High-dispersity silver powder and preparation method thereof

Abstract

The invention provides high-dispersity silver powder and a preparation method thereof. The preparation method of the high-dispersity silver powder comprises the following steps that S1, a silver source solution is prepared; s2, a reducing solution is prepared, a reducing agent and a first dispersing agent are mixed, and the first dispersing agent is one or more of gelatin, Arabic gum, PVP, stearic acid and palmitic acid; s3, the silver source solution and the reduction solution are dropwise added into a second dispersing agent, the second dispersing agent comprises citric acid and / or citrate, sedimentation is conducted after the reaction is finished, and sediment is obtained; and S4, the sediment is collected and washed, the washed sediment is dried and dispersed, and the silver powder is obtained. The preparation method of the high-dispersity silver powder aims at solving the problems that the particle size distribution of the silver powder is wide, and silver powder particles are prone to agglomeration.

Description

Technical Field

[0001] The invention relates to the technical field of silver powder preparation, and in particular to highly dispersible silver powder and a preparation method thereof. Background Art

[0002] In recent years, the domestic electronics, photovoltaic and other industries have developed rapidly, and the ultra-large-scale integration, digitization, lightweight and miniaturization of electronic equipment components have received increasing attention from researchers. As one of the key basic materials for the manufacture of microelectronic devices, conductive silver paste has a wide range of applications in aerospace, medical and health, industrial production and other fields. Among them, the circuit devices or wires printed with conductive silver paste used in microelectronic devices directly affect the performance of related electronic equipment, and the morphology and performance of the silver powder in the conductive silver paste play a decisive role in the performance of the silver paste.

[0003] At present, the methods for preparing silver powder at home and abroad mainly include grinding method, atomization method, evaporation condensation method, electrochemical deposition method, sol-gel method, liquid phase reduction method, etc. Among them, the liquid phase reduction method has simple operation process, small investment, high output, low loss and good performance, making it one of the most promising preparation methods.

[0004] However, the existing liquid phase reduction method can prepare silver powder particles with smaller particle size, but the disadvantage of silver powder particles being easy to agglomerate also comes with it. The silver powder prepared by the prior art also has problems such as wide particle size distribution that need to be solved urgently. CN115620958A discloses a method for preparing silver powder, which prepares highly vibrated micron silver powder by slow dripping to carry out redox reaction, but the silver powder prepared by this scheme has a wide particle size distribution and a slow dripping speed, which cannot meet the requirements of large-scale mass production of high-quality silver powder. CN114472917A discloses a method for synthesizing silver powder by dissolving a silver source in an alcohol solution. The prepared silver powder has a large specific surface area and a small particle size, but due to the large specific surface area, it has a high activity and is difficult to use in more sintered silver paste products. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing highly dispersible silver powder, aiming to solve the problem that the silver powder particle size distribution is wide and the silver powder particles are easy to agglomerate.

[0006] The method for preparing highly dispersible silver powder provided by the present invention comprises the following steps: S1: preparing a silver source solution; S2: preparing a reducing solution, mixing a reducing agent and a first dispersant, wherein the first dispersant comprises a mixture of one or more of gelatin, gum arabic, PVP, stearic acid, and palmitic acid; S3: dropping the silver source solution and the reducing solution into a second dispersant, wherein the second dispersant comprises citric acid and / or citrate, and waiting for the reaction to complete and then allowing the solution to settle to obtain a precipitate; S4: collecting and washing the precipitate, drying and dispersing the washed precipitate to obtain the silver powder.

[0007] Specifically, the silver source solution and the reducing solution react first to preliminarily form silver nanoparticles, and the reducing agent and the first dispersant are first mixed in the reducing solution, so that the silver source can be in contact with the reducing agent while also being in uniform contact with the first dispersant. The silver source and the reducing agent react to continuously produce silver nanoparticles, and the first dispersant disperses the silver nanoparticles in time, thereby avoiding the agglomeration of the silver nanoparticles at the initial stage of the reaction and ensuring a smaller initial particle size of the silver powder. The second dispersant is selected from citric acid or citrate or a mixture of the two. The function of the second dispersant is to directional bond with a certain crystal face of the silver nanoparticles formed at the initial stage of the reaction to form a coordination compound, so that the silver particles are directional grown into spherical silver powder. The silver source solution and the reducing agent solution are simultaneously introduced into the second dispersant, so that the second dispersant can immediately guide the directional growth of the silver nanoparticles when they are produced, thereby improving the morphology of the silver nanoparticles.

