简介:采用自蔓延高温合成技术(SHS)制备固体氧化物燃料电池(SOFC)阴极材料La1-xSrxMnO3(LSM);研究成形压力、稀释剂添加量等参数对反应过程及合成产物性能的影响;采用XRD、ICP研究SHS法合成LSM的物相和晶型结构.结果表明:自蔓延高温合成产物为钙钛矿结构菱方晶系La1-xSrxMnO3,Sr含量的变化引起合成产物特征峰的位置和半峰宽变化;随着Sr含量的增加,合成的LSM粉末粒度变细,晶格常数a和c减小.
简介:TherepresentativesampleLa0.58Dy0.09Ca0.33MnO3ofDydopedLa0.67Ca0.33MnO3rare-earthmanganiteswasinvestigated.ThemostimportanteffectofDydopingistointroducethemagnetoimpurityandformthespinclusterswhichinducedramaticallylargeCMRinLa0.58Dy0.09Ca0.33MnO3.Thefittingresultsoffield-inducedresistivitydecreasetotheBrillouinfunctionindicatethattheCMRiscausedbythespindependenthoppingbetweenspinclusters.Itisthemagneticfieldthatreducesthesizeofspinclustersandinducesafield-inducedirreversibleCMRbehaviour.
简介:作者研究了帕特里克·莫迪阿诺(1945—)的头六部小说。在这些小说中,“人的自我”这一主题萦绕着作家的脑际,他从犹太人在第二次世界大战期间的社会地位问题入手探讨人的自我,暗含地触及到六八年五月风暴后一代青年入的自我问题。“在我们这一怪诞的时代”,战争威胁和警察的淫威形成一股熵的力量,它把人的自我撕成碎片,使人失去尊严。失去身份的人一无所有,“无”是小说主题网中的一个常量,“无”只有和“有”相对立才有其意义,“无”和“有”是一对二律背反的矛盾,这种二元性现象散发在整个小说世界中,具体表现为自我的进退两难,主题的两重对立,空间地形的两分对立,和时间的往复运动。因此,二元性乃是小说结构的组织原则。失去自我的人都是些无国藉者,落魄者和生活在社会边缘者。他们四处漂泊,寻找自己的祖国,父亲和逝去的往昔,企图重组他们的自我,但“竹蓝舀水一场空”,等待他们的是种种失败和失望。在莫迪阿诺看来,只有通过写作,才能重建一个人的一生,使他的往昔经历失而复得。
简介:FluorescenceandcofluorescencepropertiesofTb(Ⅲ)solidcomplexeswerestudiedusingpyromelliticacid(PMA)asligandandfluorescenceinertionsasdopingelements.Thecofluorescenceenhancement,aresultofligandsensitizedfluorescence,wasobservedinTb(Ⅲ)solidcomplexesdopedwithfluorescentinertionsLa(Ⅲ),Gd(Ⅲ),Ca(Ⅲ),andSr(Ⅲ).Theeffectofthetypeandcontentofdopingelementsonfluorescenceenhancementwasstudied,andoptimumconditionsweredetermined.TheresultsshowthatGd(La,Ca,Sr)hasclearcofluorescenceeffectinsolidcomplexTb-M-PMAsystem,andinpresentwork,rareearthcomplexfluorescentpowderthatemitsbrightgreenfluorescenceatultravioletexcitationwasobtained,whichhadpotentialapplicationasfluorescentanti-counterfeitink.
简介:InvestigationhasbeencarriedouttofindtheeffectsofNdsubstitutionandCuadditiononthehydrogenstoragepropertiesofAB5-typealloywithamulticomponentLa0.6M0.4Ni4.8Mn0.2(M=Y,Nd)system.La0.6Y0.4Ni4.8Mn0.2,whichwasusedinanair-conditioningsystem,showedpoorhysteresisandslopingcharacteristics,whichledtoadecreaseconcerningthecoefficientofperformanceofthesystem.BythesubstitutionofNdforY,thehydrogenstoragecapacityincreased,andtheplateaupressuredecreasedalittle,butthehydrogenabsorptionkineticsdecreaseddramatically.CuadditioncaneffectivelyimprovethekineticsofhydrideformationwithoutchangingthehydrogenstoragecapacityofLa0.6Nd0.4Ni4.8Mn0.2.IthasbeenfoundthatLa0.6Nd0.4Ni4.8Mn0.2Cu0.1alloyshowedgoodhydrogenstoragecharacteristicsformetalhydrideair-conditioningsystem.Theresultsshowedthat,foreachcomponentofLa0.6Mo.4Ni4.8Mn0.2,theeffectivehydrogenstoragecapacityincreasedwithdecreaseoftheunitcellparameterc/aandthehydrogenabsorptionplateaupressureincreasedwithdecreaseoftheparametera.
