HYDROTHERMAL PREPARATION OF UNIFORM NANOSIZE RUTILE AND ANATASE PARTICLES

Uniform nanosize rutile and anatase particles were prepared by a hydrothermal method using TiCl4 as starting material. The influences of various hydrothermal conditions on the formation, phase, morphology, and grain size of products were investigated and tentatively discussed from coordination chemistry. Increasing the acidity in reaction medium and the concentration of TiCl4 aqueous solution favored of the formation of rutile type TiO2. Raising the temperature (>200 degrees C) can decrease the agglomeration among TiO2 grains. The; mineralizers SnCl4 and NaCl reduce markedly the grain size and favor the formation of rutile type TiO2. The mineralizer NH4Cl will increase greatly agglomeration among grains. The optimum conditions for preparing rutile-type TiO2 were that [TiCl4] > 0.5 mol dm(-3), 220 degrees C for 2 h and using SnCl4 or NaCl as mineralizer. The average particle size of rutile TiO2 was 20 nm by 8 nm. The optimum conditions for preparing anatase type TiO2 were that pH > 7, 200 degrees C for 2 h. The average particle size of anatase TiO2 was ca. 10 nm. The Raman spectra of nanosize rutile and anatase were studied. With decreasing grain size of rutile, the all peaks broadened and their wavenumber decreased, while a new broad band near 112 cm(-1) appeared gradually.