Preparation method of wear-resistant boron nitride reinforced copper-based composite material with high electric conductivity and heat conductivity

Abstract

The invention relates to a preparation method of a wear-resistant boron nitride reinforced copper-based composite material with high electric conductivity and heat conductivity, and belongs to the technical field of composite material preparation. According to the method, high-purity cathode copper serves as a raw material, and the copper foil with the specific thickness is prepared through the pretreatment processes of smelting, rolling, annealing and the like. And then respectively carrying out surface pretreatment on the two-dimensional boron nitride nanosheet (BNNS) and the copper foil, and further uniformly depositing a BNNS enhancement layer on the surface of the copper foil by adopting a cold spraying technology. And finally, after the copper foil deposited with the BNNS reinforcing layer is subjected to multi-layer stacking and block addition, densification and interface strengthening of the composite material are achieved through a hot isostatic pressing technology, and the BNNS / Cu composite material which is uniform and compact in structure, good in BNNS dispersion and excellent in interface bonding is finally obtained. The preparation method is controllable in process and high in practicability, the prepared copper-based composite material has outstanding heat conduction and wear resistance on the basis that the excellent electrical conductivity of a copper matrix is kept, and technical guidance is provided for research in the fields of pantograph slide plate material preparation and the like.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite technology, specifically a method for preparing a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper matrix composite material, which is particularly applicable to the field of pantograph sliding plate materials for rail transit. Background Technology

[0002] Pure copper possesses excellent electrical and thermal conductivity, making it an ideal substrate material for pantograph contactors. It effectively reduces contact resistance and Joule heating, ensuring efficient and stable power transmission. However, pure copper has drawbacks such as low hardness, poor wear resistance, and susceptibility to severe wear from long-term sliding friction with the contact wire. Therefore, improving hardness, wear resistance, and thermal conductivity while retaining the excellent intrinsic electrical conductivity of pure copper has become the core challenge in the development of next-generation high-performance pantograph contactor materials.

[0003] The key to solving this challenge lies in preparing copper-based composites by introducing a second-phase reinforcement to strengthen the matrix. Using a second-phase reinforcement to prepare copper-based composites is an effective solution to the aforementioned problems. While traditional oxide (e.g., Al₂O₃) and carbide (e.g., SiC) reinforcements can improve the hardness and wear resistance of the matrix, they severely sacrifice the electrical and thermal conductivity of copper. Two-dimensional boron nitride nanosheets (BNNS) combine high hardness, self-lubrication, oxidation resistance, and interfacial stability, with minimal negative impact on the electrical conductivity of the copper matrix, making them an ideal reinforcement. In traditional powder metallurgy, smelting, and casting processes, the prepared BNNS / Cu composites suffer from weak interfacial bonding, easy agglomeration of the reinforcing phase, and numerous porosity defects. Cold spraying combined with hot isostatic pressing (HIP) technology can ensure uniform distribution of the reinforcing phase, guaranteeing interfacial bonding of the composite material, ultimately yielding high-performance boron nitride copper-based composites. Currently, the low-cost and efficient preparation of highly conductive, thermally conductive, and wear-resistant copper-based composites remains a critical issue that urgently needs to be addressed in this field. Summary of the Invention

[0004] Based on the aforementioned research background, this invention proposes a method for preparing a high-conductivity, thermally conductive, and wear-resistant boron nitride (BNNS) reinforced copper-based composite material. The method first prepares a copper foil of a specific thickness using high-purity cathode copper. Then, a BNNS reinforcing layer is uniformly deposited on the surface of the copper foil using cold spraying technology. Finally, hot isostatic pressing (HIP) further enhances the density and dispersion of the reinforcing phase in the composite material, achieving metallurgical bonding between layers and constructing a multilayer structure of alternating "Cu-BNNS-Cu". This ultimately yields a high-performance composite material with a dense microstructure, excellent interfaces, and uniform BNNS distribution. This preparation method achieves uniform dispersion of BNNS in the copper matrix, significantly strengthening the interfacial bonding quality. Furthermore, it maximizes the preservation of the inherent high conductivity of the copper matrix while significantly improving the wear resistance of the material by leveraging the high hardness and self-lubricating properties of BNNS. This preparation process is highly controllable and practical, providing a feasible technical solution for the research and development of high-performance pantograph sliding plate materials.

[0005] The objective of this invention is achieved through the following technical solution: A method for preparing a highly electrically and thermally conductive, wear-resistant boron nitride-reinforced copper-based composite material, comprising the following steps: Preparation of high-purity copper foil 1000 g to 2000 g of high-purity cathode copper (purity ≥ 99.9%) was weighed, degreased with alcohol, and delaminated with 5 wt.% dilute sulfuric acid. 995 g to 1990 g of the copper material was then vacuum-melted under argon protection and cast to obtain a copper billet of 980 g to 1960 g. Next, the copper billet was hot-rolled to 7 mm to 10 mm in 3 to 5 passes, and after acid pickling to remove the oxide film, a copper strip of 960 g to 1920 g was obtained. Then, the copper strip was cold-rolled to a thickness of 2 mm to 3 mm, annealed at 400℃ to 500℃ in a hydrogen protective atmosphere for 1 h to 2 h, and cooled to obtain a copper strip of 950 g to 1900 g. Finally, the copper strip was precision-rolled in 12 passes to prepare a high-purity copper foil of 945 g to 1895 g with a thickness of 3 μm to 150 μm.

