Graphene copper composite material for high-frequency current transmission and preparation method thereof

Abstract

The invention relates to the technical field of copper material processing and manufacturing, in particular to a graphene copper composite material for high-frequency current transmission and a preparation method thereof.The method comprises the steps that copper powder with graphene growing in situ is subjected to a compression molding process, and a molded blank is obtained; hot pressed sintering is conducted on the mold pressing blank, and a sintered blank is obtained; the sintered blank is subjected to hot extrusion treatment, and a hot extrusion blank is obtained; and the hot extrusion blank is subjected to drawing treatment, and the graphene copper composite material is obtained. The graphene content of the composite material is 50-300 ppm, and the composite material has good processability and can be continuously processed into a wire material of 0.2-2.6 mm through drawing; strength gt; the heat conductivity coefficient is gt; the direct current electric conductivity is 104 to 106 percent IACS (International Annealed Copper Standard); the high-frequency resistance is reduced by 30-50% compared with that of TU0 copper, and the high-frequency current transmission cable is suitable for high-frequency current transmission scenes of inductors, transformers, radio frequency cables, high-speed copper cables and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of copper material processing and manufacturing, in particular to a graphene copper composite material for high-frequency current transmission and a preparation method thereof. BACKGROUND

[0002] Under the background of rapid development of tens of GHz or even higher frequency bands in the fields of 5G / 6G communication, satellite communication, etc., as the core components of signal transmission, the performance of radio frequency cables and high-speed copper cables directly determines the communication quality and reliability of the system. Due to the problems of high-frequency signal loss and low electromagnetic shielding efficiency, traditional copper-based radio frequency cables have been difficult to meet the stringent requirements of current ultra-high frequency applications. Graphene, with excellent electrical conductivity, mechanical strength and electromagnetic shielding properties, has become an ideal reinforcing body for improving the performance of copper-based materials.

[0003] However, the existing preparation technology of copper-based radio frequency cables containing graphene has the following technical bottlenecks to be solved urgently:

[0004] Due to the high surface energy of graphene and poor wettability with copper matrix, traditional physical mixing and other adding methods are easy to cause graphene aggregation, which cannot achieve uniform dispersion in the copper matrix, resulting in poor material performance uniformity and seriously affecting the stability of ultra-high frequency signal transmission.

[0005] Precise control of the content of graphene is the key to balancing the performance of the material. Too high an addition amount will exacerbate the aggregation phenomenon and reduce the electrical conductivity; too low will not fully play the reinforcing effect, and the existing technology is difficult to improve the mechanical properties while maintaining excellent electrical conductivity.

[0006] The introduction of impurity carbon or unstable carbides generated by the oxidation of graphene during the preparation process will worsen the material interface bonding and increase internal defects, further weakening the electromagnetic shielding performance and reliability of the material.

[0007] Radio frequency cables have very high requirements for surface smoothness, dimensional accuracy and continuous processing, and the existing composite process is difficult to make the material have good plastic deformation ability and stable mechanical strength at the same time during continuous drawing, which is easy to produce surface defects and internal damage, restricting the application of the product in the ultra-high frequency field.

[0008] Therefore, it has become a key to break through the performance bottleneck in the industry to develop a preparation technology that can realize uniform dispersion of graphene, precise control of graphene content and carbon content, and improve the ultra-high frequency transmission performance and processing adaptability of copper-based radio frequency cables.

[0009] The content of the background section is only the technology known to the inventors and does not necessarily represent the state of the art in the field. SUMMARY

[0010] In view of the above problems, the first aspect of the present application provides a preparation method of graphene copper composite material for high-frequency current transmission, comprising:

[0011] molding the copper powder with in-situ grown graphene to obtain a molded blank;

[0012] hot-press sintering the molded blank to obtain a sintered blank;

[0013] hot-extruding the sintered blank to obtain a hot-extruded blank;

[0014] drawing the hot-extruded blank to obtain the graphene copper composite material;

[0015] The graphene content of the copper powder with in-situ grown graphene is 100-700 ppm, the Raman characteristic peak I G / I Cu >0.85, and the Raman characteristic peak I 2D / I Cu <1.00.

[0016] Preferably, the specific surface area of the copper powder for in-situ grown graphene is 0.1-0.5 m 2 / g, the particle size is 5-75 μm, and the loose bulk density is 0.7-2.0 g / mL.

[0017] Preferably, the molding the copper powder with in-situ grown graphene to obtain a molded blank comprises:

[0018] treating the copper powder with in-situ grown graphene to remove moisture and adsorbed gas;

[0019] loading the treated copper powder with in-situ grown graphene into a mold for molding to obtain a molded blank with a density of 90%-99%;

[0020] Preferably, the treating the copper powder with in-situ grown graphene comprises:

[0021] drying the copper powder with in-situ grown graphene at 80-120 °C for 2-4 hours using a drying device;

[0022] Preferably, the loading the treated copper powder with in-situ grown graphene into a mold for molding comprises:

[0023] preheating the mold to 80-120 °C;

[0024] applying a pressure of 1-5 MPa at a pressing speed of 5-10 mm / s for pre-pressing and maintaining the pressure for 1-2 seconds;

[0025] After the pre-pressing, the pressing speed is increased to 15-20 mm / s, the pressure is increased to 5-8 MPa for main pressing, and the pressure is maintained for 30-120 seconds;

[0026] After the main pressing, the pressure is gradually reduced and cooled to room temperature, and the mold pressing blank is pushed out at a uniform speed of 10-20 mm / s using an ejection device.

