Preparation method of sphere-like submicron silver powder with controllable particle size

Abstract

The invention discloses a preparation method of sphere-like submicron silver powder with a controllable particle size. The method comprises the following steps: 1, preparing a silver nitrate solution, an organic acid reducing agent solution and a dispersing agent solution; 2, preparing an organic acid salt reducing agent solution from a small amount of organic acid reducing agent solution, uniformly mixing the organic acid salt reducing agent solution with the polyacrylamide solution to form a base solution, and adding a small amount of silver nitrate solution to react to form nano-silver crystal nucleuses; 3, adding nitric acid and a dispersing agent solution, uniformly stirring, and then dropwise adding the residual organic acid reducing agent solution and the residual silver nitrate solution for silver crystal nucleus growth; and 4, washing and drying after solid-liquid separation. By controlling the adding mode of the reducing agent and the silver nitrate and reducing the silver nitrate in two steps, formation and growth of silver crystal nucleuses are controlled, regulation and control of the particle size of the sphere-like submicron silver powder are achieved, the sphere-like submicron silver narrow in particle size distribution, regular in morphology and good in dispersity is obtained, the preparation process is simple, green and environmentally friendly, and the method is suitable for industrial production. The method is suitable for heterojunction solar cells and high-end electronic devices.

Description

Technical Field

[0001] The invention relates to the technical field of micro-nano silver powder materials, and in particular to a method for preparing spherical submicron silver powder with controllable particle size. Background Art

[0002] Micro-nano silver powder is often used as the core raw material of electronic paste due to its excellent conductivity and stability, and is widely used in electronic components and solar cell modules. The morphology, particle size, dispersibility, tap density and other properties of micro-nano silver powder directly determine the sintering, electrical and printing properties of the paste, which in turn affects the conductivity of the final device. In recent years, with the development of photovoltaic and electronic devices towards high integration, miniaturization and flexibility, the demand for low-temperature silver paste has been increasing, so the development of submicron silver powder preparation technology has important practical significance.

[0003] In the existing submicron silver powder preparation technology, a large amount of synthetic polymers, organic matter, amine reagents, and even crystal seeds are usually added to control the morphology and particle size. For example, patents with application numbers 202310619172.6, 202410582320.6, 202410187219.0, and 202210597158.6. However, the submicron silver powder prepared using these technologies has a single particle size, low controllability, and low overall dispersibility. In addition, the preparation process uses a large number of reagents, and even highly toxic substances such as formaldehyde or hydrazine hydrate are used. The process is cumbersome and the environmental protection is poor, resulting in low production efficiency. Therefore, it is very important to develop a green, simple and efficient controllable preparation method for highly dispersed submicron silver powder, which can make up for the defects in the use of micron silver powder and adapt to the needs of different types of slurries. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing spherical submicron silver powder with controllable particle size in view of the deficiencies of the above-mentioned prior art. The method controls the formation and growth of silver crystal nuclei by controlling the addition mode of the reducing agent and silver nitrate, and adopts a two-step reduction of silver nitrate, thereby realizing the regulation of the particle size of the spherical submicron silver powder, and obtaining spherical submicron silver with narrow particle size distribution, regular morphology and good dispersibility, and the preparation process is simple, easy to mass produce, uses fewer types of reagents and is green and environmentally friendly, solving the problems of the existing submicron silver powder that is difficult to control the particle size, poor dispersibility, cumbersome preparation process and low environmental protection.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing spherical submicron silver powder with controllable particle size, characterized in that the method comprises the following steps:

[0006] Step 1, preparing silver nitrate, a natural organic acid reducing agent and a dispersant into a silver nitrate solution, an organic acid reducing agent solution and a dispersant solution respectively;

[0007] Step 2: taking a small amount of the organic acid reducing agent solution prepared in step 1, adding sodium hydroxide or potassium hydroxide to form an organic acid salt reducing agent solution, then mixing the organic acid salt reducing agent solution with the polyacrylamide solution and stirring evenly to form a base solution, and then adding a small amount of the silver nitrate solution prepared in step 1 to the base solution under heating and stirring conditions to react and form nano silver crystal nuclei;

[0008] Step 3: under the condition of heating and stirring in a water bath, nitric acid and the dispersant solution prepared in step 1 are added to the base solution containing the nano silver crystal nuclei in step 2 and stirred evenly, and then the remaining organic acid reducing agent solution prepared in step 1 and the remaining silver nitrate solution prepared in step 1 are added dropwise to grow the silver crystal nuclei;

[0009] Step 4: After the dropping operation in step 3 is completed, solid-liquid separation is performed, and the obtained precipitate is washed with ultrapure water and ethanol, and dried to obtain highly dispersed spherical submicron silver powder.

