carbon(同素异形体)graphite答辩课件

1、NanotechnologyLecture 3 Carbon Nanotube第1页，共29页。Carbon Nanotube Content Introduction of Carbon nanotube (what is?)Fullerene (?, invention, structure,difference)Types of carbon nanotubes and related structures (structure)PropertiesSynthesis (to fabricate)Potential and current applicationsDiscovery an

2、d Development of Carbon Nanotube第2页，共29页。What is Carbon Nanotube?第3页，共29页。Introduction of Carbon NanotubeCarbon nanotubes (CNTs) are allotropes of carbon(同素异形体）(graphite 石墨，diamond钻石， Fullerene）with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 2

3、8,000,000:1,which is significantly larger than any other material.（novel properties）They exhibit extraordinary strength and unique electrical properties, and are efficient thermal conductors. Their final usage, however, may be limited by their potential toxicity.Nanotubes are members of the fulleren

4、e structural family, which also includes the spherical buckyballsCarbon nanotubes are among the amazing objects that science sometimes creates by accident, without meaning to, but that will likely revolutionize the technological landscape of the century ahead. Our society stands to be significantly

5、influenced by carbon nanotubes, shaped by nanotube applications in every aspect, just as silicon-based technology still shapes society today. 第4页，共29页。History and ImpactsCarbon nanotubes have been synthesized for a long time as products from the action of a catalyst over the gaseous species originat

6、ing from the thermal decomposition of Hydrocarbons.The worldwide enthusiasm came unexpectedly in 1991, after the catalyst-free formation of nearly perfect concentric multiwall carbon nanotubes (c-MWNTs） was reported as by-products of the formation of fullerenes by the electric-arc technique.Conseque

7、ntly, about five papers a day with carbon nanotubes as the main topic are currently published by research teams from around the world, an illustration of how extraordinarily active and highly competitive is this field of research.Economical aspects are leading the game to a greater and greater exten

8、t. According to experts, the world market is predicted to be more than 430M$ in 2004 and estimated to grow to several b $ before 2009.第5页，共29页。Carbon nanotubesCarbon nanotubes are fullerene-related structures which consist of graphene cylinders closed at either end with caps containing pentagonal ri

9、ngs(五角环).Discovered in 1991 by the Japanese electron microscopist Sumio Iijima.Nanotubes could be produced in bulk quantities by varying the arc-evaporation conditions. 第6页，共29页。FullereneThe substance of the Fullerene was named after the American inventor, architects and philosophers Richard Buckmin

10、ster Fuller (1895 till 1983). As an architect, R.B.Fuller designed the constructions which exist of 5-corners and 6-corners, for example, the American pavilion to the Expo in 67 in Montral(geodesic dome). A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellips

11、oid, or tube. Spherical fullerenes are also called buckyballs, and cylindrical ones are called carbon nanotubes or buckytubes. Fullerenes are similar in structure to graphite, which is composed of stacked graphene sheets of linked hexagonal rings; but they may also contain pentagonal (or sometimes h

12、eptagonal) rings.第7页，共29页。FullereneThe existence of C60 was predicted by Eiji Osawa of Toyohashi University of Technology in a Japanese magazine in 1970With mass spectrometry, discrete peaks were observed corresponding to molecules with the exact mass of sixty or seventy or more carbon atoms. In 198

13、5, Harold Kroto etc，discovered C60, and shortly thereafter came to discover the fullerenes. Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of this class of compounds. Minute quantities of the fullerenes, in the form of C60, C70, C76, and C84

14、molecules, are produced in nature, hidden in soot and formed by lightning discharges in the atmosphere.Buckminsterfullerene C60The Icosahedral Fullerene C540第8页，共29页。Discovery of Carbon C601985, Robert F. Curl, discovered a new form of carbon，that 60 or 70 carbon atoms could cluster together to form

15、 a cage-like molecule. The molecular structure resembled the pattern of a soccer ball or the geodesic designs of Buckminster Fullerenes. Thus the name buckyballs or fullerenes. Since then the discovery has led to new research in polymers, semiconductors, and other various areas.Nobel Prize to their

16、finders in 1996第9页，共29页。After the IUPAC nomenclature the C60 has the following name: .2,14.03,12. 04,59.05,10.06,58. 07,55.08,53.09,21. 011,20.013,18.015,30. 016,28.017,25.019,24. 022,52. 023.50.026,49.027,47. 029,45.032,44.033,60. 034,57.035,43.036,56. 037,41.038,54.039,51. 040,48.042,46hexaconta-1

17、,3,5(10),6,8,11,13(18), 14,16,19,21,23,25,27,29(45),30,32(44),33,35(43), 36,38(54),39(51),40(48),41,46,49,52,55,57,59-triacont 第10页，共29页。FULLERENE MOLECULAR MODELS C56-C76 C56 (Td) Model C58 (C3v) C60(C2v) C60(C2v) C72 (D6d) C76 (D2) C56 (Td)Rotating Animation 第11页，共29页。Tetrahedral Junction of four

18、Nanotubes Nanotube w/ hemispheric 第12页，共29页。Structure of Carbon NanotubesSingle-Wall Nanotubes SWNTsThe (n,m) nanotube naming scheme can be thought of as a vector (Ch) in an infinite graphene sheet that describes how to roll up the graphene sheet to make the nanotube. T denotes the tube axis, and a1

19、 and a2 are the unit vectors of graphene in real space.Most single-walled nanotubes (SWNT) have a diameter of close to 1nanometer, with a tube length that can be many millions of times longer. The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of graphite called graphen

