Superlubricity Behavior with Phosphoric Acid–Water Network Induced by Rubbing

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1、ARTICLEpubs.acs.org/LangmuirSuperlubricityBehaviorwithPhosphoricAcid
WaterNetworkInducedbyRubbingJinjinLi,ChenhuiZhang,andJianbinLuo*StateKeyLaboratoryofTribology,TsinghuaUniversity,Beijing100084,ChinaABSTRACT:Inpresentwork,asuperlubricityphenomenonofphos-phoricacid(H3PO4)wasfoundunderambie

2、ntconditions.Anultralowfrictioncoefficientofabout0.004betweenglass/Si3N4andsapphire/sapphiretribopairswasobtainedunderthelubricationofaphosphoricacidaqueoussolution(pH1.5)athighcontactpressure(themaximumpressurecanreachabout1.65GPa)afterarunning-inperiodofabout600s.Theexperimentalresultsindic

3、atethatthesuperlowfrictionstatewasverystableformorethan3h.Insuchastate,solidlikefilmsformedonthetwoslidingsurfaces,whicharehydratesofphosphoricacidwithahydrogen-bondednetworkaccordingtotheRamanspectrum.Thesuperlubricitymechanismismainlyattributedtothehydrogenbondeffectthatformsahydratedwaterl

4、ayerwithlowshearingstrength,andthedipole
dipoleeffectsthatformaninterfacialCoulombrepulsionforcealsomakesomecontributionstolowfriction.Thisworkmayhelpustointroduceanewapproachtosuperlubricityandmayleadtothewideapplicationofsuperlubricityinfuturetechnologicalandbiomedicalareas.2223’INTRODUCTI

5、ONcoefficientoflessthan0.003.Aradetal.obtainedultralowfrictioncoefficientsoflessthan0.003byusingpolysaccharidesextractedfromThetermsuperlubricitywasproposedbyHiranoandShinjoattheredalgae,resultingfromthespiralchainstructureofthepolysaccharidebeginningofthe1990stodescribeatheoreticalslidingregim

6、einwhich1,2molecules.Therearealsootherkindsoflubricantsreportedtohavethefrictionbetweentwocontactingsurfacesnearlyvanished.Infact,24,25superlubricityproperties.Here,wefoundanovelsystemofsuper-becauseofthelimitofmeasurementprecision,itisgenerallythoughtlubricitylubricatedwithphosphoricacidaq

7、ueoussolution,withathatwhentheslidingfrictioncoefficientisbelow0.01thelubricating3frictioncoefficientofabout0.004underamuchhighercontactpressurestateisconsideredtobethesuperlubricity.Obviously,superlubricitythanthatofthesurfaceforceapparatus(SFA).Considering