Concentration Of Copper Atoms Research Articles

A new approach to enhance the thermoelectric performance of quaternary chalcogenides copper zinc tin sulfide thin films by varying copper molar concentration

This manuscript revealed an enhancement in the thermoelectric performance of quaternary chalcogenides Cu2ZnSnS4 (CZTS) TFs by the copper (Cu) atoms (1–2.5 mM) modulation during solution growth. Thermo-power data suggested that various performance parameters such as electrical conductivity (σ), Seebeck coefficient (S) and thermo-power factor (P) were improved significantly [(19–183 S/cm), (97–884 μV/°C) and (1.78 × 10−5–1.43 × 10−2 Wm−1K−2)] when the atomic concentration of Copper atoms increased from 01 to 2.5 mM respectively. This trend of thermo-power for CZTS thin films is correlate with development of additional holes along with the generation of Cu based secondary phases. The presence of extra/secondary phases due to additional Cu atoms is supported by some supplementary measurements. XRD data confirmed that some Cu based extra phases were developed at higher concentration of Cu atoms. Raman spectroscopy measurements further revealed that the intensity of Cu based extra/secondary phases was noticed towards higher values when the molar ratio of Cu atoms increased. SEM micrographs demonstrated the rougher surface of CZTS samples which were prepared using higher concentration of Cu when compared with lower concentration samples. UV/VIS Spectroscopy data further confirmed our argument that numbers of other secondary phases were expended with the concentration of Cu atoms.

Interaction of edge dislocation with copper atoms in an aluminum crystal

In this work, the interaction of the moving edge dislocation with obstacles in form of copper atoms is studied using the molecular dynamics simulations. The samples are aluminum monocrystals of 52 × 60 × 15 nm3 with axes oriented along directions [110], [111], [112]. The structure of copper solid solution is reproduced with following procedure: aluminum atoms are randomly selected and replaced by copper atoms. The concentration of copper atoms varies from 0.25% to 1%. The dislocation movement occurs under action of shear deformation. It is found that zones with a low concentration of copper atoms only slow down dislocation in an aluminum matrix, and the zones with a high local concentration of copper atoms not only produces stronger resistance to dislocation movement, but also they cause the change in the slip plane of the dislocation segment. When a significant part of a dislocation line moves to a neighboring slip plane, the complete transition of the dislocation to this slip plane can occur. It is also noted that such transitions of dislocation segments from one slip plane to another are accompanied by the formation of vacancies. Also the maximum value of the shear stress σxy is estimated-its value is approximately 250 MPa.

Temperature Dependence of the Lattice Parameters of Cu2 – xSe (0.03 ≤ x ≤ 0.23) Powders Fabricated by Mechanochemical Synthesis

Abstract—The Cu2 – xSe (0.03 ≤ x ≤ 0.23) powders fabricated by mechanochemical synthesis have been studied by X-ray diffraction. The in situ study has been carried out for the temperature dependences of the lattice parameters, the structures, and the phase compositions of the powders in the temperature range 25–350°C. The powder compositions are shown to differ from the charge compositions and are shifted to lower copper concentrations. The estimation of peak half-widths of the cubic β phase indicates an increase in the structure imperfection after the phase transition from the α phase to the β phase of Cu2 – xSe at ~140°C. It is shown that the superpositions of the subtraction solutions (copper vacancies) and interstitials solutions (copper atoms in interstitial sites), whose proportion is changed as a function of temperature and the deviation from stoichiometry, are in the thermodynamic equilibrium in the copper selenide solid solution at room temperature. The change in the slope of the dependence of the lattice parameter of the powder Cu2 – xSe samples on the composition (0.03 ≤ x ≤ 0.23) in the temperature range 25–350°C enables the suggestion that interstitial copper atom concentration increases with temperature and deviation from stoichiometry.

Температурная зависимость параметра решетки порошков Cu-=SUB=-2-x-=/SUB=-Se (0.03≤ x≤0.23), полученных методом механохимического синтеза

Abstract —The Cu_2 – _ x Se (0.03 ≤ x ≤ 0.23) powders fabricated by mechanochemical synthesis have been studied by X-ray diffraction. The in situ study has been carried out for the temperature dependences of the lattice parameters, the structures, and the phase compositions of the powders in the temperature range 25–350°C. The powder compositions are shown to differ from the charge compositions and are shifted to lower copper concentrations. The estimation of peak half-widths of the cubic β phase indicates an increase in the structure imperfection after the phase transition from the α phase to the β phase of Cu_2 – _ x Se at ~140°C. It is shown that the superpositions of the subtraction solutions (copper vacancies) and interstitials solutions (copper atoms in interstitial sites), whose proportion is changed as a function of temperature and the deviation from stoichiometry, are in the thermodynamic equilibrium in the copper selenide solid solution at room temperature. The change in the slope of the dependence of the lattice parameter of the powder Cu_2 – _ x Se samples on the composition (0.03 ≤ x ≤ 0.23) in the temperature range 25–350°C enables the suggestion that interstitial copper atom concentration increases with temperature and deviation from stoichiometry.

