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 Vox = 4.38 · 10–7 mole/sec. Internal overheating of the sample activates rapid carbon oxidation reactions on the 360th\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {360}^{{\mathrm{t}}_{\mathrm{h}}} $$\end{document} sec at 973 K. In the range 1023–1173 K, the total rates increase exponentially: Vox = 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 Ea ≈ ≈ 169 ± 9 kJ/mol. The frequency characteristics of factor A0 were defined as ≈ (1.0–3.1) · 106 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).