JPH11140513A - Manufacture of spherical nickel powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method of manufacturing the nickel powder whose average grain size is 0.1-2 μm and whose particle shape is spherical at a low cost. SOLUTION: A manufacturing method of the spherical nickel powder comprises a first process in which the compound powder of magnesium and calcium is mixed with the powder of the nickel compound, a second process in which nickel in the mixture obtained in the first process is reduced to metallic nickel in the hydrogen atmosphere, a third process in which the reduced product obtained in the second process is heated at 800-1500 deg.C to improve the spherical property and the crystallinty of the metallic nickel particles, and a fourth process in which the compounds of magnesium and calcium in the heated product obtained in the third process is dissolved in acid and removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing spherical nickel powder used for producing a conductive paste for forming internal electrodes of, for example, a high multilayer ceramic capacitor (hereinafter referred to as MLC).

[0002]

2. Description of the Related Art In the production of small and high-capacity MLC, a noble metal paste represented by palladium is printed on a dielectric green sheet represented by barium titanate and dried so that internal electrodes alternately overlap. After laminating, thermocompression bonding, cutting into a chip shape and debinding, the internal electrode and the dielectric green sheet are sintered in a temperature range of about 1300 ° C., and then an external electrode such as Ag is formed.

[0003] However, in order to obtain this MLC, the number of layers must be increased, which drastically increases the amount of expensive noble metal paste used, which hinders supply of MLC at low cost. .

[0004] Therefore, attempts have been made to reduce the cost of MLC by using a base metal such as nickel for the internal electrode. In recent years, the market share of MLC using nickel as the internal electrode has rapidly increased, and the movement has been remarkable. It is fully anticipated that the product group of nickel internal electrodes MLC will increasingly shift to higher capacity types in the future.

[0005] The performance of the nickel paste used in the production of MLC is almost determined by the characteristics of the nickel powder as a component. The characteristics of the nickel powder required to fulfill the above requirements include (1) an average particle diameter of 0.1 to 2 μm, and (2) a spherical particle shape.

[0006] As a method for producing nickel powder,
Various methods are known. Also, the manufacturing method is
(1) Dry reduction method in which nickel oxide powder, nickel hydroxide powder or nickel carbonate powder is reduced with hydrogen gas, (2) Gas atomization in which molten metal nickel is blown out from a nozzle or the like and rapidly cooled with an inert gas such as argon gas. And (3) a wet reduction method in which a nickel aqueous solution is reduced.

In the above production method, it is difficult to uniformly produce spherical particles having a particle diameter of 10 μm or less by the dry reduction method and the gas atomization method. Therefore, when particles having a size of 10 μm or less are produced by the above two methods, particles having a size larger than 10 μm are removed by classification.
Nickel powder becomes very expensive because the yield of the following particles is poor.

In the wet reduction method, since the reduction reaction generally proceeds rapidly and the particle size of the obtained nickel powder tends to be excessively small, a reduction agent is added by adding a complexing agent such as an organic acid or ammonia. The reaction rate is controlled. However, the use of such a complexing agent involves difficult waste liquid treatment, which makes the produced nickel powder expensive.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and has an average particle size of 0.1 to 2 μm,
An object of the present invention is to provide a method for inexpensively producing nickel powder having a spherical particle shape.

[0010]

A method for producing a spherical nickel powder according to the present invention comprises the steps of:
A first step of mixing the nickel compound powder with the nickel compound powder, and a step of heating the mixture in a hydrogen atmosphere while preventing the formation of composite oxides in a hydrogen atmosphere in order to reduce nickel in the mixture obtained in the first step to metallic nickel. It is characterized by comprising two steps and a third step of dissolving and removing the alkaline earth metal in the heated product obtained in the second step with an acid.

