Micro fiber reinforced copper-based composite material and preparation method thereof

Abstract

The invention relates to a micro fiber reinforced copper-based composite material and a preparation method thereof, and belongs to the technical field of copper alloy materials. The high-melting-point metal micro short fibers are used for strengthening the copper-based material, and the fine high-melting-point metal micro short fibers are uniformly distributed in the copper matrix, so that the strength of the copper matrix is improved, and meanwhile, excellent electric conductivity and heat conductivity are kept. The preparation method is high in operability and good in repeatability, and the prepared micro-fiber-reinforced copper-based composite material is good in performance, high in strength, high in stability, high in thermal conductivity and electrical conductivity, high in density and higher in thermal conductivity and tensile strength at the high temperature; the urgent requirement for high strength, high stability and high thermal conductivity and electrical conductivity of the copper composite material in the industry is met, and technical support is provided for research on the mechanical performance, oxidation performance, corrosion performance, irradiation performance and the like of the copper material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of copper alloy materials, and particularly relates to a micro fiber reinforced copper-based composite material and a preparation method thereof. BACKGROUND

[0002] Copper materials are widely used in the fields of electronics, machinery, manufacturing, engineering applications, aerospace, etc. In traditional processes, they are mainly used as various resistance welding electrodes, large-current welding cables, large-scale integrated circuit lead frames, high-power microwave tube structural materials, various heat exchange materials, mold materials, continuous casting machine crystallizer inner liners and structural material parts. In addition, copper is also used in the field of nuclear materials, such as heat sink fins for divertor vertical target materials in the tokamak device of the thermal nuclear reactor, nuclear fusion power generator and its cooling pipe, antenna mirror design for ITER application, etc. In the application of nuclear fusion divertor heat sink materials, the materials are in a comprehensive field environment of super-strong heat flow impact, neutron impact and partial structural pressure, and need to have good heat conduction performance and strength. However, the copper and its composite materials prepared by traditional processes have defects such as difficult structure control and mismatch between heat conduction and strength.

[0003] The strengthening methods of copper mainly include precipitation strengthening, dispersion strengthening, solid solution strengthening, composite material strengthening and deformation strengthening, etc. Among them, the precipitation strengthening method is to strengthen by adding specific alloy elements to form precipitated phases, such as chromium-zirconium-copper alloy. The precipitation strengthened copper alloy is to use the precipitation of supersaturated solid solution to achieve the strengthening effect through aging heat treatment. However, this method has obvious defects. The precipitated phase will aggregate and grow or re-dissolve at high temperature, resulting in the disappearance of the strengthening effect and low softening temperature. The dispersion strengthening is to hinder the dislocation movement by introducing high-stability ceramic particles (such as Al2O3). The softening temperature of the material prepared by this method can reach 900℃, which is much higher than that of the precipitation strengthened alloy. However, the preparation process is complex, the cost is high, and after heat treatment, the grain of the aluminum oxide dispersion strengthened copper alloy will grow, and due to the reverse diffusion behavior of aluminum elements, large particle A12O3 particles are formed, resulting in uneven distribution of A12O3 particles. In the subsequent cold working process, stress concentration and large deformation resistance problems are easily caused, the material failure causes cracking, and the addition of insulating oxide phase will cause the overall thermal conductivity of the composite material to decrease. The solid solution strengthening is to add alloy elements to form a solid solution in the copper matrix. However, the solid solution strengthening will significantly reduce the electrical conductivity because of the increase of electron scattering caused by heterogeneous atoms. The composite material strengthening is to form a composite material by introducing ceramic particles, carbon nanomaterials and other various reinforcing phases. This method can play the synergistic effect of various reinforcing phases, but there are problems such as uneven distribution of reinforcing phases and weak interface bonding. The deformation strengthening method is to refine the grain and increase the dislocation density by processing deformation, so as to improve the strength and wear resistance. However, the plasticity is greatly reduced and the material is prone to brittle fracture.

[0004] Although the electrically and thermally conductive properties of traditional copper and copper alloy are good, the strength is insufficient. Up to now, there are few reports on effective preparation of copper-based composite material based on micron short fiber reinforcement and technical solutions in existing patent technologies. How to improve the pretreatment process and develop new composite material preparation technology to overcome the trade-off of strength, thermal conductivity, plasticity or cost in the existing technology and obtain high-performance copper composite material sample has become one of the current difficult problems to be solved. In addition, many basic research fields also urgently need to develop copper-based composite materials with uniform structure, high strength and high thermal conductivity. Scholars are eager to obtain an excellent preparation method of micro-fiber reinforced copper-based composite material, which undoubtedly plays an important role in promoting the related research and performance optimization of copper and its alloy. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a micro-fiber reinforced copper-based composite material with high density, high thermal conductivity at high temperature and higher tensile strength and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: In a first aspect, the present application provides a preparation method of a micro-fiber reinforced copper-based composite material, comprising the following steps: S1, washing the metal fiber after pretreatment to remove impurities on the surface of the metal fiber and etching the surface to obtain pretreated metal fiber; washing the obtained pretreated metal fiber after electrolytic treatment to remove the surface oxide skin to obtain activated metal fiber; modifying the obtained activated metal fiber by adding a diffusion barrier layer after electroplating, washing and drying to obtain modified metal fiber; processing the obtained modified metal fiber into micro short fiber with a length of not more than 500 μm, ultrasonic cleaning and sealing to obtain modified metal micro short fiber; The metal fiber is a high-melting-point metal fiber, and the diameter of the metal fiber is not more than 20 μm; the diffusion barrier layer is a copper layer; S2, spray drying the precursor solution for preparing copper powder to obtain precursor powder; reducing the obtained precursor powder in a protective gas atmosphere, sieving to obtain spherical copper powder with a particle size of 5-44 μm; S3, mixing the modified metal micro short fiber obtained in step S1 and the spherical copper powder obtained in step S2 uniformly to obtain mixed powder; pressing, drying and sealing the obtained mixed powder to obtain a green body of copper material; The mass ratio of the modified metal micro short fiber to the spherical copper powder is 0.1-10:100; S4, sintering the green body of copper material obtained in step S3 to obtain sintered copper blank; cladding packaging (oxygen-free protection) the obtained sintered copper blank, rolling deformation and annealing to remove internal stress to obtain a micro-fiber reinforced copper-based composite material.

