Boron nitride reinforced copper-based composite material and preparation method therefor

Abstract

A preparation method for a boron nitride reinforced copper-based composite material, comprising: introducing boron nitride in an in-situ synthesis manner to prepare boron nitride-copper composite powder; using a powder metallurgy process to prepare the composite powder into a boron nitride-copper composite material; performing mechanical deformation processing on the composite material, and densifying the composite material to form a stack structure of boron nitride and copper and obtain the boron nitride reinforced copper-based composite material, wherein the angle difference between the boron nitride in the stack structure in a main deformation direction is less than 10°. The boron nitride reinforced copper-based composite material obtained by the preparation method has high thermal conductivity, electrical conductivity, and corrosion resistance. The present invention further relates to a boron nitride reinforced copper-based composite material.

Description

Boron nitride reinforced copper-based composite material and preparation method thereof Technical Field

[0001] The present disclosure relates to the technical field of composite materials, and in particular, to a boron nitride reinforced copper-based composite material and a preparation method thereof. Background Art

[0002] Copper has excellent electrical conductivity and is widely used as an important conductor material in key fields such as electrical and electronic engineering. However, with the rapid development of fifth-generation mobile communication technology (5G), new energy, power semiconductors and other fields, the current that equipment needs to carry is getting larger and larger, and the heat generation power is also increasing, which puts new requirements on the performance of copper materials. In order to ensure the power supply and heat dissipation of the device, copper materials need to have excellent electrical and thermal conductivity, especially high electrical and thermal conductivity at high temperatures. In addition, the service conditions faced by electronic equipment are becoming more and more complex, and they are often exposed to various liquid media. Under alkaline or high salt concentration conditions, pure copper may suffer from severe corrosion, leading to device failure.

[0003] To address metal corrosion, organic or inorganic coatings are often applied to metal surfaces as an effective protective measure. For example, PVC or PE are used as insulation jackets on power transmission lines, and resins are used as insulating layers on enameled wire. These coatings provide excellent corrosion protection for copper without affecting the electrical and thermal conductivity of the copper itself. However, for copper used in fields such as micro- and nanoelectronics, coatings can affect the contact between the copper conductor and electronic devices, making traditional organic or inorganic coating methods unsuitable. A common corrosion protection method in these fields is alloying, which significantly improves copper's corrosion resistance by adding appropriate amounts of alloying elements such as tin and zinc to pure copper. However, the introduction of alloying elements can significantly reduce the electrical and thermal conductivity of copper. For example, adding just 0.15 wt.% tin can reduce copper's electrical conductivity to below 90% IACS.

[0004] Therefore, there is an urgent need to develop a copper composite material with high corrosion resistance while maintaining or even improving electrical and thermal conductivity. Summary of the Invention

[0005] In view of this, the present disclosure provides a boron nitride reinforced copper-based composite material and a preparation method thereof, in order to at least partially solve the above technical problems.

[0006] As a first aspect of the present disclosure, a method for preparing a boron nitride-reinforced copper-based composite material is provided, comprising: preparing a boron nitride-copper composite powder; using a powder metallurgy process to form the composite powder into a boron nitride-copper composite material; and mechanically deforming the composite material to densify the composite material to form a laminated structure of boron nitride and copper, thereby obtaining a boron nitride-reinforced copper-based composite material; wherein the angular difference between the boron nitrides in the laminated structure along the main deformation direction is less than 10°.

[0007] According to an embodiment of the present disclosure, the preparation method further includes: introducing copper nanoparticles into the composite powder for surface modification to improve the interface bonding performance between boron nitride and copper.

[0008] According to an embodiment of the present disclosure, the mass ratio of boron nitride to copper in the composite powder is (0.01-5):(95-99.9).

[0009] According to an embodiment of the present disclosure, the mechanical deformation process causes the composite material to have a total deformation amount greater than 30%.

[0010] According to an embodiment of the present disclosure, the boron nitride is a boron nitride nanosheet; the boron nitride nanosheet has a lateral size of 0.5 to 20 μm and a thickness of 1 to 10 nm.

[0011] According to an embodiment of the present disclosure, the composite powder further includes doping metal; the addition amount of the doping metal is 0-5% of the composite powder; the doping metal includes any one or more of silver, chromium, tin, iron, lanthanum, and zirconium.

[0012] According to an embodiment of the present disclosure, the mechanical deformation processing method includes: hot rolling the composite material at a temperature of 800-1000° C.; the reduction amount during each hot rolling process is 8-12%, and the cumulative reduction amount is 50-75%.

[0013] According to the embodiments of the present disclosure, after mechanical deformation processing, the density of the obtained boron nitride reinforced copper-based composite material is higher than 99.5%; the interlayer spacing between boron nitrides in the boron nitride reinforced copper-based composite material is 0.1 to 2 μm; and the lateral size of boron nitride in the boron nitride reinforced copper-based composite material is 100 to 1000 nm.

