Preparation method of nano silver powder

Abstract

The invention discloses a preparation method of nano silver powder, which comprises the following steps: under a stirring condition, respectively dissolving silver nitrate, a complexing agent and a reducing agent in deionized water to respectively obtain a silver nitrate solution, a complexing agent solution and a reducing agent solution with the concentration of 150-400g / L, dropwise adding the complexing agent solution into the silver nitrate solution, and stirring to obtain a nano silver powder solution; the preparation method comprises the following steps: adding a reducing agent solution into a reaction kettle, reacting to obtain a silver complexing solution, dropwise adding the silver complexing solution into the reducing agent solution, reacting to generate a silver simple substance, and carrying out solid-liquid separation, washing and drying on the silver simple substance to obtain spherical nano silver powder; according to the preparation method, reaction is carried out in a water system, a high-molecular compound is not used as a dispersing agent, potassium borohydride, sodium borohydride and vitamin C are used as reducing agents to reduce the silver complex, the prepared silver powder is good in dispersing performance, particles are spherical, the purity is high, the sintering resistance is low, the preparation method is simple, and the yield of the silver powder is as high as 97% or above.

Description

Technical Field

[0001] The invention relates to the technical field of metal powder preparation, and in particular to a method for preparing nano silver powder. Background Art

[0002] As an important component of HIT, low-temperature silver paste can reduce problems such as material structure damage or impurity diffusion caused by high-temperature sintering, and help maintain the good performance of battery materials. In addition, the high conductivity and excellent adhesion of low-temperature silver paste help improve the stability of the battery. Silver powder is an important component of low-temperature silver paste. Its lower sintering resistance means better conductivity, lower energy consumption preparation, certain stability and reliability for HIT. At the same time, the microscopic morphology of silver powder will affect the tap density, which is usually manifested as the closer the silver powder particles are to spherical, the higher the tap density, and high tap density will improve the conductivity.

[0003] At present, there have been a large number of reports on the preparation of nano silver powder at home and abroad, but there are many problems with the prepared nano silver powder, such as the complicated preparation steps, which is not conducive to large-scale industrial production. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for preparing nano silver powder, which solves the problems of irregular morphology, high sintering resistance, low yield, complicated preparation method and difficulty in large-scale industrial production in the existing preparation method.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing nano silver powder comprises the following steps:

[0007] S1, dissolving silver nitrate, a complexing agent and a reducing agent in deionized water respectively under stirring conditions to obtain a silver nitrate solution, a complexing agent solution and a reducing agent solution respectively, wherein the concentration of the prepared silver nitrate solution is 150-400 g / L;

[0008] S2, under stirring, adding the complexing agent solution dropwise to the silver nitrate solution prepared in step S1 to react and obtain a silver complexing solution;

[0009] S3, under stirring conditions, dropwise adding the silver complex solution obtained in step S2 to the reducing agent solution to react and generate silver element;

[0010] S4, separating the silver element generated in step S3, washing, and drying to obtain spherical nano silver powder;

[0011] The reducing agent is one or more of potassium borohydride, sodium borohydride and vitamin C.

[0012] Furthermore, the complexing agent is one or more of glutathione, ethylenediaminetetraacetic acid, and ammonia water.

[0013] Furthermore, the concentration of the complexing agent solution is 30-250 g / L.

[0014] Furthermore, the reducing agent solution has a concentration of 100-300 g / L.

[0015] Furthermore, the dripping rate in step S2 is 10-100 ml / min;

[0016] The dripping rate in step S3 is 30-140 ml / min.

[0017] Furthermore, the dissolving temperature in step S1 is 20-80°C;

[0018] The stirring temperature in step S2 is 20-80°C;

[0019] The reaction temperature in step S3 is 20-80°C.

[0020] Furthermore, the dissolution time in step S1 is 0.5-2h;

[0021] The stirring time in step S2 is 0.5-2h;

[0022] The reaction time of step S3 is 0.5-2h.

