Thermal effect on DWCNTs as rotational bearings

We have investigated the rotational motion and dynamic friction in a molecular bearing composed of double-walled carbon nanotubes (DWCNTs) using molecular dynamics simulations. The main study was on thermal effects due to the rotational friction. The diameters of the bearings varied between 6 and 16 Å for the inner shafts, and between 12 and 20 Å for the outer sleeves. The rotation velocity varied from 0.05 rotations ps(-1) to 0.25 rotations ps(-1). The simulations show that the energy dissipation, and hence the temperature of the system, increases linearly with rotation time. The value of energy dissipation is around 0.59 meV/atom per rotation at ω = 0.05 rotations ps(-1) for a (15, 0)@(23, 0) bearing. Correspondingly, the average friction force is around 1.75 × 10(-5) nN/atom. The dependence of the energy dissipation on the rotation velocity, the interwall distance, and the contact area of the DWCNT is also discussed. It was observed that the energy dissipation becomes lowest when the interwall distance of the DWCNT bearing reaches about 0.34 nm, the equilibrium distance of the Lennard-Jones (L-J) potential. This low energy dissipation suggests that the DWCNT can be a good candidate for a wearless rotational bearing, which supports the previous studies.