Mixture Of Zinc Research Articles

Microstructural analysis of low Ni content Zn alloy electrodeposited under applied magnetic field

The codeposition behaviour of Zn and Ni has been studied in sulphate electrolytes in presence of a superimposed magnetic field up to 1 T parallel to the surface. Structural analysis by X-Ray diffraction (XRD) method revealed that the alloys consisted of a mixture of zinc, η-phase and γ-phase. The results showed that the magnetic field B was responsible for variations of the alloy structural parameters (lattice imperfection and texture) for low pH. When the pH of electrolyte was increased, the effect of the magnetic field was erased. It was suggested that the preferential growth direction of Zn–Ni alloy was induced by the mass-transport enhancement of H + ions promoted by B which induced an increase of the pH near the cathode. Then, for high value of pH up to 3.5, the crystallographic orientation (101) of Zn was always favoured to the prejudice of the Ni 5Zn 21 phase.

Luminescence enhancement of (Ca,Zn)TiO3:Pr3+ phosphor using nanosized silica powder

The results pertaining to luminescence enhancement due to high-temperature amalgamation of nanometer-sized silica powder and the oxide mixture of calcium, zinc, titanium, and praseodymium are presented. The (Ca,Zn)TiO3:Pr3+ phosphor showed an intense and narrow band emission at ∼614nm under ambient light/ultraviolet excitation, which is associated with the typical H43→D21 transition of Pr3+. The observed red emission is quite stable and long (∼60min) for a dark-adapted human eye and shows no appreciable degradation in the optical properties for prolonged exposure to surrounding/atmosphere. With the addition of nanosized silica powder, the photoluminescence was augmented nearly 1.6 times as that of unadded sample. The present results are entirely different from those reported previously for Pr3+ doped-(Ca,Zn)TiO3 phosphor and silica-based persistent phosphors.

Hot dip fine Zn and Zn–Al alloy double coating for corrosion resistance at coastal area

A new hot dip Zn–7Al alloy coating was performed on a structural steel by double coating of fine Zn and Zn–7 wt.% Al alloy, to prevent severe corrosion in coastal area. The alloy-coated steels were exposed to seaside, quasi-industrial, and rural districts to compare with conventional Zn coating. Double coating was significantly effective in preventing corrosion, particularly in a seaside. It was estimated from the exposure test for 10 years that the life of the Zn–7Al alloy-coated steel would be almost four times that of the Zn-coated steel in the seaside. A bending test showed that no exfoliation occurred at the interface between the coated alloy and substrate steel. TEM observation revealed that the excellent adhesiveness of the doubly coated fine Zn and Zn–7Al alloy to the steel substrate was due to formation of the interface region consisting of heterogeneous fine phase mixture of zinc, aluminium and iron.

Large-scale synthesis of ZnO microhollowspheres and their optical properties

Abstract ZnO microhollowspheres (MHs) were synthesized by evaporation of a mixture of zinc, graphite, and zinc oxide powders. The microstructures of the resultant MHs have been characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), X-ray diffraction, and photoluminescence (PL). The PL results indicated that the green emission peak at 510 nm of the MHs was higher and broader than that of the nanocombs, which was due to oxygen vacancies formed in the MHs. In addition, the mechanism of ZnO MHs was discussed in detail.

Synthesis of nanosized zinc ferrites from liquid precursors in RF thermal plasma reactor

Micro- and nanosized zinc ferrite particles were prepared in RF thermal plasma conditions. Ethanol solutions of the mixture of zinc- and iron-nitrates were used as precursors. In the experiments, effects of synthesis conditions on the properties of products were investigated. The products were characterized for chemical and phase composition, morphology and magnetic properties. Zinc ferrite particles having ferrimagnetic properties were produced which refers to formation of zinc ferrites of inverse spinel structure in particular conditions.

Bioconcentration and depuration of copper, cadmium, and zinc mixtures by the freshwater amphipod Hyalella azteca

The uptake and elimination of copper (Cu), cadmium (Cd), and zinc (Zn) by the amphipod Hyalella azteca during exposure to the metals singly and in various combinations was examined in controlled laboratory experiments. In single metal exposures the accumulation of all metals was rapid and increased with exposure time. Copper elimination was slower compared to that for zinc and for cadmium no elimination was detected after 5 days in clean water. In the two-metal mixtures it appears that the presence of one metal influenced the bioconcentration of the other, since the bioconcentration factor (BCF) for copper was higher in the presence of cadmium than in the presence of zinc and in the case of cadmium, the decrease of K 1 values from cadmium single exposure to the binary and tertiary mixtures suggests possible inhibition of cadmium uptake by the other metals. In the case of the three-metal mixture the situation is less clear, with both increased and decreased BCFs recorded, in comparison to single-metal and two-metal mixtures, suggesting both stimulation and inhibition of metal accumulation.

