입내 분산형 Al₂O₃/Ag 나노복합체의 제조와 특성

천승호,한인섭,히데오 아와지,Cheon, Sung-Ho,Han, In-Sub,Awaji, Hideo 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.4

Alumina/silver ($Al_2O_3/Ag$) nanocomposites with Ag content up to 9 vol% were prepared from nanopowder by soaking method using ${\gamma}-Al_2O_3$ of needle type and spark plasma sintering (SPS). The mechanical properties of specimens were investigated three-point flexural strength and toughness as a function of the Ag contents. The maximum flexural strength of the alumina/silver nanocomposite was 850 MPa for the 1 vol% composite, and also higher than monolith alumina as about 800 MPa at 3, 5, and 7 vol% Ag contents. Fracture toughness by single edged V-notch beam (SEVNB) was $4.05MPa{\cdot}m^{1/2}$ for the 3 vol% composite and maintained about $4.00MPa{\cdot}m^{1/2}$ at 5, and 7 vol% Ag content. Microstructure of fracture surface for each fracture specimens was observed. Due to the inhibition effect of alumina grain growth, the average grain size of nanocomposites depends on the content of Ag nano particles. The fracture morphology of nanocomposite with dislocation (sub-grain boundary) by silver nano-particles of second phases in the alumina matrix also showed transgranular fracture-mode compare with intergranular of monolith alumina. Thermal conductivity of specimens at room temperature was about 40 W/mK for the 1 vol% Ag content.

철도시스템분야 실무적용을 위한 RAM Guidance 개발에 관한 연구

이중섭(Joong Sub31 Lee),백영구(Young Goo Baek),이진(Jin Lee),한미정(Mi Jung Han),김성환(Sung Hwan Kim) 한국철도학회 2015 한국철도학회 학술발표대회논문집 Vol.2015 No.10

철도시스템 기술 고도화 및 복잡성의 증대와 더불어 발주기관으로부터 시스템의 성능보증과 안전성 확보가 요구되고 있는 실정이다. 또한 국내 철도안전법 강화로 인하여 시스템 보증활동의 중요성이 증가되고 있다. 본 논문에서는 국제철도관련 규격을 바탕으로 철도시스템의 RAM 업무에 대한 절차를 정의하고, 해당 철도 프로젝트에서 RAM 업무를 원활히 수행할 수 있도록 관련된 국제 규격 및 유사시스템 적용 사례에 기반하여 철도시스템 개발 특성을 고려한 RAM 업무 수행 지침(Guidance)을 개발하였다. Performance and safety assurances for the railway system are required by the client because of the high degree of technology and increased complexity. In addition, as a result of reinforced domestic railway safety laws, the importance of system assurance activity has been growing steadily. This paper defines the task of the RAM process based on international railway industry standards for RAMS engineers to work efficiently and develops the RAM guidance considering the railway system characteristics based on domestic standards and application cases of railway systems.

Guided formation of sub-5 nm interstitial gap between plasmonic nanodisks

Jin Gyeong Son,Sang Woo Han,Jung-Sub Wi,Tae Geol Lee 한국진공학회 2015 한국진공학회 학술발표회초록집 Vol.2015 No.2

Characterization of OsJAC1 which is responding to different types of ionizing radiation

In jung Jung,Jung Eun Hwang,Sung Min Han,Hong-Il Choi,Soon-Jae Kwon,Jin-Baek Kim,Si-Yong Kang,Dong Sub Kim 한국육종학회 2015 한국육종학회 심포지엄 Vol.2015 No.07

