Gaxela N, Manaetja K.P, Mulaudzi S, Senosi R Supervisor: Dr V.L.Katkof

TABLE OF CONTENTS Introduction Classification of CNTs Applications Properties Conclusions

INTRODUCTION Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Their properties are valuable for nano-technology, electronics, optics and other fields of materials science and technology. They also possess thermal conductivity, mechanical and electrical properties. Their name is derived from their long, hollow structure with the walls formed by one- atom-thick sheets of carbon, called graphene. These sheets are rolled at specific and discrete angles. Multi-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphite. In this work, we have investigated the bandstructures and the effective mass of nanotubes. The calculations were performed using the tight-binding approach and roman lab programme was used to draw the energy bandstructures of carbon nanotubes.

A CNT is characterized by its Chiral Vector: C h = n â 1 + m â 2,   Chiral Angle with respect to the zigzag axis A Single-Walled Carbon Nanotubes structure is expressed in terms of one-dimensional unit cell. STRUCTURES

a b c a) Armchair (n=m) f.e. (5,5)  = 30 b) Zig Zag (n=0,m≠0) f.e (9,0)  = 0  c) Chiral (n≠0,m≠0) f.e (10,5) 0  <  < 30

Multi-walled carbon nanotubes

Classification of Carbon nanostructures There are several parameters that characterizes the nanostructures which include but not limited: Hybridization – Sp : - Carbine Sp 2 : - Graphene Sp 3 : -Graphite Dimensions (Lengths, Width and Thickness)

APPLICATIONS 1. Structural- properties, many structures have been proposed ranging from everyday items like clothes and sports gear to combat jackets and space elevators 2. Electrical circuits- Large structures of carbon nanotubes can be used for thermal management of electronic circuits. 3. Electric cables and wires- Wires for carrying electrical current may be fabricated from pure nanotubes and nanotube-polymer composites. 4. Paper batteries (a battery engineered to use a paper-thin sheet of cellulose) - The nanotubes act as electrodes; allowing the storage devices to conduct electricity. 5. Solar cells- developed at the New Jersey Institute of Technology use a carbon nanotube complex, formed by a mixture of carbon nanotubes and carbon buckyballs (known as fullerenes) to form snake-like structures 6. Ultracapacitors- MIT Laboratory for Electromagnetic and Electronic Systems uses nanotubes to improve ultracapacitors 7. Medical- In the Kanzius cancer therapy, single-walled carbon nanotubes are inserted around cancerous cells, then excited with radio waves, which causes them to heat up and kill the surrounding cells.

a)Metallic nanotubes b)Semiconductor nanotubes PROPERTIES p = 0, ±1, ±2 …

ENERGY BANDSTRUCTURE OF GRAPHENE MONOLAYER E Px Py E-Ef ~ |P|

ENERGY BANDSTRUCTURE OF GRAPHENE BILAYER E Px Py E-Ef ~ P 2 E

ENERGY BANDSTRUCTURE OF FEW-LAYER GRAPHENE 

CALCULATION OF EFFECTIVE MASS FOR NANOTUBES DEFINITION: RESULTS:

CONCLUSIONS The set of effective mass for carbon nanotubes was calculated. Tight binding approach was used. It was shown that for the (5, 5) nanotube eff. Mass for first branch equal to 0, for other branches it has the order of the magnitude of silicon effective mass

ACKNOWLEDGEMENTS

THANK YOU Спасиьо SPA-SÉE-BA RE A LEBOGA RI A LIVHUWA