Silver powder and method for preparing silver powder surface nanostructure

Abstract

The present invention discloses a method for preparing silver powder and a nanostructure on the surface of the silver powder. The preparation method comprises the following steps: (1) mixing micron silver powder, a nanosilver seed solution, an organic solvent, and a binder to form a mixture solution; preparing a complex silver ion solution and a reducing agent solution; wherein the binder is an organic acid containing a carbon-oxygen double bond and a hydroxyl group, and the complex silver ion solution is a silver ion solution containing a complexing agent, wherein the silver ions exist in a complexed state; (2) mixing the complex silver ion solution, the reducing agent solution, and the mixture solution to react, so that newly generated silver is formed on the surface of the micron silver powder and wraps the surface of the micron silver powder; (3) after the reaction is completed, separating and obtaining silver powder, washing, filtering, and drying to obtain a silver powder product. The present invention achieves a higher coverage rate of subsequent surface nanostructured silver powder by all-round coating of silver particles, thereby obtaining a silver powder product with high sintering activity.

Description

Technical Field

[0001] The invention belongs to the technical field of metal powder preparation, and in particular relates to a method for preparing silver powder and a nanostructure on the surface of the silver powder. Background Art

[0002] Nanosilver powder particles have high sintering activity and can improve the electrical performance of products after application to slurries and sintering. Nanosilver particles have a large surface area, which affects their viscosity. In the field of crystalline silicon solar energy, micron-sized silver particles are the preferred material for the conductive phase due to defects in nanosilver particles. However, micron-sized silver powders suffer from low sintering activity, which requires further improvement. Therefore, surface modification of micron-sized silver powders is one method to improve their sintering activity.

[0003] Currently, methods for improving the sintering activity of silver particles mainly include surface modification of silver powder, such as surface modification through ammonia complexation and pH adjustment, and surface modification of silver powder through organic silver coating. For example, patent CN117862488A improves sintering activity by reacting organic carboxylic acid with silver ammonia complex to coat silver carboxylate on the surface of silver powder. Patent CN117862498A invented a microcrystalline silver powder coated with a nanosilver film on the surface. The sintering activity is improved by reducing the silver ammonia solution with a reducing agent on the silver powder surface, and then coating the nanosilver cores generated under dispersant and pH control conditions on the surface of the microcrystalline silver powder.

[0004] The existing modification method is difficult to control the coating of silver particles, and the coating rate still has room for improvement. The present invention proposes a new modification method to achieve full coverage of micron silver particles. 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 silver powder and silver powder surface nanostructures, in which nanosilver seeds are adsorbed on the surface of micron silver powder particles through a binder, and silver atoms generated by reducing and complexing silver ions are diffused, deposited and grown near the seeds on the surface of the micron silver powder. The all-round coating of the silver particles achieves a higher coverage rate of the subsequent surface nano-silver powder, thereby obtaining a silver powder product with high sintering activity.

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

[0007] In a first aspect of the present invention, the present invention provides a method for preparing a nanostructure on the surface of silver powder, comprising the following steps:

[0008] (1) mixing micron silver powder, nano silver seed solution, organic solvent and binder to form a mixture solution;

[0009] and, preparing a complex silver ion solution and a reducing agent solution;

[0010] Wherein, the binder refers to an organic acid containing a carbon-oxygen double bond and a hydroxyl group, and the complex silver ion solution refers to a silver ion solution containing a complexing agent, wherein the silver ions exist in a complexed state;

[0011] (2) mixing the complex silver ion solution, the reducing agent solution and the mixture solution to react, so that newly generated silver forms on the surface of the micron silver powder and wraps the surface of the micron silver powder;

[0012] (3) After the reaction is completed, the silver powder is separated and filtered and dried to obtain a silver powder product.

[0013] Preferably, the binder comprises one or more of oleic acid, ricinoleic acid, lauric acid, tartronic acid, and tartaric acid.

[0014] Preferably, in step (3), after the silver powder is cleaned, a coating agent solution is added to anchor the nanostructure on the surface of the micron silver powder, and then filtered and dried to obtain a silver powder product;

[0015] The coating agent includes one or more of triethylamine, N,N-dimethylformamide, dimethyloctylamine, and dimethyldecylamine.

[0016] More preferably, the mass ratio of the coating agent to the micron silver powder is (0.001-0.005):1.

