Highly filled silver powder and method for making same

Abstract

The application provides high-filling silver powder and a preparation method thereof, and belongs to the field of metal powder, wherein a nano-silver solution is prepared, a dispersing agent is mixed with a first reducing agent to obtain a mixed solution, the nano-silver solution is mixed with the mixed solution under constant-temperature stirring to obtain a bottom solution, a second reducing agent solution and a silver nitrate solution are respectively prepared, and the second reducing agent solution and the silver nitrate solution are synchronously added to the bottom solution under constant-temperature stirring, a silver powder solution is obtained through reaction, and the silver powder solution is subjected to washing, solid-liquid separation, drying and depolymerization and shaping treatment to obtain the high-filling silver powder. The application controls the particle size and the added amount of the nano-silver, controls the heterogeneous nucleation and growth sites of silver ions, inhibits the formation of multi-stage dendrites, realizes the controllable preparation of large-size spherical silver powder, optimizes the surface charge and the steric hindrance effect of silver particles through the surface adsorption of the dispersing agent, reduces the agglomeration phenomenon of the silver powder in the growth process, and simultaneously endows the silver powder with excellent fluidity.

Description

Technical Field

[0001] This invention relates to the field of metal powder technology, specifically to a highly filled silver powder and its preparation method. Background Technology

[0002] With the rapid development of electronic components towards miniaturization, high integration, and high frequency, the performance requirements for electronic functional materials such as conductive adhesives, thermally conductive adhesives, and electromagnetic shielding materials are increasing. Silver powder, due to its excellent electrical conductivity, thermal conductivity, and chemical stability, has become a key functional filler in these fields. However, traditional silver powder preparation methods, such as chemical reduction, ball milling, or atomization, still face significant technical bottlenecks in terms of particle size control, tap density, and filling performance. In the prior art, patent CN116890110A discloses a low-temperature sinterable micron-sized silver powder and its preparation method. The micron-sized silver powder described in this patent has a nanospherical protrusion structure on its surface, with a specific surface area of ​​6-18 m². 2 / g. Although it has a high specific surface area, in highly filled systems, the protruding structure between particles can lead to poor packing density. Furthermore, the high specific surface area is accompanied by high oil absorption, resulting in a decrease in the system's filler content. When the filler content is too high, the colloidal viscosity increases sharply, the processing performance deteriorates, and the increased porosity leads to a decrease in the continuity of the conductive / thermal conductive network.

[0003] In recent years, large-size silver powder (>5μm) has attracted much attention due to its ability to reduce interfacial contact resistance and increase tap density. However, its preparation technology still faces challenges: conventional chemical methods can increase particle size by reducing the reduction rate, but this easily leads to the formation of multi-level dendritic structures, resulting in insufficient tap density; high-temperature annealing densification can improve density, but it can cause problems such as particle sintering and uncontrollable particle size; although atomization can prepare large-size silver powder (10~150μm), the process has high energy consumption, poor particle size uniformity, and the yield of small-size silver powder is less than 10%, which greatly increases costs. In addition, existing large-size silver powder preparation processes mostly rely on complex surfactant systems or special equipment (such as ultrasonic assistance, microreactors, etc.), resulting in high production costs and difficulty in large-scale production.

[0004] In view of this, it is necessary to design an improved high-filling silver powder and its preparation method to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a high-filling silver powder and its preparation method, aiming to solve the technical problems of insufficient tap density, uncontrollable particle size, and high cost of large-size silver powder caused by existing preparation methods.

[0006] In a first aspect, this application provides a method for preparing highly filled silver powder, comprising the following steps:

[0007] S1. Prepare nano-silver solution;

[0008] S2. Mix the dispersant with the first reducing agent to obtain a mixed solution;

[0009] S3. Under constant temperature and stirring conditions, the nano-silver solution is mixed with the mixed solution to obtain the base liquid;

[0010] S4. Prepare the second reducing agent solution and silver nitrate solution separately;

[0011] S5. Under constant temperature and stirring conditions, the second reducing agent solution and the silver nitrate solution are simultaneously added to the bottom liquid, and a silver powder solution is obtained through reaction;

[0012] S6. The silver powder solution is washed, separated into solid and liquid phases, dried, and depolymerized and shaped to obtain highly filled silver powder.

