Crystal face sphere-like silver powder and preparation method and application thereof

Abstract

The invention belongs to the technical field of precious metal materials, and particularly relates to crystal face sphere-like silver powder and a preparation method and application thereof. The preparation method of the crystal face sphere-like silver powder comprises the following steps that a first silver nitrate solution, a first reducing agent solution, a stabilizer and a surfactant are mixed, and a colloidal solution is obtained; mixing the colloidal solution and the neutralizer solution to obtain a reaction base solution; and a second silver nitrate solution and a second reducing agent solution are added into the reaction base solution at the same time and then mixed with a dispersing agent, and the crystal face sphere-like silver powder is obtained. According to the preparation method provided by the invention, the colloidal solution is prepared as the seed crystal, the liquid-phase reduction reaction is carried out in a manner of simultaneously adding the reducing agent solution and the oxidizing agent solution, the crystal face silver powder with a novel structure is obtained, and the prepared silver powder has relatively good dispersity, consistency and crystal face sphericity-like degree and also shows relatively high sintering activity; therefore, the conductive ink has a good printing effect and conductive performance, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal materials, and in particular relates to a crystal surface spherical silver powder and a preparation method and application thereof. Background Art

[0002] Precious metal silver has excellent electrical conductivity, thermal conductivity and stability. Silver ions and their compounds are toxic to certain bacteria, viruses, algae and fungi, but are almost completely harmless to the human body. They are widely used in antibacterial materials, medical materials, electronic pastes, decorative materials, catalysts and other fields. Among them, nano-micron silver powder has important applications in the fields of photovoltaic front silver paste and electronic component electrode paste. Nano-micron silver powder is a conductive phase with a content of 55-95%. The morphology, size, dispersibility and crystallinity of silver powder all affect the product properties of silver paste, such as printability, leveling, viscosity, fineness, etc., thereby affecting the accuracy, stacking height, density, resistance, tension and other properties of silver paste during use.

[0003] At present, silver powder mainly has spherical, quasi-spherical, flake or fibrous shapes. The morphology of silver powder will further affect its specific surface area, tap density and burn-in loss, which directly affect the performance of silver paste. At present, the silver powder on the market is mainly spherical or quasi-spherical, but the surface structure is mostly rounded or rough, which is lacking in sintering activity and dispersion performance. Therefore, the preparation of a silver powder with a crystal face structure has practical application significance. Summary of the invention

[0004] The object of the present invention is to provide a crystal face spherical silver powder and a preparation method and application thereof. The crystal face spherical silver powder prepared by the method provided by the present invention has excellent sintering activity and dispersibility.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing spherical silver powder, comprising the following steps:

[0007] mixing a first silver nitrate solution, a first reducing agent solution, a stabilizer and a surfactant to obtain a colloidal solution;

[0008] Mixing the colloidal solution and the neutralizer solution to obtain a reaction base solution;

[0009] The second silver nitrate solution and the second reducing agent solution are added into the reaction base solution at the same time, and then mixed with a dispersant to obtain the spherical silver powder.

[0010] Preferably, the reducing agents in the first reducing agent solution and the second reducing agent solution independently include one or more of hydrazine hydrate, vitamin C, triethanolamine, glucose, formaldehyde and acetaldehyde;

[0011] The stabilizer includes one or more of sodium stearate, polyethylene glycol, povidone, Tween and polyvinyl alcohol;

[0012] The surfactant includes one or more of polyacrylamide, alkylphenol polyoxyethylene ether, monobranched C12 alcohol polyoxyethylene ether, ammonia water, ethylenediamine, sodium dodecylbenzene sulfonate and N-methylpyrrolidone.

[0013] Preferably, the mass percentage of silver nitrate in the first silver nitrate solution is 5-20%;

[0014] The mass percentage of the reducing agent in the first reducing agent solution is 5 to 40%;

[0015] The mass ratio of the first silver nitrate solution to the first reducing agent solution is 3-6:1-4.

[0016] Preferably, the neutralizer in the neutralizer solution includes one or more of polyvinyl pyrrolidone, polyethylene glycol, polyacrylic acid, gum arabic and gelatin; the mass percentage of the neutralizer in the neutralizer solution is 1 to 20%;

[0017] The mass ratio of the colloid solution to the neutralizer solution is 0.1-15:280.

[0018] Preferably, the mass percentage of silver nitrate in the second silver nitrate solution is 10-40%;

[0019] The mass percentage of the reducing agent in the second reducing agent solution is 5 to 30%;

[0020] The mass ratio of the second silver nitrate solution, the second reducing agent solution and the reaction base solution is 0.5-400:0.5-400:1.

[0021] Preferably, the dispersant comprises one or more of oleic acid, ricinoleic acid, stearic acid, lauric acid, ethyl laurate, polyethylene glycol, glycerol and Tween.

