• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.369-373
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• 2020

A hydrogen sensor was fabricated by utilizing a bundle of metal oxide nanostructures whose growth positions were selectively controlled by utilizing graphene, which is a carbon of atomic-unit thickness. To verify the reducing ability of graphene, it was confirmed that the multi-composition metal oxide V₂O₅ was converted into VO₂ on the graphene surface. Because of the role of graphene as a reducing catalyst, it was confirmed that ZnO and MoO₃ nanostructures were grown at high density only on the graphene surface. The fabricated gas sensor showed excellent sensitivity.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.3
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• pp.189-198
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• 2008

Cooperative effects of Rh, Ce and Zr added to Fe-based oxide mediums were investigated using temperature programmed redox reaction (TPR/TPO) and isothermal redox reaction in the view point of hydrogen storage and release. As the results of TPR/TPO, Rh was a sale additive to remarkably promote the redox reaction on the medium as evidenced by the lower highest peak temperature, even though its addition was to accelerate deactivation of the mediums due to sintering. On the other hand, Ce and Zr additives played an important role to suppress deactivation of the medium in repeated redox cycles. The medium co-added by Rh, Ce and Zr (FRCZ) exhibited synergistic performance in the repeated isothermal redox reaction, and the amount of hydrogen produced in the water splitting step at 623 K was highly maintained at ca. $17\;mmol{\cdot}g^{-1}-Fe$ during three repeated redox cycles.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1702-1708
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• 1995

Owing to the serious problem of hydrocarbon fuel such as environmental pollution, the development of alternative fuel is very urgent. To adopt hydrogen to the internal combustion engine, a solenoid-drive type in-cylinder injection system was constructed. The injection system was installed to the single cylinder research engine, and the engine performance and the emission of citric oxide were tested upon the fuel-air equivalence ratio and the spark timing. In the case of in-cylinder injection system, hydrogen is injected after the intake valve is close, so it is possible to operate the engine without the back fire and the fall of its volumetric efficiency. In the region of the fuel-air equivalence ratio below 0.5, hydrogen and air aren't well mixed and the thermal efficiency is lowered, so the nozzle should be designed to inject hydrogen uniformly into the combustion chamber. In the region of the fuel-air equivalence ratio above 0.7,the fuel-air mixture burns very fast and the amount of citric oxide emission increases rapidly, so the spark timing should be retarded as compared with MBT.

• Journal of Powder Materials
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• v.21 no.6
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• pp.422-428
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• 2014

In this study, the reduction kinetics and behaviors of oxides in the water-atomized iron powder have been evaluated as a function of temperature ranging $850-1000^{\circ}C$ in hydrogen environment, and compared to the reduction behaviors of individual iron oxides including $Fe_2O_3$, $Fe_3O_4$ and FeO. The water-atomized iron powder contained a significant amount of iron oxides, mainly $Fe_3O_4$ and FeO, which were formed as a partially-continuous surface layer and an inner inclusion. During hydrogen reduction, a significant weight loss in the iron powder occurred in the initial stage of 10 min by the reduction of surface oxides, and then further reduction underwent slowly with increasing time. A higher temperature in the hydrogen reduction promoted a high purity of iron powder, but no significant change in the reduction occurred above $950^{\circ}C$. Sequence reduction process by an alternating environment of hydrogen and inert gases effectively removed the oxide scale in the iron powder, which lowered reduction temperature and/or shortened reduction time.

• Journal of the Korean institute of surface engineering
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• v.56 no.6
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• pp.412-419
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• 2023

Anion exchange membrane electrolysis is considered a promising next-generation hydrogen production technology that can produce low-cost, clean hydrogen. However, anion exchange membrane electrolysis technology is in its early stages of development and requires intensive research on electrodes, which are a key component of the catalyst-system interface. In this study, we optimized the pressure conditions of the hot-pressing process to manufacture cobalt oxide electrodes for the development of a high uniformity and high adhesion electrode production process for the oxygen evolution reaction. As the pressure increased, the reduction of pores within the electrode and increased densification of catalytic particles led to the formation of a uniform electrode surface. The cobalt oxide electrode optimized for pressure conditions exhibited improved catalytic activity and durability. The optimized electrode was used as the anode in an AEMWE single cell, exhibiting a current density of 1.53 A cm^-2 at a cell voltage of 1.85 V. In a durability test conducted for 100 h at a constant current density of 500 mA cm^-2, it demonstrated excellent durability with a low degradation rate of 15.9 mV kh^-1, maintaining 99% of its initial performance.

