SIZE MODIFICATION AND COATING OF TITANIUM DIOXIDE USING A PREMIXED HYDROGEN/AIR FLAME
Abstract
A study was conducted of the effect of flame processing on the size distribution of
titania nanoparticles, and a flame process was developed for producing TiO<sub>2</sub>/SiO<sub>2</sub> coreshell
particles from aqueous suspensions of TiO<sub>2</sub> and SiO<sub>2</sub> nanoparticles. Both were
performed using a premixed hydrogen/air flame. At the adiabatic flame temperature of
2400 K, the number mean diameter of titania primary particle increased considerably
from an initial value of 44 nm to 96 nm, presumably by atomic diffusion, and viscous
flow coalescence. Moreover, the majority of product particles from this high flame
temperature were smooth and spherical. Based on the results of size modification
experiments, coating experiments were performed. The dominant morphology observed
in the product particles from coating experiments was silica coated titania. The silica
coating was very smooth and dense. The total particle size and the shell volume of the
product particles were in reasonable agreement with values predicted from the atomized
droplet size distribution and the droplet concentration.