Multilayered oxide interphase concept for ceramic-matrix composites

Hi-Nicalon/SiC minicomposite specimens containing three oxide interphase layers (amorphous SiO₂, monoclinic ZrO₂, and amorphous SiO₂) were prepared by chemical vapor deposition. The minicomposites exhibited graceful composite failure behavior with reasonable load-carrying capability in room-temperature tensile tests. Much of the composite behavior and load-carrying capability was retained even after matrix precracking and subsequent oxidation in air at 960°C for 10 h. In both the as-prepared and oxidized specimens, crack deflection and fiber pull-out occurred preferentially within the multilayered interphase region. The potential merits and uncertainties associated with this multilayered oxide interphase approach were discussed in the context of designing environmentally durable interfaces for ceramic-matrix composites.