Metal Pairs Research Articles

Solvent mediated inclusion of metal oxide into block copolymer nanopatterns: Mechanism of oxide formation under UV-Ozone treatment

Uniform, periodic and ordered iron oxide nanopatterns can be generated by selective metal ion inclusion into microphase separated polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP) thin films. After solvent mediated metal ion inclusion into the PEO block, an ultraviolet-ozone (UVO) treatment was used to remove the polymer and oxidize the metallic ions to their oxides. This paper provides an in-depth study of the UVO processing steps as a function of exposure time. Surface wettability, topography, morphology, compositional and interfacial changes were analysed by contact angle measurement, microscopic and spectroscopic techniques through the UVO treatment. It was found that the UVO treatment initially cross-links the polymer network followed by oxidation and removal of the polymer simultaneously. It was also found that if short UVO exposure times are used, a post calcination treatment can be used to generate similar patterns. The iron oxide nanopatterns created due to strong coordination bond between metallic ions and free electron pairs of O atoms in the PEO and these interactions are responsible for the final pattern mimicking the original self-assembled BCP morphology. The film thicknesses, surface roughness, the size/shape of the iron oxides and patterns, the amount of residual polymers were also investigated regarding the UVO exposure time.

Joining of Dissimilar Metal Pairs by Mechanical Locking Method

Malzemeler sökülebilen ve sökülemeyen birleştirme yöntemleri kullanılarak birleştirilirler. Ancak farklı malzeme türlerinin birleştirilmesi söz konusu olduğunda birçok birleştirme yönteminin kullanılması güç ve problemlidir. Bu nedenle farklı malzeme türlerinin birleştirilmesinde mekanik kilitleme yöntemi kullanılarak uygulamada karşılaşılan bazı problemlerin önüne geçilebilecektir. Yöntem ile seramikler ile metaller, demir esaslı malzemeler ile demir dışı metaller ve diğer malzeme türleri birbirleri ile birleştirilebilir. Bu çalışma kapsamında farklı kimyasal bileşime sahip AISI1040 ve Al 1050 metal çiftleri mekanik kilitleme ile birleştirilerek yöntemin uygulanabilirliği araştırılmıştır. Birleştirilen numunelere ait mekanik analizleri yapılmış ve mikro yapı incelemeleri tamamlanmıştır. Yapılan çalışma sonucunda farklı malzeme çiftlerinin mekanik kilitleme yöntemi ile başarılı bir şekilde birleştirileceği görülmüştür.

Rubidium-Alkaline-Earth Trifluoroacetate Hybrids as Self-Fluorinating Single-Source Precursors to Mixed-Metal Fluorides.

Three novel bimetallic hybrid crystals featuring rubidium-alkaline-earth metal pairs and trifluoroacetato ligands were synthesized, and their utility as self-fluorinating single-source precursors to the corresponding mixed-metal fluorides was demonstrated. Rb2Mg2(tfa)6(tfaH)2·3H2O, RbCa(tfa)3, and RbSr2(tfa)5 (tfa = CF3COO-; tfaH = CF3COOH) were synthesized in both single-crystal and polycrystalline forms via solvent evaporation. Their crystal structures were solved using single-crystal X-ray diffraction (XRD), and chemical purity was confirmed using thermal analysis (TGA/DTA). Metal-oxygen-metal connectivity in Rb2Mg2(tfa)6(tfaH)2·3H2O was restricted to four-metal building blocks. In contrast, RbCa(tfa)3 and RbSr2(tfa)5 were found to be extended inorganic hybrids ( Cheetham et al. Chem. Commun. 2006 , 0 , 4780 - 4795 ) exhibiting infinite metal connectivity in three and two dimensions, respectively. Systematic analysis of the coordination modes of the trifluoroacetato ligand revealed its ability to bridge alkali and alkaline-earth metals. Rietveld analysis of powder X-ray diffraction data (PXRD) showed that thermal decomposition of Rb2Mg2(tfa)6(tfaH)2·3H2O and RbCa(tfa)3 under inert atmosphere yielded crystalline RbMgF3 and RbCaF3, respectively. This solid-state transformation occurred without the need for an external fluorinating agent because the trifluoromethyl group acted as a built-in fluorine source. Solid-state and solution thermolysis of Rb2Mg2(tfa)6(tfaH)2·3H2O provided access to the hexagonal and cubic polymorphs of the fluoroperovskite RbMgF3, respectively. Findings reported in this article highlight that bimetallic trifluoroacetates offer unique features from the standpoint of both crystal lattice topology and reactivity.

