Low Nickel Content Research Articles

Structural features ensuring the increase of service characteristics of high-nickel steels for pressure vessels of prospective energy-generation reactors

Complex structure studies and mechanical tests of low carbon Ni–Cr–Mo–V steels with low and high nickel content (low-Ni and high-Ni steels) were performed.Mechanical tests showed that high-Ni steels in initial state are characterized by higher strength properties and lower values of critical temperature of brittleness in comparison with low-Ni steels.Estimation of input of various structural elements in ensuring yield strength and brittle fracture stress (which is connected with critical temperature of brittleness) was performed. It was shown that increased strength characteristics of high-Ni steels are determined mostly by higher density of nanoscale carbide precipitations and dislocations. It was also shown that lower critical temperature of brittleness of high-Ni steels is associated with lower width of substructural blocks and, consequently, with higher number of barriers to brittle transcrystalline crack propagation.

Nickel in the Environment: Bioremediation Techniques for Soils with Low or Moderate Contamination in European Union

The review deals with the environmental problem caused by low or moderate nickel concentrations in soils. The main effects of this potentially toxic element on the soil biota and the most common crop species are addressed. Moreover, the paper emphasises biological remediation methods against nickel pollution in European soils. The focus is on the well-accepted phytoremediation strategy alone or in combination with other more or less innovative bioremediation approaches such as microbial bioremediation, vermiremediation and the use of amendments and sequestrants. Results acquired in real field and laboratory experiments to fight against nickel contamination are summarised and compared. The main objective was to evidence the ability of the above natural techniques to reduce the nickel concentration in contaminated sites at a not-risky level. In conclusion, the examined works agree that the efficiency of phytoremediation could be implemented with co-remediation approaches, but further studies with clear and comparable indices are strongly recommended to meet the challenges for future application at a large scale.

Hydrogen embrittlement behavior in interstitial Mn–N austenitic stainless steel

The susceptibility to hydrogen embrittlement behavior was investigated in an interstitial Mn–N austenitic steel HR183 and stainless steel 316L. Hydrogen was introduced by cathodic hydrogen charging at 363 K. HR183 has stronger austenite stability than 316L despite its lower nickel content, the addition of manganese and nitrogen inhibited martensitic transformation during the slow strain rate tensile deformation. Due to the diffusion of hydrogen being delayed by the interstitial solution of nitrogen atoms and the uniform dislocation slips, hydrogen permeates more slowly in HR183 than 316L, contributing to an 84.79 μm thinner brittle fracture layer in HR183 steel. Hydrogen charging caused elongation losses in both 316L and HR183 steels associated with the hydrogen-enhanced localized plasticity (HELP) and hydrogen-enhanced decohesion (HEDE) mechanism. However, the hydrogen embrittlement susceptibility of HR183 is 3.4 times lower than that of 316L according to the difference in elongation loss between the two steel after hydrogen charging. Deformation twins trapped a lot amount of hydrogen leading to brittle intergranular fracture in 316L. The multiple directions of slip in HR183 steel suppressed the strain localization inside grains and delayed the adverse effects conducted by HELP and HEDE mechanism, eventually inhibiting server hydrogen embrittlement in the HR183 steel. This study is assisting in the development of low-cost stainless steel with excellent hydrogen embrittlement resistance that can be used in harsh hydrogen-containing environments.

Integration of multi-sensor remote sensing, geological and geochemical data for delineation of Pb–Zn bearing carbonates of Middle Aravalli group in Zawar–Dungarpur Belt, NW India

