• 한국재료학회:학술대회논문집
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• 한국재료학회 1993년도 춘계학술발표회
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• pp.99-100
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• 1993

Calorimetric (D.S.C) studies were carried out on the nylon 4,6 single crystals grown from 1,4-butanediol solution at various crystallisation temperatures, based on the assessment of the lamellar thickness by small angle x-ray scattering. Samples were annealed mainly ot get rid of residual solvents inside the crystals. The effect of annealing on the crystal perfection is inferred from the measured thermal properties of the crystals. Accordig to the scanning rates less than 80 K/min., D. S C. melting peaks indicate that changes in the internal morphology of nylon 4,6 crystals preapred at different crystallisation temeratures yield a thermodynamic melting temperature. Tm, of 319 $^{\circ}C$, for the infinitely extended crystal thickness (1/ι). The obtained heat of fusion value for the inginite crystal thickness, Ho, was 270 J/g from the plot of measured feat of fusion ($\Delta$Hm) vs. reciprocal crystal thickness (1/ι). based on these values, the fold surface energy, $\delta$e. of 65.4 erg/$\textrm{cm}^2$ was obtained from Hoffman-Waeeks equation. The thermodynamic melting temperature and heat of fusion of the infinite crystal thickness for the solution grow nylon 4,6 single crystals are found to be higher than of the reported corresponding solution grown nylon 6,6 single crystals. pbtained crystallinity from D. S. C measurements ranges from 40 to 50 %, which is close to the reported yalue for the nylon 6,6 single ctystals but lower than we expected.

• 한국재료학회지
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• 제31권8호
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• pp.445-449
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• 2021

Zintl compound Mg₃Sb₂ is a promising candidate for efficient thermoelectric material due to its small band gap energy and characteristic electron-crystal phonon-glass behavior. Furthermore, this compound enables fine tuning of carrier concentration via chemical doping for optimizing thermoelectric performance. In this study, nominal compositions of Mg_3.8Sb_2-xTe_x (0 ≤ x ≤ 0.03) are synthesized through controlled melting and subsequent vacuum hot pressing method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are carried out to investigate phase development and surface morphology during the process. It should be noted that 16 at. % of excessive Mg must be added to the system to compensate for the loss of Mg during melting process. Herein, thermoelectric properties such as Seebeck coefficient, electrical conductivity, and thermal conductivity are evaluated from low to high temperature regimes. The results show that Te substitution at Sb sites effectively tunes the majority carriers from holes to electrons, resulting in a transition from p to n-type. At 873 K, a peak ZT value of 0.27 is found for the specimen Mg_3.8Sb_1.99Te_0.01, indicating an improved ZT value over the intrinsic value.

• 한국분말재료학회지
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• 제28권4호
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• pp.301-309
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• 2021

In this study, an AISI 316 L alloy was manufactured using a selective laser melting (SLM) process. The tensile and impact toughness properties of the SLM AISI 316 L alloy were examined. In addition, stress relieving heat treatment (650℃ / 2 h) was performed on the as-built SLM alloy to investigate the effects of heat treatment on the mechanical properties. In the as-built SLM AISI 316 L alloy, cellular dendrite and molten pool structures were observed. Although the molten pool did not disappear following heat treatment, EBSD KAM analytical results confirmed that the fractions of the low- and high-angle boundaries decreased and increased, respectively. As the heat treatment was performed, the yield strength decreased, but the tensile strength and elongation increased only slightly. Impact toughness results revealed that the impact energy increased by 33.5% when heat treatment was applied. The deformation behavior of the SLM AISI 316 L alloy was also examined in relation to the microstructure through analyses of the tensile and impact fracture surfaces.

• 한국재료학회지
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• 제32권6호
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• pp.287-292
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• 2022

Magnesium-antimonide is a well-known zintl phase thermoelectric material with low band gap energy, earth-abundance and characteristic electron-crystal phonon-glass properties. The nominal composition Mg_3.8-xZn_xSb₂ (0.00 ≤ x ≤ 0.02) was synthesized by controlled melting and subsequent vacuum hot pressing method. To investigate phase development and surface morphology during the process, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out. It should be noted that an additional 16 at. % Mg must be added to the system to compensate for Mg loss during the melting process. This study evaluated the thermoelectric properties of the material in terms of Seebeck coefficient, electrical conductivity and thermal conductivity from the low to high temperature regime. The results demonstrated that substituting Zn at Mg sites increased electrical conductivity without significantly affecting the Seebeck coefficient. The maximal dimensionless figure of merit achieved was 0.30 for x = 0.01 at 855 K which is 30% greater than the intrinsic value. Electronic flow properties were also evaluated and discussed to explain the carrier transport mechanism involved in the thermoelectric properties of this alloy system.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.489-494
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• 1997

