• Resources Recycling
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• v.18 no.4
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• pp.14-23
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• 2009

In terms of resources recycling and resolving waste disposal problems, it is very important to recover precious metals like Au, Ag and Pd and valuable metals like Cu, Sn and Ni from the scraps of waste electrical and electronic equipment(WEEE) that consists of detective electrical and electronic parts discarded during manufacturing electrical and electronic equipments and waste electrical and electronic parts generated during disassembling them. In general, the scraps of WEEE are composed of various metals and alloys as well as refractory oxides and plastic components. Precious and valuable metals from the scraps of WEEE can be recovered by gas-phase-volatilization, hydrometallurgical, or pyrometallurgical processes. However, the gas-phase-volatilization and hydrometallurgical processes have been suggested but not yet commercialized. At the present time, most of the commercial plants for recovering precious and valuable metals from the scraps of WEEE adopt pyrometallurgical processes. Therefore, in this paper, the technical and environmental aspects on the important pyrometallurgical processes through literature survey are reviewed, and the scale-up result of a new pyrometallurgical process for recovering the precious and valuable metals contained in the scraps of WEEE using waste copper slag is presented.

• 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.

• Korean Journal of Heritage: History & Science
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• v.54 no.1
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• pp.4-17
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• 2021

This study analyzed 19 samples of harness fittings and pendants, which were excavated in Tomb No. 15 in Songhyeon-dong, Changnyeong. Harness fittings and pendants are used for ostentation, rather than practicality, and were excavated from ancient tombs in Gaya culture. So, they are considered artifacts that compare the production techniques and raw materials. This study aimed to examine the production techniques and provenience studies of Bihwa Gaya, which is estimated to be from the 5th to 6th centuries. According to the research, harness fittings were made of pure copper and were gilded with Au·Ag alloys on their surfaces. Hg was detected together and plated with a mercury amalgam method. As a result of the pendant (fish scales-pattern, oval and fish-tail shape), analysis showed that Fe in the background metal, Cu in the middle layer, and Au and Ag on the surface were the main components. The method of adhesion between Cu and Au·Ag gilded layers are plated by a mercury amalgamation method. So, it was identified by the gilt-iron·gold·bronze technique. Since the pendant (heart shaped) is found to be the main component of Fe in the background metal and Ag in the surface layer, the metal was made gilt-iron·silver technique. The background metal and gilding were additionally fixed using a rivet. The raw materials of 3 harnesses excavated from Changnyeong are plotted in zone 2 in the southern Korean Peninsula. And 16 harnesses were plotted in Chinese copper ore by Mabuchi Hishao in the Chinese Peninsula.

• Journal of Ocean Engineering and Technology
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• v.24 no.5
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• pp.67-74
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• 2010

Chromate conversion coating is a coating technique used to passivate aluminum, zinc, cadmium, copper, silver, magnesium, tin, and their alloys to slow corrosion. The process uses various toxic chromium compounds, which may include hexavalent chromium. The industry is developing less toxic alternatives in order to comply with substance restriction legislation, such as RoHS. One alternative is to develop a Cr-free coating solution. In this study, eco-friendly, Cr-free solutions (urethane solution S-700, organic/inorganic solution with Si LRO-317) were used. Test specimens were dried in a drying oven at $190^{\circ}C$ for 3, 5, 7, and 9 minutes. Corrosion resistance was evaluated using a salt spray test for 72 hours. The results show that the optimum corrosion resistance was achieved at $190^{\circ}C$ for five minutes for EGI and three or five minutes for HDGI, respectively. The adhesive properties of the two types of coating solutions were superior regardless of drying time.

• 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.

• Progress in Superconductivity
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• v.10 no.1
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• pp.45-49
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• 2008

For the development of superconducting fault current limiters (SFCLs), fault current limiting elements were fabricated out of Bi-2212 bulk tubes and tested. The SFCL elements consisted of tube shaped Bi-2212 bulks and metal shunts for the stabilizers. Firstly, the Bi-2212 bulk tubes were processed based on a design of monofilar coils in order to acquire large resistance and high voltage rating. 300 mm-long Bi-2212 tubes were designed to have the current path of 410 cm in length with 24 turns and 41 mm in diameter. The processed monofilar coil, as designed, had 300 A $I_c$ at 77 K. The fabricated superconducting monofilar coils were affixed to Cu-Ni alloy as that of stabilizers. The Cu-Ni alloys were processed to have the same shape of the superconducting monofilar coils. The Cu-Ni coil had resistivity of 32 ${\mu}{\Omega}$-cm at 77 K and 37 ${\mu}{\Omega}$-cm at 300 K. The metal shunts were attached to the outside of the Bi-2212 monofilar coil by a soldering technique. After the terminals made of copper were attached to both ends of the superconductor-metal shunt composite, the gap between the turns and the surface of the elements was filled with an epoxy and a dense mesh made of FRP in order to enhance the mechanical strength. The completed SFCL elements went through fault tests, and we confirmed that the voltage rating of 143 $V_{rms}$ (E =0.35 $V_{rms}$/cm) could be accomplished.

