Stability Of Cu Research Articles

High hydrothermal stability of Cu–SAPO-34 catalysts for the NH3-SCR of NOx

The effects of calcination temperature, Cu source and co-template contents on the activity and hydrothermal stability of Cu–SAPO-34 catalysts prepared by the one-pot hydrothermal synthesis method were investigated. Appropriate calcination temperature was important for the deNOx activity of Cu–SAPO-34 catalyst. The amount of Cu source and co-template in the resulting gel could impact the Cu loading and the crystallization of the final Cu–SAPO-34. Preferably, hydrothermal treatment of the Cu–SAPO-34 catalyst with Cu loading ca. 3.44% at 750°C for 16h increased the NH3-SCR activity slightly due to migration of CuO to isolated Cu2+ and the maintenance of the crystallinity as well as the acidity. Moreover, the catalyst aged at 800°C for 16h maintained >90% NOx conversion from 225 to 400°C, and the crystallinity, active Cu2+ species and acidity in Cu–SAPO-34 were not destroyed completely after such harsh treatment. Meanwhile, kinetic analysis over fresh and aged Cu–SAPO-34 samples were conducted and the conclusion were in agreement with the NH3-SCR tests, H2-TPR and NH3-TPD results.

Molecular and Semi-Empirical Mechanic Studies of Copper-Histamine Chloride Complex

In the present work, we describe and characterized the molecular structure and molecular orbital of Cu (His)Cl2 by two methods: molecular mechanic and semi-empirical PM3 simulations. First, we determine the geometry structural properties of the Cu (Hist)Cl2 complex by molecular mechanic method. Then we compare the calculations method with the experimental data of Cu (His)Cl2 crystal complex. We find that the optimized parameters obtained by MM method are in good agreement with those observed experimentally. After, we evaluate the quantum chemical parameters using PM3 simulations and we discuss the chemical reactivity of Cu (II) ion and the stability of Cu (His)Cl2 molecule. We obtain a large gap with PM3 method. We evaluate the electrophilicity index of the complex. We also calculate the deformation energy. We deduce from quantum calculations that Cu (Hist)Cl2 molecule has high chemical reactivity and is more stable. Finally, we calculate the relative and average errors to estimate the quality of each method. We show that average errors vary as follow: for bonds are 7.833 and 2.692 %, and for angles are 7.755 and 5.309 % using MM+ and PM3 respectively. We conclude that both molecular mechanic and semi-empirical calculations agree very well with the experimental data.

Molecular and Semi-Empirical Mechanic Studies of Copper-Histamine Chloride Complex

In the present work, we describe and characterized the molecular structure and molecular orbital of Cu (His)Cl2 by two methods: molecular mechanic and semi-empirical PM3 simulations. First, we determine the geometry structural properties of the Cu (Hist)Cl2 complex by molecular mechanic method. Then we compare the calculations method with the experimental data of Cu (His)Cl2 crystal complex. We find that the optimized parameters obtained by MM method are in good agreement with those observed experimentally. After, we evaluate the quantum chemical parameters using PM3 simulations and we discuss the chemical reactivity of Cu (II) ion and the stability of Cu (His)Cl2 molecule. We obtain a large gap with PM3 method. We evaluate the electrophilicity index of the complex. We also calculate the deformation energy. We deduce from quantum calculations that Cu (Hist)Cl2 molecule has high chemical reactivity and is more stable. Finally, we calculate the relative and average errors to estimate the quality of each method. We show that average errors vary as follow: for bonds are 7.833 and 2.692 %, and for angles are 7.755 and 5.309 % using MM+ and PM3 respectively. We conclude that both molecular mechanic and semi-empirical calculations agree very well with the experimental data.

Enhanced stability of Cu(2+)-ATCUN complexes under physiologically relevant conditions by insertion of structurally bulky and hydrophobic amino acid residues into the ATCUN motif.

