Vacuum discharge as an effective source of multiply charged ions

The time-of-flight (TOF) spectra measured under high vacuum conditions revealed ion beams of a cathode material (Cu ⁿ⁺) with a maximum charge of up to +19 generated in the initial stage of a spark discharge development at a storage voltage of up to U ₀=2.5 kV. As the U ₀ value increases, the range of the multiply charged states of ions detected by the TOF technique increases, the average ion charge reaching +9.     

Spectral studies on CuO in sodium–calcium borophosphate glasses

Transparent borophosphate glasses doped with CuO were prepared by melt quenching technique. X-ray diffraction (XRD), optical and luminescence properties of sodium–calcium borophosphate glasses doped with CuO have been studied. The XRD results showed the amorphous nature of the sample. The introduction of CuO was favourable for the colour changes from light blue to dark bluish green colour. Direct optical energy bandgaps before and after doping with different percents of copper oxide obtained in the range 4.81–2.99 eV indicated the role of copper in the glassy matrix by ultraviolet (UV) spectra. The glasses have more than 80% transparency for emission wavelength range, and strong absorption bands due to the charge transition of the Cu⁺ and Cu²⁺ ions were observed. The emission bands observed in the UV and blue regions are attributed to 3d⁹4s–3d¹⁰ triplet transition in Cu⁺ ion.     

Coefficient of Ion Erosion of the Vacuum Arc of Metals and Alloys

Consideration has been given to the basic processes in the cathode spot of the vacuum arc of metals and alloys. Based on the analysis of a simplified equation of heat balance of the vacuum-arc cathode spot, formulas for evaluating the values of the coefficient of ion erosion of metals and alloys have been obtained. The calculated and experimentally measured values of the coefficients of ion erosion of certain metals have been compared and their satisfactory agreement has been shown.     

Equilibrium and kinetic studies of copper adsorption by activated carbon

Copper adsorption by granular activated carbon is reported in this paper. The experimental section includes titrations of activated carbon, as well as equilibrium and kinetic studies of copper adsorption. The potentiometric titration results show that the point of zero charge is 9.5, and that the surface charge increases with decreasing pH. The adsorption of copper strongly depends on solution pH and increases from 10 to 95% at pH ranging from 2.3 to 8. A dramatic increase in pH and emission of small gas bubbles are observed during the experiments, which may result from adsorption of hydrogen ion and/or reduction-oxidation reactions. The two-pK triple-layer model is employed to describe copper adsorption. KINEQL, an adsorption kinetics algorithm, is used to represent the experimental data, and it is found that the model can describe reasonably well the experimental measurements of surface charge, adsorption equilibrium, and adsorption kinetics. Calculations show that formation of the surface-metal complexes SO⁻Cu²⁺ and SO⁻CuOH⁺ (a hydrolysis product of SO⁻Cu ²⁺) in the outer layer around the surface of carbon results in removal of copper ion. It is also found that mass transfer controls the adsorption rate, and that adsorption occurs in the micropore region where both external mass transfer and diffusion are important.     

Fabrication and optical features of the sol–gel derived silica glasses doped with copper oxide nanoparticles and europium

Novel sol–gel derived silica glasses doped with copper oxide nanoparticles and europium ions have been fabricated in order to design a multicomponent luminescent material. The photoluminescence studies indicated the significant effect of copper oxide upon the light emission due to europium ions while the emission from copper oxide is similar with that due to Cu⁺. The emission of europium ions in the Cu₂O:Eu³⁺-codoped glasses can be done through excitation of copper oxide.     

The effect of cathode deuteration on the parameters of vacuum-arc plasma

We propose a model for determining the influence of the relative content of deuterium in a zirconium cathode on the properties of vacuum-arc plasma. It is shown that the occlusion of deuterium in the cathode leads to an additional energy consumption for its ionization and to the related decrease in the average charge of cathode material ions in the discharge plasma. Deuterium in the cathode spot is fully ionized, and the drift velocity of deuterium ions almost coincides with that of ions of the cathode material.     

