Browsing by Author "Chiu, CW"

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Assessment of fire protection performance of water mist applied in exhaust ducts for semiconductor fabrication process
(2005-09-01)
Shu, YL
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Jeng, WJ
;
Chiu, CW
;
Chen, CH
;
機械工程學系
Fume exhaust pipes used in semiconductor facilities underwent a series of fire tests to evaluate the performance of a water mist system. The parameters considered were the amount of water that the mist nozzles used, the air flow velocity, the fire intensity and the water mist system operating pressure. In order to make a performance comparison, tests were also performed with a standard sprinkler system. The base case served as a reference and applied a single water mist nozzle (100 bar operating pressure, 7.31/min water volume flux and 200 pin mean droplet size) installed in the pipe (60 cm in diameter) subjected to a 350 degrees C air flow with an average velocity of 2 m/s. In such a case, the temperature in the hot flow dropped sharply as the water mist nozzle was activated and reached a 60 degrees C saturation point. Under the same operating conditions, four mist nozzles were applied, and made no further contribution to reducing the fire temperature compared with the case using only a single nozzle. Similar fire protection performances to that in the base case were still retained when the exhaust flow velocity increased to 3 m/s and the inlet air temperature was increased to 500 degrees C due to a stronger input fire scenario, respectively. Changing to a water mist system produced a better performance than a standard sprinkler. With regard to the effect of operating pressure of water mist system, a higher operating pressure can have a better. performance. The results above indicate that the droplet size in a water-related fire protection system plays a critical role. Copyright (c) 2005 John Wiley & Sons, Ltd.
Convergent electron beam induced growth of copper nanostructures: Evidence of the importance of a soft template
(2004-01-20)
Yen, MY
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Chiu, CW
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Chen, FR
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Kai, JJ
;
Lee, CY
In a transmission electron microscope, CuCl particles were irradiated by a convergent electron beam (CEB, 200 kV, 200 pA/cm(2), beam diameter of ca. 1-2 mum) to induce growth of copper nanostructures. Upon CEB irradiation, Cu nanoparticles (5-20 nm in diameter) were formed from commercial CuCl. Using synthesized CuCl encapsulated in permethylpolysilane, growth of polycrystalline copper nanowires (50-200 nm in diameter and up to 30 mum in length) was observed. Evolution of Cu nanoparticles from the synthesized CuCl was observed from the positions with apparent incomplete encapsulation. The effect of polymer encapsulation, acting as a soft template, is shown to be important to influence the nanostructure growth. The observation supports the vapor-solid reaction growth model.
Electron lifetime in armchair carbon nanotubes
(2004-11-01)
Chiu, CW
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Shyu, FL
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Chang, CP
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Chuu, DS
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Lin, MF
The excited conduction electrons in metallic armchair carbon nanotubes can decay by inelastic electron-electron scattering. The deexcitation channels include the single-particle and collective excitations of different angular momenta. The higher conduction subbands have more deexcitation channels, or shorter electron lifetimes. Each conduction subband has certain states with very long lifetimes, and a simple relationship between the inverse electron lifetime and the state energy is absent. Such results directly reflect the characteristics of the ID excitation spectra. The inverse electron lifetime contrasts sharply with those of semiconducting carbon nanotubes, graphite, and 2D and 3D metallic systems. Dimensionalities play an important role in the many-body effects. The predicted results could be verified by femtosecond time-resolved optical spectroscopy.
Low-temperature synthesis of transition metal nanoparticles from metal complexes and organopolysilane oligomers
(2002-10-01)
Chang, YH
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Wang, HW
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Chiu, CW
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Cheng, DS
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Yen, MY
Mo, W, and Cu nanoparticles (5-50 nm) are synthesized from reactions employing a metal complex, such as MoO2Cl2(DME), MoCl5, WCl6, ((CuOBu)-Bu-t)(4), or CuCl2, and a organopolysilane oligomer Si(SiMe3)(4) or (SiMe2)(6) either in a hexane solution (343 K) or in a sealed tube (473-673 K). Oxo- and chlorophilicities of the silyl groups provide for an energetically favored reaction route to reduce the metal complexes. The reaction byproducts are removed easily either by evaporation or dissolution into hydrocarbon solvents. It is proposed that the homogeneous mixing of the reactants in vapor and solution phases allows the association and growth of molecules into small clusters, then into nanosized metal particles.
Synthesis of cable-like copper nanowires
(2003-02-05)
Yen, MY
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Chiu, CW
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Hsia, CH
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Chen, R
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Kai, JJ
Cable-like copper nanowires (1-10 mum in length and 15-80 nm in diameter) with an insulating poly(dimethylsiloxane) (PDMS) sheath (510 nm in thickness, see Figure) have been successfully synthesized by a solvent-free reaction between CuCl and (Me3Si)(4)Si in the presence of PDMS in sealed tubes. The wire formation mechanism is proposed to be vapor-solid reaction growth.
Temperature-dependent carrier dynamics in metallic carbon nanotubes
(2005-10-31)
Chiu, CW
;
Chiu, YH
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Shyu, FL
;
Chang, CP
;
Chuu, DS
The low energy states in metallic armchair carbon nanotubes can decay by the electron-electron Coulomb interactions with the intraband and the interband excitations. The inelastic scattering rate is very sensitive to the changes in the electronic distribution and the state energy (or the wavevector). The temperature dependence is linear for the Fermi-momentum state. Such dependence is hardly affected by the nanotube radius and the Fermi energy. The electron-electron interactions are more efficient in electronic deexcitations compared with the electron-phonon interactions. The calculated results are roughly consistent with the experimental measurements from the time-resolved photoemission spectroscopy. (c) 2005 Elsevier B.V. All rights reserved.