Silver powder, preparation method and application thereof

Abstract

The present invention discloses a silver powder and its preparation method and application. The preparation method of the silver powder comprises the following steps: dispersing a silver source in an alcohol amine compound solution, adding a dispersant, and then mixing with C3-C 27 The present invention adopts a hydrothermal method to prepare micron silver powder, which can make the powder heated more evenly, has a simple process, a short reaction time, and high efficiency. The obtained micron silver powder has good dispersibility and the tap density of the silver powder can be as high as 7g / cm 3 about.

Description

Technical Field

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

[0002] Silver powder, the conductive phase in silver paste, accounts for up to 80-92% of the paste's solids content. Its quality significantly impacts key technical specifications such as the paste's printing performance, sintering activity, and electrical properties. With the advancement of the photovoltaic industry, the performance requirements for silver paste are becoming increasingly stringent. Silver pastes formulated with high-tap-density silver powder offer low post-sintering porosity, high printed circuit density, and excellent electrical properties, significantly improving the paste's overall performance.

[0003] Traditional flaky silver powders have difficulty achieving high silver content due to their low tap density and high oil absorption. While spherical silver powders with high tap density can increase silver content, they lack the ability to form sintering necks at low temperatures due to the small contact area between silver powder particles, resulting in poor conductivity. Currently, many methods exist for preparing silver powder; the liquid-phase reduction method is widely used due to its simple equipment, mild process conditions, and low cost. To prevent silver powder agglomeration, dispersants or protective agents are often added during the liquid-phase reduction method. Related art discloses a method for preparing highly dispersed spherical silver powders with high tap density. The method involves first pouring a silver nitrate solution into a boiling tannic acid solution and stirring for 0.5 hours to prepare a silver nucleus solution. Then, a prepared polyvinyl pyrrolidone and ascorbic acid solution is added to the silver nucleus solution, the pH is adjusted with sodium hydroxide, and the solution is added to the silver nitrate solution. Finally, octadecylamine is added, stirred, and heated for 1 hour. The silver powder is filtered, washed, dried, pulverized, and sieved to obtain the silver powder. The preparation process is complex and requires the preparation of silver seeds first. At the same time, the reaction requires high temperature and is time-consuming, resulting in high production costs and being unfavorable for large-scale production. The tap density of the product silver powder is also low. Summary of the Invention

[0004] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the present invention aims to provide a silver powder and a preparation method and application thereof.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The first aspect of the present invention provides a method for preparing silver powder, comprising the following steps: dispersing a silver source in an alcoholamine compound solution, adding a dispersant, and then mixing with C3-C 27 The aliphatic amine solution is reacted to obtain the silver powder.

[0007] Different from the traditional strong reducing agents such as hydrazine hydrate, which easily lead to uncontrollable reaction and low tap density of the reaction product, the present invention combines the alcoholamine compound solution with C3~C27 Fatty amine solutions have a low, varying degree of reducing power for silver sources. During the silver source reduction process, silver particles of varying sizes are generated. The interaction of large and small silver particles effectively reduces the gaps between silver powders and increases tap density. The addition of a dispersant effectively improves the uniformity of the subsequent silver source reduction reaction and the dispersibility of the precipitated silver powder, further increasing the tap density of the silver powder. Furthermore, the weak alkalinity of alcoholamine solutions improves the rate of silver powder synthesis, providing an alkaline environment for the reduction reaction between the fatty amine and the silver source, effectively increasing the rate of silver powder formation.

[0008] In some embodiments of the present invention, the silver source is a soluble silver salt, including at least one of silver nitrate, silver perchlorate, silver acetate, silver oxalate, silver chlorate, silver hexafluorophosphate, silver tetrafluoroborate, silver hexafluoroarsenate, and silver sulfate.

[0009] In some embodiments of the present invention, the alcoholamine compound solution is an alcoholamine compound aqueous solution, wherein the alcoholamine compound includes C2 to C 20 Alkyl alcohol amine, C7~C 25 At least one fatty alkanolamide.

