Preparation method and application of Ag / Ni / Al three-layer shell-core structure powder

Abstract

The invention belongs to the technical field of conductive filler preparation, and particularly relates to a preparation method and application of Ag / Ni / Al three-layer shell-core structure powder. According to the preparation method, nickel replacement activation treatment is firstly carried out, so that chemical nickel plating is easily carried out on the surface of the aluminum powder; then chemical nickel plating is carried out, so that a nickel layer is uniform and dense, and corrosion resistance, oxidation resistance and high stability are provided for the aluminum powder; and finally, chemical silver plating is carried out, so that good conductivity is provided for the aluminum powder, and the silver-plated nickel-plated aluminum powder which is light in weight, excellent in conductivity, high in strength, resistant to salt mist and resistant to oxidation is obtained. The aluminum powder is specially treated through the preparation method, the obtained silver-plated nickel-plated aluminum powder has good dispersity in organic materials such as resin and rubber, the agglomeration phenomenon is avoided, and the uniformity and consistency of the materials are improved. The performance of the material in severe environments such as high heat, high salt mist and the like is remarkably superior to that of the existing conductive filler, and the material has wide application prospects and remarkable economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive filler preparation, and specifically relates to a preparation method and application of Ag / Ni / Al three-layer core-shell structure powder. Background Art

[0002] In recent years, with the vigorous development of electromagnetic shielding materials, many types of conductive fillers have emerged, such as silver-plated glass beads, silver-plated copper powder, etc. However, with the increasing complexity of the use environment, more comprehensive and more stringent requirements are put forward for materials, such as stability, oxidation resistance, corrosion resistance, conductivity, etc.

[0003] Silver-plated aluminum powder is a new type of conductive filler with excellent performance developed in recent years. The main base material of this product is aluminum powder (Al content ≥ 99%, spherical particles with a particle size of 10-200um). The silver layer is evenly plated on the surface of the aluminum powder, which can make the product have the advantages of light weight, excellent conductivity, high strength, etc., and it is very easy to disperse in organic materials such as resin and rubber after special treatment. However, due to the active nature of the aluminum substrate itself, it is easy to corrode with acids and alkalis, and it is also easy to oxidize in the air, thus affecting the stability of the silver-plated layer. The service life of the silver-plated aluminum powder is greatly shortened in high-heat and high-salt fog environments, which limits its use.

[0004] Therefore, a new type of silver-plated aluminum powder is urgently needed to improve its service life in a high-heat and high-salt fog environment.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to overcome the disadvantages of the prior art and provide a method for preparing a Ag / Ni / Al three-layer core-shell structure powder and its application.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] On the one hand, the present invention provides a method for preparing a powder with a three-layer core-shell structure of Ag / Ni / Al, wherein the aluminum powder is first subjected to a nickel replacement activation treatment to make the surface of the aluminum powder easy to be chemically nickel-plated; then chemical nickel plating is performed to obtain a uniform and dense nickel layer of the aluminum powder, providing the aluminum powder with corrosion resistance, oxidation resistance and high stability; finally, chemical silver plating is performed to provide the aluminum powder with good electrical conductivity, and finally silver-plated and nickel-plated aluminum powder with light weight, excellent electrical conductivity, high strength, salt spray resistance and oxidation resistance is obtained.

[0009] Specifically, the preparation method is as follows:

[0010] Step 1, according to the mass ratio of nickel salt, complexing agent, brightener and corrosive agent being 5-10:4-7:0.06-0.1:8-10, weigh nickel salt, complexing agent, brightener and corrosive agent and dissolve them in deionized water to prepare nickel activation solution, adjust the temperature of the nickel activation solution to 35-45°C, and stir by mechanical stirring, take a certain amount of aluminum powder and add it to the nickel activation solution, pour out the supernatant after the solution becomes colorless and transparent and the powder is flocculent, then wash with water to neutral for standby use, and obtain nickel activated aluminum powder, wherein the mass ratio of aluminum to nickel in the nickel activated aluminum powder is 1-10:100; the aluminum powder is spherical and has a particle size of 20-70 μm;

[0011] Wherein, the nickel salt is one of nickel sulfate, nickel chloride and nickel nitrate; the complexing agent is one or more of citric acid, glycolic acid, disodium ethylenediaminetetraacetate, tartaric acid, etc.; the brightener is 2-2 bipyridine; the corrosive agent is one of sodium hydroxide, ammonia water, ethylenediamine and ammonium fluoride;

