eV For Copper Research Articles

Novel α-amino acid-like structure decorated biochar for heavy metal remediation in acid soil

Neither chemical nor physical adsorption play well in heavy metals remediation in acid soil due to the competing behavior of abundant protons, where stable chelators that can be reused are of significant demand. Herein, biochar with abundant nitro and carboxyl groups is prepared, which can be assembled into self-supporting electrode. Under the catalyzation of electricity, the surface decorated -NO2 on the biochar can be in situ transformed into -NH2. Combined with the carboxyl group that attached on the same carbon atom, a special α-amino acid-like structure modified biochar (α-AC@BC) can be successfully constructed. Due to the strong affinity between the α-amino acid-like ligand and heavy metals, this α-AC@BC exhibits high removal efficiencies of 83.41%, 80.94%, 92.54% and 77.05% for available copper, cadmium, lead and zinc respectively, even in a strong acid soil with low pH of 4. After four adsorption-desorption cycles, the α-AC@BC could still eliminate 83.88% of copper. The high adsorption energy among -NH2, -COOH and heavy metals (−2.99 eV for copper, −1.90 eV for lead, −1.30 eV for zinc and −0.91 eV for cadmium) could form steady coordination structure to guarantee a highly practical application potential of α-AC@BC in strong acid soil. This study provides a novel concept for the decontamination of multiple heavy metal polluted acid soil.

Copper- and silver-containing heterometallic iodobismuthates(iii) with 4-(dimethylamino)-1-methylpyridinium cation: structures, thermal stability and optical properties

Reactions of BiI3, copper or silver iodide and 4-(dimethyl-amino)-1-methylpyridinium iodide [(Me-DMAP)I] result in formation of heterometallic complexes (MeDMAP)2{[Bi2Cu2I10]} and (MeDMAP)2{[Bi2Ag2I10]}. Their crystal structures, thermal stability and optical properties have been studied. Optical band gaps calculated from diffuse reflectance spectroscopy data are 1.81 and 2.06 eV for copper- and silver-containing complexes, respectively.

Probing plasmon excitations in copper nano-clusters with spectroscopic ellipsometry

Light induced plasmon excitations of copper nano-clusters have been probed using spectroscopic ellipsometry. Copper clusters of typically 20 nm diameter were created on the surface of a silicon wafer by means of physical vapour deposition. The growth of the clusters as well as the chemical interaction with atmosphere are monitored. Clear plasmon excitations are observed with resonance positions in the range from 1.85 to 2.1 eV for copper in its metallic state. The resonance position and amplitude scale linear with deposited amounts. Changes in resonance position and amplitude are observed when copper nano-clusters are exposed to atmosphere and a sub-nanometer thin copper oxide is formed. The resonance position red-shifts 0.4 eV (180 nm wavelength) after one day of exposure with respect to its metallic state. Spectroscopic ellipsometry is shown to have good sensitivity to ultra-thin (down to sub-nanometer thick) metal-oxide layers as well as to nanometer size changes of the copper nano-clusters. This puts the technique in a position where real-time monitoring of plasmon active material in gaseous or liquid environments of, for example, (photo-) catalytic processes becomes accessible.

Foil explosion and decay of metastable state

The mechanism of decay of the superheated metastable metal produced by a thin foil explosion was investigated experimentally. The decay of the metastable metal was indicated by the occurrence of bubbles detected using soft x-ray backlighting. The experiments were carried out on a research facility comprising three current generators. One of them was used to initiate the explosion of a test foil, and the other two, X-pinch backlighting sources, were used for diagnostics. In the experiments, an upper limit has been determined for the decay time of the metastable state of a superheated metal. For aluminum, at a foil thickness of 6 μm and a deposited energy of 1.49 ± 0.08 eV/atom, the metastable state decay time was about 90 ns; for copper, at the same foil thickness and a deposited energy of 1.46 ± 0.07 eV/atom, it was about 250 ns. Analysis of the experimental results based on the classical nucleation theory has made it possible to estimate the work required for the formation of a critical bubble, the radius of the critical bubble, and the Tolman length, which characterizes the effect of the surface curvature on the surface tension. The work required for the formation of a critical bubble has been estimated to be 16.6 ± 1.5 eV for aluminum and 18.3 ± 1.2 eV for copper. The critical bubble radius and the Tolman length turned out to be several nanometers for both test metals.

