Preparation method and device of nanometer copper-coated metal composite powder

Abstract

The application discloses a preparation method of nano copper-coated metal composite powder, which comprises the following steps: S1, selecting an oxalate of a core metal as a raw material for preparation, and performing high-temperature thermal decomposition reduction under a passivation-reduction atmosphere, and controlling a gas flow and a decomposition temperature to control a nano metal powder morphology granularity; S2, heating the nano metal powder, increasing a passivation gas flow after the nano metal powder is completely discolored, and performing dispersion grading on the nano metal powder; the nano metal powder after dispersion grading is introduced into a water-soluble copper salt solution added with a dispersant to perform a displacement reaction, so that nano copper-coated metal powder is obtained, and in the displacement reaction process, a reaction temperature, a reaction time, a pH, a stirring speed and a solution concentration are controlled; and S3, after drying treatment is performed on the nano copper-coated metal powder after the reaction is completed, the nano copper-coated metal composite powder with a core-shell structure is obtained. The process improvement is simple, controllable, low in cost and easy to realize large-scale production.

Description

Technical Field

[0001] This invention relates to the field of composite functional powder technology, specifically to a method and apparatus for preparing core-shell structured copper-coated metal composite powder. Background Technology

[0002] Copper-clad iron powder is a composite powder with a copper coating on the surface of iron powder. It combines the advantages of a copper-based shell (high electrical and thermal conductivity and strong corrosion resistance) with an iron-based core (high strength). It effectively improves the problems of uneven structure and component segregation in traditional copper-iron mixed powders and is widely used in powder metallurgy fields such as oil-impregnated bearings, diamond tools, and friction applications. With the demands of applications and technological innovation, powder sizes are no longer limited to the micrometer level but are transitioning to the nanometer level. However, due to the high activity, large specific surface area, and easy agglomeration characteristics of nanoparticles, and the extreme instability of nano-iron powder in air, which can lead to severe oxidation and spontaneous combustion, the preparation and preservation of iron-based nanoparticles are relatively difficult, severely restricting the technological development and industrial application of nano-copper-clad iron powder.

[0003] Currently, the main methods suitable for large-scale preparation of copper-clad iron include mechanical coating and chemical displacement. However, when the powder size becomes nanoscale, mechanical coating is no longer applicable due to the high reactivity and spontaneous combustion of nano-iron powder. Chemical displacement utilizes the difference in metallic reactivity between copper and iron to replace copper ions in copper salt solution with elemental copper, which then coats the surface of iron powder. By changing the reaction conditions and adding additives, the thickness, uniformity, density, and dispersibility of the copper coating layer can be effectively controlled. The preparation of nanoparticles also has extremely strong controllability and can be mass-produced industrially.

[0004] To prevent spontaneous combustion of nano-iron powder and prepare high-performance copper-coated iron powder, researchers have made numerous improvements. Patent CN1936066A discloses a method that uses passivating gas to form a protective oxide film on the surface of ultrafine iron powder, thus achieving passivation and preventing spontaneous combustion—a method worth considering. Patent CN1817509A discloses a method that uses micron-sized iron powder to replace copper in a copper sulfate solution and deposits it on the iron powder surface to form a copper film for complete coating; however, this method is no longer applicable to nano-iron powder coating. Patent 105251996A discloses a method that adds nano-iron powder to a copper acetate-dimethylformamide solution, uses organic matter to modify the surface of the nano-iron powder, and then replaces copper to obtain a copper-coated iron composite powder. This powder is stable and has strong antioxidant properties, but the presence of organic matter affects the interfacial bonding performance between copper and iron and the coating effect. Currently disclosed methods are mostly for the preparation of micron-sized copper-coated iron powder, which does not have the spontaneous combustion hazards caused by the high activity and strong oxidizing properties of nano-iron powder, and there are no reports of the integrated preparation of nano-iron powder and copper-coated iron powder.

