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890 results on '"OH, KYU HWAN"'

57. Peel-and-Stick Integration of Atomically Thin Nonlayered PtS Semiconductors for Multidimensionally Stretchable Electronic Devices

Author

Han, Sang Sub, primary, Ko, Tae-Jun, additional, Shawkat, Mashiyat Sumaiya, additional, Shum, Alex Ka, additional, Bae, Tae-Sung, additional, Chung, Hee-Suk, additional, Ma, Jinwoo, additional, Sattar, Shahid, additional, Hafiz, Shihab Bin, additional, Mahfuz, Mohammad M. Al, additional, Mofid, Sohrab Alex, additional, Larsson, J. Andreas, additional, Oh, Kyu Hwan, additional, Ko, Dong-Kyun, additional, and Jung, Yeonwoong, additional

Published
2022
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68. Layer Orientation-Engineered Two-Dimensional Platinum Ditelluride for High-Performance Direct Alcohol Fuel Cells

Author

Chang, Jinfa, primary, Ko, Tae-Jun, additional, Je, Minyeong, additional, Chung, Hee-Suk, additional, Han, Sang Sub, additional, Shawkat, Mashiyat Sumaiya, additional, Wang, Mengjing, additional, Park, Sang Jin, additional, Yu, Seung Min, additional, Bae, Tae-Sung, additional, Moon, Myoung-Woon, additional, Oh, Kyu Hwan, additional, Choi, Heechae, additional, Yang, Yang, additional, and Jung, Yeonwoong, additional

Published
2021
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79. Layer Orientation-Engineered Two-Dimensional Platinum Ditelluride for High-Performance Direct Alcohol Fuel Cells

Author

Chang, Jinfa, Ko, Tae-Jun, Je, Minyeong, Chung, Hee-Suk, Han, Sang Sub, Shawkat, Mashiyat Sumaiya, Wang, Mengjing, Park, Sang Jin, Yu, Seung Min, Bae, Tae-Sung, Moon, Myoung-Woon, Oh, Kyu Hwan, Choi, Heechae, Yang, Yang, Jung, Yeonwoong, Chang, Jinfa, Ko, Tae-Jun, Je, Minyeong, Chung, Hee-Suk, Han, Sang Sub, Shawkat, Mashiyat Sumaiya, Wang, Mengjing, Park, Sang Jin, Yu, Seung Min, Bae, Tae-Sung, Moon, Myoung-Woon, Oh, Kyu Hwan, Choi, Heechae, Yang, Yang, and Jung, Yeonwoong

Abstract

Platinum (Pt) has been considered the best catalyst for oxygen reduction reaction (ORR) based-direct liquid fuel cells (DLFCs). However, its high cost and the mixed potential issue have been obstacles for commercialization. Herein, we report a new Pt-based catalyst of two-dimensionally layered platinum ditelluride (2D PtTe2) with mixed layer orientation, termed M-PtTe2. This material constitutes vertically- and horizontally aligned 2D PtTe2 layers, which synergistically boost the ORR reaction; the former promotes O-2 adsorption and electron transfer, while the latter boosts O-O bond breaking and O-H bond coupling. The M-PtTe2 synthesized on nanostructured carbon papers significantly surpasses the ORR performances of commercial Pt/C, yielding 2.4-times higher mass activity in half-cell and 2-times higher maximum power density in actual devices. Furthermore, it exhibits extremely low alcohol adsorption energies, unveiling unprecedented suitability for alcohol tolerant DLFCs. This new understanding of the role of the 2D layer orientation in ORR kinetics and thermodynamics suggests useful catalyst design principles.

Published
2021

83. Highly stretchable and tough hydrogels

Author

Sun, Jeong-Yun, Zhao, Xuanhe, Illeperuma, Widusha R.K., Chaudhauri, Ovijit, Oh, Kyu Hwan, Mooney, David J., Vlassak, Joost J., and Suo, Zhigang

Subjects
Crosslinked polymers -- Research, Colloids -- Properties, Polyacrylamide -- Properties, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Hydrogels are used as scaffolds for tissue engineering (1), vehicles for drug delivery (2), actuators for optics and fluidics (3), and model extracellular matrices for biological studies (4). The scope [...]

