Atomized silver powder and preparation method thereof

Abstract

The invention provides atomized silver powder and a preparation method thereof, and belongs to the technical field of metal powder preparation. According to the preparation method, through the synergistic effect of atomization powder preparation, two-step ball milling and mechanical crushing, two kinds of mixed state silver powder which is wide in particle size distribution, uneven in surface and irregular in edge and is in a thick sheet shape and a small-particle sphere-like shape are prepared. According to the method, more satellite spherical micron silver powder particles are prepared by controlling gas atomization powder preparation, then the large-particle satellite spherical silver powder is ground into sheets and is prevented from being scattered into small spherical particles through a primary flaking process and large-ball slow grinding, and in a secondary flaking process, small-ball quick grinding is added, so that the large-particle satellite spherical silver powder is prepared. According to the method, the silver powder of the middle size is rapidly ground into sheets, meanwhile, the form of the small-particle spherical silver powder is prevented from being damaged, finally, the surface of the sheet-shaped silver powder is modified through mechanical crushing, the target silver powder is obtained, a pure physical powder preparing technology is adopted, the production cost is low, environment friendliness is achieved, the batch stability is good, and the method can be directly used for electronic paste.

Description

Technical Field

[0001] The present invention relates to the technical field of metal powder and preparation thereof, and in particular to an atomized silver powder and a preparation method thereof. Background Art

[0002] Flake silver powder has become one of the key raw materials for slurries in electronics and photovoltaics because of its large specific surface area, good overlap between powder particles, and the ability to achieve a good conductive path. At present, the preparation methods of flake silver powder mainly include chemical reduction and mechanical grinding. However, due to the limitations of process formulas and technical equipment, the domestic flake silver powder market generally has many problems such as poor comprehensive powder performance and batch stability. Therefore, domestic flake silver powder for electronic products such as conductive adhesives is still mainly dependent on imports, and a technological breakthrough is urgently needed. In addition, the raw materials for the mechanical grinding method are basically spherical silver powder prepared by chemical reduction. Due to the small size of the powder particles, the prepared flake silver powder has a small particle size or a thin thickness, the particle edges are flat and regular, and the powder size distribution is single, which will lead to a high slurry viscosity of the powder, resulting in poor thixotropic and conductive properties.

[0003] In the prior art, patent publication number CN117600482A discloses a method for preparing flaky silver powder with high tap density. This patent prepares spherical clusters of silver powder by chemical reduction, and then obtains flaky silver powder by shaping and sand grinding. The silver powder particles are small in size, regular in shape, and have a uniform particle size distribution. The slurry prepared with this as raw material has poor slurrying performance and conductivity, and cannot be directly applied to downstream photovoltaic, electronic and other product ends. Patent publication number CN119187547A discloses a micron block and submicron spherical mixed silver powder and its preparation method. This patent uses a liquid-phase chemical reduction method to induce the preparation of a micron block and submicron spherical mixed silver powder with good dispersion uniformity and high tap density using a nanosilver crystal suspension. However, this technical solution has problems such as difficulty in controlling process conditions and high environmental pressure, which leads to high production costs and poor batch stability of the prepared silver powder products. Summary of the Invention

[0004] In view of the technical problems existing in the background technology, the present application provides an atomized silver powder and a preparation method thereof, aiming to solve the problems that the preparation process of the existing silver powder is complicated, cannot be mass-produced industrially, and the silver powder particle size distribution cannot meet the market demand of downstream slurry.

[0005] In one aspect, the present invention provides a method for preparing atomized silver powder, comprising the following steps: S1. After the silver particles are heated and melted, they enter the nozzle system through the guide tube and are atomized, crushed, dried, and sieved under the action of an inert gas. The powder under the sieve is taken to obtain the first micron silver powder; S2. The first micron silver powder is placed in a ball mill, and an ethanol solution containing a ball milling aid is added for a first ball milling to obtain a first sheet of silver powder; S3. The first silver powder is subjected to a second ball milling, filtered, and dried to obtain a second silver powder; S4. shaping the second flaked silver powder in a crusher to obtain target silver powder.

