CN110586959A - Preparation method of flake silver powder with high tap density - Google Patents
Preparation method of flake silver powder with high tap density Download PDFInfo
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- CN110586959A CN110586959A CN201911031181.3A CN201911031181A CN110586959A CN 110586959 A CN110586959 A CN 110586959A CN 201911031181 A CN201911031181 A CN 201911031181A CN 110586959 A CN110586959 A CN 110586959A
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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
- 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
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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
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
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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
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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
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/043—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by ball milling
Abstract
The invention relates to a preparation method of flake silver powder with high tap density, which comprises the following steps: step 1: preparing a solution; step 2: carrying out reduction reaction; and step 3: cleaning and filtering; and 4, step 4: ball milling of silver powder; and 5: drying the silver powder; step 6: and sieving and testing the silver powder. The method has the advantages of simple process, good reproducibility of the preparation process and capability of realizing industrial production.
Description
Technical Field
The invention belongs to the field of silver powder preparation, and particularly relates to a preparation method of high-tap-density flaky silver powder.
Background
Along with the acceleration of the localization progress of various electronic components, the manufacturing level of the matched electronic paste is rapidly improved, more subdivided fields require subdivided electronic pastes, and the requirements of the raw silver powder are more specific and diversified. The traditional flake silver powder is more applied to silver paste with lower silver content (the silver content is less than 75%), and because of surface-to-surface contact among powder of the silver powder, the silver powder can provide better conductivity compared with spherical/spheroidal silver powder, but with the development of new varieties, such as HIT silver paste in photovoltaic industry and conductive adhesives of small people, the silver content is required to reach more than 80%, the granularity and the specific surface area are moderate to be suitable for printing, and the traditional flake silver powder can obtain more excellent conductivity and weather resistance at the curing temperature lower than 250 ℃, but can not meet the requirements.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a preparation method of high-tap-density flaky silver powder.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of flake silver powder with high tap density is characterized by comprising the following steps:
step 1: preparing a solution comprising a silver nitrate solution A, a reducing agent solution B, a regulator solution C and a dispersant solution D;
step 2: carrying out reduction reaction, namely slowly adding the regulator solution C into the silver nitrate solution A under high-speed stirring, immediately and quickly adding the reducing agent solution B, quickly adding the dispersing agent solution D within 10s after the reducing agent solution B is added, and adjusting the heating temperature by stages to be respectively between 50 and 90 ℃ for heat preservation reaction after the adding is finished;
and step 3: after the reduction reaction in the step 2 is finished, removing supernatant liquor after the reaction through sedimentation, transferring the rest part into a cleaning barrel, performing back cleaning by deionized water until the conductivity is less than or equal to 20 mu S/cm, and performing suction filtration to remove the supernatant liquor;
and 4, step 4: ball milling silver powder, namely adding the silver powder into a roller ball mill, adding zirconium oxide balls with the diameter of 1-2 mm and 4-6 mm according to the weight which is 3-6 times of the weight of the silver powder, adding a dispersing agent accounting for 0.2-0.5% of the weight of the silver powder, adding ethanol accounting for 50-80% of the weight of the silver powder, ball milling for 2-6 hours at the rotating speed of the ball mill of 50-200 r/min, controlling the particle diameter D50 of the ball-milled silver powder to be 2-5 microns, then separating the ball from the powder, and filtering the silver powder;
and 5: drying the silver powder, and drying the ball-milled flaky silver powder to constant weight at the temperature of 60-80 ℃;
step 6: and (4) sieving and testing the silver powder, and sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product for testing.
Preferably, the preparation method of the high tap density flake silver powder comprises the steps of dissolving silver nitrate in deionized water to prepare a silver nitrate solution with the mass concentration of 2-10 wt%, and controlling the temperature to be 20-60 ℃ to prepare a silver nitrate solution A.
