A method for preparing ultra-fine silver powder

Abstract

This invention relates to a method for preparing ultrafine silver powder, the method comprising the following steps: (1) dissolving silver nitrate in deionized water to obtain a metal salt solution, and maintaining the temperature at 30-50°C; (2) dissolving a reducing agent in deionized water and adding a pH adjuster to obtain a reducing agent solution, and maintaining the temperature at 30-50°C; (3) dissolving a dispersant and a dopant in deionized water to obtain a mixed solution, and maintaining the temperature at 30-50°C; (4) adding the mixed solution to the metal salt solution, stirring for 1 min, and then adding the reducing agent solution to the metal salt solution, stirring and reacting to obtain silver powder; (5) washing the silver powder until the conductivity of the washing solution is ≤10 μs, separating the solid and liquid to obtain an Ag powder filter cake; (6) adding a surface coating agent-anhydrous ethanol solution to the Ag powder filter cake, stirring evenly, and then drying, air-dispersing, and sieving to obtain ultrafine silver powder with a particle size of 0.4-0.8 μm. This invention is simple to operate, low in cost, and easy to industrialize. The resulting silver powder product has small particle size, narrow distribution, and good dispersibility.

Description

Technical Field

[0001] This invention relates to the field of precious metal material preparation technology, and in particular to a method for preparing ultrafine silver powder. Background Technology

[0002] With the continuous development of economic globalization, the research and development of electronic materials has also seen unprecedented progress. Conductive paste is a very important branch of electronic materials, among which conductive silver paste has attracted much attention due to its many excellent properties. Ultrafine silver powder, as a functional material with high surface activity and excellent conductivity, is widely used in conductive pastes, energy industry, composite materials, catalysts, antibacterial materials, and other fields. Silver powder is the most important raw material for conductive paste, and it has a significant impact on parameters such as film formation, film thickness, electrical properties, solderability, and adhesion during the preparation process. The quality of silver powder directly affects the performance of the conductive paste and the final conductor.

[0003] Currently, there are many methods for preparing silver powder both domestically and internationally, mainly including grinding, atomization, evaporation-condensation, electrochemical deposition, sol-gel method, and liquid-phase reduction method. Among them, the liquid-phase reduction method is one of the most promising preparation methods due to its simple operation, low investment, high yield, low loss, and good performance. However, the silver powder prepared by the liquid-phase reduction method currently suffers from problems such as a wide particle size distribution, easy agglomeration of silver powder particles, and difficulty in washing and settling, which urgently need to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing ultrafine silver powder that is simple to operate, low in cost, and easy to industrialize.

[0005] To address the above problems, the present invention provides a method for preparing ultrafine silver powder, comprising the following steps:

[0006] (1) Dissolve silver nitrate in deionized water to obtain a metal salt solution, and keep the temperature constant at 30~50℃;

[0007] (2) Dissolve the reducing agent in deionized water and add a pH adjuster to obtain a reducing agent solution, and keep the temperature constant at 30~50℃;

[0008] (3) Dissolve the dispersant and dopant in deionized water to obtain a mixed solution, and keep the temperature constant at 30~50℃;

[0009] (4) The mixed solution is added to the metal salt solution, and after stirring for 1 minute, the reducing agent solution is added to the metal salt solution, and the mixture is stirred to react, thereby obtaining silver powder;

[0010] (5) Wash the silver powder until the conductivity of the washing solution is ≤10μs, then perform solid-liquid separation to obtain Ag powder filter cake;

[0011] (6) Add a surface coating agent-anhydrous ethanol solution to the Ag powder filter cake, stir evenly, and then dry, disperse by airflow, and sieve to obtain ultrafine silver powder with a particle size of 0.4~0.8μm.

[0012] The silver nitrate content in the metal salt solution in step (1) is 150~250 g / L.

[0013] The reducing agent in the reducing solution of step (2) has a content of 100~200g / L; the reducing agent is any one of glucose, ascorbic acid, hydroquinone, hydrazine hydrate, formaldehyde, and organic amine.

[0014] The pH adjuster content in the reducing agent solution in step (2) is 10~100g / L; the pH adjuster is one of sodium hydroxide, ammonia, and ethylenediamine.

[0015] The content of dispersant in the mixed solution in step (3) is 20~100g / L; the dispersant is one of polyvinylpyrrolidone, polyethylene glycol, polyvinylamide, and gelatin.

[0016] The dopant content in the mixed solution in step (3) is 0.1~1.0 g / L; the dopant is one of copper nitrate, sodium nitrate, potassium sulfate, and copper sulfate.

