简介:Asoneofcandidatesforthefuelcladdingorstructurematerialusedinfourthgenerationfissionandfusiondemonstratereactor,MAXphasehasthepropertiesofbothceramicandmetal,suchashighmeltingpoint,hightemperaturestability,gooderosionresistanceandradiation-damagetolerance[1;2].Maxphaseisaseriesofceramicsofnanolamellarandhexagonalstructure.Mrepresentstransitionelement.Arepresentsthethirdorfourthmaingroupelement.XrepresentNandC.Inthedesignoflead-cooledfastreactor,itisrequiredthatthematerialshouldendurethecorrosionofliquidPb-Bialloy.Therefore,understandingoftheoxidelayersandtheirgrowthmechanismsinLBEisfundamentallyimportantforthedevelopmentofcandidatematerials.
简介:TheelectronicpropertiesandtopologicalphasesofThXY(X=Pb,Au,Pt,PdandY=Sb,Bi,Sn)compoundsinthepresenceofspin–orbitcoupling,usingdensityfunctionaltheoryareinvestigated.TheThPtSncompoundisstableintheferromagneticphaseandtheotherThXYcompoundsarestableinnonmagneticphases.Bandstructuresofthesecompoundsintopologicalphases(insulatorormetal)andnormalphaseswithingeneralizedgradientapproximation(GGA)andEngel–Voskogeneralizedgradientapproximation(GGAEV)arecompared.TheThPtSn,ThPtBi,ThPtSb,ThPdBi,andThAuBicompoundshavetopologicalphasesandtheotherThXYcompoundshavenormalphases.Bandinversionstrengthsandtopologicalphasesofthesecompoundsatdifferentpressurearestudied.Itisseenthatthebandinversionstrengthsofthesecompoundsaresensitivetopressureandforeachcompoundasecond-orderpolynomialfittedonthebandinversionstrengths–pressurecurves.
简介:Usingfirst-principlescalculations,wesystematicallystudythedissociationsofO2moleculesondifferentultrathinPb(111)films.AccordingtoourpreviousworkrevealingthemolecularadsorptionprecursorstatesforO2,wefurtherexplorewhytherearetwonearlydegenerateadsorptionstatesonPb(111)ultrathinfilms,butnoprecursoradsorptionstatesexistingatallonMg(0001)andAl(111)surfaces.Thereasonisconcludedtobethedifferentsurfaceelectronicstructures.FortheO2dissociation,weconsiderboththereactionchannelsfromgas-likeandmolecularlyadsorbedO2molecules.WefindthattheenergybarrierforO2dissociationfromthemolecularadsorptionprecursorstatesisalwayssmallerthanthatfromO2gas.ThemostenergeticallyfavorabledissociationprocessisfoundtobethesameondifferentPb(111)films,andtheenergybarriersarefoundtobeinfluencedbythequantumsizeeffectsofPb(111)films.
简介:Theelectronicstructures,dielectricfunctions,complexrefractiveindicesandabsorptionspectraforaperfectPbW04(PWO)crystalandthePWOcrystalscontainingleadvacancyV^2-pbhavebeencalculatedusingafull-potential(linearized)augmentedplane-wave(LAPW)+localorbitals(LO)methodwiththelatticestructureoptimized.Thepeaksoftheabsorptionspectracorrespondingtotheelectronictransitionshavebeenstudied.
简介:建立了非线性热力学模型,定性分析了外加应力和外加温度对外延生长在正交基底上的Pb(Zr1-xTix)O3(PZT)薄膜相变的影响。在外力场下,固定其中一个方向失配应变e1=0.005,模拟得到了不同组分的PZT薄膜的失配应变一外加应力的相图。研究发现,随着Ti组分的减少,出现了新相正交a1c相和四方相a1相,且新相区域也会随Ti组分的不同而变化。在外加拉应力下,c相是薄膜较易出现的相,而在外加压应力下薄膜易处于a1a2相。在不同温度场下,模拟非等轴失配应变的PZT薄膜得到不同组分的PZT薄膜的失配应变一外加温度相图。当组分x≤0.7时,相图中出现了正交a1c相,由于非等轴失配应变的存在,使得从顺电相向r相发生相变的过程中,多出了正交a1a2相;同时另一新的四方a1相也出现在沿失配应变正方向e2被拉伸的区域。随着Ti组分的增加,单斜r相的面积缩小且位置下移。之前存在的四相点也变为了三相点,而正交相a1a2相则向相图的中心位置移动。模拟结果对研究外场下铁电薄膜微器件的性能变化具有一定的指导意义。
简介:Basedonloadseparationtheory,theloadseparationparameterSpbmethodisaneffectiveapproachforestimatingtheJ-resistancecurvefromrecordsofloadversusdisplacementdirectly,usingonesharpcrackedspecimenandanadditionalreferencebluntcrackedspecimen.However,theeffectofthereferencebluntcrackedspecimenonJ-resistancedeterminationwasnotexplicitlyconsideredinpastwork.Inthispaper,amodifiedloadseparationparameterSpbmethodwasdevelopedtoeliminatethiseffect,andthenauniqueestimationofinstantaneouscracklengthforonesharpcrackedspecimencouldbeobtained.Furthermore,aforcedbluntingcalibrationmethodwasalsoadoptedtodeterminetheinstantaneouscracklengthintheloadinseparableregion,referringtoanormalizationmethod.ExperimentsonsteamturbinerotatorsteelCr2Ni2MoVwerecarriedouttoestimateJ-resistancecurvesusinganunloadingcompliancemethod.Byremovingunloadandreloaddatafromload-displacementrecords,theJ-resistancecurveforthesamesharpcrackedspecimenwasestimatedusingthemodifiedseparationparameterSpbmethod.TheresultsindicatethatthemodifiedSpbmethodcompletelyeliminatestheeffectofthereferencebluntcrackedspecimenontheinstantaneouscracklengthdeterminationofthesharpcrackedspecimen.However,differentJ-resistancecurvesinasmallrangeofcrackextensionarepresentwhendifferentbluntingcoefficientsareusedinthebluntinglineequation.TheJ-resistancecurveobtainedfromthemodifiedSpbmethodagreeswellwiththatobtainedfromthecompliancemethod.
简介:Temperature-dependentphotoluminescencecharacteristicsoforganic-inorganichalideperovskiteCH3NH3PbI3-xClxfilmspreparedusingatwo-stepmethodonZnO/FTOsubstrateswereinvestigated.Surfacemorphologyandabsorptioncharacteristicsofthefilmswerealsostudied.Scanningelectronmicroscopyrevealedlargecrystalsandsubstratecoverage.Theorthorhombic-to-tetragonalphasetransitiontemperaturewas140K.Thefilms’excitonbindingenergywas77.6±10.9meVandtheenergyofopticalphononswas38.8±2.5meV.TheseresultssuggestthatperovskiteCH3NH3PbI3-xClxfilmshaveexcellentoptoelectroniccharacteristicswhichfurthersuggeststheirpotentialusageinperovskitebasedoptoelectronicdevices.