简介:Thenanoparticlesγ-Fe2O3coatedwithsurfactants.DBS,STandCTAB.repsectively.weresynthesizedbymicroemulsionmethod.Thecoatedferricoxides.whichshowenhancednonlinearopticalpropertiescomparedwiththeirbulkcounterpart.wereprobedbyEXAFSinsolutionforms.Thex=-rayabsorptionspectraforFeKedgeweremeasuredatroomtemperaturebyhelpofsynchrotronradiationlightsource.Extendedx-rayabsorptionfinestructureanalysisshowsthatthecoatinglayersoforganicmoleculesinteractwithsurfaceatomsofnanopartices,theFe-Obondlengthwasextended.
简介:Themicroscopiceffectivechargesinmirrornuclei51Mnand51Feareinvestigatedwiththeparticle-vibrationcouplingmodelbasedontheself-consistentSkyrme-Hartree-Fockandcontinuumrandom-phase-approximationapproaches.Theisovectorpartsarepredictedtobearound0.15,andtheprotoneffectivechargesarearound1.25e,whichislessthantheempiricalvalueofeeffp=1.5e.Themicroscopiceffectivechargesinneutronrich51Mnareabout10%lessthanitsprotonrichmirror.TheseeffectivechargesarecombinedwiththeshellmodeltocalculatethereducedelectricquadrupoletransitionprobabilityB(E2)valuesin51Mnand51Fe.ItturnsoutthatthemicroscopiceffectivechargeshavewellreproducedtheB(E2)valuesanditsratiointheterminatingstates.
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简介:EXAFS研究FeCl3溶液中Fe^3+的区域环境结构随溶液浓度的变化,Fe^3+的径向结构函数表明,随着FeCl3溶液的浓度降低,第一配位峰的距离逐渐缩短。当溶液浓度从3.0mol/L降到0.2mol/L时,配位距离减小0.014nm,但振幅峰强度以0.8mol/L浓度为最小,其强度比浓的或稀的FeCl3浓度的低约30%。结构参数拟合结果表明,0.2mol/LFeCl3稀溶液中Fe^3+的近邻配位为6个H2O的O原子形成八面体配位;3.0mol/LFeCl3溶液中Fe^3+的近邻配位为2个Cl^-和4个H2O中的O原子。0.8mol/LFeCl3溶液中Fe^3+的近邻配位有1个Cl^-和5个O原子。其结构无序相对较大,是Cl^-与O组成的扭曲八面体配位。
简介:AseriesofoxideizedCO-K-Mo/γ-Al2O3catalystsamples,preparedbyimpregnatingoxidizedK-Mo/γ-Al2O3sampleswithanaqueoussolutionofcalculatedCo(NO3)2andthencalcininginairattemperaturesof350℃,500℃65℃and800℃respectively,weresulfidedandtheninvestigatedfortheactivityinthesynthesisofmixedalcoholsfromCOhydrogenationunderconditionsofp=5.0MPa,T=350℃andGHSV=4800h^-1.TheresultsdemonstratethattheadditionofcobaltpromoterisfavorabletotheformationofhigheralcoholsandtheopimumcalcinationtemperaturesafterimpregnatingwithCo^2+areabout500-650℃.ThestructureofCoandMospeciesontheoxidizedandsulfidedsampleswasdeterminedbyX-raydiffraction(XRD),laserRamanspectrum(LRS)andextendedX-rayabsorptionfinestructure(EXAFS).Foroxidizedsamplecalcinedat350℃,cobaltexistsasCo3O4spectiesandcoversthesurfaceofK-Mo-Ospecies,thestructureofK-Mo-OspeciesisthesameasthatinK-Mo/Al2O3sample.TheinteractionbetweencobaltandK-Mo-Ospeciesisrelativelyweak.Aftersulfidation.Cobaltexistsassulfidecrystalliteswithanoctahedralcoordinatedstructure,andmolybdenumasMoS2crystallites.Foroxidizedsamplescalcinedat500-650℃,CocomponentinteractswiththeK-Mo-Ospeciesanddestroysthelong-rangeorderoftheK-Mo-Ospectesgradually,Aftersulfidation.CotendstoexistasasulfidewithtetrahedralcoordinatedstructureandMostillasMoS2crystallites.Foroxidizedsamplecalcinedat800℃,CocomponentexistsmainlyasCoAl2O4species,mostofwhichcannotbesultidedduringsulfidation.
简介:在Al2O3(0001)衬底上用MOCDVD方法进行了GaN的外延生长,通过X射线衍射(同步辐射源)研究了GaN和Al2O3(0001)的匹配关系。结果表明,经充分氮化的衬底上,GaN以单一的匹配方式沿[0001]方向生长:在Al2O3(0001)衬底未经氮化或氮化不充分时,不同程度地出现了其它三种绕<11-20>晶带轴倾斜一定角度的匹配位向。指出了GaN/Al2O3(0001)的几种匹配方式的晶体学规律。GaN绕<11-20>晶带轴倾斜的匹配方式是其外延生长过程中降低和Al2O3(0001)的晶格失配、释放界面应变的重要机制之一。
简介:评价了具有不同Ni/(Ni+W)原子比的NiW/γ-Al2O3催化剂加氢脱硫活性,对硫化态催化剂进行了EXAFS表征。结果表明,Ni(Ni+W)原子比为0.23的催化剂表面上WS2颗粒最小,有利于形成Ni-W-S加氢脱硫活性相,其反应活性最高。