Disclosure of Invention
In order to solve the problems, the large-particle silver powder with the supporting edge structure and the preparation method and application thereof are provided, the large-particle silver powder consists of single-crystal silver powder and a convex supporting edge column structure on the surface of the single-crystal silver powder, the production of the large-particle silver powder with the supporting edge structure and the particle diameter of which is 5-10 microns is realized, the particle diameter of the large-particle silver powder with the supporting edge structure can be controlled within a certain range, the crystallinity of the large-particle silver powder with the supporting edge structure is high, and the conductive performance of the large-particle silver powder with the supporting edge structure is not influenced while the bonding strength of low-temperature slurry and conductive adhesive is improved; the preparation method has the advantages of simple steps, mild reaction conditions, short production period, good repeatability, energy conservation and environmental protection, and is suitable for industrial amplification and industrial application.
According to one aspect of the present application, there is provided a large-particle silver powder having a prismatic structure, the large-particle silver powder being composed of a single-crystal silver powder and a convex prismatic structure on a surface thereof, the large-particle silver powder having an approximately spherical morphology and a particle diameter of 5 to 10 μm.
Optionally, the height of the prismatic column is not more than 3 microns, and in a large-particle silver powder with a prismatic structure, the number ratio of the single-crystal silver powder to the prismatic column is 1: (2-8).
Preferably, the height of the prismatic column is 3 microns, and the number ratio of the single crystal silver powder to the prismatic column in a large particle silver powder with a prismatic structure is 1: (4-8).
According to still another aspect of the present application, there is provided a method for preparing the large particle silver powder having a ridge structure, including the steps of:
1) liquid preparation
Solution A: adding silver nitrate into water, stirring and dissolving, and adding a proper amount of acid liquor to prepare a solution A;
solution B: adding a dispersing agent into water, stirring and dissolving to prepare a solution B;
solution C: adding ascorbic acid into water, stirring and dissolving to prepare a solution C;
preparing two parts of solution A, solution B and solution C respectively;
2) preparation of microcrystalline silver powder
a. Adding a proper amount of acid liquor into the solution B, and adjusting the pH value to 3-5;
b. simultaneously adding a portion of all of said solution a and a portion of all of said solution C to said solution B under continuous stirring;
3) preparation of large-particle silver powder with supporting edge structure
a. Taking a proper amount of the solution after the reaction in the step 2), wherein the mass of the microcrystalline silver in the solution is 2-20% of that of the silver nitrate in the solution A, and adding the solution into the other solution B;
b. simultaneously adding another portion of all of said solution a and another portion of all of said solution C to the continuously stirred solution obtained in step a) of step 3);
c. adding a proper amount of pH regulator into the reactant obtained in the step b in the step 3), regulating the pH to 4-7, and then adding a surfactant;
4) post-treatment
And 3) carrying out solid-liquid separation on the reactant finally obtained in the step 3), washing and drying to obtain the large-particle silver powder with the supporting edge structure.
Preferably, in the step a of the step 3), a proper amount of the solution after the reaction of the step 2) is finished is taken, and the mass of the microcrystalline silver in the solution is 5-15% of the mass of the silver nitrate in the solution A, and the solution is added into another part of the solution B.
Preferably, in the step B of the step 2), the solution A and the solution C are added into the solution B which is continuously stirred at the same flow rate and constant speed in a parallel flow mode, and the adding time is 20-40 minutes.
Preferably, another part of the solution A and another part of the solution C in the step B of the step 3) are added into another part of the solution B which is continuously stirred at the same flow rate and constant speed in a parallel flow manner, and the adding time is 20-40 minutes.
Preferably, the stirring rate in step 2) and step 3) is 100-.
Optionally, the reaction temperature in step b of step 2) is 20-24 ℃; the grain size of the microcrystalline silver powder prepared in the step 2) is not more than 3 microns.
