Electromagnetic Levitation (EML) at Auburn University

Electromagnetic levitation (EML) is a mature technology that uses high frequency induction current to position and heat conductive samples.  In EML, eddy currents are induced in an electrically conductive sample subjected to high-frequency, alternating electromagnetic fields.  The induced eddy currents provide both Joule heating of  the sample and mechanical forces due to coupling of the induced eddy currents with the applied electromagnetic fields.  The induction coil used in the Auburn University device is of the  quadrapole design (i.e., upper coil opposing the bottom coil) so that a stable energy well is produced between the coils.  

 

Graduate research assistant Baojian Guo has studied the density of molten metals containerlessly positioned and melted in the electromagnetic levitator at Auburn University.  Now Mr. Guo is applying the modulation power method to EML.  In this application, the electromagnetically heated and levitated sample is exposed to a slowly varying, sinusoidally-modulated heating power. The temperature response of the levitated sample will slightly lag behind the imposed power profile depending upon the thermal inertia of the sample.   If an appropriate power modulation frequency is chosen and if the sample’s emissive properties are known (see below), the unknown specific heat can be determined.

 

Graduate research assistant George Teodorescu is using Fourier transform infrared spctroscopy  (Perkin Elmer Spectrum GX FTIR) to investigate the surface radiative properties of samples processed in the electromagnetic levitator at Auburn University.   The spectral-directional emittance measurements from high temperature metallic surfaces are compared with the emittance from a calibrated black-body radiator to yield the optical constants characteristic of the unknown surface.  The total hemispherical emissivity can then be calculated using well established theoretical relationships.