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열처리 및 바이올로젠 도입에 따른 TiO<sub>2</sub> 나노튜브의 전기변색 특성
차형철,나윤채,Cha, Hyeongcheol,Nah, Yoon-Chae 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.2
We demonstrate the electrochromic properties of $TiO_2$ nanotubes prepared by an anodization process and investigate the effects of heat treatment and viologen incorporation on them. The morphology and crystal structure of anodized $TiO_2$ nanotubes are investigated by scanning electron microscopy and X-ray diffraction. As-formed $TiO_2$ nanotubes have straight tubular layers with an amorphous structure. As the annealing temperature increases, the anodized $TiO_2$ nanotubes are converted to the anatase and rutile phases with some cracks on the tube surface and irregular morphology. Electrochemical results reveal that amorphous $TiO_2$ nanotubes annealed at $150^{\circ}C$ have the largest oxidation/reduction current, which leads to the best electrochromic performance during the coloring/bleaching process. Viologen-anchored $TiO_2$ nanotubes show superior electrochromic properties compared to pristine $TiO_2$ nanotubes, which indicates that the incorporation of a viologen can be an effective way to enhance the electrochromic properties of $TiO_2$ nanotubes.
양극산화된 TiO<sub>2</sub> 및 WO<sub>3</sub> 나노구조체로 구성된 광전기변색 소자 제작
이상훈,차형철,나윤채,Lee, Sanghoon,Cha, Hyeongcheol,Nah, Yoon-Chae 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.5
In this study, we demonstrate the photoelectrochromic devices composed of $TiO_2$ and $WO_3$ nanostructures prepared by anodization method. The morphology and the crystal structure of anodized $TiO_2$ nanotubes and $WO_3$ nanoporous layers are investigated by SEM and XRD. To fabricate a transparent photoelectrode on FTO substrate, a $TiO_2$ nanotube membrane, which has been detached from Ti substrate, is transferred to FTO substrate and annealed at $450^{\circ}C$ for 1 hr. The photoelectrode of $TiO_2$ nanotube and the counter electrode of $WO_3$ nanoporous layer are assembled and the inner space is filled with a liquid electrolyte containing 0.5 M LiI and 5 mM $I_2$ as a redox mediator. The properties of the photoelectrochromic devices is investigated and Pt-$WO_3$ electrode system shows better electrochromic performance compared to $WO_3$ electrode.
신축성있는 Ag 나노와이어 전극의 제조 및 전기변색 응용
이진영,한송이,나윤채,박종운,Lee, Jin-Young,Han, Song-Yi,Nah, Yoon-Chae,Park, Jongwoon 한국재료학회 2019 한국재료학회지 Vol.29 No.2
We report on stretchable electrochromic films of poly(3-hexylthiophene) (P3HT) fabricated on silver nanowire (AgNW) electrodes. AgNWs electrodes are prepared on polydimethylsiloxane (PDMS) substrates using a spray coater for stretchable electrochromic applications. On top of the AgNW electrode, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is introduced to ensure a stable resistance over the electrode under broad strain range by effectively suppressing the protrusion of AgNWs from PDMS. This bilayer electrode exhibits a high performance as a stretchable substrate in terms of sheet resistance increment by a factor of 1.6, tensile strain change to 40 %, and stretching cycles to 100 cycles. Furthermore, P3HT film spin-coated on the bilayer electrode shows a stable electrochromic coloration within an applied voltage, with a color contrast of 28.6 %, response time of 4-5 sec, and a coloration efficiency of $91.0cm^2/C$. These findings indicate that AgNWs/PEDOT:PSS bilayer on PDMS substrate electrode is highly suitable for transparent and stretchable electrochromic devices.
평면전극구조를 갖는 바이올로진 기반의 일체형 전기변색소자
김현정,이상래,최진희,나윤채,Kim, Hyun-Jeong,Lee, Sang-Rae,Choi, Jin-Hee,Nah, Yoon-Chae 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.1
Recently, electrochromic devices (ECDs) have gathered increasing attention owing to their high color contrast and memory effect, which make them highly applicable to smart windows, auto-dimming mirrors, sensors, etc. Traditional ECDs have a sandwich structure that contains an electrochromic layer between two ITO substrates. These sandwich-type devices are usually fabricated through the lamination of two electrodes and followed by the injection of a liquid electrolyte in the inner space. However, this process is sometimes complex and time consuming. In this study, we fabricated ECDs with a lateral electrode structure that uses only an ITO substrate and an all-in-one electrochromic gel, which is a mixture of electrolyte and electrochromic material. Furthermore, we investigated the EC properties of the lateral-type device by comparing it with a sandwich-type device. The lateral-type ECD shows strong blue absorption as the applied voltage increases and has a competitive coloration efficiency compared to the sandwich-type device.
