1. Nano Materials and NanoTechnology

2. Concepts of Nanoscience & Nanotechnology
- direct control of materials and devices
on molecular and atomic scale
includes fabrication of nano structures,
synthesis and process of nano particles, etc.

3. Nano Levels are occurring in a verity of fields and requires knowledge
Physics – behavior of matter below a certain scale and interaction of atoms
Chemistry –interaction of different materials with each other at designing part
Biology – how biological system works at lowest level
Computer Science – exchange the information and collection of large amount of data
Electrical Engineering – generate and manage power more efficiently
Mechanical Engineering – issues to be seen like load bearing, material fatigue and lubrication for preparing new technology

4. Nano Materials Made up of grains Diameter of grains are about 100 nm
Contains less than few ten thousand atoms
One nano meter = one billionth of a meter

5. Quantum Well, Wire & Dot
Quantum Well -If one dimension of a bulk materials is reduced to nano scale & other dimensions remain same, then the structure is called quantum well
Quantum Wire - If two dimensions of a bulk materials are reduced to nano scale & other dimension remains same, then the structure is called quantum wire
Quantum Dot - If all dimensions of a bulk materials are reduced to nano scale, then the structure is called quantum dot

6. Synthesis of Quantum Dots
Two approaches
Bottom –Up approach
collect and consolidate individual atoms and molecules into structure
carried out by sequence of chemical reactions controlled by catalysts.
2. Top – Down approach
reduction of dimensions of large scale object to nanoscale
carried out by lithography method, i.e., by passing radiation on a surface to remove the surface layer

7. Unique Properties of Nanomaterials
Very high magneto resistance
Low melting point
High solid state phase transition pressure
High self diffusion coefficient
High catalytic activity
Lower ferro eclectric transition temperature

8. Variation of Physical Properties with Size
Electron affinities and chemical properties
- electronic bonds become narrower
- delocalized electron states become localized
- ionization potential and reactivity are higher at smaller size
- strong catalyst effect
Magnetic Properties
- exhibit totally new class of magnetic properties
- ferro and anti ferro magnets exhibit giant magneto resistance
- low coordination number
Mechanical behavior
- low melting point
- high strength because its free from dislocation
- super hardness

9. Technological Advantages
Improved Transportation
Inexpensive shatter proof diamond is used to make air planes.
Unloaded weight is fifty times lighter than aluminum but strong.
capacity can be increased
Atom Computers
Designing gates with less than 1000 atoms, which have to be in right place
can be build mass storage device and store hundred billion bytes in a size of sugar cube
can deliver a billion of instructions per second
Military Applications
Smart weapons can be made the size of a bullet
rapid , inexpensive, stronger can be made and can be guided by the computer which is more power than super computer
Navigation, tracking can be done by this computer
Solar Energy
inexpensive and efficient can be made
Medical Uses
heeling the injuries at the molecular and cellular level that are causes of disease
Other advantages
Less Pollution, Low Production Costs & Mass production of Food and Consumables

10. Carbon Nanotubes
- thin and long straw shaped, that is tubular forms Carbon
- graphene sheets rolled into cylindrical form
- diameter is few nanometers & length is several micrometers
- made up of hexagonal covalent bonded carbon atoms
Two types
Single Walled Carbon Nanotubes (SWNT)
consists of single graphene cylinder
Multi Walled Carbon Nanotubes (MWNT)
consists of several graphene cylinders

11. In SWNT, depends on the way of rolling of graphene sheet
There are different types
Armchair (n,n)
Zigzag (n,0) and Chiral (n,m)
From selected origin, both axes rolling

12. Properties of Carbon Nanotubes
Chemical Reactivity
- related to an increased curvature
- distinction should be made between side walls and end caps
- smaller diameter increases reactivity
- solubility can be controlled
Electrical Conductivity
- depends on chiral vector, it will be either semiconductor or metal
- conducting properties derived from graphene sheet properties
- if n=m, metal
- resistance independent of length
Optical Activity
- disappears when NT length becomes longer
Mechanical Strength
- very large Young Modulus in axial direction
- very flexible because of its great length
- suitable for composite material

13. Unique Properties High electrical conductivity
Very high tensile strength
High flexible, very elastic
High thermal conductivity but low thermal expansion coefficient
Highly absorbent

14. Synthesis of Carbon Nanotubes
Three commonly used methods
Laser ablation
Intense laser pulses fall on the graphite and it gets blasted. Plasma plume is generated from which SWNTs form
Arc discharge method
When power supply is applied to two graphite rods which are placed few millimeters apart, carbon vaporizes and nanotubes forms
Chemical vapor deposition
Place gaseous carbon in energy source such as plasma or heated coil. The energy source is used to crack the molecule into a reactive radical species and diffuse down to substrate, which is heated then carbon nanotubes form

15. Applications of CNTs Energy Storage a) Hydrogen Storage
hydrogen liquid or gas can be stored in the inner core through capillary effect and hydrogen atom is absorbed, is called chemisorption
b) Lithium intercalation
all interstitial sites such as inter shells, inter tube channels and inner cores are accessible for Li intercalation. It is reversible and irreversible. In nanotubes is still unsuitable for batteries but in future it suits by altering the nanotubes
c) Electrochemical Super capacitors
capacity of energy depends the separation between the electrode and charge in electrolyte. If nanotubes are used as electrolyte and electrodes. Very large energy can be stored by small applied voltage

