Nano material or nano particles are used in a broad spectrum
of applications.
Specific synthesis process are employed to produce the
various nano particles
Defined 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.
 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)
The atoms or molecules array themselves into a structure due
to their natural properties
e.g: crystal grown
In bottom-up stratergy, structures are built up by chemical process.
The selection of the respective process depends on the chemical
composition and the desired features specified for the
nano particles
Method of preparation:
 Plasma arcing.
Physical vapour deposition(PVD).
Chemical vapour deposition(CVD).
Electro deposition.
Ball milling.
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.
Plasma torch
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 recondensed as hard cylindrical deposit on the
cathode rod.
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.
Average mass temperature of arc is higher than 104K ,
while its power density transferred onto the electrode
(anode) is approximately 2KW/mm2.
Using this method individaul carbon
nanotubes could be achieved in general several
hundred microns long.
Thus plasma arcing method is bottom-up
Plasma arc lamp
Plasma arc
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