• Korean Journal of Materials Research
• /
• v.26 no.4
• /
• pp.187-193
• /
• 2016

Fabrication of iron oxide/carbon nanotube composite structures for detection of ammonia gas at room temperature is reported. The iron oxide/carbon nanotube composite structures are fabricated by in situ co-arc-discharge method using a graphite source with varying numbers of iron wires inserted. The composite structures reveal higher response signals at room temperature than at high temperatures. As the number of iron wires inserted increased, the volume of carbon nanotubes and iron nanoparticles produced increased. The oxidation condition of the composite structures varied the carbon nanotube/iron oxide ratio in the structure and, consequently, the resistance of the structures and, finally, the ammonia gas sensing performance. The highest sensor performance was realized with $500^{\circ}C/2h$ oxidation heat-treatment condition, in which most of the carbon nanotubes were removed from the composite and iron oxide played the main role of ammonia sensing. The response signal level was 62% at room temperature. We also found that UV irradiation enhances the sensing response with reduced recovery time.

• Animal cells and systems
• /
• v.13 no.2
• /
• pp.105-112
• /
• 2009

In this study, the effects of iron on cytochrome c oxidase (CcO) in rat lung mitochondria were examined. Similar to liver mitochondria, iron accumulated considerably in lung mitochondria (more than 2-fold). Likewise, the reactive oxygen species and nitric oxide (NO) content of mitochondria were increased by more than 50% and 100%, respectively. NO might be produced by nitric oxide synthase (NOS), eNOS and iNOS type, with particular contribution by NOS in mitochondria. The respiratory control ratio of iron overloaded lung mitochondria dropped to nearly 50% due to increased state 4. Likewise, cytochrome c oxidase activity was lowered significantly to approximately 50% due to excess iron. Real-time PCR revealed that the expression of isoforms 1 and 2 of subunit IV of CeO was enhanced greatly under excess iron conditions. Taken together, these results show that oxidative phosphorylation within lung mitochondria may be influenced by iron overload through changes in cytochrome c oxidase and NO.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.4
• /
• pp.489-494
• /
• 2006

Goethite, hematite, magnetite and synthesized iron oxide are used as catalysts for Fenton-type oxidation of phenol. The synthesized iron oxides were characterized by X-ray diffraction (XRD), BET, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The catalytic activity of these materials is classified according to the observed rate of phenol oxidation. The effectiveness of the catalysts followed the sequence: ferrous ion > synthesized iron oxide >> magnetite hematite > goethite. According to these results, the most effective iron oxide catalyst had the structure similar to natural hematite. The surface oxidation state of the catalyst was between magnetite and hematite (+2.5 ~ +3.0). Phenol degraded completely in 40 min at neutral pH (pH = 7). Soluble ferric and ferrous ions were not detected in the filtrate from Fenton reaction solution by AAS. The formation of hydroxyl radicals was confirmed by EPR.

• Journal of the Korean Electrochemical Society
• /
• v.2 no.3
• /
• pp.156-162
• /
• 1999

Various types of iron oxide based materials as a cathode of lithium secondary battery have been prepared and their electrochemical characteristics have been also observed. In order to understand the fundamental characteristics of iron oxide electrode, three kinds of iron oxides such as iron oxides formed by direct oxidation of iron plate or iron powders and FeOOH powders were tested with cyclic voltammetry. The oxidation and reduction peaks due to the reaction of intercalation and deintercalation were not observed for the iron oxide prepared with iron plate and FeOOH powders. In case of iron oxide prepared from iron powders, only one reduction peak was observed. A layered form of $LiFeO_2$ was synthesized directly from $FeCl_3\cdot6H_2O,\;NaOH\;and\;LiOH$ and LiOH by hydrothermal reaction. The effect of NaOH on the electrode performance was examined. When increasing NaOH, it provides the electrode with less discharge capacity and efficiency, however, decreasing rate of discharge capacity became smaller. $LiFeO_2$ synthesized with the molar ratio of $NaOH/FeCl_3/LiOH$, 2/1/7 showed the largest capacity, but the discharging efficiency was sharply decreased after 30 cycles.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.498-503
• /
• 2017

There is no unusual difference in the initial viscosity of the propellant applied with yellow iron oxide and red iron oxide. In addition, the thermal decomposition rate of the material added with yellow iron oxide is faster than that of the addition of red iron oxide. Especially, it was confirmed that the pressure exponent was 18% lower at high temperature and high pressure. The initial viscosity was lowest at 71% of large particle/small particle ratio

