Showing papers in "Journal of The Electrochemical Society in 1969"

Glow Curves with General Order Kinetics

Abstract: Thermoluminescence and thermally stimulated current curves obeying general order kinetics laws are being investigated. For these cases, whose order is not necessarily first or second but rather may have some noninteger value, an effective method of calculating the activation energy is given. This method is based on measuring the temperature at the maximum of the glow peak and the half intensity temperatures. Numerical calculations for orders between 0.7 and 2.5, activation energies between 0.1 and 1.6 eV and frequency factors between 105 and 1013 sec−1 have been done using an I.B.M. 360 computer. The results reveal the general characteristics of these peaks and their dependence on the parameters. The new method for calculating the activation energy is also checked numerically.

The Mechanism of the Dendritic Electrocrystallization of Zinc

Abstract: Measurements have been made of the growth rate of zinc dendrites in alkaline zincate solutions as a function of overpotential (η), concentration , and temperature The tip radii have been measured by electron microscopy At constant potential, an initiation time of between 5 and 100 min is observed, depending on η, c, and T The dendrite grows linearly with time, at a rate depending on η, c, and T The total current to base and dendrite was independent of time until a time , where (the time for initiation obtained from the growth rate vs time relation) Thereafter, A critical overpotential was determined, Below this , sponge was formed Dendrites were observed up to ; above this the deposition was heavy sponge At a given , the growth rate of a given dendrite increased with η according to an exponential law The growing tip is parabolic, where No twinning was observedThe basic model used depended on the increase in cd possible for an electrodic reaction when the diffusion current depends on a radius of curvature of the substrate, rather than the linear diffusion layer thickness, When the tip of a dendrite‐precursor attains this condition, its growth is released from the diffusion control characteristic of it in the predendrite situation, and it grows further under predominantly activation control at a rate far greater than that possible in any other direction, where the radii of curvature are much greater The Gibbs radius‐dependent overpotential term is also present, although it has a minimized influence The initiation of the dendrite is treated in terms of growing pyramids on the substrate surface At first the growth is linear‐diffusion controlled, but it is shown that the rotation of the spiral, within the linear diffusion boundary surrounding the sphere, gives rise to a decrease of the effective radius of curvature of the dendrite tip until the value is attained, which is effectively the condition for the dendrite initiation The theory of the propagation in terms of the activation, diffusion and Gibbs overpotential is consistent, in terms of , with experiment A derived growth‐time line is also numerically consistent with experiment The dendrite growth rate as a function of and η are numerically calculated with reasonable consistency The tip radius can also be approximately calculated in terms of the present model

The Use of Metal‐Organics in the Preparation of Semiconductor Materials I . Epitaxial Gallium‐ V Compounds

Abstract: Single‐crystal , , and films have been grown on and a number of insulating substrates by the decomposition of alkyl‐gallium compounds in the presence of arsine, phosphine, arsine‐phosphine, and arsine‐stibine mixtures. Both triethylgallium and trimethylgallium have been used successfully in the preparation of . This process makes compound semiconductor film growth compatible with methods used for the growth of elemental semiconductors and eliminates many of the difficulties inherent in multitemperature‐zone processes.

Mechanism of the Electrochemical Reduction of Persulfates and Hydrogen Peroxide

Abstract: Electrochemical studies have shown that the reduction of persulfate and hydrogen peroxide is a two step mechanism, the first step occurs by electron transfer with the conduction band and the second step by hole injection with the valence band. It could be concluded from corresponding measurements performed with a semiconductor electrode that the electrochemical properties of these oxidizing agents have to be described by two instead of one redox (normal) potential. One normal potential is much lower and the other much larger than the theoretical value determined from thermodynamic data. These values are estimated as and .

Environmental Factors Affecting the Critical Pitting Potential of Aluminum

Abstract: The critical pitting potential determined potentiostatically of pure is −0.40V (SHE). This value is not greatly sensitive to temperature (0–40°C), to small alloying additions of Mn or Mg, nor to thickness of oxide film produced by anodizing. The value is more active the higher the Cl− concentration, but becomes more noble with additions to of nitrates, chromates, acetates, benzoates, or sulfates. The latter act as pitting inhibitors which are effective in the order as listed. Dissolved Cu++ in trace amounts deposit on the Al surface as Cu which then acts as an efficient cathode, shifting the corrosion potential of aluminum to the critical pitting potential. Trace amounts of Fe+++ and Pd++ act similarly. Anodized surfaces effectively retard penetration of the oxide by Cu ++ thereby delaying onset of pitting, but they are not similarly effective when Al is coupled to Cu. The mechanism of pitting is interpreted in terms of competitive adsorption of Cl− with oxygen for sites on the metal surface. Extraneous anions compete in turn with Cl− ions, making it necessary to shift the potential in the positive direction in order for Cl− to adsorb followed by pit initiation. Similarities in adsorption parameters of various anions other than Cl− on Al and 18‐8 stainless steel are pointed out.

