Copper-based graphene composite wire and preparation method thereof

Abstract

The invention provides a copper-based graphene composite wire and a preparation method thereof, and belongs to the field of metal powder processing. The copper-based graphene composite wire comprises copper filaments and a three-dimensional graphene network wrapping the copper filaments. Wherein the copper filaments comprise fibrous copper matrix grains oriented in one direction, among the oriented distributed copper matrix grains, 1t; 111gt, 111gt; the texture content is greater than or equal to 60%; the three-dimensional graphene network is of an oriented network structure of graphene distributed on a copper matrix grain boundary; the diameter of the copper-based graphene composite wire ranges from 0.01 mm to 0.5 mm, and the dislocation density is not larger than 10 < 14 > m <-2 >.

Description

Technical Field

[0001] The present invention belongs to the field of processing of metal powders, and specifically, relates to a copper-based graphene composite wire and a preparation method thereof. Background Art

[0002] Copper micro-fine wires are the main materials for manufacturing tiny wires and cables, and can be used as bonding wires for electronic packaging, data transmission lines for high-precision instruments, and wires and cables, and are widely used in fields such as electronic communication, artificial intelligence, and aerospace. With the continuous development of various electronic components towards miniaturization and integration, higher requirements are put forward for the performance of copper micro-fine wires: having higher strength, higher electrical conductivity, and high-temperature stability at the same time.

[0003] However, the intrinsic strength of pure copper is insufficient, which limits its industrial applications. Traditional preparation and processing technologies have problems such as high wire breakage rate and poor wire diameter consistency, and it is difficult to meet the high-performance requirements of copper micro-fine wires in key fields. Although traditional strengthening methods such as alloying and severe plastic deformation can improve the strength of copper materials, they will significantly reduce their functional properties such as electrical conductivity. Therefore, on the basis of maintaining high electrical and thermal conductivity and other functional properties, improving the strength of copper and its alloys and achieving a good match between strength and physical and chemical properties have always been the research hotspots and difficulties.

[0004] As a material with excellent mechanical, electrical, thermal, corrosion-resistant, and electromigration-resistant properties, graphene is regarded as an ideal reinforcement for copper-based materials. Graphene / copper composites can combine the performance advantages of copper and graphene, showing characteristics such as high strength and high conductivity, ultra-high conductivity, high thermal conductivity and low expansion, chemical stability, and electromigration resistance, and are expected to provide possible solutions to meet the urgent needs of integrated circuits and related fields for high-performance copper-based materials. In related technologies, the methods for preparing graphene / copper composites are mainly powder metallurgy and chemical vapor deposition. However, there are still huge challenges in preparing graphene / copper composite micro-fine wires on this basis. First, the preparation of wires is usually based on the drawing process under severe plastic deformation, and the combination of graphene and the copper matrix will bring complexity to the processing process. Second, in large plastic deformation, there is often an inverse relationship between strength and electrical conductivity and thermal stability.

[0005] Therefore, it is of far-reaching significance to obtain graphene / copper composite micro-fine wires with good comprehensive performance while improving the strength of graphene / copper composite micro-fine wires and maintaining high electrical conductivity and thermal stability. Summary of the Invention

[0006] In view of this, to solve at least one technical problem in related technologies and other aspects, the present invention provides a copper-based graphene composite wire, which includes copper fine wires and a three-dimensional graphene network wrapped around the copper fine wires. Among them, the copper fine wires contain fibrous copper matrix grains oriented along one direction, and in the oriented copper matrix grains, the content of <111> texture ≥ 60%; the three-dimensional graphene network is an oriented network structure of graphene distributed on the grain boundaries of the copper matrix; the diameter of the copper-based graphene composite wire is 0.01 - 0.5 mm, and the dislocation density is not greater than 10 14 m -2 。

[0007] According to an embodiment of the present invention, the orientation direction of the copper matrix grains is the drawing deformation direction of the copper wire, and the graphene presents a three-dimensional continuous oriented network structure distributed along the drawing direction on the grain boundaries of the copper matrix.

[0008] According to an embodiment of the present invention, the mass of the three-dimensional graphene network accounts for 0.01 - 1.2% of the total mass of the copper-based graphene composite wire.

[0009] According to an embodiment of the present invention, the strength of the copper-based graphene composite wire is 500 - 1000 MPa, the conductivity is 90 - 103.5% IACS, and the thermal stability temperature is greater than or equal to 600 °C.

[0010] In another aspect of the present invention, a method for preparing the aforementioned graphene composite wire is also provided, including: first, mixing copper precursor powder with a carbon source and performing heat treatment to obtain copper matrix powder coated with graphene, where the mass fraction of graphene in the copper matrix powder coated with graphene is 0.01 - 1.2%; then performing sintering treatment and pre-deformation treatment on the copper matrix powder coated with graphene to obtain a copper-based graphene composite block, where the density of the copper-based graphene composite block is greater than 90%; finally, performing a drawing operation on the copper-based graphene composite block to obtain a copper-based graphene composite wire, where the diameter of the copper-based graphene composite wire is 0.01 - 0.5 mm.

[0011] According to an embodiment of the present invention, the carbon source includes any one of a gaseous carbon source, a liquid carbon source, and a solid carbon source. Among them, the gaseous carbon source includes any one of methane and acetylene; the liquid carbon source includes any one of n-hexane and glycerol; the solid carbon source includes any one of glucose, sucrose, paraffin, and polymethacrylate.

