Berlin 2018 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 37: Microstructure and Phase Transformations
MM 37.1: Vortrag
Mittwoch, 14. März 2018, 11:45–12:00, TC 010
X-Ray Studies of Large Crystals with Small Holes: The Case of Virtual Nanoporous Gold — •Bao-Nam Dinh Ngô1, Matthias Graf2, Jörg Weissmüller1,2, and Jürgen Markmann1,2 — 1Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany — 2Institute of Materials Physics and Technology, Hamburg University of Technology, Hamburg, Germany
Nanoporous gold (NPG) made by dealloying is a polycrystalline material with 10 – 100 µ m sized crystallites that are interpenetrated by a network of 10 – 100 nm sized pores. X-ray powder diffraction by such structures has not been systematically studied so far. We explore the issue by theory, experiment, and virtual diffraction, with an eye on establishing a method for nondestructive microstructure characterization of NPG. Virtual diffraction studied a computer-generated NPG sample with crystal size 61 nm and ligament size 4 nm. The diffraction pattern of the truncated (porous) periodic crystal lattice in its unrelaxed state agrees well with our theory: A narrow central component of the Bragg reflections reflects the long-range lattice coherency while a broad foot reflects the loss of atomic neighbors due to nanopores. Thermal relaxation using molecular dynamics leads to a complete loss of the narrow component. This can be attributed to crystal lattice distortion (microstrain) due to surface stress. The virtual diffraction is in excellent agreement with experimental diffraction data.