[attachment=12373]
ABSTRACT:-
Nanotechnology is the study and development of particles and even machines on a cellular scale. A single particle of 10-9 has 109 applications. Nanotechnology also improves the lives and safety of persons in every area of endeavor this can be achieved by developing a nanoscale carbon fiber that could revolutionize bullet-proof vests.
In 1991, when the carbon nanotubes have just come out, had been touted as “the next generation of great invention.” Carbon nanotubes are allotropes of carbon. Carbon nanotubes do have its unique features, its strength, even more than 100 times that of steel. A traditional bullet-proof vest works by distributing the force of impact over an area larger than the bullet. Unfortunately, the impact of the bullet can still cause internal injury, depending on the distance from which the bullet was fired and the caliber and velocity of the bullet. The chemical bonding of nano tubes are composed entirely of sp2 bonds, similar to those of graphite. The fiber is very strong, lightweight and good at absorbing energy in the form of fragments traveling at very high velocity. Carbon Nanotubes woven into bullet-proof vests absorb the force of the bullet and cause the projectile to bounce off, causing no harm to the person wearing the vest. In future, these amours can be used for military applications.
INTRODUCTION:-
Technology that works at the nanometer scale of molecules and atoms will be a large part of nano technology. This technology will be enabling great improvements in all the fields of human presence .Electronics is an area where nano technology making great gain.
CARBON NANOTUBES is one of the main applications of nano technology. Carbon nano tubes are allotropes of carbon. They are of so many types. Among them single nano tubes have more significance. A carbon nano tube is a one-atom thick sheet of graphite rolled up into a seamless cylinder with diameter on the order of a nanometer. This results in a nanostructure where the length-to-diameter ratio exceeds 1,000,000. They exhibit extraordinary strength and unique electrical properties. The inherent property of elasticity made them to show rebounding property. The nano tubes are created rapidly by spraying a carbon source, like ethanol, and an iron nano catalyst through a hydrogen carrier, and into a furnace at 1,200 degrees Celsius.
The size of the nano tube is in the order of few nano meters, approximately 1/50000th of the width of a human hair, while they can be up to several millimeters in length. . Nano tubes are mainly categorized as single-walled nano tubes and multi-walled nano tubes. Among them single walled tubes are used to make bullet proof vests which are mainly used for military applications.
EVOLUTION:-
They had been discovered in 1991.The current huge interest in carbon nano tubes is a direct consequence of the synthesis of buckminsterfullerene, C60. The search was given new importance when it was shown in 1990 that C60 could be produced in a simple arc-evaporation apparatus readily available in all laboratories. The tubes contained at least two layers, often many more, and ranged in outer diameter from about 3 nm to 30 nm. They were invariably closed at both ends. In 1993, a new class of carbon nano tube was discovered, with just a single layer. It was soon established that these new fibers had a range of exceptional properties (see below), and this sparked off an explosion of research into carbon nano tubes. Recent research has focused on improving the quality of catalytically-produced nano tubes.
STRUCTURE:-
The nature of the bonding of a nano tube is described by applied quantum chemistry, specifically, orbital hybridization. The chemical bonding of nano tubes are composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, which is stronger than the sp3 bonds found in diamond, provides the molecules with their unique strength. Nano tubes naturally align themselves into "ropes" held together by Vander Waals forces. The bonding in carbon nano tubes is sp², with each atom joined to three neighbours, as in graphite.
3D Structure of carbon nanotube
Types of carbon nano tubes:
Carbon nano tubes of different types. They are
1. SINGLE WALLED:-
Most single-walled nanotubes (SWNT) have a diameter of close to 1 nanometer, with a tube length that can be many millions of times longer. The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of graphite called graphene into a seamless cylinder. The way the graphene sheet is wrapped is represented by a pair of indices (n,m) called the chiral vector. The integers n and m denote the number of unit vectors along two directions in the honeycomb crystal lattice of graphene. If m = 0, the nanotubes are called "zigzag". If n = m, the nanotubes are called "armchair". Otherwise, they are called "chiral".