A study on crystal structure, bonding and hydriding properties of Ti-Fe-Ni intermetallics - Behind substitution of iron by nickel

Intermetallic compound TiFe, known for its hydrogen storage applications, is modified by substituting iron by nickel and related changes of properties and applicability of the obtained compounds are studied. Samples TiFe1-xNix (x = 0.2-0.6) are synthesized by melt-spinning and their crystal structure, desorption characteristics and electronic structure are investigated by TPD, H-1 NMR and Mossbauer spectroscopy. State-of-the-art DFT calculations give further insight into the changes in electronic structure and bonding related to the hydrogen absorption and substitution of iron by nickel. The increase of Ni/Fe ratio in the TiFe1-xNix is found to result in the increase of hydride cohesive energies and in the systematic shifting of Fermi energy (E-F) to lower values, in both pure intermetallics and appropriate hydrides. Hydride formation was found to influence the Fermi energy lowering and the increase of number of states at E-F. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.