Preparation method of graphene copper composite wire

Abstract

The invention provides a preparation method of a high-strength and high-conductivity graphene-copper composite wire, which comprises the following steps of: (1) placing graphene-copper composite powder in a graphite mold, and preparing a graphene-copper composite block through vacuum hot pressing sintering or spark plasma sintering; (2) the graphene copper composite block obtained in the step (1) is subjected to hot extrusion treatment, and a graphene copper composite bar is prepared; and (3) the graphene copper composite bar obtained in the step (2) is subjected to cold drawing treatment, and the graphene copper composite wire is prepared.

Description

Technical Field

[0001] The invention relates to a method for preparing a composite wire material, and in particular to a method for preparing a high-strength and high-conductivity graphene copper composite wire material. Background Art

[0002] High-strength and high-conductivity cables usually refer to special cables with high strength and high conductivity. Due to their excellent physical and electrical properties, these cables have a wide range of application needs in many fields. In power systems, especially high-voltage transmission lines, there are high requirements for the strength and conductivity of cables to reduce energy loss during transmission and improve transmission efficiency. The contact wires used in high-speed railways and urban rail transit need to have good mechanical strength and conductivity to ensure the safe and stable operation of trains. In communication facilities such as local area networks and data centers, high-strength and high-conductivity cables can provide more stable signal transmission, especially in environments where external electromagnetic interference needs to be shielded, such as the military, hospitals, airports and other places. In industrial control and automation equipment, there are high requirements for cable durability and signal transmission stability, and high-strength and high-conductivity cables can better meet these needs. With the development of the global economy and the advancement of technology, especially in the development of new energy, intelligent manufacturing, 5G communications and other fields, the demand for high-strength and high-conductivity cables will continue to grow.

[0003] Graphene is a two-dimensional material with extremely high electron mobility and excellent electrical conductivity. When combined with copper, it can significantly improve the conductivity of copper-based composite materials. This high conductivity makes graphene copper composites very suitable for making high-performance wires, cables and electronic components, especially in application scenarios that require efficient transmission of electrical energy or signals. In addition, graphene also has extremely high mechanical strength and toughness. When added to the copper matrix, it can greatly increase the mechanical properties of the material without sacrificing or even improving conductivity. For components that need to withstand large mechanical stresses or work in extreme environments, such as aerospace structural parts or high-speed train contact wires, the use of graphene copper composites can significantly improve their service life and reliability.

[0004] Patent application CN106548831A discloses a method for preparing a graphene copper composite wire, wherein a copper strip covered with a graphene film is wound on a copper rod and placed in a copper sheath to obtain a pre-assembled body; the pre-assembled body is hot extruded to obtain a graphene copper rod. Although the obtained material has a certain strength, it mostly depends on the strength of the copper rod itself. Since the proportion of graphene in the entire material is very low, it not only does not bring a significant improvement in the overall strength, but also the improvement in the material's electrical conductivity is also very small.

[0005] In addition, patent application CN111145960A discloses a method for preparing a high-strength and high-conductivity copper-based composite material, including laminating two or more layers of copper foils with graphene layers deposited thereon and then hot pressing and forming them to form a graphene-copper composite material; and hot isostatic pressing and densification treatment of the graphene-copper composite material. However, this method still uses chemical deposition to deposit graphene on the surface of the copper foil to form a graphene layer. This method generally requires a high vacuum system, complex atmosphere control, and a rapid temperature rise and fall heat treatment system, and the preparation cost is relatively high.

[0006] Therefore, there is an urgent need to further improve the uniformity of graphene as a reinforcing phase in the copper matrix, give full play to the enhancing effect of graphene on the mechanical and electrical properties of the copper matrix, and at the same time reduce the processing flow and reduce costs. Summary of the invention

[0007] A first aspect of the present invention provides a method for preparing a high-strength and high-conductivity graphene copper composite wire, comprising the following steps:

[0008] (1) placing graphene-copper composite powder in a graphite mold and preparing a graphene-copper composite block by vacuum hot pressing sintering or spark plasma sintering;

[0009] (2) subjecting the graphene-copper composite block obtained in step (1) to hot extrusion to prepare a graphene-copper composite rod;

[0010] (3) The graphene copper composite rod obtained in step (2) is subjected to cold drawing to prepare a graphene copper composite wire.

