Transport modes during crystal growth in a centrifuge

Abstract

A fully nonlinear three-dimensional numerical model for a centrifugal crystal growth experiment is presented. The model includes ampoule geometry and the experimentally obtained thermal profiles for the inner furnace steel cartridge insert. Results are presented based on both steady-state and fully transient models. The flow modes are presented resulting from Coriolis effects and from average resulting acceleration and the acceleration gradient, both acting on radial and axial thermal gradients. Thus far the model has been used to simulate growth at a particular experimental g equal to the value at which non-convective type impurity profiles were obtained. The flow modes resulting from different combinations of these forces can be of the same order of magnitude and interact with one another. The importance of the gradient acceleration is determined by the value of a new nondimensional number, called Ad. Thus, Coriolis effects and g gradients may have to be included in the model in order to obtain physically meaningful results. Implications of the resulting flow and thermal fields on the growing crystal at conditions available during centrifuge processing are also discussed.