Preparation method of silver-plated copper powder with nickel transition layer

Abstract

The application belongs to the technical field of new materials, and particularly relates to a preparation method of silver-coated copper powder with a nickel transition layer, characterized by the following steps: (1) pretreatment and activation treatment, (2) preparation of nickel-coated copper powder, (3) surface organic modification, (4) surface silver plating, and (5) post-plating treatment; the application adds a transition layer of nickel in the silver-coated copper powder and performs heat treatment in a protective atmosphere, forms intermetallic compounds and intermetallic covalent bonds among copper, nickel and silver, so as to improve the adhesion of the plating layer. Meanwhile, the nickel is used as an intermediate layer, which can improve the compactness of the copper layer and the high-temperature oxidation resistance of the copper layer, and on the other hand, the nickel has good magnetic permeability, which can improve the oxidation resistance of the copper powder and increase the ferromagnetism of the powder, so that the prepared powder can realize electromagnetic shielding in a wider frequency range.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a method for preparing silver-plated copper powder with an added nickel transition layer. Background Technology

[0002] Copper powder is widely used in conductive fillers and electromagnetic shielding due to its excellent conductivity. However, copper powder is highly reactive and oxidizes easily in air, causing its conductivity to decrease rapidly. To solve this problem, the main method currently used is coating, which involves coating the surface of the copper powder with a dense organic film or inert metal to isolate it from oxygen and prevent oxidation. However, organic coatings are prone to decomposition at high temperatures, limiting their use. Inert metal coating not only improves the powder's room-temperature oxidation resistance but also gives the copper powder excellent high-temperature oxidation resistance. Silver is an excellent conductor and has very stable chemical properties. Therefore, coating copper powder with silver is the best solution to the copper powder oxidation problem.

[0003] Currently, most silver-coated copper powders are prepared using displacement, chemical reduction, or a combination of both methods. For example, Chinese patent CN102773475B describes an antioxidant copper-silver composite powder for conductive paste and its preparation method, which uses a displacement reaction to coat a layer of silver onto the surface of copper powder, and then uses a reducing agent to reduce silver nitrate to make the silver layer more dense. Chinese patent CN100467169C describes a preparation process for Cu-Ag core-shell composite metal powder, which includes pre-plating, two reduction treatments, and two atmosphere furnace densification treatments; this process is complex and costly.

[0004] Therefore, existing silver-coated copper powders suffer from problems such as complex production processes, poor coating uniformity, poor coating effect, and poor high-temperature resistance, which limit their application areas. Summary of the Invention

[0005] This invention addresses the aforementioned problems by providing a method for preparing silver-plated copper powder with an added nickel transition layer. This method solves the issues of poor oxidation resistance and poor coating adhesion found in existing silver-plated copper powders. Furthermore, by adding a nickel transition layer, the shielding performance of the powder in the low-frequency band is further improved, resulting in a wide-screen shielding effect.

[0006] This invention is achieved through the following technical solution: a method for preparing silver-plated copper powder with an added nickel transition layer, characterized by the following steps: (1) Pretreatment and activation treatment Pretreatment: Clean the copper powder in 5% sodium hydroxide solution for 30-60 minutes to remove surface oil, then clean it with deionized water; then clean it with 5% dilute sulfuric acid for 30-60 minutes to remove the oxide layer on the surface, and then clean it with deionized water. Preparation of activation solution: palladium chloride 0.5-2 g / L, 37% hydrochloric acid 100-500 mL / L, stannous chloride 20-80 g / L, temperature 18-30℃, activation time 1-3 min; Activation treatment: The copper powder is placed in an activation solution for activation, or an active metal is added to the plating solution at the beginning of nickel plating of copper powder for activation; (2) Preparation of nickel-coated copper powder Preparation of nickel plating solution: main salt: 10-50 g / L, reducing agent: 20-80 g / L, complexing agent: 20-60 g / L, stabilizer: 5-30 mg / L, temperature: 60-90℃, ultrasonic power: 40-50 W; The activated copper powder is added to the prepared nickel plating solution under ultrasonic stirring and reacted for 30-60 minutes. Then it is filtered, washed and dried to obtain nickel-coated copper powder. (3) Surface organic modification Nickel-coated copper powder is placed in a mixed solution of water and ethanol, heated and stirred in a water bath for 5-10 minutes. The volume ratio of water to ethanol is 1:1-1:3, and the water bath temperature is 60-80℃. 0.5%-10% of a surface modifier based on the mass of the nickel-coated copper powder is added, stirred until homogeneous, and the solution temperature is maintained at 60-80℃ for 0.5-4 hours. The mixture is then filtered, washed 1-2 times with anhydrous ethanol, and dried to obtain surface-modified nickel-coated copper powder. (4) Surface silver plating Organically modified nickel-coated copper powder was dispersed in 0.05-5 g / L PVP deionized water under ultrasonic stirring, while silver ammonia solution and reducing agent were added dropwise. After reacting at room temperature for 30-60 min, the mixture was filtered, washed, and dried to obtain silver-coated copper powder with nickel as the intermediate layer. (5) Post-plating treatment The composite powder obtained in step (4) is heat-treated in a protective atmosphere for 1-4 hours at a temperature of 100-400℃, and then cooled and removed from the furnace to obtain silver-coated copper powder containing a nickel interlayer.

