Preparation method of flaky silver powder and flaky silver powder

Abstract

The embodiment of the present application provides a method for preparing flaky silver powder and flaky silver powder, including preparing a reducing solution using a reducing agent, an acid substance, a dispersant and nanocrystal seeds; preparing an oxidizing solution using silver nitrate and nitric acid; stirring the reducing solution, and adding the oxidizing solution to the reducing solution in a stirring state within a first preset time, and obtaining a silver powder suspension after the reaction is completed; centrifugally washing and drying the silver powder suspension to obtain flaky silver powder. The method for preparing flaky silver powder provided by the present application does not produce silver powder of other shapes during the preparation process, and the prepared flaky silver powder has high purity and is simple to prepare, does not require complex subsequent treatment, and has a stable reaction that is conducive to scale-up and 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 flaky silver powder and flaky silver powder. Background Art

[0002] Silver powder has a wide range of applications in the electronics industry, catalysts, antibacterial materials, conductive inks and coatings due to its excellent electrical and thermal conductivity. In the silver powder industry, flake silver powder and spherical silver powder are the two most common types of silver powder. The unique properties of flake silver powder give it broad application prospects in multiple application fields such as conductive materials, EMI shielding, thermal interfaces, microelectronic packaging and photovoltaic cells. It provides a reliable material solution for various high-performance electronic products and industrial applications. In the traditional manufacturing process of flake silver powder, ball milling is the key. The quality of the microscopic morphology of the flake silver powder, the size of the diameter-to-thickness ratio, and the surface state all depend on the ball milling process. The traditional ball milling preparation method has complicated steps and uses a large number of additives. It is difficult to clean it up. The residual impurities affect the resistivity of the silver powder. In the ball milling preparation process, cold welding is prone to occur, resulting in agglomeration, resulting in low vibration of the silver powder, and the silver powder is not densely stacked, resulting in high body resistance. Therefore, how to provide a method for preparing flake silver powder with simple process steps and high purity has become a problem that technicians in this field need to solve urgently. Summary of the invention

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

[0004] In a first aspect, the present invention provides a method for preparing flaky silver powder, comprising:

[0005] preparing a reducing solution by using a reducing agent, an acid substance, a dispersant and nanocrystalline seeds;

[0006] Prepare an oxidizing solution using silver nitrate and nitric acid;

[0007] Stirring the reducing solution, and adding the oxidizing solution into the reducing solution in a stirring state within a first preset time, and obtaining a silver powder suspension after the reaction is completed;

[0008] The silver powder suspension is centrifugally washed and dried to obtain flaky silver powder.

[0009] In some possible embodiments, the method of preparing the reducing solution using the reducing agent, the acid substance, the dispersant and the nanocrystal seeds includes:

[0010] Mixing the reducing agent with deionized water to obtain an initial reducing solution after the reducing agent is dissolved;

[0011] The acid substance, the dispersant and the nano-crystal seeds are added to the initial reducing solution to obtain the reducing solution.

[0012] In some possible embodiments, preparing the oxidizing solution using silver nitrate and nitric acid includes:

[0013] Mixing silver nitrate with deionized water to obtain an initial oxidation solution after the silver nitrate is dissolved;

[0014] Nitric acid is added to the initial oxidation solution to obtain the oxidation solution.

[0015] In some possible embodiments, the reducing agent is selected from one or more of formaldehyde, ascorbic acid, glucose, glycerol, ethylene glycol, hydroxylamine and hydrogen peroxide.

[0016] In some possible embodiments, the dispersant includes one or more of polyvinyl pyrrolidone, gelatin, gum arabic, polyvinyl alcohol, polyethylene glycol, N-methyl pyrrolidone, malic acid, sodium dodecylbenzene sulfonate and Tween.

[0017] In some possible embodiments, the acid substance includes one or more of sulfuric acid, nitric acid, oxalic acid and phosphoric acid.

[0018] In some possible embodiments, before preparing the reducing solution using the reducing agent, the acid substance, the dispersant and the nanocrystal seeds, the method further includes:

[0019] Adding a preset dispersant and a preset reducing agent into a preset silver salt solution to obtain a mixed solution;

[0020] The mixed solution is stirred, and after being stirred for a second preset time period, it is allowed to stand for a third preset time period, and the mixed solution after standing is centrifugally washed and dried to obtain nano crystal seeds.