[0022] Preferably, the flow rate ratio of the second silver nitrate solution and the second reducing agent solution is 10-55:5-45;

[0023] The mass ratio of the second silver nitrate solution to the dispersant solution is 100-400:0.001-1, and more preferably 200-300:0.002-0.6.

[0024] The present invention also provides a crystal face spherical silver powder prepared by the preparation method described in the above technical scheme, wherein the crystal face spherical silver powder is an irregular polyhedron; the surface of the crystal face spherical silver powder is a crystal face structure; and the particle size distribution of the crystal face spherical silver powder is 0.5 to 3 μm.

[0025] Preferably, the specific surface area of ​​the spherical silver powder is 0.2 to 1.5 cm 2 / g, tap density is 5.5g / cm 3 Above, the burning loss is less than 0.4%.

[0026] The present invention also provides the use of the spherical silver powder described in the above technical solution in photovoltaic cells or electronic components.

[0027] The present invention provides a method for preparing a crystal face spherical silver powder, comprising the following steps: mixing a first silver nitrate solution, a first reducing agent solution, a stabilizer and a surfactant to obtain a colloidal solution; mixing the colloidal solution and a neutralizer solution to obtain a reaction base liquid; adding a second silver nitrate solution and a second reducing agent solution to the reaction base liquid at the same time, and then mixing with a dispersant to obtain the crystal face spherical silver powder. The preparation method provided by the present invention configures a colloidal solution as a seed, wherein the stabilizer and the surfactant can keep the colloidal solution stable for a long time and enhance the activity, and the liquid phase reduction reaction is carried out by adding the reducing agent solution and the oxidizing agent solution at the same time, and the neutralizer and the dispersant make the dispersion effect better, and can also improve the silver powder tap density, and obtain a crystal face silver powder with a new structure, and the obtained silver powder has good dispersibility, consistency and crystal face spherical degree, and shows high sintering activity, so it has good printing effect and conductive performance, and has good application prospects in the field of photovoltaic silver powder silver paste and electronic components. In addition, the method of the present invention is conducive to the stable synthesis of large-scale products, has good repeatability, and the particle size of the obtained product is controllable and the quality is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 This is a scanning electron microscope image of the spherical silver powder obtained in Example 1;

[0030] Figure 2 This is a scanning electron microscope image of the spherical silver powder obtained in Example 1;

[0031] Figure 3 This is a picture of the particle size test of the spherical silver powder obtained in Example 1 using a Malvern laser particle size analyzer;

[0032] Figure 4 This is a scanning electron microscope image of the spherical silver powder obtained in Example 2;

[0033] Figure 5 This is a scanning electron microscope image of the spherical silver powder obtained in Example 2;

[0034] Figure 6 This is a picture of the particle size test of the spherical silver powder obtained in Example 2 using a Malvern laser particle size analyzer;

[0035] Figure 7 This is a scanning electron microscope image of the spherical silver powder obtained in Example 3;

[0036] Figure 8 This is a scanning electron microscope image of the spherical silver powder obtained in Example 3;

[0037] Fig. 9 This is a picture of the particle size test of the spherical silver powder obtained in Example 3 using a Malvern laser particle size analyzer;

[0038] Fig.10 This is a scanning electron microscope image of the spherical silver powder obtained in Example 4;

[0039] Fig.11 This is a picture of the particle size test of the spherical silver powder obtained in Example 4 using a Malvern laser particle size analyzer;

[0040] Fig.12 This is a scanning electron microscope image of the spherical silver powder obtained in Example 5;

[0041] Fig.13 This is a picture of the particle size test of the spherical silver powder obtained in Example 5 using a Malvern laser particle size analyzer. DETAILED DESCRIPTION

[0042] The present invention provides a method for preparing spherical silver powder, comprising the following steps:

[0043] mixing a first silver nitrate solution, a first reducing agent solution, a stabilizer and a surfactant to obtain a colloidal solution;

[0044] Mixing the colloidal solution and the neutralizer solution to obtain a reaction base solution;

[0045] The second silver nitrate solution and the second reducing agent solution are added into the reaction base solution at the same time, and then mixed with a dispersant to obtain the spherical silver powder.

[0046] In the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0047] The present invention mixes a first silver nitrate solution, a first reducing agent solution, a stabilizer and a surfactant to obtain a colloidal solution.

[0048] In the present invention, the mass percentage of silver nitrate in the first silver nitrate solution is preferably 5-20%, more preferably 9-12%.

