Preparation method of high-dispersion spherical silver powder

Abstract

The invention discloses a preparation method of high-dispersion spherical silver powder, which comprises the following steps: respectively pumping a precursor solution and a reducing agent solution into a micro-channel reactor by using an injection pump at a constant flow rate, and reacting under ultrasonic and constant-temperature conditions to obtain the high-dispersion spherical silver powder, the precursor solution contains silver salt and polyvinylpyrrolidone; the reducing agent solution contains a reducing agent and lauryl sodium sulfate. According to the preparation method, nucleation is accurately controlled and particle aggregation is inhibited through a combined strategy of a microreactor, a composite dispersing agent and ultrasonic assistance, the preparation process of the spherical silver powder is comprehensively improved, and the high-dispersion spherical silver powder with excellent performance is prepared.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology, specifically to a method for preparing highly dispersed spherical silver powder. Background Technology

[0002] Due to its quantum size and other characteristics, silver nanoparticles exhibit superior electromagnetic properties, catalytic performance, excellent biocompatibility, and sensing properties compared to ordinary materials. The small size and high surface activity of silver nanoparticles allow for lower curing temperatures, enabling room-temperature curing and thus wider applications. Therefore, researching preparation methods and optimizing processes for silver nanoparticles is of great significance. However, current liquid-phase chemical reduction methods for preparing flake-shaped silver powder face several technical bottlenecks, severely restricting their application in high-end electronics, optics, and other fields.

[0003] The morphology of silver powder is synergistically controlled by various stages of crystal nucleus growth, but the reaction parameters are extremely sensitive. While increasing reactant concentration improves yield, it easily leads to chaotic silver powder morphology. For example, excessively high silver nitrate concentrations result in a mixture of flake and spherical particles, with micropores and cracks appearing on the particle surface. Dispersant residue further exacerbates structural defects; sulfur-containing dispersants are difficult to thoroughly clean and will subsequently react with silver to form silver sulfide, leading to a loose sintered film and discontinuous conductive pathways. The dispersibility of silver powder depends on the steric hindrance effect of the dispersant, but a dilemma exists: insufficient dispersant cannot effectively encapsulate silver particles, leading to severe agglomeration, reduced tap density, and easy sticking to rollers during silver paste rolling and difficulty in screen removal during printing; exceeding the critical point not only results in waste but also increases system viscosity, making subsequent cleaning more difficult. Even with the use of highly efficient dispersants (such as benzotriazole), although dispersibility can be improved, secondary agglomeration may still occur at high temperatures due to adsorption layer failure, and residual organic matter will reduce the purity of the silver powder.

[0004] Particle size uniformity is influenced by multiple factors, including pH, reaction temperature, and dropping rate; deviations from these parameters lead to distribution deterioration. This multi-parameter coupling limits the precision of particle size control, making it difficult to meet the microelectronics field's demand for narrow-distribution silver powder. Existing processes fall into a paradox of "low yield and high efficiency" versus "high yield and low efficiency": to ensure morphology and particle size uniformity, low-concentration silver solutions are required, resulting in low yield per unit volume and high production costs; increasing the silver ion concentration leads to morphology loss of control and particle size inhomogeneity, causing a sharp increase in subsequent sorting costs. Furthermore, long reaction cycles, large reagent consumption, and cumbersome organic matter handling processes further reduce production efficiency. Therefore, optimizing the preparation process of nano-silver powder is currently an important research direction in this field. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a method for preparing highly dispersed spherical silver powder. This method uses a combination strategy of "microreactor + composite dispersant + ultrasonic assistance" to precisely control nucleation, inhibit particle agglomeration, and comprehensively improve the preparation process of spherical silver powder, thereby obtaining highly dispersed spherical silver powder with excellent performance.

[0006] The present invention also proposes the application of the above preparation method.

[0007] According to a first aspect of the present invention, a method for preparing highly dispersed spherical silver powder is provided, the method comprising the following steps: The precursor solution and reducing agent solution were separately pumped into a microchannel reactor at a constant flow rate using syringe pumps, and the reaction was carried out under ultrasonic and isothermal conditions to obtain highly dispersed spherical silver powder; the precursor solution contained silver salt and polyvinylpyrrolidone; the reducing agent solution contained reducing agent and sodium dodecyl sulfate.

