Über die Beteiligung von Protonen an der Elektrizitätsleitung in Metallen

Coehn, Alfred; Specht, Werner

doi:10.1007/bf01340398

Cited by 82 publications

(17 citation statements)

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“…[1] are that no flux enters the sample rod at its ends and that zero flux of solutes passes through the surface of the rod from the environment. [1] are that no flux enters the sample rod at its ends and that zero flux of solutes passes through the surface of the rod from the environment.…”

Section: Resultsmentioning

confidence: 99%

Electrotransport Purification of Thorium under Low Pressure Conditions

Schmidt

Outlaw

Lunde

1979

J. Electrochem. Soc.

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It has been demonstrated that the ultrapurification of thorium by electrotransport refining is highly sensitive to the background gas density in which the refining takes place. The electrotransport purification of thorium has been studied over a total pressure range (predominantly H20 and CO) of 2 X 10 -2 to 2 X 10 -i2 Torr. Polycrystalline thorium samples, with an initial resistance ratio of 35, were purified to a ratio of 2040. Thorium refined a second time, yielded metal with a ratio of 4200, which is the purest thorium ever reported. Purification experiments conducted within a prescribed background of nitrogen (4 X 10 -1~ and 5 X 10 -9 Torr) show a significantly higher resistance ratio than normally achieved at such pressures having a hydrogen and CO background. It is postulated that the adsorbed nitrogen inhibits the adsorption and incorporation of CO and, therefore, limits the carbon concentration in the thorium bulk. During the purification process (1500~176 gravitationally induced grain slippage was observed to occur at the boundaries of the thorium grains. A distributed magnetic force system was applied to the sample to counteract the gravitational force, resulting in a 90% reduction of the grain slippage.The migration of solutes in solid metals under the influence of a direct current has been known since 1928 when Coehn and Specht (1) observed hydrogen transport in palladium. In this process a constant voltage is applied across the metal sample which yields an internal electric field and a constant current which heats the sample. These combined effects produce the electrotransport phenomenon. The solutes are stimulated by the charged carriers to move toward one of the ends of the sample, thereby leaving a major portion of the sample virtually free of impurities. Many of the earlier investigators of electrotransport of interstitial solutes interpreted the direction and velocity of migration on the basis of a charge on the solute particle. In 1953, Seith and Wever (2) showed this interpretation to be incomplete and one cannot separate the contributions to the force moving the solute which arise from the charge on the solute in an electric field and the momentum transfer from the scattering of electrons or holes. Reviews by Heuman (3), Verhoeven (4), Huntington (5) consider both the electrostatic force and the force resulting from moving electrons being scattered by the solute. The potential for applying electrotransport to the ultrapurification of metals has been described by Verhoeven (6) and Peterson (7). This technique has been used extensively at the Ames Laboratory, DOE, for removing interstitial solutes from many of the refractory and rare earth metals. These investigations have been summarized in a recent publication in which the direction of solute movement in an electric field is empirically correlated with the atomic radius of the solvent metal at the temperature of transport (8).However, electrotransport processing has been limited by the presence of the residual gases in the vacuum system in w...

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Section: Resultsmentioning

confidence: 99%

Electrotransport Purification of Thorium under Low Pressure Conditions

Schmidt

Outlaw

Lunde

1979

J. Electrochem. Soc.

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“…The flux J1 is set to zero for steady-state conditions and the following relation is obtained: (75) This equation is also derived by Thomson's method.…”

Section: Theory Of Belashchenk04546mentioning

confidence: 99%

“…It is interesting to note that it is possible to reduce equation (75) to equation (66) without using any equations other than those appearing in (37) 334 Verhoeven: Electrotransport in Metals Belashchenko's45 paper except those necessary to take into account the difference between activity and concentration.…”

Section: Theory Of Belashchenk04546mentioning

confidence: 99%

Electrotransport in Metals

Verhoeven¹

1963

Metallurgical Reviews

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“…Thus Janitzky concluded, from his measurements of the resistance of wires charged with gas, that the gases dissolved in the metal are dissociated into positive ions and electrons and participate in the conduction of current (72). But Coehn and Specht and Coehn and Jiirgens were the first to furnish incontestable experimental proof that hydrogen dissolved in palladium travels with the positive current and must be present, at least in part, in the form of positive ions (74,75). But Coehn and Specht and Coehn and Jiirgens were the first to furnish incontestable experimental proof that hydrogen dissolved in palladium travels with the positive current and must be present, at least in part, in the form of positive ions (74,75).…”

Section: (14)mentioning

confidence: 99%

The Mechanism of Heterogeneous Catayltic Organic Reactions. I. Catalytic Hydrogenation.

Schmidt¹

1933

Chem. Rev.

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The process of catalytic hydrogenation of organic compounds is of great interest, not only industrially but also scientifically.It comprises the hydrogenation of fatty substances, the hydrogenation of carboxides with formation of methanol, and a host of other important chemical processes. I n order to master these reactions the most important step is to understand their mechanism.I n hydrogenating fatty oils one or more double bonds between carbon atoms are converted into single bonds ; in hydrogenating carboxides one or more double bonds between carbon and oxygen atoms are reduced. This seems to be a close analogy; nevertheless the mechanism of the two processes is probably quite different, as we shall see later.We consider first the mechanism of the hydrogenation of multiple carbon bonds. For a long time I have adhered to the theory (1) that catalytic hydrogenation of multiple carbon bonds belongs to the great class of catalytic reactions that are produced by ions. I am glad now to have the opportunity of surveying the facts which seem to me to prove that ionic catalysis is involved in this type of hydrogenation.But first, what is ionic catalysis? Ostwald (2) and Arrhenius (3) were the first to find that ions 1 This is the first of a series of three articles. 11, The Dissociation of Carbon Bonds, is scheduled for publication in

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Über die Beteiligung von Protonen an der Elektrizitätsleitung in Metallen

Cited by 82 publications

References 0 publications

Electrotransport Purification of Thorium under Low Pressure Conditions

Electrotransport Purification of Thorium under Low Pressure Conditions

Electrotransport in Metals

The Mechanism of Heterogeneous Catayltic Organic Reactions. I. Catalytic Hydrogenation.

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