Method for preparing strip silver powder and strip silver powder

Abstract

The present application provides a method for preparing silver powder in strips and the silver powder in strips, comprising: fully mixing a reducing agent with deionized water, adding ammonia water and tartaric acid to obtain a reducing solution; fully mixing silver nitrate with deionized water, adding polyvinylpyrrolidone to obtain an oxidizing solution; stirring the reducing solution, and adding the oxidizing solution to the reducing solution within a first preset time to obtain a mixed reaction solution; after continuous reaction for a second preset time, washing and separating the mixed reaction solution to obtain silver powder in strips. The method for preparing silver powder in strips provided by the present application can prepare silver powder in strips, and the preparation method is simple, and the reaction is stable, which is conducive to continuous mass production.

Description

Technical Field

[0001] The present application relates to the technical field of preparation of new precious metal materials, and in particular to a method for preparing strip silver powder and the strip silver powder. Background Art

[0002] The rapid development of clean energy has driven the widespread application of solar cells. In the field of solar energy, conductive silver paste is an important auxiliary material in the production process of solar cells, and the cost of conductive silver paste currently accounts for about 15%-20% of the production cost of solar cells. As the main raw material of conductive silver paste, silver powder has various factors such as morphology, structure, particle size and distribution characteristics, loose and tap density, specific surface area, sintering performance, corrosion resistance, etc., which will affect the performance of silver paste. In particular, the morphology and particle size characteristics can directly or indirectly determine the photoelectric conversion rate of solar cells. Therefore, studying the influence of silver powder with different morphologies on the performance of silver paste has become an important research topic. Summary of the invention

[0003] The purpose of the present application is to provide a method for preparing strip silver powder and strip silver powder, which can produce strip silver powder and has a simple preparation method, stable reaction and is conducive to large-scale production.

[0004] In a first aspect, the present application provides a method for preparing strip-shaped silver powder, comprising:

[0005] After the reducing agent and deionized water are fully mixed, ammonia water and tartaric acid are added to obtain a reducing solution;

[0006] After silver nitrate and deionized water are fully mixed, polyvinylpyrrolidone is added to obtain an oxidation solution;

[0007] Stirring the reducing liquid, and adding the oxidizing liquid into the reducing liquid within a first preset time to obtain a mixed reaction liquid;

[0008] After the reaction continues for a second preset time, the mixed reaction liquid is cleaned and separated to obtain the strip-shaped silver powder.

[0009] In some possible embodiments, the concentration of the reducing agent is 10-100 g / L, the concentration of the ammonia water is 10-100 g / L, and the concentration of the tartaric acid is 0.1-10 g / L.

[0010] In some possible embodiments, the concentration of the silver nitrate is 10-200 g / L, and the concentration of the polyvinylpyrrolidone is 0.1-10 g / L.

[0011] In some possible embodiments, the first preset time length is 1-3 seconds.

[0012] In some possible embodiments, after the continuous reaction for a second preset time, the mixed reaction liquid is cleaned and separated to obtain the strip-shaped silver powder, which includes:

[0013] The mixed reaction liquid is centrifuged and washed by a centrifuge until the conductivity of the washing wastewater is no greater than a preset conductivity threshold, thereby obtaining initial silver powder;

[0014] The initial silver powder in the centrifuge is washed with ethanol until no liquid flows out of the centrifuge to obtain silver powder particles;

[0015] The silver powder particles are emulsified by using a preset fatty acid ligand, and the emulsified silver powder particles are dried to obtain the strip-shaped silver powder.

[0016] In some possible embodiments, the fatty acid ligand is one or more of oleic acid, linoleic acid, stearic acid, palmitic acid, lauric acid, myristic acid, and the like.

[0017] In some possible embodiments, the mass percentage of the fatty acid ligand is 0.01%-1%.

[0018] In some possible embodiments, the solution temperature of the reducing solution and the oxidizing solution is 28-30°C.

[0019] In some possible embodiments, the reducing agent is one or more of formaldehyde, ascorbic acid, glucose, glycerol, ethylene glycol, hydroxylamine and hydrogen peroxide.

[0020] In a second aspect, an embodiment of the present application provides a strip-shaped silver powder, which is prepared by the strip-shaped silver powder preparation method as described in any one of the above items.

