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

Abstract

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 purity mercury at 53.4°C. The results were in excellent agreement with published data. The method is nonintrusive; capable of rapid measurement of the viscosity of toxic, high vapor pressure melts at elevated temperatures. In addition, the transient torque viscometer can also be operated as an oscillation cup viscometer to measure just the viscosity of the melt or as a rotating magnetic field method to determine the electrical conductivity of a melt or a solid if desired.

Thermophysical properties of Hg0.8Cd0.2Te melt: Density, electrical conductivity and viscosity

“…The electrical conductivity and viscosity of Hg 0.8 -Cd 0.2 Te melt were simultaneously determined using a rapid and non-intrusive method -transient torque method [19,20]. The essential feature of this method was the utilization of a rotating magnetic field (RMF) to interact with the melt and generate a rotating Lorentz force.…”

“…When the RMF was applied and the ampoule rotated around its vertical axis, a MicroE optical encoder system was used to measure the angle of ampoule rotation. The electrical conductivity and viscosity of the melt were obtained simultaneously by numerically fitting the data to a set of governing equations [19,20].…”

“…The density of Hg 0.8 Cd 0.2 Te melt as a function of temperature was measured using a pycnometric method in this study. The electrical conductivity and viscosity of the melt were simultaneously determined using the transient torque method developed recently [19,20]. The measured electrical conductivity and the relationship between density and viscosity, based on BachinskiiÕs work [21,22], were used as an indication of the structural change in the Hg 0.8 Cd 0.2 Te melt.…”

Theoretical foundation of electromagnetically-driven oscillating cup viscometer

“…EOC viscometers have been developed to simultaneously measure viscosity and electrical conductivity of liquid metals [1] and molten semiconductors [2,3] at high temperatures. The measurement principle involves a liquid sample that is usually sealed in a cylindrical vessel (usually called a cup) suspended by a fiber that functions as a torsional spring.…”

Numerical analysis of an improved heating device for the electromagnetically driven oscillating cup viscometer

“…A torque equation was obtained for the case where the cup height approaches the thickness of the fluid boundary layer. 3 C Li 4 and C Li et al 5 obtained a set of fitted simultaneous control equations for the conductivity and viscosity of the fluid based on the values of the transient deflection of a sample to which a rotating magnetic field was applied. The viscosity and conductivity of high-purity mercury at 53.4°C were successfully measured.…”