Thermodynamics of oxygen solutions in liquid Ni, Co, Fe, and Mn metals

Pure gaseous oxygen at a pressure is taken as the standard state of oxygen dissolved in a liquid metal. In the case of such a standard state of oxygen, its activity is equal to the equilibrium oxygen partial pressure in the vapor, which is risen to a power of 1/2. This allowed us, using two thermodynamic functions, i.e., the standard Gibbs energy for the oxidation reaction of liquid metal with oxygen to form a lower oxide and the experimentally determined oxygen solubility in a liquid metal, to obtain equations for the energies of mixing of each metal with oxygen and to calculate them, to find linear temperature dependences of the energies of mixing, and to describe oxygen solutions in liquid metals by pseudoregular-solution model equations. Linear dependences of the solubility functions on the standard Gibbs energies for oxidation reactions of liquid metals are found. The aim of the study is to suggest the energies of mixing of four metals (Ni, Co, Fe, and Mn) with oxygen and their temperature dependences for the calculations of the activity coefficients and the activity of oxygen in the solutions of these liquid metals by the pseudoregular-solution model equations.