Preparation method of silver-coated copper powder

Abstract

The invention belongs to the technical field of preparation of silver-coated copper powder, and particularly relates to a preparation method of silver-coated copper powder, which comprises the following steps: (1) preparing a silver-coated copper powder seed crystal by using a replacement reaction; and (2) preparing the silver-coated copper powder by using a liquid-phase oxidation-reduction reaction. The preparation method of the silver-coated copper powder has the beneficial effects that the surface of the copper powder is coated with a layer of silver through the replacement method, then the silver-coated copper powder obtained through the replacement method serves as the seed crystal, the liquid-phase oxidation-reduction reaction of silver ions is carried out, and a compact silver layer slowly grows on the surface of the silver-coated copper powder seed crystal, so that the preparation method of the silver-coated copper powder is low in production cost, simple in process and suitable for industrial production. The thickness of the silver layer on the surface of the copper powder can be controlled, the coated silver layer is compact, the surface is smooth, the silver layer is firm and not prone to falling off, and the prepared silver-coated copper powder has excellent conductivity and thermal stability.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of silver-coated copper powder, and particularly relates to a method for preparing the silver-coated copper powder. Background Art

[0002] Silver-coated copper powder, as a new type of core-shell structure multifunctional powder material, effectively combines the excellent metallic properties of silver and copper. It not only solves the problem of silver migration, but also reduces the cost of slurry while maintaining the high conductivity, oxidation resistance and thermal stability of silver.

[0003] Existing methods for preparing silver-coated copper powder include mixed ball milling, melt atomization, chemical plating, reduction and replacement. The ball milling method requires inert gas protection to prepare silver-coated copper powder, and the production cost is relatively high; the melt atomization method can prepare silver-coated copper powder with different silver contents, but the process is complicated, so the production cost is high; the silver-coated copper powder prepared by the chemical plating method has low cost, but the output of the silver-coated copper powder is low, and the product quality is unstable; the silver-coated copper powder prepared by the reduction method has uniform thickness, but due to the fast reaction speed, the reaction process is difficult to control; the replacement method has a simple process for preparing silver-coated copper powder, and a high silver conversion rate. The prepared silver-coated copper powder has excellent conductivity, but the coating is uneven and discontinuous. If the requirements for a dense silver layer are to be achieved, multiple replacements are required. Therefore, a method for preparing silver-coated copper powder with low production cost, simple process, and a continuous and dense silver layer is particularly important. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems and provide a method for preparing silver-coated copper powder.

[0005] The present invention relates to a method for preparing silver-coated copper powder, comprising the following steps: (1) Preparation of silver-coated copper powder seeds by substitution reaction: The spherical copper powder is dispersed in the dispersant solution, and then fuming nitric acid is added dropwise under stirring, and the reaction is stirred for 5 minutes after the addition is completed, and finally the silver nitrate solution is added dropwise, and the reaction is stirred for 1 minute after the addition is completed, and the reaction solution is subjected to sedimentation and solid-liquid separation, and the separated solid is washed with purified water to obtain silver-coated copper powder seed crystals; (2) Preparation of silver-coated copper powder using liquid phase redox reaction: The silver-coated copper powder seed crystals prepared in step (1) are dispersed in a dispersant solution, and then a silver nitrate solution and a reducing agent solution are added in parallel. After the silver nitrate solution and the reducing agent solution are added dropwise at the same time, a surfactant is added, and then a pH adjuster is added to adjust the pH value of the reaction solution. The reaction is stirred for 10 minutes. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with ethanol and then dried to obtain the silver-coated copper powder.

[0006] Preferably, in step (1), the mass concentration of the dispersant solution is 60-100 g / L, the solvent of the dispersant solution is a mixture of ethanol and water, and the mass ratio of ethanol to water is 2:1.

[0007] Preferably, in step (1), the dispersant is one or two of polyvinyl pyrrolidone, polyethylene glycol, gelatin and gum arabic, and the mass of the dispersant is 1 to 3 times the mass of the copper powder.

[0008] Preferably, in step (1), the mass of the fuming nitric acid is 10% to 30% of the mass of the copper powder.

[0009] Preferably, in step (1), the molar concentration of the silver nitrate solution is 0.2 to 2 mol / L, and the mass of silver in the silver nitrate solution is 1% to 10% of the mass of the copper powder.

[0010] Preferably, in step (2), the mass concentration of the dispersant solution is 60-100 g / L, the dispersant is one or two of polyvinyl pyrrolidone, polyethylene glycol, gelatin and gum arabic, and the mass of the dispersant is 20%-40% of the mass of the silver-coated copper powder seed crystals.

