Energy dissipation of high-speed nanobearings from double-walled carbon nanotubes

Abstract

The behavior of nanobearings constructed from double-walled carbon nanotubes(DWCNTs) is investigated with molecular dynamics simulations. The results show that the(5, 5)/(10, 10) DWCNTs can work as stable and reliable nanobearings to a speed as high as∼2.65 r ps−1 with an inner tube as rotator. When the speed is lower than∼0.75 r ps−1, the nanobearings remain in an ultrasmooth state, beyond which the intertube frictionincreases and fluctuates sharply. The rotational friction is sensitive to many factors such asrotation speed, radial size, and flexibility of CNTs. Increase in rotation speed and theradial sizes of CNTs leads to increase of centrifugal force and decrease of intertubedistance, thus, increases the intertube friction. As a result, both the critical speed forultrasmooth rotation and the ultimate speed decrease with increasing radius of the innertube with constant intertube distance. The centrifugal force and thermal motion of atomswill stimulate flexile deformation of CNTs, namely waving tube axis and distortingcross-section, which will lead to an increase in rotational friction. When the outer tubeserves as the rotator, the DWCNT nanobearing becomes more easily damaged.