[0010] In some embodiments of the present invention, suitable alkanolamines include, but are not limited to, ethanolamine, N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-butylethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, N-methylisopropanolamine, N-ethylisopropanolamine, N-propylisopropanolamine, 2-aminopropan-1-ol, N-methyl-2-aminopropan-1-ol, N-ethyl-2-aminopropan-1-ol, 1-aminopropan-3-ol, N-methyl-1-aminopropan-3-ol, N-ethyl-1-aminopropan-3-ol, 1-aminobutan-2-ol, N-methyl-1-aminobutan-2-ol, N-ethyl-1-aminobutan-2-ol, 2-aminobutan-1-ol, N-methyl-2-aminobutan-2-ol. -1-ol, N-ethyl-2-aminobutan-1-ol, 3-aminobutan-1-ol, N-methyl-3-aminobutan-1-ol, N-ethyl-3-aminobutan-1-ol, 1-aminobutan-4-ol, N-methyl-1-aminobutan-4-ol, N-ethyl-1-aminobutan-4-ol, 1-amino-2-methylpropan-2-ol, 2-amino-2-methylpropan-1-ol, 1-aminopentan-4-ol, 2-amino-4-methylpentan-1-ol, 2-aminohexan-1-ol, 3-aminoheptan-4-ol, 1-aminooctan-2-ol, 5-aminooctan-4-ol, 1-aminopropan-2,3-diol, 2-aminopropan-1,3-diol, tris(hydroxymethyl)aminomethane, 1,2-diaminopropan-3-ol, 1,3-diaminopropan-2-ol, 2-(2-aminoethoxy)ethanol, C 10 ~C20 Alkyldiethanolamines, such as octadecyldiethanolamine.

[0011] In some embodiments of the present invention, the fatty alkanolamide may be fatty ethanolamide or fatty isopropanolamide, but is preferably fatty ethanolamide, and particularly preferably fatty diethanolamide.

[0012] Suitable preferred fatty diethanolamides include lauric acid diethanolamide, capric acid diethanolamide, caprylic acid diethanolamide, myristic acid diethanolamide, palmitic acid diethanolamide, stearic acid diethanolamide, isostearic acid diethanolamide, oleic acid diethanolamide, linoleic acid diethanolamide, octyldecanoic acid diethanolamide, 2-heptylundecanoic acid diethanolamide, coconut oil fatty acid diethanolamide, tallow fatty acid diethanolamide, soybean oil fatty acid diethanolamide, and palm kernel oil fatty acid diethanolamide. Among them, oleic acid diethanolamide, stearic acid diethanolamide, and lauric acid diethanolamide are preferred.

[0013] In some embodiments of the present invention, the alcoholamine compound solution includes ethanolamine, N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-butylethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, N-methylisopropanolamine, N-ethylisopropanolamine, N-propylisopropanolamine, C 10 ~C 20 A solution of at least one of alkyldiethanolamine, lauric acid diethanolamide, stearic acid diethanolamide, isostearic acid diethanolamide, oleic acid diethanolamide, and linoleic acid diethanolamide.

[0014] In some embodiments of the present invention, the C3~C 27 The fatty amine solution is a solution of at least one primary amine, secondary amine, or tertiary amine having a total carbon number of 3 to 27.

[0015] In some embodiments of the present invention, the primary amine includes propylamine, butylamine, pentylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, and the like.

[0016] In some embodiments of the present invention, the secondary amine includes methylethylamine, dimethylamine, trimethylamine, ethylenediamine, diethylamine, piperidine, and pyrrolidine.

