A method for preparing nano-silver powder

Abstract

The application discloses a method for preparing nano silver powder and belongs to the field of silver oxide material preparation. The method comprises the following steps: preparing and purifying a silver nitrate solution, preparing an alkali solution, preparing an emulsifier solution, preparing a surfactant solution, adding the emulsifier solution and the surfactant solution into the silver nitrate solution under stirring, adding the alkali solution into the mixed solution drop by drop after uniform dispersion, and washing and vacuum drying after neutralization reaction and precipitation are completed, so that high-purity nano silver oxide powder material is prepared. The silver oxide prepared by the method has a particle size of 40-80 nm, can realize spheroidization, has an impurity content Nb of less than 0.03%, and has an impurity content of less than 0.006%, and the method has a relatively short technological process and can realize batch industrial production.

Description

Technical Field

[0001] This invention belongs to the field of materials engineering technology, and specifically relates to a method for preparing nano-silver powder. Background Technology

[0002] Silver powder possesses high conductivity, high ductility, and oxidation resistance, making it irreplaceable by copper powder. Silver powder is a key component in intelligent manufacturing, intelligent equipment, and intelligent control within the entire electronics industry. The preparation of high-end silver powder significantly promotes technological innovation in the electronics industry, analytical chemistry, battery industry (silver-zinc batteries), and pharmaceutical industry (sterilization and preservation).

[0003] The morphology, particle size, tap density, and dispersion of silver powder are key factors that determine the electrical conductivity of the printing paste after sintering.

[0004] Foreign silver powder and paste production technologies are relatively complete and mature, producing silver powder with high cleanliness, uniform particle size distribution, uniform morphology, and good dispersibility; the produced conductive pastes have stable performance and good reliability; the development of new technologies continuously improves product quality while also continuously reducing costs.

[0005] Currently, the main methods for preparing silver powder both domestically and internationally are physical methods (ball milling, vacuum evaporation, high-frequency arc induction, electron beam irradiation, ion sputtering, atomization, etc.), chemical reduction methods (liquid-phase chemical reduction, electrochemical reduction, photochemical reduction, sol-gel method, template method, etc.), microbial synthesis, and plant reduction. These methods produce products with inconsistent morphology, particle size and diameter, tap density and loose packing density, BET (bulk osmotic pressure), pore volume and pore size, resulting in inconsistent product performance and applications. High-end silver powder from abroad is primarily prepared using liquid-phase reduction. Through strict control of process parameters, improvement of process equipment, and system integration, products with uniform particle size distribution, regular and uniform morphology, good dispersibility, stable performance, and controllable particle size can be prepared. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing nano-silver powder.

[0007] The objective of this invention is achieved by including slurry preparation, liquid-phase reduction, and post-treatment steps, specifically including:

[0008] A. Slurry preparation: Weigh Ag2O or Ag2CO3 and add high-purity water according to the liquid-solid ratio (5~7):1 to prepare slurry a;

[0009] B. Liquid-phase reduction: Heat slurry a to 40-45℃, and add coating agent solution, dispersant solution and reducing agent solution sequentially under stirring at 28-32 r / min, with an interval of 8-12 min between additions. Then raise the temperature to 90-95℃ and react under stirring at 23-25 ​​r / min for 50-70 min. Then add high-purity water to cool to 35-40℃ and react under stirring at 38-42 r / min for 15-25 min. Finally, heat to 80-90℃ and react under stirring at 26-30 r / min for 8-12 min to obtain reaction solution b.

[0010] C. Post-processing:

[0011] 1) Let the reaction solution b stand for 50-70 minutes, then extract the supernatant c;

[0012] 2) Add high-purity water to the remaining slurry and stir and wash it at room temperature and 90~110r / min. After stirring and washing, extract the supernatant. Repeat this process 2~4 times to obtain silver paste d.

[0013] 3) Allow the silver paste d to naturally percolate for 20-30 hours to obtain silver filter cake e;

[0014] 4) After drying the silver filter cake e, the target material, silver nanoparticles, with a particle size of 40-80 nm are obtained.

