• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2377-2379
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• 2005

본 논문은 유연한 영상표시 장치에 응용될 수 있는 중공음극방전 소사(hollow cathode discharge device)를 마이크로머시닝기술로 제작하고 시험한 결과를 보여준다. 중공음극방전은 평판음극방전에 비해서 전류밀도가 큰 장점이 있다. 방전 소자는 유연한 구조의 양극과 음극, 그리고 그 사이의 절연층으로 구성되어 있으면 소자의 크기는 $20mm{\times}10mm$이다. 방전이 일어나는 영역은 관통 구멍으로서 $7{\times}11$개가 배열되어 있고, 구멍의 직경은 $70{\mu}m$이다. 실리콘 기판 위에 SU-8 몰드를 형성한 후 니켈 전기도금으로 음극을 제작한다. 그 위에 폴리이미드를 스핀코팅하여 절연층을 이루고, 열증착으로 알루미늄 양극을 제작한 후, 실리콘과 SU-8을 제거하여 방전 소자를 완성한다. 진공챔버내 아르곤 가스 분위기에서 소자의 두 전극 간 전압을 변화시켜 가면서 전류-전압 특성을 측정하였고, 방전상태를 관찰하였다. 챔버 내의 절대압력이 260mmHg이고 인가전압이 230V 정도일 때 안정 방전이 관찰되었다

• Clean Technology
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• v.27 no.3
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• pp.223-231
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• 2021

In order to address many issues associated with large volume changes of silicon, which has very low electrical conductivity but offers about 10 times higher theoretical capacity than graphite (Gr), a silicon nanoparticles/hollow carbon (SiNP/HC) composite having bimodal-mesopores was prepared using silica nanoparticles as a template. A control SiNP/C composite without a hollow structure was also prepared for comparison. The physico-chemical and electrochemical properties of SiNP/HC were analyzed by X-ray diffractometry, X-ray photoelectron spectroscopy, nitrogen adsorption/desorption measurements for surface area and pore size distribution, scanning electron microscopy, transmission electron microscopy, galvanostatic cycling, and cyclic voltammetry tests to compare them with those of the SiNP/C composite. The SiNP/HC composite showed significantly better cycle life and efficiency than the SiNP/C, with minimal increase in electrode thickness after long cycles. A hybrid composite, SiNP/HC@Gr, prepared by physical mixing of the SiNP/HC and Gr at a 50:50 weight ratio, exhibited even better cycle life and efficiency than the SiNP/HC at low capacity. Thus, silicon/carbon composites designed to have hollow spaces capable of accommodating volume expansion were found to be highly effective for long cycle life of silicon-based composites. However, further study is required to improve the low initial coulombic efficiency of SiNP/HC and SiNP/HC@Gr, which is possibly because of their high surface area causing excessive electrolyte decomposition for the formation of solid-electrolyte-interface layers.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.182.2-182.2
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• 2016

Hollow cathode discharge(중공 음극)는 음극 표면에서 발생되는 2차 전자를 이용하여 높은 밀도의 플라즈마를 만들 수 있는 장점이 있다. 전원으로 microwave, RF, DC, pulsed dc등을 사용할 수 있으며 박막의 증착, 식각 등에 응용 가능하다. 물리적 현상으로는 중공 음극 재료 표면 물질의 가열 및 이온 스퍼터링, 2차 전자의 가열, 자기장 인가 구조의 경우 전자 거동이 있다. PIC(particle-in-cell)방식의 모델링과 fluid model을 이용한 방법이 있는데 본 연구에서는 상용 fluid model software인 ESI사의 CFD-ACE+를 사용하여 모델링 하였다. 구동 주파수는 13.56 MHz의 상용 고주파 전원과 보다 낮은 1 MHz, 100 kHz의 수치 모델을 이용하여 HF, MF, LF 영역에서의 동작 특성을 해석하였다. 1차적으로는 가스 유동의 특성을 2D, 3D로 조사하였고 플라즈마 거동은 2차원을 주로 진행하였으며 계산 시간이 오래 거리는 3차원 모델을 하나 만들어 그 특성을 조사하였다.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.559-564
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• 2019

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.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.819-825
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• 2018

Porous nanofibers comprising hollow ${\alpha}-Fe_2O_3$ nanospheres were prepared by applying both template method and Kirkendall diffusion effect to electrospinning process. During heat-treatment processes, the solid Fe nano-metals formed by initial heat-treatment in the carbon matrix were converted into the hollow structured ${\alpha}-Fe_2O_3$ nanospheres. In particular, PS nanobeads added in the spinning solution were decomposed and formed numerous channels in the composite, which served as a good pathway for Kirkendall diffusion gas. The resulting porous nanofibers comprising hollow ${\alpha}-Fe_2O_3$ nanospheres were applied as an anode material for lithium-ion batteries. The discharge capacities of the nanofibers for the 30th cycle at a high current density of $1.0A\;g^{-1}$ was $776mA\;h\;g^{-1}$. The good lithium ion storage property was attributed to the synergetic effects of the hollow ${\alpha}-Fe_2O_3$ nanospheres and the interstitial nanovoids between the nanospheres. The synthetic method proposed in this study could be applied to the preparation of porous nanofibers comprising hollow nanospheres with various composition for various applications, including energy storage.

