The use of neutron inelastic scattering and hydrogen isotope exchange to investigate the nature of sites occupied by hydrogen in TiMn_1.5

Abstract

Inelastic neutron scattering and isotope separation factor measurements are reported for the potential hydrogen storage system Ti0.4Mn0.6Hn. Inelastic spectra were measured for six hydrogen concentrations ranging from 0.001 to 1.0 hydrogens/metal atom, the first five in the alpha and alpha + beta phases and the last in the beta phase. The spectra consisted of two groups of peaks, the first from 70 meV to 110 meV and the second from 110 to 180 meV. The intensity of the former was independent of the hydrogen content and could be associated with a precursor region in the isotherm while that of the latter rose linearly with hydrogen content. Peak shape analysis of the high energy peaks show them to be consistent with occupation of first Ti3Mn and then Ti2Mn2 sites and with changes between the alpha - and beta -phases. The identification of the precursor sites is not easy if based entirely on the IINS spectra as both-OH and near surface interstitial sites could be involved. However, the measurement of the H/T isotope separation factor unambiguously points to the existence of TiOH because only this can explain the dramatic fall of alpha near n=0.

Electrical Contacts for n-Type Diamond

“…INS work on metal-hydrogen systems does reveal vibrations on tetrahedral sites which appear at the energies observed here (e.g. [44][45][46][47]). However, with respect to the given fcc lattice this possibility seems unlikely.…”