[0008] At the same time, the active ingredients in citric acid or citrate can regulate the chemical growth of silver particles (111 crystal plane), promote the first dispersant such as gelatin, gum arabic, PVP, stearic acid, palmitic acid, etc., to better coat the silver powder, so as to guide the silver powder to grow in a directional manner, form spherical silver powder, and improve the tap density. In addition, under the action of the first dispersant and the second dispersant, an interface effect is generated, the surface of the silver particles is coated, and the agglomeration phenomenon caused by the contact between the silver particles is avoided, forming a good dispersion effect.

[0009] In one embodiment, the ratio of the first dispersant to the second dispersant is 1:(0.5-1).

[0010] In one embodiment, the silver source solution and the reducing solution are added dropwise to the second dispersant within 20-120 minutes.

[0011] Compared with the prior art, in step S3 of the present invention, the silver source solution and the reducing agent solution are introduced into the second dispersant together, and the introduction by dropwise addition can facilitate the control of the reaction rate. The dropwise addition speed is controlled within a suitable range of 2-20 mL / min to adjust the reaction time and reaction degree.

[0012] In one embodiment, in step S3, after the silver source solution and the reducing solution are dripped into the second dispersant, the mixture is stirred at a temperature of 20-50° C. and a rotation speed of 100-500 rpm for 10-60 min.

[0013] Specifically, by controlling the dropping speed, stirring speed, reaction temperature and reaction time, the particle size, particle size distribution and tap density of the synthesized silver powder can be effectively controlled, thereby achieving controllable production of silver powder that meets the requirements.

[0014] Preferably, the stirring temperature may be 20-40°C or 30-50°C or 20-30°C or 30-50°C; the stirring speed may be 100-200rpm or 150-300rpm or 250-450rpm or 300-500rpm or 250-400rpm; the stirring time may be 10-20min or 15-35min or 20-40min or 30-50min or 45-60min.

[0015] Furthermore, the stirring temperature can be specifically 20°C, 25°C, 30°C, 35°C, 38°C, 40°C, 45°C or 50°C, etc., which is not a sole limitation here; the stirring speed can be specifically 100rpm, 200rpm, 250rpm, 300rpm, 350rpm, 380rpm, 400rpm or 450rpm, etc., which is not a sole limitation here; the stirring time can be specifically 10min, 20min, 25min, 30min, 35min, 40min, 45min, 50min or 55min, etc., which is not a sole limitation here.

[0016] In one embodiment, in step S2, the amount of the first dispersant used is 0.01-1 times the amount of the silver source.

[0017] Specifically, the first dispersant first disperses the nanosilver particles formed at the initial stage of the reaction, so that the nanosilver particles avoid agglomeration before growth or coating. Since the dosage ratio of the silver source affects the degree of reaction and the speed and amount of the generation of nanosilver particles, when the silver source is excessive or the first dispersant is insufficient, the nanosilver particles are generated in large quantities in a short period of time, and the first dispersant does not have time to disperse the silver nanoparticles, resulting in the silver nanoparticles agglomerating at the initial stage of the reaction, which increases the particle size of the silver powder. In addition, it will also cause the first dispersant and the second dispersant to fail to combine in time to coat the nanosilver particles, and guide the agglomerated silver nanoclusters to grow further, so controlling the ratio of the first dispersant to the silver source within a certain range can improve the morphology of the silver powder.

[0018] Preferably, the amount of the first dispersant used may be 0.01-0.2 times, 0.1-0.4 times, 0.3-0.6 times, 0.5-0.8 times, or 0.7-1 times of the silver source.

