Graphene copper composite material, preparation method and application thereof

Abstract

This invention relates to a graphene-copper composite material, its preparation method, and its applications, belonging to the field of high-strength, high-conductivity composite material molding technology. The specific steps of the preparation method include: S1, mixing copper powder with nanocellulose gel and drying to obtain a dried mixture; S2, vacuum annealing the mixture to obtain graphene-copper composite powder; S3, hot-pressing and sintering the graphene-copper composite powder to obtain a graphene-copper composite material of a predetermined shape; in S2, the annealing temperature is 650-950℃; the annealing time is 1-4 hours. The added graphene possesses excellent mechanical properties, intrinsic electrical conductivity, and thermal conductivity. When combined with copper-based materials, it can significantly improve the mechanical properties of the composite material without reducing its electrical conductivity, resulting in a high-strength, high-conductivity composite material suitable for electrical contact applications. Furthermore, as an excellent nano-self-lubricating material, graphene can greatly improve the wear resistance of the material and extend its service life.

Description

Technical Field

[0001] This invention belongs to the field of high-strength and high-conductivity composite material molding technology, specifically relating to a graphene-copper composite material, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Copper-based materials are widely used in electrical switches, electronic components, high-speed railway overhead contact lines, and high-voltage transmission circuit breakers. Their reliability and service life are crucial to the efficient and safe operation of electrical switches and transmission lines, as well as their operating costs. Therefore, developing high-performance, long-life copper-based materials is of great significance for maintaining the safe and stable operation of electrical appliances and power grids.

[0004] Currently, adding secondary phase materials to copper-based materials is the main method to improve their service life. The components added to these materials that can generate secondary phases mainly include alloying elements, metal carbides, and other additives with high work functions and high melting points, such as La₂O₃, Mo, Al₂O₃, TiC, and CdO.

[0005] The electrical and thermal conductivity of these added phases is much lower than that of pure copper. Although they can achieve better mechanical properties, the electrical and thermal conductivity of copper-based composites decreases inversely with increasing mass fraction of these added phases. Therefore, designing and constructing reinforced copper-based composites without reducing electrical and thermal conductivity remains challenging.

[0006] On the other hand, graphene possesses excellent intrinsic electrical and thermal conductivity, with a room-temperature electron mobility of up to 15,000 cm⁻¹. 2 / V s, with a thermal conductivity reaching up to 3500~5300W / m K; graphene has good mechanical properties, with a theoretical fracture strength of ≈130GPa and a Young's modulus of ≈1.1Tpa.

[0007] Existing methods for combining graphene and copper mainly involve the composite / reduction of graphene oxide and copper. However, due to the poor interfacial wettability and low interfacial bonding strength between graphene and the copper matrix, and the tendency of graphene to agglomerate under the influence of interlayer van der Waals forces, the performance of the composite material deteriorates. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a graphene-copper composite material, its preparation method, and its application. The prepared graphene-copper composite material has an internal structure in which graphene forms a uniform and continuous network structure at the copper grain boundaries, which can avoid the problems of graphene agglomeration and low interfacial bonding strength with the copper matrix, thereby obtaining a high-strength and high-conductivity composite material and improving its service life in the electrical field.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] In a first aspect, a method for preparing a graphene-copper composite material includes the following steps:

[0011] S1. Mix copper powder with nanocellulose gel and dry to obtain a dried mixture;

[0012] S2. Vacuum annealing is performed on the mixture to obtain graphene-copper composite powder;

[0013] S3. Hot-press and sinter the graphene-copper composite powder to obtain a graphene-copper composite material of a predetermined shape.

[0014] Optionally, in S1, the copper powder particle size is 10–80 μm.

[0015] Optionally, in S1, the mixing ratio of copper powder and nanocellulose gel is 1:0.3-1:3 by mass.

[0016] Optionally, in S1, the nanocellulose gel is a hydrogel in which the concentration of nanocellulose is dispersed to 0.3% to 1.0 wt%.

[0017] Optionally, in S1, the mixing method is high-speed shear mixing.

[0018] Optionally, in S1, the resulting mixture is: dried copper powder particles coated with nanocellulose.

[0019] Optionally, in S2, the vacuum level ranges from 10 to 200 Pa.

