Preparation method of polyhedral silver powder and polyhedral silver powder

Abstract

The embodiment of the invention provides a preparation method of polyhedral silver powder and the polyhedral silver powder. The preparation method comprises the steps that a silver nitrate solution, a reducing solution, a seed crystal solution and a dispersing agent solution are prepared; a silver nitrate solution and the reducing solution are added into the seed crystal solution at the same time within a preset duration, and a mixed reaction solution is obtained; the dispersing agent solution is added into the mixed reaction solution, and silver powder slurry is obtained after a second preset duration of reaction; and cleaning and separating the silver powder slurry to obtain the polyhedral silver powder. The preparation method of the polyhedral silver powder is simple, and the prepared silver powder is of a polyhedral structure and is high in crystallinity.

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 polyhedral silver powder and the polyhedral silver powder. Background Art

[0002] Silver powder is widely used in the electronics industry, catalysts, antibacterial materials, conductive inks and coatings due to its excellent electrical and thermal conductivity. In the electronics industry, silver powder is a key raw material for the preparation of conductive pastes, which are used to make conductive layers in products such as printed circuit boards, solar cells, and touch screens. In electronic pastes, silver powder with high crystallinity has better electron mobility and thermal conductivity, which not only improves the electrical and thermal conductivity of the material, but also enhances the mechanical strength and corrosion resistance of the material. The technical challenge in preparing highly crystalline polyhedral silver powder lies in controlling the morphology and size of silver particles and improving their crystallinity. With existing methods for preparing silver powder, the crystallinity of the silver powder is not high and the preparation is cumbersome. Summary of the invention

[0003] The purpose of the present application is to provide a method for preparing polyhedral silver powder and the polyhedral silver powder. The prepared polyhedral silver powder has high crystallinity and the preparation method is simple.

[0004] In a first aspect, an embodiment of the present application provides a method for preparing a polyhedral silver powder, comprising:

[0005] preparing a silver nitrate solution, a reducing solution, a seed solution and a dispersant solution respectively;

[0006] Adding the silver nitrate solution and the reducing solution to the seed solution simultaneously within a first preset time period to obtain a mixed reaction solution;

[0007] Adding the dispersant solution into the mixed reaction liquid and reacting for a second preset time to obtain a silver powder slurry;

[0008] The silver powder slurry is cleaned, separated and dried to obtain the polyhedral silver powder.

[0009] In some possible embodiments,

[0010] The method of separately preparing the silver nitrate solution, the reducing solution, the seed solution and the dispersant solution comprises:

[0011] An initial silver nitrate solution was prepared by adding silver nitrate to ultrapure water;

[0012] Adding a reducing agent into ultrapure water to prepare an initial reducing solution;

[0013] Respectively adjusting the pH values ​​of the initial silver nitrate solution and the initial reducing solution to obtain the silver nitrate solution and the reducing solution;

[0014] Adding a preset seed crystal and an organic auxiliary agent into ultrapure water to prepare the seed crystal solution;

[0015] The dispersant solution is prepared by adding a surfactant to an ethanol solution.

[0016] In some possible embodiments, the mass concentration of silver nitrate in the silver nitrate solution is 8% to 15%, the mass concentration of the reducing agent in the reducing solution is 5% to 10%, and the mass ratio of the reducing agent in the reducing solution to the silver nitrate in the silver nitrate solution is 40% to 60%.

[0017] In some possible embodiments, the ratio of the mass of the seed crystals in the seed solution to the mass of silver nitrate in the silver nitrate solution is 0.1% to 1%, the ratio of the mass of the organic additive in the seed solution to the mass of the silver nitrate in the silver nitrate solution is 1% to 10%, and the mass concentration of the organic additive is 5% to 15%.

[0018] In some possible embodiments, the ratio of the mass of the surfactant in the dispersant solution to the mass of the silver nitrate in the silver nitrate solution is 1-5%.

[0019] In some possible embodiments, the reducing agent is one or more of glucose, ascorbic acid, hydrazine hydrate, hydrogen peroxide, formaldehyde or acetaldehyde.

