Introduction to Nanoworld [630346]

Introduction to Nanoworld
Author: Umme Thahira Khatoon

Tentative Title: Basic Introduction To Nanotechnology And
Synthesis Strategies Of Nanomaterials W ith Its Applications
And Impact .

Corresponding Author:
Umme Thahira Khatoon,
Ph.D., National Institute of Technology,
Warangal, Telangana State, INDIA.
[anonimizat]

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Table of Contents
Tentative Title: Basic Introduction To Nanotechnology And Synthesis Strategies Of Nanomaterials With Its
Applications And Impacts. ………………………….. ………………………….. ………………………….. ………………………….. ……. 4
Chapter I – Introduction ………………………….. ………………………….. ………………………….. ………………………….. ………… 4
What is nanotechnology? ………………………….. ………………………….. ………………………….. ………………………….. ………. 4
History of nanotechnology ………………………….. ………………………….. ………………………….. ………………………….. ……. 5
How small nanoparticle is? ………………………….. ………………………….. ………………………….. ………………………….. ……. 6
Illustration of different objects in nano, micro and millimeter ………………………….. ………………………….. ………… 7
References: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 8
Chapter II ………………………….. ………………………….. ………………………….. ………………………….. ………………………….. 10
Physical and chemical characteristics of nanomaterials ………………………….. ………………………….. ……………………. 10
Color: ………………………….. ………………………….. ………………………….. ………………………….. ………………………….. .. 10
Melting point: ………………………….. ………………………….. ………………………….. ………………………….. ………………… 11
Mechanical strength: ………………………….. ………………………….. ………………………….. ………………………….. ………. 11
Electrical properties of the nanomaterials: ………………………….. ………………………….. ………………………….. …….. 11
Optical properties: ………………………….. ………………………….. ………………………….. ………………………….. ………….. 12
Chemical properties of the materials ………………………….. ………………………….. ………………………….. …………….. 12
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 13
Chapter III ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 14
Classification of nanomaterials ………………………….. ………………………….. ………………………….. …………………………. 14
According to their origin nanomaterials are classified as: ………………………….. ………………………….. …………………. 14
1. Natural nanomaterials: ………………………….. ………………………….. ………………………….. ………………………….. … 14
2. Artificial nanomaterial: ………………………….. ………………………….. ………………………….. ………………………….. … 14
1. Zero dimensional (0 -D): ………………………….. ………………………….. ………………………….. ………………………….. .. 15
3. Two dimensional (2 -D): ………………………….. ………………………….. ………………………….. ………………………….. … 15
4. Three Dimensional (3 -D): ………………………….. ………………………….. ………………………….. ………………………….. 16
Structural configuration nanomaterials ………………………….. ………………………….. ………………………….. ………………. 16
Carbon B ased Nano materials: ………………………….. ………………………….. ………………………….. ……………………… 16
Metal Based Materials: ………………………….. ………………………….. ………………………….. ………………………….. ……. 16
Dendrimers: ………………………….. ………………………….. ………………………….. ………………………….. …………………… 16

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Composites: ………………………….. ………………………….. ………………………….. ………………………….. …………………… 16
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 16
Chapter IV ………………………….. ………………………….. ………………………….. ………………………….. ………………………… 17
Structure of nanocry stalline materials ………………………….. ………………………….. ………………………….. ……………….. 17
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 18
Chapter V ………………………….. ………………………….. ………………………….. ………………………….. ………………………….. 19
Synthesis techn iques of nano materials ………………………….. ………………………….. ………………………….. ……………… 19
Inert Gas Condensation Method: ………………………….. ………………………….. ………………………….. ………………………. 19
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 20
Sol-Gel Method ………………………….. ………………………….. ………………………….. ………………………….. …………………. 20
Rapid Solidification Technique: ………………………….. ………………………….. ………………………….. ……………………….. 22
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 23
Electro -deposition Technique: ………………………….. ………………………….. ………………………….. ………………………….. 23
Theory ………………………….. ………………………….. ………………………….. ………………………….. ………………………….. ….. 23
Applications: ………………………….. ………………………….. ………………………….. ………………………….. ……………………… 27
Properties of deposited film: ………………………….. ………………………….. ………………………….. ………………………….. … 27
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 28
Spray conversion processing ………………………….. ………………………….. ………………………….. ………………………….. .. 29
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 32
Mechanical alloying ………………………….. ………………………….. ………………………….. ………………………….. ……………. 32
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 35
X-ray Diffraction: ………………………….. ………………………….. ………………………….. ………………………….. …………….. 36
Transmission electron microscopy (TEM): ………………………….. ………………………….. ………………………….. ……… 38
Positron annihilation spectroscopy (PAS) ………………………….. ………………………….. ………………………….. ……….. 39
Implementation ………………………….. ………………………….. ………………………….. ………………………….. ……………… 41
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 41
Chapter VII ………………………….. ………………………….. ………………………….. ………………………….. ……………………….. 42
Consolidation of nanopowders ………………………….. ………………………….. ………………………….. …………………………. 42
Hot isostatic pressing (HIP) ………………………….. ………………………….. ………………………….. ………………………….. . 43
Spark plasma sintering ………………………….. ………………………….. ………………………….. ………………………….. …….. 44
Shockwave consolidation ………………………….. ………………………….. ………………………….. ………………………….. … 47

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References: ………………………….. ………………………….. ………………………….. ………………………….. ……………………….. 49
Chapter VIII ………………………….. ………………………….. ………………………….. ………………………….. ………………………. 50
Current, recent and Future applications of nanotechnology and nanomaterials. ………………………….. ……………….. 50
Chapter IX ………………………….. ………………………….. ………………………….. ………………………….. ………………………… 54
Overview on recent and current developments in nanotechnology.: ………………………….. ………………………….. …… 54
List of applications considering current and future application of nanomaterials: ………………………….. …………….. 55
Future applications: ………………………….. ………………………….. ………………………….. ………………………….. ……………. 57
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 59
Impact of Nanotechnology: ………………………….. ………………………….. ………………………….. ………………………….. …. 59
Reference: ………………………….. ………………………….. ………………………….. ………………………….. …………………………. 63

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Tentative Title : Basic Introduction To Nanotechnology And Synthesis
Strategies Of Nanomaterials With Its Applications And Impacts.
Chapter I – Introductio n
What is nanotechnology?
Nano science and technology is the modern world concept which is based on the science
of tiny particle within the size range at least one dimension sized from 1 to 100
nanometers .
Nanotechnology deals with fabrication and manipula tion of the matter on an atomic,
molecular and supramolecular level. Nanotechnology is going to carve a niche in broad
and diversified field of science including micro fabrication, semiconductor, surface
science, medicine and organic chemistry etc.
The ter m nanomaterial includes all nanosized materials, including materials that can be
engineered or found in nature. Nanotechnology can be described as the technology of
composite functional systems at the nano scale of the materials.
They are important because they exhibit unique properties which are significantly
different from their conventional bulk counterpart. Because of their unique features in
terms of size and properties nano -scientists and engineers have explored the technology
to invent new miracle in diversified field of sciences.

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History of nanotechnology
The fabrication of different constructive materials at the atomic and molecular range to
form novel materials possessing new functions and properties sounds like modern
concept. But ancient scientis t was also familiar with the concept of molding and
fabricating the matter at the tiniest scales. There are a numerous famous examples of
ancient artifacts where the scientific concept based on nanotechnology was applied. The
marvelous decorative effects o f Lycurgus cup (Roman treasure from about AD400) is a
stunning example of ancient nanotechnology based artifact.

Stunning decoration of Lycurgus cup.
In addition, Damascus steel swords from the Middle East (AD300 and AD1700), a
corrosion resistant azure pigment known as Maya Blue (AD800) are some exciting
illustration of ancient nanoscience based application.
In the year of 1959 Mr. R. Feynman, the professor of California Ins titute of Technology,
first described the concept of nanotechnology at the session of the American Physical
Society in a famous after -dinner speech called "There's plenty of room at the bottom". In
this lecture he first introduced the idea to create nanosi zed products with the use of
atoms as building particles. Nowadays this lecture is referred to as the pioneer of the
technological paradigm of nanosciences and technologies. However, the word

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nanotechnology was not mentioned at that time of that speech. In 1974 N. Taniguchi
first introduced and mentioned the term "nanotechnology" at the international conference
on industrial production in Tokyo. Ideas of Nano technological strategy was first
described by E. Drexler in his famous book "Vehicles of creation: the arrival of the
nanotechnology era" published in 1986.In 1991 the first nano technological program of
National Scientific Fund was established to operate in the USA and after 10 years the
National Nanotechnological Initiative (NNI) of the USA was approv ed by the USA
government. Like USA Japan also play an important role in exploring nanotechnology in
the area of new scientific research. In 2000 the Japanese Economic Association (JAE)
started a new special department on nanotechnology and in 2001 the nano technology
research plan and framework was developed. After that all developed countries
including European countries paid a lot of attention to explore the nanotechnology for
the development of scientific research. Recently developing countries like Repub lic of
China and India are also working on the field of nanotechnology for development of the
new idea within the framework of state scientific programs.
How small nanoparticle is?
We live in such a world where it's quite impossible for us to imagine and p ercept a world
that's too small to visualize. A nanometer is one billionth (10-9) of a meter, which is very
small, only 10 times length of hydrogen atoms, only 1/80,000 the width of a human hair.
It's hard to imagine just how small nanotechnology is. One n anometer is a billionth of a
meter, or 10-9 of a meter. Some interesting examples will be helpful for the perception of
nano scale.

