How SiC Nanowires Produced from Carbon Blacks Characterize Their Structure

SiC nanowires were obtained by a reaction between silicon vapor and carbon black powder in vacuum at 1200^oC.  Their structures and properties were studied using X-ray diffraction, high resolution transmission electron microscopy, and Raman scattering techniques.
Chemical composition of SiC nanowires was similar for all the samples, but their diameters and concentration of structural defects varied and depended on carbon black grade and the history of its thermal treatment.   The smallest diameter SiC nanowires, 10 nm, were obtained from graphitized N990.   Larger wires, of diameter up to 200 nm, were obtained from thread grade carbon blacks. 
During the reaction with silicon the outer layers of carbon black formed SiC nanowires and SiC shell that coated the remaining carbon black aggregates.   Lateral sizes of graphitic crystallites in the SiC coated carbon blacks were smaller than those measured in raw carbon blacks. 
It is well known that during graphitization process lateral sizes of graphitic crystallites grow.  But crystallite sizes of graphitized carbon blacks after the reaction with silicon were all small, about 2 nm, similar to those observed before the heat treatment.  We concluded that during heat treatment of carbon blacks only crystallites in the outer layer grow, while those in the interior of the particles remain unchanged.