SFCA-II type Ca2.46Fe3+8.57 Fe2+0.52Al5.45O24 – an improved structural model for an iron-ore sinter phase

Kahlenberg, Volker; Krüger, Hannes; Tribus, Martina; Anwander, Benedikt

doi:10.1007/s00710-020-00730-y

Cited by 7 publications

(2 citation statements)

References 24 publications

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“…Kahlenberg et al also speculated on whether there exists an upper limit of the Al 2 O 3 solubility in SFCA-I, and recently demonstrated that the alumina-rich starting composition Ca 8 Al 16 Fe 16 O 56 (32 mass% Al 2 O 3 ) formed the SFCA-II-type phase rather than SFCA-I. 20) Therefore, the upper limit for Al 2 O 3 concentration in the SFCA-I structure is likely to be in the range 23-32 mass%.…”

Section: Resultsmentioning

confidence: 99%

Exploring the Composition and Structure of Triclinic SFCA-I

2022

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The synthesis and characterisation of SFCA-I compounds has been performed. SFCA-I is one of the key bonding phases in iron ore sinter, influencing physical properties such as strength, reducibility, and strength degradation during reduction. The results reported herein extend the understanding of the solid solution limits of the SFCA-I phase, with the synthesis of single-phase SFCA-I materials containing 2.71, 3.23 and 3.73 mass% Al 2 O 3 . These materials contain less Al 2 O 3 than any previously reported SFCA-I compounds. The results also confirm the low tolerance of the SFCA-I structure for SiO 2 , and a low tolerance for the variation of the CaO concentration. Finally, the results confirm that the SFCA-I structure accommodates more FeO than the related sinter phase SFCA.

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Section: Resultsmentioning

confidence: 99%

Exploring the Composition and Structure of Triclinic SFCA-I

2022

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“…The crystal structure of SFCA-I has a continuous structure with "SSP" as one block 12) . In addition to SFCA and SFCA-I, SFCA-II and SFCA-III also have been recently discovered [13][14] . SFCA-II has the periodic structure of both SFCA and SFCA-I, i.e., "SPSSP" as one block.…”

Section: Introductionmentioning

confidence: 99%

Influence of Crystal Structure and Chemical Composition on the Reducibility of Silico-Ferrite of Calcium and Aluminum in CO–CO2–H2–H2O Atmosphere

Maruoka,

Mataoka,

Kasai

et al. 2024

ISIJ Int.

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In this study, influence of crystal structure and chemical composition for Silico-Ferrite of Calcium and Aluminum (SFCA) on its reducibility are examined. Eight types of powder samples containing SFCA and SFCA-I were prepared using chemical reagents by the heat treatments in air. The samples were heated up to 800℃ in the different atmospheres of CO-CO 2 -H 2 -H 2 O systems. The reducibility of the samples was evaluated using the peak intensity ratio identified by XRD before and during the reduction experiment. The intensity of SFCA peak is not decreased up to 700℃ in CO-CO 2 atmosphere, whereas the intensity become weak in CO-CO 2 -H 2 -H 2 O atmosphere. The intensity of SFCA-I peak is decreased above 500 o C in all atmospheric condition and the reduction reactions are enhanced by the addition of H 2 -H 2 O gas. Decrease in intensity of SFCA peak is independent of Fe composition, whereas that of SFCA-I is decreased with decreasing Fe concentration. The difference in reducibility is attributed to the difference in the crystal structure of multi-component CF. SFCA and SFCA-I are composed of pyroxene and spinel units. Since the pyroxene unit contains more gangue minerals than spinel unit, it implies that the pyroxene unit shows low reducibility than the spinel units. Since SFCA-I contains more the spinel units than SFCA, SFCA-I is easily reduced than SFCA.

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Structural systematics of SFCA-I type solid-solutions in the system CaO–Fe2O3–FeO–Al2O3

2021

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Effects of Fe ↔ Al substitution on triclinic SFCA-I-type compounds with general formula A40O56 (A: Ca, Al, Fe3+, Fe2+) have been studied using single-crystal X-ray diffraction. Crystals of sufficient quality and size were synthesized in the temperature range between 1200 and 1300 °C. Six samples with Al/FeTot ratios of 0.127, 0.173, 0.216, 0.310, 0.349 and 0.459 have been structurally characterized. SFCA-I can be described with a modular approach involving the stacking sequence < PSS > of “P” and “S” modules that can be imagined as being cut from the well-known pyroxene (P) and spinel (S) structure types. Furthermore, SFCA-I is related to the sapphirine supergroup of minerals. Within the present solid-solution series, the contents in calcium show only minor variations (≈ 6.7 a.p.f.u.). The twenty crystallographically independent tetrahedrally (T) and octahedrally (M) coordinated cation sites exhibit considerable differences concerning the Al uptake. Indeed, Al is preferentially incorporated into the tetrahedra belonging to the single-chains located in the pyroxene modules. Ferrous iron, on the other hand, is restricted to one of the T-positions within the spinel blocks. Most structural aspects from unit-cell parameters and cell volumes to site occupancies, tetrahedral chain kinking as well as polyhedral distortions are defined by linear or nearly linear trends when plotted against the Al/FeTot ratio. Analysis of the < T–O > and < M–O > distances showed a complex interplay between the different coordination polyhedra resulting in a contrasting behavior of these values with positive or negative change rates as a function of composition. Evaluation of the average chemical strain tensor derived from the sets of lattice parameters for the two samples of the abovementioned series showing the highest and lowest Al/FeTot ratios indicated, that the major contraction with increasing Al content is perpendicular to the pyroxene- and spinel modules. Furthermore, the pyroxene module seems to be more affected when compared with the spinel block. There is evidence that the SFCA-I-type solid-solution series is limited on both the Al- and Fe-rich sides. The present investigation provides—for the first time—a detailed crystallographic analysis on the impact of chemical variations on a compound that is of relevance to the field of applied mineralogy related to the technologically important process of iron-ore sintering.

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SFCA-II type Ca2.46Fe3+8.57 Fe2+0.52Al5.45O24 – an improved structural model for an iron-ore sinter phase

Cited by 7 publications

References 24 publications

Exploring the Composition and Structure of Triclinic SFCA-I

Exploring the Composition and Structure of Triclinic SFCA-I

Influence of Crystal Structure and Chemical Composition on the Reducibility of Silico-Ferrite of Calcium and Aluminum in CO–CO<sub>2</sub>–H<sub>2</sub>–H<sub>2</sub>O Atmosphere

Structural systematics of SFCA-I type solid-solutions in the system CaO–Fe2O3–FeO–Al2O3

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