High Bi Content Research Articles

Composition and microstructure of Na0.5Bi0.5TiO3 ceramics with excess Bi

AbstractIn the present work, Na0.5Bi0.5TiO3 (NBT) ceramics with the addition of excess Bi in two different ways – before calcination and before sintering – are considered, revealing how the excess Bi affects their microstructure and chemical content. Average grain size is seen to decrease, with the grain size distribution becoming less diffused at higher excess Bi concentrations. The reason for such a feature is the shift of the sintering temperature region where the abnormal grain growth starts to contribute towards higher temperatures. The influence of excess Bi is more pronounced in the case if it is added before calcination. It was discovered that a small amount of excess Bi helps to prevent the formation of Bi‐deficient inclusions. While, high concentrations of excess Bi induce the formation of Bi‐rich inclusions – most probably Na0.5Bi4.5Ti4O15. Possible mechanisms of formation of both types of inclusions are discussed in detail. Instead of Bi over‐stoichiometry, elevated Na content and slightly lower O content were detected in the matrix grains of the sintered NBT ceramics prepared with excess Bi. These deviations increase upon increasing the added excess Bi concentration. The presence of another, Na‐rich phase, is assumed, which could not be detected by X‐ray diffraction or by energy‐dispersive X‐ray analysis.

Structural and Optical Properties of Bismuth-doped ZnO Nanoparticles Synthesized by Co-precipitation

Bismuth-doped zinc oxide (ZnO) nanoparticles can serve as efficient photocatalysts for various reactions. Herein, we synthesized and discussed the growth mechanisms of Bi-doped ZnO nanoflakes using co-precipitation with Bi concentrations ranging from 0 to 3 %. The resulting ZnO were hexagonal nanosheets with diameters ranging from 80 nm (ZnO) to 200 nm (ZnO: Bi 3%). The dominant crystal structure matches hexagonal wurtzite with a small presence of Bi2O3 diffraction peaks. The estimated crystallite sizes range from ~ 33 nm to ~ 45 nm, indicating multiple crystalline regions in each nanoflake. Nevertheless, as sheet resistance monotonically decreases with the Bi concentration, the higher number of grain boundaries likely has a lower effect on the conductivity compared to an increase in free carriers and larger grain size in the samples with higher Bi concentration. The bandgap decreases from ~ 3.13 eV to ~ 2.96 eV, likely due to the shrinkage effect from electron-electron or electron-impurity interaction that lowers the conduction band of ZnO.

Trace element compositions of sulfides from Pb-Zn deposits in the Northeast Yunnan and northwest Guizhou Provinces, SW China: Insights from LA-ICP-MS analyses of sphalerite and pyrite

Trace elements in sphalerite and pyrite from six deposits at the Sichuan-Yunnan-Guizhou lead–zinc metallogenic province were analysed to constrain the composition, distribution characteristics and substitution mechanisms of trace elements by LA-ICP-MS analyses. The results show that the sphalerites are characterized by high Fe, Ge, Cd and low Bi, Ni, Co and Tl contents, while pyrites characteristically have high contents of Ni, Co, As and low contents of Ge, Ga, Tl, Bi and In. Iron, Ga, Mn, Cd and Ge in sphalerite and Co, Ni and Tl in pyrite are generally lattice-bound, while Ag, Cu, As and Sb are usually present in both micro-inclusions and solid solution. Significant correlations between some elements in sphalerite suggest the substitution mechanisms: 2Zn2+ ↔ (Ag+, Cu+) + (Ga3+, As3+) and 3Zn2+ ↔ 2(Cu+, Ag+) + Ge4+, and the existence of negative correlation between Fe and Mn implies a competition between both elements. The correlation trends between trace elements in pyrite demonstrate the coupled substitution mechanism of 2Fe2+ ↔ (Tl+, Cu+, Ag+) + Sb3+.Generally, darker sphalerite is relatively rich in Fe and Ge compared to light-color sphalerite, and is deficient in Ga, In and Sn. Regionally, the Cu in sphalerite tends to gradually increase from southeast to northwest, and pyrite from Maoping has significantly higher Co and Ti concentrations and Co/Ni ratios than that from the deposits in northwestern Guizhou. The variation of the Co/Ni ratio in pyrite at the scale of these deposits may provide vectors for the geochemical exploration of Pb-Zn mineralization and the Co/Ni ratios close to 0.1 are more prospective for a larger deposit.

