3D flexible Si based-composite (Si@Si₃N₄)/CNF electrode with enhanced cyclability and high rate capability for lithium-ion batteries

Kim, Si-Jin,Kim, Min-Cheol,Han, Sang-Beom,Lee, Gyu-Ho,Choe, Hui-Seon,Kwak, Da-Hee,Choi, Sun-Yong,Son, Byung-Goo,Shin, Myoung-Sun,Park, Kyung-Won Elsevier 2016 Nano energy Vol.27 No.-

<P><B>Abstract</B></P> <P>Despite extremely high capacity of Si-based anodes in lithium-ion batteries (LIB), Si-based materials have shown a structural collapse caused by a volumetric expansion/contraction during the cycling process. The conventional electrode structure, which consists of active materials, a current collector, a conducting agent, and a binder, actually showed a low loading of active material due to the other heavy components. In this study, we prepared a 3D flexible Si-composite electrode consisting of core (Si)-shell (Si<SUB>3</SUB>N<SUB>4</SUB>) NPs (Si@Si<SUB>3</SUB>N<SUB>4</SUB>) and carbon nanofibers (denoted as Si-composite/CNF). The Si-composite/CNF was directly utilized as an anode in the absence of the other components was electrochemically evaluated using a coin-type cell. The Si-composite/CNF showed a high capacity of 665mAhg<SUP>−1</SUP> at a fairly high current density of 10Ag<SUP>−1</SUP> and an extremely low capacity loss for 2000 cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We prepared Si-composite/CNF exhibits a 3D flexible Si-composite electrode. </LI> <LI> The electrode consists of core (Si)-shell (Si<SUB>3</SUB>N<SUB>4</SUB>) NPs (Si@Si<SUB>3</SUB>N<SUB>4</SUB>) and carbon nanofibers. </LI> <LI> The Si-composite/CNF was directly utilized as an anode. </LI> <LI> Si-composite /CNF exhibited high specific capacity and improved high rate cycling performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Microstructure and Tensile Properties in Low Pressure Cast Al-Si Alloy through Cooling Rate Control

Suh, Jun-Young,Park, Sung Jin,Lee, Hee-Kwon,Chang, Si Young Materials Research Society of Korea 2020 한국재료학회지 Vol.30 No.2

In this study, three kinds of metal chills such as SS400, AC4CH and brass, with different thicknesses of 40 ~ 80 mm, were applied for low pressure casting of Al-Si alloy to control cooling rate. The microstructural characteristics with increasing cooling rate were represented using factors including D₁, D₂, size of primary α phases and shape factor and size of eutectic Si. The tensile properties were investigated and additionally analyzed based on the microstructural characteristics. As the cooling rate increased, D₁, D₂, and sizes of primary α phases and eutectic Si apparently decreased and the shape factor of eutectic Si increased to over 0.8. The ultimate tensile strength (UTS) and yield strength (YS) increased with decreasing D₁, D₂, and size of primary α phases, while elongation increased with decreasing size of eutectic Si and concurrently increasing shape factor of eutectic Si. This indicated that the primary α phases and eutectic Si in Al-Si alloy were refined with increasing cooling rate, resulting in improvement of UTS and YS without sacrificing elongation. After the tensile test, preferential deformation of primary α phases was observed in the Al-Si alloy produced at higher cooling rates of more than 0.1 K/s.

Controlled infiltration profile of SiC coating layer on graphite by Si vapor deposition reaction

Kuk-Jin Hwang,Si-Young Bae,Kyoung-Ho Kim,Yoon-Cheol Lee,Jung-Tae Hwang,Heesoo Lee,Seong Min Jeong,Myung-Hyun Lee 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.2

SiC-coated graphite was successfully fabricated at different temperatures (1300-1600 oC) through a silicon vapor depositionreaction (Si-VDR) process. Si powder was used for the Si source of the SiC coating layers. When Si powder was evaporatedat high temperature near the melting point of bulk Si, Si gases are moved and changed into Si liquid at the surface of thegraphite. The high-temperature process facilitated the formation of SiC coating layers on the graphite. The microstructural,mechanical, and thermal oxidation properties of the coated graphite were investigated.

