Characterization of Interlayer Sliding Deformation for Individual Multiwalled Carbon Nanotubes Using Electrostatically Actuated Nanotensile Testing Device

We have developed an in situ scanning electron microscopy (SEM) nanomaterial manipulation system, including a newly designed electrostatically actuated nanotensile testing device (EANAT), in order to investigate the mechanical characteristics of multiwalled carbon nanotubes (MWCNTs) synthesized by atmospheric pressure-chemical vapor deposition. The new EANAT can measure uniaxial tensile displacement of nanomaterials using a capacitive displacement sensor incorporated into a cantilever motion amplification system. The resolution of the measurement displacement was 0.28 nm at the minimum. The nanomaterial manipulation system allows for an individual MWCNT to be picked up from a substrate and to be attached to an EANAT. The stress-strain relationships for the individual MWCNTs were successfully obtained from the nanotensile tests, and Young's moduli were estimated to be in the range from 338 to 623 GPa. The deformation of individual MWCNTs under uniaxial loading was accompanied by repeated stick-slip and hard sticking events like telescopic motion. The shear strength at a stick-slip event during interlayer sliding of MWCNTs under tensile loading was directly derived from the shear interaction force in the tensile load-displacement curves and SEM observations. On the basis of the single-shot extraction model, the shear strength was estimated to be an average of 78 MPa greater than that for high-quality crystalline graphite, which might be caused by the hard sticking between layers.