Domain growth in the presence of quenched disorder

We describe the results of experiments investigating the growth dynamics of domains which form spontaneously in a portion of the one-phase region of a binary fluid mixture in the presence of quenched disorder. Dilute silica gels imbibed with mixtures of isobutyric acid and water were pressure quenched from an equilibrium one-phase state to a region of the phase diagram lying within the coexistence curve of the pure, or gel-free, system, but outside the coexistence curve of the gel-mixture system. Small-angle light-scattering measurements revealed a ring of scattered light which appeared at large scattering wave vectors and evolved to smaller scattering wave vectors in a manner consistent with $t^{1/3}$ domain growth; no evidence of domain pinning was observed during the first 1000 s following a quench. Furthermore, most measurements were consistent with dynamic scaling behavior. An unexpected feature of this system was the rapid growth of long-wavelength fluctuations immediately following the quench.