Chromium Research Articles

Effect of bias voltage on high-temperature oxidation resistance and electrical properties of Mn-Co coating with metal interconnects for solid oxide fuel cell

Abstract This study investigated the effects of bias voltage on the microstructure, high-temperature oxidation resistance, electrical conductivity, element diffusion, and barrier of chromium poisoning cathode of Mn-Co coating on the surface of SOFCs metal interconnect SUS441 ferritic stainless steel. A series of Mn-Co coatings were prepared by magnetron sputtering technique at different bias voltages (−10, −50, −90 V) and oxidized at high temperatures for 175 h at 850 °C in an air environment. The results showed that the surface of each coating before oxidation exhibited a cauliflower-like morphology, with the crystallinity of the coating increasing with higher bias voltage. After high-temperature oxidation, especially the Mn-Co coatings prepared at −90 V bias, a dense and stable MnCo2O₄ spinel structure was formed, which is crucial in inhibiting the growth of the Cr2O3 oxide layer. In addition, the coating also exhibits excellent electrical conductivity (Ea=0.35eV), good high-temperature oxidation resistance (1.182 mg/cm2), and a stronger ability to prevent the diffusion of Cr elements.

Qualidade da água envasada consumida no estado de São Paulo: análise de substâncias inorgânicas

Introduction: The availability of different brands of bottled water on the national market, combined with the growing consumption by the population, makes it important to assess the quality of its chemical composition. Objective: To quantify inorganic chemical substances (nutrients and toxic metals) in samples of bottled water from national and imported sources consumed in the State of São Paulo, in compliance with legislation and compendiums; verify the parameters of inorganic elements indicated on labeling, as well as the recommended daily intake. Method: Determinations were carried out by inductively coupled plasma mass spectrometry. Results: The evaluation indicated that 93.5% of the total of the 107 samples analyzed presented concentrations of inorganic chemical elements in accordance with the maximum values allowed in national legislation for all analytes (96.5% for national and 81.0% for imported), thus being considered suitable for human consumption. Discordant results were obtained for 6.5% for the elements chromium (2.3%) and selenium (1.2%) in national water and chromium (19.0%) in imported water. Levels above the recommended limits by the international compendia for sodium intake were quantified in an imported water sample that could cause illness in the body. Furthermore, the variability observed between the experimental results and values declared in the chemical composition tables (labeling) can lead consumers to purchase a product containing inadequate information, thereby harming their daily intake needs. Conclusions: The results highlight the importance of establishing and maintaining continuous monitoring programs in the country to monitor the sanitary quality of food consumed by the population and thus protect population’s health.

Human biomonitoring of essential and toxic trace elements (heavy metals and metalloids) in urine of children, teenagers, and young adults from a Central European Cohort in the Czech Republic.

Exposure to toxic trace elements, which include metals and metalloids, can induce adverse health effects, including life-threatening diseases. Conversely, essential trace elements are vital for bodily functions, yet their excessive (or inadequate) intake may pose health risks. Therefore, identifying levels and determinants of exposure to trace elements is crucial for safeguarding human health. The present study analyzed urinary concentrations of 14 trace elements (arsenic, cadmium, cobalt, chromium, copper, mercury, manganese, molybdenum, nickel, lead, antimony, selenium, thallium, and zinc) and their exposure determinants in 711 individuals, spanningfrom children to young adults from a Central European population from the Czech Republic. Multivariate linear regression and non-parametric Kruskal-Wallis ANOVA were used to investigate exposure determinants. Estimates of 95th percentile concentrations and confidence intervals were carried out to establish reference values(RV95). The study also assessed the percentage of population exceeding health-based guidance values (GVs) to gauge health risks. Young adults showed elevated toxic element concentrations, whereas children exhibited higher concentrations of essential elements. Mercury concentrations were associated with both dental amalgam filling count and seafood intake; arsenic concentrations were associated with seafood, rice, and mushroom consumption. Mushroom consumption also influenced lead concentrations. Sex differences were found for cadmium, zinc, nickel, and cobalt. Between 17.9% and 25% of the participants exceeded recommended GV for arsenic, while 2.4% to 2.8% exceeded GV for cadmium. Only one participant exceeded the GV for mercury, and none exceeded GVs for chromium and thallium. Essential trace elements' GVs were surpassed by 38% to 68.5% participants for zinc, 1.3% to 1.8% for molybdenum, and 0.2% to 0.3% for selenium. The present study examines trace element exposure in a Central European population from the Czech Republic, unveiling elevated exposure levels of toxic elements in young adults and essential elements in children. It elucidates key determinants of trace element exposure, including dietary and lifestyle indicators as well as dental amalgam fillings. Additionally, the study establishes novel reference values and acomparison with established health-based human biomonitoring guidance values, which are crucial for public health decision-making. This comprehensive biomonitoring study provides essential data to inform public health policies and interventions.

