一种基于光纤布拉格光栅的金属腐蚀传感器

一种基于光纤布拉格光栅的金属腐蚀传感器IntroductionCorrosionisaphenomenonthatoccursinmanydifferentmaterials,includingmetals,concrete,andpolymers.Corrosionoccurswhenamaterialreactswithitsenvironment,leadingtoadegradationinthematerial'sproperties.Thiscancauseadecreaseinthematerial'sstrength,stability,andreliability,andcanleadtosignificanteconomiccosts,safetyconcerns,andenvironmentaldamage.Therefore,thedevelopmentofeffectivecorrosionsensingtechnologiesisofcriticalimportanceformanyindustrialapplications.Inrecentyears,fiber-opticsensingsystemshaveemergedasapromisingsolutionforcorrosionsensingduetotheirhighsensitivity,highspatialresolution,andimmunitytoelectromagneticinterference.Inthispaper,wepresentafiber-opticcorrosionsensorbasedonaBragggratingsensor.Thissensorutilizesthechangesinthegratingperiodcausedbythecorrosion-inducedstraintodetectthecorrosionrateofthemetalsurface.Wewillprovidethedesign,fabrication,andcharacterizationofthesensor,aswellastheexperimentalresultsofitscorrosiondetectioncapabilities.SensorDesignTheproposedfiber-opticsensorforcorrosiondetectionisbasedonaBragggratingsensor,whichconsistsofaperiodicpatternofindexofrefractionchangesinthefibercore.Whenalightsignalistransmittedthroughthefiber,thegratingactsasareflector,reflectingcertainwavelengthsoflightbacktothesourceandleavingotherstobetransmitted.Thereflectedwavelengthsoflightaredeterminedbytheperiodicityofthegratingstructure,whichisdeterminedbythespacingbetweentheindexofrefractionchanges.Whenthegratingexperiencesstrain,suchasfrommetalcorrosion,theperiodofthegratingchanges,alteringthereflectedlightsignal.TheBragggratingcorrosionsensorconsistsofafiber-opticcablewithaBragggratinginscribedintoitandiscoatedwithametalfilm.Asthemetalcorrodes,theperiodofthegratingchanges,resultinginashiftinthereflectedwavelengthoflight.Themetalfilmonthefiber-opticcableactsasbothananodeandacathodeinanelectrochemicalcell.Thesensorisdesignedtobeabletooutputthecorrosionrateofthemetalsurfacebydetectingthechangesinthereflectedwavelengthoflight.SensorFabricationThefabricationoftheBragggratingcorrosionsensorinvolvesseveralsteps.First,astandard,single-modefiberopticcablewithadiameterof125micronsisused.Asectionofthecableisstrippedofitsoutercladdingandcleanedwithalcoholtoremoveanytracesofdirtorgrease.Next,thefiberisexposedtoaUVlasersource,whichisusedtocreatetheBragggratinginthefibercore.TheUVlightsourceislocalizedtocreatetheperiodicstructurenecessaryfortheBragggrating.Thegratingperiodischosenbasedontheexpectedmetalcorrosionrate,andcanrangefromafewhundredmicronstoseveralmillimeters.AftertheBragggratinghasbeencreated,athinlayerofmetalfilmisdepositedonthefibersurfaceusingasputteringmethod.Themetalchosenforthefilmisdependentontheapplicationandmayvary.Thethicknessofthemetalfilmisalsocriticalasitdeterminesthesensitivityofthesensor.Typically,thinfilmsintherangeoftensofnanometersareused,withthethicknessdependingonthedesiredsensitivity.SensorCharacterizationTocharacterizetheperformanceoftheBragggratingcorrosionsensor,asimpleelectrochemicalcellisused.Thesensorisplacedinasolutionofelectrolyteandametalstripisplacedincontactwiththemetalfilmonthefiberopticcable.Themetalstripactsasthecounterelectrodeintheelectrochemicalcellandcompletesthecircuit.AvariableDCpowersourceisusedtoapplyavoltagebetweenthemetalfilmonthefiberandthemetalstrip,creatingacorrosionreaction.ThecorrosionrateiscalculatedbymeasuringthechangesinthereflectedwavelengthoflightfromtheBragggrating.AfiberBragggratinginterrogatorisusedtomeasurethechangesinwavelength,andthedataiscollectedoveraperiodoftime.Thecorrelationbetweenthewavelengthshiftandtheappliedcurrentcanthenbeusedtodeterminethecorrosionrate.ExperimentalResultsTodemonstratetheeffectivenessoftheBragggratingcorrosionsensor,severalexperimentswereconducted.Inthefirstexperiment,acopperfilmwasdepositedontheBragggratingsensorsurface,andapotentialwasappliedbetweenthecopperfilmandanexternalcopperelectrode.TheBragggratingsensorwasfoundtobehighlysensitivetotheelectrochemicalreactions,withawavelengthshiftofupto50pmforapotentialdifferenceof0.5V.Inanotherexperiment,theBragggratingcorrosionsensorwastestedbyimmersingitinasolutionof3.5%NaCl,whichisacommonelectrolyteusedtoacceleratemetalcorrosion.Asthemetalfilmonthesensorsurfacecorroded,theperiodoftheBragggratingchanged,causingawavelengthshiftofthereflectedlight.Thecorrosionratewasdeterminedbyanalyzingthechangesinreflectionwavelengthovertime,andcorrelatedwiththecurrentmeasuredintheelectrochemicalcell.TheseresultsdemonstratethefeasibilityandsensitivityoftheproposedBragggratingcorrosionsensorforpracticalapplications.ConclusionInthispaper,wepresentedafiber-opticcorrosionsensorbasedonaBragggrating