简介:NominalcompositionofCa1-xZnxTiO3:0.002Pr3+(x=0.000~0.200)phosphorswerepreparedbyconventionalsolidreactionroute.XRDandPLmeasurementswereusedtoinvestigatethesolid-solutionstructureandluminescencepropertiesofZn-dopedCa1-xZnxTiO3:0.002Pr3+phosphors.Theeffectofsolid-solutionstructureformedbysubstitutionbetweenCa2+andZn2+ionsontheluminescentpropertieswasanalyzed.Theresultsrevealthat,withtheincreaseofZnsubstitutioncontentbelow0.010,latticeparametersandtheintensityofexcitationpeakatboth260and330nmaswellasthecorresponding610nmemissionintensityaremonotonouslydecreasedquicklyinasimilartendency.Also,theevolutionofluminescenceintensityandcrystalcellparametersagainstZndopingconcentrationareingoodagreement.AboveresultsarecloselyrelatedwiththestructurechangewithinCa1-xZnxTiO3:0.002Pr3+solid-solutionphaseformedbytheZnionssubstitutionfortheCasites.Presentstudyrevealsthatthesolid-solutionstructureformedbysubstitutionbetweenCa2+andZn2+ionshassignificanteffectontheluminescencepropertiesofsinglephaseCa1-xZnxTiO3:0.002Pr3+phosphors.
简介:以V、Al和C粉末为原料,采用燃烧反应合成技术制备V2AlC材料,比较了2种燃烧合成方式,即热爆合成与自蔓延高温合成工艺对反应合成V2AlC的影响。对V-Al-C体系进行热力学分析,利用X射线衍射和扫描电镜对合成产物进行物相组成和产物形貌分析,探讨反应合成V2AlC材料的反应机制。研究结果表明,2V/Al/C粉体热爆合成产物的主相为V2AlC和少量的VCx和AlV3。2V/Al/C的热爆产物中V2AlC晶粒呈板条状形貌,长度约为10μm。原料中添加过量的Al,可消除AlV3副产物,并可显著促进V2AlC的合成,但不会形成单相V2AlC。添加适量的Sn可促进单相V2AlC的合成。2V/Al/C粉体自蔓延高温合成的产物的主相为V2AlC,少量为VC0.75。原料中添加过量的Al,可促进V2AlC单相反应合成。2V-Al-C体系的绝热燃烧温度达2767K。并提出反应合成V2AlC的反应机制,即VC与V-Al液相反应合成板条状晶粒的V2AlC材料。
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简介:微观结构和当演员组Mg-4.0Sm-1.0Ca合金的机械性质在由热挤出组成的thermomechanical处理期间被调查,滚动,并且在473K变老。Mg41Sm5阶段包含Ca和像针的Mg2在Mg矩阵形成的Ca阶段,和平均谷物尺寸和延伸是4.2m并且27%,分别地在热挤出以后,它在韧性暗示了增加。在滚动以后,另外,谷物尺寸进一步被精制,并且张力的力量增加了到293MPa。一新猛抛Mg3Sm在山峰Mg-4.0Sm-1.0Ca合金被发现,这合金显示了最好的机械性质,与83HV的山峰坚硬和313MPa的最终的张力的力量;这些性质被归因于谷物精炼加强,加强的稳固的答案,变硬的工作,并且降水加强。
简介:AsystematicinvestigationofthemagneticandtransportpropertiesofTidopedLa0.67Ca0.33MnO3wasreported.TheTisubstitutionforMnionsresultsinareductioninferromagnetismandconductivity.Themetal-insulatortransitiontemperatureisclosetoCurietemperaturewhichdecreasesfrom274to82Kasxincreasesfrom0to0.17.ThemostimportanteffectofTidopingistointroducespinclustersinthesamplesduetothedistortionoflocallatticeandtheinhomogeneousmagneticstructureinducedprimarilybytherandomdistributionofMnions.Amaximummagnetoresistanceratioaslargeas90%in1Tat122Kwasobtainedforthesamplewithx=0.055,whichisfourtimeslargerthanthatobtainedforLCMOsampleat272K.Thereisaremarkablefield-historydependentMRinthecoolingprocessforthedopedsampleswhilesuchphenomenondisappearsinthewarmingrun.Theresistivityfollowswellthevariablerangehoppingbehaviorinparamagneticstate.Boththesizeeffectandspindependenthoppingofcarriersbetweenthespinclustersshouldbeconsideredinthissystem.