简介:HeteroatomM-ZSM-12zeolites(M=B,Al,Ge,Ga,Fe)arehydrothermallysynthesizedanditisprovedthattheheteroatomMisinvolvedintheframeworkofsynthesizedmolecularsievesbymeansofXRD,IRspectra.TheresultsofadsorptionanddiffusionexperimentsindicatethattheheteroatomMmodifiestheporevolume,specificsurfacearea,andthechannelofZSM-12molecularsieves.
简介:Ultrafastfiberlasersareingreatdemandforvariousapplications,suchasopticalcommunication,spectroscopy,biomedicaldiagnosis,andindustrialfabrication.Here,wereportthehighlystablefemtosecondpulsegenerationfromaMXenemode-lockedfiberlaser.Wehavepreparedthehigh-qualityTi3C2Txnanosheetsviatheetchingmethod,andcharacterizedtheirultrafastdynamicsandbroadbandnonlinearopticalresponses.Theobviousintensity-andwavelength-dependentnonlinearresponseshavebeenobservedandinvestigated.Inaddition,ahighlystablefemtosecondfiberlaserwithsignal-to-noiseratioupto70.7dBandcentralwavelengthof1567.3nmhasbeendelivered.Thestudymayprovidesomevaluabledesignguidelinesforthedevelopmentofultrafast,broadbandnonlinearopticalmodulators,andopennewavenuestowardadvancedphotonicdevicesbasedonMXenes.
简介:IncorporationofstrontiumintoV-Moalumina-supportedcatalystenhanceditsperformance(increasedconversionandselectivity,decreasedreducibilityandimprovedstability)inpropaneoxydehydrogenationtopropylene.12.5%SrloadingwasshowntobetheoptimumcontenttotheV-Mocatalyst.Theresultsweresupportedbyvariouscharacterizationtechniques,namely,BET,XRD,SEM,FTIRandTPD.
简介:Pd-containingionicliquid(IL)1-hexyl-3-methylimidazoliumtetrafluoroborate(C6MIMBF4)immobilizedon7-Al2O3(Pd-IL/γ-Al2O3)waspreparedandcharacterizedbyFouriertransforminfraredspectroscopy(FTIR),scanningelectronmicroscopy(SEM)andBrunauer-Emmett-Teller(BET)analysis.TheinfluencesofC6MIMBF4loadingandPdonmethaneconversiontoC2hydrocarbonsundercoldplasmawereinvestigated.FTIRandSEManalysesindicatedthatC6MIMBF4hadbeensuccessfullyimmobilizedon7-Al2O3andtheC6MIMBF4showedexcellentstabilityundercoldplasma.TheresultsofBETandmethaneconversionshowedthatwiththeincreaseinimmobilizationamountofC6MIMBF4ontoγ-Al2O3,thespecificsurfaceareaandporevolumeofIL/γ-Al2O3decreased,whiletheselectivityandyieldofC2hydrocarbonsincreased.TheselectivityofC2hydrocarbonswas94.6%whentheloadingofC6MIMBF4was40%,andthepercentageofC2H4inC2hydrocarbonswasashighas64%whenusingPd-IL/γ-Al2O3asacatalystwithnoconventionalthermalreductiontreatment.Opticalemissionspectra(OES)fromthecoldplasmareactorduringmethaneconversionwerealsostudied.TheresultsindicatedthattheintensityoftheC2,CH,H,andCactivespeciesfrommethaneandhydrogendecompositionincreasedwhenIL/γ-Al2O3orPd-IL/γ-Al2O3wasintroducedintotheplasmasystem.BasedontheanalysesofthegasproductandOESspectra,itcanbeconcludedthatthesurfacecatalyzedreactionsbetweenplasmaandionicliquidwereveryimportantforthereductionofPd2+andtheformationofC2H4.
简介:Inthecurrentpaper,dry(CO2)-reformingofglycerol,anewreformingroute,wascarriedoutoveralumina(Al2O3)-supported,non-promotedandlanthanum-promotednickel(Ni)catalysts.Bothsetsofcatalystsweresynthesizedviaawetco-impregnationprocedure.Physicochemicalcharacterizationofthecatalystsshowedthatthepromotedcatalystpossessedsmallermetalcrystallitesize,hencehighermetaldispersioncomparedtothevirginNi/Al2O3catalyst.ThiswasalsocorroboratedbythesurfaceimagescapturedbytheFESEManalysis.Fromtemperature-programmedcalcinationanalysis,thederivativeweightprofilesrevealedtwopeaks,whichrepresentawatereliminationpeakatatemperaturerangeof373to473Kfollowedbynickelnitratedecompositionfrom473to573K.Inaddition,BETsurfaceareameasurementsgave85.0m2g-1forthenon-promotedNicatalyst,whilstthepromotedcatalystsshowedanaverageof1%to6%improvementdependingontheLaloadings.Significantly,reactionstudiesat873KshowedthatglyceroldryreformingsuccessfullyproducedH2.The2%La-Ni/Al2O3catalyst,whichpossessedthelargestBETsurfacearea,gaveanoptimumH2generation(9.70%)ataglycerolconversionof24.5%.
