表面张力对流对BaB_2O_4晶体生长界面边界层的作用

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

利用高温光学实时观察方法,实时地观察了BaB_2O_4(BBO)高温熔体的表面张力对流效应以及BBO单晶的旋转生长过程,计算了固液界面附近的浓度、温度以及动量边界层厚度δ_C,δ_T和δ_V,并研究了热毛细对流对边界层厚度的影响.结果发现,浓度边界层厚度远远小于温度以及动量边界层厚度,说明晶体生长过程中,质量扩散在界面输运过程中起着主导性作用,同时发现,边界层厚度随体系无量纲Marangoni数的增大而线性地减小.

Surface-tension driven convection in BaB2O4 （BBO） melt was visualized by means of a hightemperature 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.