Distribution Of Nickel Research Articles

Enhancement of Electrochemical Performance of LiMn₂O₄ Spinel Cathode Material by Synergetic Substitution with Ni and S.

Nickel and sulfur doped lithium manganese spinels with a nominal composition of LiMn2−xNixO4–ySy (0.1 ≤ x ≤ 0.5 and y = 0.01) were synthesized by a xerogel-type sol-gel method followed by subsequent calcinations at 300 and 650 °C in air. The samples were investigated in terms of physicochemical properties using X-ray powder diffraction (XRD), transmission electron microscopy (EDS-TEM), N2 adsorption-desorption measurements (N2-BET), differential scanning calorimetry (DSC), and electrical conductivity studies (EC). Electrochemical characteristics of Li/Li+/LiMn2−xNixO4–ySy cells were examined by galvanostatic charge/discharge tests (CELL TEST), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The XRD showed that for samples calcined at 650 °C containing 0.1 and 0.2 mole of Ni single phase materials of Fd-3m group symmetry and nanoparticles size of around 50 nm were obtained. The energy dispersive X-ray spectroscopy (EDS) mapping confirmed homogenous distribution of nickel and sulfur in the obtained spinel materials. Moreover, it was revealed that the adverse phase transition at around room temperature typical for the stoichiometric spinel was successfully suppressed by Ni and S substitution. Electrochemical results indicated that slight substitution of nickel (x = 0.1) and sulfur (y = 0.01) in the LiMn2O4 enhances the electrochemical performance along with the rate capability and capacity retention.

Low-pH mediated goethite precipitation and nickel loss in nickel hydrometallurgy

The goethite process was conducted in nickel hydrometallurgy to examine the effects of pH levels (2.0–4.3) on the performance of iron removal and associated rate of nickel loss. The goethite precipitate was characterized by its crystallinity, particle size and microtopography using X-ray diffraction, laser particle size analyzer and scanning electron microscopy. Nickel adsorption was analyzed to study the nickel loss adsorbed on the goethite surface, and energy dispersive spectroscopy was used to detect the nickel distribution on the surface and interior of the goethite particles. Results show that as the pH decreases, the crystallinity of goethite lessens, goethite particles tend to agglomerate, the particle size increases significantly, and the filterability of the precipitate improves. Nickel is lost in iron precipitates by incorporation into the lattices and adsorption on the surface of the goethite particles. The nickel loss to the goethite lattices increases sharply with pH, and the nickel adsorption loss could be determined by the specific surface area of the goethite particles. This study demonstrates that a lower reaction pH causes the particle size of the precipitate to increase, improves the filterability, and results in a lower loss of nickel.

Fractional distribution and risk assessment of heavy metals in sediments collected from the Yellow River, China.

Bohai Sea is one of the most intensively exploited region in the world and its environment has been severely impacted by the extensive human activities. The Yellow River is the most important river which connects with the Bohai Sea. Therefore, this study focused on analyzing heavy metals (HMs) in 21 surface sediment samples collected from the Yellow River, China. Sequential extraction procedure (SEP), proposed by the Community Bureau of Reference (BCR), was applied in the present study to determine the concentration and fractionation characteristics of these HMs. The aim of this study was to investigate the spatial distribution, fractionation, risk assessment, and sources of HMs, including copper (Cu), zinc (Zn), lead (Pb), chromium (Cr), iron (Fe), manganese (Mn), and nickel (Ni). The results obtained from this research will play a significant role in understanding the migration, transformation, and accumulation of HMs for future research in study area. Results of fractionation revealed that most of the HMs in the study area mainly existed in residual fraction; however, Mn mostly existed in exchangeable fraction. A high percentage of reducible fractions was found for Cu and Pb. The mean contamination factor (Cf) values indicated that Pb was the highest. It was >1 and showed moderate contamination, followed by Cr, Cu, Mn, Ni, and Zn, had <1 and indicated low contamination. Among studied HMs Pb had higher enrichment factor (EF) as compared to others. Significant positive correlations within all studied HMs and principal component analysis (PCA) results indicated their common sources, however, Pb showed the different contamination sources. The total contents of HMs in sediment were compared with the threshold effect level (TEL) and probable effect level (PEL) sediment quality guideline (TEL/PEL-based SQGs) values for trace metals in sediment, as well as literature reported data for comparative purposes, which indicated that the selected river in present study is not severe.

