A high-strength, high-conductivity graphene-metal composite wire, its preparation method, and its applications.

Abstract

This invention relates to the field of composite material preparation technology, specifically to a high-strength, high-conductivity graphene-metal composite wire and its preparation method and application, comprising: S1, constructing a vacuum working space, the working space including a growth zone and a drawing zone; S2, a metal wire, after surface pretreatment, continuously flows through the growth zone and the drawing zone sequentially, wherein the growth zone grows graphene in situ on the metal wire using a dynamic continuous CVD process, and the drawing zone simultaneously performs a drawing process on the metal wire; S3, the metal wire flowing out of the working space is continued to be transported back to the working space, and the growth and drawing are repeated n times to obtain the graphene-metal composite wire. Based on the synchronous take-up and unwinding of the metal wire, it achieves continuous flow through the growth zone and the drawing zone sequentially, thereby enabling dynamic, continuous, in-situ growth of graphene on the surface of the growth zone, avoiding grain coarsening caused by high-temperature annealing in traditional static growth and reducing strength loss.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology, and in particular to a high-strength, high-conductivity graphene-metal composite wire, its preparation method, and its application. Background Technology

[0002] Metal wires (such as copper, aluminum, and silver) are widely used as conductor materials in electrical engineering and manufacturing due to their excellent conductivity, ductility, and flexibility. Among them, copper wire, with its low resistivity, high tensile strength, and good process adaptability, has become a core application material. However, traditional copper wire suffers from a contradiction between its mechanical properties and conductivity. When alloying to improve the strength of copper wire, such as adding silver or magnesium, its conductivity is significantly reduced. Conversely, when improving the strength of copper wire through surface coatings, such as carbon nanotube coating, problems such as weak interfacial bonding and coating peeling easily occur, leading to unstable performance. Graphene, as a high-strength (130 GPa) and high-conductivity (10⁻⁶ GPa) copper wire, offers a solution. 6 Two-dimensional materials with a strength and conductivity of (S / m) can theoretically improve the strength and conductivity of metal wires simultaneously; however, traditional composite processes, such as powder metallurgy and cold pressing after chemical vapor deposition, generally suffer from the following problems:

[0003] (1) Graphene is prone to agglomeration and is difficult to distribute uniformly in a metal matrix;

[0004] (2) The interface between graphene and metal is not tightly bonded and has defects such as pores, which prevents it from fully exerting its reinforcing effect;

[0005] (3) The process is carried out in steps (graphene is prepared first and then composited), which is complex and has low production efficiency, making it difficult to meet the needs of continuous industrial production.

[0006] Patent CN110745815A discloses a method for preparing graphene-metal composite wires, based on the twisting, tensioning, drawing, and forming of multi-strand metal wires. However, this method has the following drawbacks:

[0007] First, operating multiple strands of wire simultaneously, from twisting to drawing, makes the process more complex, making continuous production impossible and resulting in low production efficiency.

[0008] Second, some processes are carried out in the air. When the surface of the metal wire is exposed to the air, it absorbs oxygen, organic matter and dust from the air, which reduces the bonding between the metal wire and graphene.

[0009] Third, a static method is used to grow graphene on the surface of the original metal wire through chemical vapor deposition. Static growth, due to long-term high-temperature annealing, provides thermodynamic conditions for coarsening of copper grains and weakens strength.

[0010] Fourth, there is a lack of consistent and reasonable working conditions. For example, after growing graphene at around 1000℃, cold drawing is then carried out. Copper has low plasticity at room temperature, so more external force is required during drawing, and the amount of deformation per step is limited (usually ≤20%). If it exceeds this, it is prone to breakage. In addition, the process time is also longer.

[0011] Fifth, in practical applications, under complex processes, a sufficient number of drawing cycles (15-20 cycles) are required to achieve a tensile strength of only around 210 MPa.

[0012] This invention provides a high-strength, high-conductivity graphene-metal composite wire, its preparation method, and its application, to solve the problems of complex processes, severe graphene agglomeration, and reduced performance of composite wires in existing technologies. Summary of the Invention

[0013] The purpose of this invention is to provide a high-strength, high-conductivity graphene-metal composite wire, its preparation method, and its application, in order to solve the problems of complex processes, severe graphene agglomeration, and reduced performance of composite wires in existing technologies.

