Reversible and irreversible passivation of a La–Ni–Al alloy

This paper seeks to explore some of the effects of passivating a LaNi4.25Al0.75 sample by air oxidation under controlled conditions. Passivation of this metal hydride alloy seems to have two distinct regimes. The first occurs with air oxidation at 80 and 20 °C. It is characterized by complete reversibility upon hydrogen readsorption, although said readsorption is hindered substantially at room temperature, requiring the material to be heated to produce the reactivation. The second regime is illustrated by 130 °C air oxidation and is characterized by irreversible loss of hydrogen absorption capacity. This passivation does not hinder hydrogen readsorption into the remaining hydride material.