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Title: The Origins of Chemomechanical Effects in the Low-Load Indentation Hardness and Tribology of Ceramic Materials
Authors: Bull, S. J.
Moharrami, N.
Hainsworth, Sarah V.
Page, T. F.
First Published: 15-Sep-2015
Publisher: Springer Verlag
Citation: Journal of Materials Science January 2016, Volume 51, Issue 1, pp 107-125
Abstract: 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.
DOI Link: 10.1007/s10853-015-9412-3
ISSN: 0022-2461
eISSN: 1573-4803
Version: Post-print
Status: Peer-reviewed
Type: Journal Article
Rights: Archived with reference to SHERPA/RoMEO and publisher website. The final publication is available at Springer via
Appears in Collections:Published Articles, Dept. of Engineering

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