Preparation method of high-dispersity silver powder

Abstract

The invention discloses a preparation method of high-dispersity silver powder, which comprises the following steps: drying, sieving and crushing silver powder prepared by liquid-phase reduction, treating by using a protective agent, and finally drying and sieving to obtain the high-dispersity silver powder. The silver powder prepared through the method is in a sphere-like shape, the shape and particle size control technology is simple, uniformity is good, and dispersity is high.

Description

Technical Field

[0001] The invention relates to the field of contact materials for low-voltage power distribution equipment, and in particular to a method for preparing highly dispersible silver powder. Background Art

[0002] Silver is one of the most important raw materials in silver-based electrical contact materials, and silver powder is the most important raw material when silver-based electrical contact materials are manufactured by powder metallurgy. The particle size, bulk density, dispersion, and microscopic morphology of silver powder will affect the performance of silver contact products.

[0003] There are many methods for preparing silver powder at present. The main methods for preparing silver powder in the electrical contact industry are atomization, chemical method and electrolysis. Among them, the chemical method can prepare many types of silver powder due to its diverse chemical reaction changes. Among them, high-dispersibility silver powder makes the powder mixing process in powder metallurgy uniform, the product metallographic consistency meets the requirements, and the electrical performance detection of contact products is excellent. It is widely used in contact material powder metallurgy products.

[0004] Patent CN117696912 discloses a monodisperse spherical micron silver powder and a preparation method thereof and a conductive silver paste. The method is to effectively control chemical reagents such as silver nitrate solution, ascorbic acid solution and dispersant to prepare micron silver powder by chemical method. This invention uses dispersant to control the morphology and particle size of silver powder. However, the content, concentration, temperature of the chemical reaction process and silver content concentration of the dispersant are different, and the morphology and particle size of the prepared silver powder are quite different. There are many process control points, the product risk factors are large, and it is easy to be unstable. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a method for preparing highly dispersible silver powder. The silver powder of the method has a spherical morphology, a simple morphology and particle size control process, good uniformity and high dispersibility.

[0006] To achieve the above purpose, a method for preparing highly dispersible silver powder is provided, and its technical solution comprises the following steps:

[0007] S1, preparing silver powder from silver nitrate raw material by liquid phase reduction method, and preparing silver powder a after washing and drying the silver powder;

[0008] S2, crushing the silver powder a by a high-speed crusher, and then sorting the crushed silver powder by a jet mill to obtain silver powder b;

[0009] S3, mixing the silver powder b and the protective agent evenly;

[0010] S4, drying the silver powder obtained by uniformly mixing the silver powder b and the protective agent, and screening the silver powder with a vibrating screen to obtain a highly dispersed silver powder.

[0011] It is further configured that the water content of the silver powder in step S1 is 70%-90%.

[0012] It is further configured that the drying temperature of the silver powder in step S1 is 200°C-250°C.

[0013] It is further configured that the protective agent in step S3 is a mixed solution of a water-soluble polymer compound and alcohol, and the silver powder wt%: polymer compound %: anhydrous ethanol wt% = 1: (0.005-0.01): 1. The water-soluble polymer compound can be common compounds such as povidone k30, polyethylene glycol, and polyacrylamide.

[0014] It is further configured that the drying temperature in step S4 is 180°C-200°C.

[0015] The innovative mechanism of the present invention is: the irregularly shaped nano or submicron silver powder prepared by the liquid phase reduction method is agglomerated into small particles of silver powder under the action of water and high-temperature drying, and the large particles of silver powder are first cut and crushed into irregularly shaped micron silver powder by a high-speed crusher, and then the airflow and grading wheel in the airflow mill are used to collide with the micron silver powder to physically deform the appearance of the silver powder, so that the edges and corners of the silver powder are worn or bent into a spherical shape, and finally, during high-temperature drying, the protective agent acts to prevent the silver powder particles from agglomerating and growing, and the single spherical silver powder shrinks into a silver powder with high density and high dispersibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0017] Figure 1 It is a schematic diagram of the process of the present invention;

[0018] Figure 2 The electron microscope morphology of silver powder a prepared in Example 1;

[0019] Figure 3 The electron microscope morphology of silver powder b prepared in Example 1;

[0020] Figure 4 This is the highly dispersible silver powder prepared in Example 1. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail in the following examples.

[0022] Example 1

[0023] (1) dissolving silver nitrate raw material in pure water, adding ammonia water and hydrazine hydrate, and preparing silver powder by liquid phase reduction method, washing the silver powder to neutrality, and the water content of the wet silver powder is 70%;

[0024] (2) Dry the wet silver powder in an oven at 200°C to obtain silver powder a, such as Figure 2 As shown, its morphology is agglomerated;

[0025] (3) The silver powder dried at 200° C. is crushed by a traditional Chinese medicine crusher at a speed of 15,000 rpm, and the crushed silver powder is sorted by a jet mill to obtain -350 mesh silver powder to obtain silver powder b, such as Figure 3 As shown, the edges and corners of the silver powder are worn or bent into a spherical shape;

[0026] (4) dissolving povidone K30 in anhydrous ethanol to prepare a protective agent solution;

[0027] (5) mixing the protective agent solution and -350 mesh silver powder evenly in a powder mixer;

[0028] (6) drying the uniformly mixed silver powder in an oven at 180° C. for 15-30 hours;

[0029] (7) The dried silver powder is placed in a vibrating screen and sieved with a mesh size of 500. The sieved silver powder is the desired highly dispersed silver powder, such as Figure 4 As shown, the silver powder is spherical in shape, with good uniformity and high dispersibility.

[0030] Example 2

[0031] (1) dissolving silver nitrate raw material in pure water, adjusting the pH value of the solution, using a reducing agent such as glucose or ascorbic acid, and preparing silver powder by liquid phase reduction method, washing the silver powder to neutrality, wherein the water content of the wet silver powder is 70%;

[0032] (2) drying the wet silver powder in an oven at 250°C;

[0033] (3) crushing the silver powder dried at 250° C. using a traditional Chinese medicine crusher at a speed of 25,000 rpm, and separating the crushed silver powder into -350 mesh silver powder using an air flow mill;

[0034] (4) dissolving polyethylene glycol-4000 in anhydrous ethanol to prepare a protective agent solution;

[0035] (5) mixing the protective agent solution and -350 mesh silver powder evenly in a powder mixer;

[0036] (6) drying the uniformly mixed silver powder in an oven at 180° C. for 15-30 hours;

[0037] (7) The dried silver powder is placed in a vibrating screen for sieving, and the screen mesh number is 500 meshes. The sieved silver powder is the desired highly dispersed silver powder.

[0038] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing highly dispersible silver powder, characterized in that The following steps are involved: S1, preparing silver powder from silver nitrate raw material by liquid phase reduction method, and preparing silver powder a after washing and drying the silver powder; S2, crushing the silver powder a by a high-speed crusher, and then sorting the crushed silver powder by a jet mill to obtain silver powder b; S3, mixing the silver powder b and the protective agent evenly; S4, drying the silver powder obtained by uniformly mixing the silver powder b and the protective agent, and screening the silver powder with a vibrating screen to obtain a highly dispersed silver powder.

2. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: In step S1, the water content of the silver powder prepared by the liquid phase reduction method is 70%-90%.

3. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: In step S1, the silver powder is dried at a temperature of 200°C-250°C.

4. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: In step S3, the protective agent is a mixed solution of a water-soluble polymer compound and alcohol, with silver powder wt%: polymer compound wt%: anhydrous ethanol wt% = 1: (0.005-0.01):

1.

5. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: In step S4, the drying temperature is 180°C-200°C.

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