Carbon Nanotubes

1. Carbon Nanotubes

2. History of Nanotubes • Discovery of buckminsterfullerene in 1985 sparked interest in other stable carbon structures • In 1991 Sumio Iijima discovered multi-walled carbon nanotubes and created first protocol for pure nanotubes • Carbon “fibers” were seen as byproducts of catalytic experiments since 1976 • In 1993 Iijima produced single-walled nanotubes with diameter ~1nm

3. History of nanotubes • M. Endo used a catalytic chemical vapor deposition method (1976) • Not industrially feasible • Iijima used an arc-evaporation method • Purer product • Efforts to control diameter, number of layers and purity

4. Producing multi-walled nanotubes • The arc-evaporator apparatus produces the highest-quality nanotubes • The first nanotubes had two layers with diameter ranging from 3 to 30 nanometers • Pass 50 amps of current between two graphite electrodes in a cloud of helium • Some of the graphite vaporizes on the cathode, containing carbon nanotubes

5. Producing single-walled nanotubes • Pass a carbon-containing gas, like a hydrocarbon, over a nano-sized metal catalyst (Fe, Ni, or Co) • Metal particles catalyze the break down of gaseous molecules into carbon • Nanotube begins to grow with the metal at one end • Poorer quality but better for volume production • Third method comes from vaporizing a metal-graphite target with a laser • Results in high yield of single-walled nanotubes

6. Consists of 6-Membered Carbon Rings that Form Long, Thin, Tubular Structures • Similar to Graphite • Three Different Conformations • Arm Chair • Zig-Zag • Chiral Physical Properties of Carbon Nanotubes

7. Physical Properties of Nanotubes II • The properties of CNTs are unparalleled by any substance. • Strength • Conductivity and Ballistic Transport • Electrical • Fourier’s Law H=(ΔQ/Δt)=k*A*(ΔT/x) • Thermal conductivity k=(ΔQ/ΔT)*(1/A)*(x/ΔT) • Optical • CTNs will replace common infrastructures in modern technology

8. Commercial applications for CNTs are not really applicable because of the high cost of CNT production • Analysts in 2004 originally thought CNT prices would drop to a reasonable price by the present, but this was far too optimistic • There’s little doubt that once the purification and assembly costs go down, CNTs will be wildly used • In February, a company was able to make relatively large sheets (6’x3’) and are looking to mass produce by 2012 • There are also some issues with the toxicity of CNTs • They are normally made with heavy metal catalysts and if they are not purified properly this can lead to poisoning in biological systems • It is still useful to examine its possible functions on a smaller scale (following slides) Applications of CNTs Commercial

9. Electronics • The high thermal conductivity and low current resistance makes CNTs very valuable to the future of electronics • Many developers are making smaller and smaller devices and overheating is a large problem • They can also be used in electronics for electromagnetic shielding because it has good electrostatic dissipation properties • CNTs may also revolutionize the way speakers are produced. • A team in China created speakers using CNTs that were functional over a wide range of sounds including the range of human hearing • The CNT film a only a few nanometers thick and is used to make the sound using an alternating current.

10. Medicine • CNTs have many potential applications in the medical world • They can be used to generate heat (via radio waves) or as drug vectoring agents • Have major implications for tissue engineering • Can be used for “improved tracking of cells, sensing of microenvironments, delivering of transfection agents and scaffolding for incorporating with the hosts body” • CNTs are ideal for working in nano environments from 1-100 nm. • Graph below shows how drastically CNT research in the biomedical field has increased • CNTs will be most useful as structural supports as tissue scaffolding, making these tissues stronger and their conductivity can be used for directed cell growth

12. Other Applications • Preposterous • Space Elevator • Not Crazy • Tennis rackets, bikes, handlebars, hockey and lacrosse sticks • New ultra-light, ultra-strong body armor for soldiers • CNTs have been used to develop Ultra Capacitors • Swapping conventional capacitor materials with sheets of CNTs greatly maximizes surface area and creates a much more potent capacitor in a smaller space

13. Citation • Barron, A. Khan, M. “Carbon nanotubes: Opportunities and Challenges”. Advanced Materials and Processes. 2008. • Xiao, L. Chen, Z. et al. “Flexible, Stretchable, Transparent Carbon Nanotube Thin Film Loudspeakers”. NanoLetters. 2008 • Bullis, K. “The Ultra Battery” Technology Review. 2006 • Harrison, B. Atala, A. “”Carbon Nanotube applications for tissue engineering”. Biomaterials. 28(2007): 344-353 • Harris, Peter. "Carbon Nanotubes." A carbon nanotube page. 1 Mar. 2007. Centre for Advanced Microscopy at University of Reading. 1 Dec. 2008 <http://www.personal.rdg.ac.uk/~scsharip/tubes.htm>. • Ota, Masahiro. "The Carbon Nanotube, a Product of Nanotechnology." AICHI VOICE (Cutting Edge). 2002. 2 Dec. 2008 <http://www2.aia.pref.aichi.jp/voice/no15/15_cutting_edge.html>.