[0007] This invention utilizes high-melting-point metal microfibers with a length not exceeding 500 μm to strengthen copper-based materials. These fine, high-melting-point metal microfibers are uniformly distributed within the copper matrix. These microfibers possess high strength and a high softening temperature, ensuring that they do not significantly negatively impact the electrical and thermal conductivity of the copper alloy itself, while maintaining excellent electrical and thermal conductivity while improving strength. The microfiber-reinforced copper-based composite material of this invention combines the high strength and stability of metal fibers with the high thermal and electrical conductivity of copper.

[0008] This invention utilizes microfibers to prepare reinforced copper-based composite materials, addressing three key aspects: First, the issue of fiber size control. Traditional metal fibers are mostly in the millimeter range or larger, making the preparation of microfibers with a diameter of less than 20 μm and a length of no more than 500 μm extremely challenging. The small size of microfibers makes precise size control difficult. Such fine and uniform fiber structures are prone to fiber breakage, uneven morphology, or agglomeration during processing, placing extremely high demands on the precision of the preparation process, material selection, and equipment control. Pre-treatment of tungsten wires is also crucial. Second, the interfacial bonding between high-melting-point metal fibers and the copper matrix is ​​a challenge, as they easily form brittle compounds. Third, the dispersion of short microfibers in copper materials is problematic. Short fibers in alloys tend to agglomerate, resulting in poor interfacial bonding and conductivity loss. Therefore, a suitable composite preparation process is necessary.

[0009] Compared to millimeter-long high-melting-point metal fibers, this invention utilizes metal microfibers with a diameter of no more than 20 μm and a length of no more than 500 μm, with an aspect ratio between 5 and 100. These microfibers exhibit better dispersion and enhance the stress transfer efficiency from the weaker matrix to the high-strength fibers during deformation. Although millimeter-long fibers have a huge aspect ratio, they are extremely difficult to disperse uniformly in molten or powder-metallurgical copper matrices, easily agglomerating or breaking, thus forming defects. The actual effective stress transfer area is not high. Using micron-sized microfibers not only effectively transfers stress but also fully utilizes their strength potential, resulting in high-quality interfacial bonding. The uniform dispersion greatly reduces the disruption of continuous conductive / thermal conduction pathways in the copper matrix. Therefore, compared to millimeter-long fibers, the microfiber-reinforced copper matrix composite material prepared using metal microfibers in this invention exhibits higher overall mechanical, electrical, and thermal conductivity properties.

[0010] This invention combines pretreatment, electrolytic treatment, and modified electroplating to modify metal fibers. The modified metal fibers exhibit good toughness, are less prone to breakage, and have a uniform morphology without agglomeration or adhesion. The modified metal fibers are suitable for further processing into metal microfibers with a length not exceeding 500 μm.

[0011] This invention modifies the electroplating process to deposit copper on the surface of metal fibers, forming a diffusion barrier layer, and also overcomes the problem of interfacial bonding between high-melting-point metal fibers and copper substrates.

[0012] The strengthening mechanism of high-melting-point metal microfibers in copper matrices is closely related to dislocation interactions. Their core roles and influencing mechanisms are as follows: The difference in thermal expansion coefficients between high-melting-point metals such as tungsten, molybdenum, and rhenium and copper results in greater shrinkage of the copper matrix during cooling. During material preparation or deformation under stress, radial compressive stress and tangential tensile stress are generated around the microfibers. This stress field excites geometrically necessary dislocation multiplication and slip, leading to the formation of high-density dislocation walls around the fibers, with a density two orders of magnitude higher than the matrix. Secondly, the microfibers hinder dislocation movement. Their hardness is much higher than copper, preventing dislocations from cutting through rigid fibers. Instead, they bend and bypass around the high-strength fibers, leaving dislocation loops. According to the Orowan bypass mechanism, the shorter the fiber spacing, the greater the strengthening effect; therefore, micron-sized fine fibers are more effective. Furthermore, the micro-nano trenches (200–500 nm) formed during the chemical etching and diffusion barrier layer preparation of tungsten, molybdenum, or rhenium wires become dislocation pinning points, producing a dislocation pinning effect.

[0013] In a preferred embodiment of the preparation method described in this invention, in step S1, the high melting point metal fiber includes tungsten wire, molybdenum wire, or rhenium wire.

[0014] Tungsten (4.5×10) -6 / K), molybdenum (4.9×10 -6 / K), rhenium (6.7×10 -6 High-melting-point metals such as / K and copper (17×10) -6 The small difference in the coefficient of thermal expansion of tungsten, molybdenum and rhenium (K) helps to reduce thermal stress; at the same time, tungsten, molybdenum and rhenium have better high-temperature stability than copper, and have the characteristics of high strength, high hardness, non-solubility in copper matrix and high thermal conductivity.