Petrology, mineral chemistry and geochemistry of chloritite associated with Neoproterozoic ophiolitic ultramaficsin the Eastern Desert of Egypt, Arabian-Nubian Shield

This study presents for the first time, the field observations, petrography, mineral chemistry and geochemistry of chloritite hosted in the Al-Barramiya Neoproterozoic ophiolite of the Eastern Desert of Egypt, Arabian-Nubian Shield (ANS). The Al-Barramiya ophiolite is one of the most important ophiolitic sequences exposed in the ANS. It is affected by different types of alterations including carbonatization, listvenitization, chloritization and rodingitization. The Al-Barramiya chloritite occurs as thin layers associated with highly serpentinized peridotite. It is a fine-grained rock entirely composed of chlorite (85–95 vol.%) with minor talc and accessory minerals (epidote, rutile, titanite, corundum and opaque minerals). The chlorite minerals in the chloritite are represented mainly by diabantite, while those in the serpentinites include ripidolite. Depending on the chemical composition of the chlorites, the chlorite in chloritite formed at temperatures ranging between 200 and 250°C, which are lower than those of the disseminated chlorite in the serpentinite (310–345oC), indicating their formation in different hydrothermal stages. The chloritite samples are rich in total REE contents (17.9–27.3 ppm) compared with the associated serpentinites (0.69–0.87 ppm). They are characterized by slightly depleted LREE relative to HREE [(La/Lu)n = 0.8–0.9], with a moderately negative Eu-anomaly [(Eu/Eu*)n = 0.4–0.5]. The negative Eu-anomalies are derived from chloritization fluids or reflect the presence of talc in the chloritite. Based on field work, petrography, mineralogical and geochemical data, the studied chloritite has been interpreted as being derived from the associated serpentinized ultramafics by hydrothermal alterations. This is supported by an enrichment of chloritite in compatible trace elements (Cr = 2031–2534 ppm, Ni = 1264–1988 ppm, Co = 76–101 ppm) similar to that which is observed in the associate serpentinite.

Assessment of Heavy Metal Contamination in Combretum micranthum Leaves and Decoctions: Implications for Human Health

Combretum micranthum is a well-known medicinal plant in Africa and the decoction of its leaves is used as a drink or to treat various diseases such as malaria, high blood pressure and liver disorders, among others. Due to its high consumption by all sections of the Senegalese population, we felt that its heavy metal intake should be examined to see its impact on health. Leaves of two species of Combretum micranthum produced in the central (I) and southern (II) regions of Senegal and their decoctions in ultrapure water (Ii) and (IIi) were analyzed for 12 elements (Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Ag, Cd, Pb, Bi) by inductively coupled plasma optical emission spectrometer (ICP-OES). The concentrations of heavy metals (μg/g) are in the ranges 2.55 – 84.19 for Cr, 5.21 – 379.72 for Mn, 0.00 – 317.80 for Fe, 0.08 – 1.08 for Co, 1.54 – 8.88 for Ni, 1.75 – 8.08 for Cu, 0.91 – 9.70 for Zn, 0.00 – 0.16 for Cd, 0.46 – 0.84 for Pb. As, Ag and Bi are below detectable limits in any of the samples by ICP-OES analysis. Among all samples, manganese content was highest and represented 46.85% for I , 64.18% for II , 86.88% for Ii and 46.27% for IIi , of the total heavy metal concentrations. The results showed that the leaves of both varieties of Combretum micranthum and decoctions made from these leaves contain heavy metal levels lower than the values recommended by the WHO for consumed medicinal plants. Overall, Variety I harvested from peri-urban areas contains more metals than Variety II harvested from forest.

