A method for preparing micron-sized flake-shaped silver powder with adjustable particle size

Abstract

This invention discloses a method for preparing micron-sized flake-like silver powder with adjustable particle size. The steps are as follows: 1. Weigh silver nitrate and polyacrylamide, add them sequentially to DMF, and stir until completely dissolved to obtain solution A; 2. Weigh NH4Cl, add it to DMF and dissolve it completely to obtain solution B; 3. Add a reducing agent to DMF and dissolve it completely to obtain solution C; 4. Add solution A to a three-necked round-bottom flask, and while stirring at a certain speed at 40-70℃, quickly add solution B to the round-bottom flask and stir until homogeneous to obtain solution D; 5. Quickly add solution C to solution D while stirring, and react for 4 hours; 6. Separate, wash, and vacuum dry the reacted solution to obtain flake-like silver powder. This method is simple and easy to scale up. The prepared flake-like silver powder has a smooth surface, good dispersibility, uniform particle size distribution, and an adjustable particle size range of 1.26 μm-15 μm.

Description

Technical Field

[0001] This invention belongs to the field of metal powder preparation technology, specifically relating to a method for preparing micron-sized flake-shaped silver powder with adjustable particle size. Background Technology

[0002] In recent years, silver powder has been widely used in catalysis, sensing, surface-enhanced Raman scattering, and biomedicine. Simultaneously, due to its excellent electrical and thermal conductivity, silver powder is also widely used in various conductive pastes. In conductive paste applications, spherical powders primarily rely on the contact points between particles; to reduce resistivity, higher silver content is typically required. Among silver powders with different structures, flake-shaped silver powder has significant geometric advantages compared to other structures. A higher aspect ratio and larger contact area between particles generally result in lower contact resistance and higher conductivity. Moreover, even in conductive pastes with low silver content, flake-shaped silver powder still exhibits lower resistivity due to its larger particle size and larger contact area between particles. Therefore, flake-shaped silver powder has been widely used in the preparation of conductive thin films.

[0003] Currently, the synthesis methods for flake silver powder are generally divided into physical and chemical methods. Due to the toughness of bulk silver, ball milling can be used to grind spherical silver particles into flake silver powder with a nanometer thickness. However, this requires a long time to ensure effective collision between the grinding balls and silver particles. Moreover, the size of the flake silver cannot be well controlled by physical methods. To reduce energy consumption and ensure the uniformity of flake silver powder, chemical reduction methods have been more widely used in the preparation of flake silver powder. For example, Chinese invention patent application CN 111590086 A first synthesizes a nanocrystal seed solution, and then, under the combined regulation of the seed solution, reducing agent, morphology regulator, and growth control agent, prepares flake silver powder with a particle size of about 3.0 μm. However, through SEM image studies, it was found that the size difference of these micron-sized flake particles is large, reaching several times. At the same time, a large number of spherical nanoparticles and their aggregates are also present. Chinese invention patent application CN107716944 B also first prepares a seed solution, and then, with vitamin C as a reducing agent, prepares flake-shaped silver powder with a particle size in the range of 230-580 nm under the action of polyvinylpyrrolidone (PVP), citric acid (CA), and hexadecyltrimethylammonium bromide (CTAB). However, the flake-shaped silver powder prepared with this seed-assisted method is very prone to agglomeration, reducing the contact area between particles. Chinese invention patent application CN 114985758 B uses a vitamin C reduction method to prepare flake-shaped silver powder with a particle size in the range of approximately 10-30 μm. However, this reaction system requires HNO3 to adjust the solution pH to a strongly acidic state. Moreover, the prepared flake-shaped silver powder has a rough, non-smooth surface and contains numerous pores. This undoubtedly reduces its conductivity. Flake-shaped silver powder with different particle sizes has different optical and other properties, and therefore different application potentials. At the same time, increasing the size of the flake-shaped silver powder can improve its conductivity, oxidation resistance, and melting point. Therefore, it is necessary to develop a simple and effective method to prepare micron-sized flake silver powder with good dispersibility, smooth surface, and adjustable particle size in one step. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a method for preparing micron-sized flake-like silver powder with adjustable particle size. This method is simple and easily scaled up. The prepared flake-like silver powder has a smooth surface, good dispersibility, uniform particle size distribution, and an adjustable particle size range between 1.26 μm and 15 μm.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing micron-sized flake-shaped silver powder with adjustable particle size mainly includes the following steps:

[0007] Step 1: Prepare the silver precursor and polyacrylamide solution

[0008] Weigh out silver nitrate and polyacrylamide, add them sequentially to DMF, and stir until completely dissolved to obtain solution A for later use;

[0009] Step 2: Prepare the reaction solution;

[0010] Weigh out NH4Cl, add it to DMF, and after it is completely dissolved, prepare solution B for later use;

[0011] Step 3: Prepare the reducing agent solution;

[0012] Add the reducing agent to DMF and dissolve it completely to obtain solution C for later use;

[0013] Step 4: Mixing

[0014] Add the solution A obtained in step one to a three-necked round-bottom flask. Under the temperature of 40-70℃ and a certain stirring speed, quickly add the solution B obtained in step two to the round-bottom flask and stir evenly to obtain solution D for later use.

