A method for preparing graphene-reinforced copper composite material

Abstract

The present invention discloses a method for preparing a graphene-enhanced copper composite material, and belongs to the technical field of composite material preparation. The present invention adopts highly active carbon quantum dots, which are dissolved, ultrasonicated, and activated in a solution, and iodine tincture and copper powder are added and stirred evenly, and freeze-dried to uniformly adsorb the carbon source and nucleation sites on the surface of the copper powder with a complex microstructure. Graphene is then grown in situ at a low temperature by iodine catalysis to prepare a well-coated, uniformly structured, and tightly bonded graphene / copper composite powder. Graphene-enhanced copper composite materials with a continuous structure and strong interface bonding are then prepared by sintering. The large specific surface area graphene coated evenly is utilized to improve the carrier and load transfer capacity of the composite material, which is beneficial to the transmission of electricity, heat, and force, so that the electrical conductivity of the composite material is as high as 90-100.8% IACS, the tensile strength reaches 207-263 MPa, and the thermal diffusion coefficient reaches 101.8-120.8 mm 2 / s, and its comprehensive performance is better than that of pure copper. In addition, the method is simple in process and easy to produce.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and particularly relates to a method for preparing a graphene-reinforced copper composite material. Background Art

[0002] Traditional pure copper materials are widely used in aerospace, low-voltage electrical appliances, communications, and other fields due to their high electrical and thermal conductivity and high ductility. However, due to their poor high-temperature stability and low yield strength, they cannot meet the application needs of today's rapidly developing emerging industries. Although traditional copper alloys have improved yield strength, they lose a lot of electrical and thermal conductivity functionality due to the strong carrier scattering of alloying elements. Copper-based composites, by fully combining the excellent properties of the highly conductive and thermal reinforcing phase with the copper matrix, achieve a synergistic improvement in comprehensive properties such as electrical conductivity, thermal conductivity, and mechanical properties.

[0003] Currently, nanocarbon reinforcements that have received widespread attention include carbon nanotubes and graphene. By introducing nanocarbon reinforcements into a copper matrix and combining the advantages of the copper matrix and nanocarbon, single or combined properties such as strength, oxidation resistance, high-temperature stability, and wear resistance of copper-based composites can be significantly improved, showing broad application prospects. Given the excellent inherent properties of graphene and its synergistic effect with copper, graphene / copper composites are expected to develop into advanced composite materials with high electrical and thermal conductivity. Currently, one of the main methods for preparing such composite materials is to mix graphene into copper powder by external addition and then ball milling. However, this method faces problems such as insufficient interface wettability between graphene and the copper matrix, low interface bonding strength, uneven distribution of graphene, and easy agglomeration.

[0004] The present invention uses liquid-phase catalytic technology and an in-situ growth strategy to achieve in-situ growth of graphene on the surface of copper powder under relatively low temperature conditions, thereby achieving uniform and complete wrapping of the copper powder by graphene, significantly improving the problems encountered in the traditional external addition preparation process. Summary of the Invention

[0005] In view of the above shortcomings of the prior art, the present invention provides a method for preparing a graphene-reinforced copper composite material.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a graphene-reinforced copper composite material, comprising:

[0008] (1) reducing the copper powder in a reducing gas to obtain reduced copper powder;

[0009] (2) mixing the nanocarbon material suspension and the reduced copper powder, and freeze-drying the mixture to obtain a mixed powder;

[0010] (3) feeding the mixed powder into a tube furnace at room temperature, setting growth conditions, and performing in-situ growth of graphene on the surface of the copper powder. After the growth is completed, the furnace is cooled to room temperature to obtain a graphene / copper composite powder;

[0011] The in-situ growth conditions include: closing the furnace tube, evacuating the residual air in the furnace, introducing 100-200 sccm of argon and 10-50 sccm of hydrogen, and gradually increasing the temperature to 300°C at a uniform rate at room temperature and holding the temperature for 50-70 minutes; then increasing the temperature to 500-800°C at a uniform rate, introducing argon at a flow rate of 5-20 sccm, and holding the temperature for 50-70 minutes to continue in-situ growth; and then cooling to room temperature.

[0012] (4) The graphene / copper composite powder is subjected to spark plasma sintering to obtain a graphene reinforced copper composite material.

