Preparation method of aluminum oxide graphene reinforcement reinforced copper-silver electrical contact material

Abstract

The invention relates to a preparation method of an aluminum oxide graphene reinforcement reinforced copper-silver electrical contact material, and belongs to the technical field of preparation of low-voltage circuit breaker parts. According to the preparation method, firstly, an aluminum oxide graphene reinforcement and composite powder are prepared by adopting a micro-nano scale liquid phase mixing method and a powder metallurgy technology, and then preparation of the aluminum oxide graphene reinforcement reinforced copper-silver composite material is achieved through cold press molding and rapid hot pressed sintering. And finally, the aluminum oxide graphene reinforcement reinforced copper-silver electrical contact material with long service life and stable electrical contact performance is obtained through hot extrusion and cold drawing. The preparation process is simple and environment-friendly, the mechanical property and the fusion welding resistance are improved while the aluminum oxide graphene reinforcement reinforced copper-silver composite material keeps excellent conductivity, successful development of the copper-based composite material electrical contact with high comprehensive performance and long service life is achieved, and the application prospect is wide. And technical guidance is provided for research on development of composite materials applied to the field of preparation of low-voltage circuit breaker components.

Description

Technical Field

[0001] This invention belongs to the field of low-voltage circuit breaker component preparation technology, specifically a method for preparing alumina graphene-reinforced copper-silver electrical contact material. Background Technology

[0002] With the advancement of national policies on the integrated circuit and leadframe industries, and the increasing proportion of new energy power generation, the operation mode of power system flow is also changing, thus gradually increasing the demand for circuit breakers. The service performance of circuit breakers is mainly limited by their core component—the electrical contact (hereinafter referred to as electrical contact). The electrical contact must not only transmit electrical signals and current, but also withstand and extinguish the instantaneous high-temperature and high-voltage arc generated when the circuit is cut off. It is an important guarantee for ensuring the safety of circuits and electrical equipment. Currently, silver-based electrical contacts are widely used in industry under low-voltage service conditions. Silver-based electrical contacts have properties such as high conductivity, oxidation resistance, and low contact resistance, but their melting point and hardness are low, and their surface is prone to deformation, leading to unstable contact behavior and service life. At the same time, silver is a precious metal, expensive, and with limited reserves, which increases the cost of use, maintenance, and replacement of low-voltage circuit breaker components. Therefore, there is an urgent need for a new type of high-performance, high-frequency contact material to replace silver-based electrical contact materials.

[0003] Copper-based materials, with their high electrical and thermal conductivity and relatively low price, are another widely used electrical contact material in industry. However, using copper alloys as electrical contact materials sacrifices conductivity for high material hardness, significantly increasing energy consumption in power transmission networks. Copper-silver alloys, by adding a small amount of silver, can maintain high electrical and thermal conductivity, but hardness and wear resistance cannot be guaranteed. After frequent switching, contact surface deformation and damage can lead to unstable electrical contact performance. Furthermore, due to the low melting points of copper and silver (copper: 1083 ℃, silver: 961 ℃), the contact surface is prone to welding due to high-temperature, high-pressure electric arcs. Currently, material composites are considered an effective method to improve electrical contact performance. Regarding reinforcement, graphene possesses high thermal stability and high electrical and thermal conductivity, improving both hardness and wear resistance while also enhancing the resistance to arc erosion and welding. Alumina, with its simple preparation process and ability to improve overall material performance without reducing conductivity when added to a copper matrix, is often used as a reinforcement in copper-based composites. Summary of the Invention

[0004] To address the common problems of low wear resistance and high cost in silver-based electrical contact materials, as well as the unstable electrical contact performance of copper-silver alloys, this invention proposes a method for preparing alumina-graphene-reinforced copper-silver electrical contact materials. This method first employs a micro-nano scale liquid-phase mixing method and powder metallurgy to prepare alumina-graphene-reinforced composite powders. Then, alumina-graphene-reinforced copper-silver composite materials are prepared through cold pressing and rapid hot pressing sintering. Finally, alumina-graphene-reinforced copper-silver electrical contact materials with high lifespan and stable electrical contact performance are obtained through hot extrusion and cold drawing.

[0005] The objective of this invention is achieved through the following technical solutions.

