study of nano composites and nano grain. Nanotechnology

1. NANO COMPOSITE & NANO GRAIN

2. Nanocomposites and nano grained materials have been studied extensively mainly for improved physical properties.
Nanocomposites refer to materials consisting of at least two phases with one dispersed in another that is called matrix and
forms a three-dimensional network, whereas nano grained materials are generally multi-grained single phase polycrystalline
materials. A reduced particle size would definitely promote densification of composites and polycrystalline materials, due to
the large surface area and short diffusion distance. The conventional method for making small particles by attrition or milling is
also likely to introduce impurity into the particle surface. Such impurity may serve as sintering aid, and may form eutectic liquid
so as to introduce liquid phase sintering. Attrition or milling may also introduce a lot of damage and defects to the particle
surface so that the surface energy of particles is high, which is again favorable to densification. Other methods of making nano
sized powders, such as sol-gel processing and citrate combustion, would produce highly pure and less surface defect particles.
Hall-Petch relationship suggests that the mechanical properties increase inversely proportional to the square root of particle
size at micrometer scale. However, the relationship between the mechanical properties and the particle size does not
necessarily follow the Hall-Petch equation. More study is clearly needed to establish a better understanding on the size
dependence in the nanometer scale. Obviously in nanocomposites and nano grained polycrystalline materials, surface or grain
boundaries play a much more significant role in determining the mechanical properties than in large grained bulk materials.
Nanocomposites and nano grained materials are not necessarily limited to the bulk materials made by sintering nano sized
powders. Deposition of a solid inside a porous substrate, by vapor chemical reactions, is one established technique, referred to
as chemical vapor infiltration, for the synthesis of composite. Ion implantation is a versatile and powerful technique for
synthesizing nanometer-scale clusters and crystals embedded in the near-surface region of a variety of hosts. The principal
features of this synthesis technique and various materials have been reviewed by Meldrum and co-workers. Nanocomposites of
polymers and metals or polymers and semiconductors are reviewed by Caseri. Extensive research on various carbon nanotube
composites were reviewed by Terrones. Class I organic-inorganic hybrids can be considered as an organic-inorganic
nanocomposite, anodic alumina membrane filled with metal nanowires is metal-ceramic composite.

3. What are Nano grained material?
Nanograined materials are generally multi-grained single phase
polycrystalline materials. A reduced particle size would definitely promote
the densification of composites and polycrystalline materials, due to the
large surface area and short diffusion distance.

4. Nanocomposites
Definitions :
 Nanocomposites are broad range of materials consisting of two or more components, with
at least one component having dimensions in the nm regime (i.e. between 1 and 100 nm)
 Nanocomposites consist of two phases (i.e nanocrystalline phase + matrix phase) Phase
may be inorganic-inorganic, inorganic-organic or organic-organic
 Nanocomposite means nanosized particles (i.e metals, semiconductors, dielectric materials,
etc) embedded in different matrix materials (ceramics, glass, polymers, etc).

5. Nanocomposites materials : Nanocomposites can be formed by blending inorganic
nanoclusters, fullerenes, clays, metals, oxides or semiconductors with numerous organic
polymers or organic and organometallic compounds, biological molecules, enzymes, and
sol-gel derived polymers Latex Layered silicates Dispersed nanocomposites
Resulting nanocomposite may exhibit drastically different (often enhanced) properties than the
individual components
- Electrical, magnetic, electrochemical, catalytic, optical, structural, and mechanical properties

6. GENERAL CHARACTERISTICS
consist of one or more discontinuous phases of distributed in one continuous phase.
continuous phase is called “matrix”, whereas discontinuous phase is called “reinforcement"
or “reinforcing material.”

7. Nanocomposites differ from traditional composites in the smaller size of the particles in the
matrix materials.
Small size may cause
a) Physical sensitivity of bulk materials to physical or mechanical energy
b) Higher chemical reactivity of grain boundaries.

8. Conventional synthesis methods :
• Attrition or milling : reduce solid particle size by intense agitation of a slurry of material being
milled and coarse milling media.
• Ion implantation
• Powder processing
• Polymer precursor process (Ceramic based )
• Sol gel process
• Spray pyrolysis
• Rapid solidification process (RSP) (metal based)
• Vapour technique (CVD & PVD)
• Citrate combustion
• Templete synthesis
• In-situ intercalative polymerization (Polymer based)
• Sol-gel processing
 Sol gel processing and citrate combustion produce highly pure & less surface defect particles.

9. SOL GEL PROCESSING
CITRATE COMBUSTION

10. Hall-Petch relationship
We could achieve strength in materials that is as high as their own theoretical strength by reducing grain
size.
Mechanical property, s α
1
𝑑
1
2
where d is the particle size in microscale

11. Grain boundaries
Its is the interface between 2 grains or crystallites
in a polycrtstalline material. They are 2D defects in the crystal structure,
and tend to decrease the electrical and thermal conductivity of the
Material.
Vapour chemical infiltration
Ion implantation
More suitable method

12. Application of nano composites :
 electro catalyst in batteries for energy saving
 light weight materials for less fuel consumption.
 in artificial joints, economically beneficial
 carbon nanotubes most widely speaking nanomaterial which can be made as nanocomposite fibers.
 Abrasion and wear Applications
 Marine Application
 Food packaging
 Fuel tanks
 Films
 Environmental protection
 Flame ability reaction
 Erosion and corrosion Applications

13. Nanocomposites are upcoming materials which shows the great changes in
all the industrial fields and it is also going to be a economical barrier for
developing countries as a tool of Nanotechnology.