FactSage Thermochemical Software Research Articles

The simple microsegregation model for steel considering MnS formation in the liquid and solid phases

A simple microsegregation model for steel considering MnS formation in the liquid and solid phases is proposed. The concentration of the solutes during the solidification is calculated using the discretized Scheil-Gulliver model for steel (SGS). In the calculation, the planar dendrite is divided into a finite number (n) of elements to record the local solid concentrations and calculate the mass fraction of MnS precipitation during further cooling. The solidification part of the model is validated by measured solidification temperatures and the MnS formation amount predicted by the FactSage thermochemical software. The model was applied to evaluate the high-temperature ductility of the selected steel. The optimum Mn content of the assumed steel was obtained based on the simulation.

Anode reaction mechanisms of Na|NaCl-CaCl2|Zn liquid metal battery

Na|NaCl-CaCl2|Zn liquid metal battery is regarded as a promising energy storage system for power grids. Despite intensive attempts to present a real mechanism of metal electrodes reaction, those for Na||Zn LMBs are not clear yet. Herein, the anode reactions for the multiple discharge potential plateaus were deduced by means of FactSage thermochemical software, which were subsequently validated by X-ray diffraction analysis and the modeling of phase transformation in the cooling process. A pre-treatment process was proposed for the analysis of anode product composition using the atomic absorption spectrometry method, and the anode states at working temperature (560 °C) were obtained by the Na-Ca-Zn ternary phase for the first time. The results indicate the discharge of Na and Ca led to the formation of Ca-Zn intermetallic compounds, whilst the extraction of Ca in Ca-Zn intermetallic compounds was responsible for the multiple discharge plateaus. Moreover, it was found that the charging product was in electrochemical double liquid metal layers, which are composed of Na and Ca with dissolved Zn respectively..

Thermodynamic and Experimental Analyses of the Carbothermic Reduction of Tungsten Slag

Tungsten slag contains valuable elements, such as Bi, W, Fe, Nb, and Mn, and harmful elements, such as Pb. Here, the carbothermic reduction of tungsten slag was analyzed thermodynamically using FactSage thermochemical software and verified experimentally. CaO, SiO2, and Al2O3 could not react with C and were the major constituents of the slag. WO3, Fe2O3, Nb2O5, and MnO2 were reduced and collected in the alloy, and Bi2O3 and PbO were reduced and formed Bi and Pb, respectively, which volatilized and collected in the fumes. Increased temperature and decreased reductant addition contributed to an increase in the recovery of Nb, while the recovery of W was less affected. At reduction conditions of 14–16% reductant addition and 1500–1600°C, the recovery percentage of W, Fe, and Nb were over 90%, the recovery percentage of Mn was over 50%, and Bi and Pb were collected in the fumes.

Mechanical Properties of Commercial Purity Aluminum Modified by Zirconium Micro-Additives

The mechanical properties and the fractured surfaces of commercial purity aluminum modified by zirconium micro-additives were investigated by means of experimental examination. A commercial purity Al specimen was used as a reference material and seven Al-Zr alloys in the 0.02–0.14 wt.% Zr composition range (with 0.02 wt.% Zr step) were prepared by microalloying methods. Optical microscopy was used to examine the microstructures and to calculate the grain sizes of the prepared specimens. The phase assemblage diagrams were plotted and the relative amounts of solid phases were calculated at room temperature using FactSage thermochemical software and databases. Proof stress, strength coefficient and strain hardening exponent were measured from the stress-strain curves obtained from tensile experiments and Charpy impact energy was calculated for all specimens. The experiments showed that the grain size of commercial purity Al was reduced by adding any Zr concentration in the investigated composition range, which could be due to the nucleation of new grains at Al3Zr particle sites. Accordingly, the microhardness number, tensile properties and Charpy impact energy were improved, owing to the large grain-boundary areas resulted from the refining effect of Zr, which can limit the movement of dislocations in the refined samples. The basic fracture mode in all specimens was ductile, because Al has an FCC structure and remains ductile even at low temperatures. The ductile fractures took place in a transgranular manner as could be concluded from the fractured surface features, which include voids, ridges and cavitation.

