• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.4
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• pp.46-52
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• 2017

We quantitatively measured the mass transfer from friction surfaces, specifically brake pads and rotors, using laser plasma spectroscopy. Specifically, we modelled the mass transfer from the pad to the rotor and measured the elemental diffusion intensity distribution in the rotor material using laser plasma spectroscopy. The main elements measured were Cu, Ni, Ti, and Cr, and the distribution of these after transfer was measured as the ratio of the atomic peak and the ion peak of the plasma in the rotor exposed to friction and the surface composition of the rotor and the roughness, respectively. We measured and quantified the diffusion coefficient for each element through the mass transfer model and found that Cr obtained the largest diffusion coefficient (D) of the elements measured based on this system with a value of $1.9484{\times}10^{-15}m^2/s$.

• Journal of Powder Materials
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• v.22 no.6
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• pp.432-437
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• 2015

The en-riched $^{58}Ni$ powders are dissolved in acid solution and coated on a Cu target for proton irradiation at cyclotron to produce $^{57}Co$ radioisotope. The condition of the plating bath and the coating process are determined using the en-riched powders. To establish the coating conditions for $^{57}Co$, non-radioactive Co ions are dissolved in an acid solution and electroplated on to a rhodium plate. The thermal diffusion of electroplated Co into a rhodium matrix was studied to apply a $^{57}Co$ Mssbauer source. The diffusion depth from surface to matrix of Co is depended on the annealing temperature and time. The deposited Co atoms diffuse completely into a rhodium (Rh) matrix without substantial loss at an annealing temperature of 1200 for 4 hours.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.10
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• pp.1303-1313
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• 1997

A micro-macroscopic analysis on the conduction-controlled directional casting of Al-Cu alloys is performed, in which emphases are placed on the microstructural features. In order to facilitate the solution procedure, an iterative micro-macroscopic coupling algorithm is developed. The predicted results show that the effect of finite back diffusion on the transient solidification process in comparison with the lever rule depends essentially on the initial concentration of an alloy. In the final casting, the eutectic fraction is distributed in an increasing-decreasing-increasing pattern, each mode of which is named the chill, interior and end zones. This nonuniformity per se suffices to justify the necessity of this work because it originates from the combined effects of finite back diffusion and cooling path-dependent nature of the eutectic formation. As the cooling rate is enhanced, not only the influence depths of boundaries narrow, but also the eutectic fractions in the chill and interior zones increase. In addition, it is revealed for the first time that the micro segregation band is formed in response to a sudden change in cooling rate during the directional casting. An increasing change creates an overshooting band in the eutectic fraction distribution, and vice versa.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.260-260
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• 2009

In high-efficiency crystalline silicon solar cell, If high-efficiency solar cells are to be commercialized, It is need to develop superior contact formation method and material that can be inexpensive and simple without degradation of the solar cells ability. For reason of plated metallic contact is not only high metallic purity but also inexpensive manufacture. It is available to apply mass production. Especially, Nickel, Copper are applied widely in various electronic manufactures as easily formation is available by plating. Ni is shown to be a suitable barrier to Cu diffusin as well as desirable contact metal to silicon. Nickel monosilicide has been suggested as a suitable silicide due to its lower resistivitym lower sintering temperature and lower layer stress than $TiSi_2$. In this paper, Nickel as a seed layer and diffusion barrier is plated by electroless plating to make nickel monosilicide.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.217-217
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• 2003

초전도체 선재를 제작하기위해 YBa$_2$Cu$_3$$O_{7-x}$ (YBCO) 와 Ni substrates사이의 계면 문제를 해결하기 위한 buffer layer로써 CaRuO$_3$ (CRO) thu film이 제안되었는데, 이런 buffer layer의 조건으로는Ni metal과 YBCO superconductor사이의 화학적 반응이 없어야 하고 metal component가 YBCO로 diffusion되는 것을 막아주어야 하며 substrates의 산화를 막아주어야 한다. 이런 조건을 만족시키는 것 중에서 CRO thin film이 가장 적절하였지만, CRO의 orthorhombic구조의 distortion에 의만 lattice mismatch 문제가 발생하였다. 이러한 문제를 해결하기 위해 이론적인 구조 분석을 통한 CRO의superconductor buffer layer로써의 가능성을 검토해 보는 것이 목적이다.

