Density and surface tension of calcium-ferritic slags I.: The systems CaO-FeO-Fe2O3-SiO2 and CaO-FeO-Fe2O3-Al2O3

The density and surface tension of the melts of the quaternary systems CaO-FeO-Fe2O3-SiO2 and CaO-FeO-Fe2O3-Al2O3 was determined using the maximum bubble pressure method. The molar volume, the excess molar volume, and the excess surface tension were calculated on the basis of the obtained data. From the course of these properties the information on the interactions of components and the possible chemical reactions between them were obtained. Due to the low concentration of network forming oxides, isolated SiO44-, AlO45- and FeO45- tetrahedra are formed in these basic melts, the donor of the oxygen atoms being either CaO, FeO, or both CaO+FeO oxides. The observed ternary interactions may be most probably attributed to the formation of the anions SiFeO77- and FeAlO78-, in which one Si atom is substituted by the Fe and/or Al one forming two tetrahedra linked by corner.