Graphene copper composite material capable of resisting skin effect 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 capable of resisting the skin effect and a preparation method thereof.The preparation method comprises the steps that copper powder with graphene growing in situ is subjected to hot isostatic pressing treatment, and a hot isostatic pressing blank is obtained; the hot isostatic pressing blank is subjected to hot extrusion treatment, and an extrusion blank is obtained; and the extrusion blank is subjected to continuous extrusion and drawing treatment, and the graphene copper composite material is obtained. Wherein the carbon content of the graphene on the copper powder for in-situ growth of the graphene is 100-500 ppm, and the oxygen content of the graphene on the copper powder is 1t; the wavelength is 350ppm, and the Raman characteristic peak is IG / I < Cugt >; and the Raman characteristic peak I2D / ICU is less than 1. According to the method, the wire rod which is as thin as 0.01 mm can be prepared, and the wire breakage rate is reduced. And the compressive strain in the machining process is increased, and the interface of graphene and copper is enhanced, so that the composite material has good conductivity, especially under the working conditions of high frequency, high temperature and the like, and the material can resist the inherent skin effect of metal.

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 capable of resisting skin effect and a preparation method thereof. BACKGROUND

[0002] High-frequency current is ubiquitous in life and is widely used in fields such as energy, communication and medical treatment. When high-frequency alternating current passes through a conductor, the alternating magnetic field generated around the conductor will generate an induced current in the conductor, which further generates an induced magnetic field opposite to the original current direction, thereby increasing the equivalent resistance of the conductor. This phenomenon that the current tends to flow on the surface of the conductor is called skin effect. In practical applications, the skin effect is generally resisted by reducing the diameter of the conductor and increasing the electrical conductivity of the conductor. However, with the development of industry, terminal demand often hopes for higher and higher frequency, larger and larger power, and lower and lower energy consumption, which puts forward new technical requirements for the conductor. In application scenarios above GHz, due to the skin depth of copper wire being only 0.2-2 μm, conventional conductors cannot be mass-produced and meet application requirements in terms of cost and technology. Silver-plated conductors are often used in communication and medical fields to make the current transmit between the silver-plated layer (electrical conductivity about 104% IACS), and technical strategies mainly aimed at improving the surface roughness of the silver-plated layer are also widely used. However, these technical means have reached the limit of theory and industrial production and cannot solve the core demands of terminal applications in developing the next generation of products. SUMMARY

[0003] In view of the above problems, the first aspect of the present application provides a preparation method of a graphene copper composite material capable of resisting skin effect, comprising:

[0004] subjecting copper powder for in-situ growth of graphene to hot isostatic pressing to obtain a hot isostatic pressing blank;

[0005] subjecting the hot isostatic pressing blank to extrusion processing to obtain an extruded blank;

[0006] subjecting the extruded blank to drawing processing to obtain a graphene copper composite material;

[0007] wherein the graphene carbon content on the copper powder for in-situ growth of graphene is 100-500 ppm, the oxygen content is <350 ppm, the Raman characteristic peak I G / I Cu >0.9, and the Raman characteristic peak I 2D / I Cu <1.

[0008] Preferably, the specific surface area of the copper powder for in-situ growth of graphene is 0.1-0.5 m 2 / g, the particle size is 5-75 microns, and the loose bulk density is 0.7-2.0 g / mL.

[0009] Preferably, the graphene copper powder is placed in a copper sheath, and the vacuum degree of the internal space of the copper sheath is controlled to be ≤1×10 -2 Pa, a pressure of about 850 MPa-950 MPa is applied to the graphene copper powder, and hot isostatic pressing treatment is performed.

[0010] Preferably, the hot isostatic pressing treatment comprises:

[0011] Segmented holding at 200-500℃ for 10-300 minutes to remove volatile impurities and oxygen in the graphene copper powder;

[0012] The oxygen content of the hot isostatic pressing blank obtained after hot isostatic pressing is ≤80 ppm, and the density is at least 8.8 g / cm 3 ;

[0013] Preferably, the holding time is 5-90 minutes at 280-320℃ and 380-420℃, respectively.

[0014] Preferably, the extrusion treatment comprises hot extrusion treatment, the extrusion ratio of the hot extrusion treatment is 50-250, the pressure is maintained at 200-1000 MPa, the temperature is 400-800 degrees, and the extrusion speed is 20-100 mm / s.