[0020] Optionally, in S2, the vacuum environment can be replaced by a nitrogen, hydrogen, and / or argon protective environment, with the pressure maintained at a level below atmospheric pressure.

[0021] Optionally, in S2, the annealing temperature range is between 650-950℃.

[0022] Preferably, the annealing temperature is 850–950℃.

[0023] A further preferred annealing temperature is 950℃.

[0024] Optionally, in S2, the annealing time is 1 to 4 hours.

[0025] Optionally, the annealing time is 2 to 3 hours;

[0026] A further preferred annealing time is 2 hours.

[0027] Optionally, the vacuum environment in S2 can be replaced with a nitrogen, hydrogen, and / or argon protective environment, with the pressure maintained below atmospheric pressure.

[0028] Optionally, the argon flow rate is 50–200 sccm, the hydrogen flow rate is 10–50 sccm, and / or the nitrogen flow rate is 50–200 sccm;

[0029] Optionally, the argon flow rate is 100 sccm, the hydrogen flow rate is 30 sccm, and / or the nitrogen flow rate is 100 sccm.

[0030] Optionally, in S3, hot pressing sintering is vacuum hot pressing sintering;

[0031] Optionally, the graphene-copper composite material obtained in S3 undergoes a post-processing polishing process.

[0032] Optionally, vacuum hot pressing sintering specifically involves maintaining the pressure of the blank inside the mold at 20–50 MPa; and operating at 10–30 °C / min. -1 Heating rate: Heat to 750–950℃, hold at temperature and pressure for 0.5–1 hour, then heat at pressure at a rate of 10–30℃ / min. -1 Cool to room temperature at a cooling rate;

[0033] Preferably, the pressure on the blank inside the mold is maintained at 40 MPa; at 20°C / min -1 Heat to 850℃ at a heating rate, hold at that temperature and pressure for 30 minutes, and then heat at 20℃·min under pressure. -1 Cool to room temperature at a cooling rate of [missing information].

[0034] In the S2 process, copper can catalyze the repair of graphene defects and improve the quality of graphene.

[0035] During the S3 process, the internal structure of the graphene-copper composite material gradually transforms into a uniform and continuous network structure at the copper grain boundaries, with graphene forming a uniform network structure.

[0036] Secondly, a graphene-copper composite material prepared by the above-mentioned method for preparing graphene-copper composite materials.

[0037] Optionally, the graphene content in the graphene-copper matrix composite material is 0.3 wt% to 0.9 wt%.

[0038] Optionally, the graphene content in the graphene-copper matrix composite is preferably 0.3 wt%.

[0039] Optionally, the internal structure of the graphene-copper composite material is a uniform and continuous network structure of graphene at the copper grain boundaries.

[0040] Thirdly, a method for preparing the above-mentioned graphene-copper composite material and / or the application of the obtained graphene-copper composite material.

[0041] Optionally, the applications include applications in electrical contact materials, resistance welding electrode materials, and / or heat sink materials.

[0042] The beneficial effects of this invention are as follows:

[0043] 1. This application uses nanocellulose gel as a raw material to generate graphene on the surface of copper powder. Compared with the technical solution of directly combining graphene oxide with copper powder and then reducing it, the advantage lies in solving the problems of easy graphene agglomeration and low interfacial bonding strength with the copper matrix. This allows the graphene to form a uniform and continuous network structure at the copper grain boundaries, reducing the degree of graphene agglomeration; the continuously distributed graphene has a large bonding area and good bonding strength with the copper matrix. Simultaneously, copper powder, as a catalyst for graphene generation, can repair defects during the graphene generation process, contributing to the obtaining of high-quality graphene copper bulk materials.

[0044] 2. The graphene added in this invention has excellent mechanical properties, intrinsic electrical conductivity and thermal conductivity. When combined with copper-based materials, it can greatly improve the mechanical properties of the composite material without reducing the electrical conductivity, thus obtaining a high-strength and high-conductivity composite material that can be used in electrical contact applications.

[0045] 3. The graphene added in this invention is an excellent nano-self-lubricating material that can greatly improve the wear resistance of composite materials. When applied to electrical contact applications, it can continuously release graphene powder with self-lubricating properties during service, which can greatly extend the service life of the material.

