Distribution Of Cobalt Research Articles

THE EFFECT OF ANNEALING ON THE CRYSTAL STRUCTURE OF THE SURFACE OF SILICON DOPED WITH COBALT IONS

The paper reports results of the study of the distribution profiles of implanted cobalt atoms in silicon as a function of the radiation dose and annealing temperature that was performed by applying the Rutherford backscattering spectroscopy (RBS). The results obtained are in good concordance with similar data obtained by the technique of secondary-ion mass spectroscopy (SIMS). The effects of thermal annealing on the distribution of cobalt, and in particular oxygen were studied. The authors strongly suggest that under certain heat treatment conditions and by applying specific radiation doses, the so-called epitaxial silicides will build on the surface of a single crystal, which can play the role of conducting or metal layers. One could consider the RBS method for analysis of both the topological distribution of dopants and the interaction of impurities.

Distribution of Nickel, Copper and Cobalt in the Grain Fractions of Bottom Sediments of the Sokołda River and its Tributaries (Poland)

Distribution of Nickel, Copper and Cobalt in the Grain Fractions of Bottom Sediments of the Sokołda River and its Tributaries (Poland)

Calculation of Absorption Dose Value using MIRD Method with Cobalt 57 MIBI for Four Body Organs

MIRD has developed methods, assumptions, models, and mathematical formulae for estimating internal radiation doses from the injected radiopharmaceuticals into the body. This study aims to determine the radiopharmaceutical distribution of Cobalt 57 MIBI in patients identified as having breast cancer by using an oncology examination with MIRD method on 4 patient's organs with some time variations. The four organs of the patient's body are the heart, thyroid, kidney, and liver. The MIRD method developed to calculate the absorption dose of each organ is the product of the cumulative activity and the S factor of each organ studied. The results showed that the highest uptake dose in these patients was in the thyroid and kidney organs, and then followed by the heart and liver. These results indicate that the thyroid and kidney organs are the most vulnerable organs by the method of injecting radiopharmaceutical doses into the body of breast cancer patients.

Ferroelectric Control of Magnetism in Ultrathin HfO2\Co\Pt Layers.

The recent demonstration of ferroelectricity in ultrathin HfO2 has kickstarted a new wave of research into this material. HfO2 in the orthorhombic phase can be considered the first and only truly nanoscale ferroelectric material that is compatible with silicon-based nanoelectronics applications. In this article, we demonstrate the ferroelectric control of the magnetic properties of cobalt deposited on ultrathin aluminum-doped, atomic layer deposition-grown HfO2 (tHfO2 = 6.5 nm). The ferroelectric effect is shown to control the shape of the magnetic hysteresis, quantified here by the magnetic switching energy. Furthermore, the magnetic properties such as the remanence are modulated by up to 41%. We show that this modulation does not only correlate with the charge accumulation at the interface but also shows an additional component associated with the ferroelectric polarization switching. An in-depth analysis using first order reversal curves shows that the coercive and interaction field distributions of cobalt can be modulated up to, respectively, 5.8% and 10.5% with the ferroelectric polarization reversal.

Resonant Inelastic Soft X-ray Scattering Study of Co-Doped Maghemite Nanoparticles.

Cobalt ferrite nanoparticles have been attracting considerable interest in the recent years because of the large number of potential applications, including magnetic storage, magnetic fluid hyperthermia and as contrast agents for magnetic resonance imaging. Physical properties of this class of materials depend critically on a number of parameters, including crystallinity, stoichiometry and cation distribution. In this work we have performed a Resonant Inelastic soft X-ray Scattering (RIXS) study on a series of 5 nm cobalt-doped maghemite nanoparticles to obtain direct quantitative information on cation distribution as a function of cobalt doping. We found that the distribution of divalent cobalt is stable in the investigated doping range and slightly different from that of bulk, stoichiometric cobalt ferrite. These results confirm that cobalt doping can be used to finely tune the magnetic properties of nanostructured ferrites without modifying their structural integrity.

