HIGH TEMPERATURE ADVANCED STRUCTURAL CERAMICS

CURRENT INVESTIGATIONS HAVE SHOWN HOW WHISKER REINFORCEMENT HAS INCREASED THE FRACTURE TOUGHNESS OF SIC-WHISKER/CERAMIC-MATRIX COMPOSITES. HOWEVER, IT WAS FOUND THAT THE STRENGTH OF THE COMPOSITES DECREASED AS A RESULT OF FLAWS INTRODUCED WITH THE WHISKER ADDITION AND THEPOOR SINTERABILITY OF SI(3)N(4). EXTERNAL PRESSURE HAS TO BE INTRODUCED (E.G. BY HOT-PRESSING OR HOT-ISOSTATIC PRESSING) FOR ELIMINATING THE FLAWS. SIALON CERAMICS CAN REACH ALMOST FULL DENSITY THROUGH PRESSURELESS SINTERING, AND THEY ALSO OFFER THE SAME SIGNIFICANCE IN HIGH TEMPERATURE MECHANICAL PROPERTIES AS SI(3)N(4). DENSIFICATION AND STRENGTHENING BY TRANSIENT LIQUID PHASE SINTERING (TLPS) HAS BEEN EXPLORED. HOWEVER, COMBINING WHISKER REINFORCEMENT WITH TLPS HAS NOT PREVIOUSLY BEEN DEMONSTRATED. THIS PROJECT UTILIZES UNIQUE SINTERABILITY OFSIALON, TLPS, AND SIC WHISKER REINFORCEMENT TO OBTAIN FLAW FREE, HOMOGENEOUS AND HIGH TEMPERATURE (>1400 DEGREES CENTIGRADE) STRENGTH COMPOSITES THROUGH PRESSURELESS SINTERING.