The rocks of the Aravalli Protocontinent of NW India are enriched in lead–zinc bearing deposits amongst which the Zawar mineralized belt is one of the famous for base metal deposits and was mined since ancient times. In the present study, an attempt has been made to identify and map the extension of the mineralized belt and base metal prognostic zones using the integration of multi-sensor remote sensing, geological and geochemical data. Remote Sensing studies were carried out using ASTER, AVIRIS-NG, and ASAR datasets to understand the extension and associated structural features of host rocks (dolomite in the present case) of lead–zinc mineralization from the Middle Aravalli Group. Relative band depth (B6 + B9/B8) was used to delineate the dolomite of the region using the ASTER imagery. Mineral map was derived using the AVIRIS-NG dataset with the help of the MTMF algorithm. Multifrequency and multipolarization ASAR datasets demarcated the structural features in the complexly deformed rocks of the extended belt. The obtained results from remote sensing were validated with the help of geological and geochemical studies. Geological studies (field surveys and petrographic studies) confirmed the presence of dolomites and associative mafics. Mineralogical, major oxides and trace elements data further substantiated the presence of dolomite, associated sulfides such as galena, sphalerite, pyrite, and chalcopyrite, and lead, zinc and copper in the Zawar–Dungarpur Belt. Presence of chromium and nickel were observed through the trace element studies of dolomite belt. The trace elements interpolated maps were superimposed by traced structural maps using ASAR datasets. The densely populated E-W lineaments are considered the suitable zones for base metal accumulation. These lineaments carried the base metal bearing fluid along with a low concentration of Chromium and Nickel. Under the finding of this study, the northern head of Hati Magra and near Keekawat are the suitable zones for Pb–Zn sulfide mineralization.

Nickel on Oxidatively Modified Carbon as a Promising Cost-Efficient Catalyst for Reduction of P-Nitrophenol.

The reduction of p-nitrophenol to p-aminophenol has become a benchmark reaction for testing the efficiency of new catalytic systems. In this study, we use oxidatively modified carbon (OMC) as a structural support to develop a new cost-efficient nickel-based catalytic system. The newly developed material comprises single nickel ions, chemically bound to the oxygen functional groups on the OMC surface. The highly oxidized character of OMC ensures the high lateral density of nickel ions on its surface at relatively low nickel content. We demonstrate excellent catalytic properties of the new material by using it as a stationary phase in a prototype of a continuous flow reactor: the reagent fed into the reactor is p-nitrophenol, and the product, exiting the reactor, is the fully converted p-aminophenol. The catalytic properties of the new catalyst are associated with its specific morphology, and with high lateral density of active sites on the surface. The reaction can be considered as an example of single-atom catalysis. The resulting material can be used as an inexpensive but efficient catalyst for industrial wastewater treatment. The study opens the doors for the synthesis of a new series of catalytic systems comprising transition metal atoms on the OMC structural support.

Paving Pathways Toward Long‐Life Graphite/LiNi0.5Mn1.5O4 Full Cells: Electrochemical and Interphasial Points of View

AbstractThe high‐voltage spinel cathode LiNi0.5Mn1.5O4 (LNMO) with no cobalt and low nickel content is promising for lithium‐ion batteries due to its high energy and power densities, good thermal stability, and low cost. However, its high operating voltage (≈4.7 V) results in a decomposition of the electrolyte, severe chemical crossover, and deterioration of electrode‐electrolyte interphases (EEIs), hindering its practical viability. It is demonstrated here that by electrochemically pre‐cycling the graphite in an electrolyte containing 30 wt.% fluoroethylene carbonate, a robust LiF‐rich artificial solid electrolyte interphase can be constructed for surface protection; on the other hand, an electrochemical pre‐lithiation of Fe‐doped LNMO serves as a lithium source for graphite at a full‐cell voltage of 2.6 V. As a result, the full cells with the as‐modified electrodes deliver a high capacity of 129 mA h g−1 with an excellent capacity retention of 93% after 200 cycles, vastly outperforming the full cells with fresh electrodes (120 mA h g−1 initial capacity with 78% retention). Finally, pathways toward long‐life graphite||LNMO full cells are pictured based on the inspirations from the electrochemical modifications and in‐depth analyses of the EEIs in this study.

Bimetallic nickel-palladium nanoparticles with low Ni content and their enhanced ethanol oxidation performance: Using a pulsed laser as modification machinery

Currently, the synthesis of bimetallic nanoparticles (NPs) is complicated and requires several chemicals and a high amount of energy. Therefore, it is crucial to advance a novel method for synthesizing bimetallic NPs with excellent electrocatalytic activity. Herein, 3 nm bimetallic nickel-palladium (NiPd) NPs were synthesized via facile pulsed laser irradiation (PLI) method without using any reducing agents. The synthesized NPs included a very low nickel (Ni) content of approximately 4–8 wt% due to the reduction potential difference between the Ni and Pd. The cohesive force between the particles also increased, based on the high Ni content. The electrochemical results indicated that the synthesized NPs showed excellent electrocatalytic activity for use in an ethanol oxidation reaction in an alkaline electrolyte. The obtained bimetallic NiPd NPs with a Ni content of 5 wt% offered a superior mass activity of 4.26 A/mgPd compared with other NPs. This study highlighted that the PLI method showed great potential for synthesizing highly electrocatalytically active bimetallic NiPd NPs for use in an ethanol oxidation reaction.