[0017] In some embodiments of the present invention, the tertiary amine includes trimethylamine, triethylamine, tripropylamine, triisopropylamine, tributylamine, triisobutylamine, tri-sec-butylamine, tri-tert-butylamine, tripentylamine, triisopentylamine, triphenopentylamine, trihexylamine, triheptylamine, trioctylamine, triphenylamine, tribenzylamine, N,N-dimethylethylamine, N,N-dimethylpropylamine, N,N-dimethylisopropylamine, N,N-dimethylbutylamine, N,N-dimethylisobutylamine, N,N-dimethyl-sec-butylamine, N,N-dimethyl-tert-butylamine, N,N-dimethylpentylamine, N,N-dimethylisopropylamine, Pentylamine, N,N-dimethylneopentylamine, N,N-dimethylhexylamine, N,N-dimethylheptylamine, N,N-dimethyloctylamine, N,N-dimethylnonylamine, N,N-dimethyldecylamine, N,N-dimethylundecanamine, N,N-dimethyldodecylamine, N,N-dimethylaniline, N,N-dimethylbenzylamine, N,N-diethylmonomethylamine, N,N-dipropylmonomethylamine, N,N-diisopropylmonomethylamine, N,N-dibutylmonomethylamine, N,N-diisobutylmonomethylamine, N,N-dibutylmonomethylamine, N,N-di-tert-butylmonomethylamine Methylamine, N,N-dipentylmonomethylamine, N,N-diisopentylmonomethylamine, N,N-dineopentylmonomethylamine, N,N-dihexylmonomethylamine, N,N-diheptylmonomethylamine, N,N-dioctylmonomethylamine, N,N-dinonylmonomethylamine, N,N-didecylmonomethylamine, N,N-diundecylmonomethylamine, N,N-didodecylmonomethylamine, N,N-diphenylmonomethylamine, N,N-dibenzylmonomethylamine, N,N-dipropylmonomethylamine, N,N-diisopropylmonoethylamine, N,N-dibutylmonoethylamine, N,N-diisobutyl Monoethylamine, N,N-di-sec-butylmonoethylamine, N,N-di-tert-butylmonoethylamine, N,N-dipentylmonoethylamine, N,N-diisopentylmonoethylamine, N,N-dipentylmonoethylamine, N,N-dihexylmonoethylamine, N,N-diheptylmonoethylamine, N,N-dioctylmonoethylamine, N,N-dinonylmonoethylamine, N,N-didecylmonoethylamine, N,N-diondecylmonoethylamine, N,N-docosylmonoethylamine, N,N-diphenylmonoethylamine, N,N-dibenzylmonoethylamine, trinonylamine or tris(3,6-dioxaheptyl)amine.

[0018] In some embodiments of the present invention, the C3~C 27 The fatty amine solution includes at least one of hexylamine, cyclohexylamine, heptylamine, octylamine, triethylamine, tripropylamine, triisopropylamine, tributylamine, N,N-dimethyloctylamine, N,N-dipropylmonomethylamine, N,N-dimethyldecylamine, N,N-diisopropylmonomethylamine, and tri(3,6-dioxaheptyl)amine.

[0019] In some embodiments of the present invention, the dispersant includes at least one of polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, sodium citrate, sodium lauryl sulfate, cetyltrimethylammonium bromide, gelatin, methylcellulose, citric acid, Tween 60, propionic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, acrylic acid, oleic acid, linoleic acid, arachidonic acid, and ricinoleic acid.

[0020] In some embodiments of the present invention, the control of C3 to C 27 The pH of the fatty amine solution is alkaline, such as a pH of 9 to 14, such as 10 to 13, 10.5, 11, 11.5, 12, 12.5, etc.

[0021] In some embodiments of the present invention, at least one pH adjusting agent such as sodium carbonate, sodium hydroxide, ammonia, monoethanolamine, and triethanolamine may be used to adjust the pH of the C3-C 27 pH of the fatty amine solution.

[0022] In some embodiments of the present invention, the alcoholamine compound solution and C3~C 27 The molar ratio of the fatty amine solution is 0.05-8:0.005-0.3; such as 0.05-7:0.005-0.25, 0.05-6:0.005-0.2, 0.05-5:0.005-0.15, 0.1-5:0.01-0.2, 0.1-4:0.01-0.15, etc.

[0023] In some embodiments of the present invention, the mass ratio of silver atoms in the silver source to the dispersant is 1:0.01-10, such as 1:0.05-8, 1:0.1-7, 1:0.5-6, 1:1-5, etc.

[0024] In some embodiments of the present invention, the molar concentration of the silver source is controlled so that when the C3-C 27 The molar concentration of the fatty amine solution before use is 0.005-5.0 mol / L, such as 0.1 mol / L, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, and 4.5 mol / L.

[0025] In some embodiments of the present invention, the reaction is a hydrothermal reaction; the reaction temperature of the reaction is 75-235°C, such as 75-170°C, 90-210°C, 90-155°C, 100-200°C, 120-180°C, etc.; the reaction time of the reaction is 0.5-12h, such as 1-10h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, etc.; the temperature of the hydrothermal reaction can be controlled by methods known in the art, and a common method is to place the hydrothermal reactor in an oven for temperature control; to improve the uniformity of the reaction, the hydrothermal reaction can be carried out under stirring, and the stirring rate can be controlled at 200-500rpm.

[0026] In some embodiments of the present invention, the method for preparing silver powder further includes a drying step for obtaining a dry powder from a suspension containing aggregates of silver particles obtained in the particle precipitation step. The drying step may be preceded by a filtration step and a water washing step.