Serendipitous SAD phasing of an echinomycin–(ACGTACGT)2bisintercalation complex

A new crystal form was obtained for the complex between (ACGTACGT)2 and echinomycin and X-ray data were collected to 1.6 A. The structure was phased by the SAD method based on a single unexpected anomalous scatterer that could be identified as a mixture of nickel and zinc by measurements of the anomalous scattering at different wavelengths. This cation is coordinated by two guanines from two different duplexes and four water molecules. The structure resembles previously reported crystal structures of DNA-echinomycin complexes, except that three of the eight base pairs flanking the echinomycin bisintercalator sites have the Watson-Crick rather than the Hoogsteen configuration. Hoogsteen binding was found for the corresponding base pairs of the crystallographically independent duplex, indicating that the two configurations are very close in energy.

Structure and mechanism of mouse cysteine dioxygenase.

Cysteine dioxygenase (CDO) catalyzes the oxidation of l-cysteine to cysteine sulfinic acid. Deficiencies in this enzyme have been linked to autoimmune diseases and neurological disorders. The x-ray crystal structure of CDO from Mus musculus was solved to a nominal resolution of 1.75 Angstroms. The sequence is 91% identical to that of a human homolog. The structure reveals that CDO adopts the typical beta-barrel fold of the cupin superfamily. The NE2 atoms of His-86, -88, and -140 provide the metal binding site. The structure further revealed a covalent linkage between the side chains of Cys-93 and Tyr-157, the cysteine of which is conserved only in eukaryotic proteins. Metal analysis showed that the recombinant enzyme contained a mixture of iron, nickel, and zinc, with increased iron content associated with increased catalytic activity. Details of the predicted active site are used to present and discuss a plausible mechanism of action for the enzyme.

The phase composition of a diffusion zinc coating alloyed with nickel on steel 20

Peculiarities of the phase composition of a corrosion-resistant coating at a steel 20 are investigated. The coating was formed by the solid-phase thermodiffusion in a mixture of zinc and nickel powders. An x-ray microspectral analysis of a transverse microsection showed that both the surface layer of the base metal and the coating itself are formed by two elements: iron and zinc taken in varying ratios. The contents of nickel in the coating and on its surface are considerably lower than its fraction in the starting mixture. Four phases were identified by means of layer-by-layer x-ray diffraction analysis from the substrate to the coating surface. The coating becomes single-phase only in its superficial layers.

Comparative toxicity of cadmium, zinc, and mixtures of cadmium and zinc to daphnids

Investigations were conducted to determine acute (48-h) effects of cadmium and zinc presented individually and in combination on Ceriodaphnia dubia, Daphnia magna, Daphnia ambigua, and Daphnia pulex. Toxicity tests were conducted with single metals to determine lethal effects concentrations (lethal concentrations predicted for a given percent [x] of a population, LCx value). These were used to derive metal combinations that spanned a range of effects and included mixtures of LC15, LC50, and LC85 values calculated for each metal and species. In single-metal tests, 48-h LC50 values ranged from 0.09 to 0.9 micromol/L and 4 to 12.54 micromol/L for cadmium and zinc, respectively. For each metal, D. magna was most tolerant and showed a different pattern of response from all others as determined by slope of concentration-response curves. In the combined metal treatments, all daphnids showed a similar pattern of response when LC15 concentrations were combined. This trend continued with few exceptions when LC15 concentrations of cadmium were combined with LC50 or LC85 values for zinc. However, when this treatment was reversed (LC15, zinc + LC50 or LC85, cadmium), responses of all species except D. magna indicated less-than-additive effects. For C. dubia, a near complete reduction in toxicity was observed when the LC15 for zinc was combined with LC85 for cadmium. Multimetal tests with D. magna did not differ from additive. Collectively, these studies suggest that D. magna may not be representative of other cladocerans.