[0020] In some possible embodiments, the organic auxiliary agent is one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, triethylhexyl phosphoric acid, sodium dodecylbenzene sulfonate and sodium dodecyl sulfate.

[0021] In some possible embodiments, the surfactant is one or more of silane coupling agent, span, oleic acid, lauric acid, stearic acid and the like.

[0022] In some possible embodiments, the temperature for drying the washed and separated silver powder is 40-60° C., and the drying time is 60-120 min.

[0023] In a second aspect, an embodiment of the present application provides a polyhedral silver powder, which is prepared by the silver powder preparation method as described in any one of the above items.

[0024] The method for preparing the polyhedral silver powder provided in the embodiment of the present application comprises: preparing a silver nitrate solution, a reducing solution, a seed solution and a dispersant solution respectively; adding the silver nitrate solution and the reducing solution to the seed solution at the same time within a first preset time to obtain a mixed reaction liquid; adding the dispersant solution to the mixed reaction liquid, reacting for a second preset time to obtain a silver powder slurry; washing, separating and drying the silver powder slurry to obtain the polyhedral silver powder. The method for preparing the polyhedral silver powder provided in the present application is simple, and the prepared silver powder has a polyhedral structure and high crystallinity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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.

[0026] Figure 1 It is a schematic diagram of the process of preparing silver powder provided in the embodiment of the present application;

[0027] Figure 2 This is a 2k times scanning electron microscope image of the polyhedral silver powder provided in the embodiment of the present application;

[0028] Figure 3 This is a 5k times scanning electron microscope image of the polyhedral silver powder provided in the embodiment of the present application;

[0029] Figure 4 10k times scanning electron microscope image of the polyhedral silver powder provided in the examples of the present application. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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. The present application improves the specific steps of the silver powder preparation method, which is described in detail below.

[0035] See also Figure 1 , Figure 1 The present invention provides a schematic flow chart of a method for preparing polyhedral silver powder 02 according to an embodiment of the present invention. The method for preparing polyhedral silver powder may specifically include the following steps:

[0036] 101. Prepare silver nitrate solution, reducing solution, seed solution and dispersant solution respectively.

[0037] The silver powder preparation method provided in the present application still mainly converts silver ions into silver powder particles through an oxidation-reduction reaction, so it is necessary to separately prepare a silver nitrate solution including silver ions and a reducing solution for reducing the silver ions in the silver nitrate solution; the present application also needs to separately prepare a seed solution and a reducing solution, so as to control the reaction rate through different reaction solutions, and then control the reaction product to obtain polyhedral silver powders with different crystallinity, that is, to control the structure of the silver powder.

[0038] In some embodiments, silver nitrate solid can be configured as a silver nitrate solution; specifically, silver nitrate can be added to ultrapure water to prepare an initial silver nitrate solution; and when preparing a reducing solution, the reducing solution can be added to ultrapure water to prepare an initial reducing solution. After the initial silver nitrate solution and the initial reducing solution are prepared, both need to be further processed to obtain the silver nitrate solution and reducing solution required for the subsequent reaction. Specifically, the pH values ​​of the initial silver nitrate solution and the initial reducing solution can be adjusted respectively to obtain a silver nitrate solution and a reducing solution. In some embodiments, a pH adjusting agent can be added to the initial silver nitrate solution and the initial reducing solution to adjust the pH value of the initial silver nitrate fusion and the initial reducing solution; specifically, the pH values ​​of the initial silver nitrate solution and the initial reducing solution can be adjusted to 2-5 respectively to obtain a silver nitrate solution and a reducing solution. Among them, the pH adjusting agent can be one or more of ammonia water, sodium hydroxide, sodium bicarbonate, oxalic acid, phosphoric acid, nitric acid, hydrochloric acid or sulfuric acid, which can be selected according to actual needs during actual adjustment, and is not limited here.

