JP2015160988A - Method of producing nickel powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a nickel powder having high dispersibility, which is suitable for manufacturing an internal electrode of a laminated ceramic capacitor.SOLUTION: The method of producing a nickel powder sequentially performs: a first pulverization step of pulverizing a nickel dry powder obtained by removing moisture from nickel particles in water to form a first pulverized powder; a heat treatment step of heat-treating the first pulverized powder obtained in the first pulverization step at a temperature of 150-350°C to form a heat-treated powder; and a second pulverization step of further pulverizing the heat-treated powder formed through the heat treatment step.

Description

The present invention relates to a method for producing nickel powder.
The nickel powder according to the present invention can be suitably used as an internal electrode of a multilayer ceramic capacitor (MLCC).

Conventionally, nickel powder has been used as a material for a conductive paste for producing a thick film conductor.
The thick film conductor is used for forming an electric circuit, an electrode of a multilayer ceramic component such as a multilayer ceramic capacitor and a multilayer ceramic substrate. In particular, in multilayer ceramic capacitors, the increase in the number of layers has progressed due to the demand for smaller size and higher capacity, and the amount of conductive paste used for that purpose has also increased significantly. For this reason, as the metal powder used for the conductive paste, the use of expensive noble metals is avoided, and inexpensive base metals such as nickel are mainly used.

The multilayer ceramic capacitor to be used is manufactured by the following method, for example.
First, a conductive paste obtained by kneading a nickel powder, a resin such as ethyl cellulose, and an organic solvent such as terpineol is screen-printed on a dielectric green sheet to produce an internal electrode. Next, dielectric green sheets are laminated and pressure bonded so that the printed internal electrodes are alternately overlapped. Thereafter, the laminate is cut into a predetermined size, subjected to a binder removal treatment for removing the resin such as ethyl cellulose used as an organic binder, and then fired at a high temperature to 1300 ° C. to obtain a ceramic body. And an external electrode is attached to this ceramic body, and it is set as a laminated ceramic capacitor.

  Here, the metal powder in the conductive paste serving as the internal electrode is mainly a base metal such as nickel rather than a noble metal as described above. Therefore, the nickel powder or the like is not oxidized in the binder removal treatment of the laminate. Thus, it is performed in an atmosphere containing a very small amount of oxygen.

  2. Description of the Related Art In recent years, multilayer ceramic capacitors that are required to be reduced in size and increased in capacity have been made thinner both in internal electrodes and dielectrics that constitute the multilayer ceramic capacitor. In particular, the particle size of nickel powder used for the internal electrode is mainly 0.5 μm or less.

  Various characteristics are required for the nickel powder used for such an internal electrode. Among these, dispersibility when forming a conductive paste is an important characteristic. When the dispersibility is low, that is, the nickel powder is easy to form an aggregate of nickel powder, the presence of the aggregate in the region of the internal electrode layer to which a particle size of 0.2 μm or less is applied causes unevenness on the green sheet surface. Will exist. When a green chip obtained by laminating green sheets having such unevenness is baked at a high temperature, delamination is likely to occur due to poor adhesion between layers (for example, Patent Document 2, paragraph [0003] reference).

  For this reason, the nickel powder is required to have a high dispersibility that does not form an aggregate when a paste is formed, and when the coating film is formed, the coating film surface is required to be smoother. In particular, from the viewpoint that thinning can be sufficiently expected, the average particle diameter is expected in the region of fine particles of 0.2 μm or less.

  By the way, as for the manufacturing method of nickel powder, CVD method (Chemical Vapor Deposition-chemical vapor phase reaction method), the manufacturing method of nickel powder which reduces a nickel compound in a gaseous phase (for example, refer to patent documents 1, the following dry reduction methods) There are known methods for producing nickel powder in which nickel particles are reduced and precipitated from an aqueous nickel salt solution (see, for example, Patent Document 2, hereinafter referred to as a wet reduction method).

