CN118832160A - Core/shell type silver coated copper powder synthesized based on atomization drying and heat treatment process and preparation method thereof - Google Patents

Abstract

The present invention provides a synthesis of core/shell type silver-coated copper powder based on atomization drying and heat treatment process and a preparation method thereof, which belongs to the technical field of powder material preparation. The copper powder raw material is first pretreated by adopting the principle of heating and decomposing a silver-containing compound, and then a silver salt complex solution is prepared and mixed with the copper powder raw material to obtain a uniform liquid, and then the liquid is atomized and dried to make the silver salt complex uniformly coat the surface of the copper powder; finally, the coated product after atomization and drying is heat-treated to decompose and separate silver from the surface of the copper powder to obtain a core/shell type silver-coated copper composite powder material. The preparation method of the present invention is simple, and the obtained composite powder has good dispersibility and uniform size distribution, and the silver layer coated on the surface of the copper powder is complete, dense, and uniform in thickness, and has good electrical conductivity and strong high-temperature oxidation resistance. It can be used as a powder raw material for various electronic pastes and is sintered in air.

Description

A method for synthesizing core/shell type silver-coated copper powder based on atomization drying and heat treatment process and its preparation method

Technical Field

The invention belongs to the technical field of powder material preparation, and relates to silver-coated copper powder with good coating effect and strong oxidation resistance and a preparation method thereof.

Background Art

With the development of the electronic information industry, the development of electronic paste with ultrafine metal powder as the main functional phase has been driven. As electronic components develop towards miniaturization, precision, and multifunctionality, the quality requirements for electronic paste are becoming higher and higher. As a conductive coating material for devices, electronic paste has been widely used in solar cells, printed circuit boards, thick film integrated circuits, conductive inks, and other fields, and has also played an important role in aerospace, computer and communication fields. Among the common ultrafine metal powders used to prepare electronic pastes, silver powder has become one of the most popular materials for component preparation due to its good conductivity and antioxidant properties. However, as a precious metal material, silver is expensive, which increases the manufacturing cost of the paste; in addition, the problem of easy migration of silver also restricts its application. The conductivity of copper powder is similar to that of silver and is cheap, but the conductivity of copper powder will be reduced because it is easily oxidized during preparation and use. Therefore, the preparation process of silver-coated copper powder came into being. The core/shell composite powder material prepared by this production process not only solves the migration problem of silver, but also improves the antioxidant ability of copper powder.

The preparation methods of silver-coated copper powder are generally divided into chemical method and physical method, specifically:

Chemical methods include chemical reduction method, replacement method, etc. The chemical reduction method mainly uses an external reducing agent to reduce the silver ions in the solution and evenly deposit them on the surface of the copper powder. The elemental silver generated according to the self-catalytic mechanism of silver plating can be continuously deposited on the surface of the copper powder to form a uniform silver layer. However, the silver plating solution required needs to add multiple components and has poor stability. It is easy to produce free silver particles. More precise control of reaction conditions is required to prepare a uniform and dense silver coating. The replacement method uses the copper powder itself as a reducing agent to reduce the silver ions, and deposits silver on the surface of the copper powder through a replacement reaction on the surface of the copper particles. Since the replacement reaction is carried out on a copper matrix, particles with good copper-silver bonding can be prepared, but at the same time, electrochemical reactions are more likely to occur in the solution, causing silver to continue to be deposited on the already formed point-like silver particles, resulting in poor continuity of the silver coating.