Stimulation of secondary negative ion emission by implantation of alkaline ions into the surface layer of a solid followed by heating

A new method of stimulating secondary negative ion emission is suggested that is based on implantation of alkaline ions into the surface layer of a solid with subsequent heating to a temperature providing optimal coverage of the surface (about half a monolayer) by activator (alkaline) ions. It is shown that, by appropriately selecting the implantation dose (1018–1019 cm−3) and surface temperature (500–900°C), one can reach such a degree of coverage of the sample surface by activator ions that its work function eφ becomes minimal: 1.9 eV for molybdenum and 2.1 eV for copper. It is found that, with the implantation (irradiation) dose and surface temperature chosen properly, one can, by means of outdiffusion of cesium atoms, achieve such a degree of surface coverage that remains unchanged during the continuous sputtering of the surface by a cesium ion beam.

Densification dynamics of copper and iron powder billets in hot shock compaction: Simulation and analysis

The paper presents the results from computer simulation and analysis of experimental data on the densification of copper and iron powder billets during hot shock compaction. It is established for the first time that the shear viscosity of the porous material matrix shows a stronger dependence on the initial impact velocity than the billet temperature does. The estimated activation energy of the viscous flow in the matrix is equal to 0.35 eV for copper, 0.3 eV for α-Fe, and 0.5 eV for γ-Fe.

A dipole model for the cross-slip of screw dislocations in fcc metals

Abstract An attempt is made to reconcile observations and theories of cross-slip with recent models of cyclic plasticity and the fatigue endurance limit of crystals. According to this view, the stress required to separate two screw dislocations of opposite signs, which are just on the point of mutual annihilation by cross-slip, controls both the stress τIII at the end of linear (stage II) hardening and the saturation stress [sgrave]sat in the cyclic stress-strain curve. It is shown, in confirmation of conclusions by many earlier researchers, that direct annihilation of the dislocations cannot account for the temperature dependence of the stress, although it might account for observations on silver and copper at liquid-helium temperature. Based on the work of Hirsch, a model of stress-aided migration of jogs is proposed, which seems able to account for the observations if the activation energy for the migration is about 0.1 eV in copper, nickel and aluminium. A by-product of the model is a possible reinter...

A dipole model for the cross-slip of screw dislocations in fee metals

Abstract An attempt is made to reconcile observations and theories of cross-slip with recent models of cyclic plasticity and the fatigue endurance limit of crystals. According to this view, the stress required to separate two screw dislocations of opposite signs, which are just on the point of mutual annihilation by cross-slip, controls both the stress τIII at the end of linear (stage II) hardening and the saturation stress [sgrave]sat in the cyclic stress-strain curve. It is shown, in confirmation of conclusions by many earlier researchers, that direct annihilation of the dislocations cannot account for the temperature dependence of the stress, although it might account for observations on silver and copper at liquid-helium temperature. Based on the work of Hirsch, a model of stress-aided migration of jogs is proposed, which seems able to account for the observations if the activation energy for the migration is about 0.1 eV in copper, nickel and aluminium. A by-product of the model is a possible reinterpretation of the Bordoni peaks in the damping of face-centred metals in terms of jog migration.

