简介：TheapproachofutilizingcombustionsynthesistomakefineparticlesofSiO2,Al2O3andTiO2isaquitemoderntechnology.Throughthechemicalreactioninpost-flameregion,fineSiO2particlescanbeformedwithhighpurityonplatesurface.Therefore,thecombustionsynthesisofSiO2powdersisanimportantareaforfurtherresearchanddevelopment,especiallyfortheapplicationofSiO2inthesemiconductorindustry.Thisinvestigationproposesanexperimentalapproach(i.e.,agas-phasecombustionsynthesis)usingtwodifferentkindsoforganiccompounds,Hexamethyldisilazane(HMDSA)andHexamethyldisioxane(HMDSO),asthesiliconprecursors.ApremixedgasburnerischosenwithC3H8asfuel,airasoxidantandpartoftheairwasusedasthecarryinggastoentrainHMDSA/HMDSOvaporintothecombustiblemixture.ObservationsshowthattheC3H8/airflamechangedcolorfromapale-blueflametolightyellowandthenorangewhendifferentamountsofprecursorswereintroduced.Throughthechemicalreactioninthepost-flameregion,fineSiO2particleswereformedinthegasphaseandthenquenchedandcollectedonanaluminumflatplate.TheobjectiveofthispaperistostudytheeffectsofHMDSOandHMDSAconcentrationsandflametemperaturesonthesynthesisofSiO2particles.

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简介：在通常用于合成中孔ＭＣＭ－４１分子筛的反应体系中，用氨水、ＮａＯＨ或四乙基氢氧化胺作催化剂，在较低的ｐＨ值下合成出具有独特Ｎ２吸附等温线和狭窄双峰中孔分布的双中孔ＳｉＯ２材料。实验表明，在所使用的反应体系中，双中孔ＳｉＯ２结构是一种必然的物相，且反应体系的ｐＨ值调节在合成中起决定性作用。当反应体系的ｐＨ值从约９．５增加到１１时，相应产物的孔径分布由双中孔转变为单中孔分布。这些结果为进一步深入理解中孔材料的形成机理提供了新的视野。合成样品用ＸＲＤ和Ｎ２吸附等温线进行了表征。更多还原

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简介：Anewmethodforfabricatingorderedporoussiliconisreported.Atwo-dimensionalsilicananospherearrayisusedasatemplatewithahydrofluoricacid-hydrogenperoxidesolutionforetchingthenanospheres.Theinitialdiameteranddistributionoftheholesintheresultingporoussiliconlayeraredeterminedbythesizeanddistributionofthesilicananospheres.Thecorrosiontimecanbeusedtocontrolthedepthsoftheholes.ItisfoundthatthepresenceofaSiO_2layer,formedbytheoxidationoftheroughinternalsurfaceofthehole,istheprimaryreasonallowingthecorrosiontoproceed.Ultravioletreflectionandthermalconductivitymeasurementsshowthatthediameteranddistributionoftheholeshaveagreatinfluenceonpropertiesoftheporoussilicon.

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简介：采用溶胶-凝胶法制备纳米级SiO2粉，分别用X射线衍射仪、透射电子显微镜、红外光谱仪和差热扫描量热分析仪对其进行了分析测试。结果表明于凝胶在1200℃热处理1小时仍是无定型的SiO2粉，其平均粒度大小为40nm。

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简介：Inthepresentwork,core-shellNi@SiO2catalystswereinvestigatedinordertoevaluatetherelevanceofcatalyticactivityandsurfacestatesofNicoreaswellasNinanoparticlessizetocatalyticpartialoxidationofmethane(POM).ThecatalystswerecharacterizedbyN2adsorption,H2-TPR,XRD,TEMandXPStechniques.Thecatalyticperformanceofthecore-shellcatalystswasfoundtobedependentonthesurfacestatesofcatalyst,whichinfluencedtheformationofproducts.Itwasconsideredthatcarbondioxideformedontheoxidizednickelsites(NiO)andcarbonmonoxideproducedonthereducedsites(Ni).ThesurfacestatesofactivemetalinthedynamicwereinfluencedbothbythesizeofNicoreandtheporosityofsilicashell.However,thecatalyticactivitywouldbedebasedwhenthesizeofNicorewasunderacertainextent,whichcanbeascribedtothefactthecarbondepositionincreasedwiththeincreasingcontentofNiO.TheeffectsofsurfacestatesofNi@SiO2catalystonthecatalyticperformancewerediscussedandthereactionpathwayoverNicoreencapsulatedinsidesilicashellwasproposed.

