Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 23: Poster session
MM 23.2: Poster
Dienstag, 26. Februar 2008, 14:45–18:00, Poster B
Neutron Reflectometry Studies on Self-diffusion in Nano-Crystalline Fe Films: First Results — •Sujoy Chakravarty1, Michael Horisberger2, Thomas Gutberlet2, Jochen Stahn2, and Harald Schmidt1 — 1Institut für Metallurgie, AG Materialphysik, TU Clausthal, Germany — 2Laboratorium für Neutronenstreuung, ETH Zürich & PSI, Villigen, Switzerland
Nano-crystalline metals show in comparison to their coarse grained counterparts improved mechanical properties like high hardness and fracture toughness and also interesting magnetic properties. At low temperatures mechanical deformation (grain boundary creep, grain boundary sliding), grain growth, and also thermal stability are essentially controlled or influenced by self-diffusion. For an understanding of these processes close to room temperature, we carried out self-diffusion measurements on nanocrystalline Fe films using neutron reflectometry. This method enables to determine extremely low diffusivities down to 10^-25 m^2/s and also extremely small diffusion lengths < 1 nm, not possible with conventional methods. For diffusion studies, isotopic multilayers of the form Si(substrate)/[57-Fe(5 nm)/nat-Fe(10 nm)]x10 were deposited by using magnetron sputtering. The multilayers were annealed in the temperature range between 473 and 673K for different periods of time and neutron reflectivity has been measured in-situ. Further, structural characterization has been done by grazing incidence X-ray diffractometry, Moessbauer spectroscopy, atomic force microscopy, and electron microscopy. First results are presented and are discussed in the framework of grain boundary diffusion in the type C regime.