Community and Communication in the Global Context

JAECHUL SHIM 한국언론학회 2008 Asian Communication Research Vol.5 No.1

3D in-situ hollow carbon fiber/carbon nanosheet/Fe₃C@Fe₃O₄ by solventless one-step synthesis and its superior supercapacitor performance

Ju, Jaechul,Kim, Minjae,Jang, Seokhoon,Kim, Yeongseon,Choi, Yongheum,Baeck, Sung-Hyeon,Shim, Sang Eun Pergamon Press 2017 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>Herein, 3D <I>in-situ</I> hollow carbon fiber/carbon nanosheet/Fe<SUB>3</SUB>C@Fe<SUB>3</SUB>O<SUB>4</SUB> (h-CNF/CNS/Fe<SUB>3</SUB>C@Fe<SUB>3</SUB>O<SUB>4</SUB>) was constructed using ferrocene and oleic acid by a solventless one-step process that did not require additional filtering, neutralization, drying, or calcination steps. The iron-oleate chelating structure that self-assembled during annealing facilitated the fabrication of 3D <I>in-situ</I> h-CNF/CNS/Fe<SUB>3</SUB>C@Fe<SUB>3</SUB>O<SUB>4</SUB> by undergoing graphitization at 600°C. This carbon shell of the 3D <I>in-situ</I> h-CNF/CNS/Fe<SUB>3</SUB>C@Fe<SUB>3</SUB>O<SUB>4</SUB> was derived from the two cyclopentadienyl rings in ferrocene. This hybrid material made from economically cheap oleic acid exhibited superior supercapacitive behavior: high specific capacitance of 327Fg<SUP>−1</SUP> at 5mVs<SUP>−1</SUP> and 210Fg<SUP>−1</SUP> at 10mVs<SUP>−1</SUP>, good rate capability of 60Fg<SUP>−1</SUP> at 10Ag<SUP>−1</SUP> (compared to 70Fg<SUP>−1</SUP> at 1Ag<SUP>−1</SUP> for pure Fe<SUB>3</SUB>O<SUB>4</SUB>), and superior retention of 108% after 6000 cycles at 100mVs<SUP>−1</SUP>. These superior supercapacitive properties were ascribed to the 3D graphitic h-CNF/CNS for enhancing electrical conductivity and the carbonaceous shell over Fe<SUB>3</SUB>C@Fe<SUB>3</SUB>O<SUB>4</SUB> core for buffering the bulk expansion of iron-related particles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 3D <I>in-situ</I> h-CNF/CNS/Fe<SUB>3</SUB>C@Fe<SUB>3</SUB>O<SUB>4</SUB> was constructed using ferrocene and oleic acid by a solventless one-step process. </LI> <LI> h-CNF/CNS/Fe<SUB>3</SUB>C@Fe<SUB>3</SUB>O<SUB>4</SUB> exhibited higher specific capacitance of 327Fg<SUP>−1</SUP> at 5mVs<SUP>−1</SUP> and 210Fg<SUP>−1</SUP> at 10mVs<SUP>−1</SUP>, and superior retention of 108% after 6000 cycles at 100mVs<SUP>−1</SUP>. </LI> <LI> Carbon nanoshell comprising h-CNF and CNS well encapsulates Fe<SUB>3</SUB>C@Fe<SUB>3</SUB>O<SUB>4</SUB> core materials and this sturdy structure endows high cycle stability up to 6000 cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

저농도 노말헥산의 만성폭로가 말초신경계에 미치는 영향

이수진,송재철,장은철,이경영,심상효,박시복,박영재,김현주 大韓産業醫學會 1999 대한직업환경의학회지 Vol.11 No.3

Objectives: The effect of chronic exposure to low levels of n-hexane on peripheral nervous system and the relationship between duration of employment and impairment of peripheral nervous system was studied. Methods : In 21 workers at two shoe-maker factories and 21 unexposed controls, measurement of exposure of solvents, symptom Questionnaire, physical examination and electrophysiological study were conducted. Results : Mean ages of study subjects in the exposed and the unexposed were 39.9 and 40.1 years old. Mean durations of employment were 15.1 and 10.0 years, respectively. Mean concentrations of urinary 2.5-HD were 2.23 mg/g creatinine, 0.23 mg/g creatinine, respectively. Mean concentration of solvents in air were 21.1 ppm of n-hexane, 72.2 ppm of toluene and 0.5 ppm of MEK. There were no differences in the prevalence of subjective symptoms and abnormal neurological signs between the exposed and the unexposed. But vibration extinction time(VAT) of the exposed (8.8 second) was shorter than that of the unexposed (11.9 second) (p<0.05). Mean values of electrophysiological studies(EPS) of the two groups were within normal limit. However, mean conduction velocity of median motor nerve and median F wave(MMNCV and MFCV), mean amplitude of median sensory action potential(MSAP) were decreased in the exposed (p<0.05). Moreover, the rate of abnormal finding more than one in sensory nerves was increased in the exposed than those in the unexposed(p<0.05). Correlation coefficients between duration of employment and mean conduction velocity of median sensory nerve (MSNCV) and between duration of employment and MFCV were -0.57, -0.43, respectively (p<0.05). Conclusions : These results showed that chronic (mean 15 years) low level(mean 23 ppm) exposure to n-hexane cause subclinical impairment of peripheral nervous system. These results also suggest that the longer duration of employment, the shorter values of EPS and VAT.

