Hydrogenation properties of Hf–Ni intermetallics – Experimental and theoretical investigation

The hydrogenation properties of HfNi and Hf2Ni7 intermetallics were investigated at the constant pressure of 1 bar and in the temperature ranges 373–573 K for HfNi and 323–473 K for Hf2Ni7. The kinetic parameters, rate constants and activation energies of the absorption processes were determined. Maximal hydrogen absorption, i.e., number of hydrogen atoms absorbed per metal atom, H/M, are 1.05 and 0.04 achieved at 373 K for HfNi and Hf2Ni7, respectively. Multiple hydriding/dehydriding was found to influence the improvement of the kinetic parameters. XRD and SEM methods were used to investigate the structural and morphological changes of the samples due to hydrogen absorption. The thermodynamic parameters of hydriding together with the structural properties of the intermetallics and their hydrides, calculated using the full-potential linearized augmented plane waves (FP-LAPW) code based on the density functional theory (DFT), were utilized for the sake of explaining the experimental investigations.