Metallic silver and its preparation method and application

Abstract

The present invention discloses a kind of metallic silver and its preparation method and application, belonging to the technical field of material synthesis; The metallic silver provided by the present invention is in powder form, and its D 50 =0.906-2.960μm, D 10 ≥0.612μm, D 90 ≤4.723μm, particle size distribution coefficient P=(D 90 ‑D 10 ) / D 50 ≤1.003; the preparation method comprises the following steps: adding the reducing liquid into the circulating reaction liquid at a uniform speed from the top of the reactor to obtain a metallic silver suspension; then solid-liquid separation of the metallic silver suspension is performed to obtain metallic silver; the circulation direction of the circulating reaction liquid is to flow out from the bottom of the reactor and then flow into the top of the reactor; the adding or flowing-in angle of the reducing liquid and the circulating reaction liquid is 30-45°; the preparation method provided by the present invention is simple and suitable for industrial production; the metallic silver provided by the present invention has a narrow particle size distribution and high uniformity, and can be widely used in the field of electronic components.

Description

Technical Field

[0001] The invention belongs to the technical field of material synthesis, and in particular relates to metallic silver and a preparation method and application thereof. Background Art

[0002] The principle of preparing metallic silver by chemical liquid phase reduction is to use a reducing agent to deposit silver from silver salts and silver complex aqueous solutions in the form of powder, and then obtain metallic silver by solid-liquid separation, solid washing, and drying. The liquid phase reduction method has significant advantages, such as simple equipment, low preparation cost, and the reaction process is easy to control the morphology and particle size of the silver powder formed by metallic silver by adjusting process parameters such as temperature, reaction time, and amount of reactants. The process is simple, and the prepared metallic silver powder can be widely used in the field of electronics industry. However, the metallic silver prepared by the chemical reduction method is prone to poor uniformity of metallic silver powder and wide particle size distribution during the storage process. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a metallic silver with a narrow particle size distribution and a preparation method and application thereof.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a metallic silver, the metallic silver is in powder form, and its D 50 =0.906-2.960μm, D 10 ≥0.612μm, D 90 ≤4.723μm, particle size distribution coefficient P=(D 90 -D 10 ) / D 50 ≤1.003.

[0005] The technical solution of the present invention provides a kind of metallic silver, which is in powder form, and the particle size distribution coefficient P=(D 90 -D 10 ) / D 50 ≤1.003. Since the metallic silver provided by the present invention has a narrow particle size distribution and high uniformity, it can be widely used in the field of electronic components.

[0006] In addition, the present invention also provides a method for preparing metallic silver, comprising the following steps: adding a reducing liquid into a circulating reaction liquid from the top of a reactor at a uniform speed to obtain a metallic silver suspension; then solid-liquid separation of the metallic silver suspension to obtain metallic silver; the circulation direction of the circulating reaction liquid is to flow out from the bottom of the reactor and then flow into the top of the reactor; the adding or flowing angle of the reducing liquid and the circulating reaction liquid is 30-45°.

[0007] The present invention prepares metallic silver by a chemical liquid phase method. During the preparation process, the generation of metallic silver generally includes two stages, one stage is the formation of silver nuclei, and the other stage is the growth of silver nuclei. When the rates of these two stages are relatively balanced, the generated metallic silver will have good uniformity and a narrow particle size distribution. In the preparation method of metallic silver provided by the present invention, by setting the reaction liquid to a circulation mode from the bottom to the top of the reactor, and controlling the angle between the addition of reducing liquid and the inflow of the reaction liquid to be 30-45°, and the feeding position is set in front of the stirring direction, the mass transfer and heat transfer in the reaction process can be well improved. The technical solution provided by the present invention On the one hand, the problem that the formation rates of the silver nuclei in the upper and lower layers in the non-circulating reaction liquid are inconsistent or the local silver nuclei formation rate is too fast due to the excessive local reducing liquid in the reaction liquid, resulting in large differences in the distribution of metallic silver particle sizes, can be solved; on the other hand, the problem that the bottom fluidity of the reaction liquid deteriorates due to the increase in the volume of the reaction liquid and the increase in the viscosity of the reaction liquid in the later stage, resulting in uneven growth of the silver nuclei, can be solved; the preparation method provided by the present invention can make the reaction rates of the reaction liquids at different heights more balanced, and can avoid the problem of uneven growth of the silver nuclei due to the excessively fast local silver nuclei formation rate of the reaction liquid or the excessively high viscosity of the reaction liquid, and the particle size distribution coefficient P of the prepared metallic silver is (D 90 -D 10 ) / D 50 ≤1.003.

