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Effect of Layered MoS2 Nanoparticles on the Frictional Behavior and Microstructure of Lubricating Greases

Sahoo, RR and Biswas, SK (2014) Effect of Layered MoS2 Nanoparticles on the Frictional Behavior and Microstructure of Lubricating Greases. In: TRIBOLOGY LETTERS, 53 (1). pp. 157-171.

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Official URL: http://dx.doi.org/10.1007/s11249-013-0253-4


Lithium stearate soap and layered MoS2 nanoparticles encapsulated in lithium stearate soap are prepared in the laboratory, and their lubricating properties are compared with respect to the particle and particle concentration. The tribotracks after friction test was investigated with Raman Spectroscopy, scanning electron microscopy (SEM) and 3D optical profilometry to understand the action mechanism. The status of the soap particles on a tribotrack changes with time, contact pressure and sliding speed. At low pressure and speed, individual solid undeformed soap particle stand proud of the surface and the topography shows marginal difference with sliding time. In these conditions, no frictional difference between the performance of grease with and without the nanoparticles is observed. Increasing the contact pressure and temperature (low speed and high speed) has a dramatic effect as the soap particles melt and the liquid soap flows over the track releasing the hitherto encapsulated nanoparticles. Consequently, the soap smears the track like a liquid, and the nanoparticles now come directly into the interface and are sheared to generate a low-friction tribofilm. At high particle concentration, the sliding time required for melting of the soap and release of MoS2 is reduced, and the tribofilm is more substantial and uniform consisting of smeared MoS2 and carboxylate soap as observed by SEM and 3D optical profilometry. A change in the Raman Spectra is observed with particle concentration, and this is related to morphology and microstructure of the tribofilm generated.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to the SPRINGER/PLENUM PUBLISHERS,USA
Keywords: MoS2; Lubricating grease; Raman spectroscopy; Transfer film; Friction; Solid lubricant
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Date Deposited: 07 Feb 2014 06:47
Last Modified: 07 Feb 2014 06:47
URI: http://eprints.iisc.ac.in/id/eprint/48323

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