[0021] The present application provides a method for preparing silver powder in strips and the silver powder in strips, comprising: fully mixing a reducing agent with deionized water, adding ammonia water and tartaric acid to obtain a reducing solution; fully mixing silver nitrate with deionized water, adding polyvinylpyrrolidone to obtain an oxidizing solution; stirring the reducing solution, and adding the oxidizing solution to the reducing solution within a first preset time to obtain a mixed reaction solution; after continuous reaction for a second preset time, washing and separating the mixed reaction solution to obtain silver powder in strips. The method for preparing silver powder in strips provided by the present application can prepare silver powder in strips, and the preparation method is simple, and the reaction is stable, which is conducive to continuous mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0023] Figure 1 It is a schematic diagram of the process of preparing the strip silver powder provided in the embodiment of the present application;

[0024] Figure 2 This is a scanning electron microscope image of the silver powder prepared in Example 1 using the method of the present application;

[0025] Figure 3 This is a scanning electron microscope image of silver powder prepared in Example 2 using the method of the present application. DETAILED DESCRIPTION

[0026] The present application is further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only used to illustrate the present application, but are not intended to limit the scope of the present application. Similarly, the following examples are only some embodiments of the present application rather than all embodiments, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0027] In the following description of the present application, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0028] In the following description of the present application, the terms "first\second\third" involved are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second\third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described here can be implemented in an order other than that illustrated or described here.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0030] The following is a detailed description with reference to specific embodiments. It should be noted that the serial numbers of the following embodiments are not intended to limit the preferred order of the embodiments.

[0031] The silver powder preparation method provided in the present application also utilizes an oxidation-reduction reaction to convert silver ions into silver powder particles. However, unlike the silver powder preparation method in the prior art, the present application improves the specific steps of the silver powder preparation method, which is described in detail below.

[0032] See also Figure 1 , Figure 1 : is a schematic diagram of the process of preparing silver powder provided in the embodiment of the present application. The specific process of the silver powder preparation method can be as follows:

[0033] 101. After the reducing agent and deionized water are fully mixed, ammonia water and tartaric acid are added to obtain a reducing solution.

[0034] 102. After fully mixing silver nitrate and deionized water, add polyvinylpyrrolidone to obtain an oxidizing solution.

[0035] 103. Stir the reducing liquid, and add the oxidizing liquid into the reducing liquid within a first preset time to obtain a mixed reaction liquid.

[0036] 104. After the reaction continues for a second preset time, the mixed reaction liquid is cleaned and separated to obtain strip-shaped silver powder.

[0037] The silver powder preparation method provided in the present application converts silver ions into silver powder particles through an oxidation-reduction reaction, so it is necessary to prepare an oxidation solution including silver ions and a reduction solution for reducing the silver ions in the oxidation solution. In some embodiments of the present application, the reduction solution can be prepared by the following method: first, the reducing agent is fully mixed with deionized water, and then a certain amount of ammonia water and tartaric acid are added to the deionized water mixed with the reducing agent, and the reducing solution is obtained after the two are fully dissolved. Among them, in some embodiments, the reducing agent is selected from one or more of formaldehyde, ascorbic acid, glucose, glycerol, ethylene glycol, hydroxylamine and hydrogen peroxide; the concentration of the reducing agent can be 10-100g / L, the concentration of ammonia water can be 10-100g / L, and the concentration of tartaric acid can be 0.1-10g / L. When preparing the oxidation solution, silver nitrate can be fully mixed with deionized water, and then polyvinylpyrrolidone is added to the deionized water mixed with silver nitrate, and the oxidation solution is obtained after sufficient mixing. The concentration of silver nitrate can be 10-200 g / L, and the concentration of polyvinylpyrrolidone can be 0.1-10 g / L. In the embodiments of the present application, the specific steps of preparing the oxidizing solution and the reducing solution can refer to the prior art and are not limited here.

[0038] After the oxidizing liquid and the reducing liquid are prepared separately, the two need to be mixed to carry out a redox reaction. Specifically, the oxidizing liquid can be added to the reducing liquid under the condition that the reducing liquid is stirred to keep the reducing liquid rotating, and the oxidizing liquid needs to be added to the reducing liquid within a first time length to obtain a mixed reaction liquid. In some embodiments, the reducing liquid can be controlled at a speed of 100-1000 rpm to add the oxidizing liquid to the reducing liquid. It is also necessary to continue the reaction for a second preset time length so that the oxidizing liquid and the reducing liquid are fully reacted to obtain a mixed reaction liquid including silver powder, and then the silver powder is separated from the mixed reaction liquid.

[0039] In the above embodiment, the step of washing and separating the mixed reaction liquid to obtain strip-shaped silver powder may include the following steps:

[0040] The mixed reaction liquid is centrifuged and cleaned by a centrifuge until the conductivity of the washing wastewater is no greater than a preset conductivity threshold value, thereby obtaining initial silver powder; the initial silver powder in the centrifuge is rinsed by ethanol until no liquid flows out of the centrifuge, thereby obtaining silver powder particles; the silver powder particles are emulsified by a preset fatty acid ligand, and the emulsified silver powder particles are dried to obtain strip-shaped silver powder.

