KR20170030930A - The manufacturing method of silver powder using the silver crystal - Google Patents

The manufacturing method of silver powder using the silver crystal Download PDF

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KR20170030930A
KR20170030930A KR1020150128478A KR20150128478A KR20170030930A KR 20170030930 A KR20170030930 A KR 20170030930A KR 1020150128478 A KR1020150128478 A KR 1020150128478A KR 20150128478 A KR20150128478 A KR 20150128478A KR 20170030930 A KR20170030930 A KR 20170030930A
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silver
solution
silver nitrate
nitric acid
reaction solution
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KR1020150128478A
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Korean (ko)
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KR101764218B1 (en
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이창근
진우민
권태현
우상덕
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엘에스니꼬동제련 주식회사
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Priority to PCT/KR2016/009970 priority patent/WO2017043837A1/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00Making metallic powder or suspensions thereof
    • B22F9/16Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2301/00Metallic composition of the powder or its coating
    • B22F2301/25Noble metals, i.e. Ag Au, Ir, Os, Pd, Pt, Rh, Ru
    • B22F2301/255Silver or gold

Abstract

The present invention relates to a silver nitrate silver manufacturing step (S11) for preparing a silver nitrate solution by dissolving silver (Ag) grains having a specific surface area of 0.001 to 0.01 m 2 / g in a nitric acid (HNO 3 ) solution, (S1) comprising a silver nitrate silver concentration step (S12) for obtaining a concentrated silver nitrate silver solution by removing silver nitrate solution And can provide a manufacturing method capable of controlling the particle size of silver powder to be precipitated by applying a concentration process.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to silver powder,

The present invention relates to a method for producing a silver powder for a conductive paste, which is used for an electrode for a solar cell, an internal electrode of a multilayer capacitor, and a conductor pattern of a circuit board.

The conductive metal paste is a paste in which a conductive film (film) is formed and a conductive paste (metal filler) is dispersed in a vehicle composed of a resin binder and a solvent. And the like.

In particular, Silver Paste is the most chemically stable and excellent in conductivity among the conductive paste of composite system, and has a wide range of applications in various fields such as conductive bonding and coating and fine circuit formation. BACKGROUND ART [0002] The use of silver paste has been widely used for STH (Silver Through Hole), adhesive, or coating materials in electronic parts, such as PCBs (Printed Circuit Boards), where reliability is particularly important.

As a conventional method for producing silver powder, a silver ingot having a purity of 99.99% is dissolved in nitric acid, and the pH is adjusted to 10 to 11, followed by reduction and precipitation by adding a reducing agent. The type of silver currently traded in the industry is largely divided into granules and ingots. Granules are spherical particles having a diameter of 2 to 8 mm and are prepared by dropping molten silver into water to form spherical granules. The ingot is produced by casting silver in the same molten state using a hexagonal mold. Although the international standard specifies a standard of 30 kg of ingot, granules may be preferred by the convenience of the user.

Two types of granules and ingots are now used in the industry to minimize the volume and facilitate storage and minimize the cost of transportation. However, in the case of granules and ingots generally used in this form, they can be a disadvantage in the silver powder manufacturing process for producing silver nitrate using nitric acid. The silver (silver ingot) processed in the form of reducing the specific surface area in order to minimize the volume during storage and transportation has a small reaction area with silver nitrate, and it takes a long time to produce silver nitrate compound.

Therefore, the inventors of the present invention have focused on a fast and economical process by applying silver, which has a large specific surface area to granules and ingots, and silver lumps having the same properties, such as impurities, to the manufacturing process of silver powder.

On the other hand, in the conventional silver powder production, reduction reaction proceeds rapidly when silver ions (Ag + ) contained in the solution are reduced and precipitated using an organic reducing agent, so that the control of the particle diameter and the shape of the silver powder There is a problem that the particle size of the silver particles precipitated is difficult and coagulation phenomenon occurs.

Accordingly, the inventors of the present invention have focused on a process capable of controlling the particle size of the silver powder to be precipitated by the concentration process in the process of producing the silver salt for precipitating the silver powder.

