Spherical-like-sheet-shaped mixed silver powder and preparation method and application thereof
A one-step chemical synthesis method was used to prepare spherical-flaky mixed silver powder, which solved the problem of insufficient performance of single-form silver powder and achieved mixed silver powder with high conductivity and high filling capacity, suitable for electronic pastes and conductive adhesive materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-22
- Publication Date
- 2026-03-24
AI Technical Summary
Existing technologies for single-form silver powder have problems with insufficient conductivity, filling capacity and printability. Moreover, existing mixing methods are complex, energy-intensive and costly, making it difficult to meet the needs of miniaturized electronic products.
A one-step chemical synthesis method was used to prepare a spherical-flaky mixed silver powder. By controlling the pH value, temperature and the amount of inducing agent of the solution, the ratio of spherical and flake silver powder was adjusted to form a mixed silver powder.
It has achieved a hybrid silver powder that is simple to operate, low in cost, and easy to mass-produce, while also possessing high conductivity and high filler properties, meeting the needs of electronic pastes and conductive adhesives.
Smart Images
Figure CN121715567A_ABST
Abstract
Description
Technical Field
[0001] This disclosure belongs to the field of silver powder and electronic paste technology, specifically relating to a spherical-flake mixed silver powder, its preparation method, and its application. Background Technology
[0002] Silver powder, as a core solution in key electronic materials such as electronic pastes and conductive adhesives, directly affects the miniaturization, integration, and reliability of electronic devices. With the rapid development of photovoltaic solar cells, flexible batteries, 5G communications, and other fields, higher requirements are being placed on the conductivity, filling properties, printing accuracy, and cost control of silver powder.
[0003] However, single-form silver powder has inherent drawbacks. For example, while spherical silver powder has good flowability and high tap density, the particles mainly have point contact, resulting in few conductive pathways. This necessitates high addition amounts to meet conductivity requirements, leading to increased material costs. Flake silver powder forms a continuous conductive network through surface contact, offering superior conductivity, but its large stacking gaps and low tap density can easily cause pinholes, collapses, or insufficient solids content during printing, making it unsuitable for printing ultra-fine grid lines. Compared to single-form silver powder, mixed silver powder can have synergistic effects in conductivity, paste stability, and printing performance.
[0004] To address the performance bottlenecks of single-form silver powder, existing technologies often employ methods that prepare spherical and flake silver powders separately and then mix them for use. Spherical particles fill the gaps between flake particles. However, this process is complex, energy-intensive, has poor uniformity, and is prone to local agglomeration, affecting the stability of the slurry performance. Furthermore, preparing the two types of silver powder separately has drawbacks such as long cycle time (e.g., ball milling time requires 5-10 hours), high cost, and limited large-scale production. Therefore, developing a simple process and morphology-controllable spherical-flake mixed silver powder preparation technology is crucial to breaking through the performance bottlenecks of existing electronic materials and meeting the needs of miniaturized electronic products. Summary of the Invention
[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a spherical-flaky mixed silver powder, its preparation method, and its application.
[0006] One aspect of this disclosure provides a method for preparing a spherical-flaky mixed silver powder, the method comprising: S110. Add citric acid and H2O2 to the reaction vessel, mix and stir, and heat. Then add NaBH4 and AgNO3 to the reaction vessel and stir to obtain a seed solution. S120. Add the inducing agent and nitric acid solution to the dispersant in sequence, and adjust the pH of the solution to 1.5-3.5 to form a dispersant solution; S130. Add sodium hydroxide solution to the reducing agent to adjust the pH of the solution to 3-5, thus forming a reducing agent solution; S140. Add nitric acid solution to the silver salt solution to adjust the pH of the solution to 1.5-3.5, forming a silver source solution; S150. The seed solution is added to the dispersant solution and stirred to form a mixed solution. Then, the silver source solution and the reducing agent solution are added dropwise to the mixed solution and stirred to obtain a silver powder turbid liquid. S160. The silver powder turbid liquid undergoes solid-liquid separation, washing, modification, drying, and sieving to obtain a spherical-flaky mixed silver powder.
