A method for preparing nano-sheet silver powder, the nano-sheet silver powder and its applications

Abstract

This invention discloses a method for preparing nano-sheet silver powder, the sheet silver powder, and its applications. The method includes: (1) preparing a silver salt solution, a reducing agent solution, a seed crystal aid, and a dispersant base solution; (2) under stirring conditions, adding the reducing agent solution, the seed crystal aid, and 30-50% of the silver salt solution to the dispersant base solution and mixing. After the addition of 30-50% of the silver salt solution, the remaining 50-70% of the silver salt solution is added to continue the reaction. During the second addition of the silver salt solution, an alkaline carboxylate is added; (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 mixed with alcohol to obtain a silver powder-alcohol mixture. The silver powder-alcohol mixture is mechanically ground to obtain silver powder with a specific sheet structure. The process of this invention is simple and the adjustment method is stable. The obtained sheet silver powder has good monodispersity, narrow particle size distribution, and is not easy to agglomerate.

Description

Technical Field

[0001] This invention belongs to the field of silver powder preparation technology, specifically relating to a method for preparing nano-sheet silver powder, the sheet silver powder, and its applications. Background Technology

[0002] Nanoscale silver powder is a type of nanomaterial with a sheet-like microstructure, widely used in various fields such as electronics, medicine, and catalysts. Its sheet-like structure gives silver powder a high specific surface area, resulting in superior conductivity and chemical activity compared to materials with conventional forms. Specifically, the large surface area of ​​nanoscale silver powder increases the contact area between the powder and the external environment, thereby improving its catalytic efficiency and antibacterial properties. Furthermore, due to its unique structure, nanoscale silver powder exhibits excellent conductivity, making it widely used in conductive inks and other fields, especially in flexible electronic devices where it better adapts to bending and stretching.

[0003] Currently, common methods for preparing nanosheet-like silver powder include chemical reduction, electrochemical deposition, and vapor deposition. Chemical reduction is the most prevalent method, primarily using a reduction reaction to transform a metal salt solution into sheet-like metal powder; however, this method involves complex control of reaction conditions. Electrochemical deposition utilizes an electric field to guide metal ions onto a cathode, generating nanosheet-like particles. Its advantage lies in the ease of controlling particle shape and size. Vapor deposition involves evaporating or decomposing the material, followed by condensation on a substrate surface to form sheet-like nanoparticles; however, this method is costly and generally used in applications requiring higher purity and shape precision.

[0004] One of the major challenges in the preparation of nanosheet powders is improving product stability and uniformity. Traditional preparation methods often result in uneven particle size and difficulty in controlling shape, ultimately affecting product performance. This invention aims to propose a novel method for preparing nanosheet silver powder, thereby improving production stability. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method for preparing nano-flaky silver powder, the flake silver powder, and its applications. The process is simple and the adjustment methods are stable. The resulting flake silver powder exhibits good monodispersity, narrow particle size distribution, and is not prone to agglomeration.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

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

[0008] (1) Prepare silver salt solution, reducing agent solution, seed crystal aid and dispersant base solution;

[0009] (2) Under stirring conditions, the reducing agent solution, seed crystal aid and 30-50% silver salt solution are added to the dispersant base liquid and mixed. After the addition of 30-50% silver salt solution is completed, the remaining 50-70% silver salt solution is added to continue the reaction. During the second addition of silver salt solution, alkaline carboxylate is added to promote the formation of silver powder and maintain its stability in the system.

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

[0011] (4) After the reaction is complete, solid-liquid separation is performed to obtain wet silver powder. The wet silver powder is washed and then mixed with alcohol to obtain a silver powder-alcohol mixture. The silver powder-alcohol mixture is mechanically ground, and the grinding time and speed are controlled to obtain silver powder with a specific lamellar structure.

[0012] Preferably, in step (1), the method for preparing the seed crystal is as follows: at room temperature, silver nitrate solution is mixed with propylamine, followed by the addition of polyvinylpyrrolidone and mixed evenly to obtain a mixture. The mixture is then heated at 60°C for 30 minutes to obtain a brown seed crystal containing nano-micron silver.

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

[0014] Preferably, in step (2), the basic carboxylate includes one or more of alkali metal formate, acetate, propionate, valerate and hexanoate. More preferably, the basic 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.