[0049] In the present invention, the reducing agent in the first reducing agent solution preferably includes one or more of hydrazine hydrate, vitamin C, triethanolamine, glucose, formaldehyde and acetaldehyde, more preferably one or more of vitamin C, glucose, formaldehyde and acetaldehyde, and most preferably vitamin C; the mass percentage of the reducing agent in the first reducing agent solution is preferably 5-40%, more preferably 10-25%; the mass ratio of the first silver nitrate solution to the first reducing agent solution is preferably 3-6:1-4, more preferably 3-5:2-3.

[0050] In the present invention, the mass concentration ratio of the first reducing agent solution to the first silver nitrate solution is preferably 1-15:5-25, and more preferably 10-15:5-11.

[0051] In the present invention, the stabilizer preferably includes one or more of sodium stearate, polyethylene glycol, povidone, Tween and polyvinyl alcohol, and more preferably one or more of sodium stearate, polyethylene glycol and povidone; the polyethylene glycol is preferably polyethylene glycol 2000; the Tween is preferably Tween 40; the mass percentage of the stabilizer in the colloidal solution is preferably 5-40%, and more preferably 15-30%; the function of the stabilizer is to make the colloidal solution more stable and not easy to deteriorate.

[0052] In the present invention, the surfactant preferably includes one or more of polyacrylamide, alkylphenol polyoxyethylene ether, monobranched C12 alcohol polyoxyethylene ether, ammonia water, ethylenediamine, sodium dodecylbenzene sulfonate and N-methylpyrrolidone, and more preferably one or more of polyacrylamide, ammonia water, ethylenediamine and N-methylpyrrolidone; the mass percentage of the surfactant in the colloidal solution is preferably 0.1-2%, and more preferably 0.1-1%; the role of the surfactant is to ensure the activity of the colloidal solution and make the seed activity higher and better.

[0053] In the present invention, the mixing is preferably stirring; the stirring speed is preferably 500-2000 rpm, more preferably 1000-1800 rpm; the time is preferably 10-40 min, more preferably 25-40 min; the stirring is preferably followed by standing; the standing time is preferably more than 30 min.

[0054] In the present invention, the solvent in the colloidal solution is preferably water, more preferably deionized water; the mass percentage of the solvent is preferably 50-85%, more preferably 60-75%.

[0055] In the present invention, the colloidal solution functions to control the morphology and particle size of the entire silver powder system and can serve as a driving carrier in the reaction process of the silver powder.

[0056] After obtaining the colloidal solution, the present invention mixes the colloidal solution with a neutralizer solution to obtain a reaction base solution.

[0057] In the present invention, the neutralizer in the neutralizer solution preferably includes one or more of polyvinyl pyrrolidone, polyethylene glycol, polyacrylic acid, gum arabic and gelatin, more preferably one or more of polyvinyl pyrrolidone, polyethylene glycol and polyacrylic acid, and most preferably polyvinyl pyrrolidone; the mass percentage of the neutralizer in the neutralizer solution is preferably 1-20%, more preferably 2-10%; the temperature is preferably 20-50°C, more preferably 23-40°C; the role of the neutralizer is to create a good environment for the redox reaction and also to improve the dispersion effect.

[0058] In the present invention, the mass ratio of the colloid solution to the neutralizer solution is preferably 0.1 to 15:280, more preferably 0.1 to 1:280.

[0059] In the present invention, the mixing is preferably stirring; the stirring speed is preferably 500 to 1500 rpm, more preferably 1000 to 1500 rpm; the stirring time is preferably 1 to 10 min, more preferably 2 to 8 min.

[0060] After obtaining the reaction base liquid, the present invention adds the second silver nitrate solution and the second reducing agent solution into the reaction base liquid at the same time, and then mixes with a dispersant to obtain the crystal surface spherical silver powder.

[0061] In the present invention, the mass percentage of silver nitrate in the second silver nitrate solution is preferably 10-40%, more preferably 20-30%; the temperature is preferably 18-40°C, more preferably 20-30°C.

[0062] In the present invention, the reducing agent in the second reducing agent solution preferably includes one or more of hydrazine hydrate, vitamin C, triethanolamine, glucose, formaldehyde and acetaldehyde, more preferably one or more of vitamin C, triethanolamine and glucose, and most preferably vitamin C; the mass percentage of the reducing agent in the second reducing agent solution is preferably 5-30%, more preferably 10-20%; the temperature is preferably 18-40°C, more preferably 20-30°C.

[0063] In the present invention, the mass ratio of the second silver nitrate solution, the second reducing agent solution and the reaction base solution is preferably 0.5-400:0.5-400:1, more preferably 0.5-300:0.5-300:1, and most preferably 0.7-250:0.7-250:1.

[0064] In the present invention, the flow rate ratio of adding the second silver nitrate solution and the second reducing agent solution is preferably 10-55:5-45, more preferably 25-40:20-35; the second silver nitrate solution and the second reducing agent solution are preferably added simultaneously.

