Department News

Carbon Nanotubes: Kink Motion Reported for the First Time

Plastic deformation in nanotubes can lead to promising applications

Investigating the properties of carbon nanotubes is one of the hottest topics in Physics at the present time.

Nanotubes’ study, born more than a decade ago, grew nowadays into a large field of the novel materials with promising properties and far-reaching applications.

Nanotubes are quasi-one-dimentional systems. They are strong – at least 10 times stronger than steel, flexible, and if added to ceramics – increase their strength and toughness, significantly reduce brittleness, and make them difficult to break. This has a potential to widen the commercial applications of the high-temperature superconductors.

The researches at the Department of Physics at Boston College are
focused on the novel electronic materials, including nanotechnology.

FIG.1. Screw motion of a kink in a five-walled carbon nanotube under tensile stress at 2 V and 100 uA (See online movies at: http://www.aip.org/pubservs/epaps.html). The kink was emitted from lower-right wall and then propagated upward with a velocity of 0.7 nm/s. Note the kink propagation directions changed from a longitudinal to a spiral way upward, as predicted by a dislocation glide mechanism. Red sketches highlight the change of kink shapes and positions. Note also the innermost wall was detached during the kink motion process.

The laboratory of Prof. Jianyu Huang is studying the mechanical properties of the nanotubes. In their work, published in Phys. Rev. Lett. (.pdf) last month, they were observing the plastic deformation of carbon nanotubes at high temperatures (>2,000 °C) inside an atomic resolution microscope. Heated single, double, and multiwalled  carbon nanotubes were investigated by passing electric currents through them.

The screw motion of kinks was reported for the first time. The results of the elaborate study of a pattern of the kink movement along the nanotube observed under the TEM microscope were presented in this publication (see FIG.1). It was shown that the kink motion was driven by high temperatures and external stress.
 
Kink motion was observed in the carbon nanotubes of all types, suggesting that this is a universal plastic deformation mode under these conditions (see the movie here (M3.mpg, 2508.0 kB)).

These results show that the carbon nanotubes are very ductile at high temperatures, and can be used in the design and synthesis of high-strength materials based on these structures.

The work was done in collaboration with two other BC professors – Z. Ren and Z.Wang, BC graduate students, and colleagues from Harvard, MIT, and the University of Michigan.

Innovative results featured in this work have been highlighted on the Nature Nanotechnology website.