[0006] A method for preparing an alumina-graphene-reinforced copper-silver electrical contact material, the method comprising the following steps: (1) Preparation of alumina-graphene composite reinforcement (Al2O3@Gr) by micro-nano scale liquid phase mixing method Aluminum nitrate nonahydrate (Al(NO3)3·9H2O) crystals were added to deionized water in a beaker to prepare an aluminum nitrate (Al(NO3)3) solution. After complete dissolution, graphene (Gr) powder was added, and the mixture was stirred thoroughly in a constant temperature water bath at 50 ℃~70 ℃ for 30 min~50 min. After evaporating and drying the solution, aluminum nitrate graphene (Al(NO3)3@Gr) mixed powder was obtained. This powder was placed in a vacuum tube furnace and calcined to obtain an Al2O3@Gr multiphase reinforcement. (2) Preparation of copper-silver (Al2O3@Gr / CuAg) composite powder reinforced with alumina-graphene multiphase reinforcement Al2O3@Gr composite reinforcement, copper powder, and silver powder were uniformly mixed using a vacuum high-shear dispersion method; subsequently, the mixed powder was subjected to reduction deoxidation treatment to obtain Al2O3@Gr / CuAg composite powder. (3) Preparation of Al2O3@Gr / CuAg composite bulk Al2O3@Gr / CuAg composite powder was cold-pressed into a compact using a four-column hydraulic press, and then the compact was sintered into a denser state using a rapid hot pressing sintering furnace to obtain Al2O3@Gr / CuAg composite block. (4) Preparation of Al2O3@Gr / CuAg composite rods Al2O3@Gr / CuAg composite blocks were hot-extruded and deformed using a four-column hydraulic press to obtain Al2O3@Gr / CuAg composite rods.

[0007] Preferably, the above method further includes step (5) Al2O3@Gr / CuAg electrical contact processing. The specific operation of this step is: using a chain drawing machine to cold draw the Al2O3@Gr / CuAg composite rod, and then machining it to obtain the Al2O3@Gr / CuAg electrical contact.

[0008] Preferably, the aluminum nitrate crystals used in step (1) have a purity of 99%; the graphene is a single-layer graphene with a thickness of 0.8 nm to 1.2 nm and a sheet diameter of 0.5 μm to 5 μm.

[0009] Preferably, in step (1), the protective atmosphere of the vacuum tube furnace is nitrogen, the calcination temperature is 600 ℃~800 ℃, and the calcination time is 2 h~3 h. The Al(NO3)3@Gr mixed powder is calcined to generate Al2O3 on the Gr surface.

[0010] Preferably, in step (2), the copper powder used is dendritic copper powder prepared by electrolysis with a particle size of 20 μm to 50 μm; the silver powder is spherical silver powder with a particle size of 200 nm to 400 nm.

[0011] Preferably, in step (2), the vacuum high-shear dispersion method uses a vacuum stainless steel ball milling jar for high-speed vacuum ball milling. The process parameters are: ball-to-material ratio 8:1 to 15:1; ball milling speed 200 rpm to 400 rpm; and ball milling time 4 h to 8 h.

[0012] Preferably, in step (2), the reduction deoxygenation process is as follows: the reduction atmosphere is a nitrogen-hydrogen mixture (hydrogen content is 10%~20%), the reduction temperature is 350 ℃~450 ℃, and the reduction time is 3 h~5 h.

[0013] Preferably, in step (2), the mass fraction of each component of the Al2O3@Gr / CuAg composite powder (calculated by total amount) is: alumina: 1 wt%~3 wt%, graphene: 0.1 wt%~0.3 wt%, silver: 1 wt%~5 wt%, and the remaining component is copper.

[0014] Preferably, the cold pressing process described in step (3) is as follows: the pressing pressure is 30 t to 40 t, the holding time is 8 min to 15 min, and after the pressure is removed and the mold is demolded, a blank with a diameter of 30 mm and a thickness of 10 mm to 15 mm is obtained.

[0015] Preferably, the sintering process in step (3) is as follows: the initial vacuum degree is <16 Pa, the initial pressure is 0.6 MPa~1 MPa, and the temperature is increased at a rate of 50 ℃ / min~100 ℃ / min; when the temperature reaches T1 and the vacuum degree is <10 Pa, the pressure is increased; when the temperature reaches T2 and the pressure reaches 50 MPa~200 MPa, the temperature and pressure are maintained for 15 min~30 min; where T1=200℃~400 ℃, and T2 is 600 ℃~700 ℃; after the temperature and pressure maintenance program is completed, the pressure is kept constant, the furnace is cooled to room temperature, the pressure is removed, and a uniform and dense Al2O3@Gr / CuAg composite block is obtained.

[0016] Preferably, the hot extrusion process in step (4) is as follows: the extrusion temperature is 500 ℃~600 ℃, the extrusion pressure is 100t~160t, and after the pressure is removed and the die is demolded, a bar with a diameter of 8 mm is obtained.

