Thermodynamic Properties and Phase Equilibria in the CaF_2-SiO_2-Al_2O_3-CaO System: Ⅲ. Thermodynamic Properties of CaO-SiO_2-Al_2O_3 Melts

摘要

Knudsen effusion measurements combined with mass spectrometry of vapor species were used to study reactions of CaO-SiO_2-Al_2O_3 melts with niobium, tantalum, and molybdenum, leading to the formation of volatile suboxides. The CaO-SiO_2-Al_2O_3 melts were studied in the composition ranges 5.3-75.4 mol /100 SiO_2, 0-29.5 mol /100 Al_2O_3, and 12.6-66.9 mol /100 CaO at temperatures between 1634 and 1841 K. The results Are used to calculate silica activities in the melt. The experimental data are compared with the values obtained By extrapolating the thermodynamic properties of CaF_2-SiO_2-Al_2O_3-CaO melts to the CaO-SiO_2-Al_2O_3 side of the composition triangle and with the data available in the literature.