A comparative transient analyses were performed for oxide and nitride cores or a large (3000 MWt), pool-type, liquid-metal-cooled reactor (LMR). The study was focused on three representative accident initiators with failure to scram : the unprotected loss-of-flow (ULOF), the unprotected transient overpower (UTOP), and the unprotected fast transient overpower (UFTOP). The margins to fuel melting and sodium boiling have been evaluated for these representative transients. The results show that there is an increase in safety margin with nitride core which maintains the physical dimensions of the oxide core.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2003년도 춘계 학술발표회 논문집
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• pp.533-538
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• 2003

폐기물이란 쓰레기ㆍ연소재ㆍ오니ㆍ폐유ㆍ폐산ㆍ폐알칼리 등 사람의 생활이나 사업활동에 필요 없게 된 물질을 말하는 것으로, 쓰레기와는 엄밀한 의미로는 구분되지만 일반적으로는 버리는 것은 모두 폐기물이라고 볼 수 있다. 폐기물은 발생 주체에 따라 생활폐기물과 사업장폐기물로 구분되는데, 사업장폐기물은 사업장에서 발생되는 폐기물로 구성물질은 업종과 생산공정에 따라 다양하다.(중략)

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1999년도 춘계 학술발표회 논문집
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• pp.55-61
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• 1999

최근 국내외적으로 지구온난화, 산성비, 오존층파괴 등의 환경문제가 심각하게 대두되기 시작하면서 화석연료 사용에 대한 규제가 점차적으로 강화되고 있다. 이와같은 상황에서 기존의 미분탄 화력발전시스템에 비해서 NOx, SOx, $CO_2$, 분진 등의 대기오염물질을 현저히 줄일 수 있으며 발전효율도 높아서 석탄 사용에 따른 지구의 환경오염 저감과 에너지의 효율적인 이용 측면에서 석탄가스화 복합발전 시스템은 청정석탄 이용기술로 크게 관심을 모으고 있어서 국내외적으로 관련연구가 활발히 진행중이다.(중략)

• 한국해양환경ㆍ에너지학회지
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• 제13권2호
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• pp.75-82
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• 2010

FRP 선박은 제작이 쉽고 저렴한 건조비용으로 소형 선박을 중심으로 국내에 보급되었지만, 수명이 다한 노후 FRP 선박이 하천이나 어항 내에 방치되어 운항안전과 해양환경보전에 위협을 주는 등 사회문제로 대두대고 있다. 이를 개선하기 위하여 폐 FRP 선박 처리 기술과 용융처리시스템이 개발되었으며, 현지 적용을 위해 폐 FRP선박 처리 단계에 따른 전처리 지역 및 용융처리시스템 입지 방안이 필요하게 되었다. 폐 FRP선박 용융처리시스템 입지 장소는 기술적, 경제적, 환경적으로 적정해야 하므로 종합적인 차원의 평가가 요구되어 적지 선정에 어려움이 있다. 본 연구에서는 폐 FRP 용융처리시스템의 최적 입지 선정을 위해 입지경제적 요인, 생활환경 요인, 기반인프라 요인의 상위 요인과 각 상위 요인의 세부요인을 도출하여 폐 FRP선박 관련자를 대상으로 설문을 수행하였다 또한, Fuzzy AHP, 극한확률 이론을 이용하여 평가요인 간의 중요 가중치, 연관 가중치를 계산하고 후보지로 선정한 목포시, 강진군, 고흥군, 여수시에 대한 평가 결과를 검토 하였다.

• Nuclear Engineering and Technology
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• 제50권7호
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• pp.1184-1189
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• 2018

Pyroprocessing uses various molten salts during electrochemical unit processes. Reaction products after the electrochemical processes must contain a significant amount of residual salts to be separated. Vacuum distillation is a common method to separate the residual salts; however, its high operation temperature may cause side reactions. In this study, a simple rotation technique using centrifugal force was suggested to separate the residual salts from the reaction products at relatively low temperature compared to the distillation technique. When a reaction product container with porous wall rotates inside a vessel heated above the melting point of the residual salt, the residual salt in the liquid phase is separated through centrifugal force. It was shown that the $LiNO_3-Al_2O_3$ mixture can be separated by this technique to leave solid $Al_2O_3$ inside the container, with a separation efficiency of 99.4%.

• Journal of Welding and Joining
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• 제32권6호
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• pp.56-63
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• 2014

To develop and understand dissimilar metals joining of Stainless steel and Copper, ultra-high speed laser lap welding was studied using single mode fiber laser in this study. SUS304 and Cu have large differences in materials properties, and Cu and Fe have no intermetallic compounds by typical binary phase of Cu and Fe system. In this study, ultra-high speed lap welds of SUS304 and Cu dissimilar metals using single-mode fiber laser was generated, and weldability of the weld fusion zone was evaluated using a tensile shear test. To understand the phenomenon of tensile shear load, weld fusion zone of interface weld area and fracture parts after tensile shear test were observed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis system. And it was confirmed that Cu was easily melting and penetrating in the grain boundaries of SUS304 because of low melting temperature. And high thermal conductivity of copper occurred dissipate heat energy rapidly. These properties cause the solidification cracking in weld zone.