Silicon carbide filaments - Microstructure

The microstructure of chemically vapor deposited silicon carbide filaments has been examined using transmission electron microscopy. The filament bulk consisted of heavily faulted columnar subgrains of beta-SiC which were preferentially oriented such that 1 1 1 planes were parallel to the surface of the carbon fiber substrate. The protective coating on the filament surface was characterized by several microstructurally distinct layers, all of which consisted primarily of carbon. The first layers of the coating contained small crystallites of SiC in addition to turbostratic carbon, while the outer layers showed no evidence of SiC. Implications of the filament microstructure with respect to mechanical properties are discussed.