纳米碳管文献摘要2.docx
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纳米碳管文献摘要2.docx
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纳米碳管文献摘要2
文献摘要
碳源:
由CH4制备的碳纳米管长径比大,管壁光滑,形貌规整;而由C3H6制备的碳纳米管,产物中有少量无定形物,且管壁不光滑,有折点出现
气体种类对CVD法制备碳纳米管的影响研究.化工新型材料,第34卷第1期
carbonnanotube/nanofibresweresynthesizedbyheat-treatingthebulkpolymerininertatmosphereat475°Cfor1.5h,andthepolymeractedascarbonsource.
催化剂和碳源的制备处理:
催化剂的硝酸盐dissolvedin10mldistillerwater,respectively,undervigorousstirring.Inasecondbeaker2.0gofpolyethyleneglycol1000and2.0gofcitricacidmonohydrateweredissolvedin40mlethanol.Thenitrate/watersolutionwasaddedrapidlyundervigorousstirringtothepolymer/alcoholsolution.Thesiliconsubstratescleanedultrasonicallyinacetonewerecoatedwiththepolymer/alcoholsolutionbyspin-coatingataspeedof1000rpmfor2mintoformathinfilm.40
Insitufabricationofcarbonnanotube/nanofibresfromthebulkpolymeratmildtemperature
MaterialsLetters60(2006)2312–2314
催化剂:
Thefinalcatalystcontained5wt.%ofCoorFe,respectively.OurinsituXPSexperimentsshowedthatFeionsareeasilyreducedbythereactantacetyleneandwefoundnoindicationofanykindofFeoxideaftertreatmentthesampleat1000K.
Ontheroleofcatalyst,catalystsupportandtheirinteractioninsynthesisofcarbonnanotubesbyCCVD.MaterialsChemistryandPhysics77(2002)536–541
ironismoreactivethancobaltbutthequalityoftheresultingCNTs,intermsofgraphitizationandstructure,islessgoodwithiron。
Platinum,palladiumandchromiumweree.g.addedtoacobalt–nickelcatalystinordertolowerthegrowthtemperaturefrom700–1000℃to500–550℃(withdifferentsuccessrates)
金属催化剂与载体之间作用的关系,也是影响催化剂颗粒大小的因素。
表面的扩散速率不仅与载体的性能有关还与表面的粗糙度有关(Seideletal.emphasizedthatthesurfacediffusionrateofaspecificatomonasubstratedependsnotonlyonthesubstratenaturebutalsoonitsroughness[47])
多孔材料作为载体可以提高碳管的生长速率,这主要是这些空隙可以增加催化剂与碳源气体的相容性,能很快地和催化剂接触。
ThecatalystintheCCVDofcarbonnanotubes—areview.ProgressinMaterialsScience50(2005)929–961
用一个maskwithslit来在载体上面沉积一层颗粒分散的催化剂。
AsimplecombinatorialmethodtodiscoverCo–Mobinarycatalyststhatgrowverticallyalignedsingle-walledcarbonnanotubes.Carbon44(2006)1414–1419
Fe热丝产生Fe蒸气,然后再在冷却的基体上沉积制备催化剂颗粒。
NovelcatalystparticleproductionmethodforCVDgrowthofsingle-anddouble-walledcarbonnanotubes.LetterstotheEditor/Carbon44(2006)1581–1616
物理和化学方法的比较:
Physicaltechniquesforthepreparationofcatalystsareusuallycomplexprocesseswiththenecessityofusingexpensiveequipment.Onthecontrary,thechemicalcatalystpreparationtechniquesaresuitableforthedepositionofcatalystsontothesubstrateatlowcost.现在载体上面形成薄膜,然后再用NH3刻蚀,形成小颗粒。
许多文献表明Pb的家入可以减少反应的温度。
本文采用non-isothermaldeposition(NITD)技术来沉积催化剂。
TheCNTsgrowingathighertemperaturehadlargerdiameterthanthosegrowingatlowertemperature.
Experimentalinvestigationoncarbonnanotubegrownbythermalchemicalvapordepositionusingnon-isothermaldepositedcatalysts.MaterialsChemistryandPhysics97(2006)511–516
ThepresenceofametalsuchasCoappearstopreventtheformationofFeCandsuchcarbides.Itislikelythat3theoxidesupportaffordsagooddistributionofthealloynanoparticlesonitssurface.AlloyingpromotesthedecompositionofCHtoproducecarbonnan-4otubes,thequalityofwhichdependsonthealloycomposition.ItisnoteworthythatthebestperformanceisfoundwithFeConanoparticleswhichgiveahighyieldofSWNTsofgoodquality
Synthesisofsingle-walledcarbonnanotubesusingbinary_Fe,Co,Ni/alloynanoparticlespreparedinsitubythereductionofoxidesolidsolutions.ChemicalPhysicsLetters300_1999.236–242
金属催化剂会选择在相对较平的晶面上沉积碳,
Carbondepositononiron-nickelalloypartickes.AppliedcatalysisA:
Genenral148(1977)265-282
Nickel-richcatalystswerefoundtofavorthedecompositionofethylenebutonlyshowedalimitedabilitytodecomposeCO,whereasaniron-richcatalystexhibitedcompletelytheoppositepatternofbehaviorunderidenticalconditions.