[0007] Optionally, in step S110, the concentration of citric acid is 5-8 mM, and the added volume is 80-100 mL; The concentration of H2O2 is 0.15-0.45M, and the added volume is 70-90mL; The concentration of NaBH4 is 0.3-0.7 mM, and the added volume is 10-30 mL; The concentration of AgNO3 is 0.03-0.1M, and the added volume is 5-15mL; The citric acid and H2O2 are added to the reaction vessel and mixed and stirred for 0.5-1.0 h, and the heating temperature is 60-75℃; Add NaBH4 and AgNO3 to the reaction vessel and stir for 0.5-1.5 hours.
[0008] Optionally, in step S120, the concentration of the dispersant is 0.12-0.3M, and the addition volume is 300-350mL; The concentration of the inducer is 0.21-0.62 mM, and the addition volume is 2-10 mL; The pH of the dispersant solution is 1.5-3.5, and the solution temperature is controlled at 10-20℃.
[0009] Optionally, in step S120, the inducing agent includes at least one of ferric sulfate, sodium sulfate, potassium sulfate, and lithium sulfate.
[0010] Optionally, in step S130, the concentration of the reducing agent is 0.2-0.55M, and the added volume is 80-120mL; The pH of the reducing agent solution is 3-5, and the solution temperature is controlled at 10-20℃.
[0011] Optionally, in step S140, the concentration of the silver salt solution is 0.2-0.5M, and the added volume is 80-120mL; The pH of the silver source solution is 1.5-3.5, and the solution temperature is controlled at 10-20℃.
[0012] Optionally, in step S150, the amount of the seed solution added is 3-8% of the mass of AgNO3; The mixing solution is kept at a rotation speed of 200-400 ml / min; The silver source solution and reducing agent solution are slowly added diagonally to the mixed solution at a rate of 0.05L-0.4L / min, and stirred for 8-12min.
[0013] Optionally, the mixed silver powder includes spherical silver powder and flake silver powder; wherein the content of flake silver powder is 30-65% of the mixed silver powder content.
[0014] In another aspect of this disclosure, a spherical-flaky mixed silver powder is provided, which is prepared by the preparation method described above.
[0015] In another aspect of this disclosure, an application of a spherical-flake hybrid silver powder is proposed, wherein the spherical-flake hybrid silver powder described above is applied to electronic pastes or conductive adhesive materials.
[0016] This disclosure proposes a spherical-flaky mixed silver powder, its preparation method, and its applications. The preparation method includes: adding citric acid and H₂O₂ to a reaction vessel, mixing and heating, then adding NaBH₄ and AgNO₃ to the reaction vessel and stirring to obtain a seed solution; sequentially adding an inducing agent and nitric acid solution to a dispersant to form a dispersant solution; adding sodium hydroxide solution to a reducing agent to form a reducing agent solution; adding nitric acid solution to a silver salt solution to form a silver source solution; adding the seed solution to the dispersant solution and stirring to form a mixed solution; then adding the silver source solution and the reducing agent solution dropwise to the mixed solution and stirring to obtain a turbid silver powder solution; performing solid-liquid separation, washing, modification, drying, and sieving of the turbid silver powder solution to obtain the spherical-flaky mixed silver powder. This disclosure uses a chemical synthesis method to prepare the spherical-flaky mixed silver powder, eliminating the need for separate preparation of spherical and flake silver powders. The ratio of flake to spherical powder is controlled by the potassium sulfate inducing agent and the effects of pH and temperature, and the overall particle size of the silver powder is controlled by the amount of seed crystals used. Attached Figure Description
[0017] Figure 1 This is a flowchart illustrating a method for preparing spherical-flaky mixed silver powder according to a specific embodiment of this disclosure. Figure 2 This is a scanning electron microscope image of the mixed silver powder of Embodiment 1 of this disclosure; Figure 3 This is a scanning electron microscope image of the mixed silver powder of Embodiment 2 of this disclosure; Figure 4 This is a scanning electron microscope image of the mixed silver powder of Embodiment 3 of this disclosure; Figure 5 This is a scanning electron microscope image of the mixed silver powder of Embodiment 4 of this disclosure; Figure 6 This is a scanning electron microscope image of the mixed silver powder of Embodiment 5 of this disclosure; Figure 7 The image shows a scanning electron microscope (SEM) image of the silver powder in Comparative Example 1 of this disclosure. Figure 8 This is a scanning electron microscope image of the silver powder in Comparative Example 2 of this disclosure. Detailed Implementation
[0018] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.
