Monodisperse spherical micro-nano silver powder and preparation method thereof

Abstract

The application provides monodisperse spherical micro-nano silver powder and a preparation method thereof, and belongs to the technical field of metal powder preparation. The application uses silver nitrate solution as a silver source, polyvinylpyrrolidone as a dispersant, and ascorbic acid as a reducing agent to prepare micro-nano silver powder with narrow particle size distribution and high sphericity at low temperature. The kinetics of hydrolysis and reduction nucleation is effectively slowed down at low temperature, the thermal motion of polyvinylpyrrolidone molecular chains is weakened, the polyvinylpyrrolidone molecular chains can be more orderly and stably adsorbed on specific crystal faces of silver crystal nuclei, the anisotropic growth of crystal nuclei is inhibited, and the low-temperature Ostwald ripening between particles is effectively prevented, so that the uniformity of particle size is ensured; at low temperature, the reduction capacity of ascorbic acid is moderated. The'mild reduction' and 'ordered guidance' are perfectly matched, and a good balance between reaction kinetics and thermodynamics is achieved. The prepared silver powder has excellent morphology, super-high sphericity and good monodispersity, and can be applied to high-end electronic paste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal powder and its preparation, in particular to a kind of monodisperse spherical micro-nano silver powder and its preparation method. BACKGROUND

[0002] Spherical silver powder, especially sub-micron to nanometer scale spherical silver powder, because it has the highest tap density, excellent fluidity and sintering activity, becomes the ideal material for preparing high-performance, high-resolution electronic paste. Monodisperse ultra-fine spherical silver powder can form a highly dense conductive network after low-temperature sintering, thereby realizing excellent conductivity and line fineness, which is crucial for the current development of electronic devices towards miniaturization and high integration.

[0003] The existing chemical reduction technology, especially when facing high-end electronic paste applications, still has the following significant technical bottlenecks and defects. 1. Difficulty in controlling morphology and particle size: wide particle size distribution and irregular morphology can reduce the tap density of silver powder, leading to unstable rheological properties when preparing paste, and easily producing defects after printing, sintering shrinkage is uneven, which seriously affects the performance of the final device; 2. Process complexity and environmental pollution caused by morphology control: In order to achieve strong reduction and stable morphology, many methods still rely on hydrazine hydrate, sodium borohydride and other toxic or strongly corrosive reducing agents, which pose a threat to the environment and operating personnel safety, and are contrary to the development concept of green chemistry; 3. It is difficult to balance product performance: existing methods are difficult to achieve "high sphericity", "small particle size", "narrow distribution" (monodisperse) and "adjustable particle size" under simple process conditions. For example, when using ascorbic acid as a mild reducing agent, the reaction rate is slow at room temperature, and the product is prone to Ostwald ripening, resulting in uneven particle size; while small particle size can be obtained through severe reaction conditions, but the morphology is difficult to control. SUMMARY

[0004] In view of the technical problems in the background art, the present application provides a kind of monodisperse spherical micro-nano silver powder and its preparation method, to solve the problem that the preparation of existing silver powder is difficult to achieve "high sphericity", "small particle size", "narrow distribution" (monodisperse) and "adjustable particle size" under simple process conditions.

[0005] In one aspect, the present application provides a method for preparing a monodisperse spherical micro-nano silver powder, characterized in that it comprises the following steps:

[0006] S1. Mix silver nitrate solution and polyvinylpyrrolidone solution at 0-10℃, stir uniformly, and obtain a mixed solution;

[0007] S2. Under stirring conditions, add ascorbic acid solution pre-cooled to the same temperature as the mixed solution to the mixed solution, continue to react, and obtain silver powder material;

[0008] S3. The silver powder material is subjected to solid-liquid separation, washing, and drying to obtain the target silver powder.