The physical method for preparing silver-coated copper powder mainly involves mechanical ball milling, evaporation condensation, magnetron sputtering, etc. The mechanical ball milling method uses copper and silver as abrasives. Under the action of abrasive extrusion, the silver powder is spread on the surface of the copper powder to form a coating layer. Although completely coated silver-coated copper particles can be prepared, a large number of micro-nanoscale silver particles will be produced during the ball milling process, and the consumption of silver cannot be effectively reduced. The evaporation condensation method is currently one of the main means to obtain nanoparticles with clean interfaces. This method is prepared in an environment full of inert gas. Usually, the evaporation source is used to heat the material to above the melting temperature for gasification or plasma treatment. After it collides with inert atoms and loses energy, the ambient temperature is sharply reduced to condense it into particles with a certain particle size. The silver-copper powder prepared by the evaporation condensation method has the advantages of strong conductivity and controllable particle size, but the manufacturing cost is high, the yield is low, and it is difficult to form a core/shell structure of silver-coated copper. The magnetron sputtering method uses the process in which electrons are accelerated to fly toward the substrate under the action of an electric field and collide with argon atoms, ionizing a large number of argon ions and electrons. Under the action of the electric field, the argon ions are accelerated to bombard the target material, sputtering a large number of target atoms, and the neutral target atoms (or molecules) are deposited on the substrate to form a film. When preparing silver-coated copper materials, silver is used as the target material and is deposited on the surface of copper powder by sputtering. Since the sputtering object is not a bulk or plate-like material, additional means are required to process the copper powder during preparation in order to allow the silver atoms to be evenly deposited on the surface of the copper powder, resulting in complex equipment and low production efficiency.

Summary of the invention

Technical problem solved by the invention: The purpose of the invention is to provide a method for preparing a silver-coated copper composite powder with low cost, simple operation and good repeatability. The composite powder has good dispersibility and uniform size distribution, and the silver layer coated on the surface of the copper powder is complete and dense, and has good electrical conductivity and strong high-temperature oxidation resistance.

To achieve the above object, the technical solution of the present invention is:

A preparation method for synthesizing core/shell type silver-coated copper powder based on atomization drying and heat treatment process, the preparation method is based on the principle of heating and decomposing silver-containing compounds, firstly, pre-treating the copper powder raw material to remove its surface oxides and organic impurities; then, preparing a silver salt complex solution, mixing it with the copper powder raw material to obtain a uniform liquid, and then atomizing and drying the liquid, so that the silver salt complex is uniformly coated on the surface of the copper powder; finally, heat-treating the coated product after atomization and drying, so that silver is decomposed and precipitated from the surface of the copper powder, and obtaining a core/shell type silver-coated copper composite powder material. Specifically comprising the following steps:

1. Pretreatment of copper powder raw materials

Step (1) adding copper powder to a dilute sodium carbonate solution and ultrasonically cleaning the solution to obtain an alkaline solution containing copper powder; washing the alkaline solution containing copper powder after ultrasonication with deionized water at room temperature to obtain copper powder washed with deionized water;

Step (2) adding the copper powder washed with deionized water into a dilute hydrochloric acid solution, and then ultrasonically washing it to obtain acid-washed copper powder; washing the dilute hydrochloric acid solution containing the copper powder after ultrasonication with deionized water at room temperature to obtain deionized water-washed copper powder;

Step (3) adding the copper powder washed with deionized water into anhydrous ethanol for ultrasonic treatment to obtain an ethanol solution containing copper powder after ultrasonic treatment; drying the ethanol in the ethanol solution containing copper powder after ultrasonic treatment in a drying oven at 50° C. to obtain dry copper powder to be coated;

2. Prepare the liquid

Step (4) sequentially adding the complexing agent, the silver salt and the additive into deionized water and mixing and stirring to obtain a silver salt complexing solution;

Step (5) adding the copper powder to be coated obtained in step (3) into the silver salt complex solution of step (4) and stirring evenly to obtain a uniformly mixed feed solution;

3. Preparation of coated powder

Step (6) using an atomizing dryer to atomize and dry the liquid in step (5) under suitable process parameters such as drying temperature, feed rate and drying atmosphere to obtain silver salt-coated copper powder;

Step (7) uses a heat treatment furnace to perform thermal decomposition treatment on the solid product in step (6) in an inert atmosphere to obtain silver-coated copper powder, and collects the product.

in,

The preparation method of the copper powder in step (1) can be one of a melt atomization method, a chemical reduction method, a DC arc plasma method, etc.; the average particle size of the copper powder is 0.1 μm to 1 μm; 10 ml to 20 ml of dilute sodium carbonate solution is added for every 1 g of copper powder;

In step (2), 10 ml to 20 ml of dilute hydrochloric acid solution is added for every 1 g of copper powder;

In step (3), 5 ml to 8 ml of anhydrous ethanol is added for every 1 g of copper powder;

In step (4), the complexing agent is at least one of organic substances such as polyvinyl pyrrolidone, dicyandiamide, ethylenediaminetetraacetic acid, and aminoacetic acid; the additive is at least one of organic substances such as ethanol, polyethylene glycol 2000, and polyvinyl alcohol; the silver salt is at least one of silver sulfate, silver nitrate, silver acetate, and silver chloride; the mass ratio of the complexing agent, the silver salt, and the additive is 2:1:(0.02-10); the mass ratio of the silver content in the silver salt to the copper powder is (0.2-1):1.

