SHS of Zirconolite and Its Thermodynamic Analysis

Zirconolite (CaZrTi₂O₇) was prepared by self-propagating high-temperature synthesis (SHS) using Fe₂O₃, CrO₃ and Ca(NO₃)₂ as the oxidants and Ti as the reductant. The adiabatic temperature was calculated, and the combustion temperature was measured in this paper. The different molar ratios of TiO₂ to Ti (TiO₂∶Ti) in the Ca(NO₃)₂ reaction system were explored to investigate the combustion temperature of the designed SHS reactions. The results show that the SHS process can be sustained for all the designed reactions. However, pyrochlore (Ca₂Ti₂O₆), perovskite (CaTiO₃), Zr₅Ti₇O₂₄ and trace of rutile (TiO₂) were prepared using Fe₂O₃ and CrO₃ as the oxidants. Zirconolite is successfully synthesized as the main phase with CaTiO₃ and TiO₂ as the minor phases when Ca(NO₃)₂ is employed as the oxidant. The combustion temperatures are much lower than the thermodynamically calculated adiabatic temperatures. Meanwhile, the decrement of TiO₂∶Ti is beneficial for the high adiabatic temperatures and combustion temperatures when using Ca(NO₃)₂ as the oxidant.