[0017] Preferably, the mass ratio of the binder to the micron silver powder is (0.01-0.027):1.

[0018] Preferably, the size of the nano silver seeds is 10 to 80 nm, and the mass ratio of the nano silver seeds to the micron silver powder is (0.0005 to 0.005):1.

[0019] Preferably, the organic solvent is an alcohol, and the mass ratio of the organic solvent to the micron silver powder is (5-70):1. More preferably, the organic solvent includes one or more of ethanol, ethylene glycol, diethylene glycol, propylene glycol, and glycerol.

[0020] Preferably, the complexing agent includes one or more organic amines such as diethylenetriamine, triethanolamine, isopropanolamine, ethylenediamine, triethylenetetramine, tetraethylenepentamine, and ammonia.

[0021] Preferably, the silver ion concentration of the complex silver ion solution is 0.5 to 2.5 mol / L, and the mass ratio of silver ions in the complex silver ion solution to micron silver powder is (0.01 to 0.1):1, more preferably (0.03 to 0.05):1;

[0022] The concentration of the reducing agent solution is 0.4 to 1.8 mol / L, and the reducing agent includes one or more of ascorbic acid, erythorbic acid, sodium ascorbate, and sodium erythorbic acid;

[0023] The molar ratio of silver ions to reducing agent in the complex silver ion solution is 1:(0.55-1.1).

[0024] Preferably, in step (2), a dispersant is further added to mix the complex silver ion solution, the reducing agent solution, the mixture solution and the dispersant for reaction, wherein the dispersant includes one or more of a polymer dispersant, an anionic dispersant and a cationic dispersant.

[0025] In a second aspect of the present invention, the present invention provides a silver powder having a spherical or quasi-spherical structure and a surface covered with a nano-silver layer, which is prepared by the above-mentioned preparation method.

[0026] Beneficial effects:

[0027] The present invention uses a binder to adsorb nano silver seeds on the surface of micron silver powder particles, and the silver generated by reducing the complexed silver ions is diffused, deposited and grown near the seeds on the surface of the micron silver powder. The all-round coating of the silver particles achieves a higher coverage rate of the subsequent surface nano silver powder, thereby obtaining a silver powder product with high sintering activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Shown is an electron microscope image of the silver powder product prepared in Example 1;

[0029] Figure 2 Shown is an electron microscope image of the silver powder product prepared in Example 2;

[0030] Figure 3 Shown is an electron microscope image of the silver powder product prepared in Example 3;

[0031] Figure 4 Shown is an electron microscope image of the silver powder product prepared in Example 4;

[0032] Figure 5 Shown is an electron microscope image of the silver powder product prepared in Example 5;

[0033] Figure 6 Shown is an electron microscope image of the silver powder product prepared in Example 6;

[0034] Figure 7 Shown is an electron microscope image of the silver powder product prepared in Example 7;

[0035] Figure 8 Shown is an electron microscope image of the silver powder product prepared in Comparative Example 1;

[0036] Figure 9Shown is an electron microscope image of the silver powder product prepared in Comparative Example 2;

[0037] Figure 10 Shown is an electron microscope image of the silver powder product prepared in Comparative Example 3;

[0038] Figure 11 Shown is an electron microscope image of the silver powder product prepared in Comparative Example 4;

[0039] Figure 12 Shown are the sintering activity diagrams of micron silver powder, silver powder products of Example 1, Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without inventive work.

[0041] The present invention proposes a method for preparing a silver powder surface nanostructure, which is a surface modification method based on micron silver powder. The newly generated nano silver powder is evenly formed on the surface of the micron silver powder, diffused, deposited and grown near the seed crystals on the surface of the micron silver powder, thereby obtaining a silver powder product with high sintering activity. Figure 1 As shown, the silver powder product prepared by the present invention has a spherical or quasi-spherical structure, and the surface is covered with a nano silver layer.

