Ethanol has emerged as a promising alternative to fossil fuels,but its use can lead to significant dilution in lubricants,particularly during cold start or heavy traffic.This dilution can affect the performance of add...Ethanol has emerged as a promising alternative to fossil fuels,but its use can lead to significant dilution in lubricants,particularly during cold start or heavy traffic.This dilution can affect the performance of additives,including friction modifiers like molybdenum dithiocarbamate(MoDTC),which are designed to reduce friction under extreme contact conditions.Prior research suggests that ethanol may impact the performance of MoDTC,prompting this study’s goal to investigate the effects of ethanol on MoDTC tribofilms and their friction response under boundary lubrication conditions.Therefore,reciprocating tribological tests were performed with fully formulated lubricants containing MoDTC with varying ethanol concentrations.The results indicate that a critical ethanol dilution level inhibits friction reduction by MoDTC activation,resulting in friction coefficients(COFs)similar to the base oil.Surfaces tested with simple mixtures of polyalphaolefin(PAO)+MoDTC showed increased COFs with added ethanol.Analysis of tested surfaces using Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),and X-ray absorption spectroscopy near the edge structure(XANES)revealed the presence of sulfates,MoO_(3),MoS_(2),and MoS_(x)O_(y)compounds in the tribofilms formed on the surfaces,with and without ethanol diluted in the lubricant.However,the addition of ethanol increased the sulfates and MoO_(3)content of the tribofilms at the expense of friction-reducing compounds such as MoS_(2)and MoS_(x)O_(y).These findings suggest that ethanol dilution in lubricants containing MoDTC creates an oxygen-rich interfacial medium that favors the formation of compounds with insufficient friction-reducing capabilities.展开更多
Molybdenum dialkyldithiocarbamate(MoDTC)is widely used as a friction modifier in engine lubricating oil.Under MoDTC lubrication,the friction and wear behaviors of tungsten-doped diamond-like carbon(W-DLC)films anneale...Molybdenum dialkyldithiocarbamate(MoDTC)is widely used as a friction modifier in engine lubricating oil.Under MoDTC lubrication,the friction and wear behaviors of tungsten-doped diamond-like carbon(W-DLC)films annealed at 100-400℃were discussed and evaluated using scanning electron microscopy(SEM),atomic force microscopy(AFM),and Raman spectroscopy.Under(polymerized alpha olefin)PAO+MoDTC lubrication,the coefficient of friction of all samples decreased,but the wear rates of the W-DLC films annealed at 300℃increased significantly.By interacting with zinc dialkyldithiophosphate(ZDDP),the wear rates of W-DLC films annealed at different temperatures declined significantly owing to the formation of dense phosphate tribofilms on the worn surfaces.展开更多
基金funded by Fundação de AmparoàPesquisa do Estado de São Paulo(FAPESP)through the R&D ConsortiumTribological challenges in flex-fuel engines,ref.2009/54891-8,and Centro Nacional de Pesquisa em Energia e Materiais(CNPEM-LNLS-National Synchrotron Light Laboratory,grant number 20170101)the partial financial support from the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico(CNPq)grant number 305374/2021-4+1 种基金the partial financial support from Fundação de AmparoàPesquisa do Estado do Rio Grande do Sul(FAPERGS),Process number:172551-000901-0the National Research Institute on Green Tribology for the Energy Transition(CT-Trib)with financial support by CNPq/Brazil via the grant number 406654/2022-0.
文摘Ethanol has emerged as a promising alternative to fossil fuels,but its use can lead to significant dilution in lubricants,particularly during cold start or heavy traffic.This dilution can affect the performance of additives,including friction modifiers like molybdenum dithiocarbamate(MoDTC),which are designed to reduce friction under extreme contact conditions.Prior research suggests that ethanol may impact the performance of MoDTC,prompting this study’s goal to investigate the effects of ethanol on MoDTC tribofilms and their friction response under boundary lubrication conditions.Therefore,reciprocating tribological tests were performed with fully formulated lubricants containing MoDTC with varying ethanol concentrations.The results indicate that a critical ethanol dilution level inhibits friction reduction by MoDTC activation,resulting in friction coefficients(COFs)similar to the base oil.Surfaces tested with simple mixtures of polyalphaolefin(PAO)+MoDTC showed increased COFs with added ethanol.Analysis of tested surfaces using Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),and X-ray absorption spectroscopy near the edge structure(XANES)revealed the presence of sulfates,MoO_(3),MoS_(2),and MoS_(x)O_(y)compounds in the tribofilms formed on the surfaces,with and without ethanol diluted in the lubricant.However,the addition of ethanol increased the sulfates and MoO_(3)content of the tribofilms at the expense of friction-reducing compounds such as MoS_(2)and MoS_(x)O_(y).These findings suggest that ethanol dilution in lubricants containing MoDTC creates an oxygen-rich interfacial medium that favors the formation of compounds with insufficient friction-reducing capabilities.
基金This research was financially supported by the National Natural Science Foundation of China(Nos.51875537 and 41872183)the Pre-Research Program in National 14th Five-Year Plan(No.61409230614)the Fundamental Research Funds for the Central University(No.2652018094).
文摘Molybdenum dialkyldithiocarbamate(MoDTC)is widely used as a friction modifier in engine lubricating oil.Under MoDTC lubrication,the friction and wear behaviors of tungsten-doped diamond-like carbon(W-DLC)films annealed at 100-400℃were discussed and evaluated using scanning electron microscopy(SEM),atomic force microscopy(AFM),and Raman spectroscopy.Under(polymerized alpha olefin)PAO+MoDTC lubrication,the coefficient of friction of all samples decreased,but the wear rates of the W-DLC films annealed at 300℃increased significantly.By interacting with zinc dialkyldithiophosphate(ZDDP),the wear rates of W-DLC films annealed at different temperatures declined significantly owing to the formation of dense phosphate tribofilms on the worn surfaces.
