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Journal of Magnesium and Alloys 2022年第10期10卷 2901-2917页

作者： h.t.Jeong W.J.kim Departmentof Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

Samples of Mg-8.2Gd-3.8Y-1.1Zn-0.4Zr alloy with and without an intragranular lamellae-shaped long period stacking ordered(LPSO)phase were prepared through heat treatment and a series of hot compression tests on these materials were conducted to examine and evaluate the influence of LPSO on the hot compressive deformation behavior and deformation mechanisms at a given alloy *** values of activation energy for plastic flow(Qc)of the solution treated(without LPSO phase)and annealed alloys(with intragranular LPSO phase)were larger than that for pure Mg,indicating that the presence of a high amount of rare earth(RE)elements and LPSO in the Mg matrix significantly increases *** Qcvalue of the annealed alloy was larger than that of the solution treated alloy at all the strain levels(223.3 vs.195.5 k J/mol in average)and the largest difference in Qcbetween the two alloys was recorded at the smallest strain of 0.1 where precipitation of LPSO during deformation was limited in the solution treated *** observations imply that the formation of LPSO phase out of the RE-rich solid solution matrix during deformation increases Qc,but the increment is not so *** of the hot compressive data of the alloys with LPSO phase and the alloys with RE-rich solid solution matrix in literatures indicates the similarity of the effect of the LPSO and RE-rich solid solution matrix phases on Qcand high-temperature strength.

关键词： Magnesium alloys LPSO Deformation mechanism Dynamic recrystallization Activation energy for plastic flow Processing maps

Prominent cycling reversibility and kinetics enabled by CatiO3 protective layer on Zn metal for aqueous Zn-ion batteries

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Journal of Energy Chemistry 2025年第1期100卷 245-258页

作者： Gaeun Lee Yong Nam Ahn Seongjoon So Chanwoo Park Jong-Seong Bae taehyun Park Il tae kim Jaehyun hur School of Chemical Biological and Battery Engineering Gachon University Seongnam Busan Center Korea Basic Science Institute

Aqueous Zn-ion batteries （AZIBs） have received considerable attention owing to their various advantages such as safety,low cost,simple battery assembly conditions,and high ionic ***,they still suffer from serious problems,including uncontrollable dendrite growth,corrosion,hydrogen evolution reaction （hER） from water decomposition,electrode passivation,and unexpected *** creation of a uniform artificial nanocrystal layer on the Zn anode surface is a promising strategy for resolving these ***,we propose the use of a perovskite CatiO3（CtO） protective layer on Zn（CtO@Zn） as a promising approach for improving the performance of *** CtO artificial layer provides an efficient pathway for Zn ion diffusion towards the Zn metal because of the high dielectric constant （εr=180） and ferroelectric characteristics that enable the alignment of dipole moments and redistribute the Zn2+ions in the CtO *** avoiding the direct contact of the Zn anode with the electrolyte solution,the uneven dendrite growth,corrosion,parasitic side reactions,and hER are mitigated,while CtO retains its mechanical and chemical robustness during ***,CtO@Zn demonstrates an improved lifespan in a symmetric cell configuration compared with bare ***@Zn shows steady overpotential （～68 m V） for 1500 h at 1 mA cm-2/0.5 mA h cm-2,excelling bare ***,when paired with the V2O5-C cathode,the CtO@Zn//V2O5-C full battery delivers 148.4 mA h g-1（based on the mass of the cathode） after 300 *** study provides new insights into Zn metal anodes and the development of high-performance AZIBs.

