Production of Low-Cost TiNbFe Alloys from the Elemental Powders of NbFe Pre-Alloy and Their Hydrogenation Features

TiNb-based alloys with prevailing beta-phase and BCC crystal structure are currently being investigated as hydrogen storage materials due to their relatively high absorption capacities that can be reached at moderate temperatures. In this paper, low cost TiNbFe alloys were prepared by arc melting starting from the elemental powders of the pre-alloy Nb68.1Fe30.4 with the addition of pure Ti following the proportion of Nb68.1Fe30.4 + Xwt% Ti (X = 23, 33, 41, 47). The crystal structure including the phase's evolution and absorption kinetics at 30 degrees C were evaluated in detail as a function of Ti addition. XRD results in combination with SEM observations showed the presence of beta-phase (Nb-rich) with a BCC type-structure in all compositions beyond that TiFe, NbFe and alpha (Ti-rich) phases. After a simple activation step, the samples containing 41 and 47 wt% of Ti showed very fast absorption kinetics at 30 degrees C but with different hydrogen storage capacities of 1.95 and 1.37 wt% of H-2, respectively. Upon hydrogenation, the beta-BCC phase is partially converted into FCC hydride TiH1.9-X beyond that TiFeHX and NbHX hydrides. These hydrides resulted in different steps of decomposition as indicated by the DSC curves. The current study confirmed the significance of TiNbFe alloys for hydrogen storage applications at low temperatures. (AU)