The effects of post-cumulus alteration on the distribution of chalcophile elements in magmatic sulfide deposits and implications for the formation of low-S-high-PGE zones: The Luanga deposit, Carajás Mineral Province, Brazil

ABSTRACT Most of the World's platinum-group element ore deposits occur as thin stratiform layers within layered intrusions. These layers generally contain disseminated base-metal sulfides or chromite. However, cryptic platinum-group element deposits also occur without chromite or base-metal sulfides in what are known as low-S-high platinum-group element deposits. The origin of these deposits is not clearly understood. The Luanga Complex hosts the largest platinum-group elements resource in South America (i.e., 142 Mt at 1.24 ppm Pt + Pd + Au and 0.11% Ni) and hosts both a platinum-group element deposit containing disseminated base-metal sulfides (style 1) and a low-S-high platinum-group element deposit (style 2). It therefore offers the opportunity to compare the two deposit types in the same overall geological setting and consider how the low-S-high platinum-group element deposit could have formed. The first deposit style is termed the Sulfide zone and consists of a 10–50 meter-thick interval with disseminated base metal sulfides, whereas the second style is named low-S-high-Pt-Pd zone and consists of 2–10 meter-thick discontinuous lenses of 1–5 meter-thick sulfide- and oxide-free harzburgite and orthopyroxenite with discrete platinum-group minerals. Secondary assemblages commonly replace primary igneous minerals to a variable extent throughout the deposit, and thus allow for investigating the effects of post-cumulus alteration on the distribution of a wide range of chalcophile elements in a magmatic sulfide deposit at both whole-rock and mineral scale. This study presents the whole-rock distribution of S, platinum-group elements, and Te, As, Bi, Sb, and Se in both mineralization styles and the concentration of trace elements in base-metal sulfides from the Sulfide zone. The Sulfide zone has Pt/Pd ratios around 0.5 and high concentrations of Te, As, Bi, Sb, and Se, whereas the low-S-high-platinum-group element zone has Pt/Pd ratios greater than 1 and much lower Se, Te, and Bi concentrations, but comparable As and Sb contents. This is reflected in the platinum-group element assemblage, comprising bismuthotellurides in the Sulfide zone and mostly arsenides and antimonides in the low-S, high platinum-group elements zone. Moreover, the base-metal sulfides from the Sulfide zone have anomalously high As contents (50–500 ppm), which suggest that the sulfide liquid segregated from a very As-rich silicate magma, possibly illustrated by an average komatiitic basalt that assimilated a mixture of upper continental crust and black shales. We interpret the low-S-high platinum-group elements zone as a product of S loss from magmatic sulfides during post-cumulus alteration of the Luanga Complex. Selenium, Te, Bi, and Pd were also lost together with S, whereas As and Sb were expelled from base-metal sulfide structures and combined with platinum-group elements to form platinum-group minerals, suggesting they may play a role fixating platinum-group elements during alteration. The remobilization of chalcophile elements from magmatic sulfide deposits located in the Carajás Mineral Province may represent a potential source for hydrothermal deposits found in the region.

Doping Process of 2D Materials Based on the Selective Migration of Dopants to the Interface of Liquid Metals

The introduction of trace impurities within the doping processes of semiconductors is still a technological challenge for the electronics industries. By taking advantage of the selective enrichment of liquid metal interfaces, and harvesting the doped metal oxide semiconductor layers, the complexity of the process can be mitigated and a high degree of control over the outcomes can be achieved. Here, a mechanism of natural filtering for the preparation of doped 2D semiconducting sheets based on the different migration tendencies of metallic elements in the bulk competing for enriching the interfaces is proposed. As a model, liquid metal alloys with different weight ratios of Sn and Bi in the bulk are employed for harvesting Bi2 O3 -doped SnO nanosheets. In this model, Sn shows a much stronger tendency than Bi to occupy surface sites of the Bi-Sn alloys, even at the very high concentrations of Bi in the bulk. This provides the opportunity for creating SnO 2D sheets with tightly controlled Bi2 O3 dopants. By way of example, it is demonstrated how such nanosheets could be made selective to both reducing and oxidizing environmental gases. The process demonstrated here offers significant opportunities for future synthesis and fabrication processes in the electronics industries.

