Primary Phase Field Research Articles

Integrated experimental and thermodynamic modelling study of phase equilibria in the “CuO0.5”-PbO-CaO system in equilibrium with Cu/Pb metal

Phase equilibria studies were undertaken on the “CuO0.5”-PbO-CaO system in equilibrium with Cu/Pb metal as part of the integrated experimental and thermodynamic modelling study of phase equilibria in the Cu-Pb-Zn-Fe-Ca-Si-Al-Mg-O-S-(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co and Na) gas/oxide liquid/matte/speiss/metal/solids system in support of the development and optimisation of pyrometallurgical processes. The equilibration and quenching technique followed by the electron probe X-ray microanalysis (EPMA) was used in the present study. The primary phase fields of massicot (PbO), copper plumbite (Cu2PbO2), cuprite (Cu2O) and lime (CaO) were experimentally characterised. The experimental data obtained in the present study, as well as available literature data on the phase equilibria and thermodynamics of the “CuO0.5”-PbO-CaO system in equilibrium with Cu/Pb were used for the optimisation of the model parameters of the discussed system in agreement with the Cu-Pb-Zn-Fe-Ca-Si-Al-Mg-O-S-(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co and Na) gas/oxide liquid/matte/speiss/metal/solids system to obtain a self-consistent set of parameters of the thermodynamic model for all phases. The predicted liquidus surface of the “CuO0.5”-PbO-CaO system was presented for the first time in the complete range of temperatures and compositions.

Phase equilibria of TiO2–SiO2–CaO–10%Al2O3-7.5%MgO at 1773 K and effects of MgO on the distribution of phase fields

The 1773 K phase diagram of the TiO2–SiO2–CaO-10 wt%Al2O3-7.5 wt%MgO system was constructed experimentally using the quenching method, focusing on the composition range of high TiO2 content. The obtained isothermal section contains four phase fields: the liquid phase field, the primary phase field of pseudo-brookite, the primary phase field of perovskite, and the liquid + perovskite + pseudo-brookite phase field. The pseudo-brookite particle precipitated in its primary phase field is more suitable for the efficient selective enrichment and separation of titanium resources. The increase of MgO from 5 % to 7.5 % in the TiO2–CaO–SiO2-10 wt%Al2O3–MgO system leads to a decrease of the liquidus temperature and an expansion of the liquid + pseudo-brookite + perovskite phase field. The increase of MgO promotes the enrichment of TiO2 into the pseudo-brookite phase and reduces the TiO2 level in the glass phase.

Phase Equilibrium Study of Rare Earth Oxide–Fluoride Salt System: A Review

The applications of rare earth metals and alloys are becoming increasingly widespread and there is a strong market demand. Currently, most of the production enterprises adopt the fluoride–oxide system for electrolytic preparation of rare earth metals and alloys. The solubility of rare earth oxides in molten salt directly affects the selection of operational parameters in the electrolysis process. When the added amount of RE2O3 is less than its solubility, it leads to a decreased electrolytic efficiency. Conversely, an excessive amount of oxide is prone to settle at the bottom of the electrolytic cell, impeding smooth production. The RE2O3 solubility in the fluoride salt can be represented by the phase equilibrium of the RE2O3-REF3-LiF system. The isothermal lines in the primary phase field of rare earth oxide represent the solubility of the oxide in the fluoride salt at the corresponding temperature. This paper outlines the research methods and experimental results on the phase equilibria of the RE2O3-REF3-LiF system. The characteristics and existing problems in the current phase equilibrium study are analyzed. The solubility data of RE2O3 are expressed in the forms of ternary and pseudo-binary phase diagrams of the RE2O3-REF3-LiF system, providing theoretical guidance for the establishment of an accurate and reliable rare earth electrolysis system database and the optimization of electrolytic processes.

Phase Equilibria and Thermodynamic Modelling of the PbO-ZnO-FeO-FeO1.5-SiO2 system and its subsystems in equilibrium with air/metallic lead/iron

