Factors influencing the chemical vapor deposition of ZrC.pdf

《Factors influencing the chemical vapor deposition of ZrC.pdf》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。

JournalofNuclearMaterials62(1976)221-2280North-HollandPublishingCompanyFACTORSINFLUENCINGTHECHEMICALVAPORDEPOSITIONOFZrC*P.WAGNER,L.A.WAHMAN,R.W.WHITE,C.M.HOLLARAUGHandR.D.REISWIGLosAlamosScientifichboratory,UniversityofCalifornia,LosAlamos,NM87545,USAReceived3March1976ExperimentshavebeenperformedtodeterminetheeffectsontheZrCcoatingprocessofvaryingthecompositionofthegasmixtureusedforchemicalvapordepositionofZrC.TheZrCwasdepositedinafluidizedbedofThO2particlesusingagasmixtureofCH4,Ha,ZrC4andAt.TheZrC4flowwascontrolledusingapowderfeeder.EffectsofvaryingCH4andHaconcentrationsandparticlebedareaontherateofdepositionoftheZrC,theappearanceoftheZrC,thecompositionoftheZrC,andthemicrostructureoftheZrCwerestudied.IncreasesinCH4andHaconcentrationwereeffectiveinincreasingthelinearcoatingrateofZrC.IncreasesintheratioofCH4toZrC4inthecoatinggasresultedinadecreasedmetallicap-pearanceofthecoatandanincreaseintheC/Zrinthedeposit.IncreasesinHzinhibittheseeffects.Desexperiencesont6teeffect&senvuededeterminerleseffectssurleprocessusderevdtementenZrCdesvariationsdelacompositiondumelangedegazutilidspourrealiserladepositionenphasevapeurdeZrC.LecarbureZrCestdeposedamunlitfluidisedeparticulesdeTh02enutilisantunmilangedegaz(CH4,Hz,ZrC4etAr).Lecourantgazeuxitaitcontrol&enutilisantunm&ngeurdepoudres.LeseffetsdevariationsdeconcentrationenCH4etHsetdelasurfacedulitdeparticulessurlavitessededepositionducarbureZrC,lapparitiondeZrC,lacompositionetlamicrostructuredeZrCsontktudides.LaugmentationdelaconcentrationenCH4etHajoueunr6leeffectifsurlaugmentationdelavitesseli-neairededepositiondeZrC.LaugmentationdurapportCH4/ZrC4dartslemelangedegazapourresultatunediminutiondelkclatmktalliquedudip&etuneaugmentationdurapportC/Zrdartsledep6t.LaugmentationdelateneurenHain-hibeceseffets.EswurdenVersuchedurchgefiihrt,mitdenenderEinflusseinerAnderungderGaszusammensetzungaufdenZrC-Beschich-tungsprozessdurchchemischeAbscheidungvonZrCausderGasphasebestimmtwurde.DasZrCwurdeineinemFliessbettaufThOz-TeilchenmiteinemCH4-Hs-ZrC4-Ar-Gasgemischabgeschieden.DerZrC4-FlusswurdemitHilfeeinerPulver-Zuleitungkontrolliert.EswurdenderEinflusswechselnderCH4-undHa-KonzentrationenundFliessbettquerschnitteaufdieZrC-Ab-scheidegeschwindigkeitsowiedasAussehen,dieZusammensetzungunddasGefiigedesZrCuntersucht.EineZunahmederCH4-undHa-KonzentrationwirktsichaufeineErhShungderlinearenZrC-Beschichtungsgeschwindigkeitaus.EinAnstiegdesCHe/ZrC4-VerhaltnissesimBeschichtungsgashateineAbnahmedesmetallischenAussehensundeineZunahmedesC/Zr-Ver-hiiltnissesderBeschichtungzurFolge.EineHz-ZunahmeverhindertdieseEinfliisse.1.IntroductionwillyieldahighercoolanttemperatureforagivencoatedparticleoperatingtemperatureandagivenfuelReplacementbyZrCofthecurrentlyusedSICcoatelementdesign.Thesecondisthepotentialtoincreaseinhightemperature,fission-product-retaining,coatedtheoperatingtemperatureofthecoatedparticlesun-nuclearfuelparticleshastwo,potentiallymajor,ad-derirradiation,toincreaseattainablecoolanttempera-vantages.Thefirstistoincreasethetemperaturetoturesfurther