Effect of additives on titanium-hydrogen interaction under ball milling of Ti powder probed by hard x-ray emission spectroscopy

Titanium is well known as a light-weight hydrogen storage material that is applied as a component of hydrogen storage composites together with Mg and other metals. Amorphous boron, boron nitride, and graphite were used as additives to improve Ti-H(2) reactivity during ball-milling due to its anti-sticking and matrix-forming properties. The chemical state and local electronic structure of Ti atoms were studied by hard x-ray emission spectroscopy (XES). We have measured fluorescent Ti K beta(5) (4p -> 1s transition) x-ray emission spectra, which are very sensitive to the local surroundings of exciting atoms, and found additional features coinciding in energy with spectra of reference samples TiB(2), TiN, and TiC. Based on these measurements, it is concluded that atoms of additives form chemical bonding with Ti due to the occupation of interstitials in the host Ti-lattice. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3662200]