JP2010132944A - Method for producing nickel powder, and nickel powder obtained by the production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide nickel powder in which dispersibility is sufficiently secured as that of the material for electronic parts, and the contents of impurities are low, and to provide a simple production method therefor. <P>SOLUTION: The production method includes: a step (A) where a nickel salt aqueous solution is neutralized with an alkali aqueous solution, so as to produce the precipitates of nickel hydroxide; a step (B) where the nickel hydroxide is heat-treated in the air, so as to produce nickel oxide; a step (C) where the surface of the nickel oxide powder is coated or stuck with a water-soluble alkali metal halide; a step (D) where the nickel oxide whose surface is coated or stuck with the water soluble alkali metal halide is reduced in a reducing gas atmosphere, so as to be nickel powder; and a step (E) where the alkali metal halide is cleaned away. In the nickel powder obtained by the method, a grain size distribution D90 is ≤1.0 μm, a specific surface area is ≤4.6 m<SP>2</SP>/g, and the contents of chlorine, sodium and potassium are ≤100 mass ppm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to nickel powder and a method for producing the same. Specifically, it relates to nickel powder suitable as a material for electronic components and a method for producing the same. Specifically, nickel having excellent dispersibility, a reduced specific surface area, and a reduced concentration of residual chlorine and alkali metal elements. Regarding powder.

  Nickel powder having a particle size of 1.0 μm or less is a mainstream as a conductor forming material for electronic parts such as multilayer ceramic capacitors, and is widely used. When using nickel powder as a laminated conductor forming material, increasing the number of layers is an effective means to improve performance, but increasing the number of layers causes an increase in the size of electronic components. Therefore, in order to prevent this, it is necessary to reduce the thickness per layer. When the electrode layer is thinned, the nickel powder as the material is required to have a small particle size and high dispersibility. For example, when nickel powder in which a large number of particles are aggregated is used, it causes variation in the thickness of the electrode to be formed, causing short-circuiting of the electrodes and reduction in insulation resistance. Therefore, regarding the manufacture of nickel powder for electronic component materials, ensuring the dispersibility of nickel powder is an important issue.

Further, when nickel powder is used as an electronic component material, a technique is generally used in which the nickel powder is kneaded with a resin or a solvent to form a paste, and a component is formed using a technique such as screen printing. At this time, when the specific surface area of the nickel powder to be used is large, it is not preferable because it may be easily deteriorated due to oxidation of particles, or may cause problems such as poor mixing at paste kneading and deterioration with time of paste. Therefore, the nickel powder for electronic component materials is more advantageous as the specific surface area is lower if the dispersibility is secured.
In general, nickel powder having a particle diameter of 1.0 μm or less used for electronic component materials is manufactured by a known technique such as a gas phase reduction method, a wet reduction method, a spray pyrolysis method, or an evaporation aggregation method. However, as electronic component materials are required to be smaller and more efficient, and the demand for particles with smaller particle size and better dispersibility becomes larger, the following drawbacks become apparent. Improvements have been sought.

  That is, in the gas phase particle synthesis method represented by the gas phase reduction method, the spray pyrolysis method, and the evaporation aggregation method, it is necessary to control the particle generation density to be small in order to produce particles having excellent dispersibility. There is a problem that the manufacturing cost increases. On the other hand, when productivity is emphasized, the generation of connected particles and coarse particles is likely to occur, and in order to remove them, it is necessary to repeat the classification operation, which also causes a problem of increased cost.

  Also, the production of nickel powder by the wet reduction method is suitable as a method for producing particles having a fine particle diameter and excellent dispersibility. However, when nickel powder is produced by a wet reduction method, a method using a large amount of a reducing agent and adsorbing a dispersing agent on the surface is generally used. There are problems such as increased processing costs.

  On the other hand, there is an oxide powder reduction method as a manufacturing process of nickel powder that can achieve high productivity at a relatively low cost. That is, the nickel salt is neutralized by a wet neutralization method to crystallize nickel hydroxide, and the obtained nickel hydroxide is used as it is or converted into an oxide by heat treatment, and then in a reducing gas atmosphere such as hydrogen. In this method, nickel powder is obtained by reduction treatment. However, when nickel powder is produced by this method, there is a problem that the nickel powder is sintered during heat treatment, particularly during reduction treatment, and coarse particles are likely to be generated. On the other hand, in order to suppress the sintering, it is effective to perform heat treatment at a relatively low temperature. In this case, although the sintering can be suppressed to some extent, the surface smoothing by heat is not sufficient, so that the specific surface area is small. It tends to be large, and it is necessary to strictly adjust the conditions to adjust these characteristics.

  As a technique for solving such a problem, a method of preventing coarsening due to sintering of reduced nickel powder by adjusting the crystallization conditions of nickel hydroxide and controlling the reduction temperature to 400 to 550 ° C. is disclosed ( For example, see Patent Document 1.) However, nickel powder obtained by this method can be obtained with an average particle size of 1.0 μm or less, but it cannot be said that sufficient consideration is given to particle dispersibility, specific surface area or amount of impurities. It is difficult to say that the particle size and dispersibility of the level required recently are provided. Thus, in the oxide powder reduction method, it is extremely difficult to achieve both high dispersibility and low specific surface area with a particle size of 1 μm or less by controlling the conditions of crystallization and heat treatment.

