• Journal of the Korean Ceramic Society
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• v.35 no.6
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• pp.610-618
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• 1998

Alumina were added to ceria based ceramic powders upto 9.7 vol% and composite powders were sprayed by plasma spraying process in order to improve the mechanical properties such as hardness fracture tough-ness and thermal shock resistance. The ceria based coating sprayed without alumina has the typical colum-nar and lamellar structure. Alumina addition has lowered the amount of columnar and lamellar sturcture Added alumina was segreagated in the grain boundary and grain of ceria based crystal accompanied with pore. The maximum value of density and the minimum value of porosity were observed at the sprayed coating with 4.8 vol% alumina. The hardness fracture toughness and thermal shock resistance were increased with alumina addition. The improvement of mechanical properties of plasma sparyed ceria based coatings result-ed from the disapperance of the columnar and lamellar sturcture by addition of alumina.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.658-659
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• 2006

Magnetron sputtered TiN, (Ti, Al)N and TiN/(Ti, Al)N multilayer coatings grown on cemented carbide substrates have been characterized by using electron probe microanalysis (EPMA), X-ray diffraction (XRD), scanning electron spectroscopy (SEM), nanoindentation, scratcher and cutting tests. Results show that TiN coating is bell mouth columnar structures, (Ti, Al)N coating is straight columnar structures and the modulation structure has been formed in the TiN/(Ti, Al)N multilayer coating. TiN/(Ti, Al)N multilayer coating exhibited higher hardness, better adhesion with substrate and excellent cutting performance compared with TiN and (Ti, Al)N coating.

• Journal of the Korean housing association
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• v.27 no.2
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• pp.43-51
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• 2016

The purpose of this study was to search the architectural forms including the residence plan and wooden structure and the measuring unit in building sites named Bang in Gyeong_Ju, the capiatal of Silla dynasty. It includes the following three historic sites: JaMaeJung-ji, the east district of HwangLyong-sa (S1E1) and InWang-dong historic site. Especially, the data from excavating and studying the east district of HwangLyong-sa were very precious and meaningful. The results were as follows: 1) There are individual characteristics at the sites of JaMaeJung-ji, the east district of HwangLyong-sa and InWang-dong. 2) It is assumed that the builldings of the east district of HwangLyong-sa had most various types of plan and various types of wooden structures. 3) There were various types of wooden structures like as symmetrical or asymmetrical style, regular columnar or irregular columnar style and a third purlin location or a forth purlin location. 4) This study also showed there's a high probability that buildings at Bang sites had been built by the Tang dynaty scale. In Silla dynasty, there was similar tendency to BackJe Dynasty in the way that measuring unit changed according to the times.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.181.2-181.2
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• 2015

Sputtering is one of the most popular physical deposition methods due to their versatility and reproducibility. Synthesis of Cr thin films by DC magnetron sputtering using glancing angle deposition (GLAD) has been reported. Chromium thin films have been prepared at two different working pressure($2.0{\times}10-2$, 30, $3.3{\times}10-3torr$) on Si-wafer substrate using magnetron sputtering with glancing angle deposition (GLAD) technique. The thickness of Cr thin films on the substrate was adjusted about 1 mm. The electrical property was measured by four-point probe method. For the measurement of density in the films, an X-ray reflectivity (XRR) was carried out. The sheet resistance and column angle increased with the increase of glancing angle. However, nanohardness and density of Cr thin films decreased as the glancing angle increased. The measured density for the Cr thin films decreased from 6.1 to 3.8 g/cc as the glancing angle increased from $0^{\circ}$ to $90^{\circ}$ degree. The low density of Cr thin films is resulted from the isolated columnar structure of samples. The evolution of the isolated columnar structure was enhanced at the conditions of low sputter pressure and high glancing angle. This GLAD technique can be potentially applied to the synthesis of thin films requiring porous and uniform coating such as thin film catalysts or gas sensors.

• Korean Journal of Materials Research
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• v.28 no.3
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• pp.159-165
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• 2018

In order to increase the efficiency of the sputtering method widely used in thin film fabrication, a dc sputtering apparatus which supplies both high frequency and magnetic field from the outside was fabricated, and cobalt thin film was fabricated using this apparatus. The apparatus can independently control the applied voltage, the target-substrate distance, and the target current, which are important parameters in the sputtering method, so that a stable glow discharge is obtained even at a low gas pressure of $10^{-3}$ Torr. The fabrication conditions using the sputtering method were mainly performed in $Ar+O_2$ mixed gas containing about 0.6 % oxygen gas under various Ar gas pressures of 1 to 30 mTorr. The microstructure of Co thin films deposited using this apparatus was examined by electron diffraction pattern and X-ray techniques. The magnetic properties were investigated by measuring the magnetization curves. The microstructure and magnetic properties of Co thin films depend on the discharge gas pressure. The thin film fabricated at high gas pressure showed a columnar structure containing a large amount of the third phase in the boundary region and the thin film formed at low gas pressure showed little or no columnar structure. The coercivity in the plane was slightly larger than that in the latter case.

