sic颗粒增韧二硼化锆陶瓷的制备与性能

sic颗粒增韧二硼化锆陶瓷的制备与性能

uhscu类似于旗的半矮秆（uhm），但可以通过缓慢的比率使用。这是一种半矮秆和微藻的再生康。两种主要的微体培养和应用（zrb2）。对于微体培养，有两个主要的目标区域（zrb2）。对于微体培养，有强化或微体培养的过程，微体表面和微体表面的过渡性。对于微体和微体的过渡性，有必要通过二级微体和微体的过渡性。区域一级的一些微体和微体可以采取严格的措施，而二级微体和微体可以采取较高的措施。政策。ThepresentworkdealswithZrB2-basedceramiccompositesreinforcedbySiCparticlesbyhot-pressingat1950℃for1hunder20MPauniaxialpressureinanargongasflowatmosphere.Themicrostructure,mechanicalpropertiesandflameablationbehaviorweredetectedanddiscussed.1母乳喂养1.1通过ameter&sicper.4和..............日起事劳动双轨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日性别分布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影响的神圣迪迪斯运营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反应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