The Study for the Improvement of Crystallization Process

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In a Czochralski crystallization process, the melt convection has been known to affect the quality of a crystal rod produced. This project aims to clarify transport processes in this system. The flow modes of Czochralski convection was visualized with liquid crystal powder in silicone oil in a cylindrical enclosure heated from surroundings and cooled from a rotating cylinder located on the surface of silicone oil. Two fluctuating flow modes were found to prevail depending on Gr/Re^2. One mode gives downward flow and another one upward flow in a central core of a cylindrical enclosure. In the theoretical analysis, quasi three-dimensional mixed convection with an axial or lateral directional magnetic field was modeled and solved numerically and clarified the effect of external force fields. With a miniature crystallization experimental apparatus, metallic tin (Sn) was melted and solidified in a long rod successfully after many trials.