Description Of Cu Research Articles

English

English

Thermodynamic assessment of the Cu–Li system and prediction of enthalpy of mixing of Cu–Li–Sn liquid alloys

After a comprehensive review of the thermochemical and phase diagram data in the Cu–Li system, new experiments were performed to clarify existing contradictions. Several Cu–Li samples were prepared and powder X-ray diffraction (XRD) was performed on quenched Cu–Li alloys. Our experimental work could not confirm the presence of the intermetallic phase Cu2Li3 which has been recently proposed. Additionally, the results of our high temperature enthalpy of mixing measurements of the liquid phase indicate that the Li-rich liquidus line is more Cu-rich than presented in previous works. Based on our experimental data, a Calphad approach was used to obtain a self-consistent thermodynamic description of the Cu–Li binary system. Furthermore, a preliminary description of the ternary Cu–Li–Sn liquid phase was developed by combining the new description of the liquid phase in the Cu–Li system with the description of the liquid phase from our previous Cu–Sn and Li–Sn assessments. The enthalpies of mixing of the liquid phase calculated using extrapolations according to the associate, Muggianu, and Toop models are compared to the enthalpies of mixing reported in the literature. Our work shows that the enthalpies of mixing calculated using the associate model are in excellent agreement with the literature data, and no additional ternary interaction parameters are necessary. The contribution of the formation of Li4Sn associates to the enthalpy of mixing of the ternary liquid was discussed.

Evaluating the anticancer properties of liposomal copper in a nude xenograft mouse model of human prostate cancer: formulation, in vitro, in vivo, histology and tissue distribution studies.

Although Cu complexes have been investigated as anticancer agents, there has been no description of Cu itself as a cancer killing agent. A stealth liposomal Cu formulation (LpCu) was studied in vitro and in vivo. LpCu was evaluated in prostate cancer origin PC-3 cells by a metabolic cytotoxicity assay, by monitoring ROS, and by flow cytometry. LpCu efficacy was evaluated in vivo using intratumoral and intravenous injections into mice bearing PC-3 xenograft tumors. Toxicology was assessed by performing hematological and blood biochemistry assays, and tissue histology and Cu distribution was investigated by elemental analysis. LpCu and free Cu salts displayed similar levels of cell metabolic toxicity and ROS. Flow cytometry indicated that the mechanisms of cell death were both apoptosis and necrosis. Animals injected i.t. with 3.5 mg/kg or i.v. with 3.5 and 7.0 mg/kg LpCu exhibited significant tumor growth inhibition. Kidney and eye were the main organs affected by Cu-mediated toxicities, but spleen and liver were the major organs of Cu deposition. LpCu was effective at reducing tumor burden in the xenograft prostate cancer model. There was histological evidence of Cu toxicity in kidneys and eyes of animals treated at the maximum tolerated dose of LpCu 7.0 mg/kg.

Hydrodynamic evolution and jet energy loss in Cu + Cu collisions

We present results from a hybrid description of Cu + Cu collisions using (3 + 1)-dimensional hydrodynamics (music) for the bulk evolution and a Monte Carlo simulation (martini) for the evolution of high-momentum partons in the hydrodynamical background. We explore the limits of this description by going to small system sizes and determine the dependence on different fractions of wounded nucleon and binary collisions scaling of the initial energy density. We find that Cu + Cu collisions are well described by the hybrid description at least up to 20% central collisions.

Thermodynamic description of the Cu–Pb–Sn system at the Cu–Pb side

A thermodynamic description of the ternary Cu–Pb–Sn system at the Cu–Pb side is presented. The thermodynamic parameters of the sub-systems, Cu–Pb, Cu–Sn and Pb–Sn, are taken from earlier SGTE-based assessments and those of the ternary system are optimized in this study using ternary experimental lead activity and phase equilibrium data. The present ternary description is valid for tin contents up to 60 wt%.

