Copper Electrode Surface Research Articles

TWT Efficiency improvement by a low-cost technique for deposition of carbon on MDC electrodes

A simple method of improving the TWT and multistage depressed collector (MDC) efficiency has been demonstrated. The efficiency improvement was produced by the application of a thin layer of carbon to the copper electrodes of the MDC by means of a rapid low-cost technique involving the pyrolysis of hydrocarbon oil in electric arc discharges. Experimental results with a representative TWT and MDC showed an 11 percent improvement in both the TWT and MDC efficiencies as compared to those of the same TWT and MDC with machined copper electrode surfaces. An extended test with a 550-W CW TWT indicated good durability of the carbon-coated electrode surfaces.

Characterization of oxide layers on copper by linear potential sweep voltammetry

The characteristics of the electrochemical reduction of copper oxide have been studied using linear potential sweep voltammetry. Copper(II) and copper(I) oxides, formed on copper electrodes during triangular potential cycling, reduced at potentials close to the reversible values for the CuO−Cu2O and Cu2O−Cu couples, respectively. The reduction of bulk Cu2O and CuO deposited on carbon paste, glassy carbon and copper electrode surfaces required significant overpotentials. Both oxide species could be distinguished from the potentials of their cathodic reduction peaks. In each system studied, CuO was reduced before Cu2O. We discuss the implications of these findings on the Pops and Hennessy galvanostic method for determining oxides formed on copper in the wire industry.

An electrochemical and Raman spectroscopic investigation of synergetic effects in the corrosion inhibition of copper

The synergetic inhibition of copper corrosion by benzotriazole (BTA) and benzylamine (BZA) in chloride and cyanide media is assessed by voltammetric and ac impedance measurements. BZA enhances the performance of the strong inhibitor BTA by accelerating the growth of a protective surface layer; used alone, BZA is ineffective as an inhibitor. The competitive adsorption of aggressive anions and inhibitors is studied by surface enhanced Raman scattering (SERS). The dramatic increase in corrosion caused by low concentrations of cyanide ions is shown to be due to the displacement of BTA from the copper electrode surface; comparisons are made with the behaviour of mercaptobenzoxazole (MBO).

Enhanced Raman spectroscopic study of the coordination chemistry of malononitrile on copper surfaces: Removal of ν(CN) degeneracy through π-coordination

Surface-enhanced Raman spectroscopy has been used to study the molecular interactions of malononitrile with copper electrode surfaces. The doubly degenerate CN stretching frequency at 2263 cm −1 is removed when malononitrile adsorbs on copper. Two ν(CN) bands are observed at 2096 and 2204 cm −1 at −0.6 V(SCE). The result shows that only one CN group is π-coordinated with Cu, which contributes to the observed large shift (−167 cm −1) in ν(CN). The other CN group is not coordinated to the metal surface.

Surface enhanced Raman spectroscopy and electrochemistry at the copper/iodide, water interface

Normal Raman spectroscopy, ESCA, SEM and cyclic voltammetry have shown that under certain conditions both Cu 2O and CuI are formed as films on a copper electrode surface. In dilute iodide solutions (10 −1 M) the electrochemical data show that dissolution of copper, probably as CuI 2 −, is a significant process and for 1M iodide its importance is even greater. A reaction scheme is proposed. SERS spectra have shown that I − intensity is dependent upon the nature of the background metal cation and pH. In addition the SERS signal and the inelastic background continuum have been found to decay with time. This time dependence was investigated and it was found that it could be controlled by the use of low incident laser powers.

Copper deposition overvoltage on non-renewed and continuously mechanically renewed copper electrode surfaces in the Tafel potential region

The copper deposition overvoltage in the Tafel potential region on both non-renewed and continuously mechanically renewed working electrode surfaces in H 2SO 4-CuSO 4 solutions of various compositions (0.06 - 0.75 M CuSO 4 + 2 M H 2SO 4) was studied using a copper self-cleaning rotating electrode. A decrease in the overvoltage on the continuously mechanically renewed electrode surface was observed in the Tafel region for all solution compositions investigated.