Distribution of Vanadium, Nickel, and Other Trace Metals in Soot and Char from Asphaltene Pyrolysis and Gasification

Vanadium (V) and nickel (Ni) are the most abundant and troublesome metals present in oil sands. During upgrading of the oil sand bitumen, these metals become concentrated in the heavier fraction asphaltenes. Any thermochemical conversion of asphaltene causes the release of these trace metals, and their distribution in the products poses concerns with toxicity, corrosion, and fouling. The pyrolysis, partial oxidation, and steam gasification experiments of asphaltene were carried out in an electrically heated atmospheric entrained-flow reactor, and the products char and soot are analyzed for the trace metal content. It is observed that the main metals present in the char and soot are V and Ni. During pyrolysis, with an increase in the temperature, the quantity of V and Ni present in char decreases as a result of the increased liberation into the gas phase. However, more liberated V and Ni were not captured by soot formed in the same experiment. During partial oxidation of asphaltenes, an increase in the sto...

Fracture Microindentation on boride layers on AISI 1020 steel

In this paper, an attempt has been made to enhance the fracture toughness (Kc) of boride layer using multi-component (Ni, Cr and B) laser bonding. The fracture toughness of continuously pack borided, interrupted pack borided and multi-component (Ni, Cr and B) laser borided steel specimens was measured using Vickers microindentation fracture toughness test as per ASTM E384 standard. The fracture toughness of continuously pack borided layer was - 3.3 MPa.m1/2. The fracture toughness of interrupted boride layer was in the range of - 4.9 MPa.m1/2. The fracture toughness of multi-component (Ni, Cr and B) laser borided layer was in the range of 13.8 - 18.3 MPa.m1/2. A significant improvement in fracture toughness of laser treated specimens was observed from the experimental results. This may be due to better distribution of boron, nickel, chromium and other alloying elements due to laser treatment and relatively more uniform boride layer as compared with continuously pack borided layer and interrupted pack borided layer.

Amorphous iron phases in medium temperature leach residues and associated metal loss

Leach residues, produced during pilot and demonstration scale medium temperature (150°C) hydrometallurgical processing of sulfide ores contain amorphous/poorly crystalline and metastable nano-scale iron oxides/oxyhydroxide phases. These phases control the properties of the residue and contain a relatively high loading of the valuable (Cu, Ni) metals. Residue samples from CESL and Vale pilot and demonstration plant medium temperature processes were characterized using different techniques. Poor agreement between total iron analysis by inductively coupled plasma mass spectroscopy (ICP-MS) and quantitative X-ray powder diffraction QXRPD indicated the presence of amorphous/poorly crystalline iron oxide phases. QXRPD coupled with sequential extraction was used for quantification of the amorphous iron phases. Amorphous iron oxides/oxyhydroxides were found to be a major source of copper and nickel losses to the residue. The distribution of copper and nickel into the amorphous and crystalline iron oxide phases was determined by a two-stage sequential extraction process. Association of copper and nickel to the amorphous phases was found to be approximately 2–4 times higher than with the crystalline iron oxide phases.

Sol–gel growth and characterization of a new p-NiO/n-GaAs structure

A new p-NiO/n-GaAs heterostructure was fabricated by a simple and cheap sol–gel route. X-ray diffraction, atomic force microscope and UV/VIS studies indicated that nano-sized NiO film had polycrystalline cubic bunsenite crystal structure with optical band gap of 3.75 eV. The energy dispersive x-ray mapping analysis proved the homogenous distribution of nickel and oxygen elements on GaAs surface. The electrical characterization of p-NiO/n-GaAs structure showed a rectifying behavior with rectification ratio 3.3 × 104 at +2.0 V in the dark for p-NiO/n-GaAs structure. The ideality factor and barrier height were calculated as 2.21 and 0.76 eV. The results suggest that p-NiO/n-GaAs structure can be used in many electronic applications.

