A copper-tin oxide composite material and a method for preparing the same

Abstract

The application discloses a copper-tin oxide composite material and a preparation method thereof. The preparation method comprises the following steps: firstly, mixing spherical gas-atomized copper-tin alloy powder, ultrapure water and hydrogen peroxide solution, and placing the mixture in a high-temperature and high-pressure reaction kettle to perform supercritical water in-situ reaction to generate copper-tin oxide powder. After the reaction, the powder is treated by ultrasonic cleaning, water and ethanol cleaning and vacuum drying. Then, the copper oxide is reduced by using hydrogen gas in a tube furnace to obtain copper-tin oxide powder. After that, the copper powder and the copper-tin oxide powder are mixed in proportion, and stearic acid or anhydrous ethanol is added as a dispersant to perform ball milling, so as to obtain copper-tin oxide composite powder. Finally, the copper-tin oxide composite material is obtained by pressing and discharge plasma sintering technology. The copper-tin oxide composite powder is prepared by supercritical water in-situ oxidation, so that the process flow is simplified, the performance and conductivity of the composite material are improved, and the environmental protection requirement is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of contact material preparation, and particularly relates to a copper-tin oxide composite material and a preparation method thereof. BACKGROUND

[0002] As a key component of electrical equipment, the function of the electrical contact is to control the on-off of the circuit and the load current. During operation, arc is often generated between the contacts, causing high heat, which leads to melting, impact of the contact material, and further causes wear, cracking, pitting, arc corrosion and welding, affecting the performance and service life of the contact.

[0003] In view of the rapid development of modern industry and the upgrading of automatic control systems, the traditional contact material is facing unprecedented challenges, and better materials need to be sought to meet the severe requirements. The ideal electrical contact material should have the following characteristics: high electrical conductivity and thermal conductivity; low contact resistance; resistance to welding and oxidation; resistance to mechanical wear and arc erosion; moderate hardness and tensile strength. In short, the research and development goal of the electrical contact material is to improve its comprehensive performance to ensure the reliable operation and long service life of the electrical equipment.

[0004] In view of the difficulty of single metal to fully meet the high performance requirements of electrical contact material, metal matrix composite has become the preferred material in the field of electrical contact because it combines the excellent electrical and thermal conduction characteristics of the metal matrix and the unique properties of the reinforcing phase. This kind of composite material usually takes silver and copper as the basis and introduces second phases such as tungsten particles, metal oxides, ceramics, graphene and carbon nanotubes, aiming to strengthen the electrical, mechanical, corrosion-resistant and thermal properties and overcome the limitations of single metal. Silver-based materials are widely used in low-voltage electrical equipment, while copper-based materials are becoming the preferred material for high-voltage electrical contact materials due to cost advantage, especially considering the scarcity and high price of silver. Oxide ceramic particles as reinforcing phase can be introduced by two ways: external addition or in-situ oxidation. The former is simple to prepare, and the type, form and content of the oxide are easy to control, but the interface bonding force is weak; the latter is complex in process, but can ensure the close combination of the oxide and the matrix, effectively improving the strength and thermal stability of the material, but the control is difficult. Therefore, balancing the performance improvement and the preparation process is the key to the development of high-performance contact materials. It can be seen that the research and development of metal matrix composite contact materials not only focuses on the optimization of material performance, but also needs to consider the cost benefit and the feasibility of the preparation technology to meet the increasingly high standard requirements of modern electrical systems for contact materials.

[0005] Patent "Preparation method of copper tin oxide contact material" (CN112239350 B) discloses a kind of solvent thermal method with hydrated tin chloride as tin source, and with polyethylene glycol as surfactant, and tin oxide nanoparticles are assembled into smooth surface tin oxide microspheres, and a certain amount of metal lanthanum powder is introduced to improve the wettability between matrix and reinforcing phase. But this preparation method of copper tin oxide contact has problems such as complex process, long production cycle, high manufacturing cost and difficult industrial production, which needs to be improved. In addition, the existing technology usually uses formaldehyde, dimethylformamide and polyvinylpyrrolidone and other chemical drugs harmful to nature and human health in the preparation process, which is not conducive to green production and sustainable development. SUMMARY

[0006] The purpose of the embodiment of the present application is to provide a preparation method of copper tin oxide composite material, to simplify the preparation process, shorten the preparation period, reduce the cost, and the reaction process is green and pollution-free, and can better solve the problem of poor wettability between copper matrix and reinforcing phase tin oxide, and improve the comprehensive performance of copper tin oxide composite material.

[0007] The second purpose of the embodiment of the present application is to provide a copper tin oxide composite material.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is a preparation method of copper tin oxide composite material, comprising the following steps:

[0009] S1, copper tin alloy powder is in-situ oxidized in supercritical water environment, and the product after supercritical water oxidation is cleaned, filtered and vacuum dried to obtain copper tin oxide powder;

[0010] S2, the copper oxide in the copper tin oxide powder obtained in S1 is reduced to obtain copper tin oxide powder;

[0011] S3, copper powder and copper tin oxide powder obtained in S2 are ball milled and mixed according to a predetermined proportion to obtain copper tin oxide composite powder with a target tin oxide content;

[0012] S4, the copper tin oxide composite powder is pressed into a blank and then subjected to spark plasma sintering to obtain a copper tin oxide composite material.

[0013] Further, the in-situ oxidation in S1 is as follows: copper tin alloy powder is used as raw material, H2O and H2O2 solution as oxygen source are added into a high temperature and high pressure reaction kettle according to the mass ratio of (1~2):(1~4):(1~5) for supercritical water in-situ oxidation reaction, and stirring is carried out at a rate of 220~280 r / min during the reaction.

[0014] Further, the copper-tin alloy powder has a mass fraction of Sn of 5-20 wt.%, and the rest is copper; and the H2O2 solution has a mass fraction of H2O2 of 29-31 wt.%.

[0015] Further, the process parameters of the supercritical oxidation reaction are as follows: a reaction temperature of 375-400 ℃, a pressure of 22-28 MPa, and a reaction time of 5-10 min.

[0016] Further, the specific steps of S2 are as follows: the dried composite powder is placed in a ceramic crucible and put into a tube furnace, the furnace tube is vacuumed twice, argon is introduced, and then the furnace tube is heated to 190-210 ℃ at a heating rate of 9-11 ℃ / min, and then heated to 245-255 ℃ at a heating rate of 4-6 ℃ / min, the argon is turned off, hydrogen is introduced, and then the temperature is kept for 3-4 h; the flow rates of the argon and the hydrogen are both 0.1-1 L / min.

[0017] Further, the specific steps of the ball milling in S3 are as follows: the copper powder and the copper tin oxide powder are first put into a ball milling tank, then stearic acid or anhydrous ethanol is added as a dispersant, and then the milling balls are put into the ball milling tank, wherein the diameters of the milling balls are 8 mm, 5 mm, and 3 mm, and the milling balls are matched in a mass ratio of 3:7:10, the mass ratio of the balls to the material is (6-12):1, then the ball milling tank is vacuumed, and after vacuuming, the ball milling tank is put into a ball mill for ball milling.

[0018] Further, when the stearic acid is used as the dispersant, the addition amount of the stearic acid is 1-5 wt.% of the total mass of the copper powder and the copper tin oxide powder, and when the anhydrous ethanol is used as the dispersant, the anhydrous ethanol is added to just cover the powder.

[0019] Further, the target content of the tin oxide in S3 is 2-9.5 wt.%.

[0020] Further, the specific steps of S4 are as follows: the copper tin oxide powder obtained in S3 is loaded into a graphite mold and pressed into a blank, and then the blank is placed in a spark plasma sintering furnace for sintering to obtain a copper tin oxide composite material, and the sintering parameters are as follows: a sintering pressure of 40-50 MPa, a heating rate of 50-100 ℃ / min, a sintering temperature of 800-900 ℃, and a holding time of 8-15 min.

[0021] A copper tin oxide composite material prepared by the above method.