Effective target arrangement for detecting the properties of Ni doped diamond-like carbon by pulsed laser deposition

In the current study, diamond-like carbon (DLC) was synthesized by pulsed laser deposition (PLD) in a vacuum at room temperature, focusing on Ni-dopant concentration and arrangement of Ni strips in both parallel and transverse positions. The morphology and structural properties of Ni-DLC films were analyzed by Raman spectroscopy, atomic force microscopy (AFM) analysis, cross-section analysis, energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), contact angle (CA), and nanoindentation test. AFM images exhibit the new shapes of Ni-DLC thin films, named conic and nano-mushroom particles. The Raman spectra of Ni-DLC films show that the calculated intensities D-line to G-line ratio experiences a decrease with increasing Ni dopants in the transverse arrangement while the parallel arrangement represents a different trend. The stoichiometry of Ni-DLC thin films has been reported from the cross-section of thin films. It is also observed from the measured CA that the hydrophilic properties of Ni-DLCs increase in the transverse arrangement. Low nickel content in diamond-like carbon matrix exhibited the dominance of diamond phase and good mechanical properties have been found.

Distinct effects of transition metal (cobalt, manganese and nickel) ion substitutions on the abiotic oxidation of pyrite: In view of hydroxyl radical production

The abiotic oxidation of pyrite (FeS2) is a geochemically crucial reaction involved in acid mine drainage, the release of toxic trace elements and the generation of hydroxyl radicals (•OH) that can oxidize environmental substances. Studies on •OH generation from the abiotic oxidation of pyrite have drawn wide interest, but the effects of the common substitution of transition metal ions on •OH generation are still largely unknown, and worthy of comprehensive comparison. We therefore synthesized and comprehensively characterized micron-sized pyrites containing low concentrations of cobalt (Co), nickel (Ni), or manganese (Mn) ions, and tested the relative ability of these transition metal ion-substituted pyrites to generate •OH under abiotic oxidation. We found that transition metal ion substitutions inhibited the growth of pyrite crystals to various extents and increased Fe–S bond distances, leading to distinct alterations in surface chemical composition, conductivity, and the exposure of active faces. These differences resulted in an increase in •OH generation by the oxidation of transition metal ion-substituted pyrites, relative to pure pyrite, with the order of increase being Mn2+-substituted < Ni2+-substituted < Co2+-substituted pyrites. These substituent-dependent differences were explored by linking the crystal properties and physical chemistry of these pyrites to various reaction pathways that were possible in such contexts. For pure pyrite, the heterogeneous Fenton reaction was the chief generator of •OH. The substitution of pyrite with Co2+, which was redox-active, increased the conductivity of pyrite and accelerated the reduction of surface Fe3+ to Fe2+, resulting in a significant increase in H2O2 and •OH production. The substitution of pyrite with Mn2+, which was also redox-active, likewise increased the conductivity; however, the high oxidizing ability of surface Mn4+ inhibited the reduction of Fe3+ and thus decreased •OH generation. By contrast, the substitution of pyrite with Ni2+ did not affect electron transfer but led to absolute exposure of the (111) face of pyrite, which increased its activity toward O2 and H2O, slightly increasing H2O2 and •OH generation. These results highlight the vital role of transition metal ion-substituted pyrite in various geochemical processes.

