Non-isothermal oxidation kinetics of single- and multi-walled carbon nanotubes up to 1273 K in ambient

• Published in: Journal of thermal analysis and calorimetry 2012-03, Vol.107 (3), p.1093-1103
• Main Authors: Sarkar, Soumya, Das, Probal Kr
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Chemistry; Chemistry and Materials Science; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Inorganic Chemistry; Materials science; Measurement Science and Instrumentation; Nanoscale materials and structures: fabrication and characterization; Nanotubes; Oxidation-reduction reaction; Physical Chemistry; Physics; Polymer Sciences
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-011-1797-x

Non-isothermal oxidation kinetics of single- and multi-walled carbon nanotubes (CNTs) have been studied using thermogravimetry up to 1273 K in ambient using multiple heating rates. One single heating rate based model-fitting technique and four multiple heating rates based model-free isoconversional methods were used for this purpose. Depending on nanotube structure and impurity content, average activation energy ( E a ), pre-exponential factor ( A ), reaction order ( n ), and degradation mechanism changed considerably. For multi-walled CNTs, E a and A evaluated using model-fitting technique were ranged from 142.31 to 178.19 kJ mol −1 , respectively, and from 1.71 × 10 5 to 5.81 × 10 7  s −1 , respectively, whereas, E a for single-walled CNTs ranged from 83.84 to 148.68 kJ mol −1 and A from 2.55 × 10 2 to 1.18 × 10 7  s −1 . Although, irrespective of CNT type, the model-fitting method resulted in a single kinetic triplet i.e., E a , A , and reaction mechanism, model-free isoconversional methods suggested that thermal oxidation of these nanotubes could be either a simple single-step mechanism with almost constant activation energy throughout the reaction span or a complex process involving multiple mechanisms that offered varying E a with extent of conversion. Criado method was employed to predict degradation mechanism(s) of these CNTs.