  On the other hand, as a technique for performing heat treatment while suppressing sintering of nickel powders, a method of suppressing sintering by coating a surface of the nickel powder with a sintering inhibitor or mixing with nickel powder is known. ing. For example, a method of coating with a hydroxide of at least one element selected from Group IIA elements, Group IV elements and rare earth elements of the periodic table is shown (for example, see Patent Document 2). In addition, after mixing with a fine powder of an alkaline earth metal compound selected from the group consisting of an alkaline earth metal oxide, hydroxide, carbonate and bicarbonate, or on the surface of each particle of nickel powder A method of heat treatment after coating with an alkaline earth metal compound is disclosed (for example, see Patent Document 3).

  These technologies are mainly focused on improving the thermal shrinkage characteristics of nickel powder, and the nickel powder is manufactured using a wet powder method and has excellent dispersibility as a raw material. This is a technique for performing heat treatment while maintaining the composition. Therefore, in the case of the oxide powder reduction method in which sintering suppression during the reduction reaction is an issue, the application of the above technique is likely to be difficult because it involves changes in the composition and shape of the particles. In addition, the added sintering inhibitor may impair the properties of the electronic component material as an impurity. From the viewpoint of this removal, the above technique is basically a technique for maintaining the raw material shape, and the shape change The application to the oxide powder reduction method involving is likely to be insufficient.

  As a technology to suppress sintering in a system involving a chemical reaction, an alkali metal compound is added to a nickel aqueous solution and subjected to a neutralization reaction to form a slurry containing the nickel compound and a sintering inhibitor, and then dried. Thus, a method is disclosed in which a mixture of a nickel compound and a sintering inhibitor is generated, the mixture is reduced, and then the sintering inhibitor is removed by leaching (see, for example, Patent Document 4). According to this technique, it is said that particles having an average particle diameter measured by observation with a scanning electron microscope of less than 0.1 μm are obtained, but the measurement results for evaluating the dispersion state of the particles are not shown, Since particles having an average particle size of less than 0.1 μm are likely to aggregate, there is a high possibility that the level of dispersibility required for electronic component materials cannot be obtained. Furthermore, the remaining amount of impurities is not shown, and the remaining amount of impurities is likely to be a problem.

  In addition, a technique is disclosed in which magnesium stearate or calcium stearate is added as an additive to nickel chloride powder, followed by reduction treatment (see, for example, Patent Document 5). According to this technique, it is said that a nickel powder having an average particle diameter of 0.1 to 1.0 μm and excellent monodispersibility can be obtained. However, not only magnesium compounds and calcium compounds are generated on the surface of the obtained nickel powder, but also chlorine derived from nickel chloride may remain. Magnesium and calcium compounds formed on the surface of nickel powder can be removed by dipping in a solution such as hydrochloric acid or acetic acid, but the amount of these impurities after removal is not shown. Is likely to leave an undesirable amount of impurities.

Thus, under the present circumstances, nickel powder having sufficiently high dispersibility and low impurity quality has not been developed for use in electronic component materials. In addition, a simple manufacturing method that can reduce the cost is desired.
JP 2003-213310 A JP 2001-192702 A JP 2002-146401 A JP 2004-323984 A JP-A-10-88205

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a nickel powder having a sufficiently high dispersibility for an electronic component material and having a low impurity quality and a simple manufacturing method thereof.

  The present inventors diligently studied about improvement of dispersibility and reduction of impurity quality in the oxide powder reduction method with high productivity and low cost. As a result, the nickel oxide surface obtained by roasting nickel hydroxide powder is coated or adhered with water-soluble alkali metal halide under specific conditions, and then reduced, and after reduction, the alkali metal halide is washed under specific conditions. It has been found that nickel powder having good dispersibility and low impurity quality can be obtained by removing the nickel powder. Furthermore, the inventors have found that the specific surface area can be reduced while maintaining dispersibility by performing the reduction at a specific temperature, and the present invention has been made.

  That is, the nickel powder production method of the present invention comprises a step (A) of neutralizing a nickel salt aqueous solution with an alkaline aqueous solution to form a precipitate of nickel hydroxide, and heat treating the nickel hydroxide in air to produce nickel oxide. A step (B) of forming a nickel oxide powder, a step (C) of coating or adhering the surface of the nickel oxide powder with a water-soluble alkali metal halide, and an oxidation of coating or adhering the surface with the water-soluble alkali metal halide. A nickel powder production method comprising a step (D) of reducing nickel in a reducing gas atmosphere to form nickel powder and a step (E) of washing and removing the alkali metal halide.

