Preparation method of flake silver powder
By using a double coating method with stearic acid and lauric acid and adjusting the particle size with copper nitrate, combined with stirring and ball milling processes, the problem of quality instability caused by environmental fluctuations in the preparation of flake silver powder was solved, and silver powder with high regularity and uniform particle size was prepared, thus improving the consistency and dispersibility of the product.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-23
- Publication Date
- 2026-03-06
AI Technical Summary
In the existing technology for preparing flake silver powder, environmental fluctuations lead to uneven growth of silver particles, resulting in particle adhesion, clumping, uneven particle size distribution, and poor product quality consistency.
Double coating with stearic acid and lauric acid was used, and copper nitrate was used to adjust the particle size. The particles were then refined through stirring and ball milling. Polyvinylpyrrolidone was used as a dispersant to control the nucleation and growth of silver powder. Zirconia beads of different sizes were used for ball milling to optimize the particle size distribution.
The prepared flake-shaped silver powder has a regular morphology, concentrated particle size distribution, excellent dispersibility, and small batch-to-batch variation, which improves the tap density and surface activity of the silver powder.
Smart Images
Figure CN121607643A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of silver powder technology, and more particularly to a method for preparing flake silver powder. Background Technology
[0002] Flake silver powder is an important basic raw material in the field of electronic materials. The uniformity of particle size distribution, regularity of morphology and dispersion stability of flake silver powder directly affect the performance of products such as conductive pastes.
[0003] Currently, most methods for preparing flake silver powder are liquid-phase chemical reduction methods. This method involves adding a reducing agent to a silver salt solution to reduce silver ions and using a dispersant to control particle agglomeration. However, this method has the following drawbacks: the production environment is difficult to maintain at a constant temperature and humidity, leading to uneven growth of silver particles; a single coating system can cause particle adhesion and clumping; and the chemical reduction method results in large batch-to-batch variations in particle size distribution and poor product quality consistency.
[0004] Therefore, a technical solution is needed to simultaneously improve the morphology and properties of silver powder to overcome the above-mentioned defects. Summary of the Invention
[0005] In view of this, this application provides a method for preparing flake silver powder to solve the problem of how to improve the performance and morphology of silver powder.
[0006] To achieve the above technical objectives, this application adopts the following technical solution: In a first aspect, this application provides a method for preparing flake-shaped silver powder, comprising the following steps: Adding ammonia to silver nitrate solution yields silver ammonia solution; Stearic acid was added to the silver ammonia solution to obtain the first mixture; The first mixture and hydroxylamine sulfate solution were added to a polyvinylpyrrolidone solution containing copper nitrate and stirred once. Lauric acid was then added and stirred a second time. After washing and drying, the mixture was ball-milled to obtain flake silver powder.
[0007] Preferably, the hydroxylamine sulfate is 50-60% of the mass of silver nitrate.
[0008] Preferably, the secondary stirring rate is 400-600 r / min, and the stirring time is 3 min.
[0009] Preferably, the stearic acid is 1-2% of the mass of silver nitrate.
[0010] Preferably, the amount of copper nitrate is 1-2% of the mass of silver nitrate.
[0011] Preferably, the lauric acid is 1-2% of the mass of silver nitrate.
[0012] Preferably, the stirring rate is 400-600 r / min and the stirring time is 1 min.
[0013] Preferably, the polyvinylpyrrolidone is 18-25% of the mass of silver nitrate.
[0014] Preferably, the zirconia beads of different sizes include zirconia beads with a diameter of 2 mm and zirconia beads with a diameter of 0.5 mm.
[0015] Preferably, the process of mixing and ball milling is as follows: different batches of raw silver powder after cleaning and drying are mixed, then oleic acid, ethanol and zirconium oxide beads of different particle sizes are added and ball milled, and then the zirconium oxide beads are separated.
[0016] The beneficial effects of this application are as follows: This invention utilizes stearic acid and lauric acid for double coating, copper nitrate for particle size adjustment, and further refines the stirring and ball milling process to achieve control over the nucleation, growth, and morphology of flake silver powder. This overcomes the influence of environmental fluctuations on the quality of silver powder, and the prepared flake silver powder has high morphological regularity, concentrated particle size distribution, excellent dispersibility, and small batch-to-batch variation, thereby improving the tap density and surface activity of silver powder. Attached Figure Description
[0017] Figure 1 Here is a SEM image of the silver powder from Example 1; Figure 2 Here is a SEM image of the silver powder from Example 2; Figure 3 Here is a SEM image of the silver powder from Example 3; Figure 4 This is a SEM image of silver powder from Comparative Example 1; Figure 5 Here is a SEM image of the silver powder in Comparative Example 2; Figure 6 SEM image of silver powder in Comparative Example 3; Figure 7 This is a SEM image of silver powder in Comparative Example 4. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0019] This application provides a method for preparing flake-shaped silver powder, comprising the following steps: Adding ammonia to silver nitrate solution yields a silver ammonia solution; Stearic acid was added to the silver ammonia solution to obtain the first mixture; Hydroxylamine sulfate solution and the first mixture were added to a polyvinylpyrrolidone solution containing copper nitrate and stirred once. Lauric acid was then added and stirred a second time. After washing and drying, flake silver powder was obtained.