Thermodynamics of grain boundary premelting in alloys. I. Phase-field modeling

The rich nature of the premelting transition of grain boundaries in solid solutions is analyzed. Part I of this paper uses a multi-phase field model, whereas Part II employs atomistic Monte Carlo simulations. To enable comparison, Cu-rich Cu–Ag solid solutions are chosen for study. In the phase-field model, a system composed of two grains and a liquid phase is treated with three phase field parameters and with a realistic bulk thermodynamic description of Cu–Ag alloys obtained with the CALPHAD approach. Several different computation methods are employed, both rigorous and approximate, to examine the premelting behavior and relate it to the so-called “disjoining potential” between the solid–liquid interfaces in the grain boundary region. Depending on the grain boundary energy, temperature and grain composition chosen, several different classes of premelting transitions have been detected. As the grain concentration approaches the solidus line, one class shows a premelted layer whose thickness diverges continuously to infinity (complete wetting). Another class shows a discontinuity of the premelted layer thickness, exhibiting a first-order thin-to-thick transition prior to continuous thickening to infinity at the solidus line. In other cases, a metastable grain boundary state can exist above the solidus line, indicating the possibility of superheating/supersatuation of the grains together with the grain boundary. The possibility of such transitions has been predicted previously for generic thermodynamics by many authors. The results of the current investigation are compared with the atomistic calculations for the Cu–Ag system in Part II of this work.

Thermodynamic description of the Cu–Fe–Sn system at the Cu–Fe side

A thermodynamic description of the ternary Cu–Fe–Sn system at the Cu–Fe side is presented. The thermodynamic parameters of the sub-systems, Cu–Fe, Cu–Sn and Fe–Sn, are taken from earlier SGTE-based assessments, and those of the ternary Cu–Fe–Sn system are optimized in this study by using the experimental tin activity and phase equilibrium data. The present ternary description is valid for tin contents up to 60 wt%.

Thermodynamic description of Cu–Mg–Ni and Cu–Mg–Zn systems

A thermodynamic description is presented for ternary Cu–Mg–Ni and Cu–Mg–Zn systems. Thermodynamic parameters of binary sub-systems, Cu–Mg, Cu–Ni, Cu–Zn, Mg–Ni and Mg–Zn, are taken from earlier SGTE-based assessments and those of the Cu–Mg–Ni and Cu–Mg–Zn systems are optimized in this study using experimental phase equilibrium and thermodynamic data. Solution phases of the systems are described with the substitutional solution model and intermetallic compounds, treated as simple semi-stoichiometric phases of the (A,B) pC q type, are described with the sublattice model.

Synthesis of copper-rich amorphous alloys by computational thermodynamics

We have used thermodynamically calculated phase diagrams of Cu–Zr–Ti to identify two low-melting Cu-rich alloys denoted by A and B as bulk amorphous alloys where none were thought to exist. These alloys show greater stability of the glassy phase than previously discovered alloys in the same system, as evidenced by the critical casting diameter of 5mm. We also calculated a temperature-composition diagram for alloy A as a function of Y using an approximate thermodynamic description of Cu–Zr–Ti–Y. This diagram shows that the liquidus temperature of alloy A decreases with the addition of Y, reaches a minimum, and increases again. Our experiments indeed showed the glass-forming ability of A reaches a maximum diameter of 10mm when 2at.% Y was added and then decreases again. We thus propose that the thermodynamically calculated liquidus temperature is an excellent guide to synthesize bulkier glasses, which can be readily obtained from calculated phase diagrams.

Thermal power plants ash as sorbent for the removal of Cu(II) and Zn(II) ions from wastewaters

This study concerns the sorption of copper(II) and zinc(II) ions on an energy pit coal fly ash, a massive by-product of a thermal power station in Iaşi, Romania. In order to establish the optimum conditions of Cu(II) and Zn(II) sorption on the fly ash, the influence of experimental conditions (solution pH, adsorbent dose and metal ion concentration, temperature and contact time) was studied. The equilibrium data at three different temperatures were processed using the Langmuir isotherm model. The monolayer sorption capacities of energy pit coal fly ash are 4.71 mg/g and 5.75 mg/g for copper and zinc ions, respectively, at 18 °C. The thermodynamic parameters of Cu(II) and Zn(II) sorption process on the fly ash were also evaluated based on the Langmuir constant. Finally, the kinetic description of Cu(II) and Zn(II) sorption was performed by using the Lagergren pseudo-first-order equation. The results of this study suggest that fly ash may be a promising sorbent provided for environmental technologies in the future.

