Effect of calcination temperatures on structures of TiO2 powders prepared by hydrothermal method using Thai leucoxene mineral

TiO2 powders were synthesized by hydrothermal method with 10M NaOH solution at 115 degrees C for 24 h using natural Thai leucoxene mineral as the starting material. The effects of calcination temperatures on structures of the prepared materials were investigated. The structures of the prepared samples were characterized by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). The as-synthesized sample showed the nanotubes-nanofibers structures with similar to 10-20 nm in diameter of nanotubes and similar to 20-50 nm in diameter of nanofibers. The XRD result showed that the as-prepared sample before being calcined was the mixed phase of titanate and rutile. The titanate phase could transform to anatase phase at the calcination temperature higher than 500 degrees C. As the calcination temperature increased, crystallization of the anatase phase was enhanced. With further increase in the calcination temperature from 700 to 900 degrees C, the intensity of rutile phase increased. When the calcinations temperature reached 1000 degrees C, only rutile phase was found in the XRD pattern. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of CEO of Sustainable Energy System, Rajamangala University of Technology Thanyaburi (RMUTT).