An expert in electron microscopy, Voyles used a powerful, state-of-the-art scanning transmission electron microscope at UW-Madison as his window into this nanometer-scale atomic structure. The microscope can generate an electron probe beam two nanometers in diameterthe ideal size for examining atoms on a length scale of one to three nanometers. "And that, fundamentally, is what makes the experiments work and gives us access to this information that's otherwise very difficult to obtain," he says. "We can match our experimental probe in size right to the size of what we want to measure."
Voyles and his team coupled the experimental data from the microscope with state-of-the-art computational methods to conduct simulations that accurately reflect the experiments. "It's the combination of those two things that gives us this new insight," he says. "We can look at the results and abstract general principles about rotational symmetry and nanoscale clustering."
There were several clues in the properties of some metallic glasses that these competing geometric structures might exist. Those arise from the interrelationships of structure, processing and properties, says Voyles. "If we understand how the structure controls, for example, glass-forming ability or the ability to change shape on bending or pulling, and we understand how different elements participate in these different kinds of structures, that gives us a handle on controlling properties by adjusting the composition or adjusting the rate at which the material was cooled or heated to change the structure in some useful way," he says.
One of the unique characteristics of glasses is their abili
|Contact: Paul Voyles|
University of Wisconsin-Madison