[0006] Cold spray deposition of BNNS / Cu foil Weigh 1 g to 10 g of BNNS and add it to 0.5 L to 2 L of anhydrous ethanol to prepare a uniform suspension. After ultrasonic dispersion for 20 min to 40 min, transfer it to a spray dryer for drying. Next, take the copper foil obtained in step (1), ultrasonically clean it with anhydrous ethanol for 10 min to 20 min, rinse it with deionized water 3 to 5 times, and then dry it with a forced air. Then, perform cold spraying. Preheat the copper foil substrate to 80℃ to 120℃, and then feed the dried BNNS powder into the powder feeding system. Under the conditions of gas temperature 200℃ to 500℃, gas pressure 2.0 MPa to 5.0 MPa, and spraying distance 10 mm to 30 mm, BNNS is uniformly deposited on the surface of the copper foil. Finally, stack the sprayed copper foil into blocks to construct an alternating "Cu-BNNS-Cu" multilayer structure to obtain 940 g to 1890 g of block material.

[0007] Preparation of BNNS / Cu composite materials by hot isostatic pressing The block material obtained in step (2) is tightly wrapped with high-purity graphite foil and placed in the center of the hot isostatic pressing furnace cavity. Then, the furnace door is sealed and a vacuum is evacuated to 0.8 × 10⁻⁶. -2 Pa ~ 1×10 -2 The mixture was initially filled with high-purity argon gas to a slightly positive pressure to isolate oxygen. Then, a two-stage heating and pressurization process was employed: first, the temperature was increased to 300℃~400℃ at a rate of 5℃ / min~10℃ / min, simultaneously pressurized to 20MPa~30 MPa, and held at this temperature and pressure for 0.5 h~1 h; then, the temperature was increased to 750℃~850℃ at a rate of 3℃ / min~5℃ / min, simultaneously pressurized to 100 MPa~150 MPa, and held at this temperature and pressure for 1 h~3 h. Subsequently, constant-pressure cooling was performed, cooling to below 200℃ at a rate of 5℃ / min~10℃ / min, and then slowly depressurized after reaching room temperature. Finally, the composite material block was removed, and the surface graphite foil was removed, yielding 935 g~1885 g of dense BNNS / Cu composite material.

[0008] Preferably, the vacuum melting in step (1) is performed using a vacuum induction furnace with an initial vacuum degree of 5×10⁻⁶. -4 Pa~5×10 -3 Pa, heating rate of 50℃ / min~100℃ / min, melting temperature of 1100℃~1300℃, holding time of 5min~10min, melting 3~5 times.

[0009] Preferably, the rolling process in step (1) uses a four-roll mill with a hot rolling temperature of 800℃~1000℃, a cold rolling temperature of 20℃~150℃, and a finishing rolling temperature of room temperature.

[0010] Preferably, the proportion of BNNS powder in step (2) is 0.1 wt.%~0.5 wt.% (calculated by total amount), the sheet diameter is 100 nm~200 nm, and the morphology can be single-layer, double-layer or multi-layer boron nitride nanosheets.

[0011] Preferably, the spray dryer in step (2) has an inlet temperature of 100℃~120℃ and an outlet temperature of 60℃~80℃, and a recovery rate of ≥95% while removing anhydrous ethanol.

[0012] Preferably, the blowing drying in step (2) is carried out using a blowing dryer, with a drying temperature of 60℃~80℃ and a drying time of 1 h~2 h.

[0013] Preferably, other control parameters of the cold spraying process in step (2) include: the accelerating gas is helium or nitrogen, the powder feeding rate is 1 g / min to 10 g / min, the spray gun moving speed is 0.1 mm / s to 1 mm / s, the spraying angle is 80° to 90°, and the scanning spacing is 5 mm to 15 mm.

[0014] Preferably, the thickness of the high-purity graphite foil used in step (3) is 0.1 mm to 0.2 mm.

[0015] The beneficial effects of this invention are: The synergistic effect of cold spraying technology and hot isostatic pressing can effectively suppress the agglomeration of BNNS, allowing it to be uniformly dispersed in the copper matrix and form a continuous discrete layered distribution structure; at the same time, it can promote the tight metallurgical bonding between the two, strengthen the interfacial bonding strength, and effectively promote stress transfer.