[0027] Filtration can be performed by any method. During the water washing step, the conductivity of the cleaning solution is preferably measured, and water washing is repeated until the conductivity reaches 0.5 mS / m or less. During the drying step, a dryer such as a forced circulation air dryer, a vacuum dryer, or an airflow dryer can be used. During the drying step, the temperature of the silver powder can be set to 70°C or less. If the temperature of the silver powder exceeds 70°C, the silver particles in the silver powder may sinter.

[0028] The second aspect of the present invention provides silver powder prepared by the silver powder preparation method.

[0029] In some embodiments of the present invention, the average particle size of the silver powder is 1.0-3.1 μm, such as 1.1-2.99 μm, 1.1-2.5 μm, 1.1-2.2 μm, etc.

[0030] In some embodiments of the present invention, the silver powder has a cumulative 50% particle size (D50) of 3.0 μm or less, such as 2.5 μm or less, 2.0 μm or less, 1.8 μm or less, or 1.7 μm or less in the volume-based particle size distribution measured by a laser diffraction scattering particle size distribution measuring apparatus; and a cumulative 100% particle size (D100) of 20 μm or less, such as 18 μm or less, 15 μm or less, 12 μm or less, 10 μm or less, or 9 μm or less.

[0031] In some embodiments of the present invention, in the volume-based particle size distribution of the silver powder, the ratio of the difference obtained by subtracting the cumulative 10% particle size from the cumulative 90% particle size to the cumulative 50% particle size (Span, particle size distribution width) can be 2.20 or less, such as less than 2.10, less than 2.08, less than 2.01, or less than 2.00. The smaller the Span and the smaller the difference, the narrower the particle size distribution of the silver powder, the better its dispersibility, and the higher the overall tap density of the formed silver powder.

[0032] In some embodiments of the present invention, the tap density of the silver powder is 5.80 g / cm 3 Above, such as 5.85g / cm 3 Above, 6.00g / cm 3 Above, 6.30g / cm 3 Above, 6.50g / cm 3 Above, 6.60g / cm 3 Above, 6.60~7.10g / cm 3 , 6.60~7.0g / cm 3 .

[0033] The third aspect of the present invention provides a conductive paste comprising the silver powder.

[0034] In some embodiments of the present invention, the conductive paste further includes an organic binder, glass frit, and a solvent.

[0035] As the organic binder, a known resin or a resin dissolved in a solvent can be used. For example, cellulose derivatives such as methylcellulose, ethylcellulose, and carboxymethylcellulose, polyvinyl alcohols, polyvinyl pyrrolidones, acrylic resins, alkyd resins, polypropylene resins, polyvinyl chloride resins, polyurethane resins, rosin resins, terpene resins, phenol resins, aliphatic petroleum resins, vinyl acetate resins, vinyl acetate-acrylate copolymers, and organic binders of butyral resin derivatives such as polyvinyl butyral can be mentioned. These can be used alone or in combination of two or more.

[0036] The glass frit preferably contains a component primarily selected from the group consisting of lead (Pb), tellurium (Te), lithium (Li), zinc (Zn), silicon (Si), aluminum (Al), and bismuth (Bi). Other components may include sodium (Na), potassium (K), boron (B), tungsten (W), molybdenum (Mo), manganese (Mn), iron (Fe), vanadium (V), phosphorus (P), antimony (Sb), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zirconium (Zr), and lanthanum (La). Note that if the ICP analysis value for each component is 0.1% by mass or greater, it is considered "containing."

[0037] Glass frit can be appropriately selected depending on the intended use of the conductive paste. For example, for solar cell applications, Pb-Te-Bi-based glass frit is preferably used. This glass frit preferably moderately erodes the antireflection layer formed on the semiconductor layer of the solar cell, and bonds the calcined conductive paste, i.e., the silver electrode, to the semiconductor layer.

[0038] The solvent can be appropriately selected according to the purpose of use of the conductive paste. For example, one or more solvents can be selected from butyl carbitol acetate (BCA), butyl carbitol (BC), ethyl carbitol acetate (ECA), ethyl carbitol (EC), hexane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, butyl cellosolve acetate, diethylene glycol diethyl ether, diacetone alcohol, terpineol, methyl ethyl ketone, benzyl alcohol, methyl ethyl ketone, methyl isobutyl ketone, tetradecane, tetralin, propanol, isopropyl alcohol, dihydroterpineol, dihydroterpineol acetate, ethyl carbitol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol), etc. It should be noted that the content of the solvent is preferably 1 to 40% by mass relative to the conductive paste.

