Nano Phase Materials:

Nano phase materials are recently developed new materials with the grain size in the range 1 to 100nm. The particles size in nano materials is about 1nm.

Preparation of Nano materials:

    Various methods are employed to produce nano-structured materials. Depending upon the desired properties or applications, each method will have some advantages and disadvantages.

Vapours condensations Methods:

    Cluster of atom are typically synthesized via vapour condensation which is essentially the evaporation of a solid metal followed by rapid condensation to form nano sized clusters. The resulting powder can be used as filters for composite materials (or) consolidated into bulk materials. Hence this method can be used to produce ceramic or metal nano structured powders.


Chemical synthesis:

    This method can be used to produce both metals and ceramics by using a variety of chemical approaches such as sol-gel (or) thermal decomposition. These methods provide large quantities of nano-sized materials at low cost.

Mechanical deformation:

    It is a common method to producing nano structured powders and it is through mechanical deformation by deformation by milling of mechanical deformation by means of milling or shock deformation. The nanometer sized grains nucleate with in the disassociation of cell structures located in the shear bands. The resultant grain size function of

•     Amount of energy input during milling.

•    Amount of time

•     Temperature during milling and

•     Milling atmosphere.

Thermal crystallization:

    This method is also used to synthesize three dimensional nanostructured materials. By controlling the nucleation and growth, during annealing of an amorphous material one can produce bulk material with an average grain size of less than 20 nm without the need for consolidation and sintering steps. 


 Properties:

1.    With in a diameter of only a few micrometers, a cluster of particles contains less than 104 atoms or molecules.

2.    The chemical, mechanical, electrical, electronic, optical and magnetic properties of nanophase materials are different from the bulk materials.

3.    Since the size of nanophase materials is inbetween the molecular and bulk solid structures, these have hybrid properties.

They have non-linear optical and magnetic properties.

Applications:   

•   Nano phase materials are used to produce very tiny permanent magnets with high energy products.

            Hence they are used in high density magnetic recording.

•    Nano phase materials have a large volume fraction of grain boundaries between surface area and volume. To improve the mechanical behaviour like higher hardness in ceramics, this property is used.

Structural applications:

    Functional applications are based on the transformation of external signals such as filtering of the incident light, the change of electrical resistance in different gas concentration and luminescent behaviour when the materials are electrically activated.