KR20110019603A - Preparation of silver nano-powder from agcl by slurry reduction methods and silver nano-powder thereof - Google Patents

Abstract

PURPOSE: A producing method of nano-silver particles from silver chloride using a slurry reduction method, and the nano-silver particles are provided to reduce processes for producing the nano-silver particles with the high added value. CONSTITUTION: A producing method of nano-silver particles comprises the following: inserting silver chloride powder into a reactor containing an ammonia solution and a polyvinyl-pyrrolidone solution, and stirring the mixture for obtaining ammonia complex silver; inserting a hydrazine solution as a reductant to the mixture, for reducing the ammonia complex silver by being reacted with hydrazine; and collecting solid particles from the mixture by solid-liquid separating, and drying the solid particles.

Description

Preparation of nano silver particles from silver chloride by slurry reduction method and nano silver particles thereof {Preparation of silver nano-powder from AgCl by slurry reduction methods and silver nano-powder

The present invention relates to a method for producing nano-silver particles from silver chloride by the slurry reduction method, and more particularly to the nano-silver particles, and more specifically, to a silver slurry in the recovery of silver contained in an intermediate or an aqueous solution during the production of metal silver The present invention relates to a method for producing nano-sized silver particles by reduction to hydrazine (N ₂ H ₂ ) in a state, and to nano silver particles thereof.

Nano silver powder has antibacterial and bactericidal effect, excellent thermal and electrical conductivity and is widely used in industrial fields. In particular, it is used for the conductive coating of electronic components or as a sintering material in the manufacture of catalysts and alloys. In addition, dozens of nano-sized silver powders are used as raw materials for direct application in real life such as antibacterial tiles, burn treatments, and water purifier systems.

Since these nano powders have a large surface area, they are more reactive than bulk silver and have various properties. Therefore, nanoparticles of silver have the advantage of being more effective with less material than bulk silver.

Recently, the electronics industry has become smaller and more versatile. Silver powder used in the existing electronics industry has a limitation in the composition of electronic circuits in nano units in microns. Coarse powder is difficult to miniaturize when manufacturing electronic products and has a problem in surface roughness, and has a disadvantage that it is difficult to apply to glass and plastic substrates with a firing temperature of 700 ° C. or more.

Therefore, when manufacturing silver powder having nano size and excellent dispersibility, it can be applied to electronic paper with micro electronics and plastic substrate.

As described above, a technique for preparing nano-sized silver particles can be roughly classified into a liquid phase method and a gas phase method. The liquid phase method is a liquid phase reduction method for producing silver particles by reacting with a reducing agent in an aqueous solution in which silver ions are dissolved. The vapor phase method is an evaporative condensation method prepared by evaporating and condensing a liquid containing silver ions with H ₂ gas. The pyrolysis method of pyrolyzing a compound using a gas reducing agent to produce silver powder, etc. are mentioned.

The liquid phase reduction method takes a lot of manufacturing time because the filtration and washing process is repeated several times in the solution, it is difficult to produce uniform particles due to the aggregation easily occurs due to the interface effect between the solid phase and the liquid phase, Because of the use of aqueous solutions, the amount of wastewater generated is large, resulting in environmental pollution. In addition, there is a disadvantage that it is difficult to increase the production scale with low productivity. In addition, the prolonged processing time leads to aggregation of silver powder and poor uniformity. Therefore, it is known that it is very difficult to produce nano-sized silver particles by liquid phase reduction method.

In addition, evaporative condensation is a process of evaporative condensation by applying a reducing agent and heat to a liquid metal salt in a vacuum state, which requires a lot of equipment costs, and it is difficult to obtain monodisperse nanopowders. Pyrolysis is a process for producing nano-sized metal particles by spraying a metal salt together with a reducing agent at a high temperature. Since the process also uses an expensive reducing agent such as hydrogen, manufacturing costs are expensive and equipment costs are also high. In addition, there is a disadvantage that the dispersion of the particles is difficult and the recovery rate of the produced particles is poor.

Specifically, the liquid phase method that is widely used in the existing silver nano-manufacturing process, to reduce the silver chloride obtained by the addition of chlorine ions to recover the silver from a solution mixed with impurities, to produce metal silver, and then dissolved in nitric acid To make a solution containing silver ions and to reduce the silver particles of the nanoparticles. In the existing liquid phase, the nano silver manufacturing process takes a lot of time because the entire filtration and washing process is repeated in the aqueous solution as described above, it takes a lot of manufacturing time, and due to the interfacial effect between the solid phase and the liquid phase in the liquid phase, It is difficult to produce uniform particles, and there is a problem in that the amount of waste water generated due to the use of aqueous solution causes environmental pollution.