简介:铍为脆性材料,在焊接时容易使焊缝开裂。为了防止焊缝开裂,途径之一是加延展性比较好的金属或合金(如Al-Si合金或银等)作填充材料进行钎接焊。但是,铍在非真空条件下焊接,在焊缝中出现的主要缺陷是焊接气孔和缩孔。人们早已知道,纯铝在焊接或铸造时的加热过程中会吸收环境中的氢,冷却时熔体要释放氢从而形成以氢为特征的氢气孔,进而影响铝加工的质量。这表明铝及铝合金焊接形成的气孔主要是与焊接时熔体的氢含量有关。那么,在加Al-Si合金焊接铍时,产生的气孔是否也与氢含量的关系,Al-Si合金熔体随温度升高氢含量有何变化趋势,Al-Si合金中的Si对铝熔体的吸氢起何作用。
简介:采用密度泛函理论(DFT)的B3PW91方法,在混合基组水平上对Al掺杂Sn12-团簇几何结构和电子结构进行了计算分析.结果表明,Al内掺杂Sn12-团簇能量更低更稳定,但LU-MO-HOMO能隙较小.外掺杂多面体簇中,电荷从Al原子移向Sn12-笼,趋向形成[Al+Sn122-]结构;内掺杂多面体簇中,电荷从Sn12-笼移向Al原子,趋向形成[Al-@Sn12]结构.
简介:One-potachievementofethyllevulinatefromcassavawasconductedinethanol-watersystemoverseveralsimplesulfatesaltcatalysts.Al2(SO4)3catalysthadthebestperformanceinsynthesizingethyllevulinatecomparingwiththoseofaseriesofsulfatesalts.Thehighestyieldsofethyllevulinatewasupto39.27%aswellas7.78%levulinateacidwhencassavawascatalyzedinethanolmediumbyadding10wt%water.13Cand1HNMRspectroscopicinvestigationsconfirmedthatisomerizationofglucosetofructoseoverAl2(SO4)3catalystisanimportantstepinproducingethyllevulinateandlevulinateacid.DuetoaggregationsofAl3+underhydrothermalconditions,tinyamountofAl3+weredetectedinfiltrateatthepercentageof0.32%evenifinabsolutewater.BronstedandLewisacidscouldimprovetheyieldofethyllevulinateandlevulinateacidbysynergisticeffect.AllresultssuggestedthatA12(SO4)3wasasimpleandefficientcatalystforethyllevulinateandlevulinateacidproduction.
简介:Ni-CobimetalliccatalystswithdifferentNi/Cocontentwerederivedfromcoldplasmajetdecompositionandreductionofhydrotalcite-likecompoundscontainingNi,Co,MgandAl,andtheircatalyticperformancewasinvestigatedwithdryreformingofmethane.Experimentalresultsshowedthatthehydrotalcite-likeprecursorscouldbecompletelydecomposedandpartlyreducedbycoldplasmajet,andtheNicontainedcatalystsexhibitedmuchhigheractivitythanthecatalystwithoutNi.Especially,thecatalystwithNi/Coratioof8/2achievednotonlythehighestconversionsof80.3%and69.3%forCH4andCO2,respectively,butalsothebeststabilityin100htesting.ThecatalystswerecharacterizedbyXRD,XPS,TEMandN2adsorptiontechniques,andtheresultsshowedthatthebetterperformanceofthe8Ni2Cobimetalliccatalystwasattributedtoitshighermetaldispersion,smallermetalparticlesize,aswellastheinteractioneffectbetweenNiandCo,whichwerebroughtbythespecialcatalystpreparationmethod.