[0019] like Figure 1 As shown, one aspect of this disclosure provides a method S100 for preparing a spherical-flaky mixed silver powder, specifically including the following steps S110~S160: S110. Add citric acid solution and H2O2 sequentially to a 300mL round-bottom flask, heat and maintain at 60-75℃, stir for 0.5-1.0h, then quickly add NaBH4 and AgNO3 sequentially to the flask and stir for 0.5-1.5h to obtain a seed solution. The seed crystals are fine, flaky particles.
[0020] In step S110, the concentration of citric acid is 5-8 mM, for example, preferably 5 mM, 6 mM, 7 mM, 8 mM, etc., and the added volume is 80-100 mL, for example, preferably 90 mL, etc.
[0021] In step S110, the concentration of H2O2 is 0.15-0.45M, for example, preferably 0.15M, 0.25M, 0.35M, 0.45M, etc., and the added volume is 70-90mL, for example, preferably 80mL, etc.
[0022] In step S110, the concentration of NaBH4 is 0.3-0.7 mM, for example, preferably 0.3 mM, 0.4 mM, 0.5 mM, 0.6 mM, 0.7 mM, etc., and the added volume is 10-30 mL, for example, preferably 20 mL, etc.
[0023] In step S110, the concentration of AgNO3 is 0.03-0.1M, for example, preferably 0.03M, 0.05M, 0.1M, etc., and the added volume is 5-15mL, for example, preferably 10mL, etc.
[0024] It should be understood that step S110 is equivalent to the preparation process of seed crystals, forming a seed crystal solution containing fine flaky particles. In this seed crystal solution, the size of the fine flaky particles is about 20 nm. The main function is to control the size of the silver powder particles. Furthermore, the fact that the seeds are small flaky particles also makes it easier for the silver particles to develop into flaky particles in the subsequent growth.
[0025] S120. Prepare a dispersant solution. After the dispersant is completely dissolved, add a certain amount of inducing agent, then add a certain amount of nitric acid solution to adjust the pH of the solution to 1.5-3.5. Control the solution temperature at 10-20℃. After thorough mixing and uniformity, let it stand for later use to obtain the dispersant solution.
[0026] In step S120, the dispersant added here refers to a dispersant solution with a concentration of 0.12-0.3M, such as 0.12M, 0.1M, 0.2M, or 0.3M. The volume of the dispersant solution added is 300-350mL, such as 320mL.
[0027] As a further preferred embodiment, the dispersant added in step S120 includes at least one of polyvinylpyrrolidone, gum arabic, gelatin, and polyethylene glycol.
[0028] In step S120, the concentration of the inducing agent is 0.21-0.62 mM, preferably 0.21 mM, 0.35 mM, 0.45 mM, or 0.55 mM, and the added volume is 2-10 mL. Further, the inducing agent includes at least one of the following inorganic salts containing sulfate anions: ferric sulfate, sodium sulfate, potassium sulfate, and lithium sulfate.
[0029] In this embodiment, the role of the inducer is to selectively adsorb and inhibit specific crystal faces during the growth of silver particles, guiding the particles to develop in a plate-like direction. That is, a higher concentration of inducer is conducive to the growth of plate-like silver powder. However, the intensity and selectivity of sulfate and hydrogen ion adsorption on crystal faces will be different at different pH levels, which will cause changes in the growth direction and speed of silver particles. Therefore, the morphology of silver powder and the proportion of plate powder can be controlled by adjusting the amount of inducer and the pH level. For example, when the pH is too low, the silver powder will grow in a plate-like shape, and when the pH is too high, the silver powder will grow in a spherical shape.
[0030] S130. Preparation of reducing agent solution: Add a certain amount of sodium hydroxide solution to the reducing agent, adjust the pH of the reducing agent solution to between 3 and 5, control the solution temperature at 10-20℃, stir thoroughly and let stand for later use to form the reducing agent solution.
[0031] In step S130, the reducing agent added here refers to a reducing agent solution with a concentration of 0.2-0.55M, such as 0.2M, 0.35M, or 0.55M, and the volume of the reducing agent solution added is 80-120mL, such as 100mL.
