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

Decomposition during constant heating of as-received and pre-oxidized titanium hydride (TiH2) 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 H2 release with individual phase transformations. We found that every peak of H2 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 TiH2, while a TiO2 rutile shell controls the outgassing from the pre-oxidized powder.