Nanodroplet Aerosols: Formation and Structure

在这个由化学部物理化学计划资助的项目中，伍斯特理工学院的Barbara Wyslouzil将继续进行纳米液滴气溶胶的研究计划。将研究气溶胶中液滴的形成，以期从相变的角度测量和理解成核作用。小角中子散射(SANS)将用于实验监测粒子的大小、组成和结构，红外(IR)测量将用于辅助成核和液滴形成过程中的成分分析。研究计划是双管齐下的。首先，我们将对远离平衡条件下的相变有一个更深入的了解。极高的冷却速度确保在高度过饱和的条件下发生汽化和冷凝(相变)。来自SANS测量的本征尺寸分布数据有望提供喷管中成核速率的第一次直接实验测量。其次，将识别多组分液滴的内部结构。成分和结构数据将用于测试液滴结构的各种模型。要检查的组成因素中的关键是不相容相混合的程度和不相容液体之间形成的相界的清晰度。这个项目将导致对多组分液滴如何形成的更深层次的理解。这项工作的结果将有助于社会帮助理解液滴成核的物理化学，这一知识将有助于天气和气候研究以及基于气溶胶液滴形成的工业过程。这项工作也将对本科生和研究生教授高等材料科学、实验和分析技术产生很大影响。

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.