Molecular dynamics study of mechanical properties and fracture behavior of carbon and silicon carbide nanotubes under chemical adsorption of atoms

Abstract

Molecular dynamics (MD) simulations are used to investigate the tensile properties and fracture behavior of Hydrogen (H)- and Fluorine (F)-chemisorbed single-walled silicon carbide nanotubes (SWSiCNTs). Stress-strain curves are obtained and Young's modulus, toughness, tensile strength, as well as maximum strain of nanotubes are determined through stress-strain profiles. The results are compared to those of single-walled carbon nanotubes (SWCNTs) and a detailed analysis of the tensile fracture behavior of both nanotubes, i.e., SWSiCNTs and SWCNTs, is made. It is found that the functionalized nanotubes possess lower stress and strain at the breaking point than those of their pure counterparts (SWSiCNTs 0% and SWCNTs 0%). The increase of functionalization weight leads to reduced Young's modulus, toughness, and tensile strength. Concerning fluorination and hydrogenation, the fluorination of nanotubes has less influence on the weakening of Young's modulus in every functionalization degree when the findings of F-functionalized SWSiCNTs and SWCNTs (F-fSWSiCNTs and F-fSWCNTs) are compared to those of pure nanotubes. Fluorinated and hydrogenated armchair SWSiCNTs experience a nearly equal value of toughness in each weight of functionalization. Similar results are seen in the zigzag fSWSiCNTs which means that the absorption ability of strain energy in the zigzag H- and F-fSWSiCNTs is almost the same. As the weight of functionalization increases from the minimum value to the maximum one, the variation of ultimate stress with the degree of functionalization for the H-fSWCNTs and zigzag H-fSWSiCNT undergoes more reduction in comparison with their F-functionalized counterparts. Also, the armchair functionalized nanotubes are proved to be more capable of withstanding a larger fracture strain than that of their zigzag counterparts in each desired weight of functionalization. Regarding the fracture behavior of nanotubes, the rupture propagation tends to happen in a benzene ring that has at least three functional atoms and one of its grafts has been broken before.