KR940009339B1 - Method of manufacturing nikel powder - Google Patents

Abstract

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Description

Ultra-fine nickel powder and its manufacturing method

1 is a schematic diagram of an applicator which can be used suitably for the practice of the present invention.

FIG. 2 is a micrograph showing the fine nickel powder grain structure produced by the method of the present invention shown in Example 1. FIG.

FIG. 3 is a micrograph showing the fine nickel powder grain structure produced by the method of the present invention shown in Example 2. FIG.

4 is a view showing a micrograph showing the structure of the nickel fine powder particles produced by Comparative Example 1.

5 is a graph showing the relationship between the nickel chloride vapor concentration and the reaction temperature in each example.

* Explanation of symbols for main parts of the drawings

2: evaporator 3: quartz board

4: argon gas 6: reaction central nozzle

8: thermocouple 9: cooling part

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high purity and ultra fine powder spherical nickel fine powder suitable for an electrically conductive paste filter for use in electronic parts and the like and a method of manufacturing the same.

The ultrafine metal powder having a small error, the average particle diameter (hereinafter, the particle diameter is measured by the average diameter of the surface area) in the range of 0.1 to several μm, and the particles are spherical has a good face shape and is a conductor of an electronic circuit. When molding is used, since fine patterning or thinning of a conductor part is possible, such powder is strongly desired in recent years.

For example, multilayer ceramic capacitors used in electronic parts and the like are manufactured by alternately stacking ceramic derivatives and internal electrodes in a layered form, compressing them, and firing and integrating them.

In this case, it is necessary to use expensive precious metals such as Pt and Pd that are not oxidized even when the derivative ceramic is not melted at the sintering temperature and calcined in a high oxygen partial pressure without decomposing or reducing the derivative ceramic. .

For this reason, it is difficult to obtain a large capacity and low cost capacitor.

In order to solve this problem, ceramics with sufficient resistivity and excellent conductive properties have been developed as a derivative for capacitors, which must use a nonmetal such as nickel as an internal electrode and cannot be semiconductorized even when fired in a low oxygen partial pressure or a reducing atmosphere.

In addition, the miniaturization and the large capacity of electronic components have been progressed, and the necessity of thinning and low resistance of internal electrodes has been caused.

The thickness of the internal electrode is limited by the filler particle diameter in the paste to be used.

In other words, it cannot be made thinner than the particle diameter.

Therefore, it is good to use a filler powder having a small particle diameter, but there is a limit because the filling of the filler is at least bad.

As the filler, the application of nickel ultrafine powder, which is difficult to oxidize and relatively inexpensive, has been tested.

As a conventional method for producing an ultrafine nickel powder, as disclosed in Japanese Patent Application Laid-Open No. 9-7765, a velocity difference is applied to the metal halide gas stream and a reducing gas stream, and at the same time, it is generated in the interface unstable region by using the specific gravity difference between the gases. It is known to produce ultra fine powders of metals by the growth of nuclei.

In this case, the fine nickel powder is formed into particles having a crystallographic habit such as a cube shape (described in the remarks column of Table 1), and a filling problem occurs when the paste filler is used.

In addition, published in the paper by Ken Otsuga, et al., "Preparation of Ultrafine Molecules of Nickel, Cobalt, and Iron by Chloride Vapor Hydrogen Reduction," Japanese Chemical Society 1984. (6) P 869-878) A method of obtaining ultrafine powder of nickel by hydrogen reduction reaction is disclosed.

According to the present invention, an ultrafine powder having a particle diameter of 0.1 µm or less is obtained by reacting the reaction temperature at 750-960 ° C and the vapor temperature of chloride at 0.02 or less (FIG. 12).

Also in this case, there is a problem that the particle diameter is too small to produce particles having crystallographic habit.

Japanese Patent Application Laid-Open No. 02-49364 discloses a method of reducing precipitation by adding a reducing agent such as sodium bromine hydroxide to an aqueous solution containing nickel ions.

In this case, various reducing agents are required, operation conditions are complicated, and high purity high purity reducing agents are required to obtain high purity products.

Moreover, this reduction precipitation method is batch type, and it is difficult to serialize manufacture.

In addition, as a method for producing nickel and iron fine powder, there is a carbonyl method, but the grain size is large and the fine patterning or thinning of the conductor portion cannot be satisfied.

