《氮化硅陶瓷概述》PPT课件

《《氮化硅陶瓷概述》PPT课件》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、OverviewofsiliconnitrideceramicsName:000001Major:ChemicaltechnologyContents1、Propertiesofsiliconnitride2、Crystalstructures3、Synthesismethods4、Sinteringmethods5、ActualapplicationPropertiesofsiliconnitrideSi3N4isoneofthemostimportantstructureceramicsbecauseitpossessesacombinationofadvancedpro

2、perties.Suchas:HoweverthefracturebehaviourofSi3N4ceramicisconsideredtobethemajorobstacleforitswideruseasastructuralmaterial.PropertiesofSi3N4ceramicsGoodwearFlexuralstrengthCorrosiveresistanceCreepresistanceFractureresistanceHighhardnessThermalshockresistancePropertiesofSi3N4ceramicsCrystal

3、structuresofSi3N4ceramicsSiliconnitrideexistsintwomajorcrystallineforms:α-andβ-phase.（fig.1）Bothphaseshaveahexagonalcrystalstructure.α-Si3N4isthelowtemperaturemodificationandβ-Si3N4isthehightemperaturemodification.（fig.2）Morethan1400-1800℃αphasetransformintoβphase.CrystalstructuresofSi3N4ce

4、ramicsFig.1:Crystalstructuresofaα-Si3N4andbβ-Si3N4a=7.7541(4)Åc=5.6217(4)Åa=7.6044(2)Åc=2.9075(1)ÅFig.2XRDpatternsofthesamplessinteredatdifferenttemperatureholdingfor60minSynthesismethodsofSi3N4ceramics1、Carbothermicprocess2、Siliconpowderdirectnitridationmethod3、Self-propagatinghightemperat

5、uresynthesismethod(SHS)4、ChemicalVaporDeposition（CVD）SinteringmethodsHot–isostatic-pressing(HIP)pressure-lesssintering(PLS)Hot–pressing(HP)Reactionsintering(RS)Sinteringaids(烧结添加剂）Si3N4isoneofthetypicalcovalentbondedsolids.It’sself-diffusioncoefficientsisverylow.Sinteringaidsarealwaysneeded

6、tobringdownthegrainboundaryofSi3N4andtoincreasediffusivity.Reducethesinteringtemperature,pressureandsinteringtime.MgO、Y2O3、Al2O3ActualapplicationOneoftheearliestusesofSi3N4wasintheSi3N4-bondedrefractorybrickforblastfurnacesinthe1950.OwingtothebrittlenatureofSi3N4,overtheyears,therehasbeenac

7、ontinuousinterestinexploringavarietyofapproachesforenhancingitsfracturetoughnessandreliability.ThankstoadvancedpropertiesoftheSi3N4,ithasbeenwidelyusedinmanyfields,forexample:Metallurgyindustry,Metalcutting,Constructionofmotors,Nuclearfusionreactors,Semi