Raman spectroscopic and electron microscopic studies were made of multi-walled carbon nanotubes annealed in a hydrogen atmosphere at low temperatures (<1300C). The pristine samples had various ID/IG ratios (of the area of the D-peak to the area of the G-peak in Raman spectra) between 0.19 and 2.6. The ID/IG ratio reflected the defect density in graphitic structures. It was found that, as the annealing temperature was increased, the ID/IG ratio first increased and then decreased. The annealing temperature at which the ratio was a maximum, decreased with increasing pristine ID/IG value. This was explained by invoking a mathematical expression for the ID/IG ratio, consisting of an exponential and a stretched exponential term for the production and annealing of defects, respectively. The activation energies and pre-exponential factors of the two contributions were found to vary systematically with the pristine ID/IG ratio.

Defect-Dependent Annealing Behavior of Multi-Walled Carbon Nanotubes. G.M.Bhalerao, A.K.Sinha, V.Sathe: Physica E, 2008, 41[1], 54-9