[0016] By utilizing the high strength and self-lubricating properties of BNNS itself, combined with the "Cu-BNNS-Cu" layered structure design, frictional stress is effectively dispersed and peeling wear is avoided. This not only gives the composite material high wear resistance but also maintains high electrical conductivity.

[0017] The preparation process is highly controllable. Copper foil rolling, cold spraying, and hot isostatic pressing are all mature industrial technologies that do not require special equipment and have the foundation for large-scale mass production. This provides key technical support and a clear research direction for the development and application of high-performance copper-based composite materials in fields such as pantograph sliding plate materials. Attached Figure Description

[0018] 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.

[0019] Figure 1The bar charts show the electrical and thermal conductivity of the final BNNS / Cu composite materials obtained in Examples 1, 2, and 3, and the final pure copper (P-Cu) material obtained in Comparative Example 1. 0.1 wt.% BNNS / Cu, 0.3 wt.% BNNS / Cu, and 0.5 wt.% BNNS / Cu represent the BNNS / Cu composite materials of Examples 1, 2, and 3, respectively. Figure 2 The bar charts show the hardness and wear rate of the BNNS / Cu composite materials obtained in Examples 1, 2, and 3, and the pure copper (P-Cu) material obtained in Comparative Example 1. 0.1 wt.% BNNS / Cu, 0.3 wt.% BNNS / Cu, and 0.5 wt.% BNNS / Cu represent the BNNS / Cu composite materials of Examples 1, 2, and 3, respectively. Figure 3 The friction coefficient variation curves of 0.1 wt.% BNNS / Cu composite material and pure copper in Example 1 and Comparative Example 1 are shown. Figure 4 The images show the SEM morphology of the worn surfaces of the 0.1 wt.% BNNS / Cu composite material and pure copper obtained in Example 1 and Comparative Example 1. Figure 5 The friction coefficient variation curves of 0.3 wt.% BNNS / Cu composite material and pure copper in Example 2 and Comparative Example 2 are shown. Figure 6 The images show the SEM morphology of the worn surfaces of the 0.3 wt.% BNNS / Cu composite material and pure copper obtained in Example 2 and Comparative Example 2. Figure 7 The friction coefficient variation curves of 0.5 wt.% BNNS / Cu composite material and pure copper in Example 3 and Comparative Example 3 are shown. Figure 8 The images show the SEM morphology of the worn surfaces of the 0.5 wt.% BNNS / Cu composite material and pure copper obtained in Example 3 and Comparative Example 3. Detailed Implementation

[0020] 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.

[0021] In the following embodiments: BNNS powder has a purity of 99.9%, with 5 to 20 layers, a thickness of 5 nm to 20 nm, and a sheet diameter of 100 nm to 200 nm. It is produced by Zhejiang Yamei Nanotechnology Co., Ltd. Cathode copper has a purity of 99.9% and is available in sheet or irregular shape. (Yunnan Copper Co., Ltd.) Scanning electron microscope: Nova Nano-450, FEI, USA; Tribological properties of the BNNS / Cu composite material and pure copper material prepared in the examples and comparative examples were characterized by: rotating dry sliding tribological tests were conducted at room temperature using a tribological testing machine (MS-M9000, Lanzhou Huahui). The test load was 20 N; the rotation speed was 150 r / min; the test time was 30 min; and the rotation radius was 5 mm.

[0022] Example 1 A method for preparing a highly electrically and thermally conductive, wear-resistant boron nitride-reinforced copper-based composite material, the specific steps of which are as follows: Preparation of high-purity copper foil 1000 g of high-purity cathode copper was weighed, degreased with alcohol, and delaminated with 5 wt.% dilute sulfuric acid. 995 g of the copper material was then vacuum-melted under argon protection, and cast into copper billets ranging from 980 g to 1960 g. (The vacuum melting was performed in a vacuum induction furnace with an initial vacuum of 5 × 10⁻⁴ Pa, a heating rate of 50 °C / min, a melting temperature of 1100 °C, a holding time of 5 min, and three melting cycles.) Next, the copper billets were hot-rolled in three passes to 7 mm at 800 °C. After pickling to remove the oxide film, 960 g of copper strip was obtained. Then, the copper strip was cold-rolled at 20 °C to a thickness of 2 mm, annealed at 400 °C in a hydrogen protective atmosphere for 1 h, and cooled to obtain 950 g of copper strip. Finally, the copper strip was precision-rolled in 12 passes to prepare 945 g of high-purity copper foil with a thickness of 30 μm.