关键词： Artificial layer Dielectric constant Zn metal anode Zinc aqueous battery

Phase Formation and Magnetic Properties of Nanocomposite Nd-Fe-B Adjusted by Small Amount of Dy and Co

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Journal of Rare Earths 2004年第Z2期22卷 89-94页

作者： t S Jang t W Lim h S Aum D h Lee M B kim Division of Materials and Chemical Engineering Sun Moon UniversityKorea Division of Materials and Chemical EngineeringSun Moon UniversityKorea Division of Mechanical EngineeringSun Moon University 100 Kalsan LiTangjung MyonAsan CityChoongnam 336-708Korea Division of Materials and Chemical EngineeringSun Moon UniversityKorea Division of Materials and Chemical EngineeringSun Moon UniversityKorea

In order to improve and stabilize the magnetic properties of nanocomposite Nd2Fe14B/α-Fe magnetic alloys by a compositional adjustment, small amount of Dy and/or Co was added to Nd9Fe84B7 alloys. DtA analysis on the amorphous of the alloys took place as the soft magnetic phases were crystallized, and then the hard magnetic Nd2Fe14B was precipitated from them. While α-Fe and a metastable 1:7 (tbCu7-type) phase were formed simultaneously in Dy and Co-free alloys, they were crystallized separately at different temperatures after Dy or Co was added. this phase separation occurred more clearly in the Dy-treated alloys and the other soft magnetic phase Fe3B was also stabilized by Dy and/or Co. the 1: 7 phase that was stabilized by Dy and/or Co was not eliminated at 700 ℃, decreasing magnetic properties of the alloys. It was eventually disappeared above 725 ℃, but Fe3B was not eliminated even at 750 ℃ when Dy was added more than 0.5 at% or Co was added more than 2.0 at%. Amount of Nd2Fe14B in the alloys tended to increase as Dy addition increased,whereas Co addition did not lead to any appreciable change in the ratio of α-Fe and Nd2Fe14B. Moreover, Dy addition apparently increased coercivity of an alloy while Co addition had a beneficial effect on remanence. the grains in the Dytreated alloys were usually finer than those in the Co-treated alloys. the grain size of both α-Fe and Nd2Fe14B in the alloys exhibiting mr ≥ 0.72 was in the range of 20 ～ 40 nm or even larger 50 nm, which is larger than the theoretical optimum size ( ～ 10 nm). typical magnetic properties obtained from a Nd7.5Dy1.5Fe82.5Co1.5B7 alloy annealed for 12 min at 725 ℃were ihc=4.85 kOe, Br= 11.32 kG, (Bh)max = 15.73 MGOe, and mr=0.73.

关键词： nanocomposite Nd-Fe-B magnetic properties remanence coercivity

Effects of Weaving Laser on Weld Microstructure and Crack for Al 6k21-t4 Alloy

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Journal of Materials Science & technology 2011年第1期27卷 93-96页

作者： B.h.kim N.h.Kang W.t.Oh C.h.kim J.h.kim Y.S.kim Y.h.Park Department of Materials Science and Engineering Pusan National UniversitySan30Jangjeon-dongGeumjeong-guBusan 609-735Korea Department of Materials and Components Engineering Dong-Eui UniversityBusan 614-714Korea Advanced Joining technology team KITECH7-47Songdo-dongYeonsu-guIncheon 406-840Korea Division for Dongnam Area technology Service KITECHJisa-dongGanseo-guBusan 618-230Korea

For Al 6k21-t4 overlap weld joint,the shear-tensile strength by using the weaving laser was improved as compared to the case of linear *** the specimen of low strength,the porosity was distributed continuously along the intersection between the plates and fusion ***,for the optimized welding condition,large oval-shaped porosities were located only in the advancing track of the concave ***,the continuity of cracks and porosities played a key role to determine the ***,the weaving width was also the important parameter to control the ***,the concave part had more significant hot and cold cracking in the weld and heat-affected zone（hAZ）,respectively,than the convex part.

