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Ni기 초내열 합금 LESS 1의 합금설계 및 평가: 1. 합금 설계 및 고온 상 안정성 평가
윤정일 ( Jeong Il Youn ),강병일 ( Byung Il Kang ),최봉재 ( Bong Jae Choi ),김영직 ( Young Jig Kim ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.5
The alloys required for fossil power plants are altered from stainless steel that has been used below 600oC to Ni-based alloys that can operate at 700oC for Hyper Super Critical (HSC) steam turbine. The IN740 alloy (Special Metals Co. USA) is proposed for improved rupture strength and corrosion resistance at high temperature. However, previous studies with experiments and simulations on stable phases at about 700oC indicated the formation of the eta phase with the wasting of a gamma prime phase, which is the most important reinforced phase in precipitation hardened Ni alloys, and this resulted in the formation of precipitation free zones to decrease the strength. On the basis of thermodynamic calculation, the new Ni-based superalloy named LESS 1 (Low Eta Sigma Superalloy) was designed in this study to improve the strengthening effect and structure stability by depressing the formation of topologically close packed phases, especially sigma and eta phases at high temperature. A thermal exposure test was carried out to determine the microstructure stability of LESS 1 in comparison with IN740 at 800oC for 300 hrs. The experimental results show that a needle-shaped eta phase was formed in the grin boundary and it grew to intragrain, and a precipitation free zone was also observed in IN740, but these defects were entirely controlled in LESS 1.
TiO<sub>2</sub> 복합 광촉매의 표면 특성과 광촉매 효율
이종호,윤정일,김영직,오한준,Lee, Jong-Ho,Youn, Jeong-Il,Kim, Young-Jig,Oh, Han-Jun 한국재료학회 2014 한국재료학회지 Vol.24 No.10
To synthesize a high-performance photocatalyst, N doped $TiO_2$ nanotubes deposited with Ag nanoparticles were synthesized, and surface characteristics, electrochemical behaviors, and photocatalytic activity were investigated. The $TiO_2$ nanotubular photocatalyst was fabricated by anodization; the Ag nanoparticles on the $TiO_2$ nanotubes were synthesized by a reduction reaction in $AgNO_3$ solution under UV irradiation. The XPS results of the N doped $TiO_2$ nanotubes showed that the incorporated nitrogen ions were located in interstitial sites of the $TiO_2$ crystal structure. The N doped titania nanotubes exhibited a high dye degradation rate, which is effectively attributable to the increase of visible light absorption due to interstitial nitrogen ions in the crystalline $TiO_2$ structure. Moreover, the precipitated Ag particles on the titania nanotubes led to a decrease in the rate of electron-hole recombination; the photocurrent of this electrode was higher than that of the pure titania electrode. From electrochemical and dye degradation results, the photocurrent and photocatalytic efficiency were found to have been significantly affected by N doping and the deposition of Ag particles.
TiO<sub>2</sub>/CdS 복합광촉매의 밴드갭 에너지 특성과 광촉매 효율
이종호,허수정,윤정일,김영직,서수정,오한준,Lee, Jong-Ho,Heo, Sujeong,Youn, Jeong-Il,Kim, Young-Jig,Suh, Su-Jeong,Oh, Han-Jun 한국재료학회 2019 한국재료학회지 Vol.29 No.12
To improve photocatalytic performance, CdS nanoparticle deposited TiO<sub>2</sub> nanotubular photocatalysts are synthesized. The TiO<sub>2</sub> nanotube is fabricated by electrochemical anodization at a constant voltage of 60 V, and annealed at 500 for crystallization. The CdS nanoparticles on TiO<sub>2</sub> nanotubes are synthesized by successive ionic layer adsorption and reaction method. The surface characteristics and photocurrent responses of TNT/CdS photocatalysts are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectrometer and LED light source installed potentiostat. The bandgaps of the CdS deposited TiO<sub>2</sub> photocatalysts are gradually narrowed with increasing of amounts of deposited CdS nanoparticles, which enhances visible light absorption ability of composite photocatalysts. Enhanced photoelectrochemical performance is observed in the nanocomposite TiO<sub>2</sub> photocatalyst. However, the maximum photocurrent response and dye degradation efficiency are observed for TNT/CdS30 photocatalyst. The excellent photocatalytic performance of TNT/CdS30 catalyst can be ascribed to the synergistic effects of its better absorption ability of visible light region and efficient charge transport process.
