Talks & Lectures
21 Apr 2017
Kidde 228

Mesoscopic 3D Tubular Graphenes

Prof. I-Wei Chen (University of Pennsylvania)

Covalently grown 3D graphenes such as foams and honeycombs are typically closed-cell structures with a characteristic length scale of the order of microns or more. In contrast, we have grown 3D graphenes [1-3] made of 5 nm tubes covalently bonded into a tetrahedrally connected open structure of various cell sizes. Such tubular graphene can be further nitrogen doped to endow outstanding redox activity while maintaining excellent electrical conductivity. The resultant 3D graphene with low density, high surface area, facile fluid permeability and variable hydrophilicity can serve as bipolar electrodes for supercapacitors and as feather-weight aerogels for load bearing and other energy/environmental/biomedical uses. In such applications, they exhibit unprecedented figures of merits in specific capacitance, modulus and bioactivity, with remarkable endurance. 1. H. Choi and I-W. Chen, "Fibrous Composites for Tissue Engineering," U.S. Patent 8,580,291 (2013). 2. “A New Tubular Graphene Form of a Tetrahedrally-Connected Cellular Structure,” Advanced Materials, 27, 5943 (2015). 3. “Nitrogen-doped Mesoporous Carbon of Extraordinary Capacitance for Electrochemical Energy Storage,” Science, 350, 1508 (2015).

Prof. I-Wei Chen is Skirkanich Professor of Materials Innovation. He is a pioneer and a foremost academic research leader in the broad field of structural and functional ceramics with nearly 100 publications alone in Journal of the American Ceramic Society. He has made seminal contributions in ceramic science, including establishing the mechanisms of nucleation and growth for martensitic transformations, the delineation of the constitutive equation of transformation plasticity and shape memory in zirconia ceramics, and the control and understanding of ceramic superplasticity, among others. More recently, Prof. Chen invented memory devices made of amorphous thin films with enhanced electron-electron and localized electron-phonon interactions, which undergo metal-insulator transitions upon voltage tuning of localization length. Another invention is short peptides (<20 amino acids) that undergo hydrophobic-hydrophilic transition at pH6.8-7.0, releasing drugs when reaching the mildly acidic extracellular environment of active cancer.  He discovered myriad electric field effects in energy ceramics mediated by fast anion diffusion, sluggish cation diffusion and non-equilibrium potential tied to electrode kinetics, causing massive phase reconfiguration and grain size transition. Prof. Chen’s papers have been cited over 10,000 times with an ISI h-index of 58. He holds 13 US patents on ceramics, drug carriers and thin film memory. Prof. Chen is the recipient of the Sosman Award, the Edward C. Henry Award, the Humboldt Prize, and the Ross Coffin Purdy Award. He is a Fellow of The American Ceramic Society.

 

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