A first step of mixing the alkaline earth metal compound powder and the nickel compound powder, and a step of mixing the mixture in a hydrogen atmosphere to reduce nickel in the mixture obtained in the first step to metallic nickel. In the second step of heating while preventing the generation of the composite oxide in, in order to improve the sphericity of the metal nickel particles in the heated product obtained in the second step,
A third step of heating the heated object in a non-oxidizing atmosphere while preventing coarsening of particles, and a fourth step of dissolving and removing an alkaline earth metal in the heated object obtained in the third step with an acid. It is characterized by consisting of.

Here, the mixing in the first step is preferably performed between solids.

The mixing is performed while (1) suspending the nickel compound powder in an aqueous solution of an alkaline earth metal and then adding caustic or alkali carbonate to generate a precipitate of the alkaline earth metal compound. , (2) after suspending the alkaline earth metal compound powder in the nickel aqueous solution,
(3) Precipitation of an alkaline earth metal compound by adding caustic or alkali carbonate to an aqueous solution of an alkaline earth metal and nickel by adding caustic or alkali carbonate to generate a precipitate of a nickel compound. And the precipitation of a nickel compound.

Further, the mixing in the first step is preferably performed such that the weight ratio of the amount of the alkaline earth metal compound powder to the amount of nickel is 0.05 to 3.

On the other hand, (1) the heating in the second step is 3
(2) The heating in the third step, which is performed at 50 to 700 ° C., is preferably performed at 800 to 1500 ° C.

Further, the acid used in the fourth step is
It is preferable to use such that the weight ratio to the theoretical amount required to dissolve the alkaline earth metal is 1.0 to 1.1.

(1) The alkaline earth metal compound is at least one selected from the group consisting of magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium oxide, calcium carbonate and calcium hydroxide. The nickel compound is preferably at least one selected from the group consisting of nickel oxide, nickel carbonate and nickel hydroxide.

The spherical nickel powder produced preferably has an average particle size of 0.1 to 2 μm.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has conducted intensive studies to solve the above-mentioned problems. As a result, (1) when reducing nickel compounds with hydrogen gas in the above-mentioned conventional dry reduction method, particles of 10 μm or less were used. The low yield is due to the coarsening of the particles due to sintering and fusion of the generated nickel powder particles. (2) The alkaline earth metal compound acts as a barrier to the sintering and fusion. It has been found that (3) the alkaline earth metal compound is more easily soluble in acid than nickel, so that the alkaline earth metal compound can be dissolved with an acid and easily separated and removed from the nickel powder.

That is, the method for producing spherical nickel powder according to the first invention comprises a first step of mixing an alkaline earth metal compound powder and a nickel compound powder, and a step of mixing nickel in the mixture obtained in the first step with a metal. A second step of heating the mixture in a hydrogen atmosphere while preventing the formation of complex oxides in order to reduce to nickel, and dissolving and removing an alkaline earth metal in the heated product obtained in the second step with an acid And a third step.

The method for producing spherical nickel powder according to the second aspect of the present invention is to improve the spherical and crystalline properties of the metallic nickel particles in the heated product obtained by the heating (first heating) of the first aspect. After heating the heated object in a non-oxidizing atmosphere while preventing coarsening of the particles (second heating), dissolution and separation with the acid of the first invention is performed.

Each step will be described in detail below.

[Mixing] The alkaline earth metal compounds to be mixed are, for example, magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium oxide, calcium carbonate and calcium hydroxide. The nickel compound is, for example, nickel oxide, nickel carbonate, or nickel hydroxide.

During the first and second heating, the alkaline earth metal compound powder exists as a solid (a substance that thermally decomposes is a pyrolysis product), and sintering and melting of the nickel powder particles generated by reduction occur. It acts as a barrier to adhesion and prevents the nickel powder particles from becoming coarse. This coarsening prevention effect of the alkaline earth metal compound powder is considered to be due to poor wettability with the nickel powder particles. Further, the alkaline earth metal compound powder is more easily soluble in acid than the nickel powder particles, so that it is easily dissolved by an acid and easily separated from the nickel powder.