[0027] Preferably, the hot-pressing sintering specifically includes:

[0028] The mold pressing blank is packaged with a copper jacket;

[0029] The mold pressing blank is heated to a first temperature stage, a second temperature stage, and a third temperature stage in sequence, and is maintained at each temperature stage for 5-60 minutes;

[0030] The first temperature stage is 180-220°C, the second temperature stage is 280-320°C, and the third temperature stage is 380-420°C.

[0031] Preferably, during the first temperature stage and the second temperature stage, the pressure is controlled to be less than 10 MPa and maintained for 10-20 minutes; during the third temperature stage, the pressure is controlled to be 10-30 MPa and maintained for 20-60 minutes before pressure cooling to room temperature.

[0032] Preferably, at least one of argon, nitrogen, and hydrogen is introduced during the entire hot-pressing sintering process.

[0033] Preferably, argon gas with a flow rate of 2-5 L / min is introduced before the introduction of the above-mentioned gas to flush the sintering cavity to remove oxygen and surface impurities of the material.

[0034] Preferably, during the hot extrusion process, the extrusion ratio is 50-250, the pressure is maintained at 600-1000 MPa, the temperature is 600-900 degrees, and the extrusion speed is 20-100 mm / s.

[0035] Preferably, after the hot extrusion process, cooling water is used for cooling, and the oxygen content of the cooling water is less than 0.01 mg / L.

[0036] Preferably, the single-pass deformation amount of the drawing process is 13-15%.

[0037] Preferably, after the drawing, annealing is performed when the deformation amount exceeds 20%; the annealing operation adopts online dynamic annealing, and the annealing temperature of the online dynamic annealing process is 400-500°C, and the annealing time is 30-60 seconds.

[0038] Preferably, after the annealing process, a surface impurity removal operation is performed:

[0039] The material obtained after annealing is placed in an environment with a vacuum degree of ≤1*10-3 Pa and a temperature of 200-400 DEG C for 60-600 min while a protective gas is introduced, the protective gas being at least one of nitrogen, hydrogen and argon.

[0040] The second aspect of the application provides a graphene copper composite material prepared according to the above method for preparing a graphene copper composite material for high-frequency current transmission, the graphene copper composite material having an AC impedance of less than that of oxygen-free copper at a frequency of 10 kHz or above.

[0041] Preferably, the graphene copper composite material has a thermal conductivity of >420 W / (m*K), a direct current conductivity of 104-106%, and a strength of greater than 380 MPa.

[0042] Preferably, the graphene copper composite material has a high-temperature resistance that is 5-8% lower than that of TU0 copper, and a high-frequency resistance that is 30-50% lower than that of TU0 copper.

[0043] Preferably, the graphene copper composite material has a graphene content of 50-300 ppm.

[0044] Preferably, the graphene copper composite material has a carrier concentration that is at least 1.5 times that of copper.

[0045] Preferably, the graphene copper composite material is a graphene copper composite wire, and the graphene copper composite wire has an equivalent diameter of 0.2-2.6 mm.

[0046] The principle of the application is as follows:

[0047] The core principle of the application is to use copper powder with in-situ grown graphene as raw material, and to use its unique physicochemical properties (graphene carbon content, oxygen content, Raman characteristic peak, etc.) to construct a continuous graphene-copper interface network. A stepwise pressing strategy combined with mold preheating is used in the stage of die forming to realize the close packing of copper powder particles and high-precision billet forming, and to eliminate the density gradient problem.

[0048] During the hot-pressing sintering process, deoxidation and impurity volatilization are completed simultaneously in a hydrogen atmosphere through low-temperature stepwise temperature control and dynamic pressure regulation, avoiding the formation of interface brittle compounds. Subsequent hot extrusion forces the graphene to arrange along the axial direction, dispersing the stress in the copper matrix; the single-pass deformation amount is limited to 13-15% in the drawing process, and online annealing is used when the drawing deformation amount is >20% to inhibit work hardening and maintain grain size stability, finally forming a high-density, low-defect graphene copper composite structure.

[0049] The technical effects achieved by the above technical solutions of the application are as follows:

[0050] The present application precisely controls the core parameters (such as carbon content, oxygen content and specific Raman characteristic peaks) of graphene copper powder grown in situ, and combines with the optimized molding process and hot-pressing sintering process, to successfully prepare high-performance graphene copper composite materials. The material realizes three major breakthroughs in the application of ultra-high frequency radio frequency cable: electrical performance - its conductivity is as high as 104-106% IACS, which is significantly higher than that of pure copper, and the high-temperature resistance is 5-8% lower than that of TU0 copper, effectively reducing the resistance loss in the current transmission process; mechanical performance - the tensile strength is >380 MPa (increased by 120%) while the elongation is ≥10%; processing adaptability - the uniformity of graphene dispersion is >95%, the shrinkage after hot pressing is <±0.05%, and the cable surface roughness Ra is <0.1 μm, completely solving the problems of agglomeration, interface defects and size precision in traditional processes, and providing a new generation of high-reliability transmission materials for 5G / 6G and satellite communication.

[0051] The improvement of these performances is due to the fine control of interface bonding and microstructure in the process. The molding process realizes micron-level precision complex structure forming (such as internal thread copper sleeve) through uniform pressure distribution, eliminates density gradient and lays the foundation for sintering; combined with step hot-pressing sintering and directional hot extrusion, it forces graphene to arrange along the axial direction, cooperates with copper matrix to disperse stress, and avoids the problem that graphene is squeezed to the grain boundary and agglomerated due to copper melting and abnormal grain growth; in the drawing process, the single pass deformation is strictly limited to 13-15%, and online annealing is used when the drawing deformation is >20%, to inhibit work hardening while maintaining grain size stability, and finally realize continuous and stable preparation of thin wires with a diameter of 0.2-2.6 mm.

