Synthesis of nanotubes. Ewelina Broda

Transcription

1 Synthesis of nanotubes Ewelina Broda

2 Presentation Overview 1. Introduction 2. History 3. Types and structures 4. Properties 5. Synthesis 6. Applications 7. References

3 Allotropes of Elemental Carbon

4 History 1985 Discoverey of the buckyball (C 60 ) and other fullerenes R. E. Smalley (Nobel Prize winning in 1996) 1991 Discovery of multi-wall carbon nanotubes S. Iijima 1992 Conductivity of carbon nanotubes J. W. Mintmire, B. I. Dunlap and C. T. White 1993 Structural rigidity of carbon nanotubes G. Overney, W. Zhong, and D. Tománek 1993 Synthesis of single-wall nanotubes S. Iijima and T. Ichihashi 1995 Nanotubes as field emitters A.G. Rinzler, J.H. Hafner, P. Nikolaev, L. Lou, S.G. Kim, D. Tománek, P. Nordlander, D.T. Colbert, and R.E. Smalley 1997 Hydrogen storage in nanotubes A. C. Dillon, K. M. Jones, T. A. Bekkendahl, C. H. Kiang, D. S. Bethune and M. J. Heben 1998 Synthesis of nanotube peapods B.W. Smith, M. Monthioux, and D.E. Luzzi 2000 Thermal conductivity of nanotubes S. Berber, Y.K. Kwon, D. Tománek 2001 Integration of carbon nanotubes for logic circuits P.C. Collins, M.S. Arnold, and P. Avouris 2001 Intrinsic superconductivity of carbon nanotubes M. Kociak, A. Yu. Kasumov, S. Guéron, B. Reulet, I. I. Khodos, Yu. B. Gorbatov, V. T. Volkov, L. Vaccarini, and H. Bouchiat

5 Classification Non carbon nanotubes MX 2 compounds (M=transition metal; X= chalogen), eg.: WS 2 and MoS 2 ; B x C y N z, eg.: BN, BC 3 and BC 2 N Carbon nanotubes

6 Classification Single - walled nanotubes Multi - walled nanotubes

7 Multi Walled Nanotubes Parchment model Russian doll model

8 Single Walled Nanotubes Graphene Carbon Nanotube Mr. Anurak Udomvech Types of SWNT

9 Construction of Nanotubes a,a 1 2 primitive lattice vectors of graphene Chiral vector: C h = n 1 a 1 + n 2 a 2 n 1,n 2 integers: chiral numbers T tube axis Mirror lines: "zig-zag line through the midpoint of bonds "armchair line through the atoms θ - chiral angle Sixfold symmetry: 0 θ < 60

10 Armchair (n,n) Zigzag (n,0) Chiral (n,m)

11 Properties Extraordinary electric properties Very high tensile strength Highly flexible can be bent considerably without damage Very elastic ~18% elongation to failure Twice the thermal conductivity of diamonds Low thermal expansion coefficient Good electron field emitters High aspect ratio (length = ~1000 x diameter) Reported to be thermally stable in a vacuum up to 2800 deg. Centigrade (and we fret over CPU temps over 50 o C)

12 Electrical conductivity Properties

13 Properties

14 Synthesis 1.) Arc discharge 2.) Laser ablation 3.) Chemical vapor deposition (CVD) Techniques differ in: Type of nanotubes (SWNT / MWNT ) Catalyst used Yield Purity

15 Growth Mechanism

16 Arc Discharge

17 Arc Discharge Electrodes are composed of high purity graphite (>99.999%) ~70 A at ~18 V DC is applied to the electrodes Carbon nanotubes are formed at atmospheric pressures from the electrodes Information courtesy of: K. Anazawa, K. Shimotani, C. Manabe, H. Watanabe, and M. Shimizu. High-purity magnetic field

18 Laser Ablation

19 Laser Ablation A well mixed acetylene-air mixture is burned inside a tube furnace A laser is used to vaporize a metal target (either Fe or Ni) The post-flame exhaust gas is mixed with the metallic vapor and allowed to cool During cooling, carbon nanotubes are formed

20 Chemical Vapor Deposition (CVD)

21 Chemical Vapor Deposition (CVD) Source of carbon atoms usually comes from an organic compound Mixed with a metal catalyst and inert gas Atomized and sprayed into reactor with temperatures ranging from 600ºC to 1200ºC Pyrolysis of organic compound deposits carbon (as soot) and carbon nanotubes on reactor wall (usually a tube constructed from quartz)

22 Sources of Carbon Typical Organic/Catalyst Mixtures Xylene/ferrocene (Andrews et al.) Toluene, benzene, xylene, mesitylene, and n- hexane/ferrocene (Vivekchand et al.) Ethylene and ethanol/fe, Co, and Mo alloys (K. Mizuno et al.) Typical Carrier Gases Argon Hydrogen

23 Purification Contaminants: Catalyst particles Carbon clusters Smaller fullerenes: C 60 / C 70 Impossibilities: Completely retain nanotube structure Single-step purification Only possible on very small scale: Isolation of either semi-conducting SWNTs

24 Purification: Techniques Removal of catalyst: Acidic treatment (+ sonication) Thermal oxidation Magnetic separation (Fe) Removal of small fullerenes Micro filtration Extraction with CS 2 Removal of other carbonaceous impurities Thermal oxidation Selective functionalisation of nanotubes Annealing

25 Synthesis The Wondrous World of Carbon Nanotubes Eindhoven University of Technology

26 Applications Carbon Nano-tubes are extending our ability to fabricate devices such as: Molecular probes Pipes Wires Bearings Springs Gears Pumps

27 Applications Molecular transistors. Field emitters. Building blocks for bottom-up electronics. Smaller, lighter weight components for next generation spacecraft.

28 Possible Applications of CNTs

29 Thank You for Your Attention!

30 References Carbon Nano-tubes: An Overview An Undergraduate Research Paper By Scott E. Wadley Steffen Weber's Crystallography Picture Book Nanotubes & Nanocones Structure and Properties of Carbon Nanotubes Jannik Meyer R. Andrews, D. Jacques, D. Quan, and T. Rantell. Multiwall Carbon Nanotubes: Synthesis and Application. Accounts of Chemical Research. Vol. 35, No. 12, 2002 A. Zettl Non-Carbon Nanotubes Advanced Materials Vol. 8, No. 5, 1996 S.R.C. Vivekchand, L.M. Cele, F.L. Deepak, A.R. Raju, and A. Govindaraj. Carbon nanotubes by nebulized spray pyrolysis. Chemical Physics Letters. 386 (2004)