Showing papers in "Journal of The Electrochemical Society in 1953"
TL;DR: In this paper, the structural features of the porous type of anodic oxide coating applied to aluminum have been investigated with the electron microscope, and formulas were given for calculating the cell size and pore volume of these coatings.
Abstract: The structural features of the porous type of anodic oxide coating applied to aluminum have been investigated with the electron microscope. These coatings consist of close‐packed cells of oxide, predominately hexagonal in shape, each of which contains a single pore. Pore size is a function of the electrolyte used and is independent of forming voltage. Wall thickness and barrier thickness are primarily a function of forming voltage and are affected to a minor degree by the electrolyte type. Pertinent dimensions of anodic coatings formed in sulfuric acid, oxalic acid, chromic acid, and phosphoric acid electrolytes are presented, and formulas are given for calculating the cell size and pore volume of these coatings.
1,257 citations
239 citations
TL;DR: In this article, the Nusselt, Schmidt, and Grashof numbers were predicted from the boundary layer theory for mass transfer by free convection, and a general correlation of the data may be represented by the equation: Nu' = 0.673 (ScGr)m.
Abstract: Limiting currents were measured for deposition of copper on plane vertical cathodes from unstirred solutions. Electrolyte composition ranged from 0.01 to 0.7 molal CuSO4, 1.38 to 1.57 molal H2SO4, and 0 to 6.38 molal glycerol. Cathode heights varied from 0.25 to 3.0 in. Limiting current densities were from 0.4 to 108 ma/cm 2. A general correlation of the data may be represented by the equation: Nu' = 0.673 (ScGr)m, where Nu', Sc, and Gr are the mass transfer Nusselt, Schmidt, and Grashof numbers, respectively. This result is in good agreement with that predicted from the boundary layer theory for mass transfer by free convection.
214 citations
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120 citations
TL;DR: In this article, the impurity levels in the energy diagram of a zinc sulfide phosphor are considered to be localized S 2− levels lifted above the filled S2− band due to the presence of monovalent positive or trivalent negative activator ions in the lattice.
Abstract: The impurity levels in the energy diagram of a zinc sulfide phosphor are considered to be localized S2− levels lifted above the filled S2− band due to the presence of monovalent positive or trivalent negative activator ions in the lattice. Electron traps are formed similarly by the substitution of S ions by monovalent negative ions or of Zn2+ ions by trivalent positive ions. The energy produced when electrons recombine with trapped holes or when holes recombine with trapped electrons is either emitted directly as light or is first transferred to impurity ions. The elements of the iron group give rise to electron traps. The killing action of these elements is explained by assuming that the energy liberated by recombination between holes and electrons in these traps is transferred to the killer ions. The excited ions return to the ground state radiationless because of the presence of many electronic levels between the excited and the ground state. The effect of heat and infrared radiation on the luminescence is discussed. It is shown that, in a phosphor, energy may be transferred by electrons through the conduction band or by holes through the occupied S2− band.
98 citations
TL;DR: In this paper, the authors described the properties of phosphors under 3650 A excitation, including thermal glow, decay, and buildup of fluorescence, temperature dependence, and light sum.
Abstract: Some properties of phosphors under 3650 A excitation are described, viz., the thermal glow, decay, and buildup of fluorescence, temperature dependence, and light sum. Most of the experimental results can be explained by a model in which cobalt levels act both as electron traps with a trap depth of 0.5 electron volt (ev), and as acceptors for holes, ejected thermally from copper centers with an activation energy of 1.1 ev. The possibility of excitation by 3650 A radiation of electrons from traps to the conduction band is introduced to explain the observed intensity dependence of the light sum.
67 citations
61 citations
TL;DR: The electrical conductivities at 1000°C, expressed as per cent of the cryolite value, for the 10 weight per percent of the following substances are: sodium fluoride 112, calcium fluoride 96, aluminum fluoride 91, and alumina 83 as mentioned in this paper.
Abstract: The electrical conductivities at 1000°C, expressed as per cent of the cryolite value, for cryolite containing 10 weight per cent of the following substances are: sodium fluoride 112, calcium fluoride 96, aluminum fluoride 91, and alumina 83. For pure sodium fluoride at 1000°C, conductivity is 5.52 ohm−1cm−1, compared to 2.80 ohm−1cm−1 for cryolite. Molar conductance decreases linearly with mole per cent sodium fluoride, aluminum fluoride, alumina, or calcium fluoride addition to cryolite. The activation energy for conductance, calculated from a plot of the Arrhenius equation, is about 4.3 kcal/mole for the systems of cryolite with sodium fluoride, aluminum fluoride, and alumina, as well as for pure sodium fluoride, but is slightly higher for the cryolite‐calcium fluoride system. This value agrees reasonably with the 4.48 kcal/mole for pure chryolite. Densities in these systems change linearly with temperature, that for pure sodium fluoride following the equation . The stability of the complex is indicated by a density maximum.
59 citations
58 citations
TL;DR: In this article, the effect of the ohmic resistance of electrodes on current density distribution is shown to depend on the magnitudes of certain dimensionless parameters, and the exact solution of the problem is obtained in terms of infinite series, which converge rapidly enough to permit practical application.