• Journal of Physiology & Pathology in Korean Medicine
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• v.25 no.2
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• pp.294-299
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• 2011

The purpose of this study is to investigate effects of Red Ginseng-Ejung-tang (RE) on nitric oxide (NO) and hydrogen peroxide production in RAW 264.7 mouse macrophages induced by lipopolysaccharide (LPS). Cell viability was measured by modified MTT assay. NO production was measured by Griess reagent assay. Hydrogen peroxide production was measured by dihydrorhodamine 123 (DHR) assay. RE did not show cell toxicity against RAW 264.7 for 24 hr incubation at the concentrations of 10, 25, 50, 100, and $200{\mu}g/mL$ in RAW 264.7. RE significantly inhibited NO production for 24 hr incubation at the concentrations of 10, 25, 50, and $100{\mu}g/mL$ in RAW 264.7 (P < 0.05). RE significantly inhibited the LPS-induced production of NO for 24 hr incubation at the concentrations of 10, 25, 50, and $100{\mu}g/mL$ in RAW 264.7 (P < 0.05). RE significantly inhibited the LPS-induced production of hydrogen peroxide for 16, 24, 40, 48, 64, and 72 hr incubation at the concentrations of 50, 100, and $200{\mu}g/mL$ in RAW 264.7 (P < 0.05). These results suggest that RE has anti-inflammatory property related with its inhibition of NO and hydrogen peroxide production in LPS-induced macrophages.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.11
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• pp.996-1000
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• 2005

Experimental results are presented for the degradation of 3 nm-thick gate oxide $(SiO_2)$ under both Negative-bias Temperature Instability (NBTI) and Hot-carrier-induced (HCI) stresses using P and NMOSFETS, The devices are annealed with hydrogen or deuterium gas at high-pressure $(1\~5\;atm.)$ to introduce higher concentration in the gate oxide. Both interface trap and oxide bulk trap are found to dominate the reliability of gate oxide during electrical stress. The degradation mechanism depends on the condition of electrical stress that could change the location of damage area in the gate oxide. It was found the trap generation in the gate oxide film is mainly related to the breakage of Si-H bonds in the interface or the bulk area. We suggest that deuterium bonds in $SiO_2$ film are effective in suppressing the generation of traps related to the energetic hot carriers.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.174-180
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• 2006

The eutectic Mg-23.5%Ni alloy was casted by melting and solidification. The powders of Mg-23.5%Ni and (Mg-23.5%Ni)-10% iron oxide were prepared by mechanical grinding of casted Mg-Ni alloy and casted Mg-Ni alloy+oxide, respectively. As milling time increases, hydriding and dehydriding rates of Mg-Ni and Mg-Ni-oxide alloy powders increase. The additions of iron oxide to Mg-Ni alloy and Mg-Ni-oxide increase hydriding rates and slightly decrease dehydriding rates.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.2
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• pp.109-115
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• 2007

Solar energy conversion to hydrogen was carried out via a two-step thermochemical water splitting using metal oxide redox pair. To simulate the solar radiation, a 7 kW short arc Xe-lamp was used. Partially reduced iron oxide and cerium oxide have the water splitting ability, respectively. So, $Fe_3O_4$ supported on $CeO_2$ was selected as the active material. $Fe_3O_4/CeO_2$(20 wt/80 wt%) was prepared by impregnation method, then the active material was washcoated on the ceramic honeycomb monolith made of mullite and cordierite. Oxygen was released at the reduction step($1673{\sim}1823\;K$) and hydrogen was produced from water at lower temperature($873{\sim}1273\;K$). The result demonstrate the possibility of the 2-step thermochemical water splitting hydrogen production by the active material washcoated monolith. And hydrogen and oxygen was produced separately without any separation process in a monolith installed reactor. But the SEM and EDX analysis results revealed that the support used in this experiment is not suitable due to the thermal instability and coating material migration.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.429-436
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• 2012

Mg and Mg-based alloys are regarded as strong candidate hydrogen storage materials since their hydrogen capacity exceeds that of known metal hydrides. One of the approaches to improve kinetic is addition of metal oxide. In this paper, we tried to improve the hydrogenation properties of Mg-based hydrogen storage composites. The effect of transition metal oxides, such as $Nb_2O_5$ on the kinetics of the Magnesium hydrogen absorption kinetics was investigated. $MgH_x$-5wt.% $Nb_2O_5$ composites have been synthesized by hydrogen induced mechanical alloying. The powder fabricated was characterized by X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (Fe-SEM), Energy Dispersive X-ray (EDX), BET and simultaneous Thermo Gravimetric Analysis / Differential Scanning Calorimetry (TG/DSC) analysis. The Absorption / desorption kinetics of $MgH_x$-5wt.% $Nb_2O_5$ (type I and II) are determined at 423, 473, 523, 573 and 623 K.