Eui Yun Jang
Seoul National University
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Publication
Featured researches published by Eui Yun Jang.
Advanced Materials | 2013
Hee-Dae Lim; Kyu Young Park; Hyelynn Song; Eui Yun Jang; Hyeokjo Gwon; Jin-Soo Kim; Yong Hyup Kim; Marcio Dias Lima; Raquel Ovalle Robles; Xavier Lepró; Ray H. Baughman; Kisuk Kang
Recently Li-air batteries have been considered to be a promising candidate for EV and HEV applications due to their exceptionally high energy density. A key factor for the practical application of Li-air batteries is to solve the poor reversibility of nonconductive discharge products, which remains a significant limiting factor for Li-air batteries. Therefore, the air electrode needs to be designed such that it minimizes the undesirable clogging and promotes the electrochemical reactivity. As the control of the morphology and porosity of the electrode greatly affects on the capacity and rate capability, various nanostructured air electrodes have been reported using carbon nanoparticles, graphene, graphene oxide, or carbon nanotubes (CNTs). However, the poor cyclability and low rate capability remain as critical drawbacks of the Li−O2 batteries, and the ideally designed electrode architecture is still awaited.
Nano Letters | 2011
J. S. Kyoung; Eui Yun Jang; Marcio Dias Lima; Hyeong Ryeol Park; Raquel Ovalle Robles; Xavier Lepró; Yong Hyup Kim; Ray H. Baughman; Dai-Sik Kim
Utilizing highly oriented multiwalled carbon nanotube aerogel sheets, we fabricated micrometer-thick freestanding carbon nanotube (CNT) polarizers. Simple winding of nanotube sheets on a U-shaped polyethylene reel enabled rapid and reliable polarizer fabrication, bypassing lithography or chemical etching processes. With the remarkable extinction ratio reaching ∼37 dB in the broad spectral range from 0.1 to 2.0 THz, combined with the extraordinary gravimetric mechanical strength of CNTs, and the dispersionless character of freestanding sheets, the commercialization prospects for our CNT terahertz polarizers appear attractive.
Small | 2008
Eui Yun Jang; Tae June Kang; Hyeoung Wook Im; Dae Weon Kim; Yong Hyup Kim
Highly uniform and large-area single-walled carbon-nanotube (SWNT) networks are realized by the dip-coating method, which is based on fundamental fluid-dynamic phenomena such as capillary condensation and surface tension. The changes in the polarity and hydration properties of the substrate affect the morphology of the SWNT networks and result in nonlinear growth of the networks in the repetitive dip-coating process. The density and the thickness of the SWNT networks are controlled by processing variables including number of dip coatings, concentration of SWNT colloidal solution, and withdrawal velocity. The networks have uniform sheet resistances and high optical transmittance in the visible wavelength range.
Advanced Materials | 2009
Eui Yun Jang; Tae June Kang; Hyeongwook Im; Seung Jae Baek; Seongyong Kim; Dae Hong Jeong; Yung Woo Park; Yong Hyup Kim
Pure macroscopic single-walled-carbon-nanotube (SWNT) fibers are fabricated by using a dip-coating method without any additive or additional electrical equipment or complex apparatus. The present method only utilizes microfluidics, which includes capillary condensation, capillary flow, and surface tension, and results in the self-assembly and self-alignment of SWNT colloids.
Integrative Biology | 2012
Jeong Ah Kim; Eui Yun Jang; Tae June Kang; Sungjun Yoon; Raquel Ovalle-Robles; Won Jong Rhee; Taewoo Kim; Ray H. Baughman; Yong Hyup Kim; Tai Hyun Park
In order to successfully utilize stem cells for therapeutic applications in regenerative medicine, efficient differentiation into a specific cell lineage and guidance of axons in a desired direction is crucial. Here, we used aligned multi-walled carbon nanotube (MWCNT) sheets to differentiate human mesenchymal stem cells (hMSCs) into neural cells. Human MSCs present a preferential adhesion to aligned CNT sheets with longitudinal stretch parallel to the CNT orientation direction. Cell elongation was 2-fold higher than the control and most of the cells were aligned on CNT sheets within 5° from the CNT orientation direction. Furthermore, a significant, synergistic enhancement of neural differentiation was observed in hMSCs cultured on the CNT sheets. Axon outgrowth was also controlled using nanoscale patterning of CNTs. This CNT sheet provides a new cellular scaffold platform that can regulate morphogenesis and differentiation of stem cells, which could open up a new approach for tissue and stem cell regeneration.
