CN113427014A - Method for preparing nano silver powder by hydrogen reduction - Google Patents
Method for preparing nano silver powder by hydrogen reduction Download PDFInfo
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- CN113427014A CN113427014A CN202110684198.XA CN202110684198A CN113427014A CN 113427014 A CN113427014 A CN 113427014A CN 202110684198 A CN202110684198 A CN 202110684198A CN 113427014 A CN113427014 A CN 113427014A
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- 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
- B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
- B22F9/22—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
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- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
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Abstract
The invention discloses a method for preparing nano silver powder by hydrogen reduction. Firstly, reacting a silver nitrate solution and a sodium hydroxide or potassium hydroxide solution through an impinging stream reactor to prepare a silver oxide precipitate, wherein the median diameter of the prepared silver oxide is less than 1 micron; and then, mixing the separated and washed silver oxide, a surfactant and deionized water in a reactor, and introducing hydrogen into the reactor to react to prepare the nano silver powder with the median diameter of 5-800 nanometers. The reducing agent of the preparation method of the nano silver powder is hydrogen, and the preparation method is clean and environment-friendly, and has less impurity ions and high conductivity. Moreover, the method is easy to enlarge and realize batch production, and the prepared silver powder has superfine particle size, narrow particle size range distribution and better sphericity.
Description
Technical Field
The invention relates to a method for preparing silver powder, in particular to a method for preparing nano silver powder by hydrogen reduction.
Background
Silver paste is the most important material in the field of electronic industry, and with the development of miniaturization and micro-nano technology of electronic products, various conductive pastes and thick film pastes are prepared from silver powder and are widely applied to printed circuits and photovoltaic industry. With the rapid development of the new generation of HJT solar photovoltaic, higher requirements are put forward on silver powderThe use of nano-silver powder is required, and the characteristics of high conductivity, good dispersibility and the like are required. At present, there are many methods for preparing silver powder at home and abroad, such as a thermal decomposition method, an electrochemical method, an aerosol method, a wet chemical method and the like. Among them, the wet chemical method has advantages of simple production process and controllable particle size, and is therefore highly appreciated. In the wet chemical process for preparing spherical silver powder, AgNO is generally used3，Ag2CO3Silver-ammonia complex ions and other compounds of silver are used as a silver source, and reducing agents are various, such as formaldehyde, sodium borohydride, hydrazine hydrate, glucose, polyhydric alcohols, ferrous salts, ascorbic acid and the like.
The patent with publication number CN101612670B invented a method for preparing nano silver powder by using 60 Co-gamma rays in aqueous solution, but the safety investment of the Co-gamma ray device is large. Patent publication CN1106326A uses an alkanolamine as a complexing agent and reacts in the presence of a pH buffer at a temperature of 10-100 c to form dense spherical powder particles. However, the method has the disadvantages of large reagent dosage, complex process, wide particle size distribution range and insufficient tap density of the silver powder. Patent publication No. CN1266761A adopts polyvinylpyrrolidone (PVP), alkyl mercaptan (RSH) and the like as protective agents in the growth process of silver nuclei, ammonia water as a complexing agent, and ascorbic acid as a reducing agent. The patent prepares silver nitrate into silver ammonia solution as a silver source, and then adds a reducing agent to prepare silver powder. Although the prepared silver powder has the advantages of good stability and dispersibility and the like, the silver powder is not suitable for industrial production. Patent publication No. CN112387979A discloses the preparation of silver nanoparticles by using a direct current arc by using an industrial silver or silver powder compact as an anode, a tungsten rod as a cathode, and introducing hydrogen and then inert gas. Patent publication No. CN1387968A uses carbonate as a complexing agent and a surfactant as a protective agent to prepare silver powder. Although the silver powder produced by the method has good sphericity, the steps are complicated, and the method has no industrial prospect.