[0013] As a further improvement of this application, in step S1, the content of nano-silver in the nano-silver solution is 1*10 -7 ~1*10 -6 g / L, the particle size of nano-silver is 10~40nm.

[0014] As a further improvement of this application, in step S2, the dispersant is polyvinylpyrrolidone K30.

[0015] As a further improvement of this application, in step S2, the first reducing agent is one or more of sodium borohydride, triethanolamine, hydrazine hydrate, hydroquinone, hydroxylamine, ascorbic acid, sodium citrate, hydrogen peroxide, hydrazine sulfate, glucose, formaldehyde, and potassium iodide.

[0016] As a further improvement of this application, the mass ratio of the first reducing agent to the silver nitrate in the silver nitrate solution is 1:(50~200); the mass ratio of the dispersant to the silver nitrate in the silver nitrate solution is 1:(10~200).

[0017] As a further improvement of this application, in step S4, the second reducing agent is one or more of sodium borohydride, triethanolamine, hydrazine hydrate, hydroquinone, hydroxylamine, ascorbic acid, sodium citrate, hydrogen peroxide, hydrazine sulfate, glucose, formaldehyde, and potassium iodide.

[0018] As a further improvement of this application, the mass ratio of the second reducing agent to the silver nitrate in the silver nitrate solution is (0.5~0.6):1.

[0019] As a further improvement to this application, in steps S3 and S5, the constant temperature is 20~25℃.

[0020] As a further improvement of this application, in step S5, the feeding rate of the second reducing agent solution and the silver nitrate solution is 2~6 L / min.

[0021] Secondly, embodiments of this application provide a highly filled silver powder, prepared by the method described in the first aspect, wherein the highly filled silver powder has an average particle size of 5-7 μm and a tap density > 6.4 g / cm³. 3 The angle of repose is less than 35°.

[0022] The beneficial effects of this application are as follows:

[0023] This application provides a highly filled silver powder and its preparation method. A nano-silver solution is prepared by mixing a dispersant with a first reducing agent to obtain a mixed solution. Under constant temperature and stirring, the nano-silver solution is mixed with the mixed solution to obtain a base liquid. A second reducing agent solution and a silver nitrate solution are prepared separately. Under constant temperature and stirring, the second reducing agent solution and the silver nitrate solution are simultaneously added to the base liquid, and a silver powder solution is obtained after reaction. The silver powder solution is then washed, subjected to solid-liquid separation, dried, and deagglomerated and shaped to obtain highly filled silver powder. This application controls the heterogeneous nucleation and growth sites of silver ions by controlling the particle size and amount of nano-silver, inhibiting the formation of multi-level dendrites, and achieving controllable preparation of large-size spherical silver powder. Polyvinylpyrrolidone K30 (PVP K30) is introduced as a dispersant, and its surface adsorption optimizes the surface charge and steric hindrance effect of silver particles, reducing the agglomeration of silver powder during growth. By leveraging the size effect of the nano-silver crystal nuclei and the combined effect of the dispersant, silver particles are promoted to grow in a close-packed manner, achieving a breakthrough in the chemical preparation of large-size, high-tap-density silver powder, while also imparting excellent flowability to the silver powder.

[0024] This application utilizes nano-silver as a seed crystal. By precisely controlling the reaction conditions, especially by employing a strategy of simultaneously adding a second reducing agent and silver nitrate, silver is induced to grow preferentially and uniformly on the seed crystal, while inhibiting the generation of a large number of new crystal nuclei. This results in silver powder with a narrow particle size distribution and good dispersibility. Finally, through meticulous post-processing, the purity, dispersibility, and morphology of the silver powder are ensured, making it suitable for high-filling applications.