[0015] Preferably, the extrusion treatment comprises continuous extrusion treatment, the continuous extrusion treatment is performed after the hot extrusion treatment, the extrusion ratio of the continuous extrusion treatment is 2-25, the pressure is maintained at 10-20 MPa, and the extrusion speed is 8-12 revolutions per minute.

[0016] Preferably, the single pass deformation of the drawing treatment is controlled to be 4-15%.

[0017] Preferably, annealing operation is performed when the deformation amount exceeds 20%, and the annealing operation adopts online dynamic annealing operation or bell furnace annealing operation.

[0018] The annealing temperature is 300-500 degrees;

[0019] Preferably, when bell furnace annealing is used, at least one of argon, nitrogen, and hydrogen is used for flushing.

[0020] Preferably, the annealing time is 30-600 minutes

[0021] The second aspect of the present application provides a graphene copper composite material prepared according to the preparation method of the graphene copper composite material capable of resisting skin effect, the electrical resistance of the graphene copper composite material is more than 10% lower than that of TU0 oxygen-free copper of the same specification under high-frequency current of 10 kHz or more, and the alternating current impedance at 1 MHz is more than 20% lower than that of oxygen-free copper.

[0022] Preferably, the graphene content of the graphene copper composite material is 50-400 ppm, the tensile strength in annealed state is 200-260 MPa, the tensile strength in hard state is 350-450 MPa; the thermal conductivity is > 420 W / mK, the direct current conductivity is 104-106% IACS, and the carrier concentration reaches 1.33 x 1019 cm-3. 23 m -3 ;

[0023] Preferably, the graphene copper composite material is a graphene copper composite wire, and the diameter of the graphene copper composite wire is 0.01 mm to 8.0 mm.

[0024] The principle of the present application is as follows:

[0025] The core principle of the present application is to utilize the excellent electrical conductivity and thermal conductivity of graphene to improve the electrical conductivity of the graphene copper composite material, so that the electrical resistance of the graphene copper composite material is reduced under high temperature and other working conditions. In addition, when the graphene nanosheets are uniformly dispersed in the copper matrix, the copper matrix is separated into a large number of copper "single filaments" along the processing direction during the processing process, which is equivalent to increasing the specific surface area of copper in structure. For example, when 100 ppm of graphene is added into 1 kg of copper matrix, the surface area of single-layer graphene is 260 m 2 , and correspondingly, the specific surface area of 1 kg of copper wire with a diameter of 0.2 mm is only 0.223 m 2 . When the interface between graphene and copper is good and does not affect the migration of electrons on the surface of these copper "single filaments", a graphene copper wire resisting skin effect is formed. Finally, for some graphene nanosheets that are not distributed along the processing direction, electrons tend to migrate on the surface of graphene, which can also weaken the tendency of current flowing on the surface of the conductor to some extent.

[0026] In order to realize the uniform dispersion of graphene in the copper matrix, the present application utilizes the raw material of graphene uniformly wrapping copper powder, and combines the characteristics of powder metallurgy to sinter the obtained graphene copper powder below the melting point of copper, so as to avoid the agglomeration of graphene in liquid copper. Finally, through the processing process of plastic deformation and the low deformation amount in each processing process, the graphene tends to be distributed along the processing direction.

[0027] In order to improve the interface between graphene and copper and reduce the potential barrier of electron migration between graphene and copper, the present application takes the following measures:

[0028] 1. The copper powder with graphene grown by chemical vapor deposition is used as the raw material to reduce the defects and other impurities (such as oxygen, organic molecules, etc.) of graphene, so that effective connection of copper-graphene-copper can be formed during sintering;

[0029] 2. High vacuum environment is used in the sintering process to control the oxidation of copper in the powder metallurgy process.

[0030] 3, Use higher temperature processing as much as possible during the deformation process to increase the density of the composite material and the plasticity of copper, retain the structure of graphene during the processing process and enhance the orientation along the processing direction;

[0031] 4. When the deformation amount is large, annealing (preferably bell jar annealing) is used to repair the interface defects caused during the drawing process, and to avoid impurities in the air penetrating into the interface between copper and graphene;

[0032] In order to further improve the electrical conductivity and thermal conductivity of graphene copper, the application also adds a compression strain processing technology, which correspondingly reduces the process related to tensile strain, so that the graphene tends to be arranged in order in the copper matrix, thereby inducing the growth of copper grains along the crystal direction, resisting the skin effect of high-frequency current in the composite material, and reducing the alternating current impedance.

