Silver powder with uniform internal pores and surface growth nanoparticles and a preparation method thereof

Abstract

The application provides silver powder with uniform internal pores and surface growth nanoparticles and a preparation method thereof, and relates to the material field.The silver powder is prepared through the following steps: S1, configuring silver nitrate solution; S2, configuring a base solution: adding a reducing agent and a dispersing agent into deionized water and stirring until uniform; then adding lye to adjust the pH value; S3, configuring a reducing solution with a pH value of 3.0-8.0; S4, configuring secondary reaction additives: adding halogen metal salt into ammonia water, stirring and mixing until uniform; S5, adding the silver nitrate solution and the reducing solution into the base solution for the first time, mixing until uniform; adding the secondary reaction additives, mixing until uniform, and then adding the remaining silver nitrate solution and reducing solution for the second time, mixing until uniform; S6, adding coating agents, mixing until uniform to perform coating reaction, and then performing solid-liquid separation, drying and crushing to obtain the silver powder.The silver powder has good particle size uniformity, the particle size distribution is 0.7-0.8, and the internal pores are uniform.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of materials, in particular to a kind of silver powder with uniform internal porosity and surface growth nanoparticles and a preparation method thereof. BACKGROUND

[0002] With the rapid development of production technologies such as photovoltaic narrow linewidth printing and laser sintering, the requirements for the printability and rapid sintering performance of silver paste are becoming higher and higher. As the main raw material of silver paste, the particle size distribution, internal structure and micro-morphology of silver powder are particularly important for the printability and rapid sintering performance of silver paste.

[0003] The hollow structure of the polycrystalline silver powder is beneficial to reduce the silver content in the photovoltaic silver paste, thereby achieving the purpose of reducing cost. However, the silver powder on the market has single hollow hole, large hole, and uneven porosity, which can easily lead to excessive shrinkage and collapse of silver wire during sintering, resulting in low product qualification rate, short service life, and complex sintering process, which is not conducive to industrial production. SUMMARY

[0004] The present application provides a kind of silver powder with uniform internal porosity and surface growth nanoparticles, which has good particle size uniformity, particle size distribution of 0.7-0.8, and uniform internal porosity.

[0005] Another object of the present application is to provide a preparation method of silver powder with uniform internal porosity and surface growth nanoparticles, which controls the reaction rate by controlling the pH value of the reactants and the addition sequence, thereby controlling the size of silver ion crystal grain clusters and the uniformity of internal porosity of silver powder.

[0006] The present application solves the technical problem by using the following technical scheme.

[0007] In one aspect, the present application provides a preparation method of silver powder with uniform internal porosity and surface growth nanoparticles, comprising the following steps:

[0008] S1, configure silver nitrate solution;

[0009] S2, configure the bottom solution: add reducing agent and dispersing agent to deionized water and stir uniformly; then add alkali solution to adjust the pH value to 3-7;

[0010] S3, configure the reducing solution: add reducing agent to deionized water and stir uniformly, then add appropriate amount of ammonia water or sodium hydroxide to control the pH of the solution to 3.0-8.0;

[0011] S4, configuring secondary reaction additive: adding soluble halogen metal sodium salt or potassium salt into ammonia water, stirring, mixing uniformly; wherein, the soluble halogen metal sodium salt or potassium salt can be NaCl, KCl, NaBr, KBr and the like metal salt.

[0012] S5, adding silver nitrate solution, reducing solution into the bottom liquid for the first time, mixing uniformly; adding secondary reaction additive, mixing uniformly, adding the remaining silver nitrate solution, reducing solution for the second time, mixing uniformly;

[0013] S6, adding coating agent, mixing uniformly to carry out coating reaction, after the coating reaction, carrying out solid-liquid separation, drying, crushing, to obtain the silver powder.

[0014] In some embodiments of the present application, in the step S1, the step of configuring silver nitrate solution is: dissolving silver nitrate crystal in deionized water, stirring uniformly, preserving at the temperature of 20-30℃, for standby, wherein, the mass fraction of silver nitrate solution is 20-30wt%.