Cobalt distribution in the soils of São Miguel Island (Azores): From volcanoes to health effects

Volcanic soils cover only approximately 1% of the Earth's surface, yet they support 10% of the world's population due to their inherent fertility. However, deep magmatic processes may lead to depletion of certain elements in volcanic rocks. The imbalance of essential elements, such as cobalt, in soil parent materials can affect the health of plants and grazing animals and, thus, humans. Within the particular geological context of the Azores, the present study aims to assess cobalt concentration in volcanic soils to predict the risk of cobalt deficiency in animals and humans.Samples from agricultural topsoils and pasture grass were collected in six volcanic regions of São Miguel Island, and their physicochemical properties were measured, including selected transition metal element contents, such as iron, manganese and cobalt. The soil cobalt concentration was below 5 mg/kg in Povoação< Furnas/Congro< Sete Cidades< Fogo and was higher than 10 mg/kg in Picos< Nordeste. Cobalt concentrations were very low in pasture grass. Values below 0.1 mg/kg were observed in Furnas/Congro<Povoação<Fogo<Picos<Sete Cidades, and only the volcanic region of Nordeste had adequate values of cobalt (0.34 ± 0.19 mg/kg) in pasture grass to fulfill animal needs. The concentrations of iron and manganese were also significantly higher in the two latter volcanic regions. These differences result from the pedogenesis of volcanic rocks with distinct geochemical compositions related to different degrees of magmatic evolution.The results show that there is a significant lack of cobalt in agricultural soils on São Miguel and that it is important to predict the risk of cobalt deprivation due to its significant biological value. Soils deficient in cobalt can reduce plant growth, result in the impairment of vitamin B12 formation in animals, and consequently affect animal and human health.

Evolution of cobalt species in glow discharge plasma prepared CoRu/SiO2 catalysts with enhanced Fischer-Tropsch synthesis performance

Glow discharge plasma was applied to substitute thermal calcination during catalyst preparation. Evolution of cobalt particles in cobalt-ruthenium based catalysts at different stages (fresh prepared, reduced, after Fischer-Tropsch synthesis (FTS) reaction) were studied using a series of characterization techniques. Glow discharge plasma can be developed as an efficient technique to decompose metal salt. Cobalt dispersion was greatly enhanced by glow discharge plasma treatment, and higher initial cobalt dispersion was found on the one with lower treating intensity. However, cobalt crystallites generated by plasma treatment below certain intensity had poor thermal stability, they were tended to aggregate into large particles during reduction and reaction processes, and thus severe deactivations were observed during FTS tests. Besides cobalt sintering, mass transfer limitation at high FTS activity due to the pore plugging by long-chain hydrocarbons was also one of the important reasons for deactivation. The CRS-P140 catalyst with higher plasma treating intensity combined relatively high cobalt dispersion, high cobalt reducibility and relatively stable cobalt distribution during reduction or reaction, showed a high FTS activity with less activity loss.

Kinetic release and fractionation of cobalt in some calcareous soils

The availability of cobalt (Co) depends on its concentration in solution which is affected by kinetic release from solid phase, and also depends on its distribution between different soil constituents. There is very limited information on kinetic release of Co from calcareous soils. On the other hand, the lack of Co fractionation data in calcareous soils is a problem in determining mobility and availability of this element. The release kinetic of Co from 10 calcareous soils collected from different agricultural areas in Hamedan Province, western Iran, was investigated using 0.01 M calcium chloride (CaCl2) and ethylenediaminetetraacetic acid (EDTA) solutions in time intervals from 8 to 2084 h (8, 20, 44, 92, 164, 284, 452, 692, 1028, 1484 and 2084 h). The results showed that the general trends of Co release were similar for all studied soils and after 2084 h, 0.01 M EDTA released more Co than 0.01 M CaCl2. Different kinetic equations (parabolic diffusion, power function, Elovich and first order) adequately described the cumulative Co release and power function equation with the lowest Akaike Information Criterion (AIC) best described the Co release by 0.01 M CaCl2 and EDTA in studied soils. In the case of 0.01 M EDTA, the Co release rate parameters in parabolic diffusion, power function, Elovich equations were significantly correlated to pH (r = 0.80, 0.78 and 0.80, respectively; p < 0.01) and the percentages of clay (r = 0.87, 0.88 and 0.84, respectively; p < 0.01) and sand (r = −0.76, p < 0.01; −0.70 and −0.70, p < 0.05, respectively) that indicates the importance of these properties in relation to Co release from soils. Cobalt distribution between different soil constituents, before and after Co sorption in soils was investigated using sequential extraction procedure. Results indicated that the residual fraction (RES) was the dominant fraction both before and after Co sorption in soils. Sorption of Co in soils increased the proportion of Co associated with RES and carbonate-bound (CARB) fractions and decreased the proportions of exchangeable/solution (EXCH) and organically bound (OM) fractions, so it can be concluded that Co was mainly distributed between RES and CARB fractions and sorption included both adsorption and precipitation processes. Individual contamination factor (ICF) was used for Co pollution and leaching risk assessment in soils. According to results, the ICF in soil 7 (collected from Hesare Motahari) was higher than other soils, so this soil that is located close to a busy boulevard in vicinity of Hamedan city had the highest risk of Co pollution and leaching between studied soils.

