Graphene-copper composite wire and method for manufacturing the same

Abstract

The embodiment of the present application provides a graphene-copper composite wire and a preparation method thereof. The graphene-copper composite wire comprises a copper base and a plurality of graphene sheets connected with the copper base. The copper base comprises copper grains distributed along the radial direction of the wire and copper grains distributed along the axial direction of the wire. At least part of the plurality of graphene sheets is embedded at the grain boundary of adjacent copper grains. The plurality of graphene sheets comprises graphene sheets that are overlapped with each other and graphene sheets that are spaced apart. The graphene-copper composite wire provided by the embodiment of the present application has good conductivity.

Description

Technical Field

[0001] This application relates to the field of composite materials, and particularly to a type of graphene. Copper composite conductors and their preparation methods. Background Technology

[0002] Pure copper has a conductivity limit of 100% IACS, and suffers from significant skin effect and low strength at high frequencies, making it unsuitable for the performance requirements of next-generation high-end equipment. Graphene, with its ultra-high carrier mobility, excellent conductivity, and mechanical properties, has become the most promising reinforcing phase for copper-based composites. The technological development of graphene-copper composite wires has gone through three stages: the first stage was mechanical mixing, the second stage was in-situ CVD coating, and the third stage was plastic deformation orientation control. However, graphene-copper composite wires prepared by existing technologies generally suffer from low conductivity. Summary of the Invention

[0003] Based on this, the embodiments of this application provide a graphene Copper composite conductors and their preparation methods.

[0004] In a first aspect, embodiments of this application provide a graphene A copper composite conductor includes a copper substrate and a plurality of graphene sheets connected to the copper substrate. The copper substrate includes copper grains distributed radially along the conductor and copper grains distributed axially along the conductor. At least a portion of the plurality of graphene sheets is embedded at the grain boundaries of adjacent copper grains. The plurality of graphene sheets includes overlapping graphene sheets and spaced-apart graphene sheets.

[0005] In some embodiments, the overlap rate of the graphene sheets is 70% to 98%.

[0006] In some embodiments, the ratio of the sum of the number of graphene sheets with an orientation angle of less than or equal to 30° to the total number of all graphene sheets is greater than or equal to 85%, wherein the orientation angle is the angle between the graphene sheet and the graphene... The included angle between the axial directions of the copper composite conductor.

[0007] In some embodiments, the ratio of the sum of the number of graphene sheets with an orientation angle of 20° to 30° to the total number of all graphene sheets is 0 to 20%; and / or, The ratio of the sum of the number of graphene sheets with an orientation angle of 10° to 20° to the total number of all graphene sheets is 10% to 30%; and / or, The ratio of the total number of graphene sheets with an orientation angle of less than or equal to 10° to the total number of all graphene sheets is 50% to 80%.

[0008] In some embodiments, the length of the graphene sheet is 2 μm to 10 μm; and / or, The graphene On the longitudinal section of the copper composite conductor, 100μm 2 The number of graphene sheets described within the range is 5 to 40; and / or, The graphene In the copper composite wire, the graphene sheet content is 10ppm to 1000ppm; and / or, The graphene sheet has 1 to 10 graphene layers.

[0009] In some embodiments, in the graphene In the longitudinal section of the copper composite conductor, the total area of ​​the {111} crystal plane, near-{111} crystal plane, {001} crystal plane, and near-{001} crystal plane of the copper grains accounts for greater than or equal to 85%. The near-{111} crystal plane refers to a crystal plane with an angle greater than 0 and less than or equal to 15° with respect to the {111} crystal plane, and the near-{001} crystal plane refers to a crystal plane with an angle greater than 0 and less than or equal to 15° with respect to the {001} crystal plane; and / or, At least a portion of the copper grains in the copper matrix are columnar crystals, and the columnar crystals are copper grains with an aspect ratio greater than or equal to 2:1.

[0010] In some embodiments, the graphene The equivalent circular diameter of the cross-section of the copper composite conductor is 20μm~200μm; and / or, The graphene The conductivity of copper composite conductors is 110% IACS to 118% IACS.

[0011] Secondly, embodiments of this application provide a graphene The preparation method of copper composite conductors includes: A copper raw material is provided, and graphene is deposited on the surface of the copper raw material to obtain a graphene-copper composite material; The graphene-copper composite material was subjected to hot pressing to obtain a dense graphene-copper ingot. The graphene copper dense ingot is hot-extruded to obtain a graphene copper rod-shaped billet. The graphene copper rod blank is cold-drawn at a drawing rate of 20m / min to 1000m / min to obtain a graphene copper composite wire. The graphene-copper composite wire was annealed to obtain graphene. Copper composite conductor.

[0012] In some embodiments, the cumulative true strain of the cold-drawn graphene copper rod blank is 8 to 18.

[0013] In some embodiments, the cold drawing is achieved by multiple drawing operations, and the true strain of a single drawing operation is 10% to 25% of the cumulative true strain.

[0014] The graphene provided in the embodiments of this application A copper composite wire comprises a copper substrate and multiple graphene sheets connected to the copper substrate. The graphene sheets include overlapping graphene sheets and spaced-apart graphene sheets. The overlapping graphene sheets form a stable overlapping structure through end-to-end contact, creating a continuous conductive network. This provides a high-speed transport channel for electrons to bypass scattering from copper grain boundaries, significantly reducing the carbon dioxide content of the graphene. The resistivity of copper composite wires. Although the spaced graphene sheets do not form effective overlaps with adjacent graphene sheets, because they are also embedded at the grain boundaries of copper grains, electrons can directly enter the interior of the spaced graphene sheets when crossing the grain boundaries. Utilizing the ultra-high in-plane carrier mobility of graphene, low-resistance crossing is achieved, thereby reducing grain boundary scattering loss in local areas. The synergistic cooperation between the overlapping graphene sheets and the spaced graphene sheets allows electrons to achieve long-range low-resistance transport in the copper matrix through the continuous graphene network, and also obtains additional low-resistance crossing paths at local grain boundaries, thus realizing the graphene... Improved conductivity of copper composite conductors. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0016] Figure 1 Graphene provided in the embodiments of this application A schematic diagram of the structure of a copper composite conductor.

[0017] Figure 2 A flowchart illustrating the preparation method of the graphene-copper composite wire provided in the embodiments of this application.

[0018] Component symbol explanation: 100. Graphene Copper composite conductor; 20. Copper substrate; 21. Copper grains; 30. Graphene sheet. Detailed Implementation

[0019] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0020] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0021] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0022] In this application, the longitudinal section refers to a cross section parallel to the conductor's axial direction, and the cross section refers to a cross section perpendicular to the conductor's axial direction.

[0023] Please see Figure 1 This application provides a graphene embodiment. A copper composite conductor 100 includes a copper substrate 20 and a plurality of graphene sheets 30 connected to the copper substrate 20. The copper substrate 20 includes copper grains 21 distributed radially along the conductor 100 and copper grains 21 distributed axially along the conductor 100. At least a portion of the plurality of graphene sheets 30 is embedded at the grain boundaries of adjacent copper grains 21. The plurality of graphene sheets 30 includes overlapping graphene sheets 30 and spaced-apart graphene sheets 30.

[0024] The overlapping graphene sheets 30 refer to graphene sheets 30 that form an effective overlap with adjacent graphene sheets 30. An effective overlap means that the graphene sheets 30 overlap and contact each other with adjacent graphene sheets 30, and the overlap contact length is not less than 5% of the length of the graphene sheet 30 itself, thereby enabling current conduction between adjacent graphene sheets 30. The independently spaced graphene sheets 30 refer to graphene sheets 30 that do not form an effective overlap with other graphene sheets, including graphene sheets 30 that do not form direct contact with adjacent graphene sheets and graphene sheets 30 whose overlap contact length with adjacent graphene sheets 30 is less than 5% of their own length.

[0025] In the embodiments of this application, the overlapping forms between the graphene sheets 30 include pairwise overlapping between two graphene sheets 30, overlapping chains formed by three or more graphene sheets 30 connected in series along the axial direction of the wire, and mesh overlapping structures formed by three or more graphene sheets 30 being spatially stacked and cross-stacked.

[0026] The graphene provided in the embodiments of this application A copper composite conductor 100 includes a copper substrate 20 and multiple graphene sheets 30 connected to the copper substrate 20. The multiple graphene sheets 30 include overlapping graphene sheets 30 and spaced-apart graphene sheets 30. The overlapping graphene sheets 30 form a stable overlapping structure through end-overlapping contacts, creating a continuous conductive network. This provides a high-speed transport channel for electrons to bypass scattering from copper grain boundaries, significantly reducing the scattering of graphene. The resistivity of the copper composite wire 100. Although the spaced-apart graphene sheets 30 do not form effective overlaps with adjacent graphene sheets 30, because they are also embedded at the grain boundaries of the copper grains 21, electrons can directly enter the interior of the spaced-apart graphene sheets 30 when crossing the grain boundaries. Utilizing the ultra-high in-plane carrier mobility of graphene, low-resistance crossing is achieved, thereby reducing grain boundary scattering loss in local areas. The overlapping graphene sheets 30 and the spaced-apart graphene sheets 30 work together to enable electrons to achieve long-range low-resistance transport in the copper substrate 20 through the continuous graphene network, and also to obtain additional low-resistance crossing paths at local grain boundaries, thus realizing the graphene... Improved conductivity of copper composite conductor 100.

