• Laser Solutions
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• v.3 no.2
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• pp.13-24
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• 2000

The weldability of dissimilar materials between sintered materials which are consisted of Co, Co＋Ni and carbon steel has been investigated using CO$_2$ laser. Autogeneous CO$_2$ laser welding were run along the butt between two alloys using sets of parameters variation-power and travel speed. In order to study weldability, mechanical tests (bending strength test, microhardness test) and metallurgical analyses (microstructure, phase transformation, fracture mode) were carried out. From the results obtained, it was found that the porosity which exists in a weld metal greatly affects the soundness of the weld. The optimum energy input to have a proper strength over than the requirement by a specification, found to be around 0.3-0.35kJ/m. There are two kinds of fracture mode in the weld metal, depending upon alloy combination, brittle fracture in the case of Co-carbon steel and a ductile fracture in the case of Co＋Ni-carbon steel. In general, Co＋Ni sintered material showed a better weld properties as compared to the Co sintered material.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.367-373
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• 2014

In this study, the reducing agent hydrazine and precipitator NaOH were used with $NiCl_2$ as a starting material in order to compound Ni-based material with spherical nano characteristics; resulting material was used as an anode for SOFC. Synthetic temperature, pH, and solvent amounts were experimentally optimized and the synthesis conditions were confirmed. Also, a 0 ~ 0.15 mole ratio of metal(Co, Fe) was alloyed in order to increase the catalyst activation performance of Ni and finally, spherical nano $Ni_{(1-x)}-M_{(x=0{\sim}0.15)}$(M = Co, Fe) alloy materials were compounded. In order to evaluate the catalyst activation for hydrocarbon fuel, fuel gas(10%/$CH_4$+10%/Air) was added and the responding gas was analyzed with GC(Gas Chromatography). Catalyst activation improvement was confirmed from the 3% hydrogen selectivity and 2.4% methane conversion rate in $Ni_{0.95}-Co_{0.05}$ alloy; those values were 4.4% and 19%, respectively, in $Ni_{0.95}-Fe_{0.05}$ alloy.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.4
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• pp.225-232
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• 1999

The $Mg_2Ni$ hydrogen storage alloys which have much higher theoretical discharge capacity than $AB_5$ and $AB_2$ type alloys were synthesized by mechanical alloying with some additives and subjected to the electrochemical measurements. Two different processes were employed to the synthesis of $Mg_2Ni$ alloys with using the high energy ball mill SPEX 8000. One was only ball milling, 12 hrs, the Mg and Ni powders for 12 hrs with additives such as $AB_5$, Ni, Co and Cu powders. In the other process the Mg and Ni powders were ball milled for 1 hr first and then heat treated at $300{\sim}400^{\circ}C$ for 1 hr to get $Mg_2Ni$ alloy, and finally the $Mg_2Ni$ alloy powders were ball milled with the additives for 12 hrs. The alloy powders prepared were compacted at room temperature under $7.64tons/cm^2$ into disk type electrodes for the electrochemical measurements. The experimntal results showed that the electrodes prepared with the heat treated alloy powders had a higher discharge capacities than those without heat treatment. The addition of Ni caused an increase of the discharge capacity and the addition of Co improved the cycling characteristics. The electrode prepared by ball milling of $Mg_2Ni$ and 10wt% Ni powders has showed the highest discharge capacity, 546mAh/g.alloy, which was 55% of the theoretical capacity.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.17-20
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• 2002

Various compositions of CoFeNi alloys have been electrodeposited in chloride bath and in sulfate bath, and evaluated for electrodeposition characteristics and magnetic properties. For electrodeposited CoFeNi thin film alloys, the increase of Fe content in the deposits from sulfate bath was considerably faster than those from chloride bath. The current efficiencies in sulfate bath showed observable decrease from $75\%\;to\;50\%$ while those in chloride bath showed no significant decrease. From the low coercivity of 3 Oe in the minimum and the higher squarenesses of the alloys from sulfate bath than those from chloride bath, the alloy at Co, Fe, and Ni contents of $80wt.\%,\;10wt.\%,\;and\;10wt.\%$ can be considered to be the best CoFeNi alloy in this research for the soft magnetic material.

• Journal of Powder Materials
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• v.8 no.3
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• pp.157-162
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• 2001

An optimum route to fabricate the ferrous alloy dispersed $Al_2O_3$ nanocomposites such as $Al_2O_3$/Fe-Ni and $Al_2O_3$/Fe-Co with sound microstructure and desired properties was investigated. The composites were fabricated by the sintering of powder mixtures of $Al_2O_3$ and nano-sized ferrous alloy, in which the alloy was prepared by solution-chemistry routes using metal nitrates powders and a subsequent hydorgen reduction process. Microstructural observation of reduced powder mixture revealed that the Fe-Ni or Fe-Co alloy particles of about 20 nm in size homogeneously surrounded $Al_2O_3$, forming nanocomposite powder. The sintered $Al_2O_3$/Fe-Ni composite showed the formation of Fe$Al_2O_4$ phase, while the reaction phases were not observed in $Al_2O_3$/Fe-Co composite. Hot-pressed $Al_2O_3$/Fe-Ni composite showed improved mechanical properties and magnetic response. The properties are discussed in terms of microstructural characteristics such as the distribution and size of alloy particles.

