cvd+sic涂层缺陷控制与csic复合材料氧化行为研究

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1、西北工业大学硕士学位论文吴守军AbstractContinuouscarbonfiberreinforcedsiliconcarbideceramicmatrixcomposites(C/SiC)areconsideredasthemostpromisingthermalstructuralcandidatematerialsforaerospace,energyandnucleartechnologiesetc.Asakeytechnologyforimprovinghigh-temperaturestructuralapplicationsoft

2、hematerials,oxidationprotectionwithanti-oxidationcoatingsystemhadbeingpaidmoreandmoreatentions.AndCVDSiChasbeenwildlyusedactasoxidationprotectioncoatingsmaterials.Buttherewerelitleatentionspaidforcoatingsdefectscontrol.Groundontheknowledgeoftheformmechanismsofthecoatingdefects,

3、theresearchworkproposedsomethoughtsrelatedtopreparation/depositionprocesstocontrolthecoatingdefects.Basedonobservationofmicro-morphologiesofthecoatings,combinedwithrelativeweightchangeinoxidation,theefectsofthesemodificationsoncoatingdefectscontrolandthebehaviorsof2DC/SiCatcons

4、tanttemperaturesinairconditionwereinvestigated.Themaincontentsandconclusionsareasfollows:1.Thebehaviorsof2Dand3DC/SiCbothprotectedbyanormalmulti-layerCVDSiCcoatingsatconstanttemperatureinairconditionwereinvestigated.Bothmaterialsshowedanidenticaloxidationkineticsbehavior.2.Efec

5、tsofdiferentcoatingmodificationprocessoncoatingsdefectscontrolandoxidationbehaviorsofC/SiCwerestudied.Themainresultsare:grindingisfavorabletoimprovesurfacesmoothdegree,whilenitridedandslowdepositionmakesSiCgranulesfine;Thewidthofcoatingsgapincreasedinorderofgrinding,nitridedand

6、vacuumheattreatment,butgapdefectsinmultilayercoatingscouldberemovedbyslowdeposition;Temperatureofmaximumweightlosscouldbedecreaseto600`Cbygrinding,vacuumheattreatmentorslowdeposition,butitwillincreasedto8000Cafternitrided;Oxidationkineticscurvesallvariedwiththecoatingmodificati

7、ons.3.ThegapdefectsinmultilayerCVDSiCcoatingscouldbeefectively西北工业大学硕士学位论文吴守军controlledbymeansofslowdepositioninlow-pressurechemicalvapordeposition(LPCVD).2DC/SiCcompositeswithamulti-layerCVDSiCcoatingpreparedbyslowLPCVDshowedweightgainat13000Cinaircondition.4.ProductsonCVDSiCa

8、fteroxidationwereinvestigatedusingXRD.Crystallizationw