JPS60131904A - Manufacture of fine metallic nickel powder - Google Patents

Abstract

PURPOSE:To manufacture efficiently fine metallic nickel powder by adding a straight chain satd. fatty acid or a carbohydrate to nickel chloride powder and treating the mixture at a specified temp. in a flow of gas contg. hydrogen. CONSTITUTION:To nickel chloride powder is added 1-10wt% straight chain satd. fatty acid and/or carbohydrate. The fatty acid is represented by the formula (where m is >=6), and starch, glucose, dextrin or the like is used as the carbohydrate. The mixture is reduced at 400-750 deg.C in a flow of gas contg. hydrogen to obtain metallic nickel powder of <=1mum particle size.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ultrafine metallic nickel powder.

Conventionally, methods for producing metallic nickel powder include (1) a method of thermally decomposing or gaseous reduction of a powdered or gaseous nickel compound, (2) a method of producing it by reduction from a nickel-containing water bath liquid, and (3) a method of producing it by reduction from a nickel-containing water bath liquid. ) Nickel alloy (Ni
and Ae or Sl alloy) with sodium hydroxide,
These methods are broadly divided into two methods: a method for producing nickel powder with high hydrogen activity by eluting and separating Ad and Si, and a method for producing metallic nickel powder from bulk metallic nickel. It is difficult to obtain desirable fine metallic nickel powder using the second and third methods.

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 carbonyl compound.

All of the metal nickel powders obtained by the above methods have the disadvantage of being easily reoxidized, and various inactivation treatments are performed to prevent this. This passivation treatment makes it extremely difficult to produce fine metallic nickel powder.

As a method for solving the above-mentioned drawbacks, the present inventors have already filed an application for a method for producing fine metallic nickel powder using a hydrogen reduction method of nickel chloride. (Unexamined Japanese Patent Publication No. 58
-174506).

This method is characterized by treating nickel chloride powder at 500 to 700°C while flowing it in an air stream containing hydrogen gas, and it is possible to obtain fine metallic nickel powder without reoxidation as described above. However, the present invention aims to provide a method for efficiently obtaining even finer metallic nickel powder. Powders targeted by the method of the present invention with an average particle size of about 1 μm or less are called ultrafine powders, and various properties have been found that are not found in conventional powders.

For example, 1) It absorbs infrared rays well. 2) Can be used as a micropore filter. 3) The specific surface area is extremely large.

4) Improve combustion characteristics. 5) Sinter at low temperature. 6)
It has a large residual magnetic flux density and an extremely high coercive force.

As described above, metallic nickel powder of 1 .mu.In or less has many uses, has even more potential, and is expected to be put to widespread practical use.

However, ultrafine metal particles of 1 μm or less are extremely active. That is, it has an extremely high affinity with oxygen, so it is necessary to disconnect it from oxygen. For this reason, vacuum evaporators are commonly used. In other words, several to hundreds of inert gas (
H6, Ar) are put therein, and the metal is dissolved and evaporated, and the ultrafine metal powder is recovered using a special recovery device. The disadvantage of this method is that it has low productivity and consumes a lot of energy.

In order to overcome this drawback, the present inventors investigated various methods to further improve the above-mentioned method for producing fine metallic nickel powder by hydrogen reduction of nickel chloride. Discovered a method for obtaining metallic nickel powder having a preferable particle size and resistant to reoxidation by adding a compound, i.e., a linear saturated fatty acid, a carbohydrate, or a combination thereof, and reducing it in a hydrogen gas-containing gas stream. This has led to the present invention.

That is, the method of the present invention adds lauric acid and nickel chloride to nickel chloride.
Straight-chain saturated fatty acids such as myristic acid and stearic acid or carbohydrates such as starch, butuctose, and dextrin are added in an amount of 1 to 10% by weight relative to the nickel chloride hexahydrate, and the temperature is raised to 400 to 750°C. Then, solid nickel chloride is reduced in an air flow containing hydrogen gas, preferably 30% by volume or more of hydrogen gas, and the remainder is an inert gas such as N2 or Ar, and then cooled to room temperature in an inert atmosphere. The nickel powder is then extracted as fine metallic nickel powder.

The present invention will be explained in more detail below.

In carrying out the present invention, additives that can be used include m6 linear saturated fatty acids of the general formula CmH2mO2, carbohydrates, or combinations thereof. In particular, stearic acid or dextrin are preferred as they are highly effective. Among these fatty acids, those with m of 6 or less have a weak effect on forming fine nickel and are not practical (-0 Generally, straight chain saturated fatty acids are used as raw materials for soaps, metal soaps, surfactants, dispersants, etc. It is known that stearic acid has good foaming properties.In particular, stearic acid
It is often used as a saturated fatty acid soap. In terms of foaming, lauric acid and myristic acid are said to be even better. Carbohydrates are also used as raw materials for so-called glue, and have a relatively similar structure to straight-chain saturated fatty acids.

These compounds are hydrocarbon compounds consisting of G, H, and O and having the molecular formula cmHnoe. Especially m
The straight chain saturated fatty acid of >6 is shown as Cm82m0z and has a lower oxygen content than the carbohydrate GrnP2'mOm-1.

Add 1 to 10% by weight of such linear saturated fatty acids or carbohydrates to nickel chloride powder,
It has been found that fine nickel powder with an average particle size (Fsss) of 1 μm or less can be produced extremely efficiently and stably by reduction treatment at ~750°C. Even more surprisingly, according to the invention, Fs6s=1
Despite being a fine powder with a particle size of μm or less and a specific surface area of 5 m 2 /jJ or more, there is almost no reoxidation. Therefore, it is extremely easy to handle the product obtained by the method of the present invention.