[0017] Preferably, the cold drawing process in step (5) is as follows: the drawing rate is 6 cm / s to 10 cm / s, the number of drawing passes is 8 to 12, and the diameter change in each pass is 0.4 mm to 0.6 mm. Finally, Al2O3@Gr / CuAg composite rods with a diameter of 3 mm to 4.8 mm are obtained by drawing. After processing with a wire cutting machine, the rods are cleaned to obtain Al2O3@Gr / CuAg electrical contact test samples with a diameter of 3 mm and a length of 5 mm.

[0018] The beneficial effects of this invention are: (1) The preparation method of the alumina graphene-reinforced copper-silver electrical contact material of the present invention, on the one hand, uses the micro-nano scale liquid phase mixing method to prepare Al2O3@Gr composite reinforcing phase, which can uniformly attach micro-nano-sized alumina on the graphene surface, which can weaken the van der Waals forces between graphene sheets and realize the uniform dispersion of composite reinforcing phase in copper-silver matrix; on the other hand, the combination of hot extrusion and cold drawing technology can enhance the bonding between reinforcing phase and matrix and improve the performance of composite material contact.

[0019] (2) Compared with traditional alloyed or single-reinforcing phase reinforced copper-based electrical contact materials, the Al2O3@Gr / CuAg electrical contact prepared by this invention can maintain high conductivity while obtaining excellent hardness and wear resistance, and improve the anti-welding property of the contact material, thus realizing the successful development of copper-based composite material electrical contacts with high comprehensive performance and long service life.

[0020] (3) The present invention has high material utilization and strong practicality, and provides technical guidance for the research on high-performance and long-service copper-based composite materials for use in the preparation of low-voltage circuit breaker components. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0022] Figure 1 Images shown are from a scanning electron microscope (SEM) of powder particles. Image a shows the Al2O3@Gr composite reinforced material prepared by a micro / nano-scale liquid-phase mixing method; image b shows the elemental distribution spectrum of the Al2O3@Gr composite reinforced material; and images c and d show the Al2O3@Gr / CuAg composite powder. Figure 2 The diagram shows the mechanical and electrical properties of Example 1 and Comparative Example 1.

[0023] Figure 3 The curves showing the change in welding force for Example 1 and Comparative Example 1 are shown.

[0024] Figure 4 The diagrams show the mechanical and electrical properties of Example 2 and Comparative Example 2.

[0025] Figure 5 The curves showing the change in welding force in Example 2 and Comparative Example 2 are shown.

[0026] Figure 6 The diagrams show the mechanical and electrical properties of Example 3 and Comparative Example 3.

[0027] Figure 7 The curves showing the change in welding force in Example 3 and Comparative Example 3 are shown. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the methods described are conventional methods, and the raw materials described are obtainable from publicly available commercial sources.

[0029] In the following embodiments: Aluminum nitrate nonahydrate was of analytical grade (AR≥99%), produced by Shanghai Aladdin Biochemical Technology Co., Ltd. The graphene is a single-layer graphene with a thickness of 0.8 nm to 1.2 nm and a sheet diameter of 0.5 μm to 5 μm. Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. The copper powder has a purity of 99.9%, a particle size of 20 μm to 50 μm, and a dendritic morphology. (Shanghai Naio Nanotechnology Co., Ltd.) The silver powder has a purity of 99.9%, a particle size of 200 nm to 400 nm, and a morphology of near-spherical. (Shanghai Naio Nanotechnology Co., Ltd.) Scanning electron microscope: Nova Nano-450, FEI, USA; Characterization of the electrical contact welding performance of the composite materials prepared in the examples and comparative examples: Electrical contact tests were conducted at room temperature using an electrical contact material testing system (JF04C, Kunming, China). The test voltage and current were DC 24 V and 20 A; the switching frequency was 1 Hz.

[0030] Example 1 A method for preparing an alumina-graphene-reinforced copper-silver electrical contact material, comprising the following specific steps: (1) Preparation of Al2O3@Gr composite reinforcement by micro-nano scale liquid phase mixing method 8.8 g of Al(NO3)3·9H2O crystals were weighed and added to deionized water in a beaker to prepare an Al(NO3)3 solution. After complete dissolution, 0.06 g of Gr powder was added, and the mixture was stirred thoroughly in a 60 ℃ constant temperature water bath for 40 min. After evaporating and drying the solution, Al(NO3)3@Gr mixed powder was obtained. This powder was placed in a vacuum tube furnace and calcined at 800 ℃ for 3 h under a nitrogen protective atmosphere to obtain Al2O3@Gr multiphase reinforcement.

[0031] (2) Preparation of Al2O3@Gr / CuAg composite powder Weigh 1.3 g of the Al2O3@Gr composite reinforcer obtained in step (1), 2.4 g of Ag powder, and 56.3 g of Cu powder and place them in a ball mill jar. Seal the jar and evacuate it. Mix the powder uniformly at 330 rpm for 6 h using a vacuum high-shear dispersion method (ball-to-powder ratio 11:1). Then, perform reduction deoxidation treatment on the mixed powder in a vacuum tube furnace with a nitrogen-hydrogen mixture (15% hydrogen) as the reducing atmosphere at a reduction temperature of 420 °C for 4 h to obtain 2Al2O3@0.1Gr / Cu4Ag composite powder (mass fraction).