[0013] The present invention utilizes a staged in-situ growth method, which, on the one hand, ensures a good Cu-C interface, facilitating enhanced load transfer and continuous propagation, as well as improving the composite material's electrical conductivity and thermal diffusivity. Furthermore, segmented heating and insulation during the in-situ growth phase, combined with variable ventilation flow, further enhances the quality of the in-situ grown graphene, ensuring the production of high-quality graphene at low temperatures. Furthermore, the graphene exhibits excellent crystallinity, which contributes to improved tensile strength, elongation at break, electrical conductivity, and thermal diffusivity.

[0014] As a preferred embodiment of the present invention, the nano carbon material is a sp 2 Hybrid structured nanocarbon materials, including but not limited to carbon quantum dots. 2 Hybrid structured nanocarbon materials are mainly composed of sp 2 Hybridized carbon atoms are organized in a hexagonal network. The chemical structure of CQDs is primarily composed of a well-crystalline sp2 carbon core and surface groups.

[0015] The present invention adopts sp 2 A suspension of nanocarbon materials with a hybrid structure is used as a carbon source, and iodine tincture can evenly adsorb the carbon source and nucleation sites on the surface of copper powder with a complex microstructure. Moreover, iodine tincture, as a catalyst, can in situ grow high-quality graphene on the surface of copper powder at low temperature, and promote the bonding of graphene to form a large network, thereby preparing a graphene-reinforced copper composite material with uniform coating and good structure.

[0016] As a preferred embodiment of the present invention, in step (1), the reduction temperature is 300°C, the holding time is 250-360 minutes, the argon flow rate during reduction is 100-200 sccm, and the hydrogen flow rate is 10-40 sccm. Pre-reduction of the copper powder removes impurities such as oxides, facilitating the coating of the carbon source.

[0017] As a preferred embodiment of the present invention, the preparation method of the nano carbon material suspension comprises: 2 The carbon quantum dots with hybrid structure are placed in a mixed solution of ethanol, water and iodine and ultrasonically dispersed to obtain a carbon quantum dot suspension.

[0018] The sp 2 The hybrid structured carbon quantum dots are commercially available products, which are fluorescent green carbon quantum dots. The fluorescent green carbon quantum dots have very few residual impurities during the preparation process, the carbon source is of high purity, and the particle size is 2-5nm.

[0019] As a preferred embodiment of the present invention, the volume ratio of the ethanol, water and iodine tincture is (5-10): (10-20): (0.01-0.05).

[0020] As a preferred embodiment of the present invention, in step (3), the mass of carbon quantum dots in the nano-carbon material suspension accounts for 0.01%-0.2% of the mass of the copper powder; and the average particle diameter of the copper powder is 1-20 μm.

[0021] As a preferred embodiment of the present invention, the nano-carbon material suspension and copper powder are stirred and mixed at a speed of 100-200 rpm for 6-12 hours. By combining the solution stirring method with freeze drying, the carbon source can be evenly coated on the surface of the copper powder. At the same time, freeze drying does not cause loss of the carbon source, so the present invention can clearly define the amount of carbon source added.

[0022] As a preferred embodiment of the present invention, the spark plasma sintering temperature is 650-750° C., the vacuum degree is lower than 5 Pa, the heating rate is 50-150° C. / min, and the holding time is 10-30 min.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention adopts highly active carbon quantum dots, which are dissolved in a solution, ultrasonicated, activated, and iodine tincture and copper powder are added and stirred evenly, and freeze-dried to uniformly adsorb the carbon source and nucleation sites on the surface of the copper powder with a complex microstructure. Graphene is then grown in situ at low temperature under iodine catalysis to prepare a graphene / copper composite powder with good coating, uniform structure, and tight bonding. Graphene-reinforced copper composite materials with continuous structure and strong interface bonding are then prepared through sintering molding. The uniformly coated large specific surface area graphene is used to improve the carrier and load transfer capacity of the composite material, which is beneficial to the transmission of electricity, heat, and force, so that the electrical conductivity of the composite material is as high as 90-100.8% IACS, the tensile strength reaches 207-263 MPa, and the thermal diffusion coefficient reaches 101.8-120.8 mm 2 / s, and its comprehensive performance is better than that of pure copper. In addition, the method is simple in process and easy to produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 These are SEM morphologies of the graphene / copper composite powders prepared in step (3) of Examples 1-4, wherein a is Example 1, b is Example 2, c is Example 4, and d is Example 5.

