Thesis - Oztek_Muzaffer_T_200508_MA

hydrogen storage alloy has a specific equilibrium pressure of hydrogen (P eq ). At low
concentrations all isotherms have a common slope showing the relation
c∝
p
The hydrogen solubility shows a thermal-activation type of behavior, and the
overall expression of solubility takes the form [12]
p
c=
e e
p0
∆Ss/ k −∆Hs/
kT
where ∆S s is the entropy and ∆H s is the enthalpy of solution at temperature T referring to
the H 2 gas pressure p 0 . The relationship is often written in the form
p = K s c, where K s
is called the Sievert’s constant. The values of K s have been experimentally determined
and reported for most hydrides. The p-c diagram of LaNi 5 is given in Figure 1 as an
example.
P (atm)
H/M
Figure 1. Pressure-composition diagram for LaNi 5 [17].
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