[0021] In some possible embodiments, the solution temperature of the oxidizing solution and the reducing solution is 30-40° C. In some possible embodiments, the first preset time length is 1-10 seconds.

[0022] In a second aspect, an embodiment of the present application provides a flaky silver powder, which is prepared by the silver powder preparation method as described in any one of the above items.

[0023] The embodiment of the present application provides a method for preparing flaky silver powder and flaky silver powder, the preparation method comprising preparing a reducing solution using a reducing agent, an acid substance, a dispersant and nanocrystal seeds; preparing an oxidizing solution using silver nitrate and nitric acid; stirring the reducing solution, and adding the oxidizing solution to the reducing solution in a stirring state within a first preset time, and obtaining a silver powder suspension after the reaction is completed; centrifugally washing and drying the silver powder suspension to obtain flaky silver powder. The preparation method of flaky silver powder provided by the present application does not produce silver powder of other shapes during the preparation process, the prepared flaky silver powder has high purity and is simple to prepare, does not require complex subsequent treatment, and has a stable reaction that is conducive to scale-up and continuous mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] Figure 1 It is a schematic diagram of the process of preparing silver powder provided in the embodiment of the present application;

[0026] Figure 2 is an electron microscope scanning image of the silver powder in Example 1 of the present application;

[0027] Figure 3 This is an electron microscope scanning image of the silver powder in Example 2 of the present application;

[0028] Figure 4 Electron microscope scanning image of the silver powder in comparative example 1 of the present application. DETAILED DESCRIPTION

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] See also Figure 1 , Figure 1 The schematic diagram of the process of preparing the flaky silver powder provided in the embodiment of the present application is a schematic diagram of the process of preparing the flaky silver powder provided in the embodiment of the present application. The method of preparing the flaky silver powder may specifically include the following steps:

[0035] 101. Prepare a reducing solution using a reducing agent, an acid substance, a dispersant and nanocrystal seeds.

[0036] The silver powder preparation method provided in the present application can prepare flaky silver powder, which mainly uses a liquid phase reduction reaction to convert silver ions into silver powder particles, so it is necessary to separately prepare an oxidizing solution including silver ions and a reducing solution for reducing the silver ions in the oxidizing solution. Specifically, in the present application, a reducing agent, an acid substance, a dispersant and nanocrystal seeds are used to prepare a reducing solution, and silver nitrate and nitric acid are used to prepare an oxidizing solution, and then a redox reaction is carried out to obtain flaky silver powder.

[0037] In some embodiments, the preparation of a reducing solution using a reducing agent, an acidic substance, a dispersant and nanocrystal seeds may include the following steps: mixing a reducing agent with deionized water, and obtaining an initial reducing solution after the reducing agent is dissolved; adding an acidic substance, a dispersant and nanocrystal seeds to the initial reducing solution to obtain a reducing solution. For the preparation method of flaky silver powder provided in the present application, during the preparation of the silver powder, the potential of the entire solution system is lower than the isoelectric point, the surface of the silver ion carries a positive charge, and it is easy to adsorb anions, so an anionic surfactant can be selected as a dispersant. In addition, since non-ionic dispersants are not ionized in water and contain more hydrophilic groups, generally no hydrophobic groups; therefore, compared with other dispersants, non-ionic dispersants have better stability and water solubility, and are not easily affected by electrolytes and acidity and alkalinity in the entire solution system. In addition, non-ionic dispersants can easily establish hydrogen bonds and affinity with particles, and are relatively easy to adsorb on the surface of particles, which can provide both repulsion and steric hindrance, thereby playing a dispersing role; therefore, non-ionic dispersants are also selected in the preparation of silver powder.

