Exchange between Single-Crystal Cadmium and Its Ions

King, Cecil V.; Newman, David S.; Suriani, Ernest

doi:10.1149/1.2428065

Cited by 5 publications

(3 citation statements)

References 4 publications

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“…This procedure was applied to cadmium, where D is much larger (ca. 10 -1~ cm2/ sec), and the removal of uniform layers by electropolishing appeared to be valid (7).~ It is of interest to see whether this stripping procedure might be applied to silver. Two silver disks were immersed in tagged 0.1M AgNO3 for 1.20, 1.26 x 107 sec (4.5 months), and exchange occurred to the extent of 18 and 20 x 10 -9 g at./cm 2, the equivalent of 7-8 complete monolayers.…”

Section: Distribution Of Exchange In Depthmentioning

confidence: 99%

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Ion Exchange on Single-Crystal Silver and Zinc

King¹,

Simmons²,

Berlin³

1963

J. Electrochem. Soc.

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Exchange studies have been made with electropolished singIe-crystal specimens of silver and zinc immersed in dilute solutions of their salts, using Ag110 and Zn 65 ions as tracers. In 0.02M solutions of the salts, exchange in the surface layer of the metals is rapid and complete, and continued tracer pickup is due to diffusion within the crystals. At lower salt concentrations the tracer pickup is slower, apparently because complete exchange is not maintained in the surface layer of atoms.In most previous studies of exchange between silver and zinc and their ions in solution, polycrystalline specimens have been used (1-3). This has the disadvantage that both grain-boundary and 1at-rice diffusion occur within the metal. The rate of radiotracer pickup depends on the grain size and grain-boundary area, and only the ratio of the two diffusion coefficients is significant. One run with a silver single crystal was carried out by Gerischer and Tischer (4), who concluded that the behavior was not essentially different from that of polycrystalline specimens. Zinc single crystals were used by Bushmanov and Vozdvizhenskii (5), who found somewhat different exchange rates on base and prism facets. Zinc bicrystals were investigated by Sandor (3), who found that the metal specimens corroded promptly even in well-deaerated solutions.The purpose of the present investigation was to find whether single-crystal specimens, prepared with minimum surface roughness, would show a consistent and understandable pattern of exchange with their ions in aqueous solution. We find that silver specimens do so, with no complication from corrosion or surface films. On the other hand, zinc is subject to corrosion by water in the absence of oxygen Zn ~-H20-~ ZnO -P Hf; AG ~ : --19 kcal A similar free energy value applies if Zn(OH)2 is the product. A polished specimen does not acquire a visible film for a long time in deaerated water; in salt solutions the initiation of visible film formation appears to be accidental and in general occurs sooner, the more concentrated the salt. ExperimentalSingle-crystal rods of silver and zinc 2 about 2 cm in diameter were cut into disks 2 mm thick, and a 1 mm hole was drilled near the edge for suspending. After smoothing the surfaces the disks were annealed (silver at 400 ~ zinc at 120~ and cooled slowly. Before use each disk was electropolished to remove distorted material and to give a smooth, bright surface (silver in AgCN-NaCN, zinc in phosphoric acid-ethanol).active solutions the disks were electropolished to remove the active material.In electropolishing, the disks were suspended on a Pt wire, midway between 2 stainless steel cathodes. Disks were suspended in the radioactive solutions either on glass hooks or on wire hooks coated with insulating lacquer. Solutions of AgNO8 were not deaerated except in a few tests; Zn (C104)2 solutions were deaerated with nitrogen or hydrogen which was passed over hot copper, then through two wash bottles containing solution of the same concentration as the test solution. Immersi...

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Section: Distribution Of Exchange In Depthmentioning

confidence: 99%

“…It was still of interest to see whether uniform layers could be removed, and two methods were tried: (i) In a solution containing NaCN and H20~ (1), dissolution of 0.08 mg from one disk removed In Tables II, III, and IV of ref. (7), depth should be labelled cm • 10s instead of cm • 10~.…”

Section: Distribution Of Exchange In Depthmentioning

confidence: 99%

Ion Exchange on Single-Crystal Silver and Zinc

King¹,

Simmons²,

Berlin³

1963

J. Electrochem. Soc.

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“…Cadmium (3,10) Cadmium is a very satisfactory metal to work with because of its exceedingly high self-diffusion coefficient, its corrosion resistance, and its ease of electropolishing. 1)SCd is used as the tracer.…”

Section: / Journal Of Chemical Educationmentioning

confidence: 99%