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

第1页附录附录一外文翻译原文：FromCementandConcreteResearch,Volume33,Issue11,November2003,Pages1737-1740ColloidalgraphiteasanadmixtureincementandasacoatingoncementforelectromagneticinterferenceshieldingJingyaoCaoandD.D.L.ChungCompositeMaterialsResearchLaboratory,UniversityatBuffalo,StateUniversityofNewYork,Buffalo,NY14260-4400,USAReceived12December2002；accepted14April2003.；Availableonline28May2003.AbstractAwater-basedcolloidofsubmicrongraphiteparticlesisaneffectiveadmixtureforenhancingtheEMIshieldingeffectivenessofcementpaste,thoughitisineffectiveforloweringtheelectricalresistivity.Asanadmixture,itismoreeffectiveforshieldingthan15-m-diameterdiscontinuouscarbonfibers,thoughitislesseffectivethan0.1-m-diameterdiscontinuouscarbonfilaments.Ashieldingeffectivenessof22dBat1GHzisreachedbycementpasteatasolidgraphitecontentof0.92vol.%,comparedtoavalueof11dBforacoatingmadefromthegraphitecolloidandavalueof14dBforgraphite-colloid-coatedcementpaste(withoutadmixture).Keywords:Electricalproperties；Admixture；Cementpaste1.Introduction第2页EMIshielding1-4isincriticaldemandduetotheinterferenceofwireless(particularlyradiofrequency)deviceswithdigitaldevicesandtheincreasingsensitivityandimportanceofelectronicdevices.Shieldingisparticularlyneededforundergroundvaultscontainingpowertransformersandotherelectronicsthatarerelevanttoelectricpowerandtelecommunication.Itisalsoneededfordeterringelectromagneticformsofspying.Polymermatrixcompositescontainingelectricallyconductivefillersarewidelyusedfortheshieldingofelectronics.Incontrasttoatypicalpolymermatrix,whichiselectricallyinsulating,thecementmatrixisslightlyconductive.Therefore,theuseofacementmatrixallowssomedegreeofelectricalconnectivityamongtheconductivefillerunits,evenwhenthefillervolumefractionisbelowthepercolationthreshold.Aselectricalconnectivityhelpsshielding,thecementmatrixisattractiveforthedevelopmentofcompositematerialsforshielding.Electricallyconductiveadmixturesintheformofdiscontinuousfibers5-8havebeenpreviouslyusedincementforprovidingEMIshielding.Althoughthefibersareeffective,theyareexpensiveand,incontrasttoparticles,havethetendencytoclingtogether.Colloidalgraphiteisfinegraphitepowdersuspendedinaliquidcarrier(suchaswaterandalcohol),usuallytogetherwithasmallamountofapolymericbinder.Asmallparticlesizeofthepowderisnecessaryforformationofastableandworkablecolloid.Afterapplicationofcolloidalgraphiteonasurfacebypaintingorrelatedmethods,theliquidcarrierevaporates,thusallowingthegraphiteparticlestobeessentiallyindirectcontact.Theresultingcoatingisusedforshieldingintelevisionscopes,inadditiontobeingusedasalubricant.However,colloidalgraphitehasnotbeenusedonorincement-basedmaterials.Furthermore,therehasbeennoreportontheEMIshieldingeffectivenessofcolloidalgraphite,exceptforlimitedinformationinacommercialsalesdocument10.Thecostofgraphitepowderincreaseswithdecreasingparticlesize.However,duetotheskineffect,theeffectivenessofgraphitepowder(atagivenvolumefraction)forshieldingisexpectedtoincreasewithdecreasingparticlesize.Inspiteoftherelativelyhighcostoffinegraphitepowder,thecostisstilllowcomparedtothatofcarbonfibersorsubmicron-diametercarbonfilaments.Inthispaper,theterm“filaments”referstothoseofdiameterlessthan1m,whereastheterm“fibers”referstothoseofdiameteratleast1m.Thispaperaddressestheuseofgraphitecolloidasanadmixtureincementandasacoatingoncementforprovidingshielding.Forthesakeofcomparison,thispaperalsoaddressestheshieldingeffectivenessofacolloidalgraphitecoatingonMylar,whichisknownforitselectromagnetictransparency.PreviousdevelopmentofconcreteforEMIshieldingdidnot第3页involvecolloids,butonlydrysolidadmixturessuchas15-m-diametercarbonfibers9,0.1-m-diametercarbonfilaments6,and8-m-diameterstainlesssteelfibers8.Colloidsareattractiveduetothesubmicronparticlesinthemandthegooddispersionoftheseparticles,asattainedbytheuseofsurfactants.AsmallparticlesizeisadvantageousforEMIshieldingduetotheskineffectandtheincreasedtendencyforpercolation.Furthermore,colloidsareattractiveforthecementmixingprocessduetotheirhighfluidity.Inaddition,colloidscanbeusedasacoatingmaterial,whichcanbeappliedtoexistingstructures.Becauseelectricalresistivityisabasicquantitythatdescribestheelectricalconductionbehavior,thispaperincludesmeasurementofelectricalresistivity.2.ExperimentalmethodsThecementusedwasportlandcement(TypeI)fromLafarge(Southfield,MI).Thewatercementratiowas0.35.Awater-reducingagent(asodiumsaltofacondensednaphthalenesulfonicacid,TAMOLSN,RohmandHaas,Philadelphia,PA)wasusedintheamountof1.00%bymassofcementforallspecimens.Noaggregatewasused,whetherfineorcoarse.Thecolloidalgraphiteusedinthisworkwasa9lb/gallon(1g/cm3)dispersionof22wt.%graphiteparticlesofaveragesize0.70.8mindeionizedwater(GrafoHydrografAM2fromFuchsLubricant,Emlenton,PA).Thedispersioncontainsastarch-typebinder.Thedensityofsolidgraphiteis2.26g/cm3.Forshieldingtesting,theattenuationsuponreflectionandtransmissionweremeasuredusingthecoaxialcablemethod(thetransmissionlinemethod)(Fig.1).ThesetupconsistedofanElgal(Israel)SET19AshieldingeffectivenesstesterwithitsinputandoutputconnectedtoaHewlett-Packard(HP)8510Anetworkanalyzer10.AnHPAPC-7calibrationkitwasusedtocalibratethesystem.Thefrequencywasupto1.5GHz,aslimitedbythespecimendimensions.Thespecimenplacedinthecenterplaneofthetester(withtheinputandoutputofthetesteronthetwosidesofthespecimen)wasintheformofanannularringofouterdiameter97mmandinnerdiameter29mm.Silverpaintwasappliedatbothinnerandouteredgesofeachspecimenandneartheedgestomakeelectricalcontactwiththeinnerandouterconductorsofthetester11.第4页Fig.1.EMIshieldingeffectivenesstestingsetup.Intheuseofthecolloidasanadmixture,thewaterinthecolloidwasconsideredinthewatercementratiomentionedearlier.Thecolloidwasusedasanadmixtureinproportionscorrespondingtothegraphitesolidamountingto0.50%and1.00%bymassofcement(correspondingto0.46and0.92vol.%,respectively).Intheuseofthecolloidasacoating,thecolloidwasappliedmanuallyononesideofaspecimenofcementpaste(withoutadmixture,intheformofanannularringofdimensionsmentionedabove)andononesideofaMylarsheet(60mthick,whichhadbeencuttobeanannularringofdimensionsmentionedearlier).Afterdryinginairforatleast2h,silverpaintwasapplied,asmentionedearlier.Thecoatingthicknesswas0.30.4mmafterdryingforbothtypesofsubstrate,asmeasuredbyusingamicrometerbeforeandaftercoating.TheDCresistivitywasmeasuredusingtheKeithley2001multimeterandthefour-probemethod.Inthismethod,fourelectricalcontactswereappliedbysilverpaintatfourplanesperpendiculartothelengthofthespecimen(75×15×15mm).Thefourplanesweresymmetricalaroundthemidpointalongthelengthofthespecimen,suchthattheoutercontacts(forpassingcurrent)were65mmapartandtheinnercontacts(formeasuringthevoltageinrelationtoresistivitydetermination)were55mmapart.3.Resultsanddiscussion3.1.GraphitecolloidasanadmixtureTable.1showsthattheEMIshieldingeffectiveness(sameastheattenuationupontransmission)increasessignificantlywithincreasinggraphitecontent,whereastheattenuationuponreflectiondecreasesslightly.Thismeansthatthegraphiteenhancestheshieldingeffectivenessmainlybyincreasingthereflectivity.