[0042] The specific preparation steps of the present invention are as follows:

[0043] (1) mixing micron silver powder, nano silver seed solution, organic solvent and binder to form a mixture solution,

[0044] and preparing a complex silver ion solution and a reducing agent solution,

[0045] Wherein, the binder refers to an organic acid containing a carbon-oxygen double bond and a hydroxyl group, and the complex silver ion solution refers to a silver ion solution containing a complexing agent, wherein the silver ions exist in a complexed state;

[0046] (2) mixing the complex silver ion solution, the reducing agent solution and the mixture solution to react, so that newly generated silver forms on the surface of the micron silver powder and wraps the surface of the micron silver powder;

[0047] (3) After the reaction is completed, the silver powder is separated and filtered and dried to obtain a silver powder product.

[0048] The present invention first uniformly adsorbs nanosilver seed crystals onto the surface of micronized silver powder particles using a binder. During subsequent silver generation, the silver diffuses, deposits, and grows around the nanosilver seed crystals, thereby encapsulating the micronized silver powder particles. The present invention preferably uses a complex silver ion solution to slow the silver generation rate and prevent excessive silver generation from causing agglomeration.

[0049] In step (1), the micron silver powder is a micron-sized silver powder product with good dispersibility, for example, the micron silver powder can be prepared by a liquid phase redox method. The particle size distribution of the micron silver powder particles is relatively narrow, for example, the cumulative particle size distribution value D10 of the micron silver powder particles is 1.063 μm, D50 is 1.551 μm, D90 is 2.420 μm, and D100 is 4.0 μm. It is easy to understand that the present invention does not impose any specific restrictions on the particle size requirements of the micron silver powder, and any micron silver powder particles with good dispersibility are applicable to the present invention.

[0050] In step (1), a nanosilver seed solution is formed by mixing nanosilver seeds with a solvent. Generally, nanosilver seeds are prepared in ethylene glycol. The nanosilver seeds used in the present invention are retained in ethylene glycol. The size of the nanosilver seeds is 10 to 80 nm.

[0051] The mass ratio of the nano-silver seeds to the micronized silver powder is (0.0005-0.005):1, i.e., the mass of the nano-silver seeds is 0.05-0.5% of the mass of the micronized silver powder. The present invention only requires a small amount of nano-silver seeds, which are not easily agglomerated during mixing. Under the action of the binder, the nano-silver seeds can be dispersed and attached to the surface of the micronized silver powder particles.

[0052] The binder is an organic acid that is completely soluble in organic solvents. It contains carbon-oxygen double bonds (C=O bonds) and hydroxyl groups (-OH bonds), which can connect the nanosilver seed crystals to the surface of the micronized silver powder, thereby controlling the subsequent silver generation to coat the micronized silver powder at a high coverage rate. It is easy to understand that since the binder is an organic acid, the carboxyl groups in the binder already contain carbon-oxygen double bonds and hydroxyl groups. Furthermore, the binder can contain more carbon-oxygen double bonds and hydroxyl groups. For example, binders include oleic acid, ricinoleic acid, lauric acid, tartaric acid, and the like.

[0053] The mass ratio of the binder to the micron silver powder is (0.01-0.027):1, that is, the mass of the binder accounts for 1.0-2.7% of the mass of the micron silver powder.

[0054] The organic solvent is an organic compound containing hydroxyl groups, and the mass ratio of the organic solvent to the micronized silver powder is (5-70):1. The type of organic solvent affects the speed of the reaction to generate silver in the subsequent step (2). The organic solvent is preferably an alcohol, such as ethanol, ethylene glycol, diethylene glycol, propylene glycol, glycerol, etc. More preferably, the organic solvent is ethanol.

[0055] In step (1), the mixing methods of the micron silver powder, the nanosilver seed solution, the organic solvent, and the binder are various. Compared with the micron silver powder, the amount of the nanosilver seed solution and the binder is very small. Therefore, the present invention does not impose any specific restrictions on the mixing order of step (1). For example, the micron silver powder, the nanosilver seed solution, and the organic solvent are first mixed evenly, and then the binder is added and continued to mix evenly; or after the micron silver powder and the organic solvent are mixed evenly, the nanosilver seed solution is added and mixed, and finally the binder is added and mixed; or the micron silver powder, the nanosilver seed solution, the organic solvent, and the binder are mixed simultaneously.

