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Your search keyword '"De Barros Bouchet, M. I."' showing total 35 results
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35 results on '"De Barros Bouchet, M. I."'

8. Superlow friction of ta-C lubricated by glycerol: An electron energy loss spectroscopy study.

Author

Joly-Pottuz, L., Matta, C., de Barros Bouchet, M. I., Vacher, B., Martin, J. M., and Sagawa, T.

Subjects
THIN films, SURFACES (Technology), SURFACE coatings, TRANSMISSION electron microscopy, ION bombardment, ENERGY dissipation
Abstract

Energy-filtering transmission electron microscopy (EFTEM) analysis coupled with the technique of samples preparation, focused ion beam, was used to study physical, chemical, and mechanical properties of diamond-like carbon coatings (DLCs). Two different coatings (ta-C and a-C:H) were investigated, presenting different tribological behaviors in a boundary lubrication regime with glycerol. Electron energy loss spectroscopy appears to be a very powerful technique to characterize such DLC coatings. Special attention was paid to the maximum energy of the plasmon peak, which was used to evaluate some physical and mechanical properties of DLC coatings (density, sp3/sp2 ratio, hardness). For ta-C superlubric coating, EFTEM results show a rearrangement of the DLC bulk structure under the friction process. Typically, the transformation of sp3 carbon into sp2 carbon was clearly observed and permits a self-adaptation of the coating, allowing it to support shearing without any delamination in spite of important compressive residual stresses in the coating. Moreover, the formation of graphitic carbon is evidenced at the top surface. This graphitic layer certainly helps the lubrication by glycerol in forming OH termination. [ABSTRACT FROM AUTHOR]

Published
2007
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15. Superlubricity and tribochemistry of polyhydric alcohols

Author

Matta, C., Joly-Pottuz, L., De Barros Bouchet, M. I., Martin, J. M., Kano, M., Zhang, Qing, Goddard, W. A., III, Matta, C., Joly-Pottuz, L., De Barros Bouchet, M. I., Martin, J. M., Kano, M., Zhang, Qing, and Goddard, W. A., III

Abstract

The anomalous low friction of diamondlike carbon coated surfaces lubricated by pure glycerol was observed at 80 °C. Steel surfaces were coated with an ultrahard 1 µm thick hydrogen-free tetrahedral coordinated carbon (ta-C) layer produced by physical vapor deposition. In the presence of glycerol, the friction coefficient is below 0.01 at steady state, corresponding to the so-called superlubricity regime (when sliding is then approaching pure rolling). This new mechanism of superlow friction is attributed to easy glide on triboformed OH-terminated surfaces. In addition to the formation of OH-terminated surfaces but at a lower temperature, we show here some evidence, by coupling experimental and computer simulations, that superlow friction of polyhydric alcohols could also be associated with triboinduced degradation of glycerol, producing a nanometer-thick film containing organic acids and water. Second, we show outstanding superlubricity of steel surfaces directly lubricated by a solution of myo-inositol (also called vitamin Bh) in glycerol at ambient temperature (25 °C). For the first time, under boundary lubrication at high contact pressure, friction of steel is below 0.01 in the absence of any long chain polar molecules. The mechanism is still unknown but could be associated with friction-induced dissociation of glycerol and interaction of waterlike species with steel surface.

Published
2008

16. Superlubricity mechanism of diamond-like carbon with glycerol. Coupling of experimental and simulation studies

Author

De Barros Bouchet, M. I., Matta, C., Le-Mogne, Th., Martin, J. Michel, Zhang, Q., Goddard, W., III, Kano, M., Mabuchi, Y., Ye, J., De Barros Bouchet, M. I., Matta, C., Le-Mogne, Th., Martin, J. Michel, Zhang, Q., Goddard, W., III, Kano, M., Mabuchi, Y., and Ye, J.

Abstract

We report a unique tribological system that produces superlubricity under boundary lubrication conditions with extremely little wear. This system is a thin coating of hydrogen-free amorphous Diamond-Like-Carbon (denoted as ta-C) at 353 K in a ta-C/ta-C friction pair lubricated with pure glycerol. To understand the mechanism of friction vanishing we performed ToF-SIMS experiments using deuterated glycerol and 13C glycerol. This was complemented by first-principles-based computer simulations using the ReaxFF reactive force field to create an atomistic model of ta-C. These simulations show that DLC with the experimental density of 3.24 g/cc leads to an atomistic structure consisting of a 3D percolating network of tetrahedral (sp3) carbons accounting for 71.5% of the total, in excellent agreement with the 70% deduced from our Auger spectroscopy and XANES experiments. The simulations show that the remaining carbons (with sp2 and sp1 character) attach in short chains of length 1 to 7. In sliding simulations including glycerol molecules, the surface atoms react readily to form a very smooth carbon surface containing OH-terminated groups. This agrees with our SIMS experiments. The simulations find that the OH atoms are mostly bound to surface sp1 atoms leading to very flexible elastic response to sliding. Both simulations and experiments suggest that the origin of the superlubricity arises from the formation of this OH-terminated surface.

