A method for preparing a graphene-reinforced aluminum oxide dispersion copper composite

Abstract

The application belongs to the technical field of metal matrix composite material preparation, and particularly relates to a preparation method of graphene reinforced aluminum oxide dispersed copper composite material. The method comprises the following steps: taking copper aluminum and cuprous oxide as raw materials, ball-milling and mixing to obtain a mixture, carrying out internal oxidation treatment on the mixture under a vacuum atmosphere, and crushing to obtain aluminum oxide reinforced dispersed copper; mixing the aluminum oxide reinforced dispersed copper and a nano-oxidized graphene dispersion solution, carrying out stirring and ultrasonic treatment, and freeze-drying to obtain aluminum oxide dispersed copper-nano-oxidized graphene powder; and carrying out forming, hydrogen reduction sintering and hot extrusion deformation on the aluminum oxide dispersed copper-nano-oxidized graphene powder to obtain the graphene reinforced aluminum oxide dispersed copper composite material. The application can effectively introduce graphene into the aluminum oxide dispersed copper uniformly, can increase the electrical conductivity of the material while improving the strength, has high controllability, low production cost, simple equipment, a more simplified process flow, is environment-friendly in the process, and is suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite material preparation technology, specifically relating to a method for preparing a graphene-reinforced alumina-dispersed copper composite material. Background Technology

[0002] With the rapid development of new energy vehicles, rail transportation, aerospace, and nuclear fusion, the demand for high-strength, high-conductivity, and high-temperature resistant materials is increasing. The uniform distribution of nano-ceramic particles in metals can play a role in dispersion strengthening, pinning dislocations, grain boundaries, and subgrain boundaries to improve the material's strength. Alumina dispersion-strengthened copper (ODS copper), as a high-performance composite material, significantly improves the strength and high-temperature resistance of materials while maintaining the electrical conductivity of pure copper, and is widely used in the field of high-strength, high-conductivity materials.

[0003] While traditional alumina-dispersion-reinforced copper employs hydrogen reduction during preparation to remove cuprous oxide generated during internal oxidation and prevent it from lowering the material's conductivity, the low conductivity of alumina particles themselves still affects the material's overall conductivity. Typically, alumina-dispersion-reinforced copper with a high particle content exhibits a conductivity of approximately 70%–80% IACS. This limits the material's application in scenarios requiring high conductivity, such as electrified railway conductors, automotive resistance welding electrodes, and electromagnetic railgun rails.

[0004] Graphene, a two-dimensional hexagonal lattice structure consisting of a single layer of tightly packed carbon atoms, possesses excellent properties such as high strength, high electrical conductivity, and high thermal conductivity. Therefore, graphene has been extensively studied as a reinforcing agent in composite materials. However, graphene's small size, high surface energy, and tendency to aggregate, coupled with its hydrophobic nature, make it difficult to disperse in aqueous solutions, often requiring specific organic solvents. Therefore, the uniform introduction of graphene into metals has been a persistent challenge in the field of composite materials.

[0005] Several scholars have conducted research on the introduction of graphene into copper or dispersed copper. Chinese patent CN106521208 A discloses a method for preparing copper-graphene composite materials, which involves mixing and ball-milling graphene dispersion, copper powder, and polyacrylamide gel to obtain copper-graphene powder, followed by drying, cold pressing, and sintering to obtain the copper-graphene composite material. Chinese patent CN 110484803 A discloses a mixed dispersion reinforced copper-tungsten-chromium electrical contact material and its preparation method, which discloses a chemical precipitation method to disperse graphene, aluminum nitrate, and copper salt in a solution for precipitation, resulting in a graphene-ODS copper mixed powder. This powder is then densified through drying, reduction, sintering, and hot rolling to prepare graphene-reinforced ODS copper.

[0006] Although the above methods can all prepare graphene-reinforced copper or dispersed copper composite materials, ball milling can damage the structure of graphene, or chemical methods and special configuration preforms have poor electrical conductivity, complex processes and high costs, which are not conducive to industrial production. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing graphene-reinforced alumina-dispersed copper composite material. This method effectively and uniformly introduces graphene into alumina-dispersed copper, increasing both strength and electrical conductivity. The method offers high controllability, low production cost, simple equipment, a simplified process flow, and is environmentally friendly, making it suitable for industrial production.