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Illustration of different objects in nano, micro and millimeter

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• Scale (1 mm= 1000 μm,1 μm=1000 nm)
• There are 25,400, 000 nanometers in an inch
• A sheet of newspaper is about 100,000 nanometers thick
• On a comparative scale, if a marble were a nanometer, then one meter would be
the size of the Earth.
• Human hair: 50,000 -100,000 nanometers in diameter.
• DNA double -helix: ~2 na nometers in diameter.
• One piece of paper: ~100,000 nanometers thick.
• Man 6 ft tall ~ 1900 million nanometers tall.
References:
• Drexler KE (1986). Engines of Creation: The Coming Era of Nanotechnology.
Doubleday. ISBN 0 -385-19973 -2.
• Drexler KE (1992). Nano systems: Molecular Machinery, Manufacturing, and
Computatin. New York: John Wiley & Sons. ISBN 0 -471-57547 -X.
• Buzea C, Pacheco I, and Robbie K(2007). Nanomaterials and Nanoparticles:
Sources and Toxicity. Biointerphases 2 (4): MR17 -71.doi:10.1116/1.2815690 .
PMID 20419892.
• Nanoscience and nanotechnologies: opportunities and uncertainties". Royal
Society and Royal Academy of Engineering. July 2004.
• Nanotechnology: Drexler and Smalley make the case for and against 'molecular
assemblers'". Chemical & Engineerin g News (American Chemical Society) 81
(48): 37 -42. 1 December 2003. doi:10.1021/cen -v081n036.p037
• "Nanotechnology Information Center: Properties, Applications, Research, and
Safety Guidelines". American Elements.

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• "Analysis: This is the first publicly avail able on -line inventory of nanotechnology –
based consumer products". The Project on Emerging Nanotechnologies. 2008.
• Drexler KE (1986). Engines of Creation: The Coming Era of Nanotechnology.
Doubleday. ISBN 0 -385-19973 -2.
• Drexler KE (1992). Nanosystems: Mole cular Machinery, Manufacturing, and
Computatin. New York: John Wiley & Sons. ISBN 0 -471-57547 -X.
• Buzea C, Pacheco I, and Robbie K(2007). Nanomaterials and Nanoparticles:
Sources and Toxicity. Biointerphases 2 (4): MR17 -71.doi:10.1116/1.2815690.
PMID 204198 92.
• Nanoscience and nanotechnologies: opportunities and uncertainties". Royal
Society and Royal Academy of Engineering. July 2004.
• Nanotechnology: Drexler and Smalley make the case for and against 'molecular
assemblers'". Chemical & Engineering News (Ameri can Chemical Society) 81
(48): 37 -42. 1 December 2003. doi:10.1021/cen -v081n036.p037.
• "Nanotechnology Information Center: Properties, Applications, Research, and
Safety Guidelines". American Elements.
• "Analysis: This is the first publicly available on -line inventory of nanotechnology –
based consumer products". The Project on Emerging Nanotechnologies. 2008.
• Allhoff F, Lin P and Moore D (2010). What is nanotechnology and why does it
matter?: from science to ethics. John Wiley and Sons. pp 3 -5.
• Prasad SK (200 8). Modern Concepts in Nanotechnology. Discovery Publishing
House. pp. 31 -32. ISBN 81 -8356 -296-5.
• Kahn J (2006). "Nanotechnology". National Geographic 2006 (June): 98 -119.
• Rodgers P (2006). Nanoelectronics: Single file. Nature
Nanotechnology.doi:10.1038/nn ano.2006.5.

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• http://www.ck12.org/book/CK -12-21st-Century -Physics -A-Compilation -of-
Contemporary -and-Emerging -Technologies/section/7.1/
Chapter II
Physical and chemical characteristics of nanomaterial s
As compare to conventional bulk particles nanomaterials e xhibits some unique physical
properties including electrical, catalytic, magnetic, mechanical, thermal, or imaging
features that make the nanomaterials a relevant topic in medical, pharmaceutical and
different engineering sectors. The nanomaterial possesse s some remarkable and specific
peculiar properties which may be significantly distinctive from the physical properties of
bulk materials.
The specific features of those physical properties are discussed below
Color: There are few examples where the materia ls show the different color when they
are converted to nanoparticles. As per example when the gold materials are converted to
nanomaterials they turn into red color. Gold nanoparticles interaction with light is
strongly governed by the particle sizes of th e materials. Small particle sizes (~2 -150nm)
have high surface electron densities which are called as surface plasmons undergo a
collective oscillation when they are excited by light at specific wavelengths. This
oscillation is described as a surface plasm on resonance (SPR).For small (~30nm)
monodisperse gold nanoparticles the surface plasmon resonance phenomona is
responsible for an absorption of the blue -green portion of the spectrum (~450 nm) while
red light (~700 nm) is reflected, p roducing a rich red c olor.

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Suspensions of gold nanoparticles of various sizes.
Melting point: The melting point drastically falls when the particle size of the
material approaches to the nanoscale ranges. This phenomenon related to melting point
depression is very promine nt in nanoscale materials which melt at temperatures
hundreds of degrees lower than bulk materials. Melting point depression is most evident
in nanowires, nanotubes and nanoparticles, which all melt at lower temperatures than
bulk form of the same material . Changes in melting point occur because nanoscale
materials have a much larger surface to volume ratio than bulk materials, drastically
altering their thermodynamic and thermal properties.
Mechanical strength: All the nanomaterials possess high mechanical strength as
compared to their conventional counterparts. The mechanical strength of nanomaterials
is in general higher in magnitude than that of coarse grained materials. Defects in the
form of atomic vacancies or porosity can lower the tensile strength o f the materials by up
to 85%.
Electrical properties of the nanomaterials: This is quite complex phenomenon.
Reduction in material's dimensions would have two different contrasting effects on
electrical conductivity. By its property nanoparticle product enh ance the crystal

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perfection and as well as it reduce the defects. As a result electron scattering
phenomenon due to crystal defects are also reduced and a reduction in resistivity is
experienced. However, at room temperature the defect scattering incident contributes a
minor influence on the total electrical resistibility of various metals. On the other hand
surface scattering phenomenon which is highly increased due to reduction of particle
size is one of the prominent reasons for increase of the total res istivity. In addition a
reduction in particle size below a critical dimension, i.e. (electron de Broglie
wavelength), would result in a modified electronic structure with wide and discrete band
gap. The reduction of particle size into this range would resu lt in an increased electrical
resistivity.
Optical properties: Optical properties exhibited by nanomaterials are quite different
from their bulk counterparts. The reason behind this change in property is mainly due to
the effect of the surface plasmon reso nance. In addition, the increased energy level
spacing is also an important criterion for this changing behavior. Due to increased band
gap for semiconductor nanoparticles absorption edge is shifted toward shorter
wavelengths. Surface Plasmon resonance eff ect changes due to change in particle size
which in turn changes the color of metallic nanoparticles. The coherent excitation of
entire free electrons in the conduction band may produce an in -phase oscillation, called
surface plasmon resonance. When the si ze of a metal nanocrystal is smaller than the
wavelength of incident radiation, a surface plasmon resonance is generated. On
resonance, light is tightly confined to the surface of the nanostructure, until it gets
eventually absorbed inside the metal, or sc attered back into photons.
Chemical properties of the materials are also changed when it converts to nano
range. Due to increase of exposed surface area of the nanopart icles as compared with
conventional bulk objects, reactivity of those particles increase enormously.
Some important features of the nanoparticle chemical properties are given below

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1. In case of nanoparticles 50% of all the atoms are surface atoms and as a result electric
transport properties of these particles are no longer dependent on soli d state bulk
phenomenon.Electrical properties are directly related to chemical properties.
2. Due to larger proportion of surface atoms, the atoms present in nanomaterials posses a
higher energy as compare to atoms present in bulk structure.
3. The interac tions between nanoparticles depend on the chemical nature of the surface.
Due to large surface area high quantity charge species defects and impurities may be
easily attracted to surfaces and interfaces of nano particles and thus chemical nature of
the sur faces changes abruptly as compare to their bulk counterpart.
4. Surface properties of the nanoparticles and their interaction can be modified or altered
by using molecular monolayer.
Reference:
• Lubick N, Betts K. Silver socks have cloudy lining| Court bans widely used flame
retardant.
• Vollath D, KGaA WV. An Introduction to Synthesis, Properties and Application.
and Management. 2008 Nov;7(6):865 -70.

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Chapter III
Classification of nanomaterials
Nanomaterials can be categorized as different methods of cl assification including origin,
dimensions and their structural configuration
According to their origin nanomaterials are classified as:
1. Natural nanomaterials: Nanomaterials which are belonging to resource of nature
are defined as natural nanometer. As p er examples virus, protein molecules including
antibody originated from nature are some natural nano structured materials. In addition
following are few examples, mineral such as clays, natural colloids, such as milk and
blood (liquid colloids), fog (aeros ol type), gelatine (gel type), mineralised natural
materials, such as shells, corals and bones, Insect wings and opals, Spider silk, Lotus leaf
and similar (Nasturtium,). Gecko feet, volcanic ash, ocean spray etc
2. Artificial nanomaterial: Artificial nano particles are those which are prepared
deliberately through a well -defined mechanical and fabrication process. The examples of
such materials are carbon nanotubes, semiconductor nanoparticles like quantum dots etc.

