Inter-layer superlubricity in a carbon nanotube array induced by high-temperature annealing

The development of strong and ultra-stretchable CNT-based materials remains a key focus in high-tech industries. High-temperature annealing presents a promising approach to fabricating highly fused CNT-based materials, where individual CNTs merge into highly interconnected structures. To understand the underlying mechanisms, a large-scale atomic/molecular massively parallel simulator (LAMMPS) is utilized to conduct molecular dynamics (MD) simulations. Accurate CEDIP and AIREBO potentials are selected to model the dynamic behavior of carbon atoms during the annealing and compression processes. The results demonstrate that a highly connected CNT array can transition into a compact graphene-like structure through the fusion of inter-tube covalent bonds. Additionally, simulations of lateral compression, tension, and cyclic loading reveal that the mechanical properties of annealed CNT arrays are strongly influenced by their structural morphology. Moreover, inter-tube and inter-layer sliding and failure behavior significantly impact the resulting mechanical properties. In this study, the maximum stretchability of the annealed CNT array reaches up to 700%. This work sheds light on the intrinsic structural evolution of CNT arrays under high-temperature annealing and provides valuable theoretical insights for the design of next-generation CNT-based metamaterials.