Thermal ignition and self-heating of carbon nanotubes: From thermokinetic study to process safety

A comprehensive investigation on the kinetics of combustion of multiwall carbon nanotubes (MWCNTs) produced by vapour chemical deposition has been undertaken. The kinetics parameters were determined from isothermal and non-isothermal combustion tests i.e. by both thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The activation energy of CNT combustion was found to be about 150 kJ mol⁻¹. The oxidation of carbon nanotubes (CNTs) appears to be a single step reaction well represented by a cylindrical shrinking core model. The consistency of this model was assessed both by comparing the activation energy extracted from TGA and DSC, and by theoretical considerations on the geometrical development of CNT oxidation. The influence of oxygen concentration on CNT combustion was also studied. Finally, these results combined with those obtained by self-ignition tests in baskets lead to recommendations for a safe handling and storage of CNTs.