A solid-state emf study of the Cu-Cu 2 O-NiO three-phase equilibrium
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d G ~ i _ Gc(i) - G~i
dXc
[151
1 - Xc
dG~ _ 0 dXc
REFERENCES
[14]
dG___~j = dG___~j. dXc dNi(j) dXc dNi(j)
[16]
i , j va C
G.W. Toop: Trans. TMS-AIME, 1965, vol. 233, pp. 850-55. C. Colinet: D.E.S., Fac. Sci., Univ. Grenoble, France, 1967. E Kohler: Monatsh, Chem., 1960, vol. 91, p. 738. H. Kehiaian: Bull. Acad. Pol. Sci., 1966, vol. 14, p. 153. Y.M. Muggianu, M. Gambino, and J. P. Bros: J. Chim. Phys., 1975, vol. 72, pp. 83-88. 6. K.J. Jacob and K. Fitzner: Thermochimica Acta, 1977, vol. 18, pp. 197-206. 7. E. Jiran and K.T. Jacob: CALPHAD, 1983, vol. 7, no. 1, pp. 41-50. 1. 2. 3. 4. 5.
Substituting for the multi-component property and the derivative in Eq. [9] and simplifying results in: --E
Cc,Mc)
:
-
E
(x,
+ xj)[c2
E
lvx,
i,j#:C Xi
~
E -
[17]
+ ~ 1 ---Xc [Gc(i)jxc i,c
Equation [17] reduces to Eq. [3] for a ternary system. Partial properties of all other components will obey a different equation due to the asymmetry of the model. The partial property of component m which is not the component whose mole fraction is being held constant in the model (here C) can be obtained by the same procedure though the terms containing binaries in m must be treated separately. The result is: -GEm(MCS) =
--
E ( X i "]i,j~C,m
xj) 2
E
Xi Xc
Y, (x,
m
2 (1 - x c ) i-J-C,m
+
+
x,~)
i#-C,m
1 - x
-- XmXc[ac(m)]Xc,
)[c
c]xc
m =/: C
[181
In addition to the Toop model, three symmetric models are available for the computation of thermodynamic properties of multi-component solutions from binary data: (1) The Colinet model 2 uses paths of constant mole fractions to the binaries. (2) The Kohler modeP uses paths of constant ratio mole fractions to the binaries. Extension of the model to multicomponent systems is given by Kehiaian. 4 (3) The shortest distance composition path model derived by Muggianu et a1.5 and Jacob and Fitzner6 for temary properties and extended to multi-component solutions by Jiran and Jacob. 7 All these models are equivalent and strictly valid for regular solutions, but may be used in a semi-empirical manner for nonregular solutions.
The authors are grateful to the Natural Sciences and Engineering Research Council of Canada for financial support. ll04--VOLUME 17A, JUNE 1986
In assessing the thermodynamic and phase diagram data of the ternary Cu-O-Ni system, it was found that the solubility of Ni in Cu and Cu20 of the three-phase {Cu, CuzO, NiO} region was not known although believed to be small. If this is indeed the case, the emf of a cell having the two electrodes Cu + Cu20 and Cu + Cu20 + NiO will be close to zero. In the present communication, the emf's of the following cells are measured in the temperature range 969 to 1273 K to demonstrate the small solubility of Ni in the Cu and Cu20 phases.
Co, CoO I ZrO2 (+CaO) I Ni, NiO
Xi-oE ] -~[ i(m)]JX,/Xm --E
YONG-ZOO YOU, KER-CHANG HSIEH, and Y. AUSTIN CHANG
Ni, NiO [ ZrO2 (+CaO) I Cu, CuzO
[[2 x
+ (1 -
A Solid-State Emf Study of the Cu-Cu20-NiO Three-Phase Equilibrium
(I) (II)
Co, CoO I ZrO2 (+ CaO) I Cu, CuzO
(III)
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