[0041] Specifically, in some embodiments, the mixed reaction liquid can be centrifuged using a high-speed centrifuge to deposit the silver powder particles suspended in the mixed reaction liquid; when the conductivity of the washing wastewater discharged from the high-speed centrifuge is not greater than the preset conductivity threshold, such as not greater than 20us / cm, the first cleaning can be stopped. Then, 1-100L of ethanol is needed to continue to rinse the initial silver powder deposited in the high-speed centrifuge, because certain impurities will still adhere to the surface of the initial silver powder, and it is necessary to continue cleaning. When no liquid flows out of the high-speed centrifuge, the ethanol cleaning can be stopped to obtain silver powder particles. At this time, the silver powder particles obtained are still not the final strip silver powder, and the silver powder particles need to be emulsified using a preset fatty acid ligand, and the emulsified silver powder particles are subjected to high pressure to obtain the final strip silver powder. In some embodiments, the silver powder particles can be ultrasonically emulsified using a fatty acid ligand with a mass percentage of 0.01%-1%, and the ultrasonically emulsified silver powder particles are placed in an oven for drying; wherein, the drying temperature can be 50°C-55°C, and the drying time can vary from 4 to 5 hours. It is also necessary to process the silver powder that is baked too thick with a powdering machine, and sieve the powdered silver powder with a 500-mesh sieve to obtain strip silver powder of different specifications.

[0042] In some embodiments, the fatty acid ligand may be one or more of oleic acid, linoleic acid, stearic acid, palmitic acid, lauric acid, tetradecanoic acid, etc. The solution temperature of the oxidizing solution and the reducing solution prepared respectively may be controlled within the range of 28-30°C; in a specific embodiment, the solution temperature of the oxidizing solution and the reducing solution may be controlled to be 30°C. The first preset time may be 1-3 seconds, that is, the oxidizing solution is completely added to the reducing solution within 1-3 seconds; the second preset time may be 8-10 minutes, for example, ten minutes to ensure that the oxidizing solution and the reducing solution react completely.

[0043] The present application provides a method for preparing silver powder in strips and the silver powder in strips, comprising: fully mixing a reducing agent with deionized water, adding ammonia water and tartaric acid to obtain a reducing solution; fully mixing silver nitrate with deionized water, adding polyvinylpyrrolidone to obtain an oxidizing solution; stirring the reducing solution, and adding the oxidizing solution to the reducing solution within a first preset time to obtain a mixed reaction solution; after continuous reaction for a second preset time, washing and separating the mixed reaction solution to obtain silver powder in strips. The method for preparing silver powder in strips provided by the present application can prepare silver powder in strips, and the preparation method is simple, and the reaction is stable, which is conducive to continuous mass production.

[0044] The preparation process of the silver powder preparation method provided by the present application is described in detail below in conjunction with specific embodiments:

[0045] Embodiment 1:

[0046] Fully mix 4.32 kg of ascorbic acid with 90 kg of deionized water, and after the reducing agent ascorbic acid is completely dissolved, add 0.8 kg of ammonia water and 20 g of tartaric acid, and after fully dissolving, obtain a reducing solution for use; at the same time, control the solution temperature of the reducing solution to 30°C. Mix 8 kg of silver nitrate with 30 kg of deionized water, and after fully dissolving, add 22 g of polyvinyl pyrrolidone, and after fully dissolving, obtain an oxidizing solution for use; and control the solution temperature of the oxidizing solution to 30°C.

[0047] Stir the reducing liquid and keep it rotating at 600r / min. Add all the oxidizing liquid to the reducing liquid within 2.2 seconds. Continue the reaction for 10 minutes before the reaction is terminated. Then, clean and separate the mixed reaction liquid after the reaction. Specifically, the silver-containing solution (i.e., the mixed reaction liquid) can be centrifuged by a high-speed centrifuge until the conductivity of the outflowing washing wastewater is 19.02us / cm; then rinse the silver powder in the centrifuge with 20L of ethanol until no liquid flows out of the centrifuge. Then, use lauric acid with a weight ratio of 0.5%wt to ultrasonically emulsify the silver powder in the centrifuge. Place the ultrasonically emulsified silver powder in an oven, adjust the temperature to 55°C, and bake for 5 hours. Shape the baked silver powder, sieve the shaped silver powder with a 500-mesh sieve, and test its data. The particle size of the strip silver powder prepared in Example 1 is in the range of 1.076 to 7.784um, and the tap density is 5.2g / cc. Figure 2 Shown is a scanning electron microscope image of the silver powder prepared in Example 1.