Molecular interaction and orientation of selenourea on copper and silver electrode surfaces: A surface-enhanced Raman spectroscopic study

Surface-enhanced Raman spectra of selenourea on copper and silver electrodes have been obtained. The frequencies of vibrational modes involving CSe stretch for the free molecule were decreased upon adsorption, indicating a reduction in the C bond order. We conclude that selenourea is Se-bonded to the copper and silver surfaces.

Laser microzone damage in surface‐enhanced Raman scattering by pyridine on cooper electrodes

AbstractSurface‐enhanced Raman scattering (SERS) by pyridine on anodized copper electrode surfaces has been shown to arise from laser damage zones. On the basis of pH dependence studies, the intensely scattering species appears to be a copper complex. Evidence for semi‐macroscopie laser damage zones (ca 0.1 mm in diameter, ca 500 nm or ca 1400 atom layers in depth) emerges from laser perforation of thin film electrodes, visual examination, scanning electron micrescopy (SEM), Raman line intensification for laser illumination during the oxidation‐reduction cycle (ORC), uniform laser‐flux perturbations of the cyclic voltammograms and laser interruption intensity studies. These results argue for a much reduced metal surface enhancement factor for this system and against the use of copper SERS effects in studies of electrosorption on undamaged surfaces. SERS from this system at excitation wavelengths greater than 620 nm is expected to involve conventional (non‐surface)resonance enhancement arising from copper(II)‐pyridine complexes (λmax ⩾ 590 nm) formed by copper corrosion within the laser damage zone. On the basis of these findings the Cu/pyridine system has been classified as SERS Type III.

Field-Induced Electron Emission from Artificially Produced Carbon Sites on Broad-Area Copper and Niobium Electrodes

It has been experimentally demonstrated that micrometersized particles of graphite deposited on the surface of copper and niobium electrodes can promote the field emission of electrons in the range of 5-20 MV ·m-1. From measurements of the current-voltage characteristic, electron spectrum, and emission image of such sites, it has been concluded that electrons arc emitted by a mechanism similar to that operating at the naturally occurring sites responsible for prebreakdown electron emission. A hot-electron-based metal-insulator-metal (MIM) model is considered.

The effect of the surface state on the electrochemical behaviour of copper electrodes

All investigated treatments of copper electrodes, which include mechanical (grinding and polishing with abrasives of different grain size: 210, 85, 75 and 42 μm), chemical (polishing, etching and shine-etching) and electrochemical (polishing), lead to an increase both of the anodic (copper dissolution) and of the cathodic (hydrogen evolution and oxygen reduction) polarization. This effect may be explained by the combined action of several types of factors. (1) Change in the real surface area of the examined electrode. This is the only factor in the case of mechanical treatment and an important factor for all other cases. (2) Formation of oxygen layers on the surface, an important factor in all types of chemical and electrochemical treatment. (3) Removal of the deformed layer composed upon mechanical polishing. This factor fully affects the electrochemically polished samples, partially the chemically polished one and does not affect the other types of chemical treatment. (4) These data correlate well with, and confirm, the concept about the higher electrochemical homogeneity of the electrochemically polished surface in comparison to the mechanically polished one. Our investigations show that a correct choice of the nature and sequence of the preliminary treatment of copper electrode surface makes it possible to impart on it the desired surface and electrochemical properties.

Surface‐enhanced Raman spectroscopy of ruthenium‐pyridyl complexes at copper electrodes

AbstractSurface‐enhanced Raman spectra of 2,2′‐bipyridine, Ru(bpy)(py)4(CIO4)2, Ru(py)6(BF4)2 and Ru(bpy)‐(PVP)(CIO4)2 at the surface of a copper electrode are presented [bpy = 2,2′‐bipyridine; py=pyridine; and PVP =poly(4‐vinylpyridine)]. The dependence of the spectra on potential is demonstrated through presentation of complete spectra at applied potentials from −0.2 to −1 V, as well as in plots of SER intensity vs electrode potential. The effect of excitation wavelength on the spectra is discussed. Significant differences between the potential dependences of these compounds at copper and silver electrode surfaces are shown. SER spectra from the surface‐enhanced resonance Raman active ruthenium complexes could be obtained only with an excitation wavelength longer than 514.5 nm.