[0012] According to an embodiment of the present invention, when the carbon source is a gaseous carbon source or a liquid carbon source, the heat treatment operation includes: mixing copper precursor powder and the gaseous carbon source or the liquid carbon source in a mixed atmosphere of hydrogen and argon, and reacting at a temperature of 500 - 700 °C for 5 - 8 min. When the carbon source is a solid carbon source, the heat treatment operation includes: first mixing the copper precursor powder with a solution of the solid carbon source, evaporating and drying at 50 - 90 °C to obtain a composite powder; then reacting the composite powder in a mixed atmosphere of hydrogen and argon at a temperature of 500 - 900 °C for 5 - 60 min.

[0013] According to an embodiment of the present invention, the particle size of the copper precursor powder is 0.5 - 100 μm, and the copper precursor powder is copper powder or copper alloy powder, wherein the copper content in the copper alloy powder is greater than 95%. The copper alloy powder includes at least one of copper - silver alloy, copper - chromium alloy, copper - tin alloy, copper - iron alloy, copper - lanthanum alloy, and copper - zirconium alloy.

[0014] According to an embodiment of the present invention, in the sintering treatment, the sintering temperature is 400 - 1000 °C, the sintering time is 0.1 - 5 h, and the sintering pressure is 20 - 200 MPa; in the pre - deformation treatment, the hot - deformation temperature is 400 - 1000 °C, the single - deformation amount is 5 - 400%, and the cumulative deformation amount is 70 - 400%.

[0015] According to an embodiment of the present invention, the drawing operation includes: first performing the first drawing on the copper - based graphene composite block to obtain a copper - based graphene composite wire with a diameter of 0.1 - 0.5 mm; wherein, during the first drawing process, the deformation amount of a single drawing pass is 10 - 20%, and the drawing speed is 0.1 - 20 m / s; then performing the second drawing on the copper - based graphene composite wire with a diameter of 0.1 - 0.5 mm to obtain a copper - based graphene composite wire with a diameter of 0.01 - 0.05 mm; wherein, during the second drawing process, the deformation amount of a single drawing pass is 5 - 10%, and the drawing speed is 5 - 50 m / s.

[0016] According to an embodiment of the present invention, a unique composite structure is formed by combining fibrous copper matrix grains with a three-dimensional graphene network. Specifically, the fibrous copper matrix grains in the copper filaments are oriented and distributed along one direction (the drawing deformation direction) to improve the mechanical strength of the wire. The <111> crystal orientation of copper has high electrical and thermal conductivity. By controlling the grain orientation of the copper filaments, the <111> texture content reaches more than 60%, reducing the inelastic scattering of electrons at the grain boundaries, which is beneficial to significantly improving the electrical and thermal conductivity of the wire. The three-dimensional graphene network uniformly wraps the copper matrix grains, presenting a three-dimensional continuous oriented network structure distributed along the drawing direction on the grain boundaries of the copper matrix. The graphene network distributed at the grain boundaries reduces the inelastic scattering of electrons at the grain boundaries, constructing an additional electron transport path, which is beneficial to effectively reducing the grain boundary resistance, thereby further improving the overall electrical conductivity of the wire. At the same time, the continuous graphene network can limit the growth of copper matrix grains, thereby improving the heat resistance and extending its service life. The copper-based graphene composite material proposed by the present invention has the characteristics of high strength (500 - 1000 MPa), high electrical conductivity (90 - 103.5% IACS), and high-temperature stability (600 °C), and its comprehensive performance is higher than that of copper and copper alloy wires / wires of the same size. Description of the Drawings

[0017] Figure 1 is a schematic diagram of the microstructure of the copper-based graphene composite wire in the embodiment of the present invention;

[0018] Figure 2 is a scanning electron microscope image of the copper-based graphene composite wire prepared in Example 1 of the present invention. Among them, a is the scanning electron microscope image of the copper-based graphene composite wire with a resolution of 20 μm, b is the scanning electron microscope image of the copper-based graphene composite wire with a resolution of 10 μm, c is the scanning electron microscope image of the copper-based graphene composite wire with a resolution of 5 μm, and d is the scanning electron microscope image of the copper-based graphene composite wire with a resolution of 2 μm;

[0019] Figure 3 is a transmission electron microscope image of the copper-based graphene composite wire prepared in Example 1 of the present invention. Among them, a is the transmission electron microscope image of the copper-based graphene composite wire with a diameter of 0.5 mm, b is the transmission electron microscope image of the copper-based graphene composite wire with a diameter of 0.05 mm, and c is the transmission electron microscope image of the interface structure between graphene and the copper matrix in the copper-based graphene composite wire with a resolution of 10 μm;

[0020] Figure 4 is the mechanical tensile curve graph of the copper-based graphene composite wire prepared in Example 1 of the present invention and pure copper;

[0021] Figure 5It is the curve graph of the hardness of the copper-based graphene composite wire and pure copper prepared in Example 1 of the present invention varying with temperature;

[0022] Figure 6 It is the curve graph of the conductivity of the copper-based graphene composite wire and pure copper prepared in Example 1 of the present invention varying with temperature;

[0023] Figure 7 It is the scanning electron microscope image of the reduced graphene oxide / copper composite wire prepared in Comparative Example 4 of the present invention. Detailed implementation manners

[0024] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific embodiments and the accompanying drawings.

[0025] In the present invention, the endpoints and any values within the disclosed ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0026] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0027] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0028] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should have the general meanings understood by those of ordinary skill in the field to which the present invention belongs. If descriptions such as "first", "second", etc. are involved throughout the text, then such descriptions of "first", "second", etc. are only used to distinguish similar objects and cannot be understood as indicating or implying their relative importance, sequence or implicitly indicating the quantity of the indicated technical features. It should be understood that the data described by "first", "second", etc. can be interchanged under appropriate circumstances.

