Anatase and brookite TiO2with various morphologies and their proposed building block

Abstract

In this work, brookite TiO2 has been synthesized by a simple hydrothermal approach using sodium titanate as a precursor in the presence of a sodium fluoride aqueous solution. The ratio of brookite and anatase TiO2 can be tailored by the NaF concentration. In a concentrated NaF solution, high quality brookite TiO2 was acquired. Pure anatase nanoparticles were obtained in only deionized water. Moreover, the morphology and size of brookite TiO2 can be tailored by using various acid treated titanates which influence the stability of the building blocks and nucleation points of TiO2. Micro-sized flower-like brookite, submicro-sized urchin-like brookite and brookite nanorods with anatase nanoparticles were obtained. The micro-sized flower-like brookite remains the same shape and phase even at 800 °C, whereas obvious grains were formed on the matrix with brookite, rutile and anatase mixture phases at 900 °C. On the other hand, as the submicro-sized urchin-like brookite was heated, a rutile phase appeared at 750 °C and 100% grain-like rutile was obtained at 900 °C.