Electron Probe X-ray Microanalysis Research Articles

Microstructure and Properties of SUS304 Stainless Steel Joints Brazed with Electrodeposited Ni-Cr-P Alloy Coatings.

In this study, an amorphous Ni-13.4Cr-11.6P (mass%) alloy coating with a thickness of 30 μm was deposited on the surface of SUS304 stainless steel as a brazing filler metal to conduct brazing. The differential thermal analysis measurements indicate that the electrodeposited Ni-13.4Cr-11.6P alloy has a melting point of approximately 892 °C, which is almost consistent with that of the commercial BNi-7 filler metal. The microstructure, shear strength, and fracture mode of the brazed joint were investigated using an electron probe X-ray microanalyzer, a scanning electron microscope, an optical microscope, and a universal testing machine. The results showed that the brazed filler metal is filled between the SUS304 stainless steel plates without any flaws in the brazed seam. The P-containing phases, i.e., the Cr-P rich phase and the (Ni,Fe)3P phase, were formed in the brazed seam. The shear strength of the brazed joint obtained in this study is 59.0 MPa. The fracture occurs in the brazed filler zone, where the brittle P-containing phases are present. Galvanic current measurement results showed that the brazed Ni-13.4Cr-11.6P alloy coating has a better corrosion resistance than that of the brazed Ni-11P alloy coating, which can be attributed to the formation of a large amount of Ni-Fe solid solution and Cr-P rich phase in the top layer of the brazed Ni-13.4Cr-11.6P alloy coating.

Microstructural and Chemical Changes of a Ti-Stabilized Austenitic Stainless Steel After Exposure to Liquid Sodium at Temperatures Between 500 °C and 650 °C

Ti-stabilized austenitic stainless steel was carburized in sodium containing a high carbon activity at three different temperatures, 500 °C, 600 °C, and 650 °C during 1000 hours and 5000 hours. The carbon profile, the carbide volume fraction, and the lattice parameter evolution as function of depth were determined using high-energy X-ray diffraction and electron probe microanalysis. At 650 °C and 600 °C, the carbon precipitated as M23C6 and M7C3 carbides in the sample. The volume fraction of M7C3 carbides was lower than predicted by thermodynamic equilibrium using Thermo-Calc software®. At 500 °C, carbides almost did not form in the steel. Instead, high carbon supersaturation of the austenitic matrix occurred. Both results demonstrate that the carburization profile was strongly influenced by the kinetics of carbide formation at temperatures lower than 650 °C. High-energy X-ray diffraction measurements demonstrated that the austenite and carbide lattice parameters evolved along the carbon profile. Both measured lattice parameter profiles of austenite and M23C6 carbide were compared to the ones predicted from chemical changes of austenite and carbides.

Separation of arsenic and tin from Cu–As alloy based on phase transformation in a vacuum to form Cu–Fe–S compounds

Cu–As alloy is viewed as one kind of secondary copper resources. It is difficult to simultaneously recover copper and remove arsenic using conventional processes. To separate arsenic and tin from Cu–As alloy (mainly Cu3As), an innovative methodology that uses vacuum distillation in the presence of pyrite to form new phase is proposed herein. The constituents, phases and morphology of the sample before and after vacuum distillation were investigated by chemical analysis, X-ray diffraction (XRD) analysis and electron probe microanalysis (EPMA) to interpret separation performances and volatilization mechanisms of arsenic and tin. Chemical analysis results showed that it is difficult to separate arsenic from Cu-As alloy by direct vacuum distillation, but arsenic and tin were effectively separated after introducing pyrite. The effects of several factors, such as temperature, pyrite dosage and distillation time, on separation performances of arsenic and tin were examined. Volatilization ratios of copper, arsenic and tin reached 0.84%, 96.29% and 88.70%, respectively. Results of XRD analysis and EPMA revealed that arsenic had strong affinity to copper in Cu-As alloy, which inhibited free volatilization of arsenic. After introduction of pyrite, formation of copper sulfides, such as mainly Cu5.433Fe1.087S4, Cu1.96S and Cu9S5, destroyed the alloy structure, which made elemental arsenic volatilize. Excessive sulfur also interacted with elemental arsenic to form mainly As4S3 that is also easily volatilized. Nevertheless, tin was only separated in the form of SnS. It is a promising method to achieve cleaner utilization of Cu-As alloy and effective control of arsenic pollution.