[0019] Furthermore, the dosage of the first dispersant can be 0.05 times, 0.1 times, 0.3 times, 0.5 times, 0.6 times, 0.7 times, 0.8 times or 0.9 times of the silver source, etc., which is not limited here.

[0020] In one embodiment, in step S2, the reducing agent and the first dispersant are mixed and placed in a water bath at 30-60° C. and stirred at a speed of 200-400 rpm to obtain a reducing solution.

[0021] Specifically, according to the above, the purpose of mixing the reducing agent and the first dispersant is that when the reducing agent reacts with the silver source, the first dispersant can disperse the product silver nanoparticles in a timely and uniform manner, so that the particle size distribution of the silver nanoparticles is narrow, and the uniformity of the mixing of the reducing agent and the first dispersant will directly affect the dispersion effect of the silver nanoparticles. Water bath heating is one of the most uniform heating methods for heat conduction, and with the help of appropriate stirring conditions, the mixing uniformity of the reducing agent and the first dispersant can be further improved. Under multiple process condition adjustments combined with the aforementioned steps and ratios, it was found that mixing the reducing agent and the first dispersant in a water bath at 30-60°C can make the two mix evenly, and the dispersion of the mixture remains at a stable level. If the water bath temperature is too low, the activity of the substance is low, which is not conducive to uniform mixing, while if the water bath temperature is too high, the dispersed substance may be too active and unable to remain stable.

[0022] Preferably, the water bath temperature may be 30-55°C, or 40-60°C, or 45-50°C.

[0023] Furthermore, the water bath temperature may be 32° C., 35° C., 38° C., 42° C., 46° C., 51° C. or 57° C., etc., which is not limited here.

[0024] In one embodiment, in step S2, the silver source solution includes an aqueous solution of a mixture of one or more of silver salts, silver complexes and silver oxides, and the reducing agent includes at least one of aldehyde compounds, hydroquinone compounds, glucose, vitamin C, sodium borohydride, hydrazine hydrate, triethanolamine and hydrogen peroxide.

[0025] Preferably, the silver source solution is an aqueous solution including a silver salt or a silver complex, and the reducing agent is a mixture of one or more of an aldehyde compound, a hydroquinone compound, glucose and vitamin C.

[0026] Specifically, it is very important to select a reducing agent with a suitable reaction rate and moderate reducibility for the preparation of silver powder. According to the type of silver source, a specific reducing agent can be selected to stably produce silver nanoparticles, so as to control the morphology of silver nanoparticles. When the silver source is selected from a silver salt or a silver complex, it can be matched with a reducing agent such as an aldehyde compound, a diphenol compound, glucose or vitamin C, so that the reduction reaction rate of the silver source can be moderate, and it can be stably and uniformly dispersed under the action of the first dispersant.

[0027] Furthermore, the aldehyde compound is an organic substance or mixture containing an aldehyde group, specifically formaldehyde; the hydroquinone compound is an organic substance or mixture containing hydroquinone, specifically hydroquinone; and the vitamin C can be ascorbic acid.

[0028] In one embodiment, the aqueous solution concentration of the silver source solution is 0.2-2 mol / L, and the aqueous solution concentration of the reducing agent is 0.2-2 mol / L.

[0029] Specifically, the silver source solution is a silver source such as a silver salt or a silver complex prepared into an aqueous solution, wherein the concentration of the silver source is 0.2-2 mol / L, and the reducing agent is a mixture of one or more of an aldehyde compound, a hydroquinone compound, glucose and vitamin C prepared into an aqueous solution, wherein the concentration of the mixture of one or more of the aldehyde compound, the hydroquinone compound, glucose and vitamin C is 0.2-2 mol / L. In addition to the type of reducing agent, the concentrations of the silver source solution and the reducing agent are also factors that affect the reduction reaction rate of the silver source. The concentrations of the two complement each other, and the consumption rates of the two are comparable, so that the reducing agent preferentially reduces the silver source, avoiding unexpected effects caused by excessive reducing agent.

[0030] In one embodiment, step S4 is further included, wherein after the reduction reaction of step S3 is completed, the reaction stock solution is precipitated, the precipitate is collected and washed, and the washed precipitate is dried and dispersed to obtain the silver powder.