High-entropy strategy to suppress volumetric strain and enhance diffusion rate of Na3V2(PO4)2F3 cathode for durable and high-areal-capacity zinc-ion battery pouch cells

Aqueous zinc-ion batteries are pivotal contributors to the global energy transformation. Cathode materials with NASICON-type structures are promising candidates for zinc-ion batteries but are hindered by their low electrical conductivity, sluggish ionic diffusion, and structural instability. This work introduces a high-entropy, carbon-coated NASICON-type Na3V2(PO4)2F3 (HE-NVPF@C) cathode by incorporating five metal elements (Al, Zn, Mn, Cr, and Nb) mainly into the V sites of the VO4F2 octahedral structure. Systematic experimental and simulation studies of the Zn2+ storage mechanism in high-entropy NASICON-type cathode are presented for the first time. The high-entropy doping strategy contributes to significantly enhanced cycling stability by suppressing Jahn-Teller distortion, reducing lattice change during Zn2+ extraction and insertion, and decreasing the Zn2+ migration energy barrier. As a result, the HE-NVPF@C cathode demonstrates exceptional cycling stability over 6000 cycles at 20 C with a capacity loss of a mere 0.0031 % per cycle and a high areal capacity retention of 2.17 mAh cm−2. In addition, the pouch cell provides a long cycling lifespan with 90.8 % capacity retention at 5 C after 200 cycles. This feasible high-entropy approach broadens the perspective for developing practical zinc-ion batteries with a long cycle lifespan and high areal capacity.

Black shale high geological background potential toxic elements(PTEs) in middle reaches of the Yangtze River tributary basin water environment, China: Distribution, pollution sources, and risk assessment

As a typical high geological background area in the middle reaches of the Yangtze River tributary basin in China, the Loushao Basin in Hunan is covered with high mineral black shale, with an average element value 4.76–8.97 times higher than the world average rock level. The aim of this study is to analyze the water environment pollution in the middle reaches of the Yangtze River tributary basin under high geological background based on the spatial distribution differences of black shale concentration. PCA source analysis is used to track the source of pollution and highlight the differences in body shape to assess regional health risks. The research results show that Cd in water quality exceeds the background value by 7.5 times. There is a strong homology among Pb, Cd, Cr, As, and Hg elements in water bodies, mainly derived from the natural weathering, migration, and enrichment of rocks. Hg element is a pollution caused by human factors, and water pollution is more severe in areas close to high concentrations, with severe exceedance of Cr element in water quality. The main controlling factor for individual health risk differences is body shape, and men's health is more susceptible to threats.

Photoluminescence properties of SnO2 nanoparticles doped with group VI elements (Cr, Mo, W) synthesized by pulsed laser ablation in liquid

Tin oxide nanoparticles (SnO2 NPs), both pure and doped with Group VI (G6) metal ions (Cr+3, Mo+5, and W+6), were synthesized using pulsed laser ablation in liquid. This study aimed to investigate the effect of G6 doping on the electronic properties of SnO2 NPs, with an emphasis on enhancing their photoluminescence for optoelectronic applications. Transmission electron microscopy revealed well-crystallized samples with diameters of 3–6 nm, indicating quantum-confinement effects. The optical band gap, determined by UV–Vis spectroscopy, was reduced from 5.1 eV (undoped) to 4.9 eV (Cr-doped) due to defect states, while increasing to 5.3 eV and 5.7 eV for Mo- and W-doped SnO2, respectively, due to the Moss-Burstein effect. The photoluminescence spectra exhibited a redshift, with strong red emission around 700 nm, which was up to 90 % more intense than that of the undoped SnO2. This enhancement was attributed to the 2E→4A2 transition and increased defect states.