• Journal of Powder Materials
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• v.14 no.2 s.61
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• pp.123-126
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• 2007

In this work, the dispersion behavior of $Y_2O_3$ particles in binary aluminum (Al)-copper (Cu) cast alloy was investigated with respect to Cu contents of 20 (hypoeutertic), 33 (eutectic) and 40 (hypereutectic) wt.%. In cases of hypo and hypereutectic compositions, SEM images revealed that the primary Al and ${\theta}$ phases were grown up at the beginning, respectively, and thereafter the eutectic phase was solidified. In addition, it was found that some of $Y_2O_3$ particles can be dispersed into the primary Al phase, but none of them are is observed inside the primary 6 phase. This different dispersion behavior of $Y_2O_3$ particles is probably due to the difference in the val- ues of specific gravity between $Y_2O_3$ particles and primary phases. At eutectic composition, $Y_2O_3$ particles were well dispersed in the matrix since there is few primary phases acting as an impediment site for particle dispersion during solidification. Based on the experimental results, it is concluded that $Y_2O_3$ particles are mostly dispersed into the eutectic phase in binary Al-Cu alloy system.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1205-1206
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• 2006

Dispersion-strengthened copper with $TiB_2$ was produced by ball-milling and spark plasma sintering (SPS).Ball-milling was performed at a rotation speed of 300rpm for 30 and 60min in Ar atmosphere by using a planetary ball mill (AGO-2). Spark-plasma sintering was carried out at $650^{\circ}C$ for 5min under vacuum after mechanical alloying. The hardness of the specimens sintered using powder ball milled for 60min at 300rpm increased from 16.0 to 61.8 HRB than that of specimen using powder mixed with a turbular mixer, while the electrical conductivity varied from 93.40% to 83.34%IACS. In the case of milled powder, hardness increased as milling time increased, while the electrical conductivity decreased. On the other hand, hardness decreased with increasing sintering temperature, but the electrical conductiviey increased slightly

• Journal of the Korean institute of surface engineering
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• v.49 no.1
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• pp.54-61
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• 2016

Screen printing of commercially available Ag paste is the most widely used method for the front side metallization of Si solar cells. However, the metallization using Ag paste is expensive and needs high temperature annealing for reliable contact. Among many metallization schemes, Ni/Cu/Sn plating is one of the most promising methods due to low contact resistance and mass production, resulting in high efficiency and low production cost. Ni layer serves as a barrier which would prevent copper atoms from diffusion into the silicon substrate. However, Ni based schemes by electroless deposition usually have low thermal stability, and require high annealing process due to phosphorus content in the Ni based films. These problems can be resolved by adding W element in Ni-based film. In this study, Ni-W-P alloys were formed by electroless plating and properties of it such as sheet resistance, resistivity, specific contact resistivity, crystallinity, and morphology were investigated before and after annealing process by means of transmission line method (TLM), 4-point probe, X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM).

• Journal of the Korean Chemical Society
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• v.53 no.3
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• pp.233-243
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• 2009

We have investigated the infrared spectra for CO adsorbed on silica supported nickel(Ni-Si$O_2$), silica supported copper(Cu-Si$O_2$), silica supported nickel-copper alloys(Ni/Cu-Si$O_2$) of several compositions with varying CO pressures(0.2 $torr{\sim}$50 torr) at room temperature and on pumping to vacumn at room temperature within the frequency range of 1500 $cm^{-1}{\sim}2500\;cm^{-1}$. Four bands(2059.6 $cm^{-1},\;{\sim}$2036.5 $cm^{-1},\;{\sim}$ 1868.7 $cm^{-1},\;{\sim}$ 1697.1 $cm^{-1}$) were observed for Ni-Si$O_2$, two bands($\sim$2115.5 $cm^{-1},\;{\sim}$1743.0 $cm^{-1}$) were observed for Cu-Si$O_2$ and five bands(${\sim}2123.2\;cm^{-1}$, 2059.6 $cm^{-1},\;{\sim}$2036.4 $cm^{-1},\;{\sim}$1899.5 $cm^{-1},\;{\sim}$1697.1 $cm^{-1}$) were observed for Ni/Cu-Si$O_2$. These absorption bands correspond with those of the previous reports approximately. The bands below 1800 $cm^{-1}$ were only observed with Ni metal or Ni/Cu alloy crystal plane containing step at room temperature and the ${\sim}1697.1\;cm^{-1}$ bands observed with Ni-Si$O_2$ and Ni/Cu-Si$O_2$ may be ascribed to CO molecule adsorbed on the adsorption sites near step. The bands below 2000 $cm^{-1}$ were rarely observed with Cu metal crystal plane at room temperature and the 1743.0 $cm^{-1}$ bands may be ascribed to CO molecule adsorbed on the adsorption sites near step. The band shifts of adsorbed CO with varing Cu contents from 0 to 0.5 mole fraction at the same CO pressure or at the same pumping time to vacumn were below 21 $cm^{-1}$. and comparatively small than those with other ⅠB metal addition. It may means ligand effect of Cu d electron is small.