CN109663932B - Preparation method of flaky silver powder - Google Patents

Preparation method of flaky silver powder Download PDF

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CN109663932B
CN109663932B CN201910158659.2A CN201910158659A CN109663932B CN 109663932 B CN109663932 B CN 109663932B CN 201910158659 A CN201910158659 A CN 201910158659A CN 109663932 B CN109663932 B CN 109663932B
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silver
flaky
acid
sulfate
water
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CN109663932A (en
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刘福生
郜伟
党增超
马国权
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Nanjing Forestry University
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Nanjing Forestry University
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Priority claimed from CN201810237829.1A external-priority patent/CN108356282A/en
Priority claimed from CN201810237830.4A external-priority patent/CN108500289A/en
Priority claimed from CN201810237828.7A external-priority patent/CN108580920A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/06—Metallic powder characterised by the shape of the particles
    • B22F1/068—Flake-like particles

Abstract

The invention discloses a preparation method of flake silver powder, which takes water, silver salt, complexing agent, silver plating brightener, dispersant, alkali or acid, flake alkaline compound crystallization template or flake acidic compound crystallization template or sublimable flake compound crystallization template and reducing agent as raw materials, adopts a chemical plating method to plate silver on the surface of the flake compound crystallization template until silver ions completely react, and directly obtains the flake silver powder without ball milling through separation purification and processing process after the reaction is finished. The technical scheme of the invention has the advantages of low energy consumption, small environmental pollution, simple production process, short process route, small investment on large-scale production equipment, high production efficiency, low production cost and good dispersion performance and conductivity of products, is suitable for large-scale production, solves the problems in the conventional processes for preparing the flake silver powder by using a ball milling method and a template method, and has good industrial prospect.

Description

Preparation method of flaky silver powder
Technical Field
The invention belongs to the technical field of preparation of metal powder materials, and relates to a preparation method of flaky silver powder.
Background
The flake silver powder has excellent catalytic performance, sintering performance, thixotropic performance, adhesive force, shielding effect, electromagnetic wave reflecting capacity and conductivity, and may be used widely in chemical catalysis, powder metallurgy, conductive paint, conductive adhesive, conductive ink, conductive slurry, etc.
The contact between the spherical silver powder and the granular silver powder is point contact, the sectional area of a conductive channel is small, the conductivity is poor, the metal powder consumption is large, and the use cost is high; the flaky silver powder particles not only have large specific surface area, but also are in line contact and surface contact, so that the contact area among the flaky silver powder particles is greatly increased, and therefore, compared with spherical silver powder and granular silver powder, the amount of the silver powder required by the flaky silver powder particles to form a conductive channel with the same conductive performance is obviously reduced, a viscous product prepared from the flaky silver powder also has thixotropic performance, and the sedimentation stability of the product is obviously improved; because the silver powder belongs to a noble metal material, the conductive electronic material prepared by adopting the flake silver powder can obviously improve the conductivity, the adhesive force and the storage stability of the product, greatly reduce the consumption of the silver powder, save resources, reduce the production cost and improve the economic benefit; in the aspects of chemical catalysis, electromagnetic shielding and radar wave reflection, the flaky silver powder has obviously larger specific surface area than the spherical silver powder and the granular silver powder, so that the silver powder has excellent catalytic performance, electromagnetic shielding performance and radar wave reflection performance; therefore, a technique for producing the plate-like silver powder is attracting attention.
Technical reports of preparing the flake silver powder by a chemical method are few, but the technical repeatability is poor, and the flake silver powder can be rarely used for industrialization; at present, most of flake silver powder products sold on the market are obtained by ball milling spherical silver powder or granular silver powder under specific conditions, because the ball milling usually needs inert gas protection, and proper lubricant and dispersant are added to ball mill to the required granularity, then grading, surface polishing and surface modification are carried out, and finally, the flake silver powder is obtained by purification treatment; therefore, the ball milling process is generally complex and tedious, the equipment requirement is high, the production period is long, the energy consumption is high, and the production cost is high; the purity of the flake silver powder product obtained by ball milling is usually low, the particle size is large, the surface of flake particles is concave-convex rough, irregular in shape and uneven in thickness, the edge of the powder is cracked, and the specific surface area is small; therefore, the novel and efficient method for preparing the flake silver powder product is of great interest.
Chemical plating is a treatment technology capable of forming metal coatings on the surfaces of various materials, and the technology is increasingly concerned by people due to simple and convenient process, energy conservation and environmental protection; the principle of chemical plating is simple, and different from electroplating, the chemical plating is a method which does not need electricity, but reduces metal ions into metal in a solution containing a reducing agent and the metal ions by utilizing the principle of oxidation-reduction reaction and deposits the metal ions on the surfaces of various materials to form a plating layer; at present, chemical plating reported in the literature is mostly chemical plating on the surfaces of metal conductor materials and non-metal insulator materials, mainly achieves the aims of decorating and protecting substrate materials, and researches on chemical plating on the surfaces of compound crystals are rarely reported in the literature; the research of preparing the flaky silver powder by using flaky compound crystals as templates and a chemical plating method is more rarely reported in literatures; therefore, the crystal of the flake compound is taken as a template for chemical plating, reaction process conditions and technical schemes for chemical plating on the surface of the crystal template of the flake compound are discussed, and the process technology for separating, purifying and processing the obtained chemical plating product to obtain the flake silver powder are discussed, so that a brand new method for preparing the flake silver powder is provided, and the method is undoubtedly significant. A
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defects in the prior art, the invention aims to provide the preparation method of the flaky silver powder, which has the characteristics of low energy consumption, small environmental pollution, simple production process, short production process route, small large-scale production investment, high product purity and high yield.
The technical scheme is as follows: in order to achieve the purpose of the invention, the invention adopts the technical scheme that:
a preparation method of flaky silver powder comprises the following steps:
1) preparing a flaky basic compound crystallization template or a flaky acidic compound crystallization template;
2) preparing an alkaline mixture containing a flaky alkaline compound crystallization template and a silver salt; or preparing an acidic mixture containing a flaky acidic compound crystallization template and a silver salt; or preparing a mixture containing a sublimable plate-like compound crystallization template and a silver salt;
3) mixing water and a reducing agent according to the mass percentage of the reducing agent to the water of (0.1-30.0%) to (70.0-99.9%), stirring and dissolving completely to obtain a reducing agent water solution;
4) preparation of flake silver powder: adding the reducing agent aqueous solution obtained in the step 3) into the alkaline mixture containing the flaky alkaline compound crystallization template and the silver salt in the step 2), or into the acidic mixture containing the flaky acidic compound crystallization template and the silver salt, or into the mixture containing the sublimable flaky compound crystallization template and the silver salt, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the flaky crystallization template until the silver ions completely react to obtain a reaction product; when flaky alkaline compound crystals are used as templates or flaky acidic compound crystals are used as templates, reaction products are heated to boiling, the flaky compound crystal templates are dissolved in boiling water, the hot crude silver flake products are filtered to obtain silver flake crude products, the obtained silver flake crude products are purified through repeated operations of washing with boiling water for many times and filtering while hot, then the process steps of adding water, stirring, dispersing, ultrasonic crushing for 1-6 h, filtering, washing with absolute ethyl alcohol, filtering and drying are carried out, when sublimable flaky compound crystals are used as templates, solid substances obtained after the reaction products are filtered are repeatedly washed with water and filtered to obtain silvered sublimable flaky compound crystals, the material is subjected to reduced pressure heat treatment at the temperature of 70-150 ℃ to sublimate the sublimable flaky compound crystals, and the sublimable flaky compound crystals are recovered and recycled through cold trap sublimation after sublimation, until sublimable flaky compound crystals are removed, silver flakes are obtained, and the obtained silver flakes are subjected to the processes of adding absolute ethyl alcohol, stirring and dispersing, ultrasonic crushing for 1-6 hours, filtering, washing with absolute ethyl alcohol, filtering and drying; finally, flake silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm is obtained;
