AFRL Supports Research of Materials for Use in Extreme Environments Published Jan. 4, 2008 By Air Force Office of Scientific Research AFOSR Arlington, Va. -- AFRL supports leading-edge scientific research that precipitates new performance capabilities for materials used in extreme environments--materials having the potential to impact the future of hypersonics. AFRL-funded researchers are making significant headway in advancing this critical area of materials investigation. Recent successes include the discovery of novel compounds; the development of a new process known as melt texturing; and the observation of important microstructural phenomena that provide insight as to how materials interact, both with one another and with their operating environment. Researchers at the Naval Surface Warfare Center's ceramics laboratory are exploring a class of materials called cermets. Cermets are ceramic-metal composites that exhibit the high-temperature properties inherent to ceramic materials but compensate for the intrinsic brittleness of ceramics at room temperature. The researchers discovered a new compound while attempting to prepare a cermet containing tantalum as the metal component and zirconium diboride as the ceramic component. Both materials have very high melting points. The strength of the new compound is substantially greater than that of zirconium diboride, a material already demonstrating significant potential for ultra-high-temperature applications and excellent resistance to oxidation and corrosion. These characteristics suggest that the new material may be capable of withstanding thermal shock and, thus, have potential use in reentry vehicles and nozzle components. AFRL funds provided to the National Aeronautics and Space Administration (NASA) Glenn Research Center over the past 7 years--along with NASA's collaboration with the Frantsevich Institute for Problems of Materials Sciences (Kiev, Ukraine)--led to the development of "melt texturing." This new process creates highly ordered microstructures in ceramic composites, enabling their use in multifunctional aerospace applications. For instance, melt texturing facilitates the use of ceramic actuators throughout a variety of high-temperature structural applications in propulsion technology--especially for rockets and hypersonic aircraft, wherein extreme thermal environments pose a significant challenge to current materials. Melt-textured materials could also find use in electron emitter applications for the electric propulsion of satellites. AFRL's Materials and Engineering for Affordable New Systems (MEANS) program is a unique new medium for teaming colleagues from academia and industry in a way that permits them to tackle highly complex problems and derive fundamental physics-based models. The MEANS team is developing a mathematical model to describe the complicated mechanisms involved in the catastrophic failure of thermal barrier coatings (TBC) in turbine engines. The availability of this new model will permit engine designers not only to identify key material and structural parameters, but to probe the design space for improved TBCs. The team has already developed a new thermocycle test that will provide industrial colleagues a useful diagnostic technique for testing the efficacy of future coatings.