Studies on the use of nano zinc oxide and modified silica in NR, CR ...

Introduction
developed at Oxford University to produce nanoparticles of compound,,
semiconductors and some metals. In particular, CdS nano particles were
produced by generating aerosol micro-droplets containing Cd salt in the
atmosphere containing hydrogen sulphide.
Chemical vapour deposition (CVD)
CVD consists in activating a chemical reaction between the substrate
surface and a gaseous precursor. Activation can be achieved either with
temperature (thermal CVD) or with a plasma 19 (PECVD: Plasma Enhanced
Chemical Vapour Deposition). The main advantage is the nondirective aspect
of this technology. Plasma allows decreasing significantly the process
temperature compared to the thermal CVD process. CVD is widely used to
produce carbon nanotube.
Atomic or molecular condensation
This method is used mainly for metal containing nanoparticles. A bulk
material is heated in vacuum to produce a stream of vapourized and
atomized matter, which is directed to a chamber containing either inert
or reactive gas atmosphere. Rapid cooling of the metal atoms due to their
collision with the gas molecules results in the condensation and formation of
nanoparticles. If a reactive gas like oxygen is used, then metal oxide
nanoparticles are produced.
Super critical fluid synthesis
Methods using supercritical fluids are also powerful for the synthesis
of nanoparticles. For these methods, the properties of a super critical fluid
(fluid forced into supercritical state by regulating its temperature and its
pressure) are used to form nanoparticles by a rapid expansion of a
supercritical solution. Supercritical fluid method is currently developed at
the pilot scale in a continuous process.
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