CN116765417B

CN116765417B - Submicron silver powder preparation method with concentrated particle size distribution

Info

Publication number: CN116765417B
Application number: CN202310782000.0A
Authority: CN
Inventors: 赵维巍; 陆国锋
Original assignee: Shenzhen Hushen Intelligent Material Technology Co ltd
Current assignee: Shenzhen Hushen Intelligent Material Technology Co ltd
Priority date: 2023-06-28
Filing date: 2023-06-28
Publication date: 2024-02-13
Anticipated expiration: 2043-06-28
Also published as: CN116765417A

Abstract

The invention provides a preparation method of submicron silver powder with concentrated particle size distribution, and relates to the technical field of silver powder preparation. The method comprises the following steps: injecting part of the reducing solution and the base solution into a reaction container with a stirring mechanism, and regulating the temperature of a reaction system to 0-30 ℃; adding silver salt solution and the rest of reducing solution, wherein the flow rate of the silver salt solution is larger than that of the rest of reducing solution; when the reaction solution turns black, the flow rate of the silver salt solution is adjusted to be lower than the flow rate of the rest reducing solution; independently injecting a seed crystal dilution solution into the reaction container, wherein the flow rate of the seed crystal dilution solution is equal to that of the silver salt solution; in the feeding process, the stirring speed is 150-750r/min; after the material addition is finished, adding flocculant, regulating the temperature of the reaction system to 10-90 ℃ and stirring at the speed of 250-1500r/min. The method has the advantages of simple process, centralized particle size distribution of the prepared silver powder and good dispersibility.

Description

Submicron silver powder preparation method with concentrated particle size distribution

Technical Field

The invention relates to the technical field of silver powder preparation, in particular to a submicron silver powder preparation method with concentrated particle size distribution.

Background

Silver has the highest electrical and thermal conductivity of metals and is therefore used for soldering and electrical contacts, with many applications in the optical, electronic industry, energy and medical fields. With the development of electronic circuits in the directions of small volume, high precision, high reliability and the like, nano-micron superfine silver powder needs to be prepared. Silver powder has the general morphology characteristics of spheroidal and platy, and the morphology of nano-micron silver particles has a great influence on the conductivity. The general preparation method can only meet the preparation of a single morphology. Many of these synthetic chemistry techniques are typically chemical reduction directly in aqueous and nonaqueous solutions (including autoclave) or thermal decomposition using silver compounds, as well as other auxiliary reduction modes such as laser, microwave, electrochemical, sonochemical, and the like.

In all the above technologies, the basic principle is that silver salt is reduced into silver simple substance, but the morphology of the prepared silver particles is changed greatly along with the difference of reduction environments. Therefore, the current mode of industrially producing submicron silver powder mainly adopts a vacuum condensation physical method. The submicron silver powder prepared by the chemical method has low popularity, and has various shapes and increased gaps among particles due to uneven control of reaction rate, so that the serial resistance of the silver powder slurry prepared subsequently can be increased. In order to reduce gaps among silver powder particles and improve tap density of the silver powder, the silver powder with the shape similar to a hexagon has geometrical advantages. Therefore, how to produce the superfine silver powder on a large scale, simply and effectively stabilize the particle size of the nano silver particles and maintain the morphology of the silver powder is a main difficult problem of a wet chemical method.

In view of this, the present invention has been made.

Disclosure of Invention

The invention aims to provide a preparation method of submicron silver powder with concentrated particle size distribution, which has the advantages of simple process, quick production and capability of preparing high-tap submicron silver powder with nearly hexagonal morphology, and the silver powder has concentrated particle size distribution and good dispersibility.

The invention is realized in the following way:

in a first aspect, the present invention provides a method for preparing submicron silver powder with concentrated particle size distribution, comprising:

injecting part of the reducing solution, part of the seed crystal diluent and the base solution into a reaction container with a stirring mechanism, and regulating the temperature of a reaction system in the reaction container to 0-30 ℃;

injecting silver salt solution and the rest of the reducing solution into the reaction container respectively and independently, wherein the flow rate of the silver salt solution is larger than that of the rest of the reducing solution;

when the reaction solution turns black, the flow rate of the silver salt solution is adjusted to be lower than the flow rate of the rest reducing solution;

independently injecting the rest seed crystal diluting solution into the reaction container in the reaction process of the silver salt solution and the reducing solution, wherein the flow rate of the seed crystal diluting solution is equal to that of the silver salt solution; in the feeding process, the stirring speed of the stirring mechanism is 150-750r/min;

And after the material addition is finished, adding a flocculating agent into the reaction container for flocculation sedimentation, adjusting the temperature of a reaction system in the reaction container to be 10-90 ℃ in the flocculation sedimentation process, continuously maintaining stirring and increasing the stirring speed to 250-1500r/min, and after the flocculation sedimentation is finished, carrying out solid-liquid separation and drying on a reaction product.

In an alternative embodiment, the flow rate of the silver salt solution is 0.5-3L/min, and the flow rate of the reducing solution is 0.5-7.5L/min;

preferably, the flow rate of the silver salt solution is 1.01 to 1.65 times the flow rate of the remaining reducing solution before the reaction solution turns black;

preferably, the flow rate of the silver salt solution after the reaction solution turns black is 0.01 to 0.75 times the flow rate of the remaining reducing solution;

preferably, the adjustment of the flow rate is performed within a period of 2.5 to 22 seconds after the reaction solution turns black.

In an alternative embodiment, when the flow rate of the reducing solution is greater than the flow rate of the silver salt solution, the difference between the flow rates of the reducing solution and the silver salt solution is 0.005-3L/min.