[0005] Therefore, there is an urgent need to develop a new preparation method and apparatus for core-shell structured nano-copper coated metal composite powder, especially nano-copper coated iron composite powder. The preparation process is simple, the copper coating layer can be effectively controlled, and it can better meet the needs of large-scale industrial production. Summary of the Invention

[0006] One objective of this invention is to provide a method for the integrated and controllable preparation of core nano-metal powder and nano-copper-coated metal powder, comprising the following steps: S1. Oxalate of the core metal is selected as the raw material for preparation and is subjected to high-temperature thermal decomposition and reduction under a passivation-reducing atmosphere. The morphology and particle size of the nano metal powder are controlled by controlling the gas flow rate and decomposition temperature. S2. Heat the nano-metal powder. After the nano-metal powder has completely changed color, increase the passivation gas flow rate to disperse and classify the nano-metal powder. Pass the dispersed and classified nano-metal powder into a water-soluble copper salt solution with added dispersant to carry out a displacement reaction to obtain nano-copper coated metal powder. During the displacement reaction, control the reaction temperature, reaction time, pH, stirring speed and solution concentration. S3. After drying the fully reacted nano-copper coated metal powder, a core-shell structured nano-copper coated metal composite powder is obtained.

[0007] Preferably, in S1, the oxalate of the core metal is selected from raw materials that are more reactive than copper and can be thermally decomposed, and is at least one of the following materials: ferrous oxalate dihydrate (FeC2O4·2H2O), ferrous oxalate anhydrous (FeC2O4), ferric oxalate pentahydrate (Fe2(C2O4)3·5H2O), ferric oxalate anhydrous (Fe2(C2O4)3), or zinc oxalate (ZnC2O4·2H2O), with a particle size ≤50μm and a purity ≥95%.

[0008] Preferably, in S1, the passivation-reduction gas is at least one of the following gases: carbon dioxide, carbon monoxide, argon, nitrogen, hydrogen, ammonia decomposition gas, or a nitrogen-hydrogen mixture, with a gas flow rate of 0.5 to 4.0 L / min.

[0009] Preferably, in S1, the temperature is set to a two-stage heating process: the initial decomposition temperature is 100-300℃, and the holding time is 0.5-1h; the second-stage decomposition temperature is 300-800℃, and the holding time is 1-3h.

[0010] Preferably, in step S2, the nano-metal powder is ultrasonically dispersed.

[0011] Preferably, in step S2, after dispersing the nano-metal powder, a water-soluble copper salt solution is introduced under the influence of a descending purified gas flow and gravity to carry out a displacement reaction.

[0012] Preferably, in S2, the passivation gas is at least one of the following gases: carbon dioxide, argon, or nitrogen, with a gas flow rate of 3.0 to 8.0 L / min.

[0013] Preferably, in S2, the water-soluble copper salt is selected from at least one of the following materials: copper sulfate, copper chloride, copper nitrate, or copper acetate, and the concentration of the copper salt is 0.2 mol / L to 10.0 mol / L.

[0014] Preferably, in S2, the dispersant added is at least one of the following materials: cysteine, methionine, polyvinylpyrrolidone, polyethylene glycol, sodium citrate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, or hexadecyltrimethylammonium bromide, and the concentration of the dispersant is 0.1 mol / L to 1.0 mol / L.

[0015] Preferably, in S2, the reaction temperature, reaction time, pH, stirring speed and solution concentration are controlled so that the copper coating thickness of the nano-coated metal conforming powder is 20nm to 500nm.

[0016] Preferably, in S2, the reaction temperature of the displacement reaction is between 20°C and 100°C, the reaction time is between 10 and 120 min, the pH range is between 2 and 13, and the stirring speed is between 300 rpm and 2000 rpm.

[0017] Preferably, in step S3, the fully reacted nano-coated metal powder is first washed to neutrality by deionized water or by vacuum filtration, and then the washed nano-coated metal powder is vacuum dried to obtain a core-shell structured nano-coated metal composite powder.

[0018] Preferably, in step S3, the vacuum drying temperature is between 40°C and 100°C, and the drying time is between 1 hour and 10 hours.

[0019] Secondly, the present invention also provides a preparation apparatus for preparing nano-copper coated metal composite powder as described in any of the above schemes, including a well-sealed reaction vessel, the reaction vessel being filled with a passivation-reduction atmosphere, an ultrasonic vibrating screen with a sloping surface being provided in the upper part of the reaction vessel, a heating plate for heating oxalate being provided on the ultrasonic vibrating screen; a water-soluble copper salt solution with added dispersant being contained in the lower part of the reaction vessel, and a stirring blade extending into the water-soluble copper salt solution being provided at the bottom of the reaction vessel.

[0020] Preferably, the heating rate of the heating plate is 2℃ / min to 10℃ / min.

[0021] Preferably, the ultrasonic vibrating screen has a gentle slope, and the surface of the slope has micropores with a pore size of 100μm to 2000μm and a vibration frequency of 20kHz to 50kHz.

