Silver powder for conducting ring brush body material and preparation method and application thereof

Abstract

The invention relates to the technical field of metal powder preparation, in particular to silver powder for a conducting ring brush body material and a preparation method and application of the silver powder. The silver powder is prepared through an electrolytic method. The method comprises the steps that firstly, silver nitrate and pure water are prepared into a silver nitrate solution according to a certain proportion; adjusting the pH value of the silver nitrate solution, adding carbamide and other additives according to a certain proportion, and controlling the temperature of the silver nitrate solution; and by taking the silver nitrate solution as an electrolyte, adjusting electrolysis parameters such as current, voltage and powder brushing period in the electrolysis process to obtain the granular silver powder with the particle size D50 of 2-15 microns and the purity of 99.999% or above. The silver powder prepared through the method is high in purity, uniform in silver particle and good in dispersity, an alloy material prepared through the silver powder is smooth in surface, silver is evenly distributed in a metallographic phase, and the silver powder is suitable for the field of silver-based contact materials such as aerospace conducting ring brush bodies and silver bonding wires.

Description

Technical Field

[0001] The invention relates to the technical field of metal powder preparation, and in particular to silver powder used for conductive ring brush body materials, and a preparation method and application thereof. Background Art

[0002] With the rapid development of aerospace industry, the requirements for space conductive slip ring technology and product life are getting higher and higher, from life speed below 10 million revolutions to life speed of 10 million revolutions or even 100 million revolutions. Among them, silver powder is an important raw material for preparing high-quality ring brush materials. In order to achieve high-performance requirements such as high precision, high reliability, and long mission life of conductive ring products, it is necessary to develop high-quality, small-particle, and evenly dispersed silver powder.

[0003] At present, silver-based electrical contact materials mostly use liquid phase reduced silver powder and electrolytic silver powder as raw materials, but the silver powder prepared by chemical method has poor compressibility and poor material formability when preparing alloys, and has a high impurity content; the particle size and morphology of the silver powder prepared by electrolysis are mostly dendritic silver powder. For example, Japanese patent JP2009046696A discloses a method for producing silver powder, using a silver salt aqueous solution and a weak acid such as a carboxylic acid mixed solution with two or more carboxyl groups such as malic acid and citric acid as an electrolytic solution, and preparing dendritic crystals by electrolysis, which have a large particle size, poor contact between particles, and poor sintering properties, so that the prepared ring brush body has problems such as low density and component segregation. In addition, other methods such as liquid phase chemical reduction method are used, such as Chinese patent CN114769577A, which discloses a method for preparing highly dispersed micron-grade silver powder for electrical contacts, the particle size range of the silver powder is 2-3um, but in the process of silver powder synthesis, it is necessary to use photocatalysis to treat the organic matter contained in the silver powder, and the preparation process is relatively cumbersome. Summary of the invention

[0004] In order to solve the problems of the prior art, a silver powder suitable for high-quality conductive ring brush material and a method for preparing the silver powder with simple process are provided. The present invention proposes a silver powder for conductive ring brush material and a preparation method and application thereof. The specific technical scheme is as follows:

[0005] A method for preparing silver powder for a conductive ring brush body material comprises the following steps:

[0006] Step 1: prepare a silver nitrate solution by mixing silver nitrate and pure water; specifically, the concentration of the silver nitrate solution is 5-40 g / L, and preferably the concentration of the silver nitrate solution is 20-40 g / L.

[0007] Step 2: Adjust the pH value of the silver nitrate solution obtained in step 1 to 1-2, and add an additive to obtain an electrolyte, wherein the additive is one or more of formamide, amide, carbon amide, acetamide, and carbon amide; specifically, use concentrated nitric acid to adjust the pH value of the silver nitrate solution obtained in step 1, and the mass ratio of the additive to the silver nitrate solution is 0.05:1-0.1:1.

[0008] Step 3: Use the titanium plate as the cathode plate and the silver plate as the anode plate, place the plates in the electrolyte obtained in step 2 for constant current electrolysis, the plate spacing is 5-15cm, and the electrolysis current density is 5-15A / dm 2 The powder brushing cycle is 5-9s / time to prepare silver powder; wherein, the temperature of the electrolyte is maintained at 25-30°C during the electrolysis process. The preferred plate spacing is 10-15cm, and the electrolysis current density is 7-15A / dm 2 , silver powder was prepared.