[0039] In addition to the above-mentioned components, other components may be appropriately blended into the conductive paste as needed. Examples of other components include surfactants, dispersants, rheology modifiers, silane coupling agents, and ion trapping materials.

[0040] The beneficial effects of the present invention are:

[0041] 1. The preparation method of the high tap density silver powder of the present invention can produce spherical powders with different particle sizes. The silver paste prepared from the spherical silver powder usually has better fluidity. The large and small silver particles fill each other to ensure sufficient contact area between the silver powders, which can meet the requirements of the positive silver paste for the performance of the silver powder.

[0042] 2. The preparation method of high tap density silver powder of the present invention can produce spherical powders with different particle sizes, which can be applied to high and low temperature sintering silver paste. When sintering, compared with single large particles or small particles, silver powders of different particle sizes can cooperate with each other during the sintering process. Small particles can accelerate the sintering process, while large particles can better maintain their shape at higher temperatures, thereby improving structural stability and improving the overall sintering performance. Therefore, compared with single large powder and single small powder, mixed large and small powders have sintering advantages and are suitable for solar cell manufacturing.

[0043] 3. The method for preparing the high tap density silver powder of the present invention is an environmentally friendly method that can be carried out at relatively low temperature and pressure, and the by-products are generally easy to handle. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a SEM image of the silver powder obtained in Example 1 of the present invention.

[0045] Figure 2 This is a SEM image of the silver powder obtained in Example 2 of the present invention.

[0046] Figure 3 This is a SEM image of the silver powder prepared in Example 3 of the present invention.

[0047] Figure 4 This is a SEM image of the silver powder obtained in Example 4 of the present invention.

[0048] Figure 5 This is a SEM image of the silver powder obtained in Example 5 of the present invention.

[0049] Figure 6 This is the SEM image of the silver powder prepared in Comparative Example 1 of the present invention.

[0050] Figure 7 This is the SEM image of the silver powder prepared in Comparative Example 2 of the present invention.

[0051] Figure 8 This is the SEM image of the silver powder obtained in Comparative Example 3 of the present invention.

[0052] Figure 9 This is the SEM image of the silver powder prepared in Comparative Example 4 of the present invention.

[0053] Figure 10 This is the SEM image of the silver powder obtained in Comparative Example 5 of the present invention.

[0054] Figure 11 This is the SEM image of the silver powder prepared in Comparative Example 6 of the present invention. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below using specific examples. Unless otherwise specified, the raw materials, reagents, and apparatus used in the examples and comparative examples are available from conventional commercial sources or by conventional methods. Unless otherwise specified, all experimental or testing methods are conventional in the art.

[0056] In the following examples or comparative examples, unless otherwise specified, the raw materials used are as follows:

[0057] The alcoholamine compound solution uses dimethylethanolamine with an active ingredient content of 98% and triisopropanolamine with an active ingredient content of 95%;

[0058] The dispersant used is 98.5% oleic acid;

[0059] The fatty amine solution uses octylamine with an active ingredient content of 98% and cyclohexylamine with an active ingredient content of 99%;

[0060] Preparation of pH adjuster solution: sodium hydroxide solution with a mass fraction of 40%.

[0061] Other reducing agents include hydrazine hydrate and ascorbic acid.

[0062] Example 1

[0063] This embodiment prepares a silver powder, and the specific process is as follows:

[0064] S1: Weigh 2 g of silver carbonate (silver ion molar weight is 0.0145 mol) and add it to the inner container of a hydrothermal reactor. Then, add 2.468 g of dimethylethanolamine (the molar ratio of dimethylethanolamine to Ag is 2.25:1) and 0.1246 g of oleic acid (the mass of oleic acid is 6.14% of the mass of silver ions) successively. Place the inner container on a magnetic stirrer and turn on 300 rpm to stir until uniform to obtain a base solution.

[0065] S2: Add 0.0084 g of sodium hydroxide solution to 0.152 g of octylamine and adjust the pH of octylamine to 12 to obtain a reducing agent solution;

[0066] S3: Pour the reducing agent solution into the inner container of the hydrothermal reactor and mix it with the base liquid (the molar ratio of octylamine to Ag is 0.0798:1), turn on the magnetic stirring at 300 rpm and stir for 10 minutes, then put the inner container into the hydrothermal reactor and place it in a 105°C oven for 3 hours; after the reaction, wait until the hydrothermal reactor cools to room temperature (25°C), add deionized water and alcohol to the inner container of the hydrothermal reactor after the reaction, wash and dry (drying temperature is 55°C, drying time is 2.5 hours) to obtain silver particles.