[0011] The second aspect of the present invention provides a graphene copper composite wire obtained by the preparation method described in the first aspect of the present invention.

[0012] In the context of the present invention, the "graphene copper composite powder" used can be a graphene copper composite powder obtained by any method; preferably, it is a graphene copper composite powder prepared by the method described in CN113231633A. Specifically, the graphene copper composite powder is prepared by the following method: a method for preparing graphene copper-based composite powder based on high-energy beam, placing copper powder in a vibrating powder feeder, and charging the vibrating powder feeder with a protective gas; charging a reaction chamber with a protective gas, hydrogen and a carbon source gas in sequence; after charging the reaction chamber with a protective gas, hydrogen and a carbon source gas in sequence, the following steps are further included: pre-treating the protective gas, hydrogen and carbon source gas, and adjusting the gas pressure of the reaction chamber to 3 .8~9psig; wherein the pretreatment includes adjusting the gas flow ratio of hydrogen, carbon source gas and protective gas to 400:16:4; using a high-energy beam to instantly vaporize the copper powder in the reaction chamber into copper vapor; performing gradient temperature control on the reaction chamber so that the copper vapor is first converted into a molten droplet state and then quickly realizes the in-situ coating growth of graphene on its surface, and then solidifies into graphene-coated copper powder; the steps of gradient temperature control include: controlling the temperature in sequence: 6000~11000℃, 2000~6000℃, 200~2000℃, 20~200℃; the high-energy beam is selected from any one of an ion beam, a laser beam and an electron beam; the carbon source gas is a gaseous hydrocarbon, and the protective gas is argon.

[0013] The preparation method of the high-strength and high-conductivity graphene copper composite wire provided by the present application uses graphene copper composite powder as the starting material. In the process of powder metallurgy densification and deformation, high temperature and high pressure and plastic deformation process realize the metallurgical bonding between the copper matrix, so that the graphene copper composite wire has good toughness, plasticity and deformation ability. The strong plastic deformation process causes the graphene to break up and further disperse in the copper matrix, avoiding the agglomeration of graphene in the matrix, which is conducive to the enhancement of the mechanical and electrical properties of the copper matrix by graphene, and at the same time realizes the improvement of the mechanical and electrical properties of the graphene copper composite material. DETAILED DESCRIPTION

[0014] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0015] The first aspect of the present invention relates to a method for preparing a high-strength and high-conductivity graphene copper composite wire, which comprises the following steps:

[0016] (1) placing graphene-copper composite powder in a graphite mold and preparing a graphene-copper composite block by vacuum hot pressing sintering or spark plasma sintering;

[0017] (2) subjecting the graphene-copper composite block obtained in step (1) to hot extrusion to prepare a graphene-copper composite rod;

[0018] (3) The graphene copper composite rod obtained in step (2) is subjected to cold drawing to prepare a graphene copper composite wire.

[0019] In some embodiments, in step (1), the sintering step performed by vacuum hot pressing sintering or spark plasma sintering includes a temperature rising stage and a temperature keeping stage.

[0020] In some embodiments, the equipment is evacuated before the heating stage to make the pressure of the vacuum chamber less than 10 Pa, and then the temperature is increased, and the vacuum state in the furnace is maintained during the heating and pressurization process. In some embodiments, the pressure in the heating stage is maintained at 10-20 MPa (here, the pressing pressure during hot pressing sintering or spark plasma sintering).

[0021] In some embodiments, the heating rate is 10-100°C / min until a target temperature of 600-1000°C is reached, preferably 700-950°C, more preferably 750-900°C, and most preferably 800-900°C.

[0022] In some embodiments, the pressure of the holding stage in the sintering step in step (1) is 20-60 MPa, the holding temperature is 600-1000°C, preferably 700-950°C, more preferably 750-900°C, most preferably 800-900°C, and the holding time is 5-120 min, preferably 10-60 min, more preferably 15-30 min.

[0023] In some embodiments, the hot extrusion in step (2) is reverse hot extrusion.

