Metal Pairs Research Articles

Feasibility of Metal Pad Roll Instability Experiments at Room Temperature.

Combining theoretical arguments and numerical simulations, we demonstrate that the metal pad roll instability can occur in a centimeter-scale setup with reasonable values of the magnetic field and electrical current and with metal pairs that are liquid at room temperature. We investigate two fluid pairs: gallium with mercury (immiscible pair) or gallium with GaInSn eutectic alloy (miscible pair).

Research Status and Prospects of Tribological Behaviors of Key Friction Pairs of Materials in Marine Equipment

Marine environment provides a basic space for human survival and social sustainable development. The study of tribological problems and mechanism of marine engineering materials in the sea extreme environment has become one of key technologies to be developed urgently in the field of marine engineering. This review summarizes and analyzes the tribological research of key friction materials in marine environment, focuses on tribological properties of ceramic, polymer and metal, emphatically introduces the current situation and development trend of tribological research in marine environment, such as metal and metal pairs, ceramics and metal pairs, polymers and metal pairs, polymers and ceramic pairs, and aims to provide a tutorial reference for the selection and application of friction pairs of marine engineering equipment.

Umbilical Cord Blood Metal Mixtures and Birth Size in Bangladeshi Children.

Background:Studies have evaluated environmental exposure to toxic metals such as arsenic (As), cadmium (Cd), manganese (Mn), or lead (Pb) on birth size; however, information on potential effects of exposures to metal mixtures is limited.Objectives:We assessed the association between metal mixtures (As, Cd, Mn, Pb) in umbilical cord blood and neonate size in Bangladeshi children.Methods:In this birth cohort study, pregnant women who were of age with an ultrasound-confirmed singleton pregnancy of gestation were recruited from two Bangladesh clinics between 2008 and 2011. Neonate size metrics were measured at the time of delivery. Metals in cord blood were measured using inductively coupled plasma mass spectrometry. We employed multivariable linear regression and Bayesian kernel machine regression (BKMR) to estimate associations of individual metals and metal mixtures with birth size parameters.Results:Data from 1,088 participants was assessed. We found a significant negative association between metal mixture and birth length and head circumference when all metal concentrations were above the 60th and 55th percentiles, respectively, compared with the median. An interquartile range (IQR) increase in log Cd concentration {log[Cd (in micrograms per deciliter)] } was associated with a 0.13-standard deviation (SD) decrease in mean birth length (95% CI: , ) and a 0.17-SD decrease in mean head circumference (95% CI: , ), based on linear regression models adjusted for covariates and the other metals. An IQR increase in log Mn concentration {log[Mn (in micrograms per deciliter)] } was associated with a 0.07-SD decrease in mean birth weight (95% CI: , 0.002).Discussion:Metal mixtures in cord blood were associated with reduced birth size in Bangladeshi children. Results from linear regression models adjusted and the BKMR mixtures analyses suggest adverse effects of Cd and Mn, as individual metal exposures, on birth size outcomes. https://doi.org/10.1289/EHP7502

Tribological characteristics of polymer materials used for slide bearings

Abstract The automotive industry uses a variety of technologies and construction materials in production process. Knowledge of the characteristics of tribological material pairs cooperating with each other is useful for their selection from the safety point of view sliding pairs, in means of transport, and other machines. The aim of the contribution is the analysis of the characteristics of tribological ball-on-disc wear of polymeric materials used as sliding bearings. Tribological tests were carried out under dry friction for a polymer–metal pair of three types of materials. Among all three groups of the tested materials statistically significant differences (p < 0.05 in Student’s t-test) in wear were observed. The wear rate and friction coefficient of the sample were tested, and the signs of wear were submitted to SEM observations.

Control of the Regioselectivity of Alkyne Hydrostannylation by Tuning the Metal Pair of Heterobimetallic Catalysts: A Theoretical Study

In this work, the detailed reaction mechanisms of two distinct Sn–H bond activation modes of the [Cu–Fe] and [Cu–Mn] heterobimetallic catalysts were computationally investigated using density funct...

