A Review of the Chemistry, Structure and Formation Conditions of Silico-Ferrite of Calcium and Aluminum (‘SFCA’) Phases

Nicol, Stuart; Chen, Jiang; Pownceby, Mark I.; Webster, Nathan A. S.

doi:10.2355/isijinternational.isijint-2018-203

Cited by 70 publications

(49 citation statements)

References 50 publications

(72 reference statements)

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“…2(b)). 10 content is greater than in the Fe-rich SFCA). The Fe-rich SFCA, therefore, appears to be an intermediate phase between Fe 3 O 4 and SFCA in terms of composition.…”

Section: Introductionmentioning

confidence: 80%

Fundamentals of Silico-Ferrite of Calcium and Aluminium (SFCA) Iron Ore Sinter Bonding Phase Formation: Effects of Basicity and Magnesium on Crystallisation during Cooling

et al. 2019

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The effects of basicity and Mg addition on the crystallisation during cooling of complex Ca-rich ferrite iron ore sinter bonding phases SFCA and Fe-rich SFCA was investigated using in situ synchrotron X-ray diffraction. In synthetic iron ore sinter mixtures, cooling of a high temperature (T = 1 623 K) assemblage comprising magnetite and melt showed that decreasing basicity from B = 4.0 to 3.0 and 2.5 resulted in the formation of a Fe-rich SFCA phase being suppressed, with SFCA being the only Ca-rich ferrite phase to form initially from the melt at B = 2.5. Increasing the Mg concentration in the sinter mixtures to 1 and 3 wt% MgO resulted in an overall suppression of the amount of Ca-rich ferrite phase formation. However, Mg addition caused the formation of Fe-rich SFCA to be favoured over SFCA, with SFCA not observed to form at all during cooling in the 3 wt% MgO mixture. The absence of SFCA in the high-Mg experiment was rationalised on the basis that the Fe-rich SFCA structure accommodates more Fe 2 + than the SFCA structure, thereby stabilising Fe-rich SFCA relative to SFCA through replacement substitution of Fe 2 + by Mg 2 + . Observation of Fe-rich SFCA in sinter may be an indicator of localised high basicity, and/or, high Mg concentration, within a sinter blend.KEY WORDS: iron ore sinter; in situ synchrotron X-ray diffraction; complex Ca-rich ferrite iron ore sinter bonding phases; SFCA; crystallisation during cooling; CaO:SiO 2 ratio; Mg addition.

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“…2(b)). 10 content is greater than in the Fe-rich SFCA). The Fe-rich SFCA, therefore, appears to be an intermediate phase between Fe 3 O 4 and SFCA in terms of composition.…”

Section: Introductionmentioning

confidence: 80%

Fundamentals of Silico-Ferrite of Calcium and Aluminium (SFCA) Iron Ore Sinter Bonding Phase Formation: Effects of Basicity and Magnesium on Crystallisation during Cooling

et al. 2019

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“…In addition, the initial segmentation of the sample based on backscattered electron level may need further refinement in future work. As a result, distinguishing SFCA and SFCA-I on the basis of chemical composition such as Fe content [4], Si content or Fe/Si ratio as anticipated above was not possible. It was also not possible to distinguish hematite from magnetite, due to the very similar backscattered-electron signal from the two phases.…”

Section: Timamentioning

confidence: 99%

“…In addition, a common set of definitions was agreed upon allowing further collaborative research to be undertaken. One key outcome was the definition of two main types of silico-ferrite of calcium and aluminium (SFCA)-prismatic SFCA (e.g., 60-76 wt % Fe 2 O 3 , 13-17 wt % CaO, 3-10 wt % SiO 2 , 3-11 wt % Al 2 O 3 and 0-3 wt % MgO [4]), with blocky and dendritic morphological subtypes, and platy SFCA-I (e.g., 82.6 wt % Fe 2 O 3 , 13.6 wt % CaO, 1.7 wt % SiO 2 and 2.1 wt % Al 2 O 3 [4])-although an absolute alignment between the morphological definition and QXRD relative phase abundances was not possible.…”