[0023] Cold spray deposition of BNNS / Cu foil Weigh 1 g (0.1 wt.%, calculated by total amount) of BNNS and add it to 0.5 L of anhydrous ethanol to prepare a uniform suspension. After ultrasonic dispersion for 20 min, transfer it to a spray dryer for drying. The inlet temperature is 100℃ and the outlet temperature is 60℃. Next, take the copper foil obtained in step (1), ultrasonically clean it with anhydrous ethanol for 10 min, rinse it with deionized water 5 times, and then dry it with a forced air at a drying temperature of 60℃ for 1 h. Then, perform cold spraying. Preheat the copper foil substrate to 80℃, and then feed the dried BNNS powder into the powder feeding system. Under the conditions of gas temperature of 280℃, gas pressure of 3.0 MPa, spraying distance of 15 mm, powder feeding rate of 5 g / min, spray gun moving speed of 0.5 mm / s, spraying angle of 85°, and scanning interval of 10 mm, BNNS is uniformly deposited on the surface of the copper foil. Finally, the coated copper foil was stacked into a block to construct an alternating "Cu-BNNS-Cu" multilayer structure, resulting in a 940 g block material.

[0024] Preparation of BNNS / Cu composite materials by hot isostatic pressing The block material obtained in step (2) is tightly wrapped with high-purity graphite foil and placed in the center of the hot isostatic pressing furnace cavity. Then, the furnace door is sealed and a vacuum is evacuated to 0.8 × 10⁻⁶. -2 The mixture was initially filled with high-purity argon gas to a slightly positive pressure to isolate oxygen. Then, a two-stage heating and pressurization process was employed: first, the temperature was increased to 300℃ at a rate of 5℃ / min, and the pressure was simultaneously increased to 20 MPa, held for 0.5 h; then, the temperature was increased to 750℃ at a rate of 3℃ / min, and the pressure was simultaneously increased to 100 MPa, held for 1.5 h. Subsequently, constant-pressure cooling was performed, cooling to below 200℃ at a rate of 5℃ / min, and then slowly depressurized after reaching room temperature. Finally, the composite material block was removed, and the surface graphite foil was removed, yielding 935 g of dense BNNS / Cu composite material.

[0025] Comparative Example 1 Take 945 g of copper foil with a thickness of 30 μm obtained in step (1) of Example 1 and stack it into a block.

[0026] The block material obtained in step (1) is tightly wrapped with high-purity graphite foil and placed in the center of the hot isostatic pressing furnace cavity. Then, the furnace door is sealed and a vacuum is evacuated to 0.8 × 10⁻⁶. -2The pressure was increased to 300℃ and simultaneously increased to 20 MPa at a rate of 5℃ / min, and held at that temperature and pressure for 0.5 h. Then, the pressure was increased to 750℃ and simultaneously increased to 100 MPa at a rate of 3℃ / min, and held at that temperature and pressure for 1.5 h. Subsequently, constant pressure cooling was performed, cooling to below 200℃ at a rate of 5℃ / min, and then slowly depressurized after reaching room temperature. Finally, the composite material block was removed, the surface graphite foil was removed, and 940 g of dense pure copper block material was obtained.

[0027] The electrical and thermal conductivity of the BNNS / Cu composite material prepared in Example 1 and the pure copper material prepared in Comparative Example 1 were tested, and the results are as follows: Figure 1 As shown; the hardness was tested, and the results are as follows. Figure 2 As shown; a ball-disc friction test was conducted (rotational friction, room temperature dry grinding, rotation radius of 5 mm, load of 20 N, rotation speed of 150 rpm, time of 30 min, friction pair Al2O3), and the wear rate is as follows. Figure 2 As shown, the friction coefficient variation curve is as follows: Figure 3 As shown, the wear morphology is as follows Figure 4 As shown.

[0028] like Figure 1 , Figure 2 As shown, the BNNS / Cu composite material prepared by adding BNNS exhibits significantly better performance than pure copper. Comparing Example 1 and Comparative Example 1, the composite material of Example 1 still maintains excellent electrical conductivity (approximately 90.2% IACS). Regarding thermal conductivity, the composite material of Example 1 shows a certain improvement over the pure copper material of Comparative Example 1, from 392 W·m⁻¹. -1 ·K -1 Increased to 431 W·m -1 ·K -1 The increase was approximately 9.95%. Regarding hardness, the composite material of Example 1 showed a significant improvement over the pure copper material of Comparative Example 1, increasing from 86.58 HV to 127.45 HV, an increase of approximately 47.2%. The main reasons for this performance optimization are: firstly, BNNS itself possesses high thermal conductivity, and the "cold spraying + hot isostatic pressing process" enables uniform dispersion of BNNS in the copper matrix, while preserving the integrity of the copper matrix structure, enhancing interfacial bonding strength, and reducing the scattering of electron and phonon transport by interfacial defects, thus maintaining the composite material's electrical conductivity above 90% IACS and significantly improving its thermal conductivity compared to pure copper; secondly, BNNS has extremely high hardness, which can hinder dislocation movement through dispersion strengthening, greatly optimizing the hardness performance of the composite material.

