A method for preparing low-cost high-performance spherical silver powder by using a non-metallic inducer

Abstract

The application discloses a kind of low-cost high-performance spherical silver powder preparation methods using non-metallic inducer, the amount of dispersing agent such as polyvinylpyrrolidone (PVP-K30) It is reduced from 25% to 60% to 5-13% by silver powder production ratio, and the material cost ratio of dispersing agent PVP in silver powder production is reduced from 20% to 35% to below 7%, which greatly reduces the cost.The low-cost high-performance spherical silver powder preparation method using non-metallic inducer disclosed in the application uses non-metallic inducer in the reduction stage of silver powder, successfully solves the problem of how to ensure the stable performance of silver powder product, and keeps the key indicators such as particle size distribution and specific surface area of silver powder stable by stabilizing the amount of non-metallic inducer, successfully controls the parameters of silver powder.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducer. Background Technology

[0002] Green energy is a global focus, and the entire solar energy sector is experiencing rapid development. Silver powder is crucial for the solar energy industry. Currently, silver powder production technology typically uses a single silver nitrate solution or its complex as an oxidant, and then adds a reducing agent to obtain silver powder. The reducing agent used is usually L-ascorbic acid (vitamin C), and the dispersant is usually PVP-K30 (polyvinylpyrrolidone).

[0003] The silver powder produced using the above technical approach has high production costs and exhibits strong instability in terms of powder performance indicators such as microstructure, particle size distribution, and specific surface area.

[0004] Current research includes a Chinese patent application (CN201210155326.2) describing a method for preparing micron-sized highly active spherical silver powder. The method comprises the following steps: adding a 20-37% (w / w) formaldehyde solution and stearic acid to a silver ammonia solution prepared from silver nitrate, sodium hydroxide, 20-25% (w / w) ammonia, and deionized water; reacting to obtain a spherical silver powder slurry; after solid-liquid separation and drying, the resulting silver powder is mixed evenly with inorganic binder powder; a surfactant is added and dispersed at high speed; then, after heat treatment at 180-400℃ for 4-16 hours, the mixture is washed and dried to obtain micron-sized highly active spherical silver powder. The micron-sized highly active spherical silver powder prepared using this method has a narrow particle size distribution, good activity, and an inorganic binder powder on its surface, making it particularly suitable for use in the solar energy and microelectronics industries.

[0005] Currently, the main disadvantages of domestically produced silver powder products using general technology compared to foreign silver powder products are: (1) High production cost: Currently, the domestic high-dispersion, high-tapping spherical silver powder widely used in the front silver paste of the solar photovoltaic cell industry generally accounts for 25%-60% of the silver powder production, and the cost of dispersant accounts for about 20-35% of the total raw material cost. (2) Unstable performance indicators: The microstructure of domestic silver powder is relatively simple, and the microstructure of silver powder has a crucial impact on the sintering activity of silver paste. Therefore, its application window is narrow and it cannot meet the needs of different silver paste application systems. In terms of key indicators such as particle size distribution and specific surface area, there are large fluctuations between different batches of silver powder, which will affect the performance stability of downstream silver paste. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducing agent. The resulting spherical silver powder can be widely used in conductive silver paste for photovoltaic crystalline silicon solar photovoltaic cells.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducer includes the following steps: 1) Preparation of oxidizing solution: Dissolve silver nitrate in deionized water, stir thoroughly to obtain a uniform and clear aqueous solution, control the silver content to be 0.1-3 mol / L, and control and maintain the temperature at 10-50℃; 2) Preparation of reducing solution: Dissolve the reducing agent in deionized water. The mass ratio of the amount of reducing agent to the concentration of silver ions in step 1) is (0.7-2):1. Stir and dissolve thoroughly to obtain a uniform and clear aqueous solution. The volume of the solution is 0.5-2 times the volume of the oxidation solution. Control and maintain the temperature at 10-50℃. The reducing agent is selected from one or more of L-ascorbic acid, formaldehyde, glucose or hydrazine hydrate, and the mixture is in any proportion. 3) Preparation of dispersion: Add the dispersant to deionized water. The mass ratio of dispersant to deionized water is 1:(20-30). The amount of dispersant used is 1-15% of the silver powder production. After stirring and dissolving thoroughly to obtain a uniform and clear aqueous solution, control and maintain the temperature at 10-50℃. The dispersant is selected from one or more of polyvinylpyrrolidone (PVP-K30), gum arabic, Tween or gelatin, and the mixture is in any proportion. 4) Preparation of non-metallic inducer: Add non-metallic inducer to deionized water. The mass ratio of non-metallic inducer to deionized water is 1:(10-20). The total amount of non-metallic inducer is 1-20% of the silver powder production. After stirring and dissolving thoroughly to obtain a uniform and clear aqueous solution, control and maintain the temperature at 10-50℃. The non-metallic inducing agent is selected from one or more of sodium borohydride, borax, boric acid or sodium perborate (sodium perborate), and the mixture is in any proportion. 5) Reduction reaction: First, add the dispersion prepared in step 3) to the reaction vessel, then add the non-metallic inducing solution prepared in step 4), and ensure thorough stirring; The reducing solution prepared in step 2) and the oxidizing solution prepared in step 1) are simultaneously injected into the reactor at a fixed flow rate. The flow rate of the reducing solution is 20-40 L / min; the flow rate of the oxidizing solution is 20-40 L / min; the total reaction time is 5-10 min; and the temperature control range is 15-45℃. 6) Silver Powder Surface Coating: After the reaction is complete, stearic acid or oleic acid is immediately added to the reactor at a rate of 0.3%-1.2% of the silver powder yield. The mixture is stirred at high speed for 1-2 hours, then allowed to settle and separate into layers. After centrifugation, low-cost, high-performance spherical silver powders with various particle sizes are obtained: D10: 0.63-0.84 μm, D50: 1.02-1.45 μm, D90: 1.64-2.46 μm, D100: 2.70-4.00 μm; specific surface area: 0.43-0.63 m². 2 / g; Tap density: 6.02-6.34 g / cm³ 3 The burn loss rate at 550℃ is 0.39-0.43%.