Investigation on Microstructure of Heat Treated High Manganese Austenitic Cast Iron

The effect of manganese addition and annealing heat treatment on microstructure of austenitic cast irons with high manganese content (Mn-Ni-resist) were investigated. The complex relationship between the development of the solidification microstructures and buildup of microsegregation in Mn-Ni-resist was obtained by using microstructure analysis and EDS analysis. The annealing heat treatment was applied at 700°C up to 1000°C to investigate the effect of the annealing temperature on the microstructure. This experiment describes the characterization of microsegregation in Mn-Ni-reist was made by means of point counting microanalysis along the microstructure. With this method, the differences of silicon, manganese and nickel distribution in alloys solidified in the microstructure were clearly evidenced. The results show microstructure consists of flake graphite embedded in austenitic matrix and carbides. There is segregation of elements in the Late To Freeze (LTF) region after solidification from melting. Manganese positively with high concentration detected in the LTF region. As for heat treatment, higher annealing temperature on the Mn-Ni-resist was reduced carbide formation. The higher annealing temperature shows carbide transformed into a smaller size and disperses through the austenitic matrix structure. The size of carbide decreased with increasing annealing temperature as observed in the microstructure.

Distribution of vanadium and nickel in heavy oil asphaltenes

Distribution of vanadium and nickel in heavy oil asphaltenes

Elemental composition of soils and bottom sediments in streams of the eastern macroslope of the Subpolar Urals

A study is made of the lead, zinc, copper, manganese, chromium, nickel and iron distribution patterns in soils and bottom sediments of streams flowing on the eastern macroslope of the Subpolar Urals. Results were subjected to a statistical processing to show a wide variation in content levels of metals due to a set of lithological and landscape-geochemical factors. The study revealed a correlation of anomalously high concentrations in soils with occurrence zones of ore mineral resources. Particular attention is paid to the lateral differentiation of lead. It is shown that its accumulation occurs in accumulative landscapes of river valleys, and its increased content is observed in bottom sediments during deposition on the sorption barrier. It is found that formation of bottom sediments showing increased contents of metals is associated with sedimentation characteristics at the time when the flow velocity of rivers decreases at the transition from mountain landscapes to lowland landscapes. The accmulation of elements in different components of migration series is analyzed to reveal regular differences in elemental composition of soils of middle- and low-mountain, low-mountain/ piedmont and submontane-lowland landscapes and to permit the description of the background geochemical associations. Regional percent abundances are calculated and compared with results obtained for neighboring areas of the West Siberian Plain. The postulate concerning the determining role of the surrounding mountains in the formation of the trace element composition of soils in Western Siberia. A deficit of copper and zinc content in bottom sediments is pointed out. It is concluded that dissolved forms are dominant in the aquatic transport of heavy metals.

LIGHT CURVES OF CORE-COLLAPSE SUPERNOVAE WITH SUBSTANTIAL MASS LOSS USING THE NEW OPEN-SOURCE SUPERNOVA EXPLOSION CODE (SNEC)

We present the SuperNova Explosion Code (SNEC), an open-source Lagrangian code for the hydrodynamics and equilibrium-diffusion radiation transport in the expanding envelopes of supernovae. Given a model of a progenitor star, an explosion energy, and an amount and distribution of radioactive nickel, SNEC generates the bolometric light curve, as well as the light curves in different wavelength bands assuming black body emission. As a first application of SNEC, we consider the explosions of a grid of 15 M_⊙ (at zero-age main sequence) stars whose hydrogen envelopes are stripped to different extents and at different points in their evolution. The resulting light curves exhibit plateaus with durations of ∼20 − 100 days if & 1.5 − 2 M_⊙ of hydrogen-rich material is left and no plateau if less hydrogen-rich material is left. The shorter plateau lengths are unlike the Type IIP supernova light curves typically observed in nature. This suggests that, at least for zero-age main sequence masses . 20 M_⊙, hydrogen mass loss occurs as an all or nothing process, perhaps pointing to the important role binary interactions play in observed mass-stripped supernovae (i.e., Type Ib/c events). These light curves are also unlike what is typically seen for Type IIL supernovae, arguing that simply varying the amount of mass loss cannot explain these events. The most stripped models begin to show double-peaked light curves similar to what is often seen for Type IIb supernovae, confirming previous work that these supernovae can come from progenitors that have a small amount of hydrogen and a radius of ∼ 500 R_⊙.

