High-speed nano-bearings constructed from double-walled carbon nanotubes : effect of flexile deformation

Abstract

Double-walled carbon nanotubes (DWCNTs) have been proposed to be the leading candidates for high-speed nanobearings owing to superlubric characteristics between adjacent nanotubes. Performance of the DWCNT bearings is closely related to intertube friction, which is influenced by many factors, and in this work, we focus on the issue of flexibility of the nanotubes. Using molecular dynamics simulation, it has been found that considerable deformation of the nanotubes can emerge in the (5, 5)/(18, 0) DWCNT bearing with a length of ∼80 Å if the angular speed of the shaft reaches 1.3 rev/ps. Such flexile deformation results in two distinct states with differing frictional characteristics. One of the two states, the slippery rotation, represents an interim period characterized by in-phase distortions of the inner and outer tubes, while the other state, the resistant rotation, is a steady state with the inner-tube curving lags behind that of the outer tube. Such a lag leads to a considerable increase of circular deflection of the outer tube and a sharp decrease of the minimal distance between tubes, therefore preventing the inner tube from slippery rotation.