[0065] In the present invention, the dispersant preferably includes one or more of oleic acid, ricinoleic acid, stearic acid, lauric acid, ethyl laurate, polyethylene glycol, glycerol and Tween, and more preferably one or more of oleic acid, ricinoleic acid, stearic acid, lauric acid, ethyl laurate and polyethylene glycol; the feeding form of the dispersant is preferably a dispersant solution; the mass percentage of the dispersant in the dispersant solution is preferably 20-70%, more preferably 30-50%; the solvent of the dispersant solution is preferably ethanol; the mass ratio of the second silver nitrate solution to the dispersant solution is preferably 100-400:0.001-1, more preferably 200-300:0.002-0.6; the role of the dispersant is to make the reaction more complete, improve the dispersibility of the silver powder, and also play a coating role to make the silver powder settle quickly.

[0066] In the present invention, the mixing is preferably performed immediately after the second silver nitrate solution and the second reducing agent solution are added to the reaction base solution, more preferably within 420 seconds; the mixing is preferably stirring; the stirring speed is preferably 500-1500 rpm; and the time is preferably 1-10 minutes.

[0067] In the present invention, the mixing preferably further includes washing, first centrifugation, dispersion, second centrifugation, drying and screening; the present invention has no special limitation on the washing process, and the conductivity of the filtrate after washing can be less than 20 μs / cm when the process well known to those skilled in the art is adopted; the equipment for the first centrifugation and the second centrifugation are preferably centrifuges, and the centrifugation time is preferably 10 to 30 minutes, more preferably 20 to 30 minutes; the dispersion is preferably mixed with a dispersant and a solvent; the dispersant is preferably one or more of oleic acid, ricinoleic acid, stearic acid, lauric acid, ethyl laurate, polyethylene glycol, glycerol and Tween, more preferably one or more of oleic acid, ricinoleic acid, stearic acid, lauric acid and ethyl laurate, and most preferably lauric acid and ethyl laurate; the solvent is preferably ethanol or deionized water, more preferably is selected as ethanol; the mass ratio of the dispersant to the silver powder is 0.1-1.5:25-35, more preferably 0.8-1.1:28-32; the mass ratio of the solvent to the silver powder is 2-8:20-32, more preferably 4-6:23-26; the mixing is preferably ultrasonic stirring; the frequency of the ultrasonic stirring is preferably above 18 Hz, more preferably 18-20 Hz; the rotation speed is preferably 500-2500 rpm, more preferably 1000-2000 rpm; the time is preferably 0.5-3 h, more preferably 1-2 h; the drying is preferably oven drying; the drying temperature is preferably 55-95 ° C, more preferably 70-90 ° C; the time is preferably 4.5-12 h, more preferably 5-8 h; the mesh size of the sieving is preferably 10-400 mesh, more preferably 200-400 mesh.

[0068] In the present invention, the materials are fed in the form of solutions, so that the liquid phase reduction method can make the reaction more complete, controllable and stable.

[0069] The preparation method provided by the present invention configures a colloidal solution as a seed crystal, and performs a liquid phase reduction reaction by simultaneously adding a reducing agent solution and an oxidizing agent solution to obtain a crystal face silver powder with a novel structure. The obtained silver powder has good dispersibility, consistency and crystal face sphericity, and exhibits high sintering activity, thus having good printing effect and conductive properties, and has good application prospects in the field of photovoltaic silver powder and silver paste and the field of electronic components. In addition, the method of the present invention is conducive to the stable synthesis of large-scale products, has good repeatability, and the particle size of the obtained product is controllable and the quality is stable.

[0070] The present invention also provides a crystal face spherical silver powder obtained by the preparation method described in the above technical scheme, wherein the crystal face spherical silver powder is an irregular polyhedron; the surface of the crystal face spherical silver powder is a crystal face structure; the particle size distribution of the crystal face spherical silver powder is 0.5 to 3 μm, more preferably 1 to 2 μm.

[0071] In the present invention, the specific surface area of ​​the spherical silver powder is 0.2 to 1.5 cm 2 / g, more preferably 0.3 to 0.6 cm 2 / g; tap density is 5.5g / cm 3 More preferably, 6 to 6.5 g / cm 3 ; The burn loss is less than 0.4%, more preferably 0.2-0.3%.

[0072] The present invention also provides the use of the spherical silver powder described in the above technical solution in photovoltaic cells or electronic components.

[0073] In the present invention, the application in photovoltaic cells is preferably an application in photovoltaic front silver paste; the application in electronic components is preferably an application in electronic component electrode paste.

[0074] The present invention does not have any special limitation on the application process of the spherical silver powder in photovoltaic cells or electronic components, and the application process may be carried out in a manner well known to those skilled in the art.