[0015] Step 5: Perform the liquid-phase reduction reaction.

[0016] The solution C obtained in step 3 was rapidly added to solution D under stirring, and the reaction was carried out for 4 hours.

[0017] Step Six: Separation and Purification

[0018] The solution after the reaction was separated, washed, and vacuum dried to obtain flake silver powder.

[0019] Furthermore, the molar concentration of silver nitrate in solution A is 10-40 mmol / L.

[0020] Furthermore, the molar concentration of polyacrylamide in solution A is 80-300 mmol / L.

[0021] Furthermore, the reducing agent is sodium hypophosphite, with a molar concentration of 0.5-2.0 mol / L.

[0022] Furthermore, in step four, the rotation speed is 180-600 rpm.

[0023] Furthermore, the specific separation and purification operation in step six is ​​as follows: after the reaction is completed, cool to room temperature, discard the upper layer solution, wash 4 times with ethanol, and vacuum dry for 24 h to obtain flake silver powder.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. The purpose of this invention is to provide a method for preparing micron-sized flake-shaped silver powder with adjustable particle size. This method is simple and easy to scale up. The prepared silver powder has a flake-like structure with almost no other silver products. It has a uniform particle size distribution, adjustable particle size in the range of 1.26μm-15μm, good dispersibility, high crystallinity, and a smooth surface.

[0026] 2. The flake silver powder prepared in this invention has a smooth surface, high crystallinity, and large size, thus exhibiting high antioxidant properties;

[0027] 3. The flake silver powder prepared in this invention has a uniform particle size, a smooth and flat surface, and is not easily bent or deformed, thus increasing the contact area between particles, reducing the resistivity of the silver powder, and improving the conductivity of the silver powder.

[0028] 4. By adjusting the concentration, temperature, and stirring speed of the reactants, it is possible to effectively synthesize flake-shaped silver powder with uniform particle size ranging from 1.26 μm to 15 μm. Attached Figure Description

[0029] Figure 1 This is a 5000x magnified SEM image of the flake silver powder prepared in Example 1 of the present invention;

[0030] Figure 2 This is a 5000x magnified SEM image of the flake silver powder prepared in Example 2 of the present invention.

[0031] Figure 3 This is a 2000x magnified SEM image of the flake silver powder prepared in Example 3 of the present invention;

[0032] Figure 4 The XRD pattern of the flake silver powder prepared in Example 3 of this invention;

[0033] Figure 5 This is a 2000x magnified SEM image of the flake silver powder prepared in Example 4 of the present invention.

[0034] Figure 6 This is a 2000x magnified SEM image of the flake silver powder prepared in Example 5 of the present invention.

[0035] Figure 7 This is a 2000x magnified SEM image of the flake silver powder prepared in Example 6 of the present invention.

[0036] Figure 8 This is a 2000x magnified SEM image of the flake silver powder prepared in Example 7 of the present invention;

[0037] Figure 9 This is a 1000x magnified SEM image of the flake silver powder prepared in Example 8 of the present invention.

[0038] Figure 10 This is a 1000x magnified SEM image of the flake silver powder prepared in Example 9 of the present invention.

[0039] Figure 11 This is a 1000x magnified SEM image of the flake silver powder prepared in Example 10 of the present invention.

[0040] Figure 12 This is a 1000x magnified SEM image of the flake silver powder prepared in Example 11 of the present invention. Detailed Implementation

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0042] A method for preparing micron-sized flake-shaped silver powder with adjustable particle size includes the following steps:

[0043] Step 1: Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved. The molar concentration of silver nitrate is 10-40 mmol / L, and the molar concentration of polyacrylamide (repeating unit) is 80-300 mmol / L. Polyacrylamide acts as a steric stabilizer to prevent the formation of flake-like silver powder aggregates; and the amide functional groups in its molecule help to form a flake-like structure.