[0046] 4. Graphene precursors are easy to obtain or prepare and can be mass-produced. Compared with the method of adding rare earth metals to enhance the performance of materials, it can reduce the consumption of rare earth resources.

[0047] 5. The preparation method of the present invention requires simple equipment, has a simple process, is easy to control and adjust process parameters, and can be scaled up for production. Attached Figure Description

[0048] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0049] Figure 1 This is a SEM image of the graphene-copper composite powder obtained in Example 1 of this invention;

[0050] Figure 2 These are the Raman spectra of the graphene-copper composite powders obtained in Examples 1-4 of this invention;

[0051] Figure 3 XPS spectra of the graphene-copper composite powders obtained in Examples 1-4 of this invention;

[0052] Figure 4 This is a TEM image of the graphene-copper composite block obtained in Example 4 of this invention; Detailed Implementation

[0053] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, 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.

[0054] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0055] In a first aspect, a method for preparing a graphene-copper composite material includes the following steps:

[0056] S1. Mix copper powder with nanocellulose gel and dry to obtain a dried mixture;

[0057] S2. Vacuum annealing is performed on the mixture to obtain graphene-copper composite powder;

[0058] S3. Hot-press and sinter the graphene-copper composite powder to obtain a graphene-copper composite material of a predetermined shape.

[0059] Optionally, in S1, the copper powder particle size is 10-80 micrometers.

[0060] Optionally, in S1, the nanocellulose gel is a hydrogel in which the concentration of nanocellulose is dispersed to 0.3% to 1.0 wt%.

[0061] Optionally, in S1, the mixing ratio of copper powder and nanocellulose gel is 1:0.3-1:3 by mass.

[0062] Optionally, in S1, the mixing method is high-speed shear mixing, and the state of the mixture is: the powder is not agglomerated and is in a monodisperse state.

[0063] Nanocellulose is a type of nanoparticle extracted from cellulose raw materials. It can be prepared by chemical acid hydrolysis, physical pulverization, and biological extraction.

[0064] The numerous hydroxyl groups on the surface of nanocellulose can form a network structure through hydrogen bonding, enabling nanocellulose to exist stably in a gel state and be used as a dispersant.

[0065] On the other hand, nanocellulose itself is a raw material for preparing graphene.

[0066] Shear mixing, also known as shear stirring mixing, refers to a mixing method that uses a shear mixer. The shear mixer includes a fixed shear cylinder and a stirring paddle that rotates around the center of the shear cylinder inside the shear cylinder. Due to the speed difference between the stirring paddle and the wall of the shear cylinder, the raw materials are continuously dispersed into the dispersion medium in the gap between the shear cylinder and the stirring paddle.

[0067] The combined shearing effect depends on the gap between the cylinder shearing surface and the paddle shearing surface; the smaller the gap, the better the shearing effect.

[0068] The resulting mixture consisted of dried copper powder particles coated with nanocellulose.

[0069] Optionally, in S2, the vacuum level ranges from 10 to 200 Pa.

[0070] Optionally, in S2, the annealing temperature range is between 650 and 950 degrees Celsius.

[0071] Preferably, the annealing temperature is 850–950°C, and more preferably, the annealing temperature is 950°C.

[0072] Optionally, in S2, the annealing time can be selected from 1 to 4 hours.

[0073] Preferably, the annealing time is 2 to 3 hours; more preferably, the annealing time is 2 hours.

[0074] In a further preferred embodiment, in S2, the annealing temperature is 950 degrees Celsius and the annealing time is 2 hours.

[0075] Optionally, the vacuum environment in S2 can be replaced with a nitrogen, hydrogen, and / or argon protective environment, with the pressure maintained below atmospheric pressure.

[0076] A vacuum environment refers to a state in which the gas pressure inside the annealing furnace is lower than atmospheric pressure, achieved by using a vacuum pump to extract gas from the furnace cavity.

[0077] When using a gas protection scheme, i.e. a protective atmosphere, a certain gas flow rate needs to be maintained to carry out the gaseous products generated during the reaction.

[0078] Optionally, the argon flow rate is 50–200 sccm, the hydrogen flow rate is 10–50 sccm, and / or the nitrogen flow rate is 50–200 sccm;

[0079] Preferably, the argon flow rate is 100 sccm, the hydrogen flow rate is 30 sccm, and / or the nitrogen flow rate is 100 sccm.

