Simulation of radial solute segregation in vertical Bridgman growth of pyridine-doped benzene, a surrogate for binary organic nonlinear optical materials

摘要: We present steady axisymmetric computations of solute distributions and radial segregation for vertical Bridgman growth pyridine-doped benzene, a binary aromatic system with anisotropic solid-phase thermal conductivity, that serves as model transport in crystal organic nonlinear optical materials. The variation mass fraction (Cs) pyridine, which is rejected at the growing interface, depends strongly on conditions. High velocities tend to increase Cs near centerline, ampoule wall, or both, low give more nearly uniform distributions. maximum ampoule-wall temperature gradient also affects segregation, convex-to-the-liquid interfaces small gradients being associated radially monotonic distributions, ridged higher nonmonotonic having maxima centerline wall. Nonuniformity determined by both interface shape nature flow interface. Solute transported down large toroidal vortex, swept inward second, flattened cell. When depressed its junction accumulates overlying liquid, where convection relatively weak, resulting local enrichment solid. Computations normal zero gravity show two very similar shapes, distribution wall shape, while sweeping vortical significantly whether account taken anisotropy conductivity. Finally, provide guidance minimum length required produce an axially over least part boule.