• Journal of the Korean Ceramic Society
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• v.29 no.6
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• pp.419-430
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• 1992

Fabrication possibility of low-shrinkage alumina without oxidation and wetting agent was presented on the basis of observation about oxidation behavior, microstructure and physical characteristics of such reaction agents free Al2O3-Al system. The composition less than Al 10w/o where Al can act as a sintering agent for Al2O3 was excluded. Under the condition of present experiments oxidation of Al2O3-Al system was dependent not on holding time but mainly on oxidation temperature. In thes case of Al powder not comminuted effectively during powder mixing of Al2O3-Al, columnar structure which would act as a hindrance to the densification during sintering developed more during oxidation with higher Al contents, and which made the fabrication of low-shrinkage Al2O3 ceramics impossible. If Al powder was comminuted effectively due to co-mixed Al2O3 characteristics, densification was improved because of no columnar structure and made the fabrication of sintered body with -2.7% dimensional change and 81% relative density possible. As a result, it is possible to fabricate dense low-shrinkage Al2O3 ceramics without oxidation and wetting agent under conditions such as smaller particle size of Al, Al contents below 50v/o, higher green density of Al2O3-Al compact and the use of Al2O3 powder used for high-density ceramics.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.11-18
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• 2004

Asymmetric rolling, in which the circumferential velocities of the upper and lower rolls are different, can give rise to intense plastic shear strains and in turn shear deformation textures through the sheet thickness. The ideal shear deformation texture of fcc metals can be approximated by the <111> // ND and $\{001\}<110>$ orientations, among which the former improves the deep drawability. The ideal shear deformation texture for bcc metals can be approximated by the Goss $\{110\}<001>\;and\;\{112\}<111>$ orientations, among which the former improves the magnetic permeability along the <100> directions and is the prime orientation in grain oriented silicon steels. The intense shear strains can result in the grain refinement and hence improve mechanical properties. Steel sheets, especially ferritic stainless steel sheets, and aluminum alloy sheets may exhibit an undesirable surface roughening known as ridging or roping, when elongated along RD and TD, respectively. The ridging or roping is caused by differently oriented colonies, which are resulted from the <100> oriented columnar structure in ingots or billets, especially for ferritic stainless steels, that is not easily destroyed by the conventional rolling. The breakdown of columnar structure and the grain refinement can be achieved by asymmetric rolling, resulting in a decrease in the ridging problem.

• Journal of Ocean Engineering and Technology
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• v.26 no.6
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• pp.27-32
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• 2012

The effects of reheating during welding on the microstructure and impact toughness of weld metal in 25% Cr super duplex stainless steels were investigated. Using different heat inputs, weld metals with different reheated regions were obtained. This showed that, depending on the reheating temperature, the microstructure in the reheated region was quite different from that of the as-deposited microstructure. When reheated into the ${\gamma}+{\alpha}$ temperature range, fine intragranular austenite was formed in the as-deposited columnar structure. However, when reheated above the ${\alpha}$ solvus temperature range, most of the columnar structure disappeared and fine equiaxed austenite and ferrite were formed. Because of the larger amount of fine austenite in the reheated region, a higher impact toughness was obtained in the weld metal with a higher amount of reheated region.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.11a
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• pp.173-177
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• 1998

In this paper, we reported an outbreak of fire hazard of ballast for fluorescent lamp. The surface structure and composition of ballast coil analyzed by using metallurgical microscope, scanning electron microscope(SEM) and energy dispersive x-ray spectroscopy(EDX). The surface of molten mark appeared columnar structure and void. EDX analysis indicated that the molten mark spectra were composed not only of the corresponding original spectra but also of several new lines.

• Fire Science and Engineering
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• v.14 no.3
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• pp.1-5
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• 2000

In this paper, we analyzed the fire hazard of the ballast for fluorescent lamp used as the indoor lighting. In the result of being analyzed the ballast wire by stereo microscope, many melting points were discovered, it was impossible to judge a cause with the naked eye. In the Thermal-deteriorated ballast wire, elongation structure disappeared at above $700^{\circ}$, and it only showed the enlarged appearance of the copper particle. On the metallurgical microscope of short wire, as it was confirmed the regulation of the columnar structure and the void growth at the center of boundary-face, we found that electrical short-circuit generated. Also, it was confirmed the melted part on the analysis using SEM(scanning electron microscope). Not only CuL and Cuk line that is composition factor of copper but also OK line was observed uniformly on the spectra analysis using EDX(energy dispersive x-ray spectroscopy). It means that oxygen took part in reaction at the recombination process.