Temperature dependence on γ/γ' partitioning behaviors of alloying elements and γ/γ' interfacial energy of a Mo-rich Ni based single crystal superalloy

Based on three-dimensional atom probe technique and Ardell method, the influences of temperature (850℃∼1150℃) on microstructure, compositions and solid solution strengths of γ and γ′ phases, γ/γ' partitioning behaviors of alloying elements and γ/γ' interfacial energy of a Mo-rich Ni based single crystal superalloy were investigated. After quenching from 1100℃, microstructure was basically similar as heat-treated state. However, after quenching from 1150℃, γ′ phase obviously re-dissolved, and γ channel obviously widened. Meanwhile, with increasing temperature, Co, Cr, Mo and Re contents in γ phase decreased, while Al and Ta contents in γ phase increased. With increasing temperature, Co, Cr and Re contents in γ′ phase slightly decreased, Mo content in γ′ phase significantly decreased, while Al and Ta contents in γ′ phase increased. Meanwhile, with increasing temperature, solid solution strength of γ phase decreased, while solid solution strength of γ′ phase increased. In addition, with increasing temperature, partitioning ratios of Co, Cr and Re elements decreased, partitioning ratios of Mo and Al elements increased, while partitioning ratio of Ta firstly decreased and then increased. Moreover, both γ/γ′ interfacial width and γ/γ′ interfacial energy decreased with increasing temperature.

Synergistic Effect of Cr and Fe Elements on Stress Corrosion Fracture Toughness of Titanium Alloy

Synergistic Effect of Cr and Fe Elements on Stress Corrosion Fracture Toughness of Titanium Alloy

Enhancing high-temperature chloride molten salts corrosion resistance of 310S steel with Si-added Ni–Al coating

Ni–Al based coating is one of the common high temperature and corrosion resistant protective coatings. In the present paper, the effect of Si content on the formation of Al2O3 layer and the corrosion resistance of Ni–Al coating to chloride molten salt was studied. The research results show that the Ni–Al coatings with varying Si content mainly form NiAl2O4 and Al2O3 oxide layers after pre-oxidation, and form a three-layer structure after molten salt corrosion. The appropriate amount of Si added to the Ni–Al coating can promote the formation of the α-Al2O3 layer during pre-oxidation and thermal corrosion, improving the corrosion resistance of the coating to high temperature chloride molten salt, and hindering the diffusion of Cr elements. Particularly, the Ni–Al coating with Si content of 1.2 at.% has the thickest and densest Al2O3 protective layer, showing the best corrosion resistance. The simulation results shows that compared with the Ni–Al coating without Si, the Cl atoms in the Si-added Ni–Al coating need to overcome greater energy barriers to diffusion during the molten salt corrosion process, which also indicates that the addition of Si can improve the corrosion resistance of the coating.

Evading intermediate temperature embrittlement of FeCoCrNiMn high entropy alloy via N-doping

High entropy alloys (HEAs) exhibit high strength and excellent ductility at both room and low temperatures. The loss of ductility with increasing the tensile temperature above room temperature has been widely observed in single phase face-centered cubic structured HEAs. In this work, a N and Si doped FeCoCrNiMn-(N,Si) HEA with preexisting nano-sized Cr2N particles was fabricated by laser powder bed fusion (LPBF) and subsequent cold-rolling and annealing treatment. Tensile testing was conducted on the alloy at 298 K, 573 K, 773 K, 873 K, and 973 K, respectively. It has been shown that the FeCoCrNiMn-(N,Si) alloy with preexisting Cr2N phase exhibits a steady ductility with increasing the tensile temperature. The intermediate temperature embrittlement is evaded in the FeCoCrNiMn-(N,Si) alloy via N-doping. The widely reported loss of ductility with increasing deformation temperature was avoided in present FeCoCrNiMn-(N,Si) HEA by shifting fast segregation of element Cr from GBs into preexisting Cr2N phase due to the high affinity between N and Cr elements, leading to the increases in the content and size of Cr2N particles after high temperature deformation.