[0008] In some embodiments of the present invention, the power of the ultrasound is 150~350 W.

[0009] In some embodiments of the present invention, the power of the ultrasound is 200~300 W.

[0010] In some embodiments of the present invention, the frequency of the ultrasound is 20~40 kHz. In some embodiments of the present invention, the frequency of the ultrasound is 25~35 kHz. In some embodiments of the present invention, the constant temperature condition is 60°C to 80°C.

[0011] In some embodiments of the present invention, the constant temperature condition is 65°C to 75°C.

[0012] In some embodiments of the present invention, the constant flow rate is 8 to 12 mL / min.

[0013] In some embodiments of the present invention, the precursor solution contains 0.3 to 0.7 mol / L silver salt and polyvinylpyrrolidone, wherein the mass of polyvinylpyrrolidone in the precursor solution is 4% to 12% of the theoretical mass of silver.

[0014] In some embodiments of the present invention, the precursor solution contains 0.3 to 0.7 mol / L silver salt and polyvinylpyrrolidone, wherein the mass of polyvinylpyrrolidone in the precursor solution is 5% to 10% of the theoretical mass of silver.

[0015] In some embodiments of the present invention, the reducing agent solution contains 0.5 to 1 mol / L of reducing agent and 0.05 wt% to 0.6 wt% of sodium dodecyl sulfate.

[0016] In some embodiments of the present invention, the reducing agent solution contains 0.6 to 0.8 mol / L of reducing agent and 0.1 wt% to 0.5 wt% of sodium dodecyl sulfate.

[0017] In some embodiments of the present invention, the solvents for the precursor solution and the reducing agent solution are mixed solvents of equal volumes of deionized water and ethylene glycol.

[0018] In some embodiments of the present invention, the pH value of the precursor solution is adjusted to pH 9-10.

[0019] In some embodiments of the present invention, the reducing agent includes at least one of ascorbic acid, sodium citrate, and hydrazine hydrate.

[0020] In some embodiments of the present invention, the silver salt includes at least one of silver nitrate, silver sulfate, silver chloride, silver bromide, and silver carbonate.

[0021] In some embodiments of the present invention, the channel diameter of the microchannel reactor is 300 μm to 1 mm.

[0022] In some embodiments of the present invention, the microchannel reactor includes a T-type or Y-type microchannel reactor.

[0023] In some embodiments of the present invention, the preparation method further includes post-processing.

[0024] In some embodiments of the present invention, the post-processing includes sequential ethanol washing and deionized water washing, followed by freeze drying.

[0025] From a mechanistic perspective: This invention employs a T-type or Y-type microchannel reactor with a channel diameter of <1 mm. The reaction solution is pumped into the microreactor at a constant flow rate using a precision syringe pump. At the confluence of the microchannels, the two liquid streams achieve highly uniform laminar mixing within milliseconds, instantaneously generating extremely high supersaturation and triggering explosive, uniform nucleation. Using a microreactor for continuous flow reactions replaces traditional batch reactors, enabling more precise control of temperature, concentration, and mixing.

[0026] This invention employs a composite dispersant system, including a primary dispersant and an auxiliary dispersant. The primary dispersant is polyvinylpyrrolidone (PVP), an excellent steric hindrance agent whose carbonyl group has a strong adsorption effect on silver. The auxiliary dispersant, which also functions as a morphology control agent, is sodium dodecyl sulfate (SDS). As an anionic surfactant, SDS can further enhance dispersion through electrostatic repulsion and contribute to the formation of spherical particles. Using this powerful composite dispersant effectively encapsulates each crystal nucleus, preventing them from contacting each other and agglomerating.

[0027] This invention places the reaction device in an ultrasonic water bath. The cavitation effect of ultrasound can further enhance micro-mixing, break up newly formed soft aggregates, and promote heat transfer, thereby preventing local overheating. Ultrasonic assistance is helpful for mixing and nucleation.

[0028] This invention selects a mixed solvent composed of ethylene glycol and deionized water. Ethylene glycol has a certain viscosity, can be used as a reducing agent, and can better control the reaction at high temperatures.

