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Hwang, Chahwan,An, Jihyun,Choi, Byung Doo,Kim, Kwanpyo,Jung, Soon-Won,Baeg, Kang-Jun,Kim, Myung-Gil,Ok, Kang Min,Hong, Jongin The Royal Society of Chemistry 2016 Journal of Materials Chemistry C Vol.4 No.7
<▼1><P>A stretchable transparent electrode was achieved with rationally-controlled ultra-long copper nanowires and low-temperature direct spray coating.</P></▼1><▼2><P>The environmentally benign synthesis of ultra-long copper nanowires with successful control of diameter and length for stretchable transparent conducting electrodes (TCEs) is reported. Ultra-long copper nanowires (CuNWs) with an average length of 92.5 μm (maximum length up to 260 μm) and an average diameter of 47 nm were synthesized using environmentally friendly water–alcohol mixtures and l-ascorbic acid as a reducing agent. A facile removal of insulating surface layers, such as organic capping molecules and copper oxide/hydroxide, by short-chain organic acid treatment allowed low contact resistance between the CuNWs without post-reductive treatment at elevated temperatures. The CuNWs were directly spray-coated on glass or polydimethylsiloxane (PDMS) at a low processing temperature of 130 °C. The CuNW TCE on a glass substrate exhibited a low sheet resistance of 23.1 Ohm sq<SUP>−1</SUP> and a high optical transmittance of 84.1% at 550 nm. Furthermore, the CuNWs were directly spray-coated on stretchable PDMS, which showed a low sheet resistance of 4.1 Ohm sq<SUP>−1</SUP> and a high optical transmittance of 70% at 550 nm.</P></▼2>
[안전] 만도 Multi-Fuctional 모듈레이터 개발
김차환(Chahwan Kim),박성준(Soungjun Park) 한국자동차공학회 1999 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1999 No.11_2
Recently, The Vehicle Stability Control is a theme for Car maker. This paper describes the Multi-Functional Modulator of MANDO brake control system. The Modulator is verified in the rig and vehicle test, which is fully responded to the control signal. Also comparison between the MANDO Multi-Functional Modulator and a competitor is carried out. Particularly, MANDO Multi-Functional Modulator has an advantage in the early time pressure rise rate. Also, this can make a advanced system without adding a particular apparatus or changing a design.
Hwang, Chahwan,Kim, Taejin,Noh, Yohan,Cha, Wansik,Shim, Joongpyo,Kwak, Kyungwon,Ok, Kang Min,Lee, Kyung-Koo Elsevier 2016 Materials letters Vol.164 No.-
<P><B>Abstract</B></P> <P>High-capacity Li<SUB>2</SUB>MnSiO<SUB>4</SUB>/C (LMS/C) nanoparticles doped with V<SUP>3+</SUP> were prepared using sonochemistry under multibubble sonoluminescence (MBS) conditions, and the physical and electrochemical properties of the nanoparticles were characterized. The results showed that substituting Mn<SUP>2+</SUP> with V<SUP>3+</SUP> was effective in reducing the grain size, purifying the crystalline phase, and enhancing the electrochemical properties. In particular, 5 and 10mol% V<SUP>3+</SUP>-doped LMS/C exhibited diffusion coefficients of 5.58×10<SUP>−14</SUP> cm<SUP>2</SUP> s<SUP>−</SUP> <SUP>1</SUP> and 1.19×10<SUP>−13</SUP> cm<SUP>2</SUP> s<SUP>−1</SUP>, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Precursors of V-doped LMS were synthesized by a fast sonochemical reaction. </LI> <LI> The oxidation state of vanadium in V-doped LMS is assigned to trivalent. </LI> <LI> The diffusion coefficient of LMS can be improved by substituting Mn<SUP>2+</SUP> with V<SUP>3+</SUP>. </LI> </UL> </P>
Yu, Seungwoo,Hwang, Chahwan,Kim, Do Jeon,Park, Joohyung,Kim, Seonhyoung,Hong, Jongin,An, Jihyun,Lee, Tae Hoon,Kim, Myung-Gil Elsevier 2018 THIN SOLID FILMS - Vol.661 No.-
<P><B>Abstract</B></P> <P>Numerous LiCoO<SUB>2</SUB> cathode thin-films have been prepared for all-solid-state thin-film battery applications. Preparation methods include sputtering, pulsed laser deposition, electron beam evaporation, screen printing, and spin coating. When compared to vacuum deposition methods, the solution-processed fabrication methods could result in significant cost savings and large-area production. Unfortunately, high-temperature annealing (<I>T</I> <SUB>anneal</SUB> > 700 °C) of LiCoO<SUB>2</SUB> cathode thin film is usually crucial for achieving a high performance layered phase. Here, we report on phase control of spin-coated LiCoO<SUB>2</SUB> thin film by varying the molecular weight of polyvinylpyrrolidone (PVP) at low temperature. We could achieve thick and smooth film morphology by optimizing the PVP molecular weight. This method could be a promising cathode layer for low-cost thin-film batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Crystal phase of LiCoO<SUB>2</SUB> thin film cathode is controlled by PVP molecular weight. </LI> <LI> The layered phase LiCoO<SUB>2</SUB> films are formed using solution process at low temperature. </LI> <LI> The layered phase LiCoO<SUB>2</SUB> films show high charge-discharge performance. </LI> <LI> Crystal size of LiCoO<SUB>2</SUB> thin film cathode is controlled by PVP molecular weight. </LI> <LI> The layered phase LiCoO<SUB>2</SUB> films have small nanoparticle size and smooth surface. </LI> </UL> </P>
