• 한국분말재료학회지
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• 제25권6호
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• pp.466-474
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• 2018

The high theoretical energy density ($2600Wh\;kg^{-1}$) of Lithium-sulfur batteries and the high theoretical capacity of elemental sulfur ($1672mAh\;g^{-1}$) attract significant research attention. However, the poor electrical conductivity of sulfur and the polysulfide shuttle effect are chronic problems resulting in low sulfur utilization and poor cycling stability. In this study, we address these problems by coating a polyethylene separator with a layer of activated carbon powder. A lithium-sulfur cell containing the activated carbon powder-coated separator exhibits an initial specific discharge capacity of $1400mAh\;g^{-1}$ at 0.1 C, and retains 63% of the initial capacity after 100 cycles at 0.2 C, whereas the equivalent cell with a bare separator exhibits a $1200mAh\;g^{-1}$ initial specific discharge capacity, and 50% capacity retention under the same conditions. The activated carbon powder-coated separator also enhances the rate capability. These results indicate that the microstructure of the activated carbon powder layer provides space for the sulfur redox reaction and facilitates fast electron transport. Concurrently, the activated carbon powder layer traps and reutilizes any polysulfides dissolved in the electrolyte. The approach presented here provides insights for overcoming the problems associated with lithium-sulfur batteries and promoting their practical use.

• 한국수소및신에너지학회논문집
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• 제34권6호
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• pp.785-791
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• 2023

Copper sulfide (Cu_xS) has been extensively utilized as a counter electrode (CE) material for quantum dot solar cells (QDSCs) due to its exceptional catalytic activity for polysulfide electrolytes. The typical fabrication method of Cu₂S CEs based on brass substrate is dangerous, involving the use of a highly concentrated hydrochloric acid solution in a relatively high temperature. In contrast, electroplating presents a safer alternative by employing a less acidic solution at a room temperature. In addition, the electroplating method increases the probability of obtaining CEs of consistent quality compared to the brass method. In this study, the optimized electroplating cycle for CuS CEs in QDSCs has been studied for the highly efficient photovoltaic performances. The QDSCs, featuring electroplated CuS CEs, achieved an impressive efficiency of 7.18%, surpassing the conventional method employing brass CEs, which yielded an efficiency of 6.62%.

• 한국전기전자재료학회논문지
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• 제33권5호
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• pp.411-417
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• 2020

In this study, we introduce a Na β"-alumina composite thick film as a solid electrolyte, to reduce the resistance of electrolyte for a Na/S battery. An alumina/zirconia composite material was used to enhance the mechanical properties of the electrolyte. A solid electrolyte of about 40 ㎛ thick was successfully fabricated through the conversion and tape-casting methods. In order to investigate the effect of the surface treatment process of the solid electrolyte on the battery performance, the electrolyte was polished by dry and wet processes, respectively, and then the Na/S batteries were prepared for analyzing the battery characteristics. The battery with the dry process performed much better than the battery made with the wet process. As a result, the battery manufactured by the dry process showed excellent performance. Therefore, it is confirmed that the surface treatment process of the solid electrolyte has an important effect on the battery capacity and coulombic efficiency, as well as the interface reaction.

• 전기화학회지
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• 제21권1호
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• pp.6-11
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• 2018

다양한 전자제품에서 높은 성능의 이차 전지가 요구됨에 따라 안전하고 친환경적이며 경제적인 이차 전지 전극 재료의 개발을 필요로 하고 있다. 리튬-황 배터리는 높은 이론용량과 에너지밀도, 그리고 친환경적인 물질이라는 점에서 차세대 이차전지로써 주목받고 있지만, 폴리설파이드의 용출로 인한 전지 용량감소현상이 일어나고, 황의 부도체 특성으로 인해 아직 상용화 단계에 미치지 못하고 있다. 본 연구에서는 보다 향상된 이차 전지 전극 재료로서 다른 양극 물질들에 비해 에너지 밀도가 높은 황을 양극재로 사용하여 전지를 만들고 이 때 양극 활물질의 구성요소인 황, 도전재, 바인더의 비율을 다양하게 변화하면서 양극을 제조하고 여러 전기화학적 평가를 거쳐 가장 좋은 전지 성능을 낼 수 있는 구성성분 비율을 모색하고자 하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제18권5호
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• pp.68-77
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• 2014

본 연구에서는 초박층 교면포장으로 폴리설파이드 에폭시 폴리머 콘크리트 포장을 선정하여, 에폭시 아스팔트 포장, SFRC 포장과의 비교 분석을 통해 폴리머 콘크리트 포장이 강바닥판의 피로응력범위에 어떠한 영향을 미치는 지 분석하였다. 강바닥판의 피로응력범위를 산정하기 위해 Abaqus를 사용한 유한요소해석을 사용하여 비교평가하였으며, 용접부에 교축방향 및 교축직각방향의 다축응력이 발생하는 점을 감안하여 Signed Von-Mises 응력을 도입하여 피로 검토에 활용하였다. 강바닥판의 피로응력범위를 산정하기 위해 Abaqus를 사용한 유한요소해석을 사용하여 포장 재료 및 두께에 따라 비교평가하였으며, 용접부에 교축방향 및 교축직각방향의 다축응력이 발생하는 점을 감안하여 Signed Von-Mises 응력을 도입하여 피로 검토에 활용하였다.

