Graphene copper-tungsten composite material, preparation method thereof and conductive element

Abstract

The invention relates to the technical field of conductors, in particular to a graphene copper-tungsten composite material, a preparation method thereof and a conductive element. The preparation method comprises the following steps: S1, providing tungsten powder; s2, the surface of the tungsten powder is coated with a copper layer, and copper-tungsten composite powder with tungsten coated with copper is obtained; s3, the surface of the copper-tungsten composite powder is coated with a graphene layer, and graphene copper-tungsten composite powder is obtained; s4, the graphene copper-tungsten composite powder is mixed with induction copper powder, an organic adhesive and an activating agent, and mixed powder is obtained; s5, the mixed powder is subjected to cold press molding, and a green body is obtained; s6, degumming the green body to obtain a precursor; and S7, the precursor and a copper sheet are stacked and then subjected to infiltration, and the graphene copper-tungsten composite material is obtained. According to the technical scheme, under the condition that the tungsten content is not increased, the fusion welding resistance, the electric conductivity, the heat conduction performance and the mechanical performance of the graphene copper-tungsten composite material are improved, and the comprehensive performance of the prepared graphene copper-tungsten composite material is high.

Description

Technical Field

[0001] This application relates to the field of conductor technology, and more specifically, to a graphene-copper-tungsten composite material, its preparation method, and a conductive element. Background Technology

[0002] Tungsten-copper alloys are a class of composite materials with excellent properties such as electrical and thermal conductivity, high-temperature strength, resistance to arc burn-off, wear resistance, and corrosion resistance. They are widely used in electrical contact conductors, wires, and many other applications. As electrical equipment develops towards higher voltages and higher capacities, more stringent requirements are being placed on the overall performance of electrical contact conductors or wires made from tungsten-copper alloy composite materials.

[0003] To further improve material performance, the introduction of trace amounts of a third phase is considered. Relevant literature suggests that graphene, as a reinforcing phase in tungsten-copper alloys, is beneficial for improving the electrical and physical properties of the composite material. However, the proposed methods of adding graphene, particularly the composite method involving copper and tungsten, present several problems. For example, the uneven dispersion of graphene, copper, and tungsten, and the potential for damage to the graphene structure due to ultrasonic dispersion and other methods used to improve dispersion, all contribute to the poor wettability between graphene and metals, hindering the formation of strong interfacial bonds. Furthermore, the composite material is prone to uneven microstructure due to metal particle rearrangement or tungsten-tungsten bonding during hot pressing. The graphene structure is also easily damaged during hot or hydrostatic pressing. These and other issues significantly reduce the overall electrical, mechanical, and weldability properties of the composite material, limiting its development and hindering industrial production. Summary of the Invention

[0004] This application aims to provide a graphene-copper-tungsten composite material, its preparation method, and a conductive element, for improving the overall performance of the graphene-copper-tungsten composite material.

[0005] The embodiments of this application are implemented as follows:

[0006] In a first aspect, embodiments of this application provide a method for preparing a graphene-copper-tungsten composite material, comprising:

[0007] S1 provides tungsten powder;

[0008] S2, a copper layer is coated on the surface of tungsten powder to obtain copper-coated tungsten composite powder;

[0009] S3, a graphene layer is coated on the surface of the copper-tungsten composite powder to obtain graphene copper-tungsten composite powder;

[0010] S4, the graphene copper-tungsten composite powder is mixed with induced copper powder, organic binder and activator to obtain mixed powder;

[0011] S5, the mixed powder is cold-pressed into a green body;

[0012] S6, Degumming the green body to obtain the precursor;

[0013] S7, the precursor and copper sheet are stacked and then melt-infiltrated to obtain a graphene-copper-tungsten composite material.

[0014] In one embodiment of this application, in S1:

[0015] The tungsten powder is spherical; and / or

[0016] The particle size of the tungsten powder is ≤75μm; and / or

[0017] The preparation method of the tungsten powder includes: selecting raw tungsten powder with a particle size of 20-100μm, spheroidizing it, washing and drying it, and passing it through a 200-mesh sieve to obtain the tungsten powder.

[0018] In one embodiment of this application, S2 includes:

[0019] S21, The tungsten powder is placed in a magnetron sputtering oscillating container, and argon gas is introduced under vacuum to bombard a copper target for magnetron sputtering, so as to coat the surface of the tungsten powder with a first copper layer to obtain a composite powder intermediate.

[0020] S22, copper is chemically plated on the surface of the composite powder intermediate to coat a second copper layer, thereby obtaining copper-tungsten composite powder.

[0021] In one embodiment of this application, in S21:

[0022] Prior to magnetron sputtering, the vacuum level was 0.001–0.01 Pa; and / or

[0023] During magnetron sputtering, the vacuum level is 1-10 Pa; and / or

[0024] The purity of the copper target is ≥99.99%; and / or

[0025] The power of magnetron sputtering is 100-600W; and / or

[0026] The bias voltage for magnetron sputtering is 0-200V; and / or

[0027] The oscillation frequency of magnetron sputtering is 20-50 Hz; and / or

[0028] The thickness of the first copper layer is 2-10 μm.

[0029] In one embodiment of this application, in S22:

[0030] The plating solution used in electroless copper plating includes copper salts, including at least one of the following: anhydrous copper sulfate, copper pyrophosphate, copper sulfate, copper chloride, copper sulfamate, copper acetate, basic copper carbonate, copper bromide, copper formate, copper hydroxide, copper oxide, copper phosphate, copper fluoride silicon, copper stearate, and copper citrate; and / or

[0031] The plating solution used in electroless copper plating includes a reducing agent, which may include at least one of formaldehyde, aminoborane, hydroxylamine hydrochloride, sodium borohydride, and hydrazine hydrate; and / or

[0032] In the electroless copper plating solution, the mass ratio of copper salt to tungsten powder is (1-3):1; and / or

[0033] The pH value of the plating solution used in electroless copper plating is maintained at 11-13; and / or

[0034] Chemical copper plating is performed under constant temperature (55-65℃) and ultrasonic oscillation conditions; and / or

[0035] The thickness of the second copper layer is 20-50 μm.

[0036] In one embodiment of this application, before performing S22, the composite powder intermediate is reduced under a reducing atmosphere, wherein:

[0037] The reducing atmosphere includes a hydrogen atmosphere; and / or

[0038] The reduction temperature is 200-400℃.

[0039] In one embodiment of this application, before performing S22, the composite powder intermediate is subjected to activation and / or sensitization treatment, wherein:

[0040] The activation solution used in the activation treatment includes a hydrochloric acid solution of palladium chloride; and / or

[0041] The activation treatment time is 0.5-1.5 hours;

[0042] The sensitizer used in the sensitization treatment includes stannous chloride-hydrochloric acid solution; and / or

[0043] The sensitization treatment time is 20-45 minutes;

[0044] The environmental conditions for the "activation treatment and / or sensitization treatment" are constant temperature of 40-70℃ and ultrasonic oscillation.

[0045] In one embodiment of this application, in step S3, a graphene layer is coated onto the surface of the copper-tungsten composite powder by vapor deposition, including:

[0046] S31, the copper-tungsten composite powder is mixed and dispersed with silicon powder;

[0047] S32, under vacuum conditions and an oxygen-free protective atmosphere, carbon-containing gas is introduced for vapor deposition;

[0048] S33, the silicon powder is separated and removed to obtain the graphene copper-tungsten composite powder.

[0049] In one embodiment of this application, in S3:

[0050] The pressure conditions for vapor deposition in S32 range from (0.9 to 1.0) × 10⁻⁶. 5 Pa; and / or

[0051] The temperature conditions for vapor deposition in S32 are 1000-1050℃, and the temperature is maintained for 1-2.5 hours; and / or

[0052] The carbon-containing gas in S32 includes a reducing gas and a carbon source gas, wherein the reducing gas is introduced first, followed by the carbon source gas; and / or

[0053] The number of graphene layers obtained by vapor deposition in S32 is 1-10; and / or

[0054] In step S33, silicon powder is separated and removed by liquid phase separation to obtain the graphene-copper-tungsten composite powder.

[0055] In one embodiment of this application, the copper-tungsten composite powder is pretreated before performing step S3:

[0056] The copper-tungsten composite powder is polished and then subjected to micro-oxidation.

[0057] In one embodiment of this application, the polishing process is as follows: placing the copper-tungsten composite powder in a copper polishing agent, polishing for 2-5 minutes, then cleaning and drying; and / or

[0058] The micro-oxidation treatment is performed by placing the copper-tungsten composite powder in an environment with a humidity of 50-80% RH and a temperature of 80-150℃ for more than 0.5 hours.

[0059] In one embodiment of this application, in S4:

[0060] The purity of the induced copper powder is ≥99.99%; and / or

[0061] The organic adhesive includes isopropanol; and / or

[0062] The activator includes tin powder; and / or

[0063] Mixing is performed using a mixing device at a rotation frequency of 20-50 Hz; and / or

[0064] The mixing process lasts 2-6 hours; and / or

[0065] The ratio of the graphene copper-tungsten composite powder, the induced copper powder, the organic binder, and the activator is (30-70): (70-30): (0.01-0.1): (1.8-7).

[0066] In one embodiment of this application, in step S5, the mixed powder is loaded into a mold and cold-pressed, wherein:

[0067] The loading height is 5mm; and / or

[0068] The cold pressing pressure is 300-900MPa.

[0069] In one embodiment of this application, in step S6, the green preform is placed in a vacuum degumming furnace and degummed at a set temperature to prepare the precursor.

[0070] The set temperature is 900-950℃; and / or

[0071] Maintain at the set temperature for 2-2.5 hours; and / or

[0072] The degumming process is carried out in an inert atmosphere; and / or

[0073] The pressure conditions for the degumming process are in the range of (0.9-1.0)×10. 5 Pa.

[0074] In one embodiment of this application, in S7:

[0075] The purity of the copper sheet is ≥99.99%; and / or

[0076] The mass ratio of the copper sheet to the precursor is 1:3; and / or

[0077] The pressure conditions for the melting and infiltration process are in the range of 5-8 kPa; and / or

[0078] The temperature conditions for the melting and infiltration process are 1100-1300℃; and / or

[0079] The melting and infiltration process lasts for 1-2.5 hours.

