A method for preparing silver-coated copper powder

Abstract

The present application belongs to the technical field of silver-coated copper powder, and particularly relates to a preparation method of silver-coated copper powder, comprising the following steps: (1) preparing silver-coated copper powder seeds by using displacement reaction; (2) preparing silver-coated copper powder by using liquid phase oxidation-reduction reaction. The present application has the beneficial effect that a layer of silver is coated on the surface of copper powder by displacement method first, then the silver-coated copper powder obtained by displacement method is used as seeds to perform liquid phase oxidation-reduction reaction of silver ions, and a dense silver layer is slowly grown on the surface of the silver-coated copper powder seeds, so that the preparation method of the silver-coated copper powder has low production cost and simple process, can control the thickness of the silver layer on the surface of the copper powder, and the coated silver layer is dense and smooth, the silver layer is firm and not easy to fall off, and the prepared silver-coated copper powder has excellent conductivity and thermal stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silver-coated copper powder, and particularly relates to a preparation method of silver-coated copper powder. BACKGROUND

[0002] The silver-coated copper powder is a new type of multi-functional powder material with core-shell structure, which effectively combines the excellent metal properties of silver and copper, solves the problem of silver migration, maintains the high conductivity, oxidation resistance and thermal stability of silver, and reduces the cost of slurry.

[0003] The existing preparation methods of silver-coated copper powder include a mixed ball milling method, a melting atomization method, a chemical plating method, a reduction method and a displacement method. The silver-coated copper powder prepared by the ball milling method needs inert gas protection, and the production cost is high. The silver-coated copper powder with different silver contents can be prepared by the melting atomization method, but the process is complicated, and thus the production cost is high. The silver-coated copper powder prepared by the chemical plating method has low cost, but the yield 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 the reaction process is difficult to control due to the fast reaction speed. The silver-coated copper powder prepared by the displacement method has simple process and high silver conversion rate, and the prepared silver-coated copper powder has excellent conductivity, but the plating film is uneven and discontinuous. If the dense silver layer is required, multiple displacement is needed. Therefore, a method for preparing silver-coated copper powder with low production cost, simple process, continuous and dense silver layer is particularly important. SUMMARY

[0004] The application aims to solve the above problems, and provides a preparation method of silver-coated copper powder.

[0005] The application relates to a preparation method of silver-coated copper powder, and comprises the following steps:

[0006] (1) preparing silver-coated copper powder seeds by a displacement reaction:

[0007] The spherical copper powder is dispersed into a dispersant solution, then fuming nitric acid is added dropwise under stirring, the reaction is stirred for 5 min after the dropwise addition is completed, silver nitrate solution is added dropwise, the reaction is stirred for 1 min after the dropwise addition is completed, the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with purified water, and the silver-coated copper powder seeds are obtained;

[0008] (2) preparing silver-coated copper powder by a liquid phase oxidation-reduction reaction:

[0009] The silver-coated copper powder seeds prepared in the step (1) are dispersed into a dispersant solution, then silver nitrate solution and a reducing agent solution are added in parallel flow, the silver nitrate solution and the reducing agent solution are simultaneously added dropwise, a surfactant is added, a pH adjuster is added to adjust the pH value of the reaction solution, the reaction is stirred for 10 min, the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with ethanol, and the silver-coated copper powder is obtained after drying.

[0010] Preferably, 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 the ethanol to the water is 2:1.

[0011] Preferably, in the step (1), the dispersant is one or two of polyvinylpyrrolidone, polyethylene glycol, gelatin and gum arabic, and the mass of the dispersant is 1-3 times the mass of the copper powder.

[0012] Preferably, in the step (1), the mass of the fuming nitric acid is 10%-30% of the mass of the copper powder.

[0013] Preferably, in the step (1), the molar concentration of the silver nitrate solution is 0.2-2 mol / L, and the mass of the silver corresponding to the silver nitrate solution is 1%-10% of the mass of the copper powder.

[0014] Preferably, in the step (2), the mass concentration of the dispersant solution is 60-100 g / L, the dispersant is one or two of polyvinylpyrrolidone, 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.

[0015] Preferably, in the step (2), the molar concentration of the silver nitrate solution is 0.2-3 mol / L, and the mass of the silver corresponding to the silver nitrate solution is 5%-40% of the mass of the copper powder.

