Abstract
The radial stability and the irreversible transformation of triple-wall
carbon nanotubes (TWCNTs) bundles are investigated at high pressure
conditions both experimentally and theoretically (exp. up 72 GPa). The
tubes having a mean internal diameter of 0.83 nm and graphite-like
intertube distance, show an onset of the radial collapse evidenced by
the evolution of optical phonons. The nanotube collapse onset is
observed at similar to 22 GPa completes for the two external tubes at
similar to 29 GPa, however the innermost tube remains stable up to
similar to 37 GPa. Molecular dynamic calculations performed on smaller
diameter TWCNTs bundles, as a model system, confirmed the multiple-stage
pressure-induced collapse process. An analytical expression for the
collapse pressure of carbon nanotubes having an arbitrary number of
walls is proposed. Our experiments and modelling show that for pressures
beyond similar to 60 GPa an irreversible structural transformation of
TWCNTs takes place. Ex situ transmission electron microscopy
characterization on the recovered sample from 72 GPa revealed the
mechanical failure of carbon nanotubes which evolve towards ribbon-like
structures as corroborated by Raman spectroscopy. Modelling the tubes
evolution at high pressure and high temperature showed the formation of
new structures ranging from ribbon-like to graphite-like with either
different degrees of amorphization or sp(3) interlinking. (C) 2018
Elsevier Ltd. All rights reserved.
Users
Please
log in to take part in the discussion (add own reviews or comments).