[0022] The beneficial effects of the present application are: the present application uses copper-tin alloy powder as raw material, generates copper tin oxide composite powder in-situ by supercritical water in-situ oxidation, the copper tin oxide powder prepared by this method has good solubility of copper matrix and tin oxide due to the fact that tin oxide is nucleated and spontaneously grown in the copper matrix, and the surface of tin oxide is not polluted, so the interface bonding strength is high. At the same time, the process is simplified, and there is no need for complicated tin oxide reinforcing phase pre-preparation step, the preparation process is simplified, and the production cost is greatly reduced.

[0023] The tin oxide obtained by in-situ reaction of supercritical water in the present application is tetragonal system, the product tin oxide has advantages of high hardness, wear resistance, corrosion resistance, oxidation resistance, electrical insulation performance and high temperature stability, and has strong interface bonding with the copper matrix, which can avoid the separation of tin oxide and copper matrix under the action of arc erosion, improve the arc erosion resistance of copper tin oxide composite in the process of breaking and connecting, and prolong the service life.

[0024] The copper tin oxide powder and copper powder are ball milled and mixed in the present application instead of completely using copper tin oxide powder for sintering, which can reduce the influence of the introduction of tin oxide on the conductivity of the copper matrix, and ensure that the composite material has high conductivity. In addition, the reaction products in the reaction process of the present application are clean substances without pollution, which meets the concept of sustainable development. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 It is the process route map of the preparation method embodiment of the present application.

[0027] Figure 2 It is the SEM image of Cu-10 wt.% Sn atomized alloy powder raw material; (a) is a 500 times magnification image (b) is a 5000 times magnification image.

[0028] Figure 3 It is the SEM image of Cu-10 wt.% Sn atomized alloy powder after supercritical in-situ reaction; (a) is a 500 times magnification image, (b) is a 5000 times magnification image.

[0029] Figure 4 It is the SEM image of Cu-4.5 wt.% SnO2 composite powder in Example 2; (a) is a 500 times magnification image, (b) is a 5000 times magnification image.

[0030] Figure 5 SEM images of SnO2 particles extracted from the composite material; (a) is a 10000 times magnification image, and (b) is a 100000 times magnification image.

[0031] Figure 6 SEM images and element distribution maps of the Cu-4.5 wt.% SnO2 composite material in Example 2; (a) is an SEM image of the surface of the Cu-4.5 wt.% SnO2 composite material, (b) is a Cu element distribution map, (c) is an O element distribution map, and (d) is a Sn element distribution map.

[0032] Figure 7 TEM images of the interface between SnO2 and the Cu matrix in the Cu-4.5 wt.% SnO2 composite material in Example 2 and their Fourier transform and inverse Fourier transform maps. (a) is a TEM image of the interface between Cu and SnO2 in the Cu-4.5 wt.% SnO2 composite material, (b) is an HRTEM image of the yellow region in (a), (c) is an FFT map (Cu) of the yellow region in (b), (d) is an IFFT map of the yellow square in (b), (e) is an IFFT map of the yellow square in (b), and (f) is an FFT map (SnO2) of the yellow region in (b). DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0034] As Figure 1 The present embodiment provides a preparation method of a copper tin oxide composite material, which comprises the following steps:

[0035] S1, in-situ oxidation of copper tin alloy powder in a supercritical water environment to obtain copper tin oxide powder. In some possible embodiments, the copper tin alloy powder is preferably spherical gas-atomized copper tin alloy powder, and the mass fraction of Sn in the alloy powder is 5-20 wt.%. Too high or too low Sn content not only affects the uniformity of the material, but also affects the performance of the composite material. For example, too high Sn content is prone to agglomeration, which reduces the density and the electrical conductivity. Too low Sn content has poor strengthening effect, and the comprehensive performance of the composite material is poor. Therefore, an appropriate amount of content can effectively improve the comprehensive performance.

[0036] In some specific embodiments, when step S1 is implemented, the spherical gas atomized copper-tin alloy powder is first placed in a Hastelloy inner liner, and ultra-pure water and an appropriate amount of hydrogen peroxide solution are added, and then the inner liner is placed in a high-temperature and high-pressure reaction kettle for supercritical water in-situ reaction. The hydrogen peroxide solution can be a 29-31 wt.% hydrogen peroxide solution, and the mass ratio of the copper-tin alloy powder, the ultra-pure water and the hydrogen peroxide solution is (1-2):(1-4):(1-5); the supercritical water in-situ reaction temperature is 375-400 ℃, the pressure is 22-28 MPa, and the reaction time is 5-10 min; if the reaction temperature and pressure are lower than the lower limit, the supercritical state cannot be reached, and if they exceed this range, copper powder will be excessively oxidized, a large number of atoms will recombine during the reduction process, and the significance of in-situ oxidation will be lost.

[0037] After the reaction kettle is naturally cooled to room temperature, the inner liner is taken out and placed in an ultrasonic cleaning machine for ultrasonic cleaning for 10-15 min, so as to wash the copper-tin oxide powder on the wall of the inner liner, and then the inner liner is cross-washed and suction-filtered with ultra-pure water and ethanol for 2-3 times. Subsequently, the washed copper-tin oxide powder is placed in a vacuum drying box, vacuumized, heated to 50-60 ℃, and dried to constant weight for 6-8 h.

[0038] The critical point temperature of water is 374.3 ℃, and the pressure is 22.1 MPa. When the temperature and pressure of water are above the critical point, it is supercritical water, and its density, viscosity, conductivity, dielectric constant and other basic properties are very different from those of ordinary water. Supercritical water has the characteristics of high diffusivity and low viscosity. The polarity of water changes with the change of temperature and pressure. Below the critical condition, water is a polar solvent; when the supercritical condition is reached, the supercritical water becomes a non-polar solvent and can be completely miscible with oxygen to form a homogeneous reaction medium. Supercritical water oxidation refers to a process of oxidizing chemical substances in water medium with oxygen or hydrogen peroxide as an oxidizing agent under conditions of temperature and pressure higher than the critical point. Its test conditions are simple, the reaction speed is fast, the reaction time is short, and the reaction products are clean substances without pollution. Therefore, the introduction of oxide ceramic particles by using the supercritical water in-situ oxidation technology can simultaneously simplify the introduction process of oxide particles and achieve good bonding between the oxide particles and the matrix interface.

[0039] S2, the copper-tin oxide powder prepared in S1 is placed in a tube furnace to reduce the copper oxide, and copper tin oxide powder is obtained.

[0040] In some specific embodiments, when step S2 is implemented, the dried copper tin oxide powder is placed in a ceramic crucible and put in the middle of a tube furnace, the tube furnace tube is sealed at both ends, vacuum is drawn on the tube furnace tube and its airtightness is checked, then argon gas is introduced to atmospheric pressure and vacuum is drawn again, and the process is repeated twice. Then argon gas is introduced to atmospheric pressure, the gas outlet valve is opened, the argon gas flow is 0.1-1 L / min, then the furnace tube is first heated to 190-210 ℃, then heated to 245-255 ℃, the argon valve is closed and the hydrogen valve is opened, the hydrogen flow is 0.1-0.5 L / min, and the copper tin oxide powder is heated for 3-4 h. The oxide of copper in the copper tin oxide powder is reduced to copper, and the tin oxide remains in the oxidized state.

[0041] S3, the copper powder and copper tin oxide powder are ball milled according to a predetermined proportion to obtain a copper tin oxide composite powder with a target tin oxide content.

[0042] In some specific embodiments, when step S3 is implemented, the copper powder and copper tin oxide powder are first placed in a ball mill tank, then stearic acid or anhydrous ethanol is added as a dispersant, and then the grinding balls are placed in the ball mill tank. The diameter of the grinding balls is 8 mm, 5 mm, or 3 mm, and the mass ratio of the grinding balls to the material is 3:7:10. The ball-to-material mass ratio is (6-12):1. After ball milling with this ratio, the powder has a smaller flaky thickness, can break large particles, and has a uniform particle size distribution. At the same time, the composite powder is more uniformly mixed. Then the ball mill tank is evacuated, and after evacuation, the ball mill tank is placed in a ball mill for ball milling. The ball milling process parameters are as follows: the ball milling rotation speed is 100-300 r / min, and the ball milling time is 15-20 h. After ball milling, the ball mill tank is placed in a vacuum drying oven and heated to 50-60 ℃. Drying is performed for 6-8 h until the weight is constant. A uniform copper tin oxide composite powder with a target tin oxide content of 2-9.5 wt.% is obtained.