[0033] The technical effects achieved by the above technical solutions of the application are as follows:

[0034] The application performs hot isostatic pressing treatment on the copper powder with in-situ grown graphene, and through hot extrusion, continuous extrusion and drawing, a graphene copper composite wire material which can resist the inherent skin effect of metal to a certain extent is obtained. In order to retain the excellent electrical conductivity and thermal conductivity of graphene, the application uses copper powder with in-situ grown graphene, wherein the graphene content is 100-500ppm, the oxygen content is <350ppm, the Raman characteristic peak I G / I Cu >0.9, and the Raman characteristic peak I 2D / I Cu <1; by increasing the compression strain in the processing process and reducing the drawing strain, the interface between graphene and copper is enhanced, so that the graphene copper composite material has good electrical conductivity (104-106% IACS), and has lower resistance than TU0 oxygen-free copper under high frequency and high temperature working conditions. In addition, the application also precisely controls each process link and solves the problem of high wire breaking rate caused by the aggregation of graphene grain boundaries in the traditional processing method, and can stably and continuously prepare wire with a diameter of 0.01-8.0mm, the wire breaking rate is significantly reduced, and the efficient and reliable mass production of graphene copper composite wire is realized.

[0035] The graphene copper composite material prepared by the method of the application has a thermal conductivity higher than 420W / mK, a hard state tensile strength greater than 350MPa, and a direct current conductivity reaching 104-106% IACS. What is particularly prominent is its high frequency characteristics: under high frequency current (such as >10kHz), its resistance is reduced by 10% compared with standard TU0 copper, significantly improving the influence of skin effect. The carrier concentration can reach 1.33x10 23 m -3 , which provides a basis for high-frequency current application. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of the specification, illustrate embodiments of the present application and are included to provide a further understanding of the present application, and are made a part of the specification. The drawings are not intended to limit the present application but to illustrate it.

[0037] Figure 1 Flow chart of the preparation method of the graphene copper composite material capable of resisting skin effect provided for some embodiments of the present application.

[0038] Figure 2 AC impedance comparison chart of the graphene copper composite material provided for some embodiments of the present application.

[0039] Figure 3 Attenuation comparison chart of the graphene copper composite material and silver-plated conductor under different high-frequency test conditions provided for some embodiments of the present application.

[0040] Figure 4 AC resistance increase comparison chart of the graphene copper composite material and oxygen-free copper under 1-1000 kHz conditions provided for some embodiments of the present application. DETAILED DESCRIPTION

[0041] In the following description, only certain exemplary embodiments are described in full detail. As those skilled in the art will appreciate, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0042] Unless otherwise defined herein, scientific and technical terms used in connection with the present application have meanings that are 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 present application are described herein, and it is to be understood that the preferred embodiments described herein are merely illustrative of the present application and are not intended to limit the scope of the present application.

[0043] Figure 1 Flow chart of the preparation method of the graphene copper composite material capable of resisting skin effect provided for some embodiments of the present application.

[0044] AsFigure 1 As shown, the first aspect of the present application provides a preparation method of graphene copper composite material capable of resisting skin effect, comprising:

[0045] S1, using copper powder with in-situ grown graphene as raw material, the copper powder is subjected to hot isostatic pressing treatment to obtain a hot isostatic pressing blank;

[0046] S2, the hot isostatic pressing blank is subjected to extrusion treatment to obtain an extruded blank;

[0047] S3, the extruded blank is subjected to drawing treatment to obtain a graphene copper composite material.

[0048] In some embodiments, the in-situ grown graphene copper powder used needs to meet the following key indicators:

[0049] The specific surface area of the copper powder is strictly controlled at 0.1-0.5m 2 / g, which has a dendritic microstructure, and the larger the specific surface area, the more graphene will be grown.

[0050] Preferably, the copper powder is obtained by atomization method, and the surface of the copper powder cannot have any substances, including antioxidants and the like.

[0051] The particle size of the copper powder is 5-75 microns, and a particle size greater than 75 microns will result in insufficient content of the subsequently grown graphene, and cannot form a continuous graphene network after processing; a particle size less than 5 microns means that the surface atoms are more active, which means that they are more prone to oxidation and agglomeration into large particles during processing, and thus are not easy to grow graphene, and cannot be processed into qualified products.