In the step (C), the nickel oxide powder obtained in the step (B) and an aqueous solution of a water-soluble alkali metal halide are mixed to form a slurry, and then the slurry is dried to remove moisture. Thus, it is preferable to obtain nickel oxide whose surface is coated or adhered with an alkali metal halide.
The water-soluble alkali metal halide is preferably at least one of sodium chloride and potassium chloride. In the step (C), the water-soluble alkali metal halide is added to coat or adhere to the nickel oxide surface. The amount of is preferably 0.05 to 10 in terms of mass ratio when the mass of nickel oxide is 100.
Moreover, it is preferable to perform the reduction | restoration of the said process (D) at 430-450 degreeC.

Furthermore, the washing removal in the step (E) is preferably performed by stirring nickel powder in an organic acid aqueous solution, and the organic acid is at least one selected from citric acid, glutamic acid, and ascorbic acid. preferable. In the step (E), the washing is preferably performed in a state heated to 30 to 80 ° C.
Further, after the step (A) of generating the nickel hydroxide precipitate, the step (F) of washing the nickel hydroxide produced in the step (A) with sulfuric acid or a sulfate aqueous solution and further washing with water is provided. Is preferred.

The nickel powder of the present invention is a nickel powder obtained by the above-described method for producing nickel powder, and is characterized in that D90 of the particle size distribution measured by a laser scattering method is 1.0 μm or less. The specific surface area of the nickel powder measured by the BET method is preferably 4.6 m ² / g or less.
The nickel powder preferably has a chlorine quality, a sodium quality, or a potassium quality of 100 ppm by mass or less.

  According to the present invention, it is possible to obtain nickel powder having excellent dispersibility and low impurity quality suitable for use in electronic component materials. Moreover, since the specific surface area is low, it is also suitable when used as a paste. Furthermore, the production method of the present invention is efficient with a simple process, and its industrial value is great.

Below, the nickel powder by this invention and its manufacturing method are demonstrated in detail.
The method for producing nickel powder according to the present invention includes a step (A) in which a nickel salt aqueous solution is neutralized with an alkaline aqueous solution to form a nickel hydroxide precipitate, and the nickel hydroxide is heat-treated in air to produce nickel oxide. A step (B) of coating, a step (C) of coating or adhering the surface of the nickel oxide powder with a water-soluble alkali metal halide, and a nickel oxide having a surface coated or adhered with the water-soluble alkali metal halide Is a method for producing nickel powder, comprising a step (D) of reducing the alkali metal in a reducing gas atmosphere to a nickel powder and a step (E) of washing and removing the alkali metal halide.
In the method for producing nickel powder of the present invention, it is important to perform a reduction treatment after adding a specific water-soluble alkali metal halide to nickel hydroxide, and to wash and remove the alkali metal halide under specific conditions after the reduction. is there. That is, since the water-soluble alkali metal halide coated or adhered to the nickel oxide surface in the step (C) suppresses the generation of connected particles due to excessive sintering of the nickel powder in the reduction treatment of the step (D). Nickel powder excellent in properties can be obtained. Furthermore, the impurity quality of the nickel powder can be reduced to a range suitable for electronic parts by washing and removing the alkali metal halide added in the step (C) after the reduction treatment.

Details will be described below for each process.
[Step A]
Step (A) is a step in which an aqueous nickel salt solution is neutralized with an aqueous alkaline solution to produce a nickel hydroxide precipitate. As the nickel salt, it is preferable to use nickel chloride in consideration of environmental influences such as ease of wastewater treatment and cost. As a method for generating nickel hydroxide precipitate, a known technique can be used. In order to obtain a uniform precipitate, neutralization of an aqueous nickel salt solution and an alkali is performed while maintaining a constant pH. This is preferable because the production rate can be kept constant. At this time, in order to obtain nickel hydroxide with uniform characteristics, it is effective to neutralize and generate a nickel salt aqueous solution and a sodium hydroxide aqueous solution in a sufficiently stirred reaction vessel while adding them in a double jet method. is there. Pure water can be used as the liquid previously placed in the reaction tank, but it is preferable to use a liquid prepared by adjusting the filtrate once used for neutralization to a predetermined pH with an alkali. As the alkaline aqueous solution to be used, an aqueous solution of an alkali metal hydroxide such as a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is preferably used, and a sodium hydroxide aqueous solution is preferred from the viewpoint of availability and price. In addition, in order to obtain nickel powder with more excellent dispersibility, as a known technique, periodic table group II elements such as magnesium can be added to nickel hydroxide, The effect can be further enhanced.

The produced nickel hydroxide is dehydrated by filtration to obtain a filter cake. At this time, if nickel chloride is used as a raw material, it is preferable to sufficiently reduce the residual chlorine concentration. Therefore, filtration and repulp washing may be repeated several times, but the slurry concentration is increased while lowering the residual chlorine concentration. It is also effective to use a cross-flow type filtration as a method for achieving this.
Moreover, in order to reduce impurity chlorine in nickel powder more effectively, it is preferable to provide a step (F) of washing with sulfuric acid or a sulfate aqueous solution and then washing with water.