[0025] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0027] Figure 1 This is an electron microscope image of the highly filled silver powder prepared in Example 1 of this application;

[0028] Figure 2 Electron micrograph of the highly filled silver powder prepared in Comparative Example 1;

[0029] Figure 3 Electron micrograph of the highly filled silver powder prepared in Comparative Example 2;

[0030] Figure 4 Electron micrograph of the highly filled silver powder prepared for Comparative Example 3. Detailed Implementation

[0031] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0033] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0034] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0035] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0036] Large-size silver powder (>5μm) has attracted much attention due to its ability to reduce interfacial contact resistance and increase tap density, but its preparation technology still faces challenges: conventional chemical methods can increase particle size by reducing the reduction rate, but this easily leads to the formation of multi-level dendritic structures, resulting in insufficient tap density; high-temperature annealing densification treatment can improve density, but it can cause problems such as particle sintering and uncontrollable particle size; although atomization can prepare large-size silver powder (10~150μm), the process has high energy consumption, poor particle size uniformity, and the yield of small-size silver powder is less than 10%, which greatly increases costs. In addition, existing large-size silver powder preparation processes mostly rely on complex surfactant systems or special equipment (such as ultrasonic assistance, microreactors, etc.), resulting in high production costs and difficulty in large-scale production.

[0037] To address the technical problems of insufficient tap density, uncontrollable particle size, and high cost of large-size silver powder caused by existing preparation methods, this application provides a highly filled silver powder and its preparation method. In this method, by controlling the particle size and amount of silver nanoparticles, the heterogeneous nucleation and growth sites of silver ions are regulated, and the formation of multi-level dendrites is suppressed, thereby achieving controllable preparation of large-size spherical silver powder.

[0038] In a first aspect, embodiments of this application provide a method for preparing highly filled silver powder, comprising the following steps:

[0039] S1. Prepare nano-silver solution;

[0040] S2. Mix the dispersant with the first reducing agent to obtain a mixed solution;

[0041] S3. Under constant temperature and stirring, the nano silver solution is mixed with the mixed solution to obtain the base liquid;

[0042] S4. Prepare the second reducing agent solution and silver nitrate solution separately;

[0043] S5. Under constant temperature and stirring conditions, the second reducing agent solution and the silver nitrate solution are simultaneously added to the bottom liquid, and a silver powder solution is obtained through reaction;

[0044] S6. The silver powder solution is washed, separated into solid and liquid, dried and depolymerized and shaped to obtain highly filled silver powder.

[0045] In the technical solution of this application embodiment, nanoscale silver particles are first prepared as initial crystal nuclei. Compared with generating crystal nuclei from scratch, using pre-prepared nano-silver seeds can significantly reduce the nucleation energy barrier and make it easier to control the subsequent silver deposition direction and growth rate, thereby obtaining a more uniform final silver powder with more controllable particle size. The dispersant is mixed with the first reducing agent and is pre-existing in the first reducing agent solution to prevent the nano-silver seeds and subsequently generated silver particles from agglomerating. The dispersant adsorbs on the particle surface, forming steric hindrance or electrostatic repulsion, keeping the particles in a dispersed state, providing conditions for subsequent uniform growth, and is also the key to achieving a high filling rate. The nano-silver solution and the mixed solution are mixed under constant temperature stirring to form a uniform system containing seeds and reaction precursors. Constant temperature stirring ensures uniform mixing of reactants, and the constant temperature facilitates the controllability of subsequent reactions, preparing a homogeneous reaction precursor solution for rapid and simultaneous reactions. The second reducing agent is added simultaneously with silver nitrate to the base solution. The second reducing agent reduces silver ions in silver nitrate to silver atoms. These silver atoms preferentially deposit and grow on the surface of pre-existing silver nanoparticles. Simultaneous addition ensures the coexistence and relatively constant concentration of silver ions and the reducing agent in the base solution, avoiding localized over-concentration or under-concentration. This contributes to uniform and controllable nucleation and growth, and compared to stepwise addition, it better controls the final particle size distribution. Due to the presence of a large number of silver nanoparticles, the newly reduced... Silver atoms preferentially deposit on the seed crystal surface, causing the seed crystal to grow continuously rather than generating a large number of new independent crystal nuclei. The final product is silver particles of relatively uniform size, grown from the initial seed crystal. The resulting silver powder solution is washed to remove residual ions, unreacted substances, dispersants, and other impurities from the reaction system. Solid-liquid separation separates the generated silver powder from the solution. Drying removes moisture or solvent, yielding dry powder. During washing and drying, silver powder particles may agglomerate. Deagglomeration treatment breaks up these agglomerates, restoring the particles to a smaller, more dispersed state. Air jet milling is used for deagglomeration and shaping, resulting in more regular, spherical morphologies that are more conducive to filling. Good dispersibility and regular morphology contribute to achieving high filling rates in the matrix while maintaining good electrical conductivity.