Ionizing radiation affects gene expression from plant genomes. To monitor the genome-wide transcriptional changes induced by three types of ionizing radiation, we used the rice RNA sequencing to identify genes that are up- or down-regulated by gamma rays (GAs), proton (PRs) and ion beams (IBs). The Oryza sativa jacalin-like lectin domain containing proteins (OsJAC1) gene was highly induced by GAs, PRs and IBs. OsJAC1 was selected based on the expression patterns of a genome-wide dataset of RNA sequencing. Many jacalin-related lectin genes have been shown to be associated with disease resistance, biotic and abiotic stress signaling. Therefore, we studied its expression pattern in response to different abiotic stress and phytohormone treatments. The expression patterns of OsJAC1 under two different abiotic stress conditions (salt and heat stress) and phytohormones (salicylic acid and methyl jasmonate) were examined. The transcripts of OsJAC1 were significantly induced in response to abiotic stress conditions, including salt and heat treatments. In addition, it was induced in response to the salicylic acid and methyl jasmonate treatments, respectively. To investigate the sub-cellular localization of OsJAC1, the gene was expressed as a fusion protein tagged with GFP, in tobacco leaf epidermis and examined under confocal microscope. The OsJAC1 was clearly localized at the nucleus. These results provide critical insights into the molecular functions of the rice jacalin-like lectin domain containing proteins as receptors of external signals.

Antifungal Activity of Streptomyces pad anus isolate TH04 against Monilinia fructicola, Brown rot Fungus on Stone-fruits

임태헌,최용화,이동운,한상섭,차병진,Lim, Tae-Heon,Choi, Yong-Hwa,Lee, Dong-Woon,Han, Sang-Sub,Cha, Byeong-Jin The Korean Society of Pesticide Science 2008 농약과학회지 Vol.12 No.3

복숭아 미이라 과일로부터 복숭아 잿빛무늬병 Monilinia fructicola에 대하여 강한 항균활성을 보이는 방선균 Streptomyces padanus TH04를 분리하였다. TH04 균주의 배양 추출물 1%를 함유한 배지에서의 균사생육 및 포자발아는 시험한 M. fructicola의 strain에 따라 각각 $79.8{\sim}81%$와 $73.9{\sim}75.8%$ 억제되었다. 병원균과 TH04 균주 초기접종 밀도를 0.01%, 0.1% 및 1%로 달리하여 동시배양 한 결과, 항균활성은 선발 방선균의 밀도에 따라 $7.5%{\sim}94%$로 나타났다. 사과(품종; 후지)를 이용한 조추출물의 항균활성은 0.1% 처리구 85.9%, 1%처리구 100%로 나타났다. 항균활성 물질 생산, 안정성 및 제형화에 관한 연구가 이루어질 경우 선발한 Streptomyces padanus TH04는 생물학적 방제제로의 개발 가능성 있을 것으로 생각된다. The Streptomyces padanus isolate TH04, isolated from mummified peaches, showed strong antifungal activity to Monilinia fructicola. The inhibition activity of the isolate TH04 to mycelial growth and spore germination at 1% concentration of sub-antifungal powder made from culture suspension (CS) was ranged from 79.8% to 81.0% and from 73.9% to 75.8% to M. fructicola four strains, respectively. In the test of antifungal activity in mixed culture of the isolate and M. fructicola, inhibition rate was 7.5%, 86.8% and 94.0% in 0.01, 0.1, and 1% concentration of CS containing bacterial cell of the isolate, respectively. On apples (cultivar; Fuji), the control values of the isolate TH04 crude filtrates (0.1 and 1%) were 85.9% and 100%, respectively. The results suggest that the isolate TH04 indicate development possibility as biocontrol agent of brown rot caused by M. fructicola with the study on delivery method and fermentation condition to produce an antifungal compound.