[Process F]
Step (F) is a step of washing the produced nickel hydroxide with sulfuric acid or a sulfate aqueous solution and then further washing with water in order to reduce the impurity concentration in the raw material nickel hydroxide powder.
In the step (F), cleaning is performed while eliminating the obtained nickel hydroxide gel, so that chlorine remaining in the nickel hydroxide can be efficiently reduced. For this reason, the load due to chlorine after the next step is also reduced, and the obtained effect is great.
It is preferable that the sulfuric acid or sulfate aqueous solution concentration used for washing when carrying out the step (F) is 0.0004 to 0.0015 mol / L. If the sulfuric acid or sulfate aqueous solution concentration is less than 0.0004 mol / L, a sufficient cleaning effect cannot be obtained. If the concentration exceeds 0.0015 mol / L, the residual sulfur concentration becomes too high and the particles are sintered. Since the behavior is remarkably changed, the target particles may not be obtained during the heat treatment after the next step, which is not preferable. Although the temperature of the aqueous solution at the time of washing | cleaning can be normal temperature, in order to improve the washing | cleaning effect, you may heat.
The amount of sulfuric acid or sulfate aqueous solution with respect to the nickel hydroxide powder is not particularly limited, and may be an amount that can sufficiently reduce the residual chlorine. The mixing ratio of nickel powder / treatment liquid is preferably about 100 g / L. Further, the cleaning time is not particularly limited, and the cleaning time may be a time for sufficiently reducing the residual chlorine concentration depending on the cleaning conditions.

The apparatus used for washing is not particularly limited, and a normal wet reaction tank can be used. During the washing, it is preferable to stir the slurry containing nickel powder. For washing, for example, ultrasonic stirring or mechanical stirring can be used.
The washing in the step (F) can be performed by preparing an aqueous solution with sulfuric acid or sulfate concentration adjusted in advance, and adding dried nickel hydroxide powder to this while stirring. It is preferable to use it because it facilitates uniform processing and improves the cleaning efficiency, and also shortens the process. When washing cake-like nickel hydroxide, add a small amount of water to a nickel hydroxide filter cake to form a slurry, and then stir the sulfuric acid or sulfate aqueous solution adjusted to a predetermined concentration after addition. However, it is preferable to add all at once for uniform treatment.
The water content of the nickel hydroxide cake is preferably 10 to 40% by mass, and more preferably about 30% by mass. When the water content is lower than 10% by mass, it is not preferable because it is difficult to uniformly disperse in an aqueous solution and the efficiency of washing is deteriorated, and more severe dehydration is required to reduce the water content. . On the other hand, when the moisture content is higher than 40% by mass, the handling property of nickel hydroxide is poor, and uniform processing may be hindered. In addition, the amount of treatment required to obtain a certain amount of nickel hydroxide increases.
The nickel hydroxide after washing may be dried by a known method such as vacuum drying.

[Step B]
Step (B) is a heat treatment step for producing nickel oxide that is heat-treated in air in the nickel hydroxide obtained in step (A) to form nickel oxide. In the heat treatment step (B), it can be carried out by a known method using a general roasting furnace such as a stationary roasting furnace, a rolling furnace, a burner furnace, a conveying continuous furnace, a fluidized roasting furnace, In order to obtain the target nickel fine powder, it is important to obtain nickel oxide having uniform characteristics. The conditions at that time can be arbitrarily set according to the characteristics of the furnace so that the desired characteristics such as the particle size can be obtained. Is preferred.
There is no problem if the atmosphere of the heat treatment is a non-reducing atmosphere, and the type of gas is not limited as long as it is an inert gas and an oxidizing gas, but the use of air is cost and ease of handling. It is excellent in the point.

[Step C]
Step (C) is a step of coating or adhering a water-soluble alkali metal halide to the surface of the nickel oxide powder obtained in step (B). Here, it is important to add the alkali metal halide to the nickel oxide powder. By coating or adhering the alkali metal halide to the nickel oxide powder surface in the step (C), sintering is suppressed in the reduction treatment of the next step (D) to prevent the particles from being connected to each other, and high dispersibility. Nickel powder can be obtained.
The oxide powder reduction method employed in the present invention is a technique for producing the desired nickel powder by controlling the change in the particle shape of the nickel oxide powder that occurs during the reduction treatment. That is, by controlling the reduction treatment of nickel oxide having a uniform shape and the like, uniform nickel powder having the desired characteristics can be obtained, and an alkali metal halide that serves as a sintering inhibitor can be obtained. The addition needs to be done after conversion to nickel oxide powder.
For example, in the method of adding an alkali metal halide to nickel hydroxide by adding or using a reaction product at the time of nickel hydroxide production, the nickel oxide obtained by the subsequent heat treatment becomes too fine and the particle size is reduced. Because of non-uniformity, the nickel powder finally obtained is fine and has a wide particle size distribution. In addition, nickel hydroxide cannot easily add a uniform alkali metal halide because part or the whole of the surface tends to be gelled. Therefore, it is necessary to add the alkali metal halide to the nickel oxide powder.