In an alternative embodiment, the seed crystal dilution solution is introduced into the reaction vessel by spraying;

Preferably, the total addition amount of the seed crystal dilution solution is 0.00001-0.0002, i.e. 1-200ppm, of the mass percent of the theoretical silver powder yield;

preferably, the seed crystal dilution solution maintains the temperature of the seed crystal dilution solution at 20-120 ℃ in the spraying process;

preferably, the grain size of the nano silver in the seed crystal diluted solution is 10-120nm, and the concentration is 1ppm-10ppm;

preferably, before the seed crystal diluted solution is introduced into the reaction container, the method further comprises the step of detecting by adopting an ultraviolet-visible spectrophotometry, and when the absorption characteristic peak of the seed crystal diluted solution is 390-410nm and the absorption peak intensity is more than 0.5, the seed crystal diluted solution is introduced into the reaction container by a spraying method.

In an alternative embodiment, the seed crystal dilution solution is prepared by a process comprising: dissolving silver nitrate in glycol, adding gluconic acid and glucose for aging to obtain seed crystal solution, and adding water for dilution to obtain seed crystal dilution solution.

In an alternative embodiment, a dispersing agent is also added to the seed crystal diluted solution;

preferably, the dispersant comprises at least one of polyvinyl alcohol and tween 80;

preferably, the dispersing agent comprises 5% -30% by mass: 0-15% polyvinyl alcohol and tween 80.

In an alternative embodiment, the injection amount of part of the reducing solution is 0.5% -15% of the total amount of the reducing solution.

In an alternative embodiment, the base fluid comprises a dispersant comprising polyvinylpyrrolidone, gelatin, tween 40 and tween 80 and a pH adjuster comprising at least one of lysine, arginine and histidine;

preferably, the dosage of polyvinylpyrrolidone is 0.1-0.25 times of the mass of silver nitrate in the silver salt solution;

preferably, the dosages of the gelatin, the tween 40 and the tween 80 are respectively 0.001-0.01 times of the mass of the silver nitrate in the silver salt solution;

preferably, the pH regulator is added in an amount of 0.001 to 0.01 times the mass of the polyvinylpyrrolidone.

In an alternative embodiment, the flocculant comprises one or more of lauric acid, hydroxy lauric acid, oleic acid, sodium laurate, and ricinoleic acid, and the flocculant is used in an amount of 0.05% to 1.5% of theoretical silver powder yield;

preferably, the flocculant is added in a pouring way, and the adding time is within 0-2 minutes after the silver salt solution and the reducing solution are injected;

preferably, the flocculation precipitation time is 2.5-15 minutes.

In an alternative embodiment, the silver salt solution and the reducing solution are stored at 5-30 ℃ prior to being added to the reaction vessel;

preferably, the silver salt solution is silver nitrate with the mass fraction of 7-75%; the silver salt solution is also added with a high molecular protective agent;

preferably, the reducing solution comprises 0.5-7.5% of glucose by mass and 5-30% of vitamin C by mass;

preferably, the polymer protectant is polyvinylpyrrolidone.

The invention has the following beneficial effects:

according to the preparation method of the submicron silver powder with concentrated particle size distribution, the flow rates of the silver salt solution, the reducing solution and the seed crystal solution are accurately measured and regulated, the reaction initial temperature, the temperature after the flocculant is added and the stirring speed at different stages are controlled, the rate of oxidation-reduction reaction is controlled through the cooperation of the three measures, the seed crystal solution is used as a third path to be independently injected into a reaction container, the controlled aggregation of the nano particles can be enhanced, uniform spheroidal powder is formed through the difference of the reduction reaction rates, the flocculation regulation and control are carried out on the reaction solution, the aggregation effect of the silver powder is weakened, and the submicron silver powder with narrow particle size distribution is formed in one step. The preparation method of the submicron silver powder with concentrated particle size distribution can be operated simply, can realize the rapid synthesis of submicron silver powder with narrower particle size distribution, is simple to separate, can carry out industrial production, and can produce submicron silver powder with concentrated particle size distribution and good dispersibility.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of a method for preparing submicron silver powder with concentrated particle size distribution;

FIG. 2 is a schematic diagram of the synthesis process of the preparation method of submicron silver powder with concentrated particle size distribution;

fig. 3 is an SEM characterization diagram of silver powder prepared by the method for preparing submicron silver powder with concentrated particle size distribution provided in example 1 of the present application;

fig. 4 is an SEM characterization diagram of silver powder prepared by the method for preparing submicron silver powder with concentrated particle size distribution provided in example 3 of the present application;

FIG. 5 is an SEM characterization view of the silver powder prepared by the method for preparing a submicron silver powder having concentrated particle size distribution as provided in comparative example 1 of the present application;

fig. 6 is an SEM characterization diagram of the silver powder prepared by the preparation method of submicron silver powder with concentrated particle size distribution provided in comparative example 2 of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Referring to fig. 1 and 2, the present application provides a method for preparing submicron silver powder with concentrated particle size distribution, which includes the following steps:

(1) Preparing silver salt solution.

Silver nitrate solution with the mass fraction of 7% -75% (preferably 15-50%) is prepared by adopting silver nitrate as silver salt solution; then adding a high molecular protective agent into the silver salt solution; preferably, the polymeric protectant includes, but is not limited to, polyvinylpyrrolidone.

(2) Preparing a reducing solution.

Glucose and vitamin C are formulated into a solution of 0.5-7.5% (preferably 1-5%) by mass of glucose and 5-30% (preferably 10-20%) by mass of vitamin C as the reducing solution herein.

(3) Preparing a base solution.

