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Effects of Mg Enhancement and Heat Treatment on Microstructures and Tensile Properties of Al2Ca-Added ADC12 Die Casting Alloys

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Journal of Materials Science & Technology 2016年第10期32卷 1043-1048页

作者： gil-Yong Yeom Hyun Kyu lim Shae K.Kim Soong-Keun Hyun Young-Ok yoon Korea Institute of Industrial Technology lncheon 406-840 South Korea Department of Materials Science and Engineering Inha University lncheon 402-751 South Korea

The effects of Mg enhancement and heat treatment on the microstructures and tensile properties of Al_2Ca-added ADC12 die casting alloys were investigated. 0.3% and 0.5% Mg in the form of a master alloy including a trace amount of Al_2Ca were added to conventional ADC12（383 and AlSi10Cu2Fe） alloy with an initial Mg-content of 0.3% to increase the Mg content to 0.6% and 0.8%, respectively. To avoid heat treatmentinduced surface blisters, shortened solution treatment for 15 min at 490 ℃ and artificial aging for 6 h at 150 ℃ was undertaken. The results show that a 10% improvement in the shape factor of eutectic Si particles was achieved for Al_2Ca-added ADC12 with 0.8% Mg compared to the conventional ADC12 in the as-aged condition. Al_2Ca-added ADC12 with 0.8% Mg exhibited a yield strength of 289 MPa, a tensile strength of 407 MPa, and an elongation of 4.22%.

关键词： Al2Ca ADC12 alloy Heat treatment Die casting Inclusion

Effect of Ca addition on the microstructure and mechanical properties of heat-treated Mg-6.0Zn-1.2Y-0.7Zr alloy

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Journal of Magnesium and Alloys 2021年第5期9卷 1636-1648页

作者： Young gil Jung Wonseok Yang Yong Joo Kim Shae.K.Kim Young Ok yoon Hyunkyu lim Do Hyang Kim Advanced Materials and Process R&D Department Korea Institute of Industrial Technology156Gaetbeol-roIncheon 21999Republic of Korea Department of Metallurgical Engineering Yonsei University50Yonsei-roSeoulSeodaemun-gu 03722Republic of Korea

In this study,the effects of Ca addition on the microstructure,thermal properties,and mechanical properties of a Mg-6.0Zn-1.2Y-0.7Zr(ZWK611)alloy at room temperature and 150℃ were *** an increase in the Ca content,the ignition resistance of the ZWK611 alloy improved and the grains became *** as-cast ZWK611 alloy consisted mainly of the dendriticα-Mg matrix and I-phase(Mg_(3)Zn_(6)Y)at the grain *** the other hand,theτ-(Ca_(2)Mg_(6)Zn_(3))and I-phases were formed in the Ca-added ZWK611 *** fraction of theτ-phase increased with an increase in the Ca *** the solid-solution treatment,these phases remained partially at the grain boundaries of the Ca-added ZWK611 alloys and an additional W-phase(Mg_(3)Zn_(3)Y)was *** phases remaining at the grain boundaries restricted the grain growth through the grain boundary pinning *** aging treatment resulted in the formation of MgZn'precipitates in theα-Mg matrix of the *** precipitates were more uniformly distributed in the Ca-added alloys than in the alloys without ***,the heat treatment-induced precipitation improved the tensile and creep properties of the T6-treated *** T6-treated ZWK611+0.7Ca alloy exhibited the best mechanical properties at room temperature and 150℃ among all the tested alloys.