Intermolecular versus intramolecular electron-/atom- (Cl [rad]) transfer in heme-iron and copper pyridylalkylamine complexes

While outer-sphere electron-transfer reactions come with a firm experimental and theoretical basis, less is known about the redox reactions occurring by atom-transfer. In the present study, relevant reactions occur upon mixing, (F 8)Fe III(Cl) (F 8 is tetrakis(2,6-difluorophenyl)porphyrinate) with a series of [(L)Cu I] + complexes (L are tripodal tetradentate pyridylalkylamine ligands varying in effective chelate ring sizes: TMPA, PMEA, PMAP) to form (F 8)Fe II and [(L)Cu II(Cl)] +. The electron-/atom- (Cl ) transfer process is characterized by electrochemical measurements as well as UV–Vis, 1H NMR, and EPR spectroscopies. Stopped-flow UV–Vis spectroscopy in THF indicate the following relative rates ( k obs) [Cu I(pmea)] + > [Cu I(pmap)] + > [Cu I(tmpa)(thf)] +. However, the redox potentials as related to Δ G ∘ for the reaction, [ E 1/2(oxidant) − E 1/2(reductant)], predict the trend [Cu I(tmpa)(CH 3CN)] + > [Cu I(pmea)] + > [Cu I(pmap)] +. A detailed description of Cu I-to-Cu II structural changes is provided and these likely influence the observed [(L)Cu I] +/(F 8)Fe III(Cl) reaction rates. Analogous chemistry is described for a heme–copper system utilizing a heterobinucleating ligand ( 6L), which is comprised of a TMPA like moiety tethered at the 6-position of one of the pyridyl donors to a F 8-like heme. Kinetic/mechanistic insights were obtained from transient absorption spectroscopic monitoring in CH 3CN following photoejection of carbon monoxide from [( 6L)Fe II(CO)⋯Cu II(Cl)].

Thermodynamic description of the Cu–Al–Ni system at the Cu–Ni side

A thermodynamic description of the ternary Cu–Al–Ni system at the Cu–Ni side is presented. The thermodynamic parameters of the sub-systems Cu–Al, Cu–Ni and Al–Ni are taken from earlier SGTE-based assessments (modifying the Al–Ni description slightly) and those of the ternary Cu–Al–Ni system and system are optimized in this study by using the experimental thermodynamic and phase equilibrium data. The present ternary description is valid at temperatures above 500 ∘C and for aluminum contents up to 18 wt%.

Thermodynamic description of the Cu–Fe–Si system at the Cu–Fe side

Thermodynamic description of the ternary Cu–Fe–Si system at the Cu–Fe side is presented. The thermodynamic parameters of the sub-systems, Cu–Fe, Cu–Si and Fe–Si, are taken from earlier SGTE-based assessments (modifying slightly the bcc description of the Fe–Si system), and those of the ternary Cu–Fe–Si system are optimized in this study by using the experimental phase equilibrium data. The present ternary description is valid for silicon contents up to 10 wt%.

Thermodynamic description of the Cu–Ni–Sn system at the Cu–Ni side

Thermodynamic description of the ternary Cu–Ni–Sn system at its Cu–Ni side is presented. The thermodynamic parameters of the binary sub-systems, Cu–Ni, Cu–Sn and Ni–Sn, are taken from earlier SGTE-based assessments (modifying the Ni–Sn description slightly) and those of the ternary Cu–Ni–Sn system are optimized in this study by using the experimental data of mixing enthalpy and phase equilibrium. The present ternary description is valid for tin contents up to 38 wt% ( x Sn≈0.25). In addition, a new description is presented for the earlier assessed Cu–P–Sn system, due to the new Cu–Sn description adopted after its appearance (and shown in the present study).

Thermodynamic description of the Cu–Mn–Ni system at the Cu–Ni side

Thermodynamic description of the ternary Cu–Mn–Ni system at its Cu–Ni side is presented. The thermodynamic parameters of the sub-systems, Cu–Mn, Cu–Ni and Mn–Ni, are taken from earlier SGTE-based assessments and those of the ternary Cu–Mn–Ni system are optimized in this study by using the experimental phase equilibrium data. The present ternary description is valid for manganese contents up to 70 wt%.

Spectroscopic and electronic structure studies of the mu(4)-sulfide bridged tetranuclear Cu(Z) cluster in N(2)O reductase: molecular insight into the catalytic mechanism.