简介:ThetemperaturedependenceofresistivityρofYSZdopingcompositeof(1-x)La0.67Ca0.33MnO3+xYSZandY2O3dopingcompositeof(1-y)La0.67MnO3+yY2O3isinvestigated,respectively,inatemperaturerange77-300K,wheretheYSZrepresentsyttria-stabilizedzirconia(8mol%Y2O3+92mol%ZrO2).ExperimentalresultsshowthattheYSZdopinglevelhasimportanteffectsonboththemetal-insulator(M-I)transitiontemperaturesandzerofieldresistivityofthecompositesof(1-x)La0.67Ca0.33MnO3+xYSZ.However,theY2O3dopinglevelhaslittleeffectontheM-Itransitiontemperaturesandthezerofieldresistivityof(1-y)La0.67Ca0.33MnO3+yY2O3onlyincreasesslightly.Thedifferencebetweenthetwotypesofcompositesmaymainlyresultsfromthedifferentdistributionofhighresistancephasesatthegrainboundariesand/orsurfacesofLa0.67Ca0.33MnO3grainsratherthanthesubstitutionofLa^3+ionswithY^3+ions.
简介:AsystematicinvestigationofthemagneticandtransportpropertiesofTidopedLa0.67Ca0.33MnO3wasreported.TheTisubstitutionforMnionsresultsinareductioninferromagnetismandconductivity.Themetal-insulatortransitiontemperatureisclosetoCurietemperaturewhichdecreasesfrom274to82Kasxincreasesfrom0to0.17.ThemostimportanteffectofTidopingistointroducespinclustersinthesamplesduetothedistortionoflocallatticeandtheinhomogeneousmagneticstructureinducedprimarilybytherandomdistributionofMnions.Amaximummagnetoresistanceratioaslargeas90%in1Tat122Kwasobtainedforthesamplewithx=0.055,whichisfourtimeslargerthanthatobtainedforLCMOsampleat272K.Thereisaremarkablefield-historydependentMRinthecoolingprocessforthedopedsampleswhilesuchphenomenondisappearsinthewarmingrun.Theresistivityfollowswellthevariablerangehoppingbehaviorinparamagneticstate.Boththesizeeffectandspindependenthoppingofcarriersbetweenthespinclustersshouldbeconsideredinthissystem.
简介:三新奇Ba_5RNiNb_9O_(30)(R=La,Nd和Sm)陶艺在BaO-R_2O_3-NiO-Nb_2O_5系统被准备并且描绘。所有三混合物areparaelectjicphasesadopting。在房间温度的充满的四角形的钨铜(TB)结构。在1MHz,Ba_5RNiNb_9O_(30)陶艺有高电介质在范围193-245.3,在范围0.0059-0.0087的低绝缘的损失,和在范围的绝缘的常数(tau_e)的温度系数的常数-1140-1310X10~(-6)中心点degC。他们绝缘的常数的温度系数显著地Ba_5RNiNb_9O_(30)与那些相比被减少(R=La,Nd,Sm)陶艺。
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简介:La1.5Mg17Ni0.5hydrogenstoragematerialswerepreparedbyhydridingcombustionsynthesis(HCS)andmechanicalalloying(MA)methodrespectively.TheexperimentalresultsshowthatthehydrogenabsorptionpropertiesofLa1.5Mg17Nio.5preparedbyMAarebetterthanthatbyHCS.La1.5Mg17Nio.5preparedbyMAcanabsorb6.73mass%hydrogenat523Kwithin1min,and4.92mass%hydrogenat423K.TheimprovementofhydridingpropertiesofLa1.5Mg17Ni0.5alloypreparedbyMAcanbeascribedtotheformationofnano-crystallineanddefectsduringthemechanicalalloying.
简介:利用电子衍射,X射线衍射和荧光光谱等方法研究了LnBaB0O16(Ln=La,Y)的结构特性,LnBaB9O16为单斜晶系,其中LaBaB9O16的晶胞参数a=1.3660nm,b=0.7882nm,c=1.6253nm,β=106.15°,YBaB9O16的晶胞参数a=1.3476nm,b=0.776nm,c=1.6040nm,β=106.38°,荧光光谱研究表明,这两种化合物结构不同,Y^3+在YBaB9O16结构中处于中心对称格位,而LaBaB9O16中La^3+的格位则无中心对称性,Gd^3+部分取代LaBaB9O16:Eu^3+中的La^3+可改善Eu^3+离子的发光性质,LaBaB9O16:Eu^3+在真空紫外区的吸收比较弱,这可能与硼氧比较小有关。