Nanotechnology
A comparison @ nanoscale
Top –down approach
Advantages
Disadvantages
Common technique
used for fabrication
of
semiconductor
devices
Introduces
internal stress
Large wafers
used to fabricate
Nano materials
Surface defects
(i.e.
imperfections)
The material
selection is wide
Contaminations
BOTTOM-UP APPROACH
Advantages
Disadvantages
Less defects
Homogeneous
chemical composition
Better short and long
range ordering
Requires high control
on the process through
which the materials are
produced
Nano materials
Nano Particles
In nanotechnology, a particle is
defined as a small object that
behaves as a whole unit with respect
to its transport and properties.
Particles are further classified
according to diameter. Coarse
particles cover a range between
2,500 and 10,000 nanometers. Fine
particles are sized between 100 and
2,500 nanometers. Ultrafine particles,
or nanoparticles, are between 1 and
100 nanometers in size.
QUANTUM DOTS
semiconductor nanoparticles are called
Quantum dots- where excitons are
confined in all the three directions
and have properties combained
between bulk and those of atoms
Nanorings
A nanoring is a small ringformed
crystal. The first nanoring made was
a zinc oxide nanoring discovered by
researchers at Georgia Institute of
Technology. They are made by a
spontaneous self-coiling process of
nanobelts. Many layers of nanobelts
are rolled together as coils, layer-bylayer.
Nano wires
A nanowire is a wire of dimension
of the order of nanometres
Nanorods
In nanotechnology, nanorods are
one morphology of nanoscale objects.
Each of their dimensions range from
1–100 nm. They may be synthesized
from metals or semiconducting
materials. Standard aspect ratios
(length divided by width) are 3-5.
Nanorods are produced by direct
chemical synthesis. A combination of
ligands act as shape control agents
and bond to different facets of the
nanorod with different strengths. This
allows different faces of the nanorod
to grow at different rates, producing
an elongated object.
Nano -shells
Nanoshells are nanoparticles that consist of an inner core of one type
of material and an outer layer of another only a few nanometers thick.
One application of nanotechnology in biomedicine is to create
nanoshells that absorb at biologically useful wavelengths, depending
on the shell thickness.
Ceramic-matrix nanocomposites
In this group of composites the main part of the volume is occupied by a ceramic,
i.e. a chemical compound from the group of oxides, nitrides, borides, silicides
etc.. In most cases, ceramic-matrix nanocomposites encompass a metal as the
second component. Ideally both components, the metallic one and the ceramic
one, are finely dispersed in each other in order to elicit the particular nanoscopic
properties.
Metal-matrix nanocomposites
Metal matrix nanocomposites can also be defined as reinforced metal matrix
composites. This type of composites can be classified as continuous and noncontinuous reinforced materials. One of the more important nanocomposites is
Carbon nanotube metal matrix composites, which is an emerging new material
that is being developed to take advantage of the high tensile strength and
electrical conductivity of carbon nanotube materials.
Polymer-matrix nanocomposites
In the simplest case, appropriately adding nanoparticulates to a polymer matrix
can enhance its performance, often dramatically, by simply capitalizing on the
nature and properties of the nanoscale filler ]. (these materials are better
described by the term nanofilled polymer composites ). This strategy is
particularly effective in yielding high performance composites, when good
dispersion of the filler is achieved and the properties of the nanoscale filler are
substantially different or better than those of the matrix.
