Method for preparing spherical silver powder in one step through liquid phase reduction method

Abstract

The invention provides a method for preparing spherical silver powder in one step through a liquid phase reduction method, and the method for preparing the spherical silver powder in one step through the liquid phase reduction method comprises the steps of pretreatment, liquid phase reduction reaction and aftertreatment, and specifically comprises the steps that a silver nitrate solution with the concentration being 50-200 g / L is prepared, and an oxidizing agent solution a is obtained; preparing a glucose, citric acid or ascorbic acid solution with the concentration of 25-100g / L to obtain a reducing agent solution b; adjusting the pH value of the reducing agent solution to 2-4, adding a composite dispersing agent, and stirring and dissolving to obtain a material c; adding the oxidant solution a into the material c, carrying out stirring reaction, and carrying out solid-liquid separation to obtain a solid precipitate d; and cleaning and drying the solid precipitate d to obtain the target spherical silver powder. According to the method, the submicron spherical silver powder can be simply and conveniently obtained by carrying out reduction reaction in the water solution in the simple reaction kettle, the method is safe and environmentally friendly, the cost is low, the energy consumption is small, and the product powder with high purity and good fluidity can be obtained.

Description

Technical Field

[0001] The invention belongs to the field of photovoltaic cell materials, and in particular relates to a method for preparing spherical silver powder in one step by a liquid phase reduction method. Background Art

[0002] Spherical silver powder is a metal powder material with excellent performance and broad application prospects. Spherical silver powder has high electrical conductivity and thermal conductivity, which makes it an indispensable material in the electronics industry. The conductivity of silver is second only to copper, but its anti-oxidation performance is better than copper. Therefore, spherical silver powder is often used as conductive filler and conductive coating in high-frequency and high-precision electronic components. For example, in conductive glue, conductive ink and electromagnetic shielding materials, spherical silver powder can effectively improve the conductivity and stability of the material.

[0003] Patent CN118699389A discloses a green preparation method for micro-nano spherical silver powder, but it is necessary to add silver nitrate solution to the reducing agent-dispersant mixed solution at a volume ratio of 1:1 under a light-proof environment while stirring. After the addition is completed, it is matured to obtain a silver colloid solution, which is then filtered, washed and dried in sequence to obtain the final micro-nano spherical silver powder. Patent CN118455535A discloses a spherical silver powder with a narrow particle size distribution and high bulk density and a preparation method, wherein the volume ratio of the oxidant solution, the double reducing agent mixed solution and the base liquid is 2:2:1, and the oxidant solution and the double reducing agent mixed solution are respectively pumped into two microfluidizers at room temperature. After the injection is completed, continue to stir until the reaction is completed. Patent CN118287667A discloses a porous spherical silver powder and a preparation method thereof, preparing a first modifier solution, a second modifier solution, a silver nitrate solution, a reducing agent solution and a neutralizer solution; and finally separating the secondary modified silver powder from the secondary modified silver powder suspension. The above method has a complicated operation process and a long reaction time. The precipitation, growth or bridging phenomenon in the channel of the microfluidic reactor will limit the flow rate of the liquid in the microreactor, affect the mixing of the liquid, and increase the pressure. Therefore, it is very necessary to develop a method that can solve the above problems. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing spherical silver powder in one step by a liquid phase reduction method.

[0005] The object of the present invention is achieved in that the method for preparing spherical silver powder in one step by liquid phase reduction method comprises pretreatment, liquid phase reduction reaction and post-treatment steps, specifically comprising: A. Pretreatment: 1) Prepare a silver nitrate solution with a concentration of 50-200 g / L to obtain an oxidant solution a; 2) preparing a glucose, citric acid or ascorbic acid solution with a concentration of 25-100 g / L to obtain a reducing agent solution b; B. Liquid phase reduction reaction: 1) The pH value of the reducing agent solution is adjusted to 2-4, and then a composite dispersant is added and stirred to dissolve to obtain material c; 2) adding the oxidant solution a to the material c for stirring reaction, and performing solid-liquid separation to obtain a solid precipitate d; C. Post-treatment: The solid precipitate d is washed and dried to obtain the target spherical silver powder.