In any of the nickel powders obtained by any of the production methods, the dispersibility of the nickel powder that appropriately disperses the nickel powder in the organic solvent in the paste is a problem.
The nickel powder with poor dispersibility is aggregated in the electrode paste, and when the electrode paste is printed on the dielectric green sheet, the aggregate is present in the internal electrode, and finally the laminated dielectric green sheet is aggregated. Causes a defect to penetrate.

  Therefore, as a method for improving the dispersibility, a technique for pulverizing particles by pulverizing nickel powder with a jet mill or the like is disclosed (see Patent Document 3). However, with this one-time jet mill treatment as in this proposal, a sufficient crushing effect cannot be obtained with a particle size of 0.2 μm or less. Even if nickel powder of 0.2 μm or less is simply pulverized twice or more by a jet mill alone to improve dispersibility, the nickel powder once processed by the jet mill has high adhesion and has a supply port. This causes a phenomenon that cannot be continuously processed due to accumulation in the process, and a phenomenon that adheres to and clogs the inside of the machine, making continuous processing difficult.

Japanese Patent Laid-Open No. 11-236606 JP 2004-2923 A JP 2005-23395 A

  This invention is made | formed in view of this problem, Comprising: It aims at providing the manufacturing method of suitable nickel powder, in order to produce the internal electrode of a multilayer ceramic capacitor. Specifically, the present invention provides a method for producing highly dispersible nickel powder.

  The first invention of the present invention includes a first crushing step of crushing a nickel dry powder obtained by removing moisture from nickel particles in water to form a first crushing powder, and the first crushing step A heat treatment step of heat-treating the first pulverized powder obtained at 150 ° C. to 350 ° C. to form a heat-treated powder, and a second solution for further pulverizing the heat-treated powder formed through the heat treatment step. It is a manufacturing method of the nickel powder characterized by performing a crushing process in order.

  According to a second aspect of the present invention, there is provided a method for producing nickel powder, characterized in that the heat treatment step in the first aspect performs a heat treatment in a mixed atmosphere of hydrogen and an inert gas.

  According to a third aspect of the present invention, there is provided a nickel powder production method, wherein the average particle size of the nickel dry powder in the first and second aspects is 0.10 to 0.20 μm.

  4th invention of this invention is a manufacturing method of the nickel powder characterized by the 1st crushing process and 2nd crushing process in 1st-3rd invention being a dry crushing process.

  According to a fifth aspect of the present invention, the nickel dry powder according to the first to fourth aspects is a nickel powder obtained by removing moisture from nickel particles obtained by reducing and growing a nickel salt aqueous solution. It is a manufacturing method of nickel powder.

  According to a sixth aspect of the present invention, the nickel particles according to the first to fifth aspects are prepared by mixing a colloidal aqueous solution in which colloidal particles of metal other than nickel are dispersed, a reducing agent, an alkaline substance, and a protective colloid agent. A nickel powder production method obtained by adding a nickel salt aqueous solution to an alkaline colloidal aqueous solution.

  A seventh invention of the present invention is a method for producing nickel powder, wherein the colloidal particles of metal other than nickel in the sixth invention are composite colloidal particles of palladium and silver.

  An eighth invention of the present invention is the nickel powder production method, wherein the reducing agent in the fifth and sixth inventions is hydrazine.

  According to a ninth aspect of the present invention, there is provided a method for producing nickel powder, wherein the protective colloid agent in the sixth to eighth aspects is gelatin.

  In the nickel powder manufacturing method according to the present invention, when dry jet pulverization is performed, the phenomenon of depositing on the supply port and the phenomenon of adhesion clogging in the machine are prevented, and the dispersibility is improved. It has a remarkable effect.

It is a scanning electron micrograph (10000 time) of the nickel powder obtained by this invention.

  The method for producing nickel powder according to the present invention includes a first pulverization step of forming a first pulverized powder by pulverizing nickel dry powder obtained by removing moisture from nickel particles in water, and then the first solution. It is a manufacturing method characterized by sequentially performing a heat treatment step of forming a heat treated powder by subjecting the crushed powder to a heat treatment at a temperature of 150 ° C. to 350 ° C., and a second crushing step of crushing the heat treated powder.

