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RISS 인기검색어
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- 저자 : Seung-Yeop Chun(전승엽) (검색결과 4 건)
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Synthesis and Characterization of Rod-Shaped Ni-Zn Ferrite Particles
전승엽,황진아,전명표,Chun, Seung-Yeop,Hwang, Jin-Ah,Chun, Myoung-Pyo The Korean Institute of Electrical and Electronic 2018 전기전자재료학회논문지 Vol.31 No.5
The rod-shaped $Ni_{0.5}Zn_{0.5}Fe_2O_4$ particles were synthesized via a topotactic reaction, in which goethite (${\alpha}-FeOOH$) particles are the main constituents. The phases, microstructures and magnetic properties of these particles were studied using XRD, FE-SEM and VSM. The precursor solution consisted of $NiSO_4{\cdot}xH_2O$, $ZnSO_4{\cdot}xH_2O$, goethite and D.I. water werereacted at four different temperatures (50, 70, 90, $100^{\circ}C$) to generate four differently precipitated particles respectively. During the co-precipitation reaction, the pH of the solution was maintained at 8.0 using NaOH. The particles co-precipitated and calcined at a temperature of $700^{\circ}C$, exhibited a rod-shape similar to its original goethite, which means that the shape of Ni-Zn ferrite particles can be topotactically controlled by the goethite. The particles synthesized at 70 and $90^{\circ}C$ have a saturation magnetization of 29 and 35 emu/g respectively; representing better values than the ones synthesized at the 50 and $100^{\circ}C$, in which some second phases such as $Fe_2O_3$ were observed.
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Al<sub>2</sub>O<sub>3</sub>-3YSZ 복합체의 미세구조 및 기계적 특성에 대한 Al<sub>2</sub>O<sub>3</sub> 분말 크기의 영향
윤제정,전승엽,황진아,박수영,전명표,Yoon, Jea-Jung,Chun, Seung-Yeop,Hwang, Jin-Ah,Park, Su-Young,Chun, Myoung-Pyo 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.1
3YSZ + (x) $Al_2O_3$ composites (x = 20, 40, 60, 80 wt%) were fabricated and the influences of particle sizes of $Al_2O_3$ on their microstructures and mechanical properties were investigated with XRD, SEM, vickers hardness and fracture toughness. $Al_2O_3$-3YSZ composites containing $Al_2O_3$ powder of a $0.3{\mu}m$ and an $1.0{\mu}m$, which are here in after named as $Al_2O_3$($0.3{\mu}m$)-3YSZ and $Al_2O_3$($1.0{\mu}m$)-3YSZ, respectively, were made by mixing raw materials, uni-axial pressing and sintering at $1,400^{\circ}C$, $1,500^{\circ}C$, and $1,600^{\circ}C$. $Al_2O_3$($0.3{\mu}m$)-3YSZ composites show the higher density and the better mechanical properties than $Al_2O_3$($1.0{\mu}m$)-3YSZ composites. The Vickers hardness of the $Al_2O_3$($0.3{\mu}m$)-3YSZ composites show a peak value of 1,997 Hv at the content of 60 wt% $Al_2O_3$, which is a slightly higher value in comparison with 1,938 Hv of the $Al_2O_3$($1.0{\mu}m$)-3YSZ composite. However, the fracture toughness of $Al_2O_3$-3YSZ composites monotonically increases with decreasing the content of $Al_2O_3$ without any peak values. $Al_2O_3$($0.3{\mu}m$)-3YSZ and $Al_2O_3$($1.0{\mu}m$)-3YSZ composites sintered at $1,600^{\circ}C$ have a maximum value of a $6.9MPa{\cdot}m^{1/2}$ and a $6.2MPa{\cdot}m^{1/2}$, respectively at the composition of containing 20 wt% $Al_2O_3$. It should be noticed that the mechanical properties and the sintering density of the $Al_2O_3$-3YSZ composites can be enhanced by using more fine $Al_2O_3$ powder due to their denser microstructure and smaller grain size.
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최현빈,전명표,전승엽,황진아,Choi, Hyun-Bin,Chun, Myoung-Pyo,Chun, Seung-Yeop,Hwang, Jin-Ah 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.9
Goethite, ${\alpha}$-FeOOH have various applications such as absorbent, pigment and source for magnetic materials. Goethite particles were synthesized in a two step process, where $Fe(OH)_2$ were synthesized in nitrogen atmosphere using $FeSO_4$ as a raw material in the first process, and after that acicular goethite particles were obtained in an air oxidation process of $Fe(OH)_2$ in highly alkaline aqueous solution. Their phase and microstructure were investigated with XRD and FE-SEM. It was found that the morphology of goethite and the ratio of length-to-width (aspect ratio) of acicular goethite are dependent on the some factors such as R value ($OH^-/Fe^{2+}$), air flow rate and pH conditions. In particular, R value has the strongest influence on the synthesized goethite morphology. It is considered that the optimal value R is 4.5 because X-ray diffraction peaks of goethite have the highest intensity at that value. Morphology of goethite particles was controlled by air flow rates, showing that their size and aspect ratio are getting smaller and decrease, respectively as air flow rate increases. The largest goethite particle obtained is about 1,500 nm in length and 150 nm in diameter.
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Bora Jeong(정보라),Myeung-jin Lee(이명진),Bora Ye(예보라),Seung-Yeop Chun(전승엽),Taewook Kim(김태욱),Hong-Dae Kim(김홍대) 한국에너지기후변화학회 2021 한국에너지기후변화학회 학술대회 Vol.2021 No.5
Regulation of air pollution (e.g., EURO 6, TIER 3) has been strengthened in many jurisdictions due to the occurrence of problems such as particulate matter (PM). At present, selective catalytic reduction (SCR) is the most effective method to control NOX emissions. Industrial V2O5-WO3/TiO2 catalysts (usually containing 0.5–3wt% V2O5 and 5–10wt% WO3) exhibit high de-NOX efficiency, and excellent resistance to sulfur (SO2) and H2O. Nevertheless, they also have several disadvantages such as high and narrow effective temperature range(300–400°C), and a tendency to oxidize SO2 to SO3. Therefore, SCR catalysts with high de-NOX efficiency at lower operating temperatures are required in order to obtain economic benefits and reduced energy consumption. Typically, silica has a good candidate to improve catalytic properties such as led to generation acid site, specific surface area, thermal stability. In this reason, enhanced the SCR catalyst property by using colloidal silica and glass fiber. The aim of this work, we confirmed the effect of silica on the chemi-physical properties and de-NO<sub>X</sub> efficiency of vanadium based catalyst. These synthesized catalysts were analyzed by BET, TPD, FT-IR and catalytic performances using fixed-bed reactor in the range of 200-450°C.
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