[0043] S4, the copper tin oxide composite powder is pressed into a blank and then subjected to spark plasma sintering to obtain a copper tin oxide composite material.

[0044] In some specific embodiments, when step S4 is implemented, the uniformly mixed copper tin oxide composite powder is first loaded into a graphite mold and pressed into a blank, and then sintered in a spark plasma sintering furnace. The sintering parameters can be set as follows: the sintering pressure is 40-50 MPa, the heating rate is 50-100 ℃ / min, the sintering temperature is 800-900 ℃, and the holding time is 8-15 min. After sintering and cooling, a copper tin oxide composite material is obtained.

[0045] Example 1

[0046] Cu-10 wt.% Sn spherical gas-atomized alloy powder was used as raw material, Cu-10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as oxygen source were added into a high-temperature and high-pressure reactor at a mass ratio of 1:2:1 for supercritical water in-situ oxidation reaction. The stirring rate was 250 r / min during the reaction.

[0047] The process parameters of supercritical oxidation reaction were as follows: the reaction temperature was 385 ℃, the holding time was 7.5 min, and the pressure was 25 MPa. After the supercritical water in-situ oxidation reaction, the reinforcing phase element Sn in the raw material powder was in-situ oxidized to form SnO2 in the Cu matrix, and a small amount of copper was also oxidized to form CuO and Cu2O.

[0048] The product after supercritical water oxidation was washed and filtered, and vacuum dried to obtain a composite powder.

[0049] The dried composite powder was placed in a ceramic crucible and put into a tube furnace. The furnace tube was evacuated twice, and then the airtightness was checked. Then argon was introduced, and then the furnace tube was heated at a heating rate of 10 ℃ / min. After the temperature reached 200 ℃, the heating rate was increased to 5 ℃ / min, and the temperature was increased to 250 ℃. After the argon was turned off, hydrogen was introduced, and then the temperature was kept for 3 h. The gas flow was 0.3 L / min. After the program stopped, the furnace was cooled to room temperature, and then the Cu-12.36 wt.% SnO2 composite powder was obtained.

[0050] 3.24 g of the reduced composite powder and 16.76 g of pure Cu powder were added to a ball mill jar, and stearic acid was added as a dispersant. The mass fraction of stearic acid in the total mass of copper powder and copper tin oxide powder was 1%. Then the grinding balls were put into the ball mill jar. The diameters of the three grinding balls were 8 mm, 5 mm and 3 mm, and the mass ratio of the three was 3:7:10. The ball-to-material mass ratio was 10:1. Then the ball mill jar was evacuated, and after evacuation, the ball mill jar was put into the ball mill for ball milling. The ball milling process parameters were as follows: the ball milling speed was 300 r / min, and the ball milling time was 20 h. After ball milling, the Cu-2 wt.% SnO2 composite powder was obtained.

[0051] The ball-milled Cu-2 wt.% SnO2 composite powder is placed in a graphite mold with a diameter of 20 mm, sealed by a pressure head wrapped with graphite paper, and pre-pressed by external force to make the powder more dense for heat conduction, and then placed in a sintering furnace for discharge plasma sintering through a pre-set program, while the vacuum pump is used to extract the environment in the furnace to vacuum until the end of the sintering process, and then cooled down to room temperature after the end of the sintering process. The process parameters for discharge plasma sintering are as follows: vacuum degree is below 8 Pa, sintering pressure is 50 MPa, heating rate is 100 ℃ / min, sintering temperature is 850 ℃, and the holding time at the sintering temperature is 10 min.

[0052] The Cu-2 wt.% SnO2 composite material prepared in Example 1 is tested, and the density is 98.62 %, the electrical conductivity is 52.5 %IACS, the hardness and tensile strength are 92.3 HV and 284 MPa respectively, and the elongation is 54.9 %.

[0053] Example 2

[0054] The Cu-10 wt.% Sn gas-atomized alloy powder is used as the raw material, and the Cu-10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as the oxidizing agent are added into a high-temperature and high-pressure reaction kettle in a mass ratio of 1:2:1 for supercritical water in-situ oxidation reaction, and stirring is performed at a rate of 250 r / min during the reaction process. The process parameters for supercritical oxidation reaction are as follows: reaction temperature is 380 ℃, holding time is 10 min, and pressure is 23 MPa. After the supercritical oxidation reaction, the reinforcing phase element Sn in the raw material powder is in-situ oxidized to SnO2, and copper is also oxidized to form CuO and Cu2O.

[0055] The product after supercritical water oxidation is washed, filtered, and vacuum dried to obtain a composite powder.

[0056] The dried composite powder is placed in a ceramic crucible and placed in a tube furnace, the furnace tube is evacuated twice, then the airtightness is checked, then argon gas is introduced, then the furnace tube is heated at a heating rate of 10 ℃ / min, the temperature is raised to 250 ℃ at a heating rate of 5 ℃ / min after the temperature reaches 190 ℃, then the argon gas is turned off and hydrogen gas is introduced, and then the temperature is held for 3 h, wherein the gas flow is 0.3 L / min, and then the furnace is cooled to room temperature after the program stops, and the Cu-12.36 wt.% SnO2 composite powder is obtained.

[0057] Take 7.28 g of the reduced composite powder and 12.72 g of pure Cu powder into a ball milling tank, add stearic acid as a dispersant, the stearic acid accounts for 1% of the total mass of copper powder and copper tin oxide powder, then put the milling balls into the ball milling tank. Among them, the diameter of the milling ball is 8 mm, 5 mm and 3 mm, the number ratio is 3:7:10, and the ball-to-material mass ratio is 10:1. Then the ball milling tank is vacuumized, after vacuumization, the ball milling tank is put into the ball mill for ball milling, the ball milling process parameters are: ball milling speed is 300 r / min, ball milling time is 20 h, after ball milling, Cu~4.5wt.% SnO2 composite powder is obtained.

[0058] Put the ball-milled Cu~4.5 wt% SnO2 composite powder into a graphite mold with a diameter of 20 mm, seal it by wrapping it with graphite paper, and pre-press it by external force to make the powder more dense and facilitate heat conduction, then put it into a sintering furnace to perform spark plasma sintering through a pre-set program, at the same time, use a vacuum pump to extract the environment in the furnace to vacuum until the end of the sintering process, after the end, cool down with the furnace, and after cooling to room temperature, Cu~4.5 wt.% SnO2 composite material can be obtained. The process parameters of spark plasma sintering are: vacuum degree is below 6 Pa, sintering pressure is 50 MPa, heating rate is 100 ℃ / min, sintering temperature is 800 ℃, and holding time at sintering temperature is 10 min.

[0059] Comparison Figure 2 (a) (b) and Figure 3 It can be seen from (a) (b) that after supercritical water in-situ oxidation reaction, the surface of copper-tin alloy powder forms uniformly distributed and fine tin oxide particles; from Figure 4 It can be seen that the morphology of copper tin oxide powder remains basically unchanged after reduction, and the uniform distribution of tin oxide particles is maintained. From Figure 5 (a) (b), Figure 6 (a) (d), Figure 7 It can be seen from (a) (f) that after sintering, the tin oxide in the copper tin oxide composite also has a relatively uniform distribution.

[0060] The Cu~4.5 wt% SnO2 composite material prepared in Example 2 was tested, and the results are as follows: the density is 99.23%, the electrical conductivity is 39.7 %IACS, the hardness and tensile strength are 101.7 HV and 331 MPa respectively, and the elongation is 43.21%.

[0061] Example 3

[0062] Cu-10 wt.% Sn gas atomized alloy powder was used as raw material, Cu-10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as oxidant were added into a high temperature and high pressure reactor at a mass ratio of 1:2:2 for supercritical water in-situ oxidation reaction, and stirring was carried out at a speed of 220 r / min during the reaction. The process parameters of supercritical oxidation reaction are as follows: the reaction temperature is 375 ℃, the holding time is 5 min, and the pressure is 22 MPa. After supercritical oxidation reaction, the reinforcing phase element Sn in the raw material powder is in-situ oxidized to SnO2, and copper is also oxidized to form CuO and Cu2O.

