Thermodynamic properties of Cu–Ni alloys: measurements and assessment

Abstract

The activity of nickel in solid Cu–Ni alloys has been measured at 1000 K using a solid state galvanic cell incorporating calcia stabilised zirconia as the solid electrolyte. The activity of nickel shows positive deviation from Raoult's law over the entire range of concentration. Partial molar entropy of nickel in solid Cu–Ni alloys has been measured directly using a newly developed twin solid state thermocell apparatus. A consistent set of thermodynamic data for the Cu–Ni system has been derived by combining the results of the present study with selected data on enthalpy and free energy of mixing of liquid alloys and the phase diagram. The miscibility gap and the chemical spinodal boundaries obtained from the evaluated data are in good agreement with X-ray and diffuse neutron scattering studies reported in the literature.