Thermal measurement of Ostwald ripening kinetics in partially crystallized mixtures

Experiments were performed to measure the Ostwald ripening kinetics of partially crystallized solid-liquid mixtures. A precision thermometric system was constructed which was capable of measuring curvature dependent solid-liquid interfacial temperatures. Direct, in situ measurements of the interfacial temperatures of partially crystallized solid-liquid mixtures were then made over a range of volume fractions solid, f{hook}_v (0.24 < f{hook}_v < 0.87). Results show that power law coarsening kinetics were present, with a coarsening rate exponent, n, in the range 0.33 < n < 0.4 over all volume fractions studied. Theoretical modeling of the temperature of a thermal probe immersed in a solid-liquid mixture was undertaken to quantify the experimental approach. Theory shows that the thermometers employed in these experiments sensed a temperature reflecting the local distribution of curvature and not that representative of the average curvature of the two-phase coarsening medium. Since the theory employed here is based upon a solution to the diffusion equation, specific predictions can be made concerning the relationship of the mean temperature of a coarsening solid-liquid mixture to the mixture's interfacial morphology, as well as on experimental requirements needed to permit proper measurement of the mean temperature during coarsening.