LASER PROBE VAPORIZATION/OXIDATION TESTING OF HIGH TEMPERATURE COMPOSITES

THIS PROJECT WILL USE HIGHLY INSTRUMENTED MICROSCALE LASER TEST FACILITIES FOR REAL-TIME MEASUREMENT OF VAPORIZATION/OXIDATION PHENOMENA AT TEMPERATURES UP TO 4000 DEG F. THE TECHNIQUE WILL BE APPLIED TO FOUR MODEL COMPOSITE SYSTEMS, TWO OXIDATION-RESISTANT CARBONCARBON COMPOSITE SYSTEMS AND TWO OXIDATION-RESISTANT CERAMIC MATRIX COMPOSITE SYSTEMS. THE MICROSTRUCTURE OF EACH MATERIAL WILL BE CHARACTERIZED IN DETAIL BOTH BEFORE AND AFTER LASER TESTING. MICROSCALE TESTING WILL BE PERFORMED USING LOCAL AREA HEATING OF TEST SPECIMENS IN VACUUM TO STUDY VAPORIZATION PHENOMENA AND IN BOTH LOW OXYGEN PARTIAL PRESSURES AND AIR TO STUDY OXIDATION PRODUCT SPECIES AND COMBINED OXIDATION/VAPORIZATION REACION PHENOMENA. ON-LINE LASER PROBE SPECTROMETRY WILL BE USED TO PROVIDE REAL-TIME DETERMINATION OF CHEMICAL SPECIES PRESENT AT TEMPERATURE IN THE NEAR-SURFACE ENVIRONMENT. THE OBSERVED PHENOMENA WILL CORRELATE WITH MICROSTRUCTURAL AND MICROCHEMICAL CHANGES DISCERNED FROM PREAND POST-TEST CHARACTERIZATION OF THE MODEL MATERIALS. THEORETICAL MODELING OF THERMOCHEMICAL PROCESSES EXPECTED TO OCCUR AT THESE TEMPERATURES WILL BE COMPARED TO OBSERVED VAPORIZATION/OXIDATION SPECIES. THE DEVELOPEDTEST METHOD SHOULD BE USEFUL AS A MATERIALS DEVELOPMENT AND SCREENING TOOL AND MAY ALSO BE USEFUL FOR PREDICTION OF LONG-TERM HOT CORROSION BEHAVIOR FROM KNOWLEDGE OF THE BASIC REACTION INVOLVED. THE PROJECT WILL BE PERFORMED WITH THE TECHNICAL ASSISTANCE OF A CONSORTIUM OF ANTROPIX CORPORATION/HOUSTON AREA RESEARCH CENTER/RICE UNIVERSITY AS SUBCONTRACTOR.