Preferably, the preparation method of the flake silver powder with high tap density comprises the steps of dissolving a reducing agent in deionized water to prepare a reducing agent solution with the concentration of 100-300 g/L, and controlling the temperature in a water bath to be 20-60 ℃ to prepare a reducing agent solution B, wherein the reducing agent is one or more of ascorbic acid, hydrazine hydrate, hydroquinone, sodium hypophosphite, glucose, acetaldehyde, formaldehyde, ethylene glycol and the like;
preferably, in the preparation method of the flake silver powder with high tap density, the regulator solution is prepared by dissolving a regulator in deionized water to prepare the regulator solution with the concentration of 200-800 g/L, and the temperature is controlled to be 20-60 ℃ to prepare the regulator solution C, wherein the regulator is one or more of sodium hydroxide, sodium carbonate and ammonia water;
preferably, in the preparation method of the flake silver powder with high tap density, the dispersant solution is prepared by dissolving a dispersant in deionized water to prepare a dispersant solution with the concentration of 20-100 g/L, and the temperature is controlled to be 50-60 ℃ to prepare a dispersant solution D, wherein the dispersant is one or more of polyvinyl alcohol, polypropylene, polyacrylic acid and hydroxycarboxylic acid.
Preferably, in the preparation method of the high tap density flake silver powder, the dispersant in the step 4 is C6-C18 saturated fatty acid or unsaturated fatty acid or alcohol, and amide surfactant.
Preferably, the preparation method of the high tap density flake silver powder comprises the following steps:
preparation of silver nitrate solution
Accurately weighing 1kg of silver nitrate, dissolving the silver nitrate in 20L of deionized water to prepare a silver nitrate solution with the mass concentration of 4.76 percent by weight, controlling the temperature in a water bath at 22-24 ℃, and stirring for 15min to prepare a silver nitrate solution A;
preparation of reducing agent solution
Accurately weighing 0.75kg of ascorbic acid and 0.01kg of hydrazine hydrate, dissolving in 5L of deionized water, controlling the temperature of the solution at 22-24 ℃, and stirring for 30min to prepare a reducing agent solution B;
preparation of the regulator solution
Dissolving 410g of sodium hydroxide in 1L of deionized water, and adjusting the temperature to 22-24 ℃ to prepare a regulator solution C;
preparation of dispersant solutions
Adding 20g of polyvinyl alcohol into 0.5L of deionized water, heating to 50-55 ℃, and stirring for dissolving to obtain a dispersant solution D;
reduction reaction
Adding the regulator solution C into the silver nitrate solution A at the speed of 100ml/min under the stirring speed of 500 rpm; after the addition, adding the reducing agent solution B within 10s, immediately pouring the dispersing agent solution, continuously stirring, setting the heating temperature to 55 ℃, keeping the temperature for 10min, setting the heating temperature to 60 ℃, and continuously keeping the temperature for 15 min; filtering the silver powder, and cleaning until the conductivity is less than or equal to 20 mu S/cm;
ball milling of silver powder
Adding silver powder into a roller ball mill, adding 4kg of zirconia balls with the diameter of 4mm, adding 1.8g of stearic acid and 0.4kg of ethanol, ball-milling for 5 hours at the rotating speed of the ball mill of 180r/min, separating the balls from the powder, and filtering the silver powder;
drying of silver powder
Drying the ball-milled flaky silver powder at 65 ℃ to constant weight;
sieving and testing silver powder
And sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product, and testing.
Preferably, the preparation method of the high tap density flake silver powder comprises the following steps:
preparation of silver nitrate solution
Accurately weighing 1kg of silver nitrate, dissolving the silver nitrate in 15L of deionized water to prepare a silver nitrate solution with the mass concentration of 6.25 percent by weight, controlling the temperature in a water bath to be 35-37 ℃, and stirring for 15min to prepare a silver nitrate solution A;
preparation of reducing agent solution
Accurately weighing 0.5kg of glucose and 0.12kg of acetaldehyde, dissolving in 5L of deionized water, controlling the temperature of the solution at 35-40 ℃, and stirring for 30min to prepare a reducing agent solution B;
preparation of the regulator solution
Dissolving 480g of sodium carbonate in 1L of deionized water, and adjusting the temperature to 40-45 ℃ to prepare a regulator solution C;
preparation of dispersant solutions
Adding 20g of polyacrylic acid into 0.5L of deionized water, heating to 50-55 ℃, and stirring for dissolving to obtain a dispersant solution D;
reduction reaction
Adding the reducing agent solution C into the silver nitrate solution A at the speed of 100ml/min under the stirring speed of 500 rpm; after the addition, adding the reducing agent solution B within 10s, immediately pouring the dispersing agent solution, continuously stirring, setting the heating temperature to 55 ℃, keeping the temperature for 10min, setting the heating temperature to 60 ℃, and continuously keeping the temperature for 15 min; filtering the silver powder, and cleaning until the conductivity is less than or equal to 20 mu S/cm;
ball milling of silver powder
Adding silver powder into a roller ball mill, adding 3.5kg of zirconia balls with the diameter of 2mm, adding 1g of octanol, 1g of stearic acid and 0.4kg of ethanol, ball-milling at the rotating speed of the ball mill of 120r/min for 3 hours, then separating the balls from the powder, and filtering the silver powder;
drying of silver powder
Drying the ball-milled flaky silver powder at 70 ℃ to constant weight;
sieving and testing silver powder
And sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product, and testing.
