In-Situ Nanomechanics of Crystalline Nanowires
Location: EB1 Room 1011
Friday, November 22nd 2013 - 11:00 am
Recent advance in nanotechnology has brought forth a host of nanostructures, such as nanoparticles, nanowires, nanotubes and graphene that exhibit ultrahigh strength (e.g., sample-wide stress > 1/10 of their ideal strengths). Such nanostructures are not only an ideal platform to study fundamental mechanics, but also important building blocks for a broad spectrum of nanotechnology applications. In this talk, I will present in-situ scanning and transmission electron microscopy (SEM/TEM) mechanical testing of crystalline nanowires. I will focus on two types of nanowires, semiconductor and metallic nanowires with Si and Ag as examples, respectively. Both types of nanowires exhibit strong size dependent elastic properties, fracture or yield strength. For Si nanowires, we found size dependent brittle to ductile transition. For Ag nanowires, we found the yielding is due to surface dislocation nucleation and the strain hardening is due to the interaction of dislocation and the pre-existing coherent internal interfaces (e.g., twin boundaries parallel to the nanowire axial direction). I will also discuss recently observed time dependent mechanical behaviors of these nanowires. I will conclude my talk with an application that harnesses the excellent mechanical properties of nanostructures, more specifically, nanowire-enabled stretchable electronics and sensors.
Yong Zhu received his B.S. degree in Mechanics and Mechanical Engineering from the University of Science and Technology of China, China (1999), and his M.S. (2001) and Ph.D. (2005) degrees in Mechanical Engineering from Northwestern University. After a postdoctoral fellow at the University of Texas at Austin, he joined the Department of Mechanical and Aerospace Engineering at North Carolina State University in 2007, where he is currently an Associate Professor. Dr. Zhu's research interests lie at the interface between solid mechanics and micro/nano-technology, including mechanical properties and multiphysical coupling of nanostructures, micro/nano-electromechanical systems, flexible/stretchable devices for healthcare applications, and adhesion/friction of nanostructures. He has received several awards including Best Poster Award in the Gordon Research Conference on Thin Film & Small Scale Mechanical Behavior (2006), Sigma Xi Faculty Research Award (2012) and Society of Experimental Mechanics Young Investigator Award (2013).