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Nanowires highly ‘anelastic,’ research shows

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Zinc oxide nanowires return to shape slowly after being bent. That property, called anelasticity, suggests that nanowires might be good in applications that require absorption of shocks or vibrations. Image Credit: Brown University Zhu lab / NC State
Researchers from Brown University and North Carolina State University have found that nanowires made of zinc oxide are highly anelastic, meaning they return to shape slowly after being bent, rather that snapping right back. The findings add one more to the growing list of interesting properties found in nanoscale wires, tiny strands thousands of times thinner than a human hair. “What’s surprising here is the magnitude of the effect,” said Huajian Gao, the Walter H. Annenberg Professor of Engineering and a coauthor of a new paper describing the research. “Anelasticity is present but negligible in many macroscale materials, but becomes prominent at the nanoscale. We show an anelastic effect in nanowires that is four orders of magnitude larger than what is observed in even the most anelastic bulk materials.”
The findings are significant in part because anelastic materials are good absorbers of kinetic energy. These results suggest that nanowires could be useful in damping shocks and vibrations in a wide variety of applications.
“During the last decade, zinc oxide nanowire has been recognized as one of the most important nanomaterials with a broad range of applications such as mechanical energy harvesting, solar cells, sensors and actuators,” Gao said. “Our discovery of giant anelasticity and high energy dissipation in zinc oxide nanowires adds a new dimension to their functionality.” The experiments for the study were done in the lab of Yong Zhu, an associate professor of mechanical and aerospace engineering at NC State. Zhu and his colleagues used a delicate apparatus to bend nanowires under a scanning electron microscope. The work showed that, after the bending strain was released, the wires returned to about 80 percent of their original shape quickly. But they recovered the rest of their original shape much more slowly, over the course of up to 20 or 30 minutes. That is a far more prominent anelastic effect than is common at the macroscale.