Effects of Heat Treatment on Corrosion Behaviors of 3-D Printed Ni-based Alloy in Molten NaCl-MgCl2 Salt

Younghwan Jeon,Hyeongjin Byeon,Jaeyeong Park 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

Molten salt is one of the promising medium materials for molten salt reactors and energy storage systems. Molten salt is advantageous for better physical properties such as low melting point and high boiling point, high energy capacity, high thermal conductivity, and high thermal stability than other medium materials such as water or liquid metals. However, the corrosivity of the molten salt is one of the main factors that disturbs the various applications of the molten salt. On the other hand, metallic 3-D printing technologies have developed by leaps and bounds over the past 20 years and show potential for use in cutting-edge industries such as aerospace and military purposes. However, the biggest problem of 3-D printed products is that the mechanical and physical properties are very weak along the laminated plane that was generated during the manufacturing process. In particular, other research showed that corrosion is vulnerable through the laminated surface, and corrosion along the laminated plane is not completely mitigated through a general heat treatment process although the microstructure of the surface is evaluated to be partially mitigated by the heat treatment. In this study, molten salt corrosion behaviors of simple Ni-based alloy with a composition of 80Ni- 20Cr were analyzed. Ni-based alloys were fabricated by casting and 3-D printing, and some of the 3-D printed specimens were thermally treated at 1,273 K for 1 hour to examine the effects of heat treatment on corrosion behaviors. In molten eutectic NaCl-MgCl2 melts at 973 K, Ni-based alloys were corroded for 1, 3, 7, and 28 days and their microstructural changes were analyzed by SEM-EBSD-EDS and OM. The corrosion behaviors of the alloy were also evaluated by the salt composition measured with ICPOES. 3-D printed alloy with post-treatment showed more resistivity to the molten salt corrosion than as-fabricated 3-D printed alloy. However, the corrosion rate of the 3-D printed specimen after heat treatment was still higher than that made by casting.

orrosion Mitigation Strategies for Ni-based Alloy in NaCl-MgCl2 Melts at 973 K

Younghwan Jeon,Hyeongjin Byeon,Yeojin Kim,Jaeyeong Park 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

A molten salt reactor (MSR) is a conceptual nuclear reactor that uses molten salt with liquid fuel as its primary coolant. Based on the thermophysical and neutronic properties, MSR has advantages such as high efficiency, safety, combustion of transuranic (TRU) elements, and availability of miniaturization and on-power refueling. Various research on MSR such as system development, neutronic analysis, material development, and molten salt property analysis has been conducted, but the biggest problem is the molten salt corrosion. The molten salt corrosion on structural materials can be explained by two processes; electrochemical and chemical reactions. The reduction of oxidative ions such as fuel and TRU elements is one of the major causes of molten salt corrosion. Contamination by humidity and oxygen is also known as the accelerating factor of molten salt corrosion. Also, molten salt corrosion behaviors on structural material deteriorate when dissimilar alloys are introduced in the molten salt system. Various techniques to mitigate molten salt corrosion in fluoride system has been developed, but these are not well-verified in chloride system. In this research, various methodologies to mitigate molten salt corrosion are studied. The corrosion behaviors of 80Ni-20Cr alloy in molten eutectic NaCl-MgCl2 salt at 973 K are analyzed with various applications such as salt purification, sacrificial metal injection, and salt redox potential control. Oxygen and water impurities that can accelerate molten salt corrosion have been removed by electrochemical and chemical methods; Applying the reduction potential for H+/H2 and oxidation potential for O2-/O2, introducing HCl and CCl4 gas, and introducing the metallic Cr and recovering the ionized Cr. Corrosion acceleration/deceleration effects were analyzed when introducing the reducing reagent such as Mg and Nb or oxidizing reagent such as metallic Mo and the effect of inert metallic element (W) was also investigated. The salt potential was controlled by applying the potential to the salt and adjusting the Eu3+/Eu2+ ratio.