[0063] The product after supercritical water oxidation was washed and filtered, and vacuum dried to obtain a composite powder.

[0064] The dried composite powder was placed in a ceramic crucible and put into a tube furnace, the furnace tube was vacuumed twice, then the airtightness was checked, then argon was introduced, then the furnace tube was heated at a heating rate of 10 ℃ / min, the temperature reached 210 ℃, then the heating rate was increased to 5 ℃ / min, the temperature was increased to 255 ℃, then the argon was turned off and hydrogen was introduced, and the temperature was kept for 4 h, the gas flow was 0.5 L / min, after the program stopped, the furnace was cooled to room temperature, then the Cu-12.36 wt.% SnO2 composite powder was obtained.

[0065] 7.28 g of reduced composite powder and 12.72 g of pure Cu powder were added to a ball mill jar, and stearic acid was added as a dispersant, the stearic acid accounted for 1% of the total mass of copper powder and copper tin oxide powder, then the grinding balls were put into the ball mill jar. The diameter of the grinding ball is 8 mm, 5 mm and 3 mm, the number ratio is 3:7:10, and the ball-to-material mass ratio is 10:1. Then the ball mill jar was vacuumed, and after vacuuming, the ball mill jar was put into the ball mill for ball milling. The ball milling process parameters are as follows: the ball milling speed is 300 r / min, the ball milling time is 20 h, and the Cu-4.5 wt.% SnO2 composite powder is obtained after ball milling.

[0066] The ball-milled Cu-4.5 wt% SnO2 composite powder was placed in a graphite mold with a diameter of 20 mm, sealed by graphite paper, and pre-pressed by external force to make the powder more dense for heat conduction, then placed in a sintering furnace for spark plasma sintering through a pre-set program, and the vacuum pump was used to extract the environment in the furnace to vacuum until the end of the sintering process, then cooled down to room temperature to obtain the Cu-4.5 wt.% SnO2 composite material. The process parameters of spark plasma sintering are as follows: the vacuum degree is below 6 Pa, the sintering pressure is 50 MPa, the heating rate is 100 ℃ / min, the sintering temperature is 850 ℃, and the holding time at the sintering temperature is 10 min.

[0067] The Cu-4.5 wt% SnO2 composite prepared in Example 3 was tested, and the results are as follows: the density is 98.19%, the electrical conductivity is 38.3 %IACS, the hardness and tensile strength are 95.8 HV and 318 MPa respectively, and the elongation is 43.58 %.

[0068] Example 4

[0069] The Cu-10 wt% Sn gas-atomized alloy powder was used as the raw material, and the Cu-10 wt% Sn alloy powder, H2O and 30 wt% H2O2 solution as the oxidant were added into the high-temperature and high-pressure reaction kettle at a mass ratio of 1:3:3 for in-situ supercritical water oxidation reaction. The stirring rate was 220 r / min during the reaction. The process parameters of the supercritical oxidation reaction are as follows: the reaction temperature is 370 ℃, the holding time is 5 min, and the pressure is 22 MPa. After the supercritical oxidation reaction, the reinforcing phase element Sn in the raw material powder is in-situ oxidized to SnO2, and copper is also oxidized to form CuO and Cu2O.

[0070] The product after supercritical water oxidation was washed and filtered, and vacuum dried to obtain the composite powder.

[0071] The dried composite powder was placed in a ceramic crucible and put into a tube furnace. The furnace tube was evacuated twice, and then the airtightness was checked. Then argon was introduced, and then the furnace tube was heated at a heating rate of 10 ℃ / min. When the temperature reached 200 ℃, the heating rate was increased to 5 ℃ / min, and the temperature was increased to 250 ℃. Then the argon was turned off and hydrogen was introduced, and the temperature was kept for 3 h. The gas flow was 0.7 L / min. After the program stopped, the furnace was cooled to room temperature, and then the Cu-12.36 wt% SnO2 composite powder was obtained.

[0072] 7.28 g of the reduced composite powder and 12.72 g of pure Cu powder were added to a ball mill jar, and stearic acid was added as a dispersant. The mass fraction of stearic acid in the total mass of copper powder and copper tin oxide powder was 1%. Then the grinding balls were put into the ball mill jar. The diameters of the grinding balls were 8 mm, 5 mm and 3 mm, and the number ratio was 3:7:10. The ball-to-material mass ratio was 10:1. Then the ball mill jar was evacuated, and after the evacuation was completed, the ball mill jar was put into the ball mill for ball milling. The ball milling process parameters are as follows: the ball milling rotation speed is 300 r / min, and the ball milling time is 20 h. After ball milling, the Cu-4.5 wt% SnO2 composite powder was obtained.

[0073] The ball-milled Cu-4.5 wt% SnO2 composite powder is placed in a graphite mold with a diameter of 20 mm, sealed by a pressure head wrapped with graphite paper, and pre-pressed by external force to make the powder more dense for heat conduction, and then placed in a sintering furnace for discharge plasma sintering through a pre-set program, while the vacuum pump is used to extract the environment in the furnace to vacuum until the end of the sintering process, and then cooled down to room temperature after the furnace cooling, and then the Cu-4.5 wt% SnO2 composite material is obtained. The process parameters of the discharge plasma sintering are as follows: the vacuum degree is below 6 Pa, the sintering pressure is 50 MPa, the heating rate is 100 ℃ / min, the sintering temperature is 850 ℃, and the holding time at the sintering temperature is 10 min.

[0074] Example 5

[0075] The Cu-10 wt% Sn gas-atomized alloy powder is used as the raw material, and the Cu-10 wt% Sn alloy powder, H2O and 30 wt% H2O2 solution as the oxidizing agent are added into a high-temperature and high-pressure reaction kettle at a mass ratio of 1:4:4 for supercritical water in-situ oxidation reaction, and stirring is carried out at a rate of 220 r / min during the reaction. The process parameters of the supercritical oxidation reaction are as follows: the reaction temperature is 370 ℃, the holding time is 5 min, and the pressure is 22 MPa. After the supercritical oxidation reaction, the reinforcing phase element Sn in the raw material powder is in-situ oxidized to SnO2, and copper is also oxidized to form CuO and Cu2O.

[0076] The product after supercritical water oxidation is washed and filtered, and vacuum dried to obtain a composite powder.

[0077] The dried composite powder is placed in a ceramic crucible and placed in a tube furnace, the furnace tube is evacuated twice, then the airtightness is checked, then argon is introduced, then the furnace tube is heated at a heating rate of 10 ℃ / min, the temperature reaches 200 ℃, then the heating rate is increased to 5 ℃ / min, the temperature is increased to 250 ℃, then the argon is turned off and hydrogen is introduced, and then the temperature is held for 3 h, wherein the gas flow is 0.9 L / min, and then the furnace is cooled to room temperature after the program stops, and then the Cu-12.36 wt% SnO2 composite powder is obtained.

[0078] Take 7.28 g of the reduced composite powder and 12.72 g of pure Cu powder into a ball milling tank, add stearic acid as a dispersant, the stearic acid accounts for 1% of the total mass of copper powder and copper tin oxide powder, then put the milling balls into the ball milling tank. Among them, the diameter of the milling ball is 8 mm, 5 mm and 3 mm, the number ratio is 3:7:10, and the ball-to-material mass ratio is 10:1. Then the ball milling tank is vacuumized, and after vacuumization, the ball milling tank is put into the ball mill for ball milling. The ball milling process parameters are: ball milling speed is 300 r / min, ball milling time is 20 h, and Cu~4.5wt.% SnO2 composite powder is obtained after ball milling.

[0079] Put the ball-milled Cu~4.5 wt.% SnO2 composite powder into a graphite mold with a diameter of 20 mm, seal it with graphite paper wrapped into a pressure head, and pre-press it with external force to make the powder more dense for heat conduction, then put it into a sintering furnace for discharge plasma sintering through a pre-set program. At the same time, use a vacuum pump to extract the environment in the furnace to vacuum until the end of the sintering process. After the end, it is cooled with the furnace, and after cooling to room temperature, Cu~4.5 wt.% SnO2 composite material can be obtained. The process parameters of discharge plasma sintering are: vacuum degree is below 6 Pa, sintering pressure is 50 MPa, heating rate is 100 ℃ / min, sintering temperature is 850 ℃, and holding time at sintering temperature is 10 min.

