脂肪酸及表面修飾MoS2納米微粒LB膜在摩擦過程中結(jié)構(gòu)變化的XP…Title:Structuralchangesoffattyacidandsurface-modifiedMoS2nanoparticleLBfilmsduringfrictionprocess:anXPSstudy

Introduction:

Inordertoimprovetheperformanceanddurabilityoflubricants,variousadditiveshavebeendevelopedandstudied.Amongthem,MoS2nanoparticleshavebeenwidelyusedduetotheirexcellentlubricationproperties.However,thestabilityanddispersionofMoS2nanoparticlesinlubricatingoilarestillmajorissuestobeaddressed.Toaddressthisissue,surfacemodificationofMoS2nanoparticleswithfattyacidhasbeenproposedtoenhancetheirstabilityanddispersioninlubricatingoil.Inthisstudy,weinvestigatedthestructuralchangesoffattyacidandsurface-modifiedMoS2nanoparticleLBfilmsduringfrictionprocessusingX-rayphotoelectronspectroscopy(XPS).

Experimental:

FattyacidLBfilmswerepreparedonsiliconsubstrateusingLangmuir-Blodgetttechnique.MoS2nanoparticlesweresurface-modifiedwitholeicacidandweredepositedonthefattyacidLBfilmusingthesametechnique.Thesamplesweresubjectedtofrictiontestusingapin-on-disctribometerunderdryslidingcondition.

Resultsanddiscussion:

XPSspectraoffattyacidLBfilmsafterfrictiontestshowedasignificantdecreaseintheintensityofC-OandC=Opeaks,indicatingtheoxidationanddegradationoffattyacidmoleculesduringfrictionprocess.Ontheotherhand,XPSspectraofsurface-modifiedMoS2nanoparticleLBfilmsshowednosignificantchangeintheintensityofMoandSpeaks,indicatingthestabilityandpresenceofMoS2nanoparticlesonthesubstrateevenafterthefrictiontest.However,theXPSspectraofMoS2LBfilmshowedashiftinthepeakpositionofMoandSpeakstowardslowerbindingenergies,whichcouldbeattributedtotheformationandadsorptionofMoSxspeciesonthesubstrateduringfrictionprocess.

Conclusion:

Theresultsofthisstudyshowedthatfattyacidmoleculesunderwentoxidationanddegradationduringfrictionprocess,whereassurface-modifiedMoS2nanoparticlesremainedstableandpresentonthesubstrate.However,theadsorptionandformationofMoSxspeciesonthesubstrateindicatedthepossiblewearandtearofMoS2nanoparticlesduringfrictionprocess.ThesefindingscouldcontributetothedevelopmentofmoredurableandstablelubricantsusingMoS2nanoparticlesandfattyacids.FurtheranalysisoftheXPSdatarevealedthattheoxidationoffattyacidmoleculesledtotheformationofcarboxylicacidandhydroxylgroupsonthesurfaceoftheLBfilm.Thesefunctionalgroupsareknowntohaveapolarnatureandcouldenhancetheinteractionbetweenthesubstrateandthelubricant,potentiallyimprovingtheoveralllubricationperformance.

Incontrast,thesurface-modifiedMoS2nanoparticlesshowedaslightdecreaseintheintensityoftheC-OandC=Opeaks,indicatingthepossibleinteractionbetweenMoS2andfattyacidmoleculesduringthedepositionprocess.ThesurfacemodificationapproachusedinthisstudycouldfacilitatethedispersionofMoS2nanoparticlesinlubricatingoilandimprovetheirstability,whichiscrucialforlong-termlubricationperformance.

TheshiftinthepeakpositionofMoandSpeakstowardslowerbindingenergiesintheMoS2LBfilmcouldbeattributedtotheformationofMoSxspeciesduringthefrictionprocess.Thesespeciesareknowntohavealoweroxidationstateandcouldactasthelubricantlayerduringfriction,leadingtobetterlubricationperformance.

Overall,thisstudyhighlightstheimportanceofsurfacemodificationofMoS2nanoparticlesfortheirstabilityanddispersioninlubricatingoil.TheresultsalsodemonstratethepotentialofusingfattyacidsasadditivesforimprovingthelubricationperformanceofMoS2nanoparticles.Furtherstudiesareneededtofullyunderstandthemolecular-levelinteractionsbetweenthelubricantadditivesandthesubstrateduringfrictionprocess.Inadditiontofattyacids,otheradditiveshavealsobeenstudiedaspotentiallubricantadditivesforMoS2nanoparticles.Forexample,varioussurfactantsandpolymershavebeenshowntoimprovethestabilityanddispersionofMoS2nanoparticlesinlubricatingoil,aswellasenhancetheirlubricationperformance.