[0014] The technical solution of this invention is: a method for preparing high-strength, high-conductivity graphene-metal composite wire, comprising the following steps:

[0015] S1. Construct a vacuum-condition workspace, which includes a growth zone and a drawing zone;

[0016] S2. The metal wires after surface pretreatment flow continuously through the growth zone and the drawing zone. The growth zone grows graphene in situ on the metal wires based on a dynamic continuous CVD process, and the drawing zone simultaneously performs the drawing of the metal wires.

[0017] S3. The metal wire flowing out of the workspace is continued to be transported to the workspace, and the growth and drawing are repeated n times to obtain the graphene-metal composite wire.

[0018] Preferably, the temperature within the growth zone is configured as a gradually decreasing temperature sequence along the flow direction of the metal wire.

[0019] Preferably, the temperature in the growth zone is 400-1000℃, and the gradually decreasing temperature sequence creates at least three temperature spaces within the growth zone.

[0020] Preferably, the number of passes n for the growth and drawing of the metal wire in the working space growth area is an integer between 3 and 10, and the surface reduction rate per pass is controlled between 5% and 25%.

[0021] Preferably, the reduction rate of the metal wire decreases gradually with each pass;

[0022] The growth and pulling process is divided into early stages and late stages. The area reduction rate of the early stages is 15%-25%, and the area reduction rate of the late stages is 5%-15%.

[0023] Preferably, the temperature of the drawing zone is controlled within the range of 200-800℃, and the temperature in the drawing zone is lower than the end temperature value of the temperature sequence in the growth zone.

[0024] Preferably, the drawing speed in the drawing zone is 5–40 m / min.

[0025] Preferably, the electrical conductivity of the graphene-metal composite wire is not less than 102% IACS, the tensile strength is maintained in the range of 240-350MPa, and the elongation at break is maintained in the range of 25-36%.

[0026] Preferably, after the metal wire undergoes n rounds of growth and drawing, it continues to flow through the growth zone for regeneration treatment to eliminate internal stress and grow another layer of graphene.

[0027] Preferably, a mixed gas, including a carrier gas and a carbon source, is introduced into the growth zone;

[0028] The gas flow rate of the mixed gas is 50–500 sccm, and the pressure in the growth zone is maintained in the range of 10–100 Pa; the carrier gas is an inert gas and / or a reducing gas; the reducing gas includes hydrogen; the carbon source is any one or more of methane, acetylene, ethanol, propylene, and benzene.

[0029] Preferably, the surface pretreatment of the metal wire includes degreasing and pickling.

[0030] The present invention also provides a high-strength, high-conductivity graphene-metal composite wire, which is prepared by the above-described preparation method.

[0031] The present invention also provides the application of the above-mentioned high-strength and high-conductivity graphene-metal composite wire in high-frequency current transmission and energy storage. Compared with traditional metal wire, the AC resistance of the graphene-metal composite wire is reduced by 3%-18% in the frequency range of 1kHz-100kHz.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] (1) Based on the synchronous take-up and unwinding of metal wires, the wires flow continuously through the growth zone and the drawing zone, thereby enabling the metal wires to grow graphene dynamically and continuously in situ on the surface of the growth zone, avoiding grain coarsening caused by high-temperature annealing in traditional static growth and reducing strength loss; the metal wires are drawn online synchronously in the drawing zone; while growing graphene, the drawing force can make the graphene better bond with the metal matrix, and promote the uniform distribution and orientation of graphene in the metal matrix, effectively solving the problem of graphene agglomeration, while improving production efficiency and facilitating large-scale industrial production.

[0034] (2) By simultaneously growing and drawing, graphene is uniformly distributed and oriented in the metal matrix, which avoids the performance fluctuations caused by graphene agglomeration in traditional processes. It also utilizes the high strength and high electron mobility of graphene to simultaneously improve the strength and conductivity of graphene-metal composite wires, breaking through the bottleneck of "strength and conductivity cannot be obtained at the same time" in traditional metal materials. At the same time, it significantly improves the skin effect in high-frequency current transmission. Specifically, the AC resistance is reduced, and the higher the frequency, the more significant the advantage of resisting the skin effect.

[0035] (3) The working space used for growth and drawing is a vacuum condition, which can prevent the graphene on the surface of the metal wire from adsorbing oxygen, organic matter and dust in the air when exposed to air, thus preventing it from being oxidized and effectively improving the interface between the metal wire and the graphene.

[0036] (4) The temperature in the growth zone forms a gradually decreasing temperature sequence, which helps to achieve high-quality growth of graphene, so that graphene has good crystallinity and structural integrity. At the same time, it is also beneficial to adjust the interfacial bonding strength between graphene and metal matrix. Through the action of different temperature stages, specific crystal structures or surface activities will be induced on the surface of metal matrix, promoting the bonding between graphene and metal.