[0008] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0009] The purpose of this invention is to provide a method for preparing graphene-reinforced alumina-dispersed copper composite material, comprising the following steps: S1. Using copper, aluminum, and cuprous oxide as raw materials, ball milling is performed to obtain a mixture. The mixture is then subjected to internal oxidation treatment under a vacuum atmosphere and crushed to obtain alumina-reinforced dispersed copper.

[0010] S2. Mix the alumina-reinforced dispersed copper and nano-graphene oxide dispersion, stir and sonicate, and then freeze-dry to prevent graphene oxide from settling, to obtain alumina-reinforced dispersed copper-nano-graphene oxide powder.

[0011] S3. The alumina-dispersed copper-nano graphene oxide powder is sequentially shaped, hydrogen-reduced sintered, and hot-extruded to obtain a graphene-reinforced alumina-dispersed copper composite material.

[0012] Furthermore, the amount of cuprous oxide used is 4.5 wt.% to 6.5 wt.% of the mass of the mixture, the aluminum content in the copper-aluminum mixture is 0.2 wt.% to 0.8 wt.%, the particle size of cuprous oxide is 1 μm to 10 μm, and the particle size of cuprous oxide is 50 μm to 100 μm.

[0013] Furthermore, the internal oxidation treatment temperature is 850℃~1000℃, and the vacuum degree is 1×10⁻⁶. -2 MPa ~ 1×10 - 3 MPa, time 1h to 3h, after internal oxidation treatment, cool down to below 70℃, purge with argon and take out of the furnace; crushing is carried out by vacuum crushing, crushing time 5min to 15min, and take out after cooling for 30min to 60min.

[0014] Furthermore, the mass ratio of the nano-graphene oxide dispersion to the alumina-reinforced dispersed copper is 3–5:15, and the concentration of the nano-graphene oxide dispersion is 1 g / L–30 g / L.

[0015] Furthermore, during the ultrasonic treatment with stirring, the ultrasonic frequency is 15KHz~30KHz and the time is 20min~60min; during the freeze-drying process, the freezing temperature is -10℃~-30℃, the cold trap temperature is -50℃~-60℃, and the time is 8h~14h.

[0016] Furthermore, the nano-graphene oxide dispersion is obtained by placing nano-graphene oxide powder in a liquid medium and then ultrasonically dispersing it. The ultrasonic dispersion frequency is 15KHz to 30KHz, and the time is 15min to 60min. The liquid medium is at least one of anhydrous ethanol and deionized water.

[0017] Furthermore, the forming process first involves cold isostatic pressing pre-forming at a pressure of 200MPa to 400MPa, a pressurization rate of 7MPa / min to 18MPa / min, and a holding time of 5min to 15min.

[0018] Furthermore, hydrogen reduction sintering is carried out in a hydrogen atmosphere, first by raising the temperature to 300℃ to 600℃ at a rate of 2℃ / min to 10℃ / min and holding for 40min to 60min, then by raising the temperature to 900℃ to 1050℃ at a rate of 2℃ / min to 10℃ / min and holding for 60min to 200min.

[0019] Furthermore, the temperature for hot extrusion deformation is 800℃~1000℃, the time is 30min~90min, and the extrusion ratio is 10~25.

[0020] Furthermore, during the ball milling process, the ball-to-material ratio is 2-4:1, the milling time is 4-8 hours, the rotation speed is 50-120 rpm, and the milling is stopped for 20-40 minutes after every 20-40 minutes to cool down.

[0021] Compared with the prior art, the present invention has the following advantages: (0) The preparation method provided by this invention adopts a step-by-step approach to the introduction of graphene and the internal oxidation process: first, CuAl powder is internally oxidized to prepare alumina-dispersed copper powder, then graphene oxide is added, and the graphene oxide is reduced to graphene through a subsequent hydrogen reduction sintering process. Adding graphene before internal oxidation is avoided, as the presence of an oxidizing atmosphere during the subsequent high-temperature internal oxidation process will not only damage the graphene structure but also affect the internal oxidation effect of the CuAl alloy itself. The step-by-step approach to the introduction of graphene and the internal oxidation process provides high process controllability and simple operation. The introduction of graphene can enhance the comprehensive performance of alumina-dispersed copper, increasing the strength and electrical conductivity of the material. Furthermore, this method allows for precise control of the alumina content and morphology, while flexibly adjusting the amount of graphene added. Compared to chemical methods, the process is simpler and more environmentally friendly.