[0009] Step 4: washing the obtained silver powder with pure water until the pH of the washing solution reaches 7, then stopping the washing and performing solid-liquid separation;

[0010] Step 5: Dry the silver powder after solid-liquid separation to obtain granular silver powder, D 50 The particle size is 2-15μm, and the purity is over 99.999%.

[0011] The silver powder prepared according to the above method can be used in silver-based contact materials such as conductive ring brush materials and silver bonding wires.

[0012] The beneficial effects of the present invention are as follows: the method controls the particle size of the silver powder during the synthesis process by adding an amide compound, and the additive is adsorbed on the surface of the silver powder crystal to prevent the grain from growing, which is conducive to the formation of new crystal nuclei, and finally obtains a finer powder. In combination with the parameters of the plate spacing, current density, and powder brushing cycle during the electrolysis process, a granular silver powder with high purity and uniform particle size can be prepared, which is higher than the silver powder synthesized by liquid phase chemical synthesis and the existing electrolytic silver powder in terms of performance and purity. After pressing, it has good formability and compactness, meets the application requirements of high-performance silver-based electrical contact materials, and can be applied to the fields of silver-based contact materials such as aerospace conductive ring brush bodies and silver bonding wires. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0014] Figure 1 The figure shows a SEM (1000 times) schematic diagram of the silver powder for the conductive ring brush body material prepared in Example 1 of the present invention;

[0015] Figure 2 The figure shows a SEM (1000 times) schematic diagram of the silver powder for the conductive ring brush body material prepared in Example 2 of the present invention;

[0016] Figure 3 The figure shows a SEM (1000 times) schematic diagram of the silver powder for the conductive ring brush body material prepared in Example 3 of the present invention;

[0017] Figure 4 The SEM (1000 times) schematic diagram of the silver powder for the conductive ring brush body material prepared in Comparative Example 1 of the present invention is shown;

[0018] Figure 5 The metallographic diagram of the ring brush body material prepared in Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail by specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] Embodiment 1:

[0021] Step 1: Prepare a 20 g / L silver nitrate solution by mixing silver nitrate and pure water in a certain ratio;

[0022] Step 2: adding a certain amount of concentrated nitric acid to adjust the pH value of the silver nitrate solution to 1, and adding carbonamide in a ratio of 0.05:1 of the mass ratio of the additive to the silver nitrate solution to form an electrolyte, and the electrolyte temperature is 25°C;

[0023] Step 3: Use the titanium plate as the cathode plate and the 1# silver ingot as the anode plate, with the plate spacing of 10 cm, and place them in the electrolyte obtained in step 2 for constant current electrolysis with an electrolysis current density of 7A / dm 2 , brush the cathode plate every 5 seconds to obtain silver powder;

[0024] Step 4, washing the obtained silver powder with pure water until the pH of the washing solution reaches 7, then stopping the washing and performing solid-liquid separation;

[0025] Step 5: Dry the silver powder after solid-liquid separation to obtain D 50 The ring brush alloy prepared by using the silver powder has good molding and good density during the pressing process, and the surface of the material is smooth and uniform, and the silver is evenly distributed in the metallographic phase. Figure 5 shown.

[0026] Embodiment 2:

[0027] Step 1: Prepare a 30 g / L silver nitrate solution by mixing silver nitrate and pure water in a certain ratio;

[0028] Step 2: adding a certain amount of concentrated nitric acid to adjust the pH value of the silver nitrate solution to 1, and adding carbonamide in a ratio of 0.075:1 of the mass ratio of the additive to the silver nitrate solution to form an electrolyte, and the electrolyte temperature is 25°C;

[0029] Step 3: Use the titanium plate as the cathode plate and the 1# silver ingot as the anode plate, with the plate spacing of 10 cm, and place them in the electrolyte obtained in step 2 for constant current electrolysis with an electrolysis current density of 8A / dm 2 , brush the cathode plate every 9 seconds to get silver powder;

[0030] Step 4, washing the obtained silver powder with pure water until the pH of the washing solution reaches 7, then stopping the washing and performing solid-liquid separation;

[0031] Step 5: Dry the silver powder after solid-liquid separation to obtain D 50 The silver powder is 5.6μm in diameter and 99.999% in purity. The ring brush alloy prepared by using the silver powder has good molding and good density during the pressing process, and the surface of the material is smooth and uniform, and the silver is evenly distributed in the metallographic phase.