简介:Thispaperreportsonthelongevityofglycerol-dry(CO2)reformingoverthelanthanum(La)promotedNi/Al2O3catalysts.TheXRDresultsshowedthattheNiparticlewaswell-dispersedinthepresenceofLapromoter.Inaddition,viatheNH3-TPDanalysis,itwasfoundthattheLapromoterhasreducedtheacidityofNicatalystwhichmayhaveexplainedthemitigationofcarbonlaydown.Itwasdeterminedthatthe3.0wt%La-promotedNi/Al2O3catalystpossessedthelargestBETspecificsurfaceareaof97m2g-1.Consequently,ityieldedthebestcatalyticlongevityperformancewithconversionattainedmorethan90%,evenafter72hofreactionduration.Significantly,itcanbeconfirmedthatthepresenceofCO2duringtheglyceroldryreformingwasessentialinreducingcarbondeposition,mostlikelyviagasificationpathway.Thishasensuredastabilityofcatalyticactivityforalongreactionperiod(72h).
简介:AseriesofmesoporousCu-Mn-Al2O3(CMA)materialswassynthesizedatmoderatetemperatureandtheirstructureswerecharacterizedbyXRD,N2physicaladsorptionandTPRtechniques.Itwasfoundthatusingmetalcomplexion[Cu(NH3)42+-Mn(NH3)62+]asrawmaterialsiseasiertoformgood-structuremesoporousCu-Mn-Al2O3materialsthanusingitsnitratesalt[Cu(NO3)2-Mn(NO3)2].TheTPRtestsresultsindicatethatCuOandMnOxwerehomogeneouslydispersedinthemesoporousmaterials.TheircatalyticapplicationtopreferentialcatalyticoxidationofCOinahydrogen-richstreamwasstudied.TheactivityvariesintheorderofCMA(1:1,molarratio)>CMA(1:2)>CMA(2:1)>CMA(CP)>CMA(1:0)≈CMA(0:1).TheCMA(1:0)andCMA(0:1)haveloweractivitycomparedtoothersamples,implyingthatthereexistedcoordinationeffectbetweenCu-Mninthesamples.TheselectivityvariedintheorderofCMA(0:1)≥CMA(1:2)>CMA(1:1)>CMA(2:1)>CMA(1:0)athighertemperature(≥120°C),indicatingthatincreasingtheCucontentenhancedtheconversionofH2.ThesampleCMA(CP)madebycoprecipitationmethodhasalowerCOoxidationactivityandselectivitythanitscounter-partsofmesoporousCu-Mn-Al2O3materials[CMA(1:2)],thisattributedtothelowersurfaceareaoftheformerandpoorinteractionofCuOwithMnOx.
简介:ThisarticleaddressesthesynthesisoforganicallytailoredNi-Allayereddoublehydroxide(ONi-AlLDH)anditsuseinthefabricationofexfoliatedpoly(methylmethacrylate)(PMMA)nanocomposites.ThepristineNi-AlLDHwasinitiallysynthesizedbyco-precipitationmethodandsubsequentlymodifiedusingsodiumdodecylsulfatetoobtainONi-AlLDH.NanocompositesofPMMAcontainingvariousamountsofmodifiedNi-AlLDH(3wt%?7wt%)weresynthesizedviasolventblendingmethodtoinvestigatetheinfluenceofLDHcontentonthepropertiesofPMMAmatrix.SeveralcharacterizationmethodssuchasX-raydiffraction(XRD),transmissionelectronmicroscopy(TEM),Fouriertransforminfraredspectroscopy(FTIR),rheologicalanalysis,differentialscanningcalorimetry(DSC)andthermogravimetricanalysis(TGA),wereemployedtoexaminethestructural,viscoelasticandthermalpropertiesofPMMA/OLDHnanocomposites.TheresultsofXRDandTEMexaminationconfirmtheformationofpartiallyexfoliatedPMMA/OLDHnanocomposites.TheFTIRresultselucidatethatthecharacteristicbandsforbothpurePMMAandmodifiedLDHarepresentinthespectraofPMMA/OLDHnanocomposites.Rheologicalanalyseswerecarriedouttoexaminetheadhesionbetweenpolymermatrixandfillerspresentinthenanocompositesample.TheTGAdataindicatethatthePMMAnanocompositesexhibithigherthermalstabilitywhencomparedtopurePMMA.ThethermaldecompositiontemperatureofPMMA/OLDHnanocompositesincreasesby28KcomparedtothatofpurePMMAat15%weightlossasapointofreference.IncomparisonwithpurePMMA,thePMMAnanocompositecontaining7wt%LDHdemonstratesimprovedglasstransitiontemperature(Tg)ofaround3K.Theactivationenergy(Ea),reactionorders(n)andreactionmechanismofthermaldegradationofPMMA/OLDHnanocompositeswereevaluatedusingdifferentkineticmodels.WateruptakecapacityofthePMMA/OLDHnanocompositesislessthanthatofthepurePMMA.