Won, Jong Kook,Hwang, Chahwan,Ahn, Kyunghan,Choi, Seong-Young,Lee, Yongkyu,Kim, Jaehyun,Lee, Yangjin,Park, Sung Kyu,Chung, In,Kim, Choongik,Kim, Kwanpyo,Ahn, Sang Hyun,Lee, Min Hyung,Kim, Myung-Gil Elsevier 2019 Journal of solid state chemistry Vol.278 No.-
<P><B>Abstract</B></P> <P>Two-dimensional (2D) metal dichalcogenide nanomaterials have been receiving enormous research interest for electronic, optoelectronic, and catalytic applications. However, the facile tunability of alloying and doping, as well as the successful formation of ideal defect-free nanoplate morphology have been hardly achieved for 2D nanomaterials. Herein, we successfully synthesized a series of 2D solid-solution SnS<SUB>x</SUB>Se<SUB>2−x</SUB> particles of 0.20–2.00 μm width and 30–68 nm thickness with morphological defect-free nanoplate via a solvothermal reaction. With controlled reactivities of elemental chalcogen precursors, a co-surfactant hexylamine together with a structure-directing agent polyvinylpyrrolidone was found to be essential for realizing ideal defect-free nanoplate morphology of SnS<SUB>x</SUB>Se<SUB>2−x</SUB> particles without either cabbage-like or twinned structure. The successful synthesis of morphologically defect-free SnS<SUB>x</SUB>Se<SUB>2−x</SUB> nanoplates with rationally controlled energy band gaps ranging from 1.36 eV for SnSe<SUB>2</SUB> to 1.96 eV for SnS<SUB>2</SUB> could provide promising materials for electronics, optoelectronics, and electrocatalytic applications.</P> <P><B>Graphical abstract</B></P> <P>With chalcogen source control and surfactant/co-surfactant usage, morphologically defect free SnS<SUB>x</SUB>Se<SUB>2−x</SUB> nanoplates alloys were synthesized by facile solvothermal reaction.</P> <P>[DISPLAY OMISSION]</P>
Jung, Su Min,Kang, Han Lim,Won, Jong Kook,Kim, JaeHyun,Hwang, ChaHwan,Ahn, KyungHan,Chung, In,Ju, Byeong-Kwon,Kim, Myung-Gil,Park, Sung Kyu American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.4
<P>The recent development of high-performance colloidal quantum dot (QD) thin-film transistors (TFTs) has been achieved with removal of surface ligand, defect passivation, and facile electronic doping. Here, we report on high-performance solution-processed CdSe QD-TFTs with an optimized surface functionalization and robust defect passivation via hydrazine-free metal chalcogenide (MCC) ligands. The underlying mechanism of the ligand effects on CdSe QDs has been studied with hydrazine-free ex situ reaction derived MCC ligands, such as Sn2S64-, Sn2Se64-, and In2Se42-, to allow benign solution-process available. Furthermore, the defect passivation and remote n-type doping effects have been investigated by incorporating indium nanoparticles over the QD layer. Strong electronic coupling and solid defect passivation of QDs could be achieved by introducing electronically active MCC capping and thermal diffusion of the indium nanoparticles, respectively. It is also noteworthy that the diffused indium nanoparticles facilitate charge injection not only inter-QDs but also between source/drain electrodes and the QD semiconductors, significantly reducing contact resistance. With benign organic solvents, the Sn2S64-, Sn2Se64-, and In2Se42- ligand based QD-TFTs exhibited field-effect mobilities exceeding 4.8, 12.0, and 44.2 cm(2)/(V s), respectively. The results reported here imply that the incorporation of MCC ligands and appropriate dopants provide a general route to high-performance, extremely stable solution-processed QD-based electronic devices with marginal toxicity, offering compatibility with standard complementary metal oxide semiconductor processing and large-scale on-chip device applications.</P>
심대성,장덕현,박차환,김정훈,Shim, Daisung,Jang, Deakhyeon,Park, Chahwan,Kim, Jounghun 한국군사과학기술학회 2015 한국군사과학기술학회지 Vol.18 No.4
This is a study for the improvement of the fractured lug structure that connects the landing gear to the fuselage of the aircraft using the composite leaf spring landing gear. The lug surface was analyzed to find out the cause of fracture. The lug was destroyed by the crack initiation and propagation under the repeated stresses. The frictional wears of the lug structure were proceeded and that affected adversely to the crack. Also, the square protrusion of the lug has a weak shape to bring about stress concentration. The design changes were conducted and the test was performed to verify changed design results.