Chemical state of fluorine in fluoroaluminosilicate slags in glassy and molten states from perspective of electronic polarisability

S. H. Firoz, R. Endo, M. Susa

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

The electronic polarisability of F αF has been determined for fluoroaluminosilicate slags from density and refractive index data measured to investigate the chemical state of F in the slags and the effect of CaF 2 additions on depolymerisation of the aluminosllicate network. To simulate commercial mould fluxes, synthetic slags with compositions of xCaF 2-5Na2O-6Al2O3-(89 - x)CaO.SiO 2 were prepared as samples, where x ranged between 5 and 12-5 mol.-%. Densities and refractive indices of the slags were measured in glassy and molten states; for the melts, the sessile drop method and ellipsometry were applied to density and refractive index measurements respectively. Values of αF determined for the slags are on the whole in good agreement with those for CaF2, irrespective of temperature, which suggests that F ions in the slags are in ionic bonding of Ca-F with a possibility of a Na-F bond. However, only a glassy slag with a lower concentration of CaF2 exhibits a slightly smaller αF than CaF2, which would be a sign of Al-F and/or Si-F bonds being produced. From the value of αF, F Ions are likely to terminate silicate anions by forming Ca-F bonds in the slags and depolymerisation of the network by this termination would be responsible for lowering the viscosity of molten slags with CaF 2 additions.

Original languageEnglish
Pages (from-to)437-443
Number of pages7
JournalIronmaking and Steelmaking
Volume34
Issue number5
DOIs
Publication statusPublished - 2007 Sep
Externally publishedYes

Keywords

  • Chemical state of fluorine
  • Density
  • Electronic polarisability
  • Ellipsometry
  • Metallurgical slag
  • Mould flux
  • Refractive index
  • Sessile drop method

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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