## 3 Results and Discussion
### Slag Microstructure
[PERSON] explained the relation between the composition of FeO and Ti\({}_{2}\)O\({}_{3}\) in an ilmenite slag that follows M\({}_{3}\)O\({}_{5}\) stoichiometry [31]. Figure 9 shows the relation between the equivalent %Ti\({}_{2}\)O\({}_{3}\) and equivalent %FeO. In Figure 9, the long dash line shows the trend for the Canadian and South African ilmenite slags with the expected relationship in a solid solution (M\({}_{3}\)O\({}_{5}\)) [31], whereas the short dash line shows the trend for the synthetic slags. Figure 8: Microstructures of slag sample 3 analyzed by SEM. The silicate phase consisted of two different silicate phases, as represented by S\({}_{1}\) and S\({}_{2}\), the lighter and darker silicate phases, respectively. Figure 9: Comparison of an actual trend of ‘equivalent FeO’ and ‘equivalent Ti\({}_{2}\)O\({}_{3}\)’for slags from Canadian and South African ilmenites ([PERSON], 2002) and the slags prepared synthetically. It is observed that the trend for the synthetic slags deviated from the trend observed in the industrial slag. The deviation can be attributed to the lower amount of pseudobrookite formed in the synthetic slag and the composition of the slag. The linear relation for industrial slag is observed if the M\({}_{3}\)O\({}_{5}\) solid solution is simply a mixture of Ti\({}_{3}\)O\({}_{5}\) and FeTi\({}_{2}\)O\({}_{5}\) and the amount of rutile and silicate is small, which was not true for our slag composition. There were a few samples for which the silicate and rutile formation was less, and the trend was similar to the industrial slag. For samples with the highest pseudobrookite content (samples 6 and 9), the points on the trendline lay closer to the industrial slag trendline. The percentage content of pseudobrookite in all the samples was in the range of 51% to 95%. Most of the impurities added in the slag, such as Al\({}_{2}\)O\({}_{3}\), MnO, and SiO\({}_{2}\), were found in the silicate phase that consisted mostly of SiO\({}_{2}\). The silicate phases were observed between the boundaries of the pseudobrookite phase. It was found that the amount of pseudobrookite formed in the slag was proportional to the amount of impurities (FeO, MgO, MnO, SiO, and Al\({}_{2}\)O\({}_{3}\)) present in the raw material. An increase in the amount of impurity resulted in an increase in pseudobrookite formed. Samples 1, 2, and 3 had the least impurity content and the lowest amount of pseudobrookite content in the samples, whereas samples 6 and 9 had the largest amount of impurity and pseudobrookite (Tables 2 and 3). Two of the most important impurities in the ilmenite slags were FeO and MgO, as they affected the slag properties and freeze lining conditions, respectively. The other impurities were present in the oxide phase and did not have a significant effect on the smelting process as FeO or MgO. MgO had the most pronounced effect on the pseudobrookite formation than any other impurity. A higher amount of MgO in the samples resulted in higher pseudobrookite formation. The samples having a pseudobrookite amount around 85% or more were samples 4, 6, 7, and 9; these samples had the highest amount of MgO among the ten prepared samples. It should also be noted that the nominal composition of MgO in the slag varied from 1 to 2% in the industrial slags. Other impurities can have a similar effect as MgO, but no such trend was observed in this study.