[0009] In the technical scheme of the embodiment, silver nitrate solution is used as a silver source, polyvinylpyrrolidone is used as a dispersant, and ascorbic acid is used as a reducing agent, so that micro-nano silver powder with narrow particle size distribution and high sphericity is prepared at low temperature. At low temperature, the kinetics of hydrolysis and reduction nucleation is effectively slowed down, and the thermal motion of the polyvinylpyrrolidone molecular chain is weakened, so that the polyvinylpyrrolidone molecular chain can be more orderly and stably adsorbed on the specific crystal face of the silver crystal nucleus, thereby effectively inhibiting the anisotropic growth of the crystal nucleus and strongly guiding the silver atoms to uniformly deposit in the isotropic direction, so that the silver powder has extremely high sphericity, a smooth surface, and good monodispersity. Meanwhile, the stable wrapping of the polyvinylpyrrolidone effectively prevents low-temperature Ostwald ripening between particles, thereby ensuring the uniformity of the particle size. At low temperature, the reducing capacity of ascorbic acid is moderated. This "moderate reduction" and "orderly guidance" are perfectly matched, and a good balance between reaction kinetics and thermodynamics is achieved. The prepared silver powder has excellent morphology, extremely high sphericity, a smooth surface, good monodispersity, a narrow particle size distribution range, and good consistency, and can be applied to high-end electronic paste.

[0010] In some embodiments, in step S1, the concentration of the silver nitrate solution is 0.1-1.0 mol / L, and the concentration of the polyvinylpyrrolidone solution is 0.1-0.5 mol / L; the volume ratio of the silver nitrate solution to the polyvinylpyrrolidone solution is 1:1-100.

[0011] In this embodiment, by controlling the ratio of the silver nitrate solution to the polyvinylpyrrolidone solution, the particle size of the silver powder can be controlled. The polyvinylpyrrolidone acts as a steric stabilizer, and by adjusting the ratio, the number of silver crystal nuclei and the growth space can be directly affected, thereby determining the size of the final particles. At this ratio, the polyvinylpyrrolidone molecules can quickly and fully wrap each crystal nucleus to form a dense protective layer at the moment of the generation of the silver crystal nucleus, which can effectively prevent the mutual collision, agglomeration, and merging of the crystal nuclei, and ultimately obtain silver powder with smaller particle size and more uniform distribution. In addition, under the synergistic action of the low-temperature environment, the ultra-high sphericity of the silver powder can be induced and maintained.

[0012] In some embodiments, in step S2, the concentration of the ascorbic acid solution is 0.1-1.0 mol / L; and the volume ratio of the silver nitrate solution to the ascorbic acid solution is 1:1-100.

[0013] In this embodiment, by controlling the proportion of silver nitrate solution and ascorbic acid solution, the completeness of the reduction reaction and the purity of the product can be controlled, ensuring that all silver ions are fully and completely reduced, thereby obtaining the highest silver powder yield and high-purity product. By controlling the reaction rate, the nucleation density and growth environment of silver crystal nuclei are affected by controlling the speed of reduction kinetics.

[0014] In some embodiments, in step S2, the temperature of the reaction is 1-3℃; the reaction time is 0.5-2h.

[0015] In this embodiment, the reduction reaction is carried out at a specific low temperature, and the in-situ crystallization guiding effect works at low temperature. High temperature can accelerate the reaction and atomic migration, leading to too fast nucleation and growth, so that the polyvinylpyrrolidone loses the ability to control the morphology.

[0016] In some embodiments, in step S3, the drying temperature is 50-70℃.

[0017] In a second aspect, the embodiments of the present application provide a monodisperse spherical micro-nano silver powder, which is prepared by the preparation method of the monodisperse spherical micro-nano silver powder; the D50 particle size of the monodisperse spherical micro-nano silver powder is 200-900nm, the particle size distribution span satisfies (D90-D10) / D50<0.8, and the proportion of particles with a length-diameter ratio of 1.0-1.1 is more than 95%.

[0018] In the technical solution of the embodiments of the present application, the prepared silver powder has excellent morphology, super-high sphericity, smooth surface, good monodispersity, narrow and consistent particle size distribution range, and adjustable particle size. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the present application, the drawings used in the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0020] Figure 1 SEM image of the silver powder prepared for Example 1.

[0021] Figure 2 SEM image of the silver powder prepared for Examples 2-3 and Comparative Examples 1-2.

[0022] Figure 3 SEM image of the silver powder prepared for Examples 4-7.

[0023] Figure 4 SEM image of the silver powder prepared for Comparative Examples 3-6. DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and thus only serve as examples, and cannot be used to limit the protection scope of the present application.

[0025] In this document, reference to“an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase“in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that any of the features, structures, or characteristics described in connection with an embodiment can be included in at least one implementation of the application.

