Fibrous Monolithic Ceramics: III, Mechanical Properties and Oxidation Behavior of the Silicon Carbide/Boron Nitride System

Publisher Website
Google Scholar
Abstract
Fibrous monolithic ceramics were fabricated in the SiC/BN system. The microstructure consists of high‐aspect‐ratio polycrystalline cells of SiC separated by cell boundaries of BN. The fibrous monolith with aligned cells fails noncatastrophically in flexure, with delamination cracking along the BN cell boundaries. Indentations cause controlled damage on the surface, but no strength‐degrading flaws. The flexural strength is in the range 300–375 MPa, and the estimated shear strength is ∼14 MPa. The SiC/BN fibrous monoliths also show excellent resistance to high‐temperature oxidation in air. Noncatastrophic fracture behavior is observed at room temperature after heat treatments between 1200° and 1500°C. The SiC cells on the surface are oxidized to form a protective silicate scale, which prevent deterioration of the BN cell boundaries.