학술논문
Growth of single-crystal tungsten whiskers during CO reduction of NiWO4 .
Document Type
Article
Source
Subject
*TUNGSTEN
*CHROMIUM group
*ALKALI metals
*CRYSTAL lattices
*LATTICE theory
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Language
ISSN
0020-1685
Abstract
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°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 α-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 α-W single crystals in the two-phase regions. [ABSTRACT FROM AUTHOR]