Metallic Copper Oxide Research Articles

Effect of deposition temperature on the physical properties of RF magnetron sputtered Ag–Cu–O films with various Cu to Ag ratios

AbstractThin films of Ag–Cu–O were deposited on glass substrates held at various temperatures in the 303–523 K range by RF magnetron sputtering of Ag90Cu10, Ag80Cu20 and Ag70Cu30, and elemental copper and silver targets in an oxygen partial pressure of 2 × 10−2 Pa and sputtering pressure of 4 Pa. The deposited films were characterised by energy dispersive X‐ray analysis, X‐ray diffraction (XRD), atomic force microscopy, UV–Vis–NIR spectroscopy and employing four‐point probe method. The atomic ratio of Cu/Ag in the films formed at 303 K was in correlation with the composition of the starting sputter targets. The increase in substrate temperature induced the decomposition of the Ag–Cu–O films into a mixture of metallic silver and copper oxide. The electrical resistivities of silver oxide and copper oxide films formed at 303 K were 3 × 10−3 Ω cm and 29 Ω cm, respectively. The electrical resistivity of the films formed with Ag70Cu30 target at 303 K was 8.2 Ω cm and it decreased to 2.4 Ω cm with increase in substrate temperature to 523 K due to structural changes in the films. The optical band gap of the Ag–Cu–O films formed at 303 K increased from 1.60 to 1.95 eV with the increase of copper to silver atomic ratio from 0.10 to 0.30 in the films. The optical band gap of the films formed with Ag70Cu30 target increased from 1.95 to 2.15 eV with the increase in substrate temperature from 303 to 523 K, respectively.

Destruction of Polychlorinated Aromatic Compounds by Spinel-Type Complex Oxides

Destruction of polychlorinated aromatic compounds was carried out over spinel-type catalysts XY2O4 (where X = Mg, Ca, Cu, Ni, Zn, and Y = Al, Fe). The catalysts were characterized by XRD, nitrogen adsorption-desorption isotherms and FTIR. The performance of these catalysts toward the decomposition of hexachlorobenzene (HCB) and octachlorodibenzo-p-dioxin (OCDD) was evaluated in a closed system. The spinel-type catalyst with mesoporous structure demonstrated high catalytic activity for the hydrodechlorination of polychlorinated aromatic compounds. Among them, the copper-aluminum spinel (CuAl2O4), specifically calcined at 600 degrees C, exhibited the best activity. More than 85% dechlorination efficiency of HCB and 99% decomposition of polychlorinated dibenzodioxin (PCDD) were achieved at 250 degrees C for 30 min over the above catalyst which was more effective than the corresponding metallic copper and copper oxide catalysts during the thermal degradation of polychlorinated aromatic compounds. The correlation of catalytic performance to structural characteristics is discussed based on the detailed characterization. The simple preparation procedure and reasonable cost of the spinel-type catalysts present a good potential for the thermal treatment of polychlorinated aromatic pollutants at lower temperatures.

A novel method for manufacturing of aluminum foam sandwich panels

AbstractIn this study, a novel method for manufacturing aluminum foam sandwich (AFS) panels via self‐propagating high temperature synthesis (SHS) has been introduced and investigated. In this method, a powder mixture of metallic aluminum and copper oxide was placed in core–sheet interface. Sandwich panel was then heated under static pressure. During heating, SHS reaction (3CuO + 2Al = Al2O3 + 3Cu, ΔH < 0) occurred in the interface. The generated heat from this exothermic reaction caused sheets to join the core by melting the interface and nearby. In order to evaluate the shear strength of the interface, the shear test was applied on manufactured sandwich panels, and its results were compared with those obtained from testing the sandwich panels which were produced by diffusion bonding process. Furthermore, by the aid of energy dispersive spectrometer (EDS) and X‐ray diffraction (XRD) analyses, the formation of copper in the core–sheet interface and its diffusion into the sheets and the core were investigated. In addition, by plotting the hardness values of the panels' sheets across distance, it was found that the generated heat of the exothermic reaction caused a local melting of the panel sheets and the core. These results approved that core to sheet joining in metal foam sandwich panels took place because of the SHS reaction. Significantly, this new method could be applied as a proper and alternative method for production of AFS panels. Copyright © 2010 John Wiley & Sons, Ltd.