Wire Saw 슬러리로부터 Si와 SiC의 선택적 회수

한승열,이종대,전진혁,박노국,이태진,류시옥 嶺南大學校 工業技術硏究所 2004 工業技術硏究所論文集 Vol.32 No.1

This study was focused on the recovery of Si and SiC from wire saw slurry in wire saw slicing process. In order to separate Si and SiC from wire saw slurry, alkali dissolution method was used and then Na₂O showed superior dissolution property of Si. At this time, SiC was separated as powder from alkali aqueous solution. Si was dissolved as a liquid in alkali aqueous solution. After removing SiC powder, the powder was obtained by drying alkali aqueous solution and then it's XRD analysis showed that it was the water glass (Na₂SiO₃).

Wire Saw 슬러리로부터 Si, SiC 분리 및 제올라이트 합성에 대한 연구

한승열,이종대,박노국,이태진,류시옥 한국공업화학회 2004 응용화학 Vol.8 No.1

This study was focused on the separation of Si and from Wire Saw Slurry in Wire Saw Slicing process and synthesis of zeolite by mixing with water glass obtained from its process and Alumina. In order to separate Si and SiC from Wire Saw Slurry, Alkai disslution was used and then Na₂O showed superior dissoluble property of Si. At this time, SiC was separated as powder from Alkali apueous solution. Si was dissolved as a liquid in Alkali aqueous solution. After removing SiC powder, the powder formed was obtained from drying. Alkali aqueous solution and then it was the water glass (Na₂SiO₃)confirmed by XRD analysis. Water glass (Na₂SiO₃) and Alumina mixed with pure water made as a synthesis of zeolite through the crystallization by aging and hydrothermal reaction. The manufactured zeolite was Sodium Aluminum Silicate Hydrate confirmed by XRD analysis.

The Change of Skeletal Muscle Mass Is Associated with Hepatic Steatosis in Non-Alcoholic Fatty Liver Disease

( Do Seon Song ),( U Im Chang ),( Seong Woo Go ),( Jeong Won Jang ),( Si Hyun Bae ),( Seung Kew Yoon ),( Jin Mo Yang ) 대한간학회 2018 춘·추계 학술대회 (KASL) Vol.2018 No.1

Aims: We aimed to investigate the association between the change of muscle mass and change of fibrosis and steatosis in NAFLD patients. Methods: We analyzed 2,893 NAFLD subjects who had health check-up more than twice in St. Vincent’s Hospital between November 2009 and December 2017. NAFLD was diagnosed by ultrasound, and appendicular muscle mass (ASM) was assessed by Inbody 720, and Sarcopenia index was calculated as ASM divided by weight (SI%) and ASM divided by body mass index (SI-BMI). Non-invasive markers were used to evaluate the severity of hepatic fibrosis and steatosis; NAFLD fibrosis score (NFS), Fibrosis-4 (Fib-4) score, and Forn’s index for fibrosis, and hepatic steatosis index (HSI) and fatty liver index (FLI) for steatosis. Results: The mean age was 47.3±10.4 years, and 1956 subjects (67.6%) were male. Diabetes, hypertension, metabolic syndrome were more prevalent in sarcopenic subjects (P<0.01), and non-invasive fibrosis and steatosis markers were higher in sarcopenic subjects (P< 0.01). The mean interval between two health check-up was 39.8±21.9 months. There was no significant association between the change of NFS, Fib-4, and Forn’s index and the change of SI% and SI-BMI (all P >0.1). However, the changes of HIS and FLI were significantly associated with the change of SI% and SI-BMI (all P<0.01). Multivariate logistic analysis demonstrated the independent association between the change of skeletal muscle mass and the changes of non-invasive steatosis markers after adjusting for other confounding factors (all P< 0.001). However, the changes of non-invasive fibrosis markers did not show an independent association with the change of appendicular muscle mass after adjusting for other confounders (all P >0.1) Conclusions: The change of muscle mass is strongly associated with the change of hepatic steatosis, but not the change of fibrosis.

원거리 플라즈마 화학증착법으로 증착된 이산화규소박막의 물성

박영배,강진규,이시우,Park, Yeong-Bae,Gang, Jin-Gyu,Lee, Si-U 한국재료학회 1995 한국재료학회지 Vol.5 No.6

