Synthesis of nanoparticle of carbon

International audienceFriction and wear are the first causes of the decrease of the performances and the durability of mechanical systems. The role of lubrication is to minimise friction between the sliding surfaces and to protect them from wear. Conventional liquid lubricants are constituted of base oil and additives presenting specific properties, such as friction reduction, anti-wear or anti-oxidising action. Commercial lubricants generally use graphite and petroleum-based oils because of their recognised 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. So, the first objective consists in finding an optimal mixture of mineral oil and vegetable oil validated by a compromise between environmental impact and cost of the lubricant. Our study mainly concerns the synthesis of new friction reducer additives. New carbon phases are obtained from glycolic solutions, stemming from by-products of our agriculture, using the spray-pyrolysis technique. This technique consists in nebulising in the form of micro-droplets a solution of saccharose, transported via a carrier neutral gas in a tubular oven heated at temperature ranging from 600°C to 1,000°C. Carbon nanoparticles are then obtained. Here are described the promising first results related to the determination of the optimal synthesis conditions, i.e. the catalyst concentration, the carrier gas pressure and the temperature of the tubular oven. Scanning electron microscopy and Raman spectrometry analyses are carried out, allowing us to observe the spherical shape and the porosity of the particles and to determine the graphitisation degree of the carbon phases

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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Development and characterisation of a nanostructured hybrid material with vitamin B12 and bagasse-derived activated carbon for anaerobic chlordecone (Kepone) removal

Intensive use of the chlorinated pesticide chlordecone from the 1970s to 1993 to prevent crop damage in banana plantations of Guadeloupe and Martinique led to diffuse pollution of soils and surface waters, affecting both fauna and human beings in the contaminated areas. Since 2001, drinking water production plants have been equipped with filters containing activated carbon that must be treated after saturation. The objective of this work is to produce a hybrid material composed of activated carbon and vitamin B12 (VB12) for the degradation of chlordecone (CLD). The preparation of such a hybrid material is carried out by non-covalent fixation to achieve an eco-friendly solution for the serious environmental problem of contamination by chlorinated pesticides. It is thus proposed to degrade CLD by a physico-chemical treatment allowing salvage of the catalyst, which is adsorbed on the carbon surface to generate less waste that is inexpedient to treat. Activated carbon (AC) is produced locally from available sugarcane bagasse subjected to phosphoric acid activation. The main characteristics of this material are a major mesoporous structure (0.91%) and a specific (BET) surface area ranging from 1000 to 1500 m2 g-1. The experimental results showed that BagP1.5 has a high adsorption capacity for VB12 due to its large surface area (1403 m2 g-1). The binding of VB12 to the bagasse-derived AC is favoured at high temperatures. The adsorption is optimal at a pH of approximately 6. The maximum adsorption capacity of VB12 on the AC, deduced from the Langmuir model, was 306 mg g-1, confirming the high affinity between the two components. The hybrid material was characterised by FTIR, Raman, X-ray fluorescence spectroscopy and SEM analysis. CLD removal by this hybrid material was faster than that by VB12 or BagP1.5 alone. The CLD degradation products were characterised by mass spectrometry

Lubricating performances of room temperature highly fluorinated f-graphite heat-treated under fluorine atmosphere

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Comparative modifications in bacterial gill-endosymbiotic populations of the two bivalves Codakia orbiculata and Lucina pensylvanica during bacterial loss and reacquisition

International audienceUntil now, the culture of sulphur-oxidizing bacterial symbionts associated with marine invertebrates remains impossible. Therefore, few studies focused on symbiont's physiology under stress conditions. In this study, we carried out a comparative experiment based on two different species of lucinid bivalves (Codakia orbiculata and Lucina pensylvanica) under comparable stress factors. The bivalves were starved for 6months in sulphide-free filtered seawater. For C.orbiculata only, starved individuals were then put back to the field, in natural sediment. We used in situ hybridization, flow cytometry and X-ray fluorescence to characterize the symbiont population hosted in the gills of both species. In L.pensylvanica, no decrease in symbiont abundance was observed throughout the starvation experiment, whereas elemental sulphur slowly decreased to zero after 3months of starvation. Conversely, in C.orbiculata, symbiont abundance within bacteriocytes decreased rapidly and sulphur from symbionts disappeared during the first weeks of the experiment. The modifications of the cellular characteristics (SSC - relative cell size and FL1 - genomic content) of the symbiotic populations along starvation were not comparable between species. Return to the sediment of starved C.orbiculata individuals led to a rapid (2-4weeks) recovery of symbiotic cellular characteristics, comparable with unstressed symbionts. These results suggest that endosymbiotic population regulation is host-species-dependent in lucinids