Direct synthesis and characterization of novel homo- and heterometallic mixed-ligand tetrazolate complexes, Cu(en)(tz)2 and Cu(en)2Zn(tz)4 [en=ethylenediamine, tz=tetrazolate

Abstract For the first time, tetrazolate complexes have been prepared by direct synthesis. Two novel homo- and heterometallic mixed-ligand complexes, Cu(en)(tz)2 and Cu(en)2Zn(tz)4, have been synthesized using tetrazole (Htz), ethylenediamine (en), metallic copper and zinc oxide as starting materials. Both tetrazolates were characterized by single-crystal X-ray diffraction, IR spectroscopy and thermal analysis. The complexes present 1D coordination polymers, with tetrazolate anions acting as both monodentate and bridging ligands.

Surface Characteristics, Copper Release, and Toxicity of Nano‐ and Micrometer‐Sized Copper and Copper(II) Oxide Particles: A Cross‐Disciplinary Study

An interdisciplinary and multianalytical research effort is undertaken to assess the toxic aspects of thoroughly characterized nano- and micrometer-sized particles of oxidized metallic copper and copper(II) oxide in contact with cultivated lung cells, as well as copper release in relevant media. All particles, except micrometer-sized Cu, release more copper in serum-containing cell medium (supplemented Dulbecco's minimal essential medium) compared to identical exposures in phosphate-buffered saline. Sonication of particles for dispersion prior to exposure has a large effect on the initial copper release from Cu nanoparticles. A clear size-dependent effect is observed from both a copper release and a toxicity perspective. In agreement with greater released amounts of copper per quantity of particles from the nanometer-sized particles compared to the micrometer-sized particles, the nanometer particles cause a higher degree of DNA damage (single-strand breaks) and cause a significantly higher percentage of cell death compared to cytotoxicity induced by micrometer-sized particles. Cytotoxic effects related to the released copper fraction are found to be significantly lower than the effects related to particles. No DNA damage is induced by the released copper fraction.

Aerosol assisted chemical vapour deposition of Cu–ZnO composite from single source precursors

Two heterobimetallic precursors [Zn(TFA)3(micro-OH)Cu3(dmae)3Cl].THF (1) and [Zn(TFA)4Cu3(dmae)4] (2) [dmae=N,N-dimethylaminoethanolate and TFA=trifluoroacetate], have been synthesized and characterized by their melting points, elemental analysis, FT-IR spectroscopy, mass spectrometry, TGA and single crystal X-ray diffraction methods. Both complexes were used to deposit thin films of Cu-ZnO composite on glass substrates by aerosol assisted chemical vapor deposition (AACVD) method. The films were characterized by "scotch tape" test for adhesion, thickness measurement as a function of temperature, EDX for composition, SEM for surface morphology and XRD for crystalline phases. Thin film deposition studies at 250, 325, 400, 475 degrees C indicated the increase in thickness with temperature reaching a maximum at 400 degrees C and then decreasing. EDX and PXRD results showed the uniform distribution of cubic metallic copper and hexagonal zinc oxide phases which make them useful for nanocatalysis on structured surfaces.

X-ray absorption spectroscopy study of valence and site occupation of copper inLiNbO3:Cu