Anodic Dissolution Behaviors of Inconel-600 Depending on Ni and Fe Additives in LiCl-KCl

Younghwan Jeon,Jungho Hur,Seungmin Ohk,Jaeyeong Park 한국방사성폐기물학회 2020 한국방사성폐기물학회 학술논문요약집 Vol.2020 No.12

Corrosion Behavior Analysis of Ni-Cr Alloy in Molten NaCl-MgCl2 With Various Metallic Chloride at 973 K

Younghwan Jeon,Jungho Hur,Jaeyeong Park 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

Attempts to use the molten salt system in various aspects such as MSR or energy storage systems are increasing. However, there are limitations in the molten salt-assisted technique due to the harsh corrosiveness of the molten salt, and a more detailed study on salt-induced corrosion is needed to solve this problem. In this study, corrosion behaviors of 80Ni-20Cr alloy in various salt environments such as eutectic NaCl-MgCl2 with NiCl2, CrCl2, and EuCl3 additives were investigated. Meanwhile, the corrosion acceleration effects of 80Ni-20Cr specimens were analyzed for various ceramic materials such as SiC, Al2O3, SiO2, graphite, and BN, and metallic materials such as Ni-based alloy, Fe-based alloy, and pure metals in a molten salt environment. The experiments were conducted at 973 K for up to 28 days, and after the experiment, the microstructural change of the specimen was analyzed through SEM-EDS, and salt condition was analyzed by ICP-OES.

비자발적 기술수용환경에서의 공무원 전자정부 수용 영향요인에 관한 연구 -성북구 공무원의 시정정보수집 시스템 인식을 중심으로-

전영환 ( Younghwan Jeon ),김병준 ( B Joon Kim ) 한국정책학회 2016 韓國政策學會報 Vol.25 No.1

정보통신 기술의 급격한 발달은 행정의 패러다임의 변화에도 큰 영향을 초래하고 있다. 전자정부(E-Government) 기조 아래 행정의 전자화(Digitalization)를 통한 효율성(Efficiency)강화 및 시민책무성(Accountability) 강화가 이뤄지고 있으며, UN의 UNPAN을 중심으로 전자정부 구축 인프라에 대한 평가가 그 영향력을 증대해 나가고 있다. 하지만 이러한 물리적 구 축정도가 “전자정부가 잘 이루어지고 있는지”를 평가할 수 있을까? Davis(1987)에 따르면 시스템의 성공을 평가하기 위해선 물리적 구축뿐 만 아니라 구축된 시스템을 얼마나 수용 하는지의 여부가 중요하다고 주장 되어져 왔다. 이에, 본 연구에서는 전자정부의 평가지표 재편을 위해 공무원의 전자정부 수용과 그 수용에 영향을 미치는 요인을 탐구하고자 하였다. 공무원의 기술수용환경의 비자발적(Mandatory) 환경적 특성을 고려한 변수의 설정과 정보과잉(Information Overload)의 변수 추가를 통해 상관의 지원, 조직의 지원, 시민참여에 대한 태도, 정보의 질, 지각된 정보의 유용성이 공무원의 전자정부(시정정보수집 시스템) 수용에 직접적으로 어떠한 영향을 미치는 지 살펴보았으며, 그 결과 긍정적인 영향을 미치는 것으로 확인되었다. 또한 조직의 지원에 대해 지각된 유용성이 긍정적인 조절을, 정보과잉 이 부정적인 조절효과를 나타내는 것으로 나타났다. 이러한 연구 결과를 바탕으로, 본 연구에서는 공무원의 시정정보수집 시스템 수용을 증진시키기 위해서 기존 기술수용요인에 대한 강화 외에도 정보과잉을 최소화할 필요성이 있음을 주장하고자 하였다. The recent rapid development of IT has been influenced on the paradigm shift of public administration(PA) enormously. In particular, e-Government and the digitalization of public services emphasize the importance of efficiency and accountability in implementing public policy at once as well as reinforce the development of information infrastructure. Thus, the evaluation on e-Government such as UN e-Government survey become more essential for the future of PA. For example, Davis(1987) has underlined the level of acceptance on IT as a crucial factor for advancing e-Government. In this study, factors such as information overload that influence on the IT acceptance has been studied to create a proper index system for evaluation with considering the environmental situation such as mandatory rules for implementing new IT and e-Government services. Also, other crucial variables including the comprehensive supports of manager(s) & organization(s), the attitude toward citizen participation, the quality of information, the level of usefulness in the perceived information are examined. The results told us that there are two different types - positive and negative - and the result can champion that public policies on IT should move toward to enhance the positive(+) factors and to prevent the negative(-) traits such as information overload in order to increase the level of IT acceptance.