Preferably, the preparation method of the high tap density flake silver powder comprises the following steps:
preparation of silver nitrate solution
Accurately weighing 1kg of silver nitrate, dissolving the silver nitrate in 12L of deionized water to prepare a silver nitrate solution with the mass concentration of 7.7 percent by weight, controlling the temperature in a water bath at 40-45 ℃, and stirring for 15min to prepare a silver nitrate solution A;
preparation of reducing agent solution
Accurately weighing 0.9kg of hydroquinone and 0.01kg of glycol, dissolving in 5L of deionized water, controlling the temperature of the solution at 40-45 ℃, and stirring for 30min to prepare a reducing agent solution B;
preparation of the regulator solution
Dissolving 630g of sodium carbonate in 1L of deionized water, and adjusting the temperature to 40-45 ℃ to prepare a regulator solution C;
preparation of dispersant solutions
Adding 10g of hydroxybutyric acid and 5g of oxalic acid into 0.5L of deionized water, heating to 40-45 ℃, and stirring for dissolving to obtain a dispersant solution D;
reduction reaction
Adding the regulator solution C into the silver nitrate solution A at the speed of 50ml/min under the stirring speed of 500 rpm; after the addition, adding the reducing agent solution B within 10s, immediately pouring the dispersing agent solution, continuously stirring, setting the heating temperature to be 60 ℃, keeping the heating temperature for 10min, setting the heating temperature to be 85 ℃, and continuously keeping the heating temperature for 15 min; filtering the silver powder, and cleaning until the conductivity is less than or equal to 20 mu S/cm;
ball milling of silver powder
Adding silver powder into a roller ball mill, adding 4kg of zirconia balls with the diameter of 2mm and 1kg of zirconia balls with the diameter of 5mm, adding 1.5g of oleamide and 0.4kg of ethanol, ball-milling for 5 hours at the rotating speed of the ball mill of 150r/min, separating the balls from the powder, and filtering the silver powder;
drying of silver powder
Drying the ball-milled flaky silver powder at 80 ℃ to constant weight;
sieving and testing silver powder
And sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product, and testing.
By the scheme, the invention at least has the following advantages:
1. according to the invention, the proportion and the dosage of the regulator and the reducing agent are controlled, so that the chemical reduction process has a certain reaction rate, the particle size and the aggregation state of the silver powder in the synthesis process are controlled, the reduced silver powder has a certain aggregation particle size, meanwhile, the dosage of the dispersing agent is less, the organic residue (538 ℃ burning loss) of the silver powder can be kept at a lower level, and the adverse effect of the residual dispersing agent on the electrical property in the application of the silver powder can be reduced.
2. According to the invention, the prepared dispersant solution is added immediately after the oxidizing solution and the reducing solution are quickly mixed, so that the silver powder can form a certain aggregation state before the dispersant is added, the precursor silver powder with large particle size required by the invention is obtained, the silver powder particles are prevented from further aggregation at the later stage, the final silver powder is not too large to cause non-uniformity of the particles, and the controllable dispersion level of the silver powder is ensured.
3. The invention disperses the precursor silver powder which is soft agglomerated by adopting a proper ball-to-material ratio and the using amount of ethanol, and simultaneously leads the precursor silver powder to generate certain shape change to become flaky silver powder with specific indexes, thereby achieving the expected purpose.