[0032] As a further preferred embodiment, the reducing agent added in step S130 includes at least one of ascorbic acid, sodium ascorbate, formaldehyde, sodium borohydride, hydrazine hydrate, and glucose.
[0033] S140. Preparation of silver source solution: Add a certain amount of nitric acid solution to the silver salt solution, adjust the pH of the solution to 1.5-3.5, control the temperature at 10-20℃, and let it stand for later use after thorough mixing and homogenization to obtain the silver source solution.
[0034] In step S140, the concentration of the silver salt solution is 0.2-0.5M, for example, preferably 0.2M, 0.3M, 0.4M, 0.5M, etc., and the volume of the silver salt solution added is 80-120mL, for example, preferably 100mL, etc.
[0035] As a further preferred embodiment, the silver salt added in step S140 includes at least one of water-soluble silver salts such as silver nitrate, silver fluoride, silver sulfate, and silver perchlorate.
[0036] S150. Ten minutes before the reaction, add the seed solution to the dispersant solution to form a mixed solution. After stirring evenly, keep the mixing speed between 200-400 ml / min. Then, slowly add the silver source solution and reducing agent solution diagonally to the mixed solution at a rate of 0.05 L-0.4 L / min using a flow pump to allow the silver particles to grow slowly. After stirring for 8-12 minutes, a turbid silver powder solution can be obtained.
[0037] In step S150, the amount of seed solution added is 3 to 8% of the mass of silver salt in step S140. Here, the silver salt can be at least one of water-soluble silver salts such as silver nitrate, silver fluoride, silver sulfate, and silver perchlorate. That is, in step S140, when the added silver salt is silver nitrate, the amount of seed solution added is 3 to 8% of the mass of silver nitrate in the silver source solution.
[0038] S160, the silver powder turbid liquid is subjected to solid-liquid separation, washing, modification, drying and sieving to obtain spherical-flaky mixed silver powder.
[0039] It should be noted that all reagents used in the preparation process of this embodiment are deionized water.
[0040] This embodiment provides a method for simultaneously preparing a mixture of two different morphologies of silver powder: spherical and flake-shaped. By using a liquid-phase chemical reduction method, the proportion of spherical and flake-shaped silver powder can be controlled by adjusting the pH of the solution and the amount of inducing agent, thus meeting different application requirements. This method is simple to operate, low in cost, and easy to scale up for production, solving the performance defects of existing single-morphology silver powder.
[0041] The mixed silver powder prepared in this embodiment includes spherical silver powder and flake silver powder; wherein the content of flake silver powder is 30-65% of the total mixed silver powder content. The content of flake silver powder can be adjusted according to actual needs. For example, for high conductivity requirements, the proportion of flake silver powder can be increased to 65%, and for high filling requirements, the proportion of flake silver powder can be 30%, to meet different application needs.
[0042] In another aspect of this disclosure, a spherical-flaky mixed silver powder is proposed, which is prepared by the preparation method described above. For details of the process, please refer to the above description, which will not be repeated here.
[0043] Another aspect of this disclosure proposes an application of spherical-flake hybrid silver powder, which is applied to electronic pastes, such as pastes for metal meshes, and of course, it can also be used in conductive adhesive materials, such as electronic components like thin-film switches, chip resistors, thick-film resistors, and conductive adhesives.
[0044] The preparation method and specific applications of spherical-flaky mixed silver powder will be further explained below with reference to specific embodiments: Example 1 As shown in Table 1, the preparation method of the spherical-flaky mixed silver powder in this example includes the following steps: S1. Preparation of seed crystals: 90 mL of 6.5 mM citric acid solution and 80 mL of 0.3 M H2O2 were added sequentially to a 300 mL round-bottom flask. The temperature was heated and maintained at 70 °C for 1 h with stirring. Then, 20 mL of 0.5 mM NaBH4 and 10 mL of 0.065 M AgNO3 were added to the flask sequentially and stirred for 1 h to obtain a seed crystal solution. The seed crystals were fine, flaky particles.
[0045] S2. Preparation of dispersant solution: Prepare 320mL of 0.21M polyvinylpyrrolidone solution. After the dispersant is completely dissolved, add 5mL of potassium sulfate, with the potassium sulfate concentration controlled at 0.25mM. Then add a certain amount of nitric acid solution to adjust the pH of the solution to 2.5. Control the solution temperature at 10℃. After thorough mixing and uniformity, let it stand for later use.