Published
2007

29. New Trends in Boundary Lubrication of DLC Coatings.

Author

Donnet, Christophe, Erdemir, Ali, De Barros Bouchet, M. I., and Martin, J. M.

Abstract

Fuel economy and reduction of harmful elements in lubricants are becoming important issues in the automotive industry. An approach to respond to these requirements is the potential use of low friction coatings in engine components exposed to boundary lubrication conditions. Diamond-like carbon (DLC) coatings present a wide range of tribological behavior, including friction coefficients in ultrahigh vacuum below 0.02. The engine oil environment which provides similar favorable air-free conditions might lead to such low friction levels. [ABSTRACT FROM AUTHOR]

Published
2008
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30. Experimental Simulation of Tribochemical Reactions Between Borates Esters and Steel Surface.

Author

Philippon, D., De Barros-Bouchet, M.-I., Lerasle, O., Le Mogne, Th., and Martin, J.-M.

Abstract

In this study, tribochemical reactions of borate ester additives on steel surfaces were simulated experimentally by gas phase lubrication. Trimethylborate (TMB) was employed as a model molecule of the borate chemical function. TMB was introduced under gas phase up to 5 hPa in a new tribometer dedicated to gas phase lubrication. Friction tests were conducted at room temperature. In order to identify the nature of the generated tribofilm, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses were carried out inside and outside the track of the tested samples. The results showed a reduction of the friction coefficient down to 0.2 by increasing the TMB gas pressure. This reduction in friction was induced by the formation of a tribofilm of iron oxide partially digested by a borate glass network. The reduction in friction was attributed to the formation of the borate glass. The digestion of abrasive iron oxides by the borate glass was purported to be responsible for the reduction in the wear. The tribochemical reaction of TMB on steel surfaces is discussed in relation to the hard and soft acid base (HSAB) principle. [ABSTRACT FROM AUTHOR]

Published
2011
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32. A comparative study on the functionality of S- and P-based lubricant additives by combined first principles and experimental analysis

Author

Maria Clelia Righi, S. Mambingo-Doumbe, Sophie Loehlé, M. I. De Barros Bouchet, Jean Michel Martin, Righi, Maria Clelia, Loehlé, S., De Barros Bouchet, M. I., Mambingo Doumbe, S., and Martin, J. M.

Subjects
Passivation, Phosphide, General Chemical Engineering, Phosphorus, Inorganic chemistry, Chemistry (all), chemistry.chemical_element, Iron sulfide, 02 engineering and technology, General Chemistry, Tribology, 021001 nanoscience & nanotechnology, Sulfur, chemistry.chemical_compound, 020303 mechanical engineering & transports, 0203 mechanical engineering, chemistry, OXIDIZED IRON, SURFACE, PHOSPHORUS, MECHANISM, CHEMISTRY, PHOSPHATE, ESTERS, STEEL, TRIMETHYLPHOSPHITE, ADSORPTION, Lubrication, Chemical Engineering (all), Lubricant, 0210 nano-technology
Abstract

Sulfur and phosphorus are key elements for the functionality of lubricant additives used in extreme pressure applications, such as synchronizer systems in cars. To understand their mechanism of action we combine first principles calculations and gas phase lubrication experiments. The surface spectroscopy analysis performed in situ after the tribological test indicates that iron sulfide (phosphide) is formed by rubbing steel-on-steel in the presence of organo-sulfur (-phosphorus) molecules. We, thus, study the effects of elemental sulfur and phosphorus on the interfacial properties of iron by spin-polarized density functional theory calculations. The results show that both the elements are very effective in reducing the adhesion and shear strength of iron. Sulfur is predicted to be more effective than phosphorus, especially at high pressure. Gas phase lubrication experiments confirm these results, indicating that the friction coefficient of iron-sulphide is lower than that of iron-phosphide and both S and P dramatically reduce the friction of steel-on-steel. These results indicate that the release of elemental sulfur and phosphorus may be the key mechanism to controlling the tribological properties of the metal interface and elucidate that the underling microscopic phenomenon is metal passivation.