Structure and phase transformations in copper-alloyed rapidly melt-quenched Ni50Ti32Hf18-based alloys with high-temperature shape memory effect

Methods of transmission and scanning electron microscopy, chemical microanalysis, electron diffraction, and X-ray diffraction have been used to carry out the comparative study of the structure and chemical and phase composition of thin ribbons of four quasi-binary alloys (Ni50Ti32Hf18, Ni45Ti32Hf18Cu5, Ni35Ti32Hf18Cu15, and Ni25Ti32Hf18Cu25) obtained in the amorphous state by rapid quenching from the melt by jet spinning. The critical temperatures of the devitrification and B2 ↔ B19′ martensitic transformation of the alloys have been determined based on the data of temperature dependences of the electrical resistivity. The specific features of the formation of the ultrafine-grained structure upon the devitrification and of the phase transformations have been studied depending on the heat-treatment regimes and chemical composition of the alloys (concentration of copper atoms).

Калориметрия процессов распада и образования твердых растворов в системе Al–Cu

The differential scanning calorimetry behavior do eutectic of alloys of the system Al–Cu was investigated the Exo and endo detected thermal characteristics under cooling or heating near the boundary of the limited solubility of aluminum alloys containing about 4 wt. % Copper. It is shown that these effects are not caused by the flow of phase transitions of the first kind. It is assumed that upon cooling they become associated with the solid solution on the bundle of micro volumes of high and low concentration of copper atoms in them. Received 23 .0 2 .2017; accepted 25 .0 4 .2017

Molecular Dynamics Simulation Of Electric Pulse Explosion Of Metal Wires

Molecular dynamics simulation of the bicomponent particle formation as a result of simultaneous electric explosion of copper and nickel wires is carried out. The influence of the internal structure of exploding metal wires and the distance between them on the dynamics of their dispersion, the size and phase composition of the formed particles is investigated. It is shown that the basic mechanism of particle synthesis is the agglomeration of smaller clusters, and the minor one is the deposition of atoms from the gas phase on the particle surfaces. The distribution of chemical elements is non-uniform over the cross section of the synthesized particles. The concentration of copper atoms in the subsurface region is higher than in the particle volume. Varying the loading parameters (temperature, distance between the wires) allows controlling the size and phase composition of the synthesized particles

Modeling of plastic localization in aluminum and Al–Cu alloys under shock loading

Abstract This paper focuses on the modeling of plastic deformation localization in pure aluminum and aluminum–copper alloys during the propagation of a plane shock wave. Modeling is carried out with the use of continual dislocation plasticity model in 2-D geometry. It is shown that the formation of localization bands occurs at an angle of 45° to the direction of propagation of the shock front. Effective initiators for plastic localization in pure aluminum are the perturbations of the initial dislocation density, in the alloys – perturbations of the dislocation density and the concentration of copper atoms. Perturbations of temperature field in a range of tens of kelvins are not so effective for plastic localization. In the alloy plastic localization intensity decreases with an increase of strain rate due to the thermally activated nature of the dislocation motion.

Spectroscopy peculiarities of thermal plasma of electric arc discharge between electrodes with Zn admixtures

Plasma of the free burning electric arc between Ag–SnO2–ZnO composite electrodes as well as brass electrodes were investigated. The plasma temperature distributions were obtained by Boltzmann plot method involving Cu I, Ag I or Zn I spectral line emissions. The electron density distributions were obtained from the width and from absolute intensity of spectral lines. The laser absorption spectroscopy was used for measurement of copper atom concentration in plasma. Plasma equilibrium composition was calculated using two independent groups of experimental values (temperature and copper atom concentration, temperature and electron density). It was found that plasma of the free burning electric arc between brass electrodes is in local thermodynamical equilibrium. The experimental verification of the spectroscopic data of Zn I spectral lines was carried out.