원거리 플라즈마 화학증착법을 이용하여 저온에서 이산화규소박막을 제조하였다. 본 연구 에서는 공정변수인 기판의 온도, 반응기체의 조성 및 분압과 플라즈마 전력에 따른 산화막의 재료적인 물성을 평가하였다. XPS결과에서 산화막은 양론비(O/Si=2)보다 약간 적어 실리콘이 많이 함유된 막으로 나타났다. 이 경우 굴절율과 ESR분석에 의해 미결합된 실리콘의 양이 증가함을 알 수 있었다. SIMS분석에 의해 미량의 질소성분이 계면에 존재하는 것과 실리콘 미결함을 관찰하였다. FT-IR로부터 막내 수소량을 정량화하였으며 결합각 분포는 20$0^{\circ}C$이상에서 열산화막과 비슷한 값을 얻었다. 하지만 열산화막에 비해 높은 식각율을 보여 계면 스트레스에 의해 막내의 결합력이 약해진 것으로 생각된다. Silicon oxide thin films were deposited by remote plasma chemical vapor deposition (RPCYD). The effect of the operating variables, such as plasma power, deposition temperature and partial pressure of reactant on the material Properties of the silicon oxide film was investigated. By XPS, it was found out that the film was suboxide (O/Si<2) and small amount of nitrogen due to the plasma excitation was accumulated at the Si/SiO$_2$interface. The amount of dangling bonds at the Si/SiO$_2$interfaces were measured by ESR and the concentration of hydrogen bond was obtained by SIMS and FT-IR. The bond angle distribution(d$\theta$/$\theta$) was shown to be similiar to thermal oxide above 20$0^{\circ}C$ but the etch rate was higher than that of the thermal oxides due to the structural difference and the stress between silicon substrate and silicon oxide film.

Learning Theory on Foreign Policy Analysis: Concepts and Pitfalls

Jin,Si-Won 한국시민윤리학회 2005 한국시민윤리학회보 Vol.18 No.2

This paper is solely based on a theory driven literature review on learning theory. In the discipline of Foreign Policy Analysis, the concept of learning as well as argument of learning theory is highly contentious among scholars and as a result, learning theory in Foreign Policy Analysis is regarded as a conceptual minefield or a theoretical maze. This is the reason why this paper tries to compare and summarise contending discussion on learning theory developed in Foreign Policy Analysis. This paper, first of all, explains the background of the emergence of Foreign Policy Analysis and then various scholars' contentious argument are compared and summarised. And, after reviewing limits and problems of using learning theory, this paper finishes with a brief summary and author's future research topics by which actual applications of learning theory towards foreign policy issues will be pursued.

Effects of Phenytoin and Diazepam on the Seizure Activity in the Cortical Dysplasia Animal Models

Kim, Si-Hyung,Choi, In-Sun,Cho, Jin-Hwa,Park, Eun-Ju,Jang, Il-Sung,Choi, Byung-Ju,Kim, Hyun-Jung,Kim, Young-Jin,Nam, Soon-Hyeun The Korean Academy of Oral Biology 2006 International Journal of Oral Biology Vol.31 No.2

Dysplasia-associated seizure disorders are markedly resistant to pharmacological intervention. Relatively little research has been conducted studying the effects of antiepileptic drugs(AEDs) on seizure activity in a rat model of dysplasia. We have used rats exposed to methylazoxymethanol acetate(MAM) in utero, an animal model featuring nodular heterotopia, to investigate the effects of AEDs in the dysplastic brain. Pilocarpine was used to induce acute seizure in MAM-exposed and age-matched vehicle-injucted control animals. Field potential recordings were used to monitor amplitude and numbers population spikes, and paired pulse inhibition in response to stimulation of commissural pathway. Two commonly used AEDs were tested: diazepam 5, 2.5mg/kg;phenytoin 40, 60mg/kg. Diazepam(DZP) and phenytoin(PHT) reduced the amplitude of population spike in control and MAM-exposed rats. However, the amplitude of population spike was nearly eliminated in control rats as compared to the MAM-exposed rats. Pharmaco-resistance was tested by measuring seizure latencies in awake rats after pilocarpine administration(320mg/kg, i.p.) with and without pretreatment with AEDs. Pre-treatment with PHT 60 mg prolonged seizure latency in control rats, but not in MAM-exposed animals. The main findings of this study are that acute seizures initiated in MAM-exposed rats are relatively resistant to standard AEDs assessed in vivo. These data suggest that animal model with cortical dysplasia can be used to screen the effects of potential AEDs.

