A study on the hydrogen permeation in AB2 type metal hydride prepared by mechanical alloying and heat treatment

摘要

AB2 type Laves phase alloys are attractive anodematerials for Ni/MH secondary batteries because of their largehydrogen storage capacity in KOH electrolyte. However, they havea disadvantage of requiring many charge-discharge cycles foractivation. When the mechanical alloying was performed withelemental powders in Zr-Cr system, the mechanically alloyedpowders were composed of a microscopic mixture of startingelements. The milled powders could be transformed into the ZrCr2type Laves phase of C14(hcp) by the heat-treatment for 3 hours at900°C. The heat-treated powders had nano-sized grains of less thanl00nm. The hydrogen solubility and the maximum dischargecapacity of the milled electrode were less than those of the arc-melted one. However, the discharge capacity of the heat-treatedelectrode was increased and the activation behavior was improvedowing to the nano-sized microstructure.