A method for preparing silver-coated copper core-shell composite particles

Abstract

The application discloses a preparation method of silver-coated copper core-shell composite particles. The method comprises the following steps: adding a dispersing agent, a pH regulator, a film forming agent and a buffer into a copper solution in a required proportion, mixing uniformly at room temperature to obtain a mixed solution, adding the mixed solution into an electrolytic device, immersing silver wires and carbon rods into the mixed solution, connecting the silver wires and the carbon rods with a positive electrode and a negative electrode of a direct current power supply respectively, starting electroplating while stirring, and performing centrifugation and washing on the electroplated mixed solution in sequence to obtain the silver-coated copper core-shell composite particles. The silver-coated copper core-shell composite particles prepared by the method have a dense and uniform plating layer and high conductivity, and can be used as conductive paste, EMI shielding material, heat conducting material and catalyst for degrading some specific environmental pollutants.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite material preparation, and particularly relates to a preparation method of silver-coated copper core-shell composite particles, which is suitable for making the plating layer surface smooth and dense and improving the conductivity of the prepared silver-coated copper core-shell composite particles. BACKGROUND

[0002] At present, the conductive paste mainly uses silver as the conductive filler, and the silver paste has the characteristics of high precision, good reliability and high conductivity. However, silver is a noble metal material, and the production cost of the paste is increased due to the high price of silver, and there is a silver migration phenomenon. Copper, as a base metal, has similar conductivity to silver, is environmentally friendly, has low production cost, and is simple to process, but has problems such as easy oxidation and conductivity decrease after oxidation.

[0003] Silver-coated copper powder is a new type of conductive functional material, which has good crystal structure, array property and mechanical property. The silver-coated copper powder has the physicochemical properties of copper and the high conductivity of silver, and has many advantages such as good oxidation resistance, low silver ion migration and low production cost, and has a wide application market in products such as computers, integrated circuits, electrical equipment, electronic medical devices and electronic instruments.

[0004] At present, the most common preparation method of silver-coated copper powder is chemical plating. At present, silver nitrate solution or silver ammonia solution is used to react with copper powder, and silver ions in the solution are reduced by copper powder. Although this method is simple, the plating layer is loose and uneven, and the prepared silver-coated copper powder has poor conductivity. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned problems existing in the prior art, and to provide a preparation method of silver-coated copper core-shell composite particles with smooth and dense plating layer surface and good conductivity.

[0006] In order to achieve the above purpose, the present application provides the following technical scheme:

[0007] A preparation method of silver-coated copper core-shell composite particles, which is carried out in the following steps in sequence:

[0008] S1, dispersing agent, pH adjusting agent, film forming agent and buffer are added into the copper solution in the required proportion, and mixed uniformly at room temperature to obtain a mixed solution;

[0009] S2, the mixed solution is first added to an electrolytic device, then silver wire and carbon rod are immersed in the mixed solution, and the silver wire and carbon rod are connected to the positive and negative electrodes of a direct current power supply respectively, and then the electroplating is started while stirring;

[0010] S3, the mixed solution after electroplating is sequentially subjected to centrifugation and washing to obtain silver-coated copper core-shell composite particles.

[0011] In step S1, the dispersant, pH regulator, film former, buffer are polyvinylpyrrolidone solution, ammonia, potassium sodium tartrate solution, ammonium sulfate solution respectively.

[0012] The volume ratio of the copper solution, dispersant, pH regulator, film former, buffer is 0.1-1:0.2-1:0.1-1:0.02-1:0.06-0.6.

[0013] The concentration of the copper solution, dispersant, pH regulator, film former, buffer is 0.1-1mmol / mL, 10-55mg / mL, 0.1-1mol / L, 10-50mg / mL, 0.1-1mol / L respectively.

[0014] The concentration of the copper solution, dispersant, pH regulator, film former, buffer is 0.5mmol / mL, 50mg / mL, 0.1mol / L, 10mg / mL, 0.1mol / L respectively.

[0015] The copper solution is a mixture of copper particles and water, the particle size of the copper particles is 0.5-5μm, and the water is deionized water or ultrapure water.

[0016] In step S2, the electroplating time is 3-12min, and the electroplating current is 0.001-0.01A.

[0017] In step S2, the electroplating time is 5min, and the electroplating current is 0.001A.

[0018] In step S3, the operation times of centrifugation and washing are at least twice.