[0029] The reaction system in this invention is a weakly alkaline system, which helps to slow down the reduction rate and allows for better control of particle size.

[0030] The present invention has at least the following beneficial effects: The method for preparing highly dispersed spherical silver powder provided by this invention employs a combined strategy of "microreactor + composite dispersant + ultrasonic assistance" to precisely control nucleation and inhibit particle agglomeration, ultimately yielding highly dispersed, low-particle-size, highly conductive, and efficiently synthesized spherical silver powder. This method overcomes the problems of morphological defects, poor dispersibility, uneven particle size, and low efficiency that are commonly encountered in current spherical silver powder preparation processes, providing a theoretical basis and technical support for the application of nano-silver powder in high-end electronics, optics, and other technological fields.

[0031] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a SEM result image of Embodiment 1 of the present invention; Figure 2 This is a SEM result image of Embodiment 2 of the present invention; Figure 3 This is a SEM result image of Comparative Example 1 of the present invention; Figure 4 This is the SEM result image of Comparative Example 2 of the present invention. Detailed Implementation

[0033] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0034] Example 1 This embodiment provides a method for preparing highly dispersed spherical silver powder, the specific steps of which are as follows: 1. Raw material preparation 1) Preparation of precursor solution A: Weigh silver nitrate and the main dispersant polyvinylpyrrolidone (PVP) and dissolve them in a mixed solvent of equal volumes of deionized water and ethylene glycol to obtain precursor solution A containing 0.5 mol / L silver nitrate and 2.7 g / L PVP. The mass of PVP in precursor solution A is 5% of the theoretical mass of silver. Adjust the pH of precursor solution A to weakly alkaline (pH 9-10 is acceptable) using ammonia.

[0035] 2) Preparation of reducing agent solution B: Weigh out ascorbic acid and sodium dodecyl sulfate (SDS) as an auxiliary dispersant, and dissolve them in a mixed solvent of equal volumes of deionized water and ethylene glycol to obtain a reducing agent solution B containing 0.6 mol / L ascorbic acid and 0.1 wt% SDS.

[0036] 2. Preparation of spherical silver powder 1) Reaction apparatus: A T-type microchannel reactor with a channel diameter of 300 μm to 1 mm is used. The entire reaction channel is placed in an ultrasonic water bath. The water bath temperature is controlled at 70℃ throughout the process, and the ultrasonic power is 200 W with a frequency of 30 kHz.

[0037] 2) Reaction steps: Precursor solution A and reducing agent solution B are pumped into the microchannel reactor at a constant flow rate of 10 mL / min using a precision injection pump. At the confluence of the microchannels, the two liquid streams achieve highly uniform laminar mixing within milliseconds, instantly generating extremely high supersaturation, triggering explosive uniform nucleation, and obtaining highly dispersed spherical silver powder after ultrasonic reaction for 5 min.

[0038] 3) Post-processing: Collect the product flowing out of the reactor, wash it 1-2 times with ethanol, then wash it 3-5 times with deionized water to remove excess dispersant and by-products, and then freeze-dry it under vacuum to obtain the finished product. The SEM image of the highly dispersed spherical silver powder prepared in Example 1 is shown below. Figure 1 As shown.

[0039] Example 2 This embodiment provides a method for preparing highly dispersed spherical silver powder, the specific steps of which are as follows: 1. Raw material preparation 1) Preparation of precursor solution A: Weigh silver nitrate and the main dispersant polyvinylpyrrolidone (PVP) and dissolve them in a mixed solvent of equal volumes of deionized water and ethylene glycol to obtain precursor solution A containing 0.5 mol / L silver nitrate and 4.31 g / L PVP. The mass of PVP in precursor solution A is 8% of the theoretical mass of silver. Adjust the pH of precursor solution A to weakly alkaline (pH 9-10 is acceptable) using ammonia.

[0040] 2) Preparation of reducing agent solution B: Weigh out ascorbic acid and sodium dodecyl sulfate (SDS) as an auxiliary dispersant, and dissolve them in a mixed solvent of equal volumes of deionized water and ethylene glycol to obtain a reducing agent solution B containing 0.7 mol / L ascorbic acid and 0.3 wt% SDS.