[0015] In a preferred embodiment of the preparation method of the present invention, in step S1, the pretreatment is performed using a pretreatment solution, the composition of which is water, 10-50 g / L NaOH, 20-30 g / L Na2CO3, 20-30 g / L Na3PO4 and 1-5 g / L surfactant.

[0016] The pretreatment solution of this invention has advantages such as highly efficient synergistic degreasing and cleaning, preventing contaminants from hindering the bonding between fibers and the copper matrix, maintaining an alkaline environment and softening water, surface activation and passivation for corrosion prevention, and enhancing the stability of solution permeability and treatment uniformity. Compared with traditional single acid or alkaline washing, this composite formula pretreatment solution of the present invention simultaneously achieves multiple functions such as degreasing, water softening, activation, and corrosion prevention, simplifying the process flow, improving efficiency, and enabling a gentler, more comprehensive, and more effective perfect bonding between microfibers and the diffusion barrier layer (copper layer). The pretreatment solution of the present invention has superior effects compared to existing pretreatment solutions.

[0017] In a preferred embodiment of the preparation method described in this invention, the surfactant is sodium dodecylbenzenesulfonate.

[0018] In a preferred embodiment of the preparation method described in this invention, in step S1, the pretreatment conditions are 60–80°C for 3–5 minutes. These pretreatment conditions prevent insufficient removal of impurities from the metal fiber surface or excessive corrosion that could damage the metal fiber itself.

[0019] In a preferred embodiment of the preparation method of the present invention, in step S1, the electrolysis is performed using a NaOH solution with a pH value of 14-15; the mass percentage of NaOH in the NaOH solution is 5-15%; the electrolysis temperature is 5-10°C, the electrolysis time is 1 min, the electrolysis voltage is 20-60V, and the electrolysis current is 0.1-0.6A.

[0020] The electrolyte of this invention can effectively saponify and remove residual grease, organic matter, etc., that may remain on the surface of metal fibers during pretreatment. Simultaneously, the electrolyte of this invention exhibits a much lower corrosion rate on high-melting-point metals such as tungsten and molybdenum compared to strong acids (such as hydrochloric acid and sulfuric acid). The electrolysis temperature and time described in this invention can effectively suppress side reactions, ensuring a uniform and controllable process, resulting in more efficient electrolysis and avoiding overtreatment. It effectively protects the dimensional accuracy and bulk strength of the fibers, offering the advantages of efficient, precise, and controllable fiber surface cleaning and roughening while maximizing the protection of the fiber's intrinsic properties. Without damaging high-value, extremely fine metal fibers, it thoroughly removes surface contaminants such as organic matter and oxide layers, creating a suitable micro-roughness on the surface, thus providing a perfect foundation for subsequent "diffusion barrier layer" modification treatment, achieving a balance of efficiency, effectiveness, and protection. The electrolyte of this invention has better performance than treatment solutions such as strong acids.

[0021] In a preferred embodiment of the preparation method described in this invention, in step S1, the modified electroplating is performed using an electroplating solution. The electroplating solution comprises water, 50–90 g / L Cu₂P₂O₇, 300–400 g / L K₄P₂O₇, 1–3 mL / L NH₃·H₂O, 15–25 g / L KNO₃, 5–20 g / L KOH, 10–30 g / L potassium citrate, and 0.5–2 mL / L brightener. The electroplating solution of this invention, through multi-component synergistic complexation and additive optimization, can prepare a copper plating layer on the surface of microfibers with extremely fine crystals, high density, low stress, high bonding strength, and precisely controllable thickness within a wide and stable process window. This not only perfectly coats the fibers but also serves as an ideal transition layer for subsequent composite with the copper matrix. Its density also plays a crucial role in efficiently blocking diffusion, thereby significantly improving the comprehensive mechanical properties and high-temperature stability of the copper-based composite material. The electroplating solution of the present invention produces a copper plating layer that is finer and denser than that of other common copper plating solutions, with lower stress and higher bonding strength between the copper plating layer and the metal fibers.

[0022] In a preferred embodiment of the preparation method described in this invention, the brightener is NB-1 pyrocopper brightener.

[0023] In a preferred embodiment of the preparation method described in this invention, in step S1, the temperature of the modified electroplating is 30–60°C, and the current density is 0.2–2.5 A / dm³. 2 The thickness of the diffusion barrier layer is no greater than 5 μm. By utilizing the electroplating temperature, current density, and thickness of the diffusion barrier layer of this invention, a finer crystal structure is obtained in the diffusion barrier layer. The specified temperature range ensures sufficient conductivity and ionic activity in the electroplating solution, while avoiding excessively rapid decomposition of additives and volatilization of ammonia at high temperatures, thus ensuring the long-term stability of the electroplating solution and the quality of the plating layer. At the specified current density, high current efficiency, fast deposition rate, and few side reactions are achieved. The extremely dense copper layer with a thickness of no more than 5 μm is sufficient to effectively block element diffusion in a short time during subsequent composite processes; an excessively thick plating layer would significantly reduce the overall performance of the composite material.

[0024] In a preferred embodiment of the preparation method described in this invention, in step S1, the drying conditions are 100°C for 20 minutes.

[0025] In a preferred embodiment of the preparation method of the present invention, in step S1, the ultrasonic cleaning is performed using an acetone solution, and the ultrasonic cleaning conditions are 60-80°C for 5-10 minutes.

