Transformation-assisted consolidation of bulk nanocrystalline TiO2

Bulk nanocrystalline TiO2 samples have been produced by high pressure/low temperature sintering. Nanophase TiO2 powder with metastable anatase structure and particle size similar to 38 nm was used as the starting material. During sintering, the anatase phase transformed to either rutile or srilankite phase, depending on the pressure/temperature combination. Grain growth was limited by the low sintering temperature and multiple nucleation events in the parent phase. The transformed rutile grain size was found to decrease with sintering pressure, due to increasing nucleation rate and decreasing growth rate with high pressure. In contrast to previous researchers who found exaggerated grain growth during sintering of n-ceramics, we have demonstrated that it is possible to produce a dense sintered compact with grain size even smaller than that of the starting powder by proper selection of sintering parameters. (C)1999 Acta Metallurgica Inc.