[0039] In the above embodiment, the mass concentration of silver nitrate in the silver nitrate solution can be 8% to 15%; the mass concentration of the reducing agent in the reducing solution is 5% to 10%, and the first reducing agent is 60% to 80% of the mass of silver nitrate; the mass ratio of the reducing agent in the reducing solution to the silver nitrate in the silver nitrate solution is 40% to 60%. In some embodiments, the reducing agent can be one or more of glucose, ascorbic acid, hydrazine hydrate, hydrogen peroxide, formaldehyde or acetaldehyde. And in the embodiment of the present application, the solution temperature of the prepared silver nitrate solution and the reducing solution can be controlled within the range of 15-35°C. In the embodiment of the present application, the specific method and steps for preparing the silver nitrate solution and the reducing solution can refer to the prior art and are not limited here.

[0040] The silver nitrate solution and reducing solution prepared in the above embodiments are respectively required in the present application to prepare a seed solution and a dispersant solution so that the silver nitrate solution and the reducing solution are better mixed. In some embodiments, the preset seed crystals and organic additives can be added to ultrapure water to prepare a seed solution. Among them, the organic additive has a strong adsorption to a certain crystal face during the formation of silver crystals, and has an inhibitory effect on the growth in this direction. Therefore, the organic additive is used in the present application to inhibit the growth of the crystal face. At the same time, at a lower reaction rate, the reduced silver atoms will preferentially deposit on other crystal faces with higher activity, and gradually grow along the crystal face, eventually forming one of the faces of a regular polyhedron. In an embodiment of the present application, the ratio of the mass of the seed crystals in the seed solution to the mass of silver nitrate in the silver nitrate solution is 0.1% to 1%, the ratio of the mass of the organic additive in the seed solution to the mass of the silver nitrate in the silver nitrate solution is 1% to 10%, and the mass concentration of the organic additive is 5% to 15%. In the embodiment of the present application, the organic auxiliary agent may be one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, triethylhexyl phosphoric acid, sodium dodecylbenzene sulfonate and sodium dodecyl sulfate.

[0041] The present application also needs to prepare a dispersant solution to better mix the silver nitrate solution, the reaction solution and the seed solution. In some embodiments, the surfactant solution can be dissolved in ethanol by stirring to obtain a dispersant solution. The ratio of the mass of the surfactant in the dispersant solution to the mass of the silver nitrate in the silver nitrate solution is 1% to 5%. In some embodiments, the surfactant can be one or more of a silane coupling agent, a silane, an oleic acid, a lauric acid, a stearic acid, and the like.

[0042] 102. Add the silver nitrate solution and the reducing solution to the seed solution at the same time within a first preset time to obtain a mixed reaction solution.

[0043] 103. Add the dispersant solution into the mixed reaction liquid, and react for a second preset time to obtain a silver powder slurry.

[0044] After the silver nitrate solution and the reducing solution are prepared separately, the two need to be mixed to perform an oxidation-reduction reaction; in the embodiment of the present application, since there are a seed solution and a dispersant solution, when mixing the silver nitrate and the reducing solution, the silver nitrate solution and the reducing solution are added to the seed solution at the same time, and the silver nitrate solution reducing solution needs to be added to the seed solution at the same time within the first preset time according to the preset flow rate, so as to obtain a mixed reaction solution. Then, the dispersant solution is added to the mixed reaction solution, and the reaction is continued for a second preset time to obtain a silver powder slurry; the silver powder obtained by the oxidation-reduction reaction is suspended in the silver powder slurry.

[0045] It should be noted that a specific organic additive is dissolved in the seed solution in the present application to inhibit the growth of the crystal face. At a lower reaction rate, the reduced silver atoms will preferentially deposit on other crystal faces with higher activity, and gradually grow along the crystal face, eventually forming one of the sides of a regular polyhedron. A reaction rate that is too fast will result in the generation of too many silver atoms at the same time. In addition to growing on highly active crystal faces, they will also grow on suppressed crystal faces, destroying the growth of regular crystal faces; a reaction rate that is too low will result in a growth rate that is too slow, with only a few silver atoms generated at the same time, and the selectivity for specific crystal faces is not obvious, which will also lead to irregular growth. Therefore, the present application needs to combine organic additives and matching reaction rates at the same time, so as to more easily prepare regular polyhedral silver powder with high crystallinity. The addition rate or flow rate of different solutions in the present application can be adjusted according to actual needs, and no limitation is made this time.