Trace Element Geochemistry of Chalcopyrites and Pyrites from Golpu and Nambonga North Porphyry Cu-Au Deposits, Wafi-Golpu Mineral District, Papua New Guinea

Studying elemental geochemistry of hypogene sulphides can discriminate the hydrothermal fluids responsible for ore formation. To determine whether Golpu porphyry Cu-Au deposits are related to the Nambonga North porphyry system which is located 2.5 km apart in the Wafi-Golpu Mineral District, Papua New Guinea, we compare the trace element compositions of drill core chalcopyrites and pyrites analysed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). The results for the Golpu chalcopyrites revealed high concentrations of Au, As, Se, Mo, Sb, Te and Bi and lower concentrations of Ag and Zn compared to those from Nambonga. Pd and Pt were below the detection limit in chalcopyrites for both deposits. The results for the Golpu pyrites indicated high concentrations of Pt, Au, Se, Mo, Sb, and Te and lower concentrations of Cu, Zn, As, Ag, Pb, Pd and Bi compared to those from Nambonga North. Au concentrations in the pyrites from both the porphyry deposits were higher compared to chalcopyrites, which mean that pyrite is the Au-bearing sulphide responsible for the higher Au content. In contrast, Cu values in pyrites from Nambonga North are higher than those from Golpu. Overall, it is envisaged that the ore fluids were exsolved at different times during the evolution of both porphyry deposits, although these porphyry centres may be related in space and time.

Bi2O3–Nd2O3–WO3 system: Phase formation, polymorphism, and conductivity

Cubic, tetragonal, and monoclinic (Bi2O3)x (Nd2O3)y (WO3)z (x + y + z = 1) solid solutions based on the Bi2O3 oxygen ion conductor have been prepared by solid-state reactions in the ternary system Bi2O3–Nd2O3–WO3. The field of monoclinic compounds with a Bi3·24La2W0·76O10.14-type structure has been shown to account for most of the ternary system. Compounds with a cubic fluorite structure exist at the boundary of the monoclinic phase field in two small regions at high (83–91 mol% Bi2O3, δ-phase) and low (20–55 mol% Bi2O3, δ′-phase) Bi concentrations. The cubic samples of the δ-phase retain their structure only during rapid heating and cooling, but annealing in the range of 300–700 °C results in structure degradation to lower symmetry phases. The monoclinic compounds and Bi-poor cubic compounds (δ′-phase) have good thermal stability. The cubic samples of the δ′-phase are hygroscopic. Their bulk conductivity noticeably increases with atmospheric humidity, suggesting that these materials are potential proton conductors.

Trace elements in pyrite and pyrrhotite in the Pitangui Orogenic Au deposit, Pitangui greenstone belt, São Francisco Craton: Implications for the ore-forming fluids and metal sources

Orogenic Au deposits represent one of the largest sources of gold in the world and in Brazil, particularly at the Quadrilátero Ferrífero, southeastern portion of the São Francisco Craton. In the last decades, advances in in-situ analytical techniques allowed a detailed investigation of the chemistry of sulfides. This can reveal information about the origin and composition of the mineralizing fluids, potential sources of metals and sulfur and the fluid-rock interaction during the ore-forming processes. In this paper we combine Electron Microprobe Analysis and LA-ICP-MS analyses to put constraints on the nature and evolution of the Pitangui gold deposit. The Pitangui deposit represents an important Orogenic Au deposit hosted in clastic metasedimentary rocks of the Pitangui greenstone belt, northwestern portion of the Quadrilátero Ferrífero. Detailed drill hole, petrographic observations and in-situ chemical analyses of the hydrothermal alteration zones show that pyrite is the dominant ore mineral in the deposit and two possible origins are suggest including (i) syngenetic pyrite development at the early stages of the greenstone belt evolution and (ii) epigenetic pyrite, which is associated with hydrothermal processes during the Orogenic Au event. Syngenetic pyrite (PyI) has high Co, Bi, Pb, Sb, Te, Se, Ag and Au concentrations. The PyI could represent an important source of metals, a set of trace elements and likely sulfur for the later Orogenic Au mineralization. Epigenetic pyrites (PyII, PyIII and PyIV), conversely, are mainly found in association with hydrothermal minerals and within the mineralized carbonate-quartz-vein. The variations at Co, Ni, Pb, Te, Sn, Se, As, Bi, Sb, Ag, Mo and W in the epigenetic pyrite indicate that the dehydration PGB sequences during orogenesis constitutes the main fluids sources. The PyV, in turn, only appears at metamafic dyke, but its origin remains unclear.