[0029] like Figure 2 , Figure 3As shown, in terms of wear performance, the BNNS / Cu composite material is also superior to the pure copper material. Comparing Example 1 and Comparative Example 1, the wear rate of the composite material in Example 1 is significantly lower than that of the pure copper material in Comparative Example 1, decreasing from 14.9 × 10⁻⁶. -5 mm -3 ·N -1 ·m -1 It decreased to 11.7×10 -5 mm -3 ·N -1 ·m -1 The wear rate decreased by approximately 21.5%. The coefficient of friction decreased from approximately 0.55 to 0.45, a reduction of about 18%. This is attributed to the high hardness and self-lubricating properties of BNNS itself: on the one hand, BNNS strengthens the copper matrix, increasing the overall hardness of the composite material and providing stronger wear resistance during friction; on the other hand, a lubricating film forms on the material surface during sliding friction, effectively isolating it from contact with the friction pair, reducing plastic deformation, improving wear resistance, and thus simultaneously reducing the material's wear rate and coefficient of friction.

[0030] like Figure 4 As shown, the BNNS / Cu composite material obtained after adding BNNS exhibits superior wear performance compared to the pure copper material. Figure 4 (a) The surface of the composite material has shallow and narrow wear marks, little wear debris, smooth edges, and no obvious material peeling or large-area plastic deformation; Figure 4 (b) The surface of the pure copper material exhibits wide and deep wear marks, with a large accumulation of debris, accompanied by extensive plastic deformation and cracks, forming an uneven and rough wear surface. The core reason lies in the high hardness and self-lubricating properties of BNNS. When the composite material rubs against the friction pair, it can effectively resist frictional stress. The formed "Cu-BNNS-Cu" layered structure further strengthens the interfacial bonding, ensuring that BNNS is uniformly dispersed and not easily peeled off, while also effectively dispersing frictional stress and preventing crack propagation, ultimately giving the composite material superior wear resistance.

[0031] Example 2 A method for preparing a highly electrically and thermally conductive, wear-resistant boron nitride-reinforced copper-based composite material, the specific steps of which are as follows: Preparation of high-purity copper foil 1500 g of high-purity cathode copper was weighed, degreased with alcohol, and then delaminated with 5 wt.% dilute sulfuric acid. 1495 g of the copper material was then vacuum-melted under argon protection, and cast into a 1480 g copper billet. (The vacuum melting was performed using a vacuum induction furnace with an initial vacuum degree of 2.5 × 10⁻⁶.) -3The process involved: heating at 75℃ / min, melting at 1200℃, holding for 7 min, and melting four times. Next, the copper billet was hot-rolled four times to 9 mm at 900℃. After pickling to remove the oxide film, 1460 g of copper strip was obtained. Then, the copper strip was cold-rolled at 85℃ to a thickness of 2.5 mm, annealed at 450℃ in a hydrogen protective atmosphere for 1.5 h, and cooled to obtain 1450 g of copper strip. Finally, the copper strip was precision rolled 12 times to prepare 1445 g of high-purity copper foil with a thickness of 70 μm.

[0032] Cold spray deposition of BNNS / Cu foil Weigh 4.5 g (0.3 wt.%, calculated by total amount) of BNNS and add it to 1 L of anhydrous ethanol to prepare a uniform suspension. After ultrasonic dispersion for 30 min, transfer it to a spray dryer for drying. The inlet temperature is 110℃ and the outlet temperature is 70℃. Next, take the copper foil obtained in step (1), ultrasonically clean it with anhydrous ethanol for 15 min, rinse it with deionized water 4 times, and then dry it with a forced air at a drying temperature of 70℃ for 1.5 h. Then, perform cold spraying. Preheat the copper foil substrate to 100℃, and then feed the dried BNNS powder into the powder feeding system. Under the conditions of gas temperature of 350℃, gas pressure of 4.0 MPa, spraying distance of 20 mm, powder feeding rate of 1 g / min, spray gun moving speed of 0.6 mm / s, spraying angle of 80°, and scanning interval of 5 mm, BNNS is uniformly deposited on the surface of the copper foil. Finally, the coated copper foil was stacked into a block to construct an alternating "Cu-BNNS-Cu" multilayer structure, resulting in a 1440 g block material.

[0033] Preparation of BNNS / Cu composite materials by hot isostatic pressing The block material obtained in step (2) is tightly wrapped with high-purity graphite foil and placed in the center of the hot isostatic pressing furnace cavity. Then, the furnace door is sealed and a vacuum is drawn to 0.9 × 10⁻⁶. -2 The mixture was initially filled with high-purity argon gas to a slightly positive pressure to isolate oxygen. Then, a two-stage heating and pressurization process was employed: first, the temperature was increased to 350℃ at a rate of 8℃ / min, simultaneously pressurized to 25 MPa, and held for 0.5 h; then, the temperature was increased to 800℃ at a rate of 4℃ / min, simultaneously pressurized to 120 MPa, and held for 2 h. Subsequently, constant-pressure cooling was performed, cooling to below 200℃ at a rate of 8℃ / min, and then slowly depressurized after reaching room temperature. Finally, the composite material block was removed, and the surface graphite foil was removed, yielding 1435 g of dense BNNS / Cu composite material.

