SPINODAL DECOMPOSITION UNDER CONFINEMENT

The spinodal decomposition of a simple fluid or binary alloy is studie d within the Cahn model of conserved order parameter for a slab geomet ry generated by competing walls. We restrict our calculations to short -range surface forces and consider parameter values that correspond to both nonwet and wet equilibrium states. We find that, after a rapid d evelopment of thin films at the walls, phase patterns form. and grow i nto lamellar-like domains parallel to the wall surfaces. The stabiliza tion of this geometry allows for the study of the later stages of phas e separation through the use of the associated dynamical-system phase portraits of the nonlinear problem characteristic of descriptions of i nhomogeneities in one spatial direction. We observe that coarsening in the late stage slows down markedly and comes to a standstill because the driving force for the kinetic equation vanishes almost everywhere for the layered structure. The infrequent coarsening events at long ti mes can be monitored via the accompanying large and clearly defined di sjoining pressure peaks.