[0015] The specific steps are as follows:

[0016] (1) Prepare Ag2O or Ag2CO3 slurry; (2) Prepare coating agent solution; (3) Prepare dispersant solution; (4) Prepare reducing agent solution; (5) Liquid-phase reduction of Ag2O or Ag2CO3; (6) Natural percolation of Ag powder; (7) Low-temperature drying of Ag powder. The silver powder prepared by this method has small particle size, uniform particle size distribution, regular and uniform morphology, and monodisperse particles. The preparation process of this method is short and simple, and the steps are easy to refine.

[0017] The specific steps are as follows:

[0018] (1) Prepare Ag2O or Ag2CO3 slurry according to a certain liquid-solid ratio.

[0019] (2) Weigh a certain amount of coating agent according to the weight of solid Ag2O or Ag2CO3, dissolve it in alcohol at a certain temperature to form a coating agent solution.

[0020] (3) Weigh a certain amount of dispersant according to the weight of solid Ag2O or Ag2CO3, and dissolve it in alcohol at a certain temperature to form a dispersant solution.

[0021] (4) Weigh a certain amount of reducing agent according to the weight of solid Ag2O or Ag2CO3, dissolve it in alcohol at a certain temperature to form a reducing agent solution.

[0022] (5) Under a certain stirring speed, heat the slurry to a certain temperature, and add the coating agent solution → dispersant solution → reducing agent solution to the Ag2O or Ag2CO3 slurry in sequence. Precisely control the reaction temperature and time throughout the entire reaction process until the reaction is completed.

[0023] (6) After the reaction is complete, let it stand for a certain period of time and then extract the supernatant.

[0024] (7) Add high-purity water and stir to wash. After stirring, let it stand for a certain period of time, and then extract the supernatant. Repeat this process several times.

[0025] (8) The silver paste after washing is released from the bottom of the reactor and naturally filtered into the filter bucket.

[0026] (9) Place the wet silver filter cake in a tray and dry it in a drying oven, controlling the temperature and time.

[0027] The silver oxide prepared by this invention has a particle size of 40-80 nm, can achieve spherical morphology, has an impurity content of Nb < 0.03%, and the contents of other impurities are all less than < 0.006%. This method has a short process flow and can realize mass industrial production. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0030] The present invention includes slurry preparation, liquid-phase reduction, and post-treatment steps, specifically including:

[0031] A. Slurry preparation: Weigh Ag2O or Ag2CO3 and add high-purity water according to the liquid-solid ratio (5~7):1 to prepare slurry a;

[0032] B. Liquid-phase reduction: Heat slurry a to 40-45℃, and add coating agent solution, dispersant solution and reducing agent solution sequentially under stirring at 28-32 r / min, with an interval of 8-12 min between additions. Then raise the temperature to 90-95℃ and react under stirring at 23-25 ​​r / min for 50-70 min. Then add high-purity water to cool to 35-40℃ and react under stirring at 38-42 r / min for 15-25 min. Finally, heat to 80-90℃ and react under stirring at 26-30 r / min for 8-12 min to obtain reaction solution b.

[0033] C. Post-processing:

[0034] 1) Let the reaction solution b stand for 50-70 minutes, then extract the supernatant c;

[0035] 2) Add high-purity water to the remaining slurry and stir and wash it at room temperature and 90~110r / min. After stirring and washing, extract the supernatant. Repeat this process 2~4 times to obtain silver paste d.

[0036] 3) Allow the silver paste d to naturally percolate for 20-30 hours to obtain silver filter cake e;

[0037] 4) After drying the silver filter cake e, the target material, silver nanoparticles, with a particle size of 40-80 nm are obtained.

[0038] The reducing agent is borohydride, hydrazine hydrate, sodium citrate, potassium tartrate, amine compounds, glucose, ascorbic acid, sodium hypophosphite, hydrogen peroxide, alcohol compounds, aldehyde compounds, or N,N-dimethylformamide (DMF).

[0039] The coating agent is paraffin, glycerin, rosin, nylon, gelatin, agar, rubber, fat, starch, oil, protein, thermoplastic, nylon, or acetone.

[0040] The dispersant is polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), hydroxyethyl cellulose (HEC), polyethylene glycol (PEG-6000), polyacrylamide, ammonium polyacrylate, Tween 80, sodium dodecylbenzene sulfonate, polyethylene glycol fatty acid ester, or fatty acid polyoxyethylene ester.