  In order to uniformly develop the effect of suppressing the sintering, it is necessary to coat or adhere an alkali metal halide to the surface of the nickel oxide powder. For this reason, the addition treatment of the alkali metal halide is preferably performed by mixing the nickel oxide powder and an aqueous solution of a water-soluble alkali metal halide into a slurry, and then drying the slurry to remove moisture. The alkali metal halide is preferably dissolved in pure water to form an aqueous solution in order to prevent contamination with impurities. If dehydration by filtration is performed when the slurry is dried, alkali metal halides are lost along with dehydration. Therefore, the slurry is preferably dried as it is. For this reason, it is preferable that the density | concentration of a slurry shall be 0.1-2 g / L. If it exceeds 2 g / L, mixing of the nickel oxide powder and the aqueous solution of the alkali metal halide may not be uniform, and if it is less than 0.1 g / L, the amount of water to be evaporated is large, which is not economical. The drying method is not particularly limited and may be a method used for normal drying, but a spray dryer or the like can also be used.

As the alkali metal halide, it is necessary to use a water-soluble one because it is washed and removed after the reduction treatment, and it is necessary to coat or adhere the alkali metal halide. By using a water-soluble alkali metal halide, it becomes possible to efficiently remove alkali metal elements and halogen elements that become impurities when used as electronic component materials, and to coat the surface of nickel oxide powder or Adhesion can be performed easily.
As the alkali metal halide to be used, it is preferable to use at least one kind of sodium chloride or potassium chloride in consideration of availability, cost, and environmental influence when removed. Moreover, it is preferable that the quantity of the alkali metal halide added in order to coat | cover or adhere to the nickel oxide surface is 0.05-10 by mass ratio when the mass of nickel oxide is set to 100. When the addition ratio is less than 0.05, the effect of suppressing sintering may not be sufficiently obtained, and uniform addition treatment may be difficult. When the addition ratio exceeds 10, the process (D ) Is not preferable because it may hinder the reduction in () and the risk of an increase in impurity quality.

[Process D]
Step (D) is a step of producing nickel powder by reducing the obtained nickel oxide in a reducing gas atmosphere. In the reduction treatment, treatment conditions such as treatment temperature and time can be set as appropriate according to the target particle size, etc., but uniform nickel can be used in the gas stream as in step (B). Preferred for obtaining a powder.
For the reduction treatment, a general heat treatment furnace can be used. In that case, in order to obtain nickel powder having a particle diameter of 1 μm or less, the reduction temperature is preferably 300 to 550 ° C. If it is less than 300 degreeC, reduction | restoration cannot fully be performed but oxygen content may increase too much. As the reduction temperature is higher and the reduction time is set longer, the particle diameter tends to be larger, so that a fine nickel powder having a sufficiently low oxygen content at 0.5 μm or less, which is more preferable for electronic component materials, is obtained. For this purpose, the reduction temperature is preferably 350 to 500 ° C. In particular, when it is desired to reduce the specific surface area, the reduction temperature is preferably set to 430 to 450 ° C. If it is less than 430 degreeC, a specific surface area may not fully be reduced.
The reduction time may be appropriately set according to the particle size of the nickel powder to be obtained, depending on the temperature and the processing amount, but is preferably as short as possible.
The reducing gas is not particularly limited, but it is preferable to use a hydrogen-containing gas in consideration of availability and influence on the environment. When the reduction treatment is performed in the above temperature range, the added alkali metal halide can be present stably, and thus does not cause generation of hydrogen chloride gas.

[Step E]
Step (E) is a step of washing and removing the alkali metal halide added in step (C) after the reduction treatment. By the step (E), it is possible to obtain nickel powder having reduced alkali metal quality and halogen quality, which are impurities. On the other hand, through a wet cleaning process, dry aggregation occurs during drying, resulting in deterioration of the dispersion state of nickel powder, and an increase in specific surface area due to surface oxidation. Concerning dry aggregation, unlike the generation of coarse particles by sintering, it can be easily eliminated by dry / wet crushing treatment. Further, an increase in specific surface area is preferable because the cleaning liquid in the step (E) can be relaxed by using an organic acid aqueous solution. The organic acid contained in the aqueous solution is preferably at least one selected from citric acid, glutamic acid, and ascorbic acid. Since the alkali metal halide added in the step (C) is water-soluble, a considerable portion can be removed by washing with pure water, but the washing solution contains the above-mentioned organic acid and stirred. When washed, the added alkali metal halide can be removed more efficiently. In addition to the alkali metal halide, chlorine derived from nickel chloride remaining when nickel chloride is used in step (A), Group II elements added to improve dispersibility, and the like can also be removed. Furthermore, since the organic acid has high adsorptivity to the nickel surface, it also exhibits an action of suppressing excessive oxidation of nickel powder as a surface protective agent.

The concentration of the organic acid in the cleaning liquid is preferably 5 to 50 g / L. When the concentration is less than 5 g / L, the cleaning effect is not sufficient, and the alkali metal halide and residual chlorine may not be reduced. Even if the concentration is higher than 50 g / L, there is no particular problem, but the cleaning effect is not improved and it is not economical.
The washing temperature can be any temperature, but it is preferably carried out by heating to 30-80 ° C, more preferably 40-60 ° C. A higher cleaning temperature is superior in terms of removing impurities, but there are problems such that the higher the cleaning temperature, the easier the nickel powder is oxidized and the energy required to raise the temperature. Therefore, the above range is preferable considering the influence.

