Influence of thermal annealing on the hydrogenation properties of mechanically milled AB5-type alloys

The influence of mechanical milling and posterior annealing treatment on kinetic and thermodynamic H-properties of AB5-based alloys are here reported. Short milling process yields non-homogeneous microstructural (wide distribution of nano-crystallite sizes and amorphous phase) and morphological alloy powders. Annealing treatment of long-milled alloy produces a homogeneous microstructural alloy. Annealed alloy exhibits a unique nano-crystallite size without presence of amorphous structure. H-capacity in short-milled alloy is higher than for annealed alloy due to the contribution of both amorphous and well crystallised domains. The short-milled alloy exhibits extra H-trapping sites in amorphous domains as detected by thermal desorption. Absorption hydrogen kinetic in short-milled alloy is faster than for annealed alloy mainly due to fast H-transport through amorphous domains.