ICP-MS multi-element analysis for determining the origin by multivariate analysis of red pepper flakes from three different regions of Turkey

The concentrations of eleven elements in thirty traditional red pepper flake (Capsicum annuum L.) samples from three regions of Turkey were analysed by inductively coupled plasma mass spectrometry (ICP-MS). Samples were digested in a microwave system. The decreasing sequence of the mean metal concentrations (mg kg−1) in all the samples is as follows:Fe(109)>Al(89.3)>Mn(9.46)>Zn(7.44)>Cu(5.48)>Ni(4.38)>Cr(1.05)>V(0.52)>Pb (0.27)>As(0.18)>Cd(0.15). All the metal pairs showed positive correlations (except for Cu-Al, Zn-Al and Cu-Mn pairs). Multivariate statistical analysis including principal component analysis (PCA) and cluster analysis (CA) was applied to the data to evaluate the analytical results. Thirty red pepper flake samples were classified into three groups by PCA (eigenvalues higher than >1.00). The first PC loads heavily on V, Pb, Zn, Cu, Cr, and Cd. The second PC was primarily loaded by Fe and Al. The third PC correlated very strongly with Ni, As, and Mn. Cluster analysis resulted in the sorting into similar groups. The results show that PCA and CA are useful tools for the regional differentiation of red pepper flakes and for the identification of heavy metal sources. The accuracy of the results was confirmed by analysis of 1573a Tomato Leaves certified reference material.

Material scaling and frequency-selective enhancement of near-field radiative heat transfer for lossy metals in two dimensions via inverse design

The super-Planckian features of radiative heat transfer in the near-field are known to depend strongly on both material and geometric design properties. However, the relative importance and interplay of these two facets, and the degree to which they can be used to ultimately control energy flow, remains an open question. Recently derived bounds suggest that enhancements as large as $|\chi|^4 \lambda^{2} / \left(\left(4\pi\right)^{2} \Im\left[\chi\right]^{2} d^{2}\right)$ are possible between extended structures (compared to blackbody); but neither geometries reaching this bound, nor designs revealing the predicted material ($\chi$) scaling, have been previously reported. Here, exploiting inverse techniques, in combination with fast computational approaches enabled by the low-rank properties of elliptic operators for disjoint bodies, we investigate this relation between material and geometry on an enlarged space structures. Crucially, we find that the material proportionality given above does indeed emerge in realistic structures. In reaching this result, we also show that (in two dimensions) lossy metals such as tungsten, typically considered to be poor candidate materials for strongly enhancing heat transfer in the near infrared, can be structured to selectively realize flux rates that come within $50\%$ of those exhibited by an ideal pair of resonant lossless metals for separations as small as $2\%$ of a tunable design wavelength.

The Influence of the Volatile Ifhan-114 Inhibitor on the Efficiency of a Number of Contact Galvanic Metal Pairs and Rate of Corrosion of Their Constituents in the Atmosphere of Livestock Premises

The protective ability of the volatile IFHAN-114 inhibitor in the corrosion of models of macrogalvanic steel/brass, steel/copper, and copper/brass pairs under conditions simulating the atmosphere of livestock premises is studied. The content of CO2, NH3, and H2S (corrosion stimulators) was 0.2–0.6 vol %, 20–60 mg/m3, and 10–30 mg/m3, respectively. The ability of IFHAN-114 to suppress the generation of the faradaic current by the models of galvanic pairs is investigated. It is shown that the surface of metals forming the galvanic pairs undergoes intensive pitting and ulcer corrosion when there is no inhibitor under the effect of one corrosion stimulator (CS) or simultaneous effect of two or three corrosion stimulators. In most cases, the introduction of IFHAN-114 into the gas phase completely suppresses the local corrosion of metals forming the galvanic pairs and reduces the rate of their general corrosion (which is uniform when the volatile corrosion inhibitor is used) by 2–5 times. The inhibitor introduced into the 0.1 M KCl solution significantly suppresses the density of the current generated by the models of galvanic steel/brass and copper/brass pairs. However, this effect is observed only after 200 min of exposure of the pair models to corrosion.