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简介：在相同的反应体系中当ｐｈ值从约９．５调变至１１时分别合成出双中孔ＳｉＯ２和六方中孔ＳｉＯ２材料，并用ＸＲＤ、Ｎ２吸附、ＴＥＭ、ＴＧ／ＤＴＡ和ＦＴＩＲ等测试手段对合成产物进行了表征。实验结果表明，双中孔ＳｉＯ和六方中孔ＳｉＯ２是合成中必然出现的两种不同的中孔物相。与六方中孔ＳｉＯ２相比，双中孔ＳｉＯ２也具有典型中孔材料的特征ＸＲＤ谱图，虽然仅呈现一个易让人产生不完全晶化误解的相对较宽的单ＸＲＤ衍射峰（ｄ＝５．２ｎｍ），但它却给出一种独特的Ｎ２吸附等温线和窄的双峰中孔孔径分布曲线。由于孔壁的无定形及表面活性剂分子与ＳｉＯ２骨架间相似的相互作用，两类材料给出类似的ＦＴＩＲ谱图和ＴＧ／ＤＴＡ曲线。然而，在双中孔ＳｉＯ２的ＦＴＩＲ谱图中９６０ｃｍ处峰强度的微小变化可能意味着在锻烧脱除模板剂后双中孔ＳｉＯ２较六方中孔ＳｉＯ２具有更高的骨架聚合度。更多还原

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简介：Inthiswork,theinfluenceofCO2onthestructuralvariationandcatalyticperformanceofNa2WO4/Mn/SiO2foroxidativecouplingofmethanetoethylenewasinvestigated.ThecatalystwaspreparedbyimpregnationmethodandcharacterizedbyXRD,RamanandXPStechniques.AppropriateamountofCO2inthereactantgasesenhancedtheformationofsurfacetetrahedralNa2WO4speciesandpromotedthemigrationofOinMOx,Na,Wfromthecatalystbulktosurface,whichwerefavorableforoxidativecouplingofmethane.WhenthemolarratioofCH4/O2/CO2was3/1/2,enrichedsurfacetetrahedralNa2WO4speciesandhighsurfaceconcentrationofOinMOx,Na,Wweredetected,andthenhighCH4conversionof33.1%andhighC2H4selectivityof56.2%wereobtained.WithfurtherincreaseofCO2inthereagentgases,thecontentofactivesurfacetetrahedralNa2WO4speciesandsurfaceconcentrationofOinMOx,Na,Wdecreased,whilethatofinactivespecies(MnWO4andMn2O3)increaseddramatically,leadingtolowCH4conversionandlowC2H4selectivity.ItcouldbespeculatedthatNa2WO4crystalwastransformedintoMnWO4crystalwithexcessiveCO2addedunderthereactionconditions.PretreatmentofNa2WO4/Mn/SiO2catalystbymoderateamountofCO2beforeOCMalsopromotedtheformationofNa2WO4species.

简介：Ni/SiO2andbimetallicNixGa/SiO2catalystswithdifferentNi/Gaatomicratios(x=10~2)wereinvestigatedfortheselectivehydrogenationofacetylene.ItwasfoundthatNixGa/SiO2showedhigherselectivitytoethylenethanNi/SiO2.ThisisattributedtotheformationNi-GaalloyandNi3Gaintermetalliccompound(IMC)wheretherewasachargetransferfromGatoNi,whichisfavorableforreducingtheadsorptionstrengthandamountofethyleneonNiatoms.Asaresult,theover-hydrogenation,theC–Cbondhydrogenolysisandthepolymerizationweresuppressed,andsubsequentlytheselectivitytoethylenewasenhanced.WiththedecreaseofNi/Gaatomicratio,theactivityandstabilityoftheNixGa/SiO2catalystsincreasedfirstandthendecreased,whiletheethyleneselectivitytendedtoincrease.Ni5Ga/SiO2exhibitedthebestperformance.Undertheconditionsof180°C,0.1MPa,andareactant(1.0vol%acetylene,5.0vol%H2and94vol%N2)withthespacevelocityof36,000mLh-1g-1,theacetyleneconversionmaintainedat100%onNi5Ga/SiO2during120htimeonstreamandtheselectivitytoethylenewas75%~81%afterreactionfor68h.ItwasalsofoundthattheformationofNi-GaalloyandNi3GaIMCsuppressedtheincorporationofcarbontoformNiCx,subsequentlyenhancingthecatalyststability.Additionally,withincreasingtheGacontent,thecatalystacidamountandstrengthtendedtoincrease,whichpromotedthepolymerizationandcarbondepositionandsothecatalystdeactivation.