Comparative life cycle cost assessment of (lean) duplex stainless steel in wastewater treatment environments

Some unit operations in wastewater treatment plants (WWTPs), such as settling tanks and pipes for aeration or sludge transfer, are composed of austenitic stainless steel (EN 1.4307 or EN 1.4404) instead of galvanised or painted carbon steel to reduce the maintenance costs. The sensitivity to pitting and crevice corrosion of austenitic grades in certain WWTP environments has also led to the use of duplex grades. The purpose of this study is to evaluate the maintenance of piping systems (WWTPs) and its effect on their life cycle environmental impacts and costs (LCC) for both austenitic and duplex stainless steel grades. The final objective is to aid grade selection for piping in a WWTP environment. The considered functional unit (FU) is a complete piping system. Conventional austenitic stainless steel grades (e.g., EN 1.4404) are studied alongside duplex ones (e.g., EN 1.4362 and EN 1.4462). The calculated environmental impacts are the Global Warming Potential (GWP) and Primary Energy Demand (PED). The production, manufacturing, transport, use including maintenance activities, and end-of-life (burdens and credits) phases are included in the life cycle assessment (LCA). The maintenance activities consist of the required replacements of stainless steel piping during the lifespan of the WWTP. Thus, the service lives of the pipes included in the considered WWTP environment are determined based on long-term corrosion prediction models (power law), which predict the evolution of pit or crevice depth as a function of time. The model parameters are estimated based on own experimental results, supplemented by the existing literature. The corrosion rates determine the number and frequency of replacements, i.e., define the different scenarios of maintenance. The LCA, LCC and corrosion prediction models are then combined into a user-friendly tool, which can be used in industry for an appropriate grade selection for pipes in a WWTP environment. The tool includes several degrees of freedom such as piping distribution, water pressure, chloride content, replacement criteria, etc. The results show that using duplex stainless steel grade EN 1.4462 leads to lower GWP and PED at the end of the WWTP's service life of 40 years. This is mainly due to multiple replacements of the system's parts in wastewater with high levels of chloride (>3000 ppm) if more conventional austenitic stainless steel alloys such as EN 1.4404 are used. Leaner duplex stainless steel grades were also included in this LCC assessment. The duplex grade EN 1.4062 showed the lowest total LCC, thanks to its leaner chemical composition (i.e., lower nickel content) combined with good localized corrosion resistance.

Effect of environmental condition on corrosion susceptibility of GTA welded AISI 202 austenitic stainless steel

Austenitic stainless steels with low nickel content or nickel-free content are currently considered structural materials for nuclear fusion reactor applications. Even though the base metal achieves excellent performance, welding may result in premature failures due to morphological and compositional heterogeneities. The presence of pollutants in the environment results in environmental acidification, which influences the corrosion susceptibility of the weldment. This paper it is aimed to examine the influence of the gas tungsten arc welding (GTAW) process on localized corrosion and the degree of sensitization (DOS) of AISI 202 austenitic stainless steel (ASS) butt joints in three distinct regions: base-zone (BZ), heat-affected zone (HAZ), and weld-zone (WZ) in 3.5% NaCl under pH-5 environmental conditions. The localized corrosion behavior of the weldment was studied using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and degree of sensitization (DOS) using the double loop electro-chemical potentiokinetic reactivation (DL-EPR) technique. Optical microscopy (OM) is used to understand the microstructural features of weldments and pit morphologies before and after polarisation studies. The present study establishes that the heat-affected zone (HAZ) has low corrosion resistance, high DOS%, and low intergranular corrosion (IGC) resistance compared to the base and weld zones. This could be due to the thermal cycles involved in HAZ during welding, resulting in chromium depletion and the formation of chromium carbide precipitation.

