• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.432-434
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• 2009

Metal nano-wire arrays on Cu-coated seed layers were fabricated by aqueous solution method using sulfate bath at room temperature. The seed layers were coated on Anodic aluminum oxide (AAO) bottom substrates by electrochemical deposition technique, length and diameter of metal nano-wires were dominated by controlling the deposition parameters, such as deposition potential and time, electrolyte temperature. Anodic aluminum oxide (AAO) was used as a template to prepare highly ordered Ni, Fe, Co and Cu multilayer magnetic nano-wire arrays. This template was fabricated with two-step anodizing method, using dissimilar solutions for Al anodizing. The pore of anodic aluminum oxide templates were perfectly hexagonal arranged pore domains. The ordered Ni, Fe, Co and Cu systems nano-wire arrays were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Vibrating Sample Magnetometer (VSM). The ordered Ni, Fe, Co and Cu systems nano-wires had different preferred orientation. In addition, these nano-wires showed different magnetization properties under the electrodepositing conditions.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.3
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• pp.620-631
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• 1996

Bonding of resin to cast alloy has traditionally been provided by mechanical retention. But, chemical bonding methods such as silicoating, tin plating, heat treatment, application of 4-META adhesives, have been developed to overcome the problems of the mechanical bonding methods. Silicoating has been used availaby in fixed prosthodontics, but is also reported to be used in removable prosthodontics. The aim of this study is to measure the tensile bond strength between resin and metal, and compare the effect of the type of metal and the grain size of the aluminum oxide on the bond strength, after metal surface roughening, coating of the opaque resin, and curing of heat-curing resin were performed. The test groups were divided into 4 groups according to the cast alloys and the aluminum oxide particles used. Group 1 : Type 4 gold alloy(DM66) blasted with $$50{\mu}m\;Al_{2}O_3$$ Group 2 : Type 4 gold alloy(DM66) blasted with $$250{\mu}m\;Al_{2}O_3$$, Group 3 : Co-Cr alloy(Nobilium) blasted with $$50{\mu}m\;Al_{2}O_3$$ Group 4 : Co-Cr alloy(Nobilium) blasted with $$250{\mu}m\;Al_{2}O_3$$ * 10 test specimens were made on each group. The specimens were thermocycled, and Instron Universal testing machine was used to measure the tensile bond strength of the finished specimens. The results were as follows : 1. Bond strengths showed that the group of gold alloy blasted with $250{\mu}m$ aluminum oxide particle had higher bond strength, and the group of gold alloy blasted with $50{\mu}m$ aluminum oxide particles had lower bond strength than any of the other groups. 2. Gold alloy had significantly higher bond strength when blasted with $250{\mu}m$ aluminum oxide particles than $50{\mu}m$, but. Co-Cr alloy showed no statistically significant difference between the two particle sizes. 3. When blasted with $50{mu}m$ aluminum oxide particles, Co-Cr alloy showed significantly higher bond strength than gold alloy. And, when blasted with $250{\mu}m$ aluminum oxide particles, gold alloy had significantly higher bond strength than Co-Cr alloy. 4. On the examination of the fractured sites, only the group of Co-Cr alloy blasted with $50{\mu}m$ aluminum oxide particles showed a part of residual opaque resin, but all the samples of the other groups fractured between the resin and the metal.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.144-148
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• 2001

In this study, to improve the color of iron oxide from waste pickling acid at the cold rolling mill, quality control technologies to improve color were investigated. During operation of the spray roaster, the charge amount of waste acid per hour, temperature, and numbers of spray nozzles were investigated. At the admixing process, titanium oxide, silica, and goethite were tested. The color character of iron oxide can be improved by process control of the spray roaster and the admixing process at a pigment factory. Iron oxide from this study is appropriate for use as a colorant of a concrete product.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.212-212
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• 2011

