Regensburg 2007 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 20: Poster session
MM 20.27: Poster
Dienstag, 27. März 2007, 14:45–18:00, Poster C
Sintering without grain growth? A strategy for compacting nanostructured powders to high density without loss ofnanocrystallinity — •Lionel Kroner and Carl Krill — Institute of Micro and Nanomaterials, Ulm University, D-89081 Ulm
Most synthesis routes for nanocrystalline materials result in thin films or powders, which can in principle be formed into bulk specimens via compaction. However, achieving near-100% density generally requires the simultaneous application of high temperature, which in turn induces grain growth, and the final product is no longer nanocrystalline! A potential strategy for sintering without significant grain growth would be to suppress the driving force for coarsening through the deliberate addition of an atomic species that segregates to the grain boundaries. Such thermodynamic stabilization of nanocrystallinity has already been demonstrated for ball-milled Pd doped with Zr [1]; however, no attempt was made to compact the resulting powders into bulk specimens. In this work, we examine the grain size and porosity of nanocrystalline Ni1−xZrx powders as a function of Zr concentration and temperature, both under atmospheric pressure and after compaction. The microstructural evolution during pressureless annealing is followed nondestructively using high-temperature wide-angle x-ray diffraction, and the density of compacted powders is determined by Archimedes’ method. The influence of Zr addition on the sinterability of the powders is assessed.
[1] C. E. Krill III, H. Ehrhardt and R. Birringer, Z. Metallkd. 96 (2005) 1134–1141.