马尔文激光粒度仪简介.doc

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1、laParticlesizeanalysis-Laserdiffractionmethods(ISO-13320-1)IntroductionLaserdiffractionmethodsarenowadayswidelyusedforparticlesizinginmanydifferentapplications.Thesuccessofthetechniqueisbasedonthetactthatitcanbeappliedtovariouskindsofparticulatesystems,isfastandcanbeautomatedandthatavarietyofcomme

2、rcialinstrumentsisavailable.Nevertheless,theproperuseoftheinstrumentandtheinterpretationoftheresultsrequirethenecessarycaution.Therefore,thereisaneedforestablishinganinternationalstandardforparticlesizeanalysisbylaserdiffractionmethods.Itspurposeistoprovideamethodologyforadequatequalitycontrolinpa

3、rticlesizeanalysis.Historically,thelaserdiffractiontechniquestartedbytakingonlyscatteringatsmallanglesintoconsiderationand,thus,hasbeenknownbythefollowingnames:-fraunhoferdiffraction;-(near-)forwardlightscattering;-low-anglelaserlightscattering(LALLS).However,thetechniquehasbeenbroadenedtoincludel

4、ightscatteringinawiderangularrangeandapplicationoftheMietheoryinadditiontoapproximatingtheoriessuchasFraunhoferandanomalousdiffraction.Thelaserdiffractiontechniqueisbasedonthephenomenonthatparticlesscatterlightinalldirectionswithanintensitypatternthatisdependentonparticlesize.Allpresentinstruments

5、assumeasphericalshapefortheparticle.Figure1illustratesthecharacteristicsofsingleparticlescatteringpatterns:alternationofhighandlowintensities,withpatternsthatextendforsmallerparticlestowideranglesthanforlargerparticles[2-7,10,15inthebibliography].Withincertainlimitsthescatteringpatternofanensemble

6、ofparticlesisidenticaltothesumoftheindividualscatteringpatternsofallparticlespresent.Byusinganopticalmodeltocomputescatteringforunitvolumesofparticlesinselectedsizeclassesandamathematicaldeconvolutionprocedure,avolumetricparticlesizedistributioniscalculated,thescatteringpatternofwhichfitsbestwitht

7、hemeasuredpattern(seealsoannexA).Atypicaldiffractioninstrumentconsistsofalightbeam(usuallyalaser),aparticulatedispersingdevice,adetectorformeasuringthescatteringpatternandacomputerforbothcontroloftheinstrumentand