Novel CVD/MOCVD Fiber Coatings for Toughened High Temperature Composites

Structural composites have many applications to 2500 Degrees F and beyond, in oxidizing environments. Oxide fibers within intermetallic or oxide matrices are the top candidate systems for satisfying these conditions. Suitable fiber/matrix interface coatings are critical, but their development has suffered from extremely high per-pound costs and marginal thermochemical stability. CaF2 and LaPO4 have recently been suggested as coatings with excellent potential for both intermetallic and oxide matrices, although they have yet to be demonstrated on fibers or in composites. ATM, Inc. is ideally suited to exploit new, commercialized developments in chemical vapor deposition (CVD) to address both processing and cost issues. In Phase I, ATM will demonstrate established reagent chemistry, liquid source delivery, atmospheric pressure CVD, and continuous (multifilament) fiber coating technologies in preparing high quality CaF2 and LaPO4 coatings on aluminum oxide fibers. Coated fibers will be processed into TiAl matrix composites by the 3M metal matrix group and provided to Air Force researchers for evaluation in ceramic matrix composites. Microanalytical characterization by ATM and 3M will focus on coating uniformity, stoichiometry, morphology, crystallinity and reactivity, and failure mechanisms. Phase II will address process optimization for a selected coating, in conjunction with processing by a composite manufacturer. OPTION: None submitted.