Atomistic simulations of the mechanical properties of 'super' carbon nanotubes

The mechanical properties of the so-called 'super' carbon nanotubes (STs) are investigated using classical molecular dynamics simulations. The STs are built from single-walled carbon nanotubes (SWCNTs) connected by Y-like junctions forming an ordered carbon nanotube network that is then rolled into a seamless cylinder. We observed that the ST behaviour under tensile tests is similar to the one presented by fishing nets. This interesting behaviour provides a way to vary the accessible channels to the inner parts of STs by applying an external mechanical load. The Young's modulus is dependent on the ST chirality and it inversely varies with the ST radius. Smaller reduction of breaking strain values due to temperature increase is predicted for zigzag STs compared to SWCNTs. The results show that, for STs with radius similar to 5 nm, the junctions between the constituent SWCNTs play an important role in the fracture process. The Young's modulus and tensile strength were estimated for hierarchical higher-order STs using scaling laws related to the ST fractal dimension. The obtained mechanical properties suggest that STs may be used in the development of new porous, flexible, and high-strength materials.