20、e into a seamless cylinder. The way the graphene sheet is wrapped is represented by a pair of indices (n,m) called the chiral vector. The integers n and m denote the number of unit vectors along two directions in the honeycomb crystal lattice of graphene. If m = 0, the nanotubes are called zigzag. I

21、f n = m, the nanotubes are called armchair. Otherwise, they are called chiral.第13页，共29页。Single-Wall Nanotubes SWNTsArmchair (n,n)The chiral vector is bent, while the translation vector stays straightGraphene nanoribbonThe chiral vector is bent, while the translation vector stays straightZigzag (n,0)

22、Chiral (n,m)n and m can be counted at the end of the tubeGraphene nanoribbon第14页，共29页。Single-Wall Nanotubes SWNTs(n,0) zigzag nanotube (9, 0)(n,n) armchair nanotube (5, 5)(n,m) helical (chiral) nanotube (10,5)( n and m are the integers of the vector OA considering the unit vectors a1 and a2. )- hexa

23、gonal rings, pentagonal rings at each tips;- C=C bond and CC bond, inducing a unique versatile electronic behavior. 第15页，共29页。Single-Wall Nanotubes SWNTsFig. 3.3 Image of two neighboring chiral SWNTs within a SWNT bundle as seen by high resolution scanning tunneling microscopy (by courtesy of Prof.

24、Yazdani, University of Illinois at Urbana, USA)第16页，共29页。Multiwall Nanotubes MWNT Fig. 3.5 (longitudinal view) of a concentric multiwall carbon nanotube (c-MWNT) prepared by electric arc. In insert, sketch of the Russian-doll-like display of graphenesMulti-walled nanotubes (MWNT) consist of multiple

25、 rolled layers (concentric tubes) of graphite;In the Russian Doll , sheets of graphite are arranged in concentric cylinders;In the Parchment model, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper. (3.3 );第17页，共29页。Multiwall Nanotubes MWNT

26、(a) as-grown. The nanotube surfaceis made of free graphene edges. (b) after 2,900 C heat-treatment. Both the herringbone and the bamboo textures have become obvious.Fig. 3.6a,b A herringbone(箭尾型） (and bamboo) multi-wall nanotube (bh-MWNT, longitudinal view) prepared by CO disproportionation on Fe-Co

27、 catalyst.第18页，共29页。Fig. 3.7 (a) A bamboo-herringbone multi-wall nanotube (bh-MWNT) showing the nearly periodic feature of the texture,which is very frequent; (b) high resolution image of a bamboo-concentric multi-wall nanotube (bc-MWNT) . They are sometimes referred as “nanofibers”.第19页，共29页。Proper

28、ties of Carbon NanotubeStrengththe strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively. results from the covalent sp bonds formed between the individual carbon atoms. In 2000, a MWCN was tested to have a tensile strength of 63gigapascals (the

29、 ability to endure tension of 6300kg on a cable with cross-section of 1 mm2.) low density for a solid of 1.3 to 1.4gcm3KineticMulti-walled nanotubes, multiple concentric nanotubes precisely nested within one another, exhibit a striking telescoping property whereby an inner nanotube core may slide, a

30、lmost without friction, within its outer nanotube shell thus creating an atomically perfect linear or rotational bearing. Electricalmoderate semiconductor.第20页，共29页。Synthesis of Carbon Nanotube1 Laser Ablation Experimental Devices - graphite pellet containing the catalyst put in an inert gas filled

31、quartz tube; oven maintained at a temperature of 1,200 C;energy of the laser beam focused on the pellet;vaporize and sublime the graphiteSketch of an early laser vaporization apparatusThe carbon species are there after deposited as soot in different regions: water-cooled copper collector, quartz tub

32、e walls.第21页，共29页。2 Synthesis with CO2 laserFig. 3.10 Sketch of a synthesis reactor with a continuous CO2 laser device Vaporization of a target at a fixed temperature by a continuous CO2 laser beam ( = 10.6m). The power can be varied from 100Wto 1,600 W. The synthesis yield is controlled by three pa

33、rameters: the cooling rate of the medium where the active, secondary catalyst particles are formed, the residence time, and the temperature (in the 1,0002,100K range) at which SWNTs nucleate and grow.第22页，共29页。3 Electric-Arc Method Experimental Devices Sketch of an electric arc reactor. It consists

34、of a cylinder of about 30 cm in diameter and about 1m in height. After the triggering of the arc between two electrodes, a plasma is formed consisting of the mixture of carbon vapor, the rare inert gas (helium or argon), and the vapors of catalysts. The vaporization is the consequence of the energy

35、transfer from the arc to the anode made of graphite doped with catalysts. 第23页，共29页。Electric-Arc Method Experimental DevicesIn view of the numerous results obtained with this electric-arc technique, it appears clearly that both the nanotube morphology and the nanotube production efficiency strongly

36、depend on the experimental conditions and, in particular, on the nature of the catalysts.第24页，共29页。4 Solar energy reactor Sketch of a solar energy reactor in use in Odeilho (France). Gathering of sun rays, focused in F; (b) Example of Pyrex chamber placed in (a) so that the graphite crucible is at t

37、he point F.The high temperature of about 4,000K permits both the carbon and the catalysts to vaporize. The vapors are then dragged by the neutral gas and condense onto the cold walls of the thermal screen. 第25页，共29页。Application: Nanotube-based SPM (scanning probe microscopy) tipsFig. 3.27 Scanning electron microscopy image of a carbon nanotube (MWNT) mounted onto a regular ceramic tip as a probe for