i. Introduction  Carbon nanotubes (CNTs), composed of carbon and graphite sheets, are tubular shaped with the appearance of hexagonal mesh with carbon molecules at each apex.  CNTs have many uses as they have become popular over the years for being over 100 times stronger than steel, and just 1/6 as heavy.  The length, thickness, and number of layers depend on the formation of the nanotube, such as how the graphene sheet is rolled up to form a tube. This also determines if the CNT will act as a metallic or semiconductor.

ii. Mechanism and Process  Carbon Nanotubes are mostly made by a carbon arc method, chemical vapor deposition or laser evaporation.  Carbon Arc Methods: two carbon rods placed end to end with a charge running through them  Chemical Vapor deposition: contains a single or mixture of metals induce the reaction to create single walled nanotubes. The reaction is a decomposition reaction.  Laser evaporation, also known as liquid ablation, is the process of removing materials from a liquid, with a strong laser beam.  There is a liquid assistance and gas that stabilizes the reaction. This process is shown in figure 1.

iii. Applications  Health Care:  Anti-inflammatory drugs. The nanotubes can be applied directly to affected area.  Environment:  The carbon nanotubes can be formed to act like a sponge. Very good for separating water and oil.  Currently working on creating cheap filtration systems for countries who do not have access to clean water.  Electronics:  Circuits with nanotube transistors are being created.

iv. Looking Molecularly  Most of the carbon atoms in nanotubes are sp2 hybridized. However sp3 hybridized carbons are formed because of the bending in the hexagonal structure. This is what causes Young’s modulus to be high. Which gives high mechanical properties.

v. Properties  Strength & Hardness  The strongest, most flexible, and stiffest materials in terms of tensile strength and Young’s modulus.  The hardness of carbon nanotubes are greater than diamond. Hardness: (152GPa) Bulk modulus: ( GPa)  Their high stiffness, coupled with their low density, implies that nanotubes might be useful as nanoscale fibers in strong, lightweight composite materials

 Electrical & Thermal Properties  Very high current carrying capacity due to symmetry and unique electronic structure of graphene  Very good thermal conductor. Predicted that carbon nanotubes will be able to transmit up to 6000 watts/ meter per Kelvin at room temperature, over 20 times greater than copper.  Chiral angle is used to separate carbon nanotubes  Armchair- metallic  Zig-zag- semimetals or semiconductors  Chiral- semimetals or semiconductors

vi. Improving Carbon Nanotubes  Researchers have thought of blending carbon nanotubes with different polymers.  A few examples are polyvinyl fluoride, polyethylene and polymethyl methacrylate. These are very popular polymers.  However the problem with combining these different polymers with carbon nanotubes is the Van Der Waal forces are very strong between each tube.

vii. Conclusion  Through laser evaporation, these nanocomposites are made to serve many purposes.  Adding these CNTs to carbon fibers makes the composite stronger and lighter in weight while adding graphite fibers result in a higher modulus  Because they are strong, durable, and great thermal conductors, carbon nanotubes make great nanocomposites for many different industries, such as health care, electronics, and the environment.