[0015] In some embodiments of the present application, in the step S2, the reducing agent is one or a mixture of two of ascorbic acid, sodium ascorbate; the dispersing agent is one or more of PVPK30 (polyvinylpyrrolidone K30), PVPK60 (polyvinylpyrrolidone K60), gelatin, acacia, polyethylene glycol, polyvinyl alcohol.

[0016] In some embodiments of the present application, in the step S2, the mass fraction of reducing agent in the bottom liquid is 1.0-4.2wt%, and the mass fraction of dispersing agent in the bottom liquid is 1.0-3.0wt%.

[0017] In some embodiments of the present application, in the step S3, the reducing agent is one or a mixture of two of ascorbic acid, sodium ascorbate, and the mass fraction of reducing agent in the reducing agent solution is 8.0-10wt%.

[0018] In some embodiments of the present application, in the step S5, the volume of silver nitrate solution and reducing solution added for the first time is respectively 75-98% of the total amount, and the feeding is completed within 4-8min.

[0019] In some embodiments of the present application, in the step S5, the volume of silver nitrate solution and reducing solution added for the first time is respectively 95% of the total amount.

[0020] In some embodiments of the present application, in the step S6, the coating agent is one of stearic acid, lauric acid, myristic acid, oleic acid.

[0021] In some embodiments of the present application, in the step S6, the mass of the coating agent is 0.1-1% of the mass of the silver nitrate.

[0022] In another aspect, the embodiments of the present application provide a silver powder with uniform internal pores and surface grown nanoparticles, which is prepared by the above preparation method.

[0023] Compared with the prior art, the embodiments of the present application have at least the following advantages or beneficial effects:

[0024] The silver powder prepared by the preparation method has the characteristics of good particle size uniformity, the particle size distribution is 0.7-0.8, and the particles are uniform; the silver powder has relatively uniform size pores inside, which makes the silver powder maintain its high tap density performance, reduce the sintering temperature of the silver powder, and keep the silver wire in good line type after rapid sintering. The silver powder has a controllable number of nano silver particles on the surface of the silver powder particles, which makes it easier to generate sintering necks during the sintering process of the silver powder, has higher sintering activity, and has a wider sintering temperature window after being configured into silver paste.

[0025] The preparation method provided by the present application controls the redox rate of silver nitrate to obtain silver powder containing internal pores, the internal pore size is uniform, and the porosity is between 2% and 5%, which can effectively maintain the high aspect ratio of the silver wire during the sintering process without affecting the tap density. Secondly, by adding a secondary reaction additive to the reaction system, the silver powder precursor solution of the previous step is subjected to a secondary reaction to re-control the pH value, control the particle size, and re-oxidize and reduce the reaction to further attach nano silver particles to the surface of the silver powder particles. The silver powder particle size is 1.0-2.0 μm, the particle size distribution is uniform, and the tap density of the silver powder is ≥5.8 g / cm 3 . BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0027] Figure 1 Figure 1 is a silver powder section electron micrograph of Example 1 of the present application;

[0028] Figure 2 Figure 3 is a silver powder section electron micrograph of Example 3 of the present application;

[0029] Figure 3 Figure 4 is a silver powder section electron micrograph of Example 4 of the present application;

[0030] Figure 4Silver powder electron microscope image for Example 2;

[0031] Figure 5 Silver powder electron microscope image for Example 4;

[0032] Figure 6 Silver powder electron microscope image for Example 5. DETAILED DESCRIPTION

[0033] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. If specific conditions are not indicated in the embodiments, conventional conditions or conditions suggested by manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, they are all conventional products that can be purchased in the market.

[0034] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to specific embodiments.

[0035] The features and performances of the present application will be described in further detail below in combination with embodiments.

[0036] Example 1

[0037] The silver powder in the present embodiment is prepared according to the following steps:

[0038] S1, Oxidizing solution preparation: silver nitrate crystals are dissolved in pure water to prepare a solution with a concentration of 30%wt, wherein the conductivity of the pure water is required to be 1.5 μm / cm, and the temperature after dissolution is controlled at 25±1℃.

