Advanced Oxide Fibers and Coatings for High Temperature Composite Materials Applications. Phase 1.
Final rept. 15 Feb-15 Aug 97,
CONTAINERLESS RESEARCH INC EVANSTON IL
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This research investigated the feasibility of a new process for manufacturing crystalline oxide fibers for high temperature structural applications. Glass fibers were pulled from undercooled melts and then crystallized under controlled heating conditions. The research emphasized mullite Al6 Si2 013 and yttrium-aluminum garnet - YAG Y3 Al5 012 compositions. Crystallization rates were several cms at 1200-2000 degrees C. Glass fibers of uniform diameter and no defects or visual imperfections exhibited tensile strength up to 5.3 GPa for the YAG composition and 3.5 GPa for the mullite-composition. The strength of fibers crystallized below 1100 degrees C were 0.7 GPa for YAG and 1.3 GPa for mulitte. Optimum crystallization conditions will be at higher temperatures where the crystallization rate is large compared to the rate of crystal nucleation, and rapid, economical synthesis of continuous single crystal fibers may be possible. Lower temperatures may be employed to obtain very fine-grained fibers. Phase research would i synthesize long defect-free glass fibers, ii investigate kinetics of crystallization at higher temperatures where nucleation is suppressed, iii optimize mechanical properties achieved in the crystallization process, and iv provide high strength crystalline fiber materials for applications testing.
- Ceramics, Refractories and Glass