature was held for 1.5 hours. After the holding period, the furnace was kept in a vacuum environment and cooled to room temperature. The sintered composite material was then removed. Post-processing: The surface of the composite material was lightly polished with 2500-grit sandpaper to remove the extremely thin oxide layer and burrs. The polished material was then ultrasonically cleaned in anhydrous ethanol for 5 minutes to remove polishing residue. The material was then removed and placed in a 70°C drying oven for 45 minutes to obtain the final copper-aluminum composite conductive graphene material.

[0081] Example 4 A copper-aluminum composite conductive graphene material is provided, comprising a conductor structure and a stacked structure; the conductor structure includes a graphene-copper composite layer located on the upper and lower surfaces of the stacked structure; the stacked structure comprises a multilayer composite structure in which copper foil layers and aluminum sheet layers are alternately stacked, and the outermost layer directly connected to the upper and lower graphene-copper composite layers in the stacked structure is an aluminum sheet layer.

[0082] The raw materials for preparing copper-aluminum composite conductive graphene materials include: electrolytic copper foil of different thicknesses with a purity of 99.95% (15 μm thick for preparing the graphene copper composite layer; 8 μm thick for the intermediate stacked copper foil layer); industrial pure aluminum sheet with a purity of 99.8% and a thickness of 130 μm; anhydrous ethanol (analytical grade); hydrogen peroxide with a mass concentration of 40%; methane with a purity of 99.99% as a carbon source precursor; and argon with a purity of 99.99% as a protective gas.

[0083] The preparation method of copper-aluminum composite conductive graphene material includes the following steps. Copper foil pretreatment: Take a copper foil with a thickness of 15μm, put it into anhydrous ethanol, and ultrasonically clean it for 10 minutes to remove the rolling oil and impurities on the surface. Take out the cleaned copper foil, let it air dry naturally, and then immerse it in 40% hydrogen peroxide solution for 2 minutes to activate it. Then rinse it quickly with deionized water and blow it dry with nitrogen to obtain a clean and activated copper foil substrate. Graphene growth: The activated copper foil is placed into a quartz tube reaction apparatus, the quartz tube is closed, and a vacuum is drawn to 10. - 3 P; Argon gas is introduced at a flow rate of 850 sccm, and the temperature inside the quartz tube is raised to 980℃ at a heating rate of 6℃ / min. The temperature is held for 30 minutes to remove residual oxygen from the tube. While maintaining the temperature, ethylene gas is introduced at a flow rate of 55 sccm to form a mixed gas flow with the argon gas. Deposition is carried out for 40 minutes to grow a single layer of graphene on the copper foil surface. After deposition, the acetylene gas is turned off, while the argon gas flow rate is kept constant. The furnace is cooled to room temperature, and the graphene-copper composite layer is obtained. Layered construction: The stacked blank is constructed in the following order: upper graphene copper composite layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, and lower graphene copper composite layer. The intermediate layers include one set of copper foil layers (15μm thick) and two aluminum sheet layers (150μm thick / layer). After construction, the total thickness of the stacked blank is 1.3mm. The thicknesses of the upper graphene copper composite layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, and lower graphene copper composite layer are 15μm, 130μm, 8μm, 130μm, 8μm, 130μm, and 15μm, respectively. Vacuum hot pressing sintering: The laminated green bodies are placed in a vacuum hot pressing furnace, the furnace door is closed, and a vacuum is drawn to 10°C. -2 The temperature was increased to 545℃ at a rate of 7℃ / min. After reaching the set temperature, a sintering pressure of 35MPa was applied and the temperature was held for 1.2 hours. After the holding period, the furnace was kept in a vacuum environment and cooled to room temperature. The sintered composite material was then removed. Post-processing: The surface of the composite material was lightly polished with 2000-grit sandpaper to remove the extremely thin oxide layer and burrs. The polished material was then ultrasonically cleaned in anhydrous ethanol for 3 minutes to remove polishing residue. The material was then removed and placed in a drying oven at 65°C for 40 minutes to obtain the final copper-aluminum composite conductive graphene material.

[0084] Example 5 A copper-aluminum composite conductive graphene material is provided, comprising a conductor structure and a stacked structure; the conductor structure includes a graphene-copper composite layer located on the upper and lower surfaces of the stacked structure; the stacked structure comprises a multilayer composite structure in which copper foil layers and aluminum sheet layers are alternately stacked, and the outermost layer directly connected to the upper and lower graphene-copper composite layers in the stacked structure is an aluminum sheet layer.

[0085] The raw materials for preparing copper-aluminum composite conductive graphene materials include: electrolytic copper foil of different thicknesses with a purity of 99.95% (20 μm thick for preparing the graphene copper composite layer; 10 μm thick for the intermediate stacked copper foil layer); industrial pure aluminum sheet with a purity of 99.8% and a thickness of 130 μm; anhydrous ethanol (analytical grade); hydrogen peroxide with a mass concentration of 40%; methane with a purity of 99.99% as a carbon source precursor; and argon with a purity of 99.99% as a protective gas.