Effectiveness of constructed wetland technology-treated industrial wastewater on the spinach (Spinacia oleracea) health risks and biochar efficiency.

In peri-urban areas, use of industrial wastewater for irrigation is a common practice. Industrial wastewater contains cadmium, chromium, lead, nickel, and other elements that deteriorate food quality and affect human health. Biochar has been proven to remediate heavy metal contaminated soil by reducing their mobility and bioavailability. A pot experiment was conducted to evaluate the efficiency of different levels of biochar on spinach growth with low heavy metal concentration and to minimize associated health issues. The experiment lasted two months and the treatments: Control (tap water), untreated and treated industrial wastewater and both in combination with biochar (0.5% and 1%) were applied in completely randomized design. Findings suggested that treated industrial wastewater with 1% biochar resulted in maximum plant height, shoot weight, chlorophyll contents (SPAD value), photosynthetic and transpiration rate. Biochar significantly reduced heavy metal mobility in soil due to its porous structure, high pH, higher CEC, and variety of surface functional groups. The cumulative hazard index (HI), hazard quotient, cancer risk, and total cancer risk (TCR) were calculated using method provided by US-EPA for each metal. All treatments had HI values of < 1, however applying 1% biochar significantly reduced the HI values to 2.00E-01 and 2.88E-01 in adults and children, respectively. TCR for all treatments was < 1, while treated industrial wastewater and biochar (1%) has significantly reduced to 1.55E-02 and 1.91E-03 for adults and children, respectively. Thus, it was determined that irrigation with industrial effluents caused toxicity in vegetables, which had a negative impact on human health. Biochar effectively mitigated metal toxicity in both soil and spinach plants that resulted in reduced health/cancer risk.

Boron-modified super duplex stainless steels: microstructure, hardness, and industrial applications

In this work was investigated the boron modified super duplex stainless steel processed by spray-forming, to characterize the workpiece using different techniques, among them, optical microscopy, SEM-FEG, X-ray diffraction, Rama spectroscopy and Vickers hardness (VH) and Thermo-Calc software. As result, in this research was verified that in the ferrite phase the Cr element predominates, but in the austenite phase the Fe and Ni elements prevail by the EDS technique. As well as XRD spectra showed different meta-stable phases and (FeCr)2B phase. Besides, the Vickers microhardness measurement was around 460 HV, being much taller than the duplex stainless steel. This alloy can be successfully used in the chemical, oil and gas industries, petrochemical process plants, the pulp and paper industry, pollution control equipment, transportation and for general engineering thanks to their outstanding corrosion resistance and mechanical properties.

Deep Forest Modeling: An Interpretable Deep Learning Method for Mineral Prospectivity Mapping

AbstractAccurate mineral prediction is crucial for reducing costs and uncertainties in mineral discovery and extraction. The use of artificial intelligence and big data has advanced mineral prediction into intelligent forecasting. Machine learning methods have shown significant promise in enhancing outcomes. Currently, neural network‐based approaches dominate deep learning (DL), but they lack interpretability and have high modeling complexity, making them less effective for complex problems and time‐consuming. Deep Forest, an innovative DL paradigm, addresses these issues by dynamically adjusting complexity and providing importance assessments for predictive factors. This study focuses on the North American Cordillera, known for its rich geological data and potential for porphyry copper deposits (PCDs). Predictions are made using Deep Forest with factors like Euclidean distance between faults and magmatic rock, fault line density, gravity anomalies, and stream‐sediment geochemical data. Deep neural networks, random forest, convolutional neural networks, transformer model and graph convolutional networks are also used for comparison. Deep Forest shows high performance and can avoid the black box problem of DL without relying on other tools in DL, providing a new perspective for the development and application of other non‐neural network DL models for mineral prediction. Feature importance analysis shows that geological structure and magmatism significantly influence PCD prediction. Elevated levels of elements like Al, Co, and Cr in stream sediments help identify mineralization‐related alterations. These findings underscore Deep Forest's capability to accurately and efficiently guide mineral exploration, highlighting its potential as a promising approach for mineral prospecting.