[0026] Figure 2 This is the Raman spectrum of the graphene / copper composite powder prepared in step (3) of Example 1-4.

[0027] Figure 3 TEM images of the graphene coating layer of the graphene / copper composite powder prepared in step (3) of Examples 3 and 4 after dissolving copper, the left image is Example 3, and the right image is Example 4.

[0028] Figure 4 These are SEM morphologies of the powders prepared in Comparative Examples 1-2. The left picture is the SEM morphology of the pure copper powder prepared in Comparative Example 1, and the right picture is the SEM morphology of the graphene / copper composite powder prepared in step (3) of Comparative Example 2. DETAILED DESCRIPTION

[0029] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0030] Example 1

[0031] A method for preparing a graphene-reinforced copper composite material, comprising the following steps:

[0032] (1) 10 g of copper powder (average particle diameter of about 20 μm) was kept at a reduction temperature of 300 °C for 250 min, with an argon flow rate of 100 sccm and a hydrogen flow rate of 10 sccm. The heating time was 40 min. The copper powder was pre-reduced to remove impurities such as oxides, which was beneficial for the coating of the carbon source.

[0033] (2) 2.5 mg of carbon quantum dots were placed in a mixed solution of 5 ml of anhydrous ethanol, 15 ml of deionized water and 0.01 ml of iodine tincture and ultrasonically dispersed to obtain a carbon quantum dot with sp 2 The nanocarbon material suspension with hybrid structure is then 2 The hybrid nanocarbon suspension was stirred and mixed with 10 g of copper powder obtained in step (1), and freeze-dried at a stirring speed of 200 rpm for 6 hours to obtain a precursor powder coated with a carbon source. The mass of the added carbon quantum dots was 0.025% of the mass of the copper powder.

[0034] (3) The precursor powder obtained in step (2) is placed in a tubular furnace for in-situ growth of graphene, wherein the first reduction stage has a heating time of 30 minutes, a heat preservation time of 50 minutes, a temperature of 300°C, an argon flow rate of 190 sccm, and a hydrogen flow rate of 10 sccm. The second growth stage has a heating time of 30 minutes, a heat preservation time of 50 minutes, a growth temperature of 500°C, and an argon flow rate of 5 sccm to obtain a graphene / copper composite powder. By heating and heat preservation in stages, the copper powder is reduced to a certain extent in the first heat preservation stage, removing the influence of impurities such as oxides on the growth quality of graphene, and at the same time changing the gas flow rate at the in-situ growth temperature, further improving the quality of the in-situ grown graphene.

[0035] (4) The composite powder obtained in step (3) is subjected to spark plasma sintering to obtain a graphene / copper composite material. The spark plasma sintering is performed at a temperature of 650° C., a vacuum degree of less than 5 Pa, a heating rate of 70° C. / min, and a holding time of 10 min to obtain a graphene-reinforced copper composite material.

[0036] The microscopic morphology of the graphene / copper composite powder obtained in step (3) of this embodiment is as follows: Figure 1 As shown in a, graphene is uniformly grown and coated on the surface of the copper powder, but it can be seen that the graphene is partially broken and discontinuous, making it difficult to form a continuous propagation path for carriers and loads.

[0037] After spark plasma sintering, the mechanical properties test showed that the tensile strength of the graphene-enhanced copper composite material under this process condition was 210 MPa, the elongation at break was 34.8%, the electrical properties test showed that the electrical conductivity of the graphene-enhanced copper composite material was 100.8% IACS, and the thermal properties test showed that the thermal diffusion coefficient was 107 mm 2 / s.

[0038] Example 2

[0039] A method for preparing a graphene-reinforced copper composite material, comprising the following steps:

[0040] (1) 10 g of copper powder (average particle diameter of about 20 μm) was kept at a reduction temperature of 300 °C for 300 min, with an argon flow rate of 150 sccm and a hydrogen flow rate of 20 sccm. The heating time was 40 min. The copper powder was pre-reduced to remove impurities such as oxides, which was beneficial for the coating of the carbon source.

