10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Effects of Dehydration Conditions on Particle Morphology and Activation Ratio of Inorganic Nanoparticles by a HT- DMA- APM / CCNC System
TA-CHIH HSIAO, Po-Hsiang Huang, National Central University
Abstract Number: 237 Working Group: Aerosol Physics
Abstract Morphology of aerosol particles may play an important role in pharmaceuticals, powder industry, and atmospheric science. Numerous literature has shown dry particle shape depend on the dehydration condition and crystallization process. Hygroscopic tandem differential mobility analyzers (HT-DMA) are generally used to study the hygroscopic behavior of aerosol particles, however, it cannot provide the information about particle morphology and density. Therefore, in this study, in addition to a HT-DMA system, a hygroscopic coupled tandem DMA and aerosol particle mass analyzer (APM) were integrated and employed. The former size change and latter mass were used to derive the particle effective density and calculated dynamic shape factor which characterize particle shape.
The experimental results indicated that the solvent evaporation and solute diffusion dominated the morphology of the dry particles in dehydration process. In an extreme dry condition, the particle tended to form in irregular shape due to the fast remove of solvent. In contrast, there was more sufficient time for the solute diffusion in slow drying and the particle formed in spherical shape. However, drying and crystallization of aqueous aerosol particle were complicated process. Numerous factors such as materials, solute concentration, and particle size could affect the dry particle morphology. Thus, in order to investigate the dehydration process of aerosol particle, this study combined the diffusion equation and Köhler theory. In addition, quantifying the competitive relationship between solvent evaporation and solute diffusion by the dimensionless parameter: Peclet number and revealing the mechanism of particle formation in different experimental parameters setup. To understand the ability of nanoparticles to activate as cloud condensation nuclei in different drying condition. This study also conducted the HT-DMA-CCNC measurement and showed the activated fraction could be influenced by particle morphology.