[0046] Furthermore, in some embodiments, in step S1, the content of nano-silver in the nano-silver solution is 1*102 -7 ~1*10 -6 g / L, the particle size of nano-silver is 10~40nm.

[0047] In the technical solution of this application embodiment, nano-silver seeds are introduced into the reaction system. By controlling the particle size and amount of nano-silver, the heterogeneous nucleation and growth sites of silver ions are regulated, suppressing the formation of multi-level dendrites. Due to the small number of seeds, the amount of silver deposited by each seed is relatively large, which is conducive to the growth of larger, independent silver particles and avoids excessive nucleation or agglomeration. If the concentration of nano-silver is too low, there may be too few seeds, resulting in insufficient final silver powder yield or excessively large particle size and wide distribution. If the concentration is too high, there may be too many seeds, which may lead to excessively small final particle size and wide distribution, or even increase the risk of agglomeration, which is not conducive to high filling. Nano-sized silver particles help to provide a large specific surface area, providing abundant reaction sites for subsequent silver nitrate reduction and silver atom deposition, resulting in high reaction efficiency. At the same time, the suitable particle size range ensures that the seeds themselves are relatively uniform micro-particles, which helps to make the subsequent silver growth on them more uniform and facilitates the control of the particle size distribution of the final silver powder.

[0048] Furthermore, in some embodiments, in step S2, the dispersant is polyvinylpyrrolidone K30.

[0049] In the technical solution of this application embodiment, polyvinylpyrrolidone K30 has good water solubility and thermal stability. Its molecular structure contains multiple polar groups, which can coordinate with metal ions or particle surfaces. At the same time, its long chain structure can fully extend in solution to form a steric hindrance effect, thereby effectively preventing particle aggregation.

[0050] Furthermore, in some embodiments, in step S2, the first reducing agent is one or more of sodium borohydride, triethanolamine, hydrazine hydrate, hydroquinone, hydroxylamine, ascorbic acid, sodium citrate, hydrogen peroxide, hydrazine sulfate, glucose, formaldehyde, and potassium iodide.

[0051] In the technical solution of this application embodiment, the reducing agent provides electrons to reduce silver ions to metallic silver, thereby promoting the growth of silver particles. By combining the characteristics of different reducing agents, the reaction conditions can be optimized to achieve efficient and controllable silver powder preparation.

[0052] Furthermore, in some embodiments, the mass ratio of the first reducing agent to silver nitrate in the silver nitrate solution is 1:(50~200); the mass ratio of the dispersant to silver nitrate in the silver nitrate solution is 1:(10~200).

[0053] In the technical solution of this application embodiment, the ratio of reducing agent to silver nitrate can effectively control the rate of reduction reaction and avoid an overly vigorous reaction. If there is too much reducing agent, it will lead to Ag... +Instantaneous reduction results in a large number of tiny crystal nuclei, ultimately leading to excessively fine and unevenly distributed silver powder particles, and even violent exothermic reactions, affecting the stability of the system. An appropriate ratio of reducing agent helps silver atoms preferentially deposit and grow on pre-existing nano-silver seeds, rather than forming a large number of new nuclei, thus facilitating the formation of larger and more uniformly distributed silver particles. The ratio range of dispersant to silver nitrate ensures that enough dispersant molecules can cover the surface of newly formed silver particles, helping to maintain the homogeneity of the reaction system, preventing concentration gradients caused by particle sedimentation or agglomeration, and making the reaction more uniform and controllable.

[0054] Further, in some embodiments, in step S4, the second reducing agent is one or more selected from sodium borohydride, triethanolamine, hydrazine hydrate, hydroquinone, hydroxylamine, ascorbic acid, sodium citrate, hydrogen peroxide, hydrazine sulfate, glucose, formaldehyde, and potassium iodide. The mass ratio of the second reducing agent to silver nitrate in the silver nitrate solution is (0.5~0.6):1.

[0055] In the technical solutions of this application embodiment, selecting multiple reducing agents helps to flexibly control the morphology, size and dispersibility of silver powder, thereby meeting the application requirements of high-filling silver powder. By reasonably selecting the type and concentration of reducing agent, the performance of silver powder can be optimized so that it reaches the best state in terms of conductivity, dispersibility and stability. Excessive second reducing agent may lead to an excessively fast reduction rate, which may cause particle agglomeration or irregular morphology.

