Aerodynamic levitator furnace for measuring thermophysical properties of refractory liquids

Abstract

The development of novel contactless aerodynamic laser heated levitation techniques is reported that enable thermophysical properties of refractory liquids to be measured in situ in the solid, liquid, and supercooled liquid state and demonstrated here for alumina. Starting with polished crystalline ruby spheres, we show how, by accurately measuring the changing radius, the known density in the solid state can be reproduced from room temperature to the melting point at 2323 K. Once molten, by coupling the floating liquid drop to acoustic oscillations via the levitating gas, the mechanical resonance and damping of the liquid can be measured precisely with high-speed high-resolution shadow cast imaging. The resonance frequency relates to the surface tension, the decay constant to the viscosity, and the ellipsoidal size and shape of the levitating drop to the density. This unique instrumentation enables these related thermophysical properties to be recorded in situ over the entire liquid and supercooled range of alumina, from the boiling point at 3240 K, until spontaneous crystallization occurs around 1860 K, almost 500 below the melting point. We believe that the utility that this unique instrumentation provides will be applicable to studying these important properties in many other high temperature liquids.

Electrochemical Study of a Pendant Molten Alumina Droplet and Its Application for Thermodynamic Property Measurements of Al-Ir

“…While these methods are currently preferred for measuring structure, 10,11,25,26 total conductivity, 21 density, viscosity and surface tension 24,27 or even integral thermodynamic properties, 28 the sample size is necessarily small (1-4 mm) and each method is limited to their respective subset of compatible atmospheres (e.g. vacuum only for electrostatic levitation).…”

“…Given the likelihood of contamination of the refractory melts at UHT, containerless approaches are preferred, such as electrostatic, 19 aerodynamic [20][21][22] or acoustic 23,24 levitation techniques. While these methods are currently preferred for measuring structure, 10,11,25,26 total conductivity, 21 density, viscosity and surface tension 24,27 or even integral thermodynamic properties, 28 the sample size is necessarily small (1-4 mm) and each method is limited to their respective subset of compatible atmospheres (e.g.…”

Viscosity and liquidus‐based predictor of glass‐forming ability of oxide glasses

“…As a complementary test, we added 35 glasses for which the R c were experimentally determined (by different authors, using distinct methods) and the viscosities and liquidus temperatures are known. Finally, we also added an extremely poor oxide glass former, Al 2 O 3 , for which the viscosity and liquidus temperature are known . The R c for Al 2 O 3 is not known for the conditions we considered ( N S = 10 3 and X S = 10 −2 ), therefore we added the calculated Jezica value over the expected trend line.…”

Mixed alkaline‐earth effects on several mechanical and thermophysical properties of aluminate glasses and melts

“…Using the ALF, we measured the thermophysical properties, such as viscosity, density, and surface tension, of both the thermodynamically stable and metastable supercooled liquids following the procedures described elsewhere . To ensure the measurement accuracy of the above‐mentioned properties at lower temperatures (ie, in the supercooled region), we used a 80 W laser (for heating the sample from top) and a 40 W Laser (for heating from bottom), instead of the two 125 W CO 2 Lasers used in a previous work . By coupling the molten drop to acoustic vibrations via the levitating gas, controllable forced oscillations and can be realized.…”

“…Furthermore, as aluminates are extremely poor glass formers and have much higher melting points compared with silicates, their viscosity, density, and surface tension in liquid states are very difficult to measure when using conventional container techniques. However, with the rapid development of containerless aerodynamic laser heated levitation techniques, it has become possible to determine the thermo‐physical properties of thermodynamically stable and metastable (supercooled) melts of aluminates and other refractory systems. In this work, we used an advanced laser‐heated aerodynamic levitator to investigate the mixed Ca‐Sr effects on viscosity, surface tension, and coefficient of thermal expansion of aluminate melts.…”