Залежність структури ливарних сплавів системи Al-Ni-La від їх хімічного складу

The peculiarities of cast Al-Ni-La alloys structure formation depending on the content and ratio of the main components are analyzed in the work. It is shown, that so far the studied system has been considered mainly for the creation of amorphous materials. At the same time, Al-Ni and Al-La systems have phase diagrams that allow us to consider double and triple alloys of these systems to create promising creep-resistant alloys for casting. At the same time, the peculiarities of their structure formation in this context were not determined. Samples with different contents of nickel and lanthanum were prepared for research and analyzed how each of the elements, their number and ratio affect the formation of their structural-phase state. It is shown, that low nickel content of about 2 wt. % and lanthanum up to 5 wt. % eutectic is formed like thin almost monolithic intermetallic plates. As the number of components increases and, accordingly, the number of eutectics increases, the dispersion of its components increases. The analysis of the alloy structure dependence due to studied system on their chemical composition showed that, most likely, during the formation of the eutectic, Al11La3 particles, which may have the form of nanosized fibers, are formed first of all. It should be noted that at the eutectic content of lanthanum in the alloys no primary-formed Al11La3 particles were found. This may indicate that nickel shifts the eutectic concentration of lanthanum toward higher values. At the same time, at the hypoeutectic concentration of lanthanum and the hypereutectic concentration of nickel, some Al11La3 formations were outside the regions of the main eutectic with nickel aluminide. Such questions necessitate further studies of the aluminum angle of the triple state diagram of the Al-Ni-La system. Keywords: Al-Ni-La system, creep-resistant cast aluminum alloys, structure, eutectic.

Beyond the usual suspects: methanogenic communities in eastern North American peatlands are also influenced by nickel and copper concentrations.

Peatlands both accumulate carbon and release methane, but their broad range in environmental conditions means that the diversity of microorganisms responsible for carbon cycling is still uncertain. Here, we describe a community analysis of methanogenic archaea responsible for methane production in 17 peatlands from 36 to 53N latitude across the eastern half of North America, including three metal-contaminated sites. Methanogenic community structure was analysed through Illumina amplicon sequencing of the mcrA gene. Whether metal-contaminated sites were included or not, metal concentrations in peat were a primary driver of methanogenic community composition, particularly nickel, a trace element required in the F430 cofactor in methyl-coenzyme M reductase that is also toxic at high concentrations. Copper was also a strong predictor, likely due to inhibition at toxic levels and/or to cooccurrence with nickel, since copper enzymes are not known to be present in anaerobic archaea. The methanogenic groups Methanocellales and Methanosarcinales were prevalent in peatlands with low nickel concentrations, while Methanomicrobiales and Methanomassiliicoccales were abundant in peatlands with higher nickel concentrations. Results suggest that peat-associated trace metals are predictors of methanogenic communities in peatlands.

Elevated stability of nickel-rich oxide cathode material with concentration gradient of transition metals via a novel size-controllable calcination method

Consumers are increasingly demanding the range and safety of the electric vehicles. Nickel-rich layered lithium transition-metal oxide cathode material with Ni content exceeding 80% has attracted extensive attention due to its high capacity. To suppress the decrease of cyclic and thermal stability due to the increase of nickel content, LiNi0.87Co0.06Mn0.07O2 particles with transition metal concentration gradient from the interior to the surface are realized. An efficient and low-cost method is proposed involves firstly forming the shell layer with low nickel content by a dry mechanofusion process and subsequently adopting a novel particle size-controllable calcination course. Through which a concentration gradient layer with a thickness of 1 µm is successfully formed, and the particle size of primary particles is effectively controlled at the range of 250–300 nm. The relationship between the calcination conditions, the morphology, particle size of primary particles and the electrochemical performance have been established. Capacity of 211.9 mAh/g and initial coulomb efficiency of 90.29% have been achieved by LiNi0.87Co0.06Mn0.07O2 with superficial transition metal concentration gradient, and the capacity retention rate at 1 C reached 86.1% after 400 cycles in a pouch cell. In addition, the thermal decomposition temperature is elevated from 220 °C to 242 °C, the safety of the Ni-rich material has been also effectively improved.

Fabricating a thin gradient surface layer to enhance the cycle stability of Ni-rich cathode materials

Although Ni-rich cathode materials have made a great success in the field of electric vehicles due to their high capacity and low cost, many efforts are still focused on further increasing their capacity through increasing the Ni content. However, the increased Ni content usually leads to a more serious surface structure reconstruction and hence higher resistance during electrochemical cycling, which has become a major issue for Ni-rich cathodes. In order to explore a balance between surface structure stability and high energy density, a model Ni-rich material with transition metal ion gradient is prepared using a mechanical fusion and co-lithiation method, which is easy for large-scale fabrication. The gradient structure sample contains an inter bulk of LiNi0.90Co0.05Mn0.05O2 and a thin gradient outer layer with lower nickel content. The gradient sample shows a superior cycling property, rate retention, and improved safety performance. Systematic study suggests that the possible reasons for the improved electrochemical and mechanical performance of the gradient nickel-rich materials are the high stability of lower-Ni surface and the decreased surface tensile stress. This work provides an easy up-scaled method to build a gradient structure and a further in-depth understanding on its structure stabilization mechanisms, which are essential for developing high energy-density lithium-ion batteries.