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

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

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

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

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

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

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

[0022] Beneficial effects:

[0023] This invention uses crystal additives and dispersants as particle size control agents, combined with alkaline carboxylates and surface coating agents to obtain silver particles with good monodispersity. Then, alcohol is added for dispersion, and the particles are shaped into flakes by grinding. The preparation process of this invention is simple and the control method is stable, which can produce flake silver powder with good monodispersity, narrow particle size distribution and no agglomeration. Attached Figure Description

[0024] Figure 1 The image shown is an SEM image of Example 1;

[0025] Figure 2 The image shown is an SEM image of Example 2;

[0026] Figure 3 The image shown is an SEM image of Example 3;

[0027] Figure 4 The image shown is the SEM image of Comparative Example 1.

[0028] Figure 5 The image shown is a SEM image of Comparative Example 2.

[0029] Figure 6 The image shown is the SEM image of Comparative Example 3.

[0030] Figure 7 The image shown is the SEM image of Comparative Example 4.

[0031] Figure 8 The image shown is a SEM image of Comparative Example 5. Detailed Implementation

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0033] This invention proposes a method for preparing nano-sheet silver powder. First, a crystallizing agent and a dispersant are used as particle size control agents, combined with an alkaline carboxylate and a surface coating agent to obtain silver particles with good monodispersity. Then, alcohol is added for further dispersion, and the powder is shaped into sheets using a grinding mill. The preparation process of this invention is simple, the control method is stable, and it can produce sheet-like silver powder with good monodispersity, narrow particle size distribution, and resistance to agglomeration. Detailed preparation steps and related technical contents are as follows:

[0034] (1) Prepare silver salt solution, reducing agent solution, seed crystal aid and dispersant base solution;

[0035] (2) Under stirring conditions, the reducing agent solution, seed crystal aid and 30-50% silver salt solution are added to the dispersant base liquid and mixed. After the addition of 30-50% silver salt solution is completed, the remaining 50-70% silver salt solution is added to continue the reaction. During the second addition of silver salt solution, alkaline carboxylate is added to promote the formation of silver powder and maintain its stability in the system.

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

[0037] (4) After the reaction is complete, solid-liquid separation is performed to obtain wet silver powder. The wet silver powder is washed and then mixed with alcohol to obtain a silver powder-alcohol mixture. The silver powder-alcohol mixture is mechanically ground, and the grinding time and speed are controlled to obtain silver powder with a specific lamellar structure.

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

[0039] A reducing agent solution is formed by dissolving a reducing agent in a solvent, and its function is to reduce silver ions to silver. Generally, reducing agents include 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 role of the seed crystal aid is to promote the nucleation process of silver powder. Specifically, the preparation method of the seed crystal aid is as follows: at room temperature, silver nitrate solution is mixed with propylamine, and then polyvinylpyrrolidone is added and mixed evenly to obtain a mixture. The mixture is then heated at 60°C for 30 minutes to obtain a brown seed crystal aid containing nano- or micron-sized silver. Preferably, the concentration of silver in the seed crystal aid is 0.01 mol / L.

[0041] In the preparation of seed crystals, propylamine acts as both a complexing agent and a reducing agent. Propylamine complexes with silver ions, enhancing the reducing power of silver. Polyvinylpyrrolidone acts as both a dispersant and a reducing agent. Under heating conditions, propylamine and polyvinylpyrrolidone can reduce silver ions in the solution to silver, which is then uniformly dispersed under the action of polyvinylpyrrolidone to form seed crystals.

[0042] The dispersant base liquid is formed by dissolving the dispersant in a solvent. The dispersant includes one or more of polymeric surfactants, cationic surfactants, and anionic surfactants. For example, the dispersant includes one or two of polyvinyl alcohol and polyvinylpyrrolidone to enhance the dispersibility of 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 in two stages. The first stage involves a relatively small amount of silver ions, resulting in an excess of reducing agent. The silver ions in the seed crystal agent act as nuclei to generate well-dispersed silver powder. Subsequently, the silver ions in the second stage of the silver salt solution are reduced to silver and adhere to the surface of the previously generated silver powder, forming silver powder with uniform particle size. Without the seed crystal agent, the resulting silver powder has a wide particle size distribution and its morphology is difficult to control.

