The formation of cubic and monoclinic Y 2 O 3 nanoparticles in a gas-phase flame process.

Autor: Guo, B., Harvey, A., Risbud, S. H., Kennedy, I. M.
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Zdroj: Philosophical Magazine Letters; Jul2006, Vol. 86 Issue 7, p457-467, 11p, 1 Black and White Photograph, 1 Diagram, 2 Charts, 2 Graphs
Abstrakt: Synthesis of phase-pure cubic and monoclinic Y 2 O 3 nanoparticles (16–90  nm) was achieved in a gas-phase flame process. The effect of process parameters on the crystal structure of the Y 2 O 3 nanoparticles was systematically investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fuel gases, H 2 or C 2 H 4 , at various flow rates, two yttrium precursors, an oxidant stream with varying degrees of N 2 or Ar dilution and different burner diameters were used to examine the effects of chemical atmosphere, flame temperature, residence time and precursor concentration on the crystal structure of the synthesized Y 2 O 3 nanoparticles. Regardless of the other process parameters, at diluent/O 2 ratios of 0.25 or lower, monoclinic Y 2 O 3 nanoparticles were obtained, whereas at diluent/O 2 ratios of 1 or higher, cubic Y 2 O 3 nanoparticles were obtained. A lower diluent/O 2 ratio was related to higher flame temperature. Thermodynamic analyses suggest that high temperatures likely favour the formation of monoclinic Y 2 O 3 nanoparticles in this flame process. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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