Reactivity of a gold(i)/platinum(0) frustrated Lewis pair with germanium and tin dihalides.

The reactivity of germanium and tin dichlorides with a transition metal-only frustrated Lewis pair based on Au(i) and Pt(0) compounds bearing bulky phosphine ligands is described in this work. We have examined both the reactivity of tetrylene dihalides towards the individual components of the metallic pair, as well as under metal/metal cooperative conditions. These studies allowed us to isolate several uncommon homo- and heterometallic structures. Computational methods have been employed to investigate the bonding scheme of one of these highly-reduced metallic aggregates. In addition, we have developed a tin-promoted strategy to access heteroleptic diphosphine platinum(0) compounds.

Influence of the volatile inhibitor ifhan-114 on the efficiency of a number of contact galvanic metal pairs and the rate of corrosion of their constituents in the atmosphere of livestock buildings

Influence of the volatile inhibitor ifhan-114 on the efficiency of a number of contact galvanic metal pairs and the rate of corrosion of their constituents in the atmosphere of livestock buildings

A stoichiometric terbium-europium dyad molecular thermometer: energy transfer properties

The optical thermometer has shown great promise for use in the fields of aeronautical engineering, environmental monitoring and medical diagnosis. Self-referencing lanthanide thermo-probes distinguish themselves because of their accuracy, calibration, photostability, and temporal dimension of signal. However, the use of conventional lanthanide-doped materials is limited by their poor reproducibility, random distance between energy transfer pairs and interference by energy migration, thereby restricting their utility. Herein, a strategy for synthesizing hetero-dinuclear complexes that comprise chemically similar lanthanides is introduced in which a pair of thermosensitive dinuclear complexes, cycTb-phEu and cycEu-phTb, were synthesized. Their structures were geometrically optimized with an internuclear distance of approximately 10.6Å. The sensitive linear temperature-dependent luminescent intensity ratios of europium and terbium emission over a wide temperature range (50–298K and 10–200K, respectively) and their temporal dimension responses indicate that both dinuclear complexes can act as excellent self-referencing thermometers. The energy transfer from Tb3+ to Eu3+ is thermally activated, with the most important pathway involving the 7F1 Eu3+J-multiplet at room temperature. The energy transfer from the antenna to Eu3+ was simulated, and it was found that the most important ligand contributions to the rate come from transfers to the Eu3+ upper states rather than direct ligand–metal transfer to 5D1 or 5D0. As the first molecular-based thermometer with clear validation of the metal ratio and a fixed distance between the metal pairs, these dinuclear complexes can be used as new materials for temperature sensing and can provide a new platform for understanding the energy transfer between lanthanide ions.

Refined Model for Plasmon Ruler Based on Catenary-Shaped Optical Fields

The catenary, in addition to be one intriguing structure in mechanics and optics, expresses the universal rule of evanescent field coupling between metallic or dielectric nanoparticle pairs. In the present paper, the catenary-shaped optical field distributions within the gap of nanoparticle pairs as well as the distance dependence of scattering spectrum shift are investigated. A novel model defined by power attenuation functions is established to describe the scaling behavior of local field enhancement and plasmon wavelength shift of metallic nanoparticle pairs. Compared with traditional model, the proposed model can more accurately describe the scaling behavior of scattering spectrum shift, which help to refine the existing plasmon rulers. Our findings can serve as a guideline for designing and optimizing catenary-field-based plasmon rulers.