[0039] S2, Base solution preparation: 30L of pure water is added into a reaction kettle, and then a reducing agent (vitamin C, which is an industrial grade Vc that can be commonly purchased in the market) and a dispersing agent (PVP K30, which is a PVP that can be commonly purchased in the market) are added respectively. The constant stirring speed is 300 r / min, and the stirring is performed for 30 minutes to make the mixture uniform, and the temperature is controlled at 25±1℃. Then, an appropriate amount of ammonia water is added to control the pH of the mixed solution between 3.0-4.0. The mass fraction of the reducing agent in the base solution is 2.5%wt, and the mass fraction of the dispersing agent is 3.0%wt.

[0040] S3, Reducing solution preparation: vitamin C is added into deionized water, and stirred uniformly to prepare a vitamin C solution with a mass fraction of 10%wt. An appropriate amount of sodium hydroxide is added to control the pH of the solution between 3-4.

[0041] S4, Secondary reaction additive preparation: 800ml of ammonia water with a mass fraction of 25% is measured, and 0.2g of NaCl is dissolved in the ammonia water for standby.

[0042] S5, redox reaction: the reactor bottom liquid of S2 is kept at 25±1°C, the stirring speed is between 300r / min, after fully dissolved, stop temperature control. The prepared oxidizing solution of S1 and the prepared reducing solution of S3 are added into the reactor bottom liquid at the same time, when 95% of the total weight of the oxidizing solution is added (i.e. the first time), stop adding the oxidizing solution and the reducing solution, the feeding time is controlled within 8 min. Then the secondary reaction additive prepared by S4 is poured into the reactor bottom liquid, and the remaining oxidizing solution and reducing solution are added into the bottom liquid at the same flow rate (the second time);

[0043] S6, after the feeding is completed, the coating agent (stearic acid) is added into the reactor, the amount of the coating agent is 1% of the mass of silver nitrate, the coating time is controlled within 20 min, then the discharge is carried out, and after the post-processing such as centrifugation, drying and crushing, the silver powder is obtained.

[0044] Example 2

[0045] The difference from example 1 is that in this example 2, in step S2, the pH value of the bottom liquid is controlled at 4-5; in step S3, the pH value of the reducing solution is controlled at 5-6; in step S5, the amount of the first added oxidizing solution is 88%, and the amount of the second added oxidizing solution is 12%. The rest of the experimental conditions, parameters and raw materials are the same as those of example 1.

[0046] Example 3

[0047] The difference from example 1 is that in this example 3, in step S2, the pH value of the bottom liquid is controlled at 5-7; in step S3, the pH value of the reducing solution is controlled at 7-8, and the rest of the experimental conditions, parameters and raw materials are the same as those of example 1.

[0048] Example 4

[0049] The difference from example 1 is that in this example 4, in step S2, the pH value of the bottom liquid is controlled at 4-5; in step S3, the pH value of the reducing solution is controlled at 5-6; the rest of the experimental conditions, parameters and raw materials are the same as those of example 1.

[0050] Example 5

[0051] The difference from example 1 is that in this example 5, in step S2, the pH value of the bottom liquid is controlled at 4-5; in step S3, the pH value of the reducing solution is controlled at 5-6; in step S5, the amount of the first added oxidizing solution is 80%, and the amount of the second added oxidizing solution is 20%, and the rest of the experimental conditions, parameters and raw materials are the same as those of example 1.

[0052] Example 6

[0053] The silver powder of the present example is prepared by the following steps:

[0054] S1, Oxidizing solution preparation: silver nitrate crystals are dissolved in pure water to prepare a solution with a concentration of 25% wt, wherein the conductivity of the pure water is required to be 1.5 μm / cm, and the temperature after dissolution is controlled at 25±1℃.

