A method for preparing silver-coated special copper powder

Abstract

The invention discloses a method for preparing a special copper powder for silver coating. Under stirring conditions at room temperature, cuprous oxide, a composite dispersant and a circulating liquid are mixed and reacted, the pH is adjusted to 11-13, and the mixture is reacted under stirring; the mixture is heated to 50-60°C, a reducing agent is added; the mixture is heated to 60-90°C, and a reducing agent is added again; the solid-liquid separation is performed, and the solid copper powder obtained by separation is washed and dried to obtain a special ultrafine copper powder for silver coating; the filtrate obtained by solid-liquid separation is quenched, the reducing agent is removed, and the mixture is used as a circulating liquid. The present invention can be used to stably prepare spherical copper powders with excellent antioxidant properties with a particle size between 0.6-2 μm, and the filtrate can be recycled, which greatly reduces the difficulty of waste liquid treatment and discharge, and helps to achieve green preparation. In addition, the method of the present invention has low preparation cost, simple equipment, and is conducive to industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal materials, and in particular to a method for preparing silver-coated special copper powder. Background Art

[0002] Photovoltaic cells are one of the main forms of renewable energy generation. The cost per kilowatt-hour and conversion efficiency are key factors in the dominance of photovoltaic scale. In the manufacture of photovoltaic cells, traditional silver paste uses pure silver in the preparation process. For heterojunction (HJT) cells that require double-sided silver coating, the cost is even higher. In order to further improve the market competitiveness of HJT cells, the use of silver-coated copper instead of silver powder can significantly reduce the cost per kilowatt-hour of HJT cells. This is also a new option in the current market.

[0003] Silver-coated copper powder has a core-shell structure, that is, the copper core is surrounded by a silver coating; this structure not only maintains the physical properties of copper, but also enhances the oxidation resistance and thermal stability of the original copper powder, and improves its electrical conductivity. In addition, the addition of copper plays an important role in inhibiting the dissolution of silver, avoiding the problems caused by the migration of silver ions in the silver conductive glue, thus taking into account the dual purposes of cost saving and environmental protection.

[0004] The copper source for silver-clad copper used in domestic photovoltaic silver paste mainly relies on imports, and the processing fee is high, which is not conducive to the process of reducing costs and increasing efficiency. Under the pressure of quality and price from foreign companies, my country urgently needs to strengthen the research and development of copper powder suitable for photovoltaic silver paste to break the monopoly of foreign companies in the domestic market. Therefore, the development of a high-quality and low-cost copper powder preparation process has significant market value and social value. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a method for preparing a silver-coated special copper powder.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing a silver-coated special copper powder comprises the following steps:

[0008] (1) Under stirring conditions at room temperature, cuprous oxide, a composite dispersant and a circulating liquid are mixed and reacted, the pH is adjusted to 11-13, and the mixture is reacted under stirring;

[0009] (2) heating the solution obtained in step (1) to 50-60° C. and adding a reducing agent;

[0010] (3) heating the solution obtained in step (2) to 60-90° C. and adding a reducing agent again;

[0011] (4) subjecting the solution obtained in step (3) to solid-liquid separation, and washing and drying the solid copper powder obtained by separation to obtain a silver-coated copper powder;

[0012] (5) The filtrate obtained from the solid-liquid separation in step (4) is quenched to remove the reducing agent, and is returned as a circulating liquid for use in step (1).

[0013] Furthermore, in step (1), the composite dispersant uses sodium gluconate as a base and includes one or more of EDTA, SDS, PVP, and gelatin, and the sodium gluconate accounts for 20-80wt%.

[0014] Furthermore, in step (2) and step (3), the reducing agent includes one or more of hydrazine hydrate, potassium borohydride, and glucose.

[0015] Furthermore, in step (2), a low-concentration reducing agent is added, and the concentration of the low-concentration reducing agent is 5-40wt%; in step (3), a high-concentration reducing agent is added, and the concentration of the high-concentration reducing agent is 60-98wt%.

[0016] Furthermore, in step (5), the filtrate reacts to generate gas and water during the quenching process without introducing soluble solid impurities, and the mass content of the reducing agent in the solution obtained after quenching is less than 1%, and the mass content of by-products (such as furfural and gelatin and other organic matter) is less than 3%.

[0017] Furthermore, in step (5), the filtrate is quenched and then sent to a pretreatment tank, and a pre-reacted reducing agent is added to prepare the filtrate as a circulating liquid and returned to step (1).

[0018] The beneficial effects of the present invention are: the present invention can be used to stably prepare spherical copper powder with a particle size of 0.6-2 μm and excellent antioxidant performance, and the filtrate can be recycled, which greatly reduces the difficulty of waste liquid treatment and discharge, and helps to achieve green preparation. In addition, the method of the present invention has low preparation cost, simple equipment, and is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the process of each embodiment of the present invention;

[0020] Figure 2 This is an electron microscope image of the copper powder obtained in Example 1 of the present invention;

[0021] Figure 3 This is an electron microscope image of the copper powder obtained in Example 2 of the present invention;

[0022] Figure 4 This is an electron microscope image of the copper powder obtained in Example 4 of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0024] Example 1

[0025] This embodiment provides a method for preparing a silver-coated copper powder. Figure 1 As shown, the following steps are included:

[0026] (1) Take 4g of cuprous oxide and add it to 60mL of circulating liquid, which is called solution A; take 3g of sodium gluconate and 1g of gelatin and disperse them in 60mL of deionized water, which is called solution B. Add solutions A and B into the copper powder synthesis device and mix them. Then add 2mol / L sodium hydroxide solution to adjust the pH value to 11, and stir at a speed of 500r / min for 30min.

