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Non-isothermal oxidation kinetics of single- and multi-walled carbon nanotubes up to 1273 K in ambient
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...
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Published in: | Journal of thermal analysis and calorimetry 2012-03, Vol.107 (3), p.1093-1103 |
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Main Authors: | , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | 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. |
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ISSN: | 1388-6150 1588-2926 1572-8943 |
DOI: | 10.1007/s10973-011-1797-x |