[0041] (2) 5 mg of carbon quantum dots were placed in a mixed solution of 7 ml of anhydrous ethanol, 15 ml of deionized water and 0.03 ml of iodine tincture and ultrasonically dispersed to obtain a carbon quantum dot with sp 2 The nanocarbon material suspension with hybrid structure is then 2 The hybrid nanocarbon suspension was stirred and mixed with 10 g of copper powder obtained in step (1), and freeze-dried at a stirring speed of 100 rpm for 12 hours to obtain a precursor powder coated with a carbon source. The mass of the added carbon quantum dots was 0.05% of the mass of the copper powder.

[0042] (3) The precursor powder obtained in step (2) was placed in a tube furnace for in-situ growth of graphene, wherein the first reduction stage was heated for 30 min, kept warm for 60 min, at a temperature of 300° C., with an argon flow rate of 190 sccm and a hydrogen flow rate of 20 sccm. The second growth stage was heated for 30 min, kept warm for 60 min, at a growth temperature of 600° C., with an argon flow rate of 20 sccm to obtain a graphene / copper composite powder.

[0043] (4) The composite powder obtained in step (3) is molded into a graphene / copper composite material by spark plasma sintering. The spark plasma sintering is performed at a temperature of 680° C., a vacuum degree of less than 5 Pa, a heating rate of 150° C. / min, and a holding time of 15 min to obtain a graphene-reinforced copper composite material.

[0044] The microscopic morphology of the graphene / copper composite powder obtained in step (3) of this embodiment is as follows: Figure 1 As shown in Figure b, graphene is grown and coated on the surface of the copper powder, but some uncovered copper powder still exists. At the same time, it can be seen that some graphene is in thicker layers, indicating that adding carbon source can grow more graphene under this process. After sintering and molding, mechanical properties testing showed that the tensile strength of the graphene-reinforced copper composite material under this process conditions was 225MPa and the elongation at break was 36.5%. Electrical properties testing showed that the composite material had an electrical conductivity of 99.9% IACS, and thermal properties testing showed a thermal diffusivity of 112mm. 2 / s.

[0045] Example 3

[0046] A method for preparing a graphene-reinforced copper composite material, comprising the following steps:

[0047] (1) 10 g of copper powder (average particle diameter of about 20 μm) was kept at a reduction temperature of 300 °C for 360 min, with an argon flow rate of 180 sccm and a hydrogen flow rate of 20 sccm. The heating time was 40 min. The copper powder was pre-reduced to remove impurities such as oxides, which was beneficial for the coating of the carbon source.

[0048] (2) 7.5 mg of carbon quantum dots were placed in a mixed solution of 6 ml of anhydrous ethanol, 13 ml of deionized water, and 0.045 ml of iodine tincture and ultrasonically dispersed to obtain a carbon quantum dot with sp 2 The nanocarbon material suspension with hybrid structure is then 2 The hybrid nanocarbon suspension was stirred and mixed with 10 g of copper powder obtained in step (1), and freeze-dried at a stirring speed of 150 rpm for 10 hours to obtain a precursor powder coated with a carbon source. The mass of the added carbon quantum dots was 0.075% of the mass of the copper powder.

[0049] (3) The precursor powder obtained in step (2) is placed in a tubular furnace for in-situ growth of graphene, wherein the first reduction stage is heated for 30 minutes, kept warm for 60 minutes, at a temperature of 300°C, with an argon flow rate of 180 sccm and a hydrogen flow rate of 20 sccm. The second growth stage is heated for 30 minutes, kept warm for 60 minutes, at a growth temperature of 630°C, with an argon flow rate of 10 sccm, to obtain a graphene / copper composite powder. By heating and keeping warm in stages, the copper powder is reduced to a certain extent in the first keeping warm stage, removing the influence of impurities such as oxides on the growth quality of graphene, and at the same time changing the gas flow rate at the in-situ growth temperature, reducing the adverse effect of excessive gas flow on graphene growth during in-situ growth, and further improving the quality of graphene grown in-situ.

[0050] (4) The graphene / copper composite powder obtained in step (3) is molded into a graphene / copper composite material by spark plasma sintering. The spark plasma sintering is performed at a temperature of 700° C., a vacuum degree of less than 5 Pa, a heating rate of 100° C. / min, and a holding time of 10 min to obtain a graphene-reinforced copper composite material.