Section: Introductionmentioning

confidence: 99%

“…The study of SFCA remains of considerable interest, with a recent paper by Nicol et al [4] giving an excellent review of work on SFCA phases. SFCA-I and SFCA are stable in discrete compositional ranges and have distinct crystallographic structures, which are presumed to correspond to the platy and prismatic morphologies observed using reflected light microscopy, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of the Mineralogy of Iron Ore Sinters Using a Range of Techniques

et al. 2019

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Many different approaches have been used in the past to characterise iron ore sinter mineralogy to predict sinter quality and elucidate the impacts of iron ore characteristics and process variables on the mechanisms of sintering. This paper compares the mineralogy of three sinter samples with binary basicities (mass ratio of CaO/SiO 2 ) between 1.7 and 2.0. The measurement techniques used were optical image analysis and point counting (PC), quantitative X-ray diffraction (QXRD) and two different scanning electron microscopy systems, namely, Quantitative Evaluation of Materials by Scanning Electron Microscopy (QEMSCAN) and TESCAN Integrated Mineral Analyser (TIMA). Each technique has its advantages and disadvantages depending on the objectives of the measurement, with the quantification of crystalline phases, textural relationships between minerals and chemical compositions of the phases covered by the combined results. Some key differences were found between QXRD and the microscopy techniques. QXRD results imply that not all of the silico-ferrite of calcium and aluminium (SFCA types) are being identified on the basis of morphology in the microscopy results. The amorphous concentration determined by QXRD was higher than the glass content identified in the microscopy results, whereas the magnetite and total SFCA concentration was lower. The scanning electron microscopy techniques were able to provide chemical analysis of the phases; however, exact correspondence with textural types was not always possible and future work is required in this area, particularly for differentiation of SFCA and SFCA-I phases. The results from the various techniques are compared and the relationships between the measurement results are discussed.

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“…Concerning their chemical compositions, different types of SFCA compounds can be distinguished. They represent complex solid solutions corresponding to the general formula M 14+6n O 20+8n , where M = Si, Fe, Al, Ca and Mg (Hamilton et al, 1989;Mumme et al, 1998;Sugiyama et al, 2005;Liles et al, 2016;Zö ll et al, 2017;Nicol et al, 2018). The two most frequently observed representatives in industrial sinters are named SFCA (n = 0 or M 14 O 20 ) and SFCA-I (n = 1 or M 20 O 28 ) (Webster et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone

Kahlenberg

Krüger

Goettgens

2019

Acta Crystallogr Sect B

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Synthesis experiments in the system CaO–SiO2–Al2O3–Fe2O3–MgO resulting in the formation of SFCA-III are reported. SFCA-III is a new n = 2 member of a polysomatic series of M 14+6nO20+8n compounds based on pyroxene-spinel modules which are of relevance to iron-ore sintering. Single-crystal diffraction studies using synchrotron radiation revealed that the compound occurs in two polytypes representing maximum degree of order structures which explains the observed allotwinning of the sample.

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A Review of the Chemistry, Structure and Formation Conditions of Silico-Ferrite of Calcium and Aluminum (‘SFCA’) Phases

Abstract: Throughout this text the acronym 'SFCA' in single quotation marks refers to undifferentiated 'SFCA'-like phases. These may consist of substituted calcium ferrites, SFCA sensu stricto and SFCA-I.

Cited by 70 publications

References 50 publications

Fundamentals of Silico-Ferrite of Calcium and Aluminium (SFCA) Iron Ore Sinter Bonding Phase Formation: Effects of Basicity and Magnesium on Crystallisation during Cooling

Fundamentals of Silico-Ferrite of Calcium and Aluminium (SFCA) Iron Ore Sinter Bonding Phase Formation: Effects of Basicity and Magnesium on Crystallisation during Cooling

Comparison of the Mineralogy of Iron Ore Sinters Using a Range of Techniques

Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone

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