A copper-based composite material and a method for producing the same

Abstract

The application discloses a copper-based composite material and a preparation method thereof, and preparation comprises the following steps: (1) liquid-phase mixing copper modified reduced graphene oxide with copper powder and a solvent, then performing solid-liquid separation by suction filtration, and performing protective atmosphere post-treatment on the obtained solid-phase product to obtain a composite powder; (2) cold-pressing the composite powder to obtain a blank; (3) performing segmented gradient sintering on the blank, which comprises the following steps: heating to a first temperature and keeping the temperature, continuously heating to a second temperature and keeping the temperature, and again heating to a third temperature and keeping the temperature; performing hot compression treatment after the temperature keeping step at the first temperature, the second temperature or the third temperature is completed; and performing segmented gradient resintering and reverse extrusion forming after the hot compression treatment. The method improves the dispersion uniformity and interface bonding stability of the copper modified reduced graphene oxide reinforcer in the copper matrix, so that the copper-based composite material with high strength, high conductivity and high wear resistance is obtained.

Description

Technical Field

[0001] This invention relates to the fields of metal matrix composites and powder metallurgy forming technology, and in particular to a copper matrix composite and its preparation method. Background Technology

[0002] Copper and its alloys possess excellent electrical and thermal conductivity and machinability, making them widely used in electrical contact components, conductive connectors, sliding electrical contact materials, thermal management components, and rail transportation. However, pure copper has relatively low strength and wear resistance. Under service conditions involving load-bearing, electrical conductivity, and frictional coupling, it is prone to plastic deformation and surface wear, leading to performance degradation and making it difficult to meet the application requirements of high strength, high electrical conductivity, and high wear resistance.

[0003] To improve the overall performance of copper-based materials, researchers often introduce high-performance carbon materials to prepare copper-based composites. Graphene and reduced graphene oxide possess high strength, good electrical conductivity, and lubrication properties, making them important reinforcing agents for improving the strength and wear resistance of copper-based materials. However, graphene-based reinforcing agents have a large specific surface area and high surface energy, making them prone to agglomeration in copper powder systems. Furthermore, their poor wettability and weak interfacial bonding with the copper matrix can lead to uneven dispersion of the reinforcing phase, thus affecting further improvements in the strength, electrical conductivity, and wear resistance of the composite material.

[0004] In existing technologies, mechanical ball milling, ultrasonic dispersion, or the introduction of surfactants or dispersants are often used to improve the dispersibility of graphene in metal powders. However, mechanical ball milling can easily damage the graphene sheet structure and may introduce impurities. Surfactants or dispersants may leave residues during subsequent heat treatment, which can adversely affect the electrical conductivity and interface state of the composite material.

[0005] Furthermore, existing preparation routes for graphene-reinforced copper-based composites mostly focus on conventional processes such as "mixing-drying-sintering-extrusion," which are insufficient in controlling the solid-liquid separation of the mixed composite powder, the protective atmosphere heat treatment process, and the process control of pore closure and interface evolution during sintering. Especially when the content of the reinforcement is increased, if the powder cleanliness is insufficient, local agglomeration still exists, or the densification control during sintering is inadequate, it can easily lead to mutual constraints between the material's strength, electrical conductivity, and wear resistance, thus limiting the improvement of its overall performance.

[0006] For example, patent CN119530589A discloses a method for preparing a high-performance graphene / copper composite material. The method involves first sensitizing and activating graphene, then chemically plating it in a solution containing nickel and titanium salts to obtain a nickel-titanium-plated graphene composite material. Subsequently, the nickel-titanium-plated graphene composite material is ultrasonically dispersed and mixed with copper powder. The resulting composite powder is then further processed through vacuum hot pressing sintering and hot extrusion molding to obtain the graphene / copper composite material. This method, by metallizing the graphene surface, can improve the dispersion state of the reinforcement and enhance the overall performance of the composite material to a certain extent. However, this type of method introduces heterogeneous metal components such as nickel and titanium, and involves multiple process steps such as sensitization, activation, chemical plating, mixing, vacuum hot pressing sintering and hot extrusion. The overall process is relatively long, and the requirements for matching the precursor state, coating quality and subsequent forming conditions are high. At the same time, the densification of materials and interface construction still depend heavily on the subsequent hot pressing sintering and hot extrusion processes. There is still room for further optimization in terms of balancing process simplification, low-damage dispersion and stable interface bonding.