[0010] The invention first converts a small amount of organic acid reducing agent solution into an organic acid salt reducing agent solution, mixes the solution with a polyacrylamide solution to form a base solution, and then quickly adds a small amount of silver nitrate solution under heating and stirring conditions, and uses the organic acid salt with stronger reducing property to quickly reduce the small amount of silver nitrate to silver atoms, and the polyacrylamide can effectively complex the silver atoms, and promotes the formation of nano silver crystal nuclei as a carrier site, and uses its own long chain steric hindrance to inhibit the aggregation of crystal nuclei, so as to ensure the formation of monodisperse nano silver crystal nuclei, which is equivalent to the effect of seed crystals; then, nitric acid and a dispersant solution are added, and the remaining organic acid reducing agent solution and the silver nitrate solution are dripped, and the remaining silver nitrate is slowly reduced by using a natural organic acid reducing agent with weaker reducing property, so that the silver atoms grow on the surface of the nano silver crystal nuclei obtained in the early stage, and form spherical submicron silver powder, and the nitric acid reduces the generation rate of silver atoms, and further promotes the slow growth of the silver crystal nuclei. In addition, since the dispersant is a natural sugar molecule with many oxygen groups, it is easy for silver ions to bind and reduce the reduction rate, making it difficult to form nanocrystalline nuclei. Therefore, the present invention does not add such a dispersant during the first step of rapid reduction to avoid this effect and avoid adverse effects on the formation of nanosilver crystal nuclei. In addition, the first step of rapid reduction is alkaline conditions with a high reaction temperature, which easily destroys the dispersant structure and reduces the dispersibility.

[0011] The above-mentioned method for preparing a spherical submicron silver powder with controllable particle size is characterized in that the concentration of the silver nitrate solution in step one is 100g / L to 200g / L; the natural organic acid reducing agent is ascorbic acid, citric acid, malic acid or quinic acid, and the concentration of the organic acid reducing agent solution is 80g / L to 180g / L; the dispersant is agar, carrageenan, konjac gum, xanthan gum or gum arabic, and the concentration of the dispersant solution is 5g / L to 20g / L; the volumes of the silver nitrate solution, the organic acid reducing agent solution and the dispersant solution are equal. The natural organic acid reducing agent used in the present invention has weak self-reducibility, which is conducive to the slow reduction of silver nitrate during the crystal nucleus growth process, and the organic acid salt formed by it and the strong base has strong reducibility, which is conducive to the first step of forming nano silver crystal nuclei; secondly, the natural organic acid reducing agent is a natural substance, green and environmentally friendly, non-toxic and non-volatile, and highly economical. The dispersant used in the present invention is also a natural molecule, which contains many oxygen groups and is easy to complex silver ions, so that the silver source of the system is uniform, the silver ion reduction rate is reduced, and the dispersibility of the submicron silver powder is improved; secondly, the dispersant has good colloid properties, and a small amount of the dispersant can be used to thicken the system, prevent the aggregation of silver particles, and achieve a high dispersion effect.

[0012] The above-mentioned method for preparing spherical submicron silver powder with controllable particle size is characterized in that the volume of the small amount of organic acid reducing agent solution in step 2 accounts for 1 / 10 to 1 / 5 of the total volume of the organic acid reducing agent solution prepared in step 1, and the mass ratio of the sodium hydroxide or potassium hydroxide to the natural organic acid reducing agent in the organic acid reducing agent solution prepared in step 1 is 1:50 to 200; the concentration of the polyacrylamide solution is 3g / L to 12g / L, and the volume of the polyacrylamide solution accounts for 1 / 10 of the total volume of the organic acid reducing agent solution prepared in step 1; the small amount of silver nitrate solution accounts for 1 / 10 to 1 / 5 of the total volume of the silver nitrate solution prepared in step 1. The present invention controls the above-mentioned volume proportions to avoid too few nano silver nuclei obtained by the first reduction, resulting in a wide particle size distribution and low morphology regularity of the submicron silver powder, and at the same time avoids the first reduction to obtain micron silver powder with low regularity, which fails to achieve the seed effect and leads to the problem of poor consistency of silver nucleus growth. In addition, when other conditions remain unchanged, as the volume proportion of a small amount of reducing agent and silver nitrate increases, the average particle size of the silver powder finally obtained decreases.

