MECHANICAL SOLID-STATE REACTION FOR SYNTHESIS OF BETA-SIC POWDERS

Stoichiometric beta-SiC powders have been successfully prepared by solid state reaction of elemental silicon and carbon powders via the mechanical alloying process, The mechanical alloying process was performed in a high-energy ball mill under argon gas flow at room temperature. The solid-state reacted alloy powders have been characterized as a function of the milling time by means of x-ray diffraction, infrared absorption, scanning and transmission electron microscopy, and chemical analysis. Complete fcc-SiC (beta-phase) alloy powders were obtained after 1080 ks of continuous milling. The lattice parameter (a(O)) of the formed beta-SiC was calculated to be 0.4357 nm, No free silicon and/or carbon crystals were observed. The existence of transverse optical (TO) and longitudinal optical (LO)-like phonon modes is observed for the end-product alloy powders. Mechanically alloyed beta-SiC powders are stable at elevated temperatures (1773 K) and did not transform to any other phases. The end-product beta-SiC alloy powders possess excellent morphological properties, such as homogeneous shape (spherical morphology) with fine and smooth surface relief and uniform size (less than 0.5 mu m in diameter), The fabricated beta-SiC alloy powders have fine cell-like structure with nanoscale dimensions of about 7 nm.