Method for preparing nano flake silver powder, flake silver powder and application

Abstract

The invention discloses a method for preparing nano flaky silver powder, the flaky silver powder and application. The method comprises the following steps: (1) preparing a silver salt solution, a reducing agent solution, a seed crystal auxiliary agent and a dispersing agent base solution; (2) under the stirring condition, adding the reducing agent solution, the seed crystal additive and 30-50% of the silver salt solution into the dispersing agent base solution to be mixed, after the 30-50% of the silver salt solution is added, continuing to add the rest 50-70% of the silver salt solution, continuing to react, and in the process of adding the silver salt solution for the second time, adding alkaline carboxylate; (3) after the silver salt solution is added for the second time, adding a coating agent; and (4) after the reaction is finished, solid-liquid separation is conducted, wet silver powder is obtained, alcohol is added for mixing after the wet silver powder is washed, a silver powder alcohol mixture is obtained, the silver powder alcohol mixture is mechanically ground, and silver powder of a specific sheet structure is obtained. The process is simple, the adjusting means is stable, and the prepared flaky silver powder is good in monodispersity, narrow in particle size distribution and not prone to agglomeration.

Description

Technical Field

[0001] The invention belongs to the technical field of silver powder preparation, and in particular relates to a method for preparing nano-flaky silver powder, the flaky silver powder and applications. Background Art

[0002] Nano-flake silver powder is a nanomaterial with a flaky microstructure, which is widely used in the electronics industry, medicine, catalysts and other fields. The flaky structure gives the silver powder a higher specific surface area, which is superior to conventional materials in terms of conductivity and chemical activity. Specifically, the large surface area of ​​the nano-silver powder flakes increases the contact area between the nano-silver powder flakes and the outside world, thereby improving their catalytic efficiency and antibacterial properties. In addition, due to the unique structure of the nano-silver powder flakes, they have excellent conductivity and are widely used in conductive inks and other fields. In particular, in some flexible electronic devices, the nano-silver powder flakes can better adapt to changes such as bending and stretching.

[0003] At present, the common methods for preparing nano-flaky silver powder include chemical reduction, electrochemical deposition, vapor deposition, etc. Among them, chemical reduction is a more common method. It mainly converts metal salt solution into flaky metal powder through reduction reaction, but the reaction conditions of this method are complex to control. In addition, the electrochemical deposition method uses an electric field to guide metal ions to deposit on the cathode to generate nano-flaky particles. Its advantage is that it is easy to control the shape and size of the particles. The vapor deposition method is to evaporate or decompose the material and then condense it on the surface of the substrate to form flaky nanoparticles, but this method is relatively expensive and is generally used in scenarios with higher requirements for purity and shape.

[0004] One of the main challenges facing the preparation of nano-flake powder is how to improve the stability and uniformity of the product. Traditional preparation methods will result in problems such as uneven particle size and difficult to control shape, which ultimately affect product performance. The present invention is intended to provide a new method for preparing nano-flake silver powder to improve production stability. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing nano-flaky silver powder, flaky silver powder and application, the process is simple and the adjustment means are stable, the prepared flaky silver powder has good monodispersity, narrow particle size distribution, and is not easy to agglomerate.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect of the present invention, the present invention provides a method for preparing nano-flaky silver powder, as follows:

[0008] (1) preparing silver salt solution, reducing agent solution, seeding agent and dispersant base solution;

[0009] (2) under stirring conditions, adding a reducing agent solution, a seeding agent and 30-50% of a silver salt solution to a dispersant base solution and mixing, after the addition of 30-50% of the silver salt solution is completed, continuing to add the remaining 50-70% of the silver salt solution, and continuing the reaction, during the second addition of the silver salt solution, adding an alkaline carboxylate to promote the formation of silver powder and maintain stability in the system;

[0010] (3) After the second addition of the silver salt solution is completed, a coating agent is added;

[0011] (4) After the reaction is completed, solid-liquid separation is performed to obtain wet silver powder, the wet silver powder is washed and then added with alcohol to obtain a silver powder-alcohol mixture, and the silver powder-alcohol mixture is mechanically ground while controlling the grinding time and rotation speed to obtain silver powder with a specific flaky structure.