[0013] The above-mentioned method for preparing spherical submicron silver powder with controllable particle size is characterized in that the temperature under the heating and stirring conditions in step 2 is 50° C., the stirring speed is 800 r / min, and the addition time of the small amount of silver nitrate solution is within 1 minute. By controlling the addition time of a small amount of silver nitrate solution, rapid addition is achieved to avoid the formation of micron silver or nano silver aggregates with poor uniformity of particle size and morphology due to too slow addition, which fails to achieve the seeding effect.

[0014] The above-mentioned method for preparing spherical submicron silver powder with controllable particle size is characterized in that the nitric acid in step 3 is concentrated nitric acid with a mass fraction of 68%, and the volume of nitric acid accounts for 1 / 100 of the total volume of the silver nitrate solution prepared in step 1; the dripping speeds of the organic acid reducing agent solution prepared in the remaining step 1 and the silver nitrate solution prepared in the remaining step 1 are 0.1L / min and 0.2L / min respectively. By controlling the volume proportion of nitric acid and the dripping speed, the silver atom generation rate is controlled, so that the nanosilver crystal nuclei grow synchronously and slowly.

[0015] The above-mentioned method for preparing spherical submicron silver powder with controllable particle size is characterized in that the water bath temperature of the water bath heating and stirring conditions in step three is 15°C to 25°C, and the stirring speed is 800r / min.

[0016] The above-mentioned method for preparing spherical submicron silver powder with controllable particle size is characterized in that after the dropwise addition operation in step 4 is completed, waiting for 5 minutes to 20 minutes before performing solid-liquid separation.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The present invention controls the adding mode of the reducing agent and the silver nitrate, adopts a two-step reduction of the silver nitrate, that is, firstly forms the nano silver nucleus, and then grows to form the quasi-spherical submicron silver powder, thereby controlling the formation and growth of the silver nucleus, realizing the regulation of the particle size of the quasi-spherical submicron silver powder, and at the same time utilizing the seed effect of the nano silver nucleus to inhibit the spontaneous nucleation of the growth process, promoting the synchronous growth of each nucleus, and combining with the effect of the dispersant, effectively improving the dispersibility of the submicron silver powder, and the preparation process is simple and easy to implement.

[0019] 2. The present invention first uses an organic acid salt reducing agent with stronger reducing property to quickly reduce a small amount of silver nitrate, and exerts a seed effect to form nano-silver by nucleation. Therefore, by changing the amount of the organic acid salt reducing agent and silver nitrate in the reduction process, the particle size of the spherical submicron silver powder can be regulated.

[0020] 3. The reducing agent and dispersant used in the preparation method of the present invention are both natural organic substances, green and environmentally friendly, and use fewer types of reagents, and do not need to add seed crystals and complexing agents separately. The method is simple and efficient, has good controllability, is easy to mass produce, and has high industrial value.

[0021] 4. The spherical submicron silver powder prepared by the present invention has a narrow particle size distribution and is easily regulated within the range of 0.1 μm to 1 μm. It has a regular morphology, good dispersibility, high crystallinity and purity, is conducive to low-temperature sintering, and is suitable for heterojunction solar cells and high-end electronic devices.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope image of the spherical submicron silver powder prepared in Example 1 of the present invention.

[0024] Figure 2 This is a scanning electron microscope image of the spherical submicron silver powder prepared in Example 2 of the present invention.

[0025] Figure 3 This is the X-ray diffraction pattern of the spherical submicron silver powder prepared in Example 2 of the present invention.

[0026] Figure 4 This is a scanning electron microscope image of the spherical submicron silver powder prepared in Example 3 of the present invention.

[0027] Figure 5 This is a scanning electron microscope image of the micron silver powder prepared in Comparative Example 1 of the present invention.

