. Silicon Carbide - an overview | ScienceDirect Topics The specimens were heated for 0 h in a vacuum at each temperature. Nicalon commercial grade fiber (SiC f (CG)), Hi-Nicalon SiC fiber (SiC f (HI)), and Hi-Nicalon Type-S fiber (SiC f (S)) with oxygen concentrations of 00.0, 0.0, and 0.0%, respectively, were used as preforms. 