[0006] In the technical solution of the embodiment of the present application, a mixed silver powder with a wide particle size distribution, including thick flakes with uneven surfaces and irregular edges and small spherical particles below 5μm, is prepared through the organic synergistic effect of atomization powder making, two-step wet ball milling and mechanical crushing. Among them, by controlling the process parameters in the aerosol powder making process, a large number of satellite spherical micron silver powder particles are obtained, and then through a first flake process, the large-particle satellite spherical silver powder is ground into flakes by slow grinding with a large ball while preventing it from being broken up into spherical small particles, thereby controlling the proportion of spherical flakes. In the second flake process, the silver powder of the intermediate size is quickly ground into flakes by adding a small ball for fast grinding while preventing the morphology of the small-particle spherical silver powder from being destroyed. Finally, the surface structure of the flaky silver powder is modified by mechanical crushing to prepare silver powder with specific morphology and size specifications. The present application adopts a purely physical powder making process, which has low production cost, is environmentally friendly and has good batch stability.

[0007] In some embodiments, in step S1, the pressure of the inert gas is 11-15 MPa, the diameter of the flow guide tube is 2.5 mm, the superheat degree of the heating is 350° C., and in the screening, the aperture of the screen is 500 mesh.

[0008] In this embodiment, the atomization powder making process allows the first micron silver powder to contain a large number of satellite-shaped micron silver powder particles.

[0009] In some embodiments, in step S2, the diameter of the grinding balls in the first ball mill is 5 mm, the mass ratio of the grinding balls in the first ball mill to the first micron silver powder is 5-10:1, and the mass fraction of the first micron silver powder in the ethanol solution is 45%; the grinding speed in the first ball mill is 150 rpm, and the grinding time of the first ball mill is 40-60 min.

[0010] In this embodiment, large-particle satellite spherical silver powder is ground into flakes by slow grinding with a large ball while preventing it from being broken up into small spherical particles, thereby controlling the ratio of spherical flakes.

[0011] In some embodiments, in step S2, the ball milling aid is one or more of cinnamic acid, oleic acid, stearic acid and hexadecylamine, and the ball milling aid accounts for 0.5% of the mass of the first micron silver powder.

[0012] In this embodiment, a ball milling aid is added during the ball milling process. The grinding aid molecules can be adsorbed on the surface of the silver powder particles, reducing their surface energy, effectively inhibiting particle agglomeration, and ensuring the dispersibility of the silver powder.

[0013] In some embodiments, in step S3, the diameter of the grinding balls in the second ball mill is 2 mm, the mass ratio of the grinding balls in the second ball mill to the grinding balls in the first ball mill is 1:5; the grinding speed in the second ball mill is 500 rpm, and the grinding time of the second ball mill is 5 to 15 minutes.

[0014] In this embodiment, during the second ball milling process, small balls are added for rapid grinding, so that the silver powder of intermediate size is quickly ground into flakes while preventing the morphology of the small spherical silver powder from being destroyed.

[0015] In some embodiments, in step S4, the rotation speed of the crusher is 12000 r / min, and the crushing time of the crusher is 10 minutes.

[0016] In this embodiment, the surface structure of the flaky silver powder is modified by shaping it with a crusher.

[0017] In a second aspect, an embodiment of the present application provides an atomized silver powder, which is prepared using the atomized silver powder preparation method; the atomized silver powder comprises thick flake silver powder with an uneven surface and irregular edges and small spherical silver powder with a particle size of less than 5 μm; wherein the particle size of the thick flake silver powder is 5~30 μm, and the aspect ratio is 4~7.

[0018] In the technical solution of the embodiment of the present application, the prepared mixed silver powder of irregular flakes and small-particle spherical silver powder can be directly used in electronic paste without additional mixing and doping. The prepared paste has low viscosity and good thixotropic properties. In addition, due to the good overlapping performance between the powders and the filling effect of the small-particle silver powder, the density and conductivity of the paste after sintering and curing are further enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0020] Figure 1 This is a SEM image of the silver powder prepared in step S1 in Example 1.