[0031] In one embodiment, in step S4, the washing includes washing the precipitate with deionized water until the conductivity is ≤20 μs and the pH is 7.

[0032] Specifically, the sediment was washed with deionized water for multiple times, and the conductivity and pH were tested after each washing until the test results showed that the conductivity was ≤20 μs and the pH was 7, thereby ensuring the conductivity of the silver powder.

[0033] In one embodiment, in step S4, after washing and drying, a modifier is added to the silver powder to improve the dispersibility of the silver powder and obtain a highly dispersed powder.

[0034] The present invention also provides a highly dispersible silver powder prepared according to the silver powder preparation method described above.

[0035] The silver powder prepared by the preparation method of highly dispersible silver powder according to the present invention has a smaller particle size and a narrower particle size distribution. Under the influence of multiple factors such as the type and concentration of the silver source and the reducing agent, the timing of adding the first dispersant and the second dispersant and the amount thereof, the silver powder also has higher dispersibility, so that the application range of the silver powder is wider, and the conductive performance, product stability and other performance of the product made therefrom are more superior than those of the existing silver powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below.

[0037] Figure 1 This is a scanning tunneling microscope image of the silver powder obtained in Example 1.

[0038] Figure 2 This is a scanning tunneling microscope image of the silver powder obtained in Comparative Example 1. Implementation

[0039] The specific embodiments of the present invention are described in detail below. Obviously, the present invention only lists a number of representative specific embodiments, which are intended to reflect the beneficial effects of the present invention, and are not equivalent to the embodiments shown below being all embodiments of the present invention. Based on the description of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of the elements listed and may also include additional elements not expressly listed. Example

[0041] The present invention provides a method for preparing highly dispersible silver powder, comprising the following steps: S1: preparing a silver source solution, wherein the silver source is an aqueous solution of a silver salt, and the concentration of the silver source is 1 mol / L; S2: preparing a reducing solution, mixing a reducing agent and a first dispersant, wherein the reducing agent comprises an aqueous solution of an aldehyde compound, the concentration of the aqueous solution of the reducing agent is 1 mol / L, and the first dispersant comprises gelatin, and the amount of gelatin used is 0.5 times that of the silver salt; mixing the reducing agent and the first dispersant, and then placing the mixture in a water bath at 35°C and rotating at 300 rpm until the two are evenly mixed to obtain a reducing solution.

[0042] S3: adding the silver source solution and the reducing solution to the second dispersant at a dropping speed of 10 mL / min, wherein the second dispersant includes citric acid, and the ratio of the first dispersant to the second dispersant is 1:0.6. After the silver source solution and the reducing solution are added to the second dispersant, stirring is performed at a temperature of 30° C. and a speed of 300 rpm for 30 min, and the reaction is waited for sedimentation after the reaction is completed, and the reaction solution after sedimentation is filtered to obtain a sediment; S4: collecting and washing the precipitate with deionized water until the conductivity of the filtrate is ≤20μs and the pH is 7, performing solid-liquid separation and washing again, drying the precipitate after washing again at 60°C for 12h, and then mechanically dispersing and sieving to obtain silver powder. Example

[0043] The present invention provides a method for preparing highly dispersible silver powder, which is different from Example 1 in that it comprises the following steps: S1: preparing a silver source solution, wherein the silver source is an aqueous solution of a mixture of a silver salt and a silver complex, and the concentration of the silver source is 0.2 mol / L; S2: preparing a reducing solution, mixing a reducing agent and a first dispersant, wherein the reducing agent comprises an aqueous solution of ascorbic acid, the concentration of the aqueous solution of the reducing agent is 0.2 mol / L, and the first dispersant comprises palmitic acid, and the amount of palmitic acid is 0.1 times of the silver source; mixing the reducing agent and the first dispersant, placing the mixture in a water bath at 50°C and stirring at a speed of 35 rpm until the two are evenly mixed, to obtain a reducing solution.