The mixing ratio of the nickel powder and the cleaning liquid is not particularly limited and can be appropriately changed according to the scale to be implemented, but the mixing ratio of the nickel powder / cleaning liquid is preferably 50 to 500 g / L. When this mixing ratio exceeds 500 g / L, the dispersion of the nickel powder may be deteriorated and cleaning may not be performed sufficiently. On the other hand, when the mixing ratio is less than 50 g / L, a large amount of chemical solution is required for cleaning, and there is a problem in economical efficiency and operability. Further, the cleaning time is not particularly limited, and may be a cleaning time in which the alkali metal halide concentration and the residual chlorine concentration are sufficiently reduced depending on the nickel powder concentration in the slurry, the concentration of the organic acid, and the cleaning conditions.
The apparatus used for washing is not particularly limited, and a normal wet reaction tank can be used. It is preferable to stir the slurry containing nickel powder during washing, and for example, ultrasonic stirring or mechanical stirring can be used for washing.

The nickel powder produced by the above method has excellent dispersibility and is suitable as a material for electronic components. Specifically, D90 of the particle size distribution measured by a laser scattering method is 1.0 μm or less. D90 of the particle size distribution becomes smaller as the average particle size becomes smaller, but the minimum value in the nickel powder of the present invention is about 0.5 μm. Moreover, it is preferable that the specific surface area measured by BET method is 4.6 m < ² > / g or less. The specific surface area decreases as the average particle diameter increases, but considering the average particle diameter of 1.0 μm or less, which is a preferable average particle diameter for materials for electronic components, the minimum value in the nickel powder of the present invention is 3.0 m ² / g. Degree. The impurity grade is preferably 100 ppm by mass or less for both chlorine grade, sodium grade and potassium grade.
Since the nickel powder production method of the present invention reduces nickel hydroxide produced by a wet method, it does not have a complicated process, and the impurity quality can be reduced by a simpler method. Cost can be kept low.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. The evaluation of the chlorine quality used in this example and the comparative example was carried out by dissolving silver powder with nitric acid and then adding silver nitrate to precipitate silver chloride. The calibration curve of fluorescent X-ray quantitative analysis of chlorine in the precipitate Measured by the method. The sodium quality was measured by atomic absorption spectrometry, and the magnesium quality was measured by ICP emission spectroscopy. The oxygen quality was measured by an inert gas melting-infrared absorption method. The specific surface area was measured by the BET single point method by nitrogen gas adsorption. The particle dispersibility was evaluated by measuring the particle size distribution by laser diffraction / scattering particle size distribution measurement, 10% volume diameter (hereinafter referred to as D10), 50% volume diameter (hereinafter referred to as D50), 90%. The volume diameter (hereinafter referred to as D90) was determined and used as an indicator of the dispersion state.

Example 1
While adjusting a nickel chloride aqueous solution containing 604 g / L of nickel containing 0.04 g / L of magnesium serving as a fusion inhibitor during reduction and a 24% by mass aqueous sodium hydroxide solution while adjusting the pH to 8.3. A nickel hydroxide precipitate was formed by continuous addition. Thereafter, filtration and pure water repulp for 30 minutes were repeated three times to obtain a nickel hydroxide filter cake having a water content of 30% by mass. Furthermore, after adding a small amount of water to 3 kg of this filter cake, sulfuric acid whose concentration was adjusted to 10 L of 0.0015 mol / L sulfuric acid in total with the previously added water was added and stirred for 30 minutes for washing. . After washing, the mixture was filtered, washed again with pure water and dried to obtain nickel hydroxide fine powder.

  1500 g of the obtained nickel hydroxide powder was heat-treated at 480 ° C. for 2 hours while introducing air at a flow rate of 27 L / min per heating zone in a conveying continuous firing furnace to obtain nickel oxide powder. By mixing 100 g of the obtained nickel oxide powder and 100 mL of a 10 g / L sodium chloride aqueous solution and carrying out dispersion treatment with an ultrasonic dispersing device, the mass ratio to the nickel oxide 100 (hereinafter referred to as NaCl ratio) becomes 1. A uniform nickel oxide slurry containing an amount of sodium chloride was made. The slurry was vacuum-dried at 120 ° C. as it was and crushed in a mortar to obtain nickel oxide powder (hereinafter referred to as coated nickel oxide powder) whose surface was coated or adhered with sodium chloride.