[0032] Embodiment three:

[0033] Step 1: Prepare a 35 g / L silver nitrate solution by mixing silver nitrate and pure water in a certain ratio;

[0034] Step 2: adding a certain amount of concentrated nitric acid to adjust the pH value of the silver nitrate solution to 2, and adding formamide in a ratio of 0.075:1 of the mass ratio of the additive to the silver nitrate solution to form an electrolyte, and the electrolyte temperature is 30°C;

[0035] Step 3: Use the titanium plate as the cathode plate and the 2# silver ingot as the anode plate, with a plate spacing of 10 cm, and place them in the electrolyte obtained in step 2 for constant current electrolysis at a current density of 9A / dm 2 , brush the cathode plate every 8 seconds to obtain silver powder;

[0036] Step 4, washing the obtained silver powder with pure water until the pH of the washing solution reaches 7, then stopping the washing and performing solid-liquid separation;

[0037] Step 5: Dry the silver powder after solid-liquid separation to obtain D 50 The silver powder is 10μm in diameter and 99.999% in purity. The ring brush alloy prepared by using the silver powder has good molding and good compactness during the pressing process, and the surface of the material is smooth and uniform, and the silver is evenly distributed in the metallographic phase.

[0038] Comparative Example 1:

[0039] Step 1: Prepare a 20 g / L silver nitrate solution by mixing silver nitrate and pure water in a certain ratio;

[0040] Step 2: Add a certain amount of concentrated nitric acid to adjust the pH value of the silver nitrate solution to 1 to form an electrolyte with a temperature of 35°C;

[0041] Step 3: Use the titanium plate as the cathode plate and the 1# silver ingot as the anode plate, with the plate spacing of 30 cm, and place them in the electrolyte obtained in step 2 for constant current electrolysis with an electrolysis current density of 20A / dm 2 , brush the cathode plate every 60 seconds to obtain silver powder;

[0042] Step 4, washing the obtained silver powder with pure water until the pH of the washing solution reaches 7, then stopping the washing and performing solid-liquid separation;

[0043] Step 5: Dry the silver powder after solid-liquid separation to obtain D 50 Dendritic silver powder with a diameter of >20μm and a purity of 99.9%.

[0044] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.

Claims

1. A method for preparing silver powder for conductive ring brush body material, characterized in that: The following steps are involved: Step 1: Prepare silver nitrate solution by mixing silver nitrate and pure water; Step 2: adjusting the pH of the silver nitrate solution obtained in step 1 to 1-2, and adding an additive to obtain an electrolyte, wherein the additive is one or more of formamide, amide, carbon amide, acetamide, and carbon amide, and the mass ratio of the additive to the silver nitrate solution is 0.05:1-0.1:1; Step 3: Use the titanium plate as the cathode plate and the silver plate as the anode plate, place the plates in the electrolyte obtained in step 2 for constant current electrolysis, the plate spacing is 5-15cm, and the electrolysis current density is 5-15A / dm 2 , the powder brushing cycle is 5-9s / time, and silver powder is prepared; Step 4: washing the obtained silver powder with pure water until the pH of the washing solution reaches 7, then stopping the washing and performing solid-liquid separation; Step 5: Dry the silver powder after solid-liquid separation to obtain granular silver powder.

2. The method for preparing silver powder for conductive ring brush material according to claim 1, characterized in that: The concentration of the silver nitrate solution in step 1 is 5-40 g / L.

3. The method for preparing silver powder for conductive ring brush body material according to claim 1, characterized in that: In step 2, concentrated nitric acid is used to adjust the pH value of the silver nitrate solution obtained in step 1.

4. The method for preparing silver powder for conductive ring brush material according to claim 1, characterized in that: In step three, the temperature of the electrolyte is maintained at 25-30°C during the electrolysis process.

5. The method for preparing silver powder for conductive ring brush body material according to claim 1, characterized in that: In step 3, the plate spacing is 10-15 cm, and the electrolysis current density is 7-15 A / dm 2 , silver powder was prepared.

6. A silver powder prepared according to the method for preparing silver powder according to any one of claims 1 to 5, characterized in that: The silver powder is in granular form. 50 The particle size is 2-15μm, and the purity is over 99.999%.

7. Use of the silver powder according to claim 6 in silver-based contact materials in the aerospace field.

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