[0007] Therefore, there is an urgent need to provide a method for preparing graphene-reinforced copper-based composite materials, which can improve the state of composite powder, increase the degree of sintering densification and enhance the interfacial bonding stability while minimizing damage to the reinforcement structure and reducing the introduction of impurities, thereby improving the overall performance of copper-based composite materials. Summary of the Invention

[0008] The purpose of this invention is to address the problems encountered in the preparation of existing graphene-reinforced copper-based composite materials, such as reinforcement agglomeration, insufficient interfacial bonding, low powder post-processing cleanliness, and inadequate control over sintering densification. This invention provides a copper-modified reduced graphene oxide (RPO) reinforced copper-based composite material and its preparation method. The method optimizes the post-processing of the mixture of copper-modified ROP and copper powder, as well as the sintering densification path. While minimizing damage to the reinforcement structure and reducing impurity introduction, it improves the dispersion uniformity and interfacial bonding stability of the copper-modified ROP reinforcement in the copper matrix, thereby obtaining a copper-based composite material with high strength, high conductivity, and high wear resistance.

[0009] To address the aforementioned technical problems, the first aspect of this invention provides a method for preparing a copper-based composite material, comprising the following steps:

[0010] (1) Copper-modified reduced graphene oxide was mixed with copper powder and solvent in the liquid phase, and then solid-liquid separation was performed by vacuum filtration. The resulting solid product was then post-treated under a protective atmosphere to obtain composite powder.

[0011] (2) The composite powder obtained in step (1) is cold-pressed to obtain a blank;

[0012] (3) The blank obtained in step (2) is subjected to segmented gradient sintering, wherein the conditions for segmented gradient sintering include: heating to a first temperature and holding it at that temperature, continuing to heat to a second temperature and holding it at that temperature, and then heating to a third temperature and holding it at that temperature; hot compression treatment is performed after the holding steps at the first temperature, the second temperature, or the third temperature; after the hot compression treatment, a complete segmented gradient re-sintering is performed again, and then reverse extrusion molding is performed to obtain copper-based composite material.

[0013] According to the method of the present invention, copper-modified reduced graphene oxide (Cu@RGO) can be prepared in-house or commercially. Cu@RGO can be prepared using existing mature methods, such as dispersing graphene oxide, depositing copper salts, performing a reduction reaction, and subsequent heat treatment. The preparation method of Cu@RGO includes, but is not limited to: dispersing graphene oxide in deionized water, ultrasonicating it, and preparing a graphene oxide suspension; preparing a copper ammonia solution, adding the copper ammonia solution dropwise to the graphene oxide suspension under stirring, stirring until homogeneous, adding hydrazine hydrate, and reacting in a water bath; filtering, washing, and drying the resulting reaction product to obtain a copper-modified graphene oxide precursor; and then reducing the precursor by heat treatment at 450-550 °C under a hydrogen atmosphere to obtain Cu@RGO.

[0014] According to the method of the present invention, the graphene oxide sheet diameter may be, but is not limited to, 0.5-5 μm and the thickness is 1-3 nm; the graphene oxide suspension concentration is 0.1-2 mg / mL; the ultrasonic power is 300-600 W; the ultrasonic time is 100-200 min; the CuSO4·5H2O concentration is 2-8 mg / mL; the mass ratio of graphene oxide to CuSO4·5H2O is 1:4-1:8; the hydrazine hydrate concentration is 0.05-0.2 mg / mL; the reaction temperature is 80-95 °C; the reaction time is 3-6 h; the precursor drying temperature is 50-70 °C; the drying time is 5-7 h; and the subsequent heat treatment reduction is carried out at 450-550 °C for 2-4 h under a hydrogen atmosphere.

