Evolution of Porosity Profiles of Magnetite Phase during High Temperature Reduction of Hematite.

Janowski, J.; Barański, A.; Sadowski, A.

doi:10.2355/isijinternational.36.269

Cited by 9 publications

(4 citation statements)

References 2 publications

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“…Haematite grains cracks and along the walls of these cracks and fissures magnetite preferentially forms. 15 By 960°C haematite is completely converted to magnetite (Fig. 9).…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic study of evolution of sinter phases at different alumina level

Sinha

Nistala²,

Chandra

et al. 2016

Ironmaking & Steelmaking

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Though sintering is controlled by kinetics of various reactions and is far from equilibrium, a thermodynamic analysis can provide useful inputs on melt formation and helps understand deviation from actual process conditions. The thermodynamic software 'FACTSAGE™' was used for this study. The general sequence of reactions during the heating cycle is as follows: decomposition of calcium carbonate to calcined lime; formation of calcium ferrites/silicates; decomposition of calcium ferrites, reduction of haematite to magnetite and formation of spinel and silicates; assimilation of ferrites, silicates, spinel and magnetite into the melt. During the cooling stage, the amount of melt decreased with subsequent precipitation of phases such as magnetite, ferrites, silicates, spinel and formation of haematite. It is very much clear that the sinter made by using higher alumina levels generate fewer amounts of oxides and more slag phase compared to its low alumina counterpart.

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“…Haematite grains cracks and along the walls of these cracks and fissures magnetite preferentially forms. 15 By 960°C haematite is completely converted to magnetite (Fig. 9).…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic study of evolution of sinter phases at different alumina level

Sinha

Nistala²,

Chandra

et al. 2016

Ironmaking & Steelmaking

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“…The hematite-to-magnetite transformation is direct, without a metastable amorphous intermediate. It is described by the ''shrinking-core'' model with the formation of a outer magnetite layer at the surface of the hematite particles that proceeds toward the core of the reacting hematite by diffusion of oxygen throughout the newly formed magnetite layer [29,30]. This mechanism of magnetite formation is confirmed by scanning-electron micrographs of A 6 and A 1 .…”

Section: Xrd Measurementsmentioning

confidence: 74%

“…The change in texture affect the oxidation and growth since the particle density of the nuclei formed is a function of temperature, oxygen pressure and crystallographic orientation. Moreover, Janowski et al [29] reported that at the end of the hematite-to-magnetite transformation a dramatic change in the texture of the sample occurs. They ascribed this change to an increase of porosity and an increase in pore diameter.…”

Section: Xrd Measurementsmentioning

confidence: 98%

Kinetics of Oxidation of Fe–6Si

2008

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Surface oxidation of Fe-6Si during annealing in low-pressure air (*10 4 Pa) in the temperature range 500-550°C was investigated using resistivity measurements, Mössbauer spectroscopy, X-ray diffraction and scanning-electron microscopy (SEM). The time dependence of the resistivity exhibits an increase in two steps, which indicates changes in the structure and/or phase composition of the alloy. Structure and phase investigations show that the first step can be explained as formation of hematite (a-Fe 2 O 3 ) and the second step is due to transformation of the hematite to magnetite (Fe 3 O 4 ). The kinetics of the transformations were derived from the resistivity data. The activation energies (estimated from Arrhenius plots) of 194 kJ/mol and 165 kJ/mol were obtained for the formation of hematite and transformation of hematite to magnetite, respectively.

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“…[5][6][7][8][9][10][11][12][13][14][15][16] However, direct reduction with a solid carbon was not carried out and no consideration of crystallographic orientation was conducted. Furthermore, there is little publication on the in situ observation of the reaction and its mechanism between solid carbon and iron oxide.…”

Section: Introductionmentioning

confidence: 99%