• Korean Journal of Materials Research
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• v.11 no.6
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• pp.465-471
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• 2001

The effect of sintering condition on the mechanical properties and leachability of polydispersed ceramic core body made by gel-casting process in aqueous medium have been investigated. The polydispersed ceramic slip that has low viscosity($\leq$1000cP, at 1000cP (at $50sec^{-1}$ ) and high solid loading(50vo1%) was obtained. The green bodies were fabricated through casting and gelation at room temperature followed by drying at $25^{\circ}C$for 48hrs under relative humidity of 80%. Crack-free green body was successfully fabricated through the above process. The strength at room temperature, apparent bulk density, and shrinkage of the ceramic core body increased propotionally with increasing sintering temperature(1100~150$0^{\circ}C$). However, porosity of the ceramic core body showed relatively low vague. Leaching rate of sintered core body increased with increasing porosity of the sintered body, and was significantly dependent upon the concentration of alkali caustic solution at the same leaching temperature.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.751-755
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• 2005

Fibrous $Al_2O_3-(m-ZrO_2)/t-ZrO_2$ composites having core/shell structure were fabricated by multi-extrusion process. The effect o volume fraction between core ($Al_2O_3-(m-ZrO_2)$) and shell ($t-ZrO_2$ was investigated to understand the relationship between microstructure and material properites, in which the volume fractions of core and shell were varied as 40:60, 50:50 and 60:40. The material properties o hardness and bending strength were increased as the volume fraction of core was increased, and their maximum values were about 1320 Hv and 750MPa, respectively. However, as the volume fraction of core increased, the values of relative density and fracture toughness were decreased from 97.1 to $96.5\%$ and from $6.5MPa{\cdot}m^{1/2}$ to $5.7MPa{\cdot}m^{1/2}$, respectively.

• Journal of Sensor Science and Technology
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• v.28 no.4
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• pp.225-230
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• 2019

$Au@TiO_2$ core-shell decorated rGO nanocomposite (NC) was prepared using a simple solvothermal method followed by heat treatment for gas sensor application. The crystal structure and morphology of the composites were characterized by X-ray powder diffraction and transmission electron microscopy, respectively. The $NO_2$ sensing response of the $Au@TiO_2/rGO$ NC was tested at operating temperatures from $250^{\circ}C$ to $500^{\circ}C$, and was compared with those of the bare rGO and $Au@TiO_2$ core-shell NPs. The $Au@TiO_2/rGO$ NC-based sensor showed a far higher response than the rGO or $Au@TiO_2$ core-shell based sensors, with the maximum response detected when the operating temperature was $400^{\circ}C$. This improved response was due to the high rGO gas absorption capability for $NO_2$ gas and the catalytic effect of $Au@TiO_2$ core-shell NPs in oxidizing $NO_2$ to $NO_3$.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.1
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• pp.93-101
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• 1992

The purpose of this study was to evaluate the effectiveness of core materials and luting agents on the retention of full veneer gold crown. The core materials used in this study was dental amalgam, and composite resin, and the luting agents were zinc phosphate cement, polycarboxylate cement, and glass ionomer cement. The obtained results were as follows. 1. In full veneer gold crown supported by composite resin core, the crown retention with zinc phosphate cement was the highest of all. 2. In full veneer gold crown supported by amalgam core, the crown retention was shown no statistical difference by luting agent. 3. There was no statistical difference in the crown retention between the full veneer gold crown supported by composite resin core and dental amalgam core.

• Korean Journal of Materials Research
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• v.26 no.1
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• pp.17-21
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• 2016

Pt@Cu/C core-shell catalysts were successfully prepared by impregnation of a carbon support with copper precursor, followed by transmetallation between platinum and copper. The Pt@Cu/C core-shell catalysts retained a core of copper with a platinum surface. The prepared catalysts were used for hydrogen production through catalytic dehydrogenation of decalin for eventual application to an onboard hydrogen supply system. Pt@Cu/C core-shell catalysts were more efficient at producing hydrogen via decalin dehydrogenation than Pt/C catalysts containing the same amount of platinum. Supported core-shell catalysts utilized platinum highly efficiently, and accordingly, are lower-cost than existing platinum catalysts. The combination of impregnation and transmetallation is a promising approach for preparation of Pt@Cu/C core-shell catalysts.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.93-93
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• 2013

In recent years, multifunctional ternary nitride thin films have received extenstive attention due to its versatility in many applications. In particular, noble metal based ternary nitride thin films showed a promising properties in the application of Multifunctional heating resistor films because its good electrical properties and excellent resistance against oxidation and corrosion. In this study, we prepared multifunctional noble metal based ternary nitride thin films by atomic layer deposition (ALD) and plasma-enhanced ALD (PEALD) method. ALD and PEALD techniques were used due to their inherent merits such as a precise composition control and large area uniformity, which is very attractive for preparing multicomponent thin films on large area substrate. Here, we will demonstrate the design concept of multifunctional noble metal based ternary thin films. And, the relationship between microstructural evolution and electrical resistivity in noble metal based ternary thin films will be systemically presented. The useful properties of noble metal based ternary thin films including anti-corrosion and anti-oxidation will be discussed in terms of hybrid functionality.

• Journal of Powder Materials
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• v.23 no.6
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• pp.409-413
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• 2016

Electrical wire explosion in liquid media is a promising method for producing metallic nanopowders. It is possible to obtain high-purity metallic nanoparticles and uniform-sized nanopowder with excellent dispersion stability using this electrical wire explosion method. In this study, Ni-Fe alloy nanopowders with core-shell structures are fabricated via the electrical explosion of Ni-Fe alloy wires 0.1 mm in diameter and 20 mm in length in de-ionized water. The size and shape of the powders are investigated by field-emission scanning electron microscopy, transmission electron microscopy, and laser particle size analysis. Phase analysis and grain size determination are conducted by X-ray diffraction. The result indicate that a core-shell structured Ni-Fe nanopowder is synthesized with an average particle size of approximately 28 nm, and nanosized Ni core particles are encapsulated by an Fe nanolayer.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2333-2337
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• 2012

We report the synthesis and thermal annealing of Si-core/ZnO-shell nanorods using a two-step process comprising the metal-assisted electroless etching of Si and the sputter deposition of ZnO. Transmission electron microscopy and X-ray diffraction analysis showed that the cores of the annealed core-shell nanorods were single crystal diamond cubic-type Si, whereas the shells of the annealed core-shell nanorods were single crystal wurtzite-type ZnO. The PL spectra of Si nanorods consisted of a broad red emission band and a weaker blue emission band. The major emission band of Si nanorods was shifted from 700 nm (in the red region) to 440 nm (in the violet region) by ZnO coating. The violet emission of the core-shell nanorods was enhanced in intensity considerably by annealing in an oxidizing atmosphere. The origin of the PL enhancement by annealing is also discussed.

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.217-217
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• 2017

• Proceedings of the Korean Magnestics Society Conference
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• 2016.11a
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• pp.202-202
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• 2016