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Different dimensional Nanomaterials (a ) 0-D spheres and clusters, (b) 1 -D nanofibers,
wires,and rods, (c) 2 -D films, networks, (d) 3 -D nanomaterials.
Different dimensional Nanomaterials
On the other hand according to the dimensions nanomaterials also can be divided into
zero dimensional, one dimensional, two dimensional and three dimensional nano
materials.
1. Zero dimensional (0 -D): These nanomaterials have Nano -dimensions in all the
three directions. Metallic nanoparticles including gold and silver nanoparticles and
semiconductor such as qua ntum dots are the perfect example of this kind of
nanoparticles. Most of these nanoparticles are spherical in size and the diameter of these
particles will be in the 1 -50 nm range. Cubes and polygons shapes are also found for this
kind of nanomaterials.
2. One dimensional (1 -D): In these nanostructures, one dimension of the
nanostructure will be outside the nanometer range. These include nanowires, nanorods,
and nanotubes. These materials are long (several micrometer in length), but with
diameter of only a few nanometer. Nanowire and nanotubes of metals, oxides and other
materials are few examples of this kind of materials
3. Two dimensional (2 -D): In this type of nanomaterials, two dimensions are
outside the nanometer range. These include different kind of Nano films such as coatings
and thin -film-multilayers, nano sheets or nano -walls. The area of the nano films can be
large (several square micrometer), but the thickness is always in nano scale range

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4. Three Dimensional (3 -D): All dimensions of these are o utside the nano meter
range. These include bulk materials composed of the individual blocks which are in the
nanometer scale (1 -100 nm)
Structural configuration nanomaterials
On the basis of structural configuration nanomaterials can be classified into fou r types:
Carbon Based Nano materials: The nature of this kind of nanomaterials is hollow
spheres, ellipsoids, or tubes. Spherical and ellipsoidal configured carbon nanomaterials
are defined as fullerenes, while cylindrical ones are described as nanotubes.
Metal Based Materials: The main component of these particles is metal. These
nanomaterials include nanogold, nanosilver and metal oxides, such as titanium dioxide
and closely packed semiconductor like quantum dots.
Dendrimers: Dendrimers are highly branche d macromolecules with the dimensions
nanometer -scale. The surface of a dendrimer posses numerous chain which can be
modified to perform specific chemical functions. PAMAM dendrimer is the best
illustration of this kind of materials.
Composites: Nanocomposi te can be described as a multiphase solid material where at
least one of the phases has one, two or three dimensions in nanoscale. The most common
examples of these materials are colloids , gels and copolymers .
Reference:
• Alagarasi A. Chapter -Introduction To Nanomaterials.

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Chapter IV
Structure of nanocrystalline mate rials

Nanocrystalline materials are a new class of disordered solids having high density of
defect cores with 50% or more of the atoms (molecules). Depending on the type of
defects utilized (grain boundaries, interphase boundaries, dislocations, etc.)
nanocrystalline materials with different structures may be generated. Nevertheless, all of
these materials have the following microstructural feature in common. They consist of a
large volume fraction of defect cores and (strained) crystal lattice regions. As an
example, Fig. shows the structure of a two -dimensional nanocrystalline material. The
crystals are represented by hexagonal arrays of atoms with different crystallographic
orientations. Hence the atomic structures of the core regions of the various boun daries
between the crystals are different because their structure depends on the crystal mis
orientations and boundary inclinations. The boundary core regions (open circles) are
characterized by a reduced atomic density and inter atomic spacings deviating from the
ones in the perfect lattice. The physical reason for the reduced density and the non -lattice
spacings between the atoms in the boundary cores is the misfit between the crystal
lattices of different orientation joined along common interfaces. In ot her words, the
nanocrystalline system preserves in the crystals, a structure of low energy at the expense
of the boundary regions which are regions at which all the misfit is concentrated so that
a structure far away from equilibrium is formed. A structure of similar heterogeneity is
not formed in thermally induced disordered solids such as glasses. The misfit between
the crystals not only reduces the atomic density in the interfacial region in comparison to
the perfect lattice but also causes strain fields to extend from the boundary core regions
into the crystallites. These strain fields remove the atoms from their ideal lattice sites.
The amount of atomic displacement depends primarily on the interatomic potential.

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Hence different materials are expected t o exhibit different atomic structures in the
nanocrystalline state.

Fig. Atomic structure of a two -dimensional nanocrystalline material. The structure
was computed by following the procedure given in Gleiter (1982). The atoms in the
centers of the "cryst als" are indicated in black. The ones in the boundary core
regions are represented by open circles.

Reference:
• Gleiter H. On the structure of grain boundaries in metals. InInterfacial Aspects of
Phase Transformations 1982 (pp. 199 -222). Springer, Dordrech t.

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Chapter V
Synthesis techniques of nano materials
Inert Gas Condensation Method :
The inert gas evaporation –condensation (IGC) technique, in which nanoparticles are
formed via the evaporation of a metallic source in an inert gas, has been widely used in
the synthesis of ultrafine metal particles since the 1930s.
In its basic form, the method consists of evaporating a metallic source, using resistive
heating (although radio frequency heating or use of an electron or laser beam as the
heating source are all equally effective methods) inside a chamber which has been
previously evacuated to about 10-7torr and backfilled with inert gas to a low pressure.
The metal vapor migrates from the hot source into the cooler inert gas by a combination
of convective fl ow and diffusion and the evaporated atoms collide with the gas atoms
within the chamber, thus losing kinetic energy. Ultimately, the particles are collected for
subsequent consolidation, usually by deposition on a cold surface.
Most applications of the ine rt gas condensation technique carry this approach to
extremes by cooling the substrate with liquid nitrogen to enhance the deposition
efficiency.
Particles collected in this manner are highly concentrated on the deposition substrate.
While the particles d eposited on the substrate have complex aggregate morphology, the
structure tends to be classified in terms of the size of the crystallites that make up these
larger structures.The scraping and compaction processes take place within the clean
environment to ensure powder surface cleanliness (i.e., to reduce oxide formation) and to
minimize problems associated with trapped gas.

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Reference:
https://shellzero.wordpress.com/2012/05/14/inert -gas-condensation -method/
Sol-Gel Method
The sol -gel process is a capab le wet chemical process to make ceramic and glass
materials. This synthesis technique involves the conversion of a system from a colloidal
liquid, named sol, into a semi -solid gel phase. The sol -gel technology can be used to
prepare ceramic or glass materi als in a wide variety of forms: ultra -fine or spherical
shaped powders, thin film coatings, ceramic fibres, microporous inorganic membranes,
monolithics, or extremely porous aerogels. An overview of the sol -gel process is
illustrated in Fig.

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This techniq ue offers many advantages including the low processing temperature, the
ability to control the composition on molecular scale and the porosity to obtain high
surface area materials, the homogeneity of the final product up to atomic scale.
Moreover, it is p ossible to synthesize complex composition materials, to form higher
purity products through the use of high purity reagents. The sol -gel process allows
obtaining high quality films up to micron thickness, difficult to obtain using the physical
deposition t echniques. Moreover, it is possible to synthesize complex composition
materials and to provide coatings over complex geometries.
The starting materials used in the preparation of the sol are usually inorganic metal salts
or metal organic compounds, which b y hydrolysis and polycondensation reactions form
the sol. Further processing of the sol enables one to make ceramic materials in different
forms. Thin films can be produced by spin -coating or dip -coating. When the sol is cast
into a mould, a wet gel will f orm. By drying and heat -treatment, the gel is converted into

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dense ceramic or glass materials. If the liquid in a wet gel is removed under a
supercritical condition, a highly porous and extremely low density aerogel material is
obtained. As the viscosity o f a sol is adjusted into a suitable viscosity range, ceramic
fibres can be drawn from the sol. Ultra -fine and uniform ceramic powders are formed by
precipitation, spray pyrolysis, or emulsion techniques.
Rapid Solidification Technique:

Rapid Solidificati on Technology allows the production of metallic ribbons in the
amorphous (glassy) state. The lack of long range atomic order results in superior soft
magnetic properties. Via a special annealing treatment some amorphous compositions
may be transformed into nanocrystalline materials. Amorphous and nanocrystalline soft
magnetic alloys are the basis for many innovative applications as magnetic cores,

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inductive components or in labels for electronic article surveillance (EAS).VAC is one
of the pioneers in Rapid Solidification Technology to cast thin metallic ribbons of
thickness 15 -50 µm in a single process step directly from the molten metal.
Special features of this process are:
• extremely high cooling rates of 106 K/s (i.e. from about 1400°C to less than 400
°C in one millisecond)
• high casting speeds of 100 km/h
• in-line winding of the thin ribbon
• automatic reel change during winding without process interruption
Reference:
http://www.slideshare.net/legendsundar/rapid -solidification -technology
Electro -deposi tion Technique:

This technique is to understand and investigate the growth by electro deposition of metal
films on metal and glass/ITO substrates. To determine and explain aspects of
electrodeposited films including crystallinity, microstructure, adhesion and optical
properties.
Theory
Electroplating is often also called "electrodeposition", a short version of “electrolytic
deposition”, and the two terms are used interchangeably. As a matter of fact,
"electroplating" can be considered to occur by the proce ss of electro deposition. It’s a
process using electrical current to reduce cations of a desired material from a solution

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and coat that material as a thin film onto a conductive substrate surface. Figure below
shows a simple electroplating system for the d eposition of copper from copper sulphate
solution.