The average formal oxidation state of Cu in lithium niobate (LN) crystals doped with different copper levels (0.1--0.7 wt %), as well as in oxidized and reduced copper-doped LN crystals, is determined by x-ray and uv-visible and ir absorption spectroscopy and found to vary between $1.2\ifmmode\pm\else\textpm\fi{}0.2$ and $1.8\ifmmode\pm\else\textpm\fi{}0.2$. The average formal oxidation state of Cu does not notably depend on the Cu concentration (for the range 0.1--0.3 wt %) upon simultaneous diffusion and oxidation of the doped crystals; but it does depend on the Cu concentration upon simultaneous reduction of the doped crystals. The x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure analyses of the spectra measured at the Cu $K$ edge provide evidence that all copper atoms are incorporated predominantly onto Li sites. Two distinct sites can be distinguished, ${\text{Cu}}^{2+}$ and ${\text{Cu}}^{1+}$ sites, coordinated sixfold and twofold by oxygen atoms, respectively. This result is supported by calculations of Cu $K$ XANES spectra with the FEFF8.2 code. No experimental evidence is found for formation of metallic copper or copper oxide clusters in the LN crystals. One of the charge compensation mechanisms upon reduction of the LN crystals is outgassing of O atoms. Reduction of the Nb formal oxidation state is likely for total charge compensation. However, Nb ${L}_{\text{III}}$ XANES and ir absorption studies do not provide any evidence for this.

LUSTRE COLOUR AND SHINE FROM THE OLLERIES XIQUES WORKSHOP IN PATERNA (SPAIN), 13TH CENTURY AD: NANOSTRUCTURE, CHEMICAL COMPOSITION AND ANNEALING CONDITIONS*

Lustre is a medieval ceramic decoration, corresponding to a nanostructured thin layer formed by metallic copper and silver nanocrystals embedded in a glass matrix, which required deep knowledge on the part of the artisans with regard to the raw materials used and the kiln conditions. Their empirical knowledge led to the achievement of colourful lustre decorations ranging from reddish to yellowish or even greenish, some of them with a metallic shine with an associated purplish iridescence. Lustre ceramics dating from the 13th century from the Olleries Xiques workshop in Paterna (Spain) have been studied, linking their chemical composition and nanostructure with their colours and shine. Two kinds of nanostructures are found, yellowish lustre decoration constituted by a silver metal–glass nanocomposite, and reddish lustre decoration constituted by metallic copper nanocrystals and copper oxide nanocrystals; in some cases, metallic copper nanocrystals covered with an oxidized shell of CuO and partly Cu2O have been found. However, even with significant amounts of copper oxide, the lustre still exhibits a copper metal‐like shine. The bluish iridescence observed at a specular angle in the lustre could not be explained completely by means of the chemical composition, and metallic silver nanoparticle light scattering is proposed as a possible explanation.

Comparing CuAPO-5 with Cu:ZSM-5 in the Selective Catalytic Reduction of NOx: An in situ Study

The CuAPO-5 and Cu:ZSM-5 systems are compared in the selective catalytic reduction (SCR) of NOx. Within the Cu:ZSM-5 system materials with high and low metal contents were prepared by hydrothermal and conventional ion exchange, respectively. X-ray absorption spectroscopy (XAS) was used to follow changes in the valence state and the local environment of copper as the different materials reacted with the individual components of this particular deNOx process. This was effected by measuring the XAS spectra after each consecutive stage of the treatment with propene and NOx. In the CuAPO-5 system the reduction of copper(II) by propene to copper(I) is only partial and metallic copper or copper oxides are formed during the NOx and propene treatments. This can explain the relatively low activity (16-18%) of both the low and high copper content CuAPO-5 samples toward NOx reduction. By contrast, in the Cu:ZSM-5 system, copper(II) is reduced to copper(I) by propene and subsequently reoxidised by NOx. Copper is only partially reoxidised in Cu: ZSM-5 prepared by hydrothermal ion exchange (45% deNO(x) conversion), but the amount of copper exchanged by this method (133%) is significantly higher than in the conventional ion exchanged preparations (35%). The final propene treatment establishes that the Cu(I)/Cu(II) redox pair is formed in both Cu:ZSM-5 samples when reducing NOx. Previous studies suggest that dimeric copper species, in addition to isolated copper ions, are responsible for the activity of high copper content Cu:ZSM-5. We find no evidence of copper clustering in this system with the protocol used here.

