简介:Thenanoparticlesγ-Fe2O3coatedwithsurfactants.DBS,STandCTAB.repsectively.weresynthesizedbymicroemulsionmethod.Thecoatedferricoxides.whichshowenhancednonlinearopticalpropertiescomparedwiththeirbulkcounterpart.wereprobedbyEXAFSinsolutionforms.Thex=-rayabsorptionspectraforFeKedgeweremeasuredatroomtemperaturebyhelpofsynchrotronradiationlightsource.Extendedx-rayabsorptionfinestructureanalysisshowsthatthecoatinglayersoforganicmoleculesinteractwithsurfaceatomsofnanopartices,theFe-Obondlengthwasextended.
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。
简介:LocalstructuresofthemolybdenumsulfidespeciesinthesultidedRh-Mo-K/Al2O3catalystswithvariousrhodiumloadingshavebeeninvestigatedbyXAFS.Fromthefittingresults.theMo-Mocoordinationnumberforthesamplefreeofrhodium(ca.3.7)issimilartothatforthecrystallineMoS2,indicatingthatthesupportedsulfidedmolybdenumspeciesmainlypresentaslargepatechesofMoS2-likeslabs.Fortherhodium-modifiedsamples,however,theamplitudesoftheMo-SandMo-Mocoordinationshellsaresharplyreduced,revealingahighdispersionoftheMoS2-likespeciesinthecatalysts,TheschemeofthemicrostructuresofthesulfidedmolybdenumspeciesstabilizedonthealuminasupportisdiscussedbasedupontheanalysisoftheEXAFSdata.