Papers by fabrice dassenoy
Tribology Transactions
The tribological performances of polymer stabilized TiO 2 particles dispersed in mineral base oil... more The tribological performances of polymer stabilized TiO 2 particles dispersed in mineral base oil were investigated. Two polymer/TiO 2 mass ratios were investigated, with a constant polymer concentration of 0.3 wt% and two nanoparticles concentrations of 0.1 and 1 wt%. Friction tests were carried out with a pin on a reciprocating flat test configuration under boundary lubricated sliding conditions, in the presence of steel/steel contact and at two temperatures (20°C and 100°C). The results show the very good anti-wear performances of the nanoparticle-based dispersions. The most promising results were obtained with 0.1 wt% of TiO 2 particles and at 20°C. At this temperature, the wear resistance properties of the TiO 2 particles surpass those of the Zinc DialkylDithioPhosphate (ZDDP) molecule. The tribofilms generated during the friction tests were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) combined with Energy Dispersive X-Ray Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS), and X-Ray Photoelectron Spectroscopy (XPS). A tribofilm, composed of agglomerates of TiO 2 particles embedded in a matrix formed by the polymer was observed. The combination of the polymer used as a dispersant and the TiO 2 particles allows good tribological performance that was observed during the friction tests. The formulation comprising of TiO 2 particles could improve the anti-wear properties of materials in an environment where conventional wear reducing additives do not form tribofilms due to low temperatures.
Post mortem characterization techniques are essential for the understanding of the lubrication me... more Post mortem characterization techniques are essential for the understanding of the lubrication mechanisms of complex tribological systems. The information obtained using these techniques can be used to propose hypothesis of mechanisms that have then to be definitively validated by probing the interfacial material in real time during the friction test. To go further in the understanding of the action modes of some tribological systems, it is important to set up an analytical methodology using in situ experimental techniques in order to (i) probe directly the behavior of the interfacial material in the contact zone and (ii) dissociate, for a better understanding, the different components of the tribological stress (pressure and shear). There are several techniques that combine mechanical stress and in situ analysis (Raman tribology, Infra-Red tribology, EXAFS under pressure …). However, the most interesting techniques are certainly those that permit a visualization of the contact area...
Tribology International, 2017
The invention relates to a method for the preparation of molybdenum sulfide nanoparticles or by m... more The invention relates to a method for the preparation of molybdenum sulfide nanoparticles or by mixing tungsten sulfide two compositions at a temperature below the lowest boiling point of the solvents used. The invention also relates to a composition comprising particles prepared or may be prepared according to the method of the invention and a dispersing agent including a derivative of oleic acid, especially an oleate.
Lubrication Science, 2021
The most remarkable difference between electric vehicles (EVs) and conventional ones is the fuel ... more The most remarkable difference between electric vehicles (EVs) and conventional ones is the fuel burning dependency of the internal combustion engine, while the emerging EVs operate on electric motors. These alternations create staggering shifts in both lubricants' market demand and performance specifications. Lubricants for electrical powertrain constitutes greases, transmission oils, and lubricants for auxiliary systems and do not rely on engine oils as internal combustion vehicles. The new standards will be more focused on lubricants' electrical properties such as breakage voltage and conductivity, coupled with tribological performance under high rpm, corrosion resistance and thermal management benchmarks. This paper thematically reviews the different studies performed with nanolubricants, and how they match EVs' operational requirements. Conclusions from this study can be considered as guidelines for the potential application of nanolubricants in EVs and possible future research that can be accomplished on the topic.
Tribology Letters, 2020
MoS 2 :glycol hybrid nanoparticles were synthetized through a polyol route. Their tribological pr... more MoS 2 :glycol hybrid nanoparticles were synthetized through a polyol route. Their tribological properties when used as lubricant additives in a PAO 6 base oil were investigated using a pin-on-disk tribometer. An important friction reduction and good anti-wear performances were observed compared to the base oil and to the no modified particles. The MoS 2 :glycol nanoparticles were characterized by thermogravimetric analysis, transmission electron microscopy, RAMAN spectroscopy, X-ray diffraction, and Fourier transform infrared. Furthermore, the stability of the dispersion was followed by dynamic light scattering. On the other hand, Field Emission Scanning Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, and X-ray Photoelectron Spectrometry analysis showed that the tribofilm formed on the wear surfaces during the friction test is at the origin of the excellent tribological performance of the MoS 2 nanoparticles. In particular, it was demonstrated that the interaction of MoS 2 with the organic moiety of the nanoparticles plays a key role in the friction reduction and the good anti-wear properties of the dispersions.