4. The preparation method provided by the invention is simple to operate, has low requirements on equipment and has good safety performance. The flake silver powder D50 prepared by the method is 2.0-5.0 microns, thick flake silver powder is obtained, and the tap density is 5.0-6.0 g/cm3A specific surface area of 0.3 to 0.7m2/g。
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is an electron micrograph of a silver flake according to a first embodiment of the present invention;
FIG. 2 is an electron micrograph of a silver flake according to a second embodiment of the present invention;
FIG. 3 is an electron micrograph of a silver flake according to example III of the present invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
Examples
A preparation method of high tap density flake silver powder comprises the following steps:
step 1: preparing a solution comprising a silver nitrate solution A, a reducing agent solution B, a regulator solution C and a dispersant solution D;
step 2: carrying out reduction reaction, namely slowly adding the regulator solution C into the silver nitrate solution A under high-speed stirring, immediately and quickly adding the reducing agent solution B, quickly adding the dispersing agent solution D within 10s after the reducing agent solution B is added, and adjusting the heating temperature by stages to be respectively between 50 and 90 ℃ for heat preservation reaction after the adding is finished;
and step 3: after the reduction reaction in the step 2 is finished, removing supernatant liquor after the reaction through sedimentation, transferring the rest part into a cleaning barrel, performing back cleaning by deionized water until the conductivity is less than or equal to 20 mu S/cm, and performing suction filtration to remove the supernatant liquor;
and 4, step 4: ball milling silver powder, namely adding the silver powder into a roller ball mill, adding zirconium oxide balls with the diameter of 1-2 mm and 4-6 mm according to the weight which is 3-6 times of the weight of the silver powder, adding a dispersing agent accounting for 0.2-0.5% of the weight of the silver powder, adding ethanol accounting for 50-80% of the weight of the silver powder, ball milling for 2-6 hours at the rotating speed of the ball mill of 50-200 r/min, controlling the particle diameter D50 of the ball-milled silver powder to be 2-5 microns, then separating the ball from the powder, and filtering the silver powder;
and 5: drying the silver powder, and drying the ball-milled flaky silver powder to constant weight at the temperature of 60-80 ℃;
step 6: and (4) sieving and testing the silver powder, and sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product for testing.
According to the preparation method of the silver nitrate solution, silver nitrate is dissolved in deionized water to prepare the silver nitrate solution with the mass concentration of 2-10 wt%, and the temperature is controlled to be 20-60 ℃ to prepare the silver nitrate solution A.
The preparation method of the reducing agent solution comprises the steps of dissolving a reducing agent in deionized water to prepare the reducing agent solution with the concentration of 100-300 g/L, and controlling the temperature in a water bath to be 20-60 ℃ to prepare the reducing agent solution B, wherein the reducing agent is one or more of ascorbic acid, hydrazine hydrate, hydroquinone, sodium hypophosphite, glucose, acetaldehyde, formaldehyde, ethylene glycol and the like;
the preparation method of the regulator solution comprises the steps of dissolving a regulator in deionized water to prepare the regulator solution with the concentration of 200-800 g/L, and controlling the temperature to be 20-60 ℃ to prepare the regulator solution C, wherein the regulator is one or more of sodium hydroxide, sodium carbonate and ammonia water;
the preparation method of the dispersing agent solution comprises the steps of dissolving a dispersing agent in deionized water to prepare the dispersing agent solution with the concentration of 20-100 g/L, and controlling the temperature to be 50-60 ℃ to prepare the dispersing agent solution D, wherein the dispersing agent is one or more of polyvinyl alcohol, polypropylene, polyacrylic acid and hydroxycarboxylic acid.
The dispersant in the step 4 is C6-C18 saturated fatty acid or unsaturated fatty acid or alcohol, and amide surfactant.
Example one
A preparation method of high tap density flake silver powder comprises the following steps:
preparation of silver nitrate solution
Accurately weighing 1kg of silver nitrate, dissolving the silver nitrate in 20L of deionized water to prepare a silver nitrate solution with the mass concentration of 4.76 percent by weight, controlling the temperature in a water bath at 22-24 ℃, and stirring for 15min to prepare a silver nitrate solution A;
preparation of reducing agent solution
Accurately weighing 0.75kg of ascorbic acid and 0.01kg of hydrazine hydrate, dissolving in 5L of deionized water, controlling the temperature of the solution at 22-24 ℃, and stirring for 30min to prepare a reducing agent solution B;
preparation of the regulator solution
Dissolving 410g of sodium hydroxide in 1L of deionized water, and adjusting the temperature to 22-24 ℃ to prepare a regulator solution C;
preparation of dispersant solutions
Adding 20g of polyvinyl alcohol into 0.5L of deionized water, heating to 50-55 ℃, and stirring for dissolving to obtain a dispersant solution D;
reduction reaction
Adding the regulator solution C into the silver nitrate solution A at the speed of 100ml/min under the stirring speed of 500 rpm; after the addition, adding the reducing agent solution B within 10s, immediately pouring the dispersing agent solution, continuously stirring, setting the heating temperature to 55 ℃, keeping the temperature for 10min, setting the heating temperature to 60 ℃, and continuously keeping the temperature for 15 min; filtering the silver powder, and cleaning until the conductivity is less than or equal to 20 mu S/cm;
ball milling of silver powder
Adding silver powder into a roller ball mill, adding 4kg of zirconia balls with the diameter of 4mm, adding 1.8g of stearic acid and 0.4kg of ethanol, ball-milling for 5 hours at the rotating speed of the ball mill of 180r/min, separating the balls from the powder, and filtering the silver powder;
drying of silver powder
Drying the ball-milled flaky silver powder at 65 ℃ to constant weight;
sieving and testing silver powder
And sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product, and testing.