[0038] More specifically, since silver particles are face-centered cubic metals, the specific surface energy of each crystal face of the silver particles is γ(111)<γ(100)<γ(110) in order. Different types of dispersants will selectively adsorb on different crystal faces, thereby changing the crystal face energy on these crystal faces, regulating the growth rate of the crystal faces, and achieving regulation of the morphology of silver particles. For example, polyvinyl pyrrolidone easily adsorbs on the (100) face and hinders the growth of the crystal face, and polyethylene glycol dispersants with a large number of hydroxyl groups easily adsorb on the (111) face to hinder the growth of the crystal face. The mechanism of action of polyvinyl pyrrolidone on silver powder is very complicated. On the one hand, since the strong polar groups of the lactam C=O or CN bond are negatively charged, the absolute value of the particle surface potential can be increased after adsorption, thereby increasing the electrostatic repulsion between particles, which is beneficial to dispersion. At the same time, the large molecular weight of polyvinyl pyrrolidone has a good steric hindrance, which is beneficial to dispersion. Therefore, in the actual preparation process, a certain amount of polyvinyl pyrrolidone needs to be added to improve dispersibility, but because it has an adsorption effect on specific crystal faces, it is necessary to use as little as possible while ensuring dispersibility to avoid the generation of irregular particles. Since the silver powder preparation method provided in this application needs to prepare flaky silver powder, and the growth mode of flaky silver powder is directional growth, it is necessary to regulate the amount of dispersant that has an adsorption effect on specific crystal faces to synthesize and prepare flaky silver powder. In order to prepare flaky silver powder with uniform morphology, this application mainly uses a combination of polyvinyl pyrrolidone (non-ionic dispersant) and anionic dispersant as a dispersant; in other embodiments, a combination of polyvinyl pyrrolidone, polyethylene glycol and anionic surfactant can be used as a dispersant. That is, the present application can select silver ion surfactant alone as a dispersant, or can select non-ionic dispersant alone; it can also select anionic surfactant and non-ionic dispersant to act together as a dispersant.

[0039] In an embodiment of the present application, the dispersant may include one or more of polyvinyl pyrrolidone, gelatin, gum arabic, polyvinyl alcohol, polyethylene glycol, N-methyl pyrrolidone, malic acid, sodium dodecylbenzene sulfonate and Tween. For example, the dispersant may include polyvinyl pyrrolidone, polyethylene glycol and malic acid. In the actual preparation process, the selection of the dispersant may be determined according to actual needs, and is not limited in the present application. In the above-mentioned embodiment, the concentration of the dispersant may be 1-50g / L, and may be 1g / L, 5g / L, 10g / L, 15g / L, 20g / L, 25g / L, 30g / L, 35g / L, 40g / L, 45g / L, 50g / L, etc. It should be noted that the dispersant described in the aforementioned embodiment is mainly aimed at the selection of the dispersant in the process of preparing the reducing solution.

[0040] The reducing agent in the present application can be 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 10-100 g / L, more specifically, 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, etc.

[0041] For nanocrystal seeds, nanocrystal seeds provide a large number of nucleation sites, so that free dispersed silver ions can crystallize around nanocrystal seeds to obtain silver powder particles; and the selection of nanocrystal seeds of different sizes or specific types can also control the particle size and morphology of silver powder. In some embodiments, a preset dispersant and a preset reducing agent can be added to a preset silver salt solution to obtain a mixed solution; the mixed solution can be stirred, and after stirring for a second preset time, it is allowed to stand for a third preset time, and the mixed solution after standing is centrifuged and washed and dried to obtain nanocrystal seeds. Specifically, tannic acid can be used as a dispersant and hydrazine hydrate can be used as a reducing agent, and both can be added to a silver nitrate solution to obtain a mixed solution; the mixed solution can be stirred at 20°C for one hour, and after standing for 20 hours, the mixed solution can be centrifuged and washed and dried to obtain nanocrystal seeds. In the embodiment of the present application, the silver salt solution can be a silver nitrate solution, the concentration of the silver nitrate solution can be 0.2mmol / L, the molar ratio of the dispersant to the silver salt is 1:0.2; the molar ratio of the reducing agent to the silver salt is 1:0.4. In the embodiments of the present application, the amount of nanocrystal seeds used in preparing the reducing solution can be 0.1-100g, more specifically, it can be 0.1g, 5g, 10g, 20g, 30g, 40g, 50g, 60g, 70g, 80g, 90g, 100g, etc.