[0008] As a preferred embodiment of the preparation method of the present invention, the reducing solution is an aqueous solution of hydrazine hydrate, wherein the mass concentration of hydrazine hydrate in the reducing solution is 10-20 g / L.

[0009] As a preferred embodiment of the preparation method of the present invention, the reducing solution is added at a uniform rate for a duration of 30-60 minutes.

[0010] When the mass concentration of hydrazine hydrate in the reducing solution is within the above range, on the one hand, when the reducing solution is mixed with the reaction solution, the local reducing solution concentration will not be too high, thereby avoiding the problem of too fast instantaneous formation rate of silver nuclei; on the other hand, when the reducing solution is mixed with the reaction solution, there is sufficient capacity to form silver nuclei, thereby avoiding the problem of low production efficiency of metallic silver.

[0011] As a preferred embodiment of the preparation method of the present invention, the circulating reaction liquid is obtained by reacting a reducing liquid with a silver solution.

[0012] As a preferred embodiment of the preparation method of the present invention, the temperature of the silver solution is 30-40°C.

[0013] When the temperature of the silver solution is within the above range, the problem of too fast reaction rate due to too high temperature can be avoided, and at the same time, it can ensure that the solute in the silver solution can have a good dissolution rate and will not precipitate.

[0014] As a preferred embodiment of the preparation method of the present invention, the preparation method of the silver solution comprises the following steps: weighing silver nitrate, a pH adjuster and a surfactant and dissolving them in water to obtain a silver solution.

[0015] As a preferred embodiment of the preparation method of the present invention, the mass concentration of silver ions formed by the dissociation of silver nitrate in the silver solution is 10-20 g / L.

[0016] When the concentration of silver ions is within the above range, it can ensure that the concentration of silver ions and the subsequently generated metallic silver in the solution system is appropriate, and the problem of excessively large particle size due to excessively high concentration or excessively small particle size due to excessively low concentration will not occur, thereby the prepared metallic silver D 50 Between 0.906-2.960μm.

[0017] As a preferred embodiment of the preparation method of the present invention, the pH regulator includes at least one of sodium carbonate, sodium hydroxide or ammonia water.

[0018] As a preferred embodiment of the preparation method of the present invention, the pH value of the silver solution is 10-14.

[0019] When the pH value of the silver solution is within the above range, it can ensure that the acidity and alkalinity of the system is conducive to the reduction reaction. At the same time, setting the pH value at 10-14 can make a large number of generated silver nuclei agglomerate and grow to form a spherical structure, thereby increasing the uniformity of particle size distribution.

[0020] As a preferred embodiment of the preparation method of the present invention, the surfactant includes at least one of starch, polyvinyl alcohol, phytic acid or gelatin.

[0021] The above components have good dispersibility in water. When used as surfactants for preparing metallic silver by chemical reduction, they can protect the silver particles formed in the early stage due to their good dispersibility, slow down the production rate of silver particles, avoid the problem of wide particle size distribution caused by excessive growth of silver particles, and ensure that the generated metallic silver D 50 Between 0.906-2.960μm.

[0022] In addition, the present invention also provides the application of metallic silver in manufacturing electronic components.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] First: The technical solution of the present invention provides a metallic silver in powder form, with a particle size distribution coefficient P = (D 90 -D 10 ) / D 50≤1.003. Since the metallic silver provided by the present invention has a narrow particle size distribution and high uniformity, it can be widely used in the field of electronic components;

[0025] Second: In the method for preparing metallic silver provided by the present invention, by setting the reaction liquid in a circulation mode from the bottom to the top of the reactor, and controlling the angle between the addition of the reducing liquid and the inflow of the reaction liquid to be 30-45°, and setting the feeding position in front of the stirring direction, the mass transfer and heat transfer in the reaction process can be well improved, so that the particle size distribution of the prepared metallic silver is narrow and uniform;

[0026] Third: The preparation method of metallic silver provided by the present invention is simple and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : A schematic front view of a reaction device used in the preparation method of the present invention;

[0028] Figure 2 : A schematic top view of the reaction device used in the preparation method of the present invention;

[0029] Figure 3 : A: SEM image of the metallic silver prepared in Example 1, B: particle size distribution diagram of the metallic silver prepared in Example 1;

[0030] Figure 4 : A: SEM image of the metallic silver prepared in Example 2, B: particle size distribution diagram of the metallic silver prepared in Example 2;

[0031] Figure 5 : A: SEM image of the metallic silver prepared in Example 3, B: particle size distribution diagram of the metallic silver prepared in Example 3;

[0032] Figure 6 : A: SEM image of the metallic silver prepared in Example 4, B: particle size distribution diagram of the metallic silver prepared in Example 4;

[0033] Figure 7 : A: SEM image of the metallic silver prepared in Example 5, B: particle size distribution diagram of the metallic silver prepared in Example 5;

[0034] Figure 8 : A: SEM image of the metallic silver prepared in Comparative Example 1, B: particle size distribution diagram of the metallic silver prepared in Comparative Example 1;

[0035] Fig. 9 : A: SEM image of the metallic silver prepared in Comparative Example 2, B: particle size distribution diagram of the metallic silver prepared in Comparative Example 2;

[0036] Fig.10: A: SEM image of the metallic silver prepared in Comparative Example 3, B: particle size distribution diagram of the metallic silver prepared in Comparative Example 3.

[0037] Fig.11 : A: SEM image of the metallic silver prepared in Comparative Example 4, B: particle size distribution diagram of the metallic silver prepared in Comparative Example 4;

[0038] Fig.12 : A: SEM image of the metallic silver prepared in Comparative Example 5, B: particle size distribution diagram of the metallic silver prepared in Comparative Example 5;

[0039] Fig.13 : A: SEM image of the metallic silver prepared in Comparative Example 6, B: particle size distribution diagram of the metallic silver prepared in Comparative Example 6.

[0040] Fig.14 : A: SEM image of the metallic silver prepared in Comparative Example 7, B: particle size distribution diagram of the metallic silver prepared in Comparative Example 7;

[0041] Fig.15 : A: SEM image of the metallic silver prepared in Comparative Example 8, B: particle size distribution diagram of the metallic silver prepared in Comparative Example 8. DETAILED DESCRIPTION

[0042] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0043] The preparation steps of the embodiments of the present invention and the comparative examples are all Figure 1 The reaction is carried out using the reaction device shown in the figure; unless otherwise specified, the reagents used in the examples and comparative examples of the present invention can be obtained through conventional purchasing channels.

[0044] Example 1

[0045] The method for preparing metallic silver according to the embodiment of the present invention is as follows:

[0046] (1) Weigh 78.8 g of silver nitrate, 126 g of 26% ammonia water, and 0.5 g of phytic acid and dissolve them in 5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution is 10.0 g / L, and the pH value of the silver solution is 10;

[0047] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 1.28 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 10.0 g / L;

[0048] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 30° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then add it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 30 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 30°. The stirring reaction is maintained during the dropping process;

[0049] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =0.997.

[0050] Example 2

[0051] The method for preparing metallic silver according to the embodiment of the present invention is as follows:

[0052] (1) 78.8 g of silver nitrate, 126 g of 26% ammonia water, 12 g of sodium hydroxide, and 0.5 g of polyvinyl alcohol were weighed and dissolved in 3.3 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution was 15.2 g / L, and the pH value of the silver solution was 14;

[0053] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 0.85 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 15.1 g / L;

[0054] (3) adding the silver solution to the reaction apparatus and stirring, maintaining the temperature of the reaction apparatus at 35° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then add it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 45 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 30°. The stirring reaction is maintained during the dropping process;

[0055] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =1.003.

[0056] Example 3

[0057] The method for preparing metallic silver according to the embodiment of the present invention is as follows:

[0058] (1) 78.8 g of silver nitrate, 126 g of 26% ammonia water, 15 g of sodium hydroxide, 0.2 g of polyvinyl alcohol, and 0.3 g of gelatin were weighed and dissolved in 2.5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution was 20.0 g / L and the pH value of the silver solution was 14;

[0059] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 0.64 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 20.0 g / L;

[0060] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 40° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then add it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 60 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 30°. The stirring reaction is maintained during the dropping process;

[0061] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =0.678.

[0062] Example 4

[0063] The method for preparing metallic silver according to the embodiment of the present invention is as follows:

[0064] (1) Weigh 78.8 g of silver nitrate, 126 g of 26% ammonia water, and 0.5 g of phytic acid and dissolve them in 5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution is 10.0 g / L, and the pH value of the silver solution is 10;

[0065] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 1.28 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 10.0 g / L;

[0066] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 30° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then add it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 30 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction solution is 45°. The stirring reaction is maintained during the dropping process;

[0067] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =0.990.

[0068] Example 5

[0069] The method for preparing metallic silver according to the embodiment of the present invention is as follows:

[0070] (1) Weigh 78.8 g of silver nitrate, 126 g of 26% ammonia water, and 0.5 g of phytic acid and dissolve them in 5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution is 10.0 g / L, and the pH value of the silver solution is 10;

[0071] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 1.28 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 10.0 g / L;

[0072] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 30° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then adding it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 30 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 38°. The stirring reaction is maintained during the dropping process;

[0073] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =0.969.

[0074] Comparative Example 1

[0075] The preparation method of the metallic silver of the comparative example of the present invention is as follows:

[0076] (1) Weigh 78.8 g of silver nitrate, 126 g of 26% ammonia water, and 0.5 g of phytic acid and dissolve them in 5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution is 10.0 g / L, and the pH value of the silver solution is 10;

[0077] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 1.28 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 10.0 g / L;

[0078] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 30° C., uniformly dropping the reducing solution into the circulating liquid, the dropping time is 30 minutes, the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 30°, and the stirring reaction is maintained during the dropping process;

[0079] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =1.319.

[0080] Comparative Example 2

[0081] The preparation method of the metallic silver of the comparative example of the present invention is as follows:

[0082] (1) 78.8 g of silver nitrate, 126 g of 26% ammonia water, 12 g of sodium hydroxide, and 0.5 g of polyvinyl alcohol were weighed and dissolved in 3.3 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution was 15.2 g / L, and the pH value of the silver solution was 14;

[0083] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 0.85 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 15.1 g / L;

[0084] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 35° C., uniformly dropping the reducing solution into the circulating liquid, the dropping time is 45 minutes, the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 30°, and the stirring reaction is maintained during the dropping process;

[0085] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =1.304.

[0086] Comparative Example 3

[0087] The preparation method of the metallic silver of the comparative example of the present invention is as follows:

[0088] (1) 78.8 g of silver nitrate, 126 g of 26% ammonia water, 15 g of sodium hydroxide, 0.2 g of polyvinyl alcohol, and 0.3 g of gelatin were weighed and dissolved in 2.5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution was 20.0 g / L and the pH value of the silver solution was 14;

[0089] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 0.64 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 20.0 g / L;

[0090] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 40° C., uniformly dropping the reducing solution into the circulating liquid, the dropping time is 60 minutes, the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 30°, and the stirring reaction is maintained during the dropping process;

[0091] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =0.945.

[0092] Comparative Example 4

[0093] The preparation method of the metallic silver of the comparative example of the present invention is as follows:

[0094] (1) Weigh 78.8 g of silver nitrate, 126 g of 26% ammonia water, and 0.5 g of phytic acid and dissolve them in 5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution is 10.0 g / L, and the pH value of the silver solution is 10;

[0095] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 1.28 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 10.0 g / L;

[0096] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 30° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then add it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 30 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 75°. The stirring reaction is maintained during the dropping process;

[0097] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =1.237.

[0098] Comparative Example 5

[0099] The preparation method of the metallic silver of the comparative example of the present invention is as follows:

[0100] (1) Weigh 78.8 g of silver nitrate, 126 g of 26% ammonia water, and 0.5 g of phytic acid and dissolve them in 5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution is 10.0 g / L, and the pH value of the silver solution is 10;

[0101] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 1.28 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 10.0 g / L;

[0102] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 30° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then add it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 30 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction solution is 10°. The stirring reaction is maintained during the dropping process;

[0103] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D10 ) / D 50 =1.195.

[0104] Comparative Example 6

[0105] The preparation method of the metallic silver of the comparative example of the present invention is as follows:

[0106] (1) Weigh 78.8 g of silver nitrate, 100 g of 26% ammonia water, and 0.5 g of phytic acid and dissolve them in 5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution is 10.0 g / L and the pH value of the silver solution is 8;

[0107] (2) Weigh 16 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 1.28 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 10.0 g / L;

[0108] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 30° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then add it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 30 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 30°. The stirring reaction is maintained during the dropping process;

[0109] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =1.279.

[0110] Comparative Example 7

[0111] The preparation method of the metallic silver of the comparative example of the present invention is as follows:

[0112] (1) 170.0 g of silver nitrate, 252 g of 26% ammonia water, and 1.0 g of phytic acid were weighed and dissolved in 5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution was 21.6 g / L, and the pH value of the silver solution was 10;

[0113] (2) Weigh 34.56 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 2.76 L of pure water to obtain a reduced solution, in which the mass concentration of hydrazine hydrate in the reduced solution is 10.0 g / L;

[0114] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 30° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then add it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 30 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 30°. The stirring reaction is maintained during the dropping process;

[0115] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =1.201.

[0116] Comparative Example 8

[0117] The preparation method of the metallic silver of the comparative example of the present invention is as follows:

[0118] (1) Weigh 78.8 g of silver nitrate, 126 g of 26% ammonia water, and 0.5 g of phytic acid and dissolve them in 5 L of pure water to obtain a silver solution, wherein the mass concentration of silver ions in the silver solution is 10.0 g / L, and the pH value of the silver solution is 10;

[0119] (2) Weigh 48 g of hydrazine hydrate with a mass fraction of 80% and dissolve it in 1.28 L of pure water to obtain a reducing solution, in which the mass concentration of hydrazine hydrate in the reducing solution is 30.0 g / L;

[0120] (3) adding the silver solution to the reaction device and stirring, maintaining the temperature of the reaction device at 30° C., and using a peristaltic pump to extract the silver solution from the bottom of the reaction and then add it from the top. After the silver solution forms a stable up-and-down circulation, the reducing solution is uniformly added dropwise to the circulating liquid. The dropping time is 30 minutes, and the angle between the dropping of the reducing solution and the circulating addition of the reaction liquid is 30°. The stirring reaction is maintained during the dropping process;

[0121] (4) After the reaction is completed, the reaction is allowed to settle and the solid and liquid are separated to obtain metallic silver, whose particle size distribution coefficient P = (D 90 -D 10 ) / D 50 =1.661.

[0122] Effect example

[0123] The metallic silver prepared in Examples 1-5 and Comparative Examples 1-8 was observed and recorded under a scanning electron microscope, and its particle size distribution was detected. Figure 3-7 It can be seen that when the technical solution adopted is within the scope given in the present invention, the prepared metallic silver is spherical, and the particle size distribution coefficient P = (D 90 -D 10 ) / D 50 ≤1.003; from Examples 1-3 and Comparative Examples 1-3 provided Figure 3-5 and Figure 8-10 It can be seen that when the circulating feeding method is not adopted, the particle size distribution coefficient of the prepared metallic silver is P = (D 90 -D 10 ) / D 50The corresponding values ​​are generally greater than those of Examples 1-3, with the increase ranging from 22.0 to 28.0%, indicating that the use of the present invention of circulating liquid addition and controlling the feeding angle can significantly improve the uniformity of particle size distribution;

[0124] From Example 1 and Comparative Examples 4 and 5 provided Figure 3 and Fig.11 , 12 It can be seen that when the feeding angle is changed, whether the angle is increased or decreased, the particle size distribution coefficient of the prepared metallic silver is P = (D 90 -D 10 ) / D 50 All of them increase accordingly, indicating that the angle will affect the uniformity of the particle size of the prepared metallic silver;

[0125] From Example 1 and Comparative Example 6 provided Figure 3 and Fig.13 It can be seen that when the pH value of the system is lowered, some of the prepared metallic silver is not spherical, and it can be clearly seen from the figure that the size of the formed metallic silver is quite different, that is, the distribution range of the formed metallic silver particle size is relatively wide;

[0126] From Example 1 and Comparative Examples 7 and 8 provided Figure 3 and Fig.14 , 15 It can be seen that when the concentration of silver ions is increased, the metallic silver particles will become irregular spherical, the particle size will increase, and the particle size distribution range will become wider; when the concentration of hydrazine hydrate is increased, the metallic silver particles will also become irregular spherical similar to wrinkles, and the size distribution will be extremely uneven, and the particle size distribution value will increase.

[0127] Finally, it should be noted that the above embodiments are intended to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A metallic silver, characterized in that: The metallic silver is in powder form. 50 =0.906-2.960μm, D 10 ≥0.612μm, D 90 ≤4.723μm, particle size distribution coefficient P=(D 90 -D 10 ) / D 50 ≤1.003; The method for preparing metallic silver comprises the following steps: uniformly adding the reducing liquid into the circulating reaction liquid from the top of the reactor to obtain a metallic silver suspension; then solid-liquid separation of the metallic silver suspension to obtain metallic silver; The circulating reaction liquid is obtained by reacting the reducing liquid with the silver solution; The circulating reaction liquid flows out from the bottom of the reactor and then flows into the top of the reactor; The angle of addition or inflow of the reducing liquid and the circulating reaction liquid is 30-45°; The reducing solution is an aqueous solution of hydrazine hydrate, and the mass concentration of the hydrazine hydrate in the reducing solution is 10-20 g / L; The preparation method of the silver solution comprises the following steps: weighing silver nitrate, a pH regulator and a surfactant and dissolving them in water to obtain a silver solution; The mass concentration of silver ions formed by the dissociation of silver nitrate in the silver solution is 10-20 g / L; The pH value of the silver solution is 10-14.

2. The metallic silver according to claim 1, characterized in that The pH adjuster includes at least one of sodium carbonate, sodium hydroxide or ammonia water.

3. The metallic silver according to claim 1, characterized in that The surfactant includes at least one of starch, polyvinyl alcohol, phytic acid or gelatin.

4. Use of the metallic silver as claimed in claim 1 in the preparation of electronic components.

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