[0067] Example 2

[0068] In this embodiment, a silver powder is prepared. The preparation method thereof is different from that in embodiment 1 in that the molar ratio of dimethylethanolamine to Ag is 4:1.

[0069] Example 3

[0070] In this embodiment, a silver powder is prepared. The difference between the preparation method of the silver powder and that of the embodiment 1 is that the mass of oleic acid is 1.8% of the mass of silver ions.

[0071] Example 4

[0072] Silver particles were prepared in this embodiment. The preparation method thereof was different from that in embodiment 1 in that the molar ratio of octylamine to Ag was 0.12:1.

[0073] Example 5

[0074] Silver particles were prepared in this embodiment. The difference between the preparation method and that in embodiment 1 is that the molar ratio of dimethylethanolamine to Ag is 8:1.

[0075] Example 6

[0076] Silver particles were prepared in this embodiment. The preparation method was different from that in embodiment 1 in that the fatty amine solution used was cyclohexylamine with an active ingredient content of 99%, and the molar ratio of cyclohexylamine to Ag was 0.0926:1.

[0077] Example 7

[0078] Silver particles were prepared in this embodiment. The preparation method thereof was different from that in Example 1 in that the alcoholamine solution used was triisopropanolamine with an active ingredient content of 95%, and the molar ratio of triisopropanolamine to Ag was 2:1.

[0079] Comparative Example 1

[0080] This comparative example prepared a silver powder, and the specific process was as follows:

[0081] 1. Preparation before the experiment is the same as in Example 1;

[0082] 2. Weigh 2 g of silver carbonate (silver ion molar amount is 0.0145 mol) and add it to the inner liner of the hydrothermal reactor. Then add 2.468 g of dimethylethanolamine and 0.1246 g of oleic acid. Place the inner liner on a magnetic stirrer and stir at 300 rpm until it is evenly stirred to obtain a base liquid. After stirring at 300 rpm for 10 minutes, the inner liner is placed in the hydrothermal reactor and placed in a 105°C oven for 3 hours.

[0083] 3. After the reaction, wait until the hydrothermal kettle cools to room temperature (25°C), add deionized water and alcohol to the inner tank of the hydrothermal kettle after the reaction, wash and dry (drying temperature is 55°C, drying time is 2.5h) to obtain silver powder.

[0084] Comparative Example 2

[0085] This comparative example prepared a silver powder, and the specific process was as follows:

[0086] 1. Preparation before the experiment is the same as in Example 1;

[0087] 2. Weigh 2 g of silver carbonate (silver ion molar weight 0.0145 mol) and add it to the inner container of the hydrothermal reactor; add 0.0084 g of sodium hydroxide solution to 0.152 g of octylamine and adjust the pH value of octylamine to 12 to obtain a reducing agent solution; add the reducing agent solution and 0.1246 g of oleic acid to the inner container of the hydrothermal reactor; start magnetic stirring at 300 rpm and stir for 10 minutes, then place the inner container in the hydrothermal reactor and place it in a 105°C oven for 3 hours;

[0088] 3. After the reaction, wait until the hydrothermal kettle cools to room temperature (25°C), add deionized water and alcohol to the inner tank of the hydrothermal kettle after the reaction, wash and dry (drying temperature is 55°C, drying time is 2.5h) to obtain silver powder.

[0089] Comparative Example 3

[0090] In this comparative example, a silver powder was prepared. The preparation method thereof was different from that of Example 1 in that ascorbic acid was used to replace the octylamine in Example 1, and the molar ratio of ascorbic acid to Ag was 0.0798:1.

[0091] Comparative Example 4

[0092] In this comparative example, a silver powder was prepared. The difference between the preparation method and that of Example 1 lies in that hydrazine hydrate was used to replace the octylamine in Example 1, and the molar ratio of hydrazine hydrate to Ag was 0.0798:1.

[0093] Comparative Example 5

[0094] In this comparative example, a silver powder was prepared. The difference between the preparation method and that of Example 1 lies in that cyclohexylamine was used to replace the dimethylethanolamine in Example 1, and the molar ratio of cyclohexylamine to Ag was 2.25:1.

