Effect of Surface-Tension Driven Convection on Interfacial Boundary Layer during BaB_2O_4 Single Crystal Growth

Surface-tension driven convection in BaB_2O_4(BBO)melt was visualized by means of a high- temperature in situ observation method,and the streamlines of steady thermocapillary convection was marked in the form of an axially symmetric pattern.Based on the observation of crystal rotation,the widths of interfacial concentration,heat and momentum boundary layers were calculated respectively. The influence of thermocapillary convection on boundary layer thickness was also investigated.Results show that the concentration boundary layer is much thinner than heat and momentum boundary layers, which indicates that mass diffusion plays a dominating role for interfacial transport.Additionally,the width of the boundary layer is decreased with the increasing of dimensionless Marangoni number linearly.