• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.395-398
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• 2005

• 한국전기화학회:학술대회논문집
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• 2002.04a
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• pp.33-33
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• 2002

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.2
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• pp.219-248
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• 1989

The purposes of this study were to analyze the microstructural and compositional changes of metal surfaces following different conditions of preoxidizing heat treatment, to investigate the composition of metal oxides, and to evaluate the effect of preoxidation and removal of surface oxides on microstructure and diffusion profiles. The techniques of EDAX (energy-dispersive analysis of x-ray), ESCA (electron spectroscopy for chemical analysis), and EPMA (electron probe micro analysis) were used, along with SEM (scanning electron microscopy). The obtained results were as follows : 1. A surface of the specimen became rough and the amount of the metal oxides increased with increasing the heat treatment time and temperature and the partial pressure of oxygen. 2. At an air pressure of 28' vacuum, the higher the temperature and the longer the time of preoxidation, the higher Ni concentration was detected. 3. Cr concentration in the specimen heat treated with air was higher than that of with vacuum. 4. The oxides in the specimens were mainly composed of Ni and Cr oxides. On the globular growth particles, significant rises in Al concentration of Rexillium III and Ti concentration of Verabond were noted. 5. Atomic diffusion occurred at the ceramic-metal interface, furthermore the amount of the flux was increased with preoxidation heat treatment.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.1
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• pp.49-57
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• 2005

[ $MO/Al_2O_3-ZrO_2$ ](M=Ni and Cu) mixed metal oxides were prepared using sol-gel method in order to investigate the applicability to the 2-step thermo-chemical water splitting process and their redox behaviors were studied by temperature programmed reaction(TPR) from room temperature to 900$^{\circ}C$ under 5% $H_2$/Ar for the reduction and $H_2O$/Ar for the oxidation, respectively. From the results, peaks of the reduction and the oxidation on temperature were shifted with the change of crystalline phases due to the addition of $Al_2O_3$ and $ZrO_2$. The intensities of the peaks were also increased with the increase of contents of NiO or CuO that could be considered as active species. In addition, based on the observation of SEM images before and after the redox test, it seemed that $Al_2O_3-ZrO_2$ added prevented high temperature sintering of active metal components such as Ni (or Cu) on the surface and played a role of dispersing the active species homogeneously in solid solution of mixed oxides.

• Journal of the Korean Magnetics Society
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• v.11 no.4
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• pp.151-156
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• 2001

Recently many studies on manganese oxides Ln$_{1-x}$A$_{x}$MnO$_3$(Ln=La, Pr, Nd lanthannide; A=Ca, Sr, Ba, Pb +2 ions) reported CMR properties. CMR have been also found in chalcogenide spinels. We have investigated that Ni ion substitutions for Fe ion have effects on CMR properties in chacogenide spinels Ni$_{x}$Fe$_{1-x}$Cr$_2$S$_4$. It was found that with increasing Ni concentration Jahn-Teller distortion was strengthened and Curie temperature T$_{c}$ was increased. CMR properties could be explained with Jahnl-Teller effect, half-metallic electronic structure, and the alignment of magnetic domain due to the strong magnetic field, which is different in that double exchange interactions dominate CMR properties in manganese oxides.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.407-411
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• 2022

Bulk-sized PbTiO₃ (PT), which is widely known as a high-performance ferroelectric oxide but cannot be fabricated into a monolithic ceramic due to its high c/a ratio, was successfully prepared with a high tetragonality by partially substituting Ni ions for Pb ions using a solid-state reaction method. We found that Ni-doped PT was well-fabricated as a bulk monolith with a significant c/a ratio of ~1.06. X-ray diffraction on as-sintered and crushed samples revealed that NiTiO₃ secondary phase was present at the doping level of more than 2 at.%. Scanning electron microscopic study showed that NiTiO₃ secondary phase grew on the surface of PT specimens regardless of the doping level possibly due to the evaporation of Pb during sintering. We demonstrated that an unconventional introduction of Ni ions into A-site plays a key role on the fabrication of bulk PT, though how Ni ion functions should be studied further. We expect that this study contributes to a further development of displacive ferroelectric oxides with a high c/a ratio.

