The equilibrium potentials of Ni–Ln alloys over the whole composition range in the phase diagram: experiment and prediction

Abstract

The phase diagrams and equilibrium potentials of complex systems are of great importance for the material development and processing optimization. The phase diagram mainly describes the composition of the substance in equilibrium, and the relationship between the phase and external conditions (such as magnetic field, electric field, temperature and pressure). The essence of equilibrium potentials lies in that it is the reference condition for the electrolytic production of various component alloy compounds. At present, the research work of the alloy phase diagrams mainly focuses on the construction of binary systems that are extremely important for these practical applications. The knowledge of the influencing factors (concentration) of the binary alloy phase composition and its equilibrium potential are essential for understanding the alloy phase formation processes. This paper outlines a simple scheme for obtaining the binary alloy phase types from the open-circuit chronopotentiometry data. The scheme consists of determining the specific alloy phase composition of each platform in open-circuit chronopotentiometry by thermodynamic calculation; the three-dimensional phase diagrams of atomic percentage, equilibrium potential and alloy composition were established by deriving a mathematical equation from the sorting and summarizing of the data. Such relationships have been examined for the Ni–Ln (La, Ce, Pr, Nd and Gd) systems, and have shown quite a good agreement between the results and experiment. The value of the three-dimensional phase diagram is that it is easy to understand the formation conditions of different binary alloy phases, which will greatly promote the development of high temperature electrolysis technology.