In step (5), 1 g of the copper powder to be coated is added to every 500 mL of the silver salt complex solution.

The atomizing dryer in step (6) is one of an air flow atomizing dryer, an ultrasonic atomizing dryer, and a centrifugal atomizing dryer; the drying temperature is 110° C. to 160° C.; the feed rate is 5 ml/min to 10 ml/min; the drying atmosphere is one of air and nitrogen;

The heat treatment temperature in step (7) is 200°C to 600°C; the heat treatment time is 30min to 120min; and the heat treatment atmosphere is one of vacuum and nitrogen.

The working principle and innovation of the present invention are:

The existing silver-coated copper powder preparation technology mainly adopts the reduction mechanism, that is, the silver salt is reduced by adding a reducing agent or using the copper powder itself. The present invention is based on the principle that silver compounds are easily decomposed by heating to precipitate silver, and adopts atomization drying granulation first, and then heating decomposition to prepare silver-coated copper powder, wherein silver is not prepared by reducing silver ions. The preparation mechanism of the atomization drying method is: the prepared feed liquid is atomized into tiny droplets by an atomizer (ultrasonic atomizer, air flow atomizer, etc.) in the atomization system, and the droplets are mixed in the carrier gas and contacted with dry hot air through a dryer to evaporate the water therein, leaving the solute in the solution. The moisture evaporation of the droplets during the drying process is roughly divided into a constant speed drying stage and a decreasing speed drying stage. The evaporation process in the constant speed drying stage occurs on the surface of the particles, and the evaporation rate is controlled by the diffusion rate of the steam through the surrounding air film. The main driving force is determined by the temperature difference between the surrounding air and the particles, and the particle temperature is not higher than the adiabatic saturation temperature of the inlet air. In this stage, the diffusion rate of water through the particles is greater than or equal to the evaporation rate. When the diffusion rate of water through the particles cannot maintain the saturation of the particle surface, the diffusion rate becomes the controlling factor, and the process enters the deceleration stage. In this stage, the evaporation process occurs on a certain plane within the surface, and at the same time, the particle temperature begins to rise above the adiabatic saturation temperature of the air at the inlet and approaches the ambient air temperature. After completing these two processes in a very short time, most of the water in the droplets has been dried, and the non-volatile solutes originally dissolved in water have been precipitated. When there are solid particles in the droplets, the solutes are easily precipitated on the solid surface. Finally, the atomized and dried product is heated above the decomposition temperature to obtain the required coating on the surface of the solid particles.

In the present invention, the silver salt and the complexing agent are complexed and then evenly dispersed in water with the copper powder. Since no reducing agent is added and the silver ions are complexed, the reduction reaction and replacement reaction of the silver ions and copper are largely suppressed, so that the feed liquid can exist stably. The feed liquid is atomized into fine droplets by an atomizer and then flows through a dryer. After undergoing two drying processes, the solutes such as the silver salt complex in the solution gradually precipitate on the surface of the copper powder as the water evaporates to form a coating film, and then the silver is decomposed from the complex by heat treatment to obtain a silver-coated copper powder. The present invention is the first to try to use a combination of atomization drying and heat treatment, and atomization drying is used to evenly coat the silver-containing layer on the surface of the copper powder, and then decompose to obtain a copper-based composite powder with a silver coating layer. The present invention does not add an additional reducing agent to the solution, simplifies the composition of the solution, weakens the tendency of silver to spontaneously nucleate and grow in the solution, and at the same time, the coated composite powder has good dispersibility and a narrow particle size distribution. Provides a new path for subsequent coating of other coatings that are prone to chemical reactions.

The beneficial effects of the present invention are:

(1) Based on the principle that silver compounds can be easily decomposed to separate silver, the present invention provides a preparation method for synthesizing silver-coated copper powder by combining atomization drying with heat treatment decomposition. The required equipment can be scaled up, the raw materials are economical and environmentally friendly, and the production cost is low. The content of the silver coating layer of the synthesized silver-coated copper powder can be controlled by adjusting the amount of silver salt used, and the degree of agglomeration is low.