In this invention, the process which forms the surface which shows the specific property first on the surface of nickel powder is performed.
That is, it is a drying process in which the surface of the nickel powder is wetted with water and a nickel dry powder is produced from which the moisture that wets the surface is removed.
The nickel dry powder obtained by this drying step becomes a powder having nickel hydroxide on the surface. Note that nickel powder having nickel hydroxide on the surface makes it difficult to disperse the paste in an organic solvent, and forms an aggregate.

  Therefore, even a nickel powder in a dry state obtained by a dry reduction method is washed with water and used as a nickel dry powder from which moisture has been removed. Moreover, since nickel particles are produced in an aqueous solution, the nickel powder obtained by the wet reduction method is naturally used as a nickel dry powder after a predetermined process.

In other words, the nickel powder manufacturing method according to the present invention can appropriately treat the nickel dry powder obtained by removing the water from the nickel powder manufactured by the dry reduction method and the wet reduction method. This is a nickel powder that can be produced, and its production method.
Then, the manufacturing method of the nickel powder based on this invention is demonstrated below using the nickel powder manufactured by the wet reduction method as an example.

[Production of nickel powder by wet reduction method]
(A) Preparation of colloidal particles The production method of the alkaline colloidal aqueous solution is not particularly limited as long as it is a method of dispersing composite colloidal particles of palladium and silver in an alkaline reducing solution.
For example, (1) a composite colloidal solution in which colloidal particles of palladium and silver are dispersed, a reducing agent and an alkaline substance are mixed, (2) a reducing agent and an alkaline substance are added to the colloidal aqueous solution, and (3) the colloidal aqueous solution. And a step of mixing an alkaline solution containing a reducing agent.

  The palladium / silver composite colloid aqueous solution is prepared by mixing palladium and silver in a solution to which a protective colloid agent is added and dispersing the palladium / silver composite colloidal particles.

  Furthermore, since the prepared aqueous colloidal colloidal particles exist in a solution containing a reducing agent in a uniform monodispersed state, the core colloidal particles are added to the core colloidal particles when a nickel salt aqueous solution is added. In contrast, nickel tends to cause nucleation uniformly and evenly.

  Although the details of the mechanism by which the nickel particles produced by reduction are refined by using this aqueous alkaline colloidal solution are unknown, it is presumed as follows.

First, palladium and silver have higher oxidation-reduction potential than nickel, and nuclei are formed when nickel particles are deposited. It is thought that nickel precipitates and grows in these nuclei and becomes nickel particles. It is presumed that growth to nickel particles occurs without generation.
Secondly, since the core composite colloidal particles are present in a solution containing a reducing agent in a uniformly monodispersed state, when an aqueous nickel salt solution is added, nickel is not added to the core colloidal particles. Equally likely to cause nuclear growth.

  Thirdly, by adding not only palladium but also silver, aggregation of palladium is suppressed, so that formation of coarse particles and connected particles is suppressed. In particular, by controlling the mass ratio of palladium and silver within an appropriate value range, monodispersed palladium and silver composite colloidal particles having a more uniform particle size are generated, and coarse particles and connected particles Formation is suppressed.

  The reason for this is not clear, but if there is a lack of silver that is effective in suppressing the aggregation of palladium, the connected nuclei generated during the process of aggregating palladium will grow, leading to the generation of connected particles. It is done. In addition, it is considered that a plurality of composite colloids aggregate to form nuclei, and the grains grow around the nuclei to generate coarse particles. On the other hand, when silver is in an excessive amount, the generation of coarse colloidal particles composed solely of silver is considered to be involved in the generation of coarse particles and connected particles.

In addition, fourthly, it is considered that aggregation of colloidal particles is further suppressed by using a protective colloid agent.
As described above, it is considered that the generated nickel particles have a uniform particle size and are in a monodispersed state, and it is difficult to form coarse particles and connected particles. Further, by changing the number of the colloidal particles, nickel precipitation It is presumed that the number of nuclei can be changed and the particle size of the nickel particles can be controlled.

