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Background about Carbon Nanotubes

Background about Carbon Nanotubes. CAR Seminar 5 November 2010 Meg Noah. Carbon Nanotubes (CNT). A rolled up graphene sheet Unique physical & chemical properties flexibility extremely strong, about 100 times stronger (stress resistant) than steel light-weight 1/6th the weight of steel

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Background about Carbon Nanotubes

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  1. Background about Carbon Nanotubes CAR Seminar 5 November 2010 Meg Noah

  2. Carbon Nanotubes (CNT) • A rolled up graphene sheet • Unique physical & chemical properties • flexibility • extremely strong, about 100 times stronger (stress resistant) than steel • light-weight 1/6th the weight of steel • either conductors or semiconductors • intrinsic superconductivity (ballistic electron transport) • ideal thermal conductors • field emitters MAN 10Aug07

  3. Single Wall Nanotube Diameters 0.6-1.8 nm (1.4 nm is typical) Elastic Modulus 1210 GPa Strain 4% Density 1.4 g/cm3 Multi Wall Nanotube Diameters 20 - 50 nm Elastic Modulus 1260 GPa Strain 1.5% Density 1.8 g/cm3 SWNT and MWNT MAN 10Aug07

  4. Chirality MAN 10Aug07

  5. Chirality and Structural Properties • The hexagonal lattice vectors: • For graphite aC-C= 1.421 Å is the bond distance. For CNT it is about 1.44 Å and depends on radius. • SWNT Circumference from Chirality indices (n,m): • The Diameter of the SWNT: MAN 10Aug07

  6. Chirality and Electrical Properties Armchair (n=m) All metallic None semiconducting ZigZag (m=0) 1/3 are metallic 2/3 are semiconducting metallic when n=3*integer Chiral (n ≠ m) 1/3 are metallic 2/3 are semiconducting metallic when (n-m)=3*integer Example: (5,5) 200 atoms Diameter = 6.78 Å Length = 24.60 Å Example: (5,0) 200 atoms Diameter = 3.91 Å Length = 42.60 Å Example, (5,3) 196 atoms Diameter = 5.48 Å Length = 29.82 Å MAN 10Aug07

  7. Chirality – Unique ID (n,m) • The Chirality Vector indices (n,m) uniquely define the SWNT: • Diameter • Electronic Properties (metallic, insulating, semiconducting) • To know the diameter of a SWNT is to know the chirality indices (n,m), and thus it’s structural, electronic and mechanical properties. MAN 10Aug07

  8. Applications of CNT 1 2 4 3 1: Tethering cable for he space elevator 2: Low power flexible displays 3: Light weight Bicycle frames 4: Transistors for future central processing unit (CPU) Images are from: http://www.blog.speculist.com/archives/000193.html http://www.swissvalley.com.sg/07bmc_slc01.htm http://www.t3.co.uk/news/247/general/general/bendable_computer_screens_roll_into_action http://www.computerpoweruser.com/Editorial/article.asp?article=articles/archive/c0209/60c09/60c09.asp&guid=

  9. From the lower magnification (~200X to ~1000X) the CNT length is measured. SEM Images from NEU

  10. Used to visually assess the quality of CNT. Can we develop an automated algorithm for determining quality? Is quality correlated to processing parameters? SEM Images from NEU Bad Results Good Results Cobalt Sputter Time: 13 s Cobalt Sputter Current: 5 mA Ethanol Gas Flow Rate: 200 sccm 13 s 10 mA 200 sccm

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