[0027] (2) The solution finally obtained in step (1) was heated to 50° C. and kept warm for 10 min, 10 mL of 15 wt% hydrazine hydrate was added, and the temperature was raised to 80° C. after reacting for 10 min, 15 mL of 80 wt% hydrazine hydrate was added, and the reaction was continued for 60 min. In this embodiment, the particle size uniformity of the copper powder was controlled by adding reducing agents of different concentrations in multiple batches.

[0028] (3) The solution obtained in step (2) is pumped into a separation device, the solution after the reaction is filtered, the separated solid is washed with deionized water for 3 times and then dried in an oven at 60° C. for 5 hours to obtain a silver-coated copper powder product; the filtrate is pumped into a quenching device, an appropriate amount of ozone is added to quench the residual hydrazine hydrate, and then added to a pretreatment tank, 6.56 g of glucose is added as a pre-reaction reducing agent, and after uniform mixing, it is stored as a circulating liquid and returned for use in step (1).

[0029] By adopting the above process, the average particle size of the prepared ultrafine copper powder is 0.78 μm and is evenly dispersed. Figure 2 shown.

[0030] Example 2

[0031] This embodiment provides a method for preparing a silver-coated copper powder. Figure 1 As shown, the following steps are included:

[0032] (1) Take 4g of cuprous oxide and add it to 30mL of circulating liquid to prepare solution A; take 6g of sodium gluconate and 2g of PVP and disperse them in 90mL of deionized water, which is called solution B. Add solutions A and B into the copper powder synthesis device and mix them, then add 2mol / L sodium hydroxide solution to adjust the pH value to 11, and stir at a speed of 500r / min for 30min;

[0033] (2) The temperature was raised to 50° C. and kept at this temperature for 10 min, 5 mL of 10 wt % potassium borohydride was added, the reaction was continued for 10 min, the temperature was raised to 70° C., 25 mL of 80 wt % hydrazine hydrate was added and the reaction was continued for 60 min.

[0034] (3) The solution obtained in step (2) is pumped into a separation device, the solution after the reaction is filtered, the separated solid is washed with deionized water three times and then dried in an oven at 60° C. for 5 hours to obtain a copper powder product; the filtrate is pumped into a quenching device, an appropriate amount of hydrogen peroxide is added to the filtrate to quench the residual hydrazine hydrate, and then added to a pretreatment tank, 6.56 g of glucose is added, and after uniform mixing, it is stored as a circulating liquid and returned to step (1).

[0035] By adopting the above process, the average particle size of the prepared ultrafine copper powder is 1.52 μm and is evenly dispersed. Figure 3 shown.

[0036] Example 3

[0037] This embodiment provides a method for preparing a silver-coated copper powder. Figure 1 As shown, the following steps are included:

[0038] (1) Take 4g of cuprous oxide and add it to 90mL of circulating liquid, which is called solution A; take 2g of sodium gluconate and 1g of EDTA and disperse them in 30mL of deionized water, which is called solution B. Add solutions A and B into the copper powder synthesis device, mix them, and then add 2mol / L sodium hydroxide solution to adjust the pH value to 11, and stir at a speed of 500r / min for 30min;

[0039] (2) The temperature was raised to 50° C. and kept warm for 10 min, 30 mL of 35 wt % glucose was added, and the mixture was reacted for 10 min. The temperature was raised to 80° C., 15 mL of 60 wt % hydrazine hydrate was added, and the mixture was reacted for 60 min.

[0040] (3) The solution obtained in step (2) is pumped into a separation device, the solution after the reaction is filtered, the separated solid is washed with deionized water three times and then dried in an oven at 60° C. for 5 hours to obtain a copper powder product; the filtrate is pumped into a quenching device, an appropriate amount of hydrogen peroxide is added to the filtrate to quench the residual hydrazine hydrate, and then added to a pretreatment tank for storage as a circulating liquid, and returned to step (1).

[0041] By adopting the above process, the average particle size of the prepared ultrafine copper powder is 1.46 μm and is evenly dispersed. Figure 4 shown.

[0042] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a silver-coated special copper powder, characterized in that: The steps include: (1) Under stirring conditions at room temperature, cuprous oxide, a composite dispersant and a circulating liquid are mixed and reacted, the pH is adjusted to 11-13, and the mixture is reacted under stirring; (2) heating the solution obtained in step (1) to 50-60° C. and adding a reducing agent; (3) heating the solution obtained in step (2) to 60-90° C. and adding a reducing agent again; (4) subjecting the solution obtained in step (3) to solid-liquid separation, and washing and drying the solid copper powder obtained by separation to obtain a silver-coated copper powder; (5) quenching the filtrate obtained from the solid-liquid separation in step (4), removing the reducing agent, and returning it as a circulating liquid for use in step (1); In step (2), a low-concentration reducing agent is added, and the concentration of the low-concentration reducing agent is 5-40wt%; in step (3), a high-concentration reducing agent is added, and the concentration of the high-concentration reducing agent is 60-98wt%.

2. The preparation method according to claim 1, characterized in that: In step (1), the composite dispersant uses sodium gluconate as a base and includes one or more of EDTA, SDS, PVP, and gelatin, with the sodium gluconate accounting for 20-80wt%.

3. The preparation method according to claim 1, characterized in that: In step (2) and step (3), the reducing agent includes one or more of hydrazine hydrate, potassium borohydride, and glucose.

4. The preparation method according to claim 1, characterized in that: In step (5), the filtrate reacts to generate gas and water during the quenching process without introducing soluble solid impurities. The mass content of the reducing agent in the solution obtained after quenching is less than 1%, and the mass content of the by-product is less than 3%.

5. The preparation method according to claim 1, characterized in that: In step (5), the filtrate is quenched and then sent to a pretreatment tank, where a pre-reacted reducing agent is added and prepared as a circulating liquid to be returned to step (1).

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