  The protective colloid agent is added to suppress aggregation of the colloidal particles, and the protective colloid agent to be used may be any material that surrounds the composite colloidal particles composed of palladium and silver and contributes to the formation of the protective colloid, Gelatin is particularly preferable, but polyvinyl pyrrolidone, gum arabic, sodium hexametaphosphate, and polyvinyl alcohol can also be used.

  The palladium salt aqueous solution is not particularly limited. For example, an aqueous solution containing at least one selected from palladium chloride, palladium nitrate, palladium sulfate and the like can be used as the aqueous palladium salt solution. Of these, palladium chloride, which allows easy liquid adjustment, is most preferable.

As the silver salt aqueous solution, for example, a silver nitrate aqueous solution can be used.
The reason for adding not only palladium but also silver is that aggregation of palladium is suppressed, and formation of coarse particles and connected particles is suppressed.
In particular, by controlling the mass ratio of palladium and silver within an appropriate value range, monodispersed palladium and silver composite colloidal particles having a more uniform particle size are generated, and coarse particles and connected particles Formation is suppressed.

  In addition, the amount of palladium in the alkaline colloid aqueous solution used is 10 to 500 mass ppm, the amount of silver is 0.1 to 5 mass ppm, the amount of gelatin of the protective colloid agent is 0.02 to 1 mass%, and further palladium and silver. The gelatin mass ratio is preferably controlled within the range of 90 to 110: 0.9 to 1.1: 1800 to 2200.

  In addition, although the composite colloidal particle which consists of palladium and silver was demonstrated to the example for the colloidal particle, the colloidal particle is not limited to the composite colloidal particle of palladium and silver. Any metal that is nobler than nickel may be used, and for example, colloidal particles such as copper may be used. As described above, since the colloidal particles become the core of the nickel powder, the metal element of the colloidal particles is not limited as long as the number of colloidal particles is appropriate.

(B) Reducing agent Although a reducing agent is not specifically limited, For example, the hydrazine aqueous solution produced using the water-soluble hydrazine compound containing at least 1 sort (s) chosen from hydrazine, a hydrazine compound, sodium borohydride, etc. Is preferably used. Among these water-soluble hydrazine compounds, hydrazine (N ₂ H ₄ ) and hydrated hydrazine (N ₂ H ₄ H ₂ O) are most preferable because they have particularly few impurities.

(C) Alkaline substance Although an alkaline substance is not specifically limited, For example, what is necessary is just water-soluble alkaline substances, such as sodium hydroxide, potassium hydroxide, and ammonia.
In the present invention, an alkaline hydrazine aqueous solution can be prepared by mixing these water-soluble alkaline substances and water-soluble hydrazine compounds such as hydrazine and hydrazine hydrate in pure water.

  The alkaline hydrazine aqueous solution is particularly preferably a mixed aqueous solution of sodium hydroxide and hydrazine hydrate having a pH adjusted to 10 or higher. On the other hand, a pH of less than 10 is not preferable because the reaction rate is low, and nickel is less likely to be reduced and precipitated.

(D) Nickel salt aqueous solution The nickel salt aqueous solution is not particularly limited, and for example, an aqueous solution containing at least one selected from nickel chloride, nickel nitrate, nickel sulfate and the like can be used. Among these aqueous solutions, a nickel chloride aqueous solution is particularly preferable because the waste liquid treatment is simple.

(E) Drying Dry nickel powder is obtained by filtering and drying nickel particles that have been reduced and precipitated from an aqueous alkaline colloidal solution. A known method may be appropriately selected as the filtration method and the drying method.

[First crushing step]
The first crushing treatment is preferably dry crushing. Hereinafter, the nickel powder manufacturing method according to the present invention will be described with reference to an example using a jet mill.

  The obtained nickel dry powder is sieved to obtain a dry powder containing aggregates of a certain size or less. The size of the agglomerates may be selected as appropriate depending on the jet mill as long as it can pass through the powder feed port to the processing chamber of the jet mill to be processed in the next step. Moreover, what is necessary is just to take a well-known method for the crushing and sieving method.