Copper complexes formed by an amino terminal Cu(2+)- and Ni(2+)-binding (ATCUN) motif have attracted attention as metallodrug candidates that cleave DNA or RNA and inactivate enzymes. Although the stability of the Cu(2+)-ATCUN complex under physiologically relevant conditions is a key factor for medical applications, it has remained unclear. Here we prepared a series of ATCUN peptides by inserting various amino acid residues into positions 1 and 2, and investigated the stability of the Cu(2+)-ATCUN complexes in aqueous solution, blood plasma, and living animals. Systematic pH titration showed that the low basicity of the N-terminal amine of the peptide stabilized the Cu(2+)-ATCUN complex in aqueous solution. Interestingly, the stability of (64)Cu-labeled ATCUN complexes in blood plasma was significantly enhanced by the structural bulkiness and hydrophobicity of the amino acid residues at positions 1 and 2. To validate the in vivo stability, six ATCUN motifs (YYH, VVH, NNH, TTH, GGH, and DDH) were conjugated to a tumor-targeting peptide, octreotide (Oct). The stability of the (64)Cu-ATCUN-Oct complexes in blood plasma showed a similar trend to that of the (64)Cu-ATCUN complexes. The (64)Cu-YYH-Oct complex exhibited the highest stability in blood plasma. According to the positron emission tomography and competitive blocking studies of a tumor-bearing mouse model, (64)Cu-YYH-Oct specifically accumulated in tumors, suggesting that the complex was sufficiently stable to reach its target in vivo. The results show that the structural bulkiness and hydrophobicity of the residues at positions 1 and 2 are key parameters for designing metallodrugs on the basis of the Cu(2+)-ATCUN complex.

Effect of Mn doping on the activity and stability of Cu–SiO2catalysts for the hydrogenation of methyl acetate to ethanol

A series ofxMn–Cu–SiO2catalysts with different manganese contents were prepared by an ammonia-evaporation method for methyl acetate hydrogenation.

Stabilization of Cu7 clusters in azide networks: syntheses, structures and magnetic behaviour.

Two new azide bridged copper(II) coordination polymer compounds, [Cu7(N3)14(C3H10N2)(C4H13N3)]n (I) and [Cu7(N3)14(C3H10N2)(C5H15N3)2]n (II) [where C3H10N2 = 1,2-diaminopropane (1,2-DAP); C4H13N3 = diethylenetriamine (DETA); C5H15N3 = N-2-aminoethyl-1,3-propanediamine (AEDAP)] were prepared by employing a room temperature diffusion technique involving three layers. Single crystal studies reveal that both compounds I and II, have similar connectivity forming Cu7 clusters through end-on (EO) bonding of the azide. The Cu7 clusters are connected through end-to-end (EE) connectivity of the azides forming three-dimensional structures. Magnetic studies confirmed the ferromagnetic interactions within the Cu7 units and revealed the occurrence of concomitant ferro- and antiferro-magnetic interactions between these clusters. As a result I behaves as a weak-ferromagnet with TC = 10 K.

Influence of field-assisted annealing on Cu(V) barrier-less metallization

Influence of annealing process on the diffusion barrier property and thermal stability for Cu(V) barrier-less metallization has been investigated. The Cu(V) films were deposited on SiO2/Si substrates by magnetron sputtering, then Some Cu(V)/SiO2/Si samples were field-assisted annealed (−20 V) without breaking the vacuum, Another samples were vacuum-annealed without FAA. After annealing, compared with the samples without FAA, the samples with FAA has lower resistivity and higher Cu(111) signal. According to XPS results, the segregation of V at the interface in the samples with FAA is a little more than that without FAA, the thickness of the self-formed layer for samples with FAA is a little thicker than that of the samples without FAA detected by TEM. The results suggest that the FAA process can improve the thermal stability and the diffusion barrier property for the Cu(V)/SiO2/Si interconnection system.