[0012] Step 2, according to the mass ratio of nickel salt, complexing agent, first surfactant, first stabilizer and first reducing agent of 20-30:30-45:0.08-0.12:4-5:30-40, weigh nickel salt, complexing agent, first surfactant and first stabilizer and dissolve them in deionized water to prepare nickel plating solution, take a certain amount of nickel activated aluminum powder and add it to the nickel plating solution, and stir it evenly by mechanical means, take a certain amount of first reducing agent and dissolve it in deionized water to prepare first reducing solution, then pour it into the nickel plating solution, adjust the pH to 10.5, heat it in a water bath to 60-80°C, stir it mechanically for 1.5-3h, then wash it with water until it is neutral for standby use, and obtain nickel-plated aluminum powder; the mass ratio of aluminum to nickel in the nickel-plated aluminum powder is 20-60:100; the volume ratio of the nickel plating solution to the first reducing solution is 1:1;

[0013] Wherein, the nickel salt is one of nickel sulfate, nickel chloride and nickel nitrate; the complexing agent is one or more of sodium citrate, disodium ethylenediaminetetraacetate, potassium sodium tartrate, etc.; the first surfactant is one of polyethylene glycol, polyvinyl pyrrolidone, OP-10, sodium dodecylbenzene sulfonate, gelatin, etc.; the first stabilizer is ammonium sulfate; the first reducing agent is one of sodium hypophosphite, formaldehyde, sodium borohydride and hydrazine hydrate; the reagent used to adjust pH is one of sodium hydroxide, ammonia water and ethylenediamine;

[0014] Step 3, according to the mass ratio of silver salt, second reducing agent, second surfactant and second stabilizer of 10-15:9-11.25:1.5-3:40-60, weigh the second reducing agent, the second surfactant and the second stabilizer and dissolve them in deionized water to prepare a second reducing solution, take a certain amount of nickel-plated aluminum powder and add it to the second reducing solution, stir evenly, take a certain amount of silver salt and dissolve it in deionized water to prepare a silver ammonia solution, then pour it into the second reducing solution, heat it in a water bath at 40-55°C, stir for 1.5-3h, then wash it with water until it is neutral, and dry it at a temperature of 80-120°C to finally obtain the desired silver-plated nickel-plated aluminum powder;

[0015] Wherein, the mass ratio of silver to aluminum in the silver-plated nickel-plated aluminum powder is 15-40:100; the volume ratio of the second reducing solution to the silver ammonia solution is 1:1;

[0016] The second reducing agent is one or more of formaldehyde, glucose, tartaric acid, and potassium sodium tartrate; the surfactant is one of polyethylene glycol, polyvinyl pyrrolidone, OP-10, sodium dodecylbenzene sulfonate, gelatin, etc.; the second stabilizer is ethanol, methanol, and ethylene glycol; and the silver salt is silver nitrate.

[0017] Furthermore, the silver ammonia solution is prepared by dissolving silver nitrate in deionized water, and when silver nitrate is completely dissolved, concentrated ammonia water is added dropwise while stirring, and the solution becomes turbid first, and the addition is continued. When the solution becomes clear, the addition is stopped to obtain the silver ammonia solution.

[0018] On the other hand, the present invention provides an application of the preparation method as described above, and the silver-plated nickel-plated aluminum powder prepared by the preparation method is used as a conductive filler in a high-heat and high-salt fog environment.

[0019] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0020] The invention discloses a preparation method of Ag / Ni / Al three-layer core-shell structure powder, which comprises the following steps: firstly performing nickel replacement activation treatment to make the surface of aluminum powder easy to be chemically nickel plated; then performing chemical nickel plating to achieve uniform and dense nickel layer, providing the aluminum powder with corrosion resistance, oxidation resistance and high stability; finally performing chemical silver plating to provide the aluminum powder with good electrical conductivity, thereby obtaining silver-plated nickel-plated aluminum powder with light weight, excellent electrical conductivity, high strength, salt spray resistance and oxidation resistance; the aluminum powder is specially treated by the preparation method, and the obtained silver-plated nickel-plated aluminum powder has good dispersibility in organic materials such as resin and rubber, avoids agglomeration, and improves the uniformity and consistency of the material. This makes the material easier to process and use in practical applications.

