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>

1T DRAM with Raised SiGe Quantum Well for Sensing Margin Improvement

Si-Won Lee,Seongjae Cho,Il Hwan Cho,Garam Kim 대한전자공학회 2023 Journal of semiconductor technology and science Vol.23 No.1

In this paper, a novel one-transistor dynamic random-access memory (1T DRAM) with a raised SiGe quantum well (QW) under one gate in the double-gate (DG) structure is proposed. The proposed structure can improve the poor performance of the retention time and sensing margin which is the problem of the conventional 1T DRAM. In write operation, the performance is improved through the band to band tunneling (BTBT) between body and drain and through valence band offset between SiGe and Si. Also by utilizing the physical barrier of oxide, read “1” retention time can be increased. The fabrication process is also proposed.

SiC 단결정의 TSSG 공정을 위한 전이금속 특성 연구

이승준,유용재,정성민,배시영,이원재,신윤지,Lee, Seung-June,Yoo, Yong-Jae,Jeong, Seong-Min,Bae, Si-Young,Lee, Won-Jae,Shin, Yun-Ji 한국결정성장학회 2022 한국결정성장학회지 Vol.32 No.2

본 연구에서는 SiC 단결정의 TSSG 공정중 결정 품질을 저하시키지 않으면서도 의도하지 않은 질소 도핑(N-UID)을 쉽게 제어하기 위해 지금까지 Co 또는 Sc 전이금속을 첨가한 신규 용융조성을 제안한다. Co 또는 Sc의 특성을 파악하기 위해 Ar 분위기에서 1900℃ 온도에서 약 2시간 동안 열처리 실험을 수행했다. 용융조성은 Si-Ti 10 at% 또는 Si-Cr 30 at%를 비롯하여, 탄소 용해도에 효과적이라고 알려진 Co 또는 Sc을 각각 3 at% 첨가하였다. 열처리 후 도가니 단면을 가공하여 도가니-용융물 계면에서 발생한 Si-C 반응층을 관찰하고, 탄소황분석을 통해 조성에 따른 탄소 용해도를 간접적으로 분석하였다. 그 결과, Si-Sc 기반 용융조성이 TSSG 공정에 적합한 특성을 갖는 Si-C반응층을 형성하고 있었다. 또한 탄소황분석 결과에서도 Cr 다음으로 높은 탄소량이 갖는 것으로 분석되었다. Sc는 Cr에 비해 질소와의 반응성이 낮은 이점을 가지므로 TSSG 공정에 Si-Sc 용융조성을 적용하면, 본 연구에서 의도한 대로 SiC 단결정 성장속도와 질소 UID를 모두 제어할 수 있는 것으로 고려된다.

고품질 4H-SiC 단결정 성장을 위한 다공성 흑연 판의 역할

이희준,이희태,신희원,박미선,장연숙,이원재,여임규,은태희,김장열,전명철,이시현,김정곤,Lee, Hee-Jun,Lee, Hee-Tae,Shin, Hee-Won,Park, Mi-Seon,Jang, Yeon-Suk,Lee, Won-Jae,Yeo, Im-Gyu,Eun, Tai-Hee,Kim, Jang-Yul,Chun, Myoung-Chul,Lee, Si-Hyun 한국결정성장학회 2015 한국결정성장학회지 Vol.25 No.2

본 연구에서는 PVT법으로 4H-SiC 단결정 성장 시 다공성 흑연판을 사용하여 Si/C 비율이나 온도구배, 물질전달의 향상시킴으로써 고품질의 SiC 단결정 기판 제작을 목적으로 연구를 진행하였다. 연구에 사용된 SiC 소스 물질은 흑연 도가니에 넣어 흑연 단열재로 쌓인 구조로 실험을 하였다. 성장온도는 $2100{\sim}2300^{\circ}C$, 그리고 성장압력은 10~30 Torr의 압력으로 아르곤과 질소 분위기에서 성장시켰다. 종자정은 2인치의 $4^{\circ}$ off-axis 4H-SiC의 C면 (000-1)을 사용하였고 다공성 흑연판은 SiC 소스 물질 위에 삽입하였다. 4H-SiC 결정다형 안정화를 위한 C-rich 조건이나 균일한 온도구배를 만들어주기 위해 다공성 흑연판을 삽입하여 실험을 진행하였다. 일반적인 도가니의 경우, 성장된 wafer에서 6H-, 15R-SiC와 같은 다양한 결정다형이 관찰된 반면에 다공성 흑연판을 삽입한 도가니에서는 4H-SiC만 관찰되었다. 또한 다공성 흑연판을 삽입한 도가니에서 성장된 결정에서 MP나 EP의 낮은 결함밀도를 보였으며 결정성 또한 향상된 것을 학인하였다. The present research is focused on the effect of porous graphite what is influenced on the 4H-SiC crystal growth by PVT method. We expect that it produces more C-rich and a change of temperature gradient for polytype stability of 4H-SiC crystal as adding the porous graphite in the growth cell. The SiC seeds and high purity SiC source materials were placed on opposite side in a sealed graphite crucible which was surrounded by graphite insulator. The growth temperature was around $2100{\sim}2300^{\circ}C$ and the growth pressure was 10~30 Torr of an argon pressure with 5~15 % nitrogen. 2 inch $4^{\circ}$ off-axis 4H-SiC with C-face (000-1) was used as a seed material. The porous graphite plate was inserted on SiC powder source to produce a more C-rich for polytype stability of 4H-SiC crystal and uniform radial temperature gradient. While in case of the conventional crucible, various polytypes such as 6H-, 15R-SiC were observed on SiC wafers, only 4H-SiC polytype was observed on SiC wafers prepared in porous graphite inserted crucible. The defect level such as MP and EP density of SiC crystal grown in the conventional crucible was observed to be higher than that of porous graphite inserted crucible. The better crystal quality of SiC grown using porous graphite plate was also confirmed by rocking curve measurement and Raman spectra analysis.