[0006] The specific operations are as follows: (1) Prepare oxidant solution: silver nitrate concentration 50~200g / L; (2) Prepare reducing agent solution: concentration 25~100g / L, dissolve and pour into the reactor; (3) Add 2~5wt.% of composite dispersant to the reducing agent solution; (4) Quickly pouring the oxidant solution into the reducing agent solution for liquid phase reduction; (5) Separate the obtained precipitate into solid and liquid, and wash and dry the solid precipitate. In the above-mentioned preparation method, the reducing agent described in step 2 is a green reducing agent, such as glucose, citric acid, etc.; After the reducing agent described in step 2 of the above preparation method is dissolved, ammonia water needs to be added to adjust the pH to 2-4; The liquid phase preparation of spherical silver powder in the reaction vessel as described in step 2 of the above preparation method has an experimental temperature of 25-45° C., a stirring rate of 300-1500 r / min, and a reaction time of 20-40 min.

[0007] The silver powder obtained by the solid-liquid separation in step 5 of the above-mentioned preparation method can be directly used for the preparation of photovoltaic slurry after washing and drying without sieving, with good fluidity and high tap density.

[0008] The chemical reaction equations mainly occurring in the present invention are: When glucose is reduced: CH2OH(CHOH)4CHO+2Ag(NH3)2OH→CH2OH(CHOH)4COONH4+2Ag↓+3NH3+H2O When citric acid is reduced: 4AgNO3+C6H8O7+2H2O→4Ag+4HNO3+C6H6O7 When ascorbic acid is reduced: 2AgNO3+C6H8O6=2Ag+C6H6O6+2HNO3 The composite dispersant is composed of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA); its technical principle is as follows: 1. PVP and PVA, as surface protective agents, can form a uniform protective film on the surface of silver particles, preventing silver particles from agglomerating during the reduction process and ensuring that the silver powder maintains a spherical structure.

[0009] 2. PAA helps silver ions to be more evenly dispersed in the reaction solution through complexation reaction, avoiding the problem of silver ion precipitation or excessive local concentration, thereby improving the purity and uniformity of silver powder.

[0010] 3. The addition of SDBS further avoids the mutual attraction and agglomeration between silver powder particles by providing electrostatic repulsion, ensuring that the silver powder particles can be evenly distributed during the liquid phase reduction process.

[0011] The present invention innovatively proposes a composite dispersant composed of a plurality of dispersants, and the selection of the composite method and proportion thereof ensures the high quality, uniform dispersion and spherical particle formation of the silver powder.

[0012] The composite formula of PVP, PAA, SDBS and PVA adopted in the present invention can provide more excellent dispersion performance in the liquid phase reduction process, which not only improves the quality of silver powder but also reduces the particle agglomeration phenomenon in the process, and has significant advantages over the prior art.

[0013] The present invention provides a method for preparing spherical silver powder in one step by a liquid phase reduction method, which has the advantages that: 1) the product is directly used as a raw material for photovoltaic front silver paste; 2) all reactions are carried out at low temperature, the reaction is fast and complete, the silver powder productivity is high, and the energy consumption is very low compared with other methods; 3) the reducing agent is a green reducing agent, such as glucose, citric acid, etc.; 4) the obtained silver powder does not need to be sieved after washing and drying, has good fluidity, and has a high tap density. The present invention can simply obtain submicron spherical silver powder by performing a reduction reaction in a simple reaction kettle aqueous solution, which is safe and environmentally friendly, low in cost, low in energy consumption, and can obtain a product powder with high purity and good fluidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the microstructure of spherical silver powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0015] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0016] The method for preparing spherical silver powder in one step by liquid phase reduction method of the present invention comprises pretreatment, liquid phase reduction reaction and post-treatment steps, specifically comprising: A. Pretreatment: 1) Prepare a silver nitrate solution with a concentration of 50-200 g / L to obtain an oxidant solution a; 2) preparing a glucose, citric acid or ascorbic acid solution with a concentration of 25-100 g / L to obtain a reducing agent solution b; B. Liquid phase reduction reaction: 1) The pH value of the reducing agent solution is adjusted to 2-4, and then a composite dispersant is added and stirred to dissolve to obtain material c; 2) adding the oxidant solution a to the material c for stirring reaction, and performing solid-liquid separation to obtain a solid precipitate d; C. Post-treatment: The solid precipitate d is washed and dried to obtain the target spherical silver powder.