[0080] Secondly, embodiments of this application provide a graphene-copper-tungsten composite material, prepared by the method for preparing the graphene-copper-tungsten composite material described in any one of the first aspects; and / or

[0081] The composite material includes:

[0082] A plurality of graphene-copper-tungsten composite powders, wherein the graphene-copper-tungsten composite powders include a tungsten framework, a copper layer and a graphene layer, wherein the copper layer coats the tungsten framework and the graphene layer coats the copper layer;

[0083] A copper bonding layer is filled between several of the graphene-copper-tungsten composite powders.

[0084] In one embodiment of this application, the tungsten framework comprises spherical powder with a particle size ≤75μm; and / or

[0085] The thickness of the copper layer is 22-60 μm; and / or

[0086] The thickness of the graphene layer is 1-10 layers; and / or

[0087] The mass percentage of copper in the composite material is 35-75%; and / or

[0088] The tungsten content in the composite material is 25-65% by mass; and / or

[0089] The graphene content in the composite material is 0.1-0.2% by mass; and / or

[0090] The composite material also includes tin, with a tin content of 0.01-1% by mass.

[0091] In one embodiment of this application, the copper layer includes a first copper layer and a second copper layer. The first copper layer is located between the surface of the tungsten skeleton and the second copper layer. The purity of the first copper layer is greater than that of the second copper layer. The thickness of the first copper layer is 2-10 μm, and the thickness of the second copper layer is 20-50 μm.

[0092] Thirdly, embodiments of this application provide a conductive element comprising a graphene-copper-tungsten composite material prepared by the method for preparing the graphene-copper-tungsten composite material as described in any one of the first aspects; or, comprising a graphene-copper-tungsten composite material as described in any one of the second aspects.

[0093] The conductive element includes an electrical contact conductor or a wire.

[0094] Beneficial effects:

[0095] In the technical solution of this application, the structure of the graphene layer itself will not be destroyed by excessive external pressure. The tungsten in the adjacent graphene copper-tungsten composite powder is well isolated, which effectively reduces the rearrangement of metal particles and the tungsten-tungsten connectivity, and effectively limits the problems of component segregation, grain coarsening and particle aggregation that occur when tungsten and copper are at high temperatures. In addition, the copper layer plays a physical isolation role for graphene and tungsten, avoiding the formation of tungsten carbide by graphene and tungsten at high temperatures, which would lead to a decrease in the overall electrical performance of the material. Furthermore, the copper powder and copper sheet are induced to form a three-dimensional network structure of copper-tungsten skeleton after melting and infiltration, and the graphene layer of several graphene copper-tungsten composite powders also forms a three-dimensional network structure. The two structures are tightly combined to form a dense structure. Therefore, the graphene-copper-tungsten composite material obtained by the preparation method of this application has the characteristics of stable structure, dense structure, low tungsten-tungsten connectivity, non-contact tungsten-carbon combination, uniform graphene distribution, and complete graphene sheet structure. It achieves improved anti-welding performance, electrical conductivity, thermal conductivity and mechanical properties without increasing tungsten content, and has high comprehensive performance. Attached Figure Description

[0096] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0097] Figure 1 This is a flowchart of a preparation method provided in one embodiment of this application;

[0098] Figure 2 This is a schematic diagram of the structure of a composite powder intermediate provided in one embodiment of this application;

[0099] Figure 3 This is a schematic diagram of the structure of a copper-tungsten composite powder provided in an embodiment of this application;

[0100] Figure 4 This is a schematic diagram of the structure of a graphene-copper-tungsten composite powder provided in an embodiment of this application;

[0101] Figure 5 This is a schematic diagram of the structure of a graphene-copper-tungsten composite material provided in an embodiment of this application;

[0102] Figure 6 A flowchart of a preparation method provided in another embodiment of this application;

[0103] Figure 7 An SEM image of a graphene-copper-tungsten composite material provided in an embodiment of this application.

[0104] Icons: 1000 - Graphene-copper-tungsten composite material; 100 - Graphene-copper-tungsten composite powder; 100a - Composite powder intermediate; 100b - Copper-tungsten composite powder; 110 - Tungsten skeleton; 120 - Copper layer; 121 - First copper layer; 122 - Second copper layer; 130 - Graphene layer; 200 - Copper connecting layer. Detailed Implementation

[0105] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0106] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0107] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0108] 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.

[0109] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0110] 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, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0111] Tungsten-copper alloys are a class of composite materials with excellent properties such as electrical and thermal conductivity, high-temperature strength, resistance to arc burn-off, wear resistance, and corrosion resistance, and are widely used in electrical contact conductors, wires, and many other applications. As electrical equipment develops towards higher voltages and higher capacities, more stringent requirements are being placed on the overall performance of electrical contact conductors and wires made from tungsten-copper alloy composite materials. To improve performance, attempts have been made to increase the tungsten content; however, while this improves resistance to welding, the reduced copper content leads to increased contact resistance, which is detrimental to conductivity.

[0112] To further improve material properties, the introduction of trace amounts of a third phase is considered. Relevant literature suggests that graphene, as a reinforcing phase in tungsten-copper alloys, is beneficial for improving the electrical and physical properties of the composite material. Other literature proposes several methods for adding graphene, including powder metallurgy, electrochemical deposition, and sol-gel methods. For example, tungsten-copper composite powder is mixed and dispersed with a graphene suspension, dried, and then hot-pressed and sintered. However, in this method, the poor wettability between graphene and the metal makes it difficult to form a strong interfacial bond. The hot-pressing or hydrostatic pressing process easily leads to metal particle rearrangement and tungsten-tungsten bonding, resulting in uneven microstructure. Furthermore, to achieve the bonding of graphene-coated powder particles under pressure, the unique three-dimensional network structure of the graphene sheets must be destroyed. Simultaneously, graphene is prone to agglomeration, leading to uneven dispersion. If ultrasonic dispersion of the graphene suspension is used to improve the agglomeration problem, it easily destroys the complete structure of the graphene. For example, after depositing graphene on the surface of copper powder in the vapor phase, it is then mechanically mixed with tungsten powder and hot-pressed. However, this method still suffers from problems such as damage to graphene, rearrangement of metal particles, and uneven microstructure caused by bonding. Therefore, the graphene-copper-tungsten composite materials prepared by the composite methods of graphene, copper, and tungsten provided in the relevant literature have the above-mentioned problems. It is difficult to achieve a balance between electrical properties, mechanical properties, weld resistance, corrosion resistance, and wear resistance. At least one of these properties is likely to be weak, which greatly affects the overall performance of the product, limits the development of composite materials, and hinders industrial production.

[0113] In view of this, this application provides a technical solution in which a copper layer and a graphene layer are sequentially coated on the surface of tungsten powder to form a core-shell structure of graphene-copper-tungsten composite powder. Then, the graphene-copper-tungsten composite powder is mixed with inducing copper powder, organic binder and activator and cold-pressed, so that the graphene-copper-tungsten composite powder can form a relatively dense green body under relatively low cold pressing pressure. Then, the green body is degummed to remove non-metallic impurities introduced during the mixing process, and a graphene-copper-tungsten core-shell structure graphene-copper-tungsten composite powder and a precursor formed by connecting copper connecting layers are obtained. Finally, the precursor and copper sheet are melt-infiltrated, and the copper liquid fills the gaps of the precursor to form a dense graphene-copper-tungsten composite material.

[0114] In the technical solution of this application, the structure of the graphene layer itself will not be destroyed by excessive external pressure. The tungsten in the adjacent graphene copper-tungsten composite powder is well isolated, which effectively reduces the rearrangement of metal particles and the tungsten-tungsten connectivity, and effectively limits the problems of component segregation, grain coarsening and particle aggregation that occur when tungsten and copper are at high temperatures. In addition, the copper layer plays a physical isolation role for graphene and tungsten, avoiding the formation of tungsten carbide by graphene and tungsten at high temperatures, which would lead to a decrease in the overall electrical performance of the material. Furthermore, the copper powder and copper sheet are induced to form a three-dimensional network structure of copper-tungsten skeleton after melting and infiltration, and the graphene layer of several graphene copper-tungsten composite powders also forms a three-dimensional network structure. The two structures are tightly combined to form a dense structure.

[0115] Therefore, the preparation method provided by the technical solution of this application and the graphene copper-tungsten composite material obtained by the preparation method have the characteristics of stable structure, dense structure, low tungsten-tungsten connectivity, tungsten-carbon contactless combination, uniform graphene distribution, and complete graphene sheet structure. It achieves improved anti-welding performance, electrical conductivity, thermal conductivity and mechanical properties without increasing tungsten content, and has high comprehensive performance.

[0116] In a first aspect, embodiments of this application provide a method for preparing a graphene-copper-tungsten composite material, such as... Figure 1 As shown, the steps include:

[0117] S1 provides tungsten powder;

[0118] S2, a copper layer is coated on the surface of tungsten powder to obtain copper-coated tungsten composite powder;

[0119] S3, a graphene layer is coated on the surface of the copper-tungsten composite powder to obtain graphene copper-tungsten composite powder;

[0120] S4, the graphene copper-tungsten composite powder is mixed with induced copper powder, organic binder and activator to obtain mixed powder;

[0121] S5, the mixed powder is cold-pressed into a green body;

[0122] S6, degumming the green body to obtain the precursor;

[0123] S7, the precursor and copper sheet are stacked and then melt-infiltrated to obtain graphene copper-tungsten composite material.

[0124] Regarding step S1:

[0125] Tungsten powder can be commercially available or prepared, and its shape and particle size can be configured in various ways. Optionally, the tungsten powder is spherical. It should be noted that "spherical shape" in this application does not mean that any single tungsten powder must be a perfect sphere, but rather that the tungsten powder used as a whole has good sphericity. Optionally, the particle size of the tungsten powder is ≤75μm, so that the particle size is approximately uniform and the tungsten content range can be better controlled. Uniform particle size avoids the segregation of tungsten-copper alloy components caused by uneven particle size during mixing, which is beneficial for meeting the requirements of anti-fusion welding performance and low resistance.

[0126] In some embodiments, tungsten powder is prepared by the following method:

[0127] Raw tungsten powder with a particle size of 20-100μm was selected, spheroidized, washed, dried, and passed through a 200-mesh sieve to obtain the desired tungsten powder.

[0128] The spheroidizing process involves ball milling the raw tungsten powder according to a certain ball-to-powder ratio. Both the jar and the balls in the ball mill are made of cemented carbide. The ball-to-powder ratio refers to the mass ratio of cemented carbide balls to tungsten powder; optionally, the ball-to-powder ratio is (2-4):1.

