Effect of Droplet Distortion on Surface Tension in Electromagnetic Levitation Method

Abstract

The surface tension of molten Si was measured using the electromagnetic levitation method under a microgravity condition. The experiments were carried out over a wide temperature range between 1460K (below the melting point) and 1880K. The atmosphere was Ar+3%H₂ purified by Platinum asbestos and magnesium perchlorate. The oxygen partial pressure is estimated to be at least than 1.1×10^-14Pa. The shape of the droplet is controlled by changing the output ratio for two different coils. The equilibrium shape of the oscillating droplet was precisely determined by calibrating the apparent change in the droplet shape. The effect of the droplet distortion on the shift in the oscillation frequencies and the calculated surface tension value was also investigated. When the equilibrium shape of the levitating droplet is spherical, the surface tension of molten Si was obtained with very small scatter. The value is expressed as follows: γ=-0.074(T-1687)+735γ: Surface tension (mN/m), T: Temperature (K).