Abnormal Hall–Petch behavior in nanocrystalline MgO ceramic

Pure and dense nanocrystalline MgO with grain size ranging between 25 and 500 nm were prepared by hot-pressing. Vickers microhardness was found to increase with decrease in the grain size down to 130 nm, following the Hall–Petch relation. Further decrease in the grain size was followed by continuous...

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Bibliographic Details
Published in:Journal of materials science 2008-09, Vol.43 (18), p.6139-6143
Main Authors: Ehre, David, Chaim, Rachman
Format: Article
Language:English
Subjects:
Applied sciences
Building materials. Ceramics. Glasses
Ceramic industries
Ceramics
Characterization and Evaluation of Materials
Chemical industry and chemicals
Classical Mechanics
Crystallography and Scattering Methods
Diamond pyramid hardness
Exact sciences and technology
Grain boundaries
Grain size
Magnesium oxide
Materials Science
Miscellaneous
Nanocrystals
Plastic deformation
Polymer Sciences
Solid Mechanics
Technical ceramics
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Summary:Pure and dense nanocrystalline MgO with grain size ranging between 25 and 500 nm were prepared by hot-pressing. Vickers microhardness was found to increase with decrease in the grain size down to 130 nm, following the Hall–Petch relation. Further decrease in the grain size was followed by continuous decrease in microhardness. A composite model was used to describe the microhardness behavior in terms of plastic yield of the nanocrystalline grains accompanied by strain accommodation and nanocracking at the grain boundaries (gb’s). Good agreement between the experimental and the calculated values indicates that gb’s may have significant effect on strengthening and ductility of nanocrystalline-MgO ceramics in the nanometer size range. Critical grain size exists below which limited plastic deformation within the grains and nanocracking at gb’s enhance the brittleness of the ceramic.
ISSN:0022-2461
1573-4803
DOI:10.1007/s10853-008-2936-z