[0056] Furthermore, in some embodiments, the constant temperature in steps S3 and S5 is 20~25°C.

[0057] In the technical solution of this application embodiment, the temperature is controlled at room temperature of 20~25℃, which provides a stable, controllable, safe and economical reaction environment. This helps to ensure that the reaction proceeds as expected, reduce side reactions, control the growth process of silver particles, and finally obtain high-performance silver powder that meets the requirements of high-filling applications.

[0058] Furthermore, in some embodiments, in step S5, the feeding rate of the second reducing agent solution and the silver nitrate solution is 2~6 L / min.

[0059] In the technical solution of this application embodiment, the reaction rate is controlled by controlling the mixing rate of the reactants to prevent the reaction from being too violent and to ensure that the reaction proceeds smoothly, thereby obtaining silver powder with uniform particle size distribution, regular morphology and good dispersibility.

[0060] Secondly, embodiments of this application provide a highly filled silver powder, prepared by the method described in the first aspect, wherein the average particle size of the highly filled silver powder is 5-7 μm and the tap density is >6.4 g / cm³. 3 The angle of repose is less than 35°.

[0061] In the technical solution of this application embodiment, by controlling the seed crystal, selecting a suitable reducing agent, controlling the reaction temperature and feeding rate, the morphology and dispersibility of silver powder are optimized, and irregular shapes and large particle agglomerates are reduced, thereby obtaining silver powder with large size, high tap density and good flowability.

[0062] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0063] Example 1

[0064] This embodiment provides a method for preparing highly filled silver powder, including the following steps:

[0065] S1. The concentration is prepared as 5*10 -7 g / L nano silver solution;

[0066] S2. Weigh 200g of polyvinylpyrrolidone K30 and 100g of ascorbic acid, add them to 50L of pure water to dissolve and prepare a mixed solution;

[0067] S3. Under stirring conditions of 25℃ and 350r / min, add 20mL of nano silver solution to the mixed solution to obtain the base solution;

[0068] S4. Weigh 5 kg of silver nitrate and dissolve it in 20 L of pure water; weigh 2.5 kg of ascorbic acid and dissolve it in 20 L of pure water.

[0069] S5. Under stirring conditions of 25℃ and 350r / min, ascorbic acid solution and silver nitrate solution are added to the bottom liquid simultaneously at a feeding rate of 3L / min. After the feeding is completed, a silver powder solution is obtained.

[0070] S6. The silver powder solution was washed, subjected to solid-liquid separation, dried, and depolymerized and shaped to obtain highly filled silver powder, the scanning electron microscope image of which is shown below. Figure 1 As shown, the silver powder particles exhibit a relatively regular spherical or near-spherical shape, which helps to increase the tap density of the silver powder; the particle surface is relatively smooth, without obvious sharp edges and corners, which helps to reduce friction between particles, improve the flowability of the powder, and thus reduce the angle of repose.

[0071] Example 2

[0072] This embodiment provides a method for preparing highly filled silver powder. Compared with Example 1, the only difference is that in step S1, the concentration of added nano-silver is 1*10. -7 g / L, and the remaining experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0073] Example 3

[0074] This embodiment provides a method for preparing highly filled silver powder. Compared with Example 1, the only difference is that in step S1, the concentration of added nano-silver is 1*10. -6 g / L, and the remaining experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0075] Example 4

[0076] This embodiment provides a method for preparing highly filled silver powder. Compared with Example 1, the only difference is that in step S2, the amount of polyvinylpyrrolidone K30 used is 500g. The other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0077] Comparative Example 1

[0078] Comparative Example 1 provides a method for preparing highly filled silver powder. Compared to Example 1, the only difference is that in step S1, the particle size of the added silver nanoparticles is 5-20 nm. The remaining experimental parameters and conditions are basically the same as in Example 1 and will not be repeated here. The resulting scanning electron microscope image of the silver powder is shown below. Figure 2 As shown, it can be seen that smaller initial seed crystals result in smaller final silver powder particle sizes.