[0017] The conditions for adding and stirring the reducing agent solution in step (4) are as follows: addition rate of 10 L / min, addition time of 2 min, reaction time of 4-20 min, and stirring frequency of 40 Hz.

[0018] In step (6), the mass concentration of the surface coating agent-anhydrous ethanol solution is 0.1~10 g / L; wherein the surface coating agent is one of hexadecanoic acid, stearic acid, and erucic acid, and its addition amount is 0.1%~0.5% of the mass of silver powder.

[0019] In step (6), the drying conditions refer to a temperature of 60~70℃ and a time of 15~20h.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. This invention prepares silver powder by first adding a mixed solution of dispersant and dopant to a metal salt solution, and then adding a reducing agent solution at a certain flow rate, and by controlling the temperature of the reaction system and the liquid addition rate; and by controlling the amount of dopant added and the temperature of the reaction system to control the amount of silver powder nucleation in the early stage of the reaction, and controlling the liquid addition rate to control the growth rate of silver powder, so as to obtain silver powder products with small particle size, narrow distribution and good dispersibility.

[0022] 2. This invention utilizes a liquid-phase reduction method to scientifically and rationally control the reducing agent, dispersant, and dopant during the reduction process, thereby obtaining ultrafine silver powder with small particle size and good dispersibility.

[0023] 3. This invention is simple to operate, uses widely available raw materials, has low cost, does not require high-end equipment, and is easy to industrialize. Attached Figure Description

[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0025] Figure 1 This is an electron microscope image of the ultrafine silver powder in Example 1 of the present invention.

[0026] Figure 2 This is an electron microscope image of the ultrafine silver powder in Example 2 of the present invention.

[0027] Figure 3 This is an electron microscope image of the ultrafine silver powder in Example 3 of the present invention.

[0028] Figure 4 This is an electron microscope image of the ultrafine silver powder in Example 4 of the present invention. Detailed Implementation

[0029] A method for preparing ultrafine silver powder includes the following steps:

[0030] (1) Dissolve silver nitrate in deionized water to obtain a metal salt solution with a silver nitrate content of 150~250 g / L, and keep the temperature constant at 30~50℃.

[0031] (2) Dissolve the reducing agent in deionized water and add a pH adjuster to obtain a reducing agent solution, and keep the temperature constant at 30~50℃. The reducing agent content in the reducing solution is 100~200g / L, and the reducing agent is any one of glucose, ascorbic acid, hydroquinone, hydrazine hydrate, formaldehyde, or organic amine; the pH adjuster content is 10~100g / L, and the pH adjuster is one of sodium hydroxide, ammonia, or ethylenediamine.

[0032] (3) Dissolve the dispersant and dopant in deionized water to obtain a mixed solution, and keep it at a constant temperature of 30~50℃. The content of the dispersant in the mixed solution is 20~100g / L, and the dispersant is one of polyvinylpyrrolidone, polyethylene glycol, polyvinylamide, or gelatin; the content of the dopant is 0.1~1.0g / L, and the dopant is one of copper nitrate, sodium nitrate, potassium sulfate, or copper sulfate.

[0033] (4) Add the mixed solution to the metal salt solution and stir for 1 minute. Then, add the reducing agent solution to the metal salt solution at a rate of 10 L / min for 2 minutes. Stir the reaction at a frequency of 40 Hz for 4-20 minutes to obtain silver powder.

[0034] (5) Wash the silver powder until the conductivity of the washing solution is ≤10μs, then separate the solid and liquid to obtain Ag powder filter cake.

[0035] (6) Add a surface coating agent-anhydrous ethanol solution with a mass concentration of 0.1~10 g / L to the Ag powder filter cake. The surface coating agent is one of hexadecanoic acid, stearic acid, or erucic acid, and the amount added is 0.1%~0.5% of the mass of the silver powder. Then stir evenly, dry at 60~70℃ for 15~20 h, and then disperse by airflow and sieve to obtain ultrafine silver powder with a particle size of 0.4~0.8 μm.

[0036] Example 1: A method for preparing ultrafine silver powder, comprising the following steps:

[0037] (1) Dissolve 250g of silver nitrate in 1L of deionized water to obtain a metal salt solution and keep it at a constant temperature of 35℃.

[0038] (2) Dissolve 200g of ascorbic acid in 1L of deionized water, then add 45g of ethylenediamine to obtain a reducing agent solution, and keep the temperature constant at 35℃.

[0039] (3) Dissolve 20g of polyvinylpyrrolidone and 0.2g of copper nitrate in 0.2L of deionized water to obtain a mixed solution, and keep the temperature constant at 35℃.