[0017] The composite dispersant described in step B is composed of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA).

[0018] The mass ratio of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA) is: (0.5-1.5): (0.5-1.5): (0.5-1.5): (0.5-1.5).

[0019] The mass ratio of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA) is 1:1:1:1.

[0020] B. The temperature of the stirring reaction in step 2) is 25-45°C.

[0021] B. The stirring rate of the stirring reaction described in step 2) is 300-1500 r / min.

[0022] B. The stirring reaction time in step 2) is 20 to 40 minutes.

[0023] The drying described in step C is vacuum drying.

[0024] The drying temperature is 40±1°C.

[0025] The drying time is 20 to 30 hours.

[0026] The present invention is further described below with specific implementation cases: Example 1 (1) Prepare the required oxidant solution: take 100g / L AgNO3 solution in 0.5L water as the cathode electrolyte, stir and dissolve; (2) Prepare the required oxidant solution: prepare 0.5L of 25g / L glucose aqueous solution as the anode electrolyte, stir and dissolve; after the glucose solution is dissolved, add an appropriate amount of ammonia water to adjust the pH to 2~4, then add 2% dispersant, stir and dissolve; (3) Quickly pour the AgNO3 solution into the reducing agent solution, keep it at a constant temperature of 25℃, mechanically stir at 500r / min, separate the solid and liquid after 30min, and put the precipitate into a vacuum drying oven to dry at a temperature of 40±1℃ for 24h. Wherein, the dispersant is composed of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA) in a mass ratio of 1:1:1:1.

[0027] Example 2 (1) Prepare the required oxidant solution: take 50g / L AgNO3 solution in 0.5L water as the cathode electrolyte, stir and dissolve; (2) Prepare the required oxidant solution: prepare 0.5L of 25g / L citric acid aqueous solution as the anode electrolyte, stir and dissolve; after the citric acid solution is dissolved, add an appropriate amount of ammonia water to adjust the pH to 2~4, then add 2% dispersant, stir and dissolve; (3) Quickly pour the AgNO3 solution into the reducing agent solution, keep it at a constant temperature of 30℃, mechanically stir at 1000r / min, separate the solid and liquid after 30min, and put the precipitate into a vacuum drying oven for drying at a temperature of 40±1℃ for 20h. Wherein, the dispersant is composed of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA) in a mass ratio of 0.5:1:0.8:1.

[0028] Example 3 (1) Prepare the required oxidant solution: take 150g / L AgNO3 solution in 0.5L water as the cathode electrolyte, stir and dissolve; (2) Prepare the required oxidant solution: prepare 75g / L ascorbic acid aqueous solution as 0.5L anode electrolyte, stir and dissolve; after the ascorbic acid solution is dissolved, add appropriate amount of ammonia water to adjust the pH to 2~4, then add 2% dispersant, stir and dissolve; (3) Quickly pour the AgNO3 solution into the reducing agent solution, keep the constant temperature at 35℃, mechanically stir at 1500r / min, separate the solid and liquid after 30min, and put the precipitate into a vacuum drying oven for drying at a temperature of 40±1℃ for 30h. Wherein, the dispersant is composed of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA) in a mass ratio of 0.8:1.5:0.5:1.2.

