• Corrosion Science and Technology
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• v.17 no.3
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• pp.91-100
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• 2018

Development of biodegradable implants for treatment of complex bone fractures has recently become one of the priority areas in biomedical materials research. Multifunctional corrosion resistant and bioactive coatings containing hydroxyapatite $Ca_{10}(PO_4)_6(OH)_2$ and magnesium oxide MgO were obtained on Mg-Mn-Ce magnesium alloy by plasma electrolytic oxidation. The phase and elemental composition, morphology, and anticorrosion properties of the coatings were investigated by scanning electron microscopy, energy dispersive spectroscopy, potentiodynamic polarization, and electrochemical impedance spectroscopy. The PEO-layers were post-treated using superdispersed polytetrafluoroethylene powder. The duplex treatment considerably reduced the corrosion rate (>4 orders of magnitude) of the magnesium alloy. The use of composite coatings in inducing bioactivity and controlling the corrosion degradation of resorbable Mg implants are considered promising. We also applied the plasma electrolytic oxidation method for the formation of the composite bioinert coatings on the titanium nickelide surface in order to improve its electrochemical properties and to change the morphological structure. It was shown that formed coatings significantly reduced the quantity of nickel ions released into the organism.

• Journal of Welding and Joining
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• v.29 no.2
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• pp.34-39
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• 2011

Nickel-based austenitic alloys such as Alloy 82 and 182 had been employed as the weld metals in nuclear power plants (NPPs) due to their high corrosion resistance as well as good mechanical properties. However, since the 2000s, the occurrence of primary water stress corrosion cracking has been reported in conjunction with these alloys in domestic and oversea NPPs. In the present work, we assumed an imaginary crack at the inner surface of a surge nozzle weld that had previously experienced the outside repair welding, and constructed its finite element model. Finite element analysis was performed with respect to the heat transfer, and then to the residual stress for obtaining the total applied stress distributions. These stress distributions were finally converted to the stress intensity factors for estimating crack growth rate. From the comparison of crack growth rate curves for the cases of no repair welding and outside repair welding, it was found that the outside repair welding did not exhibit negative effect on the crack growth for the surge nozzle under consideration in this work; in both cases, the cracks stopped growing before they became the through-wall cracks.

• Journal of Hydrogen and New Energy
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• v.3 no.2
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• pp.45-54
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• 1992

An applicability microencapsulation, using electroless copper plating, of hydrogen storage alloy powder as an anode material for nickel-hydrogen secondary batteries was investigated. Alloys employed were $LaNi_{4.7}Al_{0.3}$ and $MmNi_{4.5}Al_{0.5}$(Mm=mischmetal) which have an appropriate equilibrium pressure and capacity. The microencapsulation of the alloy powder was found to accelerate initial activation of electrodes and to increase capacity which is about 285mAh/g for $LaNi_{4.7}Al_{0.3}$. In addition, other charge and discharge characteristics, such as polarization and flatness of charge and discharge potential, were improved due to the role of copper layer as a microcurrent collector and an oxidation barrier of the alloy powder. $MmNi_{4.5}Al_{0.5}$ alloy showed lower capacity than $LaNi_{4.7}Al_{0.3}$ because of higher equilibrium pressure. Cyclic characteristics of both alloys were somewhat poor because of mainly shedding and partial oxidation of alloy powder during the cycling. However, it was considered that the microencapsulation method is effective to improve the performances of the hydrogen storage alloy electrodes.

• Journal of the Korean institute of surface engineering
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• v.47 no.6
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• pp.293-296
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• 2014

Fe-Ni has been of great interest because it is known as one of low thermal expansion alloys as various application areas. This alloy was fabricated by electroforming process, and effect of heat treatment on thermal expansion and hardness was investigated. Nano-crystalline structure of 13.3 - 63.5 nm in size was observed in the as-deposited alloy. To investigate the effect of heat treatment on grain growth and mechanical/thermal properties, we conducted hardness and coefficient of thermal expansion (CTE). From this, we confirmed these properties were varied by heat treatment. In this nano-crystalline alloy, we could observe abnormal behavior in thermal expansion between $350-400^{\circ}C$. Additionally, an abrupt change in hardness has also been observed. However, once the grains grow up to micro-sized the mechanical and thermal properties mentioned above were stabilized similar to those of bulk alloys due to heat treatment.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.347-360
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• 2021

Currently, the demand for eco-friendly energy sources is high, which has prompted research on polymer electrolyte membrane fuel cells. Both aluminum alloys and nickel alloys, which are commonly considered as materials of bipolar plates in fuel cells, oxide layers formed on the metal surface have excellent corrosion resistance. In this research, the electrochemical characteristics of 6061-T6 aluminum alloy and Inconel 600 were investigated with chloride concentrations in an acid environment that simulated the cathode condition of the PEMFC. After potentiodynamic polarization experiments, Tafel analysis and surface analysis were performed. Inconel 600 presented remarkably good corrosion resistance under all test conditions. The corrosion current density of 6061-T6 aluminum alloy was significantly higher than that of Inconel 600 under all test conditions. Also, 6061-T6 aluminum alloy and Inconel 600 presented uniform corrosion and intergranular corrosion, respectively. The Ni, Cr, and Fe, which are the main chemical compositions of Inconel 600, are higher than Al in the electromotive force series. And a double oxide film of NiO-Cr₂O₃, which is more stable than Al₂O₃, is formed. Thus, the corrosion resistance of Inconel 600 is better.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.5
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• pp.224-228
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• 2014

Recently, the demands for separation/recovery of valuable metals such as nickel or tin from copper based alloys has been attracting much attention from the viewpoints of environmental protection and resource utilization. In this report, experimental results on concentration increasement of nickel and tin compared to the previous report are investigated. Ni is successfully separated by a organic solvent and reduced to the metal powder whose concentration is over 98 %. Sn is separated by a selective solution method and its concentration is increased to 97.5 % by three consecutive solution and reduction process. Crystal structure, surface morphology and microstructure of the separated samples are studied.