(2) Due to the characteristics of atomization drying, all silver-containing substances in the solution will be dried out, making the utilization rate of silver element very high and saving costs. The coating layer after drying is complete and the coating surface is smooth, and the dried product has good dispersibility and fluidity.

(3) The present invention does not add additional reducing agents, reduces the use of raw materials, simplifies the solution composition, and makes the solution easier to use and preserve during the production process.

(4) The present invention can be extended to coatings that can react with the substrate or that are not stable enough in nature, thereby reducing the loss of substrate particles and the coating and ensuring the integrity of the coating.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a preparation flow chart of the present invention;

FIG2 is an XRD spectrum of the silver salt-coated copper powder obtained after atomization drying and the silver-coated copper powder obtained after heat treatment in the preparation process of Example 1;

FIG3 is a thermogravimetric and heat flow curve of the silver salt-coated copper powder obtained after atomization drying in the preparation process of Example 1 under a nitrogen atmosphere;

FIG4 is a thermogravimetric curve of the silver-coated copper powder prepared in Example 1 under air atmosphere;

FIG5 is a SEM photo of the silver-coated copper powder prepared in Example 1 and its EDS element distribution diagram;

FIG6 is a SEM image of the silver-coated copper powder prepared in Example 2 and its EDS element distribution diagram;

FIG7 is a SEM image of the silver-coated copper powder prepared in Example 3 and its EDS element distribution diagram;

FIG8 is a SEM photograph of the copper-silver composite powder prepared in Comparative Example 1.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Embodiment 1:

(1) adding 1 g of copper powder with an average particle size of 1 μm to 10 ml of a sodium carbonate solution with a mass concentration of 5%, and ultrasonically cleaning the solution for 5 minutes to obtain a sodium carbonate solution containing copper powder; washing the alkaline solution containing the copper powder after ultrasonication with deionized water twice at room temperature to obtain copper powder washed with deionized water;

(2) adding the copper powder washed with deionized water into 10 ml of a 5% diluted hydrochloric acid solution, and then ultrasonically cleaning it for 6 minutes to obtain acid-washed copper powder; washing the solution containing the copper powder after ultrasonic cleaning twice with deionized water at room temperature to obtain deionized water-washed copper powder;

(3) adding the copper powder washed with deionized water to 5 ml of anhydrous ethanol and subjecting it to ultrasonic treatment for 5 minutes to obtain an ethanol solution containing copper powder after ultrasonic treatment; drying the ethanol in the ethanol solution containing copper powder after ultrasonic treatment in a drying oven at 50° C. to obtain dry copper powder to be coated;

(4) adding 1 g of polyvinyl pyrrolidone, 0.6 g of silver nitrate, and 10 g of ethanol to 500 ml of deionized water, mixing and stirring to obtain a silver nitrate complex solution;

(5) adding the copper powder obtained in step (3) to the silver nitrate complex solution in step (4) and stirring evenly to obtain a uniformly mixed liquid;

(6) using an air flow atomizing dryer to atomize and dry the liquid in step (5) at a feed rate of 5 ml/min and a drying temperature of 110° C. to obtain a silver salt-coated copper powder;

(7) Using a tubular furnace, the solid product in step (6) was heated at 600° C. for 30 min under a nitrogen atmosphere to obtain silver-coated copper powder, and the product was collected.

Example 2

(1) adding 1 g of copper powder with an average particle size of 1 μm to 15 ml of a sodium carbonate solution with a mass concentration of 5%, and ultrasonically cleaning the solution for 5 minutes to obtain a sodium carbonate solution containing copper powder; washing the sodium carbonate solution containing copper powder after ultrasonication with deionized water twice at room temperature to obtain copper powder washed with deionized water;

(2) adding the copper powder washed with deionized water into 15 ml of a 5% diluted hydrochloric acid solution, and then ultrasonically cleaning it for 6 minutes to obtain acid-washed copper powder; washing the solution containing the copper powder after ultrasonication with deionized water twice at room temperature to obtain copper powder washed with deionized water;