[0026] In a preferred embodiment of the preparation method described in this invention, in step S2, the precursor solution is a mixture of Cu2SO4·5H2O, deionized water, polyethylene glycol, and glycerol, wherein the mass ratio of Cu2SO4·5H2O, deionized water, polyethylene glycol, and glycerol in the mixture is 150–200:780–820:5–15:3–10. Using the precursor solution of this invention to prepare spherical copper powder does not produce harmful gases such as nitrogen oxides, making it more environmentally friendly and safer, and resulting in higher production efficiency and equipment utilization. Using the precursor solution of this invention to prepare spherical copper powder can prevent adhesion, delay the drying and hardening of powder particles, prevent cracking and hollowing, and better control granulation. Using the precursor solution of this invention, high-purity, high-sphericity, uniform particle size distribution, good flowability, and easy subsequent processing of micron-sized spherical copper powder can be obtained. The precursor solution used in this invention has superior effects compared to existing precursor solutions for preparing copper powder.

[0027] In a preferred embodiment of the preparation method described in this invention, in step S2, the atmosphere for spray drying is nitrogen; the pressure for spray drying is 0.1–0.5 MPa; the solution temperature for spray drying is 40–50°C; the inlet temperature of the spray drying equipment is 120–360°C, and the outlet temperature is 80–100°C; the hot air velocity for spray drying is 0.8–1.6 m / s². 3 / min. This invention utilizes nitrogen to prevent copper oxidation at the source. This invention controls the solution temperature during spray drying to 40–50°C, maintaining a warm solution reduces its viscosity and surface tension, making it easier to atomize and generate uniformly sized droplets, thus obtaining powder with a narrow particle size distribution; it also ensures that the components (polyethylene glycol) in the precursor solution are completely dissolved and function effectively.

[0028] In a preferred embodiment of the preparation method of the present invention, in step S2, the protective gas is hydrogen; the reduction conditions are 600-800℃ for 120-240 min.

[0029] In a preferred embodiment of the preparation method described in this invention, in step S3, the pressing is cold isostatic pressing, the pressing pressure is 200-300 MPa, and the drying conditions are drying at 100°C for 20 min.

[0030] In a preferred embodiment of the preparation method of the present invention, in step S4, the sintering atmosphere is hydrogen, and the sintering conditions are sintering at 780-920°C for 60-300 min.

[0031] In a preferred embodiment of the preparation method of the present invention, in step S4, the deformation amount per pass is 5-10%, and the cumulative deformation amount is 10%-50%; the annealing conditions are annealing at 300-600℃ for 60-240 min.

[0032] In a preferred embodiment of the preparation method described in this invention, in step S4, the encapsulation material is aluminum alloy or stainless steel, and both ends are welded.

[0033] Secondly, the present invention provides a microfiber-reinforced copper-based composite material prepared using the above-described preparation method.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes high-melting-point metal microfibers to strengthen copper-based materials. The fine, high-melting-point metal microfibers are uniformly distributed within the copper matrix, not only improving the strength of the copper matrix but also maintaining excellent electrical and thermal conductivity. The preparation method of this invention is highly operable and reproducible. The resulting microfiber-reinforced copper-based composite material exhibits excellent performance, possessing high strength, high stability, and high thermal and electrical conductivity. It also boasts high density, superior thermal conductivity at high temperatures, and even higher tensile strength, meeting the industry's urgent need for copper composite materials that combine high strength, high stability, and high thermal and electrical conductivity. This provides technical support for research on the mechanical, oxidation, corrosion, and irradiation properties of copper materials. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the process for preparing the microfiber-reinforced copper-based composite material of the present invention; Figure 2 This is a SEM image of the microfiber-reinforced copper-based composite material of Example 1 of the present invention; Figure 3 This is an EDS elemental distribution diagram of the microfiber-reinforced copper-based composite material of Example 1 of the present invention; Figure 4 The temperature-thermal diffusivity curve of the microfiber reinforced copper matrix composite material in Example 1 of the present invention is shown. Detailed Implementation

[0036] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0037] Unless otherwise specified, all other materials and reagents used in the examples are commercially available.

[0038] Example 1 A microfiber-reinforced copper-based composite material is prepared by the following steps: S1. Metal fibers (20 μm diameter tungsten wire) were pretreated with a pretreatment solution and then washed with water to obtain pretreated metal fibers. The pretreatment conditions were 80℃ for 3 min. The composition of the pretreatment solution was water, 28 g / L NaOH, 25 g / L Na2CO3, 25 g / L Na3PO4, and 3 g / L sodium dodecylbenzenesulfonate. The obtained pretreated metal fibers were electrolyzed with a 5% NaOH solution (pH 14.1) and then washed with water to obtain activated metal fibers. The electrolysis temperature was 6℃, the electrolysis time was 1 min, the electrolysis voltage was 30 V, and the electrolysis current was 0.4 A. The obtained activated metal fibers were then modified by electroplating in an electroplating solution to add a diffusion barrier layer, followed by washing and drying to obtain modified metal fibers. The composition of the electroplating solution was water, 60 g / L Cu2P2O7, 330 g / L K4P2O7, 2 mL / L NH3·H2O, and 22 g / L sodium dodecylbenzenesulfonate. The plating process involved KNO3, 20 g / L KOH, 25 g / L potassium citrate, and 1 mL / L NB-1 copper pyrolysis brightener. The diffusion barrier layer thickness was 3 μm. The modified electroplating temperature was 50℃, and the modified electroplating current density was 1.2 A / dm³. 2 The drying conditions were 100℃ for 20 min; the obtained modified metal fibers were processed into micro short fibers with a length of 200 μm using a fine cutting device, and then ultrasonically cleaned in acetone solution and vacuum sealed to obtain modified metal micro short fibers. The ultrasonic cleaning conditions were 60℃ for 10 min. S2. A precursor solution is prepared by mixing Cu₂SO₄·5H₂O, deionized water, polyethylene glycol, and glycerol. The mass ratio of Cu₂SO₄·5H₂O, deionized water, polyethylene glycol, and glycerol in the precursor solution is 180:800:10:3. The precursor solution is then spray-dried in a nitrogen atmosphere to obtain precursor powder, which is then reduced in a hydrogen atmosphere and sieved to obtain spherical copper powder with a particle size of 5–44 μm. The spray drying pressure is 0.3 MPa, the solution temperature is 50°C, the inlet temperature of the spray drying equipment is 220°C, the outlet temperature is 90°C, and the hot air velocity is 1 m / s². 3 / min; the reduction conditions are 720℃ for 120min; S3. The modified metal microfibers obtained in step S1 are thoroughly mixed with the spherical copper powder obtained in step S2 to obtain a mixed powder. The mass ratio of the modified metal microfibers to the spherical copper powder is 0.8:100. The mixed powder is pressed, dried, and vacuum sealed to obtain a copper material green blank. The pressing is cold isostatic pressing at a pressure of 220 MPa, and the drying conditions are 100°C for 20 min. S4. The copper material green blank obtained in step S3 is sintered in a hydrogen atmosphere to obtain a sintered copper billet. The sintering conditions are 860°C for 180 min. The sintered copper billet is encapsulated (oxygen-free protection), rolled, deformed, and annealed to obtain a microfiber-reinforced copper-based composite material. The deformation amount per pass is 5%, and the material is annealed at 560°C for 120 min to remove internal stress. The rolling and annealing are repeated 5 times, with the annealing temperature decreasing by 40°C each time.

