Reduced graphene oxide / copper-based composite material and preparation method thereof

Abstract

The invention discloses a reduced graphene oxide / copper-based composite material and a preparation method thereof, and uniform dispersion and structure optimization of graphene oxide in a copper matrix are realized through a moderate-energy ball milling method; medium-energy ball milling and sintering parameters are adjusted, thermal reduction of graphene oxide is achieved through rapid hot pressing sintering, and the reduction degree and interface bonding strength of graphene in the compounding process are effectively controlled. Compared with a traditional powder metallurgy method, graphene dispersion is more uniform, interface bonding is higher, and the conductivity and the mechanical property of the prepared material are synergistically improved; the process is simple, the application cost of high-quality graphene is reduced, the problems that graphene is poor in dispersity and weak in interface bonding are effectively solved, and the method is suitable for large-scale preparation of the high-performance reduced graphene oxide / copper-based composite material.

Description

Technical Field

[0001] This invention belongs to the technical field of metal matrix composites and their preparation, specifically relating to a reduced graphene oxide / copper matrix composite and its preparation method. Background Technology

[0002] Copper is widely used in aerospace, electronic communications, and rail transportation due to its excellent electrical and thermal conductivity and cost advantages. However, the rapid development of electronic communications and rail transportation has placed higher demands on the electrical conductivity and mechanical properties of copper-based materials. Common metal matrix composites often use ceramic phases (such as titanium boride and alumina) as reinforcements. However, while these ceramic reinforcements improve the strength, hardness, and wear resistance of the copper matrix, they also bring two prominent problems: First, the high resistivity of the ceramic phase itself, when introduced into the copper matrix, significantly increases electron scattering, leading to a substantial decrease in the overall electrical and thermal conductivity of the composite material; second, the insufficient interfacial bonding strength between the ceramic phase and the metal matrix makes it prone to becoming a crack initiation point, limiting further improvement in its mechanical properties.

[0003] Graphene, a novel two-dimensional carbon material, possesses excellent mechanical and physical properties. It is one of the strongest known materials, with a theoretical Young's modulus of 1.0 TPa and an inherent tensile strength reaching 130 GPa. Simultaneously, its high carrier mobility (approximately 200,000 cm² / V·s) makes it an ideal reinforcement for enhancing the performance of copper-based composites. Therefore, incorporating the superior properties of graphene into copper-based composites is expected to drive breakthroughs in both design and performance improvement.

[0004] Currently, the high cost of monolayer graphene, poor dispersion in copper matrices, and lack of wetting at the copper interface are limiting factors hindering the development of this type of composite material. While traditional chemical vapor deposition (CVD) can produce high-quality graphene, it typically requires high temperatures, specific atmospheres and vacuum conditions, resulting in large equipment investments, high maintenance costs, and extreme sensitivity to process parameters. Therefore, developing a simple, low-cost method for preparing high-performance graphene / copper-based composite materials that achieves uniform graphene distribution in a copper matrix is ​​crucial. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a reduced graphene oxide / copper matrix composite material with simple process, low cost, and the ability to achieve uniform dispersion of graphene in a copper matrix and good interfacial bonding, as well as its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of this invention discloses a method for preparing reduced graphene oxide / copper-based composite materials, the preparation method comprising the following steps:

[0008] S1. Graphene oxide powder is ultrasonically dispersed in anhydrous ethanol to obtain graphene oxide alcohol solution; dendritic copper powder is weighed and added to the graphene oxide alcohol solution, and then ultrasonically dispersed to obtain precursor solution.

[0009] S2. Stir the above precursor liquid with constant temperature magnetic stirring until it reaches a viscous state, and finally put it into a vacuum drying oven to dry it to obtain graphene oxide / copper precomposite powder.

[0010] S3. The above-mentioned graphene oxide / copper precomposite powder and cemented carbide balls are loaded into a stainless steel ball mill jar, the ball mill jar is evacuated, and then filled with high-purity argon gas. Graphene oxide / copper composite powder is obtained by medium-energy ball milling.

[0011] S4. The above graphene oxide / copper composite powder is loaded into a graphite mold and hot-pressed and sintered in a rapid hot-pressing sintering furnace to simultaneously achieve the thermal reduction of graphene oxide to obtain a reduced graphene oxide / copper composite material block.

