SIZE MODIFICATION AND COATING OF TITANIUM DIOXIDE USING A PREMIXED HYDROGEN/AIR FLAME
Ehrman, Sheryl H
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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.