scholarly journals Thermodynamic analysis of strontium deoxidizing ability in liquid iron at presence of aluminum

2021 ◽  
Vol 64 (10) ◽  
pp. 768-777
Author(s):  
L. A. Makrovets ◽  
O. V. Samoilova ◽  
G. G. Mikhailov ◽  
I. V. Bakin
Keyword(s):  
Thermodynamic Analysis ◽  
Liquid Iron ◽  
Equilibrium Constants ◽  
Oxide System ◽  
Ternary Oxide ◽  
Ionic Solutions ◽  
Energy Parameters ◽  
Oxide Melt ◽  
Temperature Dependences ◽  
First Time

Phase diagram of the ternary oxide system FeO - SrO -Al2O3 was constructed for the first time. In this system, the following compounds can be formed: hercynite FeAl2O4 and five strontium aluminates - Sr4Al2O7 , Sr3Al2O6 , SrAl2O4 , SrAl4O7 , SrAl12O19 . According to the calculations performed, solid solutions of oxides are not formed in the system, as it is confirmed by the literature data. In the course of modeling, the optimal energy parameters of the theory of subregular ionic solutions were selected for the components of the oxide melt (FeO, SrO, Al2O3 ). Thermodynamic analysis of strontium deoxidizing ability in liquid iron at presence of aluminum was carried out using the technique for constructing the surface of solubility of strontium and aluminum in metal for steelmaking temperatures (1550 and 1600 °C) and carbon concentrations of 0.1 and 0.4 %. The equilibrium constants of the reactions of formation of strontium aluminates Sr3Al2O6 and SrAl2O4 from the components of the metal melt were calculated for the temperature range of 1550 - 1650 °C. It was found that the rest of strontium aluminates can be formed in liquid metal only at temperatures above 1750 °C. The base of thermodynamic data for the studied systems is given: temperature dependences of equilibrium constants for reactions occurring between components; values of interaction parameters of the first order (according to Wagner) for elements in liquid iron; values of energy parameters of the theory of subregular ionic solutions (for oxide melt). It follows from the calculations that the formation of strontium monoaluminate SrAl2O4 and corundum Al2O3 is most probable as the interaction products in Fe -Al - Sr - O and Fe -Al - Sr - C - O systems.

scholarly journals Thermodynamic modeling of isotherms of oxygen solubility in liquid metal of Fe – Mg – Al – O system

2019 ◽  
Vol 62 (8) ◽  
pp. 639-645 ◽  
Author(s):  
G. G. Mikhailov ◽  
O. V. Samoilova ◽  
L. A. Makrovets ◽  
L. A. Smirnov
Keyword(s):  
Solid Solution ◽  
Liquid Metal ◽  
Liquid Iron ◽  
Thermodynamic Modeling ◽  
Equilibrium Constants ◽  
Oxygen Solubility ◽  
Ionic Solutions ◽  
Temperature Range ◽  
Oxide Melt ◽  
Oxide Phases

Studying the interaction between oxygen and magnesium and aluminum dissolved in liquid iron is an important task in order to choose optimal parameters for refining and casting of steels. Relevance of this research is caused by determining the possibility and conditions for formation of unfavorable refractory particles of magnesium oxideand magnesian spinel in a metal melt. In the course of this research, thermodynamic modeling of phase equilibria implemented in liquid metal of such systems as Fe – Mg – O, Fe – Al – O and Fe – Mg – Al – O within the temperature range of 1550 – 1650 °С was carried out. Calculation was made using the technique of constructing the solubility surfaces for the metal components which connects quantitative changes in composition of a liquid metal with qualitative changes in composition of products obtained as a result of interaction of a metallic melt’s components. The modeling method was based not only on usin­g equilibrium constants of reactions occurring between components of the systems under research in the selected temperature range, but also on taking into account the values of interaction parameters of the first order (according to Wagner) of elements in liquid iron. In order to simulate activities of the oxide melt conjugated with the metallic one, approximation of the theory of subregular ionic solutions was used. To model activities of oxides solid solution, approximation of the theory of regular ionic solutions was used. And the theory of ideal ionic solutions was used for the solid solution of spinels. In the course of the work, isotherms of oxygen’s solubility in liquid metal of systems Fe – Mg – O, Fe – Al – O and Fe – Mg – Al – O have been constructed, and regions of thermodynamic stability of oxide phases conjugated with the metallic melt have been determined. In particular, compositions area of a liquid metal which is going to be in equilibrium with the solid solution of spinels | FeAl 2 O 4 , MgAl 2 O 4 | solid solution has been determined for Fe – Mg – Al – O system. Results obtained in the course of thermodynamic modeling have been compared to experimental data.

