New High Temperature Oxide Fibers

During the last decade, oxide fiber-reinforced oxide composites have been the subject of increasing interest. This renaissance is based in part on the availability of two new oxide fibers, NEXTEL Ceramic Oxide Fiber 720 and NEXTEL Ceramic Oxide Fiber 650, which have good strength, microstructural stability and long-term creep resistance at temperatures as high as 1200°C. Superior high temperature structural properties result from the presence of crystalline, creep-resistant phases such as Y-doped Al2O3 and mullite. The physical properties, high temperature strength, strength retention and creep resistance of these composite Nextel fibers will be reviewed Further improvements in high temperature properties of polycrystalline oxide fibers are possible. High temperature BSR (bending stress rupture) results on experimental YAG fibers have demonstrated creep performance superior to Nextel 720 fiber. However, the successful synthesis of high strength, fine-grained YAG fibers has been elusive. In this work, two -phase YAG-alumina fibers were synthesized with uniform, fine grain size and high strength. The tensile creep of YAG-alumina fibers was measured and compared with commercial oxide fibers and single-phase YAG fibers.