[0026] In the description of the embodiments of the present application, the term“and / or” merely describes an associated relationship with associated objects, and indicates that there can be three relationships, for example, A and / or B, which can represent the three cases of A existing alone, A and B existing together, and B existing alone. In addition, the character“ / ” in this document generally represents an“or” relationship between the front and rear associated objects.

[0027] In order to solve the problem that the preparation of the existing silver powder is difficult to realize "high sphericity", "small particle size", "narrow distribution" (monodisperse) and "adjustable particle size" under simple process conditions, the application provides a monodisperse spherical micro-nano silver powder and a preparation method thereof. The silver nitrate solution is used as a silver source, the polyvinylpyrrolidone is used as a dispersant, and the ascorbic acid is used as a reducing agent. The micro-nano silver powder with a narrow particle size distribution and high sphericity is prepared at low temperature. At low temperature, the kinetics of hydrolysis and reduction nucleation is effectively slowed down, the thermal motion of the polyvinylpyrrolidone molecular chain is weakened, the polyvinylpyrrolidone molecular chain can be more orderly and stably adsorbed on the specific crystal face of the silver crystal nucleus, thereby effectively inhibiting the anisotropic growth of the crystal nucleus and strongly guiding the silver atoms to uniformly deposit in the isotropic direction, so that the sphericity of the silver powder is extremely high, the surface is smooth, and the monodispersity is good. At the same time, the stable wrapping of the polyvinylpyrrolidone also effectively prevents the low-temperature Ostwald ripening between the particles, and ensures the uniformity of the particle size. At low temperature, the reducing capacity of ascorbic acid is moderated. This "moderate reduction" and "ordered guidance" are perfectly matched, and a good balance between reaction kinetics and thermodynamics is achieved. At the same time, the low-temperature environment significantly reduces the reduction reaction rate of silver nitrate, so that the generation (nucleation) and growth process of the silver crystal nucleus become moderate and controllable. By accurately adjusting the concentration ratio of silver nitrate, ascorbic acid and polyvinylpyrrolidone, the final particle size of the silver powder can be accurately adjusted in the sub-micron to nanometer scale, and the particle size distribution range is narrow and the consistency is good. The application does not need complex equipment or harsh reaction conditions, and does not need the step of pH value adjustment. It can be completed in a conventional low-temperature bath. The "small particle size" and "adjustable particle size" can be realized by a simple method. The prepared silver powder has excellent morphology, high sphericity, smooth surface and good monodispersity, and can be applied to high-end electronic paste.

[0028] In one aspect, the application provides a preparation method of monodisperse spherical micro-nano silver powder, comprising the following steps:

[0029] S1. The silver nitrate solution and the polyvinylpyrrolidone solution are mixed at 0-10 DEG C, and stirred uniformly to obtain a mixed solution;

[0030] S2. The ascorbic acid solution pre-cooled to the same temperature as the mixed solution is added to the mixed solution under stirring, and the reaction is continued to obtain a silver powder material;

[0031] S3. The silver powder material is subjected to solid-liquid separation, washing and drying to obtain the target silver powder.

[0032] In the technical scheme of the embodiment of the application, silver nitrate solution is used as a silver source, polyvinylpyrrolidone is used as a dispersant, ascorbic acid is used as a reducing agent, and micro-nano silver powder with narrow particle size distribution and high sphericity is prepared at low temperature. At low temperature, the kinetics of hydrolysis and reduction nucleation is effectively slowed down, and the thermal motion of the polyvinylpyrrolidone molecular chain is weakened, so that the polyvinylpyrrolidone can be more orderly and stably adsorbed on the specific crystal face of the silver crystal nucleus, thereby effectively inhibiting the anisotropic growth of the crystal nucleus and strongly guiding the silver atoms to uniformly deposit in the isotropic direction, so that the silver powder has extremely high sphericity, a smooth surface and good monodispersity. At the same time, the stable wrapping of polyvinylpyrrolidone effectively prevents low-temperature Ostwald ripening between particles, ensuring the uniformity of the particle size. At low temperature, the reducing capacity of ascorbic acid is moderated. This "moderate reduction" and "ordered guidance" perfectly match each other, achieving a good balance between reaction kinetics and thermodynamics. The prepared silver powder has excellent morphology, extremely high sphericity, a smooth surface and good monodispersity, and can be applied to high-end electronic paste.