关键词： Mg-Zn-Y alloys Heat-treatment Precipitate Mechanical properties Thermal analysis

Synthesis and electrochemical properties of dual doped spinels LiNi_xAl_yMn_(2-x-y)O_4 via facile novel chelated sol–gel method as possible cathode material for lithium rechargeable batteries

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Journal of Energy Chemistry 2017年第1期26卷 101-114页

作者： R.Thirunakaran gil Hwan Lew Won-Sub yoon CSIR-Central Electrochemical Research Institute Sungkyunkwan University Department of Energy Science

limnOand LiNiAlyMnO（x= 0.50;y = 0.05-0.50） powders have been synthesized via facile solgel method using Behenic acid as active cheiating *** synthesized samples are subjected to physical characterizations such as thermo gravimetric analysis（TG/DTA）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,field-emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM） and electrochemical studies viz.,galvanostatic cycling properties,electrochemical impedance spectroscopy（EIS） and differential capacity curves（dQ/dE）.Finger print XRD patterns of limnOand LiNiAlMnOfortify the high degree of crystallinity with better phase *** images of the undoped pristine spinel illustrate uniform spherical grains surface morphology with an average particle size of 0.5 μm while Ni doped particles depict the spherical grains growth（50nm） with ice-cube surface *** images of the spinel limnOshows the uniform spherical morphology with particle size of（100 nm） while low level of Al-doping spinel（LiNio.5Alo.05Mn1.45O4） displaying cloudy particles with agglomerated particles of（50nm）.The limnOsamples calcined at 850℃ deliver the discharge capacity of 130 mAh/g in the first cycle corresponds to 94%coiumbic efficiency with capacity fade of 1.5 mAh/g/cycle over the investigated 10 *** all four dopant compositions investigated,LiNiAlMnOdelivers the maximum discharge capacity of 126 mAh/g during the first cycle and shows the stable cycling performance with low capacity fade of 1 mAh/g/cycle（capacity retention of 92%） over the investigated 10 *** impedance studies of spinel limnOand LiNiAlMnOdepict the high and low real polarization of 1562 and 1100 Ω.

关键词： Multi-doping Sol–gel method Behenic acid Differential capacity Spinel cathode

A Steam-Plasma Igniter for Aluminum Powder Combustion

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Plasma Science and Technology 2015年第5期17卷 392-401页

作者： Sanghyup LEE Kwanyoung NOH Jihwan lim Woongsup yoon Mechanical Engineering Department of Yonsei University

High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high- melting-temperature oxides. A plasma torch characterized by an ultrahigh-temperature plasma plume fulfills such high-temperature ignition conditions. A new steam plasma igniter is designed and successfully validated by aluminum power ignition and combustion tests. The steam plasma rapidly stabilizes in both plasma and steam jet modes. Parametric investigation of the steam plasma jet is conducted in terms of arc strength. A high-speed camera and an oscilloscope method visualize the discharge characteristics, and optical emission spectroscopy measures the thermochemical properties of the plasma jet. The diatomic molecule OH fitting method, the Boltzmann plot method, and short exposure capturing with an intensified charge coupled device record the axial distributions of the rotational gas temperature, excitation temperature, and OH radical distribution, respectively. The excitation temperature at the nozzle tip is near 5500 K, and the gas temperature is 5400 K.

关键词： steam plasma igniter aluminum emission spectroscopy energetic metal fuels powder ignition and combustion optical

Thermo-physical Characteristics of Nickel-coated Aluminum Powder as a Function of Particle Size and Oxidant

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Chinese Journal of Mechanical Engineering 2016年第6期29卷 1244-1255页

作者： LEE Sanghyup NOH Kwanyoung lim Jihwan yoon Woongsup Advanced Energy and Propulsion Laboratory Department of Mechanical Engineering Yonsei University Missile System Integration / propulsion Center Hanwha Corp.

