简介:Duetotheremarkablemagnetoresistance(MR)effectonperovskite-typemanganite,magnetoelectronicsandspintronicshavebecomeattractivesubjectsofexperimentalandtheoreticalinvestigationsfortheapplicationpurpose.(La0.9Nd0.1)2/3Ca1/3Mn1-xFexO3(x=0,x=0.05)werepreparedsuccessfullybysol-gelmethod.Thestructure,magneticproperties,andtransportpropertiesofthecompoundswereinvestigated.Themagnetoresistanceeffectdependsonthecompositionandthetemperature.XRDpatternsshowthatthecompoundisasinglephasepolycrystalwithpseudocubicstructure.Alargenegativeisotropicmagnetoresistanceeffectinthesampleswereobservedatlowtemperatureregion.ThemaximumMRofthesampleswas77%and97%,respectively.Itwasmostlikelyduetothescatteringorthetunnelingtransportofspin-polarizedcarriersinlatticeunderstrongmagneticfield.
简介:(Cu60Zr30Ti10)98Y2bulkmetallicglass(Φ4mm×70mm)wasobtainedsuccessfullybycoppermouldcoolingandspraying-casting,andsomesampleswereisothermallyannealedattemperaturesof473and623K,whichwaslowerthantheglasstransitiontemperature(Tg)for1h.Microstructureandpropertiesofas-castandannealedsampleswerestudied.Crystallizationphases(Cu10Zr7andCuZr)wereobservedinannealedsamples,andthespeciesandfractionofthesephasesincreasedwithincreasingannealingtemperature.Mic...
简介:Selectivecatalyticoxidation(SCO)ofammoniawascarriedoutoverCu-MncompoundscatalystsmodifiedwithtrivalentrareearthoxideCe2O3andLa2O3respectively.TiO2wasusedassupportanddifferentratioofO2weretestedinordertofindanappropriateO2concentration(vol.%),andtheresultsshowedthat1%O2(vol.%)waspropitioustoSCOofammonia.TheeffectsofthetworareearthoxidesmodifiedcatalystsCe2O3-Cu-Mn/TiO2andLa2O3-Cu-Mn/TiO2onthecatalyticactivityandselectivityofammoniaoxidationwereinvestigatedunderthereactionconditionof500ppmammonia,1%O2(vol.%),atthetemperaturefrom125to250oC.TheresultsrevealedthebeneficialroleofCe2O3andLa2O3incatalyticactivityatlowtemperatureandleanoxygenconcentration,whilethemodificationwithCe2O3andLa2O3ledtothenegativeinfluenceonN2selectivity.ForthecatalystsmodifiedwithCeshowedlowerNOandN2OselectivitythanthecatalystsmodifiedwithLa,thentheeffectsofdifferentCeloadingsoncatalyticactivityandselectivitywerealsoconsidered,incombinationwithcatalystspreparationmethods,whichincludeincipientwetimpregnation,sol-gelmethodandco-precipitation.Resultsrevealedthatthecatalystspreparedbysol-gelmethodobtainedpreferablecatalyticactivitycomparedwiththeothers,reaching99%ammoniaat200oC,whereas96%NOwasdetected.Italsoindicatedthatdifferentcatalystpreparationmethodsignificantlydeterminedproductiondistribution.
简介:一系列立方的稀土元素sesquioxidesRE2O3的拉曼系列(RE=Eu,Gd,Dy,惊讶,嗯,Tm,Yb,陆,Sc和Y)被拉曼光谱学与532和785根nm激光线调查。丰富的另外的乐队由于激光激动的光被观察。为Eu2O3,Dy2O3,Ho2O3,Er2O3,Tm2O3和Yb2O3,,光主要为Gd2O3,Lu2O3,Sc2O3和Y2O3来自内在的三价的lanthanide离子,他们的光被归因于象Eu3+,Nd3+和Er3+那样的另外的光lanthanide离子的踪迹杂质。这调查为检测踪迹作为一个有用工具证实了拉曼光谱学光lanthanide杂质。
简介:ThephaseandmorphologytransformationduringthehydrothermaltreatingprocessofY2O3wasevaluatedwithX-raydiffcrcnce(XRD),scanningelectronmicroscopy(SEM),transmissionelectronmicroscopy(TEM),particlesizeandspecificsurfaceareadetermination.TheresultsshowedthatthecubicY2O3didnottransferintohexagonalY(OH)3inpurewater.Therefore,purehexagonalY(OH)3withnanotubeandmicrorodmorphologieswereobtainedbyhydrothermaltreatingY2O3at150℃for12hin15mlof2mol/LNaOHsolutionwithandwith-outPVAorPEGItwassuggestedthatthecharacteristicpreferentialgrowthofY(OH)3wasattributedtothestructureanisotropyofhexahedronY(OH)3.TheadditionofPVAorPEGcouldpromotetheformingprocessofnanotubesbyselectiveadsorptionondifferentcrystalplanes,whichalteredthegrowthratealongdifferentdirectionsandresultedinthediffusionlimitofconstructingionsinthecentertopofrods.Finally,Y(OH)3:EuandY2O3:Eunanotubeswerealsosynthesizedbyusingthismethod,andtheirphotoluminescencepropertieswereevaluated.
简介:MeltspinningtechnologywasusedtopreparetheMg2Ni-type(Mg24Ni10Cu2)100–xNdx(x=0,5,10,15,20)alloysinordertoobtainananocrystallineandamorphousstructure.TheeffectsofNdcontentandspinningrateonthestructuresandelectrochemicalhydrogenstorageperformancesofthealloyswereinvestigated.ThestructurecharacterizationsofX-raydiffraction(XRD),transmissionelectronmicroscopy(TEM)andscanningelectronmicroscopy(SEM)linkedwithenergydispersivespectroscopy(EDS)revealedthattheas-spunNd-freealloydisplayedanentirenanocrystallinestructure,whereastheas-spunNd-addedalloysheldananocrystallineandamorphousstructureandthedegreeofamorphizationvisiblyincreasedwiththerisingofNdcontentandspinningrate,suggestingthattheadditionofNdfacilitatedtheglassformingoftheMg2Ni-typealloy.TheelectrochemicalmeasurementsindicatedthattheadditionofNdandmeltspinningimprovedtheelectrochemicalhydrogenstorageperformancesofthealloyssignificantly.Thedischargecapacitiesoftheas-castandspunalloysexhibitedmaximumvalueswhenNdcontentwasx=10,whichwere86.4,200.5,266.3,402.5and452.8mAh/gcorrespondingtothespinningrateof0(As-castwasdefinedasthespinningrateof0m/s),10,20,30and40m/s,respectively.Thecyclestability(S20,thecapacitymaintainrateat20thcycle)oftheas-castalloyalwaysrosewiththeincreasingofNdcontent,andthoseoftheas-spunalloysexhibitedthemaximumvaluesforNdcontentx=10,whichwere77.9%,83.4%89.2%and89.7%,correspondingtothespinningrateof10,20,30and40m/s,respectively.