IN-SITU MEASUREMENTS OF THE ICE-FORMING ACTIVITY OF METAL-OXIDE AEROSOLS WITH CONTROLLED AMOUNTS OF SURFACE-ACTIVE GROUPS

The ice-forming activity of aluminum oxide and zinc oxide aerosols was studied in a cloud chamber at 253 and 263 K. Generators for ZnO and Al2O3 aerosols with mass mean radii between 10 and 400 nm and variable concentration of surface hydroxyl groups in the range of 1-12 per nm2 are described. Particle size and the chamber temperature are shown to strongly influence ice crystal formation. A non-monotonous dependence of ice-forming activity on the concentration of the hydroxyl groups is observed and discussed.