[0027] For example, the overlap rate of the graphene sheet is 70%~98%, such as 70%, 72%, 75%, 77%, 80%, 82%, 85%, 87%, 90%, 92%, 95%, 96%, 98%, etc. It should be noted that the overlap rate of the graphene sheet 30 refers to the ratio of the number of graphene sheets 30 forming effective overlaps to the total number of all graphene sheets 30. For example, the test method for the overlap rate of the graphene sheet includes: preparing a longitudinal section sample along the axis of the conductor, observing it using a transmission electron microscope (TEM), randomly selecting no less than 6 non-overlapping fields of view at a magnification of 10,000x~50,000x, completing the statistical analysis of the graphene sheet overlap rate, and taking the average of multiple fields of view as the final result.

[0028] When the overlap rate of the graphene sheet 30 is greater than or equal to 70%, a stable end-overlap structure can be formed between adjacent graphene sheets 30, thereby constructing a continuous three-dimensional conductive network. This ensures efficient electron transport between the graphene sheets 30, thus improving the performance of graphene. Conductivity of copper composite conductor 100.

[0029] For example, the ratio of the sum of the number of graphene sheets 30 with an orientation angle of less than or equal to 30° to the total number of all graphene sheets 30 is greater than or equal to 85%, such as 85%, 88%, 90%, 92%, 95%, 98%, etc., where the orientation angle is the angle between the graphene sheet 30 and the graphene... The included angle between the axes of the copper composite conductor 100. For example, the test method for "the ratio of the sum of the number of graphene sheets 30 with an orientation angle less than or equal to 30° to the total number of all graphene sheets 30" includes: preparing a longitudinal section sample along the conductor axis, observing it using a transmission electron microscope (TEM), randomly selecting no fewer than 6 non-overlapping fields of view at a magnification of 10,000x to 50,000x, counting the number of graphene sheets with different orientation angles in each field of view, calculating the proportion of graphene sheets with an orientation angle ≤ 30° in each field of view, and taking the average of the proportions of all fields of view as the final result.

[0030] When with graphene When the proportion of graphene sheets 30 with an axial angle of less than or equal to 30° in the copper composite wire 100 is more than 85%, it means that the graphene sheets 30 in the wire are arranged with a high degree of orientation along the axial direction of the copper substrate 20. The highly oriented graphene sheets 30 can work synergistically with the axially extended copper grains 21 to significantly reduce grain boundary scattering and interface scattering in the electron transport path. At the same time, the continuously oriented graphene sheets 30 construct a highly efficient conductive path that runs through the length of the wire, giving full play to the excellent conductivity of graphene, compensating for electron loss at the grain boundaries of the copper grains 21, reducing the overall resistivity, and thus significantly improving the performance of graphene. Conductivity of copper composite conductor 100.

[0031] In some embodiments, a portion of the plurality of graphene sheets 30 are attached to the outer surface of the copper substrate 20. These graphene sheets 30 originate from the preparation process: the surface of the graphene-copper dense ingot obtained by hot pressing inevitably retains some graphene sheets 30, and after drawing, these graphene sheets 30 remain attached to the outer surface of the conductor. Therefore, the graphene-copper composite conductor 100 not only has graphene sheets 30 embedded internally, but also has graphene sheets 30 attached to its outer surface, thereby further improving the conductivity of the composite conductor.

[0032] For example, the ratio of the sum of the number of graphene sheets 30 with an orientation angle of less than or equal to 10° to the total number of all graphene sheets 30 is 50% to 80%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc. It can be seen that the graphene sheets 30 with an orientation angle ≤10° account for the majority (50% to 80%). This part of the graphene sheets 30 is parallel to the axial height of the wire, which can form the main conductive channel that runs through the length of the wire, maximizing the advantage of the high carrier mobility of graphene. In addition, the graphene sheets 30 are oriented along the axial height of the wire, which can cooperate with the axially extended copper grains 21 to effectively reduce the scattering loss of electrons at grain boundaries and phase interfaces, and further improve the conductivity of the graphene-copper composite wire.

[0033] For example, the ratio of the sum of the number of graphene sheets 30 with orientation angles of 10° to 20° to the total number of all graphene sheets 30 is 10% to 30%, such as 10%, 15%, 20%, 25%, 30%, etc. By controlling the proportion of graphene sheets with orientation angles of 10° to 20° to 10% to 30%, a highly efficient secondary conductive network can be constructed between highly oriented (orientation angle ≤ 10°) graphene sheets and the copper substrate 20. Although the orientation of these small-angle graphene sheets deviates slightly from the axis, their in-plane conductivity is still far superior to that of random distribution, and they can serve as parallel conductive branches to further reduce the overall resistivity. Meanwhile, this ratio range ensures the uniform transfer of stress from the copper substrate 20 to the highly oriented (orientation angle ≤ 10°) graphene sheets during the drawing process, avoiding stress concentration that could cause the highly oriented (orientation angle ≤ 10°) graphene sheets to break; and an appropriate amount of small-angle (10°~20°) graphene sheets can form physical anchor points at the grain boundaries of the copper grains 21, suppressing abnormal growth of copper grains during annealing and stabilizing the columnar crystal texture.

[0034] For example, the ratio of the sum of the number of graphene sheets 30 with an orientation angle of 20°~30° to the total number of all graphene sheets 30 is 0~20%, such as 0, 5%, 10%, 15%, 20%, etc. By controlling the proportion of graphene sheets 30 with an orientation angle of 20°~30° to below 20%, the interference of medium-angle graphene sheets on the conductive path can be effectively suppressed. These graphene sheets deviate to the axis of the wire to a certain extent. When electrons are transported, they need to bypass the edge of the graphene sheet, which will generate additional interface scattering and path extension, resulting in an increase in local resistance. By limiting their proportion to a low level, most graphene sheets are oriented at a smaller angle (<20°), which significantly reduces the electron loss caused by non-ideal orientation and improves the orientation uniformity of the overall conductive path.

[0035] For example, the length of the graphene sheet 30 is 2μm to 10μm, such as 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc. It should be noted that the length of the graphene sheet 30 refers to the maximum straight-line distance between the two ends of the cross-sectional profile of a single graphene sheet 30 on the axial or longitudinal cross-section of the graphene-copper composite conductor 100. It can be seen that the size of the graphene sheet 30 is not less than 2μm, ensuring that adjacent graphene sheets 30 overlap, thereby forming a continuous conductive path; at the same time, the size of the graphene sheet 30 is not greater than 10μm, which avoids excessively large graphene sheets 30 leading to layer agglomeration and stress concentration within the copper substrate 20.

[0036] Exemplary example, the graphene On the longitudinal section of copper composite conductor 100, 100μm 2The number of graphene sheets 30 within the specified range is 5 to 40, for example, 5, 10, 15, 20, 25, 30, 35, 40, etc. It can be seen that the graphene sheets 30 have a suitable distribution density within the copper substrate 20, which not only forms a continuously overlapping conductive network but also avoids the phenomenon of local agglomeration caused by excessively dense distribution of the graphene sheets 30.

[0037] For example, in the longitudinal section of the graphene-copper composite wire 100, the crystal plane distribution of the copper grains 21 includes: at least two copper grains arranged sequentially along the axial direction of the wire 100 are simultaneously {001} crystal planes; and / or, at least two copper grains arranged sequentially along the axial direction of the wire 100 are simultaneously {111} crystal planes. Since both the {001} and {111} crystal planes are low-index crystal planes of face-centered cubic copper, with a dense and regular atomic arrangement, electrons exhibit weak lattice scattering and a long mean free path when transported within grains of this orientation, resulting in a significantly lower intrinsic resistivity compared to other crystal plane orientations. Therefore, in this structure, electrons can continuously pass through multiple adjacent grains that are both {001} or both {111} oriented when transported along the axial direction of the wire 100, thereby maintaining a low-scattering transport state over a longer distance, thus improving the performance of graphene. Conductivity of copper composite conductor 100.

[0038] In some embodiments, on the longitudinal section of the graphene-copper composite conductor 100, the crystal plane distribution of the copper grains 21 includes: three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, or ten or more copper grains arranged sequentially along the conductor axis are simultaneously {001} crystal planes; and / or, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, or ten or more copper grains arranged sequentially along the conductor axis are simultaneously {111} crystal planes.

[0039] It should be noted that, in addition to the continuous {001} crystal planes and / or {111} crystal planes mentioned above, there may also be individually spaced {001} crystal planes and / or individually spaced {111} crystal planes distributed on the longitudinal section of the graphene-copper composite wire 100.

[0040] Exemplarily, in the graphene On the longitudinal section of the copper composite conductor 100, the total area of ​​the {111} crystal plane, near {111} crystal plane, {001} crystal plane, and near {001} crystal plane of the copper grains accounts for more than or equal to 85%, for example, 85%, 88%, 90%, 92%, 95%, 98%, etc. The near {111} crystal plane refers to a crystal plane with an angle greater than 0 and less than or equal to 15° with the {111} crystal plane, and the near {001} crystal plane refers to a crystal plane with an angle greater than 0 and less than or equal to 15° with the {001} crystal plane. The total area of ​​the {111} crystal plane, near {111} crystal plane, {001} crystal plane, and near {001} crystal plane is the ratio of the total area of ​​the {111} crystal plane, near {111} crystal plane, {001} crystal plane, and near {001} crystal plane on the longitudinal section to the area of ​​the longitudinal section of the copper substrate 20. For example, the method for testing the proportion of the area of ​​the {111} crystal plane, near {111} crystal plane, {001} crystal plane, and near {001} crystal plane of copper grains is as follows: backscattered electron diffraction (EBSD) is used to prepare samples along the longitudinal section of the wire axis, the grain orientation is calibrated by Kikuchi belt, the proportion of grain area of ​​the target crystal plane orientation is statistically analyzed, no less than 5 non-overlapping fields of view are selected, and the average value is taken as the final result.

