<i>In-Situ</i> X-ray Diffraction Analysis of Phase Formation during Heating of Silico-Ferrite of Calcium (SFC) Compositions

Abstract

The phase evolution during heating of two Al 2 O 3 -free mixtures designed to form the SFC iron ore sinter bonding phase was investigated using in-situ X-ray diffraction over the temperature range 293-1 623 K. Results showed that during heating at an oxygen partial pressure of 5 × 10 − 3 atm, SFC formation was preceded by the formation of γ -Ca 4 Fe 14 O 25 and γ -CFF (nominal composition Ca 3.0 Fe 14.82 O 25 ) intermediate phases. On further heating the SFC melted to form Fe 3 O 4 in a Fe 2 O 3 -FeO-CaO-SiO 2 melt. During heating of one of the mixtures in air, it was not possible to distinguish between SFCA-I and α-CFF (nominal composition Ca 3.43 Fe 14.39 O 25 ) as intermediate phases in the formation of SFC. The improved signal-to-noise ratio and angular peak resolution afforded by synchrotron-based XRD experimentation would be required to possibly distinguish between these two phases. Regardless of whether SFCA-I or α-CFF formed as intermediate phases during heating in air, this work shows that the oxygen partial pressure has a significant effect on phase formation mechanisms in the Al 2 O 3 -free SFC system. KEY WORDS: iron ore sinter; in-situ X-ray diffraction; complex Ca-rich ferrite iron ore sinter bonding phases; SFC; oxygen partial pressure; γ -CFF; SFCA-I; α-CFF.

Exploring the Relationship Between Fe-rich SFCA and SFCA-III and Their Presence in Sinter Strand and Pot-grate Sinter

“…This pO 2 was found by Hsieh and Whiteman to maximise the formation of Ca-rich ferrites whilst still producing mineral assemblages like those found in industrial sinters. 12) The heating profile was the same as that used routinely by Webster et al during their in-situ XRD experimentation; 7,[13][14][15][16] 20 K min −1 for 298-873 K, and then 10 K min − 1 for 873-1623 K The temperature adjacent to the crucible was measured using a Pt/PtRh13% thermocouple connected to an ice-point cell, and temperature measurements are considered accurate to  15 K.…”