A team of researchers led by Duke University has created a new class of materials that can survive extremely high temperatures and produce programmable plasmonic characteristics.
A technique called plasmonics essentially confines light energy within collections of vibrating electrons on a metallic surface. By interacting with the light coming in and making a strong electromagnetic field, devices can absorb, emit, or control certain frequencies across a large part of the electromagnetic spectrum.
The new materials can endure temperatures of over 7,000 degrees Fahrenheit, which is about the same as the temperatures found just a few hundred kilometers above the surface of the sun. They are tough enough to stir molten steel. When combined with their recently discovered plasmonic properties, the carbides could improve communication and temperature control in technologies like satellites and hypersonic aircraft.
The study was published online in the open access journal Nature Communications on October 11.
Arrigo Calzolari, a researcher at the Istituto Nanoscienze of the Consiglio Nazionale delle Ricerche in Modena, Italy, said: “The common metals used in plasmonics research, such as gold, silver, and copper, melt at relatively low temperatures and need protection from the elements.” Thus, they are ineligible for use in aerospace applications like satellites, rockets, and others. But because the new materials we are creating can produce plasmonic phenomena at extremely high temperatures, they open up a whole new working environment. ”
The capabilities originate from a kind of disordered ceramic known as “high-entropy” carbides, which Stefano Curtarolo, a professor of mechanical engineering and materials science at Duke, discovered in 2018. These high-entropy carbides dispense with the reliance on crystalline structures and bonds that hold conventional materials together and instead rely on a combination of numerous disordered components of varied sizes to improve stability. A stack of baseballs won’t stand by itself, but a stack of baseballs, shoes, bats, hats, and gloves could be able to support a baseball player who is taking a break.
Technically speaking, the initial set of high-entropy materials belonged to the class of carbides since they contained carbon and five different metallic elements. Since then, Curtarolo has won a $7.5 million grant through the Multidisciplinary University Research Initiative (MURI) competition of the US Department of Defense to create a set of AI-materials tools that can create comparable materials with customized features on demand.
Both these resources and the project Curtarolo was in charge of were known to Calzolari. He was also aware of the superior durability and visible spectrum plasmonic properties of tantalum carbide, a parent but simpler structure. However, the material can only be tuned within its natural range, which limits its applicability in practical applications. When Calzolari and Curtarolo put these two ideas together, they came to the conclusion that some high-entropy carbide recipes, especially those with tantalum, might have plasmonic properties that can be changed over a wide range.
They were proven correct a little more than six months later.
According to Curtarolo, Arrigo came to him to ensure that these carbide mixes would function and possess plasmonic features. We found that the recipe concepts actually have plasmonic qualities and that we can tune them by adjusting the recipes after subjecting them to the disorder models and calculations we’ve been building.
The simulations used by the researchers to produce the report reveal that 14 different high-entropy recipes exhibit plasmonic features in both the near-infrared and visible light spectrums, making them suitable for optical and telecommunication applications. They also worked with Douglas Wolfe, who is a professor of materials science and engineering at Penn State and the head of the department of metals, ceramics, and coating processing at the applied research laboratory. Together, they did experiments to see if their idea worked.
Wolfe was already acquainted with high-entropy carbides as a participant in the MURI project directed by Curtarolo. The group was able to immediately demonstrate the plasmonic properties of HfTa4C5 and prove that they corresponded well with their computational predictions because of the fact that they had a sample of one of the contested recipes.
The study lists numerous compositions and compares how well or poorly they perform across a range of frequency ranges. Researchers plan to keep coming up with new recipes and testing them on any device that is exposed to very high temperatures. These recipes could be used in antennas, controlling light and heat, and many other places.
According to Curtarolo, “These materials combine plasmonics, hardness, stability, and high temperatures into a single material.” Additionally, they can be customized for particular uses, which is not possible with ordinary materials because their natural features cannot be changed.
