Date of Award

8-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Li, Gang

Committee Member

Thompson , Lonny L

Committee Member

Huang , Yong

Abstract

Part A
Injection of particles to the side wall of single-walled carbon nanotubes (SWCNT) has been employed for doping and storage of particles on SWCNTs. In addition, particle bombardment can be used to cut and modify graphene structures. While the collision of hydrogen atoms with SWCNTs has been extensively studied, collision dynamic behavior of heavy particles with SWCNTs has not been well understood. To facilitate a better understanding of the particle-SWCNT collision process, in this work, we study the impact of five noble gas atoms (He, Ne, Ar, Kr, Xe) with SWCNTs and investigate particle impact induced CNT bond breaking phenomena. Simulation results include the bond-breaking kinetic energy ranges of the incident atoms with reflection and penetration after the collision. Effect of chirality, boundary and strain conditions of the SWCNTs and energy exchange between the incident atoms and carbon atoms of SWCNT are investigated.
Simulation results show that, except for very small SWCNTs (diameter < 0.5 nm), the minimum bond-breaking energy of the incident atom is independent of the chirality/diameter and boundary conditions of the SWCNT. However, the incident atom mass as well as strain conditions of the SWCNT plays an important role in the minimum bond-breaking energy, collision behavior and energy loss of the incident atom.
Part B
Nanocomposite materials are increasingly used in the resonators in Nanoelectromechanical systems (NEMS). While nanoresonators' ability to attain high fundamental frequencies with excellent mechanical response makes them useful for high performance sensing, a critical performance measure is the quality factor of the resonator. While quality factors of single crystal materials have been extensively studied, few work has been done on the analysis of quality factors of nanocomposites. In this work, we investigate the characteristics of intrinsic energy dissipation in nanocomposite resonators using classical molecular dynamics. The quality factors, and thereby energy dissipation rate, of various silicon and germanium configurations are calculated. The relationship between the quality factor and the temperature, material configuration and interface area are investigated.
Simulation results indicate that, due to the strong phonon scattering in the nanocomposite beams, the characteristics of the quality factor variation can not be described by the classical thermoelastic energy dissipation theory. The component material interface plays a major role in the quality factor of the beams. The disadvantageous effect of the interface area is significant, especially at lower temperatures.

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