Phase equilibria of Al2O3–TiOx system under various oxygen partial pressure: Emphasis on stability of Al2TiO5–Ti3O5 pseudobrookite solid solution

Phase equilibria of Al2O3–TiOx system were experimentally determined in a wide range of T and PO2: 1300 °C ≤T≤ 1600 °C and −16.6≤logPO2≤−8.0 (in atm). X-Ray diffraction and electron probe micro-analysis were employed to obtain equilibrium phases and compositions. Corundum (Al2O3 with limited Ti2O3), rutile (TiO2 with limited Al2O3), and pseudobrookite (Al2TiO5–Ti3O5) solid solutions were found. The liquid oxide phase was not found up to 1650 °C. At each temperature, the cationic ratio of the pseudobrookite solid solution (RTi = nTi/(nAl + Ti)) increased as PO2, thereby forming a wide range of solid solution from Al2TiO5 (RTi = 1/3) to Ti3O5 (RTi = 1.0). The pseudobrookite solid solution was a complete miscible solution at 1600 °C, while it exhibited a small miscibility gap at 1500 °C. Based on the results obtained in the present study, the behavior of Al2TiO5 was discussed in two aspects: (1) changes in physical properties and (2) evolution of Al–Ti complex oxide inclusions in liquid steel.

Experimental study and thermodynamic modeling of the Cu–Sn–Si–O system and sub-systems

Phase equilibria between slag, Cu–Sn alloy and solid oxide phases, SnO2 (cassiterite) or SiO2 (tridymite, cristobalite) are important for oxidizing fire refining of black copper produced during the recycling of copper scrap and waste electrical and electronic equipment. Integrated experimental and thermodynamic modeling study is presented for the Cu–Sn–Si–O chemical system and its sub-systems. Experimental technique involved high-temperature equilibration, followed by rapid quenching and direct measurement of Cu, Sn and Si concentrations in the liquid and solid phases using the electron probe X-ray microanalysis. Experimental results and literature data have been used to develop the thermodynamic database for the system. The database works within the environment of FactSage software, as well as ChemApp, ChemSheet and SimuSage. Combined with other assessments, it can be used to optimize and develop recycling processes using the black copper route.

Experimental study of “CuO0.5”-“FeO”-SiO2 and “FeO”-SiO2 systems in equilibrium with metal at 1400–1680 °C

The phase equilibria of the “CuO0.5”-“FeO”-SiO2 slag system in equilibrium with metallic copper and tridymite/cristobalite (SiO2), and the “FeO”-SiO2 slag system in equilibrium with metallic iron and tridymite/cristobalite (SiO2) were investigated between 1400 and 1680 °C. High temperature equilibration in closed silica ampoules, followed by quenching and the direct measurement of the phase compositions with the electron probe X-ray microanalysis (EPMA) was used. The liquidus isotherms in the tridymite and cristobalite (SiO2) primary phase fields were measured, and the shape of the two liquid slags miscibility gap over cristobalite was determined for the “CuO0.5”-“FeO”-SiO2 and “FeO”-SiO2 systems in equilibrium with metallic copper and iron respectively. The two liquid slags miscibility gap over cristobalite was found to be present at all Cu/(Cu+Fe) molar ratios in the slag. However, the difference in the SiO2 concentration between the low- and high-SiO2 slag was found to decrease as the Cu/(Cu+Fe) molar ratio in slag approached 0.5, with the minimal difference assessed to be approximately 4 mol.%. Additionally, new phase equilibria data obtained for the “FeO”-SiO2 subsystem in equilibrium with metallic iron suggested that the monotectic temperature of the subsystem is 1673 ± 3 °C, and that the low- and high- SiO2 slags contain 59.7 mol.% and 96.4 mol.% SiO2 respectively. The present study was a continuation of previous investigations by the authors into the Cu-Fe-Si-O multicomponent slag system, aimed at providing information for improving the thermodynamic models for all phases in this system.