[0055] S2, Base solution preparation: 30 L of pure water is added to the reactor, then the reducing agent (vitamin C, which is an industrial grade Vc commonly available on the market) and the dispersing agent (PVP K30, which is a PVP commonly available on the market) are added respectively, the stirring speed is kept at 300 r / min, and the mixture is stirred for 30 minutes to make it uniform, and the temperature is controlled at 25±1℃. Then, an appropriate amount of ammonia water is added to control the pH of the mixed solution between 3.0-4.0, wherein the mass fraction of the reducing agent in the base solution is 2% wt, and the mass fraction of the dispersing agent is 2% wt.

[0056] S3, Reducing solution preparation: a solution with a mass fraction of 8% wt vitamin C is prepared, and an appropriate amount of ammonia water is added to control the pH of the solution between 3.0-4.0.

[0057] S4, Secondary reaction additive preparation: 800 ml of 25% ammonia water is measured, and 0.2 g of NaCl is dissolved in the ammonia water for standby;

[0058] S5, Oxidation-reduction reaction: the base solution of S2 is kept at a constant temperature of 25±1℃, and the stirring speed is kept between 300 r / min. After complete dissolution, the temperature control is stopped. The prepared oxidizing solution of S1 and the prepared reducing solution of S3 are added to the base solution of the reactor at the same time, and when 75% of the total weight of the oxidizing solution is added (i.e. the first addition), the addition of the oxidizing solution and the reducing solution is stopped, and the addition time is controlled within 8 min. Then, the secondary reaction additive prepared in S4 is poured into the base solution of the reactor, and the remaining oxidizing solution and reducing solution are added to the base solution at the same flow rate (second addition);

[0059] S6, After the addition is completed, the coating agent (stearic acid) is added to the reactor, and the amount of the coating agent is 0.5% of the mass of silver nitrate, and the coating time is controlled within 15 min. Then, the material is discharged, and after the post-processing of centrifugation, drying, and crushing, the silver powder is obtained.

[0060] Example 7

[0061] The silver powder of the present example is prepared by the following steps:

[0062] S1, Oxidizing solution preparation: silver nitrate crystals are dissolved in pure water to prepare a solution with a concentration of 20% wt, wherein the conductivity of the pure water is required to be 1.5 μm / cm, and the temperature after dissolution is controlled at 25±1℃.

[0063] S2, bottom liquid configuration: 300L of pure water is added to the reaction kettle, then reducing agent (vitamin C, which is commonly available on the market industrial grade Vc) and dispersant (PVP K30, which is commonly available on the market PVP) are added respectively, the constant stirring speed is 300r / min, stirring for 30 minutes, make it mix evenly, and control the temperature at 25±1℃, then add appropriate amount of ammonia water, so that the pH of the mixed solution is controlled between 3.0-4.0, wherein the mass fraction of reducing agent in the bottom liquid is 1%wt, and the mass fraction of dispersant is 1.5%wt;

[0064] S3, reducing solution configuration: configure a mass fraction of 9%wt sodium ascorbate solution, add appropriate amount of ammonia water, control the pH of the solution between 3.0-4.0;

[0065] S4, secondary reaction additive configuration: measure 800ml of 25%wt ammonia water, add 0.2g of KCl dissolved in ammonia water, and reserve;

[0066] S5, oxidation-reduction reaction: the bottom liquid of S2 is kept at 25±1℃, and the stirring speed is 300r / min. After reaching the requirement, stop temperature control. The oxidation liquid prepared in S1 and the reducing solution prepared in S3 are added to the bottom liquid of the reaction kettle at the same time, when 80% of the total weight of the oxidation liquid is added (i.e. the first time), stop adding oxidation liquid and reducing liquid, and the feeding time is controlled within 8min. Then pour the secondary reaction additive prepared in S4 into the bottom liquid of the reaction kettle, and then add the remaining oxidation liquid and reducing liquid to the bottom liquid at the same flow rate (second time);

[0067] S6, after the feeding is completed, the coating agent (stearic acid) is added to the reaction kettle, the amount of coating agent is 0.1% of the mass of silver nitrate, and the coating time is controlled within 20min, then discharge, and after centrifugation, drying, crushing and other post-processing, silver powder is obtained.

