Metastable states in multicomponent liquid-solid systems -: II:: Kinetic phase separation

Compositional kinetic phase separation, indicating the simultaneous growth of solid phases with different compositions during the solification of a mixed system, is investigated on the basis of a relatively simple kinetic model. This model, which has been introduced in a previous paper (Los et al. J. Phys. Chem. B 2002, 106), is extended with an additional equation describing the evolution of the growth surfaces for the different solid phases. The kinetic model is applied to multicomponent fat mixtures (as model systems) with a focus on phase separation, and the resulting multiple solid, metastable states are compared with the equilibrium predictions. These calculations provide a qualitative, kinetic picture of compositional phase separation during the growth and reveal clearly the role of the undercooling. The extent of the deviations from the equilibrium state are closely related to the phase separation behavior and to the inhomogeneity in the solid phases. For intermediate undercoolings, the kinetically induced reduction of phase separation goes together with an increased inhomogeneity.