The Latowu Ultramafic Rock-Hosted Iron Mineralization in the Southeastern Arm Sulawesi, Indonesia: Characteristics, Origin, and Implication for Beneficiation

Latowu ultramafic block in the Southeastern Arm Sulawesi locally hosts elevated concentrations of Fe in addition to Ni. We investigated both host rock and mineralized samples' mineralogy and chemistry to find out mineralogical and chemical characteristics and interpret the iron mineralization process with beneficiation implications. The mineralogical nature of the samples was analyzed using optical microscopy and X-ray diffractometry (XRD) methods. The whole-rock and mineral chemistry analyses were performed using X-ray fluorescence (XRF) spectroscopy and electron probe microanalysis (EPMA) techniques. The analysis showed that the ultramafic rocks had been undergone a strong to complete serpentinization degree where lizardite appears to be the predominant mineral. Magnetite in this research comprised the principal iron-bearing mineral and functioned as discrete fine-grains and subhedral to anhedral crystals. Magnetite occurs as fragments in breccia, alteration rim in spinel, fine-grained disseminations, and micro veins. This research found that the whole-rock chemistry of an ultramafic breccia showed an elevated concentration in Fe2O3 with a grade of 28.44 wt%. Electron probe analysis of magnetite shows a wide variation of Fe ranging from 31.10 wt% to 67.20 wt%. It is interpreted that the formation of magnetite within ultramafic rocks is influenced by the hydration of primary minerals, mainly olivine. Iron is most likely released from olivine or pyroxene crystals during serpentinization, and the higher water content of serpentine promotes its mobility. It is suggested that the magnetic separation method can be potentially used to increase the Fe grade.

The effect of titanium and silicon addition on phase equilibrium and mechanical properties of CoCrFeMnNi-based high entropy alloy

The effects of Ti and Si addition on the phase equilibrium and mechanical properties of the equiatomic CoCrFeMnNi high entropy alloy (Cantor alloy) were investigated. The phase equilibrium at 1000 °C was determined from the result of X-ray diffraction and electron probe micro-analysis. Ti addition stabilizes the sigma phase, A12 phase and C14-Laves phase, while Si addition stabilizes the A13 phase. The phase relationships were represented by projection onto (Co, Fe, Mn, Ni)–Cr–X(Ti or Si) isothermal ternary cross-section at 1000 °C in Co–Cr–Fe–Mn–Ni–X senary system. Tensile tests were conducted on Cantor-based fcc single solid solution alloys with Ti or Si dissolution at room temperature. The 0.2% yield strength and ultimate tensile strength increased with either element addition. The Ti-added alloy showed higher strength than the Si-added alloy. The difference in ductility in the alloys is related to their strain hardening behavior in the higher strain range.Graphic abstract

Saturation profile measurement of atomic layer deposited film by X-ray microanalysis on lateral high-aspect-ratio structure

Atomic layer deposition (ALD) of aluminum oxide thin films were applied on lateral high-aspect-ratio silicon test structures. The leading front of the film thickness profile is of interest, since it is related to deposition kinetics and provides information for ALD process development. A deposited profile was characterized using energy-dispersive electron probe X-ray microanalysis (ED-EPMA) and the results were analyzed using Monte Carlo simulation. A new procedure for obtaining relative film thickness profile from X-ray microanalysis data is described. From the obtained relative thickness profile, penetration depth of film at 50% of initial thickness and corresponding slope of thickness profile were determined at the saturation front. Comparison of the developed procedure was performed against independent measurements using optical reflectometry. ED-EPMA characterization of saturation profiles on lateral high-aspect-ratio test structures, supported by Monte Carlo simulation, is expected to prove useful tool for ALD process development.

Improving stability using a mixed ion/hybrid electrolyte strategy in a sodium ion capacitor

In Sodium-ion capacitors (SICs), employing high-capacity anodes based on alloying/conversion reactions can potentially alleviate the performance issues but are susceptible to rapid capacity fading due to consistent dissolution of the electrode surface by the electrolyte. Herein, we extend the “hybrid mixed electrolyte” strategy to ion capacitors for overcoming the rapid cycle decay issues in high-energy SICs: molybdenum disulphide (MoS2, MS) nanocrystals grown on carbon nitride (C3N4, CN), denoted as MS/CN, as anode exhibited remarkable performance in both sodium electrolyte and replaced with a hybrid mixed electrolyte comprising larger Na+ ions and smaller Li+ ions. Thus, constructed SICs exhibited a high energy density of 124 Wh Kg−1 with a mixed ion electrolyte, and low energy loss (71% retention after 40000 cycles) with a hybrid electrolyte (lower than conventional sodium-ion-based electrolyte: 37% retention after 15000 cycles). Systematic investigations, including X-ray photoelectron spectroscopy and electron probe microanalysis, revealed an advantageous formation of a stable interface for electrode and electrolyte.

