8 ADVANCED MATERIALS & PROCESSES | MARCH 2026 X-RAYS EXAMINE BREATHING BATTERIES Researchers from The University of Texas at Austin, Northeastern University, Stanford University, and Argonne Na- tional Laboratory discovered that every cycle of charge and discharge causes batteries to expand and contract, similar to human breathing. This action causes battery components to warp a little bit each time, putting strain on the battery and weakening it. This phenomenon, known as chemomechanical degradation, leads to reduced performance and lifespan. One of the key discoveries was the identification of strain cascades, a chain reaction in which stress builds up in one part of the electrode and spreads to neighboring regions. The unique nature and unpredictable movements of the hundreds of thousands of particles in batteries contribute to this strain. By understanding how strain develops TESTING | CHARACTERIZATION SUPERSONIC TESTING DEFIES HALL-PETCH EFFECT Researchers at Cornell University, Ithaca, N.Y., found that when deformed at extreme speeds, metals with very small grains become softer rather than stronger. The discovery is contrary to the so-called Hall-Petch effect, which for more than 70 years has held that smaller grains mean stronger metals. “We wanted to test the limits of that rule and see whether grain boundary strengthening still holds when metals are pushed into truly extreme deformation rates,” said assistant professor Mostafa Hassani. To understand how metals behave under ultra-fast deformation, Hassani’s group used laser-induced microprojectile impact testing, which targets metals with microscopic particles at velocities that exceed the speed of sound. The team prepared copper samples with grain sizes of 1 to 100 µm, all within the range where the Hall-Petch effect normally applies. In impact tests, larger- grained samples consistently exhibited shallower indentations and dissipated more kinetic energy, clear signs of greater hardness in the copper. The scientists attribute the results to how dislocations move when a metal deforms. At ordinary strain rates, grain boundaries and other crystal defects strengthen a metal by blocking the motion of these dislocations. But at ultra-high strain rates, dislocations accelerate fast enough to start interacting with the material’s vibrating atoms. This interaction, called dislocation-phonon drag, can significantly strengthen the metal. The team is now testing other metals and alloys, and the same trend appears. At extremely high deformation rates, the strengthening effect from dislocation-phonon drag can be greatly reduced and even eliminated in smaller grains. cornell.edu. Left: SEM images of the Cu microstructure with average grain size of (a) 1 µm and (b) 100 µm. Right: EBSD inverse pole figures for Cu with (c) 1 µm and (d) 100 µm grain sizes. Courtesy of Phys. Rev. Lett., 2026, doi.org/10.1103/yp9h-sr2m. Researchers at the DOE’s Oak Ridge National Laboratory, Tenn., partnered with the University of Tennessee to develop a device that enables real-time insight into electric grid behavior. The Universal GridEdge Analyzer records tiny changes in electrical voltage and current as waveforms, then immediately streams the data to centralized servers. ornl.gov. Leica Microsystems, Germany, was awarded the Silver Medal by EcoVadis, a provider of global business sustainability ratings. The honor puts Leica among the top 15% of rated businesses worldwide and affirms the company’s commitment to environmental stewardship. leica-microsystems.com. BRIEFS From left: Guannan Qian and Tianxio Sun investigate battery performance in the lab. Courtesy of University of Texas at Austin. (a) (b) (c) (d)
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