[0014] As a second aspect of the present disclosure, a boron nitride reinforced copper-based composite material prepared by the above-mentioned preparation method is provided, wherein the angle difference between the boron nitrides along the main deformation direction in the laminated structure of the boron nitride reinforced copper-based composite material is less than 10°.

[0015] According to an embodiment of the present disclosure, the boron nitride reinforced copper-based composite material includes boron nitride, copper and impurity elements; the contents of boron nitride and copper in the boron nitride reinforced copper-based composite material are higher than 95%.

[0016] Based on the above technical solution, the present disclosure provides a boron nitride reinforced copper-based composite material and its preparation method. The boron nitride-copper composite powder is prepared into a composite material, and the composite material is mechanically deformed to form a laminated structure of boron nitride and copper during the mechanical deformation process. The angle difference between the boron nitride in the laminated structure along the main deformation direction can be controlled to be less than 10°, thereby further densifying the composite material, achieving a highly oriented arrangement of the boron nitride in the copper matrix, reducing the scattering of electrons and boron nitride, and maintaining the electrical conductivity of the boron nitride reinforced copper-based composite material above 95 IACS%. The boron nitride also fully utilizes the advantages of the high in-plane thermal conductivity of the boron nitride, and can still maintain excellent thermal conductivity at high temperatures. Furthermore, boron nitride has excellent corrosion resistance, and the preparation of the boron nitride-copper composite material can effectively improve the corrosion resistance of the copper material. Therefore, the boron nitride reinforced copper-based composite material obtained based on this preparation method has high thermal conductivity, electrical conductivity, and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is a flow chart of a method for preparing a boron nitride reinforced copper-based composite material according to an embodiment of the present disclosure;

[0018] FIG2 is a scanning electron microscope photograph of the distribution of boron nitride in the boron nitride reinforced copper-based composite material in Example 1 of the present disclosure;

[0019] FIG3 is a schematic diagram of the distribution of boron nitride in the boron nitride reinforced copper-based composite material in Example 1 of the present disclosure;

[0020] FIG4 is a transmission electron microscope photograph of the boron nitride reinforced copper-based composite material in Example 1 of the present disclosure;

[0021] FIG5 is a transmission electron micrograph of the interface of the boron nitride reinforced copper-based composite material in Example 1 of the present disclosure;

[0022] FIG6 is a graph showing the change in thermal conductivity of the boron nitride reinforced copper-based composite material and pure copper in the horizontal direction as a function of temperature in Example 1 of the present disclosure;

[0023] FIG7 is a graph showing the change in thermal conductivity of the boron nitride reinforced copper-based composite material and pure copper in the vertical direction as a function of temperature in Example 1 of the present disclosure;

[0024] FIG8 is a polarization curve diagram of the boron nitride reinforced copper-based composite material and pure copper in Example 1 of the present disclosure;

[0025] FIG9 is a Nyquist plot of the boron nitride reinforced copper-based composite material and pure copper in Example 1 of the present disclosure;

[0026] FIG10 is a Bode plot (frequency / impedance) of the boron nitride reinforced copper-based composite material and pure copper in Example 1 of the present disclosure;

[0027] FIG11 is a Bode plot (frequency / phase angle) of the boron nitride reinforced copper-based composite material and pure copper in Example 1 of the present disclosure;

[0028] FIG12 is a scanning electron microscope image of the distribution of boron nitride in the boron nitride reinforced copper-based composite material in Example 2 of the present disclosure;

[0029] FIG13 is a scanning electron microscope image of the distribution of boron nitride in the boron nitride reinforced copper-based composite material in Example 3 of the present disclosure. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0031] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0032] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0033] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0034] When expressions such as "at least one of A, B and C, etc." are used, they should generally be interpreted in accordance with the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0035] Boron nitride has excellent in-plane thermal conductivity (about 2000W·m -1 ·K -1), oxidation resistance (>900℃) and corrosion resistance. Boron nitride is expected to significantly improve the thermal conductivity and corrosion resistance of copper materials after being compounded with copper. Furthermore, if a highly directional arrangement of boron nitride in the copper matrix can be achieved, the in-plane thermal conductivity advantage of boron nitride can be fully utilized, thereby improving the thermal conductivity of the composite material. At the same time, the excellent corrosion resistance of boron nitride nanosheets helps to extend the diffusion path of the corrosive medium in the copper matrix, thereby enhancing the corrosion resistance of the copper material. More importantly, since the thickness of boron nitride is only a few atomic layers, its arrangement in the horizontal direction can minimize electron scattering in the copper matrix, thereby maintaining the high electrical conductivity of the material.