[0032] (3) Preparation of Al2O3@Gr / CuAg composite bulk The Al2O3@Gr / CuAg composite powder obtained in step (2) was filled into a cold-pressing mold with a diameter of 30 mm, pressed using a four-column hydraulic press at a pressure of 36 t, and held for 9 min. Subsequently, it was sintered in a rapid hot-pressing sintering furnace at a sintering temperature of 680 ℃ and a sintering pressure of 150 MPa for 20 min (heating rate 50 ℃ / min, vacuum degree: 5×10⁻⁶). -4 (Pressure was applied at 250 °C) to sinter the compact. After cooling and depressurization in the furnace, the vacuum was closed, and the sample was removed to obtain a 2Al2O3@0.1Gr / Cu4Ag composite block.

[0033] (4) Preparation of Al2O3@Gr / CuAg composite rods The Al2O3@Gr / CuAg composite block obtained in step (3) was placed in a mold and heated to 550 ℃. It was then extruded and deformed under a pressure of 150 t using a four-column hydraulic press. After removing the pressure and demolding, a 2Al2O3@0.1Gr / Cu4Ag composite rod with a diameter of 8 mm was obtained.

[0034] (5) Machining of Al2O3@Gr / CuAg electrical contacts The chain drawing machine was set to a working speed of 6 cm / s, and the Al2O3@Gr / CuAg composite rod obtained in step (4) was cold-drawn (10 drawing passes, with a diameter change of 0.5 mm each time) to obtain an Al2O3@Gr / CuAg composite rod with a diameter of 3 mm. Subsequently, it was processed and cleaned by a wire cutting machine to obtain a 2Al2O3@0.1Gr / Cu4Ag electrical contact test sample with a diameter of 3 mm and a length of 5 mm.

[0035] Comparative Example 1 (1) Weigh 2.4 g Ag powder and 57.6 g Cu powder and put them into a ball mill jar. Seal the jar and evacuate it. Mix the powder uniformly at 330 rpm for 6 h (ball-to-powder ratio 11:1) using the vacuum high-shear dispersion method. Then, put the mixed powder into a vacuum tube furnace with a nitrogen-hydrogen mixture (hydrogen content 15%) as the reducing atmosphere and reduce it at 420 °C for 4 h to obtain Cu4Ag composite powder (mass fraction).

[0036] (2) The CuAg composite powder obtained in step (1) is filled into a rapid hot pressing sintering mold with a diameter of 30 mm, and held at a sintering temperature of 680 ℃ and a sintering pressure of 150 MPa for 20 min using a rapid hot pressing sintering furnace (heating rate: 50 ℃ / min, vacuum degree: 5×10 -4 The compact was sintered to a dense state (Pa). After cooling and depressurization in the furnace, the vacuum was closed, and the sample was removed to obtain a Cu4Ag composite block.

[0037] (3) The CuAg composite block obtained in step (2) is placed in a mold and heated to 550 °C. It is then extruded and deformed under a pressure of 150 t using a four-column hydraulic press. After removing the pressure and demolding, a Cu4Ag composite rod with a diameter of 8 mm is obtained.

[0038] (4) Set the working speed of the chain drawing machine to 6 cm / s and perform cold drawing on the CuAg composite rod obtained in step (3) (the drawing passes are 10, and the diameter change is 0.5 mm each time) to obtain a Cu4Ag composite rod with a diameter of 3 mm. Then, after processing and cleaning by wire cutting machine, a Cu4Ag electrical contact test sample with a diameter of 3 mm and a length of 5 mm is obtained.

[0039] The electrical conductivity and hardness of the composite materials prepared in Example 1 and Comparative Example 1 were tested, and the results are as follows: Figure 2 As shown; a fusion welding force test (24 VDC, 20 A) was performed, and the results are as follows. Figure 3 As shown.

[0040] like Figure 1 As shown, the Al2O3@Gr composite reinforcement prepared by the micro-nano scale liquid phase mixing method can make Al2O3 uniformly attached to the Gr surface, which is beneficial to the uniform dispersion of Al2O3@Gr composite reinforcement in the matrix.

