Copper Sequence Research Articles

NO Reduction with CO on Copper and Ceria Oxides Supported on Alumina

The problem about decreasing the harmful emissions of nitrogen oxides in industrial gases or in motor vehicles is an important contemporary task in relation to the environmental protection and people health. Recently, the investigations on this topic increase because of the growing concern about ecological standards. One of the ways of neutralizing nitrogen oxides proposed by modern chemistry is their catalytic conversion to nitrogen. Transition metal oxides have shown very good achievements with respect to NO reduction with CO [1]. The use of spinel catalysts, which are not sensitive to catalytic poisons, is also very helpful. In addition, the spinel formation affects favorably the reduction of oxides. Nhe CuxCo(3-x)O4 spinel catalysts and those promoted with noble metals Pt-Rh/CuCo2O4/c-Al2O3 are found to possess a high activity toward NO reduction with CO [2–6]. Jiang et al. [7] have established TiO2supported and CuOpromoted cerium to demonstrate a high activity in the NO + CO reaction, 100% conversion of NO being achieved at 300 C. The high activity has been ascribed to the presence of four sites of NO adsorption NO (Cu, Cu(I), Cu(II) b Ce) and Cu(I)–Cu b Ce–Ce containing active sites for the NO + CO reaction. Studying the same reaction on preliminary reduced or re-oxidized CuO/TiO2, Jiang et al. [8] observed an activity rising during the reduction of the catalyst surface. This was attributed to reduction-provoked appearance of ‘‘oxygen caves’’ on the catalyst surface, increasing Cu species dispersion and Cu(II) formation. Park et al. [9] investigated the same catalyst type applied on Al2O3 and found the promotion of a cerium catalyst with copper to lead to an enhanced activity towards CO oxidation, the effect on methane oxidation being weaker. Larsson et al. [10] have established that the modification of alumina support with ceria before the copper oxide deposition gives well dispersed copper oxide species and enhances the activity towards CO oxidation. Zou et al. [11] has determined that the interfacial CuO and CeO2 interaction and synergistic effect enhances the red–ox properties of CuO/CeO2 catalyst and the highly dispersed copper species have been proposed as active sites for the selective CO oxidation. The purpose of the present work is to investigate how the way and the sequence of copper and cerium oxide deposition on alumina influence on the activity of the prepared catalysts in the reduction of NO with CO.

Precursor modification for preparation of CIS films by selenization technique

CuInSe 2 films have been prepared using the selenization technique. Preparation of the precursor as well as selenization were carried out by the vacuum evaporation technique. The sequence of copper and Indium layer deposition during precursor preparation affects the morphological and structural properties of precursor which directly have effects on the properties of selenized CIS films. A thin layer of amorphous selenium at the substrate/film interface has been used to improve the adherence of the film. The effect of the Se under-layer has been studied on the layers of copper, indium, CuIn precursors and CIS films, using structural, morphological and optical properties. The surface morphology of a single layer of copper and indium, with and without the Selenium under-layer, are quite different and drastically affect the properties of the precursor and selenized films. The Se under-layer does not take part in the chemical reaction of CIS formation during the selenization process. The modified CIS films are uniform, single phase, polycrystalline, chalcopyrite with (1 1 2) preferred orientation showing an energy band gap of 0.99 eV and an absorption coefficient of ∼10 5 cm −1, and have good adherence to the substrate for the scotch tape test.

Mass Spectrometric Study of Copper(II) β-Diketonates Vapour Thermolysis Mechanism and Kinetics

Vapour thermolysis processes of copper(II) bis-chelate complexes with different β-diketones in the 160-640°C temperature range were studied by using the high-temperature source of a molecular beam with mass spectrometric recording of the gas phase composition directly at the outlet from the thermal reactor. Schemes of a heterogeneous decomposition of these compounds vapour were suggested on the basis of temperature dependences of the thermolysis gaseous products composition. It was established that the mechanisms of thermal conversion of copper(II) complexes with fluorinated and non-fluorinated ligands were not similar. A comparison of the thermal behaviour of the complexes with fluorinated and non-fluorinated ligands in vacuum, hydrogen and oxygen was carried out. Effective values of kinetic parameters in the Arrhenius equation were calculated for the first-order reaction on initial compound from the temperature dependence of the rate constant. The sequence of copper(II) complexes with β-diketones having different end substituents according to the thermal stability was revealed from the values of the thermal decomposition activation energy.

Calculations of 2p lifetimes in the Li sequence.

Lifetime predictions for the 2{ital p} {sup 2}{ital P}{sub 1/2} and 2{ital p} {sup 2}{ital P}{sub 3/2} levels in the lithium isoelectronic sequence have been computed for atomic numbers {ital Z}=3--92 using the semiempirical Coulomb approximation with a Hartree-Slater core. This extends our earlier studies of the sodium and copper sequences, and the results agree well with critically selected experimental lifetime measurements. The calculations involve the inclusion of experimental energy level, ionization potential, and core-polarizability data, and we also report here a comprehensive and reliable data base developed through semiempirical parametrizations of spectroscopic measurements and {ital ab} {ital initio} calculations.

Ionization limits in Cu-like and Ni-like high-Z ions from ab initio calculations and wavelength measurements in Rydberg series.

The transitions from 3${d}^{10}$nf (n=7,8) to 3${d}^{10}$4d, from 3${d}^{10}$nd (n=6,7) and 3${d}^{10}$7s to 3${d}^{10}$4p, and from 3${d}^{10}$6p to 3${d}^{10}$4s are identified in the spectrum of laser-irradiated gold ${\mathrm{Au}}^{50+}$. The ionization limit derived is in good agreement with ab initio evaluations by means of the relativistic parametric potential method. The small deviations between experimental and theoretical ionization limits are consistent throughout the copper sequence and accurate predictions are given for unobserved elements. Similar methods are used for deriving ionization limits of nickel-like ions from 3${d}^{10}$ J=0-3${\mathrm{d}}_{5/2}^{9}$${\mathrm{nf}}_{7/2}$ J=1 known transitions and from ab initio estimates.

Lifetimes and Oscillator Strengths for the Resonance Transitions in Cu-Like Iodine, I XXV

Using the beam-foil time-of-flight technique we have measured decay curves for 4s 2S1/2 -4p 2P1/2, 3/2 and 4p 2P1/2, 3/2 -4d 2D3/2, 5/2 transitions in Cu-like iodine, I XXV. Accurate experimental lifetimes of the 4p levels have been obtained after careful cascade corrections using the ANDC technique. The results are 46.7 ± 2 ps (2P1/2) and 23.1 ± 1 ps (2P3/2). These values are in good agreement with relativistic Hartree-Fock calculations. An up-to-date comparison between experimental and theoretical oscillator strengths is given for the whole copper sequence.

Oscillator strengths for2S-2P transitions in the copper sequence

Theoretical results based on the multiconfiguration Hartree-Fock approximation are reported for 4s2S-4p2P transitions of the Cu sequence. A partially extended Hartree-Fock model was used in which at last 3d orbital was not constrained to be the same as the rest. Some core-polarization effects were also included. Non-relativistic and approximate relativistic f values are reported and compared with observation.

A positron annihilation study of the Fermi surface in concentrated α-phase CuGa alloys

High resolution positron annihilation studies upon a sequence of copper- gallium alloys have determined the variation of the important Fermi surface features with gallium concentration. The Hume-Rothery rules do not arise from contact between the Fermi surface at the [200] Brillouin zone boundary.