In addition to the catalysts' activity and selectivity, the deactivation of catalysts during use is of practical importance. It is crucial to understand the phenomena of the deactivation to predict the loss of activity during catalyst usage so that the high operational costs associated with catalyst replacement can be reduced. In this study, the activity of Ru catalysts, such as nanoparticles (3~6 nm) and polycrystalline thin film (50 nm), have been investigated under CO oxidation and oxidative/reductive reaction conditions at various temperatures with the ambient pressure X-Ray photoelectron spectroscopy (APXPS). With APXPS, the surface oxides on the catalyst are measured and monitored in-situ. It was found that the Ru film exhibited faster oxidation-and-reduction compared to that of nanoparticles showing mild oxidative-and-reductive characteristics. Additionally, the larger Ru nanoparticles showed a higher degree of oxide formation at all temperatures, suggesting a higher stability of the oxide. These observations are in agreement with the catalytic activity of Ru catalysts. The loss of activity of Ru films is correlated with bulk oxide formation, which is inactive in CO oxidation. The Ru nanoparticle, however, does not exhibit deactivation under similar conditions, suggesting that its surface is covered with a highly active ultrathin surface oxide. Since the active oxide is more stable as nanoparticles than as a film, the nanoparticles showed mild oxidative/reductive behavior, as confirmed by APXPS results. We believe these simultaneous observations of both the surface oxide of Ru catalysts and the reactivity in real time enable us to pinpoint the deactivation phenomena more precisely and help in designing more efficient and stable catalytic systems.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.156-163
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• 2018

High-performance mixed-matrix membranes that comprise both zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were synthesized with a solution casting technique to realize excellent $CO_2/CH_4$ separation. The incorporation of ZIF-8 nanocrystals alone in ODPA-TMPDA polyimide can be used to significantly enhance $CO_2$ permeability compared with that of pure ODPA-TMPDA. Meanwhile, the addition of a GO nanostack alone in ODPA-TMPDA contributes to improved $CO_2/CH_4$ selectivity. Hence, a composite membrane that contains both fillers displays significant enhancements in $CO_2$ permeability (up to 60%) and $CO_2/CH_4$ selectivity (up to 28%) compared with those of pure polymeric membrane. Furthermore, in contrast to the ZIF-8 mixed-matrix membrane, which showed decreased mechanical stability, it was found that the incorporation of GO could improve the mechanical strength of mixed-matrix membranes. Overall, the synergistic effects of the use of both fillers together are successfully demonstrated in this paper. Such significant improvements in the mixed-matrix membrane's $CO_2/CH_4$ separation performance and mechanical strength suggest a feasible and effective approach for potential biogas upgrading and natural gas purification.

• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.46-49
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• 1999

Lithium cobalt oxide cathode for thin-film rechargeable lithium batteries were fablicated by electron-beam evaporation. Annealed lithium cobalt oxide, which was deposited on to stainless steel substrate, showed well-developed (003) planes of the hexagonal structure and potential plateau at $\~3.9 V$. Lithium cobalt oxide thin films had the stoichiometric Li/co ratio at high deposition rates and exhibited high discharge capacity at $15{\AA}/s$. As the annealing temperature increased, discharge capacity increased with maximum value at $700^{\circ}C$, but showed low capacity as a result of reaction with substrate above $700^{\circ}C$. Unuiformity of the lithium and cobalt in the depth profile gave initial capacity loss with charge/discharge performance.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.307.1-307.1
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• 2016

Amorphous zinc tin oxide (ZTO) thin films are being widely studied for a variety electronic applications such as the transparent conducting oxide (TCO) in the field of photoelectric elements and thin film transistors (TFTs). Thin film transistors (TFTs) with transparent amorphous oxide semiconductors (TAOS) represent a major advance in the field of thin film electronics. Examples of TAOS materials include zinc tin oxide (ZTO), indium gallium zinc oxide (IGZO), indium zinc oxide, and indium zinc tin oxide. Among them, ZTO has good optical and electrical properties (high transmittance and larger than 3eV band gap energy). Furthermore ZTO does not contain indium or gallium and is relatively inexpensive and non-toxic. In this study, ZTO thin films were formed by UHV RF magnetron co-sputter deposition on silicon substrates and sapphires. The films were deposited from ZnO and SnO2 target in an RF argon and oxygen plasma. The deposition condition of ZTO thin films were controlled by RF power and post anneal temperature using rapid thermal annealing (RTA). The deposited and annealed films were characterized by X-ray diffraction (XRD), atomic force microscope (AFM), ultraviolet and visible light (UV-VIS) spectrophotometer.

