Electron Probe X-ray Microanalysis Research Articles

Hydrogen storage properties of Mn and Cu for Fe substitution in TiFe0.9 intermetallic compound

The present study investigates the partial substitutions of Mn and Cu for Fe in the TiFe-system to gain better understanding of the role of elemental substitution on its hydrogen storage properties. The TiFe0.88-xMn0.02Cux (x = 0, 0.02, 0.04) compositions were studied. From X-Ray Diffraction (XRD) and Electron Probe Micro-Analysis (EPMA), it was found that all alloys are multi-phase, with TiFe as a major phase, together with β-Ti and Ti4Fe2O-type as secondary precipitates, of all them containing also Mn and Cu. Increasing the Cu content augments the secondary phase amounts. Low quantity of secondary phases helps the activation of the main TiFe phase for the first hydrogen absorption, but on increasing their amounts, harsher activation occurs. Both Mn and Cu substitutions increase the cell parameter of TiFe, thus decreasing the first plateau pressure. However, Cu substitution rises the second plateau pressure revealing the predominancy of electronic effects associated to this substitution. All samples have fast kinetics and high hydrogen capacity making these substituted compounds promising for large scale stationary applications.

MICROMETEORITES FROM MODERN SEDIMENTS OF THE CENTRAL PART OF LAKE BAIKAL

The study is focused on micrometeorites from bottom sediments sampled from the Selenga-Buguldeika lintel of Lake Baikal. Their diatom analysis showed continuous sedimentation during the Holocene. Mineralogical analysis identified a complex of minerals, including micrometeorites, which amount to 0.6 % of the heavy fraction weight. A detailed study of the micrometeorites was carried out using a JXA8200 electron probe x-ray microanalyzer. It was established that their chemical composition is predominantly represented by Fe, O, C, and Zn, i.e. these are type 1 α-micrometeorites. Based on the difference in the chemical composition of the micrometeorites in the sedimentary strata section, it is proposed to refer to such micrometeorites not only for stratigraphic correlations, but also for impact stratigraphy schemes.

Textures and geochemistry of magnetite: Indications for genesis of the Late Paleozoic Laoshankou Fe-Cu-Au deposit, NW China

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and electron probe X-ray microanalysis (EPMA) have been employed to determine major and trace elemental concentrations in magnetite from different ores in the Laoshankou deposit, which is the most important Fe-Cu-Au deposit in the northern margin of East Junggar. Two magnetite-associated paragenetic sequences have been defined in Laoshankou, including amphibole-epidote-magnetite alteration/mineralization (stage II) and pyrite-chalcopyrite mineralization (stage III-B). On the basis of the magnetite textures and chemical compositions, we have identified six generations of magnetite from three types of ores/rocks, including the high-Ti inclusion-rich M-1-A and inclusion-free M-1-B in massive magnetite-epidote-amphibole ores (type H1) from stage II; the low-Ti, high-Si, inclusion-rich M-1-C in massive magnetite-sulfide ores (type H2) from stage II; the ubiquitous low-Ti M-2 and pristine low-Ti, low-Si M-3 in both H1 and H2 types; and M-4 within massive chalcopyrite-magnetite ores (type H3) from stage III-B. The discriminations of V versus Ti, Ca + Mn + Al versus Ti + V, and Fe versus V/Ti, as well as mineral assemblages and trace element concentrations of Cr (<1000 ppm) and V (<300 ppm), collectively imply that all the generations of magnetite are hydrothermal in origin, and more likely similar to those in iron-oxide copper-gold deposits. The diverse textural and chemical features among these generations of magnetite indicate that they have formed from distinct process. The earliest M-1-A and M-1-B in type H1 ore and M-1-C in type H2 ore were replaced by M-2 along fractures and/or grain boundaries of the M-1-A/B/C, forming a number of mineral inclusions via dissolution and reprecipitation. Following this, M-3 veins generally crosscut all of these above types. Finally, high-Co, Ni, and REE-rich fluid formed the chalcopyrite-associated M-4 with dark-light zoning in the type H3 ore from pyrite-chalcopyrite mineralization. These elevated lithophile (REE) and chalcophile (Co, Ni) elements within the chalcopyrite (sulfide)-associated M-4 further suggest that non-magmatic fluid dominated in the fluid system, with intensive fluid-rock interactions and low-temperature, Cl, and Cu-rich external fluid accounting for the Cu-Au mineralization.