[0080] Annealing refers to the process of heating an object to a certain temperature range, holding it at that temperature for a period of time, and then cooling it in the furnace, or cooling it in the furnace to a certain temperature and then air cooling it to shorten the process time. Annealing time refers to the holding time after reaching the set temperature.

[0081] In this process, copper can catalyze the repair of graphene defects and improve the quality of graphene.

[0082] If the temperature is higher than 1080℃, the copper powder melts into a liquid state, and the prepared graphene copper cannot achieve a monodisperse state, which is not conducive to the dispersion of graphene.

[0083] The graphene-copper composite powder obtained by S2 has the following morphology: copper powder particles are wrapped in a thin shell composed of graphene and amorphous carbon.

[0084] Preferably, in S3, hot pressing sintering is vacuum hot pressing sintering; vacuum hot pressing sintering refers to hot pressing sintering under vacuum conditions.

[0085] The specific process includes: maintaining the pressure of the blank in the mold at 20-50 MPa; heating it to 750-950℃ at a heating rate of 10-30℃·min-1, holding it at the temperature and pressure for 0.5-1h, and then cooling it to room temperature at a cooling rate of 10-30℃·min-1 while holding it under pressure.

[0086] The pressure on the blank inside the mold is maintained at 40 MPa; at 20℃·min -1 Heating rate: Heat to 850℃, hold at that temperature and pressure for 30 minutes, then continue heating at 20℃ / min under pressure. -1 Cool to room temperature at the cooling rate.

[0087] Hot pressing sintering refers to a sintering method in which dry powder is filled into a mold, and then pressure and heat are applied to complete the molding and sintering simultaneously.

[0088] The mold used for hot pressing sintering is a graphite mold, and the edges of the mold are sealed with graphite paper.

[0089] In this process, copper powder is sintered, and the sintering process catalyzes the repair of graphene defects, which helps to obtain high-quality graphene copper bulk materials.

[0090] Optionally, the graphene-copper composite material obtained in S3 needs to undergo a post-processing polishing process, specifically: polishing with 180, 400, 1000, 2000, and 4000 grit alumina sandpaper in sequence to remove uneven edges and obtain a smooth surface.

[0091] The graphene-copper composite material prepared by the above-mentioned method has the following internal structure: graphene forms a uniform and continuous network structure at the copper grain boundaries.

[0092] Optionally, the graphene content in the graphene-copper matrix composite material is 0.3 wt% to 0.9 wt%.

[0093] Preferably, the graphene content in the graphene-copper composite material is 0.3 wt%.

[0094] The preparation method of the above-mentioned graphene copper composite material and / or the application of the obtained graphene copper composite material in electrical contact materials.

[0095] This includes applications in electrical contact materials, resistance welding electrode materials, and heat sink materials.

[0096] Electrical contact materials require high conductivity, high mechanical properties, and high thermal conductivity to cope with wear or impact during cyclic electrical contact processes and to release resistance heat in a timely manner.

[0097] Resistance welding electrode materials require high electrical conductivity, high mechanical properties, and high thermal conductivity. Resistance welding electrodes need to apply a certain degree of pressure to the weld joint to facilitate interface cleaning and metallurgical bonding during the resistance welding process.

[0098] Heat sink materials refer to the heat sinks of power electronic equipment and communication equipment.

[0099] Example 1

[0100] Step 1: Using a high-speed shear mixer, mix 20g of spherical copper powder with a particle size of 10-80μm with a certain mass of 0.65% nanocellulose gel at a high speed of 3500r / min for 30s to form a uniform nanocellulose gel layer on the surface of the copper powder.

[0101] The prepared powder was vacuum dried at 60°C for 2 hours to remove excess moisture from the nanocellulose gel layer and obtain a dried mixture.

[0102] Step 2: The dried nanocellulose-coated copper powder is annealed at 650℃ for 2 hours. During annealing, the argon flow rate is 100 sccm and the hydrogen flow rate is 30 sccm. After annealing, the powder is cooled to room temperature in the furnace to obtain graphene-copper composite powder.

