JPS58171506A - Manufacture of fine metallic nickel powder - Google Patents

Abstract

PURPOSE:To obtain metallic Ni powder having a desired grain size and shape in the titled manufacture by reducing Ni chloride powder with gaseous H2, by treating the Ni chloride powder at a specified temp. while fluidizing the powder. CONSTITUTION:Solid NiCl2 is fluidized in a gas flow contg. gaseous H2, preferably a gas flow consisting of >=about 30vol.% gaseous H2 and the balance N2 or other inert gas in a furnace kept at 500-700 deg.C by heating the furnace from the outside or by blowing a heated gas. Thus, the NiCl2 is reduced, and the reduced product is cooled to ordinary temp. in an inert atmosphere and taken out as fine metallic Ni powder which is hardly reoxidized.

Description

[Detailed description of the invention] The present invention relates to a method for producing fine nickel powder.

Fine metallic nickel powder is widely used for batteries and powder metallurgy.

In general, methods for producing metallic nickel powder that have been put to practical use include (1) thermal decomposition or gas reduction of a powdered or gaseous nickel compound, and (2) reduction from a nickel-containing aqueous solution. (3) A nickel alloy (an alloy of Ni and At or Si) is treated with sodium hydroxide.

There are two main methods: a method for producing nickel powder with high hydrogen activity by eluting and separating AI +8i, and a method for producing metallic nickel powder from bulk metallic nickel. In the third method, it is difficult to obtain the desired fine metallic nickel powder.

The first method is to obtain metallic nickel powder by reducing nickel oxide, nickel hydroxide, or nickel carbonate powder with hydrogen gas, or by thermally decomposing a solid powder such as nickel oxalate or a nickel carzenyl compound. The metallic nickel powder for batteries and powder metallurgy that is the object of the present invention has an average particle size [hereinafter abbreviated as average particle size (Fsss)] measured using a Fischer subsieve sizer of about 10μ or less, preferably 3μ or less. The following are used:

The metallic nickel powder currently used in Japan in this field is manufactured by a method called the carnil process, which uses toxic nickel carzenyl, and is imported. This is because, as mentioned above, metallic nickel powder obtained by the more general method of reducing nickel salts such as nickel oxide and nickel hydroxide with hydrogen is susceptible to re-oxidation.

To prevent this, the temperature required for hydrogen reduction of nickel,
For example, methods such as inactivation by treatment at a temperature of 500 to 700°C or higher, or inactivation treatment with a rust preventive (for example, immersion in an aqueous solution containing a product name Cortamine, Pal, etc.) is being carried out.

However, inactivation treatment at high temperatures makes it difficult to produce fine metallic nickel powder, and rust prevention treatment has problems with stabilization during heat treatment, making it difficult to produce fine metallic nickel powder. be.

The object of the present invention is to eliminate the above-mentioned drawbacks and provide a method for producing metallic nickel powder having a desirable particle size and shape.

To achieve this objective, the present inventors conducted various studies on hydrogen reduction methods for nickel chloride, and found that solid nickel chloride was fluidized in a hydrogen-containing air stream at a predetermined temperature to achieve a desirable particle size and shape. However, we have found a method for producing metallic nickel powder that is less susceptible to reoxidation.

That is, in a hydrogen gas-containing air stream maintained at 500 to 700°C by heating the furnace body from outside the furnace or blowing heated gas into it, preferably 30 volumes or more of hydrogen gas, and the remainder being N2. A reduction treatment is performed while solid nickel chloride is fluidized in an inert gas such as Ar, and then it is cooled to room temperature in an inert atmosphere to extract fine metallic nickel powder.

A fluidized fluidized furnace is preferable as the furnace for this treatment, and the reason why the treatment temperature is set in the range of 500 to 700°C is because below this temperature, even if the hydrogen concentration is high, the time required for the reduction treatment is too long to be practical. On the other hand, if the processing temperature is higher than this, not only will it not be possible to obtain grains with a suitable particle size, but the volatilization loss will also increase.

If the reduction treatment is performed while fluidizing, metal powder with a small average particle size and tap density can be reliably obtained.

These will now be explained in more detail with reference to FIG.