[0033] Further, in some embodiments, in step S1, the concentration of the silver nitrate solution is 0.1-1.0 mol / L, and the concentration of the polyvinylpyrrolidone solution is 0.1-0.5 mol / L; the volume ratio of the silver nitrate solution to the polyvinylpyrrolidone solution is 1:1-100.

[0034] In the technical scheme of the embodiment of the application, by controlling the ratio of the silver nitrate solution to the polyvinylpyrrolidone solution, the particle size of the silver powder can be controlled. The polyvinylpyrrolidone acts as a steric stabilizer, and by adjusting the ratio, the number of silver crystal nuclei and the growth space can be directly affected, thereby determining the size of the final particles. When the ratio of polyvinylpyrrolidone is high, the polyvinylpyrrolidone molecules can quickly and fully wrap each crystal nucleus to form a dense protective layer, which effectively prevents the mutual collision, agglomeration and merging of the crystal nuclei, and finally obtains silver powder with smaller particle size and more uniform distribution. In addition, under the synergistic action of the low-temperature environment, the ultra-high sphericity of the silver powder can be induced and maintained.

[0035] Further, in some embodiments, in step S2, the concentration of the ascorbic acid solution is 0.1-1.0 mol / L; and the volume ratio of the silver nitrate solution to the ascorbic acid solution is 1:1-100.

[0036] In the technical scheme of the embodiment of the application, by controlling the ratio of the silver nitrate solution to the ascorbic acid solution, the completeness of the reduction reaction and the purity of the product can be controlled, and it is ensured that all silver ions are fully and completely reduced, thereby obtaining the highest silver powder yield and high-purity product. The reaction rate is regulated, and by controlling the speed of the reduction kinetics, the nucleation density and growth environment of the silver crystal nucleus are affected.

[0037] Further, in some embodiments, in step S2, the temperature of the reaction is 1-3℃; the time of the reaction is 0.5-2h.

[0038] In the technical scheme of the embodiments of the present application, the reduction reaction is carried out at a specific low temperature, and the in-situ crystallization guiding effect works at the low temperature. High temperature can intensify the reaction and atomic migration, resulting in too fast nucleation and growth, and making the polyvinylpyrrolidone lose the ability of morphology control.

[0039] Further, in some embodiments, in step S3, the temperature of the drying is 50-70℃.

[0040] In a second aspect, the embodiments of the present application provide a monodisperse spherical micro-nano silver powder, which is prepared by using the preparation method of the monodisperse spherical micro-nano silver powder; the D50 particle size of the monodisperse spherical micro-nano silver powder is 200-900nm, the particle size distribution span satisfies (D90-D10) / D50<0.8, and the proportion of particles with a length-diameter ratio of 1.0-1.1 is more than 95%.

[0041] In the technical scheme of the embodiments of the present application, the prepared silver powder has excellent morphology, super-high sphericity, smooth surface, good monodispersity, narrow and consistent particle size distribution range, and adjustable particle size.

[0042] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are used to explain the present application, and cannot be understood as limiting the present application. If the specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product manual is used. If the reagent or instrument is not specified by the manufacturer, it is a conventional product that can be obtained from the market.

[0043] Embodiment 1

[0044] The embodiment provides a preparation method of monodisperse spherical micro-nano silver powder, which comprises the following steps:

[0045] S1. 0.1 mL of silver nitrate solution with a concentration of 0.5 mol / L and 1 mL of polyvinylpyrrolidone solution with a concentration of 0.3 mol / L are mixed at 2℃, and stirred uniformly to obtain a mixed solution;

[0046] S2. Under the stirring condition, 1 mL of ascorbic acid aqueous solution with a concentration of 0.3 mol / L is pre-cooled to 2℃ in an ice water bath, and then added to the mixed solution, and continues to react at 2℃ for 0.5h to obtain a silver powder material;

[0047] S3. The silver powder material is filtered, washed with deionized water, and then dried in a 50℃ vacuum drying box for 8h to obtain the target silver powder.

[0048] The SEM image of the silver powder prepared in this example is shown in Figure 1 .

