CVD DIAMOND COATINGS FOR FIBERS AND PARTICULATES IN HIGH TEMPERATURE COMPOSITES

AMONG THE EMERGING MATERIALS OF INTEREST, DIAMOND FILMS DEPOSITED BY PLASMA ENHANCED CVD (PECVD) OFFERS GREAT PROMISE AS A FIBER COATING IN FIBER-MATRIX COMPOSITES. DIAMOND FILMS POSSESS UNSURPASSED PHYSICAL PROPERTIES INCLUDING VERY HIGH THERMAL CONDUCTIVITY, HIGH ELECTRICAL RESISTIVITY, EXTREME HARDNESS, AND CHEMICAL INERTNESS. USED AS A COATING FOR REINFORCING FIBERS IN HIGH TEMPERATURE METAL MATRIX OR CERAMIC MATRIX COMPOSITES, THESE PROPERTIES CAN SOLVE A NUMBER OF PROBLEMS ENCOUNTERED WITH THESE COMPOSITE MATERIALS. AS AN EXTREMELY INERT COATING DIAMOND CAN STABILIZE THE FIBER-MATRIX INTERFACE AND PREVENT UNWANTED CHEMICAL REACTIONS BETWEEN THE FIBER AND THE MATRIX, WHILE ITS HIGH THERMAL CONDUCTIVITY CAN REDUCE THE THERMAL STRESSES FOUND IN SOME APPLICATIONS. THE OBJECTIVE OF THIS PHASE I RESEARCH PROGRAM IS TO DEMONSTRATE THE FEASIBILITY OF USING DIAMOND AS A FIBER COATING. DIAMOND FILMS WILL BE SYNTHESIZED ON PLANAR AND FIBER FORMS OF SIC, GRAPHITE AND A SILICON-NITROGEN CERAMIC. THE CHEMICAL, STRUCTURAL, AND ADHESIVE CHARACTERISTICS OF THE FILMS WILL BE RELATED TO THE DEPOSITION CONDITIONS, SUBSTRATE MATERIAL, AND CONDITION TO THE SUBSTRATE SURFACE. THE GOAL IS ESTABLISHED THE CONDITIONS UNDER WHICH CONTINUOUS, HIGH QUALITY DIAMOND COATINGS OF FIBERS CAN BE ACHIEVED. TO ESTABLISH THE IMPROVEMENT CONFERRED BY THE DIAMOND FILM, TESTS WILL BE MADE OF THE IMPROVED THERMAL CONDUCTIVITY OF DIAMOND COATED FIBERS.