Spherical silver powder and stable preparation method thereof

Abstract

The invention provides a spherical silver powder stabilization preparation method, and belongs to the technical field of metal powder preparation methods, the spherical silver powder stabilization preparation method comprises the following steps: dispersing silver nitrate in water to obtain a solution A; dispersing a reducing agent in water to obtain a solution B; dispersing a dispersing agent in water to obtain a solution C; dispersing a coating agent in ethanol to obtain a solution D; dispersing a temperature-sensitive polymer in ethanol to obtain a solution E; and mixing the solution C and the solution E to obtain a mixed solution, adding the solution A and the solution B into the mixed solution, carrying out a first reaction, adding the solution D, carrying out a second reaction, and carrying out solid-liquid separation to obtain the spherical silver powder. In the silver powder preparation process, the raw material adding rate in the silver powder preparation process is optimized and adjusted according to the temperature and humidity dynamic feedback of the environment, the temperature-sensitive polymer is further added to conduct self-adaptive adjustment on the hydrophilicity and hydrophobicity along with the temperature change, the growth rate of silver cores is controlled, and stable production of the silver powder is achieved.

Description

TECHNICAL FIELD

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

[0002] The main method for silver powder production is currently liquid phase chemical reduction method, which is to add reducing agent into silver salt solution, and reduce silver ions into silver element by controlling the conditions of reduction reaction. Silver salt is completely dissolved in liquid to form a uniform liquid phase, and reducing agent can be selected from inorganic or organic reducing agent. In order to prepare ultrafine silver powder, a certain dispersing agent or protective agent is often added in the reduction system to reduce the agglomeration of silver particles. Liquid phase chemical reduction method uses silver nitrate solution or silver ammonia solution as oxidant precursor, and reduces silver particles by controlling the temperature and pH conditions of reaction process. After reduction, the obtained silver powder is filtered, washed and dried to obtain silver powder. In the process of silver powder preparation, many factors can affect the quality of silver powder, such as precursor, reducing agent, surfactant, reaction temperature, reactant concentration, etc.

[0003] In the preparation of traditional silver powder, the production environment of silver powder cannot be kept constant temperature and humidity, and the existing technology can only control the environment statically, which cannot adapt to seasonal or regional changes in temperature and humidity. When the temperature and humidity deviate from the control range, it will have a great impact on the process stability of silver powder. On the one hand, when the humidity is too high, water forms a liquid bridge force between silver powder particles, causing particles to stick together, agglomerate, and be difficult to disperse, affecting the specific surface area and flowability, and the tap density will also decrease; on the other hand, too high humidity may interfere with the concentration control of reducing agent, resulting in unstable reaction speed and uneven silver particle morphology. The influence of temperature is more obvious, too high temperature (such as > 50℃) may cause rapid growth of silver particles, forming coarse particles; too low temperature may form submicron ultrafine powder and may be accompanied by unreacted impurities. At the same time, temperature also affects the growth direction of crystal. For example, low temperature (20~25℃) is beneficial to the generation of spherical silver powder, while high temperature (40~50℃) may promote the formation of flaky or porous structure. SUMMARY

[0004] In view of the technical problems in the background art, the present application provides a kind of spherical silver powder and its stable preparation method, to solve the technical problems that the change of temperature and humidity of environment in the process of silver powder preparation has a great influence on the process stability of silver powder.

[0005] In the first aspect, the embodiments of the present application provide a kind of spherical silver powder and its stable preparation method, comprising the following steps: Disperse silver nitrate in deionized water to obtain solution A; Disperse reducing agent in deionized water to obtain solution B; Disperse dispersing agent in deionized water to obtain solution C; dispersing the coating agent in anhydrous ethanol to obtain solution D; dispersing the temperature-sensitive polymer in anhydrous ethanol to obtain solution E; mixing solution C and solution E to obtain a mixture, adding solution A and solution B into the mixture at a set flow rate, and performing the first reaction under stirring until the addition is completed, adding solution D, and performing the second reaction under stirring, followed by solid-liquid separation to obtain the spherical silver powder.

[0006] In some embodiments, during the first reaction, when the temperature is 0-30℃, the flow rate of solution B is 4.5 mL / min; when the temperature is >30℃, the flow rate of solution B increases by 0.05-0.15 mL / min for each 1℃ increase in temperature; when the humidity is 0%-50%, the reaction temperature is 40℃; when the humidity is >50%, the reaction temperature decreases by 1-3℃ for each 5% increase in humidity; the first reaction time is 1-5 min.