Fig : Electrolytic cell for the deposition of copper from copper sulphate solution.
The electrolytic solution contains positively charged copper ions (cations) and
negatively charged sulphate ions (anion s). Under the applied external electric field, the
cations migrate to the cath 0ode where they are discharged and deposited as metallic
copper.
Cu2+ + 2e – Cu (metal)
Copper from the anode dissolves into the solution to maintain the electrical neutrality.
Cu – Cu2+ + 2e.
The overall process is known as electrolysis. If some noble metal (such as platinum) is
used as the anode, the overall reaction at the anode is the oxidation of water.
2H 2O–4H+ + O 2 + 4e
The sulphate ions remain unchanged in quantity duri ng the electrolysis. However, if
noble metal is used as the anode, the concentration of Cu 2+ ions will decrease and that of
H+ ions will increase with time. Under this situation, extra copper sulphate must be

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added into the solution from time to time and t he hydrogen ions must be removed by
neutralization with an alkali or by using a buffering solution. In practical electro
deposition processes, the chemical reaction around the electrode area occurs in a more
complicated way than that shown in figure . Under the influence of an applied potential,
rearrangement of ions near the electrode surface results in an electrical double layer
called the Helmholtz double layer, followed by the formation of a diffusion layer as
shown in figure . These two layers are referr ed as the Gouy -Chapman layer. The process
is as follows:
Migration: The hydrated metal ions in the solution migrate towards the cathode under
the influence of impressed current as well as by diffusion and convection.
Electron transfer: At the cathode surfa ce, a hydrated metal ion enters the diffused double
layer where the water molecules of the hydrated ion are aligned. Then the metal ion
enters the Helmholtz double layer where it is deprived of its hydrate envelope. The
dehydrated ion is neutralized and ad sorbed on the cathode surface. The adsorbed atom
then migrates or diffuses to the growth point on the cathode surface.
Thickness of the electroplated layer on the substrate is determined by the time duration
of the plating. In other words, the longer the t ime the object remains in the operating
plating bath, the thicker the resulting electroplated layer will be. Typically, layer
thicknesses may vary from 0.1 to 30 microns. An electroplated layer is usually
composed of a single metallic element. Co-depositio n of two or more metals is possible
under suitable conditions of potential and polarization, such as a Cu-Zn alloy or a Au -Sn
alloy.

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Fig. : Electrical double layer

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Applications:
Since its invention in 1805 by Italian chemist, Luigi Brugnatelli, electr oplating has
become an extensively used industry coating technology. Its applications are mainly in
the following four groups:
1. Decoration: Coating a more expensive metal onto a base metal surface in order
to improve the appearance. Applications are jewelle ry, furniture fittings,
builders’ hardware and tableware.
2. Protection: Corrosion -resistant coatings such as chromium plating of
automobile parts and domestic appliances, zinc and cadmium plating of nuts,
screws and electrical components. Wear -resistant coat ings such as nickel or
chromium plating of bearing surfaces and worn shafts and journals.
3. Electroforming: Manufacture of sieves, screens, dry shaver heads, record
stampers, moulds, and dies.
4. 4.Enhancement: coatings with improved electrical and thermal cond uctivity,
solderability, reflectivity etc.
Properties of deposited film:
adhesion: As one of the most important requirements, adhesion is mostly dependant
upon the substrate. For proper adhesion, the substrate must be thoroughly cleaned and
free of any sur face films. It is desirable that the substrate and the deposited metal inter –
diffuse with interlocking grains to give a continuous interfacial region. Alloy formation
by the inter-diffusion of the substrate and the deposited metals provides good adhesion.
However, an inter -metallic compound is undesirable since it behaves like inorganic salts
and results in poor adhesion.
mechanical properties : Mechanical properties of the electrodeposited film depend to a
considerable extent on the types and amounts of gro wth-inhibiting substance at the

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cathode surfaces. The purpose of using a growth -inhibiting substance is to obtain fine –
grain structure of the deposited film, in which the grain boundaries act as the main
obstacles to dislocation motion, leading to a higher yield strength and hard surface.
Hardness of the deposited film can also be increased by introducing lattice strain through
in corporating impurities into the film -growth process. Electroplating processes
frequently result in the development of internal s tresses. The reasons for internal stresses
relate to coalescence of three -dimensional, epitaxial crystallites, dislocation
configurations, hydrogen incorporated into the crystal lattice, or other factors. Tensile
stress is more detrimental than compressive stresses since it easily causes cracks of the
deposited film, reducing the fracture strength and ductility. Certain addition agents for
some electroplating solutions have been developed to reduce tensile stress.
brightness: Brightness of deposited film is critical for decoration applications. The
brightness of thin deposited films depends on the surface finish of the substrate. Thick
layer bright deposited films are produced by additional agents in the plating solution
which result in elimination of protru sions or crevices which deviate from the surface
plane by about the wavelength of visible light. The addition agents are mostly organic
compounds such as dextrose, saccharine, lactose, formaline, citrates, tartarates, etc.
However, most good brighteners ar e sulphur compounds, especially thio -urea and its
derivatives and organic sulphonic acids. Brightening agents are foreign inclusions in the
deposited film. Over dosage of these additives can cause brittleness and lead to cracks
and peeling off of the depos ited film from the substrate.
Reference:
http://coursenotes.mcmaster.ca/4L04/Thin_Films/Electrodeposition_of_Metal.pdf

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Spray conversion processing
This route invo lves the atomization of chemical precursors into aerosol droplets that are
dispersed throughout a gas medium. The aerosols are then transported into a heated
reactor where the solution is evaporated to form ultrafine particles or thin films. This is
an ine xpensive technique as various low cost chemical solutions are available. Various
aerosol generators —including pressure, electrostatic and ultrasonic atomisers —have
been used for atomization purposes. These atomizers affect the droplet size, rate of
atomiza tion and droplet velocity. The most commonly used aerosol processing method is
spray pyrolysis . In the process, aqueous solution is atomized in a series of reactors where
the aerosol droplets undergo evaporation and solute condensation within the droplet;
drying and thermolysis is followed by sintering. Nanoparticles can be prepared directly,
synthesized from droplets or by liberating individual crystallites comprising the spray
pyrolysis -derived particles from the thermolysis stage. Spray pyrolysis can be used to
prepare several metal oxide nanoparticles such as ZnO, ZrO2 and Al 2O3.

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The Plasma Spray Process is basically the spraying of molten or heat softened material
onto a surface to provide a coating. Material in the form of powder is injected in to a very
high temperature plasma flame, where it is rapidly heated and accelerated to a high
velocity. The hot material impacts on the substrate surface and rapidly cools forming a
coating. This plasma spray process carried out correctly is called a "cold process"
(relative to the substrate material being coated) as the substrate temperature can be kept
low during processing avoiding damage, metallurgical changes and distortion to the
substrate material.
The plasma spray gun comprises a copper anode and tu ngsten cathode, both of which are
water cooled. Plasma gas (argon, nitrogen, hydrogen, helium) flows around the cathode
and through the anode which is shaped as a constricting nozzle. The plasma is initiated
by a high voltage discharge which causes localis ed ionisation and a conductive path for a
DC arc to form between cathode and anode. The resistance heating from the arc causes
the gas to reach extreme temperatures, dissociate and ionise to form a plasma. The
plasma exits the anode nozzle as a free or neu tral plasma flame (plasma which does not
carry electric current) which is quite different to the Plasma Transferred Arc coating
process where the arc extends to the surface to be coated. When the plasma is stabilised

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ready for spraying the electric arc ext ends down the nozzle, instead of shorting out to the
nearest edge of the anode nozzle. This stretching of the arc is due to a thermal pinch
effect. Cold gas around the surface of the water cooled anode nozzle being electrically
non-conductive constricts th e plasma arc, raising its temperature and velocity. Powder is
fed into the plasma flame most commonly via an external powder port mounted near the
anode nozzle exit. The powder is so rapidly heated and accelerated that spray distances
can be in the order o f 25 to 150 mm.

