Ken Nobe

Kinetics and Mechanisms of Cu Electrodissolution in Chloride Media

Ring‐disk electrode studies of anodic polarization of Cu in acidic chloride solutions indicate four distinct potential regions: the apparent Tafel region, the peak current and current minimum region, the limiting current region, and potentials above the limiting current region. Ring currents measured the flux of cuprous and cupric species from the disk. Dependence of disk and ring currents on H+ and Cl− and on rotating rate has been determined. Models are proposed to describe Cu electrodissolution in the apparent Tafel region and the potential region above the limiting currents. The results indicate mixed mass‐transfer and kinetic control with cuprous chloride complex as the limiting diffusion species in the apparent Tafel region. At potentials above the limiting current region, there is simultaneous mass‐transfer control of the cuprous chloride complex and kinetic control of Cu++ formation via the reaction, . Within the peak current and current minimum region and the limiting current region, Cu electrodissolution by mass transport is controlled in accord with previous work.

Electrochemical studies of copper, copper-aluminium and copper-aluminium-silver alloys: Impedance results in 0.5M NaCl

Abstract The electrochemical behaviour of Cu, Cu-Al and Cu-Al-Ag alloys in aqueous solutions of NaCl (0.5 M, pH = 3.00) was studied by means of voltammetric methods and electrochemical impedance spectroscopy. The surfaces were examined by SEM and EDX analysis. Cu-Al-Ag alloy shows a potentiodynamic behaviour similar to that of the pure copper electrode while the Cu-Al alloy presents some minor differences. In the active dissolution region the electrodes suffer pitting corrosion and in the other potential regions there are the formation of a passivant film with composition depending on the potential. The impedance responses of the electrodes are discussed. An electrodissolution mechanism is proposed and the effect of the alloying elements upon the impedance response and polarisation curves is explained. The main effects are due to the production of copper and silver chlorides and aluminium oxides/ hydroxides at the corroding interface. The addition of Al or (Al + Ag) increases the corrosion resistance of pure copper.

Film Formation and Current Oscillations in the Electrodissolution of Cu in Acidic Chloride Media I . Experimental Studies

Etude par la methode du disque tournant. On propose un modele pour la diffusion des ions chlorure a travers la couche poreuse de CuCl afin de rendre compte du comportement oscillatoire

Electrodeposited Iron Group Thin-Film Alloys: Structure-Property Relationships

Various iron group alloys have been electrodeposited and evaluated for properties including corrosion resistance, microstructure, electrical resistivity, magnetoresistance and other magnetic properties. Corrosion resistance depends on deposit composition and microstructure, which are controlled by solution composition and deposition variables. Maximum corrosion resistance was observed for 50Ni50Fe and 70Co30Ni binary alloys. The corrosion resistance of electrodeposited CoFe films was an order of magnitude lower than CoNi and NiFe films. Substantially increased corrosion resistance was obtained by adding Ni to CoFe alloys. However, addition of B only slightly increased corrosion resistance. For electrodeposited NiFe and CoNi thin film alloys, three distinct structural regions were observed: for NiFe alloys, fcc, mixed fcc and bcc, and bcc phases as deposit Fe content increased; for CoNi alloys, fcc, mixed fcc and hcp, and hcp as deposit Co content increased. The smallest grain size was obtained in the mixed phase region of both NiFe and CoNi alloys, For CoFe alloys, a mixed phase region was not observed; only fcc and bcc phases were obtained. Electrodeposited NiFe films from sulfate baths show superior soft magnetic properties including both lower coercivity and higher squareness than from chloride baths. Magnetic saturation (M S ) of electrodeposited NiFe films follow bulk alloys where magnetic saturation increased with increased deposit Fe content.

A Comparison of DC and Pulsed Fe‐Ni Alloy Deposits

The effect of hydrodynamics and temperature on the electrodeposition of Fe-Ni alloys has been investigated with dc, pulse, and pulse-reverse electrodeposition techniques. Strong mass-transfer effects in the co-deposition of Fe on rotating cylindrical cathodes were indicated at high current densities. Many features of the present deposition process are shown to be consistent with the Hessami and Tobias model. A comparison of the polarization behavior of single-metal and alloy deposition clearly demonstrate the lower rate of Ni co-deposition in accord with previous reports of anomalous co-deposition of Fe-Ni alloys. X-ray diffraction studies indicate that the crystalline phases (fcc, bcc, and mixed fcc+bcc) in the electrodeposited alloys depend on alloy composition and deposition conditions

Extraction of organic contaminants in aqueous solutions by pervaporation

Abstract The extraction of dichloromethane, chloroform, bromoethane, acetone, and ethanol in dilute aqueous solutions by pervaporation using silicone tubular membranes was studied. The solutes studied did not affect the permeation flux of water; the flux of organic compounds increased linearly with their concentration in the solutions while the water flux remained constant for all solute—water solutions. The presence of an electrolyte or another organic solute did not influence the permeation of a given solute. The permeant components appear to behave independently of each other in the permeation process. The selectivity of the silicone membrane for halogenated hydrocarbons was greater than that of cellulose acetate and microporous polytetrafiuoroethylene membranes.

Ferromagnetic micromechanical magnetometer

A novel micromechanical magnetometer has been designed, fabricated, and tested that consists of low-stress electrodeposited hard magnetic alloys and surface micromachined polysilicon structures. The sensor responds to applied magnetic fields without consuming any power and the magnitude of the response is scale independent. By optically measuring their response, these second-generation sensors can be used to detect fields as small as 500 nT and their experimental performance agree well with theoretical predictions.

Pulsed Electrodeposition of Iron‐Nickel Alloys

This paper reports on the effects of dc, pulse, and pulse reverse current waveforms on deposition of Fe-Ni alloys studied in unagitated solutions and with a rotating cylindrical electrode. A nickel sulfamate/ferrous chloride electrolyte system at pH 2 less than 2 A/dm{sup 2}. Pulse reverse plating led to a decrease in anomalous deposition at low current densities. Rotating cylindrical electrodes indicated significant mass transfer effects at high current densities. During pulse reverse plating an increase in anodic pulse magnitude decreased anomalous deposition; pulse frequency had its greatest effect in reducing anomalous deposition between 100 and 300 Hz.

Electrochemical Characteristics of Iron in H 2 SO 4 Containing Benzotriazole

The effect of benzotriazole on the corrosion of iron in has been studied. The experimental data are consistent with the slow proton discharge step for the hydrogen evolution reaction on iron. No change in mechanism was observed by the addition of benzotriazole, but a significant decrease in the rate of hydrogen evolution was observed. The inhibitor concentration had a significant influence on the behavior of the open‐circuit capacitance. Surface coverages determined from capacitance and corrosion rate data were consistent and found to fit a Langmuir adsorption isotherm.

Nanostructured magnetic CoNiP electrodeposits: structure–property relationships

Abstract Magnetic CoNiP thin film alloys were electrodeposited from chloride baths. The effects of solution composition, solution pH and film thickness on the magnetic properties, microstructure and phases of electrodeposited CoNiP films were investigated. Solution pH and NaH 2 PO 2 concentration significantly influenced the magnetic properties of CoNiP deposits. These films when deposited from solutions of pH 2.25, hard magnetic deposits ( H C,⊥ ≈2000 Oe and H C,// ≈1000 Oe) were obtained. X-ray diffraction revealed hcp structure consisting of nanocrystalline grains (∼50 nm) with preferred (002) planes as deposit P content and solution pH increased.