Phase equilibrium studies in V2O5‐Fe2O3 and V2O5‐TiO2 systems

AbstractV2O5‐Fe2O3 and V2O5‐TiO2 systems represent two important chemical systems with various applications, including energy, catalysts, and high‐performance materials. In the present study, high‐temperature phase equilibrium experiments were conducted at the temperature range of 670–1000°C in air. Electron probe X‐ray micro‐analyzer (EPMA) was used to analyze the microstructure and composition of the phases presented in quenched samples. Systematic experiments demonstrated that V2O5‐containing systems should not be quenched by water‐based quenching media. Phase diagrams in both systems were constructed, and the eutectic and peritectic points of the systems were confirmed and compared with previous studies. The present study improved the previous results and could be used as the base for thermodynamic modelings and further applications of the two systems.

Integrated experimental phase equilibria study and thermodynamic modelling of the binary ZnO–Al2O3, ZnO–SiO2, Al2O3–SiO2 and ternary ZnO–Al2O3–SiO2 systems

Phase equilibria of the ZnO–SiO2, Al2O3–SiO2 and ZnO–Al2O3–SiO2 systems at liquidus were characterized at 1340–1740 °C in air. The ZnO–Al2O3 subsolidus phase equilibria were derived from the experiments with the SiO2- and CaO + SiO2-containing slags. High-temperature equilibration on silica or platinum substrates, followed by quenching and direct measurement of Zn, Al, Si and Ca concentrations in the phases with the electron probe X-ray microanalysis (EPMA) was used to accurately characterize the system. Special attention was given to zincite phase that was shown to consist of two separate ranges of compositions: round-shaped low-Al zincite (<2 mol.% AlO1.5) and platy high-Al zincite (4–11 mol.% AlO1.5). A technique was developed for more accurate measurement of the ZnO solubility in the low-ZnO phases (corundum, mullite, tridymite and cristobalite) surrounded by the ZnO-containing slag, using l-line for Zn instead of K-line, avoiding the interference of secondary X-ray fluorescence. Solubility of ZnO was found to be below 0.03 mol.% in corundum and cristobalite, and below 0.3 mol.% in mullite. Present experimental data were used to obtain a self-consistent set of parameters of the thermodynamic models for all phases in this system using FactSage computer package. The modified quasichemical model with two sublattices (Zn2+, Al3+, Si4+) (O2−) was used for the liquid slag phase; the compound energy formalism was used for the spinel (Zn2+,Al3+)[Zn2+,Al3+,Va]2O2-4 and mullite Al3+2(Al3+,Si4+) (O2−,Va)5 phases; the Bragg-Williams formalism was used for the zincite (ZnO, Al2O3); other solid phases (tridymite and cristobalite SiO2, corundum Al2O3, and willemite Zn2SiO4) were described as stoichiometric. Present study is a part of the research program on the characterization of the multicomponent Pb–Zn–Cu–Fe–Ca–Si–O–S–Al–Mg–Cr–As–Sn–Sb–Bi–Ag–Au–Ni system.

Equilibrium Distributions of Pb, Bi, and Ag between Fayalite Slag and Copper-Rich Metal, Calcium Ferrite Slag and Copper-Rich Metal. Thermodynamic Assessment and Experimental Study at 1250 °C

Rising concentrations of impurities are expected at copper fire-refining stage due to lower availability of high-quality copper concentrates and due to increasing recycling of electronics and other secondary materials in primary copper smelting. Extra steps involving the removal of impurities from copper into the slag phase may provide a solution, but better understanding of thermochemistry is needed to evaluate the feasibility of changes in the process. In the present study, the distribution coefficients of Pb, Bi, and Ag between the fayalite or calcium ferrite slags and copper-based metal at 1250 °C were measured experimentally, using high-temperature equilibration, rapid quenching, and electron probe X-ray microanalysis (EPMA). The experiments were undertaken in a closed system using a modified substrate support technique, at relatively high oxidizing conditions typical for copper refining. The improved substrate technique enables the measurement of distributions coefficients for slags in equilibrium with solid spinel (Fe3O4) or dicalcium ferrite (Ca2Fe2O5). Experimental results of the present study and the literature data were analyzed together using thermodynamic modeling. As a result, thermodynamic database has been developed and used to predict the effects of oxygen partial pressure, wt% Cu in slag, temperature, and Fe/SiO2 and Fe/CaO in slags on the distribution coefficients of Pb, Bi, and Ag for the fayalite and calcium ferrite slag systems.

