Preparation method of silver powder and silver powder surface nanostructure

Abstract

The invention discloses a preparation method of silver powder and a silver powder surface nano-structure, and the preparation method comprises the following steps: (1) mixing micron silver powder, a nano silver seed crystal solution, an organic solvent and a binding agent to form a mixture solution; preparing a complexing silver ion solution and a reducing agent solution; the binding agent is organic acid containing carbon-oxygen double bonds and hydroxyl, the complexing silver ion solution is a silver ion solution containing a complexing agent, and silver ions exist in a complexing state; (2) the complexing silver ion solution, the reducing agent solution and the mixture solution are mixed and react, newly generated silver is formed on the surface of the micron silver powder, and the surface of the micron silver powder is wrapped; and (3) after the reaction is finished, separating to obtain silver powder, cleaning, filtering and drying to obtain a silver powder product. By means of all-directional coating of silver particles, the higher coating rate of follow-up surface nanocrystallization silver powder is achieved, and therefore the silver powder product with high sintering activity is obtained.

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] Nano silver powder particles have high sintering activity. They can improve the electrical properties of products after being applied to slurry and sintered. Nano silver particles have a large specific surface area, which affects their viscosity properties. In the field of crystalline silicon solar energy, due to the defects of nano silver particles, micron-level silver particles are the preferred material for the conductive phase, but micron silver powder has the problem of low sintering activity, which needs to be further improved. Therefore, modifying the surface of micron silver powder is a method to improve the sintering activity of micron silver powder.

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

[0004] The coating of the surface of silver particles by the existing modification method is not easy to control, and the coating rate still has room for improvement. The present invention proposes a new modification method to achieve all-round coating 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 nanostructure, wherein nano silver 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, so that the silver particles are fully coated to achieve 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 invention object, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect of the present invention, the present invention provides a method for preparing a silver powder surface nanostructure, the steps are as follows:

[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, and 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 is formed 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 washed, filtered and dried to obtain a silver powder product.

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

[0019] Preferably, the organic solvent is an alcohol substance, 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 water.

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

[0023] Wherein, 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 also 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 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 coating 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 obtained in Example 1;

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

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

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

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

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

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

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

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

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

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

[0039] Fig.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 implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0041] The present invention provides 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 is 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, and 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 is formed 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 washed, filtered and dried to obtain a silver powder product.

[0048] The present invention firstly uniformly adsorbs nano silver seeds on the surface of micron silver powder particles through a binder, and when silver is subsequently generated, the silver diffuses, deposits and grows around the nano silver seeds, thereby achieving the encapsulation of the micron silver powder particles. The present invention preferably uses a complex silver ion solution to slow down the silver generation rate and avoid agglomeration caused by excessive silver generation.

[0049] In step (1), the micron silver powder is a micron-grade 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, as long as the micron silver powder particles have good dispersibility, they are applicable to the present invention.

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

[0051] The mass ratio of nano silver seeds to micron silver powder is (0.0005-0.005):1, that is, the mass of nano silver seeds is 0.05-0.5% of the mass of micron silver powder. The present invention uses a small amount of nano silver seeds, which are not easy to directly agglomerate during mixing. Under the action of the binder, the nano silver seeds can be dispersed and attached to the surface of the micron silver powder particles.

[0052] The binder is an organic acid, which is completely soluble in an organic solvent. The binder contains a carbon-oxygen double bond (C=O bond) and a hydroxyl group (-OH bond), and can connect the nanosilver seed to the surface of the micron silver powder, thereby controlling the subsequent generation of silver to coat the micron silver powder with a high coverage rate. It is easy to understand that since the binder is an organic acid, the carboxyl group in the binder itself contains a carbon-oxygen double bond and a hydroxyl group. On this basis, the binder can also contain more carbon-oxygen double bonds and hydroxyl groups. For example, the binder includes 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 substance 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 substance, 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 nano silver seed solution, the organic solvent and the binder are various. Compared with the micron silver powder, the amount of the nano silver seed solution and the binder is very small, so the present invention does not specifically limit the mixing order of step (1). For example, the micron silver powder, the nano silver seed solution and the organic solvent are first mixed evenly, and then the binder is added to continue mixing evenly; or after the micron silver powder and the organic solvent are mixed evenly, the nano silver seed solution is added to mix, and finally the binder is added to mix; or the micron silver powder, the nano silver seed solution, the organic solvent and the binder are mixed at the same time.

