Silver powder and preparation method and application thereof

Abstract

The invention discloses silver powder and a preparation method and application thereof, and the preparation method of the silver powder comprises the following steps: dispersing a silver source in an alcohol amine compound solution, adding a dispersing agent, and then reacting with a C3-C27 fatty amine solution to prepare the silver powder. The micron silver powder is prepared through the hydrothermal method, the powder can be heated more evenly, the method is simple in process, short in reaction time and high in efficiency, the obtained micron silver powder is good in dispersity, and the tap density of the silver powder can reach about 7 g / cm < 3 >.

Description

Technical Field

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

[0002] Silver powder is the conductive phase in silver paste, and its solid content in silver paste is as high as 80-92%. The quality of silver powder greatly affects the key technical indicators of silver paste, such as printing performance, sintering activity, and electrical properties. With the iterative upgrade of the photovoltaic industry, the performance requirements of silver paste are getting higher and higher. Among them, the silver paste prepared with high tap density silver powder has the characteristics of low porosity after sintering, high printed circuit, and good electrical properties, which can significantly improve the overall performance of silver paste.

[0003] Traditional flaky silver powder is difficult to achieve high silver content due to its low tap density and large oil absorption. Although spherical silver powder with high tap density can increase the silver content, it cannot form a sintering neck at a low temperature due to the small contact area between the silver powder particles, resulting in poor conductivity. There are many methods for preparing silver powder at present; among them, the liquid phase reduction method is widely used due to its simple equipment, mild process conditions and low cost. In order to prevent the agglomeration of silver powder, dispersants or protective agents are added to the preparation of silver powder by the liquid phase reduction method. The related art discloses a method for preparing high tap density and highly dispersed spherical silver powder, first pouring a silver nitrate solution into a boiling tannic acid solution and stirring the reaction for 0.5h to prepare a silver crystal core solution, then adding the prepared polyvinyl pyrrolidone and ascorbic acid solution to the above silver crystal core solution, adjusting the pH by sodium hydroxide, and then adding it to the silver nitrate solution, and finally adding octadecylamine and stirring and heating for 1h, filtering, washing, drying, powdering and screening to obtain silver powder. The preparation process is complicated and requires the preparation of silver seeds first. The reaction also 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 object of the present invention is 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 alcohol amine 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 agent such as hydrazine hydrate, which easily leads to uncontrollable reaction and low tap density of the reaction product, in the present invention, the alcohol amine compound solution and C3~C27 The fatty amine solution has a small reduction performance on the silver source and the reduction performance varies. In the process of reducing the silver source, silver particles of different particle sizes can be generated. The large and small silver particles cooperate with each other, effectively reducing the gap between the silver powders and increasing the tap density. The addition of the dispersant can effectively improve 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. In terms of improving the synthesis rate of silver powder, the alcohol amine compound solution is weakly alkaline, which can provide an alkaline environment for the reduction reaction of the fatty amine and the silver source, effectively increasing the generation rate of the silver powder.

[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 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 -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 Alkyldiethanolamine, 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, octyl capric acid diethanolamide, 2-heptyl undecanoic 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 alkyl diethanolamine, 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 to C 27 The aliphatic amine solution is a solution of at least one primary amine, secondary amine or tertiary amine having 3 to 27 carbon atoms in total.

[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, tripeneopentylamine, 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, N,N-dimethylbutylamine, N,N-dimethylisobutylamine, N,N-dimethyl-sec-butylamine, N,N-dimethyl-tert-butylamine, N,N-dimethylisopentylamine, N,N-dimethylisopropylamine, N,N-dimethylisopropylamine, N,N-dimethylisopropylamine, N,N-dimethylisobutyl ... Pentylamine, N,N-dimethylneopentylamine, N,N-dimethylhexylamine, N,N-dimethylheptylamine, N,N-dimethyloctylamine, N,N-dimethylnonylamine, N,N-dimethyldecylamine, N,N-dimethylundecylamine, 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-diundecylmonoethylamine, 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 to 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, hexadecyltrimethylammonium 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 of a 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 hydrothermal reaction can be temperature controlled by methods known in the art, and a common method is to place the hydrothermal reaction kettle 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 the silver powder further comprises a drying step for the silver powder, wherein the drying step is a step for obtaining a dry powder from a suspension of aggregates of silver particles obtained in the particle precipitation step. The drying step may include a filtering step and a water washing step before the drying step.