[0023] Furthermore, the silver element after solid-liquid separation in step S4 is first washed with deionized water and then washed with anhydrous ethanol. The drying temperature in step S4 is 55° C., and the drying time in step S4 is 12 h.

[0024] In summary, this application has the following beneficial effects:

[0025] 1. The method of the present application uses potassium borohydride, sodium borohydride, vitamin C or one or more reducing agents in an aqueous solution system without using a polymer compound as a dispersant to reduce the silver complex, thereby avoiding the residue of the polymer on the surface of the silver powder, and the prepared nano silver powder has low sintering resistance;

[0026] 2. The method of the present application prepares the silver complex solution by first slowly dropping the complexing agent solution into the silver nitrate solution, which can effectively control the reaction speed of the complexing agent and the silver nitrate solution, which is beneficial to the preparation of spherical nano silver powder, and can also reduce the direct contact between silver ions and other ions or molecules that interfere with the reaction, thereby reducing the occurrence of side reactions and preventing particle agglomeration. The prepared nano silver powder has a high yield and low sintering resistance;

[0027] 3. The method of the present application prepares nano silver powder in an aqueous solution system, which is simple in preparation and easy for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a scanning electron microscope image of the nano silver powder obtained in Example 1;

[0029] Figure 2 This is a scanning electron microscope image of the nano silver powder obtained in Comparative Example 1;

[0030] Figure 3 This is a scanning electron microscope image of the nano silver powder obtained in Comparative Example 2. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] Step 1: Prepare silver nitrate solution: weigh 17g silver nitrate, dissolve in 100g deionized water, and stir and dissolve at 50°C for 1.5h; prepare complexing agent solution: weigh 2g glutathione, dissolve in 50g deionized water, and stir and dissolve at 50°C for 1.5h; prepare reducing agent solution: weigh 11.2g potassium borohydride, dissolve in 100g deionized water, and stir and dissolve at 50°C for 1.5h;

[0034] Step 2: At 50°C, slowly add the complexing agent solution to the stirred silver nitrate solution at a rate of 17 ml / min. After the addition is completed, continue stirring for 1.5 hours to form a silver complex solution;

[0035] Step 3: At 50°C, slowly add the silver complex solution to the stirring reducing agent solution at a time of 50 ml / min. After the addition is completed, continue stirring to react for 1 hour. After the reaction is completed, let it stand and precipitate to obtain silver element;

[0036] Step 4: After the precipitation is complete, pour out the supernatant, add deionized water first, stir and let it stand to precipitate, repeat 4 times, then add anhydrous ethanol, stir and let it stand to precipitate, repeat 3 times to obtain the target silver powder; put the target silver powder into a 55°C forced air drying oven and dry it for 12 hours to obtain pure nano silver powder.

[0037] Example 2

[0038] Step 1: Prepare silver nitrate solution: weigh 34g silver nitrate, dissolve in 100g deionized water, and stir and dissolve at 55°C for 1h; prepare complexing agent solution: weigh 60g ethylenediaminetetraacetic acid, dissolve in 300g deionized water, and stir and dissolve at 55°C for 1h; prepare reducing agent solution: weigh 22.4g potassium borohydride, dissolve in 100g deionized water, and stir and dissolve at 55°C for 1h;

[0039] Step 2: slowly add the complexing agent solution to the stirred silver nitrate solution at 55°C at a rate of 75 ml / min. After the addition is completed, continue stirring for 1 hour to form a silver complex solution;

[0040] Step 3: Slowly add the silver complex solution to the stirring reducing agent solution at 55°C, with a drop rate of 100 ml / min. After the drop addition is completed, continue stirring to react for 1 hour. After the reaction is completed, let it stand and precipitate to obtain silver element;

[0041] Step 4: After the precipitation is complete, pour out the supernatant, add deionized water first, stir and let it stand to precipitate, repeat 4 times, then add anhydrous ethanol, stir and let it stand to precipitate, repeat 3 times to obtain the target silver powder; put the target silver powder into a 55°C forced air drying oven and dry it for 12 hours to obtain pure nano silver powder.