Assessment of Human Health Risks Associated with Heavy Metals Accumulation in the Freshwater Fish Pangasianodon hypophthalmus in Bangladesh

In this study, pangas and feed samples were analyzed to estimate the levels of metallic elements and to profile the human health risks due to consumption of contaminated fish. This investigation confirmed significant variations in heavy metal concentrations among different tissues of pangas in the order of Ni > Cu > Pb > Cd > Cr in pre-monsoon and Ni > Cd = Cu > Pb = Cr in post-monsoon. Considerably higher concentrations of Pb, Cu, and Cr were estimated in liver; and Cd and Ni were detected in muscle than in other organs (p > 0.05). Statistically significant higher amounts of Cd, Ni, and Cu were observed in pre-monsoon than in post-monsoon. Furthermore, three metal pairs showed significant association (Pb–Ni and Pb–Cu involved positively; Cd–Ni acted negatively). In pre-monsoon, Cd, Pb, Ni, and Cu concentrations of feed significantly differed than those of pangas contents, whereas only Cu varied during the post-monsoon. Regression analysis revealed the significant effect of Ni content in feed on the Cu deposition of pangas (p-value 0.027, that was < 0.05). For the assessment of potential human health risk of the studied metals, estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), and carcinogenic risk (CR) indices were calculated. Studied EDI indicated that an average adult ingested a higher amount of Ni and Cu than the recommended intake limit. Nevertheless, only the higher EDI of Ni increases the value of THQ and HI than standard limit indicates adverse non-carcinogenic risk. However, lower CR of Pb confirmed no serious health hazard due to the ingestion of pangas. Factor analysis through principal component and cluster analysis suggested that higher concentrations of Pb and Ni may be regulated by the feed used, geochemical properties, or rapid industrialization in the study area. A proper monitoring for controlling the quality of fish feed with sustainable planning for industrialization could secure the booming of pangasius aquaculture in Bangladesh.

Selective CO2 Photoreduction into C2 Product Enabled by Charge-Polarized Metal Pair Sites.

Selective CO2 photoreduction into a high-energy-density C2 product is still challenging. Here, charge-polarized metal pair sites are designed to trigger C-C coupling through manipulating asymmetric charge distribution on the reduction intermediates. Taking the synthetic partially reduced Co3O4 nanosheets as an example, theoretical calculations unveil the asymmetric charge distribution on surface cobalt sites. The formed charge-polarized cobalt pair sites not only donate electrons to CO2 molecules but also accelerate the coupling of asymmetric COOH* intermediates through lowering the energy barrier from 0.680 to 0.240 eV, affirmed by quasi in situ X-ray photoelectron spectroscopy and Gibbs free energy calculations. Also, the electron-rich cobalt sites strengthen their interaction with O of the HOOC-CH2O* intermediate, which favors the C-O bond cleavage and hence facilitates the rate-limiting CH3COOH desorption process. The partially reduced Co3O4 nanosheets achieve 92.5% selectivity of CH3COOH in simulated air, while the CO2-to-CH3COOH conversion ratio is 2.75%, obviously higher than that in pure CO2.

Pollution assessment of the Red Sea-Gulf of Aqaba seawater, northwest Saudi Arabia.

The water pollution index (PIj), degree of contamination (Cd), heavy metal pollution index (HPI), and statistical analyses were used to assess seawater pollution and identify the possible sources of heavy metals from the Red Sea-Gulf of Aqaba coastline, northwest Saudi Arabia. Concentrations of Cr, Sb, Co, Ni, Cu, Zn, Cd, As, Fe, Mn, Hg, and Pb were analyzed and interpreted in 33 surface seawaters samples. The mean heavy metals of seawater were in the following order: Zn (5.51μg/l) > Ni (2.45) > As (2.43) > Cu (2.34) > Mn (2.20) > Fe (1.81) > Pb (1.31) > Sb (0.64) > Co (0.31) > Cr (0.26) > Cd (0.05) > Hg (0.008). The spatial distribution of heavy metals showed high levels in some individual samples, especially nearby the residential cities, may be due to anthropogenic sources. PIj and Cd indicated light and low pollution for the seawater samples, respectively, while HPI indicated low pollution for 10 samples and medium pollution for the rest ones. The lack of significant correlations between metal pairs (except Cu and As) indicated different sources of pollution. Pollution indices, principal component analysis, and Pearson's correlation coefficient reveal that the quality of seawater in the Red Sea-Gulf of Aqaba coastline is mainly controlled by geogenic processes with minor anthropogenic input.