[0022] This invention employs high-energy ultrasonic technology to disperse graphene oxide, significantly improving its distribution uniformity within the system. Due to its large specific surface area and high surface energy, graphene is highly prone to agglomeration. Conventional ball milling methods not only struggle to achieve effective graphene dispersion but also cause structural damage due to prolonged ball impact, thus affecting the final material properties. In contrast, graphene oxide exhibits superior dispersibility in water or organic solvents. Combined with the cavitation effect generated by high-energy ultrasound, a uniform and stable dispersion can be efficiently prepared. Further freeze-drying effectively prevents graphene oxide sedimentation, resulting in a uniformly dispersed powder material. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the overall process flow of the graphene-reinforced alumina-dispersed copper composite material of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0026] Existing technologies improve the performance of graphene-reinforced copper or dispersed copper composites by uniformly introducing graphene into metals. For example, Chinese patent CN 106521208 A involves ball milling a mixture of graphene dispersion, copper powder, and polyacrylamide gel to obtain copper-graphene powder, followed by drying, cold pressing, and sintering to obtain a copper-graphene composite material. Chinese patent CN 109280797 A prepares a graphene suspension, places porous foamed copper in the suspension for shaking and drying, and then prepares a graphene-copper composite material through plasma discharge sintering. Chinese patent CN 110484803 A uses a chemical precipitation method to disperse graphene, aluminum nitrate, and copper salt in a solution for precipitation, obtaining a graphene-ODS copper mixed powder, which is then densified through drying, reduction, sintering, and hot rolling to prepare graphene-reinforced ODS copper.

[0027] Although the above methods can all prepare graphene-reinforced copper or dispersed copper composite materials, either ball milling will damage the structure of graphene, or chemical methods or special configuration preforms are used, resulting in poor electrical conductivity, which is not conducive to industrial production, and efficiency and cost control need to be improved.

[0028] Based on this, the present invention aims to provide a method for preparing graphene-reinforced alumina dispersion-strengthened copper with low production cost, simple equipment, and simple process, which can effectively disperse graphene and the resulting material has excellent comprehensive performance. Specifically:

[0029] A method for preparing a graphene-reinforced alumina-dispersed copper composite material includes the following steps: S1. Using copper, aluminum, and cuprous oxide as raw materials, ball milling is performed to obtain a mixture. The mixture is then subjected to internal oxidation treatment under a vacuum atmosphere and crushed to obtain alumina-reinforced dispersed copper.

[0030] In this invention, uniform mixing is achieved by mechanical ball milling. During the ball milling process, the ball-to-material ratio is 2 to 4:1, the milling time is 4 to 8 hours, the rotation speed is 50 to 120 rpm, and the ball milling is stopped for 20 to 40 minutes every 20 to 40 minutes to cool down. Temperature control is used to avoid frictional heat generated during ball milling, and to prevent powder from overheating and agglomerating or causing runaway reactions.

[0031] In this invention, the amount of cuprous oxide is 4.5 wt.% to 6.5 wt.% of the mass of the mixture, the aluminum content in the copper-aluminum mixture is 0.2 wt.% to 0.8 wt.%, the particle size of cuprous oxide is 1 μm to 10 μm, and the particle size of cuprous oxide is 50 μm to 100 μm.

[0032] In this invention, an internal oxidation method is first employed, using cuprous oxide as an internal oxygen source to selectively oxidize the aluminum element in the copper-aluminum alloy at high temperature, thereby generating alumina particles in situ within the copper matrix. The internal oxidation treatment temperature is 850℃~1000℃, and the vacuum degree is 1×10⁻⁶. -2 MPa ~ 1×10 -3 The oxidation process is carried out at a pressure of MPa for 1 to 3 hours. After cooling to below 70°C, the furnace is purged with argon gas and then removed from the furnace. Vacuum crushing is used for 5 to 15 minutes, followed by cooling for 30 to 60 minutes before removal. Vacuum crushing breaks up the agglomerates formed during the internal oxidation process, resulting in a uniform composite powder.