[0037] (5) The gradually decreasing temperature sequence can also achieve a high temperature at the front end to eliminate the oxide layer of the metal wire to ensure better graphene deposition, and a low temperature output at the back end to achieve the effect of rapid cooling of the metal wire. However, the temperature is still maintained in the range of 200-800℃, which will not cause wire breakage. It can also reduce the defects generated during the wire drawing process and does not require the use of wire drawing oil or other substances.

[0038] (6) The growth and drawing of n-pass metal wires can not only improve the uniformity of graphene distribution and promote the directional aggregation of graphene inside the copper wire, but also build a stable strong interface bond. Through the synergistic strengthening mechanism of graphene and copper matrix, while maintaining the conductivity ≥102%-105%IACS, the tensile strength ≥240-350MPa and the elongation at break ≥25-36% can be achieved, thus enabling its application in high-frequency current transmission and energy storage. Attached Figure Description

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0040] Figure 1 This is a flowchart of the preparation method of the high-strength and high-conductivity graphene-metal composite wire according to the present invention;

[0041] Figure 2 The changes in wire conductivity obtained in Embodiment 1 and Comparative Example 1 of the present invention;

[0042] Figure 3 The change in elongation at break of the wire after each drawing pass is shown in Embodiment 1 and Comparative Example 1 of the present invention.

[0043] Figure 4 The tensile strength change of the wire after each drawing pass obtained in Embodiment 1 and Comparative Example 1 of the present invention;

[0044] Figure 5 The AC resistance of the wires obtained in Embodiment 1 and Comparative Example 1 of the present invention increases from 1kHz to 100kHz. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to specific embodiments:

[0046] A method for preparing a high-strength, high-conductivity graphene-metal composite wire, the method comprising the following steps:

[0047] S1. Construct a vacuum-conditioned workspace. This workspace includes a growth zone and a drawing zone. The growth zone is located at the front end of the workspace, and the drawing zone is located at the rear end. The metal wire is continuously fed into the workspace from the end closest to the growth zone, flows sequentially through the growth zone and the drawing zone, and is then wound up and output at the rear end of the workspace. Before using this workspace to produce high-strength, high-conductivity graphene-metal composite wires, a drawing die with a suitable aperture needs to be selected based on the diameter of the metal wire to assemble the workspace. A mixed gas, including a carrier gas and a carbon source, is introduced into the growth zone. The carrier gas is one or more of inert or reducing gases such as argon, nitrogen, and hydrogen, preferably a mixture of argon and hydrogen with a volume ratio of (2-10):1. The carbon source is any one or more of hydrocarbon gases such as ethanol, methane, acetylene, propylene, and benzene, or other organic gases, preferably hydrocarbon gases such as propylene and acetylene with a purity ≥99.9%. The flow rate of the mixed gas is controlled within the range of 50-500 sccm, and preferably within the range of 200-300 sccm, to ensure uniform distribution of the carbon source in the heating zone and provide a stable carbon source for graphene growth. During the gas generation and subsequent growth process, the pressure within the growth zone is consistently maintained within the range of 10–100 Pa; the temperature within the growth zone is controlled within the range of 400–1000 °C. Furthermore, to ensure better graphene deposition on the metal wire surface, the growth zone can be designed as a gradient temperature zone, where the temperature gradually decreases along the flow direction of the metal wire. This gradient temperature zone design allows the metal wire to pass through a high-temperature zone before being transported to the growth zone, where the oxide layer on the metal wire surface is removed, ensuring better graphene deposition. After continuous in-situ graphene growth, the wire is then cooled rapidly by exiting from a low-temperature zone. This gradient temperature zone design not only helps to precisely control the temperature within the growth zone, thus effectively achieving high-quality graphene growth with good crystallinity and structural integrity, but also helps to regulate the interfacial bonding strength between graphene and the metal matrix. In addition, the effects of different temperature stages may induce specific crystal structures or surface activities on the metal substrate surface, promoting the bonding between graphene and the metal substrate. Furthermore, within the growth zone, a gradually decreasing temperature sequence is preferred to create at least three temperature spaces within the growth zone.

