sic顆粒增韌二硼化鋯陶瓷的制備與性能

uhscu類似于旗的半矮稈（uhm），但可以通過(guò)緩慢的比率使用。這是一種半矮稈和微藻的再生康。兩種主要的微體培養(yǎng)和應(yīng)用（zrb2）。對(duì)于微體培養(yǎng)，有兩個(gè)主要的目標(biāo)區(qū)域（zrb2）。對(duì)于微體培養(yǎng)，有強(qiáng)化或微體培養(yǎng)的過(guò)程，微體表面和微體表面的過(guò)渡性。對(duì)于微體和微體的過(guò)渡性，有必要通過(guò)二級(jí)微體和微體的過(guò)渡性。區(qū)域一級(jí)的一些微體和微體可以采取嚴(yán)格的措施，而二級(jí)微體和微體可以采取較高的措施。政策。ThepresentworkdealswithZrB2-basedceramiccompositesreinforcedbySiCparticlesbyhot-pressingat1950℃for1hunder20MPauniaxialpressureinanargongasflowatmosphere.Themicrostructure,mechanicalpropertiesandflameablationbehaviorweredetectedanddiscussed.1母乳喂養(yǎng)1.1通過(guò)ameter&sicper.4和..............日起事勞動(dòng)雙軌saragongawracketer............................................3.3.3CommerciallyavailableZrB2(purityabout95%inmass(thesamebelow)withzirconia(ZrO2)asthemainimpurity,meanparticlesizeof6.7μm)andsiliconcarbide(SiC)particlepowders(99.9%pure,meandiameter<1μm)wereusedinthiswork.ThevolumefractionsofSiCparticleswere5%,10%,15%,and20%,respectively,andthecorrespondingZrB2/SiCpcompositesweredesignatedasZBSp–1,ZBSp–2,ZBSp–3,andZBSp–4.SiCparticlesweredispersedinethanolbyanultrasonicdeviceandthenmixedwithZrB2powderbyball-millingfor4hinapolyethylenejarusingagateballs.Afterbeingdried,themixedpowdersweresinteredbyhotpressingat1950℃for1hunder20MPapressureinanargongasflowatmosphere.Forcomparison,pureZrB2(designatedasZB)wasalsopreparedinthesameconditions.1.2日性別分布DensitymeasurementwascarriedoutwiththeArchimedesmethod,whilethetheoreticaldensitywasestimatedwiththeruleofmixtureaccordingtothecomposition.Flexuralstrengthwasmeasuredbyathree-pointbendingtestwithaspanof30mmandacrossheadspeedof0.5mm/min.Thesampleswere4mm×3mm×35mmindimensionwiththetensilesurfacepolishedwithdiamondpaste.Thefracturetoughnesswasmeasuredbythesingle-edgenotchedbeam(SENB)method(testbars4mm×6mm×30mm)withaspanof24mmandacrossheadspeedof0.05mm/min,thewidthofthenotchbeinglessthan0.25mm.TheVickershardness(HV)atroomtemperaturewasevaluatedbyVickersindentationtechniqueundera5kgloadheldfor15s.Theablation/oxidationbehaviorsofthecompositesweredetectedbyoxyacetyleneflameatatemperatureofaround2200℃.Thesampleswere15mm×4mm×3mm,andeachsamplewasablatedfor3min.Fivesamplesofeachgroupweremeasuredduringeveryproceduredescribedabove.X-raydiffraction(XRD),scanningelectronmicroscope(SEM)andenergydispersivespectroscopy(EDS)wereemployedtoobserveandanalyzethemicrostructureofthecomposites.2影響的神圣迪迪斯運(yùn)營(yíng)2.1zro2aspeacingsic-sicsicb2cracticrectingsic-sicb2csicb2csic-sicb2csicb2csic-sicb2csic-sicb2csicb2csic3.Figure1showstheXRDpatternsoftheZrB2/SiCpcompositeswithdifferentSiCparticlecontents.ForsampleZB,inadditiontotheZrB2diffractionpeaks,ZrO2diffractionpeakscanalsobeseen,generatedfromZrO2astheimpurityintherawmaterials.However,withtheadditionofSiC(samplesZBSp–1,ZBSp–2,ZBSp–3ZBSp–4),theZrO2peakdisappears.Inaddition,SiCdiffractionpeaksarenotpresentintheXRDpatternsofthesampleswithlowervolumefractionsofSiC,andcanonlybefoundinthesampleZBSp–4.AprobablereasonistheeutecticreactionbetweenZrO2andSiO2onthesurfaceofSiCparticlestoformglassyphase.Ifthisisthecase,theadditionofSiCparticlesshouldimprovethedensificationbehaviorofZrB2ceramics.2.2sic&sic反應(yīng)Table1liststhevaluesofthedensityandmechanicalpropertiesoftheZrB2andZrB2/SiCpcomposites.ItcanbeseenthattherelativedensityoftheZrB2/SiCpcompositesincreaseswiththeincreaseoftheamountofSiC,andsampleZBSp–3reachesalmost100%relativedensity.ThisprovesthatincorporationofSiCparticlesintoZrB2promotesthedensification,whichagreeswiththeabovediscussion.ComparedwithmonolithicZrB2ceramics,thestrengthandtoughnessofZrB2/SiCpcompositesareimprovedwiththeadditionofSiCparticlesandat15%ofSiC,theyreachmaximumvaluesof646MPaand8.52MPa?m1/2,respectively.However,whentheamountofSiCexceeds15%,thebendingstrengthandfracturetoughnessshowadecreasingtrend,whichmaybecausedbySiCparticlesagglomerateandmuchglassyphaseformsatahigherloading.2.3sicincipteritysofteringsofteringsofteringsocsicsFractographsoftheZrB2/SiCpcompositeswithdifferentcontentofSiCparticlesareshowninFig.2.TwoeffectscanbeseenfromFig.2:(1)thesizeofZrB2grainsdecreaseswiththeincreaseofSiCaddition,whichimpliesthattheadditionofSiCinhibitsZrB2graingrowthand(2)themonolithicZrB2ceramicexhibitsaflatfracturesurface,whichshowsatransgranularfracturemodewhilethefracturesurfacesoftheZrB2/SiCpcompositesaremuchrougherthanthatofthemonolithicZrB2,andshowaconcave-convexappearance,whichindicatesthathefracturemodesoftheZrB2/SiCpcompositesarechangedtomixedtransgranularandintergranularmodesItisthesetwoeffectsthatresultintheimprovedstrengthandtoughnessoftheZrB2/SiCpcomposites.2.4tiphontresexWhenZrB2-basedceramicsareablatedinahightemperatureoxyacetyleneflame,theyareoxidizedandtheirmechanicalpropertiesaredegraded.Theresistancetooxidationandablationmaybeimprovedbyaddingsomesubstances.TheeffectofSiCparticlecontentonthestrengthoftheZrB2/SiCpcompositesafterablationisillustratedinFig.3,whichshowsthattheadditionofSiCparticlesobviouslyimprovestheresistancetooxidationandablation.WhenthecontentofSiCparticlesismorethan10%,thestrengthsoftheZrB2/SiCpcompositesafter3minablationdonotshowobviouschangecomparedwiththevaluesbeforeablation.WiththeincreaseofSiCparticles,theextentofstrengthdegradationbecomesdegressive.However,theablationtimeremarkablyinfluencesthefinalstrengthofthecomposites.Thelongertheablationtimeis,themoreserioustheextentofoxidationandablationtothecomposites,andthelowerthefinalresidualstrengthofthecompositesis.TheablatedsurfaceofmonolithicZrB2changestocompletelywhiteanddisplayspeelingandcracking,whiletheablatedsurfacesoftheZrB2/SiCpcompositesdonotshowobviouscolorchanges,peelingorcracking.Figure4showstheXRDpatternsoftheablatedsurfacesoftheZrB2/SiCpcomposites.ForthemonolithicZrB2sample,themainphaseism-ZrO2aswellasZrB2,whichistheoxidizedresultofZrB2.FortheZrB2/SiCpcomposites,ZrSiO4phasecanbefoundaswellasm-ZrO2phasewithincreasingSiCcontent.AthigherSiCcontents,onlyZrO2andZrSiO4phasescanbefoundintheXRDpatterns,whichindicatesthattheoxidizedsurfaceisdenseandplaysaroleinpreventingtheZrB2underthesub-surfacefrombeingoxidized.Besidesthesephases,thereshouldbesomeamorphousglassyoxidationphases,whichcouldnotbetestedbyXRD.Figure5showsthemorphologyandEDSanalysisofsampleZBSp–3.Figure5(a)showsthecross-sectionsurfaceofSampleZBSp–3after5minhightemperatureablation.ItcanbeseenthattheoxidizedlayeroftheZrB2/SiCpcompositesisabout30μm.ThemicrographinFig.5(b)showsaglassyandporousstructure.Figure5(c)showstheEDXspectrumoftheoxidizedsurface,whichindicatesthattheelementalcompositionoftheoxidizedlayerincludesSiaswellasZrandO.ItisobviousthattheincorporationofSiCintoZrB2materialcanformadenseoxidizedfilm,whichcaninhibitthediffusionofoxygenfromthesurfacetotheinteriorandprotectthematerialunderneathfromfurtheroxidation.ThereforetheconclusioncanbedrawnthattheadditionofSiCcanimprovetheresistancetoablation/oxidationofZrB2-basedceramics.3atingdengingsicperitysicperityssicperficicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicidized(1)ZrB2/SiCpceramicscanbesuccessfullypre