报告题目：Rethink Wood

——Its Unconventional Applications in Advanced Materials Design and Energy Systems

报告人:                       Prof. Teng Li

Associate Professor, Department of Mechanical Engineering

Keystone Professor, Clark School of Engineering  

Maryland NanoCenter

University of Maryland Energy Research Center

University of Maryland, College Park, Maryland, USA

时间：2015年7月15日(周三)  09: 00—11: 30

地点：中国科学院力学研究所主楼334会议室

报告摘要：

There exists surging societal needs for products made from renewable and sustainable resources that are biodegradable, carbon neutral and non-petroleum based. Wood cellulose fibers, the major components of paper, are obtained from plants and represent one of the most abundant and renewable materials on earth. Wood cellulose fibers have an intrinsically hierarchical structure, which holds promises to enable an array of highly desirable properties and thus could enable unconventional applications beyond their traditional use. In this talk, I will show case two unconventional applications of wood cellulose fibers: (1) An anomalous scaling law of strength and toughness of cellulose nanopaper. The quest for both strength and toughness is perpetual in advanced material design; unfortunately, these two mechanical properties are generally mutually exclusive. A general mechanism to address the conflict between strength and toughness still remains elusive. We report a first-of-its-kind study of the dependence of strength and toughness of cellulose nanopaper on the size of the constituent cellulose fibers. Surprisingly, we find that both the strength and toughness of cellulose nanopaper increase simultaneously (40 and 130 times, respectively) as the size of the constituent cellulose fibers decreases (from a mean diameter of 27 μm to 11 nm), revealing an anomalous but highly desirable scaling law of the mechanical properties of cellulose nanopaper: the smaller, the stronger and the tougher.  (2) Wood-based sodium ion battery for grid-scale energy storage. Advanced energy storage technology is a crucial component in integrating renewable energy sources, whose success holds promise to revolutionize facets of our daily life through high performance batteries for personal devices and electric cars. Development of next-generation high performance batteries relies on the new choice of electrode materials and structures. We demonstrate tin film anodes coated on a natural wood nanofiber can successfully accommodate the huge volume change during charging/discharging cycling without fracture and enable fast ion transport, offering a potential solution to sodium-ion batteries for low-cost and green grid-scale energy storage.

报告人简介：

Teng Li is currently an Associate Professor of Mechanical Engineering and the Keystone Professor in the Clark School of Engineering at the University of Maryland, College Park, US. He is also an affiliated faculty of Maryland NanoCenter and University of Maryland Energy Research Center. Before joining the faculty of the University of Maryland, he received his Ph.D. degree in Engineering Science from Harvard University in 2006, M.A. degree in Materials Science from Princeton University in 2003, Ph.D. (2001) and B.S. (1996) degrees in Engineering Mechanics from Tsinghua University. His research interests include mechanics of flexible electronics and nanoelectronics, mechanics of low dimensional carbon nanomaterials, mechanics of biomaterials, and mechanics of energy systems. Among his awards includes US National Committee of Theoretical and Applied Mechanics Fellowship in 2012, E. Robert Kent Outstanding Teaching Award in 2012, and RASA Research Award in 2014, Ralph E. Powe Jr. Faculty Award in 2007. He has been a member of the Technical Committee of Integrated Structures in ASME Applied Mechanics Division since 2006 and served as the Chair of the Committee during 2008-2012. He currently serves as the Associate Editor of Extreme Mechanics Letters and a member of the Editorial Board of International Journal of Computational Materials Science and Engineering.  He is the co-founder (with Zhigang Suo) of iMechanica.org, the world’s largest online community of mechanics with 70,000+ registered users as of July 2015.

报告联系人：沈楠  (office@lnm.imech.ac.cn 82543935)