HEATTREATMENTEFFECTS ON NON-THERMALSOL-GELDRIVED MESOPOROUS TiO۲/SiO۲

TiO۲/SiO۲ nanocomposite with molar ratio ۱:۱ was synthesized by a free calcination sol-gel method using titanium tetra chloride and tetraethylorthosilicate as raw materials. In the composite, TiO۲ nanocrystals are highly dispersed in the amorphous SiO۲ matrix and the mater showed size quantization effect arising from the presence of extremely small titanium oxide species having a low coordination number. Thermal phase transformation studies of the as-prepared composite were carried out by means of X-ray diffraction (XRD) patterns and thermogravimetry–differential scanning calorimetry (TG–DSC) analyses. The studies showed existence of anatase phase in all the tested temperatures. When temperature exceeds ۴۰۰°C, brookite phase was formed beside anatase phase. At ۹۵۰°C amorphous silica matrix was transformed to crystobalite and brookite phase disappeared. Finally, small peaks of rutile phase were detectable at ۱۱۰۰°C.

کلیدواژه ها:

composite ، mesoporous ، TiO۲/SiO۲ ، crystobalite ، anatase ، phase transformation