in the step 1), preparing a flaky alkaline compound crystallization template: according to the mass percentage of (0.1-30.0%) to (55.0-95.0%) of surfactant, alkaline compound crystal and water, firstly mixing water and surfactant, and stirring and dissolving completely to obtain surfactant aqueous solution; heating a surfactant aqueous solution to boiling, adding an alkaline compound crystal, stirring until the alkaline compound crystal is fully dissolved, and filtering while the solution is hot to obtain a saturated solution of the alkaline compound crystal; placing the saturated solution of the alkaline compound crystal in a thermostat controlled at 50 ℃ for cooling crystallization, taking the material out of the thermostat when the temperature of the material is reduced to 50 ℃, and naturally cooling the material to room temperature to complete crystallization; filtering the materials to obtain a crude crystalline product of the flaky alkaline compound, recycling the mother liquor obtained by filtering, washing the crude crystalline product of the flaky alkaline compound with cold water at 0-5 ℃ of which the mass is 1-10 times that of the crystalline product for 2-3 times according to the mass of the crude crystalline product of the flaky alkaline compound, filtering to obtain crystals, and drying the crystals to obtain a crystalline template of the flaky alkaline compound;
in the step 1), preparing a flaky acidic compound crystallization template: according to the mass percentage of the surfactant, the acidic compound crystal and the water being (0.1-30.0%): 55.0-95.0%, firstly mixing the water with the surfactant, and stirring and dissolving completely to obtain a surfactant aqueous solution; heating a surfactant aqueous solution to boiling, adding an acid compound crystal, stirring until the acid compound crystal is fully dissolved, and filtering while the solution is hot to obtain a saturated solution of the acid compound crystal; placing the saturated solution of the acid compound crystals in a thermostat controlled at 50 ℃ for cooling and crystallizing, taking the materials out of the thermostat when the temperature of the materials is reduced to 50 ℃, and naturally cooling the materials to room temperature to ensure complete crystallization; filtering the materials to obtain a crude crystallization product of the flaky acidic compound, recycling the mother liquor obtained by filtering, washing the crude crystallization product of the flaky acidic compound for 2-3 times by taking cold water with the temperature of 0-5 ℃ and the mass of the product of the flaky acidic compound being 1-10 times of that of the crystallization product, filtering to obtain crystals, and drying the crystals to obtain a crystallization template of the flaky acidic compound;
in step 2): the preparation method of the alkaline mixture containing the flaky alkaline compound crystallization template and the silver salt comprises the following steps: according to the mass percentage of water, silver salt, complexing agent, silver plating brightener, dispersant, alkali and flaky alkaline compound crystallization template being (35.0-95.0%), (0.1-30.0%), (0.001-30.0%), (0.1-30.0%) and (0.1-30.0%), firstly mixing water, silver salt, complexing agent, silver plating brightener, dispersant and alkali, stirring until all the materials are completely dissolved, then adding flaky alkaline compound crystallization template, stirring and carrying out ultrasonic treatment for 1-60 min, carrying out ultrasonic crushing on the flaky alkaline compound crystallization template into flaky crystals with the particle size of 0.5-20.0 mu m, and obtaining an alkaline mixture containing the flaky alkaline compound crystallization template and silver salt;
in step 2): the preparation method of the acidic mixture containing the flaky acidic compound crystallization template and the silver salt comprises the following steps: according to the mass percentage of water, silver salt, complexing agent, silver plating brightener, dispersant, acid and flaky acidic compound crystallization template being (35.0-95.0%), (0.1-30.0%), (0.001-30.0%), (0.1-30.0%) and (0.1-30.0%), firstly mixing water, silver salt, complexing agent, silver plating brightener, dispersant and acid, stirring until all the materials are completely dissolved, then adding flaky acidic compound crystallization template, stirring and carrying out ultrasonic treatment for 1-60 min, carrying out ultrasonic crushing on the flaky acidic compound crystallization template into flaky crystals with the particle size of 0.5-20.0 mu m, and obtaining an acidic mixture containing the flaky acidic compound crystallization template and silver salt;
in step 2): the preparation method of the mixture containing the sublimable plate-shaped compound crystallization template and the silver salt comprises the following steps: according to the mass percentage of water, silver salt, complexing agent, silver plating brightener, dispersant and sublimable flaky compound crystallization template being (35.0-95.0%), (0.1-30.0%), (0.001-30.0%), (0.1-30.0%) and (0.1-30.0%), firstly mixing the water, the silver salt, the complexing agent, the silver plating brightener and the dispersant, stirring until all the materials are completely dissolved, then adding the sublimable flaky compound for crystallization, stirring and carrying out ultrasonic treatment for 1-60 min, ultrasonically crushing the sublimable flaky compound crystallization template into flaky crystals with the particle size of 0.5-20.0 mu m, and obtaining the sublimable flaky compound crystallization template and silver salt mixture;
in the step 4), when the flaky alkaline compound crystal is taken as a template, preparing the flaky silver powder: cooling an alkaline mixture containing a flaky alkaline compound crystallization template and a silver salt by using a room-temperature cold water bath to maintain the reaction system at room temperature, gradually adding a reducing agent aqueous solution under the stirring condition, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the flaky alkaline compound crystallization template until the silver ions are completely reacted; because the flaky alkaline compound crystallization template is only slightly soluble in cold water but is dissolved in hot water and boiling water, a reaction product is heated to boil, the flaky alkaline compound crystallization template is dissolved in the boiling water, the hot silver flake crystallization template is filtered to obtain a silver flake crude product, the obtained silver flake crude product is repeatedly washed by boiling water for many times and filtered for hot time to be purified, and then the silver flake crude product is subjected to the processes of adding water, stirring and dispersing, ultrasonic crushing for 1-6 hours, filtering, washing with absolute ethyl alcohol, filtering and drying, so that the flaky silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm is obtained;
in the step 4), when the flaky acidic compound crystal is taken as a template, preparing the flaky silver powder: cooling the acidic mixture containing the flaky acidic compound crystallization template and the silver salt by using a room-temperature cold water bath to maintain the reaction system at room temperature, gradually adding a reducing agent aqueous solution under the stirring condition, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the flaky acidic compound crystallization template until the silver ions completely react; because the flaky acidic compound crystallization template is only slightly soluble in cold water but is dissolved in hot water and boiling water, heating a reaction product to boiling to dissolve the flaky acidic compound crystallization template in the boiling water, filtering while the silver flake crystallization template is hot to obtain a silver flake crude product, washing the silver flake crude product with boiling water for many times, filtering while the silver flake crude product is hot, repeatedly purifying, adding water, stirring and dispersing, ultrasonically crushing for 1-6 hours by ultrasonic waves, filtering, washing with absolute ethyl alcohol, filtering and drying to obtain flaky silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm;
in the step 4), when sublimable flaky compound crystals are used as templates, preparing the flaky silver powder: gradually adding a reducing agent aqueous solution into a mixture containing the sublimable flaky compound crystallization template and silver salt under the stirring condition, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the sublimable flaky compound crystallization template until the silver ions completely react; repeatedly washing and filtering solid substances obtained by filtering reaction products for multiple times to obtain silver-plated sublimable flaky compound crystals, carrying out reduced pressure heat treatment on the materials at the temperature of 70-150 ℃ to sublimate the sublimable flaky compound crystals, carrying out sublimation on the sublimable flaky compound crystals, carrying out sublimation recovery by using a cold trap and recycling the sublimated sublimable flaky compound crystals until the sublimable flaky compound crystals are removed to obtain silver flakes, and carrying out water adding, stirring and dispersing, ultrasonic crushing for 1-6 h, filtering, washing with absolute ethyl alcohol, filtering and drying on the obtained silver flakes to obtain flaky silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm;
the flake silver powder obtained by the preparation method of the flake silver powder has the technical indexes that: appearance: grey to grey black powder; purity: not less than 99.9%; particle size range: 0.050 to 5.0 μm; average particle size: 0.5 to 3.0 μm; thickness range: 5-60 nm; average thickness: 10-30 nm; apparent density: 2.1-3.2 g/cm3(ii) a Tap density: 2.9-4.1 g/cm3。
In the method for preparing the flake silver powder, the flake alkaline compound crystal template is any one of acetanilide, p-toluidine, 1-naphthylamine and 2-naphthylamine.
In the preparation method of the flake silver powder, the flake acidic compound crystallization template is any one of 4-methoxyphenol, benzoic acid, boric acid, 2, 6-dimethylphenol and sebacic acid.
In the preparation method of the flake silver powder, the sublimable flake compound crystal template is any one of borneol, benzoic acid, naphthalene and anthracene.
