Contact angle of sapphire melt and bubble generation on crucible material

Abstract

Contact angles of sapphire melt on tungsten (W), tungsten–molybdenum alloy (W–Mo), and molybdenum (Mo) test pieces were observed. The contact angles were 30.1±3.8°, 27.5±4.2°, and 23.5±3.2° for W, W–Mo, and Mo, respectively. Bubbles were generated only in the sapphire melt on W test piece. The contact angle of bubbles on W test piece was 31.2±4.9°. Because of the large contact angle of sapphire melt, bubbles were generated in the sapphire crystal grown in W crucible. The contact angles of water and formamide were also measured at room temperature in order to calculate the specific surface free energy (SSFE). The contact angles of water were 60.0±4.2°, 56.7±4.9°, and 50.2±4.9° on W, W–Mo, and Mo, respectively. The contact angles of formamide were 44.9±3.0°, 40.7±2.9°, and 37.7±4.0° on W, W–Mo, and Mo, respectively. The SSFEs were calculated as 46.3±3.0, 48.8±2.5, and 52.5±2.0mN/m for W, W–Mo, and Mo, respectively.