In addition to nickel, copper powder and silver powder production methods are shown in Japanese Patent Application Laid-Open No. 62-63604 and Japanese Patent Laid-Open No. 62-188709.

This method vaporizes metal halides and sends them to the reaction by their own vapor pressure or inert gas as carrier to the metals in the gas immediately after contacting and mixing the metal halide vapor and reducing gas (hydrogen etc.) in the reaction part. The powder is reduced, precipitated and then discharged with the gas to the outlet.

Therefore, the metal halide which is a raw material can be continuously supplied, and a production powder can be collect | recovered.

However, in the case of nickel powder in Japanese Patent Application Laid-Open No. 62-63604 and silver powder in Japanese Patent Application Laid-Open No. 62-188709, particles having crystallization habits such as cubes and octahedrons are formed and paste fillers. When we did, there was problem in filling characteristics.

As described above, in the conventional method for preparing the fine nickel powder, particles with crystallization are generated even in the fine nickel powder having a particle diameter of 1 μm or less, so that filling of the filler is insufficient when printing the internal electrode paste.

For this reason, there is a problem that the density becomes low, there are many voids after firing and the electrical resistance is high, and peeling phenomenon often occurs during firing.

In addition, nickel powder having a particle size of less than 3 µm described above has a problem that the purity is not good, and it is difficult to reduce the resistance of the electrode or adversely affect the properties of the derivative, or to obtain high reliability as an electronic component material.

In view of the above, it is an object of the present invention to provide a method for producing an ultrafine nickel powder having a spherical shape and a particle diameter of 0.05-3 μm in order to improve high purity or filler filling.

The present invention is characterized in that the nickel chloride vapor concentration is 0.05-0.3, and nickel chloride vapor and hydrogen are chemically reacted at a temperature of 1004 ° C (1277K) -1453 ° C (1726K) to contain 99.5% by weight or more of nickel. A method for producing a spherical nickel ultrafine powder, and a spherical nickel ultrafine powder, characterized in that the spherical shape, the particle diameter is 0.1-3 占 퐉, and contains 99.5% by weight or more of nickel.

The present invention also relates to a spherical nickel ultrafine powder produced by a gas phase chemical reaction of a chloride of nickel and hydrogen and a method for producing the same. In order to prepare the ultrafine nickel powder by gas phase chemical reaction, nickel chloride is added to the reactor to evaporate, and the reaction mixture is brought into contact with the hydrogen supplied from the nozzle by sending it to the reaction part along with argon gas.

The generated ultra fine nickel powder is recovered after passing through the cooling unit together with the gas.

In this case, the grain growth of nickel is considered as follows.

At the moment when the metal halide vapor is in contact with the reducing gas, monomers of metal atoms or clusters are generated, and ultra-fine particles are generated by collision aggregation of the monomers.

In addition, particle growth occurs due to collision and coalescence. Ultrafine particles of copper and silver are generally spherical, but nickel is often polyhedron.

In particular, when the particles become a relatively rough region, the ratio of surface energy is also reduced, and the particles become more crystalline.

Particularly, in nickel, when the particle diameter is larger than about 0.1 mu m, it becomes easy to be a cubic and octahedral crystal crystalline particles.

In the present invention, the reaction production of fine nickel powder was investigated in detail. As a result, the nickel chloride vapor concentration (partial pressure in the hydrogen-depleted feed gas) was set to 0.05-0.3, and the reaction and powder formation temperature were taken as the melting point of nickel (1726K). The present invention has been found that spherical powders can be obtained by 0.74 times or more, that is, from 1004 ° C (1277K) to 1453 ° C (1726K) or less.

The reason for limiting the nickel chloride vapor concentration to 0.05-0.3 is as follows.

When the concentration was less than 0.05, it was proved by experiment that crystal habitability occurred and spherical powder could not be obtained.

This is thought to be because the particles grow at a relatively slow rate. Moreover, when it exceeds 0.3, particle diameter will coarsen and powder of predetermined diameter will not be obtained.

This is because, when the particle diameter is coarsened, crystal habits tend to occur, and the concentration is preferably 0.06-0.15.

Next, the reason for limiting the reaction temperature to 1004 ° C-1453 ° C is described.

If the reaction temperature is less than 1004 ° C., not only the crystallographic molecules are incorporated but also cause a decrease in the reaction rate.

