• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.883-884
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• 2006

A new extra-fine grade Ni powder (XF Ni) has demonstrated increased sintering activity in Co-Fe-Ni binders for diamond tool applications. XF Ni has the advantage of significantly lower cost than XF Co. Up to 30% of XF Co was substituted with XF Ni while maintaining comparable apparent hardness and transverse rupture strength to pure Co binders. Ni substantially increased the diffusion of Fe. Diamond tool producers can take advantage of the improved sintering properties of XF Ni powder to substantially lower material costs.

• Journal of the Korean institute of surface engineering
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• v.25 no.2
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• pp.57-65
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• 1992

Increasing demands of high corrosion resistant sheet steels for the automotive body panels have been leading to a tendency toward heavier coatings of electroplated sheet steels. The specimens were prepared from lab-scale electroplating simulator with various coating weights of zinc, zinc-iron and zinc-nickel coated sheet steels and evaluated in the light of the application for the automotive body panels. Corrosion resistances by sacrificial action were improved with increasing coating weights for all electroplated sheet under survey, but blistering resistances of pure zinc coated sheet steels were not as much. On the other hand, the adhesions of heavy alloy coatings showed poor powdering performances by the external compressive or tensile forces.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.108-113
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• 2001

In this paper, the real-time prediction of high temperature creep strength and creep strength and creep life for nickel-based superalloy Udimet 720 (high-temperature and high-pressure gas turbine engine materials) was performed on round-bar type specimens under pure load at the temperatures of 538, 649 and 704$^{\circ}C$. The predictive equation of ISM creep has better reliability than that of LMP and LMP-ISM, and its reliability is getting better for long time creep prediction(10$^3$~10sup/5/ｈ).

• Bulletin of the Korean Chemical Society
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• v.14 no.4
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• pp.500-506
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• 1993

$^1H$ and $^{13}C$ NMR spectra for pyridine, ${\beta}$-and ${\gamma}$-picoline, pyrazine, and 4,4'-bipyridyl complexed with paramagnetic undecatungstocobalto(II)silicate and undecatungstonickelo(II)silicate anions are reported. For these complexes the ligand exchange is slow on the NMR time scale and the pure resonance lines have been observed at room temperature. The isotropic shifts in nickel complexes can be interpreted in terms of contact shifts by ${\sigma}$-electron delocalization. Both contact and pseudocontact shifts contribute to the isotropic shifts in cobalt complexes. The contact shifts, which are obtained by subtracting the pseudocontact shifts from the isotropic shifts, require both ${\sigma}$-and ${\pi}$-electron delocalization from the cobalt ion. Slow ligand exchange has also allowed us to identify the species formed when bidentate ligands react with the heteropolyanions. Pyrazine forms a 1 : 1 complex, while 4,4'-bipyridyl forms both 1 : 1 and dumbbell-shaped 1 : 2 complexes.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.375-381
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• 2013

Kinetics data were obtained for steam reforming of methane and natural gas over the commercial nickel catalyst. Variables for the steam reforming were the reaction temperature and partial pressure of reactants. Parameters for the Power law rate model and the Langmuir-Hinshelwood model were obtained from the kinetic data. As a result of the reforming reaction using pure methane as a reactant, the reaction rate could be determined by the Power law rate model as well as the Langmuir-Hinshelwood model. In the case of methane in natural gas, however, the Langmuir-Hinshelwood model is much more suitable than the Power law rate model in terms of explaining methane reforming reaction. This behavior can be attributed to the competitive adsorption of methane, ethane, propane and butane in natural gas over the same catalyst sites.

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.439-443
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• 2010

Nano sized SiC particles (270 nm) are easily agglomerated in nickel sulfamate electrolytic bath during a composite electrodeposition process. The agglomeration of nano particles in composite coatings can significantly reduce the mechanical properties of the composite coatings. In this study, Ni-SiC nano composite coatings were fabricated using a conventional electrodeposition process with the aid of ultrasound. Nano particles were found to be distributed homogeneously with reduced agglomeration in the ultrasonicated samples. Substantial improvements in mechanical properties were observed in the composite coatings prepared in presence of ultrasound over those without ultrasound. Ni-SiC composite coatings were prepared with variable ultrasonic frequencies ranging from 24 kHz to 78 kHz and ultrasonic powers up to 300 watts. The ultrasonic frequency of 38 kHz with ultrasonic power of 200 watt was revealed to be the best ultrasonic conditions for homogeneous dispersion of nano SiC particles with improved mechanical properties in the composite coatings. The microstructures, phase compositions, and mechanical properties of the composite coatings were observed and evaluated using SEM, XRD, Vickers microhardness, and wear test. The Vickers microhardness of composite coatings under ultrasonic condition was significantly improved as compared to the coatings without ultrasound. The friction coefficient of the composite coating prepared with an ultrasonic condition was also smaller than the pure nickel coatings. A synergistic combination of superior wear resistance and improved microhardness was found in the Ni-SiC composite coatings prepared with ultrasonic conditions.

• Resources Recycling
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• v.30 no.6
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• pp.36-42
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• 2021

Spent lithium-ion batteries are treated by reduction-smelting at high temperatures to recover valuable metals. Solvent extraction and precipitation of the HCl leaching solution of reduction-smelted metallic alloys resulted in a filtrate containing Ni(II) and a small amount of Si(IV). Adsorption and precipitation experiments were conducted to recover pure Ni(II) compounds from the filtrate. Si(IV) was selectively loaded onto polyacrylamide, but this method did not efficiently filter the solution due to an increase in viscosity. The addition of Na₂CO₃ as a precipitant to the filtrate led to the simultaneous precipitation of Ni(II) and Si(IV). However, it was possible to recover nickel oxalate with a purity higher than 99.99% by selectively precipitating Ni(II) with the addition of Na₂C₂O₄ as a precipitant.