Horizontal-to-Vertical Transition of 2D Layer Orientation in Low-Temperature Chemical Vapor Deposition-Grown PtSe₂ and Its Influences on Electrical Properties and Device Applications

Han, Sang Sub,Kim, Jong Hun,Noh, Chanwoo,Kim, Jung Han,Ji, Eunji,Kwon, Junyoung,Yu, Seung Min,Ko, Tae-Jun,Okogbue, Emmanuel,Oh, Kyu Hwan,Chung, Hee-Suk,Jung, YounJoon,Lee, Gwan-Hyoung,Jung, Yeonwoong American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.14

<P>Two-dimensional (2D) transition-metal dichalcogenides (2D TMDs) in the form of MX<SUB>2</SUB> (M: transition metal, X: chalcogen) exhibit intrinsically anisotropic layered crystallinity wherein their material properties are determined by constituting M and X elements. 2D platinum diselenide (2D PtSe<SUB>2</SUB>) is a relatively unexplored class of 2D TMDs with noble-metal Pt as M, offering distinct advantages over conventional 2D TMDs such as higher carrier mobility and lower growth temperatures. Despite the projected promise, much of its fundamental structural and electrical properties and their interrelation have not been clarified, and so its full technological potential remains mostly unexplored. In this work, we investigate the structural evolution of large-area chemical vapor deposition (CVD)-grown 2D PtSe<SUB>2</SUB> layers of tailored morphology and clarify its influence on resulting electrical properties. Specifically, we unveil the coupled transition of structural-electrical properties in 2D PtSe<SUB>2</SUB> layers grown at a low temperature (i.e., 400 °C). The layer orientation of 2D PtSe<SUB>2</SUB> grown by the CVD selenization of seed Pt films exhibits horizontal-to-vertical transition with increasing Pt thickness. While vertically aligned 2D PtSe<SUB>2</SUB> layers present metallic transports, field-effect-transistor gate responses were observed with thin horizontally aligned 2D PtSe<SUB>2</SUB> layers prepared with Pt of small thickness. Density functional theory calculation identifies the electronic structures of 2D PtSe<SUB>2</SUB> layers undergoing the transition of horizontal-to-vertical layer orientation, further confirming the presence of this uniquely coupled structural-electrical transition. The advantage of low-temperature growth was further demonstrated by directly growing 2D PtSe<SUB>2</SUB> layers of controlled orientation on polyimide polymeric substrates and fabricating their Kirigami structures, further strengthening the application potential of this material. Discussions on the growth mechanism behind the horizontal-to-vertical 2D layer transition are also presented.</P> [FIG OMISSION]</BR>

Hexagonal boron nitride assisted growth of stoichiometric Al₂O₃ dielectric on graphene for triboelectric nanogenerators

Han, Sang A.,Lee, Kang Hyuck,Kim, Tae-Ho,Seung, Wanchul,Lee, Seok Kyeong,Choi, Sungho,Kumar, Brijesh,Bhatia, Ravi,Shin, Hyeon-Jin,Lee, Woo-Jin,Kim, SeongMin,Kim, Hyoung Sub,Choi, Jae-Yong,Kim, Sang-Wo Elsevier 2015 Nano energy Vol.12 No.-

<P><B>Abstract</B></P> <P>Here we demonstrate the deposition of a high-k dielectric material on graphene using hexagonal boron nitride (h-BN) nanosheets as a buffer layer. The presence of an h-BN layer on top of the graphene facilitated the growth of high-quality Al<SUB>2</SUB>O<SUB>3</SUB> by atomic layer deposition (ALD). Simulation results also support the experimental observations and provide an explanation for the suitability of h-BN as a buffer layer in terms of mixed ionic-covalent B–N bonding. Additionally, h-BN works as a protective shield to prevent graphene oxidation during ALD of Al<SUB>2</SUB>O<SUB>3</SUB> for the fabrication of graphene-based devices. Finally, triboelectric nanogenerators (TNGs) based on both Al<SUB>2</SUB>O<SUB>3</SUB>/h-BN/graphene and Al<SUB>2</SUB>O<SUB>3</SUB>/graphene structures are demonstrated for further confirming the importance of h-BN for synthesizing high-quality Al<SUB>2</SUB>O<SUB>3</SUB> on graphene. It was found that the Al<SUB>2</SUB>O<SUB>3</SUB>/h-BN/graphene-based TNG reveals meaningful electric power generation under a mechanical friction, while no significant electric power output from the Al<SUB>2</SUB>O<SUB>3</SUB>/graphene-based TNG is obtained, indicating high charge storage capacity of the dielectric Al<SUB>2</SUB>O<SUB>3</SUB> layer on h-BN.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A easy method for the formation of stoichiometric Al<SUB>2</SUB>O<SUB>3</SUB> on CVD-grown h-BN/graphene. </LI> <LI> The presence of an h-BN layer facilitates the growth of high-quality Al<SUB>2</SUB>O<SUB>3</SUB> by ALD. </LI> <LI> h-BN works as a protective layer to prevent graphene oxidation during ALD process. </LI> <LI> Flexible transparent triboelectric nanogenerators based on Al<SUB>2</SUB>O<SUB>3</SUB>/h-BN/graphene. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Bi_1/2Na_1/2TiO₃-BiAlO₃ 무연 압전 세라믹스의 유전 및 전기 기계적 변형 특성에 대한 SrTiO₃ 첨가 효과