The characteristics of V, Sc, Cr and Ni within the Cambrian terrigenous-carbonate deposits found in the Syuldyukar kimberlite field (Western Yakutia)

The investigation of the Syuldyukar kimberlite field, located within the Yakut diamond-bearing province, involved approximately 4,000 X-ray fluorescence (XFA) analyses and 150 inductively coupled plasma atomic emission spectroscopy (ICP AES) analyses on the host sedimentary rocks of the Upper Cambrian Holomolokha formation in proximity to the kimberlite bodies. The results indicated a disruption in the correlation ratios when compared to background concentrations, while subclark levels of vanadium (V), scandium (Sc), chromium (Cr), nickel (Ni), and other elements remained consistent. The elements were divided into three categories: typomorphic elements for kimberlites (Cr, Ni, Co), elements associated with carbonatites (barium (Ba), strontium (Sr), neodymium (Nd), zirconium (Zr)), and elements characteristic of basalts (V, Sc, zinc (Zn)). High positive correlation coefficients were established for the specified elements in the background concentrations. However, ICP analyses indicated significant decreases in the correlation between elements from different groups in the near-kimberlite space at the Syuldyukar site. X-ray diffraction (XRD) studies showed that in the compression areas, the correlation ratios of various elements were inconsistent when compared to the stretching areas. The analysis of the XRF and ICP data reveled that the average elemental concentrations in the background and near-tube space were nearly identical, except for some unusual hurricane values, with variations showing only slight changes. The positive correlation of several elements likely reflects background geological processes, including sedimentation in a marine basin and subsequent transformations such as hypergenesis, diagenesis, and catagenesis. The significant decrease in correlation coefficients, even with background concentrations remaining stable, is likely due to the redistribution of elements in the fluid resulting from phreatomagmatic explosions linked to the intrusion of kimberlites. Aqueous chloride fluids were observed to most actively redistribute elements in areas experiencing local tectonic compression. The identified changes in the correlation ratios of background elemental concentrations in sedimentary rocks containing kimberlite could act as a new indicator for locating hidden diamond-bearing kimberlites.

Microstructural evolution and tribological behavior of HVAF sprayed FeCoNiCrMox (x=0, 0.2, 0.5, 1) coatings

High entropy alloy coatings with a unique microstructure and excellent mechanical properties show significant potential for development in friction-related applications. In this study, the microstructure, phases, hardness and tribological behavior of FeCoNiCrMox (x = 0, 0.2, 0.5, 1.0) coatings fabricated by HVAF spraying were investigated. The coating changes from a single FCC structure (x=0, 0.2) to a dual phase structure of FCC and σ (x=0.5, 1), accompanied by an expansion in the segregation regions of Cr and Mo elements. The hardness of coatings increased with higher Mo content. Tribology tests were carried out at room temperature using Si3N4 ceramic and GCr15 steel as counterfaces. The results demonstrate that, when paired with GCr15, the wear resistance of the coatings scale proportional with hardness. However, when paired with Si3N4, the coating wear rate exhibits an initial increase followed by a decrease. Notably, the FeCoNiCr and FeCoNiCrMo0.2 coatings exhibited milder friction and wear behavior when in contact with Si3N4 compared to GCr15 steel, attributed to the dominant oxidative wear. This study provides new insights and directions for the design of customized high-entropy alloy coatings based on specific friction conditions.

