Growth of single-crystal tungsten whiskers during CO reduction of NiWO4

Experimental evidence is presented that the growth of tungsten whiskers during CO reduction of NiWO4 follows the vapor-liquid-solid mechanism. A liquid phase appears at 940 deg C owing to the melting of NiWO4-Na2WO4 eutectic regions which seem to result from the segregation of sodium impurities pres...

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Bibliographic Details
Published in:Inorganic materials 2007-07, Vol.43 (7), p.781-785
Main Authors: Lebukhova, N. V., Karpovich, N. F., Palazhchenko, V. I., Pyachin, S. A.
Format: Article
Language:English
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Summary:Experimental evidence is presented that the growth of tungsten whiskers during CO reduction of NiWO4 follows the vapor-liquid-solid mechanism. A liquid phase appears at 940 deg C owing to the melting of NiWO4-Na2WO4 eutectic regions which seem to result from the segregation of sodium impurities present in the reagents used. The presence of the liquid phase ensures comparable rates of Ni and W liberation from the crystal lattice of nickel tungstate, leading to the formation of alpha-W + NiW two-phase regions. The directional growth of tungsten whiskers during further CO reduction of the tungstate melt is associated with W deposition on the growth surfaces of alpha-W single crystals in the two-phase regions.
ISSN:0020-1685
1608-3172
DOI:10.1134/S0020168507070199