关键词： Weaving laser Weld microstructure Void Al alloy

Numerical modelling of a low power non-transferred arc plasma reactor for methane conversion

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Plasma Science and technology 2019年第6期21卷 29-37页

作者： B I MIN D K DINh D h LEE t h kim S ChOI Institute for Nuclear Science and technology Jeju National University 102 Jejudaehak-ro Jeju 63243Republic of Korea University of Science and technology(USt) 217 Gajeong-ro Yuseong-gu Daejeon 34113 Republic of Korea Korea Institute of Machinery and Materials 156 Gajeongbuk-ro Yuseong-gu Daejeon 34103 Republic of Korea Department of Nuclear and Energy Engineering Jeju National University 102 Jejudaehak-ro Jeju 63243Republic of Korea

thermal flow characteristics and the methane conversion reaction in a low power arc plasma reactor for efficient storage and transport of methane,which is the main component of shale gas,were *** temperature and velocity distributions were calculated according to the type of discharge gases and arc current level by a self-developed magnetohydrodynamics (MhD)code and a commercial ANSYS-FLUENt code;the transport of chemical species was analyzed as including the chemical reactions of methane *** simulated results were verified by the comparison of calculated and measured arc voltages with permissible low error as under 4%.three C2 hydrocarbon gases with ethane (C2h6),ethylene (C2h4),and acetylene (C2h2)were selected as the converted species of methane from experimental *** mass fraction of C2 hydrocarbons and hydrogen as the product of the conversion reaction at the reactor was also *** values show good agreement with the actual experimental results in that the major conversion reaction occurred in C2h2 and hydrogen,and the conversions to C2h6,C2h4,and hydrogen were minor reactions of methane pyrolysis conversion.

关键词： numerical modelling non-transferred arc plasma methane chemical reaction

Effect of Duct Geometry on Shock Wave Discharge

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Journal of thermal Science 2006年第4期15卷 349-354页

作者： Y.-h.Kweon Y.Miyazato t.Aoki h.-D.kim t.Setoguchi Department of Energy and Environmental Engineering Kyushu UniversityKasuga 816-8580Japan Faculty of Environmental Engineering The University of KitakyushuKitakyushu 808-0135Japan School of Mechanical Engineering Andong National UniversityAndong 760-749Korea Department of Mechanical System Engineering Saga UniversitySaga 840-8502Japan

this paper describes computational work to understand the unsteady flow-field of a shock wave discharging from an exit of a duct and impinging upon a flat plate. A flat plate is located downstream, and normal to the axis of the duct. the distance between the exit of the duct and flat plate is changed. In the present study, two different duct geometries （i.e., square and cross section） are simulated to investigate the effect of duct geometry on the un-steady flows of a shock wave. In computation, the total variation diminishing （tVD） scheme is employed to solve three-dimensional, unsteady, compressible, Euler equations. Computations are performed over the range of shock Mach number from 1.05 to 1.75. Computational results can predict the three-dimensional dynamic behaviour of the shock wave impinging upon the flat plate. the results obtained show that the pressure increase generated on the plate by the shock impingement depends on the duct geometry and the distance between the duct exit and plate, as well as the shock Mach number. It is also found that for the duct with cross-section, the unsteady loads acting on the flat plate are less, compared with the square duct.

关键词： unsteady flow compressible flow shock wave shock impingement duct geometry

A Study of the Weak Shock Wave Propagating over a Porous Wall/Cavity System

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Journal of thermal Science 2005年第4期14卷 329-333页

作者： h.D.kim S.J.JUNG t.AOKI t.SEtOGUChI School of Mechanical Engineering.Andong National University Songchun-dongAndong 760-746Korea Department of Energy and Environmental Engineering Kyushu University6-1Kasuga-kouenKasugaFukuoka 816-8580Japan Department of Mechanical Engineering Saga University1HonjoSaga 840-8502Japan

the present computational study addresses the attenuation of the shock wave propagating in a duct, using a porous wall/cavity system. In the present study, a weak shock wave propagating over the porous wall/cavity system is investigated with computational fluid dynamics. A total variation diminishing scheme is employed to solve the unsteady, two-dimensional, compressible, Navier-Stokes equations. the Mach number of an initial shock wave is changed in the range from 1.02 to 1.12. Several different types of porous wall/cavity systems are tested to investigate the passive control effects. the results show that wall pressure strongly fluctuates due to diffraction and reflection processes of the shock waves behind the incident shock wave. From the results, it is understood that for effective alleviation of tunnel impulse waves, the length of the perforated region should be sufficiently long.