Preparation and characterization of zeolite framework stabilized cuprous oxide nanoparticles

Zeolite framework stabilized copper(I) oxide nanoparticles (4.8 ± 2.6 nm) were prepared for the first time by using a four step procedure: the ion exchange of Cu²⁺ ions with the extra framework Na⁺ ions in Zeolite-Y, the reduction of the Cu²⁺ ions within the cavities of zeolite with sodium borohydride in aqueous solution, the dehydration of Zeolite-Y with the copper(0) nanoclusters, and the oxidation of intrazeolite copper(0) nanoclusters by O₂ at room temperature. Zeolite stabilized copper(I) oxide nanoparticles were thoroughly characterized by ICP-OES, XRD, HR-TEM, Raman, XPS, UV-vis spectroscopy and N₂ adsorption-desorption technique.     

Comparative investigation on the effect of alkaline earth oxides on the intensity of absorption bands due to Cu<Superscript>2+</Superscript>, Mn<Superscript>3+</Superscript> and Cr<Superscript>3+</Superscript> ions in ternary silicate glasses

Absorption characteristics of Cu²⁺, Mn³⁺ and Cr³⁺ ions in ternary silicate (20Na₂O·10RO·70SiO₂, where R=Ca, Sr, Ba) glasses were investigated. The intensities of absorption bands due to Cu²⁺ ion was found to increase with increasing ionic radii of the alkaline earth ions whereas it was found to decrease in case of Mn³⁺ and Cr³⁺ ions with increasing ionic radii of the alkaline earth ions. The results were discussed in the light of relation between linear extinction coefficients of these ions and coulombic force of alkaline earth ions. The change in intensities of Cu²⁺, Mn³⁺ and Cr³⁺ ion is attributed due to change in silicate glass compositions.     

Structural and electrical properties of fritless Ni(1?x)CuxMn2O4 (0?≤?x?≤?1) thick film NTC ceramic

Spinel structured NTC thermistor Ni_(1−x)Cu _x Mn₂O₄ (0 ≤ x ≤ 1) ceramics was prepared by oxalic precursor method and fritless thick films screen printed on alumina. The composition dependent structural and electrical properties are reported in this paper. The results show that with increasing copper ion substitution both Cu²⁺ and Mn⁴⁺ predominantly occupy the octahedral site. The concentration of Cu²⁺ ions in octahedral site increases while that of Ni²⁺ ions decreases linearly. The thick film Ni_(1−x)Cu _x Mn₂O₄ ceramic comply with Arrhenius equation. A thermistor constant of ~1,200 K has been obtained for fritless thick film NTC ceramics using inorganic binders in the RT/90 thermal range.     

In situ e.s.r. monitoring of the coordination and oxidation states of copper in Cu-ZSM-5 up to 500°C in flowing gas mixtures: 2. Interaction with CH4 and CO

A flow cell was used for the monitoring of the state of copper ions in Cu-ZSM-5 in situ at high temperatures by e.s.r. Reduction of the most reactive square-planar coordinated Cu²⁺ ions to Cu⁺ occurs at 500°C in methane flow. The reoxidation of cuprous to cupric ions at 500°C by NO or O₂ is very fast; and, at 500°C, in mixtures of CH₄ with excess oxygen, most of the copper in CuH-ZSM-5 retains the cupric state. The formation of weak adsorption complexes between isolated Cu²⁺ cations and CO molecules at 200°C leads to a measurable change in coordination. An activated formation of strong adsorption complexes, with charge transfer, takes place on treatment of the CuH-ZSM-5 by CO at 100–300°C. Subsequent heating in He flow removes all ligands at T > 400°C. At 500°C, in CO flow a slow reduction of Cu²⁺ takes place. Cooling of the CuH-ZSM-5 in a mixture [CO + NO] is accompanied by a change in Cu²⁺ coordination which is indicative of a mixed adsorption complex.     

Stacking Order Induced Anion Redox Regulation for Layer-Structured Na0.75Li0.2Mn0.7Cu0.1O2 Cathode Materials