[0044] S3: adding the silver source solution and the reducing solution to the second dispersant at a dropping speed of 7 mL / min, wherein the second dispersant includes citrate, and the ratio of the first dispersant to the second dispersant is 1:0.8. After the silver source solution and the reducing solution are added to the second dispersant, stirring is performed at a temperature of 50° C. and a speed of 500 rpm for 10 min, and the reaction is waited for sedimentation after the reaction is completed, and the reaction solution after sedimentation is filtered to obtain a sediment; S4: collecting and washing the precipitate with deionized water until the conductivity of the filtrate is ≤20μs and the pH is 7, performing solid-liquid separation and washing again, drying the precipitate after washing again at 60°C for 12h, and then mechanically dispersing and sieving to obtain silver powder. Example

[0045] The present invention provides a method for preparing highly dispersible silver powder, which is different from Example 1 in that it comprises the following steps: S1: preparing a silver source solution, wherein the silver source is an aqueous solution of a silver salt, and the concentration of the silver source is 3 mol / L; S2: preparing a reducing solution, mixing a reducing agent and a first dispersant, wherein the reducing agent comprises an aqueous solution of a mixture of glucose and vitamin C, the concentration of the aqueous solution of the reducing agent is 2 mol / L, and the first dispersant comprises gum arabic, and the amount of gum arabic is twice that of the silver source; mixing the reducing agent and the first dispersant, placing the mixture in a water bath at 20°C and stirring at 400 rpm until the two are evenly mixed, to obtain a reducing solution.

[0046] S3: adding the silver source solution and the reducing solution to the second dispersant at a dropping speed of 20 mL / min, wherein the second dispersant includes citric acid, and the ratio of the first dispersant to the second dispersant is 1:1. After the silver source solution and the reducing solution are added to the second dispersant, stirring is performed at a temperature of 20° C. and a speed of 400 rpm for 60 min, and the reaction is waited for sedimentation after the reaction is completed, and the reaction solution after sedimentation is filtered to obtain a sediment; S4: collecting and washing the precipitate with deionized water until the conductivity of the filtrate is ≤20μs and the pH is 7, performing solid-liquid separation and washing again, drying the precipitate after washing again at 60°C for 12h, and then mechanically dispersing and sieving to obtain silver powder.

[0047] Comparative Example 1 The present invention provides a method for preparing highly dispersible silver powder, which is different from Example 1 in that it comprises the following steps: S1: preparing a silver source solution, wherein the silver source is an aqueous solution of a silver salt, and the concentration of the silver source is 0.8 mol / L; S2: preparing a reducing solution, mixing a reducing agent and a first dispersant, wherein the reducing agent comprises an aqueous solution of a mixture of an aldehyde compound and glucose, the concentration of the aqueous solution of the reducing agent is 1.2 mol / L, and the first dispersant comprises a mixture of PVP and palmitic acid, and the amount of the mixture of PVP and palmitic acid is 0.3 times that of the silver source; mixing the reducing agent and the first dispersant, placing the mixture in a water bath at 45° C. and stirring at a speed of 280 rpm until the two are evenly mixed, to obtain a reducing solution; S3: The silver source solution and the reducing solution are added dropwise to the second dispersant at a dropping speed of 10 mL / min. The second dispersant is a mixed solution of polyethylene glycol and polyvinyl alcohol. The ratio of the first dispersant to the second dispersant is 1:1. After the silver source solution and the reducing solution are added dropwise to the second dispersant, the mixture is stirred at 250 rpm for 35 min at a temperature of 30°C. After the reaction is completed, the mixture is allowed to settle. The reaction solution after the settlement is filtered to obtain a precipitate. S4: collecting and washing the precipitate with deionized water until the conductivity of the filtrate is ≤20μs and the pH is 7, performing solid-liquid separation and washing again, drying the precipitate after washing again at 60°C for 12h, and then mechanically dispersing and sieving to obtain silver powder.

