• 한국재료학회지
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• 제10권11호
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• pp.743-748
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• 2000

리튬이온이차전지의 부극재로 사용되는 탄소재인 비정질 탄소(needle cokes)에 $B_2O_3$를 첨가하여 공기중의 질소 분위기와 Ar 분위기에서 고온으로 흑연화 열처리를 하였을 때의 표면미세구조의 변화와 제 2상의 분포를 투과전자현미경으로 분석하였다. 또한 전지용량, 전지효율과 같은 전지성능이 탄소재의 표면미세구조와 관련되어 있음을 고찰하였다.

• Metals and materials international
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• 제24권6호
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• pp.1221-1231
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• 2018

The effect of strain aging on tensile behavior and properties of API X60, X70, and X80 pipeline steels was investigated in this study. The API X60, X70, and X80 pipeline steels were fabricated by varying alloying elements and thermomechanical processing conditions. Although all the steels exhibited complex microstructure consisting of polygonal ferrite (PF), acicular ferrite, granular bainite (GB), bainitic ferrite (BF), and secondary phases, they had different fractions of microstructures depending on the alloying elements and thermomechanical processing conditions. The tensile test results revealed that yielding behavior steadily changed from continuous-type to discontinuous-type as aging temperature increases after 1% pre-strain. After pre-strain and thermal aging treatment in all the steels, the yield and tensile strengths, and yield ratio were increased, while the uniform elongation and work hardening exponent were decreased. In the case of the X80 steel, particularly, the decrease in uniform elongation was relatively small due to many mobile dislocations in PF, and the increase in yield ratio was the lowest because a large amount of harder microstructures such as GB, BF, and coarse secondary phases effectively enhanced work hardening.

• Corrosion Science and Technology
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• 제21권4호
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• pp.250-257
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• 2022

Transition metal sulfide materials have emerged as a new anode material for Li secondary batteries owing to their high capacity and rate capability facilitated by fast Li-ion transport through the layered structure. Among these materials, niobium disulfide (NbS₂) has attracted much attention with its high electrical conductivity and high theoretical capacity (683 mAh g^-1). In this study, we propose a facile synthesis of Fe_xNbS₂/C composite via simple ball milling and heat treatment. The starting materials of FeS and Nb were reacted in the first milling step and transformed into an Fe-Nb-S composite. In the second milling step, activated carbon was incorporated and the sulfide was crystallized into Fe_xNbS₂ by heat treatment. The prepared materials were characterized by X-ray diffraction, electron spectroscopies, and X-ray photoelectron spectroscopy. The electrochemical test results reveal that the synthesized Fe_xNbS₂/C composite electrode demonstrates a high reversible capacity of more than 600 mAh g^-1, stable cycling stability, and excellent rate performance for Li-ion battery anodes.

• 한국결정성장학회지
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• 제34권2호
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• pp.66-72
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• 2024

본 연구에서는 탈황석고(DG)에 이산화탄소를 반응시켜 제조한 탄산화물(CCMs)을 콘크리트 2차 제품의 시멘트 대체재로서 적용 가능성을 평가하고 최적 배합비 도출을 위한 탄산화물 혼입 모르타르 및 콘크리트 시편의 기초 물성 측정을 실시하였다. 탄산화물은 다량의 CaO 및 SO₃로 이루어져 있으며, 주요 결정상은 CaSO₄·2H₂O, Ca(OH)₂, CaCO₃ 및 CaSO₄로 나타났다. 또한 입도 분석 및 폐기물공정시험기준에 따른 중금속 측정 결과 콘크리트 2차 제품의 시멘트 대체재로서 탄산화물의 적용 가능성이 확인되었다. 모르타르 및 콘크리트 공시체 제작 후 강도 거동 측정 결과 탄산화물 혼입량이 증가할수록 강도가 감소하는 경향을 나타내었으나 최적 배합인 치환 비율 10 wt.% 배합까지 대상 제품인 인터로킹 블록 및 옹벽 블록의 기준에서 요구하는 모든 조건을 만족하였다. 따라서 콘크리트 2차 제품의 시멘트 대체재로서 적용 가능성이 확인되었다.