[0007] In some embodiments, the concentration of silver nitrate in solution A is 0.5-1.5 mol / L.

[0008] In some embodiments, the amount of the reducing agent added is 50%-60% of the mass of silver nitrate. The reducing agent includes at least one of ascorbic acid, glucose, formaldehyde, triethanolamine, and hydrazine hydrate.

[0009] In some embodiments, the amount of the dispersant added is 8%-15% of the mass of silver nitrate. The dispersant is polyvinylpyrrolidone, the K value of which is 31.5-33, the moisture content is <4%, the pH value is 3-4, the peroxide content is ≤200 mg / L, and the weight average molecular weight is 25000-40000.

[0010] In some embodiments, the amount of the coating agent added is 0.5%-1.5% of the mass of silver nitrate. The coating agent is at least one of oleic acid, lauric acid, stearic acid, and palmitic acid.

[0011] In some embodiments, the amount of the temperature-sensitive polymer added is 0.3%-0.5% of the mass of silver nitrate. The temperature-sensitive polymer is at least one of PNIPAM, PDEAAM, and PVCL.

[0012] In some embodiments, the pH value of solution B is adjusted to 4-6 by using a lye.

[0013] In some embodiments, the second reaction time is 3-8 min.

[0014] In a second aspect, the embodiments of the present application provide a spherical silver powder prepared by the above preparation method.

[0015] Compared with the prior art, the beneficial effects of the present application include: In the silver powder preparation process, the raw material addition rate in the silver powder preparation process is optimized and adjusted according to the dynamic feedback of the temperature and humidity of the environment, which can adapt to different temperature and humidity changes in various seasons and regions, and make corresponding process changes in real time; a temperature-sensitive polymer is also added to adjust the hydrophilicity and hydrophobicity with temperature changes, control the growth rate of the silver core, thereby reducing the influence of uncontrollable factors in the environment on the stability of silver powder production, and realizing stable production of silver powder.

[0016] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, which can be implemented according to the content of the specification, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application will be described. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the present application, the drawings used in the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0018] Figure 1 SEM image of the spherical silver powder prepared in Example 1 of the present application.

[0019] Figure 2 SEM image of the spherical silver powder prepared in Example 2 of the present application.

[0020] Figure 3 SEM image of the spherical silver powder prepared in Example 3 of the present application.

[0021] Figure 4 SEM image of the spherical silver powder prepared in Example 4 of the present application.

[0022] Figure 5 SEM image of the spherical silver powder prepared in Comparative Example 1 of the present application.

[0023] Figure 6 SEM image of the spherical silver powder prepared in Comparative Example 2 of the present application. DETAILED DESCRIPTION

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

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments of the present application, and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0026] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified.

[0027] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application. If the specific technology or condition is not specified in the examples, it is carried out according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0028] I. Preparation method Example 1 A stable preparation method of spherical silver powder, comprising the following steps: (1) Solution preparation Solution A: Take 85g of silver nitrate into a beaker, add 500ml of deionized water, stir to dissolve, and heat and keep at 25℃ to obtain solution A; Solution B: Take 45.9g of ascorbic acid into a beaker, add 500ml of deionized water, stir to dissolve. After complete dissolution, solution B is obtained; Solution C: Take 11.9g of polyvinylpyrrolidone into a beaker, add 450ml of deionized water, stir to dissolve, and after complete dissolution, solution C is obtained; Among them, the technical index of polyvinylpyrrolidone is that the K value should be 32, the moisture content is 4%, the pH value is 3, the peroxide content is equal to 100ppm, and the weight average molecular weight is 30000; Solution D: Take 0.5g of oleic acid into a beaker, add 10ml of anhydrous ethanol, stir to dissolve, and obtain solution D; Solution E: Take 0.25g of poly(N-isopropyl acrylamide) (PNIPAM) into a beaker, add 10ml of anhydrous ethanol to stir and dissolve, to obtain solution E.