[0029] In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the premise that those skilled in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0030] In the present invention, the meanings of the terms "relative density" and "relative density" are as follows: relative to the material itself, a material without any pores is considered to have a relative density of 100%. In powder metallurgy processes, there will be pores between metal powders, so the relative density is generally less than 100%.

[0031] In recent years, thanks to the rapid development of the field of metal matrix composites, many research progress have been made, breaking through the performance bottlenecks of traditional copper and its alloys, and initially achieving high strength and high conductivity in the laboratory field. Graphene has excellent physical and chemical properties such as high strength, low density, high thermal conductivity, and high carrier mobility. Coupled with the rich spatial designability brought by the two-dimensional structure of graphene, it is considered an ideal reinforcing phase for enhancing copper matrix composites.

[0032] In the process of implementing the present invention, it is found that introducing a three-dimensional graphene network into the copper matrix, using the excellent properties of graphene to make up for the deficiencies of the copper matrix, and by controlling the grain orientation of the copper matrix and the distribution of the graphene network, a synergistic effect can be formed between the two at the micro and nano scales, forming a multi-scale and multi-functional composite structure. The fibrous copper matrix provides the main conductive and heat-conductive channels, while the graphene network serves as an auxiliary channel and a reinforcing phase to comprehensively improve the performance of copper micro-filaments. Through the structural design of the copper-based graphene composite material, the present invention simultaneously realizes the optimization of multiple properties such as electrical conductivity, thermal conductivity, mechanical strength, and corrosion resistance, closely combines with the actual application requirements, and meets the higher requirements for material properties in fields such as electronic devices, power transmission, and aerospace.

[0033] Figure 1 It is a schematic diagram of the microstructure of the copper-based graphene composite wire in the embodiment of the present invention.

[0034] The present invention proposes a copper-based graphene composite wire, as Figure 1 shown. The copper-based graphene composite wire includes copper micro-filaments and a three-dimensional graphene network wrapped around the copper micro-filaments. Among them, the copper micro-filaments contain fibrous copper matrix grains oriented along one direction, and in the oriented distributed copper matrix grains, the content of <111> texture ≥ 60%; the three-dimensional graphene network is an oriented network structure of graphene distributed on the grain boundaries of the copper matrix.

[0035] According to an embodiment of the present invention, a unique composite structure is formed by combining fibrous copper matrix grains with a three-dimensional graphene network. Specifically, the fibrous copper matrix grains in the copper filaments are oriented and distributed in one direction to improve the mechanical strength of the wire. At the same time, the <111> crystal orientation of copper has high electrical and thermal conductivity. By controlling the grain orientation of the copper filaments, the <111> texture content reaches more than 60%, reducing the inelastic scattering of electrons at the grain boundaries, which is beneficial to significantly improve the electrical and thermal conductivity of the wire. The three-dimensional graphene network uniformly wraps around the grain boundaries of the copper matrix grains. The graphene network distributed at the grain boundaries reduces the inelastic scattering of electrons at the grain boundaries, constructing an additional electron transport path, which is beneficial to effectively reduce the grain boundary resistance, thereby further improving the overall electrical conductivity of the wire. At the same time, the continuous graphene network can limit the growth of copper matrix grains, thereby improving the heat resistance and extending its service life. The spatial distribution of graphene is a three-dimensional continuous oriented distribution network, and the distribution orientation is along the direction of drawing deformation. The reason for the good continuity of graphene is the good coordinated deformation ability of the graphene network configuration itself and the preferred processing technology of the present invention. According to an embodiment of the present invention, the copper-based graphene composite material proposed by the present invention has the characteristics of high strength (500-1000 MPa), high electrical conductivity (90-103.5% IACS), and high-temperature stability (600 °C), and its comprehensive performance is higher than that of copper and copper alloy wires / wires of the same size.

[0036] According to an embodiment of the present invention, the diameter of the copper-based graphene composite wire is 0.01-0.5 mm, for example, it can be 0.01 mm, 0.03 mm, 0.05 mm, 0.08 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, etc., and the dislocation density is not greater than 10 14 m -2 。

[0037] According to an embodiment of the present invention, the diameter range of the present invention is beneficial to meet the requirements of modern electronic devices for miniaturization and high integration, especially in applications such as high-frequency and high-speed signal transmission. At the same time, it also has good flexibility and processability, and can adapt to the wiring requirements of complex shapes. The high-density nano-twins effectively hinder the movement of dislocations, thereby improving the strength and hardness of the wire, which is beneficial to its application in application scenarios that need to withstand mechanical stress (such as the aerospace and automotive industries). At the same time, the nano-twin structure also reduces grain boundary scattering, inhibits the initiation and propagation of cracks, thereby reducing the resistivity, improving the fatigue resistance of the wire, and extending its service life. The control of the dislocation density can optimize the mechanical properties of the wire. An appropriate dislocation density can improve the strength and hardness of the material through the dislocation strengthening mechanism. However, too high a dislocation density may lead to an increase in electron scattering, thereby reducing the electrical conductivity. Therefore, the dislocation density needs to be controlled.

[0038] According to an embodiment of the present invention, by combining the limitation of the diameter of the copper-based graphene composite wire with the control of the nanotwin density and dislocation density, the performance can be synergistically optimized at the macroscopic, microscopic, and nanoscale levels. This not only improves the electrical conductivity, thermal conductivity, strength, and fatigue resistance of the wire, but also gives it significant advantages in miniaturization, high integration, and high-end application scenarios.

[0039] According to an embodiment of the present invention, the mass of the three-dimensional graphene network accounts for 0.01-1.2% of the total mass of the copper-based graphene composite wire.

