Nanoscale high friction in double- and triple-wall carbon nanotubes: a molecular dynamics study

Understanding friction in carbon nanotube (CNT) assemblies is essential for the development of nanoscale mechanical systems and CNT-based tribological interfaces. In this work, non-equilibrium molecular dynamics simulations are employed to investigate frictional sliding in layered CNT systems, focusing on double-wall CNT (DWCNT) and triple-wall CNT (TWCNT) configurations. Armchair nanotubes with diameters corresponding to different chiralities were considered, while the overlap ratio and nanotube length were systematically varied to explore their influence on friction. The results reveal pronounced stick-slip dynamics and demonstrate that the effective friction coefficient depends strongly on nanotube diameter, overlap ratio, and wall multiplicity. For DWCNTs, the friction coefficient varies in the rangeμ≈2.0-5.2, whereas TWCNTs exhibit slightly lower values in the rangeμ≈1.5-4.5due to the presence of an additional sliding interface and increased radial stiffness. Thin nanotubes display a compliance-dominated regime in which bending-mediated relaxation can reduce friction at large overlap ratios, while larger diameters exhibit a corrugation-dominated regime characterized by a monotonic increase in friction with contact area. Temperature elevation induces a moderate friction reduction while high temperatures lead to structural deformation in thin nanotubes. These findings provide atomistic insight into friction regulation in CNT assemblies and offer design guidelines for tunable nanoscale tribological interfaces.