Narrowing the size distribution of aerosol-made titania by surface growth and coagulation

Abstract

The attainment of narrower size distributions than those predicted by the self-preserving theory of coagulation for aerosol-made materials is explored theoretically. Titania formation by titanium-tetra-isopropoxide (TTIP) or titanium-tetra-chloride (TiCl 4) oxidation is simulated accounting for gas/surface reactions and coagulation using a moving sectional model for aerosol dynamics. First, model performance is validated by comparing its predictions with data on synthesis of non-agglomerated titania nanoparticles by TTIP oxidation in a premixed flame reactor. Then, the effects of various process parameters such as pressure, temperature and initial precursor molar fraction, on titania particle size and volume-based geometric standard deviation, are illustrated. Ranges of surface reaction rates (of TTIP and TiCl 4) and process residence times that lead to particle size distributions narrower than the corresponding self-preserving limit for particle coagulation alone are identified.