R.N. Scripa

Transient torque method: A fast and nonintrusive technique to simultaneously determine viscosity and electrical conductivity of semiconducting and metallic melts

A transient torque method was developed to rapidly and simultaneously determine the viscosity and electrical conductivity of liquid metals and molten semiconductors. The experimental setup of the transient torque method is similar to that of the oscillation cup method. The melt sample is sealed inside a fused silica ampoule, and the ampoule is suspended by a long quartz fiber to form a torsional oscillation system. A rotating magnetic field is used to induce a rotating flow in the conductive melt, which causes the ampoule to rotate around its vertical axis. A sensitive angular detector is used to measure the deflection angle of the ampoule. Based on the transient behavior of the deflection angle as the rotating magnetic field is applied, the electrical conductivity and viscosity of the melt can be obtained simultaneously by numberically fitting the data to a set of governing equations. The transient torque viscometer was applied successfully to measure the viscosity and electrical conductivity of high pur...

Thermophysical properties of liquid Te: Density, electrical conductivity, and viscosity

The thermophysical properties of liquid Te, namely, density, electrical conductivity, and viscosity, were determined using the pycnometric and transient torque methods from the melting point of Te (723 K) to approximately 1150 K. A maximum was observed in the density of liquid Te as the temperature was increased. The electrical conductivity of liquid Te increased to a constant value of 2.9×105Ω−1m−1 as the temperature was raised above 1000 K. The viscosity decreased rapidly upon heating the liquid to elevated temperatures. The anomalous behaviors of the measured properties are explained as caused by the structural transitions in the liquid and discussed in terms of Eyring’s [A. I. Gubanov, Quantum Electron Theory of Amorphous Conductors (Consultants Bureau, New York, 1965)] and Bachinskii’s [Zh. Fiz.-Khim. O-va. 33, 192 (1901)] predicted behaviors for homogeneous liquids. The properties were also measured as a function of time after the liquid was cooled from approximately 1173 or 1123 to 823 K. No relaxa...

Crystal growth of selected II–VI semiconducting alloys by directional solidification: Part I Ground-based experiments

A series of Hg0.84Zn0.16 Te crystal ingots have been grown from pseudobinary melts by the Bridgmam–Stockbarger type directional solidification using a Marshall Space Flight Center/Space Science Laboratory heat-pipe furnace and the ground control experiment laboratory furnace of the crystal growth furnace which was flown on the first United States Microgravity Mission. A number of translation rates and a series of hot- and cold-zone temperatures were employed to assess the influence of growth parameters on the crystal properties for the purpose of optimizing the in-flight growth conditions.