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이상섭,이창헌,즈엉 짱 안,웬 호앙 티엔 코이,한형수,이재신,Lee, Sang Sub,Lee, Chang-Heon,Duong, Trang An,Nguyen, Hoang Thien Khoi,Han, Hyoung-Su,Lee, Jae-Shin 한국전기전자재료학회 2021 전기전자재료학회논문지 Vol.34 No.1
This study investigated the structural, dielectric, ferroelectric, and strain properties of (0.98-x)Bi1/2Na1/2TiO3-0.02BiFeO3-xSrTiO3 (BNT-BF-100xST, x=0.20, 0.22, 0.24, 0.26, and 0.28). All samples were successfully synthesized using the conventional solid-state reaction method and sintered at 1,175℃ for 2 h. The average grain size of the BNT-BF-100x ceramics decreased with increasing ST content. Furthermore, we observed that the ferroelectric- relaxor transition temperature (TF-R) decreased with increasing ST content, which eventually vanished in the BNT-BF-24ST ceramics. The results indicated that a ferroelectric to relaxor phase transition could be induced by ST modification. Consequently, a large electromechanical strain of 633 pm/V at 4 kV/mm was observed for the BNT-BF-26ST ceramics. These results imply that our materials have the competitive advantage of larger strain under lower operating field conditions compared with other BNT-based lead-free piezoelectric ceramics. We expect that BNT-BF-ST lead-free piezoelectric ceramics are promising candidates as a novel ternary BNT-based system and can find potential applications in actuators.
이상섭,이창헌,즈엉 짱 안,김동혁,김병우,한형수,이재신,Lee, Sang Sub,Lee, Chang-Heon,Duong, Trang An,Kim, Dong Hyeok,Kim, Byeong Woo,Han, Hyoung-Su,Lee, Jae-Shin 한국재료학회 2021 한국재료학회지 Vol.31 No.10
(Bi<sub>1/2</sub>Na<sub>1/2</sub>)TiO<sub>3</sub> (BNT)-based ceramics are considered promising candidates for actuator application owing to their excellent electromechanical strain properties However, to obtain large strain properties, there remain several issues such as thermal stability and high operating fields. Therefore, this study investigates a reduction of operating field in (0.98-x)Bi<sub>1/2</sub>Na<sub>1/2</sub>TiO<sub>3</sub>-0.02 BiAlO<sub>3</sub>-xSrTiO<sub>3</sub> (BNT-2BA-100xST, x = 0.20, 0.21, 0.22, 0.23, and 0.24) via analyses of the microstructure, crystal structure, dielectric, polarization, ferroelectric and electromechanical strain properties. The average grain size of BNT-${\underline{2}}$BA-100xST ceramics decreases with increasing ST content. Results of polarization and electromechanical strain properties indicate that a ferroelectric to relaxor state transition is induced by ST modification. As a consequence, a large electromechanical strain of 592 pm/V is obtained at a relatively low electric field of 4 kV/mm in 22 mol% ST-modified BNT-2BA ceramics. We believe that the materials synthesized in this study are promising candidates for actuator applications.
이상섭,Lee, Sang-Sup 생화학분자생물학회 1974 한국생화학회지 Vol.7 No.1
When $5{\alpha}$-hydroxy-$6{\beta}$-methylcholestanol was exposed to Nocardia sp. (ATCC 19170) in nutrient broth, accumulation of 17-ketosteroids was observed. The 17-ketosteroids were characterized as $6{\beta}$-methylandrost-4-ene-3, 17-dione and 6-methylandrosta-1, 4-diene-3, 17-dione. Orientation of 6-methyl group of 6-methylandrosta-1, 4-diene-3, 17-dione was postulated to be $\beta$-form. In a typical experiment, 220mg of 6-methylandrosta-1, 4-diene-3, 17-dione was obtained from 600mg of $5{\alpha}$-hydroxy-$6{\beta}$-methylcholestanol after 90 hours of incubation in nutrient broth. Steroid의 모핵분해작용에 관여하는 $9{\alpha}$-hydroxylase의 저해제를 사용하지 않고 직접 cholesterol 유도체로부터 미생물 반응으로 17-ketosteroid류를 얻을 수 있다. 이러한 경우 cholesterol 유도체는 C-19에 산소기능단의 존재를 필요로하고 있다. 본 연구에서는 C-19 산소기능단의 존재가 필요불가결한 것으로는 보지않고 C-19 산소기능단이 없는 여러 cholesterol 유도체를 합성하여 배양시험을 해본 결과 $3{\beta}$,$5{\alpha}$-hydroxy-$6{\beta}$-methylcholestane은 Nocardia sp. (ATCC 19170)에 의해 17-ketosteroid로 산화전환되었다. 전환된 17-ketosteroid는 $6{\beta}$-methylandrost-4-ene-3, 17-dione과 6-methylandrosta-1, 4-diene-3, 17-dione으로 확인되었다 6-methylandrosta-1, 4-diene-3, 17-dione의 6-methyl기의 입체구조는 ${\beta}$-형으로 추정된다. 실험의 한예로서 $5{\alpha}$-hydroxy-$6{\beta}$-methylcholestanol 600mg를 90 시간 배양하여 220 mg의 6-methylandrosta-1, 4-diene-3, 17-dione을 얻었다. 이 물질은 androst-4-ene-3, 17-dione 보다 강한 남성호르몬 작용이 있을 것으로 믿어진다.
Molecular Level Relationships of Purple Nonsulfur Bacteria and their Relatives
이상섭,윤병수,김재수,이현순,Lee, Sang-Seob,Yoon, Byoung-Su,Kim, Jae-Soo,Lee, Hyun-Soon The Microbiological Society of Korea 1994 미생물학회지 Vol.32 No.1
광합성 세균과 비광합성 세균에 속하는 종들 사이의 유연관계를 파악하기 위해 DNA 혼성화 방법을 실시하였다. 혼성화도는 종내 균주들 사이와 Rhodobacter capsulatus와 Rhodopseudomonas blastica 사이를(72-88%) 제외하고는 전체적으로 낮게 나타났다(2-35%). 광합성 세균 Rhodopseudommonas Palustris와 비광합성 세균 Pseudomonas aeruginosa ATCC 27853, Bradyrhizobium japonicu, 사이의 D%는 광합성 세균 사이의 D%보다 약간 높게 나타났다(26-33%). Rhodopseudomonas blastica와 Rhodobacter capsulatus 사이의 D%는 72%로 유전적 유연관계가 매우 높은 것으로 나타났다. DNA-DNA hybridization by kinetic method was carried out between species of purple nonsulfur photosynthetic bacteria and nonphotosynthetic bacteria. The degrees of homology percent were shown to be low (2-35 D%) with the exception of high homology % (72-88 D%) for strains within a species and between Rhodobacter capsulatus and Rhodopseudomonas blastica. The D% between the purple nonsulfur photosynthetic bacteria, Rhodopseudomonas palustris, and nonphotosynthetic bacteria, Pseudomonas aeruginosa ATCC 27853 or Bradyrhizobium japonicum were a little higher (26-33 D%) than the D% between any other photosynthetic bacteria. The homology % between Rhodopseudomonas blastica and Rhodobacter capsulatus was 72 D%, which showed genetic relationship.