Microstructural changes of microemulsion-mediated TiO2 particles during calcination

Ultrafine titania particles were synthesized by hydrolysis of titanium tetraisoproxide (TTIP) in the nanodroplets of water/NP-5/cyclohexane microemulsions. TiO2 particles did not form at a water/surfactant molar ratio below 0.53 since water was mostly bound to the surfactant molecules. The particles grew largely by intra-agglomerate densification below 700 degreesC, whereas, they grew by inter-agglomerate densification above 700 degreesC. With raising calcination temperature, the specific surface area of the TiO2 particles decreased rapidly, whereas, their average pore radius increased considerably due to shrinkage and densification of the agglomerates, and elimination of the minute intercrystallite pores. (C) 2001 Elsevier Science B.V. All rights reserved.