FORMATION OF MESOPOROUS, ZIRCONIUM(IV) OXIDES OF CONTROLLED SURFACE-AREAS

Control of the surface areas of the calcined zirconium(IV) oxides aris es from the extent of equilibration permitted between the hydrolysed z irconyl oxychloride and the surfactant prior to calcination. The prope rties of the zirconia-surfactant materials, which are formed by a scaf folding and controlled drying mechanism, and the subsequent oxides obt ained on calcination depend more on the times allowed for equilibratio n than on the ratios of zirconia:surfactant. During the equilibration over ca. 24 hr between the hydrolysing zirconium oxychloride and CTAB, the small, unstable zirconium oxide particles mix intimately with the surfactant. These particles recrystallise (and loosely aggregate) on calcination to give tetragonal zirconias of intermediate surface areas (50 m(2) g(-1)). Equilibration over 90 h gives thermally stable (up t o 450 degrees C), small (<100 Angstrom) tetragonal zirconia nanopartic les which maintain their integrity after calcination to give high surf ace area materials.