[0033] S2. Mix the alumina-reinforced dispersed copper and nano-graphene oxide dispersion, stir and sonicate, and then freeze-dry to prevent graphene oxide from settling, to obtain alumina-reinforced dispersed copper-nano-graphene oxide powder.

[0034] In this invention, the nano-graphene oxide dispersion is obtained by ultrasonically dispersing nano-graphene oxide powder in a liquid medium. The graphene oxide has a diameter of 5 μm to 20 μm and a thickness of 1 nm to 10 nm. The ultrasonic dispersion frequency is 15 kHz to 30 kHz, and the time is 15 min to 60 min. The liquid medium is at least one of anhydrous ethanol and deionized water. Due to its large specific surface area and high surface energy, graphene is prone to agglomeration. Conventional ball milling methods not only fail to achieve effective dispersion of graphene but also cause structural damage due to prolonged ball impact, thus affecting the final material properties. In contrast, graphene oxide exhibits superior dispersibility in water or organic solvents. Combined with the cavitation effect generated by high-energy ultrasound, the dispersion of graphene oxide significantly improves its distribution uniformity in the system, efficiently preparing a uniform and stable dispersion.

[0035] In this invention, uniform and stable adsorption and coating of nano-graphene oxide on the surface of metal composite powder is achieved through physical field-assisted liquid-solid mixing via stirring and ultrasonic treatment. During the stirring and ultrasonic treatment, the ultrasonic frequency is 15 kHz to 30 kHz, the time is 20 min to 60 min, and the stirring speed is 80 rpm to 200 rpm. After stirring and ultrasonic treatment, a small amount of clear liquid is aspirated from the top, resulting in a uniformly dispersed alumina-copper-nano-graphene oxide suspension.

[0036] In this invention, freeze-drying is used to effectively prevent graphene oxide from settling, thereby obtaining a uniformly dispersed powder material. The freezing temperature is -10℃ to -30℃, the cold trap temperature is -50℃ to -60℃, and the time is 8h to 14h.

[0037] In this invention, the mass ratio of nano-graphene oxide dispersion to alumina-reinforced dispersed copper is 3-5:15, and the concentration of nano-graphene oxide dispersion is 1 g / L to 30 g / L.

[0038] S3. The alumina-dispersed copper-nano graphene oxide powder is sequentially shaped, hydrogen-reduced sintered, and hot-extruded to obtain a graphene-reinforced alumina-dispersed copper composite material.

[0039] In this invention, the forming process involves placing alumina-dispersed copper-nano graphene oxide powder in a cold isostatic pressing sleeve, typically a round or square sleeve, and pressing it into a rod or slab. The powder is first compacted and sealed before being placed in a cold isostatic pressing cylinder for pressing. The pressure is 200 MPa to 400 MPa, the pressurization rate is 7 MPa / min to 18 MPa / min, and the holding time is 5 min to 15 min.

[0040] In this invention, hydrogen reduction sintering reduces graphene oxide to graphene, which can effectively and uniformly introduce graphene into copper dispersed in alumina. Hydrogen reduction sintering is carried out in a hydrogen atmosphere. First, the temperature is raised to 300℃ to 600℃ at a rate of 2℃ / min to 10℃ / min and held for 40min to 60min. Then, the temperature is raised to 900℃ to 1050℃ at a rate of 2℃ / min to 10℃ / min and held for 60min to 200min. Finally, the temperature is cooled to room temperature with the furnace and removed.

[0041] In this invention, the temperature of hot extrusion deformation is 800℃~1000℃, the time is 30min~90min, the extrusion ratio is 10~25, the hot extrusion deformation involves heating the surface coated with an anti-oxidation coating, and the surface is straightened and then air-cooled after hot extrusion deformation.

[0042] In summary, this invention employs a step-by-step approach to introduce graphene and perform internal oxidation: first, CuAl powder is internally oxidized to prepare alumina-dispersed copper powder; then, graphene oxide is added, and subsequently reduced to graphene through a hydrogen reduction sintering process. Adding graphene before internal oxidation avoids damage to the graphene structure and negatively impacts the internal oxidation effect of the CuAl alloy during the subsequent high-temperature internal oxidation process due to the oxidizing atmosphere. This step-by-step approach to graphene introduction and internal oxidation offers high process controllability and ease of operation. The introduction of graphene enhances the overall performance of alumina-dispersed copper, increasing both strength and electrical conductivity. Furthermore, this method allows for precise control of the alumina content and morphology, while flexibly adjusting the amount of graphene added. Compared to chemical methods, the process is simpler and more environmentally friendly.

