Date of Award
Doctor of Philosophy (PhD)
Demands for hypersonic aircraft are driving the development of ultra-high temperature structural materials. These aircraft, envisioned to sustain Mach 5+, are expected to experience continuous temperatures of 1200-1800°C on the aircraft surface and temperatures as high as 2800°C in combustion zones. Breakthroughs in the development of fiber based ceramic matrix composites (CMCs) are opening the door to a new class of high-tech UHT structures for aerospace applications. One limitation with current carbon fiber or silicon carbide fiber based CMC technology is the inherent problem of material oxidation, requiring new approaches for protective environmental barrier coatings (EBC) in extreme environments. This thesis focuses on the development and characterization of SiCN-HfO2 based ceramic composite EBC systems to be used as a protective layer for silicon carbide fiber based CMCs. The presented work covers three main architectures for protection (i) multilayer films, (ii) polymer-derived HfSiCNO, and (iii) composite SiCN-HfO2 infiltration. The scope of this thesis covers processing development, material characterization, and high temperature oxidation behavior of these three SiCN-HfO2 based systems. This work shows that the SiCN-HfO2 composite materials react upon oxidation to form HfSiO4, offering a stable EBC in streaming air and water vapor at 1600°C.
Terauds, Kalvis, "Processing, Structure and High Temperature Oxidation Properties of Polymer-Derived and Hafnium Oxide Based Ceramic Systems" (2014). Mechanical Engineering Graduate Theses & Dissertations. 81.