Aluminum particles 15-25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a high melting point, so ignition is difficult. To improve the ignitability of high-energy aluminum powder and to understand the reaction phenomenon as a function of particle size（15-25 μm, 74-105 μm, and 2.38 mm） and oxidizer（air, CO2, and argon）, the natural oxide films are chemically removed. The particles are then coated with nickel using an electro-less method. The degree of nickel deposition is confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, elemental analysis is also conducted by using X-ray diffraction. Thermogravimetric analysis/differential scanning calorimetry （TGA/DSC） enable comparisons between the uncoated and coated aluminum, and the reaction process are investigated through fine structural analysis of the particle surfaces and cross sections. There are little difference in reactivity as a function of oxidant type. However, a strong exothermic reaction in the smaller nickel-coated aluminum particles near the melting point of aluminum accelerates the reaction of the smaller particles. Explanation of the reactivity of the nickel-coated aluminum depending on the particle sizes is attempted.

关键词： nickel-coated aluminum TGA/DSC aluminum ignition combustion intermetallic reaction

Determination of efficient superfinishing conditions for mirror surface finishing of titanium

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Journal of Central South University 2012年第1期19卷 155-162页

作者： KIM Jin-seob lim Eun-seong JUNG yoon-gyo School of Mechatronics Changwon National UniversityChangwon 641-773Korea

To determine mirror surface finishing conditions and efficient and economical superfinishing conditions for pure titanium and titanium alloys, an abrasive film is used when superfinishing is performed under varying conditions. These conditions include the workpiece rotation speed, the oscillation speed, the contact pressure of the roller, the hardness of the roller, and the type of abrasive film. The superfinishing device is applied to polishing a thin and long cylindrical bar. A micro-finishing film and a lapping film were used as abrasive films. A1203 grains or SiC grains were used as abrasives. The surface roughness of a polished workpiece was measured using a stylus-type surface-roughness measuring instrument. As a result, the conditions to improve the polishing surface efficiently include high values for the workpiece rotation speed, oscillation speed and contact pressure. The roller hardness has no effect on the efficient polishing conditions. The mirror finish of a surface can be created using lapping film of 3 μm with Al2O3 grains after polishing to a steady surface roughness under the efficient polishing conditions.

关键词： superfinishing mirror surface finishing abrasive film surface roughness titanium optimal polishing time

Land Response to Atmosphere at Different Resolutions in the Common Land Model over East Asia

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Advances in Atmospheric Sciences 2016年第3期33卷 391-408页

作者： Daeun KIM yoon-Jin lim Minseok KANG Minha CHO Department of Civil and Environmental Engineering Hanyang University222 Wangsimni-roSeongdong-guSeoul 04763Republic of Korea Applied Meteorological Research Division National Institute of Meteorological ResearchKorean Meteorological Administration61 Yeouidaebang-ro16-gilDongjak-guSeoul 63568Republic of Korea National Center for AgroMeteorology Bid.#36(RM.#109)Seoul National University1 Gwanak-roGwanak-guSeoul 08826Republic of Korea Department of Water Resources Graduate School of Water ResourcesSungkyunkwan University2066 Seobu-roJangan-guSuwonGyeonggi-do 16419Republic of Korea

Towards a better understanding of hydrological interactions between the land surface and atmosphere, land surface mod- els are routinely used to simulate hydro-meteorological fluxes. However, there is a lack of observations available for model forcing, to estimate the hydro-meteorological fluxes in East Asia. In this study, Common Land Model （CLM） was used in offline-mode during the summer monsoon period of 2006 in East Asia, with different forcings from Asiaflux, Korea Land Data Assimilation System （KLDAS）, and Global Land Data Assimilation System （GLDAS）, at point and regional scales, separately. The CLM results were compared with observations from Asiaflux sites. The estimated net radiation showed good agreement, with r = 0.99 for the point scale and 0.85 for the regional scale. The estimated sensible and latent heat fluxes using Asiaflux and KLDAS data indicated reasonable agreement, with r = 0.70. The estimated soil moisture and soil temperature showed similar patterns to observations, although the estimated water fluxes using KLDAS showed larger discrepancies than those of Asiaflux because of scale mismatch. The spatial distribution of hydro-meteorological fluxes according to KLDAS for East Asia were compared to the CLM results with GLDAS, and the GLDAS provided online. The spatial distributions of CLM with KLDAS were analogous to CLM with GLDAS, and the standalone GLDAS data. The results indicate that KLDAS is a good potential source of high spatial resolution forcing data. Therefore, the KLDAS is a promising alternative product, capable of compensating for the lack of observations and low resolution grid data for East Asia.