[0056] The present invention prepares a complex silver ion solution to reduce the rate of silver generation. If the silver ion solution is directly used to react with a reducing agent, the newly generated silver tends to agglomerate into larger silver particles, which cannot encapsulate the micronized silver powder. For example, the complexing agent of the present invention uses one or more organic amines such as diethylenetriamine, triethanolamine, isopropanolamine, ethylenediamine, triethylenetetramine, and tetraethylenepentamine, as well as ammonia. The complexing agent complexes with the silver ions, appropriately reducing the redox reaction rate, allowing silver to be generated at a suitable rate and diffusely deposited around the nanosilver seed crystals.

[0057] The present invention does not impose any specific restrictions on the silver source for preparing the silver ion solution. The silver source can be dissolved in water and does not react with other components (except the reducing agent). For example, the silver source can be silver nitrate.

[0058] In step (1), the silver ion concentration of the complexed silver ion solution is 0.5 to 2.5 mol / L. It is easy to understand that the amount of complexing agent used is at least sufficient to complex all the silver ions. The mass ratio of silver ions in the complexed silver ion solution to micronized silver powder is (0.01 to 0.1):1, preferably (0.03 to 0.05):1.

[0059] In step (1), the reducing agent solution is preferably formed by dissolving a mild non-toxic reducing agent in water, and the concentration of the reducing agent solution is 0.4 to 1.8 mol / L. It is easy to understand that a mild reducing agent also helps to prevent the silver from being generated too quickly. Preferably, the reducing agent includes one or more of ascorbic acid, isoascorbic acid, sodium ascorbate, and sodium isoascorbate. The molar ratio of silver ions to reducing agent in the complex silver ion solution is 1:(0.55 to 1.1). It is easy to understand that the reducing agent reduces the silver ions in the complex silver ion solution to silver as much as possible.

[0060] Since the present invention uses a complex silver ion solution and a mild reducing agent, the generation rate of silver is significantly reduced. The organic solvent can be ethanol, ethylene glycol, etc., which appropriately increases the generation rate of silver. Under the comprehensive effect, the silver is at an appropriate generation rate.

[0061] In step (2), the complex silver ion solution, the reducing agent solution, and the mixture solution can be mixed in various ways. For example, the complex silver ion solution and the reducing agent solution can be added to the mixture solution simultaneously at a uniform rate, or they can be added to the mixture solution sequentially. Preferably, the reaction temperature in step (2) is 15 to 50° C. It is easy to understand that a lower reaction temperature can also appropriately reduce the silver generation rate.

[0062] Preferably, in step (2), a dispersant may be added to improve the dispersibility of the silver powder. Since the present invention uses micron silver powder with good dispersibility, the operation of adding a dispersant in step (2) is not necessary. In the case of adding a dispersant, the dispersant may be a dispersant commonly used in the preparation of existing silver powder, such as one or more of a polymer dispersant, an anionic dispersant and a cationic dispersant, such as a dispersant such as polyvinyl pyrrolidone (PVP), polyethylene glycol, gum arabic, triethylhexyl phosphate, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide, gum guar and fatty acid polyethylene glycol esters. The present invention does not limit the amount of the dispersant used.

[0063] In step (3), the surface nano-sized silver powder is separated by a solid-liquid separator and then washed with water until the conductivity is less than 100 μS / m.

[0064] Preferably, in step (3), after the silver powder is cleaned, a coating agent solution is added to anchor the nanostructure on the surface of the micron silver powder, and then filtered and dried to obtain a silver powder product. The coating agent includes amine substances such as triethylamine, N,N-dimethylformamide, dimethyloctylamine, and dimethyldecylamine, which prevent the deactivation of the nanostructure on the surface of the micron silver powder and the agglomeration of the nanosilver particles, thereby maintaining the high sintering activity of the surface nanostructured silver powder.

[0065] More preferably, the mass ratio of the coating agent to the micron silver powder is (0.001-0.005):1.

[0066] Preferably, in step (3), the drying temperature is 40-50°C, more preferably, the drying temperature is 40°C.

[0067] The technical solution of the present invention is described in detail below with reference to specific embodiments.

[0068] Example 1

[0069] 120 g of micron silver powder prepared by liquid phase reduction method was added to 2400 g of ethanol and dispersed by ultrasonic stirring. Then, 0.12 g of nano silver seed solution and 1.44 g of oleic acid as a binder were added to form a mixture solution.

[0070] 7.6 g of silver nitrate and 13 g of diethylenetriamine were dissolved in water to prepare a complex silver ion solution with a concentration of 1.5 mol / L, and 4.54 g of ascorbic acid was dissolved in water to prepare a reducing agent solution with a concentration of 0.8 mol / L.

