• Corrosion Science and Technology
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• 제9권6호
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• pp.281-288
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• 2010

This study examined the carbon corrosion at Pt/C interface in proton exchange membrane fuel cell environment. The Pt nano particles were electrodeposited on carbon substrate, and then the corrosion behavior of the carbon electrode was examined. The carbon electrodes with Pt nano electrodeposits exhibited the higher oxidation rate and lower oxidation overpotential compared with that of the electrode without Pt. This phenomenon was more active at $75^{\circ}C$ than $25^{\circ}C$. In addition, the current transients and the corresponding power spectral density (PSD) of the carbon electrodes with Pt nano electrodeposits were much higher than those of the electrode without Pt. The carbon corrosion at Pt/C interface was highly accelerated by Pt nano electrodeposits. Furthermore, the polarization and power density curves of PEMFC showed degradation in the performance due to a deterioration of cathode catalyst material and Pt dissolution.

• 한국표면공학회지
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• 제34권2호
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• pp.151-160
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• 2001

The composition and the microstructure of the lead-tin alloy electrodeposited in a gluconate bath were invesitigated according to electrolysis conditions. The tin content of the lead-tin alloy electrodeposits increased with increasing current density and EDTA addition, while it decreased with increasing temperature and sodium gluconate concentration. The preferred orientation of the alloy deposits changed from the (220) plane through (200) to (200) + (111) planes with increasing cathode overpotential. The surface morphology of the films was closely related to both the preferred orientation and the alloy composition.

• Corrosion Science and Technology
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• 제3권3호
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• pp.112-117
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• 2004

This work investigated the material properties of Ni-P-B alloy electrodeposits obtained from a Ni sulfamate bath as a function of the contents of the P and B sources($H_3PO_3$ and dimethyl amine borane complex(DMAB), respectively) with/without additives. Chemical composition, residual stress, microstructure and micro hardness were investigated using ICP(inductively coupled plasma) mass spectrometer, flexible strip, XRD, TEM and micro Vickers hardness tester, respectively. From the results of the compositional analysis, it was observed that P and B are incorporated competitively during the electrodeposition and the sulfur from the additive is codeposited into the electrodeposit. The measured residual stress value increased in the order of Ni, Ni-P, Ni-B and Ni-P-B electrodeposits indicating that boron affects the residual tensile stress greater than phosphorus. As the contents of the alloying element sources of P and B increased, crystallinity and the grain size of the electrodeposit decreased. The effect of boron on crystallinity and grain size was also relatively larger than the phosphorus. It can be explained that the boron with a smaller atomic radius contributes to the increase of residual stress in the tensile direction and the larger restraining force against the grain growth more significantly than the phosphorus with a larger atomic radius. Introduction of an additive into the bath retarded crystallization and grain growth, which may be attributed to the change of the grain growth kinetics induced by the additive adsorbed on the substrate and electrodeposit surfaces during electrodeposition.

• 한국표면공학회지
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• 제48권2호
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• pp.62-67
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• 2015

Nickel is a commercially important and versatile element in electroplating. The applications of nickel electroplating fall into three main categories: decorative, functional and electroforming. In decorative applications, electroplated nickel is most often applied in combination with electrodeposited chromium. Nickel is deposited on surfaces to improve corrosion and wear resistance or modify magnetic and other properties. Electroforming is electroplating applied to the fabrication of products of various kinds. Nickel is deposited onto a substrate and then removed from it to create a part made entirely of nickel. In this study, mechanical property of Ni electrodeposits in various manufacturing condition such as temperature, current density, pH and electrolyte content, was investigated to understand effect of electrolysis condition on mechanical property. Vickers hardness increased as the temperature and pH increased and current density and electrolyte content decreased and pH increased. The results were explained by cathode overvoltage and hydrogen evolution.

• 한국재료학회지
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• 제22권1호
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• pp.8-15
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• 2012

Silicon-based thin film was prepared at room temperature by an electrochemical deposition method and a feasibility study was conducted for its use as an anode material in a rechargeable lithium battery. The growth of the electrodeposits was mainly concentrated on the surface defects of the Cu substrate while that growth was trivial on the defect-free surface region. Intentional formation of random defects on the substrate by chemical etching led to uniform formation of deposits throughout the surface. The morphology of the electrodeposits reflected first the roughened surface of the substrate, but it became flattened as the deposition time increased, due primarily to the concentration of reduction current on the convex region of the deposits. The electrodeposits proved to be amorphous and to contain chlorine and carbon, together with silicon, indicating that the electrolyte is captured in the deposits during the fabrication process. The silicon in the deposits readily reacted with lithium, but thick deposits resulted in significant reaction overvoltage. The charge efficiency of oxidation (lithiation) to reduction (delithiation) was higher in the relatively thick deposit. This abnormal behavior needs to clarified in view of the thickness dependence of the internal residual stress and the relaxation tendency of the reaction-induced stress due to the porous structure of the deposits and the deposit components other than silicon.