It is important to add an alkaline earth metal compound powder for the above-mentioned action of preventing coarsening. In order to exhibit these effectively, the alkaline earth metal compound powder and the nickel compound powder are mixed well, and the alkaline earth metal compound particles are sufficiently uniformly dispersed in the nickel compound particles. For that purpose, for example, the following mixing method is preferable.

(1) An alkaline earth metal compound powder (solid) and a nickel compound powder (solid) are suspended in pure water and stirred, or crushed and mixed in pure water in a crusher such as a ball mill or a bead mill.

(2) After suspending the nickel compound powder in the alkaline earth metal aqueous solution, caustic alkali or alkali carbonate is added and mixed while generating a precipitate of the alkaline earth metal compound.

(3) After suspending the alkaline earth metal compound powder in the nickel aqueous solution, caustic or alkali carbonate is added and mixed while the nickel compound precipitates.

(4) A caustic alkali or an alkali carbonate is added to an aqueous solution of an alkaline earth metal and nickel, and they are mixed while producing a precipitate of an alkaline earth metal compound and a precipitate of a nickel compound.

The slurry obtained as described in (1) to (4) above is subjected to solid-liquid separation, and the solid content is subjected to washing, drying, crushing and the like as appropriate. Further, in the above (1) to (4), a material that easily reacts with water, such as calcium oxide, is not used.

In the mixing of the present invention, the weight ratio of the amount of the alkaline earth metal compound powder to the amount of nickel is 0.05 to 0.05.
It is preferable to mix them so as to be 3. When the weight ratio is less than 0.05, the above-described coarsening prevention effect is not sufficiently exhibited. On the other hand, when the weight ratio is more than 3, the above-mentioned coarsening prevention effect does not not only increase further but also in the subsequent step of dissolution separation. To use more acid.

[First Heating] The heating temperature for the reduction is preferably from 350 to 700 ° C. Below 350 ° C,
The unreduced nickel compound remains, is hardly dissolved in the acid in the dissolution separation in the subsequent step, and is mixed as an impurity into the nickel powder. Further, the remaining nickel compound reacts with the alkaline earth metal compound in the second heating in the subsequent step to form a composite oxide. Also, this composite oxide is difficult to dissolve in an acid in the dissolution separation in the subsequent step (accordingly, the above-mentioned dissolution and separation properties of the alkaline earth metal compound are also reduced), so that the alkaline earth metal becomes a high concentration as an impurity in the nickel powder. mixing.

On the other hand, when the heating temperature exceeds 700 ° C., the alkaline earth metal compound and the nickel compound react to form a composite oxide. This composite oxide is not only difficult to reduce with hydrogen, but also hard to dissolve in an acid as described above. Therefore, the alkaline earth metal is mixed at a high concentration as an impurity in the nickel powder.

[Second Heating] In the second invention, the first heating object is heated to 800 to 1500 ° C. to perform the second heating.
By this heating, not only the sphericity of the nickel powder particles, but also the crystallinity and thus the oxidation resistance are improved.

If the heating temperature is lower than 800 ° C., the above effect cannot be sufficiently obtained. On the other hand, if the heating temperature is higher than 1500 ° C., nickel powder particles become droplets and alkaline earth metal compound particles cause sintering or fusion. Therefore, the nickel powder particles are likely to become coarse and difficult to maintain a spherical shape. Sintered and fused alkaline earth metal compounds have poor acid solubility, so that not only insufficient dissolution and removal by an acid in a later step are performed, but also impurities are mixed into the separated nickel powder.
The heating atmosphere may be non-oxidizing such as reducing, inert, or vacuum.

[Dissolution and Separation] The heated product obtained by the first heating or the second heating is pickled to dissolve the alkaline earth metal compound contained therein and separated and removed from the nickel powder. The type of acid used here is not particularly limited. The amount of acid used is
In order not to dissolve the nickel powder particles as much as possible, preferably, the weight ratio with respect to the theoretical amount necessary for dissolving the contained alkaline earth metal compound is 1.0 to 1.1.