• Journal of the Korean Vacuum Society
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• v.19 no.5
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• pp.331-340
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• 2010

3D fluid based numerical modelling is done for a VHF multi hollow cathode array plasma enhanced chemical vapor deposition system. In order to understand the fundamental characteristics of it, Ar plasma is analyzed with a condition of 40 MHz, 100 Vrf and 1 Torr. For hole array of 6 mm diameter and 20 mm inter-hole distance, plasma is well confined within the hole at an electrode gap of 10 mm. The peak plasma density was $5{\times}10^{11}#/cm^3$ at the center of the hole. When the substrate was assumed at ground potential, electron temperature showed a peak at the vicinity of the grounded walls including the substrate and chamber walls. The reaction rate of metastable based two step ionization was 10 times higher than the direct electron impact ionization at this condition. For $H_2$, the spatial localization of discharge is harder to get than Ar due to various pathways of electron impact reactions other than ionization.

• Journal of Korean Medical classics
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• v.19 no.4
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• pp.182-192
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• 2006

통과대복의육십사괘차서도(通過對伏義六十四卦次序圖), 방도(方圖), 원도적연구(圓圖的硏究), 이급장개빈대육십사괘방원도중소천발적의역학내용적연구(以及張介賓對六十四卦方圓圖中所闡發的醫易學內容的硏究), 득출여하결론(得出如下結論): 1. 육십사괘적생성원리중(六十四卦的生成原理中), 존재소강절적일분위이법설화번사전적일정팔회설(存在邵康節的一分爲二法設和繁辭傳的一貞八悔說), 이사지횡향배열적도(而使之橫向排列的圖), 칭위복의육십사괘차서원(대횡도)(稱爲伏義六十四卦次序圓(大橫圖)). 종차원(從此圓), 가청초지효육십사괘적생성근원(可淸楚知曉六十四卦的生成根源). 2. 복의육십사괘원도(伏義六十四卦圓圖), 파대횡도분위료양부분(把大橫圖分爲了兩部分), 즉전삼십이괘종좌상방향하진행료배치(卽前三十二卦從左上方向下進行了配置), 이후삼십이괘종우상방향하원형진행료배치(而後三十二卦從右上方向下圓形進行了配置). 차원이자오묘유위중심청초지현시출료양시(자)(此圓以子午卯酉爲中心淸楚地顯示出了陽始(子)), 양진(묘)(陽辰(卯)), 양극(오)(陽極(午)). 음시(오)(陰始(午)), 음진(유)(陰辰(酉)), 음극(자)등적상(陰極(子)等的象), 체현료천도순환적도리(體現了天道循環的道理). 3. 복의육십사괘방원(伏義六十四卦方圓), 야유래어대횡도(也由來於大橫圖), 역체현료지도원리급선천법상적자연지묘(亦體現了地道原理及先天法象的自然之妙). 4. 복의육십사괘방위원시근거천지지리(伏義六十四卦方位圓是根據天地之理), 재복의육십사괘원도내배치료복의육십사괘방원(在伏義六十四卦圓圖內配置了伏義六十四卦方圓). 저시유주자수차배치적(這是由朱子首次配置的). 원도이원형진행료배치(圓圖以圓形進行了配置), 중공상태체현료천지순환적질서(中空狀態體現了天之循環的秩序), 이방도이방형진행료배치(而方圖以方形進行了配置), 중간충실체현료지지존재적상태(中間充實體現了地之存在的狀態), 기작용균시어중심부(基作用均始於中心部). 방원도중포함착일개월적변화(方圓圖中包含着一個月的變化), 일년적운행(一年的運行), 129,600년지우주일년적변화(年之宇宙一年的變化), 천지적종시(天地的終始), 인물적생사(人物的生死), 고금세변적원리등(古今世變的原理等). 5. 장개빈확립료용역학원리해석의학적의역학(張介貧確立了用易學原理解釋醫學的醫易學), 파육십사괘방원여인체진행결합작료천발(把六十四卦方圓與人體進行結合作了闡發). 기일(基一), 기인위육십사괘원도적중심시태극(基認爲六十四卦圓圖的中心是太極), 차부상당어인체지심, 이건남곤북화리동감서(而乾南坤北和離東坎西), 분별대응어상수하복화좌우이목(分別對應於上首下腹和左右耳目). 기이(基二), 원도이사등분적사상(圓圖以四等分的四象), 파인생분위료사분(把人生分爲了四分), 병분별진행료배속(幷分別進行了配屬). 저설명료파육십사괘여 "소문·상고천진론" 중이팔수위변적장부원리(這設明了把六十四卦與『素問·上古天眞論』中以八수爲變的丈夫原理), 소진행적배속관계(所進行的配屬關係). 기삼(基三), 기인위재원도중(基認爲在圓圖中), 여동양시생적복괘(천근)여음시생적구괘(월굴), 相互交替進行循環一樣, 인적생장쇠로적도리화일일중오매적도리시일양적(人的生長衰老的道理和一日中寤寐的道理是一樣的). 기사(基四), 기재원도중(基在圓圖中), 이천양재남화천부족서북(以天陽在南和天不足西北), 래설명료건재남화곤재북적도리(來說明了乾在南和坤在北的道理), 병재방토중이지강재북화지불만동남(幷在方土中以地剛在北和地不滿東南), 래설명료건재서북화건재동남적도리, 이육십사괘적원리여의학밀접결합, 대지진행료설명(對之進行了說明).