Stacking order plays a key role in defining the electrochemical behavior and structural stability of layer-structured cathode materials. However, the detailed effects of stacking order on anionic redox in layer-structured cathode materials have not been investigated specifically and are still unrevealed. Herein, two layered cathodes with the same chemical formula but different stacking orders: P2-Na_0.75Li_0.2Mn_0.7Cu_0.1O₂ (P2-LMC) and P3-Na_0.75Li_0.2Mn_0.7Cu_0.1O₂ (P3-LMC) are compared. It is found that P3 stacking order is beneficial to improve the oxygen redox reversibility compared with P2 stacking order. By using synchrotron hard and soft X-ray absorption spectroscopies, three redox couples of Cu²⁺/Cu³⁺, Mn^3.5+/Mn⁴⁺, and O²⁻/O⁻ are revealed to contribute charge compensation in P3 structure simultaneously, and two redox couples of Cu²⁺/Cu³⁺ and O²⁻/O⁻ are more reversible than those in P2-LMC due to the higher electronic densities in Cu 3d and O 2p orbitals in P3-LMC. In situ X-ray diffraction reveals that P3-LMC exhibits higher structural reversibility during charge and discharge than P2-LMC, even at 5C rate. As a result, P3-LMC delivers a high reversible capacity of 190.3 mAh g⁻¹ and capacity retention of 125.7 mAh g⁻¹ over 100 cycles. These findings provide new insight into oxygen-redox-involved layered cathode materials for SIBs.     

Study of valence states of copper in copper-phosphate glasses

Phosphate glasses containing CuO with composition, [(CuO) _x (P₂O₅)_1–x ], x=0.10, 0.20, 0.25, 0.30, 0.40 and 0.50, were studied by magnetization, X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS). It was observed that compositional changes take place in going from batch to glass and these changes are more pronounced for low copper concentration. The ratio [Cu²⁺/Cu_total] as a function of x was determined from XPS and magnetization combined with RBS. The magnetization measurements suggest that more than 90% of the copper ions exist in the Cu²⁺ state in the glasses, while the XPS data show that less than 50% of the copper ions may be in the Cu²⁺ state. The low Cu²⁺ states detected by XPS may have resulted form reduction of copper ions upon exposure of the samples to X-ray radiation during measurement.Author to whom all correspondence should be addressed.     

Synthesis of new sulphides of transition metal ions in presence of sun light

New sulphides of transition metal ions [M⁺ⁿ = Cu⁺¹, Cu⁺² and Zn⁺²] have been synthesised in sunlight. XRD patterns show that these compounds are not MxSy but are mercaptyl, hydroxyl metal sulphides [M(SH)(OH)(H₂O)₂] which is further ascertained by I.R. spectra showing bands due to T _d-symmetry. ESCA of compound of copper in solid state shows presence of Cu¹⁺ and Cu²⁺ ion. The presence of hydroxyl, mercaptyl, aqua and S^–2 groups has finally been confirmed with TGA, DTA and ESCA. Conductivity and Seebeck coefficient measurements show that compound of copper is p-type semiconductor and compound of zinc is n-type semiconductor. The production of these low cost materials opens an interesting area of research and development for their use in solar cell devices.     

Highly efficient fluorescence probe for copper (II) ions based on gold nanoclusters supported on wool keratin

A highly efficient fluorescence gold nanoclusters probe for copper (II) (Cu²⁺) ions among various ions has been prepared through wool keratin as chelating and reducing agent. The main features of fluorescent gold nanoclusters supported on wool keratin (AuNCs@WK) probe are the high fluorescence in aqueous solution, the simplicity of synthesis and the hypotoxicity for living cells. The fluorescence probe exhibits high stability of pHs and shows more sensitivity under acidic condition. Upon exposure to various metal irons, only AuNCs@WK system with Cu²⁺ ions shows a fluorescence turnoff response changing from red to blue under UV light, which lead to the dramatically decreased fluorescent intensity of AuNCs@WK at 690 nm. Moreover, the high sensitivity of AuNCs@WK around 1 µM meets the need of detection standards. The slope of Stern–Volmer plot at low concentration of Cu²⁺ ions is greater than it at high concentrations, which indicates the aggregated AuNCs are from small amounts to large numbers with the increasing concentration of Cu²⁺ ions. The design mechanism of AuNCs@WK probe is the coordination of reactive groups to produce the complex (wool keratin-Cu-wool keratin) at 1:2 between Cu²⁺ ions and fluorescence probe. Furthermore, the cytotoxicity in cells indicates that AuNCs@WK system is safe for the selective imaging of copper ions in living cells.     

