Effects of calcination on the microstructures and photocatalytic properties of nanosized titanium dioxide powders prepared by vapor hydrolysis

Ultrafine titanium dioxide powders were synthesized in an aerosol reactor using vapor hydrolysis of titanium tetraisopropoxide (TTIP) at 260 °C and higher temperatures. The effect of calcination on the microstructure and the photoactivity was studied. The powders were characterized using Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction, and transmission electron microscopy analyses. As the calcination temperatures were increased, the surface area decreased but the rutile-to-anatase ratio and the anatase and rutile crystallite sizes increased. Powders produced at higher temperatures were predominantly anatase and were generally photoactive.