Copper Substitution Research Articles

Influence of Copper Substitution on the Interaction of Ethylene over Iron Clusters: A Theoretical Study

We report the results of density functional theory (DFT) calculations of ethylene adsorption over the most stable pure and bimetallic clusters of Fe(n)Cu(m) (2 ≤ m+n ≤ 4), in two adsorption modes of π and di-σ. Our results show that the quality of interaction of ethylene with iron center in bimetallic clusters of iron-copper is characteristically different from what is found over pure iron. Over the range of our studies for dimers, trimers, and tetramers, whether for π or di-σ mode, alloying iron clusters results in a substantial improvement in adsorption of ethylene over cluster and exhibits a notable increase in binding and interaction energies compared with pure iron clusters. One of the interesting features of this adsorption is that ethylene never orients toward di-σ mode for Cu-Cu or Fe-Cu bonds, and π orientation is strongly preferred. Ethylene adsorption in di-σ coordination is accompanied by the sever restructuring, larger deformation energy, and the larger interaction energy. In the next part, we answer this question of how electronic perturbations induced by copper atoms can enhance the activity of iron toward ethylene. This interpretation is done within the framework of natural bond orbital (NBO) and natural resonance theory (NRT) analyses. Different reaction pathways detected by NRT analysis (donor-acceptor, metallacyclic, and carbanion) reveal interesting aspects of differences between the nature of metal-alkene coordination in bimetallic and purely metallic clusters.

Phase transitions of (Cu,Ni)3TeO6 solid solutions

(Cu,Ni)3TeO6 solid solutions with the bixbyite (pseudocorundum) and ilmenite structures have been prepared by solid-state reactions and characterized by a variety of techniques. We have studied the effect of nickel substitution for copper on the phase composition of the materials, examined the microstructure of ceramic samples, and measured their magnetic susceptibility, heat capacity, permittivity, and loss tangent as functions of temperature. This allowed us to reveal dielectric anomalies related to structural phase transitions and to determine the antiferromagnetic ordering temperatures of the (Cu,Ni)3TeO6 ceramics.

Effect of Cu-doping on the electronic structure and optical properties of LaNi 5

Optical properties of intermetallic isostructural compounds LaNi 5− x Cu x ( x = 0, 0.6, 1, 1.2) have been studied in the spectral range from 0.22 to 15 μm using the ellipsometry method. It was found that the substitution of copper for nickel leads to local changes in the optical conductivity spectra. Theoretical calculations of the electronic structure and interband optical conductivity of LaNi 5− x Cu x compounds with x = 0, 1, 2, 3 were performed in the generalized gradient approximation within the pseudopotential plane-wave method PWSCF. Both the optical spectroscopic measurements and theoretical calculations demonstrate the presence of a broad absorption band around 4 eV associated with the Cu 3d → Ni 3d electron transitions and increasing with the growth of copper content.

Chalcopyrite formation through the metathesis of pyrrhotite with aqueous copper

The heterogeneous chemical environment which develops in the heap leaching of some pyrrhotite-containing copper ores can promote covellite and chalcopyrite formation particularly in acid-depleted regions of a heap. In such circumstances, copper recovery will be delayed until the acid and oxidation fronts move through the bed of ore and these secondary copper sulfides are re-leached. The transition from pyrrhotite to chalcopyrite most probably follows the sequence, pyrrhotite to copper-pyrrhotite to unnamed mineral CuFe 3S 4 to isocubanite to chalcopyrite, with a major structural expansion occurring prior to CuFe 3S 4. The mechanism is one in which copper is incorporated into pyrrhotite, which maintains its NiAs-type structure up to a stability limit, above which the structure rearranges to a chalcopyrite-like structure followed by isomorphic substitution of copper for iron. The structural rearrangement proceeds with significant expansion in one of the hexagonal axis directions and contractions in the other directions. Depending on the orientation, this expansion induces different levels of strain in the product chalcopyrite. The level of strain subsequently impacts on the rate of chalcopyrite metathesis to covellite. The depth of chalcopyrite formation into the pyrrhotite varies with pyrrhotite orientation.