[0021] The nickel layer as an intermediate layer effectively isolates the aluminum substrate from direct contact with the external environment, improving the chemical stability and oxidation resistance of the material. This significantly extends the service life of silver-plated aluminum powder in harsh environments such as high heat and high salt spray.

[0022] As the outer layer, the silver layer has excellent electrical conductivity and can significantly improve the overall electrical conductivity of the material. The silver-plated layer evenly and densely covers the surface of the nickel layer, ensuring the continuity and stability of the conductive path, thereby improving the electrical conductivity of the material.

[0023] In summary, the present invention provides a method for preparing a Ag / Ni / Al three-layer core-shell structure powder and its application, by sequentially plating nickel and silver on the surface of aluminum powder, to form a material with excellent stability and conductivity. This material performs significantly better than existing conductive fillers in harsh environments such as high heat and high salt spray, and has broad application prospects and significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the present invention.

[0025] 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, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0026] Figure 1 is a flow chart of the preparation method of the present invention;

[0027] Figure 2 The figure is a graph showing the powder compaction resistance test data of the embodiments of the present invention and the comparative example. DETAILED DESCRIPTION

[0028] Here, exemplary embodiments will be described in detail, and examples thereof are shown in the accompanying drawings. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are only examples consistent with some aspects of the present invention as detailed in the appended claims.

[0029] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0030] The invention provides a preparation method of Ag / Ni / Al three-layer core-shell structure powder, which comprises the following steps: firstly performing nickel replacement activation treatment on aluminum powder to make the surface of the aluminum powder easy to be chemically nickel plated; then performing chemical nickel plating to obtain a uniform and dense nickel layer of the aluminum powder; and finally performing chemical silver plating to provide the aluminum powder with good electrical conductivity, thereby finally obtaining the desired silver-plated and nickel-plated aluminum powder.

[0031] For details, see Figure 1 As shown, the specific preparation method is as follows:

[0032] Step 1, according to the mass ratio of nickel salt, complexing agent, brightener and corrosive agent being 5-10:4-7:0.06-0.1:8-10, weigh nickel salt, complexing agent, brightener and corrosive agent and dissolve them in deionized water to prepare nickel activation solution, adjust the temperature of nickel activation solution to 35-45°C, preferably 40°C, and stir by mechanical stirring, take a certain amount of aluminum powder and add it to the nickel activation solution, pour out the supernatant after the solution becomes colorless and transparent and the powder is flocculent, then wash with water to neutral for standby use, and obtain nickel activated aluminum powder, wherein the mass ratio of aluminum to nickel in the nickel activated aluminum powder is 1-10:100, and the preferred mass ratio of aluminum to nickel is 5:100; the aluminum powder is spherical and has a particle size of 20-70 μm;

[0033] Wherein, the nickel salt is one of nickel sulfate, nickel chloride and nickel nitrate, preferably nickel sulfate; the complexing agent is one or more of citric acid, glycolic acid, disodium ethylenediaminetetraacetate, tartaric acid, etc., preferably tartaric acid and citric acid are used together; the brightener is 2-2 bipyridine; the corrosive agent is one of sodium hydroxide, ammonia water, ethylenediamine and ammonium fluoride, preferably ammonium fluoride;

[0034] Step 2, according to the mass ratio of nickel salt, complexing agent, first surfactant, first stabilizer and first reducing agent of 20-30:30-45:0.08-0.12:4-5:30-40, weigh nickel salt, complexing agent, first surfactant and first stabilizer and dissolve them in deionized water to prepare nickel plating solution, take a certain amount of nickel activated aluminum powder and add it to the nickel plating solution, and stir it evenly by mechanical means, take a certain amount of first reducing agent and dissolve it in deionized water to prepare first reducing solution, then pour it into the nickel plating solution, adjust the pH to 10.5, heat it in a water bath to 60-80°C, preferably 70°C, and stir it mechanically for 1.5-3h, preferably 2h, and then wash it with water until it is neutral for standby use to obtain nickel-plated aluminum powder; the mass ratio of aluminum to nickel in the nickel-plated aluminum powder is 20-60:100, and the preferred mass ratio of aluminum to nickel is 40:100; the volume ratio of the nickel plating solution to the first reducing solution is 1:1;