[0048] In addition, a cooling zone can be added inside the workspace according to actual production needs. The cooling zone is located in the middle of the furnace body and is connected to the growth zone at the front and the drawing zone at the end. The temperature in the cooling zone is set at 200-400℃. At this time, the metal wire continuously transported to the workspace flows through the growth zone, cooling zone and drawing zone. The metal wire after being processed in the growth zone is first rapidly cooled down to 200-400℃ before being drawn. This can prevent the metal wire from breaking due to excessive temperature during the drawing process, ensuring the continuity, stability and quality of the production process.

[0049] S2. First, select raw metal wires of suitable specifications, such as copper wires, aluminum wires, etc., and pre-treat their surfaces by degreasing and pickling. For degreasing, a mixture of ethanol and deionized water is preferred as the cleaning agent, and ultrasonic cleaning is performed for 10-15 minutes. For pickling, a 5-10 wt% dilute sulfuric acid solution is preferred as the cleaning agent, and cleaning is performed for 5-8 minutes. This pre-treatment is used to deeply remove oil, oxide layers, and impurities adhering to the surface of the metal wires, thereby significantly improving the microstructure and chemical state of the metal wire surface. This creates favorable conditions and provides active sites for the subsequent in-situ growth of high-quality graphene on the metal wire surface, ensuring the quality and stability of graphene growth. Then, the pre-treated metal wires are continuously... The metal wire is continuously fed from the front end of the working space into the working space, passing through the growth zone and the drawing zone in sequence. Based on the dynamic continuous CVD process, dynamic and continuous in-situ growth is performed in the growth zone inside the working space to achieve the effect of in-situ growth of graphene on the surface of the metal wire. At the same time, the deposited metal wire is output from the output end of the growth zone in the working space and immediately transported to the drawing zone. In the drawing zone, the metal wire is simultaneously drawn under vacuum and high temperature conditions. Through the drawing process and the extrusion of the die, the diameter of the metal wire can be reduced, and the graphene grown in situ on the surface of the metal wire can be embedded into the metal wire, promoting the formation of a tight interface between the graphene and the metal. This process design, which combines growth and drawing simultaneously, allows graphene to better bond with the metal matrix through drawing force while it is growing. It also promotes the uniform distribution and orientation of graphene in the metal matrix, effectively solving the problem of graphene agglomeration and thus significantly improving the conductivity and strength of the metal wire. During the dynamic continuous in-situ growth process, the metal wire is preferably fed into the growth zone at a uniform speed of 0.5-2 m / min and output from the growth zone at the same speed to ensure uniform coverage of the graphene layer. The pressure within the growth zone of the working space needs to be maintained within the range of 10-100 Pa. During the drawing process, the drawing speed needs to be controlled between 5-40 m / min, preferably 10-20 m / min. The temperature of the drawing zone is controlled within the range of 200-800℃, and the temperature within the drawing zone is lower than the end temperature value of the temperature sequence within the growth zone. The temperature within the drawing zone can also be adjusted reasonably according to the material of the metal wire; for example, when the metal wire is copper, the temperature within the drawing zone is preferably 300-500℃. Performing the drawing operation under vacuum and high-temperature conditions not only effectively avoids wire breakage during the drawing process but also helps reduce defects in the metal substrate during wire drawing. It eliminates the need for auxiliary substances such as drawing oil, thus significantly saving preparation costs.