[0041] 2. Preparation of spherical silver powder 1) Reaction apparatus: A T-type microchannel reactor with a channel diameter of 300 μm to 1 mm is used. The entire reaction channel is placed in an ultrasonic water bath. The water bath temperature is controlled at 70℃ throughout the process, and the ultrasonic power is 250 W with a frequency of 30 kHz.

[0042] 2) Reaction steps: Precursor solution A and reducing agent solution B are pumped into the microchannel reactor at a constant flow rate of 10 mL / min using a precision injection pump. At the confluence of the microchannels, the two liquid streams achieve highly uniform laminar mixing within milliseconds, instantly generating extremely high supersaturation, triggering explosive uniform nucleation, and obtaining highly dispersed spherical silver powder after ultrasonic reaction for 5 min.

[0043] 3) Post-processing: Collect the product flowing out of the reactor, wash it 1-2 times with ethanol, then wash it 3-5 times with deionized water to remove excess dispersant and by-products, and then freeze-dry it under vacuum to obtain the finished product. The SEM image of the highly dispersed spherical silver powder prepared in Example 2 is shown below. Figure 2 As shown.

[0044] Example 3 This embodiment provides a method for preparing highly dispersed spherical silver powder, the specific steps of which are as follows: 1. Raw material preparation 1) Preparation of precursor solution A: Weigh silver nitrate and the main dispersant polyvinylpyrrolidone (PVP) and dissolve them in a mixed solvent of equal volumes of deionized water and ethylene glycol to obtain precursor solution A containing 0.5 mol / L silver nitrate and 5.39 g / L PVP. The mass of PVP in precursor solution A is 10% of the theoretical mass of silver. Adjust the pH of precursor solution A to weakly alkaline (pH 9-10 is acceptable) using ammonia.

[0045] 2) Preparation of reducing agent solution B: Weigh out ascorbic acid and sodium dodecyl sulfate (SDS) as an auxiliary dispersant, and dissolve them in a mixed solvent of equal volumes of deionized water and ethylene glycol to obtain a reducing agent solution B containing 0.8 mol / L ascorbic acid and 0.5 wt% SDS.

[0046] 2. Preparation of spherical silver powder 1) Reaction apparatus: A T-type microchannel reactor with a channel diameter of 300 μm to 1 mm is used. The entire reaction channel is placed in an ultrasonic water bath. The water bath temperature is controlled at 70℃ throughout the process, and the ultrasonic power is 300 W with a frequency of 30 kHz.

[0047] 2) Reaction steps: Precursor solution A and reducing agent solution B are pumped into the microchannel reactor at a constant flow rate of 10 mL / min using a precision injection pump. At the confluence of the microchannels, the two liquid streams achieve highly uniform laminar mixing within milliseconds, instantly generating extremely high supersaturation, triggering explosive uniform nucleation, and obtaining highly dispersed spherical silver powder after ultrasonic reaction for 5 min.

[0048] 3) Post-processing: Collect the product flowing out of the reactor, wash it with ethanol 1-2 times, then wash it with deionized water 3-5 times to remove excess dispersant and by-products, and then freeze dry it under vacuum to obtain the finished product.

[0049] Comparative Example 1 This comparative example provides a method for preparing spherical silver powder. The specific steps differ from Example 2 only in that PVP in precursor solution A is omitted; all other steps remain the same as in Example 2. The SEM image of the spherical silver powder obtained in Comparative Example 1 is shown below. Figure 3 As shown.

[0050] Comparative Example 2 This comparative example provides a method for preparing spherical silver powder. The specific steps differ from those in Example 2 only in that SDS in reducing agent solution B is omitted; all other steps remain the same as in Example 2. The SEM image of the spherical silver powder obtained in Comparative Example 2 is shown below. Figure 4 As shown.

[0051] Comparative Example 3 This comparative example provides a method for preparing spherical silver powder. The specific steps are different from those in Example 2 only in that the PVP concentration in the precursor solution A is adjusted to 1.08 g / L (i.e., PVP accounts for 2% of the theoretical silver mass). All other steps are the same as in Example 2.