Modification of Phosphorous Enrichment Behaviours in Steelmaking Slags Based on Phase Transformations

In this study, the phase transformations of steelmaking slags were identified for the purpose of phosphorus separation and material recycling, where the samples after high-temperature experiments and quenching were characterized using electron probe x-ray microanalysis and x-ray diffraction. For hot slags held under argon atmosphere, the main phases changed from (Fe,Mg)O, (Fe,Ca)O and C2S-C3P (Ca2SiO4-Ca3P2O8) at 1450–1400°C to (Fe,Mg,Ca)O, C2S-C3P and CaO-TiO2-FeO-Al2O3 liquid at 1200–600°C. From the respect of phosphorus concentration in C2S-C3P, 1400°C was an optimum temperature, which also accounted for a suitable treatment temperature for cooled slags. Moreover, air atmosphere resulted in more liquid phase, CaO-MgO-Fe2O3-SiO2, due to the oxidation of Fe2+ to Fe3+. In addition to C2S-C3P, P2O5 was also present in this liquid phase, a drawback for further phosphorus recovery. The P2O5 concentration in the liquid phase decreased with decreasing temperature, and thus, a relatively lower temperature was preferred in air.

Phase Equilibria in the Ni-Al-Bi Ternary System

The phase equilibria in the Ni-Al-Bi ternary system at 800 and 1000 °C were experimentally determined by x-ray diffraction and electron probe microanalysis. The results show that: Bi is almost insoluble in any Ni-Al compounds and (Ni) phase. There are five and four three-phase regions existing in the isothermal section at 800 and 1000 °C, respectively. The Ni-Al binary compounds are all in equilibrium with the liquid phase in these two isothermal sections. No ternary compound was found at 800 and 1000 °C.

Clay coatings on sands in the western Qaidam Basin, Tibetan Plateau, China: Implications for the Martian clay detection

The widespread clay minerals on Mars have been detected using orbital data using near-infrared spectroscopy, which is limited by its shallow detection depth, low recognition precision and resolution, and can only be qualitative etc. Terrestrial analogues on the Earth provide valuable guidance to further understand the distribution and occurrence of clay minerals on Mars. In this study, seven detrital samples with clay minerals as coatings (Abbreviated as “clay coatings”) were collected from four sites in the western Qaidam Basin, a Martian analogue terrain. We identify the mineralogy of the surface coatings to be illite and chlorite, as confirmed by a combination techniques of X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Electron Probe X-ray Microanalysis (EPMA) and Near-infrared spectroscopy (NIR). The NIR results suggested that merely small amounts of clay minerals (~0.5 mg/cm2 and about several micrometers in thickness) masking the surface of sands could lead to well-distinguished characteristic NIR absorption, and their band depth could reach those measured from Martian soil analogues with ~5 wt% to 25 wt% clay minerals at 2.20–2.40 μm. The results of the synthesized samples as coating analogues with clay minerals coated on the surface of quartz grains showed a consistent trend as that of the field samples on the Earth. The further mineralogical analysis indicated that the origin of clay minerals in the coatings of Qaidam Basin is of Aeolian source. Environmental similarities between western Qaidam Basin and Martian surface suggested that various rock coatings potentially exist on Mars and they could affect the mineral detection and the accuracy of mineral identification by remote sensing.

Synthesis of bismuth ferrite nanopowder doped with erbium ions

The potential for the practical application of bismuth ferrite (BFO) in information storage, microelectronic, and spintronic devices and in medical sensors of various purpose is limited by the presence of a spin cycloid. Its destruction, including destruction due to doping with rare earth elements and the transfer of BFO to a nanoscale state, contributes to the occurrence of ferromagnetism and the manifestation of the magnetoelectric effect. The study was aimed at the synthesis of bismuth ferrite nanopowder doped with erbium ions.By spray pyrolysis at a temperature of 760 °C, we synthesised BFO samples with a nominal degree of doping with erbium ions from 0.05 to 0.20. The data of X-ray diffraction analysis show that there is a small amount of Bi25FeO39 and Bi2Fe4O9 in the doped samples.The shift of the BFO reflections on diffraction patterns towards larger 2q angles is representative of the incorporation of erbium ions into the crystal lattice of BiFeO3. The morphological characteristics of the samples were determined using transmission electron microscopy. According to the data of electron probe X-Ray microanalysis, the real composition of the doped ErxBi1-xFeO3 samples is very close to the nominal.The particles of ErxBi1-xFeO3 powders synthesised by spray pyrolysis have a nearly spherical shape, the particle-size distribution is in the range of 5–300 nm, the predominant number of particles have a size in the range of 50-200 nm, and the agglomeration is weak. The decrease in the crystal lattice parameters and the unit cell volume of ErxBi1-xFeO3 and an increase in the degree of doping with erbium ions confirm the incorporation of Er3+ into the BFO crystal lattice to the bismuth position.