[0040] According to an embodiment of the present invention, the mass fraction of graphene is limited to 0.01-1.2%, and the volume fraction is less than 4%. Within this range, while ensuring performance improvement, the usage amount of graphene can be reduced, thereby controlling production costs.

[0041] According to an embodiment of the present invention, the strength of the copper-based graphene composite wire is 500-1000 MPa, the conductivity is 90-103.5% IACS, and the thermal stability temperature is greater than or equal to 600 °C.

[0042] According to an embodiment of the present invention, the strength of the copper-based graphene composite wire proposed by the present invention can reach 500-1000 MPa, which is much higher than the strength of pure copper (the strength of pure copper is usually 200-300 MPa). This high strength enables the wire to withstand greater mechanical stress and is suitable for high-load and high-stress application scenarios. The high-strength wire is not prone to plastic deformation or fracture during long-term use, which can significantly extend the service life and reduce maintenance and replacement costs. Its conductivity reaches 90-103.5% IACS, indicating that after introducing graphene, the wire still maintains extremely high electrical conductivity and can meet the requirements of high-frequency electronic devices for low resistance and low signal loss, and is suitable for high-end applications such as 5G communication and integrated circuits. Its thermal stability temperature is greater than or equal to 600 °C, indicating that the wire can still maintain stable performance in a high-temperature environment. This is of great significance for applications in fields such as aerospace, nuclear industry, and high-temperature electronic devices. The structure of the copper-based graphene composite wire proposed by the present invention exhibits excellent mechanical, electrical, and thermal properties through the design of the texture orientation of the copper matrix grains and the synergistic effect of the three-dimensional graphene network, and can meet the requirements of various high-end applications.

[0043] In another aspect of the present invention, a method for preparing the aforementioned graphene composite wire is also provided, including: First, mixing a copper precursor powder with a carbon source and performing heat treatment to obtain a copper matrix powder coated with graphene, wherein the mass fraction of graphene in the copper matrix powder coated with graphene is 0.01 - 1.2%; then performing sintering treatment and pre-deformation treatment on the copper matrix powder coated with graphene to obtain a copper-based graphene composite block, wherein the density of the copper-based graphene composite block is greater than 90%; finally, performing a drawing operation on the copper-based graphene composite block to obtain a copper-based graphene composite wire, wherein the diameter of the copper-based graphene composite wire is 0.01 - 0.5 mm.

[0044] According to an embodiment of the present invention, through steps such as heat treatment, sintering, pre-deformation, and drawing, a copper-based graphene composite wire with excellent performance is successfully prepared. This method not only optimizes the microstructure of the wire (such as uniform distribution of graphene, fibrous grain orientation, high density, etc.), but also significantly improves the electrical conductivity, thermal conductivity, mechanical strength, thermal stability, and corrosion resistance of the wire.

[0045] In some specific embodiments, first, by mixing a copper precursor powder with a carbon source and performing heat treatment, graphene can be uniformly coated on the surface of the copper matrix powder. This distribution ensures that graphene can form a continuous three-dimensional network structure in the final wire and is uniformly distributed at the grain boundaries of the copper matrix. Then, sintering and pre-deformation are performed to increase the density of the copper-based graphene composite block before drawing, so as to reduce internal defects of the material. Finally, during the drawing process, the grains of the copper matrix form a fibrous orientation distribution along the drawing direction, especially the <111> texture content ≥ 60%. This orientation structure significantly improves the electrical conductivity, thermal conductivity, and mechanical strength of the wire. At the same time, graphene presents a three-dimensional continuous orientation network structure distributed along the drawing direction at the grain boundaries of the copper matrix, and the number of graphene layers is 1 - 10 layers. Due to the ability of the graphene network to coordinate deformation, the diameter of the copper-based graphene composite wire can be stretched to 0.01 - 0.5 mm without intermediate annealing.

[0046] In some specific embodiments, before the heat treatment, the aforementioned preparation method further includes performing a reducing pretreatment on the copper precursor powder. Specifically, the shape of the copper precursor powder can be spherical, flaky, or irregular. The copper precursor powder is heated in a tube furnace at 300 - 400 °C for 1 - 2 h, and a mixed gas of hydrogen and argon is introduced during the heating process, and the gas flow ratio can be (20 - 100):(20 - 200) mL / min.

[0047] According to an embodiment of the present invention, the carbon source includes any one of a gaseous carbon source, a liquid carbon source, and a solid carbon source. Among them, the gaseous carbon source includes any one of methane and acetylene; the liquid carbon source includes n-hexane and glycerol; the solid carbon source includes any one of glucose, sucrose, paraffin, and polymethyl methacrylate.

[0048] According to an embodiment of the present invention, when the carbon source is a gaseous carbon source or a liquid carbon source, the heat treatment operation includes: mixing copper precursor powder and the gaseous carbon source or the liquid carbon source in a mixed atmosphere of hydrogen and argon, and reacting at a temperature of 500 - 700 °C for 5 - 8 min. When the carbon source is a solid carbon source, the heat treatment operation includes: first mixing the copper precursor powder with a solution of the solid carbon source, then evaporating and drying at 50 - 90 °C to obtain a composite powder; then, in a mixed atmosphere of hydrogen and argon, reacting the composite powder at a temperature of 500 - 900 °C for 5 - 60 min.

[0049] In some specific embodiments, when the carbon source is a gaseous carbon source or a liquid carbon source, chemical vapor growth on the surface of the copper precursor powder can be directly carried out. Specifically, taking gaseous acetylene as the carbon source as an example, a mixed gas of acetylene, hydrogen, and argon is introduced into a tube furnace containing copper precursor powder. Subsequently, the tube furnace is heated to 500 - 700 °C and reacted for 5 - 8 min to obtain copper matrix powder coated with graphene.