[0015] According to the method of the present invention, preferably, the copper powder has a particle size of 200-400 mesh and a purity of ≥99.9 wt.%.

[0016] According to the method of the present invention, preferably, the mass fraction of copper-modified reduced graphene oxide in the obtained copper-based composite material is 0.05~1.0 wt.%, wherein the mass fraction is calculated based on the total mass of the obtained copper-based composite material. In the present invention, when the mass fraction of copper-modified reduced graphene oxide is 0.05~1.0 wt.%, the tensile strength of the copper-based composite material generally shows a trend of first increasing and then decreasing, the friction coefficient generally shows a trend of first decreasing and then increasing, while the electrical conductivity generally decreases. Among them, the copper-based composite material sample with a copper-modified reduced graphene oxide mass fraction of 0.4 wt.% exhibits the best comprehensive performance; compared with the pure copper comparative sample, it shows higher strength and lower friction coefficient, while still maintaining high electrical conductivity.

[0017] According to the method of the present invention, the solvent may be an organic solvent, preferably selected from, but not limited to, at least one of anhydrous ethanol, methanol, isopropanol and acetone.

[0018] According to the method of the present invention, preferably, the conditions for liquid phase mixing include: a temperature of 25~100 °C and a time of 1~3 h.

[0019] According to the method of the present invention, preferably, the conditions for the protective atmosphere post-treatment include: holding at 100~250 °C for 1~3 h under an Ar protective atmosphere.

[0020] According to the method of the present invention, preferably, the conditions for the protective atmosphere post-treatment include: holding at 100~250 °C for 1~3 h under a H2 protective atmosphere.

[0021] According to the method of the present invention, compared with conventional evaporation drying, post-treatment with a protective atmosphere of Ar or H2 can further improve performance. In particular, H2 post-treatment is more beneficial to improving the state of the composite powder and the interfacial bonding.

[0022] According to the method of the present invention, preferably, the cold pressing conditions include: a pressure of 600~900 MPa and a time of 1~5 min. In the present invention, the temperature of the cold pressing step may be, but is not limited to, room temperature, for example, but not limited to, 20~40 °C.

[0023] According to the method of the present invention, preferably, the conditions for segmented gradient sintering include: heating to a first temperature of 140~160 ℃ and holding for 20~40 min, continuing to heat to a second temperature of 600~700 ℃ and holding for 20~40 min, and then heating to a third temperature of 900~1000 ℃ and holding for 80~100 min.

[0024] According to the method of the present invention, preferably, hot compression treatment is performed after the holding step at the first temperature, the second temperature, or the third temperature; after the hot compression treatment, a complete round of segmented gradient reheating is performed again. In the present invention, hot compression treatment after the holding step at the first temperature means that the hot compression treatment is performed after heating to the first temperature of 140~160℃ and holding for 20~40 min. Hot compression treatment after the holding step at the second temperature means that the hot compression treatment is performed after heating to the first temperature of 140~160℃ and holding for 20~40 min, then continuing to heat to the second temperature of 600~700℃ and holding for 20~40 min. The hot compression treatment after the third temperature holding step means that the hot compression treatment is carried out after heating to the first temperature of 140~160 ℃ and holding for 20~40 min, continuing to heat to the second temperature of 600~700 ℃ and holding for 20~40 min, and then heating to the third temperature of 900~1000 ℃ and holding for 80~100 min.

[0025] In this invention, if the hot compression treatment is performed after the first temperature and holding period (first temperature 140~160 ℃ and holding for 20~40 min), then the second temperature increase and holding period (second temperature 600~700 ℃ and holding for 20~40 min) and the third temperature increase and holding period (third temperature 900~1000 ℃ and holding for 80~100 min) are not performed, and a complete round of segmented gradient re-firing is directly repeated. If the hot compression treatment is performed after the second temperature and holding period (second temperature 600~700 ℃ and holding for 20~40 min), then the third temperature and holding period (third temperature 900~1000 ℃ and holding for 80~100 min) are not performed, and a complete round of segmented gradient re-firing is directly repeated.

