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Smart decontamination device for small-size radioactive scrap metal:using abrasion pin in rotating magnetic field and ultrasonic wave cleaner

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Journal of Measurement Science and Instrumentation 2013年第3期4卷 302-306页

作者： yongho hong Suri Park Sangwook Han Byungjick Kim Department of Chemical Engineering Soongsil University

A smart decontamination device is developed for small-size radioactive scrap metal(SSRSM)arisen from nuclear *** abrasion pin in rotating magnetic field and ultrasonic wave cleaner are used for solving the problems of the second decontamination and high treatment *** first,the decontamination efficiency of each device is improved by upgrading the *** operating conditions are determined for each ***,both techniques are applied *** results show that the efficiency of combined decontamination device is higher than that of each *** the use of the developed device,the various SSRSMs are decontaminated for 15 min treatment in magnetic abrasion device and15 min treatment in ultrasonic cleaning *** index ranges from18 to *** values of all decontaminated samples are below the background value.

关键词： radioactive scrap metal decontamination magnetic field ultrasonic cleaningCLC number:X771 Document code:AArticle ID:1674-8042(2013)03-0302-05

MXenes: Versatile 2D materials with tailored surface chemistry and diverse applications

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Journal of Energy Chemistry 2024年第3期90卷 253-293,I0008页

作者： Sunil Kumar Nitu Kumari yongho Seo Department of Nanotechnology and Advanced Materials Engineering and HMC Sejong UniversitySeoul 05006South Korea School of Studies in Chemistry Jiwaji UniversityGwalior 474011India

MXenes,the most recent addition to the 2D material family,have attracted significant attention owing to their distinctive characteristics,including high surface area,conductivity,surface characteristics,mechanical strength,*** review begins by presenting MXenes,providing insights into their structural characteristics,synthesis methods,and surface functional *** review covers a thorough analysis of MXene surface properties,including surface chemistry and termination group *** properties of MXenes are influenced by their synthesis,which can be fluorine-based or ***-based synthesis techniques involve etching with fluorine-based reagents,mainly including HF or LiF/HCl,while fluorine-free methods include electrochemical etching,chemical vapor deposition(CVD),alkaline etching,Lewis acid-based etching,*** techniques result in the emergence of functional groups such as-F,-O,-OH,-Cl,*** the MXenes surface,depending on the synthesis method *** of MXenes,such as electrical conductivity,electronic properties,catalytic activity,magnetic properties,mechanical strength,and chemical and thermal stability,are examined,and the role of functional groups in determining these properties is *** review delves into the diverse applications of MXenes,encompassing supercapacitors,battery materials,hydrogen storage,fuel cells,electromagnetic interference(EMI) shielding,pollutant removal,water purification,flexible electronics,sensors,additive manufacturing,catalysis,biomedical and healthcare fields,***,this article outlines the challenges and opportunities in the current and future development of MXenes research,addressing various aspects such as synthesis scalability,etching challenges,and multifunctionality,and exploring novel *** review concludes with future prospects and conclusions envisioning the impact of MXenes on future technologies and innovation.

关键词： MXenes 2D materials Surface chemistry MXenes structure Synthesis Applications

Effect of Sn on the Microstructure and Mechanical Properties of Mg-5AI-2Si Alloys

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Journal of Materials Science & Technology 2008年第3期24卷 296-301页

作者： Sangwon Lee Bonggyu Park yongho Park Ikmin Park Department of Material Science and Engineering Pusan National University 30Jangjeon-dongGeumjeong-gu

The effect of Sn addition on the microstructures and mechanical properties of Mg-5Al-2Si alloys was investigated with variations of Sn contents （3 and 6 wt pct）. The microstructure of the alloy was characterized by the presence of Mg2Sn particles within matrix and at grain boundaries. As the Sn contents increased, yield and ultimate tensile strength were increased at room temperatures and 150℃. Creep properties were improved with the increasing amount of Sn due to the fine precipitation of Mg2Sn phases within grain during creep.

