Browsing by Author "Pan, Cheng-Tang"

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Deformation behaviors of Au nanotubes under torsion by molecular dynamics simulations
(2018-08-01)
Hwang, Yeong-Maw
;
Pan, Cheng-Tang
;
Lu, Ying-Xu
;
Jian, Sheng-Rui
;
Juang, Jenh-Yih
In this study, the mechanical deformation behaviors of Au nanotubes (Au-NTs) under torsional stress are investigated using molecular dynamics (MD) simulations. The inter-atomic interaction is modeled using the embedded-atom potential. In particular, the effects of loading rate, thickness and length of the nanotube, as well as the thermal effects were systematically explored. The results indicated that higher loading rate, longer length and thinner wall thickness all led to a larger value of critical torsional angle (theta(cr)), which signifies the onset of plastic deformation. On the other hand, theta(cr) decreases with increasing temperature in all simulated results. Moreover, the torsional buckling deformation behavior and geometrical instability are found to strongly depend on the length of Au-NTs, the applied strain rate and temperature with vastly different underlying mechanisms. (C) 2018 Author(s).
Influence of Post-Annealing on the Structural and Nanomechanical Properties of Co Thin Films
(2020-02-01)
Hwang, Yeong-Maw
;
Pan, Cheng-Tang
;
Lu, Ying-Xu
;
Jian, Sheng-Rui
;
Chang, Huang-Wei
The correlations between the microstructure and nanomechanical properties of a series of thermal annealed Co thin films were investigated. The Co thin films were deposited on glass substrates using a magnetron sputtering system at ambient conditions followed by subsequent annealing conducted at various temperatures ranging from 300 degrees C to 800 degrees C. The XRD results indicated that for annealing temperature in the ranged from 300 degrees C to 500 degrees C, the Co thin films were of single hexagonal close-packed (hcp) phase. Nevertheless, the coexistence of hcp-Co (002) and face-centered cubic (fcc-Co (111)) phases was evidently observed for films annealed at 600 degrees C. Further increasing the annealing temperature to 700 degrees C and 800 degrees C, the films evidently turned into fcc-Co (111). Moreover, significant variations in the hardness and Young's modulus are observed by continuous stiffness nanoindentation measurement for films annealed at different temperatures. The correlations between structures and properties are discussed.