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Formation Mechanism of Chunky Graphite and Its Preventive Measures

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Journal of Materials Science & Technology 2008年第3期24卷 289-295页

作者： Hideo Nakae Sanghoon jung ho-Chul Shin Department of Materials Science and Engineering Waseda University National Institute of AIST Corporate Res.and Dev.Div. Hyundai.Kia Motors

The formation mechanism of chunky graphite has been reviewed and studied. The study consisted of a unidirectional solidification method, a small droplet method and a furnace cooling method. Four kinds of iron samples were prepared, namely, the pure Fe-C, Fe-C-S, Fe-C-Ce and Fe-C-Si-Ce alloys, and three kinds of nickel samples, namely the Ni-C, Ni-C-S and Ni-C-Mg alloys. The results of the unidirectional solidification of the Ni-C alloys showed that spheroidal graphite is not observed in the continuous solidified region, in which only flake-like graphite is observed, while spheroidal graphite is usually observed in the quenched liquid region. The existence of spheroidal graphite in the solidified phase is recognized only in the discontinuous growth mode of the Ni-C-Mg alloy solidified at 150 mm/h. This means that the spheroidal graphite is directly crystallized from the melt and entrapped by the flake-like chunky graphite that is formed by the continuous growth mode. In the small droplet method, a small piece of the Fe-C or Fe-C-Ce sample was melted on a pure graphite plate then cooled at a different cooling rate in a He-3%H2 atmosphere. The graphite in the Fe-C-Ce alloy is usually spherical. Nevertheless, the graphite morphology of the final solidified area changed from spherical to chunky and chunky to ledeburite with an increase in the cooling rate. This means that the chunky graphite is formed in the residual liquid region by the solidification into Fe-graphite system. The sample was cooled in a furnace, and the graphite morphology changes from spherical to chunky and chunky to ledeburite with the decrease in the Si content. These phenomena can be confirmed by the cooling curves of these samples.

关键词： Chunky graphite Spheroidal graphite Solidification Cooling curve

Adhesion and Suction Functions of the Tip Region of a Nectar-drinking Butterfly Proboscis

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Journal of Bionic Engineering 2017年第4期14卷 600-606页

作者： seung Chul Lee Jun ho Kim Sang Joon Lee Department of Mechanical Engineering Pohang University of Science and Technology Pohang 37673 Gyeongbuk Republic of Korea Center for Biofluid and Biomimic Research Pohang University of Science and Technology Pohang 37673 Gyeongbuk Republic of Korea

In this study, we investigated the dynamic functions of the tip region of the butterfly proboscis through which liquid is sucked during liquid feeding. The microstructures and flow patterns in the tip region of the proboscis were in vivo analyzed. The tip region can be divided into two functional sections： namely adhesion and suction sections. The liquid adheres to the adhesion section during liquid suction. Although the tip region has numerous slits connected to food canal of the proboscis, liquid is mainly sucked through the suction section, which section is submerged in the fluid pulled by the adhesion section and then successfully imbibes liquid. To check the dynamic functions of the tip region, we fabricated a suction tip model having adhesion and suction parts. The in vitro model experiments show that the hydrophilicity of the adhesion part and the existence of the suction inlet improve the liquid uptake driven by a suction pump. This study may provide insights for the biomimetic design of nectar-feeding butterflies.

关键词： butterfly proboscis nectar-feeding strategy suction

Spindle-like FeySs/N-doped carbon nanohybrids for high-performance sodium ion battery anodes

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Nano Research 2019年第3期12卷 695-700页

作者： Aihua Jin Mi-Ju Kim Kug-seung Lee seung-ho Yu Yung-Eun Sung Center for Nanoparticle Research Institute for Basic Science (IBS) Seoul 08826 Republic of Korea School cf Chemical and Biological Engineering Seoul National University Seoul 08826 Republic cf Korea Beamline Department Pohang Accelerator Laboratory (PAL) Pohang 790-784 Republic of Korea Department of Chemistry and Chemical Biology Cornell University Ithaca New York 14853 USA

Iron sulfides have bee n con sidered as one of the most promising can didates for sodium ion battery anode materials due to their high theoretical capacity and low cost. I n this work, spin dle-like Fe7S8 with n itroge rvdoped carb on (FeiS/N-C) nano hybrids are successfully syn thesized via a solvothermal method by sulfidation iron-based metal organic framework (FeMOF). As sodium ion battery an odes, FeySs/N-C nano hybrids exhibit high reversible capacity of 450.8 mAh g-1 at 200 mA·g^-1, and 406.7 mAh·g^-1 at 500 mA·g^-1 even after 500 cycles. They also show excellent rate properties and delivering the capacity of 327.8 mAh·g^-1 at a very high current density of 3.2 A·g^-1. These outstanding electrochemical performa nces can be attributed to the unique structure of Fe7S8/ N-C nan ohybrids. The nano scale dime nsion in their size can be ben eficial for facile ion and electro n tran sports. Furthermore, the stable n itroge n doped carb on frameworks can also improve electrical conductivity and relieve the problems related to volume expansion. X-ray absorption spectroscopy and X-ray photoelectron spectroscopy analyses have been performed to study reactions occurred in spindle-like FeySs/N-C nanohybrid electrode at both bulk and surface.