关键词： Magnesium Tin Microstructure Mechanical properties

Effect of Sb Addition on Microstructure and Mechanical Properties of Al-18B-4O-33/AS-52 Magnesium Matrix Composites

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Journal of Materials Science & Technology 2008年第1期24卷 99-101页

作者： Wookjin Lee Ikmin Park x yongho Park School of Materials Science and Engineering Pusan National University San 30 Jangjeon-dong Geumjeong-gu Busan 609-735 Korea

The effect of antimony addition on the microstructure of Mg-Al-Si magnesium matrix composite was investi- *** addition of Sb can modify the morphology of Mg-2Si particles which have Chinese script shape to fine polygonal *** matrix composite with Alborex whisker was successfully fabricated by using a squeeze infiltration *** strength and elongation were increased in the Sb modified alloy and the composite at both room and high temperatures.

关键词： Magnesium Metal matrix composites (MMC) Composite

Microstructure, precipitates and mechanical properties of powder bed fused inconel 718 before and after heat treatment

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Journal of Materials Science & Technology 2019年第6期35卷 1153-1164页

作者： Le Zhou Abhishek Mehta Brandon McWilliams Kyu Cho yongho Sohn Advanced Materials Processing and Analysis Center University of Central Florida Orlando FL 32816 USA Department of Materials Science and Engineering University of Central Florida Orlando FL 32816 USA Weapons and Materials Research Directorate US. Amy Research Laboratory Aberdeen Proving Ground MD 21005 USA

IN718 alloy was fabricated by laser powder bed fusion(PBF) for examination of microstructure, precipitates and mechanical properties in the as-built state and after different heat treatments. The as-built alloy had a characteristic fine cellular-dendritic microstructure with Nb, Mo and Ti segregated along the interdendritic region and cellular boundary. The as-built alloys were then subjected to solution heat treatment(SHT) at 980°C or 1065°C for 1 h. SHT at 980°C led to the formation of δ-phase in the interdendritic region or cellular boundary. The segregation was completely removed by the SHT at 1065°C, but recrystallization was observed, and the carbides decorated along the grain boundaries. The as-built alloy and alloys with SHT at 980°C and 1065°C were two-step aged, which consisted of annealing at 720°C for8 h followed by annealing at 620°C for 8 h. Transmission electron microscopy revealed the precipitation of λ’ and λ" in all alloys after two-step aging, but the amount and uniformity of distribution varied. The Vickers hardness of the PBF IN718 alloy increased from 296 HV to 467 HV after direct aging. The hardness decreased to 267 HV and 235 HV after SHT at 980°C and 1065°C, respectively, but increased to 458 HV and 477 HV followed by aging. The evolution of Young’s modulus after heat treatment exhibited similar trend to that of hardness. The highest hardness was observed for IN718 after SHT at 1065°C and two-step aging due to precipitation with greater amount and uniform distribution.

关键词： Laser powder bed fusion IN718 Microstructure Transmission electron microscopy

Effect of rheo-diecast process on the mechanical properties of A390 alloy by serpentine channel

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International Journal of Minerals,Metallurgy and Materials 2016年第10期23卷 1177-1186页

作者： Kunhyok Ri Wei-min Mao Zhi-kai Zheng Myongsik Kim yongho Sin School of Materials Science and Engineering University of Science and Technology Beijing School of Material Engineering Pyongyang Machinery University

In this paper, the effects of rheo-diecast process parameters and T6 heat treatment on the microstructure and mechanical properties of the rheo-diecasting（RDC） semi-solid A390 alloy prepared through pure copper serpentine channel were investigated. The results indicate that the mechanical properties of the RDC samples change with the pouring temperature and injection pressure. In this case, a lower pouring temperature results in better tensile strength and elongation of the RDC A390 alloy; however, the tensile strength and elongation decrease when the pouring temperature decreases to 660°C. Higher injection pressures result in the improved mechanical properties of the RDC A390 alloy. To some extent, T6 heat treatment improves the tensile strength and ductility of the RDC A390 alloy compared to those of the non-heat treated alloy. However, when the pouring temperature and injection pressure are greater than 670°C and 70 MPa, respectively, the mechanical properties are sharply diminished.