1. Korean Registered Patent No. 10-0982042 (September 30, 2010) 2. Korean Patent Publication No. 10-2007-0051777 (2007.05.18)

The present invention has been made to solve the above-mentioned problems, and provides a method of manufacturing a silver powder using silver lips to provide a fast and economical method of producing silver powder, And a method for producing the silver powder capable of controlling the particle size of the silver powder.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention relates to a silver nitrate silver manufacturing step (S11) for preparing a silver nitrate solution by dissolving silver (Ag) grains having a specific surface area of 0.001 to 0.01 m 2 / g in a nitric acid (HNO 3 ) solution, And a silver salt production step (S1) including a silver nitrate silver concentration step (S12) for obtaining a concentrated silver nitrate solution by removing the silver nitrate silver solution (S1).

Further characterized in that the step of preparing a silver nitrate solution so that nitric acid (HNO 3) is dissolved in 100 parts to 300 parts by weight relative to the nitric acid production step (S11) is the (Ag) 100 parts by weight.

The silver nitrate silver production step (S11) is characterized by dissolving the silver (Ag) grains in the nitric acid (HNO 3 ) solution at a temperature of 40 to 80 ° C.

Further, the concentration of silver nitrate (S12) may be such that when the ratio of the volume after heating to the volume before heating of the silver nitrate solution is a concentration (a,%), the concentration is varied within a range of 0.1 to 80% And the pH of the concentrated silver nitrate solution is adjusted to 0.1 to 5.0.

Further, the nitric acid silver concentration step (S12) is a step of heating to 90 to 150 DEG C to obtain a concentrated silver nitrate solution.

The present invention also provides a method for producing a silver halide emulsion, comprising the steps of: (S21) preparing a reaction solution for preparing a first reaction solution containing the concentrated silver nitrate solution and ammonia, and a second reaction solution containing a reducing agent, (S2) comprising a precipitation step (S22) of reacting the first reaction solution and the second reaction solution to obtain a silver powder.

The reaction solution preparation step (S21) is a step of preparing the first reaction solution so that ammonia is dissolved in an amount of 30 to 50 ml per 100 g of silver nitrate, and the second reaction solution is prepared so that a reducing agent is contained in an amount of 40 to 60 g per 100 g of silver nitrate .

The reducing agent may be at least one selected from the group consisting of hydroquinone, ascorbic acid, alkanolamine, hydrazine and formalin.

Further, the present invention is characterized in that a concentrated silver nitrate solution in a pH range of 0.1 to 5.5 is prepared by the reaction solution preparation step (S21), and the average particle size of the silver powder precipitated in the precipitation step (S22) Is adjusted to 0.1 to 2.0 mu m.

The present invention dissolves silver lignite in nitric acid at a rapid reaction rate by using silver (Ag) lip having a large specific surface area and excess nitric acid, thereby reducing the manufacturing time of nitric acid silver, reducing the operation time of equipment, It is possible to provide an economical method of producing a silver powder by reducing the use of energy for making the powder.

Also, the pH of the silver nitrate solution can be easily controlled through the process of concentrating the silver nitrate solution prepared using an excessive amount of nitric acid, thereby controlling the particle size of the finally prepared silver powder.

Further, when a dispersant for controlling the particle size is added, it acts as an impurity when used in a conductive paste and may impair electrical conductivity. According to the present invention, the particle size can be effectively controlled without adding a dispersant.

FIG. 1 shows a graph showing the relationship between specific surface area and dissolution time.
FIG. 2 shows the relationship between the concentration of silver nitrate and the pH according to an embodiment of the present invention.
FIG. 3 shows the relationship between the pH of silver nitrate and the particle size according to an embodiment of the present invention.

Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is defined solely by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise stated.

Throughout this specification and claims, the word "comprise", "comprises", "comprising" means including a stated article, step or group of articles, and steps, , Step, or group of objects, or a group of steps.

On the contrary, the various embodiments of the present invention can be combined with any other embodiments as long as there is no clear counterpoint. Any feature that is specifically or advantageously indicated as being advantageous may be combined with any other feature or feature that is indicated as being preferred or advantageous. Hereinafter, embodiments of the present invention and effects thereof will be described with reference to the accompanying drawings.