[0103] Step 3: The graphene-copper composite powder prepared by the rapid thermal annealing method is subjected to vacuum hot pressing sintering. Typical sintering process parameters are as follows:

[0104] Approximately 15g of graphene-copper composite powder was placed in a graphite mold with a diameter of 20mm, and the upper and lower pressure heads were sealed with graphite paper to prevent copper liquid from leaking out during the sintering process.

[0105] The sealed graphite mold was placed in a vacuum hot press with a pressure of 40 MPa and a pressing rate of 20 °C / min. -1 Heating rate: Heat to 850℃, hold at that temperature and pressure for 30 minutes, then continue heating at 20℃ / min under pressure. -1 Cool to room temperature at a cooling rate;

[0106] The graphene-copper composite block material prepared by hot pressing was polished sequentially using alumina sandpaper of 180, 400, 1000, 2000, and 4000 mesh.

[0107] The graphene-copper composite powder obtained in step two is as follows: Figure 1 As shown in the figure, monodisperse graphene copper powder can be obtained, with a uniform nanolayer composed of graphene and amorphous carbon deposited on the surface of the copper powder.

[0108] The graphene-copper composite powder obtained in step two was subjected to Raman spectroscopy analysis, and the results are as follows: Figure 2 The curve at 650℃ is shown in the figure.

[0109] The graphene-copper composite powder obtained in step two was analyzed by XPS, and the results are as follows: Figure 3 As shown in (a).

[0110] Example 2

[0111] Step 1: Using a high-speed shear mixer, mix 20g of spherical copper powder with a particle size of 10-80μm with a certain mass of 0.65% nanocellulose gel at a high speed of 3500r / min for 30s to form a uniform nanocellulose gel layer on the surface of the copper powder.

[0112] The prepared powder was vacuum dried at 60°C for 2 hours to remove excess moisture from the nanocellulose gel layer and obtain a dried mixture.

[0113] Step 2: The dried nanocellulose-coated copper powder is annealed at 750℃ for 2 hours. During annealing, the argon flow rate is 100 sccm and the hydrogen flow rate is 30 sccm. After annealing, the powder is cooled to room temperature in the furnace to obtain graphene-copper composite powder.

[0114] Step 3: The graphene-copper composite powder prepared by the rapid thermal annealing method is subjected to vacuum hot pressing sintering. Typical sintering process parameters are as follows:

[0115] Approximately 15g of graphene-copper composite powder was placed in a graphite mold with a diameter of 20mm, and the upper and lower pressure heads were sealed with graphite paper to prevent copper liquid from leaking out during the sintering process.

[0116] The sealed graphite mold was placed in a vacuum hot press with a pressure of 40 MPa and a pressing rate of 20 °C / min. -1 Heating rate: Heat to 850℃, hold at that temperature and pressure for 30 minutes, then continue heating at 20℃ / min under pressure. -1 Cool to room temperature at a cooling rate;

[0117] The graphene-copper composite block material prepared by hot pressing was polished sequentially using alumina sandpaper of 180, 400, 1000, 2000, and 4000 mesh.

[0118] The graphene-copper composite powder obtained in step two was subjected to Raman spectroscopy analysis, and the results are as follows: Figure 2 The 750℃ curve is shown in the figure.

[0119] The graphene-copper composite powder obtained in step two was analyzed by XPS, and the results are as follows: Figure 3 As shown in (b).

[0120] Example 3

[0121] Step 1: Using a high-speed shear mixer, mix 20g of spherical copper powder with a particle size of 10-80μm with a certain mass of 0.65% nanocellulose gel at a high speed of 3500r / min for 30s to form a uniform nanocellulose gel layer on the surface of the copper powder.

[0122] The prepared powder was vacuum dried at 60°C for 2 hours to remove excess moisture from the nanocellulose gel layer and obtain a dried mixture.

[0123] Step 2: The dried nanocellulose-coated copper powder is annealed at 850℃ for 2 hours. During annealing, the argon flow rate is 100 sccm and the hydrogen flow rate is 30 sccm. After annealing, the powder is cooled to room temperature in the furnace to obtain graphene-copper composite powder.

[0124] Step 3: The graphene-copper composite powder prepared by the rapid thermal annealing method is subjected to vacuum hot pressing sintering. Typical sintering process parameters are as follows:

[0125] Approximately 15g of graphene-copper composite powder was placed in a graphite mold with a diameter of 20mm, and the upper and lower pressure heads were sealed with graphite paper to prevent copper liquid from leaking out during the sintering process.

