Quantifying the transverse deformability of double-walled carbon and boron nitride nanotubes using an ultrathin nanomembrane covering scheme

Abstract

We investigate the characterization of the transverse deformability of double-walled carbon and boron-nitride nanotubes (i.e., DWCNTs and DWBNNTs) using an ultrathin nanomembrane covering scheme. Monolayer graphene oxide sheets (MGOSs) with a sub-nm thickness are used to cover individual double-walled nanotubes on flat substrates. Nanotube cross-section height reduction occurs due to the compression force exerted by the covering membrane, whose morphological conformation is governed by its bending/stretching rigidities and adhesion interaction with the substrate, as well as the radial height and rigidity of the underlying nanotube. The actual transverse deformation of the underlying tube and its effective radial modulus are quantified through interpreting the measured structural morphology of the covering membrane and the nanotube cross-section height reduction using nonlinear structural mechanics and Hertzian contact mechanics theories. The radial deformations in MGOS-covered tubes are found to positively correlate with the nanotube radial rigidity, thus, increasing with the nanotube outer diameter and decreasing with an increase of the number of tube walls. Our results reveal prominent radial strains of about 20% for DWCNTs of 3.55 nm in outer diameter, while about 24% for DWBNNTs of 3.85 nm in outer diameter. Our data about the effective radial moduli of individual DWCNTs and DWBNNTs are in reasonably good agreement with those obtained using atomic force microscopy-based compression methods. Our work shows that the nanomembrane covering scheme is promising as a quantitative technique for studying the radial rigidity of individual tubular nanostructures.