[0027] The filtration may be performed by any method. In the water washing process, the conductivity of the cleaning solution is preferably measured, and the water washing is repeated until the conductivity becomes 0.5 mS / m or less. In the drying process, a dryer such as a forced circulation air dryer, a vacuum dryer, or an airflow drying device may be used. In the drying process, the temperature of the silver powder may be set to be below 70°C. When the temperature of the silver powder exceeds 70°C, the silver particles in the silver powder may sinter to each other.

[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 volume-based particle size distribution measured by a laser diffraction scattering particle size distribution measuring device, and the cumulative 50% particle size (D50) is 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; the cumulative 100% particle size (D100) is 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 silver powder, the ratio of the difference between the cumulative 90% particle size and the cumulative 10% 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 powder and a solvent.

[0035] As the organic binder, known resins can be used or resins can be dissolved in solvents. For example, cellulose derivatives such as methylcellulose, ethylcellulose, 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, butyral resin derivatives such as polyvinyl butyral can be cited. They can be used alone or in combination of two or more.

[0036] As the glass powder, it is preferred that the glass powder mainly contains a component selected from lead (Pb), tellurium (Te), lithium (Li), zinc (Zn), silicon (Si), aluminum (Al) and bismuth (Bi), and may contain 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), lanthanum (La), etc. As other components, it should be noted that if the ICP analysis value is 0.1% by mass or more, it is recorded as "containing".

[0037] The glass powder can be appropriately selected according to the purpose of use of the conductive paste. For example, as a solar cell, it is preferred to use a glass powder called a Pb-Te-Bi system. The glass powder preferably moderately erodes the anti-reflection layer formed on the semiconductor layer of the solar cell, and adheres the baked product of the 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, isopropanol, dihydroterpineol, dihydroterpineol acetate, ethyl carbitol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol), etc. and used. 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 required. Examples of other components that can be used 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 high tap density silver powder of the present invention can produce spherical powders with different particle sizes. The silver paste prepared from spherical silver powder usually has better fluidity. Large-diameter and small-diameter 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 to improve structural stability, thereby improving the overall sintering performance. Therefore, compared with single large powder and single small powder, large and small mixed 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, which can be carried out at a relatively low temperature and pressure, and the by-products are usually 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 obtained 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 a SEM image of the silver powder obtained in Comparative Example 1 of the present invention.

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

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

[0052] Fig. 9 This is a SEM image of the silver powder obtained in Comparative Example 4 of the present invention.

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

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

[0055] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

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

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

[0058] The dispersant used was 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: 40% mass fraction of sodium hydroxide solution.

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

[0062] Example 1

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

[0064] S1: Weigh 2g of silver carbonate (silver ion molar amount is 0.0145mol) and add it to the inner tank of the hydrothermal reactor, then add 2.468g of dimethylethanolamine (the molar ratio of dimethylethanolamine to Ag is 2.25:1) and 0.1246g of oleic acid (the mass of oleic acid is 6.14% of the mass of silver ions) thereto, place the inner tank on a magnetic stirrer and stir at 300rpm until it is evenly stirred to obtain a base solution;

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

[0066] S3: Pour the reducing agent solution into the inner tank 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 for 10 minutes, then put the inner tank into the hydrothermal reactor and place it in a 105°C oven for 3 hours; after the reaction, wait for the hydrothermal reactor to cool to room temperature (25°C), add deionized water and alcohol to the inner tank 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] This embodiment prepares a silver powder, and its preparation method is different from that of embodiment 1 in that the molar ratio of dimethylethanolamine to Ag is 4:1.

[0069] Example 3

[0070] This embodiment prepares a silver powder, and its preparation method is different from that of embodiment 1 in that the mass of oleic acid is 1.8% of the mass of silver ions.