[0026] In this invention, performing hot compression treatment after the heat preservation step at the third temperature is more conducive to obtaining better strength, conductivity and wear resistance.

[0027] According to the method of the present invention, preferably, the conditions for the hot compression treatment include: adjusting the blank to 550~650℃ and holding it at that temperature for 1~2 h, and then holding it under pressure at 900~950 MPa for 1~2 min.

[0028] According to the method of the present invention, preferably, the conditions for the segmented gradient reheating include: heating to a first temperature of 140~160 ℃ and holding for 20~40 min, continuing to heat to a second temperature of 600~700 ℃ and holding for 20~40 min, and then heating to a third temperature of 900~1000 ℃ and holding for 80~100 min.

[0029] According to the method of the present invention, preferably, both the segmented gradient sintering and the segmented gradient re-sintering are carried out under an inert atmosphere, for example, under an Ar atmosphere.

[0030] According to the method of the present invention, preferably, the conditions for the reverse extrusion molding include: a temperature of 550~650 ℃ and an extrusion ratio of 10:1~20:1.

[0031] A second aspect of the present invention provides a copper-based composite material obtained according to the above-described method for preparing copper-based composite materials.

[0032] According to the method of the present invention, preferably, the mass fraction of copper-modified reduced graphene oxide (Cu@RGO) in the obtained copper-based composite material is 0.05~1.0 wt.%, and the mass fraction is calculated based on the total mass of the obtained copper-based composite material. In the present invention, when the mass fraction of copper-modified reduced graphene oxide (Cu@RGO) is 0.05~1.0 wt.%, the tensile strength of the copper-based composite material generally shows a trend of first increasing and then decreasing, the friction coefficient generally shows a trend of first decreasing and then increasing, while the electrical conductivity generally decreases. Among them, the copper-based composite material sample with a mass fraction of 0.4 wt.% copper-modified reduced graphene oxide (0.4 wt.% Cu@RGO / Cu) has the best comprehensive performance; compared with the pure copper comparative sample, it exhibits higher strength and lower friction coefficient, while still maintaining high electrical conductivity.

[0033] Beneficial effects:

[0034] (1) The present invention uses copper-modified reduced graphene oxide as a reinforcement, which is beneficial to improve the interfacial compatibility between graphene reinforcement and copper matrix, improve the dispersion uniformity and interfacial bonding stability of reinforcement in copper matrix, and provide a basis for improving the strength and wear resistance of copper-based composite materials and maintaining high conductivity.

[0035] (2) The present invention adopts a composite powder preparation process of liquid phase mixing-filtration-protective atmosphere post-treatment, which is beneficial to improve the uniformity and cleanliness of copper-based composite materials while minimizing the damage to the reinforcement structure, and reduces the problems of local agglomeration, oxidation and impurity introduction that may occur in the conventional direct evaporation drying process, thereby providing a more stable powder state for subsequent forming and sintering.

[0036] (3) The present invention sets up a hot compression treatment in the segmented gradient sintering process, and performs a complete segmented gradient sintering again after the hot compression treatment. This is beneficial to further promote the closure of the pores inside the blank, improve the material density and improve the bonding state of the reinforcement / copper matrix interface, thereby improving the mechanical properties and wear resistance of the composite material and maintaining high electrical conductivity.

[0037] (4) The present invention combines reverse extrusion molding process, which is conducive to further optimizing the uniformity of material structure and interface continuity, so that the resulting composite material has high strength and high wear resistance while maintaining high conductivity, and is suitable for application scenarios with comprehensive requirements for structural load-bearing, conductive transmission and friction service performance. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0039] Figure 1 Scanning electron microscope image of copper-modified reduced graphene oxide (Cu@RGO) obtained in Preparation Example 1 of this invention.

[0040] Figure 2 The energy dispersive spectroscopy (EDS) spectrum of copper-modified reduced graphene oxide (Cu@RGO) obtained in Example 1 of this invention is shown.