[0129] Optionally, the ball milling process is carried out under a protective atmosphere such as argon or nitrogen.

[0130] Optionally, the ball milling process is performed at room temperature, for example, 15-25°C.

[0131] Optionally, the rotational speed of the tank is 300-400 rad / min, the filling coefficient is 0.5-0.7, and the ball milling time is 4-12 h.

[0132] Optionally, the balling process can be followed by cleaning with deionized water.

[0133] Regarding step S2:

[0134] Methods for coating copper layers onto the surface of tungsten powder include at least one of chemical plating, electroplating, magnetron sputtering, vacuum evaporation, and rotary spraying.

[0135] In some embodiments, a first copper layer is first deposited onto the surface of tungsten powder using magnetron sputtering, and then a second copper layer is deposited onto the surface of the first copper layer using chemical plating. Exemplarily, the steps are as follows:

[0136] S21, Tungsten powder is placed in a magnetron sputtering oscillating container, and argon gas is introduced under vacuum to bombard a copper target for magnetron sputtering, so as to coat the surface of the tungsten powder with a first copper layer, thereby obtaining a composite powder intermediate, such as... Figure 2 As shown, magnetron sputtering is performed with tungsten skeleton 110 as the core, thereby continuously and uniformly coating a dense first copper layer 121 on the surface of tungsten skeleton 110 to form a tungsten-copper core-shell structured composite powder intermediate 100a.

[0137] S22, a second copper layer is coated onto the surface of the composite powder intermediate by chemical plating, resulting in a copper-tungsten composite powder, such as... Figure 3 As shown, the second copper layer 122 formed by chemical plating coats the surface of the composite powder intermediate 100a, forming a copper-tungsten composite powder 100b with a tungsten-copper-copper core-shell structure. The surface of the tungsten core is not a single copper layer, but a composite copper layer with two different structures having different densities and thicknesses.

[0138] Optionally, the thickness of the first copper layer is less than the thickness of the second copper layer.

[0139] In step S21:

[0140] Optionally, the vacuum level is 0.001-0.01 Pa before magnetron sputtering.

[0141] Optionally, the vacuum level is 1-10 Pa during magnetron sputtering.

[0142] Optionally, the purity of the copper target is ≥99.99%.

[0143] Optionally, the power of magnetron sputtering is 100-600W.

[0144] Optionally, the bias voltage for magnetron sputtering is 0-200V.

[0145] Optionally, the oscillation frequency of magnetron sputtering is 20-50Hz.

[0146] Optionally, the thickness of the first copper layer is 2-10 μm.

[0147] In step S22:

[0148] Optionally, the plating solution used in electroless copper plating includes copper salts, including at least one of anhydrous copper sulfate, copper pyrophosphate, copper sulfate, copper chloride, copper sulfamate, copper acetate, basic copper carbonate, copper bromide, copper formate, copper hydroxide, copper oxide, copper phosphate, copper fluoride, copper stearate, and copper citrate.

[0149] Optionally, the plating solution used in electroless copper plating includes a reducing agent, which may include at least one of formaldehyde, aminoborane, hydroxylamine hydrochloride, sodium borohydride, and hydrazine hydrate.

[0150] Optionally, in the electroless copper plating solution, the mass ratio of copper salt to tungsten powder is (1-3):1.

[0151] Optionally, the pH value of the plating solution used in electroless copper plating is maintained at 11-13.

[0152] Optionally, electroless copper plating is carried out under constant temperature of 55-65℃ and ultrasonic oscillation conditions.

[0153] Optionally, the thickness of the second copper layer is 20-50 μm.

[0154] In this embodiment, the magnetron sputtering method in step S21 is first used to bombard a copper target with argon gas, thereby achieving the coating of a first copper layer (e.g., argon gas) onto the surface of tungsten powder under the action of an electric field. Figure 2 As shown in the figure, copper is plated after etching tungsten powder by magnetron sputtering deposition during the process of high vacuum inert gas protection. This step S21 does not easily introduce other elements, avoids introducing impurities between the copper layer and the tungsten substrate, and provides active sites for chemical plating, ensuring that the first copper layer has high purity and quality. The density of the first copper layer is also improved, and the interfacial bonding with the tungsten powder is good, which can avoid the coating peeling off during the high temperature treatment in the subsequent steps.

[0155] Then, a second copper layer is coated using chemical copper plating (such as...). Figure 3 As shown, the second copper layer obtained by chemical copper plating has a relatively denser structure and is easier to obtain with a larger copper layer thickness.

[0156] In other words, the magnetron sputtering followed by chemical plating method provided in this application first forms a thin, continuous first copper layer with good interfacial bonding with tungsten powder, and then uses the first copper layer to connect a high-density, high-thickness second copper layer, thereby obtaining a core-shell structured copper-tungsten composite powder with stable coating, dense copper layer structure, and high copper content. Figure 3 As shown.

[0157] In related technologies, forming copper layers using methods such as electroless plating and electroplating requires a variety of reagents, which can easily introduce other impurity elements that bond with tungsten. However, the magnetron sputtering of the first copper layer in this application not only improves the interfacial bonding between copper and tungsten but also adds surface-active sites for subsequent electroless copper plating, enabling the reaction to proceed rapidly and significantly improving processing efficiency. Simultaneously, the isolation effect of the first copper layer prevents reagent contamination of the tungsten powder during electroless copper plating, thus avoiding the introduction of other impurity elements that could bond with tungsten and cause adverse effects.

[0158] In addition, the copper layer formed by the combination of the first and second copper layers has high density, high thickness and good bonding stability. The coating and isolation effect of the copper layer on tungsten powder is greatly improved, which helps to prevent tungsten from contacting other elements in subsequent processing steps. For example, it prevents graphene from diffusing into the inner layer and forming carbides by contacting tungsten.

[0159] In some embodiments, before performing S22, the composite powder intermediate obtained in step S21 is also reduced in a reducing atmosphere to avoid the problem that the surface of the composite powder intermediate is oxidized during storage or transfer, which would reduce the purity and density of the second copper layer.

[0160] Optionally, the reducing atmosphere includes a hydrogen atmosphere.

[0161] Optionally, the reduction step is carried out at a temperature of 200-400°C.

[0162] In some embodiments, prior to performing S22, the composite powder intermediate is further subjected to activation and / or sensitization treatments. These activation and sensitization treatments make it easier for a copper plating layer to adhere to the surface of the composite powder.

[0163] Activation treatment refers to immersing the composite powder intermediate in an activation solution and removing the oxide film, impurities, etc. on the surface through a chemical reaction.

[0164] Optionally, the activation solution used in the activation treatment includes a hydrochloric acid solution of palladium chloride.

[0165] Optionally, the activation treatment time is 0.5-1.5 hours.

[0166] Optionally, the activation treatment is performed under constant temperature and ultrasonic oscillation conditions of 40-70℃, such as water bath heating at a constant temperature of 55℃, accompanied by ultrasonic oscillation.

[0167] Optionally, after the activation treatment is completed, the composite powder is washed with deionized water to remove chemical reagents adhering to the surface of the composite powder.

[0168] Sensitization treatment refers to immersing the composite powder intermediate in a sensitizer for a certain period of time to improve the electrochemical activity and surface conductivity of the composite surface.

[0169] Optionally, the sensitizer used in the sensitization treatment may include a stannous chloride-hydrochloric acid solution.

[0170] Optionally, the sensitization treatment time is 20-45 min;

[0171] Optionally, the sensitization treatment is performed under constant temperature and ultrasonic oscillation conditions of 40-70℃, such as water bath heating at a constant temperature of 55℃, accompanied by ultrasonic oscillation.

[0172] Optionally, after the sensitization treatment, the composite powder is washed with deionized water to remove chemical reagents adhering to the surface of the composite powder.

[0173] Regarding step S3:

[0174] In S3, a graphene layer was coated onto the surface of copper-tungsten composite powder via vapor deposition to obtain, as shown in [example needed]. Figure 4 The graphene copper-tungsten composite powder 100 is shown. In step S3, the copper-tungsten composite powder 100b with a tungsten-copper-copper core-shell structure obtained in step S2 is used as the core to form a metal core-graphene core-shell structure again, that is, the graphene copper-tungsten composite powder 100 has a graphene-(tungsten-copper-copper) structure.

[0175] After step S2, which involves coating the tungsten powder surface with a high-density, high-thickness, and high-stability copper layer, the graphene will not diffuse and combine with tungsten at high temperatures during the vapor deposition process due to the isolation effect of the copper layer. This enables the in-situ growth of a graphene layer on the copper layer, resulting in a graphene layer with a complete structure and controllable number of layers.

[0176] Optionally, the number of graphene layers is 1-10. At this thickness, the graphene layers have good structural integrity and good coverage. At the same time, the graphene will not form graphite due to excessive thickness. The appropriate graphene content is beneficial to the improvement of electrical and mechanical properties.

[0177] In some embodiments, the method of vapor-phase deposition of graphene includes: introducing a carbon source gas in an oxygen-free protective gas atmosphere at a temperature of 1000-1050°C.

[0178] In some embodiments, step S3 includes S31, S32, and S33, as detailed below.

[0179] S31, mix and disperse copper-tungsten composite powder with silicon powder.

[0180] S32, under vacuum conditions and an oxygen-free protective atmosphere, carbon-containing gas is introduced for vapor deposition.

[0181] Optionally, the oxygen-free protective atmosphere includes at least one of nitrogen and argon.

[0182] Optionally, the pressure conditions for vapor deposition range from (0.9 to 1.0) × 10⁵ Pa.

[0183] Optionally, the temperature conditions for vapor deposition are 1000-1050℃, and the temperature is maintained for 1-2.5 hours. Optionally, the heating rate is 5-30℃ / min.

[0184] Optionally, the carbon-containing gas includes a reducing gas and a carbon source gas, with the reducing gas introduced first, followed by the carbon source gas. The reducing gas includes hydrogen. The carbon source gas includes methane.

[0185] S33, the silicon powder is separated and removed to obtain graphene copper-tungsten composite powder. Optionally, the silicon powder is separated and removed by liquid-phase separation.

[0186] By performing vapor deposition under mixed silicon powder conditions, the graphene layer can be dispersed and prevented from sintering due to high temperature, thus further ensuring the structural integrity of the graphene layer.