The stability of precepitates and the role of lattice defects in Fe-1at%Cu-1at%Ni-1at%Mn alloy: A phase-field model study

In the first part of this study, the stability of Cu precipitates, up to 2 nm in diameter, in Fe-1at%Cu-1at%Ni-1at%Mn system was evaluated within the framework of phase-field modeling by utilizing a thermodynamic database. The implanted precipitates either in isolated or in clustered arrangements, were unstable and dissolved into the matrix. The dissolution rate decreases with increasing precipitate size; however, it is strongly influenced by the spatial arrangements of the implants and the overall alloy content. In the second part, the precipitation/segregation behavior at a circular dislocation, and square prismatic loops was parametrically studied. While precipitates formed at the dislocation loop, a significant segregation of Cu was observed at prismatic loops with either vacancy or interstitial character. Although, the both types of prismatic loops provide the spatial evolution of the stress-fields with the same absolute magnitude, the vacancy loops appears to be stronger sinks and their sink strength increases with decreasing loop size. The results clearly show the necessity of inclusion of the underlying lattice defects in the microstructure modeling of materials under the irradiation environments.

Enhanced photocatalytic degradation of sulfamethoxazole by visible-light-sensitive TiO2 with low Cu addition

Abstract In this study, the one-pot microwave-assisted impregnation method was developed to prepare the visible-light-sensitive Cu–TiO 2 at low mass ratios of 0.006–0.063 wt% for the enhanced photocatalytic degradation of sulfamethoxazole (SMX) under visible light irradiation. The electron probe microanalysis and X-ray absorbance near-edge spectroscopic results indicated that the distribution of copper ions was even on TiO 2 nanoparticles and the dominant species of copper element was CuO. The photodegradation efficiency and rate of SMX by Cu–TiO 2 increased positively upon increasing Cu loading from 0.006 to 0.045 wt% Cu and then decreased when further increasing the Cu mass loading to 0.063 wt%. The pseudo-first-order rate constants for SMX photodegradation by Cu–TiO 2 were in the range 0.0103–0.0506 min −1 , which were 1.9–13.1 times higher than that of pure Degussa P25 TiO 2 . The photodegradation efficiency and rate of SMX can be maintained in the pH range of 5–9, and the release of Cu ions in the solution was only few μg/L, which indicates the stability of Cu–TiO 2 during the photocatalytic reaction in aqueous solutions. In addition, the Cu–TiO 2 could be recycled for at least 4 cycles and maintained the highly stable photoactivity toward SMX degradation under visible light irradiation. Results obtained in this study clearly demonstrate that low mass loading of Cu(II) onto TiO 2 can effectively shorten the route of electron transfer and can serve as the efficient visible-light-driven photocatalysts for photodegradation of SMX and other pharmaceutical products.

Thermal stability of Cu–Nb microcomposite wires

We studied the thermal stability of Cu–Nb microcomposite wires with Cu–Nb interface density up to 21.6μm2/μm3. This high density interface results in high hardness values. Annealing up to 500°C caused no significant changes in interface density or grain size, and hardness values. At temperatures higher than 500°C, however, hardness decreased rapidly. The higher the deformation strain, the more rapid the decreases in hardness. Differential scanning calorimetry showed a significant increment in heat flow above 500°C, which is related to drop in crystallographic lattice distortion. Because of the high-density of interfaces between Cu and Nb, stress relaxation and recovery in Cu matrix are delayed compared to pure Cu. We observed pronounced grain growth and lattice distortion relaxation after annealing at 800°C, but found neither precipitation nor detectable solid solution during the fabrication and annealing process.

Investigation of heavy metal (Cu, Pb, Cd, and Cr) stabilization in river sediment by nano-zero-valent iron/activated carbon composite.

