Preparation method of superfine spherical silver-coated copper powder

Abstract

This invention discloses a method for preparing ultrafine spherical silver-coated copper powder. A dense film is formed on the surface of copper powder using a specific activator, and this film can quickly form a complex with silver ions in the solution. At the same time, under the action of a specific reducing agent, silver ions are reduced to fine silver nanoparticles and adsorbed on the surface of copper powder. Silver ions in the solution form a dense silver layer on the surface of copper powder through two-dimensional nucleation, resulting in silver-coated copper powder with high density, high conductivity, and high oxidation resistance.

Description

Technical Field

[0001] This invention belongs to the field of conductive materials technology, specifically relating to a method for preparing ultrafine spherical silver-coated copper powder. Background Technology

[0002] Silver-coated copper powder is a functional composite material that combines the high conductivity and excellent oxidation resistance of silver with the high thermal conductivity and relatively low cost of copper powder by coating the surface of copper powder with a layer of silver. Silver-coated copper powder features high conductivity, excellent oxidation resistance, high thermal conductivity, and cost-effectiveness, making it important in many high-tech fields. Its applications include electronic components, brush materials, electromagnetic shielding, radio frequency identification (RFID), battery electrodes, supercapacitors, conductive inks, and antibacterial coatings for medical devices.

[0003] In practical applications, silver-coated copper powder is used in conductive adhesives and antenna materials for smartphones, tablets, and wearable devices; battery electrodes and motor brush materials for new energy vehicles; and electromagnetic shielding materials and conductive inks for 5G base stations and equipment. These applications significantly improve the performance and reliability of related products and promote the development of new technologies. As a multifunctional material, silver-coated copper powder's excellent performance and cost-effectiveness make it a promising candidate for applications in modern high-tech fields. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing ultrafine spherical silver-coated copper powder.

[0005] Another object of the present invention is to provide an ultrafine spherical silver-coated copper powder.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing ultrafine spherical silver-coated copper powder includes the following steps:

[0008] (1) Add copper powder to deionized water, ultrasonically clean it, add alkaline solution for alkaline washing until there is no obvious saponification reaction, then wash it with deionized water until neutral, then add acid solution for acid washing, then wash it with deionized water until neutral, then add deionized water, and finally add emulsifier and activator. Stir in a water bath at 40-60℃ for 30-60 min to obtain the treated copper powder dispersion; the activator is disodium ethylenediaminetetraacetate or sodium carboxymethyl cellulose.

[0009] (2) Dissolve soluble silver salt in deionized water to prepare a silver-containing solution;

[0010] (3) Dissolve the reducing agent in deionized water to prepare a reducing agent solution;

[0011] (4) While stirring, add the reducing agent solution obtained in step (3) and the silver-containing solution obtained in step (2) to the copper powder dispersion obtained in step (1) and carry out the reduction reaction at 20-30℃ for 10-40 min under a nitrogen atmosphere. After the reaction is completed, wash with deionized water and acetone until neutral, and then air dry to obtain ultrafine spherical silver-coated copper powder with a particle size of 200nm-10μm. The surface of the ultrafine spherical silver-coated copper powder is coated with nanoscale long rod-shaped silver particles.

[0012] The aforementioned disodium ethylenediaminetetraacetate is a good synergist in chemistry. In the above preparation method, it acts as an activator. The two carboxyl groups can be adsorbed on the surface of copper powder, while the two amino groups can complex with silver ions to form Ag(NH3)2OH. This ensures that silver ions can be reduced on the surface of copper powder during the reduction reaction.

[0013] The aforementioned sodium carboxymethyl cellulose, acting as an activator, allows for the rapid adsorption of Ag by sodium carboxymethyl cellulose molecules upon the addition of silver ions from a silver-containing solution. + Silver atoms can be generated at an extremely high rate on sodium carboxymethyl cellulose molecules, and the increased number of silver nuclei in the solution forms a fine silver layer that coats the surface of copper powder.