Next, it is desirable that the agglomerate to be crushed by a jet mill has a small particle size and is easily oxidized, and avoids dust explosion by a jet mill using an inert gas. Further, since the aggregation becomes stronger as the particles become finer, it is necessary to give a stronger crushing force. Therefore, it is desirable to treat with a jet mill using a gas lighter than air.
Specifically, there is a method of treating only nitrogen gas or helium gas as a gas medium. As a jet mill type, a counter type, a spiral type, or the like can be used.

In the first crushing step, the nickel dry powder is crushed to become a first crushed powder.
By this first crushing step, the nickel powders rub against each other or the machine wall, and the surface of the powder after the first crushing becomes smoother than the nickel dry powder. However, agglomeration remains in part even in the first crushed powder.
When further pulverization is performed in order to dissolve part of the first pulverized powder, if the average particle size of the nickel dry powder is 0.1 to 0.2 μm, the adhesion of the first pulverized powder is high. In some cases, a phenomenon may occur in which the particles are accumulated at the supply port of the jet mill and cannot be continuously processed, and the ink is adhered and blocked in the jet mill. Therefore, the crushing process cannot be performed continuously to the first crushing process.
In addition, when the average particle diameter of nickel dry powder exceeds 0.2 micrometer, the obstruction | occlusion in the supply port of the jet mill or a jet mill machine will not generate | occur | produce easily.

[Heat treatment process]
The purpose of the heat treatment step is to reduce the adherence of the first crushed powder, so that dry agglomeration is caused by removing the hydroxyl groups remaining on the surface of the nickel powder and the moisture of the nickel powder, and granulated into granules. To obtain agglomerated aggregates. The heat-treated powder is an aggregate that can be pulverized in the second pulverization step, and is in a state in which the nickel powder particles are not necked at a level where the particles cannot be separated from each other.

This heat treatment step heats the first crushed powder.
The heating atmosphere is preferably a mixed gas composed of hydrogen gas having a hydrogen concentration of 1 to 50% by volume and the remaining inert gas. When the hydrogen gas concentration is less than 1%, the change in the surface state of the nickel powder and the removal of impurities do not proceed sufficiently, and aggregates necessary for the next process cannot be formed.
Even if the hydrogen gas concentration is higher than 50%, the effect is not changed. The inert gas is not particularly limited, and nitrogen gas, argon gas, or the like can be used.

  Moreover, heating temperature is 150-350 degreeC. If the heating temperature is less than 150 ° C., aggregates cannot be formed. When heating temperature is higher than 350 degreeC, sintering of nickel powders starts and it cannot disperse | distribute powder.

The heating time is preferably 30 min to 180 min.
The furnace used for heating is not particularly limited as long as it can be used in a reducing atmosphere, and a batch furnace, a roller hearth furnace, a pusher furnace, or the like can be used.

[Second crushing step]
Next, agglomerates subjected to crushing treatment with a jet mill are easy to oxidize, easily generate dust explosions, and have strong agglomeration, so use an inert gas that is lighter than air that can provide a strong crushing force. Is desirable.
As a jet mill type, a counter type, a spiral type or the like can be used.

  Through the first crushing step, heating step, and second crushing step, it is considered that the nickel powder surface becomes smooth and foreign matters such as nickel hydroxide disappear.

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to these examples. Below, the evaluation method of nickel powder is shown.
The dispersibility of the nickel powder was evaluated by preparing a paste and using the surface roughness of the coating film using the paste.

[Average particle size]
Using a scanning electron microscope (JSM-5510: manufactured by JEOL Ltd.), an SEM image with a magnification of 10,000 times is obtained. This SEM image is measured using image analysis software (Mac-View, manufactured by Mountec Co., Ltd.) to measure the area and number of particles in which the entire shape of the particle shape can be seen, and from these, the diameter of each particle is obtained and averaged. Calculated.

