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Solubility of some transition metal oxides in cryolite-alumina melts: Part II. Solubility of TiO2 |
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| Authors: | Trond E Jentoftsen Odd-Arne Lorentsen Ernest W Dewing Geir M Haarberg Jomar Thonstad |
| Affiliation: | 1. Hydro Aluminium AS, Technology Centre ?rdal, NO-6882, ?vre ?rdal, Norway 3. Norsk Hydro ASA, Research Centre, NO-3907, Porsgrunn, Norway 5. 648 Pimlico Pl., K7M 5T8, Kingston, ON, Canada 4. the Department of Materials Technology and Electrochemistry, NTNU, NO-7491, Trondheim, Norway |
| Abstract: | The solubility of TiO2 in cryolite-alumina melts at 1020 °C was measured; it decreased with increasing alumina concentration up to ∼3.5 wt pct total oxide and then increased at higher alumina concentrations. The solubility was found to be 3.1 wt pct Ti in cryolite, and 2.7 wt pct Ti in an alumina-saturated melt. Modeling indicated that the most probable titanium species are TiOF2 and Na2TiO3, which coexist in the solution; the former dominates at low alumina concentrations and the latter at high alumina concentrations. Additional unknown amounts of fluoride may also be associated with these species. Determination of the solubility of TiO2 in alumina-saturated melts as a function of temperature showed that the solubility increased from 1.9 wt pct Ti at 975 °C to 2.8 wt pct Ti at 1035 °C, the apparent partial molar enthalpy of dissolution of TiO2 being 88±4 kJ mol−1. |
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