[0039] A schematic diagram of the process for preparing the microfiber-reinforced copper-based composite material of this invention is shown below. Figure 1 As shown.

[0040] Scanning electron microscopy (SEM) was used to observe microfiber-reinforced copper matrix composites. The results showed that the copper matrix grain size ranged from 1 to 5 μm, and the tungsten fiber diameter was 20 μm. After rolling and annealing, the microfiber-reinforced copper matrix composites obtained had high density, reaching 9.01 g / cm³. 3 The spherical copper powder prepared in step S2 of this embodiment has a density of 8.94 g / cm³. 3 The density of the composite material is significantly increased after being modified with metal micro short fibers.

[0041] The SEM image of the microfiber reinforced copper matrix composite material in this embodiment is shown below. Figure 2 As shown.

[0042] Example 2 A microfiber-reinforced copper-based composite material is prepared by the following steps: S1. Metal fibers (18μm diameter molybdenum wire) were pretreated with a pretreatment solution and then washed with water to obtain pretreated metal fibers. The pretreatment conditions were 60℃ for 5 min. The composition of the pretreatment solution was water, 10 g / L NaOH, 20 g / L Na2CO3, 20 g / L Na3PO4, and 5 g / L sodium dodecylbenzenesulfonate. The obtained pretreated metal fibers were electrolyzed with a 15% (w / w) NaOH solution (pH 14.6) and then washed with water to obtain activated metal fibers. The electrolysis temperature was 8℃, the electrolysis time was 1 min, the electrolysis voltage was 30V, and the electrolysis current was 0.6A. The obtained activated metal fibers were then modified by electroplating in an electroplating solution to add a diffusion barrier layer, followed by washing and drying to obtain modified metal fibers. The composition of the electroplating solution was water, 50 g / L Cu2P2O7, 300 g / L K4P2O7, 1 mL / L NH3·H2O, and 15 g / L sodium dodecylbenzenesulfonate. The plating process involved KNO3, 5 g / L KOH, 10 g / L potassium citrate, and 0.5 mL / L NB-1 copper pyrolysis brightener. The diffusion barrier layer thickness was 2 μm. The modified electroplating temperature was 40℃, and the modified electroplating current density was 1.6 A / dm³. 2 The drying conditions were 100℃ for 20 min; the obtained modified metal fibers were processed into micro short fibers with a length of 300 μm using a fine cutting device, and then ultrasonically cleaned in acetone solution and vacuum sealed to obtain modified metal micro short fibers. The ultrasonic cleaning conditions were 80℃ for 5 min. S2. Cu₂SO₄·5H₂O, deionized water, polyethylene glycol, and glycerol are mixed to obtain a precursor solution. The mass ratio of Cu₂SO₄·5H₂O, deionized water, polyethylene glycol, and glycerol in the precursor solution is 150:780:5:3. The obtained precursor solution is spray-dried in a nitrogen atmosphere to obtain precursor powder, which is then reduced in a hydrogen atmosphere and sieved to obtain spherical copper powder with a particle size of 5–44 μm. The spray drying pressure is 0.36 MPa, the solution temperature is 50℃, the inlet temperature of the spray drying equipment is 200℃, the outlet temperature is 90℃, and the hot air velocity is 1 m / s². 3 / min; the reduction conditions are 680℃ for 150min; S3. The modified metal microfibers obtained in step S1 are thoroughly mixed with the spherical copper powder obtained in step S2 to obtain a mixed powder. The mass ratio of the modified metal microfibers to the spherical copper powder is 0.3:100. The mixed powder is pressed, dried, and vacuum sealed to obtain a copper material green blank. The pressing is cold isostatic pressing at a pressure of 250 MPa, and the drying conditions are 100°C for 20 min. S4. The copper material green blank obtained in step S3 is sintered in a hydrogen atmosphere to obtain a sintered copper billet. The sintering conditions are 820°C for 150 min. The sintered copper billet is encapsulated (oxygen-free protection), rolled, deformed, and annealed to obtain a microfiber-reinforced copper-based composite material. The deformation amount per pass is 8%, and the material is annealed at 580°C for 120 min to remove internal stress. The rolling and annealing are repeated 3 times, with the annealing temperature decreasing by 60°C each time.