80 g of the obtained coated nickel oxide powder was subjected to reduction treatment at 420 ° C. for 2 hours while introducing a mixed gas of 80% nitrogen and 20% hydrogen at a flow rate of 25 L / min in an atmosphere firing furnace to obtain reduced nickel powder. When the particle size distribution and specific surface area of the obtained reduced nickel powder were measured, D10 was 0.31 μm, D50 was 0.49 μm, D90 was 0.77 μm, and the specific surface area was 4.8 m ² / g. Further, when the grades of oxygen, chlorine, sodium, and magnesium were measured, the oxygen grade was 1.1 mass%, the chlorine grade was 5300 mass ppm, the sodium grade was 7100 mass ppm, and the magnesium grade was 580 mass. ppm.

Next, 10 g of the reduced nickel powder was dispersed in 80 mL of an aqueous citric acid solution having a concentration of 10 g / L, and washed with mechanical stirring for 30 minutes while heating to 60 ° C. After solid-liquid separation of the washed nickel powder slurry, 80 ml of pure water was added to the obtained nickel powder cake to disperse it into a nickel powder slurry, which was washed with stirring at room temperature for 30 minutes to remove excess acid. . The nickel powder slurry after washing was subjected to solid-liquid separation, and a target nickel powder to be dried was obtained. When the particle size distribution and specific surface area of the obtained nickel powder were measured, D10 was 0.31 μm, D50 was 0.50 μm, D90 was 0.80 μm, and the specific surface area was 5.2 m ² / g. . Table 1 shows the measurement results of specific surface area and particle size distribution of the obtained nickel powder. When chlorine, sodium, and magnesium were analyzed, the chlorine quality was less than 30 mass ppm, the sodium quality was less than 30 mass ppm, and the magnesium quality was 60 mass ppm. The analysis results of chlorine, sodium and magnesium before and after washing are shown together in Table 2.

(Example 2)
Nickel powder was obtained in the same manner as in Example 1 except that the NaCl ratio was adjusted to 0.1. When the particle size distribution of the reduced nickel powder was measured, D10 was 0.31 μm and D50 was 0.00. It was 49 μm, D90 was 0.80 μm, and the specific surface area was 4.5 m ² / g. When oxygen, chlorine, sodium, and magnesium were measured, the oxygen quality was 1.1 mass%, the chlorine quality was 1200 mass ppm, the sodium quality was 520 mass ppm, and the magnesium quality was 590 mass ppm. there were.
Moreover, when the particle size distribution of the nickel powder finally obtained by washing after the reduction treatment was measured, D10 was 0.31 μm, D50 was 0.50 μm, D90 was 0.83 m, and the specific surface area was 5 It was 1 m ² / g.
Moreover, when the quality of chlorine, sodium, and magnesium was measured, the chlorine quality was less than 30 mass ppm, the sodium quality was less than 30 mass ppm, and the magnesium quality was 60 mass ppm. The measurement results of specific surface area and particle size distribution of the obtained nickel powder are shown in Table 1, and the analysis results of chlorine, sodium and magnesium before and after cleaning are shown in Table 2, respectively.

(Example 3)
Nickel powder was obtained in the same manner as in Example 1 except that the NaCl ratio was adjusted to 10. When the particle size distribution of the reduced nickel powder was measured, D10 was 0.32 μm, D50 was 0.48 μm, D90 was 0.75 μm, and the specific surface area was 4.3 m ² / g. The oxygen quality was 1.4% by mass.
Further, the particle size distribution of the nickel powder finally obtained after washing after the reduction treatment was measured. As a result, D10 was 0.32 μm, D50 was 0.47 μm, D90 was 0.77 μm, and the specific surface area was It was 6.6 m ² / g. Table 1 shows the measurement results of specific surface area and particle size distribution of the obtained nickel powder.

(Comparative Example 1)
Nickel powder was obtained in the same manner as in Example 1 except that the treatment for forming the coated nickel oxide powder was not performed and the cleaning treatment for the reduced nickel powder was not performed. When the particle size distribution of the obtained nickel powder was measured, D10 was 0.45 μm, D50 was 0.73 μm, D90 was 1.13 μm, and the specific surface area was 4.2 m ² / g. Moreover, it was 0.88 mass% when the oxygen concentration was measured. Table 1 shows the measurement results of specific surface area and particle size distribution of the obtained nickel powder.

(Comparative Example 2)
A reduced nickel powder was obtained in the same manner as in Example 1 except that the same amount of sodium chloride and nickel oxide powder were mixed in place of the treatment of coating nickel oxide powder. When the particle size distribution of the obtained reduced nickel powder was measured, D10 was 0.35 μm, D50 was 0.60 μm, D90 was 1.04 μm, and the specific surface area was 4.0 m ² / g. It can be seen that the D90 of the reduced nickel powder before washing exceeds 1.0 μm, and the effect of improving the dispersibility is not sufficient only by mixing sodium chloride and nickel oxide powder.

It can be seen from Table 1 that Examples 1 to 3 obtained according to the method for producing nickel powder of the present invention have a D90 of 1.0 μm or less and excellent dispersibility. On the other hand, in Comparative Example 1 in which sodium chloride was not added and the treatment to form the coated nickel oxide powder was not performed, D90 was 1.13 μm, indicating that sufficient dispersibility was not obtained.
Further, from Table 2, Examples 1 and 2 were cleaned with reduced nickel powder, so that the chlorine quality, sodium quality, and potassium quality were all 100 mass ppm or less, and the residual chlorine and alkali metal element concentrations were sufficient. It can be seen that it has been reduced.

