DEVELOPMENT OF HIGH TEMPERATURE OXIDES WITH SUPPRESSED OXYGEN DIFFUSIVITY

THE SUCCESSFUL DEVELOPMENT OF HIGH-TEMPERATURE CERAMICS OR CERAMIC COMPOSITES FOR USE IN COMBUSTION ENGINE ENVIRONMENTS WILL REQUIRE DEVELOPMENT OF THERMODYNAMICALLY STABLE OXIDES FOR PROTECTIVE COATINGS OR AS THE MATRIX MATERIAL IN WHISKEROR FIBER-TOUGHENED COMPOSITES. THIS PROGRAM WILL DEVELOP CUBIC FLUORITE RELATED OXIDES (BASED ON Y[2]O[3]) WITH STRUCTURES MODIFIED BY SELECTED DOPING. THE MODIFICATIONS SHOULD REDUCE OXYGEN DIFFUSIVITY BY TWO TO FOUR ORDERS OF MAGNITUDE. IF THIS CAN BE ACHIEVED, THIS OXIDE MAY PROVIDE OXIDATION PROTECTION TO MUCH HIGHER TEMEPRATURES THAN CURRENTLY POSSIBLE, WHILE RETAINING A HIGH THERMODYNAMIC STABILITY. THE MATERIALS DEVELOPED MAY EXTEND THE USE OF SUPERALLOYS, SIC, SI(3)N(4) OR CARBON FIBER BASED CERAMICS TO THE HIGHEST POSSIBLE TEMPERATURES, IN COMBUSTION ZONE ENVIRONMENTS.