[Membrane surface roughness (Ra)]
Specifically, the dry film is produced as follows.
First, ethyl cellulose (20% by mass) is heated to 80 ° C. with stirring in terpineol (80% by mass) to prepare a terpineol solution in which ethyl cellulose is dissolved.
45 mass% of this solution, 55 mass% of the nickel powder produced in the example, and the desired terpineol are kneaded in a three-roll mill to produce a nickel ink.

Next, the produced nickel ink is screen-printed on a 1 inch (2.54 cm) square alumina substrate and dried at a temperature of 120 ° C. for 1 hour to produce a dry film having a 10 mm square and a film thickness of 2 μm.
About the produced dry film | membrane, arithmetic mean surface roughness (Ra) was measured. The arithmetic average surface roughness (Ra) is based on the standard of JIS B0601-1994.

The nickel powder forming process is as follows.
An alkaline hydrazine solution was mixed with a composite colloidal solution consisting of palladium and a small amount of silver to prepare an alkaline colloidal solution for reducing nickel. The content of palladium, silver, and gelatin in the alkaline aqueous colloid solution is as follows: palladium: 40 mass ppm, silver: 0.4 mass ppm, gelatin: 800 mass with respect to the total mass of nickel in the nickel salt aqueous solution added later. ppm.

The preparation of the aqueous alkaline colloid solution for reducing nickel was specifically performed as follows.
First, gelatin was dissolved in 1800 L of pure water, and then hydrazine was mixed so that the concentration of hydrazine was 0.02 g / L. Next, a mixed solution of palladium and a small amount of silver was prepared, and dropped into the solution containing gelatin and hydrazine to obtain a colloidal aqueous solution.
After adding sodium hydroxide to the aqueous colloid solution to adjust the pH to 10 or more, hydrazine is further added until the concentration of hydrazine is 26 g / L, and an alkaline hydrazine solution in which a colloid composed of palladium and a small amount of silver is mixed is obtained. An aqueous alkaline colloid solution for reducing nickel was prepared. The hydrazine used was hydrated hydrazine and contained 60% by mass of hydrazine molecules.

  And 150 L of nickel chloride aqueous solution (nickel salt aqueous solution) whose nickel concentration is 100 g / L was dripped at this alkaline colloid aqueous solution, nickel was reduced, and nickel powder was obtained.

The nickel powder surface treatment process is as follows.
The obtained nickel powder was added to pure water at 17 g / L to prepare a nickel powder slurry. Thereafter, sodium hydrogen sulfide measured to 0.075% by weight of sulfur with respect to the nickel powder was dissolved in 500 ml of pure water, added to the prepared nickel powder slurry, stirred for 30 min, separated. Then, it dried with the vacuum dryer and obtained the nickel powder containing sulfur.

The first crushing step is as follows.
The obtained nickel powder was processed with a spiral jet mill (manufactured by Nippon Pneumatic Co., Ltd.).

The heat treatment process is as follows.
About the nickel powder (first pulverized powder) obtained through the first pulverization step, a hydrogen gas nitrogen gas mixed gas atmosphere with a hydrogen concentration of 1.4% by volume is heated at a temperature of 180 ° C. and a heating time of 60 minutes. went.

The second crushing step is as follows.
The obtained nickel powder (heat treated powder) was dissolved in a fluidized bed type counter-type jet mill (manufactured by Hosokawa Micron Co., Ltd .: Multiprocessing System 100AFG) equipped with a high-speed rotating rotor type classifier in the grinding chamber with the speed of the classifying rotor being 19000 rpm. Crushed and classified.

  FIG. 1 is an SEM image of the obtained nickel powder. A spherical nickel powder having a uniform particle size distribution, good dispersibility, and few connected particles and coarse particles is obtained.

  The nickel powder obtained by the same treatment from the nickel powder forming step of Example 1 to the heat treatment step was treated with a spiral jet mill (manufactured by Nippon Pneumatic Co., Ltd.).

  Nickel powder was obtained by treating in the same manner as in Example 1 except that the hydrogen concentration in the heat treatment step of Example 1 was changed to 1.0% by volume. Table 1 shows the results of the average particle diameter of the obtained nickel powder and the arithmetic average surface roughness of the dried film coated with the paste prepared using the nickel powder.

