• Journal of Electrochemical Science and Technology
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• v.5 no.1
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• pp.1-18
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• 2014

Li-air cell is an exotic type of energy storage and conversion device considered to be half battery and half fuel cell. Its successful commercialization highly depends on the timely development of key components. Among these key components, the catalyst (i.e., the core portion of the air electrode) is of critical importance and of the upmost priority. Indeed, it is expected that these catalysts will have a direct and dramatic impact on the Li-air cell's performance by reducing overpotentials, as well as by enhancing the overall capacity and cycle life of Li-air cells. Unfortunately, the technological advancement related to catalysts is sluggish at present. Based on the insights gained from this review, this sluggishness is due to challenges in both the commercialization of the catalyst, and the fundamental studies pertaining to its development. Challenges in the commercialization of the catalyst can be summarized as 1) the identification of superior materials for Li-air cell catalysts, 2) the development of fundamental, material-based assessments for potential catalyst materials, 3) the achievement of a reduction in both cost and time concerning the design of the Li-air cell catalysts. As for the challenges concerning the fundamental studies of Li-air cell catalysts, they are 1) the development of experimental techniques for determining both the nano and micro structure of catalysts, 2) the attainment of both repeatable and verifiable experimental characteristics of catalyst degradation, 3) the development of the predictive capability pertaining to the performance of the catalyst using fundamental material properties. Therefore, under the current circumstances, it is going to be an extremely daunting task to develop appropriate catalysts for the commercialization of Li-air batteries; at least within the foreseeable future. Regardless, nano materials are expected to play a crucial role in this field.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.157-160
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• 2007

The catalyst layer of a proton exchange membrane (PEM) fuel cell is a mixture of polymer, carbon, and platinum. The characteristics of the catalyst layer play critical role in determining the performance of the PEM fuel cell. This research investigates the role of catalyst layer composition using a Central Composite Design (CCD) experiment with two factors which are Nafion content and carbon loading while the platinum catalyst surface area is held constant. For each catalyst layer composition， polarization curves are measured to evaluate cell performance at common operating conditions, Electrochemical Impedance Spectroscopy (EIS), and Cyclic Voltammetry (CV) are then applied to investigate the cause of the observed variations in performance. The results show that both Nafion and carbon content significantly affect MEA performance. The ohmic resistance and active catalyst area of the cell do not correlate with catalyst layer composition, and observed variations in the cell resistance and active catalyst area produced changes in performance that were not significant relative to compositions of catalyst layers.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.2
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• pp.199-208
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• 2000

In this study we investigated on the possibility of platinum and silver catalysts as de-NOx catalyst for activity test of supported metal oxide catalysts. the study was performed with the change of amount of metal and support types. The catalyst was prepared the activity of alumina supported silver catalyst produced by dry and wet impregnation method respectively and the resistance of sulfur for optimum supported silver catalyst,. As a result the activity of alumina supported platinum catalyst was showed at low temperature region but the case of silver catalyst activated at high temperature region. So we finally chose alumina supported silver catalyst as de-NOx target catalyst because alumina supported catalyst showed higher activity than alumina supported platinum catalyst.

• Journal of Environmental Science International
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• v.19 no.9
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• pp.1093-1101
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• 2010

In this study, the indirect correlation of degradation characteristic and flow behavior in the de-NOx catalyst is investigated experimentally. The inner flow behavior in the de-NOx catalyst is varied from turbulent flow to laminar flow and the degradation of the de-NOx catalyst is remarkably affected by the inner flow. The degradation of the catalyst is increased in the upstream region near the inlet because injected turbulent flow enhances the adhesion of ash particle on the catalyst surface. The degradation of the catalyst near the inlet also governs the overall efficiency of the catalyst. The amount of adhered ash particles on the catalyst surface decreases as they progress downstream. This is due to the inner flow transition from turbulent flow to laminar flow.

• Journal of computational fluids engineering
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• v.16 no.2
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• pp.66-74
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• 2011

The SCR catalyst in coal-fired power plant is eroded by the collision of fly ash on the catalyst surface. However the erosion of SCR catalyst by the collision of fly ash has not been fully studied, especially in terms of fluid dynamics. Hence, in the present study, we focus on the gas and solid flows inside the SCR catalyst duct and their consequent effect on the erosion characteristics. For this purpose, computational fluid dynamics is applied to investigate the two-phase flows and to evaluate the erosion rate for different flow and particle injection conditions. Also, the erosion rate and pressure drop of commonly used square shape are compared with equilateral triangle and hexagon shapes. The pressure drop of SCR catalyst is increased when SCR catalyst surface area per unit volume increases. The erosion rate of SCR catalyst is enhanced when the particle velocity, mass flow rate of particle, particle diameter and cell density of SCR catalyst are increased. From the results, the pressure drop and erosion rate at the catalyst surface can be minimized by reducing cell density of SCR catalyst to decrease particle velocity and number of particle impacts.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.7
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• pp.101-108
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• 2010

