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The origins of chemomechanical effects in the low-load indentation hardness and tribology of ceramic materials

Lookup NU author(s): Professor Steve Bull, Dr Noushin Moharrami, Emeritus Professor Trevor Page

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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).


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, ( 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.


Publication metadata

Author(s): Bull SJ, Moharrami N, Hainsworth SV, Page TF

Publication type: Article

Publication status: Published

Journal: Journal of Materials Science

Year: 2016

Volume: 51

Issue: 1

Pages: 107-125

Print publication date: 01/01/2016

Online publication date: 15/09/2015

Acceptance date: 03/09/2015

Date deposited: 17/09/2015

ISSN (print): 0022-2461

ISSN (electronic): 1573-4803

Publisher: Springer New York

URL: http://dx.doi.org/10.1007/s10853-015-9412-3

DOI: 10.1007/s10853-015-9412-3


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