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

[0045] Preferably, the basic carboxylates include one or more of alkali metal formates, acetates, propions, valerates, and hexanoates, such as sodium formate, sodium acetate, sodium propionate, sodium valerate, sodium hexanoate, potassium formate, potassium acetate, potassium propionate, potassium valerate, and potassium hexanoate.

[0046] Preferably, the basic carboxylate is added when the total time for adding the silver salt solution reaches 60-70% of the total time, based on the total time of the two silver salt additions. The basic carboxylate should not be added too early, otherwise the silver carboxylate will adhere to the surface of the silver powder, limiting the subsequent formation of silver on the surface of the silver powder and affecting the production of silver powder with uniform particle size; the basic carboxylate should also not be added too late, otherwise the reaction for silver formation will be nearly complete, and the particle size of the silver powder can no longer be changed.

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

[0048] In step (3), the coating agent includes one or more of oleic acid, palmitic acid, myristic acid, and caprylic acid. The reaction continues for a period of time after the coating agent is added, for example, for 2–5 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 and obtain wet silver powder. First, deionized water is used to wash the silver powder to remove the residual reactants and impurities. Then, alcohol is added after the washing is completed to form a silver powder alcohol mixture, which is a silver powder suspension.

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

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

[0052] Preferably, during the mechanical grinding process, the temperature is controlled between 20 and 80°C to prevent the silver powder from melting and agglomerating during the grinding process.

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

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

[0055] To prepare the seed crystal aid, 20 g of a 0.1 mmol / L silver nitrate solution was mixed with 0.5 g of propylamine. Then, 2 g of PVP K30 powder (molecular weight approximately 40,000) was added and mixed to obtain a final mixture. PVP helps prevent silver particles from agglomerating in subsequent processes. The mixture was heated in a constant-temperature oil bath at 60°C for 30 minutes to promote the reaction. The final result was a brown seed crystal aid solution containing nano- and micron-sized silver, with an expected silver concentration of 0.01 mol / L.

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

[0057] Weigh out ascorbic acid, mix it with deionized water, and stir until completely dissolved to obtain a reducing agent solution with a volume of 100 ml and a concentration of approximately 0.8 mol / L.

[0058] Weigh 10g of polyvinylpyrrolidone K30 and mix it with 190g of deionized water. Stir until completely dissolved to obtain a dispersant solution with a concentration of 5% (w / v).

[0059] Perform the following operations under stirring conditions of 400 rpm:

[0060] First, add the seed crystal agent solution to the dispersant solution to ensure uniform dispersion. Then, simultaneously add the silver nitrate solution and reducing agent solution to the reaction mixture at a flow rate of 10 ml / min. Approximately 100 ml of silver nitrate solution is added in two portions: 30.0 ml in the first portion and 70.0 ml in the second portion, with the total addition time being 10 minutes. At 7 minutes, add sodium formate and sodium hydroxide solutions. Monitor the pH value during stirring, aiming for a pH of 8–9 to promote silver powder formation and stability.

[0061] After the silver nitrate solution has been added for 10 minutes, add 1 ml of oleic acid solution (equivalent to 0.01 mol / L). Its function is to form a coating layer with the silver particles and prevent them from agglomerating.

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

[0063] In a silver powder suspension, silver powder is suspended in an alcohol solution. Grinding zirconium beads, with a diameter controlled at 1–2 mm, are added. The mass of the zirconium beads accounts for 20% (w / v) of the silver powder suspension volume. A mechanical grinding device is used, with a grinding time set to 30 minutes and a rotation speed maintained at 500 rpm. Observation shows that the ground silver powder exhibits a flake-like structure and good dispersibility. Figure 1 As shown.

[0064] Example 2

[0065] Compared with Example 1, in this example, the diameter of the polished zirconium beads is 0.1 to 0.5 mm.

[0066] To prepare the seed crystal aid, 20 g of a 0.1 mmol / L silver nitrate solution was mixed with 0.5 g of propylamine. Then, 2 g of PVP K30 powder (molecular weight approximately 40,000) was added and mixed to obtain a final mixture. PVP helps prevent silver particles from agglomerating in subsequent processes. The mixture was heated in a constant-temperature oil bath at 60°C for 30 minutes to promote the reaction. The final result was a brown seed crystal aid solution containing nano- and micron-sized silver, with an expected silver concentration of 0.01 mol / L.