[0043] The following specific examples will provide further explanation.

[0044] Example 1 A method for preparing graphene-reinforced alumina-dispersed copper rods, such as... Figure 1 As shown, it includes the following steps: Weigh out CuAl powder with an average particle size of 50 μm and an Al content of 0.6 wt.%; weigh out Cu2O powder with an average particle size of 5 μm; and weigh out graphene oxide with a diameter of 5 μm to 10 μm to prepare nano-graphene-reinforced alumina-dispersed copper with a graphene content of 0.2 wt.% and an alumina content of 1.1 wt.%.

[0045] S1. Place CuAl powder and Cu2O powder into a ball mill jar according to the above ratio and ball-to-powder ratio of 2:1. The speed is 80 rpm. Stop the mill for 30 minutes after every 30 minutes of ball milling and cool down. The mixing time is 6 hours to obtain CuAl and Cu2O mixed powder.

[0046] S2. Place the mixed powder into a corundum crucible and place it in a vacuum furnace for internal oxidation treatment. The internal oxidation vacuum degree is 6×10⁻⁶. -3 The oxidation process was carried out at a pressure of MPa and a temperature of 950℃ for 2 hours. After the internal oxidation was completed, the furnace was cooled to below 70℃, argon gas was introduced, and the powder was removed from the furnace. The agglomerated powder was then crushed into fine powder using a grinder for 5 minutes. After cooling for 30 minutes, the powder was removed to obtain alumina-reinforced dispersed copper powder.

[0047] S3. Take 1g of graphene oxide and add it to 150mL of deionized water. Place it in an ultrasonic dispersion device for dispersion. The dispersion time is 30min and the ultrasonic power frequency is 20KHz to obtain graphene oxide dispersion.

[0048] S4. Add 300g of alumina-reinforced dispersed copper powder to 150mL of graphene oxide aqueous dispersion and magnetically stir at 120rpm for 30min. Simultaneously, insert an ultrasonic probe for dispersion at a frequency of 20kHz. After mixing, remove a small amount of supernatant to obtain a uniformly dispersed alumina-dispersed copper-nano graphene oxide suspension. Place the alumina-dispersed copper-nano graphene oxide suspension in a freeze dryer at -20℃ and -60℃ for 24h. This yields a mixed powder of alumina-dispersed copper-nano graphene oxide.

[0049] S5. The alumina-dispersed copper-nano graphene oxide mixed powder is loaded into a mold with a diameter of [diameter value], vibrated, and then subjected to cold isostatic pressing treatment at a pressure of 230 MPa, a pressurization rate of 10 MPa / min, and a holding time of 3 min to obtain a powder blank.

[0050] S6. The obtained powder blank is placed into a vacuum furnace for hydrogen reduction sintering. The heating rate is 5℃ / min to 400℃ and held for 40min. Then the temperature is increased to 950℃ at 10℃ / min and held for 2h. After the holding period, the blank is cooled with the furnace to obtain nano-graphene reinforced alumina dispersed copper rod.

[0051] S7. The nano-graphene-reinforced alumina dispersed copper rod is hot-extruded and deformed. Before entering the furnace, an anti-oxidation coating is brushed on the surface. The furnace temperature is 950℃, the holding time is 60min, and the extrusion ratio is 12.25 to obtain a graphene-reinforced alumina dispersed copper rod with a rod diameter of 10mm.

[0052] Example 2 A method for preparing graphene-reinforced alumina-dispersed copper rods, such as... Figure 1 As shown, it includes the following steps: Weigh out CuAl powder with an average particle size of 50 μm and an Al content of 0.6 wt.%; weigh out Cu2O powder with an average particle size of 5 μm; and weigh out graphene oxide with a diameter of 5 μm to 10 μm to prepare nano-graphene-reinforced alumina-dispersed copper with a graphene content of 0.4 wt.% and an alumina content of 1.1 wt.%.

