An associated solution model was developed for describing the concentration dependence of the specific heat capacity of a liquid alloy at constant pressure,
Ctp.
Using an ideal associated solution model (IASM), the following equation is derived.
(This article is not displayable. Please see full text pdf.)
where the subscript
i is a number given to each species in the A-B binary liquid alloy consecutively, and all the species are expressed by the molecular formula, A
piB
qi: A
p1B
q1(
i=1:
p1=1,
q1=0) and A
p2B
q2(
i=2:
p2=0,
q2=1) show monomers, A
1 and B
1, respectively, and A
piB
qi(
i≥3:
pi,
qi=1,2,3—) shows associated compounds;
xi,
Cip and Δ
Hi° denote the molar fraction of the
i’th speices, the molar specific heat capacity at constant pressure of the
i’th speices, and the standard enthalpy of formation of the associated compound, respectively. The first term on the right-hand side in Eq.(1) indicates the additivity of molar specific heat capacity (Neumann-Kopp’s rule). On the other hand, the second term is caused by the heat of dissociation of associated compounds, since ∂
xi\ominus⁄∂
T is a function of ∂
xi⁄∂
T. ∂
xi⁄∂
T can be calculated by IASM. Then, Δ
Ctp(=
Ctp−
XAC1p−
XBC2p) was calculated for the alloy system with one associated compound, A
lB
m (AB, AB
2, or A
2B
3 (
i=3)), assuming the
C3p=
l·
C1p+
m·
C2p, where
XA and
XB and the mole fraction of A and B in the bulk alloy. The calculated results of Δ
Ctp are shown graphically as a function of
XB, and the effects of Δ
H3° and
K3 on Δ
Ctp are discussed, where
K3 is the equilibrium constant of formation reaction of A
lB
m.
The observed specific heat capacity of the Cd-Sb System were analysed assuming the associated compounds CdSb and Cd
4Sb
3. The calculated specific heat capacities agree well with the observed values.
抄録全体を表示