[0012] Preferably, in step (1), the preparation method of the seed crystal auxiliary agent is: at room temperature, mixing a silver nitrate solution with propylamine, then adding polyvinyl pyrrolidone and mixing evenly to obtain a mixture, and heating the mixture at a constant temperature of 60° C. for 30 minutes to obtain a brown seed crystal auxiliary agent containing nano-micron-sized silver.

[0013] More preferably, the concentration of silver in the seed crystal aid is 0.01 mol / L.

[0014] Preferably, in step (2), the alkaline carboxylate comprises one or more of alkali metal formates, acetates, propionates, valerates and caproates, and more preferably, the alkaline carboxylate comprises one or more of sodium formate, sodium acetate, sodium propionate, sodium valerate, sodium caproate, potassium formate, potassium acetate, potassium propionate, potassium valerate and potassium caproate.

[0015] Preferably, in step (2), the alkaline carboxylate is added when the silver salt addition time reaches 60-70% of the total time, based on the total time of the two silver salt solution additions.

[0016] Preferably, in step (2), an alkaline carboxylate is added to adjust the pH value of the system to 8-9.

[0017] Preferably, in step (3), the coating agent comprises one or more of oleic acid, palmitic acid, myristic acid and caprylic acid.

[0018] Preferably, in step (4), a fat dispersant having a carbon chain length of 14 to 18 carbon atoms is added to the silver powder-alcohol mixture.

[0019] Preferably, in step (4), during the mechanical grinding process, the temperature is controlled at 20 to 80°C.

[0020] Preferably, in step (4), the grinding time is set to 30 to 60 min, and the rotation speed is maintained at 300 to 500 rpm.

[0021] In the second aspect of the present invention, the present invention also proposes a flaky silver powder, the diameter of the flaky silver powder is less than or equal to 1.0 μm. The silver powder obtained by the above method has both high electrical conductivity and high thermal conductivity, and is suitable for use in electronic components, medical equipment and high-end electronic coatings that require long-term stable performance.

[0022] Beneficial effects:

[0023] The invention uses a crystal auxiliary agent and a dispersant as a particle size control agent, combines an alkaline carboxylate and a surface coating agent to obtain silver particles with good monodispersity, then adds alcohol for dispersion, and performs flake shaping through a grinder. The invention has a simple preparation process and a stable control means, and can produce flaky silver powder with good monodispersity, narrow particle size distribution and not easy to agglomerate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Shown is the SEM image of Example 1;

[0025] Figure 2 Shown is the SEM image of Example 2;

[0026] Figure 3 Shown is the SEM image of Example 3;

[0027] Figure 4 Shown is the SEM image of Comparative Example 1;

[0028] Figure 5 Shown is the SEM image of Comparative Example 2;

[0029] Figure 6 Shown is the SEM image of Comparative Example 3;

[0030] Figure 7 Shown is the SEM image of Comparative Example 4;

[0031] Figure 8 Shown is the SEM image of Comparative Example 5. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0033] The present invention provides a method for preparing nano-flaky silver powder, which first uses a crystal auxiliary agent and a dispersant as a particle size control agent, combines an alkaline carboxylate and a surface coating agent to obtain silver particles with good monodispersity, then adds alcohol for dispersion, and uses a grinder to shape the particles into flakes. The present invention has a simple preparation process and a stable control method, and can produce flaky silver powder with good monodispersity, narrow particle size distribution, and not easy to agglomerate. The detailed preparation steps and related technical contents are as follows:

[0034] (1) preparing silver salt solution, reducing agent solution, seeding agent and dispersant base solution;

[0035] (2) under stirring conditions, adding a reducing agent solution, a seeding agent and 30-50% of a silver salt solution to a dispersant base solution and mixing, after the addition of 30-50% of the silver salt solution is completed, continuing to add the remaining 50-70% of the silver salt solution, and continuing the reaction, during the second addition of the silver salt solution, adding an alkaline carboxylate to promote the formation of silver powder and maintain stability in the system;

[0036] (3) After the second addition of the silver salt solution is completed, a coating agent is added to form a coating layer on the surface of the silver particles to prevent the silver powder from agglomerating;

[0037] (4) After the reaction is completed, solid-liquid separation is performed to obtain wet silver powder, the wet silver powder is washed and then added with alcohol to obtain a silver powder-alcohol mixture, and the silver powder-alcohol mixture is mechanically ground while controlling the grinding time and rotation speed to obtain silver powder with a specific flaky structure.