[0028] Figure 6 This is a scanning electron microscope image of the micron silver powder prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0029] Example 1

[0030] This embodiment includes the following steps:

[0031] Step 1, silver nitrate, natural organic acid reducing agent citric acid and dispersant carrageenan are respectively prepared into a 200 g / L silver nitrate solution, a 180 g / L citric acid solution and a 20 g / L carrageenan solution, and the volumes of the silver nitrate solution, the citric acid solution and the carrageenan solution are equal to 1 L;

[0032] Step 2: Take 0.2L of the citric acid solution prepared in step 1, add 2.0g of sodium hydroxide to form a sodium citrate solution, then mix the sodium citrate solution with 0.1L of a 12g / L polyacrylamide solution and stir evenly to form a base solution, set the reaction temperature to 50°C, and the stirring speed to 800r / min, and add 0.2L of the silver nitrate solution prepared in step 1 to the base solution within 1min to react and form nanosilver crystal nuclei;

[0033] Step 3, transfer the base solution containing nano silver nuclei in step 2 into a water bath at 15°C to 25°C, set the stirring speed to 800r / min, quickly add 0.01L of 68% concentrated nitric acid and 1L of the carrageenan solution prepared in step 1 to the base solution containing nano silver nuclei and stir evenly, then simultaneously add the remaining citric acid solution prepared in step 1 and the remaining silver nitrate solution prepared in step 1 dropwise at flow rates of 0.1L / min and 0.2L / min respectively to grow silver nuclei;

[0034] Step 4: After the addition in step 3 is completed, wait for 5 minutes before performing solid-liquid separation, wash the obtained precipitate with ultrapure water and ethanol, and obtain highly dispersed spherical submicron silver powder after drying.

[0035] Figure 1 This is a scanning electron microscope image of the spherical submicron silver powder prepared in this example. Figure 1 It can be seen that the particle size of this type of spherical submicron silver powder is 0.1 μm to 0.33 μm, and it has excellent dispersibility, a smooth surface, and a quasi-spherical morphology.

[0036] The natural organic acid reducing agent lemon in step 1 of this embodiment can also be replaced by quinic acid, and the dispersant carrageenan can also be replaced by xanthan gum or gum arabic; the sodium hydroxide in step 2 can also be replaced by potassium hydroxide.

[0037] Example 2

[0038] This embodiment includes the following steps:

[0039] Step one, silver nitrate, natural organic acid reducing agent ascorbic acid and dispersant konjac glucomannan are respectively mixed with the silver nitrate solution, 120g / L ascorbic acid solution and 10g / L konjac glucomannan solution that concentration is 150g / L, and the volume of silver nitrate solution, ascorbic acid solution and konjac glucomannan solution equals and is 1L;

[0040] Step 2: Take 0.15L of the ascorbic acid solution prepared in step 1, add 1.5g of sodium hydroxide to form a sodium ascorbate solution, then mix the sodium ascorbate solution with 0.1L of a 10g / L polyacrylamide solution and stir evenly to form a base solution, set the reaction temperature to 50°C, and the stirring speed to 800r / min, and add 0.15L of the silver nitrate solution prepared in step 1 to the base solution within 1min to react and form nanosilver crystal nuclei;

[0041] Step 3, the bottom solution containing the nano silver nucleus in step 2 is transferred into a water bath at 15°C to 25°C, the stirring speed is set to 800r / min, 0.01L of concentrated nitric acid with a mass fraction of 68% and 1L of the konjac glucoside solution prepared in step 1 are quickly added to the bottom solution containing the nano silver nucleus and stirred evenly, and then the ascorbic acid solution prepared in the remaining step 1 and the silver nitrate solution prepared in the remaining step 1 are added dropwise at flow rates of 0.1L / min and 0.2L / min respectively to grow the silver nucleus;

[0042] Step 4: After the addition in step 3 is completed, wait for 5 minutes before performing solid-liquid separation, wash the obtained precipitate with ultrapure water and ethanol, and obtain highly dispersed spherical submicron silver powder after drying.

[0043] Figure 2This is a scanning electron microscope image of the spherical submicron silver powder prepared in this example. Figure 2 It can be seen that the particle size of this type of spherical submicron silver powder is 0.35 μm to 0.58 μm, and it has excellent dispersibility, a smooth surface, and a spherical morphology.

[0044] Figure 3 The X-ray diffraction pattern of the spherical submicron silver powder prepared in this example is as follows: Figure 3 It can be seen from the diffraction peaks in the figure that this type of spherical submicron silver powder has high purity, is free of impurities, and has sharp peaks, indicating that the crystallinity is also very high.

