Biomedical Engineering Reference
In-Depth Information
physical adsorption on carbon materials [29-35]. The theoretical
values [32], reported in Fig. 2.2, are approximately 10 times lower
than the rupture energy for covalent C-H bonds, characterizing the
chemisorptions [35-40]. The manifestation of “super” van der Waals
or weak chemical interaction of hydrogen with fullerites (C
and
60
Na-C
-H) and carbon nanotubes has been also reported [41].
Sumanasekera
60
[42] noted the possibility of interpreting
their thermal electromotive force and electric resistivity data of
hydrogen-saturated single-wall nanotubes using both the model of
physical sorption with interactions stronger than the van der Waals
ones and the model of chemisorptions with an interaction weaker
than that in typical covalent C-H bonds.
In their studies regarding the mechanical synthesis of the
hydrogen with nanostructured graphite, Orimo
et al.
[14] revealed
an anomalous hydrogen-graphite sorption interaction, weaker than
in chemisorptions but stronger than in physical sorption.
The possibility of a “chemi-like” physical adsorption of hydrogen
in carbon nanomaterials has been discussed in a theoretical paper
[35].
At the same time, it should be noted that not even a single
researcher discussed the mechanisms of this weak chemical or
“superphysical” interaction. As it is emphasized in Ref. [11], there
is not yet a clear and convincing description of the mechanism of
hydrogen sorption by carbon nanotubes and nanofibers.
It is therefore worthwhile to give a more detailed analysis of
the conditions needed for the manifestation of anomalous values
of the energy characterizing the sorption of hydrogen by carbon
nanomaterials [27], aiming to propose a possible meaningful
interpretation. In such a context, nature (chemisorptions or physical
sorption), mechanisms, ultimate sorption capacity, and diffusion
kinetics of the sorption processes have to be studied using novel
concepts, methods, and analytical results [10, 17-25].
et al.
2.2.2 Hydrogen Chemisorption in Graphite and
Gelated Carbon Nanostructures
2.2.2.1
Methodological Aspects
The methods described in Refs. [10, 17-25] were primarily based
on the thermodynamics of the reversible processes and on a linear
