Testing and Modeling Ultra-High Temperature Ceramic (UHTC) Materials For Hypersonic Flight.

摘要

This project focused on zirconium diboride and hafnium diboride ultra-high temperature ceramics in two main research areas: i) their thermal and electrical transport properties; and ii) their oxidation and volatilization behavior in simulated re-entry environments. The first area involved experimental studies of the thermal and electrical properties as a function of temperature, and the analysis of these results in terms of effective conductivity and Wiedemann-Franz models. Thermal diffusivity was measured using a photothermal radiometry technique, and the electrical resistivity and Hall coefficient were measured using a van der Pauw geometry. The second area involved experiments under simulated re-entry heating conditions at the 1.2 MW Plasmatron facility of the von Karman Institute for Fluid Dynamics in Rhode- Saint-Genese, Belgium. Zirconium diboride materials were tested over a range of surface temperatures exceeding 2000 C. A temperature-jump phenomenon was observed at threshold heating levels, at which the surface temperature spontaneously increased by hundreds of degrees under constant free-stream test conditions. This temperature jump is thought to be related to an abrupt transition in surface chemistry at the gas-surface interface. Both areas of research contribute to the continuing development of diboride-based materials for leading-edge applications on future hypersonic flight vehicles.