• Bulletin of the Korean Chemical Society
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• 제18권11호
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• pp.1175-1179
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• 1997

The adsorption of oxygen on ZnO was monitored by measuring the capacitance of two contacting crystals which have depletion layers originated from the interaction between oxygen and ZnO at 298 K-473 K. An admission of oxygen to the sample induced an irreversible increase in the depth and the amount of adsorbed oxygen was less than 0.001 monolayer in the experimental condition. The relation between pressure of oxygen and variation of the depth was tested from the view point of Langmuir or Freundlich isotherm. Using Hall effect measurement and kinetic experiment, a model equation on the adsorption process was proposed. From the results, it was suggested that oxygen adsorption depended on the rate of electron transfer from ZnO to oxygen while the amount of adsorbed oxygen was kinetically restricted by the height of surface potential barrier.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.354-361
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• 2022

In a direct methanol fuel cell system (DMFC), one of the drawbacks is methanol crossover. Methanol from the anode passes through the membrane and enters the cathode, causing mixed potential in the cell. Only Pt-based catalysts are capable of operating as cathode for oxygen reduction reaction (ORR) in a harsh acidic condition of DMFC. However, it causes mixed potential due to high activity toward methanol oxidation reaction of Pt. To overcome this situation, developing Pt-based catalyst that has methanol tolerance is significant, by controlling reactant adsorption or reaction kinetics. Pt/C decorated with phosphate ion was prepared by modified polyol method as cathode catalyst in DMFC. Phosphate ions, bonded to the carbon of Pt/C, surround free Pt surface and block only methanol adsorption on Pt, not oxygen. It leads to the suppression of methanol oxidation in an oxygen atmosphere, resulting in high DMFC performance compared to pristine Pt/C.

• 한국가시화정보학회지
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• 제14권1호
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• pp.51-56
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• 2016

Oxygen is a key factor in aerobic reactions and most biological activities. Visualization of oxygen distribution of a chemical process or biological system has been a very challenging object despite of its significance and potential impact. To monitor and visualize the spatial distribution of oxygen concentration, various techniques such as electro-chemical probe, polarographic electrode, LIF(laser-induced fluorescence) and so on have been introduced. Oxygen planar optode which utilizes the oxygen quenching of fluorescence light is one of the currently available methods for time-resolved visualization of oxygen distribution on a planar surface. In this study, we utilized VisiSens oxygen planar optode system to visualize the spatial distribution of oxygen concentration on leaves of Korean azalea. As a result, temporal variation of oxygen concentration distribution caused by respiratory activity of the leaf could be quantitatively monitored.

• Nuclear Engineering and Technology
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• 제30권2호
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• pp.128-139
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• 1998

The effect of UO$_2$ powder property and oxygen potential on characteristics of sintered UO$_2$-Gd$_2$O$_3$ fuel pellets has been investigated. Two types of powder, mixture of AUC-UO$_2$ and Gd$_2$O$_3$powders (type I) and mixture of ADU-UO$_2$ and Gd$_2$O$_3$powders (type II), have been prepared, pressed, and sintered at 168$0^{\circ}C$ for 4 hours. Four sintering atmospheres with different mixing ratios of $CO_2$to H$_2$ gas ranging from 0 to 0.3 have been used. UO$_2$-Gd$_2$O$_3$ fuel has lower sintered density than UO$_2$ fuel, and the density drop is larger for powder type I than for powder type II. As the oxygen potential increases, the sintered density of UO$_2$-2wt% Gd$_2$O$_3$pellets increases but that of UO$_2$-10wt% Gd$_2$O$_3$ pellets decreases. It is found that pores are newly formed in UO$_2$-10wt% Gd$_2$O$_3$ pellets in accordance with the decrease in density. The grain size of UO$_2$-Gd$_2$O$_3$ fuel increases and a short range G4 distribution becomes homogeneous as the oxygen potential increases. A long range ed distribution and grain structure are inhomogeneous for powder type II. The lattice parameter of (U,Gd)O$_2$solid solution decreases linearly with Gd$_2$O$_3$ content. The dependence of UO$_2$-Gd$_2$O$_3$fuel characteristics on powder type and sintering atmosphere have been discussed.