Published
2012

94. Contribution of convex surfaces to magnetostatic interaction in granular medium

Author

Lee, Jehyun, Suess, Dieter, Schrefl, Thomas, Yu, Eu Sun, Lee, You Sub, Oh, Kyu Hwan, and Fidler, Josef

Subjects
Magnetization -- Observations, Magnetization -- Control, Magnetostatics -- Observations, Dielectric films -- Structure, Thin films -- Structure, Business, Electronics, Electronics and electrical industries
Abstract

Finite element micromagnetic studies on the magnetic behaviors of granular structures are performed to investigate the magnetostatic contributions of the curved surfaces of grains with various film thicknesses. From the result, it is found that the magnetization reversal process in one grain is much faster when the grains have convex surfaces. The magnetization vectors of all convex models are stabilized in shorter time by factor of 10 compared to those of flat models. And, the reversals of each grain are carried out by nucleation and domain wall propagation in the entire granular structure, whereas the grains in flat model are individually reversed. Moreover, the magnetization behaviors of the convex models are closer to the experimental results. Since the geometric and magnetic conditions are same for the two models, the only origin of the more realistic magnetic behavior is the magnetostatic interaction between the grains, enhanced by introducing the convex surfaces. From the further analysis, it is found that the convex surface induces pinning field that suppress other parts' reversal. Index Terms--Magnetic recording, magnetization reversal, magnetostatics, simulation, surfaces.

Published
2009

95. Wafer-Scale Growth of 2D PtTe2 with Layer Orientation Tunable High Electrical Conductivity and Superior Hydrophobicity

Author

Wang, Mengjing, Ko, Tae-Jun, Shawkat, Mashiyat Sumaiya, Han, Sang Sub, Okogbue, Emmanuel, Chung, Hee-Suk, Bae, Tae-Sung, Sattar, Shahid, Gil, Jaeyoung, Noh, Chanwoo, Oh, Kyu Hwan, Jung, YounJoon, Larsson, J. Andreas, Jung, Yeonwoong, Wang, Mengjing, Ko, Tae-Jun, Shawkat, Mashiyat Sumaiya, Han, Sang Sub, Okogbue, Emmanuel, Chung, Hee-Suk, Bae, Tae-Sung, Sattar, Shahid, Gil, Jaeyoung, Noh, Chanwoo, Oh, Kyu Hwan, Jung, YounJoon, Larsson, J. Andreas, and Jung, Yeonwoong

Abstract

Platinum ditelluride (PtTe2) is an emerging semimetallic two-dimensional (2D) transition-metal dichalcogenide (TMDC) crystal with intriguing band structures and unusual topological properties. Despite much devoted efforts, scalable and controllable synthesis of large-area 2D PtTe2 with well-defined layer orientation has not been established, leaving its projected structure–property relationship largely unclarified. Herein, we report a scalable low-temperature growth of 2D PtTe2 layers on an area greater than a few square centimeters by reacting Pt thin films of controlled thickness with vaporized tellurium at 400 °C. We systematically investigated their thickness-dependent 2D layer orientation as well as its correlated electrical conductivity and surface property. We unveil that 2D PtTe2 layers undergo three distinct growth mode transitions, i.e., horizontally aligned holey layers, continuous layer-by-layer lateral growth, and horizontal-to-vertical layer transition. This growth transition is a consequence of competing thermodynamic and kinetic factors dictated by accumulating internal strain, analogous to the transition of Frank–van der Merwe (FM) to Stranski–Krastanov (SK) growth in epitaxial thin-film models. The exclusive role of the strain on dictating 2D layer orientation has been quantitatively verified by the transmission electron microscopy (TEM) strain mapping analysis. These centimeter-scale 2D PtTe2 layers exhibit layer orientation tunable metallic transports yielding the highest value of ∼1.7 × 106 S/m at a certain critical thickness, supported by a combined verification of density functional theory (DFT) and electrical measurements. Moreover, they show intrinsically high hydrophobicity manifested by the water contact angle (WCA) value up to ∼117°, which is the highest among all reported 2D TMDCs of comparable dimensions and geometries. Accordingly, this study confirms the high material quality of these emerging large-area 2D PtTe2 layers, projecting va

Published
2020
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