Introduction to nanoparticles

23 January 2007

There is a special and borderless science that deals with the nanostructural materials. These nanostructural materials are derived from nanoparticles. The uses of these nanostructural materials are immense and there are sufficient evidences that these nanoparticles display distinct characteristics from the microcrystalline structures. There is no scientific field where the nanomaterials are not being investigated and explored to find the advantages of these materials in improving the desired characteristics.

Nanoparticle synthesis is one of the complex processes. There are three main categories of nanoparticle synthesis and these are vapor phase, solution precipitation and solid-state processes. Although all the three are used for synthesis of nanoparticles the more common and widely used process is solid state. The solid-state process is also the cheapest process among all the three processes used for production of micron-sized particles.

In solid state synthesis of nanoparticles generally heat treatment followed by milling is carried out to get an average particle size of 100nm or less. Mechanical milling is one of the most preferred and earliest technique to produce metallic microcrystalline powder. People claims to get a nanoparticle of very small size of up to 30nm particle size by using media milling of very small size of 200 micro meter. There are other commonly preferred milling methods used by different researchers includes dry milling and ball milling techniques.

In vapor-phase synthesis of nanoparticles, the formation of nanoparticles takes place in gas phase. In this synthesis technique the condensation of atoms and molecules is carried out. The vapor phase synthesis is not new and many multinational companies have been using flame reactors for decades for producing large quantities of nanoparticles. The flame reactors were used for forming various nanoparticles such as carbon black and titanium dioxide.

The last and most advanced technique is known as inert gas condensation. Although the technique is costly, it is considered as a controlled process as by this method the exact shape and size of the nanoparticle can be synthesized. In inert gas condensation technique, the nanoparticle as soon as they formed rapidly collide with inert gas in a low-pressure environment and thus smaller and controlled nanoparticles are formed.

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