Adsorption of water vapor on ZnO: Effects of annealing and grinding

TG, DTA, and DTGA study of water vapor adsorption on ZnO showed that the water vapor was adsorbed reversibly at 500°C (0.12 mg/g ZnO). Irreversible desorption of water vapor was also found at approximately 270°C. Both the specific surface area and the amount of water vapor adsorbed reversibly decreased with increasing annealing temperature above 500°C. When as-received ZnO was ground, the amount of water vapor adsorbed reversibly decreased sharply before any significant change took place in the specific surface area. At longer grinding time, the specific surface area increased but the amount of water vapor adsorbed reversibly increased only slightly with the grinding time. When the specimen was ground after annealing, the reversible adsorption of water vapor was not affected by the thermal history before grinding.