[0068] Example 8

[0069] The silver powder of this example is prepared according to the following steps:

[0070] S1, oxidation liquid configuration: silver nitrate crystals are added to pure water for dissolution, and a solution with a concentration of 30%wt is configured, wherein the conductivity of the pure water is required to be 1.5μm / cm, and the temperature after dissolution is controlled at 25±1℃.

[0071] S2, bottom liquid configuration: 300 L of pure water was added to the reaction kettle, then reducing agent (sodium ascorbate) and dispersing agent (PVP K30, which can be commonly purchased on the market) were added respectively, the constant stirring speed was 300 r / min, stirring for 30 minutes to make it uniformly mixed, and the temperature was controlled at 25±1°C, then appropriate amount of ammonia water was added to control the pH of the mixed solution between 3.0-4.0, wherein the mass fraction of the reducing agent in the bottom liquid was 1%wt, and the mass fraction of the dispersing agent was 2.5%wt;

[0072] S3, reducing solution configuration: a 10%wt mass fraction of sodium ascorbate solution was configured, appropriate amount of ammonia water was added, and the pH of the solution was controlled between 3.0-4.0;

[0073] S4, secondary reaction additive configuration: 800ml of 25% ammonia water was measured, 0.2g of KCl was dissolved in the ammonia water, and was ready for use;

[0074] S5, oxidation-reduction reaction: the bottom liquid of S2 was kept at a constant temperature of 25±1°C, and the stirring speed was between 300 r / min, then the temperature control was stopped after reaching the requirement. The oxidation liquid prepared in S1 and the reducing solution prepared in S3 were added to the bottom liquid of the reaction kettle at the same time, when 98% of the total weight of the oxidation liquid was added (i.e. the first time), the addition of the oxidation liquid and the reducing liquid was stopped, and the feeding time was controlled within 8 minutes. Then the secondary reaction additive prepared in S4 was poured into the bottom liquid of the reaction kettle, and the remaining oxidation liquid and reducing liquid were added to the bottom liquid at the same flow rate (second time);

[0075] S6, after the feeding was completed, the coating agent (stearic acid) was added to the reaction kettle, the amount of the coating agent was 0.5% of the mass of silver nitrate, the coating time was controlled within 20 minutes, then the discharge was carried out, and after the post-processing such as centrifugation, drying and crushing, the silver powder was obtained.

[0076] Examples 9-13

[0077] The difference between example 1 and examples 9-13 is that part of the raw materials are different from example 1, as shown in Table 1. The rest of the experimental conditions and parameters are the same as those of example 1. Among them, the reducing agent in Table 1 refers to the reducing agent in steps S2 and S3, and the reducing agent in the two steps is the same.

[0078] Table 1 Reducing agent Dispersing agent Coating agent Example 1 Vitamin C PVP K30 Stearic acid Example 9 Vitamin C Gelatin Stearic acid Example 10 Sodium ascorbate Polyethylene glycol Laurylic acid Example 11 Sodium ascorbate Gum arabic Myristic acid Example 12 Sodium ascorbate Polyvinyl alcohol Oleic acid Example 13 Vitamin C PVP K60 Laurylic acid

[0079] Experimental examples

[0080] The performances of the silver powders of examples 1-5 were tested, and the results are shown in Table 3. Among them, the differences between examples 1-5 are shown in Table 2.

[0081] Table 2

[0082]

[0083]

[0084] Table 3

[0085]

[0086] In combination with Table 2 and Table 3, comparing the three groups of data of Comparative Experimental Example 1, Example 3 and Example 4, when the pH is controlled by adding ammonia water, sodium hydroxide, etc. to the S2 base solution and S3 reducing solution, the higher the pH, the faster the reaction speed, and the smaller the particle size of the obtained silver powder. At the same time, due to the faster reaction speed, the silver powder grain size is smaller, the tap density is reduced, the specific surface area is increased, and the sintering activity is enhanced.