[0011] Preferably, in step (2), the molar concentration of the silver nitrate solution is 0.2 to 3 mol / L, and the mass of the corresponding silver in the silver nitrate solution is 5% to 40% of the mass of the copper powder.

[0012] Preferably, in step (2), the molar concentration of the reducing agent solution is 0.1 to 5 mol / L, the reducing agent is ascorbic acid, and the molar ratio of the ascorbic acid to the silver nitrate is 0.5 to 1:1.

[0013] Preferably, in step (2), the surfactant is at least one of oleic acid, sodium oleate, palmitic acid, caprylic acid and stearic acid, and the mass of the surfactant is 1% to 5% of the theoretical mass of the generated silver-coated copper powder.

[0014] Preferably, in step (2), a pH adjuster is added to adjust the pH value of the reaction solution to 5-6.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are: Compared with the prior art, the method for preparing the silver-coated copper powder of the present invention first coats a layer of silver on the surface of the copper powder by a replacement method, and then uses the silver-coated copper powder obtained by the replacement method as a seed to carry out a liquid-phase redox reaction of silver ions, and slowly grows a dense silver layer on the surface of the silver-coated copper powder seed. Thus, the method for preparing the silver-coated copper powder has low production cost and simple process, and not only can the thickness of the silver layer on the surface of the copper powder be controlled, but also the coated silver layer is dense and has a smooth surface, and the silver layer is firm and not easy to fall off, and the prepared silver-coated copper powder has excellent electrical conductivity and thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the following briefly introduces the drawings required for describing the embodiment. Figure 1 Thermogravimetric curve of the silver-coated copper powder provided in Example 1; Figure 2 This is a scanning electron microscope image of the copper powder provided in Example 1; Figure 3 A scanning electron microscope image of the silver-coated copper powder provided in Example 1; Figure 4 A scanning electron microscope image of the silver-coated copper powder provided in Example 2; Figure 5 This is a scanning electron microscope image of the silver-coated copper powder provided in Example 3; Figure 6 A scanning electron microscope image of the silver-coated copper powder provided in Example 4; Figure 7 The scanning electron microscope image of the silver-coated copper powder provided in Comparative Example 1; Figure 8 This is a scanning electron microscope image of the silver-coated copper powder provided in Comparative Example 2. DETAILED DESCRIPTION

[0017] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0018] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0019] Example 1 A method for preparing silver-coated copper powder comprises the following steps: (1) Preparation of silver-coated copper powder seeds by substitution reaction: 35g of polyvinyl pyrrolidone K30 was dissolved in a mixed solution of 300g of ethanol and 150g of water, and stirring was started at a speed of 1500rmp. 100g of spherical copper powder with a particle size of 1μm was added. After the copper powder was evenly dispersed, 15g of fuming nitric acid was added dropwise. After the addition was completed, the mixture was stirred and reacted for 5min. Finally, a silver nitrate solution with a molar concentration of 1mol / L was added dropwise, wherein the mass of silver nitrate was 12g, and the mass of silver corresponding to the silver nitrate was 7.6% of the mass of the copper powder. After 5min, the addition was completed, and the mixture was stirred and reacted for another 1min. After the reaction solution was settled and solid-liquid separated, the separated solid was washed three times with purified water to obtain silver-coated copper powder seed crystals.

[0020] (2) Preparation of silver-coated copper powder using liquid phase redox reaction: The silver-coated copper powder seed crystals prepared in step (1) are dispersed in a polyvinyl pyrrolidone solution, wherein the polyvinyl pyrrolidone solution is prepared into a solution with a mass concentration of 75 g / L by 55 g of polyvinyl pyrrolidone, prepared into a silver nitrate solution with a molar concentration of 1 mol / L by 40 g of silver nitrate, and prepared into a reducing agent solution with a molar concentration of 1.5 mol / L by 25 g of ascorbic acid. Stirring is started at a stirring speed of 2000 rpm, and then the silver nitrate solution and the reducing agent solution are added in parallel. The silver nitrate solution and the reducing agent solution are added dropwise at the same time. The dropping time is 15 min. After the dropping is completed, oleic acid of 3% of the theoretical mass of the silver-coated copper powder is added, and then a pH adjuster is added to adjust the pH value of the reaction solution to 5. The reaction is stirred for 10 min. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with ethanol and then dried to obtain the silver-coated copper powder.