[0022] In this invention, the metal oxide of the core metal is obtained by low-temperature decomposition of its oxalate. The decomposed CO gas is further reduced at high temperature to obtain nano-metal powder. The decomposition reaction product CO2 and other passivating gases can achieve flame retardancy and oxygen isolation protection. The sloping ultrasonic vibrating screen installed in the reaction vessel is used to disperse and classify the particles to avoid agglomeration. The heavier sinking CO2 hot air flow and gravity drive the decomposed core nano-metal powder to settle into the copper salt solution for a displacement reaction. This process avoids the entry of oxygen and the influence of other chemical substances, forming monodisperse particles and achieving uniform coating. The reaction process with FeC2O4·2H2O as the reactant is shown below: FeC2O4·2H2O→FeC2O4+2H2O (1) 3FeC2O4→Fe3O4+4CO+2CO2 (2) 3FeC2O4+2CO→Fe3C+7CO2 (3) Fe3C→3Fe+C (4) Fe3O4 + 4CO → 3F e +4CO2 (5) This invention offers the following advantages: The novel preparation method and apparatus for core-shell structured copper-coated metal composite powders, particularly copper-coated iron composite powders, provided by this invention, directly integrates the preparation of the core nano-metal powder with the chemical substitution of copper and metal. The presence of passivating-reducing gas eliminates the drawbacks of strong oxidation and spontaneous combustion caused by exposing the nano-metal powder to air, while effectively ensuring the completeness of decomposition and reduction. The sloping ultrasonic vibrating screen installed inside the reactor achieves graded dispersion and avoids agglomeration of the core nano-metal powder during its reduction. By controlling the decomposition temperature, vibration frequency, and gas flow rate, the morphology, particle size, and dispersion degree of the core nano-metal powder can be synergistically controlled to achieve controllable preparation. The use of this apparatus also effectively reduces the loss of core nano-metal powder during actual preparation, storage, and transfer, improving utilization and effectively reducing costs. All process and apparatus improvements are simple, controllable, low-cost, and easily scalable for large-scale production. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure principle of the reaction vessel in the embodiment of the preparation method and preparation device of the present invention for the preparation of nano-copper coated metal composite powder. Detailed Implementation

[0024] The following detailed description illustrates the specific implementation method: 1. Definition Core-shell structures are ordered, nanoscale assemblies formed by one nanomaterial encapsulating another through chemical bonds or other forces. Due to their unique structural characteristics, core-shell structures integrate the properties of both the inner and outer materials, complementing each other's shortcomings. This has become an important research direction in recent years, demonstrating the principle that morphology determines properties, and has broad application prospects in catalysis, photocatalysis, batteries, gas storage, and separation.

[0025] 2. The reference numerals in the accompanying drawings of the instruction manual include: heating plate 1, nano metal powder 2, water-soluble copper salt solution 3, ultrasonic vibrating sieve 4.

[0026] illustrate: Figure 1 The direction of the dashed arrow indicates the flow direction of CO2.

[0027] The basic implementation examples are as follows: Figure 1 As shown: The apparatus for preparing nano-copper coated metal composite powder includes a well-sealed reaction vessel filled with a passivation-reduction atmosphere. An ultrasonic vibrating screen 4 with a sloping surface is provided in the upper part of the reaction vessel. The ultrasonic vibrating screen 4 has a gentle slope and micropores on the surface of the slope with a pore size of 100μm to 2000μm and a vibration frequency of 20kHz to 50kHz. A heating plate 1 for heating oxalate is provided on the ultrasonic vibrating screen 4.

[0028] The lower part of the reactor contains a water-soluble copper salt solution 3 with added dispersant, and the bottom of the reactor is also equipped with stirring blades that extend into the water-soluble copper salt solution 3.

[0029] A method for preparing nano-copper-coated metal composite powder based on the above-mentioned apparatus for preparing nano-copper-coated metal composite powder includes the following steps: S1. Oxalate of the core metal is selected as the raw material for preparation and is subjected to high-temperature thermal decomposition and reduction under a passivation-reducing atmosphere. The morphology and particle size of the nano metal powder 2 are controlled by controlling the gas flow rate and decomposition temperature. Among them, the oxalate of the core metal is selected from raw materials that are more reactive than copper and can be thermally decomposed, and at least one of the following materials is selected: ferrous oxalate dihydrate (FeC2O4·2H2O), ferrous oxalate anhydrous (FeC2O4), ferric oxalate pentahydrate (Fe2(C2O4)3·5H2O), ferric oxalate anhydrous (Fe2(C2O4)3), zinc oxalate (ZnC2O4·2H2O). There are no special requirements for morphology, the particle size is ≤50μm, and the purity is ≥95%.