According to the preparation method of the flake silver powder, when the flake alkaline compound crystal is taken as a template, the reducing agent is any one or more of hydroxylamine, ethanolamine, diethanolamine, triethanolamine, formaldehyde, acetaldehyde, glucose, ascorbic acid, sodium hypophosphite, hydrazine hydrate and sodium borohydride; when the flaky acidic compound crystal is taken as a template, the reducing agent is any one or more of ferrous nitrate, ferrous acetate, hydrogen peroxide, formic acid, formaldehyde, acetaldehyde, glyoxal, glutaraldehyde, glucose, ascorbic acid, hypophosphorous acid, hydrazine sulfate, hydrazine hydrate and sodium borohydride; when sublimable sheet compound crystals are used as templates, the reducing agent is any one or more of hydroxylamine, ethanolamine, diethanolamine, triethanolamine, ferrous nitrate, ferrous acetate, hydrogen peroxide, formic acid, formaldehyde, acetaldehyde, glyoxal, glutaraldehyde, glucose, ascorbic acid, hypophosphorous acid, sodium hypophosphite, hydrazine sulfate, hydrazine hydrate and sodium borohydride.
The preparation method of the flake silver powder comprises the following steps of using a surfactant of sodium dodecyl sulfate, ammonium dodecyl sulfate, potassium dodecyl sulfate, monoethanolamine dodecyl sulfate, diethanolamine dodecyl sulfate, triethanolamine dodecyl sulfate, sodium hexadecyl sulfate, ammonium hexadecyl sulfate, potassium hexadecyl sulfate, monoethanolamine hexadecyl sulfate, diethanolamine hexadecyl sulfate, triethanolamine hexadecyl sulfate, sodium dodecylpolyoxyethylene ether sulfate, ammonium dodecylpolyoxyethylene ether sulfate, potassium dodecylpolyoxyethylene ether sulfate, monoethanolamine dodecylpolyoxyethylene ether sulfate, diethanolamine dodecylpolyoxyethylene ether sulfate, triethanolamine dodecylpolyoxyethylene ether sulfate, sodium hexadecyl sulfonate, ammonium hexadecyl sulfonate, potassium hexadecyl sulfonate, monoethanolamine dodecyl sulfate, diethanolamine dodecyl sulfate, sodium hexadecyl sulfate, ammonium hexadecyl sulfonate, ammonium hexadecyl sulfate, ammonium hexadecyl sulfonate, monoethanolamine hexadecyl sulfonate, ammonium dodecyl sulfate, ammonium hexadecyl ether, ammonium hexadecyl sulfate, ammonium hexadecyl ether, ammonium chloride, ammonium hexadecyl ether, ammonium chloride, ammonium hexadecyl ether, ammonium chloride, ammonium hexadecyl ether, ammonium chloride, ammonium hexadecyl ether, ammonium chloride, any one or more of diethanolamine hexadecylsulfonate, triethanolamine hexadecylsulfonate, sodium dodecylbenzenesulfonate, ammonium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, monoethanolamine dodecylbenzenesulfonate, diethanolamine dodecylbenzenesulfonate, triethanolamine dodecylbenzenesulfonate, sodium nonylphenol polyoxyethylene ether sulfate, ammonium nonylphenol polyoxyethylene ether sulfate, potassium nonylphenol polyoxyethylene ether sulfate, monoethanolamine nonylphenol polyoxyethylene ether sulfate, diethanolamine nonylphenol polyoxyethylene ether sulfate, triethanolamine nonylphenol polyoxyethylene ether sulfate, cocamide, lauramide propyl betaine, cocamide propyl betaine, soya oil amide propyl betaine, octadecyl dimethyl amine oxide, and dodecyl dimethyl amine oxide.
According to the preparation method of the flake silver powder, the silver salt is one or more of silver fluoride, silver nitrate, silver citrate, silver lactate, silver tartrate and silver acetate.
The complexing agent used in the preparation method of the flake silver powder is any one or more of N-hydroxyethyl ethylenediamine triacetic acid, N-hydroxyethyl ethylenediamine triacetic acid trisodium, nitrilotriacetic acid trisodium, ethylenediamine tetraacetic acid disodium, citric acid, sodium citrate, potassium citrate, ammonium citrate, tartaric acid, sodium tartrate, potassium tartrate, antimony potassium tartrate and ammonium tartrate.
The preparation method of the flake silver powder uses silver plating brightening agent comprising HL-SP201A/B, KYU AG-1 bright silver plating additive, Silverstar NM-02 bright silver plating process silvering agent, carbon disulfide, thiourea, potassium xanthate, antimony xanthate, tin xanthate, sodium thiosulfate, ammonium thiosulfate, sulfamic acid, antimony potassium gluconate, antimony potassium tartrate, sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, dithiocarbamic acid, sodium dithiocarbamate, ammonium dithiocarbamate, potassium dithiocarbamate, thiocarbohydrazide, thioglycolic acid and 2-mercaptopropionic acid, any one or more of 2-mercaptonicotinic acid, cystine, 2-mercaptothiazoline, 1-mercaptoglycerol, thiosalicylic acid, thiodiethylene glycol, thioglycolic acid, thiodipropionic acid, thioproline, AG-300 SILVER plating additive and SILVER B/ST bright SILVER plating additive.
In the preparation method of the flake silver powder, the used dispersing agent is any one or more of polyvinylpyrrolidone, carboxymethyl cellulose, sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, gelatin, polyacrylic acid, sodium polyacrylate, polyacrylamide, ammonium polyacrylate, potassium polyacrylate, polyvinyl alcohol, gum arabic and polyethylene glycol.
The preparation method of the flake silver powder uses alkali which is any one or more of ammonia, ammonia water, ethylenediamine, n-butylamine, n-pentylamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.
In the method for preparing the flake silver powder, the acid is any one or more of benzenesulfonic acid, p-toluenesulfonic acid, formic acid, acetic acid, propionic acid, citric acid, tartaric acid, lactic acid, nitric acid, fumaric acid and maleic acid.
In the preparation method of the flake silver powder, the used water is any one of distilled water, deionized water, ultrapure water and high-purity water.
The preparation method of the flake silver powder uses ultrasonic waves with the frequency of 20 KHz-1 MHz and the power of 30W-15 KW.
Has the advantages that: compared with the prior art, the preparation method of the flake silver powder provided by the invention has the following remarkable advantages:
1) when preparing a flaky alkaline compound crystallization template, placing a saturated solution of alkaline compound crystals in a thermostat with the temperature controlled at 50 ℃ for cooling crystallization, and reducing the cooling speed of the material by reducing the temperature difference between the material and the environment so as to reduce the crystallization speed and ensure that the formed flaky crystals are more regular; the method comprises the following steps of (1) filtering a material to obtain a crude crystallization product of a flaky alkaline compound, and washing the crude crystallization product of the flaky alkaline compound for 2-3 times by using cold water at 0-5 ℃ which is 1-10 times of the mass of the crude crystallization product, so as to reduce the loss of the crystallization of the flaky alkaline compound and improve the preparation efficiency of a crystallization template of the flaky alkaline compound; the flaky alkaline compound crystal is characterized in that the crystal shape of the alkaline compound is flaky, the flaky alkaline compound crystal is used as a template, silver is plated on the surface of the flaky alkaline compound crystal template through chemical plating to form flaky silver, and the preparation process of the flaky silver is simple;
2) the selected flaky alkaline compound crystallization template is slightly soluble in cold water and dissolved in hot water and boiling water, so that after a reaction product is heated to be boiled, the flaky alkaline compound crystallization template is dissolved in the boiling water, and is filtered when the reaction product is hot, and then is repeatedly washed by boiling water and filtered when the reaction product is hot, so that impurities and the flaky alkaline compound crystallization template can be removed, the impurities and the template are easy to remove, the purification process is simple, quick and efficient, the preparation of high-purity flaky silver powder is facilitated, the purity of the silver powder can reach more than 99.9%, and the purity of the product is high;
3) firstly, because the selected flaky alkaline compound crystallization template is slightly soluble in cold water and soluble in hot water and boiling water, the preparation reaction of the flaky silver is best maintained at room temperature, so that the amount of the flaky alkaline compound crystallization template is favorably kept not to be reduced due to dissolution in the reaction process, the amount of the flaky alkaline compound crystallization template is stable, and the controllability on the thickness of the flaky silver powder is strong; secondly, as the selected flaky alkaline compound crystallization template belongs to an alkaline compound, and the reaction must be carried out in an alkaline environment, the pH of the reactant must be kept to be more than 7, so that the reduction of the amount of the flaky alkaline compound crystallization template in an acidic environment due to acid-base neutralization reaction is avoided, and thus, the amount of the flaky alkaline compound crystallization template is stable, and the controllability on the thickness of the flaky silver powder is strong; thirdly, under the condition that the dosage of the silver salt is determined, the dosage of the flaky alkaline compound crystallization template is changed, and the proportion of the silver salt to the flaky alkaline compound crystallization template is adjusted, so that the thickness of the flaky silver powder can be effectively controlled; fourthly, ultrasonically crushing the flaky silver obtained by the flaky alkaline compound crystallization template and the chemical plating by using ultrasonic waves, and adjusting the ultrasonic crushing time, so that the particle size of the flaky silver powder can be effectively controlled, and the particle size control method is simple, convenient and effective; in a word, the thickness of the flake silver powder can be effectively controlled, the particle size of the flake silver powder can be effectively controlled, and the flake silver powder with high specific surface area can be prepared, wherein the specific surface area is 5-15 times of that of the flake silver powder by a ball milling method;
4) when the flaky alkaline compound crystal is used as a template, after the reaction for preparing the flaky silver powder is completed, when a reaction product is heated to boiling, the flaky alkaline compound crystal template is slightly soluble in cold water but soluble in hot water and boiling water, so that after the silver flake is filtered and taken out while the mother solution is hot, the flaky alkaline compound crystal template is left in the mother solution obtained by filtering, after the mother solution is cooled, the flaky alkaline compound crystal template is crystallized and precipitated, and the precipitated crystal is separated and purified by using a recrystallization method, and the flaky alkaline compound crystal template can be recycled, so that the template resource is saved, the production cost is reduced, the emission of pollutants is reduced, and the economic benefit and the environmental benefit are improved;
