A new method for the preparation of dinuclear molybdenum dithiocarbamates(MoDDCs) is reported.This new method allows for the control of the amount of sulfurization of the Mo2SxO4-x core(x = 1 to 4) in the dinuclear Mo...A new method for the preparation of dinuclear molybdenum dithiocarbamates(MoDDCs) is reported.This new method allows for the control of the amount of sulfurization of the Mo2SxO4-x core(x = 1 to 4) in the dinuclear MoDDCs.This control assists in the tailoring of specific tribological properties of the MoDDCs in both greases and lubricating oils.展开更多
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
文摘A new method for the preparation of dinuclear molybdenum dithiocarbamates(MoDDCs) is reported.This new method allows for the control of the amount of sulfurization of the Mo2SxO4-x core(x = 1 to 4) in the dinuclear MoDDCs.This control assists in the tailoring of specific tribological properties of the MoDDCs in both greases and lubricating oils.
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.
