scholarly journals Thermodynamic modeling of phase equilibria in the system Na2O – CaO – Al2O3

2019 ◽  
Vol 57 (2) ◽  
pp. 111-115
Author(s):  
Svetlana E. Pratskova ◽  
◽  
Evgenia S. Nechaeva ◽  
Keyword(s):  
Phase Equilibria ◽  
Optical Fibers ◽  
Thermodynamic Modeling ◽  
Binary Systems ◽  
Liquid Solution ◽  
Exothermic Effect ◽  
Regression Equations ◽  
Melt Mixing ◽  
Energy Parameters ◽  
State Diagrams

The thermodynamic properties of melts of the Na2O – CaO – Al2O3 system are of considerable interest for metallurgy, technology of ceramic materials, optical fibers. State diagrams CaO – Al2O3, Na2O – Al2O3 have been studied by many researchers and do not have the generally accepted version, and the system Na2O – CaO has not been specifically studied. In the work, thermodynamic modeling of the phase equilibria of the Na2O – CaO – Al2O3 system was carried out within the framework of the generalized theory of “regular” ionic solutions. Equations for the activities of the system components are derived. The energy parameters of the model are determined taking into account melting characteristics and experimental data. The state diagrams of binary systems are constructed using the calculated values of the Gibbs energies for the formation of sodium and calcium aluminates from the corresponding oxides. Using the regression equations of the temperature dependences of the energy parameters of binary melts of the Na2O – CaO – Al2O3 system, the molar mixing functions of the liquid solution раствора G_m^M, H_m^M, S_m^M and the excess thermodynamic functions G^E, H^E, S^E were calculated at 1500-1800 oC. Lime-alumina melts are stable at all temperatures, experiencing negative deviations from ideality. The Gibbs excess energy G^E is negative and in absolute value varies from 5 to 90 kJ/mol. With an increase in the concentration of Al2O3 in the melt and temperature, a tendency toward disorder is clearly manifested: the entropy of the melt mixing changes its sign from “minus” to “plus”. Na2O – Al2O3 melts are formed with an exothermic effect and ordering, and are also stable. They experience strong negative deviations (for G^E) from ideality. However, the situation changes at 55 mol. % Al2O3 and 1700-1800 oС melts of the system are unstable.

scholarly journals THERMODYNAMIC MODELING OF OXIDE MELTS OF CaO - Al2O3 - SiO2 SYSTEMS

2019 ◽  
Vol 63 (1) ◽  
pp. 45-50
Author(s):  
Svetlana E. Pratskova ◽  
Vladimir A. Burmistrov ◽  
Anna A. Starikova
Keyword(s):  
Phase Diagrams ◽  
Thermodynamic Modeling ◽  
Binary Systems ◽  
Thermodynamic Description ◽  
Ternary Systems ◽  
Oxide Melt ◽  
State Diagrams ◽  
Gibbs Energies ◽  
Metallurgical Slags ◽  
Oxide Melts

Oxide melts of the CaO – Al2O3 – SiO2 system are the basis of metallurgical slags. Therefore, the thermodynamic properties of this system have been repeatedly studied experimentally, and attempts have been made to describe them theoretically. Thermodynamic modeling of the state diagrams of the CaO – Al2O3, CaO – SiO2, Al2O3 – SiO2 binary systems, as well as the CaO – Al2O3 – SiO2 ternary system was performed. In the course of the work, expressions for the thermodynamic description of the activities of the components of the oxide melt of this system are derived. For the calculation, a generalized theory of regular ionic solutions was used. The energy parameters of the theory are determined, depending on the temperature and composition of the solution, using experimental data on the heat and melting point of oxides of calcium, aluminum and silicon. According to the results of the simulation, the coordinates of the points of nonvariant transformations in the phase diagrams of the binary and ternary systems under study are determined. The obtained results on thermodynamic modeling of the coordinates of the liquidus lines of the phase diagrams of the CaO – Al2O3, CaO – SiO2, Al2O3 – SiO2 binary systems were compared with the literature data for the studied systems. The calculated diagrams are in good agreement with the experimental ones, which indicates the applicability of the chosen system for the description of such oxide melts. The modeling technique used in this work allowed to estimate the Gibbs energies of formation of silicates and calcium aluminum silicates to be 3Al2O3∙2SiO2, 3CaO∙SiO2, 2CaO∙SiO2, 3CaO∙2SiO2, CaO∙SiO2, CaO∙Al2O3∙2SiO2, 2CaO∙Al2O3∙SiO2 on the base of obtained aquations for of activities of the components and calculated parameters of the theory. The calculated diagrams will allow to determine the nature of the interaction between the components of the system, the conditions of formation, the composition and properties of the compounds formed, without isolating them from the system.