Preferably, the reaction temperature in step b of step 2) is 20-23 ℃, and the reaction temperature in step b of step 3) is room temperature; the grain size of the microcrystalline silver powder prepared in the step 2) is 3 micrometers.
Optionally, the concentration of the solution A is 1-10 mol/L;
the using amount of the dispersing agent in the solution B is 0.1-1.0 time of the mass of the silver nitrate in the solution A, and the using amount of water in the solution B is 1.0-5.0 times of the using amount of water in the solution A;
the dosage of the ascorbic acid in the solution C is 0.5-2.0 times of the molar weight of the silver nitrate in the solution A, and the dosage of water in the solution C is the same as that of the water in the solution A.
Preferably, the concentration of the solution A is 1-2 mol/L;
the using amount of the dispersing agent in the solution B is 0.1-0.5 time of the mass of the silver nitrate in the solution A, and the using amount of water in the solution B is 1.0-1.5 times of the using amount of water in the solution A;
the dosage of the ascorbic acid in the solution C is 0.5-0.7 time of the molar amount of the silver nitrate in the solution A.
More preferably, the amount of the dispersant in the solution B is 0.25 to 0.5 times the mass of the silver nitrate in the solution A.
Optionally, the acid solution is concentrated nitric acid, and the amount of the concentrated nitric acid in the solution A is 0.05-0.5 times of the mass of the silver nitrate.
Optionally, the dispersant is any one of polyvinylpyrrolidone K10, polyvinylpyrrolidone K20, or polyvinylpyrrolidone K30.
Preferably, the dispersant is polyvinylpyrrolidone K30.
Optionally, the PH adjuster is any one of ammonia, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium carbonate, sodium hydroxide, or potassium hydroxide.
Preferably, the pH regulator is ammonia water.
Optionally, the surfactant is aliphatic carboxylic acid, and the dosage of the surfactant is 0.5-5.0% of the mass of the silver nitrate in the solution A.
Preferably, the dosage of the surfactant is 1.0-2.0% of the mass of the silver nitrate in the solution A.
Preferably, the surfactant is any one of caprylic acid, lauric acid, stearic acid or oleic acid.
According to still another aspect of the present application, there is provided a use of the above large particle silver powder having a ridge structure in a low temperature silver paste and a low temperature conductive paste.
In this application, "water" refers to deionized water at room temperature of 25 ℃.
Benefits of the present application include, but are not limited to:
1. according to the large-particle silver powder with the supporting edge structure, the large-particle silver powder is composed of the single-crystal silver powder and the protruding supporting edge column structure on the surface of the single-crystal silver powder, the production of the large-particle silver powder with the supporting edge structure and the particle size of the large-particle silver powder with the supporting edge structure is 5-10 micrometers, and the particle size of the large-particle silver powder with the supporting edge structure can be controlled within a certain range; this large granule silver powder crystallinity is high, and the arris structure on silver powder surface can reduce the cohesiveness between the silver powder, has strengthened the dispersibility of silver powder, nevertheless also can increase the area of contact between the silver powder when guaranteeing certain cohesive strength, has improved electric conductive property.
2. According to the preparation method of the large-particle silver powder with the supporting edge structure, the microcrystalline silver powder of 3 micrometers is firstly synthesized, the solution obtained after the reaction in the step 2) with the limited proportion is added into the other solution B, and then the large-particle silver powder is continuously synthesized, so that the convex supporting edge structure of 3 micrometers is formed on the surface of the large-particle silver powder, the silver powder with the supporting edge structure is deposited in the low-temperature slurry and the conductive adhesive more three-dimensionally, the comprehensive performance is excellent, and the weather resistance is good.
3. According to the preparation method of the large-particle silver powder with the supporting edge structure, the solution A and the solution C are added into the solution B which is continuously stirred at the constant speed in the parallel flow mode at the same flow rate in the step 2) and the step 3), so that the phenomenon that the reaction is uneven and the particle size is uncontrollable due to the fact that the adding speeds of the silver nitrate solution and the ascorbic acid solution are different is avoided.
