Preparation of sub-micron sized titania particles of hollow morphology

Abstract

Hollow titania particles are prepared in the gas-phase synthesis route by pyrolyzing titania-coated PS (polystyrene) colloidal solution. Preparation of titania hollow sphere requires 800℃ processing temperature to completely remove organic templates and fully increase crystallinity of shells in a single-step process. Stresses in a high-temperature processing fracture titania hollow spheres. To produce fracture-free titania hollow spheres, optimum aerosol processing conditions are investigated. Under 800℃ with 1 ℓ/min air carrier, intact hollow spheres are produced by spray pyrolysis process. Morphology of prepared particles is observed by SEM and TEM. Remnants of organic templates are measured by TGA and crystal sizes of shells are determined by XRD analysis. Light-absorption and reflection are measured by PL and UV-Vis spectrometer. The sizes of hollow particle produced by the aerosol process are determined by the sizes of PS bead and crystal sizes are determined by the titania coating thickness. The methylene blue (MB) decomposition by the photocatalytic reaction of hollow particles is investigated with BET surface area analysis. Results indicate that complete removal of templates is important to increase photoactivity. Also, hollow titania particles are prepared by using salt-assisted spray pyrolysis. Kinds of salts are varied to change melting temperature of salt-matrix as LiCl, KCl, LiCl/KCl eutectic salt, and NaCl. In the results, only NaCl is effective to disintegrate hollow spheres.