Interfacial Energy in Phase Separated Borate and Silicate Systems

ABSTRACT

Liquid–liquid immiscibility occurs in binary silicate and borate systems. The kinetics of phase separation in these systems is a complex phenomenon that requires accurate knowledge of thermodynamic state functions and interfacial energy. Since it is difficult to determine this property experimentally, theoretical models are necessary. To compute the interfacial energy, the molar Gibbs free energy is determined using a Redlich–Kister excess potential for 14 binary systems with monotectic lines or metastable solvus miscibility gaps. The thermodynamic data are assessed by determining the critical conditions and miscibility gap for each system. The interfacial energy is determined from the thermodynamic balance occurring at the interface between two separated phases. The dependence on the reduced temperature, , is then determined. A clear difference emerges between systems with liquid–liquid phase separation and those with subliquidus phase separation. The dependence on the ionic potential is established for which the effect of network modifiers and formers are similar to the behavior observed for the surface tension of oxide liquids in contact with an atmosphere. Interfacial energies for binary borate systems obtained by the thermodynamic model are similar to recent experimental data obtained for immiscibility liquids.