[0021] Figure 2 This is the SEM image of the silver powder prepared in Example 1.

[0022] Figure 3These are SEM images of the silver powders prepared in Examples 2-3 and Comparative Examples 1-2.

[0023] Figure 4 3 to 8 are SEM images of the silver powders prepared in Comparative Examples 3 to 8. DETAILED DESCRIPTION

[0024] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0026] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0027] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] To address the problems of the existing silver powder preparation process being complex, unable to be mass-produced industrially, and the silver powder particle size distribution failing to meet the market demand for downstream slurries, the present application provides an atomized silver powder and a preparation method thereof. Through the organic synergistic effect of atomization powder preparation, two-step wet ball milling, and mechanical crushing, a mixed silver powder with a wide particle size distribution, including thick flakes with uneven surfaces and irregular edges and small spherical particles below 5 μm, is prepared. The process parameters during the atomization powder preparation process are controlled to obtain a large number of satellite-shaped micron silver powder particles. A primary flake process is then performed using large balls for slow grinding to grind the large satellite-shaped silver powder into flakes while preventing it from breaking up into small spherical particles, thereby controlling the proportion of spherical flakes. A secondary flake process is performed using small balls for rapid grinding to rapidly grind the intermediate-sized silver powder into flakes while preventing the morphology of the small spherical silver powder particles from being destroyed. Finally, mechanical crushing is used to modify the surface structure of the flake silver powder, thereby producing a silver powder with a specific morphology and size specification. This application adopts a purely physical powder making process, which has low production cost, is environmentally friendly and has good batch stability. The prepared micron silver powder does not require additional mixing or doping and can be directly used in electronic paste. The prepared paste has low viscosity and good thixotropic properties. In addition, due to the good overlapping performance between the powders and the filling effect of small-particle silver powder, the density and conductivity of the paste after sintering and curing are further enhanced, and the market application prospects are broad.

[0029] The present invention provides a method for preparing atomized silver powder, comprising the following steps: S1. After the silver particles are heated and melted, they enter the nozzle system through the guide tube and are atomized, crushed, dried, and sieved under the action of an inert gas. The powder under the sieve is taken to obtain the first micron silver powder; S2. The first micron silver powder is placed in a ball mill, and an ethanol solution containing a ball milling aid is added for a first ball milling to obtain a first sheet of silver powder; S3. The first silver powder is subjected to a second ball milling, filtered, and dried to obtain a second silver powder; S4. shaping the second flaked silver powder in a crusher to obtain target silver powder.

[0030] In the technical solution of the embodiment of the present application, a mixed silver powder with a wide particle size distribution, including thick flakes with uneven surfaces and irregular edges and small spherical particles below 5μm, is prepared through the organic synergistic effect of atomization powder making, two-step wet ball milling and mechanical crushing. Among them, by controlling the process parameters in the aerosol powder making process, a large number of satellite spherical micron silver powder particles are obtained, and then through a first flake process, the large-particle satellite spherical silver powder is ground into flakes by slow grinding with a large ball while preventing it from being broken up into spherical small particles, thereby controlling the proportion of spherical flakes. In the second flake process, the silver powder of the intermediate size is quickly ground into flakes by adding a small ball for fast grinding while preventing the morphology of the small-particle spherical silver powder from being destroyed. Finally, the surface structure of the flaky silver powder is modified by mechanical crushing to prepare silver powder with specific morphology and size specifications. The present application adopts a purely physical powder making process, which has low production cost, is environmentally friendly and has good batch stability.

[0031] Furthermore, in some embodiments, in step S1, the diameter of the silver particles is 5 mm and the purity is 99.99%.

[0032] Furthermore, in some embodiments, in step S1, the pressure of the inert gas is 11-15 MPa, the diameter of the flow guide tube is 2.5 mm, the superheat degree of the heating is 350° C., and in the screening, the aperture of the screen is 500 mesh.

[0033] In the technical solution of the embodiment of the present application, the atomization powder making process is used to make the first micron silver powder contain a large number of satellite spherical micron silver powder particles.