Abstract: The effect of ohmic resistance of electrodes on current density distribution is shown to depend on the magnitudes of certain dimensionless parameters. For plane parallel electrode systems, exact solution of the problem is obtained in terms of infinite series, which, however, converge rapidly enough to permit practical application. It is demonstrated that, for small interelectrode‐electrode length ratio, the assumption of parallel flow is permissible, yielding a convenient expression in closed form for current density distribution, which contains only one parameter.
TL;DR: In this article, the authors studied the trap characteristics of zinc sulfide phosphors as a function of chemical composition and found that the simplest phosphor systems have simple, single-peaked glow curves, and the trap depths are 0.37 electron volt (ev) for Cl−, Br−, and Al3+, 0.51 ev for Sc3+ and 0.62 ev for Ga3+ as coactivators.
Abstract: Trap characteristics of zinc sulfide phosphors are studied as a function of chemical composition. The simplest phosphor systems are found to have simple, single‐peaked glow curves. They contain only activators and coactivators in pure sulfide base materials. Coactivators are defined as impurities necessary to stabilize the activators in the zinc sulfide lattice. They are found to exert a major influence upon trap characteristics. The trap depths are found to be 0.37 electron volt (ev) for Cl−, Br−, and Al3+, 0.51 ev for Sc3+, 0.62 ev for Ga3+, and 0.74 ev for In3+ as coactivators in . Additional glow peaks and traps are produced by oxygen and by the killers cobalt and nickel. The formation of mixed crystals with cadmium sulfide or zinc selenide generally results in a shift of the glow curves toward lower temperatures.
TL;DR: In this article, the standard electrode potential for the gallium−gallic ion electrode in aqueous solution at 25°C was found to be −38,800 cal mole−1.
Abstract: Electromotive force measurements were made on cells of the type where is chloride or perchlorate at 20°, 25°, 28°, and 35°C, for various gallic ion concentrations at several constant acidities. The standard electrode potential for the gallium‐gallic ion electrode in aqueous solution at 25°C is found to be . The standard free energy at 25°C was calculated to be −38,800 cal mole−1. The standard entropy and enthalpy for the cell reaction at 25°C were estimated to be −39.2 cal mole−1 deg−1 and −50,500 cal mole−1, respectively.The liquid gallium electrode behaved in an irreversible manner, but electroplated solid electrodes behaved satisfactorily.
TL;DR: In this article, a modification of Ewles' theory of efficiency based on the idea of a large center was presented. But the authors did not consider the competition of these centers in the luminescent process.
Abstract: The explanation of the variation of efficiency with concentration of activator in terms of a large center, given by Ewles, was oversimplified. The recent suggestion of Johnson and Williams that an activator can only function as a luminescent center if no other activator occupies any of lattice sites surrounding it, leads to the same expression for the number of centers as that originally given by Ewles and is effectively based on the same idea. Making use of the experimental findings reported in the present work that lattice defects can act as luminescent centers, and taking into account the competition of these centers in the luminescent process, a modification of Ewles' theory of efficiency based on the idea of a large center leads to the expression for the efficiency. The preparation of two series of calcium oxide phosphors from highly purified and annealed calcium oxide is described. The modified theory is shown to agree well with efficiency measurements on these phosphors and with those quoted by Johnson and Williams, except at high concentrations. Estimates of the "radial extent" of the centers are given.
TL;DR: In this article, it was shown that the mode of smoothing in electrolytic (and chemical) polishing is not specific to these processes, but results solely from the variations in concentration gradient within the diffusion layer set up on the anode surface.
Abstract: Experiments with a composite anode having projections and recesses on its surface insulated from each other showed that the current distribution between projections and recesses underwent very little change when the total current fell and polishing conditions were established This called for a radical revision of previous views of electropolishing, and prompted a quantitative investigation of the smoothing efficiency under different conditions on a surface of standard roughness The observed efficiencies were compared with those calculated for a wholly diffusion‐controlled distribution of attack (identical with primary current distribution) and for equal dissolution at all points on the surface The conclusion reached is that the mode of smoothing in electrolytic (and chemical) polishing is not specific to these processes, but results solely from the variations in concentration gradient within the diffusion layer set up on the anode surface For any surface of known shape there is, therefore, a maximum possible smoothing efficiency
TL;DR: A review of these measurements and their correlation to the general thermodynamic treatment of ion exchange resins is presented in this article, where applications such as the use of resinous membranes as ionic sieves, electrolytic regeneration of ion-exchange resins, and use of ion exchanged resins as media for electrophoretic separations are discussed.
Abstract: Electrochemical properties of ion‐exchange resins such as specific conductances, ionic mobilities in the resins, and potentials across resinous membranes have been measured recently. A review of these measurements and their correlation to the general thermodynamic treatment of ion‐exchange resins is presented. Applications such as the use of resinous membranes as ionic sieves, electrolytic regeneration of ion‐exchange resins, and the use of ion‐exchange resins as media for electrophoretic separations are discussed.