Metallic etching by high power Nd:yttrium–aluminum–garnet pulsed laser irradiation

A Nd:yttrium–aluminum–garnet pulsed laser, with 1064 nm wavelength, 9 ns pulse width, and 0.9 J maximum pulse energy, is employed to irradiate in vacuum different metal targets (Al, Ti, Ni, Cu, Ta, W, Au, and Pb). In order to measure the erosion thresholds, the etching rates, and the chemical yields, a mass quadrupole spectrometer is interfaced to the vacuum chamber. Etching process shows a threshold, which ranges between 0.1 and 1.6 J/cm2 for lead and tungsten, respectively. Etching rates range between 0.3 and 10 μg/pulse for copper and lead, respectively. The irradiation produces chemical yields ranging between 0.04 and 0.6 atoms/100 eV for copper and lead, respectively. A simple theoretical approach is presented to justify obtained results. The objective of collected data concerns the possibility to use ejected atoms, neutral and ionized, in an electron cyclotron resonance ion source, in order to provide high current, multiply charge ion beams.

A chemical reaction-based boundary condition for flow electrification

A physical model is developed for the charge transfer boundary condition in semi-insulating liquids. The boundary condition is based upon interfacial chemical reactions and extends established relations for the interface by including the effects of interfacial surface charge and charge desorption at the interface. A steady state model for flow electrification in a rotating cylindrical electrode apparatus incorporated this boundary condition and described polarity changes in the open-circuit voltage and short-circuit current as a function of the fluid velocity, the volume charge density dependence an the terminal constraints, and the charge density dependence on applied dc voltages. Previously used boundary conditions are shown to be special cases of the chemical reaction rate boundary condition. A general methodology is developed for combining the volume charge density and voltage/current terminal measurements to estimate the parameters describing the interfacial charge transfer kinetics. Volume charge densities /spl rho//sup w/ on the liquid side of the interfaces of 1 to 20 mC/m/sup 3/ were estimated from the open-circuited electrode measurements, with the stainless steel /spl rho//sup w/ typically larger than that of copper but smaller than that of transformer pressboard. Activation energies for an Arrhenius temperature dependence of /spl sim/0.16 eV for pressboard, 0.25 eV for stainless steel and 0.28 eV for copper were obtained. Interfacial adsorption reaction velocities, estimated to be 10/sup -5/ m/s, were not large enough to make the terminal current transport limited which contradicts the often used assumption that the reaction velocities can be considered 'infinite'. Estimated surface reaction rates at a 70/spl deg/C stainless steel/oil interface of /spl sim/20 /spl mu/m/s for adsorption and /spl sim/0.5 s/sup -1/ for desorption were obtained. The additive BTA reduced the /spl rho//sup w/ for pressboard and stainless steel at concentrations >8 ppm in transformer oil.

Simulation of Surface Diffusion Using Embedded Atom Potentials in FCC Metals

AbstractThe binding energies of gold, silver and copper adatoms and their clusters to each (111) surface have been calculated. The binding energy EN of an N-adatom cluster can be roughly written as EN=3NE1+mE2, where 3E1, is the binding energy of a single adatom to the (111) surface and m is the number of bonds within the cluster and E2 is the binding energy of the bond within the cluster. It was found that E1=0.95eV, E2=0.42–0.49eV for gold, E1=0.62eV, E2=0.38-0.44eV for silver and E1=0.81eV, E2=0.43–0.49eV for copper (by use of a newly determined N-body embedded atom potential). The activation energies of motion of these adatom clusters on each (111) surfaces have been calculated by use of a newly determined N-body embedded atom potential and molecular dynamics method.

Contrast in triple bound excitons in copper-doped gallium phosphide

The bound exciton (BE) recombination no-phonon lines at 1.911 eV and 2.177 eV in copper doped gallium phosphide have been studied under uniaxial stress. The 1.911 eV centre exhibits splitting characteristic of a BE at an axial centre having rhombohedral I symmetry. The electronic degeneracy within each centre is not reduced, in agreement with ODMR and Zeeman spectroscopy. By contrast, the stress splitting of the 2.177 eV (COL) no-phonon line indicates a pure trigonal centre with additional electronic degeneracy in the initial BE state characteristic of an E to A transition with no splitting under (111) stress. The difference is attributed to the character of the electron which is deduced to be in a valley-orbit E state for the 2.177 eV BE, but has normal A character for the 1.911 eV BE. This difference may account for the failure of ODMR studies on the 2.177 eV system while the 1.911 eV BE shows very strong ODMR signal strength, previously incomprehensible since both BE behave as near isotropic spin triplets.