[0038] In step (1), a silver salt solution is formed by dissolving a silver salt in a solvent to provide silver ions as a silver source. Generally, the silver salt solution is a silver nitrate solution. It is easy to understand that the silver salt may also be other soluble inorganic silver salts or organic silver salts, and the present invention does not make specific restrictions. The silver ion concentration of the silver salt solution is 1.0 to 3.0 mol / L, preferably 1.5 mol / L.

[0039] The reducing agent solution is formed by dissolving the reducing agent in the solvent, and its function is to reduce the silver ions to silver. Generally, the reducing agent includes one or more of ascorbic acid, formalin, glucose, hydrazine hydrate and sodium borohydride. The concentration of the reducing agent solution is 0.5-1.5 mol / L, preferably 0.8 mol / L.

[0040] The function of the seeding agent is to promote the nucleation process of the silver powder. Specifically, the preparation method of the seeding agent is: at room temperature, silver nitrate solution is mixed with propylamine, then polyvinyl pyrrolidone is added and mixed evenly to obtain a mixture, and the mixture is heated at a constant temperature of 60° C. for 30 minutes to obtain a brown seeding agent containing nano-micron silver. Preferably, the concentration of silver in the seeding agent is 0.01 mol / L.

[0041] In the preparation process of seed crystal auxiliary agent, propylamine not only plays the role of complexing agent, but also has a certain reducing effect. Propylamine complexes with silver ions to improve the reducing ability of silver. Polyvinyl pyrrolidone not only plays the role of dispersant, but also has a certain reducing effect. Under heating conditions, propylamine and polyvinyl pyrrolidone can reduce the silver ions in the solution to silver, and then evenly disperse them under the action of polyvinyl pyrrolidone to form a seed crystal auxiliary agent.

[0042] The dispersant base liquid is formed by dissolving the dispersant in the solvent. The dispersant includes one or more of a polymer surfactant, a cationic surfactant and an anionic surfactant. For example, the dispersant includes one or two of polyvinyl alcohol and polyvinyl pyrrolidone to enhance the dispersibility of the silver powder in the system. The mass fraction of the dispersant base liquid is 2.5 to 7.5%, accounting for 20 to 100% of the theoretical silver powder.

[0043] In step (2), the silver salt solution is added twice, wherein the first addition amount is relatively small, at which time the reducing agent is excessive, and the silver ions use the silver seeds in the seeding agent as nuclei to generate silver powder with good dispersion, and then the silver ions in the second added silver salt solution are reduced to silver attached to the surface of the previously generated silver powder to form silver powder with uniform particle size. If the seeding agent is not added, the generated silver powder has a wide particle size distribution and the morphology is difficult to control.

[0044] In step (2), the alkaline carboxylate is generally a strong base and weak acid salt, which is alkaline and can adjust the pH value of the system to promote the reaction. In addition, the alkaline carboxylate is added when the silver salt solution is added for the second time. At this time, part of the silver ions will combine with the carboxylate to form carboxylate silver salt, which adheres to the surface of the generated silver powder, reduces the surface energy of the silver powder, and thus plays a role in adjusting the particle size of the silver powder.

[0045] Preferably, the alkaline carboxylate includes one or more of the alkali metal formates, acetates, propionates, valerates and caproates, such as alkaline carboxylates including sodium formate, sodium acetate, sodium propionate, sodium valerate, sodium caproate, potassium formate, potassium acetate, potassium propionate, potassium valerate, potassium caproate and the like.

