A NOVEL TECHNIQUE TO FABRICATE TIB(2) FIBERS DIRECTLY FROM MELT

DEVELOPMENT OF SUITABLE REINFORCEMENT FIBERS FOR HIGH TEMPERATURE COMPOSITE MATERIALS IS THE MAJOR TECHNICAL BARRIER LIMITING THE INTRODUCTION OF THESE NEW MATERIALS FOR ADVANCED AIRCRAFT ENGINES. WE PROPOSE TO FABRICATE MONOFILAMENT TIB(2) FIBERS USING A NOVEL CONCEPT. THE CHOICE OF TIB(2) FIBERS IS BASED ON ITS CHEMICAL COMPATIBILITY WITH ALUMINIDE MATRICES, HIGHER COEFFICIENTS OF THERMAL EXPANSION AND ELASTIC MODULUS, AND LOWER DENSITY COMPARED TO OTHER CANDIDATE REINFORCEMENT FIBERS. IN THE FIRST STEP OF THE PROPOSED NOVEL FABRICATION TECHNIQUE, WE WILL OBTAIN A B RICH TI FILAMENT DIRECTLY FROM THE MELT USING AN ADVANCED MELT SPINNING TECHNIQUE. IN THE SECOND STEP THE B RICH TI FILAMENT WILL BE COATED WITH LOWCOST B COATINGS USING AN INNOVATIVE CHEMICAL VAPOR DEPOSITION (CVD) PROCESS THAT COMBINES THE LOW COST OF PACK METALLIZATION WITH THE HIGH HEAT AND MASS TRANSFER OF A FLUIDIZED BED REACTOR. WE WILL CHARACTERIZE THE MECHANICAL AND MICROSTRUCTURAL PROPERTIES OF THE TIB(2) FIBERS FABRICATED USING THE ABOVE TECHNIQUE, GIVING PARTICULAR ATTENTION TO THE EXTENT OF DEGREE OF DIFFUSION AND REACTION BETWEEN THE B RICH TI SUBSTRATE AND B COATING. THE LOW COST B COATINGS VIA CVD IN A FLUIDIZED BED REACTOR WILL BE PERFORMED IN COLLABORATION WITH DRS. ANGEL SAN JURJO AND DIGBY MACDONALD OF SRI INTERNATIONAL, MENLO PARK, CA.