[0041] Both the {111} and {001} crystal planes are low-index crystal planes of face-centered cubic copper, with dense and regular atomic arrangement. When electrons propagate within these oriented grains, lattice scattering is weak and the mean free path is long. The orientation deviation of the near {111} and near {001} crystal planes from their corresponding ideal crystal planes does not exceed 15°, and they also possess low lattice scattering characteristics. By controlling the area ratio of the above four types of low-scattering crystal planes to above 85%, it means that the vast majority of copper grains 21 on the longitudinal section of the conductor 100 have a low-impedance orientation for electron transport, which can significantly reduce the intrinsic resistivity of the copper substrate 20, thereby improving the conductivity of the graphene-copper composite conductor 100.

[0042] For example, the near-{001} crystal plane includes at least one of the {601} crystal plane, {701} crystal plane, and {801} crystal plane; the near-{111} crystal plane includes at least one of the {223} crystal plane, {334} crystal plane, and {445} crystal plane.

[0043] In some embodiments, a portion of the plurality of graphene sheets 30 are attached to the outer surface of the copper substrate 20, in which case the graphene... The copper composite wire 100 not only has graphene sheets 30 embedded inside, but also has graphene sheets 30 attached to its outer surface, thereby further enhancing the graphene content. Conductivity of copper composite conductor 100.

[0044] Exemplarily, in the graphene In the longitudinal section of the copper composite conductor 100, the area ratio of the {111} crystal planes of the copper grains 21 is 20% to 90%, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%. The area ratio of the {111} crystal planes of the copper grains 21 is the ratio of the total area of ​​the {111} crystal planes in the longitudinal section to the area of ​​the longitudinal section of the copper substrate 20. It can be understood that the {111} crystal planes in the copper grains 21 have a low electron scattering probability and optimal conductivity. A higher proportion of {111} crystal planes can directly reduce the resistivity of the copper substrate 20, thereby improving the conductivity of the graphene-copper composite conductor 100.

[0045] Exemplarily, in the graphene In the longitudinal section of the copper composite wire 100, the area ratio of the {001} crystal plane of the copper grains 21 is 20%~90%, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc. The area ratio of the {001} crystal plane of the copper grains 21 is the ratio of the total area of ​​the {001} crystal planes on the longitudinal section to the area of ​​the longitudinal section of the copper substrate 20. It can be understood that, in addition to good electrical conductivity, the {001} crystal plane also possesses excellent plastic deformation capability, which can guide the copper grains 21 to elongate along the wire axis and form columnar crystals during multi-pass drawing processes. This reduces transverse grain boundaries perpendicular to the wire axis, lowers electron grain boundary scattering loss, and thus improves the electrical conductivity of the graphene-copper composite wire 100.

[0046] For example, at least a portion of the copper grains 21 in the copper substrate 20 are columnar crystals, wherein the columnar crystals are copper grains 21 with an aspect ratio greater than or equal to 2:1, and the aspect ratio is the ratio of the length of the major axis to the length of the minor axis of the copper grain 21. For example, the method for testing the aspect ratio of the columnar crystals is as follows: backscattered electron diffraction (EBSD) combined with metallographic microscopy is used for analysis. The test sample is prepared along the longitudinal section of the conductor axis (parallel to the major axis of the conductor). After mechanical polishing and electrolytic polishing, at a magnification of 100 to 10000 times, no less than 5 non-overlapping fields of view are selected to complete the statistical analysis of the aspect ratio of the columnar crystals, and the average value of multiple fields of view is taken as the final result.

[0047] When at least a portion of the copper grains 21 in the copper substrate 20 are columnar crystals, the number of transverse grain boundaries perpendicular to the axis of the graphene-copper composite wire can be reduced. When electrons propagate along the length of the wire, the grain boundary scattering effect is weakened, which can reduce the resistivity of the copper substrate 20, thereby improving the performance of the graphene-copper composite wire. Conductivity of copper composite conductor 100.

[0048] For example, the area ratio of columnar crystals is greater than or equal to 80%, such as 80%, 85%, 90%, 95%, 98%, 100%, etc., where the columnar crystal area ratio refers to the percentage of columnar crystal area in the graphene. The ratio of the sum of the cross-sectional areas of all columnar crystals on the longitudinal section of the copper composite conductor 100 to the cross-sectional area of ​​the copper substrate 20.

[0049] When the area ratio of columnar crystals is greater than or equal to 80%, it means that columnar crystals have a high area ratio. The high proportion of columnar crystals makes the copper matrix 20 form a continuous axial orientation structure, which greatly reduces the lateral grain boundary density per unit length, minimizes electron scattering loss, and steadily improves conductivity. At the same time, the large-area columnar crystal distribution can suppress the disordered orientation and random distribution of copper grains 21, avoid local agglomeration and orientation disorder of graphene, and ensure the stability of the graphene-copper bonding interface.

[0050] For example, the short axis length of the columnar crystals is 0.1 μm to 10 μm, such as 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, etc. By controlling the short axis length of the columnar crystals within the range of 0.1 μm to 10 μm, the conductivity and mechanical properties of the wire can be balanced. Setting the short axis length ≥ 0.1 μm avoids excessive grain size leading to a dramatic increase in grain boundaries and intensified electron scattering; setting the short axis length ≤ 10 μm avoids coarse grains causing surface defects and uneven graphene distribution. This range ensures that the wire has sufficient strength and plasticity, provides a continuous distribution interface for graphene, and achieves high conductivity and good processing performance.

[0051] Preferably, the short axis length of the columnar crystals is 0.2 μm to 5 μm, such as 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc. By controlling the short axis length of the columnar crystals within the range of 0.2 μm to 5 μm, the overall performance of the conductive wire can be further improved. The lower limit of 0.2 μm avoids excessive grain boundary scattering and annealing instability caused by ultrafine grains (<0.2 μm); the upper limit of 5 μm suppresses the strength reduction and surface defects caused by coarse grains (>5 μm). This range balances low electron scattering and excellent mechanical properties, providing size-matched grain boundary anchors for graphene, making the conductive network denser and more uniformly oriented, and achieving higher conductivity.

[0052] In some embodiments, the aspect ratio of the columnar crystals is (5~100):1, for example 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, 85:1, 90:1, 95:1, 100:1, etc. When the aspect ratio of the columnar crystal is (5~100):1, the copper grains 21 can be fully elongated along the axis of the graphene-copper composite wire. Compared with grains with a smaller aspect ratio, the number of transverse grain boundaries perpendicular to the wire axis per unit length can be further reduced, significantly reducing grain boundary scattering loss during electron transport, continuously reducing the resistivity of the copper substrate 20, and thus improving the conductivity of the graphene-copper composite wire.

[0053] In some embodiments, the aspect ratio of the columnar crystals is preferably ≥8:1, such as 8:1, 9:1, 10:1, 12:1, 15:1, 20:1, 25:1, 30:1, etc. When the aspect ratio reaches 8:1 or higher, the number of transverse grain boundaries per unit length of the conductor is further reduced, the electron grain boundary scattering loss is further reduced, and the reduction in the intrinsic resistivity of the copper matrix is ​​more significant. In some embodiments, for ultrafine graphene-copper composite wires with a diameter ≤30μm, due to the larger cumulative true strain from cold drawing (typically ≥15), the aspect ratio of the columnar crystals can be further increased to ≥10:1, such as 10:1, 12:1, 15:1, 18:1, 20:1, 25:1, 30:1, etc. When the aspect ratio is ≥10:1, the number of transverse grain boundaries is reduced by more than 90%, and the electron grain boundary scattering loss is reduced by an order of magnitude. In a more preferred embodiment, for ultrafine wires with a diameter less than 30μm, the aspect ratio of the columnar crystals is further preferably ≥15:1, such as 15:1, 18:1, 20:1, 22:1, 25:1, 28:1, 30:1, etc. When the aspect ratio reaches 15:1 or higher, the number of transverse grain boundaries is reduced by more than 93%, and the resistivity contributed by the scattering of copper matrix grain boundaries has been compressed to an extremely low level.

[0054] For example, the test method for columnar crystal short axis length, columnar crystal aspect ratio, and columnar crystal area ratio is as follows: backscattered electron diffraction (EBSD) combined with metallographic microscopy is used for analysis. The test sample is prepared along the longitudinal section of the conductor axis (parallel to the conductor's long axis). After mechanical polishing and electrolytic polishing, at a magnification of 100 to 10000 times, no less than 5 non-overlapping fields of view are selected to complete the statistical analysis of columnar crystal short axis length, columnar crystal aspect ratio, and columnar crystal area ratio. The average value of multiple fields of view is taken as the final result.

[0055] In some embodiments, the axial direction of the columnar crystals is parallel to that of the graphene. The included angle between the axes of the copper composite conductor 100 is less than or equal to 15°, such as 0°, 3°, 6°, 9°, 12°, 15°, etc.

