Decomposition of TiH2 studied in situ by synchrotron X-ray and neutron diffraction

Abstract Decomposition during constant heating of as-received and pre-oxidized titanium hydride (TiH 2 ) powder under flowing and stationary Ar was studied in situ by synchrotron X-ray and neutron diffraction. Diffraction data were compared to corresponding thermoanalysis traces in order to relate peaks of H 2 release with individual phase transformations. We found that every peak of H 2 release is correlated with regimes of lattice parameter contraction. Core–shell models to describe the decomposition processes measured were found, and further verified by electron microscopy. The models show that a shell of the hexagonal close-packed hydrogen solid solution (α) around each particle core controls its dehydrogenation for as-received TiH 2 , while a TiO 2 rutile shell controls the outgassing from the pre-oxidized powder.