박보성,김현정,신현호,박성민,이재운,전성건,나윤채,Park, Bo-Seong,Kim, Hyun-Jeong,Shin, Hyeonho,Park, Seongmin,Lee, Jaeun,Jeon, Sunggun,Nah, Yoon-Chae 한국재료학회 2021 한국재료학회지 Vol.31 No.3
Electrochromic devices (ECDs) have been drawing great attention due to their high color contrast, low power consumption, and memory effect, and can be used in smart windows, automatic dimming mirrors, and information display devices. As with other electronic devices such as LEDs (light emitting diodes), solar cells, and transistors, the mechanical flexibility of ECDs is one of the most important issue for their potential applications. In this paper, we report on flexible ECDs (f-ECDs) fabricated using an all-in-one EC gel, which is a mixture of electrolyte and EC material. The f-ECDs are compared with rigid ECDs (r-ECDs) on ITO glass substrate in terms of color contrast, coloration efficiency, and switching speed. It is confirmed that the f-ECDs embedding all-in-one gel show strong blue absorption and have competitive EC performance. Repetitive bending tests show a degradation of electrochromic performance, which must be improved using an optimized device fabrication process.
전기증착법으로 제조된 WO<sub>3</sub> 박막의 광촉매 특성
강광모,정지혜,이가인,임재민,천현정,김덕현,나윤채,Kang, Kwang-Mo,Jeong, Ji-Hye,Lee, Ga-In,Im, Jae-Min,Cheon, Hyun-Jeong,Kim, Deok-Hyeon,Nah, Yoon-Chae 한국분말재료학회 (*구 분말야금학회) 2019 한국분말재료학회지 (KPMI) Vol.26 No.1
Tungsten trioxide ($WO_3$) is a promising candidate as a photocatalyst because of its outstanding electrical and optical properties. In this study, we prepare $WO_3$ thin films by electrodeposition and characterize the photocatalytic degradation of methylene blue using these films. Depending on the voltage conditions (static and pulse), compact and porous $WO_3$ films are fabricated on a transparent ITO/glass substrate. The morphology and crystal structure of electrodeposited $WO_3$ thin films are investigated by scanning electron microscopy, atomic force microscopy, and X-ray diffraction. An application of static voltage during electrodeposition yields a compact layer of $WO_3$, whereas a highly porous morphology with nanoflakes is produced by a pulse voltage process. Compared to the compact film, the porous $WO_3$ thin film shows better photocatalytic activities. Furthermore, a much higher reaction rate of degradation of methylene blue can be achieved after post-annealing of $WO_3$ thin films.
전기증착법으로 제조된 다공성 텅스텐 산화물의 고대비 전기변색 특성
박성혁,모호진,임재근,김상권,최재효,이승현,장세화,차경호,나윤채,Park, Sung-Hyeok,Mo, Ho-Jin,Lim, Jae-Keun,Kim, Sang-Gwon,Choi, Jae-Hyo,Lee, Seung-Hyun,Jang, Se-Hwa,Cha, Kyung-Ho,Nah, Yoon-Chae 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.1
In this study, we synthesize tungsten oxide thin films by electrodeposition and characterize their electrochromic properties. Depending on the deposition modes, compact and porous tungsten oxide films are fabricated on a transparent indium tin oxide (ITO) substrate. The morphology and crystal structure of the electrodeposited tungsten oxide thin films are investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). X-ray photoelectron spectroscopy is employed to verify the chemical composition and the oxidation state of the films. Compared to the compact tungsten oxides, the porous films show superior electrochemical activities with higher reversibility during electrochemical reactions. Furthermore, they exhibit very high color contrast (97.0%) and switching speed (3.1 and 3.2 s). The outstanding electrochromic performances of the porous tungsten oxide thin films are mainly attributed to the porous structure, which facilitates ion intercalation/deintercalation during electrochemical reactions.
부사관학과 학생들의 소방안전교육 경험과 생활안전의식에 관한 연구
이원주 ( Wonjoo Lee ),권신영 ( Shin Young Kwon ),강순형 ( Soon Hyung Kang ),나윤채 ( Yoon Chae Nah ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.4
The main purpose of this study is to evaluate the awareness survey on the experience of fire fighting safety education and living safety consciousness of college students in the department of noncommissioned officer. Additionally, making provision of basic references and the effective fire fighting safety education is another important purpose of this study. In order to evaluate the awareness, the survey consist of 43 queries based on 6 queries for general characters, 9 queries for experiences of fire fighting safety education and 30 queries for living safety consciousness. The collected data from survey was analyzed using SPSS 20.0 win program. The interrelationship for general characters was confirmed using analysis of frequency, percentage, independent T-tset, ANONVA analysis, and regression analysis. The results show that the experience of fire fighting safety education and living safety consciousness of students from the combatant branch and ordnance corps are higher than those students from quartermaster corps. This may be attributed to the presence or absence of safety relevant courses on a curriculum. Therefore, the presence of safety courses on a curriculum should be one of important points for improving the experience of fire fighting safety education and living safety consciousness of these college students.