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Phase relationships in the system Ni-W-O and thermodynamic properties of NiWO,

Jacob, KT (1977) Phase relationships in the system Ni-W-O and thermodynamic properties of NiWO,. In: Journal of Meterials Science, 12 (8). pp. 1647-1652.

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The phase diagram of the Ni-W-O system at 1200 K was established by metallographic and X-ray identification of the phases present after equilibration at controlled oxygen potentials. The oxygen partial pressures over the samples were fixed by metered streams of CO+CO2 gas mixtures. There was only one ternary oxide, nickel tungstate (NiWO4), in the Ni-W-O system at a total pressure of 1 atm, and this compound decomposed to a mixture of Ni+WO2.72 on lowering the oxygen potential. The Gibbs' free energy of formation of NiWO4 was determined from the measurement of the e.m.f. of the solid oxide galvanic cell, Pt, Ni+NiWO4+WO2.72/CaO-ZrO2/Ni+NiO, Pt and thermodynamic properties of tungsten and nickel oxides available in the literature. For the reaction, NiO(s)+WO3(s)rarrNiWO4(s) DeltaG°=–10500–0.708 T (±250) cal mol–1.

Item Type: Journal Article
Publication: Journal of Meterials Science
Publisher: Springer
Additional Information: Copyright of this article belongs to Springer
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 31 Dec 2010 07:41
Last Modified: 31 Dec 2010 07:41
URI: http://eprints.iisc.ac.in/id/eprint/34733

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