• Transactions of the Korean hydrogen and new energy society
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• v.21 no.6
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• pp.526-532
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• 2010

The anode may inevitably undergo a number of reduction.oxidation (redox) cycles during solid oxide fuel cells (SOFCs) operation. The re-oxidation of Ni to NiO causes significant mechanical stress to be developed across the anode, which may destroy the integrity of the whole cell. In this study, the redox behavior of Ni-YSZ composite was examined at $800^{\circ}C$ using various characterization techniques.

• Carbon letters
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• v.4 no.3
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• pp.133-139
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• 2003

Carbon/carbon composites are ideal candidates for a number of aerospace applications including structural materials for advanced vehicles, leading edges, structures of re-entry and hypersonic vehicles and propulsion systems. One serious defect for such application of the carbon/carbon composites is their poor oxidation resistance in high temperature oxidizing environments. SiC coating was employed to protect the composites from oxidation. It is mechanically and chemically stable under extreme thermal and oxidative environments, provides good adhesion to the substrate, and offers good thermal shock resistance. The SiC layer on the nozzle machined from the carbon/carbon composites was formed by pack-cementation method. Then, erosion characteristic of SiC coated carbon/carbon nozzle was examined by combustion test using a liquid rocket motor. The erosion rates were measured as function of combustion pressure, ratio of oxygen to fuel, combustion time, density of the composites and geometry of reinforced carbon fibre in the composites. The morphology change of the composites after combustion test was investigated using SEM and erosion mechanism also was discussed.

• Journal of Magnetics
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• v.10 no.4
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• pp.137-141
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• 2005

We confirmed that the improvement in properties of magnetic tunnel junctions prepared by radical oxidation after thermal treatment was mostly resulted from the redistribution of oxygen at the $AIOx/Co_{90}Fe_{10}$ interface. The as-deposited Al oxide barrier was oxygen-deficient but most of it re-oxidized into $Al_2O_3$, the thermodynamically stable stoichiometric phase, through thermal treatment. As a result, the effective barrier height was increased from 1.52 eV to 2.27 eV. On the other hand, the effective barrier width was decreased from 8.2 ${\AA}$ to 7.5 ${\AA}$. X-ray absorption spectra of Fe and Co clearly showed that the oxygen in the CoFe layer diffused back into the Al barrier and thereby enriched the barrier to close to a stoichiometirc $Al_2O_3$ phase. The oxygen bonded with Co and Fe diffused back by 6.8 ${\AA}$ and 4.5 ${\AA}$ after thermal treatment, respectively. Our results confirm that controlling the chemical structures of the interface is important to improve the properties of magnetic tunnel junctions.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.7
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• pp.1027-1035
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• 2019

Objective: The aim of this study was to investigate the effects of aged garlic powder (AGP) on physicochemical characteristics, texture profiles, and oxidative stability of ready-to-eat (RTE) pork patties. Methods: There were five treatment groups: a control; 1% fresh garlic powder (T1); 0.5%, 1%, and 2% AGP (T2, T3, and T4). Pork patties with vacuum packaging were roasted at $71^{\circ}C$ for core temperature, stored at $4^{\circ}C$ for 14 d, and then reheated for 1 min using a microwave. Results: The AGP groups showed a lower the level of lipid oxidation and higher thiol contents than the control and T1. The pH value of the control increased whereas that of aged garlic groups decreased after re-heating process. In addition, the redness significantly increased with increasing level of AGP whereas the redness of the control and T1 decreased after reheating process. T4 added patties improved textural and sensory properties compared to the control. Conclusion: The results of this study suggest that AGP addition to RTE pork patties can improve their sensory characteristics and oxidative stability.

• Journal of Ceramic Processing Research
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• v.20 no.1
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• pp.18-23
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• 2019

Chemical looping combustion (CLC) is a promising carbon capture and storage (CCS) technology whose efficiency and cost primarily relies on the oxygen carrier materials used. In this paper, gadolinium-doped ceria (GDC, Ce0.9Gd0.1O1.95) was added as a promoter to improve the oxygen transfer rate of MgMnO3-δ oxygen carrier materials. Increasing GDC content significantly increased the oxygen transfer rate of MgMnO3-δ-GDC composites for the reduction reaction due to an increase in the surface adsorption of CH4 via oxygen vacancies formed on the surface of the GDC. On the other hand, the oxygen transfer rate for the oxidation reaction decreased linearly with increasing GDC content due to the oxygen storage ability of GDC. Adsorbed oxygen molecules preferentially insert themselves into oxygen vacancies of the GDC lattice rather than reacting with (Mg,Mn)O to form MgMnO3-δ during the oxidation reaction.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.359-370
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• 2009

