• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.2019-2024
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• 2014

NiCu alloys have been suggested as potential candidates for catalysts in glucose oxidation. In this study, NiCu alloys with different compositions were prepared on a glassy carbon substrate by changing the electrodeposition potential to examine the effect of Ni/Cu ratios in alloys on catalytic activity toward glucose oxidation. Cyclic voltammetry and chronoamperometry showed that NiCu alloys had higher catalytic activity than pure Ni and Cu catalysts. Especially, Ni59Cu41 had superior catalytic activity, which was about twice that of Ni at a given oxidation potential. X-ray analyses showed that the oxidation state of Ni in NiCu alloys was increased with the content of Cu by lattice expansion. Ni components in alloys with higher oxidation state were more effective in the oxidation of glucose.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.6
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• pp.354-360
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• 2009

This paper reports the oxidation mechanism of epitaxial Ni thin films grown on GaN/sapphire(0001) substrates, investigated by real-time x-ray diffraction and scanning electron microscopy. At the initial stage of oxidation process, a thin NiO layer with a thickness of ${\sim}50\;{\AA}$ was formed on top of the Ni films. The growth of such NiO layer was saturated and then served as a passive oxide layer for the further oxidation process. For the second oxidation stage, host Ni atoms diffused out to the surfaces of initially formed NiO layer through the defects running vertically to form NiO grains, while the sites that were occupied by host Ni, became voids. The crystallographic properties of resultant NiO films, such as grain size and mosaic distribution, rely highly on the oxidation temperatures.

• Journal of the Korean institute of surface engineering
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• v.36 no.6
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• pp.430-436
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• 2003

The nanoocrystalline Ni-l5W(at.%) coating electrodeposited on the high carbon steel was oxidized at 700 and $800^{\circ}C$ in air, and the resultant oxidation properties were investigated using XRD, EPMA, TGA and TEM. The oxidation resistance of the coating was not so good that most of the coating was oxidized after oxidation at $800^{\circ}C$ for 5 hrs. The oxidation led to the formation of the outer, thin NiO oxide scale and the inner, porous, rather thick ($NiWO_4$＋NiO) mixed layer containing a bit of $WO_2$. During oxidation, substrate elements such as Fe and Cr diffused outwardly toward the coating, according to the concentration gradient.

• Applied Science and Convergence Technology
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• v.25 no.6
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• pp.149-153
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• 2016

Thermal oxidation has significant potential for use in synthesizing metal-oxide nanostructures from metallic materials. However, this method has limited applicability to the synthesis of multi-morphology NiO from Ni foil. Techniques consisting of mechanical and chemical approaches were used to pre-treat the Ni foil (prior to oxidation) to promote the formation of nanowires and nanoplates on the NiO layer. These morphologies were realized on the Ni foils scratched by sand paper and a knife, respectively, and subsequently heat-treated at $500^{\circ}C$ for 24 h. Small nanowires (diameter: <10 nm) formed on the Ni foil treated by absolute $HNO_3$ and then oxidized at $500^{\circ}C$ for 24 h. The formation of various morphologies (on the pre-treated Ni foil), which differ from that formed in the case of pristine Ni foil after oxidation, may be attributed to the surface melting phenomenon that occurs during the nucleation process.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.1
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• pp.1-6
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• 2013

The B2-ordered NiAl has attracted much attention as one of the candidates as a next generation high temperature material, because it has a high melting temperature, a low specific gravity and an excellent high temperature oxidation resistance. However, the application of NiAl to structural materials needs the improvement of its brittleness at room temperature. The study was carried out on the relation between several properties of NiAl and some variation of Ni content within NiAl phase, which means deviations from the stoichiometric composition. The main results were as follows; (i) Good ductility was obtained at the testing temperature more than 1073 K irrespective of Ni content. (ii) Increasing Ni content offered preferable tensile properties. (iii) Every NiAl with varying Ni contents showed the superior oxidation resistance.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.106-111
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• 2005