[0043] Scanning electron microscopy (SEM) was used to observe microfiber-reinforced copper matrix composites. The results showed that the copper matrix grain size ranged from 1 to 5 μm, and the molybdenum fiber diameter was 18 μm. After rolling and annealing, the microfiber-reinforced copper matrix composites obtained had high density, reaching 8.97 g / cm³. 3 .

[0044] Example 3 A microfiber-reinforced copper-based composite material is prepared by the following steps: S1. Metal fibers (20 μm diameter rhenium wire) were pretreated with a pretreatment solution and then washed with water to obtain pretreated metal fibers. The pretreatment conditions were 80℃ for 3 min. The composition of the pretreatment solution was water, 10 g / L NaOH, 20 g / L Na2CO3, 20 g / L Na3PO4, and 1 g / L sodium dodecylbenzenesulfonate. The obtained pretreated metal fibers were electrolyzed with a 10% (w / w) NaOH solution (pH 14.3) and then washed with water to obtain activated metal fibers. The electrolysis temperature was 5℃, the electrolysis time was 1 min, the electrolysis voltage was 20 V, and the electrolysis current was 0.1 A. The obtained activated metal fibers were then modified by electroplating in an electroplating solution to add a diffusion barrier layer, followed by washing and drying to obtain modified metal fibers. The composition of the electroplating solution was water, 50 g / L Cu2P2O7, 300 g / L K4P2O7, 1 mL / L NH3·H2O, and 15 g / L sodium dodecylbenzenesulfonate. The plating process involved KNO3, 5 g / L KOH, 10 g / L potassium citrate, and 0.5 mL / L NB-1 copper pyrolysis brightener. The diffusion barrier layer thickness was 5 μm. The modified electroplating temperature was 30℃, and the modified electroplating current density was 2.5 A / dm³. 2The drying conditions were 100℃ for 20 min; the obtained modified metal fibers were processed into micro short fibers with a length of 500 μm using a fine cutting device, and then ultrasonically cleaned in acetone solution and vacuum sealed to obtain modified metal micro short fibers. The ultrasonic cleaning conditions were 60℃ for 10 min. S2. A precursor solution was prepared by mixing Cu₂SO₄·5H₂O, deionized water, polyethylene glycol, and glycerol. The mass ratio of Cu₂SO₄·5H₂O, deionized water, polyethylene glycol, and glycerol in the precursor solution was 150:780:5:3. The precursor solution was spray-dried in a nitrogen atmosphere to obtain precursor powder, which was then reduced in a hydrogen atmosphere and sieved to obtain spherical copper powder with a particle size of 5–44 μm. The spray drying pressure was 0.3 MPa, the solution temperature was 50℃, the inlet temperature of the spray drying equipment was 220℃, the outlet temperature was 90℃, and the hot air velocity was 1 m / s. 3 / min; the reduction conditions are 600℃ for 240min; S3. The modified metal microfibers obtained in step S1 are thoroughly mixed with the spherical copper powder obtained in step S2 to obtain a mixed powder. The mass ratio of the modified metal microfibers to the spherical copper powder is 0.1:100. The mixed powder is pressed, dried, and vacuum sealed to obtain a copper material green blank. The pressing is cold isostatic pressing at a pressure of 220 MPa, and the drying conditions are 100°C for 20 min. S4. The copper material green blank obtained in step S3 is sintered in a hydrogen atmosphere to obtain a sintered copper billet. The sintering conditions are 780°C for 300 min. The sintered copper billet is encapsulated (oxygen-free protection), rolled, deformed, and annealed to obtain a microfiber-reinforced copper-based composite material. The deformation amount per pass is 10%, and the material is annealed at 300°C for 240 min to remove internal stress. The rolling and annealing are repeated 5 times, with the annealing temperature decreasing by 20°C each time.

[0045] Scanning electron microscopy (SEM) was used to observe microfiber-reinforced copper matrix composites. The results showed that the copper matrix grain size ranged from 1 to 5 μm, and the rhenium fiber diameter was 20 μm. After rolling and annealing, the microfiber-reinforced copper matrix composites obtained had high density, reaching 8.95 g / cm³. 3 .