[0037]

EXAMPLES Example 1 (1) Mixing of Nickel Hydroxide and Magnesium Hydroxide 100 g of reagent nickel hydroxide and 30 g of reagent primary magnesium hydroxide were suspended in 1 liter of pure water. The mixture was stirred for 30 minutes with a stirrer, separated into solid and liquid by suction filtration, and then dried at 80 ° C. for 12 hours in the air. The dried product was crushed in a mortar.

(2) First Heat The crushed material was heated at 400 ° C. for 1 hour in a tubular heating furnace (furnace cross-sectional area: 71 cm ² ) in a hydrogen stream (2 liters per minute).

(3) Second heating After the first heating, the atmosphere is changed from hydrogen to nitrogen while changing the atmosphere to 12 atmospheres.
The temperature was raised to 50 ° C. and kept at 1250 ° C. for 30 minutes.

(4) Dissolution and removal of magnesium compound The second heated product was suspended in 1 liter of pure water, 55 g of reagent primary sulfuric acid was added, and the mixture was stirred for 30 minutes to dissolve the contained magnesium compound. .

After dissolution, solid-liquid separation was performed by suction filtration. The separated nickel powder was washed twice with 1 liter of pure water and air dried at 60 ° C. for 12 hours. With the above operation, 60
g of nickel powder was obtained.

(5) Evaluation of Physical Properties of Nickel Powder The particle shape and average particle size of the manufactured nickel powder were measured. In addition, this measurement was based on observation with a scanning electron microscope. As a result, the particle shape was spherical, and the average particle size was 0.5 μm. FIG. 1 shows a scanning electron micrograph (magnification: 10,000 times).

(6) Analysis of Nickel Powder The produced nickel powder was dissolved with nitric acid and subjected to ICP emission analysis to measure the magnesium content. as a result,
Magnesium content of nickel powder is 200 weight pp
m.

Example 2 (1) Mixing of Nickel Hydroxide and Magnesium Hydroxide 50 g of nickel hydroxide reagent and 80 g of primary magnesium hydroxide reagent were ground in a ball mill for 24 hours in pure water.
After mixing and solid-liquid separation by suction filtration,
The solid was air dried for hours. The dried product was crushed in a mortar.

(2) First Heating The crushed material was heated at 450 ° C. for 1 hour in a tubular heating furnace (furnace cross-sectional area: 71 cm ² ) in a hydrogen stream (1 liter per minute).

(3) Second heating After the first heating, the atmosphere is changed from hydrogen to nitrogen for 10 minutes.
The temperature was raised to 00 ° C and kept at 1000 ° C for 2 hours.

(4) Dissolution and removal of magnesium compound The second heated product is suspended in 0.5 liter of pure water,
6.2 g of reagent primary sulfuric acid was added and stirred for 30 minutes to dissolve the magnesium compound contained.

After dissolution, solid-liquid separation was performed by suction filtration. The separated nickel powder was washed twice with 1 liter of pure water and air dried at 60 ° C. for 12 hours. 31
g of nickel powder was obtained.

(5) Evaluation of Physical Properties of Nickel Powder The particle shape and average particle diameter of the produced nickel powder were measured in the same manner as in Example 1. As a result, the particle shape was spherical, and the average particle size was 0.27 μm.

(6) Analysis of Nickel Powder The produced nickel powder was dissolved with nitric acid and subjected to ICP emission analysis to measure the magnesium content. as a result,
The magnesium content of the nickel powder is 300 weight pp
m.

Example 3 (1) Mixing of nickel hydroxide and calcium carbonate 31 g of reagent primary calcium chloride (dihydrate) was added in an amount of 0.5 g.
50 g of reagent nickel hydroxide was suspended in an aqueous solution dissolved in 1 liter of pure water. An aqueous solution of 25 g of reagent primary sodium carbonate (anhydrous) dissolved in 0.1 liter of pure water was added thereto, and the mixture was stirred at room temperature for 30 minutes while generating a precipitate (calcium carbonate). After the obtained slurry is subjected to solid-liquid separation by suction filtration, the solid is separated with 1 liter of pure water.
The solid was washed with water, filtered and air dried at 80 ° C. for 12 hours. The dried product was crushed in a mortar.