[0056] The present invention prepares the complex silver ion solution in order to reduce the silver generation rate. If the silver ion solution is directly used to react with the reducing agent, the newly generated silver is easy to agglomerate to form larger silver particles, and cannot wrap the micron silver powder. For example, the complexing agent of the present invention uses any one or more of organic amines such as diethylenetriamine, triethanolamine, isopropanolamine, ethylenediamine, triethylenetetramine, tetraethylenepentamine, and ammonia water. The complexing agent complexes with the silver ions, appropriately reduces the redox reaction rate, generates silver at a suitable rate, and diffuses and deposits around the nano silver 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 without reacting 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 complex silver ion solution is 0.5-2.5 mol / L. It is easy to understand that the amount of complexing agent is at least enough to achieve the complexation of all silver ions. The mass ratio of silver ions in the complex silver ion solution to micron silver powder is (0.01-0.1):1, preferably (0.03-0.05):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 0.4-1.8 mol / L. It is easy to understand that the mild reducing agent also plays a role in preventing the silver generation rate from being too fast. 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:(0.55-1.1). 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 can appropriately increase 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 at the same time at a uniform speed, or can be added to the mixture solution one after another. Preferably, the reaction temperature of step (2) is 15 to 50° C. It is easy to understand that a lower reaction temperature can also appropriately reduce the generation rate of silver.

[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 powders, 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 phosphoric acid, 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 to prevent the inactivation 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 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 for ultrasonic stirring and dispersion, and then 0.12 g of nano silver seed solution and 1.44 g of binder oleic acid 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 nano-silver seeds and the micron silver powder, gradually wrapping the surface of the micron silver powder.

[0072] After the reaction of the complex silver ion solution and the reducing agent solution is completed, the silver powder is separated from the solid and liquid and washed with water for multiple times until the conductivity of the silver powder is less than 100 μS / m, and then the silver powder is added to the coating agent solution containing 0.22 g of triethylamine for coating. The coated silver powder is centrifuged and dried at 40° C. for 5 hours to obtain silver particles with nanostructures on the surface.

[0073] In this embodiment, the cumulative particle size distribution of the micron silver powder used has a D10 value of 0.867 μm, a D50 value of 1.295 μm, and a D90 value of 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, see Appendix Fig.12 As shown, the 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 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 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, some agglomerated morphology appeared, and the cumulative particle size distribution D50 value of the silver particles increased to 1.581μm. The overall particle size was still small and did not affect the sintering, and it also had a high sintering activity.

[0081] Example 5

[0082] The preparation steps of this example are the same as those of Example 1, wherein the solvent is ethylene glycol, and the microscopic morphology of the obtained silver particles is shown in the attached 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 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 NN dimethylformamide is selected as the coating agent, and the microscopic morphology of the silver particles is shown in the attached Figure 7 As shown, the particles have good dispersion, a nanoscale microstructure on the surface, and a cumulative particle size distribution D50 value of 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 are distributed in large and small particles, 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 Fig.12 As shown, there are few surface nanostructures 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, and small-sized silver particles that do not grow on the surface of the silver powder appear. The final silver powder surface nanostructure is less, the coverage is low, and the sintering activity is poor. The microscopic morphology of the silver particles is shown in the attached Fig. 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. Fig.10 As shown, the cumulative particle size D50 value of the silver particles is 6.293 μm, and the applicability is poor.

[0094] Comparative Example 4

[0095] Compared with Example 1, the solvent of this comparative example is changed to water. In the water 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 silver powders. The microscopic morphology is shown in FIG. Fig.11 As shown, 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 describe the principles and implementation methods of the present invention, and the description of the above embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing 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; 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, and 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, the silver powder is separated and washed, filtered and dried to obtain a silver powder product.

2. The method for preparing the silver powder surface nanostructure according to claim 1, characterized in that: The binder includes one or more of oleic acid, ricinoleic acid, lauric acid, tartaric acid.

3. The method for preparing the 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; Wherein, the coating agent includes one or more of triethylamine, N,N-dimethylformamide, dimethyloctylamine, and dimethyldecylamine.

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

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 the binder to the micron silver powder is (0.01-0.027):

1.

6. The method for preparing the silver powder surface nanostructure according to any one of claims 1 to 4, 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.

7. The method for preparing the silver powder surface nanostructure according to any one of claims 1 to 4, characterized in that: The organic solvent is an alcohol substance, and the mass ratio of the organic solvent to the micron silver powder is (5-70):

1. Preferably, the organic solvent includes one or more of ethanol, ethylene glycol, diethylene glycol, propylene glycol, and glycerol.

8. The method for preparing the silver powder surface nanostructure according to any one of claims 1 to 4, characterized in that: The silver ion concentration of the complex silver ion solution is 0.5-2.5 mol / L, and the mass ratio of the silver ions in the complex silver ion solution to the micron silver powder is (0.01-0.1):1, preferably (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, isoascorbic acid, sodium ascorbate and sodium isoascorbate; Wherein, the molar ratio of silver ions to reducing agent in the complex silver ion solution is 1:(0.55-1.1).

9. The method for preparing the silver powder surface nanostructure according to claim 8, characterized in that: The complexing agent includes one or more organic amines such as diethylenetriamine, triethanolamine, isopropanolamine, ethylenediamine, triethylenetetramine, tetraethylenepentamine, and ammonia water.

10. 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 nano structure according to any one of claims 1 to 9.

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