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

[0068] Weigh out ascorbic acid, mix it with deionized water, and stir until completely dissolved to obtain a reducing agent solution with a volume of 100 ml and a concentration of approximately 0.8 mol / L.

[0069] Weigh 10g of polyvinylpyrrolidone K30 and mix it with 190g of deionized water. Stir until completely dissolved to obtain a dispersant solution with a concentration of 5% (w / v).

[0070] Perform the following operations under stirring conditions of 400 rpm:

[0071] First, add the seed crystal agent solution to the dispersant solution to ensure uniform dispersion. Then, simultaneously add the silver nitrate solution and reducing agent solution to the reaction mixture at a flow rate of 10 ml / min. Approximately 100 ml of silver nitrate solution is added in two portions: 40.0 ml in the first portion and 60.0 ml in the second portion, with the total addition time being 10 minutes. At 7 minutes, add sodium acetate and sodium hydroxide solutions. Monitor the pH value during stirring, aiming for a pH of 8–9 to promote silver powder formation and stability.

[0072] After the silver nitrate solution has been added for 10 minutes, add 1 ml of oleic acid solution (equivalent to 0.01 mol / L). Its function is to form a coating layer with the silver particles and prevent them from agglomerating.

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

[0074] In a silver powder suspension, silver powder is suspended in an alcohol solution. Grinding zirconium beads, with a diameter controlled at 0.1–0.5 mm, are added. The mass percentage of the zirconium beads in the silver powder suspension is 20% (w / v). A mechanical grinding device is used, with a grinding time set to 60 minutes and a rotation speed maintained at 300 rpm. Observation shows that the ground silver powder exhibits a flake-like structure and good dispersibility. Figure 2 As shown.

[0075] Example 3

[0076] To prepare the seed crystal agent, 20 g of a 0.1 mmol / L silver nitrate solution was mixed with 1.5 g of propylamine. Then, 2 g of PVP K30 powder (molecular weight approximately 40,000) was added and mixed to obtain a final mixture. PVP helps prevent silver particles from agglomerating in subsequent processes. The mixture was heated in a constant-temperature oil bath at 60°C for 30 minutes to promote the reaction. The final result was a brown seed crystal agent solution containing nano- and micron-sized silver, with an expected silver concentration of 0.01 mol / L.

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

[0078] Weigh out ascorbic acid, mix it with deionized water, and stir until completely dissolved to obtain a reducing agent solution with a volume of 100 ml and a concentration of approximately 0.8 mol / L.

[0079] Weigh 10g of polyvinylpyrrolidone K30 and mix it with 190g of deionized water. Stir until completely dissolved to obtain a dispersant solution with a concentration of 5% (w / v).

[0080] Perform the following operations under stirring conditions of 400 rpm:

[0081] First, add the seed crystal agent solution to the dispersant solution to ensure uniform dispersion. Then, simultaneously add the silver nitrate solution and reducing agent solution to the reaction mixture at a flow rate of 10 ml / min. Approximately 100 ml of silver nitrate solution is added in two portions: 50.0 ml in the first portion and 50.0 ml in the second portion, with the total addition time being 10 minutes. At 7 minutes, add sodium formate and sodium hydroxide. Monitor the pH value during stirring, aiming for a pH of 8–9 to promote silver powder formation and stability.

[0082] After the silver nitrate solution has been added for 10 minutes, add 1 ml of oleic acid solution (equivalent to 0.01 mol / L). Its function is to form a coating layer with the silver particles and prevent them from agglomerating.

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

[0084] In a silver powder suspension, silver powder is suspended in an alcohol solution. Grinding zirconium beads, with a diameter controlled at 0.1–0.5 mm, are added. The mass percentage of the zirconium beads in the silver powder suspension is 20% (w / v). A mechanical grinding device is used, with a grinding time set to 45 minutes and a rotation speed maintained at 450 rpm. Observation shows that the ground silver powder exhibits a flake-like structure and good dispersibility. Figure 3 As shown.

