Structural characterization and hydrogen storage properties of the Ti31V26Nb26Zr12M5 (M = Fe,Co, or Ni) multi-phase multicomponent alloys

Structure and hydrogen storage properties of three Ti₃₁V₂₆Nb₂₆Zr₁₂M₅ multicomponent alloys with M = Fe, Co and Ni are investigated. The alloys synthesized by arc melting are characterized via X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The as-cast ingots present multi-phase dendritic structures composed mainly of BCC phases and small amounts of C14 Laves phases. Upon hydrogenation, each alloy absorbs around 1.9 H/M (number of hydrogen atoms per metal atoms) at room temperature. XRD of fully hydrogenated samples shows the formation of multi-phase structures composed of FCC and C14 hydrides. Thermo Desorption Spectroscopy (TDS) shows that the hydrogenated alloys present multi-step desorption processes with wide temperature ranges and low onset temperatures. XRD of partially hydrogenated samples indicate the presence of intermediate BCC hydrides. XRD of desorbed samples suggest reversible reactions of absorption/desorption: BCC + C14 alloy ? intermediate BCC hydride + C14 hydride ? FCC + C14 hydrides.