When Ni04 dehydrated at 150°C is subjected to static hydrogen reduction at a predetermined temperature and fluidized hydrogen reduction in Figure 1, the nickel powder obtained by the fluidized reduction method is different from that obtained by the static reduction method. The average particle size (Fss
s) and tap density are both small.

Furthermore, when the treatment temperature is 750° C. or higher, both the average particle size and the tap density increase rapidly even in the fluidized reduction method.

Therefore, in order to obtain an average particle size of 3 μm or less suitable for use in batteries and powder metallurgy, the temperature should be about 650° C. or less for static reduction roasting, and about 750° C. or less for fluidized reduction roasting. The same can be said about tap density.

Also, if the processing temperature is 750°C or higher, Ni CJ! Since the vapor pressure of , becomes extremely high, recovery equipment for this is also required.

On the other hand, when the treatment temperature is below 00°C, the reaction rate is extremely slow (not shown in the figure), and the static reduction method takes a long reaction time and requires a large amount of hydrogen gas to metalize nickel, and the fluidized reduction method requires a large amount of hydrogen gas. This is not preferable because not only the reaction time is long, but also the chlorine content in the produced nickel metal powder tends to be high.

When fluidized reduction is carried out in an appropriate temperature range and in a hydrogen gas flow, a product with good properties and low average particle size (Fs-ss) + tap density Cf/ld) can be obtained on an industrial scale.

Figure 2 shows the results when impure NiC4 is reduced with H2. Since the H2 reduction method of NIC4 removes the zt, pb contained in the product metal powder, it is especially Suitable for manufacturing high purity products.

Regarding this phenomenon, similar results can be obtained by both the static reduction method and the fluidized reduction method.

The present invention will be described below with reference to Examples.

Example 1 Nickel chloride 51Q, which had been dehydrated at 150°C and had a particle size of -48 to +100 mesh, was heated in a hydrogen stream at a constant concentration of pIr% (
Inner diameter 100mm maintained at a temperature of 700℃ with balance nitrogen)
charged into a fluidized fluidized furnace and subjected to fluidized reduction for a predetermined residence time.
The obtained metallic nickel powder was cooled to room temperature in a nitrogen atmosphere and then taken out into the air. The results are shown in Table 1.

As is clear from Table 1, there are some differences in residence time (reduction time) depending on the hydrogen concentration, but metallic nickel powders with satisfactory average particle diameter and tap density were obtained in all cases.

As the hydrogen concentration decreased, the residence time (reduction time) became longer, but this varies depending on the equipment, and even if the hydrogen concentration is low, for example, increasing the furnace inner diameter will increase the reduction time. Although the time was short, the obtained metallic nickel powder was observed with a scanning electron microscope and was found to be very porous, and no reoxidation was observed even when it was left in the air.

Fluid reduction was carried out in the same manner as in Example 1, except that the hydrogen concentration was 80 volumes, the balance was nitrogen, and the treatment temperature and residence time were set to predetermined values. The results are shown in Table 2.

As can be seen from Table 2, this was outside the scope of the method of the present invention.

For No. 6, the time required for reduction was long, and for No. 10, both the average particle diameter and the tap density were large, but otherwise satisfactory results were obtained.

The obtained metallic nickel powder was porous like the product of Example 1, and no reoxidation in air was observed.

As explained above, when anhydrous nickel chloride is reduced at a predetermined temperature while flowing with a hydrogen-containing gas, it is possible to reliably produce metallic nickel powder having a particle size and tap density suitable for use in batteries and powder metallurgy. Can be done.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the tap density of reduced nickel and F'sss, where the vertical axis is the tap density (f/CC) on the left.
, the right side shows Fsss (μ), and the horizontal axis shows reduction temperature (°C). O and 口 appear in the case of static reduction, and ・■ appears in the case of fluid reduction. Note that the apparent tap density is a value measured using a tapping measuring device in the specific volume range. FIG. 2 is a graph showing the behavior of the removal rate of impurities in reduced nickel, where the vertical axis shows the removal rate (ch) and the horizontal axis shows the temperature. Patent applicant Sumitomo Metal Mining Co., Ltd. Izumi 72 Melon 2 sides

Claims (1)

[Claims] A method for producing metallic nickel powder by reducing nickel chloride powder with hydrogen gas, characterized in that the nickel chloride powder is treated at 500 to 700°C while flowing in an air stream containing hydrogen gas. Method for producing nickel powder.