Variation of the Passive Film on Compositionally Concentrated Dual-Phase Al0.3Cr0.5Fe2Mn0.25Mo0.15Ni1.5Ti0.3 and Implications for Corrosion

AbstractThe passive film on a dual-phase Al0.3Cr0.5Fe2Mn0.25Mo0.15Ni1.5Ti0.3 FCC + Heusler (L21) compositionally concentrated alloy formed during extended exposure to an applied potential in the passive range in dilute chloride solution was characterized. Each phase, with its own distinct composition of passivating elements, formed unique passive films separated by a heterophase interface. High-resolution, surface sensitive characterization enabled chemical analysis of the passive film formed over individual phases. The film formed over the L21 phase had a higher concentration of Al, Ni, and Ti, while the film formed over FCC phase was of similar thickness but contained comparatively higher Cr, Fe, and Mo concentrations, consistent with the differences in bulk microstructure composition. The passive film was continuous across phase boundaries and the distribution of passivating elements (Al, Cr, and Ti) indicated both phases were independently passivated. Spatially resolved analysis of the surface chemistry of the dual-phase CCA revealed that the cation with the highest composition in passive film formed on the FCC phase was Cr (52.4 at. pct) and for the L21 phase was Ti (53.1 at. pct) despite the bulk concentration of each element being below 20 at. pct in their respective phases. Al, Cr, and Ti were enriched in both phases within the passive film relative to their respective bulk compositions. In parallel studies, single-phase alloys with compositions representative of the FCC and L21 phases were synthesized to evaluate the corrosion behavior of each phase in isolation. The corrosion behavior of the dual-phase alloy showed passivity evidenced by a pitting potential of 0.615 VSCE in 0.01 M NaCl. The pitting potential and other electrochemical parameters suggested a combination of behaviors of both single-phase samples, suggesting that the global corrosion behavior may be represented by a composite theory applied to phases, their area fractions, and interphase length. However, the interphase in the dual-phase CCA was a local corrosion initiation site and may limit localized corrosion protectiveness. The alloy design implications for optimization of second phase structure and morphology are discussed.

"Development of a statistical calculation model for the carbon diffusion parameters in metals and alloys"

Carbon diffusion in metals has received a lot of attention and has been the subject of intensive theoretical investigations in recent years. The purpose of this work is development the statistical calculation model (SCM) on the diffusion of carbon in metals and its application for calculating the diffusion coefficients of carbon in alloys. It includes first-principles calculation of the diffusion coefficient according to a statistical model, physicochemical calculation of activation energies for carbon, and linear approximation of carbon diffusion in alloys. The calculated values of the diffusion coefficient for metals are within the range of the experimental values. For low-melting metals, carbon diffusion coefficients are mainly unknown from experiment, but the statistical model allows us to predict their values. The calculations are compared with known experimental data on the diffusion of carbon atoms in some metals Fe, V, Ta and W at high temperatures with fairly good agreement between the results. The SCM-model allows us to determine the influence of the alloying elements Si, Mo and Cr on the diffusion of carbon in the F – C alloy.

First report of metals and metalloids on bone and claw tissues of Humboldt penguins (Spheniscus humboldti)

Samples of bones (humerus) and claws of adult Humboldt penguins (Spheniscus humboldti) were opportunistically obtained from twenty-seven carcasses at two important nesting sites in northern Chile: Chañaral Island (CHI) and Pan de Azúcar Island (PAI). The concentrations of trace elements (Cu, Zn, Pb, Ni, Fe, Se, As, Br, Mn and Cr) were determined by X-ray fluorescence. The highest levels (mean ± standard deviation, micrograms/g dry weight) of Cu (26.57 ± 4.08), Zn (163.9 ± 42.7), Pb (1.86 ± 1.53), Ni (0.31 ± 0.03), Se (7.70 ± 4.87) and Cr (0.25 ± 0.24) were detected in bones, whereas the highest levels of Fe (3,162 ± 1,579), As (6.75 ± 4.21), Br (0.12 ± 0.06) and Mn (76.7 ± 47.9) were found in claws. In bones, Se and Ni levels were higher (P &lt; 0.05) in CHI than in PAI. In claws, the contents of Pb, Fe, and Mn were higher at CHI than those at PAI, whereas only As exhibited higher contents at PAI than those found at CHI. The trace element content in the claws and bones found herein may be the result of either acute or chronic exposure to penguins, respectively. These findings may serve as a baseline for further studies to design adequate and opportune plans to protect this vulnerable species.