• 한국환경교육학회지:환경교육
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• 제20권4호
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• pp.65-83
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• 2007

The purpose of this study was to survey science teachers, perception and attitudes on disposal of school laboratory waste water and materials. To fulfill this aim, a questionnaire was administered to 244 secondary school science teachers. The result of this study revealed that there was no large disparity in the degree of understanding of laboratory waste disposal and the laboratory waste water treatment, and in secondary science teachers' perception and practicing attitude on the environment. While science teachers had deep understanding of laboratory waste disposal and its influence on environmental pollution, they expressed less positive attitude toward the actual disposal of waste materials and waste water, and participation in teacher training. Therefore, it is necessary to provide standards of systematized disposal methods and proper disposal facilities in middle and high school laboratories, as well as to investigate teachers' needs before providing teacher training program.

• ETRI Journal
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• 제25권5호
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• pp.412-417
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• 2003

Using a galvanostatic charge/discharge cycler and cyclic voltammetry, we investigated for the first time the electrochemical properties of iron-containing minerals, such as chalcophanite, diadochite, schwertmannite, laihuite, and tinticite, as electrode materials for lithium secondary batteries. Lithium insertion into the mineral diadochite showed a first discharge capacity of about 126 mAh/g at an average voltage of 3.0 V vs. $Li/Li^+$, accompanied by a reversible capacity of 110 mAh/g at the 60th cycle. When the cutoff potential was down to 1.25 V, the iron was further reduced, giving rise to a new plateau at 1.3 V. Although the others showed discharge plateaus at low potentials of less than 1.6 V, these results give an important clue for the development of new electrode materials.

• 상하수도학회지
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• 제13권2호
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• pp.82-88
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• 1999

This study was to evaluate disinfection efficiency of chlorine and chloramine as secondary disinfectants in the distribution systems. Indicator organism, HPC in the suspended and attached were measured for copper, galvanized steel, PVC, and carbon steel pipes. For suspended microorganism, the PVC pipe was markedly dense among the assessed pipe materials. The attached microorganism was markedly equivalent roughness of pipe materials. In copper and galvanized pipes, chloramine was more effective that free chlorine to disinfect suspended microorganism in the contact time of 2 hours. The contact time for the 99% inactivation of suspended microorganism by chloramine was longer than that of free chlorine. Regardless of pipe materials, chloramine was effective on both disinfection efficiency and 99% inactivation time for attached microorganism. In conclusion, chloramine which is good disinfectant for long contact time was recommended as secondary disinfectant in distribution system.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.555-556
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• 2006

The study examines hardness pattern of SH737-2Cu-.9C samples transient liquid phase sintered at different temperatures viz. $1120^{\circ}C$, $1180^{\circ}C$ and $1250^{\circ}C$, heat treated by various methods and then tempered at different temperatures. Sintered samples were characterized for density and densification parameter, and austenitized at $900^{\circ}C$, subsequently cooled by four different methods viz. annealing, normalizing, oil and brine quenching. Hardness pattern was found minimum for air cooled and maximum for brine quenched, and samples sintered at $1250^{\circ}C$ had relatively higher hardness. The O.Q and B.Q samples were then tempered at $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$ and $700^{\circ}C$. Hardness pattern typically showed secondary hardness taking place, with maximum around $600^{\circ}C$.

• Design & Manufacturing
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• 제17권2호
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• pp.33-41
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• 2023

Metal raw materials and chemical additives, which are raw materials for secondary batteries, are pulverized by the high-speed rotation of the Grinding Disc of the Classifier Separator Mill (CSM). Grinding discs are required to withstand abrasion, corrosion, high-speed rotational force and impact. In order to analyze the stability of domestic and foreign grinding discs, quality tests including surface roughness, surface lubrication, surface state measurement, and surface 3D shape measurement were analyzed. When producing developed products, it shows that excellent products can be produced.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.11-25
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• 2024

Lithium-ion batteries (LIBs) have attracted great attention as the common power source in energy storage fields of large-scale applications such as electrical vehicles (EVs), industries, power plants, and grid-scale energy storage systems (ESSs). Insertion, alloying, and conversion reactions are the main electrochemical energy storage mechanisms in LIBs, which determine their electrochemical properties and performances. The electrochemical reaction mechanisms are determined by several factors including crystal structure, components, and composition of electrode materials. This article reviews a new strategy to compensate for the intrinsic shortcomings of each reaction mechanism by introducing the material systems to form a single compound with different types of reaction mechanisms and to allow the simultaneous hybrid electrochemical reaction of two different mechanisms in a single solid solution phase.