[0080] Example 6

[0081] Take Cu~10 wt.% Sn gas-atomized alloy powder as raw material, and add Cu~10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as oxidant into a high-temperature high-pressure reaction kettle according to a mass ratio of 1:4:5 for supercritical water in-situ oxidation reaction. Stir at a rate of 220 r / min during the reaction. The process parameters of supercritical oxidation reaction are as follows: reaction temperature is 370 ℃, holding time is 5 min, and pressure is 22 MPa. After supercritical oxidation reaction, the enhanced phase element Sn in the raw material powder is in-situ oxidized to SnO2, and copper is also oxidized to form CuO and Cu2O.

[0082] Wash and filter the product after supercritical water oxidation, and vacuum dry to obtain a composite powder.

[0083] The dried composite powder was placed in a ceramic crucible and put into a tube furnace, the furnace tube was vacuumed twice, then the air tightness was checked, then argon was introduced, then the furnace tube was heated at a heating rate of 9 ℃ / min, the temperature reached 200 ℃, then the heating rate was 4 ℃ / min, the temperature was raised to 250 ℃, then the argon was turned off, hydrogen was introduced, and the temperature was kept for 3 h, the gas flow was 1.0 L / min, after the program stopped, the furnace was cooled to room temperature, and the Cu~12.36wt.% SnO2 composite powder was obtained.

[0084] 7.28 g of the reduced composite powder and 12.72 g of pure Cu powder were added to a ball mill tank, and stearic acid was added as a dispersant, the mass fraction of stearic acid was 1% of the total mass of copper powder and copper tin oxide powder, then the grinding balls were put into the ball mill tank. Among them, the diameter of the grinding ball is 8 mm, 5 mm and 3 mm, the number ratio is 3:7:10, and the ball-to-material mass ratio is 10:1. Then the ball mill tank was vacuumed, and after vacuuming, the ball mill tank was put into the ball mill for ball milling. The ball milling process parameters are: ball milling speed is 300 r / min, ball milling time is 20 h, and Cu~4.5 wt.% SnO2 composite powder is obtained after ball milling.

[0085] The ball-milled Cu~4.5 wt.% SnO2 composite powder was placed in a graphite mold with a diameter of 20 mm, sealed by graphite paper, and pre-pressed by external force to make the powder more dense and facilitate heat conduction. Then it was put into a sintering furnace to perform spark plasma sintering through a pre-set program, and a vacuum pump was used to pump the environment in the furnace to vacuum until the end of the sintering process. After the end, the furnace was cooled, and the Cu~4.5 wt.% SnO2 composite material was obtained after cooling to room temperature. The process parameters of spark plasma sintering are: vacuum degree is below 6 Pa, sintering pressure is 50 MPa, heating rate is 100 ℃ / min, sintering temperature is 850 ℃, and holding time at sintering temperature is 10 min.

[0086] Example 7

[0087] Cu~10 wt.% Sn gas-atomized alloy powder was used as raw material, Cu~10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as oxidant were added to a high-temperature high-pressure reaction kettle in a mass ratio of 2:4:5 for supercritical water in-situ oxidation reaction, and stirring was carried out at a rate of 220 r / min during the reaction. The process parameters of supercritical oxidation reaction are as follows: reaction temperature is 370 ℃, holding time is 5 min, and pressure is 22 MPa. After supercritical oxidation reaction, the reinforcing phase element Sn in the raw material powder is in-situ oxidized to SnO2, and copper is also oxidized to form CuO and Cu2O.

[0088] The product after supercritical water oxidation is washed, filtered, and vacuum dried to obtain a composite powder.

[0089] The dried composite powder is placed in a ceramic crucible and put into a tube furnace. The furnace tube is evacuated twice, and then checked for air tightness. Then, argon is introduced, and then the furnace tube is heated at a heating rate of 11 ℃ / min. When the temperature reaches 200 ℃, the heating rate is increased to 6 ℃ / min until the temperature reaches 250 ℃. Then, the argon is turned off, hydrogen is introduced, and the temperature is maintained for 3 h. The gas flow is 0.1 L / min. After the program stops, the furnace is cooled to room temperature, and the Cu-12.36 wt.% SnO2 composite powder is obtained.

[0090] 7.28 g of the reduced composite powder and 12.72 g of pure Cu powder are added to a ball mill jar, and stearic acid is added as a dispersant. The stearic acid accounts for 1% of the total mass of the copper powder and the copper tin oxide powder. Then, the grinding balls are placed in the ball mill jar. The grinding balls have diameters of 8 mm, 5 mm, and 3 mm, and the number ratio is 3:7:10. The ball-to-material mass ratio is 10:1. Then, the ball mill jar is evacuated, and after evacuation, it is placed in a ball mill for ball milling. The ball milling parameters are: ball milling speed of 300 r / min, ball milling time of 20 h. After ball milling, the Cu-4.5 wt.% SnO2 composite powder is obtained.

[0091] The ball-milled Cu-4.5 wt.% SnO2 composite powder is placed in a graphite mold with a diameter of 20 mm. The graphite paper is wrapped around the pressing head to seal it, and the powder is pre-pressed to make it more dense and facilitate heat conduction. Then, it is placed in a sintering furnace for spark plasma sintering using a pre-set program. A vacuum pump is used to evacuate the furnace environment to vacuum until the end of the sintering process. After the end of the sintering process, the furnace is cooled, and the Cu-4.5 wt.% SnO2 composite material is obtained after cooling to room temperature. The spark plasma sintering parameters are: vacuum degree of 6 Pa or less, sintering pressure of 50 MPa, heating rate of 100 ℃ / min, sintering temperature of 850 ℃, and holding time at the sintering temperature of 10 min.

[0092] Example 8

[0093] Cu-10 wt.% Sn gas atomized alloy powder was used as raw material, Cu-10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as oxidant were added into a high temperature and high pressure reactor at a mass ratio of 2:1:1 for supercritical water in-situ oxidation reaction, and stirring was carried out at a speed of 280 r / min during the reaction. The process parameters of supercritical oxidation reaction are as follows: the reaction temperature is 370 ℃, the holding time is 5 min, and the pressure is 22 MPa. After supercritical oxidation reaction, the reinforcing phase element Sn in the raw material powder is in-situ oxidized to SnO2, and copper is also oxidized to form CuO and Cu2O.

[0094] The product after supercritical water oxidation was washed and filtered, and vacuum dried to obtain a composite powder.

[0095] The dried composite powder was placed in a ceramic crucible and put into a tube furnace, the furnace tube was vacuumed twice, then the airtightness was checked, then argon was introduced, then the furnace tube was heated at a heating rate of 10 ℃ / min, the temperature reached 200 ℃, then the heating rate was increased to 5 ℃ / min, the temperature was increased to 250 ℃, then the argon was closed and hydrogen was introduced, and the temperature was kept for 3 h, wherein the gas flow was 0.1 L / min, after the program stopped, the furnace was cooled to room temperature, and then taken out, to obtain a Cu-12.36 wt.% SnO2 composite powder.

[0096] 7.28 g of reduced composite powder and 12.72 g of pure Cu powder were added to a ball mill jar, and stearic acid was added as a dispersant, the stearic acid accounted for 1% of the total mass of copper powder and copper tin oxide powder, then the grinding balls were put into the ball mill jar. The diameter of the grinding ball is 8 mm, 5 mm and 3 mm, and the number ratio is 3:7:10, and the ball-to-material mass ratio is 10:1. Then the ball mill jar was vacuumed, and after vacuuming, the ball mill jar was put into the ball mill for ball milling, and the ball milling process parameters were as follows: the ball milling speed was 300 r / min, the ball milling time was 20 h, and the Cu-4.5 wt.% SnO2 composite powder was obtained after ball milling.