The phase equilibria of the ZnO-“FeO1..5”, ZnO-“FeO1.5”-SiO2, PbO–ZnO-“FeO1.5” and PbO–ZnO-“FeO1.5”-SiO2 slag systems in equilibrium with air or metallic lead/iron were studied as part of the investigation of the 19-component PbO–ZnO–Cu2O–FeO–Fe2O3–CaO–SiO2–Al2O3–MgO–S-(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co as minor elements) slag/matte/metal/speiss/gas system, supporting the operation/development of existing and emerging pyrometallurgical processes. In the experimental part of the study, samples underwent high temperature equilibration followed by quenching, and the direct measurement of the lead, zinc, iron and silicon concentrations in the liquid slag, solid oxide, and metal phases by electron probe microanalysis (EPMA). The a) massicot (PbO), b) spinel ((Zn, Fe)Fe2O4), c) zincite ((Zn,Fe)O1+x, 2 polymorphs), d) lead ferrite (Pb2+xFe2O5+x), e) plumboferrite (Pb4Fe22-xZnxO37), f) magnetoplumbite (Pb(Fe2O3,PbFeO2,PbZnO2)Fe10O16), and g) W-ferrite (PbZn2-xFe16+xO27) primary phase fields of the PbO–ZnO-“FeO1.5” system in equilibrium with air were studied between 780 and 1300 °C. The ZnO-“FeO1.5”, ZnO-“FeO1.5”-SiO2 and PbO–ZnO-“FeO1.5”-SiO2 systems in equilibrium with air were studied up to 1745 °C, significantly improving the availability of information on the composition range of the high- and low-Fe zincite ((Zn,Fe)O1+x) phases, and on the liquid slag composition at the boundaries of their primary phase fields. Lastly, the solubilities of iron in larsenite (Pb(Zn,Fe)SiO4) and melilite (Pb2(Zn,Fe)Si2O7) in equilibrium with air or metal were studied between 700 and 800 °C. The newly obtained and existing experimental data were used to develop a self-consistent set of thermodynamic parameters describing all phases in the system using the FactSage computer package.

Phase equilibrium study of the CaO–SiO2–CrOx system at 1600°C in reducing atmospheres

AbstractPhase equilibria in the CaO–SiO2–CrOx system were experimentally investigated at 1600°C and pO2 of 10−10 to 10−11 atm using the high‐temperature isothermal equilibration/drop quenching/electron probe X‐ray microanalysis technique. The constrained isothermal sections of the CaO–SiO2–CrOx system were constructed at 1600°C and pO2 of 10−10 to 10−11 atm based on the experimental results. The primary phase fields including cristobalite (SiO2), larnite (Ca2SiO4), (Ca,Cr)Cr2O4, and corundum (Cr2O3) were determined. Simulations by thermodynamic software MTDATA, FactSage, and Thermo‐Calc were compared with the present experimental results.

Dynamic high‐temperature crystallization and processing properties of industrial soda–lime–silica glasses

AbstractIn situ dynamic crystallization properties of industrial soda–lime–silica glasses at realistic processing temperatures have not yet been explored. Hence, we collected in situ high‐temperature X‐ray diffraction patterns for 10 different industrially manufactured soda–lime–silica glasses as a function of temperature between 900 and 1200°C to investigate the phase relations in their devitrified melts. The high‐temperature X‐ray diffraction study was complemented by measuring the liquidus temperature of those glasses by the temperature gradient technique. A multiple variable regression analysis was applied to the experimental and modeled data to produce a predictive model for the rate of solidification and liquidus temperature based on glass composition. We have demonstrated that forms of quartz (SiO2) and Na2CaSiO4, which are not traditionally identified by room temperature X‐ray diffraction studies of commercial soda–lime–silica glasses, are the dominant crystalline phases at 800 and 900°C. Upon further heating, different forms of cristobalite become the primary phase field prior to the formation of X‐ray amorphous melts, irrespective of the glass composition. Sporadic unidentified as well as high‐temperature stable SiO2 polymorphs that are not recoverable to room temperature were also observed. In contrast to the literature, wollastonite (CaSiO3) and devitrite (Na2Ca3Si6O16), which are the main predictor variables in previously developed liquidus temperature models, were not observed prior to the formation of X‐ray amorphous glass melts, and hence their influence on liquidus temperature may be questionable. It was also found that the difference between glass processing and liquidus temperatures can be excessively high, and such large temperature differences can potentially be exploited and reduced to enable decreases in melting or processing temperatures of industrial soda–lime–silica glass melts.

