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계층적 구조를 갖는 중공형 ZnCo<sub>2</sub>O<sub>4</sub> 나노 섬유의 리튬이온배터리 음극소재 적용
정순영,조중상,Jeong, Sun Young,Cho, Jung Sang 한국화학공학회 2019 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.57 No.4
본 연구는 계층적 구조를 갖는 중공형 $ZnCo_2O_4$ 나노 섬유를 전기방사공정 및 후 열처리 공정을 통해 합성했다. 용액에 polystyrene (PS) 나노비드를 첨가하여 방사된 섬유는 열처리 과정을 통해 PS가 제거됨으로써 구조체 내 기공이 균일하게 생성되었으며 이는 구조체 내로 열 전달 및 가스의 침투를 원활히 함으로써 계층적 구조를 갖는 중공형 $ZnCo_2O_4$ 나노 섬유가 합성될 수 있었다. 계층적 구조를 갖는 중공형 $ZnCo_2O_4$ 나노 섬유를 리튬 이차전지의 음극활물질로 적용한 결과, $1.0A\;g^{-1}$의 높은 전류밀도에도 불구하고 300 사이클 동안 $815mA\;h\;g^{-1}$ ($646mA\;h\;cm^{-3}$)의 높은 가역 용량을 유지했다. 반면 $ZnCo_2O_4$ 나노 분말은 300 사이클 후 $487mA\;h\;g^{-1}$ ($450mA\;h\;cm^{-3}$)의 방전 용량을 나타냈다. 계층적 구조를 갖는 중공형 $ZnCo_2O_4$ 나노 섬유의 우수한 리튬 저장 특성은 중공 구조 및 섬유 표면을 구성하는 $ZnCo_2O_4$ 나노결정에 기인한 결과이다. 본 연구에서 제안한 계층적 구조를 갖는 중공형 나노 섬유 구조체는 다양한 금속 산화물로 확장 적용이 가능하며 에너지 저장 분야를 포함한 여러 분야에 응용 가능하다. Hierarchical $ZnCo_2O_4$ hollow nanofibers were prepared by electrospinning and subsequent heat-treatment process. The spinning solution containing polystyrene (PS) nanobeads was electrospun to nanofibers. During heat-treatment process, PS nanobeads in the composite were decomposed and therefore generated numerous pores uniformly in the structure, which facilitated the heat transfer and gas penetration into the structure. The resulting hierarchical $ZnCo_2O_4$ hollow nanofibers were applied as an anode material for lithium-ion batteries. The discharge capacity of the nanofibers was $815mA\;h\;g^{-1}$ ($646mA\;h\;cm^{-3}$) after the 300th cycle at a high current density of $1.0A\;g^{-1}$. However, $ZnCo_2O_4$ nanopowders showed the discharge capacity of $487mA\;h\;g^{-1}$ ($450mA\;h\;cm^{-3}$) after 300th cycle. The excellent lithium ion storage property of the hierarchical $ZnCo_2O_4$ hollow nanofibers was attributed to the synergetic effects of the hollow nanofiber structure and the $ZnCo_2O_4$ nanocrystals composing the shell. The hierarchical hollow nanofiber structure introduced in this study can be extended to various metal oxides for various applications, including energy storage.
CoSm / Cr 박막의 자성층 두께에 따른 자기역전부피
정순영(Soon-Young Jeong),김현수(Hyeon Soo Kim) 한국자기학회 2001 韓國磁氣學會誌 Vol.11 No.6
The magnetic switching volume is known as an important parameter to understand the magnetization reversal process, thermal stability of the written information and media noise. This parameter is influenced significantly by the microstructure of the magnetic layer as well as underlayer. Therefore, we fabricated CoSm/Cr thin films with varying magnetic layer thickness under constant sputtering by using a dc magnetic sputtering machine. The magnetic layer thickness effect on the magnetic switching volume have been studied by the means of magnetic viscosity and dc demagnetization remanence curve measurements. From these measurements, we found that the switching volumes increased with increasing the magnetic layer thickness, whereas the coercivity showed different behavior. These may be a result of the increased intergranular coupling and the larger volume fraction of the magnetic layer.