As for the upper limit of reaction temperature, below melting | fusing point of nickel 1453 degreeC (1726K) is preferable.

This is because the particles produced in the liquid phase above the melting point may generate excessively large grown particles, and the particles also become denser and more adhere to the reactor walls.

As for reaction temperature, 1,010-1,100 degreeC is especially preferable.

The temperature dependence of the particle shape is assumed to be related to the reaction rate, that is, the rate of monomer generation of metal atoms or clusters.

In other words, it is thought that the growth rate of the particles influences the shape.

The higher the temperature, the less anisotropic the growth of the particles, and therefore, the particles are likely to grow into a spherical shape.

The concentration dependence of the shape is thought to be related to the uniform nucleation rate affected by the concentration.

It is understood that this case also depends on the growth rate of the particles in the same manner as the temperature.

When the reaction occurs in a reaction tube heated in an electric furnace, for example, since the reaction is exothermic, the purpose of spheronization can be achieved as long as the temperature of the electric furnace can be exothermic even if the set temperature is lower than the specified temperature. Can be.

In other words, in the gas phase chemical reaction method, it has been found that it is important to control the temperature at which particle formation by collision, particle formation by coalescence, and coalescence occur.

This invention further limits the nickel content of nickel powder to spherical shape which is 99.5 weight% or more, and the particle diameter is 0.05 micrometer or more and less than 3 micrometers.

If the nickel content is less than 99.5% by weight, the high reliability of the electronic component material cannot be sufficiently achieved due to the weakening of the electrode or the deterioration of the dielectric properties, so the nickel content is 99.5% by weight or more.

Particles with a particle diameter of less than 0.05 μm are agglomerated easily, and when printed in a paste state as an internal electrode such as a multilayer ceramic capacitor, the filling of the filler is extremely insufficient, so that the electrode layer is porous after firing, and thus the electrical resistance becomes high. In addition, the bonding force with the dielectric layer becomes poor, and as a result, peeling phenomenon occurs.

In powder of 3 micrometers or more, thinning of an electrode layer is physically impossible.

In addition, because of the spherical shape, a structure close to the closest filling can be obtained at the time of internal electrode printing, and a low-resistance electrode with uniformly small voids can be obtained after firing, and as a result, cracking and peeling of the dielectric layer can be prevented.

Example 1

As shown in FIG. 1, 10 g of nickel chloride as a raw material was placed on the quartz board 3 of the evaporator 2 using the reactor 1, and the concentration (partial pressure) was 5.0 in 2 l / min of argon gas 4. is evaporated so that the × 10 ^-2.

This raw material mixed gas is transferred to the reaction part 5 set at 1050 ° C (0.77 times the nickel melting point in terms of absolute temperature) and contacted and mixed with hydrogen supplied at a rate of 1 l / min from the reaction central nozzle 6. To cause a reaction.

The temperature of the reaction portion was measured by a thermocouple 8 protected by a quartz tube, and as a result, the temperature rose to 1090 ° C (0.79 times the melting point of nickel in terms of absolute temperature).

The generated nickel powder was recovered from the cylindrical filter paper after passing through the cooling unit 9 together with the gas.

The specific surface area of this powder was 3.5 m 2 / g, and the electron microscopic observation showed a spherical particle having a particle diameter of 0.2 μm.

2 shows an electron micrograph of the nickel powder obtained by the present example.

It was found that the shape of the nickel powder was a spherical shape close to perfection.

Example 2

In Example 1, nickel powder was manufactured on the same conditions except having made reaction temperature 960 degreeC (0.714 times nickel melting point in the absolute temperature).

As a result of measuring by the thermocouple 8, it rose to 1004 degreeC (0.74 times of nickel melting point in the absolute temperature).

The specific surface area of the generated nickel powder was 3.7 m 2 / g, and electron microscopic observation showed a spherical powder having a particle diameter of 0.18 mu m.

Example 3

In Example 1, nickel powder was manufactured on the same conditions except reaction temperature being 960 degreeC (0.714 times nickel melting point in the absolute temperature), and concentration (partial pressure) to 8.0x10 <^-2> .

As a result of measuring by the thermocouple 8, it rose to 1006 degreeC (0.74 times of nickel melting point in conversion at absolute temperature).

