简介:ThetransportpropertieswerestudiedforrareearthmanganeseoxideLa0.67Cao.33Mn1-xFexO3(x=0-O.3)systems.ItisfoundthatwithincreasingFe^3+-dopingcontentx,theresistanceincreasesandtheinsulator-metaltransitiontemperature(T1M)shiftstolowertemperature.Ifthedopingcontentissmall,thetransportpropertiesmanifestmetalliccharacteristicsinthetemperaturerangeofT<T1M,whiletheywillobeyathermalactivationmodelinthetemperaturerangeofT>T1M.SuchabehaviormaybeattributedtotheFe^3+-dopingandpossibleMnionsscatteringtoelectrons.TheFe^3+dopingmayleadtotheformationofFe^3+-O^2--Mn^4+channels,whichcouldterminatethedoubleexchangeMn^3+-O^2--Mn^4+channels.TheantiferromagneticclustersofFeionsmayinducetheMnionstoscettertotheelectrons.
简介:InordertoimprovethehydrogenationanddehydrogenationperformancesoftheMg2Ni-typealloys,MgwaspartiallysubstitutedbyLainthealloy,andmeltspinningtechnologywasusedforthepreparationoftheMg20-xLaxNi10(x=0,2,4,6)hydrogenstoragealloys.ThestructuresofthealloyswerestudiedbyX-raydiffraction(XRD),scanningelectronmicroscopy(SEM)andhigh-resolutiontransmissionelectronmicroscopy(HRTEM).Itwasfoundthatnoamorphousphaseformedintheas-spunLa-freealloy,buttheas-spunalloyscontainingLaheldamajoramorphousphase.WhenLacontentx≤2,themajorphaseintheas-castalloyswasMg2Niphase,butwithfurtherincreaseofLacontent,themajorphaseoftheas-castalloyschangedintoLaNi5+LaMg3phase.Thermalstabilityoftheas-spunalloyswasstudiedbydifferentialscanningcalorimetry(DSC),showingthatspinningratewasanegligiblefactoronthecrystallizationtemperatureoftheamorphousphase.Thehydrogenabsorptionanddesorptionkineticsoftheas-castandas-spunalloysweremeasuredusinganautomaticallycontrolledSievertsapparatus,confirmingthatthehydrogenabsorptionanddesorptioncapacitiesandkineticsoftheas-castalloysclearlyincreasedwithrisingLacontent.ForLacontentx=2,theas-spunalloydisplayedoptimalhydrogendesorptionkineticsat200°C.
简介:采用水热法制备表面活性剂聚甲基丙烯酸-季戊四醇四-3-巯基丙酸酯(PTMP-PMAA)修饰的具有光热效应的纳米WO3-x粉末,通过X射线衍射(XRD)分析、透射电镜(TEM)观察、X射线光电子能谱(XPS)分析、傅里叶变换红外光谱(FT-IR)分析以及紫外-可见吸收光谱(UV-Vis谱)分析及光热性能测试等,研究所得纳米粉体材料的结构及其在不同浓度与pH值下的光热性能。结果表明,水热法制备的WO3-x粉末为球形的非整比结构的W17O47,粒径小于10nm。随WO3-x的pH值降低或质量浓度降低,粉末的紫外吸光度增加,光热效应提高。pH值为6.4、质量浓度为800μg/mL的WO3-x经光热转换后,可实现在5min内约19℃的温度上升。考虑到人体体温为37℃,肿瘤部位的pH值为6.0~6.5之间,此质量浓度下纳米WO3-x粉末可用于光热治疗并实现对肿瘤细胞的杀伤效果。
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.