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The origins of triboemission - correlating electron emission with surface damage

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Title: The origins of triboemission - correlating electron emission with surface damage
Authors: Ciniero, A
Le Rouzic, J
Baikie, I
Reddyhoff, T
Item Type: Journal Article
Abstract: Triboemission – i.e. the emission of photons, electrons and other charged particles that arise from a sliding contact – may play a key role in tribochemical processes, such as lubricant degradation. However, the mechanisms that give rise to this type of emission are not well understood. For the first time, we present spatially resolved measurements of electron emission, obtained as a range materials are worn. These are obtained from scratch tests, carried out under vacuum conditions (10−5 Torr), in which microchannel plates coupled to a phosphor screen are used to image electron emission. The results show that electron emission occurs at specific locations on the worn surface and, depending on the conductivity of the material, these sites remain active and decay with a time constant of up to several seconds. SEM images of the worn surface at these sites reveal that either surface fractures or grain defects are present. This suggests that fractoemission mechanisms are at least partially responsible for triboemission (however, the possible contribution of tribocharging mechanisms are also discussed). Specifically, this provides evidence to support the theory that triboemission results from the imbalance of charge on opposing faces of wear cracks and that this generates an electric field sufficient to accelerate molecular fracture products, which then bombard the surface leading to secondary emission. The strong geometric correlation between damage topography and electron emission distributions shows the potential of using this technique to monitoring wear and crack formation in real time and under high (30x) magnification.
Issue Date: 15-Mar-2017
Date of Acceptance: 3-Jan-2017
URI: http://hdl.handle.net/10044/1/43766
DOI: 10.1016/j.wear.2017.01.013
ISSN: 0043-1648
Publisher: Elsevier
Start Page: 113
End Page: 119
Journal / Book Title: Wear
Volume: 374-375
Issue: 1
Copyright Statement: & 2017 The Authors. Published by Elsevier B.V. All rights reserved. This is an open access article distributed under a Creative Commons License 4.0 (https://creativecommons.org/licenses/by/4.0/)
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
Funder's Grant Number: EP/J002100/1
Keywords: Science & Technology
Engineering, Mechanical
Materials Science, Multidisciplinary
Materials Science
Wear monitoring
Mechanical Engineering & Transports
0910 Manufacturing Engineering
0912 Materials Engineering
0913 Mechanical Engineering
Publication Status: Published
Online Publication Date: 2017-01-11
Appears in Collections:Mechanical Engineering
Faculty of Engineering