[0071] The complex silver ion solution and the reducing agent solution are added to the mixture solution at a uniform speed at the same time for 15 minutes, so that the generated silver is deposited and grown on the surface of the nanosilver seeds and micron silver powder, gradually wrapping the surface of the micron silver powder.

[0072] After the reaction between the complexed silver ion solution and the reducing agent solution is complete, the silver powder undergoes solid-liquid separation and is washed multiple times with water until its conductivity drops below 100 μS / m. The silver powder is then coated in a coating agent solution containing 0.22 g of triethylamine. The coated silver powder is centrifuged and dried at 40°C for 5 hours to obtain silver particles with a nanostructured surface.

[0073] In this embodiment, the cumulative particle size distribution of the micron silver powder used is 0.867 μm, D50 is 1.295 μm, and D90 is 2.341 μm. Figure 1 This is a microscopic morphology of the silver particles obtained in Example 1. The surface has a granular nanostructure and has excellent sintering activity.

[0074] The sintering activity of the surface microstructured silver particles was tested using a thermomechanical analyzer. Figure 12 Silver particles begin to sinter at 150°C to 200°C and sinter quickly at 300°C, indicating that the silver powder product prepared by the present invention has higher sintering activity.

[0075] Example 2

[0076] The preparation steps of this embodiment are the same as those of embodiment 1, wherein the complexing agent is ammonia water, and the molar ratio of silver ions to ammonia water is 1:1. The microscopic morphology of the obtained silver particles is shown in the attached figure. Figure 2 As shown, the surface has nanoscale microstructures.

[0077] Example 3

[0078] The preparation steps of this embodiment are the same as those of embodiment 1, wherein the complexing agent is ethylenediamine, and the molar ratio of silver ions to N in ethylenediamine is 1:1.2. The microscopic morphology of the obtained silver particles is shown in the attached figure. Figure 3 As shown, the surface has a nanoscale protruding microstructure, which is beneficial to the improvement of sintering activity.

[0079] Example 4

[0080] The preparation steps of this example are the same as those of Example 1, wherein the amount of oleic acid used as the binder is 2.52 g, and the microscopic morphology of the silver particles is shown in the attached Figure 4, the morphological characteristics of partial agglomeration appear, and the cumulative particle size distribution D50 value of the silver particles increases to 1.581μm. The overall particle size is still small and does not affect the sintering. It also has high sintering activity.

[0081] Example 5

[0082] The preparation steps of this embodiment are the same as those of embodiment 1, wherein the solvent is ethylene glycol, and the microscopic morphology of the obtained silver particles is shown in the attached figure. Figure 5 As shown, the surface nanoscale protrusion microstructure is slightly enlarged and also has higher sintering activity.

[0083] Example 6

[0084] The preparation steps of this embodiment are the same as those of embodiment 1, wherein the binder is tartronic acid, and the microscopic morphology of the silver particles is shown in the attached figure. Figure 6 As shown, the surface nanoscale protrusion microstructure is slightly enlarged and also has higher sintering activity.

[0085] Example 7

[0086] The preparation steps of this embodiment are the same as those of embodiment 1, wherein another coating agent is selected from NN dimethylformamide, and the microscopic morphology of the silver particles is shown in the attached figure. Figure 7 As shown, the particles have good dispersion, the surface has a nanoscale microstructure, and the cumulative particle size distribution D50 value is 1.878 μm.

[0087] Comparative Example 1

[0088] Compared with Example 1, this comparative example does not use nano silver seeds, and the obtained silver powder surface nanostructure is less, the coverage is low, and the sintering activity is poor. The silver particles show a state of large and small particle distribution, and the microscopic morphology is shown in the attached Figure 8 In the absence of seed crystals, the reduced silver atoms partially nucleate and grow spontaneously to produce small-sized silver particles, thereby increasing the specific surface area, which is not conducive to the application in the slurry.

[0089] The sintering activity of silver particles was tested by thermomechanical analyzer, see attached Figure 12 As shown, the surface nanostructure is less and the sintering activity is significantly reduced compared with Examples 1 and 2.