5) when preparing a flaky acidic compound crystallization template, placing a saturated solution of acidic compound crystallization in a thermostat controlled at 50 ℃ for cooling crystallization, wherein the cooling speed of the material is reduced by reducing the temperature difference between the material and the environment so as to reduce the crystallization speed, so that the formed flaky crystallization is more regular; washing a flaky acidic compound crystallization crude product obtained by filtering the material for 2-3 times by using cold water with the temperature of 0-5 ℃ and the mass of 1-10 times that of the crystallization crude product, so as to reduce the loss of the flaky acidic compound crystallization and improve the preparation efficiency of a flaky acidic compound crystallization template; the flaky acidic compound crystal means that the crystal shape of the acidic compound is flaky, the flaky acidic compound crystal is used as a template, silver is plated on the surface of the flaky acidic compound crystal template through chemical plating to form flaky silver, and the preparation process of the flaky silver is simple;
6) the selected flaky acidic compound crystallization template is slightly soluble in cold water and dissolved in hot water and boiling water, so that after a reaction product is heated to be boiled, the flaky acidic compound crystallization template is dissolved in the boiling water, and is filtered when the reaction product is hot, and then is repeatedly washed by boiling water and filtered when the reaction product is hot, so that impurities and the flaky acidic compound crystallization template can be removed, the impurities and the template are easy to remove, the purification process is simple, quick and efficient, the preparation of high-purity flaky silver powder is facilitated, the purity of the silver powder can reach more than 99.9%, and the purity of the product is high;
7) firstly, because the selected flaky acidic compound crystallization template is slightly soluble in cold water and soluble in hot water and boiling water, the preparation reaction of the flaky silver is best maintained at room temperature, so that the amount of the flaky acidic compound crystallization template is favorably kept not to be reduced due to dissolution in the reaction process, the amount of the flaky acidic compound crystallization template is stable, and the controllability on the thickness of the flaky silver powder is strong; secondly, because the selected flaky acidic compound crystallization template belongs to an acid compound, and the reaction must be carried out in an acid environment, the pH of the reactant must be kept less than 7, so that the reduction of the amount of the flaky acidic compound crystallization template in an alkaline environment due to acid-base neutralization reaction is avoided, and thus, the amount of the flaky acidic compound crystallization template is stable, and the controllability on the thickness of the flaky silver powder is strong; thirdly, under the condition that the dosage of the silver salt is determined, the dosage of the flaky acidic compound crystallization template is changed, and the proportion of the silver salt to the flaky acidic compound crystallization template is adjusted, so that the thickness of the flaky silver powder can be effectively controlled; fourthly, ultrasonic crushing the flaky acidic compound crystallization template and the flaky silver obtained by chemical plating by using ultrasonic waves, and adjusting the ultrasonic crushing time, the particle size of the flaky silver powder can be effectively controlled, and the particle size control method is simple, convenient and effective; in a word, the thickness of the flake silver powder can be effectively controlled, the particle size of the flake silver powder can be effectively controlled, and the flake silver powder with high specific surface area can be prepared, wherein the specific surface area is 5-15 times of that of the flake silver powder by a ball milling method;
8) when the flaky acidic compound crystal is used as a template, the reaction for preparing the flaky silver powder is complete, and when a reaction product is heated to boiling, the flaky acidic compound crystal template is slightly soluble in cold water but soluble in hot water and boiling water, so that after the silver flake is filtered and taken out while the mother solution is hot, the flaky acidic compound crystal template is left in the filtered mother solution, the flaky acidic compound crystal template is crystallized and precipitated after the mother solution is cooled, the precipitated crystal is separated and purified by a recrystallization method, and the flaky acidic compound crystal template can be recycled, so that the template resource is saved, the production cost is reduced, the emission of pollutants is reduced, and the economic benefit and the environmental benefit are improved;
9) sublimable flaky compound crystals are selected as templates, so that after a solid product obtained by chemical plating is washed by water for multiple times and filtered to remove water-soluble impurities, the templates can be directly removed by a sublimation method, the templates are extremely easy to remove, the purification process is very simple, quick and efficient, the preparation of high-purity flaky silver powder is facilitated, the purity of the silver powder can reach more than 99.9 percent, and the purity of the product is high;
10) under the condition that the dosage of the silver salt is determined, the thickness of the flaky silver powder can be effectively controlled by changing the dosage of the sublimable flaky compound crystallization template and adjusting the proportion of the silver salt to the sublimable flaky compound crystallization template; ultrasonic crushing sublimable flaky compound crystallization templates and flaky silver obtained by chemical plating by using ultrasonic waves, adjusting ultrasonic crushing time, effectively controlling the particle size of flaky silver powder, and having a simple, convenient and effective particle size control method; therefore, the thickness of the flake silver powder can be effectively controlled, the particle size of the flake silver powder can be effectively controlled, and the flake silver powder with high specific surface area which is 5-15 times of that of the flake silver powder prepared by the ball milling method can be prepared;
11) in the preparation process of the flake silver powder, a silver plating brightener is added for brightening and flattening the chemical silver plating layer and improving the flatness and smoothness of the surface of the flake silver powder particles; in the preparation process of the flake silver powder, the purpose of adding the complexing agent is to form dynamic balance of free silver ions and silver complex ions in a reaction system, so as to effectively control the concentration of the free silver ions and further control the reduction reaction speed of the silver ions and the deposition speed of silver, so as to obtain a uniform silver coating, and also to ensure that a chemical silver coating is bright and smooth and effectively improve the smoothness and finish of the surface of flake silver powder particles; the method is favorable for improving the contact area among the flaky silver powder particles and the conductivity of a product prepared from the flaky silver powder particles, and compared with the flaky silver powder prepared without adding a silver plating brightener and a complexing agent, the conductivity of the flaky silver powder prepared by the method can be improved by about 35 percent, and the improvement effect is obvious;
12) in the preparation process of the flake silver powder, the dispersant is added for preventing the particles from agglomerating and improving the dispersibility of the flake silver powder particles, so that the flake silver powder is easy to disperse when the flake silver powder is used for preparing a product, the use is convenient for a user, and the use performance of the flake silver powder is improved;
13) compared with a viscous product prepared by using spherical silver powder, the viscous product prepared by using the flaky silver powder produced by the invention, such as conductive adhesive, conductive paste, conductive coating, conductive ink and the like, has the advantages that the sedimentation stability and the storage stability of the product are improved by about 50 percent due to the thixotropic property of the flaky silver powder in a viscous system, and the stability of the product is good;
14) silver belongs to soft metal, and silver powder particles are pressed into clusters when being pressed or impacted, so that the silver powder particles are pressed into clusters and agglomerated together when being subjected to ball milling crushing and grinding crushing;
15) when sublimable flaky compound crystals are used as templates, after the reaction for preparing the flaky silver powder is completed, filtering a reaction product to obtain a solid product, washing the solid product for multiple times, filtering and repeating the operation to remove water-soluble impurities, obtaining silver-plated sublimable flaky compound crystals, sublimating the sublimable flaky compound crystals by performing reduced pressure heat treatment on the material at the temperature of 70-150 ℃, and condensing and recovering the sublimable flaky compound crystals by using a cold trap for recycling, so that template resources are saved, the production cost is reduced, the emission of pollutants is reduced, and the economic benefit and the environmental benefit are improved;
16) the reported process for preparing the flake silver powder by the soft membrane plate method has high requirements and harsh reaction conditions, and the granular silver powder rather than the flake silver powder is usually obtained by improper control, so the process for preparing the flake silver powder by the soft membrane plate method has poor repeatability and stability, the product quality is unstable, even the flake silver powder cannot be obtained, and the product production success rate is not high; the reported technology for preparing the flake silver powder by the hard mask method has the problems that the template is difficult to remove or even cannot be removed, or the process for removing the template is complex and the treatment cost is high, and the like, for example, when the silver powder is prepared by taking titanium dioxide, porous alumina and other substances as the template, the template is difficult to remove or even cannot be removed, even if the template is removed by using a complex process, the template is difficult to remove, the treatment cost is high, the product purity is not high, and the flake silver powder cannot be obtained; the operation process for preparing the flake silver powder by the biological template is complex, the control difficulty is high, the reaction process is slow, and the production efficiency is low; the success rate of preparing the flake silver powder by the technical scheme of the invention is 100%, the template is easy to remove, the product purity is over 99.9%, the production cost is low, and the production efficiency is high;
17) the technical scheme of the invention has the advantages of low energy consumption, small environmental pollution, simple production process, short process route, small investment on large-scale production equipment, high production efficiency, low production cost and good dispersion performance and conductivity of products, is suitable for large-scale production, solves the problems in the conventional processes for preparing the flake silver powder by using a ball milling method and a template method, and has good industrial prospect.