[0040] (4) Add the mixed solution to the metal salt solution and stir for 1 min. Then add the reducing agent solution to the metal salt solution at a rate of 10 L / min for 2 min. Stir the reaction at 40 Hz for 10 min to obtain 152.6 g of silver powder.

[0041] (5) Wash the silver powder until the conductivity of the washing solution is ≤10μs, then separate the solid and liquid to obtain Ag powder filter cake.

[0042] (6) Add a surface coating agent-anhydrous ethanol solution with a mass concentration of 8 g / L [modified] to the Ag powder filter cake. The surface coating agent-anhydrous ethanol solution refers to the solution obtained by dissolving 0.8 g of erucic acid in 0.1 L of anhydrous ethanol. Then stir evenly, dry at 65℃ for 20 h, and then disperse and sieve by airflow to obtain ultrafine silver powder with an average particle size of 0.66 μm.

[0043] Example 2: A method for preparing ultrafine silver powder, comprising the following steps:

[0044] (1) The metal salt solution is the same as in Example 1.

[0045] (2) Dissolve 180g of glucose in 1L of deionized water and add 100g of ammonia to obtain a reducing agent solution, and keep the temperature constant at 35℃.

[0046] (3) Dissolve 20g of polyvinylpyrrolidone and 0.1g of copper nitrate in 0.2L of deionized water to obtain a mixed solution, and keep the temperature constant at 35℃.

[0047] (4) Add the mixed solution to the metal salt solution and stir for 1 min. Then add the reducing agent solution to the metal salt solution at a rate of 10 L / min for 2 min. Stir the reaction at 40 Hz for 10 min to obtain 138.3 g of silver powder.

[0048] (5) Wash the silver powder until the conductivity of the washing solution is ≤10μs, then separate the solid and liquid to obtain Ag powder filter cake.

[0049] (6) A surface coating agent-anhydrous ethanol solution with a mass concentration of 0.32 g / L was added to the Ag powder filter cake. The surface coating agent-anhydrous ethanol solution refers to the solution obtained by dissolving 0.16 g of hexadecanoic acid in 0.5 L of anhydrous ethanol. Then, the mixture was stirred evenly, dried at 65 °C for 20 h, and then dispersed by airflow and sieved to obtain ultrafine silver powder with a particle size of 0.42 μm.

[0050] Example 3 A method for preparing ultrafine silver powder, comprising the following steps:

[0051] (1) Dissolve 150g of silver nitrate in 1L of deionized water to obtain a metal salt solution and keep it at a constant temperature of 35℃.

[0052] (2) Dissolve 115g of formaldehyde and 10g of sodium hydroxide in 1L of deionized water and keep the temperature constant at 35℃.

[0053] (3) The mixed solution is the same as in Example 1.

[0054] (4) Add the mixed solution to the metal salt solution and stir for 1 min. Then add the reducing agent solution to the metal salt solution at a rate of 10 L / min for 2 min. Stir the reaction at 40 Hz for 10 min to obtain 151.9 g of silver powder.

[0055] (5) Wash the silver powder until the conductivity of the washing solution is ≤10μs, then separate the solid and liquid to obtain Ag powder filter cake.

[0056] (6) A surface coating agent-anhydrous ethanol solution with a mass concentration of 0.16 g / L was added to the Ag powder filter cake. The surface coating agent-anhydrous ethanol solution was the same as in Example 2. Then, the mixture was stirred evenly, dried at 65°C for 20 h, and then dispersed by airflow and sieved to obtain ultrafine silver powder with a particle size of 0.54 μm.

[0057] Example 4: A method for preparing ultrafine silver powder, comprising the following steps:

[0058] (1) The metal salt solution is the same as in Example 1.

[0059] (2) Dissolve 180g of hydrazine hydrate in 1L and 80g of ammonia in 1L of deionized water to obtain a reducing agent solution, and keep the temperature constant at 30℃.

[0060] (3) Dissolve 30g of gelatin and 0.1g of copper sulfate in 0.5L of deionized water to obtain a mixed solution, and keep the temperature constant at 30℃.

[0061] (4) Add the mixed solution to the metal salt solution and stir for 1 min. Then add the reducing agent solution to the metal salt solution at a rate of 10 L / min for 2 min. Stir the reaction at 40 Hz for 4 min to obtain 148.7 g of silver powder.

[0062] (5) Wash the silver powder until the conductivity of the washing solution is ≤10μs, then separate the solid and liquid to obtain Ag powder filter cake.