The specific target of the produced nickel powder was 3.0 m <2> / g, and the electron microscope showed spherical powder with a particle diameter of 0.22 micrometer.

Example 4

In Example 1, nickel powder was manufactured on the same conditions except reaction temperature being 1000 degreeC (0.74 times absolute melting point of nickel), and concentration (partial pressure) to 8.5x10 <^-2> .

As a result of measuring by the thermocouple 8, it rose to 1053 degreeC (0.77 times the nickel melting point in conversion at absolute temperature).

The specific target of the produced nickel powder was 2.9 m <2> / g, and the electron microscope observation showed spherical powder with a particle diameter of 0.23 micrometer.

Example 5

In Example 1, nickel powder was manufactured on the same conditions except reaction temperature being 1050 degreeC (0.767 times of nickel melting point in absolute temperature), and concentration (partial pressure) to 3.0 * 10 <^-1> .

As a result of measuring by the thermocouple 8, it rose to 1120 degreeC (0.81 times the melting point of nickel at the time of conversion to absolute temperature).

The specific surface area of the produced nickel powder was 0.9 m <2> / g, and the electron microscope observation showed spherical powder with a particle diameter of 0.8 micrometer.

Comparative Example 1

In Example 1, nickel powder was manufactured on the same conditions except reaction temperature being 950 degreeC (0.71 times nickel melting point in absolute temperature), and concentration (partial pressure) to 4.5x10 <^-2> .

As a result of measuring by the thermocouple 8, it rose to 993 degreeC (0.73 times the nickel melting point in conversion at absolute temperature).

The specific surface area of the nickel powder generated was 3.6 m 2 / g, and as shown in FIG. 4, the electron microscopic observation showed that the powder had crystal habits such as a cube and an octahedron with a particle diameter of 0.2 µm.

Comparative Example 2

In Example 1, nickel powder was manufactured on the same conditions except reaction temperature being 950 degreeC (0.71 times nickel melting point in absolute temperature), and concentration (partial pressure) to 8.0x10 <^-2> .

As a result of measuring by the thermocouple 8, it rose to 998 degreeC (0.73 times the nickel melting point in conversion at absolute temperature).

The specific surface area of the generated nickel powder was 3.4 m 2 / g, and by electron microscopic observation, it was a powder having crystallization habits such as a cube and an octahedron with a particle diameter of 0.2 μm.

Comparative Example 3

In Example 1, nickel powder was manufactured on the same conditions except having made reaction temperature 1000 degreeC (0.74 times of nickel melting point in absolute temperature), and concentration (partial pressure) to 4.5x10 <^-2> .

As a result of measuring by the thermocouple 8, it rose to 1042 degreeC (0.76 times the nickel melting point in conversion at absolute temperature).

The specific surface area of the generated nickel powder was 3.4 m 2 / g, and electron microscopic observation revealed that the powder had a crystallographic habit such as a cube octahedron with a particle diameter of 0.2 μm.

[Comparative Example 4]

In Example 1, nickel powder was manufactured on the same conditions except reaction temperature being 1100 degreeC (0.795 times of nickel melting point in conversion to absolute temperature), and concentration (partial pressure) to 3.6x10 <^-1> .

As a result of measuring by the thermocouple 8, it rose to 1160 degreeC (0.83 times the nickel melting point in conversion at absolute temperature).

The specific surface area of the nickel powder generated was 1.0 m 2 / g, and the electron microscopic observation showed that the powder had crystallographic properties such as a cube octahedron with a particle diameter of 0.8 μm.

Fig. 5 shows the result of combining the relationship between the nickel chloride vapor concentration and the reaction temperature in each of the above Examples and Comparative Examples.

According to the present invention, an ultrafine nickel powder having a particle diameter of 0.05-3 占 퐉, a spherical shape, and a nickel content of 99.5% by weight or more can be continuously produced according to the present invention.

Claims (2)

The nickel chloride vapor concentration is 0.05-0.3, and the nickel chloride vapor and hydrogen are chemically reacted at a temperature of 1004 ° C (1277K) -1453 ° C (1726K) to contain nickel at least 99.5% by weight. Method for preparing the powder. An ultrafine nickel powder having a spherical shape, wherein the particle diameter is 0.1-3 µm and contains 99.5% by weight or more of nickel.