[0048] Comparative Example 2 The present invention provides a method for preparing highly dispersible silver powder, which is different from Example 1 in that it comprises the following steps: S1: preparing a silver source solution, wherein the silver source is an aqueous solution of a silver complex, and the concentration of the silver source is 0.2 mol / L; S2: preparing a reducing solution, mixing a reducing agent and a first dispersant, wherein the reducing agent comprises an aqueous solution of a mixture of a hydroquinone compound and vitamin C, the concentration of the aqueous solution of the reducing agent is 0.2 mol / L, the first dispersant is hexadecyltrimethylammonium bromide, and the amount of the first dispersant is 0.6 times that of the silver source; mixing the reducing agent and the first dispersant, placing the mixture in a water bath at 60° C. and stirring at a speed of 200 rpm until the two are evenly mixed, to obtain a reducing solution; S3: The silver source solution and the reducing solution are added dropwise to the second dispersant at a dropping speed of 10 mL / min, the second dispersant includes citric acid, and the ratio of the first dispersant to the second dispersant is 1:0.8. After the silver source solution and the reducing solution are added dropwise to the second dispersant, the mixture is stirred at 350 rpm for 25 min at a temperature of 38° C., and the mixture is waited for sedimentation after the reaction is completed. The reaction solution after sedimentation is filtered to obtain a sediment; S4: collecting and washing the precipitate with deionized water until the conductivity of the filtrate is ≤20μs and the pH is 7, performing solid-liquid separation and washing again, drying the precipitate after washing again at 60°C for 12h, and then mechanically dispersing and sieving to obtain silver powder.

[0049] Comparative Example 3 The present invention provides a method for preparing highly dispersible silver powder, which is different from Example 1 in that it comprises the following steps: S1: preparing a silver source solution, wherein the silver source is an aqueous solution of a silver complex, and the concentration of the silver source is 1.3 mol / L; S2: preparing a reducing agent and a first dispersant, wherein the reducing agent is sodium citrate, the concentration of the reducing agent aqueous solution is 2 mol / L, the first dispersant includes stearic acid, and the amount of stearic acid is 0.7 times that of the silver source; S3: The silver source solution, the reducing agent and the first dispersant are simultaneously added dropwise to the second dispersant at a dropping speed of 2 mL / min, the second dispersant includes citric acid, and the ratio of the first dispersant to the second dispersant is 1:0.5. After the silver source solution and the reducing solution are added dropwise to the second dispersant, the mixture is stirred at a speed of 450 rpm for 55 min at a temperature of 42° C., and sedimentation is waited for after the reaction is completed, and the reaction solution after sedimentation is filtered to obtain a sediment; S4: Collect and wash the sediment with deionized water until the conductivity of the filtrate is ≤20μs, pH=7, perform solid-liquid separation and wash again, dry the washed sediment at 60°C for 12h, and then mechanically disperse and sieve to obtain silver powder Comparative Example 4 The present invention provides a method for preparing highly dispersible silver powder, which is different from Example 1 in that it comprises the following steps: S1: preparing a silver source solution, wherein the silver source is an aqueous solution of a silver complex, and the concentration of the silver source is 2 mol / L; S2: preparing a reducing agent and a first dispersant, wherein the reducing agent comprises an aqueous solution of a mixture of a hydroquinone compound and glucose, the concentration of the aqueous solution of the reducing agent is 0.6 mol / L, and the first dispersant comprises PVP, and the amount of PVP used is 1 times that of the silver source; S3: The silver source solution, the reducing agent and the first dispersant solution are sequentially added to the second dispersant at a dropping speed of 15 mL / min, the second dispersant includes citrate, and the ratio of the first dispersant to the second dispersant is 1:0.5. After the silver source solution and the reducing solution are added to the second dispersant, the mixture is stirred at a temperature of 45°C and a speed of 380 rpm for 45 minutes, and the reaction is waited for sedimentation after the reaction is completed, and the reaction solution after sedimentation is filtered to obtain a sediment; S4: collecting and washing the precipitate with deionized water until the conductivity of the filtrate is ≤20μs and the pH is 7, performing solid-liquid separation and washing again, drying the precipitate after washing again at 60°C for 12h, and then mechanically dispersing and sieving to obtain silver powder. Test Case The silver powder samples prepared by the preparation methods of highly dispersible silver powders of Examples 1 to 5 and Comparative Examples 1 to 4 were respectively tested for particle size and particle size distribution using a laser particle size analyzer, and the tap density of the silver powder was tested using a tap density meter.