16. Molecular electronics with CNT
Field Emitting Devices
extract an electron from the solid surface potential barrier by high applied electric field.
an ideal emitter requires nano meter diameter, low threshold emission field, high electrical conductivity,chemical stability. CNT possess all the properties. Used in electron microscopes, telecom network
Transistors
by applying voltage to a gate electrode ie. CNT, it can be switch from conducting state to insulating state, that is, it works as a switch
Nanoprobes and Sensors
as a scanning probe, in STM and AFM. It does get suffered from crashes because of high elasticity. Used as molecular probes because modified by chemically
Composites
used as reinforcements because of its stiffness, high strength, low weight, high flexible.used in polymer composites, it will increase toughness by absorbing energy during the elastic behavior
used as membrane for molecular separation
Templates
holding gas and fluids

17. Material Processing Sol – Gel Method
Modification of silicon compounds, which can’t withstand high temperature
It is a chemical solution process to make ceramics and glass materials in the form thin
films, fibers and powders
Sol is a colloidal, which are suspended molecules of solid particles in a solvent
Gel is a semi rigid mass that forms when the solvent begins to evaporate and the
particles or ions (sol) left behind begin to join together in a continuous network
Metal alkoxides and metal chlorides, which undergo hydrolysis and poly condensation
reactions to form a colloid and dispersed in a solvent. Then sol evolves and forms of an
inorganic network containing liquid phase(gel)
Connecting the metal centers with oxo (M-O-M) or hydroxo (M-OH-M), therefore metal
oxo of metal hydroxo polymers in solution.
Drying process serves to remove the liquid phase and forms porous material, then
thermal treatment is used to make poly condensation to enhance mechanical properties
It can be deposited on a substrate, cast into a suitable container with desired shape and
synthesized as powder

18. Sol gel method consists the following steps
Colloidal particles are dispersed in a liquid to form sol
Particles in sol are polymerized through the removal of stabilizing components and produce a gel in a state of continuous network
Heat treatments form an amorphous or crystalline coating
Deposition of sol solution on the substrates by spraying, dipping or spinning

19. Advantage
thin coating provides adhesion between the metallic substrate and the top and thick coating provides corrosion protection
can shape the materials in gel state and produce the high purity products
low temperature sintering, simple, economic and effective method to produce high quality coatings
Application
used in ceramics production and diverse applications in optics, electronics, energy, sensors, medicine and separation technology
used for silicated gel formation

20. Chemical Vapour Deposition
Depositing a solid material from gaseous phase and also produces synthetic diamond
Materials forms are in mono crystalline, polycrystalline and amorphous , materials are
silicon, carbon fiber, carbon nanofibers, carbon nanotubes
Working Concept
From the chemical reaction of gaseous precursors at a heated substrate to yield a fully dense
deposit. Thermodynamics and kinetics generate and decomposes of gas precursor Control of
thermodynamics and kinetics through temperature, pressure and concentrations yields the desired deposit.
Metal deposition – Metal halide (g) → Metal (s) + byproduct (g)
Ceramic deposition - Metal halide (g) + Oxygen/Carbon/Nitrogen/Boron (g) z→ Ceramics (s) + byproduct g)
Process
Following steps are involved, Mix of reactant gases and diluent inert gases are introduced into the reaction
chamber at a specified flow rate, Gas species move to the substrate, Reactants get absorbed on the
surface of the substrate, Reactants undergo chemical reactions with the substrate to form the film, Gaseous
byproducts of the reactions are absorbed and evacuated from the reaction chamber

21. System consists of
Sources and feed lines for gases
Mass flow controllers for gases
Reaction chamber
System for heating
During the process, the reactant gas react with Substrate, is known as heterogeneous
reaction and occurs on the heated surface.
Also the reactant gas react with gas phase in reactor’s atmosphere, is known as
homogeneous reaction and produce poor and low density film with lots of defects
Types of Chemical vapour deposition
Process differs in means of chemical reactions and process condition
Two types of reactor wall can be used, one is hot wall, in which the both substrate and the
reactor wall are heated and another is cold wall, in which only the substrate is heated
Based on their operating pressure it is classified. Atmospheric pressure CVD (APCVD),
in which the reactors operate at atmospheric pressure and it is simplest in design.
Low pressure CVD (LPCVD), in which reactors operate at medium pressure and higher
temperature.
Plasma enhanced CVD (PECVD) in which the reactors operate also under low Pressure and it
does not depend on thermal energy

22. Advantages & Applications
Used for wide range of metals & ceramics,
fabricating complex shapes, high purity deposits, homogeneously joining substrate surface, thickness can be controlled, can be coated powders, multiple components, internal passages
Applications
used to promote or prevent adhesion, photo resist adhesion in semiconductor, reduce stiction, drift
Promote biocompatibility between natural and synthetic materials, anti corrosive coating

