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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 additi...

This article describes a hybrid electrostatic–aerodynamic levitation furnace for the containerless processing and study of oxide materials on the ground. Its operation principle relies on an aerodynamic levitator that allows sufficient electric charge to be accumulated on a sample, due to high-temperature heating, before electrostatic levitation can be effective. The article discusses the concept of this new levitator and presents the proof of the technical feasibility of electrostatically levitating and melting oxide material samples (BiFeO3, 49.5CaO–50.5Al2O3 mol %) in a pressurized atmosphere. In addition, superheating–undercooling cycles can be performed while maintaining an exceptional sample positioning stability along the three directions. Moreover, we report the first vitrification of dielectric oxide material samples (49.5CaO–50.5Al2O3 mol %) using an electrostatic levitation method. The article also discusses the advantages of this facility compared with other existing instruments for the contai...

Two new methods that substantially ease the processing and study of refractory metals, when an electrostatic levitation furnace is used, are reported. The first technique is concerned with preheating the sample on a pedestal, prior to launch, to a temperature (∼1500 K) at which thermionic emission dominates all other charging/discharging mechanisms that may be going on simultaneously. Launched into levitation at that temperature, the sample can be quickly heated to its molten state without encountering further charge loss problems. This procedure thus shortens substantially the time it takes to bring the samples to their final high temperature states at which their thermophysical properties can be measured. This technique can be applied to most materials whose melting temperatures are higher than their thermionic temperatures. The second technique described is an ultraviolet-based sample imaging configuration. Due to the excellent sample–background contrast it continuously provides during all phases of pr...

Accepted: 2008-12-29, 資料番号: SA1000898000