[0041] like Figure 2 As shown, the composite material prepared by micro / nano-scale liquid-phase mixing and deformation treatments such as hot extrusion and cold drawing exhibits superior properties. Comparing Example 1 and Comparative Example 1, Example 1, while maintaining good electrical conductivity (64 MS / m), showed a significant increase in hardness (from 110 HV to 200 HV, an increase of 81%). The main mechanisms of this gain are: first, the Al2O3@Gr composite reinforcement prepared by micro / nano-scale liquid-phase mixing can achieve uniform dispersion in the matrix, avoiding the decrease in electrical conductivity caused by reinforcement agglomeration; second, the Al2O3@Gr composite reinforcement can better utilize the intrinsic properties of the reinforcement and refine the grains, thereby improving the overall performance of the composite material.

[0042] like Figure 3 As shown, the welding force in Example 1 remained consistently at a low level (approximately 25 cN), effectively weakening the welding behavior caused by arc erosion and extending the service life of the electrical contacts. This is mainly attributed to the high thermal stability and thermal conductivity of the Al2O3@Gr composite reinforcement, which can rapidly disperse heat when a high-temperature arc is generated, avoiding heat concentration that could lead to severe welding behavior. Furthermore, the low density of the Al2O3@Gr composite reinforcement allows it to float to the surface and form a protective layer when the molten pool is formed, resulting in a smooth and flat contact surface, preventing the aggravation of welding behavior and extending the service life of the electrical contact material.

[0043] Example 2 A method for preparing an alumina-graphene-reinforced copper-silver electrical contact material, comprising the following specific steps: (1) Preparation of Al2O3@Gr composite reinforcement by micro-nano scale liquid phase mixing method 8.8 g of Al(NO3)3·9H2O crystals were weighed and added to deionized water in a beaker to prepare an Al(NO3)3 solution. After complete dissolution, 0.06 g of Gr powder was added, and the mixture was stirred thoroughly in a 50 ℃ constant temperature water bath for 30 min. After evaporating and drying the solution, Al(NO3)3@Gr mixed powder was obtained. The powder was placed in a vacuum tube furnace and calcined at 600 ℃ for 2 h under a nitrogen protective atmosphere to obtain Al2O3@Gr multiphase reinforcement.

[0044] (2) Preparation of Al2O3@Gr / CuAg composite powder Weigh 1.3 g of the Al2O3@Gr composite reinforcer obtained in step (1), 2.4 g of Ag powder, and 56.3 g of Cu powder and place them in a ball mill jar. Seal the jar and evacuate it. Mix the powder uniformly at 200 rpm for 4 h using a vacuum high-shear dispersion method (ball-to-powder ratio 8:1). Then, perform reduction deoxidation treatment on the mixed powder in a vacuum tube furnace at a reduction temperature of 350℃ for 3 h with a nitrogen-hydrogen mixture (10% hydrogen) as the reducing atmosphere to obtain 2Al2O3@0.1Gr / Cu4Ag composite powder (mass fraction).

[0045] (3) Preparation of Al2O3@Gr / CuAg composite bulk The Al2O3@Gr / CuAg composite powder obtained in step (2) was filled into a cold-pressing mold with a diameter of 30 mm, pressed using a four-column hydraulic press at a pressure of 30 t, and held for 8 min. Subsequently, it was held in a rapid hot-pressing sintering furnace at a sintering temperature of 600 ℃ and a sintering pressure of 50 MPa for 15 min (heating rate: 70℃ / min, vacuum degree: 5×10⁻⁶). -4 (Pressure was applied at 200 °C) to sinter the compact. After cooling and depressurization in the furnace, the vacuum was closed, and the sample was removed to obtain a 2Al2O3@0.1Gr / Cu4Ag composite block.

[0046] (4) Preparation of Al2O3@Gr / CuAg composite rods The Al2O3@Gr / CuAg composite block obtained in step (3) is placed in a mold and heated to 500°C. It is then extruded and deformed under a pressure of 100 t using a four-column hydraulic press. After removing the pressure and demolding, a 2Al2O3@0.1Gr / Cu4Ag composite rod with a diameter of 8 mm is obtained.

[0047] (5) Machining of Al2O3@Gr / CuAg electrical contacts The chain drawing machine was set to a working speed of 8 cm / s, and the Al2O3@Gr / CuAg composite rod obtained in step (4) was cold-drawn (8 drawing passes, with a diameter change of 0.4 mm each time) to obtain an Al2O3@Gr / CuAg composite rod with a diameter of 4.8 mm. Subsequently, it was processed and cleaned by a wire cutting machine to obtain a 2Al2O3@0.1Gr / Cu4Ag electrical contact test sample with a diameter of 3 mm and a length of 5 mm.

