ELABORATION AND COMPRESSIBILITY BEHAVIOR OF NANOSTRUCTURED SIC

Nanostructured SiC has been elaborated from coarse grained SiC by mech anical attrition. Milling time ranged from 1 h to 14 h. Crystallites s izes and microstrains have been determined from X-ray diffraction peak profile analysis using a ''one peak method''. According to this metho d, the average crystallite size calculated from the (11.0) and (10.4) 6H-SiC reflections is less than 50 nm with a milling time of one hour. Up to 6 h milling time, crystallite sizes determined from these two p eaks are very close, indicating that crystallite size evolution versus milling time is nearly identical for these two crystallographic direc tions. We observe a strong decrease of the crystallite size up to 3 h milling time. A saturation value is reached after 6 h milling time, as sociated with a strong increase of microstrains. From density-pressure measurements performed in uniaxial compression, the powder's compress ibility behavior appears to be strongly related to changes in powder m orphology and granularity during ball milling. The evolution of the po wder morphology was followed by scanning electron microscopy. The iron contamination level by the steel vial and balls was controlled by X-r ay microanalysis. (C) 1998 Acta Metallurgica Inc.