Umbilical Cord Concentrations of Selected Heavy Metals and Risk for Orofacial Clefts

Although arsenic (As), cadmium (Cd), lead (Pb), and nickel (Ni) have the ability to induce orofacial clefts (OFCs) in rodents, evidence is absent from human epidemiological investigations with markers of in utero exposure. We investigated the associations between concentrations of As, Cd, Pb, and Ni in umbilical cord tissues and risk of OFCs, and the interactions between each pair of metals on OFC risk in a case-control study. Umbilical cord concentrations of metals were determined by inductively coupled plasma mass spectrometry in 92 OFC cases and 200 nonmalformed controls. Concentrations above the median of all subjects was associated with an elevated OFC risk of 8.36-fold for As, 7.22-fold for Cd, 15.32-fold for Pb, and 6.79-fold for Ni. Concentrations of As, Cd, Pb, and Ni were also associated with risks for OFC subtypes. When metal concentrations were divided into tertiles by levels of metal concentrations of all subjects, dose-response relationships of risks for total OFCs and subtypes with As, Cd, Pb, and Ni concentrations were demonstrated. Significant synergistic interaction between As and Ni on the risk of OFCs was also observed. Therefore, elevated in utero exposure to As, Cd, Pb, and Ni may increase the risks of OFCs in newborns.

A Pair of Rare Three-Dimensional Chiral Polyoxometalate-Based Metal–Organic Framework Enantiomers Featuring Superior Performance as the Anode of Lithium-Ion Battery

Two rare three-dimensional (3D) chiral polyoxometalate-based metal–organic framework (POMOF) materials, d- [PMo8VMo4VIO37(OH)3Zn4][BPP]2·2[pyridine]·H2O (d-1) and l-[PMo8VMo4VIO37(OH)3Zn4][BPP]2·2[pyridine]·H2O (l-1) (BPP = 1,3-bis(4-pyridyl)propane) were prepared with achiral ligand under solvothermal conditions. They are the first 3D chiral POM-based frameworks based on a Zn-e-Keggin unit and achiral ligands. The CD spectra and structural analyses indicate that the two polyoxometalate-based metal–organic frameworks are enantiomers. The alternate connection of Zn-e-Keggin cluster and BPP ligands generate helical infinite chains, while each single spiral chain is further interlinked to adjacent neighboring units to produce a 3D regular ordered chiral architecture with a qtz topology. Compound 1 (mixtures of d-1 and l-1) exhibited excellent stability in both acid and base aqueous solutions. When compound 1 was used as an anode electrode material of rechargeable Li-ion batteries (LIBs), outstanding reversib...

Temperature dependent polarity inversion in double‐metal terahertz emitters

The temperature dependent polarity inversion in double-metal (DM) terahertz (THz) emitters was investigated. DM emitters utilising different metal pairings and single edge metal emitters were cooled in a helium flow cryostat and their THz emission was measured over a range of temperatures. Most emitters, including those with insulating layers between the metal and semiconductor, exhibit a flip in polarity of their THz emission between 50 and 100 K. This shows the inversion is a trait intrinsic to the semiconductor and not influenced by the metallic contact on the surface.

Biliary and hepatic metallothionein, metals and trace elements in environmentally exposed neotropical cichlids Geophagus brasiliensis

One of the metal detoxifying mechanisms that occurs in fish is metallothionein (MT) induction and metal binding. Hepatic MT induction has been well described, but biliary MT metal detoxification has only recently been described in fish. In this scenario, metal-metal interactions have been increasingly evaluated to further understand the behavior of these contaminants regarding homeostasis and biological functions, as well as their toxic effects. Studies, however, have been mainly conducted concerning the elemental pair Se-Hg, and scarce reports are available concerning other metal pairs. Therefore, this study aimed to evaluate biliary and hepatic MT metal detoxification mechanisms in a territorial neotropical cichlid, Geophagus brasiliensis. Fish were sampled from the anthropogenically impacted estuarine Rodrigo de Freitas Lagoon, located in Southern Rio de Janeiro, and trace elements and MT were determined by inductively coupled plasma mass spectrometry (ICP-MS) and UV-Vis spectrophotometry, respectively, in fish liver and bile. MT in bile were significantly lower than in liver. Significant differences between bile and liver were observed for many trace elements, and, although most were higher in liver, Cd and Ni were significantly higher in bile, indicating efficient excretion from the body via the biliary route. A significant correlation was observed between MT and Fe in bile, and between MT in liver and Cu and Zn in bile. Molar ratio calculations demonstrated protective elements effects against Al, As, Cd, Hg, Pb and V in both bile and liver, as well as some novel interrelationships, indicating the importance of these investigations regarding the elucidation of element detoxifying mechanisms. Furthermore, investigation of other elemental associations may aid in decision-making processes regarding environmental contamination scenarios linked to public health.