[0014] In a preferred embodiment of the present invention, the emulsifier is at least one of OP-4, OP-7, OP-10, OP-15 and OP-20.

[0015] More preferably, the emulsifier is OP-10.

[0016] In a preferred embodiment of the present invention, the acid solution is a sulfuric acid solution or a nitric acid solution.

[0017] In a preferred embodiment of the present invention, the reducing agent is ascorbic acid or sodium citrate.

[0018] In a preferred embodiment of the present invention, the soluble silver salt is at least one of silver nitrate, silver formate, silver acetate, and silver ammonia solution.

[0019] More preferably, the soluble silver salt is silver nitrate.

[0020] In a preferred embodiment of the present invention, the emulsifier is OP-10; the acid solution is a sulfuric acid solution or a nitric acid solution; the reducing agent is ascorbic acid or sodium citrate; and the soluble silver salt is silver nitrate.

[0021] In a preferred embodiment of the present invention, the molar ratio of silver ions in the silver-containing solution to copper powder in the copper powder dispersion is 0.35-1.5:1, and the molar ratio of reducing agent in the reducing agent solution to silver ions in the silver-containing solution is 1-2:1.

[0022] An ultrafine spherical silver-coated copper powder is prepared by the above-described method.

[0023] The beneficial effects of this invention are:

[0024] 1. The present invention uses a specific activator to form a dense film on the surface of copper powder, and the film can quickly form a complex with silver ions in the solution.

[0025] 2. In this invention, under the action of a specific reducing agent, silver ions are reduced to fine silver nanoparticles that are adsorbed on the surface of copper powder. The silver ions in the solution form a dense silver layer that coats the surface of copper powder through two-dimensional nucleation, resulting in silver-coated copper powder with high density, high conductivity, and high oxidation resistance. Attached Figure Description

[0026] Figure 1 This is a SEM image of the untreated copper powder in Example 1 of the present invention.

[0027] Figure 2 This is a SEM image of the copper powder dispersion after treatment in Example 1 of the present invention.

[0028] Figure 3 This is a SEM image of the silver-coated copper powder-1 prepared in Example 1 of the present invention.

[0029] Figure 4 This is an EDS image of the silver-coated copper powder-1 prepared in Example 1 of the present invention.

[0030] Figure 5 This is a SEM image of the silver-coated copper powder-2 prepared in Example 2 of the present invention.

[0031] Figure 6 This is the EDS image of the silver-coated copper powder-2 prepared in Example 2 of the present invention.

[0032] Figure 7 This is a SEM image of the silver-coated copper powder-3 prepared in Example 3 of the present invention.

[0033] Figure 8 This is an EDS image of the silver-coated copper powder-3 prepared in Example 3 of the present invention.

[0034] Figure 9 This is a comparison diagram of the untreated copper powder of the present invention and the ultrafine spherical silver-coated copper powder prepared in Examples 1 to 3. Detailed Implementation

[0035] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0036] Example 1:

[0037] (1) Add 1g of copper powder to 70mL of deionized water, ultrasonically clean at 25℃ for 10min, then add 20mL of alkaline solution (100g / L NaOH+NaCO3) and stir for 10min. Then wash with deionized water until neutral, then add 20mL of 10% sulfuric acid solution and stir for 10min. Then wash with deionized water until neutral, then add 70mL of deionized water, and finally add 0.05g of OP-10 solution and 2g of sodium carboxymethyl cellulose. After stirring in a water bath at 60℃ for 60min, the treated copper powder dispersion is obtained.

[0038] (2) Take 10 mL of 0.5 mol / L AgNO3 and add it to 30 mL of deionized water to prepare a silver-containing solution.

[0039] (3) Take 0.8g of ascorbic acid and add it to 70mL of deionized water to prepare a reducing agent solution.

