Carbon nanoparticles from local biomass for tribological applications First results

International audienceFriction and wear phenomena are the main causes of the decrease in performances and durability of mechanical systems. Manufacturing techniques for metal parts must meet the growing economic demands of the market, such as improved material durability, reduced maintenance costs and energy consumption. The use of tribology is essential and constitutes an important economic issue. Pure lubricating bases (mineral or synthetic oil) cannot provide all protective functions, so that additives are added to improve their reducing properties of friction and wear. New lubrication strategies use dispersed colloidal particles in lubricants. The approach is to supply the sliding contact with solid particles, which can instantly form the tribological film. My thesis project focuses on the synthesis of new friction reducer additives from local biomass, in order to produce ecofriendly lubricants. These new carbon phases are obtained using the spray-pyrolysis technique [1] with sugarcane from local biomass. It consists in nebulizing a solution of saccharose in the form of micro-droplets, transported to a tubular oven heated at temperatures ranging from 800°C to 1000°C. The first results have permitted to see the effects of the different synthesis conditions, i.e. oven temperature, catalyst concentration and carrier gas pressure, using scanning electron microscopy to observe the spherical shape and the porosity of the particles. This part will concern the tribological properties of our particles, measured with a sphere/plan contact tribometer. The effect of an annealing process on these particles will also be studied

FROM SUGARCANE TO CARBON NANOSPHERES FOR TRIBOLOGICAL APPLICATIONS

International audienceFriction and wear phenomena are the main causes of the decrease in performances and durability of mechanical systems. The use of tribology, defined as the science that studies the phenomena of friction, wear and lubrication, is essential and constitutes an important economic issue. It is the role of lubrication to minimize friction and protect surfaces from wear. The strategy used to reduce these phenomena is to introduce a lubricant between the sliding surfaces. This lubricant can be solid, liquid or gaseous, and must prevent direct contact between surfaces, with specific properties such as friction reduction, anti-oxidizing or antiwear action. Pure lubricating bases (mineral or synthetic oil) cannot provide all protective functions, so that additives are added to improve their reducing properties of friction and wear. New lubrication strategies use dispersed nanoparticles in lubricants. The approach is to supply the sliding contact with solid particles, which can instantly form a protected low shearing tribological film. This work focuses on the synthesis of new friction reducer additives from local biomass, in order to produce ecofriendly lubricants. These new carbon phases are obtained using the spray-pyrolysis technique [1] with sugarcane from local biomass. It consists in nebulizing a solution of saccharose in the form of micro-droplets, transported to a tubular oven heated at temperatures ranging from 800°C to 1000°C, in order to obtain carbon nanospheres. The first results have permitted to evidence the effects of synthesis conditions (oven temperature, catalyst concentration and carrier gas pressure), on the nanoparticles morphology, using scanning electron microscopy. Raman spectroscopy gives us information about the graphitization degree of the carbon phase .The effect of an annealing process on these particles is studied in order to improve the nanospheres tribological propertie

From sugarcane to carbon nanospheres for tribological applications

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BIOMASS CARBONS AS ADDITIVES FOR LUBRICATION: FRICTION REDUCTION KEY PARAMETERS

International audienceIn boundary lubrication regime, friction reduction and antiwear processes are associated to the presence of additives in the lubricating oils or greases. These processes are due to the formation of protective tribofilms resulting from chemical reactions between the additives and the sliding surfaces, in the physico-chemical conditions of the sliding contact. But the main problems encountered with conventional additives (transition metal dithiophosphates or carbamates) are their inefficiency in the case of non metallic surfaces and the film formation period (induction period), in which the contacting surfaces undergo sever wear. Recently developed lubrication strategies consist in the use of dispersion in oils of nano additives able to build the protective tribofilm in the sliding contact without reaction with the surfaces [1]. We pointed out in previous studies the good friction reduction properties of various (nano) carbon materials [2, 3]. This work is concerned with the use of activated carbons synthetized from biomass as new additives for lubricants. Special attention is paid to the role of the carbon structure, in terms of morphology, size, (nano)structuration, porosity of the carbon particles on the friction properties of the additives. 1 Mansot, J.L, et al, Brazil

Contribution to the formulation of green lubrificants using local biomass

International audienceFriction and wear are the first causes of the decrease of the performances and the durability in mechanical systems. The role of lubrication is to minimize friction between the sliding surfaces to protect them from wear. Conventional liquid lubricants are constituted of a base oil and solid additives particles presenting specific properties, such as friction reduction and antiwear performances. The role of friction reducers is to ensure the lubricating performances in boundary lubrication regime. Commercial lubricants generally use graphite and petroleum-based oils because of their recognized lubricating properties, their stability and low cost. However, such lubricants induce health and environmental hazards due to their life cycle.The aim of this work is to investigate the possibility to use local biomass in order to produce environmentally-friendly lubricants. Local vegetable oils are interesting candidates because of their inherent qualities like renewability, bio-degradability, non-toxicity. This work shows that such natural oils present better friction performances than petroleum-based ones. Then considering friction reduction additives, the tribological behaviour of activated carbons synthetized from biomass is evaluated and special attention is paid to the role of the carbon structure, in terms of morphology, size, porosity of the carbon particles on the friction properties of the additives. The tested activated carbons are obtained from either terrestrial (sugar cane bagasse, banana tree, etc.) or alga (sargassum alga) precursors. Very good friction performances are observed by selecting the adequate precursor and tunning the activation experimental conditions. Finally, the determination of the tribological properties of activated carbons/natural oils mixtures results in the first formulation step of our lubricant made from local biomass

