Yield Of Cu Research Articles

A new insight in the unusual adsorption properties of Cu + cations in Cu-ZSM-5 zeolite

ZSM-5 zeolites modified with Cu + ions were prepared either by the high-temperature chemical reaction of hydrogen form with CuCl vapour or by the wet ion exchange with subsequent reduction of the modified samples in CO at 873 K. Adsorption of H 2, N 2 or C 2H 6 by Cu + ions was studied by DRIFTS and by volumetric technique. The conclusions about the structure of adsorption complexes were supported by the DFT cluster quantum chemical calculations. The obtained results indicated that in addition to the previously reported strong adsorption of nitrogen, the univalent copper also unusually strongly adsorbs molecular hydrogen and ethane. Adsorption of hydrogen is the most amazing since the observed low-frequency shifts of the H H stretching vibrations were as high as about 1000 cm −1. This is quite different from much weaker H 2 perturbation by Cu 2+ cations. Adsorption of ethane by Cu + ions also resulted in the low-frequency shifts of some of C H IR stretching bands up to 400 cm −1. The DFT cluster modelling indicated that both adsorption of hydrogen and ethane could be explained by interaction with the isolated Cu + ions localized at the α sites of the ZSM-5 framework. Quantum chemical calculations indicated the important role in the bonding of adsorbed hydrogen and ethane of electron back donation from d π-orbitals of Cu + ions to the σ *H H or C H orbitals. The overall yield of Cu + sites of the strong H 2 or N 2 adsorption is about twice lower than the total copper content.

Indirect Determination of Sulfide by Extraction Flotation Spectrophotometry of Copper(II) with Ammonium Sulfate-Ethanol-Water System

A new extraction flotation spectrum method for indirect determination of trace amounts of sulfide by ammonium sulfate-ethanol-water system was developed. It showed that Cu(II) could combine with S 2 - into precipitate (CuS) which was floated in the surface of ethanol and water in the presence of ammonium sulfate. The sulfide can be indirectly determined by determining the flotation yield of Cu(II). The linear range from 2.4 x 10 - 8 to 3.2 x 10 - 6 g/mL and the detect limit of 2.0 x 10 - 8 g/mL was achieved. The results showed the determination of S 2 - was not affected by Pb(II), Zn(II), Cd(II), Fe(II), Co(II), Ni(II), Mn(II) and Cl - , Br - , I - , etc. In the paper, the method was successfully applied to the determination of a trace amount of sulfide in polluted water samples with the advantages of simplicity of equipment, rapidity, low cost, etc.

Simultaneous Optimization of Preparation Conditions and Composition of the Methanol Synthesis Catalyst by an All-Encompassing Calculation on an Artificial Neural Network

A combinatorial approach comprised of a high-pressure high-throughput screening (HTS) reactor, an artificial neural network (ANN), and an all-encompassing calculation was applied to the development of catalyst for methanol synthesis at 1 MPa. Because the optimum catalyst composition is usually dependent on both preparation parameters and reaction conditions, the composition of the catalyst (Cu-Zn-Al-Sc-B-Zr), calcination temperature (300-360 °C), and amount of precipitant (1.0-2.5 times that equivalent to total cations) were optimized simultaneously. In the HTS reactor using 96-well microplates, activities of 190 catalysts with random composition, prepared using the random amount of precipitant and calcined at random temperature, were measured under pressure (1 MPa). The results with an additional 44 datasets were used for the training of ANN. After training, the ANN can map the catalyst activities as a function of the catalyst composition, amount of precipitant, and calcination temperature. An all-encompassing calculation of the 2.6 million activities of all possible combinations of the parameters was conducted to find that the space-time yield of Cu 0.43 Zn 0.17 Al 0.23 Sc 0.11 B 0.00 Zr 0.06 O 1.22 precipitated by 2.2 equiv of oxalic acid and calcined at 334 °C was the global optimum activity.