[0050] Table 1 shows the particle size and tap density test results of the silver powder obtained by the preparation methods of Examples 1 to 3 and Comparative Examples 1 to 4: According to the test data, the silver powder of Examples 1 to 3 has a smaller particle size, is relatively evenly distributed, and has a large tap density. Figure 1 The silver powder obtained in Example 1 has good dispersibility, high sphericity, uniform particle size, and almost no agglomeration phenomenon is observed. However, compared with Example 1, the average particle size of the silver powder in Example 3 is larger, the particle size distribution is wider, and the tap density is reduced. This may be due to the fact that the silver source concentration and the dispersant concentration exceed the optimal range, and the reaction temperature is low, which leads to agglomeration.

[0051] The second dispersant in Comparative Example 1 is a mixed solution of polyethylene glycol and polyvinyl alcohol, which cannot effectively improve the sphericity of the silver powder particles. Figure 1-2 , relative to Example 1 ( Figure 1 ) selected citric acid, comparative example 1 ( Figure 2 ) The silver powder obtained has a significant decrease in morphology.

[0052] In Comparative Example 2, the first dispersant is hexadecyltrimethylammonium bromide. Compared with gelatin, gum arabic, PVP, stearic acid or palmitic acid in Example 1, the synergistic effect of hexadecyltrimethylammonium bromide and the second dispersant citric acid is not good, and the sphericity of the silver powder particles is greatly reduced.

[0053] In Comparative Examples 3 and 4, the reducing agent and the first dispersant were not mixed, but were added to the silver source solution simultaneously or sequentially, resulting in the inability to synchronize reduction and dispersion, which easily caused the silver powder ion agglomeration phenomenon. Therefore, compared with Example 1, the particle size of Comparative Examples 3 and 4 was large and the tap density was small.

[0054] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing highly dispersible silver powder, characterized in that: The following steps are involved: S1: preparing silver source solution; S2: preparing a reducing solution, mixing a reducing agent and a first dispersant, wherein the first dispersant comprises a mixture of one or more of gelatin, gum arabic, PVP, stearic acid and palmitic acid; S3: adding the silver source solution and the reducing solution dropwise to a second dispersant, wherein the second dispersant comprises citric acid and / or citrate.

2. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: In step S3, after the silver source solution and the reducing solution are dripped into the second dispersant, the mixture is stirred at a temperature of 20-50° C. and a rotation speed of 100-500 rpm for 10-60 min.

3. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: The dosage ratio of the first dispersant to the second dispersant is 1:0.5-1.

4. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: The silver source solution and the reducing solution are added dropwise to the second dispersant within 20-120 minutes.

5. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: In step S2, the dosage of the first dispersant is 0.01-1 times of the silver source.

6. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: In step S2, the reducing agent and the first dispersant are mixed and placed in a water bath at 30-60°C and stirred at a speed of 200-400 rpm until the two are evenly mixed and no dispersant particles are present, thereby obtaining a reducing solution.

7. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: In step S2, the silver source solution includes an aqueous solution of a silver salt or a silver complex, and the reducing agent includes one or a mixture of aldehyde compounds, hydroquinone compounds, glucose and vitamin C.

8. The method for preparing highly dispersible silver powder according to claim 7, characterized in that: The aqueous solution concentration of the silver source solution is 0.2-2 mol / L, and the aqueous solution concentration of the reducing agent is 0.2-2 mol / L.

9. The method for preparing highly dispersible silver powder according to claim 1, characterized in that: The step S4 is also included. After the reduction reaction of step S3 is completed, the reaction stock solution is precipitated, the precipitate is collected and washed, and the washed precipitate is dried and dispersed to obtain the silver powder.

10. Highly dispersible silver powder obtained according to the method for preparing highly dispersible silver powder according to any one of claims 1 to 9.

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