Effect of cobalt incorporation in copper-ceria based anodes for hydrocarbon utilisation in Intermediate Temperature Solid Oxide Fuel Cells

MCuCo40 (CuCo-CeO 2, 40 at.% metal load, 1/1 Cu–Co atomic ratio), synthesised by inverse microemulsion method, was evaluated as the anode for SOFC at intermediate temperature. This material presents optimal physicochemical and electrical characteristics as well as excellent thermal and chemical compatibility with 8YSZ electrolyte. The evaluation of single-cell performance, with 8YSZ electrolyte and LSM cathode and this anode material, operating in H 2 and methane fuels, in comparison with a similar single-cell using Cu-ceria-based anode allows to conclude that the substitution of copper (20 at.%) by cobalt in the anode composition enhances the single cell performance as well as reduces the carbon deposit formation on the anode after running on hydrocarbon fuels (methane).

Optical Properties and Electronic Structure of LaNi<sub>5-X</sub>Cu<sub>x</sub> (x=0–1.2) Intermetallic System

Optical properties of the LaNi5-xCux (x = 0, 0.6, 1, 1.2) compounds were studied. It was shown that substitution of copper for nickel led to noticeable changes in the optical conductivity spectra. Calculations of the electronic structure of compounds with x = 0, 1, 2 were performed using a generalized gradient approximation. The interband optical conductivity of these intermetallics was calculated. The optical ellipsometrical measurements and theoretical calculations testify to the appearance of a broad absorption structure associated with the Cu 3d  Ni 3d electron transitions and increasing with the growth of copper content.

Structure and IRR spectra of copper-exchanged soda-lime silica glass

Multi-component soda lime silica glass (SLSG) specimens, with composition from the miscibility gap in the SiO2-Na2O system, were investigated after the substitution of copper for sodium and after thermal treatment of the exchanged samples in gaseous hydrogen. The behaviour of the obtained composite materials was studied by infrared reflection spectroscopy (IRRS). Some optical absorption micro-spectrophotometry (OAMS) measurements and X-ray-diffraction (XRD) analyses complemented these investigations. It has been stated that after exchange in the CuCl molten bath, the dopant was present in the glassy matrix in the form of cuprous and cupric ions. The cuprous ions participate in the formation of semiconducting Cu2O nanoparticles. Hydrogenation of the exchanged specimens leads to the formation of metallic copper atoms which due to the van der Waals interactions precipitate in the form of colloidal copper nanoparticles. Changes of the matrix morphology are mainly related with the presence of cupric ions which behave as glass forming cations and such as these participate in the formation of mixed copper-sodium silicates. The effectiveness of these processes is substantially dependent on the exchange and hydrogenation parameters.

THE CRYSTAL CHEMISTRY OF COSALITE BASED ON NEW ELECTRON-MICROPROBE DATA AND SINGLE-CRYSTAL DETERMINATIONS OF THE STRUCTURE

Crystal-structure refinements done on six samples of cosalite with different types and degrees of copper and silver substitutions, as well as electron-microprobe studies of 33 different samples of cosalite, both enlarged and clarified the spectrum of cation substitutions and the crystal chemistry of this species. The Ag + Bi ↔ 2Pb scheme of substitution acts at the structural site Me 1. The 2(Cu + Ag) ↔ Pb scheme is a result of two combined mechanisms: creation of vacancies in the Bi-containing octahedral site Me2 accompanied by a progressive occupancy of two triangular faces of this octahedron by Cu + Ag [ i.e. , Bi ↔ 2(Cu + Ag)], which is combined with progressive replacement of Pb in the adjacent Me 1 octahedron by Bi; their combination gives the resulting closely followed chemical relationship. The structural mechanism of the 3Cu ↔ Bi substitution observed in thin zones in cosalite from Felbertal remains unknown. Cosalite offers a unique case of solid solution based on a combined omission – interstitial insertion substitution.

ChemInform Abstract: Hall Effect in Iron-Doped Bi1.6Pb0.4Sr2Ca2Cu3Oy Superconductors.