[0046] S3. Preparation of reducing agent solution: Prepare 100mL of 0.38M ascorbic acid solution, use a certain amount of sodium hydroxide solution to adjust the pH of the reducing agent solution to 2.5, control the solution temperature at 10℃, stir thoroughly and let stand for later use.
[0047] S4. Preparation of silver source solution: Prepare 100mL of 0.35M AgNO3 solution, use a certain amount of nitric acid solution to adjust the pH of the solution to 2.5, control the temperature at 10℃, and let it stand for later use after thorough mixing.
[0048] S5. Reaction steps: 10 minutes before the reaction, add a seed solution of 3.5% silver nitrate by mass to the dispersant solution. After stirring evenly, keep the solution rotation speed at 300 r / min. Then, slowly add the reaction solution containing the silver source and the reducing agent solution diagonally to the dispersant solution at a rate of 0.25 L / min using a flow pump, so that the silver particles can grow slowly. After stirring for 10 minutes, a turbid liquid of silver powder can be obtained.
[0049] S6. The finished silver powder can be obtained by solid-liquid separation, washing, modification, drying and sieving of the turbid silver powder liquid.
[0050] As shown in Table 2, the silver powder prepared in Example 1 has particle sizes of D10=0.729μm, D50=1.125μm, and D90=1.694μm, and a specific surface area of 1.67m². 2 / g, the flake powder accounts for 30% of the mixed silver powder content, the filling value of the slurry used to form the metal mesh is 1.67, and the resistivity is 7.99Ω / cm.
[0051] like Figure 2 As shown, the mixed silver powder prepared in Example 1 includes spherical silver powder and flake silver powder. The flake silver powder has a flat, polygonal or irregular flake structure, while the spherical silver powder appears as near-spherical or ellipsoidal particles.
[0052] As shown in Table 3, in the mixed silver powder of this embodiment, the content of flake silver powder accounts for 30%.
[0053] Example 2 As shown in Table 1, the preparation process of the mixed silver powder in Example 2 is the same as that in Example 1, except that the reaction temperature is 15°C, the solution pH is 2.0, and the concentration of the inducer (potassium sulfate) is 0.35 mM.
[0054] As shown in Table 2, the silver powder prepared in Example 2 has particle sizes of D10=1.101μm, D50=1.196μm, and D90=1.715μm, and a specific surface area of 1.89m². 2 / g, the flake powder accounts for 50% of the mixed silver powder content, the filling value of the slurry used to form the metal mesh is 1.71, and the resistivity is 8.24Ω / cm.
[0055] like Figure 3 As shown, the mixed silver powder prepared in this embodiment 2 includes spherical silver powder and flake silver powder. The flake silver powder has a flat, polygonal or irregular flake structure, while the spherical silver powder appears as near-spherical or ellipsoidal particles.
[0056] Example 3 As shown in Table 1, the preparation process of the mixed silver powder in Example 3 is the same as that in Example 1, except that the reaction temperature is 20°C, the solution pH is 1.5, and the concentration of the inducer (potassium sulfate) is 0.45 mM.
[0057] As shown in Table 2, the silver powder prepared in Example 3 has particle sizes of D10=0.765μm, D50=1.246μm, and D90=1.863μm, and a specific surface area of 2.13m². 2 / g, the flake powder accounts for 65% of the mixed silver powder content, the filling value of the slurry used to form the metal mesh is 1.73, and the resistivity is 8.36Ω / cm.
[0058] like Figure 4 As shown, the mixed silver powder prepared in this embodiment 3 includes spherical silver powder and flake silver powder. The flake silver powder has a flat, polygonal or irregular flake structure, while the spherical silver powder appears as near-spherical or ellipsoidal particles.
[0059] Example 4 As shown in Table 1, the preparation process of the mixed silver powder in Example 4 is the same as that in Example 1, except that the concentration of the inducer (potassium sulfate) is 0.40 mM.
[0060] As shown in Table 3, in the mixed silver powder of this embodiment, the content of flake silver powder accounts for 55%.
[0061] like Figure 5 As shown, the mixed silver powder prepared in Example 4 includes spherical silver powder and flake silver powder, relative to... Figure 2 In general, flake-shaped silver powder increases while spherical silver powder decreases.