[0053] S1. Place CuAl powder and Cu2O powder into a ball mill jar according to the above ratio and ball-to-powder ratio of 2:1. The speed is 80 rpm. Stop the mill for 30 minutes after every 30 minutes of ball milling and cool down. The mixing time is 6 hours to obtain CuAl and Cu2O mixed powder.

[0054] S2. Place the mixed powder into a corundum crucible and place it in a vacuum furnace for internal oxidation treatment. The internal oxidation vacuum degree is 6×10⁻⁶. -3 The oxidation process was carried out at a pressure of MPa and a temperature of 950℃ for 2 hours. After the internal oxidation was completed, the furnace was cooled to below 70℃, argon gas was introduced, and the powder was removed from the furnace. The agglomerated powder was then crushed into fine powder using a grinder for 5 minutes. After cooling for 30 minutes, the powder was removed to obtain alumina-reinforced dispersed copper powder.

[0055] S3. Take 2g of graphene oxide and add it to 150mL of deionized water. Place it in an ultrasonic dispersion device for dispersion. The dispersion time is 30min and the ultrasonic power frequency is 20KHz to obtain graphene oxide dispersion.

[0056] S4. Add 300g of alumina-reinforced dispersed copper powder to 150mL of graphene oxide aqueous dispersion and magnetically stir at 120rpm for 30min. Simultaneously, insert an ultrasonic probe for dispersion at a frequency of 20kHz. After mixing, remove a small amount of supernatant to obtain a uniformly dispersed alumina-dispersed copper-nano graphene oxide suspension. Place the alumina-dispersed copper-nano graphene oxide suspension in a freeze dryer at -20℃ and -60℃ for 24h. This yields a mixed powder of alumina-dispersed copper-nano graphene oxide.

[0057] S5. The alumina-dispersed copper-nano graphene oxide mixed powder is loaded into a mold with a diameter of [diameter value], vibrated, and then subjected to cold isostatic pressing treatment at a pressure of 230 MPa, a pressurization rate of 10 MPa / min, and a holding time of 3 min to obtain a powder blank.

[0058] S6. The obtained powder blank is placed into a vacuum furnace for hydrogen reduction sintering. The heating rate is 5℃ / min to 400℃ and held for 40min. Then the temperature is increased to 950℃ at 10℃ / min and held for 2h. After the holding period, the blank is cooled with the furnace to obtain nano-graphene reinforced alumina dispersed copper rod.

[0059] S7. The nano-graphene-reinforced alumina dispersed copper rod is hot-extruded and deformed. Before entering the furnace, an anti-oxidation coating is brushed on the surface. The furnace temperature is 950℃, the holding time is 60min, and the extrusion ratio is 12.25 to obtain a graphene-reinforced alumina dispersed copper rod with a rod diameter of 10mm.

[0060] Example 3 A method for preparing graphene-reinforced alumina-dispersed copper rods, such as... Figure 1 As shown, it includes the following steps: Weigh CuAl powder with an average particle size of 50 μm and an Al content of 0.6 wt.%; weigh Cu2O powder with an average particle size of 5 μm; and weigh graphene oxide with a diameter of 5 μm to 10 μm to prepare nano-graphene-reinforced alumina-dispersed copper with a graphene content of 0.6 wt.% and an alumina content of 1.1 wt.%.

[0061] S1. Place CuAl powder and Cu2O powder into a ball mill jar according to the above ratio and ball-to-powder ratio of 2:1. The speed is 80 rpm. After each 30 min of ball milling, stop for 30 min and allow the mixture to cool down for 6 h to obtain CuAl and Cu2O mixed powder.

[0062] S2. Place the mixed powder into a corundum crucible and place it in a vacuum furnace for internal oxidation treatment. The internal oxidation vacuum degree is 6×10⁻⁶. -3The oxidation process was carried out at a pressure of MPa and a temperature of 950℃ for 2 hours. After the internal oxidation was completed, the furnace was cooled to below 70℃, argon gas was introduced, and the powder was removed from the furnace. The agglomerated powder was then crushed into fine powder using a grinder for 5 minutes. After cooling for 30 minutes, the powder was removed to obtain alumina-reinforced dispersed copper powder.

[0063] S3. Take 3g of graphene oxide and add it to 150mL of deionized water. Place it in an ultrasonic dispersion device for dispersion. The dispersion time is 30min and the ultrasonic power frequency is 20KHz to obtain graphene oxide dispersion.