Published
2016
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33. Tribochemistry of phosphorus additives: Experiments and first-principles calculations

Author

A. Bouffet, M. I. De Barros-Bouchet, S. Mambingo-Doumbe, David Philippon, Jean Michel Martin, Maria Clelia Righi, T. Le-Mogne, De Barros Bouchet, M. I, Righi, Maria Clelia, Philippon, D., Mambingo Doumbe, S., Le Mogne, T., Martin, J. M., and Bouffet, A.

Subjects
Work (thermodynamics), Materials science, General Chemical Engineering, Phosphorus, Inorganic chemistry, Chemistry (all), Friction modifier, chemistry.chemical_element, General Chemistry, Tribology, VAPOR-PHASE LUBRICATION, BOUNDARY LUBRICATION, SURFACE-CHEMISTRY, IMMERSION TEST, OXIDIZED IRON, TOF-SIMS, PHOSPHATE, FRICTION, WEAR, ADSORPTION, chemistry.chemical_compound, Iron phosphide, chemistry, Lubrication, Shear strength, Friction reduction, Chemical Engineering (all)
Abstract

Organophosphorus compounds are common additives included in liquid lubricants for many applications, in particular automotive applications. Typically, organic phosphites function as friction-modifiers whereas phosphates as anti-wear additives. While the antiwear action of phosphates is now well understood, the mechanism by which phosphites reduce friction is still not clear. Here we study the tribochemistry of both phosphites and phosphates using gas phase lubrication (GPL) and elucidate the microscopic mechanisms that lead to the better frictional properties of phosphites. In particular, by in situ spectroscopic analysis we show that the friction reduction is connected to the presence of iron phosphide, which is formed by tribochemical reactions involving phosphites. The functionality of elemental phosphorus in reducing the friction of iron-based interfaces is elucidated by first principle calculations. In particular, we show that the work of separation and shear strength of iron dramatically decrease by increasing the phosphorus concentration at the interface. These results suggest that the functionality of phosphites as friction modifiers may be related to the amount of elemental phosphorus that they can release at the tribological interface.

Published
2015
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34. Trimethyl-phosphite dissociative adsorption on iron by combined first-principle calculations and XPS experiments

Author

David Philippon, Sophie Loehlé, Maria Clelia Righi, J.M. Martin, M. I. De Barros Bouchet, Righi, Maria Clelia, Loehlé, S., De Barros Bouchet, M. I., Philippon, D., and Martin, J. M.

Subjects
General Chemical Engineering, Inorganic chemistry, Chemistry (all), Trimethyl phosphite, General Chemistry, Dissociation (chemistry), Metal, chemistry.chemical_compound, Adsorption, X-ray photoelectron spectroscopy, chemistry, Ab initio quantum chemistry methods, Chemisorption, visual_art, visual_art.visual_art_medium, First principle, Chemical Engineering (all)
Abstract

The reaction of trimethyl-phosphite, TMPi, with a clean Fe(110) surface has been investigated by ab initio calculations. The most stable configurations and energies are identified for both molecular and dissociative adsorption. The calculated reaction energies indicate that dissociation is energetically more favorable than molecular adsorption and we provide a description of the dissociation path and the associated energy barrier. In situ XPS analysis of adsorbed TMPi on metallic iron confirmed molecular chemisorption and dissociation at high temperature. These results shed light on the mechanism of phosphorus release from organophosphites at the iron surface, which is important for the functionality of these phosphorus-based additives, included in lubricants for automotive applications.

Published
2015

35. MoS 2 formation induced by amorphous MoS 3 species under lubricated friction.

Author

Oumahi C, De Barros-Bouchet MI, Le Mogne T, Charrin C, Loridant S, Geantet C, Afanasiev P, and Thiebaut B

Abstract

Amide molybdate has been recently introduced as a friction modifier for tribological applications. Combined with zinc dithiophosphate (ZDDP) and fatty amines, it provides an ultralow friction coefficient. The ultimate product of Mo compound transformations in tribological contact, due to frictional heating and shearing, as well as chemical interactions with oil additives, is molybdenum sulfide (MoS 2 ). Understanding the decomposition of amide molybdate leading to MoS 2 is of primary importance to the optimization of the design of lubricant formulations. This study focuses on the investigation by Raman spectroscopy of amide molybdate decomposition intermediates. Raman spectra of tribofilms, obtained after friction tests under different temperatures and pressures, revealed the formation of an amorphous MoS 3 intermediate coexisting with MoS 2 . However, under severe conditions, the tribofilms are mostly composed of MoS 2 ., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Published
2018
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