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Si<sub>0.8</sub>Ge<sub>0.2</sub>계 합금에서 열전특성에 미치는 B의 영향
황성두,최우석,박익민,박용호,Hwang, Sung-Doo,Choi, Woo-Suk,Park, Ik-Min,Park, Yong-Ho 한국분말야금학회 2007 한국분말재료학회지 (KPMI) Vol.14 No.4
P-type thermoelectric material $Si_{0.8}Ge_{0.2}$ was sintered by Hot Press process (HP) and the effect of boron ($0.25{\sim}2$ at%) addition on the thermoelectric properties were reported. To enhance the thermoelectric performances, the $Si_{0.8}Ge_{0.2}$, alloys were fabricated by mechanical alloying (MA) and HP. The carrier of p-type SiGe alloy was controlled by B-doping. The effect of sintering condition and thermoelectric properties were investigated. B-doped SiGe alloys exhibited positive seebeck coefficient. The electrical conductivity and thermal conductivity were increased at the small amount of boron content ($0.25{\sim}0.5$ at%). However, they were decreased over 0.5 at% boron content. As a result, the small addition of boron improved the Z value. The Z value of 0.5 at% B doped $Si_{0.8}Ge_{0.2}$ B alloy was $0.9{\times}10{-4}/K$, the highest value among the prepared alloys.
In uence of Fe3O4 on the BiSb4Te7.5 Thermoelectric Materials Prepared by Mechanical Alloying
최우석,황성두,박익민,박용호 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1
Because of their high figure of merit (Z) value, bismuth antimony tellurides are widely used in various thermoelectric cooling devices operating at temperatures near room temperature. The in uence of Fe3O4 (0 ~ 0.1 wt.%) addition on the thermoelectric properties of p-type BiSb4Te7.5 alloy is reported. Specimens were fabricated by mechanical alloying and pulse discharge sintering. The electrical conductivity and the power factor were decreased and the Seebeck coefficient was increased with increasing Fe3O4 content. The thermal conductivity decreased with the addition of Fe3O4 and the measured value in the alloy containing 0.1 wt.% Fe3O4 was 0.814 W/Km, 20 % lower than that of the Fe3O4 free alloy. The highest Z value was, therefore, achieved in the alloy containing 0.01 wt.% Fe3O4 and was 3.1 × 10-3 /K. Because of their high figure of merit (Z) value, bismuth antimony tellurides are widely used in various thermoelectric cooling devices operating at temperatures near room temperature. The in uence of Fe3O4 (0 ~ 0.1 wt.%) addition on the thermoelectric properties of p-type BiSb4Te7.5 alloy is reported. Specimens were fabricated by mechanical alloying and pulse discharge sintering. The electrical conductivity and the power factor were decreased and the Seebeck coefficient was increased with increasing Fe3O4 content. The thermal conductivity decreased with the addition of Fe3O4 and the measured value in the alloy containing 0.1 wt.% Fe3O4 was 0.814 W/Km, 20 % lower than that of the Fe3O4 free alloy. The highest Z value was, therefore, achieved in the alloy containing 0.01 wt.% Fe3O4 and was 3.1 × 10-3 /K.
해양플랜트용 후판강의 미세조직과 기계적 특성에 미치는 압연 조건의 영향
김종철,서용찬,황성두,신상용,Kim, Jongchul,Suh, Yonhchan,Hwang, Sungdoo,Shin, Sang Yong 한국재료학회 2018 한국재료학회지 Vol.28 No.8
In this study, three kinds of steels are manufactured by varying the rolling conditions, and their microstructures are analyzed. Tensile and Charpy impact tests are performed at room temperature to investigate the correlation between microstructure and mechanical properties. In addition, heat affected zone(HAZ) specimens are fabricated through the simulation of the welding process, and the HAZ microstructure is analyzed. The Charpy impact test of the HAZ specimens is performed at $-40^{\circ}C$ to investigate the low temperature HAZ toughness. The main microstructures of steels are quasi-polygonal ferrite and pearlite with fine grains. Because coarse granular bainite forms with an increasing finish rolling temperature, the strength decreases and elongation increases. In the steel with the lowest reduction ratio, coarse granular bainite forms. In the HAZ specimens, fine acicular ferrites are the main features of the microstructure. The volume fraction of coarse bainitic ferrite and granular bainite increases with an increasing finish rolling temperature. The Charpy impact energy at $-40^{\circ}C$ decreases with an increasing volume fraction of bainitic ferrite and granular bainite. In the HAZ specimen with the lowest reduction ratio, coarse bainitic ferrite and granular bainite forms and the Charpy impact energy at $-40^{\circ}C$ is the lowest.