[0085] Comparative Example 1

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

[0087] After solid-liquid separation, the wet silver powder was washed and dried to obtain silver powder. The morphology of the silver powder was observed, such as... Figure 4 As shown.

[0088] Clearly, the silver powder is in the form of spherical or other irregular shapes, and does not form flakes. Therefore, flake-shaped silver powder cannot be obtained without grinding.

[0089] Comparative Example 2

[0090] Compared with Example 3, no seed crystal additive was added in this comparative example.

[0091] After grinding, observe the morphology of the silver powder, such as... Figure 5 As shown, without the addition of seed crystals, the morphology of the generated silver powder is difficult to control, and it is impossible to obtain flake-shaped silver powder with good monodispersity, narrow particle size distribution, and resistance to agglomeration.

[0092] Comparative Example 3

[0093] Compared to Example 3, the silver nitrate solution in this comparative example was added all at once, instead of being added in two separate additions.

[0094] After grinding, observe the morphology of the silver powder, such as... Figure 6 As shown, the silver powder cracked, indicating that adding silver nitrate solution once has a significant impact on the morphology of the silver powder.

[0095] Comparative Example 4

[0096] Compared to Example 3, this comparative example added an alkaline carboxylate at 50% of the time when silver nitrate was added.

[0097] After grinding, observe the morphology of the silver powder, such as... Figure 7 As shown, the silver powder particles become larger and agglomerate, demonstrating that the timing of the addition of alkaline silver nitrate is important.

[0098] Comparative Example 5

[0099] Compared to Example 3, this comparative example added an alkaline carboxylate at 80% of the time when silver nitrate was added.

[0100] After grinding, observe the morphology of the silver powder, such as... Figure 8 As shown, the silver powder particles showed obvious agglomeration. After the alkaline carboxylate was added later, the morphology of the silver powder was determined, and the effect of the alkaline carboxylate was not obvious.

[0101] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing nanosheet-like silver powder, characterized in that, as follows: (1) Prepare silver salt solution, reducing agent solution, seed crystal aid and dispersant base solution; (2) Under stirring conditions, the reducing agent solution, seed crystal aid and 30-50% silver salt solution are added to the dispersant base liquid and mixed. After the addition of 30-50% silver salt solution is completed, the remaining 50-70% silver salt solution is added to continue the reaction. During the second addition of silver salt solution, an alkaline carboxylate is added. (3) After the second addition of the silver salt solution is completed, add the coating agent; (4) After the reaction is complete, solid-liquid separation is performed to obtain wet silver powder. The wet silver powder is washed and then mixed with alcohol to obtain a silver powder-alcohol mixture. The silver powder-alcohol mixture is mechanically ground to obtain silver powder with a plate-like structure. In step (1), the method for preparing the seed crystal is as follows: at room temperature, silver nitrate solution is mixed with propylamine, followed by the addition of polyvinylpyrrolidone and mixed evenly to obtain a mixture. The mixture is then heated at 60°C for 30 minutes to obtain a brown seed crystal containing nano-micron silver. In step (2), based on the total time of the two silver salt solution additions, when the silver salt addition time reaches 60-70% of the total time, alkaline carboxylate is added to adjust the pH of the system to 8-9.

2. The method for preparing nanosheet silver powder according to claim 1, characterized in that, In step (2), the basic carboxylate includes one or more of alkali metal formate, acetate, propionate, valerate and hexanoate.

3. The method for preparing nanosheet silver powder according to claim 2, characterized in that, Basic carboxylates include 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 nanosheet silver powder according to any one of claims 1-3, characterized in that, In step (4), a fatty dispersant is added to the silver powder-alcohol mixture.

5. The method for preparing nanosheet silver powder according to any one of claims 1-3, characterized in that, During the mechanical grinding process, the temperature is controlled between 20 and 80°C.

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

7. A flake-shaped silver powder, characterized in that, The silver nanoparticles are prepared by the method for preparing nanosheet silver powder according to any one of claims 1-6, wherein the diameter of the nanosheet silver powder is less than or equal to 1.0 μm.

8. An application of flake silver powder, characterized in that, The flake silver powder prepared by the method for preparing nano-flake silver powder according to any one of claims 1-6 can be used in electronic components, medical devices and high-end electronic coatings.

Images