Optimizing the fabrication process for superior mechanical properties in the FCVI SiC matrix/stoichiometric SiC fiber composite system

The optimization of the fabrication of SiC composites with stoichiometric SiC fibers (Hi-Nicalon Type S and Tyranno SA) was carried out by the forced thermal-gradient chemical vapor infiltration (FCVI) process. These SiC/SiC composites had a low porosity (11%) with uniform pore distribution and uniform thickness of carbon interphase between advanced SiC fibers and SiC matrix. The tensile strength was slightly increased with the thickness of the carbon interphase in the range of 75-300 nm. The effectiveness of the carbon interphase for the excellent mechanical properties was confirmed by scanning electron microscopy observation.