[0008] In this invention: The preferred range for controlling the silver content in step 1) is 0.5-2 mol / L.

[0009] The mass ratio of the amount of reducing agent used in step 2) to the concentration of silver ions in step 1) is 0.7:1.1.

[0010] The dispersant mentioned in step 3) is preferably polyvinylpyrrolidone (PVP-K30); the amount of dispersant used is preferably 5-13% of the silver powder production.

[0011] The non-metallic inducer mentioned in step 4) is preferably used in a total amount of 5%-15% of the silver powder production.

[0012] The reduction reaction described in step 5) involves the addition of a non-metallic inducer to the base solution, which plays an inductive role in the reaction of the silver powder. The nucleation stage involves encapsulating some non-metals in the core of the silver powder, which also lays the foundation for the growth of the silver powder and its surface morphology.

[0013] Compared with the prior art, the present invention has the following advantages: 1. The present invention describes a method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducing agent, which reduces the amount of dispersants such as polyvinylpyrrolidone (PVP-K30) used in silver powder production from 25%-60% to 5-13%, and reduces the proportion of material costs of dispersants such as PVP-K30 in silver powder production from 20%-35% to below 7%, thereby significantly reducing costs.

[0014] 2. The present invention describes a method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducer. In the reduction stage of the silver powder, the use of a non-metallic inducer successfully solves the problem of how to ensure the stability of the silver powder product performance. By stabilizing the amount of non-metallic inducer, the silver powder maintains stability in key indicators such as particle size distribution and specific surface area, and the parameters of the silver powder are successfully regulated.

[0015] 3. The method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducer described in this invention allows for convenient and flexible adjustment of key indicators such as silver powder particle size distribution and specific surface area by adjusting the amount of non-metallic inducer, thereby achieving the goal of diversifying silver powder product models; and by adjusting the non-metallic inducer, the microstructure of the silver powder can be influenced. Attached Figure Description

[0016] Figure 1 This is an electron microscope image of the low-cost, high-performance spherical silver powder prepared in Example 1 of this invention. Figure 1 a is a 5000x magnified electron microscope image of the ultrafine silver powder prepared in Example 1; Figure 1 b is a 10,000x magnified electron microscope image of the ultrafine silver powder prepared in Example 1. Figure 2 This is an electron microscope image of the low-cost, high-performance spherical silver powder prepared in Example 2 of this invention. Figure 2 a is a 5000x magnified electron microscope image of the ultrafine silver powder prepared in Example 2; Figure 2 b is a 10,000x magnified electron microscope image of the ultrafine silver powder prepared in Example 2). Figure 3 This is a process flow diagram of a method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducer, as described in this invention. Figure 4 Electron micrograph of the spherical silver powder prepared in the comparative example ( Figure 4 a is a 5000x magnified electron microscope image of the ultrafine silver powder prepared in the comparative example; Figure 4 b is a magnified electron microscope image of the ultrafine silver powder prepared in the comparison example (10,000x magnification). Detailed Implementation

[0017] The present invention is further described in detail below through embodiments, but these embodiments should not be considered as limitations on the present invention. Unless otherwise specified, the raw materials and equipment used in the embodiments of this application were purchased commercially, and the methods in the embodiments, unless otherwise specified, are conventional methods in the art.