[0052] Comparative Example 4 This comparative example provides a method for preparing spherical silver powder. The only difference between this method and Example 2 is that the concentration of PVP in the precursor solution A is adjusted to 8.1 g / L (i.e., PVP accounts for 15% of the theoretical silver mass). All other steps are the same as in Example 2.

[0053] Comparative Example 5 This comparative example provides a method for preparing spherical silver powder. The specific steps are different from those in Example 2 only in that the concentration of SDS in the reducing agent solution B is adjusted to 0.01 wt%, while the other steps are consistent with those in Example 2.

[0054] Comparative Example 6 This comparative example provides a method for preparing spherical silver powder. The specific steps are different from those in Example 2 only in that the concentration of SDS in the reducing agent solution B is adjusted to 1 wt%, while the other steps are the same as in Example 2.

[0055] Comparative Example 7 This comparative example provides a method for preparing spherical silver powder. The only difference between this method and Example 2 is that the ultrasonic treatment during the reaction process is omitted, while the other steps are consistent with those in Example 2.

[0056] Comparative Example 8 This comparative example provides a method for preparing spherical silver powder. The specific steps are different from those in Example 2 only in that the ultrasonic power during the reaction process is adjusted to 500 W, while the other steps are the same as in Example 2.

[0057] Test case This experiment prepared spherical silver powder samples based on the methods provided in Examples 1-3 and Comparative Examples 1-8. The main differences between Examples 1-3 and Comparative Examples 1-8 are shown in Table 1. Performance tests were conducted on the above samples, and the specific experimental methods and results are as follows: Table 1. Key Difference Parameters between Examples 1-3 and Comparative Examples 1-8

[0058] 1. Particle size detection The particle size of the spherical silver powder sample was measured using a laser particle size analyzer (Mastersizer3000), and the results are shown in Table 2.

[0059] 2. Morphological assessment The morphology of the spherical silver powder samples was evaluated using a KYKY-2800 scanning electron microscope (SEM), and the results are shown in Table 2. The SEM morphologies of Examples 1-2 and Comparative Examples 1-2 are as follows: Figures 1-4 As shown.

[0060] 3. Dispersion detection The dispersibility of the spherical silver powder samples was detected using a KYKY-2800 scanning electron microscope (SEM), and the results are shown in Table 2.

[0061] 4. Conductivity testing The conductivity of spherical silver powder samples was tested using a Shanghai Huayan SX1934 digital four-probe tester. The spherical silver powder samples were pressed into circular sheets at 50 MPa, and the resistivity of the pressed sheets was measured using the four-probe tester. The results are shown in Table 2.

[0062] Table 2 Test Results

[0063] The results in Table 2 show that: 1) In Comparative Example 1, since the key dispersant PVP was omitted, the primary silver nuclei generated by the reduction of silver ions lacked surface coating and were easily attracted to each other by van der Waals forces or metallic bonds, resulting in irreversible agglomeration. This led to a significant increase in particle size compared to Example 2 and a substantial decrease in dispersibility. At the same time, the lack of PVP caused the conductivity of the silver powder to be affected by contact defects and organic residues caused by agglomeration, resulting in a significant decrease in conductivity. Regarding the SEM morphology, the silver powder no longer maintained the monodisperse spherical shape as it did when the dispersant was present, but instead formed blocky or dendritic agglomerates composed of dozens to hundreds of small particles. The surface of the agglomerates was rough, and obvious particle accumulation traces were visible.

[0064] 2) Comparative Example 2 showed a significant decrease in overall performance due to the omission of the auxiliary dispersant SDS. The mechanism was similar to that of Comparative Example 1, both resulting in large silver powder particle size and poor dispersion due to the lack of dispersant. However, compared to PVP, the lack of SDS had a slightly smaller overall impact on the silver powder.

[0065] 3) Comparative Example 3 reduced the amount of PVP, and its particle size was significantly larger than that of Example 2. The reason may be that after reducing PVP, the "nucleation-growth" balance during the silver nucleus growth process was broken, and small particles continued to adsorb onto the surface of larger particles, forming agglomerates, which led to an increase in the particle size and a decrease in the dispersion of silver powder. Its conductivity was also affected by the particle size and dispersion, and the resistivity increased by about two orders of magnitude compared with Example 2.