Currently, there are a few research methods for reducing silver ions using hydrogen. Wu Jian reduces the dried silver oxide powder at 150-200 deg.C to obtain silver powder with particle size distribution of 2-3 μm (Wu Jian, preparation of superfine silver powder by hydrogen reduction, 2 nd stage 22-24 of 1998, Hunan nonferrous metals). Under the gas-solid two-phase reaction condition, the silver powder is easy to agglomerate into large particles, and the nano-scale silver powder is difficult to prepare. EBIN and the like adopt a high-frequency ultrasonic generator to generate silver nitrate aerosol droplets, then hydrogen is used for reducing silver nitrate to prepare nano silver powder, and the influence of the precursor concentration and the reaction temperature on the particle size, the morphology and the grain size of a product is researched (EBIN and the like, the hydrogen is used for reducing the silver nitrate aerosol to prepare the nano silver powder (English), and the book of non-ferrous metals of China, English edition, 3 rd year 841-848). In the hydrogen atmosphere of 200 ℃, the nano silver powder prepared by taking silver nitrate as a raw material contains oxides. It is required that the reaction temperature exceeds 200 c to obtain pure silver powder.
An impinging stream reactor is an important method for achieving rapid mixing, and an impinging stream reactor is a device for achieving an impinging stream process. The reaction process in the impinging stream reactor is that two jets flow and impinge oppositely after leaving a nozzle, a highly turbulent impinging zone is formed in the middle of the reactor, the axial velocity tends to zero, and the two jets turn into radial flow. Because a high-turbulence impact area is generated after jet flow impact, the external resistance in the transfer process can be effectively reduced, the heat and mass transfer is strengthened, the mixing is promoted, and the nano-particles are prepared by using the micro-reactor. Publication numbers CN103611487B, CN110542490A and CN105749828B describe several types of impinging stream reactors, and the present invention includes but is not limited to these several impinging stream reactors.
The existing silver powder preparation method has the following defects:
1. the existing formaldehyde, hydrazine hydrate, sodium borohydride, glucose, polyalcohol and ascorbic acid can generate a large amount of waste water, and the environment-friendly treatment cost is high. In addition, the reducing agents can bring impurities into the product, reduce the purity of the product and reduce the conductivity of the silver powder;
2. at present, the preparation method using hydrogen as a reducing agent has complex process and high reaction temperature, easily causes silver particles to agglomerate into large particles, and does not use a silver oxide raw material with finer particle size.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for preparing nano silver powder by hydrogen reduction.
The technical scheme adopted by the invention for solving the problems is as follows:
a method for preparing nano silver powder by hydrogen reduction comprises the following steps,
s1, reacting the silver nitrate solution with sodium hydroxide or potassium hydroxide solution through an impinging stream reactor to prepare silver oxide precipitate, wherein the median diameter of the prepared silver oxide is less than 0.5 micron;
s2, mixing the separated and washed silver oxide, a surfactant and deionized water in a reactor, introducing hydrogen into the reactor, and reacting to obtain nano silver powder, wherein the proportion of the silver oxide is 0.5-40%, the proportion of the surfactant is 0.1-5%, and the balance is deionized water;
s3, after centrifugal separation or natural sedimentation of the nano silver powder, washing the nano silver powder for a plurality of times by using deionized water, and then washing the nano silver powder for a plurality of times by using absolute ethyl alcohol;
s4, vacuum drying at 20-80 ℃ to obtain the nano silver powder with the median diameter of 5-800 nanometers.
Preferably, the molar ratio of silver nitrate to sodium hydroxide or potassium hydroxide in step S1 is 1: (1-1.05).
Preferably, the mass ratio of the silver oxide to the deionized water in step S2 is 1: (1-100).
Preferably, in step S2, the pressure of the hydrogen gas is 0.1 to 50 MPa.
Preferably, in step S2, the reaction temperature is 15-95 ℃.
Preferably, in step S2, the surfactant is one or a mixture of polyvinylpyrrolidone, polyoxyethylene sorbitan fatty acid ester and polyvinyl alcohol.
Preferably, the molecular weight of the polyvinylpyrrolidone, the molecular weight of the polyoxyethylene sorbitan fatty acid ester and the molecular weight of the polyvinyl alcohol are all less than 2000.
Preferably, in step S2, ammonia water is added to adjust the pH value to 10-12.
The invention has the beneficial effects that:
1. the reducing agent of the preparation method of the nano silver powder is hydrogen, and the preparation method is clean and environment-friendly, and has less impurity ions and high conductivity.