Toxicity of cadmium and zinc mixtures to the decaudized cercarial life span of Diplostomum spathaceum

The effects of cadmium and zinc mixtures at concentrations ranging from 0.1 to 10,000 microg l(-1) on the life-span of decaudized cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum (Trematoda: Diplostomatidae) was investigated. Cercariae were exposed to metal mixtures of equal and unequal concentrations, and a low-dose pre-treatment followed by a high-dose exposure mixtures. Metal mixtures demonstrated variable effects on decaudized cercariae either by increasing or reducing their life-span compared to single metal exposures dependent on concentration and the type of mixed metal treatment. Prolonged exposure to equal metal mixtures at low concentrations (0.1-100 microg l(-1)) resulted in a reduction in the life-span of decaudized cercariae at 0.1 and 100 microg l(-1) in those individuals decaudized during the initial 24 h exposure period compared with those decaudized during the final 24 h period of cercarial survival, whilst in controls there was no significant life-span change between the two time periods. Decaudized cercariae which were exposed to low concentrations (0.1-100 microg l(-1)) of equal metal mixtures were also evaluated for their role as an indicator of larval 'fitness' for migrating through the tissues of their target fish host for those individuals decaudized during the initial 24 h exposure period, and demonstrated only a limited change in their life-span compared to control and single metal exposures. The importance of metal mixtures in parasite establishment in the fish host is discussed.

Synthesis of hollow microspheres of nickel using spheres of metallic zinc as templates under mild conditions

In recent years, hollow spheres of nanometer to micrometer dimensions have attracted special interests because of their potential applications in many areas [1, 2]. For example, they can serve as extremely small container for encapsulation which may benefit the control of delivery and release process of drugs and protection of environment-sensitive materials such as enzymes [3]. When it comes to fillers in making composite materials, hollow spheres can also show some advantages over their counterparts for their relatively low densities [4]. Various approaches have been proposed for preparing hollow spheres. For example, hollow polymer, oxide and glass composite spheres in micrometer-size range can be synthesized by physical methods such as spray drying techniques [5, 6]. Chemical methods can also be used to fabricate hollow spheres and soft template synthesis is a general one [7, 8]. For example, Micrometer-sized hollow spheres of CdS have been also been synthesized through an in situ source-template interface reaction route [9]. However, so far there are few reports on the fabrication of metal hollow spheres by chemical methods [10, 11]. Fortunately, a template-engaged method has been introduced recently and presents good prospect for the synthesis of metal hollow spheres by simple chemical methods [12]. But in this approach, only noble metals were used as templates and no further experimental data were given to prove the possibility of applying this method to other metals. Here our experiment will give a strong support to the generality of this method and provide a cheap approach to fabricate hollow nickle spheres for future industrial application. In our experiment, we utilize the replacement reaction between nickel and zinc to form nickel shells on the surfaces of zinc spheres by reacting nickel salt solution with solid template of zinc under carefully controlled conditions. Hollow nickel micrometer spheres were obtained by removing the residual cores of zinc and zinc oxide via washing with NaOH aqueous solution. In a typical experiment, 0.50 g zinc powders were first dispersed into 5 ml acetone, which was then added into 100 ml distilled water. After strongly stirring for 10 min, the mixture of zinc and water were kept for 40 s to separate the few large zinc spheres from the main part of zinc spheres by gravity, and then the suspended part

Effects of metal and organophosphate mixtures on Ceriodaphnia dubia survival and reproduction

The toxicity of mixtures of copper, zinc, and diazinon were determined for Ceriodaphnia dubia using 7-d survival and reproduction tests. Fifteen treatments, including combinations of the chemicals at 0, 25, 50, 75, and 100% of their individual median lethal concentrations, adding up to one toxic unit (TU) were tested. The TU was then used to classify each mixture response as additive, greater than additive, or less than additive. For survival, additive responses occurred in the 75% zinc plus 25% diazinon and the 50% copper plus 25% zinc plus 25% diazinon treatments. For reproduction, additive responses occurred in the 75% copper plus 25% zinc, 75% copper plus 25% diazinon, and 75% zinc plus 25% diazinon treatments. Copper and zinc played a greater role in toxicity than diazinon did. Less-than-additive interactions were found in all remaining mixtures, perhaps because of differences in mode of action between diazinon and metals. Consideration of dose-response curves can help to explain inconsistencies regarding toxic response in treatments with different ratios of the same chemicals. As TU percentages changed, mixture components were taken from different locations on differently shaped dose-response curves. Because most responses were less than additive, however, water-quality criteria based on individual concentrations probably are protective for most metal-organophosphate mixtures.