• Journal of Powder Materials
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• v.4 no.4
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• pp.252-257
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• 1997

Cu-brazed layer between the sintered-cam(Fe-5Cr-lMo-0.5P-2.5C, wt%) and seamless steelpipe(0.25-0.35C, 0.3-1.0 Mn, bal Fe, wt%) in the camshaft shows a columnar structure of $\gamma$-phase growing from the steel pipe. Liquid phase sintered 60Fe-40Cu alloys are carburized to simulate the brazing process giving rise to the columnar growth. Liquid film migrations and columnar growth of $\gamma$-grains are observed in the carburized regions. The $\gamma$-grains grow in the same direction as the C-diffusion. Fe-solubility in the liquid of carburized region is higher than in the uncarburized by about 0.3 at%. The columnar growth is driven by the gradient of the supersaturated Fe-solute in the liquid between two adjacent $\gamma$-grains.

• Journal of Environmental Science International
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• v.11 no.5
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• pp.437-443
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• 2002

The chemical behavior and properties of the redox state of environmental pollutants were investigated using electrochemical methods. Cyclic voltammograms were performed on the compounds to measure the variations in the redox reactions. Temperature and pH were established as influencing the redox potential and current. The electrode reactions were a mixture of quasi-reversible and irreversible Precesses, which changed according to the reaction current. Although the Co(BPA)$_2$ and Cu(BPA)$_2$ compounds were not found to dissociate in wastewater, they were very unstable(K=1.02).

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.59-63
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• 2010

Immersion Sn plating was produced on Cu foil by distributing nano-sized diamonds (ND). The ND distributed on the coating surface broke the continuity of Sn-oxide layer, therefore leading to penetrate the molten solder through the oxide and retarding the wettability degradation during a reflow process. Furthermore, the ND in the Sn coating played a role of diffusion barrier for Sn atoms and decreased the growth rate of intermetallic compound ($Cu_6Sn_5$) layer during the solid-state aging. The study confirmed the importance of ND to improve the wettability and reliability of the Sn plating. Complete dispersion of the ND within the immersion Sn plating needs to be further developed for the electronic packaging applications.

• Journal of environmental and Sanitary engineering
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• v.13 no.1
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• pp.174-184
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• 1998

Biosorption characteristics were investigated to discuss the use of agar entrapped Spirulina to remove of heavy metal ions from polluted waters. Agar immobilized algae were used as bioadsorbent in continuous reactor for heavy metal ions removal. The process solution contains Pb, Cu, and Cd as single ion and binary ions. In the adsorption of single heavy metal ions by agar immobilized Spirulina, the adsorption reached within 1hr and observed diffusion limitation differed from the free algal cell adsorption. The optimum pH for the adsorption of heavy metals was 4.5 but the influence of pH decreased less than that of free algal cell. Also, the adsorption characteristics of single heavy metal ions with agar immobilized Spirulina fitted the BET isotherm. Both of experiments of free algal cell and agar immobilized algae showed higher removal efficiency in the single ion solutions than binary ions solutions. The experimental results in the packed column with agar immobilized algae were over 90% of removal efficiency for the Pb, Cu, and Cd in single ion solutions.

• Journal of Powder Materials
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• v.9 no.2
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• pp.116-123
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• 2002

The characteristics of two commercial 2xxx series Al alloy powders, AMB2712 and 201AB, were evaluated and their compacting and sintering characteristics were discussed in tems of compacting pressure. The particle shapes of both two powder mixtures were irregular and their particle size distributions were broad. The compactibility of AMB2712 was superior to that of 201AB because of better fluidity. The sintered density was higher than the green density at low compacting pressure, however, it was lower than the green density when the samples were compacted at higher pressure due to the selling during sintering. The sintered density was alomost the same as the green density at the "homogeneous deformation" stage. It was observed that pores were created at the triple points due to the rapid diffusion of Cu in Al. Cu in Al.