Reassembly of single-walled carbon nanotubes into hybrid multilayered nanostructures inside nanotube extruders

High-pressure induced structural reassembly of single-walled carbon nanotubes (SWNTs) inside carbon nanotube extruders is investigated by reactive molecular dynamics simulations. It is found that the encapsulated SWNTs undergo a series of structural transformations depending on tube diameters with increasing internal pressure, and finally reassemble into hybrid $s{p}^{2}\text{\ensuremath{-}}s{p}^{3}$ cross-linked multilayered tubular nanostructures inside the nanotube extruders. Density-functional calculations show that strong compression causes a semiconducting-to-metallic transition in the encapsulated tubes. The metallic properties of the formed nanostructures are mainly attributed to the shortening of carbon bonds and strong interlayer correlation.