스퍼터링 압력에 따른 CoSm / Cr 자성 박막의 Magnetic Switching Volumes
정순영(Soon-Young Jeong),김성봉(Sung-Bong Kim) 한국자기학회 2000 韓國磁氣學會誌 Vol.10 No.5
CoSm thin films with a Cr underlayer have received continuous attention as a potential material for a high density longitudinal magnetic recording media. In this study the Ar gas sputtering pressure effects on the magnetic properties of CoSm thin films, which were fabricated by using a dc magnetron sputtering machine, were investigated. The magnetic switching volume is especially important parameter to understand the thermal stability of the written information, magnetization reversal process and media noise. Therefore, in this paper the effects of sputtering pressure on the magnetic switching volume of CoSm thin films grown on Cr underlayer with the same sputtering conditions was studied. As the Ar sputtering pressure during sputtering of the CoSm magnetic layer increases from 5 to 30 mTorr, the measured switching volumes decreased from 9.0 to 5.2×10^(-18)㎤. The calculated diameter of switching unit from V* was less than 22 ㎚, which satisfies the Sharrock's requirement on the thermal stability of the high density longitudinal magnetic recording media.
상변화물질(PCM)을 이용한 공기조화 시스템용 동파방지밸브에 관한 실험적 연구
정순영(Jeong, Soon-young),윤재호(Yun, Jea-ho),김종하(Kim, Joung-ha),양윤섭(Yang, Yoon-sub),김성현(Kim, Seong-Hyun),송덕용(Song, Duk-yong) 한국태양에너지학회 2012 한국태양에너지학회 학술대회논문집 Vol.2012 No.11
This paper is an experimental study on the freezing protection valve used for solar water heating, air-conditioning systems, and plumbing systems. When the phase change occurs from liquid to solid, most of the substances except water volumetrically shrink. And referred to as PCM(Phase Change Material) a substance with such properties, the phase change temperature varies depending on the material. To prevent the freezing of the plumbing system, such as air-conditioning system in the winter season, we developed a several types of freezing protection valve using PCM whose freezing temperature are 2-4℃. The working principle of the freezing protection valve is that the fluid inside the pipe is released to prevent the system-collapse when fluid temperature reaches the freezing temperature of the PCM. And then the valve is closed and returned to the original position automatically when the temperature of the operating fluid rises. In this paper, the operating temperatures, discharge flow rate and the response characteristics of the valve during the operation are tested and investigated. From the results of this research the freezing protection valves employing PCM are expected to be commercialized in the near future.
냉각탑 백연방지 최적 설계 및 성능향상에 관한 실험적 연구
정순영(Soon Young Jeong),윤재호(Jae Ho Yun),김종하(Joung Ha Kim),이병천(Byeong Cheon Lee),양현철(Hyeon Cheol Yang) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
The occurrence of white plume in the cooling tower is phenomenon that the steam in the air through the cooling tower fan is condensed again by the cold ambient air to become saturated moist air. Accordingly, this can cause many problems like spoiling landscape around the cooling tower, odor of ambient air, falling accident by frozenness in the winter, and traffic accident, etc. This study was to install the heat exchanger in the inside of the cooling tower in order to prevent the white plume phenomenon in the cooling tower without affecting the performance of cooling tower. In addition, this study was to discharge the part of cooling water into the atmosphere through the recirculation of heat exchanger after creating dry air by heating the saturated moist air to the dew point temperature. At that time, this study was to conduct the experimental study in order to secure the optimal design data to prevent the white plume in the cooling tower because it checked the dry·moist temperature and relative humidity in the inside·outside of cooling tower on the moist air, and evaluated the performance of the heat exchanger.
스크레이퍼형 반응기에서의 R134a를 이용한 하이드레이트 생성특성에 관한 실험적 연구
정순영(Soon-Young Jeong),김종하(Joung-Ha Kim),윤재호(Jae-Ho Yun),이주동(Joo-Dong Lee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Because methane hydrate has high gas storage ability as much as 164m<SUP>3</SUP> in 1m<SUP>3</SUP>, it is attracting attention as a new transporter and reservoir of natural gas as a substitute for LNG. Generally, an agitator-assisted hydrate reactor has been used to produce methane hydrate, but it has drawbacks in that the hydrate formation time is long and the formation amount is small. To make up for these shortcomings an experimental study on the R134a-hydrate formation was carried out by developing a scraper-type reactor that can increase the formation amount of hydrate and decrease the hydrate reaction time. The sraper-type reactor created reaction by flowing water and gas for the hydrate formation in the internal tube and hydrate-formation by flowing cooling water in external tube. In order to investigate the performance characteristics according to experimental conditions, an experiment was carried out by changing flow rate and reaction pressure in the hydrate reactor. The results showed that the formation time of hydrate according to flow rate decreases when reaction pressure is constant and hydrate formation speed increases when the reaction pressure increases under the condition of the constant cooling water temperature.