Atomic changes in metals could lead to longer-lasting batteries

Researchers at Pacific Northwest National Laboratory (PNNL) are studying the atomic-level changes in metals undergoing shear deformation in order to deduce the effects of physical forces on these materials, according to a report by Phys.org published on Monday.

The work could lead to many new and improved applications such as longer-lasting batteries and lighter vehicles.

Understanding metals on an atomic level

"If we understand what happens to metals on an atomic level during shear deformation, we can use that knowledge to improve countless other applications where metals experience those same forces—from improving battery life to designing metals with specific properties, like lighter, stronger alloys for more efficient vehicles," said Chongmin Wang, PNNL Laboratory fellow and leader of the research team behind these new experiments.

Physical forces are the same regardless of where they are applied meaning that the forces that are applied during metals manufacturing to create alloys can also damage structures inside batteries. However, shear deformation can also alter the microstructure of metals in ways that can actually improve the material making them stronger, lighter, and more flexible. But how exactly that occurs remains a mystery.

"If you were to snap a picture of a track runner at the start and end of their run, you might think they didn't move at all," explained Arun Devaraj, PNNL materials scientist. "But if you film the runner while they are going around the track, you'll know just how far they traveled. It's the same here. If we understand exactly what happens to metals on the atomic level during shear deformation, we could apply that knowledge strategically to design materials with specific properties."

To come to this understanding, researchers used a specialized probe inside a transmission electron microscope at PNNL to record how individual rows of atoms within metals moved during shear deformation. They began their process with gold because it is easiest to visualize on an atomic level.

Crystals of gold

During the metal’s transformation, they witnessed crystals of gold dividing into smaller grains and found that natural defects in the arrangement of the metal’s atoms changed how shear deformation moved them. 

"The defects in crystal, grain size and microstructure in a metal can affect the metal's characteristics, like strength and toughness. That's why it's important to understand how shear deformation moves metal atoms around and affects the overall microstructure of the metal," said Shuang Li, PNNL postdoc and the first author on three studies sharing these results.

The next metal to be examined was copper. In this material, shear deformation created nanotwins, structural features that make metals stronger. When further blended with niobium, the results showcased that shear deformation affected atoms differently inside the copper and niobium phases of the metal mixture. The insights deduced from this process can be used to manufacture alloys with specific properties.

The data gathered from these experiments can now be further directly translated and applied wherever metals experience similar physical forces resulting in longer lasting batteries, lighter alloys for more efficient vehicles, and the custom design of next-generation metals.