[0041] Figure 3 This is a schematic diagram of the preparation process of the copper-based composite material in Example 1 of the present invention.

[0042] Figure 4a This is a scanning electron microscope image of the microstructure of pure copper in Comparative Example 1.

[0043] Figure 4b This is a scanning electron microscope image of the microstructure of a copper-based composite material with a copper-modified reduced graphene oxide (Cu@RGO) mass fraction of 0.4 wt.%, as described in Example 4 of the present invention. Detailed Implementation

[0044] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention. The present invention can be implemented in many different forms and is not limited to the specific embodiments of the invention described herein, but includes all technical solutions falling within the scope of the claims.

[0045] These embodiments are provided to make the invention thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0046] It should be noted that, in the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0047] Furthermore, the terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible range of error. "Parallel" is not strictly parallel, but within the permissible range of error. Terms such as "including" or "comprising" mean that the element preceding the word encompasses the element listed after the word, and do not exclude the possibility of encompassing other elements as well.

[0048] It should also be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0049] All terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this invention pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0050] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0051] The copper-based composite material and its preparation method described in this invention will be further explained in detail below through specific embodiments.

[0052] Preparation Example 1

[0053] Preparation of Cu@RGO:

[0054] Graphene oxide (2 μm in diameter, 2 nm in thickness) was dispersed in deionized water and sonicated (400 W for 150 min) to prepare a 1 mg / mL suspension. A copper ammonia solution (CuSO4·5H2O, 5 mg / mL) was prepared and added dropwise to the graphene oxide suspension with stirring. The mass ratio of graphene oxide to CuSO4·5H2O was 1:4. After thorough stirring, 0.1 mg / mL hydrazine hydrate was added, and the reaction was carried out in an 85 °C water bath for 4 h. The resulting reaction product was filtered, washed, and dried at 60 °C for 6 h to obtain a copper-modified graphene oxide precursor. The precursor was then reduced by heat treatment at 500 °C for 3 h under a hydrogen atmosphere to obtain Cu@RGO. Scanning electron microscopy images are shown below. Figure 1 As shown, the energy spectrum analysis diagram is as follows: Figure 2 As shown.

[0055] Example 1

[0056] Examples 1-7 all employed the following process route to prepare copper-based composite materials (Cu@RGO / Cu composite materials), as shown in the schematic diagram of the preparation process. Figure 3 As shown:

[0057] The Cu@RGO obtained in Preparation Example 1 was mixed with copper powder (300 mesh, purity ≥99.9 wt.%) in anhydrous ethanol as a medium in the liquid phase. The mass fraction of Cu@RGO in the resulting copper-based composite material was 0.05 wt.%, calculated based on the total mass of the resulting copper-based composite material. The mixture was stirred magnetically at room temperature for 2 h. After liquid-phase mixing, solid-liquid separation was performed by vacuum filtration. The resulting solid product was then subjected to a protective atmosphere post-treatment at 100 ℃ for 2 h under Ar protection. Subsequently, it was cold-pressed at 25 ℃ and 700 MPa for 1 min to obtain a green body. The green body was then subjected to segmented gradient sintering under Ar protection. The segmented gradient sintering process was as follows: heating to 150 ℃ and holding for 30 min, heating to 650 ℃ and holding for 30 min, heating to 950 ℃ and holding for 90 min, and then heating to 950 ℃ and holding for 90 min. After the initial heat treatment at ℃, a hot compression process is performed. The hot compression process involves adjusting the green body to 600 ℃ and holding it at that temperature for 1 h, then pressing it at 900 MPa for 1 min. After the hot compression process, a complete segmented gradient sintering process is performed again. The complete segmented gradient sintering process involves heating to 150 ℃ and holding it for 30 min, then heating to 650 ℃ and holding it for 30 min, then heating to 950 ℃ and holding it for 90 min. Subsequently, the resulting green body is reverse-extruded at 600 ℃ with an extrusion ratio of 15:1 to obtain the Cu@RGO / Cu composite material.