• Journal of Powder Materials
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• v.27 no.4
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• pp.311-317
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• 2020

In this study, the effects of Co content on the microstructure and Charpy impact properties of Fe-Cr-W ferritic/martensitic oxide dispersion strengthened (F/M ODS) steels are investigated. F/M ODS steels with 0-5 wt% Co are fabricated by mechanical alloying, followed by hot isostatic pressing, hot-rolling, and normalizing/tempering heat treatment. All the steels commonly exhibit two-phase microstructures consisting of ferrite and tempered martensite. The volume fraction of ferrite increases with the increase in the Co content, since the Co element considerably lowers the hardenability of the F/M ODS steel. Despite the lowest volume fraction of tempered martensite, the F/M ODS steel with 5 wt% Co shows the highest micro-Vickers hardness, owing to the solid solution-hardening effect of the alloyed Co. The high hardness of the steel improves the resistance to fracture initiation, thereby resulting in the enhanced fracture initiation energy in a Charpy impact test at - 40℃. Furthermore, the addition of Co suppresses the formation of coarse oxide inclusions in the F/M ODS steel, while simultaneously providing a high resistance to fracture propagation. Owing to these combined effects of Co, the Charpy impact energy of the F/M ODS steel increases gradually with the increase in the Co content.

• Journal of Conservation Science
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• v.25 no.4
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• pp.465-471
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• 2009

In this study, the substitution fumigation gases (15% Ethylene Oxide + 85% HFC 134a, 20% Ethylene Oxide + 80% $CO_2$, 99% Sulfuryl Fluoride + 1% Inert Gas) were applied on the metal, pigment, fabric and paper specimen. The result of the fumigation treatment with 15% Ethylene Oxide + 85% HFC 134a (200g/$m^3$, 48hours) is the color changes (${\Delta}E$) of 1st and 2nd Cu specimens showed significant difference as 3.40, 4.17. On the other hand, other specimens except for Cu showed less than 3.0 in chrominance values. The result with 20% Ethylene Oxide + 80% $CO_2$ (150g/$m^3$, 48hours) is that the color changes (${\Delta}E$) of 1st and 2nd specimens were overall less than 3.0 so that color differences were subtle and hardly recognized with naked eyes. So it is proved that the fumigation treatment with Ethylene Oxide 20% + $CO_2$ 80% is relatively stable on materials in this study. In the case of 99% Sulfuryl Fluoride + 1% Inert Gas (50g/$m^3$, 48hours), the color difference of Lead red ($PbO_4$) of pigment was more than 3.0 that was compared with contrast specimens. But chrominance values in the other specimens were less than 3.0 on average.

• Journal of the Korean Magnetics Society
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• v.22 no.1
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• pp.11-14
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• 2012

The composites of expanded graphite oxide and magnetic nanoparticle (Ni and Co) were synthesized by using simple chemical method. From the raw material natural graphite, the expanded graphite was fabricated using sulfuric acid and $1^{st}$ heat treatment at $600^{\circ}C$ for 1 hour. The expanded graphite was changed to expanded graphite oxide by 2nd heat treatment at $1050^{\circ}C$ for 15 sec and chemical oxidation. The expanded graphite oxide/1-methyl-2-pyrrolidone solution reacts with the magnetic nanoparticle to form a magnetic graphite oxide composite. These graphite-based materials were characterized by x-ray diffractometer, Raman spectroscopy, transmission electron microscope, and vibration sample magnetometer. We expect that these results of this paper were become basis research of graphite oxide composite.