Thermodynamic Modeling of Phase Equilibria in the FeO-Al2O3-Cr2O3 and MgO-Al2O3-Cr2O3 Systems

2020 ◽  
Vol 989 ◽  
pp. 204-209 ◽  
Author(s):  
Gennady G. Mikhailov ◽  
L.A. Makrovets ◽  
O.V. Samoilova
Keyword(s):  
Phase Equilibria ◽  
Phase Diagrams ◽  
Thermodynamic Modeling ◽  
Liquidus Surface ◽  
Complex Oxide ◽  
Thermodynamic Models ◽  
Ionic Solutions ◽  
Calculated Phase ◽  
Energy Parameters

Thermodynamic modeling of phase equilibria and further construction of a full projection of the liquidus surface in the FeO–Al2O3–Cr2O3 and MgO–Al2O3–Cr2O3 systems were carried out. Theories of sub-regular ionic solutions, regular ionic solutions and ideal ionic solutions were used for calculation. Values of energy parameters of the used thermodynamic models were obtained in the course of the research. These values might be applicable for further modeling of more complex oxide slag systems which are formed in the process of manufacture of chromic steels. Calculated phase diagrams for the FeO–Al2O3–Cr2O3 and MgO–Al2O3–Cr2O3 systems were compared with available data from literature sources.

scholarly journals MODELING OF QUASIBINARIES OF Na+, Сa2+ // O2-, F- SYSTEM

2018 ◽  
Vol 59 (1) ◽  
pp. 19
Author(s):  
S.E. Pratskova ◽  
A.G. Tyurin
Keyword(s):  
Gibbs Energy ◽  
Phase Equilibria ◽  
Phase Diagrams ◽  
Exchange Reaction ◽  
Thermodynamic Modeling ◽  
Binary Systems ◽  
Standard Gibbs Energy ◽  
Ionic Solutions ◽  
System Components ◽  
F System

Thermodynamic modeling of phase equilibria of the Na +, Ca2 + // O2-, F- system in the frame of the generalized theory of "regular" ionic solutions was carried out. The equations for the activities of the system components were derived. The standard Gibbs energy of the exchange reaction was calculated. The values of the energy parameters of the model were determined and the phase diagrams of the binary systems were constructed.

Thermodynamic Properties and Phase Equilibria in the Ternary Cu-Pb-Fe System

2013 ◽  
Vol 58 (2) ◽  
pp. 541-548 ◽  
Author(s):  
B. Onderka ◽  
D. Jendrzejczyk-Handzlik ◽  
K. Fitzner
Keyword(s):  
Experimental Data ◽  
Phase Diagram ◽  
Thermodynamic Properties ◽  
Phase Equilibria ◽  
Thermodynamic Functions ◽  
Binary Systems ◽  
Liquid Solution ◽  
Calculated Diagram ◽  
Calculated Equilibrium ◽  
Good Agreement

Using experimental data available in the literature, two binary systems, namely Cu-Pb and Fe-Pb were recalculated. Next, accepting Cu-Fe phase diagram assessment as given by Ansara and Jansson, the ternary Cu-Fe-Pb system was analyzed. Calculated equilibrium lines and thermodynamic functions are compared with existing experimental data. Good agreement was found between the calculated diagram and the experimental results. Having the system optimized, functional dependences of the logarithms of the activity coefficients on temperature and concentrations for Cu, Fe and Pb in the liquid solution are given.

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