• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.140.2-140.2
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• 2013

Strong metal-support interaction effect is an important issue in determining the catalytic activity for heterogeneous catalysis. In this work, we report the catalytic activity of $Au/TiO_2$, $Au/Al_2O_3$, and $Au/Al_2O_3-CeO_2$ nanocatalysts under CO oxidation fabricated by arc plasma deposition (APD), which is a facile dry process with no organic materials involved. These catalytic materials were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and $N_2$-physisorption. Catalytic activity of the materials has measured by CO oxidation using oxygen, as a model reaction, in a micro-flow reactor at atmospheric pressure. Using APD, the catalyst nanoparticles were well dispersed on metal oxide powder with an average particle size (3~10 nm). As for catalytic reactivity, the result shows $Au/Al_2O_3-CeO_2$ nanocatalyst has the highest catalytic activity among three samples in CO oxidation, and $Au/TiO_2$, and $Au/Al_2O_3$ in sequence. We discuss the effects of structure and metal-oxide interactions of the catalysts on catalytic activity.

• Journal of IKEEE
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• v.15 no.2
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• pp.143-148
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• 2011

MOS (Metal-Oxide Semconductor) devices among the most sensistive of all semiconductors to radiation, in particular ionizing radiation, showing much change even after a relatively low dose. The necessity of a radiation dosimeter robust enough for the working environment has increased in the fields of aerospace, radio-therapy, atomic power plant facilities, and other places where radiation exists. The power MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor) has been tested for use as a gamma radiation dosimeter by measuring the variation of threshold voltage based on the quantity of dose, and a maximum total dose of 30 krad exposed to a $^{60}Co$ ${\gamma}$-radiation source, which is sensitive to environment parameters such as temperature. The gate oxide structures give the main influence on the changes in the electrical characteristics affected by irradiation. The variation of threshold voltage on the operating temperature has caused errors, and needs calibration. These effects can be overcome by adjusting gate oxide thickness and implanting impurity at the surface of well region in MOSFET.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.5
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• pp.282-285
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• 2001

Based on the mass balance of anion and cation fluxes, the parabolic rate constant ($K_p$) of oxide grown during the high-temperature oxidation of metal is theoretically calculated. It is assumed that the diffusion of oxygen anion and metal cation through oxide scale obeys the Fick's 1st law, the growth of oxide is controlled by the diffusion of ions, electrical potential gradient as driving force for diffusion of ions is ignored, and oxidation occurs within an existing oxide layer. Then, the parabolic rate constant can be expressed by $K_p=[2{\rho}_{MmOn}{M^2}_{MmOn}(mD_oC_o{^e}+nD_MC_M{^e})/nm]$.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11b
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• pp.86-91
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• 2005

A metal product obtained from an electrolytic reduction process, possesses less volume and radioactivity than those of the unprocessed spent oxide fuels. The chemical composition of the metal product varies according to the process condition. In this work, a basic study was performed to evaluate the chemical forms of the spent oxide fuel components in an electrolytic reduction process with the operation conditions. One of the most important operation conditions is the cell potential applied for the reduction cell. It is expected that $PU_{2}O_3$ is difficult to reduce even though the cell potential is negative enough to reduce the lithium oxide when the activity of $Li_{2}O$ exceeds 0.003. The reduction of actinide oxides via the reduction of $Li_{2}O$ is assumed to have a greater reduction yield than a direct reduction of the actinide oxides.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.4
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• pp.373-377
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• 2004

We have investigated the electrical characterization of metal-oxide-semiconductor (MOS) capacitors formed on the inductively coupled plasma (ICP) etch-damaged both n- and p-type 4H-SiC. We found that there was an effect of a sacrificial oxidation treatment on the etch-damaged surfaces. Current-voltage and capacitance-voltage measurements of these MOS capacitors were used and referenced to those of prepared control samples without etch damage. It has been found that a sacrificial oxidation treatment can improve the electrical characteristics of MOS capacitors on etch-damaged 4H-SiC since the effective interface density and fixed oxide charges of etch-damaged samples have been found to increase while the breakdown field strength of the oxide decreased and the barrier height at the SiC-SiO$_2$ interface decreased for MOS capacitors on etch-damaged surfaces.