Behavior of Al4C3 Particles During Flotation and Sedimentation in Aluminum Melts

Al4C3 particles form during the primary production of aluminum via molten salt electrolysis due to the carbon solubility and direct contact between bath, metal, and carbon anodes. Additional Al4C3 may form during melt processing through direct contact between the melt and carbonaceous materials. As a result of their small size and similar density to aluminum, removal of aluminum carbide particles can be challenging. If not removed, carbides can produce inclusion defects or poor surface condition in aluminum products. The current work studies the removal and behavior of Al4C3 particles during flotation with different gas mixtures, as well as sedimentation. The interaction between carbide particles and Al2O3 films during the melt treatment processes was also studied and reported. Factsage thermochemical software was used to model the interactions at the interface of inclusions and bubbles covered by films. The highest degree of carbide removal was obtained after flotation with an H2O-containing argon gas mixture, where the carbide concentration dropped below the measured solubility limit of carbon at the corresponding temperature. Strong interaction between Al4C3 particles and Al2O3 films was observed during sedimentation which worked as an efficient removal method for the particles. Oxidation of carbides and formation of oxycarbides were suggested as the mechanisms promoting the attachment of carbides on oxide films.

On the Application of the FactSage Thermochemical Software and Databases in Materials Science and Pyrometallurgy

The discovery of new metallic materials is of prime importance for the development of new technologies in many fields such as electronics, aerial and ground transportation as well as construction. These materials require metals which are obtained from various pyrometallurgical processes. Moreover, these materials need to be synthesized under extreme conditions of temperature where liquid solutions are produced and need to be contained. The design and optimization of all these pyrometallurgical processes is a key factor in this development. We present several examples in which computational thermochemistry is used to simulate complex pyrometallurgical processes including the Hall–Heroult process (Al production), the PTVI process (Ni production), and the steel deoxidation from an overall mass balance and energy balance perspective. We also show how computational thermochemistry can assist in the material selection in these extreme operation conditions to select refractory materials in contact with metallic melts. The FactSage thermochemical software and its specialized databases are used to perform these simulations which are proven here to match available data found in the literature.

Minimizing of copper losses to converter slag by a boron compound addition

In copper production, the concentrate obtained after ore-flotation follows by pyrometallurgical route; Smelting, Converting and Fire Refining stages to obtain the anode plates. In this production process, a significant amount of copper (4–8 %Cu) goes to converter slag (CS) which is the most serious problem facing the copper sector. Therefore, in this study, it was aimed to minimize the copper losses to CS in converter stage by adding calcined colemanite (CC) which is a boron compound. After characterization of CS in detail, effect of the reaction temperature and CC addition were experimentally investigated. Then, thermochemical calculations of the slag with the addition of CC were carried out by using the Equilib and Phase Diagram modules of the FactSage thermochemical software. Experimental results show that the amount of copper losses to the CS can be decreased from 4.45% to 1.2% by adding 2% CC to the converter slag at the temperature of 1250 °C for 3 h reaction time.

In-situ synthesis and densification of CeB6 ceramics by spark plasma sintering from CeO2 and B powders: Effect of boron content and boron particle size on microstructural, mechanical and electrical properties

In-situ synthesis and densification of polycrystalline bulk CeB6 ceramics were carried out by Spark Plasma Sintering technique using CeO2 and coarse & nano B powders. Two-step heating schedule was applied via optimizing both synthesis and sintering temperatures using FactSage thermochemical software. The influence of boron particle size and content on the physical, microstructural, mechanical and electrical properties of CeB6 ceramics were investigated. The obtained results exhibited that the content of additional phases (B2O3 & B4C) decreased with the decreasing of boron content (from 31.5 to 23.5 wt%). The reduction of boron particle size (from 1 μm to 250 nm) enhanced fracture toughness values of the investigated ceramics. CeB6 ceramic sintered using nano boron in 8 wt% lack ratio possessed highest CeB6 content (98.4 vol%), high hardness (16.0 ± 2.0 GPa), high fracture toughness (2.8 ± 0.5 MPa m1/2) and low electrical resistivity (1.58x10−1 Ω m). Hence, polycrystalline bulk CeB6 ceramics, sintered at 1950 °C for 15 min under 15 kN by SPS from CeO2 - coarse B powder mixture in 8 wt % lack B ratio, have a usage potential as electron emitters especially in electron microscopes.

Application of molecular interaction volume model in separation of Ti-Al alloys in vacuum distillation

The separating effects of Al from Ti-Al alloys were investigated via the molecular interaction volume model in vacuum distillation. The vapour-liquid equilibrium (VLE) composition and the activity coefficients of Ti-Al alloys at 1773 K–2273 K were predicted using only the properties of pure components. The calculated values of components activities are in good agreement with the corresponding FactSage data used for comparison. Predicted results of VLE show that the content of Ti in vapour and liquid phases increases with increasing distillation temperature. At 1873 K, in the vapour phase, the content of Ti was 0.000379 and 0.001353, while in the liquid phase it was 20 and 70 (all in wt %), respectively. The predicted separation coefficients indicate that Al can be separated from Ti completely by vacuum distillation. This study verified that FactSage Thermo-Chemical Software and Databases could serve as suitable source of experimental data for binary liquid alloys.

Formation of TaB2 powders from high energy ball milling and borothermal reduction process

TaB2 powders were fabricated at reduced temperatures via borothermal reduction route by high energy ball milling of Ta2O5 and B powder blends. The effects of milling media (Steel, ZrO2 and WC), milling time (1,3,5 and 7 h) and heat treatment temperature (1650 °C and 1350 °C) on the formation and microstructural characteristics of TaB2 and related phases were extensively investigated. Increasing the milling time up to 7h was found to be decreased the common formation temperature of the TaB2. Ta-rich Ta3B4 and TaB phases were formed after heat treatment at 1650 °C for 5 h milled samples in ZrO2 and WC media which were associated with the generation of different impact energies. Depending on the C diffusion from graphite mold and the wearing of milling jar and balls, TaC formation was also observed. The predicted reactions and experimental results were compared, and the reaction mechanism of the Ta2O5–B system was explained by using FactSage thermochemical software, differential thermal analysis (DTA) and X-ray diffractometry (XRD). TaB2 based fine powders comprising TaC were obtained from powder blends milled for 3 h in ZrO2 and WC media and heat treated at 1350 °C for 1 h.

A systematic study on solid-state synthesis of monticellite (CaMgSiO4) based ceramic powders obtained from boron derivative waste

Solid-state synthesis of monticellite based ceramic powders from boron derivative waste in an eco-friendly route and the investigation of phase transformation mechanisms were studied. The heat-treatment of boron derivative waste, mainly composed of dolomite, calcite and quartz, was systematically carried out at 650 °C and 800 °C for various dwell times between 1 min and 4 h. The heat-treatment temperatures were selected considering TG-DTA curves of waste and ΔG – T diagrams obtained using FactSage Thermochemical Software. XRF, XRD, FTIR, TG-DTA and SEM analysis, particle size measurement and crystallite size determination carried out extensively. The obtained results showed that monticellite based ceramic powder synthesized at 800 °C for 4 h was composed of monticellite, akermanite, diopside, calcium magnesium borate and zeolite. The calcination of dolomite was completed both at 650 °C for 1 h and up to 800 °C, and calcite was decomposed at 800 °C for 30 min. Both diopside and monticellite were firstly detected at 650 °C for 30 min and at 800 °C for 1 min. Also, akermanite was presented at 800 °C for 1 min. The presented method offers the lowest temperature (800 °C) in literature for synthesis of monticellite and akermanite which reduces the energy consumption during heat-treatment.

Thermodynamic analysis of the carbothermic reduction of a high-phosphorus oolitic iron ore by FactSage

A thermodynamic analysis of the carbothermic reduction of high-phosphorus oolitic iron ore (HPOIO) was conducted by the FactSage thermochemical software. The effects of temperature, C/O ratio, additive types, and dosages both on the reduction of fluorapatite and the formation of liquid slag were studied. The results show that the minimum thermodynamic reduction temperature of fluorapatite by carbon decreases to about 850°C, which is mainly ascribed to the presence of SiO2, Al2O3, and Fe. The reduction rate of fluorapatite increases and the amount of liquid slag decreases with the rise of C/O ratio. The reduction of fluorapatite is hindered by the addition of CaO and Na2CO3, thereby allowing the selective reduction of iron oxides upon controlled C/O ratio. The thermodynamic results obtain in the present work are in good agreement with the experimental results available in the literatures.

Reprint of: FactSage thermochemical software and databases, 2010–2016

The FactSage computer package consists of a series of information, calculation and manipulation modules that enable one to access and manipulate compound and solution databases. With the various modules running under Microsoft Windows® one can perform a wide variety of thermochemical calculations and generate tables, graphs and figures of interest to chemical and physical metallurgists, chemical engineers, corrosion engineers, inorganic chemists, geochemists, ceramists, electrochemists, environmentalists, etc. This paper presents a summary of the developments in the FactSage thermochemical software and databases during the last six years. Particular emphasis is placed on the new databases and developments in calculating and manipulating phase diagrams.

FactSage thermochemical software and databases, 2010–2016

The FactSage computer package consists of a series of information, calculation and manipulation modules that enable one to access and manipulate compound and solution databases. With the various modules running under Microsoft Windows® one can perform a wide variety of thermochemical calculations and generate tables, graphs and figures of interest to chemical and physical metallurgists, chemical engineers, corrosion engineers, inorganic chemists, geochemists, ceramists, electrochemists, environmentalists, etc. This paper presents a summary of the developments in the FactSage thermochemical software and databases during the last six years. Particular emphasis is placed on the new databases and developments in calculating and manipulating phase diagrams.