[0007] Furthermore, step (1) can also be replaced by the following scheme: acidify the copper powder with 37% hydrochloric acid by mass, and then add the acidified copper powder to a hydrochloric acid solution containing 5g / L stannous chloride and soak for 5-20min to activate it; Alternatively, acidify the copper powder with 37% hydrochloric acid for 15-30 minutes, then clean it, and then activate the copper powder with 37% hydrochloric acid for 15-30 minutes before cleaning.

[0008] Further, in step (2) when preparing the nickel plating solution, the main salt is any one of nickel sulfate, nickel acetate or nickel hypophosphite; the reducing agent is any one of hydrazine hydrate, sodium hypophosphite or sodium borohydride; the complexing agent is any one of sodium citrate, ammonium sulfate, lactic acid, malic acid, boric acid, succinic acid or salicylic acid; and the stabilizer is any one of unsaturated fatty acid, maleic acid or thiourea.

[0009] Furthermore, in step (3), the surface modifier is any one of a silane coupling agent containing thiol, tannic acid, or dopamine hydrochloride, wherein the drying temperature is 100-150℃ and the drying time is 1-24h.

[0010] Furthermore, the reducing agent in step (4) is glucose, potassium sodium tartrate or formaldehyde, with a concentration of 4-20 g / L; the concentration of silver ammonia solution is 10-50 g / L.

[0011] The beneficial effects of this invention are as follows: By adding a nickel transition layer in the middle of the silver-coated copper powder and performing heat treatment under a protective atmosphere, an intermetallic compound is formed through diffusion between copper, nickel, and silver, resulting in intermetallic covalent bonds and thus improving the adhesion of the coating. Simultaneously, using nickel as an intermediate layer improves the density of the copper coating and enhances its high-temperature oxidation resistance. Furthermore, due to its excellent magnetic permeability, nickel not only improves the oxidation resistance of the copper powder but also increases the ferromagnetism of the powder, achieving magnetic shielding at low frequencies. This allows the resulting powder to achieve electromagnetic shielding over a wider frequency range. Detailed Implementation

[0012] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be further described below in conjunction with embodiments. Example

[0013] A method for preparing silver-plated copper powder with an added nickel transition layer includes the following steps: (1) Preprocessing The copper powder was cleaned in a 5% sodium hydroxide solution for 30 minutes to remove the oil. Then it was cleaned in a 5% dilute sulfuric acid solution for 30 minutes to remove the oxide layer on the surface. Finally, it was cleaned with deionized water.

[0014] (2) Activation treatment Since copper does not exhibit autocatalytic activity during electroless nickel plating, the deposition of nickel-phosphorus alloy on copper powder surfaces typically requires activation through contact activation or electrochemical methods. The copper powder activation process of this invention can be implemented as follows: Copper powder is placed in an activation solution, which is prepared as follows: 0.5 g / L palladium chloride, 100 mL / L 37% hydrochloric acid, 20 g / L stannous chloride, at a temperature of 20°C for 2 minutes. (3) Preparation of nickel plating solution Nickel sulfate 10g / L, hydrazine hydrate 20g / L, sodium citrate 20g / L, maleic acid 5mg / L, temperature 60℃, ultrasonic power 40w.

