Browsing by Author "Wu, S. C."

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Enhancement of mechanical properties of electron beam-welded D6ac steel tube
(2015-04-01)
Wu, S. C.
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Tseng, K. H.
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Wen, H. C.
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機械工程學系
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Department of Mechanical Engineering
A forward flow-formed D6ac steel tube was joined through the electron beam welding process and was then subjected to post-weld heat treatment. The mechanical properties and hardness profiles of the as-welded (without heat treatment after welding) steel and different post-weld heat treatment weldments were investigated. The results show that the as-welded D6ac steel exhibited very poor mechanical strength and elongation. After post-weld heat treatment, a large improvement in the mechanical properties of the weldment was achieved. Forward flow-formed D6ac electron beam weldment subjected to post-weld heat treatment at 350 degrees C reached the largest yield strength and ultimate tensile strength values (approximately 1359.2 and 1494.3 MPa, respectively). Forward flowformed D6ac electron beam weldment subjected to post-weld heat treatment at a temperature of 650 degrees C exhibited an overtempered state, which led to mechanical strength and hardness deteriorations of the weldment. This study found that the forward flow-formed D6ac electron beam weldment heat-treated at 350-450 degrees C and held at this temperature range for 2 h exhibits high mechanical strength, sufficient elongation and a yield strength/ultimate tensile strength ratio of 0.91.
Ion beam studies of InAs/GaAs quantum dots after annealing
(2008-04-01)
Niu, H.
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Chen, C. H.
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Wang, H. Y.
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Wu, S. C.
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Lee, C. P.
The microstructure changes of self-assembled InAs/GaAs quantum dots during RTA treatment was investigated using ion channeling and photoluminescence (PL). A small blueshift of the PL emission is observed for annealing temperatures of 650-800 degrees C and an obvious blueshift at 850 degrees C. The yield of channeled spectra decreased as annealing temperature was increased, but the yield increased while temperature above 800 degrees C in RTA. These results imply the strain of QD varied during RTA treatments. In addition, the As/Ga atomic ratio near the surface was determined from the surface peaks of the channeled spectrum. (c) 2008 Elsevier B.V. All rights reserved.
The strain status of the buried self-assembled InAs quantum dots using MeV technique
(2006)
Wang, H. Y.
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Chen, C. H.
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Niu, H.
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Wu, S. C.
;
Lee, C. P.
The strain status of the buried self-assembled InAs quantum dots was comprehended by measurement first time. Results show the in-plane strain is compressive and the lattice in the growth direction is lager than the lattice of GaAs. The strain of the sample annealed at 650 degrees C relaxes in the growth direction. The growth and the lateral direction become relaxed in the sample annealed at 750 degrees C.