Showing papers in "Journal of The Electrochemical Society in 1965"

Design of Primary and Secondary Cells II . An Equation Describing Battery Discharge

Abstract: A discussion is given of the derivation and application of an equation which gives an excellent description of a wide variety of cell and battery discharges. This equation gives the cell potential during discharge as a function of discharge time, current density, and certain other factors. It makes possible a complete description of cell discharge characteristics, using a minimum of experimental data and at the same time pinpointing experimental errors. It can also be used to describe cell charges, capacities, power evolution, and to predict capacities. A description is given of a simple numerical method for fitting this equation to a particular set of battery discharge curves. A graphical method is described for comparing characteristics of various types of cells.

Structural Evaluation of Silicon Oxide Films

Abstract: Techniques for physical and chemical evaluation of silicon oxide films formed by a wide variety of techniques have been developed It has been established that by the use of infrared absorption spectroscopy, preferential etching procedures, precise optical measurements of thickness, density, and refractive indices, and carefully chosen environmental tests, differences in the oxide films can be determined Techniques of oxidation studied were: thermal (oxygen and steam), evaporated, pyrolytic, lead catalyzed, sputtered and anodic In many cases, improvement of oxide film properties can be achieved by simple thermal treatment of the original films

The Anomalous Codeposition of Iron‐Nickel Alloys

Abstract: The dependence of the anomalous codeposition of iron‐nickel alloys on the pH at the cathode surface is investigated. An equation is derived to evaluate the surface pH as a function of bulk pH, rate of hydrogen evolution, buffer concentration, and diffusion conditions. The results obtained on rotating disk electrodes show that anomalous codeposition is due to a suppression of nickel discharge and that suppression occurs only when the surface pH is high enough to cause hydroxide formation. A type of mechanism is proposed by which the adsorption of ferrous hydroxide suppresses the deposition of nickel but permits a high rate of iron discharge. Experimental results which support this mechanism are discussed. This type of mechanism could be of general importance for other systems exhibiting anomalous codeposition.

The Hydrogen Evolution Kinetics and Hydrogen Entry into a‐Iron

Abstract: An investigation of the permeation rate of electrolytic hydrogen through Armco iron single crystals and polycrystals by an electrochemical technique is described. The variation of the permeation rate with cathodic overpotential has been determined in alkaline , alkaline cyanide, acidic , acidic iodide, acidic napthalene, and acidic nitrile (valeronitrile, napthonitrile, benzonitrile) solutions. The potential‐permeation behavior as a function of temperature has been investigated in acid solutions. The permeation potential behavior in alkaline solutions indicate a coupled discharge recombination mechanism for hydrogen evolution at low overpotentials while at higher overpotentials the mechanism is slow discharge‐fast electrochemical. The effects of CN−, I−, and napthalene which increase permeation rate has been interpreted in terms of a lowering of the bond energy. Nitriles were found to decrease the permeation rate, and their effect on the permeation rate is interpreted in terms of their vertical adsorption on the electrode hindering the discharge process. The results indicate that hydrogen goes through an adsorbed intermediate state on discharge before entering the metal lattice. Grain boundaries play no part in the hydrogen evolution kinetics or in the entry of hydrogen to the metal.

The Solubility and Diffusivity of Oxygen in Electrolytic Solutions

Abstract: Measurements of the solubility of oxygen in sulfuric acid, phosphoric acid, and potassium hydroxide are reported, together with values of the diffusivity of oxygen in potassium hydroxide solutions at 25°C. It is shown that for the electrolyte concentrations commonly employed in fuel cells the solubility and diffusivity of oxygen may each be reduced to as little as 2% of their corresponding values for pure water.

The Cathodic Reduction Mechanism of Electrolytic Manganese Dioxide in Alkaline Electrolyte

Abstract: Constant‐current discharge curves for electrodeposited on graphite showed a two‐stage reduction; to and to . Potential decreased continuously during the first stage and in some discharges was constant for at least half of the second. The first stage was not influenced by current density, concentration, thickness, or a complexing agent. The constant‐potential portion was observed with , low current density; the potential was near the standard redox potential of Mn(II) and Mn(III) species in solution as determined polarographically. The first stage is considered a homogeneous phase reduction, while the second stage involves a heterogeneous system. A new mechanism is suggested for the latter.

The Structure and Mechanical Properties of Electroless Nickel

Abstract: Effects of variations in phosphorus content of electroless nickel from 4.6 to 9.4 w/o on structure, strength, ductility, and hardness were studied. Electron diffraction proved the crystallinity of many as‐plated alloys, and x‐ray data established a conventional precipitation hardening mechanism during heat treatment. Changes in properties after heat treatment at 200°–750°C have been correlated with structural changes shown by x‐ray diffraction and with those revealed in optical and electron back scatter micrographs. Abrupt changes in the structure, strength, and ductility of as‐plated alloys and of alloys heat treated at 750°C occurred at phosphorus contents of about 7%.

