• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.383-384
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• 2007

The nano and micro-sized $ZnGa_2O_4$ phosphor were prepared by precipitation method and solid-state method. The luminescence, formation process and structure of phosphor powders were investigated by means of XRD, SEM and PL. The result of XRD analysis showed that $ZnGa_2O_4$ spinel structure was formed at as-prepared in the case of precipitation method. However, micro-sized phosphor was required high heating treatment to have a satisfactory spinel structure. The CL intensity of nano-sized phosphor was about 4-fold higher than that of micro-sized phosphor. The emission spectra of all $ZnGa_2O_4$ phosphor show a self activated blue emission band at around 420 nm in the wide range of 300~600 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.303-307
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• 2000

The crystal structure of ZnS fabricated by gas-liquid phase reaction was obtained by XRD and refined by RIETAN near R$_{wp}$ factor 10%. The increasement of HCP phase depended on extra H$_2$S gas and the lattice parameter and crystalline size changed by the relative ratio of multiphase. Using ZnS of the different multiphase ratio and crystalline size, sintered ZnS:Cu, Al green phosphor and the CL property resulted optimum luminescence in the range of 91~94% and 150~190$\AA$, respectably, FCC/HCP ratio and crystalline size. As changing of structure ratio, the reason of different luminescence property is now studying. As well as, after XRD pattern of TiO$_2$powder fitted by RIETAN and the structure factor using MEED method simulated about each atom of (002) plane. Additionally, we proposed RIETAN and MEED were the methods of the study of luminescence mechanism for many phosphor materials.s.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.521-524
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• 2010

Low loss perovskite niobates and tantalates have been placed on a short list of functional materials for future technologies. In this study, we fabricated Ag(Ta,Nb)$O_3$ thick films on the $Al_2O_3$ substrates by the screen printing method. The Ag(Ta,Nb)$O_3$ powders were fabricated by the mixed oxide method. The sintering temperature and time were $1150^{\circ}C$ and 2 hrs, respectively. The results of XRD analysis showed that the specimens employed in this study had the pesudo cubic structure. The dielectric permittivity and loss tangent of the films have been characterized from 1 kHz to 1 MHz. Also the dielectric permittivity and loss tangent were measured from 303 K to 393 K. The electrical properties of the film are also discussed.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.588-593
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• 2012

In this study, selective catalytic reduction (SCR) reaction was performed using liqufied petroleum gas (LPG) as a reductant for removing NOx. The catalysts were manufactured with different amounts of Cu and Fe supported on HZSM-5 in order to remove NOx. The NOx conversion ratio was studied with changing the temperature and the catalyst amount. The catalysts were manufactured by calcination with flowing the ambient air at $500^{\circ}C$ for three hours. Cupper of 1~4 wt% and iron of 0.5~2 wt% were supported on HZSM-5 of which Si/Al ratio were 80. According to the reaction results, the catalyst which Cu of 3 wt% supported on HZSM-5 showed the highest conversion rate. XRD, XPS, and TPR analysis were also performed for the characterization of catalysts.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.951-954
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• 2004

본 논문에서는 DLC(Diamond-like Carbon) 박막과 기판 사이에 금속층을 포함하는 DLC 박막의 기계적 특성을 분석하였다. 금속층은 sputtering법을 사용하고, DLC 박막은 PECVD법을 사용하여 각각 중착하였다. 티타늄(Ti), 니켄(Ni), 크롬(Cr)을 각 중간 금속층으로 사용한 후 DLC 박막과 실리콘(Si) 기판 간의 기계적 특성을 분석하였다. 각 막의 두께는 FE-SEM으로 확인하였고, DLC 박막의 구조 평가는 Raman spectrometer를 사용하여 분석하였으며, 각 금속층과 DLC 박막의 표면 상태는 AFM을 이용하여 확인하였다. XRD 분석을 통하여 박막의 격자분석을 하였고, SIMS(secondary ion mass spectrometry) 분석을 통하여 DLC 박막의 depth Profile을 확인하였다.