Abstract Hall effect and resistivity studies have been performed on Bi1.6Pb0.4Sr2Ca2Cu3−x,FexOy superconductor samples (x = 0-0.3) from liquid nitrogen to room temperature. The transition temperature, resistivity and carrier concentration of the doped superconductors are observed to decrease systematically with doping concentration. The Hall number of a unit cell is observed to reach nearly unity at higher concentrations of iron. Similarly to the undoped sample, the Hall coefficient RH of doped samples varied linearly with temperature until a particular doping concentration (x = 0.07) and then showed a lesser temperature dependence. Different possibilities such as skew scattering, the presence of multiple bands and coupling, between CuO planes are discussed in order to understand the temperature variation of RH. The Hall mobility of the carriers is understood as being due to electron-phonon and electron-electron scattering, except for the highest concentration of iron (x = 0.3) when an additional scattering mechanism is expected. The results are explained in terms of defects arising from the substitution of copper by iron.

ChemInform Abstract: Georgeite and Azurite as Precursors in the Preparation of Co- Precipitated Copper/Zinc Oxide Catalysts.

Abstract Georgeite, a recently identified basic copper carbonate mineral, can be synthesised in aqueous solutions from copper salts. It has now been shown that a zincian georgeite (i.e. georgeite with some substitution of copper by zinc) is formed by precipitation with sodium carbonate in copper-zinc systems. Conversion of zincian georgeite to a malachite phase in an aqueous medium occurs more slowly than the equivalent conversion of pure copper georgeite. The possibility of georgeite formation as a precursor to malachite in the manufacture of copper/zinc catalysts is discussed: it is suggested that the blue/green colour transition seen during the ageing of precipitated copper/zinc catalyst precursors can be attributed to the conversion of georgeite to malachite. Synthetic azurite materials, with and without zinc inclusion, were prepared from aqueous suspensions of georgeite with azurite seeding under 40 bar carbon dioxide. These were used as precursors to prepare active copper/zinc catalysts but their performance was inferior to that of a conventional catalyst.

The solid solution Gd2NixCu2−xMg: Large reversible magnetocaloric effect and a drastic change of the magnetism by substitution

Various samples of the solid solution Gd2NixCu2−xMg were synthesized from the elements in sealed tantalum ampoules in an induction furnace. All members crystallize with the tetragonal Mo2FeB2 type structure, space group P4/mbm, and they were characterized on the basis of Guinier powder patterns and energy dispersive X-rays analyses. The lattice parameters decrease with increasing nickel content in a Vegard-like manner. The Gd2NixCu2−xMg samples show Curie–Weiss behavior with slightly higher magnetic moment values than the theoretical one for a free Gd3+ ion. The substitution of copper by nickel has a drastic influence on the magnetism and magnetic ordering temperature. For Gd2Ni0.5Cu1.5Mg a temperature induced FM→AFM order-to-order transition was observed, whereas Gd2Ni1.0Cu1.0Mg is a metamagnet with HCr of about 8 kOe at 5 K. For both compounds, a large reversible magnetocaloric effect (MCE) near their ordering temperatures occurs. The values of the maximum magnetic entropy change −ΔSMmax reach 9.5 and 11.4 J kg−1 K−1 for the field change of 5 T with no obvious hysteresis loss around 65 K for Gd2Ni0.5Cu1.5Mg and Gd2Ni1.0Cu1.0Mg, respectively. The corresponding relative cooling power with 688 and 630 J kg−1 is relatively high as compared to other MCE materials in that temperature range. These results indicate that Gd2NixCu2−xMg could be a promising system for magnetic refrigeration at temperatures below liquid N2.

Influence of copper substitution on structural, electrical and dielectric properties of Ni (1− x) Cu xMn 2O 4 (0 ≤ x ≤ 1) ceramics

Copper substituted polycrystalline nickel manganite viz. Ni (1− x) Cu x Mn 2O 4 (0 ≤ x ≤ 1) ceramics were prepared by oxalate process. The replacement of nickel by copper plays an important role in changing the lattice parameter, X-ray density, sintered density, porosity, grain size, DC resistivity at different temperatures, drift mobility and dielectric properties at different frequencies. The lattice parameter and crystallite size decreases with increase in copper content. The addition of copper promotes grain growth, decrease in porosity and increase in sintered density. The room temperature DC electrical resistivity decreases from 43.50 to 32.92 MΩ cm and dielectric constant increases from ∼2 × 10 3 to 3 × 10 5 at low frequency (20 Hz) as copper concentration increases.

