Browsing by Author "Lu, Hao"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Electromechanical Investigation of Low Dimensional Nanomaterials for NEMS Applications
    (2011) Lu, Hao; Lou, Jun
    Successful operation of Nano-ElectroMechanical Systems (NEMS) critically depends on their working environment and component materials' electromechanical properties. It is equally important that ambient or liquid environment to be seriously considered for NEMS to work as high sensitivity sensors with commercial viabilities. Firstly, to understand interaction between NEMS oscillator and fluid, transfer function of suspended gold nanowire NEMS devices in fluid was calculated. It was found that NEMS's resonance frequency decreased and energy dissipation increased, which constrained its sensitivity. Sensitivity limit of NEMS oscillators was also considered in a statistical framework. Subsequently, suspended gold nanowire NEMS devices were magnetomotively actuated in vacuum and liquid. Secondly, electromechanical properties of gold nanowires were carefully studied and the observed size effect was found to agree with theory, which predicted small changes of electromechanical property compared with bulk gold materials. Finally, it is well recognized that continuous development of new NEMS devices demands novel materials. Mechanical properties of new two-dimensional hexagonal Boron Nitride films with a few atomic layers were studied. Outlook of utilizing ultrathm BN films in next generation NEMS devices was discussed.
  • Thumbnail Image
    Item
    Frictional properties of vertically aligned multiwalled carbon nanotube superlattices and fluorinated nano diamond films
    (2009) Lu, Hao; Lou, Jun
    Quantitative adhesion and friction properties of Vertically Aligned Multiwalled Carbon Nanotubes (VAMWNT) and Fluorinated Nano Diamond (F-ND) Films were studied using commercially available AFM probes and customized microprobes under controlled environments. This thesis demonstrated that no significant adhesion force difference was found in dry environment and ambient conditions for both VAMWNT and F-ND samples while a clear dependence of friction behavior on relative humidity was found. There was no significant correlation between adhesion and friction at the nanometer length scales. A chemical dangling bond hypothesis was proposed to explain experiment results. An interesting reverse stick-slip phenomenon was also found on scanning VAMWNT and molecular dynamic simulations were used to understand this behavior.