Mechanical characterization of reinforced vertically-aligned carbon nanotube array synthesized by shock-induced partial phase transition: insight from molecular dynamics simulations

Abstract

Despite intriguing mechanical properties of carbon nanotubes (CNTs), vertically-aligned carbon nanotube (VACNT) array does not possess a high strength against compression along the CNT axis and also the loadings perpendicular to the CNT axis. Here in this study, shock compression is introduced as a means for partial phase transition (PPT) in the VACNT array to reinforce the structure against the mentioned loadings. Molecular dynamics simulations are exploited to investigate the synthesis of a novel nanostructure from a VACNT array with 10 nm long (5, 5) CNTs. Employing Hugoniostat method, shockwave pressures of 6.6 GPa and 55 GPa are extracted from Hugoniot curves as the instability limit and the PPT point, respectively. Coordination analysis reveals the nucleation of carbon atoms in sp3 hybridization while preserving the dominant nature of CNT due to the high percent of sp2 hybridization. Recovery of the shocked samples yields the final structure to be tested for mechanical characteristics. Tensile and compression tests on the samples reveal that for the shockwave pressures below the PPT point, an increase of the shock strength leads to higher compliance in the VACNT array. However, beyond the PPT point the novel nanostructure shows an extraordinary strong behavior against loading along all directions.