[0042] Example 3

[0043] Step 1: Prepare silver nitrate solution: weigh 17g silver nitrate, dissolve in 100g deionized water, and stir and dissolve at 40°C for 2h; prepare complexing agent solution: weigh 2g glutathione, dissolve in 50g deionized water, and stir and dissolve at 40°C for 2h; prepare reducing agent solution: weigh 11.2g sodium borohydride, dissolve in 100g deionized water, and stir and dissolve at 40°C for 2h;

[0044] Step 2: At 40°C, slowly add the complexing agent solution to the stirred silver nitrate solution at a rate of 10 ml / min. After the addition is completed, continue stirring for 2 hours to form a silver complex solution;

[0045] Step 3: At 40°C, slowly add the silver complex solution to the stirring reducing agent solution at a rate of 30 ml / min. After the addition is completed, continue stirring and reacting for 2 hours. After the reaction is completed, let it stand and precipitate to obtain silver element;

[0046] Step 4: After the precipitation is complete, pour out the supernatant, add deionized water first, stir and let it stand to precipitate, repeat 4 times, then add anhydrous ethanol, stir and let it stand to precipitate, repeat 3 times to obtain the target silver powder; put the target silver powder into a 55°C forced air drying oven and dry it for 12 hours to obtain pure nano silver powder.

[0047] Example 4

[0048] Step 1: Prepare silver nitrate solution: weigh 34g silver nitrate, dissolve in 100g deionized water, and stir and dissolve at 60°C for 0.5h; prepare complexing agent solution: weigh 60g ethylenediaminetetraacetic acid, dissolve in 300g deionized water, and stir and dissolve at 60°C for 0.5h; prepare reducing agent solution: weigh 22.4g sodium borohydride, dissolve in 100g deionized water, and stir and dissolve at 60°C for 0.5h;

[0049] Step 2: At 60°C, slowly add the complexing agent solution to the stirred silver nitrate solution at a rate of 100 ml / min. After the addition is completed, continue stirring for 0.5 h to form a silver complex solution;

[0050] Step 3: At 60°C, slowly add the silver complex solution to the stirring reducing agent solution at a rate of 134 ml / min. After the addition is completed, continue stirring to react for 0.5 h. After the reaction is completed, let it stand and precipitate to obtain silver element;

[0051] Step 4: After the precipitation is complete, pour out the supernatant, add deionized water first, stir and let it stand to precipitate, repeat 4 times, then add anhydrous ethanol, stir and let it stand to precipitate, repeat 3 times to obtain the target silver powder; put the target silver powder into a 55°C forced air drying oven and dry it for 12 hours to obtain pure nano silver powder.

[0052] Example 5

[0053] Step 1: Prepare silver nitrate solution: weigh 17g silver nitrate, dissolve it in 100g deionized water, and stir and dissolve it at 50℃ for 2h; prepare complexing agent solution: weigh 2g glutathione, dissolve it in 50g deionized water, and stir and dissolve it at 50℃ for 2h; prepare reducing agent solution: weigh 20g vitamin C, dissolve it in 100g deionized water, and stir and dissolve it at 50℃ for 2h;

[0054] Step 2: At 50°C, slowly add the complexing agent solution to the stirred silver nitrate solution at a rate of 10 ml / min. After the addition is completed, continue stirring for 2 hours to form a complex solution;

[0055] Step 3: At 50°C, slowly add the silver complex solution to the stirring reducing agent solution at a rate of 30 ml / min. After the addition is completed, continue stirring and reacting for 2 hours. After the reaction is completed, let it stand and precipitate to obtain silver element;

[0056] Step 4: After the precipitation is complete, pour out the supernatant, add deionized water first, stir and let it stand to precipitate, repeat 4 times, then add anhydrous ethanol, stir and let it stand to precipitate, repeat 3 times to obtain the target silver powder; put the target silver powder into a 55°C forced air drying oven and dry it for 12 hours to obtain pure nano silver powder.