[0046] Preferably, the alkaline carboxylate is added when the silver salt addition time reaches 60-70% of the total time, based on the total time of the two silver salt solution additions. The alkaline carboxylate cannot be added too early, otherwise the carboxylate silver salt will adhere to the surface of the silver powder, limiting the subsequent generation of silver on the surface of the silver powder, affecting the production of silver powder with uniform particle size; the alkaline carboxylate cannot be added too late, otherwise the reaction of generating silver is close to completion and the particle size of the silver powder cannot be changed.

[0047] In step (2), an alkaline carboxylate is added to adjust the pH value of the system to 8 to 9. If the pH value of the system cannot be adjusted to 8 to 9 after adding the alkaline carboxylate, a diluted sodium hydroxide solution or potassium hydroxide solution can be added to adjust the pH value of the system to 8 to 9.

[0048] In step (3), the coating agent includes one or more of oleic acid, palmitic acid, myristic acid and caprylic acid. After adding the coating agent, the reaction is continued for a period of time, for example, for 2 to 5 minutes.

[0049] In step (4), after the reaction is completed, the reaction system can be kept still for 30 minutes, and then centrifuged to achieve solid-liquid separation to obtain wet silver powder. The silver powder is first washed with deionized water to remove residual reactants and impurities, and then washed with alcohol. After washing, alcohol is added to form a silver powder alcohol mixture, that is, a silver powder suspension.

[0050] In step (4), the main function of alcohol is to dissipate heat to prevent the temperature from being too high during the mechanical grinding process, which would cause the silver powder to stick together after melting.

[0051] Preferably, a long-chain fatty acid dispersant with a carbon chain length of 14 to 18 carbon atoms, such as stearic acid, palmitic acid, etc., is added to the silver powder alcohol mixture. Alcohol also acts as a solvent, and the fatty dispersant is dissolved in alcohol. The flaky silver powder formed by grinding the silver powder is dispersed by the fatty dispersant to maintain its morphology and particle size. In addition, alcohol and fatty dispersants also have a lubricating effect.

[0052] Preferably, during the mechanical grinding process, the temperature is controlled at 20-80° C. to avoid melting and agglomeration of the silver powder during the grinding process.

[0053] Preferably, the grinding time is set to 30 to 60 minutes, and the rotation speed is maintained at 300 to 500 rpm.

[0054] The technical solution of the present invention is described in detail below with specific embodiments.

[0055] Prepare the seeding agent, take 20g of 0.1mmol / L silver nitrate solution, add 0.5g of propylamine and mix evenly, then add 2g of PVP K30 powder (molecular weight is about 40,000) and mix to obtain a mixture. PVP can prevent silver particles from aggregating in the subsequent process. Heat the mixture in a constant temperature oil bath for 30 minutes, and keep the temperature at 60°C to promote the reaction. Finally, a brown seeding agent solution containing nano-micron silver is obtained, and the expected silver concentration is 0.01mol / L.

[0056] Weigh silver nitrate (AgNO3), mix it with deionized water, and stir until it is completely dissolved to obtain a silver nitrate solution with a volume of about 100 ml and a concentration of about 1.5 mol / L.

[0057] Ascorbic acid was weighed, mixed with deionized water, and stirred until completely dissolved to obtain a reducing agent solution with a volume of 100 ml and a concentration of about 0.8 mol / L.

[0058] Weigh 10 g of polyvinyl pyrrolidone K30 and add it to 190 g of deionized water, and stir until it is completely dissolved to obtain a dispersant solution. The concentration of the obtained dispersant solution is 5% (w / v).

[0059] Under stirring conditions of 400 rpm, perform the following operations:

[0060] First, add the seed additive solution to the dispersant solution to ensure uniform dispersion, and add the silver nitrate solution and reducing agent solution to the reaction solution at the same time, with a flow rate of 10 ml / min. The silver nitrate solution is about 100 ml and is added twice, with 30.0 ml of silver nitrate solution added the first time and 70.0 ml of silver nitrate solution added the second time. The silver nitrate solution is added for a total of 10 minutes. Sodium formate and sodium hydroxide solution are added at 7 minutes. During the stirring process, the pH value is monitored, with a target of pH 8 to 9 to promote the formation and stability of silver powder.