[0019] In step S1, the room temperature is specifically 20-30℃.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] In the preparation method of the silver-coated copper core-shell composite particles, the dispersant, pH regulator, film former and buffer are sequentially added to the copper solution in the required proportion, and mixed uniformly at room temperature to obtain a mixed solution. Then the mixed solution is added to an electrolytic device, silver wire and carbon rod are immersed in the mixed solution, and the silver wire and carbon rod are connected to the positive and negative poles of a direct current power supply respectively. The electroplating is started while stirring. Finally, the electroplated mixed solution is sequentially subjected to centrifugation and washing to obtain silver-coated copper core-shell composite particles. The present method uses electroplating combined with a special electroplating solution, so that the finally prepared silver-coated copper core-shell composite particles not only have a dense and uniform plating layer, but also have high conductivity. The silver-coated copper core-shell composite particles can be used as conductive paste, EMI shielding material, heat conducting material and catalyst for degrading certain specific environmental pollutants. Attached Figure Description

[0022] Figure 1 This is a SEM image of the silver-coated copper core-shell composite particles prepared in Example 1. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments.

[0024] A method for preparing silver-coated copper core-shell composite particles, wherein the preparation method is carried out in sequence according to the following steps:

[0025] S1. Add dispersant, pH adjuster, film-forming agent and buffer to copper solution in the required proportions, mix well at room temperature to obtain a mixed solution;

[0026] S2. First, add the mixed solution to the electrolysis device, then immerse the silver wire and carbon rod in the mixed solution, and connect the silver wire and carbon rod to the positive and negative terminals of the DC power supply respectively, and start electroplating while stirring.

[0027] S3. The electroplated mixed solution is centrifuged and washed sequentially to obtain silver-coated copper core-shell composite particles.

[0028] In step S1, the dispersant, pH adjuster, film-forming agent, and buffer are respectively polyvinylpyrrolidone solution, ammonia, potassium sodium tartrate solution, and ammonium sulfate solution.

[0029] The volume ratio of the copper solution, dispersant, pH adjuster, film-forming agent, and buffer is 0.1-1:0.2-1:0.1-1:0.02-1:0.06-0.6.

[0030] The concentrations of the copper solution, dispersant, pH adjuster, film-forming agent, and buffer are 0.1-1 mmol / mL, 10-55 mg / mL, 0.1-1 mol / L, 10-50 mg / mL, and 0.1-1 mol / L, respectively.

[0031] The concentrations of the copper solution, dispersant, pH adjuster, film-forming agent, and buffer are 0.5 mmol / mL, 50 mg / mL, 0.1 mol / L, 10 mg / mL, and 0.1 mol / L, respectively.

[0032] The copper solution is a mixture of copper particles and water, wherein the copper particles have a particle size of 0.5-5 μm, and the water is deionized water or ultrapure water.

[0033] In step S2, the electroplating time is 3-12 minutes and the electroplating current is 0.001-0.01A.

[0034] The plating time in step S2 is 5 min, and the plating current is 0.001 A.

[0035] In step S3, the number of centrifugation and washing operations is at least twice.

[0036] In step S1, the room temperature is specifically 20-30 DEG C.

[0037] The principle of the present application is described as follows:

[0038] In the plating solution of the method, polyvinylpyrrolidone is used as a dispersant and stabilizer, which can form an adsorption layer on the surface of copper particles, increase the surface charge of the copper particles, and make the copper particles far away from each other due to electrostatic repulsion, so that the system is uniform and not easy to precipitate, thereby enabling each copper particle to be coated with a silver plating layer in the plating process. In addition, ammonium sulfate is used as a conductive salt and buffer in the system, which improves the conductivity of the system and adjusts the pH value of the solution. Furthermore, ammonia provides an alkaline environment for the system, which is conducive to the coordination of potassium sodium tartrate and copper particles to form a soluble complex, providing favorable conditions for the uniform and dense coating of silver on the surface of copper particles. The specific principle is that the tartrate contains two hydroxyl groups and two carboxyl groups, the carboxyl oxygen atoms and the adjacent hydroxyl oxygen atoms are chelated and coordinated with copper particles to form two stable five-membered chelate rings. Subsequently, silver ions generated by electrolysis are adsorbed onto the complex formed by potassium sodium tartrate and copper particles through static and coordination interactions. Finally, under the reducing action of the double bond and hydroxyl group of potassium sodium tartrate, silver ions are reduced in situ on the surface of copper particles, thereby forming silver-coated copper composite particles with a smooth and dense surface and a core-shell structure. Moreover, since the source of silver is silver wire electrolysis (the purity of silver wire is 99.99 %), the impurities in the system are relatively small. In addition, during the reduction reaction, the electrolysis speed of silver can be controlled by adjusting the current and voltage of the direct current power supply, so that the concentration of silver ions in the solution is always maintained within a suitable range, thereby controlling the coating speed of the plating layer and making the coating more uniform. The finally obtained silver-coated copper core-shell composite particles not only have a dense and uniform plating layer, but also have high conductivity, and can be used as conductive paste, EMI shielding material, heat-conducting material, and catalyst for degrading certain specific environmental pollutants.