[0126] The sealed graphite mold was placed in a vacuum hot press with a pressure of 40 MPa and a pressing rate of 20 °C / min.-1 Heating rate: Heat to 850℃, hold at that temperature and pressure for 30 minutes, then continue heating at 20℃ / min under pressure. -1 Cool to room temperature at a cooling rate;

[0127] The graphene-copper composite block material prepared by hot pressing was polished sequentially using alumina sandpaper of 180, 400, 1000, 2000, and 4000 mesh.

[0128] The graphene-copper composite powder obtained in step two was subjected to Raman spectroscopy analysis, and the results are as follows: Figure 2 The curve at 850℃ is shown in the figure.

[0129] The graphene-copper composite powder obtained in step two was analyzed by XPS, and the results are as follows: Figure 3 As shown in (c).

[0130] Example 4

[0131] Step 1: Using a high-speed shear mixer, mix 20g of spherical copper powder with a particle size of 10-80μm with a certain mass of 0.65% nanocellulose gel at a high speed of 3500r / min for 30s to form a uniform nanocellulose gel layer on the surface of the copper powder.

[0132] The prepared powder was vacuum dried at 60°C for 2 hours to remove excess moisture from the nanocellulose gel layer and obtain a dried mixture.

[0133] Step 2: The dried nanocellulose-coated copper powder is annealed at 950℃ for 2 hours. During annealing, the argon flow rate is 100 sccm and the hydrogen flow rate is 30 sccm. After annealing, the powder is cooled to room temperature in the furnace to obtain graphene-copper composite powder.

[0134] Step 3: The graphene-copper composite powder prepared by the rapid thermal annealing method is subjected to vacuum hot pressing sintering. Typical sintering process parameters are as follows:

[0135] Approximately 15g of graphene-copper composite powder was placed in a graphite mold with a diameter of 20mm, and the upper and lower pressure heads were sealed with graphite paper to prevent copper liquid from leaking out during the sintering process.

[0136] The sealed graphite mold was placed in a vacuum hot press with a pressure of 40 MPa and a pressing rate of 20 °C / min. -1 Heating rate: Heat to 850℃, hold at that temperature and pressure for 30 minutes, then continue heating at 20℃ / min under pressure. -1 Cool to room temperature at a cooling rate;

[0137] The graphene-copper composite block material prepared by hot pressing was polished sequentially using alumina sandpaper of 180, 400, 1000, 2000, and 4000 mesh.

[0138] The graphene-copper composite powder obtained in step two was subjected to Raman spectroscopy analysis, and the results are as follows: Figure 2 The 950℃ curve is shown in the figure.

[0139] The graphene-copper composite powder obtained in step two was analyzed by XPS, and the results are as follows: Figure 3 As shown in (d).

[0140] Example 5

[0141] Step 1: Using a high-speed shear mixer, mix 20g of spherical copper powder with a particle size of 10-80μm with a certain mass of 0.65% nanocellulose gel at a high speed of 3500r / min for 30s to form a uniform nanocellulose gel layer on the surface of the copper powder.

[0142] The prepared powder was vacuum dried at 60°C for 2 hours to remove excess moisture from the nanocellulose gel layer and obtain a dried mixture.

[0143] Step 2: The dried nanocellulose-coated copper powder is annealed at 950℃ for 2 hours with a nitrogen flow rate of 100 sccm during annealing. After annealing, the powder is cooled to room temperature in the furnace to obtain graphene-copper composite powder.

[0144] Step 3: The graphene-copper composite powder prepared by the rapid thermal annealing method is subjected to vacuum hot pressing sintering. Typical sintering process parameters are as follows:

[0145] Approximately 15g of graphene-copper composite powder was placed in a graphite mold with a diameter of 20mm, and the upper and lower pressure heads were sealed with graphite paper to prevent copper liquid from leaking out during the sintering process.