[0090] Comparative Example 2

[0091] Compared with Example 1, this comparative example does not use a binder. Similarly, the bonding between the seed crystal and the silver powder is poor, resulting in the appearance of small-sized silver particles that do not adhere to and grow on the surface of the silver powder. The resulting silver powder has fewer surface nanostructures, a low coverage rate, and poor sintering activity. The microscopic morphology of the silver particles is shown in the attached figure. Figure 9 shown.

[0092] Comparative Example 3

[0093] Compared with Example 1, this comparative example does not use a complexing agent. The silver atoms grown on the surface of the silver powder are rapidly deposited and grown without complexing, resulting in serious agglomeration between the silver powders. The microscopic morphology is shown in FIG. Figure 10 As shown, the cumulative particle size D50 value of the silver particles is 6.293 μm, which has poor applicability.

[0094] Comparative Example 4

[0095] Compared with Example 1, the solvent of this comparative example is changed to water. In the aqueous phase, the silver ions are reduced to silver atoms in complex state. The growth rate of silver atoms in water is fast and the diffusion and deposition rate is faster, which leads to partial agglomeration between the silver powders. The microscopic morphology is shown in FIG. Figure 11 As shown in FIG. 3 , the cumulative particle size D50 value of the silver particles is 3.183 μm, and the sintering activity and applicability are also poor.

[0096] The embodiments provided by the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. 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 a silver powder surface nanostructure, characterized in that: Here are the steps: (1) mixing micron silver powder, nano silver seed solution, organic solvent and binder to form a mixture solution; and, preparing a complex silver ion solution and a reducing agent solution; (2) mixing the complex silver ion solution, the reducing agent solution and the mixture solution to react, so that newly generated silver forms on the surface of the micron silver powder and wraps the surface of the micron silver powder; (3) After the reaction is completed, the silver powder is separated and filtered and dried to obtain a silver powder product; The binder comprises one or more of oleic acid, ricinoleic acid, lauric acid, tartaric acid, and the mass ratio of the binder to the micron silver powder is (0.01-0.027):1; The organic solvent includes one or more of ethanol, ethylene glycol, diethylene glycol, propylene glycol, and glycerol, and the mass ratio of the organic solvent to the micron silver powder is (5-70):1; The complex silver ion solution refers to a silver ion solution containing a complexing agent, in which the silver ions exist in a complexed state. The silver ion concentration of the complex silver ion solution is 0.5 to 2.5 mol / L, and the mass ratio of the silver ions in the complex silver ion solution to the micron silver powder is (0.01 to 0.1):

1.

2. The method for preparing silver powder surface nanostructure according to claim 1, characterized in that: In step (3), after the silver powder is cleaned, a coating agent solution is added to anchor the nanostructure on the surface of the micron silver powder, and then filtered and dried to obtain a silver powder product; The coating agent includes one or more of triethylamine, N,N-dimethylformamide, dimethyloctylamine, and dimethyldecylamine.

3. The method for preparing the silver powder surface nanostructure according to claim 2, wherein: The mass ratio of the coating agent to the micron silver powder is (0.001-0.005):

1.

4. The method for preparing the silver powder surface nanostructure according to any one of claims 1 to 3, characterized in that: The size of the nano silver seed crystal is 10-80 nm, and the mass ratio of the nano silver seed crystal to the micron silver powder is (0.0005-0.005):

1.

5. The method for preparing the silver powder surface nanostructure according to any one of claims 1 to 4, characterized in that: The mass ratio of silver ions in the complex silver ion solution to micron silver powder is (0.03-0.05):1; The concentration of the reducing agent solution is 0.4 to 1.8 mol / L, and the reducing agent includes one or more of ascorbic acid, erythorbic acid, sodium ascorbate, and sodium erythorbic acid; The molar ratio of silver ions to reducing agent in the complex silver ion solution is 1:(0.55-1.1).

6. The method for preparing silver powder surface nanostructures according to claim 5, characterized in that: The complexing agent includes one or more organic amines such as diethylenetriamine, triethanolamine, isopropanolamine, ethylenediamine, triethylenetetramine, tetraethylenepentamine, and ammonia water.

7. A silver powder, characterized in that: The silver powder is spherical or quasi-spherical in structure, and the surface of the silver powder is covered with a nano-silver layer, which is prepared by the method for preparing the silver powder surface nanostructure according to any one of claims 1 to 6.

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