[0029] (2) Preparation of silver powder a. Transfer solution C to the reaction kettle, start mechanical stirring, add solution E to solution C, control the stirring speed at 500rpm; b. Adjust the pH value of solution B to 5.5 using a 10mol / L concentration of sodium hydroxide solution; c. Add solution A and solution B to the reaction kettle at the same time at a certain flow rate, start mechanical stirring, control the stirring speed at 400rpm, at this time monitor the environmental temperature and humidity at 25℃ and 60% respectively, the flow rate of the oxidizing solution is 4.88ml / min, the flow rate of the reducing solution is 4.55ml / min, and the reaction temperature is set to 38℃; d. After the feeding is completed, stir for 5min, and add solution D, continue to stir for 5min, and the reaction is completed; e. The reaction suspension is settled, the supernatant is poured out, solid-liquid separation is carried out, and the silver powder is washed with deionized water and anhydrous ethanol respectively, the conductivity of the filtrate is <20μS / m, and the silver powder is dried in a 60℃ air-drying oven for 22h.

[0030] Example 2 A method for stabilizing the preparation of spherical silver powder, comprising the following steps: 1) Liquid preparation Solution A: Take 42.5g of silver nitrate into a beaker, add 500ml of deionized water to stir and dissolve, heat and keep at 25℃ to obtain solution A; Solution B: Take 25.5g of ascorbic acid into a beaker, add 500ml of deionized water to stir and dissolve. After complete dissolution, solution B is obtained; Solution C: Take 6.4g of polyvinylpyrrolidone into a beaker, add 450ml of deionized water to stir and dissolve, and after complete dissolution, solution C is obtained; Among them, the technical index of polyvinylpyrrolidone is that the K value should be 32, the moisture is 4%, the pH value is 3, the peroxide content is equal to 100ppm, and the weight average molecular weight is 30000; Solution D: Take 0.5g of oleic acid into a beaker, add 10ml of anhydrous ethanol to stir and dissolve, to obtain solution D; Solution E: Take 0.21g of poly(N-isopropyl acrylamide) (PNIPAM) into a beaker, add 10ml of anhydrous ethanol to stir and dissolve, to obtain solution E.

[0031] (2) Preparation of silver powder a. Transfer solution C to the reactor, add solution E to solution C, start mechanical stirring, and control the stirring rate at 500 rpm; b. Adjust the pH value of solution B to 5.5 using a 10 mol / L concentration of sodium hydroxide solution; c. Simultaneously add solution A and solution B to the reactor at a certain flow rate, start mechanical stirring, and control the stirring rate at 400 rpm. At this time, monitor the ambient temperature and humidity, which are 33℃ and 45%, respectively. The flow rates of the oxidizing solution and the reducing solution are 4.88 ml / min and 4.85 ml / min, respectively. The reaction temperature is set to 40℃; d. After the feeding is completed, stir for 5 min, add solution D, continue stirring for 5 min, and end the reaction; e. Sediment the reaction suspension, pour out the supernatant, perform solid-liquid separation, and wash the silver powder with deionized water and anhydrous ethanol, respectively. Wash until the conductivity of the filtrate is <20 μS / m, and dry in a 60℃ air-drying oven for 22 h.

[0032] Example 3 A method for stabilizing the preparation of spherical silver powder, comprising the following steps: 1) Liquid preparation Solution A: Take 127.5 g of silver nitrate and add it to a beaker. Add 500 ml of deionized water and stir to dissolve. Heat and maintain the temperature at 25℃ to obtain solution A; Solution B: Take 63.75 g of ascorbic acid and add it to a beaker. Add 500 ml of deionized water and stir to dissolve. After complete dissolution, obtain solution B; Solution C: Take 10.2 g of polyvinylpyrrolidone and add it to a beaker. Add 450 ml of deionized water and stir to dissolve. After complete dissolution, obtain solution C; Among them, the technical indicators of polyvinylpyrrolidone are: K value should be 32, moisture content is 4%, pH value is 3, peroxide content is equal to 100 ppm, and weight average molecular weight is 30000; Solution D: Take 1.9 g of oleic acid and add it to a beaker. Add 10 ml of anhydrous ethanol and stir to dissolve, obtaining solution D; Solution E: Take 0.38 g of poly(N-isopropyl acrylamide) (PNIPAM) and add it to a beaker. Add 10 ml of anhydrous ethanol and stir to dissolve, obtaining solution E.