[0036] In the process of realizing the present disclosure, it was found that the boron nitride-copper composite powder can be prepared by an in-situ generation method or an external addition method, and the external addition method mainly includes a mechanical ball milling method and a molecular-level mixing method. Among them, the mechanical ball milling method can solve the agglomeration problem of boron nitride, but because the ball milling process causes great damage to the structure of boron nitride, and the interface bonding between boron nitride and copper is weak, the strength, elongation, electrical conductivity and thermal conductivity of the prepared composite material are difficult to meet the application requirements. Although the molecular-level mixing method can obtain better reinforcing phase dispersion and interface bonding, the stability of the material performance is difficult to guarantee due to the uneven size and thickness of the added boron nitride nanosheets. Compared with the external addition method, the in-situ preparation method can achieve a tighter interface bonding between the reinforcing phase and the matrix, give full play to the performance advantages of the reinforcing phase, and thus improve the comprehensive performance of the material. In addition, compared with composite materials with uniform configuration, composite materials with layered configuration can better exert the excellent performance of boron nitride within the surface. However, the current temperature for preparing boron nitride on copper surfaces is generally higher than 900°C, and high-cost raw materials such as boron ammonia are often used, making it difficult to achieve batch and controllable preparation of boron nitride on the surface of copper powder.

[0037] In view of this, the present disclosure provides a boron nitride reinforced copper-based composite material and a preparation method thereof, wherein boron nitride is controllably prepared in batches on a copper surface to obtain a boron nitride-copper composite powder, and after the composite material is prepared, mechanical deformation processing is performed to form a laminated structure of boron nitride and copper, thereby obtaining good interface bonding and directional arrangement of boron nitride, and preparing a high-performance boron nitride reinforced copper-based composite material.

[0038] As a first aspect of the present disclosure, a method for preparing a boron nitride reinforced copper-based composite material is provided.

[0039] Figure 1 is a flow chart of the method for preparing a boron nitride-reinforced copper-based composite material according to an embodiment of the present disclosure. As shown in Figure 1 , the preparation method includes steps S101 to S103: Step S101: Preparing a boron nitride-copper composite powder; Step S102: Using a powder metallurgy process to form a boron nitride-copper composite material from the composite powder; Step S103: Mechanically deforming the composite material to densify the composite material, forming a laminated structure of boron nitride and copper, and obtaining a boron nitride-reinforced copper-based composite material.

[0040] According to an embodiment of the present disclosure, the angular difference between the boron nitrides in the stacked structure along the main deformation direction is less than 10°, which can ensure that the orientation of the boron nitride is highly consistent.

[0041] According to the embodiments of the present disclosure, the boron nitride-copper composite material prepared by the powder metallurgy process has a certain density. After mechanical processing, a laminated structure is formed in the composite material, which further densifies the composite material and makes the boron nitride highly directional in the copper matrix, which can reduce the scattering of electrons and boron nitride, and can give full play to the advantage of the high thermal conductivity of the boron nitride surface, and can still maintain excellent thermal conductivity at high temperatures. Furthermore, boron nitride has excellent corrosion resistance. Boron nitride in the copper matrix can improve the corrosion resistance of copper materials. The prepared boron nitride-copper composite material can exhibit good corrosion resistance.

[0042] According to an embodiment of the present disclosure, in step S101, the method for preparing a boron nitride-copper composite powder includes: any one or more of physical vapor deposition, chemical vapor deposition and chemical reduction, preferably chemical vapor deposition. The interface between boron nitride and copper in the composite powder prepared by chemical vapor deposition has better bonding performance. The particle size of the composite powder can be 1 to 200 μm, for example, 5 μm, 80 μm, 120 μm, 160 μm, 180 μm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. Among them, the size of the copper powder can be 0.1 to 200 μm, and there is no restriction on the morphology of the metallic copper. Its morphology can be spherical, nearly spherical, dendritic, irregular, flaky, etc., and can be selected according to actual conditions. The metallic copper powder can be copper powder or copper alloy powder (copper-silver alloy, copper-iron alloy, copper-lanthanum alloy, etc.). The use of copper alloy powder can increase the strength of the composite material by about 200 MPa without significantly reducing the electrical conductivity and thermal conductivity of the material (reduction of no more than 10%), which can effectively expand the application range of boron nitride reinforced copper-based composite materials.

[0043] According to the embodiments of the present disclosure, boron nitride is preferably introduced into the composite powder by in-situ synthesis. The boron material used to prepare boron nitride can be boron oxide or other boron-containing salts, and the nitrogen raw material can be ammonia or other substances that can decompose and release ammonia. Furthermore, other methods can also be used to introduce boron nitride and mix it with copper powder. Regardless of the method used to introduce boron nitride, the mass fraction of boron nitride needs to be controlled within 0.01 to 5 wt.%.

[0044] According to an embodiment of the present disclosure, the preparation method further includes: introducing copper nanoparticles into the composite powder for surface modification to improve the interface bonding performance between boron nitride and copper.

[0045] According to an embodiment of the present disclosure, after the boron nitride in the composite powder obtained in step S101 is loaded onto the surface of the copper powder, copper nanoparticles can be further introduced for surface modification based on the composite ratio of boron nitride to copper powder. This ensures good interfacial bonding between the copper and boron nitride, and allows the composite material to have better formability. The average particle size of the copper nanoparticles can be 100 nm to 1000 nm, and the mass fraction of the introduced copper nanoparticles can be 10% to 50% of the composite powder. The modification method can be any one or more of electrodeposition, electroless plating, and copper salt impregnation reduction.