Design and analysis of improved configuration for antenna-less unbiased THz photomixer emitters

We propose an antenna-less unbiased CW terahertz photomixer comprising an array of recessed contact electrodes. Each unit of the recessed contact electrodes array embedded in the photoconductive layer includes two pairs of unsymmetrical metals making up heterogeneous Schottky contacts. As compared to the analogous array emitters of the same size with planar electrodes, by optimizing the geometrical and physical properties of the recessed contact electrodes in the proposed emitter to excite the appropriate resonant modes in the larger volume of the active region, it is possible to benefit from the having of high optical absorption and so terahertz photo-current, which in turn leads to enhance the obtainable THz power by more than three orders of magnitude. This is also more than an order of magnitude larger THz power than that is radiated from the similar antenna-coupled emitter with planar contact electrodes. Furthermore, the calculation results show the proposed emitter has a frequency tuning capability in a broad range of 0.1–5 THz.

A Replacement Reaction Enabled Interdigitated Metal/Solid Electrolyte Architecture for Battery Cycling at 20 mA cm-2 and 20 mAh cm-2.

Metal anodes represent as a prime choice for the coming generation rechargeable batteries with high energy density. However, daunting challenges including electrode volume variation and inevitable side reactions preclude them from becoming a viable technology. Here, a facile replacement reaction was employed to fabricate a three-dimensional (3D) interdigitated metal/solid electrolyte composite electrode, which not only provides a stable host structure for buffering the volume change within the composite but also prevents side reactions by avoiding the direct contact between active metal and liquid electrolyte. As a proof-of-concept demonstration, a 3D interdigitated zinc (Zn) metal/solid electrolyte architecture was fabricated via a galvanic replacement reaction between Zn metal foil and indium (In) chloride solution followed by electrochemical activation, featuring the interdigitation between metallic Zn and amorphous indium hydroxide sulfate (IHS) with high Zn2+ conductivity (56.9 ± 1.8 mS cm-1), large Zn2+ transference number (0.55), and high electronic resistivity [(2.08 ± 0.01) × 103 Ω cm]. The as-designed Zn/IHS electrode sustained stable electrochemical Zn plating/stripping over 700 cycles with a record-low overpotential of 8 mV at 1 mA cm-2 and 0.5 mAh cm-2. More impressively, it displayed cycle-stable performance with low overpotential of 10 mV under ultrahigh current density and areal capacity (20 mA cm-2, 20 mAh cm-2), which outperformed all the reported Zn metal electrodes in mild aqueous electrolyte. The fabrication of interdigitated metal/solid electrolyte was generalized to other metal pairs, including Zn/Sn and Zn/Co, which provide inspiration for next-generation Zn metal batteries with high energy density and reversibility.

Transitions in the sliding wear mechanisms of binary Cu-Al alloys having a range of solute contents and microstructures

Sliding wear damage to non-lubricated metallic bearing surfaces results from the dissipation of frictional work. Damage features at or near worn surfaces depend on alloy-specific modes of deformation that are influenced by stacking fault energy (SFE) and other microstructural properties. Metal pairs having similar friction coefficients do not necessarily wear equally due to differences in energy partition. Dissipative mechanisms include highly-deformed layer (HDL) formation, deformation twinning, recrystallization, amorphization, and texturing. In some tribosystems, a portion of the frictional work is dissipated in third-body layers. HDL thickness can vary from grain-to-grain, depending on crystallographic orientation relative to the sliding direction. Thus, the energy used in texturing can also vary grain-by-grain. Composition and surface processing methods affect the manner and degree of friction/wear correlation. Transitions in wear mechanisms are investigated in a series of Cu-Al binary alloys ranging from 0 to 15 wt% Al that are processed by different routes. These bronzes were worn against bearing steels in a non-lubricated block-on-ring configuration. Application of established and less common imaging methods supports the transition from sharpened dislocation cell formation at higher SFE to deformation twinning at lower SFE. At the wear process level, primary and secondary wear debris affect model development because their relative influence changes over time.