[0039] The overall reaction time of the method is short, only 3-12 min is needed, and the raw materials used are simple and easy to obtain. In the production process, no harmful waste gas or wastewater is generated, and no high requirements are required for the operating environment, only room temperature is needed.

[0040] Example 1:

[0041] A silver-coated copper core-shell composite particle preparation method is specifically performed according to the following steps:

[0042] S1, add dispersant, pH regulator, film former, buffer to copper solution in the required proportion, mix uniformly at room temperature 25℃ to obtain a mixed solution;

[0043] The copper solution is a mixture of copper particles and water, the particle size of the copper particles is 1 μm, the water is deionized water, the dispersant, the pH regulator, the film former and the buffer are polyvinylpyrrolidone solution, ammonia, potassium sodium tartrate solution and ammonium sulfate solution respectively, the volume ratio of the copper solution, the dispersant, the pH regulator, the film former and the buffer is 0.2:0.4:0.2:0.2:0.12, and the concentrations of the copper solution, the dispersant, the pH regulator, the film former and the buffer are 0.5 mmol / mL, 25 mg / mL, 0.5 mol / L, 25 mg / mL and 0.5 mol / L respectively.

[0044] S2, first add the mixed solution to the electrolytic device, then immerse the silver wire and the carbon rod into the mixed solution, and connect the silver wire and the carbon rod to the positive electrode and the negative electrode of the direct current power supply respectively, start the electroplating while stirring, in the electroplating process, it can be observed that the color of the mixed solution gradually changes from red to light gray, then slowly turns to gray black, which can be preliminarily judged that the silver nanoparticles are coated on the surface of the copper particles, and the mixed solution after electroplating is left for a period of time, and there are black fine particles precipitated at the bottom of the mixed solution, which are silver-coated copper core-shell composite particles;

[0045] The electroplating time is 5 min, and the electroplating current is 0.001 A, and it is calculated that the silver electrolysis amount under the condition is about 0.019 mmol.

[0046] S3, repeat centrifugation and washing twice to obtain silver-coated copper core-shell composite particles.

[0047] Example 2:

[0048] The steps are the same as those in Example 1, except that:

[0049] In step S1, the room temperature is specifically 30℃, the volume ratio of the copper solution, the dispersant, the pH regulator, the film former and the buffer is 0.1:0.2:0.1:0.02:0.06, the concentrations of the copper solution, the dispersant, the pH regulator, the film former and the buffer are 1 mmol / mL, 55 mg / mL, 1 mol / L, 50 mg / mL and 1 mol / L respectively, and the particle size of the copper particles is 0.1 μm.

[0050] In step S2, the electroplating time is 12 min, and it is calculated that the silver electrolysis amount under the condition is about 0.04 mmol.

[0051] Example 3:

[0052] The steps are the same as those in Example 1, except that:

[0053] In step S1, the room temperature is specifically 20℃, the volume ratio of the copper solution, the dispersant, the pH adjuster, the film forming agent, and the buffer is 0.5:1:0.5:1:0.6, the concentrations of the copper solution, the dispersant, the pH adjuster, the film forming agent, and the buffer are 0.1 mmol / mL, 10 mg / mL, 0.1 mol / L, 10 mg / mL, and 0.1 mol / L respectively, and the particle size of the copper particles is 3 μm.

[0054] In step S2, the electroplating time is 3 min, and it is calculated that the silver electrolysis amount under this condition is about 0.009 mmol.

[0055] Example 4:

[0056] The steps are the same as those in Example 1, except that:

[0057] In step S1, the room temperature is specifically 26℃, the volume ratio of the copper solution, the dispersant, the pH adjuster, the film forming agent, and the buffer is 1:0.5:0.2:0.3:0.06, the concentrations of the copper solution, the dispersant, the pH adjuster, the film forming agent, and the buffer are 0.1 mmol / mL, 20 mg / mL, 0.5 mol / L, 50 mg / mL, and 1 mol / L respectively, and the particle size of the copper particles is 5 μm.

[0058] In step S2, the electroplating time is 10 min, and it is calculated that the silver electrolysis amount under this condition is about 0.030 mmol.

[0059] Example 5:

[0060] The steps are the same as those in Example 1, except that:

[0061] In step S1, the room temperature is specifically 20℃, the volume ratio of the copper solution, the dispersant, the pH adjuster, the film forming agent, and the buffer is 0.5:0.5:1:0.8:0.2, the concentrations of the copper solution, the dispersant, the pH adjuster, the film forming agent, and the buffer are 0.2 mmol / mL, 20 mg / mL, 0.1 mol / L, 10 mg / mL, and 0.5 mol / L respectively, and the particle size of the copper particles is 0.5 μm.