• Corrosion Science and Technology
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• v.13 no.4
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• pp.145-151
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• 2014

The objectives of this study are to investigate the effect of the concentration ratios of Ni and Fe ions on crud deposition onto the fuel cladding surface in the simulated primary environments of a pressurized water reactor. Crud deposition tests were conducted in the Ni and Fe concentration ratios of 20:20 ppm, 39:1 ppm and 1:39 ppm at $325^{\circ}C$ for 14 days. In the case of the same Ni and Fe ion ratio (20:20), nickel ferrite with a polyhedral shape was formed. Nickel oxide deposits with a needle shape were formed in the condition of high Ni to Fe ion ratio (39:1), While polyhedral iron oxide and needle-like nickel oxide formed in the condition of low Ni to Fe ion ratio (1:39). The amount of deposits increased, when Fe oxides were formed. This indicates that Fe rich oxides stimulated Ni oxide deposition.

• Journal of the Korean institute of surface engineering
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• v.39 no.3
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• pp.129-136
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• 2006

The high velocity oxy-fuel sprayed coatings of 38Ni-23Co-20Cr-11Al-3Y-5Ta, 25Ni-34Co-20Cr-11Al-3Y-2Re and 32Ni-34.5Co-22Cr-11Al-0.5Ir (in wt%) were oxidized at 1000 and $1100^{\circ}C$ in air in order to find the alloying effect of Ta, Re and Ir on the oxidation properties of the NiCoCrAlY-base coatings. The primary phase of the coatings was $Ni_3Al$. The oxides formed on the coatings consisted primarily of ${\alpha}-Al_2O_3$, together with some $CoCr_2O_4,\;CoAl_2O_4$, and $Al_5Y_3O_{12}$. Tantalum oxidized to $Ta_2O_5$ and $Ta_2O_{22}$. However, no oxides of Re and Ir were detected by XRD owing to their thermodynamic inertness and/or their small amount.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.412-412
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• 2008

ENIG(Electroless Nickel Immersion Gold)is a surface treatment method that is used most widely at fine pitch's SMT and BGA packaging process. ENIG has good diffusion barrier of Ni against solder and good wettability due to Au finish. But when the discoloration occurred on the Au finish of ENIG, some key characteristics related to the quality and reliability of PCB such as bondability, solderability and electrical flowing of packaging process could be deteriorated. In this paper, we have performed the water dip test ($88^{\circ}C$ purified water) which accelerates the galvanic corrosion of Ni diffused from the Ni-P layer. That is, the excessive oxidation of the Ni layer could result in non-wetting of the solder because the flux may not be able to remove excessive oxides. Though Au discoloration have been reported to be caused by Ni oxides in many literature, it is still open to verify and discuss The microstructures and chemical compositions have been investigated using FE-SEM, TEM, FIB, EDS and XPS. As a result, authors have found that the Au discoloration in ENIG type is severely caused by the oxidation of the Ni and the mechanism of Au discoloration can be confirmed through the experiment result of water dip test.

• Journal of Korea Foundry Society
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• v.22 no.4
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• pp.160-166
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• 2002

The structure and properties of Fe-29Ni-17Co alloy which had been melted using induction furnace in air atmosphere and than electroslag-remelted were investigated. The oxygen content was reduced to 0.03% when the ingot was refined from $0.09{\sim}0.12%$ of that air melted. The amounts of spheroidal oxides inclusions and gas porosities of ingot were markedly reduced by the ESR process. CTE of ESR ingot contained small amount of oxides and porosities was found to be lower than that of AIM ingot, and tensile properties of ESR ingot and plate were found to be superior than that of AIM ingot and plate.