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 degrees C, most of the TiO2 powders were crystallized to an anatase type, whereas at 750 degrees 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 degrees C showed excellent efficiency for the removal of methyl orange (MO). However, in the powders calcined at 750 degrees C, the photocatalytic activity was decreased due to the appearance of a rutile phase. (c) 2005 Elsevier B.V. All rights reserved.