Showing papers in "Journal of The Electrochemical Society in 1950"

Phase Relationships in the Binary Systems of Nitrides and Carbides of Zirconium, Columbium, Titanium, and Vanadium

Abstract: Previous investigators have shown that the binary systems involving the monocarbides of zirconium, columbium, tantalum, titanium, and vanadium are of the solid solution type, with the exception of which are almost completely insoluble in each other. In the present study it is shown that the mononitrides of zirconium, columbium, titanium, and vanadium, which have the same type crystal structure as the corresponding carbides, are also soluble in each other, with the exception of the pair . As in the case of the carbides, this exception can be explained on the basis of the atomic size rule governing the formation of solid solution. Furthermore, it is established that most of the binary systems formed by a carbide and a nitride are of the solid solution type, providing the atomic diameters of the metal atoms do not differ by more than about 15 per cent. The systems involving zirconium carbide with the nitrides were not investigated because zirconium carbide decomposed in a nitrogen atmosphere at high temperature.

The Kinetics of the Reactions of Beryllium with Oxygen and Nitrogen and the Effect of Oxide and Nitride Films on its Vapor Pressure

Abstract: A systematic study of the reaction of beryllium with oxygen is made over the temperature range of 350 ~ to 950~ The experimental data may be fitted by the parabolic rate law except for the initial period of the reaction. A plot of log K/T vs. 1/T gives an energy of activation of 50,300 calories per mole. A comparison of this rate data with other metals and alloys shows that vacuum-treated beryllium has the smallest parabolic reaction rate constant at 900~ of any metal or alloy that we have studied. The reaction with nitrogen is studied over the temperature range of 600 ~ to 925~ The data may be fitted by the parabolic rate law. A comparison with the oxygen reaction shows that the rate of reaction is somewhat smaller. A plot of log K/T vs. 1/T gives an energy of activation of 75,000 calories per mole. No reaction is observed with hydrogen over the temperature range of 300 ~ to 882~ A study of the vapor pressure of beryllium and the influence of oxide and nitride films is made using the Langmuir method. Excellent agreement is found for the vacuumtreated specimens with the recent results of Holden, Speiser, and Johnston. Oxide films exert a strong effect in reducing the vapor pressure, the effect varying as the square root of the oxide thickness. A film of 99 micrograms per cm ~ lowers the vapor pressure 100-fold.

The Kinetics of the Reactions of Vanadium with Oxygen and Nitrogen

Abstract: A study is made of the reaction of rolled vanadium sheet with oxygen over the temperature range of 400° to 600°C using specimens weighing 0.1264 g and having a surface area of 1.4 cm2. The data may be fitted to the parabolic rate law except for the initial period of the reaction. A plot of gives an energy of activation of 30,700 calories per mole. The oxidation of vanadium may be compared to the corresponding reactions on columbium and tantalum since the oxide is soluble at high temperatures and the extent of reaction is of the same order of magnitude.The reaction with nitrogen is studied over the temperature range of 600° to 900°C. The rate of reaction with nitrogen is much less at a given temperature than the corresponding oxidation reaction. The nitrogen reaction is similar to that found for columbium and tantalum in the magnitude of the reaction and in the fact that the nitride film dissolves in the metal as fast as it is formed. The data may be fitted to the parabolic rate law.

Preparation of Ductile Vanadium by Calcium Reduction

Abstract: A method is described for preparing ductile vanadium of about 99.5 per cent purity by calcium reduction of vanadium pentoxide. On the scale investigated, metal so reduced collects in a solid regulus weighing about 100 grams and can be cold worked directly from the button to thin foils without annealing. Oxygen is the principal cause of embrittlement in vadium produced by this technique.

Studies on Alternating Current Electrolysis IV . Mathematical Treatment of Reversible Electron Transfer with Alternating Voltage Control and Distorted Current

Abstract: A mathematical treatment is developed which yields equations relating faradaic current, voltage, and time when an alternating voltage is applied to an electrolytic cell composed of a plane and auxiliary electrodes immersed in a solution containing initially supporting electrolyte and only reversibly oxidizable or reducible species. Both oxidant and reductant are taken to be soluble, and specific adsorption is assumed to be absent. The voltage across that branch of the equivalent circuit through which only faradaic current flows is assumed to be periodic with fixed amplitude and with or without an additional direct applied voltage component; the resultant current is distorted. Diffusion controlled kinetics is postulated, and it is assumed that equilibrium is essentially established at the electrode surface. The equations developed show that a “steady state” (i.e., a periodic state) is quickly attained, yield diagnostic tests of use in establishing the reversible mechanism, make it possible to determine the standard potential, and finally yield for the periodic state a relation between faradaic current and time. These results are then generalized so as to include systems in which the reversible electrochemical step is followed by a sufficiently slow secondary reaction step. One diagnostic result of interest in the latter connection is that the mean faradaic current vanishes in the periodic state, regardless of the amplitude or of the shape of the applied periodic potential, when the follow‐up reaction occurs to a negligible extent.