[0086] The preparation method of copper-aluminum composite conductive graphene material includes the following steps. Copper foil pretreatment: Take a copper foil with a thickness of 20μm, put it into anhydrous ethanol, and ultrasonically clean it for 13 minutes to remove the rolling oil and impurities on the surface. Take out the cleaned copper foil, let it air dry naturally, and then immerse it in a 20% hydrogen peroxide solution for 3 minutes to activate it. Then rinse it quickly with deionized water and blow it dry with nitrogen to obtain a clean and activated copper foil substrate. Graphene growth: The activated copper foil is placed into a quartz tube reaction apparatus, the quartz tube is closed, and a vacuum is drawn to 10. - 3 P; Argon gas is introduced at a flow rate of 950 sccm, and the temperature inside the quartz tube is raised to 900℃ at a heating rate of 10℃ / min. The temperature is held for 30 minutes to remove residual oxygen from the tube. While maintaining the temperature, ethylene gas is introduced at a flow rate of 60 sccm to form a mixed gas flow with the argon gas. The mixture is deposited for 35 minutes to grow a single layer of graphene on the copper foil surface. After the deposition is completed, the acetylene gas is turned off, and the argon gas flow rate is kept constant. The furnace is cooled to room temperature, and the graphene-copper composite layer is obtained. Layered construction: The stacked blank is constructed in the following order: upper graphene copper composite layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, and lower graphene copper composite layer. The intermediate stacks include one set of copper foil layers (15μm thick) and two aluminum sheet layers (150μm thick / layer). After construction, the total thickness of the stacked blank is 1.1mm, and the thicknesses of the upper graphene copper composite layer, aluminum sheet layer, copper foil layer, aluminum sheet layer, and lower graphene copper composite layer are 20μm, 110μm, 10μm, 110μm, and 120μm, respectively. Vacuum hot pressing sintering: The laminated green bodies are placed in a vacuum hot pressing furnace, the furnace door is closed, and a vacuum is drawn to 10°C. -2 The temperature was increased to 550°C at a rate of 7°C / min. After reaching the set temperature, a sintering pressure of 45 MPa was applied and the temperature was held for 1.5 hours. After the holding period, the furnace was kept in a vacuum environment and cooled to room temperature. The sintered composite material was then removed. Post-processing: The surface of the composite material was lightly polished with 2500-grit sandpaper to remove the extremely thin oxide layer and burrs. The polished material was then ultrasonically cleaned in anhydrous ethanol for 5 minutes to remove polishing residue. The material was then removed and placed in a drying oven at 60°C for 40 minutes to obtain the final copper-aluminum composite conductive graphene material.

[0087] Comparative Example 1 A copper-aluminum composite conductive graphene material is provided, with the sintering temperature changed to 700℃, and the remaining steps and parameters are the same as in Example 1.

[0088] Comparative Example 2 A copper-aluminum composite conductive graphene material is provided, which does not require a copper foil surface activation treatment step, and the remaining steps and parameters are the same as in Example 4.

[0089] Comparative Example 3 A copper-aluminum composite conductive graphene material is provided, wherein the chemical deposition temperature is set to 750°C, and the remaining steps and parameters are the same as in Example 4.

[0090] Performance testing 1. Porosity test: The porosity of the copper-aluminum composite conductive graphene materials in Examples 1-5 and Comparative Examples 1-3 was tested using metallographic microscopy combined with Image-ProPlus image analysis software. The results were verified according to GB / T19587-2017 "Determination of Specific Surface Area of ​​Solid Materials by Gas Adsorption BET Method". Five different cross-sectional fields of view were taken and the average value was calculated. The results are shown in Table 1.

[0091] 2. Pore size: The pore size of the copper-aluminum composite conductive graphene materials in Examples 1-5 and Comparative Examples 1-3 was tested. The cross-section of the material was observed by scanning electron microscopy (SEM), and the maximum diameter of the pores was measured by image analysis. According to GB / T13298-2015 "Methods for Testing the Microstructure of Metals", no less than 30 pores were counted for each sample, and the maximum value was taken. The results are shown in Table 1.

[0092] 3. AlC3 mass fraction: Phase analysis was performed using X-ray diffraction (XRD), and quantitative composition analysis was performed using energy dispersive spectroscopy (EDS). The content was calculated by the intensity of characteristic diffraction peaks according to GB / T2039-2012 Calibration of extensometer system for uniaxial tensile testing of metallic materials and GB / T15247-2008 Determination of residual stress of metallic materials by X-ray diffraction. The results are shown in Table 1.