[0020] In this application, hydroxylamine sulfate is used as a reducing agent, stearic acid as an initial coating agent, polyvinylpyrrolidone as a dispersant, copper nitrate as a particle size regulator, and lauric acid as a secondary coating agent. By using stearic acid and lauric acid for double coating and copper nitrate for particle size regulation, and further refining the process through stirring and ball milling, the nucleation, growth, and morphology of flake silver powder are controlled. This overcomes the influence of environmental fluctuations on the quality of silver powder. The prepared flake silver powder has high morphological regularity, concentrated particle size distribution, excellent dispersibility, and small batch-to-batch variation, thereby improving the tap density and surface activity of the silver powder.
[0021] The preparation process of this application is as follows: First, silver nitrate is prepared into a silver ammonia solution, and then stearic acid, -COOH and OH are added to the silver ammonia solution. - The reaction generates stearate ions to form silver stearate, which is dispersed in the form of fine particles, facilitating subsequent morphology control and achieving good dispersibility. Then, silver ammonia solution and hydroxylamine sulfate solution are added to the PVP solution simultaneously. The coating agent ensures the dispersibility of the silver powder and guides the growth direction with silver stearate as the core. In addition, the reaction between silver ammonia solution and hydroxylamine sulfate is relatively vigorous, and the addition of PVP slows down the reaction rate, improves particle uniformity, and finally obtains silver powder with uniform particle size and good sphericity.
[0022] In some embodiments, stearic acid is 1-2% of the mass of silver nitrate.
[0023] In this embodiment, if the amount used is too small, it will result in irregular morphology.
[0024] In some embodiments, hydroxylamine sulfate is 50-60% of the mass of silver nitrate.
[0025] In some embodiments, polyvinylpyrrolidone is 18-25% of the mass of silver nitrate.
[0026] In this embodiment, if too much polyvinylpyrrolidone is used, it will affect the conductivity of the silver powder; if too little is used, it will lead to a decrease in dispersibility.
[0027] In some embodiments, lauric acid is 1-2% of the mass of silver nitrate.
[0028] In this embodiment, if too much lauric acid is used, the two coating agents will compete with each other, which will have an adverse effect on the uniformity and integrity of the coating; if too much is used, the surface of the silver particles will not be fully protected.
[0029] In some embodiments, the stirring rate is 400-600 r / min and the stirring time is 1 min.
[0030] In some embodiments, the secondary stirring rate is 400-600 r / min, and the stirring time is 3 min.
[0031] In some embodiments, copper nitrate is 1-2% of the mass of silver nitrate.
[0032] In this embodiment, if too much copper nitrate is used, it will affect the conductivity of the product and introduce impurities; if too little is used, the particle size distribution will be poorly controlled.
[0033] In some embodiments, after cleaning and drying, the process further includes the steps of: mixing different batches of flake silver powder, then adding ethanol, oleic acid and zirconium oxide beads of different particle sizes for ball milling, and then separating the zirconium oxide beads.
[0034] In this embodiment, ethanol prevents the silver powder from oxidizing during the grinding process, and oleic acid acts as a grinding aid. Ball milling breaks down soft agglomerates in the silver powder and increases the specific surface area, while also improving the powder's dispersibility.
[0035] In some embodiments, the zirconia beads of different sizes include zirconia beads with a diameter of 2 mm and zirconia beads with a diameter of 0.5 mm.
[0036] In this embodiment, using zirconia beads of different sizes helps to obtain an ideal particle size distribution and particle morphology while ensuring grinding efficiency.
[0037] The following specific embodiments further illustrate this solution.
[0038] Example 1 A method for preparing flake-shaped silver powder specifically includes the following steps: Dissolve 85g of silver nitrate in 200mL of deionized water to form a silver nitrate solution. While stirring, add 139mL of 28wt% ammonia water until the precipitate is completely dissolved to obtain a clear and transparent silver ammonia solution. Add 0.85g of stearic acid to the silver ammonia solution to obtain the first mixture.
