Biomedical Engineering Reference
In-Depth Information
s
concentration (H
≈ 0.3 (Eq. (2.33)) corresponding to the
sorption monolayer model. The adsorption enthalpy is ∆
/C
)
exp
2
m
ads
H
≈
−1
−3.7 kJ mol
), an indirect experimental value obtained by the
tabulated data of the chemical potential of gaseous H
(H
2
[77].
For the single-wall nanotube samples, a Henry−Langmuir
sorption isotherm is present for pressures up to approximately
2 MPa (curves 3 in Fig. 2.16). The adsorbate concentration at 2 MPa
reaches a value of (H
2
−2
/C) ≈ 4 × 10
, which agrees with the local
2
s
concentration (H
) ≈ 0.37 (Eq. (2.33)) close to the carbohydride
value (about 0.5, Table 2.1).
/C
exp
2
Figure 2.16
Hydrogen adsorption isotherms at 80 K for: (1) the initial
untreated single-wall nanotubes; (2) single-wall nanotubes
treated with ultra-sound prior to hydrogen saturation; (3)
samples (2) after a second round of hydrogen saturation; (4)
Saran activated carbon; (5) Saran material after reducing a
correction for the ratio of specific surface areas (3:16) [77].
exp
The
value
of
S
for
the
single-wall
nanotube
samples
th
investigated in Ref. [77] is close to the theoretical value
of the specific
surface area of the interbundle surface (Eq. (2.35)). The diameter of
such bundles (
S
b
≈ 6-12 nm) is approximately 10 times greater than
the diameter of individual nanotubes (
d
b
≈ 1.2 nm). Hence, we may
assume that at pressure ≥ 2 MPa, the adsorbate concentration in the
d
NT
