Heterogeneous nucleation of water vapor on highly charged nanoparticles of SiO2

• Main Authors: Ming-han Chow, 周明翰
• Other Authors: Chin-Cheng Chen
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/67660415362407002788

碩士 === 國立成功大學 === 化學工程學系碩博士班 === 97 === In the atmosphere, there are ions generated as a result of cosmic ray and natural radiolysis, and aerosol particles become charged due to the attachment of these ions. Charge on particle can affect the condensation of vapor on particles. So far there are scant data on the effects of the amount of charge, charge polarity, and particle size on the condensation of vapor on nanoparticles, the phenomena are not well understood yet. In this study, an electrospray aerosol generator was used to generate SiO2 nanoparticles and preparing highly charged nanoparticles by condensation charge magnification system. A flow cloud chamber(FCC) was employed to examine the effects of amount of charges particles carried on the critical supersaturation for the condensation of a supersaturated water vapor on SiO2 nanoparticles with diameters ranging from 15 nm to 25 nm, and having up to -3 unit charges. Highly charged nanoparticles were prepared by condensation charge magnification system. The concentration of highly charged nanoparticles depends on steam flow rate, corona discharge voltage, dry air flow rate and the distance between the coaxial jets. For 20 and 25 nm SiO2 particles, the experiment results show that there is no charge effect. For 15 nm SiO2 particles, an obvious charged effect on Scr is observed, and the effect is much stronger than the prediction. This phenomenon may be caused by negative ion attached on particles surface to reduce the barrier of nucleation.