[0021] Example 2 A method for preparing silver-coated copper powder comprises the following steps: (1) Preparation of silver-coated copper powder seeds by substitution reaction: 40g of polyvinyl pyrrolidone K30 was dissolved in a mixed solution of 300g of ethanol and 150g of water, and stirring was started at a speed of 2000rmp. 100g of spherical copper powder with a particle size of 2μm was added. After the copper powder was evenly dispersed, 18g of fuming nitric acid was added dropwise. After the addition was completed, the mixture was stirred and reacted for 5min. Finally, a silver nitrate solution with a molar concentration of 1mol / L was added dropwise, wherein the mass of silver nitrate was 15g, and the mass of silver corresponding to the silver nitrate was 9.5% of the mass of the copper powder. After 5min, the addition was completed, and the mixture was stirred and reacted for another 1min. After the reaction solution was settled and solid-liquid separated, the separated solid was washed three times with purified water to obtain silver-coated copper powder seed crystals.

[0022] (2) Preparation of silver-coated copper powder using liquid phase redox reaction: The silver-coated copper powder seed crystals prepared in step (1) are dispersed in a polyvinyl pyrrolidone solution, wherein the polyvinyl pyrrolidone solution is prepared into a solution with a mass concentration of 75 g / L by 60 g of polyvinyl pyrrolidone, prepared into a silver nitrate solution with a molar concentration of 1 mol / L by 35 g of silver nitrate, and prepared into a reducing agent solution with a molar concentration of 1.5 mol / L by 22 g of ascorbic acid. Stirring is started at a stirring speed of 2500 rpm, and then the silver nitrate solution and the reducing agent solution are added in parallel. The silver nitrate solution and the reducing agent solution are added dropwise at the same time. The dropping time is 15 min. After the dropping is completed, 3% of the theoretical mass of the silver-coated copper powder is added with stearic acid, and then a pH adjuster is added to adjust the pH value of the reaction solution to 6. The reaction is stirred for 10 min. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with ethanol and then dried to obtain the silver-coated copper powder.

[0023] Example 3 A method for preparing silver-coated copper powder comprises the following steps: (1) Preparation of silver-coated copper powder seeds by substitution reaction: 45g of polyvinyl pyrrolidone K30 was dissolved in a mixed solution of 300g of ethanol and 150g of water, and stirring was started at a speed of 1800rmp. 100g of spherical copper powder with a particle size of 0.5μm was added. After the copper powder was evenly dispersed, 18g of fuming nitric acid was added dropwise. After the addition was completed, the mixture was stirred and reacted for 5min. Finally, a silver nitrate solution with a molar concentration of 1mol / L was added dropwise, wherein the mass of silver nitrate was 6.3g, and the mass of silver corresponding to the silver nitrate was 4% of the mass of the copper powder. After 5min, the addition was completed, and the mixture was stirred and reacted for another 1min. After the reaction solution was settled and solid-liquid separated, the separated solid was washed three times with purified water to obtain silver-coated copper powder seed crystals.

[0024] (2) Preparation of silver-coated copper powder using liquid phase redox reaction: The silver-coated copper powder seed crystals prepared in step (1) are dispersed in a polyvinyl pyrrolidone solution, wherein the polyvinyl pyrrolidone solution is prepared into a solution with a mass concentration of 75 g / L by 55 g of polyvinyl pyrrolidone, prepared into a silver nitrate solution with a molar concentration of 1 mol / L by 25 g of silver nitrate, and prepared into a reducing agent solution with a molar concentration of 1.5 mol / L by 16 g of ascorbic acid. Stirring is started at a stirring speed of 2200 rpm, and then the silver nitrate solution and the reducing agent solution are added in parallel. The silver nitrate solution and the reducing agent solution are added dropwise at the same time. The dropping time is 15 min. After the dropping is completed, 3% of the theoretical mass of the generated silver-coated copper powder is added with palmitic acid, and then a pH adjuster is added to adjust the pH value of the reaction solution to 5.5. The reaction is stirred for 10 min. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with ethanol and then dried to obtain the silver-coated copper powder.

[0025] Example 4 A method for preparing silver-coated copper powder comprises the following steps: (1) Preparation of silver-coated copper powder seeds by substitution reaction: 45g of polyvinyl pyrrolidone K30 was dissolved in a mixed solution of 300g of ethanol and 150g of water, and stirring was started at a speed of 1500rmp. 100g of spherical copper powder with a particle size of 3μm was added. After the copper powder was evenly dispersed, 17g of fuming nitric acid was added dropwise. After the addition was completed, the mixture was stirred and reacted for 5min. Finally, a silver nitrate solution with a molar concentration of 1mol / L was added dropwise, wherein the mass of silver nitrate was 15g, and the mass of silver corresponding to the silver nitrate was 9.5% of the mass of the copper powder. After 5min, the addition was completed, and the mixture was stirred and reacted for another 1min. After the reaction solution was settled and solid-liquid separated, the separated solid was washed three times with purified water to obtain silver-coated copper powder seed crystals.