[3].ZrC,withitshightemperaturecapa-whichthegraphitefuelbody,containingtheparticles,bilityandgoodneutronicproperties,appearstohavecanbeheatedduringthefabricationprocedure,inor-allthenecessaryqualificationstoreplaceSic.dertoproduceafuelbodymatrixwithahigherther-Severalstudieshavedescribedthechemicalvapormalconductivity[1,2].Theimprovedheattransferdepositionofzirconiumcarbideandcarbon-zirconium*WorkperformedundertheauspicesoftheUnitedStatesEn-carbidealloys[4-141.AllutilizedthereactionofaergyResearchandDevelopmentAdministration.zirconiumhalidewithahydrocarbongastodeposit221 222P.Wagneretal./ChemicalvapourdepositionofZrCzirconiumcarbide.Thezirconiumhalidevaporwasob-tainedeitherbyareactionofahalidevaporwithzir-coniumsponge[4-IO]orbysublimationofZrCb[1l-141.Inbothmethods,controloftheflowrateofzirconiumhalidetotheCVDchamberwasneitherreliablenorflexible.Consequently,adetailedstudyofdepositionparametersforawiderangeofconditionswasnotpracticable.ThislimitationhasbeenovercomewiththerecentdevelopmentofaZrCbpowderfeeder[151inwhichthemassflowrateofthesaltcanbevariedandcontrolledaccurately.Thisreportdescribestheexperimentalconditionsandresultsofadetailed0M406D80100120parametricstudyofthedepositionofZrConThO2DISTANCEFROMORIFICE,mmmicrospheresinafluidizedbed.ThepurposesoftheFig.2.Typicalaxialtemperatureprofileinfluidbed.experimentsweretodefineoptimumcoatingcondi-tionswithrespecttorate,stoichiometry,andqualitywiththeothercoatinggasessuppliedfromagasmani-intheZrCcoat.fold.Thegasesaremeteredbycalibratedflowmeters.TheZrC14powderinthegasstreamisvaporizedinthecoaterbasebeforeenteringthecoatingchamber.2.ApparatusCoatertemperaturesaremeasuredwithPt-Pt10%Rhthermocouples,oneisinsertedinthecoaterbasetoaThefluidizedbedparticlecoaterapparatususedinposition34.8mmbelowtheapexofthecoaterconetheseexperimentsisshownschematicallyinfig.1.andheldtomonitorthetemperatureatthatpointMicrospheresarefluidizedinthecoatingchamberthroughthecoatingrun.Anotherthermocoupleiswhichhasa25.4mmdiameterwith60apexangleloweredthroughthetopofthecoatertomeasuretheconeand3.2mmdiameterinlet.Thegraphitecoatercoatingchambertemperatureatseveralaxialpositions.wallisheatedinductively.ZrC14powderissuppliedThesemeasurementsaremadeinthebedofmicro-fromthepowderfeeder,itsratecontrolledbythespheresfluidizedinAr,andthethermocoupleisre-augerspeedandmeteredbytheoutputoftheloadmovedbeforeintroductionoftheactivecoatinggases.cellonwhichthepowderfeederishung.ThepowderFig.2isaplotofatypicaltemperatureprofileintheissweptbyArtothecoaterbasewhereitismixedcoaterusedinthiswork.COATER3.Experimentaldescription::.::Theexperimentsweredesignedtoestablishtheef-INDUCTION::HEATER_:fectsofchangingsinglevariablesintheZrCcoating0:process.Bythenatureofthecoatingprocess,parti-clesofsomesizedistributionchangeinsizeanddensityasthecoatingproceeds,thuschangingthefluidizationbehaviorofthebed,andprobablychangingthedeple-tionmechanismofthecoatinggasesaswell.Therefore,thegoalofobservinganeffectofasinglevariablewillonlybeapproached,nottrulyattained.Theindepen-dentvariableschange8intheseexperimentswere:(1)H2concentration,Fig.1.SchematicrepresentationofZrC4powderfeederand(2)CH4concentration,particlecoater.