Biomedical Engineering Reference
In-Depth Information
in the high-pressure hydrogen adsorption case presented by Zlotea
et al.
[58], although the carbon dioxide adsorption data reported by
Gensterblum
[51] for an activated carbon showed reasonably
good agreement. The aim of future work should nonetheless be to
enhance our understanding of the relative importance of the various
sources of error for different adsorptive species and to increase the
accuracy of reported results. This could be achieved by defining
guidelines to help reduce the likelihood of unnecessary experimental
errors affecting future studies. Significant progress in this area
would benefit both the practical application and our fundamental
understanding of gas adsorption by carbon nanomaterials.
et al.
1.
Conclusion
In this chapter we have covered the experimental methods that are
typically used to determine the gas sorption properties of carbon
nanomaterials, and we have discussed some of the potential sources
of error in these measurements. The importance of the careful
consideration of these factors is particularly prominent in the case
of hydrogen adsorption measurements for carbon nanomaterials
due to the controversy created by inaccurate characterization of
the storage properties of carbon nanotubes and nanofibres. The
factors that we have discussed include temperature measurement
and control, pressure measurement accuracy, sample size
considerations, sample purity, gas purity, sample degassing, leaks
and the accuracy of the description of the compressibility of a gas
as a function of temperature and pressure. The buoyancy effect
corrections necessary for gravimetric measurements and the dead
volume corrections required for volumetric measurements are also
crucial. The accuracy of these two correction types depends on
the approach taken to the determination of the sample density or
volume, which effectively defines the location of the Gibbs dividing
surface in adsorption measurement, and so this remains a crucial
issue for high-pressure gas adsorption measurement accuracy. The
conversion of the experimentally determined excess adsorption
and the absolute adsorption is also important, particularly when
comparing theoretical calculations with experimental data. A
consistent and effective method of conversion is therefore also crucial
in the assessment of the gas adsorption properties of nanostructured
and nanoporous carbons.