[0046] 104. The silver powder slurry is cleaned, separated and dried to obtain polyhedral silver powder.

[0047] After the redox reaction of the second preset time, the obtained silver powder particles are suspended in the silver powder slurry, and the silver powder particles in the silver powder slurry need to be separated to obtain the final polyhedral silver powder. Specifically, the silver powder slurry can be allowed to settle to obtain a layered upper liquid and a lower sediment; the sediment is separated and further processed. Among them, the sediment is the silver powder particles obtained by the redox reaction, but there are impurities attached to the sediment, so the separated sediment can be further cleaned with ultrapure water to obtain pure silver powder particles without impurities. In other embodiments, the silver powder slurry can also be washed with ultrapure water first, and the sediment is separated after being cleaned. Finally, the particles are dried at a certain temperature for a certain period of time to obtain the final polyhedral silver powder. In a specific embodiment, the polyhedral silver powder particles can be obtained by drying at 40-60°C for 60 to 120 minutes.

[0048] The preparation method of polyhedral silver powder provided in the present application uses simple raw materials, and only needs to use the most basic silver powder preparation raw materials such as silver nitrate solution, reducing solution and dispersant solution; and the preparation process and the equipment used are simple, with one-time feeding and reaction, no need for multi-stage reaction, and no need to customize special feeding devices; at the same time, the concentrations of silver nitrate and reducing agent are low, and the feeding speed is slow. The silver powder prepared by controlling the reaction growth rate has high crystallinity and complete crystal faces, and is a polyhedral structure.

[0049] The method for preparing the polyhedral silver powder provided in the embodiment of the present application comprises: preparing a silver nitrate solution, a reducing solution, a seed solution and a dispersant solution respectively; adding the silver nitrate solution and the reducing solution to the seed solution at the same time within a first preset time to obtain a mixed reaction liquid; adding the dispersant solution to the mixed reaction liquid, reacting for a second preset time to obtain a silver powder slurry; washing, separating and drying the silver powder slurry to obtain the polyhedral silver powder. The method for preparing the polyhedral silver powder provided in the present application is simple, and the prepared silver powder has a polyhedral structure and high crystallinity.

[0050] The preparation process of the method for preparing the polyhedral silver powder provided by the present application is described in detail below in conjunction with specific embodiments.

[0051] Embodiment 1:

[0052] Weigh 1kg of silver nitrate solid to prepare an initial silver nitrate solution with a mass fraction of 8%; weigh 600g of ascorbic acid solid as the first reducing agent to prepare an initial reducing solution with a mass concentration of 10%; weigh 20g of hexadecyltrimethylammonium bromide as an organic auxiliary agent to prepare a solution with a mass concentration of 5%, then add 5g of seed crystals, stir evenly to obtain a seed crystal solution. Weigh 10g of lauric acid, add it to 500g of ethanol solution, stir and dissolve it as a dispersant solution. At the same time, the temperature of all the solutions prepared above is controlled at about 20°C.

