A method for preparing a silver and metal mixed powder

Abstract

The application specifically relates to a preparation method of silver and metal mixed powder, and the silver and metal mixed powder is prepared by innovatively combining a chemical method and a physical method, the metal foil is combined with silver into a silver-coated metal foil by the chemical method, the silver-coated metal foil is extended to a thickness of 10-20 mu m by a rolling mill, the foil belt is impacted to form a powder by airflow crushing, and the silver and metal mixed powder meeting the particle size requirement is sorted out. Since the thickness of the silver layer of the extended silver-coated metal foil is basically consistent, the thickness of the metal layer is also basically consistent, at this time, each metal powder after crushing has silver, the silver layer and the metal are combined to form the silver and metal mixed powder, so that the silver and the metal can be uniformly mixed, and batch production can be realized.

Description

Technical Field

[0001] This invention belongs to the field of contact materials for low-voltage power distribution equipment, and specifically relates to a method for preparing a mixture of silver and metal powder. Background Technology

[0002] In electrical contact materials, there are various types of silver and metal mixed powder materials, such as silver-nickel, silver-iron, silver-tin, and silver-copper. The main methods are physical methods, chemical methods, and mechanical powder mixing methods.

[0003] The physical method involves preparing a silver alloy solution through high-temperature melting, followed by atomization to obtain a silver-metal mixed powder. However, high-temperature melting presents problems such as metal oxidation inclusions and foreign matter inclusions in the crucible, affecting product stability. The chemical method mainly involves mixing metal powder with silver nitrate solution, then using a reducing agent to reduce the silver powder before uniformly mixing it with the metal powder to obtain a silver-metal mixed powder. The chemical method mainly utilizes the advantage of chemical coating uniformity to improve the metallographic structure of the silver and metal powders. However, it has high requirements for the particle size of the metal powder material itself; if the particle size of the metal powder does not meet the requirements, the metallographic structure of the product will be unqualified. The mechanical mixing method directly mixes silver powder and metal powder to obtain a mixed powder. Mechanical mixing has poor uniformity, and both the silver powder and metal powder require high precision in particle size and morphology; otherwise, the metallographic structure of the product will be poor.

[0004] Patent CN114093698 discloses a silver-tin oxide electrical contact material and its preparation method, wherein the silver-tin oxide powder material is prepared by chemically coating silver powder onto the surface of tin oxide. However, the small silver powder particles deposited on the surface of the tin oxide powder do not form a good coating, and the deposited silver is easily detached during subsequent material processing, causing the metallographic structure of the product to aggregate.

[0005] Therefore, there is an urgent need for a method to prepare silver and metal mixed powder that can effectively and uniformly mix silver with other metals and achieve mass production. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a method for preparing silver and metal mixed powder that combines chemical and physical methods, can effectively and uniformly mix silver with other metals, and achieve mass production.

[0007] To achieve the above objectives, a method for preparing a silver and metal mixed powder is provided, comprising the following steps: S1. Prepare silver nitrate solution; S2. Add ammonia and dispersant to silver nitrate solution to prepare silver ammonia solution; S3. Place the metal foil in a silver ammonia solution to obtain a silver-deposited coated metal foil. S4. After cleaning and drying the silver-coated metal foil one, the rolling mill presses and stretches it into silver-coated metal foil two. S5. After degreasing and drying the silver-coated metal foil, crush it using an airflow pulverizer and classifier to separate the silver and metal mixed powder with the required particle size.

[0008] A further setting is that the silver content in the silver ammonia solution in step S2 is 1%-5%.

[0009] A further setting is that, in step S3, the metal foil is one or more metals with higher reactivity than silver.

[0010] A further setting is that, in step S3, the thickness of the metal foil is 0.05-0.1 mm.

[0011] A further setting is that, in step S3, the surface roughness of the metal foil is Ra0.1-1.6μm.

[0012] A further setting is that, in step S4, the thickness of the silver-coated metal foil is 0.01-0.03 mm.