Thermodynamic Modeling of Phase Equilibrium in Fe-Y-Cr-C-O Liquid Metal System

2017 ◽  
Vol 265 ◽  
pp. 862-867 ◽  
Author(s):  
G.G. Mikhailov ◽  
L.A. Makrovets
Keyword(s):  
Liquid Metal ◽  
Chemical Reactions ◽  
Equilibrium Constants ◽  
Oxide System ◽  
Critical Parameters ◽  
Low Carbon ◽  
Metal System ◽  
Oxide Melt ◽  
Liquid Metal System ◽  
Existence Domain

The thermodynamic characteristics of processes in the liquid metal system Fe–Y–Cr–C–O are considered as applied to low-carbon and low-alloy metal. The critical parameters for the state diagram of the oxide system Y2O3–Cr2O3 were established based on the values quoted in literature. The temperature dependence of the melting reaction constant Y2O3·Cr2O3 was determined. The coordinates of eutectic transformation points for the system Y2O3–Cr2O3 were calculated. In accordance with subregular solution theory, the energetic parameters which are necessary to calculate the activities Cr2O3 and Y2O3 of oxide melts in the system Y2O3–Cr2O3 were determined. The energetic parameters of subregular solution theories for the oxide system FeO–Cr2O3–Y2O3 were determined based on the values for the binary systems FeO–Y2O3, FeO–Cr2O3 and Y2O3–Cr2O3. The view of this diagram, as coupled with the existence domain of liquid metal within the framework of the quaternary system Fe–Y–Cr–O–С, suggests that low-carbon chromic liquid metal when injected with yttrium can form the following non-metallic inclusions: |Cr2O3|, |Y2O3|, |FeO·Cr2O3|, |Y2O3·Cr2O3| or oxide melt (FeO, Y2O3, Cr2O3). Oxide melt may contain up to 2 % of divalent chrome (Cr2+). The equilibrium constants for the main reactions of steel deoxidation with the formation of liquid, solid and gas products of chemical reactions were also established. The activity of components dissolved in metal was calculated using interaction parameters. The set of derived expressions for the activity of components and the dependences of equilibrium constants of chemical reactions and phase transformations allowed us to diagram the surface of component solubility in liquid metal (SCSM). SCSM diagrams show the compositions of liquid metal and indicate oxide phases which are in equilibrium with liquid metal.

Thermodynamic Assessment of Phase Equilibria in the SrO-Al2O3 System

2021 ◽  
Vol 410 ◽  
pp. 725-729
Author(s):  
Larisa A. Makrovets ◽  
Olga V. Samoilova ◽  
Igor V. Bakin
Keyword(s):  
Experimental Data ◽  
Phase Diagram ◽  
Phase Equilibria ◽  
Thermodynamic Assessment ◽  
Equilibrium Constants ◽  
Liquidus Line ◽  
Ionic Solutions ◽  
Oxide Melt ◽  
Optimal Values ◽  
Good Agreement

Thermodynamic modeling of phase equilibria with the subsequent construction of the phase diagram of the SrO–Al2O3 system has been carried out. To calculate the activities of the oxide melt in the course of this work, we used the approximation of the theory of subregular ionic solutions, with the most optimal values of the energy parameters Q1112 = –104 349: Q1122 = –217 689; Q1222 = –104 436 J/mole. The results obtained for the liquidus line in this work are in good agreement with the literature experimental data. In the course of the calculation, the values of the equilibrium constants for the formation of strontium aluminates from the components of the oxide melt were estimated.

scholarly journals Phase equilibrium occurring during low-carbon iron-based melt deoxidation with silicostrontium

2021 ◽  
Vol 64 (6) ◽  
pp. 413-419
Author(s):  
L. A. Makrovets ◽  
O. V. Samoilova ◽  
G. G. Mikhailov ◽  
I. V. Bakin
Keyword(s):  
Liquid Metal ◽  
Liquid Iron ◽  
Equilibrium Constants ◽  
Low Carbon ◽  
Processing Technologies ◽  
Oxide Melt ◽  
Steel Modification ◽  
Oxide Phases ◽  
Steel Processing ◽  
The Moment

