Spinodal decomposition of a binary fluid with fixed impurities

The phase separation dynamics of a binary fluid containing randomly distrib uted fixed impurities is studied in two dimensions (d=2). The impurities ac t as osmotic force centers and favor one component of the fluid. We found, as expected, that hydrodynamic flow promotes the coalescence of the domains in the early stage of phase separation; at later stages for sufficiently h igh particle density and strong preferential interaction strength, the doma in growth slows down and finally is pinned at a finite domain size independ ent of the hydrodynamics. The density of impurities in the unfavorable phas e is shown to satisfy a scaling form involving the total impurity density n (0) and the ratio R/R-0 with R the domain size and R-0=n(0)(-1/d) the avera ge distance between the impurities. (C) 2001 American Institute of Physics.