[0015] (4) Preparation of nickel-coated copper powder The activated copper powder was added to the nickel plating solution in step (3) under ultrasonic stirring. After reacting for 30 minutes, the solution was filtered, washed, and dried to obtain nickel-coated copper powder.

[0016] (5) Organic modification of the surface of nickel-coated copper powder Add 1% of KH550 silane coupling agent by weight of copper powder, ultrasonically stir until homogeneous, maintain the solution temperature at 72℃, stir for 1 hour, then filter, wash once with ethanol, and dry in a 120℃ drying oven for 5 hours. (6) Nickel-coated copper powder coated with silver The nickel-coated copper powder obtained in step (5) was added to 0.05 g / L PVP deionized water and dispersed under ultrasonic stirring. At the same time, 30 g / L silver ammonia solution and 10 g / L glucose solution were added dropwise. After reacting at room temperature for 30 min, the mixture was filtered, washed, and dried to obtain silver-plated copper powder with nickel as the intermediate layer.

[0017] (7) Post-plating treatment The composite powder obtained in step (6) is heat-treated for 2 hours under a protective atmosphere and then cooled and removed from the furnace to obtain silver-coated copper powder containing a nickel interlayer. Example

[0018] A method for preparing silver-plated copper powder with an added nickel transition layer includes the following steps: (1) Pretreatment and activation treatment Copper powder is acidified with 37% hydrochloric acid, and then the acidified copper powder is soaked in a hydrochloric acid solution containing 5 g / L stannous chloride for 5-20 min.

[0019] (2) Preparation of nickel plating solution Nickel acetate 30 g / L, sodium hypophosphite 30 g / L, lactic acid 30 g / L, thiourea 10 mg / L, temperature 70℃, ultrasonic power 40 W.

[0020] (3) Preparation of nickel-coated copper powder The activated copper powder was added to the nickel plating solution in step (2) under ultrasonic stirring. After reacting for 40 minutes, the solution was filtered, washed, and dried to obtain nickel-coated copper powder.

[0021] (4) Organic modification of the surface of nickel-coated copper powder Add 10% of the copper powder mass of A189 silane coupling agent, ultrasonically stir until homogeneous, maintain the solution temperature at 75℃, stir for 0.5h, then filter, wash twice with anhydrous ethanol, and dry in a 120℃ drying oven for 3h. (5) Nickel-coated copper powder with silver coating The nickel-coated copper powder obtained in step (4) was added to 1 g / L PVP deionized water and dispersed under ultrasonic stirring. At the same time, 25 g / L silver ammonia solution and 50 g / L potassium sodium tartrate solution were added dropwise. After reacting at room temperature for 40 min, the mixture was filtered, washed, and dried to obtain silver-plated copper powder.

[0022] (6) Post-plating treatment The composite powder obtained in step (5) was heat-treated for 3 hours under a protective atmosphere and then cooled and removed from the furnace to obtain silver-coated copper powder containing a nickel interlayer. Example

[0023] A method for preparing silver-plated copper powder with an added nickel transition layer includes the following steps: (1) Pretreatment and activation treatment The copper powder was acidified with 37% hydrochloric acid for 30 minutes and then cleaned. The copper powder was then activated with 37% hydrochloric acid for 30 minutes and then cleaned. (2) Preparation of nickel plating solution Nickel hypophosphite 50g / L, sodium borohydride 60g / L, malic acid 60g / L, thiourea 20mg / L, temperature 90℃, ultrasonic power 50w.

[0024] (3) Preparation of nickel-coated copper powder The activated copper powder was added to the nickel plating solution in step (2) under ultrasonic stirring. After reacting for 60 minutes, the solution was filtered, washed, and dried to obtain nickel-coated copper powder.

[0025] (4) Organic modification of the surface of nickel-coated copper powder Add 5% tannic acid by weight of copper powder, ultrasonically stir until homogeneous, maintain solution temperature at 75℃, stir for 1 hour, then filter, wash twice with anhydrous ethanol, and dry in a 120℃ drying oven for 2.5 hours. (5) Nickel-coated copper powder coated with silver The nickel-coated copper powder obtained in step (4) was added to 3g / L PVP deionized water and dispersed under ultrasonic stirring. At the same time, 50g / L silver ammonia solution and 30g / L potassium sodium tartrate solution were added dropwise. After reacting at room temperature for 60 minutes, the mixture was filtered, washed, and dried to obtain silver-plated copper powder.

