Preparation Method of Cerium Oxide-Copper Composite Powder and Cerium Oxide Reinforced Copper Matrix Composite

Abstract

The present invention discloses a preparation method of cerium oxide - copper composite powder and cerium oxide reinforced copper matrix composite material. In the embodiment, the preparation method of the cerium oxide - copper composite powder comprises the following steps: spray - drying a mixed solution of cerium salt and copper salt to obtain a precursor powder; calcining and decomposing the precursor powder to obtain a cerium oxide - copper oxide composite powder; reducing the cerium oxide - copper oxide composite powder in a supercritical liquid - phase reduction system, and filtering and drying to obtain the cerium oxide - copper composite powder, wherein the volume ratio of cerium oxide in the cerium oxide - copper composite powder is controlled to be 0.5% - 1.5%. Further, a green compact made of the cerium oxide - copper composite powder is subjected to spark plasma sintering to obtain the cerium oxide reinforced copper matrix composite material. In the composite powder prepared by the present invention, cerium oxide is uniformly distributed in the copper matrix, and the hardness and toughness of the copper matrix composite material prepared by using the composite powder can be improved simultaneously.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of copper-based composite materials; specifically, it relates to a preparation method of cerium oxide-copper composite powder and cerium oxide-reinforced copper-based composite materials. Background Art

[0002] Particle-reinforced copper-based composite materials are widely used in fields such as integrated circuit lead frames, high-voltage power conversion switches, and automotive spot welding electrodes due to their many performance advantages such as high strength, high conductivity, high temperature resistance, wear resistance, and arc erosion resistance. However, at present, while the preparation process of particle-reinforced copper-based composite materials significantly improves the material strength, it often leads to a sharp decline in the room-temperature processing performance of the material, seriously restricting its expansion and application in the field of precision electronic equipment.

[0003] At present, the research and development focus and development direction of copper alloy strengthening and toughening mainly rely on dispersion strengthening by doping second-phase particles. In particular, the research on adding rare earth oxides has received extensive attention in the academic community and has become a research hotspot. Although the successful development of rare earth oxide-doped copper composite materials has solved the problems of difficult deep processing and insufficient strength of copper composite materials to a certain extent, there are still problems in the production of rare earth oxide-doped copper composite materials by the liquid-solid doping method, such as the scale of the second-phase particles being difficult to control and it being difficult to obtain uniformly distributed nano-scale second-phase particles.

[0004] Moreover, increasing the volume fraction of the second phase during the use of this preparation method will inevitably cause agglomeration of the second-phase particles, resulting in a decrease in the toughness of the copper composite material and a significant decline in the processing performance, which limits the breakthrough in the key technologies for the preparation of high-performance copper composite materials to a considerable extent and also restricts the development and wide application of high-value-added copper composite deep-processing products urgently needed in the market.

[0005] Therefore, in order to further improve the strength and toughness of copper-based composite materials while increasing their hardness, there is an urgent need to develop a technology that can obtain fine and uniformly distributed second-phase particles in the copper matrix to enhance the material hardness while also improving the material toughness. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the first aspect of the present invention discloses a preparation method of cerium oxide-copper composite powder, which includes the following steps:

[0007] Spray-dry a mixed solution of cerium salt and copper salt to obtain a precursor powder;

[0008] Calcine and decompose the precursor powder to obtain a cerium oxide-copper oxide composite powder;

[0009] Reduce the cerium oxide - copper oxide composite powder in a supercritical liquid phase reduction system, and obtain a cerium oxide - copper composite powder after filtration and drying;

[0010] Among them, the ratio of the cerium salt to the copper salt is controlled according to the volume ratio of cerium oxide in the cerium oxide - copper composite powder being 0.5% - 1.5%.

[0011] According to a specific embodiment of the present invention, the molar ratio of copper oxide to the reducing agent in the supercritical liquid phase reduction system is 1:1 - 2. During reduction, first heat up at a rate of 5 - 10 °C / min to 350 °C and hold for 10 min, then heat up at a rate of 2 - 5 °C / min to 380 °C, and react at 380 °C for 10 - 25 min, and then cool to room temperature in the furnace and take out.

[0012] Preferably, the pressure of the supercritical liquid phase reduction system is 25 MPa.

[0013] Preferably, the reducing agent is formaldehyde.