[0049] It can be seen that the silver powder prepared in this example has high sphericity, good dispersibility and uniformity, and the particle size is about 600 nm. Figure 1

[0050] Examples 2-3 and Comparative Examples 1-2

[0051] Examples 2-3 and Comparative Examples 1-2 respectively provide a preparation method of monodisperse spherical micro-nano silver powder, and the difference compared with Example 1 is that the volume ratio of silver nitrate solution and polyvinylpyrrolidone solution in step S1 is different, see Table 1 for details, and other steps are substantially the same as those of Example 1, which will not be repeated here.

[0052] Table 1 Volume ratio of silver nitrate solution and polyvinylpyrrolidone solution and silver powder morphology in Examples 2-3 and Comparative Examples 1-2

[0053]

[0054] The SEM image of the silver powder prepared in Examples 2-3 and Comparative Examples 1-2 is shown in Figure 2 .

[0055] From Table 1 and Figure 2 It can be seen that when the volume ratio of silver nitrate solution and polyvinylpyrrolidone solution is 1:1-100, it has high sphericity, and the higher the proportion of polyvinylpyrrolidone, the smaller the particle size of the prepared silver powder, and the particle size can be controlled between 200-900 nm; from the results of Comparative Example 1, it can be seen that when the proportion of silver nitrate solution is greater than that of polyvinylpyrrolidone solution, there is not enough polyvinylpyrrolidone molecules to uniformly cover the surface of all newly generated silver crystal nuclei, and the silver crystal will follow its own inherent crystallization habit, freely and anisotropically grow into a flaky shape along the direction with the lowest surface energy; from the results of Comparative Example 2, it can be seen that when the proportion of polyvinylpyrrolidone solution continues to increase, when the polyvinylpyrrolidone content is too high, the solution viscosity will increase significantly, and local areas with too high concentration are easy to form, making the nucleation and growth of different areas out of sync, resulting in uneven particle size and decreased sphericity, and the surface becomes rough.

[0056] Examples 4-7

[0057] Examples 4-7 respectively provide a preparation method of monodisperse spherical micro-nano silver powder, and the difference compared with Example 1 is that in Examples 4-5, the temperature in step S1 and the pre-cooling temperature in S2 are different, and in Examples 6-7, the reaction temperature in step S2 is different, see Table 2 for details, and other steps are substantially the same as those of Example 1, which will not be repeated here.​

[0058] Table 2 Temperature in step S1 and pre-cooling temperature in S2, reaction temperature in step S2 and silver powder morphology in Examples 4-7

[0059]

[0060] From Table 2 and Figure 3 It can be seen that the low temperature condition of the present application is conducive to the preparation of monodisperse spherical micro-nano silver powder, and the silver powder prepared under suitable low temperature condition has high sphericity and smooth surface.

[0061] Comparative Examples 3-6

[0062] Comparative Examples 3-6 each provide a preparation method of monodisperse spherical micro-nano silver powder, and the difference compared with Example 1 is that in Comparative Example 3, the temperature in step S1 and the pre-cooling temperature in S2 are both room temperature, in Comparative Example 4, the reaction temperature in step S2 is room temperature, in Comparative Example 5, the ascorbic acid aqueous solution is not pre-cooled, and in Comparative Example 6, the polyvinylpyrrolidone solution is replaced with stearic acid solution, and other steps are substantially the same as those of Example 1, which will not be repeated here.

[0063] Table 3 Particle size and morphology of silver powder prepared in Comparative Examples 3-6

[0064]

[0065] The SEM images of the silver powder prepared in Comparative Examples 3-6 are shown in Figure 4 respectively.

[0066] From Figure 4 and Table 3, it can be seen that in Comparative Examples 3-4, the silver powder obtained at room temperature is in irregular and agglomerated state, which is due to the fact that when the temperature is high, the reaction tends to be original and disordered; in Comparative Example 5, pre-cooling is not performed, and when the ascorbic acid solution is added to the low-temperature mixed solution, it cannot be instantly balanced with the system temperature, forming a local high-temperature area, so that the silver ions are instantaneously and massively reduced, resulting in extremely high concentration of silver crystal nucleus, leading to irregular morphology and agglomeration of the finally generated silver powder; in Comparative Example 6, the polyvinylpyrrolidone solution is replaced with stearic acid solution, since stearic acid is a small molecule, it is chemically adsorbed on the silver surface through the carboxyl group (-COOH), and this adsorption is usually selective, which can be strongly adsorbed on a certain specific crystal face, thereby greatly inhibiting the growth of the crystal face, which will lead to serious anisotropic growth and form flakes.

