• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.246-246
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• 2012

Smart catalyst design though novel catalyst preparation methods can improve catalytic activity of transition metals on reducible oxide supports such as titania by enhancement of metal oxide interface effects. In this work, we investigated Pt nanoparticles/titania catalysts under CO oxidation reaction by using novel preparation methods in order to enhance its catalytic activity by optimizing metal oxide interface. Arc plasma deposition (APD) and metal impregnation techniques are employed to achieve Pt metal deposition on titania supports which are prepared by multi-target sputtering and Sol-gel techniques. In order to tailor metal-support interface for catalytic CO oxidation reaction, Pt nanoparticles and thin films are deposited in varying surface coverages on sputtered titania films using APD. To assess the role of oxide support at the interface, APD-Pt is deposited on sputtered and Sol-gel prepared titania films. Lastly, characteristics of APD-Pt process are compared with Pt impregnation technique. Our results show that activity of Pt nanoparticles is improved when supported over Sol-Gel prepared titania than sputtered titania film. It is suggested that this enhanced activity can be partly ascribed to a very rough titania surface with the higher free metal surface area and higher number of sites at the interface between the metal and the support. Also, APD-Pt shows superior catalytic activity under CO oxidation as compared to Pt impregnation on sputtered titania support. XPS results show that bulk oxide is formed on Pt when deposited through impregnation and has higher proportion of oxidized Pt in the form of $Pt^{2+/4+}$ oxidation states than Pt metal. APD-Pt shows, however, mild oxidation with large proportion of active Pt metal. APD-Pt also shows trend of increasing CO oxidation activity with number of shots. The activity continues to increase with surface coverage beyond 100%, thus suggesting a very rough and porous Pt films with higher active surface metal sites due to an increased surface area available for the reactant CO and $O_2$ molecules. The results suggest a novel approach for systematic investigation into metal oxide interface by rational catalysts design which can be extended to other metal-support systems in the future.

• Textile Coloration and Finishing
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• v.23 no.4
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• pp.274-283
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• 2011

Effect of pH on ozone oxidation and peroxone AOP(Advanced Oxidation Process) process was analyzed and the optimal efficiency for both processes was obtained at pH 7.5. In case of ozone oxidation process, the efficiencies of color, $COD_{Mn}$ and $BOD_5$ removal were measured to 93%, 70% and 89% at a reaction time of 50 min(ozone dosage of 111.67mg/$\ell$). When reaction time increased to 90 min(ozone dosage of 201mg/$\ell$), the efficiencies of color, $COD_{Mn}$ and $BOD_5$ removal were increased by 3~5 %, indicating that the increment of removal efficiency was insignificant considering longer reaction time. Similarly, the ozone/$H_2O_2$ ratio was optimized to 0.5 for peroxone AOP process. Removal efficiencies of color, $COD_{Mn}$ and $BOD_5$ were measured 95%, 81% and 94% at a reaction time of 50 min(ozone dosage of 111.67mg/$\ell$). When reaction time increased to 90min(ozone dosage of 201mg/$\ell$), the removal efficiency of color, CODMn, and BOD5 increased slightly by 1~5%.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.261-261
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• 2013

The smart design of nanocatalysts can improve the catalytic activity of transition metals on reducible oxide supports, such as titania, via strong metal-support interactions. In this work, we investigatedtwo-dimensional Pt nanoparticle/titania catalytic systems under the CO oxidation reaction. Arc plasma deposition (APD) and metal impregnation techniques were employed to achieve Pt nanoparticle deposition on titania supports, which were prepared by multitarget sputtering and sol-gel techniques. APD Pt nanoparticles with an average size of 2.7 nm were deposited on sputtered and sol-gel-prepared titania films to assess the role of the titania support on the catalytic activity of Pt under CO oxidation. In order to study the nature of the dispersed metallic phase and its effect on the activity of the catalytic CO oxidation reaction, Pt nanoparticles were deposited in varying surface coverages on sputtered titania films using arc plasma deposition. Our results show an enhanced activity of Pt nanoparticles when the nanoparticle/titania interfaces are exposed. APD Pt shows superior catalytic activity under CO oxidation, as compared to impregnated Pt nanoparticles, due to the catalytically active nature of the mild surface oxidation and the active Pt metal, suggesting that APD can be used for large-scale synthesis of active metal nanocatalysts.

• Journal of Powder Materials
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• v.24 no.1
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• pp.53-57
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• 2017

In this study, we report the microstructure and the high-temperature oxidation behavior of Fe-Ni alloys by spark plasma sintering. Structural characterization is performed by scanning electron microscopy and X-ray diffraction. The oxidation behavior of Fe-Ni alloys is studied by means of a high-temperature oxidation test at $1000^{\circ}C$ in air. The effect of Ni content of Fe-Ni alloys on the microstructure and on the oxidation characteristics is investigated in detail. In the case of Fe-2Ni and Fe-5Ni alloys, the microstructure is a ferrite (${\alpha}$) phase with body centered cubic (BCC) structure, and the microstructure of Fe-10Ni and Fe-20Ni alloys is considered to be a massive martensite (${\alpha}^{\prime}$) phase with the same BCC structure as that of the ferrite phase. As the Ni content increases, the micro-Vickers hardness of the alloys also increases. It can also be seen that the oxidation resistance is improved by decreasing the thickness of the oxide film.

