Study of interwall interaction during the pull separation of ultra-long double-walled carbon nanotubes under lateral loading

Abstract

The successful fabrication of ultra-long carbon nanotubes (CNTs) makes CNTs ideal candidates for bearing systems due to the long sliding distance with low interwall interaction. However, it is difficult to measure the pull-out forces of ultra-long CNTs along their axes in real-time because of the difficulty of performing long-distance pull-out experiments. In this study, we proposed a lateral loading method to measure the interwall interaction force of ultra-long CNTs. By using a theoretical model and multi-scale finite element simulations, we could predict the interwall interaction force from the pull-out force in lateral loading. This pull-out force depends on the length of CNTs, and a critical length divides the pull-out force into two categories: maximum pull-out force due to local buckling and steady pull-out force due to sliding. In order to correctly measure the interwall interaction force by lateral loading, for the DWCNTs with the outer tube diameter of 0.955 nm, we have to make sure the lengths are greater than this critical value (54.2 nm) as experimental subjects.