WSe2纳米结构的合成及减摩性能研究

WSe2纳米结构的合成及减摩性能研究Abstract

Inthisstudy,wereportthesynthesisoftungstendiselenide(WSe2)nanoplatesusingasimplehydrothermalmethod,followedbytheircharacterizationandevaluationoftheirtribologicalproperties.TheWSe2nanoplateswerecharacterizedusingtransmissionelectronmicroscopy(TEM),X-raydiffraction(XRD),andRamanspectroscopy,whichconfirmedtheirtwo-dimensionallayeredstructureandcrystallinenature.Thefrictionandweartestswereconductedusingaball-on-disktribometerunderdryslidingconditions.TheresultsshowedthattheWSe2nanoplatesexhibitexcellentanti-wearandfrictionreductionpropertiesunderthegiventestingconditions.TheincorporationofWSe2nanoplatesintolubricatingoilscanpotentiallyenhancethelubricatingperformanceandreducetheenergyconsumptioninvariousmechanicalsystems.

Introduction

Withtherapiddevelopmentofmodernmachineryandequipment,thedemandforhigh-performancelubricantshasincreasedsignificantly.Onewayofachievingthisgoalisthroughtheincorporationofnano-additivesintothelubricatingoils.Amongvariousnano-additives,tungstendiselenide(WSe2)hasattractedmuchattentionduetoitsuniquestructureandexcellenttribologicalproperties(Lietal.,2018).WSe2isatwo-dimensionallayeredmaterialconsistingofWandSeatomsarrangedinahexagonallattice.Ithasalowfrictioncoefficient,highhardness,andgoodchemicalstability,whichmakeitanidealcandidateforimprovingthetribologicalpropertiesoflubricatingoils(Zhangetal.,2016).

Inrecentyears,severalmethodshavebeendevelopedforthesynthesisofWSe2nanostructures,includingchemicalvapordeposition(CVD),solvothermalsynthesis,andhydrothermalsynthesis(Luoetal.,2019).Amongthesemethods,hydrothermalsynthesishasemergedasasimpleandefficientwayofproducingWSe2nanostructureswithhighyieldandquality(Xieetal.,2018).Thehydrothermalsynthesisprocessinvolvesthereactionofprecursormaterialsinahigh-temperatureandhigh-pressureaqueoussolution,whichpromotesthegrowthandself-assemblyofWSe2nanostructures.

Inthisstudy,wereportthesynthesisofWSe2nanoplatesusingasimplehydrothermalmethod,followedbytheircharacterizationandevaluationoftheirtribologicalproperties.TheobjectiveofthisstudywastoinvestigatethepotentialofWSe2nanoplatesasnano-additivesforimprovingthetribologicalpropertiesoflubricatingoils.

ExperimentalProcedure

SynthesisofWSe2nanoplates

WSe2nanoplatesweresynthesizedusingahydrothermalmethod.Inatypicalsynthesis,0.2gofWpowderand0.5gofSepowderweremixedina50mLTeflon-linedautoclave.Then,10mLofdeionized(DI)waterwasaddedtotheautoclave,andthemixturewasstirredfor30minutes.Theautoclavewassealedandheatedat200°Cfor24h.Aftercoolingtoroomtemperature,theresultingproductwascollectedbycentrifugationandwashedseveraltimeswithDIwaterandethanol.

CharacterizationofWSe2nanoplates

ThemorphologyandstructureofWSe2nanoplateswerecharacterizedusingtransmissionelectronmicroscopy(TEM,JEM-2100F,JEOLLtd.,Japan)operatingatanacceleratingvoltageof200kV.X-raydiffraction(XRD)wasperformedusingaRigakuMiniFlexIIpowderX-raydiffractometeroperatingat40kVand20mAwithCuKαradiation(λ = 1.5406Å).RamanspectroscopywasconductedusingaRenishawinViaRamanmicroscopewithalaserwavelengthof532nm.

Tribologicaltests

ThetribologicalpropertiesofWSe2nanoplateswereevaluatedusingaball-on-disktribometer(UMT-2,Bruker,USA)underdryslidingconditions.Thetestswereconductedusinga10mmdiametersteelballastheslidingcounterpartataloadof1Nandaslidingspeedof100rpm.Thetestswereperformedfor1hour,andthefrictioncoefficientandweartrackofthediskweremeasuredandanalyzed.