The base solution in the application comprises a dispersing agent and a pH regulator, wherein the dispersing agent comprises, but is not limited to, polyvinylpyrrolidone, gelatin, tween 40 and tween 80, and the dosage of the polyvinylpyrrolidone is 0.1-0.25 times of the mass of silver nitrate in the silver salt solution; the dosage of the gelatin, the tween 40 and the tween 80 is respectively 0.001 to 0.01 times of the mass of the silver nitrate in the silver salt solution; the pH adjuster includes, but is not limited to, at least one of lysine, arginine, and histidine; the addition amount of the pH regulator is 0.001-0.01 times of the mass of the polyvinylpyrrolidone. In the application, at least one of lysine, arginine and histidine is selected as the pH regulator, so that better particle size concentration can be obtained, and compared with the conventional acid-base which is used as the pH regulator, the pH regulator can reduce the excessive use of NaOH.

(4) Preparing a seed crystal dilution solution.

Dissolving silver nitrate in glycol, adding oxidant (gluconic acid and glucose) for aging to obtain seed crystal solution, adding water for dilution to obtain seed crystal dilution solution, and preparing the seed crystal dilution solution with the grain size of nano silver of 10-120nm (preferably 20-80 nm) and the concentration of 0.5ppm-15ppm (preferably 2ppm-10 ppm).

Wherein, the dosage ratio of the silver nitrate to the glycol is 1: between 100 and 1:10, both gluconic acid and glucose were added in amounts of 0.1g/mL. The seed concentration in the seed dilution solution is 1-10ppm.

Dispersing agents are also added into the seed crystal dilution solution; the dispersing agent comprises at least one of polyvinyl alcohol and tween 80; preferably, the dispersing agent comprises 5% -30% by mass: 0-15% polyvinyl alcohol and tween 80, in certain embodiments, the dispersant comprises 10-20% by mass: 0-10% polyvinyl alcohol and tween 80.

After the seed crystal diluted solution is prepared, it needs to be tested to determine if it meets the requirements. Specifically, the prepared seed crystal diluted solution is detected by adopting an ultraviolet-visible spectrophotometry, and when the absorption characteristic peak of the seed crystal diluted solution is 390-410nm and the absorption peak intensity is more than 0.5, the preparation of the seed crystal diluted solution is successful.

(5) Preparing flocculant.

The flocculant comprises one or more of lauric acid, hydroxyl lauric acid, oleic acid, sodium laurate and ricinoleic acid, and the dosage of the flocculant is 0.05% -1.5% (preferably 0.1% -1.0%) of the theoretical silver powder yield; when the components of the flocculant include a plurality of kinds, the mass ratio between the components may be any ratio.

(6) The reaction is carried out in one step.

S1, injecting part of the reducing solution, part of the seed crystal diluent and the base solution into a reaction container with a stirring mechanism, and regulating the temperature of a reaction system in the reaction container to 0-30 ℃; the injection amount of part of the reducing solution is 0.5% -15% of the total amount of the reducing solution.

In this application, the above-prepared reducing solution is fed by an automatic sampler (including but not limited to peristaltic pump, metering pump or flow pump) capable of adjusting flow rate, the base solution is added into the reaction vessel in advance, and the stirring mechanism continuously stirs during the whole feeding and reaction process.

The stirring mechanism is selected from various stirring structures such as paddles or other high-shear stirring structures, and preferably, the paddles are used as the stirring mechanism in the application, and the paddles are made of polytetrafluoroethylene or stainless steel lining plastic, so that silver salt and stirring paddles are prevented from reacting. The paddle structure is double-layer four-blade to ensure the rotation stability of the solution and avoid the air brought in by the solution.

S2, respectively and independently injecting the silver salt solution and the residual reducing solution into a reaction container, wherein the flow rate of the silver salt solution is larger than that of the residual reducing solution; specifically, the flow rate of the silver salt solution is 1.01 to 1.65 times the flow rate of the remaining reducing solution.

In the application, the rapid generation of silver nuclei is facilitated by controlling the flow rate of the silver salt solution to be larger than the flow rate of the rest of the reducing solution in the early stage.

S3, when the reaction solution turns black, adjusting the flow rate within 2.5-22S (preferably 5-15S), and adjusting the flow rate of the silver salt solution to be lower than the flow rate of the rest reducing solution; specifically, the flow rate of the silver salt solution is 0.01 to 0.75 times of the flow rate of the residual reducing solution; when the flow rate of the reducing solution is larger than that of the silver salt solution, the flow rate difference between the reducing solution and the silver salt solution is 0.005-3L/min.

In the application, the flow rate of the silver salt solution is controlled to be larger than the flow rate of the rest reducing solution in the early stage, so that black silver peroxide particles can be generated. Silver peroxide particles can avoid silver particles to grow fast, so that the silver powder morphology and particle size are regulated and controlled by taking reaction solution to change color as an index point and adjusting the flow rate fast, and at the moment, the flow rate of silver salt is lower than that of reducing solution, meanwhile, the flow rate difference is limited, and the reaction rate can be well controlled.

S4, independently injecting the rest seed crystal dilution solution into the reaction container in the reaction process of the silver salt solution and the reducing solution, wherein the flow rate of the seed crystal dilution solution is equal to that of the silver salt solution; introducing the seed crystal diluted solution into a reaction container by a spraying method; the temperature of the seed crystal dilution solution is maintained to be 20-120 ℃ in the spraying process of the seed crystal dilution solution;

in the application, the proportion of the seed crystal diluted solution added in the step S1 and the step S4 can be any proportion, wherein the more the seed crystal diluted solution is added in the step S4, the smaller the particle size of the silver powder finally generated, and the total addition amount of the seed crystal diluted solution is 0.00001-0.0002 of the mass percent of the theoretical silver powder yield, namely 1ppm-200ppm; the addition amount of the specific step S1 and the step S4 can be adjusted according to the particle size of the silver powder to be produced.