Vapor Deposition of Metals by Hydrogen Reduction of Metal Chelates

Abstract: Thin film deposits of Cu, Ni, and Rh were obtained by hydrogen reduction of , , , and from the gas phase (tfa = trifluoroacetylacetonate anion; hfa = hexafluoroacetylacetonate anion). The chelates are well suited for gas plating purposes by virtue of their high volatility and ease of reduction by hydrogen. The deposition process can be conducted at atmospheric pressure and at temperatures as low as 250°C. The process is potentially cyclic, free chelating agent being regenerated by the reduction reaction.

Studies of the Oxidation of Nickel in the Temperature Range of 900° to 1400°C

Abstract: The parabolic oxidation of nickel has been studied between 900° and 1400°C at pressures from the dissociation pressure of nickel oxide to 1 atm of oxygen. The activation energies in various atmospheres were found to range from 36.3 to 43.6 kcal/mole. The usual equation for parabolic oxidation, did not hold over the entire pressure range because the value of varied with temperature. A marker study showed that the markers were located close to the metal‐oxide interface. A method for obtaining the self‐diffusion coefficient of the more mobile ionic species in the oxide is proposed.

Adsorption of Monomeric and Polymeric Amino Corrosion Inhibitors on Steel

Abstract: The adsorption of 4‐ethylpyridine, 4‐ethylpiperidine, and very low molecular weight poly (4‐vinylpyridines) was studied in cyclohexane solutions containing hydrogen reduced steel powder. Isotherms were obtained for the monomers at 30°C. They show that an amount equivalent to monolayer formation is adsorbed at equilibrium concentrations in the range . The polymer was adsorbed to a much greater extent. Using a specially designed chromatographic method, the heat of adsorption of the piperidine derivative from cyclohexane was determined. Simultaneous measurements of the adsorption of the polymer and the corrosion of the steel in aqueous hydrochloric acid have shown that the corrosion rate decreases by 80% as the polymer adsorbs to form a very incomplete layer. From these results, it is concluded that these compounds chemisorb to the steel surface and that the 4‐ethylpiperidine is bonded at the nitrogen atom but that the 4‐ethylpyridine is adsorbed in a position with the plane of the ring parallel to the steel surface. Attachment of polymer is at multiple sites in the molecule, but appreciable portions of the chains are left in the solution phase. The area which is deactivated toward corrosion by adsorption of poly (4‐vinylpyridine) from is considerably greater in extent than that which is physically covered by the adsorbed molecules, i.e., a large neighboring area of steel surface is ennobled by the adsorbed polymer molecules.

Effect of Surface Treatment on the Corrosion of Stainless Steels in High‐Temperature Water and Steam

Abstract: The corrosion behavior of AISI 304 and 410 steels as well as 23.5 Cr‐21.5 Ni steels in superheated steam at temperatures between 400° and 600°C was found to be influenced markedly by preliminary surface treatments: electrolytic polishing, mechanical polishing, milling, lathe‐turning, grinding. The treatments accompanied by cold‐working reduced the corrosion rate, the effect being retained for long times (at least 2000 hr for AISI 304 steel at 450°C). This enhanced corrosion resistance is attributed to the presence of cold‐worked surface layers which were detected by measurement of x‐ray line broadening. Electron microprobe analyses of the oxide layers and of the underlying metal showed that the oxide is enriched and the metal depleted in chromium and manganese. These elements thus seem to diffuse through the cold‐worked layer toward the oxide. In water, at 300°C and below, the phenomena are more complex and not yet fully understood.

The Specific Effects of Chloride and Sulfate Ions on Oxide Covered Aluminum

Abstract: The distribution of a‐c resistance throughout the thickness of oxide film on aluminum specimens, conditioned by pre‐exposure to 1.0N solutions of sodium chloride and sulfate, has been determined by an electrical method. This method involves measurement of series capacitance and dielectric loss of the oxide covered aluminum as the surface films thin slowly in a slightly alkaline, passivating, sodium chromate solution. Results show that chloride ions become included at certain selected locations in the oxide film, create additional current carriers, and lower the ionic resistance of the film. Sulfate ions do not appear to become included in aluminum oxide films under these conditions and do not lower the film resistance. Aluminum oxide films containing chloride ions dissolve more rapidly in the chromate solution than similar untreated films or films that have been treated in sodium sulfate solution. These observations are held to throw new light on the well defined tendency of oxide covered aluminum to pit severely in nearly neutral sodium chloride solutions.

Investigations of the Kinetics of Hydrogen and Oxygen Reactions on a Platinum Electrode in Acid Solution Using Pulse and Decay Techniques

Abstract: : The influence of hydrogen partial pressure, current density, and temperature on the anodic oxidation of sorbed H and the anodic generation of sorbed O were determined. Electrode processes were evaluated and separated to give the following quantities: (a) the amount of H associated with a Pt surface and its immediate vicinity, (b) the extent to reaction of H atoms, absorbed in the metal interior, that migrate to the surface of the metal and are either ionized or react with O atoms, (c) the extent of reaction of H2 from the solution phase, (d) the amount of O adsorbed on the Pt surface, and (e) the amount of O absorbed in the Pt surface layers (skin). The kinetics of the open-circuit reaction of galvanostatically determined amounts of sorbed O with H2 were also determined.