Surface Effects on the Mechanical Properties of FCC Metal Nanowires

Abstract

The major findings of this thesis are that free surfaces have enabled nanowires to show many unusual behavior and mechanical properties at nanoscale, including shape memory and pseudoelastic behavior, surface elasticity in hollow nanowires, and coupled effect from cross sectional geometry and side surface orientation, all of which could not be observed at macroscopic scale. This thesis has shown that surface stresses allow the reversibility between higher energy <100>/{100} and lower energy <110>/{111} configurations in metal nanowires and thus lead to the shape memory behavior in nanowires. It has also shown that because the elastic properties of surfaces are substantially different from those of the bulk at nanoscale, and because hollow nanowires have higher surface to volume ratio compared to solid wires, the hollowness can be used to improve the elastic properties of nanostructures. Finally, the thesis has demonstrated for the first time that cross sectional geometry and transverse surface orientation have a first-order effect on the mechanical properties of metal nanowires.