Thermal stability and creep of polycrystalline nanowires

We considered a polycrystalline cylindrical nanowire with bamboo microstructure strained uniaxially by an external load. Our estimates demonstrated that for sufficiently thin nanowires the evolution of their morphology and the creep rate are controlled by surface and grain boundary self-diffusion. We calculated the equilibrium shapes of the nanowire achieved after long annealing times. Our calculations demonstrated that for any given grain aspect ratio some critical value of the applied load exists above which the nanowire is unstable and breaks up into a string of isolated spherical particles. The kinetics of the shape change were calculated numerically. It was shown that the rate of thinning of unstable nanowires diverges as the moment of breakdown is approached. We also demonstrated that the break up may occur even for nominally stable nanowires "on the way" to achieving their equilibrium shape. The external tensile load accelerates the breakdown of nanowires.