Plasma Spray Process
The plasma spray process is most commonly used in normal atmospheric conditions and
referred as APS. Some plasma spraying is conducted in protective environments using
vacuum chambers normally back filled with a prote ctive gas at low pressure, this is
referred as VPS or LPPS.
Plasma spraying has the advantage that it can spray very high melting point materials
such as refractory metals like tungsten and ceramics like zirconia unlike combustion
processes. Plasma sprayed coatings are generally much denser, stronger and cleaner than

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the other thermal spray processes with the exception of HVOF, HVAF and cold spray
processes. Plasma spray coatings probably account for the widest range of thermal spray
coatings and applicatio ns and makes this process the most versatile.
Disadvantages of the plasma spray process are relative high cost and complexity of
process.
Reference:
http://www.gordonengland.co.uk/ps.htm
Mechanical alloy ing
The mechanical alloying (MA)/milling process was originally developed by Benjamin of
the International Nickel Company for the production of oxide dispersion strengthened
(ODS) superalloys. It is now a widely used process for the fabrication of nanocrys talline
powders. The possible spectrum of the uses of MA are shown schematically in figure
below. Recently, nanocrystalline high -entropy solid solutions with high hardness have
been synthesized in multi -component equiatomic alloys by MA. Mechanical alloyin g or
milling is usually carried out in high -energy mills such as vibratory mills (Spex 8000
mixer/mill), planetary mills (Fritsch and Retsch) and attritor mills (Szegvariattritor and
Simoloyer). The vibratory mill has one vial, containing the sample and gr inding balls
and vibrates in all three directions. Because of the amplitude (about 50 mm) and speed
(about 1200 rpm), the ball velocities are high (in the order of 5 m/s) and consequently
the force of the ball’s impact is unusually high. Another popular mi ll for conducting MA
experiments is the planetary ball mill. In this mill, the vials rotate around their own axes
and at the same time around the axis of a disc on which they are mounted. The
centrifugal force produced by the vials rotating around their ow n axes and that produced

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by the rotating support disk together act on the vial contents, consisting of material to be
ground and the grinding balls. Since the vials and the supporting disc rotate in opposite
directions, the centrifugal forces alternately a ct in opposite directions. Due to this, the
balls run down the inside wall of the vial. This is followed by the material being ground
and grinding balls being lifted off and travelling freely through the inner chamber of the
vial and colliding against the opposing inside wall. Grinding vials and balls are available
in eight different materials —agate, silicon nitride, sintered corundum, zirconia, chrome
steel, Cr –Ni steel, tungsten carbide and plastic polyamide. An attritor ball mill consists
of a stationary vertical drum in which a vertical shaft rotates with a series of horizontal
impellers attached to it. Set progressively at right angles to each other, the impellers,
through their rotation, energise the ball charge, causing powder size reduction due to th e
impact between balls, between balls and the container wall, and between balls, the
agitator shaft and impellers. Particle size reduction also occurs partially by inter -particle
collisions and by ball sliding on the walls of the vials. Attritors are the m ills in which
large quantities of powder (from about 0.5 to 40 kg) can be milled at a time. The most
recent of the ball mills is the horizontal attritor (Simoloyer) that can be operated in dry
processing at high relative velocity of the grinding media (up to 14 m/s) under controlled
condition like vacuum or inert gas and in closed circuits. In these mills, the grinding
media is accelerated by a horizontally arranged rotor inside the grinding vessel. These
mills have the advantage of highest relative velocit y of grinding media, which leads to
high level of kinetic energy transfer, an intensive grinding effect and short processing
times. The short processing times and collision -based grinding process results in low
contamination levels. The simoloyers are avai lable with 0.5 – to 990 -litre grinding
chamber capacity, which makes it very convenient to scale -up the laboratory
experiments to commercial production plants. The mechanism of nanocrystallization
during high -energy ball milling was first proposed by H.J. F echt in 1983. He

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summarised the phenomenon of the development of nanocrystalline microstructure into
three stages;

Stage 1: Localization of deformation into shear bands with high dislocation
density.
Stage 2: Dislocation, annihilation and recombination to form nanometre -scale
subgrains,
which extend throughout the sample with further milling.
Stage 3: Transformation of subgrain boundary structure to randomly oriented
high angle grain boundaries. Superplastic deformation processes such as grain
boundary sliding causes self -organisation into a random nanocrystalline state.

During high -energy milling, the powder particles are repeatedly flattened, cold welded,
fractured and re -welded. Whenever balls collide, some amount of powder is trapped in
between th em. The impact from the balls causes plastic deformation of the powder
particles, causing work hardening and fracture. The new surfaces formed by the fracture
of the particles weld together.
Mechanical alloying is akin to metal powder processing, where met als may be mixed to
produce super -alloys . Mechanical alloying occurs in three steps. First, the alloy materials
are combined in a ball mill and ground to a fine powder. A hot isostatic pressing (HIP)
process is then applied to simultaneously compress and sinter the powder. A f inal heat
treatment stage helps remove existing internal stresses produced during any cold
compaction which may have been used. This produces an alloy suitable for high heat
turbine blades and aerospace components.

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Reference:
http://www.slideshare.net/DrRamaswamyNarayanas/drrnarayanasamy -drssivasankaran –
and-drksiva -prasad -on-mechanical -alloying

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http://www.slideshare.net/rejeeshcrajendran/module -iii-32259859
Chapter VI
Characterization Techniques:
X-ray Diffraction:
X-ray diffraction is most extensively used technique for the characterization of th e
materials. A lot of information can be extracted from the XRD data. This is an
appropriate technique for all forms of samples, i.e. powder and bulk as well as thin film.
Using this technique, one can get the information regarding the crystalline nature o f a
material, nature of the phase present, lattice parameter and grain size. From the position
and shape of the lines, one can obtain information regarding the unit cell parameters and
microstructural parameters (grain size, microstrain, etc), respectively . In case of thin
films, the change in lattice parameter with respect to the bulk gives the idea about the
nature of strain present in the system.
The interaction of X -ray radiation with crystalline sample is governed by Bragg’s law,
which depicts a relat ionship between the diffraction angles (Bragg angle), X -ray
wavelength, and interplanar spacing of the crystal planes. According to Bragg’s law, the
X-ray diffraction can be visualized as X -rays reflecting from a series of crystallographic
planes as shown in Fig. 2.3. The path differences introduced between a pair of waves
travelled through the neighboring crystallographic planes are determined by the
interplanar spacing. If the total path difference is equal to nλ (n being an integer), the
constructive int erference will occur and a group of diffraction peaks can be observed,
which give rise to X -ray patterns. The quantitative account of Bragg’s law can be
expressed as:
2dhkl sin θ = nλ

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where d is the interplanar spacing for a given set of hkl and θ the Br agg angle.
The XRD measurements were carried out using Rigaku X -ray diffractometer with CuKα
(λ = 1.54187Å) radiation at room temperature, and operated at a voltage of 30kV and
filament current of 40mA. The phase identification for all the samples reported in this
thesis was performed by matching the peak positions and intensities in XRD patterns to
those patterns in the JCPDS (Joint Committee on Powder Diffraction Standards)
database.
The diffraction method is based on the effect of broadening of diffract ion reflections
associated with the size of the particles (crystallites). All types of defects cause
displacement of the atoms from the lattice sites. M.A. Krivoglaz in 1969 derived an
equation for the intensity of the Bragg reflections from a crystal defe ct, which enabled
all the defects to be derived conventionally into two groups. The defects in the first
group only lower the intensity of the diffraction reflections but do not cause the
reflection broadening. The broadening of the reflections is caused b y the defects of
second group. These defects are micro -deformations, in homogeneity (non -uniform
composition of the substance over their volume) and the small particle size. The size of
nanomaterials can be derived from the peak broadening and can be calcu lated by using
the Scherrer equation, provided that the nano crystalline size is less than 100nm.

where D is the average crystallite dimension perpendicular to the reflecting phases, λ the
X-ray wavelength, k the Scherrer constant which equals 0.9 for spherical particles,
whose value depends on the shape of the particle (crystallite, domain) and on dif fraction
reflection indices (hkl), and β is the full width at half maximum of the peaks. The
Scherrer formula is quite satisfactory for small grains (large broadening) in the absence

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of significant microstrain. A microstrain describes the relative mean squ are deviation of
the lattice spacing from its mean value. Based on the grain size dependence of the strain
it is reasonable to assume that there is a radial strain gradient, but from X -ray diffraction
only a homogeneous, volume -averaged value is obtained.
Transmission electron microscopy (TEM):
Transmission electron microscopy (TEM) is a microscopy technique where a beam of
electrons is transmitted through an ultra thin specimen, interacting with the specimen as
it passes through. An image is formed from t he interaction of the electrons transmitted
through the specimen; the image is magnified and focused onto an imaging device, such
as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor
such as a CCD camera.

TEMs are capab le of imaging at a significantly higher resolution than light microscopes,
owing to the small de Broglie wavelength of electrons. This enables the instrument's user
to examine fine detail – even as small as a single column of atoms, which is tens of
thousan ds times smaller than the smallest resolvable object in a light microscope. TEM
forms a major analysis method in a range of scientific fields, including for nano
materials.

With the help of bright -field TEM micrographs, one can directly get the hint on g rain
size, whether it is nano or not (less than 100 nm or not). In addition, one can get the hint
on grain shape and morphology etc. On the other hand, a ring type polycrystalline
diffraction pattern can be commonly obtained in the case of nanocrystalline materials.

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Positron annihilation spectroscopy (PAS)
Positron annihilation spectroscopy (PAS) or sometimes specifically referred to as
Positron annihilation lifetime spectroscopy (PALS) is a non -destructive spectroscopy
technique to study voids and defect s in solids.

A Feynman diagram of an electron and positron annihilating into a photon.