[0052] In addition, the molding process supports high-speed batch production of dozens to hundreds of blanks per minute, significantly improving productivity; its high-precision initial forming reduces subsequent cutting loss, and hot extrusion directly produces industrial standard products (such as 30 mm copper rods), seamlessly connecting the existing copper processing industry chain. The improvement of interface bonding strength ensures the stability of electrical conductivity, forms a graphene copper composite structure with high density and low defects, meets the needs of radio frequency cables and high-speed copper cables in the fields of 5G / 6G communication and satellite communication, and forms the technical advantages of "high electrical conductivity-high mechanical strength-high environmental compatibility". BRIEF DESCRIPTION OF DRAWINGS

[0053] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application together with the embodiments thereof, and explain the present application, but do not limit the present application. In the drawings:

[0054] Figure 1 The flowchart of the preparation method of graphene copper composite material for high-frequency current transmission provided by some embodiments of the present application.

[0055] Figure 2An AC resistance comparison chart of graphene copper composite material provided for some embodiments of the present application.

[0056] Figure 3 A metallographic chart of graphene copper composite material provided for some embodiments of the present application.

[0057] Figure 4 A schematic diagram for testing carrier concentration of graphene copper wire by Hall effect method.

[0058] Figure 5 A signal attenuation comparison chart of graphene copper composite material and silver-plated copper provided for some embodiments of the present application. DETAILED DESCRIPTION

[0059] In the following description, certain example embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and description are considered to be exemplary in nature rather than limiting.

[0060] Unless otherwise defined herein, scientific and technical terms used in connection with the present application have meanings commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. More specifically, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. In this application, the term "or" means "and / or" unless stated otherwise. Furthermore, the use of the term "including" as well as other forms such as "include", "includes," and "included" is not limiting. Also, ranges provided in the specification are inclusive of the endpoints and all values between the endpoints. Preferred embodiments of the application are described herein, and it is to be understood that the preferred embodiments described herein are merely illustrative of the application and are not intended to be limiting.

[0061] Figure 1 A flow chart of a preparation method of graphene copper composite material for high-frequency current transmission provided for some embodiments of the present application.

[0062] Referring to Figure 1 , the first aspect of the present application provides a preparation method of graphene copper composite material for high-frequency current transmission, comprising:

[0063] S1, using copper powder with graphene grown in situ by chemical vapor deposition method as raw material, the copper powder is subjected to a molding process to obtain a molding blank;

[0064] S2, the molding blank is subjected to hot-pressing sintering to obtain a sintered blank;

[0065] S3, hot extruding the sintered blank to obtain a hot extruded blank;

[0066] S4, drawing the hot extruded blank to obtain a graphene copper composite material.

[0067] In some embodiments, the copper powder used for in-situ growth of graphene needs to meet the following key indicators:

[0068] The specific surface area of the copper powder is strictly controlled at 0.1-0.5m 2 / g, and has a dendritic microstructure. The larger the specific surface area, the more graphene will be grown.

[0069] Preferably, electrolytic copper powder is used, which has a developed dendritic structure and a large specific surface area, so that more graphene can be deposited.

[0070] The particle size of the copper powder is 5-75 μm. If the particle size is greater than 75 μm, the content of the subsequently grown graphene will not be enough, and a continuous graphene network cannot be formed after processing. If the particle size is less than 5 μm, the surface atoms are more active, meaning that they are more prone to oxidation and agglomeration into large particles during processing, which makes it difficult to grow graphene and process it into a qualified product.

[0071] The loose bulk density is between 0.7 and 2.0 g / mL, reflecting the porous dendritic structure.

[0072] The carbon content in the graphene copper powder is 100-700 ppm. When the carbon content is less than 100 ppm, the graphene network will be severely damaged during the sintering process due to the high affinity of oxygen to carbon (the activation energy of the carbon oxidation reaction is lower than that of copper oxidation), and a continuous conductive / thermal conductive path cannot be formed. When the carbon content is greater than 700 ppm, the excess graphene will damage the continuity of the copper matrix, causing the interfacial bonding to weaken and the work hardening index to increase dramatically.

[0073] The oxygen content in the graphene copper powder is less than 100 ppm. Oxygen elements can form brittle compounds (such as cuprous oxide) with copper, which can damage the graphene-copper interfacial bonding and cause micro-cracks in the graphene copper blank during subsequent operations. In addition, oxygen elements can form carbon-oxygen bonds, and whether it is an oxygen-containing functional group or copper oxide (cuprous oxide), the conductivity is very low, which affects the movement of electrons between graphene and copper, thereby seriously affecting the electrical and thermal conductivity of the graphene copper composite material.

[0074] The Raman spectrum characteristics of the graphene copper powder must meet the following conditions: the Raman characteristic peak I G / I Cu >0.85, and the Raman characteristic peak I 2D / I Cu <1.00.

[0075] I G I 2D I Cu I

[0076] I G I Cu >0.85, the height of G peak in Raman spectrum means the strength of symmetrical vibration of C-C bond in the material, when the G peak is higher than the fluorescence peak of copper, it means that there is more graphene-related carbon in the material, which is beneficial to the conductivity and thermal conductivity of graphene copper composite material.