The Vaporization Coefficient of Silica

Free surface or Langmuir evaporation of a solid oxide often leads to a vapor flux that 1-4 orders of magnitude lower than that calculated from equilibrium vapor pressures [1]. This factor is termed the “vaporization coefficient” and clearly has a large impact on determining vaporization rates. The most common method of measuring vaporization coefficients is to measure the vapor flux from a free surface and compare it to the vapor flux calculated from equilibrium vapor pressures. In this study, we used a vacuum thermogravimetric analyzer (TGA) to measure the vapor flux from a silica coupon. Initially we had deposition on the coupon of W and Ta oxides from the furnace element and heat shields. This problem was eliminated with a graphite tube surrounding the coupon. The coupons were amorphous, however the temperatures of vaporization (1475 to 1675°C) induced surface crystallization to a surface layer of cristobalite. This was verified with x-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermodynamically, the vaporization of SiO2(cristobilite) leads SiO2(g), SiO(g), O2(g), O(g). The pressures were calculated from a free energy minimization code [2] and converted to vapor fluxes with the Hertz-Knudsen-Langmuir equation. These calculated fluxes were compared to the measured fluxes and the vaporization coefficient is simply the quotient of the two. These data are given in Table 1 below. Table 1. Vaporization coefficients obtained by comparison of free surface vapor flux to calculated flux. Temperature (°C) J(calculated) J(measured) Vaporization Coefficient mg/cm2-hr mg/cm2-hr 1475 3.797459 0.0168 4.42E-03 1525 10.20388 0.0451 4.42E-03 1575 25.95741 0.1421 5.47E-03 1625 62.79001 0.3606 5.74E-03 1675 144.9916 0.7064 4.87E-03 Other investigators have determined the vaporization coefficient for silica with the Knudsen cell method and variation of the orifice geometry [3]. This method is discussed and results for silica [4-7]. The two methods will be discussed as well as differences and similarities in the results. 1. Searcy, A.W., et al., Chemical and mechanical behavior of inorganic materials. 1970, New York,: Wiley-Interscience. xxiv, 715 p.2. Bale, C.W., et al., FactSage thermochemical software and databases. Calphad-Computer Coupling of Phase Diagrams and Thermochemistry, 2002. 26(2): p. 189-228.3. Paule, R.C. and J.L. Margrave, Free-Evaporation and Effusion Techniques, in The Characterization of High-Temperature Vapors, J.L. Margrave, Editor. 1967, John Wiley & Sons: New York.4. Firsova, L. and A.N. Nesmeyanov, Determination of the Coefficients of Condensation of Lithium, Beryllium, Boron, Silicon and Lead Oxides. Zhur. Fiz. Khim., 1960. 34.5. Shornikov, S.I., I.Y. Archakov, and M.M. Shults, Mass-spectrometric study of evaporation and thermodynamic properties of silicon dioxide - II. Determination of partial coefficients of silicon dioxide evaporation. Zhurnal Obshchei Khimii, 1999. 69(2): p. 197-206.6. Nagai, S.I., et al., Knudsen Effusion Study of Silica. Journal of the Chemical Society-Faraday Transactions I, 1973(9): p. 1628-1634.7. Rocabois, P., C. Chatillon, and C. Bernard, Vapor-Pressure and Evaporation Coefficient of SiO(Amorphous) and SiO2(S)+Si(S) Mixtures by the Multiple Knudsen Cell Mass-Spectrometric Method. Revue Internationale Des Hautes Temperatures et Des Refractaires, 1992. 28(2): p. 37-48.

Calculation and synthesis of ZrC by CVD from ZrCl4–C3H6–H2–Ar system with high H2 percentage

A thermodynamic calculation about the synthesis of ZrC from the ZrCl4–C3H6–H2–Ar system with high percentage of H2 was performed using the FactSage thermochemical software. According to the calculation, ZrC coating was synthesized on graphite substrates and carbon fibers by a low pressure chemical vapor deposition (LPCVD) process, and growth rate of the ZrC coating as a function of temperature was investigated. The surface diagrams of condensed-phases in this system were expressed as the functions of the deposition temperature, total pressure and reactant ratios of ZrCl4/(ZrCl4+C3H6), H2/(ZrCl4+C3H6), and the yield of the products was determined by the diagrams. A smooth and dense ZrC coating could be synthesized under the instruction of the calculated parameters. The morphologies of the ZrC coatings were significantly affected by temperature and gases flux. The deposition temperature is much lower than that from the ZrCl4–CH4–H2–Ar system.