[0187] The inventors discovered that due to the difference in thermal expansion coefficients between copper and graphene, the thermal stress mismatch between graphene and copper during the cooling process after chemical vapor deposition leads to steps and wrinkles in the graphene. The presence of these steps and wrinkles causes anisotropic electron transport within the graphene, reducing carrier mobility and negatively impacting its electrical properties. Further research revealed that the coarser the surface roughness of the copper, the more pronounced the wrinkles and steps, and the lower the quality of the graphene grown on the copper.

[0188] Therefore, in some embodiments, before performing S3, the copper-tungsten composite powder is pretreated, i.e., the copper-tungsten composite powder is first polished, followed by micro-oxidation. Optionally, the polishing process is as follows: the copper-tungsten composite powder is placed in a copper polishing agent and polished for 2-5 minutes, then cleaned and dried. Optionally, the micro-oxidation process is as follows: the copper-tungsten composite powder is placed in an environment with a humidity of 50-80% RH and a temperature of 80-150°C for at least 0.5 hours.

[0189] By pretreating the copper layer on tungsten powder before vapor deposition of graphene, the surface smoothness of the copper layer is improved after polishing. This alleviates the steps and wrinkles caused by thermal stress mismatch due to temperature changes. Combined with micro-oxidation, a shallow layer of copper oxide is generated on the smoother copper layer surface. Copper oxide can induce the initial nucleation of graphene on the copper material, and as the graphene grows, it can effectively reduce the solid solubility of carbon atoms, thereby reducing the nucleation rate. This allows for the fabrication of a smaller, larger graphene coating layer on the copper layer while maintaining structural continuity and integrity. This pretreatment step of polishing followed by micro-oxidation further improves the high conductivity and anti-welding performance of copper-tungsten electrical contact materials without increasing the tungsten content.

[0190] Regarding step S4:

[0191] In step S4, the graphene copper-tungsten composite powder is mixed with induced copper powder, organic binder, and activator to obtain a mixed powder. Step S4 prepares the green body for the subsequent cold pressing in step S5, so as to achieve the formation of a relatively dense green body under relatively low cold pressing pressure.

[0192] Optionally, the purity of the induced copper powder is ≥99.99%.

[0193] Alternatively, the organic adhesive may include isopropanol.

[0194] Optionally, the activator includes tin powder.

[0195] Optionally, a mixing device is used to mix the materials at a rotation frequency of 20-50 Hz. There are various types of mixing devices, such as a three-dimensional motion mixer, in which graphene copper-tungsten composite powder, induced copper powder, organic binder, and activator are loaded into the barrel of the three-dimensional motion mixer, and the barrel is rotated at a rotation frequency of 20-50 Hz to mix the materials.

[0196] Optionally, the mixing process may last for 2-6 hours, for example, 4 hours.

[0197] Optionally, the ratio of graphene copper-tungsten composite powder, induced copper powder, organic binder, and activator is in the range of (30-70):(70-30):(0.01-0.1):(1.8-7).

[0198] Regarding step S5:

[0199] In step S5, the mixed powder is loaded into the mold, and then pressure is applied for cold pressing to form a green body.

[0200] Optionally, the loading height is 5mm.

[0201] Optionally, the cold pressing pressure is 300-900 MPa.

[0202] Regarding step S6:

[0203] In S6, the green body is placed in a vacuum degumming furnace and degummed at a set temperature to remove non-metallic impurities introduced during the mixing process, thereby obtaining a precursor. The precursor includes graphene-copper-tungsten core-shell structured graphene-copper-tungsten composite powder and induced copper powder.

[0204] Optionally, the degumming temperature is set at 900-950℃.

[0205] Optionally, maintain at the set temperature for 2-2.5 hours.

[0206] Optionally, the degumming process is carried out in an inert atmosphere.

[0207] Optionally, the degumming process is carried out under normal pressure conditions, for example, the pressure conditions of the degumming process are in the range of (0.9-1.0)×105 Pa.

[0208] Regarding step S7:

[0209] In S7, the green body and precursor, which have been degummed in step S6, are stacked sequentially on a fixture (such as a graphite fixture) and placed in a sintering furnace for melting and infiltration.

[0210] Several graphene layers on the surface of the graphene-copper-tungsten composite powders form a first three-dimensional network structure through close contact via the aforementioned steps. This induces copper powder and copper sheets to form molten copper during the melting and infiltration process, filling the voids in the first three-dimensional network structure. The solidified copper bonding layer forms a second three-dimensional network structure. The two three-dimensional network structures fill and envelop each other, forming a stable and dense structure, resulting in a graphene-copper-tungsten composite material with high comprehensive performance. Figure 5 As shown.

[0211] Optionally, the purity of the copper sheet is ≥99.99%.

[0212] Optionally, the mass ratio of copper sheet to precursor is 1:3.

[0213] Optionally, the melting and infiltration process is carried out under slightly positive pressure conditions, for example, the pressure conditions of the melting and infiltration process are in the range of 5-8 kPa.

[0214] Optionally, the temperature conditions for the melting and infiltration process are 1100-1300℃. Optionally, the heating rate is 5-30℃ / min.

[0215] Optionally, the melting and infiltration process lasts for 1-2.5 hours. That is, after reaching the set temperature conditions, the temperature is maintained for 1-2.5 hours to carry out the melting and infiltration treatment.

[0216] like Figure 6 As shown, in some embodiments, this application provides a method for preparing a graphene-copper-tungsten composite material, the steps of which are as follows.

[0217] Step S1: Provide tungsten powder.

[0218] Select raw tungsten powder with a particle size of 20-100μm, weigh the raw tungsten powder and cemented carbide balls according to the ball-to-material ratio (2-4):1, put them into the jar of the ball mill, introduce inert gas and seal, and ball mill at a speed of 300-400 rad / min for 4-12 hours. Then, wash with deionized water and anhydrous ethanol and dry, and pass through a 200-mesh sieve to obtain the desired tungsten powder.

[0219] Step S2: Coat with a copper layer to prepare copper-tungsten composite powder.

[0220] Magnetron sputtering of the first copper layer. 50g of tungsten powder was placed in a magnetron sputtering oscillating container. High-purity argon gas was introduced under vacuum conditions, and the DC power supply to the copper target was turned on. A first copper layer was deposited on the surface of the tungsten powder to obtain a composite powder intermediate. The background vacuum before magnetron sputtering deposition was 0.001-0.01 Pa. Argon gas (purity ≥99.99%) was then introduced, and the sputtering vacuum was 1-10 Pa. The copper target power (purity ≥99.99%) was then turned on, with a target power of 100-600 W and a sputtering bias of 0-200 V. During deposition, the powder oscillating apparatus remained on, with an oscillation frequency of 20-50 Hz. The deposition time was 1 hour, and the sputtered copper layer thickness was 2-10 μm.

[0221] Reduction, activation, and sensitization treatments were performed. The composite powder intermediate was cleaned and dried, then reduced under a reducing atmosphere. Following this, the composite powder intermediate underwent activation and sensitization treatments. Reduction conditions: reduction temperature 200-400℃, reducing atmosphere: hydrogen atmosphere. Sensitization conditions: sensitizer was stannous chloride-hydrochloric acid solution (SnCl₂-HCl), water bath heating maintained at a constant temperature of 55℃, accompanied by ultrasonic oscillation, sensitization time 20-45 min, followed by filtration and cleaning with deionized water. Activation conditions: activator was palladium chloride (PdCl₂) hydrochloric acid solution (1.5 wt.%), water bath heating maintained at a constant temperature of 55℃, accompanied by ultrasonic oscillation, activation time 0.5-1.5 h, followed by filtration and cleaning with deionized water.

[0222] A second copper layer is electrolessly plated. A continuous second copper layer is deposited on the surface of the composite powder intermediate through electroless plating, forming a tungsten-copper core-shell copper-tungsten composite powder, with a thickness of 20-50 μm. The copper salt used for electroless copper plating is anhydrous copper sulfate (CuSO4·5H2O), and the reducing agent includes formaldehyde (CH2O). The ratio of copper to tungsten powder is (1-3):1, and the pH value is adjusted to maintain 11-13. Electroless copper plating is carried out under constant temperature water bath conditions of 55-65℃ and ultrasonic vibration. The reducing agent is continuously added until the plating solution turns red or colorless. Then, it is filtered and washed with deionized water and dried for later use. The vacuum oven temperature is 80℃, and the drying time is 2 hours.

[0223] Step S3: Coat with a graphene layer to prepare graphene-copper-tungsten composite powder.

[0224] Powder surface pretreatment. Pour copper-tungsten composite powder into copper polishing agent and stir continuously for 2 minutes. Then, filter and wash with deionized water multiple times, dry, and place in a damp heat test chamber. Set the temperature to 80-150℃ and the humidity to 50-80%RH for more than 0.5 hours for micro-oxidation. After natural cooling, it is ready for use.

[0225] Chemical vapor deposition of graphene. Copper-tungsten composite powder and silicon powder are mechanically mixed and placed in a quartz apparatus. A carbon-containing gas is introduced under an oxygen-free protective atmosphere, and the temperature is raised to the deposition temperature of 1000-1050℃. 1-10 layers of graphene are deposited on the surface of the copper-tungsten composite powder using chemical vapor deposition, forming a graphene-copper-tungsten composite powder. The protective atmosphere includes nitrogen and argon, and the chemical vapor deposition is performed at atmospheric pressure (0.9-1.0) × 10⁻⁶. 5 The process is carried out at Pa, with a heating rate of 5-30℃ / min. After reaching the deposition temperature, the temperature is maintained for 1-2.5 hours. The carbon-containing gas includes carbon source gas and reducing gas. The reducing gas is introduced first, followed by the carbon source gas. The carbon source gas includes methane (CH4), and the reducing gas includes hydrogen.

[0226] Step S4: Prepare the mixed powder.

[0227] Graphene-copper-tungsten composite powder, induced copper powder, organic binder, and activator are loaded into the mixing cylinder of a mixing device and rotated at a frequency of 20-50 Hz for 2-6 hours to obtain a mixed powder. The mixture contains 20-120 g of induced copper powder, 10-17 ml of organic binder, and 0.007-0.017 g of activator. The purity of the induced copper powder is ≥99.99%. The organic binder includes isopropanol, and the activator includes tin powder.

[0228] Step S5: Make the green body.

[0229] The mixed powder is loaded into a mold to a height of 5mm, and then cold-pressed at a pressure of 300-900MPa to form a green body.

