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멜라민 화합물을 이용한 산화 그래핀 도핑 및 특성 평가
김수민,김현,김소양,한종훈,Kim, Sumin,Kim, Hyun,Kim, So Yang,Han, Jong Hun 한국재료학회 2019 한국재료학회지 Vol.29 No.11
In this paper, nitrogen-doped reduced graphene oxide(rGO) is obtained by thermal annealing of nitrogen-containing compounds and graphene oxide (GO) manufactured by modified Hummers' method. We use melamine as a nitrogen-containing compound and treat GO thermally with melamine at over $800{\sim}1,000^{\circ}C$ and 1 ~ 3 hr under Ar atmosphere. The electrical conductivity of doped rGO is measured by 4-point probe method. As a result, nitrogen contents on rGO are found to be in the range of 2.5 to 12.5 at% depending on the doping conditions after thermal annealing. The main doping site on graphene oxide is changed from pyridinic-N and pyrrolinic N to the graphitic site as the heat treatment temperature increases. The electrical conductivity of doped rGO increases as the N doping content increases. As the thermal treatment time increases, the change of both total doping contents and doping sites is slight and the surface resistance is remarkably reduced, which is caused by healing effects of doped graphene oxide at high temperature.
2단 실린더형 싸이클론의 물 및 오일 액적 제거 성능 분석 연구
김수민,김학준,김명준,한방우,우창규,김용진,Kim, Sumin,Kim, Hak-Joon,Kim, Myungjoon,Han, Bangwoo,Woo, Chang Gyu,Kim, Yong-Jin 한국입자에어로졸학회 2017 Particle and Aerosol Research Vol.13 No.3
A novel two stage cylindrical cyclone was developed for a 3 phase separator in shale oil production industry. The cyclone performance was compared with a cone type cyclone and multi cyclone at the same experimental condition using water and oil mists generated by a humidifier and atomizer at the flow rate 1 to $2m^3/min$. The removal efficiency of total suspended water droplets by the novel cyclone, calculated using inlet and outlet concentrations measured by an optical particle counter, was 99% which is higher than 90% of oil droplet removal efficiency at $2m^3/min$. It might be due to the evaporation of small water droplets during the tests. The water and oil droplet removal performance of the novel cyclone based on the quality factor which is a function of pressure drop and removal efficiency was the highest among three cyclones. The results indicate that the cyclone could be an economical device to remove water and oil mists from shale gas generation processes where a huge three phase separator is commonly used.
김수민,송건탁,김정,Kim, Sumin,Song, Guntak,Kim, Jeong F. 한국막학회 2021 멤브레인 Vol.31 No.4
In this work, we tested commercial organic solvent nanofiltration (OSN) membranes using both in-house dead-end and crossflow systems. Four different crosslinked polyimide Duramem (DM) OSN membranes with various MWCO (molecular weight cut off) values were tested in organic solvents such as ethanol, N,N-dimethylformamide, acetone and acetonitrile. The membranes exhibited more reliable and reproducible performance in the crossflow system, and the performance changed significantly depending in the physical properties of the testing solvent. This is due to the initial stabilization period via pressure-induced compaction phenomenon, which can be vastly different between membrane samples. Hence, to obtain reliable and reproducible results, crossflow system is the preferred choice. 본 연구에서는 Dead-end와 Crossflow 시스템을 사용하여 유기용매 나노여과(Organic Solvent Nanofiltration, OSN) 상용분리막의 성능을 분석하였다. 가교된 polyimide 소재 기반의 Duramem (DM) OSN 분리막의 성능을 ethanol, dimethylformamide (DMF), acetone, acetonitrile 용매에서의 성능을 분석하였다. 네 종류의 분획분자량 성능을 갖는 DM 분리막의 성능을 평가하였을 때 dead-end보다 Crossflow에서 조금 더 정확하고 신뢰성 높은 결과를 얻을 수 있었으며, 동일한 분리막이더라도 용매의 특성에 따라 투과도와 선택도 차이가 크게 난다는 것을 확인할 수 있었다. 이는 압밀화현상으로 인한 초기 안정화 기간의 차이 때문인 것으로 판단되며 분리막마다 안정화기간이 다르므로 신뢰성 높은 결과를 얻기 위해선 Crossflow 시스템을 활용하는 것이 더 적합한 것으로 보인다.
김수민(Sumin Kim),이현숙(Hyun-Sook Lee),이우영(Wooyoung Lee) 한국자기학회 2018 韓國磁氣學會誌 Vol.28 No.6
A compelling need for high magnetic properties led to active consideration of rare-earth permanent magnets, which have been used in various applications such as communication, memory, and audio equipment. Recently, the use of rare-earth permanent magnets has expanded to green automobiles, robots, wind power plants, actuators, and generators due to the rise of the fourth industrial revolution and problematic issues of air pollution and fine dust generation. In particular, demand for high-performance permanent magnets is rapidly increasing to meet the ever growing interest in the industry of environment-friendly automobiles (hybrid/electric vehicles). However, since the rare-earth magnets are expensive and have limitation in high-temperature applications such as an automobile motor, it is essential to develop a permanent magnet with reduced rare-earth concentration that can bear high temperatures. Consequently, several major corporations have established a high-performance permanent magnet research team and are pursuing new businesses. At this point of view, the present article reviews a summary of the history and the R & D trends of rare-earth permanent magnets that have been developed in the past.
코로나 방전의 방향탐지를 위한 전기적 빔 조향 기반 라디오미터 시스템 연구
김수민(Sumin Kim),천창율(Changyul Cheon) 대한전기학회 2020 전기학회논문지 Vol.69 No.3
In this study, we designed and fabricated a radiometer using electric beam steering to improve the problems of the conventional corona discharge detection. The research was then conducted to image the data so that direction of corona discharge could be detected. When a corona discharge occurred, heat was generated around it and the electromagnetic wave generated by the heat was detected to detect the direction of the corona discharge. In addition, by selecting the electric beam steering using a phase shifter, the stability of the system is increased and the data is imaged to increase the accuracy of the detection of the measurement object. In particular, by showing the possibility of direction detection using electric beam steering, it laid the foundation for the possibility of direction detection of corona discharge.