The influence of hydrothermal activity during the origin of Co-rich manganese crusts of the N-W Pacific

The distribution of cobalt, vanadium, cadmium and molybdenum in the mineral fractions of the Co-rich manganese crusts (CMC) from Zubov and Govorov Guyots is considered. It is shown that the concentrations of cobalt in the ferrous fraction, and vanadium, cadmium in the manganese fraction indicate the ability of the CMC to record the rejuvenated volcanism in the N-W Pacific.

Local distribution of cobalt and selective enrichment of platinum in oceanic ferromanganese nodules

The distribution of cobalt in the structure of ferromanganese nodules (FMN) was studied using beta-autoradiography. In some cases, the content of element increased in the outer part of the nodules, or in thin layers within the nodules. Layered type of cobalt distribution in FMN indicates changing conditions in deposition during their formation, in particular also the living conditions of microorganisms known to inhabit oceanic ferromanganese nodules. Experimental studies suggested that colonies of micromycetes living at the surface of the nodules can have an important impact on the selective accumulation of platinum and other elements in FMN.

The influence of the WC-Co composite microstructure model on stress field heterogeneity at the microstructure level: FEM based study

Abstract The paper is devoted to finite element method based study of stress field heterogeneity at microstructure level of two-phase cemented carbides. Special attention is put on investigation of influence of the microstructure model type on the stress field distributions. Two- and three-dimensional models of the microstructures have been generated. Moreover, two different representations of the microstructure have been considered. The first one assumes uniformly distributed cobalt phase forming continuous boundaries between tungsten carbide particles. The second one assumes that the cobalt phase shape and distribution are created in a way that allows for no differentiation of continuous boundaries between tungsten carbide grains. Finite element analyses have been carried out with different microstructure models. The results of the simulations are stress distributions in each phase of the material. Furthermore, a numerical homogenization has been conducted to investigate the phase properties’ influence on the effective elastic constants of the cemented carbide.

Peculiarities of alkaline metals, aluminum, magnesium and cobalt distribution among minerals in iron ore sinter made of oxidized ferruginous quartzites concentrates

The aim of the work was to study the peculiarities and mechanism of migration of the components during the sintering of the oxidized ferruginous quartzites concentrates. As a result, it was determined thatthe silicate vitreous bond (B2= 0,9–1,1; FeO = 17–23 %; SiO2= 35–40 %) concentrates alkaline metals in its structure, MgO = 0,3–6,0 %, Al2O3= 0,2–7,2 %. It was formed at the basis of silicate minerals of the concentrate waste rock. Ore phases contain as an isomorphic impurity MgO (up to 3.0 %), Al2O3(up to 1.0 %), CoO (up to 0.43 %). The flux and iron-containing components of the original raw materials were the sources of magnesium and aluminum, the iron ore concentrate, in which cobalt is a part of magnetite as an isomorphic admixture was the source of cobalt. Fundamental differences in the distribution of elements between the ore phases in the agglomeration of oxidized ferruginous quartzites and non-oxidized (magnetite) were absent, due to the comparable composition of the waste rock and the mechanism of formation and crystallization of the melt.

Strong impact of cobalt distribution on the activity for Co3O4/CaCO3 catalyzing N2O decomposition

For the Co3O4/CaCO3 catalysts used for N2O decomposition, the activity of the catalyst prepared by stepwise precipitation is much superior to the catalysts prepared by impregnation or coprecipitation in the same composition. HRTEM observation and EDX analysis indicate that the stepwise precipitation leads to cobalt existing as little Co3O4 crystallites tightly bound to the CaCO3 particles. The special structure made the Co3O4 ideal accessibility and better interaction with the support in the catalyst, and the CaCo2.5(SP) catalyst with this structure is much more active than the CaCo2.5 catalyst reported in literature prepared in traditional method. At 300 °C, N2O in the feed gas 2000 ppmv N2O/Ar was completely converted over the CaCo2.5(SP) at 20,000 h−1. Moreover, the CaCo2.5(SP) catalyst exhibited better resistance to sintering at 800 °C and quite high activity under the presence of 5 vol% O2 and 2 vol% H2O at 350 °C as well.