• Transactions of Materials Processing
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• v.8 no.3
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• pp.247-247
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• 1999

The segregation (distribution) of nickel and the composition of its constituents influence the low thermal expansion characteristics (Invar effect) in Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy. The change of coefficient of the thermal expansion and magnetic properties were studied as an aspect of carbon addition causing the segregation of Ni in primary austenite of as-cast Fe-30 wt.% Ni-12.5 wt.% Co Invar alloy. The coefficient of thermal expansion of Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy showed its lowest value at 0.08 wt.% carbon, increased with increasing carbon content in the range of 0.08-1.0 wt.%C, kept constant at 1.0-2.0 wt.%C and decreased at carbon higher than 2.0 wt.%. The effective distribution of the coefficient of nickel in as-cast Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy increased with increasing carbon content. The volume fraction of they phase of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy increased with increasing carbon content. The microstructure of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy changed with the carbon content was independent of the coefficient of thermal expansion. The Curie temperature changed linearly with the carbon content and was similar to the change of the coefficient of thermal expansion. Moreover, the coefficient of thermal expansion decreased when the ratio of saturation magnetization to Curie temperature ($\sigma_s/T_c$) increased, decreasing the Curie temperature and showed a specific relationship with the magnetic properties of the Fe-30 wt.% Ni-12.5 wt.% Co-xCInvar alloy.

• Korean Journal of Materials Research
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• v.4 no.8
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• pp.877-887
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• 1994

Cu-Ni-Si-P alloys have been studied in order to develop connector material which has a favorable combination of strength, electrical conductivity, elastic limit, thermal softening resistence and bend formability. Three kinds of trial alloys with various nickel and silicon content were melted and cast, hot rolled at about $900^{\circ}C$ and cold rolled. Mechanical properties and electrical conductivities of these alloys annealed at $450^{\circ}C$, $500^{\circ}C$ and $550^{\circ}C$ were investigated. An alloy with the composition of Cu-2.7%Ni-0.53%Si-O.O29%P, which shows a favorable combination of high strength and high electrical conductivity, has been developed. Various characteristics of the alloy 1 connector material were evaluated and compared with phospher bronze(C521OR-H) and brass(C26OOR-EH) connector material.

• International Journal of Oral Biology
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• v.31 no.1
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• pp.15-20
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• 2006

Concerns remain regarding the biocompatibility and adverse effects of dental casting alloys. The aim of this study was to understand the cytopathogenic effect of metal ions, which might be released from dental alloys, on oral squamous carcinoma(OSC) cells. The cellular morphology, viability, the type of cell death and molecular change in response to metal ion salt solutions including aluminum(Al), cobalt(Co), copper(Cu) and nickel(Ni) were examined. The $TC_{50}$ values for the metal ions with the exception of AI were estimated to be between 400 and $600{\mu}M$. The cells treated with the metal ions showed apoptotic change with the exception of Al ions. Metal ion-induced apoptosis was further confirmed using flow cytometric analysis. This study showed that the cytotoxicity and the mode of cell death by metal ions clearly depend on the cell type, the type of metal ion and the duration of exposure. The protein level of Rb, a tumor suppressor that affects apoptosis para-doxically, was higher in the cells treated with Co, Cu and Ni. It is believed that apoptosis and cell damage in the OSC cells treated with Co, Cu or Ni can be evoked by the regulation of Rb.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.57-62
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• 2016

The over-discharging phenomena in sodium-nickel chloride batteries were investigated in relation to decomposition of molten salt electrolyte and consequent metal co-deposition. From XRD analysis, the material deposited on graphite cathode current collector was revealed to be by-product of molten salt electrolyte decomposition. In particular, the result showed that the Ni-Al alloys ($Al_3Ni_2$, $Ni_3Al$ and $Al_3Ni$) were electrochemically deposited on graphite current collectors in line with over-discharging behaviors. It is assumed that the $NiCl_2$ solubility in molten salt electrolytes leads to the co-deposition of Ni-Al alloys by increasing metal deposition potential above 1.6 V (vs. $Na/Na^+$). The cell tests have revealed that the composition of molten salt electrolytes modified by various additives makes a decisive influence on the over-discharging behaviors of the cells. It was revealed that NaOCN addition to molten salt electrolytes was advantageous to suppress over-discharge reactions by modifying the characteristics of molten salt electrolytes. NaOCN addition into molten salt electrolytes seems to suppress Ni solubility by maintaining basic melts. The cell using modified molten salt electrolyte with NaOCN (Cell D) showed relatively less cell degradation compared with other cells for long cycles.