4. According to the preparation method of the large-particle silver powder with the branch edge structure, the reaction temperature in the step 2) is limited to be lower than room temperature, so that the grain diameter and the appearance of the microcrystalline silver powder are controllable.
5. According to the preparation method of the large-particle silver powder with the branch edge structure, the surface active agent is added, so that the dispersibility of the silver powder can be improved, the surface of the silver powder can be lipophilic, the surface of the silver powder is hydrophobic, and the subsequent treatment is facilitated.
6. According to the preparation method of the large-particle silver powder with the supporting edge structure, the preparation method is simple in steps, mild in reaction conditions, short in production period, good in repeatability, energy-saving and environment-friendly, and suitable for industrial amplification and industrial application.
Detailed Description
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
Unless otherwise specified, the starting materials and catalysts in the examples of the present application were purchased commercially, wherein concentrated nitric acid, concentrated hydrochloric acid and ammonia were analytically pure concentrations, the mass fraction of concentrated nitric acid was 65%, the mass fraction of concentrated hydrochloric acid was 37% and the mass fraction of ammonia was 25%.
The silver powder particle size distribution is detected by a Malvern 2000 particle size instrument, the silver powder morphology is detected by an aspect S50 scanning electron microscope, the silver powder specific surface area is tested by a QDS-30 full-automatic nitrogen adsorption specific surface instrument, the silver powder ignition weightlessness is tested by a high-temperature furnace YX1207, and the tap density is tested by a BT-302 tap density instrument.
Example 1 preparation of Large particle silver powder 1# having a Rib Structure with a particle diameter of 6 μm
1) Liquid preparation
Solution A: dissolving 500 g of silver nitrate in 2750 g of deionized water, stirring and dissolving, and adding 25 g of concentrated nitric acid to prepare a silver nitrate solution A. Wherein the concentration of the silver nitrate solution is 1.0mol/L, and the dosage of the concentrated nitric acid is 0.05 times of the mass of the silver nitrate;
solution B: 250 g of dispersant polyvinylpyrrolidone K30 is dissolved in 3300 g of deionized water, and then the solution is stirred and dissolved to prepare dispersant solution B. Wherein the using amount of the dispersing agent is 0.5 time of the mass of the silver nitrate in the solution A; the dosage of the deionized water in the solution B is 1.2 times of that in the solution A;
solution C: dissolving 360 g of ascorbic acid in 2750 g of deionized water, stirring and dissolving to prepare an ascorbic acid solution C. Wherein the dosage of the ascorbic acid in the solution C is 0.7 times of the molar weight of the silver nitrate in the solution A;
preparing two identical parts of solution A, solution B and solution C respectively;
2) preparation of 3 micron microcrystalline silver powder
a. Adding 16 g of analytically pure concentrated nitric acid into the solution B, wherein the pH value of the solution is 4;
b. adding one part of the solution A and one part of the solution C into one part of the solution B which is continuously stirred at the flow rate of 100ml/min in a cocurrent mode, carrying out oxidation reduction to generate silver microcrystals, wherein the adding time is 30 minutes, and the temperature of the solution is controlled to be 21 ℃ in the reaction process;
3) preparation of large-particle silver powder with supporting edge structure
a. Taking 1241g of microcrystalline silver powder solution after the reaction in the step 2), wherein the mass of the microcrystalline silver is 12.5% of that of the silver nitrate in the solution A, and adding the microcrystalline silver powder solution into the other solution B;
b. simultaneously adding another portion of all of said solution a and another portion of all of said solution C to the continuously stirred solution obtained in step a) of step 3) at a flow rate of 100ml/min for a period of 30 minutes;
c. adding 360 g of analytically pure ammonia water into the reactant obtained in the step b) in the step 3), adjusting the pH value to be 6, and adding 15 g of caprylic acid, wherein the using amount of the surfactant caprylic acid is 3.0% of the mass of the silver nitrate in the solution A;
3) post-treatment
And (3) carrying out solid-liquid separation on the reactant, washing and drying to obtain 354 g of large-particle silver powder with a supporting prism structure, wherein the height of the supporting prism on the surface is 3 micrometers, and the average particle size of the silver powder is 6 micrometers.
