Flow-Electrode Capacitive Deionization Using an Aqueous Electrolyte with a High Salt Concentration

Yang, SeungCheol,Choi, Jiyeon,Yeo, Jeong-gu,Jeon, Sung-il,Park, Hong-ran,Kim, Dong Kook American Chemical Society 2016 Environmental science & technology Vol.50 No.11

<P>Flow-electrode capacitive deionization (FCDI) is novel capacitive deionization (CDI) technology that exhibits continuous deionization and a high desalting efficiency. A flow electrode with high capacitance and low resistance is required for achieving an efficient FCDI system with low energy consumption. For developing high-performance flow-electrode, studies should be conducted considering porous materials, conductive additives, and electrolytes constituting the flow-electrode. Here, we evaluated the desalting performances of flow-electrodes with spherical activated carbon and aqueous electrolytes containing various concentrations of NaCl in the FCDI unit cell for confirming the effect of salt concentration on the electrolyte of a flow-electrode on desalting efficiency. We verified the necessity of a moderate amount of salt in the flow-electrode for compensating for the reduction in the performance of the flow-electrode, attributed to the resistance of water used as the electrolyte. Simultaneously, we confirmed the potential use of salt water with a high salt concentration, such as seawater, as an aqueous electrolyte for the flow-electrode.</P>

Highly Condensed Epoxy−Oligosiloxane-Based Hybrid Material for Transparent Low-<i>k</i> Dielectric Coatings

Yang, SeungCheol,Kwak, Seung-Yeon,Jin, JungHo,Bae, Byeong-Soo American Chemical Society 2009 ACS APPLIED MATERIALS & INTERFACES Vol.1 No.7

<P>A highly condensed epoxy-oligosiloxane resin was synthesized using a sol-gel condensation reaction of (3-glycidoxypropyl)trimethoxysilane and diphenylsilanediol in the presence of solvent. A higher degree of condensation and a larger molecular size of oligosiloxanes were achieved compared to a condensation reaction without the addition of a solvent. The epoxy-hybrimer coating film was fabricated by the spin coating and thermal curing of the synthesized oligosiloxane resin. The leakage current density and the dielectric constant decreased from 25.9 to 7.6 nA cm(-2) and from 3.16 to 3.03, respectively, by using the solvent in the preparation. The hybrimer coating film of a highly condensed oligosiloxane resin had a high transmittance of over 90% in a wavelength between 300 and 800 nm. Thus, the epoxy-hybrimer coating film can be utilized as the passivation layer in the thin-film transistor.</P>

Fabrication of photocured anion-exchange membranes using water-soluble siloxane resins as cross-linking agents and their application in reverse electrodialysis

Yang, SeungCheol,Kim, Won-Sik,Choi, Jiyeon,Choi, Young-Woo,Jeong, Namjo,Kim, Hanki,Nam, Joo-Youn,Jeong, Haejun,Kim, Yong Ho Elsevier 2019 Journal of membrane science Vol.573 No.-

<P><B>Abstract</B></P> <P>The utilization of large amounts of volatile organic solvents and the complicated process required for industrial manufacturing of ion-exchange membranes necessitate the development of simple, rapid, and environmentally friendly fabrication methods such as those based on photopolymerization. We employed hydrolytic sol–gel reactions between ammonium- and acrylamide-functionalized silane coupling agents to synthesize water-soluble siloxane resins that exhibit high condensation levels (>80%) and comprise oligomers with molecular weights below 2000 Da. These resins were then mixed with a hydrophilic monomer bearing ammonium and acrylamide groups, and porous polyethylene substrates were impregnated with the resulting mixtures and then irradiated with ultraviolet light. The hydrophilicity, mechanical strength, and other properties of the resulting membranes depended on the resin composition, indicating that the substrate pores were efficiently filled with the prepared resins and further suggesting that the membrane performance could be effectively altered by varying the resin composition. Moreover, the obtained membranes exhibited chemical stability in the pH range between 0 and 11 and in hot water at 60 °C. The reverse electrodialysis stack consisting of these membranes showed higher power density than a stack of commercial membranes. Therefore, it can be concluded that without employing volatile organic solvents for reverse electrodialysis, the developed technique is well-suited for the fabrication of ion-exchange membranes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Photocured anion-exchange membranes were fabricated using water-soluble siloxane resins. </LI> <LI> All resins had a high condensation degree, containing oligomers with <I>M</I> <SUB>w</SUB> < 2000 Da. </LI> <LI> These resins acted as cross-linkers and helped to avoid the use of organic solvents. </LI> <LI> The properties of the prepared anion-exchange membranes depended on resin composition. </LI> <LI> Reverse electrodialysis using the prepared membrane shows higher power density than that of the commercial membrane. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Plate-Shaped Graphite for Improved Performance of Flow-Electrode Capacitive Deionization

