The structural evolution of thin multi-walled carbon nanotubes during isothermal annealing

Systematic isothermal annealing has been carried out on catalytic chemical vapor deposition-derived highly disordered multi-walled carbon nanotubes in order to understand the structural evolution of carbon nanotubes kinetically. After specified isothermal time the crystallographic parameters strongly depend on annealing temperature, and can be divided into three stages. Rapid structural enhancement in the range from 1800 to 2200 degrees C originates from the abrupt evolution of the residual catalytic compounds and is seen as partially aligned small fringes along the tube length. The lack of further structural ordering at temperatures above 2400 degrees C and the low activation energy (ca. 90 kJ/mol) are thought to be the result of the limited space available for further structural development considering the nanosized multi-walled carbon nanotubes. (c) 2006 Elsevier Ltd. All rights reserved.