A thermodynamic model for determining the surface tension of molten ionic mixtures derived by considering the ionic radii was extended to ternary silicate melts. The composition dependence of the surface tensions of molten silicates in ternary systems, was reproduced by the present model using surface tension information, the molar volumes of pure oxides, as well as the anionic and cationic radii of the component oxides in the system.

The authors investigated the change in the interfacial tension with time for various combinations of molten slag and liquid Fe to elucidate the mechanism of the change in interfacial tension between liquid Fe alloy and molten slag over time accompanying reduction/oxidation reactions. The behavior of the change in the interfacial tension over time can be explained by the adsorption of oxygen at the interface and the diffusion of oxygen from the interface into the bulk of the liquid Fe and molten slag. In addition to that, we found that the interfacial tension decreases slowly and greatly from its initial value to a minimum point and then increases slowly to the final equilibrium state when molten silicate slag with low viscosity is brought into contact with liquid Fe without Al content and some of its SiO 2 decomposes and dissolves into the liquid Fe. From these results, we suggest that the detachment of oxygen adsorbed at the interface into the liquid Fe is very slow and may be the rate-limiting step.

A model to evaluate the viscosity of silicate melts is proposed on the basis of the bonding states of oxygen, i.e. non-bridging oxygen and free oxygen ions, in the silicate structure, considering the flow mechanism of the melts with the network structure. Gaye's model is applied to evaluate the bonding state of oxygen ions using thermodynamic databases. The present model can reproduce the composition dependence of the viscosities for silicate melts in binary systems with a single model parameter, as well as the composition dependence of the viscosities for ternary systems in a wide composition range.KEY WORDS: viscosity; silicate melts; network-structure; flow mechanism.

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