• 대한치과보철학회지
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• 제34권4호
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• pp.755-779
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• 1996

This study was designed to development of stock tray for Korean. The subjects for this study were 374 persons(male : 204, female : 170) with age $19{\sim}28$. The study models were made with irreversible hydrocolloid impression material and conventional stock tray, Individual trays were made on the study model and the master models were made after impression with polysulfide rubber impression material. Each of the master models measured 12 measuring points on the maxillary model and 13 measuring points on the mandibular model with digital sliding caliper. The values were analyzed statistically by SAS analysis. The measuring points were analysed and were consulted for the development of new stock tray for Korean. Maxillary models were divided into four groups acceding to the width between buccal alveolar ridges below the contact point of first molar and second molar. The size of new tray of the upper first group was 82mm (width), 60mm(length). That of the upper second group was 77mm (width), 59mm (length). That of the upper third group was 72mm (width), 58mm (length). And that of the upper fourth group was 67mm (width), 57mm (length). Mandibular models were devided into three group according to the width between lingual alveolar ridges below the second molar. The size of new tray on lower first group was 40mm (width), 55mm (length). That of the lower second group was 36mm (width), 55mm (length). And that of the third group was 32mm (width), 55mm (length). The author tested the fitness of newly designed stock tray in 52 subjects with normal occlusion and obtained good results that the problems of conventional stock tray were worked out.

• 구강회복응용과학지
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• 제30권1호
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• pp.23-27
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• 2014

목적: 요오드계 소독제의 고무인상체 안정성에 미치는 영향을 조사하고자 하였다. 연구 재료 및 방법: 폴리설파이드, 실리콘, 폴리이써 고무인상재를 이용하여 72개의 인상체를 채득하였다. 이를 요오드계 소독제인 iodophor 수용액에 각각 10분, 30분간 침적시키고 모형을 제작하여 대조군과 광학현미경을 이용하여 체적 안정성을 평가하였다. 결과: 모든 고무인상체는 0.5% 미만의 체적변화를 보였으나 30분 침적은 10분 침적에 비해 통계적으로 유의하게 변화량이 증가하였다(P < 0.05). 결론: 요오드계 소독제에 고무인상재를 침적시 10분정도의 시간경과가 고무인상재의 체적변화에 영향이 적었다.

• 공업화학
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• 제32권4호
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• pp.467-471
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• 2021

본 연구에서는 가교성 작용기가 기능화된 사다리형 폴리실세스키옥산(LPMA64)을 합성하였고, 이를 액상 전해질의 열 가교 공정에 활용하여 유기-무기 하이브리드 겔 고분자 전해질을 제조하였다. 5 wt%의 낮은 LPMA64 고분자 가교제 함량으로도 전해질 내 네트워크 구조가 잘 발달하여, 우수한 형태 안정성과 높은 이온 전도도를 가지는 전해질의 제조가 가능하였다. 하이브리드 겔 고분자 전해질이 적용된 리튬-황 전지는 안정적인 율속과 장수명 성능 및 높은 쿨롱 효율을 나타냈으며, 이는 완화된 리튬 폴리설파이드 셔틀 현상에 기인했다. 본 연구결과는 제조된 유기-무기 하이브리드 겔 고분자 전해질이 리튬-황 전지 응용에 유망한 전해질임을 보여주었다.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.199-207
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• 2022

Lithium-sulfur batteries (LSBs) have emerged as a promising alternative to lithium-ion batteries (LIBs) owing to their high energy density and economic viability. In addition, all-solid-state LSBs, which use solid-state electrolytes, have been proposed to overcome the polysulfide shuttle effect while improving safety. However, the high interfacial resistance and poor ionic conductivity exhibited by the electrode and solid-state electrolytes, respectively, are significant challenges in the development of these LSBs. Herein, we apply a poly (ethylene oxide) (PEO)-based composite solid-state electrolyte with oxide Li₇La₃Zr₂O₁₂ (LLZO) solid-state electrolyte in an all-solid-state LSB to overcome these challenges. We use an electrochemical method to evaluate the degradation of the all-solid-state LSB in accordance with the carbon content and loading weight within the cathode. The all-solid-state LSB, with sulfur-carbon content in a ratio of 3:3, exhibited a high initial discharge capacity (1386 mAh g^-1), poor C-rate performance, and capacity retention of less than 50%. The all-solid-state LSB with a high loading weight exhibited a poor overall electrochemical performance. The factors influencing the electrochemical performance degradation were revealed through systematic analysis.

• 한국군사과학기술학회지
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• 제26권3호
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• pp.262-272
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• 2023

A polymer-based mechanical low-pass filter(m-LPF) for high-g accelerometers makes it possible to remove high-frequency transient noises from acceleration signals, thus ensuring repeatable and reliable measurement on high-g acceleration. We establish a prediction model for performance of m-LPF by combining a fundamental vibration model with the fractional derivative standard linear solid(FD SLS) model describing the storage modulus and loss modulus of polymers. Here, the FD SLS model is modified to consider the effect of m-LPF shape factor (i.e., thickness) on storage modulus and loss modulus. The prediction accuracy is verified by comparing the displacement transmissibility(or cut-off frequency) estimated using our model with that measured from 3 kinds of polymers(polysulfide rubber(PSR), silicone rubber(SR), and polydimethylsiloxane(PDMS)). Our findings will contribute a significant growth of m-LPF for high-g accelerometers.