Yang, SeungCheol,Park, Hong-ran,Yoo, Jungjoon,Kim, Hanki,Choi, Jiyeon,Han, Moon Hee,Kim, Dong Kook The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.13

<P>Capacitive deionization (CDI) using a flow-electrode primarily composed of porous materials and an aqueous electrolyte, exhibits continuous deionization and a high desalting efficiency. The development of flow-electrodes with high capacitance and low resistance is essential for achieving an efficient flow-electrode capacitive deionization (FCDI) system with low energy consumption. For this purpose, studies on conductive additives (CAs) that do not clog the flow-channel must be conducted. Here, we evaluated the desalting performance of flow-electrodes with spherical and plate-type conductive additives having sizes between 1 and 10 mu m and possessing powder conductivities similar to or higher than nano-sized carbon black, which is often used as the CA in solid fixed electrodes in conventional CDI systems. We confirmed that plate-shaped CAs reduced resistance near the pores and enhanced the desalting performance of the flow-electrodes in FCDI systems. The positive effect of such plate-shaped CAs appears to originate from efficient charge percolation between the ACs via the electrical conductive direction of the graphite and the alignment of the exposed graphite edges to the pumping direction of the flow-electrode. Finally, we verified that the flow-electrode with the newly discovered micro-sized CA could be operated without clogging the flow-channel in FCDI and showed an improved desalting performance of around 1.5 times compared the flow-electrode without the micro-sized CA for extended periods of time. (c) 2017 The Electrochemical Society. All rights reserved.</P>

Thermally resistant UV-curable epoxy–siloxane hybrid materials for light emitting diode (LED) encapsulation

Yang, SeungCheol,Kwak, Seung-Yeon,Jin, JungHo,Kim, Joon-Soo,Choi, Yongwon,Paik, Kyung-Wook,Bae, Byeong-Soo The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.18

<P>A UV-curable epoxy–siloxane hybrid material (epoxy hybrimer) was fabricated by photo-cationic polymerization of a sol–gel derived cyclo-aliphatic epoxy oligosiloxane (CAEO) blended with oxetane cross-linker in the presence of an onium salt. Antioxidants for fabrication of the UV-curable epoxy hybrimer with high thermal resistance against yellowing were incorporated in the UV-curable epoxy hybrimer. The UV-curable epoxy hybrimer with the antioxidants showed high thermal resistance without yellowing during 120 °C thermal aging. High thermal resistance of the UV-curable epoxy hybrimer was similar and higher compared to those of commercial thermally curable silicone and UV-curable epoxy LED encapsulants, respectively. The thermally resistant UV-curable epoxy hybrimer was successfully encapsulated on a LED without any cracking or delamination, and maintained a flat surface on the LED without distortion of the designed flat shape. Before/after thermal and blue light aging, the performance of the LED encapsulated by the UV-curable epoxy hybrimer was not changed. On the basis of its excellent properties as a LED encapsulant, the UV-curable epoxy hybrimer can be utilized as a UV-curable LED encapsulant for white LEDs.</P> <P>Graphic Abstract</P><P>A UV-curable epoxy–siloxane hybrid material has comparable thermal resistance with a thermally curable silicone LED encapsulant. The UV-curable epoxy–siloxane hybrid material successfully encapsulated a blue LED without any delamination or cracking. The LED encapsulated by the hybrid material is ordinarily emitted without blue LED performance degradation. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm16355a'> </P>

3차원 유동 시뮬레이션을 위한 Supercompact 다중 웨이블릿

양승철(Seungcheol Yang),이도형(Dohyung Lee) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.12