关键词： aluminum alloys diecasting rheo-casting microstructure mechanical properties

Ageing Behavior of Mg-xAl-Zn with Variation of Al Content

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Journal of Materials Science & Technology 2008年第1期24卷 51-53页

作者： Byoungho Kim Jongjin Jeon Yeongdo Park yongho Park Ikmin Park Department of Materials Science and Engineering Pusan National University 30 Jangjeon-dongGeumjeong-guBusan 609-735Korea Department of Advanced Materials Engineering Dong-Eui University 995 EomgwangnoJin-guBusan 614-714Korea

The ageing behavior of Mg-xAl-Zn alloys with a variation of AI contents （x=3,5,7,9 and 11 wt pct） were *** solution treatment and artificial ageing were carried out at 693 and 493 K,respectively. After the solid solution treatment,β-Mg-（17）Al-（12） was resolved to theα-Mg matrix in the specimens which contained Al up to 9 wt pct and partially resolved in the specimen of 11 wt pct *** ageing,theβ- Mg-（17）Al-（12） phase was precipitated at the grain boundary in the form of discontinuous precipitation and grown into the *** volume fraction ofβ-phase was increased with the Al *** strength increased with the volume fraction of precipitatedβ-phase,which was believed to strengthen the matrix.

关键词： Ageing Mg alloy Discontinuous precipitation

A progressive route for tailoring electrical transport in MoS2

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Nano Research 2016年第2期9卷 380-391页

作者： Muhammad Arslan Shehzad1 Sajjad Hussain Muhammad Farooq Khan Jonghwa Eom Jongwan Jung yongho Seo Graphene Research Institute Sejong University Seoul 143-747 Republic of Korea Faculty of Nanotechnology & Advanced Materials Engineering and Graphene Research Institute Sejong University Seoul 143-74 7Republic of Korea Department of Physics and Graphene Research Institute Sejong University Seoul 143-747 Republic of Korea

Typically, molybdenum disulfide （MoS2） synthesized by chemical vapor deposition （CVD） is polycrystalline; as a result, the scattering of charge carriers at grain boundaries can lead to performances lower than those observed in exfoliated single-crystal MoS2. Until now, the electrical properties of grain boundaries have been indirectly studied without accurate knowledge of their location. Here, we present a technique to measure the electrical behavior of individual grain boundaries in CVD-grown MoS2, imaged with the help of aligned liquid crystals. Unexpectedly, the electrical conductance decreased by three orders of magnitude for the grain boundaries with the lowest on/off ratio. Our study provides a useful technique to fabricate devices on a single-crystal area, using optimized growth conditions and device geometry. The photoresponse, studied within a MoS2 single grain, showed that the device responsivity was comparable with that of the exfoliated MoS2-based photodetectors.

关键词： MoS2 grain boundary liquid crystal electrical properties photoresponse

Haar wavelet discretization method for free vibration study of laminated composite beam under generalized boundary conditions

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Journal of Ocean Engineering and Science 2021年第1期6卷 1-11页

作者： Sung-Ryol So Hoyong Yun yongho Ri Ryongsik O Yong-Il Yun Institute of Advanced Science Kim Il Sung UniversityPyongyangDemocratic People’s Republic of Korea Institute of Science Kimchaek University of TechnologyPyongyangDemocratic People’s Republic of Korea Department of Engineering Machine Pyongyang University of Mechanical EngineeringPyongyangDemocratic People’s Republic of Korea Department of Transport Mechanical Engineering Pyongyang University of Mechanical EngineeringPyongyangDemocratic People’s Republic of Korea

Investigation on vibration of laminated composite beam(LCB)is an important issue owing to its wide use as fundamental *** the present work,we study the free vibration of arbitrarily LCB with generalized elastic boundary condition(BC)by using Haar wavelet discretization method(HWDM).Timoshenko beam theory is utilized to model the free vibration of *** LCB is first split into several segments,and then the displacement for each segment is obtained from the Haar wavelet series and their ***’s principle is applied to construct governing equations and the artificial spring boundary technique is adopted to obtain the general elastic boundary and continuity conditions at two ends of *** vibration characteristics of beam with different fiber orientations and lamina numbers is investigated and its displacements are compared with those in previous *** results are shown graphically and demonstrate the validation of our method.

关键词： Laminated beam Haar wavelet discretization method Elastic boundary condition Free vibration Artificial spring boundary technique