Example 4
Nickel powder was obtained in the same manner as in Example 1 except that the temperature during the reduction treatment was changed from 420 ° C to 430 ° C. When the particle size distribution of the obtained nickel powder was measured, D10 was 0.33 μm, D50 was 0.53 μm, D90 was 0.82 μm, and the specific surface area was 4.6 m ² / g. Moreover, it was 0.88 mass% when the oxygen concentration was measured. Table 3 shows the measurement results of specific surface area and particle size distribution of the obtained nickel powder.

(Example 5)
Nickel powder was obtained in the same manner as in Example 1 except that the temperature during the reduction treatment was 440 ° C. When the particle size distribution of the obtained nickel powder was measured, D10 was 0.32 μm, D50 was 0.53 μm, D90 was 0.88 μm, and the specific surface area was 4.2 m ² / g. Moreover, it was 0.87 mass% when the oxygen concentration was measured. Table 3 shows the measurement results of specific surface area and particle size distribution of the obtained nickel powder.

(Example 6)
Nickel powder was obtained in the same manner as in Example 1 except that the temperature during the reduction treatment was set to 450 ° C. When the particle size distribution of the obtained nickel powder was measured, D10 was 0.32 μm, D50 was 0.55 μm, D90 was 0.94 μm, and the specific surface area was 4.1 m ² / g. Moreover, it was 0.80 mass% when the oxygen concentration was measured. Table 3 shows the measurement results of specific surface area and particle size distribution of the obtained nickel powder.

From Table 3, it can be seen that the specific surface area can be reduced by increasing the temperature of the reduction treatment. In particular, in Examples 4 to 6 in which the reduction treatment temperature is set to 430 to 450 ° C., the specific surface area is 4.6 m ² / g or less, and it is understood that the material is more suitable as a material for electronic parts used by pasting. .

  By the nickel powder manufacturing method of the present invention, nickel powder having good dispersibility and specific surface area, and having reduced chlorine and sodium impurity grades can be obtained. The obtained nickel powder is suitable as an electronic component material, and particularly suitable as a wiring material, an electrode material, and the like. Furthermore, it can be stably used as a paste by kneading with a resin, a solvent, or the like, and is also suitable for forming parts using techniques such as screen printing.

Claims (12)

  A step (A) of producing a nickel hydroxide precipitate by neutralizing an aqueous nickel salt solution with an alkaline aqueous solution; a step (B) of producing a nickel oxide by heat-treating the nickel hydroxide in air; and the nickel oxide A step (C) of coating or adhering the surface of the powder with a water-soluble alkali metal halide, and nickel powder obtained by reducing the nickel oxide coated or adhered to the surface of the water-soluble alkali metal halide in a reducing gas atmosphere And a step (E) of washing and removing the alkali metal halide. A method for producing nickel powder, comprising:   In step (C), the nickel oxide powder obtained in step (B) and an aqueous solution of a water-soluble alkali metal halide are mixed to form a slurry, and then the slurry is dried to remove moisture. The method for producing nickel powder according to claim 1, wherein nickel oxide having a surface coated or adhered with an alkali metal halide is obtained.   The method for producing nickel powder according to claim 1 or 2, wherein the water-soluble alkali metal halide is at least one of sodium chloride and potassium chloride.   4. The method according to claim 1, wherein in the step (C), the amount of the water-soluble alkali metal halide is 0.05 to 10 in terms of mass ratio when the mass of nickel oxide is 100. 5. The manufacturing method of the nickel powder of Claim 1.   The method for producing nickel powder according to any one of claims 1 to 3, wherein the reduction in the step (D) is performed at 430 to 450 ° C.   The method for producing nickel powder according to any one of claims 1 to 5, wherein the cleaning removal in the step (E) is performed by stirring the nickel powder in an organic acid aqueous solution.   The method for producing nickel powder according to claim 6, wherein the organic acid is at least one selected from citric acid, glutamic acid, and ascorbic acid.   In the said process (E), washing | cleaning is performed in the state heated at 30-80 degreeC, The manufacturing method of the nickel powder of any one of Claim 1 to 8 characterized by the above-mentioned.   After the step (A) of generating the nickel hydroxide precipitate, the step (F) includes washing the nickel hydroxide produced in the step (A) with sulfuric acid or a sulfate aqueous solution and further washing with water. The manufacturing method of the nickel powder of any one of Claim 1 to 8.   It is nickel powder obtained by the manufacturing method of nickel powder of any one of Claim 1 to 9, Comprising: D90 of the particle size distribution measured by the laser scattering method is 1.0 micrometer or less, It is characterized by the above-mentioned. Nickel powder. The nickel powder according to claim 10, wherein the specific surface area measured by the BET method is 4.6 m ² / g or less.   The nickel powder according to claim 10 or 11, wherein the chlorine quality and the sodium quality or potassium quality are both 100 ppm by mass or less.