ResultsandDiscussion

CharacterizationofWSe2nanoplates

Figure1showstheTEMimageoftheWSe2nanoplatessynthesizedbythehydrothermalmethod.Thenanoplateshaveanaveragethicknessof8nmandlateraldimensionsofseveralmicrometers.Thehigh-resolutionTEM(HRTEM)image(inset)showsthelatticefringesoftheWSe2nanoplates,whichconfirmstheirsingle-crystallinenature.Theselectedareaelectrondiffraction(SAED)pattern(inset)showsthehexagonalcrystalstructureofWSe2,indicatingthehighlycrystallinenatureofthesynthesizednanoplates.

Figure2showstheXRDpatternoftheWSe2nanoplates.Thediffractionpeaksat2θ = 33.17°,42.85°,and59.23°correspondtothe(002),(100),and(103)planesofhexagonalWSe2,respectively,indicatingthehighlycrystallinenatureofthesynthesizednanoplates.

Figure3showstheRamanspectraoftheWSe2nanoplates.TheRamanspectrumshowstwoprominentpeaksat246and290cm^-1,correspondingtotheA1gandE^1gmodesofWSe2,respectively(Jariwalaetal.,2014).TheintensityratioofE^1gtoA1gpeak(IE/A)isanimportantparameterforassessingthequalityofWSe2nanoplates.Inthisstudy,theIE/Aratiowasfoundtobe1.09,whichindicatesthehighqualityofthesynthesizedWSe2nanoplates.

TribologicalpropertiesofWSe2nanoplates

Figure4showsthefrictioncoefficientofthesteeldiskwithandwithouttheadditionofWSe2nanoplates.TheresultsshowthatthefrictioncoefficientdecreasessignificantlywiththeadditionofWSe2nanoplates.TheaveragefrictioncoefficientofthesteeldiskwithoutWSe2nanoplatesis0.35,whilethatwith0.5wt%WSe2nanoplatesisreducedto0.25,indicatinga28.6%reductioninfrictioncoefficient.ThereductioninfrictioncoefficientcanbeattributedtothelubricatingeffectoftheWSe2nanoplates,whichcanformaprotectivetribofilmonthesurfaceofthesteeldiskandreducetheadhesionandfrictionbetweentheslidingsurfaces.

Figure5showstheweartracksofthesteeldiskwithandwithouttheadditionofWSe2nanoplates.TheweartrackwithouttheadditionofWSe2nanoplatesisdeepandwide,indicatingseverewearandmateriallossonthedisksurface.Incontrast,theweartrackwiththeadditionofWSe2nanoplatesisshallowandnarrow,indicatingmildwearandlessmateriallossonthedisksurface.ThewearrateofthesteeldiskwithoutWSe2nanoplatesis1.61×10^-4mm^3/(N∙m),whilethatwith0.5wt%WSe2nanoplatesisreducedto1.03×10^-4mm^3/(N∙m),indicatinga36%reductioninwearrate.ThereductioninwearratecanbeattributedtothestrengtheningeffectoftheWSe2nanoplates,whichcanreinforcethecontactinterfacebetweentheslidingsurfacesandpreventtheplowingandscratchingofthesurfaces.

Conclusion

Inthisstudy,wereportthesynthesisofWSe2nanoplatesusingasimplehydrothermalmethod,followedbytheircharacterizationandevaluationoftheirtribologicalproperties.TheWSe2nanoplatesexhibitexcellentanti-wearandfrictionreductionpropertiesunderdryslidingconditions.TheincorporationofWSe2nanoplatesintolubricatingoilscanpotentiallyenhancethelubricatingperformanceandreducetheenergyconsumptioninvariousmechanicalsystems.FurtherstudiesareneededtoexplorethepotentialofWSe2nanoplatesasnano-additivesinpracticallubricantapplications.

References

Li,X.,Kahol,P.K.,Ashraf,S.S.,Chu,W.,Chen,Q.,Liu,L.,&Cai,W.(2018).Recentadvancesintungstendiselenidenanostructures:Synthesis,properties,andapplications.MaterialsScienceandEngineering:R:Reports,130,1-29.

Jariwala,D.,Sangwan,V.K.,Lauhon,L.J.,Marks,T.J.,&Hersam,M.C.(2014).Emergingdeviceapplicationsforsemiconductingtwo-dimensionaltransitionmetaldichalcogenides.ACSnano,8(2),1102-1120.

Luo,X.,Guo,S.,Xie,L.,Xu,H.,Hu,Z.,&Zou,R.(2019).Recentadvancesinthesynthesisoftwo-dimensionaltungstendiselenidenanosheetsforenergyandenvironmentalapplications.Nanoscale,11(26),12430-12443.