[0050] In some specific embodiments, when the carbon source is a solid carbon source, a coating process for loading the solid carbon source precursor on the surface of copper powder needs to be added. For example, taking sucrose as the solid carbon source, 0.1 - 2 g of sucrose is dissolved in 20 - 100 mL of deionized water and 20 - 200 mL of alcohol to form an alcohol aqueous solution of sucrose. Forming the alcohol aqueous solution can improve the wettability between sucrose and the copper precursor powder, which is beneficial to the subsequent growth of graphene. Subsequently, 15 - 500 g of copper precursor powder is added to the alcohol aqueous solution of sucrose, and the mixture is stirred and heated to evaporation in a water bath at 50 - 90 °C, and then further dried in a vacuum oven at 50 - 90 °C to obtain a composite powder. Then, the composite powder is placed in a tube furnace with a powder laying thickness of 4 - 6 mm, a mixed gas of hydrogen and argon is introduced, the gas flow ratio is (20 - 100):(20 - 200) mL / min, the heating temperature is 500 - 900 °C, and the heating time is 5 - 60 min to obtain copper matrix powder coated with graphene.

[0051] According to an embodiment of the present invention, the particle size of the copper precursor powder is 0.5 - 100 μm, and the copper precursor powder is copper powder or copper alloy powder. Among them, the copper content in the copper alloy powder is greater than 95%. The copper alloy powder includes at least one of copper - silver alloy, copper - chromium alloy, copper - tin alloy, copper - iron alloy, copper - lanthanum alloy, and copper - zirconium alloy.

[0052] According to an embodiment of the present invention, in the sintering treatment, the sintering temperature is 400 - 1000 °C, the sintering time is 0.1 - 5 h, and the sintering pressure is 20 - 200 MPa; in the pre-deformation treatment, the hot deformation temperature is 400 - 1000 °C, the single deformation amount is 5 - 400%, and the cumulative deformation amount is 70 - 400%.

[0053] According to an embodiment of the present invention, in the sintering treatment, the three-dimensional continuous graphene network is formed by "welding" thousands of copper powders coated with graphene under the combined action of pressure and temperature. In order to further improve the density of the material and the dimensions suitable for subsequent drawing deformation, a copper-based graphene composite block needs to be obtained through pre-deformation treatment. Among them, the selection of appropriate temperature and deformation amount helps to maintain the integrity of the three-dimensional structure of the graphene network during the deformation process.

[0054] In some specific embodiments, the sintering treatment can be any one of cold pressing sintering, hot isostatic pressing, hot pressing sintering, and rapid hot pressing sintering, preferably hot isostatic pressing, hot pressing sintering, and rapid hot pressing sintering. The density of the copper-based graphene composite block needs to be greater than 90%, which helps subsequent processing deformation and prevents cracking. The pre-deformation treatment can be one or several of hot forging, hot extrusion, or hot rolling processes.

[0055] According to an embodiment of the present invention, the drawing operation includes: first performing a first drawing on the copper-based graphene composite block to obtain a copper-based graphene composite wire with a diameter of 0.1 - 0.5 mm; wherein, during the first drawing process, the deformation amount of a single drawing pass is 10 - 20%, and the drawing speed is 0.1 - 20 m / s; then performing a second drawing on the copper-based graphene composite wire with a diameter of 0.1 - 0.5 mm to obtain a copper-based graphene composite wire with a diameter of 0.01 - 0.05 mm; wherein, during the second drawing process, the deformation amount of a single drawing pass is 5 - 10%, and the drawing speed is 5 - 50 m / s.

[0056] According to an embodiment of the present invention, the deformation of materials usually leads to strong work hardening behavior, manifested as an increase in strength and a sharp decline in workability. Therefore, during the processing and deformation of materials, especially during the drawing process of large plastic deformation, annealing treatment is usually carried out after a certain amount of deformation to reduce the hardness of the material and improve its workability. This leads to increased process complexity and cost, and may cause oxidation of the wire during the process, reducing the surface quality of the material and causing a decrease in electrical conductivity. For the copper-based graphene composite wire in the present invention, the three-dimensional continuous graphene network strengthens the copper matrix, thus forming a copper-based graphene composite material. The graphene network has a good role in coordinating deformation. During the deformation process, the graphene network can co-deform with the copper matrix through its own interlayer slip. This characteristic can greatly improve the ductility during drawing, making it unnecessary to perform heat treatments such as annealing during the entire drawing process, and greatly improving the processing efficiency. In addition, due to the self-lubricating effect of the graphene network and the optimized processing technology, the structural integrity of the graphene network can be ensured. Finally, the graphene network in the composite wire will become an oriented network distributed along the drawing direction.

[0057] In some specific embodiments, as the drawing treatment increases the deformation amount of the copper-based graphene composite wire, the content of <111> in the copper-based graphene composite wire also shows an increasing trend. Specifically, when the diameter of the copper-based graphene composite wire is 0.1 - 0.5 mm, the content of the <111> texture is greater than 60%. When the diameter of the copper-based graphene composite wire is 0.01 - 0.05 mm, the content of the <111> texture is greater than 90%.

[0058] The following specific examples are used to illustrate the present invention. It should be noted that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0059] Example 1

[0060] Weigh 0.2 g of sucrose and dissolve it in 30 mL of deionized water. After stirring until the solution is clear, add 40 mL of alcohol and continue to stir to make it fully mixed. Subsequently, add 30 g of spherical copper powder with an average particle size of 3 - 10 μm to the sucrose alcohol aqueous solution, stir in a water bath at 75 °C until the liquid is completely evaporated, and place the obtained mixture in a vacuum oven at 70 °C and dry it for 3 h to obtain a composite powder. Then, place the obtained composite powder in a graphite boat, react with at 800 °C for 10 - 15 min, set the gas flow rate of hydrogen to 200 mL / min, and quickly cool down after the reaction is completed to obtain copper matrix powder coated with graphene.