X‐ray absorption and luminescence properties of metallic copper nanoparticles embedded in a glass matrix

AbstractA new method of ion‐exchange between raw compounds containing copper oxide and alkali glasses has been used to grow copper nanoparticles within a glass matrix, forming a metal–glass nanocomposite that is the structure on which both ancient and modern lustre glazes are based. When excited by X‐rays at 300 K, two dominant emission bands appear in the material in the visible region, peaking at 2.60 eV and 1.98 eV. Synchrotron radiation methods are deployed that enables the luminescence and structural properties of the nanocomposite to be interlinked. Standard Extended X‐ray Absorption Fine Structure (EXAFS) shows that both metallic copper and copper oxide local sites structure are present in the glass matrix, and the detailed atomic arrangement of each are derived; however, the method provides no information as to whether either structures are actually involved in the luminescence processes. In order to provide this direct link, Optically Detected X‐ray Absorption Spectroscopy (OD‐XAS) has been deployed, and this provides strong evidence that copper metal nanoparticles are responsible for the red emission. The method also shows that the X‐ray absorption processes of the metal particles and silicate lattice (that result in the red and blue emissions respectively) are distinctly different. This is the first report of OD‐XAS involving metallic nanoparticles, and opens the possibility of using the method more generally for metal nanoparticle research. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nanocomposites of metallic copper and spinel ferrite films: Growth and self-assembly of copper particles

Nanocomposites of metallic copper and iron oxides films have been prepared by RF-sputtering of pure CuFeO2 delafossite target. The films are made of copper and spinel ferrite crystallites of less than 10 nm in diameter. The content of metallic copper and the ferrite composition depend on the sputtering conditions. For the shortest substrate-target distances, films are made of copper and copper substituted magnetite with low copper content. The formation of the metallic and spinel phases is due to the loss of a small quantity of oxygen during sputtering. When annealed under inert atmosphere, nanometric copper particles located in the upper part of the film, move on the surface and grow due to coalescence phenomena. The particle motion can be stopped by small grooves allowing the self-assembly of copper particles.

New heterometallic copper zinc alkoxides: synthesis, structure properties and pyrolysis to Cu/ZnO composites

The copper compound [(THF)KCu(O t Bu) 3] ∞ 1 was obtained by interaction of a 1:1 mixture of ZnCl 2/CuCl 2 with KO t Bu. Bi- and trifunctional aminoalcohols were used to synthesize the intramolecularly donor stabilized Cu(II) alkoxides Cu(OCH(R)CH 2NMe 2) 2 ( 3: R=Me, 4: =CH 2NMe 2) where 4 was structurally characterized. Lewis acid–base adduct formation with (Me 3Si) 3CZnCl gave the heterodinuclear compounds (Me 3Si) 3CZnCl · Cu(OCH(R)CH 2NMe 2) 2 ( 5: R=Me, 6: R=CH 2NMe 2), which were characterized by X-ray single-crystal structure analysis. The two metal centers Cu and Zn of 5 and 6 are bridged by two oxygen atoms to form a Cu–O–Zn core. Pyrolysis of compounds 5 and 6 in dry argon or a H 2/N 2 mixture at atmospheric pressure forms metallic copper and zinc oxide, whereas pyrolysis under O 2/Ar forms additionally oxidized copper species. Elemental analysis of the pyrolysis products showed carbon and nitrogen contamination. Scanning electron microscopy and energy dispersive X-ray analysis were performed to get information on the morphology and the chemical composition of the pyrolysis products.

Chemistry aspects pertaining to the application of steam generator chemical cleaning formulation based on ethylene diamine tetra acetic acid