[0062] Example 5 As shown in Table 1, the preparation process of the mixed silver powder in Example 5 is the same as that in Example 1, except that the concentration of the inducer (potassium sulfate) is 0.60 mM.
[0063] As shown in Table 3, in the mixed silver powder of this embodiment, the content of flake silver powder accounts for 70%.
[0064] like Figure 6 As shown, the mixed silver powder prepared in Example 5 includes a small amount of spherical silver powder and a large amount of flake-shaped silver powder, relative to... Figure 5 In general, the amount of flake-shaped silver powder increased further, while the amount of spherical silver powder decreased.
[0065] Comparative Example 1 As shown in Table 1, the preparation process of the mixed silver powder in Example 1 is the same as that in Example 1, except that the reaction temperature is 45°C, the solution pH is 7, and the concentration of the inducer (potassium sulfate) is 0.05 mM.
[0066] As shown in Table 2, the silver powder prepared in Comparative Example 1 has particle sizes of D10 = 0.612 μm, D50 = 0.923 μm, and D90 = 1.432 μm, and a specific surface area of 1.23 m². 2 / g, the flake powder accounts for 0.5% of the mixed silver powder content, the filling value of the slurry for forming the metal mesh is 2.25, and the resistivity is 15.2Ω / cm.
[0067] like Figure 7 As shown, the silver powder prepared in Comparative Example 1 consists of single spherical particles with small particle size, smooth surface, no flaky structure, point contact between particles, high packing density, and discontinuous conductive network.
[0068] Comparative Example 2 As shown in Table 1, the preparation process of the mixed silver powder in Example 2 is the same as that in Example 1, except that the reaction temperature is 0°C, the solution pH is 0.5, the concentration of the inducer (potassium sulfate) is 0.85mM, and the amount of seed solution is 2.5%.
[0069] As shown in Table 2, the silver powder prepared in Comparative Example 2 has particle sizes D10 = 0.859 μm, D50 = 1.591 μm, and D90 = 2.633 μm, and a specific surface area of 3.24 m². 2 / g, the flake powder accounts for 99% of the mixed silver powder content, the filling value of the slurry used to form the metal mesh is 2.16, and the resistivity is 11.5Ω / cm.
[0070] like Figure 8 As shown, the silver powder prepared in Comparative Example 2 is almost entirely composed of flaky particles with large particle size and uneven thickness. It is prone to stacking gaps, and the particles are mainly in surface contact. However, the particles are loosely packed and have a high fill value, which makes it easy to produce pinholes during printing.
[0071] In summary, when the reaction temperature and pH are high and the inducer concentration is low, the mixed silver powder contains a low content of flake-shaped silver powder, and is almost entirely composed of spherical silver powder. Conversely, when the reaction temperature and pH are low and the inducer concentration is high, the mixed silver powder contains a high content of flake-shaped silver powder, and is almost entirely composed of flake-shaped silver powder. This indicates that when the reaction temperature and pH are too low and the inducer concentration is high, the silver powder will grow towards a flake-like shape, while when the reaction temperature and pH are too high and the inducer concentration is low, the silver powder will grow towards a spherical shape. As shown in Examples 1, 4, and 5, the proportion of flake-shaped powder gradually increases with the increase of inducer concentration. In addition, the resistivity values of Examples 1-3 (7.99-8.36 Ω / cm) are significantly lower than those of Comparative Example 1 (15.2 Ω / cm) and Comparative Example 2 (11.5 Ω / cm). The specific surface area of Examples 1-3 is between that of spherical and flake-shaped powders, avoiding the slurry stability problems caused by excessively high specific surface area. This indicates that the hybrid silver powder combines the high filling capacity (low filling value) of spherical silver powder with the excellent conductivity (low resistance value) of flake silver powder.
[0072] In summary, based on Examples 1-3 and Comparative Examples 1-2, it can be seen that the content of flake silver powder and spherical silver powder in the mixed silver powder can be adjusted by adjusting parameters such as reaction temperature, pH and the concentration of the inducer.
[0073] It should be noted that the above embodiments are only illustrated by using potassium sulfate as an inducing agent. When using other inducing agents given above, the relative content of flake silver powder and spherical silver powder in the mixed silver powder can also be adjusted to meet different needs, which will not be listed here.