Nano-zero-valent iron/activated carbon (nZVI/AC) composite was evaluated for its effectiveness in the stabilization of Cu, Pb, Cd, and Cr in dredged river sediment. Synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP) were adopted to compare the effects of nZVI/AC dosage, particle size, time duration, and temperature on heavy metal leachability. The results show that leachability dropped considerably with the addition of nZVI/AC and powdered particles in the size of 0.075-0.18mm was more effective in stabilization than granular ones. Stabilization effect was stable in long-term and robust against changes in temperature. Tessier sequential extraction revealed that heavy metals were associated with solid particle, inorganic or organic matters in sediment. The addition of nZVI/AC was able to convert relatively weakly bound heavy metals into more strongly bound species and thus reduce the bioavailability and toxicity. Also, the standard potential of heavy metals may decide the mechanism of stabilization process.

Differential uptake of silver, copper and zinc suggests complementary species-specific phytoextraction potential

ABSTRACTThe aim of our study, conducted as a pot experiment, was to assess the potential of willow (Salix miyabeana), alfalfa (Medicago sativa), tall fescue (Festuca arundinacea), and Indian mustard (Brassica juncea) to remediate two brownfield soils differentially contaminated with Ag, Cu and Zn (up to 113.60, 47.50, and 117.00 mg kg−1 respectively). While aboveground Ag accumulation was highest in B. juncea (4.60 ± 2.58 mg kg−1), lower levels were also measured in M. sativa and F. arundinacea. Cu accumulation was observed in all species, but only in underground parts, and was highest in F. arundinacea (269.20 ± 74.75 mg kg−1), with a bioconcentration factor of 13.85. Salix miyabeana was found to have the highest Zn aerial tissue concentration (119.96 ± 20.04 mg kg−1). Because of its high Ag uptake, the remediation potential of B. juncea should be evaluated more extensively on the site from which we excavated the soil for this study. Given the multiple forms of contamination on the site and the differential specie-related uptake evident in our findings, we hypothesize that an optimal plantation allowing expression of complementary remediation functions would include B. juncea for extraction of Ag, in combination with F. arundinacea for stabilization of Cu and S. miyabeana for extraction of Zn.

Engineering the Cu2O–reduced graphene oxide interface to enhance photocatalytic degradation of organic pollutants under visible light

In this work, Cu2O–reduced graphene oxide (rGO) composites were synthesized with tunable Cu2O crystal facets ({111}, {110} and {100} facets). The degradation performance of methylene blue under visible light was ranked: o-Cu2O{111}–rGO>d-Cu2O{110}–rGO>c-Cu2O{100}–rGO. UV–vis diffuse reflectance and photoluminescence spectra showed that o-Cu2O–rGO exhibited the enhanced visible-light absorption and the faster charge-transfer rate. Furthermore, X-ray photoelectron spectroscopy and Raman characterizations showed that o-Cu2O–rGO was beneficial for the stabilization of Cu+ species and the formation of oxygen defects. With the help of in-situ electron spin resonance (ESR), more superoxide radicals were detected over o-Cu2O–rGO, which promoted organic pollutants degradation. The above results confirmed that the catalytic behaviors of three Cu2O–rGO composites were related to the electronic structures and interfacial connections. The o-Cu2O{111}–rGO displayed the superior performance, for the highly-active coordinated unsaturated Cu and the intensive interfacial connection, which was beneficial for the rapid the photo-generated electron transfer and the formed active superoxide species. This study showed that engineering the interfacial structures could provide a scientific basis for the design of efficient photo-catalysts.