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1993.05a
• /
• pp.104-108
• /
• 1993

Thin films of MgO-doped and CaO-doped iron oxide were prepared y spray pyrolysis. The films were characterized b X-ray diffraction, scanning electron microscopy and voltammetric techniques. The photoelectrochemical behavior of thin film electrodes depended greatly on the doping level, sintering temperature, substrate temperature and added photosensitizing compounds in solution, showed p-type photoelectrochemical behavior, while the CaO-doped iron oxide thin films prepared at low temperature showed n-type photoelectrochemical behavior. This characteristic change was interpreted in terms of the surface structure change of the thin films and doping effect of metal oxide.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.2
• /
• pp.123-129
• /
• 2005

In situ permeable reactive barrier (PRB) technologies have been proposed to reductively remove organic contaminants from the subsurface environment. The major reactive material, zero valent iron ($Fe^0$), is oxidized to ferrous iron or ferric iron in the barriers, resulting in the decreased reactivity. Iron-reducing bacteria can reduce ferric iron to ferrous iron and iron reduced by these bacteria can be applied to dechlorinate chlorinated organic contaminants. Iron reduction by iron reducing bacteria, Shewanella algae BrY, was observed both in aqueous and solid phase and the enhancement of TCE removal by reduced iron was examined in this study. S. algae BrY preferentially reduced Fe(III) in ferric citrate medium and secondly used Fe(III) on the surface of iron oxides as an electron acceptor. Reduced iron formed reactive materials such as green rust ferrihydrite, and biochemical precipitation. These reactive materials formed by the bacteria can enhance TCE removal rate and removal capacity of the reactive barrier in the field.

• Korean Chemical Engineering Research
• /
• v.46 no.6
• /
• pp.1029-1038
• /
• 2008

Transition-metal-oxide-incorporated hydrotalcites were prepared by hydrothermal reaction of their synthetic mixtures containing precursors of transition metal oxides and their properties of nitrogen dioxide adsorption was investigated. The dispersion of transition metal oxides on the hydrotalcites and the amount and the state of nitrogen dioxide adsorbed on them were examined by using XRD, SEM, XPS, nitrogen adsorption, a gravimetric adsorption system, FT-IR spectroscopy and temperature programmed desorption techniques. Transition metal oxides were mainly incorporated on their surface and the incorporation of iron and nickel oxides to the hydrotalcites increased their adsorption amounts of nitrogen dioxide. The dispersion of iron oxide on the hydrotalcites was effective in increasing the amount of nitrogen dioxide adsorption, while too much amount of iron oxide incorporation reduced the amount of nitrogen dioxide adsorption due to masking of surface basic sites by agglomerated iron oxide. Although the incorporation of iron oxide to the hydrotalcites lowered the adsorption strength of nitrogen dioxide, the incorporation of it with a proper amount enhanced the amount of nitrogen dioxide adsorption and the stability against the hydrothermal treatment.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.446-447
• /
• 2006

Magnetic oxide-coated iron nanoparticles with the mean size ranging from 6 to 75 nm were synthesized by aerosol method using iron carbonyl as a precursor under the flowing inert gas atmosphere. Oxide shells were formed by passivation of asprepared iron particles. The influence of experimental parameters on the nanoparticles' microstructure, phase composition and growth behavior as well as magnetic properties were investigated and discussed in this study.

• Journal of the Mineralogical Society of Korea
• /
• v.24 no.3
• /
• pp.189-194
• /
• 2011

Martian satellite missions indicate that Martian equatorial plains are covered by ferric iron oxide. As a non-destructive technique, low-temperature treatment of remanent magnetization is effective in identifying magnetic minerals in rocks. In the present study, four sets of ferric iron oxides were prepared by aqueous alteration of ferrihydrite at warm conditions and four others by dehydration of goethite. As the amount of aluminous trivalent cations increases, crystallographic lattice parameters and N$\acute{e}$el temperatures decrease. Such declines originate from lattice distortion as the smaller aluminous trivalent cations substitue the larger terric irons. Whilst high remanence memory was observed for aqueously produced ferric iron oxide, low remanence memory was observed for dehydrated ferric iron oxide. In the future. magnetic remanence memory would be powerful in diagnosing the origin of ferric iron oxide.