[0035] Wherein, the nickel salt is one of nickel sulfate, nickel chloride, and nickel nitrate, preferably nickel sulfate; the complexing agent is one or more of sodium citrate, disodium ethylenediaminetetraacetate, potassium sodium tartrate, etc., preferably sodium citrate; the first surfactant is one of polyethylene glycol, polyvinyl pyrrolidone, OP-10, sodium dodecylbenzene sulfonate, gelatin, etc., preferably sodium dodecylbenzene sulfonate; the first stabilizer is ammonium sulfate; the first reducing agent is one of sodium hypophosphite, formaldehyde, sodium borohydride, and hydrazine hydrate, preferably sodium hypophosphite; the reagent used to adjust pH is one of sodium hydroxide, ammonia water, and ethylenediamine, preferably ammonia water;

[0036] Step 3, according to the mass ratio of silver salt, second reducing agent, second surfactant and second stabilizer of 10-15:9-11.25:1.5-3:40-60, weigh the second reducing agent, the second surfactant and the second stabilizer and dissolve them in deionized water to prepare a second reducing solution, take a certain amount of nickel-plated aluminum powder and add it to the second reducing solution, stir evenly, take a certain amount of silver salt and dissolve it in deionized water to prepare a silver ammonia solution, then pour it into the second reducing solution, heat it in a water bath at 40-55°C, preferably 50°C, stir for 1.5-3h, preferably 2h, then wash with water until neutral, and dry it at a temperature of 80-120°C, preferably at 80°C, to finally obtain the desired silver-plated nickel-plated aluminum powder;

[0037] The mass ratio of silver to aluminum in the silver-plated nickel-plated aluminum powder is 15-40:100, and the preferred mass ratio of aluminum to nickel is 20:100; the volume ratio of the second reducing solution to the silver ammonia solution is 1:1;

[0038] The second reducing agent is one or more of formaldehyde, glucose, tartaric acid, and potassium sodium tartrate, preferably glucose and tartaric acid are used together; the surfactant is one of polyethylene glycol, polyvinyl pyrrolidone, OP-10, sodium dodecylbenzene sulfonate, gelatin, etc., preferably polyvinyl pyrrolidone; the second stabilizer is ethanol, methanol, ethylene glycol, preferably ethanol; the silver salt is silver nitrate.

[0039] Furthermore, the silver ammonia solution is prepared by dissolving silver nitrate in deionized water, and when silver nitrate is completely dissolved, concentrated ammonia water is added dropwise while stirring, and the solution becomes turbid first, and the addition is continued. When the solution becomes clear, the addition is stopped to obtain the silver ammonia solution.

[0040] In order to verify the preparation method of the present invention, the following examples are provided.

[0041] Example 1

[0042] This embodiment provides a method for preparing Ag / Ni / Al three-layer core-shell structure powder, and the specific steps are as follows:

[0043] Step 1, weigh 8g of nickel sulfate, 1g of tartaric acid, 3g of citric acid, 0.08g of 2-2-bipyridine, and 8g of sodium fluoride, dissolve them in 1L of deionized water to prepare a nickel activation solution, heat the nickel activation solution to 40°C in a water bath, use mechanical stirring, weigh 10g of 50μm aluminum powder and add it to the nickel activation solution, after the solution becomes colorless and transparent and the powder is flocculent, pour out the supernatant, then wash with water until it is neutral for standby use, to obtain nickel-activated aluminum powder;

[0044] Step 2, weigh 20g of nickel sulfate, 32g of sodium citrate, 0.08g of sodium dodecylbenzene sulfonate, and 3.2g of ammonium sulfate, and dissolve them in 0.8L of deionized water to prepare a nickel plating solution, take nickel-activated aluminum powder and add it to the nickel plating solution, stir it mechanically, take 30g of sodium hypophosphite and dissolve it in 0.8L of deionized water to prepare a first reducing solution, then pour it into the nickel plating solution, adjust the pH to 10.5, heat the water bath at 70°C, stir mechanically for 2h, then wash it with water until it is neutral for standby use, and obtain nickel-plated aluminum powder;

[0045] Step 3, take 4g of glucose, 0.5g of tartaric acid, 0.75g of polyvinyl pyrrolidone, and 20g / L of ethanol and dissolve them in 0.5L of deionized water to prepare a second reducing solution, take nickel-plated aluminum powder and add it to the second reducing solution, stir it mechanically evenly, take 5g of silver nitrate and dissolve it in deionized water to prepare a silver ammonia solution, then pour it into the second reducing solution, heat it in a water bath at 50°C, stir it mechanically for 2h, then wash it with water until neutral, and dry it at 80°C to obtain silver-plated nickel-plated aluminum powder.