(2) First Heat The crushed material was heated at 500 ° C. for 1 hour in a tubular heating furnace (furnace cross-sectional area: 71 cm ² ) in a hydrogen stream (1 liter per minute).

(3) Second heating After the first heating, the atmosphere is changed from hydrogen to nitrogen while changing the atmosphere.
The temperature was raised to 00 ° C. and kept at 1400 ° C. for 30 minutes.

(4) Dissolution and Removal of Calcium Compound The second heated product was placed in 0.5 liter of pure water and stirred for 15 minutes to disintegrate, and then 39 ml of reagent primary hydrochloric acid (concentration: 36%) Was added and stirred for 30 minutes to dissolve the calcium compound contained.

After dissolution, solid-liquid separation was performed by suction filtration. The separated nickel powder was washed twice with 1 liter of pure water and air dried at 60 ° C. for 12 hours. 29 with the above operation
g of nickel powder was obtained.

(5) Evaluation of Physical Properties of Nickel Powder The particle shape and average particle diameter of the manufactured nickel powder were measured in the same manner as in Example 1. As a result, the particle shape was spherical, and the average particle size was 1.2 μm.

(6) Analysis of Nickel Powder The produced nickel powder was dissolved with nitric acid and subjected to ICP emission analysis to measure the calcium content. As a result, the calcium content of the nickel powder was 60 ppm by weight.

Example 4 (1) Preparation of Nickel Hydroxide To a reaction system heated to 60 ° C. with stirring, a nickel chloride aqueous solution was supplied at a constant flow rate to the reaction system to adjust the pH of the reaction system to 9.0.
While maintaining the temperature at 60 ° C. while stirring, an aqueous sodium hydroxide solution was added. The reaction product was continuously taken out by overflow so that the reaction product (nickel hydroxide) stayed in the reaction system for 2 hours. After the reaction system is stabilized and the properties of the product are stabilized, the reaction product is collected, and the obtained reaction product is filtered, washed with water, and dried.
00 g of nickel hydroxide was prepared.

(2) Mixing of nickel hydroxide and magnesium hydroxide 100 g of nickel hydroxide prepared above and 100 g
And industrial magnesium hydroxide were ground and mixed with a ball mill.

(3) First Heating The mixture was heated at 480 ° C. for one hour in a tubular heating furnace (furnace cross-sectional area: 71 cm ² ) in a hydrogen stream (1 liter per minute).

(4) Second Heating After the first heating, the atmosphere was changed from hydrogen to nitrogen to 11
The temperature was raised to 00 ° C and kept at 1100 ° C for 2 hours.

(5) Dissolution and removal of magnesium compound The second heated product is suspended in 1 liter of pure water, and 192 g
Was added and the mixture was stirred for 30 minutes to dissolve the magnesium compound contained therein.

After dissolution, solid-liquid separation was performed by suction filtration. The separated nickel powder was washed twice with 1 liter of pure water and air dried at 60 ° C. for 12 hours. With the above operation, 60
g of nickel powder was obtained.

(6) Evaluation of Physical Properties of Nickel Powder The particle shape and average particle diameter of the manufactured nickel powder were measured in the same manner as in Example 1. As a result, the particle shape was spherical, and the average particle size was 0.8 μm.

(7) Analysis of Nickel Powder The produced nickel powder was dissolved with nitric acid and subjected to ICP emission analysis to measure the magnesium content. as a result,
The magnesium content of the nickel powder is 500 weight pp
m.