[0034] Comparative Example 2 Take 1445 g of the copper foil with a thickness of 70 μm obtained in step (1) of Example 2 and stack it into a block.

[0035] The block material obtained in step (1) is tightly wrapped with high-purity graphite foil and placed in the center of the hot isostatic pressing furnace cavity. Then, the furnace door is sealed and a vacuum is drawn to 0.9 × 10⁻⁶. -2 The pressure was increased to 350°C at a rate of 8°C / min, and simultaneously increased to 25 MPa, holding the pressure for 0.5 h. Then, the pressure was increased to 800°C at a rate of 4°C / min, and simultaneously increased to 120 MPa, holding the pressure for 2 h. Following this, the material was cooled under constant pressure at a rate of 8°C / min to below 200°C, and then slowly depressurized after reaching room temperature. Finally, the composite material block was removed, the surface graphite foil was removed, and 1440 g of dense pure copper block material was obtained.

[0036] The electrical and thermal conductivity of the BNNS / Cu composite material prepared in Example 2 were tested, and the results are as follows: Figure 1 As shown; the hardness was tested, and the results are as follows. Figure 2 As shown. Ball-disc friction tests were conducted on Example 2 and Comparative Example 2, and the wear rates are as follows: Figure 2 As shown, the friction coefficient variation curve is as follows: Figure 5 As shown, the wear morphology is as follows Figure 6 As shown.

[0037] like Figure 1 , Figure 2 As shown, similar to Example 1, the prepared BNNS / Cu composite material exhibits superior performance compared to pure copper. Compared to Example 1, the electrical conductivity of Example 2 remains almost unchanged, while the thermal conductivity increases from 431 W·m. -1 ·K -1 Increased to 442 W·m -1 ·K -1 The performance of Example 2 was improved by approximately 2.6%, and the hardness was also improved by 12.7%. Example 2 showed a significant performance improvement over Example 1 because the appropriate BNNS content resulted in better dispersion, further enhancing the composite material's properties.

[0038] like Figure 2 , Figure 5 As shown, the wear rate of the composite material in Example 2 was 11.7 × 10⁻⁶. -5 mm -3 ·N -1 ·m -1 It was reduced to 9.2×10 -5 mm -3 ·N -1 ·m -1The friction coefficient of the composite material in Example 2 was reduced by approximately 21%. The friction coefficient of the composite material in Example 2 was also significantly lower than that of the pure copper material in Comparative Example 2. The friction coefficient of Example 2 remained stable at around 0.42 throughout the entire process, with a smooth curve and minimal fluctuations, indicating a stable friction interface. In contrast, the friction coefficient of Comparative Example 2 remained in the range of 0.45 to 0.5, with larger fluctuations. The reasons for this enhancement are roughly similar to those in Example 1, but compared to Example 1, the friction coefficient of Example 2 fluctuated less and the curve was smoother. This is because the appropriate amount of BNNS was dispersed more evenly, resulting in a more robust lubricating film generated during sliding and thus a better effect.

[0039] like Figure 6 As shown, the BNNS / Cu composite material obtained after adding BNNS exhibits superior wear performance compared to the pure copper material. Figure 6 (a) The wear surface of the composite material is generally flat and smooth, with only shallow and fine traces, and no obvious material peeling or large-area rough damage. Figure 6 (b) The pure copper material exhibits large wear pits on its worn surface, with a large accumulation of plastic tear debris and blocky peeling around the pit walls. There are numerous cracks, and the worn surface is uneven. The cause is basically the same as in Example 1.

[0040] Example 3 A method for preparing a highly electrically and thermally conductive, wear-resistant boron nitride-reinforced copper-based composite material, the specific steps of which are as follows: Preparation of high-purity copper foil 2000 g of high-purity cathode copper was weighed, degreased with alcohol, and then delaminated with 5 wt.% dilute sulfuric acid. 1995 g of the copper material was then vacuum-melted under argon protection, and cast into a 1980 g copper billet. (The vacuum melting was performed using a vacuum induction furnace with an initial vacuum degree of 5 × 10⁻⁶.) -3 The process involved: heating at 100℃ / min, melting at 1300℃, holding for 10 min, and melting five times. Next, the copper billet was hot-rolled to 10 mm in five passes at 1000℃. After pickling to remove the oxide film, 1960 g of copper strip was obtained. Then, the copper strip was cold-rolled at 150℃ to a thickness of 3 mm, annealed in a hydrogen protective atmosphere at 500℃ for 2 h, and cooled to obtain 1950 g of copper strip. Finally, the copper strip was precision rolled in 12 passes to prepare 1945 g of high-purity copper foil with a thickness of 105 μm.