Study on mechanical properties of high strength sorbite stainless steel S600E under monotonic and cyclic loadings

A new kind of high strength sorbite stainless steel named S600E was developed recently, which has the 65% corrosion resistance, but three times higher yield strength than commonly used austenitic stainless steel S30408. In addition, the price of S600E is only 70% of S30408 owning to the low nickel content of 1.5–2.5%. Fundamental investigations on the mechanical behaviours of S600E were presented in this study. Two monotonic and seventeen cyclic material tests were conducted subjected to different strain-controlled loading protocols including the constant strain amplitude ranging from 0.25% to 2.5%, as well as the varied strain amplitudes. Monotonic test results show that S600E presents the typical feature of rounded nonlinear strain hardening, but the 0.2% proof stress is extremely high, up to 750 MPa, and the elongation after fracture is over 20%. In the cyclic tests, little cyclic hardening was occurred in the initial few cycles, while cyclic softening tended to appear at the remaining cycles. Based on the test results, the isotropic component in the constitute model was neglected, key material parameters for the nonlinear kinematic hardening model with two pairs of backstresses were obtained and validated using the numerical analysis in ABAQUS. At last, the cyclic material properties were compared with commonly used stainless steel to reveal the advantages of S600E. The results of this study could be used in finite element modeling of members, joints and structures of S600E.

Selection of sorption materials for the extraction of nickel and cobalt from the ore of the Gornostaevskoye deposit

Oxidized nickel ores account for the majority of industrial ores suitable for nickel production. The processing of such ores using traditional pyrometallurgical technology is not economically viable due to the low nickel content. One of the most cost-effective methods of processing oxidized nickel ores is sulfuric acid leaching technology followed by sorption extraction. The aim of this work is to establish the kinetic and thermodynamic parameters of the sorption extraction of nickel and cobalt using iminodiacetate chelating ion-exchange sorbents from various manufacturers, to select a desorbing solution and to determine the degree of desorption. The sorption of nickel and cobalt was carried out in a weakly acidic medium from a model solution containing impurities of other metals in static and dynamic modes. The limiting sorption capacity for the studied sorbents is 18-26 mg/g for nickel and 1-2 mg/g for cobalt in the static mode. The sorption capacity in the dynamic mode for nickel is equal to 25.5 g/L for Purolite S 930, 29.2 g/L for Lewatit TP 207, 1.4 g/L, and 1.8 g/L for cobalt, respectively. The best desorption parameters are achieved when using a 2 M sulfuric acid solution. The degree of desorption for sorbents Purolite S 930 and Lewatit TP 207 exceeds 90%. The use of the Lewatit TP 207 sorbent for the extraction of nickel from the leaching solution of nickel ore of the Gornostaevskoye deposit in 5 cycles made it possible to obtain a commercial desorbate with a nickel content of 18 g/L. The use of a part of the commercial desorbate obtained in the previous cycle, further strengthened to the initial concentration of sulfuric acid, for re-extracting nickel from the saturated sorbent during a cyclic process leads to a deterioration in desorption characteristics. It is recommended to remove the commercial desorbate from the process after several cycles of desorption and supply new solution of sulfuric acid for desorption to restore the sorption parameters.

Hydrogen-rich gas production via steam gasification of food waste over basic oxides (MgO/CaO/SrO) promoted-Ni/Al2O3 catalysts

