Development of Advanced Crystalline Garnet Materials and Fibers

The fabrication of novel yttrium aluminum garnet (YAG) powders and their continuous polycrystalline fibers is proposed. These fibers will not only withstand oxidizing conditions but also offer excellent themomechanical properties including high strength,creep resistance, and damage tolerance above 1350 ¿C. The powders will be produced by a sol-gel process, and the Y and Al cations will be substituted with three different cations to decrease the lattice diffusion and subsequently the creep rate at hightemperatures. The fibers will be formed via Viscose Suspension Spinning Process (VSSP), which is the most economical and versatile fiber processing technique. Our approach will resolve several technical shortcomings associated with the application ofoxide fibers in CMCs due to their excessive creep at high temperatures.Creep resistant polycrystalline YAG fibers offer significant benefits for ceramic matrix composites used in oxidizing conditions and high temperatures. If successful, LMI and ACI areprepared to form a joint venture and also to license the technology to all interested CMC system companies.