[0064] S4. Add 300g of alumina-reinforced dispersed copper powder to 150mL of graphene oxide aqueous dispersion and magnetically stir at 120rpm for 30min. Simultaneously, insert an ultrasonic probe for dispersion at a frequency of 20kHz. After mixing, remove a small amount of supernatant to obtain a uniformly dispersed alumina-dispersed copper-nano graphene oxide suspension. Place the alumina-dispersed copper-nano graphene oxide suspension in a freeze dryer at -20℃ and -60℃ for 24h. This yields a mixed powder of alumina-dispersed copper-nano graphene oxide.

[0065] S5. The alumina-dispersed copper-nano graphene oxide mixed powder is loaded into a mold with a diameter of [diameter value], vibrated, and then subjected to cold isostatic pressing treatment at a pressure of 230 MPa, a pressurization rate of 10 MPa / min, and a holding time of 3 min to obtain a powder blank.

[0066] S6. The obtained powder blank is placed into a vacuum furnace for hydrogen reduction sintering. The heating rate is 5℃ / min to 400℃ and held for 40min. Then the temperature is increased to 950℃ at 10℃ / min and held for 2h. After the holding period, the blank is cooled with the furnace to obtain nano-graphene reinforced alumina dispersed copper rod.

[0067] S7. The nano-graphene-reinforced alumina dispersed copper rod is hot-extruded and deformed. Before entering the furnace, an anti-oxidation coating is brushed on the surface. The furnace temperature is 950℃, the holding time is 60min, and the extrusion ratio is 12.25 to obtain a graphene-reinforced alumina dispersed copper rod with a rod diameter of 10mm.

[0068] Comparative Example 1 A method for preparing alumina-dispersed copper rods, differing from Example 1 in that graphene is not added, includes the following steps: Weigh out CuAl powder with an average particle size of 50 μm and an Al content of 0.6 wt.%; weigh out Cu2O powder with an average particle size of 5 μm, and prepare nano-graphene-reinforced alumina-dispersed copper with an alumina content of 1.1 wt.%.

[0069] S1. Place CuAl powder and Cu2O powder into a ball mill jar according to the above ratio and mix them by ball milling. The ball-to-material ratio was 2:1, the rotation speed was 80 rpm, the ball milling was stopped for 30 minutes every 30 minutes to cool down, and the mixing time was 6 hours to obtain CuAl and Cu2O mixed powder.

[0070] S2. Place the mixed powder into a corundum crucible and place it in a vacuum furnace for internal oxidation treatment. The internal oxidation vacuum degree is 6×10⁻⁶. -3 The oxidation process was carried out at a pressure of MPa and a temperature of 950℃ for 2 hours. After the internal oxidation was completed, the furnace was cooled to below 70℃, argon gas was introduced, and the powder was removed from the furnace. The agglomerated powder was then crushed into fine powder using a grinder for 5 minutes. After cooling for 30 minutes, the powder was removed to obtain alumina-reinforced dispersed copper powder.

[0071] S3. After compacting the alumina-reinforced dispersed copper powder into a mold with a diameter of 230 MPa, cold isostatic pressing is performed at a pressure of 230 MPa, a pressurization rate of 10 MPa / min, and a holding time of 3 min to obtain a powder blank.

[0072] S4. The obtained powder blank is placed into a vacuum furnace for hydrogen reduction sintering. The heating rate is 5℃ / min to 400℃ and held for 40min. Then the temperature is increased to 950℃ at 10℃ / min and held for 2h. After the holding is completed, the furnace is cooled to obtain alumina-dispersed copper rod material.

[0073] S5. The alumina-dispersed copper rod is hot-extruded and deformed. Before entering the furnace, an anti-oxidation coating is brushed on the surface. The furnace temperature is 950℃, the holding time is 60min, and the extrusion ratio is 12.25 to obtain alumina-dispersed copper rod with a rod diameter of 10mm.

[0074] The performance of the graphene-reinforced alumina dispersed copper rods prepared in Examples 1 to 3 and the alumina dispersed copper rods prepared in Comparative Example 1 were tested, and the results are shown in Table 1 below.

