Thermodynamics of Nickel‐Aluminum‐Oxygen System Between 900 and 1400 K

Abstract

Equilibrium oxygen pressures of the univariant systems , and were determined between 1123 and 1423 K using galvanic cells with calcia‐stabilized zirconia as the solid electrolyte. Slipcast tubes of a two‐phase mixture of were used as electrolyte in cells to determine the equilibrium oxygen pressures of the univariant between 923 and 1173 K and the dissociation pressure of equilibrated with (Ni‐Al) alloys containing 0.17, 1.19, and 2.36 atomic percent Al at 1213 K. The free energy of formation of was determined between 923 and 1423 K. An electron probe microanalyzer was used to determine the composition of oxides and alloy phases of the ternary Ni‐Al‐O system that coexist with each other at 1273 K. The Ni‐Al‐O isotherm at 1273 K and Ni‐Al‐O equilibrium oxygen pressure diagrams at 1213 and 1273 K are presented.