[0051] The microscopic morphology of the graphene / copper composite powder obtained in step (3) of this embodiment is as follows: Figure 1 As shown in c, graphene is uniformly grown and coated on the surface of the copper powder. Combined with the TEM analysis of the graphene coating layer after dissolving copper in the graphene / copper composite powder obtained in step (3), it can be seen that Figure 3 (Left image) In the process of this embodiment, a continuous, uniform, large-sized graphene coating layer is obtained, which can effectively transfer the load and form a continuous carrier migration path.

[0052] After sintering, mechanical performance tests showed that the tensile strength of the graphene-enhanced copper composite material under this process condition was 240 MPa, and the elongation at break was 31.5%. The tight interface bonding between the surface graphene and copper effectively improved the load transfer capacity and facilitated the continuous propagation of carriers. The electrical performance test showed that the conductivity of the graphene-enhanced copper composite material was 99.6% IACS, and the thermal performance test showed that the thermal diffusion coefficient was 114 mm 2 / s.

[0053] Example 4

[0054] The preparation method of the graphene-reinforced copper composite material in this embodiment is different from that in Example 3, except that:

[0055] The amount of carbon quantum dots added in step (2) was 9 mg, which was 0.09% of the mass of the copper powder.

[0056] The microscopic morphology of the graphene / copper composite powder obtained in step (3) of this embodiment is as follows: Figure 1 d, combined with the TEM analysis of the graphene coating layer after the copper was dissolved in the composite powder obtained in step (3), it can be seen that Figure 3 (right image), a more continuous and larger uniform graphene coating layer is generated on the surface of the copper powder. After sintering, a continuous graphene structure can be formed inside the composite material. Raman detection shows that the degree of defects in the graphene is not high. Figure 2 .

[0057] Mechanical performance tests show that under this process condition, the tensile strength of the graphene-enhanced copper composite material is 253 MPa, the elongation at break is 29.5%, the electrical performance test shows that the electrical conductivity of the graphene-enhanced copper composite material is 98.2% IACS, and the thermal performance test shows that the thermal diffusion coefficient is 118 mm 2 / s.

[0058] Example 5

[0059] A method for preparing a graphene-reinforced copper composite material, comprising the following steps:

[0060] (1) 10 g of copper powder (average particle diameter of about 20 μm) was kept at a reduction temperature of 300 °C for 360 min, with an argon flow rate of 200 sccm and a hydrogen flow rate of 40 sccm. The heating time was 40 min. The copper powder was pre-reduced to remove impurities such as oxides, which was beneficial for the coating of the carbon source.

[0061] (2) 20 mg of carbon quantum dots were placed in a mixed solution of 10 ml of anhydrous ethanol, 20 ml of deionized water, and 0.05 ml of iodine tincture and ultrasonically dispersed to obtain a carbon quantum dot with sp 2 The nanocarbon material suspension with hybrid structure is then 2 The hybrid nanocarbon suspension was stirred and mixed with 10 g of copper powder obtained in step (1), and freeze-dried at a stirring speed of 150 rpm for 10 hours to obtain a precursor powder coated with a carbon source. The mass of the added carbon quantum dots was 0.2% of the mass of the copper powder.

[0062] (3) The precursor powder obtained in step (2) is placed in a tubular furnace for in-situ growth of graphene, wherein the first reduction stage is heated for 30 minutes, kept warm for 70 minutes, at a temperature of 300°C, with an argon flow rate of 100 sccm and a hydrogen flow rate of 50 sccm. The second growth stage is heated for 30 minutes, kept warm for 70 minutes, at a growth temperature of 800°C, with an argon flow rate of 20 sccm, to obtain a graphene / copper composite powder. By segmented heating and heat preservation, the copper powder is reduced to a certain extent in the first heat preservation stage to remove the influence of impurities such as oxides on the growth quality of graphene. At the same time, the gas flow rate introduced is changed at the in-situ growth temperature, reducing the adverse effect of excessive gas flow on graphene growth during in-situ growth, thereby further improving the quality of graphene grown in situ.

[0063] (4) The composite powder obtained in step (3) is molded into a graphene / copper composite material by spark plasma sintering. The spark plasma sintering is performed at a temperature of 750° C., a vacuum degree of less than 5 Pa, a heating rate of 50° C. / min, and a holding time of 30 min to obtain a graphene-reinforced copper composite material.