[0045] Example 3

[0046] This embodiment includes the following steps:

[0047] Step 1, silver nitrate, natural organic acid reducing agent malic acid and dispersant agar are respectively prepared into a 100 g / L silver nitrate solution, an 80 g / L malic acid solution and a 5 g / L agar solution, and the volumes of the silver nitrate solution, the malic acid solution and the agar solution are equal to 1 L;

[0048] Step 2: Take 0.1L of the malic acid solution prepared in step 1, add 1.0g of sodium hydroxide to form a sodium malate solution, then mix the sodium malate solution with 0.1L of a 3g / L polyacrylamide solution and stir evenly to form a base solution, set the reaction temperature to 50°C, and the stirring speed to 800r / min, and add 0.1L of the silver nitrate solution prepared in step 1 to the base solution within 1min to react and form nanosilver crystal nuclei;

[0049] Step 3, transfer the base solution containing the nano-silver crystal nuclei in step 2 into a water bath at 15°C to 25°C, set the stirring speed to 800r / min, quickly add 0.01L of 68% concentrated nitric acid and 1L of the agar solution prepared in step 1 to the base solution containing the nano-silver crystal nuclei and stir evenly, and then simultaneously add the remaining malic acid solution prepared in step 1 and the remaining silver nitrate solution prepared in step 1 dropwise at flow rates of 0.1L / min and 0.2L / min respectively to grow the silver crystal nuclei;

[0050] Step 4: After the dropwise addition in step 3 is completed, wait for 20 minutes before performing solid-liquid separation, wash the obtained precipitate with ultrapure water and ethanol, and obtain highly dispersed spherical submicron silver powder after drying.

[0051] Figure 4 This is a scanning electron microscope image of the spherical submicron silver powder prepared in this example. Figure 4 It can be seen that the particle size of this type of spherical submicron silver powder is 0.48 μm to 1.0 μm, and it has excellent dispersibility, a smooth surface, and a quasi-spherical morphology.

[0052] Comparative Example 1

[0053] This comparative example comprises the following steps:

[0054] Step 1, silver nitrate, natural organic acid reducing agent citric acid and dispersant carrageenan are respectively prepared into a 200 g / L silver nitrate solution, a 180 g / L citric acid solution and a 20 g / L carrageenan solution, and the volumes of the silver nitrate solution, the citric acid solution and the carrageenan solution are equal to 1 L;

[0055] Step 2: Take 1L of the citric acid solution prepared in step 1, add 2.0g of sodium hydroxide to form a citric acid-sodium citrate solution, and at the same time, mix 1L of the carrageenan solution prepared in step 1 with 0.1L of a 12g / L polyacrylamide solution, stir evenly, and add 0.01L of 68% concentrated nitric acid to form a base solution;

[0056] Step 3: simultaneously adding 1L of the citric acid-sodium citrate solution prepared in step 2 and 1L of the silver nitrate solution prepared in step 1 to the base solution obtained in step 2 at flow rates of 0.1L / min and 0.2L / min, respectively, first reacting in a 50°C water bath for 1min, and then transferring to a 15°C-25°C water bath for silver nucleus growth;

[0057] Step 4: After the dropwise addition in step 3 is completed, wait for 5 minutes before performing solid-liquid separation, wash the obtained precipitate with ultrapure water and ethanol, and obtain micron silver powder after drying.

[0058] Figure 5 The scanning electron microscope image of the micron silver powder prepared in this comparative example is Figure 5 It can be seen that the micron silver powder is composed of stacked small grains, the overall outline is spherical, the agglomeration is serious, and the particle size is about 8μm.

[0059] Comparing Example 1 of the present invention with Comparative Example 1, it can be seen that in Comparative Example 1, silver nitrate is reduced in one step, and the formation and growth of nanosilver nuclei are not separated. Silver atoms spontaneously form nanosilver nuclei for a long time, resulting in low consistency of nucleus growth, a wide particle size distribution of the final silver powder, low morphology regularity, and much adhesion and agglomeration of silver particles. Micron silver powder is prepared with severe agglomeration, while in Example 1, silver nitrate is reduced in two steps. The growth of silver nuclei is effectively controlled by the first step of reduction to ensure the formation of nanosilver nuclei. The growth of silver atoms on the surface of the nanosilver nuclei is promoted by the first step of reduction, thereby forming a uniform spherical submicron silver powder.

[0060] Comparative Example 2

[0061] The difference between this comparative example and Example 1 is that in step 2, no sodium hydroxide is added to the citric acid solution.

[0062] Figure 6 The scanning electron microscope image of the micron silver powder prepared in this comparative example is Figure 6 It can be seen that the micronized silver powder is severely agglomerated and its morphology regularity is much lower than that of Example 1.