[0030] At least one of the following gases should be selected for passivation-reduction: carbon dioxide, carbon monoxide, argon, nitrogen, hydrogen, ammonia decomposition gas, or nitrogen-hydrogen mixture, with a gas flow rate of 0.5–4.0 L / min.

[0031] The temperature inside the reactor is set to rise in two stages. The initial decomposition temperature is 100-300℃ and the holding time is 0.5-1h. The second decomposition temperature is 300-800℃ and the holding time is 1-3h. The heating rate of heating plate 1 is 2-10℃ / min.

[0032] S2. Heat the nano-metal powder 2. After the nano-metal powder 2 has completely changed color, increase the passivation gas flow rate. Use the added slope ultrasonic vibrating screen 4 to ultrasonically disperse the reduced nano-metal powder 2 to make it dispersed and graded to avoid agglomeration. Then, under the action of the sinking CO2 airflow and gravity, it is passed into the water-soluble copper salt solution 3 with added dispersant for displacement reaction. Control the reaction temperature, reaction time, pH, stirring speed and solution concentration to control the thickness, uniformity and dispersibility of the copper coating layer.

[0033] The passivation gas should be at least one of the following: carbon dioxide, argon, or nitrogen, with a flow rate of 3.0–8.0 L / min. The water-soluble copper salt should be at least one of the following: copper sulfate, copper chloride, copper nitrate, or copper acetate, with a concentration of 0.2 mol / L–10.0 mol / L. The dispersant should be at least one of the following: cysteine, methionine, polyvinylpyrrolidone, polyethylene glycol, sodium citrate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, or hexadecyltrimethylammonium bromide, with a concentration of 0.1 mol / L–1.0 mol / L. The reaction temperature, reaction time, pH, stirring speed, and solution concentration should be controlled to ensure that the copper coating thickness of the nano-coated metal powder is 20 nm–500 nm. The displacement reaction temperature should be between 20 °C and 100 °C, the reaction time between 10 and 120 min, the pH between 2 and 13, and the stirring speed between 300 rpm and 2000 rpm.

[0034] S3. The fully reacted copper-coated metal powder is dried to obtain a core-shell structured copper-coated metal composite powder. Specifically, the fully reacted copper-coated metal powder is washed until neutral using deionized water or by vacuum filtration. The washed copper-coated metal powder is then vacuum-dried to obtain the core-shell structured copper-coated metal composite powder. The vacuum drying temperature is between 40℃ and 100℃, and the drying time is between 1 hour and 10 hours. Washing methods include, but are not limited to, centrifugation and filtration, and drying methods include, but are not limited to, vacuum drying and freeze-drying.

[0035] Example 1: S1: According to the scheme settings, select and weigh 100g of ferrous oxalate dihydrate (FeC2O4·2H2O) raw material and spread it evenly on the heating plate 1 in the reactor. Place it in the upper part of the reactor. Under the mixed atmosphere of CO2 with a flow rate of 0.7L / min and H2 with a flow rate of 0.3L / min, the heating rate is 10℃ / min. Set the initial decomposition temperature to 150℃ and the holding time to 0.5h. Then raise the temperature to 500℃ and react for 2.5h to carry out high-temperature thermal decomposition and reduction to prepare nano iron powder. At the same time, turn on the ultrasonic vibrating screen 4 and set the vibration frequency to 30kHz.

[0036] S2: Weigh 30g of copper sulfate pentahydrate (CuSO4·5H2O) and dissolve it in 200mL of deionized water. Simultaneously add 3g of polyvinylpyrrolidone (PVPK30) to the solution and stir vigorously at 500rpm. Adjust the pH to 3.0 by adding NaOH and maintain the solution temperature at 50℃. When the yellow powder on heating plate 1 completely turns black, increase the flow rate of CO2 and H2 gases to 5L / min, so that the nano-iron powder settles into the prepared copper sulfate solution at the bottom under the action of the descending CO2 gas flow and gravity to carry out the displacement reaction. After all the nano-iron powder has settled into the copper sulfate solution, react for another 30min.

[0037] S3: After the reaction is complete, the nano copper-coated iron composite powder is washed 5 times with deionized water until neutral. The washed powder is then vacuum dried in a vacuum drying oven at 50°C for 4 hours to obtain nano copper-coated iron powder.