The seed crystal diluent solution is used as seed crystal of silver particles, so that the silver particles can grow orderly, but if the silver particles are added excessively, the problem of size particles can be caused. Therefore, the seed crystal diluting solution is added through a single path, the controlled aggregation of nano particles can be enhanced, the silver particles grow orderly, and the stirring speed of the stirring mechanism is 150-750r/min in the feeding process.

(7) And (5) separating and drying.

After the material addition is finished, the reaction is finished, a flocculating agent is added into a reaction vessel for flocculation sedimentation, the temperature of a reaction system in the reaction vessel is regulated to be 10-90 ℃ (preferably 20-60 ℃), stirring is continuously kept, the stirring speed is increased to 250-1500r/min (preferably 500-1000 r/min), and after the flocculation sedimentation is finished, the solid-liquid separation and drying are carried out on a reaction product.

In this embodiment, the flocculant is added by pouring for a period of time within 0-2 minutes after the completion of the injection of the silver salt solution and the reducing solution, preferably, for a period of time of flocculation precipitation of 2.5-15 minutes.

In the process of preparing the superfine silver powder, as the particle size of the silver powder is smaller, the surface action energy of the silver powder is larger, and the agglomeration phenomenon among particles is more serious, in the embodiment, the agglomeration effect of the silver powder can be weakened by regulating and controlling the addition of the base solution and the flocculating agent in the reaction container.

The features and capabilities of the present invention are described in further detail below in connection with the examples.

Example 1

The embodiment provides a preparation method of submicron silver powder with concentrated particle size distribution, which comprises the following steps:

(1) Weighing 1kg of silver nitrate, putting into 3L of water, stirring, dissolving, adding 20g of polyvinylpyrrolidone, uniformly mixing, and storing in a storage tank at a low temperature of 20 ℃;

(2) 0.1kg of glucose and 0.5kg of vitamin C are weighed and placed in 3L of water, and are dissolved after stirring. Then storing the mixture in a storage tank at a low temperature of 20 ℃;

(3) 250g of polyvinylpyrrolidone (PVP), 1g of gelatin, 1g of Tween 40, 1g of Tween 80 were weighed as a dispersant and dissolved in 4L of water, and 2.5g of lysine was added. After the preparation is completed, the mixture is taken as a base solution and is put into a reaction cylinder;

(4) 15g of silver nitrate was dissolved in 89.85ml (100 g) of ethylene glycol, 9g of gluconic acid and 9g of glucose were further added to age to obtain a seed solution, and the obtained solution was mixed with 1:99 mass ratio, adding deionized water for dilution to obtain seed crystal diluted solution, adding polyvinyl alcohol and tween 80 into the seed crystal diluted solution as dispersing agents, and enabling the concentrations of the dispersing agents to be 0.03g/L and 0.01g/L respectively, uniformly mixing, and detecting by adopting an ultraviolet-visible spectrophotometry, wherein the detection result is as follows: the absorption characteristic peak of the crystal seed diluted solution is 460.1nm, the absorption peak intensity is 0.7, wherein the grain size of nano silver in the crystal seed diluted solution is 20-80nm, and the concentration is 2ppm; meets the standard, and can be used as seed crystal dilution solution.

(5) The temperature of the reaction cylinder is controlled to be 20 ℃ by a cold water circulating pump, peristaltic pump pipeline valves on two sides are simultaneously opened, silver salt solution and reducing solution in a storage tank are pumped into the reaction cylinder, a peristaltic pump of the reducing solution is firstly opened, the flow rate of the reducing solution is controlled to be 0.1L/min, 5% of the total amount of the reducing solution is pumped into the reaction cylinder to be mixed with base solution, then the peristaltic pump of the silver salt solution is opened, the flow rate of the silver salt solution is controlled to be 0.11L/min, and meanwhile the rotating speed of paddles of a reaction kettle is kept to be 400r/min.

(6) At the moment, the third seed crystal solution is added in a spraying mode, and the spraying speed is equivalent to that of the silver salt solution. When the reaction solution turns black, the flow rate of the silver salt solution is regulated to 0.05L/min within 10s, and at the moment, the flow rate of the silver salt solution is lower than the flow rate of the rest reducing solution, and the speed difference of the silver salt solution and the rest reducing solution is 0.05L/min.

(7) After 30-35mins of material conveying, the reaction is finished, at the moment, 2g and 1g of prepared flocculant (lauric acid and stearic acid) are respectively added into a reaction cylinder in a dumping way, meanwhile, the temperature of a reaction system in the reaction cylinder is regulated to 40 ℃, the rotating speed of a blade of the reaction cylinder is increased to 800r/min, and flocculation and sedimentation of silver powder are completed after the reaction is continuously maintained for 10 mins.

(8) Centrifuging the silver powder-containing solution for solid-liquid separation, washing with ethanol for the second time, and filtering with a filter screen to obtain wet powder. And (3) putting the wet powder into a vacuum oven, and drying at a low temperature to obtain a silver powder finished product.

Example 2

This example is substantially the same as example 1 except that in this example, the storage temperature of the silver salt solution in step (1) is 15 ℃, the storage temperature of the reducing solution in step (2) is 15 ℃, the temperature of the reaction system in the reaction cylinder in step (5) is 15 ℃, and the temperature of the reaction system in the reaction cylinder in step (7) is adjusted to 60 ℃.

Example 3

This example is substantially the same as example 1 except that in this example, the storage temperature of the silver salt solution in step (1) is 10 ℃, the storage temperature of the reducing solution in step (2) is 10 ℃, the temperature of the reaction system in the reaction cylinder in step (5) is 10 ℃, and the temperature of the reaction system in the reaction cylinder in step (7) is adjusted to 25 ℃.

Example 4

The present embodiment is substantially the same as embodiment 1, except that in this embodiment, the blade rotation speed in step (5) is 300r/min, and the blade rotation speed in step (7) is 900r/min.