Experimental Study on the Phase Equilibrium of Copper Matte and Silica-Saturated FeOx-SiO2-Based Slags in Pyrometallurgical WEEE Processing

The effects of the amphoteric and basic oxides alumina and lime on the phase equilibria of copper matte and silica-saturated slags were investigated at 1300 °C and P_{{{text{SO}}_{ 2} }} = 0.1 atm in a controlled CO-CO2-SO2-Ar gas atmosphere using a high-temperature isothermal equilibration technique followed by rapid quenching. The equilibrium phase compositions were obtained by Electron Probe X-ray Microanalysis. The relationship between the copper concentration in matte and the oxygen partial pressure, iron, and sulfur in matte was quantified. The pure iron-silicate slag exhibited the highest copper loss in slag, although the addition of alumina and lime decreased its value by approximately a quarter and a half, respectively, at a matte grade of 65 wt pct Cu. In contrast, copper and sulfur were highly distributed in the matte phase, and their deportment to the matte was favored by addition of alumina and lime.

Experimental investigation of slag/matte/metal/ tridymite equilibria in the Cu–Fe–O–S–Si system at 1473 K (1200°C), 1523 K (1250°C) and 1573 K (1300°C)

Abstract Laboratory experimental study was undertaken to characterise the four-phase slag/matte/metal/tridymite equilibria of the Cu-Fe-O-S-Si system at 1473 K [1200°C], 1523 K [1250° C] and 1573 [1300°C] in a "closed" system without interaction with gas phase. The research methodology involved high temperature equilibration, ultra-fast quenching of the equilibrated samples followed by quantitative measurement of the equilibrated phases by electron probe X-ray microanalysis. Attainment of chemical equilibrium was carefully checked by the 4-points test approach. The results obtained in the present study provide reliable fundamental experimental information, which is crucial for the development and optimisation of the multicomponent thermodynamic database for copper-containing systems.

Concentration of Rare Earth Elements (Sc, Y, La, Ce, Nd, Sm) in Bauxite Residue (Red Mud) Obtained by Water and Alkali Leaching of Bauxite Sintering Dust

One of the potential sources of rare-earth elements (REE) is the industrial waste known as red mud (bauxite residue), in which the majority of REE from the initial bauxite are concentrated via the Bayer process. Therefore, the studies of the subject, both in Russia and outside, focus almost exclusively on red mud processing. This article looks into the possibility of REE concentration into red mud by leaching an intermediate product of the bauxite sintering process at Russian alumina refineries, namely electrostatic precipitator (ESP) dust. The experimental works were performed by X-ray diffraction (XRD)and electron probe microanalysis (EPMA) of the sinter and sinter dust. The determination of major and rare-earth elements in the sinter from the rotary kilns and in the ESP dust before and after leaching was carried out by X-ray fluorescence (XRF) and plasma mass spectrometry (ICP-MS). The study showed that it is possible to obtain red mud that contains three times more REE than traditional waste red mud after two-stage leaching ESP dust in the water at 95 °C followed by leaching in an alkaline-aluminate liquor at 240 °C. The shrinking core model was used to study the kinetics of leaching of the original ESP dust and water-treated dust in alkaline-aluminate liquor. The study showed the change in the limiting stage of the alkaline leaching process after water treatment, with the activation energy growing from 24.98 to 33.19 kJ/mol.