An object of the present invention for solving the problems described above is a simple method of slurrying silver chloride having a very low solubility obtained during recovery of silver contained in an intermediate product or an aqueous solution during the production of metal silver into an ammonia solution, and through a reduction process. By providing high value-added nano silver particles to provide a method of producing nano silver and nano silver produced therefrom to reduce the process, prevent impurity mixing, reduce waste water generation and production costs.

In the present invention to achieve the object as described above and to perform the problem for removing the conventional drawbacks,

In order to form ammonia silver complex from silver chloride powder, the complex is heated by adding silver chloride powder to a reaction tank loaded with ammonia (NH ₄ OH) solution and a dispersant polyvinylpyrrolidone (PVP _k-30 ) solution. Forming step;

Thereafter, a solution of hydrazine (N ₂ H ₂ ), which is a reducing agent, is continuously added to reduce the ammonia silver complex by reacting with the hydrazine; And

To recover the solid particles by solid-liquid separation of the reduced reaction solid particles in a centrifuge with distilled water, and drying the recovered solid particles: to prepare nano silver particles from silver chloride by a slurry reduction method characterized in that By providing a method.

The amount of the silver chloride powder is characterized by adding 10 to 100 g per 1000 ml of the total mixed solution.

PVP constituting the complexing solution And the mixing ratio of NH ₄ OH is the total mixed solution 1000 ㎖ reference PVP 10-30g and NH ₄ OH is characterized by mixing a 40-160 ㎖.

The hydrazine continuously added is added at a rate of 1-4 ml / mim per minute based on 1000 ml of the total mixed solution, and the amount is 10-40 ml.

The reactor is characterized in that to use a semi-batch constant temperature reaction tank that can adjust the reducing agent injection rate.

The semi-batch constant temperature reactor is characterized in that the stirring at a speed of 200-800rpm at a reaction temperature of 20 ~ 60 ℃.

The silver chloride (AgCl) powder particle size is characterized by using 50 to 200 ㎛.

The drying of the solid particles is characterized by drying for 24 hours at a temperature of 40 ~ 60 ℃ in a vacuum oven.

In another embodiment, the present invention is prepared from the silver chloride by the slurry reduction method characterized in that the particles produced by the above method has a size of 30-50 nanometers, and the particles do not aggregate and have a uniformly dispersed round shape. By providing nano silver particles.

Nano silver manufacturing method according to the present invention is simple to operate by a semi-batch process and by applying both nano silver particle production and anti-aggregation at the same time, it is possible to manufacture nano silver particles in a simple, economical low production cost and industrial use It is easy. In addition, it is an invention that is expected to be greatly used in the industry as a process for producing nano-particle silver, which is directly nano-sized from the silver chloride, an intermediate product generated during the silver metal manufacturing process, and dispersed than conventional nano silver.

Hereinafter, the configuration and the operation of the embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is a manufacturing process chart of nano silver particles according to the present invention.

As shown in the present invention, silver chloride (AgCl) powder particles are used as a starting material for producing nano silver particles, and the starting materials are reacted by slurrying them in an ammonia solution. Complex forming agent is ammonia (NH ₄ OH) solution, reducing agent is hydrazine (N ₂ H ₂ ) solution, dispersing agent is PVP (polyvinylpyrrolidone, PVP _k-30 ), the experimental device can control the reducing agent injection rate It is a slurry reduction method using a batch semi-batch reaction bath.

The reason why the ammonia (NH ₄ OH) solution is used as the complexing agent in the above is that ammonia reacts with silver to form a silver-ammonium complex to prevent the formation of free silver ions, thereby producing monodisperse particles, and reducing hydrazine. This is because the basicity is provided to the reaction system during the reaction to maintain the pH at which the reduction reaction is possible.

The reason why the hydrazine (N ₂ H ₂ ) solution is used as a reducing agent is that the reduction rate for silver is higher, higher than the reduction potential of the ammonia-silver complex, and the environmental pollution by the by-products is less than that of the organic reducing agent.

The reason why PVP is used as a dispersant is because it promotes nucleation of silver metal and inhibits aggregation and growth of metal particles, which is effective for controlling the size and particle size distribution of fine metal particles.

Silver chloride (AgCl) powder particle size was used in the 50-200 ㎛.

Specifically, the method for preparing nano-silver particles of the present invention comprises adding silver chloride (AgCl) powder to a semi-batch incubator containing NH ₄ OH solution as a complexing agent, followed by stirring and adding PVP to form ammonia silver complex (complex formation. step),

The complexed ammonia is a method of producing nano-sized silver particles through the step of continuously and constantly adding hydrazine to the solution to reduce the ammonia silver complex and hydrazine.

