• Journal of Integrative Natural Science
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• v.2 no.3
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• pp.207-210
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• 2009

Multiple rugate structures can be etched on a silicon wafer and placed in the same physical location, showing that many sharp spectral lines can be obtained in the optical reflectivity spectrum. Porous silicon samples were prepared by electrochemical etch of heavily doped p-type silicon wafers. The etching solution consisted of a 3:1 volume mixture of aqueous 48% hydrofluoric acid and absolute ethanol. Galvanostatic etch was carried out in a Teflon cell by using a two-electrode configuration with a Pt mesh counterelectrode. A sinusoidal current density waveform varying between 51.5 and $74.6mA/cm^2$ is applied. The anodization current was supplied by a Keithley 2420 high-precision constant current source which is controlled by a computer to allow the formation of PSi multilayer.

• Corrosion Science and Technology
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• v.5 no.6
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• pp.213-217
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• 2006

Titania coatings were prepared on commercially pure Ti by plasma electrolytic oxidation (PEO) method with various electrolytes and process condition. Coatings were formed under galvanostatic condition with several current density values, and the change of applied voltage with process time was recorded. The microstructure of the titania coatings was observed using XRD, SEM, TEM, and the time-voltage diagrams were analyzed in terms of microstructure evolution.

• Journal of the Korean institute of surface engineering
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• v.24 no.3
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• pp.125-136
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• 1991

a mathematical model is presented to describe the current distribution on a rotaing disk electrode under the galvanostatic pulse conlitions. A numerical technique by finite difference method to the transient convective diffusion equation, coordinate transformation and separation of variables to Laplace equation, and an iterative algorithm to solve the above equations simtltaneously with approximate boundary conditions were developed. An experimental investigated based on copper deposition in a copper sulfate-sulfuric acid system was performed and satisfactory agreement was obtained between expermental and theoretical current distribution. The current distribution of copper deposition is secondary current distribution within the experimental conditions. Dimensionless variables, N and J as well as Wagner number were used to determine the criteria for the uniformity of current distribution.

• Journal of the Korean institute of surface engineering
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• v.39 no.5
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• pp.223-228
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• 2006

The current efficiency of copper anode containing impurities in copper sulfate solution for electrorefining was studied at various current type such as direct current, variable current and periodic reverse current. The passivity behavior was investigated by galvanostatic technique. The results obtained were that current efficiency of variable current was higher than those of direct current and periodic reverse current. The increased current efficiency could be explained by the formation of slime structure with lower average resistance due to variable current. The frequency of various factors in variable current condition has a greatest effect on current efficiency. It appeared that frequency increased current efficiency when increased from 1 to 4, but further increases did not have an effect.

• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.136-142
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• 2011

$Li_4Ti_5O_{12}$ is prepared through a solid-state reaction between $Li_2CO_3$ and anatase $TiO_2$ for applications in lithium-ion batteries. The rate capability is measured and the electrode polarization is analyzed through the galvanostatic intermittent titration technique (GITT). The rate characteristics and electrode polarization are highly sensitive to the amount of carbon loading. Polarization of the $Li_4Ti_5O_{12}$ electrode continuously increases as the reaction proceeds in both the charge and discharge processes. This relation indicates that both electron conduction and lithium diffusion are significant factors in the polarization of the electrode. The transition metal (Cu, Ni, Fe) ion added during the synthesis of $Li_4Ti_5O_{12}$ for improving the electrical conductivity also greatly enhances the rate capability.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.3
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• pp.374-379
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• 1996

Effects of reactant gas flow rates and starvation on phosphoric acid fuel cell performance were studied. As the reactant gas flow rates increased, the cell performance increased and then the cell maintained constant performance. The optimum flow rates of hydrogen, oxygen and air under galvanostatic condition of 150 mA/cm$_{2}$ are found to be 5cc/min cm$_{2}$ 5cc/min cm$_{2}$ and 15cc/min cm$_{2}$ at room temperature and 1 atm, respectively. Also the open circuit voltage of single cell decreased with increasing oxygen flow rate due probably to the decreased probably to the decreased oxygen pressure in the cathode side. Hydrogen and oxygen starvation resulted in voltage loss of about 5mV and 0-2mV, respectively. The voltage loss was independent of starvation time. These results were discussed from point of view of electrochemical reaction of the cell. (author). 9 refs., 8 figs.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2315-2319
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• 2012

To improve the performance of $LiFePO_4F$, a novel sol-gel process is developed. For comparison, ceramic process is also implemented. From X-ray diffraction results we know that each sample adopts a triclinic $P{\bar{1}}$ space group, and they are isostructural with amblygonite and tavorite. The scanning electron microscope images show that the homogeneous grains with the dimension of 300-500 nm is obtained by the sol-gel process; meanwhile the sample particles obtained by ceramic process are as big as 1000-3000 nm. By galvanostatic tests and at electrochemical impedance spectroscopy method, the sample obtained by sol-gel process presents better electrochemical properties than the one obtained by ceramic process.

• Advances in Energy Research
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• v.3 no.1
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• pp.45-57
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• 2015

This article is addressed to define a new composite electrode constituted by porous nickel and an array of highly ordered $TiO_2$ nanotubes obtained by a previous galvanostatic anodization treatment in an ethylene glycol solution. The electrochemical performances of the composite anode were evaluated in a photo-electrolyser, which showed good solar conversion efficiency with respect to the UV irradiance together with a reduction of energy consumption. Such a combination of materials makes our system simple and able to work both in dark and under solar light exposure, thus opening new perspectives for industrial-scale applications.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.455-456
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• 2017

본 논문에서는 리튬 인산철 배터리($LiFePO_4$)의 내부 파라미터 추출 방법으로 전기화학적 기반인 정전류식 간헐적 적정 테크닉(galvanostatic intermittent titration technique;GITT)을 사용하였다. 배터리 관리 시스템(battery management system;BMS) 알고리즘의 기본적으로 들어가는 충방전 저항을 미세 구간으로 나누어 볼 수 있다. SOC(state-of-charge)에 맞는 저항 성분을 찾을 수 있고, 미소 용량 정보를 알아내어 특정 SOC 구간에서의 LFP 배터리 최적 운용 구간을 알 수 있다.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.172-177
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• 2016

In this paper, various electrochemical experiments were conducted in seawater solution to evaluate corrosion damage behavior of arc thermal sprayed Inconel 625 coating on SS400 steel in marine environment. As a result, corrosion damages of thermal sprayed Inconel 625 coating preferentially occurred at the defect area, and they were observed as a form of pitting corrosion in the galvanostatic experiments. In Tafel analysis, corrosion current density of Inconel 625 coating was relatively high due to influence of interconnected pores and Cr oxides in the thermal spray coating layer. On the other hand, the result of the potential measurement, thermal sprayed Inconel 625 coating should need the post-treatment which can compensate the defects like pores and cracks because Inconel 625 coating presented a higher potential of about 290 mV than that of the SS400 steel.