Probing Kinetics and Mechanism of Formation of Mixed Metallic Nanoparticles in a Polymer Membrane by Galvanic Replacement between Two Immiscible Metals: Case Study of Nickel/Silver Nanoparticle Synthesis.

Galvanic replacement between metals has received notable research interest for the synthesis of heterometallic nanostructures. The growth pattern of the nanostructures depends on several factors such as extent of lattice mismatch, adhesive interaction between the metals, cohesive forces of the individual metals, etc. Due to the difficulties in probing ultrafast kinetics of the galvanic replacement reaction and particle growth in solution, real-time mechanistic investigations are often limited. As a result, the growth mechanism of one metal on the surface of another metal at the nanoscale is poorly understood so far. In the present work, we could successfully probe the galvanic replacement of silver ions with nickel nanoparticles, stabilized in a polymer membrane, using two complementary methods, namely, small-angle X-ray scattering (SAXS) and radiolabeling, and the results are supported by density functional theory (DFT) computations. The silver-nickel system has been chosen for the present investigation because of the high degree of bulk immiscibility caused by the large lattice mismatch (15.9%) and the weak adhesive interaction, which makes it a perfect model system for immiscible metal pairs. Membrane, as a host medium, plays a crucial role in retarding the kinetics of atomic and particle rearrangements (nucleation and growth) due to slower mobility of the atoms (monomers) and particles within the polymer network. This allowed us to examine the real-time concentration of silver monomers during galvanic replacement of silver ions with nickel nanoparticles and evolution of Ni/Ag nanoparticles. From combined experiment and DFT computations, it has been demonstrated, for the first time to the best of our knowledge, that the majority of silver atoms, which are produced on the nickel nanoparticle surface by galvanic reactions, do not form traditional core-shell nanostructures with nickel and undergo a self-governing sequential nucleation and growth of silver nanoparticles via formation of intermediate prenucleation silver clusters, leading to the formation of mixed metallic nanoparticles in the membrane. The surface of NiNPs has a heterogeneous effect on the silver nucleation pathway, which is evident from the reduced critical free energy barrier of nucleation (ΔGcrit). The present work establishes an original mechanistic pathway based on a sequential nucleation model for formation of mixed metallic nanoparticles by the galvanic replacement route, which opens up future possibilities for size-controlled synthesis in mixed systems.

Promoting the formation of Co (III) electrocatalyst with diamond anodes

In this work, the catalytic effect of electrode substrate on the electrochemical oxidation of cobalt (II) using boron doped diamond (BDD) anodes was studied. A significant increase of the Co (III) formation was observed in using BDD coatings on tantalum substrate (91.43% at around 90 min of galvanostatic electrolysis), with respect to the Si-BDD anode, which only attained a poorer Co (III) conversion (8.33%) after applying the same electric charge. Electrochemical impedance spectroscopy showed that the Ta/BDD electrode has a lower charge-transfer resistance for the Co (II)/Co(III) metallic pair and the process is controlled by diffusion of cobalt towards the electrode surface, due to its rapid adsorption at the interface. This was further confirmed by cyclic voltammetry (CV) where the electrodeposition of Co (II) on the electrode surface is obviously significant if we compare it with that of Si/BDD anode. This difference in the electrode behavior, caused by the substrate on which the diamond coating is deposited, opens a line of research to improve the efficiency of mediated electrolytic treatments based on the use of Co, with important industrial applications in the treatment of many pollutants including volatile organic compounds (VOCs).

Integrated geospatial analysis linking metal contamination among three different compartments of Lake Edku ecosystem in Egypt to human health effects.