Monte Carlo simulation of absolute secondary electron yield of Cu

A Monte Carlo simulation model of electron interaction with solids that includes cascade secondary electron production has been used to study secondary electron emission from Cu. An optical dielectric function was used to describe electron energy loss and the associated secondary electron excitation. From the simulation, the absolute primary energy dependence of the secondary yield and the energy distribution of secondary electrons has been obtained. We have compared the calculated true secondary yield and total secondary yield curves with experiment. Good agreement has been found only for those experiment data obtained in ultrahigh vacuum.

Electron emission yield from thin Al and insulating layers induced by 3 MeV He 2+ and 3 keV electron impact

The kinetic electron yield was measured for the impact of 3 MeV He 2+ ions and 3 keV electrons on thin layers of Al on Cu, of Al 2O 3 on Al, and of CeO 2 and CaF 2 on Si backings. The dependence of the yield on the layer thickness was determined. For Al on Cu a decreasing yield was observed for increasing Al layer thickness, since the yield of Cu is higher than that of Al. For insulating layers increasing yields were measured for increasing layer thickness. The observed yield dependencies were fitted by sums of exponential functions. The characteristic lengths of the exponential terms were interpreted as emission lengths. For Al and the metal oxides a small emission length in the range of 2–3 nm was found, for CeO 2 and electron impact on Al a second exponential term with a large emission length, 20–100 nm, was necessary to describe the measured yield dependence, which is probably due to backscattered projectile electrons and δ-electrons. The Al results are compared with computer simulations. The increasing yield of CaF 2 layers could be fitted by a function with only one exponential term and an emission length of 10.8 nm for He impact and 20.6 nm for electron impact.

Indirect Determination of Thiocyanate with Ammonium Sulfate and Isopropyl Alcohol by Extraction‐Flotation of Copper

AbstractA new method for the in direct determination of thiocyanate with ammonium sulfate and isopropyl alcohol by extraction‐flotation of cop per in the presence of ascorbic acid is described. A small amount of Cu(II) is reduced to Cu(I) by ascorbic acid, then Cu(I) is precipitated with SCN−. In the course of phase separation of isopropyl alcohol from water, the precipitated CuSCN stays in the interface of isopropyl alcohol and water. A good linear relationship is observed between the flotation yield of Cu(II) and the amount of SCN−. The detection limit for thiocyanate is 1.0 × 10−5 M, and the linear range is 1.0 × 10−5 ∼ 7.8 × 10−5M. Every parameter was optimized and the reaction mechanism was studied. The method is simple and rapid and it was successfully applied to the determination of thiocyanate in urine and saliva of smokers and non‐smokers and in venous blood of patients in fused with sodium nitroprusside.

Indirect Determination of Ascorbic Acid with Ammonium Sulfate and Ethanol by Extraction and Flotation of Copper

AbstractA new method of indirect determination of ascorbic acid with ammonium sulfate and ethanol by extraction and flotation of copper in the presence of thiocyanate has been studied in this paper. The study shows that a small amount of Cu(II) is reduced to Cu(I) by ascorbic acid, then Cu(I) precipitates with SCN−. In the course of phase separation of ethanol from water, the precipitated CuSCN is extracted and stays in the interface of ethanol and water. A good linear relationship is observed between the extraction yield of Cu(II) and the amount of ascorbic acid. The detection limit for ascorbic acid is 1 10−5 M. Every parameter has been optimized and the reaction mechanism has been studied. The method is simple, rapid (5 min) and suffers from few interferences of common anions and cations. It has been successfully applied for the determination of ascorbic acid in pharmaceuticals and fruits.

Electron emission yield from thin Cu layers on Al induced by 3 MeV He++ and 3 keV electron impact

