Formation of Non-Agglomerated Titania Nanoparticles in a Flame Reactor

Abstract

The formation of non-agglomerated titania particles by oxidation of titanium-tetra-isopropoxide (TTIP) has been studied in a methane/oxygen coflow diffusion-flame reactor. A change in the proportion of virtually non-agglomerated particles in TEM images was observed using a rapid cooling of the entire flame aerosol with a blow of cold Ar quenching gas and supercooling in a Laval nozzle placed above the flame. The proportion of non-agglomerates was 25% for TiO2 particles produced without any cooling steps. When the quenching gas of 25 L/min Ar cooled at −70°C blew on the tip of the flame, the proportion of non-agglomerates was 70%. When the flame aerosol was supercooled in the Laval nozzle after blowing −70°C Ar quenching gas, a decrease in the aerosol temperature was induced from approximately 1500 to 300°C in 0.9 ms and, as a result, the proportion of non-agglomerates was as large as 90%. It was found that the rapid cooling in the region of the flame tip is quite effective for preventing agglomeration.