Deformations and Thermal Stability of Carbon Nanotube Ropes

TL;DR

This paper investigates the structural and thermal properties of crystalline single-wall carbon nanotube ropes, revealing new polygonized shapes, metastable structures, and the mechanisms behind their transformation into multiwall nanotubes through molecular dynamics simulations.

Contribution

It introduces novel crystalline nanotube structures produced by laser irradiation and elucidates the mechanisms of SW to MWCNT transformation via MD simulations.

Findings

Polygonized SWCNTs exhibit rounded-hexagonal cross sections.

Multiple metastable lattice structures with different shapes are identified.

SW to MWCNT transformation involves a patching-and-tearing coalescence mechanism.

Abstract

Structural and thermal characteristics of crystalline ropes of single-wall carbon nanotubes (SWCNTs) are investigated. Novel crystalline ropes of polygonized SWCNTs produced by laser irradiation exhibit rounded-hexagonal cross sections in contrast to earlier observations of circular tubes. Extensive molecular dynamics (MD) simulations lead to several metastable structures of the lattice characterized by different tube cross sections, hexagonal, rounded-hexagonal and circular, and increasing cell volume. The competition between different tube shapes is analyzed and compared to experiments. On the other hand, bundles of SWCNTs coalesce forming multiwall carbon nanotubes (MWCNTs) under thermal treatment at high temperatures. Extensive MD simulations confirm the SW-to-MW transformation and suggest the physical patching--and--tearing mechanism underlying the concerted coalescence of the tubes.