Heterogeneous Nucleation of n-nonane Vapor on charged/neutral nanoparticles of SiO2 (6nm~30nm) and D-mannose (8nm~30nm)
| Autor: | Shien-wei Li, 李先偉 |
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| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 Nanoparticles may have a property different from the bulk due to their small size. Recently, the subjects concerning their production, properties and applications have received extensively attention and been intensively investigated. On the other hand, nanoparticles are generated due to natural and anthropogenic activities, and become an important component of the atmospheric aerosols. In the study, an electrospray aerosol generator was used to generate organic/inorganic nanoparticles and a flow cloud chamber(FCC) was employed to examine the effects of particle size and charge on the critical supersaturation for the condensation of a supersaturated n-nonane vapor on organic/inorganic nanoparticles with a diameter from 6 to 30nm, each carrying a single positive or negative charge or no charge. The results show that the experimental critical supersaturation(Scr) decreases with increasing particle size, at a rate in reasonable agreement with that predicted by Fletcher’s version of Volmer’s theory of heterogeneous nucleation. There are almost no different in the experimental Scr between the neutral and charged SiO2 particles. That means there is no charge effect observed in the SiO2 particle size range we measured. But it is observed in mannose particles. In the sign preference, for 6nm SiO2 particles, the experiment results show that nonane could condense more readily on positively charged particle, while for mannose there is no such different, agreeing with the theoretical prediction. Furthermore, nonane condense on organic mannose particles more efficiently than on inorganic SiO2 particles. This phenomenon may be caused by their difference in the wettability and contact angle. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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