• Nano
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• v.13 no.12
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• pp.1850143.1-1850143.9
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• 2018

Natural biotemplates - such as bacteria, fungi and viruses - are used in nanostructured metal oxide production. The pollen can be found abundantly in nature, and their microcapsules can be easily isolated from the pollen by chemical treatments. To date, pollen microcapsules are mostly used as drug carriers and catalytic agent templates. In the present study, nanoporous-structured nickel oxide is produced using Pistachio pollen microcapsules. The raw pollen, chemically treated pollen and metal-coated pollen were characterized using scanning electron microscopy, Brunauer-Emmett-Teller (BET) surface area analysis, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and X-ray diffraction (XRD) techniques. The natural Pistachio pollen which were procured from Gaziantep, Turkey, are spherical, with a diameter of approximately $23{\mu}m$. The maximum surface area obtained for nickel oxide-coated microcapsules is $228.82m^2/g$. This result shows that Pistachio pollen are an excellent candidate for the production of porous nanostructured materials for supercapacitor electrodes.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.2
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• pp.255-266
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• 2021

Solid-state mechanochemical reduction combined with subsequent melting consolidation was suggested as a technical option for the oxide reduction in pyroprocessing. Ni ingot was produced from NiO as a starting material through this technique while Li metal was used as a reducing agent. To determine the technical feasibility of this approach for pyroprocessing, which handles spent nuclear fuels, thermodynamic calculations of the phase stabilities of various metal oxides of U and other fission elements were made when several alkaline and alkali-earth metals were used as reducing agents. This technique is expected to be beneficial, not only for oxide reduction but also for other unit processes involved in pyroprocessing.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.245-245
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• 2012

Syntheses of oxide supported metal catalysts by wet-chemical routes have been well known for their use in heterogeneous catalysis. However, uniform deposition of metal nanoparticles with controlled size and shape on the support with high reproducibility is still a challenge for catalyst preparation. Among various synthesis methods, arc plasma deposition (APD) of metal nanoparticles or thin films on oxide supports has received great interest recently, due to its high reproducibility and large-scale production, and used for their application in catalysis. In this work, Au and Pt nanoparticles with size of 1-2 nm have been deposited on titania powder by APD. The size of metal nanoparticles was controlled by number of shots of metal deposition and APD conditions. These catalytic materials were characterized by x-ray diffraction (XRD), inductively coupled plasma (ICP-AES), CO-chemisorption and transmission electron microscopy (TEM). Catalytic activity of the materials was measured by CO oxidation using oxygen, as a model reaction, in a micro-flow reactor at atmospheric pressure. We found that Au/$TiO_2$ is reactive, showing 100% conversion at $110^{\circ}C$, while Pt/$TiO_2$ shows 100% conversion at $200^{\circ}C$. High activity of metal nanoparticles suggests that APD can be used for large scale synthesis of active nanocatalysts. We will discuss the effect of the structure and metal-oxide interactions of the catalysts on catalytic activity.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1161-1168
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• 1999

The redox property of oxide materials of the 3rd period transition metals(Cr~Zn), V, Mo, and W was studied with temperature-programmed reduction/temperature-programmed oxidation(TPR/TPO) experiment. The peak temperatures of TPO spectra were equal to or lower than those of TPR spectra. And the peak shapes of TPO spectra were broader than those of TPR ones. The activation energies of TPR/TPO for the oxides of the 3rd period transition metals showed in the range of 33~149 kJ/mol, while for the oxides of V, Mo, and W, they showed relatively higher values. The change of activation energies of TPR/TPO with various metal oxides showed a similar trend to the change of their metal-oxygen bond strengths. The change of activation energies of o-xylene oxidation for various metal oxides was proportional to the difference (${\Delta}E_a$) between the activation energy of TPR and that of TPO. From these results, we concluded that the oxidation of o-xylene over various metal oxide catalysts follows the Mars-van Krevelen mechanism including the surface reduction-oxidation of the metal oxide itself.

• 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.