Theuseofsurfacemodificationtechniques,suchaschemicalfunctionalizationandphysicalcoating,hasalsobeenexploredtofurtherimprovethestabilityanddispersionofMoS2nanoparticlesinlubricatingoil.Forexample,thecoatingofMoS2nanoparticleswithsilicaorgrapheneoxidehasbeenshowntoimprovetheirdispersibilityandstabilityinoilandtoenhancetheirtribologicalperformance.

Inadditiontotheconventionallubricationapplications,MoS2nanoparticlesarealsobeingexploredfortheirpotentialinotherareas,suchasinenergystorageandconversion,wheretheycouldbeusedaselectrodematerialsinbatteriesorascatalystsinfuelcells.ThesurfacemodificationtechniquesandlubricantadditivesdevelopedforMoS2nanoparticlesinlubricationapplicationscouldalsobeappliedintheseareastoimprovetheirperformanceandstability.

Overall,thestudyofMoS2nanoparticlesaslubricantadditivesisarapidlydevelopingarea,withsignificantpotentialforimprovingtheperformanceoflubricatingoils.Furtherresearchinthisareaisneededtofullyunderstandtheunderlyingmechanismsandtodevelopoptimizedlubricantformulationsforspecificapplications.ResearchinthefieldofMoS2nanoparticlesaslubricantadditivesisongoing,withnewfindingsanddevelopmentsemergingregularly.OnepromisingareaofresearchisintheoptimizationofthesizeandshapeofMoS2nanoparticlesforenhancedperformance.Forexample,ithasbeenfoundthatMoS2nanoparticleswithsmallerparticlesizestendtohavebetterfrictionandwearreductionproperties,whilenanoparticleswithahexagonalshapeexhibitbetterdispersibilityinlubricatingoils.

AnotherareaoffocusisinthedevelopmentofnewmethodsforthesynthesisofMoS2nanoparticles,suchasmicrowave-assistedsynthesisandhydrothermalmethods,whichofferadvantagesintermsoftime,cost,andscalability.Additionally,theuseofMoS2hybridnanoparticles,whichcontainothermaterialssuchaspolymers,metals,ormetaloxides,isanotherareaofexploration,withpromisingresultsseenintermsofimprovedlubricationperformanceandstability.

DespitethepotentialbenefitsofMoS2nanoparticlesinlubricationapplications,therearealsopotentialconcernsregardingtheirenvironmentalimpactandtoxicity.Assuch,researchersarealsoinvestigatingthepotentialforusingalternativematerials,suchasboronnitrideandtungstendisulfide,whichoffersimilarlubricationpropertiesbutwithpotentiallylowerenvironmentalimpact.

Inconclusion,thestudyofMoS2nanoparticlesaslubricantadditivesisapromisingareaofresearch,withplentyofopportunitiesforinnovationandoptimization.Continuedresearchinthisareacouldleadtothedevelopmentofnewlubricantformulationswithenhancedperformanceandreducedenvironmentalimpact,benefitingawiderangeofindustriesandapplications.AnotherareaofresearchinthefieldofMoS2nanoparticlesaslubricantadditivesistheirinteractionwithothercomponentsfoundinlubricatingoils,suchasdetergents,dispersants,andanti-wearadditives.UnderstandingtheseinteractionscanleadtoamorecomprehensiveunderstandingoftheoveralllubricationsystemandhelpidentifyoptimalconditionsfortheapplicationofMoS2nanoparticles.

Furthermore,researchersareexploringthepotentialbenefitsofusingMoS2nanoparticlesincombinationwithothernovellubricanttechnologies,suchasionicliquidsandgraphene-basedlubricants.Thesecombinationscouldofferuniquesynergiesandfurtherimprovethelubricationperformanceofthesystem.

AnotherareaoffocusisonachievingstabledispersionofMoS2nanoparticleswithinthelubricantoil.Astabledispersioniscrucialforensuringtheefficienttransferoflubricanttothe