Thermodynamic study of solid copper–nickel alloys by use of copper–beta-alumina Original Research Article

Copper–β″-alumina was prepared by ion exchange reactions starting with a sodium–β″-alumina. Exchange from sodium ion to copper ion was done by immersing the sample in liquid cuprous chloride. Exchange of Na+ ion in β″-alumina to Cu+ ion was not complete as Na+ ion remained within the β″-alumina. Copper activity in solid copper–nickel alloys was measured by electromotive force (EMF) technique incorporating the partially exchanged (Cu+–Na+)–β″-alumina as a solid electrolyte for temperatures between 870 and 1300 K. The activities of copper and nickel in the solid solution at these temperatures exhibited positive deviations from Raoultʹs law. The activity coefficients of copper and nickel at infinite dilution at 973 K were estimated to be 5.55 and 3.71, respectively. Furthermore, the free energies, enthalpies and entropies of mixing were derived from EMF data.