Enhanced Ductile Behavior of Tensile-Elongated Individual Double-Walled and Triple-Walled Carbon Nanotubes at High Temperatures

We report exceptional ductile behavior in individual double-walled and triple-walled carbon nanotubes at temperatures above $2000°\mathrm{C}$, with tensile elongation of 190% and diameter reduction of 90%, during in situ tensile-loading experiments conducted inside a high-resolution transmission electron microscope. Concurrent atomic-scale microstructure observations reveal that the superelongation is attributed to a high temperature creep deformation mechanism mediated by atom or vacancy diffusion, dislocation climb, and kink motion at high temperatures. The superelongation in double-walled and triple-walled carbon nanotubes, the creep deformation mechanism, and dislocation climb in carbon nanotubes are reported here for the first time.

Figure 1

Tensile elongation (190%) of a DWCNT at a constant bias voltage of 2.2 V ([11], movie Ml). (a) Experimental setup. A dog-bone-shaped sample was produced by electric breakdown of a MWCNT. (b)–(e) Sequential HRTEM images showing the tensile elongation of a DWCNT. In (e) the nanotube is broken near the middle (pointed out by two arrowheads), (f) Current ($I$) versus time ($t$) plot for the same DWCNT [(b)–(d)].

Figure 2

Tensile elongation (130%) of a TWCNT at a constant bias of 2.3 V ([11], movie M2). (a) Electric breakdown produced a double-hollow tube with a TWCNT inside a DWCNT with a length of about 15 nm. (b) The outer DWCNT breaks upon pulling, (c) the innermost wall breaks (pointed out by an arrowhead) upon further tensile-loading, (d) the nanotube breaks entirely at a length of about 34 nm. (e) $I\mathrm{\text{−}}t$ curves of the nanotube during the elongation. Inset is magnified $I\mathrm{\text{−}}t$ curves showing a current drop of $11\mu \mathrm{A}$ when the innermost wall is broken.

Figure 3

Tensile elongation of a DWCNT without applying a bias voltage. Electric breakdown produces a DWCNT section with an initial length of 72 nm and diameter of 4.8 nm (a), and it is elongated to a length of 77 nm and a diameter of 4.7 nm (b) before it breaks (c).

Figure 4

Sequential HRTEM images showing dislocation climb in a MWCNT at a bias voltage of 1.7 V. The cores of the dislocations are marked by ellipses. The arrowheads mark a feature that is not changed. Stars mark cracks. The upper dislocation in (a) and (b) has moved out of the field of view in (c).