[0079] Comparative Example 2

[0080] Comparative Example 2 provides a method for preparing highly filled silver powder. Compared with Example 1, the only difference is that in step S1, the concentration of added nano-silver is 1*10⁻⁶. -5 The concentration was g / L, and the remaining experimental parameters and conditions were basically the same as in Example 1, and will not be repeated here. The obtained scanning electron microscope image of the silver powder is shown below. Figure 3 As shown, the increased concentration of nano-silver leads to the appearance of a large number of fine particles in the final product, resulting in poor overall uniformity.

[0081] Comparative Example 3

[0082] Comparative Example 3 provides a method for preparing highly filled silver powder. Compared to Example 1, the only difference is that in step S2, 1 kg of polyvinylpyrrolidone K30 is added. The remaining experimental parameters and conditions are basically the same as in Example 1 and will not be repeated here. The resulting scanning electron microscope image of the silver powder is shown below. Figure 4As shown, excessive dispersant can interfere with the normal growth process of silver powder particles, resulting in silver powder particles with irregular shapes, rough surfaces, and uneven size distribution.

[0083] The silver powders prepared in Example 1 and Comparative Examples 1-3 were tested for relevant parameters, and the results are shown in the table below.

[0084] Table 1. Detection results of silver powder parameters in Example 1 and Comparative Examples 1-3

[0085]

[0086] As shown in Table 1, the silver powder prepared by the method of this application has a relatively uniform particle size and a good morphological structure. Furthermore, the silver powder has a high tap density and good interparticle flowability. The silver powder prepared in Comparative Examples 1 and 2 has a smaller particle size and poorer flowability. The silver powder prepared in Comparative Example 3 has a wide particle size distribution, irregular morphology, low tap density, and poor flowability.

[0087] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing highly filled silver powder, characterized in that, Includes the following steps: S1. Prepare nano-silver solution; The nano-silver content in the nano-silver solution is 1*10 -7 ~1*10 -6 g / L, the particle size of nano silver is 10~40nm; S2. Mix the dispersant with the first reducing agent to obtain a mixed solution; S3. Under constant temperature and stirring conditions, the nano-silver solution is mixed with the mixed solution to obtain the base liquid; S4. Prepare the second reducing agent solution and silver nitrate solution separately; S5. Under constant temperature and stirring conditions, the second reducing agent solution and the silver nitrate solution are simultaneously added to the bottom liquid, and a silver powder solution is obtained through reaction; S6. The silver powder solution is washed, separated from solids and liquids, dried and depolymerized and shaped to obtain highly filled silver powder; Wherein, the mass ratio of the first reducing agent to the silver nitrate in the silver nitrate solution is 1:(50~200); the mass ratio of the dispersant to the silver nitrate in the silver nitrate solution is 1:(10~200).

2. The method for preparing highly filled silver powder according to claim 1, characterized in that, In step S2, the dispersant is polyvinylpyrrolidone K30.

3. The method for preparing highly filled silver powder according to claim 1, characterized in that, In step S2, the first reducing agent is one or more of sodium borohydride, triethanolamine, hydrazine hydrate, hydroquinone, hydroxylamine, ascorbic acid, sodium citrate, hydrogen peroxide, hydrazine sulfate, glucose, formaldehyde, and potassium iodide.

4. The method for preparing highly filled silver powder according to claim 1, characterized in that, In step S4, the second reducing agent is one or more of the following: sodium borohydride, triethanolamine, hydrazine hydrate, hydroquinone, hydroxylamine, ascorbic acid, sodium citrate, hydrogen peroxide, hydrazine sulfate, glucose, formaldehyde, and potassium iodide.

5. The method for preparing highly filled silver powder according to claim 4, characterized in that, The mass ratio of the second reducing agent to the silver nitrate in the silver nitrate solution is (0.5~0.6):

1.

6. The method for preparing highly filled silver powder according to claim 1, characterized in that, In steps S3 and S5, the constant temperature is 20~25℃.

7. The method for preparing highly filled silver powder according to claim 1, characterized in that, In step S5, the feeding rate of the second reducing agent solution and the silver nitrate solution is 2~6 L / min.

8. A highly filled silver powder, characterized in that, The high-filled silver powder is prepared by the method according to any one of claims 1-7, wherein the high-filled silver powder has an average particle size of 5-7 μm and a tap density > 6.4 g / cm³. 3 The angle of repose is less than 35°.

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