Mg-Ti based materials for electrochemical hydrogen storage

Results of the mechanical alloying of binary Mg-Ti and ternary Mg-Ti-Ni mixtures using two different process control agents are reported. Both high- and low-energy milling resulted in the formation of cubic compounds. When all starting reactants had disappeared, a mixture of two face-centered cubic (fcc) phases was formed with lattice constants around 4.40 and 4.25 angstrom. The electrochemical hydrogen storage capacity, 450 mAh/g for (Mg(0.65)Ti(0.35))0.95Ni(0.05), was about one-third that reported for Mg-Ti thin films. This suggested that only one of the two fee phases was active at ambient conditions. Prolonged mechanical alloying of (Mg(0.60)Ti(0.40))(0.95)Ni(0.05) resulted in full conversion of the material into one fcc-phase with a very small crystallite size, an intermediate lattice constant (4.33 angstrom), and a sharply decreased storage capacity.