CarbonDepositiononIron–NickelDuringInteractionwithEthylene–CarbonMonoxide–HydrogenMixtures.JournalofCatalysis190,104–117(2000)
在600℃下,分解CO制备碳纳米纤维,Fe的催化作用要比Ni的强。
催化剂在725℃开始钝化,但温度降低时又恢复活性。
Ni的含量增加会导致沉积碳量的减少,theadditionofnickeltoironresultsinareconstructionoftheparticlesurfacesthatleadstoadiminutioninthelikelihoodofironatomsbeingnearestneighborsandthegenerationofatomicarrangementsatcarbonprecipitatingfacesthatdonotfavortheformationofgraphiteplateletsinthedepositedfilamentousstructures.
AreversibledeactivationprocesswasshowntoexistforalltheseFe–Nicatalysts.
theamountofsolidcarbonincreasedasthehydrogencontentinthereactantwasraisedtobetween20to30%andthereafterexhibitedasteadydeclinewithfurtheradditionofhydrogen.H2可以作为反应物参加反应,可以还原催化剂的金属碳化物,净化金属表面的其他形式的碳。
CarbonDepositiononIron–NickelduringInteractionwithCarbonMonoxide–HydrogenMixtures.JOURNALOFCATALYSIS169,212–227(1997)
Co与Mo的配比为1∶1.06才是较佳配比.对于负载型的催化剂,并不是负载的活性组分
越多其催化性能越好,其活性组分总是有一个负载量的限制,超过或低于这个负载量均不能发挥最佳催化活性.在pH为7~9时得到催化剂具有良好的催化活性.在这样的pH值范围内沉淀出来的钴和钼可以均匀地负载于二氧化锆表面,同时钼对钴的协调作用也达到较佳的状态.
以不同升温速率得到的碳纳米管在质量上的差别分析如下:
以较低升温速率生长碳纳米管时,反应体系所处低温环境时间长,乙炔分解产生的碳原子活性相对较低,其周围形成局部较低的气相分压,碳原子的形核功相对较小,这时碳原子易形核生长成碳纳米管晶核.但在较低温度下,催化剂活性组分不易形成准液态金属,增加了扩散的距离,使吸附碳原子通过金属内部扩散难以进行.此时乙炔分解产生的碳原子浓度降低,使得碳纳米管活性端易封口,因而此后产生的碳原子无法继续生长成碳纳米管.随着升温速率的加快,乙炔分解成碳原子速率也相应增加,催化剂活性组分也易形成准液态金属,使吸附碳原子通过金属内部的扩散易于进行,有效地阻止了碳纳米管活性端的封口,从而可以长出石墨化程度较好的碳纳米管.
Co-MoZrO2催化剂CVD法制备碳纳米管.浙江工业大学学报,第33卷第1期2005年2月
thedecomposedproductofsulfurcouldincreasethecatalyticactivityofironandcauseCCbondingtobebrokeneasily。
workingpressureof15kPamaybetheoptimumparameterforCNTsgrowth,此时所得碳管的石墨化度最高,IG/ID的比值最大,G峰的半高宽也最小。
压强对试验的影响:
whentheworkingpressureishigh(suchas21kPa),thegasresidencetimewouldbemuchlonger.Thedecomposedcarbondepositcouldbeover-saturatedrelativetothequantityofcatalystparticles[14];moreover,thesizeofcatalystparticlescouldbelargerbecauseofmorecollision.Thisweakensthecatalyticactivityofironparticlescausinglargeamountofamorphouscarbonorcarbon-wrappedironnanoparticlestobeformedunderhighworkingpressure.Ontheotherhand,alowerworkingpressurewouldleadtoashorterresidencetime.Thismaybringaboutseveralpossibilities[15,16]:
thecarbonsourcecannotbedecomposedcompletelyorthedecomposecarboncannotbeabsorbed,dissolvedintimeforsaturationandprecipitationtoCNTsbeforetheyareevacuatedfromthereactor.