Precipitate stability in Cu–Ag–W system under high-temperature irradiation

The kinetics of precipitation was investigated in the ternary Cu alloy, Cu83.5Ag15W1.5 during irradiation with MeV Kr ions at elevated temperatures. The alloy was prepared as a solid solution by physical vapor deposition and then irradiated at room temperature to create a high density of nano-sized W precipitates. These precipitates served as effective sinks for point defects during subsequent elevated-temperature irradiation, suppressing radiation-enhanced diffusion. As a consequence the size of the Ag precipitates formed during elevated-temperature irradiation was stabilized below 20nm, up to temperatures in excess of 300°C, thus significantly extending the regime for “compositional patterning” above 175°C, found for Cu85Ag15. For higher temperature irradiations (above 400°C), the role of the W precipitates in stabilizing the size of the Ag precipitates switched from simply acting as point-defect sinks to serving as pinning sites for the Ag precipitates. At 500°C, the average Ag precipitate diameter is ∼30nm compared to ∼300nm in the Cu85Ag15 binary alloy. Rate theory calculations and kinetic Monte Carlo simulations are employed to illustrate how this transition takes place.

Calculation of Defect Concentrations and Phase Stability in Cu$_2$ ZnSnS$_4$ and Cu$_2$ ZnSnSe$_4$ From Stoichiometry

The application of the quarternary compounds Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ZnSnS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (CZTS) and Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ZnSnSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (CZTSe) as efficient solar cell absorber materials is dependent on the complex behavior of the large variety of intrinsic lattice defects. In this paper, a canonical approach is presented and applied to calculate the defect concentrations and the position of the Fermi level for CZTS and CZTSe at a given temperature as a function of stoichiometry (or a combination of stoichiometry and elemental chemical potentials). With the defect concentrations, the chemical potentials (which are generally not experimentally accessible) can be calculated, allowing the relation of sample composition to the phase stability of CZTS and CZTSe with respect to secondary compounds. Based on the model, it is shown that the stable CZTS with off-stoichiometric composition requires both Cu-poor and Zn-rich conditions, while the compositional space corresponding to stable CZTSe is wider than for CZTS. Additionally, the determination of the Fermi level directly relates the desired p-type conductivity to phase stability in both materials. The method used in this study is applicable to a wide range of complex materials.

The role of the acidity of alumina prepared by aluminum-carbon black composite for CO hydrogenation to dimethyl ether on hybrid Cu–ZnO–Al2O3/alumina

The effects of surface area and the acidity of mesoporous γ-Al2O3, which is prepared by calcining aluminum-carbon black composite (Al/CB) of the precipitated aluminum nitrate on carbon black at different weight ratios, were investigated to verify the roles of carbon black in the surface properties and stability of Cu–ZnO–Al2O3 for the direct synthesis of dimethyl ether (DME) from syngas. A high surface area of ~100 m2/g with a large pore diameter of ~25 nm originated from the occupied spaces of carbon black enhanced the dispersion of the active Cu–ZnO–Al2O3 particles by forming a strong and stable interaction with mesoporous solid acid γ-Al2O3 surfaces. The enhanced dispersion of copper-containing particles, being strongly interacted with the acid sites of the hybrid Cu–ZnO–Al2O3/Al2O3 catalyst using γ-Al2O3 prepared at an optimal Al/CB weight ratio of 10, is mainly responsible for the high CO conversion with a high yield to oxygenates and a suppressed aggregation of active copper species during the direct synthesis of DME from syngas.

Effects of post-treatment method and Na co-cation on the hydrothermal stability of Cu–SSZ-13 catalyst for the selective catalytic reduction of NOx with NH3

Post-treatment with dilute HNO3 solution after one-pot synthesis was an effective method to prepare excellent Cu–SSZ-13 catalysts for the selective catalytic reduction of NOx with NH3 (NH3–SCR). Using solutions with varying levels of acidity, catalysts with different Cu and Na contents were obtained, and the Cu3.9Na0.8–SSZ-13 catalyst showed the optimal NH3–SCR activity and hydrothermal stability. As co-cations, Na+ ions affected the hydrothermal stability of the one-pot-synthesized Cu–SSZ-13 catalysts greatly. Poorer hydrothermal stability was observed for catalysts with higher Na+ contents. The results of 27Al and 29Si NMR spectra proved that Na+ ions did not influence the Si(nAl) distributions in the catalysts significantly. However, H2–TPR profiles indicated that excess Na+ ions in the catalysts decreased the stability of Cu species seriously. Thus, poor stability of Cu species caused by excess Na+ ions was the direct reason for the poor hydrothermal stability of the catalysts. Because of the negative effect on hydrothermal stability, excess Na+ ions should be avoided in Cu–SSZ-13 catalysts prepared by the one-pot synthesis method.

