Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Nano-Materials
Nano: The word “nano” has a Greek origin meaning small
...
1nm=10-9meter
...

Nanotechnology: Are the design, characterization, production and application of structure,
devices and systems
...
A unique aspect of nanotechnology is the vastly increased surface area to available
volume ratio
...

1
...

2
...
The process of cutting materials is called the milling of
material
...
They are hard in structure: The substance so obtained in nano materials form must
be harder than diamond
...
Low processing temperatures by high operating temperatures
...
Superconductivity at comparatively high temperature from 1580K
...
Substitute for silicon chip
...
High density magnetic storage
...
They are chemically very active
...
They are wear resistant
...
They are elastic at high temperature
...

2
...

4
...


Next generation drug delivery system
...

Development of superconductivity materials at room temperature
...

Production of nano fibers, nano solar cells, automobile parts, heat resistant cloths,
LED’s and ultra capacitor etc
...
Development of quantum dots and quantum well: The shape of a materials after
reducing its size to nano in one dimension is termed as quantum dot and in two
dimensions is known as quantum well
...
Development of molecular structure and quantum dot lasers
...
Protein chips Proteins play the central role in establishing the biological phenotype
of organisms in healthy and diseased states and are more indicative of functionality
...

1
...
Inorganic nano materials
Fullerene:
Fullerenes are a family of carbon allotropes
...

Ø No other element has such superb properties as carbon
...

Ø The most famous fullerene is C60, known also by “buckyball "
...

Ø The suffix “ene” indicates that each C atom is covalently bounded to three others
...

Fullerenes are the only known allotrope of carbon that can be dissolved in common
solvents at room temperature
...

In fullerenes, 12 pentagonal rings are necessary and sufficient to affect the cage
closure
...
The chemical formula is C20+2n
...


Applications of fullerenes:
Ø

Portable power: Proton exchange membranes for fuel cells
...
Many drug molecules can be attached to a fullerene
...
Antibodies are Y-shaped
proteins that can recognize and attach to things in the body called antigens
...
The antibody finds the
disease in the body then the attached fullerene delivers the appropriate medicine
...

Flat panel display screens: When a nanotube is put into an electric field, it will
emit electrons from the end of the nanotube like small cannon
...
Several
companies (Samsung, in particular) are researching how to use this technology to
replace the bulky electron guns of conventional TV sets with these significantly
smaller carbon nanotube electron guns
...
e
...
g
...
Researchers have been able to use nanotubes as sensors by exposing
them to gas and measuring the change in conductance
...


Types of fullerene
A fullerene is any molecule composed entirely of carbon
...

It is in DNA, proteins, fats, and carbohydrates
...
Two general types fullerene are:
·
·

Buckyball :
Carbon Nano Tubes (CNTs):

[GBTU 2008-2009]
[GBTU 2009-2010, 2011-2012]

Buckyballs:
Two known form of carbon are graphite
and diamond
...
Buckyballs are very strong
case-like structure based on its interlocked
shape
...

The buckyballs has carbon atoms at 60 chemically equivalent vertices that are connected
by 32 faces, 12 of which are pentagonal and 20 hexagonal
...
Hexagons should be surrounded by three hexagons and three
Shyam Kishore Dwivedi, PhD (Physics)

pentagons placed next to each other alternately
...

The 6:6 ring bonds (between two hexagons) can be considered "double bonds" and are
shorter than the 6:5 bonds (between a hexagon and a pentagon)
...
4 angstroms
...
When an electric
arc is generated between two carbon
electrodes placed very near to each
other in a reaction chamber filled with
low pressure of He and Ne, buckyballs
are generated along with carbon soot
...

Properties of Buckyballs:
1
...

2
...
Television screens:
a
...
High thermal conductivity may lead to better heat sinks for electronics
...
Solar Cells:Buckyballs can act as transparent film in solar cells to allow light to pass
through active layers and generate current
...
Televisions and Monitors
3
...

4
...
This property suggests that buckyball can be a
better storage medium for hydrogen fuel than metal hydrides
...
Anti-ageing creams are also being developed using buckyballs
...
Buckyballs are being used to develop stronger polymers
...
Lubricant: Buckyballs have very high strength bonds between the carbons, the same
strength as in a diamond
...
And because of those bonds they are very
temperature resistant (like graphite) and will not break down under high heat and
pressure like petroleum based lubricants can
...
The properties of each
material change as the arrangement of atoms changes
...
We can say tha CNT is a
one dimensinal wire or a seamless
cylinder with diameter of the order of a
nanometre made by rolling a sheet of
graphene which is another allotrope of
carbon with two dimenstional structure
...

Structure of Carbon nanotubes:
The bonding in carbon nanotube is sp2, with each atom joined to three neighbors similar to
those in graphite structure
...
The structure of a nanotube can be specified as chiral vector (n, m) which defines
how the graphite sheet is rolled up, where n and m are integers of the vector equation:

Shyam Kishore Dwivedi, PhD (Physics)

Chiral vector is defined as
R= n i+ m j;
Using the vectors i and j for the hexagonal
lattice
...

openings
...

d = (a/π) (n2 +m2+nm) 1/2 nm
or
d= (0
...
a = 0
...

Types of Carbon Nanotubes
Carbon nanotubes are single sheets of graphite (called graphene) rolled into cylinders
...
This huge aspect ratio leads to unusual electrical transport
...

Carbon nanotubes are placed in two broad categories:
1
...

2
...

Synthesis of Carbon Nanotubes:
There are three common methods for developing the carbon nanotubes
...
Arc discharge method
...
Laser ablation (vaporization)
...
Chemical Vapour Deposition (CVD)
...
No Arc discharge method

Laser ablation
(vaporization)

Chemical vapor deposition

1
...
At 100 amps,
carbon vaporizes in hot
plasma
...


Place substrate in oven, heat
to 6000 C, and slowly add a
carbon-bearing gas such as
methane
...


2
...


NTs are usually MWNTs and
often riddled with defects

4

Structure of Carbon nano tubes:
The structure of a carbon nanotube is like a sheet of graphite rolled up into a tube
...
Different types of nanotubes have different properties
...
A major challenge in
nanoscience today is finding a way to make just one type of nanotube
...
Axis of rotation in parallel to the C-C bond
...
Axis of rotation is perpendicular to the C-C bond
...
Axis of rotation is any random direction with respect to C-C bond
...
Find the
diameter of carbon nanotubes
...
0783(n2 +m2+nm) 1/2 (Unit= nm)
Given n =2 and m =1
d = 0
...
21nm
Shyam Kishore Dwivedi, PhD (Physics)

Properties of Carbon Nanotubes
Carbon nanotubes feature a number of extraordinary properties, amongst which are
1
...

3
...

5
...


High thermal conductivity
...

Thermal conductivity of SWNT more than copper at room temperature
...

CNT’s are highly flexible- can be bent considerably without damage
...


Potential Risks of Nanomaterials
1
...

2
...

3
...

4
...

Answer yourself:
1
...

3
...

5
...

What are buckyballs? How it can be created?
What are carbon nanotubes? What are their different types?
What are potential risks of using nanomaterials to human body?

References:
[1] Iijima, S
...
Nature, 1991
...
56-58
...
and T
...
Nature,
1993
...
603-605
...
S
...
, Cobalt-catalyzed growth of carbon nanotubes with single-atomiclayer walls
...
363: p
...

[4] Mintmire, J
...
, B
...
Dunlap, and C
...
White, Are fullerene tubules metallic? Physica
Review Letters, 1992
...
631-634
...
Technol Cancer Res
Treat 2005, 4:363-374

---