[0041] Cold spray deposition of BNNS / Cu foil Weigh 10 g (0.5 wt.%, calculated by total amount) of BNNS and add it to 2 L of anhydrous ethanol to prepare a uniform suspension. After ultrasonic dispersion for 40 min, transfer it to a spray dryer for drying. The inlet temperature is 120℃ and the outlet temperature is 80℃. Next, take the copper foil obtained in step (1), ultrasonically clean it with anhydrous ethanol for 20 min, rinse it three times with deionized water, and then dry it with a forced air at 80℃ for 2 h. Then, perform cold spraying. Preheat the copper foil substrate to 120℃, and then feed the dried BNNS powder into the powder feeding system. Under the conditions of gas temperature 400℃, gas pressure 3.5 MPa, spraying distance 10 mm, powder feeding rate 10 g / min, spray gun moving speed 1 mm / s, spraying angle 90°, and scanning interval 15 mm, BNNS is uniformly deposited on the surface of the copper foil. Finally, the sprayed copper foil was stacked into a block to construct an alternating "Cu-BNNS-Cu" multilayer structure, resulting in a 1940 g block material.

[0042] Preparation of BNNS / Cu composite materials by hot isostatic pressing The block material obtained in step (2) is tightly wrapped with high-purity graphite foil and placed in the center of the hot isostatic pressing furnace cavity. Then, the furnace door is sealed and a vacuum of 1×10⁻⁶ is created. -2 The mixture was initially filled with high-purity argon gas to a slightly positive pressure to isolate oxygen. Then, a two-stage heating and pressurization process was employed: first, the temperature was increased to 380℃ at a rate of 10℃ / min, and the pressure was simultaneously increased to 27 MPa, held for 1 h; then, the temperature was increased to 850℃ at a rate of 5℃ / min, and the pressure was simultaneously increased to 150 MPa, held for 2.5 h. Subsequently, constant-pressure cooling was performed, cooling to below 200℃ at a rate of 10℃ / min, and then slowly depressurized after reaching room temperature. Finally, the composite material block was removed, and the surface graphite foil was removed, yielding 1935 g of dense BNNS / Cu composite material.

[0043] Comparative Example 3 Take 1945 g of copper foil with a thickness of 105 μm obtained in step (1) of Example 3 and stack it into a block.

[0044] The block material obtained in step (1) is tightly wrapped with high-purity graphite foil and placed in the center of the hot isostatic pressing furnace cavity. Then, the furnace door is sealed and a vacuum of 1×10⁻⁶ is created. -2The pressure was increased to 380℃ and simultaneously increased to 27 MPa at a rate of 10℃ / min, and held for 1 hour. Then, the pressure was increased to 850℃ and simultaneously increased to 150 MPa at a rate of 5℃ / min, and held for 2.5 hours. Afterward, constant pressure cooling was performed at a rate of 10℃ / min to below 200℃, and then slowly depressurized after reaching room temperature. Finally, the composite material block was removed, the surface graphite foil was removed, and 1940 g of dense pure copper block material was obtained.

[0045] The electrical and thermal conductivity of the BNNS / Cu composite material prepared in Example 3 were tested, and the results are as follows: Figure 1 As shown; the hardness was tested, and the results are as follows. Figure 2 As shown. Ball-disc friction tests were conducted on Example 3 and Comparative Example 3, and the wear rates are as follows: Figure 2 As shown, the friction coefficient variation curve is as follows: Figure 7 As shown, the wear morphology is as follows Figure 8 As shown.

[0046] like Figure 1 , Figure 2 As shown, although Example 3 has a slight improvement in thermal conductivity compared to Example 2, its hardness is reduced and its wear rate is increased. Excessive BNNS will reduce the interfacial bonding strength, and some BNNS will agglomerate, which will reduce the performance of the composite material.

[0047] like Figure 7 As shown, the friction coefficient of the composite material in Example 3 is significantly lower than that of the pure copper material in Comparative Example 3. However, compared to Example 2, the friction coefficient curve of Example 2 is relatively flat and smooth with less fluctuation, and the friction interface state is more stable.

[0048] like Figure 8 As shown, the wear morphology of the composite material in Example 3 is significantly better than that of the pure copper material in Comparative Example 3. However, compared with Example 2, its surface wear is still greater, with more debris accumulation. Excessive BNNS will reduce the interfacial bonding strength and decrease the wear performance of the composite material.

[0049] In summary, this invention provides a method for preparing a boron nitride (BNN) reinforced copper-based composite material with high electrical and thermal conductivity and wear resistance. This method offers strong process controllability and is suitable for large-scale mass production. The resulting composite material exhibits high strength and wear resistance while maintaining good electrical conductivity. The combination of cold spraying and hot isostatic pressing (HIP) processes ensures a more uniform distribution of BNNN, effectively suppressing its agglomeration and improving the interfacial bonding between BNNN and the copper matrix, thus effectively addressing the problems in the prior art. The resulting copper-based composite material demonstrates excellent mechanical and wear resistance properties, providing technical guidance for the development of high-performance copper-based composite materials for application in pantograph sliding plate materials.