Example 5 (1) Mixing of Nickel Hydroxide and Magnesium Hydroxide 129.7 g / l nickel chloride aqueous solution, 60 g / l
Was supplied to the reaction system at the same flow rate, and an aqueous sodium hydroxide solution was added while heating to 80 ° C. with stirring so as to maintain the reaction system pH at 11.5. The reaction product was continuously taken out by overflow so that the reaction product (nickel hydroxide, magnesium hydroxide) stayed in the reaction system for 10 hours. After the properties of the reaction product were stabilized, the product was collected, and the reaction product taken out was filtered, washed with water, and dried to prepare 100 g of a mixture.

(2) First Heating The mixture was heated at 450 ° C. for one hour in a tubular heating furnace (furnace cross-sectional area: 71 cm ² ) in a hydrogen stream (1 liter per minute).

(3) Second Heating After the first heating, the atmosphere is changed from hydrogen to nitrogen for 12 minutes.
The temperature was raised to 00 ° C, and kept at 1200 ° C for 30 minutes.

(4) Dissolution and Removal of Magnesium Compound The second heated product was suspended in 1 liter of pure water, 55 g of reagent primary sulfuric acid was added, and the mixture was stirred for 30 minutes to dissolve the magnesium compound contained therein.

After dissolution, solid-liquid separation was performed by suction filtration. The separated nickel powder was washed twice with 1 liter of pure water and air dried at 60 ° C. for 12 hours. 39 above
g of nickel powder was obtained.

(5) Evaluation of Physical Properties of Nickel Powder The particle shape and average particle diameter of the produced nickel powder were measured in the same manner as in Example 1. As a result, the particle shape was spherical, and the average particle size was 0.3 μm.

(6) Analysis of Nickel Powder The produced nickel powder was dissolved with nitric acid, and subjected to ICP emission analysis to measure the magnesium content. as a result,
The magnesium content of the nickel powder is 400 weight pp
m.

Example 6 (1) Mixing of Basic Nickel Carbonate and Magnesium Hydroxide 50 g of reagent basic nickel carbonate and 10 g of industrial magnesium hydroxide were made into a slurry with 1 liter of pure water and pulverized by a ball mill. , Mixed. After the solid-liquid separation, the mixture was air-dried at 110 ° C. for 12 hours, and then dried and crushed in a mortar.

(2) First Heat The crushed material was heated at 600 ° C. for 1 hour in a tubular heating furnace (furnace cross-sectional area: 71 cm ² ) in a hydrogen stream (1 liter per minute).

(3) Second heating After the first heating, the atmosphere is changed from hydrogen to nitrogen for 10 minutes.
The temperature was raised to 00 ° C. and maintained for 30 minutes.

(4) Dissolution and Removal of Magnesium Compound The second heated substance was suspended in 1 liter of pure water, 19 g of reagent primary sulfuric acid was added, and the mixture was stirred for 30 minutes to dissolve the magnesium compound contained therein.

After dissolution, solid-liquid separation was performed by suction filtration. The separated nickel powder was washed twice with 1 liter of pure water and air dried at 80 ° C. for 12 hours. With the above operations, 19
g of nickel powder was obtained.

(5) Evaluation of Physical Properties of Nickel Powder The particle shape and average particle diameter of the manufactured nickel powder were measured in the same manner as in Example 1. As a result, the particle shape was spherical, and the average particle size was 0.6 μm.

(6) Analysis of Nickel Powder The produced nickel powder was dissolved with nitric acid, and ICP emission analysis was performed to measure the magnesium content. as a result,
The magnesium content of the nickel powder is 500 weight pp
m.

Example 7 (1) Mixing of Basic Nickel Carbonate and Calcium Carbonate 50 g of reagent basic nickel carbonate and 21 g of reagent primary calcium carbonate were slurried with 1 liter of pure water and pulverized by a ball mill. , Mixed. After the solid-liquid separation, the mixture was air-dried at 110 ° C. for 12 hours, and then dried and crushed in a mortar.

(2) First Heat The crushed material was heated at 600 ° C. for 1 hour in a tubular heating furnace (furnace cross-sectional area: 71 cm ² ) in a hydrogen stream (1 liter per minute).

