Microstructure of metatitanic acid and its transformation to rutile titanium dioxide

Abstract

The microstructure of metatitanic acid and its transformations to titanium dioxide during calcination have been investigated previously. However, the detailed microstructure of metatitanic acid has not been elucidated. Herein, we report the high-resolution scanning electron microscopy and X-ray powder diffraction determinations of the microstructure of metatitanic acid and its transformation to titanium dioxide during calcination. It is the first time that the detailed microstructure of metatitanic acid and its transformation to rutile titanium dioxide during calcination have been observed and elucidated. A mechanism of the transformation from metatitanic acid to crystalline titanium dioxide during calcination is described. The basic building blocks of metatitanic acid are the ultrafine crystals with an averaged diameter of a few nanometres, and these ultrafine crystals aggregate to form the porous primary particles. The primary particles further agglomerate to form the porous secondary particle. During the calcination, metatitanic acid undergoes size enlargement of ultrafine crystals, anatase-rutile transformation, merge of primary particles, and the crystal growth of titanium dioxide.