Title page for etd-0726114-165459


[Back to Results | New Search]

URN etd-0726114-165459
Author Wei-Chih Chen
Author's Email Address No Public.
Statistics This thesis had been viewed 5571 times. Download 615 times.
Department Physics
Year 2013
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title First-Principles Studies of Thermodynamic Properties and Dehydrogenation Processes of Hydrogen Storage Material (LiBH4)n Nanoclusters
Date of Defense 2014-06-18
Page Count 52
Keyword
  • LiBH4
  • nanoclusters
  • dehydrogenation
  • reaction temperature
  • reaction path
  • first principles
  • hydrogen storage
  • Abstract Several experimental studies have found improved thermodynamic, kinetic, and reversibility properties when LiBH4 is confined in nano-porous materials. In this study, we used Monte Carlo method and genetic algorithm to search the conformations of reactant (LiBH4)n and one of products (LiB)n. Other products, Lin, Bn, and Li2BnHn, were obtained from literatures. We used the density functional theory to calculate the total energies of reactants and all possible products, and found that the stability of LiBH4 nanoclusters have only little difference compared with that of bulk-LiBH4. However, for the products, the stabilities decrease with reducing sizes. This phenomenon indicates nano-LiBH4 would have higher reaction temperatures. We also investigated the reaction paths of nano-LiBH4, and the results show that the reaction path change from bulk-phase reaction (LiBH4 → LiH + B + 3/2H2) to ((LiBH4)n → (LiB)n + 2nH2) after reducing size. We also found intermediate compound Li2BnHn might appear dehydrogenation. The possible intermediate compounds of (LiBH4)m(m=2,3,4,6) were further included in the calculations to understand the hydrogenation releasing processes. Our results show that different (LiBH4)m have different hydrogen release properties. When m=3 and 6, under 1 bar, both of them release hydrogen rapidly in small temperature interval near their starting points of hydrogen release. When m=2 and 4, we found the amount of releasing hydrogen has a linear relation with temperature near their starting points. However, our results do not replicate experimental results due to the exclusion of the substrate effects i.e. to the nano-porous materials used in experiments which improve the thermodynamic properties of nano-LiBH4.
    Advisory Committee
  • Q. Y. Chen - chair
  • Wan-Sheng Su - co-chair
  • Feng-Chuan Chuang - advisor
  • Files
  • etd-0726114-165459.pdf
  • Indicate in-campus at 2 year and off-campus access at 2 year.
    Date of Submission 2014-08-26

    [Back to Results | New Search]


    Browse | Search All Available ETDs

    If you have more questions or technical problems, please contact eThesys