It was noted that, during the fabrication of metal nanowires, an oxide shell could surround the metal core. Such an oxide-covered nanowire could be viewed as being a cylindrical core/shell nanostructure, with a lattice-mismatch between the core and the shell. Experimental evidence showed that, in response to this mismatch, mechanical stresses induced plastic deformation into the shell, and misfit dislocations nucleated at the core/shell interface. As a result, the mechanical properties of the nanowire were affected. It was therefore important to be able to predict the critical conditions under which misfit-dislocation nucleation at the interface took place, and the critical applied load at which the interface began to deform plastically. Two approaches were used to analyze the stress-relaxation processes. Energy considerations, within a classical elasticity framework were used to predict the critical radii of core and shell at which dislocation nucleation took place at the nanowire interface. A strain-gradient plasticity approach was also used to estimate the flow stress at which the interface would begin to deform plastically. This so-called interfacial-yield stress, predicted by gradient plasticity, depended upon the radii of the core and shell. Both approaches demonstrated that the geometrical parameters of nanowires could be chosen so as to avoid undesirable plastic deformation. The first method predicted radii-values that prevented misfit dislocation formation. The second method predicted, for given radii-values, the critical stress at which interface deformation nucleated.

Nucleation of Misfit Dislocations and Plastic Deformation in Core/Shell Nanowires. K.E.Aifantis, A.L.Kolesnikova, A.E.Romanov: Philosophical Magazine, 2007, 87[30], 4731-57