(3) adding the copper powder washed with deionized water to 6 ml of anhydrous ethanol and subjecting it to ultrasonic treatment for 5 minutes to obtain an ethanol solution containing copper powder after ultrasonic treatment; drying the ethanol in the ethanol solution containing copper powder after ultrasonic treatment in a drying oven at 50° C. to obtain dry copper powder to be coated;

(4) adding 0.8 g of ethylenediaminetetraacetic acid, 0.4 g of silver acetate, and 0.2 g of polyethylene glycol 2000 to 500 ml of deionized water in sequence, mixing and stirring to obtain a silver acetate complex solution;

(5) adding the copper powder obtained in step (3) to the silver acetate complex solution in step (4) and stirring evenly to obtain a uniformly mixed liquid;

(6) using an ultrasonic atomizing dryer to atomize and dry the liquid in step (5) at a feed rate of 7.5 ml/min at a drying temperature of 140° C. in an air atmosphere to obtain a silver salt-coated copper powder;

(7) Using a tubular furnace, the solid product in step (6) was heated at 400° C. for 60 min under a nitrogen atmosphere to obtain silver-coated copper powder, and the product was collected.

Example 3

(1) adding 1 g of copper powder having an average particle size of 0.5 μm to 20 ml of a sodium carbonate solution having a mass concentration of 5%, and ultrasonically cleaning the solution for 5 minutes to obtain a sodium carbonate solution containing copper powder; washing the sodium carbonate solution containing copper powder after ultrasonication with deionized water twice at room temperature to obtain copper powder washed with deionized water;

(2) adding the copper powder washed with deionized water into 20 ml of a 5% diluted hydrochloric acid solution, and then ultrasonically cleaning it for 6 minutes to obtain acid-washed copper powder; washing the solution containing the copper powder after ultrasonication with deionized water twice at room temperature to obtain copper powder washed with deionized water;

(3) adding the copper powder washed with deionized water into 8 ml of anhydrous ethanol and subjecting it to ultrasonic treatment for 5 minutes to obtain an ethanol solution containing copper powder after ultrasonic treatment; drying the ethanol in the ethanol solution containing copper powder after ultrasonic treatment in a drying oven at 50° C. to obtain dry copper powder to be coated;

(4) adding 0.6 g of aminoacetic acid, 0.2 g of silver sulfate, and 0.02 g of polyvinyl alcohol to 500 ml of deionized water in sequence, mixing and stirring to obtain a silver sulfate complex solution;

(5) adding the copper powder obtained in step (3) to the silver sulfate complex solution in step (4) and stirring evenly to obtain a uniformly mixed liquid;

(6) using a centrifugal atomizing dryer to atomize and dry the liquid in step (5) at a feed rate of 10 ml/min at a drying temperature of 160° C. in a nitrogen atmosphere to obtain a silver salt-coated copper powder;

(7) Using a tube furnace, the solid product in step (6) is kept warm at 200° C. in a vacuum atmosphere for 120 min to obtain silver-coated copper powder, and the product is collected.

Example 4

(1) adding 1 g of copper powder having an average particle size of 0.1 μm to 10 ml of a sodium carbonate solution having a mass concentration of 5%, and ultrasonically cleaning the solution for 5 minutes to obtain a sodium carbonate solution containing copper powder; washing the sodium carbonate solution containing copper powder after ultrasonic cleaning with deionized water twice at room temperature to obtain copper powder washed with deionized water;

(2) adding the copper powder washed with deionized water into 10 ml of a 5% diluted hydrochloric acid solution, and then ultrasonically cleaning it for 6 minutes to obtain acid-washed copper powder; washing the solution containing the copper powder after ultrasonic cleaning twice with deionized water at room temperature to obtain deionized water-washed copper powder;

(3) adding the copper powder washed with deionized water into 8 ml of anhydrous ethanol and subjecting it to ultrasonic treatment for 5 minutes to obtain an ethanol solution containing copper powder after ultrasonic treatment; drying the ethanol in the ethanol solution containing copper powder after ultrasonic treatment in a drying oven at 50° C. to obtain dry copper powder to be coated;

(4) adding 0.6 g of dicyandiamide, 0.4 g of silver chloride, and 0.02 g of polyvinyl alcohol to 500 ml of deionized water in sequence, mixing and stirring to obtain a silver chloride complex solution;

(5) adding the copper powder obtained in step (3) to the silver chloride complex solution in step (4) and stirring evenly to obtain a uniformly mixed feed solution;

(6) using an air flow atomizing dryer to atomize and dry the liquid in step (5) at a feed rate of 10 ml/min at a drying temperature of 160° C. in a nitrogen atmosphere to obtain a silver salt-coated copper powder;

(7) Using a tube furnace, the solid product in step (6) is kept warm at 200° C. in a vacuum atmosphere for 120 min to obtain silver-coated copper powder, and the product is collected.