关键词： compressible flow perforated wall railway tunnel shock wave.

Superplasticity of fine-grained Mg-10Li alloy prepared by severe plastic deformation and understanding its deformation mechanisms

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Journal of Magnesium and Alloys 2024年第1期12卷 316-331页

作者： h.t.Jeong S.W.Lee W.J.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

the superplastic behavior and associated deformation mechanisms of a fine-grained Mg-10.1 Li-0.8Al-0.6Zn alloy(LAZ1011)with a grain size of 3.2μm,primarily composed of the BCCβphase and a small amount of the hCPαphase,were examined in a temperature range of 473 K to 623 *** microstructural refinement of this alloy was achieved by employing high-ratio differential speed *** best superplasticity was achieved at 523 K and at strain rates of 10^(-4)-5×10^(-4)s^(-1),where tensile elongations of 550±600%were *** the heating and holding stage of the tensile samples prior to tensile loading,a significant increase in grain size was observed at temperatures above 573 ***,it was important to consider this effect when analyzing and understanding the superplastic deformation behavior and *** the investigated strain rate range,the superplastic flow at low strain rates was governed by lattice diffusion-controlled grain boundary sliding,while at high strain rates,lattice diffusion-controlled dislocation climb creep was the rate-controlling deformation *** was concluded that solute drag creep is unlikely to *** the late stages of deformation at 523 K,it was observed that grain boundary sliding led to the agglomeration of theαphase,resulting in significant strain *** mechanism maps were constructed forβ-Mg-Li alloys in the form of 2D and 3D formats as a function of strain rate,stress,temperature,and grain size,using the constitutive equations for various deformation mechanisms derived based on the data of the current tests.

关键词： Magnesium-lithium alloy Superplasticity Severe plastic deformation Grain size Grain growth

Computational Analysis of a Variable Ejector Flow

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Journal of thermal Science 2006年第2期15卷 140-144页

作者： h.D. kim J.h. LEE t. SEtOGUChI S.MAtSUO School of Mechanical Engineering Andong National University 388 Songchun-dong Andong 760-749 Korea Department of Mechanical Engineering Saga University 1 Honjo Saga 840-8502 Japan

the present study addresses a variable ejector which can improve the ejector efficiency and control the re-circulation ratio under a fixed operating pressure ratio. the variable ejector is a facility to obtain specific recirculation ratio under a given operating pressure ratio by varying the ejector throat area ratio. the numerical simulations are carried out to provide an understanding of the flow characteristics inside the variable ejector. the sonic and supersonic nozzles are adopted as primary driving nozzles in the ejector system, and a movable cone cylinder, inserted into a conventional ejector-diffuser system, is used to change the ejector throat area ratio. the numerical simulations are based on a fully implicit finite volume scheme of the compressible, Reynolds-Averaged Navier-Stokes equations. the results show that the variable ejector can control the recirculation ratio at a fixed operating pressure ratio.

关键词： variable ejector ejector throat area ratio re-circulation ratio

Development of mathematical model with a genetic algorithm for automatic arc welding process

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Acta Metallurgica Sinica(English Letters) 2010年第3期23卷 230-240页

作者： D.t.thao I.S.kim J.W.Jeong J.h.Lee J.Y.Shim h.h.kim Department of Mechanical Engineering Mokpo National University

this paper is to represent new algorithms to predict process parameters on top-bead width in robotic gas metal arc（GMA） welding *** models have been developed：linear, curvilinear and intelligent model based on full factorial design with two *** analysis was employed for optimization of the coefficients of linear and curvilinear models, while genetic algorithm（GA） was utilized to estimate the coefficients of an intelligent *** only the fitting of these models were checked and compared by using a variance test（ANOVA）, but also the prediction on top-bead width using the developed models were carried out based on the additional *** developed models were employed to investigate the characteristic between process parameters and top-bead *** solutions and graphical representation showed that the intelligent model developed can be employed for prediction of bead geometry in GMA welding process.

关键词： top-bead width Genetic algorithm Multiple regression Robotic arc welding GMA welding