[0061] Weigh 50 g of the copper matrix powder coated with graphene and pour it into a graphite mold with a diameter of 30 mm for hot pressing and sintering. Among them, the hot pressing temperature is set at 900 °C, the pressure is 50 MPa, and the pressure holding time is 1 h. Then, use the hot rolling deformation method to carry out densification and pre-deformation treatment on it to achieve a size suitable for drawing deformation. Hot roll the composite block at 800 °C to obtain a copper-based graphene composite block. Among them, the single-pass rolling reduction is 10%, and the total rolling reduction is 70%. Detect its composition. The graphene content in the copper-based graphene composite block is 0.3%, and the relative density is 99.8%.

[0062] Rough draw the copper-based graphene composite block to obtain a wire with a diameter (φ) of 0.5 mm. The deformation amount per pass is 10%, and the drawing speed is 5 m / s; then, through fine drawing, the composite wire is processed into a copper-based graphene composite wire with a diameter of 0.05 mm. The deformation amount per pass is 8%, and the drawing speed is 20 m / s.

[0063] Test the morphology of the copper-based graphene composite wire prepared in Example 1.

[0064] Figure 2 It is the scanning electron microscope image of the copper-based graphene composite wire prepared in Example 1 of the present invention. Among them, a is the scanning electron microscope image of the copper-based graphene composite wire with a resolution of 20 μm, b is the scanning electron microscope image of the copper-based graphene composite wire with a resolution of 10 μm, c is the scanning electron microscope image of the copper-based graphene composite wire with a resolution of 5 μm, and d is the scanning electron microscope image of the copper-based graphene composite wire with a resolution of 2 μm.

[0065] As Figure 2 shown in a of [], the surface of the copper-based graphene composite wire prepared in Example 1 of the present invention is smooth and flat, without obvious scratches and defects caused by processing, which structurally guarantees the service life and avoids energy loss when used as a wire. As Figure 2 shown in b-d of [], the three-dimensional graphene network is evenly distributed and completely wraps the fibrous copper matrix grains.

[0066] Figure 3 It is the transmission electron microscope image of the copper-based graphene composite wire prepared in Example 1 of the present invention. Among them, a is the transmission electron microscope image of the copper-based graphene composite wire with a diameter of 0.5 mm, b is the transmission electron microscope image of the copper-based graphene composite wire with a diameter of 0.05 mm, and c is the transmission electron microscope image of the interface structure between graphene and the copper matrix in the copper-based graphene composite wire at a resolution of 10 μm.

[0067] As Figure 3As shown in a-c, in the copper-based graphene composite wire, the grains of the copper matrix are elongated along the direction of drawing deformation and form fibrous grains. Graphene is distributed at the grain boundaries of the copper matrix, showing a continuous network distribution. The interface between the in-situ synthesized graphene and the copper matrix is tightly and cleanly bonded, which helps to improve the strength and conductivity of the copper-based graphene. In addition, a high density of nanotwins is found inside the grains of the copper-based graphene composite wire prepared in the present invention, which improves the strength of the material without reducing the conductivity of the material. Specifically, as Figure 3 in a and Figure 3 in b, it can be seen that with the increase of the deformation amount, the nanotwins in the copper-based graphene composite wire continuously increase. Further, the mechanical properties, thermal stability and electrical properties of the copper-based graphene composite wire prepared in Example 1 were tested.

[0068] Figure 4 is the mechanical tensile curve of the copper-based graphene composite wire (denoted as graphene / copper, the same below) and pure copper (denoted as pure copper, the same below) prepared in Example 1 of the present invention.

[0069] As Figure 4 shown, the stress of the two materials gradually increases with the strain. Among them, the copper-based graphene composite wire has an obvious yield platform after reaching about 800 MPa, showing typical plastic deformation characteristics; pure copper fractures after the stress rapidly rises to about 450 MPa. It can be seen that the copper-based graphene composite wire proposed in the present invention has better mechanical properties. The three-dimensional graphene network is distributed at the grain boundaries of the copper matrix grains, hindering the movement of dislocations and coordinating plastic deformation. At the same time, the good interface bonding between graphene and the copper matrix relieves stress concentration and improves the overall strength.

[0070] The change of the hardness of the copper-based graphene composite wire and the pure copper microfilament with temperature after annealing at different temperatures for 1 h was tested.

[0071] Figure 5 is the change curve of the hardness of the copper-based graphene composite wire and pure copper prepared in Example 1 of the present invention with temperature.

[0072] As Figure 5 shown, the thermal stability temperatures of the copper-based graphene composite wire and the pure copper microfilament are 600 °C and 200 °C respectively, verifying the excellent thermal stability of the copper-based graphene composite wire proposed in the present invention. Among them, the meaning of the thermal stability temperature is: for metal materials, it is generally considered that the temperature at which the hardness of the material can still maintain 80% of the hardness of the unheat-treated material after annealing for 1 h is the anti-softening temperature of the material, that is, the thermal stability temperature of the material.

[0073] The change of the conductivity of the hardness of the copper-based graphene composite wire and the pure copper microfilament with temperature after annealing at different temperatures for 1 h was tested.

[0074] Figure 6 It is a graph showing the variation of the electrical conductivity of the copper-based graphene composite wire and pure copper prepared in Example 1 of the present invention with temperature.