[0012] This invention is the first to propose achieving in-situ thermal reduction of graphene oxide while simultaneously densifying the composite material through hot pressing, and to achieve a good bond between the copper and graphene interface. Technically, it integrates rapid hot pressing sintering and in-situ thermal reduction into a single process, realizing integrated forming, sintering, and reduction.

[0013] S5. The reduced graphene oxide / copper composite material is obtained by hot extrusion treatment of the above-mentioned reduced graphene oxide / copper composite material block.

[0014] Furthermore, in step S1, the mass ratio of the graphene oxide powder to the dendritic copper powder is (0.1-0.5):100. This ratio ensures the reinforcing effect of graphene while avoiding agglomeration problems caused by excessive addition.

[0015] Furthermore, the ultrasonic dispersion time in step S1 is 30-60 minutes. This time allows for sufficient dispersion of the graphene oxide sheets, ensuring uniform distribution of the graphene oxide in the solution and creating favorable conditions for subsequent uniform adsorption onto the copper powder surface.

[0016] Furthermore, the temperature of the isothermal magnetic stirring in step S2 is 80-100℃, and the stirring time is 0.5-1 hour. Under heating and continuous stirring, the dendritic copper powder has a large specific surface area, which allows it to fully contact the graphene oxide suspension, promoting the coating of the copper powder surface by the graphene oxide through physical adsorption and partial interaction.

[0017] Furthermore, the drying process in the vacuum drying oven described in step S2 is carried out at a temperature of 60-80°C for 8-12 hours.

[0018] Furthermore, in step S3, the rotation speed of the medium-energy ball mill is 200-400 rpm, the ball-to-material ratio is 8:1-12:1, and the milling time is 2-8 hours. The definition of medium-energy ball milling lies in its energy input falling between that of traditional high-energy ball milling (milling speed > 400 rpm, ball-to-material ratio > 15:1) and low-energy ball milling (milling speed < 200 rpm, ball-to-material ratio < 5:1). By precisely controlling mechanical energy, it achieves full exfoliation and uniform dispersion of graphene oxide while perfectly maintaining the integrity of its crystal structure.

[0019] At this ball milling time and speed, graphene oxide sheets can be effectively exfoliated and embedded into the copper powder surface to enhance interfacial bonding. At the same time, graphene structure damage and excessive work hardening of copper powder caused by excessive shear force or long working time can be avoided, thus ensuring the subsequent sinterability of the composite powder and the final material properties.

[0020] In the preparation of reduced graphene oxide / copper composite material, this invention employs ball milling with moderate intensity (appropriate ball milling speed and ball-to-material ratio) and optimal time, achieving low-cost interlayer exfoliation of multilayer graphene oxide and uniform mixing of graphene oxide and copper powder while maintaining the structural integrity of graphene oxide.

[0021] Furthermore, the sintering temperature in step S4 is 800-1000℃, the sintering pressure is 20-40 MPa, the holding time is 30-60 minutes, and the heating rate is 50-200℃ / min. Rapid heating can quickly overcome the low-temperature zone and suppress the coarsening of copper grains during the heating process; at the same time, short-term holding at high temperature (800-1000℃) can provide sufficient energy to drive the thermal reduction reaction of graphene oxide, while avoiding damage to the graphene structure caused by prolonged high temperature.

[0022] Furthermore, in step S4, the shape of the reduced graphene oxide / copper composite material is formed into a block of a specified shape according to the shape of the graphite mold, wherein the shape of the graphite mold includes circular, elliptical, quadrilateral, pentagonal and hexagonal.

[0023] Furthermore, the hot extrusion treatment in step S5 is carried out at a temperature of 600-900℃, and the extrusion deformation is 70%-90%. Large plastic deformation closes the residual pores in the material and simultaneously orients the graphene along the extrusion direction, improving the mechanical and electrical properties of the composite material in a specific direction.

