• 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.

• Restorative Dentistry and Endodontics
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• v.9 no.1
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• pp.101-106
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• 1983

It was the purpose of this study to investigate the fracture mode of dental amalgam by observing the crack propagation, and to relate this to the microstructure of the amalgam. Caulk 20th Century Regular, Caulk Spherical, Dispersalloy, and Tytin amalgam alloys were used for this study. After each amalgam alloy and Hg measured exactly by the balance was triturated by the mechanical amalgamator (Capmaster, S.S. White), the triturated mass was inserted into the cylindrical metal mold which was 4 mm in diameter and 12 mm in height and was pressed by the Instron Universal Testing Machine at the speed of 1mm/min with 120Kg. The specimen removed from the mold was stored in the room temperature for a week. This specimen was polished with the emery papers from #100 to #200 and finally on the polishing cloth with 0.06${\mu}Al_2O_3$ powder suspended in water. The specimen was placed on the Instron testing machine in the method similar to the diametral tensile test and loaded at the crosshead speed of 0.05mm/min. The load was stopped short of fracture. The cracks on the polished surface of specimen was examined with scanning electron microscope (JSM-35) and analyzed by EPMA (Electron probe microanalyzer). The following results were obtained. 1. In low copper lathe-cut amalgam, the crack went through the voids and ${\gamma}_2$ phase, through the ${\gamma}_1$ phase around the ${\gamma}$ particles. 2. In low copper spherical amalgam, it was observed that the crack passed through the ${\gamma}_2$ and ${\gamma}_1$ phase, and through the boundary between the ${\gamma}_1$ and ${\gamma}$ phase. 3. In high copper dispersant (Dispersalloy) amalgam, the crack was found to propagate at the interface between the ${\gamma}_1$ matrix and reaction ring around the dispersant (Ag-Cu) particles, and to pass through the Ag-Sn particles. 4. In high copper single composition (Tytin) amalgam, the crack went through the ${\gamma}_1$ matrix between ${\eta}$ crystals, and through the unreacted alloy particle (core).

• Journal of Powder Materials
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• v.9 no.6
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• pp.381-393
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• 2002

Recent developments in nanocrystalline and nanocomposite rare earth-transition metal magnets are reviewed and emphasis is placed on research work at IFW Dresden. Principal synthesis methods include high energy ball milling, melt spinning, mold casting and hydrogen assisted methods such as reactive milling and hydrogenation-disproportionation-desorption-recombination. These techniques are applied to NdFeB-, PrFeB- and SmCo-type systems with the aim to produce high remanence magnets with high coercivity. Concepts of maximizing the energy density in nanostructured magnets by either inducing a texture via anisotropic HDDR or hot deformation or enhancing the remanence via magnetic exchange coupling are evaluated. With respect to high temperature applications melt spun $Sm(Co_{0.74}Fe_{0.1}Cu_{0.12}Zr_{0.04})_{7.5}$ ribbons were prepared, which showed coercivities of up to 0.53 T at 50$0^{\circ}C$. Partially amorphous $Nd_{60}Fe_xCo_{30-x}Al_{10}(0{\leq}x{\leq}30)$ alloys were prepared by copper mold casting. The effect of transition metal content on the glass-forming ability and the magnetic properties was investigated. The $Nd_{60}Co_{30}Al_{10}$ alloy exhibits an amorphous structure shown by the corresponding diffraction pattern. A small substitution of Co by 2.5 at.% Fe results In the formation of Fe-rich crystallites embedded in the Nd-rich amorphous matrix. The Fe-rich crystallites show hard magnetic behaviour at room temperature with a coercivity value of about 0.4 T, relatively low saturation magnetization and a Curie temperature of 500 K.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.98-103
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• 2012

Recently, development of Al-based alloys for high mechanical performance has been an important issue in automotive industry. The present study focused on the design of a high strength Al-based alloy for rheo-diecasting. The research was based on thermodynamic calculation and experimentals to optimize the alloy compositions. Two important considerations were carried out: i) to obtain uniform slurry with fine and globular microstructures for rheo-diecasting, ii) to be strengthend by T6 heat treatment. In order to evaluate the effect of Si content on the slurry microstructure and castability, thermodynamic calculation and fluidity test were carried out. The effects of various alloying components, such as Mg, Cu and Zn, on age hardenability were also investigated. The mechanical properties of the rheo-diecasting products using the newly developed alloy are 324MPa in tensile strength, 289MPa in yield strength, and 11.2% in elongation after T6 heat treatment.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.392-396
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• 1999

Superconducting YBa$_2Cu_3O_{7-{\delta}}$(YBCO) thin films were grown on Hastelloy(Ni-Cr-Mo alloys) with CeO$_2$ buffer layer in-situ by pulsed laser deposition in a multi-target processing chamber. To apply superconducting property on power transmission line, we have deposited YBCO thin film on flexible metallic substrate. However, it is difficult to grow the YBCO films on flexible metallic substrates due to both interdiffusion problem between metallic substrate and superconducting overlayers and non-crystallization of YBCO on amorphous substrate. It is necessary to use a buffer layer to overcome the difficulties. We have chosen CeO$_2$ as a buffer layer which has cubic structure of 5.41 ${\AA}$ lattice parameter and only 0.2% of lattice mismatch with 3.82 ${\AA}$ of a-axis lattice parameter of YBCO on [110] direction of CeO$_2$ In order to enhance the crystallization of YBCO films on metallic substrates, we deposited CeO$_2$ buffer layers with varying temperature and 02 pressure. By XRD, it is observed that dominated film orientation is strongly depending on the deposition temperature of CeO$_2$ layer. The dominated orientation of CeO$_2$ buffer layer is changed from (200) to(111) by increasing the deposition temperature and this transition affects the crystallization of YBCO superconducting film on CeO$_2$ buffered Hastelloy.