Example 2 preparation of Large particle silver powder 2# having a Rib Structure with a particle diameter of 8 μm
1) Liquid preparation
First portion of solution a: dissolving 750 g of silver nitrate in 2750 g of deionized water, stirring and dissolving, and adding 60 g of concentrated nitric acid to prepare a silver nitrate solution A. Wherein the concentration of the silver nitrate solution is 1.5mol/L, and the dosage of the concentrated nitric acid is 0.08 times of the mass of the silver nitrate;
second part solution a: 760 g of silver nitrate is dissolved in 2750 g of deionized water, stirred and dissolved, and 60 g of concentrated nitric acid is added to prepare a silver nitrate solution A. Wherein the concentration of the silver nitrate solution is 1.6mol/L, and the dosage of the concentrated nitric acid is 0.079 times of the mass of the silver nitrate;
first portion of solution B: 300 g of dispersant polyvinylpyrrolidone K30 is dissolved in 3850 g of deionized water, and then the dispersant solution B is prepared by stirring and dissolving. Wherein the using amount of the dispersing agent is 0.4 time of the mass of the silver nitrate in the solution A; the dosage of the deionized water in the solution B is 1.4 times of that in the solution A;
second part solution B: 300 g of dispersant polyvinylpyrrolidone K30 is dissolved in 3575 g of deionized water, stirred and dissolved to prepare dispersant solution B. Wherein the using amount of the dispersing agent is 0.4 time of the mass of the silver nitrate in the solution A; the dosage of the deionized water in the solution B is 1.3 times of that in the solution A;
first portion solution C: 460 g of ascorbic acid is dissolved in 2750 g of deionized water, and then the ascorbic acid solution C is prepared by stirring and dissolving. Wherein the dosage of the ascorbic acid in the solution C is 0.6 times of the molar weight of the silver nitrate in the solution A;
second part solution C: dissolving 550 g of ascorbic acid in 2750 g of deionized water, stirring and dissolving to prepare an ascorbic acid solution C. Wherein the dosage of the ascorbic acid in the solution C is 0.7 times of the molar weight of the silver nitrate in the solution A;
2) preparation of 3 micron microcrystalline silver powder
a. Adding 18 g of analytically pure concentrated nitric acid to the solution B, wherein the pH value of the solution is 4;
b. adding the first solution A and the first solution C into the continuously stirred first solution B at the flow rate of 100ml/min in a concurrent manner, carrying out oxidation reduction to generate silver microcrystals, wherein the adding time is 30 minutes, and the temperature of the solutions is controlled at 23 ℃ in the reaction process;
3) preparation of large-particle silver powder with supporting edge structure
a. Taking 580g of microcrystalline silver powder solution after the reaction in the step 2), wherein the mass of the microcrystalline silver is 5.27% of that of the silver nitrate in the solution A, and adding the microcrystalline silver powder solution into the second solution B;
b. simultaneously adding a second portion of all of said solution a and a second portion of all of said solution C to the continuously stirred solution obtained in step a) of step 3) at a flow rate of 100ml/min for a period of 30 minutes;
c. adding 420 g of analytically pure ammonia water into the reactant obtained in the step b) in the step 3), adjusting the pH value to 6, and adding 15 g of lauric acid, wherein the dosage of surfactant lauric acid is 2.0% of the mass of silver nitrate in the solution A;
3) post-treatment
And (3) carrying out solid-liquid separation on the reactant, washing and drying to obtain 500 g of large-particle silver powder with a supporting prism structure, wherein the height of the supporting prism on the surface is 3 micrometers, and the average particle size of the silver powder is 8 micrometers.