A method of manufacturing a silver powder according to an embodiment of the present invention includes: a silver salt producing step (S1); Silver salt reduction step (S2); Purification step such as filtration and washing (S3); And a surface treatment step (S4). The method for producing silver powder according to the present invention necessarily includes the silver salt producing step (S1) and the silver salt reducing step (S2), and the other steps may be omitted.

One. (S1)

The silver salt production step (S1) according to an embodiment of the present invention can produce a silver salt through a silver nitrate silver production step (S11) of dissolving silver lips in a nitric acid solution to produce a silver nitrate solution, The silver salt may be prepared by further including a nitric acid silver concentration step (S12) to obtain a concentrated silver nitrate solution by heating the solution to remove nitric acid.

The silver nitrate silver manufacturing step (S11) according to an embodiment of the present invention is a step of dissolving the silver in the acid in the present embodiment to produce a silver salt. Silver means silver now in the form of a twig. It can be used with silver lips having a length of 1 to 10 mm, which is generated in an electrochemical refining process for increasing the purity in the process of smelting non-ferrous metals.

The silver lips use silver (Ag) lips having a specific surface area of 0.001 to 0.01 m 2 / g. When silver lips with a specific surface area of less than 0.001 m 2 / g are used, the reaction time is slowed to increase the operation time of the equipment due to the increase of the process time, and the energy for maintaining the temperature is excessively used, which is not economical. And the yield is lowered. As the specific surface area increases, the contact area with the nitric acid solution is increased, resulting in a rapid dissolution reaction. As a result, the dissolution time can be shortened by at least 10 times as compared with the ingot. However, in the case of using a silver lip having a specific surface area exceeding 0.01 m 2 / g, it is not easy to handle in the progress of the process, and when the silver is added during the process, There is a problem that the reactor overflow occurs. Therefore, in order to solve this problem, it is more preferable to use silver lips of 0.003 to 0.008 m 2 / g.

The silver lips are dissolved in an acid solution, especially a nitric acid (HNO 3 ) solution to prepare a silver nitrate solution. The silver and the nitric acid solutions are metered and reacted so that 100 parts by weight of silver (Ag) is dissolved in 100 to 300 parts by weight of nitric acid (HNO 3 ). This is because nitric acid equal to or greater than the reaction equivalent necessary for dissolving silver (Ag) can be used to further accelerate the reaction time and induce sufficient dissolution. The prepared silver nitrate silver solution contains an excessive amount of nitric acid, which is effective in easily adjusting the pH in the silver nitrate silver concentration step (S12) described later. When the content of the nitric acid is less than 100 parts by weight, the dissolution rate of the added silver lips is delayed, which increases the processing time and insufficient to dissolve the charged silver lips. If it exceeds 300 parts by weight, the dissolution rate can be increased. However, excessive nitric acid may cause excessive NOx gas during the concentration reaction, thereby increasing the environmental treatment cost. Therefore, it is more preferable to conduct the metering so that 100 parts by weight of silver is dissolved in 170 to 230 parts by weight of nitric acid. The nitric acid solution is preferably 30% solution.

The silver nitrate silver production step (S11) preferably dissolves the silver (Ag) grains in the nitric acid (HNO 3 ) solution at a temperature of 40 ° C to 80 ° C. It is generally known that when the metal is dissolved in an acid, the reaction rate can be increased by adding an appropriate temperature. If the reaction temperature is lower than 40 ° C, the dissolution rate of the silver is lowered. If the reaction temperature is higher than 80 ° C, the reaction becomes too fast, and the solution is boiled over in the reactor. Therefore, it is more preferable to dissolve at 60 to 70 占 폚.

The silver nitrate silver concentration step (S12) according to an embodiment of the present invention is a step of concentrating a silver nitrate solution by removing nitric acid from a silver nitrate silver solution prepared using silver lips. In this system, nitric acid can be removed by heating the nitric acid solution to vaporize the nitric acid. The pH of the silver nitrate solution can be easily adjusted through the nitric acid silver concentration step (S12) according to the present invention, and the pH of the silver nitrate solution can be easily adjusted by adjusting the pH So that the particle size of the finally prepared silver powder can be easily controlled.