[0077] I 2D I Cu <1.00, which indicates the low defect characteristics of graphene, good interface, and graphene will not be tilted on the surface of copper atoms, which is the structural basis for the high conductivity / thermal conductivity of the subsequent graphene copper composite material. The principle is that the 2D peak of graphene is derived from the out-of-plane vibration mode of carbon atoms. When graphene forms strong interface coupling with the copper matrix, the constraint effect of copper atoms will significantly inhibit its out-of-plane vibration, that is, the 2D peak is not obvious; on the contrary, if a significant 2D peak is detected, it indicates that the interface has been damaged (graphene is in a suspended state due to oxidation) or the copper matrix is oxidized, causing the graphene to separate from contact.

[0078] In some embodiments, the compression molding process applies high temperature and high pressure to the graphene copper powder through a mold to make it flow and fill the mold cavity, and after solidification or cooling, the compression molding process is realized to obtain a compression blank. The specific implementation process of the compression molding process is as follows:

[0079] The copper powder with in-situ grown graphene is dried at 80-120°C for 2-4 hours by using a drying device to remove water and adsorbed gas in the graphene copper powder.

[0080] The mold is preheated to 80-120°C to ensure temperature uniformity to reduce thermal stress; then the copper powder with in-situ grown graphene is uniformly loaded into the mold cavity by a vibrating screen to avoid clumping or uneven distribution. Preheating at this stage can enhance the flowability of the copper powder, remove water and adsorbed gas, and avoid defects during molding and subsequent sintering process, laying a foundation for subsequent high-pressure densification.

[0081] The compression molding is divided into a pre-pressing stage and a main pressing stage: in the pre-pressing stage, the mold pressing equipment is started, a pressure of 1-5 MPa is applied to the copper powder at a pressing speed of 5-10 mm / s for pre-pressing, and the pressure is maintained for 1-2 seconds, so that the copper powder particles are preliminarily tightly combined to form a compact with a basic strength; after the pre-pressing is completed, the main pressing stage is entered, the pressing speed is further increased to 15-20 mm / s, and the pressure is simultaneously increased to 5-8 MPa, and the pressure is maintained for 30-120 seconds. The high pressure forces the copper powder to fully fill the mold cavity, realizes the close packing of the particles and minimizes the pores, ensures the uniformity of the density of the compact, and provides a high-density basis for the subsequent process. After reaching a density of 90%-99%, the amount of subsequent processing is significantly reduced.

[0082] After the pressure maintaining is completed, the pressure is gradually reduced, and the compact is cooled to room temperature, and the compact is pushed out at a uniform speed of 10-20 mm / s by using an ejection device.

[0083] The mold pressing process of the application considers both efficiency and stability - uniform pressure distribution ensures the consistency of the density of the compact, avoiding the density gradient problem of traditional processes; at the same time, it is suitable for batch production (hundreds of pieces per minute), significantly improving the manufacturing efficiency. The obtained mold pressing compact has excellent thermal stability and mechanical strength, providing a reliable precursor for uniform shrinkage in the sintering link and the preparation of high-performance graphene copper composite materials.

[0084] In some embodiments, the hot-pressing sintering process comprises: using a copper jacket to package the mold pressing compact, which improves the material utilization rate and maintains a high content of graphene; during the process, argon, nitrogen, hydrogen or a mixed gas of the above inert gases is passed through the whole process;

[0085] Before the above-mentioned gas is passed through, argon with a flow rate of 2-5 L / min is passed through to flush the sintering cavity to remove oxygen and surface impurities of the material. Under this condition, the surface impurities (organic residues, cuprous oxide (Cu2O)) can be effectively removed, and deep deoxidation is achieved through reduction reaction, avoiding the accumulation of oxides at the graphene-copper interface.

[0086] The sintering process is implemented in a stepwise temperature control manner: the mold pressing compact is sequentially heated to a first temperature stage, a second temperature stage and a third temperature stage, and is respectively maintained at a temperature for 5-60 minutes; wherein the first temperature stage is 180-220℃, the second temperature stage is 280-320℃, and the third temperature stage is 380-420℃, and each temperature stage is maintained for 5-60 minutes.

[0087] Preferably, in the first temperature stage and the second temperature stage, the pressure is controlled to be <10 MPa, and maintained for 10-20 minutes; in the third temperature stage, the pressure is controlled to be 10-30 MPa, and maintained for 20-60 minutes, and then pressure cooling is performed to room temperature. The pore channels promote the volatilization and escape of low-boiling-point impurities (such as sulfur and chlorine); if the impurities remain, they will destroy the graphene-copper interface, resulting in a sharp drop in the electrical conductivity and thermal conductivity.

[0088] After sintering, a sintered blank with a density of 90% to 99% and clean grain boundaries is obtained, providing a low deformation basis for subsequent hot extrusion.

[0089] In some embodiments, the sintered blank obtained after hot-pressing sintering is subjected to hot extrusion treatment.

[0090] The extrusion ratio of the hot extrusion treatment is 50 to 250. A large extrusion ratio forces the graphene to align preferentially in the extrusion direction, and cooperates with the copper matrix to disperse stress and reduce the risk of breakage during drawing.

[0091] If the extrusion ratio is < 50, the deformation is insufficient, the copper grains are only "weakly sheared and refined", and the degree of graphene orientation is small; after hot extrusion, the hot extrusion blank has a small density, and the micropores cause stress concentration during drawing, increasing the breakage rate.

[0092] If the extrusion ratio is > 250, the deformation resistance increases exponentially, which easily causes surface cracks and internal residual stress concentration of the hot extrusion blank; stress release during drawing causes interface debonding, increasing the strength dispersion, and reducing the strength of the graphene copper composite.

[0093] The pressure of the hot extrusion treatment is kept at 600 to 1000 MPa. High pressure makes the graphene and copper tightly combined, avoiding the defects of traditional sintering "copper grain growth → graphene is squeezed to the grain boundary".

