High Temperature NMR Study of Aluminum Metal Influence on Speciation in Molten NaF-AlF3 Fluorides

Abstract

In situ high temperature NMR spectroscopy has been used to characterize the interactions between aluminum metal and cryolitic melts. (27)Al, (23)Na, and (19)F NMR spectra have been acquired in NaF-AlF(3) and NaF-AlF(3)-Al melts over a wide range of compositions. The evolution of the signals evidence a chemical reaction between the metal and the salt. The different samples have been also described after solidification at room temperature by Environmental Scanning Electronic Microscopy, high resolution solid state NMR, and X-ray diffraction. The combination of in situ high temperature NMR characterization of the melts, with experimental description of solidified samples after cooling, evidence an enrichment of the melts with AlF(3) and different reactions with metallic aluminum depending on the initial bath composition.