[0024] The second aspect of this invention discloses a reduced graphene oxide / copper composite material, which is prepared by the above-described method for preparing reduced graphene oxide / copper composite material. The reduced graphene oxide / copper composite material is applied in the fields of aerospace structural components, electronic packaging heat dissipation materials, or rail transit contact wires.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) This invention proposes a "medium-energy ball milling" process for the first time. By precisely controlling the ball milling energy within the "energy balance window" of 200-400 rpm and ball-to-material ratio of 8:1-12:1, it is positioned between high-energy and low-energy ball milling. The energy is sufficient to overcome the van der Waals forces between graphene oxide layers to achieve effective exfoliation, resulting in high-quality few-layer and single-layer graphene oxide, but not enough to destroy the sp² conjugated structure of graphene. This process achieves full exfoliation and uniform embedding of graphene oxide on the surface of copper powder while perfectly maintaining the integrity of its lattice structure, laying the foundation for subsequent interface bonding and breaking through the technical bottleneck of "dispersion and structure cannot be achieved simultaneously" in traditional ball milling.

[0027] (2) This invention integrates rapid hot pressing sintering with the thermal reduction of graphene oxide into a single process, achieving both reduction reaction and interfacial bonding while simultaneously densifying the composite material through hot pressing. Rapid heating (50-200℃ / min) suppresses copper grain coarsening, and high temperature and pressure reduce graphene oxide to highly conductive graphene. The reduction product directly contacts the copper surface to form Cu-OC chemical bonds. This method achieves thermal reduction, microstructure control, and complete densification in one step, avoiding secondary damage to the pre-reduced graphene in the traditional "reduction followed by sintering" process. This allows the composite material to simultaneously achieve high tensile strength and high conductivity, realizing a synergistic unity of process simplification and performance improvement. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a scanned image of graphene oxide from Example 1 of the present invention;

[0030] Figure 2 This is a scanning electron microscope image of the graphene oxide / copper precomposite powder in Example 1 of this invention;

[0031] Figure 3 This is a scanning electron microscope image of the graphene oxide / copper composite powder in Example 1 of this invention;

[0032] Figure 4 This is a comparison of the Raman spectra of graphene oxide / copper composite powders in Examples 1 and 3 of this invention;

[0033] Figure 5 This is a high-resolution transmission electron microscope image of the reduced graphene oxide / copper composite material in Example 1 of the present invention;

[0034] Figure 6 This is a flowchart of a method for preparing a reduced graphene oxide / copper-based composite material disclosed in this invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0036] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0037] Example 1

[0038] like Figure 6 As shown, this embodiment discloses a method for preparing reduced graphene oxide / copper-based composite material, including the following steps: S1, 0.15g of graphene oxide powder is ultrasonically dispersed in anhydrous ethanol for 30min to obtain a graphene oxide alcohol solution. The graphene oxide has a typical sheet-like wrinkled morphology, and its microstructure is as follows. Figure 1 As shown; 49.85g of dendritic copper powder was weighed and added to the graphene oxide alcohol solution, and then ultrasonically dispersed for 30min to obtain the precursor solution;

[0039] S2. The above precursor solution was magnetically stirred at 80℃ for 30 minutes until it reached a viscous state. Finally, it was placed in a vacuum drying oven and dried at 80℃ for 12 hours to obtain graphene oxide / copper precomposite powder. The morphology of the precomposite powder is as follows: Figure 2 As shown, graphene oxide has been uniformly attached to the surface of dendritic copper powder.

[0040] S3. The above-mentioned graphene oxide / copper precomposite powder and cemented carbide balls are loaded into a stainless steel ball mill jar, and the jar is evacuated to below 5 Pa. Then, high-purity argon gas with a purity ≥ 99.99% is filled in. Graphene oxide / copper composite powder is obtained by medium-energy ball milling at a speed of 300 rpm, a ball-to-powder ratio of 10:1, and a milling time of 6 hours. The morphology of this composite powder is as follows: Figure 3 As shown, the copper powder is flattened and graphene oxide sheets are embedded in its surface;

[0041] S4. The above graphene oxide / copper composite powder is loaded into a cylindrical graphite mold with a diameter of 30 mm. Under an argon atmosphere in a rapid hot pressing sintering furnace, the temperature is raised to 900 °C at a heating rate of 100 °C / min. The mixture is then hot-pressed and sintered under a pressure of 30 MPa for 1 hour to obtain a cylindrical block of reduced graphene oxide / copper composite material.