Example 3 preparation of Large particle silver powder 3# having a Rib Structure with a particle diameter of 7 μm
1) Liquid preparation
Solution A: dissolving 750 g of silver nitrate in 2750 g of deionized water, stirring and dissolving, and adding 60 g of concentrated nitric acid to prepare a silver nitrate solution A. Wherein the concentration of the silver nitrate solution is 1.5mol/L, and the dosage of the concentrated nitric acid is 0.08 times of the mass of the silver nitrate;
solution B: 260 g of dispersant polyvinylpyrrolidone K30 is dissolved in 3300 g of deionized water, and then the solution is stirred and dissolved to prepare dispersant solution B. Wherein the dosage of the dispersant is 0.35 times of the mass of the silver nitrate in the solution A; the dosage of the deionized water in the solution B is 1.2 times of that in the solution A;
solution C: 425 g of ascorbic acid is dissolved in 2750 g of deionized water, and then the ascorbic acid solution C is prepared by stirring and dissolving. Wherein the dosage of the ascorbic acid in the solution C is 0.55 times of the molar weight of the silver nitrate in the solution A;
preparing two identical parts of solution A, solution B and solution C respectively;
2) preparation of 3 micron microcrystalline silver powder
a. Adding 14 g of analytically pure concentrated nitric acid to the solution B, wherein the pH value of the solution is 4;
b. adding one part of the solution A and one part of the solution C into one part of the solution B which is continuously stirred at the flow rate of 100ml/min in a cocurrent mode, carrying out oxidation reduction to generate silver microcrystals, wherein the adding time is 30 minutes, and the temperature of the solution is controlled to be 22 ℃ in the reaction process;
3) preparation of large-particle silver powder with supporting edge structure
a. Taking 810g of the microcrystalline silver powder solution after the reaction in the step 2), wherein the mass of the microcrystalline silver is 7.87% of that of the silver nitrate in the solution A, and adding the microcrystalline silver powder solution into the other solution B;
b. simultaneously adding another portion of all of said solution a and another portion of all of said solution C to the continuously stirred solution obtained in step a) of step 3) at a flow rate of 100ml/min for a period of 30 minutes;
c. adding 430 g of analytically pure ammonia water into the reactant obtained in the step b) in the step 3), adjusting the pH value to be 6, and adding 15 g of oleic acid, wherein the using amount of the surfactant oleic acid is 1.6% of the mass of the silver nitrate in the solution A;
3) post-treatment
And (3) carrying out solid-liquid separation on the reactant, washing and drying to obtain 500 g of large-particle silver powder with a supporting prism structure, wherein the height of the supporting prism on the surface is 3 micrometers, and the average particle size of the silver powder is 7 micrometers.
Comparative example 1 preparation of comparative silver powder D1#
Comparative silver powder D1# was prepared without preparing 3 μm microcrystalline silver powder and silver powder was synthesized directly, all other steps and conditions being the same as in example 1.
The total weight of the obtained microcrystalline silver powder is 317 g, and the average particle size of the silver powder is 1.5 microns.
Comparative example 2 preparation of comparative silver powder D2#
Preparation method of comparative silver powder D2#, in step a of step 3), 9.928g of microcrystalline silver powder solution after the reaction of step 2) was completed, wherein the mass of microcrystalline silver was 0.1% of the mass of silver nitrate in the solution A, was added to another solution B, and the other steps and conditions were the same as in example 1.
The total weight of the obtained microcrystalline silver powder with the concave-convex structure on the surface is 290 g, and the average grain diameter of the silver powder is 3.5 microns.
Comparative example 3 preparation of comparative silver powder D3#
Preparation of comparative silver powder D3#, step b of step 2) was carried out at a reaction temperature of 28 deg.C, and all other steps and conditions were the same as in example 1.
The obtained microcrystalline silver powder with irregular approximately round bulges on part of the surface is 354 grams, and the average grain diameter of the silver powder is 4.5 microns.