[0075] Table 1. Mechanical properties and electrical conductivity results of the bars. As shown in Table 1, compared with Comparative Example 1, the introduction of graphene increases the strength, hardness and electrical conductivity of alumina-dispersed copper, thus improving the overall performance of the material.

[0076] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0077] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a graphene-reinforced alumina-dispersed copper composite material, characterized in that, Includes the following steps: Copper, aluminum and cuprous oxide were ball-milled and mixed to obtain a mixture. The mixture was then subjected to internal oxidation treatment under a vacuum atmosphere and crushed to obtain aluminum oxide-reinforced dispersed copper. Alumina-reinforced dispersed copper and nano-graphene oxide dispersions were mixed, stirred and ultrasonically treated, and then freeze-dried to prevent graphene oxide sedimentation, resulting in alumina-reinforced dispersed copper-nano-graphene oxide powder. Alumina-dispersed copper-nano graphene oxide powder was sequentially shaped, hydrogen-reduced sintered, and hot-extruded to obtain a graphene-reinforced alumina-dispersed copper composite material.

2. The preparation method of the graphene-reinforced alumina-dispersed copper composite material according to claim 1, characterized in that, The amount of cuprous oxide used is 4.5 wt.% to 6.5 wt.% of the mass of the mixture, the aluminum content in the copper-aluminum mixture is 0.2 wt.% to 0.8 wt.%, the particle size of cuprous oxide is 1 μm to 10 μm, and the particle size of cuprous oxide is 50 μm to 100 μm.

3. The preparation method of the graphene-reinforced alumina-dispersed copper composite material according to claim 1, characterized in that, The internal oxidation treatment temperature is 850℃~1000℃, and the vacuum degree is 1×10 -2 MPa ~ 1×10 -3 MPa, time 1h to 3h, after internal oxidation treatment, cool down to below 70℃, purge with argon and take out of the furnace; crushing is carried out by vacuum crushing, crushing time 5min to 15min, and take out after cooling for 30min to 60min.

4. The preparation method of the graphene-reinforced alumina-dispersed copper composite material according to claim 1, characterized in that, The mass ratio of nano-graphene oxide dispersion to alumina-reinforced dispersed copper is 3–5:15, and the concentration of nano-graphene oxide dispersion is 1 g / L–30 g / L.

5. The method for preparing the graphene-reinforced alumina-dispersed copper composite material according to claim 1, characterized in that, During the ultrasonic treatment with stirring, the ultrasonic frequency is 15KHz~30KHz and the time is 20min~60min; during the freeze-drying process, the freezing temperature is -10℃~-30℃, the cold trap temperature is -50℃~-60℃, and the time is 8h~14h.

6. The method for preparing the graphene-reinforced alumina-dispersed copper composite material according to claim 1, characterized in that, The nano-graphene oxide dispersion is obtained by placing nano-graphene oxide powder in a liquid medium and then ultrasonically dispersing it. The ultrasonic dispersion frequency is 15KHz to 30KHz and the time is 15min to 60min. The liquid medium is at least one of anhydrous ethanol and deionized water.

7. The method for preparing the graphene-reinforced alumina-dispersed copper composite material according to claim 1, characterized in that, The forming process begins with cold isostatic pressing pre-forming at a pressure of 200MPa to 400MPa, a pressurization rate of 7MPa / min to 18MPa / min, and a holding time of 5min to 15min.

8. The method for preparing the graphene-reinforced alumina-dispersed copper composite material according to claim 1, characterized in that, Hydrogen reduction sintering is carried out in a hydrogen atmosphere. First, the temperature is increased to 300℃ to 600℃ at a rate of 2℃ / min to 10℃ / min and held for 40min to 60min. Then, the temperature is increased to 900℃ to 1050℃ at a rate of 2℃ / min to 10℃ / min and held for 60min to 200min.

9. The method for preparing the graphene-reinforced alumina-dispersed copper composite material according to claim 1, characterized in that, The temperature for hot extrusion deformation is 800℃~1000℃, the time is 30min~90min, and the extrusion ratio is 10~25.

10. The method for preparing the graphene-reinforced alumina-dispersed copper composite material according to claim 1, characterized in that, During the ball milling process, the ball-to-material ratio is 2-4:1, the milling time is 4-8 hours, the rotation speed is 50-120 rpm, and the ball milling is stopped for 20-40 minutes after every 20-40 minutes to cool down.

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