The nitric acid silver concentration step S12 heats the silver nitrate solution to a temperature of 90 to 150 DEG C to remove nitric acid. When the ratio of the volume after heating to the volume before heating of the silver nitrate solution is defined as the concentration (a,%), the concentration (a) is varied in the range of 0.1 to 80%. To the concentrated silver nitrate solution, distilled water is added to the volume before concentration to prepare silver nitrate solution by adjusting the silver concentration in silver nitrate. Whereby the pH value of the concentrated silver nitrate solution can be adjusted in the range of 0.1 to 5.5.

As the concentration of nitric acid is increased by heating, the pH value becomes higher and the particle size can be controlled. The higher the pH value, the smaller the size of the silver powder. Precipitation of silver powder using a first reaction solution containing a silver nitrate solution having a pH value within a range of 0.1 to 5.5 obtained by adjusting the concentration (a) to 0.1 to 80% in a silver salt reducing step (S2) , A desired size of silver powder can be produced within an average particle size range of 0.1 to 2.0 mu m.

2. (S2)

The silver salt reducing step S2 according to an embodiment of the present invention is a step of reducing silver ions by adding a reducing agent and ammonia to a silver salt solution to precipitate silver particles, and silver ions, ammonia, and nitric acid (S21) for producing a second reaction solution containing a first reaction solution containing a reducing agent and a precipitation step (S22) for obtaining a silver powder by reacting the first reaction solution and the second reaction solution .

The silver salt solution may be a concentrated silver nitrate silver solution, which is a silver salt prepared through the silver salt preparation step (S1) according to an embodiment of the present invention. Alternatively, commercially available silver nitrate silver salt complex or silver intermediate solution may be used have.

In the reaction solution preparation step (S21) according to an embodiment of the present invention, ammonia is added to a silver nitrate solution and dissolved by stirring to prepare a first reaction solution. When a silver complex or a silver intermediate solution is used, nitric acid is further added to prepare a first reaction solution. The concentration of the contained silver ions is not limited, but is in the range of 6 g / L to 40 g / L. If it is less than 6 g / L, the yield tends to be low and economical efficiency is problematic. If it exceeds 40 g / L, there is a problem that powder agglomerates.

The reaction solution preparation step (S21) is metered so that ammonia is dissolved in an amount of 30 to 50 ml per 100 g of silver nitrate silver nitrate to prepare a first reaction solution. When ammonia is added in an amount less than 30 ml / 100 gAgNO 3 , ammonia is deficient in ammonia due to lack of ammonia in the complexing reaction, and silver oxide is generated. When ammonia is added in an amount exceeding 50 ml / 100 gAgNO 3, . The ammonia water used in this case is preferably an aqueous 25% ammonia solution for industrial use.

When a silver complex or a silver intermediate solution is used, the amount of nitric acid to be used is preferably 20 to 230 parts by weight based on 100 parts by weight of silver ions. When nitric acid is added in an amount of more than 230 parts by weight, the size and the organic content of the prepared silver powder are greatly increased and the reduction reaction of the silver ions is not completed due to the low pH.

The first reaction solution containing silver ions, ammonia and nitric acid may be prepared by adding a silver nitrate solution and an aqueous ammonia solution to a solvent such as water and stirring or adding an aqueous solution of silver nitrate, an aqueous solution of ammonia and an aqueous solution of nitric acid, And can also be prepared in the form of slurries.

The reaction solution preparation step (S21) according to an embodiment of the present invention also produces a second reaction solution containing a reducing agent.

The reducing agent may be at least one member selected from the group consisting of ascorbic acid, alkanolamine, hydroquinone, hydrazine and formalin, and among them, hydroquinone can be preferably selected. In the case of using a silver nitrate solution, the second reaction solution is prepared by weighing 40 to 60 g of a reducing agent per 100 g of silver nitrate contained in the first reaction solution. When a silver complex or silver intermediate solution is used, And 40 to 60 parts by weight based on 100 parts by weight of the resin. When the reducing agent is used in an amount less than the above range, silver ions may not be all reduced. If the reducing agent is used in excess of the above range, the organic matter content may increase, which may be a problem.