[0042] Acidic substances are additionally added to the reducing solution in the present application. The added acidic substances can increase the concentration of hydrogen ions in the reducing solution and the reaction solution obtained by subsequent mixing, inhibit the reduction of silver ions, thereby increasing the growth time of silver ions, increasing the growth time of silver powder in the entire reaction system, and facilitating the growth of silver powder particles into a flaky structure with uniform morphology. That is, the additionally added acidic substances are conducive to the final reaction product to form a flaky silver powder with uniform morphology. The acidic substances in the present application include one or more of sulfuric acid, nitric acid, oxalic acid and phosphoric acid. After the acidic substances are added to the initial reducing solution, the pH of the resulting reducing solution is 1-7. In an embodiment of the present application, the concentration of the acid substance can be 0.1-50 g / L, more specifically, it can be 0.1 g / L, 0.5 g / L, 1 g / L, 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, etc.

[0043] 102. Prepare oxidizing solution using silver nitrate and nitric acid.

[0044] The use of silver nitrate and nitric acid to prepare an oxidizing solution may include: mixing silver nitrate with deionized water, and obtaining an initial oxidizing solution after the silver nitrate is dissolved; and adding nitric acid to the initial oxidizing solution to obtain an oxidizing solution. The added nitric acid can not only adjust the pH value of the oxidizing solution, but also further enhance the oxidizing property of the oxidizing solution for subsequent redox reactions. The concentration of silver nitrate in the embodiments of the present application is 1-100 g / L, for example, 1 g / L, or 10 g / L, or 20 g / L, or 30 g / L, or 40 g / L, or 50 g / L, or 60 g / L, or 70 g / L, or 80 g / L, or 90 g / L, or 100 g / L; and the concentration of nitric acid is 0.1-50 g / L, for example, 0.1 g / L, or 1 g / L, or 5 g / L, or 10 g / L, or 15 g / L, or 20 g / L, or 25 g / L, or 30 g / L, or 35 g / L, or 40 g / L, or 45 g / L, or 50 g / L.

[0045] In the process of preparing the oxidizing solution and the reducing solution, it is necessary to ensure that the solution temperature of the oxidizing solution and the reducing solution is in the range of 30-40°C; for example, the temperature of the two solutions is controlled to be 30°C, or 32°C, or 35°C, or 37°C, or 40°C.

[0046] 103. Stir the reducing solution, and add the oxidizing solution into the reducing solution in a stirring state within a first preset time, and obtain a silver powder suspension after the reaction is completed.

[0047] 104. The silver powder suspension is centrifugally washed and dried to obtain flaky silver powder.

[0048] After the oxidizing solution and the reducing solution are prepared separately, the two need to be mixed to perform a liquid phase reduction reaction to obtain flaky silver powder; specifically, the reducing solution can be stirred at a speed of 100-1000r / min, and then the oxidizing solution is added to the reducing solution in a stirring state, and the reaction is determined to be completed after a period of reaction to obtain a silver powder suspension. In the present application, it is usually necessary to add the oxidizing solution to the reducing solution in a stirring state within a first preset time, and the first preset time can be 1-10 seconds; more specifically, it can be 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, 6 seconds, 7 seconds, 8 seconds, 9 seconds, 10 seconds, etc. The stirring speed of the reducing solution can be 100r / min, 200r / min, 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min, 900r / min, 1000r / min, etc. Usually, after ten minutes of reaction, the reaction can be considered to be complete. At this time, the obtained silver powder suspension includes dispersed and suspended silver powder, and the silver powder needs to be separated from the silver powder suspension. Specifically, the silver powder suspension can be centrifuged and rinsed in a high-speed centrifuge until the conductivity of the wastewater flowing out of the high-speed centrifuge is ≦20us / cm, and then 1-100L of ethanol is used to re-centrifuge the silver powder in the high-speed centrifuge until no liquid flows out of the high-speed centrifuge, and then the silver powder is dried to obtain the final flaky silver powder.

[0049] The preparation method of flaky silver powder provided in the present application can prepare flaky silver powder simply and quickly, avoids pollution and damage to the silver powder during the grinding process, and does not produce silver powder of other shapes. The silver powder has high purity and does not require complex subsequent treatment. The reaction is stable, which is conducive to scale-up and continuous mass production.