As shown in fig. 1, the test results in the first example are as follows, and the test data are as follows, D10 ═ 2.2 μm, D50 ═ 4.3 μm, D90 ═ 7.5 μm, and D100 ═ 13.1 μm; specific surface area 0.32m2(g), tap density 5.35g/cm30.24% of burning loss at 538 ℃ and thick sheet shape.
Example two
A preparation method of high tap density flake silver powder comprises the following steps:
preparation of silver nitrate solution
Accurately weighing 1kg of silver nitrate, dissolving the silver nitrate in 15L of deionized water to prepare a silver nitrate solution with the mass concentration of 6.25 percent by weight, controlling the temperature in a water bath to be 35-37 ℃, and stirring for 15min to prepare a silver nitrate solution A;
preparation of reducing agent solution
Accurately weighing 0.5kg of glucose and 0.12kg of acetaldehyde, dissolving in 5L of deionized water, controlling the temperature of the solution at 35-40 ℃, and stirring for 30min to prepare a reducing agent solution B;
preparation of the regulator solution
Dissolving 480g of sodium carbonate in 1L of deionized water, and adjusting the temperature to 40-45 ℃ to prepare a regulator solution C;
preparation of dispersant solutions
Adding 20g of polyacrylic acid into 0.5L of deionized water, heating to 50-55 ℃, and stirring for dissolving to obtain a dispersant solution D;
reduction reaction
Adding the reducing agent solution C into the silver nitrate solution A at the speed of 100ml/min under the stirring speed of 500 rpm; after the addition, adding the reducing agent solution B within 10s, immediately pouring the dispersing agent solution, continuously stirring, setting the heating temperature to 55 ℃, keeping the temperature for 10min, setting the heating temperature to 60 ℃, and continuously keeping the temperature for 15 min; filtering the silver powder, and cleaning until the conductivity is less than or equal to 20 mu S/cm;
ball milling of silver powder
Adding silver powder into a roller ball mill, adding 3.5kg of zirconia balls with the diameter of 2mm, adding 1g of octanol, 1g of stearic acid and 0.4kg of ethanol, ball-milling at the rotating speed of the ball mill of 120r/min for 3 hours, then separating the balls from the powder, and filtering the silver powder;
drying of silver powder
Drying the ball-milled flaky silver powder at 70 ℃ to constant weight;
sieving and testing silver powder
And sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product, and testing.
As shown in fig. 2, the test results in example two above are as follows, D10 ═ 1.58 μm, D50 ═ 3.69 μm, D90 ═ 7.55 μm, and D100 ═ 12.7 μm; specific surface area 0.39m2(g), tap density 5.86g/cm30.26% of burning loss at 538 ℃ and thick sheet shape.
