background about carbon nanotubes
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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 - PowerPoint PPT PresentationTRANSCRIPT
Background about Carbon Nanotubes
CAR Seminar5 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
either conductors or semiconductors
intrinsic superconductivity (ballistic electron transport)
ideal thermal conductors field emitters
MAN 10Aug07
SWNT and MWNT
• Single Wall NanotubeDiameters 0.6-1.8 nm (1.4 nm is typical)
Elastic Modulus 1210 GPa
Strain 4%
Density 1.4 g/cm3
• Multi Wall NanotubeDiameters 20 - 50 nm
Elastic Modulus 1260 GPa
Strain 1.5%
Density 1.8 g/cm3
MAN 10Aug07
Chirality
1a
2a
1 2Chirality Vector na ma
1 25 0
(5,0)hC a a
Zigzag
1 23 3
(3,3)hC a a
Armchair
1 21 3
(1,3)hC a a
Chiral
MAN 10Aug07
Chirality and Structural Properties
MAN 10Aug07
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:
2 23h C CC ad n nm m
1 2
2 2
Chirality Vector
3
h
h C C
C na ma
C a n nm m
3 33 31 22 2 2 2, ,C C C C C C C Ca a a a a a
1a
2a
Chirality and Electrical Properties
Armchair (n=m)All metallicNone semiconducting
Chiral (n ≠ m)1/3 are metallic2/3 are semiconductingmetallic when (n-m)=3*integer
ZigZag (m=0)1/3 are metallic2/3 are semiconductingmetallic when n=3*integer
Example: (5,5) 200 atoms Diameter = 6.78 ÅLength = 24.60 Å
Example: (5,0) 200 atomsDiameter = 3.91 ÅLength = 42.60 Å
Example, (5,3) 196 atomsDiameter = 5.48 ÅLength = 29.82 Å
MAN 10Aug07
Chirality – Unique ID (n,m)
MAN 10Aug07
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.
Images are from:
http://www.blog.speculist.com/archives/000193.htmlhttp://www.swissvalley.com.sg/07bmc_slc01.htmhttp://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=
Applications of CNT
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)
12
3
4
SEM Images from NEU
• From the lower magnification (~200X to ~1000X) the CNT length is measured.
SEM Images from NEU• Used to visually assess the quality of CNT.
Can we develop an automated algorithm for determining quality? Is quality correlated to processing parameters?
13 s10 mA200 sccm
Cobalt Sputter Time: 13 sCobalt Sputter Current: 5 mAEthanol Gas Flow Rate: 200 sccm
Bad Results Good Results