[0057] Comparative Example 1

[0058] The preparation method of this comparative example is the same as that of Example 1 except that polyvinyl pyrrolidone is added during the preparation:

[0059] Step 1: Prepare a silver nitrate mixed solution: weigh 17g of silver nitrate, dissolve it in 100g of deionized water, add 2.3g of polyvinyl pyrrolidone, and stir and dissolve it at 50°C for 1.5h; prepare a complexing agent solution: weigh 2g of ethylenediaminetetraacetic acid, dissolve it in 50g of deionized water, and stir and dissolve it at 50°C for 1.5h; prepare a reducing agent solution: weigh 11.2g of sodium borohydride, dissolve it in 100g of deionized water, and stir and dissolve it at 50°C for 1.5h;

[0060] Step 2: At 50°C, slowly add the complexing agent solution to the stirred silver nitrate mixed solution at a rate of 17 ml / min. After the addition is completed, continue stirring for 1.5 hours to form a silver complex solution;

[0061] Step 3: At 50°C, slowly add the silver complex solution to the stirring reducing agent solution at a rate of 50 ml / min. After the addition is completed, continue stirring to react for 1 hour. After the reaction is completed, let it stand and precipitate to obtain silver element;

[0062] Step 4: After the precipitation is complete, pour out the supernatant, add deionized water, stir and let stand to precipitate, repeat 4 times, then add anhydrous ethanol, stir and let stand to precipitate, repeat 3 times to obtain the target silver powder; put the target silver powder into a blast drying oven at 55°C and dry it for 12 hours to obtain nano silver powder, such as Figure 2 As shown, although the addition of polyvinyl pyrrolidone can play a dispersing role, the polyvinyl pyrrolidone molecules may be adsorbed at specific positions of the silver particles, thereby affecting their growth direction, resulting in inconsistent growth rates of silver particles in different directions, and further forming a messy silver powder morphology.

[0063] Comparative Example 2

[0064] The preparation method of this comparative example is the same as that of Example 1 except that the dropping rate is:

[0065] Step 1: Prepare silver nitrate solution: weigh 17g silver nitrate, dissolve in 100g deionized water, and stir and dissolve at 50°C for 1.5h; prepare complexing agent solution: weigh 2g glutathione, dissolve in 50g deionized water, and stir and dissolve at 50°C for 1.5h; prepare reducing agent solution: weigh 11.2g potassium borohydride, dissolve in 100g deionized water, and stir and dissolve at 50°C for 1.5h;

[0066] Step 2: At 50°C, slowly add the complexing agent solution to the stirred silver nitrate solution at a rate of 1000 ml / min. After the addition is completed, continue stirring for 1.5 hours to form a silver complex solution;

[0067] Step 3: At 50°C, slowly add the silver complex solution to the stirring reducing agent solution at a dropping rate of 1000 ml / min. After the addition is completed, continue stirring to react for 1 hour. After the reaction is completed, let it stand and precipitate to obtain silver element;

[0068] Step 4: After the precipitation is complete, pour out the supernatant, add deionized water, stir and let stand to precipitate, repeat 4 times, then add anhydrous ethanol, stir and let stand to precipitate, repeat 3 times to obtain the target silver powder; put the target silver powder into a blast drying oven at 55°C and dry it for 12 hours to obtain nano silver powder, such as Figure 3 As shown, a too fast droplet acceleration rate leads to excessive local complexing agent and excessive local silver source, which in turn leads to excessive local concentration and produces side effects, causing particle agglomeration and messy and irregular morphology.

