High thermal stability of amorphous TiO2 enhanced by OH

Amorphous titanium dioxide (A-TiO₂), a key component of lunar ilmenite's surface layer and a promising material for helium bubble encapsulation, plays a vital role in lunar resource utilization. This study focuses on its thermal stability, a critical factor for practical applications. A-TiO₂ is successfully synthesized via the sol-gel method, and its thermodynamic properties are systematically investigated using TG-DSC. It is found that hydroxyl groups enhance the thermal stability of A-TiO₂ at ambient temperature by forming hydrogen bond networks. Specifically, after 15 days of aging, hydroxyl‑rich A-TiO₂ exhibit a crystallization enthalpy of 147.8 J/g, significantly larger than that of hydroxyl‑free counterparts (110.2 J/g). Isochronal crystallization analysis reveals that the instantaneous A-TiO₂ after dehydration exhibits much lower crystallization activation energy (E_a = 321.1 kJ/mol) than the relaxed hydroxyl‑free A-TiO₂ (E_a = 415.7 kJ/mol). This suggests that hydrogen bond network stabilize the amorphous structure of A-TiO₂. These findings are also helpful for understanding the long-time stability for the lunar amorphous TiO₂.