[0016] Preferably, in the step (2), the molar concentration of the reducing agent solution is 0.1-5 mol / L, the reducing agent is ascorbic acid, and the molar ratio of the ascorbic acid to the silver nitrate is 0.5-1:1.

[0017] Preferably, in the step (2), the surfactant is at least one of oleic acid, sodium oleate, palmitic acid, octanoic acid and stearic acid, and the mass of the surfactant is 1%-5% of the theoretical mass of the silver-coated copper powder.

[0018] Preferably, in the step (2), a pH regulator is added to adjust the pH value of the reaction solution to 5-6.

[0019] Compared with the prior art, the application has the advantages and positive effects that:

[0020] Compared with the prior art, the silver-coated copper powder is prepared by the method, a layer of silver is coated on the surface of the copper powder by the displacement method, the silver-coated copper powder obtained by the displacement method is used as a crystal seed, a liquid phase oxidation-reduction reaction of silver ions is carried out, and a dense silver layer is slowly grown on the surface of the silver-coated copper powder crystal seed, so that the silver-coated copper powder prepared by the method has low production cost and simple process, the thickness of the silver layer on the surface of the copper powder can be controlled, the coated silver layer is dense and smooth, 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 DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced,

[0022] Figure 1 Thermogravimetric curve of the silver-coated copper powder provided for Example 1;

[0023] Figure 2 Scanning electron microscope image of the copper powder provided for Example 1;

[0024] Figure 3 Scanning electron microscope image of the silver-coated copper powder provided for Example 1;

[0025] Figure 4 Scanning electron microscope image of the silver-coated copper powder provided for Example 2;

[0026] Figure 5 Scanning electron microscope image of the silver-coated copper powder provided for Example 3;

[0027] Figure 6 Scanning electron microscope image of the silver-coated copper powder provided for Example 4;

[0028] Figure 7 Scanning electron microscope image of the silver-coated copper powder provided for Comparative Example 1;

[0029] Figure 8 Scanning electron microscope image of the silver-coated copper powder provided for Comparative Example 2. DETAILED DESCRIPTION

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced,

[0031] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the present application is not limited to the specific embodiments disclosed in the following description.

[0032] Example 1

[0033] A silver-coated copper powder preparation method comprises the following steps:

[0034] (1) Preparation of silver-coated copper powder seed by displacement reaction:

[0035] Dissolve 35 g of polyvinylpyrrolidone K30 in a mixed solution of 300 g of ethanol and 150 g of water, start stirring at a speed of 1500 rpm, add 100 g of spherical copper powder with a particle size of 1 μm, and after the copper powder is uniformly dispersed, add 15 g of fuming nitric acid dropwise. After the addition is complete, stir for 5 min, and then add a 1 mol / L silver nitrate solution, where the mass of silver nitrate is 12 g. The mass of silver corresponding to silver nitrate is 7.6% of the mass of the copper powder. After 5 min, the addition is complete, and stirring is continued for another 1 min. After the reaction solution is settled and solid-liquid separation is performed, the separated solid is washed three times with purified water to obtain silver-coated copper powder seed.

[0036] (2) Preparation of silver-coated copper powder by liquid-phase redox reaction:

[0037] Disperse the silver-coated copper powder seed prepared in step (1) into a polyvinylpyrrolidone solution, where the polyvinylpyrrolidone solution is a 55 g / L solution prepared from 55 g of polyvinylpyrrolidone. Prepare a 1 mol / L silver nitrate solution from 40 g of silver nitrate, and a 1.5 mol / L reducing agent solution from 25 g of ascorbic acid. Start stirring at a speed of 2000 rpm, and then add the silver nitrate solution and the reducing agent solution in parallel flow. The addition of the silver nitrate solution and the reducing agent solution is complete simultaneously, and the addition time is 15 min. After the addition is complete, add 3% of the theoretical mass of the silver-coated copper powder of oleic acid, and then add a pH adjuster to adjust the pH of the reaction solution to 5. Stir for 10 min, and then perform solid-liquid separation on the reaction solution after it is settled. Wash the separated solid with ethanol, and then dry it to obtain silver-coated copper powder.

