This paper reports the quantitative measurement of a full spectrum of mechanical properties of fivefold twinned silver (Ag) nanowires (NWs), including Young’s modulus, yield strength, and ultimate tensile strength. In-situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a scanning electron microscope (SEM). Young’s modulus, yield strength, and ultimate tensile strength all increased as the NW diameter decreased. The maximum yield strength in our tests was found to be 2.64 GPa, which is about 50 times the bulk value and close to the theoretical value of Ag in the <110> orientation. The size effect in the yield strength is mainly due to the stiffening size effect in the Young’s modulus.

We systematically investigated the interesting electric response of the aligned CNT ribbons under mechanical strain. We found that CNTs slide on a PDMS substrate under tension, but buckle under compression (releasing). Such an irreversible mechanical deformation is responsible for the observed irreversibility in the electric resistance upon the first stretching/releasing. In addition, we found that the resistance of the buckled MWNTs remains constant under mechanical strain, which explains why the resistance of the CNT ribbon did not change for the second and subsequent stretching/releasing.

A postdoctoral research position is available in Dr. Yong Zhu’s lab in the Department of Mechanical and Aerospace Engineering at North Carolina State University. We are looking for a self-motivated researcher to work on projects involving mechanics of nanostructures including nanowires and nanotubes. A Ph.D. in Mechanical Engineering, Materials Science and Engineering, Physics or a related area is required. Experience with in-situ nanomechanical testing using SEM, TEM, AFM or Raman are desirable.