Influence of copper substitution on magnetic and electrical properties of MgCuZn ferrite prepared by microwave sintering method

Polycrystalline MgCuZn ferrites with chemical formula Mg 0.50-xCu xZn 0.50Fe 2O 4 ( x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) were prepared by microwave sintering method. These powders were calcined, compacted and sintered at 950 °C for 30 min. Structural, microstructural and elemental analyses were carried out using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectrometry (EDS), respectively. The lattice parameter is found to increase with increasing copper content. A remarkable densification is observed with the addition of Cu ions in the ferrites. The sintered ferrite was characterized for initial permeability, dielectric constant and dielectric loss tangent and ac conductivity measurements. The temperature variation of the initial permeability of these samples was carried out from 30 °C to 200 °C. The dielectric constant, dielectric loss tangent and ac conductivity have been measured in the frequency range of 100 Hz to 1 MHz. Initial permeability and dielectric constant were found to increase and dielectric loss decreased with Cu substitution for Mg, up to x = 0.20. The ferrite powder prepared is suitable for the application in multilayer chip inductor due to its low-temperature sinterability, good magnetic properties and low loss at high frequency.

Copper substituted heteropolyacid catalysts for the selective dehydration of ethanol

The catalytic conversion of ethanol was carried out over H 3PMo 12O 40· xH 2O (H 3PMo) and its substituted copper ions with formula Cu 0.5 x H 3− x PMo 12O 40 (where x = 1, 2 and 3). Pure and Cu-substituted catalyst samples were calcined at 350 °C. The effect of copper ions substitution on the thermal behaviour, structural, acidic, surface and catalytic properties of the investigated samples were studied using TG, DSC, FTIR, pyridine adsorption at 25 °C, N 2 adsorption at −196 °C. Maximum selectivity of diethyl ether and the second major reaction product ethylene was obtained at 350 °C. The substitution of copper in the H 3PMo resulted in increase of the selectivity towards diethyl formation to attain a maximum value using Cu 2PMo-350 catalyst. Very high diethyl ether over ethylene yield values obtained in this study at 350 °C are highly promising for the production of petrochemicals from ethanol.

Copper flows in buildings, infrastructure and mobiles: a dynamic model and its application to Switzerland

During the last century, the consumption of materials for human needs increased by several orders of magnitude, even for non-renewable materials such as metals. Some data on annual consumption (input) and recycling/waste (output) can often be found in the federal statistics, but a clear picture of the main flows is missing. A dynamic material flow model is developed for the example of copper in Switzerland in order to simulate the relevant copper flows and stocks over the last 150 years. The model is calibrated using data from statistical and published sources as well as from interviews and measurements. A simulation of the current state (2000) is compared with data from other studies. The results show that Swiss consumption and losses are both high, at a level of about 8 and 2 kg/(cap year), respectively, or about three times higher than the world average. The model gives an understanding of the flows and stocks and their interdependencies as a function of time. This is crucial for materials whose consumption dynamics are characterised by long lifetimes and hence for relating the current output to the input of the whole past. The model allows a comprehensive discussion of possible measures to reduce resource use and losses to the environment. While increasing the recycling reduces losses to landfill, only copper substitution can reduce the different losses to the environment, although with a time delay of the order of a lifetime.

EFFECT OF COPPER OXIDE ON THE GRAIN GROWTH AND INITIAL PERMEABILITY OF Mg–Cu–Zn FERRITES

The microstructure and magnetic properties of Mg – Cu – Zn ferrites prepared by using solid-state reaction method have been investigated. X-ray diffraction (XRD), a scanning electron microscope (SEM), impedance analyzer and a vibrating sample magnetometer (VSM) were utilized in order to study the effect of copper substitution and its impact on the crystal structure, grain size, microstructure and magnetic properties of the Mg – Cu – Zn ferrite. The formation of cubic spinel phase was identified using XRD technique. The microstructures of the samples show that the grain growth is greatly enhanced by the addition of CuO which is attributed to the liquid phase during sintering. The average grain size (Dm) increases significantly with increasing Cu content. The initial permeability (μ') of the samples increases appreciably with increasing Cu content which is attributed to the increase of grain size and density of the samples. The resonance frequency (fr) of the samples shifts toward the lower frequency as the Cu content increases. The sharp fall of μ' in μ'-T curves is observed for all the samples which indicate the homogeneity of the samples. The saturation magnetization (Ms) of the Mg – Cu – Zn ferrites increases slightly with increasing Cu concentration.

