• 한국결정성장학회지
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• 제9권4호
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• pp.377-380
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• 1999

Erbium (Er) doped $LiNbO_{3}(Er:LiNbO_{3})$ single crystal fibers were grown free of creacks along the c-axis by micro-pulling down method. The $Er^{3+}$ concentration was distributed homogeneously along the growth axis. The samples for optical characterization were cut from as-grown single crystal fibers and polished. When the 980nm light was incident on the sample, upconversion phenomena were observed at the green range of wavelength 510~570nm. In addition, the intensity of upconversion was remarkably increased by increasing the concentration of $Er_{2}O_{3}$ dopant in as-grown $Er:LiNbO_{3}$ crystals.

• Journal of Korean Vacuum Science & Technology
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• 제3권1호
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• pp.74-78
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• 1999

For a high efficient field emission display (FED), the specific vacuum conditions below 10-7 Torr should be required. However, because the FED has the geometrical restriction due to its micro size, the thin film getters can be proposed for chemical pumping as a way to reduce impurity gases in the panel. The thin film getters, developed by employing the coating of new materials such as NI or Pt on getter surface, can be used without any activation process and show the enhanced sorption characteristics. Especially, using the Zr (1${\mu}{\textrm}{m}$) thin film getters with the Pt surface layer, the significant gettering for various active gases could be achieved from 9$\times$10-5 Torr to 1$\times$10-6 Torr or below. this good sorption properties is mainly contributed to the surface coating layer which shows the catalytic effect for gas dissociation and protects the getter materials against oxidation.

• 열처리공학회지
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• 제11권1호
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• pp.27-34
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• 1998

Effects of different heat treatments on microstructure and damping capacity of Cu-55%Mn alloy were investigated to find an optimum heat treatment condition for a maximum damping capacity. The alloy showed the high level of damping capacity in case of the aging at 375 and $400^{\circ}C$. This is ascribed to the FCC${\rightarrow}$FCT martensitic transformation and microstructural changes from mottled to tweed band type. The damping capacity had a maximum value of 0.33 in logarithmic decrement when the alloy was aged at $375^{\circ}C$ for 14 hours followed by 20 times of thermal cycling between room temperature and $250^{\circ}C$. The refinement of tweed structure by thermal cycling is thought to be responsible for the highest damping capacity.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.978-979
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• 2006

In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve both full density and grain refinement of metallic powders with least grain growth. ECAP (Equal channel angular pressing) was used for the powder consolidation. We investigated the consolidation, plastic deformation and microstructure evolution behavior of the metallic powders during ECAP using an experimental method. It was found that high mechanical strength could be achieved effectively as a result of the well bonded powder contact surface during ECAP process of gas atomized Al-Si powders.

• Journal of Korean Vacuum Science & Technology
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• 제2권1호
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• pp.25-31
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• 1998

The reliability of fluorine doped silicon oxide (SiOF) films for intermetal dielectrics in multilevel interconnections of ultra-large scale integrated circuits (ULSIs) is investigated. SiOF films were deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECRPECVD) using H-free source gases, i.e., SiF4 and O2. The effect of post plasma treatment on the moisture absorption and dielectric properties of SiOF films was carried out I terms of air exposure time, The reliability test of Cu/TiN/SiOF/Fi specimen was carried out in terms of temperature by rapid thermal annealing (RTA) in N2 ambient. After O2 plasma treatment,, no appreciable peak directly related to moisture absorption was detected. The capacitance-voltage (C-V) characteristics of the O2 plasma treated SiOF film showed that the film remained to hold the sound dielectric properties even after boiling treatment. The Cu/TiN/SiOF/Si system was found to be reliable up to $600^{\circ}C$.

• Journal of Korean Vacuum Science & Technology
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• 제2권1호
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• pp.43-48
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• 1998

The effect of mcirostructure on the electrical properties of yttria stabilized zirconia (YSZ) was analyzed by modeling layer arrangements and mixed phase structure. The YSZ thin films were deposited by RF magnetron sputtering using 30mol% YSZ and 8 mol% YSZ targets with yttrium pellets on porous alumina substrates. The structure, composition and electricla properties of the YSZ films were investigated as functions of sputtering conditons and layer arrangements by XRD, TEM, XPS and acimpedance spectroscopy. The results showed that the triple palyered YSZ films had highermicrohardness, lower compressive stress state and higher ionic conductivity by one order than single and double layered YSZ films. However, sputtered YSZ films have low conductivity compared to YSZ pellets or doctor bladed YSZ thin plates. These results were probably due to the influence of insulating alumina substrates, impractical for most stacking geometries and inductance induced by relatively long platinum, lead wire on YSZ conductivity.

• Transactions on Electrical and Electronic Materials
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• 제12권1호
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• pp.1-6
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• 2011

This paper summarized concept, manufacture and results of the micro-tubular solid oxide fuel cells (SOFCs). The cells were fabricated by co-sintering of extruded micro-tubular anode support and electrolyte coating layer, and then additional cathode coating. The cells showed quick voltage rising within 1 minute, and the electrochemical performances were closely related to the balance of fuel utilization and performance loss. And a thermal-fluid simulation model was also reported in combination with the electrochemical evaluation results on the GDC-based micro-tubular SOFCs.

• Corrosion Science and Technology
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• 제22권2호
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• pp.73-89
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• 2023

Due to continuous promotion of green alternatives to toxic petrochemicals by government policies, research efforts towards the development of green corrosion inhibitors have intensified recently. The objective of the current work was to develop novel green and sustainable corrosion inhibitors derived from 4-aminoantipyrine to effectively prevent corrosion of mild steel in corrosive environments. Gravimetric methods were used to investigate corrosion inhibition of 4-((furan-2-ylmethylene)amino)antipyrine (FAP) and 4-((pyridin-2-ylmethylene)amino)antipyrine (PAP) for mild steel in 1 M HCl. FAP and PAP were subjected to quantum chemical calculations using density functional theory (DFT). DFT was used to determine the mechanism of mild steel corrosion inhibition using inhibitors tested in HCl. Results demonstrated that these tested inhibitors could effectively inhibit mild steel corrosion in 1.0 M HCl. At 0.0005 M, these inhibitors' efficiencies for FAP and PAP were 93.3% and 96.5%, respectively. The Langmuir adsorption isotherm was obeyed by these inhibitors on the mild steel surface. Values of adsorption free energies, ΔG^o_ads, revealed that FAP followed chemical and physical adsorptions.

• Advances in materials Research
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• 제8권1호
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• pp.47-73
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• 2019

Joining of Mg/Ti hybrid structures by welding for automotive and aerospace applications has attracted great attention in recent years due mainly to its potential benefit of energy saving and emission reduction. However, joining them has been hampered with many difficulties due to their physical and metallurgical incompatibilities. Different joining processes have been employed to join Mg/Ti, and in most cases in order to get a metallurgical bonding between them was the use of an intermediate element at the interface or mutual diffusion of alloying elements from the base materials. The formation of a reaction product (in the form of solid solution or intermetallic compound) along the interface between the Mg and Ti is responsible for formation of a metallurgical bond. However, the interfacial bonding achieved and the joints performance depend significantly on the newly formed reaction product(s). Thus, a thorough understanding of the interaction between the selected intermediate elements with the base metals along with the influence of the associated welding parameters are essential. This review is timely as it presents on the current paradigm and progress in welding and joining of Mg/Ti alloys. The factors governing the welding of several important techniques are deliberated along with their joining mechanisms. Some opportunities to improve the welding of Mg/Ti for different welding techniques are also identified.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.513.2-513.2
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• 2006