Arsenic and heavy metals leached out as a result of oxidation of tailings exposed to the surface pose a serious environmental contamination of mine areas. This study investigated how arsenic behavior is controlled by a variety of processes, such as oxidation of sulfides and formation or alteration of secondary minerals, based on mineralogical methods. The study was carried out using the tailing samples obtained from Nakdong mine located in Jeongseongun, Gangwondo. After separating magnetic and non-magnetic minerals using pretreated tailing samples, each mineral sample was classified according to their colors and metallic lusters observed by the stereoscopic microscope. Subsequently, the mineralogical properties were determined using various instrumental analyses, such as x-ray diffractometer (XRD), energy dispersive spectroscopy (EDS), and electron probe micro analyzer (EPMA). The literature review confirmed that various ore minerals were identified in the Nakdong ore deposits. In this study, however, there were observed a few original ore minerals as well as secondary and/or tertiary minerals newly formed as a result of weathering including oxidation. In particular, we did not recognize pyrrhotite which has been known to originally exist in a large abundance, but peculiarly colloform-type iron (oxy)hydroxides were identified, which indicates most of pyrrhotite has been altered by rapid weathering due to its large reactivity. In addition, a secondary scorodites filling the fissure of weathered primary arsenopyrites were identified, and it is speculated that arsenic is immobilized through such a alteration reaction. Also, we observed tertiary iron (oxy)hydroxides were formed as a result of re-alteration of secondary jarosites, and it suggests that the environment of tailing has been changed to high pH from low pH condition which was initiated and developed by oxidation reactions of diverse primary ore minerals. The environmental change is mainly attributed to interactions between secondary minerals and parental rocks around the mine. As a result, not only was the stability of secondary minerals declined, but tertiary minerals were newly formed. As such a process goes through, arsenic which was immobilized is likely to re-dissolve and disperse into surrounding environments.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.30.1-30.1
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• 2009

정보화가 급속히 진전됨에 따라 보다 많은 양의 정보를 전송, 처리, 저장하게 되면서 이를 위해 대용량, 고속, 비휘발성의 특징을 갖는 차세대 메모리의 개발이 절실히 요구되고있다. 이 중 저항 변화 메모리(ReRAM)는 일반적으로 TiO2, Al2O3, NiO2, HfO2, ZrO2 등의 전이금속산화물을 이용한 MIM 구조로서 적당한 전기 신호를 가하면 저항이 높아서 전도되지 않는 상태(Offstate)에서 저항이 낮아져 전도가 가능한 상태(On state)로 바뀌는 메모리 특성을가진다. ReRAM은 비휘발성 메모리이며 종래의 비휘발성 기억소자인 Flash memory 보다 access time 이105 배 이상 빠르고, 5V 이하의 낮은 전압에서도 동작이 가능하다. 또한 구조가 간단하여 공정 단순화가 가능하고 소자의 집적화도 쉽다는 점 등 많은 장점들이 있어서 Flash memory를 대체할 수 있는 유력한 후보로 여겨지고 있다. 본연구에서는 DC-magnetron Sputtering 방법으로 전이금속 박막을 증착하고, Dry furnace로 산화시켜 전이금속산화물 박막을 제작한 후 저항변화 특성을 연구하였다. 두 개의 전이금속산화물 박막을 dual-layer로 형성시켜 저항변화특성을 관찰하였으며 또한, 전이금속산화물 박막의 조성을 달리 하여 저항변화를 관찰 하였다. 전이금속산화물 박막의 전기적 특성을 알아보기 위해 Si(100) wafer 위에 Pt를 이용 MIM 형태로 capacitor 시편을 제작 하여, probe station으로 I-V 측정을 하였고 조성 및 표면 분석을 위해서는 AES와 AFM을, 미세구조를 분석을 위해서는 TEM과 SEM 을 사용하였다.

• Korean Journal of Food Science and Technology
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• v.24 no.6
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• pp.547-551
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• 1992

The antioxidative effects of Rhus javanica $Linn{\acute{e}}$ ethanol extract (RE) with or without some synergists were determined by measurement of POV and TBA of oil in ramyun and potato flake fried in palm oil or lard. RE with ascorbic acid and with tocopherol significantly increased the oxidative stability of ramyun. The results obtained from sensory evaluation were similar to those of POV and TBA values. RE with phosphoric acid and with ascorbic acid retarded the oxidation of potato flakes fried in palm oil or lard during storage.

• Journal of Soil and Groundwater Environment
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• v.22 no.4
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• pp.27-32
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• 2017

In this study, a remedial investigation using reductive stabilization was conducted to treat Cr(VI)-contaminated soil. The influences of various operational parameters, including reaction time and the mass of ferrous iron, were also evaluated. The study site was contaminated with a large amount of Cr(III) and Cr(VI), and the selected treatment method was to stabilize Cr(VI) with ferrous iron, which reduced Cr(VI) to Cr(III) and stabilized the chromium, although a greater mass of ferrous iron than the stoichiometric amount was required to stabilize the Cr(VI). However, some Cr(III) re-oxidized to Cr(VI) during the drying process, and addition of a strong reducing agent was required to maintain reducing conditions. With this reducing agent, the treated soil met the required regulatory standard, and the mass of Cr(III) re-oxidized to Cr(VI) was significantly reduced, compared to the use of only Fe(II) as a reducing agent.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.1
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• pp.41-45
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• 2012

We observed that in chemical vapor deposition (CVD) tungsten silicide (WSix) poly gate scheme, the gate oxide thickness decreases as gate length is reduced, and it intensifies the roll-off properties of transistor. This is because the fluorine diffuses laterally from WSix to the gate sidewall oxide in addition to its vertical diffusion to the gate oxide during gate re-oxidation process. When the channel length is very small, the gate oxide thickness is further reduced due to a relative increase of the lateral diffusion than the vertical diffusion. In DRAM cells where the channel length is extremely small, we found the thinned gate oxide is a main cause of poor retention time.