Spectral models for early time SN 2011fe observations

We use observed UV through near IR spectra to examine whether SN 2011fe can be understood in the framework of Branch-normal SNe Ia and to examine its individual peculiarities. As a benchmark, we use a delayed-detonation model with a progenitor metallicity of Z_solar/20. We study the sensitivity of features to variations in progenitor metallicity, the outer density profile, and the distribution of radioactive nickel. The effect of metallicity variations in the progenitor have a relatively small effect on the synthetic spectra. We also find that the abundance stratification of SN 2011fe resembles closely that of a delayed detonation model with a transition density that has been fit to other Branch-normal Type Ia supernovae. At early times, the model photosphere is formed in material with velocities that are too high, indicating that the photosphere recedes too slowly or that SN 2011fe has a lower specific energy in the outer ~0.1 M_sun than does the model. We discuss several explanations for the discrepancies. Finally, we examine variations in both the spectral energy distribution and in the colors due to variations in the progenitor metallicity, which suggests that colors are only weak indicators for the progenitor metallicity, in the particular explosion model that we have studied. We do find that the flux in the U band is significantly higher at maximum light in the solar metallicity model than in the lower metallicity model and the lower metallicity model much better matches the observed spectrum.

Defect Formation of Nickel-Incorporated Large-Diameter Czochralski-Grown Silicon and Their Effect on Gate Oxide Reliability

Nickel, the related defect distribution of as-grown nickel-incorporated p-type Czochralski-grown silicon crystals, and its effect on the gate oxide reliability were investigated with respect to the boron doping concentration. The segregation of nickel at the surface was more likely in the doping range of 5.5–7.4 × 1014 cm−3 than in the doping range of 1.1–1.7 × 1015 cm−3, which was due to the active formation of Ni–B pairs in the crystal with a higher boron doping concentration. The formation of surface defects was affected by the atomic nickel distribution; that is, the surface defect density was relatively high in the crystal with a lower boron doping concentration. The gate-oxide reliability was aggravated by nickel-related defects, but this effect was noticeably suppressed in the crystal with a higher boron doping concentration. From the breakdown yield and measured laser scattering tomographic defect density, we found the “transferred portion” of bulk nickel defects that causes a degradation in the gate-oxide reliability.

Electrochemical properties of composite materials based on poly-3,4-Ethylenedioxythiophene with nickel oxide inclusions

The electrochemical behavior of PEDOT/NiO composite films obtained by electrochemical deposition of nickel into poly-3,4-ethylenedioxythiophene (PEDOT) films followed by oxidation in weakly alkaline solutions was studied by cyclic voltammetry. When a complex polymer composite with two sequentially deposited PEDOT/NiO layers was prepared, the charge almost doubled. The morphology of the obtained composite films was studied by scanning electron microscopy (SEM); the element composition was analyzed by local energy dispersion (EDX) analysis. The nickel distribution over the surface was mapped for the PEDOT/Ni and PEDOT/NiO composite films. The specific capacity of the obtained materials and their dependence on the potential scan rate were determined by cyclic voltammetry.

Spatial Patterns and Risk Assessment of Heavy Metals in Soils in a Resource-Exhausted City, Northeast China.

Northeast China is an intensive area of resource-exhausted city, which is facing the challenges of industry conversion and sustainable development. In order to evaluate the soil environmental quality influenced by mining activities over decades, the concentration and spatial distribution of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and Zinc (Zn) in surface soils (0-20cm) of a typical resource-exhausted city were investigated by analyzing 306 soil samples. The results showed that the average concentrations in the samples were 6.17 mg/kg for As, 0.19 mg/kg for Cd, 51.08 mg/kg for Cr, 23.27 mg/kg for Cu, 31.15 mg/kg for Ni, 22.17 mg/kg for Pb, and 54.21 mg/kg for Zn. Metals distribution maps produced by using the inverse distance weighted interpolation method and results revealed that all investigated metals showed distinct geographical patterns, and the concentrations were higher in urban and industrial areas than in farmland. Pearson correlation and principal component analysis showed that there were significant positive correlations (p<0.05) between all of the metals, and As, Cd, Cr, Mn, Ni, Pb, and Zn were closely associated with the first principal component (PC1), which explained 39.81% of the total variance. Cu and As were mainly associated with the second component (PC2). Based on the calculated Nemerow pollution index, percentage for slightly polluted (1<P ≤ 2) surface soils were reached 57.33%, while 42.65% topsoil samples are moderate polluted (2<P≤ 3). According to the results above-mentioned, different soil environmental function areas were classified and proper soil environmental management policy was proposed to decrease the environmental risks in the process of industrial city transformation.

