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UBC Theses and Dissertations

Activity of ZnO in the ternary system ZnO-CaO-SiO2 Fairweather, Michael John


The activity of ZnO in ternary Zno-CaO-SiO₂ slags has been measured at 1300 C by equilibration with copper rich brass and low oxygen potential gas utilizing the following reversible galvanic cell: Pt I H₂,H₂O |0.85Zr0₂-0.15CaO | 0₂(Air)|Pt Thermodynamic data on the component binaries was employed to calculate the excess free energy of the ternary system and the isoactivity patterns of the three components at 1600 C with respect to the metastable pure liquid standard states. An estimate of 6 E.U. was made for the entropy of fusion of ZnO. The measured activities are in good agreement with the calculated values. The proposed excess free energy contours in the Zno-CaO-SiO₂ ternary are similar in shape to those calculated in a similar manner for the FeO-CaO-SiO₂ system. Also the calculated zinc oxide isoactivity figure resembles the ferrous oxide isoactivity diagram. This zinc oxide isoactivity pattern projects towards the lime orthosilicate composition. This shape is characteristic of FeO, but in the case of ZnO the projection is less pronounced. Both these observations are in keeping with the slightly more basic behaviour of zinc oxide.

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