Mechanical properties of ZnO nanowires under different loading modes

In this paper, we report the size effects on elastic modulus and fracture strength of ZnO nanowires from the tension, and that the measured (nominal) elastic moduli under tension and bending (from the buckling experiment) are different as a manifestation of the size effects. 

F. Xu, Q. Qin, A. Mishra, Y. Gu, and Y. Zhu, Nano Research, DOI: 10.1007/s12274-010-1030-4, 2010

Abstract:

A systematic experimental and theoretical investigation of the
elastic and failure properties of ZnO nanowires (NWs) under different
loading modes has been carried out. In situ scanning electron
microscopy (SEM) tension and buckling tests on single ZnO NWs along the
polar direction [0001] were conducted. Both tensile modulus (from
tension) and bending modulus (from buckling) were found to increase as
the NW diameter decreased from 80 to 20 nm. The bending modulus
increased more rapidly than the tensile modulus, which demonstrates
that the elasticity size effects in ZnO NWs are mainly due to surface
stiffening. Two models based on continuum mechanics were able to fit
the experimental data very well. The tension experiments showed that
fracture strain and strength of ZnO NWs increased as the NW diameter
decreased. The excellent resilience of ZnO NWs is advantageous for
their applications in nanoscale actuation, sensing, and energy
conversion.