Abstract：TiO₂ nano-powders were synthesized by supercritical hydrothermal synthesis (SCHS) technology. The effects of reaction conditions including temperature, pressure, reaction time on the particle size, morphology and crystallinity were studied. The present results indicated that the particle size of synthesized TiO₂ decreases dramatically but the crystallinity of particles increases with the temperature increasing from subcritical state to supercritical state. Finally ellipsoidal nanoparticles of 10 nm are obtained. In pressure range of 26~30MPa, higher pressure is found to be in favor of improving the crystallinity degree of TiO₂ nano-particles, but the particle size changes very little. The titania phase is detected in 1 min reaction time, well-crystallized ellipsoid crystals are obtained when reaction time is 5 min. With the increase of reaction time, the number of rod-shaped particles increases gradually. The particle growth seems to be driven by dissolving-crystallization mechanism.

Keywords: SCHS; nano- particles; morphology; particle size; crystallinity