[0064] The graphene / copper composite powder obtained in step (3) of this embodiment is a graphene-coated copper powder with graphene uniformly grown on its surface. In the process of this embodiment, a continuous, uniform, large-sized graphene coating layer is obtained, which can effectively transfer load and form a continuous carrier migration path. Mechanical performance tests after sintering and molding show that under this process condition, the graphene-enhanced copper composite material has a tensile strength of 263MPa and an elongation at break of 30.5%. The tight interface bonding between the surface graphene and copper effectively improves the load transfer capacity and facilitates the continuous propagation of carriers. The electrical performance test shows that the electrical conductivity of the graphene-enhanced copper composite material is 98.9% IACS, and the thermal performance test shows that the thermal diffusion coefficient is 120.8mm2 / s.

[0065] Comparative Example 1

[0066] The only difference between the preparation method of the copper material described in this comparative example and that of Example 3 is that the reduction and subsequent coating of the carbon source and the in-situ growth process in steps (2) and (3) are not performed; only the copper powder is reduced in step (1), as shown in FIG. Figure 4 (Left image), pure copper blocks were subsequently produced through spark plasma sintering. Mechanical performance tests showed that the tensile strength of the pure copper blocks produced under this process was 207 MPa, and the elongation at break was 45.5%. Electrical performance tests showed that the material had an electrical conductivity of 100.3 IACS%, and thermal performance tests showed a thermal diffusivity of 101.8 mm. 2 / s.

[0067] Compared with Comparative Example 1, the graphene-copper composite materials prepared in the examples of the present invention show that the tensile strength of the graphene-enhanced copper composite materials in Examples 1-5 is improved, and good elongation and electrical conductivity are maintained. At the same time, the thermal conductivity of the graphene-enhanced copper composite materials is improved compared with pure copper, indicating that the preparation method proposed in the present invention is beneficial to improving the comprehensive performance of pure copper-based composite materials.

[0068] Comparative Example 2

[0069] The preparation method of the graphene-enhanced copper composite material described in this comparative example is different from that in Example 3 in that the average particle diameter of the copper powder reduced in step (1) is adjusted to 1 μm, and the amount of carbon quantum dots added in step (2) is adjusted to 0.5 mg.

[0070] In this comparative example, the particle diameter and morphology of the copper powder were changed, resulting in changes in the morphology and structure of the graphene coating layer grown in situ on the surface of the copper powder. Figure 4 (Right picture), graphene grows only on the surface of the copper powder, and it is difficult to densify during the sintering process. It is difficult for graphene to form a continuous structure in the graphene / copper composite powder. The mechanical properties test shows that under this process condition, the tensile strength of the graphene-reinforced copper composite material is 215MPa, the elongation at break is 35.5%, the electrical properties test shows that the electrical conductivity of the composite material is 90% IACS, and the thermal properties test shows that the thermal diffusion coefficient is 104mm 2 / s.

[0071] Comparative Example 3

[0072] A method for preparing a graphene-reinforced copper composite material, comprising the following steps:

[0073] (1) 10 g of copper powder (average particle diameter of about 20 μm) was kept at a reduction temperature of 300 °C for 360 min, with an argon flow rate of 180 sccm and a hydrogen flow rate of 20 sccm. The heating time was 40 min. The copper powder was pre-reduced to remove impurities such as oxides, which was beneficial for the coating of the carbon source.

[0074] (2) 7.5 mg of carbon quantum dots were placed in a mixed solution of 6 ml of anhydrous ethanol and 13 ml of deionized water and ultrasonically dispersed to obtain a carbon quantum dot with sp 2 The nanocarbon material suspension with hybrid structure is then 2 The hybrid nanocarbon suspension was stirred and mixed with 10 g of copper powder obtained in step (1), and freeze-dried at a stirring speed of 150 rpm for 10 hours to obtain a precursor powder coated with a carbon source. The mass of the added carbon quantum dots was 0.075% of the mass of the copper powder.

