TEM microstructure characterization of nano TiO2 coated on nano ZrO2 powders and their photocatalytic activity

Nano TiO2 coated commercial nano ZrO2 powders (20 and 80 wt.%) were synthesized by a sol–gel process. Their microstructure and crystal structure depending on the calcination temperatures were investigated using XRD and HRTEM techniques. In the as-received powders, the nano TiO2 particles attached to the ZrO2 particles existed in an amorphous phase. After calcination at 450 and 600 °C, most of the TiO2 powders were crystallized to an anatase type, whereas at 750 °C, they were changed to a rutile phase.From the comparison of photocatalytic activity, the nano TiO2 coated ZrO2 powders calcined at 450 and 600 °C showed excellent efficiency for the removal of methyl orange (MO). However, in the powders calcined at 750 °C, the photocatalytic activity was decreased due to the appearance of a rutile phase.