Example 5

This example is substantially the same as example 1 except that in this example, in the step (5), the flow rate of the reducing solution is 1L/min, and the flow rate of the silver salt solution is 1.01L/min; the flow rate of the silver salt solution in the step (6) is 0.25L/min.

Example 6

This example is substantially the same as example 1 except that in this example, in the step (5), the flow rate of the reducing solution is 2L/min, and the flow rate of the silver salt solution is 2.05L/min; the flow rate of the silver salt solution in the step (6) is 0.05L/min.

Example 7

This example is essentially the same as example 1, except that the solutions prepared in steps (1) - (4) are used in different amounts, specifically:

(1) Weighing 1kg of silver nitrate, putting into 5L of water, stirring, dissolving, adding 10g of vinylpyrrolidone, uniformly mixing, and then preserving in a storage tank at a low temperature of 20 ℃;

(2) 0.1kg of glucose and 0.5kg of vitamin C are weighed and put into 5L of water, and are dissolved after stirring. Then storing the mixture in a storage tank at a low temperature of 20 ℃;

(3) 250g of polyvinylpyrrolidone (PVP), 1g of gelatin, 1g of Tween 40 and 1g of Tween 80 are weighed as dispersing agents to be dissolved in 4L of water, and 2.5g of lysine and 1.5g of arginine are added. After the preparation is completed, the mixture is taken as a base solution and is put into a reaction cylinder;

(4) 10g of silver nitrate is dissolved in 100g of glycol, 5g of gluconic acid and 1g of glucose are added for aging to obtain a seed crystal solution, water is added for dilution to obtain a seed crystal dilution solution, 4 polyvinyl alcohol and 1g of tween 80 are added into the seed crystal dilution solution as dispersing agents, and after uniform mixing, the detection is carried out by adopting an ultraviolet-visible spectrophotometry, and the detection result is that: the absorption characteristic peak of the crystal seed diluted solution is 460nm, the absorption peak intensity is 0.6, wherein the grain size of nano silver in the crystal seed diluted solution is 80nm, and the concentration is 8ppm; meets the standard, and can be used as seed crystal dilution solution.

Example 8

(1) Weighing 1kg of silver nitrate, putting into 2L of water, stirring, dissolving, adding 15g of polyvinylpyrrolidone, uniformly mixing, and storing in a storage tank at a low temperature of 20 ℃;

(2) 0.1kg of glucose and 0.5kg of vitamin C are weighed and placed in 2L of water, and are dissolved after stirring. Then storing the mixture in a storage tank at a low temperature of 20 ℃;

(3) 250g of polyvinylpyrrolidone (PVP), 10g of Tween 80 (40 g) and 1g of Tween 80 (1 g) were weighed and dissolved in 4L of water as a dispersing agent, and 2.5g of lysine and 2.5g of arginine were added. After the preparation is completed, the mixture is taken as a base solution and is put into a reaction cylinder;

(4) 25g of silver nitrate was dissolved in 89.85ml (100 g) of ethylene glycol, 9g of gluconic acid and 9g of glucose were further added to age to obtain a seed solution, and the obtained solution was mixed with 1:99 mass ratio, adding deionized water for dilution to obtain seed crystal diluted solution, adding polyvinyl alcohol and tween 80 into the seed crystal diluted solution as dispersing agents, and enabling the concentrations of the dispersing agents to be 0.05g/L and 0.01g/L respectively, uniformly mixing, and detecting by adopting an ultraviolet-visible spectrophotometry, wherein the detection result is as follows: the absorption characteristic peak of the crystal seed diluted solution is 462, the absorption peak intensity is 0.9, the grain size of nano silver in the crystal seed diluted solution is 80nm, and the concentration is 10ppm; meets the standard, and can be used as seed crystal dilution solution.

Comparative example 1

This comparative example is substantially the same as example 1 except that in this comparative example, the storage temperature of the silver salt solution in step (1) was 45 ℃, the storage temperature of the reducing solution in step (2) was 45 ℃, the temperature of the reaction system in the reaction cylinder in step (5) was 45 ℃, and the temperature of the reaction system in the reaction cylinder in step (7) was adjusted to 100 ℃.

Comparative example 2

This comparative example is substantially the same as example 1 except that in this comparative example, the blade rotation speed in step (5) was 2000r/min and the blade rotation speed in step (7) was 2000r/min.

Comparative example 3

This example is substantially the same as example 1 except that in this comparative example, the reducing solution, silver salt solution and seed solution in steps (5) and (6) were fed at all times while maintaining 0.1L/min, and the flow rate was not adjusted.

Comparative example 4

The difference between this example and example 1 is that in this comparative example, the peristaltic pump of the reducing solution is first turned on, the flow rate of the reducing solution is controlled to be 0.1L/min, 5% of the total amount of the reducing solution is pumped into the reaction tank to be mixed with the base solution, then the peristaltic pump of the silver salt solution is turned on, the flow rate of the silver salt solution is controlled to be 0.05L/min, the rotation speed of the paddle of the reaction tank is maintained to be 400r/min, when the reaction solution turns black, the flow rate of the silver salt solution is adjusted to be 0.11L/min, at this time, the flow rate of the silver salt solution is higher than the flow rate of the rest reducing solution, and the speed difference between the two is 0.01L/min.

Comparative example 5

This example is substantially the same as example 1 except that in this comparative example, when the reaction solution in step (6) was changed to black, the flow rate of the silver salt solution was adjusted to 0.05L/min within 30 seconds.

Comparative example 6

This example is substantially the same as example 1 except that in this comparative example, the seed crystal diluting solution is directly dropped into the reaction tank.