(3) Second heating After the first heating, the atmosphere was changed from hydrogen to nitrogen for 10 minutes.
The temperature was raised to 00 ° C. and maintained for 30 minutes.

(4) Dissolution and Removal of Calcium Compound The second heat was suspended in 0.5 liter of pure water,
1 ml of reagent primary hydrochloric acid (concentration: 36%) was added and stirred for 30 minutes to dissolve the calcium compound contained therein.

After dissolution, solid-liquid separation was performed by suction filtration. The separated nickel powder was washed twice with 1 liter of pure water and air dried at 80 ° C. for 12 hours. With the above operations, 20
g of nickel powder was obtained.

(5) Evaluation of Physical Properties of Nickel Powder The particle shape and average particle diameter of the manufactured nickel powder were measured in the same manner as in Example 1. As a result, the particle shape was spherical, and the average particle size was 0.8 μm.

(6) Analysis of Nickel Powder The produced nickel powder was dissolved in nitric acid, and the content of calcium was measured by ICP emission analysis. As a result, the calcium content of the nickel powder was 100 ppm by weight.

Comparative Example 1 (1) Mixing of Basic Nickel Carbonate and Magnesium Hydroxide 100 g of reagent basic nickel carbonate and 21 g of industrial magnesium hydroxide were slurried with 1 liter of pure water and pulverized by a ball mill. , Mixed. After the mixture was subjected to solid-liquid separation by suction filtration, the solid was air-dried at 80 ° C. for 12 hours. The dried product was crushed in a mortar.

(2) Heating The crushed material was placed in a tubular heating furnace (cross-sectional area of the furnace: 71 cm ² ), and the temperature was raised from room temperature to 1000 ° C. at a speed of 15 ° C./min, and kept as it was for 30 minutes. Atmosphere at that time is 4
The temperature was switched from nitrogen to 400 ° C. to hydrogen (flow rate: 1 liter per minute) until 00 ° C.

(3) Dissolution and removal of magnesium compound The heated substance was suspended in 1 liter of pure water, and 39 g of reagent 1 was suspended.
Grade sulfuric acid was added and stirred for 30 minutes to dissolve the contained magnesium compound.

After dissolution, solid-liquid separation was performed by suction filtration. The separated nickel powder was washed twice with 1 liter of pure water and air dried at 60 ° C. for 12 hours. 40 above
g of nickel powder was obtained.

(4) Evaluation of Physical Properties of Nickel Powder The particle shape and average particle diameter of the produced nickel powder were measured in the same manner as in Example 1. As a result, the particle shape was spherical, and the average particle size was 0.5 μm.

(5) Analysis of Nickel Powder The produced nickel powder was dissolved with nitric acid and subjected to ICP emission analysis to measure the magnesium content. as a result,
The magnesium content of the nickel powder was 3.2% by weight.

Comparative Example 2 (1) Mixing of Basic Nickel Carbonate and Calcium Carbonate 100 g of Reagent Basic Nickel Carbonate and 42 g of Reagent 1
Grade calcium carbonate was slurried with 1 liter of pure water and pulverized and mixed with a ball mill. After the solid-liquid separation, the mixture was air-dried at 110 ° C. for 12 hours, and then dried and crushed in a mortar.

(2) Heating The crushed material was placed in a tubular heating furnace (cross-sectional area of the furnace: 71 cm ² ), and the temperature was raised from room temperature to 1000 ° C. at a speed of 15 ° C./min, and held for 30 minutes. Atmosphere at that time is 4
The temperature was switched from nitrogen to 400 ° C. to hydrogen (flow rate: 1 liter per minute) until 00 ° C.

(3) Dissolution and removal of calcium compound The heated substance was suspended in 1 liter of pure water, and 78 ml of reagent primary hydrochloric acid (concentration: 36%) was added, followed by stirring for 30 minutes.
The calcium compound contained was dissolved.

After dissolution, solid-liquid separation was performed by suction filtration. The separated nickel powder was washed twice with 1 liter of pure water and air dried at 60 ° C. for 12 hours. 40 above
g of nickel powder was obtained.

