纳米材料课件6.pdf

STM image of a single-walled carbon nanotubeAFM image of SWNTs and SWNT bundlesMethods for Preparation of SWNTs Arc-Charge Laser Ablation Chemical Vapor Deposition1200C FurnaceNd:YAG Laser500 torr ArC target(2%Ni:Co)Cold finger as collectorLaser Ablation1200C FurnacecatalystFeed gasFeedStock Gas:CO,CH4,etc.Catalyst:Fe,Mo,Ni,Co etc.Temperature:700 1100 CChemical Vapor DepositionLaser MethodCVD MethodArc MethodSchematic show of the growth mechanism of SWNT by CVDDeposition of carbonSchematic show of the growth mechanism of SWNT by CVDDeposition of carbonSchematic show of the growth mechanism of SWNT by CVDDeposition of carbonCarbon getting SaturatedSchematic show of the growth mechanism of SWNT by CVDDeposition of carbonCarbon getting SaturatedSchematic show of the growth mechanism of SWNT by CVDDeposition of carbonCarbon getting SaturatedTop-growthSchematic show of the growth mechanism of SWNT by CVDDeposition of carbonCarbon getting SaturatedBase-growthTop-growthSchematic show of the growth mechanism of SWNT by CVD普通化学第2-4 章SubstrateCH4Purification of SWNTSWNTSmall carbon pieces soluble in basic H2OCatalytic particlesReflux in HNO3Raw Materials:SWNTAmorphous carbonCatalytic particlesCross FlowFiltrationSWNTCatalytic particlesStrong magnetSWNT(Jie Liu et al.,Science,280,1253-1256)Acid Based PurificationBefore PurificationAfter PurificationCutting SWNTs:Why we need to do it and what is the challenge As-purified SWNTs are tangled,nearly endless ropes.Some applications prefer short nanotubes:Using SWNT as quantum wires in molecular electronic devices Challenge:The end of nanotubes are much more reactive than the side wall!AFM Images of Cut SWNTShortening of Cut SWNTLength(nm)0200400600800100012001400Distribution(a.u.)0123456SN cut(no polishing)266 nmLength(nm)0200400600800100012001400Distribution(a.u.)02468101214In hot SN for one hour147 nmSolution Properties of SWNTs Water with Surfactant;nanotubes are in bundles DMF and Similar Solvent;Form very good suspension/solution with purified SWNT;Nanotubes in solution are all individual.Properties of Single Walled Carbon NanotubesSizeDensityTensile StrengthResilienceCurrent Carrying CapacityField EmissionHeat TransmissionE-beam lithography can create lines 50 nm in wide,a few nm thickSWNT0.6 to 0.8 nm in diameterBy comparison1.33 to 1.40 g/cm345 billion pascals Can be bent at large angels and restraightened without damageEstimated at 1 billion amps per square centimeterCan activate phosphors at 1-3 V if electrodes are spaced 1m apartPredicted to be as high as 6,000 W/mKStable up to 2,800C in vacume,750 C in air$1,500/g from Bucky USAAl:2.7 g/cm3High-strength steel alloys break at 2 billion PaMetals and carbon fibres fracture at grain boundariesCopper wires burn out at about 1 milion A/cm2Mo tips require fields of 50-100 V/pm and have limited lifetimesNearly pure diamond transmits 3,320 W/mKMetal wires in microchips melt at 600 to 1,000 C Au:about$10/gTemperature StabilityCost