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

[0051] Embodiment 1:

[0052] 1.61 kg of ascorbic acid was fully mixed with 15 kg of deionized water, and the initial reduction solution was obtained after the ascorbic acid was completely dissolved. 103 g of nitric acid, 40 g of malic acid, 52 g of polyvinyl pyrrolidone and 122 g of polyethylene glycol were added to the initial reduction solution, and 15 g of nanocrystal seeds were added after they were fully dissolved. The reduction solution was obtained after all the added substances were dissolved. In the process of preparing the reduction solution, the temperature of the solution was kept at 30 ° C. 2.76 kg of silver nitrate was mixed with 28 kg of deionized water, and the initial oxidation solution was obtained after the silver nitrate was fully dissolved. 84 g of nitric acid was added to the initial oxidation solution, and the oxidation solution was obtained after sufficient stirring. In the process of preparing the oxidation solution, the temperature of the solution was also kept at 30 ° C. Then the reduction solution was controlled to maintain a state of 600 r / min, and in this state, the oxidation solution was completely added to the rotating reduction solution within 2.5 seconds; after the reaction was continued for ten minutes, a mixed reaction solution was obtained, and the mixed reaction solution at this time contained silver powder particles. Then, the mixed reaction liquid is centrifuged and cleaned using a high-speed centrifuge until the conductivity of the wastewater flowing out of the centrifuge is 19.02us / cm, and then the silver powder in the centrifuge is rinsed with 20L of ethanol until no liquid flows out of the centrifuge. The silver powder rinsed with ethanol needs to be placed in an oven at 70°C for 3 hours to obtain the final flaky silver powder after drying.

[0053] Embodiment 2:

[0054] 1.61 kg of ascorbic acid was fully mixed with 15 kg of deionized water, and the initial reducing solution was obtained after the ascorbic acid was completely dissolved. 103 g of nitric acid, 40 g of malic acid, 52 g of polyvinyl pyrrolidone and 122 g of polyethylene glycol were added to the initial reducing solution, and 15 g of nanocrystal seeds were added after they were fully dissolved. The reducing solution was obtained after all the added substances were dissolved. In the process of preparing the reducing solution, the temperature of the solution was kept at 30 ° C. 2.76 kg of silver nitrate was mixed with 28 kg of deionized water, and the initial oxidation solution was obtained after the silver nitrate was fully dissolved. 84 g of nitric acid was added to the initial oxidation solution, and the oxidation solution was obtained after sufficient stirring. In the process of preparing the oxidation solution, the temperature of the solution was also kept at 40 ° C. Then the reducing solution was controlled to maintain a state of 600 r / min, and in this state, the oxidation solution was completely added to the rotating reducing solution within 2.5 seconds; after the reaction was continued for ten minutes, a mixed reaction solution was obtained, and the mixed reaction solution at this time contained silver powder particles. Then, the mixed reaction liquid is centrifuged and cleaned using a high-speed centrifuge until the conductivity of the wastewater flowing out of the centrifuge is 19.02us / cm, and then the silver powder in the centrifuge is rinsed with 20L of ethanol until no liquid flows out of the centrifuge. The silver powder rinsed with ethanol needs to be placed in an oven at 70°C for 3 hours to obtain the final flaky silver powder after drying.

[0055] Comparative Example 1:

[0056] 1.61 kg of ascorbic acid was fully mixed with 15 kg of deionized water, and the initial reduction solution was obtained after the ascorbic acid was completely dissolved. 103 g of nitric acid, 40 g of malic acid, 26 g of polyvinyl pyrrolidone and 122 g of polyethylene glycol were added to the initial reduction solution, and 15 g of nanocrystal seeds were added after they were fully dissolved. The reduction solution was obtained after all the added substances were dissolved. In the process of preparing the reduction solution, the temperature of the solution was kept at 30 ° C. 2.76 kg of silver nitrate was mixed with 28 kg of deionized water, and the initial oxidation solution was obtained after the silver nitrate was fully dissolved. 84 g of nitric acid was added to the initial oxidation solution, and the oxidation solution was obtained after sufficient stirring. In the process of preparing the oxidation solution, the temperature of the solution was also kept at 30 ° C. Then the reduction solution was controlled to maintain a state of 600 r / min, and in this state, the oxidation solution was completely added to the rotating reduction solution within 2.5 seconds; after the reaction was continued for ten minutes, a mixed reaction solution was obtained, and the mixed reaction solution at this time contained silver powder particles. Then, the mixed reaction liquid is centrifuged and cleaned using a high-speed centrifuge until the conductivity of the wastewater flowing out of the centrifuge is 19.02us / cm, and then the silver powder in the centrifuge is rinsed with 20L of ethanol until no liquid flows out of the centrifuge. The silver powder rinsed with ethanol needs to be placed in an oven at 70°C for 3 hours to obtain the final flaky silver powder after drying.