L2,3M45M45Auger Spectra of Metallic Copper and Zinc: Theory and Experiment

The ${L}_{2}{M}_{45}{M}_{45}$ and ${L}_{3}{M}_{45}{M}_{45}$ Auger spectra of clean metallic copper and zinc were measured. A theory was developed to predict the Auger energies. The theory employs experimental electron binding energies, which were also measured, two-electron integrals, and Hartree-Fock energies. It accounts for multiplet splitting in the ${d}^{8}$ final state, predicting structure in excellent agreement with experiment in zinc and in very good agreement in copper. It also accounts for atomic relaxation and for static extra-atomic relaxation (screening), which is related to the Friedel theory of alloys. The theory developed here predicts the Auger energies to within 1 eV in zinc and 2-3 eV in copper. Since atomic integrals were used, the success of the theory implies that an atomistic approach to Auger energies is valid for these metals. The magnitude of the extra-atomic relaxation energy (\ensuremath{\sim} 10 eV) suggests that it may be a crucial factor in Auger energy shifts arising from chemical environment or surface condition.

Vacancy-formation energies in copper and silver from positron annihilation

The method of McKee, Triftshäuser and Stewart has been used to determine the vacancy formation energies in copper and silver. The values obtained are 0.98 ± 0.07 eV for copper and 0.99 ± 0.06 eV for silver.

Atomistics of helium diffusion in copper and tungsten

Abstract Using previously determined interatomic potentials, the activation energy for migration of a single substitutional helium atom in copper and tungsten has been determined. The mechanism of migration involves the jump of the helium atom out of the vacancy concurrent with the jump of a host atom into that vacancy. The helium then occupies the vacant site created by the jumping host atom, resulting in a substitutional helium at a distance of √2 r 0 (√3r 0) from its original site in copper (tungsten). The rate-limiting step in the process is found to be the jump of the helium out of the vacancy, the activation energy for which is 2.15 eV in copper and 4.69 eV in tungsten.

Slow electron scattering from metals: I. The emission of true secondary electrons

The energies and angular distributions of electrons inelastically scattered and emitted from polycrystalline evaporated films of copper and silver and epitaxially grown silver single crystal films have been measured for primary electron energies between 5 and 300 eV. The results of these experiments on the secondary electron emission are presented in this series of papers under the three headings, “I, The emission of true secondary electrons”; “II, The inelastically scattered primary electrons” and “III, The coherently elastically scattered primary electrons”. The true secondary electrons are shown to have a “cascade” form of energy spectrum following the relation ( E s + 4.5) − X , where X = 2.0 for silver and 1.6 for copper, inside the metal. This spectrum is of the same form as that predicted by Wolff and also by Streitwolf. The surface threshold function for slow electrons emitted from copper and silver rises much more rapidly than predicted by the Sommerfield model and is attributed to a free-electron-like electron band starting approximately 0.4 eV below the vacuum level in both copper and silver. For silver, two emission peaks are superimposed on the true secondary electron cascade spectrum at 12.8 and 17.3 eV with intensity halfwidths of 0.75 and 4.0 eV respectively. Both of these emission peaks are most intense along the surface normal and are strongest for a well ordered surface. They are interpreted as due to the decay of hitherto unpredicted surface related excited states. The emissions at 14.1 and 11.7eV in copper and gold are thought to have an origin similar to that of the 12.8 eV emission in silver.

