What is it about?
The paper present an example of arriving on a bimetallic Pd-Ag (7:3) supported on silica sample that shows full reversibility of in situ surface segregation: of Ag in He at 400 deg.C, and of Pd in CO atmosphere at 400 deg.C. This allows monitoring of the difusion kinetics and a deep insight into its elementary mechanism. Segregation of Pd appears to be orders of magnitude slower and to run following non vacancy mechanism.
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Why is it important?
Operando PXRD shows slow diffusion kinetics of controllable, reversible segregation in PdAg nanoalloy that is explained by atomistic modeling. Diffusion is solids is a phenomenon of principal significance for engineering. This is why Kirkendall discovery of the vacancy mechanism of self-diffusion with later experimental studies of Balluffi were so important. With increasing role of nanotechnology the diffusion phenomena in nanocrystals become technologically important. This includes surface segregation - non Fick diffusion running against the concentration gradient.
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This page is a summary of: Self-diffusion in nanocrystalline alloys, Physical Chemistry Chemical Physics, January 2015, Royal Society of Chemistry, DOI: 10.1039/c5cp00312a.
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