[0056] It is understandable that when the axial direction of the columnar crystals is aligned with that of the graphene... When the included angle between the axes of the copper composite wire 100 is less than or equal to 15°, it means that the columnar crystals are oriented along the length of the wire, and the grains are arranged in a regular and orderly manner, which can avoid the phenomenon of increased transverse grain boundaries caused by grain tilting and disorder. When electrons are transported along the axis of the wire, the path is smoother, and the grain boundary scattering is further reduced, which is conducive to stabilizing and improving the conductivity of the composite wire. At the same time, it can ensure that the 30 layers of graphene sheets are simultaneously oriented along the axis of the wire to form a continuous and through conductive path, thereby improving the conductivity of the graphene-copper composite wire.

[0057] For example, in the graphene-copper composite wire 100, the content of the graphene sheet 30 is 10ppm to 1000ppm, such as 10ppm, 30ppm, 50ppm, 80ppm, 100ppm, 300ppm, 500ppm, 800ppm, 1000ppm, etc. The method for testing the content of the graphene sheet 30 is as follows: quantitative testing is performed using a high-frequency infrared carbon-sulfur analyzer. During the test, no less than 3 sets of wire samples are taken, and the mass of each sample is not less than 0.1g. After high-temperature combustion, the total carbon content in the sample is detected. After deducting the background carbon content of pure copper wire of the same process, the actual mass percentage of graphene is calculated.

[0058] When the content of graphene sheet 30 is less than 10 ppm, the proportion of graphene in the copper matrix 20 is too low to form a continuous three-dimensional conductive network, and the conductivity enhancement effect on the copper matrix 20 is completely negligible. The performance of the finished product is not significantly different from that of traditional oxygen-free copper. When the content of graphene sheet 30 is higher than 1000 ppm, the graphene sheet 30 is prone to stacking and agglomeration, introducing a large number of interface defects and electron scattering centers into the copper matrix 20. This leads to a decrease in the conductivity of the wire instead of an increase, and at the same time, it destroys the continuity of the copper matrix 20, causing brittle fracture during the drawing process. This application designs the content of graphene sheet 30 to be between 10 ppm and 1000 ppm, which can achieve a significant enhancement of conductivity while avoiding the problems of plastic degradation of the copper matrix 20 and wire breakage during the drawing process caused by high content of graphene sheet 30. In some embodiments, the content of the graphene sheet 30 is 20ppm to 500ppm, such as 20ppm, 50ppm, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, etc.

[0059] For example, the graphene sheet 30 has 1 to 10 graphene layers, such as 1, 2, 4, 6, 8, or 10 layers. It should be noted that by controlling the number of layers in the graphene sheet 30 to be within the range of 1 to 10 layers of few-layer graphene, both the high carrier mobility of graphene and the insufficient structural stability of single-layer graphene can be avoided, thereby achieving excellent electrical performance and structural stability.

[0060] In some embodiments, the equivalent circular diameter of the cross-section of the graphene-copper composite wire 100 is 20μm to 200μm, such as 20μm, 50μm, 80μm, 120μm, 150μm, 180μm, 200μm, etc. It can be seen that the graphene-copper composite wire of this application embodiment can achieve ultra-fine wire diameter (below 200μm). It is understood that, according to product design needs, the graphene-copper composite wire of this application embodiment can also be designed as a product with a larger wire diameter (equivalent circular diameter above 200μm), such as equivalent circular diameters of 250μm, 300μm, 400μm, 500μm, 800μm, 1000μm, 2000μm, 3000μm, etc.

[0061] For example, the conductivity of the graphene-copper composite wire 100 is 110% IACS to 118% IACS, such as 110% IACS, 112% IACS, 114% IACS, 116% IACS, 118% IACS, etc. It can be seen that the graphene-copper composite wire in this application embodiment can achieve a high conductivity, solving the problem that the conductivity of traditional graphene-copper composite wire cannot break through 110% IACS. The ultra-high conductivity of 110% IACS or more can bring the following technical effects: (1) For conductors with the same cross-section, the current carrying capacity is increased by more than 10%, which can realize the miniaturization and lightweight design of electronic device conductors, and adapt to the miniaturization development trend of semiconductor packaging and 5G / 6G terminals; (2) Under the same current carrying capacity, the Joule heat loss of the conductor is reduced by more than 20%, which greatly reduces the heat generation of electronic devices and improves the stability and service life of device operation; (3) In high-frequency signal transmission scenarios, the signal transmission attenuation can be significantly reduced, the signal transmission distance and transmission rate can be increased, and the low-loss transmission requirements of 5G / 6G communication and high-speed data centers can be adapted.

[0062] When the cross-sectional area, length, environmental heat dissipation conditions, and allowable maximum temperature rise of the conductor remain constant, an increase in conductivity of x% will cause the conductor resistance R to decrease strictly inversely proportional to the conductivity, with a decrease of x / (100+x). In the constant current I power supply condition commonly used in most engineering fields such as motor windings and power transmission cables, the Joule heat loss of the conductor P=I²R is proportional to the resistance, and therefore will decrease synchronously by the same amount of x / (100+x). This change will directly reduce the actual operating temperature of the conductor, reduce thermal aging damage, and improve the energy utilization efficiency of the entire system. Simultaneously, the conductor's safe current carrying capacity I will increase proportionally to the square root of the conductivity, with an increase of... This means that wires of the same thickness can carry a larger current without exceeding the maximum allowable temperature. Compared with pure copper wires, the graphene-copper composite wire 100 provided in this application embodiment has a 10%~20% higher conductivity, and the wire resistance and Joule heat loss decrease inversely proportionally by 9.09%~16.67%, which can effectively reduce operating temperature rise and thermal aging damage, and improve system energy efficiency; the safe current carrying capacity increases proportionally to the square root of conductivity by 4.88%~9.54%.

[0063] Please see Figure 2 This application also provides a graphene embodiment. A method for preparing copper composite wires, used to prepare the above-mentioned graphene. The copper composite conductor, wherein the preparation method includes: S100, providing copper raw material, depositing graphene on the surface of the copper raw material to obtain a graphene copper composite material.

[0064] For example, the copper raw material can be copper powder or copper foil. The copper powder has a particle size D50 of 5μm to 100μm and a copper purity greater than 99.99%. The copper foil has a thickness of 5μm to 100μm and a copper purity greater than 99.99%. The particle size D50 of the copper powder is tested using a laser particle size analyzer using a dry method. Before testing, the powder is ultrasonically dispersed to avoid agglomeration. The average of three parallel tests is taken as the final result. The thickness of the copper foil refers to the nominal uniform thickness of the copper foil. At least 10 uniformly distributed test points are selected along the transverse and longitudinal directions of the copper foil, and a high-precision contact thickness gauge is used for testing. After removing edge outliers, the arithmetic mean is taken as the final result. Copper purity refers to the mass percentage of copper in the copper raw material. The total elemental impurity content is determined using the ICP method, and the oxygen content is accurately determined using a high-frequency infrared oxygen and nitrogen analyzer. The two results are combined to calculate the actual purity of the copper raw material.

[0065] For example, graphene can be deposited on the surface of the copper raw material using chemical vapor deposition (CVD). By depositing graphene on the surface of the copper raw material using CVD, continuous and uniform graphene coating can be achieved on the copper raw material surface, fundamentally solving the core defects of existing mechanical mixing and liquid-phase composite methods, such as graphene agglomeration, uneven dispersion, and numerous interfacial impurities. This provides a composite raw material with excellent monodispersity of graphene, strong interfacial bonding, and a complete intrinsic structure for subsequent ultra-fine wire drawing processing. Specifically, the graphene coverage on the copper powder / copper foil surface reaches over 80%, for example, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, 100%, etc. The coverage is tested using field emission scanning electron microscopy (FE-SEM), selecting no fewer than 20 random particles for copper powder and no fewer than 10 non-overlapping fields of view for copper foil.

[0066] Specifically, when graphene is deposited on the surface of the copper raw material using chemical vapor deposition, the atmospheric system parameters include: argon gas flow rate of 0~1000 sccm, hydrogen gas flow rate of 0~500 sccm, methane gas flow rate of 1 sccm~100 sccm; growth temperature of 850℃~1090℃; growth time of 5 minutes~240 minutes; and gas pressure of low pressure (1~760 Torr) or atmospheric pressure (approximately 760 Torr).

[0067] Argon serves as both the carrier and protective gas, its core function being to maintain a stable atmosphere within the furnace and isolate the copper raw material from high-temperature oxidation. The preferred flow rate is 200 sccm to 800 sccm. Hydrogen acts as both a reducing and etching gas. On one hand, it thoroughly removes the native oxide layer from the copper raw material surface, providing a clean and highly active copper catalyst surface for graphene growth. On the other hand, it selectively etches amorphous carbon impurities generated during the growth process, improving the quality of graphene crystallization. The preferred flow rate is 100 sccm to 300 sccm. Methane serves as the carbon source, providing carbon atoms for graphene growth. This is a crucial control parameter. When the flow rate is below 1 sccm, the carbon source supply is insufficient, preventing graphene from completing nucleation and island fusion, thus hindering continuous coating. When the flow rate is above 100 sccm, the carbon source is excessive, leading to an excessively rapid graphene nucleation rate, easily forming thick stacks and amorphous carbon impurities, thus losing the inherent advantages of few-layer graphene. The preferred flow rate is 5 sccm to 50 sccm, suitable for the controllable growth of 1 to 10 layers of few-layer graphene.