Integrated experimental liquidus and modelling studies of the ternary AgO0.5-FeO1.5-SiO2 system in equilibrium with metallic Ag

Phase equilibria of the AgO 0.5 -“FeO 1.5 ”-SiO 2 system was investigated in the range of 1563–1913 K (1290–1640 °C) for oxide liquid (slag) in equilibrium with the gas with controlled oxygen partial pressure, Ag metal or Ag-Au alloy, and solid oxide phases: (a) tridymite, cristobalite (SiO 2 ); (b) hematite (Fe 2 O 3 ), spinel (Fe 3 O 4 ) and wüstite (FeO 1+x ). High-temperature equilibration on silica, iridium or iron substrates, followed by quenching and direct measurement of the Ag, Au, Fe and Si concentrations in the liquid and solid phases with the electron probe X-ray microanalysis (EPMA) or laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) were used for accurate characterization of the system. Present data were used to develop the thermodynamic models for all phases in this system using FactSage computer package. The present study is a part of the investigation of the thermochemistry of complex multicomponent pyrometallurgical systems. • As a part of the recycling process, the copper and lead smelters require a reliable thermodynamic database for successful recovery of the precious metals such as Ag. • This article demonstrates the high temperature phase equilibria of the AgO 0.5 -“FeO 1.5 ″-SiO 2 ternary system. • This system is a part of the complex multicomponent pyrometallurgical systems (PbO-ZnO-Cu 2 O-FeO-Fe 2 O 3 -CaO-SiO 2 -Al 2 O 3 -MgO-S-As, Sn, Sb, Bi, Ag, Au, Ni, Cr) for the copper and lead smelting and recycling industries. • The data obtained in this study were used for developing FactSage thermodynamic database.

Precious Metal Distributions Between Copper Matte and Slag at High P_{{{text{SO}}_{ 2} }} in WEEE Reprocessing

The distributions of precious metals (gold, silver, platinum, and palladium) between copper matte and silica-saturated FeOx-SiO2/FeOx-SiO2-Al2O3/FeOx-SiO2-Al2O3-CaO slags were investigated at 1300 °C and P_{{{text{SO}}_{ 2} }} = 0.5 atm. The experiments were carried out in silica crucibles under flowing CO-CO2-SO2-Ar gas atmosphere. The concentrations of precious metals in matte and slag were analyzed by Electron Probe X-ray Microanalysis and Laser Ablation-High-Resolution Inductively Coupled Plasma-Mass Spectrometry, respectively. The precious metal concentrations in matte and slag, as well as the distribution coefficients of precious metals between matte and slag, were displayed as a function of matte grade. The present results obtained at P_{{{text{SO}}_{ 2} }} of 0.5 atm were compared with previous results at P_{{{text{SO}}_{ 2} }} of 0.1 atm for revealing the effects of P_{{{text{SO}}_{ 2} }} and selected slag modifiers (CaO and Al2O3) on precious metal distributions at copper matte smelting conditions. The present results also contribute experimental thermodynamic data of precious metal distributions in pyrometallurgical reprocessing of electronic waste via copper smelting processes.

Experimental Study and Thermodynamic Calculations in the CaO–Cu2O–FeO–Fe2O3–SiO2 System for Applications in Novel Copper-Based Processes

A combination of high-temperature experiments and thermodynamic modeling in the CaO–Cu2O–FeO–Fe2O3–SiO2 system provides the fundamental information necessary to design and improve processes such as WEEE recycling through black copper route, continuous converting of copper matte, copper dross smelting, slag cleaning, and valorization of copper slag. In the experiments, samples were equilibrated on a primary phase substrate or Fe metal foil, then rapidly quenched and studied using the Electron Probe X-ray Microanalysis. The FactSage software was used for calculations, combined with custom developed thermodynamic database. A systematic analysis is provided to select the fluxing strategy and increase the copper recovery in industrial processes. Slag liquidus and concentration of copper in slag were assessed as functions of oxygen partial pressure, temperature, Fe/SiO2 in slag, and wt% CaO in slag.