外文翻译--用胶体石墨掺合水泥或者作为水泥表面涂层来防护电磁干扰.doc -- 5 元

第1页附录附录一外文翻译原文FromCementandConcreteResearch,Volume33,Issue11,November2003,Pages17371740ColloidalgraphiteasanadmixtureincementandasacoatingoncementforelectromagneticinterferenceshieldingJingyaoCaoandD.D.L.ChungCompositeMaterialsResearchLaboratory,UniversityatBuffalo,StateUniversityofNewYork,Buffalo,NY142604400,USAReceived12December2002accepted14April2003.Availableonline28May2003.AbstractAwaterbasedcolloidofsubmicrongraphiteparticlesisaneffectiveadmixtureforenhancingtheEMIshieldingeffectivenessofcementpaste,thoughitisineffectiveforloweringtheelectricalresistivity.Asanadmixture,itismoreeffectiveforshieldingthan15μmdiameterdiscontinuouscarbonfibers,thoughitislesseffectivethan0.1μmdiameterdiscontinuouscarbonfilaments.Ashieldingeffectivenessof22dBat1GHzisreachedbycementpasteatasolidgraphitecontentof0.92vol.,comparedtoavalueof11dBforacoatingmadefromthegraphitecolloidandavalueof14dBforgraphitecolloidcoatedcementpastewithoutadmixture.KeywordsElectricalpropertiesAdmixtureCementpaste1.Introduction第2页EMIshielding14isincriticaldemandduetotheinterferenceofwirelessparticularlyradiofrequencydeviceswithdigitaldevicesandtheincreasingsensitivityandimportanceofelectronicdevices.Shieldingisparticularlyneededforundergroundvaultscontainingpowertransformersandotherelectronicsthatarerelevanttoelectricpowerandtelecommunication.Itisalsoneededfordeterringelectromagneticformsofspying.Polymer–matrixcompositescontainingelectricallyconductivefillersarewidelyusedfortheshieldingofelectronics.Incontrasttoatypicalpolymermatrix,whichiselectricallyinsulating,thecementmatrixisslightlyconductive.Therefore,theuseofacementmatrixallowssomedegreeofelectricalconnectivityamongtheconductivefillerunits,evenwhenthefillervolumefractionisbelowthepercolationthreshold.Aselectricalconnectivityhelpsshielding,thecementmatrixisattractiveforthedevelopmentofcompositematerialsforshielding.Electricallyconductiveadmixturesintheformofdiscontinuousfibers58havebeenpreviouslyusedincementforprovidingEMIshielding.Althoughthefibersareeffective,theyareexpensiveand,incontrasttoparticles,havethetendencytoclingtogether.Colloidalgraphiteisfinegraphitepowdersuspendedinaliquidcarriersuchaswaterandalcohol,usuallytogetherwithasmallamountofapolymericbinder.Asmallparticlesizeofthepowderisnecessaryforformationofastableandworkablecolloid.Afterapplicationofcolloidalgraphiteonasurfacebypaintingorrelatedmethods,theliquidcarrierevaporates,thusallowingthegraphiteparticlestobeessentiallyindirectcontact.Theresultingcoatingisusedforshieldingintelevisionscopes,inadditiontobeingusedasalubricant.However,colloidalgraphitehasnotbeenusedonorincementbasedmaterials.Furthermore,therehasbeennoreportontheEMIshieldingeffectivenessofcolloidalgraphite,exceptforlimitedinformationinacommercialsalesdocument10.Thecostofgraphitepowderincreaseswithdecreasingparticlesize.However,duetotheskineffect,theeffectivenessofgraphitepowderatagivenvolumefractionforshieldingisexpectedtoincreasewithdecreasingparticlesize.Inspiteoftherelativelyhighcostoffinegraphitepowder,thecostisstilllowcomparedtothatofcarbonfibersorsubmicrondiametercarbonfilaments.Inthispaper,thetermfilamentsreferstothoseofdiameterlessthan1μm,whereasthetermfibersreferstothoseofdiameteratleast1μm.Thispaperaddressestheuseofgraphitecolloidasanadmixtureincementandasacoatingoncementforprovidingshielding.Forthesakeofcomparison,thispaperalsoaddressestheshieldingeffectivenessofacolloidalgraphitecoatingonMylar,whichisknownforitselectromagnetictransparency.PreviousdevelopmentofconcreteforEMIshieldingdidnot第3页involvecolloids,butonlydrysolidadmixturessuchas15μmdiametercarbonfibers9,0.1μmdiametercarbonfilaments6,and8μmdiameterstainlesssteelfibers8.Colloidsareattractiveduetothesubmicronparticlesinthemandthegooddispersionoftheseparticles,asattainedbytheuseofsurfactants.AsmallparticlesizeisadvantageousforEMIshieldingduetotheskineffectandtheincreasedtendencyforpercolation.Furthermore,colloidsareattractiveforthecementmixingprocessduetotheirhighfluidity.Inaddition,colloidscanbeusedasacoatingmaterial,whichcanbeappliedtoexistingstructures.Becauseelectricalresistivityisabasicquantitythatdescribestheelectricalconductionbehavior,thispaperincludesmeasurementofelectricalresistivity.2.ExperimentalmethodsThecementusedwasportlandcementTypeIfromLafargeSouthfield,MI.Thewater–cementratiowas0.35.Awaterreducingagentasodiumsaltofacondensednaphthalenesulfonicacid,TAMOLSN,RohmandHaas,Philadelphia,PAwasusedintheamountof1.00bymassofcementforallspecimens.Noaggregatewasused,whetherfineorcoarse.Thecolloidalgraphiteusedinthisworkwasa9lb/gallon1g/cm3dispersionof22wt.graphiteparticlesofaveragesize0.7–0.8μmindeionizedwaterGrafoHydrografAM2fromFuchsLubricant,Emlenton,PA.Thedispersioncontainsastarchtypebinder.Thedensityofsolidgraphiteis2.26g/cm3.Forshieldingtesting,theattenuationsuponreflectionandtransmissionweremeasuredusingthecoaxialcablemethodthetransmissionlinemethodFig.1.ThesetupconsistedofanElgalIsraelSET19AshieldingeffectivenesstesterwithitsinputandoutputconnectedtoaHewlettPackardHP8510Anetworkanalyzer10.AnHPAPC7calibrationkitwasusedtocalibratethesystem.Thefrequencywasupto1.5GHz,aslimitedbythespecimendimensions.Thespecimenplacedinthecenterplaneofthetesterwiththeinputandoutputofthetesteronthetwosidesofthespecimenwasintheformofanannularringofouterdiameter97mmandinnerdiameter29mm.Silverpaintwasappliedatbothinnerandouteredgesofeachspecimenandneartheedgestomakeelectricalcontactwiththeinnerandouterconductorsofthetester11.第4页Fig.1.EMIshieldingeffectivenesstestingsetup.Intheuseofthecolloidasanadmixture,thewaterinthecolloidwasconsideredinthewater–cementratiomentionedearlier.Thecolloidwasusedasanadmixtureinproportionscorrespondingtothegraphitesolidamountingto0.50and1.00bymassofcementcorrespondingto0.46and0.92vol.,respectively.Intheuseofthecolloidasacoating,thecolloidwasappliedmanuallyononesideofaspecimenofcementpastewithoutadmixture,intheformofanannularringofdimensionsmentionedaboveandononesideofaMylarsheet60μmthick,whichhadbeencuttobeanannularringofdimensionsmentionedearlier.Afterdryinginairforatleast2h,silverpaintwasapplied,asmentionedearlier.Thecoatingthicknesswas0.3–0.4mmafterdryingforbothtypesofsubstrate,asmeasuredbyusingamicrometerbeforeandaftercoating.TheDCresistivitywasmeasuredusingtheKeithley2001multimeterandthefourprobemethod.Inthismethod,fourelectricalcontactswereappliedbysilverpaintatfourplanesperpendiculartothelengthofthespecimen751515mm.Thefourplanesweresymmetricalaroundthemidpointalongthelengthofthespecimen,suchthattheoutercontactsforpassingcurrentwere65mmapartandtheinnercontactsformeasuringthevoltageinrelationtoresistivitydeterminationwere55mmapart.3.Resultsanddiscussion3.1.GraphitecolloidasanadmixtureTable.1showsthattheEMIshieldingeffectivenesssameastheattenuationupontransmissionincreasessignificantlywithincreasinggraphitecontent,whereastheattenuationuponreflectiondecreasesslightly.Thismeansthatthegraphiteenhancestheshieldingeffectivenessmainlybyincreasingthereflectivity.