Ultra-high temperature ceramics (UHTCs) are a special class of materials with excellent mechanical properties and superior resistance to oxidation, corrosion, and ablation at high temperatures more than 2,000 degrees Fahrenheit. These characteristics make UHTC materials ideal for structural components in hypersonic jets, space vehicles such as satellites and reentry vehicles, commercial jets, and other advanced propulsion systems. The design of new UHTC materials with improved thermomechanical properties requires a detailed knowledge of the factors affecting their thermal and mechanical stabilities.
In a recent study, funded by the U.S. Air Force Office of Scientific Research (AFOSR), a research group led by Suneel Kodambaka, a UCLA assistant professor of materials science and engineering, used scanning tunneling microscopy (STM) at high temperatures to investigate the thermal stability of single-crystalline silicon carbide (SiC), a well-known UHTC material often mixed with other UHTC materials such as zirconium boride to make UHTC composites.
STM is a sophisticated tool capable of imaging surfaces with atomic resolution. The key aspect of this study was the use of STM at temperatures as high as 1,100 degree Celsius, or greater than 2,000 degrees Fahrenheit. With this technique, they were able to image the SiC surfaces with near-atomic resolution at these extremely hot temperatures, where the group observed the formation of layers of graphene, an ultra-thin material used in high-speed electronics. The research group’s study helps understand the graphitization process at the atomic scale. They also identified new pathways of surface decomposition and the formation of graphene.
These studies are expected to improve the understanding of the surface stability of ceramics such as SiC and SiC composites. For example, for commercial vehicles, such as automobiles and airplanes, these new materials could enable efficient operation at higher temperatures, meaning faster transport and lower fuel consumption.
The research group also includes lead author Yuya Murata, a UCLA post-doctoral scholar in materials science and engineering; and Ivan Petrov and Vania Petrova, from the Frederick-Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign.
Results of this work have been published as a Letter in the peer-reviewed journal Thin Solid Films. http://dx.doi.org/10.1016/j.tsf.2012.03.040