Inhibition Mechanism of Medium‐Sized Polymethyleneimine

Abstract: The inhibitive effect of medium‐sized polymethyleneimines on the corrosion of iron in solution is particularly good, and this effective inhibition is closely related to the angle of C‐N‐C bond or to strain in the ring as has been observed previously. The inhibition mechanism of the cyclic imines is developed further in this paper. Comparative studies on inhibition effectiveness of dimethylpolymethyleneammonium chlorides, N‐phenylpolymethylene‐imines, and the cyclic imines were carried out. Synergistic effects of iodide ion on the inhibition by cyclic imines and cyclic ammonium chlorides were also studied. Corrosion rate measurements on pure iron were made in solution by polarization, hydrogen evolution, and weight loss. From the results, it was concluded that good inhibition of medium‐sized polymethyleneimine is caused by donation of the unshared π‐electron pair of its nitrogen atom to the metal.

Electron Resists for Microcircuit and Mask Production

Abstract: The properties of poly‐(methyl methacrylate), a new electron resist developed at IBM Research, are presented in comparison to commercial photoresists under electron beam exposure. It is shown that methacrylate resist, with suitable processing, presents a means for submicron device fabrication with reasonable speed. Transistors with one‐ and half‐micron emitter stripe widths have been fabricated using this resist as a medium for diffusion masking with . Also, a method for producing high‐resolution, defect‐free masks through methacrylate resist is presented.

The Mechanism of Operation of the Teflon‐Bonded Gas Diffusion Electrode: A Mathematical Model

Abstract: A mathematical analysis of the working mechanism of the Teflon‐bonded gas diffusion electrode, based on the concept of "flooded agglomerates," is discussed. This model is used to predict the performance of the electrode as a function of such measurable physical characteristics as intrinsic activity of catalyst, agglomerate size, internal porosity, real surface area, etc. The alkaline oxygen electrode is taken as an example for the discussion.

Split‐Ring Disk Study of the Anodic Processes at a Copper Electrode in Alkaline Solution

Abstract: The anodic oxidation of copper in hydroxide solutions has been reexamined with the rotating ring and split‐ring disk techniques. A soluble Cu(III) species has been identified in the anodic region at the onset of oxygen evolution. This species has also been generated at gold rings from disk‐produced Cu(II). Passivation processes in the copper (I) and (II) oxidation regions have been analyzed by means of the corresponding ring currents.

A High Energy Density Lithium/Dichloroisocyanuric Acid Battery System

Abstract: High energy density lithium/dichloroisocyanuric acid battery system discharging under constant voltage and load conditions

Solid Solubility and Diffusion Coefficients of Boron in Silicon

Abstract: The solid solubility and diffusion coefficients of boron in silicon have been determined as a function of temperature over the range of 700°–1151°C, by anodically sectioning diffused layers. The solid solubility was found to vary from at 700°C to at 1151°C. The diffusion coefficients for impurity levels below 1018 atoms/cm3 may be represented by . The diffusion coefficients above 1018 atoms/cm3 were found to be dependent on the impurity level.

Crystal Growth and Properties of Mica‐Like Potassium Niobates

Abstract: Large single crystals of and can be grown by Czochralski pulling from the melt. In the case of a small amount of excess is used to avoid incongruent crystallization. Both materials show pronounced cleavage very similar to that of mica. The electrical properties of are also very similar to those of mica, making this material a possible mica substitute as well as being an interesting new dielectric material in its own right. is orthorhombic Pmmm, with , not the previously reported perovskite structure. Other characteristics determined include optical, mechanical, and chemical properties. When exposed to atmospheres between about 25 and 85% relative humidity, becomes a trihydrate, with higher hydration above about 85% relative humidity. Optical, electrical, and structural properties of all three forms of are described.