Ferromagnetic Cu and Al doped ZnO thin films by PLD

The present study is focused on the detailed characterization of (ZnO)1−x(CuO)x(Al2O3)0.002 bulk samples and their thin films. XRD of bulk samples showed ZnO peaks without impurity phase which indicates maximum substitution of copper inside the ZnO lattice. Raman spectra showed a random shift of modes which might be due to point defects created by copper and aluminium substitution in ZnO. VSM showed weak ferromagnetic behavior in samples indicating Cu ion substitution in ZnO. XPS further confirmed the presence of Cu+2 states in the bulk samples. After detailed characterization of bulk samples, these samples were utilized as targets for deposition of thin films using PLD technique. Highly crystalline films of doped ZnO with (002) orientation were grown on (100) Si substrates. Compositional analysis of thin films done by XPS showed the presence of Cu+2 ions which is the source of ferromagnetism in our thin film samples. M-H curves showed the ferromagnetic behavior for the films. Thin films are magnetic and conductive at room temperature.

Effect of Copper Substitution and Preparation Methods on the LaMnO3±δ Structure and Catalysis of Methane Combustion and CO Oxidation

Abstract LaMn 1− x Cu x O 3± δ perovskite oxides ( x = 0, 0.2, 0.4, 0.6, 0.8, 1) were prepared by two different methods, the Pechini and sol-gel methods. The catalysts were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray fluorescence spectroscopy, N 2 adsorption, and temperature-programmed reduction. Their catalytic activity in the oxidation of methane and CO was evaluated. EDS and SEM results showed that the Pechini samples had more homogeneity and smaller particles (higher specific surface area). The catalytic activity for methane combustion was highest for x = 0.2. In CO oxidation, the oxides with x = 0.2 and x = 0.4 were the most active. The Pechini samples had higher activity and stability than the sol-gel samples.

A study on Cu substituted Ni–Cu–Zn ferrites synthesized using egg-white

This paper examines the effect of copper substitution on the structural and magnetic properties in nano-crystalline ferrite series of nominal composition; Ni0.7−xCuxZn0.3Fe2O4 (where x = 0.1–0.6) synthesized by a simple method using metal nitrates and freshly extracted egg-white. X-ray diffraction measurements (XRD) confirmed the formation of single-phase cubic spinel structure. The average crystallite size was calculated using XRD pattern and confirmed by transmission electron microscope (TEM). The nearly constant lattice parameters obtained with Cu substitution was attributed to the small difference in the ionic radius between Ni2+ and Cu2+ ions. FT-IR spectra showed two absorption bands assigned to the tetrahedral and octahedral complexes. The effect of Cu concentration on the magnetic properties was investigated using vibrating sample magnetometer (VSM) and molar magnetic susceptibility measurements. The decrease in the saturation magnetization and the Curie temperature values with increasing Cu content was explained in terms of the magnetic moments and magnetic exchange interaction existing between the antiparallel uncompensated electron spin of A and B sublattices. The magnetic measurements also proved that the entire preparation method has a great effect on enhancing the magnetic properties of the system.

Copper substitution alone and in the presence of chromium, zinc, cadmium and lead in goethite (α-FeOOH)

AbstractA series of Cu-substituted goethites, single and co-substituted with Cr, Zn, Cd and/or Pb was prepared, having molar ratios equal to 2.00, 3.33 and 5.00 mol%. All the samples contained only goethite, except Cu-, (Cu,Zn)- and (Cu,Pb)-samples synthesized at 5.00 mol% where hematite was also formed. The presence of Cr/Cd suppressed the hematite-forming effects of Cu. The general sequence of metal entry into the single-metal-substituted goethites was Zn = Cr > Cd > Cu > Pb and in di- (5.00 mol%) and tri- (3.33 mol%) metal-substituted goethites was Cu > Zn > Cd > Cr >> Pb. Cu incorporation increased all the unit-cell parameters in single-metal-substituted goethite, and these parameters increased in combination with other metals as follows: Cd > Zn > Cr > Pb in the multimetal-substituted goethites. The Cu-substituted goethite dissolved faster than pure goethite. Co substitutions of Cr/Pb reduced the dissolution rate (kFe), while substitutions of Cd/Zn increased kFe.