By Souradipta Chowdhury3rd Year ECE Roll:18700312107

Introduction To NanotechnologyBasics of NanoparticlesSurface to volume comparisonIntroduction to NanotubeSynthesizing ProcessesArchitecture behind NanotubesBasics of Nano fibersSynthesis of Nano fiberUses of Nano tubes and FibersApplications in present market

Contents

Nanotechnology• The study of control of matter on

an atomic and molecular scale.

– Deals with structures the size of 100nanometers or smaller (1 nm = 1/1,000,000,000 m or 10-9 m).

– Involves engineering on a small scale to create smaller cheaper lighter and faster devices that can do more things with less raw materials.

Key Dimensions in Nanometers• An atom is about 0.3 nm in size.

• DNA double helix has a diameter

of about 2 nm.

• Typical spacing between 2 carbon atoms in a molecule is 0.12 – 0.15 nm.

Properties of Nanoparticles

• Materials reduced to the nano scale can show different properties compared to what they exhibit on the macro scale.– Opaque substances become transparent

(copper);stable materials turn combustible (aluminum); semiconductor become conductors (silicon); and solids turn to liquids at room temperature (gold).

– Nanoparticles tend to be more chemically reactive than their ordinary state

Model of Surface-to-Volume Comparisons

• Neglecting spaces between the smaller boxes, the volumes of the box on the left and the boxes on the right are the same but the surface area of the smaller boxes added together is much greater than the single box.

Single Box Ratio6 m2

1 m3 = 6 m-1

Smaller Boxes Ratio12 m2

1 m3 = 12 m-1

Carbon Nanotube

Great potential for storage memory (116 Gb/cm2 )

Small size offers faster switching speeds (100GHz )

and low power

Easy to fabricate: standard semiconductor process

Nonvolatile nature: no need to refresh.

Faster than SRAM, denser than DRAM, cheaper

than flash memory.

Have an almost unlimited life, resistant to radiation

and magnetism—better than hard drive.

Arc Discharge:

Two carbon rods are placed end to end with a separation distance of about 1mm and are used as electrodes

In an enclosed volume of usually an inert gas (He, Ar) at a low p1ressure (50-70 mbar), a current of 50-100 A, driven by 20 V creates a high temperature arc between the electrodes.Conti……..

Nanotube : Synthesis

Producing nanotubes in high yield depends upon the uniformity in the plasma arc, and also upon the temperature of the deposit on the second carbon electrode

The discharge vaporizes one rod forming a rod shaped deposit on the other.

Laser Ablation :A pulsed or continuous laser is used to vaporize a graphite target placed in an oven at 1200ºC

The oven is filled with an argon gas which is used to keep the pressure at 500 Torr.

A very hot vapor plume forms, which then expands and cools rapidly.

As the vaporized species cools, small carbon molecules and atoms condense to form larger clusters.Conti…….

From the initial clusters, tubular molecules grow into SWNT.

This stops when the catalyst particles (which also condense) become too large, or when the conditions have cooled enough where carbon can no longer diffuse through or over the surface of the catalyst particles.

The SWNT’s formed in this case are bundled together by Van der Waals forces.

Types of NantubeDepending on “WALL” Nanotube has TWO types

Single Wall CNT (SWCNT)

Multi Wall CNT(MWCNT)

Architecture behind it:• Chiral Vector: A carbon nanotube can be viewed as a rolled

graphene sheet along its circumferential direction, is determined by its chiral vector.

• The chiral vector is defined as

– Armchair

– Zig-Zag

– Chiral Armchairθ= 30° (m=n)

Zig-Zag θ= 0°(m=0)

Chiral0° <θ < 30°(n>m)

Nano fiber• A nano fiber is a

continuous fiber which has a diameter in the range of billionths of a meter.

• The smallest nano fibers made today are between 1.5 and 1.75 nanometers.

• At the right a human hair (80,000 nanometers) is place on a mat of nano fibers

Electrospinning to Make Nanofibers

• An electric field pulls on a droplet of polymer solution at the tip of the syringe and pulls out a small liquid fiber. It is pulled thinner and thinner as it approaches the collection plate. Electrospinning Apparatus

Electrospinning a Polymer Solution to Produce Nanofibers

• This picture shows the actual spinning of a solution made of the polymer PEO (polyethylene oxide) dissolved in water.

• The resulting fiber is collected below on a grounded plate.

Unique Properties of Nanofibers

• Size: nano fibers are very small which allows them to be used in very small places.

• Surface-to-volume ratio: nano fibers have a huge surface area compared to their volume.

• High surface area• Support: Provides huge structural support.

Fibroblast cells grown on nano fibers.

Uses of Nano fibers

• Strength: Reinforced composites by nano fibers, twisted in yarns.

here nano fibers are spun into yarns.

Uses of Nanofibers… continued.

• Encapsulation: Drug delivery, Scaffolds for growing cells, Agriculture.

– Water filtration: a chelating compound has been encapsulated in nanofibers.

– These fibers in a water filter can remove heavy metals, particularly lead, cadmium and copper.

Uses of Nanofibers… continued.

• Structure: Fuel cell, Micro/Nano electronic devices

– Nanofibers can be used to greatly decrease the size of a fuel cell while increasingthe electrical output.

Uses of Nanofibers… continued.

• Light Weight: Produce Solar sails in space, Aircraft wings, Bullet-proof vests.

– New breathable bullet-proof vest: Nomex Nanofibers

Products Currently on the Market Using Nanotechnology

• Over 600 nanotech enabled products are on the market today. Some examples are:

– Carbon nanotubes in bike frames and tennis rackets make the products stronger and lighter This bike frame weights 2.75 pounds

Applications:

• Electronics:– Nano Transistors– Nano Diodes– OLED (Organic Light Emitting Diode)– Plasma Displays– Quantum

Computers

• Energy: – Batteries– Fuel Cells– Solar Cells

Resources

1. Micro manufacturing and Nanotechnology by N.P Mahalik (Springer)

2. Nanotechnology and Nanotubes by Benjamin Fry and Kouras' Kelantan

3. nanotechnews.com

4. electro spun. BlogSpot

5. www.nnin.org

6. www.nano.gov.us