Optimizationofcarbonnanotubepowdergrowthusinglowpressurefloatingcatalyticchemicalvapordeposition.MaterialsChemistryandPhysics98(2006)256–260
Ni/Co和Ni具有良好的催化活性,Co催化效果较差。
Ni/Co〉Ni〉Co=Fe
朱宏伟,吴德海,徐才录著.碳纳米管.械工业出版社.2003
Baker[1]等人检测了气相生长炭纤维的生长活化能与碳在相应催化剂金属中的歉意活化能相近,从而断定纤维的生长速率受碳在金属中的扩散控制,因此,催化剂的颗粒越小,碳的迁移路程就越短,纤维的生长速率就越快。
实验证明:
在一定温度下纤维的生长速率与催化剂颗粒直径有一定的关系[2]:
R∝d-0.5,R为炭纤维的生长速率,d为催化剂颗粒直径。
[1]R.T.K.Baker,J.J.Chludzinski,Jr.,N.S.Dudash,A.J.Simoens.Theformationoffilamentouscarbonfromdecompositionofacetyleneovervanadiumandmolybdenum.Carbon,1983,21(5);463-468
[2]R.T.K.Baker.Catalyticgrowthofcarbonfilaments.Carbon,1989,27(3);315-323
载气/载体:
H2的加入可以使不利于碳源气体分解的金属碳化物出去,提高催化剂的催化性能。
氢气的流量越大生成的碳纤维的直径也随着增大,这主要由于H2的存在使碳源气体的分解速率减小,而催化剂则用充分的时间长大。
Preparationofcarbonnanofibersbythefloatingcatalystmethod.Carbon38(2000)1933–1937
Co/CNTs催化剂的制备流程如下:
取一定量纯化后的多壁碳纳米管,加入适量的甲醇超30min后磁搅拌;另取一定量的Co(NO3)2.6H2O加蒸馏水配成溶液,加入到上述碳纳米管溶液中(Co和C的摩尔比为1:
8)继续磁搅拌4h;在搅拌的同时缓慢滴入稀释了的氨水直至PH值接近12,继续搅拌24小时,将最后所得沉淀离心洗涤,110℃条件下烘干,置于瓷舟中,最后在Ar气氛下450℃煅烧1h
升温速度是10℃/min,首先通Ar气(40mlPmin)由室温升至550℃,通入H2气(80ml/min)和Ar气(16ml/min)还原1h;再升温至指定的裂解温度,通入C2H4(80ml/min)和H2气(16ml/min),恒温反应40min.TEM照片可以明显地看到,温度过低或者过高都不利于碳纳米管的生成,最佳反应温度为770℃.
由于Co颗粒与碳管间存在较强的作用力,温度过低,催化剂颗粒活性不足,碳原子难于向催化剂内扩散;如果温度过高,部分催化剂熔融变大,使碳原子沉积速度加快,大量的碳沉积在催化剂上,或形成无定形碳,沉积在已长成的碳纳米管上,或形成碳纤维
表明Co/CNTs催化剂的碳沉积量在40min以前和60min以后,碳沉积量增加的速度比较缓慢;40~60min内碳沉积量增加得最快.
钴/碳纳米管催化剂CVD法制备碳纳米管.材料科学与工程学报,第23卷第6期,2005.12
Zhuetal.[9]suggesteddifficultiesinsynthesizingCNTsoncarbonsubstrates,whicharearisenfromthediffusionofFeintothecarbonsubstratematrixandthecatalyticbutnonselectiveformationofmixedsp3–sp2carbons.TheinhomogeneousformationofCNTsuponcarbonfibers,asreportedbyZhaoetal.[3],impliesthatFe-bearingcatalysts
aredepositedoncarbonsurfacesfarlessreadilythanonquartz,butthecauseisunknown.
depositionofcatalystparticleswasenhancedwhenH2Swasaddedtothevaporphase.
H2S的存在能使催化剂颗粒更小,更均匀(如图)
ThermodynamiccalculationsindicatethatmuchofthesulfurinvolvedintheFe-bearingparticlesispresentasFeSorFe1_xS—withintherangeofH2Sconcentrationsexamined.
pointtoH2SsuppressingthedegreeofsupersaturationbylimitingtherateofcarbondissolutionintoFe-bearingparticles,oralternatively,decreasingthesolubilityofcarbonintheparticles.ThepresenceofH2Sinthevaporphaseataconcentrationof0.014–0.034vol%
Synthesisofcarbonnanotubesoncarbonfibersbymeansoftwo-stepthermochemicalvapordeposition.Carbon44(2006)1754–1761
therearetwoproblemsinCNTsgrowthoncarbonsubstrates:
Firstthecatalystsoftransitionmetalscaneasilydiffuseintothecarbonsubstrates,secondmixedphases
ofcarbonmaterialscanformonthecarbonsubstratesbecausegrowthconditionsaresimilartodiamondordiamond-likecarbongrowth[3].
thefloatingcatalystmethodismorefavorableforthegrowthofCNTsoncarbonfiberscomparingwiththermalmorefavorableforthegrowthofCNTsoncarbonfiberscomparingwiththermal,Itdecreasestheinter-diffusionamountofthetransitionmetalonthecarbonsurfacewhilethecontacttimedecreasesbetweenthetransition
metalandcarbonfibersurface
aligned
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