[0066] 4) Comparative Example 4 increased the amount of PVP, and its particle size was significantly larger than that of Example 2, but slightly smaller than that of Comparative Example 3. The reason may be that excessive PVP is adsorbed on the silver crystal surface through chain segments. The strong adsorption caused by excessive PVP will inhibit crystal growth, resulting in the silver nuclei not being able to grow sufficiently, which ultimately affects the performance of the silver powder.

[0067] 5) Comparative Example 5 reduced the amount of SDS, and its overall performance deteriorated significantly. The mechanism was similar to that of Comparative Example 3, which was due to the reduction of dispersant, resulting in larger silver powder particle size and poor dispersion. However, compared with PVP, the reduction of SDS had a slightly smaller overall impact on the silver powder.

[0068] 6) Comparative Example 6 increased the amount of SDS, and its particle size was significantly larger than that of Example 2, but slightly smaller than that of Comparative Example 2. The reason may be that SDS is adsorbed through sulfonic acid groups. When there is an excess, the negative charge on the particle surface is excessive, which leads to an imbalance of electrostatic repulsion between particles, forming unstable flocculents, which in turn leads to increased particle size, reduced dispersibility, irregular morphology and reduced conductivity.

[0069] 7) Comparative Example 7 omitted the ultrasonic treatment during the reaction process, and its overall performance was significantly worse. Ultrasonic treatment can enhance the micro-mixing between solutions during the reaction process and break up the newly formed soft agglomerates. By omitting the ultrasonic step, not only was the reaction efficiency reduced, but the degree of particle agglomeration was also increased.

[0070] 8) Comparative Example 8 increased the power of ultrasonic treatment, and its particle size was significantly larger than that of Example 2, but its overall performance was better than that of Comparative Example 7. The reason may be that excessive ultrasonic power can lead to severe cavitation effect, which may destroy the formed silver powder crystal structure, resulting in uneven particle size distribution. At the same time, it will cause the temperature of the reaction system to rise sharply and become difficult to control; thus, it leads to increased particle size, reduced dispersibility, irregular morphology, and reduced conductivity.

[0071] Based on the above results, it can be seen that the method for preparing highly dispersed spherical silver powder provided by the present invention, through a specific dispersant ratio combined with a microchannel reactor reaction under ultrasonic conditions, can efficiently prepare highly dispersed spherical silver powder with excellent performance.

[0072] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

Claims

1. A method for preparing highly dispersed spherical silver powder, characterized in that, The preparation method includes the following steps: The precursor solution and reducing agent solution were separately pumped into a microchannel reactor at a constant flow rate using syringe pumps, and the reaction was carried out under ultrasonic and isothermal conditions to obtain highly dispersed spherical silver powder; the precursor solution contained silver salt and polyvinylpyrrolidone; the reducing agent solution contained reducing agent and sodium dodecyl sulfate.

2. The preparation method according to claim 1, characterized in that, The power of the ultrasound is 150~350 W.

3. The preparation method according to claim 1, characterized in that, The frequency of the ultrasound is 20~40 kHz.

4. The preparation method according to claim 1, characterized in that, The constant temperature conditions are 60℃~80℃.

5. The preparation method according to claim 1, characterized in that, The constant flow rate is 8~12 mL / min.

6. The preparation method according to claim 1, characterized in that, The precursor solution contains 0.3~0.7 mol / L silver salt and polyvinylpyrrolidone, and the mass of polyvinylpyrrolidone in the precursor solution is 4%~12% of the theoretical mass of silver.

7. The preparation method according to claim 1, characterized in that, The reducing agent solution contains 0.5~1 mol / L of reducing agent and 0.05 wt%~0.6 wt% of sodium dodecyl sulfate.

8. The preparation method according to claim 1, characterized in that, The solvents for the precursor solution and the reducing agent solution are a mixed solvent of equal volumes of deionized water and ethylene glycol.

9. The preparation method according to claim 1, characterized in that, The reducing agent includes at least one of ascorbic acid, sodium citrate, and hydrazine hydrate.

10. The application of the preparation method according to any one of claims 1 to 9 in the preparation of spherical silver powder.

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