  A nickel powder was obtained by the same treatment as in Example 1 except that the reduction treatment temperature in the heat treatment step of Example 1 was set to 150 ° C. Table 1 shows the results of the average particle diameter of the obtained nickel powder and the arithmetic average surface roughness of the dried film coated with the paste prepared using the nickel powder.

  A nickel powder was obtained by the same treatment as in Example 1 except that the reduction treatment temperature in the heat treatment step of Example 1 was set to 350 ° C. Table 1 shows the results of the average particle diameter of the obtained nickel powder and the arithmetic average surface roughness of the dried film coated with the paste prepared using the nickel powder.

(Comparative Example 1)
Except for omitting the first crushing step of Example 1, the nickel powder obtained by the same processing from the nickel powder forming step to the heat treatment step was treated with a fluidized-bed counter type jet mill (manufactured by Hosokawa Micron Corporation: Multiprocessing). System 100AFG), and again with a fluidized bed type counter-type jet mill (multi-processing system 100AFG manufactured by Hosokawa Micron Corporation).

(Comparative Example 2)
Except for omitting the first crushing step in Example 1, the nickel powder obtained by the same processing from the nickel powder forming step to the heat treatment step was treated with a spiral jet mill (manufactured by Nippon Pneumatic Co., Ltd.). Then, it was treated again with a spiral jet mill (manufactured by Nippon Pneumatic Co., Ltd.).

(Comparative Example 3)
Except for omitting the first crushing step of Example 1, the nickel powder obtained by the same processing from the nickel powder forming step to the heat treatment step was treated with a fluidized-bed counter type jet mill (Hosokawa Micron Corporation: Multiprocessing System). 100 AFG).

(Comparative Example 4)
Except for omitting the first crushing step of Example 1, the nickel powder obtained by the same processing from the nickel powder forming step to the heat treatment step was treated with a spiral jet mill (Nippon Pneumatic Co., Ltd.).

(Comparative Example 5)
Except that the reduction treatment temperature in the heat treatment step of Example 1 was set to 400 ° C., the same treatment as in Example 1 was performed from the nickel powder formation step to the second crushing step to obtain nickel powder. Since the temperature of the reduction treatment was high, the nickel powder was sintered, so the evaluation was stopped.

Claims (9)

A first crushing step of crushing a nickel dry powder obtained by removing moisture from nickel particles in water to form a first crushing powder, and a first crushing powder obtained by the first crushing step A heat treatment step of forming a heat treated powder by heat treatment at a temperature of 150 ° C. to 350 ° C .;
A method for producing nickel powder, comprising sequentially performing a second crushing step of further crushing the heat-treated powder formed through the heat treatment step.   The method for producing nickel powder according to claim 1, wherein the heat treatment step is performed in a mixed atmosphere of hydrogen and an inert gas.   The nickel powder production method according to claim 1 or 2, wherein the nickel dry powder has an average particle size of 0.10 to 0.20 µm.   The said 1st crushing process and the 2nd crushing process are dry crushing processes, The manufacturing method of the nickel powder of any one of Claim 1 to 3 characterized by the above-mentioned.   5. The nickel powder according to claim 1, wherein the nickel dry powder is a nickel powder obtained by removing moisture from nickel particles obtained by reducing and growing a nickel salt aqueous solution. Production method.   The nickel particles were obtained by adding an aqueous nickel salt solution to an aqueous colloidal solution prepared by mixing a colloidal aqueous solution in which colloidal particles of metal other than nickel are dispersed, a reducing agent, an alkaline substance, and a protective colloidal agent. The method for producing nickel powder according to any one of claims 1 to 5, wherein:   The method for producing nickel powder according to claim 6, wherein the colloidal particles of metal other than nickel are composite colloidal particles of palladium and silver.   The method for producing nickel powder according to claim 5 or 6, wherein the reducing agent is hydrazine.   The method for producing nickel powder according to any one of claims 6 to 8, wherein the protective colloid agent is gelatin.