[0068] The optimal temperature range for copper-catalyzed graphene growth is 850℃ to 1090℃. Below 850℃, the catalytic activity of the copper substrate is insufficient, making graphene nucleation difficult and preventing continuous film formation. Above 1090℃, the copper raw material approaches its melting point, easily leading to powder sintering and adhesion, abnormal grain growth, and excessively rapid graphene growth, resulting in uncontrollable layer count and increased defects. The preferred growth temperature is 900℃ to 1050℃, balancing the quality of graphene film formation with the structural stability of the copper substrate.

[0069] When the growth time is less than 5 minutes, graphene can only achieve isolated nucleation and cannot fuse island structures into a film, resulting in a large number of exposed areas on the surface of the copper raw material. When the growth time exceeds 240 minutes, the continuous growth of graphene leads to excessively thick layers, and the production efficiency is greatly reduced, making it unsuitable for industrial mass production. The optimal growth time is 30-120 minutes, which can stably achieve precise control over 1-10 layers of few-layer graphene.

[0070] Low-pressure environments can improve the uniformity of graphene growth, reduce gas-phase side reactions, and are suitable for small-batch, high-precision product preparation. A low-pressure environment of 10 Torr to 100 Torr is preferred. Atmospheric pressure environments do not require high-vacuum systems and can be directly adapted to continuous CVD mass production equipment, significantly reducing industrial production costs. The appropriate type can be selected flexibly according to capacity requirements.

[0071] By depositing graphene on the surface of copper raw materials, a continuous, uniform coating layer without exposed areas or breaks can be formed on the entire surface of copper powder and both sides of copper foil, without localized thick layer stacking or pinhole defects. The number of graphene layers is stably controlled between 1 and 10 layers, ensuring the ultra-high carrier mobility and structural stability of graphene. The graphene content in the obtained graphene-copper composite material is 10 ppm to 1000 ppm, and in some embodiments it is 20 ppm to 500 ppm.

[0072] S200, the graphene copper composite material is subjected to hot pressing treatment to obtain a dense graphene copper ingot.

[0073] For example, before hot pressing the graphene-copper composite material, a pretreatment can be performed on the graphene-copper composite material. Specifically, the pretreatment includes: placing the graphene-copper composite material in a drying device and drying it at 60℃~150℃ under low pressure or normal pressure inert atmosphere for 4~6 hours to thoroughly remove the moisture and residual organic matter adsorbed on the surface of the raw material, so as to avoid the vaporization of moisture during the subsequent hot pressing process, which would cause bubbling and pore defects in the ingot, and ensure the density of the ingot; at the same time, it avoids the reaction between water and copper and graphene at high temperature, which would cause oxidation of the copper matrix and damage to the graphene structure, and ensures the cleanliness and bonding force of the interface between graphene and copper matrix.

[0074] The drying temperature is set to 60℃~150℃, for example, 80℃~120℃, because: when the temperature is below 60℃, the moisture cannot be completely vaporized and removed, the drying is insufficient, and the residual moisture inside the raw material and between the powder particles cannot be completely removed; when the temperature is above 150℃, the surface of copper powder / copper foil is prone to secondary oxidation, which damages the interface between the graphene coating layer and the copper substrate and degrades the performance of the subsequent wire.

[0075] The drying time is set to 4 to 6 hours, preferably 4.5 to 5.5 hours, because when the drying time is less than 4 hours, the moisture inside the composite material cannot be completely removed, and the drying is incomplete; when the drying time exceeds 6 hours, the production efficiency is greatly reduced, and the risk of copper substrate oxidation is increased, with no additional drying gain.

[0076] Atmosphere selection: For graphene-copper composite materials (graphene-copper composite powder) with copper powder as the raw material, a vacuum drying oven with a vacuum degree ≤100Pa is preferred. The low-pressure environment can lower the boiling point of water, improve drying efficiency, and completely isolate oxygen to avoid oxidation. For graphene-copper composite materials (graphene-copper composite foil) with copper foil as the raw material, an atmospheric pressure inert atmosphere drying oven is preferred, using high-purity argon or high-purity nitrogen with a purity ≥99.999% as the protective atmosphere to meet the needs of continuous production.

[0077] Before drying, the composite powder / foil needs to be sealed and transported to avoid contact with air and moisture absorption. After drying, it needs to be cooled to room temperature under an inert atmosphere before being taken out for subsequent hot pressing processes to avoid oxidation caused by contact with air at high temperatures.

[0078] For example, when hot-pressing the graphene-copper composite material, the pressure applied to the graphene-copper composite material is 10MPa~200MPa, such as 10MPa, 30MPa, 60MPa, 100MPa, 140MPa, 180MPa, 200MPa, etc.; the heating temperature is 500℃~900℃, such as 500℃, 550℃, 650℃, 750℃, 800℃, 850℃, 900℃, etc.; the heat preservation and pressure holding time is 20 minutes~120 minutes, such as 20 minutes, 40 minutes, 60 minutes, 80 minutes, 100 minutes, 120 minutes, etc.

[0079] During the hot pressing process of the graphene-copper composite material, the composite material can be densified under the synergistic effect of high temperature and high pressure, while maintaining the structural stability of graphene to the maximum extent and avoiding graphene agglomeration and structural damage. Compared with the two-step method of cold isostatic pressing + vacuum sintering, the hot pressing process can significantly shorten the process flow, improve production efficiency, and achieve an ingot density of ≥99.5%, providing high-quality ingots with no pores, no defects, and uniform structure for subsequent hot extrusion and ultra-fine wire drawing.

[0080] For example, for graphene-copper composite materials (graphene-copper composite powder) where the copper raw material is copper powder, the "hot pressing treatment of the graphene-copper composite material" includes: The pretreated composite powder is uniformly loaded into a high-purity graphite mold. The inner wall of the mold is coated with boron nitride release agent to prevent copper from sticking to the mold. After loading, the mold is sent to a vacuum hot press. First, a vacuum is drawn to ≤5Pa, then the temperature is raised to the target temperature and held for 10-30 minutes. Subsequently, the pressure is slowly increased to the target pressure, and after holding the pressure, it is cooled to room temperature with the furnace. Key parameters: pressure is preferably 30MPa-150MPa, temperature is preferably 600℃-850℃, and holding time is preferably 30-90 minutes. When the pressure is below 10MPa, the powder cannot achieve sufficient densification, the ingot porosity is high, and the density does not meet the standard. When the pressure is above 200MPa, the copper powder particles undergo severe plastic deformation, the graphene coating on the surface is squeezed and broken, and the graphene agglomerates, destroying its monodispersity. When the temperature is below 500℃, the copper matrix has insufficient plastic deformation capacity, and metallurgical bonding cannot be achieved between powder particles, resulting in insufficient ingot density. When the temperature is above 900℃, the copper matrix grains grow abnormally, and graphene is prone to agglomeration, thickening, and graphitization, losing the advantages of the few-layer structure.

[0081] For example, for graphene-copper composite materials (graphene-copper composite foil) where the copper raw material is copper foil, the "hot pressing treatment of the graphene-copper composite material" includes: The pretreated composite foil is neatly stacked according to the preset number of layers, with strict alignment during the stacking process to avoid misalignment and wrinkles. It is then placed into a high-purity graphite mold. The inner wall of the mold is coated with a boron nitride release agent. After being placed in a vacuum hot press, the mold is first evacuated to ≤5Pa, then heated to the target temperature and held for 10-20 minutes, followed by pressurization to the target pressure and holding. After pressurization, it is cooled with the furnace. Key parameters: pressure preferably 20MPa-100MPa, temperature preferably 550℃-800℃, and holding time preferably 20-60 minutes. Compared to the powder route, the foil route requires lower pressure, temperature, and shorter holding time. The key is to avoid graphene layer damage and wrinkles caused by high temperature and high pressure. When the pressure is below 5MPa, the interlayer bonding force of the foil is insufficient, and delamination and cracking are likely to occur during subsequent drawing. When the pressure is above 150MPa, the graphene layer is crushed and damaged, destroying the structural integrity.

[0082] S300, the graphene copper dense ingot is hot-extruded to obtain a graphene copper rod-shaped billet.

[0083] For example, the "hot extrusion of the graphene copper dense ingot" includes: hot extruding the hot-pressed graphene copper dense ingot in an extruder after preheating the die to obtain graphene copper rod-shaped billet; the core process parameters are: extrusion ratio 20~300, extrusion rate 10mm / s~120mm / s, extrusion temperature 600℃~900℃. Through high-temperature plastic deformation, the following effects can be achieved: (1) the copper grains that grow during hot pressing are broken, and the grains are refined through dynamic recrystallization, laying the foundation for the formation of columnar crystal texture in the subsequent drawing process; (2) the axial shear stress in the extrusion process guides the graphene sheets to achieve preliminary orientation along the extrusion direction, laying the core foundation for the high orientation structure of the subsequent large true strain drawing; (3) the material density is further improved, the micropore defects inside the ingot are eliminated, and a rod-shaped billet with uniform size and dense structure is obtained, which is suitable for the subsequent ultra-fine wire drawing process.