This study is the first in forming an integrated up-to-date spatial analysis linking heavy metal contamination among three different compartments of Lake Edku ecosystem to human health effects. The study determined the concentrations of iron (Fe), nickel (Ni), lead (Pb), chromium (Cr), and cadmium (Cd) in sediment and water samples collected from 12 stations covering the entire lake, as well as in the liver and muscle tissues of the three commercially edible fish species (African sharptooth catfish (Clarias gariepinus), Blue tilapia (Oreochromis aureus), and Redbelly tilapia (Tilapia zillii)), during winter 2019. Cartographic maps investigating the spatial contamination pattern of each metal in sediment and water samples along the entire lake, as well as correlation analysis between metal pairs, were generated. Moreover, the study examined the affinity of metal transfer among the three compartments and assessed the probability of being exposed to non-carcinogenic health hazards from the consumption of the abovementioned species. Results revealed that Fe and Cd recorded the highest and lowest mean concentrations, respectively, in sediment, water, and fish samples. The mean concentrations of Cd, Pb, and Ni in the water of Lake Edku, as well as the mean concentrations of Cd, Pb, and Cr in muscle tissues of the three examined fish species, exceeded the permissible limits. The northwestern part of the lake exhibited the highest concentrations of Fe, Ni, and Cr in Lake Edku's sediment with strong significant positive correlations recorded between Fe-Ni, Fe-Cr, and Ni-Cr pairs suggesting sharing the same contamination source. Concerning Lake Edku's water, the northwestern area displayed the highest concentrations for all metals. Moreover, Cd, Pb, and Cr exhibited nearly the same spatial contamination pattern with the hotspot located in the western part of the lake. Strong significant positive correlations were found between Cd-Pb, Cd-Cr, and Pb-Cr pairs in surface water, suggesting sharing the same origin of dispersion. The three fish species accumulated heavy metals from water several folds higher than from sediments, indicating that water is the main source of the intensive transfer of heavy metals to the three fish species. Based on the consumption of the three investigated fish species, children recorded the highest estimated daily (EDI) and weekly intakes (EWI) of heavy metals followed by adults. Regardless Pb, EWI values indicated that there are no significant health risks through fish consumption from the examined metals recommending that children should consume less than 85.227 g/day African sharptooth catfish muscle, 108.696 g/day Blue tilapia muscle, and 97.403 g/day Redbelly tilapia muscle to assure their health. Moreover, adults should consume less than 397.727 g/day African sharptooth catfish muscle, 507.24 g/day Blue tilapia muscle, and 454.54 g/day Redbelly tilapia muscle. The estimated hazard quotient (HQ) of all metals was lower than or close to the safe values of one for children and adults in the three investigated fish species indicating the absence of potential non-carcinogenic threats. The hazard index (HI) estimated for the five examined heavy metals in each of the investigated fish species was below one in adults only. Regarding the total hazard index estimated from consuming the three fish species, both children and adults may be subjected to non-carcinogenic risk.

An enantiomeric pair of alkaline-earth metal based coordination polymers showing room temperature phosphorescence and circularly polarized luminescence

Preparation and characterization of an enantiomeric pair of coordination polymers based on alkaline-earth metals and chiral pyroglutamate ligands showing room temperature phosphorescence and sizeable circularly polarized luminescence is discussed.

Asymmetric metal–organic frameworks with double helices for enantioselective recognition

A pair of homochiral metal–organic frameworks are elaborated by employing flexible enantiopure ligands.

Fluorescent sensor for in-vivo bio-imaging, precise tracking of Fe3+ ions in Zebrafish embryos and visual measuring of Cu2+ ions in pico-molar level

Feasibly synthesized novel rhodamine based chemosensor (RS) has been described for the detection of paramagnetic and biologically important Cu2+ and Fe3+ ions. Among all the transition metal ions, this chemosensor was able to precisely spot out the Cu2+/Fe3+ ion couple by its spirolactam cleavage, consequently enhanceing their absorbances at 521 and 529 nm for Cu2+ and Fe3+ ions respectively even at low concentrations [263 pM (Cu2+) and 2 nM (Fe3+)], which is prominently lower than the WHO and the United States Environmental Protection Agency (USEPA) strategies. This metal pair (Cu2+/Fe3+) has more tendencies to cleave the lactam ring even in the presence of higher concentrations of other relevant metal ions. Such remarkable behaviour of RS has been motivated us to apply zebrafish bio-imaging and molecular logic circuits.