[0046] Example 4 A microfiber-reinforced copper-based composite material is prepared by the following steps: S1. Metal fibers (10 μm diameter tungsten wire) were pretreated with a pretreatment solution and then washed with water to obtain pretreated metal fibers. The pretreatment conditions were 80℃ for 3 min. The composition of the pretreatment solution was water, 50 g / L NaOH, 30 g / L Na2CO3, 30 g / L Na3PO4, and 5 g / L sodium dodecylbenzenesulfonate. The obtained pretreated metal fibers were electrolyzed with a 5% NaOH solution (pH 14.1) and then washed with water to obtain activated metal fibers. The electrolysis temperature was 10℃, the electrolysis time was 1 min, the electrolysis voltage was 60 V, and the electrolysis current was 0.6 A. The obtained activated metal fibers were then modified by electroplating in an electroplating solution to add a diffusion barrier layer, followed by washing and drying to obtain modified metal fibers. The composition of the electroplating solution was water, 90 g / L Cu2P2O7, 400 g / L K4P2O7, 3 mL / L NH3·H2O, and 25 g / L sodium dodecylbenzenesulfonate. The plating process involved KNO3, 20 g / L KOH, 30 g / L potassium citrate, and 2 mL / L NB-1 copper pyrolysis brightener. The diffusion barrier layer thickness was 3 μm. The modified electroplating temperature was 60℃, and the modified electroplating current density was 0.2 A / dm³. 2 The drying conditions were 100℃ for 20 min; the obtained modified metal fibers were processed into micro short fibers with a length of 200 μm using a fine cutting device, and then ultrasonically cleaned in acetone solution and vacuum sealed to obtain modified metal micro short fibers. The ultrasonic cleaning conditions were 60℃ for 10 min. S2. A precursor solution was prepared by mixing Cu₂SO₄·5H₂O, deionized water, polyethylene glycol, and glycerol. The mass ratio of Cu₂SO₄·5H₂O, deionized water, polyethylene glycol, and glycerol in the precursor solution was 200:820:15:10. The precursor solution was spray-dried in a nitrogen atmosphere to obtain precursor powder, which was then reduced in a hydrogen atmosphere and sieved to obtain spherical copper powder with a particle size of 5–44 μm. The spray drying pressure was 0.3 MPa, the solution temperature was 50℃, the inlet temperature of the spray drying equipment was 220℃, the outlet temperature was 90℃, and the hot air velocity was 1 m / s. 3 / min; the reduction conditions are 800℃ for 120min; S3. The modified metal microfibers obtained in step S1 are thoroughly mixed with the spherical copper powder obtained in step S2 to obtain a mixed powder. The mass ratio of the modified metal microfibers to the spherical copper powder is 10:100. The mixed powder is pressed, dried, and vacuum sealed to obtain a copper material green blank. The pressing is cold isostatic pressing at a pressure of 220 MPa, and the drying conditions are 100°C for 20 min. S4. The copper material green blank obtained in step S3 is sintered in a hydrogen atmosphere to obtain a sintered copper billet. The sintering conditions are 920°C for 60 min. The sintered copper billet is encapsulated (oxygen-free protection), rolled, deformed, and annealed to obtain a microfiber-reinforced copper-based composite material. The deformation amount per pass is 5%. The material is annealed at 600°C for 60 min to remove internal stress. The rolling and annealing are repeated twice, with the annealing temperature decreasing by 60°C each time.

[0047] Scanning electron microscopy (SEM) was used to observe microfiber-reinforced copper matrix composites. The results showed that the copper matrix grain size ranged from 1 to 5 μm, and the tungsten fiber diameter was 10 μm. After rolling and annealing, the microfiber-reinforced copper matrix composites obtained had high density, reaching 9.52 g / cm³. 3 .

[0048] Test Example 1 The elemental distribution of the microfiber-reinforced copper matrix composite material in Example 1 was determined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The accelerating voltage of the SEM was 15 kV, and the working distance was 10 nm.

[0049] The EDS elemental distribution diagram of the microfiber reinforced copper matrix composite material in Example 1 is shown below. Figure 3 As shown, the results indicate that the presence of the diffusion barrier layer added during the modified electroplating process results in a tight bond between the tungsten fiber and the copper substrate, thus improving the interfacial bonding between the high-melting-point tungsten fiber and the copper substrate.

[0050] This application also measured the EDS elemental distribution of the microfiber reinforced copper matrix composites of Examples 2-4. The results showed that the high-melting-point metal fibers were tightly bonded to the copper matrix, which improved the interfacial bonding problem between the high-melting-point metal fibers and the copper matrix.

[0051] Test Example 2 The thermal diffusivity of the microfiber-reinforced copper matrix composite material in the examples was determined using a laser scintillation thermal conductivity analyzer, and temperature-thermal diffusivity curves were plotted. Samples had diameters of 10 mm or 12.7 mm and thicknesses of 2–3 mm. The surface treatment consisted of double-sided graphite coating in an argon atmosphere with temperature increments of 50 °C. A short, uniform laser pulse was applied to the front surface of the sample, causing it to absorb light energy and raise its temperature, thus serving as a heat source. The temperature change of the back surface of the sample over time was monitored using an infrared detector or other types of temperature sensors. The time required for the back surface temperature to rise to half of its maximum value (half-peak time t) was analyzed. 50 The thermal diffusivity of the material in the thickness direction can be calculated by using this method.

[0052] The results show that the high-temperature thermal diffusivity of the microfiber-reinforced copper matrix composite material of the present invention is significantly improved. Specifically, the spherical copper powder prepared in step S2 of Example 1 has a thermal diffusivity of 45 mm at 650℃. 2 The thermal diffusivity of the microfiber-reinforced copper matrix composite material obtained after modification with metal microfibers is 85 mm² / s at 650℃. 2 / s, significantly improving high-temperature thermal diffusion performance.

[0053] Example 1: Temperature-thermal diffusivity curve of microfiber reinforced copper matrix composite material as shown in the figure. Figure 4 As shown.

[0054] The thermal diffusivity of the microfiber-reinforced copper matrix composites in Examples 1-4 is shown in Table 1. Table 1 Thermal Diffusivity (650°C) Example 1 85mm 2 / s]]> Example 2 87 mm 2 / s]]> Example 3 88 mm 2 / s]]> Example 4 73 mm 2 / s]]> Test Example 3 The tensile strength of the microfiber-reinforced copper-based composite material in the example was determined using a high-temperature tensile test. The high-temperature tensile testing machine was used, operating in a vacuum environment with a vacuum level of up to 10. -3 To simulate a high-temperature service environment, a unidirectional static axial tensile force was applied to a composite material specimen until it fractured. The tensile strength (Rt) of the material was calculated by recording the load-displacement curves during the process. m The key mechanical performance indicators were determined, and its deformation behavior at high temperatures was evaluated.