[0040] (4) Under a nitrogen atmosphere, while stirring, the reducing agent solution obtained in step (3) and the silver-containing solution obtained in step (2) were added to the copper powder dispersion obtained in step (1) at a rate of 10 mL / min. The reduction reaction was carried out at 25°C for 30 min, and the stirring speed was 2400 r / min. The washed product was then dried in a ventilated environment at 60°C to obtain silver-coated copper powder. The obtained silver-coated copper powder had a particle size of approximately 2 μm and a surface coated with a layer of nanoscale long rod-shaped silver particles. The length of these long rod-shaped silver particles was approximately 100 nm, and the diameter was approximately 30 nm. This material is designated as silver-coated copper powder-1.

[0041] Example 2:

[0042] (1) Add 1g of copper powder to 100mL of deionized water, ultrasonically clean for 10min, then add 20mL of alkaline solution (100g / LNaOH+NaCO3) and stir for 10min. Then wash with deionized water until neutral, then add 20mL of 10% nitric acid solution and stir for 10min. Then wash with deionized water until neutral, then add 100mL of deionized water, and finally add 0.05g of OP-10 solution and 1g of disodium ethylenediaminetetraacetate. Stir in a water bath at 40℃ for 30min to obtain the treated copper powder dispersion.

[0043] (2) Take 7 mL of 0.5 mol / L AgNO3 and add it to 14 mL of deionized water to prepare a silver-containing solution.

[0044] (3) Take 1g of sodium citrate and add it to 100mL of deionized water to prepare a reducing agent solution.

[0045] (4) Under a nitrogen atmosphere, while stirring, the reducing agent solution obtained in step (3) and the silver-containing solution obtained in step (2) were added to the copper powder dispersion obtained in step (1) at a rate of 10 mL / min. The reduction reaction was carried out at 25°C for 30 min, and the stirring speed was 2400 r / min. After the reaction was completed, the mixture was washed with deionized water and isopropanol until neutral, and then dried in a ventilated environment at 60°C. The resulting silver-coated copper powder had a particle size of approximately 2 μm and was coated with a layer of nanoscale long rod-shaped silver particles. The length of the long rod-shaped silver particles was approximately 200 nm, and the diameter was approximately 50 nm. This material is designated as silver-coated copper powder-2.

[0046] Example 3:

[0047] (1) Add 1g of copper powder to 70mL of deionized water, ultrasonically clean for 10min, then add 20mL of alkaline solution (100g / LNaOH+NaCO3) and stir for 10min. Then wash with deionized water until neutral, then add 20mL of 10% sulfuric acid solution and stir for 10min. Then wash with deionized water until neutral, then add 70mL of deionized water, and finally add 10mL of OP-10 solution containing 0.01g. Stir in a 50℃ water bath for 30min to obtain the treated copper powder dispersion.

[0048] (2) Take 5 mL of 0.5 mol / L AgNO3 and add it to 10 mL of deionized water to prepare a silver-containing solution.

[0049] (3) Take 1g of sodium citrate and add it to 100mL of deionized water to prepare a reducing agent solution.

[0050] (4) Under a nitrogen atmosphere, while stirring, the reducing agent solution obtained in step (3) and the silver-containing solution obtained in step (2) were added to the copper powder dispersion obtained in step (1) at a rate of 10 mL / min. The reduction reaction was carried out at 25°C for 30 min, and the stirring speed was 2400 r / min. After the reaction was completed, the mixture was washed with deionized water and isopropanol until neutral, and then dried in a ventilated environment at 60°C. The resulting silver-coated copper powder had a particle size of approximately 2 μm and was coated with a layer of nanoscale long rod-shaped silver particles. The length of the long rod-shaped silver particles was approximately 300 nm, and the diameter was approximately 30 nm. However, due to the reduced silver content, the silver layer coating was incomplete. This was designated as silver-coated copper powder-3.

