An International Space Station experiment has led to a new discovery in metallic glasses and liquids – a durable, scratch- and corrosion-resistant material that is often stronger than steel and can be used in a variety of items, from phone cases to electrical transformers to lubricant-free gears for Moon rovers.
Metals and glasses are seemingly very different – glasses are generally transparent and fragile, while metals are opaque and extremely strong. However, metals can form glasses under the right conditions.
Recently, NASA’s Space Life and Physical Sciences Research and Applications division in the Human Exploration and Operations Mission Directorate funded experiments on the space station to better understand how metallic glass is formed, how it could be used in space and how it could make life easier on Earth. This experiment is among the space station science operations managed by Marshall Space Flight Center.
Ken Kelton, a physics professor at Washington University in St. Louis, and his colleagues oversaw the experiments and found that metallic glass characteristics can be determined while the metal is still molten liquid. The liquid’s thickness can indicate whether a glass will form, what kind of glass will form as well as some of its properties. This is a new development in metallic glass research and liquids in general.
“We have uncovered something that was totally unknown and has no current quantitative explanation,” Kelton said. “The work does show that there is a fundamental connection between the liquid structure and the ways in which atoms move which determines its viscosity, or thickness. This is a very important fundamental and new point about liquids.”
Kelton and his colleagues have been working to determine what metals turn into glass, the temperature at which the transformation happens, what properties the glass will have and what are practical uses for it.
Many physicists thought the answers to those questions could be found by observing what occurs at the temperature at which the metal transitions to a glass as it cools down. The Kelton team’s discovery shows this information can be determined before that. They also found that temperature does not affect electrical resistance at these temperatures.
Atoms move faster when they’re heated, so an electron stream trying to get through a heated liquid or solid has a hard time because it keeps running into rapidly moving atoms. These collisions and impediments are what cause electrical resistance. The higher the temperature, the more resistance there is.
Kelton and his team found that when some metal alloys are heated and become liquids, the electrical resistance does not change as much as the temperature increases, and the electron stream can still move through them fairly easily.
The team was surprised to learn that above certain temperatures, the electrical resistance of these metal liquids does not change at all. This gives physicists different temperature regimes in which to work and a whole new set of phenomena to explore.
“By understanding more about how metallic glasses form, we open the door a bit wider to the invention of new metallic glasses for novel applications,” said Michael SanSoucie, NASA’s Biological and Physical Science’s lead scientist at Marshall.
Editor’s note: NiCarla Friend, an ASRC Federal/Analytical Services employee, supports the Office of Strategic Analysis and Communications.