[0038] Example 2

[0039] A method for preparing silver-coated copper powder, comprising the following steps:

[0040] (1) Preparation of silver-coated copper powder seed by displacement reaction:

[0041] Dissolve 40 g of polyvinylpyrrolidone K30 in a mixed solution of 300 g of ethanol and 150 g of water, start stirring at a stirring speed of 2000 rpm, add 100 g of spherical copper powder with a particle size of 2 μm, after the copper powder is uniformly dispersed, add 18 g of fuming nitric acid dropwise, stir for 5 min after the addition is completed, finally add a silver nitrate solution with a molar concentration of 1 mol / L, the mass of the silver nitrate is 15 g, the mass of the silver corresponding to the silver nitrate is 9.5% of the mass of the copper powder, and the addition is completed after 5 min, then stir for 1 min, after the reaction solution is settled and solid-liquid separated, wash the separated solid with purified water three times to obtain silver-coated copper powder seeds.

[0042] (2) Preparation of silver-coated copper powder by liquid phase redox reaction:

[0043] Dissolve 40 g of polyvinylpyrrolidone K30 in a mixed solution of 300 g of ethanol and 150 g of water, start stirring at a stirring speed of 2000 rpm, add 100 g of spherical copper powder with a particle size of 2 μm, after the copper powder is uniformly dispersed, add 18 g of fuming nitric acid dropwise, stir for 5 min after the addition is completed, finally add a silver nitrate solution with a molar concentration of 1 mol / L, the mass of the silver nitrate is 15 g, the mass of the silver corresponding to the silver nitrate is 9.5% of the mass of the copper powder, and the addition is completed after 5 min, then stir for 1 min, after the reaction solution is settled and solid-liquid separated, wash the separated solid with purified water three times to obtain silver-coated copper powder seeds.

[0044] Example 3

[0045] A method for preparing silver-coated copper powder, comprising the following steps:

[0046] (1) Preparation of silver-coated copper powder seeds by displacement reaction:

[0047] Dissolve 45 g of polyvinylpyrrolidone K30 in a mixed solution of 300 g of ethanol and 150 g of water, start stirring at a stirring speed of 1800 rpm, add 100 g of spherical copper powder with a particle size of 0.5 μm, after the copper powder is uniformly dispersed, add 18 g of fuming nitric acid dropwise, stir for 5 min after the addition is completed, finally add a silver nitrate solution with a molar concentration of 1 mol / L, the mass of the silver nitrate is 6.3 g, the mass of the silver corresponding to the silver nitrate is 4% of the mass of the copper powder, and the addition is completed after 5 min, then stir for 1 min, after the reaction solution is settled and solid-liquid separated, wash the separated solid with purified water three times to obtain silver-coated copper powder seeds.

[0048] (2) Preparation of silver-coated copper powder by liquid phase redox reaction:

[0049] The silver-coated copper powder seed prepared in step (1) is dispersed into a polyvinylpyrrolidone solution, wherein 55 g of polyvinylpyrrolidone is prepared into a solution with a mass concentration of 75 g / L, 25 g of silver nitrate is prepared into a silver nitrate solution with a molar concentration of 1 mol / L, 16 g of ascorbic acid is prepared into a reducing agent solution with a molar concentration of 1.5 mol / L, stirring is started at a speed of 2200 rpm, and then the silver nitrate solution and the reducing agent solution are added in parallel flow. The silver nitrate solution and the reducing agent solution are added dropwise at the same time, and the dropwise addition is completed in 15 min. After the dropwise addition is completed, 3% of the theoretical mass of the silver-coated copper powder of stearic acid is added, a pH adjuster is added to adjust the pH value of the reaction solution to 5.5, and stirring reaction is performed 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.

[0050] Example 4

[0051] A method for preparing a silver-coated copper powder, comprising the following steps:

[0052] (1) Preparing silver-coated copper powder seed by displacement reaction:

[0053] 45 g of polyvinylpyrrolidone K30 is dissolved in a mixed solution of 300 g of ethanol and 150 g of water, stirring is started at a speed of 1500 rpm, 100 g of spherical copper powder with a particle size of 3 μm is added, the copper powder is uniformly dispersed, 17 g of fuming nitric acid is then added dropwise, stirring is performed for 5 min after the dropwise addition is completed, and finally a silver nitrate solution with a molar concentration of 1 mol / L is added dropwise, wherein the mass of the silver nitrate is 15 g, and the mass of silver corresponding to the silver nitrate is 9.5% of the mass of the copper powder. The dropwise addition is completed after 5 min, and stirring is performed for another 1 min. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with purified water for three times to obtain the silver-coated copper powder seed.