[0075] In order to further illustrate the present invention, the crystal face spherical silver powder provided by the present invention and its preparation method and application are described in detail below in combination with the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0076] Example 1

[0077] Preparation of colloidal solution: 30g vitamin C was dissolved in deionized water to prepare a reducing agent solution with a mass concentration of 13.1%, 46g silver nitrate was dissolved in deionized water to prepare an oxidant solution with a mass concentration of 10.3%, the prepared reducing agent solution with a mass concentration of 10.3% was quickly added to the prepared silver nitrate solution with a mass concentration of 13.1%, and then a stabilizer and a surfactant were added. The stabilizer was povidone, and the surfactant was a mixture of ammonia water and N-methylpyrrolidone in a mass ratio of 1:10. The stirring speed was 1800rpm, stirred for 40min, and stood for more than 0.5h. The mass concentrations of the stabilizer and the surfactant in the obtained colloidal solution accounted for 26.41% and 0.1% of the colloidal solution respectively, and the solvent in the colloidal solution was deionized water, which accounted for 72.02% of the mass concentration of the colloidal solution.

[0078] Weigh 35g of polyvinyl pyrrolidone and add deionized water to prepare a neutralizer solution with a mass concentration of 2.8% and a solution temperature of 23-27° C. Add 2.6g of the colloid solution to 1410g of the neutralizer solution and stir for 5min at a stirring speed of 1500rpm to obtain a reaction base solution.

[0079] Weigh 250g of silver nitrate crystals with a silver content of 63.4% and add them to deionized water to prepare an oxidant solution with a mass concentration of 22.4%, and the solution temperature is controlled at 23-27°C. Weigh 135g of food-grade vitamin C and add them to deionized water to prepare a reducing agent solution with a mass concentration of 13.4%, and the solution temperature is controlled at 25-35°C. The dispersant in the dispersant solution is oleic acid, lauric acid and ethyl laurate in a mass ratio of 0.2:5.5:1, and the solvent is ethanol. The mass concentration of the dispersant in the obtained solution is 39.02%.

[0080] The oxidant solution and the reductant solution were added to the reaction base liquid in the reactor, and the flow rates of the two were controlled at 33.4 kg / min and 30.1 kg / min, respectively. After 7 minutes, the two were added simultaneously, and then 2.4 g of the dispersant solution was added. After stirring for 5 minutes, the supernatant of the silver powder mixture obtained by the reaction was pumped into a solid-liquid separator through a diaphragm pump to filter out the waste liquid. After adding a certain amount of RO water for washing several times, the silver powder mixture was washed until the conductivity was less than 20 μs / cm. Then, the silver powder that passed the cleaning was placed in a centrifuge for high-speed water removal. The centrifugal drying time was 30 minutes, and the centrifuged silver powder was centrifuged. The powder was transferred to a disperser, and a solvent and a dispersant were added to ultrasonically disperse the silver powder. The solvent was ethanol, the dispersant was a mixture of lauric acid and ethyl laurate in a mass ratio of 5:1, the mass ratio of the dispersant to the silver powder was 1:30, and the mass ratio of the solvent to the silver powder was 6:25. Ultrasound with a frequency of 18 Hz was introduced, stirring was turned on, the speed was 1500 rpm, and the dispersion time was 2 hours. After the dispersion was completed, the centrifugal spin-drying was performed again, and then the spin-dried silver powder was placed in an explosion-proof oven for drying. The drying temperature was set at 90°C and the drying time was 8 hours. Finally, the dried silver powder was sieved by a powder sifter, and a screen mesh of 400 mesh was used to obtain crystal surface spherical silver powder.

[0081] The scanning electron microscope image and laser particle size detection distribution diagram of the spherical silver powder obtained in this example are shown in Figures 1-2 and Figure 3 , laser particle size detection data is shown in Table 1, and the tap density is measured.

[0082] Table 1 Laser particle size detection data of the spherical silver powder obtained in Example 1

[0083] Test serial number <![CDATA[D 10 (μm)]]> <![CDATA[D 50 (μm)]]> <![CDATA[D 90 (μm)]]> <![CDATA[D 98 (μm)]]> <![CDATA[D 99.99 (μm)]]> 1 0.871 1.408 2.271 2.891 3.994 2 0.871 1.409 2.273 2.895 3.995 3 0.861 1.408 2.293 2.930 4.005 average value 0.868 1.408 2.279 2.906 3.998

[0084] Depend on Figures 1 to 3 As can be seen from the data in Table 1, the spherical silver powder obtained in this embodiment has good particle size dispersibility and its surface is spherical. 50 The diameter is 1.41 μm and the tap density is 6.25 g / cm 3 .

[0085] Example 2

[0086] The colloidal solution was prepared using the scheme described in Example 1.