[0074] Table 1 Reaction conditions for each embodiment and comparative example
[0075] Table 2. Silver powder results for each embodiment and comparative example.
[0076] Table 3. Process parameters and results of silver powder mixing in Examples 1, 4, and 5.
[0077] This disclosure presents a spherical-flaky hybrid silver powder, its preparation method, and its applications, which have the following advantages compared to existing technologies: Conventional methods for preparing spherical and flake silver powder typically involve separately preparing spherical and flake silver powders and then mixing them. This disclosure, however, prepares spherical and flake silver powder in one step by controlling factors influencing the reaction, such as the pH and temperature of the solution. Furthermore, the proportion of spherical and flake silver powders can be adjusted based on these factors to meet various customer requirements.
[0078] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.
Claims
1. A method for preparing a spherical-flaky mixed silver powder, characterized in that, The preparation method includes: S110. Add citric acid and H2O2 to the reaction vessel, mix and stir, and heat. Then add NaBH4 and AgNO3 to the reaction vessel and stir to obtain a seed solution. S120. Add the inducing agent and nitric acid solution to the dispersant in sequence to form a dispersant solution; S130. Add sodium hydroxide solution to the reducing agent to form a reducing agent solution; S140. Add nitric acid solution to silver salt solution to form silver source solution; S150. The seed solution is added to the dispersant solution and stirred to form a mixed solution. Then, the silver source solution and the reducing agent solution are added dropwise to the mixed solution and stirred to obtain a silver powder turbid liquid. S160. The silver powder turbid liquid undergoes solid-liquid separation, washing, modification, drying, and sieving to obtain a spherical-flaky mixed silver powder.
2. The preparation method according to claim 1, characterized in that, In step S110, the concentration of citric acid is 5-8 mM, and the added volume is 80-100 mL; The concentration of H2O2 is 0.15-0.45M, and the added volume is 70-90mL; The concentration of NaBH4 is 0.3-0.7 mM, and the added volume is 10-30 mL; The concentration of AgNO3 is 0.03-0.1M, and the added volume is 5-15mL; The citric acid and H2O2 are added to the reaction vessel and mixed and stirred for 0.5-1.0 h, and the heating temperature is 60-75℃; Add NaBH4 and AgNO3 to the reaction vessel and stir for 0.5-1.5 hours.
3. The preparation method according to claim 1, characterized in that, In step S120, the concentration of the dispersant is 0.12-0.3M, and the added volume is 300-350mL; The concentration of the inducer is 0.21-0.62 mM, and the addition volume is 2-10 mL; The pH of the dispersant solution is 1.5-3.5, and the solution temperature is controlled at 10-20℃.
4. The preparation method according to claim 3, characterized in that, In step S120, the inducing agent includes at least one of ferric sulfate, sodium sulfate, potassium sulfate, and lithium sulfate.
5. The preparation method according to claim 1, characterized in that, In step S130, the concentration of the reducing agent is 0.2-0.55M, and the added volume is 80-120mL; The pH of the reducing agent solution is 3-5, and the solution temperature is controlled at 10-20℃.
6. The preparation method according to claim 1, characterized in that, In step S140, the concentration of the silver salt solution is 0.2-0.5M, and the added volume is 80-120mL; The pH of the silver source solution is 1.5-3.5, and the solution temperature is controlled at 10-20℃.
7. The preparation method according to claim 1, characterized in that, In step S150, the amount of the seed solution added is 3-8% of the mass of the silver salt in step S140; The silver source solution and reducing agent solution are slowly added diagonally to the mixed solution at a rate of 0.05L-0.4L / min, and stirred for 8-12min.
8. The preparation method according to claim 1, characterized in that, The mixed silver powder includes spherical silver powder and flake silver powder; wherein the content of flake silver powder is 30-65% of the mixed silver powder content.
9. A spherical-flaky mixed silver powder, characterized in that, The spherical-flaky mixed silver powder is prepared by the preparation method described in any one of claims 1 to 8.
10. An application of a spherical-flaky mixed silver powder, characterized in that, The spherical-flaky mixed silver powder described in claim 9 is used in electronic pastes or conductive adhesive materials.