In the method of the present invention, the amount of additives such as fatty acids added is 1 to 10% by weight relative to nickel chloride (hexahydrate).
This is because no effect is observed below this range, and no particular improvement in effect occurs above this range. The reason why the temperature during reduction is set to 400 to 750°C is that below this temperature, the reduction rate is low, and above this temperature, nickel will volatilize.

These will be explained in detail below.

First, the amount of stearic acid added as an additive is determined by the average particle size (F
Fig. 1 shows an investigation of the effect on sssμm).

From FIG. 1, it is clear that when the treatment temperature is 500° C., the average particle size (Fs, ss) becomes smaller as the amount of stearic acid added increases. Figure 2 shows Ni
Ce2・5H20 and stearic acid are divided into 1 weight 7o
The amount of nickel chloride added increases the average particle size of nickel powder (
(hereinafter abbreviated as F'sss). The reduction treatment temperature is 500G.

In the case of no additives, along with the amount of nickel chloride charged,
F'sss tends to increase, but when stearic acid is added, F'sss tends to decrease. Furthermore, the arrows in the figure indicate the variation in F'sss of the produced fine metallic nickel powder, and it is clear that the variation is smaller when stearic acid is added. That is, the addition of stearic acid makes it possible to more stably obtain fine metallic nickel powder.

As can be seen from the above specific examples, in the method of the present invention, F
A so-called ultrafine metallic nickel powder of 1 μm or less can be efficiently obtained, and a product that is hardly reoxidized can be obtained. Further, this powder has the advantage that it can be obtained with a large specific surface area of 5.12/g or more.

Examples will be described below.

Example 1 Nickel chloride (hexahydrate salt) was made anhydrous at 150°C and 1% by weight of dextrin was added and mixed.The mixture was placed in a nickel boat and heated to 500°C using an annular furnace. Average particle size FS of fine metallic nickel powder obtained by reduction with 5% hydrogen by volume and balance nitrogen atmosphere
When SS was measured, F'sss = 0.97μIT
It was I. Further, the specific surface area was 5 ■''2'/, ¥. It should be noted that when handling this fine metallic nickel powder, almost no corner oxidation accompanied by heat generation was observed.

For confirmation, oxygen was analyzed and found to be 0.74%.

Example 2 Nickel chloride, which was made by adding 1N amount of lauric acid to hexahydrate nickel chloride 1500.9 and mixing it and making it anhydrous at 150°C, was placed in a nickel boat and heated at 600°C Example 1 When the average particle size F'sss of the fine metallic nickel powder obtained by reducing hydrogen (4O hydrogen by volume, balance argon) was measured in the same manner as above, Fsss = 1.00 pm.
Met. Further, the specific surface area was 4.5 m2/@.

It should be noted that when this fine metallic nickel powder was handled, almost no reoxidation due to heat generation was observed. For confirmation, the oxygen content was analyzed and found to be 0.50%.

Example 3 5% by weight of stearic acid was added to hexahydrate nickel chloride, mixed, and anhydrous at 150°C. 1500g of nickel chloride was placed in a nickel boat and heated to 700°C.
The average particle diameter Fsss of the fine metallic nickel powder obtained by reducing hydrogen (hydrogen 30% by volume, balance nitrogen) was measured, and it was found that Fsss=0.60μ■. Further, the specific surface area was 10 m 2 /jJ. In addition, almost no reoxidation due to heat generation was observed in this fine metallic nickel powder during handling. For confirmation, oxygen was analyzed and found to be 0.85%. As is clear from the above examples, in all cases, F'SSS was less than 1.0 μITI and specific surface area was greater than 5 m2/y.

Comparative Example Nickel chloride 6H20 was made anhydrous at 150°C and nickel chloride 150 (l) was placed in a nickel boat and heated to 500°C.
When the average particle diameter F'sss of the fine metallic nickel powder obtained by hydrogen reduction (hydrogen 50% by volume balance nitrogen) was measured, it was found to be Fsss = 2.15 μm. Further, the specific surface area was Q, 5 m 2 /jj.

In this fine metallic nickel powder, almost no reoxidation accompanied by heat generation was observed during handling.

For confirmation, the oxygen content was analyzed and found to be 0.6%.

[Brief explanation of drawings]

Figure 1 shows that the amount of stearic acid added is determined by the average particle size (Fsssμ
In this graph, the horizontal axis shows the amount of stearic acid added (vehicle weight%/NjCg2.6H20), and the vertical axis shows the amount of nickel chloride added at 1% by weight on the average particle size of nickel powder (F' sss, μm), the horizontal axis is the NiCd2 charge (Cg/batch), and the vertical axis is the average particle size (Fsss, μm).

Claims (1)

[Claims] 1) In a method for producing metallic nickel powder by reducing nickel chloride powder with hydrogen gas, after adding linear saturated fatty acids and/or carbohydrates as additives to nickel chloride powder, hydrogen gas-containing A method for producing fine metallic nickel powder, characterized by processing at 400 to 750°C in an air stream. 2) The linear saturated fatty acid has the general formula CmH2mC)2, where m is 6 or more. Claim 1
The method described in section. 3) The method according to claim 1, wherein the amount of the additive is 1 to 10% by weight based on the nickel chloride of the hexahydrate salt.