Jacob, Thomas K and Seetharaman, Seshadri (1996) Phase Equilibria, Oxygen Potentials, and Activities in the System Ni-Co-Si-O at 1373 K. In: Journal of the American Ceramic Society, 79 (11). pp. 2815-2820.
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In the system Ni-Co-Si-O, the compositions of coexisting phases participating in two-phase equilibria between the monoxide $(Ni_yCo_{1-y}O)$ and orthosilicate $(Ni_zCo_{1-z}Si_{0.5}O_2)$ crystalline solutions, and alloy $(Ni_xCo_{1-x})$ and orthosilicate phase, have been determined at 1373 K. The samples were equilibrated at 1373 K under argon gas, and the equilibrium compositions of the phases present after quenching were measured by electron probe microanalysis (EPMA). A solid-state cell incorporating yttria-stabilized zirconia as the solid electrolyte was used to measure the oxygen chemical potential corresponding to the three-phase equilibrium between the alloy, orthosilicate solution, and quartz as a function of alloy composition. From these measurements, activity-composition relationships in the alloy and orthosilicate solid solutions have been derived using a new method. Activities in the silicate solution have also been obtained independently using the mixing properties of the rock-salt solid solution available in the literature and the tie-line information obtained in this study. Both methods yield almost identical results. All three solid solution series-alloy, monoxide, and orthosilicate-exhibit mild positive derivations from ideality. The excess Gibbs free energy of mixing of the orthosilicate solid solution $(Ni_zCo_{1-z}Si_{0.5}O_2)$ at 1373 K can be represented by the relation $\Delta GE=(2110 \pm 30)^.z(1-z) J^. mol^{-1}$
| Item Type: | Journal Article |
|---|---|
| Publication: | Journal of the American Ceramic Society |
| Publisher: | John Wiley and Sons |
| Additional Information: | Copyright of this article belongs to John Wiley and Sons. |
| Department/Centre: | Division of Chemical Sciences > Materials Research Centre Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy) |
| Date Deposited: | 31 Aug 2007 |
| Last Modified: | 10 Jan 2012 05:45 |
| URI: | http://eprints.iisc.ac.in/id/eprint/10804 |
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