• Transactions of the Korean hydrogen and new energy society
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• v.15 no.1
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• pp.62-71
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• 2004

$LiMn_{1.92}Co_{0.08}O_4-x\;wt.%LiNi_{0.7}Co_{0.3}O_2$를 단순화한 연소법에 의하여 합성하고, 그것들의 전기화학적 특성을 조사하였다. 또한 30분동안 밀링하여 준비한 $LiMn_{1.92}Co_{0.08}O_4-x\;wt.%LiNi_{0.7}Co_{0.3}O_2$ (x=9, 23, 33, 41 and 47) 혼합물 전극의 전기화학적 특성을 조사하였다. x=33 조성의 전극이 가장 큰 초기방전용량(132.0mAh/g at 0.1C)을 나타내었다. x=9조성의 전극은 비교적 큰 초기방전용량(109.9mAh/g at 0.1C)과 우수한 싸이클 특성을 나타내었다. 싸이클링에 따른 혼합물 전극의 방전용량의 감소는 주로 $LiNi_{0.7}Co_{0.3}O_2$의 퇴화에 기인한다고 생각된다. 그런데 $LiNi_{0.7}Co_{0.3}O_2$의 퇴화는 $LiMn_{1.92}Co_{0.08}O_4$로부터 용해된 Mn이 $LiNi_{0.7}Co_{0.3}O_2$를 둘러쌈(coating)으로써 야기되는 것으로 생각된다.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.52-58
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• 2020

Electrochemical characterization and thermal stability were investigated for MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ cathode. The ratio of MgF₂ was controlled by 0.5, 1, 3 wt%. Cyclic voltammetry, charge-discharge profiles, rate capability, cycle life were measured for electrochemical properties. DSC analysis was measured for thermal stability. The first discharge capacities of MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ were decreased at 0.1C-rate compared to pristine LiNi_0.8Co_0.15Al_0.05O₂. But the rate capability and cycle life of MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ were improved at 2C-rate. In DSC analysis result, the exothermic temperature of MgF₂ coated LiNi_0.8Co_0.15Al_0.05O₂ was increased and peak height was decreased.

• Journal of Korea Foundry Society
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• v.14 no.3
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• pp.274-284
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• 1994

SiC fibers were coated with Cu, Ag and Ni metallic thin films by magnetron sputtering in order to improve wetting properties between Al matrix and SiC fiber. The wetting behavior of metal coated SiC fiber by pure Al has been studied at $670^{\circ}C{\sim}900^{\circ}C$ range for $10{\sim}90min$. under vacuum atmosphere. Besides, the effect of coated film thickness on the wettability has been investigated. The wetting behavior and interfacial reaction between Al and SiC fibers were analysed with optical microscope and SEM (scanning electron microscope). The wetting behavior of the as-received SiC fiber with Al melt was not uniform, indicated by the contact angles from less than $90^{\circ} to more Al melt was appeared in the initial stage of reation. It was considered that the metallic thin film played an important role in reducing the interfacial free energy and breaking down the aluminum oxide film by eutectic reaction with Al melt. However the wettability of Ni coated SiC fiber was not improved as much as that of Cu or Ag coated SiC fiber. The improvement of wettability by coating thickness is clearly showed in $1{\mu}m$ coated SiC fiber compared with $0.25{\mu}m$ coated SiC.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.4
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• pp.1-10
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• 2001

Chip-on-glass(COG) mounting of area array electronic packages was attempted by heating the rear surface of a contact pad film deposited on a glass substrate. The pads consisted of an adhesion (i.e. Cr or Ti) and a top coating layer(i.e. Ni or Cu) were healed by the UV laser beam transmitted through the glass substrate. The lather energy absorbed on the pad raised the temperature of a solder ball which is in physical contact with the pad, and formed a reflowed solder bump. The effects of the adhesion and top coating layer on the laser reflow soldering were studied by measuring temperature profile of the ball during the laser heating process. The results were discussed based on the measurement of reflectivity of the adhesion layer. In addition, the microstructures of solder bumps and their mechanical properties were examined.

• Korean Journal of Materials Research
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• v.13 no.2
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• pp.126-132
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• 2003

In order to evaluate the corrosion resistance at the anode side separator for molten carbonate fuel cell, STS316 and SACC-STS316 (chromium and aluminum were simultaneously deposited by diffusion into STS316 authentic stainless steel substrate by pack-cementation process) were applied as the separator material. In case of STS316, corrosion proceeded via three steps ; a formation step of corrosion product until stable corrosion product, a protection step against corrosion until breakaway occurs, a advance step of corrosion after breakaway. Especially, STS316 would be impossible to use the separator without suitable surface modification because of rapid corrosion rate after formation of corrosion product, occurs the severe problem on stability of cell during long-time operation. Whereas, SACC-STS316 was showed more effective corrosion resistance than the present separator, STS316 due to the intermetallic compound layer such as NiAl, Ni3Al formed on the surface of STS316 specimen. And it is anticipated that, in order to use SACC-STS316 alternative separator at the anode side, coating process, which can lead to dense coating layer, has to be developed, and by suitable pre-treatment before using it, very effective corrosion resistance will be achieved.