[0230] Step S6:

[0231] The green body was placed in a vacuum degreasing furnace and heated at atmospheric pressure (0.9-1.0) × 10⁻⁶. 5 Under a protective atmosphere (nitrogen or argon), the temperature is increased to 900-950℃ at a rate of 5-30℃ / min. After reaching the temperature, the temperature is maintained for 2-2.5 hours to remove the gel and obtain the precursor.

[0232] Step S7:

[0233] Copper sheets were cut to a mass ratio of 1:3 to the precursor. The precursor and the cut copper sheets (purity ≥99.99%) were placed sequentially on a graphite fixture and then placed in a sintering furnace. The furnace pressure was set to 5-8 kPa, and the temperature was increased to the melting infiltration temperature of 1100-1200℃ at a heating rate of 5-30℃ / min. The melting infiltration temperature was maintained for 1-2.5 hours to complete the melting infiltration process and obtain graphene copper-tungsten composite material.

[0234] In a second aspect, embodiments of this application provide a graphene-copper-tungsten composite material, which is prepared by the preparation method of the graphene-copper-tungsten composite material provided in any embodiment of the first aspect;

[0235] Or, such as Figure 5 As shown, the graphene-copper-tungsten composite material 1000 includes several graphene-copper-tungsten composite powders 100 and a copper connecting layer 200, such as... Figure 4 As shown, the graphene copper-tungsten composite powder 100 includes a tungsten skeleton 110, a copper layer 120 and a graphene layer 130. The copper layer 120 covers the tungsten skeleton 110, and the graphene layer 130 covers the copper layer 120. A copper connecting layer 200 is filled between several graphene copper-tungsten composite powders 100.

[0236] In some embodiments, the tungsten framework 110 comprises spherical powder with a particle size ≤75μm.

[0237] In some embodiments, the thickness of the copper layer 120 is 22-60 μm.

[0238] In some embodiments, the thickness of the graphene layer 130 is 1-10 layers.

[0239] In some embodiments, the mass percentage of copper in the graphene copper-tungsten composite material 1000 is 35-75%.

[0240] In some embodiments, the mass percentage of tungsten in the graphene copper-tungsten composite material 1000 is 25-65%.

[0241] In some embodiments, the graphene content in the graphene-copper-tungsten composite material 1000 is 0.1-0.2% by mass.

[0242] In some embodiments, the graphene copper-tungsten composite material 1000 also includes tin, with the tin content being 0.01-1% by mass.

[0243] In some embodiments, the copper layer 120 includes a first copper layer 121 and a second copper layer 122. The first copper layer 121 is located on the surface of the tungsten skeleton 110 and between the second copper layer 122. The purity of the first copper layer 121 is greater than that of the second copper layer 122. The thickness of the first copper layer 121 is 2-10 μm and the thickness of the second copper layer 122 is 20-50 μm.

[0244] Thirdly, embodiments of this application provide a conductive element comprising a graphene-copper-tungsten composite material prepared by the method for preparing the graphene-copper-tungsten composite material provided in any embodiment of the first aspect; or, comprising a graphene-copper-tungsten composite material provided in any embodiment of the second aspect. The conductive element includes an electrical contact conductor or a wire.

[0245] 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.

[0246] Example 1

[0247] Step S1: Provide tungsten powder.

[0248] 500g of raw tungsten powder with a particle size of 50μm and 250g of cemented carbide balls were selected and placed together in the jar of a ball mill. Argon gas was introduced and the mill was sealed. The mill was ball-milled at a speed of 400 rad / min for 4 hours. Then, the mill was washed with deionized water and anhydrous ethanol and dried. The powder was then passed through a 200-mesh sieve to obtain tungsten powder with uniform particle size and good sphericity.

[0249] Step S2: Coat with a copper layer to prepare copper-tungsten composite powder.

[0250] Magnetron sputtering of the first copper layer. 50g of tungsten powder was placed in a magnetron sputtering oscillating container. High-purity argon gas was introduced under vacuum conditions, and the DC power supply to the copper target was turned on. A first copper layer was deposited on the surface of the tungsten powder to obtain a composite powder intermediate. The background vacuum before magnetron sputtering deposition was 0.006Pa, followed by the introduction of argon gas (purity ≥99.99%) to a sputtering vacuum of 5Pa. The copper target power supply (purity ≥99.99%) was then turned on at 300W, with a sputtering bias of 100V. During the deposition process, the oscillating powder apparatus remained on at a frequency of 50Hz, the deposition time was 1 hour, and the sputtered copper layer thickness was 5μm.

[0251] Reduction, activation, and sensitization treatments were performed. The composite powder intermediate was cleaned and dried, then reduced under a reducing atmosphere. Following this, the composite powder intermediate underwent activation and sensitization treatment. Reduction conditions: reduction temperature was 300℃, and the reducing atmosphere was hydrogen. Sensitization conditions: the sensitizer was stannous chloride-hydrochloric acid solution (SnCl₂-HCl), heated in a water bath at a constant temperature of 55℃, accompanied by ultrasonic oscillation, for 30 minutes. After sensitization, the sample was filtered and cleaned with deionized water. Activation conditions: the activator was palladium chloride (PdCl₂) hydrochloric acid solution (1.5 wt.%), heated in a water bath at a constant temperature of 55℃, accompanied by ultrasonic oscillation, for 0.5 hours. After activation, the sample was filtered and cleaned with deionized water.

[0252] A second copper layer is electrolessly plated. A continuous second copper layer is deposited on the surface of the composite powder intermediate through electroless plating, forming a tungsten-copper core-shell copper-tungsten composite powder, with a second copper layer thickness of 35 μm. The copper salt used for electroless copper plating is anhydrous copper sulfate (CuSO4·5H2O), and the reducing agent includes formaldehyde (CH2O). The ratio of copper to tungsten powder is 1:1, and the pH value is adjusted to maintain 12. Electroless copper plating is carried out under constant temperature water bath conditions of 55-65℃ and ultrasonic vibration. The reducing agent is continuously added until the plating solution turns red or colorless. Subsequently, the solution is filtered and washed with deionized water and dried for later use. The drying time is 2 hours in a vacuum oven at 80℃.

[0253] Step S3: Coat with a graphene layer to prepare graphene-copper-tungsten composite powder.

[0254] Powder surface pretreatment. Pour copper-tungsten composite powder into copper polishing agent and stir continuously for 2 minutes. Then, filter and wash with deionized water several times, dry, and place in a damp heat test chamber. Set the temperature to 100℃ and the humidity to 50%RH for 0.5 hours for micro-oxidation. After natural cooling, it is ready for use.

[0255] Chemical vapor deposition of graphene. Copper-tungsten composite powder and silicon powder are mechanically mixed and placed in a quartz apparatus. A carbon-containing gas is introduced under an oxygen-free protective atmosphere, and the temperature is raised to the deposition temperature of 1000-1050℃. 1-10 layers of graphene are deposited on the surface of the copper-tungsten composite powder using chemical vapor deposition, forming a graphene-copper-tungsten composite powder. The protective atmosphere includes nitrogen and argon, and the chemical vapor deposition is performed at atmospheric pressure (0.9-1.0) × 10⁻⁶. 5 The process is carried out at Pa, with a heating rate of 10℃ / min. After reaching the deposition temperature, the temperature is maintained for 1.5h. The carbon-containing gas includes carbon source gas and reducing gas. The reducing gas is introduced first, followed by the carbon source gas. The carbon source gas includes methane, and the reducing gas includes hydrogen.

[0256] Step S4: Prepare the mixed powder.

[0257] Graphene-copper-tungsten composite powder, induced copper powder, organic binder, and activator are loaded into the mixing cylinder of a mixing device and rotated at a frequency of 20-50 Hz for 2-6 hours to obtain a mixed powder. The mixture contains 25 g of induced copper powder (purity ≥99.99%), 4 ml of organic binder (isopropanol), and 0.005 g of activator (tin powder).

[0258] Step S5: Make the green body.

[0259] The mixed powder is loaded into a mold with a diameter of 20 mm and a height of 5 mm, and then cold-pressed at a pressure of 3 t / cm2 to form a green body.

[0260] Step S6:

[0261] The green body was placed in a vacuum degreasing furnace and heated at atmospheric pressure (0.9-1.0) × 10⁻⁶. 5 Under a protective atmosphere (nitrogen), the temperature is increased to 950℃ at a rate of 10℃ / min. After reaching the temperature, the temperature is maintained for 2 hours for degumming to obtain the precursor.

[0262] Step S7:

[0263] Copper sheets were cut to a copper-to-precursor mass ratio of 1:3. The precursor and the cut copper sheets (purity ≥99.99%) were placed sequentially on a graphite apparatus and then placed in a sintering furnace. The furnace pressure was set to 5-8 kPa, and the temperature was increased to the melting point of 1200℃ at a rate of 10℃ / min. The melting point was maintained for 1 hour to complete the melting process, yielding a graphene-copper-tungsten composite material. The composition of the graphene-copper-tungsten composite material is Cu 61.8%, W 38%, Sn 0.05%, and Gr 0.15%, denoted as Cu. 62 W 38 Gr 0.15 .

[0264] It should be noted that in this application, Gr refers to graphene.

[0265] Example 2

[0266] Step S1: Provide tungsten powder.

[0267] 500g of raw tungsten powder with a particle size of 50μm and 250g of cemented carbide balls were selected and placed together in the jar of a ball mill. Argon gas was introduced and the mill was sealed. The mill was ball-milled at a speed of 400 rad / min for 4 hours. Then, the mill was washed with deionized water and anhydrous ethanol and dried. The powder was then passed through a 200-mesh sieve to obtain tungsten powder with uniform particle size and good sphericity.

[0268] Step S2: Coat with a copper layer to prepare copper-tungsten composite powder.

[0269] Magnetron sputtering of the first copper layer. 50g of tungsten powder was placed in a magnetron sputtering oscillating container. High-purity argon gas was introduced under vacuum conditions, and the DC power supply to the copper target was turned on. A first copper layer was deposited on the surface of the tungsten powder to obtain a composite powder intermediate. The background vacuum before magnetron sputtering deposition was 0.006Pa, followed by the introduction of argon gas (purity ≥99.99%) to a sputtering vacuum of 5Pa. The copper target power supply (purity ≥99.99%) was then turned on at 300W, with a sputtering bias of 100V. During the deposition process, the oscillating powder apparatus remained on at a frequency of 50Hz, the deposition time was 1 hour, and the sputtered copper layer thickness was 5μm.