The second reaction solution containing a reducing agent can be prepared in an aqueous solution state by adding a reducing agent to a solvent such as water and dissolving it by stirring.

The precipitation step (S22) according to an embodiment of the present invention is a step of reacting the first reaction solution and the second reaction solution to obtain a silver powder, wherein the first reaction solution produced by the reaction solution production step (S21) The second reaction solution may be slowly added dropwise or may be added in a batch to react. Preferably, the addition of the components in a batch may terminate the reduction reaction in a short period of time, thereby preventing agglomeration of particles and increasing dispersibility.

In the meantime, in the embodiment of the present invention, the addition of the above-mentioned dispersant is not excluded from the scope of right to improve the dispersibility of silver particles and to prevent agglomeration. Examples of the dispersing agent include fatty acids, fatty acid salts, surfactants, organic metals, chelating agents and protective colloids.

However, when a dispersant for controlling the particle size is added, it acts as an impurity when used in a conductive paste, thereby deteriorating the electrical conductivity. According to the present invention, the particle size can be effectively controlled without adding a dispersant .

3. Purification step (S3)

In the refining step S3 according to an embodiment of the present invention, the silver powder dispersed in the aqueous solution or slurry is separated and washed by filtration after completing the silver particle precipitation reaction through the silver salt reducing step S2 Step S31. More specifically, after precipitating silver particles in the silver powder dispersion, the supernatant of the dispersion is discarded, filtered using a centrifugal separator, and the filter material is washed with pure water. It is not excluded from the scope of the present invention to apply various methods for solid-liquid separation such as filter presses and decanters in addition to the centrifugal separator mentioned in the present invention. The process of washing is done by completely removing the washing water from which the powder is washed. Thus reducing the water content to less than 10%. It is also possible to prevent agglomeration of the silver powder by optionally adding the above-mentioned dispersant to the reaction-completed solution before filtration.

Further, the purification step S3 according to an embodiment of the present invention may further include a post-cleaning drying and decoloring step (S34).

4. In the surface treatment step (S4)

The surface treatment step S4 according to an embodiment of the present invention is a step of hydrophobizing the hydrophilic surface of the silver powder, and may be selectively performed. More specifically, after adjusting the moisture content of the wet cake obtained after filtration to less than 10%, a surface treating agent may be added to the surface of the powder to adjust the water content to 70% to 85%. After that, the silver powder can be obtained through drying and decolorizing process. When the powder is surface-treated, the powder should be well dispersed to achieve sufficient surface treatment. If the water content is low, the dispersion efficiency is lowered.

The silver powder prepared according to an embodiment of the present invention has a size of 0.1 to 2.0 .mu.m, which is measured by measuring a diameter of each of 100 powders using a scanning electron microscope (SEM) At a temperature raising rate of 10 캜 / min. From room temperature to 500 캜. The organic content measured by TGA analysis was 1.0% by weight or less.

Examples and Experimental Examples

<Preparation of silver nitrate>

(1) Example 1

10 ml of pure water and 60% of industrial nitric acid were weighed to prepare a 30% nitric acid solution, and the mixture was heated and stirred at 60 ° C to prepare an acid solution. 5 g of a silver lip having a specific surface area of 0.0058 m 2 / g was dissolved at a rate of 1 kg / min while the flow of the acid solution was smooth through the stirring. The time at which the silver lips completely dissolve was measured and is shown in Table 1.

(2) Comparative Example 1

10 ml of pure water and 60% of industrial nitric acid were weighed to prepare a 30% nitric acid solution, and the mixture was heated and stirred at 60 ° C to prepare an acid solution. 5 g of silver granules having a specific surface area of 0.00017 m 2 / g was added to dissolve in a state where the flow of the acid solution was smooth through stirring. Table 1 shows the time for completely dissolving the granules.

