Monday, March 2, 2009 4:00 – 5:00 pm
Room 610, M&M Building
Dr. Kathleen Sevener
Mechanical Engineering Department
Valparaiso University, Valparaiso, IN
With the continuing interest in hypersonic flight, much work is focused on developing andcharacterizing ultra-high temperature ceramics (UHTCs) for leading edge applications andincorporating UHTCs into composites for hot structures. There is a lack of understanding of thetrue aerothermal effects on UHTC materials, which is required for optimization of UHTCcomposition. While means to explore such effects are in progress within the aerospacecommunity, parallel efforts to develop UHTC compositions with improved properties areunderway. This presentation will focus on work performed at AFRL to evaluate several HfB2-SiCUHTC compositions via isothermal anneals. Initial studies focused on the effect of compositionvariation. To establish a baseline on the materials, samples were subjected to furnace oxidationat 1500°C and 1600°C and the oxidation behavior was characterized via weight change,scanning electron microscopy, and energy dispersive spectroscopy. The baseline data werecompared to published data for similar compositions. Follow-on studies focused on the effect ofprocessing parameters for HfB2-20vol% SiC, the most promising candidate from the initialstudies. Milling time and consolidation method were varied to determine if the resultingmicrostructural changes would influence oxidation behavior. Results of these studies will bepresented and analyzed in the context of oxidation models under development at AFRL, andwith consideration to future applications of UHTCs on hypersonic vehicles.