[0024] In this article, reverse hot extrusion means that the billet is fixed and the die moves. The advantage of reverse hot extrusion is that during the reverse extrusion process, the billet is fixed and the die moves, and the friction between the billet and the extrusion barrel is small, which is conducive to reducing the wear on the billet surface; the pressure applied by reverse extrusion is more evenly distributed, reducing or eliminating internal defects, and helping to obtain better microstructures and mechanical properties. Reverse extrusion has a more efficient manufacturing process and is conducive to improving production efficiency.

[0025] In some embodiments, in step (2), the hot extrusion temperature is 400-1000°C, preferably 600-950°C, more preferably 700-850°C, and most preferably about 800°C. In some embodiments, in step (2), the extrusion die insulation temperature is 200-800°C, preferably 300-650°C, more preferably 500-600°C. In some embodiments, in step (2), the extrusion ratio is 4-36, preferably 5-20, more preferably 7-15. In some embodiments, in step (2), the extrusion pressure is 10-100 MPa, and the extrusion speed is 0.2-4.0 m / min, preferably 1.0-2.0 m / min, and more preferably 1.2 m / min.

[0026] In some embodiments, in step (3), the drawing speed is 0.2-10 m / s, preferably 1-5 m / s, more preferably 1.5-3 m / s. In some embodiments, in step (3), the diameter of the graphene copper composite wire after drawing is 0.1-5 mm.

[0027] In some embodiments, the particle size of the graphene copper composite powder used in step (1) is 0.1-150 μm, preferably 0.1-100 μm, and more preferably 0.1-50 μm. In some embodiments, the sphericity of the graphene copper composite powder used in step (1) is greater than 95%, and / or the fluidity is less than 20s / 50g, and / or the bulk density is greater than 4g / cm3. In some embodiments, the carbon content of the graphene copper composite powder used in step (1) is 0.01-1wt.%. In some embodiments, the number of graphene layers of the graphene copper composite powder used in step (1) is less than 5 layers.

[0028] In some embodiments, step (3) further comprises the step of annealing under vacuum or inert atmosphere protection. In some embodiments, if the wire is difficult to continue to deform during the drawing process of step (3), annealing is performed under vacuum or inert atmosphere protection to eliminate internal stress and restore its deformation ability. In some embodiments, the annealing temperature is 100-600°C and the holding time is 0.5-12h.

[0029] In some embodiments of the present invention, the “graphene copper composite powder” used may be a graphene copper composite powder in the prior art, or a graphene copper composite powder obtained by any preparation method.

[0030] In some embodiments of the present invention, the "graphene copper composite powder" used is a graphene copper composite powder prepared by the method described in CN113231633A. More specifically, the graphene copper composite powder is prepared by the following method: a method for preparing graphene copper-based composite powder based on high-energy beam, placing copper powder in a vibrating powder feeder, and charging the vibrating powder feeder with a protective gas; charging the reaction chamber with a protective gas, hydrogen and a carbon source gas in sequence; after charging the reaction chamber with a protective gas, hydrogen and a carbon source gas in sequence, the following steps are also included: pre-treating the protective gas, hydrogen and carbon source gas, and adjusting the gas pressure of the reaction chamber to 3.8 to 9 psig; wherein the pre-treatment includes adjusting the gas flow ratio of hydrogen, carbon source gas and protective gas to 400:16:4; using a high-energy beam to instantly vaporize the copper powder in the reaction chamber into copper vapor; performing gradient temperature control on the reaction chamber so that the copper vapor is first transformed into a molten droplet state and then quickly realizes the in-situ coating growth of graphene on its surface, and then solidifies into graphene-coated copper powder; the steps of gradient temperature control include: controlling the temperature in sequence: 6000-11000°C, 2000-6000°C, 200-2000°C, 20-200°C; the high-energy beam is selected from any one of an ion beam, a laser beam and an electron beam; the carbon source gas is a gaseous hydrocarbon, and the protective gas is argon.

[0031] The second aspect of the present invention relates to a graphene copper composite wire prepared by the method described in the first aspect of the present invention.

