Date of Graduation

5-2018

Document Type

Thesis

Degree Name

Bachelor of Science in Mechanical Engineering

Degree Level

Undergraduate

Department

Mechanical Engineering

Advisor/Mentor

Zou, Min

Committee Member/Reader

Wejinya, Uchechukwu C.

Abstract

Nanostructure-textured surfaces can reduce friction and increase the reliability of micro- and nanoelectromechanical systems (NEMS/MEMS). For MEMS incorporating moving parts, the fatigue properties of nanostructures pose a challenge to their reliability in long-term applications. In this study, the fatigue behavior of hemispherical Al/a-Si core-shell nanostructures (CSNs), bare hemispherical Al nanodots, and a flat Al/a-Si layered thin film have been studied using nanoindentation and nano-scale dynamic mechanical analysis (nano-DMA) techniques. Fatigue testing with nano-DMA shows that the deformation resistance of CSNs persists through 5.0 × 104 loading cycles at estimated contact pressures greater than 15 GPa. When the a-Si shell is removed, as in the Al nanodots, significant nanostructure deformation results due to repeated cyclic loading. In addition, for the Al/a-Si layered thin film, which lacks the geometry and core-confinement properties of CSNs, cyclic loading results in fatigue failure of the a-Si layer. CSNs demonstrate none of the failure mechanisms exhibited by these control structures. The unique properties displayed by CSNs when subjected to fatigue testing establish their prolonged durability when implemented in micro- and nano-scale applications.

Keywords

core-shell nanostructure; nanoindentation; fatigue; dynamic mechanical analysis; continuous stiffness measurement

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