Food waste, a renewable resource, was converted to H2-rich gas via a catalytic steam gasification process. The effects of basic oxides (MgO, CaO, and SrO) with 10 wt% Ni/Al2O3 on the gasification properties of food waste were investigated using a U-shaped gasifier. All catalysts prepared by the precipitation method were analyzed by X-ray diffraction, H2-temperature-programmed reduction, NH3-temperature-programmed desorption, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The Ni/Al2O3 catalyst was reduced incompletely, and low nickel concentrations were detected on the surface of the alumina. The basic oxides minimized the number of acid sites and suppressed the formation of nickel-aluminate (NiAlxOy) phase in catalyst. In addition, the basic oxides shifted nickel-aluminate reduction reaction to lower temperatures. It resulted in enhancing nickel concentration on the catalyst surface and increasing gas yield and hydrogen selectivity. The low gas yield of the Ni/Al2O3 catalyst was attributed to the low nickel concentration on the surface. The maximum gas yield (66.0 wt%) and hydrogen selectivity (63.8 vol%) of the 10 wt% SrO- 10 wt% Ni/Al2O3 catalyst correlated with the highly dispersed nickel on the surface and low acidity. Furthermore, coke deposition during steam gasification varied with the surface acidity of the catalysts and less coke was formed on 10 wt% SrO- 10 wt% Ni/Al2O3 due to efficient tar cracking. This study showed that the steam gasification efficiency of the Ni/Al2O3 catalyst could be improved significantly by the addition of SrO.

Bacterial Exposure to Nickel: Influence on Adhesion and Biofilm Formation on Orthodontic Archwires and Sensitivity to Antimicrobial Agents.

The presence of nickel could modify bacterial behavior and susceptibility to antimicrobial agents. Adhesion and biofilm formation on orthodontic archwires can be a source of bacterial colonization and possible health hazards. Staphylococcus aureus was subjected to exposure and adaptation to various sub-inhibitory concentrations of nickel. Five strains of bacteria adapted to nickel in concentrations of 62.5–1000 μg/mL were tested for adhesion and biofilm formation on nickel-titanium archwires. Archwires were previously incubated in artificial saliva. Bacteria were incubated with orthodontic wire with stirring for 4 h (adhesion) and 24 h (biofilm formation). The number of adherent bacteria was determined after sonication and cultivation on the Muller-Hinton agar. Disk diffusion method was performed on all bacteria to assess the differences in antimicrobial susceptibility. Bacteria adapted to lower concentrations of nickel adhered better to nickel-titanium than strains adapted to higher concentrations of nickel (p < 0.05). Biofilm formation was highest in strains adapted to 250 and 500 μg/mL of nickel (p < 0.05). The highest biofilm biomass was measured for strains adapted to 250 μg/mL, followed by those adapted to 1000 μg/mL. Bacteria adapted to lower concentrations of nickel demonstrated lower inhibition zone diameters in the disk diffusion method (p < 0.05), indicating increased antimicrobial resistance. In conclusion, bacteria adapted to 250 μg/mL of nickel ions adhered better, demonstrated higher biofilm formation and often had higher antimicrobial resistance than other adapted and non-adapted strains.

A comparative study for the rejection of nickel ions from waste water by PES, fMWCNTs/PES, TiO2/PES and TiO2-fMWCNTs/PES mixed matrix membranes

In this study, the neat polyethersulfone (PES) membrane and the mixed matrix membranes (MMMs) containing 20 wt. %polyethersulfone (PES) and different amounts of functionalized multi-walled carbon nanotubes (fMWCNTs), TiO2, and TiO2 coated on fMWCNTs were fabricated by wet phase inversion and conventional casting methods. The nickel ions rejection and permeate flux performance were then investigated and compared by these fabricated membranes. The characteristics of the membranes were performed by field emission scanning electron microscopy (FESEM), transmissionelectron microscopy (TEM), and contact angle (CA) measurement. The operational parameters such as polymer concentration, pressure, pH, time and nickel ion concentration for nickel ions rejection and permeability were firstly optimized on the neat PES membrane. The performance of MMMs containing various amounts of nanoparticles was then evaluated and compared under these optimized conditions. The obtained results indicated that the membrane containing 20 wt. % PES, and operational conditions like pressure 15bar, low concentration of nickel, time =30min, and various amounts of pH were the best conditions to achieve the highest rejection percentage of nickel ions and permeate flux. In such operational conditions, PES/fMWCNTs and PES/TiO2 membranes have the highest nickel ion rejection and permeate flux, respectively. Totally the prepared mixed matrix membranes showed that they have higher ability to reject nickel ions from wastewater and a higher permeate flux value compared with the neat PES membrane.