The technique operates on the principle that a positron or positronium will annihilate
through interaction with electrons. This annihilation releases gamma rays that can be
detected; the time between emission of positrons from a radioactive source and detection
of gamma rays due to annihilation corresponds to th e lifetime of positron or positronium.
When positrons are injected into a solid body, they interact in some manner with the
electrons in that species. For solids containing free electrons (such as metals or
semiconductors ), the implanted positrons annihilate rapidly unless voids such as vacancy
defects are present. If voids are available, positrons will reside in them and annihilate
less rapidly than in the bulk of the material, on time scales up to ~1 ns. For insulators

INTRODUCTION TO NANOWORLD
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such as polymers or zeolites , implanted positrons interact with electrons in the material
to form positronium.
Positronium is a metastable hydrogen -like bound state of an electron and a positron
which can exist in two spin states. Para -positronium, p-Ps, ( the positron and electron
spins are anti -parallel) is a singlet state with a characteristic self -annihilation lifetime of
125 ps in vacuum. Ortho -positronium, o-Ps, is a triplet state (the positron and electron
spins are parallel) with a characteristic self -annihilation lifetime of 142 ns in vacuum. In
molecular materials, the lifetime of o-Ps is environment dependent and it delivers
information pertaining to t he size of the void in which it resides. Ps can pick up a
molecular electron with an opposite spin to that of the positron, leading to a reduction of
the o-Ps lifetime from 142 ns to 1 -4 ns (depending on the size of the free volume in
which it resides). Th e size of the molecular free volume can be derived from the o-Ps
lifetime via the semi -empirical Tao -Eldrip model.
Pore structure in insulators can be determined using the quantum mechanical Tao -Eldrup
model and extensions thereof. By changing the tempera ture at which a sample is
analyzed, the pore structure can be fit to a model where positronium is confined in one,
two, or three dimensions. However, interconnected pores result in averaged lifetimes
that cannot distinguish between smooth channels or chann els having smaller, open,
peripheral pores due to energetically favored positronium diffusion from small to larger
pores.
The behavior of positrons in molecules or condensed matter is nontrivial due to the
strong correlation between electrons and positrons . Even the simplest case, that of a
single positron immersed 0 in a homogeneous gas of electrons, has proved to be a
significant challenge for theory. The positron attracts electrons to it, increasing the
contact density and hence enhancing the annihilation rate. Furthermore, the momentum

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density of annihilating electron -positron pairs is enhanced near the Fermi surface.
Theoretical approaches used to study this problem have included the Tamm -Dancoff
approximation, Fermi and perturbed hypernetted chain appro ximations, density
functional theory methods and quantum M onte Carlo .
Implementation
The experiment itself involves having a radioactive positron source (often 22Na) situated
near the analyte. Positrons are emitted near -simultaneously with gamma rays. These
gamma rays are detected by a nearby scintillator and act as the "start" signal. The
positrons interact with the analyte (either annihilating directly or forming positronium
which subsequently annihilates) and on annihilation, gamma rays of lower energy than
the start signal are emitted and detected as the "stop" signal. After enough correlated
start and stop signals are detected (on the order of 1,000,000 such start/stop signals are
required), average positron or positronium lifetimes can be fit to a histogram containing
the frequency of individual lifetimes.
Reference:
https://en.wikipedia.org/ wiki/Positron_annihilation_spectroscopy

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Chapter VII
Consolidation of nanopowders

The commercial application of nanomaterials beyond the boundaries of materials science
laboratories is possible only on successful consolidation of these materials int o bulk –
sized components preserving the nanostructures. Due to the long duration of sintering at
high temperature that is involved in conventional consolidation techniques, it is difficult
to retain the nanograin -size due to grain growth in such techniques.
The density of the green compact depends on the frictional forces of the powder particles
that originate from electrostatic, van der Waals and surface adsorption forces. These
forces are significantly high in nanoparticles, forming hard agglomerates and inter-
agglomerates, which are relatively large. Further, nanoparticles contain a large number
of pores which require not only higher temperature but also prolonged sintering times for
their successful elimination; consequently, it becomes difficult to reta in the grain size in
the nanometer domain. Large pores undergo pore –boundary separation that restricts the
attainment of full density in the consolidated nanoparticles. During sintering of
nanoparticles, pores smaller than the critical size shrink, while l arger pores undergo
pore–boundary separation. The fraction of grain boundaries in nanomaterials is large
compared to that in coarse -grained materials. The density of the grain boundary regions
is less than the grain interior due mainly to the relaxation of atoms in the grain
boundaries; they also contain other lattice defects.
Therefore, consolidated nanoparticles with retained nanostructure are expected to exhibit
a density lower than the theoretical density of the bulk counterpart. There are numerous
conflicting views on the sintering behaviour of nanoparticles.

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Hot isostatic pressing (HIP) is a manufacturing process, theorized in the 1970s,
used to reduce the porosity of metals and increase the density of ma ny ceramic materials.
This improves the material's mechanical properties and workability.
The HIP process subjects a component to both elevated temperature and isostatic gas
pressure in a high pressure containment vessel. The pressurizing gas most widely used is
argon . An inert gas is used, so that the material does not chemically react. The chamber
is heated, causing the pressure inside the vessel to increase. Many systems use associated
gas pumping to achieve the necessary pressure level. Pressure is applied to the material
from all directions (hence the term "isostatic").
For processing castings , metal powders can also be turned to compact solids by this
method, the inert gas is applied between 7,350 psi (50.7 MPa) and 45,000 psi
(310 MPa), with 15,000 psi (100 MPa) being most common. P rocess soak temperatures
range from 900 °F (482 °C) for aluminium castings to 2,400 °F (1,320 °C) for nickel –
based superalloys . When castings are treated with HIP, the simultaneous application of
heat and pressure eliminates internal voids and microporosity through a combination of
plastic deformation , creep, and diffusion bonding ; this process improves fatigue
resistance of the component. Primary applications are the reduction of microshrinkage ,
the consolidation of powder metals, ceramic composites and metal cladding . Hot
isostatic pressing is a lso used as part of a sintering (powder metallurgy ) process and for
fabrication of metal matrix composites .

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Fig. Schematic of a hot isostatic pressing setup.

Spark plasma sintering
Sintering is the process of making objects from powder, by heating the materia l in a
furnace below its melting point so that bonding takes place by diffusion of atoms. This
leads to individual powder particles adhering to each other in a dense compact. The
process is usually used for ceramics. Sintering can be done using various met hods as
Conventional Sintering, Spark Plasma Sintering (SPS), Microwave Sintering etc. Spark
Plasma sintering is one of the processing routes to process biomaterials in laboratory.
The SPS process is based on the electrical spark discharge phenomenon: a hi gh energy,
low voltage spark pulse current momentarily generates spark plasma at high localized
temperatures, from several to ten thousand ℃ between the particles resulting in optimum

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thermal and electrolytic diffusion. SPS sintering temperatures range from low to over
2000 ℃ which are 200 to 500 ℃ lower than with conventional sintering. Vaporization,
melting and sintering are completed in sh ort periods of approximately 5 to 20 minutes,
including temperature rise and holding times.
The SPS process concentrates high energy pulses at the point of intergranular bonding
offering significant improvements over conventional hot -press and hot isostat ic press
sintering. Now, a look at the mechanism of neck formation during the SPS process. We
have already explained under Principles that when spark discharge appears in the gap
between the particles of a material, a local high temperature state of severa l to ten
thousand ℃ momentarily occurs. This causes vaporization and the melting of the
surfaces of the powder particles during the SPS process; constricted shapes or “necks”
are formed around the contact area between the particles. These necks gradually d evelop
and plastic transformation progresses during sintering, resulting in a sintered compact of
over 99% density. Since only the surface temperature of the particles rises rapidly by
self-heating, particle growth of the starting powder materials is contr olled. Therefore, a
precision sintered compact is manufactured in a shorter time. At the same time, bulk
fabrication of particles with amorphous structure and nano -crystallization formation are
now possible without changing their characteristics.

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ON-OFF pulsed current path Material transfer path during sintering
SPS process is a pressure assisted pulsed current sintering process utilizing ON -OFF DC
pulse energizing. The repeated application of an ON -OFF DC pulse voltage and current
between powder mate rials, the spark discharge point and the Joule heating point (local
high temperature -state) are transferred and dispersed to the overall specimen and the
homogeneously repeated phenomena and the effects during the ON stage on the
specimen, result in effici ent sintering at low power consumption.

Neck formation

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Basic mechanism of neck formation by spark plasma
Shockwave consolidation
Shock wave consolidation, also termed dynamic consolidation , is used to densify
powdered materials without inducing therma l activated microstructural and
compositional changes that are normal in conventional thermomechanical processing.
Such densification is possible because of the interparticle bonding due to localized
melting at the interfaces between the particles. High pr essure and rapid loading rates that
create high plastic deformation finally lead to high shock initiated chemical reactions
completely different from the conventional ones. Metallic or alloy powders are usually
processed through this route due to the fact that plastic deformation in metal is
comparatively easier than for ceramics.
In this process, particles are enclosed in a steel block that looks similar to a cold
compaction chamber that is covered using a plate, on top of which a driver plate usually
bears the brunt of explosions and drives the shock wave towards the sample (Fig. 2). The

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driver plate is usually made of highly conductive and ductile material. Explosives are
packed on top of this plate carefully and the spillage, if any, has to be removed. T he
detonator is set on top of the explosive and the set up is ready for processing to start.
Ammonium nitrate is usually used as the explosive. Shock compaction of powders is a
dynamic consolidation technique which provides a viable method for densificatio n of
amorphous as well as ultrafine powders.
Fe-, Ni- and Ti -based alloys have been studied more often using this technique. Pure
metals and alloys with retained nanostructures can be consolidated using this technique.
Some of the systems that have been i nvestigated are: F e73.5Cu1Nb3Si13.5B9, Fe, Fe –
Al, diamond –Si, Al, Pr2Fe14B/α -Fe, Ti5Si3 and NiAl.