A Thermodynamic Model for the NH4+, K+ // H2PO4-, H2P2O72-, NO3-, Cl- - H2O System

We have developed a quantitative thermodynamic description of the NH4H2PO4-(NH4)2H2P2O7-KH2PO4-K2H2P2O7-NH4NO3-KNO3-NH4Cl-KCl-H2O system, which is of great importance for fertilizers applications. The liquid phase and all solid solutions were modeled using the Modified Quasichemical Model for short-range ordering. The liquid model includes the reaction of dimerization of AH2PO4 (where A = NH4+ or K+) according to: 2 AH2PO4(liquid) ↔ A2H2P2O7(liquid) + H2O(liquid or gas). The model parameters are mainly obtained by the critical evaluation and optimization of available thermodynamic and phase equilibrium data for the lower-order subsystems. The model is then used to estimate the properties of multicomponent salts from these assessed parameters for the lower-order subsystems, using interpolation methods along with Gibbs energy minimization software. When used in conjunction with thermodynamic databases for solids, solid solutions, and gases, these databases permit the calculation of complex multiphase equilibria in multicomponent systems, using the FactSage thermochemical software. In particular, calculations of interest for the production and storage of fertilizers may be performed.

Activity Measurements of Mg in the Ternary Cu-Mg-Si System Using Thermogravimetric Knudsen Effusion Method

The high vapor pressure of Mg in comparison with Cu and Si enables the use of thermogravimetric Knudsen effusion method (KEM) to determine the thermodynamic properties of binary Cu-Mg, Mg-Si, and ternary Cu-Mg-Si alloys. In the current study, the weight loss of solid Mg with time has been determined at different constant temperatures between 705 K and 788 K (432 °C and 515 °C) by using KEM, and from these diagrams, the sublimation rate of Mg was calculated. By introducing the sublimation rates into the equation derived from the kinetic gas theory, the enthalpy change of sublimation reaction of Mg at the experimental temperatures was calculated to be 147.5 ± 6.5 kJ mol−1, which is close to the 143.8 ± 0.5 kJ mol−1 calculated using the thermodynamic data available in the literature. Similar procedure was also applied to the binary Cu-Mg, Mg-Si, and ternary Cu-Mg-Si alloys where the activities of Mg with respect to the Mg wt pct with WCu:WSi = 20:80 were calculated. The diversion points in the activity–composition diagrams gave the phase boundary compositions in the phase diagrams. The phase boundary compositions of Mg in the alloys determined using KEM were in good agreement with the known binary and the constructed ternary phase diagram using FactSage thermochemical software and databases.

Thermodynamic analysis on the codeposition of ZrC–SiC by chemical vapor deposition using the ZrCl4–C3H6–MTS–H2–Ar system

A thermodynamic calculation on co-deposition of ZrC–SiC from the ZrCl4–C3H6–MTS–H2–Ar system was performed using the FactSage thermochemical software and verification experiments were performed. The surface diagrams of condensed-phases in this system were expressed as functions of the deposition temperature, total pressure, reactant ratio of MTS/(MTS+C3H6) and ratio of H2/(ZrCl4+MTS+C3H6), and the composition of the products was determined by the diagram. The calculation results indicate that their yields strongly depend on the molar ratio of the injected reactants and temperature, and ZrC–SiC can be co-deposited under a proper condition. The experimental results show that ZrC–SiC coating was successfully co-deposited on graphite substrates and carbon fibers according to the thermodynamic calculation.

Thermodynamics of the Mg Recycling Process

With the increasing demand of Mg alloys, their recycling will become an important issue in the near future. In the current study, the chemical reactions involved during the recycling process are investigated using thermodynamic calculations. It is found that the melting temperature, density, and MgO solubility of conventional refining fluxes composed of MgCl2-NaCl-KCl-CaF2 salts are very sensitive to the flux composition. According to chemical reaction calculations, the solubility of MgO in the refining flux is much lower than the MgO impurity level in molten Mg. Therefore, the refining of Mg alloy, and in particular the removal of MgO by submersing molten flux, seems to be mainly achieved by physical attachment rather than chemical reaction. As a result, it is suggested that the liquidus temperature and density of the molten flux are important physicochemical properties to be considered in the selection of a proper refining flux for a given Mg alloy. In addition, calculations show that expensive and reactive alloying elements such as Ca, Sr, and rare-earth elements can be easily consumed by the molten flux during the refining process, which limits current refining fluxes. All thermodynamic calculations were performed using the FactSage thermochemical software.