[0050] 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 a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper-based composite material, characterized in that: The method steps are as follows: Preparation of high-purity copper foil Weigh 1000 g to 2000 g of high-purity cathode copper, degrease it with alcohol and remove the film with dilute sulfuric acid, then melt the copper material under vacuum under argon protection and cast it into a billet. Then, hot-roll and cold-roll the copper billet to thin it to obtain a copper strip of 2 mm to 3 mm. Finally, the copper strip is precision rolled 12 times to prepare a high-purity copper foil with a thickness of 3 μm to 150 μm. Cold spray deposition of BNNS / Cu foil Weigh 1 g to 10 g of BNNS and disperse it in anhydrous ethanol. Sonicate it to form a uniform suspension. Spray dry it to obtain BNNS powder. Then, take the copper foil obtained in step (1), sonicate it in anhydrous ethanol and dry it with a blower. Then, use cold spraying technology to preheat the copper foil substrate and use nitrogen as the accelerating gas to uniformly deposit BNNS powder on the surface of the copper foil. Finally, stack the sprayed copper foil into blocks to construct an alternating multilayer structure of "Cu-BNNS-Cu". Preparation of BNNS / Cu composite materials by hot isostatic pressing The block sample obtained in step (2) was wrapped with high-purity graphite foil, placed in the center of the hot isostatic pressing furnace, the furnace door was sealed, and after evacuation, high-purity argon gas was introduced. Then, a two-stage heating and pressurization process was used for heating and isostatic pressing. Finally, the composite block was taken out and the surface graphite foil was removed to obtain a dense BNNS / Cu composite material.

2. The method for preparing a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper-based composite material according to claim 1, characterized in that: In step (1), the vacuum melting is carried out using a vacuum induction melting furnace with an initial vacuum degree of 5×10⁻⁶. -4 Pa~5×10 -3 Pa, heating rate of 50℃ / min~100℃ / min, melting temperature of 1100℃~1300℃, holding time of 5 min~10 min, melting 3~5 times.

3. The method for preparing a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper-based composite material according to claim 1, characterized in that: In step (1), the rolling process uses a four-roll mill. The hot rolling process involves hot rolling the copper billet to a thickness of 7 mm to 10 mm in 3 to 5 passes at 800℃ to 1000℃ to obtain 960 g to 1920 g of copper strip. The cold rolling process involves cold rolling the copper strip to a thickness of 2 mm to 3 mm at 20℃ to 150℃, annealing it in a hydrogen protective atmosphere at 400℃ to 500℃ for 1 h to 2 h, and then cooling it to obtain 950 g to 1900 g of copper strip.

4. The method for preparing a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper-based composite material according to claim 1, characterized in that: In step (2), the proportion of BNNS powder is calculated as follows: 0.1 wt.%~0.5 wt.%, with a sheet diameter of 100 nm~200 nm and a morphology of single-layer, double-layer or multi-layer boron nitride nanosheets.

5. The method for preparing a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper-based composite material according to claim 1, characterized in that: In step (2), the spray drying is carried out using a spray dryer with an inlet temperature of 100℃~120℃ and an outlet temperature of 60℃~80℃. While removing anhydrous ethanol, the recovery rate is ≥ 95%.

6. The method for preparing a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper-based composite material according to claim 1, characterized in that: In step (2), the blowing drying is carried out in a blowing drying box with a drying temperature of 60℃~80℃ and a drying time of 1 h~2 h.

7. The method for preparing a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper-based composite material according to claim 1, characterized in that: In step (2), the control parameters of the cold spraying process include: gas temperature of 200℃~500℃, gas pressure of 2.0 MPa~5.0 MPa, spraying distance of 10 mm~30 mm, powder feeding rate of 1 g / min~10 g / min, spray gun moving speed of 0.1 mm / s~1 mm / s, spraying angle of 80°~90°, and scanning spacing of 5 mm~15 mm.

8. The method for preparing a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper-based composite material according to claim 1, characterized in that: In step (3), the high-purity graphite foil used has a thickness of 0.1 mm to 0.2 mm.

9. The method for preparing a high electrical conductivity, thermal conductivity, and wear-resistant boron nitride reinforced copper-based composite material according to claim 1, characterized in that: In step (3), the hot isostatic pressing process adopts a two-stage heating and pressurizing process. The process parameters of the first stage are: heating rate: 5℃ / min~10℃ / min, holding temperature: 300℃~400℃, holding pressure: 20 MPa~30 MPa, and holding time: 0.5 h~1 h. The process parameters of the second stage are: heating rate: 3℃ / min~5℃ / min, holding temperature: 750℃~850℃, holding pressure: 100 MPa~150 MPa, and holding time: 1 h~3 h.

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