[0013] A further provision is that the preparation method further includes the following steps: S6. The sorted silver and metal mixed powder is placed in a high-temperature furnace for oxidation to obtain silver metal oxide mixed powder.

[0014] The beneficial effects of this invention are as follows: This invention innovatively combines chemical and physical methods to prepare a mixed powder of silver and metal. The chemical method combines metal foil with silver to form a silver-coated metal foil. The physical method uses a rolling mill to extend the silver-coated metal foil to a thickness of 10-20 μm, then uses airflow milling to impact the foil strip into powder, and finally sorts out the silver and metal mixed powder that meets the particle size requirements. Because the silver layer thickness and metal layer thickness of the extended silver-coated metal foil are basically uniform, each metal powder particle after crushing contains silver. The silver layer and metal composite form a silver and metal mixed powder, thus effectively and uniformly mixing silver and metal, enabling mass production.

[0015] Figure 2 This invention relates to a silver and metal mixed powder produced by an air jet milling and classifying machine. Under the action of the air jet milling machine, the powder becomes a near-spherical powder. The surface of the sphere may be metallic silver or other metals, and the interior of the sphere may also be metallic silver or other metals. Each powder particle is a mixture of silver and metals. Figure 3 It has the obvious advantage that silver and metal are not easily separated. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0017] Figure 1 This is a process flow diagram of the preparation method of the present invention; Figure 2 The image shows an electron microscope image of the mixed powder prepared in Example 1 of this invention. Figure 3 The image shows an electron microscope image of a mixed powder prepared by chemical coating of powder and silver deposition, as shown in Comparative Example 1. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0019] Example 1 (1) Prepare a silver nitrate solution by stirring and dissolving silver nitrate crystals and pure water in a reaction vessel, with a silver ion concentration of 1-10 g / L; (2) Add ammonia water to the reaction vessel to make the solution pH value 8.5-9.5, add PVP k30 dispersant at a weight of 0.1-0.5% of the weight of silver, stir to dissolve and prepare silver ammonia solution; (3) A nickel foil strip with a thickness of 0.08 mm and a roughness of less than Ra1.6 μm is immersed in a silver ammonia solution for 20-30 min by roller traction, so that silver is coated on the surface of the nickel foil; (4) The silver-coated nickel foil strip that has been treated with silver ammonia solution is then washed with ammonia water and pure water and dried in sequence using a roller traction device. (5) Use a rolling mill to roll the silver-coated nickel foil to a thickness of 0.02 mm; (6) After crushing the 0.02mm thick silver-coated nickel foil using an air jet milling and classifying machine, the silver-nickel mixed powder with the required particle size is sorted out. Example 2 (1) Prepare a silver nitrate solution by stirring and dissolving silver nitrate crystals and pure water in a reaction vessel, with a silver ion concentration of 1-10 g / L; (1) Add ammonia water to the reaction vessel to make the solution pH value 8.5-9.5, add PVP k30 dispersant at a weight of 0.1-0.5% of the weight of silver, stir to dissolve and prepare silver ammonia solution; (2) Immerse a 0.05 mm thick iron foil strip with a roughness less than Ra1.0 μm in a silver ammonia solution for 20-30 min using a roller to coat the iron foil surface with silver. (3) The silver-coated tin foil strip that has been treated with silver ammonia solution is then washed with dilute sulfuric acid and pure water and dried in sequence using a roller traction device. (4) Use a rolling mill to roll the silver-coated iron foil to a thickness of 0.015 mm; (5) After crushing the 0.015mm thick silver-coated iron foil using an air jet milling and classifying machine, the silver-iron mixed powder with the required particle size is separated.