Quantitative mapping of elemental distribution in leaves of the metallophytes Helichrysum candolleanum, Blepharis aspera, and Blepharis diversispina from Selkirk Cu–Ni mine, Botswana

Multi-element profiling is essential in understanding the metal-tolerant behavior of metallophytes. Although previous reports using multi-elemental analyses show that the metallophytes Blepharis aspera, Blepharis diversispina (Acanthaceae) and Helichrysum candolleanum (Asteraceae) take up metals, no information exists on elemental spatial distribution and concentrations in specific tissues of these plants. The aim of this study therefore was to assess the spatial distribution and concentration of copper, nickel and other elements in leaf tissues of these plants using micro-PIXE. Whole plants were collected with soil in pots from an operational copper and nickel mine (i.e., a copper and nickel mineralized area), Selkirk, about 40km north-east of Francistown, Botswana. On the same day the samples were transported by air to iThemba LABS in South Africa. Leaf specimens were cryofixed in liquid propane cooled by LN2. Parallel samples were embedded in resin for anatomical studies to facilitate interpretation of elemental maps. The distribution and concentration of copper, nickel, and other elements in leaf tissues were determined using micro-PIXE and proton backscattering spectrometry. Data evaluation was performed using GeoPIXE II software. Micro-PIXE showed that H. candolleanum had the highest whole leaf content of copper (70±3μgg−1 DW) and nickel (168±5μgg−1 DW), followed by B. aspera (Cu: 25±1μgg−1 DW; Ni: 166±4μgg−1 DW) and B. diversispina (Cu: 3±1μgg−1 DW; Ni, below detection limit). For specific leaf tissues, the highest levels of copper were found in the vascular bundle for H. candolleanum (167±7μgg−1 DW) and the lower epidermis for B. aspera (70±9μgg−1 DW). The highest levels of nickel were present in the vascular bundle of B. aspera (479±10μgg−1 DW) and H. candolleanum (90±5μgg−1 DW). Elemental maps showed a similar distribution pattern for copper and nickel in B. aspera and B diversispina, with these elements concentrated in the upper and lower epidermal regions. However, for H. candolleanum, both copper and nickel were concentrated in the mesophyll. The difference in concentration and accumulation patterns between B. aspera, B. diversispina and H. candolleanum suggests that the metal-tolerant adaptation of these metallophytes may differ.

Improving the cycling stability of Li2MnO3 by surface treatment

An electrochemically stable and cobalt-free cathode material is prepared by impregnating Li2MnO3 with nickel nitrate and subsequent calcination at 650 °C. X-ray diffraction and scanning electron microscopy reveal a phase pure material with a homogenous distribution of nickel over the particle surface. Structural changes related to the treatment before and after cycling as well as electrochemical performance are investigated. The surface modified samples exhibit improved cycling stability and rate capability. In particular, the material with a nickel content of 5.7 wt% shows 173 mAh g−1 at rate C/10 and 104 mAh g−1 at rate 3C. Furthermore, a constant capacity of 155 mAh g−1 is obtained at rate C/5. Derivative plots of galvanostatic curves in combination with Raman spectroscopy depict a reduced transition from a layered to spinel-like structure compared with pristine Li2MnO3, while ICP measurements reveal a drastically decreased dissolution of manganese.