For 3 MeV He++ and 3 keV electron projectiles the kinetic electron emission yield for copper layers of different thickness on an aluminum backing was measured. Since the electron emission yield of Cu is almost a factor of 2 higher than that of Al an increasing electron yield was measured for increasing thickness of the Cu layer until the yield of pure Cu was reached. For impinging He++ ions the measured yields can be fitted by a function of the layer thickness which contains an exponential term with a characteristic length of 2.6 nm. For 3 keV electron projectiles a much longer characteristic length of 4.8 nm was observed.To explain this dependence our Monte-Carlo simulation program for electron excitation and transport in metals was extended to handle layered structures. In this program the incoming projectiles generate primary electrons due to excitation or ionization of the target (electron gas and core electrons). The primary electrons propagate through the amorphous target and interact with the atomic cores and with the target electrons, thereby generating electron cascades. The propagating electrons are traced until they possibly leave the target or until their energy drops below the energy of the surface barrier. At the layer interfaces the energy levels of the metals are adjusted to have equal Fermi energy. Possible reflection of moving electrons at the interface is taken into account.Using this model the electron emission yield from the surface has been calculated as a function of layer thickness. The measured thickness dependence of the electron yield is well reproduced by the simulation which permits an interpretation on the basis of the underlying interaction processes.

Indirect determination of thiocyanate with ammonium sulfate and ethanol by extraction-flotation of copper.

A new method for the indirect determination of thiocyanate with ammonium sulfate and ethanol by extraction-flotation of copper in the presence of ascorbic acid is described. A small amount of Cu(II) is reduced to Cu(I) by ascorbic acid, then Cu(I) is precipitated with SCN-. In the course of phase separation of ethanol from water, the precipitated CuSCN stays in the interface of ethanol and water. A good linear relationship is observed between the flotation yield of Cu(II) and the amount of SCN-. Using 1.0 ml of 1 x 10(-3) M ascorbic acid solution, 50 micrograms of Cu(II), 3.5 g of (NH4)2SO4 and 3.0 ml of ethanol with a total volume of 10 ml, the concentration of thiocyanate could then be determined by determining the flotation yield of Cu(II). The detection limit for thiocyanate is 5 x 10(-5) M. Every parameter was optimized and the reaction mechanism was studied. The method is simple and rapid and it was successfully applied to the determination of thiocyanate in urine and saliva of smokers and non-smokers and in venous blood of patients infused with sodium nitroprusside.

Mechanistic Studies of Palladium Thin Film Growth from Palladium(II) β-Diketonates. 2. Kinetic Analysis of the Transmetalation Reaction of Bis(hexafluoroacetylacetonato)palladium(II) on Copper Surfaces

The reaction pathways and kinetics for the selective deposition of palladium on copper from the metal−organic precursor Pd(hfac)2 have been established by means of reactive molecular beam−surface scattering where a flux of Pd(hfac)2 (ranging from 1013 to 1014 molecules cm-2 s-1) impinges continuously on the copper surface. The surface selectivity of the deposition process is a consequence of a “redox transmetalation” reaction, which is best described by the stoichiometric equation Pd(hfac)2 + Cu → Pd + Cu(hfac)2. On polycrystalline copper foils, the production and subsequent desorption of Cu(hfac)2 from the surface occurs with unit efficiency at temperatures between 400 and 600 K. At temperatures above 600 K, the yield of Cu(hfac)2 decreases and eventually falls to zero at 800 K as the thermolytic decomposition of the hfac ligands on the surface becomes kinetically competitive. We have devised a steady-state kinetic model of the adsorption of Pd(hfac)2, desorption of Cu(hfac)2, and thermolytic decompositi...

Effect of copper(II) ions on the stability of spin adducts formed by the reaction of 5,5-dimethylpyrroline-N-oxide with hydroxyl and hydroxylalkyl radicals

The reactions of copper(II) species with spin adducts formed by reaction of OH·, CH3CHOH or (CH3)2COH with DMPO (5,5-dimethylpyrroline-N-oxide) have been investigated. The spin adducts prepared by γ-irradiation of appropriate solutions were detected using esr. Copper(II) in the form of aqua, phen, or 1-alanine complexes reacted rapidly with the OH· adduct to give products that gave no esr signal, but with the hydroxylalkyl adducts, reacted to give a new 9-line esr signal, identified as due to the H· adduct, (DMPO-H·). Measurement of the yield of Cu(phen) 2 + formed by reaction of the copper(II) complex with the spin adduct showed that approximately 25% of the radiation-produced radicals formed esr detectable spin adducts. The implications of these findings for the use of spin trapping to detect radical intermediates in biological systems is discussed.

