• Journal of Mechanical Science and Technology
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• v.16 no.2
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• pp.270-278
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• 2002

In order to reduce the exhaust emissions of a spark ignition engine, it is important not only to improve the catalyst conversion efficiency, but also to directly reduce the engine-out exhaust emissions during a cold starting of the engine and warm up periods. The purpose of this study is to evaluate feasibility of a glow plug for an early fuel evaporator. In order to promote atomization, gasoline is injected on the glow plug with room temperature(20$\^{C}$) and high temperature(250$\^{C}$). To analyze the spray behavior characteristics, a PMAS is used to measure the SMD and the dropsize distribution of an impinging spray and a free spray. Results show that the evaporation rate of the impinging spray on the high temperature surface of the glow plug was higher than that of the free spray on the room temperature surface.

• Transactions on Semiconductor Engineering
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• v.1 no.1
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• pp.9-13
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• 2023

An AlGaN/GaN heterojunction-based hydrogen sensor with SnO₂ nanoparticles/Pd catalyst layer was fabricated for room-temperature hydrogen detection. The fabricated sensor exhibited unstable drift in standby current when it was operated at room temperature. The instability in the sensing signal was dramatically improved when the sensor was operated under UV illumination.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.674-678
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• 2020

In this study, a Pd/TiO2 catalyst which oxidized H2 at room temperature without an additional energy source was prepared. And a specific surface area of TiO2 as a support was not proportional to H2 oxidation reaction performance of Pd/TiO2 catalyst. In addition La2O3 was added to Pd/TiO2 catalyst in order to evaluate the performance effect due to the change of catalysts physical properties. A Pd/La2O3-TiO2 was prepared by adding different amounts of La2O3 to TiO2 and CO chemisorption analysis was performed. Compared to the conversion rate (14% at 0.5% H2) of the Pd/TiO2(G) catalyst, the Pd/La2O3-TiO2 catalyst showed 74% which was improved by more than five times. It was found that the larger the metal dispersion of Pd as an active metal is, the more favorable to H2 oxidation reaction is. However, when the added La2O3 amount exceeded 10%, the catalyst performance decreased again. Finally, it was concluded that the physical properties of the Pd/La2O3-TiO2 catalyst have a dominant influence on the catalytic activity until 0.3~0.5% of injected H2 concentrations and the catalyst reaction rate was controlled by substance transfer from 1% or more concentrations of H2.

• Journal of Adhesion and Interface
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• v.2 no.4
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• pp.1-9
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• 2001

Silicone sealants are composed of polymer, plasticizer, crosslinker, catalyst and filler. Types and compositions of components are effected on sealant performances. In recent, use of alkoxy type silicone sealant increased due to environmental advantage. In this study, we investigated effects of component types and ratios on one-part room temperature curable alkoxy type silicone sealant preparation and adhesion properties. Alkoxy type silicone sealants were prepared with various PDMS (polydimethylsiloxane) viscosities. In addition, the effect of plasticizer, crosslinkers, and catalyst on sealant obtained from by mixture of PDMS viscosities of 20000 and 80000 was investigated. Reaction temperature on change of mixing time was observed, and then proper crosslinking systems were found. Adhesion (properties) of silicone sealants were measured. In the sealants preparation, stable reaction was achieved by adjusting composition variance ratio in the sealant mixture temperature below $40^{\circ}C$. The adhesion properties of sealant differ from substrate composition. The order of adhesion strength was glass/glass > glass/aluminum > aluminum/aluminum system. The elongation of sealant was increased as polymer viscosity and plasticizer content increased. The strength was increased as crosslinker and plasticizer decreased, while catalyst increased.

• Journal of the Korean Chemical Society
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• v.53 no.6
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• pp.727-730
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• 2009

A series of quinoxaline derivatives were efficiently synthesized in excellent yield using phosphomolybdic acid as a catalyst. The advantages of present methods are ambient reaction temperature, simplicity of operation, high atom economy, recyclability of HPA catalyst and ecofriendly nature of reaction medium.

