This Spartan engineer is probing materials known as thermoelectrics that help power space exploration
Michigan State University’s Alexandra Zevalkink always knew she wanted to be an engineer, but she didn’t decide which subfield to pursue until she saw a demonstration of what’s known as a Peltier cooler.
“It’s this chunk of material that can move heat around to make one side cooler, but there are no moving parts. Everything’s happening internally, inside the material,” says Zevalkink, an assistant professor in the Chemical Engineering and Materials Science Department in the College of Engineering.
“I remember thinking, ‘What’s going on inside that chunk of material?’ I still love thinking about that,” she says.
Now, she’ll be thinking about new materials with the support of a 2021 National Science Foundation CAREER award. Specifically, she and her team are researching compounds that are useful as thermoelectric materials that turn heat differences into electrical power. These materials are already at work in the real world, notably in NASA’s Mars Curiosity Rover and other space exploration missions. Zevalkink and her colleagues want to know how these materials work so researchers can design even more efficient versions.
This is tricky for a couple reasons. First, former physics students might remember that a material that conducts electricity also conducts heat.
“But, for a thermoelectric, you need something that conducts electricity and is a really bad conductor for heat,” Zevalkink says, so thermoelectrics often rely on complicated crystal structures that resist heat flow but not electricity.
Secondly, even though researchers know that a material’s crystal structure is important, they don’t know how important compared to what the crystal is made of. That is, how important are a material’s atomic ingredients versus how these atoms are put together?
So Zevalkink and her team are focusing on what are known as Zintl compounds, which have attractive thermoelectric properties. Zevalkink is using different synthesis approaches to trick Zintl compounds into forming different crystal structures using the same ingredients.
“For comparison, think of diamond and graphite,” Zevalkink said. “They have very different crystal structures, but they’re both made of carbon.” Her team’s Zintl compounds, however, have much more complicated recipes, for example, involving a mixture of calcium, magnesium and antimony.
With the CAREER award, Zevalkink and her team can more thoroughly investigate the connection between a material’s composition, structure and its performance, but that’s not all. She and her students will have funding to explore new ways of teaching materials science, taking advantage of new tech available at the MSU Libraries and Abrams Planetarium. The grant will also facilitate new research collaborations on campus.
“The fact that MSU is such a big university means that there are so many faculty to collaborate with,” Zevalkink says. For example, she’ll be teaming up with Susannah Dorfman in the Department of Earth and Environmental Sciences to squeeze Zintl compounds between two diamonds. The pressure will force the compounds’ atoms into different arrangements, some of which have never been made before.
Which is par for the course in the lab whose leader who has spent her career thinking about what goes on inside materials. “Most of the things we work on, people have never heard of before,” Zevalkink says. “Because they’re completely new.”