[0048] Embodiment 2:

[0049] Fully mix 4.32 kg of ascorbic acid with 90 kg of deionized water, and after the reducing agent ascorbic acid is completely dissolved, add 0.8 kg of ammonia water and 10 g of tartaric acid, and after fully dissolving, obtain a reducing solution for use; at the same time, control the solution temperature of the reducing solution to 30°C. Mix 8 kg of silver nitrate with 30 kg of deionized water, and after fully dissolving, add 22 g of polyvinyl pyrrolidone, and after fully dissolving, obtain an oxidizing solution for use; and control the solution temperature of the oxidizing solution to 30°C.

[0050] Stir the reducing liquid and keep it rotating at 600r / min. Add all the oxidizing liquid to the reducing liquid within 2.2 seconds. Continue the reaction for 10 minutes and then terminate the reaction. Then clean and separate the mixed reaction liquid after the reaction. Specifically, the silver-containing solution (i.e., the mixed reaction liquid) can be centrifuged by a high-speed centrifuge until the conductivity of the outflowing washing wastewater is 19.02us / cm; then rinse the silver powder in the centrifuge with 20L of ethanol until no liquid flows out of the centrifuge. Then use lauric acid with a weight ratio of 0.5%wt to ultrasonically emulsify the silver powder in the centrifuge. Place the ultrasonically emulsified silver powder in an oven, adjust the temperature to 55°C, and bake for 5 hours. Shape the baked silver powder, sieve the shaped silver powder with a 500-mesh sieve and test its data; the particle size of the strip silver powder prepared in Example 2 is in the range of 1.223 to 6.487um, and the tap density is 5.32g / cc. Figure 3 Shown is a scanning electron microscope image of the silver powder prepared in Example 2.

[0051] It can be seen that the present application discloses a simple method for preparing strip-shaped silver powder, which is simple and easy to implement, and the reaction is stable and is conducive to continuous mass production. It has broad application prospects in the field of photovoltaic silver paste.

[0052] The present application also provides a strip silver powder, which is prepared by the strip silver powder preparation method provided by any of the above embodiments, and thus has all the same beneficial effects, and this embodiment will not be repeated here. It should be noted that the silver powder prepared by the strip silver powder preparation method provided by the embodiment of the present application is not actually a regular strip structure, but also includes a spherical structure at one end of the strip structure; that is, the silver powder actually includes a spherical part and a strip part, and the details can be referred to Figure 2 and Figure 3 The particle size of the silver powder described in the above embodiment is actually the overall length of the spherical part and the strip part, rather than the length of the individual strip part.

[0053] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0054] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application. The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing strip silver powder, characterized in that: include: After the reducing agent and deionized water are fully mixed, ammonia water and tartaric acid are added to obtain a reducing solution; After silver nitrate and deionized water are fully mixed, polyvinylpyrrolidone is added to obtain an oxidation solution; Stirring the reducing liquid, and adding the oxidizing liquid into the reducing liquid within a first preset time to obtain a mixed reaction liquid; After the reaction continues for a second preset time, the mixed reaction liquid is cleaned and separated to obtain the strip-shaped silver powder; After the reaction continues for a second preset time, the mixed reaction liquid is cleaned and separated to obtain the strip-shaped silver powder, which includes: The mixed reaction liquid is centrifuged and washed by a centrifuge until the conductivity of the washing wastewater is no greater than a preset conductivity threshold, thereby obtaining initial silver powder; The initial silver powder in the centrifuge is washed with ethanol until no liquid flows out of the centrifuge to obtain silver powder particles; emulsifying the silver powder particles by using a preset fatty acid ligand, and drying the emulsified silver powder particles to obtain the strip-shaped silver powder; The concentration of the reducing agent is 10-100 g / L, the concentration of the ammonia water is 10-100 g / L, the concentration of the tartaric acid is 0.1-10 g / L; the concentration of the silver nitrate is 10-200 g / L, and the concentration of the polyvinylpyrrolidone is 0.1-10 g / L; One end of the strip-shaped silver powder has a spherical structure.

2. The method for preparing strip silver powder according to claim 1, characterized in that: The first preset time length is 1-3 seconds.

3. The method for preparing strip silver powder according to claim 1, characterized in that: The fatty acid ligand is one or more of oleic acid, linoleic acid, stearic acid, palmitic acid, lauric acid, and myristic acid.

4. The method for preparing strip silver powder according to claim 3, characterized in that: The mass percentage of the fatty acid ligand is 0.01%-1%.

5. The method for preparing strip silver powder according to claim 1, characterized in that: The solution temperature of the reducing solution and the oxidizing solution is 28-30°C.

6. The method for preparing strip silver powder according to claim 1, characterized in that: The reducing agent is one or more of formaldehyde, ascorbic acid, glucose, glycerol, ethylene glycol, hydroxylamine and hydrogen peroxide.

Images