2. The method is easy to enlarge and realize batch production, and the prepared nano silver powder has superfine particle size, narrow particle size range distribution and better sphericity.
Drawings
FIG. 1 is a transmission electron microscope photograph of a nano silver powder prepared in example 1 of the present invention;
FIG. 2 is a transmission electron microscope photograph of a nano silver powder prepared in example 3 of the present invention;
FIG. 3 is a transmission electron microscope photograph of the nano silver powder prepared in example 5 of the present invention.
Detailed Description
The following detailed description of embodiments of the invention, but the invention can be practiced in many different ways, as defined and covered by the claims.
The following describes an example of the specific size selection of the equipment and the process control parameters through specific embodiments.
Example 1
1mol/L silver nitrate solution and 1mol/L potassium hydroxide solution react through an impinging stream reactor to prepare silver oxide precipitate, and after centrifugal separation, the prepared silver oxide has a median diameter of 161 nanometers.
Weighing 3g of Ag2O (undried isolated solid, 20% water) and 0.5g polyvinyl alcohol (molecular weight 1400) were placed in a 250mL beaker, to which was added 100mL of deionized water. After being stirred evenly, the mixture is put into a quick-opening reaction kettle and is treated by H2The air in the kettle was displaced 3 times. Without turning on the agitator, without passing H2Heating to 70 deg.C, introducing H2To 1MPa and the stirrer was switched on at 500 rpm. And after 3 hours of reaction, ending the reaction, opening the reactor to obtain dark yellow thick slurry, centrifuging at the rotating speed of 12000rpm, separating supernatant, washing the bottom silver powder with deionized water, and washing for 3 times. Then placing the silver powder into a vacuum drying chamber at the temperature of 60 ℃ to obtain the nano silver powder product, wherein the median diameter is 19 nanometers.
Comparative example 1
2L of 1mol/L potassium hydroxide is added into 2L of 1mol/L silver nitrate solution at one time, the rest experimental conditions are consistent with those of the example 1, and the median diameter of the prepared silver powder is 753 nanometers. The silver powder prepared using the silver oxide prepared by the impinging stream reactor had a smaller particle size than example 1,
example 2
Reacting 3mol/L silver nitrate solution and 3.1mol/L sodium hydroxide solution through an impinging stream reactor to prepare silver oxide precipitate, and centrifugally separating to prepare silver oxide with the median diameter of 396 nanometers.
Weighing 25g of Ag2O (undried isolated solid, 15% water) and 3g polyvinylpyrrolidone (molecular weight 850) were placed in a 250mL beaker, to which was added 100mL of deionized water. After being stirred evenly, the mixture is put into a quick-opening reaction kettle and is treated by H2The air in the kettle was displaced 3 times. Without turning on the agitator, without passing H2Heating to 90 deg.C, introducing H2To 10MPa and the stirrer was switched on at 500 rpm. After the reaction is finished for 1.5 hours, the reaction is finished, the reaction solution is placed at the rotating speed of 12000rpm for centrifugation, the silver powder at the bottom is washed by deionized water after the supernatant is separated, and the washing is carried out for 3 times. Then placing the silver powder into a vacuum drying chamber at the temperature of 60 ℃ to obtain the nano silver powder product, wherein the median diameter is 360 nanometers.
Comparative example 2
The experimental conditions were the same as those of example 2, except that polyvinylpyrrolidone was not added, and the silver powder having a median diameter of 1.85 μm was prepared. The particle size of the silver powder prepared using polyvinylpyrrolidone was smaller compared to example 2.
Example 3
The experimental conditions were the same as in example 2, Ag2And mixing O, polyvinylpyrrolidone and deionized water, adding ammonia water, and adjusting the pH value to 11. Obtaining the nano silver powder product with the median diameter of 15 nanometers.
Example 4
And (3) reacting 2mol/L silver nitrate solution and 2.1mol/L potassium hydroxide solution through an impinging stream reactor to prepare silver oxide precipitate, and performing centrifugal separation to prepare silver oxide with the median diameter of 261 nm.