Low molecular weight metal complexes in the freshwater moss Rhynchostegium riparioides exposed to elevated concentrations of Zn, Cu, Cd and Pb in the laboratory and field

The possible occurrence of low molecular weight, soluble ligands binding copper, zinc, cadmium and lead was investigated in Rhynchostegium riparioides, a widespread moss in flowing waters, which occurs at sites influenced by “heavy” metal contamination as well as ones free of contamination. In order to identify metal complexes with any such ligands, Rhynchostegium plants from an uncontaminated site were first incubated for 48 hr in medium including the metal (10 or 100 μM) in question. Fractionation of cell extracts of this material by gel permeation HPLC revealed the presence of complexes with a similar retention time to poly(γ-glutamylcysteinyl)glycine metal complexes extracted from cell suspension cultures of Datura innoxia. However, the peaks corresponding to metal associated with these complexes in HPLC profiles of extracts from Rhynchostegium were low, so an acetone precipitation step was introduced to concentrate the bound metal. The estimated yield of Cu associated with low M r ligands following acetone precipitation was 65% for Rhynchostegium and 106% for D. innoxia; the equivalent values for Cd were 25 and 40%, respectively. A Zn complex with a different apparent retention time was also present; the possibility that this might be an artifact associated with the extraction procedure is discussed. There was no evidence for intracellular binding of Pb by low M r ligands. Estimates of the amount of Cu and Cd associated with low M r ligands increased following incubation of Rhynchostegium from an uncontaminated site in media containing increasing concentrations (10, 50, 100 μM) of metal. Similar complexes were also detected in populations of the same species taken directly from a contaminated site, i.e. without laboratory incubation in the presence of metal. Estimates of the proportions of Cu and Cd in Rhynchostegium from contaminated sites which were bound by these complexes, expressed as a percentage of the total metal accumulated by the moss, ranged from 0.06 to 0.65% for Cu and 0.24 to 2.08% for Cd.

Study of Cunand Cun+(n=1, 2, 3) cluster formation under ion bombardment

Abstract Yields and energy spectra of neutral and charged particles sputtered from Cu target under 5.5 keV Ar+ ion bombardment have been measured. The yield of Cu n neutrals falls off rapidly with increasing n that can be explained by the recombination model. The yield of Cu n + ions depends unmonotonously on n. The ionization probability of sputtered particles is described by an exponential dependence exp[-(I n - ϕ)/∊0], where I n is the ionization potential of Cu n cluster, ϕ is the work function and ∊0 is a parameter.

Measurements of energy distributions and yields of neutral Cu 2 and Cu 3 species sputtered from Cu by low energy Ar + ions

Polycrystalline copper was bombarded by normally incident, very low energy argon ions ( E 0 = 100–1000 eV). The translational kinetic energy distributions and relative yields of neutral Cu 2 and Cu 3 species sputtered normally from the copper surface were measured using a secondary neutral mass spectrometer. The energy distribution of a given species (Cu 2 or Cu 3) was found to be approximately constant in shape for 600 < E 0 < 1000 eV. However, for E 0 < 600 eV, the distributions narrowed as the bomba ion energy was lowered. For a given bombarding ion energy, the energy distributions were found to be narrower for higher-order sputtered species, and the asymptotic falloff was steeper for the latter. The average kinetic energies ( E ) were in the order: E(Cu 1) > E(Cu 2) > E(Cu 3) . E(Cu 2) increased with increasing bombarding ion energy. The relat depend on the total sputtering yield of copper squared and the relative yield of Cu 3 on the total yield cubed. The measured polyatomic energy distributions and relative yields indicate that a multiple-collision process is responsible for sputtered neutral metallic cluster formation in this system.

Sputtering yield of Cu and Ag at target temperatures close to the melting point

Cu and Ag were sputtered at normal incidence by H + , D + , He + , Ne + , and Ar + ions at energies between 3 and 6 keV. The target temperature was varied between room temperature and 80–90% of the melting temperature. The sputtering yield was measured by the weight loss method. Within the accuracy of the measured data, no temperature dependent change of the sputtering yield was found, but the surface structure did show a significant change. Only in the case of recrystallisation could a change of the sputtering yield of about 20% be detected.