Fig: Schematic of shock wave consolidation setup.

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References:
• Ikram A. SPARK PLASMA SINTERING STUDY OF METAL BONDED Nd –
Fe-B & Sm -Co PERMANENT MAGNETS.
• Murty BS, Shankar P, Raj B, Rath BB, Murday J. Textbook of nanoscience and
nanotechnology. Springer Science & Business Media; 2013 Dec 6.
• Atkinson HV, Davies S. Fundamental aspects of hot isostatic pressing: an
overview. Metallurgical and Materials Transactions A. 2000 Dec 1;3 1(12):2981 –
3000.
• https://en.wikipedia.org/wiki/Hot_isostatic_pressing#cite_note -1

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Chapter VIII
Current, recent and Future applications of nanotechnology and
nanomaterial s.

Nanomaterials (nanocrystalline materials) are materials possessing grain sizes on the
order of a billionth of a meter. They manifest extremely fascinating and useful
properties, which can be exploited for a variety of structural and non -structural
applications. Nanotechnology Applications in:
1. Medicine : Researchers are developing customized nanoparticles the size of
molecules that can deliver drugs directly to diseased cells in the body. Whe n it's
perfected, this method should greatly reduce the damage treatment such as
chemotherapy does to a patient's healthy cells.
2. Electronics : Nanotechnology holds some answers f or how we might increase
the capabilities of electronics devices while we reduce their weight and power
consumption.

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3. Food : Nanotechnology is having an impact on several aspects of food science,
from how food is grown to how it is packaged. Companies are developing
nanomaterials that will make a difference not only in the taste of food, but also in
food safety, and the health benefits that food delivers.

4. Fuel Cells : Nanotechnology is being used to reduce the cost of catalysts used in
fuel cells to produce hydrogen ions from fuel such as methanol and to improve the

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efficiency of membranes used in fuel cells to separate hydrogen ions from other
gases such as oxygen.
5. Solar Cells : Companies have developed nanotech solar cells that can be
manufactured at significantly lower cost than conventional solar cells.
6. Batteries : Companies are currently developing batteries using nanomaterials.
One such battery will be a good as new after sitting on the shelf for decades.
Another battery can be recharged significantly faster than conventional batteries.
7. Space : Nanotechnology may hold the key to making space -flight more practical.
Advancements in nanomaterials make lightweight spacecraft and a cable for the
space elevator pos sible. By significantly reducing the amount of rocket fuel
required, these advances could lower the cost of reaching orbit and traveling in
space.
8. Fuels : Nanotechnology can address the shortage of fo ssil fuels such as diesel and
gasoline by making the production of fuels from low grade raw materials
economical, increasing the mileage of engines, and making the production of fuels
from normal raw materials more efficient.
9. Better Air Quality : Nanotechnology can improve the performance of catalysts
used to transform vapors escaping from cars or industrial plants into harmless
gasses. That's because catalysts made from nanoparticles have a greater sur face
area to interact with the reacting chemicals than catalysts made from larger
particles. The larger surface area allows more chemicals to interact with the
catalyst simultaneously, which makes the catalyst more effective.
10. Cleaner Water : Nanotechnology is being used to develop solutions to three
very different problems in water quality. One challenge is the removal of
industrial wastes, such as a cleaning solvent called TCE (trichloroethene), from
groundwater. Nanoparticles can be used to convert the contaminating chemical

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through a chemical reaction to make it harmless. Studies have shown that this
method can be used successfully to reach contaminates dispersed in underground
ponds and at much low er cost than methods which require pumping the water out
of the ground for treatment.
11. Chemical Sensors : Nanotechnology can enable sensors to detect very small
amounts of chemical vapors. Various ty pes of detecting elements, such as carbon
nanotubes, zinc oxide nanowires or palladium nanoparticles can be used in
nanotechnology -based sensors. Because of the small size of nanotubes, nanowires,
or nanoparticles, a few gas molecules are sufficient to cha nge the electrical
properties of the sensing elements. This allows the detection of a very low
concentration of chemical vapors.
12. Sporting Goods : If you're a tennis or golf fan, you'll be gl ad to hear that even
sporting goods has wandered into the nano realm. Current nanotechnology
applications in the sports arena include increasing the strength of tennis racquets,
filling any imperfections in club shaft materials and reducing the rate at whi ch air
leaks from tennis balls.
13. Fabric : Making composite fabric with nano -sized particles or fibers allows
improvement of fabric properties without a significant increase in weight,
thickness, or stiffness as might have been the case with previously –
used techniques.
Currently, nanotechnology is described as revolutionary discipline in terms of its
possible impact on industrial applications. Nanotechnology offers potential solutions to
many problems using emerging nanotechniques. Depending on the strong
interdisciplinary character of nanotechnology there are many research fields and several
potential applications that involve nanotechnology.

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Chapter IX
Overview on recent and current developments in nanotechnology.:
Since research on nanotechnology is developing, One cant provide an exhaustive report
of the developments in nanoscience and nanotechnologies in all scientific and
engineering fields.
While considering three main categories (broad nanotech nology categories).
• Nanomaterials;
• Nanoelect ronic (information and communication technology);
• Nanomedicine and bio nanotechnology.
We can define nanomaterials as those which have nanostructured components with at
(less than 100nm).
Materials with one dimension in the nanoscale are layers, such as a thin films or surface
coatings.
Materials that are nanoscale in two dimensions are nanowires and nanotubes. Materials
that are nanoscale in three dim ensions are particles quantum dots (tiny particles of
semiconductor materials). Nanocrystalline materials, made up of nanometre -sized grains,
also fall into this category.
Two principal factors cause the properties of nanomaterials to differ significantly from
other materials: increased relative surface area, and quantum effects. These factors can
change or enhance properties such as reactivity, strength and electrical properties, optical
characteristics.

Nanomaterial in one dimension : In this category bel ong nanomaterials such as thin films
and engineered surfaces. This type of nanomaterial can't be really considered as a new

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material considering that have been developed and used for decades in fields such as
electronic device manufacture, chemistry and en gineering.
Nanomaterials in two dimensions: Two dimensional nanomaterials such as tubes and
wires. Carbon -nanotubes, Inorganic nanotubes, example. Halloysite nanotubes are
hollow tubes with high aspect ratios that are tens to hundreds of nanometers (billio nths
of a meter) in diameter, with lengths typically ranging from about 500 nanometers to
over 1.2 microns (millionths of a meter).
Nanowires: Nanowires are ultrafine wires or linear arrays of dots, formed by self –
assembly. They can be made from a wide ra nge of materials. Semiconductor nanowires
made of silicon, gallium nitride and indium phosphide have demonstrated remarkable
optical, electronic and magnetic characteristics.
Nanoscale in three dimensions: Nanoparticles are often defined as particles of le ss than
100nm in diameter. Fullerenes (carbon 60): Spherical molecule formed of exagonal
carbon structure recently discovered 1986. Dendrimers are spherical polymeric
molecules, formed through a nanoscale hierarchical self -assembly process.
List of applic ations considering current and future application of
nanomaterials:
1. Cosmetics application of nanoparticle (e.g sunscreen lotions: ray absorb
properties)
2. Nanocomposite materials: nanoparticle silicate nanolayer (clay nanocomposites)
and nanotubes can be use d as reinforzed filler not only to increase mechanical
properties of nanocomposites but also to impart new properties (optical, electronic
etc.)

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3. Nanocoatings: surface coating with nanometre thickness of nanomaterial can be
used to improve properties like w ear and scratch -resistant, optoelectonics,
hydrophobic properties.
4. Hard cutting tools: current cutting tools (e.g mill machine tools) are made using a
sort of metal nanocomposites such as tungsten carbide, tantalum carbide and
titanium carbide that have mo re wear and erosion -resistant, and last longer than
their conventional (large -grained) materials.
5. More performed paint using nanoparticles to improve paint properties.
6. Fuel cells: could use nano -engineered membranes to catalytic processes for
improve effic iency of small -scale fuel cells.
7. Displays: new class of display using carbon nanotubes as emission device for the
next generation of monitor and television (FED field -emission displays).
8. Using nanotechnology based knowledge may be produce more efficient,
lightweight, high -energy density batteries.
9. Nanoparticles can be used as fuel additivities and catalytic more efficient
materials.
10. Nanospheres in lubricants technology like a sort of nano balls bearing Nanoscale
magnetic materials in data storage device.
11. Nanostructured membranes for water purification.
12. Nanoelectronic (information and comunication technology): In some sense,
electronic miniaturization has been the true driving force for nanotechnology
research and applications.
The main aim in this area is un derstand nanoscale rules and mechanism in order to
implement new ICT systems more economic, little and reliable.
It's a sure thing that silicon era is on the way up. Only nanotechnology can
radically change ICT systems in order to continue to follow Moore' s law.

