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Lahouij I.,LTDS ECL Ecully | Dassenoy F.,LTDS ECL Ecully | De Knoop L.,Nanofactory Instruments AB | Martin J.-M.,LTDS ECL Ecully | Vacher B.,LTDS ECL Ecully
Tribology Letters | Year: 2011

Inorganic fullerene-(IF)-like nanoparticles made of metal dichalcogenides (IF-MoS 2, IF-WS 2) have been known to be effective as anti-wear and friction modifier additives under boundary lubrication. The lubrication mechanism of these nanoparticles has been widely investigated in the past and even if the exfoliation and third body transfer of molecular sheets onto the asperities constitute the prevalent mechanism for the improved tribological behavior of IF nanoparticles, it has also been suggested that a rolling friction process could also play a role for well crystallized and spherical particles. In this study, in situ Transmission Electron Microscopy (TEM) observations of the behavior of single IF-MoS 2 nanoparticles were conducted using a sample holder that combines TEM and Atomic Force Microscopy (AFM) which simultaneously can apply normal and shear loads. It was shown that depending on the test conditions, either a rolling process or a sliding of the fullerenes could be possible. These in situ TEM observations are the first carried out with IF nanoparticles. © 2011 Springer Science+Business Media, LLC.


Lahouij I.,LTDS ECL Ecully | Vacher B.,LTDS ECL Ecully | Dassenoy F.,LTDS ECL Ecully
Lubrication Science | Year: 2014

Direct observation of the behaviour of individual inorganic fullerenes (IF)-MoS2 nanoparticles in a sliding interface is essential for the understanding of the influence of the intrinsic characteristics of the nanoparticles on their lubrication mechanisms, when they are used as additives in lubricant oil. In this work, in situ transmission electron microscopy sliding tests were performed on two different types of MoS2 nanoparticles synthesised by two different methods. It is shown that the IF-MoS2 nanoparticles having perfect structure with a high crystalline order and without defects are able to roll and to slide under the combined effect of pressure and shear stress, whereas the IF-MoS2 nanoparticles containing many defects exfoliate immediately in the same conditions to deliver MoS2 layers covering the mating surfaces. A link between these results, the lubrication mechanisms of the nanoparticles and their tribological properties at the macro-scale was established, proving that the lubrication mechanisms of fullerenes depend on their intrinsic characteristics. Copyright © 2013 John Wiley & Sons, Ltd.


Lahouij I.,LTDS ECL Ecully | Dassenoy F.,LTDS ECL Ecully | Vacher B.,LTDS ECL Ecully | Sinha K.,Infineum | And 3 more authors.
Tribology Letters | Year: 2014

This work investigates the effect of compression and sliding on diesel soot in a confined space. Experiments were conducted in a high-resolution transmission electron microscope equipped with an in situ nanoindenter mounted with a truncated diamond tip to manipulate single soot particles and agglomerates. It was shown that both, agglomerates and single particles, were quite resistant to load. Agglomerates did not break during the compression tests; instead, partially reversible compaction of the particles to fill the free space was witnessed, proving that strong cohesive forces exist between the soot particles. The primary particles exhibited good elastic behavior under compression, and the agglomerates mirrored this behavior. Sliding tests have shown the ability of both the agglomerates and single primary particles to roll in the contact zone. This work showed that diesel soot is highly resilient to stress. © Springer Science+Business Media New York 2013.


Lahouij I.,LTDS ECL Ecully | Dassenoy F.,LTDS ECL Ecully | Vacher B.,LTDS ECL Ecully | Martin J.-M.,LTDS ECL Ecully
Tribology Letters | Year: 2012

The deformation and degradation behavior of single inorganic fullerenes nanoparticles of MoS 2 under compression and shear has been observed in real time using a high-resolution transmission electron microscope equipped with a nanoindentation holder. The MoS 2 nanoparticles were compressed using a nanoindenter and a truncated diamond tip. For the first time, real time imaging of the deformation of individual nanoparticles clearly shows first orientation changes in the particle shape during loading process followed by a large deformation and the exfoliation of the outer sheets of the fullerene nested structure. Exfoliation was observed for a contact pressure estimated at 1 GPa. Additional sliding tests performed with the nanoindenter gave evidence for a rolling process for lower contact pressures up to 100 MPa. © 2011 Springer Science+Business Media, LLC.


Tannous J.,LTDS ECL Ecully | Dassenoy F.,LTDS ECL Ecully | Lahouij I.,LTDS ECL Ecully | Le Mogne T.,LTDS ECL Ecully | And 3 more authors.
Tribology Letters | Year: 2011

Inorganic fullerene-(IF)-like nanoparticles made of metal dichalcogenides (IF-MoS 2, IF-WS 2) have been known to be effective as anti-wear and friction modifier additives under boundary lubrication. The lubrication mechanism of these nanoparticles has been widely investigated in the past and it is now admitted that their lubrication properties are attributed to a gradual exfoliation of the external sheets of the particles during the friction process leading to their transfer onto the asperities of the reciprocating surfaces. However, the chemical interaction between these molecular sheets and the rubbing surfaces has so far never been investigated in detail. In this study, the tribochemistry of the IF nanoparticles was carefully investigated. A series of friction test experiments on different rubbing surfaces (Steel, Alumina, Diamond-Like Carbon) were performed with IF-MoS 2 nanoparticles. High-resolution transmission electron microscopy, scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the tribostressed areas on rubbing surfaces. A tribofilm composed of hexagonal 2H-MoS 2 nanosheets was only observed on the steel surface. This transfer film was found to be incorporated into an iron oxide layer. A tribochemical reaction between the 2H-MoS 2 nanolayers and the iron/iron oxide has been proposed as an explanation for the adhesion of this tribofilm. The tribochemical mechanism of the IF-MoS 2 nanoparticles is discussed in this article. © 2010 Springer Science+Business Media, LLC.

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