[0095] Comparative Example 6

[0096] In this comparative example, a silver powder was prepared. The difference between the preparation method and that of Example 1 lies in that diethanolamine was used instead of octylamine in Example 1, and the molar ratio of diethanolamine to Ag was 0.0798:1.

[0097] Test example

[0098] The obtained silver powder was characterized, and the results are shown in Table 1:

[0099] Table 1

[0100]

[0101]

[0102] Figures 1 to 11 The SEM images of the silver powder obtained in Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Table 1 and Figures 1 to 11 It can be seen that the silver powders of Examples 1 to 5 have good dispersibility, a low particle size distribution width (Span), good particle fluidity, and a high tap density.

[0103] Comparative Example 1 Figure 6 There is no big or small powder in the middle, all are small powder, and the tap density is low; Comparative Example 2 Figure 7It shows that there is too much large powder and almost no small powder. In the process of preparing the slurry, due to the lack of small powder filling, the large powder is easy to agglomerate, and its fluidity is poor, resulting in a decrease in its performance; in Comparative Examples 3 and 4, the reducing property of the reducing agent used is very strong, resulting in a significant increase in the average particle size, D50, and D100 of the product silver powder, and a decrease in the overall tap density of the silver powder. It can be seen that hydrazine hydrate has a stronger reducing property on silver ions than ascorbic acid, and the silver powder obtained by reduction has the worst tap density; in Comparative Examples 5 and 6, only fatty amine solution or alcoholamine solution is used for reduction before and after. Although large and small powders are also produced in the product silver powder, the particle size of both small and large powders is significantly enlarged, the particles are obviously agglomerated, the powder dispersibility is deteriorated, and the tap density is also low.

[0104] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing silver powder, characterized in that: The following steps are involved: Disperse the silver source in the alcohol amine compound solution, add the dispersant, and then mix with C3~C 27 The aliphatic amine solution is reacted to obtain the silver powder; The mass ratio of silver atoms in the silver source to the dispersant is 1:0.01-10; Control the molar concentration of the silver source so that when the C3~C 27 The molar concentration of the fatty amine solution before use is 0.005~5.0mol / L; Control the C3~C 27 The pH of the fatty amine solution is 9 to 14; The alcoholamine compound solution and C3~C 27 The molar ratio of the fatty amine solution is 0.05~8:0.005~0.3; The alcoholamine compound solution includes ethanolamine, N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-butylethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, N-methylisopropanolamine, N-ethylisopropanolamine, N-propylisopropanolamine, C 10 ~C 20 A solution of at least one of alkyl diethanolamine, lauric acid diethanolamide, stearic acid diethanolamide, isostearic acid diethanolamide, oleic acid diethanolamide, and linoleic acid diethanolamide; The C3~C 27 The fatty amine solution includes at least one of hexylamine, cyclohexylamine, heptylamine, octylamine, triethylamine, tripropylamine, triisopropylamine, tributylamine, N,N-dimethyloctylamine, N,N-dipropylmonomethylamine, N,N-dimethyldecylamine, N,N-diisopropylmonomethylamine, and tris(3,6-dioxaheptyl)amine; The silver powder meets the following conditions: (I) the average particle size of the silver powder is 1.0-3.1 μm; (II) D50 is less than 3.0 μm; (III) D100 is less than 20 μm; (IV) the tap density is 5.80 g / cm 3 above.

2. The method for preparing silver powder according to claim 1, wherein: The silver source includes at least one of silver nitrate, silver perchlorate, silver acetate, silver oxalate, silver chlorate, silver hexafluorophosphate, silver tetrafluoroborate, silver hexafluoroarsenate, and silver sulfate.

3. The method for preparing silver powder according to claim 1, wherein: The dispersant includes at least one of polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, sodium citrate, sodium lauryl sulfate, cetyltrimethylammonium bromide, gelatin, methylcellulose, citric acid, Tween 60, propionic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, acrylic acid, oleic acid, linoleic acid, arachidonic acid, and ricinoleic acid.

4. Silver powder obtained by the method for preparing silver powder according to any one of claims 1 to 3.

5. The silver powder according to claim 4, characterized in that: The silver powder meets the following conditions: (I) the average particle size of the silver powder is 1.0 to 3.1 μm; (II) D50 is 3.0 μm or less; (III) D100 is less than 20 μm; (IV) Tap density is 6.00 g / cm 3 above.

6. A conductive paste comprising the silver powder according to claim 4 or 5, an organic binder, glass powder and a solvent.

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