[0093] 4. Interlayer peel strength: A 180° peel test was conducted using a universal testing machine, according to GB / T2790-1995 "Adhesives 180° Peel Strength Test Method Flexible Materials vs. Rigid Materials". The sample width was 25 mm, the tensile rate was 5 mm / min, and the average value of 5 samples was taken. The results are shown in Table 1.

[0094] 5. Conductivity: Measured using an eddy current conductivity meter, according to GB / T3048.2-2007 Electrical Performance Test Methods for Wires and Cables Part 2, Resistivity Test of Metallic Conductor Materials. The test temperature was 23℃±2℃. Three different locations were measured for each sample, and the average value was taken. The results are shown in Table 1.

[0095] 6. Tensile strength: Tensile tests were conducted using a universal testing machine, in accordance with GB / T228.1-2010 Metallic materials, tensile testing—Part 1: Tests at room temperature. The specimens were dumbbell-shaped with a gauge length of 50 mm and a tensile rate of 2 mm / min. Three specimens were tested for each sample, and the average value was taken. The results are shown in Table 1.

[0096] Table 1: Performance Test Results The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A copper-aluminum composite conductive graphene material, characterized in that, It includes a conductor structure and a multilayer structure; the conductor junction includes graphene-copper composite layers located on the upper and lower surfaces of the multilayer structure; the multilayer structure includes a multi-layer composite structure in which copper foil layers and aluminum sheet layers are alternately stacked, and the outermost layer in the multilayer structure that is in direct contact with the upper and lower graphene-copper composite layers is an aluminum sheet layer; there is a transition layer between the copper foil layer and the aluminum sheet layer where copper and aluminum elements diffuse into each other; the copper element in the graphene-copper composite layer diffuses bidirectionally with the aluminum element in the aluminum sheet layer, forming a copper-aluminum alloy transition layer with a continuous composition gradient at the interface region between the two.

2. The copper-aluminum composite conductive graphene material according to claim 1, characterized in that, The graphene-copper composite layers located on the upper and lower surfaces of the stacked structure have the same thickness; the thickness of the graphene-copper composite layer is 10-30 μm; the graphene in the graphene-copper composite layer is a single-layer structure, uniformly covering the surface of the copper layer.

3. The copper-aluminum composite conductive graphene material according to claim 2, characterized in that, In the stacked structure, the thickness of a single aluminum sheet layer is 100-150 μm, the thickness of a single copper foil layer is 5-15 μm, and the total thickness of the stacked structure is 1-1.5 mm.

4. The copper-aluminum composite conductive graphene material according to claim 1, characterized in that, The copper-aluminum composite conductive graphene material has a porosity of ≤1% and a pore size of ≤50μm, with no penetrating pores.

5. The copper-aluminum composite conductive graphene material according to claim 1, characterized in that, In copper-aluminum composite conductive graphene materials, the mass fraction of the low-conductivity mesophase AlC3 is ≤0.5%.

6. A method for preparing a copper-aluminum composite conductive graphene material as described in any one of claims 1-5, characterized in that, Includes the following steps: Copper foil pretreatment: Surface cleaning and activation treatment of copper foil; Graphene growth: The pretreated copper foil is placed in a quartz tube reaction device, and a single layer of graphene is grown on the surface of the copper foil using chemical vapor deposition with carbon source precursor as carbon donor and argon as protective gas at a set temperature to obtain a graphene copper composite layer. Construction of the laminated structure: The laminated blank is constructed with graphene copper composite layers on the top and bottom surfaces and copper foil and aluminum sheets arranged alternately in the middle layer. Vacuum hot pressing sintering: The above-mentioned laminated blanks are placed in a vacuum hot pressing furnace for sintering to obtain copper-aluminum composite conductive graphene material.

7. The preparation method according to claim 6, characterized in that, The copper foil pretreatment steps are as follows: use anhydrous ethanol for ultrasonic cleaning for 10-15 minutes to remove oil stains, and then immerse the copper foil in a surface treatment solution for activation. The surface treatment solution is selected from any one of hydrogen peroxide, dilute sulfuric acid, and dilute hydrochloric acid, and the activation time is 1-3 minutes.

8. The preparation method according to claim 6, characterized in that, In the graphene growth step, the process parameters of the chemical vapor deposition method are: temperature 980-1000℃, carbon source precursor flow rate 50-60 sccm, argon flow rate 800-1000 sccm, and deposition time 30-60 minutes.

9. The preparation method according to claim 6, characterized in that, In the vacuum hot pressing sintering step, the sintering temperature is 500–550℃ and the vacuum degree is 10. -1 ~10 -3 Pa, sintering time 1-2 hours, sintering pressure 30-50 MPa, heating rate 5-10℃ / min, and cooling to room temperature with the furnace after holding.

10. The preparation method according to any one of claims 6-9, characterized in that, It also includes a post-processing step: the sintered composite material is surface-polished to remove the oxide layer, then cleaned with anhydrous ethanol and dried at a temperature of 60-80℃ for 30-60 minutes.

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