Recent Advances in Thermochemical Energy Storage via Solid–Gas Reversible Reactions at High Temperature

The exploitation of solar energy, an unlimited and renewable energy resource, is of prime interest to support the replacement of fossil fuels by renewable energy alternatives. Solar energy can be used via concentrated solar power (CSP) combined with thermochemical energy storage (TCES) for the conversion and storage of concentrated solar energy via reversible solid–gas reactions, thus enabling round the clock operation and continuous production. Research is on-going on efficient and economically attractive TCES systems at high temperatures with long-term durability and performance stability. Indeed, the cycling stability with reduced or no loss in capacity over many cycles of heat charge and discharge of the material is pursued. The main thermochemical systems currently investigated are encompassing metal oxide redox pairs (MOx/MOx−1), non-stoichiometric perovskites (ABO3/ABO3−δ), alkaline earth metal carbonates and hydroxides (MCO3/MO, M(OH)2/MO with M = Ca, Sr, Ba). The metal oxides/perovskites can operate in open loop with air as the heat transfer fluid, while carbonates and hydroxides generally require closed loop operation with storage of the fluid (H2O or CO2). Alternative sources of natural components are also attracting interest, such as abundant and low-cost ore minerals or recycling waste. For example, limestone and dolomite are being studied to provide for one of the most promising systems, CaCO3/CaO. Systems based on hydroxides are also progressing, although most of the recent works focused on Ca(OH)2/CaO. Mixed metal oxides and perovskites are also largely developed and attractive materials, thanks to the possible tuning of both their operating temperature and energy storage capacity. The shape of the material and its stabilization are critical to adapt the material for their integration in reactors, such as packed bed and fluidized bed reactors, and assure a smooth transition for commercial use and development. The recent advances in TCES systems since 2016 are reviewed, and their integration in solar processes for continuous operation is particularly emphasized.

Dynamically Switchable Multispectral Plasmon-Induced Transparency in Stretchable Metamaterials

We propose dynamically switchable multispectral plasmon-induced transparency (PIT) with high modulation depth in a three-dimensional metamaterial standing on a flexible substrate. The proposed metamaterial is composed of a pair of metal–insulator–metal (MIM) nano-cut-wires and a pair of insulator–metal–insulator (IMI) nano-cut-wires. Results show that two PIT windows can be achieved because of the near-field coupling between the dipole supported by the IMI nano-cut-wire and two quadrupoles supported by the MIM structures. These two PIT windows can be blue-shifted or even flipped over by stretching the substrate along one direction, or be switched off by stretching along the other direction. A classical coupled oscillator model is developed to quantitatively describe and explain these results. We expect this work will find promising applications in multispectral sensors, slow light devices and nonlinear optical devices.

The price relationship between main-byproduct metals from a multiscale nonlinear Granger causality perspective

Basing on the relationship of joint production, we take lead-bismuth, lead-selenium, zinc-cadmium, and zinc-germanium as examples to study the nonlinear Granger causal relationship between the prices of main-byproduct metal pairs. The price relationship between the main metal and byproduct metal is nonlinear and varies with the time scales. Therefore, we use an Ensemble Empirical Modal Decomposition method (EEMD) to break down the price series of the main metals and byproduct metals into different frequency bands, and then test these different frequency bands for nonlinear Granger causality. The results show that a two-way nonlinear Granger causal relationship exists between the prices of the main metals and byproduct metals, and this nonlinear Granger causal relationship is reflected primarily in the short- and medium-term time scales. Moreover, the effect of the main metal price on the price of the byproduct metal is not as significant as previously thought, and the influence of the byproduct metal price on the main metal price has been previously underestimated.