Experimental and thermodynamic modeling study of phase equilibria in the PbO–NiO–SiO2 system

AbstractAn integrated experimental and thermodynamic modeling investigation of the phase equilibria in the PbO–NiO–SiO2 system in air and also in equilibrium with liquid metal has been undertaken to better characterize the chemical reactions taking place in the Ni‐containing Pb processing slags. New experimental phase equilibria data at 720°C–1740°C were obtained for this system using high‐temperature equilibration of synthetic mixtures with predetermined compositions in sealed silica ampoules or in Au/Pt–Ir foils, a rapid quenching technique, and electron probe x‐ray microanalysis of the equilibrated phase compositions. Phase equilibria and liquidus isotherms in the quartz/tridymite/cristobalite (SiO2), olivine (Ni2SiO4), monoxide (NiO), Ni‐barysilite (Pb8NiSi6O21), massicot (PbO), and di‐lead silicate (Pb2SiO4) primary phase fields were revealed and the extent of the high‐SiO2 two‐liquid immiscibility gap in equilibrium with cristobalite was determined. New experimental data were used in the development of a thermodynamic database describing this ternary system. Also, modeling revision of the NiO–SiO2 binary system was conducted, resulting in a smaller miscibility gap in ternary systems that was closer to the experimental results.

Phase Equilibrium studies in the system “FeO”–SiO2–Al2O3–CaO–MgO at 1200 °C and Po2 10-8atm

Iron oxides and silica are the major components of copper smelting slag. The oxides of aluminum, calcium and magnesium are also present in the slag that is introduced through copper concentrate, flux and refractories. Liquidus temperatures of the copper smelting slags are usually controlled by Fe/SiO2. The concentrations of Al2O3, CaO and MgO, and FeO/Fe2O3 in the slag can also affect the liquidus temperatures where FeO/Fe2O3 is a function of oxygen partial pressure. High temperature equilibration under controlled oxygen partial pressure followed by quenching and electron probe microanalysis were used to determine the compositions of the liquid and solid phases at 1200 °C and Po2 10-8 atm. The experimental results are presented in the forms of pseudo-ternary sections “FeO”-CaO-SiO2 at fixed 2, 4 and 6 wt pct MgO, and 2 + 2, 4 + 4 and 6 + 6 wt pct MgO + Al2O3. Spinel and tridymite are the major primary phases in the composition range investigated. In addition, CaSiO3, pyroxene, olivine, and melilite are also present. The isotherms in the spinel and tridymite primary phase fields move towards higher SiO2 concentration directions with increasing CaO, Al2O3, and MgO concentrations. The experimentally determined results are compared with the FactSage calculations.

Experiment and thermodynamic modelling of phase equilibria in PbO−“CuO0.5” and PbO−“CuO0.5”−“FeO1.5” slag systems with metal

The phase equilibria of the PbO−“CuO0.5” and PbO−“CuO0.5”−“FeO1.5” slag systems in equilibrium with solid metallic copper and/or liquid metallic lead−copper alloy were studied as part of the investigation of the 19-element PbO−ZnO−Cu2O−FeO−Fe2O3−CaO−SiO2−Al2O3−MgO−S−(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co as minor elements) multicomponent slag/matte/metal/speiss system, supporting the operation and development of the existing and emerging pyrometallurgical processes. In the experimental portion of this study, samples underwent high temperature equilibration followed by quenching, after which the compositions in the liquid slag, solid oxide and metallic phases were directly measured by electron probe microanalysis (EPMA). Phase equilibria data on the massicot (PbO), spinel ((Fe, Cu)Fe2O4), cuprite (Cu2O), lead ferrite (Pb2+xFe2O5+x), magnetoplumbite (Pb1+xFe12−xO19−x), copper plumbite (Cu2PbO2), and delafossite (CuFeO2) primary phase fields were obtained between 688 and 1000 °C. A key finding of the experimental study of the PbO−“CuO0.5” subsystem was that the copper plumbite (Cu2PbO2) phase melted incongruently, contradicting previous studies that suggested it apparently decomposed below the binary eutectic temperature to form massicot (PbO) and cuprite (Cu2O). Based on the results of past and present experimental studies, a self-consistent set of thermodynamic model parameters describing all phases in the system was derived using the FactSage software package.