Spectroscopic methods combined with density functional calculations are used to develop a detailed bonding description of the mu(4)-sulfide bridged tetranuclear Cu(Z) cluster in N(2)O reductase. The ground state of Cu(Z) has the 1Cu(II)/3Cu(I) configuration. The single electron hole dominantly resides on one Cu atom (Cu(I)) and partially delocalizes onto a second Cu atom (Cu(II)) via a Cu(I)-S-Cu(II) sigma/sigma superexchange pathway which is manifested by a Cu(II) --> Cu(I) intervalence transfer transition in absorption. The observed excited-state spectral features of Cu(Z) are dominated by the S --> Cu(I) charge-transfer transitions and Cu(I) based d-d transitions. The intensity pattern of individual S --> Cu(I) charge-transfer transitions reflects different bonding interactions of the sulfur valence orbitals with the four Cu's in the Cu(Z) cluster, which are consistent with the individual Cu-S force constants obtained from a normal coordinate analysis of the Cu(Z) resonance Raman frequencies and profiles. The Cu(I) d orbital splitting pattern correlates with its distorted T-shaped ligand field geometry and accounts for the observed low g( parallel ) value of Cu(Z) in EPR. The dominantly localized electronic structure description of the Cu(Z) site results from interactions of Cu(II) with the two additional Cu's of the cluster (Cu(III)/Cu(IV)), where the Cu-Cu electrostatic interactions lead to hole localization with no metal-metal bonding. The substrate binding edge of Cu(Z) has a dominantly oxidized Cu(I) and a dominantly reduced Cu(IV). The electronic structure description of Cu(Z) provides a strategy to overcome the reaction barrier of N(2)O reduction at this Cu(I)/Cu(IV) edge by simultaneous two-electron transfer to N(2)O in a bridged binding mode. One electron can be donated directly from Cu(IV) and the other from Cu(II) through the Cu(II)-S-Cu(I) sigma/sigma superexchange pathway. A frontier orbital scheme provides molecular insight into the catalytic mechanism of N(2)O reduction by the Cu(Z) cluster.

On the validity of the cluster model to describe the evolution of Cu precipitates in Fe–Cu alloys

Recently M.H. Mathon et al. [J. Nucl. Mater. 245 (1997) 224] applied the so called `cluster model' for the description of Cu precipitates evolution in Fe–Cu model alloys both during aging and irradiation. It was concluded that the model does not work in both cases. The main purpose of this letter is to show that the model can be successfully applied for the case of aging and to discuss the reasons why the cluster evolution is different in the case of irradiation.

Structure and dynamics of high-current arc cathode spots in vacuum

Experiments are reported on the number and displacement velocity of arc spots on CuCr and Cu cathodes in the current range 40 - 1500 A. The spot number was found to increase linearly with current. The average current per resolvable spot amounted to for CuCr and for Cu. For times after ignition random spot displacement R was observed, having mean square values of for Cu and for CuCr. The Cu spots showed brightness fluctuations with intervals of . Because of this obvious dynamics, the theoretical models of the spot plasma must be time-dependent. A self-consistent theoretical description of Cu and Cr plasmas is given, yielding the cathode temperature, plasma density, electric field strength, current density and plasma velocity in the time range 10 ns to 3 ms.

Modeling of Trade Wind Cumuli with a Low-Order Turbulence Model: Toward a Unified Description of Cu and Se Clouds in Meteorological Models

Abstract A simple method is proposed to extend a low-order turbulence scheme including a subgrid-scale cloudiness scheme to represent not only nonconvective (stratiform) cloudiness and turbulence but also shallow, nonprecipitating cumulus convection by utilizing an appropriate subgrid-scale distribution function. A simple approach is chosen that avoids the knowledge of the skewness parameter. All cloud water-related variables (cloud water content, partial cloudiness, liquid water flux) are computed by interpolating linearly as a function of the saturation deficit between two limit cases: the stratocumulus case, which can be well represented by a Gaussian distribution function, and the trade wind cumulus case, characterized by a positively skewed distribution function with a skewness of 2. Comparisons of the scheme with a third-order turbulence scheme and large-eddy simulations (LES) for the Puerto Rico Field Experiment show satisfying results. It is shown that the liquid water flux term, which is strongly...