Carbon Black and Multi-Walled Carbon Nanotube Supported Cobalt for Anion Exchange Membrane Fuel Cell

Carbon black (CB) and multi-wall carbon nanotube (MWCNTs) supported cobalt, namely, CoPc/CB and CoPc/MWCNTs, respectively, with different metal loads was synthesized and used as the cathode catalyst for anion exchange membrane fuel cells. The prepared catalysts were characterized using X-ray diffraction and scanning electron microscopy. The surface morphology analysis revealed heterogeneous cobalt distribution on the carbon support. Cyclic Voltammetry was also studied to investigate the best combination ratio. The results indicated that the electrochemically largest active surface area was observed when 30 and 40 wt% cobalt was combined with 70 wt% CB and 60 wt% MWCNTs, respectively. The anion exchange membrane fuel cell performance showed that both cathode catalysts exhibited the highest peak power density at 40 wt%t. Co load. The peak power density of 55 mW/cm2 at 0.4 volts was obtained using CoPc/CB. Meanwhile, the promising catalyst CoPc/MWCNTs only produced 35mW/cm2, which did not meet the expectation. According to some references, the alkaline fuel cell performance might be bothered by the acid residues, sulfates and nitrates produced by the MWCNT purification process.

Catalytic performance of N-doped activated carbon supported cobalt catalyst for carbon dioxide reforming of methane to synthesis gas

Abstract Activated carbon (AC) was treated with melamine to prepare nitrogen-doped carbon materials (AC-N), which used as support to prepare Co supported catalysts for CH4–CO2 reforming (DRM) reaction and its catalytic performance was investigated. The modified (Co/AC-N) and unmodified (Co/AC) catalyst were characterized by BET, H2-TPR, XRD, TEM, XPS, CO2-TPD and FTIR. It was found that the modified catalyst not only showed excellent stability, but also had better catalytic activity than the unmodified catalyst. Although the physical structure of modified catalysts is almost same with the unmodified catalysts, nitrogen and some oxygen functional groups such as pyridine nitrogen, pyrrole nitrogen, hydroxyl and oxygen incarbonyl groups were generated on the AC surface during the amination treatment. The generated surface nitrogen and oxygen functional groups affect not only influence the dispersion of active metals but affect the valence distributions of cobalt. Compared with the untreated catalyst, small active particle size with a narrow size distribution formed on the surface of N-doped catalyst. Moreover, the modified catalyst also provides more basic sites for the reforming reaction to accelerate the adsorption and dissociation of CO2 on the active site of the catalyst.

Исследование сорбционной активности фармакофорсодержащих пектинов по отношению к катионам кобальта (II)

Рассмотрены закономерности сорбции ионов кобальта (II) нативным и модифицированным органическими фармакофорами (салициловая, антраниловая, никотиновая кислоты) пектинами. Определено влияние различных факторов (кислотность, температура, модуль раствор/сорбент) на процесс распределения ионов кобальта (II) в гетерофазной системе полисахаридный сорбент - водный раствор. Исследован механизм кинетики сорбции ионов металла (II) биосорбентами. Определено влияние природы биосорбентов на термодинамику распределения ионов кобальта (II). Установлено, что сорбция ионов Cо2+ модифицированными пектиновыми сорбентами описывается уравнением Ленгмюра.

Influence of the Cobalt Concentration and Chromium Alloying on the Structure of (β-NiAl + γ'-Ni3Al + γ-Ni) Ni–Al–Co Superalloys

The influence of cobalt (5 and 16 at %) and chromium (4.25 at %) on the structure of a (β-NiAl + γ'-Ni3Al + γ-Ni) alloy with 27 at % Al of the Ni–Al–Co system, which is chosen as the basis of alloys with given physicochemical properties, in particular, moderate density (≤7.2 g/cm3) and sufficient heat resistance at 1100–1300°C, is studied. A high stability of the high-temperature γ phase is found. It forms upon solidification according to the reaction L$$ \rightleftarrows $$ β + γ and is nonequilibrium at 1200 and 1300°C (below the temperatures of the transformations β + γ $$ \rightleftarrows $$ β + γ + γ' $$ \rightleftarrows $$ β + γ'). The volume fraction of the γ-Ni phase increases with the cobalt content or upon chromium addition in comparison with its fraction in the base alloy. The influence of alloying on the cobalt and chromium distribution in alloy phases is estimated. Additional alloying increases the differences in the phase compositions in cobalt and chromium.