[0270] Reduction, activation, and sensitization treatments were performed. The composite powder intermediate was cleaned and dried, then reduced under a reducing atmosphere, followed by activation and sensitization. Reduction conditions: reduction temperature 300℃, reducing atmosphere: hydrogen atmosphere. Sensitization conditions: sensitizer was stannous chloride-hydrochloric acid solution (SnCl₂-HCl), water bath heating maintained at a constant temperature of 55℃, accompanied by ultrasonic oscillation, sensitization time 30 min, after which the sample was filtered and cleaned with deionized water. Activation conditions: activator was palladium chloride (PdCl₂) hydrochloric acid solution (1.5 wt.%), water bath heating maintained at a constant temperature of 55℃, accompanied by ultrasonic oscillation, activation time 0.5 h, after which the sample was filtered and cleaned with deionized water.

[0271] A second copper layer is electrolessly plated. A continuous second copper layer is deposited on the surface of the composite powder intermediate through electroless plating, forming a tungsten-copper core-shell copper-tungsten composite powder, with a second copper layer thickness of 35 μm. The copper salt used for electroless copper plating is anhydrous copper sulfate (CuSO4·5H2O), and the reducing agent includes formaldehyde (CH2O). The ratio of copper to tungsten powder is 1:1, and the pH value is adjusted to maintain 12. Electroless copper plating is carried out under constant temperature water bath conditions of 55-65℃ and ultrasonic vibration. The reducing agent is continuously added until the plating solution turns red or colorless. Subsequently, the solution is filtered and washed with deionized water and dried for later use. The drying time is 2 hours in a vacuum oven at 80℃.

[0272] Step S3: Coat with a graphene layer to prepare graphene-copper-tungsten composite powder.

[0273] Powder surface pretreatment. Pour copper-tungsten composite powder into copper polishing agent and stir continuously for 2 minutes. Then, filter and wash with deionized water several times, dry, and place in a damp heat test chamber. Set the temperature to 100℃ and the humidity to 50%RH for 0.5 hours for micro-oxidation. After natural cooling, it is ready for use.

[0274] Chemical vapor deposition of graphene. Copper-tungsten composite powder and silicon powder are mechanically mixed and placed in a quartz apparatus. A carbon-containing gas is introduced under an oxygen-free protective atmosphere, and the temperature is raised to the deposition temperature of 1000-1050℃. 1-10 layers of graphene are deposited on the surface of the copper-tungsten composite powder using chemical vapor deposition, forming a graphene-copper-tungsten composite powder. The protective atmosphere includes nitrogen and argon, and the chemical vapor deposition is performed at atmospheric pressure (0.9-1.0) × 10⁻⁶. 5 The process is carried out at Pa, with a heating rate of 10℃ / min. After reaching the deposition temperature, the temperature is maintained for 1 hour. The carbon-containing gas includes carbon source gas and reducing gas. The reducing gas is introduced first, followed by the carbon source gas. The carbon source gas includes methane, and the reducing gas includes hydrogen.

[0275] Step S4: Prepare the mixed powder.

[0276] Graphene-copper-tungsten composite powder, induced copper powder, organic binder, and activator are loaded into the mixing cylinder of a mixing device and rotated at a frequency of 20-50 Hz for 2-6 hours to obtain a mixed powder. The mixture contains 25 g of induced copper powder (purity ≥99.99%), 4 ml of organic binder (isopropanol), and 0.005 g of activator (tin powder).

[0277] Step S5: Make the green body.

[0278] The mixed powder is loaded into a mold with a diameter of 20 mm and a height of 5 mm, and then cold-pressed at a pressure of 3 t / cm2 to form a green body.

[0279] Step S6:

[0280] The green body was placed in a vacuum degreasing furnace and heated at atmospheric pressure (0.9-1.0) × 10⁻⁶. 5 Under a protective atmosphere (nitrogen), the temperature is increased to 950℃ at a rate of 10℃ / min. After reaching the temperature, the temperature is maintained for 2 hours for degumming to obtain the precursor.

[0281] Step S7:

[0282] Copper sheets were cut to a copper-to-precursor mass ratio of 1:3. The precursor and the cut copper sheets (purity ≥99.99%) were placed sequentially on a graphite apparatus and then placed in a sintering furnace. The furnace pressure was set to 5-8 kPa, and the temperature was increased to the melting point of 1200℃ at a rate of 10℃ / min. The melting point was maintained for 1 hour to complete the melting process, yielding a graphene-copper-tungsten composite material. The composition of the graphene-copper-tungsten composite material is Cu 61.8%, W 38%, Sn 0.05%, and Gr 0.1%, denoted as Cu. 62 W 38 Gr 0.1 .

[0283] Comparative Example 1

[0284] Step S1: Provide tungsten powder.

[0285] 500g of raw tungsten powder with a particle size of 50μm and 250g of cemented carbide balls were selected and placed together in the jar of a ball mill. Argon gas was introduced and the mill was sealed. The mill was ball-milled at a speed of 400 rad / min for 4 hours. Then, the mill was washed with deionized water and anhydrous ethanol and dried. The powder was then passed through a 200-mesh sieve to obtain tungsten powder with uniform particle size and good sphericity.

[0286] Step S2: Coat with a copper layer to prepare copper-tungsten composite powder.

[0287] Magnetron sputtering of the first copper layer. 50g of tungsten powder was placed in a magnetron sputtering oscillating container. High-purity argon gas was introduced under vacuum conditions, and the DC power supply to the copper target was turned on. A first copper layer was deposited on the surface of the tungsten powder to obtain a composite powder intermediate. The background vacuum before magnetron sputtering deposition was 0.006Pa, followed by the introduction of argon gas (purity ≥99.99%) to a sputtering vacuum of 5Pa. The copper target power supply (purity ≥99.99%) was then turned on at 300W, with a sputtering bias of 100V. During the deposition process, the oscillating powder apparatus remained on at a frequency of 50Hz, the deposition time was 1 hour, and the sputtered copper layer thickness was 5μm.

[0288] Reduction, activation, and sensitization treatments were performed. The composite powder intermediate was cleaned and dried, then reduced under a reducing atmosphere. Following this, the composite powder intermediate underwent activation and sensitization treatment. Reduction conditions: reduction temperature was 300℃, and the reducing atmosphere was hydrogen. Sensitization conditions: the sensitizer was stannous chloride-hydrochloric acid solution (SnCl₂-HCl), heated in a water bath at a constant temperature of 55℃, accompanied by ultrasonic oscillation, for 30 minutes. After sensitization, the sample was filtered and cleaned with deionized water. Activation conditions: the activator was palladium chloride (PdCl₂) hydrochloric acid solution (1.5 wt.%), heated in a water bath at a constant temperature of 55℃, accompanied by ultrasonic oscillation, for 0.5 hours. After activation, the sample was filtered and cleaned with deionized water.

[0289] A second copper layer is electrolessly plated. A continuous second copper layer is deposited on the surface of the composite powder intermediate through electroless plating, forming a tungsten-copper core-shell copper-tungsten composite powder, with a second copper layer thickness of 35 μm. The copper salt used for electroless copper plating is anhydrous copper sulfate (CuSO4·5H2O), and the reducing agent includes formaldehyde (CH2O). The ratio of copper to tungsten powder is 1:1, and the pH value is adjusted to maintain 12. Electroless copper plating is carried out under constant temperature water bath conditions of 55-65℃ and ultrasonic vibration. The reducing agent is continuously added until the plating solution turns red or colorless. Subsequently, the solution is filtered and washed with deionized water and dried for later use. The drying time is 2 hours in a vacuum oven at 80℃.

[0290] Step S3: Prepare the mixed powder.

[0291] The copper-tungsten composite powder, induced copper powder, organic binder, and activator are loaded into the mixing cylinder of a mixing device and rotated at a frequency of 20-50 Hz for 2-6 hours to obtain a mixed powder. The mixture contains 25 g of induced copper powder (purity ≥99.99%), 4 ml of organic binder (isopropanol), and 0.005 g of activator (tin powder).

[0292] Step S4: Make the green body.

[0293] The mixed powder is loaded into a mold with a diameter of 20 mm and a height of 5 mm, and then cold-pressed at a pressure of 3 t / cm2 to form a green body.

[0294] Step S5:

[0295] The green body was placed in a vacuum degreasing furnace and heated at atmospheric pressure (0.9-1.0) × 10⁻⁶. 5 Under a protective atmosphere (nitrogen), the temperature is increased to 950℃ at a rate of 10℃ / min. After reaching the temperature, the temperature is maintained for 2 hours for degumming to obtain the precursor.

[0296] Step S6:

[0297] Copper sheets were cut to a copper-to-precursor mass ratio of 1:3. The precursor and the cut copper sheets (purity ≥99.99%) were placed sequentially on a graphite apparatus and then placed in a sintering furnace. The furnace pressure was set to 5-8 kPa, and the temperature was increased to the infiltration temperature of 1200℃ at a rate of 10℃ / min. This temperature was maintained for 1 hour to complete the infiltration process, yielding a copper-tungsten composite material. The composition of the copper-tungsten composite material was Cu 61.95%, W 38%, and Sn 0.05%, denoted as Cu. 62 W 38 .

[0298] Comparative Example 2

[0299] Step S1: Provide tungsten powder.

[0300] 500g of raw tungsten powder with a particle size of 50μm and 250g of cemented carbide balls were selected and placed together in the jar of a ball mill. Argon gas was introduced and the mill was sealed. The mill was ball-milled at a speed of 400 rad / min for 4 hours. Then, the mill was washed with deionized water and anhydrous ethanol and dried. The powder was then passed through a 200-mesh sieve to obtain tungsten powder with uniform particle size and good sphericity.

[0301] Step S2: Coat with a copper layer to prepare copper-tungsten composite powder.

[0302] Magnetron sputtering of the first copper layer. 50g of tungsten powder was placed in a magnetron sputtering oscillating container. High-purity argon gas was introduced under vacuum conditions, and the DC power supply to the copper target was turned on. A first copper layer was deposited on the surface of the tungsten powder to obtain a composite powder intermediate. The background vacuum before magnetron sputtering deposition was 0.006Pa, followed by the introduction of argon gas (purity ≥99.99%) to a sputtering vacuum of 5Pa. The copper target power supply (purity ≥99.99%) was then turned on at 300W, with a sputtering bias of 100V. During the deposition process, the oscillating powder apparatus remained on at a frequency of 50Hz, the deposition time was 1 hour, and the sputtered copper layer thickness was 5μm.

