| Spinodal decomposition of deeply quenched, low-viscosity liquid mixtures has been studied. Observing the phase separation of these liquid mixtures in a small cell, it has been inferred that the process is driven by the convection due to capillary forces, and not by molecular diffusion neither by gravity, heat or surface effects. After quenching a partially miscible critical mixture to a temperature deeply below its critical point of miscibility, the formation of rapidly coalescing droplets of the minority phase, moving in random directions at speeds exceeding 100mum/s, has been observed. This behavior was observed for both density-segregated and density-matched systems, irrespectively whether they were kept in horizontal or vertical cells. Phase separation was very rapid, even in the presence of coalescence retardants.; Spinodal decomposition of an isopycnic system (i.e., a system with a very small density difference between the two phases) has been studied; rapid flows up to 6cm/s in a horizontal direction of a 20cm-long condenser tube have been observed. After droplets formed, they started moving horizontally to a forming interface. After 10 seconds phase separation is complete, resulting in a vertical interface. Depending on which phase was the dispersed, the droplets moved either to the colder or hotter section of the temperature gradient, created unintentionally during the quenching. The results described in this work, show that this horizontal motion is not due to conventional thermo-capillary migration but it is driven by chemical potential gradients.; These results could open up new possibilities for studying flows in a microgravity environment and opportunities for practical applications in separation processes. |
