AN INNOVATIVE APPROACH FOR THE FORMATION OF SILICON CARBIDE/SILICON CARBIDE COMPOSITES

AN INNOVATIVE ALTERNATIVE FOR PREPARING SILICON CARBIDE (SIC)/SIC COMPOSITES INVOLVES THE DIMOX(TM) DIRECTED METAL OXIDATION APPROACH TO FORM A SIC MATRIX. IN THE DIRECTED METAL OXIDATION PROCESS A MOLTEN METAL IS OXIDIZED TO GROW AN OXIDATION REACTION PRODUCT INTO AN ADJACENT PREFORM OF REINFORCEMENT MATERIAL. ALTHOUGH THIS PROCESS IS CURRENTLY HIGHLY DEVELOPED FOR ALUMINIUM OXIDE MATRIX MATERIALS, THE PROPOSED EXTENSION TO THE SIC MATRIX COMPOSITE SYSTEM IS NEW AND ORIGINAL. A CARBON-BEARING GAS WILL BE USED AS THE REACTION GAS WITH MOLTEN SILICON (SI) TO GROW TO A SIC CERAMIC MATRIX. THIS GAS MUST NOT DECOMPOSE AT THE REACTION TEMPERATURE, AND MUST REACT WITH MOLTEN SI TO FORM SIC. ONE SUCH CLASS OF GASES, CURRENTLY CONSIDERED PROPRIETARY, HAS BEEN TENTATIVELY IDENTIFIED. PHASE I WILL INCLUDE A COMPLETE SURVEY OF APPROPRIATE, COMMERCIALLY AVAILABLE CARBON-BEARING GASES TO IDENTIFY THE MOST PROMISING ALTERNATIVES FROM BOTH THERMODYNAMIC STABILITY AND COST VIEWPOINTS. THE GAS SHOWING THE BEST COMBINATION OF HIGH STABILITY, LOW COST, AND FEWEST UNDESIREABLE REACTION PRODUCTS WILL BE USED AS THE "OXIDANT" TO TEST THE FEASIBILITY OF FORMING SIC FROM MOLTEN SI BOTH IN THE PRESENCE AND IN ABSENCE OF A SIC PARTICULATE REINFORCEMENT PHASE. THE PRODUCTS WILL BE EVALUATED USING WEIGHT CHANGE FROM THE REACTION, VISUAL OBSERVATION, X-RAY DIFFRACTION, AND OPTICAL AND SCANNING ELECTRON MICROSCOPY OF MOUNTED CROSS-SECTIONS. THE PROJECT OFFERS THE POTENTIAL OF PROVIDING INEXPENSIVE, DENSE, REINFORCED COMPOSITES, AND SHOULD ALLOW FOR THE FABRICATION OF LOW COST COMPLEX COMPONENTS WITH DESIRABLE PROPERTIES.