• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1199-1202
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• 2003

In this research, microfabrication technique using localized electrochemical deposition is presented. Electric field is localized near the tip end region by applying ultra short pulses. Platinum tip is used as the counter electrode and copper is deposited on the copper substrate in 0.5 M CuSO$_4$ and 0.5 M H$_2$SO$_4$ electrolyte. The deposition characteristics such as size, shape, and structural density according to pulse duration and applied voltage are investigated. Micro-columns less than 10 $\mu\textrm{m}$ in diameter are fabricated using the presented technique. The process can be potentially used for three dimensional metal structure fabrications with micrometer feature size.

• International Journal of Precision Engineering and Manufacturing
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• 제6권4호
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• pp.49-54
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• 2005

In this paper, micro structuring technique using localized electrochemical deposition (LECD) with ultra short pulses was investigated. Electric field in electrochemical cell was localized near the tool tip end region by applying pulses of a few hundreds of nano second duration, Pt-Ir tip was used as a counter electrode and copper was deposited on the copper substrate in mixed electrolyte of 0.5 M $CuSO_4$ and 0.5 M $H_2SO_4$, The effectiveness of this technique was verified by comparison with ECD using DC voltage. The deposition characteristics such as size, shape, surface, and structural density according to applied voltage and pulse duration were investigated. The proper condition was selected based on the results of the various experiments. Micro columns less than $10{\mu}m$ in diameter were fabricated using this technique. The real 3D micro structures such as micro spring and micro pattern were made by the presented method.

• 한국정밀공학회지
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• 제21권11호
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• pp.186-194
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• 2004

In this research, microfabrication technique using localized electrochemical deposition (LECD) with ultra short pulses is presented. Electric field is localized near the tool tip end region by applying a few hundreds of nano second pulses. Pt-Ir tip is used as a counter electrode and copper is deposited on the copper substrate in 0.5 M CuSO$_4$ and 0.5 M H$_2$SO$_4$ electrolyte. The effectiveness of this technique is verified by comparison with LECD using DC voltage. The deposition characteristics such as size, shape, surface, and structural density according to applied voltage and pulse duration are investigated. The proper condition is selected from the results of the experiments. Micro columns less than 10 $\mu$m in diameter are fabricated using this technique. The real 3D micro structures such as micro pattern and micro spring can be fabricated by this method. It is suggested that presented method can be used as an easy and inexpensive method for fabrication of microstructure with complex shape.

• International Journal of Precision Engineering and Manufacturing
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• 제9권2호
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• pp.75-80
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• 2008

The fabrication of complex three-dimensional electrodes for micro electrical discharge machining (micro-EDM) is an important issue in the field of micromachining Localized electrochemical deposition (LECD) is a simple and inexpensive technique for fabricating micro-EDM electrodes. This study presents a new process for manufacturing electrodes with complex cross-sections using masks of different shapes, In this process, a non-conductive mask is placed between an anode and cathode that are immersed in a plating solution of acidified copper sulfate. The LECD is achieved by applying a pulsed voltage between the anode and cathode, which are separated by a small distance. In this setup, the cathode is placed above the anode and the mask, so that the deposited electrode can be used directly for EDM without changing the tool orientation. We found that the microstructure of the deposited electrode is influenced by the concentration of the plating solution and organic additives. Moreover, the values of the voltage, frequency, and duty cycle of the pulsed input have significant effects on the microstructure of the fabricated electrode. Finally, the optimum values of the voltage, frequency, and duty cycle were determined for the most effective fabrication of complex-shaped electrodes.

• 한국표면공학회지
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• 제36권4호
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• pp.301-306
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• 2003

Multilayered WC-Ti/suv $1-x/Al_{x}$ N coatings were deposited on AISI D2 steel using cathodic arc deposition (CAD) method. These coatings contain structural defects such as pores or droplets. Thus, the substrate is not completely isolated from the corrosive environment. The growth defects (pores, pinholes) in the coatings are detrimental to corrosion resistance of the coatings used in severe corrosion environments. The localized corrosion behavior of the coatings was studied in deaerated 3.5 wt.% NaCl solution using electrochemical techniques (potentiodynamic polarization test) and surface analyses (GDOES, SEM, AES, TEM). The porosity was calculated from the result of potentiodynamic polarization test of the uncoated and coated specimens. The calculated porosity is higher in the $WC-Ti_{0.6}$ $Al_{0.4}$ N than others, which is closely related to the packing factor. The positive effects of greater packing factor act on inhibiting the passage of the corrosive electrolyte to the substrate and lowering the localized corrosion kinetics. From the electrochemical tests and surface analyses, the major corrosion mechanisms can be classified into two basic categories: localized corrosion and galvanic corrosion.

• Journal of Electrochemical Science and Technology
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• 제3권2호
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• pp.57-62
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• 2012

In this report, we demonstrate that the longitudinal localized surface plasmon resonance mode can be suppressed when the nanorods were in dumbbell shape. The seed nanorods were synthesized by electrochemical deposition of metals into the pores of anodic aluminum oxide templates. The dumbbell-like nanorods were grown from seed Au-Ni-Au nanorods by a rate-controlled seed-mediated growth strategy. The selective deposition of Au atoms onto Au blocks of Au-Ni-Au nanorods produced larger diameter of Au nanorods with bumpy surface resulting in dumbbell-like nanorods. The morphology of nanorods depended on the reduction rate of $AuCl_4^-$, slow rate producing smooth surface of Au nanorods, but high reduction rate producing bumpy surface morphology. Through systematic investigation into the UV-Vis-NIR spectroscopy, we found that the multiple localized surface plasmon resonance (LSPR) modes were available from single-component Au nanorods. And, their LSPR modes of Au NRs with bumpy surface, compared to the smooth seed Au NRs, were red-shifted, which was obviously attributed to the increased electron oscillation pathways. While the longitudinal LSPR modes of smoothly grown Au NRs were blue-shifted except for a dipole transverse LSPR mode, which can be interpreted by decreased aspect ratio. In addition, dumbbell-like nanorods showed an almost disappeared longitudinal LSPR mode. It reflects that the plasmonic properties can be engineered using complex nanorods structure.