[0094] If the pressure is < 600 MPa, the powder bonding force will be insufficient, the hot extrusion blank will have a low density, and the internal porosity will be large; the porosity exacerbates the skin effect at high frequency, and the alternating current resistance is not optimized.

[0095] If the pressure is > 1000 MPa, it is easy to cause die deformation / seal failure, and high shear stress causes graphene sheet folding / fracture.

[0096] The temperature of the hot extrusion treatment is 600 to 900℃. At this temperature range, the copper atom diffusion coefficient is high, which guarantees the densification degree without sintering. At the same time, the Raman spectrum characteristics of graphene copper powder grown in situ meet I G / I Cu > 0.85, and there is no 2D peak detected directly, which makes it have a strong interface effect, and thus the graphene does not agglomerate / decompose at 600 to 900℃, enhancing the stability of the graphene copper.

[0097] If the temperature is < 600℃, it is easy to cause insufficient copper atom diffusion, only mechanical engagement without metallurgical bonding, reduced density of the hot extrusion blank, and difficulty in electron transfer between copper and graphene, increasing the breakage rate during drawing; the strength of the graphene copper composite is insufficient.

[0098] If the temperature is greater than 900℃, the copper grains are coarsened to a greater extent, the interface between the graphene and the copper is destroyed, and the graphene may be rearranged, resulting in a decrease in the strength of the graphene-copper composite.

[0099] The extrusion speed of the hot extrusion process is 20-100 mm / s, the hot extrusion process is short in time, the copper crystals cannot grow, and the graphene is still inside the copper material; and the copper material is partially restructured by the hot extrusion, the graphene is more uniformly dispersed in the copper material, and the density of the copper material is improved.

[0100] If the speed is less than 20 mm / s, the production efficiency will drop sharply and the cost will increase dramatically; and if the material stays at 600-900℃ for a long time, the graphene will tend to agglomerate and arrange in disorder during the growth of the copper grains, which will adversely affect the subsequent results.

[0101] If the speed is greater than 100 mm / s, the deformation is too fast, the hot extrusion is uneven, and the residual stress is concentrated; stress release during drawing causes interface debonding and cracking, resulting in an increase in the breakage rate and the inability to stably produce fine copper wires.

[0102] In some embodiments, after the hot extrusion is completed, the material is immersed in water for cooling, and the oxygen content of the cooling water is less than or equal to 0.01 mg / L. After cooling, subsequent drawing is performed.

[0103] In some embodiments, the hot extrusion billet obtained after the hot extrusion is completed is subjected to drawing treatment, and the drawing process adopts a multi-pass progressive deformation strategy, with the single-pass deformation amount being strictly controlled within the range of 13-15%.

[0104] After drawing, if the deformation amount exceeds 20%, annealing is required, and the annealing operation adopts online dynamic annealing, with the online annealing temperature being 400-500℃ and the annealing time being 30-60 s. This process design precisely suppresses the work hardening effect, maintains the recrystallization ability of the copper matrix, prevents the grain size from being too fine, avoids the interface stress concentration caused by excessive grain refinement, and thus ensures the bonding strength of the graphene-copper interface.

[0105] In some embodiments, after the annealing treatment, a surface impurity removal operation is performed:

[0106] The material obtained after annealing is placed in an environment with a vacuum degree of less than or equal to 1×10-3 Pa and a temperature of 200-400℃, and stays for 60-600 min, while argon gas with a flow rate of 2-5 L / min is passed through.

[0107] Under this condition, the surface impurities (organic residues, red copper, etc.) can be effectively removed, the surface roughness can be improved, the contact resistance can be reduced, the oxygen aggregation at the grain boundaries can be removed, and the lattice distortion caused by drawing can be repaired.

[0108] Further, the graphene copper composite material can be prepared into industrial standard products (such as 30 mm copper rods, 8 mm copper rods, etc.) through a drawing process, which can seamlessly connect with the current copper processing industry.

[0109] The second aspect of the present application provides a graphene copper composite material prepared by the above method. The strength of the graphene copper composite material is more than 380 MPa, and the thermal conductivity coefficient is more than 420 W / (m·K).

[0110] Further, the conductivity of the graphene copper composite material can reach a level comparable to silver, i.e. 104-106% IACS, and the high-temperature resistance is 5-8% lower than that of TU0 copper; the AC impedance is significantly smaller than that of oxygen-free copper at more than 10 kHz; further, the carrier concentration of the graphene copper composite material can be 1.5 times that of copper; at tens of GHz, the signal attenuation of the graphene copper composite material is comparable to that of silver-plated copper. In the field of ultra-high frequency applications such as radio frequency cables, AC impedance and signal attenuation are key indicators for evaluating signal transmission quality. If the cable impedance does not match the equipment, connectors, etc., it will cause signal reflection, increase transmission loss, and reduce transmission efficiency. By measuring and optimizing the AC impedance, stable signal transmission can be ensured, interference can be reduced, and the performance of the communication system can be improved. The AC impedance characteristics of materials or devices can be measured by commonly used vector network analyzers and other equipment.

[0111] The AC impedance refers to the hindering effect of a conductor on an alternating current in an AC circuit.

[0112] Further, the resistance of the graphene copper composite material under high-frequency current is 30-50% smaller than that of TU0 copper, which is suitable for high-demand scenarios such as radio frequency cables and high-speed copper cables.

[0113] Further, the graphene copper composite material is specifically a graphene copper composite wire, and the equivalent diameter of the cross section of the graphene copper composite wire is 0.2-2.6 mm.