[0303] Reduction, activation, and sensitization treatments were performed. The composite powder intermediate was cleaned and dried, then reduced under a reducing atmosphere. Following this, the composite powder intermediate underwent activation and sensitization treatment. Reduction conditions: reduction temperature was 300℃, and the reducing atmosphere was hydrogen. Sensitization conditions: the sensitizer was stannous chloride-hydrochloric acid solution (SnCl₂-HCl), heated in a water bath at a constant temperature of 55℃, accompanied by ultrasonic oscillation, for 30 minutes. After sensitization, the sample was filtered and cleaned with deionized water. Activation conditions: the activator was palladium chloride (PdCl₂) hydrochloric acid solution (1.5 wt.%), heated in a water bath at a constant temperature of 55℃, accompanied by ultrasonic oscillation, for 0.5 hours. After activation, the sample was filtered and cleaned with deionized water.

[0304] A second copper layer is electrolessly plated. A continuous second copper layer is deposited on the surface of the composite powder intermediate through electroless plating, forming a tungsten-copper core-shell copper-tungsten composite powder, with a second copper layer thickness of 35 μm. The copper salt used for electroless copper plating is anhydrous copper sulfate (CuSO4·5H2O), and the reducing agent includes formaldehyde (CH2O). The ratio of copper to tungsten powder is 1:1, and the pH value is adjusted to maintain 12. Electroless copper plating is carried out under constant temperature water bath conditions of 55-65℃ and ultrasonic vibration. The reducing agent is continuously added until the plating solution turns red or colorless. Subsequently, the solution is filtered and washed with deionized water and dried for later use. The drying time is 2 hours in a vacuum oven at 80℃.

[0305] Step S3: Coat with a graphene layer to prepare graphene-copper-tungsten composite powder.

[0306] Powder surface pretreatment. Pour copper-tungsten composite powder into copper polishing agent and stir continuously for 2 minutes. Then, filter and wash with deionized water several times, dry, and place in a damp heat test chamber. Set the temperature to 100℃ and the humidity to 50%RH for 0.5 hours for micro-oxidation. After natural cooling, it is ready for use.

[0307] Chemical vapor deposition of graphene. Copper-tungsten composite powder and silicon powder are mechanically mixed and placed in a quartz apparatus. A carbon-containing gas is introduced under an oxygen-free protective atmosphere, and the temperature is raised to the deposition temperature of 1000-1050℃. 1-10 layers of graphene are deposited on the surface of the copper-tungsten composite powder using chemical vapor deposition, forming a graphene-copper-tungsten composite powder. The protective atmosphere includes nitrogen and argon, and the chemical vapor deposition is performed at atmospheric pressure (0.9-1.0) × 10⁻⁶. 5 The process is carried out at Pa, with a heating rate of 10℃ / min. After reaching the deposition temperature, the temperature is maintained for 1.5h. The carbon-containing gas includes carbon source gas and reducing gas. The reducing gas is introduced first, followed by the carbon source gas. The carbon source gas includes methane, and the reducing gas includes hydrogen.

[0308] Step S4: Make the green body.

[0309] Graphene copper-tungsten powder is loaded into a mold with a diameter of 20 mm and a height of 5 mm, and then cold-pressed at a pressure of 3 t / cm2 to prepare a green body.

[0310] Step S5:

[0311] Copper sheets were cut to a copper-to-precursor ratio of 1:3. The precursor and the cut copper sheets (purity ≥99.99%) were placed sequentially on a graphite fixture and then placed in a sintering furnace. The furnace pressure was set to 5-8 kPa, and the temperature was increased to the infiltration temperature of 1200℃ at a rate of 10℃ / min. This temperature was maintained for 1 hour to complete the infiltration process, yielding a graphene-copper-tungsten composite material. The composition of this graphene-copper-tungsten composite material is Cu 61.8%, W 38%, and Gr 0.15%, denoted as Cu. 62 W 38 Gr 0.15 .

[0312] Comparative Example 3

[0313] Step S1: Provide tungsten powder.

[0314] 500g of raw tungsten powder with a particle size of 50μm and 250g of cemented carbide balls were selected and placed together in the jar of a ball mill. Argon gas was introduced and the mill was sealed. The mill was ball-milled at a speed of 400 rad / min for 4 hours. Then, the mill was washed with deionized water and anhydrous ethanol and dried. The powder was then passed through a 200-mesh sieve to obtain tungsten powder with uniform particle size and good sphericity.

[0315] Step S2: Coat with a copper layer to prepare copper-tungsten composite powder.

[0316] Magnetron sputtering of the first copper layer. 50g of tungsten powder was placed in a magnetron sputtering oscillating container. High-purity argon gas was introduced under vacuum conditions, and the DC power supply to the copper target was turned on. A first copper layer was deposited on the surface of the tungsten powder to obtain a composite powder intermediate. The background vacuum before magnetron sputtering deposition was 0.006Pa, followed by the introduction of argon gas (purity ≥99.99%) to a sputtering vacuum of 5Pa. The copper target power supply (purity ≥99.99%) was then turned on at 300W, with a sputtering bias of 100V. During the deposition process, the oscillating powder apparatus remained on at a frequency of 50Hz, the deposition time was 1 hour, and the sputtered copper layer thickness was 5μm.

[0317] Reduction, activation, and sensitization treatments were performed. The composite powder intermediate was cleaned and dried, then reduced under a reducing atmosphere, followed by activation and sensitization. Reduction conditions: reduction temperature 300℃, reducing atmosphere: hydrogen atmosphere. Sensitization conditions: sensitizer was stannous chloride-hydrochloric acid solution (SnCl₂-HCl), water bath heating maintained at a constant temperature of 55℃, accompanied by ultrasonic oscillation, sensitization time 30 min, after which the sample was filtered and cleaned with deionized water. Activation conditions: activator was palladium chloride (PdCl₂) hydrochloric acid solution (1.5 wt.%), water bath heating maintained at a constant temperature of 55℃, accompanied by ultrasonic oscillation, activation time 0.5 h, after which the sample was filtered and cleaned with deionized water.

[0318] A second copper layer is electrolessly plated. A continuous second copper layer is deposited on the surface of the composite powder intermediate through electroless plating, forming a tungsten-copper core-shell copper-tungsten composite powder, with a second copper layer thickness of 35 μm. The copper salt used for electroless copper plating is anhydrous copper sulfate (CuSO4·5H2O), and the reducing agent includes formaldehyde (CH2O). The ratio of copper to tungsten powder is 1:1, and the pH value is adjusted to maintain 12. Electroless copper plating is carried out under constant temperature water bath conditions of 55-65℃ and ultrasonic vibration. The reducing agent is continuously added until the plating solution turns red or colorless. Subsequently, the solution is filtered and washed with deionized water and dried for later use. The drying time is 2 hours in a vacuum oven at 80℃.

[0319] Step S3: Coat with a graphene layer to prepare graphene-copper-tungsten composite powder.

[0320] Powder surface pretreatment. Pour copper-tungsten composite powder into copper polishing agent and stir continuously for 2 minutes. Then, filter and wash with deionized water several times, dry, and place in a damp heat test chamber. Set the temperature to 100℃ and the humidity to 50%RH for 0.5 hours for micro-oxidation. After natural cooling, it is ready for use.

[0321] Chemical vapor deposition of graphene. Copper-tungsten composite powder and silicon powder are mechanically mixed and placed in a quartz apparatus. A carbon-containing gas is introduced under an oxygen-free protective atmosphere, and the temperature is raised to the deposition temperature of 1000-1050℃. 1-10 layers of graphene are deposited on the surface of the copper-tungsten composite powder using chemical vapor deposition, forming a graphene-copper-tungsten composite powder. The protective atmosphere includes nitrogen and argon, and the chemical vapor deposition is performed at atmospheric pressure (0.9-1.0) × 10⁻⁶. 5 The process is carried out at Pa, with a heating rate of 10℃ / min. After reaching the deposition temperature, the temperature is maintained for 1.5h. The carbon-containing gas includes carbon source gas and reducing gas. The reducing gas is introduced first, followed by the carbon source gas. The carbon source gas includes methane, and the reducing gas includes hydrogen.

[0322] Step S4: Cut copper sheets to a mass ratio of 1:3 for both copper and graphene copper-tungsten composite powder. Place the graphene copper-tungsten composite powder and the cut copper sheets (purity ≥ 99.99%) sequentially into a mold and perform hot pressing sintering to obtain the graphene copper-tungsten composite material. The composition of the graphene copper-tungsten composite material is Cu 61.8%, W 38%, Sn 0.05%, and Gr 0.15%, denoted as Cu. 62 W 38 Gr 0.15 .

[0323] The composite materials obtained in Examples 1, 2, and Comparative Examples 1-3 were used as research objects. The density, conductivity, and Brinell hardness of the copper-tungsten composite materials were characterized and analyzed using a densitometer, eddy current conductivity meter, and Brinell hardness tester, respectively. The results are shown in Table 1. The graphene-copper-tungsten composite material of Example 1 was also subjected to scanning electron microscopy (SEM), and the SEM images are shown below. Figure 7 As shown.

[0324] Table 1

[0325]

[0326] Compare the data of Example 1 and Comparative Example 1 in Table 1, and combine them with... Figure 7 As shown, the graphene-copper-tungsten composite material obtained in the technical solution provided in this application has uniform particle size of graphene-copper-tungsten composite powder, high graphene coverage, relatively complete graphene structure with few defects, and tight interconnection between the graphene-copper-tungsten composite powder and the copper connecting layer. The graphene-copper-tungsten composite material prepared by the technical solution provided in this application further improves the material's density, hardness, and other mechanical properties, as well as its electrical conductivity, based on the copper-tungsten composite material. Comparing Example 1 with Example 2, it is shown that in the graphene-copper-tungsten composite material provided in this application, a good improvement effect can still be obtained when the ratio of graphene, copper, and tungsten is adjusted within a certain range.

[0327] Comparing Table 1 with Comparative Examples 2 and 3, it can be seen that the technical solution provided in this application significantly improves the density, hardness, and graphene integrity of the graphene-copper-tungsten composite material, thereby obtaining better electrical conductivity and mechanical properties.

