Numerical analysis for co-condensation processes in silicide nanoparticle synthesis using induction thermal plasmas at a
- PDF / 3,248,010 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 59 Downloads / 188 Views
Numerical analysis is conducted to clarify the formation mechanisms of silicide nanoparticles synthesized in an induction thermal plasma maintained at atmospheric pressure. The induction thermal plasma is analyzed by an electromagnetic fluid dynamics approach, in addition to a multi-component co-condensation model, proposed for the silicide nanoparticle synthesis. In the Cr–Si and Co–Si systems, silicon vapor is consumed by homogeneous nucleation and heterogeneous condensation processes; subsequently, metal vapor condenses heterogeneously onto liquid silicon particles. The Mo–Si system shows the opposite tendency. In the Ti–Si system, vapors of silicon and titanium condense simultaneously on the silicon nuclei. Each system produces nanoparticle diameters of around 10 nm, and the required disilicides, with the stoichiometric composition, are obtained. Only the Ti–Si system has a narrow range of silicon content. The numerical analysis results agree with the experimental findings. Finally, the correlation chart, predicting the saturation vapor pressure ratios and the resulting silicon contents, is presented for estimation of nanoparticle compositions produced in the co-condensation processes.
I. INTRODUCTION
Induction thermal plasmas (ITPs) have been widely utilized for some decades for material and environmental processes, such as nanoparticle synthesis, reactive plasma spraying, surface treatment, waste treatment, and decomposition of harmful substances.1–4 Indeed, induction thermal plasmas have several advantages for these purposes, such as high enthalpies, high chemical reactivities, variable properties, large plasma volumes, and long residence/reaction times due to the comparatively low plasma velocities. Furthermore, induction thermal plasmas are inherently unpolluted because they are generated without the use of internal electrodes.5,6 The synthesis of metallic and ceramic nanoparticles of high purity can be readily achieved through the use of high quenching rates present in the tails of induction thermal plasmas.7–9 Disilicide nanoparticles, in particular, can provide raw materials of high electrical conductivity and heat/oxidation resistance. Nanoparticles of disilicides are, therefore, expected to be interesting for application to electromagnetic shielding, solar control windows, and very large scale integration (VLSI) electrodes. a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0351 J. Mater. Res., Vol. 20, No. 10, Oct 2005
Induction thermal plasmas (ITPs) are considered to be very useful for the synthesis of silicide nanoparticles with a wide range of large vapor pressures. Furthermore, mass production of silicide nanoparticles is expected to be eventually achieved using induction thermal plasmas operated at atmospheric pressure. The actual synthesis process is, however, a complicated phenomenon involving many variables, including co-condensation processes at a range of vapor pressures. Unfortunately, only a few studies and researches have been conduct
Data Loading...
