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 sim ple tubular flow reactor at 400 and 800 degrees C. Well-defined sphero idal 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). Part icles of the high-temperature product were distinguished by a low poro sity and a uniform morphology (composite). The heat-induced modificati ons 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 secondar y pyrolysis product of the alkoxide, (b) particle growth via coalescen ce rather than by vapor deposition, and (c) particle sintering. The py rolysis products were characterized by X-ray diffractometry, high-reso lution transmission electron microscopy, and volumetry of nitrogen ads orption at liquid nitrogen temperature. (C) 1997 Elsevier Science B.V.