Effects of ZrOCl2 Concentration and Reaction Temperature on the Formation Process of Hydrous-Zirconia Fine Particles.

Abstract

The crystal phase, the primary particle size, and the formation rate of hydrous-zirconia fine particles produced by hydrolysis conditions of various ZrOCl2 concentrations (0.05-0.4mol·dm-3) and reaction temperatures (358-373K) were measured to clarify the effects of the ZrOCl2 concentration and the reaction temperature on the formation process. Chemical analysis and X-ray diffraction measurements revealed that hydrous-zirconia particles synthesized from all of the hydrolysis conditions were similar to those observed in monoclinic crystalline ZrO2, except that the crystal structure changed with increasing chlorine content at the preparation conditions of 0.4mol·dm-3 and ≤363K. The primary particle size of monoclinic hydrous-zirconia particles decreased with increasing ZrOCl2 concentration and was independent of the reaction temperature. The rate constants (k) of hydrous-zirconia particles were determined experimentally by applying Avrami-Erofeev's equation. The determined k-value decreased, as the ZrOCl2 concentration increased and the reaction temperature decreased. From Arrhenius plots of k, the activation energies for hydrous-zirconia particles in the monoclinic phase and containing high chlorine contents were determined to be 3.8×102-4.0×102 and 2.5×102kJ·mol-1, respectively. The nucleation and the particle growth mechanisms of hydrous-zirconia particles were determined on the basis of the present experimental results.