Metal anomalies in till in the Sarvlaxviken area, Lovisa, southern Finland

Geochemical investigations of till is a widely used method in metal exploration as the till commonly inherits the geochemical signature (including the metal contents) of the parent bedrock. In this investigation, over 2000 till samples were collected in the Sarvlaxviken area, southern Finland, where several polymetallic (Cu, Zn, Pb, As, Sn, W and In) veins recently have been discovered in Proterozoic crust along the border between Late Svecofennian granites and the Wiborg Batholith. The bedrock is commonly covered by compact and poorly sorted basal till, formed during the Late Weichselian glaciation event. Several glacial-transported boulders, with high contents of Cu, Zn, As, Sn, Mo and Bi and derived from the local bedrock, have also been discovered on top of the till and provide evidence for concealed mineralisation in the local bedrock under the till cover. The frequent distribution of till in the Sarvlaxviken area provides excellent conditions for the search of such hidden mineralisation by means of systematic till sampling, even if large farm field areas, composed of clay-rich sediments, and seawater-covered areas (Sarvlaxviken bay), had to be avoided in the sampling program. The till samples were collected during university courses and training programs led by the authors and were analysed in a cost-efficient and certified laboratory. Obtained geochemical data were statistically processed by using K-means clustering algorithms which can be used to treat large sets of geochemical data. The results provided anomalies that mainly occur in till with a thickness of <1 m and are considered to be derived from a local bedrock source. The discovered anomalies provide strong evidence for numerous undiscovered veins beneath the till cover.

Polyphase gold mineralization at the Yaou deposit, French Guiana

Abstract The Yaou deposit, located in French Guiana within the Guiana Shield, is one of the most promising gold deposits of the regional Paleoproterozoic greenstone belt. It displays numerous quartz monzodiorite bodies aligned along a sinistral shear zone where a five-deformation phases model is established at the camp scale. The ductile D 1/2YA phase is responsible for the main penetrative foliation while the D 3YA phase is related to shearing. An intrusive event is identified as being pre to syn-D 3YA . The following phase D 4YA represents a brittle quartz-carbonate veining set hosted preferentially within intrusive bodies and along the shear zone. A local D 5YA brecciation event crosscuts the D 4YA veins. Among this deformation history, two auriferous events (D 3YA and D 4YA ) control the overall grade of the Yaou gold deposit. More specifically, most of the Au grade is associated with the main economic D 4YA veining event, where the gold is visible and linked to Py 4 within an ankerite/hematite rich alteration halo. At the microscopic scale, results of in situ analyses using LA-ICP-MS on pyrite show that metasediment-hosted Py 0 is a primary source of submicroscopic gold having a low contribution to the total endowment. Py 3 shows some gold content due to possible remobilization of Au D0YA . Gold in Py 4 is found as submicroscopic gold, as micro-inclusions and as infilling fractures in association with elements such as Te, Ag and Bi. Most contribution to the Au grade is from micro-inclusions and, to a lesser extent, from free and submicroscopic gold. The ore shoot locations are lithologically controlled for Au D0YA (metasedimentary unit-hosted), structurally controlled (shear zone-hosted) for Au D3YA and rheologically controlled for the Au D4YA (intrusion-hosted). The deposit is clearly polyphase both at the macroscopic and the microscopic scales, invisible gold is associated with As whereas visible gold is observed as inclusions in pyrite with high contents of Ag, Te and Bi. We define an early low-grade enrichment of Au D0YA to Au D3YA followed by a later high-grade event, Au D4YA supporting polyphase mineralization processes. This study confirms that orogenic gold deposits can be formed by remobilization and/or new gold inputs during multiple deformation, veining and hydrothermal events.

