SYNTHESIS OF HIGH-STRENGTH ALUMINA WHISKERS FOR REINFORCING CERAMIC AND METALLIC MATRICES

COMPOSITES CONSISTING OF SILICON CARBIDE (SIC) WHISKERS IN AN ALUMINA MATRIX HAVE RECENTLY DEMONSTRATED THE VIABILITY OF USING WHISKERS TO TOUGHEN CERAMICS. EFFORTS TO INCORPORATE SIC WHISKERS INTO IMPORTANT OXIDE CERAMICS, SUCHAS ZIRCONIA, MULLITE, AND CORDIERITE HAVE RESULTED IN DEGRADATION OF WHISKERS DURING FABRICATION. IT IS CLEAR THAT HIGH STRENGTH ALUMINA WHISKERS WOULD BE ADVANTAGEOUS TOCERAMIC COMPOSITES. ALUMINA WHISKERS ARE NOT COMMERCIALLY AVAILABLE, AND PREVIOUS RESEARCH ON THE GROWTH OF SUCH WHISKERS HAS SHOWN LIMITATIONS IN THE SYNTHESIS ROUTES USED TO DATE. ALUMINA WHISKERS THAT ARE 1 TO 5 MICRONS IN DIAMETER AND HAVE AN ASPECT RATIO GREATER THAN 1000 HAVE BEEN FABRICATED. THE PLANNED PHASE I RESEARCH WILL INVESTIGATE THREE NOVEL SYNTHESIS ROUTES AND CHARACTERIZE THE WHISKERS SYNTHESIZED USING ELECTRON MICROSCOPY, X-RAY DIFFRACTION, AND GRAVIMETRIC TECHNIQUES. THE SYNTHESIS ROUTE SHOWING THE BEST YIELD AND THE POTENTIAL FOR LOW COST WILL BE INVESTIGATED IN FURTHER DETAIL IN PHASE II. RESEARCH DURING PHASE II WILL INVESTIGATE REACTION MECHANISMS, DETERMINE MECHANICAL PROPERTIES, AND DEMONSTRATETHE ABILITY TO INCORPORATE ALUMINA WHISKERS INTO A ZIRCONIA MATRIX CERAMIC COMPOSITE. PHASE III WILL CONCENTRATE ON DEVELOPMENT OF AN ECONOMICAL PROCESS FOR ALUMINA WHISKER PRODUCTION.