|M.Sc Student||Bass Oren|
|Subject||The Impact of Solution Fluid Dynamics on Interface|
Evolution during Crystal Growth from Solution
|Department||Department of Chemical Engineering||Supervisor||Professor Simon Brandon|
|Full Thesis text|
Understanding crystal growth from solution requires a multidisciplinary approach. Relevant topics include solid state chemistry and physics of the growing crystal, chemistry of the liquid solution, interfacial transport and kinetics at the crystal/solution interface as well as the physics underlying fluid flow and mass transport within the liquid (solution) phase. Large-scale numerical analysis has been proved to be a useful tool for understanding the impact of all these topics on the growth process and on the resultant quality of the grown crystal. In particular, details of the process which are very difficult or even impossible to obtain from experiments can be derived from computational analyses.
In this thesis the focus is on the transport of solute from the bulk of the liquid towards the surface of the growing crystal and the kinetics of its incorporation into the crystal lattice. We are particularly interested in the influence of realistic flow fields on the crystal morphology and in the identification of the onset of instabilities leading to defects. Specifically, a computational analysis approach is applied in the study of three-dimensional time-dependent flows, bulk solute mass transport and associated mass transport with interfacial kinetics taking place in the Lawrence Livermore National Laboratory (LLNL) system for rapid growth of potassium dihydrogen phosphate (KDP) crystals. We embrace the approach taken by Weinstein and Brandon, Int. J. Multiscale Comp. Eng. 6 (2008) 585, and references within, for modeling the time-dependent evolution of faceted liquid/crystal interfaces in large-scale melt as well as solution growth systems. This approach involves decoupling between mass transport, which includes flow and concentration fields, and interface motion. The interface motion algorithm is consistent with step-flow and step-source kinetics and depends on the orientation of the interface with respect to the crystal singular faces as well as on the concentration field adjacent to it.
Our results, which characterize the evolution of the interface, are the first to have coupled realistic meso-scopic growth mechanisms and real 3D flow effects in the bulk and on the crystal surface within a large-scale crystal growth system. We have presented quantitative and qualitative evidence of the impact of solution hydrodynamics on the surface evolution at the meso-scale; the forming steps displayed sensitivity to the flow direction and the supersaturation levels in the sense of lateral and longitudinal instabilities.