[0046] Example 2

[0047] This embodiment provides a method for preparing Ag / Ni / Al three-layer core-shell structure powder, and the specific steps are as follows:

[0048] Step 1, weigh 12g of nickel sulfate, 1.2g of tartaric acid, 4g of citric acid, 0.08g of 2-2-bipyridine, and 8g of sodium fluoride, dissolve them in 1L of deionized water to prepare a nickel activation solution, heat the nickel activation solution to 40°C in a water bath, use mechanical stirring, weigh 10g of 50μm aluminum powder and add it to the nickel activation solution, after the solution becomes colorless and transparent and the powder is flocculent, pour off the supernatant, then wash with water until it is neutral for standby use, to obtain nickel-activated aluminum powder;

[0049] Step 2, weigh 25g of nickel sulfate, 40g of sodium citrate, 0.1g of sodium dodecylbenzene sulfonate, and 4g of ammonium sulfate, dissolve them in 0.8L of deionized water to prepare a nickel plating solution, take nickel-activated aluminum powder and add it to the nickel plating solution, stir it mechanically evenly, take 40g of sodium hypophosphite and dissolve it in 0.8L of deionized water to prepare a first reducing solution, then pour it into the nickel plating solution, adjust the pH to 10.5, heat the water bath at 70°C, stir mechanically for 2h, then wash it with water until it is neutral for standby use, and obtain nickel-plated aluminum powder;

[0050] Step 3, take 4g of glucose, 0.5g of tartaric acid, 0.75g of polyvinyl pyrrolidone, and 20g / L of ethanol and dissolve them in 0.5L of deionized water to prepare a second reducing solution, take nickel-plated aluminum powder and add it to the second reducing solution, stir it mechanically evenly, take 5g of silver nitrate and dissolve it in deionized water to prepare a silver ammonia solution, then pour it into the second reducing solution, heat it in a water bath at 50°C, stir it mechanically for 2h, then wash it with water until neutral, and dry it at 80°C to obtain silver-plated nickel-plated aluminum powder.

[0051] Example 3

[0052] This embodiment provides a method for preparing Ag / Ni / Al three-layer core-shell structure powder, and the specific steps are as follows:

[0053] Step 1, weigh 8g of nickel sulfate, 1g of tartaric acid, 3g of citric acid, 0.08g of 2-2-bipyridine, and 8g of sodium fluoride, dissolve them in 1L of deionized water to prepare a nickel activation solution, heat the nickel activation solution to 40°C in a water bath, use mechanical stirring, weigh 10g of 50μm aluminum powder and add it to the nickel activation solution, after the solution becomes colorless and transparent and the powder is flocculent, pour out the supernatant, then wash with water until it is neutral for standby use, to obtain nickel-activated aluminum powder;

[0054] Step 2, weigh 20g of nickel sulfate, 32g of sodium citrate, 0.08g of sodium dodecylbenzene sulfonate, and 3.2g of ammonium sulfate, dissolve them in 0.8L of deionized water to prepare a nickel plating solution, take nickel-activated aluminum powder and add it to the nickel plating solution, stir it mechanically, take 30g of sodium hypophosphite and dissolve it in 0.8L of deionized water to prepare a first stock solution, then pour it into the nickel plating solution, adjust the pH to 10.5, heat the water bath at 70°C, stir mechanically for 2h, then wash it with water until it is neutral for standby use, and obtain nickel-plated aluminum powder;

[0055] Step 3, take 6g of glucose, 1g of tartaric acid, 1.5g of polyvinyl pyrrolidone, and 30g / L of ethanol and dissolve them in 0.5L of deionized water to prepare a second reducing solution, take nickel-plated aluminum powder and add it to the second reducing solution, stir it mechanically evenly, take 6g of silver nitrate and dissolve it in deionized water to prepare a silver ammonia solution, then pour it into the second reducing solution, heat it in a water bath at 50°C, stir it mechanically for 2h, then wash it with water until neutral, and dry it at 80°C to obtain silver-plated nickel-plated aluminum powder.

