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My research interests are surface modifications of metals by electrochemical reactions to attain advanced functionalities. Due to beneficial combination of mechanical strength and ductility, metals and metal alloys are widely used in many industries ranging from home appliances and infra structures to marine, petrochemical and biomedical. Therefore, the extensive and varied applicability of metals often require exposure to various environment including liquids, ice, seawater, hydrocarbons and physiological solutions. My research focuses on understanding phenomena at metal-environment interfaces and design of the metal surfaces to advance their functionalities.

To establish rational strategy to control the interfacial behavior and improve their functionalities, controls over surface structure and surface chemistry are critical. Electrochemical methods enable tuning surface structures from micrometer to nanometer scale as well as chemical composition. My first research goal is to attain relationship between electrochemical variables (i.e. potential, current density, and electrolyte) and metal surface characteristics. Second step is to investigate interactions between modified metal surfaces and exposed environment such as wettability, phase change (i.e. condensation and icing), fouling, and corrosion. Based upon the knowledge I would acquire from my first and second goals, design strategy to improve functionalities can ultimately be suggested. I believe that fundamental studies on metal surface engineering can also be applied to energy related fields such as electrode designs in battery and fuel cells.

PhD Dissertation: Modification of Metal Surfaces for Advanced Functionalities

Research Experiences:

My academic trainings have been focused on surface/interface engineering of metals and polymers to improve performance of applications. During my Ph.D. study in Georgia Tech, I have mainly focused on surface modification of metals by electrochemical reactions. I have developed new strategies to control topography of metals and studied effect of structures in multi-length scale on wettability, corrosion resistance, and interaction with bio-organisms such as protein, bacteria and cells. My M.S. study in Seoul National University in South Korea focused on engineering nano-morphology of polymer blend thin films in organic solar cells. For this study, I utilized small angle neutron scattering to scrutinize the phase separated morphology and correlated the morphological information to performance of organic solar cells. In addition, I have research experience in developing remote control fuel cell airplane during my internship in Korea Institute of Science and Technology. Bevy with diverse research experience ranging from surface/interface engineering to device/system development, I can be a mentor to students performing diverse research projects.

Teaching Interests:

During my teaching carrier development, I enjoyed serving as a teaching assistant in “Thermodynamics” and “Senior Design” at Georgia Tech. Thermodynamics is one of the core course in chemical engineering and I was fortunate to teach recitation class every week. During recitation sessions, I learned how to clarify concepts step by step to help students’ understanding. Senior design requires students to tackle real industrial problems with their chemical engineering knowledge. As a TA, I needed to be prepared to guide their problems with multiple aspects such as thermodynamic feasibility, kinetical concerns, and process designs and economics. These experiences made me confident in teaching chemical engineering stem courses. Also, from my research experience, I am confident in teaching specific courses “Electrochemistry”, “Surface and Interface Engineering”, and “Scattering Theory and Applications”. Also, I have experience mentoring undergraduate students, and helped them to develop and trim their creative thought processes. Based on these teaching and mentoring experiences, I learned PI’s roles how to help students to overcome obstacles and encourage them to proceed.

Future Direction:

I would like to continue my academic career on modification of metal surfaces and understanding interfacial behaviors. Particularly, I am interested in surface modifications of metals and metal alloys used in chemical and petrochemical industry such as heat exchangers and hydrocarbon cracking reactors. Surface characteristics play a pivotal role in interfacial behavior and/or reactions at metal surfaces. Therefore, proper control of metal surfaces with mechanical stability can improve performance of their applications. For example, surface wettability of heat exchanger has much to do with condensation rate and mobility of condensate at the metal surface, which can largely influence on heat transfer efficiency. Like this, I would like to focus on understanding role of surface characteristics on interfacial behavior and developing functional metal surfaces that have practical relevance. Besides, I have interests in predicting interfacial behavior depending on surface characteristics. In order to achieve this goal, I would like to collaborate with researchers who have expertise in simulations and modeling, which I think will shed light on in-depth understanding on interfacial phenomena and future pathways on my research.

Selected Publications:

(1) W. T. Choi, K. Oh, P. M. Singh, V. Breedveld, and D. W. Hess, Hydrophobicity and improved localized corrosion resistance of grain boundary etched stainless steel in chloride-containing environment, Journal of The Electrochemical Society, 164, C61-C65 (2017)

(2) W. T. Choi, K. Oh, P. M. Singh, V. Breedveld, and D. W. Hess, Wettability control of stainless steel via evolution of intrinsic grain structures, Journal of Materials Science, 51, 5196-5206 (2016)

(3) W. T. Choi, J. Song, J. K. Ko, Y. Jang, T. Kim, Y. Han, J. Lim, C. Lee, and K. Char, Effect of solvent additives on bulk heterojunction morphology of organic photovoltaics and their impact on device performance, Journal of Polymer Science Part B: Polymer Physics, 54, 128-134 (2016)

(4) W. T. Choi, K. Oh, P. M. Singh, V. Breedveld, and D. W. Hess, Systems and methods for producing anti-wetting structures on metallic surfaces, US Patent No. 2017/0114472 A1, Assignee: Georgia Tech Research Corporation (2017)