[0062] In step S2, the electroplating time is 8 min, and the electroplating current is 0.01 A, and it is calculated that the silver electrolysis amount under this condition is about 0.08 mmol.

[0063] Performance test:

[0064] 1. The silver-coated copper core-shell composite particles prepared in Example 1 were subjected to electron microscopy scanning. The results are shown in the figure. Figure 1 ,Depend on Figure 1 It can be seen that the coating of the silver-coated copper core-shell composite particles prepared by the method described in this invention is dense and uniform.

[0065] 2. Commercially available silver-coated copper powder (purchased from Huizhou Tenghui Metal Technology Co., Ltd., model T2040) was used as Comparative Example 1, and silver-coated copper powder prepared by chemical plating was used as Comparative Example 2. The conductivity of the silver-coated copper core-shell composite particles prepared in Examples 1-3 was tested. The test results are shown in Table 1. The preparation steps of Comparative Example 2 are as follows:

[0066] A1. Take 30g of copper powder and add it to 100mL of 5% dilute sulfuric acid to remove the oxides on the surface of the copper powder. Then rinse with deionized water until the pH value is neutral. Filter out the deionized water and add the copper powder to 300mL of water. At the same time, add 3g of OP-10 and 6g of triethylenetetramine and stir thoroughly to form a plating solution.

[0067] A2. Dissolve 10.6g of silver nitrate in 100mL of water, add 3g of triethylenetetramine to form a main salt solution, and at the same time dissolve 4g of potassium sodium tartrate in 100mL of water to prepare a reducing agent solution.

[0068] A3. While stirring, add the main salt solution and reducing agent solution to the plating solution at a constant rate for 2 hours. After the reaction is complete, filter the above mixed solution, take the filter residue, rinse it with deionized water until neutral, wash it three times with ethanol, and dry it in a vacuum oven at 60°C to obtain silver-coated copper powder.

[0069] Table 1 Comparison of electrical conductivity

[0070] .

[0071] As shown in Table 1, the silver-coated copper core-shell composite particles prepared in Examples 1-3 of this invention have better electrical conductivity than comparative examples 1 and 2.

Claims

1. A method for preparing silver-coated copper core-shell composite particles, characterized in that: The preparation method is carried out in the following steps: S1. Add dispersant, pH adjuster, film-forming agent and buffer to copper solution in the required proportions, mix well at room temperature to obtain a mixed solution; S2. First, add the mixed solution to the electrolysis device, then immerse the silver wire and carbon rod in the mixed solution, and connect the silver wire and carbon rod to the positive and negative terminals of the DC power supply respectively, and start electroplating while stirring. S3. The electroplated mixed solution is centrifuged and washed sequentially to obtain silver-coated copper core-shell composite particles. In step S1, the dispersant, pH adjuster, film-forming agent, and buffer are respectively polyvinylpyrrolidone solution, ammonia water, potassium sodium tartrate solution, and ammonium sulfate solution; The electrolyzed silver ions are adsorbed onto the complex formed by potassium sodium tartrate and copper particles through static and coordination interactions. Under the reducing effect of potassium sodium tartrate, the silver ions are reduced in situ on the surface of the copper particles to form silver-coated copper core-shell composite particles. The volume ratio of the copper solution, dispersant, pH adjuster, film-forming agent, and buffer is 0.1-1:0.2-1:0.1-1:0.02-1:0.06-0.6; The concentrations of the copper solution, dispersant, pH adjuster, film-forming agent, and buffer are 0.1-1 mmol / mL, 10-55 mg / mL, 0.1-1 mol / L, 10-50 mg / mL, and 0.1-1 mol / L, respectively.

2. The method for preparing silver-coated copper core-shell composite particles according to claim 1, characterized in that: The concentrations of the copper solution, dispersant, pH adjuster, film-forming agent, and buffer are 0.5 mmol / mL, 50 mg / mL, 0.1 mol / L, 10 mg / mL, and 0.1 mol / L, respectively.

3. The method for preparing silver-coated copper core-shell composite particles according to claim 1, characterized in that: The copper solution is a mixture of copper particles and water, wherein the copper particles have a particle size of 0.5-5 μm, and the water is deionized water or ultrapure water.

4. The method for preparing silver-coated copper core-shell composite particles according to claim 1, characterized in that: In step S2, the electroplating time is 3-12 minutes and the electroplating current is 0.001-0.01A.

5. The method for preparing silver-coated copper core-shell composite particles according to claim 3, characterized in that: In step S2, the electroplating time is 5 minutes and the electroplating current is 0.001A.

6. The method for preparing silver-coated copper core-shell composite particles according to claim 1, characterized in that: In step S3, the centrifugation and washing operations are performed at least twice.

7. The method for preparing silver-coated copper core-shell composite particles according to claim 1, characterized in that: In step S1, the room temperature is specifically 20-30℃.

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