[0052] The loose bulk density is between 0.7 and 2.0 g / mL, reflecting its porous dendritic structure; the micron-level particle size cooperates with the loose bulk density to avoid damage to the graphene structure during hot isostatic pressing, while providing a uniform preform for the subsequent forming process.

[0053] The carbon content of the graphene in the graphene copper powder is 100-500 ppm, when the carbon content is less than 100 ppm, the graphene network will be severely damaged during processing 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 higher than 500 ppm, the excess graphene will destroy the continuity of the copper matrix, causing the interface to weaken and the work hardening index to increase dramatically, resulting in an increase in the drawing breakage rate, the inability to prepare continuous fine wires, and even the complete loss of processability due to material brittleness.

[0054] The oxygen content of graphene in the graphene copper powder is less than 350 ppm. Oxygen elements will form brittle compounds (such as cuprous oxide) with copper, which will generate micro-cracks in subsequent high-temperature processing (hot extrusion / drawing treatment) and destroy the graphene-copper interface bonding force. Moreover, oxygen elements may also form carbon-oxygen bonds. Whether it is oxygen-containing functional groups of carbon-oxygen bonds or cupric (cuprous) oxide, the conductivity is very low, which affects the movement of electrons between graphene and copper, thereby seriously affecting the electrical conductivity and thermal conductivity.

[0055] The Raman spectrum characteristics of the graphene copper powder must satisfy I G / I Cu >0.9, the Raman characteristic peak I 2D / I Cu <1.00.

[0056] wherein, I G represents the peak value of the G peak in the Raman spectrum of the graphene copper powder, I 2D represents the peak value of the 2D peak in the Raman spectrum of the graphene copper powder, and I Cu represents the peak value of the fluorescence peak in the Raman spectrum of the graphene copper powder.

[0057] The height of the G peak in the Raman spectrum means the strength of the symmetrical vibration of C-C bonds in the material. When the G peak is high relative to the fluorescence peak of copper, it means that there is more carbon related to graphene in the material, which is beneficial to the electrical conductivity and thermal conductivity of the final product.

[0058] The Raman characteristic peak I 2D / I Cu <1, which indicates the low defect characteristics of graphene, a good interface, and graphene will not be lifted on the surface of copper atoms, which is the structural basis for the high electrical conductivity / thermal conductivity of the subsequent graphene copper composite material. The principle lies in 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 the 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 graphene has been separated from contact due to oxidation of the copper matrix.

[0059] In some embodiments, the graphene copper powder for in-situ growth of graphene specifically adopts the CP series products of Suzhou Shengguang Material Co., Ltd., such as CP200 and CP300.

[0060] In some embodiments, for the copper powder for in-situ growth of graphene, the present application adopts a hot isostatic pressing process to complete the blank pretreatment. Unlike the conventional path of "needing to be sintered to be dense after hot isostatic pressing", the present application adopts a specific graphene copper powder for in-situ growth of graphene and precise control of hot isostatic pressing to provide a structure-stable blank for subsequent hot extrusion and drawing without a sintering process.

[0061] In the hot isostatic pressing process, the copper powder in which graphene is grown in situ is packaged with a copper jacket, and the inside of the jacket is pumped to high vacuum and then sealed. This operation implements high-pressure forming in an environment completely isolated from oxygen, and the copper jacket acts as a vacuum barrier to block the contact between the copper powder and oxygen, so that the oxygen content of the blank is strictly controlled to be < 150 ppm, providing a low-oxygen blank basis for subsequent sintering-free direct hot extrusion.

[0062] The application adopts a copper jacket to package copper powder in which graphene is grown in situ, and performs hot isostatic pressing under an environment with a vacuum degree ≤10 -2 Pa, and applies a pressure of 850-950 MPa.

[0063] The hot isostatic pressing process specifically includes:

[0064] Segmented heat preservation at 200-500°C for 10-300 minutes to remove volatile impurities and oxygen in the graphene copper powder.