[0046] According to an embodiment of the present disclosure, the mass ratio of boron nitride to copper in the composite powder is (0.01-5): (95-99.9), for example, it can be 0.2:99.8, 1.5:98.5, 3:97, 4.55:95.45, etc., but it is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable. Composite materials with too high a boron nitride content will crack during the thermal processing process, and the electrical conductivity and thermal conductivity will decrease. This mass ratio range ensures the formability and performance of the composite material. By adjusting the mass ratio of boron nitride to copper in the composite powder, the composite material can be further formed into a dense structure, and can form a laminated structure under the action of mechanical tensile / compression deformation, which can improve the thermal conductivity and corrosion resistance while ensuring the electrical conductivity of the copper material.

[0047] According to an embodiment of the present disclosure, in step S102, the boron nitride-copper composite material is a block and / or granular material; the powder metallurgy process includes any one or more of cold pressing and sintering, hot pressing and sintering, and granulation. In order to ensure that the mechanical deformation processing in the subsequent operation steps forms a laminated structure, the density of the block and / or granular material of the composite material prepared by the powder metallurgy process should be ensured to be higher than 90%.

[0048] According to an embodiment of the present disclosure, in step S103, the composite material is made into a desired size and shape by mechanical deformation processing, and the mechanical deformation processing method includes any one or more of extrusion, pressing / calendering, and drawing, wherein the deformation temperature in the initial stage of the mechanical deformation processing should exceed the thermal softening temperature of the pellets or blocks (>300°C).

[0049] According to the embodiments of the present disclosure, the total deformation amount of the composite material caused by mechanical deformation processing is higher than 30%. Among them, the total deformation amount of the composite material can be 35%, 50%, 65%, 80%, 95%, etc., but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable. In the process of mechanical deformation processing to deform the composite material, the shear force causes the boron nitride to be oriented and distributed in the copper matrix, and to be arranged in a directional manner, thereby obtaining a laminated structure of boron nitride and copper. At the same time, the density of the deformed composite material can be made greater than 99.5%.

[0050] According to an embodiment of the present disclosure, preferably, the boron nitride is in the shape of a boron nitride nanosheet, and the lateral size of the boron nitride nanosheet can be 0.5 to 20 μm, for example, 1 μm, 5 μm, 12 μm, 15 μm, etc. The thickness of the boron nitride nanosheet can be 1 to 10 nm, for example, 2 nm, 4 nm, 6 nm, 8 nm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0051] According to an embodiment of the present disclosure, the composite powder also includes a doping metal. By adding a doping metal to the composite powder, a composite material containing other metal elements can be formed, expanding the application scenarios of boron nitride-reinforced copper-based composite materials. The doping metal includes any one or more of silver (Ag), chromium (Cr), tin (Pb), iron (Fe), lanthanum (La), and zirconium (Zr). This is beneficial for improving the strength, thermal stability, and other properties of the boron nitride-reinforced copper-based composite material.

[0052] According to the embodiments of the present disclosure, the amount of doping metal added is 0-5% of the composite powder, for example, it can be 0.5%, 1.2%, 2.6%, 3.5%, 4.9%, etc., but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. Among them, the amount of each type of doping metal added can be Ag (<5%), Cr (<0.5%), Sn (<1%), Fe (<1%), La (<1%), Zr (<0.15%), and the total content of the added doping metal elements is controlled within 5%, which can ensure that the boron nitride reinforced copper-based composite material has a higher conductivity.

[0053] According to an embodiment of the present disclosure, a mechanical deformation method includes hot rolling the composite material at a temperature of 800°C to 1000°C, for example, 820°C, 850°C, 900°C, 920°C, 980°C, etc. Within this temperature range, the plasticity and ductility of the composite material are significantly improved, making the material easier to deform during the hot rolling process, helping to fill the pores within the material and thereby increasing density.

[0054] According to the embodiments of the present disclosure, the amount of each reduction in hot rolling treatment is 8 to 12%, for example, it can be 8.5%, 9.2%, 10.5%, 11%, 11.5%, etc., and the cumulative reduction is 50 to 75%, for example, it can be 50%, 55%, 58%, 62%, 72%, etc., preferably 70%. However, it is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable. Through multiple rolling, the material can undergo sufficient plastic deformation, which helps to break and refine the original grain structure, make the material structure more uniform, and promote the formation of a highly oriented arrangement of boron nitride in the copper-based material. With the increase in density and the homogenization of the material structure, the mechanical properties of the composite material (such as strength, hardness and wear resistance) will also be improved accordingly, so that it has better performance in practical applications.

[0055] According to the embodiments of the present disclosure, after mechanical deformation processing, the density of the obtained boron nitride reinforced copper-based composite material is higher than 99.5%, and the porosity inside the material is low, which helps to improve the mechanical properties and durability of the material.

