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란타넘 산화물의 분산을 통해 향상된 파괴인성을 갖는 몰리브데넘 합금의 제조
최원준,박천웅,박정효,김영도,변종민,Choi, Won June,Park, Chun Woong,Park, Jung Hyo,Kim, Young Do,Byun, Jongmin 한국분말재료학회 (*구 분말야금학회) 2019 한국분말재료학회지 (KPMI) Vol.26 No.3
In this study, lanthanum oxide ($La_2O_3$) dispersed molybdenum ($Mo-La_2O_3$) alloys are fabricated using lanthanum nitrate solution and nanosized Mo particles produced by hydrogen reduction of molybdenum oxide. The effect of $La_2O_3$ dispersion in a Mo matrix on the fracture toughness at room temperature is demonstrated through the formation behavior of $La_2O_3$ from the precursor and three-point bending test using a single-edge notched bend specimen. The relative density of the $Mo-0.3La_2O_3$ specimen sintered by pressureless sintering is approximately 99%, and $La_2O_3$ with a size of hundreds of nanometers is uniformly distributed in the Mo matrix. It is also confirmed that the fracture toughness is $19.46MPa{\cdot}m^{1/2}$, an improvement of approximately 40% over the fracture toughness of $13.50MPa{\cdot}m^{1/2}$ on a pure-Mo specimen without $La_2O_3$, and this difference in the fracture toughness occurs because of the changes in fracture mode of the Mo matrix caused by the dispersion of $La_2O_3$.
탄화 규소가 균일 분산된 규화 몰리브데넘계 복합재의 제조
최원준,박천웅,김영도,변종민,Choi, Won June,Park, Chun Woong,Kim, Young Do,Byun, Jong Min 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.5
Molybdenum silicide has gained interest for high temperature structural applications. However, poor fracture toughness at room temperatures and low creep resistance at elevated temperatures have hindered its practical applications. This study uses a novel powder metallurgical approach applied to uniformly mixed molybdenum silicide-based composites with silicon carbide. The degree of powder mixing with different ball milling time is also demonstrated by Voronoi diagrams. Core-shell composite powder with Mo nanoparticles as the shell and ${\beta}-SiC$ as the core is prepared via chemical vapor transport. Using this prepared core-shell composite powder, the molybdenum silicide-based composites with uniformly dispersed ${\beta}-SiC$ are fabricated using pressureless sintering. The relative density of the specimens sintered at $1500^{\circ}C$ for 10 h is 97.1%, which is similar to pressure sintering owing to improved sinterability using Mo nanoparticles.
최원준,박천웅,박정효,김영도,변종민,Choi, Won June,Park, Chun Woong,Park, Jung Hyo,Kim, Young Do,Byun, Jong Min 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.2
Over the last decade, the next generation's ultra-high-temperature materials as an alternative to Nickel-based superalloys have been highlighted. Ultra-high-temperature materials based on refractory metals are one of several potential candidates. In particular, molybdenum alloys with small amounts of silicon and boron (Mo-Si-B alloys) have superior properties at high temperature. However, research related to Mo-Si-B alloys were mainly conducted by several developed countries but garnered little interest in Korea. Therefore, in this review paper, we introduce the development history of Mo-Si-B alloys briefly and discuss the properties, particularly the mechanical and oxidation properties of Mo-Si-B alloys. We also introduce the latest research trends of Mo-Si-B alloys based on the research paper. Finally, for domestic research related to this field, we explain why Mo-Si-B alloys should be developed and suggest the potential directions for Mo-Si-B alloys research.
안치형,최원준,박천웅,이승영,김영도,Ahn, Chi Hyeong,Choi, Won June,Park, Chun Woong,Lee, Seung Yeong,Kim, Young Do 한국재료학회 2018 한국재료학회지 Vol.28 No.3
Molybdenum (Mo) is one of the representative refractory metals for its high melting point, superior thermal conductivity, low density and low thermal expansion coefficient. However, due to its high melting point, it is necessary for Mo products to be fabricated at a high sintering temperature of over $1800-2000^{\circ}C$. Because this process is expensive and inefficient, studies to improve sintering property of Mo have been researched actively. In this study, we fabricated Mo nanopowders to lower the sintering temperature of Mo and tried to consolidate the Mo nanopowders through ultra high pressure compaction. We first fabricated Mo nanopowders by a mechano-chemical process to increase the specific surface area of the Mo powders. This process includes a high-energy ball milling step and a reduction step in a hydrogen atmosphere. We compacted the Mo nanopowders with ultra high pressure by magnetic pulsed compaction (MPC) before pressureless sintering. Through this process, we were able to improve the green density of the Mo compacts by more than 20 % and fabricate a high density Mo sintered body with more than a 95 % sintered density at relatively low temperature.
Ni<sub>5</sub>Y 합금상이 형성된 Ni계 산화물 분산강화 아토마이징 분말의 밀링 거동 분석
박천웅,변종민,최원준,김영도,Park, Chun Woong,Byun, Jong Min,Choi, Won June,Kim, Young Do 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.2
Ni-based oxide dispersion strengthened (ODS) alloys have a higher usable temperature and better high-temperature mechanical properties than conventional superalloys. They are therefore being explored for applications in various fields such as those of aerospace and gas turbines. In general, ODS alloys are manufactured from alloy powders by mechanical alloying of element powders. However, our research team produces alloy powders in which the $Ni_5Y$ intermetallic phase is formed by an atomizing process. In this study, mechanical alloying was performed using a planetary mill to analyze the milling behavior of Ni-based oxide dispersions strengthened alloy powder in which the $Ni_5Y$ is the intermetallic phase. As the milling time increased, the $Ni_5Y$ intermetallic phase was refined. These results are confirmed by SEM and EPMA analysis on microstructure. In addition, it is confirmed that as the milling increased, the mechanical properties of Ni-based ODS alloy powder improve due to grain refinement by plastic deformation.