[0020] Example 3 (1) Prepare a silver nitrate solution by stirring and dissolving silver nitrate crystals and pure water in a reaction vessel, with a silver ion concentration of 1-10 g / L; (2) Add ammonia water to the reaction vessel to make the solution pH value 8.5-9.5, add PVP k30 dispersant at a weight of 0.1-0.5% of the weight of silver, stir to dissolve and prepare silver ammonia solution; (3) A copper foil strip with a thickness of 0.08 mm and a roughness of less than Ra1.6 μm is immersed in a silver ammonia solution for 20-30 min by roller traction, so that silver is coated on the surface of the copper foil. (4) The silver-coated copper foil strip that has been treated with silver ammonia solution is then washed with ammonia water and pure water and dried in sequence using a roller traction device. (5) Use a rolling mill to roll the silver-coated copper foil to a thickness of 0.02 mm; (6) After crushing the 0.02mm thick silver-coated copper foil using an air jet milling and classifying machine, the silver-copper mixed powder with the required particle size is sorted out. (7) Silver-copper mixed powder is oxidized in a high-temperature furnace to obtain silver-copper oxide mixed powder.

[0021] Example 4 (1) Prepare a silver nitrate solution by stirring and dissolving silver nitrate crystals and pure water in a reaction vessel, with a silver ion concentration of 1-10 g / L; (2) Add ammonia water to the reaction vessel to make the solution pH value 8.5-9.5, add PVP k30 dispersant at a weight of 0.1-0.5% of the weight of silver, stir to dissolve and prepare silver ammonia solution; (3) Immerse a tin foil strip with a thickness of 0.05 mm and a roughness of less than Ra1.0 μm in a silver ammonia solution for 20-30 min using a roller to coat the surface of the tin foil with silver. (4) The silver-coated tin foil strip that has been treated with silver ammonia solution is then washed with ammonia water and pure water and dried in sequence using a roller traction device. (5) Use a rolling mill to roll the silver-coated tin foil to a thickness of 0.015 mm; (6) After crushing the 0.015mm thick silver-coated tin foil using an air-jet milling and classifying machine, the silver-tin mixed powder with the required particle size is sorted out. (7) The tin foil mixed powder is placed in a high-temperature furnace for oxidation to obtain silver tin oxide mixed powder.

[0022] Comparative Example 1 (1) Silver nitrate crystals and pure water are stirred and dissolved in reaction vessel 1 to prepare silver nitrate solution with silver ion concentration of 1-10 g / L; (2) Add ammonia water to reaction vessel 1 to make the solution pH 8-9, stir to dissolve and prepare silver ammonia solution; (3) Add nickel powder, pure water and reducing agent (hydrazine hydrate solution) to reaction vessel 2, stir and ultrasonically disperse for 30 min; (4) Add the silver ammonia solution in reaction vessel 1 to reaction vessel 2 at a flow rate of 3-5 L / min; (5) After cleaning and drying the mixed powder in reaction vessel 2, silver-nickel mixed powder is obtained.

[0023] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a silver and metal mixed powder, characterized in that, Includes the following steps: S1. Prepare a silver nitrate solution with a silver ion concentration of 1-10 g / L; S2. Add ammonia and a dispersant to silver nitrate solution to prepare silver ammonia solution, making the pH of the silver ammonia solution 8.5-9.

5. The weight of the added dispersant is 0.1-0.5% of the weight of silver in the silver nitrate solution. S3. Place the metal foil in a silver ammonia solution to obtain a silver-deposited coated metal foil. S4. After cleaning and drying the silver-coated metal foil one, the rolling mill presses and stretches it into silver-coated metal foil two. S5. After degreasing and drying the silver-coated metal foil, crush it using an airflow pulverizer and classifier to separate the silver and metal mixed powder with the required particle size. In step S3, the metal foil is one or more metals with higher reactivity than silver, the thickness of the metal foil is 0.05-0.1 mm, and the surface roughness of the metal foil is Ra0.1-1.6 μm; In step S4, the thickness of the silver-coated metal foil is 0.01-0.03 mm.

2. The method for preparing a silver and metal mixed powder according to claim 1, characterized in that, The preparation method further includes the following steps: S6. The sorted silver and metal mixed powder is placed in a high-temperature furnace for oxidation to obtain silver metal oxide mixed powder.

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