初等學校 校庭內 生態園 造成技法 : With a Special Reference to Hu-am Elementary School in Yong-san gu, Seoul 서울 龍山區 厚岩 初等學校 事例를 중심으로

진시현,심우경,이광우 韓國植物ㆍ人間ㆍ環境學會 2000 인간식물환경학회지 Vol.3 No.1

이 논문의 연구목적은 초등학교내에 생태원을 조성함으로써 아이들에게 자연과의 접촉기회를 제공하고자 실시한 바, 그 결과는 다음과 같다. 1. 초등학교 교과서에 나타나는 모든 동, 식물의 종류 초등학교의 교과서 분석 경과 274종의 식물종과 227종의 동물종이 나타났으며, 가장 높은 빈도수를 나타낸 곤충은 나비 78회, 잠자리 64회, 개미 51회, 벌 41회, 그리고 매미가 31회의 순으로 나타났다. 이는 교과서별 학년별로 빈도수를 조사한 결과와도 비슷한 양상을 나타낸 것이다. 초등학교 교과서 중 자연과 과목의 교육내용을 살펴본 결과, 1∼2학년 과정에서는 학교내의 뜰과 화단의 4계절 변화를 관찰하고 3∼6학년 과정에서는 생태계 전반에 걸친 세부적인 내용을 공부하도록 교육내용이 설정되었음을 알 수 있었다. 2. 용산구에 있는 15개의 초등학교의 옥외환경 조사 용산구에는 15개 학교가 있고, 그들의 옥외환경의 형태는 교재원과 생산원의 두 가지 종류로 나타났다. 대부분의 학교가 이 두 가지 형태로 나타났으나 남정, 보광, 원효로, 한강 초등학교는 생태원의 시설중 소동물 사육장 시설이 없었고, 교재원의 시설도 빈약하였다. 사례지역인 후암 초등학교는 도시의 중심부에 위치해 있는 다른 초등학교와는 달리 풍부한 생물상을 가지고 있는 남산에 인접하고 있기 때문에 생태원으로서의 기능성이 있는 것으로 보여진다. 3. 사례연구와 생태원 조성계획 생태원의 조성방법으로서 우선, 사례지인 후암 초등학교 부지의 현황조사를 하였고, 두 번째로 4가지 곤충(나비, 잠자리, 벌, 매미)들을 유치하기 위한 식물들을 선별하기 위해 이들이 식이식물로 조사된 식물들 중에서 교과서에 나오고 사례지역에 적합하며 내공해성을 가지며, 자생종이 식물들을 선별한 결과, 나비, 잠자리, 새를 유치하기 위한 식이식물로 각각 44, 17, 16종이 선별되었다. 또한 이 학교의 건물이 도로와 맞닿는 점을 감안하여 건물옥상에 생물서식지를 조성함으로서 남산으로부터의 풍부한 생물종의 유입을 유도하고, 더 나아가 학교 내에 조성되는 생태원으로 자연스럽게 유도하고자 하였다. 따라서 옥상 위의 생물서식공간은 수변공간계획과 식재계획을 통하여 곤충류와 조류뿐만 아니라 다양한 생물종이 서식되도록 하였고, 이를 통해 초등학교 학생들은 자연과의 친밀한 접촉기회를 가지게 될 것이다. The purpose of this study was to offer the opportunity of contact with the nature to urban children by the creation of the biotope in the elementary school ground. The results for this study were as follow: 1. The kinds of animals and plants the elementary school textbooks were 275 species and 227 animals. The frequencies of insect species in the elementary school textbook were the butterfly(75), dragonfly(64), ant(51), bee(41), and cicada(31) in order. These results were analogous to the numbers in each textbook and grade. In the 'Nature' textbook of the elementary school, there were educational contents to observe the ground and garden in 1, 2 grade courses and to study the detail of ecosystem in 3-6 grade course. 2. Inventory of the out-door environments of 15 elementary schools in Young-san Gu, Seoul. The number of total elementary school in Young-san Gu were fifteen, which had two garden types appeared as nature study and experimental farm. Two types of gardens were appeared mostly in all the elementary school but Nam-jung, Bu-kwang, Wonhyo-ro, Sin-swang, and Han-gang elementary school didn't have the experimental farms and also have the poor facilities of the nature study gardens. Huam elementary school had the possibility of the biotope creation because it was connected to Namsan park which posseses the abundant biota in contrast to the others in the center of the city. 3. Case study and biotope planning. To create the biotope, the site analysis was carred out and then plant species for inducing 4 kinds of insect (butterfly, dragonfly, bee, and cicada) were selected under the criteria as pollution-resistant, the school tree and flower, tolerance, and original habitat. Consequently, the numbers of plants for inducing butterflies, dragonflies and birds were 44, 17, 16 species separately. Also, it was planned to the induce abundant biota to building's roof as stepping stone from Namsan. These two biotopes were planned to be a habitat of various biota in addition of the water pond and the planting plan. Through the biotope created by this plan, the students of the elementary school will have more opportunity of contact with the nature.