• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.45-45
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• 1993

• Proceedings of the Korean Magnestics Society Conference
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• 2004.06a
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• pp.130-131
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• 2004

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.163-164
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• 2011

• Korean Journal of Materials Research
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• v.10 no.8
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• pp.532-539
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• 2000

Co-0.5C-(15~20)Cr-20Ni-8W-(2~7)Fe alloy bond in diamond-impregnated abrasive tool was synthesized by ball-milling and mechanical alloying process. When the powders were mechanical alloyed for 6h, micro-welding in most metal powders was observed irrespective of addition of stearic acid. Without stearic acid in metal powders, partial-ly coarse powders were obtained, which could be unfaverable to the densification of composite of composite powders. The hot-pressed compacts showed rupture strength of 1100MPa and hardness of about $46H_{RC}$, respectively.

• Korean Journal of Materials Research
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• v.24 no.8
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• pp.401-406
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• 2014

In this study, we investigated the precipitation behavior of the R-phase precipitated at the initial stage of aging and its effects on the mechanical properties of 25%Cr-7%Ni-2%Mo-4%W super duplex stainless steel. The R-phase was mainly precipitated at the interface of ferrite/austenite phases and inside of the ferrite phase during the initial stage of aging. It was transformed into the ${\sigma}$-phase with an increase of the aging time. The ferrite phase was decomposed into a new austenite(${\gamma}_2$)phase and the ${\sigma}$-phase by an aging treatment. The R phase was an intermetallic compound showing higher molybdenum and tungsten concentrations than the matrix and also showed higher molybdenum and tungsten concentrations than the ${\sigma}$ phase. In the initial stage of aging, precipitation of the R-phase did not change the hardness, the strength and the elongation. The hardness and the strength increased upon a longer aging time, but the elongation rapidly decreased. These results show that the R-phase did not significantly affect the hardness and the strength, though it did influence the elongation.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.2
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• pp.264-270
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• 2011

This paper focuses on possibility to design and fabrication new combination of bullet core to substitute current toxic material of heavy metal such as lead by environment-friendly ones. The core is designed as dual structure to manipulate the core center of gravity easily by combining materials, which of basis is tungsten of low cost and easily acquired. Those combinations are W-M series such as W-Cu, W-Sn, W-Cu-Sn, and W-Cu-Ni to target the density of lead, $11.34g/cm^3$ through powder-metallurgy. Out of four, combination of W-Cu-Ni shows the highest compression density of 96% and is confirmed as the most suitable substitution for lead due to the excellent property of matter and sintering. All combination samples is simulated on the PRODAS software for designing and structure analysis by adjusting the center of gravity of dual core samples forward and backward. The simulations confirm the similarity of current bullet core with respect to properties of mass, aero dynamics, and flying stability.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.1
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• pp.3-7
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• 2009

Variation in oxidation behavior with heat treatment temperature is investigated for a Ni-Ti alloy using X-ray diffraction, DSC (differential scanning calorimetry) and Auger electron spectroscopy. And the effect of oxidation on transformation behavior and superelasticity is characterized. A cold-worked 50.6Ni-Ti alloy is oxidized at 300-$700^{\circ}C$ for 1 hr in the air atmosphere. With an increase in heating temperature, the structure of $TiO_2$ changes from amorphous (300 and $400^{\circ}C$) to anatase ($500^{\circ}C$), and to rutile ($700^{\circ}C$). Activation energy of oxidation for NiTi is measured to be 51 Kcal/mol when heating temperature is $500^{\circ}C$ or above. Since Ti reacts preferably with oxygen, Ni content increases between matrix and oxide, forming $Ni_{3}Ti$ compounds. The resultant of oxidation decreases significantly $M_s$ and $A_s$ temperature in the specimen oxidized at $900^{\circ}C$ with $B_2{\rightarrow}M$ transformation path. An extra is found on cooling between two peaks in the specimen with $B_2{\rightarrow}R{\rightarrow}M$ one which is oxidized at $900^{\circ}C$ and aged at $500^{\circ}C$. Oxidation deteriorates superelasticity due to formation of Ni-rich compound.

• New & Renewable Energy
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• v.4 no.1
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• pp.11-18
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• 2008

In-situ lithiated NiO has been manufactured as a conventional cathode material of molten carbonate fuel cell (MCFC), however this material has a weakness for commercialization of MCFC because NiO is spontaneously dissolved into the electrolyte under MCFC operating conditions, resulting in short circuit between cathode and anode. In this research, therefore, $Co(OH)_2$-coated Ni powder was prepared by precipitation method with controlling pH at low temperature and atmospheric pressure. Modified cathode was fabricated by a conventional tape casting method and sintered at 700$^{\circ}C$ in a $H_2/N_2$ atmosphere, Based on characterization result, Pore size distribution and porosity was suitable for the cathode of MCFC. According to the result of dissolution, Ni solubility of modified cathode was 33% lower than that of conventional cathode. In addition, modified electrode showed a good performance from the single cell operation.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1149-1153
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• 2002

CH4/CO2 dry reforming was carried out to make syn gas on the Ni/Al2O3 catalysts calcined at different temperatures. The Ni/Al2O3 (850 $^{\circ}C)$ catalyst gave good activity and stability w hereas the Ni/Al2O3 $(450^{\circ}C)$ catalyst showed lower activity and stability. The NiO/Al2O3 catalyst calcined at $850^{\circ}C$ for 16 h (Ni/Al2O3 $(850^{\circ}C))$ formed the spinel structure of nickel aluminate, which was confirmed by TPR. The carbon formation rate on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was very low till 20 h, and then steeply increased with reaction time without decreasing the activity for CH4 reforming. The Ni/Al2O3 $(450^{\circ}C)$ catalyst showed high carbon formation rate at the initial reaction time and then, the rate nearly stopped with continuous decreasing the activity for CH4 reforming. Even though the amount of carbon deposition on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was higher than that on the Ni/Al2O3 $(450^{\circ}C)$ catalyst, the activity for CH4ing was also high, which could be attributed to the different type of the carbon formed on the catalyst surface.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.19-22
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• 2006

Desirable substrates for $YBa_2Cu_3O_{7-\delta}$ coated conductor are highly cube textured Ni or Ni-alloy tapes, which can be produced by cold rolling and recrystallization annealing. We have fabricated hi-axially textured pure Ni tapes for the application of coated conductors. The sintered Ni rod was cold-rolled into the thin tapes of $50{\mu}m$ thickness and the tapes were heat-treated for texture development with line-focused infrared heater. The temperature was maintained at $800\sim1050^{\circ}C$, using 1kW double ended linear halogen lamp in $96%Ar-4%H_2$ atmosphere The biaxially tortured Ni tapes were successfully formed by line-focused infrared heat treatment The texture of the annealed Ni tapes was analysed using the GADDS (general area detector diffraction system). The full width at half maximum values of phi and omega scan for the Ni tapes were less than $10^{\circ}$ and the grain size was $20-50{\mu}m$.