SYNTHESIS AND CHARACTERIZATION OF SIC WHISKERS

SiC whiskers were synthesized by the carbothermal reduction of silica with an addition of halide (3NaF.AlF3 or NaF) as an auxiliary bath. The whiskers were beta-phase (3C) and grew in the [111] direction. Three distinctive morphologies were observed: (1) Type A: thin and straight; (2) Type B: thick and bamboo-like; and (3) Type C: thick, straight, and smooth. Type A whiskers contained a high density of basal plane (111) stacking faults along their entire length, whereas Type B whiskers showed periodic changes between stacking faults and well-defined single crystals. Type C whiskers showed stacking faults on the other {111} planes instead of on the basal (111) plane. Silica formed molten fluorosilicate with halide and SiC grew via a vapor-solid reaction mechanism through gaseous SiO. These reactions can be expressed as (SiO2) + C (S) = SiO (g) + CO (g) and SiO (g) + 3CO (g) = SiC (s) + 2CO2 (g). The effects of processing parameters on the morphology and size of the whiskers were examined and the relationship between the morphological development of the whiskers and the stacking fault energy was determined.