简介:Atomized,pre-alloyedTi—24Nb—4Zr—7.9Sn(wt%)powderwasusedtofabricatesolid,prototypecomponentsbyelectronbeammelting(EBM).Vickersmicroindentationhardnessvalueswereobservedtoaverage2GPafortheprecursorpowderand2.5GPaforthesolid,EBM-fabricatedproducts.Thepowderandsolidproductmicrostructureswereexaminedbyopticalandelectronmicroscopy.X-raydiffractionanalysesshowedthattheyhadbccβ-phasemicrostructure.However,itwasfoundbytransmissionelectronmicroscopythattheEBM-fabricatedproducthadplatemorphologywithspace~100—200nm.Althoughthecorrespondingselectedareadiffractionpatternscanbeindexedbyβ-phaseplusα'-martensitewithorthorhombiccrystalstructure,thedark-fieldanalysesfailedtoobservethea'-martensite.Suchphenomenonwasalsofoundindeformedgummetalsandexplainedbystress-induceddiffusionscatteringduetophononsoftening.
简介:采用机械球磨技术制备了MgH2-10%Al2O3(质量分数)储氢复合体系,通过XRD、SEM、DSC-TG等检测手段考查了微量Al2O3陶瓷颗粒掺杂对MgH2体系组织结构及解氢性能的影响,并对其相关机理进行了分析.结果表明:机械球磨可有效细化MgH2颗粒;在微量Al2O3陶瓷颗粒与机械球磨的协同作用下,MgH2颗粒的细化效果更为显著;相对于纯MgH2球磨体系而言,微量Al2O3的掺杂有效降低了MgH2体系的解氢温度(降低近50℃),且其解氢速率也有所提高;MgH2-Al2O3储氢复合体系解氢性能的改善主要源于Al2O3陶瓷颗粒对MgH2体系的组织细化效应.
简介:采用溶胶-凝胶(Sol-gel)法和旋涂法在单晶硅片表面制备了5%(摩尔分数)Er3+掺杂的Yb2Ti2O7薄膜.采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对薄膜的相结构和表面及截面形貌进行了表征,通过荧光光谱仪检测了薄膜的上转换发光特性.结果表明:Ep+掺杂的Yb2Ti2O7薄膜为单一面心立方Yb2Ti2O7相结构,薄膜表面较光滑平整,颗粒尺寸约为80nm.976nm半导体激光器(LD)激发Er3+掺杂的Yb2Ti2O7薄膜获得了较强的绿色、红色和红外上转换发光,分别对应于Er3+的2H11/2/4S3/2→4I15/2、4F9/2→4I15/2和4S3/2→4I13/2跃迁.Er3+掺杂Yb2Ti2O7薄膜的绿色和红色上转换发光均为双光子吸收过程.Er3+掺杂Yb2Ti2O7薄膜和粉末的上转换发光光谱还出现了绿色和红色上转换发光强度的变化.
简介:TheeffectoftitaniumadditiononthemicrostructureandmechanicalpropertiesofbrassCu40Znhasbeenstudiedviathepowdermetallurgy(P/M)route.Thewater-atomizedCu40Zn—1.0wt%Tialloypowderwasconsolidatedatdifferenttemperaturesintherangeof400—600℃usingsparkplasmasintering(SPS)andhotextrusionsubsequently.Resultsshowthatthesuper-saturatedsolidsolutiontitaniumelementinrapidlycooledbrassCu40Znpowdercreatedhighchemicalpotentialforaprecipitatereaction,showingsignificantgrainrefinementeffectsontheconsolidatedCu40Znmatrix.Consequently,excellentmechanicalpropertieswereobtainedbyprecipitationhardeningandworkhardeningaftersinteringandextrusion,withyieldstrengthof390MPa,ultimatetensilestrengthof617MPa,andVickersmicro-hardnessof192HV,whichare28.7%,23.4%,and23.9%highervaluesthanthoseofextrudedCu40Znbrass,respectively.
简介:Inthisstudy,theeffectofmulti-walledcarbonnanotubes(MWCNTs)additiveonthedehydridingpropertiesoftheZn(BH4)2/NaCIcompositepreparedbyhighenergyballmillingwereinvestigated.X-raydiffraction(XRD),Fouriertransforminfraredspectroscopy(FTIR)resultsdemonstratedthatZn(BH4)2wasproducedfrommechanochemicalreactionbetweenZnCI2andNaBH4.Comparedwiththeundopedsample,10wt%MWCNTseffectivelyloweredthedecompositiontemperatureofZn(BH4)2by15℃.Thecomplexreleased3.6wt%hydrogenwithin250sat100℃andtotallyreleased4.5wt%hydrogenwithin2500s,indicatingithasaconsiderablepotentialasahydrogenstoragematerial.
简介:Inthisstudy,Almatrixcompositesreinforcedby7.5and15vol.%B4CparticlesandalsomonolithicAl(AlwithouttheB4Cparticles)wereproducedbywetattritionmillingandsubsequenthotforwardextrusionprocesses.Themicrostructureofthecomposites,evaluatedbyscanningelectronmicroscopy(SEM),showedthattheB4CparticleswereproperlydistributedintheAlmatrix.MechanicalpropertiesoftheAI/B4CcompositesandmonolithicAlwereinvestigatedbytensile,wearandhardnesstests.TheresultsrevealedthatwithincreasingcontentofB4Cparticles,thetensilestrengthandmicrohardnessofcompositesincreasedbuttheelongationdecreased.Inaddition,thetensilestrengthandmicrohardnessofcompositesampleswerehigherthanthoseofmonolithicAl.ThedensitymeasurementsrevealedthatthedensityofcompositesdecreasedwithincreasingcontentoftheB4Cparticles.