Phase equilibria and thermodynamic modelling of the PbO–ZnO-“CuO0.5”-SiO2 system

The phase equilibria of the PbO–ZnO-“CuO0.5“- SiO2 system were studied as part of the investigation of the 19-component PbO–ZnO–Cu2O–FeO–Fe2O3–CaO–SiO2–Al2O3–MgO–S-(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co as minor elements) slag/matte/metal/speiss/gas system in support of the development and optimization of pyrometallurgical processes. In the experimental study, samples were equilibrated at high temperatures, then quenched, and the lead, zinc, copper and silicon concentration in the phases were directly measured by electron probe X-ray microanalysis (EPMA). The cristobalite (SiO2) primary phase field of the PbO–SiO2 system was experimentally studied between 1575 and 1717 °C. The massicot (PbO), zincite ((Zn,Cu)O), cuprite (Cu2O), copper plumbite (Cu2PbO2) and Pb2SiO4 primary phase fields of the PbO-“CuO0.5”-SiO2, PbO–ZnO-“CuO0.5” and PbO–ZnO–SiO2 systems were studied between 664 and 1100 °C. The cuprite (Cu2O), willemite ((Zn,Cu)2SiO4), larsenite (PbZnSiO4) and melilite (Pb2ZnSi2O4) secondary phase fields of the PbO–ZnO-“CuO0.5”-SiO2 system in equilibrium with metal and tridymite/quartz (SiO2) or zincite ((Zn,Cu)O) were studied between 745 and 1100 °C. The zincite ((Zn,Cu)O), tenorite ((Cu,Zn)O) and willemite ((Zn,Cu)2SiO4) solid solutions in equilibrium with air or pure O2 at 1 atm were studied between 900 and 1100 °C. Using the FactSage thermodynamic calculation software, a self-consistent set of parameters based on the Modified Quasichemical Model (MQM) were developed to describe the newly obtained and existing experimental data.

Experimental phase equilibria study and thermodynamic modelling of the “CuO0.5”-AlO1.5-SiO2 ternary system in equilibrium with metallic copper

Phase equilibria studies were undertaken on the “CuO0.5”-AlO1.5-SiO2 system in equilibrium with metallic copper using equilibration and quenching technique followed by the electron probe X-ray microanalysis (EPMA). The liquidus of the “CuO0.5”-AlO1.5-SiO2 system, including the two 2-liquid miscibility gaps in the system as well as the cuprite (Cu2O), corundum (Al2O3), delafossite (CuAlO2), tridymite and cristobalite (Si1-x(CuAl)xO2), and mullite (Al6+2xSi2-2xO13-x) primary phase fields has been characterized. New experimental results together with phase equilibria and thermodynamic literature data were used to obtain a self-consistent set of parameters of the thermodynamic model for all phases. The liquidus projection of the “CuO0.5”-AlO1.5-SiO2 system was presented for the first time in the full range of temperatures and compositions. It was found that the simultaneous dissolution of a small amount of alumina and copper oxide (CuAlO2) in SiO2 phases stabilize cristobalite over tridymite at low temperatures.

Phase equilibria of FeOx-SiO2-Al2O3 slag system at 1200 °C and pO2 of 10−8.6 atm

The increasing concentrations of metallic Al or Al2O3 in secondary copper resources like electronic wastes motivate research into the slag chemistry of high-Al2O3 iron silicate slags for optimizing the industrial smelting process. In this study, the effect of Al2O3 in slag on the phase equilibria of the FeOx-SiO2-Al2O3 slag system was experimentally investigated at 1200 °C and pO2 of 10−8.6 atm. The high-temperature experiments were undertaken in silica and spinel crucibles in a controlled CO–CO2 gas atmosphere, followed by rapid quenching and Electron Probe Microanalysis. The equilibrium compositions of liquid slags in the tridymite primary phase field, spinel primary phase field, and the three-phase invariant point were determined. The 1200 °C isothermal section was constructed for the FeOx-SiO2-Al2O3 system, and the results showed that Al2O3 can dissolve in the liquid slags to a maximum concentration of 17 wt%. The present experimental results were compared with the predictions by MTDATA and FactSage. It was found that the present experimentally determined liquid domain agreed well with the calculations by FactSage except the invariant point. However, the present isotherm in the spinel primary phase field of spinel displayed lower Al2O3 concentrations. The present results help regulating fluxing strategies of FeOx-SiO2-Al2O3 slags and optimizing smelting operations of recycling high-alumina concentration copper resources.

