Conical coiled carbon nanotubes with highly controllable mechanical properties

Nanostructures composed of carbon nanotubes (CNTs) show great diversity in geometrical morphology, leading to effective augmentability in their unique properties and practical technological applications. In the present study, for the first time, highly controllable mechanical properties of three-dimensional (3D) conical coiled CNTs (CCNTs) structure, which are assembled from straight CNTs in a form of nanocone, were reported, resourcing to molecular dynamics simulations. As a result of the conical morphology, tensile mechanical behaviors of conical CCNTs are dominated by van der Waals (vdW) forces and covalent forces. Tensile stiffness and the way of phase transformation are controlled by geometrical characteristics in vdW forces' domination section. Stretchability that is situated in section of covalent forces' domination - can vastly range from 250% to 23000%, depending on radius of each coil. More interestingly, originating from the hollow conical geometry, conical CCNTs can be highly compressed, as well as show different behaviors between cyclic compression and tension. This work provides new insights into mechanics of carbon nanostructures, and indicates that conical CCNTs are good potential candidates for mechanical robust nanodevices.