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Investigation of Nucleation and Growth of Metallic Nanoparticlaes from the Gas Phase by Molecular Dynamic Simulation

Naghibi Nezhad, Mohsen | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39188 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Askari, Masoud; Simchi, Abdolreza
  7. Abstract:
  8. Formation of nanoparticles by the gas phase condensation process is one of the most promising methods for the nanoparticles synthesis. Finding the correlations between adjustable parameters of the process and nanoparticles properties depends on how parameters affect the mechanism of nucleation and growth. The use of classical nucleation theory at nanoscale leads to unacceptable results; hence, approaches such as molecular dynamic simulation (MD) have been proposed to investigate the mechanism of nucleation and growth at atomic scale. In the present work, the formation of iron clusters from a supersaturated gas phase was investigated via molecular dynamics simulation. For thermalization of the iron phase, a heat bath consisting of an argon gas was considered. The argon-argon and the argon–iron interactions were modeled by the Lennard-Jones potential. The interaction between iron atoms was modeled by the Embedded Atom method (EAM) potential. Results of simulation for 343 iron atoms showed that coalescence of the clusters is the dominant mechanism at the time of collision. Although the cooling rate of iron atoms in the simulation was too high (in the range of 1011 K/s), however, radial distribution function (RDF) predicted bcc structure for the clusters. The contraction of the lattice parameter was observed via RDF results which can be attributed to the high amounts of the surface tension. The results revealed that the particles formation was accelerated with increasing the number of argon atoms as well as iron atoms density. Moreover, decreasing of the heat bath temperature increased the nucleation and growth rate
  9. Keywords:
  10. Simulation ; Molecular Dynamics ; Nanoparticles ; Radial Distribution Functions ; Gasphase Condensation

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