Structural and electrical study of ZnCuTiO4, ZnCuSnO4 and ZnCuGeO4 synthesised using metallic copper

The structural study of ZnCuTiO₄, ZnCuSnO₄ and ZnCuGeO₄ reveals that while the cooperativeJ-T effect of Sn⁴⁺ is responsible for the orthorhombic symmetry of ZnCuSnO₄, the hexagonal influence of Ge⁴⁺ is more predominant in ZnCuGeO₄. Ti⁴⁺ is uninfluential either in initiating the distortive tendency or cooperating with other ions for the same. The XRD,ρ _RT, ΔE and the nature of the charge carriers, all suggest that the air oxidation of metallic copper leads to the minority concentration of Cu⁺ along with a majority concentration of Cu²⁺, as demanded by the stoichiometric considerations of these compositions.     

Montmorillonite surface properties and sorption characteristics for heavy metal removal from aqueous solutions

Surface properties of montmorillonite (MMT) and its adsorption characteristics for heavy metals have been investigated with nickel and copper as sorbate from aqueous solutions. Employing the potentiometric and mass titration techniques in batch experimental methods, the point of zero charge (PZC) and point of zero net proton charge (PZNPC) of MMT edges at different ionic strengths present pH_PZC and pH_PZNPC to be 3.4 ± 0.2. A crossing point was observed for the proton adsorption vs. pH curves at different ionic strengths of KCl electrolyte and in investigating MMT remediation potentialities as sorbent for heavy metals polluted waters, the effects of heavy metal concentration, pH, MMT dosage, reaction time and temperature for Cu²⁺ and Ni²⁺ uptake were studied. The sorption of metal ions by MMT was pH dependent and the adsorption kinetics revealed sorption rate could be well fitted by the pseudo-second-order rate model. The data according to mass transfer and intraparticle diffusion models confirmed diffusion of solutes inside the clay particles as the rate-controlling step and more important for the adsorption rate than the external mass transfer. Adsorption isotherms showed that the uptake of Cu²⁺ and Ni²⁺ could be described by the Langmuir model and from calculations on thermodynamic parameters, the positive ΔG° values at different temperatures suggest that the sorption of both metal ions were non-spontaneous. Change in enthalpy (ΔH°) for Ni²⁺ and Cu²⁺ were 28.9 and 13.27 kJ/mol K respectively, hence an endothermic diffusion process, as ion uptake increased with increase in temperature. Values of ΔS° indicate low randomness at the solid/solution interface during the uptake of both Cu²⁺ and Ni²⁺ by MMT. Montmorillonite has a considerable potential for the removal of heavy metal cationic species from aqueous solution and wastewater.     

Metal-reduction-induced changes in the paramagnetic properties and the rate of oxygen and hydrogen exchange in copper-containing coal-tar carbon fibers

Changes in the binding of copper to a carbon matrix during the reduction of Cu²⁺ ions to metallic state (Cu⁰) influence the EPR spectra of unpaired electrons and the rate of hydrogen (H₂) and oxygen (O₂) exchange in coal-tar carbon fibers (CFs) with copper chloride (CuCl₂ · 2H₂O) deposited from solution. In the presence of the carbon matrix, Cu²⁺ ions are reduced to Cu⁰ by H₂ at a lower temperature (150°C) than in a pure copper salt. The Cu²⁺ → Cu⁰ transition on the CF surface is accompanied by changes in the EPR spectra of unpaired electrons (g value, linewidth, saturation of resonance transitions). The binding of H₂ to the CF-Cu⁰ surface becomes stronger and the rate of H₂ displacement by O₂ from the pores decreases and becomes equal to the rate of O₂ displacement by H₂.     

Effect of high-pressure/high-temperature processing on V, Mn, Fe, Co, and Ni substitutions for copper in the structure of CaCu3V4O12

X-ray diffraction data demonstrate that high-pressure (7.0–8.0 GPa), high-temperature (700–1100°C) processing enables partial V, Mn, Fe, Co, and Ni substitutions for copper in the structure of the double perovskite CaCu₃V₄O₁₂. The lattice parameter of CaCu_{3 ? x} Ni _x V₄O₁₂ (a = 7.294–7.298 Å) exceeds that of CaCu₃V₄O₁₂ (a = 7.2845 Å) even though the Ni²⁺ ion (0.69 Å) is smaller than the Cu²⁺ ion (0.72 Å). This may be due to lattice distortion caused by the presence of two Jahn-Teller ions (Cu²⁺ and Ni²⁺). The oxides CaCu₂CoV₄O₁₂ and CaCu₂FeV₄O₁₂ are shown to have metallic conductivity.