Changes in the Phase Composition of Calcium Aluminoferrites Based on the Synthesis Condition and Al(2)O(3)/Fe(2)O(3) 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 Al(2)O(3)/Fe(2)O(3) molar ratio (A/F). The A/F molar ratio extends beyond the limiting composition of C(6)A(2)F (6CaO·2Al(2)O(3)·Fe(2)O) towards phases richer in Al(2)O(3). An increase in the A/F ratio above unity favours the formation of other crystalline phases such as C(12)A(7) and C(3)A, 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 C(12)A(7) and C(3)A 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 C(22.19)A(10.94)F and C(14.61)A(6.29)F 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.