본 논문에서는 supercompact 다중 웨이블릿 기법과 이 기법의 유동 시뮬레이션 데이터에의 적용을 발표한다. Supercompact 웨이블릿 방법은 간결한 지원(support)을 제공할 수 있고 또 속성이 다른 떨어져 있는 데이터와(예: 충격파의 불연속구간 또는 와동을 가로지르는 부분) 불필요한 상호작용을 피할 수 있는 점에서 유동 시뮬레이션 데이터를 위한 적합한 웨이블릿 방법이라 할 수 있다. 데이터 압축을 위한 임계처리법(thresholding)은 다중 웨이블릿의 공분산 벡터 구조 기반 하에 적용된다. 본 논문은 3차원으로의 기법 확장이 설명 분석되었다. 수치실험은 본 방법이 여러 이론적인 이점을 제공할 수 있고 실제 결과에 있어서 큰 데이터 압축 비율을 산출 할 수 있음을 보여준다. This paper presents a supercompact multi-wavelet scheme and its application to fluid simulation data. The supercompact wavelet method is an appropriate wavelet for fluid simulation data in the sense that it can provide compact support and avoid unnecessary interaction with remotely located data (e.g. across a shock discontinuity or vortices). thresholding for data compression is applied based on a covariance vector structure of multi-wavelets. The extension of this scheme to three dimensions is analyzed. The numerical tests demonstrate that it can allow various analytic advantages as well as large data compression ratios in actual practice.

흐름전극 기반 전기화학적 염분차발전 연구

양승철(SeungCheol Yang),송태섭(Taeseup Song) 한국신재생에너지학회 2023 한국신재생에너지학회 학술대회논문집 Vol.2023 No.6

흐름전극 기반 염분차발전 연구 개발 현황

양승철(SeungCheol Yang),김하은(Haeun Kim),김동현(Donghyun Kim),정연길(Yeon-Gil Jung),권화빈(Hwabhin Kwon),박희성(Heesung Park),이동수(Dongsoo Lee),황인성(Insung Hwang),송태섭(Taeseup Song) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.5

염분차발전은 해수와 담수 사이의 염분농도차를 이용해 전기를 생산하는 해양 신재생 에너지원이다. 최근 새로운 염분차발전 기술로 무한한 이온흡착용량을 지니는 흐름전극의 이온 흡착/탈착을 활용하는 흐름전극-축전식혼합 (F-Capmix, flow-electrode capacitive mixing)이 제안되었다. 하지만, F-Capmix는 타 염분차발전 기술 대비 낮은 출력밀도를 지니고 있어 향후 상용화를 위해 이를 개선해야 할 필요가 있다. 본 연구에서는 F-Capmix 염분차발전 기술의 낮은 출력밀도의 개선을 위해, (1) 흐름전극 내 다공성 탄소 입자 사이의 효율적인 charge percolation을 위한 개선된 조성을 지니는 흐름전극, (2) 그래파이트가 코팅된 금속 집전체를 활용해 전기저항이 낮아진 집전체, (3) 집전체와 흐름전극 내 다공성 탄소 입자 사이의 효율적인 charge percolation을 위한 유로 디자인에 대한 연구를 수행하였다. 이를 통해, F-Capmix 염분차발전의 낮은 출력밀도가 개선되었음을 확인했다. Salinity differential power generation (SGP) is a marine renewable energy that generates electricity by salt concentration difference between seawater and freshwater. As a new SGP technology, flow-electrode capacitive mixing (F-Capmix) has been proposed that utilizes ion adsorption/desorption of a flow-electrode with infinite ion adsorption capacity. However, F-Capmix has a lower power density compared to other SGP technologies, so it needs to be improved for commercialization. In this study, in order to improve the low power density of the F-Capmix, we conducted various studies on (1) a flow-electrode with an improved composition for efficient charge percolation between porous carbon particles in the flow-electrode, (2) a current collector with low electrical resistance by using a graphite-coated metal current collector, and (3) flow path design for efficient charge percolation between the current collector and the porous carbon particles in the flow electrode. Through this, it was confirmed that the low power density of the F-Capmix was improved.

역전기투석 발전을 위한 저저항 실리콘-비닐 하이브리드 음이온교환막 제막 및 특성 평가

양승철(SeungCheol Yang),최지연(Jiyeon Choi),최영우(Young-Woo Choi) 한국신재생에너지학회 2017 한국신재생에너지학회 학술대회논문집 Vol.2017 No.9

Measuring the Cumulative Effect of G Force on Aviator Neck Pain

Seungcheol Kang,Sangho Hwang,Eun Taek Lee,Solmon Yang,Jinhee Park 한국항공우주의학협회 2011 항공우주의학 학술대회 Vol.2011 No.11