This paper investigates the effect of unsaturated fatty acid additives on the lubricating properties of a biodiesel,composed of a blend of fatty acid methyl esters(FAMEs)and a conventional diesel fuel.The presence of ...This paper investigates the effect of unsaturated fatty acid additives on the lubricating properties of a biodiesel,composed of a blend of fatty acid methyl esters(FAMEs)and a conventional diesel fuel.The presence of fatty acids as additives for biodiesel improves their lubricating properties at elevated temperature conditions.The formation of a protective lubricating tribochemical film on the steel contact surfaces has been evidenced.Elevated temperature conditions and possibly oxygen are needed to form this film that reduces friction and limits wear.Several analytical tools have revealed the insulating nature of the formed tribofilm and its chemical properties.Friction-induced reticulation is thought to play a major role in the growth of this insulating film.展开更多
To meet the surging needs in energy efficiency and eco-friendly lubricants,a novel superlubricious technology using a vegetable oil and ceramic materials is proposed.By coupling different hydrogen-free amorphous carbo...To meet the surging needs in energy efficiency and eco-friendly lubricants,a novel superlubricious technology using a vegetable oil and ceramic materials is proposed.By coupling different hydrogen-free amorphous carbon coatings with varying fraction of sp^(2) and sp^(3) hybridized carbon in presence of a commercially available silicon nitride bulk ceramic,castor oil provides superlubricity although the liquid vegetable oil film in the contact is only a few nanometres thick at most.Besides a partial liquid film possibly separating surfaces in contact,local tribochemical reactions between asperities are essential to maintain superlubricity at low speeds.High local pressure activates chemical degradation of castor oil generating graphitic/graphenic-like species on top of asperities,thus helping both the chemical polishing of surface and its chemical passivation by H and OH species.Particularly,the formation of the formation of–(CH_(2)–CH_(2))n–noligomers have been evidenced to have a major role in the friction reduction.Computer simulation unveils that formation of chemical degradation products of castor oil on friction surfaces are favoured by the quantity of sp^(2)-hybridized carbon atoms in the amorphous carbon structure.Hence,tuning sp^(2)-carbon content in hydrogen-free amorphous carbon,in particular,on the top layers of the coating,provides an alternative way to control superlubricity achieved with castor oil and other selected green lubricants.展开更多
文摘This paper investigates the effect of unsaturated fatty acid additives on the lubricating properties of a biodiesel,composed of a blend of fatty acid methyl esters(FAMEs)and a conventional diesel fuel.The presence of fatty acids as additives for biodiesel improves their lubricating properties at elevated temperature conditions.The formation of a protective lubricating tribochemical film on the steel contact surfaces has been evidenced.Elevated temperature conditions and possibly oxygen are needed to form this film that reduces friction and limits wear.Several analytical tools have revealed the insulating nature of the formed tribofilm and its chemical properties.Friction-induced reticulation is thought to play a major role in the growth of this insulating film.
基金This research is supported by TOTAL,Solaize Research Center and Federal Ministry of Economic Affairs and Energy Germany(BMWi)within project CHEOPS3(Funding number 03ET1286B).
文摘To meet the surging needs in energy efficiency and eco-friendly lubricants,a novel superlubricious technology using a vegetable oil and ceramic materials is proposed.By coupling different hydrogen-free amorphous carbon coatings with varying fraction of sp^(2) and sp^(3) hybridized carbon in presence of a commercially available silicon nitride bulk ceramic,castor oil provides superlubricity although the liquid vegetable oil film in the contact is only a few nanometres thick at most.Besides a partial liquid film possibly separating surfaces in contact,local tribochemical reactions between asperities are essential to maintain superlubricity at low speeds.High local pressure activates chemical degradation of castor oil generating graphitic/graphenic-like species on top of asperities,thus helping both the chemical polishing of surface and its chemical passivation by H and OH species.Particularly,the formation of the formation of–(CH_(2)–CH_(2))n–noligomers have been evidenced to have a major role in the friction reduction.Computer simulation unveils that formation of chemical degradation products of castor oil on friction surfaces are favoured by the quantity of sp^(2)-hybridized carbon atoms in the amorphous carbon structure.Hence,tuning sp^(2)-carbon content in hydrogen-free amorphous carbon,in particular,on the top layers of the coating,provides an alternative way to control superlubricity achieved with castor oil and other selected green lubricants.
