矿物材料现代测试技术3X荧光分析

武汉理工大学资环学院管俊芳,1,第二部分xrayFluorescenceSpectroscope(XRF)X荧光成分分析,武汉理工大学资环学院管俊芳,2,某些物质被一定波长的光照射时，会在一定时间内发射出波长比入射光长的光，如果这个时间比较短，这种光就称为荧光。荧光由一种能发荧光的矿物萤石(fluosrite)而得名。除了紫外光和可见光可能激发荧光外，其它的光如红外光、X射线也可能激发出荧光，因此除紫外荧光或可见荧光外，还有红外荧光、X射线荧光等。,武汉理工大学资环学院管俊芳,3,1方法特点2分析原理3仪器构成4WDS-XRF5EDS-XRF6定量分析,武汉理工大学资环学院管俊芳,4,1方法特点（1）,XRF是一种最有效的无损成分分析手段之一。优点：(1)速度快，一般测定一种元素(定量)需10100秒；(2)可检测固态、粉末、液态样品，以及晶质、非晶质等样品的化学成分；(3)非破坏性测试，不损伤样品(但对于某些高分子物质，如有机物，则会引起颜色变化)；(4)是一种物理分析方法，分析元素范围F9U92，分析的浓度范围1ppm100%；,武汉理工大学资环学院管俊芳,5,1方法特点（2）,优点：(5)制样简单，板状样品把被照射面加工成平面即可，粉末样品经粉碎、压片即可；(6)系表面分析，一般测定深度为0.1mm范围，另外也是表面整体分析，即分析整个照射面范围内的元素种类和含量；Pros:FastNon-destructivetechniquePerformselementalanalysisHighsensitivity,detectsupto50ppmCandetectthinsingleormulti-layerfilmsandmeasuretheirthickness.,武汉理工大学资环学院管俊芳,6,1方法特点(3),缺点：(1)难以作绝对分析，因此定量分析时需参照标准物质进行；(2)原子序数低的元素，其检出限及测定误差都相对较大。Cons:DoesnotassistinobtainingchemicalinformationNotapplicabletoidentifyingthefirst11elements.Interferingx-raylinesbymatrixeffectscanpossiblycomplicateanalysis.,武汉理工大学资环学院管俊芳,7,1方法特点（4）,样品要求及处理方法：,武汉理工大学资环学院管俊芳,8,1方法特点（4）,仪器外观：依据光源系统的不同、探测方式的不同，仪器的大小、形状有一定差异。,武汉理工大学资环学院管俊芳,9,1方法特点（5）,光源：X射线光源：白色X射线。即具有各种波长的X射线，可分析前面所列范围的所有元素。放射性同位素光源：放射出的射线亦在X射线范围，但能量是固定的。因此只能分析部分元素。仪器的体积可以很小，最新型的相当于一个计算器的大小。同步辐射光源：光源的能量更大，对后续的二次射线检测很有利，所以分析精度更高，但仪器造价很昂贵。,武汉理工大学资环学院管俊芳,10,2分析原理（1）,Whentheatomsinasamplematerialareirradiatedwithhigh-energyprimaryx-rayphotons,electronsareejectedintheformofphotoelectrons.Thiscreateselectronholesinoneormoreoftheorbits,convertingtheatomsintoions-whichareunstable.,武汉理工大学资环学院管俊芳,11,2分析原理（2）,Torestoretheatomstoamorestablestate,theholesininnerorbitsarefilledbyelectronsfromouterorbits.Suchtransitionsmaybeaccompaniedbyanenergyemissionintheformofasecondaryx-rayphoton-aphenomenonknownasfluorescence.,武汉理工大学资环学院管俊芳,12,2分析原理（3）,ThevariouselectronorbitsarecalledK,L,M,etc.,whereKisclosesttothenucleus.Eachcorrespondstoadifferentenergylevel-andtheenergy(E)ofemittedfluorescentphotonsisdeterminedbythedifferenceinenergiesbetweentheinitialandfinalorbitsfortheindividualtransitions.,武汉理工大学资环学院管俊芳,13,2分析原理（4）,Characteristicx-rayemissionsresultinanenergyspectrumthatisafingerprintoftheelement.Sowecandeterminetheelementkindsinthesample.Andalsotheintensitiesofthepeaksinthespectrumareroughlyproportionaltotheconcentrationsoftheconstituentelements.,武汉理工大学资环学院管俊芳,14,3仪器构成（1）,波长色散型XRF：WAVELENGTHDISPERSIVEXRF(WDS-XRF)通过分析样品在入射X射线作用下产生的二次X射线(荧光射线)的波长，来定性或定量分析样品的元素组成及含量。能量色散型XRF:ENERGY-DISPERSIVEXRF（EDSXRF）通过分析样品在入射X射线作用下产生的二次X射线(荧光射线)的能量，来定性或定量分析样品的元素组成及含量。