Tyranno SA3 fiber-ZrB2 composites. Part I: Microstructure and densification

ZrB 2 -ceramics containing 3rd generation SiC short fibers were hot pressed with different kinds of sinter- ing agents in order to obtain an increase of fracture toughness. Several sintering temperatures were explored keeping fixed the amount of fiber to define the most suitable additive able to fully densify ZrB 2 with minimal fiber deterioration. In Part I of this article, the microstructure of the composites was examined through scanning electron microscope, to study the distribution of the secondary phases, and transmission electron microscope, to analyse the microstructure at nanoscale level, with particular attention to the evolution of the fiber morphology and to the study of the interfaces with the matrix in high resolution mode. For the first time the chemical stability of Tyranno SA3 fibers towards different sintering additives and ZrB 2 is presented. Comparison with Hi-Nicalon fiber is also discussed.