[0048] Comparative Example 2 (1) Weigh 1.2 g Al2O3, 2.4 g Ag powder and 56.4 g Cu powder and put them into a ball mill jar. Seal the jar and evacuate it. Mix the powder uniformly at 200 rpm for 4 h using the vacuum high-shear dispersion method (ball-to-powder ratio 8:1). Then, put the mixed powder into a vacuum tube furnace with a nitrogen-hydrogen mixture (hydrogen 10%) as the reducing atmosphere and a reduction temperature of 350 °C for 3 h to obtain 2Al2O3 / Cu4Ag composite powder (mass fraction).

[0049] (2) The Al2O3 / CuAg composite powder obtained in step (1) is filled into a rapid hot pressing sintering mold with a diameter of 30 mm, and held at a sintering temperature of 600 ℃ and a sintering pressure of 50 MPa for 15 min using a rapid hot pressing sintering furnace (heating rate: 70 ℃ / min, vacuum degree: 5×10 -4 The compact was sintered to a dense state (Pa). After cooling and depressurization in the furnace, the vacuum was closed, and the sample was removed to obtain a 2Al2O3 / Cu4Ag composite block.

[0050] (3) The Al2O3 / CuAg composite block obtained in step (2) is placed in a mold and heated to 500 ℃. It is then extruded and deformed under a pressure of 100 t using a four-column hydraulic press. After removing the pressure and demolding, a 2Al2O3 / Cu4Ag composite rod with a diameter of 8 mm is obtained.

[0051] (4) Set the working speed of the chain drawing machine to 8 cm / s and perform cold drawing on the Al2O3 / CuAg composite rod obtained in step (3) (8 drawing passes, with a diameter change of 0.4 mm each time) to obtain a 2Al2O3 / Cu4Ag composite rod with a diameter of 4.8 mm. Then, after processing and cleaning by wire cutting machine, a 2Al2O3 / Cu4Ag electrical contact test sample with a diameter of 3 mm and a length of 5 mm is obtained.

[0052] The electrical conductivity and hardness of the composite materials prepared in Example 2 and Comparative Example 2 were tested, and the results are as follows: Figure 4 As shown; a fusion welding force test (24 V DC, 20 A) was performed, and the results are as follows. Figure 5As shown.

[0053] like Figure 4 As shown, the Al2O3@Gr composite reinforcement prepared by the micro / nano-scale liquid-phase mixing method has a better performance enhancement effect on the material. Compared with Comparative Example 2, the hardness increased by 68% to 202 HV, and the electrical conductivity increased by 17% to 63 MS / m. The main mechanism of this enhancement effect is that Al2O3, as a reinforcement, can improve the overall performance of the composite material without sacrificing electrical conductivity. Graphene has high electrical conductivity, but single reinforcements are prone to agglomeration in the matrix, leading to performance degradation. The micro / nano-scale liquid-phase mixing method can improve the dispersibility of the Al2O3@Gr composite reinforcement and enhance the overall performance of the composite material.

[0054] like Figure 5 As shown, the welding force in Example 2 remained consistently low, at approximately 25 cN, while the minimum welding force in Comparative Example 2 was 36 cN, effectively weakening the welding behavior caused by arc erosion. This is mainly attributed to the fact that the Al2O3@Gr composite reinforcement prepared by the micro-nano scale liquid phase mixing method can be uniformly dispersed in the matrix, avoiding agglomeration that leads to localized arc concentration, thus fully leveraging the gain effect of the reinforcement and weakening the welding behavior caused by arc erosion.

[0055] Example 3 A method for preparing an alumina-graphene-reinforced copper-silver electrical contact material, comprising the following specific steps: (1) Preparation of Al2O3@Gr composite reinforcement by micro-nano scale liquid phase mixing method 8.8 g of Al(NO3)3·9H2O crystals were weighed and added to deionized water in a beaker to prepare an Al(NO3)3 solution. After complete dissolution, 0.06 g of Gr powder was added, and the mixture was stirred thoroughly in a 70 ℃ constant temperature water bath for 50 min. After evaporating and drying the solution, Al(NO3)3@Gr mixed powder was obtained. The powder was placed in a vacuum tube furnace and calcined at 700 ℃ for 2.5 h under a nitrogen protective atmosphere to obtain Al2O3@Gr multiphase reinforcement.

[0056] (2) Preparation of Al2O3@Gr / CuAg composite powder Weigh 1.3 g of the Al2O3@Gr composite reinforcer obtained in step (1), 2.4 g of Ag powder, and 56.3 g of Cu powder and place them in a ball mill jar. Seal the jar and evacuate it. Mix the powder uniformly at 400 rpm for 8 h using a vacuum high-shear dispersion method (ball-to-powder ratio 15:1). Then, perform reduction deoxidation treatment on the mixed powder in a vacuum tube furnace with a nitrogen-hydrogen mixture (15% hydrogen) as the reducing atmosphere at a reduction temperature of 450 °C for 5 h to obtain 2Al2O3@0.1Gr / Cu4Ag composite powder (mass fraction).