[0328] Therefore, the technical solution provided in this application provides that the tungsten powder, after being ball-milled with high energy, has a uniform and refined particle size, significantly improving the strength of the initial tungsten skeleton. Then, a copper layer with good interfacial bonding is first coated onto the surface of the tungsten powder to form a copper-coated tungsten core-shell structure powder. Next, graphene is grown in situ on the surface of the copper layer via vapor deposition to form a tungsten-copper-graphene core-shell structure. The resulting graphene-copper-tungsten composite powder has a high coating rate, few defects, and controllable number of graphene layers. Furthermore, the graphene-copper-tungsten composite powder exhibits strong interlayer bonding, and graphene and tungsten do not easily diffuse into each other. Subsequently, the graphene-copper-tungsten composite powder is mixed with inducing copper powder, an organic binder, and an activator, and then cold-pressed. This effectively reduces the possibility of graphene layer damage during the cold-pressing process. This process ensures the integrity of the graphene layer, avoids graphene-tungsten contact and chemical bonding, and maintains high bonding strength between powders, resulting in a green body with good molding rate and high density. After debinding, the graphene-copper-tungsten composite powder and induced copper powder form a three-dimensional network structure. This three-dimensional network structure interweaves and tightly bonds with the copper-tungsten skeleton formed by subsequent melting and infiltration, forming a high-density graphene-copper-tungsten composite material with high mechanical and electrical properties. At the same time, the graphene layer obtained in this application, due to its complete structure and few defects, effectively restricts the growth and connection of tungsten particles during the high-temperature melting and infiltration process under the coating force of graphene. The tungsten particles are evenly distributed, ensuring high conductivity and resistance to welding while reducing the tungsten content. This allows for more flexible composition design and a wider range of applications.

[0329] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a graphene-copper-tungsten composite material, characterized in that, include: S1 provides tungsten powder; S2, a copper layer is coated on the surface of tungsten powder to obtain copper-coated tungsten composite powder; S3, a graphene layer is coated on the surface of the copper-tungsten composite powder to obtain graphene copper-tungsten composite powder; S4, the graphene copper-tungsten composite powder is mixed with induced copper powder, organic binder and activator to obtain mixed powder; S5, the mixed powder is cold-pressed into a green body; S6, Degumming the green body to obtain the precursor; S7, the precursor and copper sheet are stacked and then melt-infiltrated to obtain a graphene-copper-tungsten composite material.

2. The method for preparing the graphene-copper-tungsten composite material according to claim 1, characterized in that, In S1: The tungsten powder is spherical; and / or The particle size of the tungsten powder is ≤75μm; and / or The preparation method of the tungsten powder includes: selecting raw tungsten powder with a particle size of 20-100μm, spheroidizing it, washing and drying it, and passing it through a 200-mesh sieve to obtain the tungsten powder.

3. The method for preparing the graphene-copper-tungsten composite material according to claim 1, characterized in that, S2 includes: S21, the tungsten powder is placed in a magnetron sputtering oscillating container, and argon gas is introduced under vacuum to bombard a copper target for magnetron sputtering, so as to coat the surface of the tungsten powder with a first copper layer and obtain a composite powder intermediate. S22, copper is chemically plated on the surface of the composite powder intermediate to coat a second copper layer, thereby obtaining copper-tungsten composite powder.

4. The method for preparing the graphene-copper-tungsten composite material according to claim 3, characterized in that, In S21: Prior to magnetron sputtering, the vacuum level was 0.001–0.01 Pa; and / or During magnetron sputtering, the vacuum level is 1-10 Pa; and / or The purity of the copper target is ≥99.99%; and / or The power of magnetron sputtering is 100-600W; and / or The bias voltage for magnetron sputtering is 0-200V; and / or The oscillation frequency of magnetron sputtering is 20-50 Hz; and / or The thickness of the first copper layer is 2-10 μm.

5. The method for preparing the graphene-copper-tungsten composite material according to claim 3, characterized in that, In S22: The plating solution used in electroless copper plating includes copper salts, including at least one of the following: anhydrous copper sulfate, copper pyrophosphate, copper sulfate, copper chloride, copper sulfamate, copper acetate, basic copper carbonate, copper bromide, copper formate, copper hydroxide, copper oxide, copper phosphate, copper fluoride silicon, copper stearate, and copper citrate; and / or The plating solution used in electroless copper plating includes a reducing agent, which may include at least one of formaldehyde, aminoborane, hydroxylamine hydrochloride, sodium borohydride, and hydrazine hydrate; and / or In the electroless copper plating solution, the mass ratio of copper salt to tungsten powder is (1-3):1; and / or The pH value of the plating solution used in electroless copper plating is maintained at 11-13; and / or Chemical copper plating is performed under constant temperature (55-65℃) and ultrasonic oscillation conditions; and / or The thickness of the second copper layer is 20-50 μm.

6. The method for preparing the graphene-copper-tungsten composite material according to claim 3, characterized in that, Before performing step S22, the composite powder intermediate is reduced under a reducing atmosphere, wherein: The reducing atmosphere includes a hydrogen atmosphere; and / or The reduction temperature is 200-400℃.

7. The method for preparing the graphene-copper-tungsten composite material according to claim 3 or 6, characterized in that, Before performing S22, the composite powder intermediate is activated and / or sensitized, wherein: The activation solution used in the activation treatment includes a hydrochloric acid solution of palladium chloride; and / or The activation treatment time is 0.5-1.5 hours; The sensitizer used in the sensitization treatment includes stannous chloride-hydrochloric acid solution; and / or The sensitization treatment time is 20-45 minutes; The environmental conditions for the "activation treatment and / or sensitization treatment" are constant temperature of 40-70℃ and ultrasonic oscillation.

8. The method for preparing the graphene-copper-tungsten composite material according to claim 1, characterized in that, In step S3, a graphene layer is coated onto the surface of the copper-tungsten composite powder by vapor deposition, including: S31, the copper-tungsten composite powder is mixed and dispersed with silicon powder; S32, under vacuum conditions and an oxygen-free protective atmosphere, carbon-containing gas is introduced for vapor deposition; S33, the silicon powder is separated and removed to obtain the graphene copper-tungsten composite powder.

9. The method for preparing the graphene-copper-tungsten composite material according to claim 8, characterized in that, In S3: The pressure conditions for vapor deposition in S32 range from (0.9 to 1.0) × 10⁻⁶. 5 Pa; and / or The temperature conditions for vapor deposition in S32 are 1000-1050℃, and the temperature is maintained for 1-2.5 hours; and / or The carbon-containing gas in S32 includes a reducing gas and a carbon source gas, wherein the reducing gas is introduced first, followed by the carbon source gas; and / or The number of graphene layers obtained by vapor deposition in S32 is 1-10; and / or In step S33, silicon powder is separated and removed by liquid phase separation to obtain the graphene-copper-tungsten composite powder.

10. The method for preparing the graphene-copper-tungsten composite material according to claim 1, 8, or 9, characterized in that, Before performing step S3, the copper-tungsten composite powder is pretreated: The copper-tungsten composite powder is polished and then subjected to micro-oxidation.

11. The method for preparing the graphene-copper-tungsten composite material according to claim 10, characterized in that, The polishing process is as follows: the copper-tungsten composite powder is placed in a copper polishing agent, polished for 2-5 minutes, then cleaned and dried; and / or The micro-oxidation treatment is performed by placing the copper-tungsten composite powder in an environment with a humidity of 50-80% RH and a temperature of 80-150℃ for more than 0.5 hours.

12. The method for preparing the graphene-copper-tungsten composite material according to claim 1, characterized in that, In S4: The purity of the induced copper powder is ≥99.99%; and / or The organic adhesive includes isopropanol; and / or The activator includes tin powder; and / or Mixing is performed using a mixing device at a rotation frequency of 20-50 Hz; and / or The mixing process lasts 2-6 hours; and / or The mass ratio of the graphene copper-tungsten composite powder, the induced copper powder, the organic binder, and the activator is (30-70): (70-30): (0.01-0.1): (1.8-7).

13. The method for preparing the graphene-copper-tungsten composite material according to claim 1, characterized in that, In step S5, the mixed powder is loaded into a mold and cold-pressed, wherein: The loading height is 5mm; and / or The cold pressing pressure is 300-900MPa.

14. The method for preparing the graphene-copper-tungsten composite material according to claim 1, characterized in that, In step S6, the green body is placed in a vacuum degumming furnace and degummed at a set temperature to prepare the precursor. The set temperature is 900-950℃; and / or Maintain at the set temperature for 2-2.5 hours; and / or The degumming process is carried out in an inert atmosphere; and / or The pressure conditions for the degumming process are in the range of (0.9-1.0)×10. 5 Pa.

15. The method for preparing the graphene-copper-tungsten composite material according to claim 1, characterized in that, In S7: The purity of the copper sheet is ≥99.99%; and / or The mass ratio of the copper sheet to the precursor is 1:3; and / or The pressure conditions for the melting and infiltration process are in the range of 5-8 kPa; and / or The temperature conditions for the melting and infiltration process are 1100-1300℃; and / or The melting and infiltration process lasts for 1-2.5 hours.

16. A graphene-copper-tungsten composite material, characterized in that, Prepared by the method for preparing the graphene-copper-tungsten composite material according to any one of claims 1-15; and / or The composite material includes: A plurality of graphene-copper-tungsten composite powders, wherein the graphene-copper-tungsten composite powders include a tungsten framework, a copper layer and a graphene layer, wherein the copper layer coats the tungsten framework and the graphene layer coats the copper layer; A copper bonding layer is filled between several of the graphene-copper-tungsten composite powders.

17. The graphene-copper-tungsten composite material according to claim 16, characterized in that: The tungsten framework comprises spherical powder with a particle size ≤75μm; and / or The thickness of the copper layer is 22-60 μm; and / or The thickness of the graphene layer is 1-10 layers; and / or The mass percentage of copper in the composite material is 35-75%; and / or The tungsten content in the composite material is 25-65% by mass; and / or The graphene content in the composite material is 0.1-0.2% by mass; and / or The composite material also includes tin, with a tin content of 0.01-1% by mass.

18. The graphene-copper-tungsten composite material according to claim 16, characterized in that, The copper layer includes a first copper layer and a second copper layer. The first copper layer is located between the surface of the tungsten skeleton and the second copper layer. The purity of the first copper layer is greater than that of the second copper layer. The thickness of the first copper layer is 2-10 μm, and the thickness of the second copper layer is 20-50 μm.

19. A conductive element, characterized in that, The graphene copper-tungsten composite material prepared by the method of preparing the graphene copper-tungsten composite material according to any one of claims 1-15; or, the graphene copper-tungsten composite material according to any one of claims 16-18. The conductive element includes an electrical contact conductor or a wire.

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