Experimental example 1

The silver powder provided in the above examples and comparative examples was subjected to particle size analysis and SEM photographing comparison. The results of the particle size analysis are shown in table 1, and the sem photo comparison analysis is shown in fig. 3, 4, 5 and 6.

	D10/μm	D50/μm	D90/μm	Aspect ratio (L/D)	Tap density
						Example 1	0.405	0.535	0.72	1.21	4.7
Example 2	0.391	0.547	0.75	1.23	5.1
						Example 3	0.554	0.690	0.859	1.19	4.8
Example 4	0.456	0.564	0.679	1.21	5.3
						Example 5	0.439	0.638	0.778	1.19	4.6
Example 6	0.653	0.705	0.892	1.25	5.1
						Example 7	0.594	0.716	0.859	1.22	5.4
Example 8	0.575	0.679	0.896	1.28	4.9
						Comparative example 1	1.35	6.24	14.06	1.62	3.5
Comparative example 2	1.78	3.12	9.51	1.42	4.3
						Comparative example 3	1.41	9.59	18.60	1.36	4.2
Comparative example 4	3.137	8.13	15.90	1.62	4.1
						Comparative example 5	3.57	5.754	11.13	1.54	3.7
Comparative example 6	4.036	6.473	12.01	1.47	3.9

As can be seen from the table, the particle size range of the silver powder prepared by the embodiment of the application is between 0.6 mu m and 1.0 mu m, and the requirements of the superfine silver powder are met. As can be seen from fig. 3 and 4, the silver powder prepared in the examples of the present application has good dispersibility and maintains good dispersibility. The silver powder prepared by the method has high tap density and has a value in the range of 4.5-5.5g/cm because the silver powder is nearly hexagonal in shape ³ Between them. Can meet the requirement of subsequent high-precision slurry.

As can be seen from the data of comparative example 1 and fig. 5, the silver powder has formed large particles, which does not meet the requirements of the use scenario.

As shown in FIG. 6, the silver powder prepared in comparative example 2 has a significantly larger particle size of 2-4 μm and a different size, so that larger voids are formed between the silver powders, resulting in a smaller tap density of 3.5-4.5g/cm ³ Between them.

As can be seen from the data of comparative examples 2 to 4, the presence of the silver powder in the form of particles of a size results in a significantly larger concentration ratio (d 90-d 10)/d 50.

As can be seen from the data of comparative examples 5 to 6, the agglomeration of the silver powder among the silver powders resulted in a significantly lower tap density of less than 4.0g/cm ³ 。

In summary, according to the preparation method of submicron silver powder with concentrated particle size distribution, the flow rates of the silver salt solution, the reducing solution and the seed crystal solution are accurately measured and regulated, the initial reaction temperature, the temperature after adding the flocculating agent and the stirring speed at different stages are simultaneously controlled, the rate of oxidation-reduction reaction is controlled through cooperation of the three measures, meanwhile, the seed crystal solution is independently injected into the reaction container as a third path, the controlled aggregation of nano particles can be enhanced, uniform spheroidic powder is formed through the difference of the reduction reaction rate, and flocculation regulation and control are carried out on the reaction solution, so that the aggregation effect of silver powder is weakened, and the submicron silver powder with narrow particle size distribution is formed in one step. The preparation method of the submicron silver powder with concentrated particle size distribution can be operated simply, can realize the rapid synthesis of submicron silver powder with narrower particle size distribution, is simple to separate, can carry out industrial production, and can produce submicron silver powder with concentrated particle size distribution and good dispersibility.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The preparation method of the submicron silver powder with concentrated particle size distribution is characterized by comprising the following steps of:

(1) Weighing 1kg of silver nitrate, putting into 3L of water, stirring, dissolving, adding 20g of polyvinylpyrrolidone, uniformly mixing, and storing in a storage tank at a low temperature of 20 ℃ to obtain silver salt solution;

(2) Weighing 0.1kg of glucose and 0.5kg of vitamin C, putting into 3L of water, stirring and dissolving; then storing the mixture in a storage tank at a low temperature of 20 ℃ to be used as a reducing solution;

(3) Weighing 250g of polyvinylpyrrolidone, 1g of gelatin, 1g of tween 40 and 1g of tween 80 as dispersing agents, dissolving in 4L of water and adding 2.5g of lysine; after the preparation is completed, the mixture is taken as a base solution and is put into a reaction cylinder;

(4) 15g of silver nitrate was dissolved in 100g of ethylene glycol, 9g of gluconic acid and 9g of glucose were further added to age to obtain a seed solution, and the obtained solution was mixed with 1:99 mass ratio, adding deionized water for dilution to obtain seed crystal diluted solution, adding polyvinyl alcohol and tween 80 into the seed crystal diluted solution as dispersing agents, and enabling the concentrations of the dispersing agents to be 0.03g/L and 0.01g/L respectively, uniformly mixing, and detecting by adopting an ultraviolet-visible spectrophotometry, wherein the detection result is as follows: the absorption characteristic peak of the crystal seed diluted solution is 460.1nm, the absorption peak intensity is 0.7, wherein the grain size of nano silver in the crystal seed diluted solution is 20-80nm, and the concentration is 2ppm; meets the standard, can be used as seed crystal dilution solution;

(5) The temperature of a reaction cylinder is controlled to be 20 ℃ by a cold water circulating pump, peristaltic pump pipeline valves on two sides are simultaneously opened, the silver salt solution and the reducing solution in a storage tank are pumped into the reaction cylinder, the peristaltic pump of the reducing solution is firstly opened, the flow rate of the reducing solution is controlled to be 0.1L/min, 5% of the total amount of the reducing solution is pumped into the reaction cylinder to be mixed with the base solution, then the peristaltic pump of the silver salt solution is opened, the flow rate of the silver salt solution is controlled to be 0.11L/min, and meanwhile the rotating speed of a blade of the reaction kettle is kept to be 400r/min;