[0075] As Figure 6 shown, the electrical conductivities of both show a trend of first increasing and then decreasing with the increase of the annealing temperature. The difference is that the electrical conductivity of the copper-based graphene composite wire reaches the highest value at 600 °C, while that of the pure copper micro wire reaches the highest value at 200 °C. The reason for the increase in the electrical conductivity of both materials is that the dislocation density of the materials decreases after annealing. The different temperature inflection points are due to the different thermal stabilities of the two materials. The graphene / copper micro wire can still maintain a fibrous grain structure after annealing at 600 °C, while pure copper cannot maintain such a grain structure, thus increasing the electron scattering at the grain boundaries and resulting in a decrease in electrical conductivity.

[0076] Example 2

[0077] In this Example 2, the preparation method of the copper-based graphene composite wire is the same as or similar to that of Example 1. The difference from Example 1 is that in this Example 2, the average particle size of the copper precursor powder is 1 - 3 μm.

[0078] Example 3

[0079] In this Example 3, the preparation method of the copper-based graphene composite wire is the same as or similar to that of Example 1. The difference from Example 1 is that in this Example 3, the average particle size of the copper precursor powder is 10 - 40 μm.

[0080] Example 4

[0081] In this Example 4, the preparation method of the copper-based graphene composite wire is the same as or similar to that of Example 1. The difference from Example 1 is that in this Example 4, the pre-deformation method is hot extrusion. Among them, the extrusion temperature is 950 °C and the extrusion ratio is 16:1.

[0082] Example 5

[0083] In this Example 5, the preparation method of the copper-based graphene composite wire is the same as or similar to that of Example 1. The difference from Example 1 is that in this Example 5, the solid carbon source is 0.1 g of sucrose, and the graphene content in the prepared copper-based graphene composite wire is 0.1%.

[0084] Example 6

[0085] In this Example 6, the preparation method of the copper-based graphene composite wire is the same as or similar to that of Example 1. The difference from Example 1 is that in this Example 6, the solid carbon source is 0.4 g of sucrose, and the graphene content in the prepared copper-based graphene composite wire is 0.5%.

[0086] Example 7

[0087] In this Example 7, the preparation method of the copper-based graphene composite wire is the same as or similar to that of Example 1. Different from Example 1, the diameter of the finally obtained copper-based graphene composite wire in this Example 7 is 0.5 mm.

[0088] Example 8

[0089] In this Example 8, the preparation method of the copper-based graphene composite wire is the same as or similar to that of Example 1. Different from Example 1, the copper precursor powder in this Example 8 is irregular copper powder.

[0090] Example 9

[0091] In this Example 9, the preparation method of the copper-based graphene composite wire is the same as or similar to that of Example 1. Different from Example 1, the copper precursor powder in this Example 9 is copper-silver alloy powder, in which the silver content is 1% and the copper content is 99%.

[0092] Comparative Example 1

[0093] In this Comparative Example 1, the preparation method of the graphene-copper composite material is the same as or similar to that of Example 1. Different from Example 1, the graphene-copper composite material in this Comparative Example 1 is a composite wire with a diameter of 2 mm. Among them, during the drawing process, the deformation amount per pass is 20% and the drawing speed is 20 m / s.

[0094] Comparative Example 2

[0095] In this Comparative Example 2, the preparation method of the graphene-copper composite material is the same as or similar to that of Example 1. Different from Example 1, the graphene-copper composite material in this Comparative Example 2 is a composite wire with a diameter of 1 mm.

[0096] Comparative Example 3

[0097] In this Comparative Example 3, the preparation method of the graphene-copper-based composite material is as follows, where copper exists in the form of a copper-lanthanum alloy.

[0098] Take 50 g of spherical copper-lanthanum alloy powder with an average particle size of 3 - 5 μm (lanthanum content is 0.5% and copper content is 99.5%), and lay it flat in a rotary tube furnace. After the vacuum in the tube furnace reaches 1×10 -1 Torr, introduce a mixed gas of acetylene, hydrogen and argon with a ratio of 30:20:30 sccm. Among them, acetylene is used as the gas carbon source. Subsequently, heat the system to 500 - 700 °C and react for 5 - 8 min to deposit graphene on the surface of the copper-lanthanum alloy powder to obtain graphene / copper-lanthanum alloy composite powder with a graphene content of 0.3%.

[0099] Then, according to the processing technology in Example 4, the graphene / copper lanthanum alloy composite powder is processed to obtain a graphene / copper lanthanum composite wire with a diameter of 0.8 mm.

[0100] Comparative Example 4

[0101] In this Comparative Example 4, a reduced graphene oxide / copper composite wire is prepared. Its preparation method is the same as or similar to that of Example 1. The difference from Example 1 is that in this Comparative Example 4, the carbon source is 0.2 g of graphene oxide nanosheets with a thickness of 5 layers and a planar size of 100 - 200 nm, and the diameter of the reduced graphene oxide / copper composite wire is 0.5 mm.

[0102] Test the morphology of the reduced graphene oxide / copper composite wire prepared in Comparative Example 4.

[0103] Figure 7 It is the scanning electron microscope image of the reduced graphene oxide / copper composite wire prepared in Comparative Example 4 of the present invention.

