TiFe Hydrogen Storage Alloys Produced by “Hydride Cycle” Method

Abstract—The present work was focused on the studies of TiFe hydrogen storage materials synthesis. The TiFe and TiFe + 4 wt % Zr alloys were produced by non-conventional “Hydride Cycle” (HC) method for the first time. For HC method we use metal hydrides synthesized by self-propagating high-temperature (SHS) method as precursor materials. In this work TiH₂ and ZrH₂ hydrides were used. Crystal structure and lattice parameters of obtained materials were determined by using powder X-ray diffraction (XRD) analysis. Microstructure was studied using scanning microscopy (SEM) and electron dispersive spectroscopy (EDS). It was shown that obtained alloys contain Fe₂Ti (C14 Laves phase, MgZn₂ structure type, space group P6₃/mmc) and TiFe (CsCl structure type, space group Pm$\bar {3}$m) phases. First hydrogenation of TiFe and TiFe + 4 wt % Zr alloys by different processes was investigated. It was shown that compacted pellets of TiFe and TiFe + 4 wt % Zr alloys are able to react with hydrogen in SHS, activation and conventional high-pressure modes without preliminary crushing. Irrespective of alloy composition and hydrogen pressure, SHS combustion temperatures T_c for TiFe and TiFe + 4 wt % Zr alloys were always within the range 80–150°C. These reactions are reversible, which is a very important characteristic for cycling and use of alloys as hydrogen storage materials. These studies concluded that conventional first hydrogenation process of TiFe + 4 wt % Zr at high pressure gives best hydrogen sorption capacity (1.52 wt %).