Weighing 40g of Ag2O (undried isolated solid, 20% water) and 2g of Tween 60 (polyoxyethylene sorbitan fatty acid ester, molecular weight 2000) in a 250mL beaker, to which 100mL of deionized water was added. After being stirred evenly, the mixture is put into a quick-opening reaction kettle and is treated by H2The air in the kettle was displaced 3 times. Without turning on the agitator, without passing H2Heating to 50 deg.C, introducing H2To 50MPa and the stirrer was switched on at 500 rpm. After reacting for 3 hours, the reaction was terminated, and the reaction mixture was centrifuged at 12000rpm, and the silver powder at the bottom was washed with deionized water after separating the supernatant, and then washed 3 times. Then the silver powder is dried in vacuum at the temperature of 80 ℃ to obtain the silver powder product with the median diameter of 756 nanometers.
Example 5
Using the silver oxide prepared in example 1, 15g of Ag was weighed2O (undried isolated solid, 20% water) and 1g polyvinylpyrrolidone (molecular weight 850) were placed in a 250mL beaker, to which was added 100mL of deionized water. After being stirred evenly, the mixture is put into a quick-opening reaction kettle and is treated by H2The air in the kettle was displaced 3 times. Without turning on the agitator, without passing H2Heating up under the condition of (1), and introducing H at 20 DEG C2To 0.1MPa and the stirrer was switched on at 500 rpm. After the reaction is carried out for 12 hours, the reaction is finished, the reactor is opened to obtain dark yellow thick slurry, the thick slurry is placed at the rotating speed of 12000rpm for centrifugation, the silver powder at the bottom is washed by deionized water after the supernatant is separated, and the washing is carried out for 3 times. Then placing the silver powder into a vacuum drying chamber at the temperature of 60 ℃ to obtain the nano silver powder product, wherein the median diameter is 22 nanometers.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A method for preparing nano silver powder by hydrogen reduction is characterized in that: comprises the following steps of (a) carrying out,
s1, reacting the silver nitrate solution with sodium hydroxide or potassium hydroxide solution through an impinging stream reactor to prepare silver oxide precipitate, wherein the median diameter of the prepared silver oxide is less than 0.5 micron;
s2, mixing the separated and washed silver oxide, a surfactant and deionized water in a reactor, and introducing hydrogen into the reactor to react to prepare nano silver powder, wherein the proportion of the silver oxide is 0.5-40%, and the proportion of the surfactant is 0.1-5%;
s3, after centrifugal separation or natural sedimentation of the nano silver powder, washing the nano silver powder for a plurality of times by using deionized water, and then washing the nano silver powder for a plurality of times by using absolute ethyl alcohol;
s4, vacuum drying at 20-80 ℃ to obtain the nano silver powder with the median diameter of 5-800 nanometers.
2. The method for preparing silver nanoparticles powder by hydrogen reduction according to claim 1, wherein the molar ratio of silver nitrate to sodium hydroxide or potassium hydroxide in step S1 is 1 (1-1.05).
3. The method for preparing silver nanoparticles powder by hydrogen reduction according to claim 1, wherein the mass ratio of silver oxide to deionized water in step S2 is 1 (1-100).
4. The method for preparing silver nanopowder by hydrogen reduction according to claim 1, wherein in step S2, the pressure of hydrogen is 0.1-50 MPa.
5. The method for preparing silver nanoparticles through hydrogen reduction according to claim 1, wherein the reaction temperature in step S2 is 15-95 ℃.
6. The method for preparing silver nanoparticles powder by hydrogen reduction according to claim 1, wherein in step S2, the surfactant is one or a mixture of polyvinylpyrrolidone, polyoxyethylene sorbitan fatty acid ester and polyvinyl alcohol.
7. Polyvinylpyrrolidone, polyoxyethylene sorbitan fatty acid ester and polyvinyl alcohol according to claim 6 have a molecular weight of less than 2000.
8. The method for preparing silver nanoparticles through hydrogen reduction according to claim 1, wherein in step S2, ammonia water is added to adjust the pH value to 10-12.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114226711A (en) * | 2021-12-31 | 2022-03-25 | 江苏纳美达光电科技有限公司 | Silver nanoparticles and method for preparing same |
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| CN101554664A (en) * | 2009-05-20 | 2009-10-14 | 广东风华高新科技股份有限公司 | Method for preparing nano-scale silver powder |
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Application publication date: 20210924 |