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

• Proceedings of the Korean Magnestics Society Conference
• /
• 2017.05a
• /
• pp.123-123
• /
• 2017

• Proceedings of the Korean Magnestics Society Conference
• /
• 2016.11a
• /
• pp.121-122
• /
• 2016

• 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.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2004.06a
• /
• pp.200-200
• /
• 2004

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.242-242
• /
• 2016

Magnetite, Fe3O4, is a ferrimagnet with a cubic inverse spinel structure and exhibits a metal-insulator, Verwey, transition at about 120 K.[1] It is predicted to possess as half-metallic nature, 100% spin polarization, and high Curie temperature (850 K). Cobalt ferrite is one of the most important members of the ferrite family, which is characterized by its high coercivity, moderate magnetization and very high magnetocrystalline anisotropy. It has been reported that the CoFe2O4/Fe3O4 bilayers represent an unusual exchange-coupled system whose properties are due to the nature of the oxide-oxide super-exchange interactions at the interface [2]. In order to evaluate the effect of interface interactions on magnetic and transport properties of ferrite and cobalt ferrite, the CoFe2O4/Fe3O4 superlattices on MgO (100) substrate have been fabricated by molecular beam epitaxy (MBE) with the wave lengths of 50, and $200{\AA}$, called $25{\AA}/25{\AA}$ and $100{\AA}/100{\AA}$, respectively. Streaky RHEED patterns in sample $25{\AA}/25{\AA}$ indicate a very smooth surface and interface between layers. HR-TEM image show the good crystalline of sample $25{\AA}/25{\AA}$. Interestingly, magnetization curves showed a strong antiferromagnetic order, which was formed at the interfaces.

• Tuberculosis and Respiratory Diseases
• /
• v.87 no.3
• /
• pp.329-337
• /
• 2024

Background: Fractional exhaled nitric oxide (FeNO) is known to useful biomarker for detecting eosinophilic airway inflammation. However, there is a lack of evidence regarding the role of FeNO in chronic obstructive pulmonary disease (COPD). We aimed to assess whether elevated FeNO and its impact on treatment change into an inhaled corticosteroid (ICS)-containing regimen and association with acute exacerbation (AE) in patients with COPD. Methods: We retrospectively analyzed 107 COPD patients without a history of asthma from March 2016 to December 2019. The patients whose FeNO value was more than 50 parts per billion (ppb) were defined into the high FeNO group. Multivariable analysis with logistic regression was used to identify factors associated with AE in COPD. Results: The median FeNO value was 32 ppb (interquartile range, 19 to 45) and 34 (20.0%) patients were classified as high FeNO group (median 74 ppb). In the high FeNO group, changes in inhaler treatment into an ICS-containing regimen occurred in 23 of 34 patients after the measurement of FeNO. In multivariate analysis, high FeNO was not a contributing factor for AE, but only the high blood eosinophil count (≥300 cells/µL) was associated with AE (adjusted odds ratio, 2.63; 95% confidence interval, 1.01 to 6.91; p=0.049). Conclusion: High FeNO value had a significant impact on the prescription of ICSs in COPD patients, but it did not show a significant association with AE either on its own or with changes in treatment.

• Korean Journal of Materials Research
• /
• v.22 no.4
• /
• pp.174-179
• /
• 2012

In this study, we demonstrated a simple and eco-friendly method, including mechanical polishing and attrition milling processes, to recycle sputtered indium tin oxide targets to indium tin oxide nanopowders and targets for sputtered transparent conductive films. The utilized indium tin oxide target was first pulverized to a powder of sub- to a few- micrometer size by polishing using a diamond particle coated polishing wheel. The calcination of the crushed indium tin oxide powder was carried out at $1000^{\circ}C$ for 1 h, based on the thermal behavior of the indium tin oxide powder; then, the powders were downsized to nanometer size by attrition milling. The average particle size of the indium tin oxide nanopowder was decreased by increasing attrition milling time and was approximately 30 nm after attrition milling for 15 h. The morphology, chemical composition, and microstructure of the recycled indium tin oxide nanopowder were investigated by FE-SEM, EDX, and TEM. A fully dense indium tin oxide sintered specimen with 97.4% of relative density was fabricated using the recycled indium tin oxide nanopowders under atmospheric pressure at $1500^{\circ}C$ for 4 h. The microstructure, phase, and purity of the indium tin oxide target were examined by FE-SEM, XRD, and ICP-MS.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2007.05a
• /
• pp.71.2-71.2
• /
• 2007

• Journal of the Korean Ceramic Society
• /
• v.52 no.5
• /
• pp.308-314
• /
• 2015

The electrochemical performance and Cr poisoning behavior of $La_{1-x}Ba_xCo_{0.9}Fe_{0.1}O_{3-{\delta}}$ (LBCF, x = 0.3, 0.4, 0.5) and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LSCF) cathodes were investigated for solid oxide fuel cells (SOFCs). The polarization resistance of the LBCF/GDC/LBCF symmetrical cell was found to decrease with increasing Ba content (x value). This phenomenon might be associated with the high oxygen vacancy concentration in the LBCF sample, with x = 0.5. In addition, there was no chromium poisoning in the LBCF cathode. On the other hand, the polarization resistance of the LSCF cathode was found to significantly increase after exposure to gaseous chromium species; it appears that this result stemmed from the formation of $SrCrO_4$ phase. Therefore, it can be expected that LBCF can be a durable potential cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFC).