Preparation method of spherical silver powder with patterns on surface

Abstract

The invention relates to the field of metal powder preparation, and particularly discloses a surface pattern spherical silver powder preparation method which comprises the following preparation steps: S1, preparing a reaction base solution: dissolving silver salt in water to obtain a silver salt solution, and then regulating the pH value and temperature of the silver salt solution by using a pH regulator to obtain the reaction base solution; s2, preparing a dispersion liquid: dissolving a dispersing agent in water, and adjusting the temperature to obtain the dispersion liquid; s3, preparing alkali liquor: dissolving an alkaline solvent in water to obtain the alkali liquor; s4, preparing a reducing solution: dissolving a reducing agent in water, and adjusting the temperature to obtain the reducing solution; s5, preparing a modified liquid: dissolving a modifier in absolute ethyl alcohol to obtain the modified liquid; s6, carrying out a reaction; s7, cleaning is conducted; the alkali liquor further comprises a glucose capsule. The silver powder prepared through the method is regular in morphology and uniform in particle size and is in a pattern sphere shape.

Description

Technical Field

[0001] The present application relates to the technical field of metal powder preparation, and more specifically, to a method for preparing spherical silver powder with surface patterns. Background Art

[0002] With the rapid development of social science and technology, the miniaturization of the volume and weight of electronic industrial products has increased the demand for ultrafine metal powders, and at the same time, higher requirements have been put forward for the properties of ultrafine metal powders. Among them, silver powder, as an excellent micro-nano material, has wide applications in the fields of optical materials, electronic pastes, medicine, and catalysis due to its excellent electrical and thermal conductivity, high plasticity, low-temperature sintering, and antioxidant properties.

[0003] Considering cost and process requirements, currently, the chemical reduction method is the most widely used method for preparing silver powder. This method uses a reducing agent to reduce silver particles from a silver salt or silver complex system. Chemical reduction involves the processes of silver nucleation and growth. Generally, the final morphology and particle size of silver powder are adjusted by methods such as adjusting the pH, temperature, concentration, dispersant, and type of reducing agent in the experiment. The morphology of silver powder is one of the important detection items during the research and development of silver powder. The morphology of silver powder may be dendritic, flaky, spherical, or other complex morphologies. These different morphologies will affect the printing performance and sintering performance of silver paste, as well as the density and resistance of the electrode, and have a great impact on the specific surface area of silver powder. Among them, dendritic and other complex morphologies will lead to poor leveling and density during the printing of silver paste, thereby reducing the density of the electrode after sintering and increasing the electrode resistance. Therefore, spherical silver powder and flaky silver powder will be the main objects of sintered silver paste. Spherical silver powder is divided into quasi-spherical silver powder, smooth spherical silver powder, and rough spherical silver powder. The performance of quasi-spherical silver powder is worse than that of spherical silver powder, and the performance of smooth spherical silver powder is so good that the leveling is too good, resulting in possible collapse during printing. Therefore, how to better control the surface morphology of silver powder and prepare rough spherical silver powder with uniform patterns can well solve this problem. Summary of the Invention

[0004] In order to make the silver powder uniform, dense, and have surface patterns, the present application provides a method for preparing spherical silver powder with surface patterns.

[0005] The present application provides a method for preparing spherical silver powder with surface patterns, including the following steps: S1: Prepare the reaction bottom solution: Dissolve the silver salt in water to obtain a silver salt solution, and then use a pH regulator to adjust the pH value and temperature of the silver salt solution to obtain the reaction bottom solution. The silver salt includes one or more of silver nitrate, silver sulfate, silver carbonate, and silver oxalate. The pH regulator includes one or more of nitric acid, sulfuric acid, hydrochloric acid, oxalic acid, acetic acid, benzenesulfonic acid, sodium hydroxide, ammonia water, sodium carbonate, sodium citrate, potassium citrate, monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, formamide, acetamide, and propionamide; S2: Prepare the dispersion: Dissolve the dispersant in water and adjust the temperature to obtain the dispersion. The dispersant includes one or more of methyl cellulose, carboxymethyl cellulose, gelatin, polyvinylpyrrolidone, gum arabic, guar gum, ethanol, Tween, polyethylene glycol, glycerol, methyl amyl alcohol, octylamine, polyethylamide, fatty acid polyethylene glycol ester, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, glycolic acid, glyceric acid, malic acid, succinic acid, sodium citrate, potassium citrate, phthalic acid, isophthalic acid, terephthalic acid, triethylhexyl phosphate, sodium dodecyl sulfate, and sodium dodecylbenzenesulfonate; S3: Prepare the alkaline solution: Dissolve the alkaline solvent in water to obtain the alkaline solution. The alkaline solvent includes one or more of sodium hydroxide, ammonia water, sodium carbonate, sodium citrate, potassium citrate, monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, formamide, acetamide, and propionamide; S4: Prepare the reducing solution: Dissolve the reducing agent in water and adjust the temperature to obtain the reducing solution. The reducing agent includes one or more of ascorbic acid, glucose, hydrazine hydrate, formaldehyde, hydrogen peroxide, sodium hypochlorite, sodium borohydride, sulfite glycol, glycerol, and hydroquinone; S5: Prepare the modifying solution: Dissolve the modifier in anhydrous ethanol to obtain the modifying solution. The modifier includes one or more of oleic acid, linoleic acid, linolenic acid, stearic acid, palmitic acid, arachidic acid, myristic acid, lauric acid, oleylamine, palmitic acid, monoethanolamine, diethanolamine, and triethanolamine; S6: Reaction: Add the dispersion prepared in S2 to the reaction bottom solution prepared in S1, stir for the first time, add the alkaline solution prepared in S3 to the reaction bottom solution prepared in S1, stir for the second time, then add the reducing solution prepared in S4, stir for the third time, and then add the modifying solution prepared in S5, stir for the fourth time, and react to obtain the reaction mixture; S7: Cleaning: Put the reaction mixture prepared in S6 into a filter press, wash it with water until the conductivity < 10 us / cm, and then dehydrate it with anhydrous ethanol to obtain dehydrated silver powder; S8: Heat and dry the dehydrated silver powder prepared in S7, and then pulverize it to obtain spherical silver powder with surface patterns.

[0006] By adopting the above preparation method, the preparation conditions are simple and the implementation difficulty is low. An alkaline solution is added to the reaction bottom liquid to rapidly generate a large number of unstable microcrystal nuclei. In order to reduce the internal energy, the microcrystal nuclei aggregate into a spherical shape. The spherical silver powder with surface patterns prepared by the preparation method of the present invention has regular morphology, uniform particle size, and the spherical silver powder with controllable particle size can be realized through process operations. The average particle size D50 of the prepared silver powder is between 1.0 - 3.0 um, the tapped density is above 4.5 g / cm 3 and the specific surface area is less than 0.8 m 2 / g.

[0007] In a specific embodiment, the molar concentration of the silver salt solution in S1 is 0.1 - 0.5 mol / L, the pH value is 1.0 - 2.0, and the temperature is 25 - 65 °C; the concentration of the dispersion liquid in S2 is 1% - 4% wt, the temperature is 35 - 65 °C, and the mass of the dispersion liquid is 0.5% - 5% of the reaction bottom liquid; the mass concentration of the alkaline solution in S3 is 0.1% - 5% wt, and the molar ratio of the alkaline solvent to the silver salt is 1:90 - 110; the molar concentration of the reducing liquid in S4 is 0.25 - 0.7 mol / L, the temperature is 25 - 65 °C; the mass concentration of the modifying liquid in S5 is 0.1 - 0.2 wt%; the first stirring time in S6 is 1 - 2 minutes, the second stirring time is 1 - 2 minutes, the third stirring time is 1 - 2 minutes, and the fourth stirring time is 20 - 25 minutes.

[0008] The reaction bottom liquid prepared in this application has a low concentration, and it is not easy for silver powder particles to agglomerate. A large number of crystal nuclei grow, and the particle size of the prepared silver powder is more uniform. Adding a certain mass of the dispersion liquid further inhibits the agglomeration between silver powder particles, and the particle size of the prepared silver powder is even more uniform. By adjusting the pH value, the reaction rate is suitable for the crystal growth rate of the silver powder in this application. By limiting the temperature, the nucleation process is relatively mild, the silver powder has uniform particle size, high tapped density, and more uniform surface patterns. By limiting the stirring time, the reduction of silver powder is sufficient at the concentration of this application, the surface patterns are not damaged, and the shape is regular.

[0009] In a specific embodiment, the rate of adding the reducing liquid prepared in S4 in S6 is 200 - 250 ml / min.

[0010] At this adding rate, the reduction rate of silver ions is more suitable for the reaction of this application, and the surface patterns of the silver powder grow evenly with high tapped density.

[0011] In a specific embodiment, the temperature of heating and drying in S8 is 50 - 80 °C.

[0012] By adopting the above preparation method, the drying effect is good and the morphology of the silver powder is stable.

[0013] In a specific embodiment, the average particle size D50 of the surface-patterned spherical silver powder is 1.0 - 3.0 μm, and the tapped density > 4.5 g / cm 3 , and the specific surface area < 0.8 m 2 / g.

[0014] By adopting the above preparation method, the prepared silver powder is suitable for preparing conductive silver paste, is not easy to collapse, and the prepared electrode is more stable.

[0015] In a specific embodiment, the alkali solution further includes glucose capsules, the core material of the glucose capsules includes glucose, and the wall material includes gelatin and chitosan.

[0016] Glucose has relatively low reducibility and reacts gently with silver salts. Excessive glucose is gradually released during the growth process of silver powder, and there is a certain concentration gradient of glucose in the system during the release process, further regulating the surface morphology of silver powder. Chitosan is insoluble in alkali, and gelatin is soluble in hot water and can be used as a protective agent to replace the complex formed by silver ions and water with the complex formed by anions and gelatin, providing more electrons, making it easier for silver ions to obtain electrons and be reduced. Mixing chitosan and gelatin evenly as the wall material to coat glucose, the capsule slowly dissolves after adding a certain stable solution. At this time, the slow release of glucose and gelatin can cause fluctuations in the concentrations of the reducing agent and gelatin in the solution, and the patterns on the crystal surface grow more evenly and complexly. The prepared silver powder has a larger tapped density and specific surface area, is not easy to collapse while having greater friction, and is more suitable for preparing electrodes.

[0017] In a specific embodiment, the mass ratio of gelatin to chitosan in the wall material is 1:1 - 1.5.

[0018] After uniformly mixing gelatin and chitosan as the wall material and adding it to the reaction solution, glucose is evenly released in all directions in the solution, and the glucose concentration in the solution increases evenly. By limiting the mass ratio of gelatin to chitosan, the release rate of glucose is suitable for the reduction rate of the silver powder in this application, and the surface morphology of the prepared silver powder is more regular and the tapped density is high.

[0019] In a specific embodiment, the temperature of the alkali solution is 30 - 40 °C, the temperature of the reaction bottom solution is 50 - 65 °C, and the reducing solution is 50 - 65 °C.

[0020] After limiting the temperature of the alkali solution, the dissolution rate of the capsule is more suitable for the system of this application, glucose and gelatin are more evenly dispersed, diffuse to the surface of the growing silver particles for protection, slow down the growth rate of silver powder, and glucose regulates the growth rate and direction of silver powder, further optimizing the pattern shape on the surface of silver powder.

[0021] In a specific embodiment, the preparation steps of the glucose capsules include: uniformly mixing gelatin, chitosan, and water, and heating to obtain a wall material mixture; adding glucose to the mixture and stirring to obtain a mixture; adjusting the pH value of the mixture, cooling with ice water to precipitate and agglomerate chitosan, and filtering, washing, and drying to obtain glucose capsules.

[0022] The glucose capsules prepared through the above steps have a relatively regular structure. Gelatin and chitosan form a certain cross-linking to obtain a gel structure, which can achieve the effect of uniform release of glucose and gelatin in this application. The process requirements for the preparation process are not high, and it is suitable for large-scale and stable preparation.

[0023] Preferably, the stirring speed is 4000 - 5000 r / min, and the pH value is 8 - 9.

[0024] Under these parameters, the prepared capsules are more regular and have a good coating effect.

[0025] In summary, this application has at least the following beneficial effects: 1. The preparation conditions of this application are simple and the implementation difficulty is low. The surface-patterned spherical silver powder prepared by using the preparation method of the present invention has a regular morphology, uniform particle size, and spherical silver powder with controllable particle size can be achieved through process operations. By limiting the process parameters of each step, the average particle size D50 of the prepared silver powder is between 1.0 - 3.0 um, the tapped density is above 4.5 g / cm 3 And the specific surface area is less than 0.8 m 2 / g.

[0026] 2. By adding a certain content of glucose capsules to the reducing solution in this application, limiting the capsule wall material to include gelatin and chitosan, and further limiting their mass ratio and the temperature of the alkali solution, glucose is uniformly released, and the release rate is suitable for the process parameters of this application, and the surface pattern shape of the growing silver powder is further optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the electron micrograph of the surface-patterned spherical silver powder prepared in Example 1 of this application; Figure 2 is the electron micrograph of the surface-patterned spherical silver powder prepared in Example 2 of this application; Figure 3 is the electron micrograph of the spherical silver powder prepared in Comparative Example 1 of this application; Figure 4 is the electron micrograph of the spherical silver powder prepared in Comparative Example 2 of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To further assist in understanding the technical solution of the present invention, several specific embodiments are provided to describe the technical solution of the present invention more specifically. All these described embodiments are only partial embodiments of the present invention, not all; the embodiments can be combined with each other, and the same or similar concepts or processes may not be elaborated in some embodiments. The following embodiments are further explanations of the present invention, and the present invention is not limited thereto.

[0029] The raw materials used in the embodiments and preparation examples of this application are all conventional commercially available brands or can be obtained according to conventional processes. Preparation Example

[0030] Preparation of glucose capsules: Preparation Example 1: Mix 100 g of gelatin, 100 g of chitosan, and 800 ml of water evenly, and heat at 55 °C to obtain a wall material mixture; add 200 g of glucose to the mixture, stir at 5000 r / min for 20 minutes to obtain a mixture; adjust the pH value of the mixture to 8, cool with ice water to precipitate and coagulate chitosan, filter, wash with pure water, and dry at room temperature to obtain glucose capsules.

[0031] Preparation Example 2: Mix 80 g of gelatin, 120 g of chitosan, and 800 ml of water evenly, and heat at 55 °C to obtain a wall material mixture; add 200 g of glucose to the mixture, stir at 5000 r / min for 20 minutes to obtain a mixture; adjust the pH value of the mixture to 8, cool with ice water to precipitate and coagulate chitosan, filter, wash with pure water, and dry at room temperature to obtain glucose capsules.

[0032] Preparation Example 3: Mix 120 g of gelatin, 80 g of chitosan, and 800 ml of water evenly, and heat at 55 °C to obtain a wall material mixture; add 200 g of glucose to the mixture, stir at 5000 r / min for 20 minutes to obtain a mixture; adjust the pH value of the mixture to 8, cool with ice water to precipitate and coagulate chitosan, filter, wash with pure water, and dry at room temperature to obtain glucose capsules.

[0033] Preparation of ascorbic acid capsules: Preparation Example 4: Mix 100 g of ascorbic acid, 100 g of chitosan, and 800 ml of water evenly, and heat at 55 °C to obtain a wall material mixture; add 200 g of glucose to the mixture, stir at 5000 r / min for 20 minutes to obtain a mixture; adjust the pH value of the mixture to 8, cool with ice water to precipitate and coagulate chitosan, filter, wash with pure water, and dry at room temperature to obtain glucose capsules.

[0034] The components of the preparation examples used in the embodiments refer to the components obtained by the methods of the preparation examples. Example 1

[0035] S1: Prepare the reaction bottom solution: Dissolve 170 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, and control the temperature at 35 °C to obtain the reaction bottom solution; S2: Prepare the dispersion solution: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, and then control the temperature at 35 °C to obtain the dispersion solution; S3: Prepare the alkali solution: Dissolve 1.06 g of sodium carbonate in 100 ml of deionized water, and control the temperature at 35 °C to form the alkali solution; S4: Prepare the reducing solution: Dissolve 102 g of ascorbic acid in 2 L of deionized water, and control the temperature at 35 °C to form the reducing solution; S5: Prepare the modification solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form the modification solution; S6: Reaction: Add the dispersion solution prepared in S2 to the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, add the alkali solution prepared in S3 to the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, then add the reducing solution prepared in S4 at a rate of 200 ml / min, stir at 10000 rpm for 1 minute, and then add the modification solution prepared in S5, stir at 10000 rpm for 1 minute to obtain the reaction mixture; S7: Cleaning: Put the reaction mixture prepared in S6 into a filter press, wash it with water until the conductivity < 10 us / cm, and then dehydrate it with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder prepared in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns. Example 2

[0036] S1: Prepare the reaction bottom solution: Dissolve 170 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, and control the temperature at 35 °C to obtain the reaction bottom solution; S2: Prepare the dispersion solution: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, and then control the temperature at 35 °C to obtain the dispersion solution; S3: Prepare the alkali solution: Dissolve 3.6 g of sodium hydroxide in 1000 ml of deionized water, and control the temperature at 35 °C to form the alkali solution; S4: Prepare the reducing solution: Dissolve 102 g of ascorbic acid in 2 L of deionized water, and control the temperature at 35 °C to form the reducing solution; S5: Prepare the modification solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form the modification solution; S6: Reaction: Add the dispersion prepared in S2 into the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, add the alkali solution prepared in S3 into the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, then add the reducing solution prepared in S4 at a rate of 200 ml / min, add the modified solution prepared in S5 after stirring at 10000 rpm for 1 minute, stir at 10000 rpm for 1 minute, and react to obtain a reaction mixture; S7: Cleaning: Put the reaction mixture prepared in S6 into a filter press, wash with water until the conductivity < 10 us / cm, and then dehydrate with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder prepared in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns. Example 3

[0037] S1: Prepare the reaction bottom solution: Dissolve 312 g of silver sulfate in 5 L of deionized water, adjust the pH to 1 with nitric acid, and control the temperature at 35 °C to obtain the reaction bottom solution; S2: Prepare the dispersion: Dissolve 10 g of ethanol in 200 ml of deionized water at 70 °C, and then control the temperature at 35 °C to obtain the dispersion; S3: Prepare the alkali solution: Dissolve 3 g of sodium carbonate in 100 ml of deionized water, and control the temperature at 35 °C to form the alkali solution; S4: Prepare the reducing solution: Dissolve 102 g of ascorbic acid in 2 L of deionized water, and control the temperature at 35 °C to form the reducing solution; S5: Prepare the modified solution: Dissolve 0.1 g of stearic acid in 50 ml of absolute ethanol to form the modified solution; S6: Reaction: Add the dispersion prepared in S2 into the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, add the alkali solution prepared in S3 into the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, then add the reducing solution prepared in S4 at a rate of 200 ml / min, add the modified solution prepared in S5 after stirring at 10000 rpm for 1 minute, stir at 10000 rpm for 1 minute, and react to obtain a reaction mixture; S7: Cleaning: Put the reaction mixture prepared in S6 into a filter press, wash with water until the conductivity < 10 us / cm, and then dehydrate with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder prepared in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns. Example 4

[0038] S1: Prepare the reaction bottom solution: Dissolve 400 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, and control the temperature at 35 °C to obtain the reaction bottom solution; S2: Preparation of dispersion: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, then control the temperature to 35 °C to obtain a dispersion; S3: Preparation of alkaline solution: Dissolve 2.5 g of diethanolamine in 100 ml of deionized water, control the temperature to 35 °C to form an alkaline solution; S4: Preparation of reducing solution: Dissolve 102 g of ascorbic acid in 2 L of deionized water, control the temperature to 35 °C to form a reducing solution; S5: Preparation of modified solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form a modified solution; S6: Reaction: Add the dispersion prepared in S2 to the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, add the alkaline solution prepared in S3 to the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, then add the reducing solution prepared in S4 at a rate of 200 ml / min, stir at 10000 rpm for 1 minute and then add the modified solution prepared in S5, stir at 10000 rpm for 1 minute to obtain a reaction mixture; S7: Cleaning: Put the reaction mixture prepared in S6 into a filter press, wash with water until the conductivity < 10 us / cm, and then dehydrate with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder prepared in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns. Example 5

[0039] S1: Preparation of reaction bottom solution: Dissolve 170 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, control the temperature to 35 °C to obtain a reaction bottom solution; S2: Preparation of dispersion: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, then control the temperature to 35 °C to obtain a dispersion; S3: Preparation of alkaline solution: Dissolve 1.06 g of sodium carbonate in 100 ml of deionized water, control the temperature to 35 °C to form an alkaline solution; S4: Preparation of reducing solution: Dissolve 102 g of ascorbic acid in 2 L of deionized water, control the temperature to 35 °C to form a reducing solution; S5: Preparation of modified solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form a modified solution; S6: Reaction: Add the dispersion prepared in S2 to the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, add the alkaline solution prepared in S3 to the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, then add the reducing solution prepared in S4 at a rate of 300 ml / min, stir at 10000 rpm for 1 minute and then add the modified solution prepared in S5, stir at 10000 rpm for 1 minute to obtain a reaction mixture; S7: Cleaning: Put the reaction mixture obtained in S6 into a filter press, wash it with water until the conductivity < 10 us / cm, and then dehydrate it with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder obtained in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns. Example 6

[0040] S1: Prepare the reaction bottom liquid: Dissolve 170 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, and control the temperature at 65 °C to obtain the reaction bottom liquid; S2: Prepare the dispersion liquid: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, and then control the temperature at 35 °C to obtain the dispersion liquid; S3: Prepare the alkali solution: Dissolve 1.06 g of sodium carbonate in 100 ml of deionized water, and control the temperature at 35 °C to form the alkali solution; S4: Prepare the reducing solution: Dissolve 240 g of glycerol in 2 L of deionized water, and control the temperature at 65 °C to form the reducing solution; S5: Prepare the modification solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form the modification solution; S6: Reaction: Add the dispersion liquid obtained in S2 to the reaction bottom liquid obtained in S1, stir at 10000 rpm for 1 minute, add the alkali solution obtained in S3 to the reaction bottom liquid obtained in S1, stir at 10000 rpm for 1 minute, then add the reducing solution obtained in S4 at a rate of 200 ml / min, stir at 10000 rpm for 1 minute, and then add the modification solution obtained in S5, stir at 10000 rpm for 1 minute, and react to obtain the reaction mixture; S7: Cleaning: Put the reaction mixture obtained in S6 into a filter press, wash it with water until the conductivity < 10 us / cm, and then dehydrate it with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder obtained in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns. Example 7

[0041] S1: Prepare the reaction bottom liquid: Dissolve 170 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, and control the temperature at 65 °C to obtain the reaction bottom liquid; S2: Prepare the dispersion liquid: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, and then control the temperature at 35 °C to obtain the dispersion liquid; S3: Prepare the alkali solution: Add 1.06 g of sodium carbonate and 100 g of the glucose capsule prepared in Preparation Example 1 to 100 ml of deionized water, and control the temperature at 35 °C to form the alkali solution; S4: Prepare the reducing solution: Dissolve 240 g of glycerol in 2 L of deionized water, and control the temperature at 65 °C to form the reducing solution; S5: Prepare the modification solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form the modification solution; S6: Reaction: Add the dispersion obtained in S2 to the reaction bottom solution obtained in S1, stir at 10000 rpm for 1 minute, add the lye obtained in S3 to the reaction bottom solution obtained in S1, stir at 10000 rpm for 1 minute, then add the reducing solution obtained in S4 at a rate of 200 ml / min, stir at 10000 rpm for 1 minute, and then add the modification solution obtained in S5, stir at 10000 rpm for 1 minute to obtain a reaction mixture; S7: Cleaning: Put the reaction mixture obtained in S6 into a filter press, wash it with water until the conductivity < 10 us / cm, and then dehydrate it with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder obtained in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns. Example 8

[0042] S1: Prepare the reaction bottom solution: Dissolve 170 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, and control the temperature at 65 °C to obtain the reaction bottom solution; S2: Prepare the dispersion: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, and then control the temperature at 35 °C to obtain the dispersion; S3: Prepare the lye: Add 1.06 g of sodium carbonate and 100 g of the glucose capsule prepared in Preparation Example 2 to 100 ml of deionized water, and control the temperature at 35 °C to form the lye; S4: Prepare the reducing solution: Dissolve 240 g of glycerol in 2 L of deionized water, and control the temperature at 65 °C to form the reducing solution; S5: Prepare the modification solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form the modification solution; S6: Reaction: Add the dispersion obtained in S2 to the reaction bottom solution obtained in S1, stir at 10000 rpm for 1 minute, add the lye obtained in S3 to the reaction bottom solution obtained in S1, stir at 10000 rpm for 1 minute, then add the reducing solution obtained in S4 at a rate of 200 ml / min, stir at 10000 rpm for 1 minute, and then add the modification solution obtained in S5, stir at 10000 rpm for 1 minute to obtain a reaction mixture; S7: Cleaning: Put the reaction mixture obtained in S6 into a filter press, wash it with water until the conductivity < 10 us / cm, and then dehydrate it with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder obtained in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns. Example 9

[0043] S1: Prepare the reaction bottom solution: Dissolve 170 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, and control the temperature at 65 °C to obtain the reaction bottom solution; S2: Prepare the dispersion solution: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, and then control the temperature at 35 °C to obtain the dispersion solution; S3: Prepare the alkaline solution: Add 1.06 g of sodium carbonate and 100 g of the glucose capsules prepared in Preparation Example 3 to 100 ml of deionized water, and control the temperature at 35 °C to form the alkaline solution; S4: Prepare the reducing solution: Dissolve 240 g of glycerol in 2 L of deionized water, and control the temperature at 65 °C to form the reducing solution; S5: Prepare the modification solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form the modification solution; S6: Reaction: Add the dispersion solution prepared in S2 to the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, add the alkaline solution prepared in S3 to the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, then add the reducing solution prepared in S4 at a rate of 200 ml / min, stir at 10000 rpm for 1 minute, add the modification solution prepared in S5, stir at 10000 rpm for 1 minute, and react to obtain the reaction mixture; S7: Cleaning: Put the reaction mixture prepared in S6 into a filter press, wash with water until the conductivity < 10 us / cm, and then dehydrate with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder prepared in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns.

[0044] Example 10: S1: Prepare the reaction bottom solution: Dissolve 170 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, and control the temperature at 65 °C to obtain the reaction bottom solution; S2: Prepare the dispersion solution: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, and then control the temperature at 35 °C to obtain the dispersion solution; S3: Prepare the alkaline solution: Add 1.06 g of sodium carbonate and 100 g of the ascorbic acid capsules prepared in Preparation Example 4 to 100 ml of deionized water, and control the temperature at 35 °C to form the alkaline solution; S4: Prepare the reducing solution: Dissolve 240 g of glycerol in 2 L of deionized water, and control the temperature at 65 °C to form the reducing solution; S5: Prepare the modification solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form the modification solution; S6: Reaction: Add the dispersion obtained in S2 into the reaction bottom solution obtained in S1, stir at 10000 rpm for 1 minute, add the alkali solution obtained in S3 into the reaction bottom solution obtained in S1, stir at 10000 rpm for 1 minute, then add the reducing solution obtained in S4 at a rate of 200 ml / min, stir at 10000 rpm for 1 minute, and then add the modified solution obtained in S5, stir at 10000 rpm for 1 minute to obtain a reaction mixture; S7: Cleaning: Put the reaction mixture obtained in S6 into a filter press, wash it with water until the conductivity < 10 us / cm, and then dehydrate it with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder obtained in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns.

[0045] Comparative Example 1: S1: Prepare the reaction bottom solution: Dissolve 170 g of silver nitrate in 5 L of deionized water, control the temperature at 35 °C to obtain the reaction bottom solution; S2: Prepare the dispersion: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, and then control the temperature at 35 °C to obtain the dispersion; S3: Prepare the alkali solution: Dissolve 1.06 g of sodium carbonate in 100 ml of deionized water, control the temperature at 35 °C to form the alkali solution; S4: Prepare the reducing solution: Dissolve 102 g of ascorbic acid in 2 L of deionized water, control the temperature at 35 °C to form the reducing solution; S5: Prepare the modified solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form the modified solution; S6: Reaction: Add the dispersion obtained in S2 into the reaction bottom solution obtained in S1, stir at 10000 rpm for 1 minute, add the alkali solution obtained in S3 into the reaction bottom solution obtained in S1, stir at 10000 rpm for 1 minute, then add the reducing solution obtained in S4 at a rate of 200 ml / min, stir at 10000 rpm for 1 minute, and then add the modified solution obtained in S5, stir at 10000 rpm for 1 minute to obtain a reaction mixture; S7: Cleaning: Put the reaction mixture obtained in S6 into a filter press, wash it with water until the conductivity < 10 us / cm, and then dehydrate it with absolute ethanol to obtain dehydrated silver powder; S8: Dry the dehydrated silver powder obtained in S7 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns.

[0046] Comparative Example 2: S1: Prepare the reaction bottom solution: Dissolve 170 g of silver nitrate in 5 L of deionized water, adjust the pH to 1 with nitric acid, control the temperature at 35 °C to obtain the reaction bottom solution; S2: Preparation of dispersion: Dissolve 5 g of gelatin in 200 ml of deionized water at 70 °C, and then control the temperature to 35 °C to obtain a dispersion; S3: Preparation of reducing solution: Dissolve 102 g of ascorbic acid in 2 L of deionized water and control the temperature to 35 °C to form a reducing solution; S4: Preparation of modified solution: Dissolve 0.1 g of oleic acid in 50 ml of absolute ethanol to form a modified solution; S5: Reaction: Add the dispersion prepared in S2 to the reaction bottom solution prepared in S1, stir at 10000 rpm for 1 minute, then add the reducing solution prepared in S3 at a rate of 200 ml / min, stir at 10000 rpm for 1 minute, add the modified solution prepared in S4, and stir at 10000 rpm for 1 minute to obtain a reaction mixture; S6: Cleaning: Put the reaction mixture prepared in S5 into a filter press, wash with water until the conductivity < 10 us / cm, and then dehydrate with absolute ethanol to obtain dehydrated silver powder; S7: Dry the dehydrated silver powder prepared in S6 at 50 °C for 10 hours, and then pulverize it to obtain spherical silver powder with surface patterns.

[0047] Performance test Perform tap density, particle size distribution, and specific surface area tests on the silver powder prepared in the examples and comparative examples. The test results are shown in Table 1.

[0048] Table 1

[0049] Combined with Table 1, it can be seen from Examples 1-6 and Comparative Examples 1-2 that by limiting the raw materials, steps, and process parameters of the preparation process in this application, the spherical silver powder prepared has regular morphology and uniform particle size.

[0050] Combined with Table 1, it can be seen from Examples 1 and 6-10 that by further adding glucose capsules and limiting the raw materials and mass ratio of the glucose wall material, and limiting the temperature of the raw materials in each step, the glucose capsules can slowly release glucose and gelatin, regulate and protect the reduction process of silver powder, and the morphology of the prepared silver powder is further improved, with high tap density and large specific surface area.

[0051] This specific embodiment is only an explanation of this application and does not limit this application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A method for preparing spherical silver powder with surface patterns, characterized in that: The following steps are involved: S1: preparing a reaction base liquid: dissolving a silver salt in water to obtain a silver salt solution, and then using a pH adjuster to adjust the pH value and temperature of the silver salt solution to obtain a reaction base liquid, wherein the silver salt comprises one or more of silver nitrate, silver sulfate, silver carbonate, and silver oxalate, and the pH adjuster comprises one or more of nitric acid, sulfuric acid, hydrochloric acid, oxalic acid, acetic acid, benzenesulfonic acid, sodium hydroxide, ammonia water, sodium carbonate, sodium citrate, potassium citrate, monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, formamide, acetamide, and propionamide; S2: preparing a dispersion: dissolving a dispersant in water and adjusting the temperature to obtain a dispersion, wherein the dispersant comprises one or more of methylcellulose, carboxymethylcellulose, gelatin, polyvinyl pyrrolidone, gum arabic, gum guar, ethanol, Tween, polyethylene glycol, glycerol, methylpentanol, octylamine, polyethylamide, polyethylene glycol esters of fatty acids, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, glycolic acid, glyceric acid, malic acid, succinic acid, sodium citrate, potassium citrate, phthalic acid, isophthalic acid, terephthalic acid, triethylhexyl phosphoric acid, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate; S3: preparing alkali solution: dissolving an alkaline solvent in water to obtain an alkali solution, wherein the alkaline solvent comprises one or more of sodium hydroxide, ammonia water, sodium carbonate, sodium citrate, potassium citrate, monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, formamide, acetamide, and propionamide; S4: preparing a reducing solution: dissolving a reducing agent in water and adjusting the temperature to obtain a reducing solution, wherein the reducing agent comprises one or more of ascorbic acid, glucose, hydrazine hydrate, formaldehyde, hydrogen peroxide, sodium hypochlorite, sodium borohydride, sulfite glycol, glycerol, and hydroquinone; S5: preparing a modification liquid: dissolving a modification agent in anhydrous ethanol to obtain a modification liquid, wherein the modification agent comprises one or more of oleic acid, linoleic acid, linolenic acid, stearic acid, palmitic acid, arachidic acid, myristic acid, lauric acid, oleylamine, palmitic acid, monoethanolamine, diethanolamine, and triethanolamine; S6: reaction: adding the dispersion liquid prepared by S2 to the reaction base liquid prepared by S1, stirring for the first time, adding the alkali solution prepared by S3 to the reaction base liquid prepared by S1, stirring for the second time, then adding the reducing solution prepared by S4, stirring for the third time, adding the modifying solution prepared by S5, stirring for the fourth time, and reacting to obtain a reaction mixture; S7: Cleaning: Put the reaction mixture obtained in S6 into a filter press, wash with water until the conductivity is less than 10us / cm, and then dehydrate with anhydrous ethanol to obtain dehydrated silver powder; S8: The dehydrated silver powder obtained in S7 is heated and dried, and then crushed to obtain spherical silver powder with surface patterns.

2. The method for preparing the surface patterned spherical silver powder according to claim 1, characterized in that: The molar concentration of the silver salt solution in S1 is 0.1-0.5 mol / L, the pH value is 1.0-2.0, and the temperature is 25-65°C; the concentration of the dispersion in S2 is 1%-4%wt, the temperature is 35-65°C, and the mass of the dispersion is 0.5%-5% of the reaction base liquid; the mass concentration of the alkali solution in S3 is 0.1%-5%wt, and the molar ratio of the alkaline solvent to the silver salt is 1:90-110; the molar concentration of the reducing solution in S4 is 0.25-0.7 mol / L, and the temperature is 25-65°C; the mass concentration of the modifying solution in S5 is 0.1-0.2wt%; the first stirring time in S6 is 1-2 minutes, the second stirring time is 1-2 minutes, the third stirring time is 1-2 minutes, and the fourth stirring time is 20-25 minutes.

3. The method for preparing the surface patterned spherical silver powder according to claim 1, characterized in that: The speed of adding the reducing solution prepared by S4 into S6 is 200-250 ml / min.

4. The method for preparing the surface patterned spherical silver powder according to claim 1, characterized in that: The temperature of heating and drying in S8 is 50-80°C.

5. The method for preparing the surface patterned spherical silver powder according to claim 1, characterized in that: The average particle size D50 of the surface patterned spherical silver powder is 1.0-3.0um, and the tap density is >4.5g / cm 3 , specific surface area <0.8m 2 / g.

6. The method for preparing the surface patterned spherical silver powder according to claim 1, characterized in that: The alkaline solution also includes glucose capsules, the core material of the glucose capsules includes glucose, and the wall material includes gelatin and chitosan.

7. The method for preparing the surface patterned spherical silver powder according to claim 6, characterized in that: The mass ratio of gelatin to chitosan in the wall material is 1:1-1.

5.

8. The method for preparing the surface patterned spherical silver powder according to claim 6, characterized in that: The temperature of the alkali solution is 30-40°C, the temperature of the reaction base solution is 50-65°C, and the temperature of the reducing solution is 50-65°C.

9. The method for preparing the surface patterned spherical silver powder according to claim 6, characterized in that: The preparation steps of the glucose capsule include: uniformly mixing gelatin, chitosan and water, and heating to obtain a wall material mixture; adding glucose to the mixture, and stirring to obtain a mixture; adjusting the pH value of the mixture, cooling with ice water to precipitate and condense chitosan, and filtering, washing and drying to obtain the glucose capsule.

10. The method for preparing the surface patterned spherical silver powder according to claim 9, characterized in that: The stirring speed is 4000-5000 r / min, and the pH value is 8-9.

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