关键词： sodium ion batteries iron sulfides metal organic frameworks X-ray absorption spectroscopy X-ray photoelectron spectroscopy

Environmental friendly synthesis of hierarchical mesoporous platinum nanoparticles templated by fucoidan biopolymer for enhanced hydrogen evolution reaction

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Journal of Materials Science & Technology 2020年第11期42卷 185-190页

作者： seung Man Lim Kyunglee Kang hongje Jang jung Tae Park Department of Chemical Engineering Konkuk University120 Neungdong-roGwangjin-guSeoul 05029Republic of Korea Department of Chemistry Kwangwoon University20 Cwangwoon-roNowon-guSeoul 01897Republic of Korea

Researching novel hydrogen evolution reaction(HER)catalysts with enhanced electrocatalytic activity,excellent stability,and cost-efficiency is of great significance for the large-scale hydrogen production from industrial electrolysis *** report the preparation of hierarchical mesoporous-Pt nanoparticles(HM-Pt NPs)with coral-like rough surface morphologies using environmental friendly and biocompatible fucoidan(Fu)biopolymer as a surface engineering compound and its application to electrocatalysts for *** designed HM-Pt NPs yields better mass activity of electrocatalysts compared to a commercial Pt/***-Pt NPs showed an overpotential of 33 mV at 10 mA cm-2 for the HER in 0.5 MH2SO4,which was highly comparable to that of the commercial Pt/C catalysts(29 mV).however,the amount of HM-Pt NPs loaded in glassy carbon electrode(0.033 mg mL-1)was approximately 20 times lower than that of the commercial Pt/C(0.64 mg *** HM-Pt NPs also maintained high catalytic stability with a consistent HER current density after 1000 continuous *** excellent HER performance is attributed to the improved electrochemical surface area,highly porous structure,and good surface wettability of the HM-Pt NPs,which results in enhanced electrocatalytic activity,decreased resistance at the electrode/electrolyte interface,and facile penetration of the electrolytes inside the electrode.

关键词： Mesoporous Fucoidan Biopolymer Low Pt content Hydrogen evolution reaction

Application of Thermodynamic Database to Corrosion of ZrO_(2) Containing Submerged Entry Nozzle in Steel Continuous Casting Process

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China's Refractories 2024年第2期33卷 10-15页

作者： In-ho jung Department of Materials Science and Engineering Seoul National UniversitySeoul 08826South Korea Research Institute of Advanced Materials Seoul National UniversitySeoul 08826South Korea

The CALPHAD thermodynamic databases are very useful to analyze the complex chemical reactions happening in high temperature material *** FactSage thermodynamic database can be used to calculate complex phase diagrams and equilibrium phases involving refractories in industrial *** this study,the FactSage thermodynamic database relevant to ZrO_(2)-based refractories was reviewed and the application of the database to understanding the corrosion of continuous casting nozzle refractories in steelmaking was presented.

关键词： thermodynamic database ZrO_(2)containing submerged entry nozzle continous casting

Radiologic evaluation of nonalcoholic fatty liver disease

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World Journal of Gastroenterology 2014年第23期20卷 7392-7402页

作者： seung Soo Lee Seong ho Park Department of Radiology and Research Institute of Radiology University of Ulsan College of MedicineAsan Medical CenterSeoul 138-736South Korea

Nonalcoholic fatty liver disease(NAFLD)is a frequent cause of chronic liver diseases,ranging from simple steatosis to nonalcoholic steatohepatitis(NASH)-related liver *** liver biopsy is still the gold standard for the diagnosis of NAFLD,especially for the diagnosis of NASH,imaging methods have been increasingly accepted as noninvasive alternatives to liver *** is a well-established and costeffective imaging technique for the diagnosis of hepatic steatosis,especially for screening a large population at risk of *** has a reasonable accuracy in detecting moderate-to-severe hepatic steatosis although it is less accurate for detecting mild hepatic steatosis,operator-dependent,and rather *** tomography is not appropriate for general population assessment of hepatic steatosis given its inaccuracy in detecting mild hepatic steatosis and potential radiation ***,computed tomography may be effective in specific clinical situations,such as evaluation of donor candidates for hepatic *** resonance spectroscopy and magnetic resonance imaging are now regarded as the most accurate practical methods of measuring liver fat in clinical practice,especially for longitudinal followup of patients with *** elastography and magnetic resonance elastography are increasingly used to evaluate the degree of liver fibrosis in patients with NAFLD and to differentiate NASH from simple *** article will review current imaging methods used to evaluate hepatic steatosis,including the diagnostic accuracy,limitations,and practical applicability of each *** will also briefly describe the potential role of elastography techniques in the evaluation of patients with NAFLD.