[0042] S5. The reduced graphene oxide / copper composite material was obtained by hot extrusion treatment of the cylindrical block of the above-mentioned reduced graphene oxide / copper composite material at an extrusion temperature of 700℃ and an extrusion deformation of 90%. The above-mentioned graphene / copper composite material has a conductivity of 95.86% IACS, a tensile strength of 233 MPa, and an elongation after fracture of 45%, respectively.

[0043] Depend on Figure 5 As can be seen, the graphene sheets are tightly bonded to the copper substrate, with no pores or impurities, forming a smooth and tightly bonded interface. This robust interface structure ensures the effective transfer of load between the graphene and the copper substrate, while reducing electron scattering at the interface. This provides the microstructural basis for the composite material to achieve excellent mechanical and electrical properties.

[0044] Example 2

[0045] like Figure 6 As shown, this embodiment further discloses a method for preparing reduced graphene oxide / copper-based composite materials, including the following steps:

[0046] S1. 0.15g of graphene oxide powder was ultrasonically dispersed in anhydrous ethanol for 30min to obtain a graphene oxide alcohol solution; 49.95g of dendritic copper powder was weighed and added to the graphene oxide alcohol solution, and then ultrasonically dispersed for another 30min to obtain a precursor solution.

[0047] S2. Stir the above precursor liquid at a constant temperature of 80℃ for 30 minutes until it becomes viscous. Finally, dry it in a vacuum drying oven at 80℃ for 12 hours to obtain graphene oxide / copper precomposite powder.

[0048] S3. The above-mentioned graphene oxide / copper precomposite powder and cemented carbide balls are loaded into a stainless steel ball mill jar, and the ball mill jar is evacuated to below 5 Pa. Then, high-purity argon gas with a purity ≥ 99.99% is filled in. Graphene oxide / copper composite powder is obtained by medium-energy ball milling at a speed of 300 rpm, a ball-to-powder ratio of 10:1, and a milling time of 6 hours.

[0049] S4. The above graphene oxide / copper composite powder is loaded into a quadrilateral graphite mold with a side length of 30 mm. Under the argon atmosphere in a rapid hot pressing sintering furnace, the temperature is raised to 900°C at a heating rate of 100°C / min. The powder is then hot-pressed and sintered under a pressure of 30 MPa for 1 hour to obtain a quadrilateral columnar block of reduced graphene oxide / copper composite material.

[0050] S5. The reduced graphene oxide / copper composite material is obtained by hot extrusion treatment of the above-mentioned quadrilateral columnar block of reduced graphene oxide / copper composite material at an extrusion temperature of 700℃ and an extrusion deformation of 90%.

[0051] The electrical conductivity, tensile strength, and elongation after fracture of the above-mentioned reduced graphene oxide / copper composite material are 95.68% IACS, 230 MPa, and 46%, respectively.

[0052] Example 3

[0053] like Figure 6 As shown, this embodiment further discloses a method for preparing reduced graphene oxide / copper-based composite materials, including the following steps:

[0054] S1. 0.15g of graphene oxide powder was ultrasonically dispersed in anhydrous ethanol for 30min to obtain a graphene oxide alcohol solution; 49.85g of dendritic copper powder was weighed and added to the graphene oxide alcohol solution, and then ultrasonically dispersed for another 30min to obtain a precursor solution.

[0055] S2. Stir the above precursor liquid at a constant temperature of 80℃ for 30 minutes until it becomes viscous. Finally, dry it in a vacuum drying oven at 80℃ for 12 hours to obtain graphene oxide / copper precomposite powder.

[0056] S3. The above-mentioned graphene oxide / copper precomposite powder and cemented carbide balls are loaded into a stainless steel ball mill jar, and the ball mill jar is evacuated to below 5 Pa. Then, high-purity argon gas with a purity ≥ 99.99% is filled in. Graphene oxide / copper composite powder is obtained by high-energy ball milling at a speed of 500 rpm, a ball-to-powder ratio of 20:1, and a milling time of 6 hours.

