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SEM and TEM based characterization of particulate matter from disc-brake wear
Poster Presentation XML
Authors
Department of Industrial Engineering, University of Trento, Trento, Italy
Abstract
The un-regulated non-exhaust emissions from automobiles are a cause of concern across the world. In particular, disc-brake wear contributes a significant fraction of particulate matter (PM) in the fine (PM2.5) and ultrafine (PM0.1) range. An exhaustive analysis involving single particle analysis (SPA) of the constituents of these micro/nano-sized materials is the way forward for the development of clean materials for the disc brakes, and also for understanding the relevant wear mechanisms. In this regard, electron microscopy provides a broad range of investigation tools from microstructural, structural, and compositional standpoints. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDXS) favors relatively simpler sample preparation and can provide the morphology and elemental composition of the particles that are too thick for transmission electron microscopy (TEM) based analysis. As for TEM, although the sample preparation could be quite challenging, still, again in association with EDXS, it provides information at a much higher spatial resolution. Moreover, with the incorporation of electron diffraction data, yields direct information of the crystallographic structure. A combined analysis of the two approaches is particularly effective for analyzing the complex thermo-mechanical-chemical transformations taking place between the brake pads and disc. In this paper, this combined methodology was applied to the airborne PM collected during bench and lab tests on disc brake systems. The tests were designed in a way to rank the particles based on their respective sizes using impactors, and were collected on suitable substrates, although not always appropriate for materials characterization purposes. Whenever required, appropriate sample preparation protocols have to be followed in the case of both SEM as well as TEM samples, with a focus on not altering the pristine and original features of the particles during the extraction stage from the substrates. In particular, reliable information could be obtained from a very small amount of particles, which is often a constraint in the case of other bulk characterization techniques.
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