During the course of reactor operation, corrosion products and impurities from the make-up water and condenser leak, accumulates on the tubes and tube sheets of the steam generators. These deposits cause several problems such as loss in heat transfer efficiency, under deposit attack of the tubes leading to tube failure etc. Though, various techniques are being employed to remove these deposits, cleaning by chemical methods has been shown to be the most efficient means of solving this problem. In this paper, the work carried out to understand the various chemistry aspects involved in the application of Ethylene Diamine Tetra Acetic acid (EDTA) based chemical formulations, for cleaning the steam generators of nuclear power reactors, has been brought out. The preparation of highly concentrated solution of EDTA and the variation in the solubility with the nature of the base used for pH adjustment has been studied. Identification of the various chemical components present in the sludge of a nuclear steam generator especially the portion that remains insoluble in chemical formulations has been carried out. The steam generator sludge was subjected to a detailed study so as to understand the role played by various additives such as pH adjusting, reducing and oxidizing agents, in affecting the kinetics of dissolution of various phases present in the sludge. Observations made in the sludge dissolution study have been corroborated by the studies carried out with constituent oxides such as magnetite, oxides of copper and copper metal. The importance of the presence of reducing agent in dissolving the iron oxides and the effect of oxidizing agents like air and hydrogen peroxide in dissolving the metallic copper and copper oxides have been discussed. Various bases like ammonia, sodium hydroxide and ethylene diamine (EDA) have also been evaluated for their effectiveness as pH adjusting agents in dissolving the sludge. In addition, the thermodynamic quantities such as heats of neutralization, dilution and the various decomposition reactions have been calorimetrically determined. It was observed that the presence of certain impurities and temperature conditions of the formulation containing hydrogen peroxide could initiate a fast exothermic reaction resulting in the total decomposition of the formulation constituents. The role of various metal ions in the mutual decomposition of hydrogen peroxide and EDTA and the catalytic effect of iron ions in the decomposition of the hydrogen peroxide has been explained.

Copper and copper compounds as coatings on polystyrene particles and as hollow spheres

Submicron-sized anionic polystyrene latices have been coated with uniform layers of copper compounds by aging dispersions of the polymer colloid in the presence of aqueous solutions of Cu(NO3)2, urea, and poly(N-vinylpyrrolidone) at 85 °C. The thickness and morphology of the deposited layers can be altered by suitable adjustment of the reactant concentrations and the aging time. Hollow colloidal spheres of metallic copper and copper oxide were obtained by calcination of the coated polystyrene latices at elevated temperatures in nitrogen and air, respectively.

Synthesis, Characterization, and Properties of Metallic Copper Nanoparticles

Nanoscale particles of metallic copper clusters have been prepared by two methods, namely the thermal reduction and sonochemical reduction of copper(II) hydrazine carboxylate Cu(N2H3COO)2·2H2O complex in an aqueous medium. Both reduction processes take place under an argon atmosphere over a period of 2−3 h. The FT-IR, powder X-ray diffraction, and UV−visible studies support the reduction products of Cu2+ ions as metallic copper nanocrystallites. The powder X-ray analysis of the thermally derived products show the formation of pure metallic copper, while the sonochemical method yields a mixture of metallic copper and copper oxide (Cu2O). The formation of Cu2O along with the copper nanoparticles in the sonochemical process can be attributed to the partial oxidation of copper by in situ generated H2O2 under the sonochemical conditions. However, the presence of a mixture of an argon/hydrogen (95:5) atmosphere yields pure copper metallic nanoparticles, which could be due to the scavenging action of the hydroge...

Preparation of copper and copper oxide films by metal-organic chemical vapour deposition using β-ketoiminato complexes

Two β-ketoiminato complexes of copper (II), namely bis-(acetylacetone)ethylenediiminato-copper(II) ( 1) and [4-[ N′-dimethylethylamino)- N-iminato]-pentan-2-one](acetano)copper( II) ( 2) were investigated as precursors for the growth of metallic copper films by metal-organic chemical vapour deposition (MOCVD). Evaporation experiments showed a rather low volatility compared with β-diketonato compounds as Cu(acac), Cu(dpm) 2 and Cu(tfa) 2 and Cu(hfa) 2. The more volatile complex 1 was used in MOCVD experiments in a horizontal quartz reactor using a graphite susceptor covered with copper or copper oxide. Thin films (thickness, 0.1–0.7 μm) were grown on quartz, sappire, Si[100], MgO[100] and Al. The kinetic dependence of the growth rate on partial pressure of 1 and the reaction gas hydrogen is discussed. Single-phase films or mixtures of metallic copper and copper oxide could be identified by X-ray diffraction. Scanning Auger microscopy yielded a rather high level (about 6 at.%) of carbon and no nitrogen (1 at.% or less) in the films.

