Processing and sintering of fiber-containing UHTCs

Ultra high temperature ceramics (UHTC) include borides and carbides of early transition metals and are presently considered a class of promising materials for several applications, the most appealing ones being in the aerospace and energy sectors. Crucial issues for application in severe environment is the improvement of fracture toughness and thermal shock resistance. Incorporation of SiC or C fibers in UHTC matrices is currently adopted to overcome these problems and effects on densification, microstructure and thermo-mechanical properties are studied. In this talk, processing and sintering are first shown for short SiC of C fibers incorporation, considering different kinds of commercial products and different starting compositions. On the basis of fundamental studies on boride/fiber interaction, the best systems are selected for subsequent processing of continuous SiC or C fibers - ZrB2 composites. Reactivity at the fiber/matrix interface is one of the most critical issues for this kind of composites, either in case of short or long fiber use due to high temperatures involved in the sintering stage. Preliminary characterization and oxidation studies are shown.