Abstract: Recent advance in nanotechnology has brought forth a spectrum of nanomaterials that exhibit ultrahigh mechanical strength. Measuring their mechanical properties and understanding their deformation mechanisms is of important relevance for many of their device applications. To address this need innovative experimental methods have been developed, among which a promising one is based upon microelectromechanical systems (MEMS). In this talk, I will present an innovative MEMS-based method for in-situ scanning and transmission electron microscopy (SEM/TEM) mechanical testing of 1D nanomaterials. In addition, I will discuss two recent nanomechanics studies that reveal important roles of defects in mechanics of crystalline nanowires (NWs) using. For metal NWs containing internal twin boundaries along the NW length, we observed a time-dependent and fully reversible plastic behavior, and concluded that vacancies reduce dislocation nucleation barrier, facilitating stress relaxation, while the twin boundaries and their intrinsic stress field promote retraction of partial dislocations, resulting in full strain recovery. For single-crystalline nanowires containing point defects, we discovered giant anelastic behaviour that is up to four orders of magnitude larger than the largest observed in bulk materials, with a timescale on the order of minutes. This behavior was attributed to point defect diffusion under a high strain gradient and short diffusion distance. This talk will conclude with stretchable/wearable electronics, sensors and actuators based on such nanomaterials especially silver NWs.
Bio: Dr. Yong Zhu received his B.S. degree in Mechanics and Mechanical Engineering from the University of Science and Technology of China in 1999, and his M.S. and Ph.D. degrees in Mechanical Engineering from Northwestern University in 2001 and 2005, respectively. He was a postdoctoral fellow at the University of Texas at Austin before he joined NCSU in 2007, where he is currently an Associate Professor in Department of Mechanical and Aerospace Engineering (affiliated in Materials Science and Engineering and Biomedical Engineering). Zhu’s group conducts research at the intersection of solid mechanics and micro/nano-technology, including nanomechanics, micro/nano- electromechanical systems, and stretchable/wearable devices. He has received several awards including Sigma Xi Faculty Research Award, College of Engineering Alcoa Foundation Research Achievement Award, Society of Experimental Mechanics Young Investigator Lecture Award, and ASME Sia Nemat-Nasser Early Career Award. He is a University Faculty Scholar at NCSU.
Date(s) - Apr 11, 2017
2:30 pm - 3:30 pm