[0057] (3) Preparation of Al2O3@Gr / CuAg composite bulk The Al2O3@Gr / CuAg composite powder obtained in step (2) was filled into a cold-pressing mold with a diameter of 30 mm, pressed using a four-column hydraulic press at a pressure of 40 t, and held for 15 min. Subsequently, it was held in a rapid hot-pressing sintering furnace at a sintering temperature of 700 ℃ and a sintering pressure of 200 MPa for 30 min (heating rate: 100 ℃ / min, vacuum degree: 5 × 10⁻⁶). -4 (Pressure was applied at 300 °C) to sinter the compact into a dense structure. After cooling and depressurization in the furnace, the vacuum was closed, and the sample was removed to obtain a 2Al2O3@0.1Gr / Cu4Ag composite block.

[0058] (4) Preparation of Al2O3@Gr / CuAg composite rods The Al2O3@Gr / CuAg composite block obtained in step (3) was placed in a mold and heated to 600 ℃. It was then extruded and deformed using a four-column hydraulic press under a pressure of 160 t. After removing the pressure and demolding, a 2Al2O3@0.1Gr / Cu4Ag composite rod with a diameter of 8 mm was obtained.

[0059] (5) Machining of Al2O3@Gr / CuAg electrical contacts The chain drawing machine was set to a working speed of 10 cm / s, and the Al2O3@Gr / CuAg composite rod obtained in step (4) was cold-drawn (12 drawing passes, with a diameter change of 0.4 mm each time) to obtain an Al2O3@Gr / CuAg composite rod with a diameter of 3.2 mm. Subsequently, it was processed and cleaned by a wire cutting machine to obtain a 2Al2O3@0.1Gr / Cu4Ag electrical contact test sample with a diameter of 3 mm and a length of 5 mm.

[0060] Comparative Example 3 (1) Weigh 0.06 g Gr, 2.4 g Ag powder and 57.5 g Cu powder and put them into a ball mill jar. Seal the jar and evacuate it. Mix the powder uniformly at 400 rpm for 8 h (ball-to-powder ratio 15:1) by vacuum high-shear dispersion. Then, perform reduction deoxidation treatment on the mixed powder in a vacuum tube furnace with a nitrogen-hydrogen mixture (hydrogen content 15%) as the reducing atmosphere at a reduction temperature of 450 °C for 5 h to obtain 0.1 Gr / Cu4Ag composite powder (mass fraction).

[0061] (2) Fill the Gr / CuAg composite powder obtained in step (1) into a rapid hot pressing sintering mold with a diameter of 30 mm, and use a rapid hot pressing sintering furnace to hold the sintering temperature at 700 ℃ and the sintering pressure at 200 MPa for 30 min (heating rate: 100 ℃ / min, vacuum degree: 5×10 -4 The compact was sintered to a dense state using a pressure of 0.1 Pa. After cooling and depressurization in the furnace, the vacuum was closed, and the sample was removed to obtain a 0.1 Gr / Cu4Ag composite block.

[0062] (3) The Gr / CuAg composite block obtained in step (2) is placed in a mold and heated to 600 °C. It is then extruded and deformed using a four-column hydraulic press under a pressure of 160 t. After removing the pressure and demolding, a 0.1Gr / Cu4Ag composite rod with a diameter of 8 mm is obtained.

[0063] (4) Set the working speed of the chain drawing machine to 10 cm / s and perform cold drawing on the Gr / CuAg composite rod obtained in step (3) (the drawing passes are 12, and the diameter change is 0.4 mm each time) to obtain a 0.1Gr / Cu4Ag composite rod with a diameter of 3.2 mm. Then, after processing and cleaning by wire cutting machine, a 0.1Gr / Cu4Ag electrical contact test sample with a diameter of 3 mm and a length of 5 mm is obtained.

[0064] The electrical conductivity and hardness of the composite materials prepared in Example 3 and Comparative Example 3 were tested, and the results are as follows: Figure 6 As shown; a fusion welding force test (24 V DC, 20 A) was performed, and the results are as follows. Figure 7 As shown.

[0065] like Figure 6 and Figure 7 As shown, the Al2O3@Gr composite reinforcement prepared by the micro / nano-scale liquid-phase mixing method exhibits better performance enhancement in the material. Its enhancement mechanism is essentially the same as that in Example 1.

[0066] In summary, this invention provides a method for preparing copper-silver electrical contact materials reinforced with alumina-graphene. This method is simple, yields significant gains, has a short experimental cycle, and is highly practical. The resulting composite material exhibits high conductivity and hardness while also possessing good weld resistance and service life. By combining micro-nano-scale liquid-phase mixing with extrusion and drawing processes, uniform dispersion of the reinforcement and good interfacial bonding are achieved, effectively solving the problems in the prior art. This provides technical guidance for the development of high-performance copper-silver electrical contact materials to replace silver-based electrical contacts and for their application in low-voltage circuit breaker components.

