HIGH TEMPERATURE EVALUATION OF NEW FERROELASTIC TOUGHENED CERAMIC MATERIALS

IT IS PROPOSED THAT NEW CERAMIC MATERIALS WITH POTENTIAL FOR STRENGTH AND TOUGHNESS RETENTION TO ELEVATED TEMPERATURES WILL BE FABRICATED AND CHARACTERIZED. THESE NEW CERAMIC MATERIALS EXHIBIT A PHENOMENON KNOWN AS FERROELASTICITY. THE PHENOMENON OF FERROELASTICITY IS VERY SIMILAR TO THAT OF FERROELECTRICITY AND FERROMAGNETISM. THE FERROELASTIC STATE IS CHARACTERIZED BY THE EXISTENCE OF AT LEAST TWO ENERGETICALLY EQUIVALENT STATES CORRESPONDING TO TWO VALUES OF STRAIN.IT HAS BEEN RECENTLY PROPOSED THAT FERROELASTIC DOMAIN REORIENTATION PROVIDES A MECHANISM OF TOUGHENING FERROELASTIC CERAMICS. IN OUR WORK, TOUGHNESS VALUES IN EXCESS OF 16 MPA.M(1/2) AS MEASURED BY THE DOUBLE CANTILEVER BEAM (DCB) TECHNIQUE WERE RECORDED. SUCH HIGH VALUES OF TOUGHNESS MAKE THESE MATERIALS IDEALLY SUITED FOR ADVANCED APPLICATIONS SUCH AS THE ADIABATIC DIESEL ENGINE. THE PRINCIPAL OBJECTIVES OF THE PHASE I EFFORT INCLUDE FABRICATION OF THESE CERAMIC MATERIALS OF CERAMATEC PROPRIETARY COMPOSITIONS AND EVALUATION OF STRENGTH AND TOUGHNESS AS A FUNCTION OF TEMPERATURE UP TO 1100 DEG C. HIGH TEMPERATURE TESTING WILL BE CONDUCTED IN COLLABORATION WITH THE ARMY MATERIALS TECHNOLOGY LABORATORY. THE RESULTS OF THE HIGH TEMPERATURE TESTING WILL BE USED IN AN ITERATIVE FASHION TO MAKE APPROPRIATE COMPOSITION AND PROCESS MODIFICATIONS TO YIELD MATERIALS WITH EXCELLENT STRENGTH AND TOUGHNESS RETENTION TO ELEVATED TEMPERATURES.