Influence of phase composition of Mg2NiH4 upon the hydrogen desorption kinetics

Mg2NiH4 exists in two low-temperature modifications: monoclinic LT1 and monoclinic microtwinned LT2. Three samples of Mg2NiH4 were prepared containing predominantly LT1 phase, predominantly LT2 phase and similar portions of both phases. Hydrogen desorption curves were measured and a parallel X-ray diffraction (XRD) study was performed. It was found that the great difference between amount of LT2 and LT1, measured by the ratio of the characteristic XRD peaks, leads to distinctly double-branched desorption curves. The LT2 phase substantially decelerates the desorption of hydrogen.