Thermal Conductivity of Molten Al, Si and Ni Measured under Microgravity

Abstract

The thermal conductivities of molten Si, Ni, Al and their alloys have been measured by means of the non-stationary hot wire method under 1 G and microgravity of 10 -5 G. A Mo wire was used as the heating wire and coated with alumina by the electrophoretic deposition to prevent an electric current leakage through the melts. Natural convection in the melts was suppressed by measuring the thermal conductivity under the microgravity of 10 -5 G using the drop shaft facility of the Japan Microgravity Center. Moreover, the free surface of the melts was covered with a ceramics plate to prevent Marangoni flow. The thermal conductivity of molten Si is about 10 Wm -1 K -1 , and that of molten Al is 47 Wm -1 K -1 at 1260 K. The thermal conductivity of molten Al-30 mass% Si alloy is about 30 Wm -1 K -1 , and that of molten Ni is 5 Wm -1 K -1 at 1773 K. The thermal conductivities of some molten metals are discussed on the deviation from the Wiedemann-Franz law.