[0087] Comparing the three groups of data of Comparative Example 2, Example 4 and Example 5, when the amount of silver nitrate participating in the secondary reaction increases, the number of nano small particles wrapped on the surface of the silver powder increases, the overall tap density of the silver powder decreases, the specific surface area increases, and the sintering activity is enhanced.

[0088] Therefore, by controlling the pH of the base solution and the reducing solution to be 3-4, the tap density of the prepared silver powder is high, and the sintering performance of the silver powder is good.

[0089] (2) The cross-section of the silver powder of Example 1, Example 3-2 was observed, and the results are shown in Figures 1-3 From the electron microscope image, it can be seen that, in the comparison of the three groups of CP electron microscopes of Example 1, Example 3 and Example 4, when the pH is controlled by adding ammonia water, sodium hydroxide to the S2 base solution and S3 reducing solution, the higher the pH, the faster the reaction speed, the more silver microcrystals are formed, and it is easier to form silver microcrystal clusters, thereby resulting in larger holes in the silver powder.

[0090] From Example 4, when the pH of the system is controlled in a suitable range, the oxygen reduction reaction speed is uniform during the reaction process, and the internal space holes of the generated silver powder are uniformly distributed, and the hole size is uniform and moderate. In the sintering process of the photovoltaic silver paste, the silver powder maintains high sintering activity while maintaining good aspect ratio, and the take-up is better.

[0091] (3) The surface microstructure of the silver powder of Example 2, Example 4-3 was observed, and the results are shown in Figures 4-6 It can be seen that, in the comparison of the three groups of electron microscopes of Example 4, Experimental Example 2 and Example 5, when the amount of silver nitrate for the secondary reaction increases from 5% to 12% and 20%, the number of nano small powder wrapped on the surface of the silver powder increases significantly, and thus the sintering activity of the silver powder can be controlled by controlling the number of small powder.

[0092] Due to the current photovoltaic silver paste screen printing plate line width is more and more thin, the excess of nano small powder particles on the surface of silver powder can increase the silver powder roughness, the high oil absorption of silver powder, and the viscosity of silver paste, thereby affecting the printability of silver paste, causing the silver paste to increase the grid rate in the screen printing process, so the secondary reaction silver nitrate amount of 20% or less is preferred, and the printability of the prepared silver powder is optimal.

[0093] (4) 90% of the silver powder, 1% of the glass powder and 10% of the organic matter (containing carbinol, epoxy resin or acrylic resin, ethyl cellulose, etc.); pass through the defoaming agent, three-roll machine to mix evenly to make silver paste; print the silver paste to the photovoltaic cell substrate through the screen printing machine; put the photovoltaic cell substrate into the high-temperature sintering furnace, the sintering temperature is 750℃, and the photovoltaic cell is sintered; finally, use the HALM machine to test the electrical performance of the cell. The preparation of silver powder into silver paste, and the preparation and implementation process of electrical performance test all adopt existing common technical means, and the required materials and equipment are all conventional equipment that can be purchased on the market, and the influence of the model of the equipment and the supplier of the material on the test results is not large, so it is not described in detail here.

[0094] Table 4 Comparison of paste screen printing performance

[0095]

[0096] From the comparison of the performance data of the three groups of silver powder prepared by the above experimental examples 1, 3 and 4, when the pH value of the reaction system is increased, the oxidation-reduction rate is faster, the generated silver grain cluster is larger, and the internal hole is larger. For example, the silver powder of example 3 has high sintering activity, but it is easy to cause excessive shrinkage in the sintering densification process of silver line, the aspect ratio is poor, and the current and efficiency of the cell are relatively worse. The reaction rate of the reaction system of the silver powder of example 4 is controlled moderately, the size of the internal hole of the silver powder is uniform, the pore distribution is uniform, the high sintering activity and high filling are maintained at the same time, the shrinkage of the silver powder in the sintering process is moderate, the aspect ratio is good, and the current and efficiency of the silver powder are relatively improved.