(3) Comparative Example 2

10 ml of pure water and 60% of industrial nitric acid were weighed to prepare a 30% nitric acid solution, and the mixture was heated and stirred at 60 ° C to prepare an acid solution. 5 g of a silver ingot having a specific surface area of 0.00038 m 2 / g was added to dissolve in the state that the flow of the acid solution was smooth by stirring. The time at which the silver lips completely dissolve was measured and is shown in Table 1.

Is now kind Specific surface area (m 2 / g) Dissolution time (sec) Example 1 Silver lips
(Silver Crystal)
0.0058 605
Comparative Example 1 The granules
(Silver Granule)
0.00017 2890
Comparative Example 2 Silver ingot
(Silver Ingot)
0.00038 6060

As shown in Table 1, in the case of Example 1 in which silver lips having a specific surface area of 0.0058 m 2 / g were dissolved in the same nitric acid solution, the silver granules of the inventive example 1 were 4 times or more times the silver granules of 0.00017 m 2 / the dissolution time can be shortened by 10 times or more than the silver ingot of m 2 / g. FIG. 1 shows a graph showing the relationship between specific surface area and dissolution time.

<Concentration of silver nitrate>

(1) Example 2

The silver nitrate solution prepared in Example 1 was completely melted and heated at 150 캜 with stirring to remove the nitric acid. The volume ratio of the silver nitrate solution after heating to the volume of the silver nitrate solution before heating was 0.1% The silver nitrate solution was concentrated. The pH value of the concentrated silver nitrate solution was measured and shown in Table 2.

(2) Example 3

The silver nitrate silver solution prepared in Example 1 was completely melted and heated at 150 캜 with stirring to remove the nitric acid. The volume ratio of the silver nitrate silver solution after heating to the volume of the silver nitrate solution before heating was 15.8% The silver nitrate solution was concentrated. The pH value of the concentrated silver nitrate solution was measured and shown in Table 2.

(3) Example 4

The silver nitrate silver solution prepared in Example 1 was completely melted and heated at 150 캜 with stirring to remove nitric acid. The volume ratio of silver nitrate solution after heating to the volume of the silver nitrate solution before heating was 46% The silver nitrate solution was concentrated. The pH value of the concentrated silver nitrate solution was measured and shown in Table 2.

(4) Example 5

The silver nitrate silver solution prepared in Example 1 was completely melted and heated at 150 캜 with stirring to remove nitric acid. The volume ratio of the silver nitrate silver solution after heating to the volume of the silver nitrate solution before heating was 60% The silver nitrate solution was concentrated. The pH value of the concentrated silver nitrate solution was measured and shown in Table 2.

(5) Example 6

The silver nitrate solution prepared in Example 1 was completely melted and heated at 150 캜 with stirring to remove the nitric acid. The volume ratio of the silver nitrate solution after heating to the volume of the silver nitrate solution before heating was 67% The silver nitrate solution was concentrated. The pH value of the concentrated silver nitrate solution was measured and shown in Table 2.

(6) Example 7

The silver nitrate solution prepared in Example 1 was completely melted and heated at 150 캜 with stirring to remove the nitric acid. The volume ratio of silver nitrate solution after heating to the volume of the silver nitrate solution before heating was 77.5% The silver nitrate solution was concentrated. The pH value of the concentrated silver nitrate solution was measured and shown in Table 2.

Concentration of silver nitrate (%) Nitric acid pH Example 2 0.1 0.4 Example 3 15.8 0.8 Example 4 46 1.6 Example 5 60 2 Example 6 67 3.9 Example 7 77.5 5.1

As shown in Table 2, it can be seen that the pH of the silver nitrate solution can be easily adjusted from 0.4 to 5.1 by adjusting the concentration of silver nitrate silver from 0.1% to 77.5%, and FIG. 2 shows the relationship between the concentration of silver nitrate and the pH .

