Effects of structural defects on strength and fracture properties of multi-walled carbon nanotubes

Abstract

In this study, we report the relationship between the mechanical properties and structural defects of multi-walled carbon nanotubes (MWCNTs) synthesized by a chemical vapor deposition (CVD) method. The tensile strength, Young's modulus and Weibull modulus of the individual MWCNTs were determined by conducting uniaxial tensile tests using a manipulator tool operated inside a scanning electron microscope. In addition, the structural defects which induced the failure of the MWCNTs were observed by a transmission electron microscope (TEM). TEM observations revealed that the MWCNTs exhibited several types of structural defects: discontinuous flaws such as holes; kinks and bends; impurities i.e., catalysts even though highly crystalline layers were almost perfectly aligned with the MWCNT axis. The tensile-loading experiments demonstrated that the average tensile strength, Young's modulus and Weibull modulus of the 23 MWCNTs were 5.2 ± 2.1 GPa, 210 ± 140 GPa and 2.7, respectively. The MWCNTs underwent failure leaving either a clean break or a very short sword and sheath failure, suggesting that a significant interwall load transfer might be facilitated by the irregular wall structures as mentioned above.

Mechanical and Fracture Properties of Carbon Nanotubes

“…Here, we review our recent studies in which the strength properties of individual MWCNTs synthesized by a CVD method, followed by a series of high-temperature annealing steps that culminate with annealing at 2900°C, are investigated by a manipulator tool operated inside an SEM [52][53][54]. The relationship between the MWCNT structure and strength properties of MWCNTs with a significantly different nanostructure is investigated through tensile tests of individual MWCNTs, transmission electron microscope (TEM) observations, and Raman spectroscopy analysis.…”