[0061] After 10 minutes of adding the silver nitrate solution, add 1 ml (equivalent to 0.01 mol / L) of oleic acid solution to form a coating with the silver particles to prevent them from aggregating.

[0062] After the reaction is completed, the reaction solution is centrifuged at 4000 rpm to separate the wet silver powder, and then the wet silver powder is washed three times with deionized water, each time with an amount of 50 ml to remove the surface dispersant and unreacted products, and then the wet silver powder is washed twice with alcohol to reduce the moisture content, and the washed wet powder is added to the wet powder, stearic acid coating agent, and alcohol to form a silver powder suspension.

[0063] In the silver powder suspension, the silver powder is suspended in an alcohol solution, and grinding zirconium beads are added, the diameter of which is controlled at 1-2 mm, and the mass of the grinding zirconium beads accounts for 20% (w / v) of the volume of the silver powder suspension. Mechanical grinding equipment is used, the grinding time is set to 30 minutes, and the speed is maintained at 500 rpm. According to observation, the shape of the silver powder after grinding is a flaky structure with good dispersibility, such as Figure 1 shown.

[0064] Example 2

[0065] Compared with Example 1, in this embodiment, the diameter of the grinding zirconium beads is 0.1-0.5 mm.

[0066] Prepare the seeding agent, take 20g of 0.1mmol / L silver nitrate solution, add 0.5g of propylamine and mix evenly, then add 2g of PVP K30 powder (molecular weight is about 40,000) and mix to obtain a mixture. PVP can prevent silver particles from aggregating in the subsequent process. Heat the mixture in a constant temperature oil bath for 30 minutes, and keep the temperature at 60°C to promote the reaction. Finally, a brown seeding agent solution containing nano-micron silver is obtained, and the expected silver concentration is 0.01mol / L.

[0067] Weigh silver nitrate (AgNO3), mix it with deionized water, and stir until it is completely dissolved to obtain a silver nitrate solution with a volume of about 100 ml and a concentration of about 1.5 mol / L.

[0068] Ascorbic acid was weighed, mixed with deionized water, and stirred until completely dissolved to obtain a reducing agent solution with a volume of 100 ml and a concentration of about 0.8 mol / L.

[0069] Weigh 10 g of polyvinyl pyrrolidone K30 and add it to 190 g of deionized water, and stir until it is completely dissolved to obtain a dispersant solution. The concentration of the obtained dispersant solution is 5% (w / v).

[0070] Under stirring conditions of 400 rpm, perform the following operations:

[0071] First, add the seed additive solution to the dispersant solution to ensure uniform dispersion, and add the silver nitrate solution and reducing agent solution to the reaction solution at the same time, with a flow rate of 10 ml / min. The silver nitrate solution is about 100 ml and is added twice, with 40.0 ml of silver nitrate solution added for the first time and 60.0 ml of silver nitrate solution added for a total of 10 minutes. Sodium acetate and sodium hydroxide solutions are added at 7 minutes. During the stirring process, the pH value is monitored, with a target of pH 8 to 9 to promote the formation and stability of silver powder.

[0072] After 10 minutes of adding the silver nitrate solution, add 1 ml (equivalent to 0.01 mol / L) of oleic acid solution to form a coating with the silver particles to prevent them from aggregating.

[0073] After the reaction is completed, the reaction solution is centrifuged at 4000 rpm to separate the wet silver powder, and then the wet silver powder is washed three times with deionized water, each time with an amount of 50 ml to remove the surface dispersant and unreacted products, and then the wet silver powder is washed twice with alcohol to reduce the moisture content, and the washed wet powder is added to the wet powder, stearic acid coating agent, and alcohol to form a silver powder suspension.

[0074] In the silver powder suspension, the silver powder is suspended in an alcohol solution, and grinding zirconium beads are added, the diameter of which is controlled at 0.1-0.5 mm, and the mass of the grinding zirconium beads accounts for 20% (w / v) of the volume of the silver powder suspension. Mechanical grinding equipment is used, the grinding time is set to 60 minutes, and the speed is maintained at 300 rpm. According to observation, the shape of the silver powder after grinding is a flaky structure with good dispersibility, such as Figure 2 shown.

