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pISSN : 1225-1429 / eISSN : 2234-5078

2020 KCI Impact Factor : 0.17
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2021, Vol.31, No.3

  • 1.

    Hexagonal shape Si crystal grown by mixed-source HVPE method

    이강석 | Kyoung-Hwa Kim | Jung Hyun Park and 10other persons | 2021, 31(3) | pp.103~111 | number of Cited : 0
    Abstract PDF
    Hexagonal shape Si crystals were grown by the mixed-source hydride vapor phase epitaxy (HVPE) method ofmixing solid materials such as Si, Al and Ga. In the newly designed atmospheric pressure mixed-source HVPE method,nuclei are formed by the interaction between GaCln, AlCln and SiCln gases at a high temperature of 1200°C. In addition, itis designed to generate a precursor gas with a high partial pressure due to the rapid reaction of Si and HCl gas. Theproperties of hexagonal Si crystals were investigated through scanning electron microscopy (FE-SEM), energy dispersive Xrayspectroscopy (EDS), high-resolution X-ray diffraction (HR-XRD), and Raman spectrum. From these results, it is expectedto be applied as a new material in the Si industry.
  • 2.

    Evidence of spin-phonon coupling in La2NiMnO6 double perovskite

    Mohammad Nasir | Ateeq Ahmed | Park, Hee Jung and 1other persons | 2021, 31(3) | pp.112~115 | number of Cited : 0
    Abstract PDF
    Herein, a correlation between B-site cation order and spin-phonon coupling in La2NiMnO6 double perovskite hasbeen investigated. Raman spectra of La2NiMnO6 double perovskite annealed at 950 and 1400°C have been measured in the140-598 K range. A substantial softening of the phonon modes has been observed below the Curie temperature, whichemphasized the presence of the spin-phonon coupling in the system. The spin-phonon coupling was found to be stronger inrelatively more ordered La2NiMnO6 double perovskite. Thus, the magnitude of spin-phonon coupling was influenced by theNi/Mn cation order.
  • 3.

    Characterization of crystal phase evolution in cordierite honeycomb for diesel particulate filter by using rietveld refinement and SEM-EDS methods

    KiWoong Chae | KIM KANG SAN | JeongSeog Kim and 1other persons | 2021, 31(3) | pp.116~126 | number of Cited : 0
    Abstract PDF
    코디어라이트(Mg2Al4Si5O18) 하니컴 세라믹스의 대표적 응용분야는 자동차 배기가스 정화용 필터(diesel particulatefilter(DPF))이다. 천연광물, 조공제, 유기바인더를 혼합한 슬러리를 압출하여 DPF용 하니컴 코디어라이트를 성형한 후 980~1450°C 범위에서 소결하였다. 소결온도에 따른 결정상(indialite, cordierite, cristobalite, alumina, spinel, mullite, pro-enstatite)의형성과정을 XRD Rietveld 정밀화법을 이용하여 정량분석 하였다. 동시에, 세라믹 에칭(etching) 방법으로 소결 시료 표면의비정질상을 제거한 후 SEM/EDS법을 사용하여 결정상들의 형상과 조성을 확인하였다. 이들 결과로부터 DPF 하니컴에서결정상 형성 과정을 명확히 밝힐 수 있었다. 또한, DPF 하니컴의 소결온도에 따른 열팽창계수(linear coefficient of thermalexpansion, CTE) 변화를 분석하였고, 결정상의 정량분석결과를 바탕으로 계산된 CTE와 비교하였다. 소결된 DPF 하니컴 내의 결정상들이 CTE 특성에 미치는 영향을 고찰하였다.
  • 4.

    Studies on Nusselt and Sherwood number for diffusion-advective convection during physical vapor transport of Hg2Br2

    Geug-Tae Kim | Moo Hyun Kwon | 2021, 31(3) | pp.127~136 | number of Cited : 0
    Abstract PDF
    This paper is dedicated to numerical simulation for diffusion-advective convection in a square cavity duringphysical vapor transport of Hg2Br2. Flow characteristics of the temperature difference between the source and crystal regions, 50°C (300°C→250°C), partial pressures of component argon of 20 Torr and 100 Torr are investigated and presented as velocityvectors and streamlines, isotherms and iso-mass concentrations contours. Moreover, alterations of average Nusselt and averageSherwood numbers with (a) the source and crystal regions, (b) the pressures of component argon of 20 Torr and 100 Torrare analyzed and addressed in details. Both average Nusselt and average Sherwood numbers are seen to decrease with theincreasing values of the partial pressures of component argon. Also, it is found that for the two different partial pressuresof component argon, average Nusselt numbers at the source region are greater than at the crystal region, and inversely,average Sherwood numbers at the crystal region are greater than the source region by a factor of 3.
  • 5.

    Preparation and application of silica-based coatings for corrosion protection of marine structures

    BYEONG WOO LEE | 2021, 31(3) | pp.137~142 | number of Cited : 0
    Abstract PDF
    본 연구에서는 상온경화형 silica-based 코팅제의 제조 및 해양구조물에 적용하여 가혹한 해양환경에서 방식 및방오 성능 발현을 위한 실용화 개발 연구를 수행하였다. 구조상 외부에 노출된 부분이 많은 해양(플랜트) 구조물은 강한 자외선, 극심한 온도차, 염수에 의한 부식 등 가혹한 해양환경에 고립되어 운용된다. 이러한 환경 하에서는 쉽게 열화 되고파도 등 물리적 자극에도 쉽게 침식되는 유기계 페인트들은 그 역할을 제대로 할 수 없다. 해양구조물에 치밀한 세라믹 코팅을 형성시킬 경우 녹이 발생하지 않고 경도가 높아 시설물을 해수환경 하에서도 치밀하게 보호할 수 있다. 세라믹 코팅제의 경우 그 기능의 장점들로 인해 해양 구조물에서 그 용도와 적용범위는 크게 증진될 수 있을 것이다. 따라서 colloidalsilica를 기반으로 실란계 커플링제, 경화제 및 세라믹 충진제로 구성된 silica-based 코팅제 조성개발과 해수중 방식 및 방오용 보호코팅제로의 응용에 대해 연구하였다.
  • 6.

    Heat-treatment effects on oxygen evolution reaction of nickel-cobalt layered double hydroxide

    Lee, Jung-il | 김대현 | Sungwook Mhin and 1other persons | 2021, 31(3) | pp.143~148 | number of Cited : 0
    Abstract PDF
    Alkaline oxygen evolution reaction (OER) electrocatalysts have been widely studied for improving the efficiencyand green hydrogen production through electrochemical water splitting. Transition metal-based electrocatalysts have emergedas promising materials that can significantly reduce the hydrogen production costs. Among the available electrocatalysts,transition metal-based layered double hydroxides (LDHs) have demonstrated outstanding OER performance owing to theabundant active sites and favorable adsorption-desorption energies for OER intermediates. Currently, cobalt doped nickel LDHs(NiCo LDHs) are regarded as the benchmark electrocatalyst for alkaline OER, primarily owing to the physicochemicalsynergetic effects between Ni and Co. We report effects of heat-treatment of the as-grown NiCo LDH on electrocatalyticactivities in a temperature range from 250 to 400°C. Electrocatalytic OER properties were analysed by linear sweep voltammetry(LSV) and electrochemical impedance spectroscopy (EIS). The heat-treatment temperature was found to play a crucial rolein catalytic activity. The optimum heat-treatment temperature was discussed with respect to their OER performance.