Jingqiu Chen

Three-dimensional oscillatory convection of LiCaAlF6 melts in Czochralski crystal growth

Abstract Three-dimensional (3D) unsteady mixed thermal buoyancy, Marangoni and forced convection of LiCaAlF 6 (LiCAF) melts (Prandtl number Pr ≈1.4) are investigated numerically for model set up typically for Czochralski crystal growth. With increasing crystal rotation rate, convection evolves from steady axisymmetric to three-dimensional oscillatory convection with varying spatio-temporal features. The details of the oscillatory convection structures are presented.

Numerical Simulation of the Evolution of Focusing Shock Wave in Extracorporeal Shock Wave Lithotripsy by Using Space-Time Conservation Element and Solution Element Scheme

Extracorporeal shock wave lithotripsy (ESWL) is the most common treatment of kidney stone disease. By firing shock waves at the stone, it can be broken down into small fragments. Although the treatment is non-invasive, both short- and long-term side effects occur. Lithotripsy has been the subject of ongoing research. Various solutions designed to maximize stone comminution and minimize tissue damage have been proposed over the years. However, the particulars of the comminution mechanism are still undetermined. Different types of lithotripters have been approved for clinical use and are classified by the type of shock wave source they utilize, such as, electro-hydraulic lithotripter, piezoelectric lithotripter, electromagnetic lithotripter, etc. ....

Effect of Rotating Magetic Field on Three‐dimensional Instabilities of Thermocapillary Convection under Microgravity

Thermocapillary flow dominates melt convection in floating zone crystal growth under microgravity, and a steady and axisymmetrical thermocapillary flow is helpful for the high quality crystal growth, however thermocap‐illary flow tends to become non‐axisymmetrical and unsteady with increasing grown crystal size. To investigate the convection control by rotating magnetic field (RMF) in semiconductor crystal growth, thermocapillary flow in a three dimensional floating half zone model is simulated. The result indicates the three‐dimensional unstable thermocapillary flow returns to a steady and axisymmetric convection in a proper RMF under microgravity.

Model for Czochralski Crystal Growth

The Czochralski technique is the most widely applied method for the growth of large bulk single crystal. In the Czochralski crystal growth, heat and mass transfer plays an important role in the quality of grown crystal. With the performance improvement of computer, numerical simulation is becoming a more and more important measure for optimizing the conditions of crystal growth. A reasonable model is the premises for a precise numerical experiment of Czochralski crystal growth. In literature, the unbalanced surface tension along the interface of melt-gas is often ignored in the model setup typically for Czochralski crystal growth, and the melt is modeled as the incompressible flow with the Boussinesq approximation. Because of the temperature gradient in melt, the Boussinesq approximation may results in error with the strong centrifugal and Coriolis forces in melt due to crystal and crucible rotation, and a revised model of Boussinesq approximation is proposed. Our result of numerical simulation indicates that ignoring the unbalance surface tension can results in a large deviation in melt convection, especially in the three-dimensional unsteady convection, however, the revised Boussinesq model has no contribution to further improve the precision of numerical simulation under the investigated parameter conditions for 2-inch LiCaAlF6 crystal growth.