Non-isothermal and isothermal hydrogen desorption kinetics of zirconium hydride

• The mechanism of ZrH2 decomposition was studied by simultaneous TG-TDS technique.
• Phase transformation sequences under different heat treatments were obtained.
• The held temperature would affect the isothermal phase transformation sequences.
• The γZrH phase can be formed by quenching from high temperature.

Thermal desorption behaviors of zirconium hydride powder under non-isothermal and isothermal heat treatment conditions were studied using simultaneous TG-TDS. The phase transformation sequences were established by correlating the observed peaks of H2 release and mass loss. The origins of the peaks or shoulders in the TDS spectra were described as the equilibrium hydrogen pressures of a number of consecutive phase regions that decomposition reaction passed through. Effect of held temperature on the isothermal desorption behavior was taken into consideration, which was shown to be essential for the phase transformation sequence during ZrH2 decomposition. The zirconium monohydride γZrH was observed at ambient conditions, which has been supposed to be metastable for a long time.