The thermodynamic activity of silica and of oxides in silicate melts

Rey, M.J.

doi:10.1039/df9480400257

Cited by 27 publications

(11 citation statements)

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“…Therefore, the activity of Si with a constant ratio of 2 and 3 components can be calculated by integration of Eq. (18). For the binary alloy, the activity of Si can be obtained by an even simpler method.…”

Section: Estimation Of the Activity Of Simentioning

confidence: 99%

A Newly Developed Method for Determining SiO2 Activity of the Silicate Slags Equilibrated with Molten Silicon Alloys.

2000

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IntroductionThermodynamic properties of the CaO-SiO 2 -AlO 1.5 -MgO slags are of great importance for the investigation of the refining reactions in iron-and steelmaking processes.The SiO 2 activities of silicate systems have been measured by many researchers, but there are considerable discrepancies among them, which accordingly affect the derived activity values of other oxide components.Rein and Chipman 1) determined the activity of SiO 2 in the ternary systems of CaO-SiO 2 -AlO 1.5 and CaO-SiO 2 -MgO, and at the 10, 20, 30 mass% MgO of CaO-SiO 2 -AlO 1.5 -MgO quaternary system mainly at 1 873 K by measuring the silicon distribution between slags and Fe-Si-C alloys saturated with either graphite or silicon carbide under a CO atmosphere.Kay and Taylor 2,3) determined the activity of SiO 2 in the entire liquid region in the CaO-SiO 2 -AlO 1.5 system and on the 11, 21 mass% AlO 1.5 planes of the CaO-SiO 2 -AlO 1.5 -MgO system mainly at 1 823 K by measuring the equilibrium CO partial pressure of the reaction: SiO 2 ϩ3Cϭ SiCϩ2CO, and the values at 1 873 K were also estimated by extrapolation.In the binary and ternary silicate systems, activities of components other than SiO 2 have been derived by integrating the Gibbs-Duhem equation, hence the curvatures of iso-activity contours for SiO 2 affect the accuracy in the calculation, and the activity values at many compositions are required as integration limits in the calculation.On the other hand, by applying a slag-metal equilibration technique using Si based alloys, the activities of components other than SiO 2 can be obtained directly at each experimental point when SiO 2 activity and that of each component in such alloys are available. The activity coefficients of such components together with interaction effects in such alloys at concerned temperatures have been extensively studied by Miki et al. 4,5) In the present study, SiO 2 activities for the CaO-SiO 2 , CaO-SiO 2 -AlO 1.5 and CaO-SiO 2 -MgO systems have been derived over a wide range of liquid composition by a newly developed analytical method from the equilibrium compositions of slags and molten Si alloys in prior to determination of the activities of oxide components other than SiO 2 for these slag systems. Experimental ProcedureAn electric resistance furnace was used for equilibration of silicate slags and Si based alloys. The temperature was controlled at 1 823 and 1 873 K within the accuracy of Ϯ2 K by a Pt-6%Rh/Pt-30%Rh thermocouple. The slags were prepared from reagent grade AlO 1.5 , SiO 2 , MgO and CaO calcined from CaCO 3 in air, while Si based alloys were from semiconductor grade Si with a small amount of reagent grade Ca, Al and Mg.Sixteen grams of CaO-SiO 2 , CaO-SiO 2 -AlO 1.5 or CaOSiO 2 -MgO slags and 8 g of Si based alloys with various Ca, Al and Mg contents in a graphite crucible were held in a ISIJ International, Vol. 40 (2000), No. 6, © In the determination of activities of components other than SiO 2 for the CaO-SiO 2 -AlO 1.5 -MgO slags equilibrated with molten Si alloys, activities of...

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Section: Estimation Of the Activity Of Simentioning

confidence: 99%

A Newly Developed Method for Determining SiO2 Activity of the Silicate Slags Equilibrated with Molten Silicon Alloys.

2000

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“…If x A = 1, then Equation 2 is equivalent to the approximate expression which is often used to calculate free energy differences for liquids that crystallize without a change in composition. Equation 2 has been derived for a "regular" solution [5,6] and is only approximate when the solution is not regular. A regular solution is defined by Hildebrand as…”

Section: Introductionmentioning

confidence: 99%

Theory for incongruent crystallization: Application to a ZBLAN glass

et al. 1992

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Equations which describe incongruent nucleation and subsequent crystal growth have been derived. A ZrF4-BaF2-LaF3-AIF3-NaF glass was used to test the validity of these equations. Nucleation rate measurements were fitted to theory and some growth rate measurements were found in reasonable agreement with theoretical predictions. Both nucleation theory and crystal growth theory were used for computer simulations of the crystallization behaviour during heat treatments. Some heat treatments were performed in a differential scanning calorimeter to verify the theories. The experimental results were in good agreement with the numerical data. Using these theoretical results it is possible to estimate fibre scattering losses due to crystallization. Depending on drawing temperature, estimated losses can vary from 0.01 4 (310~ to 25 (320~ or more dB km -1

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“…To validate the accuracy of established model to predict the activity of various components in flux melts, the comparisons between the prediction by the current study and the calculation by Factsage and the literature [17,[25][26][27][28] were made on the activity of the reactive component, SiO 2 . The flux melts were CaO-Al 2 O 3 -SiO 2 -CaF 2 , CaO-BaO-Al 2 O 3 -SiO 2 , and Li 2 O-SiO 2 , respectively.…”

Section: Model Validationmentioning

confidence: 99%

Study of Thermodynamic for Low-Reactive CaO-BaO-Al2O3-SiO2-CaF2-Li2O Mold Flux Based on the Model of Ion and Molecular Coexistence Theory

Zhao

et al. 2022

Metals

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A thermodynamic model was proposed to calculate the activity of components in low-reactive CaO-BaO-Al2O3-SiO2-CaF2-Li2O mold flux, which was chosen to improve the castability of high Al steel, based on the ion and molecular coexistence theory. The model was indirectly validated, and the effects of the mass ratio of Al2O3/SiO2, contents of CaF2 and Li2O on the reactivity of components were discussed. The results reveal that the reactivity of mold flux attenuated with the increase in the mass ratio of Al2O3/SiO2. The decrease in reactivity was insignificant as the mass ratio was over 3.5. The steel–slag reaction experiment confirmed that the reactivity of mold flux is weakened when the content of SiO2 below 8 wt%. The reactivity of mold flux increased nearly linearly with the increase in CaF2 content, indicating that the proportion of CaF2 should be kept to a minimum in the flux. In addition, the compositional regions involving around 6 wt% Li2O should be avoided to develop low-reactive mold flux.

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The thermodynamic activity of silica and of oxides in silicate melts

Cited by 27 publications

References 0 publications

A Newly Developed Method for Determining SiO2 Activity of the Silicate Slags Equilibrated with Molten Silicon Alloys.

A Newly Developed Method for Determining SiO2 Activity of the Silicate Slags Equilibrated with Molten Silicon Alloys.

Theory for incongruent crystallization: Application to a ZBLAN glass

Study of Thermodynamic for Low-Reactive CaO-BaO-Al2O3-SiO2-CaF2-Li2O Mold Flux Based on the Model of Ion and Molecular Coexistence Theory

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