A TGA investigation of hydrated monoclinic zirconia

Thermogravimetric analysis (TGA) was used to monitor the surface hydroxyl and carbonate concentrations on porous zirconia after various vapor- and liquid-phase treatments. After equilibration with humid nitrogen, each of the surface zirconium atoms bears a single hydroxyl group and all surface oxygen atoms are present as bridged hydroxyl groups. Hydrochloric acid and sodium hydroxide treatments further increase the surface hydroxyl group concentration. In the presence of sufficient water, carbon dioxide chemisorption is inhibited. Once adsorbed, however, surface carbonates and bicarbonates are not removed by hydrochloric acid, sodium hydroxide or sodium fluoride washings.