Tribology Online, 2019
There has been growing interest in nanoparticles for tribological applications over the past 20 y... more There has been growing interest in nanoparticles for tribological applications over the past 20 years. Studies have shown their remarkable lubricating properties, namely friction-reduction and anti-wear, especially when used as lubricant additives. This makes them potential candidates for replacing the additives currently used in automobile lubricants, known to be pollutants and less efficient in certain specific conditions. Among the nanoparticles with proven tribological performance are carbon nanoparticles (nanotubes, onion, diamond, etc.), BN and TiO 2 nanoparticles, and Inorganic Fullerene-like (IF) metal disulfides (IF-MoS 2 , IF-WS 2). At the Laboratory of Tribology and Dynamic of Systems (LTDS) of the Ecole Centrale of Lyon (ECL), these nanoparticles have been the subject of detailed investigation for more than fifteen years. Many key issues have been tackled, such as the conditions leading to these properties, the lubrication mechanisms involved, and the influence of parameters such as the size, the structure, and the morphology of the nanoparticles on both their tribological properties and lubrication mechanisms. In order to answer such questions, state-of-theart characterization techniques are required, often in situ, and sometimes extremely complex to set up. Some of them can even visualize the behavior of a nanoparticle in real time while it is undergoing tribological testing. Researchers now have good understanding of the way these nanoparticles behave, and are able to identify the key parameters to be adjusted to optimize their lubrication properties. In this article, the performance of nanoparticles when used as additives will be described, with particular attention given to metal disulfide nanoparticles. Furthermore, the influence of key parameters on the performance of oils containing nanoparticles will be discussed and the lubrication mechanisms of the metal disulfide nanoparticles will be presented in detail. The issues remaining to be solved before developing new lubricants containing nanoparticles will be also discussed. Finally, we show how fully formulated lubricants containing nanoparticles behave when tested under conditions close to the final application (automotive engine and gearboxes).
RSC Advances, 2018
Tribocatalytic behaviour of TiO2 APS coatings in presence of MoDTC additive under boundary lubric... more Tribocatalytic behaviour of TiO2 APS coatings in presence of MoDTC additive under boundary lubrication conditions – decomposition mechanism
Tribology International, 2018
Gasoline soot nanoparticles (SNPs) were studied by performing in situ compression tests on indivi... more Gasoline soot nanoparticles (SNPs) were studied by performing in situ compression tests on individual nanoparticles inside a transmission electron microscope. After consecutive compressions, the SNPs exhibited an elasto-plastic behavior, and an increasing trend in Young's modulus and hardness values. Molecular dynamics were used to simulate compression cycles, the results of which confirmed the observations made during the experiments. The simulations were used to investigate how the different structural components of the nanoparticles affect their elastic and plastic response. By comparing the behavior of gasoline and diesel SNPs under compression, differences were observed both experimentally and in the simulations: the former were found to be more elastic and less prone to become hard under compression compared to the latter.
Nanotechnology, Jan 23, 2018
Incomplete fuel burning inside an internal combustion engine results in the creation of soot in t... more Incomplete fuel burning inside an internal combustion engine results in the creation of soot in the form of nanoparticles. Some of these soot nanoparticles (SNP) become adsorbed into the lubricating oil film present on the cylinder walls, which adversely affects the tribological performance of the lubricant. In order to better understand the mechanisms underlying the wear caused by SNPs, it is important to understand the behavior of SNPs and to characterize potential changes in their mechanical properties (e.g. hardness) caused by (or during) mechanical stress. In this study, the behavior of individual SNPs originating from diesel engines was studied under compression. The experiments were performed in a transmission electron microscope using a nanoindentation device. The nanoparticles exhibited elasto-plastic behavior in response to consecutive compression cycles. From the experimental data, the Young's modulus and hardness of the SNPs were calculated. The Young's modulus a...
Tribology Letters, 2017
An in situ friction test was carried out on a single WS 2 nanoparticle in a transmission electron... more An in situ friction test was carried out on a single WS 2 nanoparticle in a transmission electron microscope (TEM) using a nanoindentation device able to measure normal and lateral forces independently. For the first time, quantitative results are reported: friction forces were recorded during the test, and thus, friction coefficient values were calculated. The exfoliation of the particle was observed during the experiment, and it was linked to the friction coefficient modification. The success of using this technique opens many possibilities of doing in situ friction tests in a TEM, especially for revealing and studying lubrication mechanisms.
Tribology International, 2017
Abstract The development of new advanced lubricants is a key factor for the production of cleaner... more Abstract The development of new advanced lubricants is a key factor for the production of cleaner and more durable internal combustion engines. New improved anti-friction and anti-wear additives are required to improve the fuel economy and reduce the greenhouse gases emission. The inclusion of nanoparticles known as solid lubricants (MoS2 and WS2 inorganic fullerenes) in engine oils could help to improve the performance of internal combustion engines. This paper describes the results of the testing activities performed on a fully formulated engine oil incorporating MoS2 nanoparticles. The nano-lubricant allowed demonstrating on the New European Driving Cycle (NEDC) a reduction of 0.9% of fuel consumption with respect to the reference lubricant without nanoparticles.