Stress-relieved Si anode on a porous Cu current collector for high-performance lithium-ion batteries

Moon, Sang-Hyun,Kim, Si-Jin,Kim, Min-Cheol,So, Jin-Young,Lee, Ji-Eun,Shin, Yeon-Kyung,Bae, Won-Gyu,Park, Kyung-Won Elsevier 2019 Materials chemistry and physics Vol.223 No.-

<P><B>Abstract</B></P> <P>To overcome the mechanical stress generated during the cycling process in lithium-ion batteries, Si anode is fabricated on a porous Cu current collector with holes using sputtering deposition method. The porous Cu/Si shows superior high-rate and cycling performance in lithium-ion batteries compared to the Si anode on the flat Cu. The excellent high-rate performance and stable cyclability of the porous Cu/Si can be predominantly attributed to the efficient relief of the stress generated by the volumetric expansion of the Si anode on the porous Cu current collector.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Si anode for LIBs was fabricated on a porous Cu current collector having holes. </LI> <LI> The porous Cu/Si showed the superior high-rate and cycling performance. </LI> <LI> The excellent performance of the porous Cu/Si can be due to the relief of the stress. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fungi Associated with the Traditional Starter Cultures Used for Rice Wine in Korea

( Si Young Yang ),( Jung Kwan Lee ),( Jung Ki Kwak ),( Ki Hyun Kim ),( Min Jae Seo ),( Yin Won Lee ) 한국응용생명화학회(구 한국농화학회) 2011 Applied Biological Chemistry (Appl Biol Chem) Vol.54 No.6

The ``Nuruk`` starter culture has been used for many years in the fermentation of rice wine in Korea. In present study, mycobiota in Nuruk cultures was identified by performing morphological, physiological, and phylogenetical analyses. Mucorales was the most common mycobiota in Nuruk, followed by yeast and Aspergillus. The composition of fungal species in Nuruk was different among samples and did not correlate with the geographical location from where the Nuruk culture was manufactured. For more detailed identification, 174 filamentous fungal strains were isolated from 39 Nuruk samples. Although the morphological and molecular analyses showed that the strains were identical at the genus level, some discordance was identified between species. Of the 174 strains, 160 showed thermotolerance, and the level of thermotolerance matched the clade generated by phylogenetic analysis. Six genera (Lichtheimia, Aspergillus, Rhizopus, Rhizomucor, Mucor, and Syncephalastrum) and 17 fungal species were identified. Among the genera, the genus Syncephalastrum had not been previously identified in Nuruk cultures, and the isolate was identified as Syncephalastrum racemosum. Two genera, Lichtheimia and Aspergillus, comprised approximately 84% of the filamentous fungal isolates from the Nuruk samples, and Lichtheimia ramosa and Aspergillus oryzae were the most commonly found species. The controversy regarding the presence of mycobiota in Nuruk starter cultures was addressed, and results showed that Nuruk contains unique mycobiota not yet found in other Asian starter cultures.

