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컴퓨터 시뮬레이션 기법을 이용한 입계면 - 이상 입자 간 상호작용 모사 연구 동향
장근옥,Chang, Kunok 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.4
Since the interaction between the second-phase particle and grain boundary was theoretically explained by Zener and Smith in the late 1940s, the interaction of the second-phase particle and grain boundary on the microstructure is commonly referred to as Zener pinning. It is known as one of the main mechanisms that can retard grain growth during heat treatment of metallic and ceramic polycrystalline systems. Computer simulation techniques have been applied to the study of microstructure changes since the 1980s, and accordingly, the second-phase particle-grain boundary interaction has been simulated by various simulation techniques, and further diverse developments have been made for more realistic and accurate simulations. In this study, we explore the existing development patterns and discuss future possible development directions.
장근옥 ( Kunok Chang ) 한국공업화학회 2020 공업화학 Vol.31 No.4
재료는 방사선과 상호작용을 통해 그 물리적, 화학적 특성이 변화하며 여러 방사선 중에서 전하를 띄고 있지 않아 침투깊이가 깊은 중성자 조사에 의한 금속소재의 조사손상은 원자력발전소의 안전과 관련해서 오랜 기간 동안 집중적인 연구대상이었다. 중성자 조사에 의한 조사손상은 초반 피코 초 스케일에서 벌어지는 원자단위의 점결함의 생성으로 시작되며 그 이후의 전개 양상은 전위 고리나 공극과 같은 미세구조상 결함으로 확인될 수 있다. 이러한 미세구조상 결함의 형상과 분포에 따라 소재의 특성에 미치는 효과는 상이하게 된다. 그러므로 중성자 조건에 따른 미세구조를 예측하는 것은 매우 중요한 일로, 본 논문에서는 중성자 조사에 의한 재료 내의 미세구조 발달에 대해 리뷰한 뒤 조사된 소재의 미세구조 변화 예측에 널리 사용될 수 있는 상장 모델에 대해 간략히 소개하였다. A material changes its physical and chemical properties through the interaction with radiation and also the neutrons, which is electronically neutral so that the penetration depth is relatively deeper than that of other radioactive way including alpha or beta ray. Therefore, the radiation damage by neutron irradiation has been intensively investigated for a long time with respect to the safety of nuclear power plants. The damage induced by neutron irradiation begins with the creation of point defects in atomic scale in the unit of picoseconds, and their progress pattern can be characterized by microstructural defects, such as dislocation loops and voids. Their morphological characteristics affect the properties of neutron-irradiated materials, therefore, it is very important to predict the microstructure at a given neutron irradiation condition. This paper briefly reviews the evolution of radiation damage induced by neutron irradiation and introduces a phase-field model that can be widely used in predicting the microstructure evolution of irradiated materials.
Effective thermal conductivity model of porous polycrystalline UO 2 : A computational approach
윤보현,장근옥 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.5
The thermal conductivity of uranium oxide (UO2) containing pores and grain boundaries is investigatedusing continuum-level simulations based on the finite-difference method in two and three dimensions. Steady-state heat conduction is solved on microstructures generated from the phase-field model of theporous polycrystal to calculate the effective thermal conductivity of the domain. The effects of porosity,pore size, and grain size on the effective thermal conductivity of UO2 are quantified. Using simulationresults, a new empirical model is developed to predict the effective thermal conductivity of porouspolycrystalline UO2 fuel as a function of porosity and grain size
이경근,진형하,장근옥,임상엽,김민철,이봉상,권준현 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8
Ni-Cr-Mo low alloy steels are being considered as alternative materials to replace the Mn-Mo-Ni low alloy steels used in reactor pressure vessels in nuclear power plants, because of their higher strength and toughness. However, the neutron irradiation occurring during reactor operation causes degradation of Ni-Cr-Mo low alloy steel. In this study, irradiation-induced clusters in a Ni-Cr-Mo model alloy irradiated in the High-flux advanced neutron application reactor (HANARO) research reactor were investigated via Atom probe tomography (APT). The irradiated specimens showed irradiation-induced hardening and embrittlement. The neutron irradiation caused Si clustering, and these spherical clusters were homogeneously distributed within the matrix. Ni was also clustered at the Si clusters. However, the other elements did not clearly exhibit clustering behavior. Si and Ni atoms were also located at the dislocations. To quantify the nano-sized clusters, a method based on the Density-based spatial clustering of applications with noise (DBSCAN) algorithm was implemented. The total number of clusters was calculated to be ~7 × 10 -4 n/nm 3 and the average cluster radius was less than 2 nm. The APT approach was demonstrated to be well suited for discovering the irradiation defect structures.
COMSOL을 활용한 신 마그네슘 전해 공정 수치해석 모델 개발
조매현,정형준,강정신,장근옥 대한금속·재료학회 2023 대한금속·재료학회지 Vol.61 No.8
Magnesium (Mg) has good physical properties including light weight, excellent specific strengthand high stiffness, and Mg is used in many fields. But current production methods of Mg have disadvantages,such as the generation of sulfur oxide and chlorine gas. In this situation, The Korea Institute of Geoscienceand Mineral Resources (KIGAM) developed a Molten Salt Electrolysis Using Liquid Metal Cathode (MSELMC)method to produce high-purity magnesium. The MSE-LMC method can obtain 99.998-99.999% highpuritymagnesium by the electrolysis of MgO dissolved in (MgF2)-LiF molten salt at 1053-1083 K, and byvacuum distilling an alloy generated by reacting with a metallic liquid cathode at 1200-1300 K. This studydeveloped a numerical analysis model using COMSOL Multiphysics electrodeposition module to optimize thedesign of the electrolysis process. The model temperature was 1053K and molten salt was 54MgF2-46LiF witha 0.6wt% MgO system. 10A constant current was applied at the anode. This model uses the Butler-Volmerequation and the Nernst equation for the electric reaction. The Stokes-Einstein equation and Nernst-Einsteinrelation were used to calculate the diffusivity and electric mobility of salts. Unlike the experiment, in thismodel chlorine gas was generated. However, this model satisfied Faraday’s law. Therefore we define a newparameter using electric flux and voltage to conduct a quantitative evaluation according to the electrodeshape, and compared that parameter by the changing angle of the anode.
Defect structure classification of neutron-irradiated graphite using supervised machine learning
김지호,김건,허균영,장근옥 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8
Molecular dynamics simulations were performed to predict the behavior of graphite atoms under neutron irradiation using large-scale atomic/molecular massively parallel simulator (LAMMPS) package with adaptive intermolecular reactive empirical bond order (AIREBOM) potential. Defect structures of graphite were compared with results from previous studies by means of density functional theory (DFT) calculations. The quantitative relation between primary knock-on atom (PKA) energy and irradiation damage on graphite was calculated. and the effect of PKA direction on the amount of defects is estimated by counting displaced atoms. Defects are classified into four groups: structural defects, energy defects, vacancies, and near-defect structures, where a structural defect is further subdivided into six types by decision tree method which is one of the supervised machine learning techniques