Example 4 Performance test of Large-grained silver powders 1# -3# and comparative silver powders D1# -D3# having a branched structure
The large-grain silver powder 1# -3# and the comparative silver powder 1# -3# with the fine-grained structures prepared above were respectively subjected to average particle size, specific surface area, tap density and weight loss on ignition tests, and the results are shown in table 1.
TABLE 1
The result shows that the large-particle silver powder 1# -3# with the supporting edge structure prepared by the embodiment of the application has narrow particle size distribution and good dispersibility, compared with the silver powder D1# which is prepared without preparing 3-micron microcrystalline silver powder, the silver powder is directly synthesized, and the finally prepared silver powder has the average particle size of 1.5 microns, smaller particle size and smooth surface; compared with the microcrystalline silver powder solution added in the step 2) during the preparation of the silver powder D2#, the microcrystalline silver powder solution after the reaction is less, the microcrystalline silver powder is spontaneously nucleated in the reaction process, the finally formed silver powder has a smaller particle size, the average particle size of the finally prepared silver powder is slightly larger than that of the comparative silver powder D1#, the average particle size of the finally prepared silver powder is 3.5 micrometers, and a micro concavo-convex structure appears on the surface of the silver powder; compared with silver powder D3#, the reaction temperature is high when 3-micron microcrystalline silver powder is prepared, the finally generated approximately circular bulges with irregular surfaces are generated, and the average grain diameter of the silver powder is 4.5 microns.
Example 5 Large-grained silver powder 1# -3#, comparative silver powder D1# -D3#, and commercially available plate-like silver powder conductive paste having a branched structure were tested
The large-particle silver powder with the branch edge structure, No. 1-3, the comparative silver powder, No. D1-D3, are used as conductive particles and commercially available silver powder with a smooth surface and a particle size of 8 micrometers, and are uniformly mixed with 20 weight percent of boron modified phenolic resin, 10 weight percent of 4, 4' -diaminodiphenylmethane, 20 weight percent of beta-hydroxyethyl methacrylate and 10 weight percent of ethylene-acrylic acid copolymer in 40 weight percent, and then the 7 conductive adhesives are prepared after three-roll rolling.
Volume resistivity: the prepared sample is uniformly coated between two glass sheets on an organic glass plate wiped by absolute ethyl alcohol, cured at 25 ℃ and tested by a four-electrode resistance test method.
And (3) testing the bonding strength: the bonding strength sample takes conductive silver adhesive as a bonding agent, an aluminum sheet as a substrate and a single-side lap joint test piece as a sample. The bonding strength test is carried out on a microcomputer controlled electronic universal testing machine.
And (3) weather resistance test: the prepared seven conductive adhesives are placed in the same outdoor environment with the same mass, and after 30 days of testing, the bonding strength and the volume resistivity of the seven conductive adhesives are respectively obtained. The results of the tests are shown in Table 2.
TABLE 2
The result shows that the bonding strength of the conductive adhesive made of the large-particle silver powder 1# -3# with the supporting edge structure in the embodiment of the application is obviously improved, and is equivalent to the bonding strength of the conductive adhesive made of the comparative silver powder D1# -D3#, but the resistivity is obviously reduced, which shows that the bonding strength of the conductive adhesive made of the large-particle silver powder 1# -3# with the supporting edge structure in the embodiment of the application is high, and meanwhile, the supporting edge structure increases the contact area between the silver powders, so that the resistivity is finally low, the conductivity is excellent, the weather resistance is good, and the bonding strength and the volume resistance are not obviously changed after 30-day test.
Compared with the silver powder D1#, the preparation method of the microcrystalline silver powder with the size of 3 microns is not adopted, so that the finally prepared silver powder is poor in dispersity, small in particle size, small in contact area, high in final resistivity and poor in conductivity.
The above description is only an example of the present application, and the protection scope of the present application is not limited by these specific examples, but is defined by the claims of the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the technical idea and principle of the present application should be included in the protection scope of the present application.