Sintering of nano-sized titania particles and the effect of chlorine impurities

The consolidation behaviour of two titania nanopowders with comparable specific surface area is reported in this study. Surface impurities were identified as a key element influencing the sintering behaviour of titania nanopowders. Raw materials for the synthesis processes of the nanopowders were titanium tetrachloride (TiCl4) and titanium tetraisopropoxide (TTIP), respectively. Particle properties, densification and sintering behaviour were investigated by several techniques (SEM, TEM, XRD, MIP and dilatometry). Phase transformation and densification of the nanopowder, prepared from TiCl4, started at lower temperature compared to the powder synthesized from TTIP. However, a drastic grain growth occurred during the final stage of sintering of the TiCl4 synthesized nanopowder. Chlorine impurities were identified by STA-MS. After purification of this nanopowder, the chlorine was effectively removed from particle surfaces and grain growth was reduced.