PbS/ZnO/TiO<sub>2</sub> 나노복합체의 광촉매 특성
이종호,허수정,윤정일,김영직,김인기,장경욱,오한준,Lee, Jong-Ho,Heo, Sujeong,Youn, Jeong-Il,Kim, Young-Jig,Kim, In-Ki,Jang, Kyung-Wook,Oh, Han-Jun 한국재료학회 2017 한국재료학회지 Vol.27 No.10
To improve photocatalytic performance, a $PbS/ZnO/TiO_2$ nanotube catalyst was synthesized, and its surface characteristics and photocatalytic efficiency were investigated. The hybrid photocatalysts were produced by anodic oxidation and successive ionic layer adsorption and reaction(SILAR). The photocatalytic efficiency was evaluated using the dye degradation rate. The $PbS/ZnO/TiO_2$ photocatalyst significantly enhanced the photocatalytic activity for dye degradation, which was ascribed to the synergistic effect of their better absorption of solar light and a decrease in the rate of excited electron-hole recombination.
Characteristics of Interruption Ability in DC Circuit Breaker using Superconducting Coil
In-Sung Jeong(정인성),Hye-Won Choi(최혜원),Jeong-Il Youn(윤정일),Hyo-Sang Choi(최효상) 대한전기학회 2019 전기학회논문지 Vol.68 No.1
Development of DC interruption technology is being studied actively for enhanced DC grid reliability and stability. In this study, coil type superconductor DC circuit breaker was proposed as DC interruption. It is integration technology that combined current-limiting technique using superconductor and cut-off technique using mechanical DC circuit breaker. Superconductor was applied to the coil type. In simulation, Mayr arc model was applied to realize the arc characteristic in the mechanical DC circuit breaker. PSCAD/EMTDC had used to model and perform the simulation. To find out the protection range of coil type superconductor DCCB, the working operation have analyzed based on the rated voltage of DCCB. The results confirmed that, according to apply the limiting device, the protection range was increased in twice. Therefore, the probability of failure of interruption has lowered significantly.
알루미늄탄소나노튜브 복합재의 가공 방법과 탄소나노튜브 함량에 따른 트라이볼로지 특성
이중희(Jung-Hee Lee),김일영(Il-Young Kim),이규선(Gyu-Sun Lee),백승현(Seung-Hyun Baik),윤정일(Jeong-Il Youn),김영직(Young-Jig Kim),이영제(Young-Ze Lee) 한국트라이볼로지학회 2008 한국윤활학회지(윤활학회지) Vol.24 No.5
Carbon nanotube composite is considered to be a good candidate material for composite material because of its excellent mechanical property and low density under high temperature as well as good wear and frictional properties. In this study, tribological characteristics of carbon nanotube aluminum composite were evaluated using pin-on-disk wear tester. Spark Plasma Sintering method is more effective than Hot Pressing method in terms of wear and friction. The composite with 1% CNT has the lowest friction and wear characteristic.
알루미늄ㆍ탄소나노튜브 복합재의 분산 조건에 따른 마찰 마멸 특성
이중희(Jung-Hee Lee),김일영(Il-Young Kim),이규선(Gyu-Sun Lee),윤정일(Jeong-Il Youn),김영직(Young-Jig Kim),백승현(Seung-Hyun Baik),이영제(Young-Ze Lee) 한국트라이볼로지학회 2008 한국트라이볼로지학회 학술대회 Vol.2008 No.6
To improve a lightweight property and mechanical properties, carbon nanotube-aluminum composites were fabricated using HP(Hot Pressing) method. These composites are fabricated under three different conditions. To know the friction and wear characteristics according to dispersion conditions, the coefficient of friction and the wear rate were evaluated using pin-on-disk tester. And conglomerated CNT particles are observed using SEM(Scanning Electron Microscope). As a result, it was proven that irregular dispersion of CNT leads an increase in friction coefficient and wear rate.
한랭지역 철도 시스템분야 사용온도 기준 제안에 대한 검토
조호령(Ho-Ryung Cho),김인철(In-Chol Kim),전찬웅(Chan-Woong Jeon),김종락(Jong-Rak Kim),윤정일(Jeong-Il Youn),김시환(See-Whan Kim),최용은(Yong-Eun Choi),오효석(Hyo-Seok Oh),김재문(Jae-Moon Kim) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.10
철도 시스템은 반영구적으로 옥외에 노출상태로 설치되어 운용되며, 가혹한 대기온도 및 온도, 습도 등이 복합적으로 작용하고, 온도가 제어되는 실내 장치보다 상당히 가혹조건에서 운용되므로 사용온도 조건에 대한 기준의 설정은 관련 기기의 신뢰성과 안전성에 관련된 중요 요소이다. 본 논문에서는 최근 활발히 논의되고 있는 남북철도 연계에 따라 시베리아 횡단철도(TSR) 및 중국 횡단철도(TCR)와 연결하여 운용하는 상황이 도래할 것에 대비하여 북한 및 러시아와 중국의 한랭지역을 통과하는 철도시스템에 대하여 기후환경 영향을 고려한 온도에 관련한 설계기준의 제시가 요구되는 시점에서 러시아 및 중국지역의 사용온도 기준을 알아보고 북한지역 철도시스템분야에 적용 가능한 온도기준을 제안하였다.