[0054] (2) Preparing silver-coated copper powder by liquid phase redox reaction:

[0055] The silver-coated copper powder seed prepared in step (1) is dispersed into a polyvinylpyrrolidone solution, wherein 55 g of polyvinylpyrrolidone is prepared into a solution with a mass concentration of 75 g / L, 55 g of silver nitrate is prepared into a silver nitrate solution with a molar concentration of 1 mol / L, 35 g of ascorbic acid is prepared into a reducing agent solution with a molar concentration of 1.5 mol / L, stirring is started with a stirring speed of 2500 rpm, and then the silver nitrate solution and the reducing agent solution are added in parallel flow. The silver nitrate solution and the reducing agent solution are added dropwise at the same time, and the dropwise addition is completed in 15 min. After the dropwise addition is completed, 3% of the theoretical mass of stearic acid for generating the silver-coated copper powder is added, a pH adjuster is added to adjust the pH value of the reaction solution to 6, and the reaction solution 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.

[0056] Comparative Example 1

[0057] (1) Preparation of silver-coated copper powder by displacement reaction

[0058] 40 g of polyvinylpyrrolidone K30 is dissolved in a mixed solution of 300 g of ethanol and 150 g of water, stirring is started with a stirring speed of 2000 rpm, 100 g of spherical copper powder with a particle size of 2 μm is added, the copper powder is uniformly dispersed, 18 g of fuming nitric acid is added dropwise, stirring is performed for 5 min after the dropwise addition is completed, a silver nitrate solution with a molar concentration of 1 mol / L is finally added dropwise, wherein the mass of the silver nitrate is 15 g, the mass of silver corresponding to the silver nitrate is 9.5% of the mass of the copper powder, the dropwise addition is completed after 5 min, and stirring is performed for 1 min. After the reaction solution is subjected to sedimentation and solid-liquid separation, the separated solid is washed with purified water three times to obtain the silver-coated copper powder seed.

[0059] (2) After the reaction is completed, 3% of the theoretical mass of oleic acid for generating the silver-coated copper powder is added for surface treatment, a pH adjuster is added to adjust the pH value of the reaction solution to 6, 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.

[0060] Comparative Example 2 Preparation of silver-coated copper powder by liquid phase oxidation-reduction reaction

[0061] (1) Pretreatment of copper powder

[0062] 100 g of spherical copper powder with a particle size of 2 μm is sequentially washed with an acid solution, an alkali solution and purified water. The final waste water is neutral and colorless and transparent.

[0063] (2) Preparation of silver-coated copper powder by liquid phase oxidation-reduction reaction

[0064] The copper powder washed in step (1) was dispersed in a polyvinylpyrrolidone solution, wherein the polyvinylpyrrolidone solution was prepared by 60g of polyvinylpyrrolidone to a mass concentration of 75g / L; 35g of silver nitrate was prepared to a molar concentration of 1mol / L silver nitrate solution, and 22g of ascorbic acid was prepared to a molar concentration of 1.5mol / L reducing agent solution. Stirring was started at a speed of 2500rpm, and then the silver nitrate solution and reducing agent solution were added in parallel. The silver nitrate solution and reducing agent solution were added dropwise at the same time, and the dropwise addition time was 15min. After the dropwise addition was completed, stearic acid of 3% of the theoretical mass of silver-coated copper powder was added, and then a pH adjuster was added to adjust the pH value of the reaction solution to 5. The reaction was stirred for 10min. After sedimentation and solid-liquid separation, the separated solid was washed with ethanol and then dried to obtain silver-coated copper powder.

[0065] Performance testing

[0066] (1) Thermogravimetric analysis was performed on the silver-coated copper powder prepared in Example 1, and the obtained thermogravimetric analysis curve is shown below. Figure 1 As shown. From Figure 1 It can be seen that the silver-coated copper powder prepared in Example 1 only begins to undergo oxidation and weight gain at 300℃, and has excellent antioxidant properties.