[0029] Example 4 (1) Prepare the required oxidant solution: take 100g / L AgNO3 solution in 0.5L water as the cathode electrolyte, stir and dissolve; (2) Prepare the required oxidant solution: prepare 50g / L ascorbic acid aqueous solution as 0.7L anode electrolyte, stir and dissolve; after the ascorbic acid solution is dissolved, add appropriate amount of ammonia water to adjust the pH to 2~4, then add 2% dispersant, stir and dissolve; (3) Quickly pour the AgNO3 solution into the reducing agent solution, keep it at a constant temperature of 40℃, mechanically stir at 1500r / min, separate the solid and liquid after 30min, and put the precipitate into a vacuum drying oven for drying at a temperature of 40±1℃ for 25h. Wherein, the dispersant is composed of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA) in a mass ratio of 1.5:0.8:1.3:1.5.

[0030] Example 5 (1) Prepare the required oxidant solution: take 50g / L AgNO3 solution in 0.5L water as the cathode electrolyte, stir and dissolve; (2) Prepare the required oxidant solution: prepare 0.6L of 25g / L ascorbic acid aqueous solution as the anode electrolyte, stir and dissolve; after the ascorbic acid solution is dissolved, add an appropriate amount of ammonia water to adjust the pH to 2~4, then add 2% dispersant, stir and dissolve; (3) Quickly pour the AgNO3 solution into the reducing agent solution, keep it at a constant temperature of 45℃, mechanically stir at 1500r / min, separate the solid and liquid after 30min, and put the precipitate into a vacuum drying oven for drying at a temperature of 40±1℃ for 24h. Wherein, the dispersant is composed of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA) in a mass ratio of 1.2:0.8:1.8:0.6.

Claims

1. A method for preparing spherical silver powder in one step by liquid phase reduction, characterized in that: The method for preparing spherical silver powder in one step by liquid phase reduction method comprises pretreatment, liquid phase reduction reaction and post-treatment steps, specifically comprising: A. Pretreatment: 1) Prepare a silver nitrate solution with a concentration of 50-200 g / L to obtain an oxidant solution a; 2) preparing a glucose, citric acid or ascorbic acid solution with a concentration of 25-100 g / L to obtain a reducing agent solution b; B. Liquid phase reduction reaction: 1) The pH value of the reducing agent solution is adjusted to 2-4, and then a composite dispersant is added and stirred to dissolve to obtain material c; 2) adding the oxidant solution a to the material c for stirring reaction, and performing solid-liquid separation to obtain a solid precipitate d; C. Post-treatment: The solid precipitate d is washed and dried to obtain the target spherical silver powder.

2. The method for preparing spherical silver powder by one step using a liquid phase reduction method according to claim 1, characterized in that: The composite dispersant described in step B is composed of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA).

3. The method for preparing spherical silver powder by one step using a liquid phase reduction method according to claim 2, characterized in that: The mass ratio of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA) is: (0.5-1.5): (0.5-1.5): (0.5-1.5): (0.5-1.5).

4. The method for preparing spherical silver powder by one step using a liquid phase reduction method according to claim 2 or 3, characterized in that: The mass ratio of polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium dodecylbenzene sulfonate (SDBS) and polyvinyl alcohol (PVA) is 1:1:1:

1.

5. The method for preparing spherical silver powder by one step using a liquid phase reduction method according to claim 1, characterized in that: B. The temperature of the stirring reaction in step 2) is 25-45°C.

6. The method for preparing spherical silver powder by one step using a liquid phase reduction method according to claim 1, characterized in that: The stirring rate of the stirring reaction described in step B 2) is 300-1500 r / min.

7. The method for preparing spherical silver powder by one step using a liquid phase reduction method according to claim 1, characterized in that: B. The stirring reaction time in step 2) is 20 to 40 minutes.

8. The method for preparing spherical silver powder by one step using a liquid phase reduction method according to claim 1, characterized in that: The drying described in step C is vacuum drying.

9. The method for preparing spherical silver powder in one step by liquid phase reduction method according to claim 1 or 6, characterized in that: The drying temperature is 40±1°C.

10. The method for preparing spherical silver powder in one step by liquid phase reduction method according to claim 1 or 6, characterized in that: The drying time is 20 to 30 hours.

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