Ceramics-Silikáty 39, (3) 92 - 98 (1995)

The effect of SiO₂ on the density and surface tension of Fe₂O₃-FeO-CaO-SiO₂ slag melts was studied at concentrations of up to 10 wt.% SiO₂. The maximum gas bubble pressure method was employed in the measurements. Silica reduces density and surface tension, while increasing the molar volume and statistically mean size of ions present in the ferritic-lime melt. The results showed that the physical properties of slag systems are for the most part influenced by the character of anionic ferric oxide complex compounds. The Fe³⁺ cation can form FeO⁺, FeO₂; Fe₂O₅⁴⁻ and FeO₄⁵⁻ complex compounds with oxygen while possibly also changing oxygen coordination of the iron ions. At the concentrations in question, SiO₂ occurs mostly in the form of SiO₄⁴⁺ tetrahedrons.