Recovery of Precious Metals (Au, Ag, Pt, and Pd) from Urban Mining Through Copper Smelting

With the aim of investigating deportments of precious metals in pyrometallurgical processing of waste electrical and electronic equipment, the distributions of selected precious metals (gold, silver, platinum, and palladium) between copper matte and three different silica-saturated slags (pure FeOx-SiO2, FeOx-SiO2-Al2O3, and FeOx-SiO2-Al2O3-CaO slag) were investigated at 1300 °C in controlled flowing CO-CO2-SO2-Ar gas atmosphere by a high-temperature isothermal equilibration technique. The phase compositions were analyzed by Electron Probe X-ray Microanalysis and Laser Ablation-High Resolution Inductively Coupled Plasma-Mass Spectrometry. It was shown that the distribution coefficients of gold, platinum, and palladium between matte and slag (Lm/s(Me) = [Me]in matte/(Me)in slag) were very high and increased with increasing matte grade. The distributions to the matte phase were increased by adding basic oxides alumina and lime into the acidic silicate slags. The experimentally measured distribution coefficients Lm/s(Me) followed the order of platinum > palladium > gold > silver. The present experimental results can be used for upgrading thermodynamic databases for the complex recycling processes through nonferrous smelting.

Sulfidization mechanism in malachite flotation: A heterogeneous solid-liquid reaction that yields CuxSy phases grown on malachite

Sulfidizationfollowed byxanthateflotation is an effective technique to recover copper oxide minerals. However, the sulfidization mechanism of malachite has not been determined. In this work, the sulfidization mechanism was investigated by microflotation, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), electron probe X-ray microanalysis (EPMA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The flotation results showed that sulfide ions at an appropriate concentration could activate malachite flotation while excess sulfide ions could depress this. The depression of malachite flotation by excess sulfide ions was attributed to the residual sulfide species in the liquid. FESEM–EDS showed that sulfidization product grown on the malachite surface was heterogeneously distributed, which was consistent with the EPMA results. The XRD results for the sulfidized malachite samples showed that the amount of sulfidization product was insufficient for detection under flotation-related conditions. By the selective solvent action of sulfuric acid, the sulfidization product was extracted from the sulfidized malachite. The XRD results for the extracts indicated that the sulfidization product comprised djurleite (Cu31S16) and anilite (Cu7S4), which both were compounds of the chalcocite group (Cu2−xS), suggesting transformation of solid Cu2(OH)2CO3 to Cu2−xS on the malachite surfaces during sulfidization. Moreover, the XPS results were consistent with the XRD results. These results demonstrated that sulfidization of malachite is a phase-transition process driven by the solubility difference between Cu2(OH)2CO3 and Cu2−xS. In this case, Cu2−xS phases formation on malachite involves heterogeneous nucleation and growth, and sulfide ions act as a reductant and sulfidizing agent in malachite sulfidization. The copper sulfide grown on malachite radically changed the surface properties of malachite particles, rendering malachite amenable to xanthate flotation. Based on these findings, we present a new formula for malachite sulfidization and a schematic diagram of the sulfidized malachite particle.

Thermodynamic Modeling of the Pb-S and Cu-Pb-S Systems with Focus on Lead Refining Conditions

Thermodynamic modeling of the Pb-S and Cu-Pb-S systems is presented. All available experimental data in these systems are collected, assessed and used to optimize the model parameters. For the liquid phase, a solution (CuI, PbII, SII) is developed using the modified quasichemical model in pair approximation. Liquid copper, liquid lead metal, as well as matte phases are described using single solution with miscibility gaps. Earlier thermodynamic assessments available in the literature did not include all the data on the solubility of Cu and S in liquid Pb at low temperatures, 900 °C (1123 K), a significant discrepancy among different sets of literature data and existing thermodynamic assessments is revealed. Preliminary experiments are performed with the goal to understand the nature of the problem and to develop the methodology based on high-temperature equilibration, rapid quenching and electron probe x-ray microanalysis. The results of this study help to select accurate literature results in the optimization of model parameters. The resulting database is applicable to calculate slag/matte/metal distribution of lead in copper smelting and converting, as well as for predictions in the lead smelting and fire refining.

