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- 저자 : 조중영(Jung Young Cho) (검색결과 5 건)
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M-type Sr-Hexaferrite에서 MnCO<sub>3</sub> 첨가에 따른 소결 거동
정민석,유창재,조중영,문경석,Jeong, MinSeok,You, Changjae,Cho, Jung Young,Moon, Kyoung-Seok 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.2
The grain growth behavior of M-type Sr hexaferrite (SrM) grains is investigated with the addition of MnCO<sub>3</sub>. First, the SrM powder is synthesized by a conventional solid-state reaction. The powder compacts of SrM are sintered at 1250℃ for 2 h with various amounts of MnCO<sub>3</sub> (0, 0.5, 1.0, and 4.0 mol%). There is no secondary solid phase in any of the sintered samples. Relative density increases when MnCO<sub>3</sub> is added to the SrM. Obvious abnormal grain growth does not appear in any of the SrM samples with MnCO<sub>3</sub>. The average grain size increases when 0.5 mol% MnCO<sub>3</sub> is added to the SrM. However, as the amount of MnCO<sub>3</sub> increase to over 0.5 mol%, the average grain size decreases. These observations allow us to conclude that the growth of SrM grains is governed by the two-dimensional nucleation grain growth mechanism, and the critical driving force for the growth of a grain decreases as the amount of MnCO<sub>3</sub> increases.
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남우현(Woo Hyun Nam),조중영(Jung Young Cho) 한국세라믹학회 2021 세라미스트 Vol.24 No.2
To solve the global energy problems, investigating renewable and environmentally friendly energy resources has considerable significance. Thermoelectric materials and modules have gained considerable attention because they can directly convert waste heat into electric power while leaving no environmental pollution. The performance of the thermoelectric materials can be determined using the dimensionless figure of merit, ZT. However, trade-off relationships between the thermoelectric parameters (electrical conductivity, Seebeck coefficient, and thermal conductivity) have hindered significant improvement of ZT over the decades. Therefore, independent control of the charge and phonon transports is of great importance. In this respect, CoSb3–based skutterudites showing PGEC (phonon-glass electron-crystal) properties are considered to be promising thermoelectric materials for mid-temperature power generation. In this paper, we review the current status of research in the fields of CoSb3-based thermoelectric materials and modularization techniques.
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Fe/Co 비율 제어를 통한 P형 Nd-Fe-Co-Sb계 Skutterudite 소재의 열전특성 향상
남우현(Woo Hyun Nam),조중영(Jung Young Cho) 한국환경에너지공학회 2023 한국열환경공학회 학술대회지 Vol.2023 No.2
본 연구는 Fe/Co 비율 제어를 통한 P 형 Nd-Fe-Co-Sb계 skutterudite 합금의 열전 특성 향상에 대해 보고한다. 유도 용해 및 급속 응고법을 통해 분말을 제작한 후 방전 플라즈마 소결법 (903 K, 50 MPa, 15 min)으로 Ndo_9fe4-~oxSb12(x = 0.5, 0.75, 1, 1.25, 1.5) 소결체를 합성하였다. 소결체의 XRD 분석을 통해 skutterudite 단일상이 형성되었으며, Fe/Co 비율 조절에 따른 주요 회절 피크의 이동을 통해 Co가 Fe 자리로 효과적으로 치환된 것을 확인하였다. Co 치환량 중가에 따른 캐리어 농도 감소로 전기전도도는 감소하고 제벡계수는 중가하는 경향을 보였으며, 캐리어 농도 최적화에 따라 X = 0.75 샘플에서 최대출력인자(28.9 x 10-4 wm-1K-2 @ 769 K)를 얻었다. 또한, 열전도도는 Co 치환량 중가에 따른 전자 전도 기여분의 저하로 감소하는 경향을 보였다 결과적으로 Fe/Co 비율 조절을 통해 p 형 skutterudite 소재의 전기적 및 열적특성을 동시에 제 어하여 열전성능이 향상되는 것을 확인하였으며. X = 0.75 샘플(Nd0.9Fe3.25CO0.7Sb12.2)에서 1.0(@ 769 K)의 최대 열전성능지수를 보였다.
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Sb가 결핍된 N형 Skutterudite Co<sub>4</sub>Sb<sub>12</sub>의 열전 특성
탁장렬,정민석,이나영,남우현,서원선,조중영,Tak, Jang-Yeul,Van Du, Nguyen,Jeong, Min Seok,Lee, NaYoung,Nam, Woo Hyun,Seo, Won-Seon,Cho, Jung Young 한국전기전자재료학회 2019 전기전자재료학회논문지 Vol.32 No.6
In this study, we investigate the effect of an Sb-deficiency on the thermoelectric properties of double-filled n-type skutterudite ($In_{0.05}Yb_{0.15}Co_4Sb_{12-x}$). Samples were prepared by encapsulated induction melting, consecutive long-time annealing, and finally spark plasma sintering processes. The Sb-deficient sample contained a $CoSb_2$ secondary phase. Both the double-filled n-type skutterudite pristine and Sb-deficient samples showed metallic behavior in electrical conductivity with increasing temperature. The carrier concentration of the Sb-deficient sample decreased compared with that of the pristine sample. Due to a decrease in carrier concentration, the Sb deficient sample showed decreased electrical conductivity and an increased Seebeck coefficient compared with the conductivity and coefficient of the pristine sample. Furthermore, the Sb deficient sample showed an increase in the power factor (${\sigma}{\cdot}S^2$); the power factor maximum shifted to athe lower temperature side than ones of the pristine sample. As a result, the Sb-deficient sample represents an improved average figure of merit (ZT) and a $ZT_{max}$ temperature lower than that of the pristine sample. Therefore, we propose that Sb-deficient double-filled n-type skutterudite thermoelectric material ($In_{0.05}Yb_{0.15}Co_4Sb_{12-x}$) be used in the 573~673 K temperature range.
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남우현(Woo Hyun Nam),신원호(Weon Ho Shin),조중영(Jung Young Cho),서원선(Won-Seon Seo) 한국세라믹학회 2019 세라미스트 Vol.22 No.2
Thermoelectric energy conversion has attracted much attention because it can convert heat into electric power directly through solid state device and vice versa. Current research is aimed at increasing the thermoelectric figure of merit (ZT ) by improving the power factor and reducing the thermal conductivity. Although there have been significant progresses in increasing ZT of material systems composed of Bi, Te, Ge, Pb, and etc. over the last few decades, their relatively high cost, toxicity, and the scarcity have hindered further development of thermoelectrics to expand practical applications. In this paper, we review the current status of research in the fields of nanostructured thermoelectric materials with eco-friendly and low cost elements, such as skutterudites and oxides, for mid-high temperature applications, highlighting the strategies to improve thermoelectric performance.
ScienceON
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