Domestic three-way catalyst satisfies exhaust gas conversion efficiency or pressure drop etc. but doesn't satisfy thermal durability. Thermal stress analysis for three-way catalyst was performed based on experimental temperature distribution. Thermal safety of three-way catalyst was estimated by safety factor. Aspect ratio variable had the most significant effect on thermal stress. Thickness variable had the least significant effect on thermal stress. Optimal conditions for premature failure prevention of three-way catalyst were as follows : (1) aspect ratio of three-way catalyst : 0.6:1 (2) 2.84mm thick (3) silicon nitride. The safety of Taguchi-optimized three-way catalyst were 4.7 times higher than that of existent three-way catalyst.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1255-1260
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• 2004

Decomposition of ozone at room temperature was investigated comparatively with commercial monolithic ozone decomposition catalyst (ODC, $MnO_2$) and monolithic photo catalyst ($TiO_2$). The effects of residence time, UV (ultraviolet) light dependence and ozone concentration on the conversion was presented. UV ray was irradiated using BLB (black light blue) lamp ($315{\sim}400$ nm), supplied with a constant intensity in the reactor. The concentration of ozone in the square-shape reactor can be controlled by combining the DBD (dielectric barrier discharge) reactor with an AC high voltage supply system. The catalytic performance, in presence of UV irradiation did not show significant changes for $MnO_2$ catalyst. $TiO_2$ catalyst was the different case, which showed higher decomposition activity in presence of UV irradiation. Deactivation of catalyst detected by real-time ozone monitor for 120 hours with a constant inlet ozone concentration.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.137-141
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• 2004

Many monopropellant thrusters use a catalyst for decompose the propellant, hydrazine. The catalyst directly affects the thruster performances and lifetime. Therefore, it is important to confirm that the catalyst is suitable for our thrusters. Until 2002, we used She1l405 catalyst, for satellite RCS thrusters, and H-IIA and M-V launch vehicle upper-stage RCS thrusters. In 2002, however, Shell Chemical Inc. ceased manufacturing She1l405 catalyst and transferred the product to AEROJET, where it was renamed S405. We subsequently investigated the characteristics of AEROJET's S405 catalyst and SOLVAY's KC12GA catalyst, (SOLVAY is a Belgian chemical company, and KC12GA is used for ASTRIUM's thruster) and conducted thruster firing tests using the new catalysts. After conducting, we confirm that the KC12GA catalyst was suitable for our thrusters, and decided to use KC12GA for two satellite programs.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.272-274
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• 2008

A development of hydrazine decomposition catalyst for monopropellant thruster has been performed by Korea Aerospace Research Institute(KARI). The goal of this development is to product a catalyst showing the equivalent performance with space-proven catalysts. Catalyst production and physical/chemical analysis were conducted by Chonnam National University and the analysis result was compared with the result of other catalysts and our own specification. Using the developed prototype catalyst, short firing test was performed in a reactor to verify basic performance of catalyst. After the successful reactor test, hot firing tests were carried out in atmospheric and vacuum condition using 5N thruster to verify durability and safety of catalyst. In this paper, the catalyst development status will be presented.

• Journal of the Korean institute of surface engineering
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• v.46 no.4
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• pp.175-180
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• 2013

Carbon nanofilaments (CNFs) could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under thermal chemical vapor deposition system. Ni powders were used as the catalyst for the formation of the CNFs. During the initial deposition stage, the initiation of the CNFs on the Ni catalyst was investigated. The geometries of the as-grown CNFs on Ni catalyst were strongly dependent on the size and/or the shape of Ni catalyst. Small size catalyst (<150 nm in diameter) gives rise to the unidirectional growth of the CNFs. On the other hand, large size catalyst (150~500 nm), the bidirectional growth of the CNFs could be observed. Particularly, the well faceted parallelogram-shaped Ni catalyst could give rise to the bidirectional growth of the CNFs having the symmetrically opposite direction. Eventually, these bidirectional growths of CNFs were understood to form the well-developed carbon microcoils (CMCs). Based on these results, the optimal shape and the size of the Ni catalyst to form the CMCs were discussed.