The solution (l or 1000 ml) described below refers to the total mixed solution including the component elements mixed in distilled water.

The ammonia is complexed with a complex formation solution in which PVP and 8% (weight fraction 80 mL / L) NH ₄ OH are mixed in the formation step of the complex.

The ammonia complex formed in the pretreatment step is subjected to a reduction reaction with a solution containing hydrazine in the solution.

The amount of silver chloride powder added is 10-100 g (preferably 50 g) per 1000 ml. At this time, less than 10g the amount of the filtering solution compared to the nanoparticles produced is inefficient at the time of filtration, if more than 100g agglomeration of the produced nanoparticles is severe.

PVP constituting the complexing solution And the mixing ratio of NH ₄ OH is 10-30 g (preferably 30 g) of PVP on the basis of 1000 ml and 40-160 ml (preferably 160 ml) of NH ₄ OH.

The reducing solution is hydrazine and is added continuously. It is added at a rate of 1-4 ml / mim per minute on a 1000 ml basis and the amount is 10-40 ml (preferably 40 ml).

The reason for limiting the numerical value as described above is that in the case of PVP, the aggregation of silver particles is severe when less than 10 g, and when more than 30 g, the reaction of the reducing agent is inhibited.

In the case of NH ₄ OH, when it is less than 40 ml, complex formation is difficult. If it is more than 160 ml, the reaction with the reducing agent is inhibited and the aggregation becomes severe.

In the case of hydrazine as a reducing agent, it is added continuously and less than 10 ml does not reduce, and when it is added more than 40 ml, the reducing agent consumption is large and the aggregation becomes severe.

The silver chloride powder is added to a pyrex semi-batch incubator and then stirred at a speed of 200-800 rpm, preferably at 200 rpm. When the salt is less than 200 rpm, the salt is agglomerated and the reaction does not occur. The powder is suspended and its reactivity is poor. At this time, the reaction temperature is heated to 20-60 ℃ (preferably 40 ℃).

In the case of the reaction temperature, the reduction reaction does not occur if it is lower than 20 ℃, the nuclear growth increases if it is higher than 60 ℃ does not produce nanoparticles.

The composition forming the complex forming solution during the complex forming reaction is PVP And the mixing ratio of NH ₄ OH is 10-30 g (preferably 30 g) of PVP on the basis of 1000 ml and 40-160 ml (preferably 160 ml) of NH ₄ OH. Or less, the same fluctuations).

In the reduction reaction, the complex formation reaction is performed by injecting hydrazine (N ₂ H ₂ ) into a semi-batch incubator at a rate of 1-4 ml per minute to proceed with a reduction experiment.

The reason why hydrazine (N ₂ H ₂ ) is added at a rate of 1-4 ml per minute is lower than 1 ml, so that the amount of reducing agent is insufficient, so that the reduction reaction does not occur. This gets worse.

When the generation of nitrogen gas in the semi-batch incubator is stopped, the semi-batch incubator is dismantled, and then the reactants are rotated at 10000 rpm in a centrifuge to recover solid particles by solid-liquid separation. The recovered solid particles were dried in a vacuum oven at a temperature of 40-60 ° C. and then weighed, chemically analyzed, XRD and SEM were observed.

If the drying temperature is lower than 40 ℃ in the above it does not dry, if higher than 60 ℃ the aggregation of the particles is severe.

Hereinafter will be described a preferred embodiment according to the present invention.

Example 1

1 liter of a mixture of 160 ml of NH ₄ OH and 30 g of PVP (which varies equally when the amount of reference solution is large or small) is added to the distilled water in a semi-batch incubator and 50 g of silver chloride powder is added.

The reaction solution is heated to a reaction temperature of 40 ℃ while stirring at 200 rpm.

When the reaction temperature is reached, the hydrazine (N ₂ H ₂ ) solution required for the experimental conditions is injected for 10 minutes using a solution injection device at a rate of 1 ml per minute, and then a reduction reaction is performed.

When the reduction reaction is complete, the reaction product is centrifuged at 1000 rpm in a centrifuge. After centrifugation, the solution is discarded, distilled water is charged and re-centrifugation is performed three times.

According to the above method, the dried silver powder was dried at 40 ° C. for 24 hours or more in a vacuum oven, and the crystal phase of the silver powder was confirmed using XRD.

When preparing nano silver particles by the method of the present invention as described above, the size of the silver particles is about 30-50 nanometers. Therefore, it can be seen that the nano-silver particle production method using the present invention is very effective.

Figure 2 is a SEM photograph of the silver chloride used in Example 1 and Example 2, as shown, the silver chloride is shown that the particles having an elongated shape of about 20-30 ㎛ are agglomerated to have a size of about 100 ㎛ or more Can be.

