Electron microscope image of carbide pillar carved from a single crystal with focused ion beams. Micrometer-scale image from Lawrence Berkeley National Laboratory.
Traditionally, ceramics are known for their brittleness, causing them to shatter on impact. However, transition-metal carbides might prove tough enough, thanks to the ionic, covalent and metallic bonds that are present in the material.
"Ultra-high-temperature ceramics are highly desirable in aerospace and other industries where durable structural components are required to maintain their strength and stability at elevated temperatures,” said UCLA professor Suneel Kodambaka. “Transition-metal carbides are attractive for these applications because they are very hard and do not melt until they reach very high temperatures.”
Kodambaka isn’t kidding. While the hardness of steel may withstand pressures of a gigapascal or two, transition-metal carbides can take up to a whopping 20 gigapascals. And they won’t melt until they reach over 6,300ºF (3500ºC) — versus steel’s melting point around 2,700ºF (1500ºC).
Within a transmission electron microscope, researchers performed compression tests of single-transition metal carbide crystals. The two materials tested were zirconium carbide and tantalum carbide.
Matthew Chin , of the UCLA Newsroom, reports that the crystals deformed under compression without cracking at room temperature. Therefore, the size and orientation of the crystals impacted the material’s mechanical properties. The results suggest that ductile ceramics could be created by transition metal carbides and their transition-metal nitride cousins, which have similar properties. However, additional research is needed to understand the atomic mechanism responsible.
“Our studies showed how their crystals slip, an atomic-scale process that controls malleability, at room temperature. These results could help engineer the microstructures of ceramic components to tailor their mechanical properties,” said Kodambaka.
With the right ductile mechanical properties, the researchers note that the ceramics could improve the performance of parts in aircraft engines, turbines and nuclear power plants. Additionally, micro and nano electromechanical systems, such as radiation-resistant foils in solar sails, could also be improved by the ceramics.
To learn more on these findings, read this science paper .