[0034] Furthermore, in some embodiments, in step S2, the diameter of the grinding balls in the first ball mill is 5 mm, the mass ratio of the grinding balls in the first ball mill to the first micron silver powder is 5-10:1, and the mass fraction of the first micron silver powder in the ethanol solution is 45%; the grinding speed in the first ball mill is 150 rpm, and the grinding time of the first ball mill is 40-60 min.

[0035] In the technical solution of the embodiment of the present application, large-particle satellite spherical silver powder is ground into flakes by slow grinding with a large ball while preventing it from being broken up into small spherical particles, thereby controlling the ratio of spherical flakes.

[0036] Furthermore, in some embodiments, in step S2, the ball milling aid is one or more of cinnamic acid, oleic acid, stearic acid and hexadecylamine, and the ball milling aid accounts for 0.5% of the mass of the first micron silver powder.

[0037] In the technical solution of the embodiment of the present application, a ball milling aid is added during the ball milling process. The grinding aid molecules can be adsorbed on the surface of the silver powder particles, reducing their surface energy, effectively inhibiting particle agglomeration, and ensuring the dispersibility of the silver powder.

[0038] Furthermore, in some embodiments, in step S3, the diameter of the grinding balls in the second ball mill is 2 mm, the mass ratio of the grinding balls in the second ball mill to the grinding balls in the first ball mill is 1:5; the grinding speed in the second ball mill is 500 rpm, and the grinding time of the second ball mill is 5 to 15 min.

[0039] In the technical solution of the embodiment of the present application, during the second ball milling process, small balls are added for rapid grinding, so that the intermediate-sized silver powder is quickly ground into flakes while preventing the morphology of the small-particle spherical silver powder from being destroyed.

[0040] Furthermore, in some embodiments, in step S4, the rotation speed of the crusher is 12000 r / min, and the crushing time of the crusher is 10 min.

[0041] In the technical solution of the embodiment of the present application, the surface structure of the flaky silver powder is modified by shaping it through a crusher.

[0042] In a second aspect, an embodiment of the present application provides an atomized silver powder, which is prepared using the atomized silver powder preparation method; the atomized silver powder comprises thick flake silver powder with an uneven surface and irregular edges and small spherical silver powder with a particle size of less than 5 μm; wherein the particle size of the thick flake silver powder is 5~30 μm, and the aspect ratio is 4~7.

[0043] In the technical solution of the embodiment of the present application, the prepared mixed silver powder of irregular flakes and small-particle spherical silver powder can be directly used in electronic paste without additional mixing and doping. The prepared paste has low viscosity and good thixotropic properties. In addition, due to the good overlapping performance between the powders and the filling effect of the small-particle silver powder, the density and conductivity of the paste after sintering and curing are further enhanced.

[0044] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0045] Example 1 This embodiment provides a method for preparing atomized silver powder, comprising the following steps: S1. Silver particles with a diameter of 5 mm and a purity of 99.99% were placed in a vacuum induction melting furnace and heated to 1310°C to completely melt. The particles then entered a nozzle system through a 2.5 mm diameter flow tube. The particles were atomized and crushed under an inert gas pressure of 13 MPa, and then dried. The particles were sieved using a 500-mesh sieve, and the remaining powder was removed to obtain the first micron silver powder. S2. The first micron silver powder and a grinding ball with a diameter of 5 mm were placed in a ball mill at a mass ratio of 1:5, and an ethanol solution containing stearic acid was added to obtain a solid content of 45% for the first micron silver powder, wherein stearic acid accounted for 0.5% of the mass of the first micron silver powder, and then fully ground at a speed of 150 rpm for 45 min to obtain a first sheet of silver powder; S3. The ball mill was further added with a diameter of 2 mm and a mass of 1 / 5 of the mass of the grinding balls in step S2, and the silver powder particles were ground at a speed of 500 rpm for 10 min, and then filtered and dried to obtain a second sheet of silver powder; S4. The second flaked silver powder is placed in a crusher and shaped at a speed of 12000 r / min for 10 minutes to obtain the target silver powder.