[0044] Step 2: Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. After complete dissolution, set aside. The molar concentration of NH4Cl is 4.2-22.2 mol / L. Add a small amount of NH4Cl... - Can be with Ag + Small amounts of AgCl and NH4 are formed. + Cl - Both AgCl and AgCl selectively adsorb and passivate the (111) crystal plane;

[0045] Step 3: Weigh a certain amount of reducing agent sodium hypophosphite and add it to 5 mL of DMF. After complete dissolution, set aside for later use. The molar concentration of sodium hypophosphite is 0.5-2.0 mol / L. In the above steps, N,N-dimethylformamide DMF solution is used as the solvent. DMF has good dissolving ability and firstly acts as a solvent. Secondly, the amide functional groups it contains help to form a sheet-like structure.

[0046] Step 4: Add the solution from Step 1 to a 200 mL three-necked round-bottom flask. At a temperature of 40-70℃ and a stirring speed of 180-600 rpm, quickly add the solution from Step 2 to the round-bottom flask and stir for 3 minutes.

[0047] Step 5: Quickly add the solution from Step 3 to the solution from Step 4, and react for 4 hours at a temperature of 40-70℃ and a rotation speed of 180-600 rpm.

[0048] Step 6: Separate, wash, and vacuum dry the solution after the reaction to obtain flake silver powder.

[0049] Example 1:

[0050] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 40 mmol / L and 300 mmol / L respectively, and set aside.

[0051] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 22.2 mmol / L. Set aside for later use.

[0052] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 2.0 mol / L. Set aside for later use.

[0053] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 70 °C, with stirring at 600 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0054] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 600 rpm, and react for 4 h;

[0055] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 1 As shown, the prepared flake silver powder has an average particle size of about 1.26 μm, a smooth surface, and good dispersibility.

[0056] Example 2:

[0057] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 30 mmol / L and 260 mmol / L, respectively, for later use;

[0058] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 13.3 mmol / L. Set aside for later use.

[0059] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 1.5 mol / L. Set aside for later use.

[0060] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 70 °C, with stirring at 480 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0061] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 480 rpm, and react for 4 h;

[0062] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 2 As shown, the prepared flake silver powder has an average particle size of about 2.68 μm, a smooth surface, and good dispersibility.

[0063] Example 3:

[0064] 1) Weigh out a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 20 mmol / L and 200 mmol / L respectively, and set aside for later use;

[0065] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 8.9 mmol / L. Set aside for later use.

[0066] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 1.0 mol / L. Set aside for later use.

[0067] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 65°C, with stirring at 420 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0068] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 420 rpm, and react for 4 h;

[0069] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 3 As shown in the SEM image, the prepared flake silver powder has an average particle size of about 3.76 μm, a very smooth surface, very uniform particle size, and excellent dispersibility. Figure 4 The XRD pattern of the sample shows strong diffraction peaks, indicating high crystallinity and a face-centered cubic structure. No other impurity peaks were observed, demonstrating high product purity. Furthermore, the (111) peak intensity was dominant, indicating that the outer surface of the flake silver powder was mainly dominated by the (111) plane, meaning that the upper and lower surfaces of the prepared flake silver powder were (111) crystal planes.

[0070] Example 4:

[0071] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 18 mmol / L and 200 mmol / L, respectively, for later use;

[0072] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 8.0 mmol / L. Set aside for later use.

[0073] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 1.0 mol / L. Set aside for later use.

[0074] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 60°C, with stirring at 400 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0075] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 400 rpm, and react for 4 h;

[0076] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 5 The SEM image shows that the prepared flake silver powder has an average particle size of about 4.22 μm, a smooth surface, uniform particle size, and good dispersibility.

[0077] Example 5:

[0078] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 15 mmol / L and 180 mmol / L respectively, and set aside.

[0079] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 6.7 mmol / L. Set aside for later use.

[0080] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 0.75 mol / L. Set aside for later use.

[0081] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 60 °C, with stirring at 300 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0082] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 300 rpm, and react for 4 h;

[0083] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 6 As shown in the SEM image, the prepared flake silver powder has an average particle size of about 5.63 μm, a smooth surface, relatively uniform particle size, and good dispersibility.

[0084] Example 6:

[0085] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 15 mmol / L and 160 mmol / L, respectively, for later use;

[0086] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 6.7 mmol / L. Set aside for later use.

[0087] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 0.75 mol / L. Set aside for later use.

[0088] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 60 °C, with stirring at 200 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0089] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 200 rpm, and react for 4 h;

[0090] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 7 As shown in the SEM image, the prepared flake silver powder has an average particle size of about 6.40 μm, a smooth surface, relatively uniform particle size, and good dispersibility.

[0091] Example 7:

[0092] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 12 mmol / L and 150 mmol / L respectively, and set aside.

[0093] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 5.3 mmol / L. Set aside for later use.

[0094] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 0.6 mol / L. Set aside for later use.