[0033] (2) Silver powder preparation a. Transfer solution C to the reactor, add solution E to solution C, start mechanical stirring, and control the stirring rate at 500 rpm; b. Adjust the pH value of solution B to 5.5 using a 10 mol / L concentration of sodium hydroxide solution; c. Solution A and solution B are added into the reactor at a certain flow rate at the same time, the mechanical stirring is started, and the stirring rate is controlled at 400 rpm. At this time, the monitored ambient temperature and humidity are 32℃ and 60% respectively, the flow rate of the oxidizing solution is 4.88 ml / min, the flow rate of the reducing solution is 4.75 ml / min, and the reaction temperature is set at 38℃; d. After the feeding is completed, stirring is continued for 5 min, and solution D is added, and stirring is continued for 5 min, and the reaction is completed; e. The reaction suspension is allowed to settle, the supernatant is poured out, solid-liquid separation is performed, and the silver powder is washed with deionized water and anhydrous ethanol respectively, the washing is continued until the conductivity of the filtrate is <20 μS / m, and the silver powder is dried in a 60℃ air-drying oven for 22 h.

[0034] Example 4 A method for the stable preparation of spherical silver powder, comprising the following steps: (1) Solution preparation Solution A: 85 g of silver nitrate is taken into a beaker, 500 ml of deionized water is added, and stirring and dissolution are performed, and the temperature is raised and maintained at 25℃ to obtain solution A; Solution B: 45.9 g of ascorbic acid is taken into a beaker, 500 ml of deionized water is added, and stirring and dissolution are performed. After complete dissolution, solution B is obtained; Solution C: 11.9 g of polyvinylpyrrolidone is taken into a beaker, 450 ml of deionized water is added, and stirring and dissolution are performed. After complete dissolution, solution C is obtained; Among them, the technical index of polyvinylpyrrolidone is that the K value should be 32, the moisture content is 4%, the pH value is 3, the peroxide content is equal to 100 ppm, and the weight average molecular weight is 30000; Solution D: 0.5 g of oleic acid is taken into a beaker, 10 ml of anhydrous ethanol is added, and stirring and dissolution are performed to obtain solution D.

[0035] (2) Silver powder preparation a. Solution C is transferred into the reactor, and the mechanical stirring is started, and the stirring rate is controlled at 500 rpm; b. The pH value of solution B is adjusted to 5.5 using a 10 mol / L concentration of sodium hydroxide solution; c. Solution A and solution B are added into the reactor at a certain flow rate at the same time, the mechanical stirring is started, and the stirring rate is controlled at 400 rpm. At this time, the monitored ambient temperature and humidity are 23℃ and 45% respectively, the flow rate of the oxidizing solution is 4.88 ml / min, the flow rate of the reducing solution is 4.5 ml / min, and the reaction temperature is set at 40℃; d. After the feeding is completed, stirring is continued for 5 min, and solution D is added, and stirring is continued for 5 min, and the reaction is completed; e. The reaction suspension is allowed to settle, the supernatant is poured out, solid-liquid separation is performed, and the silver powder is washed with deionized water and anhydrous ethanol respectively, the washing is performed until the conductivity of the filtrate is <20 μS / m, and the silver powder is dried in a blast drying oven at 60°C for 22 h.

[0036] Comparative Example 1 A method for the stable preparation of spherical silver powder, comprising the following steps: (1) Liquid preparation Solution A: 85 g of silver nitrate is taken into a beaker, 500 ml of deionized water is added, stirring is performed to dissolve, and the temperature is raised and maintained at 25°C to obtain solution A; Solution B: 45.9 g of ascorbic acid is taken into a beaker, 500 ml of deionized water is added, stirring is performed to dissolve, and after complete dissolution, solution B is obtained; Solution C: 11.9 g of polyvinylpyrrolidone is taken into a beaker, 450 ml of deionized water is added, stirring is performed to dissolve, and after complete dissolution, solution C is obtained; The technical index of the polyvinylpyrrolidone is that the K value should be 32, the moisture content is 4%, the pH value is 3, the peroxide content is equal to 100 ppm, and the weight average molecular weight is 30000; Solution D: 0.5 g of oleic acid is taken into a beaker, 10 ml of anhydrous ethanol is added, stirring is performed to dissolve, and solution D is obtained; Solution E: 0.25 g of poly(N-isopropyl acrylamide) (PNIPAM) is taken into a beaker, 10 ml of anhydrous ethanol is added, stirring is performed to dissolve, and solution E is obtained.