[0084] The extrusion ratio is set to 20~300, preferably 50~200. The extrusion ratio refers to the ratio of the cross-sectional area of ​​the ingot to the cross-sectional area of ​​the extruded rod, which is the core control parameter of this process. When the extrusion ratio is lower than 20, the deformation is insufficient, the grain refinement effect is poor, the graphene cannot achieve initial directional arrangement, and the improvement of material density is limited. When the extrusion ratio is higher than 300, the deformation is too large, the extrusion die wears severely, the rod is prone to surface cracking and uneven internal structure, and the graphene sheets undergo brittle fracture, failing to maintain structural integrity and losing subsequent conductivity enhancement effect.

[0085] The extrusion temperature is set to 600℃~900℃, preferably 650℃~850℃. When the temperature is below 600℃, the copper matrix has high deformation resistance and the extrusion load is too high, which can easily lead to die blockage and rod cracking. When the temperature is above 900℃, the copper matrix undergoes rapid grain growth after dynamic recrystallization, and the graphene structure deteriorates at high temperature, affecting the final wire performance.

[0086] The extrusion rate is set to 10mm / s~120mm / s, preferably 20mm / s~80mm / s. When the rate is too low, the production efficiency is low, the rod stays at high temperature for too long, and the grains grow abnormally. When the rate is too high, the deformation is uneven, bamboo joints and cracks are easy to appear on the surface of the rod, and the internal structure and graphene orientation distribution are uneven.

[0087] Before extrusion, the ingot needs to be preheated in a heating furnace for 1 to 4 hours, preferably 2 to 3 hours, to ensure uniform temperature inside and outside the ingot and avoid uneven deformation during extrusion. The extrusion die is a conical die with a die angle of 120° to 150°. The inner wall of the die is sprayed with glass lubricant to reduce frictional resistance and ensure the surface quality of the rod. The diameter of the hot-extruded rod billet is controlled at φ5 to φ12mm. The surface is free of cracks, scratches, and eccentric defects. The internal structure is dense, without pores or inclusions, and the graphene sheets remain intact, initially achieving directional arrangement along the axial direction.

[0088] S400, the graphene copper rod-shaped blank is cold-drawn at a drawing rate of 20m / min to 1000m / min, such as 20m / min, 100m / min, 300m / min, 500m / min, 700m / min, 900m / min, 1000m / min, etc., to obtain graphene copper composite wire.

[0089] Cold drawing is a plastic deformation processing technology that involves drawing metal materials at room temperature (0–50°C). Cold drawing of the graphene copper rod-shaped billet is the core key to achieving the columnar crystal texture of the copper matrix, the highly oriented arrangement of graphene, and the construction of a three-dimensional continuous conductive network. It is also the core process for achieving stable forming of ultrafine wires of 20μm to 200μm.

[0090] Specifically, the drawing rate can be set in stages according to the target wire diameter (equivalent circle diameter of the cross-section). For wires of 20μm to 100μm, a low-speed drawing rate of 20m / min to 200m / min is used to ensure dimensional accuracy and forming stability, avoiding wire breakage caused by high-speed drawing. For wires of 100μm to 200μm, a high-speed drawing rate of 200m / min to 1000m / min is used to meet the needs of continuous industrial production. At speeds below 20m / min, production efficiency is too low to meet the needs of industrial mass production; at speeds above 1000m / min, the friction between the wire and the die generates significant heat, easily leading to problems such as wire oxidation, excessive die wear, and wire breakage.

[0091] For example, the cumulative true strain of the graphene copper rod blank during cold drawing is 8 to 18, such as 8, 10, 12, 14, 16, 18, etc. The following effects can be achieved by accumulating ultra-large plastic deformation with true strain ≥ 8: (1) Through continuous axial shear stress of multiple pulls, the copper matrix grains are forced to undergo axial preferred orientation, forming ultra-fine columnar crystals along the current transmission direction, reducing the number of transverse grain boundaries perpendicular to the current direction by more than 90%, and maximizing the reduction of electron grain boundary scattering from the matrix level; (2) Drive the graphene sheets to achieve high orientation along the wire axis, so that the high conductivity surface of graphene is completely matched with the current transmission direction, maximizing the advantage of ultra-high carrier mobility of graphene; (3) Through the shearing effect of large plastic deformation, the adjacent graphene sheets form an end-overlapping and interlayer interlocking structure, constructing a three-dimensional continuous conductive network that runs through the entire wire, providing a high-speed transmission channel for electrons without grain boundary scattering, and finally breaking through the bottleneck of ultra-high conductivity of 110% IACS; (4) Through the design of multiple small deformations, the continuous and stable pull of 20μm~200μm ultra-fine wires is ensured, avoiding wire breakage and realizing industrial continuous production.

[0092] It should be noted that the process of cold drawing the graphene copper rod blank is a continuous cold drawing process. No intermediate annealing is performed during the continuous cold drawing process, so that the accumulated true strain of the graphene copper rod blank during the cold drawing process continues to be superimposed without being interrupted by the recrystallization process. This forces the copper matrix grains to continue to grow axially preferentially under uniaxial tensile stress, forming a high aspect ratio columnar crystal structure that runs through the entire length of the wire.

[0093] For example, the cold drawing is achieved through multiple drawing passes, with the true strain of a single drawing pass being 10% to 25% of the cumulative true strain, such as 10%, 13%, 16%, 19%, 22%, 25%, etc., preferably 12% to 20%. When the deformation amount in a single pass is less than 10%, it is impossible to generate effective axial shear force on the copper matrix and graphene, resulting in poor grain preferential orientation and graphene orientation effect. When the deformation amount in a single pass is greater than 25%, the work hardening rate is too fast, the internal stress of the wire is too large, and wire breakage is very likely to occur, especially for ultra-fine wires below 50μm, which are prone to plastic deformation instability. By using a small deformation amount in a single pass and accumulating it over multiple passes, the deformation requirement of cumulative true strain ≥8 is ensured, while avoiding the wire breakage problem caused by excessive deformation in a single pass.

[0094] For example, diamond drawing dies are used throughout the cold drawing process, with the die inlet angle preferably between 10° and 20°. For ultra-fine diameter wires of 20μm to 100μm, nano-coated diamond dies are used, achieving a mirror-like finish on the inner hole of the die. This ensures dimensional accuracy and surface quality of the wire, preventing graphene layer peeling and wire breakage caused by die scratches. For example, an oil-based drawing fluid is used for online lubrication throughout the process, with the fluid viscosity preferably between 10° and 30°. 2 / s (40℃), add extreme pressure anti-wear agent to form a continuous lubricating oil film between the wire and the mold, avoid surface scratches, mold wear and graphene layer peeling caused by dry friction, and reduce wire temperature rise and oxidation caused by frictional heat generation.

[0095] S500, the graphene-copper composite wire is annealed to obtain graphene. Copper composite conductor.

[0096] For example, the annealing process for the graphene-copper composite wire can be either online continuous annealing or offline vacuum annealing. Online continuous annealing can be linked with the drawing process to achieve integrated continuous production of drawing-annealing-winding, which has high production efficiency and is suitable for large-volume industrial production with large roll weights; offline vacuum annealing can achieve more precise temperature and time control and is suitable for the preparation of ultra-fine wires with small specifications and high precision requirements.

[0097] For example, the annealing temperature is 200℃~800℃, such as 200℃, 300℃, 450℃, 550℃, 650℃, 750℃, 800℃, etc.; the annealing time is 5 minutes~60 minutes, such as 5 minutes, 15 minutes, 25 minutes, 35 minutes, 45 minutes, 55 minutes, 60 minutes, etc.

[0098] By setting the annealing temperature to 200℃~800℃ and the annealing time to 5 minutes~60 minutes, the synergistic balance of "stress elimination-structural stability-performance optimization" is achieved through short-time precise annealing: (1) Eliminate the work hardening and residual stress generated by large true strain drawing, restore the plasticity and ductility of the wire, ensure the formability of subsequent bonding, stranding and winding processing, and avoid brittle fracture; (2) Stabilize the axial columnar crystal and {111} and {001} crystal orientation of the copper matrix through recovery and static recrystallization, and avoid grain coarsening and texture weakening caused by long-term high-temperature annealing; (3) Repair the lattice defects generated by graphene during the drawing process, restore the intrinsic high carrier mobility of graphene, and strengthen the interface bonding between graphene and copper matrix, and finally achieve a balance between ultra-high conductivity and good mechanical properties.

[0099] The reason for choosing an annealing temperature of 200℃~800℃ is as follows: Below 200℃, residual stress from drawing cannot be effectively eliminated, work hardening cannot be eliminated, the wire lacks plasticity, and subsequent processing is prone to brittle fracture; above 800℃, the copper matrix undergoes intense grain growth and recrystallization, axial columnar crystals transform into coarse equiaxed crystals, strong texture is destroyed, and graphene agglomerates and thickens, leading to a sharp decrease in conductivity. For ultrafine wires of 20μm~50μm, a low-temperature annealing of 200℃~500℃ is preferred to avoid wire oxidation and grain coarsening caused by high temperatures; for wires of 100μm~200μm, a medium-temperature annealing of 500℃~800℃ is preferred to ensure uniform stress elimination across the entire cross-section.

[0100] The reason for selecting an annealing time of 5 to 60 minutes is that when the annealing time exceeds 60 minutes, the copper matrix grains become abnormally coarsened, graphene agglomerates and graphitizes, the interfacial bonding force decreases, and ultimately the conductivity and mechanical properties of the wire deteriorate. For ultrafine wires of 20μm to 50μm, online continuous annealing is preferred, with an annealing time of 1 to 10 minutes, suitable for large-scale continuous production; for large coils of heavy wire, offline vacuum annealing is used, with an annealing time of 10 to 30 minutes.