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Nanotechnologies are therefore expected to enable the production of smaller,
cheaper devices with increasing efficiency.
13. Bio-nanotechnology and nanomedicine: Bio -nanotechnology is concerned with
biological nanostructures and is a strong interdiscipl inary matter (chemical,
biological and the physical sciences.) Biological systems are the most perfect
nanosystems one can image.
Biomolecular structures possess highly specific morphology and functions and
somehow nanotechnologist must study their in dept h in order to understand
general nanotechnology aspects. Bio nanotechnology is a new research that may
product great break through in applications in the field of medicine such as
disease diagnosis, drug delivery and molecular imaging that has been already
intensively researched.
Future applications:
1. Electronics information and communication technology: In this area, "smart"
molecules may be integrated into devices for specific ICT (information and
communication technology) applications, in order to obtai n a protein based
transistor. For this and other type of nanotech application will be important to
understand the fundamental electronic properties of bio molecules in particular the
mechanisms by which electronic charge is transferred between them and me tals
semiconductors and novel nanoelectronic properties of Carbon Nano Tubes.
2. Drug -delivery systems: One of the most potential applications of nanotechnology
might be related to gene and drug delivery system on order to improve therapy
efficacy. The chal lenge is devise nanoparticle capable of targeting specific
diseased cells, which contains both therapeutic agents that are released into the
cell and an on -board sensor that regulates the release. As related approach already

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in use is that of polymer based drug delivery systems but the functionalities
previous outlined are obviously more powerful.
3. Medical Imaging for diagnosis: Nanotechnologies already use quantum dots or
synthetic chromophores to selected molecules (e.g proteins) for intracellular
imaging. Also incorporation of naturally fluorescent proteins has been
experimented which, with optical techniques allow intracellular biochemical
processes to be investigated directly.
4. Nanomaterial Applications using Carbon Nanotubes: Applications being
developed for carbon nanotubes include adding antibodies to nanotubes to form
bacteria sensors, making a composite with nanotubes that bend when electric
voltage is applied bend the wings of morphing aircraft, adding boron or gold to
nanotubes to trap oil spills, i nclude smaller transistors, coating nanotubes with
silicon to make anodes the can increase the capacity of Li -ion batteries by up to
10 times.
5. Nanomaterial Applications using Graphene: Applications being developed for
graphene include using graphene sheet s as electodes in ultracapacitors which will
have as much storage capacity as batteries but will be able to recharge in minutes,
attaching strands of DNA to graphene to form sensors for rapid disease
diagnostics, replacing indium in flat screen TVs and mak ing high strenght
composite materials.
6. Nanomaterial Applications using Nanocomposites: Applications being developed
for nanocomposites include a nanotube -polymer nanocomposite to form a scaffold
which speeds up replacement of broken bones, making a graphen e-epoxy
nanocomposite with very high strength -to-weight ratios, a nanocomposite made
from cellulous and nanotubes used to make a flexible battery.

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7. Nanomaterial Applications using Nanofibers: Applications being developed for
nanofibers include stimulating t he production of cartilage in damaged joints,
piezoelectric nanofibers that can be woven into clothing to produce electricty for
cell phones or other devices, carbon nanofibers that can improve the performan ce
flame retardant in furniture.

Reference:
• http://www.understandingnano.com/nanomaterials.html
• http://www.understandingnano.com/nanoparticles.html
• http://www.azom.com/article.aspx?ArticleID=1066
Impact of Nanotechnology:
1. The health impact of nanotechnology are the possible effects that the use of
nanotechnological materials and devices will have on human health. As
nanotechnology is an emerging field, there is great debate regarding to what
extent nanotechnology will benefit or pose risks for human health.
Nanotechnologys health impact can be split into two aspects: the potential for
nanotechnological innovations to have medical applications to cure disease, and
the potential health hazards posed by exposure to nanomaterials.
2. The extremely small size of nanomaterials also means that they are much more
readily taken up by the human body than larger sized particles . How these
nanoparticles behave inside the body is one of the issues that needs to be resolved.
The behavior of nanoparticles is a function of their size, shape and surface
reactivity with the surrounding tissue. They could cause overload on phagocytes,
cells that ingest and destroy foreign matter, thereby triggering stress reactions that

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lead to inflammation and weaken the body’s defense against other pathogens.
Apart from what happens if non -degradable or slowly degradable nanoparticles
accumulate in org ans, another concern is their potential interaction with biological
processes inside the body: because of their large surface, nanoparticles on
exposure to tissue and fluids will immediately adsorb onto their surface some of
the macromolecules they encount er. This may, for instance, affect the regulatory
mechanisms of enzymes and other proteins.
3. Other properties of nanomaterials that influence toxicity include: chemical
composition, shape, surface structure, surface charge, aggregation and solubility,
and the presence or absence of functional groups of other chemicals. The large
number of variables influencing toxicity means that it is difficult to generalise
about health risks associated with exposure to nanomaterials – each new
nanomaterial must be asses sed individually and all material properties must be
taken into account.
4. In October 2008, the Department of Toxic Substances Control (DTSC), within
the California Environmental Protection Agency, announced its intent to request
information regarding analy tical test methods, fate and transport in the
environment, and other relevant information from manufacturers of carbon
nanotubes.[DTSC is exercising its authority under the California Health and
Safety Code, Chapter 699,sections 57018 -57020.These sections were added as a
result of the adoption of Assembly Bill AB 289 (2006). They are intended to make
information on the fate and transport, detection and analysis, and other
information on chemicals more available. The law places the responsibility to
provide this information to the Department on those who manufacture or import
the chemicals.

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5. On January 22, 2009, a formal information request letter was sent
to manufacturers who produce or import carbon nanotubes in California, or who
may export car. This lette r constitutes the first formal implementation of the
authorities placed into statute by AB 289 and is directed to manufacturers of
carbon nanotubes, both industry and academia within the State, and to
manufacturers outside California who export carbon nano tubes to California. This
request for information must be met by the manufacturers within one year. DTSC
is waiting for the upcoming January 22, 2010deadline for responses to the data
call-in. The California Nano Industry Network and DTSC hosted a full -day
symposium on November 16, 2009 in Sacramento, CA. This symposium provided
an opportunity to hear from nanotechnology industry experts and discuss future
regulatory considerations in California. DTSC is expanding the Specific Chemical
Information Call -in to members of the nanometal oxides.
6. Nanomedicine is the medical application of nanotechnology. The approaches to
nanomedicine range from the medical use of nanomaterials,
to nanoelectronic biosensors, and even possible future applications of molecular
nano technology. Current problems for nanomedicine involve understanding the
issues related to toxicity and environmental impact of nanoscale materials.
Nanomedicine research is directly funded, with the US National Institutes of
Health in 2005 funding a five -year plan to set up four nanomedicine centers. In
April 2006, the journal Nature Materials estimated that 130 nanotech -based drugs
and delivery systems were being developed worldwide.
7. Nanomedicine research is directly funded, with the US National Institute s of
Health in2005 funding a five -year plan to set up four nanomedicine centers. In
April 2006, the journal Nature Materials estimated that 130 nanotech -based drugs
and delivery systems were being developed worldwide. Nanomedicine seeks to

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deliver a set of research tools and clinical devices in the near future. The National
Nanotechnology Initiative expects new commercial applications in the
pharmaceutical industry that may include advanced drug delivery systems, new
therapies, and in vivo imaging. Neuro -electronic interfaces and other nano
electronics -based sensors are another active goal of research. Further down the
line, the speculative field of molecular nanotechnology believes that cell repair
machines could revolutionize medicine and the medical fie ld. Nanomedicine is a
large industry, with nanomedicine sales reaching $6.8 billion in 2004.With over
200 companies and 38 products worldwide, a minimum of $3.8 billion in
nanotechnology R&D is being invested every year. As the nanomedicine industry
contin ues to grow, it is expected to have a significant impact on the economy.
8. Currently, nanotech gene therapy has been able to kill ovarian cancer in mice
while avoiding the side effects of cisplatin and paclitaxel; it is speculated that this
technology could save 15000 women in the United States each year if the
treatment proves effective and safe in humans. Research on nanoelectronics -based
cancer diagnostics could lead to tests that can be done in pharmacies. The results
promise to be highly accurate and th e product promises to be inexpensive. They
could take a very small amount of blood and detect cancer anywhere in the body
in about five minutes, with a sensitivity that is a thousand times better than in a
conventional laboratory test. These devices that are built with nanowires to detect
cancer proteins; each nanowire detector is primed to be sensitive to a different
cancer marker. The biggest advantage of the nanowire detectors is that they could
test for anywhere from ten to one hundred similar medical c onditions without
adding cost to the testing device.[13]Nanotechnology has also helped to
personalize oncology for the detection, diagnosis, and treatment of cancer. It is
now able to be tailored to each individual’s tumor for better performance. They

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have found ways that they will be able to target a specific part of the body that is
being affected by cancer.
9. Along with the possibility of curing cancer, doctors have found ways to make
surgery come a long way with nanotechnology. Arthroscopic surgery would be the
best example. Nanotechnology is helping to advance the use of arthroscopes,
which are pencil -sized devices that are used in surgeries with lights and cameras
so surgeons can do the surgeries with smaller incisions. The smaller the incisions
the faster the healing time which is better for the patients. Arthroscopic surgery is
hoping to make the scope smaller then a strand of hair in the future. Also using
nanotechnology doctors are looking to find a way to reuse the material of an old
part of the bod y to rebuild new tissue. The use of old parts of the body to rebuild
new tissue would help to make sure you are using your own tissue in the your
body and will also help so your body will not reject the tissue.
Reference:
http://www.slideshare.net/v15_vipin/health -impect -of-nanotechnology