Monodisperse hollow TiO2 spheres for thermal insulation materials: Template-free synthesis, characterization and properties

Hollow TiO2 spheres were easily fabricated through a template-free solvothermal route only using tetrabutyl titanate (TBT) as raw material and absolute ethanol as solvent. The morphology of hollow TiO2 spheres was successfully controlled by adjusting the reaction time and reaction temperature. The formation process of hollow TiO2 spheres includes three steps based on the experimental results: the hydrolysis of TBT to produce Ti(OH)4 clusters in water formed from an ethanol etherification reaction under high temperature and high pressure, the assembly of Ti(OH)4 clusters into solid spheres, and the transformation of solid TiO2 spheres into hollow TiO2 spheres. Furthermore, the as-prepared hollow TiO2 spheres exhibited good thermal insulation performance including heat barrier and heat reflection.