2000 Volume 40 Issue Suppl Pages S153-S156
oxygen partial pressure in ambient atmosphere has been considered to affect the surface tension of molten silicon and its temperature coefficient. However, the effect of the oxygen partial pressure on the Marangoni convection, which is driven by the surface tension gradient on a silicon melt, has not yet been made clear through experimentation. The temperature oscillation due to Marangoni convection in the half-zone bridge molten silicon (5 mm in height; 10 mm in diameter) was measured by fine thermocouples in 1-G experiments. We conducted X-ray flow visualization with tracer particles in ambient atmosphere at a variety of oxygen partial pressures in argon gas under microgravity using the parabolic flight of an aircraft. The mode transition from an oscillatory flow with multiple frequencies to that with a single frequency took place when the oxygen partial pressure was increased to PO2=1.8×10-5 MPa. Also, the tracer velocity of the Marangoni convection clearly decreased with increasing oxygen partial pressure under microgravity. These experimental results can be explained by the dependence of temperature coefficient of surface tension of molten silicon on oxygen partial pressure of ambient atmosphere.
