Sol-gel TiO2 in self-organization process: growth, ripening and sintering

TiO2 nanoparticles were synthesised by a self-organization method using a continuous water vapour hydrolysis system without mixing. Formation of TiO2 particles was based on pure colloidal interactions of hydrolyzed alkoxide molecules generated at the interface between titanium alkoxide solution and water vapour. The effect of ethanol was proved to increase aggregation and packing of primary particles, leading to a significant size enlargement of secondary particles in a post annealing process above 500 degrees C. A new model to describe sol-gel TiO2 growth has been proposed, which considers the formation of secondary particles to be the result of nucleation of oversaturated primary particles, while the primary particles are the result of irreversible oligomerization of Ti oxo molecules.