[0101] The entire annealing process is protected with inert gas (such as high-purity argon or high-purity nitrogen with a purity of ≥99.999%). During offline vacuum annealing, the vacuum degree is ≤10Pa, which completely isolates oxygen and water vapor, avoiding wire oxidation and graphene structure damage.

[0102] The present application will be specifically described below through specific embodiments. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0103] Example 1 A type of graphene The preparation method of copper composite wire includes: CVD composite powder preparation: High-purity oxygen-free copper powder with a D50 particle size of 20~30μm and a purity of 99.995% was selected and placed in a horizontal CVD furnace. Argon gas was introduced at 500sccm, hydrogen gas at 200sccm, and methane gas at 20sccm. The growth temperature was 1000℃, the growth time was 60min, and the growth pressure was 50Torr. Composite copper powder with 3~5 layers of graphene 100% coating and graphene content of 80ppm was obtained.

[0104] Raw material pretreatment: The composite copper powder was placed in a vacuum drying oven and dried at 100℃ and 50Pa for 5 hours. After cooling to room temperature, it was taken out.

[0105] Vacuum hot pressing: Composite copper powder is loaded into a high-purity graphite mold, and vacuum hot pressing is performed at a pressure of 100MPa, a temperature of 800℃, a holding time of 60min, and a vacuum degree of 5Pa to obtain a dense ingot with a diameter of φ80mm and a density of 99.7%.

[0106] Hot extrusion pre-deformation: After the ingot is preheated for 2 hours, hot extrusion is carried out with an extrusion ratio of 100, an extrusion temperature of 750℃, and an extrusion rate of 50mm / s to obtain a round bar billet with a diameter of φ8mm.

[0107] Large true strain cold drawing: Round bar billets are subjected to multi-pass continuous cold drawing with a single-pass deformation of 15%, a cumulative true strain of 12, a drawing rate of 100m / min, a polycrystalline diamond die, and oil-based wire drawing fluid for lubrication, and finally a φ50μm ultrafine wire is drawn.

[0108] Short-time precise annealing: The wire is continuously annealed online at a temperature of 250℃ for 5 minutes under the protection of high-purity argon gas to obtain the final finished wire.

[0109] Example 2 A type of graphene The preparation method of copper composite wire includes: CVD composite foil preparation: High-purity oxygen-free copper foil with a thickness of 25μm and a purity of 99.995% was selected and placed in a horizontal CVD furnace. Argon gas was introduced at 600 sccm, hydrogen gas at 250 sccm, and methane gas at 15 sccm. The growth temperature was 950℃, the growth time was 45 min, and the growth pressure was 30 Torr. Composite copper foil with 2-4 layers of graphene double-sided coating and a graphene content of 50 ppm was obtained.

[0110] Raw material pretreatment: The composite copper foil was placed in an argon-protected drying oven and dried at 110℃ for 4.5h. After cooling to room temperature, it was taken out.

[0111] Vacuum hot pressing: After the composite copper foil is neatly stacked, it is placed into a graphite mold and vacuum hot pressing is performed at a pressure of 80 MPa, a temperature of 750℃, a holding time of 40 min, and a vacuum degree of 5 Pa to obtain a dense ingot with a density of 99.6%.

[0112] Hot extrusion pre-deformation: The ingot is preheated for 2.5 hours and then hot extruded with an extrusion ratio of 150, an extrusion temperature of 780℃, and an extrusion rate of 40mm / s to obtain a φ6mm round bar billet.

[0113] Large true strain cold drawing: Round bar billets are subjected to multi-pass continuous cold drawing with a single-pass deformation of 12%, a cumulative true strain of 15, and a drawing rate of 50m / min. A nano-coated diamond die is used to finally draw an ultra-fine wire with a diameter of φ25μm.

[0114] Short-time precision annealing: The wire is subjected to offline vacuum annealing at a temperature of 400℃ for 15 minutes and a vacuum degree of 5Pa to obtain the final finished wire.

[0115] Example 3 A type of graphene The preparation method of copper composite wire includes: CVD composite powder preparation: High-purity oxygen-free copper powder with a D50 particle size of 20~30μm and a purity of 99.995% was selected and placed in a horizontal CVD furnace. Argon gas was introduced at 500sccm, hydrogen gas at 200sccm, and methane gas at 20sccm. The growth temperature was 1000℃, the growth time was 60min, and the growth pressure was 50Torr. Composite copper powder with 3~5 layers of graphene 100% coating and graphene content of 80ppm was obtained.

[0116] Raw material pretreatment: The composite copper powder was placed in a vacuum drying oven and dried at 100℃ and 50Pa for 5 hours. After cooling to room temperature, it was taken out.

[0117] Vacuum hot pressing: Composite copper powder is loaded into a high-purity graphite mold, and vacuum hot pressing is performed at a pressure of 100MPa, a temperature of 800℃, a holding time of 60min, and a vacuum degree of 5Pa to obtain a dense ingot with a diameter of φ80mm and a density of 99.7%.

[0118] Hot extrusion pre-deformation: After the ingot is preheated for 2 hours, hot extrusion is carried out with an extrusion ratio of 100, an extrusion temperature of 750℃, and an extrusion rate of 50mm / s to obtain a round bar billet with a diameter of φ8mm.

[0119] Large true strain cold drawing: Round bar billets are subjected to multi-pass continuous cold drawing with a single-pass deformation of 15%, a cumulative true strain of 12, a drawing rate of 100m / min, a polycrystalline diamond die, and oil-based wire drawing fluid for lubrication, and finally a φ50μm ultrafine wire is drawn.

[0120] Short-time precision annealing: The wire is continuously annealed online at a temperature of 400℃ for 20 minutes under the protection of high-purity argon gas to obtain the final finished wire.

[0121] Example 4 A type of graphene The preparation method of copper composite wire includes: CVD composite powder preparation: High-purity oxygen-free copper powder with a D50 particle size of 20~30μm and a purity of 99.995% was selected and placed in a horizontal CVD furnace. Argon gas was introduced at 500sccm, hydrogen gas at 200sccm, and methane gas at 20sccm. The growth temperature was 1000℃, the growth time was 60min, and the growth pressure was 50Torr. Composite copper powder with 3~5 layers of graphene 100% coating and graphene content of 80ppm was obtained.

[0122] Raw material pretreatment: The composite copper powder was placed in a vacuum drying oven and dried at 100℃ and 50Pa for 5 hours. After cooling to room temperature, it was taken out.

[0123] Vacuum hot pressing: Composite copper powder is loaded into a high-purity graphite mold, and vacuum hot pressing is performed at a pressure of 100MPa, a temperature of 800℃, a holding time of 60min, and a vacuum degree of 5Pa to obtain a dense ingot with a diameter of φ80mm and a density of 99.7%.

[0124] Hot extrusion pre-deformation: After the ingot is preheated for 2 hours, hot extrusion is carried out with an extrusion ratio of 100, an extrusion temperature of 750℃, and an extrusion rate of 50mm / s to obtain a round bar billet with a diameter of φ8mm.

[0125] Large true strain cold drawing: Round bar billets are subjected to multi-pass continuous cold drawing with a single-pass deformation of 15%, a cumulative true strain of 8.7, a drawing rate of 100m / min, a polycrystalline diamond die, and oil-based wire drawing fluid for lubrication, ultimately producing an ultra-fine wire with a diameter of φ100μm.

[0126] Short-time precise annealing: The wire is continuously annealed online at a temperature of 250℃ for 5 minutes under the protection of high-purity argon gas to obtain the final finished wire.

[0127] Example 5 A type of graphene The preparation method of copper composite wire includes: CVD composite powder preparation: High-purity oxygen-free copper powder with a D50 particle size of 20~30μm and a purity of 99.995% was selected and placed in a horizontal CVD furnace. Argon gas was introduced at 500sccm, hydrogen gas at 200sccm, and methane gas at 20sccm. The growth temperature was 1000℃, the growth time was 60min, and the growth pressure was 50Torr. Composite copper powder with 3~5 layers of graphene 100% coating and graphene content of 80ppm was obtained.

[0128] Raw material pretreatment: The composite copper powder was placed in a vacuum drying oven and dried at 100℃ and 50Pa for 5 hours. After cooling to room temperature, it was taken out.

[0129] Vacuum hot pressing: Composite copper powder is loaded into a high-purity graphite mold, and vacuum hot pressing is performed at a pressure of 100MPa, a temperature of 800℃, a holding time of 60min, and a vacuum degree of 5Pa to obtain a dense ingot with a diameter of φ80mm and a density of 99.7%.

[0130] Hot extrusion pre-deformation: After the ingot is preheated for 2 hours, hot extrusion is carried out with an extrusion ratio of 100, an extrusion temperature of 750℃, and an extrusion rate of 50mm / s to obtain a round bar billet with a diameter of φ8mm.

[0131] Large true strain cold drawing: Round bar billets are subjected to multi-pass continuous cold drawing with a single-pass deformation of 15%, a cumulative true strain of 8.7, a drawing rate of 100m / min, a polycrystalline diamond die, and oil-based wire drawing fluid for lubrication, ultimately producing an ultra-fine wire with a diameter of φ100μm.

[0132] Short-time precision annealing: The wire is continuously annealed online at a temperature of 400℃ for 20 minutes under the protection of high-purity argon gas to obtain the final finished wire.