[0056] According to the embodiments of the present disclosure, the interlayer spacing between boron nitride in the boron nitride reinforced copper-based composite material is 0.1 to 2 μm, for example, it can be 0.2 μm, 0.5 μm, 0.8 μm, 1.4 μm, 1.8 μm, etc.; the lateral size of boron nitride in the boron nitride reinforced copper-based composite material is 100 to 1000 nm, for example, it can be 120 nm, 280 nm, 360 nm, 520 nm, 750 nm, etc. However, it is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable. In general, the smaller the interlayer spacing and the larger the boron nitride size, the better the thermal conductivity and corrosion resistance of boron nitride, thereby improving the thermal conductivity and corrosion resistance of the composite material.

[0057] As a second aspect of the present disclosure, a boron nitride reinforced copper-based composite material prepared by the above-mentioned preparation method is provided, wherein the angle difference between the boron nitrides along the main deformation direction in the laminated structure of the boron nitride reinforced copper-based composite material is less than 10°.

[0058] According to the embodiments of the present disclosure, the boron nitride is highly oriented in the copper matrix, which can give full play to the advantages of the high thermal conductivity of the boron nitride in the plane. The thermal conductivity of the prepared boron nitride reinforced copper matrix composite material can reach 424W·m -1 ·K -1 , which is increased by 10% compared with pure copper. In addition, the self-corrosion current density of the copper-based material added with boron nitride in an alkaline environment is reduced by one order of magnitude, showing good corrosion resistance.

[0059] According to an embodiment of the present disclosure, the boron nitride reinforced copper-based composite material includes boron nitride, copper and impurity elements; the contents of boron nitride and copper in the boron nitride reinforced copper-based composite material are higher than 95%.

[0060] According to the embodiments of the present disclosure, impurity elements will be introduced in the process of preparing boron nitride reinforced copper-based composite materials, and the content of the impurity elements needs to be controlled to be less than 5%, where the impurity elements and their contents can be oxygen (O<0.1%), phosphorus (P<0.01%), silicon (Si<0.03%), lead (Pb<0.05%), sulfur (S<0.03%), and arsenic (As<0.01%).

[0061] In order to make the purpose, technical solutions and advantages of the present disclosure more clear and explicit, the technical solutions and principles of the present disclosure are further explained below through specific embodiments in combination with the accompanying drawings. It should be noted that the following specific embodiments are only for illustration and the scope of protection of the present disclosure is not limited thereto.

[0062] Unless otherwise specified, the experimental materials and reagents used in the following examples are commercially available. Where specific techniques or conditions are not specified in the examples, these are conventional methods and can be performed according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0063] Example 1

[0064] Weigh 0.25g of boron oxide and dissolve it in 25mL of deionized water. Stir until the solution is clear, then add 50mL of alcohol and continue stirring to ensure uniform mixing. Then, pour 25g of flaky copper powder into the boron oxide solution and stir in a 75°C water bath until the solution is completely evaporated. The resulting mixture is placed in a vacuum oven, dried at 70°C for 2h and ground to obtain a boron oxide-copper precursor powder. Subsequently, weigh 25g of boron oxide-copper precursor powder and place it in a graphite ark. React with ammonia at 600°C for 15min, set the ammonia flow rate to 50mL / min, and quickly cool after the reaction to obtain a boron nitride-copper composite powder.

[0065] Weigh 96 g of copper nitrate trihydrate and dissolve it in 250 mL of alcohol. Then add 25 g of boron nitride-copper composite powder and stir in a 75°C water bath until the solution is completely evaporated to obtain a copper nitrate-coated composite powder. This powder is reduced in a hydrogen atmosphere at 400°C for 2 h, with the hydrogen flow rate set to 200 mL / min, to obtain nano-copper modified boron nitride-copper composite powder.

[0066] Weigh 50g of nano-copper modified boron nitride-copper composite powder and pour it into a graphite mold with a diameter of 30mm for hot pressing and sintering. The hot pressing temperature is set to 900℃, the pressure is 50MPa, and the holding time is 1h to obtain a bulk boron nitride-copper composite material.

[0067] Furthermore, the composite material was densified by hot rolling, and the bulk boron nitride-copper composite material was mechanically deformed at 900°C, with the reduction in each pass controlled at 10%, and the cumulative reduction in each pass reaching 70%, that is, the deformation of the composite material was 70%, to obtain a boron nitride reinforced copper-based composite material, labeled as BN / Cu composite material, in which the boron nitride content was 0.18%, and the density of the composite material at this time was 8.83g / cm 3 (Relative density is 99.8%).

[0068] Figure 2 is a scanning electron micrograph of the distribution of boron nitride in the boron nitride-reinforced copper-based composite material of Example 1 of the present disclosure; Figure 3 is a schematic diagram of the distribution of boron nitride in the boron nitride-reinforced copper-based composite material of Example 1 of the present disclosure. As can be seen from Figure 2, the boron nitride is distributed almost horizontally in the copper matrix. Based on Figure 2, the schematic diagram shown in Figure 3 shows that the boron nitride nanosheets are distributed in a stacked orientation in the copper matrix.