&Lt; Preparation of silver powder &

Examples 8 to 13

22 mL of the silver nitrate concentrated solution and 17.6 mL of ammonia (concentration 25%) concentrated by means of the second to seventh examples were added to 960.4 g of pure water at normal temperature and dissolved by stirring to prepare a first aqueous solution. On the other hand, 5.5 g of hydroquinone was added to 1000 g of pure water at room temperature and dissolved by stirring to prepare a second aqueous solution.

Subsequently, the first aqueous solution was stirred, and the second aqueous solution was added all at once to the first aqueous solution, and the mixture was further stirred for 5 minutes from the completion of the addition to grow particles in the mixed solution. Thereafter, stirring was stopped and the particles in the mixed solution were settled. Then, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, and the filter material was washed with pure water and dried to obtain silver powder.

The diameters of each of the 100 powder samples were measured using a scanning electron microscope (JEOL) manufactured by JEOL Ltd., and the average SEM size was measured. The results are shown in Table 3.

Use nitric acid Nitric acid pH SEM size (m) Example 8 Example 2 0.4 1.6 Example 9 Example 3 0.8 1.5 Example 10 Example 4 1.6 1.3 Example 11 Example 5 2 One Example 12 Example 6 3.9 0.8 Example 13 Example 7 5.1 0.6

As shown in Table 3, it can be seen that the respective particle sizes prepared using silver nitrate adjusted to a pH value of 0.4 to 5.1 were prepared from 1.6 μm to 0.6 μm. In FIG. 3, the relationship between the silver nitrate pH and the particle size Respectively.

The features, structures, effects, and the like illustrated in the above-described embodiments can be combined and modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

Claims (10)

A silver nitrate silver manufacturing step (S11) for preparing silver nitrate solution by dissolving silver (Ag) grains having a specific surface area of 0.001 to 0.01 m 2 / g in a nitric acid (HNO 3 ) solution and
And a silver salt production step (S1) including a silver nitrate silver concentration step (S12) for obtaining a concentrated silver nitrate solution by heating the prepared silver nitrate silver solution to remove nitric acid.
The method according to claim 1,
Phase of the method the powder preparation for preparing a silver nitrate solution to the nitric acid production step (S11) is silver (Ag) melting relative to 100 parts by weight of nitric acid (HNO 3) is 100 parts to 300 parts by weight.
The method according to claim 1,
The nitric acid production step (S11) is a step in the method for manufacturing the powder is dissolved in the above silver (Ag) nitrate granules (HNO 3) solution at a temperature of 40 to 80 ℃.
The method according to claim 1,
The concentration of silver nitrate (S12)
When the ratio of the volume after heating to the volume before heating of the silver nitrate solution is defined as the concentration (a,%)
And adjusting the pH of the concentrated silver nitrate solution to 0.1 to 5.0 by changing the concentration in the range of 0.1 to 80%.
The method according to claim 1,
Wherein the silver nitrate silver concentration step (S12) is a step of heating to a temperature of 90 to 150 DEG C to obtain a concentrated silver nitrate solution.
5. The method of claim 4,
After the silver salt preparation step (S1)
A reaction solution preparation step (S21) for producing a first reaction solution containing the concentrated silver nitrate solution and ammonia and a second reaction solution containing a reducing agent, and
And a silver salt reducing step (S2) comprising a precipitation step (S22) of reacting the first reaction solution and the second reaction solution to obtain a silver powder.
The method according to claim 6,
The reaction solution preparation step (S21) is a step of preparing the first reaction solution so that ammonia is dissolved in an amount of 30 to 50 ml per 100 g of silver nitrate.
The method according to claim 6,
Wherein the reaction solution preparation step (S21) is a step of preparing the second reaction solution so that the reducing agent is contained in an amount of 40 to 60 g per 100 g of silver nitrate.
The method according to claim 6,
Wherein the reducing agent is at least one selected from the group consisting of hydroquinone, ascorbic acid, alkanolamine, hydrazine, and formalin.
The method according to claim 6,
In the reaction solution preparation step (S21), a concentrated silver nitrate solution in the pH range of 0.1 to 5.5 is prepared and prepared for the production of the first reaction solution,
Wherein the silver powder precipitated in the precipitation step (S22) has an average particle size of 0.1 to 2.0 mu m.
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