Altered and Enhanced Iodargyrite with Bismuth Thiiodide for Use in Precipitation Enhancement Operations

摘要

A new ice nucleant aerosol is developed from the principles of synergism. Two known ice nucleants, silver iodide (AgI) and bismuth triiodide (BiI3) are combined as 2% AgI-NH4I X mole % BiI3 NH4I in a water-acetone solution. The resultant aerosol after combustion is tested for effectiveness in the Colorado State University Isothermal Cloud Chamber (ICC), and the optimum ratio of AgI and BiI3 is determined to be 0.5 mole % BiI3. The effectiveness at this optimum ratio is an order of magnitude greater than AgI alone, although the temperature spectrum, rate, and mechanism are similar. A subsequent x-ray powder analysis identifies the optimum ratio aerosol as the iodargyrite form of AgI having the closet match to ice ever reported for a hexagonal crystal. Unlike other mixed AgI containing aerosols the resultant aerosol maintained its hexagonal form of AgI at all mole ratios of BiI3 tested. Bismuth is at too small of a ratio to be identified through the method employed although it appears to be fully incorporated into the AgI crystal as an oxide or iodo-oxide. The plausible structure is looked at in light of epitaxial and active site theories of heterogeneous ice nucleation.