Thermophysical Properties of Dense Molten Al2O3 Determined by Aerodynamic Levitation

Abstract

Aerodynamic levitation (ADL) is a widely used contactless technique for evaluating the thermophysical properties of molten materials. During data analysis, these molten samples are typically assumed to be bubble-free and to adopt an oblate spheroid shape. However, these assumptions have not been empirically validated. The presence of trapped bubbles and potential deformation at the bottom of the levitated sample, which is obscured from view by the levitation nozzle, can lead to an underestimation of the sample's density. These factors could also interfere with the sample's damped oscillation, thereby affecting the reliability of the measured surface tension and viscosity. Consequently, in this study, we address these issues by using smaller alumina samples to minimize sample deformation and by inspecting each sample's cross-section after cooling for trapped bubbles. This approach enabled us to mitigate the impact of these potential distortions on the measured thermophysical properties of molten alumina. Our findings reveal that the density of dense molten alumina can be expressed as 2.917- 1.228x10(-4)(T-2327) [g & sdot;cm(-3) ] from 1978 K to 2789 K. Additionally, between 2375 K and 2770 K, we determined the surface ten-sion of alumina to be 0.632-2.310x10(-5)(T-2327)[N & sdot;m(-1) ] and the viscosity to be 0.577e(9.743x103/T) [m & sdot; Pa & sdot; s].