Experimental Investigation of Gas/Slag/Matte/Tridymite Equilibria in the Cu-Fe-O-S-Si-Al-Ca-Mg System in Controlled Gas Atmosphere: Experimental Results at 1473 K (1200 °C), 1573 K (1300 °C) and p(SO2) = 0.25 atm

The effect of temperature, CaO, MgO and AlO on important technological copper smelting parameters, such as the chemically dissolved copper in slag and the composition of the liquid phase in equilibrium with tridymite, are experimentally characterised as a function of copper concentration in matte. Two series of experiments for the gas/slag/matte/tridymite equilibria in the Cu-Fe-O-S-Si system at p(SO) = 0.25 atm have been carried out. The effect of CaO at 1573 K (1300 °C), and the combined effect of AlO + CaO + MgO at 1473 K (1200 °C) and 1573 K (1300 °C) have been measured in the first and second series of experiments respectively. The experimental methodology involves high temperature equilibration of samples on a substrate made from the primary phase under controlled gas atmosphere (CO/CO/SO/Ar), followed by rapid quenching of the equilibrium condensed phases and direct measurement of the phase compositions using the Electron Probe x-ray Microanalysis. The resulting data are used in the optimization of the thermodynamic database for the copper-containing systems.

Experimental Liquidus Studies of the ZnO-“CuO0.5” and ZnO-“CuO0.5”-SiO2 Liquidus in Equilibrium with Cu-Zn Metal

Phase equilibria in the ZnO-“CuO0.5”-SiO2 system have been investigated at 1403-1948 K (1130-1675 °C) for oxide liquid in equilibrium with Cu-Zn metal (> 99% Cu) and solid oxide phases: (a) tridymite or cristobalite SiO2; (b) willemite Zn2SiO4; (c) zincite ZnO; and (d) cuprite Cu2O. Two-liquid immiscibility range in the high-SiO2 slags has also been studied. High-temperature equilibration on primary phase (SiO2, Cu2O), inert metal (platinum-iridium wire), or ceramic (Al2O3 for high-Cu2O slags) substrates, followed by quenching and direct measurement of Zn, Cu, Si and possible impurities (Al, Pt, Ir) concentrations in the phases with the electron probe x-ray microanalysis (EPMA) has been used to accurately characterize the system in equilibrium with metal. All results are projected onto the ZnO-“CuO0.5”-SiO2 plane for presentation purposes.

The effect of Al2O3 on fayalite-based copper smelting slags in equilibrium with matte and tridymite at 1 2008C and P(SO2) = 0.25 atm

Abstract Experimental investigations have been undertaken to determine the effect of Al2O3in slag on the gas/slag/matte/tridymite equilibria in the multi-component Cu-Fe-O-S-Si-Al system at 1 200 8C, and P(SO2) = 0.25 atm. The experimental technique involves high temperature equilibration of synthetic samples on the open silica substrate in controlled gas atmospheres (CO/CO2/SO2/Ar), rapid quenching after a designated equilibration time followed by the compositional analysis of the condensed phases with electron probe X-ray microanalyzer. The experimental data of the present study provide information on the effect of alumina on the slag composition, such as the chemically dissolved copper, dissolved sulphur, and Fe/SiO2 ratio in slag at tridymite saturation at different Cu in matte. The new data have been used as inputs for the optimization of the thermodynamic databases for the copper-containing systems and can also be used to evaluate the fluxing strategy in the copper smelting operation.

