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Lecture

The MgO-TiO2 and Al2O3-MgO-TiO2 system: experiments and thermodynamic assessment

Thursday (27.09.2018)
15:00 - 15:15 S1/01 - A01
Part of:


The Al2O3-MgO-TiO2 system obeys interesting properties important for industry: MgAl2O4-based materials have a good combination of physical and chemical properties such as high refractoriness, high mechanical strength, and high resistance to chemical attack, while the Al2TiO5 addition improves the thermal shock resistance of alumina-rich magnesium aluminate spinel. Thus, the aim of the work is to derive the thermodynamic description of the Al2O3-MgO-TiO2 system which is also important for steel making processing and Al alloy melt filtration. Samples were prepared by a sol-gel method followed by annealing experiments. For the MgO-TiO2 system: structural analysis was done by XRD, which detected the formation of Mg2TiO4 and MgTi2O5 from oxides at 1150 and 650°C, respectively. Following results were obtained using DTA and SEM/EDX: MgTi2O5 melts congruently at 1667°C, peritectic reactions with formation of Mg2TiO4 and MgTiO3 occur at 1767 and 1636°C, respectively. Two eutectics were observed at 1631°C and 1638°C. The Cp measurements of Mg2TiO4, MgTiO3, and MgTi2O5 were carried out within the range 200-1100°C using DSC. A new thermodynamic description of the MgO-TiO2 system was derived based on the latest exper-imental data and literature data and taking into account the cation disordering of Mg2TiO4 and MgTi2O5. The liquid phase was described by the two-sublattice partially ionic model.

For Al2O3-MgO-TiO2: the isothermal sections at 996, 1100, 1274, and 1464°C were constructed based on obtained results which are mainly in an agreement with the literature data [1-3]. However, the solid-state invariant reaction involving the intermediate phase of Psbk s.s. was indicated at about 1150°C for the first time. On the liquidus surface, the eutectic invariant reaction between MgTiO3, Psbk s.s. and Sp. s.s. was detected at 1602°C. Other invariant reaction was observed at 1733°C. This reaction was proposed to be of a eutectic type [3], while in the present work the reaction is a transitional type according to DTA followed by SEM/EDX investigations. Obtained experi-mental data as well as previously reported databases of the MgO-TiO2, Al2O3-TiO2, and Al2O3-MgO systems were used to derive the thermodynamic description of the Al2O3-MgO-TiO2 system.

[1] Hauck, J., Solid state Chem., 36(1) (1981): 52-65.

[2] Boden, P., Glasser, F.P., Trans. J. Br. Ce-ram. Soc., 72(5) (1973): 215-220.

[3] Berezhnoi, A.S., Gul’ko, N.V., Ukr. Khim. Zh. (Russ. Ed.) 21(2) (1955): 158-166.

Speaker:
Dipl.-Ing. Mariia Ilatovskaia
TU Bergakademie Freiberg
Additional Authors:
  • Ivan Saenko
    TU Bergakademie Freiberg
  • Galina Savinykh
    TU Bergakademie Freiberg
  • Dr. Olga Fabrichnaya
    TU Bergakademie Freiberg