Browsing by Author "Tsai, C. J."

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Formation of metal oxide nanoparticles in combustion of titanium and aluminum droplets
(2006-11-01)
Karasev, V. V.
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Onishchuk, A. A.
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Khromova, S. A.
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Glotov, O. G.
;
Zarko, V. E.
A study was performed of the formation of metal oxide nanoparticles during combustion of aluminum and titanium drops which moved in air at a velocity of up to 3 m/sec. The source of the burning particles was a pyrotechnic mixture which contained an oxidizer, a binder, and metal particles of size 4-350 mu m. Transmission electron microscopic studies showed that the combustion products were 1-10 mu m aggregates of fractal structure consisting of primary particles (spherules) of Al(2)Oi(3)/TiO2 5-150 nm in diameter. The Brownian diffusion of the aggregates and their motion in electric and gravitational fields were observed using videomicroscopic recording. The charge distribution of TiO2 aggregates and the equivalent radius of Brownian mobility were determined. In Al combustion, the zone of nanoparticle formation is separated from the particle surface by a distance approximately equal to the particle radius, and in Ti combustion, this zone is located directly near the surface. Coagulation of the oxide aerosol in the track of a burning particle leads to aerogelation with the formation of huge aggregates. Analytical expressions for approximate calculation of the parameters of the oxide particles and zones of their formation are proposed.
Implementation of Fuchs' model of ion diffusion charging of nanoparticles considering the electron contribution in dc-corona chargers in high charge densities
(2009-06-21)
Aliat, A.
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Hung, C. T.
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Tsai, C. J.
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Wu, J. S.
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機械工程學系
A 1D corona discharge model coupled to a 2D-axisymmetric particle charging model are proposed in this paper to simulate nanoparticle charging process within a wire-tube air corona discharge subjected to an applied positive or negative dc voltage. This 1D discharge model provides the distribution of the electric field, the air ion and free electron concentrations for the 2D charging model which in turn solves the spatial distributions of the various charged nanoparticles within the tube. This 2D charging model takes into account the effect of electrons, on the basis of Fuchs' law usually employed in the literature for modelling of ion diffusion nanoparticle charging. The current approach is valid when the concentration of nanoparticles is much lower than the concentration of ionic species in the gas. Numerical results show that the positive air ions can be assumed to be solely responsible for the charging process in a positive air corona charger, while both the negative air ions and electrons play an important role in the negative charging. At high negative charge intensities, the effect of the electrons becomes appreciable due to their high conduction velocity. In general, the numerical results obtained are in good agreement with the experimental data reported in the literature.
Overview of the Gas and Aerosol Metrology
(2013-09-01)
Tsai, C. J.
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Aggarwal, S. G.
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環境工程研究所
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Institute of Environmental Engineering
There are several exciting developments noted in gas and aerosol measurements in recent years. On the other hand not much work has been done on the calibration facility, traceable standards, and certified reference materials for this field of science. More attention and concerns are needed for the comparable and SI traceable data quality in gas and aerosol measurements. The aim of this special issue of MAPAN-Journal of Metrology Society of India is to highlight such issues.
Rapid Synthesis of Semipolar ZnO Nanorod Arrays on M-Sapphire by Microwave-Assisted Chemical Bath Deposition
(2018-01-01)
Tsai, C. J.
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Do, H.
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Chang, C.
;
Chiu, K. A.
;
Hsiang, C. C.
Microwave-assisted chemical bath deposition (CBD) is a newly developed technique for fast growth of single-crystalline ZnO nanorods in a solution containing zinc nitrate at temperature below 100 degrees C. ZnO nanorods have many applications for devices, however, semipolar oriented ZnO nanorods have been rarely reported. In this study, epitaxial growth of well-aligned arrays of inclined semipolar ZnO nanorods on a ZnO seed layer on m-plane sapphire substrates is successfully fabricated by using microwave-assisted chemical bath deposition for 10 min at 90 degrees C. TEM analysis reveals that The ZnO nanorods have an inclined angle about 30 degrees with m-sapphire surface and an average length about 500 nm which gives a growth rate of 3 mu m/h. Micro-photoluminescence measurements show that ZnO nanorods are of a reasonably good quality.
Study of a Nanoparticle Charger Containing Multiple Discharging Wires in a Tube
(2008)
Tsai, C. J.
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Chen, S. C.
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Chen, H. L.
;
Chein, H. M.
;
Wu, C. H.
A unipolar charger containing multiple discharging wires in a tube (inner diameter: 50mm) was developed and tested in order to increase the aerosol flow rate and the charging efficiency of nanoparticles. Four gold wires of 25 mm in diameter and 15 mm in length were used as the discharging electrodes to generate positive ions (Ni) from 2.72 x 10(8) ions/cc to 3.87 x 10(9) ions/cc in concentration at the discharging voltage of + 4.0 similar to + 10 KV. Monodisperse NaCl particles of 10 similar to 50nm in diameter were used to test the charging efficiency and the particle loss of charged particles with different aerosol flow rates, corona voltages and sheath flow rates. The sheath air near the tube wall was found to increase the extrinsic charging efficiency, and the highest efficiency was obtained at + 6.0KV discharging voltage, 10 L/min aerosol flow rate and 9 L/min sheath flow rate. The extrinsic charging efficiency increased from 10.6% to 74.2% when the particle diameter was increased from 10 to 50 nm. The TDMA (tandem differential mobility analyzer) method was used to determine the charge distribution and the mean charge per particle and it was found that the Fuchs charging theory corrected for the extrinsic charging efficiency matched with the experimental data very well.