Thermogravimetric analysis had demonstrated that multi-walled nanotubes annealed at 2200 to 2800C were more air-stable than were as-produced multi-walled carbon nanotubes, diamond, graphite and annealed diamond. The annealed multi-walled carbon nanotubes were similar in stability to annealed graphite. Defect sites along the walls and at the ends of the raw multi-walled carbon nanotubes facilitated the thermal oxidative destruction of the nanotubes. Thermal annealing removed these defects, thus yielding multi-walled carbon nanotubes with enhanced air stability.

Thermogravimetric Analysis of the Oxidation of Multiwalled Carbon Nanotubes: Evidence for the Role of Defect Sites in Carbon Nanotube Chemistry. D.Bom, R.Andrews, D.Jacques, J.Anthony, B.Chen, M.S.Meier, J.P.Selegue: Nano Letters, 2002, 2[6], 615-9