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Hyunseok Oh
January 22, 2024

With NSF CAREER award, Hyunseok Oh will search for metal alloys that can withstand the cold

Written By: Jason Daley

Future technologies are going to be fast, energy efficient … and cold. Very cold. Liquid hydrogen, a potential game-changing fuel, needs to be stored at -423 degrees Fahrenheit; the most advanced superconducting materials need to be kept at -300 degrees or below. And temperatures on parts of the moon, where researchers hope to set up a base in the next decade, can dip below -200 degrees during the night.

The problem, however, is that most of the structural materials traditionally used in cryogenic conditions, like special formulations of stainless steel, are not rugged enough to survive these temperatures long-term, becoming brittle over time. That’s why Hyunseok Oh, an assistant professor of materials science and engineering at the University of Wisconsin-Madison, will use a National Science Foundation CAREER award to identify and investigate new metal alloys that are strong and cheap enough to enable the frozen future.

The solution may lie with complex concentrated alloys. In traditional metal alloys, a single element usually dominates, with a few percent of another element introduced to add strength, ductility or the other properties. Complex concentrated alloys, however, combine elements in roughly equal proportions, leading to whole new properties. One particular complex concentrated alloy, a nickel-chromium-cobalt combination, shows great tolerance for cryogenic applications.

However, cobalt, a type of transition metal, is problematic. “Cobalt is very expensive and involved with child labor. I want to replace cobalt with a more sustainable element like iron by changing the local chemical ordering,” says Oh. “But the major effects of cobalt have not been fully elucidated. I have some ideas for elemental combinations that don’t use cobalt.”

In his project, Oh plans to investigate the behavior of these alloys at cryogenic temperatures to understand what’s happening at the molecular level. Using these insights, he then plans to develop new alloys and implement new strategies for both strengthening and toughening materials without the addition of elements like cobalt. Using sophisticated high-pressure metallurgy techniques, Oh also hopes to increase the nitrogen percentage in the alloys beyond conventional limits, an addition he hypothesizes will also increase the strength of the alloys.

As part of the outreach portion of the project, he plans to teach high school teachers about sustainable metallurgy and recycling challenges of metals, an important part of decarbonizing the industrial supply chain.