[0050] S3, such as Figure 1 As shown, the metal wire flowing out of the working space is continuously fed back into the working space, and the growth and drawing process is repeated n times to obtain a graphene-metal composite wire. That is, every time graphene is dynamically grown in the growth zone inside the working space, a drawing operation is immediately performed. After repeating n times, the finished graphene-metal composite wire is obtained. The number of drawing passes needs to be determined based on the original diameter and target diameter of the metal wire. As the number of drawing passes increases, the diameter of the metal wire gradually decreases, and the degree of graphene aggregation inside the metal wire continuously deepens. The number of passes is determined based on the final required performance and diameter of the metal wire, generally ranging from 3 to 10 passes. To form an effective interfacial bonding network on the metal wire surface, a minimum of 4 passes is preferred; 5-8 passes are most preferred. The area reduction rate per pass is controlled between 5% and 25%. Furthermore, it is preferable to adopt a gradually decreasing strategy for the area reduction rate per pass, dividing the growth and drawing processes into early and late passes, with the early passes having an area reduction rate of 15%-25% and the late passes having an area reduction rate of 5%. -15%; In the early stages, under high-temperature conditions, the metal wire exhibits high plasticity, and larger deformation promotes atomic diffusion between graphene and the metal wire, forming a Cu-C interface transition layer with a thickness of approximately 2–5 nm; simultaneously, it avoids excessive damage to the graphene. In later stages, mechanical anchoring is the primary method, and smaller deformation prevents wire breakage. Simultaneously, the accumulation of multiple small deformations gradually "breaks" and evenly disperses the graphene sheets, promoting directional alignment of graphene within the matrix (along the wire axis) and preventing agglomeration. Furthermore, after drawing, transporting the metal wire to the growth zone for in-situ graphene growth is equivalent to performing an annealing treatment on the metal wire. Dynamic and continuous in-situ graphene layer formation on the metal wire surface avoids grain coarsening caused by high-temperature annealing during traditional static growth, thus reducing strength loss in the metal wire. According to the Hall-Petch relation, as grain size increases, the yield strength and tensile strength of a material decrease significantly. This is because smaller grain sizes result in more grain boundaries, which in turn hinder dislocation movement, thus increasing the material's strength. For traditional alloys, electrical conductivity and strength cannot be simultaneously achieved due to grain size limitations. This application utilizes the high strength and excellent conductivity of graphene to bond graphene to a metal matrix in a vacuum environment. This eliminates the barrier to electron transfer between the metal matrix and graphene interface. Furthermore, drawing allows graphene to be oriented within the metal substrate, achieving a simultaneous enhancement of both conductivity and strength.

[0051] To further improve the performance of graphene-metal composite wires, the graphene-metal composite wires obtained after n repeated growth and drawing processes can be further processed by flowing through the growth zone for regrowth treatment. This process eliminates internal stress in the graphene-metal composite wires and allows for the growth of another layer of graphene on the surface of the wires. The regrowth treatment temperature is set at 200–400℃, preferably 300℃, and the treatment time is 30–120 min, preferably 60 min. This process not only allows for in-situ growth of graphene on the surface of the semi-finished metal wire, repairing defects in the graphene layer during drawing, but also enables annealing of the metal wire to eliminate internal stress generated during drawing, further reducing internal stress in the metal matrix and thus optimizing the overall performance of the metal wire.

[0052] The graphene-metal composite wires prepared using the above method exhibit significantly improved strength and conductivity compared to the original metal wires due to the uniform distribution and tight bonding of graphene. Tests show that tensile strength is increased by 30%-50% and electrical conductivity by 2%-8%, meeting the stringent requirements of aerospace and high-end electronic equipment for high-performance metal wires. Furthermore, this preparation method offers strong controllability. By precisely controlling parameters such as temperature, pressure, and gas flow in the growth zone, as well as drawing speed and die aperture in the drawing zone, the growth of graphene and the drawing process of the metal wires can be flexibly adjusted, thereby precisely controlling the performance of the graphene-metal composite wires to meet the needs of different application scenarios. The entire process of this preparation method achieves continuous operation, reducing manual intervention and material transfer in intermediate stages, increasing production efficiency by more than 40% compared to traditional step-by-step processes. It is suitable for large-scale industrial applications and has significant economic benefits.

[0053] This invention also provides a high-strength, high-conductivity graphene-metal composite wire, which is prepared using the above-described method. This high-strength, high-conductivity graphene-metal composite wire can be applied to high-frequency current transmission, energy storage, and other fields.

[0054] This invention also provides applications of the aforementioned high-strength, high-conductivity graphene-metal composite wire, including its use as a key conductor material in high-stress, high-transmission-efficiency scenarios, applicable to fields such as electrical engineering, high-frequency current transmission and energy storage, and high-end manufacturing where high mechanical and electrical properties of conductor materials are required.

[0055] Example 1

[0056] S1. Construct a vacuum working space, including a growth zone at the front and a drawing zone at the end. Set the temperature sequence within the growth zone from the end where the metal wire enters the growth zone to the end where it exits, sequentially as 800℃-730℃-665℃-600℃. Then, supply the mixed gas required for in-situ graphene growth on the copper wire surface to the growth zone of the working space at a gas flow rate of 100 sccm, and maintain the pressure inside the growth zone within the range of 10–100 Pa. The mixed gas contains argon and hydrogen in a flow rate ratio of 4:1, and acetylene at a concentration of 4 vol%.