Spectroscopic diagnostics for an electrical discharge plasma in a liquid

We conducted spectroscopic studies of an electrical discharge plasma in a liquid, used for synthesis of nanosized particles of metals and their compounds. From the intensity ratio of the copper lines, we estimated the electron temperature, and from the Stark broadening of the hydrogen lines H α we determined the electron density in the electrical discharge plasma. Information about the concentration of copper atoms in the discharge was obtained from analysis of the spectra in the region of resonance lines of copper. We carried out a comparative analysis of the plasma parameters for spark and arc discharges in water, ethanol, and air. Based on the equation of state for an ideal plasma, taking into account the Debye correction, we estimated the pressure in the plasma channel.

A high efficiency indoline-sensitized solar cell based on a nanocrystallineTiO2 surface doped with copper

Dye-sensitized photoelectrochemical solar cells made from nanocrystalline films ofTiO2 doped with copper and sensitized with indoline 149 dye are found tohave impressively higher efficiencies compared to equivalent cells madefrom undoped films. The surface concentration of copper atoms on theTiO2 where this effect is optimized is nearly the same as the concentration of dye molecules on theTiO2 surface. Copper doping shifts the flat-band potential ofTiO2 in the negative direction, which is favorable for increasing the open-circuit voltage of the cell.It is suggested that in addition to the linkage of the carboxylate ligand of the dye to theTiO2 surface, moieties in the rhodanine rings of the dye coordinate to the copper atoms on theTiO2 surface. The coordination of the dye to copper seems to have a positive influence on theefficiency of the cell.

Structural defects in Cu-doped Bi2Te3 single crystals

The relation between the concentration of free charge carriers and the concentration of copper atoms in Bi2Te3 single crystals doped with copper over a wide range of concentrations has been investigated, with the aim of clarifying the existence of inactive Cu ions. Changes in the concentration of free charge carriers arising from Cu-doping of the melt with that induced by electrochemical intercalation of copper are compared. Models of possible defect structures are proposed for both doped and intercalated single crystals of Bi2Te3.

A new optical technique for investigations of low-Voltage circuit breakers

The technique of broad-band optical absorption spectroscopy has been successfully used for investigations of transient media in low-voltage circuit breakers, thanks to an intense radiation source developed at our laboratory. It enabled the determination of the concentration of copper atoms and C/sub 2/ molecules in hot gas behind a moving arc. The temperature of this gas was estimated using the molecular absorption spectrum of C/sub 2/ Swan bands. Thanks to the high-spectral intensity of the auxiliary source, measurements were also performed in an electrical arc. The measurements allowed the determination of the population of excited levels for several metallic atoms in the arc. Assuming local thermodynamic equilibrium, the electron temperature of the arc and the total concentration of these metallic atoms, coming from contacts and splitters, were deduced. This temperature is in good agreement with the one deduced from optical emission spectroscopy.

Localization of copper atoms in the structure of the ZnO catalyst for methanol synthesis

The microstructure of a copper–zinc oxide catalyst for methanol synthesis has been studied using high resolution electron microscopy. Two alternatives for the arrangement of copper atoms in the zinc oxide crystallite were suggested and discussed. The high concentration of copper atoms in the sample (up to 10 atom%) against the known solubility of Cu2+ ions in ZnO (not more than 2 atom%), as well as the high density of dislocations seen in micrographs of the catalyst, may be accounted for by the occurrence of octahedral copper atom clusters of 0.25 nm radius built up into the host oxide lattice. These clusters lie at the dislocation wall along the (001) plane of ZnO. Copper atoms were also shown to be involved in isolated square planar CuO clusters not more than 0.5–1 nm in size.

REMOTE PLASMA COPPER CVD WITH HYDROGEN AND OXYGEN ATOMS

Thin copper films have been deposited by the room temperature reaction of gaseous copper (II) hexa-fluoroacetylacetonate [Cu(hfa)2] with hydrogen atoms produced in a remote discharge tube. The resulting films are conductive and adherent on a wide variety of substrates. Copper atoms have been observed and measured in the gas phase and were found by atomic absorption spectroscopy to have a maximum concentration of approximately 1011 atoms/cc in the mixing/reaction zone. The reaction of Cu(hfa)2 with oxygen atoms was also studied. The reaction again resulted in the deposition of a film and in addition a green chemiluminescent glow was observed which was identified as due to the gaseous diatomic CuF molecule. Copper atoms were also observed by absorption spectroscopy within this chemiluminescent reaction with oxygen atoms. The copper atom concentration was found to be approximately the same as that found with the H-atom reaction. The copper atom concentrations and the relative emission intensities of CuF were studied as a function of time and position to gain insight into the deposition process.