Stress Relaxation in Single Crystals of Copper and α-Brasses

Stress relaxation at constant strains has been studied in crystals of copper and α-brasses containing 10, 20, or 30 at.-% zinc at 77,200, and 291° K after consecutive small plastic deformations. Close to the yield point the relaxation was generally within 1% of the applied stress, but at large deformations, notably within the third stage of work-hardening, it attained ∼ 10%. Any given relaxation was observed for ∼ 1000 sec, over most of which period the decay of the stress was logarithmic in time. Energy barriers of the activated process were from ∼ 0.08 eV for copper and 0.2–0.3 eV for brasses. Their significance is discussed in terms of a model in which unpinning of dislocations from rows of solute atoms is the principal process determining the relaxation rate.

Stage III Annealing in Proton-Irradiated Noble Metals

Pulsing and annealing data are given for 99.999% pure copper specimens which have been proton irradiated at 90\ifmmode^\circ\else\textdegree\fi{}K. It is shown that stage II obeys first-order annealing kinetics and that the structure observed is probably not associated with impurities. Stage III obeys second-order kinetics, and its activation energy in the case of copper is not dependent on dose in the range $\ensuremath{\Delta}{\ensuremath{\rho}}_{0}=3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ cm to $\ensuremath{\Delta}{\ensuremath{\rho}}_{0}=3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ cm. Pulsing experiments in which samples are heated in a msec from -50\ifmmode^\circ\else\textdegree\fi{}C to temperatures up to 230\ifmmode^\circ\else\textdegree\fi{}C and held for 30 msec before quenching show no evidence for any change in the annealing process (i.e., the results can be predicted assuming $E_{M}^{}{}_{}{}^{\mathrm{III}} (\mathrm{Cu})=0.71$ eV and using second-order kinetics). It is shown that if di-interstitial migration is responsible for stage III then the binding energy of di-interstitials exceeds 1.0 eV in copper. If, conversely, two kinds of interstitials migrate in stages I and III, then the pulsing experiment suggests that the barrier preventing conversion of the stage III type to the stage I type is greater than 1.14 eV in copper. No evidence for vacancy migration in proton-irradiated silver is observed during annealing at temperatures above stage III. Existing models suggested to explain the annealing of irradiation damage are reviewed.

Experiments on Stage III Annealing in the Noble Metals

High purity copper, silver, and gold specimens have been irradiated with 10-MeV protons near 80\ifmmode^\circ\else\textdegree\fi{}K. An integrated flux of 1\ifmmode\times\else\texttimes\fi{} ${10}^{17}$ p/${\mathrm{cm}}^{2}$ produced a resistivity increase of 3.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ \ensuremath{\Omega}-cm in copper, 7.4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ \ensuremath{\Omega}-cm in silver, and 16.6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ \ensuremath{\Omega}-cm in gold. The specimens were isothermally annealed in steps of 20\ifmmode^\circ\else\textdegree\fi{}K for 64 min at each temperature from 143 to 363\ifmmode^\circ\else\textdegree\fi{}K. The recovery in stage III follows second-order kinetics with an activation energy of 0.71\ifmmode\pm\else\textpm\fi{}0.04 eV for copper, 0.67\ifmmode\pm\else\textpm\fi{}0.03 eV for silver, and 0.80\ifmmode\pm\else\textpm\fi{}0.04 eV for gold. Distribution curves of the fractional concentration of defects annealing with a given activation energy have been calculated. In the case of copper and silver they show a complex structure followed by a large broad maximum at 0.71 eV for copper and 0.67 eV for silver. In gold there is only one large peak at 0.80 eV. The relationship of these results to the various models is discussed.

Sur la trempe des lacunes dans un polycristal á grains fins

When quenched vacancies disappear preferentially at the outside surface or at grain boundaries, the measured resistance should decrease exponentially with time, after a few minutes. The time constant varies with the dimensions of the grains and gives an absolute value of the diffusion constant D = D 0 exp (− U/ kT) of the vacancies. This analysis should be valid for fine grains and quenches from moderate temperatures. These conditions seem to be fulfilled in recent experiments by Germagnoli et al. leading to D 0 ∼- 5 c. g. s. with U = 1.3 eV for copper and D 0 ∼- 15 c. g. s. with U = 1.5 eV for platinum.