[0057] S2. Select copper wire with a diameter of 0.80 mm. First, use a 1:1 volume ratio mixture of ethanol and deionized water as a cleaning agent to degrease the surface of the copper wire. Then, use 3wt% dilute sulfuric acid to pickle it to deeply remove oil stains, oxide layers, etc. attached to the surface of the copper wire. Next, the surface-pretreated metal wire is continuously fed from the front end of the working space to the working space at a speed of 1.5 m / min and flows through the growth zone and the drawing zone in sequence. Based on the dynamic continuous CVD process, graphene is continuously grown in situ in the growth zone and grown in situ on the surface of the metal wire. In the drawing zone, the metal wire is drawn simultaneously at a drawing speed of 15 m / min. The first pass has a surface area reduction rate of 22.5%, so that the diameter of the copper wire is drawn to 0.62 mm and the graphene is embedded 1 μm into the surface layer of the copper wire. Throughout the process, the pressure in the growth zone inside the working space needs to be maintained in the range of 10–100 Pa, and the pressure in other areas inside the working space needs to be maintained in a vacuum state.

[0058] S3. The metal wire flowing out of the working space is continued to be fed into the working space, and the growth and drawing process is repeated for 6 passes. The area reduction rate of each pass is as follows: 20% for the 2nd pass, 17% for the 3rd pass, 15% for the 5th pass, 12% for the 6th pass, 10% for the 6th pass, 8% for the 6th pass, and 6% for the 7th pass, to obtain a graphene-copper composite wire with a diameter of 0.2mm.

[0059] The temperature of the growth zone in the workspace was adjusted to 350℃, and the obtained graphene-copper composite wire was fed from one end of the workspace near the growth zone to the growth zone within the workspace for re-growth treatment. After 40 minutes of treatment, the wire was retrieved. Samples of graphene-copper composite wire after each drawing were taken out and their performance was tested. Samples of graphene-copper composite wire after each drawing and subsequent in-situ growth (i.e., annealed graphene-copper composite wire) were also taken out and their performance was tested.

[0060] Comparative Example 1

[0061] Select copper wire with a diameter of 0.80 mm; use the traditional cold drawing process to prepare copper wire with a small wire diameter; that is, through 7 passes of cold drawing (without graphene growth), the finished copper wire with a diameter of 0.2 mm is obtained; during the drawing process, the area reduction rate per pass is the same as that in Example 1. After each drawing and after annealing, part of the copper wire is taken out and its properties are tested.

[0062] Test the graphene-copper composite wire or copper wire taken out after each pass of drawing and after annealing above, specifically test its conductivity, elongation at break, tensile strength and other aspects of performance, and the test results are shown in Table 1, Table 2, Table 3; among them, in the early processing passes, the carbon content in the wire is relatively high, and this part of the carbon comes from the original content of the wire itself; after subsequent heat treatment, the carbon contained in the wire itself has been completely removed under high temperature conditions, and the remaining carbon is the content of graphene in the wire; the Raman ratio is I G / I Cu , which characterizes the strength of the graphene characteristic peak. Generally, for graphene products, it is stipulated that I G / I Cu > 1.0 is qualified.

[0063] Table 1. Performance test results of the drawn wires taken out in Example 1 and Comparative Example 1

[0064]

[0065] Table 2. Partial performance test results of the drawn wires taken out in Example 1 and Comparative Example 1

[0066]

[0067] Table 3. Performance test results of the annealed wires taken out in Example 1 and Comparative Example 1

[0068]

[0069] As shown in Tables 1 and 3, the graphene-copper composite wire finally prepared in Example 1 has a significantly better conductivity than the copper wire finally prepared in Comparative Example 1. Furthermore, the graphene-copper composite wire prepared in Example 1 exhibits superior and more stable performance in terms of mechanical properties. Table 2 shows that the carbon content of the copper wire obtained after each drawing pass in Comparative Example 1 is consistently between 26-31 ppm. This carbon content is mainly related to the carbon content in the wire itself, not originating from the carbon element in graphene. In Example 1, the carbon content of the graphene-copper composite wire obtained after each drawing pass steadily increases with the number of drawing passes. Moreover, the Raman ratio of the graphene-copper composite wire obtained after each drawing pass is greater than 1. This indicates that with the increase of drawing passes, the content of graphene in the wire matrix steadily increases, meaning that graphene infiltrates into the copper wire matrix.