[0097] The ball-milled Cu-4.5 wt.% SnO2 composite powder was placed in a graphite mold with a diameter of 20 mm, sealed by graphite paper, and pre-pressed by external force to make the powder more dense for heat conduction, then put into a sintering furnace for spark plasma sintering through a pre-set program, and the vacuum pump was used to extract the environment in the furnace to vacuum until the end of the sintering process, and then cooled down to room temperature to obtain Cu-4.5 wt.% SnO2 composite material. The process parameters of spark plasma sintering are as follows: the vacuum degree is below 6 Pa, the sintering pressure is 50 MPa, the heating rate is 100 ℃ / min, the sintering temperature is 850 ℃, and the holding time at the sintering temperature is 10 min.

[0098] Example 9

[0099] Cu-10 wt.% Sn spherical gas-atomized alloy powder was used as raw material, Cu-10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as a supplemental oxygen source were added into a high-temperature high-pressure reactor at a mass ratio of 1:2:1 for supercritical water in-situ oxidation reaction. Stirring was carried out at a rate of 280 r / min during the reaction.

[0100] The process parameters of the supercritical oxidation reaction were as follows: the reaction temperature was 385 ℃, the holding time was 7.5 min, and the pressure was 25 MPa. After the supercritical water in-situ oxidation reaction, the reinforcing phase element Sn in the raw material powder was oxidized in-situ to form SnO2 in the Cu matrix, and copper was also oxidized to form CuO and Cu2O.

[0101] The product after supercritical water oxidation was washed and filtered, and vacuum dried to obtain a composite powder.

[0102] The dried composite powder was placed in a ceramic crucible and put into a tube furnace. The furnace tube was evacuated twice, then checked for airtightness, then argon was introduced, then the furnace tube was heated at a rate of 10 ℃ / min, the temperature reached 200 ℃, then heated to 250 ℃ at a rate of 5 ℃ / min, then the argon was turned off and hydrogen was introduced, then the temperature was held for 3 h, the gas flow was 0.3 L / min, after the program stopped, the furnace was cooled to room temperature, then taken out, to obtain a Cu-12.36 wt.% SnO2 composite powder.

[0103] 15.37 g of reduced composite powder and 4.63 g of pure Cu powder were added to a ball mill jar, and stearic acid was added as a dispersant, the stearic acid accounted for 1% of the total mass of copper powder and copper tin oxide powder, then the grinding balls were put into the ball mill jar. Among them, three kinds of grinding balls with diameters of 8 mm, 5 mm and 3 mm were selected, and the mass ratio of the three was 3:7:10, and the ball-to-material mass ratio was 10:1. Then the ball mill jar was evacuated, and after evacuation, the ball mill jar was put into the ball mill for ball milling. The ball milling process parameters were as follows: the ball milling speed was 300 r / min, the ball milling time was 20 h, and after ball milling, a Cu-9.5 wt.% SnO2 composite powder was obtained.

[0104] The ball-milled Cu~9.5 wt.% SnO2 composite powder is placed in a graphite mold with a diameter of 20 mm, sealed by a pressure head wrapped with graphite paper, and pre-pressed by external force to make the powder more dense for heat conduction, and then placed in a sintering furnace for discharge plasma sintering through a pre-set program, while the vacuum pump is used to extract the environment in the furnace to vacuum until the end of the sintering process, and then cooled down to room temperature after the furnace cooling, and the Cu~9.5 wt.% SnO2 composite material is obtained. The process parameters of discharge plasma sintering are as follows: the vacuum degree is below 6 Pa, the sintering pressure is 50 MPa, the heating rate is 100 ℃ / min, the sintering temperature is 850 ℃, and the holding time at the sintering temperature is 10 min.

[0105] The Cu~9.5 wt.% SnO2 composite material prepared in Example 9 is tested, and the results are as follows: the density is 97.69%, the electrical conductivity is 27.6 %IACS, the hardness and tensile strength are 124.7 HV and 293 MPa respectively, and the elongation is 20.11%.

[0106] Example 10

[0107] The Cu~10 wt.% Sn spherical gas-atomized alloy powder is used as the raw material, and the Cu~10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as the supplemental oxygen source are added into a high-temperature and high-pressure reaction kettle at a mass ratio of 1:1:2 for supercritical water in-situ oxidation reaction, and stirring is performed at a rate of 250 r / min during the reaction.

[0108] The process parameters of the supercritical oxidation reaction are as follows: the reaction temperature is 385 ℃, the holding time is 7.5 min, and the pressure is 25 MPa. After the supercritical water in-situ oxidation reaction, the reinforcing phase element Sn in the raw material powder is oxidized in-situ in the Cu matrix to form SnO2, and copper is also oxidized to form CuO and Cu2O.

[0109] The product after supercritical water oxidation is washed, filtered, and vacuum dried to obtain a composite powder.

[0110] The dried composite powder is placed in a ceramic crucible and placed in a tube furnace, the furnace tube is evacuated twice, then the airtightness is checked, then argon is introduced, then the furnace tube is heated at a heating rate of 10 ℃ / min, the temperature is raised to 250 ℃ at a heating rate of 5 ℃ / min after the temperature reaches 200 ℃, then the argon is turned off and hydrogen is introduced, and then the temperature is held for 3 h, wherein the gas flow is 0.3 L / min, and then the furnace is cooled to room temperature after the program stops, and the Cu~12.36 wt.% SnO2 composite powder is obtained.

[0111] Take 9.30 g of the reduced composite powder and 10.70 g of pure Cu powder into a ball milling tank, add stearic acid as a dispersant, the stearic acid accounts for 1% of the total mass of copper powder and copper tin oxide powder, then put the milling balls into the ball milling tank. Among them, three kinds of milling balls with diameters of 8 mm, 5 mm and 3 mm are selected, and the mass ratio of the three is 3:7:10, and the ball-to-material mass ratio is 10:1. Then the ball milling tank is vacuumized, after vacuumization, the ball milling tank is put into the ball mill for ball milling, the ball milling process parameters are: ball milling speed is 300 r / min, ball milling time is 20 h, after ball milling, Cu~5.75 wt.% SnO2 composite powder is obtained.

[0112] Put the ball-milled Cu~5.75 wt.% SnO2 composite powder into a graphite mold with a diameter of 20 mm, seal it with graphite paper wrapped into a pressure head, and then pre-press it with external force to make the powder more dense and facilitate heat conduction. Then put it into a sintering furnace to perform spark plasma sintering through a pre-set program, and use a vacuum pump to extract the environment in the furnace to vacuum until the end of the sintering process. After the end, it is cooled with the furnace, and after cooling to room temperature, Cu~5.75 wt.% SnO2 composite material is obtained. Among them, the process parameters of spark plasma sintering are: vacuum degree is below 6 Pa, sintering pressure is 50 MPa, heating rate is 100 ℃ / min, sintering temperature is 850 ℃, and holding time at sintering temperature is 10 min.

[0113] The Cu~5.75 wt% SnO2 composite material prepared in Example 10 is tested, and the results are as follows: the density is 98.52%, the electrical conductivity is 35.2 %IACS, the hardness and tensile strength are 106.5 HV and 308 MPa respectively, and the elongation is 33.6 %.

[0114] In this embodiment, the process parameters of supercritical oxidation reaction need to be strictly controlled. Excessive oxidation can lead to the increase of SnO2 particle size and quantity, which can reduce the overall plasticity and ductility of the composite material. Excessive oxidation can also increase the generation of CuO and Cu2O, which have higher resistivity than copper, thereby reducing the electrical conductivity of the composite material. Excessive oxides can also form a thick oxide layer between the Cu matrix and the SnO2 reinforcing phase, leading to a decrease in interfacial bonding strength between the two, affecting the mechanical properties of the composite material, such as tensile strength and hardness. With the increase of oxide content, due to the difference in thermal expansion coefficient between different materials, the composite material can have greater stress concentration during subsequent processing (such as sintering), leading to the generation of cracks. Further, the gas (such as water vapor) generated during the oxidation reaction cannot be completely discharged, which can form pores or bubbles inside the composite material, reducing the density of the composite material and further affecting its mechanical properties and electrical conductivity. Therefore, in order to ensure that the final composite material has good overall performance, it is necessary to accurately control the reaction conditions during the supercritical oxidation reaction stage, including temperature, pressure, reaction time, etc., to achieve the best oxidation degree.