Detailed Description
The present invention will be described in further detail with reference to examples. In the following examples, all percentages are by mass unless otherwise specified.
Examples 1 to 9
When the flaky alkaline compound crystal is taken as a template, the preparation method of the flaky silver powder comprises the following specific steps:
1) preparing a flaky basic compound crystallization template: according to the mass percentages of the surfactant, the alkaline compound crystals and the water in the embodiment 1-9 in the table I, firstly mixing the water with the surfactant, and stirring and dissolving completely to obtain a surfactant aqueous solution; heating a surfactant aqueous solution to boiling, adding an alkaline compound crystal, stirring until the alkaline compound crystal is fully dissolved, and filtering while the solution is hot to obtain a saturated solution of the alkaline compound crystal; placing the saturated solution of the alkaline compound crystal in a thermostat controlled at 50 ℃ for cooling crystallization, taking the material out of the thermostat when the temperature of the material is reduced to 50 ℃, and naturally cooling the material to room temperature to complete crystallization; filtering the materials to obtain a crude crystalline product of the flaky alkaline compound, recycling the mother liquor obtained by filtering, washing the crude crystalline product of the flaky alkaline compound with cold water at 0-5 ℃ of which the mass is 1-10 times that of the crystalline product for 2-3 times according to the mass of the crude crystalline product of the flaky alkaline compound, filtering to obtain crystals, and drying the crystals to obtain a crystalline template of the flaky alkaline compound;
2) preparation of alkaline mixture containing plate-like alkaline compound crystallization template and silver salt: according to the mass percentages of the water, the silver salt, the complexing agent, the silver plating brightener, the dispersing agent, the alkali and the flaky alkaline compound crystallization template in the first embodiment 1-9, the water, the silver salt, the complexing agent, the silver plating brightener, the dispersing agent and the alkali are mixed and stirred until all materials are completely dissolved, the flaky alkaline compound crystallization template is added, the mixture is stirred and treated by ultrasonic waves for 1-60 min, the flaky alkaline compound crystallization template is ultrasonically crushed into flaky crystals with the particle size of 0.5-20.0 mu m by the ultrasonic waves, and then the alkaline mixture containing the flaky alkaline compound crystallization template and the silver salt is obtained;
3) preparation of a reducing agent aqueous solution: according to the mass percentage of the reducing agent and the water in the embodiment 1-9 in the table I, mixing the water and the reducing agent, and stirring and dissolving completely to obtain a reducing agent water solution;
4) preparation of flake silver powder: cooling an alkaline mixture containing a flaky alkaline compound crystallization template and a silver salt by using a room-temperature cold water bath to maintain the reaction system at room temperature, gradually adding a reducing agent aqueous solution under the stirring condition, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the flaky alkaline compound crystallization template until the silver ions are completely reacted; because the flaky alkaline compound crystallization template is only slightly soluble in cold water but is dissolved in hot water and boiling water, a reaction product is heated to boil, the flaky alkaline compound crystallization template is dissolved in the boiling water, the hot silver flake crystallization template is filtered to obtain a silver flake crude product, the obtained silver flake crude product is repeatedly washed by boiling water and filtered for a plurality of times to be purified, and then the silver flake crude product is subjected to the processes of adding water, stirring and dispersing, ultrasonic crushing for 1-6 hours, filtering, washing with absolute ethyl alcohol, filtering and drying, so that the flaky silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm is obtained.
TABLE 1, examples 1-9 raw materials and proportions
Figure BSA0000179820580000101
Figure BSA0000179820580000111
Figure BSA0000179820580000121
Note [1 ]: wang Chong Guo, Chen Weidong. Influence of the ball ratio on the high-density flake silver powder. China metallurgy, 2015, 25 (8): 15-17.
Examples 10 to 18
When the flaky acidic compound crystal is taken as a template, the preparation method of the flaky silver powder comprises the following specific steps:
1) preparing a flaky acidic compound crystallization template: according to the mass percentages of the surfactant, the acidic compound crystals and the water in the second table of examples 10-18, firstly mixing the water with the surfactant, and stirring and dissolving completely to obtain a surfactant aqueous solution; heating a surfactant aqueous solution to boiling, adding an acid compound crystal, stirring until the acid compound crystal is fully dissolved, and filtering while the solution is hot to obtain a saturated solution of the acid compound crystal; placing the saturated solution of the acid compound crystals in a thermostat controlled at 50 ℃ for cooling and crystallizing, taking the materials out of the thermostat when the temperature of the materials is reduced to 50 ℃, and naturally cooling the materials to room temperature to ensure complete crystallization; filtering the materials to obtain a crude crystallization product of the flaky acidic compound, recycling the mother liquor obtained by filtering, washing the crude crystallization product of the flaky acidic compound for 2-3 times by taking cold water with the temperature of 0-5 ℃ and the mass of the product of the flaky acidic compound being 1-10 times of that of the crystallization product, filtering to obtain crystals, and drying the crystals to obtain a crystallization template of the flaky acidic compound;
2) preparation of an acidic mixture comprising a crystalline template of a platy acidic compound and a silver salt: according to the mass percentages of the water, the silver salt, the complexing agent, the silver plating brightener, the dispersing agent, the acid and the flaky acidic compound crystallization template in the second table of examples 10-18, the water, the silver salt, the complexing agent, the silver plating brightener, the dispersing agent and the acid are mixed and stirred until all materials are completely dissolved, the flaky acidic compound crystallization template is added, the mixture is stirred and treated by ultrasonic waves for 1-60 min, the flaky acidic compound crystallization template is ultrasonically crushed into flaky crystals with the particle size of 0.5-20.0 mu m by the ultrasonic waves, and then an acidic mixture containing the flaky acidic compound crystallization template and the silver salt is obtained;
3) preparation of a reducing agent aqueous solution: according to the mass percentage of the reducing agent and the water in the embodiment 10-18 in the table II, the water and the reducing agent are mixed, and the reducing agent aqueous solution is obtained after the water and the reducing agent are completely stirred and dissolved;
4) preparation of flake silver powder: cooling the acidic mixture containing the flaky acidic compound crystallization template and the silver salt by using a room-temperature cold water bath to maintain the reaction system at room temperature, gradually adding a reducing agent aqueous solution under the stirring condition, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the flaky acidic compound crystallization template until the silver ions completely react; because the flaky acidic compound crystallization template is only slightly soluble in cold water but is dissolved in hot water and boiling water, a reaction product is heated to boiling, the flaky acidic compound crystallization template is dissolved in the boiling water, the hot silver flake crystallization template is filtered to obtain a silver flake crude product, the obtained silver flake crude product is repeatedly washed by boiling water and filtered for a plurality of times to be purified, and then the silver flake crude product is subjected to the processes of adding water, stirring and dispersing, ultrasonic crushing for 1-6 hours, filtering, washing with absolute ethyl alcohol, filtering and drying, so that the flaky silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm is obtained.