[0146] The sealed graphite mold was placed in a vacuum hot press with a pressure of 40 MPa and a pressing rate of 20 °C / min. -1 Heating rate: Heat to 850℃, hold at that temperature and pressure for 30 minutes, then continue heating at 20℃ / min under pressure. -1 Cool to room temperature at a cooling rate;

[0147] The graphene-copper composite block material prepared by hot pressing was polished sequentially using alumina sandpaper of 180, 400, 1000, 2000, and 4000 mesh.

[0148] Tests revealed that, under conditions below atmospheric pressure, the inert protective atmosphere had virtually no impact on the conversion rate of graphene.

[0149] Process temperature results analysis

[0150] It can be seen that, Figure 2 In the process, as the annealing temperature increases, the graphene defect concentration in the prepared composite powder decreases continuously.

[0151] Figure 3 In the figure, since the target component graphene is a two-dimensional material, sp 2 The higher the proportion, the more graphene is generated;

[0152] Figure 3 In (a), sp 2 -C is 38%, sp 3 -C is 48%, indicating that the dispersion of the generated graphene is poor;

[0153] Figure 3 In (b), sp 2 -C is 44%, sp 3 -C is 42%, indicating that as the temperature increases, the dispersion of graphene improves and the aggregation phenomenon is alleviated;

[0154] Figure 3 In (c), sp 2 -C is 47%, sp 3 The -C concentration is 42%, and the C=O concentration decreases, indicating that the graphene generation efficiency is improved at this temperature.

[0155] Figure 3 In (d), sp 2 -C reached 58%, indicating that Example 4 produced the most graphene. 3 -C = 36%, indicating that the graphene in Example 4 is well dispersed, and the decrease in C=O concentration indicates that the graphene in Example 4 has the highest degree of reduction.

[0156] Figure 4 TEM image showing the graphene-copper composite block obtained in Example 4;

[0157] It can be seen that the graphene structure is continuously distributed, indicating that the graphene has a low degree of aggregation and that the continuous graphene has a large bonding area with the copper matrix, resulting in a good bonding degree.

[0158] Graphene concentration analysis

[0159] According to the preparation method in Example 4, the particle size of the spherical copper powder was selected as 10 μm, 40 μm or 80 μm;

[0160] By adjusting the amount of nanocellulose gel added, graphene-copper composite blocks with different copper powder particle sizes and graphene contents of 0.3wt%, 0.6wt%, and 0.9wt% were prepared.

[0161] Due to the different amounts of nanocellulose gel added, in order to ensure that a uniform nanocellulose gel layer can be formed on the surface of copper powder, hydrogels with nanocellulose concentrations dispersed to 0.3% to 1.0% were prepared respectively.

[0162] Different concentrations of nanocellulose hydrogel were added based on different graphene contents to ensure that copper powders of different particle sizes could achieve similar wetting and mixing states, and to ensure that different powders could achieve a monodisperse state without agglomeration.

[0163] The graphene content refers to the mass fraction of graphene, which is determined by carbon and sulfur analysis.

[0164] Performance testing and analysis

[0165] The mechanical properties of the materials with different graphene contents were tested, specifically as follows:

[0166] The electrical life test of the electrical contact material was conducted by using a precision electric slide to drive the electrical contact at an action frequency of "1 second on-1 second off" to obtain its life data.

[0167] The experimental load voltage was 28V, the load current was 10A, and the load was resistive; the initial static pressure of the contact pair was set to 1.7N, the initial opening distance was 1.2mm, and the contact breaking speed was set to 60mm / s.

[0168] The electrical contact materials are: commercial pure copper blocks, graphene-copper composite blocks with 0.3 wt% graphene content, graphene-copper composite blocks with 0.6 wt% graphene content, and graphene-copper composite blocks with 0.9 wt% graphene content.

[0169] Regarding conductivity, the percentage of conductivity was measured. The test results are shown in Table 1.

[0170] Table 1

[0171]

[0172]

[0173] The electrical contact life of commercial pure copper electrical contacts is 58 cycles.

[0174] The graphene-copper composite blocks with a graphene content of 0.3 wt% all have high lifespans. Among them, the copper powder has a particle size of 40 μm and an electrical life of 152 cycles when the blank pressure is 40 MPa in vacuum hot pressing.

[0175] The lifespan of graphene-copper composite blocks with 0.6 wt% graphene content is lower than that of graphene-copper composite blocks with 0.3 wt% graphene content. The copper powder particle size is 40 μm, and the electrical life is only 60 cycles when the blank pressure is 40 MPa in vacuum hot pressing, which is almost equivalent to that of pure copper.