[0056] Example 4

[0057] This embodiment provides a method for preparing Ag / Ni / Al three-layer core-shell structure powder, and the specific steps are as follows:

[0058] Step 1, weigh 8g of nickel sulfate, 15g of disodium ethylenediaminetetraacetate, 0.08g of 2-2-bipyridine, and 8g of ethylenediamine, dissolve in 1L of deionized water to prepare a nickel activation solution, heat the nickel activation solution to 40°C in a water bath, use mechanical stirring, weigh 10g of 50μm aluminum powder and add it to the nickel activation solution, after the solution becomes colorless and transparent and the powder is flocculent, pour out the supernatant, then wash with water until it is neutral for standby use, to obtain nickel-activated aluminum powder;

[0059] Step 2, weigh 20g of nickel sulfate, 20g of potassium sodium tartrate, 0.08g of sodium dodecylbenzene sulfonate, and 3.2g of ammonium sulfate, and dissolve them in 0.8L of deionized water to prepare a nickel plating solution, take nickel-activated aluminum powder and add it to the nickel plating solution, stir it mechanically, take 15ml of hydrazine hydrate and dissolve it in 0.8L of deionized water to prepare a first stock solution, then pour it into the nickel plating solution, adjust the pH to 10.5, heat the water bath at 70°C, stir mechanically for 2h, then wash it with water until it is neutral for standby use, and obtain nickel-plated aluminum powder;

[0060] Step 3, take 5 ml of formaldehyde, 1.5 ml of polyethylene glycol (200), and 30 g / L of methanol and dissolve them in 0.5 L of deionized water to prepare a second reducing solution, take nickel-plated aluminum powder and add it to the second reducing solution, stir it mechanically to make it uniform, take 6 g of silver nitrate and dissolve it in deionized water to prepare a silver ammonia solution, then pour it into the second reducing solution, heat it in a water bath at 40°C, stir it mechanically to react for 2 hours, then wash it with water until it is neutral, and dry it at 80°C to obtain silver-plated nickel-plated aluminum powder.

[0061] Comparative Example 5

[0062] This comparative example provides a method for preparing silver-plated aluminum powder, and the specific steps are as follows:

[0063] Step 1, weigh 0.5g of silver nitrate, 12.5g of disodium ethylenediaminetetraacetate, 0.08g of 2-2-bipyridine, and 7.5ml of ammonia water and dissolve them in 1L of deionized water to prepare a silver activation solution, heat the nickel activation solution to 40°C in a water bath, use mechanical stirring, weigh 10g of 50μm aluminum powder and add it to the silver activation solution, after the solution becomes colorless and transparent and the powder is flocculent, pour off the supernatant, then wash with water until it is neutral for standby use, to obtain silver activated aluminum powder;

[0064] Step 2: Take 6 g of glucose, 1 g of tartaric acid, 1.5 g of polyvinyl pyrrolidone, and 30 g / L of ethanol and dissolve them in 0.5 L of deionized water to prepare a reducing solution. Take silver-activated aluminum powder and add it to the reducing solution. Stir it mechanically evenly. Take 5 g of silver nitrate and dissolve it in deionized water to prepare a silver ammonia solution. Then pour it into the reducing solution. Heat it in a water bath at 40°C. Stir it mechanically for 2 hours. Then wash it with water until it is neutral, and dry it at 80°C to obtain silver-plated aluminum powder.

[0065] For the powder resistance of the examples and comparative examples, see Figure 2As shown. The high temperature resistance test condition is to test after 6 hours of heat preservation at 150°C; the salt spray performance test condition is to test after 48 hours of neutral salt spray and 80°C drying for 2 hours. Referring to the silver-plated aluminum powder in comparative example 1, it can be shown that the silver-plated and nickel-plated aluminum powder of the present invention has good stability in high temperature environment and salt spray environment. Compared with other embodiments, it can be shown that the preferred embodiment 3 formula has low resistance and stable performance.

[0066] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0067] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing Ag / Ni / Al three-layer core-shell structure powder, characterized in that: First, the aluminum powder is activated by nickel replacement to make the surface of the aluminum powder easy to be chemically nickel-plated; then chemical nickel plating is performed to obtain a uniform and dense nickel layer of the aluminum powder; finally, chemical silver plating is performed to provide the aluminum powder with good electrical conductivity, and finally the desired silver-plated and nickel-plated aluminum powder is obtained.