The Anodic Dissolution and Passivation of Zinc in Concentrated Potassium Hydroxide Solutions

Abstract: In this study, mainly two sets of experiments were carried out to obtain a better understanding of the tendency of the alkaline zinc electrode to passivate Either photomicrographs of the electrode surface were taken in‐situ at different potentials during an anodic voltage sweep or the two components of the electrode impedance were measured with a small signal of superimposed 1000 Hz AC The course of the passivation was found to depend strongly on the convective conditions in the electrolyte near the zinc electrode The conditions for the formation of two different types of solid films have been defined and their effects on the current‐potential curve have been determined Type I film is white, loose, and flocculent It forms in the absence of convection by precipitation from a supersaturated layer of zincate near the surface When the conditions for supersaturation are largely removed by stirring, the formation of the type II film can be observed The latter is more compact and appears to form directly at the surface rather than by precipitation Its color can range from light gray to black depending on the potential and time of formation The type II film is considered responsible for the transition from the active to the passive state of zinc in alkaline solution

A Preliminary Investigation of Fluidized Bed Electrodes

Abstract: The paper describes results of preliminary experimental observations on a fluidized bed electrode. This consists of a bed of electrically conducting spherical particles fluidized by electrolyte flow. The present results are confined to the cathodic reduction of m‐nitro benzene sulfonic acid to metanilic acid in aqueous sulfuric acid. The investigations have demonstrated that charge is dispersed throughout the bed such that an electrochemical reaction takes place at the particulate surface. Results show that the fluidized electrode is capable of scaling up electrode processes having low exchange currents to give high over‐all currents in relatively small cell volumes.

Two‐Dimensional Nucleation in Electrocrystallization

Abstract: The transient and steady‐state responses of electrodes under conditions where two‐dimensional nucleation is rate determining are considered.

Infrared Reflection Studies of the Oxidation of Copper and Iron

Abstract: Infrared multiple reflectance spectra were used to record the growth of oxide films on copper and iron mirrors. Cuprous oxide and cupric oxide films were readily distinguished since they exhibit intense single bands at 640 cm−1 and ~560 cm−1, respectively. Iron oxide films of a single composition also exhibit highly characteristic bands in the 230 to 1100 cm−1 region of the reflectance spectra. Spectra of mixed iron oxide films were composed of many highly overlapping bands making quantitative interpretations difficult. The intensities of the infrared bands from the copper oxide and iron oxide films were directly proportional to the oxide film thicknesses. Using a seven reflection −73° incidence optical accessory, sensitivity to detect oxide films as thin as about 5Aa was achieved.

The Dissolution of MgO and Mg ( OH ) 2 in Aqueous Solutions

Abstract: This paper reports studies of the rates of dissolution of natural Brucite, optical grade , and commercial in aqueous solutions. Natural Brucite dissolves by means of a surface reaction requiring protons, and while some protonated ions accelerate the dissolution no inhibitors were found. Dissolution of less perfect is normally diffusion limited; several substances which reduced the rate of dissolution of such were found. first reacts with water to form an layer and the rate is controlled by dissolution of the .

Stabilized Zirconia as an Oxygen Pump

Abstract: Electrolytic cells based on stabilized zirconia as a solid electrolyte may be used to remove oxygen from stationary or streaming gas. The minimum pressures (activities) that can be accurately measured are limited by the onset of electronic conduction in the electrolyte. In buffered gases, the lowest pressure that can be attained either by the capacity of the buffer or by the decomposition kinetics of the buffer molecules. Typical values of the oxygen pressures that can be reached when using commercial high‐density sintered stabilized zirconia tubes as an electrolyte, are , , and .

Studies of Electrooxidation of Dextrose in Neutral Media

Abstract: Electrooxidation of dextrose on platinized platinum electrodes has been studied in phosphate buffer at pH 7.4. Rest potentials are interpreted as mixed potentials. Galvanostatic curves have been observed to exhibit oscillatory voltage behavior. In the range of potentials investigated gluconic acid is observed as the reaction product and is found to inhibit oxidation of dextrose due to adsorption on the electrode surface. From the measurements of the adsorption characteristics of the acid, the oscillatory voltage behavior of the galvanostatic curves have been ascribed to kinetic effects of formation of the product and the potential dependence of its adsorption.

Evidence for Eu+3 Emission from Two Symmetry Sites in Y 2 O 3 : Eu + 3

Abstract: In two possible symmetry sites exist for the Eu+3 ions, namely S6 and C2. The emission spectrum is primarily due to ions but two additional lines are reported corresponding to emissions. The lines were identified by their long lifetime relative to the C2 emission and represent the Stark splitting of the transition. This is a pure magnetic dipole transition in S6 symmetry and consequently has a low oscillator strength. The absorption transition due to has also been identified. Similar results have been found for the low temperature form of , which is isostructural with .