Thermophysical Property Measurement of Molten Semiconductors: Preparatory Work for SEMITHERM Program

摘要

In the course of preparatory work for the SEMITHERM program, thermophysical properties of molten silicon, such as density, surface tension, thermal conductivity and total hemispherical emissivity, were successfully measured on earth using electromagnetic levitation. By superimposing a static magnetic field with electromagnetic levitation, the thermal conductivity of molten silicon was measured by an AC (alternative current) calorimetry for the first time through suppression of convective heat transfer within a droplet; a molten silicon droplet behaves, as if it were solid from the viewpoint of heat transfer. Superimposition of a static magnetic field strongly reduced uncertainty of density because an axisymmetric droplet shape was assured. The superimposition of a static magnetic field shifts the surface oscillation to a higher frequency; a new theoretical approach is required to understand surface oscillation in a static magnetic field, so as to calculate surface tension.