Migration, Formation, and Growth of Pure Cd Whiskers in Cd-Based Compounds
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The migration, formation, and growth of Cd islands and long whiskers were studied in single crystals of Cd84Yb16, Cd51Yb14, and Cd17Ca3 and polycrystals of Cd85Ni15 and high-purity Cd. It was found that Cd moves rapidly to the sample surface in quasi-crystal Cd84Yb16, forming islands in less than 2 h. The Cd whiskers that have submicron diameters and lengths of several hundred microns to millimeters can grow in several days under high vacuum. Evidence was presented to demonstrate that the whiskers grow from the base instead of the tip. While whiskers are easily observed in hex-CdYb, i-CdYb, and CdCa single crystals, no Cd whisker formation or migration of any kind was present on the surfaces of Cd85Ni15 and pure Cd samples, subjected to similar environmental conditions for even longer durations. This result suggests that oxidation of the reactive element is essential for the enhanced whisker growth kinetics observed. Because Cd islands and whiskers grow spontaneously in a matter of hours instead of months required for tin or zinc whiskers, CdYb alloys would be good candidates for detailed whisker formation and growth mechanisms studies.
KeywordsMetal whiskers quasi-crystal cadmium
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