[0063] (6) A surface coating agent-anhydrous ethanol solution with a mass concentration of 0.16 g / L was added to the Ag powder filter cake. The surface coating agent-anhydrous ethanol solution was the same as in Example 2. Then, the mixture was stirred evenly, dried at 60°C for 20 h, and then dispersed by airflow and sieved to obtain ultrafine silver powder with a particle size of 0.44 μm.

[0064] The ultrafine silver powder obtained in Examples 1-4 above was scanned by electron microscopy, as shown in... Figures 1-4 As shown in the figure, the silver powder particles are small in size, uniformly distributed, and well dispersed.

[0065] Example 5: A method for preparing ultrafine silver powder, comprising the following steps:

[0066] (1) Dissolve 200g of silver nitrate in 1L of deionized water to obtain a metal salt solution and keep it at a constant temperature of 35℃.

[0067] (2) Dissolve 150g hydroquinone and 100g ammonia in 1L of deionized water to obtain a reducing agent solution, and keep the temperature constant at 35℃.

[0068] (3) Dissolve 40g of polyethylene glycol and 0.1g of sodium nitrate in 0.6L of deionized water to obtain a mixed solution, and keep the temperature constant at 35℃.

[0069] (4) Add the mixed solution to the metal salt solution and stir for 1 min. Then add the reducing agent solution to the metal salt solution at a rate of 10 L / min for 2 min. Stir the reaction at 40 Hz for 10 min to obtain 123.9 g of silver powder.

[0070] (5) Wash the silver powder until the conductivity of the washing solution is ≤10μs, then separate the solid and liquid to obtain Ag powder filter cake.

[0071] (6) A surface coating agent-anhydrous ethanol solution with a mass concentration of 4 g / L was added to the Ag powder filter cake. The surface coating agent-anhydrous ethanol solution refers to the solution obtained by dissolving 0.4 g of stearic acid in 0.1 L of anhydrous ethanol. Then, the mixture was stirred evenly, dried at 60 °C for 20 h, and then dispersed by airflow and sieved to obtain ultrafine silver powder with a particle size of 0.77 μm.

Claims

1. A method for preparing ultrafine silver powder, comprising the following steps: (1) Dissolve silver nitrate in deionized water to obtain a metal salt solution, and keep the temperature constant at 30~50℃; (2) Dissolve the reducing agent in deionized water and add a pH adjuster to obtain a reducing agent solution, and keep the temperature constant at 30~50℃; the content of the pH adjuster in the reducing agent solution is 10~100g / L; the pH adjuster is one of sodium hydroxide, ammonia, and ethylenediamine; (3) Dissolve the dispersant and dopant in deionized water to obtain a mixed solution, and keep it at a constant temperature of 30~50℃; the content of the dopant in the mixed solution is 0.1~1.0g / L; the dopant is one of copper nitrate, sodium nitrate, potassium sulfate, and copper sulfate. (4) The mixed solution is added to the metal salt solution, and after stirring for 1 min, the reducing agent solution is added to the metal salt solution and stirred to react, thereby obtaining silver powder; the addition and stirring conditions of the reducing agent solution are as follows: addition rate is 10 L / min, addition time is 2 min, reaction time is 4~20 min, and stirring frequency is 40 Hz. (5) Wash the silver powder until the conductivity of the washing solution is ≤10μs, then perform solid-liquid separation to obtain Ag powder filter cake; (6) A surface coating agent-anhydrous ethanol solution is added to the Ag powder filter cake, stirred evenly, dried, dispersed by airflow, and sieved to obtain ultrafine silver powder with a particle size of 0.4~0.8μm; the mass concentration of the surface coating agent-anhydrous ethanol solution in step (6) is 0.1~10g / L; wherein the surface coating agent is one of hexadecanoic acid, stearic acid, and erucic acid, and its addition amount is 0.1%~0.5% of the mass of the silver powder.

2. The method for preparing ultrafine silver powder as described in claim 1, characterized in that: The silver nitrate content in the metal salt solution in step (1) is 150~250 g / L.

3. The method for preparing ultrafine silver powder as described in claim 1, characterized in that: The reducing agent in the reducing solution of step (2) has a content of 100~200g / L; the reducing agent is any one of glucose, ascorbic acid, hydroquinone, hydrazine hydrate, formaldehyde, and organic amine.

4. The method for preparing ultrafine silver powder as described in claim 1, characterized in that: The content of dispersant in the mixed solution in step (3) is 20~100g / L; the dispersant is one of polyvinylpyrrolidone, polyethylene glycol, polyvinylamide, and gelatin.

5. The method for preparing ultrafine silver powder as described in claim 1, characterized in that: In step (6), the drying conditions refer to a temperature of 60~70℃ and a time of 15~20h.

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