• Korean Journal of Materials Research
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• v.31 no.8
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• pp.439-444
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• 2021

The oxidation resistance of the diffusion aluminide bond coat (BC) is compromised largely by interdiffusion (ID) effects on coated turbine blades of aeroengines. The present study is designed to understand the influence of ID on βNiAl coatings or BC. In this regard, nickel substrate and CMSX-4 superalloy are deposited. In total, four sets of BCs are developed, i.e. pure βNiAl (on Ni substrate), simple βNiAl (on CMSX-4 substrate), Zr-βNiAl (on CMSX-4 substrate) and Pt-βNiAl (on CMSX-4 substrate). The main aim of this study is to understand the interdiffusion of Al, Zr and Pt during preparation and oxidation. In addition, the beneficial effects of both Zr and platinum are assessed. Pure βNiAl and simple βNiAl show Ni-out-diffusion, whereas for platinum inward diffusion to the substrate is noticed under vacuum treatment. Interestingly, Zr-βNiAl shows the least ID in all BCs and exhibit stability under both vacuum and oxidation treatments. However, its spallation resistance is slightly lower than that of Pt-βNiAl BC. All BCs show similar oxide growth trends, except for Zr-βNiAl, which exhibits two-stage oxidations, i.e. transient and steady-state. Moreover, it is suggested that the localized spallation in all BCs is caused by βNiAl - γ'-Ni₃Al transformation.

• The Journal of Advanced Prosthodontics
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• v.7 no.2
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• pp.172-177
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• 2015

PURPOSE. The purpose of this study was to evaluate cell toxicity due to ion release caused by galvanic corrosion as a result of contact between base metal and titanium. MATERIALS AND METHODS. It was hypothesized that Nickel (Ni)-Chromium (Cr) alloys with different compositions possess different corrosion resistances when contacted with titanium abutment, and therefore in this study, specimens ($10{\times}10{\times}1.5mm$) were fabricated using commercial pure titanium and 3 different types of Ni-Cr alloys (T3, Tilite, Bella bond plus) commonly used for metal ceramic restorations. The specimens were divided into 6 groups according to the composition of Ni-Cr alloy and contact with titanium. The experimental groups were in direct contact with titanium and the control groups were not. After the samples were immersed in the culture medium - Dulbecco's modified Eagle's medium[DMEM] for 48 hours, the released metal ions were detected using inductively coupled plasma mass spectrometer (ICP-MS) and analyzed by the Kruskal-Wallis and Mann-Whitney test (P<.05). Mouse L-929 fibroblast cells were used for cell toxicity evaluation. The cell toxicity of specimens was measured by the 3-{4,5-dimethylthiazol-2yl}-2,5-diphenyltetrazolium bromide (MTT) test. Results of MTT assay were statistically analyzed by the two-way ANOVA test (P<.05). Post-hoc multiple comparisons were conducted using Tukey's tests. RESULTS. The amount of metal ions released by galvanic corrosion due to contact between the base metal alloy and titanium was increased in all of the specimens. In the cytotoxicity test, the two-way ANOVA showed a significant effect of the alloy type and galvanic corrosion for cytotoxicity (P<.001). The relative cell growth rate (RGR) was decreased further on the groups in contact with titanium (P<.05). CONCLUSION. The release of metal ions was increased by galvanic corrosion due to contact between base metal and titanium, and it can cause adverse effects on the tissue around the implant by inducing cytotoxicity.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.167-173
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• 2011

Nickel cobalt ferrite($Ni_{0.5}Co_{0.5}Fe_2O_4$) powder was prepared through the ceramic route by the calcination of a stoichiometric mixture of NiO, CoO and $Fe_2O_3$ at $1100^{\circ}C$. The pressed pellets of $Ni_{0.5}Co_{0.5}Fe_2O_4$ were isothermally reduced in pure hydrogen at $800{\sim}1100^{\circ}C$. Based on the thermogravimetric analysis, the reduction behavior and the kinetic reaction mechanisms of the synthesized ferrite were studied. The initial ferrite powder and the various reduction products were characterized by X-ray diffraction, scanning electron microscopy, reflected light microscope and vibrating sample magnetometer to reveal the effect of hydrogen reduction on the composition, microstructure and magnetic properties of the produced Fe-Ni-Co alloy. The arrhenius equation with the approved mathematical formulations for the gas solid reaction was applied to calculate the activation energy($E_a$) and detect the controlling reaction mechanisms. In the initial stage of hydrogen reduction, the reduction rate was controlled by the gas diffusion and the interfacial chemical reaction. However, in later stages, the rate was controlled by the interfacial chemical reaction. The nature of the hydrogen reduction and the magnetic property changes for nickel cobalt ferrite were compared with the previous result for nickel ferrite. The microstructural development of the synthesized Fe-Ni-Co alloy with an increase in the reduction temperature improved its soft magnetic properties by increasing the saturation magnetization($M_s$) and by decreasing the coercivity($H_c$). The Fe-Ni-Co alloy showed higher saturation magnetization compared to Fe-Ni alloy.