Interactive toxic effects of heavy metals and humic acids on Vibrio fischeri

The effect of humic acids (HAs) on the toxicity of copper, zinc, and lead was investigated using the photobacterium Vibrio fischeri (Microtox test) as a test organism. The effects of HAs on metal toxicity were evaluated as functions of time and concentration in pure compound solutions. The toxicities of copper and lead were generally comparable, while the toxicity of zinc was lower than those of the other two metals. The toxicity of copper decreased with the addition of HAs, while the toxicity of zinc remained almost constant. On the other hand, the toxicity of lead increased, depending on the concentration of HAs. The interactive effects between copper and zinc and between lead and zinc were synergistic, while the interactive effect between copper and lead on the bioluminescence of V. fischeri was additive. The presence of HAs caused relatively high toxicity reduction in the binary mixtures of zinc and copper or zinc and lead, while the toxicity reduction in the case of the binary mixture of copper and lead was negligible.

Amalgam: Eine Risikobewertung unter Berücksichtigung der neuen Literatur bis 2005

Amalgam, which has been in use in dentistry for 150 years, consists of 50 % elemental mercury and a mixture of silver, tin, copper and zinc. Minute amounts of mercury vapour are released continuously from amalgam. Amalgam contributes substantially to human mercury load. Mercury accumulates in some organs, particularly in the brain, where it can bind to protein more tightly than other heavy metals (e. g. lead, cadmium). Therefore, the elimination half time is assumed to be up to 1 - 18 years in the brain and bones. Mercury is assumed to be one of the most toxic non-radioactive elements. There are pointers to show that mercury vapour is more neurotoxic than methyl-mercury in fish. Review of recent literature suggests that mercury from dental amalgam may lead to nephrotoxicity, neurobehavioural changes, autoimmunity, oxidative stress, autism, skin and mucosa alterations or non-specific symptoms and complaints. The development of Alzheimer's disease or multiple sclerosis has also been linked to low-dose mercury exposure. There may be individual genetical or acquired susceptibilities for negative effects from dental amalgam. Mercury levels in the blood, urine or other biomarkers do not reflect the mercury load in critical organs. Some studies regarding dental amalgam reveal substantial methodical flaws. Removal of dental amalgam leads to permanent improvement of various chronic complaints in a relevant number of patients in various trials. Summing up, available data suggests that dental amalgam is an unsuitable material for medical, occupational and ecological reasons.

Under-film corrosion of epoxy-coated galvanised steel: An EIS and SVET study of the effect of inhibition at defects

In most metallic systems that are protected by organic coatings, the absolute performance depends not so much on the quality of the coating but more on the response of the coating to defects that are either initially present, or that arise in the course of service. Here we study inhibition at a controlled through-thickness defect in organic-coated galvanised steel thus exposing both a disc of bare steel (local cathode) and a surrounding annulus of zinc (local anode). Chemical species, leached from the organic coating, affect the local electrochemistry in this cell. Macroscopic electrochemical impedance (EIS) and a local scanning vibrating probe (SVET) were used to follow the progress of inhibition over a few days. Impedance data show a relatively rapid rise in both the charge transfer resistance and the Warburg (diffusional) impedance with exposure time confirming a rapid slowing of corrosion at the defect. SVET data illustrate clearly that the exposed zinc is a persistent local anode while the exposed steel is a persistent local cathode. Also, cathodic activity is seen to extend beneath the coating with increased time of exposure. A chromate-free inhibitor composition, containing a mixture of zinc, calcium and phosphate species, was found to perform with comparable efficiency to chromate.

Quantification of ternary mixtures of heavy metal cations from metallochromic absorbance spectra using neural network inversion.

A new method based on artificial neural networks (ANN) for the processing of spectrophotometric data is proposed and illustrated on the example of the simultaneous quantification of ternary mixtures of zinc, cadmium, and mercury cations in aqueous solutions. Three types of commercially available metallochromic indicators were used as a simple model setup to create spectral data analogous to those normally received from an optical sensor array. In conventional ANN training methods for chemical sensors based on spectrophotometric data, a calibration is established by mathematically correlating the measured optical signal as network input with the concentration of the calibration sample as network output. In several situations, however, especially when dealing with mixed sample solutions, the relationship between a measured absorption spectrum and the corresponding ion concentrations is ambiguous, resulting in an "ill-posed problem". On the other hand, if the training direction is reversed by correlating known sample concentrations with measured optical signals, the relationship becomes reasonable for the ANN to obtain its structure. The proposed model illustrated in this paper is based on a more reasonable direct mapping and estimation by artificial neural network inversion (ANNI). In the training step, sample mixtures of known concentrations are optically measured to construct networks correlating the input data (ion concentrations) and the output data (absorption spectra). In the estimation step, the ion concentrations of unknown samples are estimated using the constructed ANN. The measured spectra of the unknown samples are fed to the output layer, and the appropriate input concentrations are determined by ANNI. When training the ANN system with 143 ternary mixtures of Zn2+, Cd2+, and Hg2+ in a concentration range from 1 to 100 microM, root-mean-square errors of prediction (RMSEP) of 0.45 (Zn2+), 0.96 (Cd2+), and 0.32 microM (Hg2+) were observed for the estimation of concentrations in 30 test samples, using the ANNI procedure. This newly proposed model, which involves the construction of an ANN based on direct mapping and estimation by ANNI, opens up one way to overcome the limitations of nonselective sensors, allowing the use of more easily accessible semiselective receptors to realize smart chemical sensing systems.