[0058] Examples 2-7

[0059] The method is the same as in Example 1, except that the only difference between Examples 2 to 7 is the amount of Cu@RGO added, as detailed below:

[0060] In Example 1, the mass fraction of Cu@RGO was 0.05 wt.%;

[0061] In Example 2, the mass fraction of Cu@RGO was 0.1 wt.%;

[0062] In Example 3, the mass fraction of Cu@RGO was 0.2 wt.%.

[0063] In Example 4, the mass fraction of Cu@RGO was 0.4 wt.%.

[0064] In Example 5, the mass fraction of Cu@RGO was 0.6 wt.%;

[0065] In Example 6, the mass fraction of Cu@RGO was 0.8 wt.%;

[0066] In Example 7, the mass fraction of Cu@RGO was 1.0 wt.%.

[0067] The comprehensive properties of the composite materials obtained in Examples 1-7 are shown in Table 1.

[0068] Comparative Example 1

[0069] Comparative Example 1 used pure copper powder directly as raw material, without adding any reinforcing agents (no Cu@RGO), and prepared pure copper samples using the same powder post-treatment, cold pressing, segmented gradient sintering, hot compression treatment, and reverse extrusion molding process as Example 4. Its comprehensive properties are shown in Table 1.

[0070] Table 1. Comprehensive properties of composite materials with different Cu@RGO mass fractions and comparative sample samples

[0071] Figure 4 shows the scanning electron microscope (SEM) images of the microstructure of pure copper (Comparative Example 1) and the copper-based composite material of Example 4 of the present invention, with a copper-modified reduced graphene oxide (Cu@RGO) mass fraction of 0.4 wt.%. Figure 4(a) shows the SEM image of pure copper, and Figure 4(b) shows the SEM image of the copper-based composite material with a mass fraction of 0.4 wt.%. As shown in Table 1 and Figure 4, within the range of 0.05–1.0 wt.%, with the increase of Cu@RGO mass fraction, the tensile strength of the composite material generally shows a trend of first increasing and then decreasing, the COF shows a trend of first decreasing and then increasing, while the electrical conductivity generally shows a decreasing trend. Among them, Example 4 has the best overall performance, with a tensile strength of 276.9 MPa, an electrical conductivity of 93.99% IACS, and a COF of 0.561 ± 0.008. Compared with pure Cu in Comparative Example 1, the tensile strength of Example 4 was significantly improved, the COF was significantly reduced, and the electrical conductivity was still maintained. This indicates that the introduction of an appropriate amount of Cu@RGO is beneficial to improving the strength and wear resistance of copper-based composite materials while maintaining high electrical conductivity, thereby achieving comprehensive performance optimization.

[0072] Examples 8-9 and Comparative Example 2

[0073] To investigate the effect of powder post-processing on the properties of 0.4 wt.% Cu@RGO / Cu composite material, the 0.4 wt.% Cu@RGO / Cu system of Example 4 was selected as the subject for comparative experiments.

[0074] Example 8: Except for drying the solid product after filtration at 250 °C for 2 h under an Ar protective atmosphere, the other steps are the same as in Example 4.

[0075] Example 9: Except for drying and reducing the solid product after filtration at 250 °C for 2 h under H2 protective atmosphere, the other steps are the same as in Example 4.

[0076] Comparative Example 2: Using the same raw material system and subsequent cold pressing, sintering and reverse extrusion conditions as Example 4, the only difference was that after the liquid phase was mixed, no protective atmosphere post-treatment was performed, and conventional evaporation drying (250 ℃ × 2 h) was used to obtain a solid product.

[0077] The comprehensive properties of the composite materials obtained in Examples 8, 9 and Comparative Example 2 are shown in Table 2.