승강장 스크린도어의 유한 요소해석을 통한 피로하중 안전성 검토
최문덕(Mood-duck Choi),조종두(Chon-gdu Cho),최원준(Won-june Choi),김정엽(Jung-yup Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Subway railway systems are being increasingly adopted in metro cities to ease the passenger transportation. But there are some concerns related to the safety of the passengers. Nowadays, PSD(Platform Screen Doors) are commonly used to assure the safety of passengers. PSD is used to prevent the fire disasters, air turbulence, and dust which may pose a threat to the passenger's safety. Moreover the design of PSD itself has to take some parameters into consideration, crowd loading, wind pressure, etc. In our present study we perform a fatigue analysis considering these parameters. Commercial finite element software package ANSYS Workbench 11.0 has been used for the structural analysis. In correlation with this analysis, the structural safety of the testing PSD equipment was confirmed, and the critical load condition was found.
박푸른솔,이호준,조영준,구본승,최원준,변종민,Park, Pureunsol,Lee, Ho Joon,Jo, Youngjun,Gu, Bonseung,Choi, Won June,Byun, Jongmin 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.6
High-entropy alloys (HEAs) are generally defined as solid solutions containing at least 5 constituent elements with concentrations between 5 and 35 atomic percent without the formation of intermetallic compounds. Currently, HEAs receive great attention as promising candidate materials for extreme environments due to their potentially desirable properties that result from their unique structural properties. In this review paper, we aim to introduce HEAs and explain their properties and related research by classifying them into three main categories, namely, mechanical properties, thermal properties, and electrochemical properties. Due to the high demand for structural materials in extreme environments, the mechanical properties of HEAs including strength, hardness, ductility, fatigue, and wear resistance are mainly described. Thermal and electrochemical properties, essential for the application of these alloys as structural materials, are also described.
이정섭(Jungsub Lee),최원준(Won June Choi),김민기(Min Ki Kim),문기현(Ki Hyun Moon),송승환(Seong Hwan Song),권세진(Sejin Kwon) 한국추진공학회 2008 한국추진공학회 학술대회논문집 Vol.2008 No.11
본 연구에서는 과산화수소 분해 반응을 이용하여 세계 최초로 10뉴턴 급의 추진력을 갖는 액체 추진 소형 모델 로켓을 제작하고 발사 시험을 하였다. 일련의 설계를 통해 인젝터에 지름 200㎛의 오리피스를 7개 만들었고, 목의 지름이 2.5mm 이고 면적비가 2.56인 노즐을 제작하였다. 촉매로 백금을 코팅한 아이솔라이트(Isolite)를 사용하였다. 90wt% 과산화수소를 질소 가스를 통해 20bar로 가압하여 촉매 베드의 길이와 베드에 올린 백금의 적재량을 변수로 하여 추력 실험을 행하였다. 그 결과, 5wt%의 백금을 4cm의 베드에 올렸을 때 가장 높은 c* 효율과 추력 안전성을 보여주었다. 경량화를 위해 로켓의 몸체는 알루미늄으로 만들었으며, 제작한 로켓에서는 솔레노이드 벨브를 통해 유량을 조절하였다. 발사 시험을 행한 결과 비교적 일정한 속도로 10m 가량을 올라갔다. In this paper, a 10N class liquid propellant rocket utilizing a dissolving reaction of hydrogen peroxide is constructed and tested. Through a series of designs, seven orifices with a diameter of 200㎛ and a nozzle with a neck of 2.5mm in diameter and area ratio of 2.56 were made. The platinum coated on Isolite was used for catalyst. 90wt% peroxide pressed at 20 bar by nitrogen gas was used for performance evaluation. The length of the catalyst bed and the load of platinum was taken as the parameters for this experiment. For the catalyst support length of 4cm loaded on 5wt% platinum, satisfactory c* efficiency and stable thrust was observed. The light weight body of the rocket was composed of aluminum. Rocket rose about 10m with relatively constant velocity in launching test.
냉연강판에서의 표면결함 분류를 위한 생성적 적대 신경망 기반 데이터 증강
강재민(Jae Min. Kang),최원준(Won June Choi),감진규(Jin Kyu Gahm) 한국멀티미디어학회 2024 멀티미디어학회논문지 Vol.27 No.2
With the recent increase in demand for steel products, the need for high-quality steel has intensified. Cold-rolled steel strip often exhibit various surface defects due to numerous roll pressing processes. Some of these surface defects can lead to critical issues in steel product manufacturing. Thus, developing a high-performance model for classifying steel sheet defects is crucial for producing and maintaining high-quality metal products. In this paper, we propose a data augmentation model using Generative Adversarial Networks (GANs) to generate images of defects for classes with insufficient data. Additionally, we introduce a pre-processing method designed to minimize the loss of defect information when resizing images. Our experimental results demonstrate that applying the proposed method significantly improves performance, evidenced by an increase of up to 6% in the classification F1-score.