[0014] According to a specific embodiment of the present invention, the inlet air temperature of the spray drying can be 180 - 200 °C, the outlet air temperature can be 115 °C - 130 °C, the fan speed can be 60 - 70 r / min, and the feeding rate can be 300 - 360 mL / h.

[0015] According to a specific embodiment of the present invention, the temperature of the calcination decomposition is 400 - 500 °C, and the calcination time is 1 - 2 h.

[0016] According to a specific embodiment of the present invention, both the cerium salt and the copper salt are nitrates.

[0017] Preferably, the ratio of the cerium salt to the copper salt is controlled according to the volume ratio of cerium oxide in the cerium oxide - copper composite powder being 1%.

[0018] The second aspect of the present invention discloses a preparation method of a cerium oxide - enhanced copper composite material, which includes the following steps:

[0019] Press the cerium oxide - copper composite powder obtained by any of the above preparation methods into a green body;

[0020] Perform spark plasma sintering on the green body to obtain a cerium oxide - enhanced copper - based composite material.

[0021] Preferably, the temperature of the spark plasma sintering is 800 °C - 850 °C, and the holding time is 5 min - 7 min.

[0022] The technical solution of the present invention has the following beneficial effects:

[0023] 1) Deeply integrate the supercritical water coal gasification hydrogen production technology with the powder metallurgy process of copper-based composites. Through supercritical water coal gasification hydrogen production, in the supercritical water closed high-pressure environment, the hydrogen concentration in contact with the powder increases, deeply reducing copper oxide, shortening the reduction time, and reducing the growth of powder particles.

[0024] 2) Use the spray drying method to prepare precursor powder, enabling copper and cerium to achieve molecular-level mixing, solving their agglomeration problem. At the same time, the high reaction rate under the supercritical system makes cerium oxide evenly distributed in the copper matrix. The prepared reduced cerium oxide-copper composite material grains are basically in the micron level, without other impurities, effectively improving the mechanical properties of the composite material.

[0025] 3) The traditional hydrogen reduction process has a long reduction time (2 - 5h) and needs to continuously introduce hydrogen to maintain its reduction system, resulting in waste of energy and reduction of efficiency. Compared with the traditional hydrogen reduction process, the formaldehyde reducing agent used in the supercritical liquid phase reduction system of the present invention is inexpensive, the reaction products are water and hydrogen, the reaction is rapid, the process is novel and green and efficient, and finally the mechanical properties of the material are significantly improved compared with pure copper.

[0026] To more clearly illustrate the technical solutions, objectives, and advantages of the present invention, the present invention will be further described in detail below with specific embodiments. Description of the Drawings

[0027] Figure 1 It is the scanning energy spectrum diagram of the cerium oxide-copper composite powder in Example 1;

[0028] Figure 2 It is the XRD diagram of the cerium oxide-copper composite powder in Example 1;

[0029] Figure 3 It is the trend diagram of the Vickers hardness change of the cerium oxide-reinforced copper-based composite material at different cerium oxide volume fractions and different sintering temperatures;

[0030] Figure 4 It is the stress-strain diagram of the cerium oxide-reinforced copper-based composite material at different cerium oxide volume fractions and a sintering temperature of 850°C. Detailed Embodiments

[0031] The preparation method of the present invention includes the following steps:

[0032] The mixed solution of cerium salt and copper salt is spray-dried to obtain precursor powder. Among them, both the cerium salt and the copper salt can be nitrates, and the ratio of the cerium salt to the copper salt is preferably controlled according to the volume ratio of cerium oxide in the cerium oxide-copper composite powder being 0.5% to 1.5% (for example, 1%); the inlet air temperature for spray drying can be 180 to 200 °C, the outlet air temperature can be 115 °C to 130 °C, the fan speed can be 60 to 70 r / min, and the feeding rate can be 300 to 360 mL / h.

[0033] The precursor powder is calcined and decomposed to obtain cerium oxide-copper oxide composite powder. Among them, the temperature for calcination and decomposition can be 400 to 500 °C, and the calcination time can be 1 to 2 h.

[0034] The cerium oxide-copper oxide composite powder is reduced in a supercritical liquid phase reduction system, and after filtration and drying, cerium oxide-copper composite powder is obtained. Among them, the molar ratio of copper oxide to the reducing agent (such as formaldehyde) in the supercritical liquid phase reduction system is 1:1 to 2. During reduction, it is first heated to 350 °C at a rate of 5 to 10 °C / min and held for 10 min, then heated to 380 °C at a heating rate of 2 to 5 °C / min, and reacted at 380 °C for 10 to 25 min and then cooled to room temperature with the furnace and taken out. The pressure of the supercritical liquid phase reduction system can be 25 MPa.

