Characterization of a mould flux glass

A simplified mould flux glass composition used for the continuous casting of steel was synthesized and then characterized using X-ray powder diffraction (XRD) differential thermal analysis (DTA) and F-19 and Si-29 magic angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR). DTA showed the glass to have a low glass transition temperature and to crystallize readily, at 600degreesC. XRD of the heat-treated glass showed it to crystallize to cuspidine. 19F MAS-NMR showed the principal fluorine species, to be F-Ca(n) with no evidence of Si-F or Al-F species. Fluoride ions therefore. complex calcium in this glass. rather than forming non-bridging fluorines. The network connectivity of the glass was calculated on this basis and found to be 2.07 this would be expected to correspond to a Q(2) Si species which was supported by the 29 Si data that gave a chemical shift of -78ppm corresponding to Q(2) Si. (C) 2004 Published by Elsevier B.V.