Non-Newtonian behavior of solid-bearing silicate melts: An experimental study

The non-Newtonian behavior and its mechanism have not been clarified for the solid-bearing silicate melts, leading to difficulties and even errors in estimating silicate melt viscosity. In this study, a typical metallurgical slag was employed as a model system of solid-bearing silicate melt. The flow behavior of the slag was measured via a rotational type rheometer at various shear rates. The results demonstrate that the slags exhibit non-Newtonian behavior for solid fractions exceeding a critical value (Φc, i.e. 0.33-0.40 for the investigated samples), at which an abrupt viscosity increase occurs. Shear thinning (the viscosity decreases with increasing shear rate), thixotropy (a time-dependent shear thinning) and an apparent yield stress of 0.2-74.4 Pa for the investigated samples are the non-Newtonian characteristics observed in this study. The higher the solid fraction, the more pronounced the shear thinning. The shear thinning is mainly attributed to the disruption of crystal clusters. Thixotropic behavior is found to be caused by the irreversible microstructural evolution within the experimental time scale. The apparent yield stress is mainly due to the formation of a solid network and is increased with increasing the solid fraction.