Carbon nanotubes

CARBON NANOTUBES

WANAMBWA ZACK NICHOLAS

CARBON NANOTUBES

• CNT is a tubular form of carbon with diameter as small as 1nm. Length: few nm to microns.

• CNT is configurationally equivalent to a two dimensional graphene sheet rolled into a tube.

CARBON NANOTUBES

• A CNT is characterized by its Chiral Vector: Ch = n â1 + m â2,

Chiral Angle with respect to the zigzag axis.

CARBON NANOTUBES• Their electrical

characteristics differ depending on these variations, and variations in diameter acting either as metals or as semiconductors.

CARBON NANOTUBES

CARTEGORIES:• Carbon Nanotubes can be categorized by their

structures:1. Single-wall Nanotubes (SWNT)2. Multi-wall Nanotubes (MWNT)3. Double-wall Nanotubes (DWNT)

CARBON NANOTUBES

CARBON NANOTUBESPROPERTIES:• Carbon nanotube is one of the strongest

materials in nature. • Overall, Carbon Nanotubes show a unique

combination of stiffness, strength, and tenacity.

• Thermal and electrical conductivity are also very high, and comparable to other conductive materials.

CARBON NANOTUBES

PROPERTIES: • CNTs have Very High Tensile StrengthSheet of graphite form a planar honeycomb lattice, each atom is connected via a strong chemical bond to three neighboring atoms. Because of these strong bonds, the basal-plane elastic modulus of graphite is one of the largest of any known material.

CARBON NANOTUBES

PROPERTIES:CNTs have High Electrical Conductivity:• Their conductivity has been shown to

be a function of their chirality , as well as their diameter.

• CNTs can be either metallic or semi-conducting in their electrical behavior.

• (a) Armchair NT exhibits metalic behavior at Fermi energy, while (b) zigzag NT is a small gap semicinductor

CARBON NANOTUBES

PROPERTIES:CNTs have High Thermal Conductivity• New research from the University of

Pennsylvania indicates that CNTs may be the best heat-conducting material man has ever known.

• Ultra-small SWNTs have even been shown to exhibit superconductivity below 20oK,

• May someday also find applications as miniature heat conduits in a host of devices and materials

CARBON NANOTUBES

APPLICATIONS:-

• Conductive plastics• Structural composite

materials• Flat-panel displays• Gas storage• Antifouling paint• Micro- and nano-

electronics• Radar-absorbing coating

• Technical textiles• Ultra-capacitors• Atomic Force Microscope

(AFM) tips• Batteries with improved

lifetime• Biosensors for harmful gases• Extra strong fibers

CARBON NANOTUBES

Advantages:• Extremely small and

lightweight, making them excellent replacements for metallic wires

• Resources required to produce them are plentiful, and many can be made with only a small amount of material

• Are resistant to temperature changes, meaning they function almost just as well in extreme cold as they do in extreme heat

Disadvantages• Despite all the research, scientists still

don't understand exactly how they work

• Extremely small, so are difficult to work with.

• Currently, the process is relatively expensive to produce the nanotubes

• Would be expensive to implement this new technology in and replace the older technology in all the places that we could

• At the rate our technology has been becoming obsolete, it may be a gamble to bet on this technology

CARBON NANOTUBESFABRICATION OF CARBON NANOTUBES:

1. Elecritic Arc Discharge: Most common method of CNT fabrication

1. A current is run through an anode, or a positively charged piece of carbon.

2. This current jumps through a plasma material to a cathode, or a negatively charged piece of carbon, where there is an evaporation and deposition of carbon particles in through the plasma.

3. Finally an outer hard-shell region made of decomposed graphite is formed and an inner core region with loosely packed columns which consist of straight, stiff multishell carbon nanotubes and closed polyhedral particles


2. Laser Ablation:

• Uses an intense laser pulse to vaporize a carbon target, which also contains small amount of metals such as nickel and cobalt and is placed in a tube furnace at 1200oC.

• Inert gas is passed through the chamber carrying the grown nanotubes on a cold finger for collection.

• This method mainly produces SWCNT in the form of ropes


3. Chemical vapor deposition• A mixture of hydrocarbon, metal catalyst

along with inert gas is introduced into the reaction chamber.

• During the reaction, nanotubes form on the substrate by the decomposition of hydrocarbon at temperatures 700–900oC and atmospheric pressure.

• The diameters of nanotubes that are to be grown are related to the size of the metal particles

• This technique offers more control over the length and structure of the produced nanotubes compared to arc and laser methods.

Technology

Carbon nanotubes