ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2024 12 EVALUATING NEXT GEN METAL ALLOYS A new predictive tool for high-entropy alloy behavior was developed by a multidisciplinary research team from the DOE’s Pacific Northwest National Laboratory (PNNL), Richland, Wash., and North Carolina State University, Raleigh. The team combined atomic-scale experiments with theory to create a tool to predict how high-entropy alloys behave under high-temperature oxidative environments. The research offers a road map toward rapid design and testing cycles for oxidation-resistant complex metal alloys. Researchers studied the degradation of a high-entropy alloy with equal amounts of cobalt, chromium, iron, nickel, and manganese—CoCrFeNiMn, also called the Cantor alloy. They examined oxide formed on the Cantor alloy using a variety of advanced atomic-scale methods to understand how each element arranges itself in the alloy and the oxide. The team discovered that chromium and manganese tend to migrate quickly toward the surface and form stable chromium and manganese oxides. Subsequently, iron and cobalt diffuse through these oxides to form additional layers. By adding a small amount of aluminum, they discovered that aluminum oxide can act as a barrier for other elements migrating to form the oxide, thereby reducing the overall oxidation of the aluminum-containing Cantor alloy and increasing its resistance to degradation at high temperatures. A next step will be to introduce automated experimentation and integrate additive manufacturing methods, along with advanced artificial intelligence, to rapidly evaluate promising new alloys. pnnl.gov. ULTRATHIN CRYSTALS FOR ELECTRONICS Scientists from the University of California, Irvine, created a new method to make ultrathin crystals of the element bismuth—a process that may make the manufacturing of cheap flexible electronics an everyday reality. The newly developed bismuth sheets are only a few nanometers thick. Theorists previously predicted that bismuth contains special electronic states, allowing it to become magnetic when electricity flows through it—an essential property for quantum electronic EMERGING TECHNOLOGY devices based on the magnetic spin of electrons. Researcher Amy Wu likened the team’s new method to a tortilla press. To make the ultrathin sheets of bismuth, Wu explains, they had to squish bismuth between two hot plates. To make the sheets as flat as they are, they had to use molding plates that are perfectly smooth at the atomic level, meaning there are no microscopic divots or other imperfections on the surface. “We then made a kind of quesadilla or panini where the bismuth is the cheesy filling and the tortillas are the atomically flat surfaces,” says Wu. After a year of developing the thin crystals, the team says, they had no idea whether the resulting electrical properties would be something extraordinary. But when they cooled the device in the lab, they were amazed to observe quantum oscillations, which had never been previously seen in thin bismuth films. The researchers believe their method will generalize to other materials, such as tin, selenium, tellurium, and related alloys with low melting points. Next, the team wants to explore other ways in which compression and injection molding methods can be used to make the next computer chips for phones or tablets. uci.edu. Researchers at the University of Illinois UrbanaChampaign’s Grainger College of Engineering received a $3 million grant from the U.S. Army Corps of Engineers Construction Engineering Research Laboratory. The team aims to develop the foundational technology required to enable solid-state rechargeable lithium batteries. grainger.illinois.edu. BRIEF A new tool can predict how new high-entropy alloys, used in aerospace parts, will behave under hightemperature oxidative environments. Courtesy of Nathan Johnson/PNNL. Squeezing bismuth between atomically smooth molding plates made of hexagonal boron nitride results in thin crystals with electronic properties. Courtesy of Eli Krantz/Krantz NanoArt.
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