Comparative Example 1

(1) adding 1 g of copper powder with an average particle size of 1 μm to 10 ml of a sodium carbonate solution with a mass concentration of 5%, and ultrasonically cleaning the solution for 5 minutes to obtain a sodium carbonate solution containing copper powder; washing the alkaline solution containing the copper powder after ultrasonication with deionized water twice at room temperature to obtain copper powder washed with deionized water;

(2) adding the copper powder washed with deionized water into 10 ml of a 5% diluted hydrochloric acid solution, and then ultrasonically cleaning it for 6 minutes to obtain acid-washed copper powder; washing the solution containing the copper powder after ultrasonic cleaning twice with deionized water at room temperature to obtain deionized water-washed copper powder;

(3) adding the copper powder washed with deionized water to 5 ml of anhydrous ethanol and subjecting it to ultrasonic treatment for 5 minutes to obtain an ethanol solution containing copper powder after ultrasonic treatment; drying the ethanol in the ethanol solution containing copper powder after ultrasonic treatment in a drying oven at 50° C. to obtain dry copper powder to be coated;

(4) adding 1 g of polyvinyl pyrrolidone, 0.6 g of silver nitrate, and 10 g of ethanol to 500 ml of deionized water, mixing and stirring to obtain a silver nitrate complex solution;

(5) adding the copper powder obtained in step (3) to the silver nitrate complex solution in step (4), stirring and reacting for 2 hours to obtain a uniformly mixed liquid;

(6) filtering the liquid in step (5), washing and drying the product to obtain a copper-silver composite powder.

Figure 1 shows the X-ray diffraction pattern of the silver salt-coated copper powder before heat treatment in Example 1 and the X-ray diffraction pattern of the silver-coated copper powder after heat treatment. After atomization and drying, the silver salt complex coating layer does not show obvious diffraction peaks, nor does it show other impurity peaks, indicating that the atomization and drying process is completely different from other preparation methods. The main diffraction peaks of silver all appear after heat treatment, and their intensity is greatly enhanced compared with that before heat treatment, which means that the silver complex decomposes and precipitates silver during the heat treatment stage; Figure 4 shows the thermogravimetric curve of the silver-coated copper powder prepared in Example 1. After heating to 800°C in an air atmosphere, the oxidation weight gain is only 13.04%, and the oxidation starting point is about 318°C, indicating that it has good antioxidant properties. The morphology and coating effect of the silver-coated copper powders of Examples 1-3 and Comparative Example 1 were observed using a scanning electron microscope, and the corresponding EDS element distribution diagrams were also given, as shown in Figures 5-8.

From the surface morphology and energy spectrum element distribution diagram of the powder in each embodiment, it can be seen that the silver element is evenly distributed on the surface of the copper powder, and has a good coating effect. In Comparative Example 1, since no reducing agent is added, the silver ions cannot be reduced on the surface of the copper powder to form a coating layer; most of the silver ions are filtered out with the solution, and a small part of the solution remains on the surface of the copper powder, causing the silver ions to spontaneously nucleate and grow, thus eventually forming free silver or adhering to the surface of the copper powder, resulting in poor coating effect.