• Corrosion Science and Technology
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• v.22 no.1
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• pp.64-72
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• 2023

Ni-Ti shape memory alloy for dental nerve treatment devices was prepared by adding Mo to Ni-Ti alloy to improve flexibility and fatigue fracture characteristics and simultaneously increase corrosion resistance. Surface properties of the alloy were evaluated. Microstructure analysis of the Ni-Ti-xMo alloy revealed that the amount of needle-like structure increased with increasing Mo content. The shape of the precipitate showed a pattern in which a long needle-like structure gradually disappeared and changed into a small spherical shape. As a result of XRD analysis of the Ni-Ti-xMo alloy, R-phase structure appeared as Mo was added. R-phase and B2 structure were mainly observed. As a result of DSC analysis, phase transformation of the Ti-Ni-Mo alloy showed a two-step phase change of B2-R-B19' transformation with two exothermic peaks and one endothermic peak. As Mo content increased, R-phase formation temperature gradually decreased. As a result of measuring surface hardness of the Ti-Ni-Mo alloy, change in hardness value due to the phase change tended to decrease with increasing Mo content. As a result of the corrosion test, the corrosion potential and pitting potential increased while the current density tended to decrease with increasing Mo content.

• Korean Journal of Materials Research
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• v.28 no.10
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• pp.595-600
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• 2018

This study investigates the microstructural properties of CoCrFeMnNi high entropy alloy (HEA) oxynitride thin film. The HEA oxynitride thin film is grown by the magnetron sputtering method using nitrogen and oxygen gases. The grown CoCrFeMnNi HEA film shows a microstructure with nanocrystalline regions of 5~20 nm in the amorphous region, which is confirmed by high-resolution transmission electron microscopy (HR-TEM). From the TEM electron diffraction pattern analysis crystal structure is determined to be a face centered cubic (FCC) structure with a lattice constant of 0.491 nm, which is larger than that of CoCrFeMnNi HEA. The HEA oxynitride film shows a single phase in which constituting elements are distributed homogeneously as confirmed by element mapping using a Cs-corrected scanning TEM (STEM). Mechanical properties of the CoCrFeMnNi HEA oxynitride thin film are addressed by a nano indentation method, and a hardness of 8.13 GPa and a Young's modulus of 157.3 GPa are obtained. The observed high hardness value is thought to be the result of hardening due to the nanocrystalline microstructure.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.2993-2999
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• 2015

Steel companies are applying Ni-B or Ni-Co alloy plating to protect the surface of Continuous casting mold, and they are using saccharin polish which causes crack on plating layer due to sulfur in saccharin. It is considered that the Ni-S compound causes the cracking and additional tensile stresses. The Ni-Mn-B ternary alloy plating was developed for suppression of crack by forming Mn-S compound before Ni-S compound is formed, but there were no domestic or international standard on the Ni-Mn-B alloy plating. Therefore, reliability evaluation standard was established to evaluate the newly developed Ni-Mn-B plating. To develop accelerating life testing method, FMEA(Failure Mode & Effective analysis) was used to analyze the cause of the main failure in plating. The Ni-Mn-B reliability standard included accelerating life test method, and it was categorized by the fundamental performance test, environment test, and accelerated life test, and was designed to guarantee 1 000 hours of B10 life with 80 % reliable level.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.1
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• pp.23-27
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• 2003

Structural properties of Cu-Ni alloy films, such as preferred orientation, crystallite size, in-ter-planar spacing, cross-sectional morphology, and electrical resistivity, are investigated in terms of tar-get configurations that are used in the film deposition by means of magnetron co-sputtering. Two different target configurations are considered in this study: a dual-type configuration in which two separate tar-gets (Cu and Ni) and different bias types (RF and DC) are used and a Ni-on-Cu type configuration in which Ni chips are attached to a Cu target. The dual-type configuration appears to have some advantages over the Ni-on-Cu type regarding the accurate control of atomic composition of the deposited Cu-Ni alloy. However, the dual-type-produced film exhibits a porous and columnar structure, the relatively large internal stress, and the high electrical resistivity, which are mainly due to the relatively low mobility of adatoms. The affects of thermal treatment and deposition conditions on the structural and electrical properties of dual-type Cu-Ni films are also discussed.