Low Cost, YAG and Mullite Fibers by Continuous Extrusion an Pyrolysis of Metal Carboxylate Precursors

Optimal ceramic reinforced CMS's and MMC's are the key to the success of many Air Force programs because of the significant promise these lightweight, high strength materials offer for meeting projected performance and protection requirements for a wide variety of aerospace applications. This Phase I program has explored methods of producing continuous yttrium aluminum garnet (Y3Al5O12) and mullite (3Al2O3.SiO2) fibers. In Task 1, synthesis reactors have been constructed with 12:1 and 50:1 capacities that will enable us to produce up to 2 kg of precursor compounds in a single reactor directly from Al(OH)3 and/or SiO2. In Task 2, fiber processing properties were optimized. We can produce 3 m/min of 30 um ave. dia. Fiber and spool it. This translates to 180 m/h. We have initiated efforts to optimize the spinning process to meet the expectations of Phase II work to produce 10s m/h of multi-fiber tows suitable for manufacture of ceramic/ceramic composites. In Task 3, Fiber properties for hand drawn fibers produced in earlier studied showed bend strengths as 1.9 Gpa (assuming e=280 Gpa), but tensile tests on continuously processed fibers have yet to be done. Phase I goals will be to refine the processing steps necessary to produce larger quantities of fibers, with better control of fiber diameters, pyrolysis treatments and finally mechanical properties. We also expect to extend our efforts to improve the mullite fiber system. We must learn to cure these fibers as they are being spun and then conduct pyrolysis studies. Prepared in cooperation with Michigan Univ., Ann Arbor, MI.