[0032] Example

[0033] Example 1

[0034] In this embodiment, the graphene copper composite wire is prepared by the following method:

[0035] (1) Graphene copper composite powder was prepared by the method described in Example 1 of CN113231633A:

[0036] In the first step, copper powder with a purity of 99.9% and a particle size of 400 mesh (38 μm) was loaded into a vibrating powder feeder, the cooling water of the equipment was turned on, all impurity gases in the device were discharged through the gas purification system, and inert protective atmosphere argon gas was filled at the same time, and the flow rate of argon gas was controlled to be 17 slpm;

[0037] The second step is to wait until the system self-checks that there is no vacuum leakage and the air and other impurities in the reaction chamber are exhausted, then turn off the argon gas and turn on the vacuum pump;

[0038] The third step is to adjust the vibration frequency to 117 Hz and the vibration amplitude to 68.5 μm through the powder feeding controller to control the actual powder feeding rate of the copper powder to 7.5 g / min in this state;

[0039] Step 4: Turn on the argon gas source and adjust the carrier gas pressure regulating valve to 60 mm (5 slpm), the reaction gas pressure regulating valve to 40 mm (10 slpm), and the argon pressure regulating valve to 70 mm (25 slpm), and manually set the pressure in the reaction chamber to 3.80 psig.

[0040] Step 5: Switch to high frequency mode, increase the voltage to 4V, and after the actual current stabilizes to 2.2A, increase the pressure in the reaction chamber to 7.0psig while stabilizing the actual current value.

[0041] Step 6: Open the methane gas source and adjust the methane pressure regulating valve to 6 mm (0.4 slpm). When the actual power and the gas pressure in the reaction chamber are stable, the flame temperature tends to be stable, and powder feeding begins at the constant powder feeding rate set previously.

[0042] Step 7. After the powder feeding is completed, turn off the high frequency mode, turn off all gas sources, and the system will automatically shut down. The temperature will be controlled in sequence: 6000-11000℃, 2000-6000℃, 200-2000℃, 20-200℃,

[0043] After the entire device is cooled to room temperature, the graphene copper-based composite powder with larger particle size in the collection tank is taken out, and the graphene copper-based composite powder with smaller particle size adhering to the wall of the reaction chamber is collected through the spiral powder scraping device added inside the reactor.

[0044] (2) placing the graphene copper composite powder with a particle size of 0.1-50 μm in a vacuum drying oven for drying at a vacuum degree of less than 10 Pa and a temperature of 60° C. for 6 hours to remove the water vapor adsorbed in the powder;

[0045] Cut round and square graphite papers and place them inside the graphite mold to protect the graphite mold and facilitate sample demoulding after sintering. The inner diameter of the mold is 30 mm.

[0046] According to the predetermined mass of the sintered block, 320g of graphene copper composite powder was weighed, and the dried graphene copper composite powder was evenly loaded into the mold and vibrated to avoid stratification and uneven distribution of the powder. After filling the powder, the powder was pre-pressed to preliminarily compact the powder to remove air bubbles and preliminarily increase the density of the powder. The pre-pressing pressure was 20 MPa. The mold filled with powder was placed in a vacuum hot pressing sintering furnace, the furnace door was closed and the vacuum pump was started to extract the gas in the furnace. After reaching below 10Pa, the heating program was started. The vacuum state in the furnace was maintained during the heating and pressurizing process to prevent oxygen and other gases from entering and avoid oxidation of the material. The heating system was started and the temperature in the furnace was gradually increased at a heating rate of 10℃ / min. After reaching the sintering temperature of 900℃, pressurization was performed with a pressure of 40 MPa and a pressurization time of 1min. After the sintering pressure and temperature reached the predetermined value, the heat was kept for 20min to achieve the densification of the graphene copper composite material. After cooling to below 100℃, the furnace door was inflated and the furnace door was opened.