Applied Physics Letters | 2012
Seok Hwan Lee; Mi-ae Park; Jack J. Yoh; Hyelynn Song; Eui Yun Jang; Yong Hyup Kim; Sung-Chan Kang; Yong Seop Yoon
We demonstrate that reduced graphene oxide (rGO) coated thin aluminum film is an effective optoacoustic transmitter for generating high pressure and high frequency ultrasound previously unattainable by other techniques. The rGO layer of different thickness is deposited between a 100 nm-thick aluminum film and a glass substrate. Under a pulsed laser excitation, the transmitter generates enhanced optoacoustic pressure of 64 times the aluminum-alone transmitter. A promising optoacoustic wave generation is possible by optimizing thermoelasticity of metal film and thermal conductivity of rGO in the proposed transmitter for laser-induced ultrasound applications.
ACS Applied Materials & Interfaces | 2012
Hyeongwook Im; Eui Yun Jang; Ajeong Choi; Wal Jun Kim; Tae June Kang; Yung Woo Park; Yong Hyup Kim
A strategy for enhancing the heating performance of freestanding carbon nanotube (CNT) sheet is presented that involves decorating the sheet with granular-type palladium (Pd) particles. When Pd is added to the sheet, the heating efficiency of CNT sheet is increased by a factor of 3.6 (99.9 °C cm(2)/W vs 27.3 °C cm(2)/W with no Pd). Suppression of convective heat transfer loss attributes to the enhanced heat generation efficiency. However, higher heating response of CNT/Pd sheet was observed compared to CNT sheet, hence suggesting that the electron-lattice energy exchange could be additional heating mechanism in the presence of granular-type particles of Pd having a diameter of 10 nm or less. CNT sheet/Pd is quite stable, retaining its initial characteristics even after 300 cycles of on-off voltage pulses and shows fast thermal responses of the heating and cooling rates being 154 and -248 °C/s, respectively.
Applied Physics Letters | 2016
Byounghwak Lee; Ali Mousavian; Michael J. Paul; Zachary J. Thompson; Andrew D. Stickel; Dalton R. McCuen; Eui Yun Jang; Yong Hyup Kim; J. S. Kyoung; Dai-Sik Kim; Yun-Shik Lee
We demonstrate that unidirectionally aligned, free-standing multi-walled carbon nanotubes (CNTs) exhibit highly anisotropic linear and nonlinear terahertz (THz) responses. For the polarization parallel to the CNT axis, strong THz pulses induce nonlinear absorption in the quasi-one-dimensional conducting media, while no nonlinear effect is observed in the perpendicular polarization configuration. Time-resolved measurements of transmitted THz pulses and a theoretical analysis of the data reveal that intense THz fields enhance permittivity in carbon nanotubes by generating charge carriers.
Scientific Reports | 2015
Tae June Kang; Taewoo Kim; Eui Yun Jang; Hyeongwook Im; Xavier Lepro-Chavez; Raquel Ovalle-Robles; Jiyoung Oh; Mikhail E. Kozlov; Ray H. Baughman; Hong H. Lee; Yong Hyup Kim
Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical energy. This mechanism has not been exploited fully because of lack of a material with a sufficiently low force constant. We here show that carbon nanotube (CNT) aerogel sheets can exploit EMI to provide mechanical actuation at very low applied voltages, to harvest mechanical energy from small air pressure fluctuations, and to detect infrasound at inaudible frequencies below 20 Hz. Using conformal deposition of 100 nm thick aluminum coatings on the nanotubes in the sheets, mechanical actuation can be obtained by applying millivolts, as compared with the thousand volts needed to achieve giant-stroke electrostatic actuation of carbon nanotube aerogel sheets. Device simplicity and performance suggest possible applications as an energy harvester of low energy air fluctuations and as a sensor for infrasound frequencies.
Nanotechnology | 2007
Woo Yong Sung; Jong Girl Ok; Wal Jun Kim; Seungmin Lee; Eui Yun Jang; Yong Hyup Kim
Uniformity is one of the most important qualifications for reliable field emission devices based on carbon nanofibers (CNFs). We synthesized CNFs by thermal chemical vapor deposition at 600 °C on the glass substrate, promising practical large-area applications. A glass cap was introduced to enhance the uniformity of CNF emitters vertically grown under the guidance of micro-grooves, which provided passages for the diffusion of precursor gas to CNF growth sites. Our CNFs, vertically leveled by the glass cap with the support of the micro-grooves, and without any post-treatments, showed excellent uniformity in field emission as well as long-term stability.