Metallobiochemistry of ultratrace levels of bismuth in the rat II. Interaction of 205+206Bi3+ with tissue, intracellular and molecular components

BackgroundKnowledge on Bi metabolism in laboratory animals refers to studies at “extreme” exposures, i.e. pharmacologically relevant high-doses (mg kg−1 b.w.) in relation to its medical use, or infinitesimal doses (pg kg−1b.w.) concerning radiobiology protection and radiotherapeutic purposes. There are no specific studies on metabolic patterns of environmental exposure doses (ultratrace level, μg kg−1 b.w.), becoming in this context Bi a “heavy metal fallen into oblivion”. We previously reported the results of the metabolic fate of ultratrace levels of Bi in the blood of rats [1]. In reference to the same study here we report the results of the retention and tissue binding of Bi with intracellular and molecular components. MethodsAnimals were intraperitoneally injected with 0.8 μg Bi kg−1 b.w. as 205+206Bi(NO)3, alone or in combination with 59Fe for the radiolabeling of iron proteins. The use of 205+206Bi radiotracer allowed the determination of Bi down to pg fg−1 in biological fluids, tissues, subcellular fractions, and biochemical components isolated by differential centrifugation, size exclusion chromatography, solvent extraction, precipitation, immunoprecipitation and dialysis. Main findingsAt 24 h post injection the kidney contained by far the highest Bi concentration (10 ng g−1 wt.w.) followed by the thymus, spleen, liver, thyroid, trachea, femur, lung, adrenal gland, stomach, duodenum and pancreas (0.1 to 1.3 ng g−1 wt.w.). Brain and testis showed smaller but consistently significant concentrations of the element (0.03 ng g−1 wt.w). Urine was the predominant route of excretion. Intracellularly, liver, kidney, spleen, testis, and brain cytosols displayed the highest percentages (35%–58%) of Bi of homogenates. Liver and testis nuclei were the organelles with the highest Bi content (24 % and 27 %). However, when the recovered Bi of the liver was recorded as percent of total recovered Bi divided by percent of total recovered protein the lysosomes showed the highest relative specific activity than in other fractions. In the brain subcellular fractions Bi was incorporated by neuro-structures with the protein and not lipidic fraction of the myelin retaining 18 % of Bi of the total homogenate. After the liver intra-subcellular fractionation: (i) 65 % of the nuclear Bi was associated with the protein fraction of the nuclear membranes and 35 % with the bulk chromatin bound to non-histone and DNA fractions; (ii) about 50 % of the mitochondrial Bi was associated with inner and outer membranes being the other half recovered in the intramitochondrial matrix; (iii) in microsomes Bi showed a high affinity (close to 90 %) for the membranous components (rough and smooth membranes); (iv) In the liver cytosol three pools of Bi-binding proteins (molecular size > 300 kDa, 70 kDa and 10 kDa) were observed with ferritin and metallothionein–like protein identified as Bi-binding biomolecules. Three similar protein pools were also observed in the kidney cytosol. However, the amount of Bi, calculated in percent of the total cytosolic Bi, were significantly different compared to the corresponding pools of the liver cytosol. ConclusionsAt the best of our knowledge the present paper represents the first in vivo study, on the basis of an environmental toxicology approach, aiming at describing retention and binding of Bi in the rat at tissue, intracellular and molecular levels.

Discovering hidden spatial patterns and their associations with controlling factors for potentially toxic elements in topsoil using hot spot analysis and K-means clustering analysis