[0065] In some embodiments, the hot isostatic pressing process includes a step of removing impurities by stepwise heating: heat preservation at 180-220°C, 280-320°C and 380-420°C respectively for 25-35 minutes, to effectively remove volatile impurities, and the obtained blank has an oxygen content ≤80 ppm and a density of at least 8.8 g / cm 3 The total processing time of the hot isostatic pressing process is controlled to be within 300 minutes.

[0066] This process realizes the preparation of ultra-low oxygen content (≤80 ppm) and high-density blank under high pressure and precise temperature control by isolating oxygen through the copper jacket, and provides a high-quality preform with a stable structure for subsequent sintering-free direct hot extrusion, fundamentally avoiding the problem of graphene grain boundary segregation caused by copper grain coarsening in the sintering densification process.

[0067] In some embodiments, after obtaining the hot isostatic pressing blank by hot isostatic pressing, the application adopts a sintering-free direct extrusion process to obtain an extruded blank. The extrusion process includes a hot extrusion process and a continuous extrusion process after the hot extrusion process.

[0068] The extrusion ratio of the hot extrusion process is 50-250, and the extrusion ratio forces the graphene to align preferentially along the extrusion direction, and the continuous extrusion disperses stress and reduces the risk of breakage.

[0069] If the extrusion ratio is < 50, the deformation amount is insufficient, the copper grains are only "weakly sheared and refined", and the degree of graphene orientation is small; after hot extrusion, the density of the extruded blank is small, and stress concentration is caused by micropores during drawing, which increases the breakage rate.

[0070] If the extrusion ratio is greater than 250, the deformation resistance index rises exponentially, which easily leads to surface cracks and internal residual stress concentration of the extrusion billet; stress release during drawing leads to interface debonding, increasing the strength discreteness and reducing the strength of graphene-copper composite.

[0071] The pressure of hot extrusion treatment is maintained at 200-1000 MPa. High pressure makes graphene and copper tightly combined, avoiding the defects of traditional sintering "copper grain growth→graphene is squeezed to the grain boundary".

[0072] If the pressure is less than 200 MPa, it will lead to insufficient powder bonding force, low density of extrusion billet, and large internal porosity; the porosity aggravates the skin effect at high frequency, and the alternating current resistance is not optimized.

[0073] If the pressure is greater than 1000 MPa, it is easy to cause mold deformation / seal failure, and high shear stress makes graphene layers fold / break.

[0074] The temperature of hot extrusion treatment is 400-800℃. 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 >0.9, and there is no 2D peak in direct detection, which makes it have strong interface effect, and thus the graphene does not agglomerate / decompose at 400-800℃, enhancing the stability of graphene-copper.

[0075] If the temperature is less than 400℃, it is easy to lead to insufficient copper atom diffusion, only mechanical engagement without metallurgical bonding, low density of extrusion billet, and difficulty in electron transfer between copper and graphene, increasing the drawing breakage rate; the strength of graphene-copper composite is insufficient.

[0076] If the temperature is greater than 800℃, the copper grain coarsening degree is greater, which destroys the interface between the in-situ grown graphene and copper, and the graphene may rearrange, reducing the strength of graphene-copper composite.

[0077] The extrusion speed of hot extrusion treatment is 20-100 mm / s. The hot extrusion process time is short, the copper crystal cannot grow, and the graphene is still inside the copper material; and the copper material is partially reconstructed by hot extrusion, the graphene is more uniformly dispersed in the copper material, and the copper material density is improved.

[0078] If the speed is less than 20 mm / s, it will lead to a sharp drop in production efficiency and a sharp increase in cost; and long time retention at 400-600℃ easily makes the graphene tend to agglomerate and disorderly arrange in the process of copper grain growth, which has an adverse effect on the subsequent effect.

[0079] If the speed is greater than 100 mm / s, the deformation is too fast to cause uneven hot extrusion, and the residual stress is concentrated; when drawing, stress release causes interface debonding and cracking, the breakage rate increases, and fine copper wires cannot be stably prepared.

[0080] The extrusion billet after hot extrusion is immersed in cooling water for cooling, and the cooling water needs to be deoxidized.

