Biomedical Engineering Reference
In-Depth Information
graphite) of elasticity modulus, elongation modulus and tensile
strength are declared. Hence, it follows:
(i) that the blister formation at room temperatures (Figs. 2.21-
2.23) can occur within the elastic deformation conditions,
(ii) that a contrasting blister pressure (of the fugacity order)
should be taken into account, and
(iii) that the hydrogen pressure in the blisters [5] can be much
higher than the above estimated values (at least, within the
experimental and approximation errors).
The above considerations are consistent with the thermodynamic
estimation of the equilibrium hydrogen fugacity (
) in a blister which
can be performed by using the “acting masses law” for the “reaction”
of (fH2)
f
H2
H
as follows:
(gas)
2(gas in_blisters),
0
0
2
f
/
P
≈ (
P
/
P
)
exp{[∆
H
-
T
S
f
(∆
V
/
n
)]/
RT
},
(2.37)
H2
H
dis
dis
H2
where
P
≈ 1 Pa is the atomic hydrogen pressure in the atomizer
H
[5],
P
0
= 1 Pa is the standard pressure, ∆
H
= 448 kJ/mol(H
) is
dis
2
the known experimental value of the dissociation enthalpy per
mole
of gaseous hydrogen (at room temperatures), ∆
S
≈ 0 (in the used
dis
approximation) is the dissociation entropy, ∆
V
V
, n
(
Q S
)/
N
,
b
b
A
N
is the Avogadro number,
R
is the gas constant,
T
≈ 300 K [5].
A
Therefore, it results
Pa.
It is necessary to emphasize that the adsorbed hydrogen amount
f
≥ 10
9
H2
Q
mainly localized in the blisters between two graphene layers
(Figs. 2.21-2.23) corresponds to a relatively low hydrogen/carbon
average atomic ratio in the monolayer: (H/C) ≈ (2
,
Q/N
)
≈ 0.1, with
C
N
being the number of carbon atoms per 1 cm
2
of two graphene
C
layers.
On the other hand, the hydrogen mass density in the blisters
can be estimated
is the
hydrogen molecule mass; this is close (within the experimental
errors) to the liquid hydrogen mass density (70.8 kg/m
as ρ
(
QM
S
)/
V
≈ 45 kg/m
3
, where
M
H2
b
b
H2
3
at 21.2 K
and 0.1 MPa).
On the basis of the experimental and estimated results, one can
conclude that in the graphite monolayer (between the two graphene
layers) some three-dimensional clustering of hydrogen molecules
occurs, and that under the conditions of [5] there is formation and
growth of liquid-like three-dimensional nanoclusters (Figs. 2.21-2.23).
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