Experimental investigation of slag/matte/metal/ tridymite equilibria in the Cu–Fe–O–S–Si system at 1473 K (1200°C), 1523 K (1250°C) and 1573 K (1300°C)

Abstract Laboratory experimental study was undertaken to characterise the four-phase slag/matte/metal/tridymite equilibria of the Cu-Fe-O-S-Si system at 1473 K [1200°C], 1523 K [1250° C] and 1573 [1300°C] in a "closed" system without interaction with gas phase. The research methodology involved high temperature equilibration, ultra-fast quenching of the equilibrated samples followed by quantitative measurement of the equilibrated phases by electron probe X-ray microanalysis. Attainment of chemical equilibrium was carefully checked by the 4-points test approach. The results obtained in the present study provide reliable fundamental experimental information, which is crucial for the development and optimisation of the multicomponent thermodynamic database for copper-containing systems.

Crystal Structure of Niobium-Rich Lomonosovite with Symmetry P1 from the Khibiny Massif (Kola Peninsula)

A new niobium-rich lomonosovite variety with a high degree of ordering of Ti and Nb atoms has been investigated by X-ray diffraction analysis and electron probe microanalysis. Its simplified formula is Na10Ti2(Nb,Fe,Ti)2(Si2O7)2(PO4)2O4. The triclinic unit-cell parameters are a = 5.411(1) A, b = 7.108(1) A, c = 14.477(2) A, α = 99.78(1)°, β = 96.59(1)°, γ = 90.26(1)°, V = 544.94(5) A3, Z = 1, sp. gr. P1. The crystal structure has been refined to the final reliability factor R = 6.3% within the anisotropic approximation of atomic displacements using 3674 reflections with F > 3σ(F). The problem of niobium distribution in minerals with structures of lomonosovite and related types is discussed.

Thermodynamic re-assessment and experimental confirmation for the Zn–Mn system

The Zn–Mn system has been critically re-assessed based on available experimental data from literature by CALPHAD (CALculation of PHAse Diagram) approach. Solution phases, viz. liquid, (δMn), (γMn), (βMn), (αMn) and (Zn) were described using substitutional solution model. Besides, the ε, αˊ, γ, δ, δ1 and ζ phases were described by the sub-lattice models based on the reported crystallographic information and homogeneity ranges. The β1 phase was treated as a stoichiometric compound since no distinct homogeneity range of this phase was reported. Thermodynamic parameters on the whole system compatible with the databases of Thermo-Calc and Pandat were first obtained. Compared with previous assessments, calculations using the presently obtained thermodynamic parameters achieved a significant improvement. To further verify the reliability of the obtained thermodynamic parameters, eight as-cast Zn–Mn alloys were prepared and the phase compositions and solidified microstructures were analyzed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA). It was shown that the observed experimental results agreed well with the Scheil solidification calculations.

Solvothermal synthesis of n-type Bi2(SexTe1\u2212x)3 nanoplates for high-performance thermoelectric thin films on flexible substrates

To improve thermoelectric performance of materials, the utilization of low-dimensional materials with a multi-alloy system is a promising approach. We report on the enhanced thermoelectric properties of n-type Bi2(SexTe1−x)3 nanoplates using solvothermal synthesis by tuning the composition of selenium (Se). Variation of the Se composition within nanoplates is demonstrated using X-ray diffraction and electron probe microanalysis. The calculated lattice parameters closely followed Vegard’s law. However, when the Se composition was extremely high, an impurity phase was observed. At a reduced Se composition, regular-hexagonal-shaped nanoplates with a size of approximately 500 nm were produced. When the Se composition was increased, the shape distribution became random with sizes more than 5 μm. To measure the thermoelectric properties, nanoplate thin films (NPTs) were formed on a flexible substrate using drop-casting, followed by thermal annealing. The resulting NPTs sufficiently adhered to the substrate during the bending condition. The electrical conductivity of the NPTs increased with an increase in the Se composition, but it rapidly decreased at an extremely high Se composition because of the presence of the impurity phase. As a result, the Bi2(SexTe1−x)3 NPTs exhibited the highest power factor of 4.1 μW/(cm∙K2) at a Se composition of x = 0.75. Therefore, it was demonstrated that the thermoelectric performance of Bi2(SexTe1−x)3 nanoplates can be improved by tuning the Se composition.

