Biomedical Engineering Reference
In-Depth Information
system becomes endothermic. At this stage it has not been possible
to identify enough experimental data to verify this, but as the focus
on environmental stability intensifies it is likely that this will change
in the near future.
7.6
Conclusion
Presented here are details of an analytical thermodynamic model
for predicting the relative stability of single-walled CNTs exposed
to gas adsorbates. The model has been parameterized using first
principle's computer simulations for hydrogen, oxygen, nitrogen,
and water. These parameterizations have then been applied to a
range of CNT sizes and chiralities, to demonstrate how the model
may be used to explore different adsorption configurations and
degree of gas coverage, as well as including important aspects of
adsorbate clustering and rehybridization. In the present context the
results indicate that the adsorption of water is thermodynamically
preferred among the atmospheric gases considered, and that the
stability of small diameter nanotubes may even be improved by a
sparse coverage of water. The parameterization was also used to
model the stability of CNTs in humid air, showing that the relative
humidity of the air surrounding (and interacting with) CNTs has a
strong influence on the overall thermodynamic stability, and the
degree of chemisorption that is likely to occur. In general, however,
this model may be applied to any gas species adsorbing on a CNT, by
following the simple parameterization procedure [58, 60].
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Nanotubes
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