[0069] Comparative Example 3

[0070] The preparation method of this comparative example is the same as that of Example 1 except that the dropping rate is:

[0071] Step 1: Prepare silver nitrate solution: weigh 17g silver nitrate, dissolve in 100g deionized water, and stir and dissolve at 50°C for 1.5h; prepare complexing agent solution: weigh 2g glutathione, dissolve in 50g deionized water, and stir and dissolve at 50°C for 1.5h; prepare reducing agent solution: weigh 11.2g potassium borohydride, dissolve in 100g deionized water, and stir and dissolve at 50°C for 1.5h;

[0072] Step 2: At 50°C, slowly add the complexing agent solution to the stirred silver nitrate solution at a rate of 1 ml / min. After the addition is completed, continue stirring for 1.5 hours to form a silver complex solution;

[0073] Step 3: At 50°C, slowly add the silver complex solution to the stirring reducing agent solution at a dropping rate of 1 ml / min. After the addition is completed, continue stirring to react for 1 hour. After the reaction is completed, let it stand and precipitate to obtain silver element;

[0074] Step 4: After the precipitation is complete, pour out the supernatant, add deionized water first, stir and let it stand to precipitate, repeat 4 times, then add anhydrous ethanol, stir and let it stand to precipitate, repeat 3 times to obtain the target silver powder; put the target silver powder into a 55°C forced air drying oven and dry it for 12 hours to obtain nano silver powder. If the addition rate is too slow, the complexing agent will decompose and transform, and the reducing agent will reduce the silver to other substances excessively to generate other by-products. At the same time, it will also cause the ion concentration in the solution to change, affecting the yield of the silver powder. Too long a reaction time will cause the silver powder particle size to increase, and even agglomeration will occur, affecting the dispersibility of the silver powder.

[0075] The particle morphology, particle size distribution range, resistivity and product yield of the products of Examples 1-5 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1, wherein the particle morphology of the product was measured by SEM electron microscope scanning, the particle size distribution was measured by a laser particle size analyzer, and the sintering resistivity was measured by a powder resistivity tester.

[0076] Table 1

[0077]

[0078]

[0079] It should be understood that the preferred specific embodiments of the present invention can be modified and varied by ordinary technicians in the field without creative work. Therefore, any technical solution that can be obtained by technicians in the field of technology through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing nano silver powder, characterized in that: The steps include: S1, dissolving silver nitrate, a complexing agent and a reducing agent in deionized water respectively under stirring conditions to obtain a silver nitrate solution, a complexing agent solution and a reducing agent solution respectively, wherein the concentration of the prepared silver nitrate solution is 150-400 g / L; S2, under stirring, adding the complexing agent solution dropwise to the silver nitrate solution prepared in step S1 to react and obtain a silver complexing solution; S3, under stirring conditions, dropwise adding the silver complex solution obtained in step S2 to the reducing agent solution to react and generate silver element; S4, separating the silver element generated in step S3, washing, and drying to obtain spherical nano silver powder; The reducing agent is one or more of potassium borohydride, sodium borohydride and vitamin C.

2. The method for preparing nano silver powder according to claim 1, characterized in that: The complexing agent is one or more of glutathione, ethylenediaminetetraacetic acid, and ammonia water.

3. The method for preparing nano silver powder according to claim 1, characterized in that: The concentration of the complexing agent solution is 30-250 g / L.

4. The method for preparing nano silver powder according to claim 1, characterized in that: The reducing agent solution has a concentration of 100-300 g / L.

5. The method for preparing nano silver powder according to claim 1, characterized in that: The dripping rate in step S2 is 10-100 ml / min; The dripping rate in step S3 is 30-140 ml / min.

6. The method for preparing nano silver powder according to claim 1, characterized in that: The dissolving temperature in step S1 is 20-80°C; The stirring temperature in step S2 is 20-80°C; The reaction temperature in step S3 is 20-80°C.

7. The method for preparing nano silver powder according to claim 1, characterized in that: The dissolution time in step S1 is 0.5-2h; The stirring time in step S2 is 0.5-2h; The reaction time of step S3 is 0.5-2h.

8. The method for preparing nano silver powder according to claim 1, characterized in that: In step S4, the silver element after solid-liquid separation is first washed with deionized water and then washed with anhydrous ethanol. The drying temperature in step S4 is 55° C. and the drying time in step S4 is 12 h.

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