Mesostructured Cu–Mn–Ce–O composites with homogeneous bulk composition for chlorobenzene removal: Catalytic performance and microactivation course

Cu–Mn–Ce–O composites with enhanced surface area and developed mesoporosity were synthesized using a homogeneous coprecipitation (hcp) method, and were tested in the catalytic destruction of chlorobenzene (CB). X-ray diffraction (XRD), N2 adsorption/desorption, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (H2-TPR), temperature programmed desorption of CB/O2 (CB/O2-TPD), and diffuse reflectance ultraviolet visible spectroscopy (DRUV-Vis) were used to characterize the structure and textural properties of catalysts. Mn and Cu enter CeO2 matrix with a fluorite-like structure, and produce large amounts of oxygen vacancies. Addition of manganese promotes the formation of reduced copper phase, and the presence of large numbers of high valence Mn4+ ions strongly enhances the redox couple of Cu+–Cu2+ in the composites. Both the synthesis protocol and metal doping amount significantly affect the catalyst reducibility, surface state and oxygen density. Cu0.15Mn0.15Ce0.85Ox synthesized via the hcp method exhibits the highest catalytic activity with 90% of chlorobenzene destructed at 255 °C (CO2 selectivity > 99.5%). Enriched surface oxygen, excellent active oxygen mobility and CB adsorption ability guarantee the superior activity and stability of Cu–Mn–Ce–O composite catalysts. Nucleophilic and electrophilic substitutions happen in sequence during chlorobenzene destruction, and the adsorbed Cl can be finally removed in the form of Cl2 via the Deacon reaction. Furthermore, the incorporation of CuO and MnOx phases can inhibit the formation of organic byproducts, such as phenolates, maleates, and o-benzoquinone-type species, especially at elevated reaction temperatures.

Aluminium–copper–nickel thin film compositional spread: Nickel influence on fundamental alloy properties and chemical stability of copper

An Al–Cu–Ni thin film compositional spread was deposited by thermal evaporation and investigated in order to study the Ni influence on the overall properties. The chemical composition was detected by energy dispersive X-ray spectroscopy and showed a compositional spread of approximately 20at.% Ni. Decreasing the Ni content in the Al–Cu–Ni thin films resulted in an increased grain size and characteristic surface microstructure evolution. Scanning Kelvin probe measurements were performed to investigate the surface potential variation along the compositional gradient, and a distinct surface potential drop was observed between Al–Cu–7at.% Ni and Al–Cu–13at.% Ni. The results of the X-ray photoelectron spectroscopy surface analysis and Auger electron spectroscopy as well as the electrochemical investigations by cyclic voltammetry evidenced mainly the presence of Al2O3 but also CuO and Cu2O together with metallic Cu were clearly identified along the compositional gradient. Chemical dissolution experiments have shown that Ni is enhancing the chemical stability of Cu, excepting inside the compositional region between 7 and 13at.% Ni.

Copper nanoparticles on dichromium trioxide: a highly efficient catalyst from copper chromium hydrotalcite for oxidant‐free dehydrogenation of alcohols

Stable copper(0) nanoparticles supported on chromium (Cu(0)/Cr2O3) are prepared from the composite precursor copper chromium hydrotalcite. The resulting Cu(0)/Cr2O3 catalyst is first used in the selective dehydrogenation of alcohols to aldehydes. More impressively, these dehydrogenations are performed without oxidants and yields of products are high. The stability of Cu(0)/Cr2O3 is also assessed by studying its recoverability and reusability for up to five cycles. Copyright © 2015 John Wiley &amp; Sons, Ltd.