[0035] The cerium oxide-copper composite powder is pressed into a green body, and then the green body is subjected to spark plasma sintering to obtain a cerium oxide-reinforced copper matrix composite. Among them, the temperature for spark plasma sintering can be 800 °C to 850 °C, and the holding time is 5 min to 7 min.

[0036] The present invention uses the spray drying method to prepare precursor powder, enabling Cu and Ce to achieve molecular-level mixing, solving the problem of their agglomeration. At the same time, many unique physical and chemical properties such as the high reaction rate under the supercritical system and the green recycling and reuse of water are incomparable to the traditional hydrogen reduction method.

[0037] Hereinafter, detailed descriptions will be given in combination with specific examples and comparative examples.

[0038] Example 1

[0039] The preparation method of Example 1 specifically includes the following steps:

[0040] S1. 99.466 g of copper nitrate trihydrate and 0.534 g of cerium nitrate hexahydrate are dissolved in 1000 mL of deionized water, and mixed precursor powder is prepared through a spray dryer; the inlet air temperature for spray drying is 200 °C, the outlet air temperature is 120 °C, and the feeding rate is 6 mL / min.

[0041] S2. Place the precursor powder in a muffle furnace and calcine it at 500 °C for 1 h to decompose it into cerium oxide - copper oxide composite powder.

[0042] S3. Place the cerium oxide - copper oxide composite powder in a supercritical liquid phase reduction system for reduction. The molar ratio of the reducing agent formaldehyde to copper ions is 2:1. The reaction termination temperature and pressure are 380 °C and 25 MPa respectively. Keep it warm for 10 min, then cool it with the furnace after the reaction. After cooling, filter it by suction and dry it in vacuum. The temperature for vacuum drying is 60 °C and keep it warm for 6 h. The volume fraction of cerium oxide in the obtained cerium oxide - copper composite powder is 1%.

[0043] S4. Press the composite powder into a green compact and then place it in a graphite mold with a diameter of 20 mm for spark plasma sintering at a temperature of 850 °C for a holding time of 7 min to obtain a cerium oxide - copper composite block.

[0044] Example 2

[0045] The difference from Example 1 is only that the sintering temperature is adjusted to 800 °C, and other conditions and parameters remain unchanged.

[0046] Comparative Example 1

[0047] The preparation method of the blank control group specifically includes the following steps:

[0048] S1. Dissolve 100 g of copper nitrate trihydrate in 1000 mL of deionized water, and prepare a mixed precursor powder through a spray dryer; the inlet air temperature of the spray dryer is 200 °C, the outlet air temperature is 120 °C, and the feeding rate is 6 mL / min.

[0049] S2. Place the precursor powder in a muffle furnace and calcine it at 500 °C for 1 h to decompose it into copper oxide powder.

[0050] S3. Place the copper oxide powder in a supercritical liquid phase reduction system for reduction. The molar ratio of the reducing agent formaldehyde to copper ions is 2:1. The reaction termination temperature and pressure are 380 °C and 25 MPa respectively. Keep it warm for 10 min, then cool it with the furnace after the reaction. After cooling, filter it by suction and dry it in vacuum. The temperature for vacuum drying is 60 °C and keep it warm for 6 h to obtain pure copper powder.

[0051] S4. Press the pure copper powder into a green compact and then place it in a graphite mold with a diameter of 20 mm for spark plasma sintering at a temperature of 850 °C for a holding time of 7 min.

[0052] Grind and polish the prepared pure copper material, and measure its Vickers hardness to be 62.34 HV.

[0053] Comparative Example 2

[0054] The difference between Comparative Example 2 and Example 1 is that the amount of copper nitrate trihydrate used is 97.84 g, the amount of cerium nitrate hexahydrate used is 2.16 g, and the volume fraction of cerium oxide in the obtained cerium oxide-copper composite powder is 4%.

[0055] Comparative Example 3

[0056] The difference between Comparative Example 3 and Example 1 is that the amount of copper nitrate trihydrate used is 94.418 g, the amount of cerium nitrate hexahydrate used is 5.582 g, and the volume fraction of cerium oxide in the obtained cerium oxide-copper composite powder is 10%.

