Calcium Segregation to a Magnesium Oxide (100) Surface

McCune, R.C.; Wynblatt, P.

doi:10.1111/j.1151-2916.1983.tb09985.x

Cited by 151 publications

(45 citation statements)

References 28 publications

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“…The kinetics basic equation 13) that expresses the reduction rate as a function of temperature is shown as follows: where dα/dt is the reduction rate, and k(T) and f(α) are the rate constant and model function of the reduction reaction. f(α) is influenced by the reaction mechanism.…”

Section: Model Function Resultsmentioning

confidence: 99%

Isothermal Reduction Kinetics of Powdered Hematite and Calcium Ferrite with CO–N2 Gas Mixtures

Ding

Xuan

et al. 2016

ISIJ Int.

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CF is regarded as the best bonding phase with superior strength and reducibility in sintering. The comparison of hematite and CF reduction process was made in this study. Isothermal reduction experiments of powdered hematite and CF in a continuous stream of 30% CO and 70% N 2 at 1 123 K, 1 173 K and 1 223 K were conducted through thermo-gravimetric analysis (TGA). Reduction rate analysis revealed that the reduction of hematite comprises three independent steps (H→M→W→I), whereas that of CF mainly comprises two steps (H→M→I). The reduction of powdered hematite and CF can be described by shrinking layer model, not shrinking core model completely. Results of the ln-ln and Sharp analysis methods indicated that the reduction of hematite included two kinetics stages, namely, plane-like mechanism and then spherulitic-type mechanism. The reduction of CF only included the plane-like mechanism stage. The model free method revealed that the activation energy of hematite and CF reduction were 5.81 kJ·mol − 1 and 46.89 kJ·mol − 1 , respectively.

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Section: Model Function Resultsmentioning

confidence: 99%

Isothermal Reduction Kinetics of Powdered Hematite and Calcium Ferrite with CO–N2 Gas Mixtures

Ding

Xuan

et al. 2016

ISIJ Int.

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“…For instance, ∆m 0 accounts for 30% and 22.22% of the total mass of Fe 2 O 3 and CF, respectively. The basic kinetic equation 13) that describes the relationship between reduction rate and time can be expressed as…”

Section: Thermal Analysis Kineticsmentioning

confidence: 99%

Effect of Silica on Reduction of Calcium Ferrite with CO–N2 Gas Mixtures

Ding

Xuan

et al. 2017

ISIJ Int.

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“…Step for C 2 F, CF, and CF 2 Reduction The basic kinetic equation 22) that describes the relation- ship between the reduction rate and time can be expressed as follows: (4) where A is the pre-exponential factor, E is the apparent activation energy, and R is the gas constant [8.314 J/(mol·K)]. Equation (3) can be further expressed as follows: Given that the reduction degree α is a constant, ln f(α) remains unchanged.…”

Section: Apparent Activation Energy and Rate-determiningmentioning

confidence: 99%

Reduction of CaO–Fe2O3 Series Compounds by CO

Ding

et al. 2017

ISIJ International

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The isothermal reduction kinetics of C 2 F, CF, and CF 2 by 30% CO and 70% N 2 at 1 123 K (850°C), 1 173 K (900°C), and 1 223 K (950°C) were investigated by thermogravimetric analysis in this study. Results indicated that the maximum reduction degree increased and its corresponding reduction time decreased by the order of C 2 F, CF, and CF 2 . The reduction rate analysis by peak fitting based on the Gauss rule revealed that the C 2 F, CF, and CF 2 reductions were typical one-step, two-step, and three-step reactions, respectively. Fe 3 O 4 to FeO stage overlaps with the following FeO to Fe stage and tends to approach the previous Fe 2 O 3 to Fe 3 O 4 stage in reduction of CaO-Fe 2 O 3 system with an increase in Fe 2 O 3 content. The apparent activation energy of the sample C 2 F, CF, and CF 2 reductions were 51.74, 46.89, and 34.37 kJ/mol, respectively, indicating that reduction proceeds more easily for them. The ln-ln and Sharp analysis implied that the C 2 F reduction was described by the Avrami-Erofeev function, thus appeared as a 2D reaction during the whole reaction, whereas the CF and CF 2 reductions were expressed initially by a 2D reaction when α < 0.5 and subsequently by a 3D reaction when α > 0.5. In the new proposed reduction model, the Fe 2 O 3 content increases in the CaO-Fe 2 O 3 system from C 2 F to CF 2 and the gradual promotion of the reduction rate leads to the reduction process of the C 2 F, CF, and CF 2 samples occurring by a 2D tending to 3D reaction mechanism.

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Calcium Segregation to a Magnesium Oxide (100) Surface

Cited by 151 publications

References 28 publications

Isothermal Reduction Kinetics of Powdered Hematite and Calcium Ferrite with CO–N<sub>2</sub> Gas Mixtures

Isothermal Reduction Kinetics of Powdered Hematite and Calcium Ferrite with CO–N<sub>2</sub> Gas Mixtures

Effect of Silica on Reduction of Calcium Ferrite with CO–N<sub>2</sub> Gas Mixtures

Reduction of CaO–Fe<sub>2</sub>O<sub>3</sub> Series Compounds by CO

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