[0087] Weigh 7 kg of polyvinyl pyrrolidone and add deionized water to prepare a neutralizer solution with a mass concentration of 2.8% and a solution temperature of 23-27° C. Add 520 g of the colloid solution to 282800 g of the neutralizer solution and stir for 5 min at a stirring speed of 1500 rpm to obtain a reaction base solution.

[0088] Weigh 50kg of silver nitrate crystals with a silver content of 63.4% and add them to deionized water to prepare an oxidant solution with a mass concentration of 22.4%. The solution temperature is controlled at 23-27°C. Weigh 27kg of food-grade vitamin C and add them to deionized water to prepare a reducing agent solution with a mass concentration of 13.4%. The solution temperature is controlled at 25-35°C. The dispersant in the dispersant solution is oleic acid, lauric acid and ethyl laurate in a mass ratio of 0.2:5.5:1, and the solvent is ethanol. The mass concentration of the dispersant in the obtained solution is 39.02%.

[0089] An oxidant solution and a reductant solution were added to the reaction base liquid in the reactor, and the flow rates of the two were controlled at 33.4 kg / min and 30.1 kg / min, respectively. After 7 minutes, the two were added simultaneously, and then 480 g of a dispersant solution was added. After stirring for 5 minutes, the supernatant was filtered, and the obtained solid phase was washed several times until the conductivity was qualified, and then centrifuged, dispersed, dried, and sieved to obtain a spherical silver powder.

[0090] The scanning electron microscope image and laser particle size detection distribution diagram of the spherical silver powder obtained in this example are shown in Figures 4-5 and Figure 6 , laser particle size detection data is shown in Table 2, and the tap density is measured.

[0091] Table 2 Laser particle size detection data of the spherical silver powder obtained in Example 2

[0092] Test serial number <![CDATA[D 10 (μm)]]> <![CDATA[D 50 (μm)]]> <![CDATA[D 90 (μm)]]> <![CDATA[D 98 (μm)]]> <![CDATA[D 99.99 (μm)]]> 1 0.934 1.459 2.272 2.849 3.978 2 0.936 1.458 2.290 2.886 3.990 3 0.936 1.459 2.291 2.887 3.990 average value 0.935 1.459 2.284 2.874 3.986

[0093] Depend on Figures 4 to 6 As can be seen from the data in Table 2, the spherical silver powder obtained in this embodiment has good particle size dispersibility and its surface is spherical. 50 The diameter is 1.45 μm and the tap density is 6.24 g / cm 3 Example 2 In Example 1, the mass of each raw material is increased to 200 times, the concentration of each raw material solution remains unchanged, and the amount of the colloidal solution and the dispersant is also increased by 200 times, showing good consistency and stability.

[0094] Example 3

[0095] The colloidal solution was prepared using the scheme described in Example 1.

[0096] Weigh 35g of polyvinyl pyrrolidone and add deionized water to prepare a neutralizer solution with a mass concentration of 2.8% and a solution temperature of 23-27° C. Add 3.4g of colloid solution to 1413g of the neutralizer solution and stir for 5min at a stirring speed of 1500rpm to obtain a reaction base solution.

[0097] Weigh 250g of silver nitrate crystals with a silver content of 63.4% and add them to deionized water to prepare an oxidant solution with a mass concentration of 22.4%, and the solution temperature is controlled at 23-27°C. Weigh 135g of food-grade vitamin C and add them to deionized water to prepare a reducing agent solution with a mass concentration of 13.4%, and the solution temperature is controlled at 25-35°C. The dispersant in the dispersant solution is oleic acid, lauric acid and ethyl laurate in a mass ratio of 0.2:5.5:1, and the solvent is ethanol. The mass concentration of the dispersant in the obtained solution is 39.02%.

[0098] An oxidant solution and a reductant solution were added to the reaction base liquid in the reactor, and the flow rates of the two were controlled at 33.4 kg / min and 30.1 kg / min, respectively. After 7 minutes, the two were added simultaneously, and then 2.8 g of a dispersant solution was added. After stirring for 5 minutes, the supernatant was filtered out, and the obtained solid phase was washed several times until the conductivity was qualified, and then centrifuged, dispersed, dried, and sieved to obtain a spherical silver powder.

[0099] The scanning electron microscope image and laser particle size detection distribution diagram of the spherical silver powder obtained in this example are shown in Figures 7-8 and Fig. 9 , laser particle size detection data is shown in Table 3, and the tap density is measured.

