Production of nanomaterials 1 Nano material or nano particles are used in a broad spectrum of applications Specific synthesis process are employed to produce the ID: 213476
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Slide1
PLASMA ARCING
Production of nanomaterials
1Slide2
Nano material or nano
particles are used in a broad spectrum of applications.Specific synthesis process are employed to produce the various nano particlesDefined production and reaction condition are crucial in obtaning such
size dependent
paricle
.
Particle size, chemical
compositoin
,
crystallinity
and shape
can be controlled by temperature ,ph-value, concentration,
chemical composition, surface modification and
process control.Slide3
Two basic strategies are used to produce nano
particles… Top-down and Bottom-up. Top-down:Producing very small structures from larger pieces of material.One way of acheving
this is mechanical crushing of solid into
fine
nano
powder (ball milling)
Bottom-up:
The atoms or molecules array themselves into a structure due
to their natural properties
e.g
:
crystal grown
(or)
In bottom-up
stratergy
, structures are built up by chemical process.Slide4
The selection of the respective process depends on the chemical composition and the desired features specified for the
nano particlesMethod of preparation: Plasma arcing.Physical vapour deposition(PVD).
Chemical
vapour
deposition(CVD).
Sol-gels.
Electro deposition.
Ball milling.Slide5
Plasma arcing method:
Plasma is an ionized gas.A plasma is achieved by making a gas conduct electricity by providing a potential difference
across two
electrodes.
Electrodes are made of
conducting
material.
Electrodes can be made of
mixture
of
conducting
and
non-conducting
materials.
A contracted plasma arc is generated by a
plasma torch
using
an
inert gas
which is used as
heat source.Slide6
Plasma torchSlide7
In arc discharge method, two high purity
graphite electrodes as anode and cathode are held at a distance under helium atmosphere.
Under these conditions, some of
the carbon
evaporated from the anode
re-condensed
as
hard cylindrical
deposit
on the
cathode rod.Slide8
An
arc passes from one electrode to the other.The electrons are emitted from the first electrode (anode) due to
potential difference.
Positively charged
ions pass to the other electrode
(cathode)
and gets
deposited
to form
nano
particle.
The depth of deposited surface must by only
few layers
Each particle must be
nanosized
and independent.Slide9
Conditions:Average mass temperature of arc is higher than 104K ,
while its power density transferred onto the electrode(anode) is approximately 2KW/mm2.Slide10
Using this method individaul
carbon nanotubes could be achieved in general several hundred microns long.
Thus plasma arcing method is
bottom-up
method
.Slide11
Plasma arc lampSlide12
Plasma arc