Multi-walled carbon nanotubes under focused electron beam: metal passivation effect and nanoscaled curvature effect

The elongation and length contraction in multi-walled carbon nanotubes without/with metal (Au) nanoparticles under focused electron beam irradiation is in situ studied experimentally at room temperature with transmission electron microscopy. It is observed that the plastic flow and direct evaporation of carbon atoms strongly rely on the nanoscaled negative curvature and surface energy of the nanotubes. The multi-walled carbon nanotubes without metal nanoparticles shrink and elongate by the diffusion and plastic flow of carbon atoms along the shells in the tube axis direction by self contraction of shells. In contrast, multi-walled carbon nanotubes with metal nanoparticles shrink and reduce their lengths by direct evaporation (sputtering) of carbon atoms into the free space under passivation by the metal nanoparticles. Thus, experimental demonstration is provided that the non-uniform structural evolution process in multi-walled carbon nanotubes induced fleetly by the nanoscaled negative curvature effect under athermal activation effect of electron beam passivates by metal nanoparticles. (paper)