Influence of Li₂O on the Viscous Behavior of CaO–Al₂O₃–12 mass% Na₂O–12 mass% CaF₂ Based Slags

Abstract

The viscous behavior of the CaO–Al₂O₃–12 mass%Na₂O–12 mass%CaF₂ based slag system with various concentrations of Li₂O has been studied using the rotating spindle method to understand the effects on the viscosity with these additives. Li₂O additions up to 1 mass% significantly lowered the viscosity by breaking the [AlO₄]-tetrahedral network structure of molten fluxes, but Li₂O concentrations above this level was comparatively less effective in lowering the viscosity. The viscosity was lower at higher temperatures and from an Arrhenius relationship, the activation energy was calculated to be between approximately 180 to 190 kJ/mol. Fourier Transform Infra-Red (FTIR) analysis of as-quenched slag samples showed the characteristic Al–O stretching vibration in the wavenumber of 800 cm^–1 and 660 cm^–1. Slags with higher viscosity showed a slightly wider trough near the 800 cm^–1 and 660 cm^–1 Al–O stretching bands. XPS analysis of slags with various concentrations of Li₂O indicated the fraction of bridged oxygen (O^o) decreased and the non-bridged oxygen (O^–) increased with higher concentrations of Li₂O. Li₂O additions up to 1 mass% significantly decreased the bridged oxygen fraction, which seem to correlate well with the viscosity measurements.