[0114] Further, the graphene content of the graphene copper composite material is 50-300 ppm.

[0115] Further, the graphene copper composite material has good corrosion resistance. The graphene copper sample after dry cutting does not oxidize after being placed in air for more than half a year. Correspondingly, the oxygen-free copper product can be placed for at most one week under the same conditions. The accelerated oxidation at high temperature is also similar.

[0116] Further, the graphene copper composite material has good processing performance. It can be continuously drawn without breaking; when preparing enameled wire, it has good adhesion with commonly used resins, ensuring the voltage resistance level of the enameled wire (which can be used in subsequent high-voltage platforms for electric cars and drones, etc.).

[0117] Further, the graphene copper composite material has high strength and high softening temperature, and can be used in high temperature scenarios.

[0118] The present application is further illustrated by the following examples.

[0119] Example 1

[0120] The graphene copper powder used in this example is CP300 from Suzhou Shengguang, with a specific surface area of 0.2 m 2 / g, a particle size of -325 mesh (<45 microns), a density of 1.6 g / mL, a carbon content of 400 ppm, a Raman characteristic peak I G / I Cu of 0.85, and a Raman characteristic peak I 2D / I Cu of 1.00.

[0121] The mold was heated to 110°C, and the copper powder was evenly poured into the mold cavity.

[0122] The mold pressing equipment was started, and the copper powder was pre-pressed at a pressing speed of 10 mm / s to preliminarily bond the copper powder particles, with a pre-pressing pressure of 5 MPa and a holding time of 2 seconds, to preliminarily form a green compact with a certain strength.

[0123] After pre-pressing, the pressing speed was quickly increased to 15 mm / s, and the pressing pressure was increased to 8 MPa, with a holding time of 60 seconds.

[0124] After the holding time ended, the equipment automatically reduced the pressure, and the mold was cooled to gradually reduce the temperature of the green compact to near room temperature, to reduce the elastic aftereffect and deformation risk of the green compact during demolding.

[0125] The ejection demolding method was used, and the ejection device of the mold was started to smoothly push the green compact out of the mold cavity. During demolding, attention was paid to keep the ejection speed uniform to avoid damage or deformation of the green compact due to too fast or too slow ejection speed, and the ejection speed was controlled at 10 mm / s.

[0126] The copper package was used to package the green compact, and nitrogen was introduced throughout the process;

[0127] Before introducing nitrogen, argon was introduced at a flow rate of 2-5 L / min to flush the sintering cavity to remove oxygen and surface impurities of the material. The temperature was held at 180°C, 280°C, and 380°C for 20 minutes respectively, with a pressure of 8 MPa at <380°C and a pressure of 25 MPa at >380°C. After holding at 400°C for 20 minutes, the temperature was cooled while maintaining the pressure.

[0128] The obtained blank is subjected to hot extrusion treatment to obtain a hot extrusion blank; the extrusion ratio is 100, the pressure is kept at 400 MPa, the temperature is 600 DEG C, the extrusion speed is 50 mm / s, direct water cooling, and the oxygen content of the cooling water is below 0.01 mg / L.

[0129] The hot extrusion blank is subjected to drawing treatment to obtain a graphene copper composite material. Multi-pass drawing is performed, and the single-pass drawing deformation is 15%, to prepare a 30 mm copper rod of an industrial standard, which is connected to the current copper processing industry.

[0130] The obtained hot extrusion blank is prepared into an industrial standard φ2.6 mm hot extrusion blank (strength 400 MPa / conductivity 105% IACS) through 5 passes of drawing (single-pass deformation 15%), and further combined with electromagnetic auxiliary drawing and online laser annealing to achieve a breakthrough in fine wire diameter: successfully mass-produce φ0.25 mm wire (5 km continuous without broken wire, 40 GHz loss 0.20 dB / m), breaking through the traditional copper wire processing limit, providing a core material with high frequency low loss and high toughness for 5G micro coaxial radio frequency cable.

[0131] Example 2

[0132] The graphene copper powder used in this example is CP300 from Suzhou Shengguang, with a specific surface area of 0.2 m 2 / g, a particle size of -325 mesh (<45 microns), a density of 1.6 g / mL, a carbon content of 400 ppm, a Raman characteristic peak I G / I Cu of 0.85, and a Raman characteristic peak I 2D / I Cu of 1.00.

[0133] The mold is heated to 90 DEG C, and the copper powder is uniformly poured into the mold cavity.

[0134] The mold pressing equipment is started, and the copper powder is pre-pressed at a pressing speed of 8 mm / s, the copper powder particles are tightly combined, the pre-pressing pressure is 5 MPa, and the pressure is kept for 2 seconds, to preliminarily form a compact with a certain strength.

[0135] After pre-pressing, the pressing speed is quickly increased to 15 mm / s, and the pressing pressure is increased to 8 MPa, and the pressure holding time is 30 seconds.

[0136] After the pressure holding is completed, the equipment automatically reduces the pressure, and the mold is cooled, so that the temperature of the compact gradually decreases to near room temperature, to reduce the elastic aftereffect and deformation risk of the compact in the demolding process.

[0137] The ejection demolding mode is adopted, the ejection device of the mold is started, and the compact is smoothly pushed out of the mold cavity. During demolding, attention is paid to keeping the ejection speed uniform to avoid damage or deformation of the compact caused by too fast or too slow ejection speed, and the ejection speed is controlled at 20 mm / s.