Topographical distribution of cobalt in different agro-climatic zones of Jharkhand state, India

ABSTRACTThe main aim of the study was to understand the present status of cobalt in different agro-climatic zones. The soil samples were collected from different locations and topo-sequences of three agro-climatic zones of Jharkhand, India, viz. zone-IV (Baliapur, Jharia, and Dhanbad), zone-V (Bagru, Pakharpat, Kisko, and Lohardaga), and zone-VI (Moshabani, Jadugonda, and Chandil). The soil samples were analyzed in a laboratory to estimate the total cobalt and Diethylene-triamine pentaacetic acid (DTPA) extractable cobalt. Results show mean concentration of DTPA extractable cobalt in zones-IV, V, and VI have been determined as 0.65, 0.5, and 1.03 mg kg−1, whereas the mean total cobalt content in different agro-climatic zones was 109.17, 107.58, and 102.58 mg kg−1, respectively. The work highlights the higher amount of DTPA-extractable and the total content of cobalt was observed in lowland against the different topo-sequences. Further, the results of multiple regression equations have revealed that the distribution of extractable cobalt is primarily controlled by pH, clay, and organic carbon. Whereas, organic carbon controls the distribution of total cobalt content hence, the organic carbon plays a critical role in the distribution of cobalt in the soil.

The Role of External Inputs and Internal Cycling in Shaping the Global Ocean Cobalt Distribution: Insights From the First Cobalt Biogeochemical Model.

Cobalt is an important micronutrient for ocean microbes as it is present in vitamin B12 and is a co‐factor in various metalloenzymes that catalyze cellular processes. Moreover, when seawater availability of cobalt is compared to biological demands, cobalt emerges as being depleted in seawater, pointing to a potentially important limiting role. To properly account for the potential biological role for cobalt, there is therefore a need to understand the processes driving the biogeochemical cycling of cobalt and, in particular, the balance between external inputs and internal cycling. To do so, we developed the first cobalt model within a state‐of‐the‐art three‐dimensional global ocean biogeochemical model. Overall, our model does a good job in reproducing measurements with a correlation coefficient of >0.7 in the surface and >0.5 at depth. We find that continental margins are the dominant source of cobalt, with a crucial role played by supply under low bottom‐water oxygen conditions. The basin‐scale distribution of cobalt supplied from margins is facilitated by the activity of manganese‐oxidizing bacteria being suppressed under low oxygen and low temperatures, which extends the residence time of cobalt. Overall, we find a residence time of 7 and 250 years in the upper 250 m and global ocean, respectively. Importantly, we find that the dominant internal resupply process switches from regeneration and recycling of particulate cobalt to dissolution of scavenged cobalt between the upper ocean and the ocean interior. Our model highlights key regions of the ocean where biological activity may be most sensitive to cobalt availability.

Levels and distribution of cobalt and nickel in the aquatic macrophytes found in Skadar Lake, Montenegro.

Macrophytes react to changes in the quality of the environment in which they live (water/sediment), and they are good bioindicators of surface water conditions. In the present study, the content of the metals cobalt (Co) and nickel (Ni) was determined in the sediment, the water, and different organs of macrophytes from six localities around Lake Skadar, across four different seasons of year. The aquatic macrophytes that have been used as bioindicator species in this study are Phragmites australis (an emerged species), Ceratophyllum demersum (a submerged species), and Lemna minor (a floating species). The aim of this study was to determine the distribution of metals in macrophyte tissues and also to discover the degree of bioaccumulation of the investigated metals, depending both on the location and on the season. The content of Co and Ni in the examined parts of the macrophytes was in the range of 0.04-8.78 and 0.30-28.5ppm, respectively. The greatest content of the investigated metal in the organs of P. australis and C. demersum was recorded at the beginning of and during the growing season. Greater concentrations of metals in the tissue of L. minor were observed at the end of the growing season.