TABLE II, examples 10-18 raw materials and their mixture ratios
Figure BSA0000179820580000131
Figure BSA0000179820580000141
Figure BSA0000179820580000151
Note [1 ]: wang Chong Guo, Chen Weidong. Influence of the ball ratio on the high-density flake silver powder. China metallurgy, 2015, 25 (8): 15-17.
Examples 19 to 27
When sublimable flaky compound crystals are taken as templates, the preparation method of the flaky silver powder comprises the following specific steps:
1) preparation of a mixture containing sublimable plate-like compound crystallization template and silver salt: according to the mass percentages of the water, the silver salt, the complexing agent, the silver plating brightener, the dispersing agent and the sublimable flaky compound crystals in the third embodiment 19-27, the water, the silver salt, the complexing agent, the silver plating brightener and the dispersing agent are mixed and stirred until all materials are completely dissolved, the sublimable flaky compound crystals are added, the mixture is stirred and treated with ultrasonic waves for 1-60 min, the sublimable flaky compound crystal template is ultrasonically crushed into flaky crystals with the particle size of 0.5-20.0 mu m by the ultrasonic waves, and then the sublimable flaky compound crystal template and the silver salt containing mixture are obtained;
2) preparation of a reducing agent aqueous solution: according to the mass percentage of the reducing agent and the water in the third embodiment 19-27, mixing the water and the reducing agent, and stirring and dissolving completely to obtain a reducing agent water solution;
3) preparation of flake silver powder: gradually adding a reducing agent aqueous solution into a mixture containing the sublimable flaky compound crystallization template and silver salt under the stirring condition, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the sublimable flaky compound crystallization template until the silver ions completely react; and repeatedly washing and filtering the solid substance obtained by filtering the reaction product for multiple times to obtain silver-plated sublimable flaky compound crystals, carrying out reduced pressure heat treatment on the material at the temperature of 70-150 ℃ to sublimate the sublimable flaky compound crystals, sublimating the sublimable flaky compound crystals, recovering the sublimable flaky compound crystals by using a cold trap for sublimation and recycling the sublimable flaky compound crystals until the sublimable flaky compound crystals are removed to obtain silver flakes, and carrying out water adding, stirring and dispersing, ultrasonic crushing for 1-6 hours, filtering, washing with absolute ethyl alcohol, filtering and drying on the obtained silver flakes to obtain the flaky silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm.
TABLE III, examples 19-27 raw materials and proportions
Figure BSA0000179820580000161
Figure BSA0000179820580000171
Note [1 ]: wang Chong Guo, Chen Weidong. Influence of the ball ratio on the high-density flake silver powder. China metallurgy, 2015, 25 (8): 15-17.

Claims (1)

1. A preparation method of flaky silver powder is characterized by comprising the following steps:
preparation of a mixture containing sublimable plate-like compound crystallization template and silver salt: according to the mass percentage of water, silver salt, complexing agent, silver plating brightener, dispersant and sublimable flaky compound crystal being (35.0-95.0%), (0.1-30.0%), (0.001-30.0%), (0.1-30.0%), firstly mixing the water, the silver salt, the complexing agent, the silver plating brightener and the dispersant, stirring until all the materials are completely dissolved, then adding the sublimable flaky compound crystal, stirring and carrying out ultrasonic treatment for 1-60 min, ultrasonically crushing the sublimable flaky compound crystal template into flaky crystals with the particle size of 0.5-20.0 mu m, and obtaining a sublimable flaky compound crystal template and silver salt mixture;
preparation of a reducing agent aqueous solution: mixing water and a reducing agent according to the mass percentage of the reducing agent to the water of (0.1-30.0%) to (70.0-99.9%), stirring and dissolving completely to obtain a reducing agent water solution;
preparation of flake silver powder: gradually adding a reducing agent aqueous solution into a mixture containing the sublimable flaky compound crystallization template and silver salt under the stirring condition, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the sublimable flaky compound crystallization template until the silver ions completely react; repeatedly washing and filtering solid substances obtained by filtering reaction products for multiple times to obtain silver-plated sublimable flaky compound crystals, carrying out reduced pressure heat treatment on the materials at the temperature of 70-150 ℃ to sublimate the sublimable flaky compound crystals, carrying out sublimation on the sublimable flaky compound crystals, carrying out sublimation recovery by using a cold trap and recycling the sublimated sublimable flaky compound crystals until the sublimable flaky compound crystals are removed to obtain silver flakes, and carrying out water adding, stirring and dispersing, ultrasonic crushing for 1-6 h, filtering, washing with absolute ethyl alcohol, filtering and drying on the obtained silver flakes to obtain flaky silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm;
wherein the water used is any one of distilled water, deionized water, ultrapure water and high-purity water;
wherein the sublimable plate-like compound crystal is any one of borneol, benzoic acid, naphthalene and anthracene;
wherein the ultrasonic wave is the ultrasonic wave with the frequency of 20 KHz-1 MHz and the power of 30W-15 KW;
the flake silver powder prepared by the method has the following technical indexes:
1) appearance: grey to grey black powder;
2) purity: not less than 99.9%;
3) particle size range: 0.050 to 5 μm;
4) average particle size: 0.5 to 3.0 μm;
5) thickness range: 5-60 nm;
6) average thickness: 10-30 nm;
7) apparent density: 2.1-3.2 g/cm3；
8) Tap density: 2.9-4.1 g/cm3；
Wherein the silver salt is one or more of silver fluoride, silver nitrate, silver citrate, silver lactate, silver tartrate and silver acetate;
wherein the complexing agent is any one or more of N-hydroxyethyl ethylenediamine triacetic acid, N-hydroxyethyl ethylenediamine triacetic acid trisodium, nitrilotriacetic acid trisodium, ethylenediamine tetraacetic acid disodium, citric acid, sodium citrate, potassium citrate, ammonium citrate, tartaric acid, sodium tartrate, potassium tartrate, antimony potassium tartrate and ammonium tartrate;
wherein the used silver plating brightener is HL-SP201A/B, KYU AG-1 bright silver plating additive, Silverstar NM-02 bright silver plating process silvering agent, carbon disulfide, thiourea, potassium xanthate, antimony xanthate, tin xanthate, sodium thiosulfate, ammonium thiosulfate, sulfamic acid, antimony potassium gluconate, antimony potassium tartrate, sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, dithiocarbamic acid, sodium dithiocarbamate, ammonium dithiocarbamate, potassium dithiocarbamate, thiocarbazone, thioglycolic acid, 2-mercaptopropionic acid, any one or more of 2-mercaptonicotinic acid, cystine, 2-mercaptothiazoline, 1-mercaptoglycerol, thiosalicylic acid, thiodiethylene glycol, thioglycolic acid, thiodipropionic acid, thioproline, AG-300 SILVER plating additive and SILVER B/ST bright SILVER plating additive;
wherein the dispersant is one or more of polyvinylpyrrolidone, carboxymethylcellulose, sodium carboxymethylcellulose, methylcellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, gelatin, polyacrylic acid, sodium polyacrylate, polyacrylamide, ammonium polyacrylate, potassium polyacrylate, polyvinyl alcohol, gum arabic and polyethylene glycol;
wherein the reducing agent is one or more of hydroxylamine, ethanolamine, diethanolamine, triethanolamine, ferrous nitrate, ferrous acetate, hydrogen peroxide, formic acid, formaldehyde, acetaldehyde, glyoxal, glutaraldehyde, glucose, ascorbic acid, hypophosphorous acid, sodium hypophosphite, hydrazine sulfate, hydrazine hydrate and sodium borohydride;
or:
preparing a flaky acidic compound crystallization template: according to the mass percentage of the surfactant, the acidic compound crystal and the water being (0.1-30.0%): 55.0-95.0%, firstly mixing the water with the surfactant, and stirring and dissolving completely to obtain a surfactant aqueous solution; heating a surfactant aqueous solution to boiling, adding an acid compound crystal, stirring until the acid compound crystal is fully dissolved, and filtering while the solution is hot to obtain a saturated solution of the acid compound crystal; placing the saturated solution of the acid compound crystals in a thermostat controlled at 50 ℃ for cooling and crystallizing, taking the materials out of the thermostat when the temperature of the materials is reduced to 50 ℃, and naturally cooling the materials to room temperature to ensure complete crystallization; filtering the materials to obtain a crude crystallization product of the flaky acidic compound, recycling the mother liquor obtained by filtering, washing the crude crystallization product of the flaky acidic compound for 2-3 times by taking cold water with the temperature of 0-5 ℃ and the mass of the product of the flaky acidic compound being 1-10 times of that of the crystallization product, filtering to obtain crystals, and drying the crystals to obtain a crystallization template of the flaky acidic compound;
preparation of an acidic mixture comprising a crystalline template of a platy acidic compound and a silver salt: according to the mass percentage of water, silver salt, complexing agent, silver plating brightener, dispersant, acid and flaky acidic compound crystallization template being (35.0-95.0%), (0.1-30.0%), (0.001-30.0%), (0.1-30.0%) and (0.1-30.0%), firstly mixing water, silver salt, complexing agent, silver plating brightener, dispersant and acid, stirring until all the materials are completely dissolved, then adding flaky acidic compound crystallization template, stirring and carrying out ultrasonic treatment for 1-60 min, carrying out ultrasonic crushing on the flaky acidic compound crystallization template into flaky crystals with the particle size of 0.5-20.0 mu m, and obtaining an acidic mixture containing the flaky acidic compound crystallization template and silver salt;
preparation of a reducing agent aqueous solution: mixing water and a reducing agent according to the mass percentage of the reducing agent to the water of (0.1-30.0%) to (70.0-99.9%), stirring and dissolving completely to obtain a reducing agent water solution;
preparation of flake silver powder: cooling the acidic mixture containing the flaky acidic compound crystallization template and the silver salt by using a room-temperature cold water bath to maintain the reaction system at room temperature, gradually adding a reducing agent aqueous solution under the stirring condition, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the flaky acidic compound crystallization template until the silver ions completely react; because the flaky acidic compound crystallization template is only slightly soluble in cold water but is dissolved in hot water and boiling water, heating a reaction product to boiling to dissolve the flaky acidic compound crystallization template in the boiling water, filtering while the silver flake crystallization template is hot to obtain a silver flake crude product, washing the silver flake crude product with boiling water for many times, filtering while the silver flake crude product is hot, repeatedly purifying, adding water, stirring and dispersing, ultrasonically crushing for 1-6 hours by ultrasonic waves, filtering, washing with absolute ethyl alcohol, filtering and drying to obtain flaky silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm;
wherein the water used is any one of distilled water, deionized water, ultrapure water and high-purity water;
wherein the acid compound crystal is any one of 4-methoxyphenol, benzoic acid, boric acid, 2, 6-dimethylphenol and sebacic acid;
wherein the ultrasonic wave is the ultrasonic wave with the frequency of 20 KHz-1 MHz and the power of 30W-15 KW;
the flake silver powder prepared by the method has the following technical indexes:
1) appearance: grey to grey black powder;
2) purity: not less than 99.9%;
3) particle size range: 0.050 to 5 μm;
4) average particle size: 0.5 to 3.0 μm;
5) thickness range: 5-60 nm;
6) average thickness: 10-30 nm;
7) apparent density: 2.1-3.2 g/cm3；
8) Tap density: 2.9-4.1 g/cm3；
Wherein the surfactant is selected from sodium dodecyl sulfate, ammonium dodecyl sulfate, potassium dodecyl sulfate, monoethanolamine dodecyl sulfate, diethanolamine dodecyl sulfate, triethanolamine dodecyl sulfate, sodium hexadecyl sulfate, ammonium hexadecyl sulfate, potassium hexadecyl sulfate, monoethanolamine hexadecyl sulfate, diethanolamine hexadecyl sulfate, triethanolamine hexadecyl sulfate, sodium dodecylpolyoxyethylene ether sulfate, ammonium dodecylpolyoxyethylene ether sulfate, potassium dodecylpolyoxyethylene ether sulfate, monoethanolamine dodecyl polyoxyethylene ether sulfate, diethanolamine dodecyl polyoxyethylene ether sulfate, triethanolamine dodecyl sulfate, ammonium hexadecyl sulfonate, potassium hexadecyl sulfonate, monoethanolamine hexadecyl sulfonate, diethanolamine hexadecyl sulfonate, triethanolamine dodecyl sulfate, diethanolamine lauryl sulfate, triethanolamine cetyl sulfate, ammonium hexadecyl sulfonate, potassium hexadecyl sulfonate, diethanolamine hexadecyl sulfonate, triethanolamine cetyl sulfate, diethanolamine cetyl sulfonate, triethanolamine lauryl sulfate, triethanolamine cetyl sulfate, potassium hexadecyl sulfate, triethanolamine cetyl sulfate, triethanolamine lauryl sulfate, diethanolamine cetyl sulfate, triethanolamine lauryl sulfate, triethanolamine cetyl sulfate, triethanolamine lauryl sulfate, triethanolamine lauryl sulfate, triethanolamine cetyl sulfate, diethanolamine, triethanolamine lauryl sulfate, diethanolamine, triethanolamine lauryl sulfate, triethanolamine lauryl sulfate, triethanolamine lauryl sulfate, triethanolamine, diethanolamine, triethanolamine lauryl sulfate, triethanolamine, diethanolamine, triethanolamine, any one or more of triethanolamine hexadecylsulfonate, sodium dodecylbenzenesulfonate, ammonium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, monoethanolamine dodecylbenzenesulfonate, diethanolamine dodecylbenzenesulfonate, triethanolamine dodecylbenzenesulfonate, sodium nonylphenol polyoxyethylene ether sulfate, ammonium nonylphenol polyoxyethylene ether sulfate, potassium nonylphenol polyoxyethylene ether sulfate, monoethanolamine nonylphenol polyoxyethylene ether sulfate, diethanolamine nonylphenol polyoxyethylene ether sulfate, triethanolamine nonylphenol polyoxyethylene ether sulfate, cocamido-propyl betaine, cocamidopropyl betaine, soya oil amidopropyl betaine, octadecyl dimethyl amine oxide, and dodecyl dimethyl amine oxide;
wherein the silver salt is one or more of silver fluoride, silver nitrate, silver citrate, silver lactate, silver tartrate and silver acetate;
wherein the complexing agent is any one or more of N-hydroxyethyl ethylenediamine triacetic acid, N-hydroxyethyl ethylenediamine triacetic acid trisodium, nitrilotriacetic acid trisodium, ethylenediamine tetraacetic acid disodium, citric acid, sodium citrate, potassium citrate, ammonium citrate, tartaric acid, sodium tartrate, potassium tartrate, antimony potassium tartrate and ammonium tartrate;
wherein the used silver plating brightener is HL-SP201A/B, KYU AG-1 bright silver plating additive, Silverstar NM-02 bright silver plating process silvering agent, carbon disulfide, thiourea, potassium xanthate, antimony xanthate, tin xanthate, sodium thiosulfate, ammonium thiosulfate, sulfamic acid, antimony potassium gluconate, antimony potassium tartrate, sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, dithiocarbamic acid, sodium dithiocarbamate, ammonium dithiocarbamate, potassium dithiocarbamate, thiocarbazone, thioglycolic acid, 2-mercaptopropionic acid, any one or more of 2-mercaptonicotinic acid, cystine, 2-mercaptothiazoline, 1-mercaptoglycerol, thiosalicylic acid, thiodiethylene glycol, thioglycolic acid, thiodipropionic acid, thioproline, AG-300 SILVER plating additive and SILVER B/ST bright SILVER plating additive;
wherein the dispersant is one or more of polyvinylpyrrolidone, carboxymethylcellulose, sodium carboxymethylcellulose, methylcellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, gelatin, polyacrylic acid, sodium polyacrylate, polyacrylamide, ammonium polyacrylate, potassium polyacrylate, polyvinyl alcohol, gum arabic and polyethylene glycol;
wherein the acid is any one or more of benzenesulfonic acid, p-toluenesulfonic acid, formic acid, acetic acid, propionic acid, citric acid, tartaric acid, lactic acid, nitric acid, fumaric acid and maleic acid;
wherein the reducing agent is any one or more of ferrous nitrate, ferrous acetate, hydrogen peroxide, formic acid, formaldehyde, acetaldehyde, glyoxal, glutaraldehyde, glucose, ascorbic acid, hypophosphorous acid, hydrazine sulfate, hydrazine hydrate and sodium borohydride;
or:
preparing a flaky basic compound crystallization template: according to the mass percentage of (0.1-30.0%) to (55.0-95.0%) of surfactant, alkaline compound crystal and water, firstly mixing water and surfactant, and stirring and dissolving completely to obtain surfactant aqueous solution; heating a surfactant aqueous solution to boiling, adding an alkaline compound crystal, stirring until the alkaline compound crystal is fully dissolved, and filtering while the solution is hot to obtain a saturated solution of the alkaline compound crystal; placing the saturated solution of the alkaline compound crystal in a thermostat controlled at 50 ℃ for cooling crystallization, taking the material out of the thermostat when the temperature of the material is reduced to 50 ℃, and naturally cooling the material to room temperature to complete crystallization; filtering the materials to obtain a crude crystalline product of the flaky alkaline compound, recycling the mother liquor obtained by filtering, washing the crude crystalline product of the flaky alkaline compound with cold water at 0-5 ℃ of which the mass is 1-10 times that of the crystalline product for 2-3 times according to the mass of the crude crystalline product of the flaky alkaline compound, filtering to obtain crystals, and drying the crystals to obtain a crystalline template of the flaky alkaline compound;
preparation of alkaline mixture containing plate-like alkaline compound crystallization template and silver salt: according to the mass percentage of water, silver salt, complexing agent, silver plating brightener, dispersant, alkali and flaky alkaline compound crystallization template being (35.0-95.0%), (0.1-30.0%), (0.001-30.0%), (0.1-30.0%) and (0.1-30.0%), firstly mixing water, silver salt, complexing agent, silver plating brightener, dispersant and alkali, stirring until all the materials are completely dissolved, then adding flaky alkaline compound crystallization template, stirring and carrying out ultrasonic treatment for 1-60 min, carrying out ultrasonic crushing on the flaky alkaline compound crystallization template into flaky crystals with the particle size of 0.5-20.0 mu m, and obtaining an alkaline mixture containing the flaky alkaline compound crystallization template and silver salt;
preparation of a reducing agent aqueous solution: mixing water and a reducing agent according to the mass percentage of the reducing agent to the water of (0.1-30.0%) to (70.0-99.9%), stirring and dissolving completely to obtain a reducing agent water solution;
preparation of flake silver powder: cooling an alkaline mixture containing a flaky alkaline compound crystallization template and a silver salt by using a room-temperature cold water bath to maintain the reaction system at room temperature, gradually adding a reducing agent aqueous solution under the stirring condition, reducing silver ions into metallic silver, and chemically plating the metallic silver on the surface of the flaky alkaline compound crystallization template until the silver ions are completely reacted; because the flaky alkaline compound crystallization template is only slightly soluble in cold water but is dissolved in hot water and boiling water, a reaction product is heated to boil, the flaky alkaline compound crystallization template is dissolved in the boiling water, the hot silver flake crystallization template is filtered to obtain a silver flake crude product, the obtained silver flake crude product is repeatedly washed by boiling water for many times and filtered for hot time to be purified, and then the silver flake crude product is added with water, stirred, dispersed, ultrasonically crushed for 1-6 hours by ultrasonic waves, filtered, washed by absolute ethyl alcohol, filtered and dried to obtain flaky silver powder with the average particle size of 0.5-3.0 mu m and the average thickness of 10-30 nm;
wherein the water used is any one of distilled water, deionized water, ultrapure water and high-purity water;
wherein the basic compound crystal is any one of acetanilide, p-toluidine, 1-naphthylamine and 2-naphthylamine;
wherein the ultrasonic wave is the ultrasonic wave with the frequency of 20 KHz-1 MHz and the power of 30W-15 KW;
wherein the prepared flake silver powder has the technical indexes that:
1) appearance: grey to grey black powder;
2) purity: not less than 99.9%;
3) particle size range: 0.050 to 5 μm;
4) average particle size: 0.5 to 3.0 μm;
5) thickness range: 5-60 nm;
6) average thickness: 10-30 nm;
7) apparent density: 2.1-3.2 g/cm3；
8) Tap density: 2.9-4.1 g/cm3；
Wherein the surfactant is selected from sodium dodecyl sulfate, ammonium dodecyl sulfate, potassium dodecyl sulfate, monoethanolamine dodecyl sulfate, diethanolamine dodecyl sulfate, triethanolamine dodecyl sulfate, sodium hexadecyl sulfate, ammonium hexadecyl sulfate, potassium hexadecyl sulfate, monoethanolamine hexadecyl sulfate, diethanolamine hexadecyl sulfate, triethanolamine hexadecyl sulfate, sodium dodecylpolyoxyethylene ether sulfate, ammonium dodecylpolyoxyethylene ether sulfate, potassium dodecylpolyoxyethylene ether sulfate, monoethanolamine dodecyl polyoxyethylene ether sulfate, diethanolamine dodecyl polyoxyethylene ether sulfate, triethanolamine dodecyl sulfate, ammonium hexadecyl sulfonate, potassium hexadecyl sulfonate, monoethanolamine hexadecyl sulfonate, diethanolamine hexadecyl sulfonate, triethanolamine dodecyl sulfate, diethanolamine lauryl sulfate, triethanolamine cetyl sulfate, ammonium hexadecyl sulfonate, potassium hexadecyl sulfonate, diethanolamine hexadecyl sulfonate, triethanolamine cetyl sulfate, diethanolamine cetyl sulfonate, triethanolamine lauryl sulfate, triethanolamine cetyl sulfate, potassium hexadecyl sulfate, triethanolamine cetyl sulfate, triethanolamine lauryl sulfate, diethanolamine cetyl sulfate, triethanolamine lauryl sulfate, triethanolamine cetyl sulfate, triethanolamine lauryl sulfate, triethanolamine lauryl sulfate, triethanolamine cetyl sulfate, diethanolamine, triethanolamine lauryl sulfate, diethanolamine, triethanolamine lauryl sulfate, triethanolamine lauryl sulfate, triethanolamine lauryl sulfate, triethanolamine, diethanolamine, triethanolamine lauryl sulfate, triethanolamine, diethanolamine, triethanolamine, any one or more of triethanolamine hexadecylsulfonate, sodium dodecylbenzenesulfonate, ammonium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, monoethanolamine dodecylbenzenesulfonate, diethanolamine dodecylbenzenesulfonate, triethanolamine dodecylbenzenesulfonate, sodium nonylphenol polyoxyethylene ether sulfate, ammonium nonylphenol polyoxyethylene ether sulfate, potassium nonylphenol polyoxyethylene ether sulfate, monoethanolamine nonylphenol polyoxyethylene ether sulfate, diethanolamine nonylphenol polyoxyethylene ether sulfate, triethanolamine nonylphenol polyoxyethylene ether sulfate, cocamido-propyl betaine, cocamidopropyl betaine, soya oil amidopropyl betaine, octadecyl dimethyl amine oxide, and dodecyl dimethyl amine oxide;
wherein the silver salt is one or more of silver fluoride, silver nitrate, silver citrate, silver lactate, silver tartrate and silver acetate;
wherein the complexing agent is any one or more of N-hydroxyethyl ethylenediamine triacetic acid, N-hydroxyethyl ethylenediamine triacetic acid trisodium, nitrilotriacetic acid trisodium, ethylenediamine tetraacetic acid disodium, citric acid, sodium citrate, potassium citrate, ammonium citrate, tartaric acid, sodium tartrate, potassium tartrate, antimony potassium tartrate and ammonium tartrate;
wherein the used silver plating brightener is HL-SP201A/B, KYU AG-1 bright silver plating additive, Silverstar NM-02 bright silver plating process silvering agent, carbon disulfide, thiourea, potassium xanthate, antimony xanthate, tin xanthate, sodium thiosulfate, ammonium thiosulfate, sulfamic acid, antimony potassium gluconate, antimony potassium tartrate, sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, dithiocarbamic acid, sodium dithiocarbamate, ammonium dithiocarbamate, potassium dithiocarbamate, thiocarbazone, thioglycolic acid, 2-mercaptopropionic acid, any one or more of 2-mercaptonicotinic acid, cystine, 2-mercaptothiazoline, 1-mercaptoglycerol, thiosalicylic acid, thiodiethylene glycol, thioglycolic acid, thiodipropionic acid, thioproline, AG-300 SILVER plating additive and SILVER B/ST bright SILVER plating additive;
wherein the dispersant is one or more of polyvinylpyrrolidone, carboxymethylcellulose, sodium carboxymethylcellulose, methylcellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, gelatin, polyacrylic acid, sodium polyacrylate, ammonium polyacrylate, potassium polyacrylate, polyvinyl alcohol, gum arabic and polyethylene glycol;
wherein the alkali is one or more of ammonia, ammonia water, ethylenediamine, n-butylamine, n-pentylamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine;
wherein the reducing agent is one or more of hydroxylamine, ethanolamine, diethanolamine, triethanolamine, formaldehyde, acetaldehyde, glucose, ascorbic acid, sodium hypophosphite, hydrazine hydrate and sodium borohydride.
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