(3)bedarea(surfaceareaoftheparticles). P.Wagneretal./ChemicalvapourdepositionofZrC223Table1EffectsofcoatinggascompositionsonZrCcoatingrates,coatappearancesandcompositionsRunMolfractionTotalThicknessVolumeSurfaceCoatingChemicalIDno.--____.___-flowraterategasanalysisofZrC*ArHaCH4ZrC4(cm3/s)bm/min)(cm3/min)ClZrC,/ZrCT/Zr10.820.140.0070.03488.00.090.005Smooth0.210.870.8720.810.140.0160.03488.80.300.017Smooth0.470.840.8930.800.140.0340.03390.50.380.023Matte1.00.891.1840.780.130.0490.03291.90.570.037Tumulose1.50.631.8850.770.130.0600.03293.00.630.042Tumulose1.90.452.4060.690.270.0060.029104.00.140.005Smooth0.210.760.7670.690.270.0130.029104.80.180.0098Smooth0.450.840.8880.680.270.0290.028106.50.400.024Smooth1.00.900.9390.670.260.0420.028107.90.460.028Matte1.50.941.12100.660.260.0510.028109.00.610.040Tumulosei.80.961.19110.490.480.0050.026114.10.140.006Smooth0.190.740.74120.430.480.0120.026114.90.260.015Smooth0.460.870.91130.480.470.0270.026116.60.380.023Smooth1.00.830.97140.470.470.0380.025118.00.490.031Smooth1.50.991.09150.470.460.0470.025119.10.660.045Tumulose1.90.581.08__-__*CT=totalcarboncontentinZrCcoat;Cc=combinedcarboninZrCx.Theparticlestobecoatedhadaverynarrowsizedis-wherex<1andZrC,ismonophaseandstableinthetribution,timeandtemperaturewereheldconstantregion0.591,therelationshipbe-Thethreesetsofcoatingexperimentscompiledincomeslesscertain,anditisundertheseconditionstable1weredoneusingaconstantinitialbedareaofthatthecoatlosesitsmetallicappearance.Thedra-0.05m2(20g).Todeterminetheeffectofbedareamaticchangesintheappearanceofthecoatsathighonthedepositionparameters,additionalexperimentsvaluesofC/Zrinthegasstreamsuggestchangesintheweredonewithbedareasof0.075m2and0.1m2.depositionandcharacteroftheZrC;however,thisisTheresultsoftheseexperimentsaresummarizedinspeculative.ThehigherHzextendstherangeofCH4table2.Onceagain,anattemptwasmadetoholdev-concentrationswhichproduceZrCcoatswithame-erythingconstantexceptforoneindependentvariable,talliclustre.thebedarea.ThiswasdoneforthreedifferentHzAftercoating,representativesampleswereradio-concentrations.Ineachcase,thelinearcoatingrategraphedandtheZrCthicknessesobtainedfromdiam-decreasedwithincreasedbedarea.Theappearanceofeterdifferencesbeforeandaftercoating.BecauseoftheZrCcoatsmadewithXHa=0.47,thehighestH2theinherentlylargeerrorsassociatedwithsuchaconcentration,ismoremetallic(smooth,silvery)thanmethod,thesemeasurementswerelaterrepeatedbythosemadewithXH2=0.14,thelowestHzconcen-makingdirectmeasurementsofthecoatthicknesstration,(xiisthemolfractionoftheithspecies).usingmetallographicmounts.Theagreementbetweenthetwomethodswasquitegoodandtheaveragestan-4.Lkcus3iondarddeviationforthemeasuredZrCcoatthicknessiscalculatedtobe9%.WhencoatvolumesarecalculatedAccordingtoWallace[141,chemicalvapordeposi-fromcoatthicknesses,thisintroducesanuncertaintytionofstoichiometricZrCmaybeexpressedbytheofabout12%inthecalculationofthevolume.overallequation,Metallographicsectionsofrepresentativesamplesweretakenaftereachrun.ThesewerepreparedtoZrCh+CI&+ZrC+4HC1,(2)Table2EffectsofbedareaonZrcoatingratesandappearanceRunMolfractionTotalBedareaThicknessVolumeSurfaceIDno.flowCm21raterateArHzCHqzIc4(cm3/s1Olmlmin)(cm3/min)30.800.140.0340.03390.50.050.380.023Matte160.800.140.0340.03390.50.0750.290.025Matte170.800.140.0340.03390.50.100.240.026Smooth80.680.270.0290.028106.50.050.430.026Smooth180.680.270.0290.028106.50.0750.330.029Smooth130.680.270.0290.028106.50.100.280.032Smooth130.480.470.0270.026116.60.050.380.023Smooth200.480.470.0270.026116.60.0750.350.031Smooth210.480.470.0270.026116.60.100.290.033Smooth