[0115] Comparative Example 1

[0116] Cu-10 wt.% Sn spherical gas-atomized alloy powder was used as raw material. Cu-10 wt.% Sn alloy powder, H2O, and 30 wt% H2O2 solution as a supplemental oxygen source were added to a high-temperature high-pressure reaction kettle in a mass ratio of 1:2:1 for supercritical water in-situ oxidation reaction. Stirring was carried out at a rate of 250 r / min during the reaction.

[0117] The process parameters of supercritical oxidation reaction are as follows: the reaction temperature is 350 ℃, the holding time is 10 min, and the pressure is 16 MPa (not reaching the supercritical state). After supercritical water in-situ oxidation reaction, the reinforcing phase element Sn in the raw material powder is oxidized in-situ to form SnO2 in the Cu matrix, and copper is also oxidized to form CuO and Cu2O.

[0118] The product after supercritical water oxidation was washed and filtered, and vacuum dried to obtain a composite powder.

[0119] The dried composite powder was placed in a ceramic crucible and put into a tube furnace. The furnace tube was evacuated twice, then checked for air tightness, then argon was introduced, then the furnace tube was heated at a rate of 10 ℃ / min, the temperature reached 200 ℃, then the heating rate was increased to 5 ℃ / min, the temperature was increased to 250 ℃, then the argon was turned off and hydrogen was introduced, and the temperature was held for 3 h, the gas flow was 0.3 L / min, after the program stopped, the furnace was cooled to room temperature, then taken out, to obtain a Cu-12.36 wt.% SnO2 composite powder.

[0120] Take 3.24 g of the reduced composite powder and 16.76 g of pure Cu powder into a ball milling jar, add stearic acid as a dispersant, the stearic acid accounts for 1% of the total mass of copper powder and copper tin oxide powder, then put the milling balls into the ball milling jar. Among them, three kinds of milling balls with diameters of 8 mm, 5 mm and 3 mm are selected, and the mass ratio of the three is 3:7:10, and the ball-to-material mass ratio is 10:1. Then the ball milling jar is vacuumized, and after vacuumization, the ball milling jar is put into the ball mill for ball milling. The ball milling process parameters are: ball milling speed is 300 r / min, ball milling time is 20 h, and Cu~4.5 wt.% SnO2 composite powder is obtained after ball milling.

[0121] Put the ball-milled Cu~4.5 wt% SnO2 composite powder into a graphite mold with a diameter of 20 mm, seal it by wrapping it with graphite paper, and pre-press it by external force to make the powder more dense and facilitate heat conduction, then put it into a sintering furnace to perform spark plasma sintering through a pre-set program. At the same time, use a vacuum pump to extract the environment in the furnace to vacuum until the end of the sintering process, and then cool down to room temperature after the sintering process is completed. The Cu~4.5 wt.% SnO2 composite material can be obtained. The process parameters of spark plasma sintering are: vacuum degree is below 6 Pa, sintering pressure is 50 MPa, heating rate is 100 ℃ / min, sintering temperature is 800 ℃, and holding time at sintering temperature is 10 min.

[0122] Test the Cu~4.5 wt% SnO2 composite material prepared in Comparative Example 1, and the results are as follows: the density is 98.14%, the electrical conductivity is 28.7% IACS, the hardness and tensile strength are 78.1 HV and 237 MPa respectively, and the elongation is 25.27%.

[0123] Comparative Example 2

[0124] Take Cu~10 wt.% Sn spherical gas-atomized alloy powder as raw material, and add Cu~10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as an additional oxygen source into a high-temperature high-pressure reaction kettle at a mass ratio of 1:2:1 for supercritical water in-situ oxidation reaction. Stir at a rate of 250 r / min during the reaction.

[0125] The process parameters of supercritical oxidation reaction are as follows: reaction temperature is 385 ℃, holding time is 7.5 min, and pressure is 25 MPa. After supercritical water in-situ oxidation reaction, the reinforcing phase element Sn in the raw material powder is oxidized in-situ to form SnO2 in the Cu matrix, and copper is also oxidized to form CuO and Cu2O.

[0126] The product after supercritical water oxidation is washed, suction filtered, and vacuum dried to obtain a composite powder.

[0127] The dried composite powder is placed in a ceramic crucible and put into a tube furnace. The furnace tube is vacuumed twice, and then the air tightness is checked. Then argon is introduced, and then the furnace tube is heated at a heating rate of 10 °C / min. When the temperature reaches 200 °C, the heating rate is increased to 5 °C / min, and the temperature is increased to 250 °C. Then the argon is turned off, and hydrogen is introduced. The gas flow is 0.3 L / min. After 3 h of holding, the program is stopped. The furnace is cooled to room temperature, and then the Cu-12.36 wt.% SnO2 composite powder is obtained.

[0128] 1.62 g of the reduced composite powder and 18.38 g of pure Cu powder are added to a ball mill tank. Stearic acid is added as a dispersant, accounting for 1% of the total mass of copper powder and copper tin oxide powder. Then the grinding balls are put into the ball mill tank. The diameters of the three grinding balls are 8 mm, 5 mm, and 3 mm, and the mass ratio of the three is 3:7:10. The ball-to-material mass ratio is 10:1. Then the ball mill tank is vacuumed, and after vacuuming, it is put into the ball mill for ball milling. The ball milling parameters are: ball milling speed is 300 r / min, and ball milling time is 20 h. After ball milling, the Cu-1 wt.% SnO2 composite powder is obtained.

[0129] The ball-milled Cu-1 wt.% SnO2 composite powder is placed in a graphite mold with a diameter of 20 mm. The graphite paper is wrapped around the pressing head to seal it. The powder is pre-pressed by external force to make it more dense and facilitate heat conduction. Then it is put into a sintering furnace for spark plasma sintering through a pre-set program. A vacuum pump is used to vacuum the furnace environment until the end of the sintering process. After the end of the sintering process, the furnace is cooled, and the Cu-1 wt.% SnO2 composite material is obtained when the temperature cools to room temperature. The spark plasma sintering parameters are: vacuum degree is below 6 Pa, sintering pressure is 50 MPa, heating rate is 100 °C / min, sintering temperature is 850 °C, and holding time at sintering temperature is 10 min.

[0130] The Cu-1 wt% SnO2 composite material prepared in Comparative Example 2 is tested, and the results are as follows: the density is 97.75%, the electrical conductivity is 58.4 %IACS, the hardness and tensile strength are 84.7 HV and 263 MPa respectively, and the elongation is 45.9 %.

[0131] Comparative Example 3

[0132] Cu-10 wt.% Sn spherical gas-atomized alloy powder was used as raw material, Cu-10 wt.% Sn alloy powder, H2O and 30 wt.% H2O2 solution as a supplemental oxygen source were added into a high-temperature and high-pressure reactor at a mass ratio of 1:2:1 for supercritical water in-situ oxidation reaction. Stirring was performed at a rate of 250 r / min during the reaction.

[0133] The process parameters of supercritical oxidation reaction were as follows: reaction temperature was 450 ℃, holding time was 10 min, and pressure was 34 MPa. After supercritical water in-situ oxidation reaction, the reinforcing phase element Sn in the raw material powder was in-situ oxidized to form SnO2 in the Cu matrix, and copper was also oxidized to form CuO and Cu2O.

[0134] The product after supercritical water oxidation was washed and filtered, and vacuum dried to obtain a composite powder.

[0135] The dried composite powder was placed in a ceramic crucible and put into a tube furnace. The furnace tube was evacuated twice, and then the airtightness was checked. Then argon was introduced, and then the furnace tube was heated at a heating rate of 10 ℃ / min. After the temperature reached 200 ℃, the heating rate was increased to 5 ℃ / min to 250 ℃, and then the argon was closed and hydrogen was introduced. The holding time was 3 h, and the gas flow was 0.3 L / min. After the program stopped, the furnace was cooled to room temperature, and then the Cu-12.36 wt.% SnO2 composite powder was obtained.