[0081] The traditional process path of "hot isostatic pressing + sintering" needs to realize the densification of the billet through high-temperature sintering. In this process, under the driving of sintering thermodynamics, the copper grains in the hot isostatic pressing billet are rapidly coarsened. Due to the difference in interface energy between graphene and the copper matrix, the growing copper grains will drive a large amount of graphene away to the grain boundary through the "pushing effect", resulting in the aggregation of graphene at the grain boundary and the failure of the dispersion of graphene in the grain, which seriously weakens the strengthening and modification effect of graphene on the copper matrix. The aggregation of graphene at the grain boundary will cause the sudden drop of the "graphene-copper" interface bonding force. In the subsequent drawing process, stress concentration easily causes interface debonding, delamination and even cracking, resulting in a high breakage rate during the preparation of graphene copper wires, and it is difficult to stably prepare fine copper wires with a diameter of 0.2 mm to 2.0 mm. In addition, the graphene at the grain boundary forms an "electrically conductive barrier", and the coarse grains intensify the skin effect, resulting in limited reduction of the alternating current resistance of the graphene copper composite material and limited improvement of the wire strength.

[0082] The present application skips the sintering process and directly enters the hot extrusion link with the hot isostatic pressing billet. Under the above temperature and pressure environment, the hot extrusion with a large extrusion ratio allows the graphene nanosheet to have the opportunity to arrange radially during the thermal deformation of the composite material, forming an ordered structure, which provides core structural support for the subsequent breakthrough in electrical and mechanical properties.

[0083] In some embodiments, the hot extrusion billet obtained after the end of hot extrusion is continuously extruded, the extrusion ratio during continuous extrusion is 2-25, the pressure is kept at 10-20 MPa, and the extrusion speed is 8-12 revolutions per minute.

[0084] In some embodiments, the drawing process adopts a 2-3 pass gradual deformation strategy, and the single pass deformation amount is strictly controlled within the range of 4-15%.

[0085] When the deformation amount exceeds 20%, annealing treatment is required, and online dynamic annealing operation or bell furnace annealing operation can be selected, the annealing temperature is 300-500 degrees, and the annealing time is 30-600 minutes.

[0086] In some embodiments, during bell furnace annealing, at least one of argon, nitrogen and hydrogen is used for flushing before heating, hydrogen reduces and removes oxides, and nitrogen maintains an inert environment, which can significantly optimize the microstructure of copper (low oxygen grain boundary + fine grain), thereby improving the plastic deformation ability of the material and allowing more drawing passes.

[0087] 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, and avoids the interface stress concentration caused by excessive grain refinement, thereby ensuring the graphene-copper interface bonding strength.

[0088] Furthermore, through drawing processing, graphene copper composite materials can be prepared into industrial standard products (such as 30mm copper rods, 8mm copper rods, etc.), which are seamlessly connected with the current copper processing industry.

[0089] In a second aspect, the present application provides a graphene-copper composite material prepared by the above method. Under high-frequency currents above 10 kHz, the graphene-copper composite material has a resistance that is more than 10% lower than that of TU0 oxygen-free copper of the same specification, and an AC impedance that is more than 20% lower than that of oxygen-free copper at 1 MHz.

[0090] Furthermore, the graphene content in the graphene copper composite material is 50-400 ppm, the tensile strength in the annealed state is 200-260 MPa, and the tensile strength in the hard state is 350-450 MPa; the thermal conductivity is greater than 420 W / mK, the DC conductivity is 104-106% IACS, and the carrier concentration reaches 1.33×10 23 m -3 .

[0091] Furthermore, the graphene copper composite material may be a graphene copper composite wire having a wire diameter of 0.01 mm to 8.0 mm.

[0092] Furthermore, the graphene-copper composite material has excellent processing properties. It can achieve continuous wire drawing without breakage. When preparing enameled wire, it has good adhesion to currently used resins, ensuring the voltage resistance of the enameled wire (enabling it to be used in subsequent high-voltage platforms such as electric vehicles and drones).

[0093] Furthermore, graphene copper composite materials have high strength and high softening temperature and can be used in high-temperature scenarios.

[0094] The present application is further illustrated by the following examples.

[0095] Example 1

[0096] The parameters of the graphene copper powder used in this embodiment are a specific surface area of ​​0.2m 2 / g, particle size is -325 mesh (<45 microns), density is 1.6g / mL, carbon content is 175ppm, graphene characteristic peak I G / I Cu is 0.95.

