We propose to develop low-cost, creep-stable, polycrystalline yttrium aluminum garnet (YAG) and mullite (3Al203.2Si02) fibers (10-20 µm dia.) for evaluation as reinforcement for advanced ceramic composites. The fibers will be produced by spinning optimized alkoxide and carboxylate metalloorganic precursors. The critical issues that must be resolved fall into three categories: 1) control of fiber mechanical properties (tensile strength, creep resistance, etc.); 2) production of commercial quantities of fibers, and 3) development of low-cost processes. Phase I studies will focus on producing 10s of meters of single tows of fibers/h of both mullite and YAG fibers. Phase II will scale-up studies to 100s of meters of multiple tows of fibers/h. Efforts will be made to develop interfacial coatings that these tows can be used to fabricate oxide/oxide (e.g. YAG/YAG) ceramic matrix composites. Finally, examples of oxide/oxide composites will be fabricated.The potential success of the proposed program hinges on the need for inexpensive precursors and processing methods. Two low-cost routes to spinnable aluminum carboxylate and silicon alkoxide precursors were recently discovered. In one instance the precursor source is boehmite and the other, fused silica. These spinnable precursors offer direct access to YAG and mullite fibers and matrices.
Keywords: CERAMIC FIBER YAG MULLITE HIGH TEMPERATURE CERAMIC COMPOSITES