EXAMPLE III
A preparation method of high tap density flake silver powder comprises the following steps:
preparation of silver nitrate solution
Accurately weighing 1kg of silver nitrate, dissolving the silver nitrate in 12L of deionized water to prepare a silver nitrate solution with the mass concentration of 7.7 percent by weight, controlling the temperature in a water bath at 40-45 ℃, and stirring for 15min to prepare a silver nitrate solution A;
preparation of reducing agent solution
Accurately weighing 0.9kg of hydroquinone and 0.01kg of glycol, dissolving in 5L of deionized water, controlling the temperature of the solution at 40-45 ℃, and stirring for 30min to prepare a reducing agent solution B;
preparation of the regulator solution
Dissolving 630g of sodium carbonate in 1L of deionized water, and adjusting the temperature to 40-45 ℃ to prepare a regulator solution C;
preparation of dispersant solutions
Adding 10g of hydroxybutyric acid and 5g of oxalic acid into 0.5L of deionized water, heating to 40-45 ℃, and stirring for dissolving to obtain a dispersant solution D;
reduction reaction
Adding the regulator solution C into the silver nitrate solution A at the speed of 50ml/min under the stirring speed of 500 rpm; after the addition, adding the reducing agent solution B within 10s, immediately pouring the dispersing agent solution, continuously stirring, setting the heating temperature to be 60 ℃, keeping the heating temperature for 10min, setting the heating temperature to be 85 ℃, and continuously keeping the heating temperature for 15 min; filtering the silver powder, and cleaning until the conductivity is less than or equal to 20 mu S/cm;
ball milling of silver powder
Adding silver powder into a roller ball mill, adding 4kg of zirconia balls with the diameter of 2mm and 1kg of zirconia balls with the diameter of 5mm, adding 1.5g of oleamide and 0.4kg of ethanol, ball-milling for 5 hours at the rotating speed of the ball mill of 150r/min, separating the balls from the powder, and filtering the silver powder;
drying of silver powder
Drying the ball-milled flaky silver powder at 80 ℃ to constant weight;
sieving and testing silver powder
And sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product, and testing.
As shown in fig. 3, the test results in example three above are as follows, D10 ═ 1.35 μm, D50 ═ 2.43 μm, D90 ═ 6.44 μm, and D100 ═ 10.5 μm; specific surface area 0.57m2(g), tap density 5.47g/cm30.35% of 538 ℃ burning loss, uniform silver powder distribution and thick flake shape.
The invention has at least the following advantages:
1. according to the invention, the proportion and the dosage of the regulator and the reducing agent are controlled, so that the chemical reduction process has a certain reaction rate, the particle size and the aggregation state of the silver powder in the synthesis process are controlled, the reduced silver powder has a certain aggregation particle size, meanwhile, the dosage of the dispersing agent is less, the organic residue (538 ℃ burning loss) of the silver powder can be kept at a lower level, and the adverse effect of the residual dispersing agent on the electrical property in the application of the silver powder can be reduced.
2. According to the invention, the prepared dispersant solution is added immediately after the oxidizing solution and the reducing solution are quickly mixed, so that the silver powder can form a certain aggregation state before the dispersant is added, the precursor silver powder with large particle size required by the invention is obtained, the silver powder particles are prevented from further aggregation at the later stage, the final silver powder is not too large to cause non-uniformity of the particles, and the controllable dispersion level of the silver powder is ensured.
3. The invention disperses the precursor silver powder which is soft agglomerated by adopting a proper ball-to-material ratio and the using amount of ethanol, and simultaneously leads the precursor silver powder to generate certain shape change to become flaky silver powder with specific indexes, thereby achieving the expected purpose.
4. The preparation method provided by the invention is simple to operate, has low requirements on equipment and has good safety performance. The flake silver powder D50 prepared by the method is 2.0-5.0 microns, thick flake silver powder is obtained, and the tap density is 5.0-6.0 g/cm3A specific surface area of 0.3 to 0.7m2/g。
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A preparation method of flake silver powder with high tap density is characterized by comprising the following steps:
step 1: preparing a solution comprising a silver nitrate solution A, a reducing agent solution B, a regulator solution C and a dispersant solution D;
step 2: carrying out reduction reaction, namely slowly adding the regulator solution C into the silver nitrate solution A under high-speed stirring, immediately and quickly adding the reducing agent solution B, quickly adding the dispersing agent solution D within 10s after the reducing agent solution B is added, and adjusting the heating temperature by stages to be 50-90 ℃ for heat preservation reaction respectively after the adding is finished;
and step 3: after the reduction reaction in the step 2 is finished, removing supernatant liquor after the reaction through sedimentation, transferring the rest part into a cleaning barrel, performing back cleaning by deionized water until the conductivity is less than or equal to 20 mu S/cm, and performing suction filtration to remove the supernatant liquor;
and 4, step 4: ball milling silver powder, namely adding the silver powder into a roller ball mill, adding zirconium oxide balls with the diameter of 1-2 mm and 4-6 mm according to the weight which is 3-6 times of the weight of the silver powder, adding a dispersing agent accounting for 0.2-0.5% of the weight of the silver powder, adding ethanol accounting for 50-80% of the weight of the silver powder, ball milling for 2-6 hours at the rotating speed of the ball mill of 50-200 r/min, controlling the particle diameter D50 of the ball-milled silver powder to be 2-5 microns, then separating the ball from the powder, and filtering the silver powder;
and 5: drying the silver powder, and drying the ball-milled flaky silver powder to constant weight at the temperature of 60-80 ℃;
step 6: and (4) sieving and testing the silver powder, and sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product for testing.