[0026] (2) Preparation of silver-coated copper powder using liquid phase redox reaction: The silver-coated copper powder seed crystals prepared in step (1) are dispersed in a polyvinyl pyrrolidone solution, wherein the polyvinyl pyrrolidone solution is prepared into a solution with a mass concentration of 75 g / L by 55 g of polyvinyl pyrrolidone, prepared into a silver nitrate solution with a molar concentration of 1 mol / L by 55 g of silver nitrate, and prepared into a reducing agent solution with a molar concentration of 1.5 mol / L by 35 g of ascorbic acid. Stirring is started at a stirring speed of 2500 rpm, and then the silver nitrate solution and the reducing agent solution are added in parallel. The silver nitrate solution and the reducing agent solution are added dropwise at the same time. The dropping time is 15 min. After the dropping is completed, 3% of the theoretical mass of the generated silver-coated copper powder is added with palmitic acid, and then a pH adjuster is added to adjust the pH value of the reaction solution to 6. The reaction is stirred for 10 min. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with ethanol and then dried to obtain the silver-coated copper powder.

[0027] Comparative Example 1 (1) Preparation of silver-coated copper powder by substitution reaction 40g of polyvinyl pyrrolidone K30 was dissolved in a mixed solution of 300g of ethanol and 150g of water, and stirring was started at a speed of 2000rmp. 100g of spherical copper powder with a particle size of 2μm was added. After the copper powder was evenly dispersed, 18g of fuming nitric acid was added dropwise. After the addition was completed, the mixture was stirred and reacted for 5min. Finally, a silver nitrate solution with a molar concentration of 1mol / L was added dropwise, wherein the mass of silver nitrate was 15g, and the mass of silver corresponding to the silver nitrate was 9.5% of the mass of the copper powder. After 5min, the addition was completed, and the mixture was stirred and reacted for another 1min. After the reaction solution was settled and solid-liquid separated, the separated solid was washed three times with purified water to obtain silver-coated copper powder seed crystals.

[0028] (2) After the reaction is completed, oleic acid in an amount of 3% of the theoretical mass of the generated silver-coated copper powder is added for surface treatment, and then a pH adjuster is added to adjust the pH value of the reaction solution to 6. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with ethanol and then dried to obtain the silver-coated copper powder.

[0029] Comparative Example 2 Preparation of Silver-Coated Copper Powder by Liquid Phase Redox Reaction (1) Pretreatment of copper powder 100 g of spherical copper powder with a particle size of 2 μm was washed with acid solution, alkali solution and purified water in sequence, and the final wastewater after washing was neutral, colorless and transparent.

[0030] (2) Preparation of silver-coated copper powder using liquid phase redox reaction: The copper powder washed in step (1) is dispersed in a polyvinyl pyrrolidone solution, wherein the polyvinyl pyrrolidone solution is 60g polyvinyl pyrrolidone prepared into a solution with a mass concentration of 75g / L; 35g silver nitrate is prepared into a silver nitrate solution with a molar concentration of 1mol / L, and 22g ascorbic acid is prepared into a reducing agent solution with a molar concentration of 1.5mol / L, stirring is started at a stirring speed of 2500rmp, and then the silver nitrate solution and the reducing agent solution are added in parallel, and the silver nitrate solution and the reducing agent solution are added dropwise at the same time, and the dropping time is 15min. After the dropwise addition is completed, 3% of the theoretical mass of stearic acid to generate the silver-coated copper powder is added, and then a pH adjuster is added to adjust the pH value of the reaction solution to 5, and the reaction is stirred for 10min. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with ethanol and then dried to obtain the silver-coated copper powder.

[0031] Performance Testing (1) The silver-coated copper powder prepared in Example 1 was subjected to a thermogravimetric test, and the obtained thermogravimetric analysis curve is as follows: Figure 1 As shown. Figure 1 It can be seen that the silver-coated copper powder prepared in Example 1 begins to oxidize and increase in weight at 300° C., and has excellent oxidation resistance.

[0032] (2) The silver-coated copper powders prepared in Examples 1-4 and Comparative Examples 1-2 were observed by scanning electron microscopy. Figure 2-Figure 8 .from Figure 2-Figure 8 It was found that the silver-coated copper powder prepared in Examples 1-4 had higher surface smoothness and better dispersibility than that prepared in Comparative Examples 1-2.