[0051] Depend on Figure 1 , 2 As can be seen from point 3, the ultrafine spherical silver-coated copper powder prepared in Example 1 of this invention is formed by the self-assembly of silver nanoparticles with a diameter of about 50 nm, with a coating layer thickness of about 100 nm, exhibiting an overall spherical shape, and having a uniform silver powder coating on its surface with good dispersibility; Figure 4 It can be seen that silver accounts for 76.74% of the total mass of the powder, and the ratio of silver atoms to copper atoms is 2:1.

[0052] Depend on Figure 5 It can be seen that the coating layer of the ultrafine spherical silver-coated copper powder prepared in Example 2 of the present invention is more dense, and the surface nanostructure is more complete, with higher sphericity; Figure 6 It can be seen that silver accounts for 60.02% of the total mass of the powder, and the ratio of silver atoms to copper atoms is approximately 1:1.

[0053] Depend on Figure 7 It can be seen that the ultrafine spherical silver-coated copper powder prepared in Example 3 of this invention has incomplete coating due to the decrease in the proportion of silver powder; however, the silver layer thickness on the surface of the silver-coated copper powder-3 prepared under these conditions is about 200 nm; Figure 8 It can be seen that silver accounts for 51.43% of the total mass of the powder, and the ratio of silver atoms to copper atoms is approximately 3:2.

[0054] Depend on Figure 9 It can be seen that the characteristic peak intensity of copper gradually decreases as silver is coated. Among them, the characteristic peak intensity of copper in silver-coated copper powder-2 is the lowest, and its coating effect is the best.

[0055] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing ultrafine spherical silver-coated copper powder, characterized in that: Includes the following steps: (1) Add copper powder to deionized water, ultrasonically clean it, add alkaline solution for alkaline washing until there is no obvious saponification reaction, then wash with deionized water until neutral, then add acid solution for acid washing, then wash with deionized water until neutral, then add deionized water, and finally add emulsifier and activator. Stir in a water bath at 40-60℃ for 30-60 min to obtain the treated copper powder dispersion; the activator is disodium ethylenediaminetetraacetate or sodium carboxymethyl cellulose; the emulsifier is at least one of OP-4, OP-7, OP-10, OP-15 and OP-20; (2) Dissolve a soluble silver salt in deionized water to prepare a silver-containing solution. The soluble silver salt is at least one of silver nitrate, silver formate, silver acetate, and silver ammonia solution. (3) Dissolve the reducing agent in deionized water to prepare a reducing agent solution. The reducing agent is ascorbic acid or sodium citrate. (4) While stirring, add the reducing agent solution obtained in step (3) and the silver-containing solution obtained in step (2) to the copper powder dispersion obtained in step (1) and carry out the reduction reaction at 20-30℃ for 10-40 min under nitrogen atmosphere. After the reaction is completed, wash with deionized water and acetone until neutral, and then air dry to obtain ultrafine spherical silver-coated copper powder with a particle size of 200nm-10μm. The surface of the ultrafine spherical silver-coated copper powder is coated with nanoscale long rod-shaped silver particles. The molar ratio of silver ions in the silver-containing solution to copper powder in the copper powder dispersion is 0.35-1.5:1, and the molar ratio of reducing agent in the reducing agent solution to silver ions in the silver-containing solution is 1-2:

1.

2. The preparation method according to claim 1, characterized in that: The emulsifier is OP-10.

3. The preparation method according to claim 1, characterized in that: The acid solution is a sulfuric acid solution or a nitric acid solution.

4. The preparation method according to claim 1, characterized in that: The soluble silver salt is silver nitrate.

5. The preparation method according to claim 1, characterized in that: The emulsifier is OP-10; the acid solution is a sulfuric acid solution or a nitric acid solution; the reducing agent is ascorbic acid or sodium citrate; and the soluble silver salt is silver nitrate.

6. An ultrafine spherical silver-coated copper powder, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 5.

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