[0095] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 60 °C, with stirring at 200 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0096] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 200 rpm, and react for 4 h;

[0097] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 8 As shown in the SEM image, the prepared flake silver powder has an average particle size of about 7.20 μm, a smooth surface, relatively uniform particle size, and good dispersibility.

[0098] Example 8:

[0099] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 12 mmol / L and 120 mmol / L respectively, and set aside.

[0100] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 5.3 mmol / L. Set aside for later use.

[0101] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 0.6 mol / L. Set aside for later use.

[0102] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 55°C, with stirring at 200 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0103] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 200 rpm, and react for 4 h;

[0104] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 9 The SEM image shows that the prepared flake silver powder has an average particle size of about 8.12 μm, a smooth surface, uniform particle size, and good dispersibility.

[0105] Example 9:

[0106] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 10 mmol / L and 120 mmol / L respectively, and set aside.

[0107] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 4.5 mmol / L. Set aside for later use.

[0108] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 0.45 mol / L. Set aside for later use.

[0109] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 55 °C, with stirring at 200 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0110] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 200 rpm, and react for 4 h;

[0111] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 10 The SEM image shows that the prepared flake silver powder has an average particle size of about 9.21 μm, a smooth surface, and good dispersibility.

[0112] Example 10:

[0113] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 10 mmol / L and 100 mmol / L respectively, and set aside for later use;

[0114] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 4.5 mmol / L. Set aside for later use.

[0115] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 0.5 mol / L. Set aside for later use.

[0116] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 45 °C, with stirring at 180 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0117] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 180 rpm, and react for 4 h;

[0118] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 11 The SEM image shows that the prepared flake silver powder has an average particle size of about 12.21 μm, a smooth surface, relatively uniform particle size, and good dispersibility.

[0119] Example 11:

[0120] 1) Weigh a certain amount of silver nitrate and polyacrylamide, add them to 50 mL of DMF, and stir until completely dissolved, so that their concentrations are 10 mmol / L and 80 mmol / L, respectively, for later use;

[0121] 2) Weigh a certain amount of NH4Cl and add it to 45 mL of DMF. Dissolve it completely to obtain a concentration of 4.2 mmol / L. Set aside for later use.

[0122] 3) Weigh a certain amount of sodium hypophosphite and add it to 5 mL of DMF. Dissolve it completely to obtain a concentration of 0.5 mol / L. Set aside for later use.

[0123] 4) Add the solution from step 1) to a 200 mL three-necked round-bottom flask. At 40 °C, with stirring at 180 rpm, quickly add the solution from step 2) to the round-bottom flask and stir for 3 min.

[0124] 5) Quickly add the solution from step 3) to the solution from step 4), stir at 180 rpm, and react for 4 h;

[0125] 6) Separate, wash, and vacuum dry the solution after the reaction in step 5) to obtain flake-like silver powder. For example... Figure 12 The SEM image shows that the prepared flake silver powder has an average particle size of about 14.79 μm, a smooth surface, a narrow particle size distribution, and good dispersibility.

[0126] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing micron-sized flake-shaped silver powder with adjustable particle size, wherein the particle size of the flake-shaped silver powder prepared by this method is adjustable from 1.26 μm to 15 μm, characterized in that: The main steps include: Step 1: Prepare the silver precursor and polyacrylamide solution Weigh silver nitrate and polyacrylamide, add them sequentially to DMF, and stir until completely dissolved to prepare solution A. The molar concentration of silver nitrate in solution A is 10-40 mmol / L, and the molar concentration of polyacrylamide is 80-300 mmol / L. Set aside for later use. Step 2: Prepare the reaction solution; Weigh out NH4Cl, add it to DMF, and after it is completely dissolved, prepare solution B for later use; Step 3: Prepare the reducing agent solution; A reducing agent, sodium hypophosphite, with a molar concentration of 0.5-2.0 mol / L, is added to DMF and completely dissolved to obtain solution C for later use. Step 4: Mixing Add the solution A obtained in step one to a three-necked round-bottom flask. Under the temperature of 40-70℃ and a certain stirring speed, quickly add the solution B obtained in step two to the round-bottom flask and stir evenly to obtain solution D for later use. The stirring speed in this step is 180-600 rpm. Step 5: Perform the liquid-phase reduction reaction. The solution C obtained in step 3 was rapidly added to solution D under stirring, and the reaction was carried out for 4 hours. Step Six: Separation and Purification The solution after the reaction was separated, washed, and vacuum dried to obtain flake silver powder.

2. The method for preparing micron-sized flake-shaped silver powder with adjustable particle size according to claim 1, characterized in that: The specific steps for separation and purification in step six are as follows: After the reaction is completed, cool to room temperature, discard the upper layer solution, wash with ethanol 4 times, and vacuum dry for 24 hours to obtain flake silver powder.

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