P.WagneretaL/ChemicalvapourdepositoinofZrC22swhichestablishesthelowerthermodynamicboundaryIIIIforthecoatinggascomposition.Onemust,however,AalsoconsidertheH2reductionreactions,0lZrCl4t3H2+ZrCljtHCl,(3)0ZrC13t$Hz+ZrC12tHClAI-lfortheinfluenceofH2canbeexplainedonlythroughtheserelationships.InhisanalysisWallacefoundthat:AthedepositionratemaybeexpressedbyPCH4P(Hn-2)2%ltlR=Aexp(-BIT),(4)A1+aP&,wherellMOLFRACTIONH2=0.14nMOLFRACTlONH2-p27n=(4PZrCLj+3PZrC13+2PZrC12YPZrCl~9AAMOLFRACTIONH2'0.47and0246a10Psalt=pzlC4+pzrc13+pzrc1*(5)'Zr.'CH4.,112'.104Cl4H2AsimilaranalysisinthisworkshowedthatthecoatingFig.3.ZrCvolumetriccoatingratesshowingtheeffectsofratedependsonZrC14,CH4,andH2,butnotonHCl.compositionofthecoatinggasstream.Thisisillustratedbyfig.3wherethevolumetriccoat-ingrateisplottedagainstxZrC4lxc&lxg,f.Theda-taconfirmthatforthisexperimentthevolumetricratecanbeexpressedbyR,=KXZrC4XCH4Xy;.(6)0.6LThisissimilarinformto(4)forthecasewherecr<1.5Eq.(6)isusefultodescribethecoatingprocess,but$0.5forsimplicityinapplication,thelinear(thickness)4coatingrateplottedagainstonlyCH4ismoreuseful.Yz0.4Resultsoftheexperimentplottedthusareshowninazfig.4.YThevolumetricandthicknessofthecoatsarere-=latedby,$0.2B0.31V2ZrC=$rN[(q)tty-ri],0MOLFRACTIONH2=0.14lMOtFRACT10NH2'0.27whereNisthenumberofmicrospheres,r.theradiusAMOLFRACT10NH2=0.47ofmicrospheres,andtthethicknessofZrC.Thisdem-onstratethattherelationshipdependsonthenumber0.030.040.050.06ofparticlesandparticlesize.Inordertoinvestigate,MOLFRACTIONCH4quantitatively,theeffectofnumberofparticles,theFig.4.ZrClinearcoatingratesshowingtheeffectsofCH4bedarea,Nineq.(7)wasvariedholdingallothercoat-andHz. 226P.Wagneretal./ChemicalvapourdepositionofZrCingparametersconstant.Theeffectsonthecoatingratesareshowninfig.5.Figs.6,7,and8showhowtheappearanceoftheZrCcoatedparticlesandthemicrostructureoftheZrCchangewithcoatinggascomposition.Thesefig-ureshavebeenpreparedtoallowdirectcomparisonstobemadewiththedatasummaryintable1.Fig.6iscomprisedofthecoatingresultsfromrunsl--5,fig.7fromruns6-10andfig.8fromruns1l-l5inclusive.Thelowmagnificationphotographsshowingthesur-faceappearancearepairedwiththecorrespondingphotomicrographsoftheZrCcoat.Theoverallobser-vationtobemadeisthatastheC/Zrinthecoatinggasisincreased,theZrCdepositprogressesbystagesfromasilvery,smooth,metallicappearingcoattoonewhichisroughandblack.Whetherthenon-metallicO.B-MCXFRACTIONHp=0.47-0.4appearanceofthesehighcarboncoatsisduetolightscatteringattheparticlesurface,orwhetherthecar-0.25-bonreflectioncharacteristicsdominatethoseofZrC-0.3isnotclear.AtsufficientlyhighC/ZrvaluesintheIIIIII0.2coatinggas,theparticlesurfacesactuallybecome0.20'0.050.060.070.080.090.10roughandbumpy(tumulose).Thisprogressioninsur-BEDAREAdifaceappearanceandmicrostructurewithincreasesinFig.5.Comparisonsofvolumetricandlinearcoatingratesvsbedarea.Solidline,volumetricrate;dashedline,hearrate.Fig.6.SurfaceandmicrostructureofZrCcoats;runnos.l-5,table1. P.WagneretaL/ChemicalvapourdepositionofZrC221Fig.7.SurfaceandmicrostructureofZrCcoats;runnos.6-10,table1.Fig.8.SurfaceandmicrostructureofZrCcoats;runnos.11-15,table1. 