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1、One-Dimensional Nanomaterials Carbon Nanotubes,Reporter : Teammates: Wan jun Wu Yuanhe Wang Binbin Yang Yongzhu,1,1,4,2,3,Outline,Introduction,Structure and Properties,Preparation,Applications,Introduction,Sumio Iijima,Carbon nanotubes (CNTs) was first discovered by Iijima in 1991,CNTs: rolling up a
2、 thin graphene sheet.,CNTs,SWCNTs,MWCNTs,Production Methods,1.Arc-discharge method 2.Laser Vaporization method 3.Chemical Vapor Deposition (CVD),Preparation,CVD methods have been successfully applied in making carbon nanotubes. The growth process with this method involves heating a catalyst material
3、 to high temperatures in a tube furnace 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 tempera
4、ture.,Left diagram: base growth mode. Right diagram: tip growth mode,CVD growth mechanism,Process : 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
5、 leads to the formation of tubular carbon solids in sp2 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
6、 open end. Tubule formation is favored over other forms 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 methods,Single-walled nanotubes grown by laser ablation,Structure and Properties,The uniquen
7、ess of the nanotube arises from its structure and the inherent 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 rep
8、eating structural unit) introduces significant changes in the electronic density of states, and hence provides a unique electronic character for the nanotubes.,Wet Spinning,An aqueous suspension of carbon nanotubes, stabilized by a surfactant, is injected into a flowing solution of polyvinyl alcohol
9、 which causes the fiber to coagulate. It is then removed from the bath and washed to remove excess polymer.,Organization into Fibers,Dry Spinning,Dry spinning from carbon nanotube forests. (a) A typical “forest” of multiwall carbon nanotubes grown from a substrate. (b) Photograph of the spinning of
10、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 cylindrical pillars.,Organization on Surfaces,Vacuum Microelectronics: Electron field emis
11、sion materials have been investigated extensively for technological applications, such as flat panel displays, electron guns in electron microscopes, microwave amplifiers. Energy Storage: rechargeable lithium batteries, Hydrogen Storage. Filled Composites: reinforcements in high strength, light weig
12、ht, 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: fabricate one-dimensional nanowires.,Applications,Cathode-Ray Lighting Elements,Demo
13、nstration field emission light source using carbon nanotubes as the cathodes,Left: Schematic of a prototype field emission display using carbon nanotubes. Right: A prototype 4.5 field emission display fabricated by Samsung using carbon nanotubes,Flat Panel Display,(c) Stress-strain relationship obse
14、rved 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 can be seen that the load transfer to the nanotube is higher during the c
15、ompression 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 nanotube-doped polymers and their use in Organic Light Emitting Diodes (OLED
16、) . The construction of the OLED is shown in the schematic of (top). The bottom figure shows emission from OLED structures. Nanotube doping tunes the emission color. With SWNTs in the buffer layer, holes are blocked and recombination takes place in the transport layer and the emission color is red. Without nanotubes present in the buffer layer, the emission 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 fo