• Korean Journal of Materials Research
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• v.14 no.10
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• pp.683-687
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• 2004

The BON thin films were grown on the Si substrate by the RF-PECVD method. When stored at the room temperature, the phase separation or transition of BON thin films occurred on the surface, due to the hydrophilic property of BON. The oxidation of BON thin films occurred mainly by the evaporation of B, O and N. The oxidized BON thin films consisted of an amorphous phase and a bit of the polycrystalline phase.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.188-191
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• 2003

In this wort. the effect of anodic oxidation on surface characteristics of high strength PAN-based carbon fibers is investigated in terms of surface and mechanical interfacial properties of the composites. As a result, the acidity of carbon fiber surfaces is increased, due to the development of oxygen functional groups in the presence of anodic oxidation. Also. it is found that the critical stress intensity factor ($K_{IC}$) is improved in the oxidized fibers-reinforced composites. which can be attributed to the good wettability between fibers and epoxy resin matrix.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3778-3787
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• 2022

The stress-assisted oxidation behaviour of Inconel 52 M/316 austenitic stainless-steel (SS) dissimilar weld joints (DMWJ) in a simulated pressurised water reactor environment was investigated. A corrosion galvanic couple formed between the Inconel 52 M and 316 SS due to differences in their nonferrous metal content. The electric field from the corrosion couple attracted metal cations (e.g. Fe²⁺, Cr³⁺) to the Inconel 52 M that were deposited as FeCr₂O₄. An additional corrosion galvanic couple was generated due to variations in the plastic deformation of the DMWJ. The superposition of electric fields from the different couples resulted in ridge-like oxide depositions in the fusion zone.

• Journal of the Korean Applied Science and Technology
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• v.33 no.1
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• pp.100-109
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• 2016

In this study, the NO oxidation using dry oxidant produced by catalytic $H_2O_2$ conversion was conducted. It was shown that Mn-based $Fe_2O_3$ support catalyst has the best performance in the catalytic $H_2O_2$ conversion and its combined-NO oxidation. The reaction characteristics of NO oxidation was investigated by the various operation conditions such as $H_2O_2$ amount, oxidation temperature and space velocity. As a results, the oxidation efficiency of NO greatly depends on the oxidation reaction temperature, $H_2O_2$ amount and space velocity. The performance of NO oxidation was increased with increasing the oxidation temperature and $H_2O_2$ amount. Also, the performance of NO oxidation was decreased with increasing the space velocity.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.71-79
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• 2023

Air ingress incidents are major safety accidents in very-high-temperature reactors (VHTRs). Air containing a high volume fraction of oxygen may cause severe oxidation of core components at the VHTR, especially for the significantly thin alloy tube wall in the intermediate heat exchanger (IHE). The research objects of this study are Inconel 617 and Incoloy 800H, two candidate alloys for IHE in VHTR. The air ingress accident scenario is simulated with high-temperature air flow at 950 ℃. A continuous oxide scale was formed on the surfaces of both the alloys after the experiment. Because the oxide scale of Inconel 617 has a loose structure, whereas that of Incoloy 800H is denser, Inconel 617 exhibited significantly more severe internal oxidation than Incoloy 800H. Further, Inconel 617 showed a significant decrease in ultimate tensile strength and plasticity after aging for 200 h, whereas Incoloy 800H maintained its tensile properties satisfactorily. Through control experiment under vacuum, we preliminarily concluded that serious internal oxidation is the primary reason for the decline in the tensile properties of Inconel 617.

• Journal of Powder Materials
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• v.28 no.2
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• pp.91-96
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• 2021

Rare earth magnets with excellent magnetic properties are indispensable in the electric device, wind turbine, and e-mobility industries. The demand for the development of eco-friendly recycling techniques has increased to realize sustainable green technology, and the supply of rare earth resources, which are critical for the production of permanent magnets, are limited. Liquid metal extraction (LME), which is a type of pyrometallurgical recycling, is known to selectively extract the metal forms of rare earth elements. Although several studies have been carried out on the formation of intermetallic compounds and oxides, the effect of oxide formation on the extraction efficiency in the LME process remains unknown. In this study, microstructural and phase analyses are conducted to confirm the oxidation behavior of magnets pulverized by a jaw crusher. The LME process is performed with pulverized scrap, and extraction percentages are calculated to confirm the effect of the oxide phases on the extraction of Dy during the reaction. During the L ME process, Nd is completely extracted after 6 h, while Dy remains as Dy₂Fe₁₇ and Dy-oxide. Because the decomposition rate of Dy₂Fe₁₇ is faster than the reduction rate of Dy-oxide, the importance of controlling Dy-oxide on Dy extraction is confirmed.