[0069] Figure 4 is a transmission electron micrograph of the boron nitride reinforced copper-based composite material in Example 1 of the present disclosure. As can be seen from Figure 4, the grains of the boron nitride reinforced copper-based composite material are lath-shaped, about 1 μm in length and about 200 nm in thickness.

[0070] Figure 5 shows a transmission electron micrograph of the interface of the boron nitride-reinforced copper-based composite material in Example 1 of the present disclosure. As can be seen in Figure 5 , the interface between the boron nitride and copper in the boron nitride-reinforced copper-based composite material is tight and clean, demonstrating that the material ensures smooth heat transfer through the interface to the boron nitride nanosheets.

[0071] As can be seen from Figures 2 to 5, the boron nitride nanosheets in the boron nitride reinforced copper-based composite material are highly oriented in the copper matrix, showing a layered structure.

[0072] The test results show that the strength of the copper-based composite reinforced with boron nitride is 265 MPa, which is 25% higher than that of pure copper (202 MPa). The corrosion current density of the copper-based composite reinforced with boron nitride in 0.1M NaOH solution is 4.76×10 -5 A.cm -2 , only pure copper (1.66×10 -4 A.cm -2 ) and exhibits excellent corrosion resistance.

[0073] Furthermore, the thermal conductivity of the boron nitride-reinforced copper-based composite was tested. Figure 6 shows the thermal conductivity of the boron nitride-reinforced copper-based composite material and pure copper in the horizontal direction as a function of temperature, as described in Example 1 of the present disclosure. Figure 7 shows the thermal conductivity of the boron nitride-reinforced copper-based composite material and pure copper in the vertical direction as a function of temperature, as described in Example 1 of the present disclosure.

[0074] As can be seen from Figure 6, in the horizontal direction, the thermal conductivity of the boron nitride reinforced copper matrix composite material at room temperature is 424 W·m - 1 ·K -1 , compared with pure copper (387W·m -1 ·K -1 ) increased by 10%; at a temperature of 400°C, the thermal conductivity of the boron nitride-reinforced copper-based composite material increased by 20%. As shown in Figure 7, the thermal conductivity of the boron nitride-reinforced copper-based composite material does not decrease significantly in the vertical direction. When the temperature reaches above 100°C, the thermal conductivity of the boron nitride-reinforced copper-based composite material is higher than that of pure copper.

[0075] Figure 8 is a polarization curve diagram of the boron nitride reinforced copper-based composite material and pure copper in Example 1 of the present disclosure. It can be seen from Figure 8 that the ordinate is the corrosion current and the abscissa is the voltage. The voltage corresponding to the minimum corrosion current is the self-corrosion potential of the material. The self-corrosion potential of the boron nitride reinforced copper-based composite material is 10 mV higher than that of pure copper. The linear region in the logJ vs. E (V vs Ag / AgCl) diagram is extrapolated to the intersection of the self-corrosion potential. The current density at the intersection is the self-corrosion current density of the material, which reflects the corrosion rate of the material under natural conditions. The self-corrosion current of the boron nitride reinforced copper-based composite material is only one-fourth of that of pure copper.

[0076] Figure 9 is a Nyquist plot of the boron nitride reinforced copper-based composite material and pure copper in Example 1 of the present disclosure. It can be seen from the figure that the impedance curve of the boron nitride copper-based composite material is part of an impedance circle with a larger radius, so the boron nitride copper-based composite material has a higher impedance. Figure 10 is a Bode plot (frequency / impedance) of the boron nitride reinforced copper-based composite material and pure copper in Example 1 of the present disclosure. It can be seen from the figure that the impedance (|Z|) of the composite material is significantly higher than that of pure copper at low frequencies. Figures 9 and 10 show that the boron nitride reinforced copper-based composite material has a higher impedance, which can hinder the passage of corrosive media. Therefore, boron nitride can improve the corrosion resistance of the composite material.

[0077] Figure 11 shows the Bode plots (frequency, phase) of the boron nitride-reinforced copper-based composite material and pure copper in Example 1 of the present disclosure. Figure 11 shows that the minimum phase angle of pure copper is -36.5°, while that of the boron nitride-reinforced copper-based composite material is -44.9°, indicating that the boron nitride-reinforced phase hinders the penetration of corrosive media to a certain extent, thereby improving the corrosion resistance of the material.

[0078] Example 2

[0079] The boron nitride reinforced copper-based composite material was prepared by the same preparation method as in Example 1, except that the cumulative reduction in the mechanical deformation process in Example 1 was adjusted to 30%, that is, the deformation amount of the composite material was 30%.