• Journal of the Korean Chemical Society
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• v.57 no.4
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• pp.425-431
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• 2013

Oxidation of glutamic acid is performed in aqueous acid media at $30^{\circ}C$ under the kinetic condition [glutamic acid]$_T{\gg}[Cr(VI)]_T$. Effect of combination of micellar catalyst (SDS, TX-100) and promoter (PA, bpy, phen) has been studied. Among the promoters phen accelerates the reaction most in aqueous media. But the rate acceleration is small in the case. Combination of promoter and catalyst produces much better result. Maximum rate enhancement occurs in presence of the combination of bpy and SDS.

• Journal of Sensor Science and Technology
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• v.20 no.3
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• pp.168-171
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• 2011

Porous 3C-SiC(pSiC) samples with different pore diameters were prepared from poly crystalline N-type 3C-SiC by electrochemical anodization. The pSiC surface was chemically modified by the sputtering of Pd and Pt nano-particles as a hydrogen catalyst. Changes in resistance were monitored with hydrogen concentrations in the range of 110 ppm - 410 ppm. The variations of the electrical resistance in the presence of hydrogen demonstrated that Pd and Pt-deposited pSiC samples have the ability to detect hydrogen at room temperature. Regardless of the catalyst, the 25 nm pore diameter samples showed good response and recovery properties. However, the 60 nm samples showed unstable and slow response. It was found that the pore size affects the catalyst reaction and consequently, results in changes of the sensitivity to hydrogen.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.237-240
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• 2002

Micro catalytic reactors are alternative propulsion device that can be used on a nano satellite. When used with a monopropellant, $H_2O_2$, a micro catalytic reactor needs only one supply system as the monopropellant reacts spontaneously on contact with catalyst and releases heat without external ignition, while separate supply lines for fuel and oxidizer are needed for a bipropellant rocket engine. Additionally, $H_2O_2$ is in liquid phase at room temperature, eliminating the burden of storage for gaseous fuel and carburetion of liquid fuel. In order to design a micro catalytic reactor, an appropriate catalyst material must be selected. Considering the safety concern in handling the monopropellants and reaction performance of catalyst, we selected hydrogen peroxide at volume concentration of 70% and perovskite redox catalyst of lantanium cobaltate doped with strondium. Perovskite catalysts are known to have superior reactivity in reduction-oxidation chemical processes. In particular, lantanium cobaltate has better performance in chemical reactions involving oxygen atom exchange than other perovskite materials. In the present study, a process to prepare perovskite type catalyst, $La_{0.8}Sr_{0.2}CoO_3$, and measurement of its propellant decomposition performance in a test reactor are described.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.425-429
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• 2014

Pd on charcoal particles were prepared by wet impregnation to develop commercial catalyst for aerobic benzyl alcohol oxidation. Especially, one of room temperature ionic liquids, [Hmim][$PF_6$], was used as an effective solvent in the synthesis to improve the metal dispersion of the catalysts. Among the Pd/Charcoal with various Pd concentrations, 7.5 wt% catalyst showed the higher catalytic activity and stability. Moreover, Ag was used as a promoter with various ratios in catalyst preparation. Under identical reaction conditions, the catalyst with 9 : 1 of Pd and Ag weight ratios was most active due to higher metal dispersion.

• Journal of Hydrogen and New Energy
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• v.12 no.1
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• pp.65-73
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• 2001

Carbon nanotubes were prepared by catalytic decomposition of $CH_4$ using Ni-MgO catalyst at various temperatures. $H_2$ effect on crystallinity and morphology during the synthesis of carbon nanotubes was investigated. The crystallinity and morphology were characterized by SEM, TEM, XRD, TGA, and Raman spectroscopy. In addition, the hydrogen adsorption properties were evaluated by PCT measurement in a hydrogen pressure range between 1 and 120 bar. The optimal synthesis temperature of carbon nanotubes was elevated in the presence of $H_2$, although significant difference of carbon nanotube morphology was not found. It is believed that hydrogen served as self-cleaner mops the amorphous carbon on the catalyst surface. It is proved that the carbon nanotubes have multi-walled structure, short length with a outer diameter of 20 ~40nm and open tips after elimination of the catalyst. The amount of hydrogen adsorbed in carbon nanotubes is increased as the pressure of hydrogen is increased and reaches 1.3 wt % under the hydrogen pressure of 120 bar at room temperature.