TadGAN 모델 기반 배터리 사이클 데이터의 이상치 탐지 기법 연구

전영환(Younghwan Jeon),김지용(Jiyong Kim),이강훈(Kanghoon Lee) 한국정보과학회 2023 한국정보과학회 학술발표논문집 Vol.2023 No.6

A 220–320-GHz Vector-Sum Phase Shifter Using Single Gilbert-Cell Structure With Lossy Output Matching

Younghwan Kim,Sooyeon Kim,Iljin Lee,Urteaga, Miguel,Sanggeun Jeon Professional Technical Group on Microwace Theory a 2015 IEEE Transactions on Microwave Theory and Techniqu Vol. No.

<P>This paper presents a wideband vector-sum phase shifter (VSPS) that operates over the entire WR-3 band (220-320 GHz). Compared to conventional VSPSs with double Gilbert cells, the proposed phase shifter employs a single Gilbert-cell structure for vector modulation. This reduces the output current combining ratio from 8:2 to 4:2, and boosts the impedance at the combining node, thus facilitating wideband output matching at upper millimeter-wave and terahertz bands. The simplified structure leads to a reduction in dc power consumption and chip area without sacrificing the 360 <SUP>°</SUP> phase-shifting property. Lossy matching is applied at the Gilbert-cell output to further increase bandwidth and stability at the expense of relatively high loss. The phase shifter is implemented using a 250-nm InP DHBT technology that provides f T and f max exceeding 370 and 650 GHz, respectively. The measurements exhibit a wideband phase shift with continuous 360 <SUP>°</SUP> coverage and average insertion loss ranging from 11.8 to 15.6 dB for the entire WR-3 band. The root mean square amplitude and phase error among different phase states are less than 1.2 dB and 10.2 <SUP>°</SUP>, respectively. The input-referred 1-dB compression is measured at 0.7 dBm on average. The dc power consumption is 21.8-42.0 mW at different phase states.</P>

Design and analysis of the link mechanism for the flapping wing MAV using flexible multi-body dynamic analysis

Jeon, JaeHyeok,Cho, Haeseong,Kim, Younghwan,Lee, JunHee,Gong, DuHyun,Shin, SangJoon,Kim, Chongam SAGE Publications 2017 International journal of micro air vehicles Vol.9 No.4

스마트 강연선에 내장된 FBG 센서의 온도보정 기법

전세진(Jeon, Se-Jin),박성용(Park, Sung Yong),김성태(Kim Sung Tae),홍지수(Hong Jisu),박영환(Park, YoungHwan) 대한토목학회 2021 대한토목학회 학술대회 Vol.2021 No.10

Prediction of the Salinization in Reclaimed Land by Soil and Groundwater Characteristics

( Jihun Jeon ),( Donggeun Kim ),( Taejin Kim ),( Keesung Kim ),( Hosup Jung ),( Younghwan Son ) 한국농공학회 2021 한국농공학회논문집 Vol.63 No.6

It is becoming more important to utilize reclaimed lands in South Korea, due to the increasing competition for its usage among different sectors. However, the high groundwater level and poor permeability are exposing them to deterioration by salinization. Salinization is difficult to predict because the pattern changes according to various characteristics of soil and groundwater. In this study, the capillary rising time was studied by the water content profile in the soil. The prediction equation of soil salinity was developed based on simulation result of the CHEMFLO model. to enable prediction considering various soil water content and groundwater level. The two terms constituting the equation showed the coefficients of determination of 0.9816 and 0.9824, respectively. Using the prediction equation of the study, the surface salinity can be easily predicted from the initial surface salinity and the salinity of the groundwater. In the future, more precise predictions will be possible with the results of studies on the hydraulic characteristics of various reclaimed soils, changes in water content profile by seasonal and climate events.