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Monday, January 2, 2012

What are nano materials?

These are materials whose dimensions are less than 100nm. They act as one dimensional systems or zero dimensional.For comparison, a human hair is about 50,000nm in diameter, while a smoke particle is about 1000nm in diameter.

The term nano materials is less specific since it refers to coatings that are less than 100nm.

The nano particles consist only thousands of atoms. They are called quantum dots.

Methods of Synthesis of Nano Structured Materials:

Synthesis and assembly strategies can be accommodated from Liquid, Solid or Gas Phase

i) By employing chemical or physical deposition approaches.

ii) Relying on either chemical reactivity or physical compaction to integrate nano structure building blocks to form final nano material structure.  

Variety of techniques are
i) Assembling from nano building blocks
ii) Powder/Aerosol compaction
iii) Chemical Synthesis
iv) Mechanical attrition
v) Lithography/Etching

These above techniques can be classified into two approaches:

i) Bottom up Approach: Here first building blocks are formed and then assembled to form final material.

ex:- Aerosol /Powder technique in which powder components are compacted into final material.

This approach has been widely used in formation of structural composite materials.

ii) Top-Down Approach: Here first a suitable nano material is taken and then sculpted according to functionality of material. This approach is very similar to techniques employed semiconductor industries in forming devices from electric substrate by etching a pattern from it.Lithography/etching, Ball milling fall in this category.

Classification of Nano Crystalline Materials:

i) Nano crystalline materials are single phase or multi phase poly crystals, the crystal size of which is of order of few (1-100nm) is at least one dimension.

ii) They can be equiaxed and can be formed nano strucuture Crystallites -3D nano structures

iii) They can consist of lamellar structure and will be termed as layered nano structure-1D

iv) They can be filamentary in nature - 2D

v) They can be clusters or cluster assembly - 0D