Surface Chemical Structure of Carbon Electrodes and Electrochemical Behavior of Redox Couples in Flow Batteries

Due to their decoupling from electrical power and energy storage capacity, redox flow batteries represent a high-capacity, versatile and low-cost energy storage system. However, the low energy density (related to the potential difference, the low solubility and the solvent electrochemical window of stability), and the steadiness to the oxidation-reduction cycle of the species used (long-term spice instability) are two factors that have prevented its massive use [1, 2]. Among the species that have been explored for these purposes are those with metallic centers: VIV/VV, VII/VIII, Ti3+/TiO2+, Fe2+/Fe3+, Cr2+/Cr3+, Ce4+/Ce3+; halogens (Br−/ClBr2 [3-6], redox pairs of coordination metals [7], in addition to multiple quinones [8], sometimes having an acceptable performance a commercial level. Moderately successful devices use transition metal species (vanadium) with less accessibility and greater restriction in optimization possibilities than synthesizable organic species, so the need to get proper substitutes continues. A factor that is fundamental to the electrochemical performance and long-term stability of the species is the chemical nature of the electrode used. In redox flow cells, the most commonly used electrode material is carbon such as graphite, felt, carbon paper, glassy carbon, fiber, and carbon polymer composites. These materials are highly sensitive to the chemical treatment they are subjected to activate them. It has been reported that the current response varies up to an order of magnitude for the same redox species when the electrode has been activated [4]. It is widely known that exist an influence of the electrodes on the electrochemical response of the redox species, when they are used in flow batteries, however, a profound ignorance of the chemical factors that direct this effect persists. The lack of knowledge of the effect of different electrode surface conditions makes the results reported in the literature incomparable in many cases. The evaluation of new electrode candidates must consider the physicochemical structure of the electrode material and its relationship with the redox couples. In this work, we present the ab-initio computational modeling of the chemical interactions between the redox molecule/carbon electrode. The chemical composition of the surface of the electrodes and different redox couples used in flow batteries are considered such as VIV/VV, VII/VIII, (Br−/ClBr2, [Ru(bpy)3]2+, 2-hydroxynaphtoquinone. The theoretical results are compared with those obtained by electrochemical characterization of carbon paper, and carbon felt, previously subjected to chemical treatments for their activation. The electrochemical responses of redox species are related to molecule-electrode chemical interactions. The objective is to show that the pretreatment-structure-reactivity relationships of the electrodes influence a more effective investigation and allow a better selection of the redox pairs for the flow batteries. [1] Pan et al., Molecules, 20 (2015) 20499. [2] P. Leung et al., Journal of Power Sources, 360 (2017) 243. [3] Xiang and Daoud, Journal of The Electrochemical Society, 164 (2017)A2256. [4] Bourke et al., ECS Transactions, 66 (2015) 181. [5] Wang et al., Advanced Functional Materials, 23 (2013) 970. [6] Bartolozzi et al., Journal of Power Sources, 27 (1989) 219. [7] Matsuda et al., Journal of Applied Electrochemistry, 18 (1988) 909. [8] Huskinson et al., Nature Letters 505 (2014) 195.