[0080] Figure 12 is a scanning electron microscope image of the distribution of boron nitride in the boron nitride reinforced copper-based composite material in Example 2 of the present disclosure. It can be seen that the boron nitride is mostly distributed horizontally in the copper matrix, but the angle with the rolling direction is larger than that of the boron nitride distribution in Example 1. The boron nitride in the boron nitride reinforced copper-based composite material obtained in Example 2 basically presents a stacked distribution. After testing, the density of the composite material at this time is 8.82g / cm 3 , the relative density is 99.62%. The material density is >99.5%

[0081] Example 3

[0082] The boron nitride reinforced copper-based composite material was prepared by the same preparation method as in Example 1, except that the cumulative reduction in the mechanical deformation process in Example 1 was adjusted to 20%, that is, the deformation amount of the composite material was 20%.

[0083] Figure 13 is a scanning electron microscope photograph of the distribution of boron nitride in the boron nitride reinforced copper-based composite material in Example 3 of the present disclosure. It can be seen that the boron nitride is mostly distributed in the copper matrix, but some boron nitride still has a disordered distribution, such as some boron nitride is still perpendicular to the rolling direction. The boron nitride in the boron nitride reinforced copper-based composite material obtained in Example 3 does not show a complete stacking distribution. After testing, the density of the composite material at this time is 8.81g / cm 3 , the relative density is 99.54%.

[0084] The electrical conductivity of the boron nitride reinforced copper-based composite materials prepared in Examples 1 to 3 was tested, and the results are shown in Table 1.

[0085] Table 1 Electrical conductivity of boron nitride reinforced copper matrix composites at different rolling rates

[0086] As can be seen from Table 1, the addition of boron nitride does not cause a significant decrease in the electrical conductivity of the composite material. When the cumulative rolling reduction is 70%, the conductivity of the boron nitride-reinforced copper-based composite material is 96.7% IACS; when the cumulative rolling reduction is 30%, the conductivity of the boron nitride-reinforced copper-based composite material is 96% IACS; when the cumulative rolling reduction is 20%, the conductivity of the boron nitride-reinforced copper-based composite material is only 91.4% IACS. This shows that for boron nitride-reinforced copper-based composites, when the deformation of the composite material is greater than 30% during mechanical deformation processing, the boron nitride can be better oriented under shear force, which is beneficial to improving the electrical conductivity of the composite material.

[0087] Example 4

[0088] The boron nitride reinforced copper-based composite material was prepared by the same preparation method as in Example 1, except that 0.25 g of boron oxide in Example 1 was replaced with 0.125 g. The content of boron nitride in the obtained boron nitride reinforced copper-based composite material was 0.1%.

[0089] Example 5

[0090] The boron nitride reinforced copper-based composite material was prepared by the same preparation method as in Example 1, except that 0.25 g of boron oxide in Example 1 was replaced with 0.375 g. The content of boron nitride in the obtained boron nitride reinforced copper-based composite material was 0.25%.

[0091] Example 6

[0092] The boron nitride reinforced copper-based composite material was prepared by the same preparation method as in Example 1, except that 0.25 g of boron oxide in Example 1 was replaced with 0.5 g. The content of boron nitride in the obtained boron nitride reinforced copper-based composite material was 0.33%.

[0093] The properties of the boron nitride reinforced copper-based composite materials prepared in Example 1 and Examples 4 to 6 were tested, and the results are shown in Table 2.

[0094] Table 2 Properties of boron nitride reinforced copper matrix composites with different boron nitride contents

[0095] As shown in Table 2, the addition of boron nitride to the boron nitride reinforced copper-based composite material can improve the strength and corrosion resistance of the material. In addition, the degree of decrease in the electrical conductivity of the boron nitride reinforced copper-based composite material is relatively low. When the boron nitride content is high or low, the thermal conductivity of the boron nitride reinforced copper-based composite material will decrease. When the boron nitride content is preferably 0.18-0.25, the thermal conductivity of the material can be significantly improved.

[0096] Example 7

[0097] Weigh 0.25g of boron oxide and dissolve it in 25mL of deionized water. Stir until the solution is clear, then add 50mL of alcohol and continue stirring to ensure uniform mixing. Then, pour 25g of flaky copper powder into the boron oxide solution and stir in a 75°C water bath until the solution is completely evaporated. The resulting mixture is placed in a vacuum oven, dried at 70°C for 2h, and ground to obtain a boron oxide-copper precursor powder. Subsequently, weigh 30g of the boron oxide-copper precursor powder and place it in a graphite ark. React with ammonia at 600°C for 15min, with an ammonia flow rate of 50mL / min. After the reaction is complete, cool it rapidly and then ball mill it. The ball milling parameters are set to a ball-to-material ratio of 15:1, a rotation speed of 400r / min, and a grinding time of 2h to obtain a boron nitride-copper composite powder.

[0098] The boron nitride-copper composite powder obtained after ball milling was poured into a graphite mold with a diameter of 30 mm for hot pressing and sintering. The hot pressing temperature was set to 900°C, the pressure was 50 MPa, and the holding time was 1 hour to obtain a bulk boron nitride-copper composite material.

