STRENGTH, RELIABILITY AND SURFACE HARDNESS IMPROVEMENT OF STRUCTURAL CERAMICS THROUGH ION IMPLANTATIONS

THE OBJECTIVE OF THIS PROGRAM IS TO ACHIEVE STRENGTH AND RELIABILITY IMPROVEMENTS IN STRUCTURAL CERAMICS THROUGH ION IMPLANTATIONS. THE APPROACH WILL BE TO PRODUCE PRECIPITABLEPHASES BY HIGH DOSE ION IMPLANTATION AND SUBSEQUENT ANNEALING. IF THE DESIRED PRECIPITATE PHASE HAS LOWER THERMAL EXPANSION COEFFICIENT THAN THE CERAMIC MATRIX THAN DURING COOLING AFTER ANNEALING, A COMPRESSIVE STRESS WILL BEDEVELOPED ON THE SURFACE THAT SHOULD HELP IN STRENGTHENING THE CERAMIC. IN ADDITION, STRENGTHENING CAN BE ACHIEVED THROUGH CRACK DEFLECTION BY NEAR SURFACE PRECIPITATES. AND, IF THE PRECIPITATE PHASE IS HARDER THAN THE MATRIX, A SURFACE HARDENING MAY RESULT. IN PHASE I, WE PROPOSE TO IMPLANT C(+) AND C(+)+N(+) INTO SI3N4 TO STUDY THE FORMATION OF C3N4 OR OTHER CARBONITRIDE PHASES. HEXAGONAL C3N4 PHASE WAS RECENTLY PROPOSED TO BE AS HARD OR HARDER THAN DIAMOND BASED ON RECENT THEORETICAL CALCULATIONS. CHARACTERIZATION WILL BE PERFORMED BY USING TEM, XPS, RAMAN SPECTROSCOPIES. FOUR POINT BEND TESTING WILL PROVIDE THE STRENGTH AND RELIABILITY DATA. SURFACE HARDNESS WILL BE MEASURED BY A NANO-INDENTER.