Phase Equilibrium of the V2O5–Na2O System

Knowledge of the equilibrium phase relationship in the V2O5–Na2O system is critical and essential for the sodium salts roasting process of slag-bearing vanadium, and those fundamental studies can be used to accelerate industrial optimization and update the process. Therefore, phase equilibrium and quenching and thermal analysis experiments on the V2O5–Na2O binary system were carried out in the present work under pO2 of 10−3.5 atm. The V2O5–Na2O system has 7 primary phase fields including two simple oxides (V2O5 and Na2O), and 5 binary compounds (Na2V12O31, Na10V24O65, NaVO3, Na4V2O7, and Na3VO4). The existence of Na2V12O31 and Na10V24O65 was experimentally confirmed and then characterized by EPMA, no extensive compounds or solid solutions were detected in the present study. The liquidus lines were experimentally determined in most of the primary phase fields in the temperature range from 500 °C to 800 °C. The temperatures and components of some invariant reactions, including Liq → V2O5 + Na2V12O31 (640 °C, 53 mol pct Na2O), Liq → Na10V24O65 + NaVO3 (504 °C, 40.2 mol pct Na2O), Liq → NaVO3 + Na4V2O7 (540 °C, 59.0 mol pct Na2O), and a new peritectic reaction at 570 °C with 32 mol pct Na2O were rechecked, and Liq + Na2V12O31 → Na10V24O65 was also reconstructed. The large amount of new phase equilibrium data proposed in this work will serve as reliable input for future thermodynamic reassessments of the V2O5–Na2O system within the CALPHAD framework to extensively improve the current V2O5-based thermodynamic databases.Graphical Abstract

Experimental Study of the Cu2O-FeOx-CaO System in Equilibrium With Metallic Copper at 1200 °C to 1300 °C and at P(O2)s = 10−5 to 10−7 Atm

The experimental study of the phase equilibria between calcium ferrite slag, metallic copper, spinel and/or dicalcium ferrite in the Cu2O-FeOx-CaO system has been carried out. Effects of temperature, oxygen partial pressure and Fe/CaO ratio on phase assemblages and compositions have been estimated. The advanced experimental technique including high-temperature equilibration on primary phase substrates, rapid quenching of the samples and quantitative measurements of equilibrated phase compositions using electron probe X-ray microanalysis has been applied. Spinel and dicalcium ferrite substrates have been specially designed to study phase equilibria at certain primary phase fields. Obtained experimental results have been compared with thermodynamic assessment of the Cu2O-FeOx-CaO system and available literature data.

Phase equilibria in TiO2-rich part of the MgO–CaO–TiO2 system at 1500–1600 °C

The equilibrium phase relations of the MgO–CaO–TiO2 system were investigated at 1500–1600 °C in air using the high-temperature isothermal equilibration of samples in platinum crucibles followed by the rapid quenching technique. The phase compositions were analyzed using an electron probe X-ray microanalyzer (EPMA). The isothermal sections at 1500 °C and 1600 °C were constructed based on the experimentally determined liquid phase compositions. The present results deviate significantly from previous observations as well as the predictions by MTDATA and FactSage using their oxide databases, in particular in the perovskite primary phase field.

Integrated experimental and thermodynamic modeling study of phase equilibria in the ‘CuO0.5’-MgO-SiO2 system in equilibrium with liquid Cu metal for characterizing refractory-slag interactions

An integrated experimental and thermodynamic modeling study of the phase equilibria in the ‘CuO0.5’-MgO-SiO2 system in equilibrium with liquid Cu metal has been undertaken to better understand the reactions between MgO-based refractories and liquid slag in copper converting and refining processes. New experimental phase equilibria data at 1250–1680 °C were obtained for this system using a high-temperature equilibration of synthetic mixtures with predetermined compositions in silica ampoules or magnesia crucibles, a rapid quenching technique, and electron probe X-ray microanalysis of the equilibrated phase compositions. The system has been shown to contain primary phase fields of cristobalite (SiO2), tridymite (SiO2), pyroxene/protoenstatite (MgSiO3), olivine/forsterite (Mg2SiO4), periclase (MgO), and cuprite (Cu2O). Three regions of 2-liquid immiscibility were found—two in the high-silica range of compositions above the cristobalite primary phase field (close to ‘CuO0.5’-SiO2 and MgO–SiO2 binaries) and one in the low-SiO2, high-‘CuO0.5’ compositional region above the periclase and olivine phase fields. The results obtained in this study indicate that silica in high-copper refining slags likely led to olivine and pyroxene phase formation, increased solubility of MgO in liquid slag, and decline in the performance of MgO-based refractories. New experimental data were used in the development of a thermodynamic database describing this pseudo-ternary system.

