An aerodynamic levitation system for drop tube and quenching experiments

This article describes an aerodynamic levitation system for the processing and study of undercooled insulator materials by drop tube and quenching experiments. Its operation principle relies on a convergent-divergent type aerodynamic levitator made of two halves that can be quickly separated along a plane collinear with gas flow through the action of air-actuated pistons. This article reports the concept of this new levitator and presents the proof of the technical feasibility of contactlessly melting, undercooling, and accurately free falling alumina samples. Short duration microgravity conditions could therefore be accessed with this system for a superheated or undercooled insulator sample. In addition, sample behavior in terms of position stability and rotation was investigated. It was found that tilt of the diffuser permitted sample rotation control. Moreover, experiments showed promise for the control of the cooling rate and the selection of the temperature at which quenching occurs due to the addition of computer-controlled hammer/anvil-type device, from which thin alumina strips were obtained. The paper further highlights the unique advantages of this novel facility and its potential uses for drop calorimetry of refractory or corrosive materials. Finally, it briefly addresses issues that need to be improved, especially in the context of thermophysical properties measurements.