Preparation of Ultrafine Crystalline TiO2 Powders from Aqueous TiCl4 Solution by Precipitation

Ultrafine crystalline TiO2 powders were prepared by just heating and stirring aqueous TiOCl2 solution with a Ti+4 concentration of 0.5 mol/l at room temperature to 100 degrees C under one atmosphere. The crystallinity, the phase transformation and the par tide shape of ultrafine TiO2 powders obtained by this simple precipitation method were analyzed using an X-ray diffractometer (XRD), transmission electron microscopy (TEM), differential thermal analyzer (DTA), and scanning electron microscopy (SEM). TiO2 crystalline precipitates with a pure rutile phase were formed below 65 degrees C, then TiO2 crystalline precipitates with an anatase phase started forming at temperatures higher than 65 degrees C, which ends with the pure anatase phase at 100 degrees C. The direct formation of TiO2 crystalline precipitates from an aqueous TiOCl2 solution is due to the existence of the OH- ions in distilled water which cause the crystallization of TiOCl2 to TiO2 without hydrolyzation to Ti(OH)(4). Conventionally, rutile-phase TiO2 is obtained at much higher temperatures. However, in this study a stable rutile-phase TiO2 was obtained by a simple method at close to room temperature.