• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3660-3665
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• 2011

CO-tolerant PtMo/C alloy electrocatalyst was prepared by a colloidal method, and its electrocatalytic activity toward CO oxidation was investigated. Electrochemical study revealed that the alloy catalyst significantly enhanced catalytic activity toward the electro-oxidation of CO compared to Pt/C counterpart. Cyclic voltammetry suggested that Mo plays an important role in promoting CO electro-oxidation by facilitating the formation of active oxygen species. The effect of Mo on the electronic structure of Pt was investigated using X-ray absorption spectroscopy to elucidate the synergetic effect of alloying. Our in-depth spectroscopic analysis revealed that CO is less strongly adsorbed on PtMo/C catalyst than on Pt/C catalyst due to the modulation of the electronic structure of Pt d-band. Our investigation shows that the enhanced CO electrooxidation in PtMo alloy electrocatalyst is originated from two factors; one comes from the facile formation of active oxygen species, and the other from the weak interaction between Pt and CO.

• Design & Manufacturing
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• v.10 no.2
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• pp.34-38
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• 2016

In this paper, a transversely isotropic behavior of AZ31 Mg alloy produced by equal-channel angular pressing (ECAP) process was investigated through tensile test and microstructure observation. The effects of initial ECAP pass number on the anisotropic behavior and mechanical properties of the Mg alloy are evaluated after conventional direct extrusion test, which are carried out at a temperature of $200^{\circ}C$. As a result of the tensile test in three directions ($0^{\circ}$, $45^{\circ}$, and $90^{\circ}$ to the extrusion direction of the sheet) at room temperature, elongation of as-extruded AZ31 alloy(ECAP for 0 pass) showed an unusual anisotropic behavior depending on the extrusion direction although the yield strength and tensile strength are similar to the ECAPed AZ31 alloy. After ECAP for 4 passes at $200^{\circ}C$, microstructural observations of ECAPed magnesium alloy showed a significant grain refinement, which is leading to an equiaxed grain structure with average size of $2.5{\mu}m$. The microstructures of the extruded billet are observed by the use of an electron back-scattering diffraction (EBSD) technique to evaluate of the influence on the grain refinement during extrusion process and re-crystallization mechanism of AZ31 Mg alloy.

• 한국전기화학회:학술대회논문집
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• 2002.10a
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• pp.3-4
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• 2002

• Proceedings of the Korean Magnestics Society Conference
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• 1995.05a
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• pp.90-91
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• 1995

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.275-276
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• 2011

• Journal of Welding and Joining
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• v.27 no.3
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• pp.80-84
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• 2009

The Plasma Transferred Arc (PTA) overlay welding method is lately introduced as one of the most useful surface overlay method of the engine component. In this paper, the overlay welding on the SNCrW heat resisting alloy was conducted by the PTA overlay welding process using the super alloy powder. The characteristics of the overlay layers were investigated through the metallurgical and abrasive test. Experimental results showed that the overlay on the SNCrW heat resisting alloy surface was successfully made without hot cracking. The friction wear characteristics of the Co-base Stellite 6 overlayer were most superior. However the abrasive wear characteristics were most inferior in the Co-base Stellite 6 overlayer.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.204-210
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• 2016

This study analyzed the amount of displacement of window wipers according to pressure by using finite element analysis (FEA) with KS standards for aluminum alloy window wipers manufactured by die-casting method. The product design was changed over four steps considering the die-casting process to achieve strength greater than that of the conventional steel window wiper. According to the FEA results, the strength of final aluminum alloy window wiper improved by 55% over that of a steel window wiper, and the weight of the former was less by approximately 45%. Therefore, there is the possibility of module downsizing for driving motor capacity. Further, the cost competitiveness improved, and the manufacturing process of aluminum alloy window wipers was simplified.

• Journal of Korea Foundry Society
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• v.22 no.4
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• pp.160-166
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• 2002

The structure and properties of Fe-29Ni-17Co alloy which had been melted using induction furnace in air atmosphere and than electroslag-remelted were investigated. The oxygen content was reduced to 0.03% when the ingot was refined from $0.09{\sim}0.12%$ of that air melted. The amounts of spheroidal oxides inclusions and gas porosities of ingot were markedly reduced by the ESR process. CTE of ESR ingot contained small amount of oxides and porosities was found to be lower than that of AIM ingot, and tensile properties of ESR ingot and plate were found to be superior than that of AIM ingot and plate.

• Journal of Power System Engineering
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• v.18 no.1
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• pp.106-111
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• 2014

This article describes effect of post heat treatment on wear characteristics of thermally sprayed Co-based self-flux alloy coating. Co-based self-flux alloy coatings were deposited on steel substrates using a flame spray process. Post heat treatments were carried out at 800, 900, 1000 and $1100^{\circ}C$ for 30min in a vacuum chamber. For analysis of effect of post heat treatment on mechanical properties, wear test and hardness test were performed for post heat-treated coating specimen. Microstructures of heat treated coating layer and wear track were examined using SEM and EDS. Wear loss and hardness became lower with increasing post heat treatment temperature.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.40-44
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• 2014

The purpose of this paper is to investigate polarization characteristics of WC-based alloy coatings in alkaline solution. The coatings were fabricated with WC-CrC-Ni, WC-Co-Cr and WC-Co composite powders by HVOF process. Corrosion tests of coatings and substrate were carried out using potentiostat/galvanostat at solution with pH 8 and pH 13. Corrosion potential(Ecorr) and corrosion current density(Icorr) could be studied from polarization curve, and corrosion behavior was analyzed by SEM and EDS. WC-Co-Cr coating and WC-CrC-Ni coating showed more favorable anti-corrosion characteristics than WC-Co coating and substrate at solution with pH 8 and pH 13.