At the moment, to improve quality of metal (especially low-alloyed), out-of-furnace steel processing technologies are used with complex alloys utilization, which include alkaline earth metals (ALM) in addition to silicon. Study of strontium additives effect on deoxidation and liquid steel modification processes is one of the promising areas of research in field of metallurgical technologies. Thermodynamic modeling of phase equilibria in Fe – Sr – Si –C– O system melt was carried out using method of constructing surface of components solubility in metal. Solubility surface determines stability limits of non-metallic phases formed during deoxidation, depending on composition of liquid metal of the studied system. The  calculation was carried out using equilibrium constants of reactions occurring in the melt during deoxidation, as well as the first order interaction parameters (according to Wagner) of elements in liquid iron. Activity of the oxide melt components was determined using theory of subregular ionic solutions. Activity of the gas phase was calculated taking into account partial pressures. Simulations were performed for two temperatures (1550 and 1600  °C) for fixed carbon concentrations (0 (no carbon in liquid iron) and 0.1 % (low-carbon metal melt)). It has been shown that, in comparison with silicon, strontium is stronger deoxidizing agent in liquid metal. According to the simulation results, liquid oxide non-metallic inclusions of variable composition or strontium ortho- and metasilicates Sr2SiO4 and SrSiO3 (with an increase in strontium concentration) should be the main oxide phases in deoxidation products. Decrease in the temperature of liquid metal leads to changes in phase formation (formation of SrSiO3 silicate becomes possible).

scholarly journals The Physical and Thermodynamic Functions of Borides

2017 ◽  
Vol 18 (1) ◽  
pp. 58-63
Author(s):  
N.Yu. Filonenko
Keyword(s):  
Free Energy ◽  
Physical Properties ◽  
Thermodynamic Functions ◽  
Point Of View ◽  
Energy Potential ◽  
High Temperature Expansion ◽  
Temperature Dependences ◽  
Function Calculation ◽  
First Time ◽  
Good Agreement

In the paper the physical properties and thermodynamic functions of borides Х2В (Х=W, Mo, Mn, Fe, Co, Ni та Cr) are studied with accounting for fluctuation processes. We use the microstructure analysis, the X-ray structural and the durometric analyses to determine the physical properties of alloys. In the paper it is determined the phase composition and physical properties of borides. In this paper for the first time it is determined the thermodynamic functions of borides using the Hillert and Staffansson model with accounting for the first degree approximation of high-temperature expansion for the free energy potential of binary alloys. We obtain the temperature dependences for such thermodynamic functions as Gibbs free energy, entropy, enthalpy and heat capacity Ср along with their values at the formation temperature for Х2В (Х=W, Mo, Mn, Fe, Co, Ni та Cr). The approach under consideration enables to give more thorough from the thermodynamic point of view description of borides formed from the liquid. The outcomes of the thermodynamic function calculation for borides are in good agreement with experimental data and results of other authors.

Strongly coupled thermal and chemical expansion in the perovskite oxide system Sr(Ti,Fe)O3−α

2015 ◽  
Vol 3 (7) ◽  
pp. 3602-3611 ◽  
Author(s):  
Nicola H. Perry ◽  
Jae Jin Kim ◽  
Sean R. Bishop ◽  
Harry L. Tuller
Keyword(s):  
Energy Conversion ◽  
Oxide System ◽  
Perovskite Oxide ◽  
Oxygen Stoichiometry ◽  
Temperature Dependent ◽  
Chemical Expansion ◽  
Strongly Coupled ◽  
Expansion Coefficients ◽  
Energy Conversion Devices ◽  
First Time

To evaluate stability in energy conversion devices, thermal and chemical expansion coefficients (CTE, CCE) of Sr(Ti,Fe)O3−α were measured and deconvoluted for the first time, revealing an oxygen stoichiometry-dependent CTE and temperature-dependent CCE.

scholarly journals Electronic properties of the Sn1−xPbxO alloy and band alignment of the SnO/PbO system: a DFT study

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
N. Kelaidis ◽  
S. Bousiadi ◽  
M. Zervos ◽  
A. Chroneos ◽  
N. N. Lathiotakis
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Density Functional ◽  
Hydrogen Generation ◽  
Valence Band Maximum ◽  
Oxide System ◽  
Band Alignment ◽  
Oxide Thin Film ◽  
Ternary Oxide ◽  
P Type