2. The method for preparing a high tap density silver flake according to claim 1, wherein: and preparing a silver nitrate solution A by dissolving silver nitrate in deionized water to prepare the silver nitrate solution with the mass concentration of 2-10 wt%, and controlling the temperature to be 20-60 ℃.
3. The method for preparing a high tap density silver flake according to claim 1, wherein: the preparation method of the reducing agent solution comprises the steps of dissolving a reducing agent in deionized water to prepare the reducing agent solution with the concentration of 100-300 g/L, and controlling the temperature in a water bath to be 20-60 ℃ to prepare the reducing agent solution B, wherein the reducing agent is one or more of ascorbic acid, hydrazine hydrate, hydroquinone, sodium hypophosphite, glucose, acetaldehyde, formaldehyde, ethylene glycol and the like.
4. The method for preparing a high tap density silver flake according to claim 1, wherein: and (2) preparing a regulator solution, namely dissolving a regulator in deionized water to prepare the regulator solution with the concentration of 200-800 g/L, and controlling the temperature to be 20-60 ℃ to prepare a regulator solution C, wherein the regulator is one or more of sodium hydroxide, sodium carbonate and ammonia water.
5. The method for preparing a high tap density silver flake according to claim 1, wherein: the preparation method of the dispersing agent solution comprises the steps of dissolving a dispersing agent in deionized water to prepare a dispersing agent solution with the concentration of 20-100 g/L, and controlling the temperature to be 50-60 ℃ to prepare a dispersing agent solution D, wherein the dispersing agent is one or more of polyvinyl alcohol, polypropylene, polyacrylic acid and hydroxycarboxylic acid.
6. The method for preparing a high tap density silver flake according to claim 1, wherein: the dispersant in the step 4 is C6-C18 saturated fatty acid or unsaturated fatty acid or alcohol, and amide surfactant.
7. The method for producing a high tap density silver flake according to any one of claims 1 to 6, comprising the steps of:
preparation of silver nitrate solution
Accurately weighing 1kg of silver nitrate, dissolving the silver nitrate in 20L of deionized water to prepare a silver nitrate solution with the mass concentration of 4.76 wt%, controlling the temperature to be 22-24 ℃, and stirring for 15min to prepare a silver nitrate solution A;
preparation of reducing agent solution
Accurately weighing 0.75kg of ascorbic acid and 0.01kg of hydrazine hydrate, dissolving in 5L of deionized water, controlling the temperature of the solution at 22-24 ℃, and stirring for 30min to prepare a reducing agent solution B;
preparation of the regulator solution
Dissolving 410g of sodium hydroxide in 1L of deionized water, and adjusting the temperature to 22-24 ℃ to prepare a regulator solution C;
preparation of dispersant solutions
Adding 20g of polyvinyl alcohol into 0.5L of deionized water, heating to 50-55 ℃, and stirring for dissolving to obtain a dispersant solution D;
reduction reaction
Adding the regulator solution C into the silver nitrate solution A at the speed of 100ml/min under the stirring speed of 500 rpm; after the addition, adding the reducing agent solution B within 10s, immediately pouring the dispersing agent solution, continuously stirring, setting the heating temperature to 55 ℃, keeping the temperature for 10min, setting the heating temperature to 60 ℃, and continuously keeping the temperature for 15 min; filtering the silver powder, and cleaning until the conductivity is less than or equal to 20 mu S/cm;
ball milling of silver powder
Adding silver powder into a roller ball mill, adding 4kg of zirconia balls with the diameter of 4mm, adding 1.8g of stearic acid and 0.4kg of ethanol, ball-milling for 5 hours at the rotating speed of the ball mill of 180r/min, separating the balls from the powder, and filtering the silver powder;
drying of silver powder
Drying the ball-milled flaky silver powder at 65 ℃ to constant weight;
sieving and testing silver powder
And sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product, and testing.