[0018] Example 1: A method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducer includes the following steps: The amount of silver nitrate to be fed is 40 kg. (1) Preparation of oxidizing solution: Add 40 kg of silver nitrate to a 500 L mixing tank A, add 270 L of deionized water, dissolve and stir evenly, then heat to 35 °C for later use. (2) Preparation of reducing solution: Add 22.8 kg of L-ascorbic acid to 500 L mixing tank B, add 200 L of deionized water, dissolve and stir evenly, then heat to 35 °C for later use. (3) Preparation of dispersion: Add 3Kg of PVP-K30 (polyvinylpyrrolidone) to a 500L mixing tank C, add 330L of deionized water, dissolve and stir evenly, then heat to 35℃ for later use. (4) Preparation of non-metallic inducing agent: Add 1.5 kg of boric acid to a 50 L mixing tank D, add 20 L of deionized water, dissolve and stir evenly, then heat to 35 °C for later use. (5) Reduction reaction: First, add the dispersion to the reactor. Under the premise of stirring the reactor, add the non-metallic inducer to the reactor. Then, use a pump with metering function to add the pre-prepared oxidizing solution and reducing solution to the reactor at the same time. The flow rate of the oxidizing solution is 40 L / min and the flow rate of the reducing solution is 40 L / min. (6) Coating the surface of silver powder: After the reduction reaction is completed, oleic acid is added to the reactor. The amount added is 0.5%-1.5% of the silver powder yield. After stirring at high speed for 1-2 hours, the mixture is allowed to stand and separate into layers. After centrifugation, spherical silver powder with different particle size ranges is obtained.

[0019] Example 2: A method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducer includes the following steps: The amount of silver nitrate to be fed is 40 kg. (1) Preparation of oxidizing solution: Add 40 kg of silver nitrate to a 500 L mixing tank A, add 270 L of deionized water, dissolve and stir evenly, then heat to 35 °C for later use. (2) Preparation of reducing solution: Add 20 kg of L-ascorbic acid to 500 L mixing tank B, add 200 L of deionized water, dissolve and stir evenly, then heat to 35 °C for later use. (3) Preparation of dispersion: Add 2Kg of PVP-K30 (polyvinylpyrrolidone) to a 500L mixing tank C, add 330L of deionized water, dissolve and stir evenly, then heat to 35℃ for later use. (4) Preparation of non-metallic inducing agent: Add 2.5 kg of boric acid to a 50 L mixing tank D, add 20 L of deionized water, dissolve and stir evenly, then heat to 35 °C for later use. (5) Reduction reaction: First, add the dispersion to the reactor. Under the premise of stirring the reactor, add the non-metallic inducer to the reactor. Then, use a pump with metering function to add the pre-prepared oxidizing solution and reducing solution to the reactor at the same time. The flow rate of the oxidizing solution is 40 L / min and the flow rate of the reducing solution is 40 L / min. (6) Coating the surface of silver powder: After the reduction reaction is completed, oleic acid is added to the reactor. The amount added is 0.5%-1.5% of the silver powder yield. After stirring at high speed for 1-2 hours, the mixture is allowed to stand and separate into layers. After centrifugation, spherical silver powder with different particle size ranges is obtained.

[0020] result: The technical specifications of the silver powder products in this invention are shown in Example 1 (Silver Powder G020) and Example 2 (Silver Powder G030). Table 1 shows the test data of the two types of silver powder obtained by this invention.

[0021] Examples 1 and 2 yielded low-cost, high-performance spherical silver powders with various particle sizes after centrifugation. The particle sizes were: D10: 0.63-0.84 μm, D50: 1.02-1.45 μm, D90: 1.64-2.46 μm, D100: 2.70-4.00 μm, and the specific surface area was 0.43-0.63 m². 2 / g, tap density: 6.02-6.34g / cm³ 3 The burn loss rate at 550℃ is 0.39-0.43%.

[0022] Electron micrographs of silver powder G020 and silver powder G030 are shown below: Figure 1 This is an electron microscope image of the low-cost, high-performance spherical silver powder prepared in Example 1. Figure 1 a is a 5000x magnified electron microscope image of the ultrafine silver powder prepared in Example 1; Figure 1 b is a 10,000x magnified electron microscope image of the ultrafine silver powder prepared in Example 1. Figure 2 This is an electron microscope image of the low-cost, high-performance spherical silver powder prepared in Example 2. Figure 2 a is a 5000x magnified electron microscope image of the ultrafine silver powder prepared in Example 2; Figure 2 b is a 10,000x magnified electron microscope image of the ultrafine silver powder prepared in Example 2.

