简介:为了明确团聚现象及表面性质对ZnS纳米材料发光性质的影响,采用SiO2对ZnS材料进行了表面修饰,并对ZnS及ZnS/SiO2复合材料的光学性质进行对比研究。采用吸收光谱分析了包覆前后光吸收性质的差异,发现SiO2包覆后ZnS纳米材料的带边由333nm红移至360nm。为了研究ZnS纳米材料与ZnS/SiO2纳米复合材料的光发射性质,分别对含纳米材料的水溶液样品及粉末样品的发光光谱进行了采集。对比研究的结果表明,SiO2包覆后ZnS纳米材料在蓝紫光区的发光得到了明显增强。以氙灯作为激发光源所获得荧光光谱显示ZnS/SiO2粉末样品发光的积分强度增大为原来的17.5倍,但相同条件下针对溶液样品的测试结果显示其发光强度只增大了1.1倍,这种增强可用SiO2的存在抑制了ZnS纳米粒子间的团聚来解释,且这一推断由325nm紫外激光激发下获得的光致发光数据进行了验证。
简介:Variousagriculturalcropresiduesincludingcornstover,corncob,andsorghumstalkwithamoisturecontentof75wt%weresubjectedtoalongpretreatment(12-60h)withsupercriticalCO2(scCO2),atlowtemperature(50-80℃)andapressureof17.5-25.0Mpa.Thesugaryieldsfromtheenzymatichydrolysis(EH)ofthepretreatedsampleswereasmuchasthree-tofourfoldgreaterthanthoseaffordedbytherawmaterials.However,whenpretreatmentwasconductedwithinashorttime(e.g.0.5h),aspreviouslyreportedintheliterature,onlyaslightincreaseintheEHsugaryieldswasobserved.TheproposedscCO2pretreatmentmechanismdemonstratedtheroleofmoistureinthesystem.Wetting,softening,andswellingwereobservedtomainlyaffectthelignocellulosewhenasuitableamountofwaterwasadded.Finally,thesampleswereanalysedbyX-raydiffractionandscanningelectronmicroscopy,beforeandafterpretreatment,toinvestigatethechangesinthemicroscopicstructureofthebiomass.
简介:Anovelgas-phaseelectrocatalyticcellcontainingalow-temperatureprotonexchangemembrane(PEM)wasdevelopedtoelectrochemicallyconvertCO2intoorganiccompounds.TwodifferentCu-basedcathodecatalysts(CuandCu-C)werepreparedbyphysicalvapordepositionmethod(sputtering)andsubsequentlyemployedforthegas-phaseelectroreductionofCO2atdifferenttemperatures(70-90℃).ThepreparedelectrodesCuandCu-CwerecharacterizedbyX-raydiffraction(XRD),X-rayphotoemissionspectroscopy(XPS)andscanningelectronmicroscopy(SEM).Asrevealed,CuispartiallyoxidizedonthesurfaceofthesamplesandtheCuandCu-Ccathodiccatalystswerecomprisedofaporous,continuous,andhomogeneousfilmwithnanocrystallineCuwithagrainsizeof16and8nm,respectively.Theinfluenceoftheappliedcurrentandtemperatureontheelectro-catalyticactivityandselectivityofthesematerialswasinvestigated.Amongthetwoinvestigatedelectrodes,thepureCucatalystfilmshowedthehighestCO2specificelectrocatalyticreductionratesandhigherselectivitytomethanolformationcomparedtotheCu-Celectrode,whichwasattributedtothehigherparticlesizeoftheformerandlowerCuO/Curatio.Theobtainedresultsshowpotentialinterestforthepossibleuseofelectrical「enewableenergyforthetransformationofCO2intovaluableproductsusinglowmetalloadingCubasedelectrodes(0.5mgCucm2)preparedbysputtering.
简介:Inthiswork,MoOxpromotedIr/SiO2catalystswerepreparedandusedfortheselectivehydrogenolysisoftetrahydrofurfurylalcohol(THFA)to1,5-pentanediolinacontinuousflowreactor.Theeffectsofdifferentnoblemetals(Ir,Pt,Pd,Ru,Rh),supportsandIrcontentswerescreened.Amongtheinvestigatedcatalysts,4wt%Ir-MoOx/SiO2withaMo/Iratomicratioof0.13exhibitedthebestcatalyticperformance.ThesynergybetweenIrparticlesandthepartiallyreducedisolatedMoOxspeciesattachedonthemisessentialfortheexcellentcatalyticperformanceofIr-MoOx/SiO2.ThecatalystexhibitedabetterhydrogenolysisefficiencyofTHFAwiththeselectivityof1,5-pentanediolof65%–74%ataconversionofTHFAof70%–75%whentheinitialTHFAconcentrationisrangingfrom20wt%and40wt%.AndhighersystempressurewasalsoinfavoroftheconversionofTHFA.Duringastabilitytest,theconversionofTHFAand1,5-pentanediolyieldoverIr-MoOx/SiO2decreasedwithreactiontime,whichcanbeexplainedbytheleachingofMospeciesduringthereaction.
