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The effect of MgO, TiO 2 , or Fe 2 O 3 on the viscosity of 40CaO-40SiO 2 -20Al 2 O 3 (mass pct) slags has been measured by the rotating crucible viscometer. Viscosity of these quaternary slags decreased with an increase in the content of additive oxide. At the same content of additive oxide, the viscosity decreases from MgO, TiO 2 to Fe 2 O 3 . In addition, the effect of SiO 2 or Al 2 O 3 on the viscosity of 26.1CaO-73.9Fe 2 O 3 (mass pct) (CF) and 14.9CaO-85.1Fe 2 O 3 (mass pct) (CF 2 ) slags has been measured. Viscosity of calcium ferrite slags increased with increasing SiO 2 or Al 2 O 3 content. Al 2 O 3 was found to be more effective for increasing the viscosity at the same content of the additive oxide.

In the present work, we measured the density and the surface tension of CaO-SiO2-Al2O3-R2O (CaO/ SiO2=0.67, Al2O3=20 mass%, R2O=10.8 mol%, R=Li, Na, K) quaternary melts at elevated temperature using the double-bob Archimedean method and the ring method, respectively.The density of the CaO-SiO2-Al2O3-R2O melts decreased with temperature due to the thermal expansion of the melts. In addition, the density of the CaO-SiO2-Al2O3 ternary melt decreased with the addition of the alkali oxides. We converted the density into the molar volume to have a consideration on the microstructure of the melts. The molar volumes of the CaO-SiO2-Al2O3-R2O melts are proportional to cube of the cationic radius for the alkali ions, which indicates the structural roles of the alkali oxides are mainly charge compensator to AlO4 5-anions. The surface tension of the CaO-SiO2-Al2O3-R2O melts changed only slightly with temperature. The surface tension of the CaO-SiO2-Al2O3 ternary melt increased with the addition of Li2O. In contrast, the surface tension decreased with the addition of Na2O or K2O. As for quaternary system, the surface tension increased with the ionic potential of the additive alkali ions; it is the same tendency with the binary alkali silicate melts. However, the mechanism of the surface tension change with the addition of the alkali oxides has not been clarified in the present study.KEY WORDS: density; surface tension; structure of aluminosilicate melts and glasses; CaO-SiO2-Al2O3 based slags; physical property; alkali oxides; charge compensating cation.

The viscosity and solubility of nitrogen in Y2O3–Al2O3–SiO2 melts have been systematically examined. The effects of nitrogen content on viscosity for Y‐Al‐Si‐O‐N melts and on Vickers hardness of oxynitride glasses also have been examined. Although the viscosity of Y2O3–Al2O3–SiO2 melts was decreased, the solubility of nitrogen into the melts was increased with increased Y2O3 content. These results indicated that the yttrium ion behaved as a network modifier. Therefore, the structural units for viscous flow became small, and the amount of nonbridging oxygen increased in the melts when the Y2O3 content increased. The viscosity of Y‐Al‐Si‐O‐N melts and Vickers hardness of oxynitride glasses remarkably increased with increased nitrogen content. These results suggested that the substitution of nitrogen for oxygen in the melts may have led to a high average coordination of nonmetal atoms and that the increased cross‐linking produced a more rigid glass network.