• Corrosion Science and Technology
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• 제14권5호
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• pp.218-225
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• 2015

The electrochemical behaviors of various metals with and without diamond-like-carbon (DLC) coating in 3.5 wt% NaCl solution were investigated. The effect of hydrodynamic conditions was focused by employing a rotating disc electrode (RDE). The experimental results showed that each bare metal had a more positive corrosion potential and a higher corrosion rate due to enhanced oxygen transport at the higher rotating speed of the RDE. DLC coating caused a substantial increase in the corrosion resistance of all metals studied. However, localized corrosion was still found in the DLC-coated metal at sites where deposition defects existed. Surface morphology examination was performed after the electrochemical test to confirm the roles of hydrodynamic conditions and DLC coating.

• 한국진공학회지
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• 제21권4호
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• pp.205-211
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• 2012

인듐주석산화막/폴리에틸렌 테레프탈레이트(ITO/PET: indium tin oxide/polyethylene terephthalate) 유연 기판 위에 성장된 산화아연(ZnO) 나노로드(nanorods)를 이용하여 형성된 은(Ag) 입자의 광학적 특성 및 소수성 표면에 대해 조사하였다. 시료를 준비하기 위해 스퍼터링법(sputtering)으로 코팅된 산화아연 씨드층(seed layer)을 이용하여 전기화학증착법(electrochemical deposition)으로 산화아연 나노로드를 성장시킨 후, 열증발증착법(thermal evaporation)을 사용하여 은을 증착하였다. 산화아연 나노로드의 불연속적인 표면 특성 때문에 은이 증착되면서 나노크기를 갖는 입자로 형성되었다. 비교를 위해 같은 조건으로 은을 평평한 ITO/PET에 증착하여 시료를 준비하였으며, 증착되는 은의 양을 조절하기 위해 100초에서 600초까지 열증발증착시간을 변화시켰다. 은 증착시간이 증가할수록 산화아연 나노로드 표면에 형성되는 은 입자의 크기와 양이 증가하였으며, 또한 빛의 흡수율이 가시광 영역에서 크게 증가하는 것을 확인하였다. 이는 은 입자의 국소표면플라즈몬공명(localized surface plasmon resonance)에서 기인된 것으로 짐작한다. 또한 물방울 테스트실험에서 평평한 ITO/PET에 증착된 은에서의 접촉각(contact angle)보다 산화아연 나노로드에 증착된 은 입자에서의 접촉각이 크게 증가함을 보여, 개선된 소수성 표면을 가질 수 있음을 확인하였다. 이러한 광학적 특성과 소수성 표면 결과는 산화아연 나노로드의 기반의 염료감응형 태양전지 또는 자정효과(self-cleaning)를 갖는 표면구조로 유연소자에 유용하게 응용할 수 있을 것으로 기대된다.

• 통합자연과학논문집
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• 제5권4호
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• pp.211-215
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• 2012

Single-crystalline silicon nanowire arrays (SiNWAs) using electroless metal-assisted etchings of p-type silicon were successfully fabricated. Ag nanoparticle deposition on silicon wafers in HF solution acted as a localized micro-electrochemical redox reaction process in which both anodic and cathodic process took place simultaneously at the silicon surface to give SiNWAs. The growth effect of SiNWs was investigated by changing of etching times. The morphologies of SiNWAs were obtained by SEM observation. Well-aligned nanowire arrays perpendicular to the surface of the silicon substrate were produced. Optical characteristics of SiNWs were measured by FT-IR spectroscopy and indicated that the surface of SiNWs are terminated with hydrogen. The thicknesses and lengths of SiNWs are typically 150-250 nm and 2 to 5 microns, respectively.

• 한국표면공학회지
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• 제36권1호
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• pp.79-84
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• 2003

$WC-Ti_{1}$ -xA $l_{x}$ N multilayered coatings are performed by their periodically repeated structures of lamellae of WC-Ti/$WC-Ti_{1}$ -xA $l_{x}$ Nmaterials. The $WC-Ti_{1}$ -xA $l_{x}$ N coatings with variable Al content were deposited onto AISI D2 steel by cathodic arc deposition (CAD) method. The electrochemical behavior of multilayered $WC-Ti_{1}$ -xA $l_{x}$ N coatings with different phases (WC- Ti$0.6/Al_{0.4}$ N, $WC-Ti_{0.53}$$Al_{0.47}$N, $WC-Ti_{0.5}$ $Al_{0.5}$ N and $WC-Ti_{ 0.43}$$Al_{0.57}$ N) was investigated in deaerated 3.5% NaCl solution at room temperature. The corrosion behaviors for the multilayered coatings were investigated by electrochemical techniques (potentiodynamic polarization) and surface analyses (X-ray diffraction (XRD), scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES)). In the petentiodynamic polarization test, the corrosion current density of $WC-Ti_{0.5}$$Al_{0.5}$N was lower than others.