简介:Weexperimentallydemonstratea4×4nonblockingsiliconthermo-optic(TO)switchfabricconsistingofthreestagesoftunablegeneralizedMach–Zehnderinterferometers.All24routingstatesfornonblockingswitchingarecharacterized.Thedevice’sfootprintis4.6mm×1.0mm.Measurementsshowthattheworstcrosstalkofallswitchingstatesis-7.2dB.Theon-chipinsertionlossisintherangeof3.7–13.1dB.TheaverageTOswitchingpowerconsumptionis104.8mW.
简介:Catalyticpropertiesofthemetal-organicframeworkCr-MIL-101insolvent-freecycloadditionofCO2toepoxidestoproducecycliccarbonatesusingtetrabutylammoniumbromideasco-catalysthavebeenexploredundermildreactionconditions(8barCO2,25C).Styreneandpropylenecarbonateswereformedwithhighyields(95%and82%,respectively).CatalyticperformanceofCr-MIL-101wascomparedwithotherMOFs:Fe-MIL-101,Zn-MOF-5andHKUST-1.Thecatalyticpropertiesofdifferentquaternaryammoniumbromides,Cr-MIL-101aswellasPW12/Cr-MIL-101compositematerialhavebeenassessedinoxidativecarboxylationofstyreneinthepresenceofbothtert-butylhydroperoxideandH2O2asoxidantsat8100barCO2and2580Cwithselectivitytostyrenecarbonateupto44%at57%substrateconversion.
简介:Wehavedevelopedacost-effectiveandhighlycompact100-Gb/scoarsewavelengthdivisionmultiplexing(CWDM)transmitteropticalsubassembly(TOSA)usinglens-freehybridintegration.Toachievelargealignmenttolerances,distributedfeedbacklaserdiodes(DFB-LDs)arebutt-coupledtoafour-channelsilica-basedplanarlightwavecircuit(PLC)arrayedwaveguidegrating,withthesiliconsub-mountsandPLCadhesivelybonded.Then,aflexibleprintedcircuitisemployedtoconnecttheinternalDFB-LDsandtheexterioroftheTOSApackageforradiofrequencysignaltransmission,eliminatingtheexpensiveceramicfeed-through.ThepackagedCWDMTOSA,whichis15.8mm×7.0mm×6.0mminsize,showsaside-modesuppressionratioof>40dB,a3dBbandwidthof>18GHz,anderror-freetransmissionwithanaverageopticaloutputpowerof>0dBmanddynamicextinctionratioof>4.0dBat25.78125Gb/sovera10kmsingle-modefiberforallfourlanes.
简介:On △I=4 Bifurcation PhenomenaOn△I=4BifurcationPhenomena¥ZhangJingye;YangSunandMikeGuidryTheexperiments-bythenew7--raydetector...
简介:Therearemoreandmorecountriestoakeanefforttothestudiesofvanadiumalloyforfusionapplication.NIFSinJapanhasrecentlydevelopedan80kgheatV4Cr4Tialloy(NIFS-heat2)aftertheproductionofa500kgscaleV4Cr4TiinU.S.severalyearsago.PropertyevaluationofthealloyhasbeenputintoaninternationalcollaborationprogramunderthecoordinationofIEA(InternationalEnergyAgency).SWIPhasjoinedthecollabrationonthehydrogenembrittlementresistanceevaluationofthealloyt.
简介:SinceitserliestyearsofR&D[1],theGEANT4simulationtoolkithasbeendevelopedfollowingsoftwareprocessstandardswhichdictatedtheoverallevolutionoftheproject.Thecomplexityofthesoftwareinvolved,thewideareasofapplicationofthesoftwareproduct,thehugeamountofcodeandCategorycomplexity,thesizeanddistributednatureoftheCollaborationitselfareallingredientswhichinvolveandcorrelatetogetherawidevarietyofsoftwareprocesses.Althoughin"production"andavailabletothepublicsinceDecember1998,theGEANT4softwareproduct[1]includesCategoryDomainswhicharestillunderactivedevelopment.Thereforetheyrequiredifferenttreatmentalsointermsofimprovementofthedevelopmentcycle,system,testingandusersupport,ThisarticleismeanttodescribesomeofthesoftwareprocessesastheyareappliedinGEANT4forbothdevelopment,testingandmaintenanceofthesoftware.