[0047] (3) The sintered graphene copper composite block is rough-turned to remove the graphite paper adhered to the surface during the sintering process. The graphene copper composite block is placed in a heating furnace protected by an argon atmosphere, the heating temperature is 700℃, and the temperature is kept for more than 20 minutes to keep the internal temperature of the material uniform. The reverse hot extrusion process is adopted. Its advantages are: 1. During the reverse extrusion process, the billet is fixed, while the die moves, and the friction between the billet and the extrusion barrel is small, which is beneficial to reduce the wear of the billet surface; 2. The pressure applied by reverse extrusion is more evenly distributed, reducing or eliminating internal defects, which helps to obtain better microstructure and mechanical properties; 3. Reverse extrusion has a more efficient manufacturing process, which is beneficial to improve production efficiency. The extrusion die is heated to 300℃ and then hot extruded. Graphite lubricant is applied to the inside of the die and the extrusion head. The heated graphene copper composite block is placed in the extrusion barrel, the die extrusion ratio is 9, the extruder is started for hot extrusion, and the extrusion speed is 1.2 m / min to obtain a graphene copper composite rod with a diameter of 10 mm.

[0048] (4) Use a grinder and a polishing wheel to grind and remove the oxide layer on the surface of the extruded graphene copper composite rod. In order to reduce the friction between the raw material and the mold, lubricating oil is applied to the drawing die and the rod. Use a grinder to grind one end of the rod so that one end of the rod partially passes through the drawing die and is installed on the drawing machine. Cold drawing is performed at room temperature at a drawing speed of 2m / s. After multiple drawing, the desired diameter is reached, and finally a graphene copper composite wire with a diameter of 1 mm is obtained.

[0049] (5) The tensile strength of the graphene copper composite wire with a diameter of 1 mm was tested using a universal tensile machine. The wire remained straight without obvious bending. Its length was 100 mm, the gauge length was 60 mm, and the tensile rate was 1 mm / min. The average value was taken after 3 tests. The tensile strength was 512 MPa. The resistance of the graphene copper composite wire with a diameter of 1 mm was tested using a digital DC resistance tester. The length was 150 mm, and the conductivity was converted based on the length and cross-sectional area. The average value was taken after 5 tests. The test result was 105.7% IACS.

[0050] Example 2

[0051] In this embodiment, the graphene copper composite wire is prepared by the following method:

[0052] (1) The method for preparing the graphene copper composite powder is the same as step (1) of Example 1 above, and will not be repeated here.

[0053] (2) placing the graphene copper composite powder with a particle size of 0.1-50 μm in a vacuum drying oven for drying at a vacuum degree of less than 10 Pa and a temperature of 60° C. for 6 hours to remove the water vapor adsorbed in the powder;

[0054] Cut round and square graphite papers and place them inside the graphite mold to protect the graphite mold and facilitate sample demoulding after sintering. The inner diameter of the mold is 30 mm.

[0055] According to the predetermined mass of the sintered block, 320g of graphene copper composite powder was weighed, and the dried graphene copper composite powder was evenly loaded into the mold and vibrated to avoid stratification and uneven distribution of the powder. After filling the powder, the powder was pre-pressed to preliminarily compact the powder to remove air bubbles and preliminarily increase the density of the powder. The pre-pressing pressure was 30 MPa. The mold filled with powder was placed in a spark plasma sintering furnace, the furnace door was closed and the vacuum pump was started to extract the gas in the furnace. After reaching below 10Pa, the heating program was started. The vacuum state in the furnace was maintained during the heating and pressurizing process to prevent oxygen and other gases from entering and avoid oxidation of the material. The heating system was started and the temperature in the furnace was gradually increased at a heating rate of 100℃ / min. After reaching the sintering temperature of 800℃, pressurization was performed with a pressure of 60 MPa and a pressurization time of 1min. After the sintering pressure and temperature reached the predetermined value, the heat was kept for 10 min to achieve the densification of the graphene copper composite material. After cooling to below 100℃, the furnace door was inflated and the furnace door was opened.

[0056] (3) Rough turning the sintered graphene copper composite block to remove the graphite paper adhered to the surface during the sintering process. Place the graphene copper composite block in a heating furnace protected by an argon atmosphere, heat it to 700 °C, and keep it warm for more than 20 min to keep the internal temperature of the material uniform. Heat the extrusion die to 300 °C and perform hot extrusion. Apply graphite lubricant inside the die and on the extrusion head. Put the heated graphene copper composite block into the extrusion barrel, set the die extrusion ratio to 9, start the extruder for hot extrusion, and the extrusion speed to 1.2 m / min to obtain a graphene copper composite rod with a diameter of 10 mm.

