Surface tension measurement using sample rotation combined with electrostatic levitation

In order to measure the surface tension of high temperature melts with high viscosity, a sample rotation method was developed. An electrostatically levitated melt was spun with a rotating magnetic field, and the shape evolution of the sample was observed. Especially, the bifurcation behavior (shape transformation from axisymmetric to non-axisymmetric) was closely monitored by a high speed camera. The experiments confirmed that the rotation frequency at the bifurcation could be precisely measured by monitoring the fluctuation of the power of the beam of a He-Ne laser reflected at the sample surface, and thus, the surface tension could be calculated based on the theory by Brown and Scriven. The validity of this measurement technique was demonstrated with ZrCoAl bulk glass forming alloy.