[0097] Under the premise of keeping the internal uniformity of the silver powder, the performance data of the three groups of silver powder prepared by the above experimental examples 4, 2 and 5 are compared, when the amount of secondary reaction silver nitrate is increased, the number of nano particles on the surface of the silver powder is increased, the roughness of the silver powder is higher, and the sintering activity is higher. For example, the surface of the silver powder of example 5 has the most nano particles, the aspect ratio after screen printing is the best, and the current is also more advantageous, but the viscosity of the paste is too high, the printed silver line has large ups and downs, the grid line is easy to break, and the open pressure, filling and efficiency have no special obvious advantages. The surface particles of the silver powder of example 2 are moderate, the increase of the viscosity of the paste is less (within a reasonable range), which ensures the printability of the paste while obviously improving the current, filling and efficiency of the cell.

[0098] The embodiments described above are only part of the embodiments of the present application, rather than all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only to represent selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

Claims

1. A method for preparing silver powder with uniform internal pores and surface-grown nanoparticles, characterized in that, The method comprises the following steps: S1, preparing silver nitrate solution; S2, preparing base solution: adding reducing agent and dispersing agent into deionized water and stirring until uniform; then adding alkali solution to adjust pH value to 3-7; S3, preparing reducing solution: adding reducing agent into deionized water and stirring until uniform; then adding appropriate amount of ammonia water or sodium hydroxide to control pH value of the solution to 3.0-8.0; S4, preparing secondary reaction additive: adding soluble halogen metal sodium salt or potassium salt into ammonia water and stirring until uniform; S5, adding silver nitrate solution and reducing solution into the base solution for the first time, stirring until uniform; then adding secondary reaction additive, stirring until uniform; and then adding the remaining silver nitrate solution and reducing solution for the second time, stirring until uniform; S6, adding coating agent, stirring until uniform to perform coating reaction; after the coating reaction, performing solid-liquid separation, drying and crushing to obtain the silver powder.

2. The method for preparing silver powder with uniform internal pores and surface-grown nanoparticles according to claim 1, characterized in that, In step S1, the preparation of silver nitrate solution comprises the following steps: dissolving silver nitrate crystal into deionized water, stirring until uniform, and storing at 20-30°C for standby use; wherein the mass fraction of silver nitrate solution is 20-30wt%.

3. The method for preparing silver powder with uniform internal pores and surface-grown nanoparticles according to claim 1, characterized in that, In step S2, the reducing agent is one or a mixture of two of ascorbic acid and sodium ascorbate; and the dispersing agent is one or more of polyvinylpyrrolidone, gelatin, acacia, polyethylene glycol and polyvinyl alcohol.

4. The method for preparing silver powder with uniform internal pores and surface-grown nanoparticles according to claim 1, characterized in that, In step S2, the mass fraction of reducing agent in the base solution is 1.0-4.2wt%, and the mass fraction of dispersing agent in the base solution is 1.0-3.0wt%.

5. The method for preparing silver powder with uniform internal pores and surface-grown nanoparticles according to claim 1, characterized in that, In step S3, the reducing agent is one or a mixture of two of ascorbic acid and sodium ascorbate; and the mass fraction of reducing agent in the reducing solution is 8.0-10wt%.

6. The method for preparing silver powder with uniform internal pores and surface-grown nanoparticles according to claim 1, characterized in that, In step S5, the volume of silver nitrate solution and reducing solution added for the first time is 75-98% of the total amount, and the feeding is completed within 4-8min.

7. The method for preparing silver powder with uniform internal pores and surface-grown nanoparticles according to claim 6, characterized in that, In step S5, the volume of silver nitrate solution and reducing solution added for the first time is 95% of the total amount.

8. The method for preparing silver powder with uniform internal pores and surface-grown nanoparticles according to claim 1, characterized in that, In step S6, the coating agent is one of stearic acid, lauric acid, myristic acid and oleic acid.

9. The method for preparing silver powder with uniform internal pores and surface-grown nanoparticles according to claim 1, characterized in that, In step S6, the mass of coating agent added is 0.1-1% of the mass of silver nitrate.

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