[0057] (4) Use a grinding wheel and a polishing wheel to grind and remove the oxide layer on the surface of the extruded graphene copper composite rod. In order to reduce the friction between the raw material and the mold, lubricating oil is applied to the drawing die and the rod. Use a grinding wheel to grind one end of the rod so that one end of the rod partially passes through the drawing die and is installed on the drawing machine. Cold drawing is performed at a drawing speed of 2m / s to obtain a graphene copper composite wire with a diameter of 1mm.

[0058] (5) After strong plastic deformation, the toughness and plasticity of the composite wire decreased and it was difficult to continue to deform. Therefore, the graphene copper composite wire was annealed. To avoid oxidation of the wire, it was annealed under argon atmosphere protection at a temperature of 400 ° C and a holding time of 60 min. The composite wire treated with stress relief annealing was further drawn to obtain a graphene copper composite wire with a diameter of 0.1 mm.

[0059] (5) The tensile strength of the graphene copper composite wire with a diameter of 1 mm was tested using a universal tensile machine. The wire remained straight without obvious bending. Its length was 100 mm, the gauge length was 60 mm, the tensile rate was 1 mm / min, and the average value was taken after 3 tests. The tensile strength was 546 MPa. The resistance of the graphene copper composite wire with a diameter of 1 mm was tested using a digital DC resistance tester. Its length was 150 mm, and the conductivity was converted based on the length and cross-sectional area. The average value was taken after 5 tests, and the test result was 105.2%IACS.

Claims

1. A method for preparing a high-strength and high-conductivity graphene copper composite wire, comprising the following steps: (1) placing graphene copper composite powder as a starting material in a graphite mold, and preparing a graphene copper composite block by vacuum hot pressing sintering or spark plasma sintering; (2) subjecting the graphene-copper composite block obtained in step (1) to hot extrusion to prepare a graphene-copper composite rod; (3) The graphene copper composite rod obtained in step (2) is subjected to cold drawing to prepare a graphene copper composite wire.

2. The method according to claim 1, characterized in that: In the step (1), the sintering step by vacuum hot pressing sintering or spark plasma sintering includes a heating stage and a heat preservation stage. Before the heating stage, the vacuum chamber is evacuated to a pressure of less than 10 Pa, and then the temperature is increased, and the vacuum state in the furnace is maintained during the heating and pressurizing process, and the heating rate is 10-100°C / min until the target temperature of 600-1000°C is reached, preferably 700-900°C, and most preferably 750-850°C; and The pressure in the insulation stage is 20-60 MPa, the insulation temperature is the target temperature reached in the heating stage, and the insulation time is 5-120 min.

3. The method according to claim 1 or 2, characterized in that: The hot extrusion in step (2) is reverse hot extrusion.

4. The method according to any one of claims 1 to 3, characterized in that: In the step (2), the hot extrusion temperature is 400-1000°C, preferably 600-950°C, more preferably 700-850°C, and most preferably about 800°C.

5. The method according to any one of claims 1 to 4, characterized in that: In the step (2), the extrusion ratio of hot extrusion is 4-36, the extrusion pressure is 10-100 MPa, and the extrusion speed is 0.2-4.0 m / min, preferably 1.0-2.0 m / min, and more preferably 1.2 m / min.

6. The method according to any one of claims 1 to 5, characterized in that: In the step (3), the drawing speed is 0.2-10 m / s, and the diameter of the graphene copper composite wire after drawing is 0.1-5 mm.

7. The method according to any one of claims 1 to 6, characterized in that: The particle size of the graphene copper composite powder is 0.1-150 μm.

8. The method according to any one of claims 1 to 7, characterized in that: Step (3) also includes the step of performing annealing treatment under vacuum or inert atmosphere protection.

9. The method according to claim 8, wherein the annealing temperature is 100-600°C and the holding time is 0.5-12h.

10. A graphene copper composite wire prepared by the method according to any one of claims 1 to 9.