Parametric study of a high-voltage hollow-cathode infrared copper-ion laser

A new, segmented-electrode, high-voltage, hollow-cathode, Cu II laser, operating on the 780.8 and 782.5 nm transitions, is studied. Parametric measurements are presented for the discharge voltage, the spatially averaged copper-atom concentration and, for the two transitions, the small-signal gain coefficient, the laser threshold current and the laser output power. The dependence of the laser output power on the active length, the buffer-gas pressure and the transmission of the output coupler is modelled using equations for a low-loss, homogeneously broadened, standing-wave laser. For the 780.8 nm line, the lowest threshold current is 0.19 A for a 5 cm active length and a 0.1% transmission output coupler, and the maximum output power is 58 mW for a 3 A discharge current, a 7.5 cm active length and a 2% transmission output coupler. This performance exceeds that of conventional hollow-cathode lasers on the same transition, the improvement being attributed to the increased operating voltage, which gives a more efficient pumping discharge by simultaneously raising the ground-state copper-atom concentration (through the increased sputtering yield of ions bombarding the cathode) and increasing the efficiency of ionization.

Gain measurements at 780.8 nm in a copper hollow anode cathode laser

The results of a parametric study of a copper hollow anode cathode laser operating on the He-Cu+ infrared lines are reported. The discharge voltage, the small-signal unsaturated gain on the 780.8-nm transition, and the ground-state copper atom concentration each exhibit a universal dependence on the ratio J/p of the discharge current density to the total pressure of the helium-argon buffer gas mixture. The laser output power dependencies (780.8 and 782.5 nm) on J/p, while not resulting in universal curves, have common threshold values of J/p. The threshold value of J/p for the 782.5-nm line is approximately twice that for the 780.8-nm line.

Radial inhomogeneities of the active medium plasma parameters in a self-heated copper vapor laser during the interpulse period

An investigation was made of the radial profiles and temporal relaxation of metastable copper atoms during the interpulse period in a self-heated copper vapor laser. The copper atom concentration in the ground state and the electron temperature, together with their radial profiles and time dependences, were determined from the experimental data. In a copper vapor laser with a 2-cm gas discharge-tube diameter the conditions were sometimes characterized by the presence of a radial electron temperature gradient and also a steady-state distribution of the copper atoms differing from the equilibrium distribution by a deficiency of copper atoms on the axis which arose due to an insufficiently high rate of diffusion of the copper atoms to the central zone from the periphery.

Kinetics of precipitation in 17–4 PH stainless steel

The sequence of precipitation and its kinetics in 17–4 PH (precipitation hardening) stainless steel were studied by observing the electrical resistivity and microstructure of the alloy during isothermal aging at various temperatures in the range 320–600°C. By the absence of an incubation period for the onset of precipitation it is shown that there is no free energy barrier to nucleation. The electrical resistivity of the specimen decreased on prolonged aging approaching a steady value asymptotically with time. The alloys aged above 550°C were found to have higher final resistivity values than those aged at lower temperatures. By transmission electron microscopy, local reversion of the martensite to austenite, attributed to enhanced diffusion and concentration of copper atoms at the lath boundaries, was revealed in the specimens aged at temperatures above 550°C. The kinetics of precipitation in the system obeyed the Johnson–Mehl equation. The activation energy Q of the precipitation process was estimated to be 112·2 ± 3·6 kJ mol−l from the resistivity measurements. This may be understood in terms of an enhanced diffusion of copper atoms in the supersaturated matrix caused by a higher dislocation density and a higher concentration of quenched-in vacancies.MST/826

Kinetics of precipitation in 17–4 PH stainless steel

AbstractThe sequence of precipitation and its kinetics in 17–4 PH (precipitation hardening) stainless steel were studied by observing the electrical resistivity and microstructure of the alloy during isothermal aging at various temperatures in the range 320–600°C. By the absence of an incubation period for the onset of precipitation it is shown that there is no free energy barrier to nucleation. The electrical resistivity of the specimen decreased on prolonged aging approaching a steady value asymptotically with time. The alloys aged above 550°C were found to have higher final resistivity values than those aged at lower temperatures. By transmission electron microscopy, local reversion of the martensite to austenite, attributed to enhanced diffusion and concentration of copper atoms at the lath boundaries, was revealed in the specimens aged at temperatures above 550°C. The kinetics of precipitation in the system obeyed the Johnson–Mehl equation. The activation energy Q of the precipitation process was est...