Evidence of Metal Interaction in the Bioaccumulation of Cadmium and Zinc in Porcellio Laevis (Isopoda) after Exposure to Individual and Mixed Metals

The aim of this study was to determine the accumulation of cadmium and zinc in Porcellio laevis after separate and mixed exposure to these metals. This would give an indication whether cadmium and zinc influence each other’s bioaccumulation. Decaying oak leaves collected from an uncontaminated site (Botanical Gardens of the University of Stellenbosch) were used as substrate in the experiments. The concentrations used were 20, 80 and 160 mg kg−1 (dry mass) cadmium sulphate and 1000, 4000 and 8000 mg kg−1 (dry mass) zinc sulphate. These metals were administered separately and mixed in the experiments. The cadmium and zinc mixtures used were 20 mg kg−1 CdSO4 with 1000 mg kg−1 ZnSO4, 80 mg kg−1 CdSO4 with 4000 mg kg−1 ZnSO4 and 160 mg kg−1 CdSO4 with 8000 mg kg−1 ZnSO4. It was shown that cadmium and zinc accumulated in P. laevis, especially in the hepatopancreas, in both the single-metal and mixed-metal exposures. Cadmium and zinc also exhibited the ability to influence the bioaccumulation of each other in the mixed-metal exposures. It is also concluded that the interaction of these two metals is at least partly dependent on the ratio of exposure concentrations, the actual exposure concentrations, and also the period of exposure.

Organic p-i-n solar cells

We introduce a p-i-n-type heterojunction architecture for organic solar cells where the active region is sandwiched between two doped wide-gap layers. The term p-i-n means here a layer sequence in the form p-doped layer, intrinsic layer and n-doped layer. The doping is realized by controlled co-evaporation using organic dopants and leads to conductivities of 10-4 to 10-5 S/cm in the p- and n-doped wide-gap layers, respectively. The photoactive layer is formed by a mixture of phthalocyanine zinc (ZnPc) and the fullerene C60 and shows mainly amorphous morphology. As a first step towards p-i-n structures, we show the advantage of using wide-gap layers in M-i-p-type diodes (metal layer–intrinsic layer–p-doped layer). The solar cells exhibit a maximum external quantum efficiency of 40% between 630-nm and 700-nm wavelength. With the help of an optical multilayer model, we optimize the optical properties of the solar cells by placing the active region at the maximum of the optical field distribution. The results of the model are largely confirmed by the experimental findings. For an optically optimized device, we find an internal quantum efficiency of around 82% under short-circuit conditions. Adding a layer of 10-nm thickness of the red material N,N′-dimethylperylene-3,4:9,10-dicarboximide (Me-PTCDI) to the active region, a power-conversion efficiency of 1.9% for a single cell is obtained. Such optically thin cells with high internal quantum efficiency are an important step towards high-efficiency tandem cells. First tandem cells which are not yet optimized already show 2.4% power-conversion efficiency under simulated AM 1.5 illumination of 125 mW/cm2 .

Inhibition of steel and galvanised steel corrosion by zinc and calcium ions in the presence of phosphate

Mixtures of zinc, calcium and phosphate ions have been found to be effective (>90%) in inhibiting the corrosion of steel and zinc during immersion in acid rain solution and when used as pigment additions to organic coatings. The presence of calcium ions, in addition to zinc ions, appears to be fundamental in the inhibition mechanism since, in the absence of calcium, the inhibition efficiency is 50% or less. Although some anodic inhibition occurs, the predominant mechanism appears to be classical cathodic inhibition caused by the precipitation of a sparingly soluble, thin, but persistent, solid film. Surface analysis, by XPS, confirms that phosphorus is present in the form of phosphate species containing zinc and calcium. Also, the atomic ratios of zinc:calcium:phosphorus present in the inhibitive film strongly suggest that it consists of a mixture of CaZn2(PO4)2 (Scholzite) and Zn3(PO4)2 (Hopeite) in a 1 : 1 ratio.