[0097] After the graphene copper powder is placed in the copper sleeve, it is cold pressed and the copper sleeve is directly vacuum sealed. The vacuum degree is maintained at 1×10 -2(200℃ for 30 min, 300℃ for 30 min, 400℃ for 30 min, all for removing impurities, control oxygen content less than 350ppm)

[0098] The graphene copper powder is subjected to hot isostatic pressing treatment at a temperature of 920℃, a pressure of 920MPa, and a time of 4 hours to obtain a hot isostatic pressing blank;

[0099] The hot isostatic pressing blank is subjected to hot extrusion treatment to obtain an extruded blank; the extrusion ratio is 120, the pressure is kept at 500MPa, the temperature is 800℃, and the extrusion speed is 50mm / s. After completion, direct water cooling is performed, and the cooling water is subjected to deoxidation treatment.

[0100] After the hot extrusion treatment, continuous extrusion treatment is performed, and the extrusion ratio during the continuous extrusion treatment is 2-25, the pressure is kept at 10-20MPa, and the extrusion speed is 8-12 revolutions per minute.

[0101] Drawing treatment is performed, and a 4.624mm rod is finally extruded at an extrusion ratio of 20:1.

[0102] Example 2

[0103] The graphene copper powder used in this example has a specific surface area of 0.3m 2 / g, a particle size of -325 mesh (<45 microns), a density of 1.8g / mL, a carbon content of 200ppm, and a graphene characteristic peak I G / I Cu of 0.96.

[0104] The graphene copper powder is subjected to hot isostatic pressing treatment at a temperature of 900℃, a pressure of 900MPa, and a time of 270 minutes, and the copper powder is packaged with a copper jacket. The copper jacket is directly vacuum sealed. The pressure is 200MPa, and the time is 60min to obtain a blank;

[0105] The blank is subjected to hot extrusion treatment in a continuous hot extrusion device to obtain an extruded blank; the extrusion ratio is 200:1, the pressure is kept at 700MPa, the temperature is 750℃, and the extrusion speed is 15mm / s.

[0106] Drawing treatment is performed, and a 0.3mm wire is finally extruded at an extrusion ratio of 10:1.

[0107] Example 3

[0108] The graphene copper powder used in this example has a specific surface area of 0.2m 2 / g, a particle size of -325 mesh (<45 microns), a density of 1.0g / mL, a carbon content of 217ppm, and a graphene characteristic peak I G / I Cu of 0.97.

[0109] The graphene copper powder is subjected to hot static pressing treatment, the copper sheath is used to pre-press and shape the copper powder under a pressure of 4 tons, and the copper sheath is directly vacuumized and sealed. The pressure is 920 MPa, and the time is 240 min, to obtain a blank;

[0110] The blank is subjected to continuous hot extrusion treatment in a hot extrusion device, the extrusion ratio is 800, the pressure is kept at 650 MPa, the temperature is 700 ℃, and the extrusion speed is 65 mm / s.

[0111] Subsequently, continuous extrusion is performed, the extrusion ratio is 70, the pressure is kept at 650 MPa, the temperature is 700 ℃, and the extrusion speed is 12 mm / s. An extruded blank is obtained;

[0112] The blank is subjected to drawing treatment, and an extruded blank of 4.6 mm is finally extruded at an extrusion ratio of 20:1.

[0113] Figure 2 The AC impedance comparison diagram of the graphene copper composite material provided by some embodiments of the present application is shown in FIG. 1. Figure 2 As can be seen from FIG. 1, the AC resistance of the graphene copper composite material (4.6 mm) prepared in the present application is obviously reduced compared with that of oxygen-free copper when the frequency is greater than 10 kHz.

[0114] Figure 3 The attenuation comparison diagram of the graphene copper composite material provided by some embodiments of the present application with a silver-plated conductor under different high-frequency test conditions is shown in FIG. 2.

[0115] As shown in FIG. 2, the attenuation of the graphene copper composite material prepared in the present application under different high-frequency test conditions is better than that of silver-plated copper and oxygen-free copper. Figure 3

[0116] The AC resistance increase comparison diagram of the graphene copper composite material provided by some embodiments of the present application with oxygen-free copper under the condition of 1-1000 kHz is shown in FIG. 3. Figure 4 As can be seen from FIG. 3, the AC impedance of the graphene copper composite material at 1 MHz is about 9% lower than that of oxygen-free copper.