[0100] Table 3 Laser particle size detection data of the spherical silver powder obtained in Example 3

[0101] Test serial number <![CDATA[D 10 (μm)]]> <![CDATA[D 50 (μm)]]> <![CDATA[D 90 (μm)]]> <![CDATA[D 98 (μm)]]> <![CDATA[D 99.99 (μm)]]> 1 0.607 0.974 1.543 1.940 2.709 2 0.597 0.974 1.569 1.992 2.727 3 0.591 0.973 1.582 2.014 2.732 average value 0.598 0.974 1.565 1.982 2.723

[0102] Depend on Figures 7 to 9 As can be seen from the data in Table 3, the spherical silver powder obtained in this embodiment has good particle size dispersibility and its surface is spherical. 50 The diameter is 0.97 μm and the tap density is 6.27 g / cm 3 In Example 3, the preparation of each raw material in Example 1 remains unchanged, and the amount of the colloidal solution dispersant solution is increased, which better demonstrates the controllability of the silver powder particle size.

[0103] Example 4

[0104] The colloidal solution was prepared using the scheme described in Example 1.

[0105] Weigh 35g of polyvinyl pyrrolidone and add deionized water to prepare a neutralizer solution with a mass concentration of 2.8% and a solution temperature of 23-27° C. Add 1.0g of the colloid solution to 1413g of the neutralizer solution and stir for 5min at a stirring speed of 1500rpm to obtain a reaction base solution.

[0106] Weigh 250g of silver nitrate crystals with a silver content of 63.4% and add them to deionized water to prepare an oxidant solution with a mass concentration of 22.4%, and the solution temperature is controlled at 23-27°C. Weigh 135g of food-grade vitamin C and add them to deionized water to prepare a reducing agent solution with a mass concentration of 13.4%, and the solution temperature is controlled at 25-35°C. The dispersant in the dispersant solution is oleic acid, lauric acid and ethyl laurate in a mass ratio of 0.2:5.5:1, and the solvent is ethanol. The mass concentration of the dispersant in the obtained solution is 39.02%.

[0107] An oxidant solution and a reductant solution were added to the reaction base liquid in the reactor, and the flow rates of the two were controlled at 33.4 kg / min and 30.1 kg / min, respectively. After 7 minutes, the two were added simultaneously, and then 2.4 g of a dispersant solution was added. After stirring for 5 minutes, the supernatant was filtered out, and the obtained solid phase was washed several times until the conductivity was qualified, and then centrifuged, dispersed, dried, and sieved to obtain a spherical silver powder.

[0108] The scanning electron microscope image and laser particle size detection distribution diagram of the spherical silver powder obtained in this example are shown in Fig.10 and Fig.11 , laser particle size detection data is shown in Table 4, and the tap density is measured.

[0109] Table 4 Laser particle size detection data of the spherical silver powder obtained in Example 4

[0110] Test serial number <![CDATA[D 10 (μm)]]> <![CDATA[D 50 (μm)]]> <![CDATA[D 90 (μm)]]> <![CDATA[D 98 (μm)]]> <![CDATA[D 99.99 (μm)]]> 1 0.941 2.012 4.431 9.468 23.902 2 0.938 2.005 4.419 9.698 23.876 3 0.937 2.001 4.402 9.628 23.734 average value 0.939 2.006 4.417 9.598 23.837

[0111] Depend on Figures 10-11 As can be seen from the data in Table 4, the spherical silver powder obtained in this embodiment has good particle size dispersibility and its surface is spherical. 50 2.0μm, tap density 6.25g / cm 3 In Example 4, the preparation of each raw material remains unchanged in Example 1, and the amount of colloidal solution used is reduced. Compared with Example 1 and Example 3, Example 4 better demonstrates the controllability and stability of the silver powder particle size.

[0112] Example 5

[0113] The colloidal solution was prepared using the scheme described in Example 1.

[0114] Weigh 35g of polyvinyl pyrrolidone and add deionized water to prepare a neutralizer solution with a mass concentration of 3.8% and a solution temperature of 23-27° C. Add 2.6g of the colloid solution to 1413g of the neutralizer solution and stir for 5min at a stirring speed of 1500rpm to obtain a reaction base solution.

[0115] Weigh 250g of silver nitrate crystals with a silver content of 63.4% and add them to deionized water to prepare an oxidant solution with a mass concentration of 25.6%, and the solution temperature is controlled at 23-27°C. Weigh 135g of food-grade vitamin C and add them to deionized water to prepare a reducing agent solution with a mass concentration of 15.9%, and the solution temperature is controlled at 25-35°C. The dispersant in the dispersant solution is oleic acid, lauric acid and ethyl laurate in a mass ratio of 0.2:5.5:1, and the solvent is ethanol. The mass concentration of the dispersant in the obtained solution is 39.02%.

[0116] An oxidant solution and a reductant solution were added to the reaction base liquid in the reactor, and the flow rates of the two were controlled at 33.4 kg / min and 30.1 kg / min, respectively. After 7 minutes, the two were added simultaneously, and then 2.4 g of a dispersant solution was added. After stirring for 5 minutes, the supernatant was filtered out, and the obtained solid phase was washed several times until the conductivity was qualified, and then centrifuged, dispersed, dried, and sieved to obtain a spherical silver powder.