The understanding of sources and controlling factors of potentially toxic elements (PTEs) in soils plays an important role in the improvement of environmental management. With the rapid growth of data volume, effective methods are required for data analytics for the large geochemical data sets. In recent years, spatial machine learning technologies have been proven to have the potential to reveal hidden spatial patterns in order to extract geochemical information. In this study, two spatial clustering techniques of Getis-Ord Gi* statistic and K-means clustering analysis were performed on 15 PTEs in 6,862 topsoil samples from the Tellus datasets of Northern Ireland to investigate the hidden spatial patterns and association with their controlling factors. The spatial clustering patterns of hot spots (high values) and cold spots (low values) for the 15 PTEs were revealed, showing clear association with geological features, especially peat and basalt. Peat was associated with high concentrations of Bi, Pb, Sb and Sn, while basalt was associated with high concentrations of Co, Cr, Cu, Mn, Ni, V and Zn. The high concentrations of As, Ba, Mo and U were associated with mixture of various lithologies, indicating the complicated influences on them. In addition, three hidden patterns in the 6,862 soil samples were revealed by K-means clustering analysis. The soil samples in the first and second clusters were overlaid on the peatland and basalt formation, respectively, while the samples in the third cluster were overlaid on the mixture of the other lithologies. These hidden patterns of soil samples were consistent with the spatial clustering patterns for PTEs, highlighting the dominant control of peat and basalt in the topsoil of Northern Ireland. This study demonstrates the power of spatial machine learning techniques in identifying hidden spatial patterns, providing evidences to extract geochemical knowledge in environmental studies.

GaAsBi Quantum Dots for 1.55 μm Laser Diode

Bi incorporations can reduce the bandgap of GaAs1-xBix. With a Bi content of 10.5%, GaAsBi is predicted to emit light at 1.55 μm. However, high Bi incorporation is difficult for material growth and deteriorates the optical property of GaAsBi. In this work, a GaAsBi quantum dot (QD)/InAlAs structure on InP platform is proposed to fabricate 1.55 μm laser diodes. Strain distributions and band structures are calculated with different Bi contents and QD sizes using finite element method. High Bi contents and large QD sizes are beneficial for achieving long wavelengths. GaAsBi QD/InAlAs structures with a low Bi content of 5.6% and proper QD sizes, such as a diameter of 30 nm and a height of 6 nm, can emit light at 1.55 μm. The proposed structure can be realized by migration enhanced epitaxy and droplet epitaxy and provides a feasible way for fabricating GaAsBi based 1.55 μm laser diodes applied in fiber-optic communications. The emission wavelength of GaAsBi QDs with different sizes and Bi contents

Trace Elements and Sulfur Isotopes of Sulfides in the Zhangquanzhuang Gold Deposit, Hebei Province, China: Implications for Physicochemical Conditions and Mineral Deposition Mechanisms

The Zhangquanzhuang gold deposit is a special deposit in the Zhangjiakou district, on the northern margin of the North China Craton. It is characterized by the enrichment of sulfides, the scarcity of tellurides and zero to positive sulfur isotope compositions compared with the famous Dongping and Xiaoyingpan Te-Au-Ag deposit types of the same district. In this paper, we use the in-situ LA-(MC)-ICP-MS and bulk trace element concentrations of pyrite, and in-situ sulfur isotope compositions of sulfides, to study physicochemical conditions and mechanisms of mineral deposition in the Zhangquanzhuang deposit. Pyrite from stage I (PyI) contains high Te contents, pyrite from stage II (PyII) has the highest Co and Ni contents, and pyrite from stage III (PyIII) contains high Cr, Zn, Pb, Ag, Cu, Sb, Bi and Au contents. The calculated in-situ δ34SH2S values range from 0.9‰ to 6.1‰, and the values for stages I and II are higher than those for stage III. The mineral assemblages and trace element contents in pyrite show that large amounts of metals precipitated during stage III, in which the pH and logfO2 were constrained within the range of 4.1 to 5.2 and −36.9 to −32.1, respectively. Sulfidation and boiling derived from decreasing pressure may be the main mechanisms leading to mineral deposition in stage III. The Zhangquanzhuang gold deposit was formed in a mineral system that was different from the one that formed the Dongping and Xiaoyingpan Te-Au-Ag deposits, and should thus be called the “Zhangquanzhuang−type” deposit and considered a third gold deposit type in the Zhangjiakou ore field.