[0041] The drying process described in step 4) involves drying at a temperature of 70-80°C for 45-50 hours. The invention will be further illustrated below with specific implementation examples:

[0042] Example 1

[0043] (1) Weigh 30 kg of Ag2O or Ag2CO3 and add 180 L of high-purity water to adjust the slurry according to a liquid-solid ratio of 6:1.

[0044] (2) Weigh 120g of coating agent into a 5L reaction vessel, add 2L of anhydrous alcohol, and dissolve at 40℃ to form a coating agent solution.

[0045] (3) Weigh 300g of dispersant ammonium polyacrylate into a 5L reaction tank, add 1L of anhydrous ethanol, and dissolve at 25℃ to form a dispersant solution.

[0046] (4) Weigh 4.5 kg of sodium hypophosphite, the reducing agent, into a 20 L reaction vessel, add 10 L of 90% alcohol, and dissolve at 25 °C to form a reducing agent solution.

[0047] (5) At a stirring speed of 30 r / min, heat the slurry to 40℃~45℃, and add 2L of coating agent solution, 1L of dispersant solution, and 10L of reducing agent solution to the Ag2O or Ag2CO3 slurry in sequence, with a time interval of 10 min between the addition of coating agent, dispersant and reducing agent. After the reducing agent is added, continue to heat to 91℃, adjust the stirring speed to 24 r / min, and stir for 1 hour. Then add high-purity water to cool down to 35℃~40℃, adjust the stirring speed to 40 r / min, and react for 20 minutes. Then heat to 85℃ three times and react for 10 minutes, with a stirring speed of 28 r / min.

[0048] (6) After the reaction is complete, let it stand for 1 hour and then extract the supernatant.

[0049] (7) Add 600L of high-purity water, stir and wash, and let stand for 1 hour. The stirring temperature is room temperature and the stirring speed is 100r / min. After stirring and washing, remove the supernatant. Repeat this process 3 times.

[0050] (8) After washing, the silver paste is released from the bottom of the reactor and allowed to naturally percolate in the filter bucket for 24 hours.

[0051] (9) Place the wet silver filter cake in a tray and dry it in a drying oven at 75°C for 48 hours.

[0052] Example 2

[0053] (1) Weigh 30 kg of Ag2O or Ag2CO3 and add 180 L of high-purity water to adjust the slurry according to a liquid-solid ratio of 6:1.

[0054] (2) Weigh 150g of coating agent glycerin into a 5L reaction vessel, add 2L of anhydrous ethanol, and dissolve at 40℃ to form a coating agent solution.

[0055] (3) Weigh 300g of dispersant polyvinylpyrrolidone (PVP) into a 5L reaction vessel, add 2L of anhydrous ethanol, and dissolve at 25℃ to form a dispersant solution.

[0056] (4) Weigh 2.5 kg of reducing agent hydrazine hydrate into a 20 L reaction vessel, add 10 L of 90% alcohol, and dissolve at 25 °C to form a reducing agent solution.

[0057] (5) At a stirring speed of 28 r / min, heat the slurry to 40℃~45℃, and add 2L of coating agent solution, 2L of dispersant solution, and 10L of reducing agent solution to the Ag2O or Ag2CO3 slurry in sequence, with an 8-minute interval between the addition of coating agent, dispersant, and reducing agent. After the reducing agent is added, continue to heat to 90℃, adjust the stirring speed to 23 r / min, and stir for 50 minutes. Then add high-purity water to cool down to 35℃~40℃, adjust the stirring speed to 38 r / min, and stir for 25 minutes. Then heat to 80℃ three times and react for 12 minutes each time, with a stirring speed of 30 r / min.

[0058] (6) After the reaction is complete, let it stand for 50 minutes and then remove the supernatant.

[0059] (7) Add 500L of high-purity water, stir and wash, and let stand for 1 hour. The stirring temperature is room temperature and the stirring speed is 90r / min. After stirring, remove the supernatant. Repeat this process 3 times.

[0060] (8) After washing, the silver paste is released from the bottom of the reactor and allowed to naturally percolate in the filter barrel for 25 hours.

[0061] (9) Place the wet silver filter cake in a tray and dry it in a drying oven at 70°C for 48 hours.