[0057] S4. The above graphene oxide / copper composite powder is loaded into a circular graphite mold with a diameter of 30 mm. In a rapid hot pressing sintering furnace under an argon atmosphere, the temperature is raised to 900°C at a heating rate of 100°C / min. The mixture is then hot-pressed and sintered under a pressure of 30 MPa for 1 hour to obtain a cylindrical block of reduced graphene oxide / copper composite material.

[0058] S5. The reduced graphene oxide / copper composite material is obtained by hot extrusion treatment of the above-mentioned reduced graphene oxide / copper composite cylindrical block at an extrusion temperature of 700℃ and an extrusion deformation of 90%.

[0059] like Figure 4 As shown, Raman spectroscopy analysis of the composite material prepared in this embodiment revealed an ID / IG ratio (the ID / IG ratio is the ratio of the D peak intensity to the G peak intensity in a Raman spectrum, used to assess the graphitization degree and defect density of carbon materials; a larger ratio indicates a higher degree of defects) as high as 1.35, significantly higher than that of the original graphene oxide (1.21) and Example 1 (0.91). This indicates that the severe mechanical impact during high-energy ball milling disrupted the sp² conjugated structure of graphene, leading to structural damage and increased defects. Correspondingly, its conductivity, tensile strength, and elongation after fracture were 83.25% IACS, 180 MPa, and 30%, respectively, all significantly lower than those of Example 1.

[0060] Example 4

[0061] like Figure 6 As shown, this embodiment further discloses a method for preparing reduced graphene oxide / copper-based composite materials, including the following steps:

[0062] S1. 0.15g of graphene oxide powder was ultrasonically dispersed in anhydrous ethanol for 30min to obtain a graphene oxide alcohol solution; 49.85g of dendritic copper powder was weighed and added to the graphene oxide alcohol solution, and then ultrasonically dispersed for another 30min to obtain a precursor solution.

[0063] S2. Stir the above precursor liquid at a constant temperature of 80℃ for 30 minutes until it becomes viscous. Finally, dry it in a vacuum drying oven at 80℃ for 12 hours to obtain graphene oxide / copper precomposite powder.

[0064] S3. The above-mentioned graphene oxide / copper precomposite powder and cemented carbide balls are loaded into a stainless steel ball mill jar, and the ball mill jar is evacuated to below 5 Pa. Then, high-purity argon gas with a purity ≥ 99.99% is filled in. Graphene oxide / copper composite powder is obtained by medium-energy ball milling at a speed of 300 rpm, a ball-to-powder ratio of 10:1, and a milling time of 6 hours.

[0065] S4. The above graphene oxide / copper composite powder is loaded into a circular graphite mold with a diameter of 30 mm. Under the argon atmosphere in a rapid hot pressing sintering furnace, the temperature is raised to 900°C at a heating rate of 10°C / min. The mixture is then hot-pressed and sintered under a pressure of 30 MPa for 2 hours to obtain a cylindrical block of reduced graphene oxide / copper composite material.

[0066] S5. The reduced graphene oxide / copper composite material is obtained by hot extrusion treatment of the above-mentioned reduced graphene oxide / copper composite cylindrical block at an extrusion temperature of 700℃ and an extrusion deformation of 90%.

[0067] The conductivity, tensile strength, and elongation after fracture of the above-mentioned reduced graphene oxide / copper composite material are 93.25% IACS, 260 MPa, and 40%, respectively.

[0068] Example 5

[0069] like Figure 6 As shown, this embodiment further discloses a method for preparing reduced graphene oxide / copper-based composite materials, including the following steps:

[0070] S1. 0.15g of graphene oxide powder was ultrasonically dispersed in anhydrous ethanol for 30min to obtain a graphene oxide alcohol solution; 49.85g of dendritic copper powder was weighed and added to the graphene oxide alcohol solution, and then ultrasonically dispersed for another 30min to obtain a precursor solution.

[0071] S2. Stir the above precursor liquid at a constant temperature of 80℃ for 30 minutes until it becomes viscous. Finally, dry it in a vacuum drying oven at 80℃ for 12 hours to obtain graphene oxide / copper precomposite powder.