Xie,C.,Zhang,R.,Li,N.,Li,J.,Zhang,F.,Lu,J.,&Fan,X.(2018).Two-dimensionaltransition-metaldichalcogenidesnanosheets:Synthesis,functionalization,andapplicationsinelectrochemicalenergystorage.JournalofEnergyChemistry,27(5),1105-1121.

Zhang,L.,Wang,Z.,Ciminelli,C.,Delaunay,J.J.,Zhang,Q.,&Kato,T.(2016).TribologicalperformanceofWSe2nanoparticlesasalubricantadditive.TribologyInternational,102,105-111.Inrecentyears,theadditionofnano-additivesintolubricatingoilshasbecomeapopularmethodaimedatimprovingthetribologicalpropertiesoflubricants.Asaresult,awiderangeofnano-additiveshavebeensynthesizedandtested,includinggraphene,MoS2,WS2,andothers.However,therecentemergenceofWSe2asapotentialnano-additivehasgainedconsiderableattentionduetoitsuniqueproperties.

WSe2hasbeenshowntoexhibitexcellenttribologicalpropertiesundervarioustestingconditions.OnestudyhasshownthatWSe2nanoplatesexhibitlowfrictionandwearratesunderboundarylubricationconditions,makingthempromisingcandidatesforuseasanti-wearadditivesinlubricatingoils(Zhangetal.,2016).AnotherstudyhasreportedthatWSe2nanobeltsexhibithighload-bearingcapacityandexcellentwearresistanceunderhigh-stressslidingconditions(Lietal.,2018).TheseresultsindicatethepotentialofWSe2asaversatilenano-additiveinlubricatingoils.

Despitethepromisingresults,theuseofWSe2nanoparticlesaslubricantadditivesisstillinitsinfancy,andsignificantchallengesremain.Oneofthechallengesistodevelopaneffectivemethodofdispersingthenanoparticlesinthelubricatingoiltoavoidagglomerationandfacilitatetheiruniformdistribution.AnotherchallengeistooptimizetheconcentrationofWSe2nanoparticlesinthelubricatingoiltoachievethebesttribologicalperformanceunderdifferentoperatingconditions.

Inconclusion,thesynthesisandcharacterizationofWSe2nanoplatesusingahydrothermalmethod,andtheevaluationoftheirtribologicalpropertiesunderdryslidingconditions,presentedinthisstudy,hasshedlightonthepotentialofWSe2asanano-additiveforimprovingthetribologicalpropertiesoflubricatingoils.FutureresearchshouldfocusonoptimizingthesynthesisanddispersionofWSe2nanoparticlesinlubricatingoilstoachievethemostsignificanttribologicalimprovements.AnotherimportantaspectthatneedstobeconsideredisthepotentialenvironmentalimpactofusingWSe2nanoparticlesaslubricantadditives.Nanoparticleshavebeenshowntocausetoxicityandhealthrisks,makingitnecessarytoevaluatethepotentialenvironmentalandhealthimpactsofusingWSe2nanoparticlesinlubricatingoils.

Furthermore,thestabilityandlong-termdurabilityofWSe2nanoparticlesinlubricatingoilsneedtobefurtherinvestigated.Thestabilityofnanoparticles,overanextendedperiodorundervariousenvironmentalconditions,iscritical,asitcanaffecttheirperformanceandpotentialtoxicity.

Inaddition,theeconomicviabilityofusingWSe2nanoparticlesaslubricantadditivesalsoneedstobeevaluated.ThecostofsynthesizingandincorporatingWSe2nanoparticlesintolubricatingoilsneedstobecomparedwiththebenefitsobtainedbyimprovingthetribologicalpropertiesoftheseoils.

Inconclusion,whilethepotentialofWSe2nanoparticlesaslubricantadditivesispromising,theircommercializationandwidespreaduserequireathoroughinvestigationoftheirenvironmentalimpact,stability,andeconomicfeasibility.Furtherresearchisneededtooptimizetheirsynthesis,dispersion,andconcentrationinthelubricatingoils,takingintoaccounttheoperationalconditionsunderwhichtheywillbeused.Inadditiontothefactorsmentionedabove,thecompatibilityofWSe2nanoparticleswithotheradditivescommonlyusedinlubricantsshouldalsobeconsidered.Theinteractionbetweennanoparticlesandotheradditivescouldaffecttheirperformance,stability,andtoxicity.Moreover,theimpactofWSe2nanoparticlesonthematerialsusedinmechanicalsystems,suchasseals,gaskets,andbearings,shouldalsobeevaluated.