228P.Wagneretal./ChemicalvapourdepositionofZrCCH4concentrationisseenineachofthefigures.Thecoatingrate,coatappearanceandcoatcompositionthreefiguresalsoshowtheeffectofH2onsurfaceap-havebeenevaluated.IncreasesinCH4andH2concen-pearanceandmicrostructureoftheZrCcoats.TheHztrationareeffectiveinincreasingthecoatingrateofconcentrationislowestinfig.6andhighestinfig.8.ZrConabedoffluidizedThO2particles.IncreasesinTheoveralleffectoftheH2istoinhibittheeffectoftheratioofC!H4toZrChinthecoatinggas(C/Zr)re-increasingtheCI-$concentration.Thatis,withhighersultsinZrCcoatsofdecreasingmetallicappearance.H2concentration,theincreasedC/ZrinthecoatingIncreasesinH2concentrationinhibits,butdoesnotgasstillresultsindegradationofthemetalliclustreofeliminate,thiseffect.theZrCcoat,butahighervalueofC/Zrisrequiredtoachieveagivenresult.Thiseffectisalsoclearlydemon-stratedinfigs.6,7and8.ReferencesThemicrostructureobservedincoatsfromruns3,4,5,9,10and15alsoshowalayeredortreering111P.Wagner,C.M.HolIabaughandR.J.Bard,Proc.IAEAstructure.SuperficiallythesebeararesemblancetoSfmp.onGasCooledReactorswithEmphasisonAd-theringstructureseeninlowtemperatureisotropicvancedSystems,JueIich,FRG(1975).121P.Wagner,Carbon(inpress).carboncoatsthathavebeenplasmaoxidized[161.InI31J.D.BalcombandP.Wagner,Proc.BNESIntern.Conf.,thecaseofthecarboncoats,ithasbeenshownthatLondon(1974).theseringshavedifferent,anisotropies.Ithasbeen141K.IkawaandK.Iwamoto,J.Nucl.Mater.45(1972/73)speculatedthatthisstructureisanaturalconsequence67.[51K.Ikawa,J.LessCommonMetals27(1972)325.ofcoatingparticlesinaspoutingbedinaverticalcoat-WIK.Ikawa,J.LessCommonMetals29(1972)233.ingfurnacewithanaxialtemperaturegradient,asthe171K.IkawaandK.Iwamoto,J.Ceram.Sot.ofJapanparticlescirculatethecoatingtakesplaceatdifferent(Yogyo-Kyakai-Shi)81(1973)403.ratesindifferenttemperatureregimes.WethinkthatPIK.IkawaandK.Iwamoto,J.Nucl.Mat.52(1974)128.asimilarphenomenonisresponsibleforthetreeringPIK.IkawaandK.Iwamoto,J.Nucl.Sci.andTech.11(1974)263.structureseeninsomeoftheZrCcoats.Astheparti-[lOIG.H.Reynolds,J.Nucl.Mat.50(1974)215.clesmoveupanddowninthespoutingbedofthe(111R.Harris,E.Kelley,D.H.LeedsandW.V.Kotlensky,coatingfurnace,theyareexposedtoregionsofslightlyChemicalVaporDeposition(ElectrochemicalSociety)differentgascompositionsandtemperatures.Itispos-3(1972)183.siblethatananalysisonafineenoughscalewouldre-[121A.R.Driesner,E.K.Storms,P.WagnerandT.C.Wallace,vealsmallcompositionaldifferencesinthedifferentChemicalVaporDeposition(ElectrochemicalSociety)4(1973)473.layers,thustheringlikeappearanceonsomeofthe[13]P.Wagner,LASLreportLA-5224(1973).coats.[141T.C.Wallace,ChemicalVaporDeposition(Electrochem-icalSociety)4(1973)91.[15]C.M.Hollabaugh,R.D.Reiswig,P.Wagner,L.A.Wahman3.summaryandR.W.White,J.Nucl.Mat.57(1975)325.1161E.Balthesen,K.Ehlers,K.G.HacksteinandH.Nickel,AsetofZrCcoatingexperimentshasbeendescribedProc.ANSmeetingonGas-CooledReactors,Gatlinburg,inwhicheffectsofCI-14,H2andparticlebedareaonTN(1974)p.201.