CONTRIBUTION TO THE FORMULATION OF GREEN LUBRICANTS USING LOCAL BIOMASS

International audienceFriction and wear are the first causes of the decrease of the performances and the durability in mechanical systems. The role of lubrication is to minimize friction between the sliding surfaces to protect them from wear. Conventional liquid lubricants are constituted of a base oil and solid additives particles presenting specific properties, such as friction reduction and antiwear performances. The role of friction reducers is to ensure the lubricating performances in boundary lubrication regime. Commercial lubricants generally use graphite and petroleum-based oils because of their recognized lubricating properties, their stability and low cost. However, such lubricants induce health and environmental hazards due to their life cycle. The aim of this work is to investigate the possibility to use local biomass in order to produce environmentally-friendly lubricants. Local vegetable oils are interesting candidates because of their inherent qualities like renewability, bio-degradability, non-toxicity. This work shows that such natural oils present better friction performances than petroleum-based ones. Then considering friction reduction additives, the tribological behaviour of activated carbons synthetized from biomass is evaluated and special attention is paid to the role of the carbon structure, in terms of morphology, size, porosity of the carbon particles on the friction properties of the additives. The tested activated carbons are obtained from either terrestrial (sugar cane bagasse, banana tree, etc.) or alga (sargassum alga) precursors. Very good friction performances are observed by selecting the adequate precursor and tunning the activation experimental conditions. Finally, the determination of the tribological properties of activated carbons/natural oils mixtures results in the first formulation step of our lubricant made from local biomass

Utilisation des carbones issus de la biomasse en lubrification

International audienceLes phénomènes de frottement et d’usure sont les causes principales des pertes de performances et de durabilité des systèmes mécaniques. Les techniques de fabrication de pièces métalliques telles que les engrenages, les roulements à billes, les segments, pistons et chemises, doivent répondre aux exigences économiques grandissantes du marché, comme l’amélioration de la durabilité des matériaux, l’augmentation des performances, la réduction du coût de la maintenance, ou encore la baisse de la consommation en énergie. Le recours à la tribologie, définie comme la science qui étudie les phénomènes de frottement, d’usure et de lubrification, est alors primordial et constitue un enjeu économique important. Les résultats d’une étude publiée par le Cetim en 1994 confirment que l’économie potentiellement réalisable serait de l’ordre de 26 milliards d’euros par an en France, soit 1% du PIB (chiffres de 2010), si toutes les connaissances acquises en tribologie étaient appliquées à l’industrie [1].C'est la lubrification qui a pour rôle de minimiser le frottement et de protéger les surfaces de l'usure. La stratégie mise en place pour lutter contre ces phénomènes consiste à introduire un lubrifiant entre les surfaces frottantes. Ce lubrifiant peut être solide, liquide ou gazeux, et il doit permettre d’empêcher le contact direct entre les surfaces. Plusieurs régimes de lubrification sont identifiés : hydrodynamique, élastohydrodynamique, mixte et limite. Ils dépendent des vitesses de déplacement relatif des surfaces, de la viscosité du lubrifiant et de la charge supportée par le contact, et sont caractérisés par des épaisseurs de films lubrifiants variées, divers coefficients de frottement et des usures associées différentes. Le régime de lubrification limite sera étudié car il conduit aux coefficients de frottement les plus élevés et aux plus fortes usures. Ce régime limite est rencontré pour une faible vitesse de glissement et une charge élevée.Les bases lubrifiantes pures (huile minérale ou de synthèse) ne pouvant assurer toutes les fonctions protectrices, des additifs sont ajoutés afin d’améliorer leurs propriétés réductrices de frottement et d’usure. Les nouvelles stratégies de lubrification utilisent des particules colloïdales en dispersion dans les lubrifiants. L’approche consiste à approvisionner le contact glissant en particules solides, susceptibles de constituer instantanément le film tribologique. Les matériaux lamellaires, tel le graphite, sont généralement de bons candidats, leur structure en feuillets assurant de bonnes propriétés tribologiques.Ce travail porte sur la revalorisation de la biomasse locale dans le domaine de la lubrification. L’utilisation de charbons actifs en tant qu’additifs solides dans un mélange huile végétale/huile de base est étudiée. L’influence des paramètres entrant dans la phase de synthèse des charbons actifs est également étudiée, tels que température et durée de pyrolyse, type de précurseurs, mode d’activation. Des mélanges huiles végétale/huile de base/additifs carbonés sont effectués dans diverses proportions afin d’optimiser les propriétés tribologiques en vue de la formulation d’un nouveau lubrifiant, plus respectueux de l’environnement qu’un lubrifiant minéral actuel

Tribological properties of vegetable oil added with graphite particles in dodecane

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