Synthesis and growth mechanism of ThO2–W–Mo alloy nanocomposite powder |
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Authors: | X Devaux A Thomy J Ghanbaja |
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Affiliation: | (1) Laboratoire de Metallurgie Physique & Science des Materiaux, URA CNRS 155, Ecole des Mines, 54042 Nancy Cedex, France;(2) Service Commun de Microscopie Electronique, Universite Henry Poincare, BP 239, F54506 Vandoeuvre les Nancy, France |
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Abstract: | Nanocomposite ultrafine powders of thorium oxide and tungsten molybdenum alloy were prepared by arcing between a pure molybdenum
cathode and a thoriated tungsten anode under an argon–hydrogen atmosphere. The microstructure, morphology and chemical analyses
of the ultrafine powders were examined by X-ray diffraction, transmission electron microscopy and associated techniques. The
powders are composed of thorium oxide single-crystalline nano-grains decorated by tungsten molybdenum alloy particles which
are crystallized in a metastable A15 structure. Two morphologies were observed: octahedra and needle-like particles. Every
octahedral particle bigger than 15 nm had on each corner a metallic grain generally less than 8 nm in size. The needles had
a length below 600 nm and their width to length ratio ranged from 1/3–1/15. They all presented on one of their ends a metallic
particle which was comparable in size to the needle width. Other smaller particles (<10 nm) may be encountered along the edges.
The metallic particles were found to be epitaxial on the thorium oxide grains according to the relation: (100) 011]ThO2∥(100) 011]A15. The extensive study of the microstructural and morphological properties of the powders leads us to suggest a growth mechanism
of the nanocomposite particles.
This revised version was published online in November 2006 with corrections to the Cover Date. |
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