The angular distribution of particles sputtered from Cu, Zr, and Au surfaces by ion bombardment at grazing incidence

The angular distribution of particles sputtered from polycrystalline Cu, Zr, and Au targets has been measured for bombardment with Ar +- and Xe +-ions at perpendicular and grazing ion incidence (80° and 85° with respect to the surface normal). The ion energy was varied between 100 keV and 900 keV. The measured distributions follow approximately a cosine-squared curve rather than the cosine function, they are found to be symmetric with respect to the surface normal and almost independent of the ion species, the ion energy and the angle of incidence. Values of sputtering yield of Cu, Au and Zr are also presented.

Low energy sputtering of neutral Cu 2 molecules

The ratios of relative yields of neutral sputtered Cu 2 molecules to neutral sputtered Cu atoms were found to be linearly proportional to the sputtering yield of Cu, from a Cu target under bombardment by Ar + ions (energy 50–90 eV), as determined by secondary neutral mass spectrometry.

Sensitized photolysis of bis(acetylacetonato)copper(II); general reaction pattern

Bis(acetylacetonato)copper(II) was sensitized by some ketones with a wide range of triplet energies to undergo photodecomposition to give the same products as that obtained in the direct photolysis but with much better efficiency. Other sensitizers such as fluorenone and aromatic hydrocarbons failed to sensitize the reaction. There exists no correlation of the sensitizer triplet energies with the sensitization results. This, and rapid quenching processes, indicated that the classical energy transfer process was unlikely. The sensitization process by an electron transfer within an encounter complex was proposed to explain the decomposition of Cu(acac)2; the calculated free energy changes (ΔG) associated with the electron transfer from the available data support the proposal. Chemical reactions of excited state anthracene and 1-cyanonaphthalene with Cu(acac)2 may also occur. Irradiation of Cu(acac)2 in the presence of triphenylphosphine and benzophenone led to an excellent yield of Cu(acac)(PPh3)2 without causing precipitation of copper(I) complexes.

EXAFS in photoelectron yield spectra and optimisation of the photon glancing angle

The variation with the photon energy of the photoelectron yield of Cu has been measured near the K edge. The fine structure of the yield agrees with the fine structure of absorption spectra (EXAFS). The radial structure function, the envelope function, and the scattering phase of a single Cu shell have been calculated from the yield spectrum. The results are similar to those extracted from the absorption coefficient. The yield increases with decreasing glancing angle of the incident photons. A variation of the height of the Cu edge and the amplitude of the EXAFS modulation with this angle is observed. This is explained by the escape mechanism of the electrons.

スパッタ率測定へのマイクロバランスの応用

The torsion vacuum microbalance technique useful for the determination of the sputtering yield of wall materials for fusion reactors was developed. In order to measure the rate of weight change of the samples during sputtering continuously, it is very important to keep the null point drift of the microbalance as small as possible. The deflection angle of the balance beam was detected and amplified by optical lever, and was transformed to electrical output by linear photopotentiometer. The null point drift was mainly caused by temperature change in the laboratory, which induced relative displacement by thermal expansion between the balance system and the optical measuring system. The drift was reduced less than the equivalent weight of 4 × 10 -7 g/hr when the balance system wosset in the thermostat kept at 20 ± 0.5 °C. The sensitivity of the balance was 8.3 × 10 -7 g/mV.The microbalance technique developed was applied to the measurement of sputtering yield of Cu by Ar+. The measurement was carried out with Ar+ ion energy of 0.22 keV, beam current of 0.51.5 μA, and sputtering time of 2 hrs. The initial weight of Cu sample was 0.4g (15 mm × 15 mm sheet) and the sample temperature during sputtering was about 120 °C. The sputtering yields obtained show good agreement with the results reported by Wehner et al. [8] and Weijsenfeld [9].