[0067] (2) The silver-coated copper powders prepared in Examples 1-4 and Comparative Examples 1-2 were observed by scanning electron microscopy, with reference to... Figures 2-8 .from Figures 2-8 It was found that, compared with the silver-coated copper powder prepared in Examples 1-4, the silver-coated copper powder prepared in Examples 1-4 had higher surface smoothness and better dispersibility.

[0068] (3) The particle size, specific surface area and tap density of copper powder, silver-coated copper powder of Examples 1-4 and silver-coated copper powder of Comparative Examples 1-2 were tested, and the results are shown in Table 1.

[0069] Table 1

[0070]

[0071] As shown in Table 1, the silver-coated copper powder prepared in Examples 1-4 has a layer of silver powder coated on the copper surface, resulting in a larger particle size compared to pure copper powder, but the dispersibility is not affected and the particle size distribution does not change significantly. 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 of the coated silver layer is highly smooth. In contrast, 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 significantly. Comparative Example 2 was prepared using a liquid-phase oxidation-reduction method of silver, which resulted in the doping of silver nanoparticles into the silver-coated copper powder, thus reducing the particle size. At the same time, because the reduced silver particles are small, the specific surface area of ​​the silver-coated copper powder is higher than that of pure copper powder.

[0072] The above merely describes preferred embodiments of the present application, but is not intended to limit the present application in other forms, any skilled person in the art can use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes applied to other fields, but any simple modification, equivalent change made according to the technical essence of the present application to the above embodiments, still belongs to the protection scope of the present application technical solution.

Claims

1. A method for producing silver-coated copper powder, characterized by, The method comprises the following steps: (1) preparing silver-coated copper powder seeds by using a displacement reaction: dispersing spherical copper powder into a dispersant solution, then adding fuming nitric acid dropwise under stirring, stirring for 5 minutes after the addition is completed, then adding silver nitrate solution dropwise, stirring for 1 minute after the addition is completed, washing the separated solid with purified water after the reaction solution is subjected to sedimentation and solid-liquid separation, and obtaining silver-coated copper powder seeds; (2) preparing silver-coated copper powder by using a liquid-phase oxidation-reduction reaction: dispersing the silver-coated copper powder seeds prepared in step (1) into a dispersant solution, then adding silver nitrate solution and a reducing agent solution in parallel flow, adding a surfactant after the silver nitrate solution and the reducing agent solution are both added dropwise, adjusting the pH value of the reaction solution by adding a pH adjuster, stirring for 10 minutes, washing the separated solid with ethanol after the reaction solution is subjected to sedimentation and solid-liquid separation, and drying to obtain silver-coated copper powder. 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 the ethanol to the water is 2:

1. In step (1), the dispersant is one or two of polyvinylpyrrolidone, polyethylene glycol, gelatin and gum arabic, and the mass of the dispersant is 1-3 times the mass of the copper powder. In step (1), the molar concentration of the silver nitrate solution is 0.2-2 mol / L, and the mass of silver corresponding to the silver nitrate solution is 1%-10% of the mass of the copper powder. In step (2), the molar concentration of the silver nitrate solution is 0.2-3 mol / L, and the mass of silver corresponding to the silver nitrate solution is 5%-40% of the mass of the copper powder. In step (2), the molar concentration of the reducing agent solution is 0.1-5 mol / L, the reducing agent is ascorbic acid, and the molar ratio of the ascorbic acid to the silver nitrate is 0.5-1:

1. In step (2), the pH value of the reaction solution is adjusted to 5-6 by adding a pH adjuster.

2. The method of claim 1, wherein the silver-coated copper powder is prepared by the steps of: In step (1), the mass of the fuming nitric acid is 10%-30% of the mass of the copper powder.

3. The method of claim 2, wherein the silver-coated copper powder is prepared by the steps of: In step (2), the mass concentration of the dispersant solution is 60-100 g / L, the dispersant is one or two of polyvinylpyrrolidone, polyethylene glycol, gelatin and gum arabic, and the mass of the dispersant is 20%-40% of the mass of the silver-coated copper powder seeds.

4. The method of claim 1, wherein the silver-coated copper powder is prepared by the steps of: In step (2), the surfactant is at least one of oleic acid, sodium oleate, palmitic acid, octanoic acid and stearic acid, and the mass of the surfactant is 1%-5% of the theoretical mass of the generated silver-coated copper powder.

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