Metallic Nanoparticles, Inert Gas Condensation

The preparation of metallic nanoparticles by pyrolysis was discussed in the last article, metallic nanoparticles part III (pyrolysis). We saw how different metallic, metallic oxide nanoparticles and nanocomposite can be prepared by the transformation of the precursor solution into aerosols and the evaporation of solvent by excessive heat to form solid particles. Here we take a look at gas condensation method for the preparation of the metallic nanoparticles.
Inert gas condensation is one of the first and easiest methods for the synthesis of metallic nanoparticles. There are two steps in gas condensation. First, a metallic or inorganic material is vaporized using evaporation sources. Second, a rapid controlled condensation is done to produce the required particle size. Evaporation of the source can be done by thermal evaporation, laser vaporization, sputtering, electrical arc discharge or plasma heating. The rapid condensation is achieved by collecting the particles on a cold surface. The whole process is done under an inert atmosphere of (He, Xe, or Ar) gas. Nucleation of the source and the growth of the nanoparticles are controlled by the type of the inert gas and the pressure of the chamber.

The production of metallic nuclei by the evaporation method can be done to solid sources or gaseous sources. Gas condensation method can be named as Chemical Vapor Deposition and Chemical Vapor Condensation according to the nucleation of the source. The inert gas condensation method is used for the preparation of different metallic nanoparticles such as, Mn, Fe, Co, Zn, and Mo nanoparticles. It can be also used to prepare metal alloy nanoparticles such as Fe-Ni and Fe-Cu. Carbon nanomaterials such as, Carbon Nanotubes and Graphene are synthesized by Chemical Vapor Deposition.
There are many advantages for the inert gas condensation methods for the preparation of metallic nanoparticles. A wide range of nanomaterials can be prepared by this method. Beside metallic and metallic oxide nanoparticles, alloys, intermetallic compounds, ceramics, semiconductors, and composites can be synthesized by this technique. Another advantage is the flexibility of the technique in terms of the range of particle sizes which can be controlled by different factors which include the temperature, pressure, and the inert gas used. Moreover, nanoparticle synthesis is usually a continuous process using this method. Stopping the agglomeration of the nanoparticles is the most challenging issue for the gas condensation method which can be prevented by achieving the optimum conditions for the synthesis of the nanoparticles.

Posted by Mohammed ZABARA on December 07, 2016

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