[0046] The SEM image of the silver powder prepared in step S1 of this embodiment is as follows: Figure 1 The SEM image of the silver powder prepared in step S4 is shown in FIG. Figure 2 shown.

[0047] Depend on Figure 1 and Figure 2 It can be seen that the silver powder produced in this embodiment includes thick flake silver powder with uneven surface and irregular edges and small spherical silver powder with a particle size of less than 5 μm. The silver powder obtained in step S1 is in the shape of satellite spheres and contains a small amount of micron-sized spherical silver powder particles.

[0048] Examples 2-3 and Comparative Examples 1-2 Example 2 and Comparative Examples 1-2 respectively provide a method for preparing atomized silver powder. Compared with Example 1, the difference is that the time of the first ball milling in step S2 is different, as shown in Table 1. The other steps are roughly the same as those in Example 1 and are not repeated here.

[0049] Table 1 Time of the first ball milling in Examples 2-3 and Comparative Examples 1-2 The SEM images of the silver powders obtained in Examples 2-3 and Comparative Examples 1-2 are as follows: Figure 3 shown.

[0050] Depend on Figure 3It can be seen that the morphology of the silver powder in Examples 2-3 is similar to that in Example 1. However, in Comparative Example 1, due to the short first ball milling time, the particle size and diameter-to-thickness ratio of the prepared flaky silver powder are too small. In Comparative Example 2, due to the long first ball milling time, the prepared powder contains flaky silver powder with a particle size greater than 40 μm. After slurry formation, it is easy to clog the mesh or gun tip in downstream applications, and cannot be smoothly passed through the screen for printing or dispensing.

[0051] Comparative Examples 3~8 Comparative Examples 3 to 8 each provide a method for preparing atomized silver powder. Compared with Example 1, the difference is that in Comparative Example 3, the grinding ball size and rotation speed in step S2 and step S3 are exchanged, step S3 is omitted in Comparative Example 4, step S3 is omitted in Comparative Example 5, and the grinding balls in step S2 are replaced with grinding balls with diameters of 5 mm and 2 mm, respectively, with a mass ratio of 5:1. The grinding time is changed to 55 minutes, and then filtered and dried. In Comparative Example 6, the grinding speed in step S2 is changed to 500 rpm, step S2 is omitted in Comparative Example 7, and step S4 is omitted in Comparative Example 8. The other steps are substantially the same as in Example 1 and are not repeated here.

[0052] The SEM images of the silver powders obtained in Comparative Examples 3 to 8 are as follows: Figure 4 shown.

[0053] Depend on Figure 4 It can be seen that in Comparative Example 3, due to the first small ball fast milling, the satellite spherical silver powder is first broken up into small spherical silver powder particles, and then further ground into thin flake silver powder with a thickness of nanometer level. The powder has a large specific surface area and a large slurry viscosity. In Comparative Example 4, due to the lack of small ball milling, the prepared powder contains large particles of micron-type spherical silver powder, and the contact resistance of the powder is high and the conductivity is poor. In Comparative Example 5, two kinds of grinding balls of different particle sizes are used to grind the silver powder particles at the same time. Under the same grinding time, the proportion of small-particle silver powder in the prepared powder is large, and the degree of flake is high. The viscosity in downstream slurry applications is large and the thixotropic performance is poor. In Comparative Example 6, large balls are used in the first ball milling stage. The rapid grinding method will quickly squeeze and cold-weld the satellite spherical silver powder and the small-particle micron silver powder prepared in step S1 together, and then a secondary fragmentation process will occur after a long period of grinding, eventually forming smaller flaky silver powder particles, which cannot meet the downstream slurry application requirements. In Comparative Example 7, small ball rapid grinding is directly performed, resulting in the rapid dispersion of the satellite spherical silver powder, the reduction of the powder particle size, and finally the formation of thick flake, thin flake and quasi-spherical mixed silver powder after grinding, and the powder particle size is ≤10μm. In Comparative Example 8, the silver powder after two stages of ball milling is not crushed and modified, and the surface of the prepared flaky silver powder is smooth and flat, the contact points between the powder particles are small, and the oil absorption in the slurry is poor, resulting in poor downstream application effect.