[0057] like Figure 2 As shown, it is the electron microscope scanning image of the silver powder of Example 1 of the present application, Figure 3 This is a scanning electron microscope image of the silver powder in Example 2 of the present application. Figure 4 This is an electron microscope scanning image of the silver powder of Comparative Example 1 of the present application. Compared with Example 1, only the solution temperature of the oxidizing solution and the reducing solution was changed in Example 2; however, the morphology of the flaky silver powder prepared in Example 1 and Example 2 is basically the same, which effectively proves the stability of the preparation method of the flaky silver powder provided in the present application, and the loose conditions of the preparation scheme are conducive to large-scale production. Compared with Example 1, Comparative Example 1 only reduces the content of polyvinyl pyrrolidone in the reducing solution, that is, reduces the content of the dispersant; as the content of the dispersant decreases, silver ions are more likely to agglomerate into a sphere, which is not conducive to the growth of flaky silver powder. Therefore, in this application, it is necessary to determine the concentration of the dispersant according to the actual choice of the dispersant to ensure that other irregular silver powders other than flaky silver powder will not be produced.

[0058] The present application also provides a flaky silver powder, which is prepared by the preparation method of the flaky 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 herein.

[0059] 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.

[0060] 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 flaky silver powder, characterized in that: include: preparing a reducing solution by using a reducing agent, an acid substance, a dispersant and nanocrystalline seeds; Prepare an oxidizing solution using silver nitrate and nitric acid; Stirring the reducing solution, and adding the oxidizing solution into the reducing solution in a stirring state within a first preset time, and obtaining a silver powder suspension after the reaction is completed; The silver powder suspension is centrifugally washed and dried to obtain flaky silver powder.

2. The method for preparing flaky silver powder according to claim 1, characterized in that: The method of preparing the reducing solution by using a reducing agent, an acid substance, a dispersant and nanocrystalline seeds comprises: Mixing the reducing agent with deionized water to obtain an initial reducing solution after the reducing agent is dissolved; The acid substance, the dispersant and the nano-crystal seeds are added to the initial reducing solution to obtain the reducing solution.

3. The method for preparing flaky silver powder according to claim 1, characterized in that: The method of preparing the oxidizing solution by using silver nitrate and nitric acid comprises: Mixing silver nitrate with deionized water to obtain an initial oxidation solution after the silver nitrate is dissolved; Nitric acid is added to the initial oxidation solution to obtain the oxidation solution.

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

5. The method for preparing flaky silver powder according to claim 1, characterized in that: The dispersant includes one or more of polyvinyl pyrrolidone, gelatin, gum arabic, polyvinyl alcohol, polyethylene glycol, N-methyl pyrrolidone, malic acid, sodium dodecylbenzene sulfonate and Tween.

6. The method for preparing flaky silver powder according to claim 1, characterized in that: The acid substance includes one or more of sulfuric acid, nitric acid, oxalic acid and phosphoric acid.

7. The method for preparing flaky silver powder according to claim 1, characterized in that: Before preparing the reducing solution by using the reducing agent, the acid substance, the dispersant and the nanocrystalline seeds, the method further comprises: Adding a preset dispersant and a preset reducing agent into a preset silver salt solution to obtain a mixed solution; The mixed solution is stirred, and after being stirred for a second preset time period, it is allowed to stand for a third preset time period, and the mixed solution after standing is centrifugally washed and dried to obtain nano crystal seeds.

8. The method for preparing flaky silver powder according to claim 1, characterized in that: The solution temperature of the oxidizing solution and the reducing solution is 30-40°C.

9. The method for preparing flaky silver powder according to claim 1, characterized in that: The first preset time length is 1-10 seconds.

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

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