Physical And Chemical Properties Of Agi Aerosols Formed At Simulated Airborne Conditions

AgI [silver iodide] cloud-seeding nuclei were produced in a wind tunnel by both a flame generator and pyrotechnic at simulated aircraft speeds (150 to 200 mph). These aerosols were collected with isokenetic and anisokinetic samplers. By using electron microscope combined with X-ray energy spectrometer, we determined that particles' size, shape, chemical composition, photostability, and hygroscopicity. We also studied the relationship between these properties and the AgI aerosols' effectiveness as sublimation, condensation-freezing, and contact nuclei. All the aerosols' properties depend on the generating techniques, the additives mixed with AgI before combustion, and the quenching rate of the exhaust plume. From our study of the existing aerosol-generating methods, we developed a new method: combusting solid AgI in a flame generator. We found the aerosol's size distribution, chemical arrangement, and physical properties can be controlled by mixing another salt with the solid AgI; this promotes heterogeneous nucleation or modifies the surface characteristics during the vapor-to-particle transition. This new method has the potential of delivering an AgI aerosol having these properties required for ice nuclei in a particular cloud seeding operation.