[0037] (2) Silver powder preparation a. Solution C is transferred to a reaction kettle, mechanical stirring is started, solution E is added to solution C, and the stirring rate is controlled to be 500 rpm; b. The pH value of solution B is adjusted to 5.5 using a 10 mol / L concentration sodium hydroxide solution; c. Solution A and solution B are simultaneously added to the reaction kettle at a certain flow rate, mechanical stirring is started, the stirring rate is controlled to be 400 rpm, at this time, the environmental temperature and humidity are monitored to be 33°C and 65% respectively, the flow rate of the oxidizing solution is 4.88 ml / min, the flow rate of the reducing solution is 4.5 ml / min, and the reaction temperature is set to be 40°C; d. After the addition is completed, stirring is performed for 5 min, solution D is added, and stirring is continued for 5 min, and the reaction is completed; e. The reaction suspension is allowed to settle, the supernatant is poured out, solid-liquid separation is performed, and the silver powder is washed with deionized water and anhydrous ethanol respectively, the washing is performed until the conductivity of the filtrate is <20 μS / m, and the silver powder is dried in a blast drying oven at 60°C for 22 h.

[0038] Comparative Example 2 A method for stabilizing preparation of spherical silver powder, comprising the following steps: (1) Liquid preparation Solution A: Take 85g of silver nitrate into a beaker, add 500ml of deionized water, stir to dissolve, and heat and keep at 25℃ to obtain solution A; Solution B: Take 45.9g of ascorbic acid into a beaker, add 500ml of deionized water, stir to dissolve. After complete dissolution, solution B is obtained; Solution C: Take 11.9g of polyvinylpyrrolidone into a beaker, add 450ml of deionized water, stir to dissolve, and after complete dissolution, solution C is obtained; Among them, the technical index of polyvinylpyrrolidone is that the K value should be 32, the moisture is 4%, the pH value is 3, the peroxide content is equal to 100 ppm, and the weight average molecular weight is 30000; Solution D: Take 0.5g of oleic acid into a beaker, add 10ml of anhydrous ethanol, stir to dissolve, and obtain solution D; (2) Silver powder preparation a. Transfer solution C to the reaction kettle, start mechanical stirring, and control the stirring speed at 500rpm; b. Adjust the pH value of solution B to 5.5 using a 10mol / L concentration of sodium hydroxide solution; c. Simultaneously add solution A and solution B to the reaction kettle at a certain flow rate, start mechanical stirring, and control the stirring speed at 400rpm. At this time, the environmental temperature and humidity are monitored at 25℃ and 60% respectively, the oxidation liquid flow rate is 4.88ml / min, the reducing liquid flow rate is 4.55ml / min, and the reaction temperature is set at 38℃; d. After the feeding is completed, stir for 5min, add solution D, continue to stir for 5min, and the reaction is completed; e. The reaction suspension is settled, the supernatant is poured out, solid-liquid separation is carried out, and the silver powder is washed with deionized water and anhydrous ethanol respectively, the washing is carried out until the conductivity of the filtrate is <20μS / m, and the silver powder is dried in a 60℃ air-drying oven for 22h.

[0039] II. Test method 1. Particle size detection method: GB / T 19077-2016 "Particle size analysis - Laser diffraction method".

[0040] 2. SPAN detection method: calculated according to the particle size test results, the calculation method is SPAN=(D90-D10) / D50.

[0041] 3. Loose bulk density and tap density detection method: GB / T 1479.1-2011 Loose bulk density meter / funnel method; GB / T 5162-2021 Tap density meter / tap method.

[0042] 4. Specific surface area detection method: GB / T13390-2008 Specific surface area analyzer / nitrogen adsorption method.

[0043] III. Analysis of test results of each embodiment and comparative example (1) The spherical silver powder obtained in Examples 1-4 and Comparative Examples 1-2 was subjected to SEM detection, and the results are shown in FIG. 1. Figures 1-6 As can be seen from the figure, the silver powder prepared by the method in Examples 1-4 has uniform particle size and good sphericity, and the silver powder prepared in Comparative Examples 1-2 has a wide particle size range and poor sphericity.

[0044] (2) The spherical silver powder obtained in Examples 1-4 and Comparative Examples 1-2 was subjected to detection of various physical parameters, and the results are shown in Table 1 below.