[0067] In summary, the present application provides a monodisperse spherical micro-nano silver powder and a preparation method thereof, in which silver nitrate solution is used as a silver source, polyvinylpyrrolidone is used as a dispersant, and ascorbic acid is used as a reducing agent, and the micro-nano silver powder with narrow particle size distribution and high sphericity is prepared at low temperature. At low temperature, the kinetics of hydrolysis and reduction nucleation is effectively slowed down, and the thermal motion of the polyvinylpyrrolidone molecular chain is weakened, so that it can be more orderly and stably adsorbed on the specific crystal face of the silver crystal nucleus, thereby effectively inhibiting the anisotropic growth of the crystal nucleus and strongly guiding the silver atoms to uniformly deposit in the isotropic direction, so that the silver powder has extremely high sphericity, a smooth surface and good monodispersity. At the same time, the stable wrapping of polyvinylpyrrolidone also effectively prevents low-temperature Ostwald ripening between particles, ensuring the uniformity of the particle size; at low temperature, the reducing capacity of ascorbic acid is moderated. This "mild reduction" and "ordered guidance" perfectly match each other, achieving a good balance between reaction kinetics and thermodynamics. At the same time, the low-temperature environment significantly reduces the reduction reaction rate of silver nitrate, making the generation (nucleation) and growth process of silver crystal nucleus mild and controllable. By accurately adjusting the concentration ratio of silver nitrate, ascorbic acid and polyvinylpyrrolidone, the final particle size of the silver powder can be accurately controlled in the sub-micron to nanometer scale, and the particle size distribution range is narrow and the consistency is good. The present application does not require complex equipment or harsh reaction conditions, nor does it need steps such as pH value adjustment, and can be completed in a conventional low-temperature bath. Through a simple method, "small particle size" and "adjustable particle size" can be achieved, and the prepared silver powder has excellent morphology, high sphericity, a smooth surface and good monodispersity, and can be applied to high-end electronic paste.

[0068] The above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing monodisperse spherical micro / nano silver powder, characterized in that, Includes the following steps: S1. Mix silver nitrate solution and polyvinylpyrrolidone solution at 0~10℃ and stir until homogeneous to obtain a mixed solution; S2. Under stirring conditions, ascorbic acid solution pre-cooled to the same temperature as the mixed solution is added to the mixed solution, and the reaction continues at a temperature of 1~3℃ to obtain silver powder material; S3. The silver powder material is subjected to solid-liquid separation, washing, and drying to obtain the target silver powder; The concentration of the silver nitrate solution is 0.1~1.0 mol / L, and the concentration of the polyvinylpyrrolidone solution is 0.1~0.5 mol / L. The volume ratio of the silver nitrate solution to the polyvinylpyrrolidone solution is 1:1 to 100.

2. The method for preparing monodisperse spherical micro / nano silver powder according to claim 1, characterized in that, In step S2, the concentration of the ascorbic acid solution is 0.1~1.0 mol / L.

3. The method for preparing monodisperse spherical micro / nano silver powder according to claim 2, characterized in that, The volume ratio of the silver nitrate solution to the ascorbic acid solution is 1:1 to 100.

4. The method for preparing monodisperse spherical micro / nano silver powder according to claim 1, characterized in that, In step S2, the reaction time is 0.5 to 2 hours.

5. The method for preparing monodisperse spherical micro / nano silver powder according to claim 1, characterized in that, In step S3, the drying temperature is 50~70℃.

6. A monodisperse spherical micro / nano silver powder, characterized in that, The monodisperse spherical micro / nano silver powder was prepared using the method described in any one of claims 1 to 5.

7. The monodisperse spherical micro / nano silver powder according to claim 6, characterized in that, The monodisperse spherical micro / nano silver powder has a D50 particle size of 200~900nm, a particle size distribution range that satisfies (D90~D10) / D50 < 0.8, and particles with an aspect ratio between 1.0 and 1.1 account for more than 95%.

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