DETERIORATION OF COPPER-CONTAINING MISCHMETAL-NICKEL-BASED HYDROGEN ABSORPTION ELECTRODE MATERIALS

The deterioration process of a series of Cu-containing mischmetal (Mm)-nickel-based multi-component alloy electrodes was investigated by electrochemical measurements, X-ray diffraction, magnetic measurements, scanning electron microscopy acid microhardness measurement techniques. It was noted that this deterioration process was accompanied by decomposition of the materials into rare earth hydroxide and metallic Ni, and marked differences in the tendency for pulverization on hydrogenation for alloy powders of different compositions were observed, in spite of the fact that there was no significant difference in the volume expansion rates of the alloys during hydrogen absorption. It is suggested that the differences in the alloy pulverization could be attributed to differences in the microhardness of the alloys. With respect to decreasing microhardness properties of the materials, Cu had a beneficial effect on the Mm-Ni-Al system, although its effects were not as good as those of Co.