[0033] (3) The particle size, specific surface area and tap density of the copper powder, the silver-coated copper powder of Examples 1-4 and the silver-coated copper powder of Comparative Examples 1-2 were tested. The results are shown in Table 1.

[0034] Table 1 As can be seen from Table 1, the silver-coated copper powder prepared in Examples 1-4 has a layer of silver powder coated on the copper surface, and the particle size is larger than that of pure copper powder, but the dispersibility is not affected, and the particle size distribution does not change much; the specific surface area of ​​the silver-coated copper powder prepared in Examples 1-4 is lower than that of pure copper powder, indicating that the surface smoothness of the wrapped silver layer is high; while the silver-coated copper powder prepared in Comparative Example 1 has an incomplete silver layer coating on the copper surface, so the specific surface area does not change much; and Comparative Example 2 is prepared by a liquid phase redox method of silver, resulting in the doping of silver nanoparticles in the silver-coated copper powder, so the particle size is reduced. At the same time, due to the small particle size of the reduced silver particles, the specific surface area of ​​the silver-coated copper powder measured is higher than that of pure copper powder.

[0035] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes for application in other fields. However, any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing silver-coated copper powder, characterized in that: The following steps are involved: (1) Preparation of silver-coated copper powder seeds by substitution reaction: The spherical copper powder is dispersed in the dispersant solution, and then fuming nitric acid is added dropwise under stirring, and the reaction is stirred for 5 minutes after the addition is completed, and finally the silver nitrate solution is added dropwise, and the reaction is stirred for 1 minute after the addition is completed, and the reaction solution is subjected to sedimentation and solid-liquid separation, and the separated solid is washed with purified water to obtain silver-coated copper powder seed crystals; (2) Preparation of silver-coated copper powder using liquid phase redox reaction: The silver-coated copper powder seed crystals prepared in step (1) are dispersed in a dispersant solution, and then a silver nitrate solution and a reducing agent solution are added in parallel. After the silver nitrate solution and the reducing agent solution are added dropwise at the same time, a surfactant is added, and then a pH adjuster is added to adjust the pH value of the reaction solution. The reaction is stirred for 10 minutes. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with ethanol and then dried to obtain the silver-coated copper powder.

2. The method for preparing silver-coated copper powder according to claim 1, characterized in that: In the step (1), the mass concentration of the dispersant solution is 60-100 g / L, the solvent of the dispersant solution is a mixture of ethanol and water, and the mass ratio of ethanol to water is 2:

1.

3. The method for preparing silver-coated copper powder according to claim 2, characterized in that: In the step (1), the dispersant is one or two of polyvinyl pyrrolidone, polyethylene glycol, gelatin and gum arabic, and the mass of the dispersant is 1 to 3 times the mass of the copper powder.

4. The method for preparing silver-coated copper powder according to claim 3, characterized in that: In the step (1), the mass of the fuming nitric acid is 10% to 30% of the mass of the copper powder.

5. The method for preparing silver-coated copper powder according to claim 4, characterized in that: In the step (1), the molar concentration of the silver nitrate solution is 0.2 to 2 mol / L, and the mass of silver in the silver nitrate solution is 1% to 10% of the mass of the copper powder.

6. The method for preparing silver-coated copper powder according to claim 5, characterized in that: In the step (2), the mass concentration of the dispersant solution is 60-100 g / L, the dispersant is one or two of polyvinyl pyrrolidone, polyethylene glycol, gelatin and gum arabic, and the mass of the dispersant is 20%-40% of the mass of the silver-coated copper powder seed crystal.

7. The method for preparing silver-coated copper powder according to claim 6, characterized in that: In the step (2), the molar concentration of the silver nitrate solution is 0.2 to 3 mol / L, and the mass of the corresponding silver in the silver nitrate solution is 5% to 40% of the mass of the copper powder.

8. The method for preparing silver-coated copper powder according to claim 7, characterized in that: In the step (2), the molar concentration of the reducing agent solution is 0.1 to 5 mol / L, the reducing agent is ascorbic acid, and the molar ratio of the ascorbic acid to the silver nitrate is 0.5 to 1:

1.

9. The method for preparing silver-coated copper powder according to claim 8, characterized in that: In the step (2), the surfactant is at least one of oleic acid, sodium oleate, palmitic acid, caprylic acid and stearic acid, and the mass of the surfactant is 1% to 5% of the theoretical mass of the generated silver-coated copper powder.

10. The method for preparing silver-coated copper powder according to claim 9, characterized in that: In the step (2), a pH adjuster is added to adjust the pH value of the reaction solution to 5-6.

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