[0039] 48.45 g of hydroxylamine sulfate was dissolved in 100 mL of deionized water to obtain a hydroxylamine sulfate solution. Then, 17 g of polyvinylpyrrolidone and 0.85 g of copper nitrate were dissolved in 100 mL of anhydrous ethanol to obtain a mixed solution containing PVP and copper nitrate. The hydroxylamine sulfate solution and the first mixed solution were added to the mixed solution containing PVP and copper nitrate simultaneously. The mixture was stirred at 500 r / min for 1 min for a first stirring reaction. Then, 0.85 g of lauric acid was added, and the mixture was stirred at 500 r / min for 3 min for a second stirring reaction. After the reaction was completed, the product was washed three times alternately with deionized water and anhydrous ethanol, and then dried at 95 °C for 10 hours to obtain raw silver powder. This process was repeated three times to obtain different batches of raw silver powder.
[0040] Take 500g of the dried raw silver powder in equal proportions, add 1000g of zirconia beads with a particle size of 2mm and 1000g of zirconia beads with a particle size of 0.5mm, then add 600g of anhydrous ethanol and 5g of oleic acid. Ball mill at 180r / min for 12 hours, then sieve to remove the zirconia beads, filter, and dry at 70℃ for 8 hours to obtain the flake silver powder product. Its SEM image is shown below. Figure 1 As shown.
[0041] Example 2 A method for preparing flake silver powder is the same as in Example 1, except that 0.425g of copper nitrate is added when preparing the PVP solution.
[0042] Example 3 A method for preparing flake silver powder is the same as in Example 1, except that 1.7g of copper nitrate is added when preparing the PVP solution.
[0043] Example 4 A method for preparing flake silver powder is the same as in Example 1, except that 1.7g of stearic acid is added to the silver ammonia solution.
[0044] Comparative Example 1 A method for preparing silver powder, which is otherwise the same as in Example 1, except that lauric acid is not added.
[0045] Comparative Example 2 A method for preparing silver powder is the same as in Example 1, except that copper nitrate is not added.
[0046] Comparative Example 3 A method for preparing silver powder, which is otherwise the same as in Example 1, except that PVP is not added.
[0047] Comparative Example 4 A method for preparing silver powder is the same as in Example 1, except that the powder mixing and ball milling step is omitted.
[0048] Testing and Evaluation The performance of the flake silver powder in different embodiments and comparative examples was evaluated, and the results are shown in Table 1.
[0049] Table 1 Test Results
[0050] This invention utilizes stearic acid and lauric acid for double coating, copper nitrate for particle size adjustment, and further refines the stirring and ball milling processes to achieve control over the nucleation, growth, and morphology of flake silver powder. This overcomes the influence of environmental fluctuations on the quality of silver powder, and the prepared flake silver powder has high morphological regularity, concentrated particle size distribution, excellent dispersibility, and small batch-to-batch variation, thereby improving the tap density and surface activity of the silver powder.
[0051] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for producing a flaky silver powder, characterized by, The method comprises the following steps: adding ammonia water into silver nitrate solution to obtain silver ammonia solution; adding stearic acid into the silver ammonia solution to obtain a first mixed solution; adding the first mixed solution and hydroxylamine sulfate solution into polyvinylpyrrolidone solution containing copper nitrate to perform primary stirring reaction, adding lauric acid to perform secondary stirring reaction, cleaning, drying, mixing, ball milling, and obtaining the flaky silver powder.
2. The production method according to claim 1, characterized by, The hydroxylamine sulfate is 50-60% of the mass of the silver nitrate.
3. The production method according to claim 1, characterized by, The stirring rate of the secondary stirring is 400-600 r / min, and the stirring time is 3 min.
4. The method of claim 1, wherein, The stearic acid is 1-2% of the mass of the silver nitrate.
5. The preparation method according to claim 1, characterized in that, The copper nitrate is 1-2% of the mass of the silver nitrate.
6. The method of claim 1, wherein, The lauric acid is 1-2% of the mass of the silver nitrate.
7. The preparation method according to claim 1, characterized in that, The stirring rate of the primary stirring is 400-600 r / min, and the stirring time is 1 min.
8. The method of claim 1, wherein, The polyvinylpyrrolidone is 18-25% of the mass of the silver nitrate.
9. The method of claim 1, wherein, The zirconia beads with different particle sizes include zirconia beads with a particle size of 2 mm and zirconia beads with a particle size of 0.5 mm.
10. The method of claim 1, wherein, The process of the powder mixing and ball milling is as follows: mixing the original silver powder of different batches after cleaning and drying, adding oleic acid, ethanol and zirconia beads with different particle sizes for ball milling, and then separating the zirconia beads.