Browsing by Author "Chou, SL"

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Experimental and theoretical studies of rate coefficients for the reaction O(P-3)+CH3OH at high temperatures
(2005-06-22)
Lu, CW
;
Chou, SL
;
Lee, YP
;
Xu, SC
;
Xu, ZF
Rate coefficients of the reaction O(P-3)+CH3OH in the temperature range of 835-1777 K were determined using a diaphragmless shock tube. O atoms were generated by photolysis of SO2 with a KrF excimer laser at 248 nm or an ArF excimer laser at 193 nm; their concentrations were monitored via atomic resonance absorption excited by emission from a microwave-discharged mixture of O-2 and He. The rate coefficients determined for the temperature range can be represented by the Arrhenius equation, k(T)=(2.29 +/- 0.18)x10(-10) exp[-(4210 +/- 100)/T] cm(3) molecule(-1) s(-1); unless otherwise noted, all the listed errors represent one standard deviation in fitting. Combination of these and previous data at lower temperature shows a non-Arrhenius behavior described as the three-parameter equation, k(T)=(2.74 +/- 0.07)x10(-18)T(2.25 +/- 0.13) exp[-(1500 +/- 90)/T] cm(3)molecule(-1) s(-1). Theoretical calculations at the Becke-3-Lee-Yang-Parr (B3LYP)/6-311+G(3df,2p) level locate three transition states. Based on the energies computed with coupled clusters singles, doubles (triples) [CCSD(T)]/6-311+G(3df,2p)//B3LYP/6-311+G(3df,2p), the rate coefficients predicted with canonical variational transition state theory with small curvature tunneling corrections agree satisfactorily with the experimental observations. The branching ratios of two accessible reaction channels forming OH+CH2OH (1a) and OH+CH3O (1b) are predicted to vary strongly with temperature. At 300 K, reaction (1a) dominates, whereas reaction (1b) becomes more important than reaction (1a) above 1700 K. (c) 2005 American Institute of Physics.
Nondestructive characterization of the film quality and stress states in diamond films on various substrates
(2000)
Kuo, CT
;
Wu, JY
;
Chou, SL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Diamond films deposited on various substrates were characterized nondestructively by Raman spectroscopy and X-ray diffraction (XRD) to evaluate their stress states and film quality. The X-ray diffraction method is further divided into two methods, i.e., the low incident beam angle X-ray diffraction (LIBAD), and Clemens-Bain method for the textured films. The whole-pattem-fitting structure refinement method, or called "Rietveld method" was adapted in XRD method to improve its accuracy. The film adhesion, film morphology and film structures including its non-diamond carbon content, crystal size, texture coefficient, film thickness and surface roughness were also examined. The correlations between structure and residual stress of the films on various substrates and under various deposition and pretreatment conditions were analyzed. The feasibility of nondestructive evaluation the Blm quality and stress states, and the origins of the residual stress of the films were discussed.