简介：Thegreenlong-after-glowluminescencefromTb3+-dopedSr2SiO4phosphors,whicharesynthesizedbythehightemperaturesolidstatereactioninareductiveatmosphere,isobservedinthispaper.Theresultsshowthatunderultravioletexcitation,theobtainedphosphorsproduceanintensegreen-lighting-emissionfromtheTb3+,andthegreen-lightinglongafter-glowluminescencerelatedtoTb3+canlasthalfanhouraftertheirradiationsourcehasbeenremoved.Moreover,theeffectsofco-dopingLi+,Dy3+,Er3+,Gd3+,andYb3+withTb3+onthedecaypropertiesandthermoluminescencepropertiesareinvestigatedtoconfirmthelong-after-glowmechanism.

简介：Inthiswork,syngasmethanationoverNi-W/TiO2-SiO2catalystwasstudiedinafluidized-bedreactor(FBR)anditsperformancewascomparedwithafixed-bedreactor(FIXBR).Theeffectsofmainoperatingvariablesincludingfeedstockgasesspacevelocity,cokecontent,bedtemperatureandsulfur-tolerantstabilityof100hlifewereinvestigated.ThestructureofthecatalystswascharacterizedbyXRD,N2adsorptiondesorptionandTEM.Itisfoundthatundersamespacevelocityfrom5000h1to25000h1FBRgaveahigherCH4yield,lowercokecontent,andlowerbedtemperaturethanthoseobtainedinFIXBR.Ni-W/TiO2-SiO2catalystpossessedexcellentsulfur-tolerantstabilityonthefeedstockgaseslessthan500ppmH2SinFBR.ThecarbondepositsformedonthespentcatalystwereintheformofcarbonfibersinFBR,whileintheformofdenseaccumulationdistributionappearanceinFIXBR.

简介：水晶的Au5Si2/Si异质接面nanowires(Au5Si2/SiNWs)被热蒸发的SiO粉末在一个低真空系统在厚黄金涂的硅底层上获得。生产Au5Si2/Si异质接面的结构分析被采用一台传播电子显微镜(TEM)和一个选择区域执行电的衍射计。化学作文被纳入TEM的一个精力散的X光分光镜学习。一个二拍子的圆舞生长模型被建议描述Au5Si2/SiNWs的形成。在第一步期间，水晶的SiNWs经由在相对高的温度把帮助氧化物的生长过程与vapour-liquid-solid模型相结合的生长机制被形成。在第二步，preformedSiNWs的温度减少和减少片断与残余Au反应由一个solid-liquid-solid过程形成单个水晶的Au5Si2nanowires。现在的工作应该基于nanowires为未来合成和高质量的金silicidenanowires和微电子设备的研究是有用的。

简介：HydrotalciteprecursorsofLamodifiedNi-Al2O3andNi-SiO2catalystspreparedbyco-precipitationmethodandthecatalyticactivitieswereexaminedfortheproductionofCOx-freeH2byCH4decomposition.Physico-chemicalcharacteristicsoffresh,reducedandusedcatalystswereevaluatedbyXRD,TPRandO2pulsechemisorptions,TEMandBET-SAtechniques.XRDstudiesshowedphasesduetohydrotalcite-likeprecursorsinovendriedformproduceddispersedNiOspeciesuponcalcinationinstaticairabove450C.Ramanspectraofdeactivatedsamplesrevealedthepresenceofbothorderedanddisorderedformsofcarbon.Ni-La-Al2O3catalystwithamoleratioofNi:La:Al=2:0.1:0.9exhibitedtremendouslyhighlongevitywithahydrogenproductionrateof1300molH2mol1Ni.AdirectrelationshipbetweenNimetalsurfaceareaandhydrogenyieldswasestablished.