Microstructures and mechanical properties of Hi-Nicalon fiber reinforced Si{sub 3}N{sub 4} matrix composites

1D BN-coated Hi-Nicalon fiber reinforced Si{sub 3}N{sub 4} composites were fabricated by a slurry route followed by hot pressing. Microstructures of the composites were observed by either EPMA, SEM or TEM. Flexural strength and fracture toughness were measured at room temperature and 1400{degrees}C (Ar). BN-interphase seems to have loose bonding for a fiber and a matrix. Flexural strength and fracture toughness at RT were 702 MPa and 20.2 MPa{radical}m, whereas those at 1400{degrees}C were 426 MPa and 16.3 MPa{radical}m, respectively.