Thermal decomposition of titanium hydride and its application to low pressure hydrogen control

Abstract

Thermal decomposition behavior of titanium hydride (TiH2) powder at temperatures between 250 and 330 °C (523 and 603 K) has been studied from both thermodynamic and kinetic viewpoints. Equilibrium hydrogen pressure measured in a closed system was found to vary from the order of 10−3 to 10−2 Torr (10−1 to 1 Pa) and the enthalpy of formation of titanium hydride in the two phase (α+γ) region was evaluated to be 31 kcal/mol (130 kJ/mol). It has been found that steady state decomposition can be realized also in an open (continuously pumped) system as long as the two phases coexist. Hydrogen pressure at the steady state was in the order from 10−4 to 10−3 Torr (10−2 to 10−1 Pa) and the activation energy for the decomposition was determined to be 29 kcal/mol (122 kJ/mol). In addition, it has been demonstrated that hot titanium hydride can simply be applied to low pressure hydrogen control in vacuum systems.