In-situ EXAFS study on the thermal decomposition of TiH₂

Thermal decomposition behaviors of TiH₂ powder under a flowing helium atmosphere and in a low vacuum condition have been studied using an in situ EXAFS technique. By an EXAFS analysis containing the multiple scattering paths including H atoms, the changes of the hydrogen stoichiometric ratio and the phase transformation sequence are obtained. The results demonstrate that the initial decomposition temperature is dependent on experimental conditions, which occurs, respectively, at about 300 and 400 °C in a low vacuum condition and under a flowing helium atmosphere. During the decomposition process of TiH₂ in a low vacuum condition, the sample experiences a phase change process: δ(TiH₂) → δ (TiH_x) → δ(TiH_x)+ β(TiH_x) → δ(TiH_x)+ β(TiH_x) + α(Ti) → β(TiH_x) + α(Ti) → α(Ti) + β(Ti). This study offers a way to detect the structural information of hydrogen. A detailed discussion about the decomposition process of TiH₂ is given in this paper. (authors)