• Journal of the Korean Ceramic Society
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• v.45 no.9
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• pp.549-555
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• 2008

The thermal barrier coating must withstand erosion when subjected to flowing gas and should also maintain good stability and mechanical properties while it must also protect the turbine component from high temperature, hot corrosion, creep, and oxidation during operation. In this study we investigated the influence of subsurface layer, $Al_2O_3$ or NiCrCoAIY bond coat layer, on the indentation damage behavior of YSZ thermal barrier coating layers deposited by electron beam physical vapor deposition (EB-PVD). The bond coat is deposited using different process such as air plasma spray (APS) or spray of high velocity oxygen fuel (HVOF) and the thickness is varied. Hertzian indentation technique is used to induce micro damages on the coated layer. The stress-strain behaviors are characterized by results of the indentation tests.

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.202-206
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• 2005

The present investigation provides an electromagnetic radiation absorptive composition which comprises silver-coated ferrite microspheres dispersed in silicon rubber matrix for the aim of thin microwave absorber in GHz frequencies. Ni-Zn ferrite spheres with $50{\mu}m$ size in average were prepared by spray-drying and sintering at $1130^{\circ}C$. Conductive silver layer was plated on ferrite spheres by electroless plating. Conductive Ni-Zn ferrite sphere with uniform silver layer were obtained in the concentration of 10 g/L $AgNO_3$ per 20 g ferrite spheres. For this powder, electrical resistance is reduced as low as $10^{-2}\~10^{-3}\;\Omega$. The most sensitive material parameters with silver plating is real and imaginary parts of complex permittivity. The conductive Ni-Zn ferrite spheres have large values of dielectric constant. Due to this high dielectric constant of microspheres, matching thickness is reduced to as low as 2 mm at the frequency of 7 GHz, which is much thinner than conventional ferrite absorbers.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.4
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• pp.161-167
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• 1998

It has been investigated the effects of alloying elements and binders on the corrosion behavior of metal hydride electrodes for anode of Ni/MH secondary battery. The $AB_5$-type alloys, $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$ and $(LM)Ni_{3.6}Co_{0.7}Mn_{0.3}Al_{0.4}$, were used for the experiments. The electrodes were prepared by mixing and cold-pressing of alloy powders with Si sealent or PTFE powders, or cold-pressing the electroless copper coated alloy powders. The amount of copper coating was 20wt%. In order to examine corrosion behavior of the electrodes, the corrosion current and the current density, in 6M KOH aqueous solution after removal of oxygen in the solution, were measured by potentiodynamic and cyclic voltamo methods. The results showed that Co in the alloy increased corrosion resistance of the electrode whereas Ni decreased the stability of the electrode during the charge-discharge cycles. The electrode used Si sealant as a binder showed a lower corrosion current density than the electrode used PTFE and the electrode used Cu-coated alloy powders showed the best corrosion resistance.

• Applied Chemistry for Engineering
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• v.2 no.1
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• pp.47-55
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• 1991

Regeneration of carbon-deposited Ni catalyst used for hydrogenation reaction was studied. Deposited carbon was removed by oxidation with various concentrations of oxygen. Activity of the catalysts was tested on aniline hydrogenation as a model reaction. When a carbon-deposited catalyst was treated under oxygen atmosphere, the specific surface area of the catalyst increased and then decreased with the increase of treatment temperature. The treatment temperature which gives maximum specific surface area increased with the decrease of oxygen concentration. Pore size of the support was decreased and sintering of nickel particles was more significant with the increase of oxygen concentration. The catalyst treated under 5 % oxygen concentration recovered its catalytic activity up to 90 % of the initial value, but the treatment under 20 % oxygen concentration gave no significant increase of the catalytic activity. Catalytic activity increased with treatment time when the catalyst was treated under 5 % oxygen concentration, but nearly constant after 1 hour.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.4
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• pp.395-404
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• 1994

Ni-graphite composite powders were prepared by reduction of $Ni^{++}$ from ammoniacal nickel sulfate solution on graphite core by hydrogen gas. Effect of reaction factors on the reduction rate and the properties of nickel layer were investigated by SEM, Optical Microscopy, size and chemical analysis. Induction period, a time lag between the injection of hydrogen gas and the start of the reduction, was 20~110 mins and affected by the reaction temperature and stirring speed. The reduction rate of $Ni^{++}$ was $4.5g/{\ell}/min$ at optimum condition and increased with increasing reaction temperature and stirring speed.