Low temperature vapor-phase preparation of TiO2 nanopowders

The preparation of TiO2 nanopowders by vapor-phase hydrolysis of TiCl4 below 600 degrees C is studied in this paper. Influences of preparation variables, such as preparative temperature, residence time, reactant concentration, and H2O/TiCl4 mole ratio, on TiO2 particle size, morphology and chlorine contamination are investigated, followed by discussion. It shows that the hydrolysis temperature exerts greatest influences, while the residence time hardly have impact on product particles below 400 degrees C, among the hydrolysis variables investigated. The chlorine contamination on nanopowders occurs during the preparation which can be greatly reduced by proper control on preparation variables. Unlike the high temperature gas-phase processes such as oxidation route and flame synthesis, low-temperature route shows the ready control on product powders, and thus obtains titania powders with small size, narrow size distribution and very weak agglomeration. In addition, the decreased energy consumption, retarded corrosion on the reactor and the reduced operation problems would be expected for the low temperature processes. (C) 1999 Kluwer Academic Publishers.