The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims (10)

1. A preparation method for synthesizing core/shell type silver-coated copper powder based on atomization drying and heat treatment process, characterized in that the preparation method first pre-treats the copper powder raw material; then, prepares a silver salt complex solution, mixes it with the copper powder raw material to obtain a uniform slurry, and then atomizes and dries the slurry so that the silver salt complex is uniformly coated on the surface of the copper powder; finally, the coated product after atomization drying is heat-treated to obtain a core/shell type silver-coated copper composite powder material. 2. The method for preparing a core/shell type silver-coated copper powder based on atomization drying and heat treatment process according to claim 1, characterized in that it comprises the following steps: The first step is to pre-treat the copper powder raw materials Step (1) adding copper powder to a dilute sodium carbonate solution and ultrasonically cleaning the solution to obtain an alkaline solution containing copper powder; washing the alkaline solution containing copper powder with deionized water to obtain copper powder washed with deionized water; Step (2) adding the copper powder washed with deionized water into a dilute hydrochloric acid solution, and ultrasonically washing the copper powder to obtain the acid-washed copper powder; washing the dilute hydrochloric acid solution containing the copper powder with deionized water to obtain the copper powder washed with deionized water; Step (3) adding the copper powder washed with deionized water into anhydrous ethanol for ultrasonic treatment to obtain an ethanol solution containing copper powder after ultrasonic treatment, and drying to obtain dry copper powder to be coated; Step 2: Prepare the liquid Step (4) sequentially adding the complexing agent, the silver salt and the additive into deionized water and mixing and stirring to obtain a silver salt complexing solution; Step (5) adding the copper powder to be coated obtained in step (3) into the silver salt complex solution of step (4) and stirring evenly to obtain a uniformly mixed feed solution; Step 3: Preparation of coated powder Step (6) using an atomizing dryer to atomize and dry the liquid in step (5) at a suitable drying temperature, feed rate and drying atmosphere to obtain a silver salt-coated copper powder; Step (7) uses a heat treatment furnace to perform thermal decomposition treatment on the solid product in step (6) in an inert atmosphere to obtain silver-coated copper powder, and collects the product; the heat treatment temperature is 200° C. to 600° C.; the heat treatment time is 30 min to 120 min. 3. The method for preparing core/shell type silver-coated copper powder based on atomization drying and heat treatment process according to claim 2 is characterized in that the average particle size of the copper powder in step (1) is 0.1 μm to 1 μm. 4. The method for preparing a core/shell type silver-coated copper powder based on atomization drying and heat treatment process according to claim 2, characterized in that in step (1), 10 ml to 20 ml of dilute sodium carbonate solution is added to every 1 g of copper powder; in step (2), 10 ml to 20 ml of dilute hydrochloric acid solution is added to every 1 g of copper powder; in step (3), 5 ml to 8 ml of anhydrous ethanol is added to every 1 g of copper powder. 5. A method for preparing a core/shell type silver-coated copper powder based on atomization drying and heat treatment process according to claim 2, characterized in that the complexing agent in step (4) is at least one of polyvinyl pyrrolidone, dicyandiamide, ethylenediaminetetraacetic acid, aminoacetic acid and other organic substances; the additive is at least one of ethanol, polyethylene glycol 2000, polyvinyl alcohol and other organic substances; the silver salt is at least one of silver sulfate, silver nitrate, silver acetate, and silver chloride; the mass ratio of the complexing agent, silver salt, and additive is 2:1:(0.02~10); the mass ratio of the silver content in the silver salt to the copper powder is (0.2~1):1. 6. The method for preparing a core/shell type silver-coated copper powder based on atomization drying and heat treatment process according to claim 2, characterized in that in step (5), 1 g of the copper powder to be coated is added to every 500 mL of silver salt complex liquid. 7. The method for preparing a core/shell type silver-coated copper powder based on atomization drying and heat treatment process according to claim 2, characterized in that in step (6), the atomization dryer is one of an air flow atomization dryer, an ultrasonic atomization dryer, and a centrifugal atomization dryer. 8. The method for preparing core/shell type silver-coated copper powder based on atomization drying and heat treatment process according to claim 2 is characterized in that, in step (6), the drying temperature is 110°C to 160°C; the feed rate is 5ml/min to 10ml/min; and the drying atmosphere is one of air and nitrogen. 9. The method for preparing a core/shell type silver-coated copper powder based on atomization drying and heat treatment process according to claim 2, characterized in that in step (7), the heat treatment atmosphere is one of vacuum and nitrogen. 10. A method for synthesizing core/shell type silver-coated copper powder based on atomization drying and heat treatment process, characterized in that the core/shell type silver-coated copper powder is obtained by the preparation method described in any one of claims 1 to 9.