[0176] When the graphene mass fraction is increased to 0.9 wt%, the lifespan of the graphene-copper composite block is also lower than that of the graphene-copper composite block with 0.3 wt% graphene content. The copper powder particle size is 40 μm, and the electrical contact life of the composite block is only 76 cycles when the blank pressure is 40 MPa in vacuum hot pressing.

[0177] Since the generated graphene or amorphous carbon and copper are both materials with good electrical conductivity, the conductivity of their composite materials is also excellent, with a test result of 85-94% IACS.

[0178] The material can meet the requirements for use in high-strength, high-conductivity composite materials.

[0179] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a graphene-copper composite material, characterized in that, The specific steps include: S1. Mix copper powder with nanocellulose gel and dry to obtain a dried mixture; The copper powder is spherical copper powder with a particle size of 10-80μm; The mixing ratio of copper powder to nanocellulose gel is 1:0.3-1:3 by mass. The nanocellulose gel is a hydrogel in which nanocellulose concentration is dispersed to 0.3~1.0 wt%. S2. Vacuum annealing is performed on the mixture to obtain graphene-copper composite powder; S3. Hot-press and sinter the graphene-copper composite powder to obtain a graphene-copper composite material of a predetermined shape. In S2, the annealing temperature is 650-950℃; the annealing time is 1-4 hours. In S1, the mixing method is high-speed shear mixing, and the state of the mixture is: the powder is not agglomerated and is in a monodisperse state.

2. The preparation method of the graphene-copper composite material as described in claim 1, characterized in that, In S2, the vacuum environment can be replaced by a nitrogen, hydrogen, and / or argon protective environment, with the pressure maintained at a level below atmospheric pressure.

3. The method for preparing the graphene-copper composite material as described in claim 2, characterized in that, Argon flow rate is 50~200 sccm, hydrogen flow rate is 10~50 sccm and / or nitrogen flow rate is 50~200 sccm.

4. The method for preparing the graphene-copper composite material as described in claim 3, characterized in that, Argon flow rate is 100 sccm, hydrogen flow rate is 30 sccm, or nitrogen flow rate is 100 sccm.

5. The method for preparing the graphene-copper composite material as described in claim 1, characterized in that, In S2, the annealing temperature is 850~950℃ and the annealing time is 2~3 hours.

6. The method for preparing the graphene-copper composite material as described in claim 5, characterized in that, The annealing temperature was 950℃ and the annealing time was 2 hours.

7. The preparation method of graphene-copper composite material as described in claim 1, characterized in that, in S3, the hot pressing sintering is vacuum hot pressing sintering; specifically: the graphene-copper composite powder is placed in a graphite mold and wrapped with graphite paper, and the sealed graphite mold is placed in a vacuum hot press. The pressure of the press rod in the vacuum hot press is maintained at 20~50 MPa; the pressure is maintained at 10~30℃·min. -1 Heat to 750~950℃ at a heating rate, hold at that temperature and pressure for 0.5~1h, then heat at a rate of 10~30℃·min under pressure. -1 Cool to room temperature at the cooling rate.

8. The method for preparing the graphene-copper composite material as described in claim 7, characterized in that, The pressure bar of the vacuum hot press is maintained at 40 MPa; at a rate of 20 °C / min. -1 The temperature was raised to 850 °C and held at that temperature and pressure for 30 min. Then, under pressure, the temperature was increased at a rate of 20 °C / min. -1 Cool to room temperature at the cooling rate.

9. A graphene-copper composite material prepared by the method of any one of claims 1-8.

10. The graphene-copper composite material as described in claim 9, characterized in that graphene... The graphene content in the copper-based composite material is 0.3%~0.9 wt%. The internal structure of the graphene-copper composite material is a uniform and continuous network structure of graphene at the copper grain boundaries.

11. The graphene-copper composite material as described in claim 10, characterized in that, The graphene content in the graphene-copper composite material is 0.3 wt%.

12. An application of the graphene-copper composite material as described in any one of claims 9-11, characterized in that, the application... include: Applications in electrical contact materials, resistance welding electrode materials, or heat sink materials.

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