Friction mechanism of individual multilayered nanoparticles
Open Access
- 14 November 2011
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 108 (50), 19901-19906
- https://doi.org/10.1073/pnas.1106553108
Abstract
Inorganic nanoparticles of layered [two-dimensional (2D)] compounds with hollow polyhedral structure, known as fullerene-like nanoparticles (IF), were found to have excellent lubricating properties. This behavior can be explained by superposition of three main mechanisms: rolling, sliding, and exfoliation-material transfer (third body). In order to elucidate the tribological mechanism of individual nanoparticles in different regimes, in situ axial nanocompression and shearing forces were applied to individual nanoparticles using a high resolution scanning electron microscope. Gold nanoparticles deposited onto the IF nanoparticles surface served as markers, delineating the motion of individual IF nanoparticle. It can be concluded from these experiments that rolling is an important lubrication mechanism for IF-WS2 in the relatively low range of normal stress (0.96±0.38 GPa). Sliding is shown to be relevant under slightly higher normal stress, where the spacing between the two mating surfaces does not permit free rolling of the nanoparticles. Exfoliation of the IF nanoparticles becomes the dominant mechanism at the high end of normal stress; above 1.2 GPa and (slow) shear; i.e., boundary lubrication conditions. It is argued that the modus operandi of the nanoparticles depends on their degree of crystallinity (defects); sizes; shape, and their mechanical characteristics. This study suggests that the rolling mechanism, which leads to low friction and wear, could be attained by improving the sphericity of the IF nanoparticle, the dispersion (deagglomeration) of the nanoparticles, and the smoothness of the mating surfaces.This publication has 27 references indexed in Scilit:
- Insights on uniaxial compression of WS2 inorganic fullerenes: A finite element studyJournal of Materials Research, 2011
- Gold Nanoparticles as Surface Defect Probes for WS2 NanostructuresThe Journal of Physical Chemistry Letters, 2009
- Preparation and tribological properties of WS2 nanoparticles modified by trioctylamineProceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2009
- Fabrication of self-lubricating cobalt coatings on metal surfacesNanotechnology, 2007
- Simple Model of Microscopic Rolling FrictionPhysical Review Letters, 2005
- Deformation and tribology of multi-walled hollow nanoparticlesEurophysics Letters, 2000
- Microtribology and Direct Force Measurement of WS2 Nested Fullerene-Like NanostructuresAdvanced Materials, 1999
- Bulk Synthesis of Inorganic Fullerene-like MS2(M = Mo, W) from the Respective Trioxides and the Reaction MechanismJournal of the American Chemical Society, 1996
- Polyhedral and cylindrical structures of tungsten disulphideNature, 1992
- A study of the nucleation and growth processes in the synthesis of colloidal goldDiscussions of the Faraday Society, 1951