8. The method for producing a high tap density silver flake according to any one of claims 1 to 6, comprising the steps of:
preparation of silver nitrate solution
Accurately weighing 1kg of silver nitrate, dissolving the silver nitrate in 15L of deionized water to prepare a silver nitrate solution with the mass concentration of 6.25 wt%, and stirring the silver nitrate solution for 15min at the temperature of between 35 and 37 ℃ to prepare a silver nitrate solution A;
preparation of reducing agent solution
Accurately weighing 0.5kg of glucose and 0.12kg of acetaldehyde, dissolving in 5L of deionized water, controlling the temperature of the solution at 35-40 ℃, and stirring for 30min to prepare a reducing agent solution B;
preparation of the regulator solution
Dissolving 480g of sodium carbonate in 1L of deionized water, and adjusting the temperature to 40-45 ℃ to prepare a regulator solution C;
preparation of dispersant solutions
Adding 20g of polyacrylic acid into 0.5L of deionized water, heating to 50-55 ℃, and stirring for dissolving to obtain a dispersant solution D;
reduction reaction
Adding the reducing agent solution C into the silver nitrate solution A at the speed of 100ml/min under the stirring speed of 500 rpm; after the addition, adding the reducing agent solution B within 10s, immediately pouring the dispersing agent solution, continuously stirring, setting the heating temperature to 55 ℃, keeping the temperature for 10min, setting the heating temperature to 60 ℃, and continuously keeping the temperature for 15 min; filtering the silver powder, and cleaning until the conductivity is less than or equal to 20 mu S/cm;
ball milling of silver powder
Adding silver powder into a roller ball mill, adding 3.5kg of zirconia balls with the diameter of 2mm, adding 1g of octanol, 1g of stearic acid and 0.4kg of ethanol, ball-milling at the rotating speed of the ball mill of 120r/min for 3 hours, then separating the balls from the powder, and filtering the silver powder;
drying of silver powder
Drying the ball-milled flaky silver powder at 70 ℃ to constant weight;
sieving and testing silver powder
And sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product, and testing.
9. The method for producing a high tap density silver flake according to any one of claims 1 to 6, comprising the steps of:
preparation of silver nitrate solution
Accurately weighing 1kg of silver nitrate, dissolving the silver nitrate in 12L of deionized water to prepare a silver nitrate solution with the mass concentration of 7.7 wt%, controlling the temperature to be 40-45 ℃, and stirring for 15min to prepare a silver nitrate solution A;
preparation of reducing agent solution
Accurately weighing 0.9kg of hydroquinone and 0.01kg of glycol, dissolving in 5L of deionized water, controlling the temperature of the solution at 40-45 ℃, and stirring for 30min to prepare a reducing agent solution B;
preparation of the regulator solution
Dissolving 630g of sodium carbonate in 1L of deionized water, and adjusting the temperature to 40-45 ℃ to prepare a regulator solution C;
preparation of dispersant solutions
Adding 10g of hydroxybutyric acid and 5g of oxalic acid into 0.5L of deionized water, heating to 40-45 ℃, and stirring for dissolving to obtain a dispersant solution D;
reduction reaction
Adding the regulator solution C into the silver nitrate solution A at the speed of 50ml/min under the stirring speed of 500 rpm; after the addition, adding the reducing agent solution B within 10s, immediately pouring the dispersing agent solution, continuously stirring, setting the heating temperature to be 60 ℃, keeping the heating temperature for 10min, setting the heating temperature to be 85 ℃, and continuously keeping the heating temperature for 15 min; filtering the silver powder, and cleaning until the conductivity is less than or equal to 20 mu S/cm;
ball milling of silver powder
Adding silver powder into a roller ball mill, adding 4kg of zirconia balls with the diameter of 2mm and 1kg of zirconia balls with the diameter of 5mm, adding 1.5g of oleamide and 0.4kg of ethanol, ball-milling for 5 hours at the rotating speed of the ball mill of 150r/min, separating the balls from the powder, and filtering the silver powder;
drying of silver powder
Drying the ball-milled flaky silver powder to constant weight at the temperature of 60-80 ℃;
sieving and testing silver powder
And sieving the dried silver powder by using a 200-mesh screen to obtain a flaky silver powder product, and testing.
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