JPH06306411A - Production of hydrogen storage alloy powder - Google Patents

Abstract

PURPOSE:To drastically reduce the time required for pulverization after coarse crushing, to increase crushing efficiency and to reduce the crushing cost in the production of a hydrogen storage alloy powder. CONSTITUTION:The ingot of a hydrogen storage alloy is coarsely crushed, hydrogen is occluded in the surface of the coarsely crushed alloy powder to generate cracks, and the powder is pulverized. When hydrogen is occluded in the coarsely crushed alloy powder, the powder is sealed in a plastic vessel along with hydrogen, and then >=100atm hydrogen pressure is applied on the coarsely crushed alloy powder by cold isostatic pressing.

Description

Detailed Description of the Invention

[0001]

[Industrial application] Nickel-cadmium batteries have been widely used as an energy source that can be charged and discharged in various devices that are required to be miniaturized. The use of nickel-hydrogen batteries with a hydrogen storage alloy for the negative electrode is expected. The present invention is a negative electrode of such a nickel hydrogen battery,
The present invention also relates to a method for producing a hydrogen storage alloy powder used in a hydrogen tank, a heat pump or the like.

[0002]

2. Description of the Related Art Conventionally, a hydrogen storage alloy powder is crushed (indexed) into a hydrogen storage alloy casting ingot to a size of 1 to 2 cm, and then a coarse crusher such as a pin mill is used in an inert atmosphere such as argon. After roughly pulverizing to a size of about 2 mm or less, it was finely pulverized in a similar atmosphere with a mechanical fine pulverizing device such as a jet mill until a desired particle size was obtained to produce a powder. The pulverization process of these hydrogen storage alloys is usually performed continuously, and after coarse pulverization is performed in an inert atmosphere such as argon.

However, in the prior art, since the fine pulverization process after the coarse pulverization of the hydrogen storage alloy is simply performed by pulverizing with a mechanical fine pulverizing device such as a jet mill, it takes a long time to reach a desired grain size. In addition, the crushing efficiency was poor and the cost was high.

[0004]

The problem to be solved by the present invention is to eliminate the above-mentioned drawbacks of the prior art, to significantly shorten the time required for fine pulverization, to improve the pulverization efficiency, and to reduce the cost required for pulverization. It is to reduce.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to cause hydrogen to be stored in a coarse hydrogen-absorbing alloy coarse powder before fine pulverization, thereby generating cracks on the surface of the coarse-crush alloy powder. Then, the subsequent fine pulverization step is efficiently performed. That is, the present invention is to coarsely pulverize a casting mass of a hydrogen storage alloy, and then finely pulverize it in a state in which hydrogen is stored on the surface of the coarsely pulverized alloy powder and cracks are generated. When occluding hydrogen in the powder, the coarsely crushed alloy powder is enclosed in a plastic container together with hydrogen, and then a cold isostatic press is used to apply a hydrogen pressure of 100 atm or more to the coarsely crushed alloy powder. .

[0006]

According to the present invention, since hydrogen is temporarily stored in the coarsely pulverized alloy powder having a particle size of about 2 mm before fine pulverization to cause cracks on the surface of the coarsely pulverized alloy powder, the subsequent fine pulverization step can be efficiently performed. It can be easily pulverized into a fine powder having a particle size of 50 μm or less in a short time. INDUSTRIAL APPLICABILITY The present invention can be applied to a general production process of hydrogen storage alloy powder, and applicable component systems include misch metal-nickel system, iron-titanium system, magnesium system and the like.

[0007]

Example: Alumina crucible with MnNi ₃ alloy and Ni, Mn,
By charging lumps or particles of Al and Co simple metals, and by induction melting
A hydrogen storage alloy having a composition of MmNi _3.2 CoMn _0.6 Al _{0.2 was} melted. After cooling in an argon atmosphere to solidify, the alloy ingot was taken out, crushed with a hammer to a size of 1 to 2 cm, and then crushed to a size of about 2 mm with a pin mill.

The coarsely pulverized powder was sealed in a polyethylene bag together with hydrogen gas, and then cooled in a cold isostatic press at 100 to 4 times.
After treating with a hydrostatic pressure up to 000 atm, fine pulverization was carried out in a jet mill in an argon atmosphere.

Table 1 shows the results of evaluation of these fine pulverization processes.

[0010]

[Table 1]

The evaluation scale was the treatment time required for pulverizing 10 kg of powder. Further, the average particle size was obtained as an evaluation that the powder after fine pulverization exhibits a substantially constant particle size under any condition.

As can be seen from Table 1, both the cold isostatic pressing treatment in the hydrogen atmosphere of the method of the present invention was carried out at a hydrogen pressure of 100 atm for 2 minutes and at 4000 atm for 2 minutes. The fine pulverization treatment time for obtaining 10 kg of fine powder having an average particle size of about 12 μ is within 2 hours to 2 hours 45 minutes, whereas the conventional fine pulverization method to which the method of the present invention is not applied takes 3 hours 20 minutes, It is understood that the method of the present invention shortens the pulverization time by 35 minutes to 1 hour and 20 minutes as compared with the conventional method, and the pulverization efficiency is significantly improved.

[0013]

As described above, according to the present invention, since hydrogen is once stored in the coarse powder before fine pulverization, cracks are generated in advance on the surface of the coarsely pulverized alloy powder, so that fine pulverization is performed. The time required for fine pulverization can be greatly reduced as compared with the above method, and therefore the fine pulverization process can be efficiently performed at low cost.

Claims (2)

[Claims] 1. A method for producing a hydrogen-absorbing alloy powder, comprising: roughly crushing a cast ingot of hydrogen-absorbing alloy, and then finely crushing hydrogen on the surface of the roughly-crushed alloy powder while causing hydrogen to be absorbed therein. And a method for producing a hydrogen storage alloy powder. 2. When the coarsely crushed alloy powder according to claim 1 absorbs hydrogen, after the coarsely crushed alloy powder is enclosed in a plastic container together with hydrogen, the coarsely crushed alloy powder is subjected to cold isostatic pressing. The method for producing a hydrogen storage alloy powder according to claim 1, wherein a hydrogen pressure of 100 atm or more is applied.