[0026] (6) Post-plating treatment The composite powder obtained in step (5) was heat-treated for 4 hours under a protective atmosphere and then cooled and removed from the furnace to obtain silver-coated copper powder containing a nickel interlayer.

[0027] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. Except for the technical features described in the specification, all other technical features are known to those skilled in the art.

Claims

1. A method for preparing silver-plated copper powder with an added nickel transition layer, characterized in that, The steps are as follows: (1) Pretreatment and activation treatment Pretreatment: Clean the copper powder in 5% sodium hydroxide solution for 30-60 minutes to remove surface oil, then clean it with deionized water; then clean it with 5% dilute sulfuric acid for 30-60 minutes to remove the oxide layer on the surface, then clean it with deionized water. Preparation of activation solution: palladium chloride 0.5-2 g / L, 37% hydrochloric acid 100-500 mL / L, stannous chloride 20-80 g / L, temperature 18-30℃, activation time 1-3 min; Activation treatment: Activate the copper powder in an activation solution, or add an active metal to the plating solution at the beginning of nickel plating of copper powder; (2) Preparation of nickel-coated copper powder Preparation of nickel plating solution: main salt: 10-50 g / L, reducing agent: 20-80 g / L, complexing agent: 20-60 g / L, stabilizer: 5-30 mg / L, temperature: 60-90℃, ultrasonic power: 40-50w; The activated copper powder is added to the prepared nickel plating solution under ultrasonic stirring and reacted for 30-60 minutes. Then it is filtered, washed and dried to obtain nickel-coated copper powder. (3) Surface organic modification Nickel-coated copper powder is placed in a mixed solution of water and ethanol, heated and stirred in a water bath for 5-10 minutes. The volume ratio of water to ethanol is 1:1-1:3, and the water bath temperature is 60-80℃. 0.5%-10% of a surface modifier based on the mass of the nickel-coated copper powder is added, stirred until homogeneous, and the solution temperature is maintained at 60-80℃ for 0.5-4 hours. The mixture is then filtered, washed 1-2 times with anhydrous ethanol, and dried to obtain surface-modified nickel-coated copper powder. The surface modifier is any one of a silane coupling agent containing thiol, tannic acid, or dopamine hydrochloride, wherein the drying temperature is 100-150℃ and the drying time is 1-24h; (4) Surface silver plating Organically modified nickel-coated copper powder was dispersed in 0.05-5 g / L PVP deionized water under ultrasonic stirring, while silver ammonia solution and reducing agent were added dropwise. After reacting at room temperature for 30-60 min, the mixture was filtered, washed, and dried to obtain silver-coated copper powder with nickel as the intermediate layer. The reducing agent used is glucose, potassium sodium tartrate, or formaldehyde, with a concentration of 4-20 g / L; the silver ammonia solution concentration is 10-50 g / L. (5) Post-plating treatment The composite powder obtained in step (4) is heat-treated in a protective atmosphere for 1-4 hours at a temperature of 100-400℃, and then cooled and removed in the furnace to obtain silver-coated copper powder containing a nickel interlayer.

2. The method for preparing silver-plated copper powder with added nickel transition layer according to claim 1, characterized in that, Step (1) can also be replaced by the following scheme: acidify the copper powder with 37% hydrochloric acid, and then soak the acidified copper powder in a hydrochloric acid solution containing 5g / L stannous chloride for 5-20min to activate it; or acidify the copper powder with 37% hydrochloric acid for 15-30min and then clean it, and then activate the copper powder with 37% hydrochloric acid for 15-30min and then clean it.

3. The method for preparing silver-plated copper powder with added nickel transition layer according to claim 1, characterized in that, In step (2), when preparing the nickel plating solution, the main salt is any one of nickel sulfate, nickel acetate, or nickel hypophosphite; the reducing agent is any one of hydrazine hydrate, sodium hypophosphite, or sodium borohydride; the complexing agent is any one of sodium citrate, ammonium sulfate, lactic acid, malic acid, boric acid, succinic acid, or salicylic acid; and the stabilizer is any one of unsaturated fatty acid, maleic acid, or thiourea.