Phase equilibria in the Na2O-WO3 system

The Na2O-WO3 binary system is an important chemical system with various applications, such as catalysts, energy and corrosion resistant materials. In this study, phase equilibria and liquidus temperatures in the Na2O-WO3 binary system have been experimentally determined in air. The system was investigated at the temperature range from 550 to 830 °C using a high-temperature equilibration and quenching technique. The microstructure and compositions of the phases obtained in the quenched samples were then analyzed by an electron probe micro-analyzer (EPMA). Binary compounds Na2W2O7, Na2W4O13 and Na2W6O19 have been identified and the liquidus temperature temperatures in these primary phase fields were determined. Two peritectic points in the system were confirmed and compared with previous data. The present study provided useful thermodynamic data including liquidus and solid solutions. Accurate phase equilibria data will be used as the base for the development of thermodynamic modelling.

Integrated Experimental and Thermodynamic Modeling Investigation of Phase Equilibria in the PbO\u2013MgO\u2013SiO2 System in Air

Magnesium oxide-based refractory materials are used industrially to contain the chemically aggressive slags present in lead smelting systems. In the present study an integrated experimental and thermodynamic modeling approach was taken to provide fundamental information on the chemical reactions taking place in these systems. New experimental phase equilibria and liquidus data were obtained for the PbO–MgO–SiO2 system in air in the temperature range 750 °C to 1740 °C. In the MgO–SiO2 binary, new experimental results were obtained at 1550 °C to 1740 °C and compared to the available thermodynamic data in the literature. The experiments were carried out using the high-temperature equilibration of oxide powder mixtures followed by rapid quenching of the samples. Electron probe X-ray microanalysis (EPMA) was used to determine the compositions of the solid and liquid phases present at equilibrium conditions. Phase equilibria and liquidus isotherms in the cristobalite and tridymite (SiO2), pyroxene (protoenstatite MgSiO3), olivine (forsterite Mg2SiO4), barysilite (Pb8MgSi6O21), massicot (PbO) and periclase (MgO) primary phase fields were measured, and the extent of the high-silica two-liquid immiscibility gap in equilibrium with cristobalite was determined. The experimental results were used to optimize the parameters in a thermodynamic database that was subsequently used to describe this multi-component, multi-phase system and predict the liquidus for the PbO–MgO–SiO2 system. The new data were used to characterize the chemical interactions of magnesia-based refractory with PbO–MgO–SiO2 slags.

Impact of recently discovered sodium calcium silicate solutions on the phase diagrams of relevance for glass-ceramics in the Na2O-CaO-SiO2 system

Although phase relations in the Na2O-CaO-SiO2 system are vital to melting and thermal treatments in glass and glass-ceramics industries, the available data for thermodynamic modeling are mostly based on reports published in 1920s and 1950s. The present investigation verifies the formation of solid solutions of Na2CaSiO4 and Na2Ca2Si2O7 which have previously assumed to be stoichiometric compounds. The impact of these solid solutions on the features of the phase diagram were investigated using the equilibration-quenching-EDS/EPMA technique. The data were reported as liquidus projections and in isothermal sections within the temperature range of 1000 and 1400 °C. Ten primary phase fields were identified, namely SiO2, Na2Ca3Si6O16, combeite, Na4CaSi3O9ss, CaSiO3, Na2CaSiO4ss, Na2Ca2Si2O7ss, Na2Ca6Si4O15, Ca3Si2O7 and Ca2SiO4. In addition, some novel liquidus data and invariants points were examined in more detail. The fundamental data obtained can be employed for the thermodynamic reassessment of the Na2O-CaO-SiO2 system. The present study also discusses the findings and their impact on melting and annealing processes during the manufacture of glass and glass-ceramics.

Experimental phase equilibria studies in the “CuO0.5”-CaO-SiO2 ternary system in equilibrium with metallic copper

Phase equilibria studies were undertaken on the “CuO0.5”-CaO-SiO2 system in equilibrium with metallic copper to provide fundamental information on the reactions taking place between slags and refractory materials in metallurgical furnaces. The liquidus isotherms between 1160 and 1706 °C in the tridymite and cristobalite (SiO2), cuprite (Cu2O), pseudowollastonite (CaSiO3), rankinite (Ca3Si2O7) and dicalcium silicate (Ca2SiO4) primary phase fields, and the 2-liquid miscibility gaps in the silica-rich corner and low-silica area of the system, were experimentally determined using the equilibration and quenching technique, followed by the electron probe X-ray microanalysis (EPMA) of phase compositions. The liquidus surface of the “CuO0.5”-CaO-SiO2 system has been constructed. The dissolution of copper oxide in the tridymite and cristobalite (SiO2) was shown to be negligible. The data obtained are used for the optimization of the thermodynamic database for the copper-containing systems.