The heterogeneous crystallization of colloidal suspensions of Yukawa particles on a wall was observed by Bragg microscopy. The growth velocity V~lo of the fluidcrystal interface can be very well described by a Wilson-Frenkel growth law, while the limiting velocity is found to be lower than in previous investigations. Twinned bcc domains in lateral direction (parallel to the wall) and their ripening behavior are for the first time investigated systematically. A strong anisotropic growth behavior is found: in the direction of the shear flow, which shear melts the suspension prior to the crystallization process, the extension of the domains is much larger than perpendicular to that. The increase in domain size for short and intermediate times is found to follow a Lifshitz-Allen Cahn ripening law, while unexpectedly for long times the ripening halts and the size of the domains remains constant.
Nucleation and crystal growth in a suspension of charged colloidal silica spheres with bi-modal size distribution studied by time-resolved ultra-small-angle X-ray scattering The Journal of Chemical Physics 141, 214906 (2014) Growth of heterogeneously nucleated, wall based crystals plays a major role in determining the micro-structure during melt casting. This issue is here addressed using a model system of charged colloidal spheres in deionized aqueous suspension observed by Bragg microscopy which is a combination of light scattering and microscopy. We examine the evolution of the three-dimensional size, shape, and orientation of twin domains in monolithic crystals growing from two opposing planar walls into a meta-stable (shear-) melt. At each wall crystal orientation and twinning emerges during nucleation with small domains. During growth these widen and merge. From image analysis we observe the lateral coarsening velocities to follow a power law behaviour L XY ∝ t 1/2 as long as the vertical growth continues at constant speed. Lateral coarsening terminates upon intersection of the two solids and hardly any further ripening is seen. Initial lateral coarsening velocities show a Wilson Frenkel type dependence on the melt meta-stability.
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