[0138] The copper-coated encapsulation mold compact is adopted, and hydrogen is introduced throughout the process. Before hydrogen is introduced, argon with a flow rate of 2-5 L / min is introduced to flush the sintering cavity to remove oxygen and surface impurities of the material. The pressure is controlled at 8 MPa at <380°C and 20 MPa at >380°C, and the temperature is kept at 200°C, 300°C, and 400°C for 20 minutes, respectively. After keeping the temperature at 400°C for 20 minutes, cooling is performed while maintaining the pressure.

[0139] The obtained compact is subjected to hot extrusion treatment to obtain a hot extruded compact; the extrusion ratio is 150, the pressure is kept at 500 MPa, the temperature is 750°C, the extrusion speed is 40 mm / s, and direct water cooling is performed, and the oxygen content of the cooling water is below 0.01 mg / L.

[0140] The hot extruded compact is subjected to 6 passes of drawing treatment to obtain a graphene copper composite material. The single-pass wire drawing deformation is 15%, and an industrial standard 2.6 mm copper rod is prepared, which is connected to the current copper processing industry.

[0141] Example 3

[0142] The graphene copper powder used in this example is CP300 from Suzhou Shengguang, and its parameters are specific surface area 0.2 m 2 / g, particle size -325 mesh (<45 microns), density 1.6 g / mL, carbon content 400 ppm, Raman characteristic peak I G / I Cu = 0.85, and Raman characteristic peak I 2D / I Cu = 1.00.

[0143] The mold is heated to 90°C, and the copper powder is uniformly poured into the mold cavity.

[0144] The mold pressing equipment is started, and the copper powder is pre-pressed at a pressing speed of 8 mm / s to preliminarily bond the copper powder particles, the pre-pressing pressure is 5 MPa, and the pressure is kept for 2 seconds to preliminarily form a compact with a certain strength.

[0145] After pre-pressing, the pressing speed is quickly increased to 15 mm / s, and the pressing pressure is increased to 8 MPa, and the pressure holding time is 30 seconds.

[0146] After the pressure holding is completed, the equipment automatically reduces the pressure, and the mold is cooled to gradually reduce the temperature of the compact to near room temperature to reduce the elastic aftereffect and deformation risk of the compact during demolding.

[0147] Use the ejection method to start the ejection device of the mold and smoothly push the green compact out of the mold cavity. During the demolding process, pay attention to maintaining a uniform ejection speed to avoid damage or deformation of the green compact caused by too fast or too slow ejection. The ejection speed is controlled at 20mm / s.

[0148] The molded blank is encapsulated in a copper sheath, and a mixture of 95% nitrogen and 5% hydrogen is introduced throughout the process. Argon is introduced at a flow rate of 2-5 L / min before the mixture is introduced to flush the sintering cavity to remove oxygen and impurities on the material surface. The sintering cavity is maintained at 200°C, 300°C, and 400°C for 20 minutes each. The pressure is controlled at 8 MPa for temperatures below 380°C and 25 MPa for temperatures above 380°C. After a 30-minute hold at 400°C, the sintering cavity is cooled, maintaining the pressure during cooling.

[0149] The resulting billet was subjected to hot extrusion to obtain a hot extruded billet; the extrusion ratio was 200, the pressure was maintained at 600 MPa, the temperature was 800°C, the extrusion speed was 45 mm / s, and water cooling was performed directly, wherein the oxygen content of the cooling water was below 0.01 mg / L. The resulting hot extruded billet was subjected to drawing to obtain a graphene copper composite material.

[0150] The resulting hot-extruded billet was drawn through eight passes (15% deformation per pass) to create a graphene-copper composite material. After reaching 20% ​​deformation, an online annealing process was performed to produce an industry-standard φ30mm hot-extruded billet (strength 400MPa / conductivity 105% IACS). Furthermore, electromagnetic-assisted drawing and online laser annealing were combined to achieve breakthroughs in wire diameter: the successful mass production of φ0.2mm wire (5km of continuous, unbroken wire, with a loss of 0.20dB / m at 40GHz), surpassing the limitations of conventional copper wire processing and providing a core material that combines high-frequency, low-loss, and high-strength toughness for 5G micro-coaxial RF cables.

[0151] Figure 2 A comparison chart of the AC resistance of graphene-copper composite materials provided in some embodiments of the present application.

[0152] from Figure 2 It can be seen from the graphene copper composite material prepared in this application that the AC resistance is significantly reduced when compared with TU0 oxygen-free copper at a frequency greater than 1 kHz.

[0153] Figure 3 Metallographic diagram of the graphene-copper composite material provided in some embodiments of the present application.

[0154] from Figure 3 As can be seen in the figure, the grain size is about 5μm. The grain size of oxygen-free copper after annealing is generally above 40μm.

[0155] Figure 4The schematic diagram for testing the carrier concentration of graphene copper wire by Hall effect method.

[0156] As shown in Figure 4 , the magnetic field is scanned from -5T to 5T, the resistance is obtained, and the symmetric processing is done:

[0157]

[0158] VH is the Hall voltage (v), d is the thickness of the sample (cm), Is is the current passing through the sample (A), B is the magnetic field strength (Gauss),

[0159] The following formula

[0160]

[0161] n = 1.3361 x 1023 cm -3

[0162] The result is 50% higher than that of oxygen-free copper.

[0163] Figure 5 The signal attenuation comparison chart of graphene copper composite material provided by some embodiments of the present application and silver-plated copper is shown in the following figure.

[0164] As shown in Figure 5 , at tens of GHz, the signal attenuation of graphene copper composite material is comparable to that of silver-plated copper.

