Diffusion Coefficients and Structural Parameters of Molten Slags

This paper presents the results of two experimental studies on diffusion of SiO2 in “silicomanganese” (SiO2-MnO-CaO-Al2O3- MgO) slag and CaO in calcium aluminosilicate slag. The diffusivity of SiO2 was measured in the temperature range of 1400-1550 °C; while the diffusivity of CaO was determined at 1430-1600°C. The effects of additives on the chemical diffusivities of SiO2 and CaO were also examined. Addition of CaO and MnO to the silicomanganese slag increased silica diffusivity, while addition of SiO2 and Al2O3 slowed it down. Addition of TiO2 and MnOx to the aluminosilicate slag increased the diffusivity of CaO, while the addition of SiO2 had a negative effect on the diffusivity of CaO. Analysis of diffusivity in relation to the structure of silicate melts demonstrated a good correlation between diffusion coefficients of SiO2 and CaO and NBO/T (non-bridging oxygen per tetrahedrally coordinated atom).