Thermal Oxidation Kinetics of Multi-Walled Carbon Nanotubes in an Oxygen Flow

The oxidation reactions of multi-walled carbon nanotubes in isothermal conditions have been studied for the first time. With a steady increase in temperature from 923 to 1173 K, the time dependence for the oxidation of multi-walled carbon nanotubes changes from a straight line to an S-shaped curve that reaches its saturation point. The sample’s oxidation rate on linearly increasing sections at 923 K is V ox = 4.38 · 10 –7 mole/sec. Internal overheating of the sample activates rapid carbon oxidation reactions on the 360^t_h sec at 973 K. In the range 1023–1173 K, the total rates increase exponentially: V ox = 1.19 · 10 –6 –1.97 · 10 –5 mole/sec. The Arrhenius equation was used to calculate the kinetic parameters of carbon thermal oxidation. The activation energies for the oxidation reactions of multi-walled carbon nanotubes in the range 973–1173 K were found at E a ≈ ≈ 169 ± 9 kJ/mol. The frequency characteristics of factor A 0 were defined as ≈ (1.0–3.1) · 10 6 sec –1 . The activation parameters of the oxidation reactions of multi-walled carbon nanotubes are close to the theoretical activation energy of graphite oxidation (172 kJ/mole).