• 마이크로전자및패키징학회지
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• 제15권4호
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• pp.71-76
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• 2008

전기도금법에 의한 니켈-철 합금 도금층은 전류인가방식, 전류밀도, 첨가제, 도금 욕에서 철과 니켈에 농도비 등과 같은 공정 변수에 따라 그 조성이 민감하게 변화하고 특히 전류인가방식에 따라 도금 층의 조성과 기계적인 특성이 달라지는 경향을 보이고 있다. 본 연구에서는 전류의 인가방식과 전류밀도 변화에 따른 경도, 내마모성, 인성,표면 거칠기 및 잔류응력 등의 기계적인 물성의 변화를 연구하였다. 전류인가방식을 직류에서 펄스전류로 변환시킴에 따라 인장강도가 15% 증가하였으며, 잔류음력이 10% 감소하였고, 내마모성이 30% 향상되었다.

• 한국표면공학회지
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• 제48권4호
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• pp.131-135
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• 2015

We investigated the surface morphology and the change of Ag concentration for SnAg electrodeposits according to the current density using labmade and commercial plating solutions. The concentration of Ag in the SnAg electrodeposits decreased with increasing the current density. The Ag concentrations at the conditions of over $50mA/cm^2$ were below 3 wt% and the surface was relatively smooth. Cu pillar bump was fabricated by using SnAg electroplating, and it was reflowed at $240^{\circ}C$ for 90 sec. The cross-sectional microstructure was investigated by using EBSD measurement and it was found that the grain size of SnAg became smaller by increasing the number of reflow treatments.

• 한국표면공학회지
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• 제36권5호
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• pp.379-385
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• 2003

The surface morphology, the glossiness and the hardness of Zn-Cr and Zn-Cr-X(X:Co, Mn) alloy electrodeposits were investigated by using chloride bath with EDTA additive and flow cell system. The surface morphology of Zn-Cr alloy and Zn-Cr-Mn alloy changed from fine needle shape crystalline structure to colony structure of fine granular crystallites with increasing current density in the range of 20-100 $A/dm^2$. The surface morphology of Zn-Cr-Co alloy deposited from low Co concentration bath(2.5-10 g/$\ell$) was similar to that of Zn-Cr alloy, while that of Zn-Cr-Co alloy deposited from high cobalt concentration bath was fine granular crystalline structure in the same range of current density. The glossiness of Zn-Cr and Zn-Cr-Mn alloy increased noticeably with increasing current density, while that of Zn-Cr-Mn alloy decreased with increasing Mn concentration of bath in high current density region. The glossiness of Zn-Cr-Co alloy deposited from low Co concentration bath increased with current density while that of the alloy from high Co concentration bath decreased with increasing current density. The hardness of Zn-Cr and Zn-Cr-X alloy increased noticeably with current density.

• Corrosion Science and Technology
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• 제10권4호
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• pp.143-150
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• 2011

Copper electroplating has been applied to various fields such as decorative plating and through-hole plating. Technical realization of high strength copper preplating for wear-resistant tools and molds in addition to these applications is the aim of this work. Brighters and levelers, such as MPSA, Gelatin, Thiourea, PEG and JGB, were added in copper sulfate electrolyte, and the effects of these organic additives on the hardness were evaluated. All additives in this work were effective in increasing the hardness of copper electrodeposits. Thiourea increased the hardness up to 350 VHN, and was the most effective accelarator in sulfate electrolyte. It was shown from the X-ray diffraction analysis that preferred orientation changed from (200) to (111) with increasing concentration of organic additives. Crystallite size decreased with increasing concentration of additive. Hardness was increased with decreasing crystallite size, and this result is consistent with Hall-Petch relationship, and it was apparent that the hardening of copper electrodeposits results from the grain refining effect.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2004년도 춘계총회 및 학술발표회
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• pp.48-49
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• 2004