3 is an X-ray diffraction analysis result of the nano-silver particles prepared according to Example 1, it shows that it has an X-ray diffraction shape of typical metal silver as shown. This fact indicates that the nano silver particles produced in this manufacturing process are pure silver metals.

4 is an enlarged photograph of the nano silver particles prepared according to Example 1 by a transmission electron microscope, in which nano silver particles are dispersed by particles and have a size of 30-50 nm.

Example 2

1 liter of a mixture of 160 ml of NH ₄ OH and 30 g of PVP (which varies equally when the amount of reference solution is large or small) is added to the distilled water in a semi-batch incubator and 50 g of silver chloride powder is added.

The reaction solution is heated to a reaction temperature of 40 ℃ while stirring at 200 rpm.

When the reaction temperature is reached, the hydrazine (N ₂ H ₂ ) solution required for the experimental conditions is injected at a rate of 4 ml per minute using a solution injector for 10 minutes and then subjected to a reduction experiment.

When the reduction reaction is complete, the reaction product is centrifuged at 1000 rpm in a centrifuge. After centrifugation, the solution is discarded, distilled water is charged and re-centrifugation is performed three times.

It dried at 40 degreeC by vacuum oven for 24 hours or more, and the dried silver powder confirmed the crystal phase of silver powder using XRD.

5 is an enlarged photograph of the resultant of Example 2 used in the present invention as seen through a transmission electron microscope. As shown, the nano silver particles are more aggregated than in Example 1 and have a size of 30-50 nm.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by those skilled in the art without departing from the gist of the invention as claimed in the claims. Of course, such changes are within the scope of the claims.

1 is a manufacturing process chart of nano silver particles according to the present invention,

2 is an enlarged photograph of an electron micrograph of silver chloride used in Examples 1 and 2 of the present invention,

3 is an X-ray diffraction analysis of nano silver particles prepared according to Example 1 of the present invention.

4 is a magnified photograph of a transmission electron microscope of nano silver particles prepared according to Example 1 of the present invention.

5 is a magnified photograph of a transmission electron microscope of nano silver particles prepared according to Example 2 of the present invention.

Claims (9)

In the method for producing nano silver particles, In order to form ammonia silver complex from silver chloride powder, the complex is heated by adding silver chloride powder to a reaction tank loaded with ammonia (NH ₄ OH) solution and a dispersant polyvinylpyrrolidone (PVP _k-30 ) solution. Forming step; Thereafter, a solution of hydrazine (N ₂ H ₂ ), which is a reducing agent, is continuously added to reduce the ammonia silver complex by reacting with the hydrazine; And To recover the solid particles by solid-liquid separation of the reduced reaction solid particles in a centrifuge with distilled water, and drying the recovered solid particles: to prepare nano silver particles from silver chloride by a slurry reduction method characterized in that Way. The method according to claim 1, The method for producing nano-silver particles from silver chloride by the slurry reduction method characterized in that the amount of the silver chloride powder is added per 1000 ml of the total mixed solution. The method according to claim 1, PVP constituting the complexing solution And a method for the mixing ratio of NH ₄ OH is the total mixed solution 1000 ㎖ reference PVP 10-30g and NH ₄ OH is by slurry reduction method comprising a step of mixing a 40-160 ㎖ producing a nano-silver particles from silver chloride. The method according to claim 1, The continuously added hydrazine is added at a rate of 1-4 ml / mim per minute based on 1000 ml of the total mixed solution, the addition amount is 10-40 ml to prepare nano silver particles from silver chloride by the slurry reduction method Way. The method according to claim 1, The reactor is a method for producing nano-silver particles from silver chloride by the slurry reduction method, characterized in that using a semi-batch constant temperature reaction tank that can adjust the reducing agent injection rate. The method according to claim 5, The semi-batch constant temperature reactor is a method for producing nano-silver particles from silver chloride by the slurry reduction method characterized in that the stirring at a rate of 200-800rpm at a reaction temperature of 20 ~ 60 ℃. The method according to claim 1, The silver chloride (AgCl) powder particle size is 50 ~ 200 ㎛ method for producing nano-silver particles from silver chloride by the slurry reduction method characterized in that used. The method according to claim 1, Drying the solid particles is a method for producing nano-silver particles from silver chloride by a slurry reduction method characterized in that the drying for 24 hours at a temperature of 40 ~ 60 ℃ in a vacuum oven. The particles prepared by the method of any one of claims 1 to 8 are 30-50 nanometers in size, and the particles are prepared from silver chloride by the slurry reduction method, characterized in that they have a rounded shape in which the particles are uniformly dispersed. Nano silver particles.

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