(6) At the moment, the third path of crystal seed dilution solution is added in a spraying mode, and the spraying speed is equivalent to that of the silver salt solution; when the reaction solution turns black, the flow rate of the silver salt solution is regulated to 0.05L/min within 10 seconds, and at the moment, the flow rate of the silver salt solution is lower than the flow rate of the rest reducing solution, and the speed difference of the silver salt solution and the reducing solution is 0.05L/min;

(7) After 30-35mins of material conveying, adding 2g and 1g of prepared flocculant lauric acid and stearic acid into a reaction cylinder in a dumping way, adjusting the temperature of a reaction system in the reaction cylinder to 40 ℃, increasing the rotating speed of a blade of the reaction cylinder to 800r/min, and continuously maintaining for 10mins to finish flocculation and sedimentation of silver powder;

(8) Centrifuging the silver powder-containing solution for solid-liquid separation, washing with ethanol for the second time, and filtering with a filter screen to obtain wet powder; and (3) putting the wet powder into a vacuum oven, and drying at a low temperature to obtain a silver powder finished product.

2. The preparation method of the submicron silver powder with concentrated particle size distribution is characterized by comprising the following steps of:

(1) Weighing 1kg of silver nitrate, putting into 3L of water, stirring, dissolving, adding 20g of polyvinylpyrrolidone, uniformly mixing, and storing in a storage tank at a low temperature of 15 ℃ to obtain silver salt solution;

(2) Weighing 0.1kg of glucose and 0.5kg of vitamin C, putting into 3L of water, stirring and dissolving; then storing the mixture in a storage tank at a low temperature of 15 ℃ to be used as a reducing solution;

(5) The temperature of a reaction cylinder is controlled to be 15 ℃ by a cold water circulating pump, peristaltic pump pipeline valves on two sides are simultaneously opened, the silver salt solution and the reducing solution in a storage tank are pumped into the reaction cylinder, the peristaltic pump of the reducing solution is firstly opened, the flow rate of the reducing solution is controlled to be 0.1L/min, 5% of the total amount of the reducing solution is pumped into the reaction cylinder to be mixed with the base solution, then the peristaltic pump of the silver salt solution is opened, the flow rate of the silver salt solution is controlled to be 0.11L/min, and meanwhile the rotating speed of a blade of the reaction kettle is kept to be 400r/min;

(7) After 30-35mins of material conveying, adding 2g and 1g of prepared flocculant lauric acid and stearic acid into a reaction cylinder in a dumping way, adjusting the temperature of a reaction system in the reaction cylinder to 60 ℃, increasing the rotating speed of a blade of the reaction cylinder to 800r/min, and continuously maintaining for 10mins to finish flocculation and sedimentation of silver powder;

3. The preparation method of the submicron silver powder with concentrated particle size distribution is characterized by comprising the following steps of:

(1) Weighing 1kg of silver nitrate, putting into 3L of water, stirring, dissolving, adding 20g of polyvinylpyrrolidone, uniformly mixing, and storing in a storage tank at a low temperature of 10 ℃ to obtain silver salt solution;

(2) Weighing 0.1kg of glucose and 0.5kg of vitamin C, putting into 3L of water, stirring and dissolving; then storing the mixture in a storage tank at a low temperature of 10 ℃ to be used as a reducing solution;

(5) The temperature of a reaction cylinder is controlled to be 10 ℃ by a cold water circulating pump, peristaltic pump pipeline valves on two sides are simultaneously opened, the silver salt solution and the reducing solution in a storage tank are pumped into the reaction cylinder, the peristaltic pump of the reducing solution is firstly opened, the flow rate of the reducing solution is controlled to be 0.1L/min, 5% of the total amount of the reducing solution is pumped into the reaction cylinder to be mixed with the base solution, then the peristaltic pump of the silver salt solution is opened, the flow rate of the silver salt solution is controlled to be 0.11L/min, and meanwhile the rotating speed of a blade of the reaction kettle is kept to be 400r/min;

(7) After 30-35mins of material conveying, adding 2g and 1g of prepared flocculant lauric acid and stearic acid into a reaction cylinder in a dumping way, adjusting the temperature of a reaction system in the reaction cylinder to 25 ℃, increasing the rotating speed of a blade of the reaction cylinder to 800r/min, and continuously maintaining for 10mins to finish flocculation and sedimentation of silver powder;

4. The preparation method of the submicron silver powder with concentrated particle size distribution is characterized by comprising the following steps of:

(5) The temperature of a reaction cylinder is controlled to be 20 ℃ by a cold water circulating pump, peristaltic pump pipeline valves on two sides are simultaneously opened, the silver salt solution and the reducing solution in a storage tank are pumped into the reaction cylinder, the peristaltic pump of the reducing solution is firstly opened, the flow rate of the reducing solution is controlled to be 0.1L/min, 5% of the total amount of the reducing solution is pumped into the reaction cylinder to be mixed with the base solution, then the peristaltic pump of the silver salt solution is opened, the flow rate of the silver salt solution is controlled to be 0.11L/min, and meanwhile the rotating speed of a blade of the reaction kettle is kept to be 300r/min;

(7) After 30-35mins of material conveying, adding 2g and 1g of prepared flocculant lauric acid and stearic acid into a reaction cylinder in a dumping way, adjusting the temperature of a reaction system in the reaction cylinder to 40 ℃, increasing the rotating speed of a blade of the reaction cylinder to 900r/min, and continuously maintaining for 10mins to finish flocculation and sedimentation of silver powder;

5. The preparation method of the submicron silver powder with concentrated particle size distribution is characterized by comprising the following steps of:

(5) The temperature of a reaction cylinder is controlled to be 20 ℃ by a cold water circulating pump, peristaltic pump pipeline valves on two sides are simultaneously opened, the silver salt solution and the reducing solution in a storage tank are pumped into the reaction cylinder, the peristaltic pump of the reducing solution is firstly opened, the flow rate of the reducing solution is controlled to be 1L/min, 5% of the total amount of the reducing solution is pumped into the reaction cylinder to be mixed with the base solution, then the peristaltic pump of the silver salt solution is opened, the flow rate of the silver salt solution is controlled to be 1.01L/min, and meanwhile, the rotating speed of blades of the reaction kettle is kept to be 400r/min;

(6) At the moment, the third path of crystal seed dilution solution is added in a spraying mode, and the spraying speed is equivalent to that of the silver salt solution; when the reaction solution turns black, the flow rate of the silver salt solution is regulated to 0.25L/min within 10 seconds, and at the moment, the flow rate of the silver salt solution is lower than the flow rate of the rest reducing solution, and the speed difference of the silver salt solution and the reducing solution is 0.75L/min;

6. The preparation method of the submicron silver powder with concentrated particle size distribution is characterized by comprising the following steps of:

(5) The temperature of a reaction cylinder is controlled to be 20 ℃ by a cold water circulating pump, peristaltic pump pipeline valves on two sides are simultaneously opened, the silver salt solution and the reducing solution in a storage tank are pumped into the reaction cylinder, the peristaltic pump of the reducing solution is firstly opened, the flow rate of the reducing solution is controlled to be 2L/min, 5% of the total amount of the reducing solution is pumped into the reaction cylinder to be mixed with the base solution, then the peristaltic pump of the silver salt solution is opened, the flow rate of the silver salt solution is controlled to be 2.05L/min, and meanwhile, the rotating speed of blades of the reaction kettle is kept to be 400r/min;

(6) At the moment, the third path of crystal seed dilution solution is added in a spraying mode, and the spraying speed is equivalent to that of the silver salt solution; when the reaction solution turns black, the flow rate of the silver salt solution is regulated to 0.05L/min within 10 seconds, and at the moment, the flow rate of the silver salt solution is lower than the flow rate of the rest reducing solution, and the speed difference of the silver salt solution and the reducing solution is 1.95L/min;

7. The preparation method of the submicron silver powder with concentrated particle size distribution is characterized by comprising the following steps of:

(1) Weighing 1kg of silver nitrate, putting into 5L of water, stirring, dissolving, adding 10g of polyvinylpyrrolidone, uniformly mixing, and storing in a storage tank at a low temperature of 20 ℃ to obtain silver salt solution;

(2) Weighing 0.1kg of glucose and 0.5kg of vitamin C, putting into 5L of water, stirring and dissolving; then storing the mixture in a storage tank at a low temperature of 20 ℃ to be used as a reducing solution;

(3) Weighing 250g of polyvinylpyrrolidone, 1g of gelatin, 1g of tween 40 and 1g of tween 80 as dispersing agents, dissolving in 4L of water, and adding 2.5g of lysine and 1.5g of arginine; after the preparation is completed, the mixture is taken as a base solution and is put into a reaction cylinder;

(4) 10g of silver nitrate is dissolved in 100g of ethylene glycol, 5g of gluconic acid and 1g of glucose are added for aging to obtain seed crystal solution, and the obtained solution is mixed with 1: adding deionized water into the 99 mass ratio to dilute the solution to obtain a seed crystal diluted solution, adding 4g of polyvinyl alcohol and 1g of tween 80 into the seed crystal diluted solution as a dispersing agent, uniformly mixing, and detecting by adopting an ultraviolet-visible spectrophotometry, wherein the detection result is as follows: the absorption characteristic peak of the crystal seed diluted solution is 460 nm, the absorption peak intensity is 0.6, wherein the grain size of nano silver in the crystal seed diluted solution is 80nm, and the concentration is 8ppm; meets the standard, can be used as seed crystal dilution solution;

8. The preparation method of the submicron silver powder with concentrated particle size distribution is characterized by comprising the following steps of:

(1) Weighing 1kg of silver nitrate, putting into 2L of water, stirring, dissolving, adding 15g of polyvinylpyrrolidone, uniformly mixing, and storing in a storage tank at a low temperature of 20 ℃ to obtain silver salt solution;

(2) Weighing 0.1kg of glucose and 0.5kg of vitamin C, putting into 2L of water, stirring and dissolving; then storing the mixture in a storage tank at a low temperature of 20 ℃ to be used as a reducing solution;

(3) Weighing 250g of polyvinylpyrrolidone, 10g of tween 40 and 1g of tween 80 as dispersing agents, dissolving in 4L of water, and adding 2.5g of lysine and 2.5g of arginine; after the preparation is completed, the mixture is taken as a base solution and is put into a reaction cylinder;

(4) 25g of silver nitrate was dissolved in 100g of ethylene glycol, 9g of gluconic acid and 9g of glucose were further added to age to obtain a seed solution, and the obtained solution was mixed with 1:99 mass ratio, adding deionized water for dilution to obtain seed crystal diluted solution, adding polyvinyl alcohol and tween 80 into the seed crystal diluted solution as dispersing agents, and enabling the concentrations of the dispersing agents to be 0.05g/L and 0.01g/L respectively, uniformly mixing, and detecting by adopting an ultraviolet-visible spectrophotometry, wherein the detection result is as follows: the absorption characteristic peak of the crystal seed diluted solution is 462nm, the absorption peak intensity is 0.9, wherein the grain size of nano silver in the crystal seed diluted solution is 80nm, and the concentration is 10ppm; meets the standard, can be used as seed crystal dilution solution;