Texture and morphology of titania particles prepared by vapor-phase pyrolysis of titanium tetra-isopropoxide

Ti(OPri)(4) vapor was pyrolyzed in dry nitrogen atmosphere using a simple tubular flow reactor at 400 and 800 degrees C. Well-defined spheroidal anatase TiO2 particles showing mesoporous surfaces of 30 m(2) g(-1) and assuming two different morphologies (fused and composite) were produced at the low temperature (ca. 400 degrees C), whereas deformed spheroidal particles of rutile-structured TiO, and surfaces of 12 m(2) g(-1) were obtained at the high temperature (ca. 800 degrees C). Particles of the high-temperature product were distinguished by a low porosity and a uniform morphology (composite). The heat-induced modifications at 800 degrees C may be ascribed to enhancements in (a) hydrolysis of Ti(OPri)(4), by a possible generation of water vapor as a secondary pyrolysis product of the alkoxide, (b) particle growth via coalescence rather than by vapor deposition, and (c) particle sintering. The pyrolysis products were characterized by X-ray diffractometry, high-resolution transmission electron microscopy, and volumetry of nitrogen adsorption at liquid nitrogen temperature. (C) 1997 Elsevier Science B.V.