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| Last Updated:: 27/12/2016

Nanoparticle

Nanoparticles

  

particle is defined as a small object that behaves as a whole unit with respect to its transport and properties. Coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized between 2,500 and 100 nanometers. Ultrafine particles or nanoparticles are sized between 1 and 100 nanometers. Nanoparticles are a discovery of modern science and they   have a very long history. Nanoparticles were used by artisans as far back as the 9th century in Mesopotamia for generating a glittering effect on the surface of pots. This lustre or glitter over pottery from the Middle Ages and Renaissance is due to a metallic film that was applied to the transparent surface of a glazing. The lustre can still be visible if the film has resisted atmospheric oxidation and other weathering. There are several methods for   production of nanoparticles. 

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  • In   attrition  method,   a  macro  or   micro  scale   particles   are   ground  in  a   ball  mill,  a planetary   ball  mill,  or  other  size  reducing  mechanism.  The   resulting   particles  are   air classified to recover nanoparticles.

 

  • In pyrolysis method, a vaporous precursor (liquid or gas) is forced through an orifice at  high pressure and burned. The resulting solid (a version of soot) is air  classified  to  recover  oxide particles from by-product gases. Pyrolysis often results in  aggregates and agglomerates rather  than single primary particles.
  • Inert-gas  condensation  is  frequently  used  to  make  nanoparticles from  metals  with   low melting points. In this process the metal is vaporized  in  a  vacuum  chamber  and  then  super cooled    with   an   inert   gas   stream.  The   super    cooled    metal   vapor  condenses  in  to nanometer-sized particles, which can be entrained in the inert gas stream and  deposited  on  a substrate or studied in situ.
  • Nanoparticles can also be  formed  using  radiation chemistry.  Radiolysis  from gamma        rays  can create  strongly  active free radicals  in  solution. This  relatively  simple  technique uses a minimum  number  of  chemicals.  These  including water,  a  soluble  metallic  salt,  a  radical scavenger  (often a secondary alcohol), and a surfactant (organic capping agent). Formation of nanoparticles  using  the  radiolysis  method  allows for tailoring of  particle size and shape by adjusting precursor concentrations and gamma dose.

 

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