A Rotating Disk Cell for Raman Spectroelectrochemistry: Investigation of an Electrode Surface Species and an Electrogenerated Solution Species

A Raman spectroelectrochemical cell has been developed which incorporates a rotating disk design. This cell has been shown to be useful for the Raman investigation of electrode surface species (spinning electrode) and electrogenerated solution species (static electrode). It has been used to characterize the Raman spectroelectrochemical behavior of photolabile dithizone anion adsorbed at silver and copper electrode surfaces. Use of this cell for the study of electrogenerated solution species was demonstrated by the resonance Raman characterization of the tetracyanoethylene anion radical electrogenerated with a cyclic potential step. Cell construction is described and its merits discussed.

Influence of the Copper Electrode Surface on Initial Arc Movement

To investigate the influence of the copper electrode surface condition on the initial arc movement and the immobility time respectively, a special experimental device was developed. It permits to keep constant, or vary those parameters independently, which influence the initial movement, i.e., arc current (170 A), magnetic flux density (10-1000 × 10-4 T), electrode distance (1 mm), and surface condition (oxide-film thickness, roughness). The magnetic field can be applied at any moment and can be varied independently of the arc current. The arc is ignited by means of a dielectrical breakdown in order to eliminate the ignition effects, such as liquid and vaporizing electrode material. The most striking result of the experiments was that only arc movements of various velocities, but no absolute immobility was measured. This observation is due to the elimination of ignition effects as well as to the use of an adequate sensitive measuring technique. Impeded arc motion characterized by shorter or longer lasting creeping (υ≲3 m/s) occurs, if certain magnetic flux density or copper surface conditions do not permit velocities υ>10m/s or if the electrode surface is thermally prestressed by a deliberately standing arc.

Tunable laser excitation profile of surface enhanced raman scattering from pyridine adsorbed on a copper electrode surface

The wavelength dependence of surface enhanced Raman (SER) scattering from pyridine on a copper electrode surface has been measured and found to correlate closely with the optical properties of copper metal. The results are interpreted in the light of the image field model of the SER mechanism.

Laser Raman spectroscopy at the surface of a copper electrode

Laser Raman spectroscopy at the surface of a copper electrode

Melting and Evaporation Phenomena During Electrical Erosion

A modeling method is presented for the evaluation of the eroded crater during electrical discharge machining. The method is based on the propagation of the melting crater when other effects such as evaporation can take place. Calculations are performed for a point heat source on the surface of copper and steel electrodes. An experimental technique for the measurement of the amount of eroded material is described: the method consists of extraction of the metal from the dielectric fluid by chemical reactions and measurement of the resulting color intensity.

高感度反射電子スペクトルからみたベンゾトリアゾールによる銅の腐食抑制機構

Ultraviolet high sensitivity reflection spectra of the copper electrode surface have been measured in situ under the potentiostatic polarization in 3% NaCl aqueous solution. In the deaerated nearly neutral 3% NaCl solution containing 0.0002 M BTA (benzotriazole), BTA-Cu (I) (benzotriazole-cuprous salt) film was formed on copper and did not diminish by cathodic polarization, but at pH 3 the formation of BTA-Cu (I) film was not found. These behaviors can be explained as follows; The reaction (1), Cu++BTA\ ightleftharpoonsBTA-Cu (I)+H+, proceeds to the right hand side of the equation in the nearly neutral solution, and in acidic (pH 3), to the left. This is because the concentration of BTA-Cu (I) is a function of pH as shown by Eq. (2)(This article is not displayable. Please see full text pdf.) \ oindentwhere K is an equilibrium constant of Eq. (1).The polarization curves showed that BTA inhibited mainly the anodic reaction and in the cathodic region the retardation of hydrogen evolution was more effective than that of the oxygen reduction. The corrosion reaction was much more markedly inhibited in the nearly neutral than in the acidic solutions. It is concluded that the inhibition is due to the protection of BTA-Cu (I) film, but not due to the chemisorbed BTA film.