title: Micro-structure evolution of wall based crystals after casting of model suspensions as obtained from Bragg microscopy.
abstract: 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.
authors.affiliation: University of Mainz, Institute of Physics, Staudingerweg 7, D-55099 Mainz, Germany. Thomas.Palberg@uni-mainz.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Palberg
authors.forename: Martin R
authors.initials: MR
authors.lastname: Maaroufi
authors.forename: Andreas
authors.initials: A
authors.lastname: Stipp
authors.forename: Hans Joachim
authors.initials: HJ
authors.lastname: Schöpe