[0054] In summary, the present application provides an atomized silver powder and a preparation method thereof. Through the organic synergistic effect of atomization powder making, two-step wet ball milling and mechanical crushing, a mixed silver powder with a wide particle size distribution, including thick flakes with uneven surfaces and irregular edges and small spherical particles below 5 μm, is prepared. Among them, by controlling the process parameters in the aerosol powder making process, a large number of satellite spherical micron silver powder particles are obtained, and then through a flaking process, the large-particle satellite spherical silver powder is ground into flakes by slow grinding with a large ball while preventing it from being broken up into small spherical particles, thereby controlling the proportion of spherical flakes. In the secondary flaking process, the intermediate-sized silver powder is quickly ground into flakes by adding a small ball for fast grinding while preventing the morphology of the small-particle spherical silver powder from being destroyed. Finally, the surface structure of the flaky silver powder is modified by mechanical crushing to obtain silver powder with specific morphology and size specifications. This application adopts a purely physical powder making process with low production cost, environmental friendliness and good batch stability. The prepared micron silver powder does not require additional mixing and doping and can be directly used in electronic paste. The prepared paste has low viscosity and good thixotropic properties. In addition, due to the good overlapping performance between the powders and the filling effect of the small-particle silver powder, the density and conductivity of the paste after sintering and curing are further enhanced, and the market application prospects are broad.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing atomized silver powder, characterized in that: The steps include: S1. After the silver particles are heated and melted, they enter the nozzle system through the guide tube and are atomized, crushed, dried, and sieved under the action of an inert gas. The powder under the sieve is taken to obtain the first micron silver powder; S2. The first micron silver powder is placed in a ball mill, and an ethanol solution containing a ball milling aid is added for a first ball milling to obtain a first sheet of silver powder; S3. The first silver powder is subjected to a second ball milling, filtered, and dried to obtain a second silver powder; S4. shaping the second flaked silver powder in a crusher to obtain target silver powder.

2. The method for preparing atomized silver powder according to claim 1, characterized in that: In step S1, the pressure of the inert gas is 11-15 MPa, the diameter of the flow guide tube is 2.5 mm, the superheat degree of the heating is 350° C., and the aperture of the screen during the screening is 500 mesh.

3. The method for preparing atomized silver powder according to claim 1, wherein: In step S2, the diameter of the grinding balls in the first ball mill is 5 mm, the mass ratio of the grinding balls in the first ball mill to the first micron silver powder is 5-10:1, and the mass fraction of the first micron silver powder in the ethanol solution is 45%.

4. The method for preparing atomized silver powder according to claim 1, wherein: In step S2, the grinding speed in the first ball mill is 150 rpm, and the grinding time of the first ball mill is 40-60 min.

5. The method for preparing atomized silver powder according to claim 1, wherein: In step S2, the ball milling aid is one or more of cinnamic acid, oleic acid, stearic acid and hexadecylamine, and the ball milling aid accounts for 0.5% of the mass of the first micron silver powder.

6. The method for preparing atomized silver powder according to claim 1, characterized in that: In step S3, the diameter of the grinding balls in the second ball mill is 2 mm, and the mass ratio of the grinding balls in the second ball mill to the grinding balls in the first ball mill is 1:

5.

7. The method for preparing atomized silver powder according to claim 1, characterized in that: In step S3, the grinding speed in the second ball mill is 500 rpm, and the grinding time of the second ball mill is 5 to 15 minutes.

8. The method for preparing atomized silver powder according to claim 1, wherein: In step S4, the rotation speed of the crusher is 12000 r / min, and the crushing time of the crusher is 10 minutes.

9. An atomized silver powder, characterized in that: The atomized silver powder is prepared by the preparation method of any one of claims 1 to 8.

10. The atomized silver powder according to claim 9, characterized in that The atomized silver powder includes thick flake silver powder with an uneven surface and irregular edges and small spherical silver powder with a particle size less than 5 μm; wherein the particle size of the thick flake silver powder is 5-30 μm and the aspect ratio is 4-7.

Images