[0038] Example 2: S1: According to the scheme settings, select and weigh 100g of ferrous oxalate (FeC2O4·2H2O) raw material and spread it evenly on the heating plate 1 in the upper part of the reactor. Under the mixed atmosphere of N2 with a flow rate of 0.5L / min and CO2 with a flow rate of 0.5L / min, the heating rate is 10℃ / min. Set the initial decomposition temperature to 180℃ and the holding time to 0.5h. Then raise the temperature to 600℃ and react for 2h to carry out high-temperature thermal decomposition and reduction to prepare nano iron powder. At the same time, turn on the ultrasonic vibrating screen 4 and set the vibration frequency to 30kHz.

[0039] S2: Weigh 50g of copper nitrate (Cu(NO3)2) and dissolve it in 100mL of deionized water. Simultaneously add 10g of polyethylene glycol 2000 (PEG2000) to the solution and stir vigorously at 800rpm. Adjust the pH to 4.5 by adding NaOH and maintain the solution temperature at 70℃. When the yellow powder on heating plate 1 completely turns black, increase the flow rate of N2 and CO2 gases to 5L / min, so that the nano-iron powder settles into the prepared copper sulfate solution at the bottom under the action of the descending CO2 gas flow and gravity to carry out the displacement reaction. After all the nano-iron powder has settled into the copper sulfate solution, react for another 10min.

[0040] S3: After the reaction is complete, the nano copper-coated iron composite powder is washed 5 times with deionized water until neutral. The washed powder is then vacuum dried in a vacuum drying oven at 60°C for 2 hours to obtain nano copper-coated iron powder.

[0041] Example 3: S1: According to the scheme settings, select and weigh 50g of ferric oxalate (Fe2(C2O4)3) raw material and spread it evenly on the heating plate 1 in the reactor. Place it in the upper part of the reactor. Under the mixed atmosphere of Ar with a flow rate of 0.4L / min and CO2 with a flow rate of 0.6L / min, the heating rate is 10℃ / min. Set the initial decomposition temperature to 200℃ and the holding time to 0.5h. Then raise the temperature to 700℃ and react for 1h to carry out high-temperature thermal decomposition and reduction to prepare nano iron powder. At the same time, turn on the ultrasonic vibrating screen 4 and set the vibration frequency to 30kHz.

[0042] S2: Weigh 40g of copper chloride dihydrate (CuCl·2H2O) and dissolve it in 100mL of deionized water. Simultaneously add 10g of methionine (Met) to the solution and stir vigorously at 600rpm. Adjust the pH to 11 by adding NaOH and maintain the solution temperature at 80℃. When the yellow powder on heating plate 1 completely turns black, increase the flow rate of Ar and CO2 gases to 4L / min, allowing the nano-iron powder to settle into the prepared copper sulfate solution at the bottom under the influence of the descending CO2 gas flow and gravity for a displacement reaction. After all the nano-iron powder has settled into the copper sulfate solution, continue the reaction for another 60min.

[0043] S3: After the reaction is complete, the nano copper-coated iron composite powder is washed 5 times with deionized water until neutral. The washed powder is then vacuum dried in a vacuum drying oven at 60°C for 2 hours to obtain nano copper-coated iron powder.

[0044] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing nano-copper-coated metal composite powder, characterized in that: Includes the following steps: S1. Oxalate of the core metal is selected as the raw material for preparation and is subjected to high-temperature thermal decomposition and reduction under a passivation-reducing atmosphere. The morphology and particle size of the nano metal powder are controlled by controlling the gas flow rate and decomposition temperature. S2. Heat the nano-metal powder. After the nano-metal powder has completely changed color, increase the passivation gas flow rate to disperse and classify the nano-metal powder. Pass the dispersed and classified nano-metal powder into a water-soluble copper salt solution with added dispersant to carry out a displacement reaction to obtain nano-copper coated metal powder. During the displacement reaction, control the reaction temperature, reaction time, pH, stirring speed and solution concentration. S3. After drying the fully reacted nano-copper coated metal powder, a core-shell structured nano-copper coated metal composite powder is obtained. The apparatus for preparing the nano-copper coated metal composite powder includes a well-sealed reaction vessel filled with a passivation-reduction atmosphere. The upper part of the reaction vessel is equipped with a sloping ultrasonic vibrating screen, and the ultrasonic vibrating screen is equipped with a heating plate for heating oxalate. The lower part of the reaction vessel is filled with a water-soluble copper salt solution with added dispersant, and the bottom of the reaction vessel is also equipped with stirring blades that extend into the water-soluble copper salt solution.