[0099] Furthermore, the composite material is densified by hot rolling, and the bulk boron nitride-copper composite material is mechanically deformed at 900°C. The rolling reduction in each pass is controlled at 10%, and the cumulative rolling reduction reaches 70%, that is, the deformation of the composite material is 70%, thereby obtaining a boron nitride reinforced copper-based composite material.

[0100] According to tests, the boron nitride reinforced copper-based composite material prepared in Example 7 has a strength of 320 MPa and a conductivity of 93% IACS.

[0101] Example 8

[0102] The boron nitride reinforced copper-based composite material was prepared by the same preparation method as in Example 1, except that 25 g of flaky copper powder in Example 1 was replaced with 25 g of flaky copper-silver alloy powder, wherein the mass fraction of silver was 1%.

[0103] Example 9

[0104] The boron nitride reinforced copper-based composite material was prepared by the same preparation method as in Example 1, except that 25 g of flaky copper powder in Example 1 was replaced with 25 g of flaky copper-lanthanum alloy powder, wherein the mass fraction of lanthanum was 0.5%.

[0105] The properties of the boron nitride reinforced copper-based composite materials prepared in Example 1 and Examples 8 and 9 were tested, and the results are shown in Table 3.

[0106] Table 3 Properties of boron nitride reinforced copper matrix composites with different copper matrices

[0107] As shown in Table 3, the boron nitride-reinforced copper-based composites prepared in Examples 8 and 9 achieved strengths of 450 MPa and 410 MPa, respectively, which is double that of pure copper, and the self-corrosion current density is reduced by an order of magnitude. Using copper alloy as the substrate for boron nitride-reinforced copper-based composites significantly improves the material's strength and corrosion resistance, enabling its use in copper materials with higher mechanical properties and in more demanding environments, further broadening the application prospects of boron nitride-reinforced copper-based composites.

[0108] Based on the above technical solution, the boron nitride-reinforced copper-based composite material and its preparation method provided by the present disclosure, by regulating the mixing ratio of boron nitride and copper powder in the composite powder and controlling the deformation of the composite material through mechanical deformation processing, the boron nitride in the composite material is oriented, forming a laminated structure of boron nitride and copper, thereby reducing the scattering of electrons and boron nitride. Furthermore, the advantages of high in-plane thermal conductivity and corrosion resistance of boron nitride are utilized to obtain a boron nitride-reinforced copper-based composite material with high thermal conductivity, electrical conductivity, and corrosion resistance. This can ensure low energy consumption, low heat generation, and high reliability in the electrical and electronic fields, showing great application prospects.

[0109] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A method for preparing a boron nitride reinforced copper-based composite material, wherein: The preparation method comprises: preparing boron nitride-copper composite powder; The composite powder is made into a boron nitride-copper composite material by using a powder metallurgy process; Performing mechanical deformation processing on the composite material to densify the composite material and form a laminated structure of boron nitride and copper to obtain a boron nitride reinforced copper-based composite material; Wherein, the angle difference between the boron nitrides in the stacked structure along the main deformation direction is less than 10°.

2. The preparation method according to claim 1, wherein Also includes: Copper nanoparticles are introduced into the composite powder for surface modification to improve the interface bonding performance between boron nitride and copper.

3. The preparation method according to claim 1, wherein The mass ratio of boron nitride to copper in the composite powder is (0.01-5):(95-99.9).

4. The preparation method according to claim 1, wherein The mechanical deformation process causes the composite material to undergo a total deformation greater than 30%.

5. The preparation method according to claim 3, wherein The boron nitride is a boron nitride nanosheet; The boron nitride nanosheet has a lateral size of 0.5 to 20 μm and a thickness of 1 to 10 nm.

6. The preparation method according to claim 1, wherein The composite powder further includes a doping metal; The amount of the doping metal added is 0 to 5% of the composite powder; The doping metal includes any one or more of silver, chromium, tin, iron, lanthanum, and zirconium.

7. The preparation method according to claim 1, wherein The mechanical deformation processing method includes: hot rolling the composite material at a temperature of 800 to 1000° C.; The reduction amount in each hot rolling process is 8-12%, and the cumulative reduction amount is 50-75%.

8. The preparation method according to claim 1, wherein After the mechanical deformation process, the density of the obtained boron nitride reinforced copper-based composite material is higher than 99.5%; The interlayer spacing between boron nitrides in the boron nitride reinforced copper-based composite material is 0.1 to 2 μm; The lateral size of the boron nitride in the boron nitride reinforced copper-based composite material is 100-1000 nm.

9. A boron nitride reinforced copper-based composite material prepared by the preparation method according to any one of claims 1 to 8, wherein: The angle difference between the boron nitrides in the laminated structure of the boron nitride reinforced copper-based composite material along the main deformation direction is less than 10°.

10. The boron nitride reinforced copper-based composite material according to claim 9, wherein: The boron nitride reinforced copper-based composite material comprises boron nitride, copper and impurity elements; The contents of boron nitride and copper in the boron nitride reinforced copper-based composite material are higher than 95%.

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