[0067] The embodiments described above are merely preferred embodiments of the present invention, and not all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art through any modifications, substitutions, improvements, etc., without making any innovation, are within the protection scope of the present invention.

Claims

1. A method for preparing an alumina-graphene-reinforced copper-silver electrical contact material, characterized in that, The method includes the following steps: (1) Preparation of Al2O3@Gr composite reinforcement by micro-nano scale liquid phase mixing method Aluminum nitrate nonahydrate (Al(NO3)3·9H2O) crystals were added to deionized water in a beaker to prepare an aluminum nitrate (Al(NO3)3) solution. After complete dissolution, graphene (Gr) powder was added, and the mixture was stirred thoroughly in a constant temperature water bath at 50 ℃~70 ℃ for 30 min~50 min. After evaporating and drying the solution, aluminum nitrate graphene (Al(NO3)3@Gr) mixed powder was obtained. The powder was then placed in a vacuum tube furnace and calcined to obtain Al2O3@Gr multiphase reinforcement. (2) Preparation of Al2O3@Gr / CuAg composite powder Al2O3@Gr composite reinforcement, copper powder and silver powder were uniformly mixed by vacuum high shear dispersion method, and then the mixed powder was subjected to reduction deoxidation treatment to obtain Al2O3@Gr / CuAg composite powder. (3) Preparation of Al2O3@Gr / CuAg composite bulk Al2O3@Gr / CuAg composite powder was cold-pressed into a compact using a four-column hydraulic press, and then the compact was sintered into a denser state using a rapid hot pressing sintering furnace to obtain Al2O3@Gr / CuAg composite block. (4) Preparation of Al2O3@Gr / CuAg composite rods Al2O3@Gr / CuAg composite blocks were hot-extruded and deformed using a four-column hydraulic press to obtain Al2O3@Gr / CuAg composite rods.

2. The method for preparing an alumina-graphene-reinforced copper-silver electrical contact material according to claim 1, characterized in that: The method further includes step (5), which specifically involves: using a chain drawing machine to cold draw the Al2O3@Gr / CuAg composite rod, and then machining it to obtain the Al2O3@Gr / CuAg electrical contact.

3. The method for preparing an alumina graphene-reinforced copper-silver electrical contact material according to claim 1, wherein in step (1), the calcination protective atmosphere is nitrogen; the calcination temperature is 600 ℃~800 ℃; and the calcination time is 2 h~3 h.

4. The method for preparing an alumina-graphene-reinforced copper-silver electrical contact material according to claim 1, characterized in that: In step (2), the vacuum high-shear dispersion method uses a vacuum stainless steel ball mill jar for high-speed vacuum ball milling; the ball-to-material ratio is 8:1 to 15:1; the ball milling speed is 200 rpm to 400 rpm; and the ball milling time is 4 h to 8 h.

5. The method for preparing an alumina-graphene-reinforced copper-silver electrical contact material according to claim 1, characterized in that: In step (2), the reducing atmosphere of the reduction deoxygenation treatment is a nitrogen-hydrogen mixture, wherein the hydrogen content is 10%~20%; the reduction temperature is 350 ℃~450 ℃; and the reduction time is 3 h~5 h.

6. The method for preparing an alumina-graphene-reinforced copper-silver electrical contact material according to claim 1, characterized in that: In step (3), the cold pressing pressure is 30 t to 40 t; the holding time is 8 min to 15 min.

7. The method for preparing an alumina-graphene-reinforced copper-silver electrical contact material according to claim 1, characterized in that: In step (3), the initial vacuum degree of the rapid hot pressing sintering furnace is <16 Pa; the initial pressure is 0.6 MPa~1 MPa; the heating rate is 50 ℃ / min~100 ℃ / min; the sintering temperature is 600 ℃~700 ℃; and the sintering pressure is 50 MPa~200 MPa. The heat preservation and pressure holding time is 15 min to 30 min.

8. The method for preparing an alumina-graphene-reinforced copper-silver electrical contact material according to claim 1, characterized in that: In step (4), the hot extrusion temperature is 500 ℃~600 ℃; the extrusion pressure is 100 t~160 t.

9. The method for preparing an alumina-graphene-reinforced copper-silver electrical contact material according to claim 2, characterized in that: In step (5), the cold drawing rate is 6 cm / s to 10 cm / s; the number of drawing passes is 8 to 12; and the diameter change per pass is 0.4 mm to 0.6 mm.

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