Reaction mechanisms of waste printed circuit board recycling in copper smelting: The impurity elements

Feeding Waste Printed Circuit Boards (WPCBs) into existing pyrometallurgical processes is developing as an easy-to-adapt and efficient way to recycle them. To fulfill sustainability and circular economy targets, kinetics and distributions are the key factors when recovering metals and trace elements from WPCBs. We investigated the reaction mechanisms and distribution behavior of impurity elements Sb, As and Bi between copper matte and slag at a typical smelting temperature of 1300 °C both in air and argon atmospheres. Laboratory-scale heat-quench experiments indicated that vaporization can effectively eliminate arsenic in the matte phase, but not antimony or bismuth either in air or in an argon atmosphere. Sufficient contact time between the gas and matte phase is also needed to transfer the trace elements into gas and slag. In this work, kinetic data and distribution ratios of these impurity elements in the matte and slag phase were calculated. They can be used in process development for WPCB recycling and, equally, when using complex copper concentrates with high As, Sb, and Bi contents. The results also complement CFD models to simulate flash smelting processes more precisely.

Hydrogeochemistry in the Yukon-Tanana upland region of east-central Alaska: Possible exploration tool for porphyry-style deposits

A hydrogeochemical study using high resolution ICP-MS was undertaken at the Taurus and other porphyry Cu–Mo(-Au) occurrences and Ag–Au–Cu (+/− Pb, Zn) occurrences with epithermal-style characteristics in the Yukon-Tanana upland region of eastern Alaska. Surface water samples were collected from 30 sites on creeks that drain known deposits and occurrences and surrounding presumably unmineralized areas. Water samples for the entire ~9 km length of McCord Creek, which drains the Taurus deposit, and those from streams draining the areas at and near the Bluff and Dennison porphyry occurrences have high conductivity values (492–1250 μS/cm) and consistently high concentrations of B (3–250 μg/L), Co (2.3–42 μg/L), Mn (339–4750 μg/L), Re (0.012–0.1 μg/L), and SO42− (>200 mg/L), all of which are well above the median value for this data set and significantly greater than concentrations in water samples from the unmineralized areas. These are the best pathfinder elements specifically for porphyry style deposits because most of them are not anomalous in waters near epithermal occurrences. Copper concentrations are high (up to 115 μg/L) in some low-pH water samples from McCord Creek and drainages around Bluff, and a few near neutral pH waters have high molybdenum (>1 μg/L), but neither element is consistently anomalous in close vicinity to the porphyry occurrences, possibly due to a metal-poor, sulfide-poor leached cap (average of ~50 m) that overlies supergene and hypogene mineralized zones and is the dominant rock at surface. High concentrations of Bi and/or As occur in many waters associated with mineralized areas, particularly the Bluff and Dennison occurrences. In general, the element associations related to porphyry deposits reflect the deposit mineralogy, as well as size of the footprint related to alteration and mineralization.

Photoluminescence and Raman Scattering of GaAs1-xBix Alloy

Photoluminescence (PL) and Raman spectra of GaAs1-xBix samples grown at different rates (0.09 to 0.5 µm/h) were investigated. The PL peak wavelength initially redshifted with the increase of growth rate and reached the longest wavelength (1158 nm) for sample grown at 0.23 µm/h. This is followed by PL peak wavelength blueshift for higher growth rates. The Raman data show peaks at 162, 228, 270, and 295 cm-1 which can be attributed to GaAs like phonons. GaBi like vibrational modes were also observed at 183 and 213 cm-1. However, the intensity of Bi induced phonons is significantly weaker compared to GaAs due to low concentration of Bi compared to As and thin GaAs1-xBix epilayer. The PL data and GaAs transverse optical (TO) to longitudinal optical (LO) phonons intensity ratio indicate that Bi concentration is highly dependent on the growth rate and the highest Bi concentration was obtained by sample grown at 0.23 µm/h. It is found that the full-width-at-half-maximum (FWHM) of GaAs LO mode increases significantly for samples grown at high growth rates suggesting crystal quality degradation due to lack of surfactant effects.

