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The Origins of Chemomechanical Effects in the Low-Load Indentation Hardness and Tribology of Ceramic Materials

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journal contribution
posted on 04.09.2015, 08:28 by S. J. Bull, N. Moharrami, Sarah V. Hainsworth, T. F. Page
We have used high-resolution techniques (nanoindentation, atomic force microscopy) to further isolate and identify environmental effects previously reported as possibly affecting both the microindentation response of a range of ceramic materials and their tribological behaviour. In order to make meaningful comparisons, these new experiments have been conducted alongside conventional Knoop and Vickers microhardness experiments conducted under identical conditions on the same samples. A range of polycrystalline, single crystal and amorphous ceramic materials have been studied including some only available as coatings. Our results show that thin adsorbate-modified layers (of dimensions ~1nm) are almost invariably present on all the materials studied but their presence is not directly identifiable by nanoindentation in most cases even if it does affect friction response. However, in crystalline materials, (1012 sapphire and ZnO), we have been able to distinguish a further softening effect seen as a thicker layer (tens of nm) and believed associated with an adsorption-induced near-surface band-structure change affecting the motion of charged dislocations. This produces a measurable softening that is clearly evident in nanoindentation tests but less clear in microindentation tests. Finally, we present conclusions on the suitability of indentation testing for studying these phenomena, together with the implications of chemomechanical effects for influencing tribological performance and, thus, materials selection.

History

Citation

Journal of Materials Science January 2016, Volume 51, Issue 1, pp 107-125

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Engineering

Version

AM (Accepted Manuscript)

Published in

Journal of Materials Science January 2016

Publisher

Springer Verlag

issn

0022-2461

eissn

1573-4803

Acceptance date

03/09/2015

Copyright date

1007

Available date

15/09/2016

Publisher version

http://link.springer.com/article/10.1007/s10853-015-9412-3

Language

en