A high voltage cathode prepared by using polyvinyl acetate as a binder

This paper describes the preparation and characterization of a high voltage composite cathode for lithium ion-batteries based on LiNi0.5Mn1.5O4 as the active material and poly vinyl acetate (PVAc) as the binder. To assess the effect of the PVAc binder on the electrode properties, the PVAc-based electrode is compared with a traditional one prepared by using Teflon as the binder. The electrode morphologies are investigated by scanning electron microscopy and the thermal behavior of the PVAc-based electrode evaluated by thermo gravimetry and differential thermal analysis. The distribution of oxygen, manganese, and nickel on the electrode is investigated by X-ray electron diffraction spectroscopy. The electrodes are used as cathodes to prepare lithium metal cells and their electrochemical properties are investigated through galvanostatic charge/discharge cycles conducted at various discharge currents.

Contamination and spatial variation of heavy metals in the soil-rice system in Nanxun County, Southeastern China.

There is an increasing concern about heavy metal contamination in farmland in China and worldwide. In order to reveal the spatial features of heavy metals in the soil-rice system, soil and rice samples were collected from Nanxun, Southeastern China. Compared with the guideline values, elevated concentrations of heavy metals in soils were observed, while heavy metals in rice still remained at a safe level. Heavy metals in soils and rice had moderate to strong spatial dependence (nugget/sill ratios: 13.2% to 49.9%). The spatial distribution of copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) in soils illustrated that their high concentrations were located in the southeast part. The high concentrations of cadmium (Cd) in soils were observed in the northeast part. The accumulation of all the studied metals is related to the long-term application of agrochemicals and industrial activities. Heavy metals in rice showed different spatial distribution patterns. Cross-correlograms were produced to quantitatively determine the spatial correlation between soil properties and heavy metals composition in rice. The pH and soil organic matter had significant spatial correlations with the concentration of heavy metals in rice. Most of the selected variables had clear spatial correlation ranges for heavy metals in rice, which could be further applied to divide agricultural management zones.

The influence of natural trace element distribution on the mobility of radionuclides. The exemple of nickel in a clay-rock

The natural distribution of nickel (Ni) in the Callovian–Oxfordian clay-rich rock of Bure (France) was investigated, together with that of cobalt (Co), zinc (Zn) and lead (Pb). The most Ni-enriched phases are pyrite (∼400×10−6gg−1 Ni), sphalerite (∼300×10−6gg−1), chlorite (∼285×10−6gg−1), organic matter (∼300×10−6gg−1), muscovite (100–200×10−6gg−1) and possibly carbonate minerals (mainly calcite and minor dolomite, ∼10×10−6gg−1). Despite their high abundance (up to ∼80% in the upper part of the formation), carbonate minerals are quantitatively a minor Ni reservoir; most of the Ni is borne by chlorite and pyrite, which are minor mineral phases. Co and Ni have a similar distribution, whereas Pb and Zn have partly different reservoirs (e.g. sphalerite – ZnS).In parallel, the equilibrium between rock and pore water was investigated, and importance of pyrite (or reduced sulfur minerals) as Ni reservoir in the formation was confirmed from an in situ experiment perturbed by oxidation processes. Under unperturbed conditions (laboratory kinetics experiments and in situ pore water sampling), Ni solubility ranges from ∼0.2 to 1×10−6molL−1. The rock sorption capacities with regards to radioactive Ni (in the range of ∼1.5×10−10molL−1 to ∼1.5×10−9molL−1 of spiked 63Ni) were also tested using batch experiments. Sorption kinetics of 63Ni on the Callovian–Oxfordian clay-rich rock was explained by two mechanisms: fast and reversible sorption onto clay minerals and slow incorporation in another phase. Indirect evidences point out the likely major role of calcite in this latter process albeit pyrite and organic matter may also be involved. Reversible sorption of Ni onto clay minerals surfaces is shown to be hindered by competition processes with other naturally occurring bivalent metals (e.g. naturally-occurring Ni and Zn), thus decreasing the 63Ni Rd value as compared to the value predicted from a bottom-up approach considering only 63Ni sorption on clay minerals. At longer time scale, irreversible 63Ni trapping is observed and compensates the competition processes. These two mechanisms were implemented in a reactive transport model to illustrate their influence on the prediction of long-term behavior of radioactive Ni. Migration distances are increased by the effect of cation competition, and reduced in a comparable extent by irreversible trapping in the time frame investigated.