[0104] As Figure 7 shown, in the composite wire prepared by the external addition method in Comparative Example 4, the existence form of graphene is graphene sheets. Compared with the foregoing Figure 2 it can be seen that the distribution of graphene in the composite wire prepared by the external addition method in Comparative Example 4 and the graphene in the composite wire prepared by the in-situ synthesis method in Example 1 of the present invention are significantly different. The graphene in the composite wire prepared by the external addition method in Comparative Example 4 is scattered in the copper matrix, and there is no synergistic improvement in the good processability and performance brought by the graphene network. At the same time, the graphene / copper composite wire prepared by the external addition method can only be processed to a diameter of 0.5 mm and cannot be further processed into a micro-fine wire with a diameter of 0.05 mm. Its performance is basically the same as that of pure copper of the same size, and there is no performance improvement.

[0105] Comprehensively test the properties of the materials prepared in the above Examples 1 - 9 and Comparative Examples 1 - 4, and the results are recorded in Table 1 below.

[0106] Table 1

[0107] Strength (MPa) Conductivity (%IACS) Thermal stability (°C) Pure copper 460 97.3 200 Example 1 909 99.4 600 Example 2 755 99.4 600 Example 3 680 100 600 Example 4 870 99 600 Example 5 712 100 600 Example 6 762 100 600 Example 7 576 97.6 600 Example 8 608 99 600 Example 9 810 90 500 Comparative Example 1 413 94.5 500 Comparative Example 2 446 95.6 600 Comparative Example 3 333 87.5 400 Comparative Example 4 391 95.8 200

[0108] As shown in Table 1, the copper-based graphene composite wire proposed by the present invention has the characteristics of high strength (500 - 1000 MPa), high conductivity (90 - 103.5% IACS), and high-temperature stability (600 °C), and its comprehensive performance is higher than that of copper and copper alloy wires / wires of the same size.

[0109] The specific embodiments described above further elaborate on the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc., made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A copper-based graphene composite wire, characterized in that: The copper-based graphene composite wire comprises: A copper filament comprising fibrous copper matrix grains oriented in one direction, and A three-dimensional graphene network wrapped on the copper filament, wherein the three-dimensional graphene network is an oriented network structure of graphene distributed on the grain boundaries of the copper matrix, Among them, in the oriented copper matrix grains, <111> Texture content ≥ 60%; The diameter of the copper-based graphene composite wire is 0.01-0.5 mm, and the dislocation density is not more than 10 14 m -2 .

2. The copper-based graphene composite wire according to claim 1, characterized in that: The mass of the three-dimensional graphene network accounts for 0.01-1.2% of the total mass of the copper-based graphene composite wire.

3. The copper-based graphene composite wire according to claim 1, characterized in that: The copper-based graphene composite wire has a strength of 500-1000 MPa, a conductivity of 90-103.5% IACS, and a thermal stability temperature greater than or equal to 600°C.

4. A method for preparing a copper-based graphene composite wire according to any one of claims 1 to 3, characterized in that: The preparation method comprises: The copper precursor powder is mixed with a carbon source and subjected to heat treatment to obtain a graphene-coated copper matrix powder, wherein the mass fraction of graphene in the graphene-coated copper matrix powder is 0.01-1.2%; The copper-based graphene-coated powder is sintered and pre-deformed to obtain a copper-based graphene composite block, wherein the density of the copper-based graphene composite block is greater than 90%; The copper-based graphene composite block is subjected to a drawing operation to obtain a copper-based graphene composite wire, wherein the diameter of the copper-based graphene composite wire is 0.01-0.5 mm.

5. The preparation method according to claim 4, characterized in that: The carbon source includes any one of a gaseous carbon source, a liquid carbon source, and a solid carbon source; wherein, The gaseous carbon source includes any one of methane and acetylene; The liquid carbon source includes any one of n-hexane and glycerol; The solid carbon source includes any one of glucose, sucrose, paraffin and polymethyl methacrylate.

6. The preparation method according to claim 5, characterized in that: In the case where the carbon source is the gaseous carbon source or the liquid carbon source, the heat treatment operation includes: In a mixed atmosphere of hydrogen and argon, the copper precursor powder and the gaseous carbon source or the liquid carbon source are mixed and reacted at a temperature of 500-700° C. for 5-8 minutes; In the case where the carbon source is the solid carbon source, the heat treatment operation includes: After mixing the copper precursor powder with the solution of the solid carbon source, evaporating and drying at 50-90° C. to obtain a composite powder; The composite powder is reacted at a temperature of 500-900° C. for 5-60 minutes in a mixed atmosphere of hydrogen and argon.

7. The preparation method according to claim 4, characterized in that: The particle size of the copper precursor powder is 0.5-100 μm, and the copper precursor powder is copper powder or copper alloy powder, wherein the copper content in the copper alloy powder is greater than 95%; The copper alloy powder includes at least one of copper-silver alloy, copper-chromium alloy, copper-tin alloy, copper-iron alloy, copper-lanthanum alloy and copper-zirconium alloy.

8. The preparation method according to claim 4, characterized in that: In the sintering process, the sintering temperature is 400-1000° C., the sintering time is 0.1-5 h, and the sintering pressure is 20-200 MPa; In the pre-deformation treatment, the thermal deformation temperature is 400-1000° C., the single deformation amount is 5-400%, and the cumulative deformation amount is 70-400%.

9. The preparation method according to claim 4, characterized in that: The drawing operation includes: The copper-based graphene composite block is subjected to a first drawing to obtain a copper-based graphene composite wire having a diameter of 0.1-0.5 mm; wherein, during the first drawing process, the deformation amount of a single drawing pass is 10-20%, and the drawing speed is 0.1-20 m / s; The copper-based graphene composite wire with a diameter of 0.1-0.5 mm is drawn for a second time to obtain the copper-based graphene composite wire with a diameter of 0.01-0.05 mm; wherein, during the second drawing process, the deformation amount of a single drawing pass is 5-10%, and the drawing speed is 5-50 m / s.

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