In situ X-ray Diffraction Investigation of the Formation Mechanisms of Silico-Ferrite of Calcium and Aluminium-I-type (SFCA-I-type) Complex Calcium Ferrites

抄録

The formation mechanisms of the complex Ca-rich ferrite phase SFCA-I, an important bonding material in iron ore sinter, during heating of synthetic sinter mixtures in the temperature range 298–1623 K in air and at pO₂ = 5 × 10^–3 atm, were determined using in situ X-ray powder diffraction. In air, the initial formation of SFCA-I at ~1438 K (depending on composition) was associated with reaction of precursor phases Fe₂O₃, CaO·Fe₂O₃, SiO₂, amorphous Al-oxide and a CFA phase of approximate composition 71.7 mass% Fe₂O₃, 12.9 mass% CaO, 0.3 mass% SiO₂ and 15.1 mass% Al₂O₃. At temperatures above ~1453 K, the decomposition of another phase, γ-CFF, resulted in the formation of additional SFCA-I. At lower oxygen partial pressure the initial formation of SFCA-I occurred at similar temperatures and was associated with reaction between similar phases as its formation in air. However, the decomposition of γ-CFF did not result in the formation of additional SFCA-I, with the maximum SFCA-I concentration (25 mass%) lower than the values attained in air (54 and 34 mass%). Hence, more oxidising conditions appear to favour the formation of the desirable SFCA-I phase.