Phase field simulations in miscibility gaps

Abstract

Using phase field simulations, it is possible to simulate the dynamics and morphology of immiscible liquids/solids appearing at the miscibility gap of any system. These simulations may also be used to determine the asymptotic compositions of the fluids for a given Gibbs energy. Even more, it is known that different parameters of the excess Gibbs energy of a certain phase may exhibit different asymptotic morphologies, in spite of the similarity of the associated equilibrium curves. This method can be used to choose the best excess Gibbs energy’ parameters for the liquid (or solid) phase of a system that will suffer spinodal decomposition. It can also be important (like in the sol–gel process) to choose the best composition, temperature and time to obtain a certain wanted morphology, just by means of the Gibbs energy of the respective phase. In this work, we have performed phase field simulations of the two liquid’s separation occurring in the Bi–Zn system, for different temperatures, concentrations and times. We have found a rich diversity of asymptotic morphologies for different points of the Bi–Zn phase diagram. Two different Gibbs energies were used to show how the morphologies will be affected by different parameters of the excess Gibbs energy.