Nano material
classification
Organic
Fullerene(C60)
Carbon
nanotubes(CNT)
In organic
DNA
The requirement of fast growing world cannot meet these Nano
materials, so new class of materials are introduced known as Nano
composites –materials derived the combination of two or more
building blocks containing atleast one component in nanometer scale
Carbon based nanomaterials
Fullerene
Compsed of stacked graphene
sheets of linked hexagonal
rings/ pentagonal rings as the
basis of a closed cage structure
They are spherical or ellipsoidal
shapes. Spherical fullerenes are
called Bucky balls
Carbon nanotubes
There can be single walled or
multiwalled CNTs obtained by
wrapping one atom thick layer of
graphite into continuous smooth
cylinder. They are cylindrical
nanostructures with aspect ratio
(length to diameter) of the order of
10 8 and are called Bucky tubes
Fullerene
C60
C70
Fullerene, a molecule composed of carbon atoms that
form a hollow, cage like structure. The arrangement of
the atoms produces pentagonal and hexagonal shapes—
that is, shapes with five or six sides,
Carbon nanotube
Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical
nanostructure. Nanotubes have been constructed with length-to-diameter
ratio of up to 132,000,000:1, significantly larger than for any other
material. These cylindrical carbon molecules have unusual properties,
which are valuable for nanotechnology, electronics, optics and other fields
of materials science and technology
Dendrimers
These are nano sized polymers
builtfrom branched unitsIts
surface has numerous chain ends
which can be tailored to perform
specific chemical functions
PROPERTIES OF NANOMATERIALS
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Optical properties
Electrical properties
Chemical properties
Physical prperties
Mechanical properties
Magnetic properties
Optical properties
At nanocsale level physical properties
become size dependent. Colour and
transparency are obseved to change at
nanoscale
-nanoparticles are so small that
electrons in them are not as much free
to move as in the bulk material, due to
this nanoparticles react differently with
light
Electrical properties
The ionization potential at small sizes are higher than
that of the bulk. The ionization potential show
marked fluctuation as function of size
The change in electrical properties
can not be generalized
in nanomatrials
The current –voltage characteristics (I-V ) of
nanoparticles is a staircase type
In nanoceramics and magnetic nanocomposites , the
electrical conductivity increases with reduction in
particle size, while in nanometals the electrical
conductivity decreases with reduction particle size.
In the case of carbon nanotubes the conductivity
changes with change in diameter, it also changes with
twist applied to the nanotubes
Chemical properties
Since the percentage of surface
atoms is large in the nanoparticles as
compared with bulk materials , the
reactivities of nanomaterials are more
than the bulk materials
Physical properties
Properties like strength, melting point eic. Change
drasitcally at nanoscale
At macro level steel is stronger than carbon, however at
nanolevel the CNTs are found to be 100 times stronger
than steel and it is more flexible too
The melting point usually does not change with change in
size at maroscopic level, however at nanoscale, if the size
of the object is changed , then the percentage change in
the no. of atoms on the surface is very large , the melting
point start depending on the size of the object and goes on
decreaseing with decrease in size
Mechanical properties
 In nanometre scale , the surface atoms face different
potentials in different directions .The resulting stress
modifies the mechanical and structural properties
 They become more hard and wear resistant
 The elastic properties like Youngs modulus decreases
with decrease in size
 The fatigue strength increases with reduction in grain
size of the materials - which finds application ins in the
construction of air crafts
 They superelastic materials as they have extensive
tensile deformation without cracking or fracture
 Energy dissipation , mechanical coupling within array of
components and mechanical non-linearities are
influenced by structuring components at the nm scale
Magnetic properties
Magnetic Nanoparticles show unusual
magnetic behaviour compared to the bulk
materials
Nanosized particles of magnetite show
supermagnetism at transition tempertature
which is smaller than the transition temp of
the bulk
APPLICATIONS
Nanomaterials posses unique and benificialchemical
physical and mechanical properties , they can be used
for a variety of applications
1. Cosmetics- eg. Sunscreen lotions, creams etc.
2. Nanocomposite materials
3. Nanocoatings
4. High performance paints
5. Next generation computer chips
6. Better insulating materials
7.
High performance TV- use of nanophosphors render
very high resolution low cost flat panel displays
8. Tougher and harder cutting tools
Applications– continue…
 9. Elimination of pollutants
 10.High power magnets
 11.High sensitivity sensors
 12. Automobiles with greater fuel efficiency
 13. Better weapons
 14. Long lasting medical implants
 15. Ductile ,machinable ceramics
 16. In medicine- discease diagnosis, drug delivery etc.
 17. In Biotechnology
 18. Electromagnetic display devices
Thank You
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