Browsing by Author "Lai, R. L."

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Controlled density growth of carbon nanotubes and its improvement on field emission properties
(2004)
Juan, C. P.
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Tsai, C. C.
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Chen, K. J.
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Hong, W. K.
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Lin, K. C.
The density distribution of the CNTs is one of the crucial parameters for the field emission property of CNTs.We use an inactive thin film layer that was deposited on the catalyst to effectively control the density of the CNTs. The results showed the improved field emission property could be obtained with a thin SiO layer on the catalyst layer as the precursor. For the 3.5 nm Fe and 3.5 nm SiO on 3.5 nm Fe as the catalyst, the turn-on field can be reduced from 3.7 V/ mu m. to 2.2 V/ mu m and the field emission current density increased from 2.6x 10(-8) A/cm(2) to 2.4x 10(-4) A/cm(2) when the applied field was 4 V/mu m. The extremely low turn-on field of 1.3 V/ mu m was also discovered for the CNTs grown with the precursor contained 1.5 nm SiO on 1.5 nm Fe; the extremely high emission current density of 4x 10(-2) A/cm(2) was also achieved under the low electric field of 3.5 V/ mu m.
Experimental study of evaporation pressure drop characteristics of refrigerants R-134a and R-407C in horizontal small tubes
(2008-01-01)
Lie, Y. M.
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Su, F. Q.
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Lai, R. L.
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Lin, T. F.
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機械工程學系
An experiment is carried out in the present study to investigate the characteristics of the frictional pressure drops for the evaporation of refrigerants R-134a and R-407C in horizontal small tubes having the same inside diameter of 0.83 mm or 2.0 mm. In the experiment for the 2.0-mm tubes, the refrigerant mass flux G is varied from 200 to 400 kg/m(2) s, imposed heat flux q from 5 to 15 kW/m(2), inlet vapor quality x(in) from 0.2 to 0.8, and refrigerant saturation temperature T-sat from 5 to 15 degrees C. While for the 0.83-mm tubes, G is varied from 800 to 1500 kg/m(2) s with the other parameters varied in the same ranges as those for D-i = 2.0 mm. In this study, the effects of the inlet refrigerant vapor quality, mass flux, saturation temperature and imposed heat flux on the measured frictional pressure drops are examined in detail. Our experimental data clearly show that both the R-134a and R-407C frictional pressure drops increase significantly with the inlet vapor quality of the refrigerant, except at low mass flux and high heat flux. Besides, the effect of the imposed heat flux on the frictional pressure drop is rather weak. Moreover, a significant decrease in the frictional pressure drop results for a rise in T-sat. Furthermore, both the R-134a and R-407C frictional pressure drops increase substantially with the refrigerant mass flux. We also note that under the same x(in), T-sat, q and D-i, refrigerant R-407C has a lower frictional pressure drop when compared with that for R-134a. For the same refrigerant, a reduction in the duct size from 2.0-mm to 0.83-mm causes a significant increase in Delta P-f. Finally, an empirical correlation for the friction factor for the R-134a and R-407C evaporation in the 0.83-mm and 2.0-mm small tubes is proposed. (C) 2007 Elsevier Ltd. All rights reserved.
Growth and Field Emission Characteristics of Pillar-like Carbon Nanotubes Using Co-Ti/Al Co-deposited Catalysts at Low Temperature
(2010)
Chang, C. T.
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Lee, C. Y.
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Lin, K. C.
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Lai, R. L.
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Tsai, Wan-Lin
In this essay, the pillar-like CNT field emission arrays synthesis with co-deposited catalysts at low temperature (550 degrees C) was proposed. Pillar-like CNT has been successfully synthesized by thermal CVD system. The current density of this proposed pillar like CNTs was as high as 1272 mu A/cm(2) at 6 V/mu m and the turn-on field was 3.6 V/mu m. Additionally, the reliability was more stable as lower than 7% degradation of initial current density.