关键词： Common Land Model Korea Land Data Assimilation System Global Land Data Assimilation System Asi-aflux hydro-meteorological fluxes

Loose-fit graphitic encapsulation of silicon nanowire for one-dimensional Si anode design

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Journal of Materials Science & Technology 2017年第10期33卷 1120-1127页

作者： Seh-yoon lim Sudong Chae Su-Ho Jung Yuhwan Hyeon Wonseok Jang Won-Sub yoon Jae-Young Choi Dongmok Whang School of Advanced Materials Science and Engineering SKKU Advanced Institute of Nanotechnology Sungkyunkwan University Suwon 440-746 South Korea Department of Energy Sdence Sungkyunkwan University Suwon 440-746 South Korea

Silicon nanowires（SiNWs） encapsulated with graphene-like carbon sheath（GS） having a void space in between（SiNW@V@GS） are demonstrated for the improved electrochemical performance of Si anode in lithium ion battery. The Si NW@V@GS structure was synthesized by a scalable fabrication method including four successive reactions： metal-catalyzed CVD growth of Si NWs, controlled thermal oxidation, and deposition of the graphitic layer, to form Si NW@SiO2@GS and additional chemical etching of sacrificial SiO2 layer between Si NWs and carbon sheath. During the synthetic process, the thickness of the void spacing was controlled by adjusting the oxidation-dependent process. The well-controlled void space and crystalline graphitic carbon sheath of the SiNW@V@GS structure enable good reversible capacity of1444 m Ahg^（-1） and cycling stability of 85% over 150 cycles.

关键词： Lithium ion battery Silicon nanowire Graphene Void spacing Anode

Nanoconfinement effect of nanoporous carbon electrodes for ionic liquid-based aluminum metal anode

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Journal of Energy Chemistry 2022年第11期31卷 121-127,I0005页

作者： Juhee yoon Seongbak Moon Son Ha Hyung-Kyu lim Hyoung-Joon Jin Young Soo Yun Program in Environmental and Polymer Engineering Inha UniversityIncheon 22212South Korea Department of Polymer Science and Engineering Inha UniversityIncheon 22212South Korea KU-KIST Graduate School of Converging Science and Technology Korea UniversitySeoul 02841South Korea Division of Chemical Engineering and Bioengineering Kangwon National UniversityGangwon-do 24341South Korea Department of Integrative Energy Engineering Korea UniversitySeoul 02841South Korea

Rechargeable aluminum batteries(RABs),which use earth-abundant and high-volumetric-capacity metal anodes(8040 m Ah cm-3),have great potential as next-generation power sources because they use cheaper resources to deliver higher energies,compared to current lithium ion ***,the mechanism of charge delivery in the newly developed,ionic liquid-based electrolytic system for RABs differs from that in conventional organic ***,targeted research efforts are required to address the large overpotentials and cycling decay encountered in the ionic liquid-based electrolytic *** this study,a nanoporous carbon(NPC)electrode with well-developed nanopores is used to develop a high-performance aluminum *** negatively charged nanopores can provide quenched dynamics of electrolyte molecules in the aluminum deposition process,resulting in an increased collision *** fast chemical equilibrium of anionic species induced by the facilitated anionic collisions leads to more favorable reduction reactions that form aluminum *** nanoconfinement effect causes separated nucleation and growth of aluminum nanoparticles in the multiple confined nanopores,leading to higher coulombic efficiencies and more stable cycling performance compared with macroporous carbon black and 2D stainless steel electrodes.

关键词： Nanoconfinement effect Nanoporous carbon Ionic liquid electrolyte Metal anode Aluminum batteries Multivalent batteries