Heliophyllite: a discredited mineral species identical to ecdemite

Abstract. The type material for heliophyllite, preserved in the Swedish Museum of Natural History in Stockholm, was re-investigated through a combined EPMA (electron probe X-ray microanalysis), Raman, and X-ray powder diffraction (XRPD) and single-crystal study. EPMA chemical data, together with Raman and single-crystal structural studies, point to heliophyllite being identical to ecdemite. XRPD synchrotron data highlight the presence of a minor quantity of finely admixed finnemanite in the analyzed material, explaining the presence of some additional diffraction peaks, not indexable with the ecdemite unit cell, reported in the literature. The discreditation of heliophyllite has been approved by the IMA Commission on New Minerals and Mineral Names (proposal 19-H, 2019).

The effect of Al2O3 on fayalite-based copper smelting slags in equilibrium with matte and tridymite at 1 2008C and P(SO2) = 0.25 atm

Abstract Experimental investigations have been undertaken to determine the effect of Al2O3in slag on the gas/slag/matte/tridymite equilibria in the multi-component Cu-Fe-O-S-Si-Al system at 1 200 8C, and P(SO2) = 0.25 atm. The experimental technique involves high temperature equilibration of synthetic samples on the open silica substrate in controlled gas atmospheres (CO/CO2/SO2/Ar), rapid quenching after a designated equilibration time followed by the compositional analysis of the condensed phases with electron probe X-ray microanalyzer. The experimental data of the present study provide information on the effect of alumina on the slag composition, such as the chemically dissolved copper, dissolved sulphur, and Fe/SiO2 ratio in slag at tridymite saturation at different Cu in matte. The new data have been used as inputs for the optimization of the thermodynamic databases for the copper-containing systems and can also be used to evaluate the fluxing strategy in the copper smelting operation.

Enhancement of Tetrahedral Chromium (Cr4+) Concentration for High-Gain in Single-Mode Crystalline Core Fibers

Tetrahedral chromium (Cr4+)-ions is the main contributor to gain in the broadband single-mode Cr-doped crystalline core fibers (SCCFs). We have demonstrated a gross gain of 8-dB on a length of 27-cm for a 300-nm broadband SCCF using a thermal annealing technique. Gross gain and fiber length are the highest yet reported for the SCCF. The record gain is mainly due to both the longer fiber by aligned molten-zone growth and Cr4+-ions enhancement by thermal annealing. The enhancement mechanism of the Cr4+-ions in the SCCF is experimentally verified by the means of superconducting quantum interference device (SQUID) and electron probe X-ray micro-analysis (EPMA). As a practical application of the proposed 8-dB gain in the SCCFs in fiber transmissions, a 25-Gb/s error-floor free link is successfully demonstrated.

Development of Ferrous-Calcium Silicate Slag for the Direct to Blister Copper-Making Process and the Equilibria Investigation

To mitigate possible environmental pollutions, the direct to blister (DTB) route is an important process for copper making because a single, SO2-concentrated stream can be produced. In this study, the ferrous-calcium silicate (FCS) slag system for the DTB process with a CaO content of ~ 15 wt pct was studied, as well as its equilibria with spinel, blister, and gas phases. The investigation was targeted in the spinel primary phase field with accurately controlled P(SO2) and P(O2) to be 0.4 and 1 × 10−5 atm, respectively. The equilibrium chemical compositions of various phases in the samples after high-temperature experiments were quantified using an electron probe X-ray microanalyzer (EPMA). Accordingly, the relationship between the liquidus temperature of slags and Fe/SiO2 was established, as well as that between the equilibrium “Cu2O” content and temperature. The solid solubilities in the spinel phase were also identified, including the concentrations of S, CaO, SiO2, and “Cu2O.” Last, the present results on FCS slags were compared with those on iron silicate (IRS) slags and the FactSage predictions, which provided more clues for further slag development and thermodynamic modeling.