Preparation of zirconia nanocrystals from concentrated zirconium aqueous solutions

A high concentration (0.8 M) zirconium solution turned into a stable aqueous colloid of about 60 nm in size upon low temperature (96°C) incubation. Changing the acid concentration did not affect the colloidal growth rate nor the final colloid size much. However, the induction time before the rapid growth of colloidal particle could be altered. By limiting the incubation to just before the rapid growth of colloidal zirconia, and the addition of organic acids as surface modifiers, non-agglomerated primary crystallites (∼10nm) of m-ZrO₂ could be recovered. These modified primary crystallites could then be repeatedly flocculated and redispersed in water by adjusting the pH.