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

Physical Sciences, Inc. (PSI) will demonstrate the technical and economic feasibility of scaling up our method for applying uniform interphases to fibers within a woven fabric. During the Phase I program, we established that our self-limiting, scalable vapor phase deposition process can fabricate stoichiometric BN/Si_3N_4 interface coatings of consistent thickness using traditional CVD precursors such as BCl_3, NH_3, and SiCl_4 but at significantly lower temperatures. Due to the improved uniformity of the fiber coating, the interphase thickness can be reduced, increasing the flexibility of the fabric and ease of handling. In Phase II, we will fabricate a CMC plate from coated fabric and measure the composite strength to verify toughening. We will optimize the deposition processes and will perform more extensive materials testing. We will formulate a computational model of our reactor and provide a conceptual design for a commercial-scale system to coat full bolts of fabric. More uniform, thinner interphases will improve the high temperature performance and reduce the manufacturing costs of CMCs for long-life applications in advanced propulsion components.