Nanodroplet Aerosols: Formation and Structure

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In this project funded by the Physical Chemistry Program of the Chemistry Division, Barbara Wyslouzil of the Worcester Polytechnic Institute will pursue a program of research on nanodroplet aerosols. The formation of liquid droplets in aerosols will be studied with a view to measuring and understanding nucleation from a phase transition perspective. Small angle neutron scattering (SANS) will be used to experimentally monitor particle size and composition and structure, and infrared (IR) measurements will be used to aid in the compositional analysis during nucleation and droplet formation. The research program is two pronged. First, a deeper understanding of phase transitions under conditions that are far from equilibrium will be obtained. Very high cooling rates insure that nuleation and condensation (phase transition) occur under highly supersaturated conditions. Intrinsic size distribution data from SANS measurements are expected to provide the first direct experimental measurements of nucleation rates in nozzles. Second, the internal structure of multi-component droplets will be discerned. The compositional and structural data will be used to test various models for the droplet structure. Key among the compositional factors to be examined is the degree to which immiscible phases mix and the clarity with which phase boundaries develop between immiscible liquids. This project will lead to a deeper understanding of how multicomponent droplets form. The results of the work will benefit society in helping to understand the physical chemistry of droplet nucleation, and this knowledge will benefit weather and climate studies and industrial processes based upon aerosol droplet formation. The work also will have a high impact on teaching undergradute and graduate students advanced materials science experimental and analysis techniques.