[0063] By comparing Example 1 with Comparative Example 2, it can be seen that in Comparative Example 2, citric acid with a weaker reducing property is used for the first reduction, and the reduced silver atoms spontaneously nucleate for a long time, which is easy to generate uneven silver powder particles, and the silver powder particles are easy to aggregate. In Example 1, sodium citrate with a stronger reducing property is used for the first reduction, which can quickly reduce silver nitrate to form nanocrystals, which is equivalent to the seed effect and is conducive to the subsequent growth of silver crystal nuclei.

[0064] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing spherical submicron silver powder with controllable particle size, characterized in that: The method comprises the following steps: Step 1, preparing silver nitrate, a natural organic acid reducing agent and a dispersant into a silver nitrate solution, an organic acid reducing agent solution and a dispersant solution respectively; Step 2: taking a small amount of the organic acid reducing agent solution prepared in step 1, adding sodium hydroxide or potassium hydroxide to form an organic acid salt reducing agent solution, then mixing the organic acid salt reducing agent solution with the polyacrylamide solution and stirring evenly to form a base solution, and then adding a small amount of the silver nitrate solution prepared in step 1 to the base solution under heating and stirring conditions to react and form nano silver crystal nuclei; Step 3: under the condition of heating and stirring in a water bath, nitric acid and the dispersant solution prepared in step 1 are added to the base solution containing the nano silver crystal nuclei in step 2 and stirred evenly, and then the remaining organic acid reducing agent solution prepared in step 1 and the remaining silver nitrate solution prepared in step 1 are added dropwise to grow the silver crystal nuclei; Step 4: After the dropping operation in step 3 is completed, solid-liquid separation is performed, and the obtained precipitate is washed with ultrapure water and ethanol, and dried to obtain highly dispersed spherical submicron silver powder.

2. The method for preparing spherical submicron silver powder with controllable particle size according to claim 1, characterized in that: The concentration of the silver nitrate solution in step 1 is 100 g / L to 200 g / L; the natural organic acid reducing agent is ascorbic acid, citric acid, malic acid or quinic acid, and the concentration of the organic acid reducing agent solution is 80 g / L to 180 g / L; the dispersant is agar, carrageenan, konjac gum, xanthan gum or gum arabic, and the concentration of the dispersant solution is 5 g / L to 20 g / L; the volumes of the silver nitrate solution, the organic acid reducing agent solution and the dispersant solution are equal.

3. The method for preparing spherical submicron silver powder with controllable particle size according to claim 1, characterized in that: The volume of the small amount of organic acid reducing agent solution in step 2 accounts for 1 / 10 to 1 / 5 of the total volume of the organic acid reducing agent solution prepared in step 1, and the mass ratio of the sodium hydroxide or potassium hydroxide to the natural organic acid reducing agent in the organic acid reducing agent solution prepared in step 1 is 1:50 to 200; the concentration of the polyacrylamide solution is 3 g / L to 12 g / L, and the volume of the polyacrylamide solution accounts for 1 / 10 of the total volume of the organic acid reducing agent solution prepared in step 1; the small amount of silver nitrate solution accounts for 1 / 10 to 1 / 5 of the total volume of the silver nitrate solution prepared in step 1.

4. The method for preparing spherical submicron silver powder with controllable particle size according to claim 1, characterized in that: The temperature under the heating and stirring conditions in step 2 is 50° C., the stirring speed is 800 r / min, and the addition time of the small amount of silver nitrate solution is within 1 minute.

5. The method for preparing spherical submicron silver powder with controllable particle size according to claim 1, characterized in that: The nitric acid in step three is concentrated nitric acid with a mass fraction of 68%, and the volume of nitric acid accounts for 1 / 100 of the total volume of the silver nitrate solution prepared in step one; the dropping speeds of the organic acid reducing agent solution prepared in the remaining step one and the silver nitrate solution prepared in the remaining step one are 0.1 L / min and 0.2 L / min respectively.

6. The method for preparing spherical submicron silver powder with controllable particle size according to claim 1, characterized in that: The water bath temperature of the water bath heating and stirring conditions in step 3 is 15° C. to 25° C., and the stirring speed is 800 r / min.

7. The method for preparing spherical submicron silver powder with controllable particle size according to claim 1, characterized in that: After the dropwise addition in step 4 is completed, wait for 5 to 20 minutes before performing solid-liquid separation.

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