Central OC Times

Researchers at the University of California, Irvine, along with international collaborators, have achieved a breakthrough in understanding polycrystalline materials by observing grain rotation at an atomic scale. This research could lead to advancements in electronics, aerospace, and automotive technologies.

The team used advanced microscopy tools at UC Irvine's Materials Research Institute to heat platinum nanocrystalline thin films and observe grain rotation mechanisms in detail. Their findings were published in Science.

Utilizing techniques like four-dimensional scanning transmission electron microscopy (4D-STEM) and high-angle annular dark-field STEM, the researchers developed a machine learning algorithm to interpret complex datasets. This allowed them to directly view atomic processes, focusing on disconnections at grain boundaries.

"Scientists have speculated and theorized on phenomena occurring at the boundaries of crystalline grains for decades," said Xiaoqing Pan, lead author and Distinguished Professor of materials science and engineering at UC Irvine. The study found that grain rotation occurs through disconnections—line defects with step and dislocation characteristics—along grain boundaries. This discovery enhances the understanding of microstructural evolution in nanocrystalline materials.

The research also identified a statistical correlation between grain rotation and growth or shrinkage due to shear-coupled boundary migration driven by disconnection motion. "Our results provide unequivocal, quantitative and predictive evidence of the mechanism by which grains rotate in polycrystals on an atomic scale," said Pan.

Pan's collaborators included researchers from UC Irvine, the University of Hong Kong, Colombia National University, Karlsruhe Institute of Technology in Germany, University of Oklahoma, and City University of Hong Kong. The study received support from the National Science Foundation’s Materials Research Science and Engineering Centers program, U.S. Army Research Office, and Hong Kong Research Grants Council.

UC Irvine is actively involved in initiatives like the Brilliant Future campaign aimed at raising awareness and support for its academic programs.