(4) Evaluation of Physical Properties of Nickel Powder The particle shape and average particle diameter of the produced nickel powder were measured in the same manner as in Example 1. As a result, the particle shape was spherical, and the average particle size was 0.5 μm.

(5) Analysis of Nickel Powder The produced nickel powder was dissolved with nitric acid and subjected to ICP emission analysis to measure the calcium content. As a result, the calcium content of the nickel powder was 1.8% by weight.

[0099]

According to the present invention, the average particle size is 0.1 to 2
μm and spherical nickel powder can be produced at low cost.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph (magnification: 10000 times) of the nickel powder produced in Example 1.

Claims (13)

[Claims] 1. A first step of mixing an alkaline earth metal compound powder and a nickel compound powder, and a step of mixing the mixture obtained in the first step with a hydrogen atmosphere to reduce nickel in the mixture to nickel metal. Production of spherical nickel powder comprising: a second step of heating while preventing formation of a composite oxide in step (a), and a third step of dissolving and removing an alkaline earth metal in the heated product obtained in the second step with an acid. Method. 2. A first step of mixing an alkaline earth metal compound powder and a nickel compound powder, and a step of mixing the mixture in a hydrogen atmosphere to reduce nickel in the mixture obtained in the first step to metallic nickel. A second step of heating while preventing the formation of a composite oxide in the heating step, and heating the heated nickel particles in a non-oxidizing atmosphere in order to improve the sphericity of the metallic nickel particles in the heated substance obtained in the second step. A method for producing spherical nickel powder, comprising: a third step of heating while preventing coarsening of the powder; and a fourth step of dissolving and removing the alkaline earth metal in the heated product obtained in the third step with an acid. 3. The method for producing a spherical nickel powder according to claim 1, wherein the mixing in the first step is performed between solids. 4. The mixing in the first step is performed while suspending a nickel compound powder in an alkaline earth metal aqueous solution and then adding caustic or alkali carbonate to generate a precipitate of the alkaline earth metal compound. A method for producing a spherical nickel powder according to claim 1. 5. The mixing in the first step is performed while suspending an alkaline earth metal compound powder in a nickel aqueous solution and then adding a caustic alkali or an alkali carbonate to generate a precipitate of the nickel compound. Or the method for producing spherical nickel powder according to item 2. 6. The method of claim 1, wherein the mixing in the first step is performed by adding a caustic alkali or an alkali carbonate to an aqueous solution of an alkaline earth metal and nickel to form a precipitate of the alkaline earth metal compound and a precipitate of the nickel compound. Item 1
Or the method for producing spherical nickel powder according to item 2. 7. The mixing in the first step is such that the weight ratio of the amount of the alkaline earth metal compound powder to the amount of nickel is 0.0
The method for producing a spherical nickel powder according to any one of claims 1 to 6, wherein the method is performed so as to be 5 to 3. 8. The heating in the second step is performed at 350 to 70.
The method for producing spherical nickel powder according to claim 1 or 2, which is performed at 0 ° C. 9. The heating in the third step is from 800 to 15
The method for producing spherical nickel powder according to claim 2, which is performed at 00 ° C. 10. The method according to claim 1, wherein the acid in the fourth step is used such that the weight ratio between the amount used and the theoretical amount necessary for dissolving the alkaline earth metal is 1.0 to 1.1. 2
3. The method for producing a spherical nickel powder described in 1. above. 11. The alkaline earth metal compound is at least one selected from the group consisting of magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium oxide, calcium carbonate and calcium hydroxide. 8. The method for producing a spherical nickel powder according to any one of claims 1 to 7. 12. The production of spherical nickel powder according to claim 1, wherein the nickel compound is at least one selected from the group consisting of nickel oxide, nickel carbonate and nickel hydroxide. Method. 13. The method for producing a spherical nickel powder according to claim 1, wherein the produced spherical nickel powder has an average particle diameter of 0.1 to 2 μm.