Development of Textured and Single Crystal Garnet Fibers for Advanced Oxide CMCs

The proposed research effort focuses on developing a method to synthesize and crystallize doped YAG to produce textured or single crystal fibers that exhibit little degredation in strength and excellent creep resistance at temperatures in excess of 1400C.YAG will be synthesized from polymerized sol gel precursors, drawn into fibers and continuously crystallized using a quadrapole crystallizer. This approach is continuous, and fully scaleable. The effect of cationic dopants on the recrystallization of YAGwill be investigated by electron microscopy. Measurment of the individual tensile strengths and creep resistance of the fibers at temperatures up to 1400C will be performed. Microstructures and mechanical property information that is obtained will beused to influence the processing conditions that are selected. The results will establish further understanding of the structure-process relationship for the fabrication of stable, creep resistant oxide fibers for a broad range of applications.It isexpected that the proposed research will lead to the development of a stable high temperature oxide fiber with little loss in strength and exceptional creep resistance at temperatures in excess of 1400C. When scaled to commercial size and quantities,these fibers will be used extensively for oxide preforms for a range of CMC engine components - combustors, turbines, commpressors, exhaust nozzles, vanes, blades and shrouds etc.. Additionally, if single crystals can be produced, extensive opportunitiesexist for fiber optic applications.