[0075] Example 3

[0076] Prepare the seeding agent, take 20g of 0.1mmol / L silver nitrate solution, add 1.5g of propylamine and mix evenly, then add 2g of PVP K30 powder (molecular weight is about 40,000) and mix to obtain a mixture. PVP can prevent silver particles from aggregating in the subsequent process. Heat the mixture in a constant temperature oil bath for 30 minutes, and keep the temperature at 60°C to promote the reaction. Finally, a brown seeding agent solution containing nano-micron silver is obtained, and the expected silver concentration is 0.01mol / L.

[0077] Weigh silver nitrate (AgNO3), mix it with deionized water, and stir until it is completely dissolved to obtain a silver nitrate solution with a volume of about 100 ml and a concentration of about 1.5 mol / L.

[0078] Ascorbic acid was weighed, mixed with deionized water, and stirred until completely dissolved to obtain a reducing agent solution with a volume of 100 ml and a concentration of about 0.8 mol / L.

[0079] Weigh 10 g of polyvinyl pyrrolidone K30 and add it to 190 g of deionized water, and stir until it is completely dissolved to obtain a dispersant solution. The concentration of the obtained dispersant solution is 5% (w / v).

[0080] Under stirring conditions of 400 rpm, perform the following operations:

[0081] First, add the seed additive solution to the dispersant solution to ensure uniform dispersion, and add the silver nitrate solution and reducing agent solution to the reaction solution at the same time, with a flow rate of 10 ml / min. The silver nitrate solution is about 100 ml and is added twice, with 50.0 ml of silver nitrate solution added for the first time and 50.0 ml of silver nitrate solution added for the second time. The silver nitrate solution is added for a total of 10 minutes. Sodium formate and sodium hydroxide are added at 7 minutes. During the stirring process, the pH value is monitored, with a target of pH 8 to 9 to promote the formation and stability of silver powder.

[0082] After 10 minutes of adding the silver nitrate solution, add 1 ml (equivalent to 0.01 mol / L) of oleic acid solution to form a coating with the silver particles to prevent them from aggregating.

[0083] After the reaction is completed, the reaction solution is centrifuged at 4000 rpm to separate the wet silver powder, and then the wet silver powder is washed three times with deionized water, each time with an amount of 50 ml to remove the surface dispersant and unreacted products, and then the wet silver powder is washed twice with alcohol to reduce the moisture content, and the washed wet powder is added to the wet powder, stearic acid coating agent, and alcohol to form a silver powder suspension.

[0084] In the silver powder suspension, the silver powder is suspended in an alcohol solution, and grinding zirconium beads are added, the diameter of which is controlled at 0.1-0.5 mm, and the mass of the grinding zirconium beads accounts for 20% (w / v) of the volume of the silver powder suspension. The mechanical grinding equipment is used, the grinding time is set to 45 minutes, and the speed is maintained at 450 rpm. According to observation, the shape of the silver powder after grinding is a flaky structure with good dispersibility, such as Figure 3 shown.

[0085] Comparative Example 1

[0086] Compared with Example 3, no grinding operation was performed in this comparative example.

[0087] The wet silver powder after solid-liquid separation is washed and dried to obtain silver powder. The morphology of the silver powder is observed. Figure 4 shown.

[0088] Obviously, the silver powder is in a spherical shape or other irregular shapes, and does not form flakes. It can be seen that flake silver powder cannot be obtained without grinding.

[0089] Comparative Example 2

[0090] Compared with Example 3, no seeding agent was added in this comparative example.

[0091] After grinding, observe the morphology of the silver powder. Figure 5 Without adding a seed crystal additive, the morphology of the generated silver powder is difficult to control, and it is impossible to obtain a flaky silver powder with good monodispersity, narrow particle size distribution and not easy to agglomerate.

[0092] Comparative Example 3

[0093] Compared with Example 3, the silver nitrate solution of this comparative example is added all at once, rather than being added in two divided portions.