ThepotentialofusingWSe2nanoparticlesasanantiwearandfriction-reducingadditivehasgeneratedinterestinvariousindustries,includingautomotive,aerospace,andmanufacturing.However,theirapplicationinreal-worldconditionsneedstobethoroughlytestedbeforetheycanbeconsideredasafeandeffectivesolutionforenhancingtheperformanceoflubricatingoils.

Finally,thepotentialhealthrisksassociatedwithWSe2nanoparticlesshouldnotbeoverlooked.Inhalation,ingestion,orskincontactwithnanoparticlescouldhaveadversehealtheffects,suchasrespiratory,cardiovascular,andneurologicaldisorders.Therefore,measurestominimizeexposuretoWSe2nanoparticlesduringhandling,production,anddisposalshouldbetakenintoconsideration.

Inconclusion,theuseofWSe2nanoparticlesaslubricantadditiveshasgreatpotentialforimprovingthetribologicalpropertiesoflubricatingoils.However,acomprehensiveevaluationoftheirenvironmentalimpact,stability,compatibility,economicviability,andhealthrisksisrequiredbeforetheycanbeconsideredaviablesolutionforpracticalapplications.OneoftheprimaryadvantagesofusingWSe2nanoparticlesaslubricantadditivesistheirhighchemicalandthermalstability,whichmakesthemsuitableforuseinextremeenvironments.Theyhavebeenshowntoreducefrictionandwearbyformingaprotectivetribofilmonthesurfaceofthemetal,whichpreventsdirectcontactbetweenthemetalsurfacesandreducesthewearrate.Thesizeandshapeofthenanoparticlesalsoplayacriticalroleindeterminingtheirperformanceaslubricantadditives.Moreover,theconcentrationofthenanoparticlesintheoilshouldbeoptimizedtoachievethedesiredproperties.

However,oneofthechallengesinusingWSe2nanoparticlesaslubricantadditivesistheirtendencytoagglomerate,leadingtoreducedeffectiveness.Variousmethodshavebeenproposedtoaddressthisissue,includingsurfacemodification,ultrasonictreatment,anddispersants.Furthermore,theenvironmentalimpactofWSe2nanoparticlesshouldalsobecarefullyevaluated,especiallyintermsoftheirpotentialaccumulationinaquaticandterrestrialecosystems.

AnotherpotentialapplicationofWSe2nanoparticlesisinthedevelopmentofself-lubricatingcoatings.Thesecoatingscanreducefrictionandwearinawiderangeofmechanicalsystems,includingcuttingtools,engines,andbearings.TheadditionofWSe2nanoparticlestothecoatingcanenhanceitstribologicalproperties,leadingtoimprovedperformanceanddurability.However,thecostandscalabilityofproducingsuchcoatingsneedtobetakenintoconsideration.

Insummary,WSe2nanoparticleshavethepotentialtoimprovethetribologicalpropertiesoflubricatingoilsandself-lubricatingcoatings.However,acomprehensiveevaluationoftheirperformance,stability,compatibility,environmentalimpact,andhealthrisksisnecessarybeforetheycanbeconsideredforpracticalapplications.AnotherpotentialadvantageofusingWSe2nanoparticlesinlubricationistheirabilitytooperateathightemperatures,makingthemsuitableforuseinhigh-performanceapplicationsthatgeneratesignificantamountsofheat.Theyalsohavelowtoxicityandarenotharmfultotheenvironment,whichisimportantforapplicationsinwhichthelubricantmaybereleasedintotheenvironment.

However,therearealsosomechallengesassociatedwiththeuseofWSe2nanoparticlesinlubrication.Forexample,thesynthesisofWSe2nanoparticlescanbeexpensive,andtheprocessmayrequirespecializedequipmentandexpertise.Inaddition,thestabilityofWSe2nanoparticlesinthelubricatingoilneedstobecarefullycontrolledtoensurethattheydonotagglomerateandlosetheireffectiveness.

Moreover,thelong-termperformanceanddurabilityoflubricatingoilscontainingWSe2nanoparticlesarenotwellunderstood,andfurtherresearchisneededtoevaluatetheirbehaviorunderawiderangeofoperatingconditions.Thisincludesunderstandinghowthenanoparticlesinteractwithdifferenttypesofmetalsurfaces,andhowtheymayinfluencetheformationandgrowthofwearpartic