AlF₃ Reactive Al₂O₃ Foam Filter for the Removal of Dissolved Impurities from Molten Aluminum: Preliminary Results


Filters coated with AlF3 can be used to filter molten aluminum to simultaneously remove nonmetallic inclusions and dissolved alkali and alkaline earth metal impurities. Coating experiments were carried out in which anhydrous HF gas was generated from reactions involving NaF or CaF2 and concentrated H2SO4, and used in a reaction with Al2O3 ceramic foam filter to produce a layer of AlF 3 coating on the surface of the Al2O3 filter. Samples from these experiments were studied by X-ray diffraction, scanning electron microscopy and electron probe microanalysis. Preliminary results of the coating experiments showed that it is possible to coat Al2O 3 filters with AlF3 by this method. Increasing the pressure of HF gas increased the yield of AlF3 in the filter. Theoretical evaluation of the removal efficiency of dissolve impurity elements showed that dissolved calcium can be removed up to 99.8% within 30 s of contact time between the filter material and the molten aluminum.


Materials Science and Engineering


Laboratory of Green Process Metallurgy and Modeling
University of Missouri--Rolla. Materials Research Center
Missouri University of Science and Technology. Intelligent Systems Center
Research Board Grant

Keywords and Phrases

AlF3 Reactive Filter; Dissolved Impurities; Filtration; Inclusions; Aluminum

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Document Type

Article - Journal

Document Version


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© 2011 Elsevier, All rights reserved.

Publication Date

01 Feb 2011