Characterization of tellurium and silicon as n-type dopants for GaAsBi

Films of n-GaAs1-xBix films were grown via molecular beam epitaxy using both Si and Te as dopant sources. Electron mobility was characterized by Hall effect measurements as a function of carrier concentration and Bi content for films with bismuth fractions of x = 0.02 and x = 0.06. While GaAsBi:Te shows lower majority carrier mobility than GaAsBi:Si at low Bi concentrations, the two become comparable as Bi content increases. Furthermore, it was observed that in the presence of bi-metallic Bi-Ga droplets on the film surface, films doped with Si display p-type behavior, likely due to Si preferentially occupying group-V sites. The use of Te as a dopant always resulted in n-type epilayers, making it a more reliable dopant choice for high Bi content films. Finally, ex situ annealing was studied as a method to improve majority carrier mobility in GaAs0.98Bi0.02:Te films, with a 10 min anneal at 350 °C resulting in a 30% improvement in electron mobility. Improvement of film quality was confirmed through spectroscopic ellipsometry examination of film optical properties. Annealing at higher temperatures resulted in electrical, optical, and structural degradation of the GaAsBi films.

Pyrite Varieties at Pobeda Hydrothermal Fields, Mid-Atlantic Ridge 17°07′–17°08′ N: LA-ICP-MS Data Deciphering

The massive sulfide ores of the Pobeda hydrothermal fields are grouped into five main mineral microfacies: (1) isocubanite-pyrite, (2) pyrite-wurtzite-isocubanite, (3) pyrite with minor isocubanite and wurtzite-sphalerite microinclusions, (4) pyrite-rich with framboidal pyrite, and (5) marcasite-pyrite. This sequence reflects the transition from feeder zone facies to seafloor diffuser facies. Spongy, framboidal, and fine-grained pyrite varieties replaced pyrrhotite, greigite, and mackinawite “precursors”. The later coarse and fine banding oscillatory-zoned pyrite and marcasite crystals are overgrown or replaced by unzoned subhedral and euhedral pyrite. In the microfacies range, the amount of isocubanite, wurtzite, unzoned euhedral pyrite decreases versus an increasing portion of framboidal, fine-grained, and spongy pyrite and also marcasite and its colloform and radial varieties. The trace element characteristics of massive sulfides of Pobeda seafloor massive sulfide (SMS) deposit are subdivided into four associations: (1) high temperature—Cu, Se, Te, Bi, Co, and Ni; (2) mid temperature—Zn, As, Sb, and Sn; (3) low temperature—Pb, Sb, Ag, Bi, Au, Tl, and Mn; and (4) seawater—U, V, Mo, and Ni. The high contents of Cu, Co, Se, Bi, Te, and values of Co/Ni ratios decrease in the range from unzoned euhedral pyrite to oscillatory-zoned and framboidal pyrite, as well as to colloform and crystalline marcasite. The trend of Co/Ni values indicates a change from hydrothermal to hydrothermal-diagenetic crystallization of the pyrite. The concentrations of Zn, As, Sb, Pb, Ag, and Tl, as commonly observed in pyrite formed from mid- and low-temperature fluids, decline with increasing crystal size of pyrite and marcasite. Coarse oscillatory-zoned pyrite crystals contain elevated Mn compared to unzoned euhedral varieties. Framboidal pyrite hosts maximum concentrations of Mo, U, and V probably derived from ocean water mixed with hydrothermal fluids. In the Pobeda SMS deposit, the position of microfacies changes from the black smoker feeder zone at the base of the ore body, to seafloor marcasite-pyrite from diffuser fragments in sulfide breccias. We suggest that the temperatures of mineralization decreased in the same direction and determined the zonal character of deposit.

Bi-sulfide existence in 0Cr18Ni9 steel: correlation with machinability and mechanical properties

This work investigates the effect of Bi addition on the formation of sulfide inclusions, and also aims to improve the machinability and mechanical properties of type 0Cr18Ni9 stainless steel. Smelting experiments as well as machining and tensile tests were carried out in various low and high Bi content steels. Results show that the forms of Bi-MnS inclusions were: isolated particle, cavity-bridge link, semi- and complete encapsulation. The forms of MnS inclusions were found as: mushroom or rod-like, long strip, spherical, and spindle shape. The normalized frequency of 0.065, corresponding to the inclusion area above 50 μm2, was the greatest at 2300 ppm Bi, reflecting an increase in the number of larger-sized inclusions. The averge hardness of steel matrix and the inclusions at 0 ppm Bi was 179 and 166 kgf/mm2, while that after Bi addition was 154∼168 and 155∼166 kgf/mm2, respectively. The Bi addition to steel improved the surface finish of the steels after machining and increased the ductility of steel, but had little effect on the yield strength of steel.