2. The preparation method according to claim 1, characterized in that: The specific preparation steps are as follows: Step 1, weighing nickel salt, complexing agent, brightener, and corrosive agent in a certain proportion and dissolving them in deionized water to prepare a nickel activation solution, adjusting the nickel activation solution to a suitable temperature and stirring, taking a certain amount of aluminum powder and adding it to the nickel activation solution, and after the solution becomes colorless and transparent and the powder is flocculent, pouring out the supernatant, then washing with water until it is neutral for standby use, to obtain nickel-activated aluminum powder; Step 2, weighing nickel salt, complexing agent, first surfactant, and first stabilizer in a certain proportion, dissolving them in deionized water to prepare a nickel plating solution, taking a certain amount of nickel-activated aluminum powder, adding it to the nickel plating solution, and stirring evenly, taking a certain amount of the first reducing agent, dissolving it in deionized water to prepare a first reducing solution, and then pouring it into the nickel plating solution, adjusting the pH to alkaline, heating in a water bath, stirring for a certain period of time, and then washing with water to neutral for standby use to obtain nickel-plated aluminum powder; Step 3, weigh a second reducing agent, a second surfactant, and a second stabilizer in a certain proportion and dissolve them in deionized water to prepare a second reducing solution, take a certain amount of nickel-plated aluminum powder and add it to the second reducing solution, stir evenly, take a certain amount of silver salt and dissolve it in deionized water to prepare a silver ammonia solution, then pour it into the second reducing solution, heat it in a water bath, stir it for a certain period of time, then wash it with water until it is neutral, and dry it to finally obtain the required silver-plated nickel-plated aluminum powder.

3. The preparation method according to claim 2, characterized in that: In step 1, the mass ratio of the nickel salt, the complexing agent, the brightener and the corrosive agent is 5-10:4-7:0.06-0.1:8-10, and the mass ratio of aluminum to nickel in the nickel-activated aluminum powder is 1-10:

100.

4. The preparation method according to claim 2, characterized in that: In step 1, the nickel salt is one of nickel sulfate, nickel chloride, and nickel nitrate, the complexing agent is one or more of citric acid, glycolic acid, disodium ethylenediaminetetraacetate, tartaric acid, etc., the brightener is 2-2-bipyridine, and the corrosive agent is one of sodium hydroxide, ammonia water, ethylenediamine, and ammonium fluoride.

5. The preparation method according to claim 2, characterized in that: In step 2, the mass ratio of the nickel salt, the complexing agent, the first surfactant, the first stabilizer, and the first reducing agent is 20-30:30-45:0.08-0.12:4-5:30-40, and the mass ratio of aluminum to nickel in the nickel-plated aluminum powder is 20-60:

100.

6. The preparation method according to claim 2, characterized in that: In step 2, the nickel salt is one of nickel sulfate, nickel chloride, and nickel nitrate; the chelating agent is one or more of sodium citrate, disodium ethylenediaminetetraacetic acid, potassium sodium tartrate, etc.; the first surfactant is one of polyethylene glycol, polyvinyl pyrrolidone, OP-10, sodium dodecylbenzene sulfonate, and gelatin; the first stabilizer is ammonium sulfate; and the first reducing agent is one of sodium hypophosphite, formaldehyde, sodium borohydride, and hydrazine hydrate.

7. The preparation method according to claim 2, characterized in that: In step 3, the mass ratio of the silver salt, the second reducing agent, the second surfactant and the second stabilizer is 10-15:9-11.25:1.5-3:40-60, and the mass ratio of silver to aluminum in the silver-plated nickel-plated aluminum powder is 15-40:

100.

8. The preparation method according to claim 2, characterized in that: In step 3, the second reducing agent includes one or more of formaldehyde, glucose, tartaric acid, and potassium sodium tartrate; the second surfactant includes one of polyethylene glycol, polyvinyl pyrrolidone, OP-10, sodium dodecylbenzene sulfonate, and gelatin; the second stabilizer includes one of ethanol, methanol, and ethylene glycol; and the silver salt is silver nitrate.

9. The preparation method according to claim 2, characterized in that: The volume ratio of the first reducing solution to the nickel plating solution is 1:1, and the volume ratio of the second reducing solution to the silver ammonia solution is 1:

1.

10. The use of the preparation method according to any one of claims 1 to 9, characterized in that: The silver-plated and nickel-plated aluminum powder prepared by the preparation method is used as a conductive filler in a high-heat and high-salt fog environment.

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