[0078] Table 2. Effect of powder post-treatment process on the properties of 0.4 wt.% Cu@RGO / Cu composite material

[0079] Table 2 shows that, under the same Cu@RGO mass fraction (0.4 wt.%), different post-treatment methods for the solid products significantly affect the tensile strength, electrical conductivity, and COF of the composite material. Compared with Comparative Example 2, which obtained the solid product using conventional evaporation drying, Examples 8 and 9, which underwent post-treatment with filtration and a protective atmosphere, exhibited higher tensile strength and electrical conductivity, and lower COF. This indicates that post-treatment with a protective atmosphere after filtration is beneficial for improving the surface state of the composite powder, reducing the influence of adverse factors during post-treatment, and further optimizing the interface bonding between the reinforcement and the copper matrix. Further comparison of Examples 8 and 9 shows that the samples post-treated with an H2 protective atmosphere exhibited higher tensile strength and electrical conductivity, and lower COF. This indicates that under the experimental conditions, a reducing atmosphere is more conducive to improving the state of the composite powder and the interface bonding, thus having a positive impact on the overall performance of the composite material.

[0080] Examples 10-11 and Comparative Example 3

[0081] To investigate the effects of hot compression insertion nodes and subsequent heat treatment paths on the properties of 0.4 wt.% Cu@RGO / Cu composite materials, a 0.4 wt.% Cu@RGO / Cu system was selected for further comparative experiments. Specifically, the process route corresponding to Example 4 was as follows: hot compression treatment was performed after holding at 950 ℃, followed by a complete round of segmented gradient sintering.

[0082] Example 10: Except that the hot compression treatment is set to be carried out after the heat preservation at 150 ℃, and a complete round of segmented gradient sintering is carried out again after the hot compression treatment, the other steps are the same as in Example 4.

[0083] Example 11: Except that the hot compression treatment is set to be carried out after the heat preservation at 650 ℃, and a complete round of segmented gradient sintering is carried out again after the hot compression treatment, the other steps are the same as in Example 4.

[0084] Comparative Example 3: The same raw material system and solid product post-processing technology as Example 4 were used. The only difference was that the hot compression treatment was set after the heat preservation at 950 °C. However, after the hot compression treatment, segmented gradient sintering was no longer performed. Instead, the product directly entered the subsequent reverse extrusion molding.

[0085] The hot compression treatment process for all the above samples was as follows: the preform was adjusted to 600 °C and held for 1 h, then pressed at 900 MPa for 1 min. The comprehensive properties of the composite materials obtained in Examples 10, 11, 4 and Comparative Example 3 are shown in Table 3.

[0086] Table 3. Effects of hot-compression insertion nodes and subsequent heat treatment path on the properties of 0.4 wt.% Cu@RGO / Cu composite materials

[0087] Table 3 shows that, under the same Cu@RGO mass fraction (0.4 wt.%), the hot compression insertion node and subsequent heat treatment path have a significant impact on the overall performance of the composite material. Compared with Comparative Example 3, which underwent hot compression after holding at 950 ℃ (the third temperature and the end of the holding period) but was not re-fired and directly reverse-extruded, Example 4 showed better performance in terms of tensile strength, electrical conductivity, and friction coefficient. This indicates that after hot compression at 950 ℃, a complete round of segmented gradient sintering is beneficial to further improve the microstructure and interfacial bonding. Further comparison of Examples 10, 11, and 4 shows that as the hot compression insertion node temperature increased from holding at 150 ℃ (the first temperature and the end of the holding period) to holding at 650 ℃ (the second temperature and the end of the holding period), and then to holding at 950 ℃ (the third temperature and the end of the holding period), the tensile strength of the samples generally increased, the electrical conductivity also generally increased, and the friction coefficient generally decreased. Among them, Example 4 showed the best overall performance, with a tensile strength of 276.9 MPa, an electrical conductivity of 93.99% IACS, and a friction coefficient of 0.561±0.008. This indicates that under the experimental conditions, setting the hot compression treatment at 950 ℃ and then performing a complete round of segmented gradient sintering is more conducive to obtaining better strength, electrical conductivity, and wear resistance.