The Properties of Spin Valves with a Partially Oxidized Fe or CoFe Ultra-Thin Layer Inserted in the Magnetic Layers

Jangsik In,Yoonsung Han,Sunghoon Kim,Jaechul Shim,Jongill Hong 한국자기학회 2006 Journal of Magnetics Vol.11 No.3

We successfully enhanced the performance of a spin valve by inserting an ultra-thin layer of partially oxidized Fe in the pinned and free layers. With the exchange bias field kept large, the spin valve reached a GMR of 12%, which corresponded to a 55% increase in GMR when we compared it with that of spin valves without any inserted layer. The layer of partially oxidized Fe was more effective for improving the properties of the spin valve than the layer of partially oxidized Co??Fe₁?. Considering all the results, we can contribute the significant improvement to the combined effect of the modified local electronic structures at the Fe impurities and the enhanced spin-dependent reflections at the α-Fe₂O₃ phase in the magnetic layer.

차량 안정성 관련 Fe-Mn-Si-C계 TRIP형 복합조직강의 화학조성에 따른 인장특성

이기열(Kiyeol Lee),김덕환(Duckwhan Kim),김재철(Jaechul Kim),심주현(Joohyun Shim),황종원(Jongwon Hwang),백일기(Ilki Baik) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

The effect of chemical compositon on the microstructural change and tensile property in TRIP-assisted steels with different chemical composition was investigated by using SEM, TEM, XRD and UTM. As a result of microscopic observation, the morphology of retained austenite could be identified as two types : a granular type in a steel containing higher Si and a film type in a steel having higher C. For the case of higher C-containing steel with a tensile strength of 860 ㎫ and a total elongation of 38%, film-typed retained austenite could be observed between lath bainitic ferrite. Actually, metastable retained austenite was a requisite for the good formability, which means that chemical composition plays a significant role in the microstructure and tensile property of TRIP-assisted steels. With respect to tensile property, the steels containing suitable Si and Mn, respectively, showed a typical TRIP effect in stress-strain curve, while a steel containing higher Mn content exhibited the as similar behavior shown in dual phase steel.

금강산(金剛山)에서 관측한 미세먼지 농도

김정은(Jeong Eun Kim),심원보(Wonbo Shim),임재철(Jaechul Lim),전영신(Youngsin Chun) 한국기상학회 2011 대기 Vol.21 No.4

The electrochemical enhancement due to the aligned structural effect of carbon nanofibers in a supercapacitor electrode

Lee, Eunsoo,Kim, Minjae,Ju, Jaechul,Jang, Seokhoon,Baeck, Sung Hyeon,Shim, Sang Eun Elsevier Sequoia 2017 Synthetic metals Vol.226 No.-

<P><B>Abstract</B></P> <P>Aligned carbon nanofibers (ACNFs) were fabricated by electrospinning using a high speed of rotary collector (2000rpm). To achieve a synergy effect of the electron double layer and redox faradaic reaction, NiCo<SUB>2</SUB>O<SUB>4</SUB> was deposited on the surface of the ACNFs using an electrodeposition method. The improved electrochemical performance of the electrodes was investigated by cyclic voltammetry, galvanostatic charge-discharge testing, and electrochemical impedance analysis. Among the prepared electrodes, which were deposited for different times (5, 10, 20, and 30s), the sample deposited by NiCo<SUB>2</SUB>O<SUB>4</SUB> for 10s had the highest specific capacitance (90.1Fg<SUP>−1</SUP> at 5mVs<SUP>−1</SUP>), good rate capability (64.7%), and cycle stability (85.2% after 1000 cycles). In addition, to examine the effects of the alignment and redox faradaic reaction of NiCo<SUB>2</SUB>O<SUB>4,</SUB> the ACNFs covered with NiCo<SUB>2</SUB>O<SUB>4</SUB> for 10s (NC-ACNFs) were compared with the ACNFs deposited by Co<SUB>3</SUB>O<SUB>4</SUB> (C-ACNFs) and randomly oriented carbon nanofibers covered with NiCo<SUB>2</SUB>O<SUB>4</SUB> (NC-RCNFs)<SUB>.</SUB> The NC-ACNFs had a 15.8% and 11.3% higher specific capacitance than that of the C-ACNFs and NC-RCNFs, respectively. These results suggested that the electrochemical properties of carbon nanofibers could be improved through the structural effects of aligned nanofibers and a redox faradaic reaction of NiCo<SUB>2</SUB>O<SUB>4</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Supercapacitor using CNFs’ aligned structure and deposition of NiCo<SUB>2</SUB>O<SUB>4</SUB> is proposed. </LI> <LI> Alignment of carbon nanofibers improves the electrochemical properties. </LI> <LI> Mixed transition metal oxides, NiCo<SUB>2</SUB>O<SUB>4,</SUB> can offer rich redox faradaic reactions. </LI> <LI> Availability of aligned carbon nanofiber as supercapacitor’s electrode is proposed. </LI> </UL> </P>

On-film tunneling resistance measurements of unpatterned magnetic tunnel junctions

Lee, Sangho,Han, Yoonsung,Bae, Taejin,Hong, Jongill,Shim, Jaechul,Kim, Eunsik,Sunwoo, Kukhyun American Institute of Physics 2010 JOURNAL OF APPLIED PHYSICS - Vol.108 No.9