[0062] Example 3

[0063] (1) Weigh 30 kg of Ag2O or Ag2CO3 and add 180 L of high-purity water to adjust the slurry according to a liquid-solid ratio of 7:1.

[0064] (2) Weigh 120g of coating agent gelatin into a 5L reaction vessel, add 1L of anhydrous alcohol, and dissolve at 40℃ to form a coating agent solution.

[0065] (3) Weigh 400g of dispersant polyethylene glycol (PEG-6000) into a 5L reaction vessel, add 2L of anhydrous ethanol, and dissolve at 25℃ to form a dispersant solution.

[0066] (4) Weigh 3 kg of sodium citrate, the reducing agent, into a 20 L reaction vessel, add 10 L of 90% alcohol, and dissolve at 25 °C to form a reducing agent solution.

[0067] (5) At a stirring speed of 32 r / min, the slurry is heated to 40℃~45℃. 1 L of coating agent solution, 2 L of dispersant solution, and 10 L of reducing agent solution are added sequentially to the Ag2O or Ag2CO3 slurry, with a time interval of 21 min between each addition. After the reducing agent is added, the temperature is raised to 95℃, the stirring speed is adjusted to 25 r / min, and the reaction is carried out for 50 min. Then, high-purity water is added to lower the temperature to 35℃~40℃, the stirring speed is adjusted to 42 r / min, and the reaction is carried out for 15 min. Then, the temperature is raised to 90℃ three times and the reaction is carried out for 8 min each time, with a stirring speed of 30 r / min.

[0068] (6) After the reaction is complete, let it stand for 1 hour and then extract the supernatant.

[0069] (7) Add 600L of high-purity water, stir and wash, and let stand for 1 hour. The stirring temperature is room temperature and the stirring speed is 110r / min. After stirring and washing, remove the supernatant. Repeat this process 3 times.

[0070] (8) After washing, the silver paste is released from the bottom of the reactor and allowed to naturally percolate in the filter bucket for 24 hours.

[0071] (9) Place the wet silver filter cake in a tray and dry it in a drying oven at 60°C for 48 hours.

Claims

1. A method for preparing nano-silver powder, characterized in that, It includes slurry preparation, liquid-phase reduction, and post-processing steps, specifically including: A. Slurry preparation: Weigh Ag2O or Ag2CO3 and add high-purity water according to the liquid-solid ratio (5~7):1 to prepare slurry a; B. Liquid-phase reduction: Heat slurry a to 40-45℃, and add coating agent solution, dispersant solution and reducing agent solution sequentially under stirring at 28-32 r / min, with an interval of 8-12 min between additions. Then raise the temperature to 90-95℃ and react under stirring at 23-25 ​​r / min for 50-70 min. Then add high-purity water to cool to 35-40℃ and react under stirring at 38-42 r / min for 15-25 min. Finally, heat to 80-90℃ and react under stirring at 26-30 r / min for 8-12 min to obtain reaction solution b. The reducing agent is borohydride, hydrazine hydrate, sodium citrate, potassium tartrate, amine compounds, glucose, ascorbic acid, sodium hypophosphite, hydrogen peroxide, alcohol compounds, aldehyde compounds, or N,N-dimethylformamide; The coating agent is paraffin, glycerin, rosin, nylon, gelatin, agar, rubber, fat, starch, oil, protein, thermoplastic, nylon, or acetone. The dispersant is polyvinylpyrrolidone, polyvinyl alcohol, hydroxyethyl cellulose, polyethylene glycol, polyacrylamide, ammonium polyacrylate, Tween 80, sodium dodecylbenzene sulfonate, polyethylene glycol fatty acid ester or fatty acid polyoxyethylene ester; C. Post-processing: 1) Let the reaction solution b stand for 50-70 minutes, then extract the supernatant c; 2) Add high-purity water to the remaining slurry and stir and wash it at room temperature and 90~110r / min. After stirring and washing, extract the supernatant. Repeat this process 2~4 times to obtain silver paste d. 3) Allow the silver paste d to naturally percolate for 20-30 hours to obtain silver filter cake e; 4) After drying the silver filter cake e at a temperature of 70~80℃ for 45~50h, the target material, silver nanoparticles, with a particle size of 40-80nm are obtained.

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