Tribological Behavior of Polyethylene/Light Metal Pairs in Low Viscosity Organic Solvents

Tribological Behavior of Polyethylene/Light Metal Pairs in Low Viscosity Organic Solvents

A Low-Loss Bandpass Filter using Edge-Coupled Resonator With Capacitive Feeding in (Bi)-CMOS Technology

In this Letter, a flexible approach for low-loss on-chip bandpass filter (BPF) design in CMOS technology is presented. The proposed approach takes the advantages of a combination of an edge-coupled electromagnetic structure, namely resonator, and a pair of metal–insulator–metal capacitors for BPF implementation. To demonstrate the insight of the approach, the designed resonator is analyzed in details by means of a simplified equivalent LC-circuit model. Then, the impact on the BPF design due to the variations of the feeding capacitance is investigated. To prove the concept, both the resonator and BPF are fabricated in a standard 0.13- $\mu \text{m}$ CMOS technology. The measured results show that the designed resonator can generate a notch with 20-dB attenuation at 59.4 GHz, while the BPF has a center frequency of 35.4 GHz with an insertion loss of 1.7 dB. The chip size of both devices, excluding the test pads, is only 0.039 mm2 ( $0.15 \times 0.26$ mm2).

The Effect of Kinematic Conditions and Synovial Fluid Composition on the Frictional Behaviour of Materials for Artificial Joints.

The paper introduces an experimental investigation of frictional behaviour of materials used for joint replacements. The measurements were performed using a ball-on-disc tribometer, while four material combinations were tested; metal-on-metal, ceramic-on-ceramic, metal-on-polyethylene, and ceramic-on-polyethylene, respectively. The contact was lubricated by pure saline and various protein solutions. The experiments were realized at two mean speeds equal to 5.7 mm/s and 22 mm/s and two slide-to-roll ratios, −150% and 150%. It was found that the implant material is the fundamental parameter affecting friction. In general, the metal pair exhibited approximately two times higher friction compared to the ceramic. In particular, the friction in the case of the metal varied between 0.3 and 0.6 while the ceramic pair exhibited friction within the range from 0.15 to 0.3 at the end of the test. The lowest friction was observed for polyethylene while it decreased to 0.05 under some conditions. It can be also concluded that adding proteins to the lubricant has a positive impact on friction in the case of hard-on-hard pairs. For hard-on-soft pairs, no substantial influence of proteins was observed. The effect of kinematic conditions was found to be negligible in most cases.

Gasless Reactive Compositions for Materials Joining: An Overview

Some results of recent studies on materials joining by using exothermic reactive compositions that burn without notable gas evolution are overviewed. We also considered some possible routes to controlling wave propagation velocity in conditions of strong heat sink, to lowering ignition temperature for exothermic combustion reactions, and to improving the adhesion strength. The use of exothermic powder compositions opens up new horizons for combustion‐aided joining of materials, including refractory and dissimilar ones. Further advance in the field can be reached through mechanical activation (nanostucturing) of green compositions in ball mills and by cold rolling of reactive mixtures to fabricate reactive tapes. The examples of joining carbon materials, metals, and ceramic–metal pairs were presented. To date, the technique of combustion‐assisted joining of materials has become a promising and rapidly developing branch of modern R & D.

Heavy metals' contamination in sediments of Wadi Al-Aqiq water reservoir dam at Al-Baha region, KSA: Their identification and assessment

ABSTRACTSediments are the ultimate sump for heavy metal pollutants. The main purpose was to investigate the ecological and health risk assessment of heavy metals in the sediments of Wadi Al-Aqiq water reservoir. The metals detected were arranged in decreasing order Fe > Mn > Cr > Cu > Zn > Ni > Co > Pb. Pearson correlation analysis indicated strong positive association and significant linear relation between various pairs of metals. Different evaluation indices used indicated that source of contamination from lithogenic sources and sediments can be classified as low polluted quality. A comparison of the concentrations of metals with International Sediment Quality Guidelines criteria showed that only Cu and Ni concentrations above the ERL and below the ERM guideline values suggest possible adverse effects. On comparing with US Environmental Protection Agency prepared sediment quality criteria it indicated that Pb and Zn have concentrations below the non-polluted criteria, Fe, Mn, and Ni lies in the range of moderately polluted criteria, and Co and Cu are within the heavily polluted criteria. Non-carcinogenic risk quantification indicated health concern from ingestion route and no health effects for dermal exposure. On considering additive effect, the dermal exposure may cause health harm. The carcinogenic risk assessment for lead and chromium showed an acceptable risk to human health.