[0057] Comparative Example 4

[0058] The difference between Comparative Example 4 and Example 1 is that the amount of copper nitrate trihydrate used is 92.634 g, the amount of cerium nitrate hexahydrate used is 7.366 g, and the volume fraction of cerium oxide in the obtained cerium oxide-copper composite powder is 13%.

[0059] In other examples / comparative examples, cerium oxide-copper composite powders with cerium oxide volume fractions of 0.5%, 2% and 7% were also prepared. In addition, the composite powders were sintered at different temperatures to obtain copper-based composites to investigate the effect of sintering temperature on the material properties.

[0060] Characterization and Testing of Composite Powders and Bulk Materials

[0061] Figure 1 is the scanning energy spectrum of the cerium oxide-copper composite powder prepared in Example 1, where red represents the matrix copper and green is cerium dioxide. From Figure 1 it can be seen that the distribution of cerium oxide on the copper matrix is very uniform, and the size of cerium oxide is in the nanoscale with fine grains. Figure 2 is the XRD pattern of the cerium oxide-copper composite powder prepared in Example 1. From Figure 2 it can be seen that the composite powder has a pure phase and no other phases and impurities.

[0062] The sintered bulk materials were polished, and then their hardness and stress-strain were tested. The results are as Figure 3 and 4 shown. It can be seen that the material properties at sintering temperatures of 800 °C and 850 °C are better than those at 750 °C. When the volume ratio of cerium oxide is controlled at 1%, both the Vickers hardness and toughness of the cerium oxide-reinforced copper-based composite material are improved simultaneously. When the volume ratio of cerium oxide exceeds 2%, although the Vickers hardness of the copper-based composite material also increases relative to pure copper, its toughness deteriorates accordingly.

[0063] Although the present invention is disclosed above by way of specific embodiments, it should be understood that the above specific embodiments are not intended to limit the scope of implementation of the present invention. Any ordinary person skilled in the art can make some improvements without departing from the scope of the present invention. That is, any equivalent improvements made in accordance with the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a cerium oxide-copper composite powder, characterized in that It includes the following steps: Spray-dry the mixed solution of cerium salt and copper salt to obtain precursor powder; Calcine and decompose the precursor powder to obtain cerium oxide-copper oxide composite powder; Reduce the cerium oxide-copper oxide composite powder in a supercritical liquid-phase reduction system using formaldehyde as a reducing agent, and filter and dry to obtain cerium oxide-copper composite powder; Among them, the ratio of the cerium salt to the copper salt is controlled according to the volume ratio of cerium oxide in the cerium oxide-copper composite powder being 0.5% to 1.5%.

2. The preparation method according to claim 1, characterized in that: In the supercritical liquid-phase reduction system, the molar ratio of copper oxide to the reducing agent is 1:1 to 2. During reduction, first heat up at a rate of 5 to 10 °C / min to 350 °C and hold for 10 min, then heat up at a rate of 2 to 5 °C / min to 380 °C, and react at 380 °C for 10 to 25 min and then cool to room temperature in the furnace and take out.

3. The preparation method according to claim 2, characterized in that: The pressure of the supercritical liquid-phase reduction system is 25 MPa.

4. The preparation method according to claim 1, wherein: The inlet air temperature of the spray drying is 180 to 200 °C, the outlet air temperature is 115 °C to 130 °C, the fan speed is 60 to 70 r / min, and the feeding rate is 300 to 360 mL / h.

5. The preparation method according to claim 1, wherein: The temperature of the calcination decomposition is 400 to 500 °C, and the calcination time is 1 to 2 h.

6. The preparation method according to claim 1, characterized in that: Both the cerium salt and the copper salt are nitrates.

7. The preparation method according to claim 1, wherein: The ratio of the cerium salt to the copper salt is controlled according to the volume ratio of cerium oxide in the cerium oxide-copper composite powder being 1%.

8. A method for preparing a cerium oxide reinforced copper composite material, characterized in that It includes the following steps: Press the cerium oxide-copper composite powder obtained by the preparation method of any one of claims 1-7 into a green body; Perform spark plasma sintering on the green body to obtain a cerium oxide-reinforced copper-based composite material.

9. The preparation method according to claim 8, characterized in that: The temperature of the spark plasma sintering is 800 °C to 850 °C, and the holding time is 5 min to 7 min.

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