• International Journal of Ocean System Engineering
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• v.2 no.2
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• pp.82-91
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• 2012

Fillet welding is widely used in the assembly of ships and offshore structures. The T-joint configuration is frequently reported to experience fatigue damage when a marine structure meets extreme loads such as storm loads. Fatigue damage is affected by the magnitude of residual stresses on the weld. Recently, many shipping registers and design guides have required that the fatigue strength assessment procedure of seagoing structures under wave-induced random loading and storm loading be compensated based on the effect of residual stresses. We propose a computational procedure to analyze the residual stresses in a T-joint. Residual stresses are measured by the X-ray diffraction (XRD) method, and a 3-D finite element analysis (FEA) is performed to obtain the residual stress profile in the T-joint. The proposed finite element model is validated by comparing experiments with computational results, and the characteristics of the residual stresses in the T-joint are discussed.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.102-102
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• 2009

The purpose of this study is to establish the predictive equation of transversal residual stress at the thick weldment of large container ship. In order to do it, the variables used for this study were restraint degree, yield strength of base material, thickness of weldment and welding heat input. Here, the level of restraint degree at the thick weldment of container ship having the various welding sequence was calculated using FEA. From the result, the h-type specimen was designed to simulate the level of restraint degree at the actual weldment of containership. With H-type test specimen designed, the effect of the variables on the distribution of transversal residual stress at the weldment in a container ship was evaluated using the comprehensive FEA. Based on the results, the predictive equations of mean value and the distribution of transverse residual stress in each location of residual stress were established using dimensional analysis and multiple-regression method. The validation of predictive equations was verified by comparing with measured results by XRD in the actual weldment of the ship.

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.674-682
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• 2010

Fe-fullerene/$TiO_2$ composite photocatalysts were prepared with titanium (IV) n-butoxide (TNB) by a sol-gel method. The samples were characterized by scanning electron microscopy (SEM), Transmission electron microscope (TEM), specific surface area (BET), X-ray diffraction analysis (XRD) and energy dispersive X-ray spectroscopy (EDX). The photocatalytic activities were evaluated by the photocatalytic degradation of methylene blue (MB) solution. XRD patterns of the composites showed that the Fe-fullerene/$TiO_2$ composite contained a typical single and clear anatase phase. The surface properties shown by SEM present a characterization of the texture on Fe-fullerene/$TiO_2$ composites and showed a homogenous composition in the particles for the titanium sources used. The EDX spectra for the elemental identification showed the presence of C and Ti with strong Fe peaks for the Fe-fullerene/$TiO_2$ composite. From the photocatalytic results, the excellent activity of the Fe-fullerene/$TiO_2$ composites for degradation of methylene blue under UV light irradiation could be attributed to both the effects between photocatalytic reaction of the supported $TiO_2$, decomposition of the organometallic reaction by the Fe compound and energy transfer effects such as electron and light of the fullerene.

• Korean Journal of Metals and Materials
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• v.56 no.11
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• pp.829-834
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• 2018

Although magnesium-based alloys are attractive materials for hydrogen storage applications, their activation properties, hydrogenation/dehydrogenation kinetics, thermodynamic equilibrium parameters, and degradation characteristics must be improved for practical applications. Further, magnesium poses several risks, including explosion hazard, environmental pollution, insufficient formability, and industrial damage. To overcome these problems, CaO-added Mg alloys, also called Eco-Mg (environment-conscious Mg) alloys, have been developed. In this study, $Eco-MgH_x$ composites were fabricated from Mg-CaO chips by hydrogen-induced mechanical alloying in a high-pressure atmosphere. The balls-to-chips mass ratio (BCR) was varied between a low and high value. The particles obtained were characterized by X-ray diffraction (XRD), and the absorbed hydrogen was quantified by thermogravimetric analysis. The XRD results revealed that the $MgH_2$ peaks broadened for the high BCR. Further, PSA results revealed particles size were decreased from $52{\mu}m$ to $15{\mu}m$.

• Bulletin of the Korean Chemical Society
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• v.21 no.7
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• pp.679-684
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• 2000

The Sr2Co0.5Nb(Ta)0.5O4 and Sr3CoNb(Ta)O7 compounds, both with Ruddlesden-Popper structures, have been synthesized by the ceramic method at $1150^{\circ}C$ under atmospheric pressure. The crystallographic structure of the compounds was assigned to the tetr agonal system with space group 14/mmm by X-ray diffraction(XRD) Rietveld refinement. The reduced lattice volume and lattice parameters increased as the Ta with 5d substitutes for the Nb with 4d in the compounds. The Co/Nb(Ta)O bond length has been determined by X-ray absorption spectroscopic(EXAFS/XANES) analysis and the XRD refinement. The CoO6,octahedra were tetragonally distorted by elongation of Co-O bond along the c-axis. The magnetic measurement shows the compounds Sr2Co0.5Nb(Ta)0.5O4 and Sr3CoNb(Ta)O7 have paramagnetic properties and the Co ions with intermediate spin sates between high and low spins in D4h symmetry. All the compounds showed semiconducting behavior whose electrical conductivity increased with temperature up to 1000 K. The electrical conductiviy increased and the activation energy for the conduction decreased as the number of perovskite layers increased in the compounds with chemical formula An+1BnO3n+1.