Failure mechanisms were investigated for the two layer thermal barrier coatings consisting of NiCrAlY bond coat and $ZrO_2-8wt.\% Y_{2}O_3$ ceramic coating during cyclic oxidation. $Al_{2}O_3$ developed at the ceramic coating/bond coat interface first, followed by the Cr/Ni rich oxides such as $NiCr_{2}O_4 and Ni(Al,Cr)_{2}O_4$ during cyclic oxidation It was observed that the spalling of ceramic coatings took place primarily within the NiCrAlY bond coat oxidation products or at the interface between the bond coat oxidation products and zirconia based ceramic coating or the bond coat. It was also observed that the fracture within these oxidation products occurred with the formation of $Ni(Cr,Al)_{2}O_4$ spinel or Cr/Ni rich oxides. It was therefore concluded that the formation of these oxides was a life-limiting event for the thermal barrier coatings.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.179-184
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• 1999

When the steel containing Si is oxidated in hi temperature, Re2O3, Red scale is made on the metal side as the spike phase, and this scale invasion into matrix. Therefore, it affects the feature, after rolling. It is reported that the role of Si is FeO/Fe2SiO4 eutectic compound, but Si can not affect pure iron independently. There must be Ni, then the spike phase can exist. Prominence and depression made by Ni that is necessity at the process to work iron. Therefore, in this study after the change of the amount of Ni in pure iron and steel and oxidation, the structure of the oxide and the surface, and the distribution of the elements were considered. In conclusion, at 100$0^{\circ}C$, 110$0^{\circ}C$, 120$0^{\circ}C$ the curves of oxidation weight are all S curves. Especially, in the beginning of oxidation as the amount of Ni increase, the amount of oxidation also increase. Practical steel has less oxidation than pure steel added Ni. There is much FeO in Fe-Ni alloy, compare to practical steel which has much Fe3O4. Especially, we could know considerable Ni was concentrated on the metal side in Fe-Ni alloy, practical steel. and the surface of the scale.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.387-391
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• 2019

A highly porous Ni@MIL-101catalyst for urea oxidation was synthesized by anchoring Ni into a Cr-based metal-organic framework, MIL-101, particles. The morphology, structure, and composition of as synthesized Ni@MIL-101 catalysts were characterized by X-Ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. The electro-catalytic activity of the Ni@MIL-101catalysts towards urea oxidation was investigated using cyclic voltammetry. It was found that the structure of Ni@MIL-101 retained that of the parent MIL-101, featuring a high BET surface area of $916m^2g^{-1}$, and thus excellent electro-catalytic activity for urea oxidation. A $urea/H_2O_2$ fuel cell with Ni@MIL-101 as anode material exhibited an excellent performance with maximum power density of $8.7mWcm^{-2}$ with an open circuit voltage of 0.7 V. Thus, this work shows that the highly porous three-dimensional Ni@MIL-101 catalysts can be used for urea oxidation and as an efficient anode material for urea fuel cells.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1199-1203
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• 2012

Catalytic filters consisting of Ni nanoparticle and carbon fiber with different oxidation states of Ni (either metallic or oxidic) were prepared using a chemical vapor deposition process and various post-annealing steps. CO oxidation reactivity of each sample was evaluated using a batch type quartz reactor with a gas mixture of CO (500 mtorr) and $O_2$ (3 torr) at $300^{\circ}C$. Metallic and oxidic Ni showed almost the same CO oxidation reactivity. Moreover, the CO oxidation reactivity of metallic sample remained unchanged in the subsequently performed second reaction experiment. We suggested that metallic Ni transformed into oxidic state at the initial stage of the exposure to the reactant gas mixture, and Ni-oxide was catalytically active species. In addition, we found that CO oxidation reactivity of Ni-oxide surface was enhanced by increase in the $H_2O$ impurity in the reactor.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.109-109
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• 2011

CO oxidaition reacitvity of bare and $TiO_2$ -coated NiO/$Ni(OH)_2$ nanoparticles was studied. For the deposition of $TiO_2$ atomic layer deposition was used, and formation of three-dimensional island of $TiO_2$ on NiO/$Ni(OH)_2$ could be identified. Based on the data of X-ray Photoelectron Spectroscopy, we suggest that only $Ni(OH)_2$ existed on the surface, whereas NiO disappeared upon $TiO_2$ deposition. Both CO adsorption and CO oxidation took place on NiO/$Ni(OH)_2$ surfaces under our experimental conditions. CO adsorption was completely suppressed after $TiO_2$ deposition, whereas CO oxidation activity was maintained to large extent. It is proposed that bare NiO can uptake CO under our experimental condition, whereas hydroxylated surface of NiO can be active for CO oxidation.