Prof Yong Lak Joo, Professor
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Controlling the assembly of 2D materials at nanoscale has a significant effect on the performance of energy storage and coating materials. Employing circumferentially uniform air flow through the sheath layer of the concentric coaxial nozzles, gas-assisted electrospinning and air-controlled electrospray utilize both high electric field and controlled air flow which can offer i) enhanced stretching of fluid jet and drops, and thus much higher throughput than conventional electrospinning/spray processes, and ii) better control of folding and stacking of 2D nanomaterials such as graphene oxide (GO) and graphene in a jet or droplet even at high loadings. The ability to tailor the folding of GO sheets in a polymer jet was demonstrated by varying air flow rates in gas-assisted electrospinning. The fiber cross section SEM and HRTEM images reveal that micrometer graphene is heavily folded into nanometer fibers during electrospinning, while silicon nanoparticles (Si NPs) are incorporated into the folds with nanospace in between. The interconnected graphene network ensures the excellent conductivity, and the nanospace between Si NPs and folded graphene provides the space needed for volume expansion of Si particles. The direct deposit approach has been extended to the air-controlled electrospray process to create a compact stacking of graphene layers. Our results reveal that graphene layers can be completely flattened and stacked on top of a conformal surface by applying high speed air to electrically charged droplets of graphene solution. We demonstrate that the resulting coating of graphene sheets on a metal electrode can offer a great protection from corrosion in various electrolysis and electrochemical applications.
講演者の経歴 (Yong Lak Joo)
Yong Lak Joo is the BP Amoco/H. Laurance Fuller Professor in the School of Chemical & Biomolecular Engineering at Cornell University. He received his B.S. degree at Seoul National University in Korea in 1989, and received his Ph.D. in Chemical Engineering at Stanford University in 1993. From 1993 and 1999, he was a senior research engineer at Hanwha Chemical Corporation in Korea. Prior to joining Cornell in 2001, Yong Lak Joo did two years of a postdoctoral research in the Department of Chemical Engineering at MIT.
His research focuses on the integration of molecular details into a macroscopic level in nanomaterials processing. In particular, he has recently laid the new foundation for experimental and theoretical studies on advanced, scalable nano-manufacturing processes based on the flow instability such as gas-assisted electrospinning and air-controlled electrospray. He is a fellow of American Institute of Chemical Engineers (AIChE). He received a 3M Faculty Award and is a recipient of a National Science Foundation CAREER Award and a DuPont Young Professor Award. He also received an Excellence in Teaching Award in College of Engineering, Cornell University.