[0070] like Figure 2 As shown, the graphene-copper composite wire obtained after each drawing pass in Example 1 has a significantly better conductivity than the copper wire obtained after each drawing pass in Comparative Example 1. Furthermore, the conductivity of the graphene-copper composite wire obtained after each drawing pass in Example 1 gradually increases, and the increase in conductivity is relatively stable. However, in Comparative Example 1, the conductivity of the copper wire after each drawing pass is slightly reduced. And, as... Figure 3 , Figure 4 As shown, although the tensile strength of the graphene-copper composite wire obtained after each drawing pass in Example 1 is lower than that of the copper wire obtained after each drawing pass in Comparative Example 1, and the tensile strength of the graphene-copper composite wire gradually decreases with the increase of the number of drawing passes, the elongation at break of the graphene-copper composite wire obtained after each drawing pass in Example 1 is significantly better than that of the copper wire obtained after each drawing pass in Comparative Example 1. However, comparing Table 1 and Table 3, it can be seen that compared with Example 1, the annealed copper wire obtained in Comparative Example 1 has a larger increase in elongation at break, and the tensile strength decreases more significantly, showing a significant loss in the strength of the copper wire. This may be because the work hardening effect completely disappears after annealing, and the residual dislocation stress is eliminated during the recovery stage, resulting in a significant decrease in material strength. In comparison, the graphene-copper composite wire prepared in Example 1 exhibits superior properties due to the graphene interface strengthening mechanism. After annealing, the graphene-copper composite wire prepared by this process can still maintain a fine-grained structure and play an interface strengthening role due to the presence of graphene, and its strength reduction is much smaller than that of the copper wire prepared in Comparative Example 1. At the same time, some internal stress is eliminated during the recovery process, resulting in a significant increase in its electrical conductivity. This further demonstrates that the preparation process provided by this invention has unique advantages in comprehensively improving the electrical and mechanical properties of metal wires.

[0071] Therefore, the preparation method of the high-strength and high-conductivity graphene-metal composite wire provided by this invention is a preparation method that deeply integrates the dynamic growth process of graphene with the drawing process of metal wire. Through a multi-stage cycle of "growth-drawing-growth-drawing-...", graphene is directionally aggregated inside the metal matrix and a stable strong interfacial bond is constructed. Through the synergistic strengthening mechanism of graphene and metal matrix, the final prepared metal wire maintains a conductivity of not less than 102% IACS while achieving a tensile strength of 240-350MPa and an elongation at break of 25-36%, thus breaking through the performance bottleneck of metal conductors.

[0072] The graphene-copper composite wire and copper wire from Example 1 and Comparative Example 1 were taken out after each drawing process, and their AC resistance at different frequencies was tested. The test results are shown in Table 4.

[0073] Table 4. AC resistance test results of the wires obtained after drawing in Example 1 and Comparative Example 1.

[0074]

[0075] Based on the AC resistance data of graphene-copper composite wires and copper wires after different drawing passes in Example 1 and Comparative Example 1, as recorded in Table 4, and combined with the skin depth calculation formula, the following conclusion can be drawn: In Example 1, the copper wire with optimized graphene structure exhibits significant effectiveness in resisting the skin effect. Specifically, as shown in... Figure 5As shown, when the frequency increases from 1kHz to 100kHz, the increase in AC resistivity of the wires obtained in Example 1 for each pass is significantly smaller than that of the corresponding passes obtained in Comparative Example 1. This indicates that under different pass and frequency conditions, the skin depth of the graphene-copper composite wire prepared in Example 1 is greater than that of the copper wire in Comparative Example 1, and the skin effect of the graphene-copper composite wire prepared in Example 1 is smaller. This advantage is particularly prominent in the middle passes (passes 3-5) and at high frequencies (100kHz). Taking pass 5 as an example, at 100kHz, its skin depth is increased by 11.8% compared to Comparative Example 1, showing the most significant improvement. This phenomenon fully demonstrates that graphene composite wires can effectively expand the effective current distribution depth, providing key performance support for the application of copper wires in high-frequency transmission scenarios. The fifth pass exhibits a significant advantage, primarily due to the most complete directional arrangement of graphene in this pass. Its continuous conductive layer on the surface exerts the strongest "current guiding" effect, effectively suppressing current concentration under high-frequency conditions. Furthermore, analyzing the overall trend, in copper processing, the wire diameter gradually decreases with increasing passes. As the wire diameter thins, the current transmission path is more constrained, leading to a smaller skin depth. Simultaneously, based on the skin effect's characteristic that "the higher the frequency, the more concentrated the current on the surface," the skin depth decreases significantly with increasing frequency. From a structural mechanism perspective, graphene's high conductivity (approximately 10⁻⁶) contributes to this advantage. 6 The S / m ratio and axial orientation distribution form a "conductive gradient" from the surface to the substrate. With this "conductive gradient", the current can not only be transmitted in the surface layer, but also diffuse to the subsurface layer through the graphene channels, which is equivalent to increasing the skin depth and ultimately manifesting as a reduction in AC resistance. These are also important reasons why the graphene-copper composite wire in Example 1 can significantly resist the skin effect.

