Title page for etd-0718114-124252


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URN etd-0718114-124252
Author Jia-yun Li
Author's Email Address No Public.
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Department Mechanical and Electro-Mechanical Engineering
Year 2013
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Mechanical, Electronic and thermal properties of ultrathin tungsten nanowires and nanotubes
Date of Defense 2014-07-18
Page Count 89
Keyword
  • CO oxidation
  • W nanowire
  • W nanotube
  • partial density of states
  • Molecular dynamics
  • Density functional theory
  • Abstract In this study, the structures of ultrathin W nanowires and nanotubes were predicted by the simulated annealing basin-hopping method (SABH) with the tight-binding potential. The mechanical properities and thermal stability of the W nanowires and nanotubes were further examined by the molecular dynamic (MD) calculation and density functional theory molecular dynamics (DFT-MD) simulation. Furthermore, the oxidation of CO molecules on W helical nanotube has also been investigated by DFT calculations. The mechanical properties results of nanowires and nanotubes are presented that W nanowires and nanotubes possess good ductility and their Young's moduli decrease with decreasing of size. In terms of thermal stability, these W nanowires are still stable at temperatures as high as 1300 K. In the electronic properties, we analyze the PDOS of W nanowires and nanotubes with different sizes to understand orbital hybridization. The results show that one-dimension W nanostructures possess better charge transfer capabilities than bulk W, and the W helical nanotube has the best chemical activity in six structures. Therefore, Eley-Radeal (ER) mechanism is considered for examining and comparing the mechanism of CO oxidation on W helical nanotube and W (111) surface. Then the PDOS of the CO oxidation were analyzed to understand the interaction between W nanotube and adsorbed molecules. The calculations show that the energy barrier for W nanotubes is only 0.468 eV, lower than W(111) surface, this result means that W nanotubes have good catalytic activity which can be replaced other structures as catalysts.
    Advisory Committee
  • Jin-Yuan Hsieh - chair
  • Jenn-Sen Lin - co-chair
  • Jian-Ming Lu - co-chair
  • Hsin-Tsung Chen - co-chair
  • Shin-Pon Ju - advisor
  • Files
  • etd-0718114-124252.pdf
  • Indicate in-campus at 3 year and off-campus access at 3 year.
    Date of Submission 2014-08-18

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