Rapid Deposition of Uniform Thickness Fiber Interfaces in Bulk Fabric for CMC Toughening

Physical Sciences Inc. will develop a BN/Si3N4 fiber interface coating that can be applied uniformly to fibers in a woven fabric and provide toughening in SiC fiber reinforced ceramic matrix composites (CMCs). Using traditional CVD precursors such as BCl3, NH3, and SiCl4, we will demonstrate a rapid, self-limiting, scalable vapor phase deposition process to create coatings of uniform thickness throughout the tows. Due to the improved uniformity of the fiber coating, the interface thickness can be reduced, increasing the flexibility of the fabric and ease of handling. We will fabricate a CMC plate from the coated fabric, measure the composite strength to verify toughening, and provide a conceptual design for a commercial-scale reactor to coat full bolts of fabric. During Phase II, we will optimize the thickness, composition, and morphology of the coating and will perform more extensive materials testing including stress oxidation. More uniform, thinner interfaces will improve the high temperature performance and reduce the manufacturing costs of CMCs for long-life applications in advanced propulsion components.