Formulation development and pharmacokinetic evaluation of enteric-coated dexrabeprazole tablets

Lee Tae Jin,Kim Dohyun,Kim Jae Cheon,Ro Si Won,Na Dong Hee 한국약제학회 2023 Journal of Pharmaceutical Investigation Vol.53 No.2

Purpose This study investigated the development of an enteric-coated tablet of dexrabeprazole, the R(+)-isomer of rabeprazole, and evaluated the stability and pharmacokinetic properties in beagle dogs. Methods The optimal alkaline excipient was investigated for stabilizing dexrabeprazole through drug-excipient compatibility test. The enteric-coated tablets were prepared comprising a core containing dexrabeprazole and the optimal stabilizer, an enteric-coat surface layer, and an intervening thin seal coat. Dissolution test of the enteric-coated dexrabeprazole tablets was performed in various buffer settings, and the dissolution pattern was compared with that of commercial rabeprazole tablets. The optimized dexrabeprazole tablet was characterized by accelerated stability testing for 6 months and pharmacokinetic study in beagle dogs. Results The enteric-coated dexrabeprazole tablets were successfully prepared using magnesium oxide as an alkaline stabilizer. In the dissolution study, all dexrabeprazole tablets exhibited delayed-drug-release properties; the optimal formulation indicated similar dissolution behavior to the commercial rabeprazole product. A dose-proportional pharmacokinetic profile was observed in beagle dogs for the optimized formulation, which achieved higher stability compared to the commercial rabeprazole, as proved by the 6-month accelerated stability testing. Conclusion The novel dexrabeprazole enteric-coated tablet that was developed showed superior stability and similar dissolution as the commercial rabeprazole product with dose-proportional pharmacokinetics. These findings suggest that the dexrabeprazole tablet has a high potential for commercialization.

Preparation and in vivo Evaluation of a Sildenafil Lactate-Loaded Solid Self-emulsifying Drug Delivery System

( Si Young Jung ),( Dong Wuk Kim ),( Dong Won Lee ),( Jong Soo Woo ),( Jong Oh Kim ),( Chul Soon Yong ),( Han Gon Choi ) 한국약제학회 2011 Journal of Pharmaceutical Investigation Vol.41 No.4

To develop a sildenafil lactate-loaded solid self-emulsifying drug delivery system (SEDDS) with a fast onset of action and immediate action of erection, sildenafil lactate (0.3 g), which was prepared using a spray dryer, was dissolved in 4.7 g of the mixture of glyceryl monooleate/Transcutol/ Tween 20 (3/0.5/1, g). Its emulsion droplet size and pharmacokinetics in rabbits were evaluated compared with sildenafil citrate-loaded commercial tablet. The sildenafil lactateloaded SEDDS showed an emulsion droplet size of about 300 nm. In pharmacokinetics study, it gave significantly faster Tmax than did the commercial tablet. Thus, the sildenafil lactate-loaded SEDDS at the one-third drug dose compared to sildenafil citrate-loaded conventional tablet might induce a fast onset of action and immediate erection without enhanced bioavailability compared with the sildenafil citrate-loaded commercial tablet.

[P10-149] 3'-Deoxyadenosine isolated from Cordycepsis millitaris inhibits differentiation of 3T3-L1 cell to adipocytes

Si-Kwan Kim,Sung-Won Kim,Su-Chan Lee,Il-Woong Kim 한국식품영양과학회 2006 한국식품영양과학회 학술대회발표집 Vol.2006 No.10

Disorders of Small and Large Intestine : Histological Quality Of Polyps Less Than 1cm Resected Using Different Electric Current

( Si Hyung Lee ),( Heon Ju Lee ),( Joon Hyuk Choi ),( Byung Ik Jang ),( Kyu Hyung Lee ),( Kyeong Ok Kim ),( Jae Won Choi ),( Yoon Sun Park ),( Jong Ryul Eun ),( Tae Nyeun Kim ) 대한소화기학회 2007 SIDDS Vol.9 No.-

Background/Aims: Colonoscopic polypectomy effectively prevent colorectal cancer. Recent studies have shown that advanced histology including carcinoma was found in 10.1% of small (5-10 mm) adenoma. Thus, accurate evaluation of small polyp histology is paramount in decision-making process. The aim of this study was to assess and compare the histologic quality of polyps obtained by snare polypectomy using two different electric current. Methods: Consecutive polyps less than 1 cm were identified and removed by using either blended mode (Circon, BC-200) or automatic cutting and coagulation mode (Endocut Q mode, affect 3, 40 watt, Erbe, VAIO-300). An experienced gastrointestinal pathologist evaluated the specimens for cautery damage(amount and degree), margin evaluability, architecture, presence of muscularis mucosa and general histologic quality. Results: Sixty-seven patients (76% men, mean age 59.9±9.7) underwent 111 polypectomies (54 using blended mode and 57 using Endocut Q mode, mean diameter 0.88±0.17 mm). Age, gender, location, diameter, histology of polyp was not different in both group. Cautery amount (more than moderate severity) was higher in polyp resected using blended mode (51%) than Endocut Q mode (50%) but this difference did not reach statistical significance. Also, we found that the cautery degree, margin evaluability, architecture, presence of muscular mucosa, overall histologic quality was not different in both group (p>0.05). Conclusions: Histologic quality of polyps less than 1 cm by using either blended mode or Endocut Q mode was not different. Further study is needed to evaluate the correlation between size of polyp and histologic quality.