2. The method for preparing nano-copper-coated metal composite powder according to claim 1, characterized in that: In S1, the oxalate of the core metal is selected from raw materials that are more reactive than copper and can be thermally decomposed, and can be any of the following materials: ferrous oxalate dihydrate (FeC2O4·2H2O), ferrous oxalate anhydrous (FeC2O4), ferric oxalate pentahydrate (Fe2(C2O4)3·5H2O), ferric oxalate anhydrous (Fe2(C2O4)3), or zinc oxalate (ZnC2O4·2H2O), with a particle size ≤50μm and a purity ≥95%.

3. The method for preparing nano-copper-coated metal composite powder according to claim 2, characterized in that: In S1, the passivation-reducing atmosphere gas shall be at least one of the following gases: carbon dioxide, carbon monoxide, argon, nitrogen, hydrogen, ammonia decomposition gas, or nitrogen-hydrogen mixture, with a gas flow rate of 0.5 to 4.0 L / min.

4. The method for preparing nano-copper-coated metal composite powder according to claim 3, characterized in that: In S1, the decomposition temperature is set to a two-stage heating process. The initial decomposition temperature is 100-300℃, and the holding time is 0.5-1h. The second decomposition temperature is 300-800℃, and the holding time is 1-3h.

5. The method for preparing nano-copper-coated metal composite powder according to any one of claims 1-4, characterized in that: In step S2, the nano-metal powder is ultrasonically dispersed.

6. The method for preparing nano-copper-coated metal composite powder according to claim 5, characterized in that: In step S2, after the nano-metal powder is dispersed, the water-soluble copper salt solution is introduced under the action of a descending passivation gas flow and gravity to carry out a displacement reaction.

7. The method for preparing nano-copper-coated metal composite powder according to claim 6, characterized in that: In step S2, at least one of the following gases shall be selected as the passivation gas: carbon dioxide, argon, or nitrogen, with a gas flow rate of 3.0 to 8.0 L / min.

8. The method for preparing nano-copper-coated metal composite powder according to claim 7, characterized in that: In S2, at least one of the following materials shall be selected as the water-soluble copper salt: copper sulfate, copper chloride, copper nitrate, or copper acetate, and the concentration of the copper salt shall be 0.2 mol / L to 10.0 mol / L.

9. The method for preparing nano-copper-coated metal composite powder according to claim 8, characterized in that: In step S2, the dispersant added shall be at least one of the following materials: cysteine, methionine, polyvinylpyrrolidone, polyethylene glycol, sodium citrate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, or hexadecyltrimethylammonium bromide, and the concentration of the dispersant shall be 0.1 mol / L to 1.0 mol / L.

10. The method for preparing nano-copper-coated metal composite powder according to claim 9, characterized in that: In step S2, the reaction temperature, reaction time, pH, stirring speed, and solution concentration are controlled so that the copper coating thickness of the nano-coated metal composite powder is 20 nm to 500 nm.

11. The method for preparing nano-copper-coated metal composite powder according to claim 10, characterized in that: In S2, the reaction temperature of the displacement reaction is between 20℃ and 100℃, the reaction time is between 10 and 120 min, the pH range is between 2 and 13, and the stirring speed is between 300 rpm and 2000 rpm.

12. The method for preparing nano-copper-coated metal composite powder according to claim 11, characterized in that: In step S3, the fully reacted nano-copper coated metal powder is first washed to neutrality by deionized water or vacuum filtration, and then the washed nano-copper coated metal powder is vacuum dried to obtain a core-shell structured nano-copper coated metal composite powder.

13. The method for preparing nano-copper-coated metal composite powder according to claim 11, characterized in that: In step S3, the vacuum drying temperature is between 40℃ and 100℃, and the drying time is between 1h and 10h.

14. The method for preparing nano-copper-coated metal composite powder according to claim 1, characterized in that: The heating plate has a heating rate of 2℃ / min to 10℃ / min.

15. The method for preparing nano-copper-coated metal composite powder according to claim 1 or 14, characterized in that: The ultrasonic vibrating screen has a gentle slope with micropores on its surface. The pore size is 100μm to 2000μm, and the vibration frequency is 20kHz to 50kHz.

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