Unipolar charging of nanoparticles by the Surface-discharge Microplasma Aerosol Charger (SMAC) |
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Authors: | Soon-Bark Kwon Hiromu Sakurai Takafumi Seto |
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Institution: | (1) Environment and Fire Control Research Team, Korea Railroad Research Institute, 360-1 Woram-dong, Uiwang-si, Gyeonggi-do, 437-757, Korea;(2) National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba Ibaraki, 305-8563, Japan;(3) Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology, Namiki 1-2-1, Tsukuba, Ibaraki 305-8564, Japan |
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Abstract: | In this paper, we report the development of a novel unipolar charger for nanoparticles, a system that achieves low particle
loss and high charging efficiency without the use of sheath air. The efficient unipolar charging of the system is realized
mainly by the surface-discharge microplasma unit, a device previously applied with good success to the neutralization or charging
of submicron particles Kwon et al., 2005, Aerosol Sci. Technol., 39, 987–1001; 2006, J. Aerosol Sci., 37, 483–499]. The unipolar
charger generates unipolar ions using the surface discharge of a single electrode with a DC pulse supply. This marks an advance
from our previous method of generating bipolar ions with the use of dual electrodes in earlier studies. We evaluated the efficiency
of the penetration (or loss) and charging of nanoparticles in the size range of 3–15 nm, then compared the charging efficiencies
measured with those predicted by diffusion charging theory. More than 90% of inlet nanoparticles penetrated the charger (less
than 10% of the particle were lost) without the use of sheath air. Other chargers have only realized this high penetration
efficiency by relying on sheath air flow. Moreover, the measured charging efficiencies agreed well with those predicted by
diffusion charging theory and were somewhat higher and more size-dependent than the charging efficiencies of other nanoparticle
chargers. |
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Keywords: | nanoparticle charging efficiency surface-discharge microplasma DC pulse aerosols |
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