The equilibrium partitioning of titanium between Ti3+ and Ti4+ valency states in CaO-SiO2-TiO x slags |
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Authors: | Gabriella Tranell Oleg Ostrovski Sharif Jahanshahi |
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Affiliation: | (1) Process Metallurgy and Ceramics, SINTEF Materials Technology, N-7465 Trondheim, Norway;(2) Present address: the School of Materials Science and Engineering, University of New South Wales, 2052 Sydney, NSW, Australia;(3) CSIRO Minerals, 3169 Clayton South, Victoria, Australia |
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Abstract: | The redox behavior of titanium in CaO-SiO2-TiO x melts was investigated using a slag-gas equilibrium technique. Titanium partitioning between Ti3+ and Ti4+ valency states and the ratio of activity coefficients of TiO1.5 and TiO2 were determined as functions of oxygen partial pressure, temperature, and slag composition. The equilibrium experiments were carried out at temperatures between 1783 and 1903 K under CO-CO2-Ar gas atmosphere with oxygen partial pressure ranging from 10−12 to 10−7 atm (1.01×10−10 kPa to 1.01×10−5 kPa). The slags had CaO/SiO2 ratios between 0.55 and 1.35 and total titanium oxide concentrations from 7 to 50 mass pct. Experimental results showed that the Ti3+/Ti4+ ratio in CaO-SiO2-TiO x slags, containing up to 50 mass pct TiO x , increased with decreasing oxygen partial pressure and decreased with increasing CaO/SiO2 ratio and decreasing temperature. Measured variation of the redox ratio Ti3+/Ti4+ with oxygen partial pressure closely followed the ideal behavior. Increasing the CaO/SiO2 ratio increased the ratio of activity coefficients of TiO1.5 and TiO2. The effect of total titania content on this ratio was more complex and in accord with Raman spectroscopy data. |
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