[0117] Figure 4 Table 1 is a performance comparison table of the graphene copper wire (oxygen content 50 ppm) obtained by powder metallurgy and oxygen-free copper. As shown in Table 1, the graphene copper composite material prepared in the present application is better than oxygen-free copper in terms of carrier concentration, thermal conductivity, AC impedance, and oxidation resistance time.

[0118] Table 1

[0119]

[0120]

[0121] ​​

[0122] It should be pointed out finally 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 will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced equivalently. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle 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 capable of resisting skin effect, characterized in that: include: The copper powder with in-situ graphene growth is subjected to hot isostatic pressing to obtain a hot isostatic pressed blank; Extruding the hot isostatically pressed billet to obtain an extruded billet; Drawing the extruded billet to obtain a graphene-copper composite material; The carbon content of the graphene on the copper powder used for in-situ growth of graphene is 100-500ppm, the oxygen content is less than 350ppm, and the Raman characteristic peak I G / I Cu >0.9, Raman characteristic peak I 2D / I Cu <1.

2. The method for preparing a graphene-copper composite material capable of resisting skin effect according to claim 1, wherein: The specific surface area of ​​the copper powder for in-situ graphene growth is 0.1 to 0.5 m 2 / g, particle size is 5 to 75 microns, and bulk density is 0.7 to 2.0 g / mL.

3. The method for preparing a graphene-copper composite material capable of resisting skin effect according to claim 1, wherein: Place the graphene copper powder in a copper sheath and control the vacuum degree of the inner space of the copper sheath to be ≤1×10 -2 Pa, and a pressure of about 850MPa to 950MPa is applied to the graphene copper powder to perform hot isostatic pressing.

4. The method for preparing a graphene-copper composite material capable of resisting skin effect according to claim 3, wherein: The hot isostatic pressing treatment comprises: Keeping the temperature between 200°C and 500°C for 10 to 300 minutes in stages to remove volatile impurities and oxygen from the graphene copper powder; The hot isostatically pressed blank obtained after hot isostatic pressing has an oxygen content of ≤80ppm and a density of at least 8.8g / cm 3 ; Preferably, the temperature is kept at 280-320°C and 380-420°C for 5 to 90 minutes respectively.

5. The method for preparing a graphene-copper composite material capable of resisting skin effect according to claim 1, wherein: The extrusion process includes hot extrusion process, wherein the extrusion ratio of the hot extrusion process is 50-250, the pressure is maintained at 200-1000 MPa, the temperature is 400-800 degrees, and the extrusion speed is 20-100 mm / s.

6. The method for preparing a graphene-copper composite material capable of resisting skin effect according to claim 5, wherein: The extrusion process includes continuous extrusion process, which is performed after the hot extrusion process. The extrusion ratio during the continuous extrusion process is 2-25, the pressure is maintained at 10-20 MPa, and the extrusion speed is 8-12 rpm.

7. The method for preparing a graphene-copper composite material capable of resisting skin effect according to claim 1, wherein: The deformation amount of a single drawing process is controlled within a range of 4 to 15%.

8. The method for preparing a graphene-copper composite material capable of resisting skin effect according to claim 7, wherein: When the deformation exceeds 20%, an annealing operation is performed, wherein the annealing operation adopts an online dynamic annealing operation or a bell furnace annealing operation; Annealing temperature is 300-500 degrees; Preferably, when annealing is performed in a bell-shaped furnace, at least one of argon, nitrogen and hydrogen is used for flushing; preferably, the annealing time is 30 to 600 minutes.

9. The graphene-copper composite material prepared by the method for preparing a graphene-copper composite material capable of resisting skin effect according to any one of claims 1 to 8, characterized in that: Under high-frequency currents above 10 kHz, the resistance of the graphene-copper composite material is more than 10% lower than that of TU0 oxygen-free copper of the same specification, and the AC impedance at 1 MHz is more than 20% lower than that of oxygen-free copper.

10. The graphene copper composite material according to claim 9, characterized in that: The graphene copper composite material has a graphene content of 50 to 400 ppm, a tensile strength of 200 to 260 MPa in the annealed state, and a tensile strength of 350 to 450 MPa in the hard state; a thermal conductivity greater than 420 W / mK, a DC conductivity of 104 to 106% IACS, and a carrier concentration of 1.33×10 23 m -3 ; Preferably, the graphene-copper composite material is a graphene-copper composite wire, and the diameter of the graphene-copper composite wire is 0.01 mm to 8.0 mm.

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