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Retarded Growth of Nano-sized Carbide Particles in Liquid Metals at 1500°C

J. Kim, J. Kim, M. Seo, J. Kim, S. Kang
Seoul National Univ., KR

Keywords: nanocrystalline, bulk, retarded particle growth, thermal stability

Abstract:

The nanocrystalline solid-solution carbide powders were prepared by carbo-thermal reduction after high-energy planetary milling of proper oxide mixture. Then, particle growth behaviours of nanocrystalline transitional metal carbides such as (W,V)C and (Ti,W,M1,M2)(CN) were investigated and compared each other when those carbides were present in a Ni or Co melt at 1500˚C. From experiments it is found that the growth of (W,V)C and (Ti,W,M1,M2)(CN) in a liquid melt was significantly retarded compared to other single-phase carbides such as WC, TiC or Ti(CN). It is known that the carbide particles grow fast from nano to micron size by particle coalescence and dissolution/precipitation phenomena. In order to elucidate the mechanisms of their growth retardation, we studied the roles of solutes in the melt and in the carbides with X-ray diffraction and high-resolution TEM. Further we calculate the formation energy of these carbides to evaluate their thermal stabilities at high temperatures.
 
 
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