[0075] (3) The precursor powder obtained in step (2) is placed in a tubular furnace for in-situ growth of graphene, wherein the first reduction stage has a heating time of 30 minutes, a heat preservation time of 60 minutes, a temperature of 300°C, an argon flow rate of 180 sccm, and a hydrogen flow rate of 20 sccm. The second growth stage has a heating time of 30 minutes, a heat preservation time of 60 minutes, a growth temperature of 630°C, and an argon flow rate of 10 sccm to obtain a graphene / copper composite powder. By segmented heating and heat preservation, the copper powder is reduced to a certain extent in the first heat preservation stage, removing the influence of impurities such as oxides on the growth quality of graphene, and at the same time changing the gas flow rate at the in-situ growth temperature, reducing the adverse effect of excessive gas flow on graphene growth during in-situ growth, and further improving the quality of graphene grown in situ.

[0076] (4) Sintering the graphene / copper composite powder obtained in step (3) to obtain a graphene / copper composite material. Spark plasma sintering is adopted at a temperature of 700° C., a vacuum degree of less than 5 Pa, a heating rate of 100° C. / min, and a holding time of 10 min to obtain a graphene-reinforced copper composite material.

[0077] In this comparative example, since no iodine was added, the carbon source and nucleation sites were difficult to be adsorbed on the surface of the copper powder. Therefore, it was difficult to fully grow into graphene during the low-temperature growth stage, resulting in changes in the morphology and structure of the graphene coating grown in situ on the copper powder surface. It was difficult to partially grow graphene on the copper powder surface, and the original discontinuous carbon source structure was still maintained. It was also difficult to densify during the sintering process. Mechanical performance tests showed that the tensile strength of the graphene-reinforced copper composite material under this process condition was 220MPa, and the elongation at break was 38.5%. The electrical performance test showed that the electrical conductivity of the composite material was 94% IACS, and the thermal performance test showed that the thermal diffusion coefficient was 103.5mm 2 / s.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a graphene-reinforced copper composite material, characterized in that: include: (1) reducing the copper powder in a reducing gas to obtain reduced copper powder; (2) mixing the nanocarbon material suspension and the reduced copper powder, and freeze-drying the mixture to obtain a mixed powder; (3) The mixed powder is placed in a tube furnace at room temperature, growth conditions are set, and graphene is grown in situ on the surface of the reduced copper powder. After the growth is completed, the furnace is cooled to room temperature to obtain a graphene / copper composite powder; The growth conditions include: closing the furnace tube, evacuating the residual air in the furnace, introducing 100-200 sccm of argon and 10-50 sccm of hydrogen, uniformly heating the temperature to 300°C at room temperature and holding the temperature for 50-70 minutes; then uniformly heating the temperature to 500-800°C, introducing argon at a flow rate of 5-20 sccm, and holding the temperature for 50-70 minutes for in-situ growth; (4) subjecting the graphene / copper composite powder to spark plasma sintering to obtain a graphene reinforced copper composite material; The preparation method of the nano-carbon material suspension comprises: placing carbon quantum dots in a mixed solution of ethanol, water and iodine and performing ultrasonic dispersion to obtain the carbon quantum dot suspension.

2. The method for preparing the graphene-enhanced copper composite material according to claim 1, wherein: In step (1), the reduction temperature is 300°C, and the holding time is 250-360 min; the reducing gas is a mixture of hydrogen and argon, the argon flow rate is 100-200 sccm, and the hydrogen flow rate is 10-40 sccm.

3. The method for preparing the graphene-enhanced copper composite material according to claim 1, wherein: The volume ratio of the ethanol, water and iodine tincture is (5-10): (10-20): (0.01-0.05).

4. The method for preparing the graphene-enhanced copper composite material according to claim 1, wherein: In step (2), the mass of the carbon quantum dots in the nano-carbon material suspension accounts for 0.01%-0.2% of the mass of the reduced copper powder; and the average particle diameter of the copper powder is 1-20 μm.

5. The method for preparing the graphene-reinforced copper composite material according to claim 1, wherein: The nano-carbon material suspension and the reduced copper powder are stirred and mixed at a rotation speed of 100-200 rpm for 6-12 hours.

6. The method for preparing the graphene-reinforced copper composite material according to claim 1, wherein: The spark plasma sintering temperature is 650-750° C., the vacuum degree is lower than 5 Pa, the heating rate is 50-150° C. / min, and the holding time is 10-30 min.

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