,武汉理工大学资环学院管俊芳,15,3仪器构成（2）,WDS-XRFandEDS-XRF,武汉理工大学资环学院管俊芳,16,4WDS-XRF(1),WavelengthdispersiveXRFusesacrystaltoseparatethevariouswavelengths:foreveryangleofincidentradiation,theonlywavelengthreflectedtothedetectoristheonethatconformstoBraggsformula:n=2dsinwhereisthewavelengthofthex-rayradiationproducedbythesample;disaconstantcharacteristicofeverycrystallinesubstance(i.e.thex-raycrystal);andistheangleonincidenceofthex-radiationonthesample.,武汉理工大学资环学院管俊芳,17,4WDS-XRF(2),Thecrystalsandtheirplanesoftenusedareasfollow.,武汉理工大学资环学院管俊芳,18,4WDS-XRF(3),Howtodeterminethewavelength:Detectorisrotatingwhendoingthewavelengthdetermination,alsothecrystalisrotatingbyhalfspeed.,武汉理工大学资环学院管俊芳,19,4WDS-XRF(4),So,bychangingtheangleofthecrystal,youcanselectanywavelengthforspecificelementsofinterest.Differentcrystalcanbeuseddeterminedifferentelements.Whendoingmeasurement,weoftenneedtochangecrystalsforthevariouselements,finallywecanyieldresultsinanyformdesired:qualitative,ratio,quantitative,graphic,etc.,武汉理工大学资环学院管俊芳,20,4WDS-XRF(5),Therelationshipbetweentherangeofanalyzingelementandthecrystals,andthe2thetascanningrange.,武汉理工大学资环学院管俊芳,21,4WDS-XRF(6),AnalyzingProcedure:EveryelementhaveastrongestXraywavelength.Inordertodetermineit,firstweshouldmeasuretheintensityofthatwavelength.Forexample,strongestLineandtheir2positionforNi,Fe,&Ru,whendetectedbydifferentcrystal.,武汉理工大学资环学院管俊芳,22,4WDS-XRF(7),AnalyzingProcedure:Inordertomakethedeterminationmoreaccurate,weshouldalsomeasuretheiraccompanyingpeaks.,武汉理工大学资环学院管俊芳,23,4WDS-XRF(8),AnalyzingProcedure:,武汉理工大学资环学院管俊芳,24,4WDS-XRF(9),WDSwasintroducedintheearly1950s.WDSspectrometersystemsemploydiffractionbyasinglecrystaltoseparatecharacteristicwavelengthsemittedbythesample.INWDS,polychromaticradiationsemanatingfromtheX-raytubeimpingeonthespecimenandrejectK,L,levelelectronsfromatomsoftheelementspresentinthespecimen.Thisresultsintheemissionoffluorescenceradiation(K,L,.serieslines)whicharedispersedbyanappropriatecrystalaccordingtothewell-knownBraggequation.,武汉理工大学资环学院管俊芳,25,4WDS-XRF(10),Inordertomeasurex-raysofdifferentenergies(wavelengths),thepositionofthediffractingcrystalanddetectormustbemechanicallychangedrelativetothefixedspecimentoaltertheangles.TocovertherangeofX-raywavelengthtobemeasured,severaldifferentdiffractioncrystalsmustbeutilized.Thedetectorsusedwilloftenbeaflow-proportionaldetectoragas-filledscintillatorandphotomultipliertube,武汉理工大学资环学院管俊芳,26,5EDS-XRF(1),ThesecondandmorecommonmethodforanalyzingobsidianisEDS-XRF.EDSXRFsystemsdetectelementsontheperiodictablebetweenatomicnumbers11(Na)and92(U).Samplescanbeanalyzednon-destructivelywithlittleornosamplepreparationinminutesandinsomecasesseconds.Elementsinconcentrationsfromaslowasafewpartspermillionto100%maybeanalyzedinthesamesamplesimultaneously.Accuracyoflessthanonepercentrelativeerrorareattainablewithcomparablereproducibility,武汉理工大学资环学院管俊芳,27,5EDS-XRF(2),AnalysisbyEDSXRF,likeWDSXRFinvolvesuseofionizingradiationtoexcitethesample,followedbydetectionandmeasurementofX-raysleavingthesamplethatarecharacteristicoftheelementsinthesample.However,unlikethecrystal(wavelength)XRF,EDSXRFspectrometerelectronicsdigitizethesignalproducedbyX-raysenteringthelithiumdrifteddetector,andsendthisinformationtothePCfordisplayandanalysis.TheNatoUspectraldataareinthe1-37KeVrange.,武汉理工大学资环学院管俊芳,28,5EDS-XRF(3),武汉理工大学资环学院管俊芳,29,5EDS-XRF(4),ThehighresolutionlithiumdriftedsiliconX-raydetectorsprovidelowdetectionlimits,fewspectralinterferences,andaccuracyoverawiderangeofconcentrations.Thesedetectorsareabletoseparatetheelectronenergycomingfromthesampleintoelementalcomponents,whichinturnaretranslatedintoratio,qualitative,orquantitativeelementaldatainspreadsheetorwordprocessorformats.Additionally,thetubevoltagesonEDSXRFarequitelowandtheentireinstrumentispluggedintoastandardwallsocket.WDSXRFrequiresfilteredvoltageat220V.,武汉理工大学资环学院管俊芳,30,5EDS-XRF(5),Advantages:(1)NON-DESTRUCTIVEInthevastmajorityofcases,analyzedsamplesarenotdestroyedorchangedbyexposuretox-rays.Theycanthusbesavedforfuturereferenceorusedforothertypesoftestingthatmaybedestructive.(2)MINIMALPREPARATIONManysamplescanbeexaminedwithlittleornopre-treatment.Manyofthealternativetechniquesrequiredissolutionproceduresthatarebothtime-consumingandcostlyintermsoftheacidsorotherreagentsrequired.,武汉理工大学资环学院管俊芳,31,5EDS-XRF(6),Advantages:(3)FASTX-rayspectrometryenableschemicalcompositionstobedeterminedinseconds.(4)EASYTOUSEModerninstrumentsrunundercomputercontrol,witheffectivesoftwaretohandlemeasurementset-upandresultscalculation.Tasksthatoncerequiredtheconstantattentionofatrainedanalystcannowbehandledbyskilledoperatorsorevencarriedoutbyfullyautomatedsystems.,武汉理工大学资环学院管俊芳,32,5EDS-XRF(7),ComparingwithWDS-XRFWDS-slow,butaccuracyishigh.EDS-fast,butaccuracyislow.WDSQuantitativeiseasierthanqualitative.EDSbotharesame.GenerallythedifferentiatingabilityofWavelengthishigherthenthatofEnergy.,武汉理工大学资环学院管俊芳,33,5EDS-XRF(8),AdvantagesofEnergyDispersion:*simplicityofinstrumentation-nomovingparts*simultaneousaccumulationoftheentireX-rayspectrum*qualitativeanalysiscanbeperformedin30s,orso*arangeofalternativeexcitationsourcescanbeusedinplaceofhigh-powerx-raytubeswiththeirlarge,heavy,expensiveandpower-consumingsupplies,武汉理工大学资环学院管俊芳,34,5EDS-XRF(9),AdvantagesofEnergyDispersion:*alternativesourcesinclude,lowpowerx-raytubes,secondarymonochromaticradiators,radioisotopesandionbeams.,武汉理工大学资环学院管俊芳,35,5EDS-XRF(10),AdvantagesofWavelengthDispersion:*resolutionisbetteratwavelengthslongerthan0.08nm*higherindividual