Temperature dependent anisotropy of normal-state magnetic susceptibility of metallic copper oxides

The normal-phase anisotropy of the magnetic susceptibility, Δ χ ( T), has been measured for La 2− x Sr x Cu 2O 4, YBa 2Cu 3O 7− y and Bi 2.2Sr 1.75Ca 1Cu 2O 8.15 single crystals. A temperature dependent diamagnetic contribution to Δ χ ( T) is found below some characteristic temperature, T dia , in all the metallic samples. The total change, | Δ χ ( T dia ) − Δ χ ( T c )|, is significant and can exceed the room temperature anisotropy quite substantially. The functional form of Δ χdia ( T) and the total change between T dia and T c are found to be rather similar in all the metallic copper oxides. Writing diamagnetic component as, Δ χdia(T) = -C dia ( T Θ dia−1 ) , we find, for La 1.9Sr 0.1Cu 2O 4 ( T c = 16.7 K), Θ dia = 15.89 K and C La dia = 1.62 × 10 -5 [ emu mol -1], while for YBa 2Cu 3O 7 ( T c = 87.6 K), Θ dia = 72.17 K and C Y dia = 2.12 × 10 -5 [ emu mol -1]. The ratio T c Θ dia is roughly the same for both compounds. The normal-phase torque data for high T c samples seem to indicate that (i) significant temperature dependent diamagnetism precedes the onset of superconductivity; (ii) the functional form of susceptibility anisotropy exhibits universal features.

Dynamic scaling of binary composites (Ag-YBa2Cu3O7- delta ).

The scaling properties of the electrical conductivity (Σ) are studied in a binary composite system consisting of metallic silver (Ag) and ceramic copper oxide (YBa 2 Cu 3 O 7-δ ). A percolation transition is observed when p, the volume fraction of Ag, is varied systematically from 0% (pure YBa 2 Cu 3 O 7-δ ) to 100% (pure Ag)

Crystal structure of the new metallic copper oxide La 2Sr 6Cu 8O 18-δ

The structure of metallic copper oxide La 2Sr 6Cu 8O 18-δ (δ≈0.4) has been determined by electron diffraction and neutron powder diffraction. The correct space group was found to be P 4/mbm with lattice parameters a=10.8502 (3) Å≈2√2a p and c=3.7658 (1) Å≈a p, where a p is the lattice parameter of the cubic perovskite. The oxygen vacancies are ordered both in the basal plane, along [001], and in the z= 1 2 plane, along [110]. The idealised framework of [Cu 8O 18] consists of square planar CuO 4 groups and CuO 5 square pyramids by sharing their corner oxygen, leading to the formation of hexagonal tunnels along the c-axis. La 3+ and Sr 2+ ions are located in these tunnels in a disordered manner.

Normal-state susceptibility anisotropy of metallic copper oxides

Normal-phase anisotropy of La 1.9Sr 0.1Cu 2O 4, YBa 2Cu 3O 7− y and Bi 2.2Sr 1.75Ca 1Cu 2O 8.15 single crystals has been measured. Below some characteristic temperature, T dia, an anomalous temperature-dependent diamagnetic contribution develops in all the metallic samples. Δ ξdia( T) increases until, at some lower temperature, the superconducting phase starts to influence the response. The total change, |Δ ξ( T dia)−Δ ξ( T c)|, is significant and can exceed the room temperature anisotropy quite substantially. Δ ξdia( T) is of a similar form in all the metallic copper oxides. We find, Δ ξdia( T)= - C dia/( T/ϑ dia−1) for La 1.9Sr 0.1Cu 2O 4 ( T c=16.7K, ϑ dia=15.89 K, C La dia=1.62x10 -5emu/ mol) and for YBa 2Cu 3O 7( T c =87.6 K, ϑ dia=72.17 K, C Y dia=2.12x10 -5 emu/mol). The torque data seem to indicate that significant temperature-dependent diamagnetism precedes the onset of superconductivity and that Δ ξdia( T) exhibits a universal form.