[0136] 3.24 g of the reduced composite powder and 16.76 g of pure Cu powder were added to a ball mill jar, and stearic acid was added as a dispersant. The mass ratio of stearic acid to the total mass of copper powder and copper tin oxide powder was 1%. Then the grinding balls were put into the ball mill jar. The diameters of the three grinding balls were 8 mm, 5 mm and 3 mm, and the mass ratio of the three was 3:7:10, and the ball-to-material mass ratio was 10:1. Then the ball mill jar was evacuated, and after evacuation, the ball mill jar was put into the ball mill for ball milling. The ball milling process parameters were as follows: ball milling speed was 300 r / min, and ball milling time was 20 h. After ball milling, Cu-4.5 wt.% SnO2 composite powder was obtained.

[0137] The ball-milled Cu-4.5 wt.% SnO2 composite powder is placed in a graphite mold with a diameter of 20 mm, sealed by a pressure head wrapped with graphite paper, and pre-pressed by external force to make the powder more dense for heat conduction, and then placed in a sintering furnace for discharge plasma sintering through a pre-set program. At the same time, a vacuum pump is used to extract the environment in the furnace to vacuum until the end of the sintering process. After the end, the furnace is cooled, and after cooling to room temperature, the Cu-4.5 wt.% SnO2 composite material can be obtained. The process parameters of discharge plasma sintering are as follows: vacuum degree is below 6 Pa, sintering pressure is 50 MPa, heating rate is 100 ℃ / min, sintering temperature is 800 ℃, and holding time at sintering temperature is 10 min.

[0138] The Cu-4.5 wt.% SnO2 composite material sample prepared in Comparative Example 3 is tested, and the results are as follows: the density is 97.63%, the electrical conductivity is 33.6% IACS, the hardness and tensile strength are 96.2 HV and 286 MPa respectively, and the elongation is 35.34%.

[0139] Comparative Example 4

[0140] Cu-10 wt.% Sn gas-atomized alloy powder and pure copper powder are used as raw materials. 3.71 g of Cu-10 wt.% Sn alloy powder, 6.29 g of pure copper powder, 20 g of H2O and 10 g of 30 wt.% H2O2 solution are added to a high-temperature and high-pressure reaction kettle according to the ratio of 3.71:6.29:20:10 for supercritical water in-situ oxidation reaction. The reaction process is stirred at a rate of 500 r / min.

[0141] The process parameters of supercritical oxidation reaction are as follows: reaction temperature is 380 ℃, holding time is 10 min, and pressure is 23 MPa. After supercritical oxidation reaction, the reinforcing phase element Sn in the raw material powder is oxidized in-situ to SnO2, and copper is also oxidized to form CuO and Cu2O.

[0142] The product after supercritical water oxidation is washed and filtered, and vacuum dried to obtain a composite powder. The vacuum degree of the vacuum drying box is below 200 Pa, the drying temperature is 60 ℃, and the drying time is 6 h.

[0143] The dried composite powder is placed in a ceramic crucible and put into a tube furnace, the furnace tube is vacuumed twice, then the air tightness is checked, then argon is introduced, then the furnace tube is heated at a heating rate of 10 ℃ / min, the temperature reaches 200 ℃, then the heating rate is increased to 5 ℃ / min, the temperature is increased to 250 ℃, then the argon is closed, hydrogen is introduced, and then the temperature is kept for 3 hours, the gas flow is 0.5 L / min, then argon and hydrogen are introduced, the program is stopped, the furnace is cooled to room temperature, and then the Cu~4.5 wt.% SnO2 composite powder is taken out.

[0144] The Cu~4.5 wt.% SnO2 composite powder is placed in a graphite mold with a diameter of 20 mm, sealed by a pressure head wrapped with graphite paper, and pre-pressed by external force to make the powder more dense and facilitate heat conduction, then put into a sintering furnace and perform discharge plasma sintering through a pre-set program, at the same time, use a vacuum pump to pump the environment in the furnace to vacuum until the end of the sintering process, after the end, the furnace is cooled, and the temperature is reduced to room temperature to obtain the Cu~4.5 wt.% SnO2 composite material. The process parameters of the discharge plasma sintering are as follows: the vacuum degree is below 10 Pa, the sintering pressure is 55 MPa, the heating rate is 110 ℃ / min, the sintering temperature is 900 ℃, and the holding time at the sintering temperature is 15 min.

[0145] The Cu~4.5 wt% SnO2 composite material prepared in Comparative Example 4 is tested, and the results are as follows: the density is 98.19 %, the electrical conductivity is 26.3 %IACS, the hardness and tensile strength are 96.8 HV and 278 MPa respectively, and the elongation is 27.4 %.

[0146] Each of the embodiments in the specification is described in a related manner, and the same and similar parts between the embodiments can be referred to each other, and each embodiment mainly explains the difference from other embodiments. Especially, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the related parts can be referred to the part of the method embodiment.

[0147] The above only describes the preferred embodiments of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing a copper-tin oxide composite material, characterized by, The method comprises the following steps: S1, oxidizing the copper-tin alloy powder in-situ in a supercritical water environment, cleaning and filtering the product after supercritical water oxidation, and vacuum drying to obtain copper tin oxide powder; The specific steps are: the copper-tin alloy powder is used as raw material, H2O and H2O2 solution as oxygen source are added into a high-temperature and high-pressure reaction kettle according to the mass ratio of (1-2):(1-4):(1-5) for supercritical water in-situ oxidation reaction, and stirring is performed at a speed of 220-280 r / min during the reaction; In the copper-tin alloy powder, the mass fraction of Sn is 5-20 wt.%, and the rest is copper; the mass fraction of H2O2 in the H2O2 solution is 29-31 wt.%; The process parameters of the supercritical oxidation reaction are specifically: the reaction temperature is 375-400 ℃, the pressure is 22-28 MPa, and the reaction time is 5-10 min; S2, reducing the copper oxide in the copper tin oxide powder obtained in S1 to obtain copper tin oxide powder; The specific steps are: the dried composite powder is placed in a ceramic crucible and put into a tube furnace, the furnace tube is vacuumed twice, argon is introduced, the furnace tube is heated to 190-210 ℃ at a heating rate of 9-11 ℃ / min, then heated to 245-255 ℃ at a heating rate of 4-6 ℃ / min, argon is turned off, hydrogen is introduced, and then heat preservation is carried out for 3-4 h; the flow rates of argon and hydrogen are both 0.1-1 L / min; S3, the copper powder and the copper tin oxide powder obtained in S2 are ball milled and mixed according to a predetermined proportion to obtain a copper tin oxide composite powder with a target tin oxide content; The target tin oxide content in S3 is 2-9.5 wt.%; S4, the copper tin oxide composite powder is pressed into a blank and then subjected to spark plasma sintering to obtain a copper tin oxide composite material.

2. The method of claim 1, wherein the copper-tin oxide composite is prepared by the steps of: The specific steps of ball milling in S3 are: first, the copper powder and the copper tin oxide powder are put into a ball mill tank, then stearic acid or anhydrous ethanol is added as a dispersant, then the grinding balls are put into the ball mill tank, wherein the grinding balls have diameters of 8 mm, 5 mm and 3 mm, and are matched according to a mass ratio of 3:7:10, the ball-to-material mass ratio is (6-12):1, then the ball mill tank is vacuumed, and after vacuuming, the ball mill tank is put into a ball mill for ball milling.

3. The method for preparing a copper-tin oxide composite material according to claim 2, characterized in that, When stearic acid is used as a dispersant, the amount of stearic acid added is 1-5 wt.% of the total mass of the copper powder and the copper tin oxide powder, and when anhydrous ethanol is used as a dispersant, anhydrous ethanol is added to just cover the powder.

4. The method for preparing a copper-tin oxide composite material according to claim 1, characterized in that, The specific steps of S4 are: the copper tin oxide powder obtained in S3 is loaded into a graphite mold and pressed into a blank, then placed in a spark plasma sintering furnace for sintering to obtain a copper tin oxide composite material, and the sintering parameters are: sintering pressure is 40-50 MPa, heating rate is 50-100 ℃ / min, sintering temperature is 800-900 ℃, and heat preservation time is 8-15 min.

5. A copper tin oxide composite material prepared by the method of any one of claims 1-4.

Images