SGER: Development of Scanning Electron Microscope Techniquesto Ascertain the Microscopic Mixing Characteristics of Atmospheric Aerosols

大多数大气颗粒物的化学分析都是在大样本上进行的。然而，颗粒物组成的不同对大气变化、能见度下降和颗粒物污染物的去向有很大影响。此外，对燃烧产物微观混合特性的了解对于理解燃烧中颗粒的形成是必不可少的。随着计算机控制的扫描和X射线探测器的发展，扫描电子显微镜(SEM)在这方面的应用前景广阔。然而，还需要开展更多的开发工作，以确保元素分析准确地反映气溶胶的组成。这项研究的目标是用电子显微镜获得准确的大气气溶胶单粒子分析。已知组成的单分散气溶胶将用于1)研究电子束对大气气溶胶主要成分的损伤，2)减少光束损伤的测试方法，以及3)验证现有的定量方法。还将评估扫描电子显微镜测量碳的潜力。所开发的技术将在未来用于确定决定气雾剂吸收水的基本特征。

Most chemical analyses of atmospheric particles are carried out on bulk samples. However, particle by particle variations in composition strongly influence atmospheric transformations, visibility degradation, and the fate of particulate pollutants. In addition, knowledge of the microscopic mixing characteristics of combustion products is essential to understanding particle formation in combustion. With the development of computer- controlled scanning and x-ray detectors which measure elements as light as carbon, the scanning electron microscope (SEM) has a great deal of promise for this application. However, more development work is needed to assure that the elemental analysis accurately reflects the composition of the aerosol. The goal of this research is to obtain accurate single particle analyses of atmospheric aerosols with an electron microscope. Monodisperse aerosols of known composition will be used to 1) conduct studies of electron beam damage to major components of atmospheric aerosols, 2) test methods to reduce beam damage, and 3) validate existing quantitation methods. The potential of the SEM for measuring carbon will also be assessed. The techniques developed will be used in the future to identify the elemental characteristics determining the uptake of water by aerosols.