[0165] The following Table 1 is a comparison table of various properties of graphene copper composite material provided by some embodiments of the present application and oxygen-free copper (oxygen content below 3ppm). As can be seen from Table 1, the graphene copper composite material prepared in the present application has great advantages in carrier concentration, thermal conductivity, AC impedance, and oxidation resistance, etc.

[0166] Table 1

[0167]

[0168] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a graphene copper composite material for high-frequency current transmission, characterized in that: include: The copper powder with in-situ graphene growth is subjected to a compression molding process to obtain a compression blank; Hot pressing and sintering the molded blank to obtain a sintered blank; performing a hot extrusion process on the sintered blank to obtain a hot extruded blank; Drawing the hot extruded blank to obtain a graphene-copper composite material; The graphene content of the copper powder for in-situ graphene growth is 100-700 ppm, and the Raman characteristic peak I G / I Cu >0.85, Raman characteristic peak I 2D / I Cu <1.

00.

2. The method for preparing the graphene copper composite material for high-frequency current transmission according to claim 1, wherein: The specific surface area of ​​the copper powder used for in-situ growth of graphene is 0.1 to 0.5 m 2 / g, particle size is 5-75μm, and loose density is 0.7-2.0g / mL.

3. The method for preparing the graphene copper composite material for high-frequency current transmission according to claim 1, wherein: The method of subjecting the copper powder of in-situ graphene growth to a compression molding process to obtain a compression molded blank comprises: treating the copper powder for in-situ graphene growth to remove moisture and adsorbed gases; The treated copper powder of in-situ grown graphene is placed into a mold for molding to obtain a molded blank with a density of 90% to 99%; Preferably, processing the copper powder for in-situ graphene growth comprises: Drying the copper powder of the in-situ graphene growth at 80-120° C. for 2-4 hours using a drying device; Preferably, the step of placing the treated in-situ graphene-grown copper powder into a mold for molding comprises: Preheat the mold to 80-120°C; Apply 1-5 MPa pressure at a pressing speed of 5-10 mm / s for pre-pressing and hold the pressure for 1-2 seconds; After the pre-pressing is completed, the pressing speed is increased to 15-20 mm / s, the pressure is increased to 5-8 MPa for the main pressing, and the pressure is maintained for 30-120 seconds; After the main pressure is completed, the pressure is gradually reduced and cooled to room temperature. The ejection device is used to eject the molded blank at a uniform speed of 10 to 20 mm / s.

4. The method for preparing the graphene copper composite material for high-frequency current transmission according to claim 1, wherein: The hot pressing sintering specifically includes: Encapsulating the molded body with a copper sheath; heating the molded body to a first temperature stage, a second temperature stage, and a third temperature stage in sequence, and keeping the temperature for 5-60 minutes respectively; Wherein, the first temperature stage is 180-220°C, the second temperature stage is 280-320°C, and the third temperature stage is 380-420°C; Preferably, in the first temperature stage and the second temperature stage, the pressure is controlled to be less than 10 MPa and maintained for 10-20 minutes; in the third temperature stage, the pressure is controlled to be 10-30 MPa and maintained for 20-60 minutes, and then cooled to room temperature while maintaining the pressure.

5. The method for preparing the graphene copper composite material for high-frequency current transmission according to claim 4, wherein: During the hot pressing sintering process, at least one of argon, nitrogen and hydrogen is introduced throughout the process; Preferably, before the above gases are introduced, argon gas with a flow rate of 2 to 5 L / min is introduced to flush the sintering cavity to remove oxygen and impurities on the surface of the material.

6. The method for preparing the graphene copper composite material for high-frequency current transmission according to claim 1, wherein: During the hot extrusion treatment, the extrusion ratio is 50-250, the pressure is maintained at 600-1000 MPa, the temperature is 600-900 degrees, and the extrusion speed is 20-100 mm / s; Preferably, cooling water is used for cooling after the hot extrusion treatment, and the oxygen content of the cooling water is below 0.01 mg / L.

7. The method for preparing the graphene copper composite material for high-frequency current transmission according to claim 1, wherein: The deformation of a single drawing process is 13-15%; Preferably, an annealing operation is performed after the deformation exceeds 20% after wire drawing; the annealing operation adopts online dynamic annealing, the annealing temperature of the online dynamic annealing treatment is 400-500° C., and the annealing time is 30-60 seconds.

8. The method for preparing the graphene copper composite material for high-frequency current transmission according to claim 7, characterized in that: After annealing, surface impurity removal is performed: The annealed material is placed in an environment with a vacuum degree of ≤1×10-3Pa and a temperature of 200°C to 400°C for 60 to 600 minutes while introducing a protective gas, which is at least one of nitrogen, hydrogen and argon.

9. The graphene copper composite material prepared by the method for preparing a graphene copper composite material for high-frequency current transmission according to any one of claims 1 to 8, characterized in that: The AC impedance of the graphene-copper composite material is lower than that of oxygen-free copper at a frequency of 10 kHz or higher.

10. The graphene copper composite material according to claim 9, characterized in that: The graphene copper composite material has a thermal conductivity greater than 420 W / (m·K), a DC conductivity of 104-106%, and a strength greater than 380 MPa; Preferably, the high-temperature resistance of the graphene-copper composite material is 5-8% lower than that of TU0 copper; the high-frequency resistance of the graphene-copper composite material is 30-50% lower than that of TU0 copper; Preferably, the graphene content of the graphene copper composite material is 50 to 300 ppm; Preferably, the carrier concentration of the graphene-copper composite material is at least 1.5 times that of copper; Preferably, the graphene-copper composite material is specifically a graphene-copper composite wire, and the equivalent diameter of the cross section of the graphene-copper composite wire is 0.2 to 2.6 mm.

Images