## 3 Results and Discussion
### Micro-Analyses  
The results of the EDS analysis for sample 7 and sample 10 are summarized in Tables 4 and 5, respectively. These two samples were selected for comparison due to them having the lowest and the highest amount of FeO present among all samples. The analysis was conducted in three different regions on the sample cross-section. The outer surface undergoes the fastest cooling, and toward the inner surface, the cooling rate decreases. The silicate and the pseudobrookite phase present near the outer surface had a smaller amount of FeO as compared to the center region. This was consistent with the expected solidification behavior that when the pseudobrookite phase solidified first, it will have a higher TiO\({}_{2}\) content and lower iron content than the phases that were solidified later. Similar trends were observed in the industrial slag samples and the pilot plant slag samples studied by [PERSON] [23]. The difference was more pronounced in their work as the sample size was large, and thus, the cooling rate would vary significantly. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Position** & **TiO\({}_{2}\)** & **SiO\({}_{2}\)** & **FeO** & **MgO** & **MnO** & **Al\({}_{2}\)O\({}_{3}\)** \\ \hline Pseudobrookite & & & & & & \\ Outer surface & 91.04 & & 0.79 & 5.74 & 0.64 & 1.79 \\ Center & 90.77 & & 1.04 & 6.22 & & 1.97 \\ Inner Surface & 91.19 & & 0.88 & 5.90 & 0.21 & 1.83 \\ Silicate & & & & & & \\ Outer surface & 24.14 & 55.77 & 1.44 & 5.52 & 4.88 & 8.25 \\ Center & 19.76 & 53.92 & 2.90 & 7.55 & 7.39 & 8.48 \\ Inner Surface & 20.06 & 55.16 & 2.20 & 7.60 & 6.52 & 8.46 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average composition of different regions in the slag sample 7 obtained with energy dispersive X-ray microscopy (EDS). The effect of the cooling speed on the grain size can be observed in Figure 10, which presents electron microscopy images of different slag regions for slag samples 7 and 10. As mentioned earlier, the cooling was fastest for the outer surface; this is reflected in the grain size. As we move from the outer surface to the inner surface, the grain got larger as the cooling slowed down. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Position** & **TiO2** & **SiO2** & **FeO** & **MgO** & **MnO** & **Al2O3** \\ \hline Pseudobrookite & & & & & & \\ Outer surface & 82.14 & & 14.07 & 1.05 & 1.36 & 1.39 \\ Center & 83.94 & & 12.31 & 1.19 & 1.11 & 1.44 \\ Inner Surface & 85.10 & & 11.96 & 1.37 & 0.00 & 1.57 \\ Silicate & & & & & \\ Outer surface & 23.63 & 61.36 & 7.08 & 0.00 & 2.67 & 5.25 \\ Center & 14.48 & 69.00 & 7.24 & 0.00 & 2.65 & 6.64 \\ Inner Surface & 14.17 & 64.60 & 11.05 & 0.00 & 3.27 & 6.91 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Average composition of different regions in the slag sample 10 obtained with EDS. Figure 10: Microstructure for samples 7 and 10 obtained with energy dispersive X-ray microscopy (EDS) at the same magnification of 2000\(\times\). (**a**) Outer surface of sample 7, (**b**) Outer surface of sample 10, (**c**) Center part of sample 7, (**d**) Center part of sample 10, (**e**) Inner surface of sample 7, (**f**) Inner surface of sample 10. The silicate phases were trapped between the pseudobrookite grains and could be observed around the larger grains in the center and inner surface regions. The grain size near the outer surface was relatively small, representing more nucleation due to faster cooling. It is interesting to note that cracks were present in the pseudobrookite phase in slag 7, having the lowest amount of FeO but not in sample 10, having the highest amount. The cracks were more often present within the rutile and silicate phases in sample 10. In the center, the pseudobrookite grain was more elongated and with larger segregation of silicate phases. The silicate phases had more defined boundaries, as observed in sample 10. The synthetic slags showed similar characteristics to industrial slags.