[0094] After grinding, observe the morphology of the silver powder. Figure 6 As shown, the silver powder is cracked, indicating that adding silver nitrate solution once has a great influence on the morphology of the silver powder.

[0095] Comparative Example 4

[0096] Compared with Example 3, in this comparative example, the alkaline carboxylate is added at 50% of the time of adding silver nitrate.

[0097] After grinding, observe the morphology of the silver powder. Figure 7 As shown, the silver powder particles become larger and agglomerated, proving that the time of adding alkaline silver nitrate is important.

[0098] Comparative Example 5

[0099] Compared with Example 3, in this comparative example, the alkaline carboxylate is added at 80% of the time of adding silver nitrate.

[0100] After grinding, observe the morphology of the silver powder. Figure 8 As shown, the silver powder particles are obviously agglomerated. After the delayed addition of the alkaline carboxylate, the morphology of the silver powder has been determined and the effect of the alkaline carboxylate is not obvious.

[0101] The embodiments provided by the present invention are described in detail above. Specific examples are used herein to describe the principles and implementation methods of the present invention, and the description of the above embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing nano-flaky silver powder, characterized in that: as follows: (1) preparing silver salt solution, reducing agent solution, seeding agent and dispersant base solution; (2) adding a reducing agent solution, a seeding agent and a 30-50% silver salt solution to a dispersant base solution under stirring and mixing, and after the addition of 30-50% of the silver salt solution is completed, continuing to add the remaining 50-70% of the silver salt solution to continue the reaction, and adding an alkaline carboxylate during the second addition of the silver salt solution; (3) After the second addition of the silver salt solution is completed, a coating agent is added; (4) After the reaction is completed, solid-liquid separation is performed to obtain wet silver powder, the wet silver powder is washed and then added with alcohol to obtain a silver powder-alcohol mixture, and the silver powder-alcohol mixture is mechanically ground to obtain silver powder with a flaky structure.

2. The method for preparing nano-flaky silver powder according to claim 1, characterized in that: In step (2), based on the total time of adding the two silver salt solutions, the alkaline carboxylate is added when the silver salt addition time reaches 60-70% of the total time.

3. The method for preparing nano-flaky silver powder according to claim 1, characterized in that: In step (2), the alkaline carboxylate comprises one or more of alkali metal formate, acetate, propionate, valerate and caproate; Preferably, the alkaline carboxylate includes one or more of sodium formate, sodium acetate, sodium propionate, sodium valerate, sodium hexanoate, potassium formate, potassium acetate, potassium propionate, potassium valerate and potassium hexanoate.

4. The method for preparing nano-flaky silver powder according to any one of claims 1 to 3, characterized in that: In step (2), alkaline carboxylate is added to adjust the pH value of the system to 8-9.

5. The method for preparing nano-flaky silver powder according to any one of claims 1 to 3, characterized in that: In step (4), a fat dispersant is added to the silver powder-alcohol mixture.

6. The method for preparing nano-flaky silver powder according to any one of claims 1 to 3, characterized in that: During the mechanical grinding process, the temperature is controlled at 20-80°C.

7. The method for preparing nano-flaky silver powder according to any one of claims 1 to 3, characterized in that: In step (4), the grinding time is 30 to 60 minutes and the rotation speed is 300 to 500 rpm.

8. The method for preparing nano-flaky silver powder according to claim 1, characterized in that: In step (1), the preparation method of the seed crystal auxiliary agent is: at room temperature, silver nitrate solution is mixed with propylamine, then polyvinyl pyrrolidone is added and mixed evenly to obtain a mixture, and the mixture is heated at a constant temperature of 60° C. for 30 minutes to obtain a brown seed crystal auxiliary agent containing nano-micron-sized silver.

9. A flaky silver powder, characterized in that: The nano-flaky silver powder is prepared by the method for preparing the nano-flaky silver powder according to any one of claims 1 to 8, and the diameter of the flaky silver powder is less than or equal to 1.0 μm.

10. An application of flaky silver powder, characterized in that: The flaky silver powder prepared by the method for preparing nano-flaky silver powder according to any one of claims 1 to 8 is used in electronic components, medical equipment and high-end electronic coatings.

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