[0045] Table 1: Physical parameter detection results of the spherical silver powder obtained in Examples 1-4 and Comparative Examples 1-2

[0046] As can be seen from Table 1, Example 4 is the result of temperature and humidity within the process requirements, and Examples 1, 2, and 3 are process changes made when the temperature and humidity exceed the process requirements (temperature 0-30℃, humidity <50%), and the reduction liquid flow rate and reaction temperature are adjusted. After adjustment, the various indicators and distribution width SPAN value of the silver powder are close to those of Example 4. Comparative Example 1 did not make process changes when the temperature and humidity exceeded the requirements, and the results were unstable compared to Example 4, with a wide particle size range. Comparative Example 2 differs from Example 1 in that no temperature-sensitive polymer is added, resulting in a wide particle size distribution and poor sphericity. This shows that the temperature-sensitive polymer adjusts its hydrophilic and hydrophobic properties with temperature changes, controls the growth rate of silver nuclei, and obtains uniform-sized silver nanoparticles. In summary, dynamic regulation of the silver powder production process by temperature and humidity changes and the addition of temperature-sensitive polymers help to improve the stability of silver powder production.

[0047] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are only examples, and embodiments having the same technical idea and playing the same role within the scope of the technical solutions of the present application are all included within the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art, and other ways constructed by combining part of the components of the embodiments are also included within the scope of the present application.

Claims

1. A process for the stable production of spherical silver powder, characterized in that The method comprises the following steps: dispersing silver nitrate in deionized water to obtain solution A; dispersing a reducing agent in deionized water to obtain solution B; dispersing a dispersant in deionized water to obtain solution C; dispersing a coating agent in anhydrous ethanol to obtain solution D; dispersing a temperature-sensitive polymer in anhydrous ethanol to obtain solution E; mixing solution C and solution E to obtain a mixed solution, adding solution A and solution B into the mixed solution at a set flow rate, and performing a first reaction under stirring until the addition is completed, then adding solution D, performing a second reaction under stirring, and then performing solid-liquid separation to obtain spherical silver powder.

2. The process for the stable production of spherical silver powder according to claim 1, characterized in that, During the first reaction, when the temperature is 0-30℃, the flow rate of solution B is 4.5 mL / min; when the temperature is >30℃, the flow rate of solution B increases by 0.05-0.15 mL / min for each 1℃ increase in temperature; when the humidity is 0%-50%, the reaction temperature is 40℃; when the humidity is >50%, the reaction temperature decreases by 1-3℃ for each 5% increase in humidity; the first reaction time is 1-5 min.

3. The process for the stable production of spherical silver powders according to claim 1, characterized in that, The concentration of silver nitrate in solution A is 0.5-1.5 mol / L.

4. The process for the stable production of spherical silver powders according to claim 1, characterized in that, The adding amount of the reducing agent is 50%-60% of the mass of silver nitrate. The reducing agent comprises at least one of ascorbic acid, glucose, formaldehyde, triethanolamine, and hydrazine hydrate.

5. The process for the stable production of spherical silver powders according to claim 1, characterized in that, The adding amount of the dispersant is 8%-15% of the mass of silver nitrate. The dispersant is polyvinylpyrrolidone, the K value of the polyvinylpyrrolidone is 31.5-33, the moisture content is <4%, the pH value is 3-4, the peroxide content is ≤200 mg / L, and the weight average molecular weight is 25000-40000.

6. The process for the stable production of spherical silver powders according to claim 1, characterized in that, The adding amount of the coating agent is 0.5%-1.5% of the mass of silver nitrate. The coating agent is at least one of oleic acid, lauric acid, stearic acid, and palmitic acid.

7. The process for the stable production of spherical silver powders according to claim 1, characterized in that, The adding amount of the temperature-sensitive polymer is 0.3%-0.5% of the mass of silver nitrate. The temperature-sensitive polymer is at least one of PNIPAM, PDEAAM, and PVCL.

8. The process for the stable production of spherical silver powders according to claim 1, characterized in that, The pH value of solution B is adjusted to 4-6 by using a lye.

9. The process for the stable production of spherical silver powders according to claim 1, characterized in that, The second reaction time is 3-8 min.

10. A spherical silver powder, characterized by, The spherical silver powder is prepared by using any one of the preparation methods in claims 1-9.

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