Page 375 - Fiber Fracture

Fiber Fracture
M. Elices and J. Llorca (Editors)
0 2002 Elsevier Science Ltd. All rights reserved

ATOMIC TRANSFORMATIONS, STRENGTH,

PLASTICITY, AND ELECTRON TRANSPORT

IN STRAINED CARBON NANOTUBES

J. Bernholc, M. Buongiorno Nardelli, D. Orlikowski,
C. Roland and Q. Zhao

Depurtment qf Physics. North Carolina State Universi@, Ruleigh, NC 27695, USA

Introduction ..................................... 359
Mechanical Properties ................................ 360
Adatoms-Induced Transformations and Plasticity ................. 368
Electron Transport Properties of Strained Nanotubes ............... 37 1
Summary ...................................... 375
Acknowledgements ................................. 375
References. ..................................... 375

Abstract

Nanotubes are hollow cylinders consisting of ‘rolled-up’ graphitic sheets. They
form spontaneously in the same apparatus as the famed C~O molecule, and have been
predicted and/or observed to have even more spectacular properties than C~O, including
extremely high strength and flexibility, ability to form nanoscale electronic devices
consisting entirely of carbon, strong capillary effects, cold cathode field emission, etc.
Carbon nanotubes have also been theoretically predicted to be among the strongest
materials known. Their strength, which has already been verified experimentally, may
enable unique applications in many critical areas of technology. While very high strain
rates must lead to tube breakage, nanotubes with (n,rn) indices, where n,rn < 14, can
display plastic flow under suitable conditions. This occurs through the conversion of
four hexagons to a 5-7-7-5 defect, which then splits into two 5-7 pairs. The index
of the tube changes between the 5-7 pairs, potentially leading to metal-semiconductor
junctions. Furthermore, carbon adatoms-induced transformations in strained nanotubes
can lead to the formation of quantum dots. The high-strain conditions can be imposed