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NanoScience and Technology Free Preview. After having applied the image processing image C , the circular wear track clearly contrasts with the background and details such as wear debris accumulation not visible on the topographic image A before the wear experiment become visible and help to understand the wear process.
Figure 4: A and B grey scale is 35 nm are the AFM contact mode topographic images before and after the wear An application example to assess the promising potential of CM-AFM to explore wear of materials at the nanoscale is addressed with a copper-based nanocomposite see the Experimental section for details. This material is of industrial relevance as it is widely used in electrical sliding contacts such as those in railway overhead current collection system, lead frames in large-scale integrated circuitd, welding electrodes, transfer switches and electrical contact material.
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Experimental details about the wear experiments with CM-AFM and the recording of the topographic images are described in the Experimental section. In particular, all wear experiments are carried out at different locations on the sample and tips of different nature were used to access to a broad range of cantilever stiffness. This makes clear that CM-AFM is able to locally analyze wear mechanisms and wear properties of the material.
Experiments were carried with a diamond-like carbon DLC probe. Error bars are the standard deviation and the data result from an average between the maximum wear volume and the minimum wear volume issued from the calculation described in the Experimental section. This result shows that the wear volume varies linearly with the sliding distance running-in regime until reaching 16 min of wear, where a plateau steady-state regime indicates that the wear volume is almost independent of the sliding time.
Tribology: Friction, Wear, and Lubrication
The plateau could not be attributed to the wear of the probe during the wear process. At least, if the tip wear occurs, its worn volume contribution is negligible compared to the sample worn volume. One should rather consider that while the probe is going deeper and deeper into the wear track, the contact pressure is decreasing as the surface contact between the AFM tip and the substrate is increased.
Consequently, the shear stress applied to the contact appears to be not high enough to wear the material. Then an atom-by-atom or atomic cluster by atomic cluster or nanograin-by-nanograin removal process may be involved in the wear mechanism. However, SEM imaging was of satisfactory resolution to precisely distinguish the morphology of the wear track and to confirm any of these assumptions.
Experiments were carried with the Si 3 N 4 probe. These results show that for high loads, the behavior follows an Archard-like wear law since the wear volume or wear rate is proportional to the applied load. For small applied loads, the wear rate is almost zero and it is necessary to reach a threshold load of approximately 50 nN to get a significant wear volume.
This paper reported on an original approach for generating and quantitatively measuring nanoscale wear tracks resulting from the sliding contact between an AFM tip and an interacting sample counter-body. Using the AFM circular mode with a high sliding velocity allows a significant and valuable decrease of the drift together with a well-defined wear track and consequent wear.
Accordingly, quantitative wear volumes at the nanoscale are accessible using an image processing method. The used strategy to calculate the wear volume consists of attenuating the roughness of the surface that is of the same order as the nanometer dimension of the wear track which may interfere in the calculation of the wear volume by subtracting relevant topographic images after and before wear. The investigated copper-based nanocomposite was produced by powder metallurgy technology and contained approximately 4.
For each set of wear experiments, a unique AFM tip was used.
After each measurement, force curves on a silicon wafer were performed to verify the state of the tip. Scanning electronic microscopy images of the probes after wear showed that no significant wear of the AFM tip occurred after the set of experiments. Such facts were also confirmed by the adhesion force measurements before each wear experiment, with quite similar resulting values.
Another piece of evidence highlighting that the probe is not damaged is given by the AFM topographic images before and after each experiment, which were recorded with the same AFM tip that was used for wear experiments. In case of damaged tips, the features of the surface would have been dilated due to tip self-imaging .
For improving the imaging processing, AFM topographic images before and after wear were always recorded from the left to the right and from top to bottom directions. Proceeding in such a way reduces the nonlinearity behavior of the piezoelectric actuator with regards to imaging. Sukenik, David Barlam and Sidney R. Christian D. Twitter: BeilsteinInst. Beilstein J. Toggle navigation.
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Olivier Noel. Messiaen, cedex 09, Le Mans, France All articles from this author. Aleksandar Vencl. Pierre-Emmanuel Mazeran. Results and Discussion. Jump to Figure 1. Submission closed. Overview Articles Authors Impact Comments. Keywords : Tribology, Friction, Wear, Lubrication, Interface Important Note : All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements.
Tribology: Friction, Wear, and Lubrication
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