An Alkoxide Free Sol-Gel Synthesis of Nanosized TiO2

Abstract

Nanosized TiO2 with anatase structure has been prepared by a non-alkoxide sol-gel route from an aqueous solution of titanyl sulfate. This paper investigated the influence of stirrer speed on anatase precipitation carried out in batch mode. Stirrer speed was varied between 400 and 1000 rpm. The intensity of stirring determined the final particle size of anatase aggregates in suspension. Changes to primary agglomerate and crystal population due to varying stirrer speed were reported. In our study, the smallest aggregates (mean size of 6-8 nm) were obtained at a stirrer speed of 1000 rpm. It was also found that the anatase to rutile phase transformation began at 800°C of calcination. A calcination treatment, from 400 to 1000°C, was applied. The degree of crystallinity and purity of the synthesized materials were reported. The crystalline anatase particles had an average particle size of 10-20 nm between the calcination temperature 400-600°C. The powders were characterized by powder X-ray diffraction (XRD), the morphology and grain size of the titania particles were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD patterns indicated that the samples were crystalline titania which had very broad and small peaks of anatase phase. The TEM observations showed the vast majority of particles were quasispherical; the average size distribution of particle was about 20 nm. The TEM results supported the conclusions derived from the XRD data. Finally, the amorphous hydrous and crystalline titania particles were characterized by thermogravimetric (TGA) and differential thermal analysis (DTA).