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Basics of CNT
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APRESENTATION ON
CARBON NANOTUBES
Contents # Discovery # Introduction # Properties # Synthesis # Applications
Discovery
Discovered by Sumio Iijima Multi-walled Nanotube in 1991
Single-walled Nanotube in 1993
Introduction
# Basic Structure
# Classification of Nanotube 1. Single-walled Nanotube 2. Multi-walled Nanotube
Basic Structure
Types of Nanotubes
1.Single –Walled Nanotubes a. Zigzag b. Armchair c. Chiral
Single –Walled Nanotubes
Single –Walled Nanotubes
How to Classify ?
Chiral Vector R = na1 + ma2
Single –Walled Nanotubes
d = (n2 + m2 + nm) 1/2 0.0783 nm Chiral angle = tan-1( n/(2m + n))
Ropes of Carbon Nanotubes
Lattice Parameter in CNT ropes = d + 0.34 nm
Types of Nanotubes
2. Multi-walled Carbon Nanotubes
Properties of CNT
1. Physical 2. Optical3. Electrical4. Thermal5. Elastic
Physical PropertiesAverage Diameter of SWNT 1.2-1.4 nm
Distance from opposite carbon atoms (line 1) 2.83 A
Analogous Carbon atom separation (line 2) 2.456 A
Parallel carbon bond separation (line 3) 2.45 A
Carbon bond length (line4) 1.42 A
C – C tight bonding overlap energy ~ 2.5 ev
Lattice constant 17 A
Density(10,10) Armchair(17,0) Zigzag(12,6) Chiral
1.33 g/cm3
1.34 g/cm3
1.40 g/cm3
Interlayer Spacing(n,n) Armchair(n,0) Zigzag(2n,n) Chiral
3.38 Å3.41Å3.39 Å
Optical Properties
Fundamental Gap: For (n, m); n-m is divisible by 3 [Metallic] 0 eVFor (n, m); n-m is not divisible by 3 [Semi-Conducting] ~ 0.5 eV
Egap=2y0acc/d
Optical Properties
Density of States
Optical Properties
Electrical Properties
Resistance 6500 Ω
Maximum Current Density 1013 A/m2
Thermal Properties
Thermal Conductivity ~2000 W /m-K
Phonon Mean Free Path ~ 100 nm
Relaxation Time ~ 10-11 s
Elastic Properties
Young's Modulus (SWNT) ~ 1 Tpa
Young's Modulus (MWNT) 1.28 Tpa
Maximum Tensile Strength(MWCT) ~63 GPa
Electronic Properties
Synthesis Of carbon Nanotubes
1. Arc Method
2. Laser Ablation
3. Chemical Vapour Deposition
1. Arc Method
--Yield up to 30% by weight
--Further purification is required
--Both SWNT and MWNT upto length of 50um can be produced
2. Laser Ablation
--Yield >70% by weight
--Produces primarily SWNT
--Further purification is required
--Most expensive method
3. Chemical Vapour Deposition
Chemical Vapour Deposition
--Large volume of CNTs can be formed
--Plasma enhanced chemical deposition- synthesize vertically aligned carbon nanotubes --Without the plasma, the resulting nanotubes are often randomly oriented
Advantages
- Single-Walled Nanotubes
- Multi-Walled Nanotubes
Single-Walled Nanotubes
1.In MWNT-electron scattering, and electrical contact cannot be made reliably to all of the constituent nanotubes. 2. Less Defective
3. Experimental studies are easy to perform
Multi-Walled Nanotubes
1. Their resistance to chemicals is improved
2. Do not need a catalyst for growth
3. Do not contain magnetic impurities
Applications
# Field Emission # Molecular Electronics # Fibres and Fabrics # Conductive Plastics # Catalyst Supports # Biomedical Applications # Energy Storage
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