[0072] S3. The above-mentioned graphene oxide / copper precomposite powder and cemented carbide balls are loaded into a stainless steel ball mill jar, and the ball mill jar is evacuated to below 5 Pa. Then, high-purity argon gas with a purity ≥ 99.99% is filled in. Graphene oxide / copper composite powder is obtained by medium-energy ball milling at a speed of 300 rpm, a ball-to-powder ratio of 10:1, and a milling time of 6 hours.

[0073] S4. The above graphene oxide / copper composite powder is loaded into a circular graphite mold with a diameter of 30 mm. In a rapid hot pressing sintering furnace under an argon atmosphere, the temperature is raised to 400 °C at a heating rate of 100 °C / min and held for 2 h. Then, the temperature is raised to 900 °C at a heating rate of 100 °C / min and held for 1 h. The entire process is hot pressing sintered under a pressure of 30 MPa to obtain a cylindrical block of reduced graphene oxide / copper composite material.

[0074] S5. The reduced graphene oxide / copper composite material is obtained by hot extrusion treatment of the above-mentioned reduced graphene oxide / copper composite cylindrical block at an extrusion temperature of 700℃ and an extrusion deformation of 90%.

[0075] The electrical conductivity, tensile strength, and elongation after fracture of the above-mentioned reduced graphene oxide / copper composite material are 93.18% IACS, 215 MPa, and 36%, respectively.

[0076] The performance testing methods in the above embodiments are consistent: the conductivity test is conducted according to standard GB / T 351-2019 "Method for Measurement of Resistivity of Metallic Materials", using the four-probe method to measure the material resistivity at room temperature, and expressed as a percentage of the International Association of Standards for Annealed Copper (IACS). The tensile strength and elongation after fracture tests are conducted according to the standard GB / T228.1-2021 "Metallic Materials Room Temperature Tensile Testing", using a universal testing machine to test standard tensile specimens, thereby obtaining the material's tensile strength (maximum tensile stress) and elongation after fracture (plastic deformation capacity).

[0077] Table 1. Mechanical properties and electrical conductivity of the embodiments

[0078]

[0079] As shown in Table 1, the influence of mold shape: Example 2 used a quadrilateral graphite mold for sintering, and other process parameters were exactly the same as in Example 1. Compared with Example 1, Example 2 had an electrical conductivity of 95.68% IACS, a tensile strength of 230 MPa, and an elongation after fracture of 46%. The fluctuation range of each performance index was within 2%, indicating that changing the mold shape had no significant impact on the performance of the composite material. This shows that the preparation method of the present invention has good process adaptability to molds of different shapes, and the mold shape can be flexibly selected according to actual needs to prepare composite material blocks with different geometric shapes, reflecting the universality and designability of the method of the present invention.

[0080] Impact of ball milling energy: Example 3 used a high-energy ball mill with a ball milling speed of 500 rpm and a ball-to-material ratio of 20:1, with other parameters the same as in Example 1. Compared with Example 1, the conductivity decreased from 95.86% IACS to 89.63% IACS, the tensile strength decreased from 233 MPa to 196 MPa, and the elongation after fracture decreased from 45% to 28%. This indicates that excessively high ball milling energy severely damages the graphene structure, leading to loss of reinforcement effect and overall performance degradation; while the medium-energy ball milling of this invention maintains the integrity of the graphene structure while achieving uniform dispersion, laying a structural foundation for subsequent interfacial bonding.

[0081] Effects of heating rate and holding time: Example 4 employed a slower heating rate of 10℃ / min and a holding time of 2h, along with a longer holding time for sintering, while other parameters remained the same as in Example 1. Compared to Example 1, the conductivity decreased to 92.74% IACS, the tensile strength decreased to 221 MPa, and the elongation after fracture decreased to 39%. Slow heating leads to grain coarsening and thermal damage to graphene, while the rapid sintering of this invention achieves densification and thermal reduction while inhibiting grain growth, protecting the graphene structure, and synergistically improving performance.

[0082] Impact of Sintering Process Path: Example 5 employed a segmented sintering process, holding at 400℃ for 2 hours followed by a further increase to 900℃ for 1 hour. All other process parameters were identical to those in Example 1. Compared to Example 1, the conductivity of Example 5 decreased from 95.86% IACS to 93.18% IACS, tensile strength decreased from 233 MPa to 215 MPa, and elongation after fracture decreased from 45% to 36%, resulting in a significant decline in all properties. This is because during the long-term holding at 400℃, copper grains prematurely coarsen; simultaneously, at this temperature, graphene oxide may undergo partial thermal reduction, but the reduction is insufficient, and the resulting intermediate products are difficult to completely repair in subsequent high-temperature stages, leading to an increase in graphene structural defects. Grain coarsening and interface weakening together reduce the material's strength and plasticity.

