TANCET study material for Physics: Unit IX

Nanomaterials: Preparation – properties – applications – Carbon nano tubes.

Nanomaterials are materials where the sizes of the individual building blocks are less than 100 nm,at least in one dimension.They may be zero dimensional (nano particles) , one dimensional (nano rods/nano tubes/nano wires) and two dimensional(thin films).
Preparation :
Nano materials are prepared by the following methods;
  Sol-Gel Method
  Chemical Vapor Deposition
Physical Vapor Deposition
Electrodeposition
  Plasma Arcing method
Laser pulsed deposition method

Sol-Gel method:

The colloidal solution is made from the base material which is kept at suitable temperature.Gelling agents are added. Evaporation of the solution results nano particles. Nano rods,nano tubes are prepared by using sol-gel template method

Chemical Vapor Deposition :

Chemical vapor deposition (CVD) is a chemical process used to produce high-purity, high-performance solid materials. In a typical CVD process, the substrate is exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit. Frequently, volatile by-products are also produced, which are removed by gas flow through the reaction chamber.

Physical Vapour Deposition:

The process is similar to chemical vapor deposition (CVD) except that the raw materials/precursors, i.e. the material that is going to be deposited starts out in solid form, whereas in CVD, the precursors are introduced to the reaction chamber in the gaseous state.

The process involved four steps

i.Evaporation : target material is evaporated by high energy electron beams

ii.Transport : vaporized target atoms are moving to substrate

iii.Reaction : vaporized target atoms are reacting with appropriate gas (oxygen,methane ,nitrogen)
iv.Deposition: after reaction the target atoms are coated on the substrates

Electro deposition:

Plasma Arcing method:

Laser pulsed deposition method:

Pages

Unit IX