[0071] Example 4

[0072] This embodiment prepares a silver particle, and its preparation method is different from that of embodiment 1 in that the molar ratio of octylamine to Ag is 0.12:1.

[0073] Example 5

[0074] This embodiment prepares a silver particle, and its preparation method is different from that of embodiment 1 in that the molar ratio of dimethylethanolamine to Ag is 8:1.

[0075] Example 6

[0076] This embodiment prepares a silver particle, and its preparation method is different from that of embodiment 1 in that: the fatty amine solution uses cyclohexylamine with an effective ingredient content of 99%, and the molar ratio of cyclohexylamine to Ag is 0.0926:1.

[0077] Example 7

[0078] This embodiment prepares a silver particle, and its preparation method is different from that of embodiment 1 in that: the alcohol amine solution uses triisopropanolamine with an effective ingredient content of 95%, and the molar ratio of triisopropanolamine to Ag is 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 tank of the hydrothermal reactor. Add 2.468 g of dimethylethanolamine and 0.1246 g of oleic acid successively. Place the inner tank on a magnetic stirrer and stir at 300 rpm to obtain a base liquid. Stir at 300 rpm for 10 min, then place the inner tank in the hydrothermal reactor and place it in a 105 ° C oven for 3 h.

[0083] 3. After the reaction, wait until the hydrothermal kettle drops 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 2g of silver carbonate (silver ion molar amount is 0.0145mol) and add it to the inner tank of the hydrothermal reactor; add 0.0084g of sodium hydroxide solution to 0.152g of octylamine, adjust the pH value of octylamine to 12, and obtain a reducing agent solution; add the reducing agent solution and 0.1246g of oleic acid to the inner tank of the hydrothermal reactor; turn on the magnetic stirring at 300rpm and stir for 10min, then put the inner tank into the hydrothermal reactor and place it in a 105℃ oven for 3h;

[0088] 3. After the reaction, wait until the hydrothermal kettle drops 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 difference between the preparation method and that of Example 1 is 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 is prepared. The preparation method thereof is different from that of Example 1 in that hydrazine hydrate is used to replace the octylamine in Example 1, and the molar ratio of hydrazine hydrate to Ag is 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 is 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 is that diethanolamine was used to replace the 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 powders 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 large tap density.

[0103] Comparative Example 1 Figure 6 There is no large or small powder in the middle, all are small powder, and the tap density is low; Comparative Example 2 Figure 7It is shown 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 tap density of the silver powder obtained by reduction is the worst; in Comparative Examples 5 and 6, only fatty amine solution or alcohol amine 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 poor, 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 equivalent replacement methods and are included in the protection scope 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.

2. The method for preparing silver powder according to claim 1, characterized in that: 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.

3. The method for preparing silver powder according to claim 1, characterized in that: C3~C 27 The aliphatic amine solution is a solution of at least one primary amine, secondary amine or tertiary amine having 3 to 27 carbon atoms in total.

4. The method for preparing silver powder according to claim 1, characterized in that: 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.

5. The method for preparing silver powder according to claim 1, characterized in that: The dispersant includes at least one of polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, sodium citrate, sodium lauryl sulfate, hexadecyltrimethylammonium 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.

6. The method for preparing silver powder according to claim 1, characterized in that: Control the C3~C 27 The pH of the fatty amine solution is 9-14.

7. The method for preparing silver powder according to claim 1, characterized in that: The alcohol amine compound solution and C3~C 27 The molar ratio of the fatty amine solution is 0.05-8:0.005-0.

3.

8. Silver powder obtained by the method for preparing silver powder according to any one of claims 1 to 7.

9. The silver powder according to claim 8, characterized in that: The silver powder satisfies at least one of the following conditions: (I) the average particle size of the silver powder is 1.0 to 3.1 μm; (II) D50 is less than 3.0 μm; (III) D100 is less than 20 μm; (IV) Tap density is 5.80 g / cm 3 above.

10. A conductive paste comprising the silver powder according to claim 8 or 9, an organic binder, glass powder and a solvent.

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