[0088] In summary, this invention, by introducing Cu@RGO into a copper matrix and combining it with a liquid-phase mixing-filtration-protective atmosphere post-treatment process, segmented gradient sintering, and staged hot compression treatment, can achieve synergistic optimization of the strength, conductivity, and wear resistance of copper-based composite materials over a wide range of reinforcement content. The 0.4 wt.% Cu@RGO sample exhibits superior overall performance, and further optimization of the post-treatment atmosphere and hot compression insertion nodes under the 0.4 wt.% condition can continue to influence the final properties of the composite material.

[0089] The various embodiments of the present invention have now been described in detail. To avoid obscuring the concept of the invention, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions of this invention based on the above description.

[0090] While specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of the invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any manner.

Claims

1. A method for preparing a copper-based composite material, comprising the following steps: (1) Copper-modified reduced graphene oxide was mixed with copper powder and solvent in the liquid phase, and then solid-liquid separation was performed by vacuum filtration. The resulting solid product was then post-treated under a protective atmosphere to obtain composite powder. (2) The composite powder obtained in step (1) is cold-pressed to obtain a blank; (3) The blank obtained in step (2) is subjected to segmented gradient sintering, wherein the conditions for segmented gradient sintering include: heating to a first temperature and holding it at that temperature, continuing to heat to a second temperature and holding it at that temperature, and then heating to a third temperature and holding it at that temperature; hot compression treatment is performed after the holding steps at the first temperature, the second temperature, or the third temperature; after the hot compression treatment, a complete segmented gradient re-sintering is performed again, and then reverse extrusion molding is performed to obtain copper-based composite material.

2. The method for preparing the copper-based composite material according to claim 1, characterized in that, The mass fraction of copper-modified reduced graphene oxide in the obtained copper-based composite material is 0.05~1.0 wt.%, and the mass fraction is calculated based on the total mass of the obtained copper-based composite material.

3. The method for preparing the copper-based composite material according to claim 1, characterized in that, The copper powder has a particle size of 200-400 mesh and a purity of ≥99.9 wt.%.

4. The method for preparing the copper-based composite material according to claim 1, characterized in that, The conditions for liquid phase mixing include: a temperature of 25~100 ℃ and a time of 1~3 h.

5. The method for preparing the copper-based composite material according to claim 1, characterized in that, The conditions for the protective atmosphere post-treatment include: holding at 100~250 ℃ for 1~3 h under an Ar protective atmosphere; And / or, the conditions for the protective atmosphere post-treatment include: holding at 100~250 ℃ for 1~3 h under an H2 protective atmosphere.

6. The method for preparing the copper-based composite material according to claim 1, characterized in that, The conditions for cold pressing include: pressure of 600~900 MPa and time of 1~10 min.

7. The method for preparing the copper-based composite material according to claim 1, characterized in that, The conditions for the segmented gradient sintering include: heating to a first temperature of 140-160 °C and holding for 20-40 min, then heating to a second temperature of 600-700 °C and holding for 20-40 min, and finally heating to a third temperature of 900-1000 °C and holding for 80-100 min; and / or, The conditions for the segmented gradient reheating include: heating to a first temperature of 140~160 ℃ and holding for 20~40 min, continuing to heat to a second temperature of 600~700 ℃ and holding for 20~40 min, and then heating to a third temperature of 900~1000 ℃ and holding for 80~100 min.

8. The method for preparing the copper-based composite material according to claim 1, characterized in that, The conditions for the hot compression treatment include: adjusting the billet to 550~650 ℃ and holding it at that temperature for 1~2 h, and then holding it under pressure at 900~950 MPa for 1~2 min.

9. The method for preparing the copper-based composite material according to claim 1, characterized in that, The conditions for reverse extrusion molding include: a temperature of 550~650 ℃ and an extrusion ratio of 10:1~20:

1.

10. A copper-based composite material prepared by the method of any one of claims 1-9, characterized in that, In the copper-based composite material, the mass fraction of copper-modified reduced graphene oxide is 0.05~1.0 wt.%, and the mass fraction is calculated based on the total mass of the obtained copper-based composite material.

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