[0076] Therefore, the preparation method of the high-strength and high-conductivity graphene-metal composite wire provided by this invention significantly improves the skin effect of the metal wire in high-frequency current transmission because the graphene is oriented along the axial direction and forms a continuous high-conductivity layer on the metal surface. In the frequency range of 1kHz-100kHz, its AC resistance is reduced by 3%-18% compared with traditional copper wire, and the higher the frequency, the greater the reduction in resistance. It can effectively reduce energy loss in high-frequency transmission and is more suitable for high-frequency micro transmission systems.

[0077] The above embodiments are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and thus all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

Claims

1. A method for preparing a high-strength, high-conductivity graphene-metal composite wire, characterized in that, Includes the following steps: S1. Construct a vacuum-condition workspace, which includes a growth zone and a drawing zone; S2. The metal wire, after surface pretreatment, flows continuously through the growth zone and the drawing zone. The growth zone grows graphene in situ on the metal wire using a dynamic continuous CVD process. The temperature in the growth zone is configured as a gradually decreasing temperature sequence along the flow direction of the metal wire. The drawing zone synchronously performs the drawing of the metal wire. The temperature in the drawing zone is controlled within the range of 200-800℃. S3. The metal wire flowing out of the working space is continued to be transported back into the working space, and the growth and drawing are repeated n times to obtain the graphene-metal composite wire.

2. The method for preparing a high-strength, high-conductivity graphene-metal composite wire according to claim 1, characterized in that: The temperature in the growth zone is 400-1000℃, and the gradually decreasing temperature sequence creates at least three temperature spaces within the growth zone.

3. The method for preparing a high-strength, high-conductivity graphene-metal composite wire according to claim 1, characterized in that: The number of passes n for the growth and drawing of the metal wire is an integer between 3 and 10, and the reduction rate of the surface area per pass is controlled between 5% and 25%.

4. The method for preparing a high-strength, high-conductivity graphene-metal composite wire according to claim 3, characterized in that: The area reduction rate of the metal wire decreases gradually with each pass; The growth and pulling process is divided into early stages and late stages. The area reduction rate of the early stages is 15%-25%, and the area reduction rate of the late stages is 5%-15%.

5. The method for preparing a high-strength, high-conductivity graphene-metal composite wire according to claim 1, characterized in that: The temperature in the drawing zone is lower than the end temperature value of the temperature sequence in the growth zone.

6. The method for preparing a high-strength, high-conductivity graphene-metal composite wire according to claim 5, characterized in that: The drawing speed in the drawing zone is 5–40 m / min.

7. The method for preparing a high-strength, high-conductivity graphene-metal composite wire according to claim 1, characterized in that: After the metal wire is repeatedly grown and drawn n times, it continues to flow through the growth zone for regeneration treatment to eliminate internal stress and grow another layer of graphene.

8. The method for preparing a high-strength, high-conductivity graphene-metal composite wire according to claim 1, characterized in that: The electrical conductivity of the graphene-metal composite wire is not less than 102% IACS, the tensile strength is maintained in the range of 240-350MPa, and the elongation at break is maintained in the range of 25-36%.

9. The method for preparing a high-strength, high-conductivity graphene-metal composite wire according to claim 1, characterized in that: A mixed gas, including a carrier gas and a carbon source, is introduced into the growth zone. The gas flow rate of the mixed gas is 50–500 sccm, and the pressure in the growth zone is maintained in the range of 10–100 Pa; the carrier gas is an inert gas and / or a reducing gas; the reducing gas includes hydrogen; the carbon source is any one or more of methane, acetylene, ethanol, propylene, and benzene.

10. The method for preparing a high-strength, high-conductivity graphene-metal composite wire according to claim 1, characterized in that: The surface pretreatment of the metal wire includes degreasing and pickling.

11. A high-strength, high-conductivity graphene-metal composite wire, characterized in that: It is prepared by the preparation method according to any one of claims 1-10.

12. The application of the high-strength, high-conductivity graphene-metal composite wire of claim 11 in high-frequency current transmission and energy storage, characterized in that... Compared with traditional metal wires, graphene-metal composite wires reduce AC resistance by 3%-18% in the frequency range of 1kHz-100kHz.

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