• Journal of the Korean Magnetics Society
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• v.17 no.5
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• pp.194-197
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• 2007

Understanding the spin polarization (P) has been an ongoing research challenge. The $Co_{1-x}Mn_x$ (x=0.27, 1) and $Co_{1-x}Fe_x$ (x=0, 0.5, 1) films were prepared using UHV-MBE system. For these films, the magnetic properties and spin polarization were investigated using SQUID and Meservey-Tedrow technique, respectively. Although measured P is uncorrelated to the bulk magnetic moment (M) in Co-Fe and Ni-Fe alloy films, it correlates with M in some alloys such as Co-Mn and Ni-Cu. The results can be understood by the tunneling currents made up of the hybridized sp-d electrons near the Fermi-energy level. Our work shows the feasibility to tailor new materials with large P values.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.4
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• pp.47-52
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• 2013

Gold wire has long been used as a proven method of connecting a silicon die to a substrate in wide variety of package types, delivering high yield and productivity. However, with the high price of gold, the semiconductor packaging industry has been implementing an alternate wire material. These materials may include silver (Ag) or copper (Cu) alloys as an alternative to save material cost and maintain electrical performance. This paper will analyze and compare the electrical characteristics of several wire types. For the study, typical 0.6 mil, 0.8 mil and 1.0 mil diameter wires were selected from various alloy types (2N gold, Palladium (Pd) coated/doped copper, 88% and 96% silver) as well as respective pure metallic wires for comparison. Each wire model was validated by comparing it to electromagnetic simulation results and measurement data. Measurements from the implemented test boards were done using a vector network analyzer (VNA) and probe station setup. The test board layout consisted of three parts: 1. Analysis of the diameter, length and material characteristic of each wire; 2. Comparison between a microstrip line and the wire to microstrip line transition; and 3. Analysis of the wire's cross-talk. These areas will be discussed in detail along with all the extracted results from each type the wire.

• Journal of Technologic Dentistry
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• v.22 no.1
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• pp.69-78
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• 2000

The microstructure and corrosion behavior of commercially dental casting gold alloys were investigated to clarify the effect of burn-out temperature and cooling rate. In the case of water quenching after casting, only the αphase, which is typical dendritic microstructure of golda alloy, was detected. However, the precipitates along the grain boundary were detected only at the slow cooling rate and they increased inversely proportional to the burn-out temperature. This might be due to the time difference which solute atom could diffuse. EPMA and SEM results also demonstrated that the precipitate should be lamellar structure consisted of Ag rich phase(${\alpha}_1$) and Cu rich phase (${\alpha}_2$). In terms of corrosion, the galvanic coupling was formed due to the difference of composition between precipitates and matrix at the slow cooling rate. In the case of water quenching, the critical current density($i_p$) which indicate the degree of corrosion was lowest at $650^{\circ}C$ and below the burnout temperature, $i_p$ increased with it because of the effect of grain boundary segregation. But above the temperature, $i_p$ increased with it. This may be due to the strain field effect by residual thermal stress.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.583-588
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• 2015

Asymptotic method has been often used to theoretically analyze the complete contact problem. The error of the asymptotic results increases as the distance from the contact edge increases. The singularity cannot be properly obtained from a finite element (FE) analysis owing to the finiteness of the element size. In the present work, the complete contact problem in bonded condition is analyzed using a combined experimental-numerical approach to assist and/or compare with the asymptotic results. Al and Cu alloys are used for the material combination of the punch and substrate. 120 and 135 degrees are used for the punch angle. The FE models are validated by comparison of displacement distributions obtained by the FE analysis and $moir{\acute{e}}$ experiment. Generalized stress intensity factors are evaluated using the validated FE models. Stress field in the vicinity of the sharp contact edges obtained from the FE and asymptotic analyses are compared. The discrepancies are also discussed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.153-153
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• 2017

The application of the coating supports the mechanical characteristics of the implant, and various materials and coatings are currently being used in the implant in a way to accelerate adhesion. Especially, plasma electrolytic oxidation (PEO) coating has been proposed continually with good surface treatment of titanium alloys. Also, the PEO process can incorporate Ca and P ions on the titanium surface through variables varied factor. PEO process for bioactive surface has carried out in electrolytes containing Ca and P ions. Natural bone is composed of mineral elements such as Mg, Si, Zn, Sr, and Mn, etc. Especially, Mg and Si of these elements play role in bone formation and growth after clinical implantation of bio-implants. In this study, corrosion charateristics of PEO-treated Ti-6Al-4V alloy in solution containing Si and Mg ions has been investigated using several experimental techniques. The PEO-treated surfaces were identified by X-ray diffraction, using a diffractometer (XRD, Philips X' pert PRO, Netherlands) with Cu $K{\alpha}$ radiation. The morphology was observed by field-emission scanning electron microscopy (FE-SEM, Hitachi 4800, Japan) and energy-dispersive X-ray spectroscopy (EDX, Oxford ISIS 310, England). The potentiodynamic polarization and AC impedance tests for electrochemical degradations were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67mV/s and potential range from -1500mV to + 2000mV.