• Applied Biological Chemistry
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• 제28권4호
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• pp.271-277
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• 1985

소량의 시료로서 미토콘드리아 및 SMP호흡의 속도론적 연구에 이용할 수 있는 적하수은전극 polarograph를 제작하여 그 성능, 실험조건 및 응용성을 검토하였다. 산소의 제 2단계환원이 일어나는 전위 (약 -1.2 vs SCE)는 막에 결합된 환원성물질의 환원전류로 해석되는 상당한 크기의 잔존전류를 일으키기 때문에 부적절한 것으로 판단되었다. 그러나 산소의 제 1단계환원이 일어나는 -0.4V(vs SCE)하에서는 잔존전류가 관찰되지 않았으며 산소농도의 변화는 정량적으로 추적되었다. 호흡기질의 농도를 충분히 크게 유지하는한 호흡에 의한 용존산소 소모는 O차반응의 처리가 가능하였으며, 그속도 상수와 미토콘드리아 호흡활성간에는 비례관계가 성립되었다. 내냉성이 서로 다른 몇가지 식물조직으로부터 분리한 미토콘드리아의 호흡활성에 미치는 온도효과를 조사하고 호흡활성전이온도를 측정하므로서 제작한 장치의 효용성을 확인하였다.

• 한국세라믹학회지
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• 제49권1호
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• pp.37-42
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• 2012

Mass transport near grain boundary in a magnetite bi-crystal has been estimated at 823 K by finite element method. Mass transport near grain boundary strongly depends on the diffusivities along grain boundary. If grain boundary diffusion has the same oxygen activity dependence as lattice diffusion, there is no mass transport between grains and grain boundary. On the other hand, mass transport between grains and grain boundary is observed in the case that grain boundary diffusion has different oxygen activity dependence.

• 응용화학
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• 제15권1호
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• pp.81-84
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• 2011

Platinum catalyst activity and stability is excellent in terms of fuel cells as a catalyst here. Although it is widely used, to compensate for the high price issue non-precious fuel cell catalysts are being developed. In this study, Co/PANi/CNT composite and non-precious as a catalyst for oxygen reduction was applied. Polyaniline on the interaction between cobalt and the oxygen reduction reaction and the structural characteristics observed in the impact and heat treatment was carried out according to the improved catalytic performance. Potential range is oxygen reduction reaction 0.55 V to 0.78 V(vs. NHE) after pyrolysis. Through this study, Co /PANi/CNT composites as a potential catalyst for fuel cells were non-precious.

• Transactions on Electrical and Electronic Materials
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• 제7권2호
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• pp.58-61
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• 2006

Carefully designed ZnO nanowire-film hybrid nanostructure, composed of a bottom ZnO film, ZnO nanowire arrays, and a top ZnO film, was consecutively fabricated by adjusting the supersaturation conditions using a metal-organic chemical vapor deposition (MOCVD) to utilize the vertically aligned ZnO nanowires as the oxygen sensors. The decrease of current flow through ZnO nanowire arrays increasing oxygen pressure showed the high potential for the application of the ZnO hybrid nanostructure to the oxygen sensors. In addition, it was confirmed that the oxygen sensing characteristics of this hybrid nanostructure were attributed to the defects near the surface of the nanowires.

• International Journal of Advanced Culture Technology
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• 제9권2호
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• pp.130-135
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• 2021

Because of the COVID-19 epidemic, many countries have made the obligation to wear masks normal. Wearing masks in public places has become a must. At present, wearing a mask to participate in sports makes it very common. People seek to gain health through exercise but ignore the potential respirato-ry health threat. That is, wearing a mask will cause a decrease in oxygen content in the body. This neg-ative impact becomes more prominent as the wear-ing time and oxygen consumption increase. To pro-tect people from viruses and enjoy a healthy life. This paper proposes a breathing pattern that im-proves blood oxygen saturation while wearing a jogging mask and walking. Namely, shouting breathing pattern. Use a pulse oximeter to measure the blood oxygen saturation of running at different speeds and compare the normal breathing pattern and the shouting breathing pattern. The results show that the shouting breathing pattern has a sig-nificant improvement in the blood oxygen satura-tion of low-speed walking and medium-speed jog-ging.

• 전기학회논문지
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• 제56권8호
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• pp.1450-1454
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• 2007

This paper presents a microfabricated Clark-type sensor which exactly can measure dissolved oxygen in the cell containing solution. We designed, fabricated, and characterized a microfabircated Clark-type oxygen sensor for measuring dissolved oxygen. The microfabricated oxygen sensor consists of 3-electrodes on a glass substrate, a FEP (Fluorinated ethylene propylene) oxygen-permeable membrane, and PDMS (Polydimethylsiloxane) reservoir for storing sample solution. Thin-film Ag/AgCl was employed as a reference electrode and its durability was verified by obtaining a stable open circuit potential for 2 hours against a commercial Ag/AgCl electrode and a stable cyclic voltammetry curve. Selectivity, response time, and linearity of the fabricated oxygen sensor were also verified well by cyclic voltammetry and amperometry depending. The fabricated oxygen sensor showed a 90% response time of 40sec and an excellent linearity with a correlation coefficient of 0.994.