[0023] Comparative example: Compared with Example 1, no non-metallic inducer was added to the comparative example, but everything else was the same as in Example 1.

[0024] 24.95 kg of ultrafine silver powder was prepared in a comparative example, with a yield of 98.20%. The particle sizes were: D10~0.530 μm, D50~0.843 μm, D90~1.314 μm, D100~3.108 μm, and the tap density was 4.35 g / cm³. 3 Specific surface area: 1.057 m² 2 / g, burn loss rate at 550℃ is 0.64%.

[0025] Figure 4 Electron micrograph of the spherical silver powder prepared in the comparative example ( Figure 4 a is a 5000x magnified electron microscope image of the ultrafine silver powder prepared in the comparative example; Figure 4 b is a magnified electron microscope image of the ultrafine silver powder prepared in the comparison example (10,000x magnification).

[0026] Results analysis: 1. As can be seen from the results of Examples 1-2 in Table 1, the present invention provides a method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducing agent, achieving a tap density of 6.0 g / cm³. 3 The above parameters have a burn loss rate of ≤0.5% and a specific surface area of ​​0.43-0.63 m². 2 The ultrafine silver powder of / g was obtained by adding a non-metallic inducer to the dispersion to induce the crystal nuclei to grow along a specific crystal orientation. By adding the reducing and oxidizing solutions in a co-current droplet manner with almost the same flow rate, the morphology of the silver powder particles during the growth process was effectively guaranteed. At the same time, the prepared silver powder has a smaller range and a more concentrated particle size, and the median particle size of the silver powder can be precisely controlled between 1.0-1.5μm.

[0027] 2. Comparison of Example 1 and Comparative Example: The surface morphology after adding non-metallic inducer is significantly smoother and more rounded, while the surface without non-metallic inducer has more sharp edges and relatively poor dispersibility.

[0028] By comparing the basic performance of the examples and the comparative examples, the formulation and silver powder preparation process of the examples are significantly better than those of the comparative examples.

[0029] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing low-cost, high-performance spherical silver powder using a non-metallic inducer, characterized in that: Includes the following steps: 1) Preparation of oxidizing solution: Dissolve silver nitrate in deionized water, stir thoroughly to obtain a uniform and clear aqueous solution, control the silver content to be 0.5-2 mol / L, and control and maintain the temperature at 10-50℃; 2) Preparation of reducing solution: Dissolve the reducing agent in deionized water. The mass ratio of the amount of reducing agent to the concentration of silver ions in step 1) is 0.7:

1. Stir and dissolve thoroughly to obtain a uniform and clear aqueous solution. The volume of the solution is 0.5-2 times the volume of the oxidation solution. Control and maintain the temperature at 10-50℃. The reducing agent is L-ascorbic acid; 3) Preparation of dispersion: Add the dispersant to deionized water. The mass ratio of dispersant to deionized water is 1:(20-30). The amount of dispersant used is 1-15% of the silver powder production. After stirring and dissolving thoroughly to obtain a uniform and clear aqueous solution, control and maintain the temperature at 10-50℃. The dispersant is polyvinylpyrrolidone; the amount of dispersant used is 5-13% of the silver powder production. 4) Preparation of non-metallic inducer: Add non-metallic inducer to deionized water. The mass ratio of non-metallic inducer to deionized water is 1:(10-20). The total amount of non-metallic inducer is 1-20% of the silver powder production. After stirring and dissolving thoroughly to obtain a uniform and clear aqueous solution, control and maintain the temperature at 10-50℃. The non-metallic inducing agent is boric acid; 5) Reduction reaction: First, add the dispersion prepared in step 3) to the reaction vessel, then add the non-metallic inducing solution prepared in step 4), and ensure thorough stirring; The reducing solution prepared in step 2) and the oxidizing solution prepared in step 1) are simultaneously injected into the reactor at a fixed flow rate. The flow rate of the reducing solution is 20-40 L / min; the flow rate of the oxidizing solution is 20-40 L / min; the total reaction time is 5-10 min; and the temperature control range is 15-45℃. 6) Silver Powder Surface Coating: After the reaction is completed, stearic acid or oleic acid is immediately added to the reactor at a rate of 0.3%-1.2% of the silver powder yield. The mixture is stirred at high speed for 1-2 hours, then allowed to stand and separate into layers. After centrifugation, low-cost, high-performance spherical silver powders with various particle sizes are obtained. The particle sizes are: D10: 0.63-0.84μm, D50: 1.02-1.45μm, D90: 1.64-2.46μm, D100: 2.70-4.00μm; specific surface area: 0.43-0.63m² / g; tap density: 6.02-6.34g / cm³; burn-off rate at 550℃: 0.39-0.43%.

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