[0053] Add pH regulators to the initial silver nitrate solution and the initial reducing solution, respectively, to adjust the pH values ​​of the two to about 3, to obtain a silver nitrate solution and a reducing solution. Then, under stirring, add the pH-adjusted silver nitrate solution and the reducing solution to the seed solution at a certain flow rate, and add both within 12 minutes to obtain a mixed reaction solution; then add the dispersant solution to the mixed reaction solution. Stir the mixed dispersant solution and the mixed reaction solution to carry out an oxidation-reduction reaction, and obtain silver powder and silver paste after continuous stirring for 10 minutes. Then the silver powder slurry is filtered to collect the suspended silver powder particles, and the collected silver powder particles are washed with ultrapure water to remove impurities. At the same time, the washed silver powder particles also need to be dried in a drying oven at 60°C, and after drying for 120 minutes, a polyhedral silver powder with high crystallinity can be obtained. Figure 2As shown, it is a 2k times scanning electron microscope image of the polyhedral silver powder provided in the embodiment of the present application, Figure 3 This is a 5k times scanning electron microscope image of the polyhedral silver powder provided in the embodiment of the present application. Figure 4 This is a 10k times scanning electron microscope image of the polyhedral silver powder provided in the embodiment of the present application. Figure 2 Figure 3 Figure 4 It can be determined that the silver powder prepared by the method for preparing polyhedral silver powder provided in the present application has a polyhedral structure and high crystallinity.

[0054] The present application also provides a polyhedral silver powder, which is prepared by adopting the preparation method of the polyhedral silver powder provided by any of the above embodiments, and thus has all the same beneficial effects, and this embodiment will not be described in detail here.

[0055] 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.

[0056] 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 polyhedral silver powder, characterized in that: include: preparing a silver nitrate solution, a reducing solution, a seed solution and a dispersant solution respectively; Adding the silver nitrate solution and the reducing solution to the seed solution simultaneously within a first preset time period to obtain a mixed reaction solution; Adding the dispersant solution into the mixed reaction liquid and reacting for a second preset time to obtain a silver powder slurry; The silver powder slurry is cleaned, separated and dried to obtain the polyhedral silver powder.

2. The method for preparing polyhedral silver powder according to claim 1, characterized in that: The method of separately preparing the silver nitrate solution, the reducing solution, the seed solution and the dispersant solution comprises: An initial silver nitrate solution was prepared by adding silver nitrate to ultrapure water; Adding a reducing agent into ultrapure water to prepare an initial reducing solution; Respectively adjusting the pH values ​​of the initial silver nitrate solution and the initial reducing solution to obtain the silver nitrate solution and the reducing solution; Adding a preset seed crystal and an organic auxiliary agent into ultrapure water to prepare the seed crystal solution; The dispersant solution is prepared by adding a surfactant to an ethanol solution.

3. The method for preparing polyhedral silver powder according to claim 2, characterized in that: The mass concentration of silver nitrate in the silver nitrate solution is 8% to 15%, the mass concentration of the reducing agent in the reducing solution is 5% to 10%, and the mass ratio of the reducing agent in the reducing solution to the silver nitrate in the silver nitrate solution is 40% to 60%.

4. The method for preparing polyhedral silver powder according to claim 2, characterized in that: The mass ratio of the seeds in the seed solution to the mass ratio of the silver nitrate in the silver nitrate solution is 0.1% to 1%, the mass ratio of the organic additive in the seed solution to the mass ratio of the silver nitrate in the silver nitrate solution is 1% to 10%, and the mass concentration of the organic additive is 5% to 15%.

5. The method for preparing polyhedral silver powder according to claim 2, characterized in that: The mass ratio of the surfactant in the dispersant solution to the silver nitrate in the silver nitrate solution is 1 to 5%.

6. The method for preparing polyhedral silver powder according to claim 2, characterized in that: The reducing agent is one or more of glucose, ascorbic acid, hydrazine hydrate, hydrogen peroxide, formaldehyde or acetaldehyde.

7. The method for preparing polyhedral silver powder according to claim 2, characterized in that: The organic auxiliary agent is one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, triethylhexyl phosphoric acid, sodium dodecylbenzene sulfonate and sodium dodecyl sulfate.

8. The method for preparing polyhedral silver powder according to claim 2, characterized in that: The surfactant is one or more of silane coupling agent, span, oleic acid, lauric acid, stearic acid and the like.

9. The method for preparing polyhedral silver powder according to claim 1, characterized in that: The temperature for drying the washed and separated silver powder is 40-60° C., and the drying time is 60-120 min.

10. A polyhedral silver powder, characterized in that: The polyhedral silver powder is prepared by the preparation method of any one of claims 1 to 9.

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