• Title/Summary/Keyword: advanced materials

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Gradient Microstructure and Mechanical Properties of Fe-6%Mn Alloy by Different Sized Powder Stacking (다른 크기의 분말 적층을 통해 얻은 Fe-6%Mn합금의 경사 미세조직과 기계적 특성)

  • Seo, Namhyuk;Lee, Junho;Shin, Woocheol;Jeon, Junhyub;Park, Jungbin;Son, Seung Bae;Jung, Jae-Gil;Lee, Seok-Jae
    • Journal of Powder Materials
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    • v.29 no.5
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    • pp.382-389
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    • 2022

  • A typical trade-off relationship exists between strength and elongation in face-centered cubic metals. Studies have recently been conducted to enhance strength without ductility reduction through surface-treatment-based ultrasonic nanocrystalline surface modification (UNSM), which creates a gradient microstructure in which grains become smaller from the inside to the surface. The transformation-induced plasticity effect in Fe-Mn alloys results in excellent strength and ductility due to their high work-hardening rate. This rate is achieved through strain-induced martensitic transformation when an alloy is plastically deformed. In this study, Fe-6%Mn powders with different sizes were prepared by high-energy ball milling and sintered through spark plasma sintering to produce Fe-6%Mn samples. A gradient microstructure was obtained by stacking the different-sized powders to achieve similar effects as those derived from UNSM. A compressive test was performed to investigate the mechanical properties, including the yielding behavior. The deformed microstructure was observed through electron backscatter diffraction to determine the effects of gradient plastic deformation.

  • https://doi.org/10.4150/KPMI.2022.29.5.382 인용 PDF KSCI

Progress In Commercialization Of Light Emitting Polymers: Dow Polyfluorenes

  • Wu, W.;Inbasekaran, M.;Hudack, M.;Welsh, D.;Yu, W.;Chen, Y.;Wang, C.;Kram, S.;Tacey, M.;Bernius, M.;Fletcher, R.;Kiszka, K.;Munger, S.;O'Brien, J.;Hills, M.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2002.08a
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    • pp.340-343
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    • 2002

  • We report here our recent progress in the development and commercialization of polyfluorenes emitting red, green and blue (ROB) colors as materials for light emitting diodes (LEDs). Our patented version of the Suzuki coupling process has been used to synthesize a variety of fluorenebased homopolymers and copolymers emitting colors across the entire visible spectrum. The optical and electronic properties of the polymers are tailored through selective incorporation of different aromatic units into the polyfluorene backbone. Our latest green emitter, reported herein, provides very efficient devices with a low turn-on voltage of 2.25 V, a peak efficiency of 10.5 Cd/A at 6,600 Cd/$m^2$ at 4.85 V. These devices maintain an efficiency of greater than 10 Cd/A up to 50,000 Cd/$m^2$ and demonstrate very good stability as exemplified by a device half-life of greater than 1,500 hours starting from 1,100 Cd/$m^2$. Considerable progress has also been made with red and blue emitters and will be the subject of this presentation.

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Light Leakage Comparison in a Homogeneously Aligned Nematic Liquid Crystal Display Depending on an Angle between Polarizer Axis and Optic Axis of a Liquid Crystal

  • Song, I.S.;Baik, I.S.;Won, H.K.;Kim, D.S.;Soh, H.S.;Kim, W.Y.;Lee, S.H.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.1182-1184
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    • 2004

  • We have studied contrast ratio of a homogeneously aligned nematic liquid crystal (LC) display as a function of the angle between the polarizer axis and LC director. The results show that a cell configuration in which a polarizer axis facing a light source coincides with a short LC axis has a better process margin in terms of high contrast ratio than that of the cell coinciding with a long LC axis.

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