[0055] The results show that the high-temperature tensile strength of the microfiber-reinforced copper matrix composite material of the present invention is significantly improved. Specifically, the spherical copper powder prepared in step S2 of Example 1 has a tensile strength of 24 MPa at 650℃, while the microfiber-reinforced copper matrix composite material obtained after modification with metal microfibers has a tensile strength of 156 MPa at 650℃, demonstrating a significant improvement in high-temperature tensile strength.

[0056] The tensile strengths of the microfiber-reinforced copper-based composite materials in Examples 1-4 are shown in Table 2. Table 2 Tensile Strength (650°C) Example 1 156 MPa Example 2 97 MPa Example 3 71 MPa Example 4 187 MPa Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a microfiber-reinforced copper-based composite material, characterized in that, Includes the following steps: S1. After pretreatment, the metal fibers are washed with water to remove impurities from the surface of the metal fibers and then etched on the surface to obtain pretreated metal fibers. The obtained pretreated metal fibers were electrolyzed and then washed with water to remove the surface oxide scale, resulting in activated metal fibers. The activated metal fibers were modified by electroplating to add a diffusion barrier layer, then washed with water and dried to obtain modified metal fibers. The obtained modified metal fibers were processed into micro short fibers with a length of no more than 500 μm, ultrasonically cleaned and sealed to obtain modified metal micro short fibers. The metal fiber is a high-melting-point metal fiber, and the diameter of the metal fiber is no greater than 20 μm; the diffusion barrier layer is a copper layer. S2. Spray dry the precursor solution for preparing copper powder to obtain precursor powder; reduce the obtained precursor powder in a protective gas atmosphere, sieve it to obtain spherical copper powder with a particle size of 5-44 μm. S3. The modified metal micro short fibers obtained in step S1 are thoroughly mixed with the spherical copper powder obtained in step S2 to obtain a mixed powder; the mixed powder is pressed, dried and sealed to obtain a copper material green blank. The mass ratio of the modified metal microfibers to the spherical copper powder is 0.1–10:100; S4. Sinter the copper material green blank obtained in step S3 to obtain sintered copper billet; encapsulate the obtained sintered copper billet, roll and deform it, and anneal it to obtain microfiber reinforced copper matrix composite material.

2. The preparation method according to claim 1, characterized in that, In step S1, the high-melting-point metal fiber includes tungsten wire, molybdenum wire, or rhenium wire; And / or, in step S1, the pretreatment is performed using a pretreatment solution, the composition of which is water, 10-50 g / L NaOH, 20-30 g / L Na2CO3, 20-30 g / L Na3PO4 and 1-5 g / L surfactant; And / or, in step S1, the pretreatment conditions are 60-80℃ for 3-5 minutes.

3. The preparation method according to claim 1, characterized in that, In step S1, the electrolysis is carried out using a NaOH solution with a pH value of 14-15; And / or, in step S1, the electrolysis temperature is 5-10°C, the electrolysis time is 1 min, the electrolysis voltage is 20-60V, and the electrolysis current is 0.1-0.6A.

4. The preparation method according to claim 1, characterized in that, In step S1, the modified electroplating is performed using an electroplating solution, which consists of water, 50–90 g / L Cu2P2O7, 300–400 g / L K4P2O7, 1–3 mL / L NH3·H2O, 15–25 g / L KNO3, 5–20 g / L KOH, 10–30 g / L potassium citrate, and 0.5–2 mL / L brightener. And / or, in step S1, the modified electroplating temperature is 30–60°C, and the current density is 0.2–2.5 A / dm³. 2 .

5. The preparation method according to claim 1, characterized in that, In step S1, the thickness of the diffusion barrier layer is no greater than 5 μm; And / or, in step S1, the ultrasonic cleaning is performed using an acetone solution; And / or, in step S1, the ultrasonic cleaning conditions are ultrasonic cleaning at 60-80℃ for 5-10 minutes.

6. The preparation method according to claim 1, characterized in that, In step S2, the precursor solution is a mixture of Cu2SO4·5H2O, deionized water, polyethylene glycol and glycerol, wherein the mass ratio of Cu2SO4·5H2O, deionized water, polyethylene glycol and glycerol in the mixture is 150-200:780-820:5-15:3-10.

7. The preparation method according to claim 1, characterized in that, In step S2, the atmosphere for spray drying is nitrogen. And / or, in step S2, the pressure of the spray drying is 0.1 to 0.5 MPa; And / or, in step S2, the temperature of the spray-dried solution is 40–50°C; And / or, in step S2, the inlet temperature of the spray drying equipment is 120-360°C and the outlet temperature is 80-100°C; And / or, in step S2, the hot air flow rate of the spray drying is 0.8–1.6 m / s. 3 / min.

8. The preparation method according to claim 1, characterized in that, In step S2, the protective gas is hydrogen. And / or, in step S2, the reduction conditions are 600-800℃ for 120-240 min.

9. The preparation method according to claim 1, characterized in that, In step S4, the sintering atmosphere is hydrogen. And / or, in step S4, the sintering conditions are sintering at 780–920°C for 60–300 min; And / or, in step S4, the deformation amount per pass is 5% to 10%, and the cumulative deformation amount is 10% to 50%. And / or, in step S4, the annealing conditions are annealing at 300-600°C for 60-240 minutes.

10. A microfiber-reinforced copper-based composite material prepared by the preparation method according to any one of claims 1-9.

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