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