材料結構及其性能(英文版)

1、One-Dimensional NanomaterialsCarbon NanotubesReporter : Teammates: Wan jun Wu Yuanhe Wang Binbin Yang Yongzhu11423OutlineIntroductionStructure and PropertiesPreparationApplications IntroductionCarbon nanotubes (CNTs) was first discovered by Iijima in 1991CNTs: rolling up a thin graphene sheet. CNTsS

2、WCNTs MWCNTsProduction Methods1.Arc-discharge method 2.Laser Vaporization method3.Chemical Vapor Deposition (CVD)PreparationCVD methods have been successfully applied in making carbon nanotubes. The growth process with this method involves heating a catalyst material to high temperatures in a tube f

3、urnace and flowing a hydrocarbon gas through the tube reactor for a period of time. Materials grown over the catalyst are collected upon cooling the system to room temperature. parameters: hydrocarbons, catalysts: such as transition-metal nanoparticles growth temperature. Left diagram: base growth m

4、ode. Right diagram: tip growth modeProcess : Dissociation of hydrocarbon molecules catalyzed by the transition metal. Dissolution and saturation of carbon atoms in the metal nanoparticle. Precipitation of carbon from the saturated metal particle leads to the formation of tubular carbon solids in sp2

5、 structure. Growth mechanism of a carbon nanotube at an open end by the absorption of C2 dimers and C3 trimers (in black), respectively The adsorption of a C2 dimer or a C3 trimer at the active dangling bond edge site will add one hexagon to the open end. Tubule formation is favored over other forms

6、 of carbon, because a tube contains no dangling bonds and therefore is in a low energy form. Schematic experimental setups for other two nanotube growth methodsSingle-walled nanotubes grown by laser ablationStructure and Properties The uniqueness of the nanotube arises from its structure and the inh

7、erent subtlety in the structure, which is the helicity in the arrangement of the carbon atoms in hexagonal arrays on their surface honeycomb lattices. The helicity (local symmetry), along with the diameter (which determines the size of the repeating structural unit) introduces significant changes in

8、 the electronic density of states, and hence provides a unique electronic character for the nanotubes.CNTsCNTssuperior mechanical propertieslowmassdensityhighelectronmobilitylarge current-carrying capabilityhigh thermal conductivitylarge aspect ratioWet SpinningAn aqueous suspension of carbon nanotu

9、bes, stabilized by a surfactant, is injected into a flowing solution of polyvinyl alcohol which causes the fiber to coagulate. It is then removed from the bath and washed to remove excess polymer. Organization into FibersDry SpinningDry spinning from carbon nanotube forests. (a) A typical “forest” o

10、f multiwall carbon nanotubes grown from a substrate. (b) Photograph of the spinning of a carbon nanotube fiber from a forest of multiwall nanotubes.(a) Picture of a SWNTs forest. (b) SEM image of the SWNTs forest ledge. (c) HRTEM image of SWNTs. (d) A large area TEM image. (e) SEM image of SWNT cyli

11、ndrical pillars.Organization on SurfacesVacuum Microelectronics: Electron field emission materials have been investigated extensively for technological applications, such as flat panel displays, electron guns in electron microscopes, microwave amplifiers.Energy Storage: rechargeable lithium batterie

12、s, Hydrogen Storage.Filled Composites: reinforcements in high strength, light weight, high performance composites, such as spacecraft and aircraft body.Nanoprobes and Sensors: such as high resolution imaging, nano-lithography, nanoelectrodes, drug delivery, sensors and field emitters.Templates: fabr

13、icate one-dimensional nanowires.ApplicationsCathode-Ray Lighting ElementsDemonstration field emission light source using carbon nanotubes as the cathodesLeft: Schematic of a prototype field emission display using carbon nanotubes.Right: A prototype 4.5 field emission display fabricated by Samsung us

14、ing carbon nanotubesFlat Panel Display (c) Stress-strain relationship observed during the tension/compression testing of the nanotube-epoxy composite (the curve that shows larger slope, both on the tension and compression sides of the stress-strain curve, belongs to the nanotube epoxy composite). It

15、 can be seen that the load transfer to the nanotube is higher during the compression cycle (seen from the deviation of the composite curve from that of the pure epoxy), because in tension the individual layers of the nanotubes slide with respect to each other. Results from the optical response of na

16、notube-doped polymers and theiruse in Organic Light Emitting Diodes (OLED) . The construction of the OLEDis shown in the schematic of (top). The bottom figure shows emission from OLEDstructures. Nanotube doping tunes the emission color. With SWNTs in the bufferlayer, holes are blocked and recombinat

17、ion takes place in the transport layer andthe emission color is red. Without nanotubes present in the buffer layer, theemission color is green.Use of a MWNT as an AFM tip. At the center of the Vapor Grown Carbon Fiber (VGCF) is a MWNT which forms the tip. The VGCF provides a convenient and robust te

18、chnique for mounting the MWNT probe for use in a scanning probe instrumentMWCNTsMWCNTs as templates. The left-hand figure as templates. The left-hand figure is a schematic that shows is a schematic that shows the filling of the empty one-dimensional hollow core ofthe filling of the empty one-dimensional hollow core of nanotubes with nanotubes with foreign substances. (a) Shows a foreign substances. (a) Shows a HRHRTEM image of aTEM image of a tube tip that has tube tip that has been attacked by oxidation; the preferential attackbeen attacked by oxidatio