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_1/2Na_1/2)TiO₃ (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_1/2Na_1/2TiO₃-0.02 BiAlO₃-xSrTiO₃ (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.

Bi_0.5Na_0.5TiO₃-BiFeO₃-SrTiO₃ 삼성분계 무연 압전 세라믹스의 강유전체-완화형 강유전체 상전이 거동

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.

Versatile approaches to tune a nanocolumnar structure for optimized electrical properties of In₂O₃ based gas sensor

Han, Soo Deok,Noh, Myoung-Sub,Kim, Sangtae,Shim, Young-Seok,Song, Young Geuon,Lee, Kwangjae,Lee, Hae Ryung,Nahm, Sahn,Yoon, Seok-Jin,Kim, Jin-Sang,Kang, Chong-Yun Elsevier 2017 Sensors and actuators. B, Chemical Vol.248 No.-

<P><B>Abstract</B></P> <P>In this study, we demonstrate tuning of electrical properties and sensing responses of In<SUB>2</SUB>O<SUB>3</SUB> nanocolumnar structure via varying glancing angle (GLAD) deposition conditions by e-beam evaporator. The varied deposition conditions include glancing angle, vacuum level and deposition rate. The electrical property of In<SUB>2</SUB>O<SUB>3</SUB> nanostructured thin films, demonstrated by the base resistance, change up to 3 orders of magnitude from 110Ω to 103104Ω depending on the porosity of nanocolumnar structure and oxygen vacancy concentration. This variation in electrical property transfers to the tuning of gas sensing response, and we achieve tuning the same material (In<SUB>2</SUB>O<SUB>3</SUB>) based gas sensors to better perform for specific type of gases (either oxidizing or reducing). The highest responses achieved in this work reached up to 176 for oxidizing gases (5ppm NO<SUB>2</SUB>, R<SUB>gas</SUB>/R<SUB>air</SUB>) and 929 for reducing gases (50ppmC<SUB>2</SUB>H<SUB>5</SUB>OH, R<SUB>air</SUB>/R<SUB>gas</SUB>). Therefore, we demonstrate that gas sensors can be optimized for specific type of target gases with the same material, via simple control of deposition conditions. Along with the high reproduciblility and sensitivity, this puts the nanocolumnar thin film based gas sensors by GLAD with huge potential for further miniaturization and mass production, suitable for the upcoming IoT era.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanocolumnar In<SUB>2</SUB>O<SUB>3</SUB> thin film based gas sensor is fabricated by glancing angle deposition (GLAD). </LI> <LI> Electrical properties of In<SUB>2</SUB>O<SUB>3</SUB> can be optimized for specific target gases, tuning simple deposition conditions of GLAD. </LI> <LI> In<SUB>2</SUB>O<SUB>3</SUB> sensors have excellent performances with high repeatability, recovery, and extremely low detection limit. </LI> </UL> </P>