关键词： Nonalcoholic fatty liver disease Nonalcoholic steatohepatitis Liver steatosis Magnetic resonance spectroscopy Magnetic resonance imaging Ultrasonography Computed tomography Elastography

Regulating lithium nucleation and growth by zinc modified current collectors

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Nano Research 2020年第1期13卷 45-51页

作者： Na Zhang seung-ho Yu Héctor D.Abruna Baker Laboratory Department of Chemistry and Chemical BiologyCornell UniversityIthacaNew York14853USA Department of Chemical and Biological Engineering Korea University145 Anam-roSeongbuk-guSeoul02841Republic of Korea

Lithium metal is commonly regarded as the“holy Grail”anode material for high energy density rechargeable ***,the uncontrollable growth of Li dendrites has posed safety concerns and thus greatly hindered its large-scale *** we have modified the surface of a commercial anode current collector,Cu foil,with a thin layer of Zn by a facile electroplating method,in order to regulate the Li nucleation and the following growth *** of the formation of a solid solution buffer layer and Li-Zn alloy phases,the Li nucleation overpotential was dramatically reduced,realizing a uniform Li nucleation and a smooth Li plating *** a result,significantly improved long-term cycling performance with a high Coulombic efficiency was achieved by the lithiophilic Zn coated Cu foil as a current *** cells of Li-LiFePO4 and Li-S using the Li deposited on the Zn modified Cu as the anode,showed increased capacity with low voltage hysteresis and greatly enhanced cycling stability,ascribed to the uniform Li deposition and formation of a stable SEI *** work demonstrates the feasibility of employing lithiophilic modified Cu foils as Li metal current collectors for practical applications.

关键词： lithium metal anode lithium dendrite current collector zinc layer

Properties of ZnO Thin Films Grown on Si (100) Substrates by Pulsed Laser Deposition

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Journal of Materials Science & Technology 2010年第11期26卷 973-976页

作者： Young Rae Jang Keon-ho Yoo seung Min Park Department of Physics Kyung Hee University Department of Chemistry Kyung Hee University

ZnO thin films were grown on Si （100） substrates by pulsed laser deposition using a ZnO *** substrate temperature was varied in the range of room temperature to 800 ℃,and the oxygen partial pressure of 0.1333 Pa （1 m Torr） to 1333 Pa （10 Torr）.The properties of the resulting films were investigated by photoluminescence （PL）,grazing incidence X-ray diffraction （GIXRD）,X-ray photoelectron spectroscopy （XPS）,and field emission scanning electron microscopy （FESEM）.Based on the ultraviolet （UV,～380 nm） to visible emission ratio in the PL spectrum,the optimum growth conditions were determined to be 600 ℃ and 133.3 Pa （1 Torr）,*** oxygen 1s peak in the XPS spectrum was decomposed into two *** peak at lower binding energy increased in intensity with the oxygen partial pressure from 0.1333 Pa （1 m Torr） to 133.3 Pa （1 Torr） while the other peak *** GIXRD curve at the optimum condition showed strong two peaks （002） and （103）.A strong correlation between the （103） peak intensity and the UV emission intensity was found.

关键词： ZnO Pulsed laser deposition Photoluminescence

Comparative Study of Visual and Instrumental Analyses of Shade Selection

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Journal of Wuhan University of Technology(Materials Science) 2010年第1期25卷 62-67页

作者： Jee-Ha Choi Ju-Mi Park seung-Geun Ahn Kwang-Yeob Song Min-ho Lee Jae-Youn jung Xinyu Wang Department of Prosthodontics and Institute of Oral Bioscience School of Dentistry Chonbuk National University Jeonju Republic of Korea Department of Dental Biomaterials and Institute of Oral Bioscience School of Dentistry Chonbuk National University Jeonju Republic of Korea Division of Mechanical & Aerospace System Engineering and RCIT Chonbuk National University Jeonju Republic of Korea Biomedical Materials and Engineering Research Center Wuhan University of Technology Wuhan 430070 China

The difference between visual and instrumental analyses of a shade selection on natural teeth was investigated. With visual analysis, five prosthodontist examined the middle third of the unrestored maxillary right central incisor of a patient using VITAPEN classical and Vita Toothguide 3D-MASTER tooth shade guide. In instrumental analysis, one prosthodontist examined the same teeth using a spectrophotometer （ShadepilotTM, Degudent, Hanau-Wolfgang, Germany, software 2.40）. Overall, instrumental analysis is more accurate and reproducible than a visual assessment. however, the difference is clinically acceptable.

关键词： shade selection visual analysis instrumental analysis spectrophotometer