[0117] The scanning electron microscope image and laser particle size detection distribution diagram of the spherical silver powder obtained in this example are shown in Fig.12 and Fig.13 , laser particle size detection data is shown in Table 5, and the tap density is measured.

[0118] Table 5 Laser particle size detection data of the spherical silver powder obtained in Example 5

[0119]

[0120]

[0121] Depend on Figures 12-13 As can be seen from the data in Table 5, the spherical silver powder obtained in this embodiment has good particle size dispersibility and its surface is spherical. 50 1.3μm, tap density 6.24g / cm 3 In Example 5, the concentration of each raw material in Example 1 is changed, the amount of colloidal solution and the amount of dispersant solution are unchanged, and the particle size of the obtained silver powder is changed, which better demonstrates the controllability and stability of the silver powder particle size.

[0122] Test Case

[0123] The specific surface area and burning loss of the spherical silver powder obtained in Examples 1 to 5 were measured. The burning loss was measured by placing 5 g of the sample in a sintering box at 538° C. for 30 min, measuring the mass before and after sintering, and calculating the burning loss rate.

[0124] Table 6 Specific surface area and burning test data of the spherical silver powder obtained in Examples 1 to 5

[0125]

[0126] As can be seen from Table 6, the specific surface area changes with the particle size of the silver powder and is controllable. In addition, the burn-in loss is low and the organic matter in the silver powder is relatively small, which makes the conductive performance of the silver powder better.

[0127] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing spherical silver powder. It is characterized in that The following steps are involved: mixing a first silver nitrate solution, a first reducing agent solution, a stabilizer and a surfactant to obtain a colloidal solution; Mixing the colloidal solution and the neutralizer solution to obtain a reaction base solution; The second silver nitrate solution and the second reducing agent solution are added into the reaction base solution at the same time, and then mixed with a dispersant to obtain the crystal surface spherical silver powder.

2. The preparation method according to claim 1, It is characterized in that The reducing agents in the first reducing agent solution and the second reducing agent solution independently include one or more of hydrazine hydrate, vitamin C, triethanolamine, glucose, formaldehyde and acetaldehyde; The stabilizer includes one or more of sodium stearate, polyethylene glycol, povidone, Tween and polyvinyl alcohol; The surfactant includes one or more of polyacrylamide, alkylphenol polyoxyethylene ether, monobranched C12 alcohol polyoxyethylene ether, ammonia water, ethylenediamine, sodium dodecylbenzene sulfonate and N-methylpyrrolidone.

3. The preparation method according to claim 1 or 2, It is characterized in that The mass percentage of silver nitrate in the first silver nitrate solution is 5 to 20%; The mass percentage of the reducing agent in the first reducing agent solution is 5 to 40%; The mass ratio of the first silver nitrate solution to the first reducing agent solution is 3-6:1-4.

4. The preparation method according to claim 1, It is characterized in that The neutralizer in the neutralizer solution includes one or more of polyvinyl pyrrolidone, polyethylene glycol, polyacrylic acid, gum arabic and gelatin; the mass percentage of the neutralizer in the neutralizer solution is 1 to 20%; The mass ratio of the colloid solution to the neutralizer solution is 0.1-15:

280.

5. The preparation method according to claim 1, It is characterized in that The mass percentage of silver nitrate in the second silver nitrate solution is 10-40%; The mass percentage of the reducing agent in the second reducing agent solution is 5 to 30%; The mass ratio of the second silver nitrate solution, the second reducing agent solution and the reaction base solution is 0.5-400:0.5-400:

1.

6. The preparation method according to claim 1, It is characterized in that The dispersant includes one or more of oleic acid, ricinoleic acid, stearic acid, lauric acid, ethyl laurate, polyethylene glycol, glycerol and Tween.

7. The preparation method according to claim 1, 5 or 6, It is characterized in that The flow rate ratio of adding the second silver nitrate solution and the second reducing agent solution is 10-55:5-45; The mass ratio of the second silver nitrate solution to the dispersant solution is 100-400:0.001-1, and more preferably 200-300:0.002-0.

6.

8. The quasi-spherical silver powder obtained by the preparation method according to any one of claims 1 to 7, It is characterized in that The crystal face spherical silver powder is an irregular polyhedron; the surface of the crystal face spherical silver powder is a crystal face structure; the particle size of the crystal face spherical silver powder is distributed in the range of 0.5 to 3 μm.

9. The spherical silver powder according to claim 8, It is characterized in that The specific surface area of ​​the spherical silver powder is 0.2 to 1.5 cm 2 / g, tap density is 5.5g / cm 3 Above, the burning loss is less than 0.4%.

10. Use of the spherical silver powder according to claim 8 or 9 in photovoltaic cells or electronic components.

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