[0083] In summary, through comparative analysis of the above embodiments, it can be seen that the present invention adopts a synergistic design integrating medium-energy ball milling, sintering densification, and thermal reduction of graphene oxide. This achieves uniform dispersion and interfacial embedding of graphene while maintaining its structural integrity. Simultaneously, hot-pressing densification and in-situ thermal reduction of graphene oxide are integrated into a single process, allowing the reduction product to directly contact the fresh copper surface and form a strong interfacial bond. This preparation method, through precise control of key parameters such as ball milling energy, heating rate, holding time, and sintering path, overcomes the technical bottlenecks of traditional processes where "dispersion and structure cannot be simultaneously achieved" and "separate reduction and densification" leads to interfacial weakening. It successfully achieves the controllable preparation of high-performance reduced graphene oxide / copper composite materials with a synergistic match of high strength, high conductivity, and good plasticity.

[0084] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing reduced graphene oxide / copper-based composite material, characterized in that, The preparation method includes the following steps: S1. Graphene oxide powder is ultrasonically dispersed in anhydrous ethanol to obtain graphene oxide alcohol solution; dendritic copper powder is weighed and added to the graphene oxide alcohol solution, and then ultrasonically dispersed to obtain precursor solution. S2. Stir the above precursor liquid with constant temperature magnetic stirring until it reaches a viscous state, and finally put it into a vacuum drying oven to dry it to obtain graphene oxide / copper precomposite powder. S3. The above-mentioned graphene oxide / copper precomposite powder and cemented carbide balls are loaded into a stainless steel ball mill jar, the ball mill jar is evacuated, and then filled with high-purity argon gas. Graphene oxide / copper composite powder is obtained by medium-energy ball milling. S4. The above graphene oxide / copper composite powder is loaded into a graphite mold and hot-pressed and sintered in a rapid hot-pressing sintering furnace to simultaneously achieve the thermal reduction of graphene oxide to obtain a reduced graphene oxide / copper composite material block. S5. The reduced graphene oxide / copper composite material is obtained by hot extrusion treatment of the above-mentioned reduced graphene oxide / copper composite material block.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of the graphene oxide powder to the dendritic copper powder is (0.1-0.5):

100.

3. The preparation method according to claim 1, characterized in that, The ultrasonic dispersion time in step S1 is 30-60 minutes.

4. The preparation method according to claim 1, characterized in that, The temperature of the constant temperature magnetic stirring in step S2 is 80-100℃, and the stirring time is 0.5-1 hour.

5. The preparation method according to claim 1, characterized in that, The drying process described in step S2 is carried out in a vacuum drying oven at a temperature of 60-80°C for 8-12 hours.

6. The preparation method according to claim 1, characterized in that, The ball milling speed in step S3 is 200-400 rpm, the ball-to-material ratio is 8:1-12:1, and the milling time is 2-8 hours.

7. The preparation method according to claim 1, characterized in that, The sintering temperature in step S4 is 800-1000℃, the sintering pressure is 20-40 MPa, the holding time is 30-60 minutes, and the heating rate is 50-200℃ / min.

8. The preparation method according to claim 1, characterized in that, In step S4, the shape of the reduced graphene oxide / copper composite material is formed into a block of a specified shape according to the shape of the graphite mold, wherein the shape of the graphite mold includes circular, elliptical, quadrilateral, pentagonal and hexagonal.

9. The preparation method according to claim 1, characterized in that, The temperature of the hot extrusion treatment in step S5 is 600-900℃, and the extrusion deformation is 70%-90%.

10. A reduced graphene oxide / copper composite material, characterized in that, Prepared by the method described in any one of claims 1 to 9, the reduced graphene oxide / copper composite material is used in aerospace structural components, electronic packaging heat dissipation materials, or rail transit contact wires.

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