The effects of Al 2 O 3 and SiO 2 on the formation process of silico-ferrite of calcium and aluminum (SFCA) by solid-state reactions

Abstract

The silico-ferrite of calcium and aluminum (SFCA) is a significant crystalline phase that bonds in high basicity sinter. Al 2 O 3 and SiO 2 play an important role in the formation of SFCA in the Fe 2 O 3 –CaO–SiO 2 –Al 2 O 3 system, but the effect mechanism of Al 2 O 3 and SiO 2 on the formation of SFCA is unclear. To investigate this effect, sintering experiments were carried out with different temperatures and different times. It was found that the reaction of Al 2 O 3 with CaFe 2 O 4 (CF) as an initial product was easier to form during the calcium iron aluminum oxide (CFA) than that of SiO 2 with CF to form SFC. This was due to the former directly forming to CFA while the latter initially formed Ca 2 SiO 4 (C 2 S) and Ca 2.5 Fe 15.5 O 25 , and then SFC. It was also observed that when Al 2 O 3 and SiO 2 existed simultaneously, the Al 2 O 3 initially reacted with CF to form CFA at 1100 °C, while the SiO 2 participated in the formation of SFCA at 1150 °C without the formation of SFC. Moreover, it was understood that these were different effects in that the Al 2 O 3 promoted the transformation from the orthorhombic crystal system to the triclinic crystal system, while the SiO 2 dissolved into CFA to form the SFCA phase when Al 2 O 3 existed.