[0133] Comparative Example 1 A type of graphene The preparation method of copper composite wire includes: CVD composite powder preparation: High-purity oxygen-free copper powder with a D50 particle size of 20~30μm and a purity of 99.995% was selected and placed in a horizontal CVD furnace. Argon gas was introduced at 500sccm, hydrogen gas at 200sccm, and methane gas at 20sccm. The growth temperature was 1000℃, the growth time was 60min, and the growth pressure was 50Torr. Composite copper powder with 3~5 layers of graphene 100% coating and graphene content of 80ppm was obtained.

[0134] Raw material pretreatment: The composite copper powder was placed in a vacuum drying oven and dried at 100℃ and 50Pa for 5 hours. After cooling to room temperature, it was taken out.

[0135] Vacuum hot pressing: Composite copper powder is loaded into a high-purity graphite mold, and vacuum hot pressing is performed at a pressure of 100MPa, a temperature of 800℃, a holding time of 60min, and a vacuum degree of 5Pa to obtain a dense ingot with a diameter of φ80mm and a density of 99.7%.

[0136] Hot extrusion pre-deformation: After the ingot is preheated for 2 hours, hot extrusion is carried out with an extrusion ratio of 100, an extrusion temperature of 750℃, and an extrusion rate of 50mm / s to obtain a round bar billet with a diameter of φ8mm.

[0137] Intermediate multiple cold drawing and annealing: The round bar billet is subjected to multiple continuous cold drawing, with a deformation of 15% per pass. Polycrystalline diamond molds are used, and oily wire drawing fluid is used for lubrication. An intermediate annealing is performed on the φ3mm section at a temperature of 400℃ for 15 minutes. Then, the wire is drawn to obtain the φ1mm wire.

[0138] Final annealing process: φ1mm wire is subjected to offline vacuum annealing at a temperature of 400℃ for 15 minutes and a vacuum degree of 5Pa to obtain the final finished wire.

[0139] Performance testing: Graphene prepared in Examples 1 to 5 and Comparative Example 1 The copper composite conductor underwent performance testing, and the test indicators and methods are as follows: Conductivity: According to GB / T 3048.2 "Test Methods for Electrical Properties of Wires and Cables - Part 2: Test for Resistivity of Metallic Materials", the DC resistivity of the wire is tested in a constant temperature and humidity environment of 20℃±0.5℃ using a high-precision double-arm bridge or micro-ohmmeter. The length of the test sample is not less than 1m. Before the test, the sample is placed in a constant temperature environment for not less than 4h to ensure that the sample temperature is consistent with the ambient temperature. The average value of the test of not less than 3 sets of parallel samples is taken as the final result, and the test deviation of the parallel samples does not exceed ±0.5% IACS.

[0140] Tensile strength and elongation after fracture: According to the national standard GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Test method at room temperature," the room temperature uniaxial tensile test method is used to test the tensile strength and elongation of copper wire. The test principle is to apply a monotonically increasing tensile force along the axial direction to a specimen with a specified size and shape at room temperature until the specimen breaks. By continuously measuring the applied force and the elongation of the specimen, a force-displacement or stress-strain curve is obtained, thereby determining the tensile strength and elongation after fracture of the material.

[0141] The columnar crystal minor axis length, columnar crystal aspect ratio, and columnar crystal area percentage were analyzed using backscattered electron diffraction (EBSD) combined with metallographic microscopy. The test sample was prepared along the longitudinal section of the conductor (parallel to the conductor's long axis). After mechanical polishing and electrolytic polishing, at magnifications of 100 to 10000x, at least five non-overlapping fields of view were selected to statistically determine the columnar crystal minor axis length, columnar crystal aspect ratio, and columnar crystal area percentage. The average of multiple fields of view was taken as the final result. It should be noted that the columnar crystal minor axis length is the average of the columnar crystal minor axis lengths measured on the conductor's longitudinal section; the columnar crystal aspect ratio is the ratio of the long axis length to the minor axis length of the columnar crystal; and the columnar crystal area percentage is the ratio of the sum of the cross-sectional areas of all columnar crystals on the conductor's longitudinal section to the cross-sectional area of ​​the copper substrate.

[0142] The area ratio of {111} and {001} crystal planes: Backscattered electron diffraction (EBSD) was used to prepare samples along the longitudinal section of the wire axis. The grain orientation was calibrated by Kikuchi belt. The area ratio of the grains with the target crystal plane orientation was statistically analyzed. At least 5 non-overlapping fields of view were selected, and the average value was taken as the final result.

[0143] Graphene axial orientation and graphene sheet overlap rate: Longitudinal cross-sectional samples were prepared along the wire axis and observed using a transmission electron microscope (TEM). At least six non-overlapping fields of view were randomly selected at magnifications ranging from 10,000x to 50,000x. The graphene axial orientation and graphene sheet overlap rate were statistically analyzed, and the average of multiple fields of view was taken as the final result. Graphene axial orientation refers to the proportion of graphene sheets with an angle ≤30° to the long axis of the wire out of the total number of graphene sheets in the field of view. Graphene sheet overlap rate refers to the proportion of graphene sheets forming an effective overlap out of the total number of graphene sheets in the field of view. An effective overlap is defined as a contact length between graphene sheets ≥5% of the graphene sheet's own length.

[0144] The test results are shown in Table 1.

[0145] Table 1

[0146] As can be seen from Table 1: Graphene prepared in Examples 1 to 5 Copper composite wires outperform graphene in Comparative Example 1 in terms of conductivity, tensile strength, and elongation after fracture. The copper composite wire illustrates the graphene prepared in the embodiments of this application. Copper composite conductors have better conductivity and structural stability.

[0147] The above describes the graphene provided in the embodiments of this application. Copper composite conductors and their preparation methods are described in detail. Specific examples are used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A type of graphene Copper composite conductor, characterized in that, The invention includes a copper substrate and a plurality of graphene sheets connected to the copper substrate. The copper substrate includes copper grains distributed radially along the conductor and copper grains distributed axially along the conductor. At least a portion of the plurality of graphene sheets are embedded at the grain boundaries of adjacent copper grains. The plurality of graphene sheets include overlapping graphene sheets and spaced-apart graphene sheets.

2. The graphene according to claim 1 Copper composite conductor, characterized in that, The overlap rate of the graphene sheets is 70%~98%.

3. The graphene according to claim 2 Copper composite conductor, characterized in that, The ratio of the sum of the number of graphene sheets with an orientation angle of less than or equal to 30° to the total number of all graphene sheets is greater than or equal to 85%, where the orientation angle is the angle between the graphene sheet and the graphene... The included angle between the axial directions of the copper composite conductor.

4. The graphene according to claim 3 Copper composite conductor, characterized in that, The ratio of the sum of the number of graphene sheets with an orientation angle of 20° to 30° to the total number of all graphene sheets is 0 to 20%; and / or, The ratio of the sum of the number of graphene sheets with an orientation angle of 10° to 20° to the total number of all graphene sheets is 10% to 30%; and / or, The ratio of the total number of graphene sheets with an orientation angle of less than or equal to 10° to the total number of all graphene sheets is 50% to 80%.

5. The graphene according to claim 1 Copper composite conductor, characterized in that, The graphene sheet has a length of 2μm to 10μm; and / or, The graphene On the longitudinal section of the copper composite conductor, 100μm 2 The number of graphene sheets described within the range is 5 to 40; and / or, The graphene In the copper composite wire, the graphene sheet content is 10ppm to 1000ppm; and / or, The graphene sheet has 1 to 10 graphene layers.

6. The graphene according to claim 1 Copper composite conductor, characterized in that, In the graphene In the longitudinal section of the copper composite conductor, the total area of ​​the {111} crystal plane, near-{111} crystal plane, {001} crystal plane, and near-{001} crystal plane of the copper grains accounts for greater than or equal to 85%. The near-{111} crystal plane refers to a crystal plane with an angle greater than 0 and less than or equal to 15° with respect to the {111} crystal plane, and the near-{001} crystal plane refers to a crystal plane with an angle greater than 0 and less than or equal to 15° with respect to the {001} crystal plane; and / or, At least a portion of the copper grains in the copper matrix are columnar crystals, and the columnar crystals are copper grains with an aspect ratio greater than or equal to 2:

1.

7. The graphene according to any one of claims 1-6 Copper composite conductor, characterized in that, The graphene The equivalent circular diameter of the cross-section of the copper composite conductor is 20μm~200μm; and / or, The graphene The conductivity of copper composite conductors is 110% IACS to 118% IACS.

8. A type of graphene A method for preparing copper composite conductors, characterized in that, include: A copper raw material is provided, and graphene is deposited on the surface of the copper raw material to obtain a graphene-copper composite material; The graphene-copper composite material was subjected to hot pressing to obtain a dense graphene-copper ingot. The graphene copper dense ingot is hot-extruded to obtain a graphene copper rod-shaped billet. The graphene copper rod blank is cold-drawn at a drawing rate of 20 m / min to 1000 m / min to obtain a graphene copper composite wire. The graphene-copper composite wire was annealed to obtain graphene. Copper composite conductor.

9. The graphene according to claim 8 A method for preparing copper composite conductors, characterized in that, The cumulative true strain of the graphene copper rod blank during cold drawing is 8~18.

10. The graphene according to claim 9 A method for preparing copper composite conductors, characterized in that, The cold drawing is achieved through multiple drawing operations, and the true strain of a single drawing operation is 10% to 25% of the cumulative true strain.

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