European Microscopy Congress 2016: Proceedings, 2016
Tribology International, 2016
The effect of WS 2 nanoparticles used as lubricant additives in PAO alone and in presence of ZDDP... more The effect of WS 2 nanoparticles used as lubricant additives in PAO alone and in presence of ZDDP additive on the lubrication of rough surfaces has been studied at 100°C in the boundary lubrication regime. The results showed that the use of nanoparticles in PAO base oil reduces both wear and friction by around 70% compared to PAO. The surface analyzes revealed that a tribofilm is formed on the steel surface and that nanoparticles can be trapped in the steel grooves. These trapped nanoparticles could provide proper lubrication of the contact zone in case of nanoparticle starvation. The presence of ZDDP additive in the lubricant enhances the friction reducing and anti-wear effect of the nanoparticles.
Http Www Theses Fr, 1999
Les caracteristiques morphologiques et structurales (taille, dispersion, structure) des particule... more Les caracteristiques morphologiques et structurales (taille, dispersion, structure) des particules metalliques de taille nanometrique conditionnent largement leur proprietes physiques ou physico-chimique. Ce travail vise a determiner l'evolution de ces caracteristiques en fonction des conditions de synthese et de la composition chimique dans des particules mono- et bi-metalliques. Pour cela, nous avons developpe une methodologie combinant les informations obtenues par deux techniques structurales adaptees aux tres petites dimensions : la diffusion des rayons x aux grands angles (waxs) et la microscopie electronique en transmission dans son mode haute resolution (mehr). Les particules etudiees (pt, ru, co, pt xru 1 x et pt xco 1 x) ont ete synthetisees dans des conditions douces, par decomposition de precurseurs organometalliques zerovalents par un gaz reactif approprie et en presence d'un polymere stabilisant. Nos etudes ont montre que la taille des particules de platine et de ruthenium est fonction du polymere utilise et du gaz reducteur. Ces particules cristallisent dans la meme structure que les materiaux massifs, a savoir cfc pour pt et hc pour ru, qu'elles que soient leur dimension. Par contre, leurs parametres cristallins sont tres sensibles a la taille. Nous avons egalement mis en evidence une structure originale, exclusivement polytetraedrique, dans les particules de co. Dans les systemes pt/ru et pt/co, nos resultats mettent en evidence le caractere bimetallique des particules formees. Une evolution structurale continue de la structure cfc (pt) vers la structure hc (ru) avec l'augmentation de la teneur en ru a ete observee. Les particules pt xco 1 x ne presentent pas de structures periodiques et se differentient des particules monometalliques pt pur et co pur. L'evolution de leurs caracteristiques structurales est en accord avec une segregation des especes, le pt etant situe au cur des particules.
Catalysis Science & Technology, 2016
Core–shell Co9S8@MoS2 unsupported catalysts prepared by a solution reaction in ethylene glycol de... more Core–shell Co9S8@MoS2 unsupported catalysts prepared by a solution reaction in ethylene glycol demonstrate high catalytic activity and exceptional thermal stability.
Physical Review B, 2001
Ultrafine Pt x Ru 1Ϫx particles ͑with 0рxр1͒, synthesized by decomposition of organometallic prec... more Ultrafine Pt x Ru 1Ϫx particles ͑with 0рxр1͒, synthesized by decomposition of organometallic precursors in the presence of a stabilizing polymer, are studied using both high-resolution transmission electron microscopy and wide-angle x-ray scattering techniques. In this paper, we focus on the influence of the size and the composition on the atomic organization and structural features of Pt, Ru, and Pt-Ru particles. It is shown that the pure Pt and Ru particles crystallize in the same structure as in the bulk, i.e., face centered cubic ͑fcc͒ for platinum and hexagonal close packed ͑hcp͒ for ruthenium. A modification of the cell parameters due to size reduction is observed. In particular, evidence is given for the change of the c/a ratio in Ru particles. The alloy particles are also crystalline, whatever the composition. The role of the composition in the structural transition from the fcc structure to the hcp one in nanoscaled particles is demonstrated. The mechanism of structural transition is fully described.
NATO Science Series II: Mathematics, Physics and Chemistry
Tribology Transactions, 2016
ABSTRACT The effect of WS2 nanoparticles used as lubricant additives in the lubrication of automo... more ABSTRACT The effect of WS2 nanoparticles used as lubricant additives in the lubrication of automotive gearboxes has been studied. The results suggest that nanoparticles can be used to increase the life span of the mechanical parts of gears. Chemical analyses and observations made after transmission tests have shown that nanoparticles are able to go inside cracks and may have a sealing effect, preventing spalling and further failure of the material. Moreover, the addition of nanoparticles in fully formulated oil reinforces the antispalling properties of the lubricant.
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Papers by fabrice dassenoy