Abstract Tin monoxide (SnO) has attracted attention due to its p-type character and capability of ambipolar conductivity when properly doped, properties that are beneficial for the realization of complementary oxide thin film transistors technology, transparent flexible circuits and optoelectronic applications in general. However, its small fundamental band gap (0.7 eV) limits its applications as a solar energy material, therefore tuning its electronic properties is necessary for optimal performance. In this work, we use density functional theory (DFT) calculations to examine the electronic properties of the Sn1−xPbxO ternary oxide system. Alloying with Pb by element substitution increases the band gap of SnO without inducing defect states in the band gap retaining the anti-bonding character of the valence band maximum which is beneficial for p-type conductivity. We also examine the properties of the SnO/PbO heterojunction system in terms of band alignment and the effect of the most common intrinsic defects. A broken gap band alignment for the SnO/PbO heterojunction is calculated, which can be attractive for energy conversion in solar cells, photocatalysis and hydrogen generation.

Rapid Reactions of Phthalocyanines with Tellurium Tetrachloride in Non-aqueous Solutions

1999 ◽  
Vol 03 (06) ◽  
pp. 537-543 ◽  
Author(s):  
YUTAKA KAGAYA ◽  
HIROAKI ISAGO
Keyword(s):  
Aqueous Solutions ◽  
Zinc Complex ◽  
Magnetic Circular Dichroism ◽  
Equilibrium Constants ◽  
Lewis Base ◽  
Molar Ratios ◽  
Spectral Changes ◽  
Acid Base Equilibrium ◽  
Tellurium Tetrachloride ◽  
First Time

Rapid reactions of tetra(tert-butyl)phthalocyanine, H 2( tbpc ), and its zinc complex, [ Zn ( tbpc )], with tellurium tetrachloride ( TeCl 4) in non-aqueous solutions have been investigated. Upon mixing respective solutions containing the reactants, drastic spectral changes occurred in chloroform and toluene even at room temperature. The electronic spectra of the products indicated that the reactions involved an acid-base equilibrium where the phthalocyanines and tellurium tetrachloride acted as a Lewis base and a Lewis acid respectively. By monitoring the spectral changes based on various initial molar ratios of the reactants, the compositions of the products for each system have been determined. [ Zn ( tbpc )] formed a 1:1 ( tbpc : TeCl 4) adduct in both chloroform and toluene, showing the same spectra close to those of the known monoprotonated phthalocyanines. On the other hand, H 2( tbpc ) formed a 1:1 adduct in chloroform but a 1:3 adduct in toluene even though both products showed essentially the same spectra close to those of the known diprotonated phthalocyanines. Equilibrium constants have been calculated for the four systems. Magnetic circular dichroism (MCD) spectra of conjugated acids of phthalocyanines have been studied for the first time.

DTA Analysis on the Solidification Behavior of the Al2O2-Y2O3-ZrO2 Ternary Oxide System and Microstructural Investigation

2012 ◽  
Vol 706-709 ◽  
pp. 2424-2427
Author(s):  
Hai Jun Su ◽  
Jun Zhang ◽  
Wei Guo ◽  
Jian Zheng Yu ◽  
Lin Liu ◽  
...  
Keyword(s):  
Heating Temperature ◽  
Solidus Temperature ◽  
Ternary Eutectic ◽  
Eutectic Structure ◽  
Oxide System ◽  
Ternary Oxide ◽  
Oxide Ceramic ◽  
Solidification Behavior ◽  
Microstructural Investigation ◽  
Dta Analysis

The well-aligned growth structures which derive from directional solidification of ceramic eutectics are of great interests due to their potential use in electronic devices and as structural materials at high temperatures. Because of the complexity of the component system and very high melting points, the solidification behavior on the oxide ceramic eutectic is still unclear up to date. In the presented paper, the Al2O3-Y2O3-ZrO2ternary eutectic ceramic is remelted by a DTA apparatus. The maximal heating temperature is 1950 °C. The melting and solidification behavior are investigated by the DTA analysis. The solidification microstructure is investigated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD). The results show that solidus temperature and the liquidus temperature are 1738.4 °C and 1750.1 °C, respectively. The formation path of eutectic phase is discussed. The microstructure of as-solidified eutectic ceramic shows a divorced ternary eutectic structure consisting of Al2O3, YAG and ZrO2phases with a random distribution. Furthermore, the microstructural comparison with directionally solidified ternary eutectic ceramic is presented and discussed.

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