Changes in the Phase Composition of Calcium Aluminoferrites Based on the Synthesis Condition and AlO/FeO Molar Ratio.

The presented work concerns the study of the changes in the phase composition of calcium aluminoferrites which depend on the synthesis conditions and the selection of the AlO/FeO molar ratio (A/F). The A/F molar ratio extends beyond the limiting composition of CAF (6CaO·2AlO·FeO) towards phases richer in AlO. An increase in the A/F ratio above unity favours the formation of other crystalline phases such as CA and CA, in addition to calcium aluminoferrite. Slow cooling of melts characterised by an A/F ratio below 0.58, results in the formation of a single calcium aluminoferrite phase. Above this ratio, the presence of varying contents of CA and CA phases was found. The process of rapid cooling of the melts with an A/F molar ratio approaching the value of four favours the formation of a single phase with variable chemical composition. Generally, an increase in the A/F ratio above the value of four generates the formation of a calcium aluminoferrite amorphous phase. The rapidly cooled samples with compositions of CAF and CAF were fully amorphous. Additionally, this study shows that as the A/F molar ratio of the melts decreases, the elemental cell volume of the calcium aluminoferrites decreases.