A COATED TIB2 WHISKER TOUGHENED SIC MATRIX COMPOSITE FOR AEROSPACE PROPULSION

SILICON CARBIDE IS A VERY DESIRABLE STRUCTURAL CERAMIC BUT STATE-OF-THE-ART MONOLITHS ARE LACKING IN TOUGHNESS AND RELIABILITY. WHISKER TOUGHENING HAS NOT BEEN EFFECTIVE DUE TO THE DISAPPEARANCE OF THE SICW IN THE VERY HIGH TEMPERATURE CONSOLIDATION PROCESS. TIB2 PARTICLES HAVE BEENDEMONSTRATED STABLE IN THE SIC CONSOLIDATION PROCESS, BUT DO NOT HAVE A MAJOR IMPACT ON INCREASING TOUGHNESS AND LACK OXIDATION STABILITY ABOVE ABOUT 1200 DEGREES CENTIGRADE. MER PROPOSES TO UTILIZE TIB2 WHISKERS WHICH SHOULD SUBSTANTIALLY INCREASE TOUGHNESS AND APPLY A Y2O3 COATING TOTHE TIB2 WHISKERS THAT SHOULD PROVIDE OXIDATION PROTECTION 1400 DEGREES CENTIGRADE. THE TARGET PROPERTIES ARE 8 MPAM(1/2) TOUGHNESS AND 800 MPA STRENGTH 1400 DEGREES CENTIGRADE. RIGOROUS AND UNIQUE PROCESSING WILL BE UTILIZED TO AVOID LARGE PARTICLES OR AGGLOMERATIONS TO PRODUCE A THEORETICAL DENSE COMPOSITE WITHFLAW SIZES LESS THAN THE CRITICAL SIZE.