23. Physical Vapour Deposition
It is an alternative process of electroplating, which involves transfer of material on an atomic level. It is similar to CVD except the precursors, that is solid is deposited in PVD
Working Concept
carried out under vacuum condition, the process involves
Evaporation – Material (target) to be deposited is bombarded by a high energy such as beam of electrons or ions, to vaporize the atoms
Transport – Movement of vaporized atoms from the material (target) to the substrate
Reaction – In case of target material with metal, the atoms of metal will react with appropriate gas during the transport stage and for target material alone then this process would not be part of the process
Deposition – process of coating on the substrate. Reaction between target materials and reactive gases may take place at the substrate with the deposition process
Target material is placed in a vacuum champer, due to intense heat the target material is evaporated then the coating is formed

24. Various method of PVD
Evaporative deposition –Material is heated by electrically resistive heating at high pressure and vacuum
Electron beam PVD – heated by electron bombardment at high pressure and vacuum
Sputter deposition – heated by plasma discharge and material sputtering as a vapour
Cathode arc deposition – blasted by high power arc into vapour
Pulsed Laser deposition – high power laser is used to produce vapour

25. Importance
To improve hardness, reduce friction and oxidation resistance
Advantages
Improve the properties of the substrate, inorganic material can be used as organic material and environmental friendly
Disadvantages
High capital cost, requires skilled operators, large amount of heat and the rate of coating is slow
Applications
In aerospace, automotive,surgical,dies and moulds, cutting tools and fire arms

26. Microwave synthesis of Materials
Microwaves are form of electromagnetic energy with the wavelength between
1mm and 1m. When the bulk material is placed in the microwave field, material
either absorbs, reflects or transparent, which depends on its chemical
composition,physical size, shape and frequency of the microwaves.
Two principle mechanisms for interaction with matter are 1. Dipole interaction
and 2. Ionic conduction. These mechanisms require coupling between material
and electric field
Dipole interaction occurs with polar molecules. Heat will be produced by
friction and moving molecules in the field of microwave.
Ionic conduction – Ions don’t have dipole moment , they are distributed and
can couple with oscillating electric field of microwaves, produce heat. Heat is a
function of concentration of ions in solution
Dissipation factor can be calculated, often called loss tangent. It is a ratio of
the dielectric loss to the dielectric constant

27. Material synthesis
Gaseous plasma which is produced by microwave radiation is used for material synthesis.
300 watt microwave produces plasmas of oxygen, fluorine and nitrogen, which are highly reactive and contain electrons, ions and radicals. They may be used to oxidize or reduce various function materials and oppose to thermal activating the sample itself.
Carbides, nitrides, silicates, etc are synthesized by using the microwaves
Advantages
Greater flexibility, speed,energy savings, product quality, cleaner and more
economical. Other heating methods cannot be produced new materials.

28. Electron Microscopy Techniques
It is scientific instruments that use a beam of highly energetic electrons
to examine objects on a very fine scale.
Electrons wavelength is about .005nm, which increase the resolving power.
It is used to examine the following information
Topography – Surface of an object, which are its texture, hardness, reflectivity,
etc.
Morphology – Shape and size of the particles making up object and ductility,
strength, reactivity, etc.
Composition – Elements and compounds that the object is composed and
melting point, reactivity, hardness, etc.
Crystallographic Information – Arrangement of atoms in the object and
conductivity, electrical properties, strength, etc.
Types
Transmission electron microscopy – Looks through a thin slice of a specimen
Scanning electron microscopy – Looks at the surface of a solid object

29. Transmission Electron Microscope (TEM)
It works like a slide projector. A projector shines a beam of light through the object, which is on the slide. Only certain light beam being transmitted through certain part of slide and projected onto viewing screen. In TEMs work the same way except they shine a beam of electrons and phosphor will be the screen
Working
Electron gun producing stream of electrons
Stream is focused to a small, thin, coherent beam by using lens
Beam is restricted by the condenser aperture to high angle electron
Beam strikes the specimen and parts of it transmitted
Transmitted portion is focused by the objective lens into an image
The image is passed through the projector lens and being enlarged
The image strikes the phosphor image screen and light is transmitted, allowing the user to see image

30. Specimen interactions and utilization
Unscattered Electrons
Source – Incident electron transmitted without any interaction occurring inside the specimen
Utilization – Unscattered electron is inversely proportional to the specimen thickness.
Elasticity Scattered electrons
Source – Incident electrons that are scattered by atoms in an elastic fashion
Utilization – Electrons wavelength =2 X atomic space X angle of scattering and enters normal to surface. Entered electrons scattered by atomic spacing and angle, which are formed a pattern by magnetic lenses.This pattern gives the information about orientation, atomic arrangements and phase present
Inelastically Scattered Electrons
Source – Incident electron interacts with specimen in a inelastic fashion and losses energy. Then the electrons are transmitted to rest of the specimen
Utilization – Electron Energy Loss Spectroscopy – Inelastic loss of energy is characteristic of the elements that were interacted with
Kakuchi Bands – Bands of alternating light and dark lines that are formed by inelastic scattering interactions that are related to atomic spacing in the specimen

31. Scanning Electron Microscope (SEM)